YCOB,a member of the new crystal family of ReCOB (ReCOB=ReCa 4O(BO 3) 3,Re=La 3+ ,Nd 3+ ,Sm 3+ ,Gd 3+ ,Er 3+ ,Y 3+ ),has received mo re and more attentions in recent few years,because of its excellent nonlinear op tic...YCOB,a member of the new crystal family of ReCOB (ReCOB=ReCa 4O(BO 3) 3,Re=La 3+ ,Nd 3+ ,Sm 3+ ,Gd 3+ ,Er 3+ ,Y 3+ ),has received mo re and more attentions in recent few years,because of its excellent nonlinear op tical (N LO) properties and a great promise as a laser host material.Unfortunately,liking most of nonlinear optical crystals,the laser induced damages were also created in the new crystal family when irradiated by ultraviolet laser.In this report we present our preliminary results of the investigation on the radiation induced damage in YCOB crystals.展开更多
A global routing algorithm with performance optimization under multi constraints is proposed,which studies RLC coupling noise,timing performance,and routability simultaneously at global routing level.The algorithm is...A global routing algorithm with performance optimization under multi constraints is proposed,which studies RLC coupling noise,timing performance,and routability simultaneously at global routing level.The algorithm is implemented and the global router is called CEE Gr.The CEE Gr is tested on MCNC benchmarks and the experimental results are promising.展开更多
This paper summarizes recent progress by the authors in developing two solution frameworks for dual control. The first solution framework considers a class of dual control problems where there exists a parameter uncer...This paper summarizes recent progress by the authors in developing two solution frameworks for dual control. The first solution framework considers a class of dual control problems where there exists a parameter uncertainty in the observation equation of the LQG problem. An analytical active dual control law is derived by a variance minimization approach. The issue of how to determine an optimal degree of active learning is then addressed, thus achieving an optimality for this class of dual control problems. The second solution framework considers a general class of discrete-time LQG problems with unknown parameters in both state and observation equations. The best possible (partial) closed-loop feedback control law is derived by exploring the future nominal posterior probabilities, thus taking into account the effect of future learning when constructing the optimal nominal dual control.展开更多
A wavelet-based spectral correlation algorithm to detect and estimate BPSK signal chip rate is proposed. Simulation results show that the proposed method can correctly estimate the BPSK signal chip rate, which may be ...A wavelet-based spectral correlation algorithm to detect and estimate BPSK signal chip rate is proposed. Simulation results show that the proposed method can correctly estimate the BPSK signal chip rate, which may be corrupted by the quadratic characteristics of the spectral correlation function, in a low SNR environment.展开更多
When all the rules of sensor decision are known, the optimal distributeddecision fusion, which relies only on the joint conditional probability densities, can be derivedfor very general decision systems. They include ...When all the rules of sensor decision are known, the optimal distributeddecision fusion, which relies only on the joint conditional probability densities, can be derivedfor very general decision systems. They include those systems with interdependent sensorobservations and any network structure. It is also valid for m-ary Bayesian decision problems andbinary problems under the Neyman-Pearson criterion. Local decision rules of a sensor withcommunication from other sensors that are optimal for the sensor itself are also presented, whichtake the form of a generalized likelihood ratio test. Numerical examples are given to reveal someinteresting phenomena that communication between sensors can improve performance of a senordecision, but cannot guarantee to improve the global fusion performance when sensor rules were givenbefore fusing.展开更多
AIM: To investigate whether gastric myoelectrical activity was impaired in patients with chronic pancreatitis (CP) and to explore the role of pancreatic enzyme in regulating gastric myoelectrical activity. METHODS: Tw...AIM: To investigate whether gastric myoelectrical activity was impaired in patients with chronic pancreatitis (CP) and to explore the role of pancreatic enzyme in regulating gastric myoelectrical activity. METHODS: Twenty CP patients and 20 controls participated in the study. Gastric myoelectrical activity was recorded by a homemade electrogastrography (EGG) device. Two experiments were carried out. In experiment one, EGG was recorded in both controls and CP patients. While in experiment two, either pancreatic enzymes or placebo was given together with test meals. Spectral analysis was used to generate various EGG parameters. RESULTS: The control subjects, but not the CP patients, showed typically increased postprandial dominant frequency. The postprandial dominant power (DP) increment (2.24±1.13 vs 5.35±0.96 dB, P= 0.04) and the percentage of normal 2-4 cpm slow waves (63.0±3.8% vs 77.4±3.1%, P<0.05) were lower in CP patients when compared with the control. In the 20 CP patients, the DP increment (4.76±1.02 vs 2.53±1.20 dB, P<0.05) and the postprandial percentage of normal 2-4 cpm (74.4±2.8% vs 64.8±5.7%, P<0.05) were significantly higher with pancreatic enzyme replacement than the placebo. CONCLUSION: CP patients have an abnormal postprandial stomach myoelectricity showing poor response in dominant frequency/power and regularity, whereas these abnormalities are corrected after pancreatic enzyme replacement. Maldigestion is likely to be the factor leading to abnormal postprandial gastric myoelectricity of CP patients.展开更多
