The aim of the study was to assess correlations between the lipid profile and glycated hemoglobin in order to define their prognostic value as a criterion for the development and progression of type 2 diabetes mellitus (DM2) in individuals with metabolic syndrome and low body mass.The study included the results of examining 50 patients with metabolic syndrome (group 1), 50 with low body mass index (BMI) (group 2), 50 with DM2 (group 3), and 50 apparently healthy people (control group). Biochemical indices of the lipid profile and glycated hemoglobin in the venous blood were assessed using analyzers Clima MC-15 (Spain), BS-200, and BS-200 E (China).It has been established that correlations of the parameters such as high-density lipoproteins (HDL), low-density lipoproteins (LDL), urea, and creatinine with BMI are expressed statistically more significantly in women in groups 1 and 2 in comparison with group 3, while in men the reverse situation is observed. Besides, correlation of triglyceride levels with BMI is statistically more marked in patients with DM2 than in apparently healthy people being positive in women and negative in men.Thus, HDL, LDL, creatinine, and urea may be diagnostically significant in the assessment of the development and progression of DM2 in men with metabolic syndrome since a strong positive correlation has been found between them and BMI, triglycerides were also found to be significant because a strong negative correlation has been detected between them and BMI.For women with metabolic syndrome, the combination of a weak correlation of BMI with the levels of HDL, LDL, urea, and creatinine and a strong positive correlation with triglycerides may be considered to be a prognostically significant index.New correlation characteristics of biochemical blood indices in DM2 may serve as prognostic criteria for disease development and progression. In adults with diabetes, risk of infarction and stroke increases 2–3 times. In combination with blood flow reduction, neuropathy (nerve damage) of lower extremities increases the probability of appearing ulcers on the legs, their infection, and, ultimately, the necessity of limb amputation. Diabetes is included into the list of the main causes of renal failure, and general risk of death in these people is at least 2 times higher than in individuals of the same age without diabetes , 2.According to WHO prognoses, diabetes may occupy the seventh place among the causes of death in 2030. Rigid control of the glucose level has fallen short of expectations, therefore, there is a strong necessity to control other parameters as well [In this connection, it may be interesting to investigate the changes in the indices of the lipid profile and glycated hemoglobin and their interconnections with the body mass index (BMI) and with metabolic syndrome (MS) in patients with type 2 diabetes mellitus (DM2).Though there is a great number of works devoted to this problem, questions of etiopathogenesis have not been fully studied, therefore, the number of people with MS and diabetes mellitus is steadily growing whereas traditional methods of treatment are not always sufficiently effective. As DM2 occurs not only in individuals with an increased BMI, it was interesting to know how these indices are changing in those with low BMI. We did not find any data on this question in the available literature –6. The iThe aim of the study was to define the presence and assess the correlation dependences between the lipid profile and glycated hemoglobin in individuals with metabolic syndrome and with a low body mass as well as in type 2 diabetes mellitus.The study was carried out at the Department of Pathological Physiology and Department of Therapy and Cardiology of Privolzhsky Research Medical University (Nizhny Novgorod). The study included the results of examining 50 patients with metabolic syndrome (group 1), 50 with a low body mass index (BMI) (group 2), 50 with DM2 (group 3), and 50 apparently healthy people (control group). The diagnoses were established by therapeutists and endocrinologists according to the diagnostic criteria of the International Classification of Diseases (ICD-10). The participants underwent clinical and instrumental examination. Biochemical indices of the lipid profile and glycated hemoglobin were assessed using analyzers Clima MC-15 , BS-200, and BS-200 E .The study complied with the Declaration of Helsinki (2013) and was approved by the Ethics Committee of Privolzhsky Research Medical University. Written informed consent was obtained from every patient.Venous blood was collected from all participants to define the levels of the lipid profile and glycated hemoglobin. Glycated hemoglobin was assessed according to the WHO standards: values up to 5.6% for a normal state, 5.7–6.4% is a high level connected with the risk of diabetes development, 6.4% and higher are values for diabetes mellitus.Identification of glycated hemoglobin has an advantage over the usual blood test for glucose as it makes it possible not only to diagnose the glucose level over a sufficiently long period of time, i.e. about 3 months which corresponds to the erythrocyte lifetime of 90–120 days, but also to trace the dynamics of its changes by finding the average daily levels of glucose in the body over the given period.th century. One of the difficult tasks for studying this syndrome was the choice of diagnostic criteria. Recommendations of the International Diabetes Federation (IDF) issued in 2005 are used most commonly. According to the data of the IDF consensus on MS, the main factors of the syndrome development are abdominal obesity and insulin resistance. In this connection, a patient is said to have MS if abdominal obesity is combined with two of the four factors: 1) blood triglyceride level of more than 1.7 mmol/L; 2) HDL level below 1.3 mmol/L in men and below 1.29 mmol/L in women; 3) arterial pressure over 130/85 mm Hg; fasting blood serum glucose level over 5.6 mmol/L [Metabolic syndrome is a multifactorial complex of pathological changes with insulin resistance lying at its basis. The information about the combination of insulin resistance, arterial hypertension, hyperlipidemia, and obesity appeared as early as the end of the 20Statistical data processing included determination of average values and standard deviations, analysis of data for normal distribution (asymmetry (A) and excess (E)), and was performed using methods of assessing the significance of the results, analysis of variance, detection, and assessment of correlations. The results were processed and analyzed using Microsoft Office (Excel) programs, a package of statistical programs Stada and Statistica v. 7.0, programming language R (RStudio 3.5.3.) and embedded and additional packages for processing and statistical analysis ggplot2, viridis, hrbrthemes.Metabolic syndrome often precedes the development of DM2 and, therefore, represents one of the main risk factors for cardiovascular diseases in modern society. Besides, it is associated with the development of hepatic steatosis, renal function disorder, and a high risk of oncological diseases .Lipid profile and glycated hemoglobin have been investigated in four groups of patients: with MS, body mass deficit, DM2, and control. Correlations between the examined indices have been established and evaluated.The analysis of the results obtained showed that correlations of the parameters such as the levels of high-density lipoproteins (HDL), low-density lipoproteins (LDL), urea, creatinine with BMI were expressed statistically much more significantly in women with MS (group 1). The reverse situation is observed in the men. Besides, the correlation of triglyceride levels with BMI in the patients with DM2 has been established to be expressed stronger than in the healthy persons, it being positive in the women and negative in men.The revealed dependences signified the presence of multidirectional interconnections between the examined indices in all the groups. These interconnections were different for the examined men and women. These differences reflected the changes in the metabolic processes in the body in DM2 and without it and, consequently, may serve as a prognostic criterion for the development of this pathology in different cohorts of people both with MS and low BMI.It has been found that strong positive correlations of LDL, cholesterol, creatinine, urea with BMI were observed in the women without DM2 (groups 1 and 2), whereas these correlations were weaker in the women with DM2 . A stronA different picture was observed for the women with DM2 (group 3). All correlations of the lipid profile with BMI were positive, weakly expressed, while the correlation between triglycerides and BMI was positive and strong. Therefore, the presence of strong correlations in this case may become a prognostic criterion of further DM2 development in these women.Different relationships were found for the men. Correlations of HDL, LDL, urea, and creatinine with BMI were expressed stronger in the men with DM2 than in other groups .The analysis of the gender-differentiated results of correlation of glycated hemoglobin with the levels of BMI, glucose, and the lipid profile  in the patients with DM2 has shown that they were statistically significantly more expressed in the men than in women .Thus, in men with MS and low BMI, it is necessary to pay special attention to the following biochemical indices important for the development and progression of DM2: HDL, LDL, creatinine, and urea as, according to the findings of the investigation, a strong correlation was found between them and BMI, attention should also be paid to triglycerides because a strong negative correlation was estimated between them and BMI.For women with MS and low BMI, a combination of a weak correlation of BMI with HDL, LDL, creatinine, and urea and a strong positive correlation of BMI with triglycerides will be prognostically significant for the development and progression of DM2.The results of the study also showed a multidirectional (opposite) correlation of BMI, cholesterol, HDL, LDL with glycated hemoglobin in men and women that should be taken into consideration when assessing the development of diabetes mellitus.New correlation characteristics of biochemical blood indices in DM2 may serve as prognostic criteria of the disease development and progression.


