In order to improve the interface and mechanical properties of aramid fiber (AF)-reinforced epoxy resin (EP) composites (AF/EPs), the surface modification of AF was carried out with atmospheric pressure air plasma, and the effects of plasma treatment time and discharge power on the AF surface and the interface and mechanical properties of AF/EPs were investigated. The results show that, when plasma treatment time was 10 min and discharge power was 400 W, AF showed the best modification effect. Compared to the unmodified material, the total content of active groups on the surface of AF increased by 82.4%; the contact angle between AF and EP decreased by 20%; the interfacial energy and work of adhesion increased by 77.1% and 19.1%, respectively; the loss of AF monofilament tensile strength was controlled at only 8.6%; and the interlaminar shear strength and tensile strength of AF/EPs increased by 45.5% and 10.4%, respectively. The improvement in AF/EP interfacial and mechanical properties is due to the introduction of more active groups on the AF surface with suitable plasma processing parameters, which strengthens the chemical bonding between the AF and EP matrix. At the same time, plasma treatment effectively increases the surface roughness of AF, and the mechanical meshing effect between the AF and EP matrix is improved. The synergistic effect of chemical bonding and mechanical meshing improves the wettability and interfacial bonding strength between the AF and EP matrix, which enables the load to be transferred from the resin to the fiber more efficiently, thereby improving the mechanical properties of the AF/EP. In recent years, the world’s main high-performance fibers, and advanced composites reinforced by these high-performance fibers, have developed rapidly. For example, carbon fiber is used as a load-bearing structure in many engineering fields due to its excellent mechanical properties, fatigue resistance and corrosion resistance. However, the oxidation of carbon fiber at high temperature will lead to its decreased fire resistance. Li  conducteAramid fiber is a new high-tech synthetic organic fiber composed of aromatic rings and amide bonds on the main chain of macromolecules. As an important national defense material, aramid fiber is widely used in aviation, aerospace, military, transportation and other fields due to its excellent comprehensive properties, such as impact resistance, high strength, high modulus, low density, high temperature resistance, wear resistance and acid and alkali resistance ,5,6,7. FHowever, the surface of aramid fibers is relatively smooth, the specific surface area is small, the surface energy is low and the active surface generally does not exceed 10% of the total surface area; it is thus difficult for such fibers to form a solid connection with the matrix through chemical or physical action , and theAt present, the surface modification methods of aramid fibers mainly include chemical modification and physical modification. Chemical modification is to use chemical reagents to chemically react with aramid fibers to introduce polar groups on the surface to increase the surface activity of the fibers, thereby promoting the adhesion between the fibers and the matrix . Althoug2 and Ar/N2 atmosphere media blocking plasma treatments, the different effect mechanisms of the fiber surface were explored, and the influence of O2 and N2 flow on the surface modification effect of aramid fiber was also investigated. The results show that, after the dielectric barrier discharge plasma treatment, the C on the aramid surface decreases, while the O and N increase and new polar functional groups such as -C-O- and -COOH are generated. At the same time, due to the etching effect of plasma, the surface of aramid fiber becomes rough and the bonding ability of aramid fiber and epoxy resin is thus improved. Li Shuang et al. [Gu Ruqian et al.  used dieg et al.  used ammg et al.  used helIn recent years, atmospheric pressure air plasma treatment has solved the above problems very well, it has thus been widely favored by researchers and become a research hotspot in the field of fiber surface plasma modification. Therefore, this paper uses atmospheric pressure air plasma treatment to modify the surface of AF. By changing the plasma treatment time and discharge power, the effects of these two key process parameters on the aramid fiber surface and the interface properties and mechanical properties of its reinforced epoxy composite are systematically studied. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the surface morphology and surface element composition of AF. Static contact angle analysis was used to measure the wettability of AF, and its interface energy and work of adhesion were calculated. The tensile strength of AF monofilament, the interlaminar shear strength (ILSS) between AF and EP, and the tensile strength of AF/EP under different plasma process parameters were tested, and the failure mode and reinforcement mechanism of the composites were studied. The object is to provide technical support for the further research and development and engineering application of aramid fiber-reinforced epoxy composite materials.2, width 100 cm, Yixing Xinli Weaving Co., Ltd. ; ethyl acetate and deionized water were obtained from Shanghai Aladdin Biochemical Technology Co., Ltd. ; IN2 infusion epoxy resin, AT300SLOW curing agent (IN2:AT300SLOW = 100:30), Beijing Composite Yigou Technology Co., Ltd. .Aramid fiber (AF): DuPont Kevlar-29, with an average diameter of 14 µm; Aramid fiber cloth: Model XL-AF480B-100, made of Kevlar-29 fibers, twill weave, square gram weight 480 g/cmThe surface of AF was modified by atmospheric pressure air plasma. The atmospheric pressure air plasma treatment device is manufactured by Nanjing Jiayang Engineering Technology Co., Ltd. , model PT800, and its structure and principle are shown in The technological process and steps are as follows:(1) Aramid fibers were surface pretreated prior to plasma treatment. First, AF was soaked in ethyl acetate for 24 h for surface pretreatment to remove impurities on the fiber surface, then washed with deionized water 3 times and dried in an oven at 60 °C for 12 h.(2) The dried aramid fiber was taken out, placed at a distance of 10 mm from the plasma spray gun nozzle, and the plasma spray gun nozzle was moved in the form of a uniform reciprocating movement of 3 cm/s so that the plasma jet at the spray gun mouth could evenly irradiate the fiber surface to ensure the fiber surface treatment effect. Special attention should be paid to not leave the fibers in the plasma jet area for an extended period of time so as to avoid high temperature burns.−8 Pa. The excitation power and voltage were 40 W and 15 KV, respectively. The Gauss–Lorentz function was used to fit the peaks of C1s spectrum, and the percentage of functional groups on the fiber surface was determined according to the relative peak areas of each peak in the spectrum. Peak C at the binding energy of 284.6 eV was used to correct the displacement.The microscopic morphology of the AF surface was observed with a scanning electron microscope (SEM) (Zhongke Keyi KYKY-EM6900), and the samples were sprayed with gold for 2 min before the observation. The acceleration voltage was 25 KV and the magnification of the AF sample was 5000×. Photoelectron spectroscopy (XPS)  was used to analyze the chemical composition and group composition of the AF surface. An Al Kα X-ray light source was used in the test. The vacuum of the sample chamber was 2 × 10The static contact angle and surface energy of the AF were measured with a contact angle measuring instrument  to characterize the wettability of the AF surface. During the test, a single fiber wire with a length of about 5 cm was cut and bonded to an aluminum hook with adhesive tape. A steel needle was dipped into a small amount of the test liquid and used to gently touch the surface of the single fiber wire to form stable microdroplets. The droplet was photographed with a charge-coupled device and, finally, the static contact angle of the AF was fitting measured by Young–Laplace software.Based on the GB/T 31290-2014 standard, the tensile strength of the AF monofilament under plasma treatment conditions with different process parameters was tested, and the effect of plasma treatment process parameters on the tensile strength of the AF monofilament was studied. Each AF monofilament was firmly fixed on a paper card frame with adhesive. At room temperature, a 100 N sensor was used for testing, the length of the monofilament was 20 mm and the stretching speed was 1 mm/min. Ten monofilaments were measured in each group.The aramid fiber-reinforced epoxy resin composites were prepared using the vacuum diversion method. According to the ASTM D2344 standard, the interlaminar shear strength (ILSS) of the composite was measured on the electronic universal testing machine CMT 5105, and the sample was subjected to 3-point bending load. The sample size was 15 mm × 5 mm × 3 mm, the loading speed was 1 mm/min, the span was 12 mm, the test temperature and relative humidity were 25 °C and 50%, respectively, and the average value was taken from 5 samples in each group. The ILSS value of composite materials can be calculated by Formula (1):2.The tensile strength of the composite was measured on an electronic universal testing machine (UTM 5504) according to the ASTM D3039 standard. The sample size was 250 mm × 25 mm × 3 mm. In order to prevent slippage or clamping damage, the two ends of the sample were bonded with an aluminum alloy reinforcement sheet (50 mm × 25 mm × 2 mm), the tensile rate was 5 mm/min, the test temperature and relative humidity were 25 °C and 50% and the average value was taken for each group of 5 samples. The tensile strength of the composite can be calculated by Formula (2):Scanning electron microscopy (SEM)  was used to observe the microscopic morphology of a cross-section of the tensile specimen of composite materials. Before observation, the specimen was put into an ion sputtering instrument to spray gold for 2 min, and the accelerating voltage was 5 KV.Under certain discharge power conditions (300 W), when the treatment time was short (5 min), slight etching marks appeared on the surface of the AF, and grooves distributed parallel to the fiber axis were formed on the surface; however, the number of grooves was relatively small, the depth was relatively shallow, the width was relatively narrow and the etching effect was relatively weak b. When tComparing Therefore, the plasma treatment has an etching effect on the surface of the aramid fiber, such that the surface roughness of the fiber is significantly increased. Moreover, with increases in plasma treatment time and discharge power, the degree of etching and roughness on the fiber surface both increased gradually. Without damaging the fiber body structure, when the plasma treatment conditions are 10 min-400 W, the fiber surface can obtain greater roughness, which helps to improve the wettability and the interfacial adhesion between the fiber and the matrix and ultimately improves the mechanical properties of the composite. However, it should be noted that when the treatment time is too long  or the discharge power is too large , the fiber body structure will be damaged due to severe surface peeling, which may lead to the deterioration of the fiber and its composite’s material properties.The untreated AF surface had C content of 82.63%, O content of 13.8%, N content of 3.57%, an O/C ratio of 0.167 and N/C ratio of 0.043 a. Under Under the condition that treatment time is 10 min, with the increase in discharge power  the element content on the AF surface shows the same change rule as the above treatment time; the C content first decreases and then increases, while the O and N content both first increase and then decrease. Among them, when the discharge power was 400 W e, the C It can be seen from the above analysis that the changes in the relative content of C, O and N fully prove that the plasma treatment has indeed produced a modification effect on the surface of the aramid fiber. In particular, under the appropriate plasma treatment process parameters , O and N content on the AF surface increased significantly, which indicates that a large number of oxygen- and nitrogen-containing functional groups may be introduced into the AF surface. The introduction of these polar functional groups can improve the polarity and chemical activity of the fiber surface, help to improve the wettability of the fiber surface and enhance chemical bonding between the fiber and the matrix.In order to further explore the effects of plasma treatment time and discharge power on AF surface functional groups, advantage software was used to perform peak fitting processing on the sub-spectra under different plasma treatment process parameters, and the fitting results are shown in The results showed that the content of C-C/C=C groups on the surface of untreated AF a was 81.Under the condition of a certain discharge power (300 W) and when the treatment time was short (5 min) b, when cThe next consider condition was a treatment time of 10 min with a gradual increase in discharge power . Compared to the discharge power of 300 W c, as theAs mentioned in the analysis, the chemical bonds included in aramid fibers include C-C, C-N, C=O, O=C-O, etc. These chemical bonds can match the energy of electrons, ions, metastable particles, UV-visible light and other particles in plasma. Therefore, in the process of plasma treatment, the particles can cause these chemical bonds to break and recombine to generate new chemical bonds and new functional groups ,21. The Reaction with atomic oxygen:Reacts with