A method of improving the stability of multiple-motor drive system fed by a 3-leg single inverter has been devised that employs the averages and differences of estimated parameters for field-oriented control. The para...A method of improving the stability of multiple-motor drive system fed by a 3-leg single inverter has been devised that employs the averages and differences of estimated parameters for field-oriented control. The parameters of each motor (stator current, rotor flux, and speed) are estimated using adaptive rotor flux observers to achieve sensorless control. The validity and effective of the proposed method have been demonstrated through simulations and experiments.展开更多
A new PWM converter based on soft switching is introduced. The converter uses a minimum number of devices, and requires less switching operations than conventional techniques. Switching is realized solely in a ZVS (z...A new PWM converter based on soft switching is introduced. The converter uses a minimum number of devices, and requires less switching operations than conventional techniques. Switching is realized solely in a ZVS (zero voltage switching) mode, therefore the loss is reduced and EMI (electromagnetic interference) is suppressed. The paper analyzes the operation of ZVS, and discusses the methods for maintaining a unit power factor and constant DC voltage. Changing the modulation index M and the phase angle θ keeps the input current in phase with the voltage. It also keeps the current sinusoidal, and ensures a constant output voltage.展开更多
This paper presents an adaptive strategy for controlling chaotic systems. By employing the phase space reconstruction technique in nonlinear dynamical systems theory, the proposed strategy transforms the nonlinear sys...This paper presents an adaptive strategy for controlling chaotic systems. By employing the phase space reconstruction technique in nonlinear dynamical systems theory, the proposed strategy transforms the nonlinear system into canonical form, and employs a nonlinear observer to estimate the uncertainties and disturbances of the nonlinear system, and then establishes a state-error-like feedback law. The developed control scheme allows chaos control in spite of modeling errors and parametric variations. The effectiveness of the proposed approach has been demonstrated through its applications to two well-known chaotic systems : Duffing oscillator and Rǒssler chaos.展开更多
Transient magnetic circuit method is adopted to calculate the power loss in winding and shading coil. Based on the analysis of heat transfer process in AC contactor, a thermal model is proposed and the temperature fie...Transient magnetic circuit method is adopted to calculate the power loss in winding and shading coil. Based on the analysis of heat transfer process in AC contactor, a thermal model is proposed and the temperature field distribution is simulated with 3-D FEM of ANSYS. Comparison of simulation results with measurements shows that the proposed method is effective.展开更多
文摘YCOB,a member of the new crystal family of ReCOB (ReCOB=ReCa 4O(BO 3) 3,Re=La 3+ ,Nd 3+ ,Sm 3+ ,Gd 3+ ,Er 3+ ,Y 3+ ),has received mo re and more attentions in recent few years,because of its excellent nonlinear op tical (N LO) properties and a great promise as a laser host material.Unfortunately,liking most of nonlinear optical crystals,the laser induced damages were also created in the new crystal family when irradiated by ultraviolet laser.In this report we present our preliminary results of the investigation on the radiation induced damage in YCOB crystals.
文摘A global routing algorithm with performance optimization under multi constraints is proposed,which studies RLC coupling noise,timing performance,and routability simultaneously at global routing level.The algorithm is implemented and the global router is called CEE Gr.The CEE Gr is tested on MCNC benchmarks and the experimental results are promising.
基金the Research Grants Council of Hong Kong, P.R.China under Grant CUHK 4180/03E
文摘This paper summarizes recent progress by the authors in developing two solution frameworks for dual control. The first solution framework considers a class of dual control problems where there exists a parameter uncertainty in the observation equation of the LQG problem. An analytical active dual control law is derived by a variance minimization approach. The issue of how to determine an optimal degree of active learning is then addressed, thus achieving an optimality for this class of dual control problems. The second solution framework considers a general class of discrete-time LQG problems with unknown parameters in both state and observation equations. The best possible (partial) closed-loop feedback control law is derived by exploring the future nominal posterior probabilities, thus taking into account the effect of future learning when constructing the optimal nominal dual control.
