Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress ...Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure (tr3) of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.展开更多
To meet the exponentially growing demand fbr bandwidth in Optical Transport Networks (OTNs), 100-Gb/s (100G) coherent technology based oil Polarization-Division Multiplexed Quadrature Phase Shift Keying (PDM-QPSK...To meet the exponentially growing demand fbr bandwidth in Optical Transport Networks (OTNs), 100-Gb/s (100G) coherent technology based oil Polarization-Division Multiplexed Quadrature Phase Shift Keying (PDM-QPSK), which enables the capacity of a Wavelength Division Multiplexing (WDM) system to approach 10 Tb/s, is being widely deployed globally. As the first vendor to intro- duce a single-carrier 100G solution, A1- catel-Lucent has developed key transponder and network management technologies, which are reviewed in this paper together with their commercial evolution to 400G. Focusing on the Chinese market, we also review some key bench-mark testing results obtained in partner- ship with major Chinese operators. Finally, we discuss enabling technologies that are currently being researched to allow interfaces to scale to Terabit/s rates.展开更多
The fast deployment and penetration of 4G has cultivated human behaviors on mobile data consumption, leading to explosive growth in mobile traffic and stimulating new requirements on the capabilities of mobile network...The fast deployment and penetration of 4G has cultivated human behaviors on mobile data consumption, leading to explosive growth in mobile traffic and stimulating new requirements on the capabilities of mobile networks. To meet the requirements of mobile networks toward year 2020, the next genera- tion of mobile networks (termed as IMT-2020, or 5G) is designed to support 100 Mbps-1 Gbps user-experienced data rate, 1 ms radio transmission latency, and 1 million connec- tions per square kilometer. Recalling the vision and requirements of 5G targeting for commer- cial launch in 2020, this article overviews the key features of 5G and compares with those of 4G, and reports the world first field trials conducted to validate the key performance of 5G radio interface in 3.SGHz band. The trial results show that a 1 ms transmission latency and 1 Gbps data rate are achievable.展开更多
A three-dimensional numerical torsion shear test is presented on hollow cylinder specimen which is performed on a spherical assemblage with fixed principal stress axes using the discrete element code PFC3D.Stack wall ...A three-dimensional numerical torsion shear test is presented on hollow cylinder specimen which is performed on a spherical assemblage with fixed principal stress axes using the discrete element code PFC3D.Stack wall technique boundary conditions are employed and optimized to reasonably capture the microstructure evolution.Parametric studies are conducted in terms of the ratio κ,normal and shear stiffness of particles,wall stiffness and friction coefficients.Afterwards,in comparison with physical test,numerical results for a fixed principal stress angle(α=45°) are presented.The results show that the numerical test could capture the macro-micro mechanical behavior of the spherical particle assembly.The evolution of the coordination number demonstrates that particles in shear banding undergo remarkable decrease.The effects of localization on specimens illustrate that global stress and strain recorded from a hollow cylinder apparatus could not represent the localized response.The shearing band initiation and evolution from porosity and shear rate are visualized by contour lines in different shear strains.展开更多
Rapid and accurate identification of the characteristics(source location,number,and intensity)of pollution sources is essential for emergency assessment of contamination events.Compared with single-point source iden-t...Rapid and accurate identification of the characteristics(source location,number,and intensity)of pollution sources is essential for emergency assessment of contamination events.Compared with single-point source iden-tification,the reconstruction of multiple sources is more challenging.In this study,a two-step inversion method is proposed for multi-point pollution source reconstruction from limited measurements with the number of sources unknown.The applicability of the proposed method is validated with a set of synthetic experiments correspond-ing to one-,two-,and three-point pollution sources.The results show that the number and locations of pollution sources are retrieved exactly the same as prescribed,and the source intensities are estimated with negligible errors.The algorithm exhibits good performance in single-and multi-point pollution source identification,and its accuracy and efficiency of identification do not deteriorate with the increase in the number of sources.Some limitations of the algorithm,together with its capabilities,are also discussed in this paper.展开更多
