An improved Gaussian mixture model （GMM）- based clustering method is proposed for the difficult case where the true distribution of data is against the assumed GMM. First, an improved model selection criterion, the ...An improved Gaussian mixture model （GMM）- based clustering method is proposed for the difficult case where the true distribution of data is against the assumed GMM. First, an improved model selection criterion, the completed likelihood minimum message length criterion, is derived. It can measure both the goodness-of-fit of the candidate GMM to the data and the goodness-of-partition of the data. Secondly, by utilizing the proposed criterion as the clustering objective function, an improved expectation- maximization （EM） algorithm is developed, which can avoid poor local optimal solutions compared to the standard EM algorithm for estimating the model parameters. The experimental results demonstrate that the proposed method can rectify the over-fitting tendency of representative GMM-based clustering approaches and can robustly provide more accurate clustering results.展开更多
We formulate a “Moore’s law” for photonic integrated circuits (PICs) and their spatial integration density using two methods. One is decomposing the integrated photonics devices of diverse types into equivalent bas...We formulate a “Moore’s law” for photonic integrated circuits (PICs) and their spatial integration density using two methods. One is decomposing the integrated photonics devices of diverse types into equivalent basic elements, which makes a comparison with the generic elements of electronic integrated circuits more meaningful. The other is making a complex compo- nent equivalent to a series of basic elements of the same functionality, which is used to calculate the integration density for func- tional components realized with different structures. The results serve as a benchmark of the evolution of PICs and we can con- clude that the density of integration measured in this way roughly increases by a factor of 2 per year. The prospects for a continued increase of spatial integration density are discussed.展开更多
In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to ...In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to the rise in temperature. If such expansion is resisted, for example by frictional effects over a kilometer or so of pipeline, compressive axial stress will be built up in the pipe-wall. The compressive forces are often so large that they induce vertical buckling of buffed pipelines, which can jeopardize the structural integrity of the pipeline. A typical initial imperfection named continuous support mode of submarine pipeline was studied. Based on this type of initial imperfection, the analytical solution of vertical thermal buckling was introduced and an elastic-plasticity finite element analysis （FEA） was developed. Both the analytical and the finite element methodology were applied to analyze a practice in Bohai Gulf, China. The analyzing results show that upheaval buckling is most likely to build up from the initial imperfection of the pipeline and the buckling temperature depends on the amplitude of initial imperfection. With the same amplitude of initial imperfection, the triggering temperature difference of upheaval buckling increases with covered depth of the pipeline, the soil strength and the friction between the pipeline and subsoil.展开更多
This work was focused on the model-based design method of two-axis four-actuator(TAFA) fast steering mirror system(FSM), in order to improve the design efficiency. The structure and operation principle commonality of ...This work was focused on the model-based design method of two-axis four-actuator(TAFA) fast steering mirror system(FSM), in order to improve the design efficiency. The structure and operation principle commonality of normal TAFA FSM were investigated. Based on the structure and the commonality, the conditions of single-axis idea, high-frequency resonance and coupling were modeled gradually. Combining these models, a holonomic system model was established to reflect and predict the performance of TAFA FSM. A model-based design method was proposed based on the holonomic system model. The design flow and design concept of the method were described. In accordance with the method, a TAFA FSM was designed. Simulations and experiments of the FSM were done, and the results of them were compared. The compared results indicate that the holonomic system model can well reflect and predict the performance of TAFA FSM. The bandwidth of TAFA FSM is more than 250 Hz; adjust time is less than 15 ms;overshoot is less than 8%; position accuracy is better than 10 μrad; the FSM prototype can satisfy the requirements.展开更多
In this work, we investigate the stabilization control design of nonholonomic stochastic system in strict-feedback form. Under the condition of all states being available for feedback, a state feedback controller was ...In this work, we investigate the stabilization control design of nonholonomic stochastic system in strict-feedback form. Under the condition of all states being available for feedback, a state feedback controller was developed via the stochastic Lyapunov-like theorem and backstepping design technique. The controllers guarantee all states of the closed-loop system are bounded in probability, and largely asymptotically stable when the stochastic disturbances equal to zero at the equilibrium point of the open-loop system. Besides, the time-varying technique was introduced to avoid the uncontrollable state of chained system.展开更多
