The key problem in unstructured P2P system is how to control "Flood".Some studies focus on constructing more efficient topology while others focus on better query algorithms.This paper presents HICUS(Hierarc...The key problem in unstructured P2P system is how to control "Flood".Some studies focus on constructing more efficient topology while others focus on better query algorithms.This paper presents HICUS(Hierarchical Interest-driven Community-based Unstructured System) motivated by a basic thought-whether the resources correlate with topology distinguishes structured and unstruc-tured P2P essentially.By introducing hierarchical "interest",HICUS organizes a quasi-structured topology through a pure distributed way,and provides a new platform for query algorithms.We study the procedure and performance of topology organization,and the simulations show that HICUS forms a small-world which can significantly improve the routing efficiency.展开更多
The frequency of digitally controlled iodine stabilized He-Ne laser locked to a hyperfine component in ^127I2 was measured using the National Metrology Institute of Japan's reference iodine stabilized He-Ne laser. Th...The frequency of digitally controlled iodine stabilized He-Ne laser locked to a hyperfine component in ^127I2 was measured using the National Metrology Institute of Japan's reference iodine stabilized He-Ne laser. This laser is operated under the conditions of the practical implementation and its frequency with respect to the International Committee for Weights and Measure recommended value is known from international comparisons. Adopting a sampling rate of 120 kHz for the control system of an iodine stabilized He-Ne laser enables frequency deviation of the test laser from the reference laser by + 5 kHz (relative accuracy of 1 ×10^11) thus limited only by the reproducibility of the iodine stabilized He-Ne laser itself.展开更多
This paper focuses on how the implementation of a single regional political instrument is perceived, understood and communicated. Designed as a regional political instrument, the Norwegian Ministry of Transport and Co...This paper focuses on how the implementation of a single regional political instrument is perceived, understood and communicated. Designed as a regional political instrument, the Norwegian Ministry of Transport and Communications started a pilot project: "Driver education as a part of upper secondary school in district Norway". The focal point in this paper is to explore how the professional participants understand and interpret the project as a regional political instrument in order to maintain the local community, identity and local belonging. The theoretical approach is based on Giddens's actor/structure theory, while the analysis based on discourse analysis, in the analysis we separated the arguments used in the professional discourse. We detected different categories of argument in the discourses among the professionals. In addition to the professional discourse, we became aware of a personal discourse. In both discourses the political instrument was perceived to be important in order to maintain the local community, create equality and maintain local identity and a sense of belonging.展开更多
Because of its light weight, broadband, and adaptable properties, smart material has been widely applied in the active vibration control (AVC) of flexible structures. Based on a firstorder shear deformation theory, ...Because of its light weight, broadband, and adaptable properties, smart material has been widely applied in the active vibration control (AVC) of flexible structures. Based on a firstorder shear deformation theory, by coupling the electrical and mechanical operation, a 4-node quadrilateral piezoelectric composite element with 24 degrees of freedom for generalized displacements and one electrical potential degree of freedom per piezoelectric layer was derived. Dynamic characteristics of a beam with discontinuously distributed piezoelectric sensors and actuators were presented. A linear quadratic regulator (LQR) feedback controller was designed to suppress the vibration of the beam in the state space using the high precise direct (HPD) integration method.展开更多
Thanks to the special physical architectures and various locomotion gaits,snake robots may offer significant benefits over traditional legged or wheeled locomotion designs in vast types of scenarios.This paper propose...Thanks to the special physical architectures and various locomotion gaits,snake robots may offer significant benefits over traditional legged or wheeled locomotion designs in vast types of scenarios.This paper proposes an innovative snake robot with digitally-actuated Stewart platforms as its modules and mainly focuses on the simulations of various snake gaits.Three categories of fitting algorithms are elaborated in simulations of lateral undulation and Configuration-Fitting Algorithm of Four Modules is demonstrated as a universal gait fitting algorithm for all kinds of snake robots with binary actuators.Several typical snake gaits are simulated and the results demonstrate the excellent mobility of the snake robot.展开更多