molecular oxygen:Reacts with peroxide free radicals:According to the above reaction, the principle of modifying an aramid fiber surface by plasma treatment is mainly reflected in two aspects. On the one hand, the plasma bombardment of the aramid fiber surface produces a large number of free radicals and triggers a chain reaction of free radicals. N and O are implanted into the aramid surface, and a large number of oxygen-containing groups are introduced, such as carbonyl, carboxyl and hydroxyl groups. On the other hand, the plasma also etched the AF surface and increased the surface roughness of the fiber. The plasma modification mechanism is actually the combined effect of these two factors. For the aramid fiber samples treated with 15 min, 300 W d and 10 Therefore, the change in group content on the surface of aramid fiber before and after plasma modification is completely consistent with the change in C, O and N element content on the fiber surface discussed above. Under the premise that the modification process and other plasma discharge parameters are determined, treatment time and discharge power have a significant impact on the chemical composition of the fiber surface. Appropriate treatment time and discharge power, such as 10 min and 400 W in this study, can ensure that the content of polar groups introduced on the fiber surface achieves a relatively ideal value, which can greatly improve the chemical inertness of the fiber surface, help the matrix to infiltrate the fiber, and strengthen the chemical bonding and polar effect of the interface between the two phases.The interfacial and mechanical properties of aramid fiber-reinforced resin matrix composites are closely related to the wettability between fibers and resins . Figure Under the condition of constant discharge power (300 W) a and witIn order to quantitatively analyze the surface energy of AF under different plasma treatment process parameters, the interfacial energy and work of adhesion between AF and EP under different plasma treatment process parameters were calculated according to the Young–Dupre equation . The relIn the above formula, According to the surface energy component method of Owens, D.K.J. and Wendt, R.C.J. , two typ2 and 51 mJ/m2, respectively. 2 and 0 mJ/m2, respectively.In the above formula, The contact angles between AF and deionized water and diiodomethane under different plasma treatment process parameters are shown in 2. Under the condition of a discharge power of 300 W  plasma treatment, 2 again. At the same time, with 10 min treatment time –(7), the change law of the surface energy of AF can be calculated from the contact angles of AF with deionized water and diiodomethane, as shown in of 300 W a and wits 10 min b with a of 300 W a, γA incent time b and an θ < 90°, the increase in surface roughness will decrease the contact angle [Through analysis and discussion of the test results for AF static contact angle and the calculation results of AF surface energy, it can be found that: (1) Proper prolongation of treatment time and increases in discharge power can both produce better fiber surface modification effects (AF surface contact angle decreases and surface energy increases). This is because the fibers will be bombarded by active particles more with longer treatment time, and the modified positions will be more uniform. Additionally, increasing discharge power can directly increase the average energy and number of active particles in the plasma, such that the intensity of the plasma modification on the fiber surface increases under the same length of treatment time. (2) There are two reasons for the above changes in the contact angle and surface energy of AF. On the one hand, some new polar groups were generated on the AF surface after plasma modification (confirmed by the XPS test results), thus increasing the polar component of fiber surface energy. On the other hand, as can be calculated from the Wentzel equation, when ct angle . The etc2 [The interfacial energy and work of adhesion between the AF and EP under different plasma treatment process parameters were further calculated by Formulas (3) and (4), and quantitative analysis of the interfacial properties between AF and EP was realized. The calculation results are listed in 41 mJ/m2 .2 and 61.1 mJ/m2, respectively), representing increases of 77.1% and 19.1%, respectively, compared with the untreated condition.It can be seen from Therefore, when the treatment time for the atmospheric pressure air plasma modified AF surface is 10 min and the discharge power is 400 W, the surface contact angle of AF is the smallest, the surface energy of the AF is the largest, and the interfacial energy and work of adhesion between AF and EP are the highest. These conditions also allow for the best wettability, which will be beneficial through increases in van der Waals force, enhanced chemical bonding and mechanical locking between EP and AF in the interface region, and a reduced number of defects such as bubbles, holes and cracks existing in the AF/EP composite, thereby improving its interfacial and mechanical properties.From the previous SEM observations, it can be seen that the surface morphology of AF changed significantly after plasma treatment: the AF surface is etched and the roughness is also significantly increased. These changes may have some impact on the body properties of the fibers. In order to study the surface modification of AF by plasma in terms of the body properties of the fibers, the fiber monofilament tensile strength test was used to analyze changes in fiber tensile properties before and after plasma modification. In this study, statistical analysis is used to test the experimental results, that is, the Weibull distribution function ,28,29 isThe one-dimensional two-parameter Weibull distribution function  is expreL, is the cumulative distribution function of fracture probability for AF when the fracture stress is not higher than In Equation (9), Equation (9) with survival probability Subsequently, taking the natural logarithm of both sides of Equation (9) obtains Equation (10):It can be seen from Equation (10) that there is a linear relationship between s method  can be uThe failure probability In Equation (11): By linear distribution of Equation (10), Equations (12)–(15) can be obtained as follows:Equation (16) can be obtained by slightly changing Equation (15):Using the least squares method to perform linear regression analysis on the 10 pairs of numbers , the average single-filament tensile strength of AF under different plasma treatment process parameters can be obtained, as shown in From observation of the SEM images of AF above, it can be concluded that after plasma modification of the AF surface, the modification process will etch the AF surface due to chemical reactions and destroy the surface structure of the AF; the bombardment of active particles in the plasma will also introduce some defects on the fiber surface. When the external load acts on the AF surface, it becomes easy to form a stress concentration at the defect such that the AF will break under a small load, resulting in the phenomenon of reduced average monofilament tensile strength in the AF . In partThe test results and analysis of the tensile strength of AF monofilaments show that plasma modification with different process parameters causes different degrees of damage to the tensile properties of the AF’s body. However, under suitable plasma treatment process parameters, such as the 10 min-400 W treatment in this study, this damage can be controlled to within a relatively small range, which can effectively improve the chemical composition and physical morphology of the AF surface and improve the wettability of the AF surface; importantly, the reduced average monofilament tensile strength was controlled at 8.6%. This quality control is very important for improvements to the interfacial and mechanical properties of AF/EP composites.In order to analyze and evaluate the interfacial bonding properties of aramid fiber-reinforced epoxy resin composites (AF/EP), the interlaminar shear strength (ILSS) of AF/EP under different plasma treatment times and discharge power was tested according to the ASTM D2344 standard. The test results are shown in It can be seen from The degree of ILSS improvement is affected by the physical structure, roughness, polarity and chemical activity of the AF surface and the ability of the resin to wet the fibers. In particular, under suitable plasma treatment conditions , the ILSS of AF/EP is significantly improved. This is because (1) plasma treatment introduces a large number of polar groups  on the surface of the AF, and these polar groups form strong chemical bonds with the resin matrix through a series of reactions; and (2) the etching effect of plasma on the AF surface increases the surface roughness of the fiber, and many grooves and bumps are generated on the fiber surface. These grooves and bumps are equivalent to creating many anchorage points for resin infiltration, which thus increases the contact area between AF and EP and enhances the mechanical chimerism between the two phases. It is precisely under the synergistic effect of chemical bonding and mechanical chimerism that the interfacial bonding strength of AF/EP has been greatly improved. However, plasma treatment for a longer time or with higher power (such as 15 min-300 W or 10 min-500 W) will destroy the active groups formed on the AF surface at the initial stage of plasma treatment such that the content of polar groups on the AF surface is reduced, the chemical bonding between the fibers and the resin is weakened, and the synergistic effect with the mechanical chimerism is weakened, resulting in a decrease in the interface bonding performance of the AF/EP. This also shows that, although the surface roughness of AF and the content of polar groups both have an effect on the interface bonding performance of AF/EP, the content of polar groups on the AF surface has a greater effect on the interface bonding performance of AF/EP than that of AF surface roughness. That is to say, after plasma modification of AF/EP, the contribution of chemical bonding between the AF and EP matrix to improving the interface bonding performance of AF/EP is greater than that of mechanical chimerism.In order to analyze and evaluate the mechanical properties of aramid fiber-reinforced epoxy resin composites (AF/EP), according to the ASTM D3039 standard, the tensile strength . As a result, interface bonding performance between the AF and EP is poor (ILSS is 46.8 MPa), it is difficult to effectively transfer the load from the resin matrix to the aramid fiber through the interface, and the reinforcing effect and load-bearing effect of the aramid fiber cannot be fully exerted. Therefore, at this time, the tensile strength of AF/EP is relatively low (415 MPa), and only a small load is required to cause an interfacial debonding phenomenon that causes the overall failure of the composite material; its failure mode is mainly an interface debonding failure.In order to further analyze the reinforcement mechanism and failure mechanism of the fiber composites, the microscopic morphology of the tensile section of AF/EP under 0 min-0 W (untreated) and 10 min-400 W plasma treatment conditions was observed by SEM, as shown in 2) and work of adhesion (61.1 mJ/m2) between the AF and EP, and improved interfacial bonding strength between the AF and EP (ILSS is 68.1 MPa). Additionally, its internal fiber bundles were subjected to greater shear stress when loaded, which results in slippage and then tearing of microfibers of fiber [As can be seen from of fiber  and promIn order to improve the interface properties and mechanical properties of aramid fiber-reinforced epoxy resin composites, the surface of AF was modified by atmospheric pressure air plasma and aramid fiber-reinforced epoxy composites were prepared. The effects of the key process parameters (plasma treatment time and discharge power) on aramid fiber surface modification and its reinforced epoxy composite’s interfacial and mechanical properties were investigated.The results show that when the plasma treatment conditions are 10 min and 400 W, the AF exhibits the best modification and enhancement effect. Compared to untreated material (0 min-0 W), the surface O/C ratio and N/C ratio of AF increased by 70% and 144%, respectively, and the total content of polar groups increased by 82.4%; the contact angle between AF and EP reduced by 20%, the interfacial energy and work of adhesion increased by 77.1% and 19.1%, respectively, and the loss of average single-filament tensile strength was controlled at 8.6%. Additionally, the ILSS and tensile strength of AF/EP were increased by 45.5% and 10.4%, respectively. The improvement in the interfacial and mechanical properties of aramid-reinforced epoxy composites is due to the introduction of more active groups on the surface of the AF through the use of suitable plasma treatment conditions, which strengthens the chemical bonding between the AF and EP matrix. At the same time, the plasma treatment effectively increased the surface roughness of the AF and improved its mechanical engagement with the EP matrix. The synergistic effect of chemical bonding and mechanical meshing makes aramid and epoxy form an organic whole, which significantly improves wettability and interfacial bonding strength between the AF and EP matrix and enables the load to be transferred from the resin to the fiber more effectively. This also allows for more uniform load bearing within the AF, which enables full exertion of its energy absorption, stress relaxation and enhancement effects, thereby improving the mechanical properties of AF/EP.


