Each block was standardized and photographed before and after shaping in the same position, with the foramen oriented to the left. Post-shaping images were superimposed onto the initial ones. Thirteen measurement points were used for evaluation, spaced with 1 mm distance from one another, from level 0, apical foramen, to level 12, coronal orifice. The amount of removed resin from inner (X1) and outer (X2) walls, the direction of transportation (X1 − X2), and the centering ability (X1 − X2)/Y were measured, calculated, and comparatively analyzed. Statistical differences (p < 0.05) were observed between the shaping capacity of the considered systems in the middle and coronal thirds. PTG had a better centering ability than WOG and RB in the coronal third, while RB was more centered in the middle third in comparison to both WOG and PTG. In the apical third, the centering capacity of WOG was higher, without being statistically significant. WOG 25/07 and PTG 25/08 tend to cut more on the inner wall of the root canals, and RB 25/08 on the external one.Maintaining the original trajectory of the root canal is a major challenge in endodontic therapy, especially in narrow and curved root canals. The present study aims to assess the shaping capacity of three endodontic systems made of different nickel–titanium alloys on simulated curved root canals. Thirty-six endodontic resin blocks  divided into three groups, each of twelve blocks ( One of the most significant steps of the root canal treatment is represented by the preparation of the root canal system . The insAchieving a continuous tapered shape and respecting the original morphology in terms of narrow and curved root canals is still a major challenge in current practice. Traditionally, mechanical canal instrumentation using stainless steel hand tools is a time-consuming method, with which it is difficult to meet the above criteria when preparing narrow and curved canals .Recently, several modern endodontic nickel–titanium (NiTi) systems with different mechanical characteristics have been designed to improve the behavior of endodontic instruments . The conThus, to increase the efficiency and safety of the mechanical preparation of the root canal, the companies that manufacture NiTi instruments have been constantly focused on improving their physical properties by increasing their flexibility and the resistance threshold to bending and fracture. These new approaches and changes include not only different tapers and designs of the cross-section of the instruments, but also novel NiTi alloys to improve their mechanical characteristics ,7.ProTaper Gold (PTG), WaveOne Gold (WOG), and Reciproc Blue (RB) are relatively novel root canal shaping systems. They were developed from the improvement of NiTi alloys . LiteratDifferent studies have been already carried out to investigate such aspects, either on simulated root canals ,3,4,5, iThe aim of the present study was to assess the shaping efficiency of two reciprocating NiTi systems, RB and WOG, as well as of one system with continuous rotation, PTG, on endodontic resin blocks with simulated curved root canals. The standardized photographic method was chosen to obtain before/after shaping images, which were digitally processed and analyzed using a computerized program for precise measurements. Statistical analysis was performed to observe the differences between the study groups.The tested null hypothesis was that no differences can be observed between the shaping capacity of the three tested systems.n = 12). The samples from Group 1 were shaped with the Protaper Gold system , instruments S1-S2-F1-F2, up to a final size of 25/08; the blocks from Group 2 were shaped with the Reciproc Blue system  instrument RB 25/08; in Group 3 the WaveOne Gold system , instrument WOG Primary 25/07 was utilized.The present study utilized thirty-six endodontic resin blocks,  with simulated curved root canals. They were divided into three groups, each consisting of twelve resin blocks  and an AF-S MICRO NIKKON 60 MM 1:2:8G ED camera lens in a standardized manner. The improvised stand was used to ensure that all the resin blocks were fixed in the exact same position, with the foramen to the left with regard to the sensor of the camera. All pictures were taken under the same conditions. Each root canal was injected with Castellani red dye solution to make the root canal trajectory more visible on the before/after photographs.An X-Smart Plus  endodontic motor was used for the shaping phase, with the corresponding settings of the manufacturer for each file. During shaping, the root canals were filled with NaOCl 5.25% irrigant solution 1:1 .n = 12) was shaped with the PTG rotary system, using the S1-S2-F1-F2 sequence; therefore, the final shape had the size of 0.25 mm at the foramen and 8% apical taper. Between each instrument of the PTG system, the canals were irrigated with NaOCl. The patency was re-confirmed with K-file #10, and then re-irrigated with the same solution; therefore, during shaping, canals were permanently filled with irrigant.Group 1 (n = 12) was shaped using the RB system, using the RB25 instrument with a 0.25 tip diameter and 8% taper on the first 3 mm. Three passages of the RB25 instrument were used until the complete shaping of each root canal in reciprocating motion was completed, according to the manufacturers’ instructions. Irrigation and patency were recapitulated before each passage of the RB25 instrument inside the root canal.Group 2 (n = 12) was shaped using the WOG endodontic system, instrument WaveOne Gold Primary, with a tip diameter of 0.25 mm and a 7% taper, in the same manner as for Group 2, until the WOG 25/07 instrument reached the working length.Group 3  to eliminate any variables regarding the shaping ability of different operators.All photographs taken after shaping were processed using the Adobe Photoshop CC  program, by overlaying  the final images over the initial ones. As a result, images with the differences between the initial morphology of the root canal and the final shape were obtained. The obtained images were cropped to certain dimensions in order to enclose them into a standardized frame of 1054 × 442 px (15.5 × 6 mm). Each image was then measured with the Adobe Photoshop Measuring Tool. This allowed for the exact measurement of the investigated distances in mm, which represents an advantage of the current study. The measurements were made at thirteen different levels, with a 1 mm distance between each level .the amount of resin removed on the inner part of the curvature, X1the amount of resin removed on the outer part of the curvature, X2the total amount of resin removed, X1 + X2the amount and direction of transportation, X1 − X2the centering ratio (X1 − X2)/Y, where Y is the total width of the shaped root canal.The images were then structured depending on the utilized file and the obtained result with Microsoft Excel program, in documents that contained all the measurements, in a non-blinded study. The distance between the initial root canal margin and the margin after shaping on the internal side of the curvature (X1), the external side of the curvature (X2), as well as the total width of the shaped root canal (Y) were measured. Using the following equations, the obtained data served for a qualitative and quantitative assessment of the modelling capacity of the three considered systems by evaluating the following parameters:The closer the centering ratio was to zero, the better the centering ability of a certain system was considered .No instrument fractured during shaping. All root canals remained patent by using the 0.10 ISO K-file in recapitulation after each used NiTi instrument associated with co-pious irrigation.The obtained results are based on the total number of thirty-six endodontic resin blocks included in the study. In each group, face L (left) of the plastic blocks was photographed and evaluated.Measurements were made on all photographs taken for the three-dimensional (3D) reproduction of changes resulting after instrumentation from mm to mm along the entire root canal length. Thus, thirteen levels of analysis were obtained, from 0 to 12. On each level, the parameters pointed out above were measured. The results were comparatively analyzed for each root canal third, as follows: From level 0 to 4, the apical third; from 5 to 8, the middle third; from 9 to 12, the coronal third .All data was recorded using Microsoft Excel. Statistical analysis of the data was performed using SPSS 22.0 . Each set of measurements was analyzed using the Kolmogorov–Smirnov test for normality.p < 0.05. Descriptive statistics (mean and standard deviation) were provided for all data sets. For a comparison between data sets, the ANOVA test was performed. Tukey’s post hoc test was also performed to determine the exact location of the differences between groups.Statistical significance level was set at In the apical third of the simulated root canals (levels 0 to 4), no statistically significant differences were recorded between the three analyzed systems for X1, X2, and for (X1 − X2)/Y. However, as it can be observed , RB remoOn the external part of the curvature, RB removed the highest amount of resin in comparison to WOG and PTG at all five analyzed levels, while WOG was the most conservative system at levels 3 and 4, and PTG at levels 0 to 2, but the differences observed between all three systems were not statistically significant.In the middle third of the root canals, the most statistically significant differences were observed between the three systems in comparison to the apical and coronal thirds. For X1 , signifiFor X2 , differeFor the (X1 − X2)/Y formula, statistically significant differences were recorded at all levels. At level 5, the mean value for RB was lower only compared to WOG. At level 6, RB had a value closer to 0, while at level 7 and 8, PTG and WOG had values closer to 0. These values mean that they had a more centered preparation at the specified level.In the coronal part of the root canals, several statistically significant differences were also observed. For X1 , differeMoreover, an overall comparative analysis of the efficiency of the considered systems on each root canal third was performed . RegardiAccording to extensive literature data, despite the limitations of the present study, it is widely known that image superposition is an accepted method utilized to assess the shaping efficiency of different instrumentation methods on resin blocks with simulated root canals ,21,22. HResin blocks were chosen in the present study instead of extracted teeth to rule out variations in the anatomy of the root canal that could influence the result of the instrumentation. The resin blocks ensure the standardization of the diameter, length, and curvature of the root canal in all three dimensions. They also facilitate the modeling capacity of various instruments to be directly compared. There are two significant limitations associated with the use of resin blocks: First, it is important to take care to extrapolate the effects to the clinical situation; second, the heat produced in the resin blocks by the rotating instruments may soften the resin material and lead to the binding of the cutting blade and to the instrument being separated, as the hardness of the resin blocks is half of that of natural human dentine and exhibits completely different thermal properties ,25. NoneIn most of the investigations performed on radiographs or superimposing photographic before/after images of the plastic blocks, as in the present study, the investigators used mathematical formulas to assess the differences between pre-operative and post-operative outer lines. However, this method of examination does not specify the exact amount of material removed, or the effects of the preparation symmetry, since these investigations are only two-dimensional , and there is also another dimension  in the samples . Due to This study aimed to compare three different mechanical systems made of various NiTi alloys, such as the blue wire and the gold wire NiTi, which are characterized by an advanced metallurgy and heat treatment process that increases the instruments flexibility. In extended research, the effects of the thermo-mechanical treatments applied to NiTi alloys have been evaluated using differential scanning calorimetry ,31.Previous studies compared the modelling capacity of gold wire, M-wire, and traditional NiTi alloys. They indicated that gold wire and M-wire alloys showed substantially less canal transport, which was attributed to the higher flexibility of the alloys . SeveralTemperature is considered to be one of the crucial factors that influences the mechanical properties of NiTi alloy. It also results in differences in their bending properties ,35. ReseFor a better standardization of the shaped samples, all three instruments compared in the present study had a tip diameter equivalent to a size of 0.25 mm and similar taper in the first mm of the active part . These similar diameters and tapers can explain the similar results obtained in the apical thirds of the root canals, with no significant