A two-bit phase shifter with distributed microelectromechanical system (MEMS) transmission line (DMTL) is developed,and a novel structure which be actuated by coplanar waveguide transmission line (CPW-actuation struct...A two-bit phase shifter with distributed microelectromechanical system (MEMS) transmission line (DMTL) is developed,and a novel structure which be actuated by coplanar waveguide transmission line (CPW-actuation structure) is proposed,which can reduce the actuation voltage significantly.The measured result,with actuation voltage less than 20V,0°/20.1°/41.9°/68.2° phase shift and -1.2dB insert loss at 20GHz,is demonstrated,and insertion loss/return loss is better than -1.8dB/-11dB from DC to 32GHz.The experimental results highlight the potential of a low-loss and broadband digital MEMS phase shifter on a high-permittivity substrate.展开更多
A three-DOF (degree of freedom) planar robot completely restrained and positioned parallel pulled by four wires was studied. The wire driving properties were analyzed through experiments. The restrained three-DOF plan...A three-DOF (degree of freedom) planar robot completely restrained and positioned parallel pulled by four wires was studied. The wire driving properties were analyzed through experiments. The restrained three-DOF planar platform was established based on slippery course and bearing, and dSPACE real-time control system was used to perform the platform's motion control experiment on robot. Based on the kinematic equation and mechanical balance equation of moving platform, the stiffness of the robot system was analyzed and the calibration scheme of the system considering wire tension was put forward. Position servo control experiments were carried out, position servo tracking precision was analyzed, and real-time wire tension was detected. The results show that the moving error of the moving platform tracking is small (the maximum difference is about 3%), and the rotation error is large (the maximum difference is about 12%). The wire tension has wave properties (the wire tension fluctuation is about 10 N).展开更多
The trapezoidal cross-section roadway, driven along with its medium and fine grain sandstone roof in special thick stratum, was situated in shale strata. Rock-lining wall was employed in roadway, which its roof is in ...The trapezoidal cross-section roadway, driven along with its medium and fine grain sandstone roof in special thick stratum, was situated in shale strata. Rock-lining wall was employed in roadway, which its roof is in the free situation. Under the action of virgin stress, the surrounding rock of roadway was in stability. While under the action of fixed abutment pressure arisen from protection pillar of roadway, which its two sides?seams were extracted, free strong roof of roadway was in the stability. But its two sides?rock-lining walls was fractured, partially broken into pieces, and its floor heave was ob-vious. The velocity of floor heave is 0.4～0.8 mm/d. The size of broken zone of sur-rounding rock of roadway increases doubly. An effective load coefficient of surrounding rock to was quoted illustrate these phenomena. The main reasons of roadway conver-gence are that, rock property of surrounding rock is inferior, protection pillar affects its stability, and supporting pattern employed is improper. At last, effective measures to control roadway convergence should be bolting and grouting lining, which mainly con-solidates surrounding rock of roadway.展开更多
In this paper, a model of translation gateway is proposed. The communications between IPv4 network and IPv6 network are realized by using the Microsoft intermediate driver technology in environment of Windows 2000.