Investigations are conducted in order to maintain or to improve the selected properties of the group of foundry copper-tin alloys with nickel and titanium additions, at a limited fraction of the critical (deficit) element such as tin. The crystallisation process, as well as changes of the microstructure and selected mechanical properties of the CuSn8 alloy—occurring due to introducing alloying additions—were analysed. Investigations of the macro and microstructure were performed using optical and scanning electron microscopy. Based on the thermal analysis and thermodynamic modelling using the CALPHAD (CALculations of PHAse Diagrams) method, the crystallisation process was analysed. The identification of phases was performed by XRD (X-ray diffraction). In addition, such parameters as tensile strength-UTS, elongation-A and hardness-HBS were tested. Under the influence of the introduced titanium, the columnar crystals are reduced due to the crystallisation of the alloy at the walls of the mould. Precipitations  crystallize first (primary). The intermetallic phases associated with the presence of the alloying elements nickel and titanium are located in the interdendritic regions. In tin bronzes with titanium additions, hardness (HBS) increases, tensile strength (UTS) negligibly decreases, while elongation (A) significantly decreases. In the case of CuSnNi bronze, the addition of 0.2 wt.% Ti increases the hardness and increases ultimate tensile strength (UTS), while reducing the elongation (A). Higher Ti additions increase HBS, slightly decrease the tensile strength, and significantly reduce the elongation. Copper alloys are the most known and researched alloys ,2. Tin bThe authors have already carried out research concerning various alloy additions influencing the properties of bronzes ,31,32,33The main aim of performed studies was the optimisation of alloys based on the Cu-Sn system by means of alloying additions, i.e., nickel and titanium at a decreased tin content (8 wt.%). It was assumed that introductions of alloying additions would influence, maintain, and even improve tin’s bronzes mechanical properties—primarily increasing its hardness (HBS) and ultimate tensile strength (UTS) at a determined ductility ,43,44.The investigations concerning changes caused by titanium additions to tin bronzes were realised in the Laboratory of Non-Ferrous Metals Casting of the Faculty of Foundry Engineering of AGH–University of Science and Technology, Krakow. The influence of titanium additions was analysed with using two base alloys: CuSn8 and CuSn8Ni3. The additives Ni and Ti were selected on the basis of their own experimental research, so as to show the effect at different contents. The selection of the amount of additives was also preceded by an analysis of phase diagrams ,2.Investigations of properties of tin and tin-nickel bronzes were realised by the application of a metal charge prepared from the CuSn10 bronze  , electrolytic nickel and cathodic copper, Cu-ETP (EN 1652) . The Ti addition was introduced into a metal bath at a temperature of 1150–1200 °C. Melts were carried out in the inductive furnace of a medium frequency, in the chamotte-graphite crucible. Bronze CuSn10 was added in the form of cast billets, nickel and cathode copper in the form of cut pieces of cathodes, and titanium in the form of pieces of sheet metal 0.5 mm thick. The entire metal charge was approximately 8 kg. Producer of charge materials: CuSn10-Hutmen LLC, nickel and copper-KGHM Polska Miedź S.A.While performing melts, protective coverings of charcoal were applied on surfaces of a charge and metal bath. Applying charcoal to the surface of a liquid copper alloy reduces the oxygen contamination of the alloy. A deoxidising addition in the form of phosphorous copper CuP8 (0.03 wt.%)  was also introduced to take care of the stable and reproducible conditions of the melt’s production. The melts were poured to metal moulds for solidification. Eight alloys of various chemical compositions, different contents of tin, nickel, titanium and copper, were realised. The remaining metal elements were treated as contaminations.The chemical compositions of alloys obtained according to the planned experiment were determined by the X-ray fluorescence spectrometer with the energy dispersion . Results of the tested chemical composition of individual alloys are given in Metallographic macro- and microstructure observations were carried out by the optical microscopy  and scanning electron microscopy . In addition, elemental analysis in microregions by energy dispersive X-ray spectroscopy  was made. The phase identification was carried out by the X-ray powder diffraction method in Bruker D-8 Discover Advance diffractometer  with a Cu tube. The X-ray powder diffraction scan was made in a range 2θ of 20–120° with a step of 0.02°. The results of powder diffraction are presented for samples with the maximum concentration of alloying elements, since they were the most distinct and characteristic for the analysed group of alloys.The tensile strength UTS and elongation A (number of tests—5), were determined by LabTest ZD20 Labor Tech (V = 10 MPa/s), while Brinell hardness HBS 2.5/62.5 (number of tests-3) measurements were made using the HPO-250 hardness tester .With the use of the thermal-derivative (TDA) analysis, the characteristic thermal effects resulting from phase changes occurring during the crystallisation of the tested Cu-Sn alloys were recorded and determined. For the thermal analysis, the mantle K-type thermoelement (diameter 0.5 mm) was used. Temperature measurements were made by the laboratory multimeter Keysight 34972A , equipped with a 16-channel Reed Multiplexer Module 34902A.Ready alloys were cast into the metal mould in order to obtain castings for further research. On the bases of the TDA curves and thermodynamic modelling using the CALPHAD (CALculation of PHAse Diagrams) software with a packet Thermo-Calc for copper alloys TCCU:TCS Cu-based Alloys Database, investigations of the phase analysis were also made.On the basis of TDA results, temperatures of characteristic changes were determined. The most noticeable influence of alloying elements is observed at the beginning of the crystallisation of the examined alloys. Addition of 3 wt.% Ni makes the melting point to increase by 20 °C in relation to the alloy without this additive. The increasing proportion of titanium addition in both cases successively lowers the melting point. The temperatures T2, T3 are characteristic for the formation of chemical composition-dependent intermetallic phases during crystallisation. The disclosed T4 temperature, taken as the solidus temperature, fluctuates in the range of 751–773 °C for most of the tested alloys, with the exception of the CuSn8Ti2 alloy for which this temperature was 860 °C. Values of temperatures T1–T4 are shown in Changes occurring in the thermal analysis diagrams allow for observing different solidification character of CuSn8 and CuSn8Ni3 alloys with titanium additions. In the CuSn8Ti2 alloy, the additional, newly formed phases, especially the Cu4Ti1 phase, are the result of CALPHAD calculation .− CuSn8Ti2: T3-Cu4Ti1, T5-Cu41Sn11, T6-Cu3Sn,− CuSn8Ni3: T3-CuSn_GAMMA, T4-Cu10Sn3, T5-Cu6Sn5_HT, T6-Cu3Sn,− CuSn8Ni3Ti2: T3-CuSn_GAMMA, Cu4Ti1, T4-Cu10Sn3, T5-Cu6Sn5_HT, T6-Cu3Sn.Both thermal analyses: experimental and the one determined on the basis of thermodynamic modelling by the CALPHAD method, allowed for presenting the crystallisation process of tested alloys . The detThe macrostructure images also indicate the changing nature of the solidifying of CuSn8 alloys . The graThe titanium addition in CuSn8 and CuSn8Ni3 alloys causes narrowing of the skin zone and a significant refinement of equiaxial grains in the central part of the sample. The observed changes result from the influence of titanium in terms of crystallisation . However, this scope of changes requires further detailed research. The influence of the titanium addition also causes changes in the microstructure images . These cThe precipitates related to the presence of alloying additions of nickel and titanium are located in interdendritic regions.6Sn5, Ti2Sn, CuSn3Ti5, Ni2SnTi, NiSnTi, Cu6Sn5).The selected samples of analysed alloys were subjected to investigations by means of the scanning electron microscopy. SEM images of the surfaces of investigated samples are shown in The performed analyses of SEM-EDS  confirmeThe X-ray diffraction tests (XRD) allowed for identifying the crystallised phases, while, on the basis of their correlation with the thermodynamic modelling by the CALPHAD method, it was possible to determine their amounts. The results of analyses for the selected alloys are presented in 6Sn5, Ti2Sn, and CuSn3Ti5. The phase analysis for CuSn8Ni3Ti2 alloy was also indicated at various fractions of intermetallic phases Ni2SnTi, NiSnTi and Cu6Sn5 , elongation (A) and hardness (HBS) are presented in The obtained results of mechanical properties , Table 8The group of Cu-Sn alloys selected for tests as well as the obtained results caused by nickel and titanium additions indicated several interesting changes within crystallisation, optical and scanning metallography and identifications of precipitates and phases, which were tested by means of the scanning microscopy SEM-EDS and XRD.The obtained alloys had variable chemical compositions with respect to their main components and also with respect to applied alloying additions. The thermal analysis of CuSn8Ti and CuSn8Ni3Ti alloys indicates changes of temperatures of individual, characteristic phase transformations. Nickel increases a temperature of the beginning of solidification T1, while the addition of titanium decreases T1 value, especially in alloys with nickel additions. Solidus temperature of the alloys, marked T4, also decreases when nickel and titanium are added. This decrease is more intensive in the case of alloys with nickel.3Sn, Cu4Ti and Cu(Sn) (which is mainly Cu). The chemical composition of Cu4Ti phase: 84.4% copper and 15.6% titanium, while the chemical composition of Cu3Sn phase: 61.7% Cu and 38.3% Sn. An introduction of nickel into this system causes changes in the composition of the Cu3Sn phase for the Cu2(NiSn) phase. The copper fraction falls to 46.6% and one of nickel increases to 15.5%, while the tin fraction remains the same as before (38.3%).By introducing the addition of nickel to CuSn alloys, the solidification range of the stack alloy changes slightly; however, as a result of the increased crystallisation temperature, the casting temperature of these alloys should be higher. Modelling CALPHAD with the TC method allows the analysis of the alloy’s crystallisation process and helps in the TDA analysis of solidification of alloys under real casting crystallisation conditions. The slight differences in the results obtained with both methods are certainly caused by an imperfect adjustment of the crystallisation conditions for theoretical and real research. CALPHAD modelling measurably indicates the specific temperature values of the crystallizing phases and their chemical composition. According to TC (CALPHAD), the equilibrium modelling of the investigated alloys suggests