The 20,000-ton combined train running has greatly promoted China’s heavy-haul railway transportation capability. The application of controllable train-tail devices could improve the braking wave of the train and brak...The 20,000-ton combined train running has greatly promoted China’s heavy-haul railway transportation capability. The application of controllable train-tail devices could improve the braking wave of the train and braking synchronism, and alleviate longitudinal impulse.However, the characteristics of the controllable train-tail device such as exhaust area, exhaust duration and exhaust action time are not uniform in practice, and their effects on the longitudinal impulse of the train are not apparent,which is worth studying. In this work, according to the formation of the Datong-Qinhuangdao Railway, the train air brake and longitudinal dynamics simulation system(TABLDSS) is applied to establish a 20,000-ton combined train model with the controllable train-tail device, and the braking characteristics and the longitudinal impulse of the train are calculated synchronously with changing the air exhaust time, exhaust area, and action lag time under initial braking. The results show that the maximum coupler force of the combined train will decrease with the extension of the continuous exhaust time, while the total exhaust time of the controllable train-tail device remains unchanged;the maximum coupler force of the combined train reduces by32.5% with the exhaust area increasing from 70% to 140%;when the lag time between the controllable train-tail device and the master locomotive is more than 1.5 s, the maximum coupler force of the train increases along with the time difference enlargement.展开更多
This paper presents an analytical solution for the thermoelastic stress in a typical in-plane＇s thin-film micro- thermoelectric cooling device under different operating con- ditions. The distributions of the permissi...This paper presents an analytical solution for the thermoelastic stress in a typical in-plane＇s thin-film micro- thermoelectric cooling device under different operating con- ditions. The distributions of the permissible temperature fields in multilayered thin-films are analytically obtained, and the characteristics, including maximum temperature dif- ference and maximum refrigerating output of the thermo- electric device, are discussed for two operating conditions. Analytical expressions of the thermoelastic stresses in the layered thermoelectric thin-films induced by the tempera- ture difference are formulated based on the theory of mul- tilayer system. The results demonstrate that, the geometric dimension is a significant factor which remarkably affects the thermoelastic stresses. The stress distributions in layers of semiconductor thermoelements, insulating and support- ing membrane show distinctly different features. The present work may profitably guide the optimization design of high- efficiency micro-thermoelectric cooling devices.展开更多
To reduce the longitudinal coupler forces of heavy haul trains and improve the running safety, the velocity method and New-mark method were used for the coupler simulation and numerical integration, and a numerical mo...To reduce the longitudinal coupler forces of heavy haul trains and improve the running safety, the velocity method and New-mark method were used for the coupler simulation and numerical integration, and a numerical model on the longitudinal dynamics of heavy haul trains was established. Validation was performed against the experimental data. Using this model, the emergency braking process for a combined marshalling heavy haul train was investigated to obtain the distributions of the longitudinal compressive forces and strokes of coupler devices. Then, the influences of the initial braking velocity, the synchronization time of master and slave locomotives, the coupler stiffness and the vibrator mass on the longitudinal forces and strokes were analyzed. The results show that it should be avoided that the emergency braking starts at a low initial speed. Keeping synchronism between master locomotive and slave locomotives effectively helps to reduce the longitudinal forces. Reducing the coupler stiffness appropriately and adding rigid arm connections, the longitudinal vibration frequency can be brought down and the longitudinal forces will be decreased, which improves the running safety of heavy haul trains. All of these research results can provide a reference for the operation and development of heavy haul trains.展开更多
A haptic device is proposed which gives the user feedback information on their location and orientation of the obstacle through the mobile robot that detects the obstacle in an environment where the user cannot see.Mo...A haptic device is proposed which gives the user feedback information on their location and orientation of the obstacle through the mobile robot that detects the obstacle in an environment where the user cannot see.Mobile robot recognizes the exact position of the obstacle through configuring the nested ultrasonic sensor and giving feedback information to the haptic device.The haptic device consisting of five vibration motors can realize the haptic through the vibration of user's finger using the position information of the obstacle received feedback.In addition,it has high accuracy to recognize the surrounding environment and realizes the various situations with the fuzzy controller and the nested ultrasonic sensors.展开更多
micro-electro-mechanical system （MEMS） device has the advantages of both electronic system and mechanical system. With the development of MEMS devices for satellite, it is possible to establish much lighter and smal...micro-electro-mechanical system （MEMS） device has the advantages of both electronic system and mechanical system. With the development of MEMS devices for satellite, it is possible to establish much lighter and smaller nanosatellites with higher performance and longer lifecyele. The power consumption of MEMS devices is usually much lower than that of traditional devices, which will greatly reduce the consumption of power. For its small size and simple architecture, MEMS devices can be easily integrated together and achieve redundancy. Launched on April 18, 2004, NS - 1 is a nanosatellite for science exploration and MEMS devices test. A mass of science data and images were acquired during its running. NS - 1 weights less than 25 kg. It consists of several MEMS devices, including one miniature inertial measurement unit（MIMU） , three micro complementary metal oxide semiconductor （CMOS）cameras, one sun sensor, three momentum wheels, and one micro magnetic sensor. By applying micro components based on MEMS technology, NS - 1 has made success in the experiments of integrative design, manufacture, and MEMS devices integration. In this paper, some MEMS devices for nanosatellite and picosatellite are introduced, which have been tested on NS -1 nanosatellite or on the ground.展开更多
基金China National Railway Group Co.,Ltd(N2020J037).