Type A aortic dissection (TAAD) is associated with high morbidity and mortality, and open surgery is the best treatment option. Development of endovascular repair devices for TAAD will benefit patients deemed unfit for open surgery. In this study, we performed a thorough investigation of anatomical features in Asian patients with TAAD to learn about the patient eligibility of a novel ascending aortic endograft technique.Computed tomography angiography (CTA) images of TAAD cases in our institution from January 2015 to November 2021 were reviewed, and three-dimensional reconstructions were performed with the Endosize software . Anatomic structures including length measured along centerline and greater/lesser curvature, ascending aorta/aortic root dimensions, as well as location of entry tear and extent of dissection were analyzed.A total of 158 patients were included . In 99 (62.7%) of the cases, entry tear was distal to the sinotubular junction (STJ). In 106 (67.1%) of the cases, the pathology proximally extended into the aortic root, which was intramural hematoma in 37 (23.4%) of the cases, and the aortic root was free from the pathology in 52 (32.9%) of the cases. The median distance from the STJ to the proximal edge of the ostium of the innominate artery (IA) measured along the centerline was 65 mm (IQR 58–74 mm). The median distance from the distal edge of the higher coronary ostium to the STJ was 7.95 mm (IQR 5.625–10.9 mm). The bare metal stent part was set between the edge of the higher coronary ostium and the STJ. In our series, 63 (39.9%) of the cases had this distance >10 mm. The relative difference was <20% between the STJ and the proximal edge of the ostium of the IA in 92 (58.2%) of the cases. Ascending aorta radius of curvature was 52.2 mm (IQR 43.7–63.7 mm).Our study demonstrates that 56.3% of the TAAD cases would be amenable to endovascular repair by the novel ascending aortic endograft, with sufficient landing zone free of the dissected aorta. Stanford type A aortic dissection (TAAD) is one of the most catastrophic emergent aortic diseases; the mortality rate of which could be up to 57% with medical treatment , 2. SurgIn the last decade, many clinicians reported the outcomes of endovascular repair for TAAD, most of which were case reports and case series . Off-labConsidering the significant difference in morphological and physiological characteristics between the ascending aorta and the descending aorta, a dedicated ascending aortic endograft technique is desperately needed for endovascular repair of TAAD. In this study, we aim to evaluate the feasibility of extending endograft into the region between the distal edge of the higher coronary ostium and the sinotubular junction (STJ) in patients with TAAD, and collect data for future design and manufacture of a dedicated ascending aortic endograft device.Between January 2015 and November 2021, a total of 1,060 patients were discharged from our center with a diagnosis of “aortic dissection.” The report on the computed tomography angiography (CTA) of each patient was studied, and those without CTA examination or diagnosed with type B aortic dissections were excluded. In total, 164 patients diagnosed with type A aortic dissections by available preoperative high-resolution CTA were included, but 6 patients were excluded because of previous artificial aortic valve implantation. The institutional review committee approved this retrospective study, and the need for informed consent was waived.Aortic diameters and segmental lengths were analyzed according to CTA. An axial slice thickness of 1 mm or less was present in all the patients. All CTA image sets were analyzed with the Endosize software  for three-dimensional spatial analysis. All measurements were taken by multiplanar reconstruction always in the plane perpendicular to the manually corrected local aortic centerline. Entry tear location was determined by discontinuity in the intima with visualization of contrast flow into the false lumen. The plane of the aortic annulus was defined by the virtual basal ring, or the lowest point of eachaortic valve leaflet's attachment point to the sinus of Valsalva. This plane also served as the reference point along the centerline. The STJ was signified by transition from the bulbous portion of the sinuses of Valsalva to the tubular proximal ascending aorta.The aortic length L1-L3 is measured along the centerline from the distal edge of the aortic annulus to the: (1) distal edge of the left coronary ostium (L1); (2) distal edge of the right coronary ostium (L2); and (3) STJ (L3). Length from the distal edge of the left coronary ostium to the STJ (L4) was calculated by subtraction: L4 = L3–L1. The same is applied for the length from the distal edge of the right coronary ostium to the STJ (L5): L5 = L3–L2. The aortic length L6-L8 is measured along the center line from the STJ to the: (1) proximal extent of the dissected aorta or intramural hematoma (L6); (2) primary entry tear (L7); and (3) proximal edge of the ostium of the innominate artery (IA) (L8). For L6 and L7, if the proximal extent of pathology and primary entry tear was distal to the STJ, the distance would be documented as “proximal to the STJ.” The aortic length from the STJ to the proximal edge of the ostium of the IA was also measured on the greater curvature side (L9) and the lesser curvature side (L10). In cases where the STJ was not definable, it was set 10 mm distally to the origin of the more distal coronary artery.According to L8, the ascending aorta was divided into 4 equal parts. The diameter of the following was measured co-axially because of the centerline flow axis: (1) sinus of the Valsalva (D1); (2) STJ (D2); (3) 1/4 plane of the ascending aorta (D3); (4) 1/2 plane of the ascending aorta (D4); (5) 3/4 plane of the ascending aorta (D5); (6) plane at the proximal edge of the ostium of the IA (D6). (D2-D5)/D2 is calculated to determine whether tapered stent-graft is required.*length of ascending aorta)/(angle*π)  .The simulated tubular stent-graft is composed of two parts: a bare metal stent part  and a covered stent part (the rest part). The bare metal stent is intended to protrude into the aortic root, the junction of the bare metal stent and the covered stent is right in the position of the STJ, and the covered stent is in the ascending aorta. The bare metal stent is structured for fixation, and located in the segment between the distal edge of the higher coronary ostium and the STJ. The distal landing zone is defined as 10 mm proximal to the ostium of the IA for simple interpretation of outcomes, because this region is mostly involved in the pathology and, thus, not an ideal landing zone in conventional thoracic endovascular repair (TEVAR). Inclusion criteria were: (1) distance between the distal edge of the higher coronary ostium and the STJ > 10 mm; (2) entry tear located distally to the STJ; (3) aortic root free from the pathology. When the aortic root is proximally involved by intramural hematoma, it was deemed as a relative indication and calculated exclusively. Exclusion criterion was entry tear in the aortic root or aortic root is proximally involved by the dissected aorta.All values are expressed as median  or as number (percentage). Measurement was performed by two independent clinicians, with <5% variation in reported values considered as acceptable. If a ≥5% variation occurred, measurement would be performed by another more experienced clinician.All the patients were Asian and had a median age of 58 years (IQR 30–76 years), including 115 (72.8%) males. In 50 (31.6%) of the cases, the primary entry tear was found in a coverable zone in the ascending aorta, and in the distal landing zone in 16 (10.1%) of the cases. In 33 (20.9%) of the case, the primary entry tear was found beyond the distal landing zone. In 25 (15.8%) of the cases, the primary entry tear was unidentified. Considering only the location of entry, endovascular repair with the device would be possible in 99 (62.7%) of the cases.n = 87) of all the cases. In 106 (67.1%) of the cases, the pathology proximally extended into the aortic root, which was intramural hematoma in 37 (23.4%) cases. In 52 (32.9%) of the cases, the aortic root was free from the pathology, including proximally extended to the upper 1/3 of the ascending aorta in 17 cases, middle 1/3 of the ascending aorta in 11 cases, and lower 1/3 of the ascending aorta in 24 cases. Among these patients, the pathology was entirely confined in the ascending aorta in 5 (3.2%) of the cases. In total, 89 (56.3%) of the cases met the relative indication. For the supra-aortic trunks, the innominate artery (IA) was involved in the pathology in 64 (40.5%) of the cases, the left common carotid artery (LCCA) was involved in 43 (27.2%) of the cases, and the left subclavian artery (LSA) was involved in 42 (26.6%) of the cases. The pathology distally extending into zone 9 or beyond was most common, and accounted for 55.1%  of the cases, the diameter of the STJ was longer than 40 mm. The median absolute difference between the STJ and the proximal edge of the ostium of the IA was 5.2 mm (IQR 2.125–9.35 mm). The relative difference was <10, 15, and 20% between the STJ and the proximal edge of the ostium of the IA in 54 (34.2%), 73 (46.2%), and 92 (58.2%) of the cases, respectively. Among those with a relative difference <10 and 20%, the diameter of the STJ was larger than that of the proximal edge of the ostium of the IA in 19 and 37 of the cases, respectively.Our study collective of adequate and high-quality image data of 158 patients is one of the largest studies in Chinese and Asian population screening for anatomic feasibility of endovascular repair for type A aortic dissection.A potential technique for endovascular repair of TAAD is a valve-carrying endograft. Kreibich et al.  conducteTubular endograft is another option, and only few studies have explored the feasibility of tubular endograft with the proximal landing zone (10/15/20 mm) in