The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Aut...The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Autodesk Inventor 2017 software. The modelled piston was then imported into Ansys for further analysis. Static structural and thermal analysis were carried out on the pistons of the four different materials namely: Al 413 alloy, Al 384 alloy, Al 390 alloy and Al332 alloy to determine the total deformation, equivalent Von Mises stress, maximum shear stress, and the safety factor. The results of the study revealed that, aluminium 332 alloy piston deformed less compared to the deformations of aluminium 390 alloy piston, aluminium 384 alloy piston and aluminium 413 alloy piston. The induced Von Mises stresses in the pistons of the four different materials were found to be far lower than the yield strengths of all the materials. Hence, all the selected materials including the implementing material have equal properties to withstand the maximum gas load. All the selected materials were observed to have high thermal conductivity enough to be able to withstand the operating temperature in the engine cylinders.展开更多
The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influen...The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influence of soil characteristics on the propagating seismic stress waves from the bedrock level to the ground surface during an earthquake. For the northeastern region of India, located in the highest seismic zone in the country, conducting an extensive GRA study is of prime importance. Conventionally, most of the GRA studies are carried out using the equivalent linear method, which, being a simplistic approach, cannot capture the nonlinear behavior of soil during seismic shaking. This paper presents the outcomes of a one-dimensional effective stress based nonlinear GRA conducted for Guwahati city(located in northeast India) incorporating the non-Masing load/unload/reload characteristics. The various ground response parameters evaluated from this study help in assessing the ground shaking, soil amplification, and site responses expected in this region. 2D contour maps, which are representative of the distribution of some of these parameters throughout Guwahati city, are also developed. The results presented herein can serve as guidelines for the design of foundations and superstructures in this region.展开更多
Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform...Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.展开更多
The size-dependent effect on the biaxial and shear nonlinear buckling analysis of an isotropic and orthotropic micro-plate based on the surface stress, the modified couple stress theory （MCST）, and the nonlocal elas...The size-dependent effect on the biaxial and shear nonlinear buckling analysis of an isotropic and orthotropic micro-plate based on the surface stress, the modified couple stress theory （MCST）, and the nonlocal elasticity theories using the differential quadrature method （DQM） is presented. Main advantages of the MCST over the classical theory （CT） are the inclusion of the asymmetric couple stress tensor and the consideration of only one material length scale parameter. Based on the nonlinear von Karman assumption, the governing equations of equilibrium for the micro-classical plate consid- ering midplane displacements are derived based on the minimum principle of potential energy. Using the DQM, the biaxial and shear critical buckling loads of the micro-plate for various boundary conditions are obtained. Accuracy of the obtained results is validated by comparing the solutions with those reported in the literature. A parametric study is conducted to show the effects of the aspect ratio, the side-to-thickness ratio, Eringen＇s nonlocal parameter, the material