The Three Gorges project accelerates economic development in the Three Gorges Reservoir Area.This paper aimed to investigate the distribution,changes and features of cultivated land in this area,analyze the forces dri...The Three Gorges project accelerates economic development in the Three Gorges Reservoir Area.This paper aimed to investigate the distribution,changes and features of cultivated land in this area,analyze the forces driving the changes in cultivated land area,and propose the countermeasures for cultivated land management.Transition matrix was used to analyze the features of cultivated land changes,and quantitative analysis and qualitative analysis were adopted to research the driving forces according to the features of cultivated land changes.Cultivated land in the Three Gorges Reservoir Area mainly lay to the northwest of the Yangtze River,especially the upper reaches.The areas of cultivated land increased from 1996 to 1999,then decreased from 2000 to 2006,and finally increased again from 2007 to 2009.The important forces driving changes in cultivated land included government policies,employment and food security,increasing construction land,agriculture structure adjustment,land rearrangement,inundation.During cultivated land management,firstly,it is necessary to insist on the principle of cultivated land protection,standardize land exploitation and strictly restrict the transformation of cultivated land into non-farming land.Secondly,land rearrangement must be implemented,which can not only increase the area of the cultivated land,but also improve the quality of the cultivated land.Thirdly,it is feasible to intensify eco-agriculture construction to increase the quantity and quality of cultivated land.Fourthly,it is helpful to improve the traditional agriculture production methods to promote cultivated land quality.Lastly,it is important to propagandize cultivated land protection and realize the enormous pressure of cultivated land shortage,making more people obligated to protect cultivated land.展开更多
In order to improve the transmission accuracy and efficiency of sensing and actuating signals in Internet of Things （loT） and ensure the system stability, an adaptive resource allocation algorithm is proposed, which...In order to improve the transmission accuracy and efficiency of sensing and actuating signals in Internet of Things （loT） and ensure the system stability, an adaptive resource allocation algorithm is proposed, which dynami- cally assigns the network bandwidth and priority among components according to their signals＇ frequency domain characteristics. A remote sensed and controlled unmanned ground vehicle （UGV） path tracking test-bed was devel- oped and multiple UGV＇s tracking error signals were measured in the simulation for performance evaluation. Results show that with the same network bandwidth constraints, the proposed algorithm can reduce,, the accumulated and maximum errors of UGV path tracking by over 60% compared with the conventional static algorithm.展开更多
A robust adaptive control strategy was developed to force an underactuated surface vessel to follow a reference path,despite the presence of uncertain parameters and unstructured uncertainties including exogenous dist...A robust adaptive control strategy was developed to force an underactuated surface vessel to follow a reference path,despite the presence of uncertain parameters and unstructured uncertainties including exogenous disturbances and measurement noise.The reference path can be a curve or a straight line.The proposed controller was designed by using Lyapunov’s direct method and sliding mode control and backstepping techniques.Because the sway axis of the vessel was not directly actuated,two sliding surfaces were introduced,the first one in terms of the surge motion tracking errors and the second one for the yaw motion tracking errors.The adaptive control law guaranteed the uniform ultimate boundedness of the tracking errors.Numerical simulation results were provided to validate the effectiveness of the proposed controller for path following of underactuated surface vessels.展开更多
While urbanization has accelerated, the rural population in China has started decreasing in recent years. However, the expansion of rural settlement has not been sufficiently curbed. The questions of why this has happ...While urbanization has accelerated, the rural population in China has started decreasing in recent years. However, the expansion of rural settlement has not been sufficiently curbed. The questions of why this has happened and who has driven the land-use change(LUC) of rural settlement in China have aroused great interests among researchers. In this paper, it is suggested that population is not always a positive driving force for the LUC of rural settlement in China. Furthermore, socio-economic driving forces other than urbanization, population and industrialization are analyzed. On a national scale, the major driving forces are the per-capita rural housing area and the cultivated land area. On a regional scale, the main driving forces in the eastern China are the house-building capacity of rural households and the per-capita rural housing area; while in the central China, the main driving forces are rural housing investment, the proportion of primary industry employees in the rural working population, and the cultivated land area. For the western China, the main driving forces are rural register population and cultivated land area.展开更多
A modular flat-screen liquid crystal television display is described.The picture elements of the modules may be emissive,reflective or transmissive.The flat-screen liquid crystal television also comprised of an electr...A modular flat-screen liquid crystal television display is described.The picture elements of the modules may be emissive,reflective or transmissive.The flat-screen liquid crystal television also comprised of an electrical control circuit capable of categorizing incoming television picture signals corresponding to the modules in the array and directing the electrical signals to the drive circuits of each module according to the portion of the television picture to be reproduced by the picture elements of that module.The picture elements are preferably formed in a light modulating film composed of a liquid crystal dispersion in a polymeric binder.A color display was also produced by placing a patterned red-green-blue filter adjacent the active matrix so that each picture element could also be coordinated with the color components of a color video signal.展开更多
文摘A two-bit phase shifter with distributed microelectromechanical system (MEMS) transmission line (DMTL) is developed,and a novel structure which be actuated by coplanar waveguide transmission line (CPW-actuation structure) is proposed,which can reduce the actuation voltage significantly.The measured result,with actuation voltage less than 20V,0°/20.1°/41.9°/68.2° phase shift and -1.2dB insert loss at 20GHz,is demonstrated,and insertion loss/return loss is better than -1.8dB/-11dB from DC to 32GHz.The experimental results highlight the potential of a low-loss and broadband digital MEMS phase shifter on a high-permittivity substrate.
