In the present paper we obtain the following result: Theorem Let M^R be a compact submanifold with parallel mean curvature vector in a locally symmetric and conformally flat Riemannian manifold N^(n+p)(p>1). If the...In the present paper we obtain the following result: Theorem Let M^R be a compact submanifold with parallel mean curvature vector in a locally symmetric and conformally flat Riemannian manifold N^(n+p)(p>1). If then M^n lies in a totally geodesic submanifold N^(n+1).展开更多
In order to study the safety and the comfort of high-speed trains running on a single-tower cable-stayed bridge under spatial gust,a dynamic model of wind-train-bridge analysis model is built based on the autoregressi...In order to study the safety and the comfort of high-speed trains running on a single-tower cable-stayed bridge under spatial gust,a dynamic model of wind-train-bridge analysis model is built based on the autoregressive method,the multi-body dynamics method and the finite element method.On this basis,the influence of spatial gust model loading,the suspension parameters change,wind attack angle and speed on the train-bridge system are analyzed by combining the time/frequency domain analysis and statistical methods.The results show that the spatial gust environment is one of the most important factors affecting safety and comfort and can make the calculation result tend to be conservative and more conducive.The response changes caused by K_(py),K_(px) and K_(sx) changes are nearly linear,while Ksy shows nonlinear characteristics and the most sensitivity.Wind attack angle at 75°and 90°has the greatest influence on the vehicle-bridge system.For ride comfort index,when pre-set wind speed(α=75°)reaches 20 m/s,the vertical acceleration firstly exceeds the limit value;when wind speed(α=90°)reaches 21.5 m/s,the lateral acceleration firstly exceeds the limit value,and the ride comfort of the vehicle cannot be guaranteed.For running safety index,when pre-set wind speed(α=75°)reaches 24.6 m/s,the wheel unloading coefficient firstly exceeds the limit;when pre-set wind speed(α=90°)reaches 24.5 m/s,the derailment coefficient firstly exceeds the limit,and the running safety cannot be guaranteed.The results can provide a suitable reference for the safe and stable operation of trains on the bridge.展开更多
In order to obtain direct solutions of parallel manipulator without divergence in real time,a modified global Newton-Raphson(MGNR) algorithm was proposed for forward kinematics analysis of six-degree-of-freedom(DOF) p...In order to obtain direct solutions of parallel manipulator without divergence in real time,a modified global Newton-Raphson(MGNR) algorithm was proposed for forward kinematics analysis of six-degree-of-freedom(DOF) parallel manipulator.Based on geometrical frame of parallel manipulator,the highly nonlinear equations of kinematics were derived using analytical approach.The MGNR algorithm was developed for the nonlinear equations based on Tailor expansion and Newton-Raphson iteration.The procedure of MGNR algorithm was programmed in Matlab/Simulink and compiled to a real-time computer with Microsoft visual studio.NET for implementation.The performance of the MGNR algorithms for 6-DOF parallel manipulator was analyzed and confirmed.Applying the MGNR algorithm,the real generalized pose of moving platform is solved by using the set of given positions of actuators.The theoretical analysis and numerical results indicate that the presented method can achieve the numerical convergent solution in less than 1 ms with high accuracy(1×10-9 m in linear motion and 1×10-9 rad in angular motion),even the initial guess value is far from the root.展开更多
Using two datasets of global pentad grid precipitation and global 850 hPa geopotential height during 1979-2007,this study identified global monsoon troughs and global atmospheric centers of action (ACAs) on a pentad s...Using two datasets of global pentad grid precipitation and global 850 hPa geopotential height during 1979-2007,this study identified global monsoon troughs and global atmospheric centers of action (ACAs) on a pentad scale.The global monsoon troughs consist of planetary-scale monsoon troughs and peninsula-scale monsoon troughs.Forced by seasonal variations in solar radiation,the inter-tropical convergence zones (ITCZs) represent the planetary-scale monsoon troughs,which are active and shift over the tropical North Pacific,the tropical North Atlantic,and the tropical South Indian oceans.The peninsula-scale monsoon troughs are originated from regional land-sea topography and varied with contrasts in seasonal land-sea surface temperatures and precipitation.During the boreal summer,five peninsula-scale troughs and one planetary-scale trough are distributed in the Asia-Northwest Pacific (NWP) region.In total,22 troughs,nine monsoon troughs,and 19 ACAs in the lower troposphere were identified.Relevant ACAs may be useful in constructing regional monsoon and circulation indices.展开更多
