The damage and failure law of rock mass with holes is of great significance to the stability control of roadways. This study investigates the mechanical properties and failure modes of porous rock masses under cyclic ...The damage and failure law of rock mass with holes is of great significance to the stability control of roadways. This study investigates the mechanical properties and failure modes of porous rock masses under cyclic loading, elucidates the acoustic emission (AE) characteristics and their spatial evolution, and establishes the interrelation among AE, stress, strain, time, and cumulative damage. The results reveal that the rock mass with holes and the intact rock mass show softening and hardening characteristics after cyclic loading. The plastic strain of the rock mass with holes is smaller than that of the intact rock mass, and the stress −strain curve shows hysteresis characteristics. Under uniaxial compression, the pore-bearing rock mass shows the characteristics of higher ringing count, AE energy, b-value peak, and more cumulative ringing count in the failure stage, while it shows lower characteristics under cyclic action. At the initial stage of loading, compared with the intact rock mass, the pore-containing rock mass shows the characteristics of a low b-value. The AE positioning and cumulative damage percentage are larger, and the AE positioning is denser around the hole. The specimen with holes is mainly shear failure, and the complete specimen is mainly tensile shear failure.展开更多
A low jitter phase-locked loop （PLL） that does not need analog resistors and capacitors is designed and fabrica- ted in a 90nm CMOS digital process. The metal parasitic capacitor is used in the PLL loop filter. Test...A low jitter phase-locked loop （PLL） that does not need analog resistors and capacitors is designed and fabrica- ted in a 90nm CMOS digital process. The metal parasitic capacitor is used in the PLL loop filter. Test results show that when the PLL is locked on 1. 989GHz, the RMS jitter is 3. 7977ps, the peak-to-peak jitter is 31. 225ps, and the power con- sumption is about 9mW. The locked output frequency range is from 125MHz to 2.7GHz.展开更多
Performance evaluation shows that Hierarchical Mobile IPv6 (HMIPv6) cannot outperform standard Mobile IPv6 (MIPv6) in all scenarios. Thus, adaptive protocol selection under certain circumstances is desired. Moreover, ...Performance evaluation shows that Hierarchical Mobile IPv6 (HMIPv6) cannot outperform standard Mobile IPv6 (MIPv6) in all scenarios. Thus, adaptive protocol selection under certain circumstances is desired. Moreover, it is necessary to balance the load among different Mobility Anchor Points (MAPs). This paper proposes an efficient three-level hierarchical ar- chitecture for mobility management in HMIPv6 networks, in which a mobile node (MN) may register with either a higher/lower MAP or its home agent according to its speed and the number of connecting correspondent nodes (CNs). An admission control algorithm and a replacement algorithm are introduced to achieve load balancing between two MAP levels and among different MAPs within the same MAP level. Admission control is based on the number of CNs but not MNs that an MAP serves. In case there is no capacity for an MN, the MAP chooses an existing MN to be replaced. The replaced MN uses the MAP selection al- gorithm again to choose another mobility agent. Simulation results showed that the proposed scheme achieves better performance not only in reducing the signaling overhead, but also in load balancing among different MAPs.展开更多
Aiming at the limitation of control accuracy caused by hysteresis and creep for a piezoelectric actuator, the hysteresis phenomenon is explained based on the microscopic polarization mechanism and domain wall theory. ...Aiming at the limitation of control accuracy caused by hysteresis and creep for a piezoelectric actuator, the hysteresis phenomenon is explained based on the microscopic polarization mechanism and domain wall theory. Then a control model based on polarization is established, which can reduce the hysteresis and creep remarkablely. The experimental results show that the polarization control method is with more linearity and less hysteresis compared with the voltage control method.展开更多