基金Project(20102304120007) supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProject(QC2010009)supported by the Natural Science Foundation of Heilongjiang Province, China+1 种基金Projects(20110491030, LBH-Z10219) supported by China Postdoctoral Science FoundationProject(HEUCF120706) supported by the Fundamental Research Funds for the Central Universities of China
文摘A three-DOF (degree of freedom) planar robot completely restrained and positioned parallel pulled by four wires was studied. The wire driving properties were analyzed through experiments. The restrained three-DOF planar platform was established based on slippery course and bearing, and dSPACE real-time control system was used to perform the platform's motion control experiment on robot. Based on the kinematic equation and mechanical balance equation of moving platform, the stiffness of the robot system was analyzed and the calibration scheme of the system considering wire tension was put forward. Position servo control experiments were carried out, position servo tracking precision was analyzed, and real-time wire tension was detected. The results show that the moving error of the moving platform tracking is small (the maximum difference is about 3%), and the rotation error is large (the maximum difference is about 12%). The wire tension has wave properties (the wire tension fluctuation is about 10 N).
基金Supported by Science Technology Research Project of Henan Province (0124150301)
文摘The trapezoidal cross-section roadway, driven along with its medium and fine grain sandstone roof in special thick stratum, was situated in shale strata. Rock-lining wall was employed in roadway, which its roof is in the free situation. Under the action of virgin stress, the surrounding rock of roadway was in stability. While under the action of fixed abutment pressure arisen from protection pillar of roadway, which its two sides?seams were extracted, free strong roof of roadway was in the stability. But its two sides?rock-lining walls was fractured, partially broken into pieces, and its floor heave was ob-vious. The velocity of floor heave is 0.4～0.8 mm/d. The size of broken zone of sur-rounding rock of roadway increases doubly. An effective load coefficient of surrounding rock to was quoted illustrate these phenomena. The main reasons of roadway conver-gence are that, rock property of surrounding rock is inferior, protection pillar affects its stability, and supporting pattern employed is improper. At last, effective measures to control roadway convergence should be bolting and grouting lining, which mainly con-solidates surrounding rock of roadway.
基金Supported by the Natural Science Foundation of Henan Province(0511011400) Supported by the Natural Science Foundation of Education Department of Henan Province(2004520014)
文摘In this paper, a model of translation gateway is proposed. The communications between IPv4 network and IPv6 network are realized by using the Microsoft intermediate driver technology in environment of Windows 2000.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. 2011YYL141)
文摘The Three Gorges project accelerates economic development in the Three Gorges Reservoir Area.This paper aimed to investigate the distribution,changes and features of cultivated land in this area,analyze the forces driving the changes in cultivated land area,and propose the countermeasures for cultivated land management.Transition matrix was used to analyze the features of cultivated land changes,and quantitative analysis and qualitative analysis were adopted to research the driving forces according to the features of cultivated land changes.Cultivated land in the Three Gorges Reservoir Area mainly lay to the northwest of the Yangtze River,especially the upper reaches.The areas of cultivated land increased from 1996 to 1999,then decreased from 2000 to 2006,and finally increased again from 2007 to 2009.The important forces driving changes in cultivated land included government policies,employment and food security,increasing construction land,agriculture structure adjustment,land rearrangement,inundation.During cultivated land management,firstly,it is necessary to insist on the principle of cultivated land protection,standardize land exploitation and strictly restrict the transformation of cultivated land into non-farming land.Secondly,land rearrangement must be implemented,which can not only increase the area of the cultivated land,but also improve the quality of the cultivated land.Thirdly,it is feasible to intensify eco-agriculture construction to increase the quantity and quality of cultivated land.Fourthly,it is helpful to improve the traditional agriculture production methods to promote cultivated land quality.Lastly,it is important to propagandize cultivated land protection and realize the enormous pressure of cultivated land shortage,making more people obligated to protect cultivated land.