statistical differences between the shaping capacity of the three compared systems. However, there is a better centering ability of the instruments made of gold alloy, WOG and PTG, in comparison to the blue alloy of RB. As WOG and RB are both reciprocating systems, and PTG is a rotational one, no conclusion can be drawn regarding the superiority of the reciprocation or continuous rotation movement in the apical third.However, the compared instruments have multiple different tapers along their length in accordance with literature data, which explains their cutting characteristics and the final shapes of the root canal ,39. BothIn comparison, the PTG system uses multiple files with various sizes and tapers to cut the final shape of the root canal in continuous rotation movement in a sequence where all instruments need to reach the working length one before another (S1-S2-F1-F2). The canal is first progressively enlarged with shaping instruments with a fixed small taper at the tip (2% for S1 and 4% for S2), but with a progressive increased taper at the end of the active part (up to 11%), which mainly enlarges the coronal and middle thirds of the root canal . Then, FThe shaping capacity of four single file systems with different tapers was compared in a recent study that revealed that more tapered instruments remove more resin compared to less tapered instruments, and that the taper of the instruments is the predetermining factor for the shaping capacity of the tested instruments . MoreoveOne of the most important factors that contributes to a good shaping of the root canal is the ability of the instrument to remain in the center of the root canal space without causing iatrogenic errors . The preThe most statistically significant differences were observed in the middle third of the root canals in comparison to both apical and coronal thirds. RB removed a lower amount of resin from the inner wall of the simulated root canals, when compared to WOG and PTG. This finding is in accordance with literature data which show that more flexible instruments tend to prepare the root canal in a more centered way ,22. WhilIn the coronal third, PTG and WOG had a more centered preparation, which is a similar finding to other studies, which found coronal and middle thirds to be better prepared by WOG . RB remoAs results of the present study, the null hypothesis formulated in the beginning was rejected for the middle and coronal thirds of the root canals, where differences were observed between the shaping characteristics of the three compared systems and confirmed for the apical third of the root canal, where PTG, RB, and WOG acted in a similar manner.Within the limitations of the present study, it was observed that, regarding the amount of resin removed from the interior and exterior walls of the resin blocks, WOG and PTG tend to cut more on the inner wall of the root canals, while RB acts more on the outer wall. Significant differences were recorded in the coronal and medium thirds when comparing RB to PTG and WOG, while in the apical third, all three considered systems tend to prepare in the same manner. No differences were observed between the shaping capacity of WOG and PTG. Neither of the studied instruments had the same centering ability along the entire length of the simulated root canal.Future work on this topic includes investigations of such NiTi instruments  and of t


Ordinary cement is not environmentally friendly, has high cost and lacks superior performance. Many scholars use various admixtures to adjust the properties of cement slurry, but admixtures are usually not environmentally friendly, and it is difficult to ensure that the properties after deployment meet engineering requirements. In this study, a variety of admixtures were obtained using the environmental protection method, and the optimal mixing ratio was analyzed by combining the entropy weight method and the Taguchi grey relational analysis method. The developed cement slurry was compared with conventional slurry from both macroscopic and microscopic aspects. Aiming at the problem that previous scholars lacked the engineering feasibility verification of the developed slurry, this study combined the constitutive equation regression analysis method, discrete element numerical simulation and other methods to study various actual engineering conditions. The results show that the optimal mix ratio of silica fume cement slurry has good permeability characteristics under the conditions of different roughness, grouting pressure and confining pressure. At the same time, under different geological temperatures and different erosive liquid states, the cement slurry stone body shows good properties of reinforcement materials. Grouting, as an important means of strengthening water blocking and disaster control in geotechnical engineering, can effectively improve the structure and mechanical properties of complex strata such as fractured rock mass and fractured zone, and is widely used in tunnel engineering, mining engineering, dam engineering and other underground projects, where various water hazards or unstable rock mass reinforcement are treated ,2,3. Amo2 emissions over the past few decades [Ordinary Portland cement is widely used as the main bonding material for the preparation of concrete, mortar, grouting materials, etc. However, Portland cement manufacturing has become one of the major contributors to CO decades ,9. In th decades ,11,12,133 has the characteristics of high efficiency and low price, and there are many research results for nano-CaCO3 modified cement-based materials. Sato and Beaudoin [3 improves the compressive strength of cement-based materials mainly by refining the crystal form of hydration products and reducing porosity through its crystal nucleation, thereby improving the microstructure.In recent years, many scholars have carried out valuable research on the application of nanomaterials in cement-based materials ,15,16,17Beaudoin  pointed Beaudoin  have shoBeaudoin  showed tMoreover, previous studies did not focus on environmental protection and did not verify the feasibility of the project. In terms of mineral admixture selection, studies by scholars have shown that the production source of silica fume is more environmentally friendly (compared to the production of ash) and the cost is low . Silica This study effectively alleviates the problems of high cost and environmental protection of traditional cement slurry. A variety of technical means are used in combination, and the feasibility of the developed slurry is fully verified by examining the macro and micro perspectives, laboratory and practical applications, numerical simulation and theoretical derivation. Based on the theory of synergy and complementarity, a variety of admixtures for improving cement slurry were obtained from waste on the basis of consulting a large amount of research and development literature on cement-based materials. Using theoretical analysis, laboratory test methods, combined with advanced methods such as SEM (Scanning Electron Microscope) and XRD (X-Ray Diffraction), the research and development of cement-based composite grouting materials was carried out. The basic properties of the slurry and the mechanism of cement hydration were studied. The proportion of cement slurry was optimized by designing an improved Taguchi orthogonal test, and the significant relationship between the content change of the admixture and the performance of grouting material was determined. An environmentally friendly cement slurry with excellent performance was obtained. Through experiments and numerical simulations, the multiple properties of the cement slurry under different engineering conditions were analyzed. Research results indicate that the cement slurry has good reliability and feasibility and can be applied to a wide range of construction projects.3·nH2O  and polycarboxylate superplasticizer (PS).Materials adopted in the research: FIPC, silica fume (SF), fine particle size fly ash (FIPA), mCaCOTo make the cement react sufficiently in the research process and be able to adapt to the smaller cracks in the rock, the P.O42.5# cement was ground into a smaller micron level (2.39~9.51 μm) by a grinder to obtain FIPC. Its main chemical composition and basic physical properties are shown in Combustion waste was obtained from factory waste and ground to micron level (1.02–8.62 μm) to obtain FIPA, which has the properties of aluminosilicate glass . The cheSilica fume with large particle size is obtained from the waste of the silicon refining plant and ground to the micron level (2.18~10.24 μm) to obtain SF. Its chemical composition is shown in 3 by using chemical methods from limerock, etc.;Obtaining CaCO3 is processed into nano-scale powder by a grinder;The acquired CaCO3·nH2O by sol-gel method, hereafter referred to as CH; mCaCO3·nH2O is a nanoscale sol.Obtaining mCaCOCH is obtained by:The use of waste limestone to prepare CH would not only improve the problem of wasteful economic costs in processing large amounts of waste limestone, but also play a positive role in the early hydration and consolidation strength of the slurry.The technical indicators of CH are shown in The PS used in this study is produced by a chemical company in Shanghai. The appearance is white powder, the specific gravity is 1.08, the active ingredient is ≥90% and it has the effect of air entrainment and retardation. A certain number of air bubbles can enhance the fluidity of the cement slurry, but too many air bubbles will adversely affect the mechanical properties of slurry consolidation. Therefore, the air-entraining effect of the water-reducing agent should also be considered when applying the water-reducing agent. The main properties of cement-based slurry studied in this paper are: viscosity (VSI), bleed capacity (BC), fluidity (FL), setting time (ST), compressive strength (CS) and flexural strength (FS) of stone bodies at different ages . The specific test methods for various properties of grouting materials are as follows:Flow characteristics: the VSI of the slurry was measured using an SNB-2 digital rotational viscometer. FL was tested using a truncated cone die and a glass plate.Congealing properties: BC was tested using the traditional graduated cylinder method. The ST test uses a Vicat instrument. In this study, only the initial setting time was used as an example to illustrate the coagulation characteristics.Mechanical properties (FS and CS): Tested by using a flexural testing machine and a compression testing machine, respectively.Microscopic testing (XRD and SEM): Routine experiments were performed using XRD and SEM equipment.A:Water-solid ratio (WSR).B:FIPA content.C:SF content.D:PS content.E:CH content.The experimental test factors are:The experimental factor level table is shown in According to the idea of the Taguchi-grey relational analysis method in Wu et al. , the fivThe slurry performance test was carried out according to Good flow characteristics (VSI and FL) ensure the grouting material’s castability and the best grouting effect. The orthogonal test results of slurry VSI and FL are shown in On-site construction requires the grouting material to have good fluidity. When the fluidity of the slurry is too good, the slurry is lost in large quantities due to insufficient adhesion during the grouting process, resulting in unnecessary waste of resources; when the fluidity of the slurry is insufficient, in the process of flow and diffusion, a larger grouting pressure is required to resist the resistance of the slurry. The effect of time increases the viscosity of the slurry, which makes it difficult for the slurry to pass through small cracks and affects the grouting effect. In addition, the greater the fluidity of the slurry, the more difficult is the phenomenon of segregation and stratification occurs, and good fluidity can ensure the injectability and grouting effect of the grouting material.The sample range (SR) analysis results for the SNRs of the FL and VSI are shown in To more intuitively analyze the influence of the dosage levels of each factor on the FL and VSI of the slurry, the mean value of the SNR of the FL and VSI of the slurry under each influencing factor was drawn, as shown in According to 2− rich and Ca2+ poor gels in the solution form an adhesion layer on the surface of SF particles. After a certain period of time, the gel adhesion layer begins to dissolve and reacts with Ca(OH)2 produced by cement hydration to form C-S-H gel, thereby increasing the VSI of the slurry. With the increase of Factor E, VSI showed a trend of increasing first and then decreasing. On the one hand, due to the filling effect of CH, the interstitial filling water of the cement clinker is replaced, which increases the free water molecules. On the other hand, CH has a large specific surface area and a large contact area with water molecules, which can adsorb a large number of water molecules, thereby increasing the VSI of the slurry, which is the same as the research conclusion of Qiu et al. [The morphology of FIPA is spherical microbeads, its surface is smoother than cement, and