With the rapid development of cryptography, the strength of security protocols and encryption algorithms consumedly relies on the quality of random number. In many cryptography applications, higher speed is one of the...With the rapid development of cryptography, the strength of security protocols and encryption algorithms consumedly relies on the quality of random number. In many cryptography applications, higher speed is one of the references required. A new security random number generator architecture is presented. Its philosophy architecture is implemented with FPGA, based on the thermal noise and linear feedback shift register(LFSR). The thermal noise initializes LFSRs and is used as the disturbed source of the system to ensure the unpredictability of the produced random number and improve the security strength of the system. Parallel LFSRs can produce the pseudo-random numbers with long period and higher speed. The proposed architecture can meet the requirements of high quality and high speed in cryptography.展开更多
At the middle pylon of a three-pylon two-span suspension bridge, the effect of unbalanced loads on the adjacent spans may result in a series of technical bottlenecks in design, such as stability and anti-slippage betw...At the middle pylon of a three-pylon two-span suspension bridge, the effect of unbalanced loads on the adjacent spans may result in a series of technical bottlenecks in design, such as stability and anti-slippage between saddles and main cables. This article presents the researches conducted on structure selection and behavior characteristics of middle pylon, interaction mechanism between main cables and saddles and their anti-slippage safety performance, elastic and plastic stability analysis and safety assessment of steel middle pylon, and fatigue design load and method for steel pylon of Taizhou Bridge. According to the research results, a longitudinal inverted Y shape steel middle pylon is used in design, effectively solving many technical difficulties, and this type of pylon has become a suitable middle pylon structural form for many three-ovlon two-soan susoension bridges.展开更多
We have discussed the C-totally real subrnanifolds with parallel mean curvature vector of Sasakian space form, obtained a formula of J.Simons type, and improved one result of S.Yamaguchi.
During the excavation of three-parallel-hole tunnel, the tunnel might collapse due to over-stress as a result of inadequate rock pillar width. Treating the rock overburden depth, rock strength, and rock pillar width a...During the excavation of three-parallel-hole tunnel, the tunnel might collapse due to over-stress as a result of inadequate rock pillar width. Treating the rock overburden depth, rock strength, and rock pillar width as variables, a series of 3D numerical analysis was carried out to examine the effect of each variable on the safety of the tunnel, in particular the rock pillar. A stress strength ratio (SSR) was used to define whether the safety of the rock pillar was exceeded. A simple design chart for the case of three-parallel-hole tunnel, which took into account the influence of overburden depth, rock pillar width, and rock strength, was also proposed for used in the preliminary design stage.展开更多
文摘In the present paper we obtain the following result: Theorem Let M^R be a compact submanifold with parallel mean curvature vector in a locally symmetric and conformally flat Riemannian manifold N^(n+p)(p>1). If then M^n lies in a totally geodesic submanifold N^(n+1).
基金Project(20ZR1460700) supported by the Natural Science Foundation of Shanghai,ChinaProject supported by Shanghai Collaborative Innovation Research Center for Multi-network&Multi-modal Rail Transit,China。
文摘In order to study the safety and the comfort of high-speed trains running on a single-tower cable-stayed bridge under spatial gust,a dynamic model of wind-train-bridge analysis model is built based on the autoregressive method,the multi-body dynamics method and the finite element method.On this basis,the influence of spatial gust model loading,the suspension parameters change,wind attack angle and speed on the train-bridge system are analyzed by combining the time/frequency domain analysis and statistical methods.The results show that the spatial gust environment is one of the most important factors affecting safety and comfort and can make the calculation result tend to be conservative and more conducive.The response changes caused by K_(py),K_(px) and K_(sx) changes are nearly linear,while Ksy shows nonlinear characteristics and the most sensitivity.Wind attack angle at 75°and 90°has the greatest influence on the vehicle-bridge system.For ride comfort index,when pre-set wind speed(α=75°)reaches 20 m/s,the vertical acceleration firstly exceeds the limit value;when wind speed(α=90°)reaches 21.5 m/s,the lateral acceleration firstly exceeds the limit value,and the ride comfort of the vehicle cannot be guaranteed.For running safety index,when pre-set wind speed(α=75°)reaches 24.6 m/s,the wheel unloading coefficient firstly exceeds the limit;when pre-set wind speed(α=90°)reaches 24.5 m/s,the derailment coefficient firstly exceeds the limit,and the running safety cannot be guaranteed.The results can provide a suitable reference for the safe and stable operation of trains on the bridge.
