The continued development of CMOS technology and the emergence of new applications demand continued improvement and enhancement of compact models. This paper outlines the recent work of the BSIM project at the Univers...The continued development of CMOS technology and the emergence of new applications demand continued improvement and enhancement of compact models. This paper outlines the recent work of the BSIM project at the University of California, Berkeley,including BSIM5 research, BSIM4 enhancements, and BSIMSOI development. BSIM5 addresses the needs of nano-CMOS technology and RF high-speed CMOS circuit simulation. BSIM4 is a mature industrial standard MOSFET model with several improvements to meet the technology requirements. BSIMSOI is developed into a generic model framework for PD and FD SOI technology. An operation mode choice,via the calculation of the body potential △Vbi and body current/charge,helps circuit designers in the trend of the coexistence of PD and FD devices.展开更多
An IGBT subcircuit model is proposed and optimized,which is fully SPICE compatible.Based on analytical equations describing the semiconductor device physics,the model parameters are extracted accurately from the measu...An IGBT subcircuit model is proposed and optimized,which is fully SPICE compatible.Based on analytical equations describing the semiconductor device physics,the model parameters are extracted accurately from the measured data without device destruction.The IGBT n - layer conductivity modulated resistor is effectively modeled as a voltage controlled resistor.The proposed model can be used to accurately predict the IGBT output I-V characteristics and low current gain etc.The simulation results are verified by the comparison with measurements and found to be in good agreement with them.The error in average is within 8%,which is better than the results of semi-mathematical models reported previously.展开更多
Presented is design concept for key parameters o f the reverse conducting gate commutated thyristor (RC-GCT),such as the thickness and concentration of n-base region and the transparent anode region,and the wi dth o...Presented is design concept for key parameters o f the reverse conducting gate commutated thyristor (RC-GCT),such as the thickness and concentration of n-base region and the transparent anode region,and the wi dth of separation region between asymmetric GCT and PIN diode.A structure model of the RC-GCT is set up based on the design concept and its characteristics are analyzed.The simulation results show the design concept is reasonable.展开更多
Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure.Their characteristics are analyzed.The light emitters have high spectral purity...Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure.Their characteristics are analyzed.The light emitters have high spectral purity of 4 8nm and high electroluminescence intensity of 0 7mW while injection current is 50mA.A 1×16 array of surface emitting light device is tested on line by probes and then used for module.The light detectors have wavelength selectivity and space selectivity.The required difference in input mirror reflectivity between emitters and detectors can easily be achieved though varying the numbers of top DBR period by etching.展开更多
We investigate the effects of the surface states on the Schottky contacts in 4H-SiC MESFET. The Ti/Pt/Au gate metal contacts are deposited by electron beam evaporation and patterned by a lift-off process. Based on the...We investigate the effects of the surface states on the Schottky contacts in 4H-SiC MESFET. The Ti/Pt/Au gate metal contacts are deposited by electron beam evaporation and patterned by a lift-off process. Based on thermionic theory,a simple parameter extraction method is developed for determination of the surface states in metal/4H-SiC Schottky contacts. The interface state density and interface capacitance are calculated to be 4. 386 × 10^12 cm^-2 · eV^- 1 and 6. 394 × 10^-6 F/cm^2 ,which are consistent with the device＇s terminal characteristics.展开更多
A novel analytical model for the thin film silicon on insulator (TFSOI) reduced surface field (RESURF) devices has been proposed.Based on the 2-D Poisson equation solution,the analytical expressions for the surface po...A novel analytical model for the thin film silicon on insulator (TFSOI) reduced surface field (RESURF) devices has been proposed.Based on the 2-D Poisson equation solution,the analytical expressions for the surface potential and field distributions are derived.From this analysis,the optimum design condition for the maximum breakdown voltage is obtained.The dependence of the maximum breakdown voltage on the drift region length is examined and the relationship between the critical doping concentration and the front- and back- interface oxide layer thickness is discussed.The numerical simulation performed by the advanced semiconductor simulation tool,DESSIS-ISE,has been shown to support the analytical results.展开更多