A method used to detect anomaly and estimate the state of vehicle in driving was proposed.The kinematics model of the vehicle was constructed and nonholonomic constraint conditions were added,which refer to that once ...A method used to detect anomaly and estimate the state of vehicle in driving was proposed.The kinematics model of the vehicle was constructed and nonholonomic constraint conditions were added,which refer to that once the vehicle encounters the faults that could not be controlled,the constraint conditions are violated.Estimation equations of the velocity errors of the vehicle were given out to estimate the velocity errors of side and forward.So the stability of the whole vehicle could be judged by the velocity errors of the vehicle.Conclusions were validated through the vehicle experiment.This method is based on GPS/INS integrated navigation system,and can provide foundation for fault detections in unmanned autonomous vehicles.展开更多
In this paper, the Lie-form invariance of a type of non-holonomic singular systems is studied. The differential equations of motion of the systems are given. The definition and the criterions of the Lie-form invarianc...In this paper, the Lie-form invariance of a type of non-holonomic singular systems is studied. The differential equations of motion of the systems are given. The definition and the criterions of the Lie-form invariance for the systems are presented. The Hojman conserved quantity and the Mei conserved quantity are obtained. An example is given to illustrate the application of the results.展开更多
A k-shortest path based algorithm considering layout density and signal integrity for good buffer candidatelocations is proposed in this paper. Theoretical results for computing the maximal distance betweenbuffers are...A k-shortest path based algorithm considering layout density and signal integrity for good buffer candidatelocations is proposed in this paper. Theoretical results for computing the maximal distance betweenbuffers are derived under the timing, noise and slew rate constraints. By modifying the traditional uniformwire segmenting strategy and considering the impact of tile size on density penalty function, this work proposesk-shortest path algorithm to find the buffer insertion candidate locations. The experiments show thatthe buffers inserted can significantly optimize the design density, alleviate signal degradation, save thenumber of buffers inserted and the overall run time.展开更多
This paper presents the formulation and practical implementation of positioning methodologies that compensate for the nonholonomic constraints of a mobile microrobot that is driven by two vibrating direct current(DC) ...This paper presents the formulation and practical implementation of positioning methodologies that compensate for the nonholonomic constraints of a mobile microrobot that is driven by two vibrating direct current(DC) micromotors. The open-loop and closed-loop approaches described here add the capability for net sidewise displacements of the microrobotic platform. A displacement is achieved by the execution of a number of repeating steps that depend on the desired displacement, the speed of the micromotors, and the elapsed time. Simulation and experimental results verified the performance of the proposed methodologies.展开更多
Since a sensor node handles wireless communication in data transmission and reception and is installed in poor environment, it is easily exposed to certain attacks such as data transformation and sniffing. Therefore, ...Since a sensor node handles wireless communication in data transmission and reception and is installed in poor environment, it is easily exposed to certain attacks such as data transformation and sniffing. Therefore, it is necessary to verify data integrity to properly respond to an adversary's ill-intentioned data modification. In sensor network environment, the data integrity verification method verifies the final data only, requesting multiple communications. An energy-efficient private information retrieval(PIR)-based data integrity verification method is proposed. Because the proposed method verifies the integrity of data between parent and child nodes, it is more efficient than the existing method which verifies data integrity after receiving data from the entire network or in a cluster. Since the number of messages for verification is reduced, in addition, energy could be used more efficiently. Lastly, the excellence of the proposed method is verified through performance evaluation.展开更多
基金The National Natural Science Foundation of China(No.61105048,60972165)the Doctoral Fund of Ministry of Education of China(No.20110092120034)+2 种基金the Natural Science Foundation of Jiangsu Province(No.BK2010240)the Technology Foundation for Selected Overseas Chinese Scholar,Ministry of Human Resources and Social Security of China(No.6722000008)the Open Fund of Jiangsu Province Key Laboratory for Remote Measuring and Control(No.YCCK201005)
文摘An improved Gaussian mixture model （GMM）- based clustering method is proposed for the difficult case where the true distribution of data is against the assumed GMM. First, an improved model selection criterion, the completed likelihood minimum message length criterion, is derived. It can measure both the goodness-of-fit of the candidate GMM to the data and the goodness-of-partition of the data. Secondly, by utilizing the proposed criterion as the clustering objective function, an improved expectation- maximization （EM） algorithm is developed, which can avoid poor local optimal solutions compared to the standard EM algorithm for estimating the model parameters. The experimental results demonstrate that the proposed method can rectify the over-fitting tendency of representative GMM-based clustering approaches and can robustly provide more accurate clustering results.