its adsorption force to water molecules is small. These morphological characteristics reduce the water demand of the slurry, which leads to an increase in the excess free water content when Factor B increases, and the slurry FL increases accordingly. The larger Factor C is, the larger the VSI of the slurry is, which is due to the rapid dissolution of some small particles after SF is in contact with water. The SiOu et al. .According to the index of grouting material FL, the optimal ratio of each material component is: A4B4C1D4E4. That is, the grouting material has the maximum FL at this ratio. From the perspective of grouting material VSI, according to the principle that the VSI degree of grouting material be as small as possible within a reasonable range, the optimal ratio of each material component is: A4B3C1D4E1.The results of the ST orthogonal test are shown in Analysis of From For the ST, the optimal ratio of each material component is: A1B1C1D1E4, and the grouting material has a shorter ST under this ratio.The BC is an important indicator to characterize the stability of the grouting material. Cement-based grouting material is a solid–liquid two-phase fluid with complex fluid properties. The stability of the grout directly affects the integrity and strength of the broken rock mass after grouting. The stability of the grouting material is usually expressed by BC. The slurry with low BC has good mechanical properties after coagulation, and the lower the BC, the greater the stone rate. Generally, slurries with a BC of less than 5% are considered stable slurries. The results of the BC orthogonal test are shown in The stone body strength of the grouting material is an important index to evaluate its performance after consolidation, which directly affects the grouting treatment effect of the injected rock and soil. General engineering requirements for grouting materials should have the highest possible strength. For water blocking projects, grouting materials are also required to have good early strength and erosion resistance. The results of the orthogonal test of stone body strength and the mean value of SNR are shown in The SR analysis of CS was taken as an example to represent the stone body strength, as shown in Analysis of 2, which is amorphous with high fineness and has strong pozzolanic activity. When the hydration reaction occurs, SF can undergo secondary hydration reaction with the cement hydration product Ca(OH)2 to generate C-S-H gel. At the same time, the content of Ca(OH)2 in the slurry can be reduced, and the hydration reaction can be forwarded to generate a gel and improve the mechanical properties of cement slurry consolidation. However, when the content of SF is too large, since the specific surface area of SF is much larger than that of cement, the water demand for hydration of the slurry is greater than the molecular weight of water contained in the slurry and the hydration reaction is limited, and the materials that do not participate in the reaction become inert components, so the stone body strength has decreased.Stone body strength decreased with increasing FIPA. This is because the low activity of FIPA cannot participate in the early hydration reaction, and the internal incorporation of FIPA will reduce the relative proportion of cement in the slurry. Therefore, FIPA acts as an inert component in the early stage, which leads to the reduction of early strength. However, with the progress of the hydration reaction, the volcanic ash activity of FIPA is stimulated, and the strength of the stone body increases in the later stage, which is consistent with the results in the literature . DiffereIn addition, the mean value of the SNR of CS increased first and then decreased with the increase of CH content. The reason is the filling effect of CH; as a nanoscale material it can be filled in the pores of the particles and the pores of the hydration products, thereby improving the microstructure of the slurry stone body. CH and the surrounding hydration products are bonded to the surface to form C-S-H gel, and with CH as the crystal nucleus, the C-S-H gel is connected into a stronger three-dimensional network structure  and the The influence mechanism of the content level of each factor on the grouting material FS is similar to that of CS, so it is not repeated here.The aforementioned studies have analyzed the SNR effect of each factor level on the slurry performance. During the analysis process, it can be found that the optimal slurry ratio of each performance index is not the same. Therefore, it is impossible to obtain a set of ratios that makes each performance index have better results. Therefore, the performance indicators of the grout were comprehensively analyzed using the improved Taguchi method to obtain the best mix ratio of the new cement-based composite grouting material.Based on the SNR sequence obtained by processing the experimental data using the Taguchi method, the analysis was carried out according to the grey relational analysis steps of the Taguchi method. In this paper, the objective weight of the evaluation index is determined by the entropy method of objective weighting, and the weight coefficient  analysisFrom For convenience, the ordinary cement slurries, the A3 group slurries of the orthogonal test, and the above-obtained optimal ratio (A1B3C3D3E2) slurries are named as S1, S2, and S3, respectively.From According to the VIS test results, the constitutive model  is obtaiR2 = 0.976, indicating that the regression equation is credible. The intercept of the curve on the Y-axis represents the cohesion of slurry (1.463 Pa), which is also consistent with Wu et al.’s [et al.’s  study.To further study the reasons for the difference in performance between the optimal grout and the ordinary grout, and to support the follow-up study of the cement grout, this section involved microscopic analysis (XRD and SEM) for different grouts, and briefly analyzed the theory of reinforcement mechanical properties.The 28 d stone body was taken for XRD testing and the composition of the crystal phase of the stone body was compared and analyzed. 2, CaCO3 and hydrated silicic acid calcium gel (CSH) composition. Compared with S1, the diffraction intensities of Ettringite and C-S-H peaks of S3 were increased and the content increased. This shows that the hydration degree of the cement-based composite grouting material is higher. Since the secondary hydration reaction between FIPA and silica fume requires the consumption of Ca(OH)2, the diffraction intensity of the Ca(OH)2 peak of the S3 group is lower than that of the S1 group, and the Ca(OH)2 content less.From 3 peak diffraction intensity of the S3 group is higher. This is because the CH in the cement-based composite grouting material does not participate in the hydration reaction in the system, but exists in the system by filling and nucleation. There are also CaCO3 products generated by the carbonization of calcium hydroxide during the curing and sample preparation process [In addition, it can also be seen that the CaCO process , so the Adopting SEM technology, the S1 and S3 stone bodies (28 d) were processed and observed. The hydration mechanism of the slurry system was further analyzed by comparing the microscopic morphology of the stone bodies of the S3 and S1 grouting materials. Combined with the previous section, the performance of the stone body was evaluated. 2 crystals of cement hydration products in the form of hexagonal plates are stacked on each other. Since there are only Portland cement particles in the S1, its hydration products are single, and Ca(OH)2 and hydrated calcium silicate gel (C-S-H) are the main hydration phases. The C-S-H gel is the source of the cementitious force of the slurry. Its morphology is greatly affected by clinker activity, solution supersaturation and hydration age, and is generally fibrous, reticulated, granular and flake-like. These hydration products interweave and grow to form a spatial structure, and at the same time leave many pores, resulting in a loose structure of the stone body.In 2 crystals are rare. It can be seen that the gel is wrapped in spherical pulverized coal around the ash particles, and the overall structure is denser and firmer. This is due to the addition of supplementary cementitious materials and optimized materials with smaller particle size than ordinary Portland cement in the S3 system. These granular materials have different degrees of influence on the system through their own pozzolanic effect, filling effect, rolling ball effect and crystal nucleation effect. Among them, the supplementary cementing materials FIPA and SF mainly undergo a secondary hydration reaction with the cement hydration product Ca(OH)2 to generate calcium silicate hydrate, calcium aluminate hydrate and other products, that is, the pozzolan effect. Therefore, the plate-like hydration product Ca(OH)2 crystals are less seen in As can be seen from Comparing S1 and S3, the developed cement-based composite grouting material S3 has more sufficient hydration reaction, more hydration and gelling products are generated, and particles with smaller particle size fill the space formed by the intertwining and overlapping of hydration products. Therefore, the structure of the stone body is denser, and therefore it has better stone body performance.The reinforcement mechanism of grouting on fractured rock mass is mainly reflected in two aspects: physical action and chemical cementation. After grouting the fractured rock mass, the original voids in the rock mass are filled with the grout. After the grout solidifies, it bears the force between the rock masses, so that the stress state of the rock mass is redistributed to form a stable whole.Yang and Zhang  proposedE is the elastic modulus of the grouting solid. E0 is the elastic modulus of the intact rock. D is the void ratio matrix. rE is the elastic modulus of the grouting material stone body. η is the filling coefficient matrix. S is the reinforcement factor, which is related to the crack distribution, grouting material and filling degree.Among them, S value is larger. The stress distribution in the rock body after grouting reinforcement is uniform, which effectively weakens to avoid stress concentration phenomenon, and the integrity of fractured rock mass can be well improved.From Equation (3), the elastic modulus of the fractured rock mass after reinforcement is related to the damage degree of the fractured rock mass and the reinforcement factor, which is inversely proportional to the former and proportional to the latter. Between 0 and 1, generally speaking, the grouting material has high consolidation strength, good stability and reasonable grouting process, and the The failure of grouting-reinforced jointed rock mass mostly occurs along the magma-rock cementation surface, and the jointed rock wall basically remains intact with the failure of local grout cement. To further study the force mechanism of the failure of the grouting-reinforced jointed rock mass, a schematic diagram of the force  was drawh and base angle i, and the bonding forces of the slurry–rock cement interface are f1 and f2, respectively, according to the force balance condition:Assuming that the protrusion of the slurry cement in the figure is an isosceles triangle with height According to the Mohr–Coulomb strength criterion, the shear stress and the normal stress have a linear relationship when the rock mass fails. The set of stress at the failure point is called the Mohr strength envelope, and the shear strength can be expressed as:After grouting, the cohesion and internal friction angle of the jointed rock mass change. The expression of shear strength after grouting can be transformed into the following formula from Equation (5):Combining Equations (4) and (6), the shear strength of the jointed rock mass after grouting can be obtained as:However, in practice, the bonding force between the front shear surface and the back shear surface of the protrusions on the joint surface does not play the same role, and the superposition analysis cannot be performed simply. The front shear plane is mainly due to the friction force, while the back shear plane is mainly due to the cementation force. From the safety point of view, when calculating the shear strength, only the friction force is considered in the front shear plane, and only the cementation force is considered in the back shear plane. Equation (7) can be further transformed into:From Equation (8) it is seen that the roughness of the joint surface and the interfacial bonding force can improve the shear strength to varying degrees. From the point of view of grouting, the magnitude of the bond force of the slurry–rock interface is related to the quality of the cementation of the grouting material. Generally, the higher the degree of hydration reaction of grouting materials, the greater the interface bonding force. It is very important to choose grouting materials reasonably in practical engineering.