A novel mesa ultra-thin base AlGaAs/GaAs HBT is designed and fabricated with wet chemical selective etch technique and monitor electrode technique. It has a particular and obvious voltage-controlled NDR whose PVCR is ...A novel mesa ultra-thin base AlGaAs/GaAs HBT is designed and fabricated with wet chemical selective etch technique and monitor electrode technique. It has a particular and obvious voltage-controlled NDR whose PVCR is larger than 120. By use of device simulation,the cause of NDR is that increasing collector voltage makes the ultrathin base reach through and the device transforms from a bipolar state to a bulk barrier state. In addition, the simulated cutoff frequency is about 60-80GHz.展开更多
A compact model for the integrated inversion charge density Qi in double-gate （DG-） MOSFETs is developed. For nanoscale applications,quantum confinement of the inversion carriers must be taken into account. Based on...A compact model for the integrated inversion charge density Qi in double-gate （DG-） MOSFETs is developed. For nanoscale applications,quantum confinement of the inversion carriers must be taken into account. Based on the previous work of Ge, we establish an expression for the surface potential with respect to Qi, and form an implicit equation, from which Qi can be solved. Results predicted by our model are compared to published data as well as results from Schred,a popular 1D numerical solver that solves the Poisson＇s and Schr6dinger equa- tions self-consistently. Good agreement is obtained for a wide range of silicon layer thickness,confirming the supe- riority of this model over previous work in this field.展开更多
Focused on the dynamics problems of a lunar lander during landing process, the whole process was analysed in detail, and the linear elastic model of the moon soil was established by means of experiments-analogic metho...Focused on the dynamics problems of a lunar lander during landing process, the whole process was analysed in detail, and the linear elastic model of the moon soil was established by means of experiments-analogic method. Combining the way of elastic impact with the way of velocity replacement, the dynamics model of damping free vibration dynamics model with 3-degree of freedom(DOF) for lunar lander is obtained according to the vibration mechanics elementary theory. Based on Lagrange equations and the energy principle, the damping free vibration differential equations for the lunar lander with 3-DOF are derived and the equations are solved in simulation ways by means of ADAMS software. The conclusions obtained can be used for the design and manufacture of lunar lander.展开更多
A physically based analytical model was developed to predict the performance of the plateau observed in the gate C-V characteristics of strained-Si/SiGe pMOSFET.Experimental results were used to validate this model.Th...A physically based analytical model was developed to predict the performance of the plateau observed in the gate C-V characteristics of strained-Si/SiGe pMOSFET.Experimental results were used to validate this model.The extracted parameters from our model were tOX=20 nm,ND=1×1016cm 3,tSSi=13.2 nm,consistent with the experimental values.The results show that the simulation results agree with experimental data well.It is found that the plateau can be strongly affected by doping concentration,strained-Si layer thickness and mass fraction of Ge in the SiGe layer.The model has been implemented in the software for strained silicon MOSFET parameter extraction,and has great value in the design of the strained-Si/SiGe devices.展开更多
In order to solve the problem of artificial generation and low efficiency of test sequences for zone controller (ZC), a model-based automatic generation method of test sequence is proposed. Firstly, the timed automata...In order to solve the problem of artificial generation and low efficiency of test sequences for zone controller (ZC), a model-based automatic generation method of test sequence is proposed. Firstly, the timed automata model is established based on function analysis of the zone controller, and the correctness of the model is verified by UPPAAL. Then by parsing the timed automata model files, state information and transition conditions can be extracted to generate test case sets. Finally, according to the serialization conditions of test cases, the test cases are serialized into test sequences by using the improved depth first search algorithm. A case, the ZC controls the train running within its jurisdiction, shows that the method is correct and can effectively improve the efficiency of test sequence generation.展开更多