the ascending aorta –12. The The concept of extending the endograft into the region between the distal edge of the higher coronary ostium and the STJ makes endovascular repair available for the entire tubular ascending aorta, increasing the number of potential eligible patients. In our series, 39.9% of the patients could provide a landing zone ≥10 mm for fixation. In comparison, only 4.4 and 1.9% of the patients could provide a landing zone ≥15 and 20 mm, respectively. The anatomical characteristic was similar in the Japanese population, where the median distance from the distal coronary artery to the STJ was 6 mm (range 3–11 mm). Wisneski et al.  analyzedA major challenge for extending the proximal landing zone is to maintain sufficient blood flow of coronary ostia on both sides. To avoid ischemia of the myocardium, the bare metal stent part was set between the distal edge of the higher coronary ostium and the STJ, with the junction of the covered part and the bare metal part positioned in the STJ. A preliminary experiment with the ascending aortic endograft was performed on a swine model with healthy aorta. Although the proximal part of the bare metal exceeded the proximal edge of the higher coronary ostium on the greater curvature side, coronary ostia on both sides showed sufficient blood supply in the final angiography after deployment of the ascending aortic endograft. No adverse events such as stent-graft collapse and migration were observed during the 1-month follow-up, and CTA examination after 1 month showed patent coronary ostia on both sides, suggesting the possibility and safety of extending the proximal landing zone into that region. In future preoperative designs, not only for swine models but also for patients, difference in length between the greater and lesser curvature sides should be considered and measured in detail to ensure accurate positioning of the bare metal part in the region between the distal edge of the higher coronary ostium and the STJ to avoid influencing the blood flow of the coronary ostium on each side .In recent years, a 5% oversizing ratio has been widely accepted in treatment of aortic dissection, but a 0% oversizing ratio has been suggested . An overIn cases where the pathology extended distally to the IA, which was 77.2% in our series, revascularization of supra-aortic trunks was necessary to ensure complete exclusion of the pathology and cerebral and upper limb blood supply. The combination of the novel ascending aortic endograft technique with branched aortic arch endograft could be a possible solution. Currently, all branched aortic arch endograft techniques are investigational, including the Dacron Inoue branch stent-graft , Zenith Accurate anatomical measurement of the ascending aorta is essential for selecting an appropriate size of the endograft. During the cardiac cycle, the ascending aorta moves in longitudinal and circumferential directions, resulting in pulsatile changes in its diameter. Belvroy et al.  found thEndovascular repair for TAAD has a potential to offer high-risk patients an option for effective life-saving treatment associated with lower rate of morbidity and mortality. Morphological analysis on Asian populations is essential considering the anatomical difference among different races. Our study demonstrates that 39.9% of the TAAD cases would be amenable to endovascular repair with the distance between the distal edge of the higher coronary ostium to the STJ > 10 mm, while including cases where the aortic root is proximally involved by intramural hematoma could increase the availability rate to 56.3%. The study could serve for future device development in Asian populations. Study in healthy and TAAD animal models are the ongoing steps to verify the safety of the new device, after which future clinical studies will be carried out to validate its safety and effectiveness in treatment of TAAD patients.This was a retrospective study, which was restricted by its sample size and the nature of single-center studies, for patients with TAAD with available high-quality CTA images, and many patients were excluded because of inadequate or unavailable imaging data. Despite taking many measures, systematic errors in measurement could still exist. In this study, no ECG-gated CT was analyzed, which could have significantly influenced the measurements owing to extreme true lumen collapse.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by Committee on Ethics of Medicine, Navy Medical University. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements. The animal study was reviewed and approved by Committee on Ethics of Medicine, Navy Medical University.XL, LZhu, LZha, and QL contributed to conception and design of the study. XL and LZhu organized the database. LZha performed the statistical analysis. XL wrote the first draft of the manuscript. CS, SX, HZ, WG, and ZJ wrote sections of the manuscript. All authors contributed to manuscript revision, read, and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The proposed ECFAP method improves both the polishing efficiency and the surface quality. Finally, ECFAP-treated specimens with an optimum voltage of 3 V for 10 min exhibited an average surface roughness of 0.0953 µm.Electrochemical polishing (ECP) is an efficient and low-cost technology for polishing difficult-to-machine materials with complex structures. However, when an environmentally friendly neutral salt solution is used as the polishing electrolyte, a dense passivation film forms on the surface of passive metals, such as titanium alloy, with a serious detrimental effect on the polishing efficiency and surface quality. In this paper, we introduce an ECP method assisted by a high-speed flow of micro-abrasive particles (ECFAP). The contribution of the flowing micro-abrasive particles in the ECP process enables the electrochemical dissolution and abrasive polishing to occur simultaneously on the workpiece surface. The high-speed abrasive particles remove the passivation film formed under ECP, thereby improving the polishing efficiency and quality. We carried out the comparative tests of conventional ECP and the proposed ECFAP on a Ti6Al4V alloy in 10% NaNO Polishing improves the surface quality of machined workpieces, eliminates surface fatigue cracks, reduces friction and wear, significantly improves the working performance and service life of products ,3,4,5,6,3 and NaCl solutions at different concentrations and temperatures. The results showed that a dense passivation film (PF) formed during the electrolysis of the titanium alloy, hindering the electrochemical reactions. To remove the PF and improve the surface quality, Wang et al. [3 solution. The results showed that the PF was removed in a short time at a high current density, producing a well-machined surface. Hryniewicz et al. [ECP is a nontraditional machining technology to improve surface quality by exploiting the different electrochemical dissolution rates at the convex and concave points of a surface. Compared with other polishing technologies, ECP has the advantages of high efficiency and low cost in polishing complex structural parts made up with difficult-to-machine materials. At present, ECP is generally carried out in an acidic solution. Simka et al.  analyzedg et al.  studied z et al. ,27 studiz et al.  proposedTo simplify the design and improve the accessibility of the EMCP grinding tools, in this study we propose an ECP method assisted by a high-speed flow of micro-abrasive particles (ECFAP). This method removes the PF through abrasive polishing by high-speed flowing particles, without grinding tools. The combination of electrochemical dissolution and abrasive polishing by flowing particles significantly improves the efficiency and quality of the ECP with a neutral salt electrolyte. The main purpose of this work is to explore the influence of the high-speed flowing abrasive particles on the polishing efficiency and quality. The polishing mechanism of the ECFAP process was studied using polarization curves as well as electrochemical impedance spectroscopy (EIS), micromorphology, energy-dispersive X-ray spectrometry (EDX), and surface roughness measurements. Finally, comparative ECP and ECFAP experiments were carried out to explore the effect of the high-speed flow of abrasive particles on the polishing quality and efficiency.To solve the problems associated with the PF during conventional ECP, in this study we propose the ECFAP method, whose polishing mechanism is shown in 3 (25 ± 0.5 °C) and the other was covered with an insulating epoxy resin. A saturated calcium electrode and a platinum plate (20 mm × 20 mm × 0.2 mm) were used as a reference and auxiliary electrode, respectively. The measurements were carried out in the frequency range from 100 kHz to 10 MHz, and the amplitude of the sinusoidal signal was 10 mV.Titanium alloys are often used in the manufacturing of key aerospace components but are difficult to machine and exhibit strong passivation during electrochemical machining (ECM). Therefore, the titanium alloy Ti6Al4V (TC4) was selected as substrate to compare the dissolution behaviors of conventional ECP and the proposed ECFAP. Polarization and cyclic voltammetry (CV) curves as well as EIS data of TC4 were obtained using an electrochemical workstation ; a typical three-electrode system was used in the experiment. The working electrode was a TC4 cube with dimensions 10 mm × 10 mm × 10 mm, and the TC4 composition is shown in 3 solution and 500-mesh SiC abrasive particles were mixed in a volume ratio of 9:1. To fully mix the electrolyte and abrasive particles, a slurry stirrer constantly operated in the liquid mixing tank during the experiment. A pump injected the mixed solution at a certain pressure into the fixture. In this work, the workpiece and the cathode tool were cubes with a cross-section of 15 mm × 15 mm. They were held face-to-face in the cube recesses of the fixture, and both had an exposed area of 15 mm × 15 mm in the machining