One of the main problems in controlling the shape of active structures (AS) is to determine the actuations that drive the structure from the current state to the target state. Model-based methods such as stochastic ...One of the main problems in controlling the shape of active structures (AS) is to determine the actuations that drive the structure from the current state to the target state. Model-based methods such as stochastic search require a known type of load and relatively long computational time, which limits the practical use of AS in civil engineering. Moreover, additive errors may be produced because of the discrepancy between analytic models and real structures. To overcome these limitations, this paper presents a compound system called WAS, which combines AS with a wireless sensor and actuator network (WSAN). A bio-inspired control framework imitating the activity of the nervous systems of animals is proposed for WAS. A typical example is tested for verification. In the example, a triangular tensegrity prism that aims to maintain its original height is integrated with a WSAN that consists of a central controller, three actuators, and three sensors. The result demonstrates the feasibility of the proposed concept and control framework in cases of unknown loads that include different types, distributions, magnitudes, and directions. The proposed control framework can also act as a supplementary means to improve the efficiency and accuracy of control frameworks based on a common stochastic search.展开更多
The flow induced by plasma synthetic jet actuator was simulated through solving the Reynolds-averaged Navier-Stokes equations augmented by body force phenomenological plasma model.The effect of actuation frequency on ...The flow induced by plasma synthetic jet actuator was simulated through solving the Reynolds-averaged Navier-Stokes equations augmented by body force phenomenological plasma model.The effect of actuation frequency on the plasma synthetic jet was examined by case study.The numerical results present that with the actuation frequency increasing,the stream-wise distance of the adjacent vortex pairs induced by the actuator decreases monotonically,which is the same as the situation of the velocity fluctuations field caused by the vortex pairs.When the actuation frequency is 60 Hz,the vortex pairs formed during the adjacent actuation periods merge together quickly,and the flow structure in the downstream region is more close to that of the steady case.The actuation frequency has no visible influence on the time-averaged flow field of plasma synthetic jet.However,when the actuation frequency is relatively low(f<40 Hz),the momentum flux close to the actuator increases with the actuation frequency increasing,which is contrary to the situation in the far field from the wall.展开更多
基金Supported by the National Natural Science Foundation of China (No.60602018 and 60772033)
文摘The key problem in unstructured P2P system is how to control "Flood".Some studies focus on constructing more efficient topology while others focus on better query algorithms.This paper presents HICUS(Hierarchical Interest-driven Community-based Unstructured System) motivated by a basic thought-whether the resources correlate with topology distinguishes structured and unstruc-tured P2P essentially.By introducing hierarchical "interest",HICUS organizes a quasi-structured topology through a pure distributed way,and provides a new platform for query algorithms.We study the procedure and performance of topology organization,and the simulations show that HICUS forms a small-world which can significantly improve the routing efficiency.
文摘The frequency of digitally controlled iodine stabilized He-Ne laser locked to a hyperfine component in ^127I2 was measured using the National Metrology Institute of Japan's reference iodine stabilized He-Ne laser. This laser is operated under the conditions of the practical implementation and its frequency with respect to the International Committee for Weights and Measure recommended value is known from international comparisons. Adopting a sampling rate of 120 kHz for the control system of an iodine stabilized He-Ne laser enables frequency deviation of the test laser from the reference laser by + 5 kHz (relative accuracy of 1 ×10^11) thus limited only by the reproducibility of the iodine stabilized He-Ne laser itself.