length scale parameter, Young＇s modulus of the surface layer, the surface residual stress, the polymer matrix coefficients, and various boundary conditions on the dimensionless uniaxial, biaxial, and shear critical buckling loads. The results indicate that the critical buckling loads are strongly sensitive to Eringen＇s nonlocal parameter, the material length scale parameter, and the surface residual stress effects, while the effect of Young＇s modulus of the surface layer on the critical buckling load is negligible. Also, considering the size dependent effect causes the increase in the stiffness of the orthotropic micro-plate. The results show that the critical biaxial buckling load increases with an increase in G12/E2 and vice versa for E1/E2. It is shown that the nonlinear biaxial buckling ratio decreases as the aspect ratio increases and vice versa for the buckling amplitude. Because of the most lightweight micro-composite materials with high strength/weight and stiffness/weight ratios, it is anticipated that the results of the present work are useful in experimental characterization of the mechanical properties of micro-composite plates in the aircraft industry and other engineering applications.展开更多
The determination of the ultimate load-bearing capacity of structures made of elastoplastic heterogeneous materials under varying loads is of great importance for engineering analysis and design. Therefore, it is nece...The determination of the ultimate load-bearing capacity of structures made of elastoplastic heterogeneous materials under varying loads is of great importance for engineering analysis and design. Therefore, it is necessary to accurately predict the shakedown domains of these materials. The static shakedown theorem, also known as Melan's theorem, is a fundamental method used to predict the shakedown domains of structures and materials. Within this method, a key aspect lies in the construction and application of an appropriate self-equilibrium stress field(SSF). In the structural shakedown analysis, the SSF is typically constructed by governing equations that satisfy no external force(NEF) boundary conditions. However, we discover that directly applying these governing equations is not suitable for the shakedown analysis of heterogeneous materials. Researchers must consider the requirements imposed by the Hill-Mandel condition for boundary conditions and the physical significance of representative volume elements(RVEs). This paper addresses this issue and demonstrates that the sizes of SSFs vary under different boundary conditions, such as uniform displacement boundary conditions(DBCs), uniform traction boundary conditions(TBCs), and periodic boundary conditions(PBCs). As a result, significant discrepancies arise in the predicted shakedown domain sizes of heterogeneous materials. Built on the demonstrated relationship between SSFs under different boundary conditions, this study explores the conservative relationships among different shakedown domains, and provides proof of the relationship between the elastic limit(EL) factors and the shakedown loading factors under the loading domain of two load vertices. By utilizing numerical examples, we highlight the conservatism present in certain results reported in the existing literature. Among the investigated boundary conditions, the obtained shakedown domain is the most conservative under TBCs.Conversely, utilizing PBCs to construct an SSF for the shakedown analysis leads to less conservative lower bounds, indicating that PBCs should be employed as the preferred boundary conditions for the shakedown analysis of heterogeneous materials.展开更多
Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for...Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.展开更多