文摘A wavelet-based spectral correlation algorithm to detect and estimate BPSK signal chip rate is proposed. Simulation results show that the proposed method can correctly estimate the BPSK signal chip rate, which may be corrupted by the quadratic characteristics of the spectral correlation function, in a low SNR environment.
文摘When all the rules of sensor decision are known, the optimal distributeddecision fusion, which relies only on the joint conditional probability densities, can be derivedfor very general decision systems. They include those systems with interdependent sensorobservations and any network structure. It is also valid for m-ary Bayesian decision problems andbinary problems under the Neyman-Pearson criterion. Local decision rules of a sensor withcommunication from other sensors that are optimal for the sensor itself are also presented, whichtake the form of a generalized likelihood ratio test. Numerical examples are given to reveal someinteresting phenomena that communication between sensors can improve performance of a senordecision, but cannot guarantee to improve the global fusion performance when sensor rules were givenbefore fusing.
文摘AIM: To investigate whether gastric myoelectrical activity was impaired in patients with chronic pancreatitis (CP) and to explore the role of pancreatic enzyme in regulating gastric myoelectrical activity. METHODS: Twenty CP patients and 20 controls participated in the study. Gastric myoelectrical activity was recorded by a homemade electrogastrography (EGG) device. Two experiments were carried out. In experiment one, EGG was recorded in both controls and CP patients. While in experiment two, either pancreatic enzymes or placebo was given together with test meals. Spectral analysis was used to generate various EGG parameters. RESULTS: The control subjects, but not the CP patients, showed typically increased postprandial dominant frequency. The postprandial dominant power (DP) increment (2.24±1.13 vs 5.35±0.96 dB, P= 0.04) and the percentage of normal 2-4 cpm slow waves (63.0±3.8% vs 77.4±3.1%, P<0.05) were lower in CP patients when compared with the control. In the 20 CP patients, the DP increment (4.76±1.02 vs 2.53±1.20 dB, P<0.05) and the postprandial percentage of normal 2-4 cpm (74.4±2.8% vs 64.8±5.7%, P<0.05) were significantly higher with pancreatic enzyme replacement than the placebo. CONCLUSION: CP patients have an abnormal postprandial stomach myoelectricity showing poor response in dominant frequency/power and regularity, whereas these abnormalities are corrected after pancreatic enzyme replacement. Maldigestion is likely to be the factor leading to abnormal postprandial gastric myoelectricity of CP patients.
文摘A method of improving the stability of multiple-motor drive system fed by a 3-leg single inverter has been devised that employs the averages and differences of estimated parameters for field-oriented control. The parameters of each motor (stator current, rotor flux, and speed) are estimated using adaptive rotor flux observers to achieve sensorless control. The validity and effective of the proposed method have been demonstrated through simulations and experiments.
文摘A new PWM converter based on soft switching is introduced. The converter uses a minimum number of devices, and requires less switching operations than conventional techniques. Switching is realized solely in a ZVS (zero voltage switching) mode, therefore the loss is reduced and EMI (electromagnetic interference) is suppressed. The paper analyzes the operation of ZVS, and discusses the methods for maintaining a unit power factor and constant DC voltage. Changing the modulation index M and the phase angle θ keeps the input current in phase with the voltage. It also keeps the current sinusoidal, and ensures a constant output voltage.
文摘This paper presents an adaptive strategy for controlling chaotic systems. By employing the phase space reconstruction technique in nonlinear dynamical systems theory, the proposed strategy transforms the nonlinear system into canonical form, and employs a nonlinear observer to estimate the uncertainties and disturbances of the nonlinear system, and then establishes a state-error-like feedback law. The developed control scheme allows chaos control in spite of modeling errors and parametric variations. The effectiveness of the proposed approach has been demonstrated through its applications to two well-known chaotic systems : Duffing oscillator and Rǒssler chaos.
文摘Transient magnetic circuit method is adopted to calculate the power loss in winding and shading coil. Based on the analysis of heat transfer process in AC contactor, a thermal model is proposed and the temperature field distribution is simulated with 3-D FEM of ANSYS. Comparison of simulation results with measurements shows that the proposed method is effective.