基金Supported by Natural Science Foundation of Tianjin (No. 07JCZDJC05800)Science and Technology Supporting Plan of Tianjin (No. 09ZCKFGX29200)
文摘In order to improve the transmission accuracy and efficiency of sensing and actuating signals in Internet of Things （loT） and ensure the system stability, an adaptive resource allocation algorithm is proposed, which dynami- cally assigns the network bandwidth and priority among components according to their signals＇ frequency domain characteristics. A remote sensed and controlled unmanned ground vehicle （UGV） path tracking test-bed was devel- oped and multiple UGV＇s tracking error signals were measured in the simulation for performance evaluation. Results show that with the same network bandwidth constraints, the proposed algorithm can reduce,, the accumulated and maximum errors of UGV path tracking by over 60% compared with the conventional static algorithm.
基金Supported by the National Natural Science Foundation of China （Grant No. 61074053）the Applied Basic Research Program of Ministry of Transport of China （Grant No. 2011-329-225-390）
文摘A robust adaptive control strategy was developed to force an underactuated surface vessel to follow a reference path,despite the presence of uncertain parameters and unstructured uncertainties including exogenous disturbances and measurement noise.The reference path can be a curve or a straight line.The proposed controller was designed by using Lyapunov’s direct method and sliding mode control and backstepping techniques.Because the sway axis of the vessel was not directly actuated,two sliding surfaces were introduced,the first one in terms of the surge motion tracking errors and the second one for the yaw motion tracking errors.The adaptive control law guaranteed the uniform ultimate boundedness of the tracking errors.Numerical simulation results were provided to validate the effectiveness of the proposed controller for path following of underactuated surface vessels.
基金Under the auspices of National Natural Science Foundation of China(No.41001108)China Clean Development Mechanism Fund(No.2031202400003)
文摘While urbanization has accelerated, the rural population in China has started decreasing in recent years. However, the expansion of rural settlement has not been sufficiently curbed. The questions of why this has happened and who has driven the land-use change(LUC) of rural settlement in China have aroused great interests among researchers. In this paper, it is suggested that population is not always a positive driving force for the LUC of rural settlement in China. Furthermore, socio-economic driving forces other than urbanization, population and industrialization are analyzed. On a national scale, the major driving forces are the per-capita rural housing area and the cultivated land area. On a regional scale, the main driving forces in the eastern China are the house-building capacity of rural households and the per-capita rural housing area; while in the central China, the main driving forces are rural housing investment, the proportion of primary industry employees in the rural working population, and the cultivated land area. For the western China, the main driving forces are rural register population and cultivated land area.
文摘A modular flat-screen liquid crystal television display is described.The picture elements of the modules may be emissive,reflective or transmissive.The flat-screen liquid crystal television also comprised of an electrical control circuit capable of categorizing incoming television picture signals corresponding to the modules in the array and directing the electrical signals to the drive circuits of each module according to the portion of the television picture to be reproduced by the picture elements of that module.The picture elements are preferably formed in a light modulating film composed of a liquid crystal dispersion in a polymeric binder.A color display was also produced by placing a patterned red-green-blue filter adjacent the active matrix so that each picture element could also be coordinated with the color components of a color video signal.