Numerical simulation concerning the forming and welding process of spiral welded pipe was conducted, which included three steps ： the first step was the stress analysis when the spiral was formed, and then the stress...Numerical simulation concerning the forming and welding process of spiral welded pipe was conducted, which included three steps ： the first step was the stress analysis when the spiral was formed, and then the stress was regarded as initial condition of melding during the temperature field analysis in the process of welding, the last step was the thermal stress analysis of the weld seam after the welding was over. Moreover, when the steel strip was pushed, the stress was also calculated by non-linearity contact technology using Abaqus Software. By finite element modeling and calculating of the forming and welding process of the spiral welded pipe, the key points of the multi-fields synthetic simulating were studied and discussed.展开更多
This paper examines the effective stress in indurated clay rock theoretically and experimentally.A stress concept is derived from the analysis of the microstructure and of the pore water in the highly-indurated Callov...This paper examines the effective stress in indurated clay rock theoretically and experimentally.A stress concept is derived from the analysis of the microstructure and of the pore water in the highly-indurated Callovo-Oxfordian and Opalinus clay rocks,and subsequently validated by various experiments performed on these claystones.The concept suggests that the interparticle or effective stress in a dense clay ewater system is transferred through both the adsorbed interparticle pore water in narrow pores and the solidesolid contact between non-clay mineral grains.The experiments show that the adsorbed pore water in the claystones is capable of bearing deviatoric effective stresses up to the failure strength.The applied stresses are for the most part or even totally transferred by the bound pore water,i.e.the swelling pressure in the interparticle bound pore water is almost equivalent to the effective stress.This stress concept provides a reasonable view to the nature of the effective stress in argillaceous rock and forms the fundamental basis for studies of the hydro-mechanical properties and processes in clay formations.展开更多
Cemented paste backfill(CPB) is largely used in underground mines worldwide.A key issue associated with application of CPB is to estimate the stresses in backfilled stopes and on barricades.Recent numerical and experi...Cemented paste backfill(CPB) is largely used in underground mines worldwide.A key issue associated with application of CPB is to estimate the stresses in backfilled stopes and on barricades.Recent numerical and experimental results show that arching effect is absent shortly after the placement of CPB in stopes.However,stress decreases in barricade drift with increasing distance between the measurement points and drawpoint have also been observed,demonstrating arching effect shortly after the pouring of CPB.To explain these paradoxes,CPB is considered as Bingham fluid having a yield shear stress.Three dimensional analytical solutions are proposed to evaluate the short-term total stresses in backfilled stopes and on barricades,accounting for the CPB's yield shear stress-induced arching effect.Stress diminution due to such arching effect in the backfilled stopes and on barricades is indeed obtained.But the reduction becomes insignificant using typical yield shear stress and stope geometry.More analyses indicate that the typical yield shear stress values do not fully correspond to field conditions where the yield shear stress would increase exponentially due to apparent consolidation(loss of water by drainage,a phenomenon similar to the desiccation of overly saturated fine-grained materials).展开更多
