The use of ultrasonic sensors has varied applications, but the sensor operation frequency limits the operating distance. An easy way to increase this distance is to couple a mechanical element （horn）, but it is nece...The use of ultrasonic sensors has varied applications, but the sensor operation frequency limits the operating distance. An easy way to increase this distance is to couple a mechanical element （horn）, but it is necessary to characterize this technique. In this paper the results obtained in a study of the behaviour of mechanical elements coupled to an ultrasonic sensor using finite element techniques are presented. These results have been obtained using Comsol Multiphysics modelling. Also, the effect caused by the sensor size on the radiation acoustic pressure has also been evaluated. In other way, in this paper it is presented the results obtained in the laboratory measurements. First, it is studied the influence of a straight horn attached to the ultrasonic sensor. Later, it is presented the variation in the sound pressure on the radiation axis when the sensor varies its size. In the final part of the paper, the experimental validation of the simulations is presented.展开更多
Micro heat pipe(MHP) is applied to implement the efficient heat transfer of light emitting diode(LED) device.The fabrication of MHP is based on micro-electro-mechanical-system(MEMS) technique,15 micro grooves were etc...Micro heat pipe(MHP) is applied to implement the efficient heat transfer of light emitting diode(LED) device.The fabrication of MHP is based on micro-electro-mechanical-system(MEMS) technique,15 micro grooves were etched on one side of silicon(Si) substrate,which was then packaged with aluminum heat sink to form an MHP.On the other side of Si substrate,three LED chips were fixed by die bonding.Then experiments were performed to study the thermal performance of this LED device.The results show that the LED device with higher filling ratio is better when the input power is 1.0 W; with the increase of input power,the optimum filling ratio changes from 30% to 48%,and the time reaching stable state is reduced; when the input power is equal to 2.5 W,only the LED device with filling ratio of 48% can work normally.So integrating MHP into high-power LED device can implement the effective control of junction temperature.展开更多
文摘The use of ultrasonic sensors has varied applications, but the sensor operation frequency limits the operating distance. An easy way to increase this distance is to couple a mechanical element （horn）, but it is necessary to characterize this technique. In this paper the results obtained in a study of the behaviour of mechanical elements coupled to an ultrasonic sensor using finite element techniques are presented. These results have been obtained using Comsol Multiphysics modelling. Also, the effect caused by the sensor size on the radiation acoustic pressure has also been evaluated. In other way, in this paper it is presented the results obtained in the laboratory measurements. First, it is studied the influence of a straight horn attached to the ultrasonic sensor. Later, it is presented the variation in the sound pressure on the radiation axis when the sensor varies its size. In the final part of the paper, the experimental validation of the simulations is presented.
基金supported by the State Key Development Program for Basic Research of China(No.2011CB013105)
文摘Micro heat pipe(MHP) is applied to implement the efficient heat transfer of light emitting diode(LED) device.The fabrication of MHP is based on micro-electro-mechanical-system(MEMS) technique,15 micro grooves were etched on one side of silicon(Si) substrate,which was then packaged with aluminum heat sink to form an MHP.On the other side of Si substrate,three LED chips were fixed by die bonding.Then experiments were performed to study the thermal performance of this LED device.The results show that the LED device with higher filling ratio is better when the input power is 1.0 W; with the increase of input power,the optimum filling ratio changes from 30% to 48%,and the time reaching stable state is reduced; when the input power is equal to 2.5 W,only the LED device with filling ratio of 48% can work normally.So integrating MHP into high-power LED device can implement the effective control of junction temperature.