σg, MPa): 2 MPa, 7 MPa and 12 MPa; (2) Confining pressure : 2.5 MPa, 7.5 MPa and 15 MPa; (3) Joint roughness coefficient (JRC): 2.5 and 6.5.To verify the feasibility of the cement slurry in this study under a variety of different engineering conditions, similar materials developed by researchers  were adoJRCs (the modeling method is similar to the author’s previous research [Q (10−6 m3/s).Through DEM (discrete element method), combined with UDEC software, the obtained parameters of rock-like materials  are usedresearch , and dueQ increases gradually with the increase of σg, but the increase rate of Q slows down with the increase of σc. This is mainly because the increase of confining pressure makes the seepage channel narrow, which makes the cement grout less. There is a negative correlation between Q and σc, but the decrease rate of Q slows down with the increase of σg. This is mainly due to the increase of σg, the seepage channel has a certain trend of opening, so that the cement grout seeping through increased. By comparing JRCs, Q value gradually decreases. This indicates that the more complex the roughness of the fracture is, the more influence it has on the seepage of slurry. This is consistent with previous studies [The analysis of  studies , indicatσc = 7.5 MPa, the σg = 7 MPa, and JRC = 2.5. Due to many variables, the fixed normal pressure in the shear experiment was nσ = 6 MPa. The experimental results are shown in The samples after grouting experiments were subjected to standard curing. Then the shear strength experiments at different temperatures were carried out. The temperature variables were: 20 °C, 260 °C, 460 °C and 760 °C. The time variables were 0 h, 1 h, 2 h, 3 h. Fixed From σc = 7.5 MPa, the σg = 7 MPa, and JRC = 2.5. In the shearing experiment, the nσ were set to 2 MPa, 4 MPa, 6 MPa and 8 MPa, respectively. The experimental results are shown in Different acid-base groundwater erosion studies were carried out on the samples before and after grouting. The solutions with pH of 3.5, 5 and 7 were selected for experiment. The samples were soaked in different solutions for 4 d and 7 d, respectively, and then the shear strength test was carried out. Fixed Comparing The comprehensive application of the entropy weight method and the Taguchi grey relational orthogonal analysis method obtains the optimum ratio of slurry (S3): WSR (0.6), FIPA (20%), SF (10%), PS (0.15%), CH (1%). Compared with pure cement grouting materials, the flow properties, coagulation properties and stone body strength of cement-based composite grouting materials are improved.Compared with the stone body of S1, the overall structure of S3 is more compact and firmer, and the macroscopic mechanical properties are better.The significant relationship of each factor affecting the overall performance of the grouting material is: WSR > PS > FIPA > SF > CH.The developed cement grout can be widely used for grouting reinforcement of rock mass in fissures in various types of engineering construction such as tunnel, subway and mine roadway.In this study, the cement slurry was developed using silica fume, which effectively alleviated the environmental problems, and the new slurry was low in cost and superior in performance. The main research conclusions are as follows:


Background and Objectives: Proximal humerus fractures are the second most frequent site of avascular necrosis (AVN), occurring in up to 16% of cases. The Hertel criteria have been used as a reference for the prediction of humerus head ischemia. However, these are based solely on the use of radiographs, which can make interpretation extremely difficult due to several reasons, such as the overlapping fragments, severity of the injury, and noncompliant acute pain patients. The objectives of the study were to evaluate the role of computed tomography (CT) in the interpretation of the Hertel criteria and to evaluate the intra- and interobserver agreement of orthopedic surgeons, comparing their area of expertise. Materials and Methods: The radiographs and CT scans of 20 skeletally mature patients who had fractures of the proximal humerus were converted to jpeg and mov, respectively. All images were evaluated by eight orthopedic surgeons (four trauma surgeons and four shoulder surgeons) in two different occasions. The intra- and interobserver agreement was assessed by using the Kappa coefficient. The level of significance was 5%. Results: There was a weak-to-moderate intraobserver agreement (κ < 0.59) for all examiners. Only the medial metaphyseal hinge greater than 2 mm was identified by 87.5% of evaluators both in the radiographic and CT examinations in the two rounds of the study (p < 0.05). There was no significant interobserver agreement (κ < 0.19), as it occurred only in some moments of the second round of evaluation. Conclusions: The prognostic criteria for humeral head ischemia evaluated in this study showed weak intra- and interobserver agreement in both the radiographic and tomographic evaluation. CT did not help surgeons in the primary interpretation of Hertel prognostic criteria used in this study when compared to the radiographic examination. Fractures of the proximal humerus represent 4 to 5% of all fractures, being the third most common in the human body . ApproxiRegardless of the type of treatment, proximal humerus fractures are the second most frequent site of AVN, occurring in up to 16% of cases ,8. OtherShortly after its publication, other studies from the same group observed high intra- and interobserver reliability of the Hertel classification, providing a more adequate description of proximal humerus fractures compared to the systems described by the Neer system and the AO group (Arbeitsgmenischaft für Osteosynthesefragen) ,10. HoweWe hypothesized that the adoption of computed tomography (CT) images, including three-dimensional reconstruction (3D CT), to radiographs of the proximal humerus in patients with fractures increases the reproducibility of the Hertel criteria, thus improving intra- and interobserver agreement among orthopedic surgeons. The objective of the study was to evaluate the role of CT in the interpretation of the Hertel criteria, using the radiographic evaluation of the same cases as a standard to identify the criteria described by these authors as prognostics for AVN of the humeral head.Radiographs and CT scans of 20 skeletally mature patients who had fractures of the proximal humerus treated at the Institution between January and December 2020 were selected. Patients were chosen at random. We included patients older than 18 years, with a confirmed diagnosis of proximal humerus fractures, and who signed the Informed Consent form. We excluded patients with missing demographic data; inaccurate imaging exams; and presenting a pathological fracture or previous fracture history, surgical history, congenital deformities, or degenerative changes at the same region.Patients’ privacy and security during the acquisition, storage, and transmission of their medical information were protected. The identity of the patients was not revealed. All patients were surgically treated and had standard preoperative radiographic and CT studies. The age ranged from 52 to 70 years, with a mean of 59.4 (SD ± 6.21882) years. Fifteen (75%) patients were female, and the right side was affected in 12 (60%) cases. The main injury mechanism was a fall to the ground in 17 (85.0%) cases . The imaFractures were classified radiographically, according to the Neer system ,14. In aThe Standards for Reporting of Diagnostic Accuracy (STARD) questionnaire was used to determine surgeons’ perception of their accuracy in identifying each of the three criteria ,16. The The radiographic images of the 20 cases were extracted from the DICOM  disk, which was developed by the American College of Radiology (ACR) and the National Electrical Manufacturers Association ; converted to jpeg (Joint Photographic Experts Group) with 1000 × 1000 pixels and 300 DPI resolution; and stored case by case in individual folders, from 01 to 20 . In the The images were sent by email to eight board-certified orthopedic surgeons with more than 10 years of experience in the treatment of proximal humerus fractures (Observers 1–8), in 20 individual folders, along with instructions on how to respond . All posn = 20) and multiplied by 100 (% of concordant cases). The interobserver agreement of the eight surgeons and the STANDARD was provided by four percentages of concordant cases . The significance level adopted was 5%. Statistical analysis was performed by using SPSS version 26 software .The inferential analysis consisted of the Kappa coefficient (κ) to assess intraobserver agreement in the criteria  according to radiographic and tomographic images . Landis p < 0.05), except by the evaluator SHOULDER 4. Both Criteria A and C were identified significantly less frequently in the two rounds of the study, with no difference between radiographic and tomographic evaluations (p > 0.05). The SHOULDER 4 evaluator showed no intraobserver agreement for any of the criteria evaluated in R1 and R2.There was a weak-to-moderate intraobserver agreement for all examiners. For analytical consistency, the percentage of agreement was judged useful only when the Kappa coefficient was significant . Only thThe percentage of “inconclusive” concordant cases by CT in R1 and R2 was not processed due to improper operation (division by zero), as there were no “inconclusive” cases by CT observed according to the STANDARD. There was practically no significant agreement with the STANDARD, as it occurred only in some moments of R2. Interobserver agreement was seen as weak in both R1 and R2. Despite this, it was observed that there is strong agreement between the imaging methods used in the study. There was significant agreement at a level of 5% for the criteria between the radiographic and tomographic exams of moderate-to-strong degree for almost all evaluators, regardless of the moment (R1 and R2). However, it was observed that the radiographic evaluation presented a higher number of the “inconclusive” category than the CT, regardless of the criterion  and the moment (R1 and R2), although there was no statistical significance. Overall, it was observed that intra- and interobserver agreement was weak in both R1 and R2. Analyzing individually each of the prognostic criteria used in this study, it was observed that only the presence of a medial metaphyseal hinge greater than 2 mm (Criterion B) was identified by all evaluators both in the radiographic examination and in the CT in the two rounds of the study as statistically significant, meaning that there is no evidence supporting our hypothesis. There was practically no significant agreement with the STANDARD, occurring only in some moments of R2. Nevertheless, there was a strong agreement between the imaging methods used in the study for almost all the evaluators, regardless of the moment (R1 and R2), with the CT evaluation showing a lower number of the “inconclusive” responses than the radiography evaluation, regardless of the criterion  and moment (R1 and R2).It is known that posttraumatic osteonecrosis of the proximal humerus is the most common complication after fractures in this anatomic region, occurring in up to 16% of patients, and represents a problem for both the patient and the surgeon ,20. In tThe guidelines recommend that radiographic screening should be the first imaging investigation in the emergency department . HoweverIt is known that there is a strong correlation between AVN of the humeral head and medial metaphyseal hinge ,20,26. HThe prognostic ability of the other two criteria evaluated in this study  is even more controversial and, probably, is mainly due to the inability to fully assess the proximal humerus morphology in a fractured segment with radiographs alone, as pointed out before. In this sense, the use of CT gains importance, as it allows the surgeon and the radiologist to perform the reconstruction of the proximal humerus in different planes, with slices of small sizes and in a three-dimensional perspective; however, in the light of current knowledge, there is no evidence of that 3D CT is superior to 2D CT . CampochThis study has some limitations. Although not evaluated in the study, there are other factors that may represent risk factors for AVN of the humeral head—such as the surgical approach and the quality of reduction—and generate confusion in its epidemiological estimate, which is illustrated by the widely varying rates of posttraumatic osteonecrosis between studies . In addiSome strengths of the study deserve to be highlighted. The main one was to show that none of Hertel prognostic criteria evaluated in this study present interobserver agreement, regardless of whether the assessment is performed by using radiographs, CT, or both. Other authors have already observed the same, including employing more modern imaging methods than those used in this study ,25,39,41The prognostic criteria for humeral head ischemia evaluated in this study showed weak intra- and interobserver agreement in both radiographic and tomographic evaluation. CT did not help surgeons in the primary interpretation of Hertel prognostic criteria used in this study when compared to radiographic examination.