为探讨菊茎叶总黄酮(total flavonoids from stems and leaves of Chrysanthemum morifolium,TFCSL)抗氧化应激的活性成分,阐明其药效物质基础和作用机制。采用HPLC建立不同批次TFCSL指纹图谱;以高浓度葡萄糖诱导人脐静脉内皮细胞建立...为探讨菊茎叶总黄酮(total flavonoids from stems and leaves of Chrysanthemum morifolium,TFCSL)抗氧化应激的活性成分,阐明其药效物质基础和作用机制。采用HPLC建立不同批次TFCSL指纹图谱;以高浓度葡萄糖诱导人脐静脉内皮细胞建立氧化损伤模型,将丙二醛含量、乳酸脱氢酶含量和超氧化物歧化酶活性作为药效指标;采用灰色关联度和偏最小二乘法分析其谱-效关系确定抗氧化药效物质基础;基于网络药理学结合分子对接探究核心靶点及作用通路。从12批次TFCSL指纹图谱中确定12个共有峰,指认其中9个化学成分;各批次总黄酮样品均可减少细胞凋亡、降低丙二醛及乳酸脱氢酶含量、提高超氧化物歧化酶活性;综合2种数学模型确定峰5(芹菜素-7-O-β-D-葡萄糖苷)、峰6(异绿原酸C)、峰7(香叶木素-7-O-β-D-葡萄糖苷)为抗氧化物质基础;筛选出的3个活性成分作用于抗氧化应激的33个靶点;关键靶点为TNF、CASP3、EDNRA、XDH、PTGS2、MMP2,主要涉及脂质和动脉粥样硬化信号通路、IL-17信号通路、糖尿病并发症AGE-RAGE信号通路、TNF通路、MPKA通路等信号通路;分子对接结果显示活性成分与关键靶点之间均有较好的结合力。表明TFCSL抗氧化应激的物质基础可能为芹菜素-7-O-β-D-葡萄糖苷、异绿原酸C、香叶木素-7-O-β-D-葡萄糖苷,推测通过TNF、CASP3等靶点作用动脉粥样硬化信号通路、IL17信号通路发挥作用,体现菊茎叶多成分、多靶点抗氧化的作用特点。展开更多
目的:系统评价正念减压对辅殖助孕患者的干预效果。方法:检索中国知网、中国生物医学文献数据库、万方数据知识服务平台、维普、PubMed、The Cochrane Library、Embase、Web of Science数据库,收集建库至2023年12月发表的有关正念减压...目的:系统评价正念减压对辅殖助孕患者的干预效果。方法:检索中国知网、中国生物医学文献数据库、万方数据知识服务平台、维普、PubMed、The Cochrane Library、Embase、Web of Science数据库,收集建库至2023年12月发表的有关正念减压在辅助生殖助孕患者中应用的随机对照试验。由两名研究者对文献进行筛选、评价和资料提取,并评价纳入研究的偏倚风险。采用RevMan5.4和Stata17.0软件对纳入文献进行数据分析。结果:共纳入9项研究,1642例患者。Meta分析结果显示:与常规治疗相比,正念减压干预有助于改善辅助生殖助孕患者的心理状态,减轻压力知觉,提高生活质量。以抑郁自评量表(SDS)为评价标准[MD=-8.17,95%CI(-9.16,-7.17),P<0.01],以焦虑自评量表(SAS)为评价标准[MD=-8.71,95%CI(-10.24,-7.18),P<0.01],以压力知觉量表(CPSS)为评价标准[MD=-4.38,95%CI(-5.41,-3.35),P<0.01]。健康状况量表(SF-36量表)的4个评价维度:精神健康[MD=17.50,95%CI(15.67,19.33),P<0.01]、精力[MD=12.05,95%CI(10.18,13.92),P<0.01]、生理职能[MD=8.15,95%CI(6.51,9.79),P<0.01]、生理功能[MD=14.50,95%CI(12.65,16.35),P<0.01]。结论:现有证据表明,正念减压对辅助生殖助孕患者干预效果显著,但受本次纳入研究证据数量、质量限制,尚需开展更多有关辅助生殖助孕患者正念减压干预的高质量研究。展开更多
【目的】系统评价益气养阴法联合西药治疗肾病综合征的有效性及安全性。【方法】检索中国知网(CNKI)、中国生物医学文献数据库(CBM)、万方(Wangfang)、维普(VIP)、PubMed、Web of Science、Cochrane Library、Embase等国内外主要文献数...【目的】系统评价益气养阴法联合西药治疗肾病综合征的有效性及安全性。【方法】检索中国知网(CNKI)、中国生物医学文献数据库(CBM)、万方(Wangfang)、维普(VIP)、PubMed、Web of Science、Cochrane Library、Embase等国内外主要文献数据库,筛选其中有关益气养阴法联合西药(试验组)对比单纯西药(对照组)治疗肾病综合征的临床随机对照试验(RCTs),采用Cochrane手册中的偏倚风险工具进行文献的质量评价,运用RevMan 5.3软件进行Meta分析。【结果】共纳入18个RCTs,包含1334例患者。Meta分析结果显示,益气养阴法联合西药在提高临床有效率(RR=1.24,95%CI[1.16,1.32],P<0.00001),改善24 h尿蛋白定量(24hUPRO)(MD=-0.92,95%CI[-1.09,-0.75],P<0.00001)、血清白蛋白(ALB)(MD=7.06,95%CI[4.73,9.39],P<0.00001)、尿素氮(BUN)(MD=-1.57,95%CI[-2.01,-1.13],P<0.00001)、血肌酐(SCr)(MD=-12.23,95%CI[-16.58,-7.88],P<0.00001)、总胆固醇(TC)(MD=-1.06,95%CI[-1.69,-0.43],P=0.0009)、甘油三酯(TG)(MD=-0.58,95%CI[-0.94,-0.21],P=0.002)水平,以及降低不良反应发生率(RR=0.50,95%CI[0.40,0.64],P<0.00001)方面优于单纯西药治疗。【结论】益气养阴法联合西药治疗肾病综合征在提高临床疗效及改善24hUPRO、ALB、BUN、SCr、TC、TG方面优于单纯西药治疗,且能降低激素产生的不良反应。因纳入文献较少,文献质量较低,潜在疗效需更多的高质量研究进行验证。展开更多
文摘The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Autodesk Inventor 2017 software. The modelled piston was then imported into Ansys for further analysis. Static structural and thermal analysis were carried out on the pistons of the four different materials namely: Al 413 alloy, Al 384 alloy, Al 390 alloy and Al332 alloy to determine the total deformation, equivalent Von Mises stress, maximum shear stress, and the safety factor. The results of the study revealed that, aluminium 332 alloy piston deformed less compared to the deformations of aluminium 390 alloy piston, aluminium 384 alloy piston and aluminium 413 alloy piston. The induced Von Mises stresses in the pistons of the four different materials were found to be far lower than the yield strengths of all the materials. Hence, all the selected materials including the implementing material have equal properties to withstand the maximum gas load. All the selected materials were observed to have high thermal conductivity enough to be able to withstand the operating temperature in the engine cylinders.
