Model B-I for marco rectangular element is presented for the first time in this paper. To establish the influence surf ace for resultant R of bending plates, a number of generalized distributive loads q are defined. I...Model B-I for marco rectangular element is presented for the first time in this paper. To establish the influence surf ace for resultant R of bending plates, a number of generalized distributive loads q are defined. It is shown by numerical examples that Model B-I and the formula for the generalized distributive loads advanced in this paper are featured by high accuracy, low memory space and flexibility in practical application, and that they are especially effective for plate structures subject to moving loads, such as the two-dimensional continuous plates of highway bridges and the flat stabs in piled jetty engineering.展开更多
On the basis of composition duality principles, augmented three-field macrohybrid mixed variational problems and finite element schemes are analyzed. The compatibility condition adopted here, for compositional dualiza...On the basis of composition duality principles, augmented three-field macrohybrid mixed variational problems and finite element schemes are analyzed. The compatibility condition adopted here, for compositional dualization, is the coupling operator surjectivity, property that expresses in a general operator sense the Ladysenskaja-Babulka-Brezzi inf-sup condition. Variational macro-hybridization is performed under the assumption of decomposable primal and dual spaces relative to nonoverlapping domain decompositions. Then, through compositional dualization macro-hybrid mixed problems are obtained, with internal boundary dual traces as Lagrange multipliers. Also, ＂mass＂ preconditioned aug- mentation of three-field formulations are derived, stabilizing macro-hybrid mixed finite element schemes and rendering possible speed up of rates of convergence. Dual mixed incompressible Darcy flow problems illustrate the theory throughout the paper.展开更多
Although the quality of organic crops has been intensively studied for over three decades, there is still a lack of conclusive data that can prove the superiority of organic crops over conventional ones. There is no d...Although the quality of organic crops has been intensively studied for over three decades, there is still a lack of conclusive data that can prove the superiority of organic crops over conventional ones. There is no doubt that the organic food is safer due to the lack of pesticide residues;however, it is still not entirely sure whether vegetables and fruits produced in this way are better in the context of nutritional values. The study of commonly used vegetables in the European diet was performed to evaluate the difference in concentration of macro nutrients such as Ca, Mg, Na, N, K and P between organic and conventional crops. Additionally, the soil analysis was performed on the material from two growing systems. The results showed that organically cultivated vegetables had generally a higher level of macro nutrients. Also, soil samples showed higher content of these elements in the organically treated soil. From all vegetables, the highest concentrations of macro elements were found in parsley leaves and celery roots.展开更多
Finite element(FE) simulation is a powerful tool for investigating the mechanism of machining fiber?reinforced polymer composite(FRP). However in existing FE machining simulation works,the two?dimensional(2 D) progres...Finite element(FE) simulation is a powerful tool for investigating the mechanism of machining fiber?reinforced polymer composite(FRP). However in existing FE machining simulation works,the two?dimensional(2 D) progressive damage models only describe material behavior in plane stress,while the three?dimensional(3 D) damage models always assume an instantaneous sti ness reduction pattern. So the chip formation mechanism of FRP under machin?ing is not fully analyzed in general stress state. A 3 D macro?mechanical based FE simulation model was developed for the machining of unidirectional glass fiber reinforced plastic. An energy based 3 D progressive damage model was proposed for damage evolution and continuous sti ness degradation. The damage model was implemented for the Hashin?type criterion and Maximum stress criterion. The influences of the failure criterion and fracture energy dissipa?tion on the simulation results were studied. The simulated chip shapes,cutting forces and sub?surface damages were verified by those obtained in the reference experiment. The simulation results also show consistency with previous 2 D FE models in the reference. The proposed research provides a model for simulating FRP material behavior and the machining process in 3 D stress state.展开更多