Operators suffer much diffieulty in manipulating miero-size objects without the assistance of friendly interfaces due to the scaling effects in micro worht. The paper presented a general framework for mieromanipulatio...Operators suffer much diffieulty in manipulating miero-size objects without the assistance of friendly interfaces due to the scaling effects in micro worht. The paper presented a general framework for mieromanipulation robot hased on virtual reality technology. With the framework we brought forward a FDH （Fixed Direction Hulls） based hounding box method to handle the eollision ,teteetion of the peg-in-hole mieroassembly. The eollision response model for the collision between micro needle and hole was presented. The virtual three and corresponding displacement were calculated with the model of bending deformation and pressing ,teformation. Experiments verify the validity of collision response model.展开更多
We study different types of projective synchronization （projective-anticipating, projective, and projectivelag synchronization） in a class of time-delayed chaotic systems related to optical bistable or hybrid optica...We study different types of projective synchronization （projective-anticipating, projective, and projectivelag synchronization） in a class of time-delayed chaotic systems related to optical bistable or hybrid optical bistable devices. We relax some limitations of previous work, where the scaling factor a can not be any desired value. In this paper, we achieve projective-anticipating, projective, and projective-lag synchronization without the limitation of a. A suitable controller is chosen using active control approach. Based on the Lyapunov stability theory, we derive the sufficient stability condition through theoretical analysis. The analytical results are validated by the numerical simulations using Ikeda model and Mackey-Glass model.展开更多
On the basis of analysis on the temperature monitoring methods for high voltage devices, a new type of fiber optic sensor structure with reference channel is given. And the operation principle of fiber optic sensor is...On the basis of analysis on the temperature monitoring methods for high voltage devices, a new type of fiber optic sensor structure with reference channel is given. And the operation principle of fiber optic sensor is analysed at large based on the absorption of semiconductor chip. The mathematical model of both devices and the whole system are also given. It is proved by the experiment that this mathematical model is reliable.展开更多
The Cyclonic-Static Microbubble Flotation Column (FCSMC) is currently a widely used, novel type of flotation device. The self-absorbing microbubble generator is the core component of this device. The structure of the ...The Cyclonic-Static Microbubble Flotation Column (FCSMC) is currently a widely used, novel type of flotation device. The self-absorbing microbubble generator is the core component of this device. The structure of the microbubble generator directly influences flotation column performance by affecting bubble size and distribution as well as gas holdup in the column. However, the complicated flow inside the generator results in high R&D costs and difficulty in testing. Thus, the CFD software, FLUENT, was used to simulate the gas-liquid two-phase flow inside a self-absorbing microbubble generator. The effect of area ratio, a key structural parameter, was studied in detail. Critical flow-field parameters including velocity, turbulent kinetic energy, minimum static pressure and gas holdup were obtained. The simulation results demonstrate that the optimum area ratio is 3.展开更多
In order to decisively determine the adsorption selectivity of zirconium MOF(UiO-66) towards anionic versus cationic species, the adsorptive removal of the anionic dyes(Alizarin Red S.(ARS), Eosin(E), Fuchsin Acid(FA)...In order to decisively determine the adsorption selectivity of zirconium MOF(UiO-66) towards anionic versus cationic species, the adsorptive removal of the anionic dyes(Alizarin Red S.(ARS), Eosin(E), Fuchsin Acid(FA)and Methyl Orange(MO)) and the cationic dyes(Neutral Red(NR), Fuchsin Basic(FB), Methylene Blue(MB),and Safranine T(ST)) has been evaluated. The results clearly reveal a significant selectivity towards anionic dyes. Such an observation agrees with a plethora of reports of UiO-66 superior affinity towards other anionic species(Floride, PO_4^(3-), Diclofenac sodium, Methylchlorophenoxy-propionic acid, Phenols, CrO_4^(2-), SeO_3^(2-), and AsO_4^-). The adsorption process of ARS as an example has been optimized using the central composite design(CCD). The resultant statistical model indicates a crucial effect of both pH and sorbent mass. The optimum conditions were determined to be initial dye concentration 11.82 mg.L^(-1), adsorbent amount 0.0248 g, shaking time of 36 min and pH 2. The adsorption process proceeds via pseudo-second order kinetics(R^2= 0.999). The equilibrium data were fit to Langmuir and Tempkin models(R^2= 0.999 and 0.997 respectively). The results reveal an exceptional removal for the anionic dye(Alizarin Red S.) with a record adsorption capacity of400 mg·g^(-1). The significantly high adsorption capacity of UiO-66 towards ARS adds further evidence to the recently reported exceptional performance of MOFs in pollutants removal from water.展开更多