文摘The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influence of soil characteristics on the propagating seismic stress waves from the bedrock level to the ground surface during an earthquake. For the northeastern region of India, located in the highest seismic zone in the country, conducting an extensive GRA study is of prime importance. Conventionally, most of the GRA studies are carried out using the equivalent linear method, which, being a simplistic approach, cannot capture the nonlinear behavior of soil during seismic shaking. This paper presents the outcomes of a one-dimensional effective stress based nonlinear GRA conducted for Guwahati city(located in northeast India) incorporating the non-Masing load/unload/reload characteristics. The various ground response parameters evaluated from this study help in assessing the ground shaking, soil amplification, and site responses expected in this region. 2D contour maps, which are representative of the distribution of some of these parameters throughout Guwahati city, are also developed. The results presented herein can serve as guidelines for the design of foundations and superstructures in this region.
基金The authors would like to thank the Iranian Nanotechnology Development Committee for their financial support.
文摘Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.
基金supported by the Iranian Nanotechnology Development Committee and the University of Kashan(No.363452/10)
文摘The size-dependent effect on the biaxial and shear nonlinear buckling analysis of an isotropic and orthotropic micro-plate based on the surface stress, the modified couple stress theory （MCST）, and the nonlocal elasticity theories using the differential quadrature method （DQM） is presented. Main advantages of the MCST over the classical theory （CT） are the inclusion of the asymmetric couple stress tensor and the consideration of only one material length scale parameter. Based on the nonlinear von Karman assumption, the governing equations of equilibrium for the micro-classical plate consid- ering midplane displacements are derived based on the minimum principle of potential energy. Using the DQM, the biaxial and shear critical buckling loads of the micro-plate for various boundary conditions are obtained. Accuracy of the obtained results is validated by comparing the solutions with those reported in the literature. A parametric study is conducted to show the effects of the aspect ratio, the side-to-thickness ratio, Eringen＇s nonlocal parameter, the material length scale parameter, Young＇s modulus of the surface layer, the surface residual stress, the polymer matrix coefficients, and various boundary conditions on the dimensionless uniaxial, biaxial, and shear critical buckling loads. The results indicate that the critical buckling loads are strongly sensitive to Eringen＇s nonlocal parameter, the material length scale parameter, and the surface residual stress effects, while the effect of Young＇s modulus of the surface layer on the critical buckling load is negligible. Also, considering the size dependent effect causes the increase in the stiffness of the orthotropic micro-plate. The results show that the critical biaxial buckling load increases with an increase in G12/E2 and vice versa for E1/E2. It is shown that the nonlinear biaxial buckling ratio decreases as the aspect ratio increases and vice versa for the buckling amplitude. Because of the most lightweight micro-composite materials with high strength/weight and stiffness/weight ratios, it is anticipated that the results of the present work are useful in experimental characterization of the mechanical properties of micro-composite plates in the aircraft industry and other engineering applications.
