The analysis used simple finite elements is performed to simulate the tensile behavior of corroded reinforcing bars extracted from three actual concrete structures. The cross-sectional area of the elements is set to h...The analysis used simple finite elements is performed to simulate the tensile behavior of corroded reinforcing bars extracted from three actual concrete structures. The cross-sectional area of the elements is set to have the actual distribution measured by 3D laser scanner system. The variable factor in the analysis is the length of the elements. The analysis results show that the length of the elements has a major influence on the deformation capacity after yielding. The calculated stress-strain curves, obtained using the elements with a length that is 2 times the bar diameter, are in good agreement with the tensile test results. The calculated stress-strain curves are modeled using a bi-linear model to facilitate the FEA （finite element analysis） of an overall concrete structure. From the analysis results, both the tensile and yield strengths decrease in proportion to the reduction of the minimum cross-sectional area of corroded bars. The ultimate strain has a remarkable decrement as the reduction of the minimum cross-sectional area. Formulas for determining these values are proposed as a function of the decrement ratio of the minimum cross-sectional area of a corroded bar.展开更多
The demand of further increasing bypass ratio of aeroengine will lead to low pressure turbines with higher diameter. Therefore, it is necessary to design a duct to guide the hot gas flow which is expelled from the ups...The demand of further increasing bypass ratio of aeroengine will lead to low pressure turbines with higher diameter. Therefore, it is necessary to design a duct to guide the hot gas flow which is expelled from the upstream high pressure (HP) turbine stage to the downstream low pressure (LP) turbine stage. Named by its position, this kind of duct is always called intermediate turbine ducts (ITDs). Due to the pursuit of higher thrust ratio of the aeroengine, this kind of ITDs has to beas short as possible which leads to aggressive (high diffusion) S-shaped ITDs' geometry. In this paper, two different schemes of high diffusion separation-free S-shaped ITDs were studied with the aid of three-dimensional CFD programs. Although these two ITDs have the same area ratios (AR), because of the different duct length, they have totally different area as well as area change rates. With the detailed calculation results, comparisons were made to investigate the underneath physical mechanisms. Additionally, a direct estimation of the ITDs' loss is given at the end of this paper and some ITDs' novel design idea is proposed to initiate some further discussions.展开更多
The performance of the lithium-ion cell is heavily dependent on the ability of the host electrodes to accommodate and release Li＋ ions from the local structure. While the choice of electrode materials may define para...The performance of the lithium-ion cell is heavily dependent on the ability of the host electrodes to accommodate and release Li＋ ions from the local structure. While the choice of electrode materials may define parameters such as cell potential and capacity, the process of intercalation may be physically limited by the rate of solid-state Li＋ diffusion. Increased diffusion rates in lithium-ion electrodes may be achieved through a reduction in the diffusion path, accomplished by a scaling of the respective electrode dimensions. In addition, some electrodes may undergo large volume changes associated with charging and discharging, the strain of which, may be better accommodated through nanostructuring. Failure of the host to accommodate such volume changes may lead to pulverisation of the local structure and a rapid loss of capacity. In this review article, we seek to highlight a number of significant gains in the development of nanostructured lithium-ion battery architectures （both anode and cathode）, as drivers of potential next-generation electrochemical energy storage devices.展开更多
文摘The analysis used simple finite elements is performed to simulate the tensile behavior of corroded reinforcing bars extracted from three actual concrete structures. The cross-sectional area of the elements is set to have the actual distribution measured by 3D laser scanner system. The variable factor in the analysis is the length of the elements. The analysis results show that the length of the elements has a major influence on the deformation capacity after yielding. The calculated stress-strain curves, obtained using the elements with a length that is 2 times the bar diameter, are in good agreement with the tensile test results. The calculated stress-strain curves are modeled using a bi-linear model to facilitate the FEA （finite element analysis） of an overall concrete structure. From the analysis results, both the tensile and yield strengths decrease in proportion to the reduction of the minimum cross-sectional area of corroded bars. The ultimate strain has a remarkable decrement as the reduction of the minimum cross-sectional area. Formulas for determining these values are proposed as a function of the decrement ratio of the minimum cross-sectional area of a corroded bar.
文摘The demand of further increasing bypass ratio of aeroengine will lead to low pressure turbines with higher diameter. Therefore, it is necessary to design a duct to guide the hot gas flow which is expelled from the upstream high pressure (HP) turbine stage to the downstream low pressure (LP) turbine stage. Named by its position, this kind of duct is always called intermediate turbine ducts (ITDs). Due to the pursuit of higher thrust ratio of the aeroengine, this kind of ITDs has to beas short as possible which leads to aggressive (high diffusion) S-shaped ITDs' geometry. In this paper, two different schemes of high diffusion separation-free S-shaped ITDs were studied with the aid of three-dimensional CFD programs. Although these two ITDs have the same area ratios (AR), because of the different duct length, they have totally different area as well as area change rates. With the detailed calculation results, comparisons were made to investigate the underneath physical mechanisms. Additionally, a direct estimation of the ITDs' loss is given at the end of this paper and some ITDs' novel design idea is proposed to initiate some further discussions.
基金This work was supported by Science Foundation Ireland （SFI） Grant No. 07/SRC/I1172.
文摘The performance of the lithium-ion cell is heavily dependent on the ability of the host electrodes to accommodate and release Li＋ ions from the local structure. While the choice of electrode materials may define parameters such as cell potential and capacity, the process of intercalation may be physically limited by the rate of solid-state Li＋ diffusion. Increased diffusion rates in lithium-ion electrodes may be achieved through a reduction in the diffusion path, accomplished by a scaling of the respective electrode dimensions. In addition, some electrodes may undergo large volume changes associated with charging and discharging, the strain of which, may be better accommodated through nanostructuring. Failure of the host to accommodate such volume changes may lead to pulverisation of the local structure and a rapid loss of capacity. In this review article, we seek to highlight a number of significant gains in the development of nanostructured lithium-ion battery architectures （both anode and cathode）, as drivers of potential next-generation electrochemical energy storage devices.