Deformation behavior and hydraulic properties of rock are the two main factors that influence safety of excavation and use of rock engineering due to in situ stress release.The primary objective of this study is to ex...Deformation behavior and hydraulic properties of rock are the two main factors that influence safety of excavation and use of rock engineering due to in situ stress release.The primary objective of this study is to explore deformation characteristics and permeability properties and provide some parameters to character the rock under unloading conditions.A series of triaxial tests with permeability and acoustic emission signal measurement were conducted under the path of confining pressure unloading prior to the peak stress.Deformation behavior and permeability evolution in the whole stress–strain process based on these experimental results were analyzed in detail.Results demonstrate that,under the confining pressure unloading conditions,a good correspondence relationship among the stress–axial strain curve,permeability–axial strain curve and acoustic emission activity pattern was obtained.After the confining pressure was unloaded,the radial strain grew much faster than the axial strain,which induced the volumetric strain growing rapidly.All failures under confining pressure unloading conditions featured brittle shear failure with a single macro shear rupture surface.With the decrease in deformation modulus during the confining pressure unloading process,the damage variable gradually increases,indicating that confining pressure unloading was a process of damage accumulation and strength degradation.From the entire loading and unloading process,there was a certain positive correlation between the permeability and volumetric strain.展开更多
A trial equation method to nonlinear evolution equation with rank inhomogeneous is given. As appncations, the exact traveling wave solutions to some higher-order nonlinear equations such as generalized Boussinesq equa...A trial equation method to nonlinear evolution equation with rank inhomogeneous is given. As appncations, the exact traveling wave solutions to some higher-order nonlinear equations such as generalized Boussinesq equation, generalized Pochhammer-Chree equation, KdV-Burgers equation, and KS equation and so on, are obtained. Among these, some results are new. The proposed method is based on the idea of reduction of the order of ODE. Some mathematical details of the proposed method are discussed.展开更多
A modified Gurson-Tvergaard-Needleman (GTN) model that accounts for the mixed (isotropic and kinematic) hardening of cast steel GS-20Mn5V was developed and implemented in the finite dement program ABAQUS/Standard ...A modified Gurson-Tvergaard-Needleman (GTN) model that accounts for the mixed (isotropic and kinematic) hardening of cast steel GS-20Mn5V was developed and implemented in the finite dement program ABAQUS/Standard via a user-defined material subroutine UMAT. This model couples the stress state and damage evolution (pore volume fraction increase) by a classic method that assumes that the total void volume fraction is divided into a nucleation and a growth part. A parametric study was conducted to assess the effect of modified GTN model parameters on mechanical properties such as the nucleation, growth and coalescence of voids and to obtain the optimal parameter combination by the orthogonal test method. The predicted load-displacement curves of notched specimens with the optimal parameters are favorably compared to the experimental curves. Therefore, the modified GTN model can be used to predict the damage evaluation and fracture behavior of GS-20Mn5V.展开更多
The Micropile-Mechanically Stabilized Earth(MSE) wall, specially designed for mountain roads, is proposed to improve the MSE wall local stability, global stability and impact resistance of roadside barriers. Model tes...The Micropile-Mechanically Stabilized Earth(MSE) wall, specially designed for mountain roads, is proposed to improve the MSE wall local stability, global stability and impact resistance of roadside barriers. Model tests and the corresponding numerical modeling were conducted to validate the serviceability of the Micropile-MSE wall and the reliability of the numerical method. Then, a parametric study of the stress and deformation of Micropile-MSE wall based on the backfill strength and interfacial friction angle between backfill and backslope is conducted to evaluate its performance.The test results indicate that the surcharge-induced horizontal earth pressure, base pressure and lateral displacement of the wall panel of Micropile-MSE wall decrease. The corresponding numerical results are nearly equal to the measured values. The basic failure mode of MSE wall in steep terrain is the sliding of backfill along the backslope, while A-frame style micropiles are capable of preventing the sliding trend.The maximum resultant displacement can be decreased by 6.25% to 46.9% based on different interfacial friction angles, and the displacement canbe reduced by 6% ~ 56.1% based on different backfill strengths. Furthermore, the reduction increases when the interfacial friction angle and internal friction angle of backfill decrease. In addition, the lateral displacement of wall panel, the deformation of backfill decrease and the tension strain of geogrid obviously, which guarantees the MSE wall functions and provides good conditions for mountain roads.展开更多