基金Project supported by the National Natural Science Foundation of China (Nos. 52075070 and12302254)the Dalian City Supports Innovation and Entrepreneurship Projects for High-Level Talents (No. 2021RD16)the Liaoning Revitalization Talents Program (No. XLYC2002108)。
文摘The determination of the ultimate load-bearing capacity of structures made of elastoplastic heterogeneous materials under varying loads is of great importance for engineering analysis and design. Therefore, it is necessary to accurately predict the shakedown domains of these materials. The static shakedown theorem, also known as Melan's theorem, is a fundamental method used to predict the shakedown domains of structures and materials. Within this method, a key aspect lies in the construction and application of an appropriate self-equilibrium stress field(SSF). In the structural shakedown analysis, the SSF is typically constructed by governing equations that satisfy no external force(NEF) boundary conditions. However, we discover that directly applying these governing equations is not suitable for the shakedown analysis of heterogeneous materials. Researchers must consider the requirements imposed by the Hill-Mandel condition for boundary conditions and the physical significance of representative volume elements(RVEs). This paper addresses this issue and demonstrates that the sizes of SSFs vary under different boundary conditions, such as uniform displacement boundary conditions(DBCs), uniform traction boundary conditions(TBCs), and periodic boundary conditions(PBCs). As a result, significant discrepancies arise in the predicted shakedown domain sizes of heterogeneous materials. Built on the demonstrated relationship between SSFs under different boundary conditions, this study explores the conservative relationships among different shakedown domains, and provides proof of the relationship between the elastic limit(EL) factors and the shakedown loading factors under the loading domain of two load vertices. By utilizing numerical examples, we highlight the conservatism present in certain results reported in the existing literature. Among the investigated boundary conditions, the obtained shakedown domain is the most conservative under TBCs.Conversely, utilizing PBCs to construct an SSF for the shakedown analysis leads to less conservative lower bounds, indicating that PBCs should be employed as the preferred boundary conditions for the shakedown analysis of heterogeneous materials.
基金Projects(03JJY3078, 04JJ40032) supported by the Natural Science Foundation of Hunan Province, China project(03A006) supported by Scientific Research Fund of Hunan Provincial Education Department, China
文摘Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.
基金Funded by Scientific Research Key Program of Beijing Municipal Commission of Education(KZ200610017010)Beijing Elitist Program Project(20041D0500517).
文摘Numerical simulation concerning the forming and welding process of spiral welded pipe was conducted, which included three steps ： the first step was the stress analysis when the spiral was formed, and then the stress was regarded as initial condition of melding during the temperature field analysis in the process of welding, the last step was the thermal stress analysis of the weld seam after the welding was over. Moreover, when the steel strip was pushed, the stress was also calculated by non-linearity contact technology using Abaqus Software. By finite element modeling and calculating of the forming and welding process of the spiral welded pipe, the key points of the multi-fields synthetic simulating were studied and discussed.
基金funded by the German Federal Ministry of Economics and Technology (BMWi) under contract 02E10377
文摘This paper examines the effective stress in indurated clay rock theoretically and experimentally.A stress concept is derived from the analysis of the microstructure and of the pore water in the highly-indurated Callovo-Oxfordian and Opalinus clay rocks,and subsequently validated by various experiments performed on these claystones.The concept suggests that the interparticle or effective stress in a dense clay ewater system is transferred through both the adsorbed interparticle pore water in narrow pores and the solidesolid contact between non-clay mineral grains.The experiments show that the adsorbed pore water in the claystones is capable of bearing deviatoric effective stresses up to the failure strength.The applied stresses are for the most part or even totally transferred by the bound pore water,i.e.the swelling pressure in the interparticle bound pore water is almost equivalent to the effective stress.This stress concept provides a reasonable view to the nature of the effective stress in argillaceous rock and forms the fundamental basis for studies of the hydro-mechanical properties and processes in clay formations.
基金the Natural Sciences and Engineering Research Council of Canada(NSERC)Institut de recherche Robert-Sauve en sante et en securite du travail(IRSST)industrial partners of the Research Institute on Mines and the Environment(RIME UQAT-Polytechnique)
文摘Cemented paste backfill(CPB) is largely used in underground mines worldwide.A key issue associated with application of CPB is to estimate the stresses in backfilled stopes and on barricades.Recent numerical and experimental results show that arching effect is absent shortly after the placement of CPB in stopes.However,stress decreases in barricade drift with increasing distance between the measurement points and drawpoint have also been observed,demonstrating arching effect shortly after the pouring of CPB.To explain these paradoxes,CPB is considered as Bingham fluid having a yield shear stress.Three dimensional analytical solutions are proposed to evaluate the short-term total stresses in backfilled stopes and on barricades,accounting for the CPB's yield shear stress-induced arching effect.Stress diminution due to such arching effect in the backfilled stopes and on barricades is indeed obtained.But the reduction becomes insignificant using typical yield shear stress and stope geometry.More analyses indicate that the typical yield shear stress values do not fully correspond to field conditions where the yield shear stress would increase exponentially due to apparent consolidation(loss of water by drainage,a phenomenon similar to the desiccation of overly saturated fine-grained materials).