In order to find out the bearing behavior of super-long piles located in deep soft clay over stiff layers around Dongting Lake, China, a test pile was first designed with the field loading test finished afterward. Bas...In order to find out the bearing behavior of super-long piles located in deep soft clay over stiff layers around Dongting Lake, China, a test pile was first designed with the field loading test finished afterward. Based on the measured test results, load transfer mechanism and bearing behavior of the pile shaft were discussed in detail. Then, by introducing a bi-linear model for shaft friction and the tri-linear model for pile tip resistance, respectively, the governing differential equation of pile soil system was set up by the load transfer method with the analytical solutions derived as well, taking into account the effect by stratified feature and various bearing conditions of subsoil, material nonlinearity, and the sediment under pile tip. Furthermore, formulas to determine the axial capacity of super-long piles by the pile top settlement were advised and applied to analyze the test pile. Good agreement between the predicted load settlement variations and the measured data is obtained to verify the validity of the present method. The results also show that, the axial bearing capacity of super-long piles should be controlled by the allowable pile top settlement, and buckling stability of the pile shaft should be paid attention as well.展开更多
Objectives： Heart rate variability （HRV） can be a simple, non-invasive method of gauging cardiac autonomic nervous system fluctuations across periodised training workloads and taper in elite athlete populations. Th...Objectives： Heart rate variability （HRV） can be a simple, non-invasive method of gauging cardiac autonomic nervous system fluctuations across periodised training workloads and taper in elite athlete populations. The purpose of these three case studies was to examine daily cardiac autonomic variations in Paralympic athletes leading in to the Paralympic games. Methods： Three Paralympie gold medallist swimmers were monitored daily for their resting HRV over a 17-week monitoring period leading up to the Paralympic games. Specific time- and frequency-domain measures, along with non-linear indices of HRV were calculated for all analyses. All HRV data were analysed individually using daily values, weekly average values, and average values for rest and training phases. Results： A significant difference in HRV was seen for all variables between athlete 1 and athletes 2 and 3 （amputee disabilities） during the entire monitoring period. Conclusion： Despite minimal long-term changes, both swimming classification and disability type significantly influence HRV during athlete monitoring. An increased understanding of individual responses to training, travel, and other outside influences affecting Paralympic athletes could potentially lead to improved management and monitoring of training workloads for enhanced nerformance.展开更多
基金Projects(U22A20165, 52004289) supported by the National Natural Science Foundation of ChinaProjects(2022XJNY01, BBJ2024001) supported by the Fundamental Research Funds for the Central Universities,China。
文摘The damage and failure law of rock mass with holes is of great significance to the stability control of roadways. This study investigates the mechanical properties and failure modes of porous rock masses under cyclic loading, elucidates the acoustic emission (AE) characteristics and their spatial evolution, and establishes the interrelation among AE, stress, strain, time, and cumulative damage. The results reveal that the rock mass with holes and the intact rock mass show softening and hardening characteristics after cyclic loading. The plastic strain of the rock mass with holes is smaller than that of the intact rock mass, and the stress −strain curve shows hysteresis characteristics. Under uniaxial compression, the pore-bearing rock mass shows the characteristics of higher ringing count, AE energy, b-value peak, and more cumulative ringing count in the failure stage, while it shows lower characteristics under cyclic action. At the initial stage of loading, compared with the intact rock mass, the pore-containing rock mass shows the characteristics of a low b-value. The AE positioning and cumulative damage percentage are larger, and the AE positioning is denser around the hole. The specimen with holes is mainly shear failure, and the complete specimen is mainly tensile shear failure.
文摘A low jitter phase-locked loop （PLL） that does not need analog resistors and capacitors is designed and fabrica- ted in a 90nm CMOS digital process. The metal parasitic capacitor is used in the PLL loop filter. Test results show that when the PLL is locked on 1. 989GHz, the RMS jitter is 3. 7977ps, the peak-to-peak jitter is 31. 225ps, and the power con- sumption is about 9mW. The locked output frequency range is from 125MHz to 2.7GHz.
