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
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
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
A new unified macro- and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration. In this method, the macro stress di...A new unified macro- and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration. In this method, the macro stress distribution of composite structure was calculated by commercial finite element analysis software. According to the macro stress distribution, the damage point was searched and the micro-stress distribution was calculated by reformulated finite-volume direct averaging micromechanics （FVDAM）, which was a multi-scale finite element method for composite. The micro structure failure modes were estimated with the failure strength of constituents. A unidirectional composite plate with a circular hole in the center under two kinds of loads was analyzed with the traditional macro-mechanical failure analysis method and the unified macro- and micro-mechanics failure analysis method. The results obtained by the two methods are consistent, which show this new method＇s accuracy and efficiency.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
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.
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.
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.
基金co-supported by National Basic Research Program of China, National Natural Science Foundation of China(No. 51075204)Aeronautical Science Foundation of China (No.2009ZB52028, No. 2012ZB52026)+1 种基金Research Fund for the Doctoral Program of Higher Education of China (No. 20070287039)NUAA Research Funding (No. NZ2012106)
文摘A new unified macro- and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration. In this method, the macro stress distribution of composite structure was calculated by commercial finite element analysis software. According to the macro stress distribution, the damage point was searched and the micro-stress distribution was calculated by reformulated finite-volume direct averaging micromechanics （FVDAM）, which was a multi-scale finite element method for composite. The micro structure failure modes were estimated with the failure strength of constituents. A unidirectional composite plate with a circular hole in the center under two kinds of loads was analyzed with the traditional macro-mechanical failure analysis method and the unified macro- and micro-mechanics failure analysis method. The results obtained by the two methods are consistent, which show this new method＇s accuracy and efficiency.
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.