Internet multi-robotics is a typical discrete-event system. In order to describe joint activities between multiple operators and multiple robots, a 4-level discrete-event model is proposed in this paper based on the c...Internet multi-robotics is a typical discrete-event system. In order to describe joint activities between multiple operators and multiple robots, a 4-level discrete-event model is proposed in this paper based on the controlled condition/event Petri nets (CCEP). On the first or mission level, the task splitting of the system is defined; on the second or multi-operator level, a precedence graph is introduced for every operator to plan his or her robotic actions; on the third or coordination level, the above precedence graphs are translated and integrated into the corresponding CCEPs in terms of specific rules; and on the last or multi-robot level, operators can select their control range by setting the corresponding control marks of the obtained CCEPs. As a consequence, a clear mechanism of operator-robot collaboration is obtained to conduct the development of the system.展开更多
An improved encapsulation method of a sensing element for a cement-based piezoelectric sensor used in civil engineering structure was developed and some tests were carried out for validating this method. The cement-ba...An improved encapsulation method of a sensing element for a cement-based piezoelectric sensor used in civil engineering structure was developed and some tests were carried out for validating this method. The cement-based piezoelectric sensor of this kind is mainly used in concrete structure due to its compatibility with concrete, and the encapsulation method of its sensing element is important to the effectiveness and accuracy of the transfer of the stress from concrete to the sensing element. The sensor′s measurement error of the previous encapsulation method, which was induced by the area of the encapsulation material and the inherent difference of Young′s modulus between cement and encapsulation material, was analyzed theoretically using parallel model. In the improved method, the error is minimized by decreasing the area of the encapsulation material and changing the configuration of the cement and piezoelectric material in the sensor. Two sensors made by the previous and improved methods were embedded in two prisms respectively and the prisms were compressed on Material Test System. Through the comparison of the measurement errors of the two sensors, the improved method was evaluated. The test results show that the improved encapsulation method is effective and feasible.展开更多
In order to improve the scalability and reliability of Software Defined Networking(SDN),many studies use multiple controllers to constitute logically centralized control plane to provide load balancing and fail over.I...In order to improve the scalability and reliability of Software Defined Networking(SDN),many studies use multiple controllers to constitute logically centralized control plane to provide load balancing and fail over.In this paper,we develop a flexible dormant multi-controller model based on the centralized multi-controller architecture.The dormant multi-controller model allows part of controllers to enter the dormant state under light traffic condition for saving system cost.Meanwhile,through queueing analysis,various performance measures of the system can be obtained.Moreover,we analyze the real traffic of China Education Network and use the results as the parameters of computer simulation and verify the effects of parameters on the system characteristics.Finally,a total expected cost function is established,and genetic algorithm is employed to find the optimal values of various parameters to minimize system cost for the deployment decision making.展开更多
文摘The continued development of CMOS technology and the emergence of new applications demand continued improvement and enhancement of compact models. This paper outlines the recent work of the BSIM project at the University of California, Berkeley,including BSIM5 research, BSIM4 enhancements, and BSIMSOI development. BSIM5 addresses the needs of nano-CMOS technology and RF high-speed CMOS circuit simulation. BSIM4 is a mature industrial standard MOSFET model with several improvements to meet the technology requirements. BSIMSOI is developed into a generic model framework for PD and FD SOI technology. An operation mode choice,via the calculation of the body potential △Vbi and body current/charge,helps circuit designers in the trend of the coexistence of PD and FD devices.