Content of macro- and microelements in plant and soil was studied after biochar, compost, digestate, lignite, and lignohumate application. Pot experiments were carried out in Phytotron CLF Plant Master （Wertingen, Ge...Content of macro- and microelements in plant and soil was studied after biochar, compost, digestate, lignite, and lignohumate application. Pot experiments were carried out in Phytotron CLF Plant Master （Wertingen, Germany）. As tested plant lettuce （Lactucasativa） was used. Elemental composition was determined by AAS and XRF spectroscopy. Macronutrients content （Ca, Mg, K, and P） was determined by Mehlich III. Total content of carbon and nitrogen were determined by LECO TruSpec CN analyser. Results showed that different exogenous organic amendments statistically significantly influenced macro and micronutrients content in soil and plant. Satisfactory C/N ratio for soil microorganisms was measured only after compost and digestate application. As concerns hazardous elements, no legislation limits were overstepped after application of the tested organic amendments. Bioavailability and their uptake by plants followed the order： Cd 〉 Mn 〉 Zn 〉 Fe.展开更多
A precise large range worktable with high precision, high resolution and high frequency response, driven by piezoelectrical elements, is presented. The worktable configuration and the control unit are described. Also ...A precise large range worktable with high precision, high resolution and high frequency response, driven by piezoelectrical elements, is presented. The worktable configuration and the control unit are described. Also theoretical analysis and experimental study of the static and dynamic characteristics of the worktable are performed. By combining the worktable with a general purpose robot, a macro/micro manipulator system is built up and the assembly experiments are successfully accomplished.展开更多
剪切型断裂是岩土工程中常见的破坏模式,了解剪切破坏机理并准确预测剪切型裂纹的萌生、扩展过程对保障工程结构的安全性与稳定性具有重要意义.文章建立了基于比例边界有限元法(scaled boundary finite element methods,SBFEM)和非局部...剪切型断裂是岩土工程中常见的破坏模式,了解剪切破坏机理并准确预测剪切型裂纹的萌生、扩展过程对保障工程结构的安全性与稳定性具有重要意义.文章建立了基于比例边界有限元法(scaled boundary finite element methods,SBFEM)和非局部宏-微观损伤模型的剪切型裂纹动态开裂模拟方法,定义了基于偏应变概念的物质点对的正伸长量,可作为预测剪切型裂纹扩展行为的动态开裂准则,一点的损伤定义为该点影响域范围内连接的物质键损伤的加权平均值,而物质键的损伤则与基于偏应变概念的物质点对的正伸长量相关联,并引入能量退化函数建立结构域几何拓扑损伤与能量损失之间的关系,将拓扑损伤与应力应变联系起来,通过能量退化函数修正了SBFEM的刚度系数矩阵,得到了子域在损伤状态下的刚度矩阵,推导了考虑结构损伤的SBFEM动力控制方程,采用Newmark隐式算法对控制方程进行时间离散.最后,通过3个典型算例验证了建议的模型可较好地模拟剪切型断裂问题,能够很好地捕捉剪切型裂纹的扩展路径,并得到较为准确的载荷-位移曲线.展开更多
论文建立了基于比例边界有限元法(scaled boundary finite element methods,SBFEM)框架的非局部宏微观损伤模型,考虑材料细观物理参数的空间变异性,探讨了材料参数的空间变异性对结构开裂过程的影响。结果表明:考虑材料参数空间变异性后...论文建立了基于比例边界有限元法(scaled boundary finite element methods,SBFEM)框架的非局部宏微观损伤模型,考虑材料细观物理参数的空间变异性,探讨了材料参数的空间变异性对结构开裂过程的影响。结果表明:考虑材料参数空间变异性后,裂纹扩展路径具有不确定性,建议的模型能够很好地反应材料内在的随机性;随着结构受力情况的复杂化和结构本体缺陷的增多,裂纹开裂模式的变异性也会增大。自相关长度和参数变异系数对结构开裂分析结果有重要影响。展开更多
文摘Model B-I for marco rectangular element is presented for the first time in this paper. To establish the influence surf ace for resultant R of bending plates, a number of generalized distributive loads q are defined. It is shown by numerical examples that Model B-I and the formula for the generalized distributive loads advanced in this paper are featured by high accuracy, low memory space and flexibility in practical application, and that they are especially effective for plate structures subject to moving loads, such as the two-dimensional continuous plates of highway bridges and the flat stabs in piled jetty engineering.
文摘On the basis of composition duality principles, augmented three-field macrohybrid mixed variational problems and finite element schemes are analyzed. The compatibility condition adopted here, for compositional dualization, is the coupling operator surjectivity, property that expresses in a general operator sense the Ladysenskaja-Babulka-Brezzi inf-sup condition. Variational macro-hybridization is performed under the assumption of decomposable primal and dual spaces relative to nonoverlapping domain decompositions. Then, through compositional dualization macro-hybrid mixed problems are obtained, with internal boundary dual traces as Lagrange multipliers. Also, ＂mass＂ preconditioned aug- mentation of three-field formulations are derived, stabilizing macro-hybrid mixed finite element schemes and rendering possible speed up of rates of convergence. Dual mixed incompressible Darcy flow problems illustrate the theory throughout the paper.