The extended homoclinic test function method is a kind of classic, efficient and well-developed method to solve nonlinear evolution equations. In this paper, with the help of this approach, we obtain new exact solutio...The extended homoclinic test function method is a kind of classic, efficient and well-developed method to solve nonlinear evolution equations. In this paper, with the help of this approach, we obtain new exact solutions (including kinky periodic solitary-wave solutions, periodic soliton solutions, and cross kink-wave solutions) for the new (2+1)-dimensional KdV equation. These results enrich the variety of the dynamics of higher-dimensionai nonlinear wave field.展开更多
OBJECTIVE To analyze the expression and levels of serum proinflammatory cytokines including tumor necrosis factor alpha (TNF-α), and interleukin (IL)-6 in patients with hepatocellular carcinoma (HCC), who recei...OBJECTIVE To analyze the expression and levels of serum proinflammatory cytokines including tumor necrosis factor alpha (TNF-α), and interleukin (IL)-6 in patients with hepatocellular carcinoma (HCC), who received orthotopic liver transplantation (OLT).METHODS The blood samples of 20 consecutive HCC patients who underwent liver transplantation were detected and analyzed for the clinical serum biochemical parameters, TNF-α and IL-6.Blood samples were drawn from the radial artery at planned time points: preoperatively, intraoperatively, and postoperatively.Levels of serum TNF-α and IL-6 were detected with enzymelinked immunosorbent assay (ELISA).RESULTS The levels of serum TNF-αand IL-6 increased significantly at reperfusion phase compared with those detected preoperatively (P 〈 0.01), and the level of serum IL-6 remained significantly higher until the third day after the liver transplantation. There was a significant correlation between TNF-αand IL-6 (P〈0.001).CONCLUSION This research into the effects of the proinflammatory cytokines on liver transplantation has provided new insights into the mechanisms of ischemia and reperfusion injury to OLT.展开更多
A methodology was presented relating the microstructure of asphalt mixtures to their damage behavior. Digital image techniques were used to capture the asphalt mixture microstructure, and the finite element method was...A methodology was presented relating the microstructure of asphalt mixtures to their damage behavior. Digital image techniques were used to capture the asphalt mixture microstructure, and the finite element method was used to simulate the damage evolution of asphalt mixture through splitting test. Aggregates were modeled to be linearly elastic, and the mastics were modeled to be plastically damaged. The splitting test simulation results show that the material heterogeneity, the properties of aggregates and air voids have significant effects on the damage evolution approach. The damage behavior of asphalt mixture considering material heterogeneity is quite different from that of the conventional hypothesis of homogeneous material. The results indicate that the proposed method can be extended to the numerical analysis for the other micromechanical behaviors of asphalt concrete.展开更多
There are over 100 historically black colleges and universities (HBCUs) in the United States. The majority of these HBCUs are located in the southeast section of the United States. HBCUs are a major supplier of cert...There are over 100 historically black colleges and universities (HBCUs) in the United States. The majority of these HBCUs are located in the southeast section of the United States. HBCUs are a major supplier of certified public accountants (CPAs) to the profession. Therefore, the performance of candidates from HBCUs should be of interest to various constituents including educators, employers, parents, students, and other stakeholders. The purpose of this paper is to provide statistical performance on the 2011 CPA examination for large, middle, and small HBCUs based upon the number of testing events taken. Taking a testing event is not the same as passing a testing event. This was the dichotomy between quantity and quality of HBCUs' performances. For large HBCUs, Morehouse University, North Carolina Agricultural and Technical State University (NC A&T), and Tennessee State University (TSU) were cited. For middle HBCUs, Albany State University, Norfolk State University (NSU), and North Carolina Central University (NCCU) were cited. For small HBCUs, Alcorn State University, Fisk University, and University of Maryland Eastern Shore (UMES) were cited. The dichotomy between quantity and quality is real.展开更多
A phenomenological low-filed mobility model is developed to describe the dependence ot the carrier molgmty on me gate to source bias applied for AIGaN/GaN high electron mobility transistor. The results show excellent ...A phenomenological low-filed mobility model is developed to describe the dependence ot the carrier molgmty on me gate to source bias applied for AIGaN/GaN high electron mobility transistor. The results show excellent agreement with experimental data, when compared thereby proving the validity of the model. In the proposed work the temporal evolution of the mobility degradation shows a sharp decline in emission rates below 456 s-1. We also note a sharp decline for large defects densities.展开更多
基金Projects(11172090,51009052,51109069) supported by the National Natural Science Foundation of ChinaProject(2011CB013504) supported by the National Basic Research Program of China
文摘Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure (tr3) of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.