region. In the experiment, no relative motion occurred between workpiece and cathode tool and the machining gap (the distance between cathode tool and workpiece was 2 mm).2, respectively. The parameters of the ECFAP experiments are shown in Because the flow channel structure has a significant effect on the hydrodynamic state of the mixed solution , a contiThe tests were carried out on a surface machined by electrical discharge machining (EDM). The influence of the high-speed flow of abrasive particles on the quality and efficiency of the electrolytic finishing was explored by measuring the surface micromorphology and roughness. Then, based on the polarization curve of TC4 under ECM, ECFAP experiments were carried out under appropriate voltages corresponding to the activation, passivation, and over-passivation regions and the mechanism of the ECFAP process was investigated.A comprehensive analysis of the surface integrity characteristics of machined TC4 alloy samples was then performed, including surface morphology, elemental composition, nanoindentation, 3D profiling, and surface roughness tests. The surface morphology was analyzed by scanning electron microscopy  and secondary electron imaging SEM with an acceleration voltage of 15 kV. Element contents were measured by an EDX spectrometer  in point-scanning mode. The surface mechanical properties of the samples were measured by a nanoindenter . During the measurements, the loading depth was 2 μm and the loading–unloading curve and hardness were recorded. The probe pressing rate during loading was set to 6 nm/s, and the data were recorded every 0.2 s. In addition, 3D profiles and surface roughness were measured with a 3D optical profiler  and a surface finish tester , respectively. The sampling length of the surface roughness was set to 5.6 mm, according to the dimensions of the workpiece.3 solution, as shown in To explore the polarization behavior of TC4, polarization and CV curves were obtained in 10% NaNOThe CV curve of TC4 is shown in 3 solution at 4, 6, and 8 V for 10 min. Then, EIS tests were conducted immediately under each condition, and the Zview software package was used to fit the EIS data. 3 solution; the multiple-peak phase angle plot at 8 V in w is the angular frequency (rad/s), ui is the imaginary unit (ui2 = −1), and n is the dispersion index of the CPE. The latter is related to the surface roughness of the blank or to the uneven distribution of the PF, and its values range between 0 and 1. When n = 0.5, the CPE corresponds to the Warburg impedance, whereas when n = 1, it represents the ideal capacitance; when 0.5 < n < 1, the CPE is intermediate between ideal capacitance and Warburg impedance.To further explore the characteristics of the PF, the surface structure of the matrix material was studied by EIS. The elemental composition of the PF surface was analyzed by EDX, and the passivation surface was measured by nanoindentation tests. Moreover, the impedance of the PF was measured using an electrical equivalent circuit (EEC). To study the effect of the voltage on the PF, the matrix material was passivated rapidly in 10% NaNOχ2 value in SR is the solution resistance of 10% NaNO3, ctR is the polarization resistance of the electrode–solution interface, and filmR is the resistance of the PF. The results show that filmR was 2378, 173,800, and 231,190 Ω cm2 at a potential of 4, 6, and 8 V, respectively, which indicates that increasing the potential within the passivation range increased the resistance and thickness of the PF.The EIS fitting results are shown in 3 solution and passivated at 6 V for 2 min to form a stable PF, and EDX elemental analysis was carried out on the initial and passivated surfaces. In addition, EDX was used to analyze the elemental composition on the PF surface. The workpiece was immersed in 10% NaNOTo further understand the mechanism of PF formation and dissolution by ECFAP, tests with different ECP and flowing abrasive polishing (FAP) combined pretreatments were analyzed by EIS. The specific pretreatment methods are described in The EIS results are shown in filmR values of workpieces 1, 2, 3, and 4 (2, respectively. The comparison of the EIS data for workpieces 1 and 2 shows that the corrosion resistance of the samples decreased after both ECP and FAP. This is attributed to the removal of the PF by the abrasive particles; the same conclusion was reached in the studies published by Yang et al. and Chen et al. [The radius of the capacitive arc is an important indicator of the corrosion resistance, with a larger radius denoting a greater resistance to charge conduction and a higher corrosion resistance . The rad3, and 4  were 113n et al. ,32. SimiIn conclusion, the EIS measurements show that TC4 formed a PF during ECP, which hindered the electrochemical reactions, while the nanoindentation and EDX measurements reveal that the PF consisted of a soft oxide layer. Moreover, the EIS measurements show that the high-speed flow of abrasive particles removed the PF and reduced the impedance of the substrate in ECP.To demonstrate the feasibility of the proposed method, we carried out ECP and ECFAP experiments on a sample surface obtained by EDM. 3 solution remained constant at ca. 0.85 μm. The occurrence of micro-pitting corrosion on the material surface prevented the improvement of the surface quality. Under FAP conditions, the surface roughness decreased slowly to approximately 0.7 μm after 8 min, whereas the surface roughness of the ECFAP-treated sample showed a rapid drop to less than 0.5 μm within 1.5 min. As the ECFAP treatment continued, electrolytic corrosion gradually became dominant, and the surface quality deteriorated rapidly due to micro-pitting corrosion. Therefore, the processing time significantly influences the surface quality achieved with the ECFAP method.We then explored the influence of the flowing abrasive particles on the efficiency of the ECP process. The time evolution of the surface roughness is shown in The dissolution mechanism of the high-speed flow of abrasive particles in the activation, passivation, and over-passivation regions was explored based on the polarization curves. 2; although this value was small, it still indicated the occurrence of a small amount of dissolution.The comparison of the efficiencies of FAP and ECFAP under different voltages in the activation region a reveale3 solution; the abrasive particles also removed the PF. After the latter process, a small amount of electrochemical dissolution occurred at surface protrusions, improving the polishing efficiency of the workpiece surface. After the PF removal by the high-speed abrasive particles, a new PF was immediately formed and prevented excessive dissolution of the matrix material. Therefore, the final machined surface had no pitting corrosion and good surface quality.In the activation region, the high-speed abrasive particles ground the substrate surface and improved its quality, and the matrix continuously generated a soft PF in 10% NaNOIn the over-passivation region, ECP and ECFAP experiments were carried out at voltages under 35 V. The surface microstructure after machining is shown in Based on the results of the ECFAP experiments, it can be concluded that the high-speed flow of abrasive particles was able to uniformly remove the PF and accelerate the dissolution of the substrate material, a phenomenon that could be observed at higher current densities. The processing quality and efficiency were significantly improved by the high-speed flow of abrasive particles. The initial surface was polished to a roughness of Ra = 0.3 μm using abrasive paper. By optimizing the parameters, an ECFAP test was performed at 3 V for 10 min. 3 solution. Under the action of the high-speed flow of abrasive particles, the PF on protrusions of the workpiece surface will be removed, and the electrochemical anodic dissolution reaction will thus be focused on those protrusions. In contrast, the PF on valley regions will be retained and protect the matrix material from corrosion. Therefore, the protrusion sites will dissolve first, flattening the surface of the workpiece.A model illustrating the removal of TC4 matrix material by ECFAP is shown in The material removal models by ECFAP in different voltage ranges corresponding to activation, passivation, and over-passivation are illustrated in This paper presents an ECP method assisted by a high-speed flow of abrasive particles. The combination of electrochemical dissolution and abrasive polishing by the flowing particles significantly improved the efficiency and quality of ECP using a neutral salt electrolyte.Polarization and CV measurements showed that the TC4 surface was passivated in the ECP process. In the passivation region, the matrix material hardly dissolved: nanoindentation and EDX analyses revealed that a soft PF was formed on the surface of the workpiece and hindered electrochemical reactions. Combined with EIS measurements, the results indicated the presence of a high-impedance PF, and a structural model of the TC4 PF and matrix material was obtained. In addition, based on the values of the EIS parameters, it was shown that the high-speed flow of abrasive particles under ECFAP removed the PF and reduced the impedance.The polishing effect of ECFAP at voltages within the activation, passivation, and over-passivation regions was investigated based on the polarization curves of TC4 under ECP. The tests showed that the high-speed flow of abrasive particles accelerated the dissolution of the substrate material in all voltage regions. In the passivation and over-passivation regions, pitting corrosion occurred on the substrate surface as the dissolution rate and voltage increased, preventing the improvement of the surface roughness. At voltages within the activation region, no pitting corrosion occurred on the ECFAP surface and the best polishing results were achieved. Finally, ECFAP-treated specimens at a voltage of 3 V for 10 min exhibited an average surface roughness of 0.0953 µm.


