KEY WORDScapacitive micromachined ultrasonic transducer, fabrication, image sensor, ultrasonography Capacitive micromachined ultrasonic tranducers (cMUTs) have recently emerged as an alternative to conventional piezoelectric transducers. They offer many advantages in terms of bandwidth, fabrication of layer arrays, efficiency, and sensitivity. This research presents the principles of operation, fabrication process steps, and application of the capacitive micromachined ultrasound transducer. The study also demonstrates in detail the collapse voltage design parameter of a cMUT membrane. Several important applications are presented to show the feasibility of using cMUTs which are demonstrated by imaging examples in immersion and air due to the cMUT capability of producing large bandwidth (123% fractional bandwidth) and lower impedance mismatch. Finally, the advantages of three-dimensional echographic images based on moving ultrasound linear array its technique are discussed in detail and compared with those of two-dimensional optical hand geometry. ª
The distribution of the liquid and gas flows in multi-pass channel that illustrate a compact evaporator for air-conditioning system was experimentally studies. The dividing header are design horizontal with a square cross section of 20mm x 20mm and length is 290mm, also ten curve multi-pass channel with length of 300mm each connected between the circle cross section 50mm combination tank. The distance between the dividing header and combing tank were 120mm. The test was conduct under uniform backpressure conditions; additionally, the working fluid used was water and air. This experiment conducted to examine the influence of inlet-flow at the header entrance (stratified flow and annular-mist flow) under uniform backpressure condition to improve the uniform of the water distribution inside every curve channels. It was found that the inlet-flow condition at the entrance header has relatively influence the water distribution. By comparison between two flow conditions, great value of uniformity for water distribution in each channel is improved under annular-mist flow condition.
The gas-liquid flow distributions in multi-pass upward parallel channels that simulate the evaporator for the automobile air-conditioner system were examined experimentally. In this paper, the attentions are (1) To study the influences of the backpressure condition at the branch outlets and of the flow-inlet condition at the header entrance on the gas-liquid distributions to the branches, (2) To discover the most influenced parameter to the flow distribution uniformity by using design of experiment method. Experiments were conducted in an isothermal air-water flow system. The influence of the backpressure condition on the flow distributions changed depending on the flow-inlet condition. In the stratified-flow inlet, the backpressure condition was highly influential in both the air and water distributions, and the uniform water distribution that was ideal for the evaporators could not be achieved even if air was distributed uniformly to all branches. In the mist-flow inlet, the water distribution was insensitive to the backpressure conditions and its uniformity was improved in comparison with that in the stratified-flow inlet. The flow distribution uniformity for gas phase is influenced mostly by superficial air velocity, and the flow distribution uniformity of liquid phase is mostly influence by 2-way interaction of parameters which are flow pattern and superficial air velocity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.