文摘An IGBT subcircuit model is proposed and optimized,which is fully SPICE compatible.Based on analytical equations describing the semiconductor device physics,the model parameters are extracted accurately from the measured data without device destruction.The IGBT n - layer conductivity modulated resistor is effectively modeled as a voltage controlled resistor.The proposed model can be used to accurately predict the IGBT output I-V characteristics and low current gain etc.The simulation results are verified by the comparison with measurements and found to be in good agreement with them.The error in average is within 8%,which is better than the results of semi-mathematical models reported previously.
文摘Presented is design concept for key parameters o f the reverse conducting gate commutated thyristor (RC-GCT),such as the thickness and concentration of n-base region and the transparent anode region,and the wi dth of separation region between asymmetric GCT and PIN diode.A structure model of the RC-GCT is set up based on the design concept and its characteristics are analyzed.The simulation results show the design concept is reasonable.
文摘Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure.Their characteristics are analyzed.The light emitters have high spectral purity of 4 8nm and high electroluminescence intensity of 0 7mW while injection current is 50mA.A 1×16 array of surface emitting light device is tested on line by probes and then used for module.The light detectors have wavelength selectivity and space selectivity.The required difference in input mirror reflectivity between emitters and detectors can easily be achieved though varying the numbers of top DBR period by etching.
文摘We investigate the effects of the surface states on the Schottky contacts in 4H-SiC MESFET. The Ti/Pt/Au gate metal contacts are deposited by electron beam evaporation and patterned by a lift-off process. Based on thermionic theory,a simple parameter extraction method is developed for determination of the surface states in metal/4H-SiC Schottky contacts. The interface state density and interface capacitance are calculated to be 4. 386 × 10^12 cm^-2 · eV^- 1 and 6. 394 × 10^-6 F/cm^2 ,which are consistent with the device＇s terminal characteristics.
文摘A novel analytical model for the thin film silicon on insulator (TFSOI) reduced surface field (RESURF) devices has been proposed.Based on the 2-D Poisson equation solution,the analytical expressions for the surface potential and field distributions are derived.From this analysis,the optimum design condition for the maximum breakdown voltage is obtained.The dependence of the maximum breakdown voltage on the drift region length is examined and the relationship between the critical doping concentration and the front- and back- interface oxide layer thickness is discussed.The numerical simulation performed by the advanced semiconductor simulation tool,DESSIS-ISE,has been shown to support the analytical results.
文摘A novel mesa ultra-thin base AlGaAs/GaAs HBT is designed and fabricated with wet chemical selective etch technique and monitor electrode technique. It has a particular and obvious voltage-controlled NDR whose PVCR is larger than 120. By use of device simulation,the cause of NDR is that increasing collector voltage makes the ultrathin base reach through and the device transforms from a bipolar state to a bulk barrier state. In addition, the simulated cutoff frequency is about 60-80GHz.
文摘A compact model for the integrated inversion charge density Qi in double-gate （DG-） MOSFETs is developed. For nanoscale applications,quantum confinement of the inversion carriers must be taken into account. Based on the previous work of Ge, we establish an expression for the surface potential with respect to Qi, and form an implicit equation, from which Qi can be solved. Results predicted by our model are compared to published data as well as results from Schred,a popular 1D numerical solver that solves the Poisson＇s and Schr6dinger equa- tions self-consistently. Good agreement is obtained for a wide range of silicon layer thickness,confirming the supe- riority of this model over previous work in this field.
文摘Focused on the dynamics problems of a lunar lander during landing process, the whole process was analysed in detail, and the linear elastic model of the moon soil was established by means of experiments-analogic method. Combining the way of elastic impact with the way of velocity replacement, the dynamics model of damping free vibration dynamics model with 3-degree of freedom(DOF) for lunar lander is obtained according to the vibration mechanics elementary theory. Based on Lagrange equations and the energy principle, the damping free vibration differential equations for the lunar lander with 3-DOF are derived and the equations are solved in simulation ways by means of ADAMS software. The conclusions obtained can be used for the design and manufacture of lunar lander.