In addition, the ash content for these two types of pellets was well above the standard. A 10 kW domestic biomass boiler was employed for burning the tested pellets. The consumption of analyzed fuels during boiler operation was determined. The concentration of CO, CO2, and NOx in exhaust gases was also examined. The obtained experimental results were compared with the numerical calculations with the use of ANSYS Chemkin-Pro using two mechanisms. The highest concentrations of CO2 and CO were observed during the combustion of sunflower and willow husk pellets, which probably resulted from the highest carbon content and, thus, the highest calorific value when compared to cake and straw pellets. For all analyzed pellets, the value of NO and NO2 concentration was similar and did not exceed 368 ppm and 18 ppm, respectively. The results closest to the experiment were obtained for calculations using the mechanism developed by Glarborg et al. The research carried out in the article shows that out of the four analyzed types of pellets, only sunflower and willow husk pellets can be burned in a domestic boiler adapted to burning wood pellets, which is a cheap alternative to wood pellets.The paper analyzes the suitability of four types of biomass pellets as a fuel for heating purposes. Three types of waste biomass  and one type of biomass grown for energy purposes (willow) were selected. After appropriate preparation, the selected starting materials were subjected to the pelletization process. Selected physical and chemical properties of the studied biomass pellets were determined. All four types of the analyzed pellets met the EN-ISO-17225-2:2014 standard in terms of bulk density, dimensions, as well as nitrogen and moisture content. The highest calorific value was pellets made of sunflower husk (17.27 MJ/m As it is known, the use of biomass is one of the key solutions proposed by the European Commission in order to reduce the dependence on imported fossil fuels and, thus, improve the security of the energy supply in the long term.2 emission balance is zero, as the amount generated during biomass combustion is equivalent to the amount taken up in the photosynthesis process ). Depending on the distance from the burner, the temperature was in the range of 300–800 °C. The temperature within the representative area of the most effective burning varied between 600 °C and 700 °C. During the combustion of each of the four produced pellets, the value of the excess air coefficient was close to 2 (±0.5).2, CO, and NOx) was carried out using the Vario-Plus analyzer  utilizing infrared sensors. The chamber’s temperature was continuously registered at the point of exhaust gas sampling by the gas analyzer. The concentrations of exhaust gases were read every 2 min, on average. The burning experiments were repeated for all four analyzed fuels 3 times and special care was taken to maintain constant boiler operating conditions, including ambient temperature and thermostat temperature setting The obtained experimental research results were compared with the numerical calculation using ANSYS Chemkin-Pro (Ansys Research 2021R1 2021.03 v3). The simplified scheme of the test stand is presented in Continuous chemical analysis of dry exhaust gases ;Turbulent nature of fuel combustion processes;Inadequacies of the existing computational models, especially visible in the simplified mechanisms assumed in CFD simulations.Numerical simulations were performed with the application of the ANSYS Chemkin-Pro software. This software allows the solving of complex problems concerning chemical kinetics of various processes. One of the greatest advantages of the software is that the user can select the chemical mechanism used for the calculations. The use of numerical methods to predict the chemical composition of combustion products encounters several limitations resulting, among others, from:The one developed by Glarborg et al. ,44 contaThe one developed by The CRECK Modeling Group ,46 contaDue to the large number of chemical mechanisms cited in the literature and the difficulty of specifying and selecting the proper mechanism, two mechanisms were used in the preliminary simulations:The obtained results from numerical simulations were reduced by the moisture content, and the shares of individual exhaust components were related to the dry exhaust gas content; thus, they could be compared with the experimental results .For preliminary measurements carried out for willow pellets, simulations were performed. The scheme of the calculation procedure is shown in A—pre-exponential factor;b—temperature exponent;E—activation energy, J/mol;R—universal gas constant = 8314 J/(mol K);T—absolute temperature in the reaction zone, K.As shown in The following boundary conditions were adopted for the calculations: fuel and air streams  as well A Perfectly Stirred Reactor (PSR), commonly referred to as a continuously stirred tank reactor, was used for the calculation. The selection of the chemical reactor was based on the experience of other authors who modeled the combustion and co-combustion processes of biomass ,47,48.For the PSR, the temperature range of 300–750 °C and the residence time of 1–60 s were assumed. The simulation results are shown in 2 and CO shares. For a residence time of 60 s, both mechanisms begin to show greater convergence, especially at temperatures higher than 450 °C. For CO2, at the temperature of 300 °C, there are differences of 0.15% between the discussed mechanisms, while at the temperature of 450 °C—at the level of 0.02%. Similarly, in the case of CO, a difference of 0.16% is observed for the lowest of the considered temperatures. At 450 °C, the differences of CO are at the level of 194 ppm, while at the highest of the analyzed temperatures, the mechanisms show greater convergence and differences at the level of 35 ppm.As shown in the analysis presented in The residence time of the flue gas in the combustion chamber is usually calculated as the ratio of the combustion chamber volume and the flue gas flow rate. The operating volume of the combustion chamber was not precisely known; therefore, the residence time was assumed to be 60 s as the most adequate to the real burning conditions. This is based on our earlier experience and the comparison of the preliminary numerical analysis  with theOn the basis of the conducted preliminary analyses, it was determined that both mechanisms met the expectations of the conducted research.In order to determine the selected physicochemical properties , samples of the analyzed biofuels were ground in a knife mill using a sieve matrix with a mesh size of up to 1 mm.The ash content was determined by burning a 1 g sample of all the studied biomass fuels in a muffle furnace at 250 ± 10 °C for 50 min and then at 550 ± 10 °C for 4 h, according to standard EN ISO 18122:2015. The moisture content was determined based on a 1.00 g sample weight loss after drying at 105 ± 2 °C to a constant weight according to standard EN ISO 18134-3:2015. The calorific values  of the analyzed fuels were determined using a KL-12Mn calorimeter, PRECYZJA-BIT , according to standard EN 14918:2009.For each kind of tested pellet, the contents of carbon [C], hydrogen [H], and nitrogen [N] were determined using an Elemental Analyzer Truspec CHN628 LECO . The contents of the analyzed elements were indicated by means of an infrared absorption detector (C and H) and a thermal conductivity detector (N).3, and, thus, they do not meet the EN ISO-17225-2:2014 standard in this respect. In addition, the ash content for these two types of pellets is well above the mentioned standard. In addition, it can be noticed that the analyzed pellets made of corn straw, sunflower husk, rapeseed cake, and willow do not exceed the standard in terms of dimensions, bulk density, and moisture content.As shown in The requirements concerning the content of carbon and hydrogen in pellets are not specified in the standard. However, there are requirements for nitrogen, chlorine, and sulfur content. According to the standard, the nitrogen content should not exceed 1%. Therefore, the four discussed types of pellets meet the standard in this respect.Based on a literature search ,20,21, i2 are presented in 2 are shown in Numerical calculations were carried out with the application of the ANSYS Chemkin-Pro software based on the experimental conditions fuel consumption, air stream, and elemental composition of pellets. The simulations were carried out for the temperature range observed during combustion of the analyzed pellets of 400–800 °C. For the calculations, the residence time of the reactants in the combustion chamber was assumed to be 60 s as a reference value from the first stage of calculations . The res2 and CO shares , as well as those obtained as a result of calculations using the mechanisms developed by Glarborg (G) and the CRECK Modelling Group (C). When analyzing the concentration of CO, NO, and NO2, we can observe, above all, significant calculation differences between these two mechanisms. As a greater convergence between the experimental results and the calculations is observed for the G mechanism, it can be concluded that this mechanism is closer to the conditions of the experiment. By analyzing the number of reactions adopted in individual mechanisms, it can be assumed that the G mechanism, which contains over 40 times fewer reactions compared to the C mechanism, reflects reality better. Therefore, focus is put on the comparative analysis between the results of the experiment and the calculations resulting from the G mechanism. Therefore, there is a high convergence for the concentrations of CO and NO, but the concentrations measured by the flue gas analyzer are slightly higher than those resulting from the calculations taking the G mechanism into account. However, an inverse dependency can be observed for the concentration of NO2, of which the experiment results in 2–3-fold lower values. These differences probably result from the assumption of a perfect mixing of the reagents used in the calculations, while the concentration from the experiment constitutes an instantaneous value measured at one point (number 6 in 2O), while only NO and NOx concentrations were measured during the experiment. In the comparative analysis, it was assumed that the NO2 share constitutes the difference between NOx and NO. When analyzing the individual types of pellets in terms of exhaust emissions, the highest concentrations of CO2 and CO are observed during the combustion of willow and sunflower husk pellets, which is probably due to their highest carbon content and, thus, higher calorific value compared to rapeseed cake and straw pellets. For all analyzed pellets, the value of NO and NO2 concentration is similar, and does not exceed 368 ppm and 18 ppm, respectively.The comparative analysis of experimental data and results of numerical calculations shows a high conformity. Especially for COIn the times of rising prices and limited availability of fossil fuels, it is of great im-portance to search for new, cheaper solutions, especially in the area of fuels obtained from widely available biomass, including waste biomass. However, not all fuels of this type meet the standards in terms of the appropriate calorific value or ash content. Finding alternatives to fossil fuels is extremely important both economically and ecologically.All four types of the analyzed pellets meet the EN-ISO-17225-2:2014 standard in terms of bulk density, dimensions, as well as nitrogen and moisture content. The ash content for corn straw (7.56%) and rapeseed cake (5.77%) pellets is well above the aforementioned standard, according to which the ash content for this type of fuel should not exceed 3%.2 and CO are observed during the combustion of sunflower and willow husk pellets, which probably results from the highest carbon content and, thus, the highest calorific value when compared to cake and straw pellets.The highest concentrations of COToo high an ash content and, at the same time, low calorific value do not make corn straw and rapeseed cake pellets good fuels, especially one that could be burned in biomass-fired domestic heating boilers.The research carried out in this article shows that, out of the four analyzed types of pellets, only sunflower husk and willow pellets can be combusted in this type of boiler and, at the same time, constitute a cheap alternative to wood pellets.2 concentration (±0.01%) and significant discrepancies in terms of NO and CO concentrations (average of 130 ppm for NO and 180 ppm for CO). The results most similar to the experiment were obtained for the calculations using the mechanism developed by Glarborg et al. The dependence between the discrepancies concerning the results of the two considered mechanisms requires further, detailed analysis.The two mechanisms used in the numerical calculations show high convergence for COThe following conclusions were drawn from the analyses carried out in the article:


Respiratory sounds have been recognized as a possible indicator of behavior and health. Computer analysis of these sounds can indicate characteristic sound changes caused by COVID-19 and can be used for diagnostics of this illness.The aim of the study is to develop 2 fast, remote computer-assisted diagnostic methods for specific acoustic phenomena associated with COVID-19 based on analysis of respiratory sounds.Fast Fourier transform (FFT) was applied for computer analysis of respiratory sound recordings produced by hospital doctors near the mouths of 14 patients with COVID-19 (aged 18-80 years) and 17 healthy volunteers (aged 5-48 years). Recordings for 30 patients and 26 healthy persons , who agreed to be tested at home, were made by the individuals themselves using a mobile telephone; the records were passed for analysis using WhatsApp. For hospitalized patients, the illness was diagnosed using a set of medical methods; for outpatients, polymerase chain reaction (PCR) was used. The sampling rate of the recordings was from 44 to 96 kHz. Unlike usual computer-assisted diagnostic methods for illnesses based on respiratory sound analysis, we proposed to test the high-frequency part of the FFT spectrum (2000-6000 Hz).Comparing the FFT spectra of the respiratory sounds of patients and volunteers, we developed 2 computer-assisted methods of COVID-19 diagnostics and determined numerical healthy-ill criteria. These criteria were independent of gender and age of the tested person.The 2 proposed computer-assisted diagnostic methods, based on the analysis of the respiratory sound FFT spectra of patients and volunteers, allow one to automatically diagnose specific acoustic phenomena associated with COVID-19 with sufficiently high diagnostic values. These methods can be applied to develop noninvasive screening self-testing kits for COVID-19. The World Health Organization (WHO) reported that till October 16, 2021, about 241 million people were infected with the novel coronavirus (COVID-19) worldwide and about 18 million people currently have the disease ), molecular tests, antigen tests, and specific antibodies to SARS-CoV-2) ,7,13. NeThe objectivity of auscultatory diagnostics can be significantly enhanced by using digitized audio signals and computer processing of these signals. Automated adventitious sound detection or classification is a promising solution to overcome the limitations of conventional auscultation and to assist in the monitoring of relevant diseases, such as asthma, chronic obstructive pulmonary disease (COPD), and pneumonia . Olvera-Reyes et al  used a sThe overview concerns the potential for computer audition (CA), that is, the use of speech and sound analysis by artificial intelligence to help in COVID-19 diagnostics . AutomatIt was considered that the acquired breathing sounds can be analyzed using advanced signal processing and in tandem with new deep machine learning and pattern recognition techniques to separate the breathing phases, estimate the lung volume, estimate oxygenation, and further classify the breathing data input into healthy or unhealthy cases . ComputeBrown et al  used theThe purpose of this study is to 2 develop fast, remote methods of diagnostics of specific acoustic phenomena associated with COVID-19 based on computer-assisted analysis of respiratory sounds. The developed methods are based on analysis of fast Fourier transform (FFT) spectra of respiratory sounds recorded near the mouth. We proposed to use a personal computer, a modern mobile telephone, or a smartphone for registration, recording of respiratory sounds, and their analysis. The developed methods can be applied as additional screening methods of COVID-19 diagnostics and as personalized screening self-testing kits for COVID-19. Such self-tests would serve as an early step before further procedures ordered by a doctor . We restricted our work to consideration of breathing sounds (and not cough and voice samples). Lung diseases, such as asthma, COPD, and pneumonia, cause specific changes in the FFT spectra of respiratory sounds in the frequency range from 100 to 2500 Hz, and this range is usually considered during development of computer-assisted diagnostic methods . The clinical examination of the patients and the recording of their respiratory sounds were carried out at Perm Infectious Hospital, and the volunteers’ respiratory sounds were recorded at Perm State Medical University .This study complied with the Declaration of Helsinki , revised in October 2000  and was overseen by the independent ethics committee of Perm State Medical University . Written agreements from the patients and volunteers were obtained.Doctors performed all the recordings, and patients and volunteers were instructed to remain calm and to breathe easily. No special measures to reduce ambient noise were applied. The respiratory sounds of patients were recorded in m4a format using a Honor dua-1 22 smartphone at a distance of 2 cm from the mouth for about 20 s; the sampling rate was 48 kHz. The respiratory sounds of volunteers were recorded near the mouth using a mobile telephone  and a computer-based recording system  . Our comSimultaneous recordings of respiratory sounds in the same point of a patient in different formats were made. The normalized integral characteristics of the FFT spectra used for diagnostics differed by less than 3% for different formats.The beginnings and ends of the recordings made using the smartphone and the mobile telephone contained temporal parts, in which respiratory sounds are not recorded. In these parts, there are short impulses, the amplitudes of which can be much larger than the respiratory sound maximum. The impulses do not reflect the processes in the airways. The applied preliminary processing removed these parts.The 2 proposed diagnostic methods were based on the fact that lung diseases cause changes in the airways and these changes are reflected in the spectra of respiratory sounds. This approach has been applied in the development of computer-assisted methods of diagnostics of various lung diseases -12,20-26We proposed to compare different parts of the FFT spectrum of a patient with COVID-19 in a higher frequency range from 2000 to 6000 Hz. Examples of the amplitude-frequency dependences (spectra) of FFT for a patient with COVID-19 and a healthy volunteer are presented in In a is the frequency of the extremum, A(f) is the harmonic amplitude at frequency f, and Δf is the half of the frequency range, chosen equal to 300 Hz. In the program, the integral is replaced by a sum of harmonic amplitudes with a frequency in the range from (fa – Δf) to (fa + Δf).where fThe criteria under test were formulated as ratios of the integrals of the harmonic amplitudes over various frequency ranges  distribution can be considered as potential healthy-ill criteria:andmin and imax are the harmonic numbers corresponding to the minimal (fmin=2000 Hz) and maximal (fmax=5900 Hz) frequencies, respectively, and fi is the frequency of the i-th harmonic.where iThe MF distribution was also independent of the breathing intensity.1, k2, k3, and k4 are presented in The results of the calculation of potential healthy-ill criteria k4.For the reader’s convenience, N=15 (88.2%) of 17 cases and incorrect in FN=2 (11.8%) cases. For patients with COVID-19, the criterion should be <1; this was observed in TP=11 (78.6%) of 14 cases. COVID-19 was not diagnosed in FP=3 (21.4%) cases.For healthy volunteers, the criterion should be >1; this was correct in Tth patient was close to the boundary value of 1. The second proposed method also had the healthy-ill criterion close to the boundary value . None of them reported that they had other lung diseases. These recordings were made by the persons themselves, who agreed to be tested at home, using a mobile telephone. The sound recordings were passed to us through WhatsApp. The cases of COVID-19 illness were confirmed by PCR tests, and in all cases, the illness was asymptomatic or mild. The proposed method gave the correct diagnosis for 26 (86.7%) of 30 patients and 22 (84.6%) of 26 healthy ones. The PCR tests for persons who were incorrectly diagnosed as ill gave negative results.4 criterion was less than 1 during the illness. The pathological process was characterized by a clearly seen increase in harmonic amplitudes in a wide frequency range. The third-day spectrum corresponded to the most severe condition of the person (according to their message).Several patients made a few recordings during the process of the disease. Development of a spectrum of a patient is presented in n  as well as MFn/MF and MFn/MF2. The best result was obtained for MF4/MF (4/MF)×10−9 is >0.8, the examined person is ill; if it is <0.8, the person is healthy. The second method, like the first one, gave incorrect diagnostics for the sixth patient and overdiagnosis for the fourth volunteer. The respiratory sound recording for this volunteer was characterized by a relatively low level of a signal and high noise. The overdiagnosis for the fourth volunteer could be the result of low quality of the recorded signal.We compared the values of MF and MFr MF4/MF . In thisP=13 (92.8%) of 14 cases and volunteers as healthy in TN=14 (82.3%) of 17 cases. The method misdiagnosed patients as healthy only once, FP=1 (7.2%), and healthy volunteers as sick in FN=3 (17.7%) cases.The second method correctly diagnosed patients as sick in TThe second method applied to the respiratory sounds recorded by persons at home demonstrated a diagnostics effectivity that was close to that of the first method.The results allow us to assess the main characteristics of the 2 proposed methods. Here, for characterization of the proposed methods, we used sensitivity, specificity, and the Youden index. The sensitivity of a method is determined by the formula and its specificity ase=0.786 and Sp=0.882, respectively, and for the second method as  than the first one.Both methods demonstrated close diagnostic characteristics when analyzing respiratory sound recordings made by persons themselves using a mobile telephone at home and submitted to us through WhatsApp. The proposed methods correctly diagnosed 86.7% of patients and 84.6% of healthy ones. These results demonstrate the possible application of the proposed methods for remote diagnostics.Although a relatively low number (due to pandemic limitations) of the examined patients with COVID-19 and healthy volunteers did not allow estimating the method characteristics with high accuracy, the proposed methods correctly diagnose patients with COVID-19 in a wide age range, and the proposed criteria of healthy/ill are independent of the patient’s age, sex, etc, as well as concomitant diseases, such as upper respiratory tract infection, pneumonia, exacerbation of COPD, and bilateral pneumonia .The patient and volunteer groups contained members of various genders and ages (from 5 to 80 years).4 of integrals over various frequency ranges was determined and compared with the boundary value: If k4>1, the examined person is healthy, and if k4<1, the person is ill. The ratio is independent of the recording devices and sampling rate, and as our results showed, the boundary value does not depend on the individual patient characteristics and even on concomitant diseases  sounds, which can be separated into several types . These abnormal sounds are characterized by their durations and specific frequency ranges being below 2500 Hz ,10,12. F4 criterion, which is determined for the high-frequency range of the FFT spectrum, from 4700 to 5900 Hz (the first proposed method).For diagnostics of specific acoustic phenomena associated with COVID-19, we proposed to consider the high-frequency range of respiratory sound FFT spectra. It can be assumed that аn upper respiratory tract injury leads to the appearance of changes in a higher-frequency part of the spectrum; it can be associated with COVID-19 . Severe 1, k2, and k3 criteria can be the result of concomitant diseases, which cause changes in the respiratory sounds in the lower-frequency range [1, k2, and k3 criteria can be a higher sensitivity of the parameters fa and Δf at low frequencies to individual characteristics of patients  and also to fatigue and anxiety.A decrease in the diagnostic value of the kcy range ,10,12. AThe second proposed method of computer-assisted diagnostics of COVID-19 is also based on the consideration of the high-frequency range of the FFT spectrum, from 2000 to 6000 Hz.The high diagnostic accuracy is achieved in both methods due to our offer to compare various parts of the FFT spectrum of a patient (volunteer). This allows us to minimize the influence of the breathing intensity as well as the gender and age dependences of the FFT spectrum.a and Δf for the first method and fmin and fmax for the second one) using machine learning.One of the ways to increase the diagnostic values of the proposed computer-assisted methods is to create a big database and determine the parameters  in the considered frequency range; changes caused by them are between 50 and 2500 Hz .The high-frequency range of the respiratory sound FFT spectrum contains information about the health state of the examined person. The proposed computer-assisted methods based on analysis of this spectrum part can be applied as fast, remote additional screening methods (telemedicine) for specific acoustic phenomena associated with COVID-19. The methods demonstrate sufficiently high diagnostic values. The methods can be a basis for the development of noninvasive screening self-testing kits for COVID-19. To increase the accuracy and reliability of the methods, a big database of respiratory sounds of patients with COVID-19 and volunteers should be created.