the formation (in an ambient temperature) of the basic three phases: CuInvestigations of macro-grains of alloy samples by means of optical microscopy indicated changes of these grains’ morphology within ingots. Columnar crystals occur from the side of a metal mould (ingot edge). Inside the ingot, equiaxial crystals can be seen. The introduced titanium narrows the zone where equiaxial crystals occur, especially in alloys with nickel. The nickel addition increases slightly the width of equiaxial crystals at a simultaneous refinement of these crystals in the central part of ingots.Microstructural tests revealed the typical structure of CuSn group alloys: solid solution dendrities within grains with marked boundaries. Precipitates of different phases occur on grain boundaries and in dendritic zones.The analysis of the SEM-EDS results indicates variable chemical composition of individual components of the structure. The elements’ distribution map also revealed the highest fraction of copper in matrix. Tin, nickel and titanium occur in the matrix and—in higher amounts—in intermetallic phases.The results of XRD investigations allowed for finding out intermetallic phases of various configurations in the alloys structure from the systems: Cu-Sn-Ti, Ti-Sn, Cu-Sn and Ni-Sn-Ti.The obtained results of OM and SEM confirmed the increased share of intermetallic phases with the introduced addition of titanium, concentrated mainly in the interdendritic spaces, which, together with the addition of nickel, are responsible for the increase in hardness.The summary of the observed changes, concerning solidifications of analysed alloys, constitutes the obtained results of the selected mechanical properties.The mechanical properties present an increase in tensile strength (UTS) and hardness (HBS) and a considerable decrease in ductility. However, the addition of only 0.2 wt.% of Ti to CuSn8Ni3 bronze causes a significant increase in the hardness (over 40%) and a negligible decrease of elongation. The presented studies, apart from providing the cognitive knowledge, indicated the possibility of improving the selected properties.The titanium introduced to the CuSn8 and CuSn8Ni3 alloys affects both the macrograin shaping process and changes the internal structure in the terms of microstructure. The macro changes were confirmed in metallographic studies using a stereoscopic microscope. The images of the surface layer of the solidified ingots in the metal form presented in In the edge zone , one can observe the crystals in the form of elongated lumps arranged along the radius of the ingot. Comparing the surface pictures of the ingots made of CuSn8 alloys a and CuSThe presence of Ti in the CuSn8Ni3 alloy causes more visible changes. The edge zone  is reduced from about 5000 µm to about 2000 µm.It is known that the casting first solidifies at the wall of the metal mould towards the center of the casting , and then the rest of the casting solidifies more evenly (volumetric solidification).Since the introduced titanium reduces the directional solidification area, it means that the presence of titanium in the analysed alloy to some extent leads to the formation of additional nuclei, which contribute to faster solidification of the bulk casting, reducing the effect of faster solidification of the casting from the wall of the metal mould.Obtaining this change in solidification conditions can lead to a more uniform structure of the casting. An additional benefit from the use of titanium was revealed in the conducted research (ingot macrostructure) in terms of the reduction of the macrosized grain size in the equiaxial crystal zone . The grain refinement should also be attributed to the role of a certain part of the titanium in terms of generating additional nucleating agents.However, this area of research requires further experience and analysis.The presence of titanium also induces changes in the image of the microstructure . However, after an in-depth analysis of the created intermetallic phases, the influence of the titanium in the formation of the nuclei for crystallisation requires in-depth research and analysis (which will certainly be the subject of further research).The studies with the use of SEM scanning microscopy  and SEM-The introduced Ti additives show a variable effect on mechanical properties depending on the proportion of the alloy additive used and the type of alloy (with or without nickel).A small amount of Ti (0.2 wt.%) in the CuSn8 alloy slightly reduces UTS and increases HBS while at the same time significantly reducing A. This is due to the grain refining effect of titanium. This amount of titanium can also favor the formation of small size intermetallic phases. These changes cause a significant reduction in ductility. Increasing the addition of Ti favors the formation of more intermetallic phases which result in an increase in hardness.In the case of the CuSn8Ni3 alloy, the presence of nickel with a small addition of Ti (0.2 wt.%) increases the tensile strength  and significantly increases the hardness (127 HBS) while reducing ductility (13.3%).Increased titanium additions up to 0.4 wt.% and more lead to the formation of intermetallic phases, which reduce ductility, increase hardness, and make the alloy brittle; thus, the strength of UTS does not increase, or even slightly decreases. Conducting additional tests with the use of Ti additives may show that the extreme strength with optimal A and HBS parameters for the CuSn8 alloy occurs at the Ti content in the range of 0 to 0.2 wt.%.The performed investigations concerning influences of nickel and titanium additions to CuSn8 tin bronze allowed for observing several changes within the crystallisation, macro- and microstructures, SEM-EDS, XRD results and selected mechanical properties. Experimental data were supplemented by the results of thermodynamic modelling performed by means of the CALPHAD method. The results of investigations were correlated and verified.The titanium addition to CuSn8 and CuSn8Ni3 alloys causes the narrowing of the edge zone  and a significant refinement of equiaxial grains in the central part of the sample.Titanium additions show more intense influence on the change of HBS, A and UTS. The addition of Ti in the amount of 0.2 wt.% increases the hardness (HBS) from 89 to 127, increases ultimate tensile strength (UTS) from 358 MPa to 429 MPa, while it reduces the elongation (A) from 63% to 13%. Higher Ti additions increase HBS and stabilize UTS at the level of 370–380 MPa while reducing the A elongation to the range of 1–4%.The optimal content of Ti in tin bronze in a Ni system is 0.2%. With this content, Ti has a modifying effect: it refines the microstructure and hardens the alloy (increasing in HBS), increasing the tensile (UTS) at the expense of reducing the elongation (A).Based on the research, the following conclusions can be drawn:


The mitigation effects of park green space on Urban Heat Island (UHI) have been extensively documented. However, the relative effects of the configuration of park components on land surface temperature (LST) inside the park and indicators  surrounding the park is largely unknown. Therefore, the main objective of this study is to explore the quantitative impacts of configuration and morphology features under different urban park scales on the cooling effect. In this study, based on Landsat-8 OLI/TIRS images on 3 August 2015 and 16 August 2020 during summer daytime, the LSTs of Shanghai City were retrieved by atmospheric correction method. Then, the relationships of park landscape features with LSTs in the park and typical indicators representing cooling efficiency of 24 parks on different grades were analyzed. The results showed that the average temperature in urban parks was, respectively, 1.46 °C and 1.66 °C lower than that in the main city of Shanghai in 2015 and 2020, suggesting that urban parks form cold islands in the city. The landscape metrics of park area (PA), park perimeter (PP), green area (GA) and water area (WA), were key characteristics that strong negatively affect the internal park LSTs. However, the park perimeter-to-area ratio (PPAR) had a significant positive power correlation with the park LSTs. Buffer zone analysis showed that LST cools down by about 0.67 °C when the distance from the park increases by 100 m. The Maximum Cooling Distance (MCD) for 2015 and 2020 had a significant correlation with PA, PC, PPAR, GA and WA, and increased sharply within the park area of 20 ha. However, the medium park group had the largest Maximum Cooling Intensity (MCI) in both periods, followed by the small park group. There could be a trade-off relationship between the MCD and MCI in urban parks, which is worth pondering to research. This study could be of great significance for planning and constructing park landscapes, alleviating Urban Heat Island effect and improving urban livability. According to the report from Intergovernmental Panel Climate Change (IPCC), over the past century global warming has been recognized as a profound universal problem and the increase is likely to happen faster than was predicted ,2. FurthIntensive studies have been conducted to assess the UHI effect for hundreds of cities around the world ,12,13. LSeveral previous studies have found that the average LST of urban parks was 1–2 °C, and sometimes even 4–8 °C, cooler than their urban surroundings, generating a “cooling island” ,28,29. TShanghai is a megacity with a subtropical monsoon climate that has undergone rapid urbanization in the last few decades. The total population has reached 24.87 million in 2021 , and theIn view of this, based on landsat-8 OLI/TIRS remote sensing images of Shanghai in 2015 and 2020, land surface temperature was retrieved by atmospheric correction method to investigate the mitigation impacts of urban park landscapes on the thermal environment. Additionally, a total of 24 parks were selected in Shanghai City, China. The purposes of this research are to explore: (1) What kind of correlations exist between landscape composition and patch morphology of parks with LST and which are the key influencing indicators; (2) How about the Maximum Cooling Distances (MCD) and maximum cooling intensities (MCI) of parks on four different park scales? (3) Are there significant differences in heat release effects among parks of different scales and does the significance change with the development of urbanization? The results could provide some decision-making bases and references for planning and constructing Shanghai parks and alleviating Urban Heat Island effect in a hot summer, humid, subtropical large metropolis.The paper is organized as follows. Following the description of the study area, the methodology of LST retrieval algorithm, extraction of park landscape features, buffer zone setting and data processing flow are presented in 2, which is located in the central point of the north and south coast of China, where the Yangtze River and the Huangpu River meet the sea , covering an area of 6340.5 km the sea . It is ps 8.6 m2 . Since ts 8.6 m2 . CurrentIn the study, 24 parks in Shanghai, which have been completed and not significantly altered in the last 15 years, were selected as