Bi layer formation in Cu/Sn-58Bi/Cu solder joints was investigated with different current densities and solder thickness. Uniform and continuous Bi layers were formed at the anode interface which indicated that Bi was...Bi layer formation in Cu/Sn-58Bi/Cu solder joints was investigated with different current densities and solder thickness. Uniform and continuous Bi layers were formed at the anode interface which indicated that Bi was the main diffusing species migrating from the cathode to the anode. The electromigration force and Joule heating took on the main driving forces for Bi diffusion and migration. In addition, two appearance types of Bi layers, planar-type and groove-type, were found during current stressing. The morphology and thickness of Bi layers were affected by current density and current stressing time.展开更多
Recent years, it has attracted more attentions to increase the porosity and pore size of nanofibrous scaffolds to provide the for the cells to grow into the small-diameter vascular grafts. In this study, a novel bi-la...Recent years, it has attracted more attentions to increase the porosity and pore size of nanofibrous scaffolds to provide the for the cells to grow into the small-diameter vascular grafts. In this study, a novel bi-layer tubular scaffold with an inner layer and an outer layer was fabricated. The inner layer was random collagen/poly （ L-lactide-co-caprolactone ） I P （ LLA- CL） ] nanofibrous mat fabricated by conventional electrospinning and the outer layer was aligned collagen/P （LLA-CL） nanoyarns prepared by a dynamic liquid dectrospinning method. Fourier transform infrared spectroscopy （FTIR） was used to characterize the chemical structure. Scanning electron microscopy （ SEM ） was employed to observe the morphology of the layers and the cross- sectioned bi-layer tubular scaffold. A liquid displacement method was employed to measure the porosities of the inner and outer layers. Stress-strain curves were obtained to evaluate the mechanical properties of the two different layers and the bi-layer membrane. The diameters of the nanofibers and the nanoyarns were （480 ± 197 ） nm and （ 19.66 ± 4.05 ） μm, respectively. The outer layer had a significantly higher porosity and a larger pore size than those of the inner layer. Furthermore, the bi-layer membrane showed a good mechanical property which was suitable as small-diameter vascular graft. The results indicated that the bi-layer tubular scaffold had a great potential application in small vascular tissue engineering.展开更多
At first, Cr-Si (28 wt% Cr, 72 wt% Si) and Ni-Cr (80 wt% Ni, 20 wt% Cr) thin-film materials were deposited by using sputtering method at the same parameters, and their physical and electrical properties were investiga...At first, Cr-Si (28 wt% Cr, 72 wt% Si) and Ni-Cr (80 wt% Ni, 20 wt% Cr) thin-film materials were deposited by using sputtering method at the same parameters, and their physical and electrical properties were investigated. The resistances of Cr-Si and Ni-Cr thin-film resistors decreased with the increase of deposition time (thickness) and their resistivity had no apparent variations as the deposition time increased. The temperature coefficient of resistance (TCR) of single-layer Cr-Si thin-film resistors was negative and the TCR value of single-layer Ni-Cr thin-film resistors was positive. For that, we used Cr-Si thin films as upper (or lower) layer and Ni-Cr thin films as lower (upper) layer to investigate a bi-layer thin-film structure. The deposition time of Ni-Cr thin films was fixed at 10 min and the deposition time of Cr-Si thin films was changed from 10 min to 60 min. We had found that as Cr-Si thin films were used as upper or lower layers they had similar deposition rates. We had also found that the thickness and stack method of Cr-Si thin films had large effects on the resistance and TCR values of the bi-layer thin-film resistors.展开更多
A theoretical model is proposed in this paper to predict the bi-stable states of initially stressed cylindrical shell structures attached by surface anisotropic piezoelectric layers.The condition for existence of bi-s...A theoretical model is proposed in this paper to predict the bi-stable states of initially stressed cylindrical shell structures attached by surface anisotropic piezoelectric layers.The condition for existence of bi-stability of the shell structural system is presented and analytical expressions for corresponding rolled-up radii of the stable shell are given based on the principle of minimum strain energy.The resulting solution indicates that the shell system may have two stable configurations besides its initial state under a combined action of the actuating electric field and initial stresses characterized by the bending moment.If the piezoelectric layer materials act as only sensor materials without the actuating electric field,initial stresses may produce the bi-stable states,but one corresponding to its initial state.For the shell without initial stresses,the magnitude in the actuating electric field determines the number of the stable states,one or two stable configurations besides the initial state.The theoretical prediction for the bi-stable states is verified by finite element method（FEM） simulation by using the ABAQUS code.展开更多