文摘We formulate a “Moore’s law” for photonic integrated circuits (PICs) and their spatial integration density using two methods. One is decomposing the integrated photonics devices of diverse types into equivalent basic elements, which makes a comparison with the generic elements of electronic integrated circuits more meaningful. The other is making a complex compo- nent equivalent to a series of basic elements of the same functionality, which is used to calculate the integration density for func- tional components realized with different structures. The results serve as a benchmark of the evolution of PICs and we can con- clude that the density of integration measured in this way roughly increases by a factor of 2 per year. The prospects for a continued increase of spatial integration density are discussed.
基金Project(51021004) supported by Innovative Research Groups of the National Natural Science Foundation of ChinaProject(40776055) supported by the National Natural Science Foundation of china+1 种基金Project(1002) supported by State Key Laboratory of Ocean Engineering Foundation, ChinaProject(NCET 11 0370) supported by the Program for New Century Excellent Talents in Universities of China
文摘In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to the rise in temperature. If such expansion is resisted, for example by frictional effects over a kilometer or so of pipeline, compressive axial stress will be built up in the pipe-wall. The compressive forces are often so large that they induce vertical buckling of buffed pipelines, which can jeopardize the structural integrity of the pipeline. A typical initial imperfection named continuous support mode of submarine pipeline was studied. Based on this type of initial imperfection, the analytical solution of vertical thermal buckling was introduced and an elastic-plasticity finite element analysis （FEA） was developed. Both the analytical and the finite element methodology were applied to analyze a practice in Bohai Gulf, China. The analyzing results show that upheaval buckling is most likely to build up from the initial imperfection of the pipeline and the buckling temperature depends on the amplitude of initial imperfection. With the same amplitude of initial imperfection, the triggering temperature difference of upheaval buckling increases with covered depth of the pipeline, the soil strength and the friction between the pipeline and subsoil.
基金Projects(51135009)supported by the National Natural Science Foundation of China
文摘This work was focused on the model-based design method of two-axis four-actuator(TAFA) fast steering mirror system(FSM), in order to improve the design efficiency. The structure and operation principle commonality of normal TAFA FSM were investigated. Based on the structure and the commonality, the conditions of single-axis idea, high-frequency resonance and coupling were modeled gradually. Combining these models, a holonomic system model was established to reflect and predict the performance of TAFA FSM. A model-based design method was proposed based on the holonomic system model. The design flow and design concept of the method were described. In accordance with the method, a TAFA FSM was designed. Simulations and experiments of the FSM were done, and the results of them were compared. The compared results indicate that the holonomic system model can well reflect and predict the performance of TAFA FSM. The bandwidth of TAFA FSM is more than 250 Hz; adjust time is less than 15 ms;overshoot is less than 8%; position accuracy is better than 10 μrad; the FSM prototype can satisfy the requirements.