objects. According to http://www.gscloud.cn/search (accessed on 15 May 2021)), and imported into ENVI 5.2 software for processing to obtain two periods of land surface temperature data in Shanghai. The maximum arbitrary land cloud cover threshold adopted in this study to ensure image reliability was less than 0.28%. Landsat-8 was successfully launched by NASA on February 11, 2013. It provides global coverage every 16 days and carries two sensors—OLI Land Imager and TIRS Thermal Infrared Sensor. Landsat-8 is basically consistent with Landsat 1-7 in terms of spatial resolution and spectral characteristics. The satellite has a total of 11 bands. Band 1–7 and 9–11 have a spatial resolution of 30 m, and band 8 is a panchromatic band with a resolution of 15 m (https://earthobservatory.nasa.gov/ (accessed on 26 August 2021)).The remote sensing data used in this study come from two periods of Landsat-8 OLI/TIRS satellite image data, two scenes of data at about 10:24 a.m. (UTC/GMT+08:00) on 3 August 2015  and two scenes of data at about 10:25 a.m. on 16 August 2020 , which are obtained from Geospatial Data Cloud platform of Computer Network Information Center, Chinese Academy of Sciences (−2·sr−1·µm−1), −2·sr−1·µm−1), A previous study result has shown that the accuracy of retrieved LST based on atmospheric profile measurement is 0.6 °C, by the radiative transfer equation . TherefoB) was applied, and for K2, a constant of 1321.08 K (Kelvin) was applied [For the number 10 band  applied . The val applied .ENVI 5.2 software was first applied to interpret Landsat-8 OLI/TIRS images to obtain the land surface temperature of Shanghai in two periods. The experimental procedure for retrieving LST is shown in https://www.ncei.noaa.gov/maps/daily/ (accessed on 10 December 2021)). The comparison between retrieved LSTs and the data from meteorological stations are shown in For result validation, the multi-point verification method in In the study, natural breaks (Jenks) were taken as the temperature division method. Natural Breaks classes are based on natural groupings inherent in the data. Class breaks are identified that best group similar values and that maximize the differences between classes . The feaThe cooling effect of parks on surrounding thermal environment was analyzed from the aspects of park plaque morphology and landscape composition in the study. Landscape composition represents the size of different landscape types in the park. Plaque morphology is also known as landscape shape indicator, which usually calculates the deviation between a patch shape and a circle or square with the same area to measure the complexity of its shape. The selected indicators of quantitative analysis of park landscape are shown in Specifically, the vector maps of 24 parks, water systems, green spaces and road networks in the study area were precisely extracted from Amap by Python crawler module. Then, the basic metrics of the parks, such as the area and perimeter of parks, green spaces and water bodies were calculated by the “computational geometry” tool of the attribute table in each vector graph through ArcGIS 10.2 software. Subsequently, the indices of proportion of impermeable layers (PIL), park perimeter-to-area ratio (PPAR) and park fractal dimension (PFD), were calculated by “Field Calculator” tool based on the above attribute table, according to the formulas in The method of buffer zone is used to explore the cooling range and intensity of the park to its surrounding environment . As the The cooling effect of a park on LST can be measured in several ways . TheoretAnother indicator is the Maximum Cooling Distance (MCD) which was defined as the largest distance where the Maximum Cooling Intensity (MCI) occurs. The maps of buffer analysis were produced using GIS software Arcmap 10.2 .First, Pearson’s correlation analysis was utilized to assess the relationship between the mean LSTs inside and outside of the parks and each park landscape metrics. Subsequently, one way analysis of variance (ANOVA) was used to explore the significant differences between the cooling effects of different levels of parks on the surrounding thermal environment. The statistical analyses were conducted by SPSS 18.0 software. Additionally, SigmaPlot 13.0 was used as a supplementary statistical regression analysis and for mapping.The Landsat-8 OLI/TIRS images in 2015 and 2020 were interpreted to obtain the results of land surface temperature in Shanghai  by atmosIn order to further compare the differences in LST and cooling capacity among these parks, the LST of the 24 parks and MCI in 2015 and 2020 are shown in r = −0.716, p < 0.01), and also with that in 2020 . (2) The park perimeter had a significant negative power correlation with the mean LST within the parks in 2015  and 2020 . (3) The park perimeter-to-area ratio had a significant positive power correlation with the mean LST within the parks in 2015 , and also in 2020 . (4) The park fractal dimension exhibited an insignificant positive polynomial correlation with the mean LST within the parks in 2015  and 2020 ; the correlation is not significant. (5) There was a significant negative exponential correlation of the green area to the mean LST within the parks in 2015  and 2020 . (6) The water area showed a significant negative polynomial correlation with the mean LST within the parks in 2015  and with that of 2020 . (7) There was an insignificant negative polynomial correlation of the proportion of impermeable layers with the mean LST within the parks in 2015 , however, there was a significant positive polynomial correlation with that of 2020 .To explore the quantitative relationship between the park landscape features and the mean land surface temperature within the parks, the quantitative indicators, such as park area, park perimeter, areas of different landscape elements and other metrics, were selected to analyze the correlation with the mean LST within the parks . AdditioThe above correlation analysis shows that PA, PP, GA, and WA are important characteristics that negatively affect the internal LST of the park. However, the more complex the shape of the park (PPAR), the higher LST inside the parks.The size and landscape composition of the public parks have an impact on the Maximum Cooling Distance and the Maximum Cooling Intensity. In the study, the buffer zones of the 24 parks were established at an interval of 100 m, with 1.5 times of the width of every park, after excluding interference space such as water bodies and impermeable layers of large size, as the area of buffer zones .R2 > 0.54) between cooling distances and cooling intensities for the 24 urban parks in Shanghai. In 2015, the MCD exhibited large variations from 197.30 m recorded in Shangnan Park to 1041.71 m observed in Binjiang Forest Park, with a difference of 844.41 m. While the MCI was largest in Jingnan Park and smallest in Zhongshan Park, with a difference of 2.98 °C. In 2020, the MCD was also largest in Binjiang Forest Park at 1016.19 m and smallest in Gushu Park at 201.60 m, with a difference of 814.59 m; the MCI was greatest in Gushu Park and lowest in Jing’an Park, with a difference of 5.92 °C. Notably, the Gushu Park had the smallest MCD but the strongest MCI.Two indicators of Maximum Cooling Distance (MCD) and Maximum Cooling Intensity (MCI) were devised to measure the park cooling effects on surrounding thermal environment. The Maximum Cooling Distances and the maximum cooling intensities of the 24 parks in 2015 and 2020  have beeThen, the correlation analysis  of park To further explore the impact of the park on the surrounding thermal environment, the additional study was conducted in six super large parks (>50 ha), five large parks (10–50 ha), seven medium parks (5–10 ha) and six small parks (<4 ha), in terms of the relationships between park size group and the two cooling effect indicators of Maximum Cooling Distance (MCD) and Maximum Cooling Intensity (MCI). The mean MCD of different park groups in both 2015 and 2020 decreased with park class, while there was no significant linear correlation between the mean MCI and park class in 2015 and 2020, with the medium park group having the largest cooling intensity in both two periods, followed by the small park group. It was also evident that the difference between the mean MCD of different park groups in 2015 and in 2020 was generally small, while the mean MCI of different park groups in 2020 was significantly higher than that in 2015 .Then, analysis of variance (ANOVA) on the mean MCD and MCI at different park classes was further performed. According to the test of homogeneity of variances by SPSS, the significance values (Sig.) of MCD and MCI of two periods (2015 and 2020) were greater than 0.05, which meant that, the variance meets the requirement of homogeneity, after which the analysis of variance (ANOVA) could be performed. Referring to ANOVA , the sigHowever, as the ANOVA was only able to determine whether the control variables had a significant effect on the observed variables, the next step was to conduct a multiple comparison test using the Least Significant Difference (LSD) method to further determine the exact degree of variation in MCD across the different park groups. As can be seen from the results , with coTo further assess the effects of the potential differences between the groups, the landscape metrics data were also applied to the one-way ANOVA . The sigAs an important part of the urban landscape, the park landscape not only provides recreational areas for the surrounding residents, but also to a certain extent regulates the regional climate. The cooling effect of green spaces inside the urban park is a phenomenon that has been widely studied and validated in various regions and cities ,42,61. Ir = 0.63, p < 0.01). Additionally, the greater the PPAR, the relatively more complex the shape of the park, the easier it is to exchange material energy within the park, and the higher the mean LST of the park. However, Zhu et al. (2021) [p < 0.01), indicating that parks with irregular shapes could have lower LSTs. This might be attributable to the differences in the range of PPAR of the parks and different climate backgrounds.This study also found that the park’s patch morphology and configuration characteristics had an impact on the thermal environment of the park. The negative relationship of mean LST of two periods to park area suggests that the LST of a park decreases with increasing park area, as well as the park perimeter. The park perimeter-to-area ratio (PPAR) had a significant positive correlation with the mean park LST (. (2021)  found thFrom the perspective of the park’s landscape composition, the negative exponential relationship of mean LST in two periods to green area suggests that the mean LST of the park decreases as the green area increases. The results of the exponential fit of the mean LST to the green area for both periods are approximately linear, and the calculation shows that for every 50-ha increase in the green space area within the park in 2015, the average park temperature decreased by approximately 0.63 °C, and for every 50-ha increase in the green space area within the park in 2020, the average