In this paper, eight different contoured cushions (S1-S8) in two categories (flat and wrapped) were designed to study the influence of different contoured cushions on passenger comfort in high-speed trains. Meanwhile, subjective data investigation by the comfort Likert Scale questionnaire and objective physical variables collection by the body-cushion contact pressure test was carried out. In addition, one-way ANOVA and Pearson correlation analysis were performed on the subjective survey and objective test data. The results show that the cushion contours had a significant effect on the subjective evaluation of the overall comfort of the participants, in which the overall comfort below the waist of the separated wrapped cushion S8 has the highest subjective comfort score. The overall comfort of the flat-front bulge type cushion S4 and the local comfort of the thighs and the root of the thighs were rated higher than other flat types. Under the flat cushion, the effect of stature characteristics (mainly weight and hip-width) on the overall comfort subjective ratings was insignificant, and the effect on the contact pressure distribution variables was significant, but the contact pressure distribution variables were not correlated with the comfort ratings. Under the wrapped cushion, the effect of stature characteristics on the overall comfort subjective ratings and contact pressure distribution variables was significant. There were positive and negative correlations between the average peak contact pressure and average contact pressure and comfort ratings, respectively. By 2020, the operating mileage of high-speed trains in China has reached 35,000 km. High-speed trains have become synonymous with technology, efficiency, safety, and comfort, and they are not only a means of transportation for passengers but also a culture of fast and comfortable travel. People’s demand for high-speed trains has gone beyond functional pragmatism, and more attention has been focused on the comfort and humanistic connotation of the riding environment, such as the CRH380 high-speed train interior environment shown and seats in At present, many researchers have carried out studies on the influence of seat shape, material, height, depth, and other factors on ride comfort, involving aircraft –3, cars The objective evaluation covers several aspects such as sitting behavior, surface electromyography , and bodPeng et al.  performeIn summary, the cushion is a crucial factor affecting the comfort of high-speed train seats. Therefore, the correlation analysis between cushion contour and comfort was carried out by designing cushions with different contour types and combining subjective and objective methods. Among them, for subjective evaluation, the Likert Scale questionnaire was used to fully collect the overall comfort and local comfort rating data below the waist of the participants. For objective evaluation, the effect of different surface morphology and body shape characteristics on body pressure distribution parameters was tested by a body pressure test system. Based on the one-way ANOVA and Pearson correlation analysis methods, we determined the significant effects of different cushion contours and body types on riding comfort and explored the correlation between the subjective evaluation of comfort and the objective evaluation of pressure distribution parameters. The study can provide a reference for the design of seat cushion surfaces for high-speed trains.For the seats in the general carriage of high-speed trains, the comfort test experiments of different contoured cushions were carried out in the rail transportation simulation laboratory of Southwest Jiaotong University. To ensure the validity of the test data, the seat dimensions are consistent with the existing high-speed trains as far as possible, except for the different geometry of the seat cushion, and the basic dimensions and sitting posture requirements are shown in This study comprised 97 human participants. All participants were informed of the aims, the study procedure, and the financial compensation for participation and were asked to follow the rules of the study. The study was approved by the Institution Review Board of Southwest Jiaotong University, and all the procedures followed the regulations for human subject research. Informed consent was obtained from all participants, and the consent was written and recorded in documents. The experimental protocol was divided into program 1 and program 2. Program 1 was a large sample, mainly through the scale to investigate the overall body comfort and local comfort scores below the waist under different cushions. Because of a large amount of pressure distribution data collection, program 1 only conducted a subjective evaluation of the large sample. Program 2, based on program 1, for three different body sizes  of the participants, conducted subjective scale data collection and objective physical index collection for the body-cushion contact pressure test, which is listed in To ensure the reliability of the subjective evaluation of cushion comfort, 97 participants were recruited, including 46 males and 51 females, and the participants were mainly university students, graduate students, and teachers. The sample frequencies of height and weight of the participants were statistically analyzed, as shown in It was found in the randomized interviews during the survey in Program 1 that the comfort of different cushions might be influenced by the participants’ weight and sitting hip-width. Therefore, three typical stature types of participants were designed in Program 2, and participants with large, medium and small stature were identified according to the 5th, 50th, and 95th percentiles of the statistical weight sample, respectively, and their basic information is listed in The geometric contour design of the cushion mainly included two types of flat (S1-S4) and wrapped (S5-S8), as shown in The material of the cushion is the polyurethane foam used in high-speed train seats. A piece of polyurethane foam size 1.2×0.6m, thickness 0.1m, hardness 45 degrees, can do two cushions. According to the design parameters, the large pieces of polyurethane foam were cut, sanded, trimmed, and tensed with gauze in sequence, as shown in It is difficult for non-specialist participants to understand the contour characteristics of each surface of the seat. The scale design of this experiment is no longer based on the satisfaction evaluation of a feature or parameter of the seat, but is converted into the comfort rating of the key parts of the human body, and the human perception parts are shown in The human body-cushion contact surface pressure distribution test and the sensor for the United States Tekscan production pressure distribution measurement system are shown in The experiment was conducted by asking participants to be in a state of sensory relaxation while testing the pressure distribution and asking them to maintain a posture on the cushion S1 as shown in One-way ANOVA was conducted using SPASS (version 24) software on the cushion subjective comfort scores and the results of the pressure distribution index test. Among them, the factor in Program 1 was the cushion, with 8 levels, S1-S8, and the observations were the ratings of 97 participants, respectively; the factor in Program 2 was stature, with 3 levels, large stature, medium stature, and small stature, and the observations were the subjective ratings of 6 typical participants and the test data of pressure distribution index, respectively. In the one-way ANOVA, the significance level p was taken as 0.05, and the results were considered significantly different when the calculated p<0.05 was obtained.According to Program 1, 97 participants performed Likert Scale scores for overall comfort after the experience with 8 cushions, and the statistical results are shown in According to Program 1, 97 participants performed body local comfort scores after experiencing eight cushions, and after one-way ANOVA on the data, the results are listed in Subjective evaluation on flat cushions(S1-S4). The average comfort scores of the flat cushion for the three typical stature are shown in Subjective evaluation on Wrapped cushions(S5-S7). The average comfort ratings of the wrapped cushion for the three typical stature of the participants are shown in The comparison of the subjective ratings of flat and wrapped cushions shows that flat cushions are more suitable for wide and obese large-statured passengers than wrapped cushions; wrapped cushions are more suitable for medium and thin-statured passengers than flat cushions.Objective evaluation on flat cushions(S1-S4). The average statistics of the three indexes of average contact area, average contact pressure, and average peak contact pressure were measured by the Tekscan pressure distribution measurement system for participants of different stature, as shown in Each figure in Objective evaluation on Wrapped cushions(S5-S7). For the wrapped cushion, the average statistics of the three indexes of average contact area, average contact pressure, and average peak contact pressure were measured for participants of different stature, as shown in Objective evaluation comparison analysis on flat and wrapped cushions. Average contact area comparison. The average contact areas of large and medium stature under the flat cushion were 1444 cm2 and 1283 cm2, which were smaller than the average contact areas of 1511 cm2 and 1361 cm2 under the wrapped cushion, while the average contact areas of small stature were not much different, 1088 cm2 and 1037 cm2, as shown in Average contact pressure comparison. The average contact pressures of 5.2 kPa, 4.9 kPa, and 4.1 kPa for large, medium, and small stature under flat cushion are higher than the average contact pressures of 5.0 kPa, 4.5 kPa, and 3.9 kPa for large, medium, and small stature under the wrapped cushion, due to the increase in average contact area resulting in lower average contact pressure.Average peak contact pressure comparison. The average peak contact pressure of 14.5 kPa for the large stature under the flat cushion was significantly lower than the average peak contact pressure of 17.1 kPa for the large stature under the wrapped cushion, and the peak contact pressure of the small and medium stature did not change much, indicating that the wrapped cushion produced a significant squeezing sensation for the large stature participants.Although the cushion S8 belongs to the wrapped type, due to the central separation design, and S5-S7 cushion is different. Cushion S8 under even the large stature passenger sitting position, the two inner thigh parts are not easy to squeeze each other, with the effect of separation wrapped. Therefore. Cushion S8 has higher overall comfort ratings of 6.0, 7.0, and 5.5 for large, medium, and small stature, respectively, and its average value is also higher than that of S5-S7 see , which iPearson correlation coefficients of the subjective ratings and pressure indexes were carried out for two types of cushions, the flat type (S1-S4) and the wrapped type (except cushion S8 because of its specificity), and the results are listed in Recent literature shows that interface contact pressure is useful for investigating discomfort during seating , 27–29. Program 1 surveyed overall and local body comfort scales, and from the one-way ANOVA, it was found that the cushion S8 has the highest subjective comfort score, followed by the cushion S4, and the cushion S1 has the lowest score. Among them, the difference between S1 and S4 is in the front-end design of the