基金Project supported by the National Natural Science Foundation of China (Nos. 60662003 and 60462003), the Huawei Funds for Scienceand Technology (No. YJCB2004025SP) and the Science and Tech-nology Plan of Zhejiang Province (No. 2005C21002), China
文摘Performance evaluation shows that Hierarchical Mobile IPv6 (HMIPv6) cannot outperform standard Mobile IPv6 (MIPv6) in all scenarios. Thus, adaptive protocol selection under certain circumstances is desired. Moreover, it is necessary to balance the load among different Mobility Anchor Points (MAPs). This paper proposes an efficient three-level hierarchical ar- chitecture for mobility management in HMIPv6 networks, in which a mobile node (MN) may register with either a higher/lower MAP or its home agent according to its speed and the number of connecting correspondent nodes (CNs). An admission control algorithm and a replacement algorithm are introduced to achieve load balancing between two MAP levels and among different MAPs within the same MAP level. Admission control is based on the number of CNs but not MNs that an MAP serves. In case there is no capacity for an MN, the MAP chooses an existing MN to be replaced. The replaced MN uses the MAP selection al- gorithm again to choose another mobility agent. Simulation results showed that the proposed scheme achieves better performance not only in reducing the signaling overhead, but also in load balancing among different MAPs.
基金the National Natural Science Foundation of China (Grant No.60604031)
文摘Aiming at the limitation of control accuracy caused by hysteresis and creep for a piezoelectric actuator, the hysteresis phenomenon is explained based on the microscopic polarization mechanism and domain wall theory. Then a control model based on polarization is established, which can reduce the hysteresis and creep remarkablely. The experimental results show that the polarization control method is with more linearity and less hysteresis compared with the voltage control method.
基金Project(50908084)supported by the National Natural Science Foundation of ChinaProject(200815)supported by the Transportation Science and Technology Program of Hunan Province,ChinaProject(531107040620)supported by the Growth Plan for Young Teachers of Hunan University,China
文摘In order to find out the bearing behavior of super-long piles located in deep soft clay over stiff layers around Dongting Lake, China, a test pile was first designed with the field loading test finished afterward. Based on the measured test results, load transfer mechanism and bearing behavior of the pile shaft were discussed in detail. Then, by introducing a bi-linear model for shaft friction and the tri-linear model for pile tip resistance, respectively, the governing differential equation of pile soil system was set up by the load transfer method with the analytical solutions derived as well, taking into account the effect by stratified feature and various bearing conditions of subsoil, material nonlinearity, and the sediment under pile tip. Furthermore, formulas to determine the axial capacity of super-long piles by the pile top settlement were advised and applied to analyze the test pile. Good agreement between the predicted load settlement variations and the measured data is obtained to verify the validity of the present method. The results also show that, the axial bearing capacity of super-long piles should be controlled by the allowable pile top settlement, and buckling stability of the pile shaft should be paid attention as well.
文摘Objectives： Heart rate variability （HRV） can be a simple, non-invasive method of gauging cardiac autonomic nervous system fluctuations across periodised training workloads and taper in elite athlete populations. The purpose of these three case studies was to examine daily cardiac autonomic variations in Paralympic athletes leading in to the Paralympic games. Methods： Three Paralympie gold medallist swimmers were monitored daily for their resting HRV over a 17-week monitoring period leading up to the Paralympic games. Specific time- and frequency-domain measures, along with non-linear indices of HRV were calculated for all analyses. All HRV data were analysed individually using daily values, weekly average values, and average values for rest and training phases. Results： A significant difference in HRV was seen for all variables between athlete 1 and athletes 2 and 3 （amputee disabilities） during the entire monitoring period. Conclusion： Despite minimal long-term changes, both swimming classification and disability type significantly influence HRV during athlete monitoring. An increased understanding of individual responses to training, travel, and other outside influences affecting Paralympic athletes could potentially lead to improved management and monitoring of training workloads for enhanced nerformance.