文摘To meet the exponentially growing demand fbr bandwidth in Optical Transport Networks (OTNs), 100-Gb/s (100G) coherent technology based oil Polarization-Division Multiplexed Quadrature Phase Shift Keying (PDM-QPSK), which enables the capacity of a Wavelength Division Multiplexing (WDM) system to approach 10 Tb/s, is being widely deployed globally. As the first vendor to intro- duce a single-carrier 100G solution, A1- catel-Lucent has developed key transponder and network management technologies, which are reviewed in this paper together with their commercial evolution to 400G. Focusing on the Chinese market, we also review some key bench-mark testing results obtained in partner- ship with major Chinese operators. Finally, we discuss enabling technologies that are currently being researched to allow interfaces to scale to Terabit/s rates.
基金supported in part by national Key Project (2016ZX03001021)
文摘The fast deployment and penetration of 4G has cultivated human behaviors on mobile data consumption, leading to explosive growth in mobile traffic and stimulating new requirements on the capabilities of mobile networks. To meet the requirements of mobile networks toward year 2020, the next genera- tion of mobile networks (termed as IMT-2020, or 5G) is designed to support 100 Mbps-1 Gbps user-experienced data rate, 1 ms radio transmission latency, and 1 million connec- tions per square kilometer. Recalling the vision and requirements of 5G targeting for commer- cial launch in 2020, this article overviews the key features of 5G and compares with those of 4G, and reports the world first field trials conducted to validate the key performance of 5G radio interface in 3.SGHz band. The trial results show that a 1 ms transmission latency and 1 Gbps data rate are achievable.
基金Project(41202186) supported by the National Natural Science Foundation of ChinaProject(LQ12E08007) supported by the Zhejiang Natural Science Foundation,ChinaProject(#11-KF-08) supported by the Partially Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering,Guilin University of Technology,China
文摘A three-dimensional numerical torsion shear test is presented on hollow cylinder specimen which is performed on a spherical assemblage with fixed principal stress axes using the discrete element code PFC3D.Stack wall technique boundary conditions are employed and optimized to reasonably capture the microstructure evolution.Parametric studies are conducted in terms of the ratio κ,normal and shear stiffness of particles,wall stiffness and friction coefficients.Afterwards,in comparison with physical test,numerical results for a fixed principal stress angle(α=45°) are presented.The results show that the numerical test could capture the macro-micro mechanical behavior of the spherical particle assembly.The evolution of the coordination number demonstrates that particles in shear banding undergo remarkable decrease.The effects of localization on specimens illustrate that global stress and strain recorded from a hollow cylinder apparatus could not represent the localized response.The shearing band initiation and evolution from porosity and shear rate are visualized by contour lines in different shear strains.
基金supported by the National Key R&D Program of China[Grant Nos.2017YFC1501803 and 2017YFC1502102].
文摘Rapid and accurate identification of the characteristics(source location,number,and intensity)of pollution sources is essential for emergency assessment of contamination events.Compared with single-point source iden-tification,the reconstruction of multiple sources is more challenging.In this study,a two-step inversion method is proposed for multi-point pollution source reconstruction from limited measurements with the number of sources unknown.The applicability of the proposed method is validated with a set of synthetic experiments correspond-ing to one-,two-,and three-point pollution sources.The results show that the number and locations of pollution sources are retrieved exactly the same as prescribed,and the source intensities are estimated with negligible errors.The algorithm exhibits good performance in single-and multi-point pollution source identification,and its accuracy and efficiency of identification do not deteriorate with the increase in the number of sources.Some limitations of the algorithm,together with its capabilities,are also discussed in this paper.