seat cushion, which is the front-end downward and upper drum types, respectively, and the comfort score of S4 is significantly higher than that of S1 (p<0.05). However, the S1 is the more popular cushion type in office seating . For offThe purpose of the design of program 2 is to test whether the comfort score in program 1 is related to stature, on the other hand, and to examine whether there is a direct link between the objective index and the subjective score of the two types of cushions under different statures. Participants with different statures preferred different sizes of seats; relatively, taller participants reported less discomfort in larger seats than in smaller seats, and vice-versa , 14. CarBased on the correlation analyses of the human body-cushion contact pressure distribution, the pressure variables were correlated with overall region discomfort ratings . Romano One-way ANOVA and Pearson’s correlation analysis of the survey and measurement data were conducted for eight different types of high-speed train passenger cushions with different surface contours, taking into account the body form characteristics of the participants, and using a combination of subjective evaluation by the comfort Likert Scale questionnaire and objective evaluation by the body-cushion contact pressure test, to draw the following conclusions:The cushion contours had a significant effect on the subjective evaluation of the overall comfort of the participants. Among them, the cushion S8 has the highest subjective comfort score, followed by the cushion S4, and the cushion S1 has the lowest score. The separated wrapped cushion S8 increased the contact area and lowered the average contact pressure, which could improve the comfort of the hip, thigh, thigh root, calf, and foot. The front-bulge type S4 could improve the comfort of the thigh and thigh root. However, the comfort ratings of the other cushions were all stature dependent, i.e., for large stature participants, flat cushions (S1~S3) were superior to wrapped cushions (S5~S7), but the results were reversed for medium and small stature.Under the flat cushion, the effect of stature characteristics (mainly weight and hip-width) on overall comfort subjective scores was not significant, and the effect on body pressure distribution parameters was significant, with the average contact pressure of small stature significantly lower than that of large and medium stature participants, and the average peak contact pressure of large stature participants, significantly lower than that of medium and small stature participants; under the wrapped cushion, the effect of stature characteristics on overall comfort subjective scores and body pressure distribution parameters were significant, with the average contact pressure of large, medium and small stature participants significantly lower in turn, and the average peak contact pressure of large stature participants significantly lower than that of medium stature participants.Pearson correlation analysis showed that the average peak contact pressure and average contact pressure did not correlate with the comfort score for flat cushions, but for wrapped cushions, the average peak contact pressure and average contact pressure correlated significantly with the comfort score. There was a positive correlation between the average peak contact pressure and comfort score; there was a negative correlation between the average contact pressure and comfort score.In future research work, the effect of the superposition effect of long-term riding and micro-vibration of high-speed trains on passenger body fatigue will be considered, and the effect of seat variables such as seat backrest and footrest on riding comfort will also be increased, to improve the seat design parameters for comfortable riding on high-speed trains.S1 File(DOCX)Click here for additional data file.


Based on the theory of magnetoacoustic coupled dynamics, the purpose of this paper is to evaluate the dynamic stress concentration near an elliptical opening in exponential-gradient piezomagnetic materials under the action of antiplane shear waves. By the wave function expansion, the solutions for the acoustic wave fields and magnetic fields can be obtained. Stress analysis is performed by the complex function method and the conformal mapping method, which are used to solve the boundary conditions problem, and is used to express the dynamic stress concentration coefficient (DSCC) theoretically. As cases, numerical results of DSCCs are plotted and discussed with different incident wave numbers and material parameters by numerical simulation. Compared with circular openings, elliptical openings are widely used in material processing techniques and are more difficult to solve. Numerical results show that the dynamic stress concentration coefficient at the elliptical opening is strongly dependent on various parameters, which indicates that the elliptical opening is more likely to cause crack and damage to exponential-gradient piezomagnetic materials. Functional-gradient piezomagnetic materials, as sophisticated materials in the field of high technology, can adapt to changes in the environment, achieve the mutual transformation of magnetic and mechanical energy, and have unique features of combining sensing, execution, and control. These materials are critical to electronics, radar, microdisplacement control, and aeronautical technologies in the future . FunctioIn recent years, in order to study the structural strength and stability of materials, many scholars have carried out a lot of experimental research and theoretical analysis on the propagation of coupled elastic waves in functional materials, and provided theoretical results at the same time ,6,7,8,9.2O4/BaTiO3 [3/CoFe2O4 [2O4 [3/PZT-4 /CoFe2O4 [2O4 [Research on functional composite materials is also attracting more and more attention. Shin et al.  consider4/BaTiO3 , PZT-5H 4/BaTiO3 , LiNbO3//CoFe2O4 , PZT-5H/2O4 [2O4 , BaTiO3//CoFe2O4 , and CoF2O4 [2O4 .According to the reviewed literature, there is no suitable method regarding the dynamic antiplane elliptical opening problem of exponential-gradient piezomagnetic materials. Based on the theory of magnetoacoustic coupled dynamics ,17, the A cylindrical coordinate system is established in an infinite exponential-gradient piezomagnetic material. The center of the ellipse is the origin, as shown in z-direction, and The antiplane shear wave propagates along the polar axis. The governing equations expressed by the acoustic field and magnetic potential, in the absence of body forces, can be written as:The constitutive equations of the exponential-gradient piezomagnetic materials can be written as :(2)τrz=cConsidering the general situation, the solution of the steady-state wave can be written as:It is assumed that all the material properties of the exponential-gradient piezomagnetic materials have the same exponential function distribution along the polar axis, and the material properties are given as :(5)c44=cSubstituting Equation (2) into Equation (1), the expressions are given as:To simplify the calculation by introducing a new function The steady-state solution to this problem is studied. Let We can write the conformational solution of Equation (9) as:Substituting Equation (10) into Equation (9) yields the standard Helmholtz equation:Denote Based on the complex function theory, the complex variable can be defined as ollowing . We use ollowing :(13)w and 8) can be written as [ can be wTaking the incident field and scattered field together, the total field of acoustic in the exponential-gradient piezomagnetic materials is expressed as:The total magnetic potential is expressed as:Without loss of generality, it should be noted that there is only a magnetic field in the opening, which can be expressed as:Considering the case of a noncircular opening with a smooth boundary, the method of conformal mapping is used, and the complex variables can be defined as taken as :(20)z=Ω, (18), and (19) into Equation (22), by magnetoacoustic coupled theory, a definite infinite system of linear algebraic equations can be obtained :(23)∑n=−Multiply both sides of Equation (23) by Using Equation (25), the mode coefficients In the complex plane, Equation (2) can be rewritten as:Substituting Equations 17) and (18) into Equation (26), we can obtain: and (18)DSCC, which is the ratio of the circumferential shear stress in the opening to the stress amplitude [According to the definition of mplitude :(29)DSCCTherefore, from Equation (29), we can obtain that the DSCC around the elliptical opening in the exponential-gradient piezomagnetic materials is expressed as:2O3 as the example of the exponential-gradient piezomagnetic materials. The related material properties are:Analysis of the above expressions reveals Equation (30) is a convergent infinite-series equation; when In the numerical results, the variables are dimensionless. The dimensionless incident wave numbers It can be obtained from the data in Taking Taking the discussion further, it can be observed that the DSCC distribution in the opening in With the frequency of the incident wave increasing, as shown in As seen in According to the above discussion, the DSCC has a great correlation with wave number The purpose of this paper is to research the response of stress concentrations to incident wave numbers and material parameters in exponential-gradient piezomagnetic materials. The expression for the considered antiplane shear wave has been obtained in a complex function. The material properties have an exponential variation, and the relative eccentricity is variable.To deal with the complexity of elliptical openings, conformal mapping is used to map the ellipse to the unit circle for the theoretical calculation. The displacement and stress components are represented by the superposition of wave functions, which are the Bessel and Hankel functions. The modal coefficients can be calculated by the boundary conditions at the opening and a nonlinear system of equations. One of the highlights of this paper is that the problem is transformed from the real number field to the complex number field by the complex function method, which greatly simplifies the complexity of the problem. In addition, the nonlinear system of equations is transformed into the solvable linear system of equations by orthogonalization. This strategy provides a solution to similar challenges.The relative eccentricity is significant to the DSCC among the material parameters. It is important to reduce relative eccentricity when designing elliptical openings in the exponential-gradient piezomagnetic materials.With other parameters unchanged, the dynamic stress concentration coefficient increases with the increase in relative eccentricity. We can regard that as the relative eccentricity increases, the material stiffness decreases.As the incident wave number The material parameter More details can be obtained from numerical calculations:


The welding experiments and numerical simulation analysis of dissimilar magnesium alloy AZ61-AM60 were carried out by TIG and A-TIG methods. The mathematical model of welding pool under three-dimensional transient moving heat source has been established, and the temperature field has been numerically simulated. The influence of welding process parameters on the surface forming quality of welded joints has been discussed. The simulation results show that temperature field distribution of dissimilar magnesium alloy AZ61-AM60 during the TIG welding process presents a certain asymmetry and the shape distribution of the melting field on both sides of the molten pool is asymmetrical. When A-TIG welding was coated with activating flux, the surface of the molten pool is ingot-shaped. These simulation results are verified through experiment investigation. The consistency between the experimental results and the simulation results reveals the variation law of temperature field and molten pool shape in the welding process, which provides an effective guidance for the optimization of welding process parameters of dissimilar magnesium alloys. With the expanding and deepening of the lightweight structural materials application field, magnesium alloys have attracted tremendous interest due to its low density and high specific strength ,2. HowevTungsten inert gas shielded welding (TIG) has become one of the most effectively used welding methods for bonding magnesium alloys, which can achieve concentrated heating, small deformation of welding parts, high arc stability, excellent weld formation, and high mechanical strength of welded joints ,10,11. SAlthough the TIG and A-TIG methods have become the common methods in recent magnesium alloy welding, few reports have been reported on their application in the welding of dissimilar magnesium alloys. Moreover, the optimizing and improving TIG welding process of dissimilar magnesium alloys by numerical simulation method is very rare. Numerical simulation is a powerful tool to analyze quantitatively the complicated multi-physical phenomena in welding dissimilar magnesium alloys ,16,17,18In order to reveal the influencing factors of the welding joints quality and improve the structural reliability of dissimilar magnesium alloys, the welding experiments and numerical simulation analysis of dissimilar magnesium alloy AZ61-AM60 are carried out by TIG and A-TIG methods in this paper. A mathematical model of welding pool under three-dimensional transient moving heat source has been established, and the temperature field has been numerically simulated. The influence of welding process parameters on the surface forming quality of welded joints has been discussed.The welding materials used in this paper are dissimilar materials. The welding base metal is magnesium alloy AZ61-AM60, and the material size is 80 mm × 40 mm × 3 mm. The schematic diagram of the sample is shown in 2 was used as the active agent. An adequate amount of TiO2 was dissolved in anhydrous ethanol and stirred evenly, and the active agent was coated on both sides of the weld seam with a brush. The schematic diagram of coating is shown in 2. The surface coating density was calculated according to Equation (1), and the coating amounts were set as 5, 10, 15, and 20 mg/cm2, respectively:m1 is the mass of the sample after coating, m0 is the mass of the sample before coating, and S is the coating area of the sample.TiOL, U, I, and v represent the welding line energy, welding voltage, welding current and welding speed, respectively; η is welding efficiency and set to 0.80 in this experiment.The experiment used the AC/DC argon arc welding machine  and adopted single-sided welding and double-sided forming as the welding process. In order to reduce the deformation of the welding, a fixture was used to fix the two horizontal plates before welding, as shown in Based on the tested parameters and comparing the macroscopic morphology of the welding seam, it is found that the welding current will evidently affect the welding formation during TIG welding of dissimilar magnesium alloys AZ61 and AM60. Therefore, selecting an appropriate welding current can obtain a good welding formation. When the welding current is set to 115 A, the appearance quality of the welding formation is the best. The above results can provide an experimental basis for setting the value of welding current in the subsequent numerical simulation.2 remains on different parts of the welding seam. There are bits of black spot slag on the welding surface, which is the most obvious at the welding current of 115 A. There are no obvious surface defects such as pores and cracks. As the welding current increases, the heat input and the width of the welding seam increase.The microstructure of AZ61-AM60 alloy TIG weld under the different welding current is shown in 17Al12 compounds are precipitated during the solidification of the molten pool, resulting in higher hardness on the AM60 side. While Mg17Al12 and MgZn compounds coexist in AZ61, and the composition of Mg17Al12 is relatively small, its contribution to hardness is therefore lower.The tensile strength curves of TIG and A-TIG welded joints under different welding currents are given in There are many factors influencing TIG welding process, such as heat transfer, radiation, convection, and phase transformation. Before simulation, the following assumption about the TIG welding process is made:(1) Assuming that the liquid metal in the molten pool is an incompressible Newtonian fluid that behaves as the laminar flow;(2) Assuming that the upper surface of the molten pool is flat, which can simplify the calculation process and ensure that the calculation results are not distorted;(3) For the forces driving the liquid metal flow in the molten pool, only buoyancy, surface tension, and electromagnetic force are considered, while arc pressure and positive pressure caused by surface curvature is ignored;(4) The distribution of current density and heat flux density of the welding arc is assumed to be double ellipsoid heat source;(5) Assuming that the thermophysical properties of the material only vary with temperature.The numerical simulation of TIG welding pool of dissimilar magnesium alloy is carried out. Numerical simulation of dissimilar metals is special. It is essential to build a complete geometric model, as shown in The accuracy of the temperature field calculation depends on the heat source model, so the establishment of the TIG welding heat source model suitable for dissimilar materials is a prerequisite for accurate simulation of the welding process.For TIG welding, the establishment of the heat source model has experienced from the initial fixed arc to moving arc, from steady state to quasi-steady state and then to transient state, from 2D to 3D, from the surface heat source (Gaussian heat source) to the double elliptic heat source and then to double ellipsoid heat source. The final model is getting closer and closer to reality. The double ellipsoid model used in this paper is shown in X, Y, and Z directions are specifically a1, b, and c, the corresponding heat source distribution is as follows:Assuming that the semi-axis lengths of the front ellipsoid in the X, Y, and Z directions are specifically a2, b, and c, the corresponding heat source distribution is as follows:Assuming that the semi-axis lengths of the rear ellipsoid in the η is the effective power coefficient of the arc, taking 0.8; I is the welding current; the welding voltage U is 20 V; and σq is the effective heat flow density distribution radius.Among them, The initial temperature of the workpiece is set to 298.15 K (ambient temperature), and the boundary conditions of the upper surface of the workpiece are as in:ε is the gray level of the material, u, v and w denote the directions of the x, y, and z-axes, respectively.Among them, The boundary conditions of the model end face are:The driving forces in the welding process simulation are performed by the source term, and the specific driving force types are as follows:z-axis direction.(1) Buoyancy(2) Electromagnetic force(3) Surface tensionAs the main driving force of welding pool, surface tension largely determines the flow pattern of molten metal. The expression of surface tension is as follows:μ is viscosity, γ is surface tension, and ∂γ/∂T is the temperature coefficient of surface tension. Many researchers have found that the temperature gradient of surface tension is very important. However, the actual surface tension coefficient of various materials is very difficult to obtain in the commonly studied temperature range. Therefore, the surface tension coefficient is taken as a constant in this study.Among them, 3, the liquidus temperature is 883 K (610 °C), the solidus is 798 K (525 °C); the liquidus of AM60 is 888 K (615 °C), and the solidus is 818 K (545 °C). Some parameters are shown in The low-temperature physical property parameters of the materials in this paper are referred to the relevant literature, and the high-temperature physical property parameters are obtained by extrapolation. Among them, the density of AZ61 is 1.8 g/cmIt can be seen from the temperature cloud diagram in The temperature field can be further understood by taking the isotherm distribution of different regions at the same time, as shown in The cross-section of the welding parts at 8.5 s is studied, and the cross-section of the molten pool is shown in In order to obtain the distribution of temperature fields on both sides of AZ61 and AM60 dissimilar magnesium alloys during TIG welding, typical nodes were selected for thermal cycle curve analysis. First, the nodes were selected at equal intervals along the welding direction and then the thermal cycle curve was calculated. The distances between the selected welding nodes and the welding starting point are 10 mm, 20 mm, 30 mm, 40 mm, 50 mm and 60 mm, respectively. The corresponding thermal cycle curves are drawn and the nodes are defined as 1–6 respectively. The temperature curves of each node are shown in It can be seen from In order to further explore the characteristics of the welding temperature field of dissimilar magnesium alloys, six nodes were selected in the vertical direction on the AZ61 side and the AM60 side, and then the thermal cycle curve analysis was carried out. The nodes were selected at 4 mm, 8 mm, 12 mm, 16 mm, 20 mm, and 24 mm away from the center of the welding seam on both sides, denoted as 1–6, respectively. Their thermal cycle curves are shown in (1) Morphological characteristics of molten pool(2) Analysis of molten pool flow fieldWith the welding current of 115 A, welding speed of 180 mm/min, and welding time of 7 s, under the combined action of buoyancy, electromagnetic force, and surface tension, the simulation of the velocity field of the molten pool perpendicular to the welding direction is shown in The conditions of dissimilar magnesium alloys AZ61 and AM60 were compared under TIG and A-TIG welding. From l et al. , as showThe mathematical model reliability of the welding process is usually verified by experiments, and its parameter settings are constantly revised to make it closer to the actual welding process. TIG (A-TIG) welding experiments were carried out on dissimilar magnesium alloys AZ61 and AM60, and the influence of welding current on the welding seam formation was studied. The mathematical model of welding pool has been established, and the welding process was numerically simulated. The following conclusions are drawn:(1) By analyzing the TIG welding of dissimilar AZ61-AM60 alloys, the optimal process parameters were obtained. In TIG welding, when the welding current was set to 115 A and the welding speed was 180 mm/min, the welding seam was well-formed and no welding defects appeared.(2) The temperature field of dissimilar magnesium alloy AZ61-AM60 under TIG welding has been simulated. Since the thermal conductivity of magnesium alloy AM60 is larger than that of AZ61 at the same temperature, the thermal conductivity of AZ61 and AM60 is different. Thus, the temperature distribution of the molten pool shows a certain asymmetry on the AZ61 side and AM60 side.(3) The simulation results show that, in the molten pool flow field on the AM60 side, the upper surface of the metal in molten pool moves from the center of the pool to the surroundings, then flows down along the boundary of the pool, finally flowing to the center of the molten pool when it is close to the center line of the welding seam. In addition, the movement direction of the AZ61 side is just symmetrical with that of the AM60 side, but the shape of the molten pool is asymmetrical.(4) Comparing the simulation results of TIG welding and A-TIG welding, it can be found that, when A-TIG welding of dissimilar magnesium alloy AZ61-AM60 coated with activating flux is carried out (