文摘This paper focuses on how the implementation of a single regional political instrument is perceived, understood and communicated. Designed as a regional political instrument, the Norwegian Ministry of Transport and Communications started a pilot project: "Driver education as a part of upper secondary school in district Norway". The focal point in this paper is to explore how the professional participants understand and interpret the project as a regional political instrument in order to maintain the local community, identity and local belonging. The theoretical approach is based on Giddens's actor/structure theory, while the analysis based on discourse analysis, in the analysis we separated the arguments used in the professional discourse. We detected different categories of argument in the discourses among the professionals. In addition to the professional discourse, we became aware of a personal discourse. In both discourses the political instrument was perceived to be important in order to maintain the local community, create equality and maintain local identity and a sense of belonging.
基金Supported by the National Natural Science Foundation of China (51079027).
文摘Because of its light weight, broadband, and adaptable properties, smart material has been widely applied in the active vibration control (AVC) of flexible structures. Based on a firstorder shear deformation theory, by coupling the electrical and mechanical operation, a 4-node quadrilateral piezoelectric composite element with 24 degrees of freedom for generalized displacements and one electrical potential degree of freedom per piezoelectric layer was derived. Dynamic characteristics of a beam with discontinuously distributed piezoelectric sensors and actuators were presented. A linear quadratic regulator (LQR) feedback controller was designed to suppress the vibration of the beam in the state space using the high precise direct (HPD) integration method.
基金supported by the Research Fund of State Key Laboratory of Mechanical System and Vibration,China(Grant No.MSV-2010-07)
文摘Thanks to the special physical architectures and various locomotion gaits,snake robots may offer significant benefits over traditional legged or wheeled locomotion designs in vast types of scenarios.This paper proposes an innovative snake robot with digitally-actuated Stewart platforms as its modules and mainly focuses on the simulations of various snake gaits.Three categories of fitting algorithms are elaborated in simulations of lateral undulation and Configuration-Fitting Algorithm of Four Modules is demonstrated as a universal gait fitting algorithm for all kinds of snake robots with binary actuators.Several typical snake gaits are simulated and the results demonstrate the excellent mobility of the snake robot.
基金Project supported by the National Key Technology R&D Program of China(No.2012BAJ07B03)the National Natural Science Foundation of China(Nos.51178415 and 51578491)
文摘One of the main problems in controlling the shape of active structures (AS) is to determine the actuations that drive the structure from the current state to the target state. Model-based methods such as stochastic search require a known type of load and relatively long computational time, which limits the practical use of AS in civil engineering. Moreover, additive errors may be produced because of the discrepancy between analytic models and real structures. To overcome these limitations, this paper presents a compound system called WAS, which combines AS with a wireless sensor and actuator network (WSAN). A bio-inspired control framework imitating the activity of the nervous systems of animals is proposed for WAS. A typical example is tested for verification. In the example, a triangular tensegrity prism that aims to maintain its original height is integrated with a WSAN that consists of a central controller, three actuators, and three sensors. The result demonstrates the feasibility of the proposed concept and control framework in cases of unknown loads that include different types, distributions, magnitudes, and directions. The proposed control framework can also act as a supplementary means to improve the efficiency and accuracy of control frameworks based on a common stochastic search.
基金supported by the National Natural Science Foundation of China (Grant No. 10872021)the Fundamental Research Funds for the Central Universities (Grant No. YWF-10-01-A05)
文摘The flow induced by plasma synthetic jet actuator was simulated through solving the Reynolds-averaged Navier-Stokes equations augmented by body force phenomenological plasma model.The effect of actuation frequency on the plasma synthetic jet was examined by case study.The numerical results present that with the actuation frequency increasing,the stream-wise distance of the adjacent vortex pairs induced by the actuator decreases monotonically,which is the same as the situation of the velocity fluctuations field caused by the vortex pairs.When the actuation frequency is 60 Hz,the vortex pairs formed during the adjacent actuation periods merge together quickly,and the flow structure in the downstream region is more close to that of the steady case.The actuation frequency has no visible influence on the time-averaged flow field of plasma synthetic jet.However,when the actuation frequency is relatively low(f<40 Hz),the momentum flux close to the actuator increases with the actuation frequency increasing,which is contrary to the situation in the far field from the wall.