文摘The 20,000-ton combined train running has greatly promoted China’s heavy-haul railway transportation capability. The application of controllable train-tail devices could improve the braking wave of the train and braking synchronism, and alleviate longitudinal impulse.However, the characteristics of the controllable train-tail device such as exhaust area, exhaust duration and exhaust action time are not uniform in practice, and their effects on the longitudinal impulse of the train are not apparent,which is worth studying. In this work, according to the formation of the Datong-Qinhuangdao Railway, the train air brake and longitudinal dynamics simulation system(TABLDSS) is applied to establish a 20,000-ton combined train model with the controllable train-tail device, and the braking characteristics and the longitudinal impulse of the train are calculated synchronously with changing the air exhaust time, exhaust area, and action lag time under initial braking. The results show that the maximum coupler force of the combined train will decrease with the extension of the continuous exhaust time, while the total exhaust time of the controllable train-tail device remains unchanged;the maximum coupler force of the combined train reduces by32.5% with the exhaust area increasing from 70% to 140%;when the lag time between the controllable train-tail device and the master locomotive is more than 1.5 s, the maximum coupler force of the train increases along with the time difference enlargement.
基金supported by the National Basic Research Program of China(2007CB607506)the Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China(111005)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(11121202)
文摘This paper presents an analytical solution for the thermoelastic stress in a typical in-plane＇s thin-film micro- thermoelectric cooling device under different operating con- ditions. The distributions of the permissible temperature fields in multilayered thin-films are analytically obtained, and the characteristics, including maximum temperature dif- ference and maximum refrigerating output of the thermo- electric device, are discussed for two operating conditions. Analytical expressions of the thermoelastic stresses in the layered thermoelectric thin-films induced by the tempera- ture difference are formulated based on the theory of mul- tilayer system. The results demonstrate that, the geometric dimension is a significant factor which remarkably affects the thermoelastic stresses. The stress distributions in layers of semiconductor thermoelements, insulating and support- ing membrane show distinctly different features. The present work may profitably guide the optimization design of high- efficiency micro-thermoelectric cooling devices.
基金Project(U1334208)supported by the National Natural Science Foundation of ChinaProject(2016zzts331)supported by the Fundamental Research Funds for the Central Universities,China
文摘To reduce the longitudinal coupler forces of heavy haul trains and improve the running safety, the velocity method and New-mark method were used for the coupler simulation and numerical integration, and a numerical model on the longitudinal dynamics of heavy haul trains was established. Validation was performed against the experimental data. Using this model, the emergency braking process for a combined marshalling heavy haul train was investigated to obtain the distributions of the longitudinal compressive forces and strokes of coupler devices. Then, the influences of the initial braking velocity, the synchronization time of master and slave locomotives, the coupler stiffness and the vibrator mass on the longitudinal forces and strokes were analyzed. The results show that it should be avoided that the emergency braking starts at a low initial speed. Keeping synchronism between master locomotive and slave locomotives effectively helps to reduce the longitudinal forces. Reducing the coupler stiffness appropriately and adding rigid arm connections, the longitudinal vibration frequency can be brought down and the longitudinal forces will be decreased, which improves the running safety of heavy haul trains. All of these research results can provide a reference for the operation and development of heavy haul trains.
基金The MOTIE(Ministry of Trade,Industry and Energy),Korea,under the Human Resources Development Program for Special Environment Navigation Localization National Robotics Research Center support program supervised by the NIPA(National IT Industry Promotion Agency)(H1502-13-1001)The MSIP(Ministry of Science,ICT&Future Planning),Korea,under the ITRC(Information Technology Research Center)support program(NIPA-2013-H0301-13-2006)supervised by the NIPA
文摘A haptic device is proposed which gives the user feedback information on their location and orientation of the obstacle through the mobile robot that detects the obstacle in an environment where the user cannot see.Mobile robot recognizes the exact position of the obstacle through configuring the nested ultrasonic sensor and giving feedback information to the haptic device.The haptic device consisting of five vibration motors can realize the haptic through the vibration of user's finger using the position information of the obstacle received feedback.In addition,it has high accuracy to recognize the surrounding environment and realizes the various situations with the fuzzy controller and the nested ultrasonic sensors.
文摘micro-electro-mechanical system （MEMS） device has the advantages of both electronic system and mechanical system. With the development of MEMS devices for satellite, it is possible to establish much lighter and smaller nanosatellites with higher performance and longer lifecyele. The power consumption of MEMS devices is usually much lower than that of traditional devices, which will greatly reduce the consumption of power. For its small size and simple architecture, MEMS devices can be easily integrated together and achieve redundancy. Launched on April 18, 2004, NS - 1 is a nanosatellite for science exploration and MEMS devices test. A mass of science data and images were acquired during its running. NS - 1 weights less than 25 kg. It consists of several MEMS devices, including one miniature inertial measurement unit（MIMU） , three micro complementary metal oxide semiconductor （CMOS）cameras, one sun sensor, three momentum wheels, and one micro magnetic sensor. By applying micro components based on MEMS technology, NS - 1 has made success in the experiments of integrative design, manufacture, and MEMS devices integration. In this paper, some MEMS devices for nanosatellite and picosatellite are introduced, which have been tested on NS -1 nanosatellite or on the ground.