基金Project(2014CB047100)supported by the National Basic Research Program of China(973 Program)Projects(51679093/E090705,51774147/E0409)supported by the National Natural Science Foundation of ChinaProject(2017J01094)supported by the Natural Science Foundation of Fujian Province,China
文摘Deformation behavior and hydraulic properties of rock are the two main factors that influence safety of excavation and use of rock engineering due to in situ stress release.The primary objective of this study is to explore deformation characteristics and permeability properties and provide some parameters to character the rock under unloading conditions.A series of triaxial tests with permeability and acoustic emission signal measurement were conducted under the path of confining pressure unloading prior to the peak stress.Deformation behavior and permeability evolution in the whole stress–strain process based on these experimental results were analyzed in detail.Results demonstrate that,under the confining pressure unloading conditions,a good correspondence relationship among the stress–axial strain curve,permeability–axial strain curve and acoustic emission activity pattern was obtained.After the confining pressure was unloaded,the radial strain grew much faster than the axial strain,which induced the volumetric strain growing rapidly.All failures under confining pressure unloading conditions featured brittle shear failure with a single macro shear rupture surface.With the decrease in deformation modulus during the confining pressure unloading process,the damage variable gradually increases,indicating that confining pressure unloading was a process of damage accumulation and strength degradation.From the entire loading and unloading process,there was a certain positive correlation between the permeability and volumetric strain.
文摘A trial equation method to nonlinear evolution equation with rank inhomogeneous is given. As appncations, the exact traveling wave solutions to some higher-order nonlinear equations such as generalized Boussinesq equation, generalized Pochhammer-Chree equation, KdV-Burgers equation, and KS equation and so on, are obtained. Among these, some results are new. The proposed method is based on the idea of reduction of the order of ODE. Some mathematical details of the proposed method are discussed.
基金The National Key Research and Development Program of China(No.2017YFC0805103)the National Natural Science Foundation of China(No.51578137,51438002,51108075)the Open Research Fund Program of Jiangsu Key Laboratory of Engineering Mechanics
文摘A modified Gurson-Tvergaard-Needleman (GTN) model that accounts for the mixed (isotropic and kinematic) hardening of cast steel GS-20Mn5V was developed and implemented in the finite dement program ABAQUS/Standard via a user-defined material subroutine UMAT. This model couples the stress state and damage evolution (pore volume fraction increase) by a classic method that assumes that the total void volume fraction is divided into a nucleation and a growth part. A parametric study was conducted to assess the effect of modified GTN model parameters on mechanical properties such as the nucleation, growth and coalescence of voids and to obtain the optimal parameter combination by the orthogonal test method. The predicted load-displacement curves of notched specimens with the optimal parameters are favorably compared to the experimental curves. Therefore, the modified GTN model can be used to predict the damage evaluation and fracture behavior of GS-20Mn5V.
基金sponsored by Colorado Department of Transportation (CDOT Award No. 12 HAA 38229) to R.Y.S.P.partial funding was received by Z.Z. from the National Natural Science Foundation of China (Grant No. 51379067, 51609040, 51420105013)+3 种基金the Natural Science Foundation of Fujian Province (Grant No. 2016J05112)Science and Technology Project of Bureau of Geology and Mineral Resources of Fujian Province (DK2016014)the Natural Science Foundation of Fujian Province (Grant No. 2015J01158)the Fundamental Research Funds for the Central Universities (Grant No. 2015B17314)
文摘The Micropile-Mechanically Stabilized Earth(MSE) wall, specially designed for mountain roads, is proposed to improve the MSE wall local stability, global stability and impact resistance of roadside barriers. Model tests and the corresponding numerical modeling were conducted to validate the serviceability of the Micropile-MSE wall and the reliability of the numerical method. Then, a parametric study of the stress and deformation of Micropile-MSE wall based on the backfill strength and interfacial friction angle between backfill and backslope is conducted to evaluate its performance.The test results indicate that the surcharge-induced horizontal earth pressure, base pressure and lateral displacement of the wall panel of Micropile-MSE wall decrease. The corresponding numerical results are nearly equal to the measured values. The basic failure mode of MSE wall in steep terrain is the sliding of backfill along the backslope, while A-frame style micropiles are capable of preventing the sliding trend.The maximum resultant displacement can be decreased by 6.25% to 46.9% based on different interfacial friction angles, and the displacement canbe reduced by 6% ~ 56.1% based on different backfill strengths. Furthermore, the reduction increases when the interfacial friction angle and internal friction angle of backfill decrease. In addition, the lateral displacement of wall panel, the deformation of backfill decrease and the tension strain of geogrid obviously, which guarantees the MSE wall functions and provides good conditions for mountain roads.