park temperature decreased by approximately 0.66 °C. Therefore, when planning the internal landscape composition of urban parks, the size of the green space area should be fully considered and the green space area inside the parks should be increased as much as possible. This is because vegetation can reduce the LST through evapotranspiration and shadows, which has been proven by several studies ,41,50.In addition to this, the water area within the park also plays an important role in reducing the mean LST. The high specific heat capacity of the water body and the fact that evaporation from the water body can absorb some of the heat from the air results in the mean LST of the park decreasing as the water area increases . The effThe scale of any cooling effect beyond the boundary of the green area is particularly important for the likely public health consequences of park greening, as park green space may not be directly accessible to all who might benefit during high temperatures . TherefoR2 = 0.70) and 2020 (R2 = 0.67) of park increased logarithmically and sharply within the park area of 20 ha but eventually reached an asymptote. After the park area exceeded the threshold (about 20–40 ha), the cooling distance tends to be gentle with the increase in the park area. Combined with the results of the MCI of the park groups, the cooling intensity of medium- (4–10 ha) and small-scale parks (<4 ha) is evidently higher than that of the super large and large group . The smaller the PPAR, the simpler the park shape, and the more pronounced the cooling effect distance of the park on the surrounding environment. When planning and building urban parks it is necessary to take into account controlling the park PPAR from 0 to 100 to achieve a better cooling effect of park. Analyzed in terms of the park’s landscape composition, MCD of the park increased logarithmically with park green area and linearly with the park’s water area. According to the fitting results of the two periods  in 2015  has been widely used to describe the cooling effect of green spaces on Urban Heat Islands ,25,55. WAccording to available studies, the intensity of cold islands in the park varies during the day and night ,45, as wUnderstanding the effects of structure and configuration characteristics in park landscape on inside-park LST and cooling efficiency in the buffer zone is important for designing effective strategies to mitigate the amplitude of UHI. In this study, Landsat-8 OLI/TIRS images in hot-summer daytime of 2015 and 2020 representing the rapid urbanization process were interpreted, from which the LSTs were retrieved. Based on that, the relationships between park landscape features with LSTs inside the park and two cooling efficiency indicators representing change in their surrounding thermal environment were studied. We found that the average LST of urban parks was 31.68 °C in 2015 and 33.42 °C in 2020, which was 1.46 and 1.66 °C lower than that of the main urban area of Shanghai, respectively. Therefore, public parks have been performing the service functions of regulating the local thermal environment of the city. For the two indicators of MCD and MCI, the MCD results exhibited large variations ranging from 197.30 m to 1041.71 m and MCI ranges from 0.10 °C to 6.02 °C in 24 parks. The cooling distance and intensity of most parks in the study were concentrated within 600 m and 3 °C.In terms of the park’s plaque morphology and configuration, the landscape metrics of PA, PP, GA and WA, were important characteristics that negatively affected the internal LST of the parks. However, the park PPAR had a significant positive power correlation with the park LST data. Subsequently, the MCD for 2015 and 2020 had a significant correlation with PA, PC, PPAR, GA and WA, while the MCI of two periods had no significant correlation with any of the seven park landscape metrics. Not surprisingly, larger parks had a longer cooling distance and the MCD increased logarithmically and sharply within the park area of 20 ha. However, the medium park group had the largest cooling intensity in both periods, followed by the small park group. Therefore, the cooling intensity of medium and small parks with less than 10 hectares should be fully utilized, especially in metropolises such as Shanghai with expensive space. This result also indicated that the more complex the shape of the park boundary, the smaller the cooling distance but the stronger the cooling intensity. Therefore, whether there is a trade-off relationship between the Maximum Cooling Distance and intensity of urban parks is worth pondering and continuing to research. Additionally, the original water systems should be included in or adjacent to parks as far as possible, so that the cooling effects of both can be superimposed on each other to produce a stronger cooling effect. The limitation of this paper is that the seasonal and diurnal changes in LST were not studied. At the same time, extracting the characteristics of the park combined with higher resolution images should be considered in the future. For future research we will also carry out multi-scale and multi-region comparison studies to advance our understanding of the trade-off relationship between the cooling distance and intensity of urban parks in order to maximizing the cooling effects.


The study of spectra of internal friction  Recently, a large number of studies aimed at the study of rheological, strength and physical–mechanical properties of PE and polymer composite materials derived from it have been conducted ,2,3,4. AHowever, early investigations of relaxation processes in amorphous-crystalline polyethylene ,25, carrrum λ=fT ,27,28,29rum λ=fT  that throbserved ,25 if soThe aim of the present work is more detailed investigation of local dissipative processes found on PE internal friction spectra, corresponding to these dissipative processes, anomalous phenomena in temperature dependencies of frequency of free damping oscillatory process, excited in PE samples of different crystallinity degree, with and without filler, monomodal and bimodal.Studies of spectra of internal friction Obtaining the temperature dependencies of the frequency A theoretical analysis of the relationship between the anomalous change in the frequency lculated .Identification of the internal friction mechanism for each local dissipative loss peak exhibited on the internal friction spectrum.In order to achieve this goal, the following objectives were pursued:Polyethylene pellets of the following grades were taken as samples for the study: HDPE 277-73 ; BorSafe HE3490-IM ; CRP100 Hostalen ; Stavrolen PE4PP-25B . Carbon black (carbon black) 2 ± 0.5 wt% was used as a light stabilizer. The main characteristics of the studied PE are given in HDPE 277-73 and Stavrolen PE4PPP-25B were synthesized by gas-phase low-pressure ethylene polymerization on complex metal-bound catalysts (using Unipol technology). Carbide technology, referred to as Unipol, is the most popular technology in the world ). HE3490Hostalen suspension polymerization is carried out in two reactors operating in parallel or in series. Switching from one reactor to cascade made it possible to produce high quality single and bimodal polyethylene with any molecular weight distribution using the same catalyst. Polymerization is carried out in a solvent, such as n-hexane, over a highly reactive Ziegler catalyst. At the end of the process, it is not necessary to deactivate the catalyst and extract it from the polymer because the concentration of residual catalyst in the polymer is very low. To obtain a unimodal product, the catalyst, solvent, monomer and hydrogen are introduced into reactors 1, 2 where polymerization takes place. To obtain bimodal grades, the catalyst is introduced only in the first reactor 1; the second stage of polymerization proceeds under conditions different from those of the first reactor. In the second reactor 2 ethylene, butene and additional amount of solvent are introduced. Process conditions are continuously controlled, which provides very high quality polyethylene .The degree of crystallinity of the polyethylenes under study was determined by differential scanning calorimetry on a DSC Q100 unit of Intertech Corporation (USA) at a rate of 5 °C/min at an argon current of 50 mL/min. Typical DSC curves are shown in The observed peaks in the thermograms correspond to endothermic melting processes of the PE crystalline phase and are in the range. The degree of crystallinity of relation .(1)α=ΔH93 kJ/kg ,36,37.T = 180 PE samples in the form of plates of rectangular cross-section with thickness of 1 mm, length of 65 mm, width of 5 mm were obtained by pressing in a closed-type mold at temperature pendulum . Figure The technique of obtaining spectra of internal friction pendulum  and subjpendulum b on vibrN is a number of periods of oscillatory process from the 1-st, where the amplitude is equal N-th, where the amplitude is equal to As a result of impulse action, the investigated sample makes damped torsional oscillations in the ium φt=0 c. At theSince the controlled parameter of the transient oscillatory process from the excited nonequilibrium state to the equilibrium state is the logarithmic decrement The temperature range of the experiment was from −150 The stresses in the cross-section of the sample are distributed as follows a,b: on tfriction  are satiCalculation of the error of these measurements on the maximum values of the stresses The structural and morphological characteristics of polyolefins were studied by transmission electron microscopy. The outer surface of the samples was used as an object of study, which was subjected to etching in high-frequency oxygen plasma to reveal their supramolecular structure. Oxygen pressure in the etching area was 0.03 mm Hg, electron energy—2–3 eV, etching time—not more than 15 min, generator power—100 W, frequency—10 MHz. The morphology of etched surfaces was examined by one-step carbon-platinum replicas using transmission electron microscope Philips EM301  at accelerating voltage of 80 keV.i of these subpeaks does not depend on the degree of crystallinity, but is related to configuration factors determined by polyethylene synthesis and amounts to 5–6 subpeaks. Each i-subspike characterizes the mobility of a specific structural-kinetic unit within an amorphous interfacial layer. As a result of mathematical processing of the experimental peak, it was found that these local subpeaks appear at different temperatures, which are included in the general temperature interval of the whole As a result of mathematical processing , the obtThe morphological pictures of PE supramolecular organization obtained by us, presented in Two temperature regions of the most intense local dissipative processes  for each of the local dissipative processes detected on the internal friction spectrum;Determine the mechanism of internal friction of a given local dissipative process located in the same temperature region of research by the magnitude of shear modulus defect Calculate the real temperature decrease of the shear modulus The obtained experimental temperature dependencies of the frequency As follows from the experimental