文摘Although the quality of organic crops has been intensively studied for over three decades, there is still a lack of conclusive data that can prove the superiority of organic crops over conventional ones. There is no doubt that the organic food is safer due to the lack of pesticide residues;however, it is still not entirely sure whether vegetables and fruits produced in this way are better in the context of nutritional values. The study of commonly used vegetables in the European diet was performed to evaluate the difference in concentration of macro nutrients such as Ca, Mg, Na, N, K and P between organic and conventional crops. Additionally, the soil analysis was performed on the material from two growing systems. The results showed that organically cultivated vegetables had generally a higher level of macro nutrients. Also, soil samples showed higher content of these elements in the organically treated soil. From all vegetables, the highest concentrations of macro elements were found in parsley leaves and celery roots.
基金Supported by Science Foundation of NPU(Grant No.3102015JCS05009)Chinese Foreign Talents Introduction and Academic Exchange Program(Grant No.B13044)
文摘Finite element(FE) simulation is a powerful tool for investigating the mechanism of machining fiber?reinforced polymer composite(FRP). However in existing FE machining simulation works,the two?dimensional(2 D) progressive damage models only describe material behavior in plane stress,while the three?dimensional(3 D) damage models always assume an instantaneous sti ness reduction pattern. So the chip formation mechanism of FRP under machin?ing is not fully analyzed in general stress state. A 3 D macro?mechanical based FE simulation model was developed for the machining of unidirectional glass fiber reinforced plastic. An energy based 3 D progressive damage model was proposed for damage evolution and continuous sti ness degradation. The damage model was implemented for the Hashin?type criterion and Maximum stress criterion. The influences of the failure criterion and fracture energy dissipa?tion on the simulation results were studied. The simulated chip shapes,cutting forces and sub?surface damages were verified by those obtained in the reference experiment. The simulation results also show consistency with previous 2 D FE models in the reference. The proposed research provides a model for simulating FRP material behavior and the machining process in 3 D stress state.
文摘Content of macro- and microelements in plant and soil was studied after biochar, compost, digestate, lignite, and lignohumate application. Pot experiments were carried out in Phytotron CLF Plant Master （Wertingen, Germany）. As tested plant lettuce （Lactucasativa） was used. Elemental composition was determined by AAS and XRF spectroscopy. Macronutrients content （Ca, Mg, K, and P） was determined by Mehlich III. Total content of carbon and nitrogen were determined by LECO TruSpec CN analyser. Results showed that different exogenous organic amendments statistically significantly influenced macro and micronutrients content in soil and plant. Satisfactory C/N ratio for soil microorganisms was measured only after compost and digestate application. As concerns hazardous elements, no legislation limits were overstepped after application of the tested organic amendments. Bioavailability and their uptake by plants followed the order： Cd 〉 Mn 〉 Zn 〉 Fe.
文摘A precise large range worktable with high precision, high resolution and high frequency response, driven by piezoelectrical elements, is presented. The worktable configuration and the control unit are described. Also theoretical analysis and experimental study of the static and dynamic characteristics of the worktable are performed. By combining the worktable with a general purpose robot, a macro/micro manipulator system is built up and the assembly experiments are successfully accomplished.
文摘剪切型断裂是岩土工程中常见的破坏模式,了解剪切破坏机理并准确预测剪切型裂纹的萌生、扩展过程对保障工程结构的安全性与稳定性具有重要意义.文章建立了基于比例边界有限元法(scaled boundary finite element methods,SBFEM)和非局部宏-微观损伤模型的剪切型裂纹动态开裂模拟方法,定义了基于偏应变概念的物质点对的正伸长量,可作为预测剪切型裂纹扩展行为的动态开裂准则,一点的损伤定义为该点影响域范围内连接的物质键损伤的加权平均值,而物质键的损伤则与基于偏应变概念的物质点对的正伸长量相关联,并引入能量退化函数建立结构域几何拓扑损伤与能量损失之间的关系,将拓扑损伤与应力应变联系起来,通过能量退化函数修正了SBFEM的刚度系数矩阵,得到了子域在损伤状态下的刚度矩阵,推导了考虑结构损伤的SBFEM动力控制方程,采用Newmark隐式算法对控制方程进行时间离散.最后,通过3个典型算例验证了建议的模型可较好地模拟剪切型断裂问题,能够很好地捕捉剪切型裂纹的扩展路径,并得到较为准确的载荷-位移曲线.
文摘论文建立了基于比例边界有限元法(scaled boundary finite element methods,SBFEM)框架的非局部宏微观损伤模型,考虑材料细观物理参数的空间变异性,探讨了材料参数的空间变异性对结构开裂过程的影响。结果表明:考虑材料参数空间变异性后,裂纹扩展路径具有不确定性,建议的模型能够很好地反应材料内在的随机性;随着结构受力情况的复杂化和结构本体缺陷的增多,裂纹开裂模式的变异性也会增大。自相关长度和参数变异系数对结构开裂分析结果有重要影响。