It is widely accepted that a robust and efficient method to compute the linear spatial amplified rate ought to be developed in three-dimensional （3D） boundary layers to predict the transition with the e^N method, es...It is widely accepted that a robust and efficient method to compute the linear spatial amplified rate ought to be developed in three-dimensional （3D） boundary layers to predict the transition with the e^N method, especially when the boundary layer varies significantly in the spanwise direction. The 3D-linear parabolized stability equation （3D- LPSE） approach, a 3D extension of the two-dimensional LPSE （2D-LPSE）, is developed with a plane-marching procedure for investigating the instability of a 3D boundary layer with a significant spanwise variation. The method is suitable for a full Mach number region, and is validated by computing the unstable modes in 2D and 3D boundary layers, in both global and local instability problems. The predictions are in better agreement with the ones of the direct numerical simulation （DNS） rather than a 2D-eigenvalue problem （EVP） procedure. These results suggest that the plane-marching 3D-LPSE approach is a robust, efficient, and accurate choice for the local and global instability analysis in 2D and 3D boundary layers for all free-stream Mach numbers.展开更多
A new ion-pair complex, [BzMeQ1]2[Ni（nmt）2]1（[BzMeQ1]^＋ = 1-benzyl-4-ntethylquino- linium, mnta- -- maleonitriledithiolate） has been synthesized and structurally characterized by IR, ESI-MS and X-ray diffraction ...A new ion-pair complex, [BzMeQ1]2[Ni（nmt）2]1（[BzMeQ1]^＋ = 1-benzyl-4-ntethylquino- linium, mnta- -- maleonitriledithiolate） has been synthesized and structurally characterized by IR, ESI-MS and X-ray diffraction methods. Complex 1 is of triclinic, space group PI, with a = 9.079（2）, b = 10.154（2）, c = 11.243（2）A, α= 81.58（1）, β= 69.63（1）, γ = 68.02（1）°, V= 940.1（3）A3, Dc = 1.427 g/cm^3, Z = 1, F（000） = 418 and R = 0.0442. A 2D layer structure is formed via the cation-cation π…π and C-H…π interactions observed in the solid state of the complex.展开更多
随着第五代移动通信(5th generation mobile communication,5G)基站建设数量的剧增,5G基站的备用电池将是一个具有巨大潜能的储能资源。我国电力市场化改革正不断推进,研究5G基站的备用储能参与电力市场交易是实现电网和通信运营商互利...随着第五代移动通信(5th generation mobile communication,5G)基站建设数量的剧增,5G基站的备用电池将是一个具有巨大潜能的储能资源。我国电力市场化改革正不断推进,研究5G基站的备用储能参与电力市场交易是实现电网和通信运营商互利共赢的有效途径。考虑到5G基站备用储能参与电力市场的特殊性,建立了计及退化成本和可调度容量的基站储能电池模型,并将零散的基站聚合成5G基站虚拟电厂(virtual power plant,VPP)。然后,将5G基站VPP作为独立的竞价主体,构建双层的电能量-调频辅助服务市场交易决策模型,并利用KKT(Karush-Kuhn-Tucker)条件和对偶理论将双层模型转化为可解的混合整数规划问题。最后,通过算例评估了5G基站备用储能的可调度容量以及所提交易决策模型的有效性。展开更多
基金supported by the China Postdoctoral Science Foundation (No. 20100480250)the Beijing Natural Science Foundation Program and Scientific Research Key Program of Beijing Municipal Commission of Education(No. KZ200910005004)
文摘Bi layer formation in Cu/Sn-58Bi/Cu solder joints was investigated with different current densities and solder thickness. Uniform and continuous Bi layers were formed at the anode interface which indicated that Bi was the main diffusing species migrating from the cathode to the anode. The electromigration force and Joule heating took on the main driving forces for Bi diffusion and migration. In addition, two appearance types of Bi layers, planar-type and groove-type, were found during current stressing. The morphology and thickness of Bi layers were affected by current density and current stressing time.
基金National Natural Science Foundations of China，Science and Technology Commission of Shanghai Municipality,China，Ph.D.Programs Foundation of Ministry of Education of China
文摘Recent years, it has attracted more attentions to increase the porosity and pore size of nanofibrous scaffolds to provide the for the cells to grow into the small-diameter vascular grafts. In this study, a novel bi-layer tubular scaffold with an inner layer and an outer layer was fabricated. The inner layer was random collagen/poly （ L-lactide-co-caprolactone ） I P （ LLA- CL） ] nanofibrous mat fabricated by conventional electrospinning and the outer layer was aligned collagen/P （LLA-CL） nanoyarns prepared by a dynamic liquid dectrospinning method. Fourier transform infrared spectroscopy （FTIR） was used to characterize the chemical structure. Scanning electron microscopy （ SEM ） was employed to observe the morphology of the layers and the cross- sectioned bi-layer tubular scaffold. A liquid displacement method was employed to measure the porosities of the inner and outer layers. Stress-strain curves were obtained to evaluate the mechanical properties of the two different layers and the bi-layer membrane. The diameters of the nanofibers and the nanoyarns were （480 ± 197 ） nm and （ 19.66 ± 4.05 ） μm, respectively. The outer layer had a significantly higher porosity and a larger pore size than those of the inner layer. Furthermore, the bi-layer membrane showed a good mechanical property which was suitable as small-diameter vascular graft. The results indicated that the bi-layer tubular scaffold had a great potential application in small vascular tissue engineering.