Mechanical ventilator is a machine that is mechanically designed to deliver breathable air in and out of the lungs to provide a breathing mechanism for a patient who is physically unable to breathe, it is an indispensable life-support device in critical care medicine and medical emergencies such as scenarios during the COVID-19 pandemic. This research presents a model design of the pneumatic circuit that is electronically controlled, by using computer-aided pneumatic rig over selected 5/3, 5/2, 3/2 solenoid gating valves, the performance of these valves must be investigated to ascertain the most appropriate valve to be used for the electro-pneumatic mechanical ventilator. An elaborate parametric investigation reported for volume-controlled ventilators illustrate the influences of key parameters on the dynamics of the ventilated respiratory system. This study presents the linearity of tidal volume, peak pressure and lung compliance for the parameters considered. However, the maximum pressure of the ventilation device increases slowly when the tidal volumes exceed 600 ml. In addition, influence of evacuation time of the ventilator predicted over high throughput in time regimes of 1 s; 1.2 s; 1.4 s; 1.6 s, and 1.8 s showed that the pressure platform in the pipe might not appear if the exhaust time of the ventilator is less than 1.6 s. The 5/2 solenoid valve was considered the best with consistent flowrate. The archetypal model of the pneumatic circuit developed in this research could find vital application in the design of patient-interfacing devices particularly in ventilators and neonatal incubator. Electro-pneumatic, Mechanical ventilator, On-delay timer, Solenoid valve, Tidal volume. A similThe incidences respiratory-related diseases pose the challenge to improve on the strategies for precision delivery of breathable air in ventilator for critical healthcare. Traditional method of operation of mechanical ventilators requires predefined settings based on pulmonological assessment of the patients, which may precipitate incidences of patient-ventilator asynchrony specifically during the early period of novel coronavirus COVID-19) pandemic , 6, 7. T pandemicDevelopment in the field of computer science has impacted on the present progress in design medical devices such clinical ventilators. In the early 1990s, microcontrollers have been identified as vital in the construction of bellows-type ventilator to simulated respiratory flow pattern for instantaneous breathing . In the The review of work done by various authors show that many Mechanical Ventilator are not automated, they must be adjusted manually by the clinicians. Involvement of Clinicians is required to determine operating parameters of the device. This could translate to sources of operational error, which may limit the performance of the Ventilator as life support device. Therefore, there is a critical need for a complete automation of the electro-pneumatic systems, which could assist in improving patient support during the use of clinical ventilators.In this research, an archetypal model of electropneumatic pathways for computer-controlled ventilation is developed, with dependable degree of patient-ventilator symphony over intermediate regimes of ventilating session. Pertinent parameters such as tidal volume, exhaust timing and exhalation timing sequence are determined. The performance of auto-delay mechanisms in the ventilating circuit is investigated while the observed implications on ventilating performance are explained in this study. A suitable solenoid valve was considered the best with consistent flowrate. This newly developed automated ventilator will overcome the operational errors often found in the existing ventilators.2(i)The air in the system follows all ideal gas laws(ii)The dynamic process is a quasi-balanced process(iii)There is no air leakage during the working processThe study considered an unsteady laminar, incompressible flow through the collapsible area of pneumatic ducts, which is a representative of the native upper respiratory tract. The prediction of the breathable air circuit is modelled by utilizing physical laws and established computational scheme subject to the assumptions that:Volume EquationSubject to the assumptions stated above, the output flow rate of a volume-controlled ventilator as described by  can be s2O while the difference between the upstream and downstream pressure is ∼ > 0.528.The mass flow rate of breathable air can be modelled with Pressure EquationThe flowrate in respect to the pressure within convective airways is represented by: al 2013 .(4)C1=dVConsidering the ventilation process as thermodynamic system where ventilation work is taken as an isothermal process and expressed using the established Clapeyron system of differential equations.After transformation of 2.1The air-current model of Shi et al 2014 is employed to validate the performance of solenoid-controlled pneumatic circuit developed in this study. The item of components similar to established report are implemented on computer-controlled pneumatic bench while modeling is complimented by using a fluidSIM software. The generation of pathways for breathable air is presented in 2.2The single-acting cylinder with detent cam and quick couplings is mounted on an advancing side, the unit is mounted on the profile plate using the quick release system with two nuts and three handles. The single-acting cylinder which has an attached trip cam and inbuilt push-in fitting, is mounted on a plastic retainer. This bitable 5/2-way solenoid valve with push-in fitting screwed to a function plate that is equipped with a port and silencer. The proximity sensor consists of the sensor of the mounting kit and cable, whereas the cable is equipped with a socket and three jack plugs as shown in If the piston is at the left stop in In the initial position of the cylinder, 1 × 1 is in the forward end position and the rear cylinder chamber is filled with compressed air. A switching position remains the same as long as its actuator with a pushbutton. The function of a normally open contact is being performed by the pushbutton, in this case, the circuit is interrupted in the normal position of the pushbutton that is in the unactuated state. By actuation the switch button, the circuit become closed and subsequently allow the current to flow to the receiving device. Upon the release of the stem of the switch, the circuit is interrupted due to the immediate return of the pushbutton to the normal position being activated by the spring forces.Actuation of pushbutton 1S1 or pushbutton K1 , causes the relay K1 to be energized, the changeover contact K2  closes and the solenoid coil 1Y1 of the 5/3-way valve 1V1 is energized as shown in This 3/2-way single solenoid valve with push-in fittings is attached to a function plate, which is equipped with a P port and silencer. The two electrical connections are equipped with safety connectors. The unit is mounted on the profile plate using a quick release detent system with a blue lever. The manifold with eight self-sealing push-in fittings is screwed on to a universal plate as shown in 33.1The data of the pressure in the flexible tube; the volume of the air flowing through the inlet of the flexible tube; the volume of the air entering and leaving the lung are shown in The tidal volume of the ventilator is set to 300 ml, 500 ml, 600 ml and 700 ml, and the simulation results are shown in Influence of the evacuation time of the Ventilator. The exhaust time of the ventilator is set to 1 s, 1.2 s, 1.4 s, and 1.6 s, and the result of other study has been presented and validated in this study. Their result shows that the pressure platform in the pipe may not appear if the exhaust time of the ventilator is less than 1.6 s. on their model.In addition, with an increase in the Electro-pneumatic exhaust time, the maximum pressure in the lung increases. When the exhaust time of the ventilator is more than 1.6 s, the maximum pressure in the lung is constant on Shi et al model. Finally, when the ventilator escape time is less than 1.6 s, the maximum lung flow increases with an increase in the discharge time. If the discharge time of the ventilator is greater than 1.6 s, the maximum flow rate is constant. The simulation results are consistent with the experimental results, which verify the mathematical model. Therefore, the mathematical model can be use in the study of VCV system, and it has better versatility and applicability. With an increase in the effective area of the exhalation valve, the maximum exhaust airflow rate of the lung.3.2The results of the three solenoid valves used in this study are presented in The experimental study of VCV on three different valves have been examined and simulation results of electro-pneumatic system of VCV in 10 s, 12 s, 14 s, and 16 s, using 5/2-way solenoid valves (PA) and single acting cylinder are shown in For the 5/3 Solenoid valves, simulation results of electro-pneumatic system of VCV in 10 s, 12 s, 14 s, and 16 s, relay using 5/3-way solenoid valves (PB) and single acting cylinder. From the analysis of the actuator in 4This study investigated the parametric modelling of clinic-bound mechanical ventilators of volume-controlled variant. The Clinical ventilator is relatively a system that employs several valves and sensors along with a processing unit to implement the required control algorithms. The performance of auto-delay mechanisms in the ventilating circuit is investigated while the observed implications on ventilating performance in terms of the linearity of tidal volume, the peak pressure and lung compliance were observed for some selected parameters. The 5/2 solenoid valve was considered the best with consistent flowrate of 4.1 l/min for 10 s, 8.1 l/min for 12 s, 12 l/min for 14 s and 16.1 l/min for 16 s. This newly developed automated ventilator will overcome the operational errors often found in the existing ventilators and It can be stated that the performance of VCV system in terms of peak time, settling time and maximum overshoot are automatic.The relationship between tidal volume of breathable air and compliance of model lung of selected class of delay-time provides better results as compared to other models. The archetypal model of pneumatic circuit developed in this research could find vital application in the design of patient-interfacing devices particularly in ventilators and neonatal incubator.Ebenezer Olubunmi Ige: Conceived and designed the experiments; Analyzed and interpreted the data.Adedotun Adetunla: Conceived and designed the experiments; Performed the experiments; Wrote the paper.Samuel Olufemi Amudipe: Performed the experiments; Wrote the paper.Adeyinka Adeoye, Matthew Glucksberg: Contributed reagents, materials, analysis tools or data.This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.The data that has been used is confidential.The authors declare no competing interests.No additional information is available for this paper.