spectra of internal friction as well The ses peak a,b,e,f. tures Ih  should hT for PE c,d,g,h. e losses . All othThe main attention in this paper is paid to the The solution of this differential equation for the damped oscillatory process (taking into account that the shear modulus It follows from relation (6) that the current change in temperature The activation energy of this process is determined from the Arrhenius dependence of relaxation time Obtained, according to the above formulas, physical–mechanical and physical–chemical characteristics for the dissipative loss process he table .G and the frequency G is shear modulus of the material of the investigated sample; I is polar moment of inertia of additional pole tips of the torsion oscillation excitation system, whose axis coincides with the longitudinal axis of the sample; l is length of the investigated sample. If in the first approximation, the temperature changes of moments of inertia of the vibrating system of the device can be neglected, then the relation (11) can be represented in the form: In order to determine the mechanism of internal friction, for each of the dissipative processes detected on the spectrum s sample . Taking s sample . In thisG is a function of temperature, i.e., G by However, it was found experimentally that the shear modulus  by 2÷4%   is given in Calculations of temperature changes of the shear modulus Calculation of modulus defects echanism . Figure The analysis of the obtained dependencies shows the generality of the change in the modulus defect in the On spectra of internal friction three (the fourth-Calculation of modulus defects The analysis of the obtained dependencies shows the generality of the modulus defect change in the area of crystallinity degree of about 45%. This qualitative generality is determined by the fact that, independently of Splitting A methodology for the quantitative calculation of the temperature dependence of the shear modulus in a wide temperature range in the regime of a freely damped oscillatory process excited in the polymer sample under study taking into account the local temperature defects of the shear modulus caused by dissipative losses introduced by each dissipative process manifested on the spectrum of


Overall CO2 resulted in a decrease in flame temperature whether on the fuel side or on the oxidizer side, with the negative effect being more obvious on the latter side. The prominent effects of CO2 on the flame temperature were derived from its thermal properties on the fuel side and its radiative properties on the oxidizer side. The results also highlighted the differences in the four effects of CO2 on the position of the flame front on different sides. In addition, an analysis of OH and H radicals and the heat release rate of the main reactions illustrated how CO2 affects the flame temperature.The effects  of CO X emissions. In recent decades, various low-nitrogen natural gas combustion technologies have been proposed to mitigate NOX emissions, among which the most widely used is the exhaust gas recirculation technique (EGR), which mixes an additional diluent  in the unburned gas mixture or in the oxidizer, thereby reducing gas temperature and NOx formation [2 is usually selected as the diluent for diluted combustion [Natural gas is a relatively clean fuel with the potential to replace traditional coal fuel; it has advantages in adjusting energy structure and controlling pollution control, as well as effectively improving the fuel combustion efficiency . Unfortunt CO, CO, and H2Oormation . Therefombustion ,4,5,6,7.2 dilution on different fuels. Xu et al. [2 replacement of N2 in air on the structure and shape of laminar coflow syngas, with the results showing that CO2 addition to the oxidizer decreased the flame temperature, thereby increasing the flame height and radius. Shih et al. [2, H2O, and N2 additions to a one-dimensional counterflow diffusion flame composed of a H2/CO synthetic mixture. The above three dilutants were added to the fuel side. CO2 dilution showed the greatest effect in terms of a decrease in flame temperature compared to the other two dilutants, and the large drop in flame temperature resulted from a combined effect of flame radiation and chemical kinetics. Fotache et al. [4 diluted with N2 and CO2 in a counterflow ignition facility, with the results showing that the ignition temperature in CH4/N2 was lower than that in CH4/CO2, which was mainly attributed to the higher heat capacity of CO2 compared to N2. Galmiche et al. [2, H2O, and N2) on the laminar burning velocities of premixed methane/air combustion through experiments and numerical simulations, while they also analyzed the kinetic and thermal effects of CO2 on the laminar burning velocities. The authors proposed an explicit correlation between the heat capacity of the diluent and the laminar burning velocity as a function of the heat capacity possessing a predominant effect on the laminar flame. Jithin et al. [2 dilution on the laminar burning velocity. Hu et al. [2 dilution, the dilution effect had a dominant effect on the laminar burning velocity. The chemical effect of CO2 on the laminar flame speeds of O2/CH4 mixtures was numerically studied in a range of oxygen concentrations and equivalence ratios by Hu et al. [2. Yang et al. [4/O2 diffusion flames diluted with CO2. Both Gascoin et al. [2 dilutant on NOX emissions in a methane flame. The former authors numerically investigated the quantitative thermal effects of CO2, by replacing N2 on the oxidizer side, on NOx formation in a counterflow diffusion flame configuration at atmospheric pressure. The latter authors studied the effect of CO2 on NOX emission in one-dimensional premixed freely propagating flames. Both sets of results showed a significant reduction in NO emissions due to the CO2 dilutant. Wang et al. carried out a numerical study on the radiation reabsorption of CO2 on NO formation in CH4/air counterflow diffusion flames [2 on soot or NOX emissions in different fuels. Moreover, some researchers studying CO2 dilution combustion focused on the influence of CO2 on other characteristics of the gas flame, such as the adiabatic flame temperature (AFT) [2 intermediate formation [Several researchers have conducted numerous studies on the effect of COu et al.  conducteh et al. ,9 carriee et al.  and Jia e et al.  studied e et al.  investign et al.  and Xie n et al.  also caru et al.  conducteg et al.  obtainedn et al.  and Ren n et al.  investign flames  and premn flames . Variousn flames ,22,23,24re (AFT) ,25, extire (AFT) ,26,27,28re (AFT) ,31,32,33ormation ,35, and ormation  using va2 dilution only focused on the synergistic effects of CO2 on the flame structure, flame characteristic parameters, and NOX emissions in a premixed flame or diffusion flame. Knowledge of the effects of CO2 dilution on the flame can be categorized into four aspects, chemical effect, thermal effect, transport effect, and radiative effect, due to the special properties of CO2. However, few studies [2, especially with respect to the diffusion flame. In this regard, CO2 can not only dilute the oxidizer side [2 dilution of the oxidizer and fuel sides as a function of these four effects on the diffusion flame are still lacking. Moreover, far too little attention has been paid to the isolated effects of these four properties of CO2 dilution on the oxidizer and fuel sides. Previous studies [2 dilutant can reduce the flame temperature; however, the authors did not demonstrate how the CO2 reduces the flame temperature. The above review highlights the importance and significance of the current research. Exploring the various uncoupled effects of CO2 provides a theoretical basis for in-depth exploration of the overall nature effect of CO2. Determining the uncoupled effects of CO2 provides important theoretical basis and technical support for the application and development of flue gas recycling technology.According to the literature review, most studies in the field of CO studies ,14 placezer side  but alsozer side . Systema studies ,8,9 reve2 dilution on the flame temperature and the position of the flame front; (2) to compare the four effects of CO2 dilution on the flame temperature and the flame front on the fuel side and oxidizer side; (3) to determine the differences in the contribution of these four effects; (4) to reveal how CO2 affects the flame temperature in terms of the OH and H radicals, as well as the heat release rate (HRR) of the main reactions.In light of the discussion above, the present study carried out a series of numerical simulations describing one-dimensional counterflow diffusion flames, with the following specific objectives: (1) to isolate and quantify the four effects  of CO−6.An axisymmetric, counterflow laminar diffusion flame with two opposite coaxial jets in models of a fuel and oxidizer was applied in this study. The configuration of the counterflow flame is displayed in 2, H2O, and CH4. The corresponding equations describing the radiative effect on the basis of the optically thin approximation are as follows:σ is the Stefan–Boltzmann constant, and T and For the radiative heat loss In order to ensure that the stagnation surface of the counterflow flame does not deviate from the center of the fuel and oxidizer nozzles, the calculation limited the two opposing gases to satisfy the following momentum balance equation :(3)ρoVo2α_s was defined as follows [O and F represent the oxidizer and fuel flow streams, respectively. ρ and V denote the density and the velocity of the flow streams. L is the distance between the fuel and oxidizer nozzles. In Equations (3) and (4), when only considering the absolute values, the expressions describing the velocity on both sides can be expressed as follows:The global strain rate  follows :(4)αs =2L was specified as 4 cm, the inlet temperature of both the fuel and the oxidizer was specified as 300 K, the strain rate −1, and the pressure was 0.1 MPa. The velocities of the oxidizer side were maintained at a constant value of 0.1 m/s, allowing the velocities of the fuel side to be obtained according to Equations (3)–(6) on the basis of the composition of the fuel and oxidizer.In the present study, the distance between the fuel and oxidizer nozzles 2 dilution on the fuel and oxidizer sides by decoupling the thermal, chemical, transport, and radiative properties of CO2. Several pairs of artificial and chemically inert species were introduced to isolate the effect of CO2: FCO2, TCO2, XCO2, and RCO2 as shown in 2 was explained as followed:2, which has the same thermal, transport, and radiative properties as CO2, but does not participate in the chemical reaction, was introduced to evaluate the chemical effect of CO2. Therefore, any differences in the results between FCO2 and CO2 were entirely contributed by the chemical effect of CO2.The chemical effect. FCO2, which has the chemical, transport, and radiative properties as FCO2, but owns the same thermal properties as normal N2, was employed. Thus, any differences in the results between FCO2 and TCO2 were totally caused by the thermal effect of CO2.The thermal effect. TCO2, which has the same chemical, thermal, and transport properties as