基金Projects(51308040203,6139801)supported by National Ministries and Commissions,ChinaProjects(72105499,72104089)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2010JQ8008)supported by the Natural Science Basic Research Plan in Shaanxi Province of China
文摘A physically based analytical model was developed to predict the performance of the plateau observed in the gate C-V characteristics of strained-Si/SiGe pMOSFET.Experimental results were used to validate this model.The extracted parameters from our model were tOX=20 nm,ND=1×1016cm 3,tSSi=13.2 nm,consistent with the experimental values.The results show that the simulation results agree with experimental data well.It is found that the plateau can be strongly affected by doping concentration,strained-Si layer thickness and mass fraction of Ge in the SiGe layer.The model has been implemented in the software for strained silicon MOSFET parameter extraction,and has great value in the design of the strained-Si/SiGe devices.
文摘In order to solve the problem of artificial generation and low efficiency of test sequences for zone controller (ZC), a model-based automatic generation method of test sequence is proposed. Firstly, the timed automata model is established based on function analysis of the zone controller, and the correctness of the model is verified by UPPAAL. Then by parsing the timed automata model files, state information and transition conditions can be extracted to generate test case sets. Finally, according to the serialization conditions of test cases, the test cases are serialized into test sequences by using the improved depth first search algorithm. A case, the ZC controls the train running within its jurisdiction, shows that the method is correct and can effectively improve the efficiency of test sequence generation.
文摘Operators suffer much diffieulty in manipulating miero-size objects without the assistance of friendly interfaces due to the scaling effects in micro worht. The paper presented a general framework for mieromanipulation robot hased on virtual reality technology. With the framework we brought forward a FDH （Fixed Direction Hulls） based hounding box method to handle the eollision ,teteetion of the peg-in-hole mieroassembly. The eollision response model for the collision between micro needle and hole was presented. The virtual three and corresponding displacement were calculated with the model of bending deformation and pressing ,teformation. Experiments verify the validity of collision response model.
基金Supported by Research Project of Hubei Provincial Department of Education under Grant No.Q20101609Foundation of Wuhan Textile University under Grant No.105040
文摘We study different types of projective synchronization （projective-anticipating, projective, and projectivelag synchronization） in a class of time-delayed chaotic systems related to optical bistable or hybrid optical bistable devices. We relax some limitations of previous work, where the scaling factor a can not be any desired value. In this paper, we achieve projective-anticipating, projective, and projective-lag synchronization without the limitation of a. A suitable controller is chosen using active control approach. Based on the Lyapunov stability theory, we derive the sufficient stability condition through theoretical analysis. The analytical results are validated by the numerical simulations using Ikeda model and Mackey-Glass model.
文摘On the basis of analysis on the temperature monitoring methods for high voltage devices, a new type of fiber optic sensor structure with reference channel is given. And the operation principle of fiber optic sensor is analysed at large based on the absorption of semiconductor chip. The mathematical model of both devices and the whole system are also given. It is proved by the experiment that this mathematical model is reliable.
基金Financial supports for this work provided by the National High Technology Research and Development Program of China (No.2008BAB31B02) is gratefully acknowledged
文摘The Cyclonic-Static Microbubble Flotation Column (FCSMC) is currently a widely used, novel type of flotation device. The self-absorbing microbubble generator is the core component of this device. The structure of the microbubble generator directly influences flotation column performance by affecting bubble size and distribution as well as gas holdup in the column. However, the complicated flow inside the generator results in high R&D costs and difficulty in testing. Thus, the CFD software, FLUENT, was used to simulate the gas-liquid two-phase flow inside a self-absorbing microbubble generator. The effect of area ratio, a key structural parameter, was studied in detail. Critical flow-field parameters including velocity, turbulent kinetic energy, minimum static pressure and gas holdup were obtained. The simulation results demonstrate that the optimum area ratio is 3.