文摘为探讨菊茎叶总黄酮(total flavonoids from stems and leaves of Chrysanthemum morifolium,TFCSL)抗氧化应激的活性成分,阐明其药效物质基础和作用机制。采用HPLC建立不同批次TFCSL指纹图谱;以高浓度葡萄糖诱导人脐静脉内皮细胞建立氧化损伤模型,将丙二醛含量、乳酸脱氢酶含量和超氧化物歧化酶活性作为药效指标;采用灰色关联度和偏最小二乘法分析其谱-效关系确定抗氧化药效物质基础;基于网络药理学结合分子对接探究核心靶点及作用通路。从12批次TFCSL指纹图谱中确定12个共有峰,指认其中9个化学成分;各批次总黄酮样品均可减少细胞凋亡、降低丙二醛及乳酸脱氢酶含量、提高超氧化物歧化酶活性;综合2种数学模型确定峰5(芹菜素-7-O-β-D-葡萄糖苷)、峰6(异绿原酸C)、峰7(香叶木素-7-O-β-D-葡萄糖苷)为抗氧化物质基础;筛选出的3个活性成分作用于抗氧化应激的33个靶点;关键靶点为TNF、CASP3、EDNRA、XDH、PTGS2、MMP2,主要涉及脂质和动脉粥样硬化信号通路、IL-17信号通路、糖尿病并发症AGE-RAGE信号通路、TNF通路、MPKA通路等信号通路;分子对接结果显示活性成分与关键靶点之间均有较好的结合力。表明TFCSL抗氧化应激的物质基础可能为芹菜素-7-O-β-D-葡萄糖苷、异绿原酸C、香叶木素-7-O-β-D-葡萄糖苷,推测通过TNF、CASP3等靶点作用动脉粥样硬化信号通路、IL17信号通路发挥作用,体现菊茎叶多成分、多靶点抗氧化的作用特点。
文摘目的:系统评价正念减压对辅殖助孕患者的干预效果。方法:检索中国知网、中国生物医学文献数据库、万方数据知识服务平台、维普、PubMed、The Cochrane Library、Embase、Web of Science数据库,收集建库至2023年12月发表的有关正念减压在辅助生殖助孕患者中应用的随机对照试验。由两名研究者对文献进行筛选、评价和资料提取,并评价纳入研究的偏倚风险。采用RevMan5.4和Stata17.0软件对纳入文献进行数据分析。结果:共纳入9项研究,1642例患者。Meta分析结果显示:与常规治疗相比,正念减压干预有助于改善辅助生殖助孕患者的心理状态,减轻压力知觉,提高生活质量。以抑郁自评量表(SDS)为评价标准[MD=-8.17,95%CI(-9.16,-7.17),P<0.01],以焦虑自评量表(SAS)为评价标准[MD=-8.71,95%CI(-10.24,-7.18),P<0.01],以压力知觉量表(CPSS)为评价标准[MD=-4.38,95%CI(-5.41,-3.35),P<0.01]。健康状况量表(SF-36量表)的4个评价维度:精神健康[MD=17.50,95%CI(15.67,19.33),P<0.01]、精力[MD=12.05,95%CI(10.18,13.92),P<0.01]、生理职能[MD=8.15,95%CI(6.51,9.79),P<0.01]、生理功能[MD=14.50,95%CI(12.65,16.35),P<0.01]。结论:现有证据表明,正念减压对辅助生殖助孕患者干预效果显著,但受本次纳入研究证据数量、质量限制,尚需开展更多有关辅助生殖助孕患者正念减压干预的高质量研究。