FCO2, but owns the same transport properties as N2. The transport effect of CO2 was revealed by the difference in results between FCO2 and XCO2.The transport effect. XCO2, which has the same chemical, thermal, and transport properties as FCO2, but is hot transparent body and cannot contribute to radiative heat transfer. Therefore, the radiative effects of CO2 were determined as a function of the difference in results between FCO2 and RCO2.The radiative effect. RCOThe purpose of this study was to compare the influence of CO2 features the same thermodynamic properties as N2; thus, the same polynomial fitting parameters were adopted to calculate their thermodynamic coefficient. This was achieved by modifying the TCO2 raw input in the THERMDAT file. XCO2, with the same transport properties as N2, could also be obtained by modifying the XCO2 raw input in the THERMDAT file.As is known, the thermodynamic properties of a gas specie are mainly derived from its enthalpy, entropy, and specific heat capacity. These properties were obtained from polynomial fitting parameters provided in the THERMDAT file. On the other hand, the transport properties of a gas specie are derived from its viscosity, thermal conductivity, and thermal diffusion coefficient, which were calculated as a function of the parameters provided in the TRANDAT file. As shown in 2 was set to 30% on both the fuel side and the oxidizer side, as the aim of the present study was to compare the difference in CO2 effects on each side of the counterflow flame, as opposed to the dilution ratio. The numerically simulated conditions taken into account in this study are summarized in 4 and has been validated by numerous research studies.The mole fraction of CO2 and various other artificial species on both sides of the counterflow diffusion flame. The dashed line represents the position of the flame front. As clearly seen in this figure, the flame temperature increased and then decreased with distance from the fuel side, reaching its maximum at the flame front . By comparing cases 1 and 2 and cases 7 and 8, it can be seen that the maximum temperature was decreased due to CO2 dilution, whether on the fuel side or the oxidizer side. Additionally, there was an obvious difference in the shift of the flame front position upon dilution of the two sides, with the flame front offset toward the side which was not diluted [2 was added to the fuel side or oxidizer side, the maximum flame temperature always resided on the oxidizer side of the configuration, which is consistent with the findings in [ diluted . Regardldings in .2 had an effect on the flame temperature distribution whether it was diluted on the fuel side or the oxidizer side. 2. When the fuel side was diluted, the effects due to the chemical and transport properties could be neglected. However, the thermal properties and the radiative properties of CO2 had a different influence on the flame temperature and the flame front. The thermal properties decreased the flame temperature ahead of the flame front, whereas it increased the flame temperature behind the flame front. The radiative properties of CO2 resulted in a slight overall decrease in flame temperature distribution. When the oxidizer side was diluted, no significant changes in temperature distribution occurred as a result of the transport properties of CO2, whereas the overall flame temperature distributions were slightly lower due to the chemical and radiative properties of CO2. Lastly, the thermal properties had a different influence on the flame temperature distribution on either side of the flame front: a bit higher than the undiluted gas mixture ahead of the flame front but apparently lower than the undiluted gas mixture behind the flame front. It is necessary to note that “no significant change” does not mean that “no change occurred”; a detailed analysis of the four effects is presented later.2 affected the flame temperature distribution as a function of the side which was diluted. A comparison of the four properties allowed distinguishing their primary and secondary effects on the counterflow diffusion flame.In summary, CO2 on the flame temperature peak value, their contributions were individually defined as follows:Before analyzing and comparing the effects of the chemical, thermal, transport, and radiative properties of CO2 was described using similar equations.Similarly, the shift in position of the flame front as a function of the four properties of CO2 dilution, the radiative properties had the primary negative effect, while the chemical and thermal properties had a roughly equivalent effect. The transport properties had the smallest influence on the maximum flame temperature. On the oxidizer side, with 30% CO2 dilution, the thermal properties had the most prominent effect on the maximum flame temperature, whereas the chemical and radiative properties effects contributed approximately one-half and one-third the effect of the thermal properties effect, respectively. Once again, the transport properties had the smallest influence on the maximum flame temperature. Lastly, the effect of the chemical, thermal, and transport properties on the maximum flame temperature was greater on the oxidizer side than the fuel side under 30% CO2 dilution. However, the effect of the radiative properties was slightly lower on the oxidizer side.2 dilution ratio. The legends of 2 on the position of the flame front differed as a function of which side was diluted. When the fuel side was diluted with CO2, the chemical and radiative effects moved the position of the flame front toward the fuel side, whereas the thermal and transport effects moved the position of the flame front toward the oxidizer side. However, when the oxidizer side was diluted with CO2, the chemical, transport, and radiative effects moved the position of the flame front toward the oxidizer side, with the opposite outcome seen due to the thermal effect. Consistently, the thermal effect on the position of the flame front was the most conspicuous regardless of which side was diluted.H and OH radicals are very important for the continuation of chain reactions; moreover, the first step in a combustion reaction starts with the fuel being attacked by free radicals such as OH and H , whereby2 had a strong influence on the flame temperature and the position of the flame front, as well as on the reaction zone (the thickness of the flame). The distributions of intermediate species and highly active radicals of combustion are associated with the flame temperature and the reaction zone. To illustrate the influence of the chemical, thermal, transport, and radiative properties of CO2 on the two most important highly active radicals (H and OH), a comparison of their effects on the mole fraction of H and OH radicals is depicted in 2 dilution on the fuel side as an example without considering the four effects on the mole fraction of H and OH radicals, the maximum H and OH mole fractions were located at 2.26 and 2.31 cm, respectively, while the flame front was located at 2.24 cm.As discussed above, CO2. As shown in 2 lowered the H and OH mole fractions regardless of the side which was diluted; however, their peak positions showed no significant change. Similarly, the thermal properties of CO2  contributed least to the overall distribution of the mole fraction and peak position of H and OH radicals.The previous temperature curves allow for analysis and understanding of the changes in H and OH radicals under the influence of the four properties of COs of CO2 b signifi2 dilution on either side of the counterflow diffusion flame led to a decrease in the concentration of H and OH radicals and, thus, a reduction in combustion intensity. Moreover, the peak position of free radicals represents the combustion area with the highest intensity, which moves toward the center of the domain. The analyses of the mole fraction of H and OH radicals were consistent with the change in temperature distribution as a function of CO2 dilution.In summary, CO2 dilution on the temperature distribution can be attributed to the behavior of the combustion heat release rate of the involved reactions. To clearly elucidate the effect of the addition of CO2 to different sides of the counterflow diffusion flame on its temperature, a heat release rate analysis was carried out. The top ten elementary reactions with the largest heat release rate were selected to show the uncoupled effects of CO2 on the HRR.The origin of the effects of CO2 to the CH4 fuel side will reduce the global heat release rate significantly. The four effects of CO2 on the profiles of heat release rate are plotted in 2 had a great effect on R84 (positive effect: less heat absorbed), R99 (negative effect: more heat absorbed), and R153 (positive effect: more heat released). However, it can be clearly seen that the negative impact was greater than the two positive impacts at the same position. Behind the flame front, the chemical properties of CO2 also had an effect on R35 (negative effect: more heat absorbed), R84 (negative effect: more heat absorbed), R287 (negative effect: more heat absorbed), and R99 (positive effect: more heat released). Similarly, the negative influence was stronger than the positive influence at the same position. Therefore, the synergistic influence of the chemical properties of CO2 on the heat release rate was negative, thereby leading to a decrease in temperature. The effects of the thermal, transport, and radiative properties on HRR are depicted in 2 declined or improved the HRR at the same position for the target elementary reaction, as well as decreased or increased the peak value. However, the thermal properties did not affect the peak value of HRR for each target elementary reaction. As shown in 2 dilution  moved toward the oxidizer side compared with TCO2 dilution, which can be explained by the change in distribution of the HRR.Wei et al.  pointed 2 on the HRR when the oxidizer side was diluted were also investigated. As shown in 2 moved the HRR distribution of the main target elementary reaction toward the fuel side, leading to a change in the HRR peaks of the exothermic and endothermic elementary reactions. On the other hand, the transport and radiative properties only affected the HRR peak of each elementary reaction, with no obvious effect on its distribution. When comparing FCO2  with CO2, a decrease occurred in the HRR of the exothermic reactions R35, R84, R287, and R52 involving H and OH radicals. 