文摘In order to decisively determine the adsorption selectivity of zirconium MOF(UiO-66) towards anionic versus cationic species, the adsorptive removal of the anionic dyes(Alizarin Red S.(ARS), Eosin(E), Fuchsin Acid(FA)and Methyl Orange(MO)) and the cationic dyes(Neutral Red(NR), Fuchsin Basic(FB), Methylene Blue(MB),and Safranine T(ST)) has been evaluated. The results clearly reveal a significant selectivity towards anionic dyes. Such an observation agrees with a plethora of reports of UiO-66 superior affinity towards other anionic species(Floride, PO_4^(3-), Diclofenac sodium, Methylchlorophenoxy-propionic acid, Phenols, CrO_4^(2-), SeO_3^(2-), and AsO_4^-). The adsorption process of ARS as an example has been optimized using the central composite design(CCD). The resultant statistical model indicates a crucial effect of both pH and sorbent mass. The optimum conditions were determined to be initial dye concentration 11.82 mg.L^(-1), adsorbent amount 0.0248 g, shaking time of 36 min and pH 2. The adsorption process proceeds via pseudo-second order kinetics(R^2= 0.999). The equilibrium data were fit to Langmuir and Tempkin models(R^2= 0.999 and 0.997 respectively). The results reveal an exceptional removal for the anionic dye(Alizarin Red S.) with a record adsorption capacity of400 mg·g^(-1). The significantly high adsorption capacity of UiO-66 towards ARS adds further evidence to the recently reported exceptional performance of MOFs in pollutants removal from water.
文摘Internet multi-robotics is a typical discrete-event system. In order to describe joint activities between multiple operators and multiple robots, a 4-level discrete-event model is proposed in this paper based on the controlled condition/event Petri nets (CCEP). On the first or mission level, the task splitting of the system is defined; on the second or multi-operator level, a precedence graph is introduced for every operator to plan his or her robotic actions; on the third or coordination level, the above precedence graphs are translated and integrated into the corresponding CCEPs in terms of specific rules; and on the last or multi-robot level, operators can select their control range by setting the corresponding control marks of the obtained CCEPs. As a consequence, a clear mechanism of operator-robot collaboration is obtained to conduct the development of the system.
基金Supported by Hong Kong Research Grant Council to HKUSTunder grant HKUST6212/O2ENational Science Fund forDistinguished Young Scholars of China(No.50425824).
文摘An improved encapsulation method of a sensing element for a cement-based piezoelectric sensor used in civil engineering structure was developed and some tests were carried out for validating this method. The cement-based piezoelectric sensor of this kind is mainly used in concrete structure due to its compatibility with concrete, and the encapsulation method of its sensing element is important to the effectiveness and accuracy of the transfer of the stress from concrete to the sensing element. The sensor′s measurement error of the previous encapsulation method, which was induced by the area of the encapsulation material and the inherent difference of Young′s modulus between cement and encapsulation material, was analyzed theoretically using parallel model. In the improved method, the error is minimized by decreasing the area of the encapsulation material and changing the configuration of the cement and piezoelectric material in the sensor. Two sensors made by the previous and improved methods were embedded in two prisms respectively and the prisms were compressed on Material Test System. Through the comparison of the measurement errors of the two sensors, the improved method was evaluated. The test results show that the improved encapsulation method is effective and feasible.
基金the National High-tech R&D Program ("863" Program) of China，the National Science Foundation of China，National Science & Technology Pillar Program of China，the National Science Foundation of China，the Post-Doctoral Funding of China，Tsinghua-Huawei joint research project
文摘In order to improve the scalability and reliability of Software Defined Networking(SDN),many studies use multiple controllers to constitute logically centralized control plane to provide load balancing and fail over.In this paper,we develop a flexible dormant multi-controller model based on the centralized multi-controller architecture.The dormant multi-controller model allows part of controllers to enter the dormant state under light traffic condition for saving system cost.Meanwhile,through queueing analysis,various performance measures of the system can be obtained.Moreover,we analyze the real traffic of China Education Network and use the results as the parameters of computer simulation and verify the effects of parameters on the system characteristics.Finally,a total expected cost function is established,and genetic algorithm is employed to find the optimal values of various parameters to minimize system cost for the deployment decision making.