Tissue differentiation varies based on patients’ conditions, such as occlusal force and bone properties. Thus, the design of the implants needs to take these conditions into account to improve osseointegration. However, the efficiency of the design procedure is typically not satisfactory and needs to be significantly improved. Thus, a deep learning network (DLN) is proposed in this study. A data-driven DLN consisting of U-net, ANN, and random forest models was implemented. It serves as a surrogate for finite element analysis and the mechano-regulation algorithm. The datasets include the history of tissue differentiation throughout 35 days with various levels of occlusal force and bone properties. The accuracy of day-by-day tissue differentiation prediction in the testing dataset was 82%, and the AUC value of the five tissue phenotypes  was above 0.86, showing a high prediction accuracy. The proposed DLN model showed the robustness for surrogating the complex, time-dependent calculations. The results can serve as a design guideline for dental implants. The bone healing process is difficult to be observed in clinical experiments. In the past, the healing performance of dental implants could only be observed through histomorphologic images  and CT iHowever, to the best of our knowledge, a systematic analysis for the bone healing process subjected to various implants and health conditions of patients, e.g., age, gender, occlusal force, is still absent. Although numerical methods allow for observing step-by-step dynamic changes revealing the underlying features, the major limitation is the demand for rising computing resources, where the calculation of the tissue differentiation process usually takes hours on a standard desktop computer. A typical solution for the above-mentioned problem is to build a neural network (NN) model to substitute and accelerate the cumbersome calculations. Several studies have been dedicated to developing NN models as surrogates for finite element analysis (FEA) ,18,19. HFE data for the deep learning network model are usually input in an image form. This is because the values of the calculated results of each pixel are location-dependent and can be stored in the image matrix. Thus, convolutional neural networks (CNN) were typically adopted as the architecture for the training in the FEA surrogating problem. Ronneberger et al.  proposedIn the current study, we proposed a DLN framework to predict the history of tissue differentiation for the cases with different dental implants and patient ages, genders and occlusal forces. The DLN framework consists of a conditional variational U-Net-based network and ANN model, where the former substitutes FEA to predict strain, fluid velocity and stem cell concentration, and the latter serves as a substitution of the mechano-regulation algorithm to identify the tissue type of each element in the model. The DLN model improves calculation efficiency while maintaining theoretical prediction accuracy. The training and testing data of the DLN includes the tissue differentiation process calculated by FEA throughout 35 differentiated days with 115 various implant geometries  aimed to replace the mechano-regulation algorithm, which classifies the differentiated tissue phenotypes based on the mechanical responses obtained from Network 1. Note that the prediction of ANN architecture is pixel-wise, and the dimensions of the input and output in Network 2 are both 1 × 5. The input of Network 2 includes principal strains I, II, and III, and fluid flow in X and Y directions, while the output is the probability of being classified as each tissue phenotype . Note that the stem cell concentration was not included in the training of Network 2 because it is assumed that the diffusion of the stem cell is independent of the tissue differentiation. On the other hand, the focal loss function  was adopAfter the training of Networks 1 and 2, tissue differentiation around the implant can be predicted. However, it was observed that some unrealistic results may occur, such as two tissue types forming a checkerboard pattern, or a singular element classified as the cell type that is different from the type of most of its surrounding elements. Thus, we further adopted a weak classifier to reinforce the tissue phenotype classification by using a random forest algorithm . FinallyNetwork 1 aims to replace the FE calculations, which can predict the image of the six mechanical responses for the next iteration based on the input images of four material properties and occlusal force. The performance of Network 1 is evaluated by Pearson’s correlation, where the correlation coefficients of the mechanical responses, i.e., principal strains I, II, III, fluid flow in X and Y directions, and stem cell concentration, were 94.2%, 93.0%, 97.6%, 98.0%, 98.2%, and 99.997%, respectively. In addition, we randomly selected 100 predicted tissue differentiation results throughout 35 days in the 180 testing cases and performed the correlation plot to illustrate the performance of Network 1, as shown in Note that the elements of the dental implant were set as not permeable see , and thuNetwork 2 predicted the differentiated tissue phenotype based on the five predicted mechanical responses from Network 1, which aim to surrogate the mechano-regulation algorithm  with different geometries, bone material properties, and occlusal forces, as shown in Next, receiver operating characteristic (ROC) curves and the corresponding area under the curve (AUC) values of day-by-day continuous prediction results were determined to further evaluate the prediction performance of the current DLN, as shown in From the perspective of image analysis in clinical treatment and animal experiments, two important performance indexes are typically used for analyzing the osseointegration between bone and the implant. They are bone area (BA) and bone–implant contact (BIC), where BA is defined as the percentage of the total area of the mature/immature bone elements in the area between all the threads; BIC is defined as the percentage of the total length of the interface between the implant elements and the mature/immature bone elements to the total length of all the threads. Note that the two indexes were obtained from the tissue phenotype distribution on the 35th day predicted by the current DLN, rather than obtained from the direct output of the DLN. To sum up, a DLN model that consists of two networks and a weak classifier (random forest) was proposed to predict the tissue differentiation throughout 35 days around different dental implants in the patient with different ages, genders, and occlusal forces. The first network based on the conditional variational U-Net predicted the six essential mechanical responses. The testing correlation coefficients of the six essential mechanical responses were all higher than 93%. The training and testing datasets both include various implant geometries, bone properties, and occlusal force   and layeTraining and testing dataset of tissue differentiation was generated based on mechano-regulation theory. All the calculations and iterative procedures were implemented by using ANSYS  and MATLAB . The differentiated tissue phenotypes are determined by the biophysical stimulus, which is calculated from principal strains I, II, III, and fluid flow X, Y (see Equation A1) in  in 1], aP1–P26) are shown in P1 and P2. For example, a platform above the first thread was formed when P1 < P2. Based on the literature [P3 is the distance from the top to the first upper thread; P5 is the distance between two upper threads; P7-P11 describe the geometry of the upper threads, as shown in P25 is the number of the upper threads. Next, considering the parameters related to the lower threads, P4 is the distance from the top to the first lower thread; P6 is the distance between two lower threads; P12–16 describe the geometry of the lower threads, as shown in P26 is the number of the lower threads. Finally, P17-P24 represent a curve of a cubic function, which alters the implant body shape, e.g., an implant with a tapered structure. Note that based on the literature [terature , both thThe values of the bone properties for all the categories can be obtained by applying the bone properties ratios. According to the relationship proposed by Carter and Hayes , the YouTissue differentiation was regarded as the short-term bone healing process, where the healing period was defined as the first 35 days after inserting the implant in the current study. Training and testing FE data included the mechanical responses, tissue differentiation history, and the changes in material properties throughout 35 days based on the mechano-regulation algorithm. We randomly selected 900 cases from combinations of 115 implant geometries and 36 types of boundary conditions, serving as the training and testing datasets. The training and testing domain were cropped into 3.2 × 6.4 mm, as shown in The hyperparameters in Networks 1, 2, and the random forest model were optimized by Bayesian optimization. The optimized hyperparameters in Network 1 were the number of filters, filter size, and activation function; those in Network 2 were the node number of each dense layer, the number of dense layers, and the parameters in the focal loss function; those in the random forest model were the estimator (tree numbers) and the max depth (tree depth). The optimizer for both Networks 1 and 2 adopted the Adam optimization algorithm. The loss function of Network 1 consisted of two parts: reconstruction mean absolute error (MAE) and the Kullback–Leibler (KL) divergence:The dataset that consists of 900 cases was randomly split into 80% for training (720 cases) and 20% for testing (180 cases). The tissue differentiation history throughout 35 days for each selected case was included in the training dataset. As shown in In this study, the proposed deep learning network (DLN) framework can provide a rapid engineering design guideline of dental implants by predicting the history of tissue differentiation throughout 35 days around the implant under various bone properties and occlusal forces . The network successfully surrogated the finite element (FE) calculation and mechano-regulation algorithm and significantly increased the calculation efficiency based on the results shown in