基金Project supported by the National Natural Science Foundation ofChina (No. 60474010) and the Research Fund for the Doctoral Pro-gram of Higher Education, China
文摘In this work, we investigate the stabilization control design of nonholonomic stochastic system in strict-feedback form. Under the condition of all states being available for feedback, a state feedback controller was developed via the stochastic Lyapunov-like theorem and backstepping design technique. The controllers guarantee all states of the closed-loop system are bounded in probability, and largely asymptotically stable when the stochastic disturbances equal to zero at the equilibrium point of the open-loop system. Besides, the time-varying technique was introduced to avoid the uncontrollable state of chained system.
基金Projects(90820302,60805027) supported by the National Natural Science Foundation of ChinaProject(200805330005) supported by Research Fund for Doctoral Program of Higher Education of China+1 种基金Projects(2009FJ4030) supported by Academician Foundation of Hunan Province,ChinaProject supported by the Freedom Explore Program of Central South University,China
文摘A method used to detect anomaly and estimate the state of vehicle in driving was proposed.The kinematics model of the vehicle was constructed and nonholonomic constraint conditions were added,which refer to that once the vehicle encounters the faults that could not be controlled,the constraint conditions are violated.Estimation equations of the velocity errors of the vehicle were given out to estimate the velocity errors of side and forward.So the stability of the whole vehicle could be judged by the velocity errors of the vehicle.Conclusions were validated through the vehicle experiment.This method is based on GPS/INS integrated navigation system,and can provide foundation for fault detections in unmanned autonomous vehicles.
文摘In this paper, the Lie-form invariance of a type of non-holonomic singular systems is studied. The differential equations of motion of the systems are given. The definition and the criterions of the Lie-form invariance for the systems are presented. The Hojman conserved quantity and the Mei conserved quantity are obtained. An example is given to illustrate the application of the results.
基金Supported by the National Key Project of Scientific and Technical Supporting Programs (No. 2006BAK07B04).
文摘A k-shortest path based algorithm considering layout density and signal integrity for good buffer candidatelocations is proposed in this paper. Theoretical results for computing the maximal distance betweenbuffers are derived under the timing, noise and slew rate constraints. By modifying the traditional uniformwire segmenting strategy and considering the impact of tile size on density penalty function, this work proposesk-shortest path algorithm to find the buffer insertion candidate locations. The experiments show thatthe buffers inserted can significantly optimize the design density, alleviate signal degradation, save thenumber of buffers inserted and the overall run time.
基金supported in part by the National Science Foundation(IIS1318638 and IIS1426752)the Shenzhen Science and Technology Project(ZDSY20120617113312191)
文摘This paper presents the formulation and practical implementation of positioning methodologies that compensate for the nonholonomic constraints of a mobile microrobot that is driven by two vibrating direct current(DC) micromotors. The open-loop and closed-loop approaches described here add the capability for net sidewise displacements of the microrobotic platform. A displacement is achieved by the execution of a number of repeating steps that depend on the desired displacement, the speed of the micromotors, and the elapsed time. Simulation and experimental results verified the performance of the proposed methodologies.
基金supported by the Sharing and Diffusion of National R&D Outcome funded by the Korea Institute of Science and Technology Information
文摘Since a sensor node handles wireless communication in data transmission and reception and is installed in poor environment, it is easily exposed to certain attacks such as data transformation and sniffing. Therefore, it is necessary to verify data integrity to properly respond to an adversary's ill-intentioned data modification. In sensor network environment, the data integrity verification method verifies the final data only, requesting multiple communications. An energy-efficient private information retrieval(PIR)-based data integrity verification method is proposed. Because the proposed method verifies the integrity of data between parent and child nodes, it is more efficient than the existing method which verifies data integrity after receiving data from the entire network or in a cluster. Since the number of messages for verification is reduced, in addition, energy could be used more efficiently. Lastly, the excellence of the proposed method is verified through performance evaluation.