基金Project(HgdJG00401D04) supported by National 921 Manned Space Project Foundation of ChinaProject(SKLRS200803B) supported by the Self-Planned Task Foundation of State Key Laboratory of Robotics and System (HIT) of China+1 种基金Project(CDAZ98502211) supported by China’s "World Class University (985)" Project FoundationProject(50975055) supported by the National Natural Science Foundation of China
文摘In order to obtain direct solutions of parallel manipulator without divergence in real time,a modified global Newton-Raphson(MGNR) algorithm was proposed for forward kinematics analysis of six-degree-of-freedom(DOF) parallel manipulator.Based on geometrical frame of parallel manipulator,the highly nonlinear equations of kinematics were derived using analytical approach.The MGNR algorithm was developed for the nonlinear equations based on Tailor expansion and Newton-Raphson iteration.The procedure of MGNR algorithm was programmed in Matlab/Simulink and compiled to a real-time computer with Microsoft visual studio.NET for implementation.The performance of the MGNR algorithms for 6-DOF parallel manipulator was analyzed and confirmed.Applying the MGNR algorithm,the real generalized pose of moving platform is solved by using the set of given positions of actuators.The theoretical analysis and numerical results indicate that the presented method can achieve the numerical convergent solution in less than 1 ms with high accuracy(1×10-9 m in linear motion and 1×10-9 rad in angular motion),even the initial guess value is far from the root.
基金supported jointly by the National Natural Science Foundation of China (40975039)the National Basic Research Program of China (2006CB403602 and 2009BAC51B04)
文摘Using two datasets of global pentad grid precipitation and global 850 hPa geopotential height during 1979-2007,this study identified global monsoon troughs and global atmospheric centers of action (ACAs) on a pentad scale.The global monsoon troughs consist of planetary-scale monsoon troughs and peninsula-scale monsoon troughs.Forced by seasonal variations in solar radiation,the inter-tropical convergence zones (ITCZs) represent the planetary-scale monsoon troughs,which are active and shift over the tropical North Pacific,the tropical North Atlantic,and the tropical South Indian oceans.The peninsula-scale monsoon troughs are originated from regional land-sea topography and varied with contrasts in seasonal land-sea surface temperatures and precipitation.During the boreal summer,five peninsula-scale troughs and one planetary-scale trough are distributed in the Asia-Northwest Pacific (NWP) region.In total,22 troughs,nine monsoon troughs,and 19 ACAs in the lower troposphere were identified.Relevant ACAs may be useful in constructing regional monsoon and circulation indices.
基金National Natural Science Foundation of China(60373087 and 90104005) Foundation for Doctoral SpecialBranch by Ministry of Education of China(20020486046)
文摘With the rapid development of cryptography, the strength of security protocols and encryption algorithms consumedly relies on the quality of random number. In many cryptography applications, higher speed is one of the references required. A new security random number generator architecture is presented. Its philosophy architecture is implemented with FPGA, based on the thermal noise and linear feedback shift register(LFSR). The thermal noise initializes LFSRs and is used as the disturbed source of the system to ensure the unpredictability of the produced random number and improve the security strength of the system. Parallel LFSRs can produce the pseudo-random numbers with long period and higher speed. The proposed architecture can meet the requirements of high quality and high speed in cryptography.
基金National Science and Technology Support Programs of China(No.2009BAG15B02)Key Programs for Science and Technology Development of Chinese Transportation Industry(No.2008-353-332-180)"333 High-level Personnel Training Project"Special Funded Projects in Jiangsu Province
文摘At the middle pylon of a three-pylon two-span suspension bridge, the effect of unbalanced loads on the adjacent spans may result in a series of technical bottlenecks in design, such as stability and anti-slippage between saddles and main cables. This article presents the researches conducted on structure selection and behavior characteristics of middle pylon, interaction mechanism between main cables and saddles and their anti-slippage safety performance, elastic and plastic stability analysis and safety assessment of steel middle pylon, and fatigue design load and method for steel pylon of Taizhou Bridge. According to the research results, a longitudinal inverted Y shape steel middle pylon is used in design, effectively solving many technical difficulties, and this type of pylon has become a suitable middle pylon structural form for many three-ovlon two-soan susoension bridges.
文摘We have discussed the C-totally real subrnanifolds with parallel mean curvature vector of Sasakian space form, obtained a formula of J.Simons type, and improved one result of S.Yamaguchi.
文摘During the excavation of three-parallel-hole tunnel, the tunnel might collapse due to over-stress as a result of inadequate rock pillar width. Treating the rock overburden depth, rock strength, and rock pillar width as variables, a series of 3D numerical analysis was carried out to examine the effect of each variable on the safety of the tunnel, in particular the rock pillar. A stress strength ratio (SSR) was used to define whether the safety of the rock pillar was exceeded. A simple design chart for the case of three-parallel-hole tunnel, which took into account the influence of overburden depth, rock pillar width, and rock strength, was also proposed for used in the preliminary design stage.
