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61.
Nan-Chyuan Tsai Jiun-Sheng Liou Chih-Che Lin Tuan Li 《Sensors and actuators. A, Physical》2010,157(1):68-76
For micro-gyroscopes, the angular rate detection components have to oscillate forwards and backwards alternatively. An innovative design of micro-electromagnetic drive module is proposed to make a Π-type thin disc reciprocally and efficiently rotate within a certain of angular interval. Twelve EM (Electromagnetic) poles, with iron cores at the center and wound by electroplated copper wires, enclosing the thin disc are designed to provide the magnetic drive power. Isotropic etching technique is employed to fabricate the high-aspect-ratio trench, housing of the follow-up electroplated copper, so that the contact angle of wire against trench can be increased and the potential defect of cavities and pores within the wire can be prevented. On the other hand, a Π-type thin disc, with a central bearing and a set of auxiliary bushing, is designed to conduct the pitch motion as an angular excitation, in addition to spinning, is exerted on the gyroscope. That is, the angular motion of the disc is two-dimensional: spinning, driven by the EM poles, and tilting, to respond to the exerted angular rate due to Coriolis effect.The efficacy of the micro-magnetic drive module is verified by theoretical analysis and computer simulations by the commercial software, Ansoft Maxewll. In comparison with the conventional planar windings in micro-scale systems, the magnetic drive force is increased by 150%. 相似文献
62.
S.W. Chang T.-M. Liou K.F. Chiang G.F. Hong 《International Journal of Heat and Mass Transfer》2008,51(3-4):457-468
A novel heat transfer enhancement (HTE) roughness with V-shaped ribs and deepened scales is devised. Performances of heat transfer and pressure drop in a rectangular channel fitted with such HTE surfaces are experimentally examined for both forward and backward flows in the Re range of 1000–30000. Relative to the smooth-walled pipe flow conditions, HTE ratios for the present test channel with forward and backward flows, respectively, reach 9.5–13.6 and 9–12.3 for laminar flows and 6.8–6.3 and 5.7–4.3 for turbulent flows. Comparisons of heat transfer data, pressure-drop measurements and thermal performance factors with previous results collected from varieties of HTE devices demonstrate the superiorities of this compound HTE device. The decrease of HTE ratio as Re increases for turbulent flows, which is a common setback for several HTE elements, is almost diminished in the channel fitted with present compound HTE surfaces. Experimental correlations of heat transfer and friction coefficient for the tested channel with forward and backward flows are derived for design applications. 相似文献
63.
We have demonstrated a graded-index-rod external coupled-cavity (GRECC) laser with backface output through a partially transmitting external cavity mirror. Laser output is monitored from the backface in a transmitter module with double-loop feedback control which stabilizes output power and maintains single-frequency operation under CW and pseudorandom pulse modulation. 相似文献
64.
65.
J. J. Liou K. Lee S. M. Knapp K. B. Sundaram J. S. Yuan D. C. Malocha M. Belkerdid 《Solid-state electronics》1990,33(12):1629-1632
The quasi-static approximation, which assumes that free-carrier propagation delay in the semiconductor device is zero, is often used in device modeling. Consequently, the quasi-static model is adequate only for low-frequency excitations for which free-carrier propagation delay is very small compared to the variation of the excitations. This paper develops a non-quasi-static model suitable for metal-semiconductor junction diodes subjected to small-signal excitation. We show that the predictions of the non-quasi-static model agree more favourably with experimental data taken from Al---Si diodes than that of the quasi-static model, particularly when the frequency of the excitation is high. 相似文献
66.
Wu W.-C. Chao T.-S. Peng W.-C. Yang W.-L. Wang J.-C. Chen J.-H. Lai C.-S. Yang T.-Y. Lee C.-H. Hsieh T.-M. Liou J. C. 《Electron Device Letters, IEEE》2007,28(3):214-216
In this letter, high-performance and reliable wrapped select gate (WSG) polysilicon-oxide-nitride-oxide-silicon (SONOS) memory cells with multilevel and 2-bit/cell operation have been successfully demonstrated. The multilevel storage is easily obtained with fast program/erase speed (10 mus/5 ms) and low programming current (3.5 muA) for our WSG SONOS by a source-side injection. Besides the excellent reliability properties of our multilevel WSG-SONOS memory including unconsidered gate and drain disturbance, long charge retention (>150degC) and good endurance (>104) are also presented. This novel WSG-SONOS memory with a multilevel and 2-bit/cell operation can be used in future high-density and high-performance memory application 相似文献
67.
A model of reverse base current characteristics which is based on device physics is presented. The model requires only physical parameters, thus allowing circuit designers to estimate the device performance under avalanche operation prior to the actual device fabrication. Previously reported experimental data are included in support of the model 相似文献
68.
Surface area-normalized rate constants (k(SA)) of reaction between metallic nanoparticles and reducible contaminants, such as chlorinated hydrocarbons, heavy metals, and nitrate, have been reported to be dramatically increased as compared to that of commercial metallic powder. However, k(SA) for individual pollutants in previously published data vary by as much as 1-2 orders of magnitude and much of this variability is due to the effect of various sizes. The size dependence of the reactivity of nanoparticles is not yet fully understood; however, yielding nanoparticles with uniform size and without agglomeration during the period of reaction would demonstrate the effect of varying particle size. In this study, resin-supported zerovalent copper with average particle size of 7, 10, 18, 26, and 29, respectively, were successfully synthesized and evidenced no agglomeration during the reaction period of 10h. The k(SA) of copper nanoparticles (k(n,SA)) was 110-120 times higher than that of powdered copper particles (k(p,SA)) when the copper particle size was about 10nm. However, for diameters of 18-29 nm, the ratio of k(n,SA)/k(p,SA) was around 10-20, indicating that the reactivity of small copper nanoparticles (approximately 10nm) varies discontinuously. Thus, most variability in previous k(SA) is attributed to the presence of small nanoparticles. 相似文献
69.
Tarak Amine Joseph W. Newkirk Hussam El-Din F. El-Sheikh Frank Liou 《The International Journal of Advanced Manufacturing Technology》2014,73(9-12):1427-1435
Several techniques can be used to improve surface properties of metals. These can involve changes on the surface chemical composition such as alloying or on the surface microstructure, such as hardening. In the present work, melting of the surface by a 9 kW CO2 CW laser of wavelength 10.6 μm was used to alter surface features of D2 tool steel. Carbon powder and nitrogen gas were used as sources of alloying elements during laser processing. The effect of various laser parameters (power and speed) on the microstructure and hardness of D2 tool steel was investigated. Laser powers from 1 to 8 kW and laser speeds from 5 to 15 mm/s were employed. It was found that as the laser power increases, the hardness of the melted zone decreases while that of the heat-affected zone increases. On the other hand, the depth of both of melted and heat-affected zones increases with power. 相似文献
70.
刘重轩 《纺织高校基础科学学报》1997,10(1):42-45
箱式组合变电站箱内温的特点跟负载特性及箱壳的散热结构有关,而变电站内的电力变压器的负载率又跟箱内温升及箱壳的散热等级有关,本文给出了变压器负载率的计算公式和参考值。 相似文献