基金Supported by the Natural Science Foundation of China under Grant Nos.10361007,10661002Yunnan Natural Science Foundation under Grant No.2006A0082M
文摘The extended homoclinic test function method is a kind of classic, efficient and well-developed method to solve nonlinear evolution equations. In this paper, with the help of this approach, we obtain new exact solutions (including kinky periodic solitary-wave solutions, periodic soliton solutions, and cross kink-wave solutions) for the new (2+1)-dimensional KdV equation. These results enrich the variety of the dynamics of higher-dimensionai nonlinear wave field.
文摘OBJECTIVE To analyze the expression and levels of serum proinflammatory cytokines including tumor necrosis factor alpha (TNF-α), and interleukin (IL)-6 in patients with hepatocellular carcinoma (HCC), who received orthotopic liver transplantation (OLT).METHODS The blood samples of 20 consecutive HCC patients who underwent liver transplantation were detected and analyzed for the clinical serum biochemical parameters, TNF-α and IL-6.Blood samples were drawn from the radial artery at planned time points: preoperatively, intraoperatively, and postoperatively.Levels of serum TNF-α and IL-6 were detected with enzymelinked immunosorbent assay (ELISA).RESULTS The levels of serum TNF-αand IL-6 increased significantly at reperfusion phase compared with those detected preoperatively (P 〈 0.01), and the level of serum IL-6 remained significantly higher until the third day after the liver transplantation. There was a significant correlation between TNF-αand IL-6 (P〈0.001).CONCLUSION This research into the effects of the proinflammatory cytokines on liver transplantation has provided new insights into the mechanisms of ischemia and reperfusion injury to OLT.
基金Project(50808086) supported by the National Natural Science Foundation of China
文摘A methodology was presented relating the microstructure of asphalt mixtures to their damage behavior. Digital image techniques were used to capture the asphalt mixture microstructure, and the finite element method was used to simulate the damage evolution of asphalt mixture through splitting test. Aggregates were modeled to be linearly elastic, and the mastics were modeled to be plastically damaged. The splitting test simulation results show that the material heterogeneity, the properties of aggregates and air voids have significant effects on the damage evolution approach. The damage behavior of asphalt mixture considering material heterogeneity is quite different from that of the conventional hypothesis of homogeneous material. The results indicate that the proposed method can be extended to the numerical analysis for the other micromechanical behaviors of asphalt concrete.
文摘There are over 100 historically black colleges and universities (HBCUs) in the United States. The majority of these HBCUs are located in the southeast section of the United States. HBCUs are a major supplier of certified public accountants (CPAs) to the profession. Therefore, the performance of candidates from HBCUs should be of interest to various constituents including educators, employers, parents, students, and other stakeholders. The purpose of this paper is to provide statistical performance on the 2011 CPA examination for large, middle, and small HBCUs based upon the number of testing events taken. Taking a testing event is not the same as passing a testing event. This was the dichotomy between quantity and quality of HBCUs' performances. For large HBCUs, Morehouse University, North Carolina Agricultural and Technical State University (NC A&T), and Tennessee State University (TSU) were cited. For middle HBCUs, Albany State University, Norfolk State University (NSU), and North Carolina Central University (NCCU) were cited. For small HBCUs, Alcorn State University, Fisk University, and University of Maryland Eastern Shore (UMES) were cited. The dichotomy between quantity and quality is real.
文摘A phenomenological low-filed mobility model is developed to describe the dependence ot the carrier molgmty on me gate to source bias applied for AIGaN/GaN high electron mobility transistor. The results show excellent agreement with experimental data, when compared thereby proving the validity of the model. In the proposed work the temporal evolution of the mobility degradation shows a sharp decline in emission rates below 456 s-1. We also note a sharp decline for large defects densities.