文摘At first, Cr-Si (28 wt% Cr, 72 wt% Si) and Ni-Cr (80 wt% Ni, 20 wt% Cr) thin-film materials were deposited by using sputtering method at the same parameters, and their physical and electrical properties were investigated. The resistances of Cr-Si and Ni-Cr thin-film resistors decreased with the increase of deposition time (thickness) and their resistivity had no apparent variations as the deposition time increased. The temperature coefficient of resistance (TCR) of single-layer Cr-Si thin-film resistors was negative and the TCR value of single-layer Ni-Cr thin-film resistors was positive. For that, we used Cr-Si thin films as upper (or lower) layer and Ni-Cr thin films as lower (upper) layer to investigate a bi-layer thin-film structure. The deposition time of Ni-Cr thin films was fixed at 10 min and the deposition time of Cr-Si thin films was changed from 10 min to 60 min. We had found that as Cr-Si thin films were used as upper or lower layers they had similar deposition rates. We had also found that the thickness and stack method of Cr-Si thin films had large effects on the resistance and TCR values of the bi-layer thin-film resistors.
文摘A theoretical model is proposed in this paper to predict the bi-stable states of initially stressed cylindrical shell structures attached by surface anisotropic piezoelectric layers.The condition for existence of bi-stability of the shell structural system is presented and analytical expressions for corresponding rolled-up radii of the stable shell are given based on the principle of minimum strain energy.The resulting solution indicates that the shell system may have two stable configurations besides its initial state under a combined action of the actuating electric field and initial stresses characterized by the bending moment.If the piezoelectric layer materials act as only sensor materials without the actuating electric field,initial stresses may produce the bi-stable states,but one corresponding to its initial state.For the shell without initial stresses,the magnitude in the actuating electric field determines the number of the stable states,one or two stable configurations besides the initial state.The theoretical prediction for the bi-stable states is verified by finite element method（FEM） simulation by using the ABAQUS code.
基金Project supported by the National Natural Science Foundation of China(Nos.11272183,11572176,11402167,11202147,and 11332007)the National Program on Key Basic Research Project of China(No.2014CB744801)
文摘It is widely accepted that a robust and efficient method to compute the linear spatial amplified rate ought to be developed in three-dimensional （3D） boundary layers to predict the transition with the e^N method, especially when the boundary layer varies significantly in the spanwise direction. The 3D-linear parabolized stability equation （3D- LPSE） approach, a 3D extension of the two-dimensional LPSE （2D-LPSE）, is developed with a plane-marching procedure for investigating the instability of a 3D boundary layer with a significant spanwise variation. The method is suitable for a full Mach number region, and is validated by computing the unstable modes in 2D and 3D boundary layers, in both global and local instability problems. The predictions are in better agreement with the ones of the direct numerical simulation （DNS） rather than a 2D-eigenvalue problem （EVP） procedure. These results suggest that the plane-marching 3D-LPSE approach is a robust, efficient, and accurate choice for the local and global instability analysis in 2D and 3D boundary layers for all free-stream Mach numbers.
基金the President's Science Foundation of South China Agricultural University (No. 2005K092)
文摘A new ion-pair complex, [BzMeQ1]2[Ni（nmt）2]1（[BzMeQ1]^＋ = 1-benzyl-4-ntethylquino- linium, mnta- -- maleonitriledithiolate） has been synthesized and structurally characterized by IR, ESI-MS and X-ray diffraction methods. Complex 1 is of triclinic, space group PI, with a = 9.079（2）, b = 10.154（2）, c = 11.243（2）A, α= 81.58（1）, β= 69.63（1）, γ = 68.02（1）°, V= 940.1（3）A3, Dc = 1.427 g/cm^3, Z = 1, F（000） = 418 and R = 0.0442. A 2D layer structure is formed via the cation-cation π…π and C-H…π interactions observed in the solid state of the complex.
文摘随着第五代移动通信(5th generation mobile communication,5G)基站建设数量的剧增,5G基站的备用电池将是一个具有巨大潜能的储能资源。我国电力市场化改革正不断推进,研究5G基站的备用储能参与电力市场交易是实现电网和通信运营商互利共赢的有效途径。考虑到5G基站备用储能参与电力市场的特殊性,建立了计及退化成本和可调度容量的基站储能电池模型,并将零散的基站聚合成5G基站虚拟电厂(virtual power plant,VPP)。然后,将5G基站VPP作为独立的竞价主体,构建双层的电能量-调频辅助服务市场交易决策模型,并利用KKT(Karush-Kuhn-Tucker)条件和对偶理论将双层模型转化为可解的混合整数规划问题。最后,通过算例评估了5G基站备用储能的可调度容量以及所提交易决策模型的有效性。
