Circular Capacitance Micromachined Ultrasonic Transducer

Capacitance micromachined ultrasonic transducers (CMUTs) have become an attractive alternative to the piezoelectric transducers, especially in air-coupled nondestructive evaluation (NDE) and ultrasound medical imaging flow metering,  micro/nanoelectronics, and industrial cleaning, etc. These are similar to other capacitance transducers as these employ a vibrating membrane to send and receive ultrasound in air and water. This paper describes the theory and design of a circular micromachined ultrasonic transducer which could lead to a CMUT with many advantages, including less loading effect. The software programs (Intellisuite 8.2 and MATLAB 7.0) were used to model a single cell of CMUT. The simulations-based studies of the critical parameters like collapse voltage and snapback voltage, which influence the operation of the CMUTs to a large extent, has been discussed. Small signal equivalent circuit model for the circular CMUT has been discussed and the program (SPICE) has been used for the simulation of the small signal equivalent circuit.Defence Science Journal, 2009, 59(6), pp.627-633, DOI:http://dx.doi.org/10.14429/dsj.59.156

Scintillation Counters for the D0 Muon Upgrade

We present the results of an upgrade to the D0 muon system. Scintillating counters have been added to the existing central D0 muon system to provide rejection for cosmic ray muons and out-of-time background, and to provide additional fast timing information for muons in an upgraded Tevatron. Performance and results from the 1994-1996 Tevatron run are presented.Comment: 30 pages, 25 postscript figure

Very low field electron emission from hot filament CVD grown microcrystalline diamond

Very low threshold field emission from undoped microcrystalline diamond films grown by the hot filament chemical vapour deposition process (HFCVD) is reported. The effect of crystal size, methane concentration and the temperature has been studied. The microcrystalline diamond films grown using 3% methane (CH4) / hydrogen (H2) gas mixture ratio under varying deposition temperatures exhibit very low emission threshold fields. The threshold fields varied from 0.4 V/μm to 1 V/μm for an emission current density of 1 μA/cm2. A correlation between the emission characteristics and the material properties is presented. These films exhibit an emission site density of ∼104-105/cm2 at an applied field of 3 V/μm

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Not AvailableA study on the strategic thinking ability among 432 scientist respondents of National Agricultural Research and Education System (NARES) in India indicated that only 29 (6.7%) have the ability to think strategically. Of all the behavioral and environmental independent variables considered for the study, only three variables viz., creativity, communication skills and climate for innovation have association with the strategic thinking capacity at 5% significance level. Four other behavioral and personal variables viz., effective leadership trait, achievement motive, indulgence in office politics and experience were found to have association with strategic thinking at 10% significance. All other independent variables found to have no association with the strategic thinking capacity of the respondents. Among all the independent variables only indulgence in office politics, existence of climate for innovation and total service experience have been found to significantly influence the ability to think strategicNot Availabl