2 and FCO2, whereby a decrease in their molar fraction inhibited the relevant elementary reactions, thus resulting in a reduction in the heat release rate. Furthermore, a noticeable thermal effect was reflected in the position of the flame front in 2  and TCO2  were at 2.3 cm and 2.36 cm, respectively. According to 2 HRR was shifted toward the fuel side compared with TCO2.The effects of the four properties of CO2 dilution on different sides of a laminar counterflow diffusion flame was conducted using the OPPDIF code of ANSYS CHEMKIN-PRO. In order to isolate the CO2 effects on the flame temperature, the position of the flame front, the H and OH mole fractions, and the heat release rate, the authors introduced four pairs of artificial CO2 species to uncouple the chemical, thermal, transport, and radiative effects of CO2 on the above characteristics of the flame. The numerical results demonstrated that the effects of the four properties of CO2 were often contrasting, as summarized below.In this paper, a numerical study of CO2 on the flame temperature were negative regardless of which side was diluted, with a greater effect seen upon dilution of the oxidizer side. The chemical, thermal, and radiative properties led to a decrease in flame temperature, whereas the transport properties increased the flame temperature. Moreover, the thermal properties had a more prominent effect on the flame temperature upon dilution of the fuel side, whereas the radiative properties had a predominant effect on the flame temperature upon dilution of the oxidizer side.The synergistic effects of CO2 showed great differences with respect to the position of the flame front. When the fuel side was diluted with CO2, the chemical and radiative effects moved the position of the flame front toward the fuel side, whereas the thermal and transport effects moved the position of the flame front toward the oxidizer side. However, when the oxidizer side was diluted with CO2, the chemical, transport, and radiative effects moved the position of the flame front toward the oxidizer side, with the opposite outcome seen due to the thermal effect. Consistently, the thermal effect on the position of the flame front was the most conspicuous regardless of which side was diluted.The effects of CO2 resulted in a slight decrease in the mole fraction of H and OH radicals regardless of which side was diluted. The thermal properties of CO2 only affected the distribution of H and OH radicals upon dilution of the fuel side, with no significant effect on its peak. However, the thermal properties of CO2 not only affected the distribution of OH and H radicals upon dilution of the oxidizer side, but also reduced their maximum mole fraction, whereas the effect of transport properties on OH and H radicals could be neglected.The chemical and radiative effects of CO2 on the heat release rate was consistent with its influence on temperature and free radical concentration regardless of which side was diluted.The influence of CO


The novelty of this work consists of obtaining original fundamental data on the laws of synthesis of new metal matrix composite materials for additive technologies. CrN + TiNi composites were obtained using the method of self-propagating high-temperature synthesis. In this work, analysis of the parameters of the synthesis of composite materials as well as their structure and phase composition were carried out. A scheme for the formation of a composite structure is established; it is shown that the phase composition is represented by 54.6 wt.% CrN and 45.4 wt.% TiNi. It was shown that composites based on the system are suitable for machines that make use of direct laser deposition to grow layers of materials. Sample structure and phase parameters were studied. It is shown that titanium nitride particles are uniformly distributed in the CrNi intermetallic matrix, the TiN particle size ranges from 0.3 to 9 μm and the average particle size is 2.8 μm. The results obtained indicate the possibility of synthesizing promising metal matrix composite materials for additive technologies. Such materials may have increased hardness, operating temperature and strength. Thanks to its technological advantages , additive manufacturing makes it possible to produce highly complex parts for various applications quickly and cost-effectively, and every year additive manufacturing integrates more deeply into modern industry ,3,4,5,6.A special case of alloys based on nickel and chromium is powder materials of the Inconel family, which are successfully used in additive manufacturing. Thus, in  the authTo improve the physical and mechanical properties and performance characteristics of a produced item, nickel and chromium-based alloys are reinforced with ceramic inclusions .In previous studies ,19,20,21Meanwhile, conventional technologies for producing composites based on nickel and chromium with ceramic inclusions have a number of disadvantages. The introduction of ceramic particles into the melt during the preparation of raw materials for AM, as well as the direct addition of ceramic powders during additive manufacturing, can lead to their agglomeration, which undoubtedly reduces the physicomechanical properties of the materials obtained. Therefore, there is a need to find methods to obtain ceramic metal composites consisting of a matrix based on a nickel-chromium alloy with uniformly distributed ceramic inclusions.One of the possible methods for obtaining powders of high elevated-temperature strength materials is self-propagating high-temperature synthesis (SHS) , which allows for obtaining various classes of compounds: carbides, borides, nitrides, silicides, oxides, intermetallic compounds, and composites . The pro2 and (Ni-Ti)-TiB2 composite materials and found that composites that were obtained by SHS consist of a metallic or intermetallic matrix  and ceramic TiB2 particles whose size varies from 0.1 to 5 μm. At the same time, it was shown by Promakhov et al. [Promakhov et al.  and Zhukv et al. , Zhukov v et al. , and Matv et al.  that by The purpose of this work is to study the phase composition and structure of composite powders that are obtained from a CrN-TiNi powder mixture by SHS and to study the phase composition of the structure and mechanical properties of materials obtained by additive manufacturing using these composite powders.CrN  and TiNi  powders were used as the initial components for producing samples of SHS composites. The initial scheme for the preparation of samples is shown in CrN and TiNi powders were mixed in the stoichiometric ratio 54.6 wt.% CrN + 45.4 wt.% TiNi a in a baThe samples were obtained from the synthesised composite powders by direct laser deposition (DLD). This method is a special case of additive manufacturing, in which there is a directed release of laser energy into powders. For direct laser deposition, the LS-3 fibre optic ytterbium laser  was used. Laser radiation was focused using the FLW D30 process head . A COAX9 coaxial weld deposition nozzle  was used to form a gas-powder jet. The LRM-200iD_7L industrial robot  was used as a manipulator. The ranges of the laser parameters that were used are presented in The direct laser deposition was carried out on a 7 mm thick steel substrate. The method of obtaining samples includes the supply of a gas-powder mixture directly to the growing zone. The schematic diagram and the principle of obtaining samples using DLD is shown in ®; PA 19073, USA). XRD analysis was performed with Shimadzu XRD-6000 X-ray diffractometer in Cu Kα-radiation (wavelength λ = 1.5406 Ǻ). The scanning range was 2θ = 10–80°, with the scanning step of 0.02°/s and acquisition time of 1 sec. Phase content, lattice parameters, and CSR size calculations were performed by structure refinement according to the full-profile analysis method (Rietveld method) [The synthesis temperature of the materials was measured using tungsten-rhenium thermocouples inserted into the sample. The measurement results were presented in the form of thermograms on a computer. The phase composition of all the synthesis products was investigated using a Shimadzu XRD-6000 diffractometer  . The phases were detected by comparing peaks and the obtained diffractograms with the Powder Diffraction File 4 database of the International Centre for Diffraction Data (ICDD method) ,32. The 2-Mg system. With a stoichiometric ratio of the components, the synthesis reaction does not proceed completely. The authors of this work explained this phenomenon as the evaporation of magnesium during synthesis, which leads to a depletion of the initial mixture and a decrease in the completeness of the reaction. An increase in the argon pressure in the reactor led to an increase in the completeness of the synthesis reaction in the system.Investigations of the composite synthesis processes, in the combustion mode of CrN-TiNi mixture samples at different argon pressures, showed that the synthesis of materials could not be fully completed at the argon pressure of 0.5 MPa in the reactor. The flame front extinguished immediately after the initiation of the fusion reaction. An increase in the argon pressure in the reactor to 1 MPa allowed the flame front to propagate to the middle of the sample in the spin combustion mode, after which the flame front decayed. It was not possible to measure the reaction temperature in the samples that were synthesised by SHS at the pressures of 0.5 and 1 MPa. An increase in the argon pressure in the reactor to 3.5 MPa made it possible to fully complete the SHS process in the sample. The flame front propagated in the spin combustion mode without attenuation. A similar dependence was observed in , where tBased on the experimental data obtained and the results presented in , it can Mossino  and ShekThe peak of the thermogram (area 1) characterises an exothermic reaction (reaction with the release of heat) of the initial components taking place in the CrN-TiNi mixture sample. The reaction is accompanied by the dissipation of a great amount of heat. The apex of the peak corresponds to the system combustion temperature, which is 2000 °C. After the peak, a small decrease in the reaction temperature is observed (area 2), due to the intense heat absorption in the adjacent areas of the initial mixture. Promakhov et al.  explain 2, N2 Cl2, etc.).The X-ray diffraction analysis of the combustion products of the CrN-TiNi powder mixture demonstrated the presence of TiN (70 wt.%) and CrNi (30 wt.%) phases. A comparison of the lattice parameters of titanium nitride in SHS composites with the data of Newport et al.  and SamsIn combination with the data presented in ,27,35, tAfter heating the upper surface of the sample with a molybdenum coil, the heat is transferred to the layer of the main initial mixture a via theThe microhardness of the samples of materials obtained by direct laser deposition from CrNi-TiN SHS composites varied in the range of 645 to 827 HV, and the average microhardness of the samples was 760 HV. Hu et al. , Kaynak This work demonstrated the possibility of obtaining new composite CrNi-TiN powders in the mode of self-propagating high-temperature synthesis, as well as their use as a powder raw material for additively manufacturing materials by direct laser deposition. The synthesis temperature, phase composition, and structure of SHS composites were investigated. A mechanism of their formation in the course of the reaction of the initial mixture components was proposed: 54.6 wt.% CrN + 45.4 wt.% TiNi. The phase composition, structure, and mechanical properties of the materials obtained by DLD from CrNi-TiN SHS composite powders were studied. It was found that the materials obtained inherit the phase composition and matrix structure of SHS composites. It was shown that titanium nitride particles make it possible to increase the hardness of the materials compared to Inconel 625/718 powders, by a factor of two to three.