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61.
Han-Bin Lin Jung-Young Su Yu-Pin Liao Way-Seen Wang 《Quantum Electronics, IEEE Journal of》1995,31(6):1131-1139
By using micro-prisms, improved three-dimensional (3-D) bends of the embedded and buried waveguides of step-index profile are proposed. A simple phase compensation rule for the optimal design of the micro-prism is also presented. Through the simulation of 3-D semivectorial finite-difference beam propagation method, the transmission characteristics of the improved bends are shown to have been enhanced dramatically as compared with those of the conventional ones. Even for a bend angle of as large as 10°, the normalized transmitted power can still be greater than 95%. These results of 3-D bends are then compared with those of the two-dimensional (2-D) ones which are simplified from 3-D structures by the effective index method, and physical explanation of the discrepancy between the 3-D and 2-D results is introduced. The influences of waveguide structures and prism parameters on the transmission characteristics are discussed in detail. Some criteria for the design of large-angle low-loss 3-D improved bends are also accessed 相似文献
62.
EK Yeong R Mann M Goldberg L Engrav D Heimbach 《Canadian Metallurgical Quarterly》1996,40(6):956-61; discussion 961-2
The utility of the laser Doppler for determining burn depth has been questioned because of problems with technology and methodology. This study prospectively evaluates the ability of a new laser Doppler technique to predict burn healing time. Using the Periflux System 4000 laser Doppler, readings were taken on 305 burns (147 patients) on postburn day 3 or 4. Sixty-six wounds were used to derive a predictive function (phase I) and 152 wounds were used to test the function (phase II). Blood flow dynamics (flux), microvascular dilation capacity of the wounds to beat stress, and flow motion wave pattern (vasomotion) were studied using the laser Doppler, and seven parameters were evaluated to determine their relative contribution to the prediction of healing time. These parameters are hyperemic flux (flux value after heating to 42 degrees C), average hyperemic wave amplitude (AHWA), number of average flux units >100(F100), number readings with wave amplitude 75 (A5), average flux change (AFC), percentage of average flux increase, and relative flow capacity (RFC = AFC/average hyperemic flux). After readings were made, the wounds were observed and divided into two groups: those that healed in less than 14 days and those that healed or were grafted after 14 days. A step-wise discriminant analysis was used to assess the relative contribution of the Doppler-derived measures to healing time prediction. AHWA, F100, and RFC were included in the final discriminant function explaining 72% of the healing time variance (Wilks' lambda value 0.28; p value <0.0001). Predicted outcome = 0.05(AHWA) + 0.31(F100) + 5.0(RFC) - 2.3. With this derived function, there is 94% accuracy in the prediction of burn wound healing time compared with a physician predictive accuracy of 70%. 相似文献
63.
随着汽车数量的迅速增加,汽车排放的有害废气也急剧增加,人们的健康受到威胁,解决这一问题的最好办法是发展清洁代用燃料汽车。介绍了天然气汽车和液化石油气汽车的主要优点,分析了目前我国清洁代用燃料汽车的发展现状,阐述了近期适宜发展我国清洁代用燃料汽车的机遇和面临的困难。最后就提高人们的环保意识、修改和完善汽车尾气污染控制法及排放标准、清洁代用燃料汽车的有关标准和安全措施。对发展这种汽车应给予优惠政策以及零部件生产和车辆改装企业的管理等方面,提出了建议。 相似文献
64.
Sarkar T.K. Su C. Adve R. Salazar-Palma M. Garcia-Castillo L. Boix R.R. 《Antennas and Propagation Magazine, IEEE》1998,40(5):49-68
The objective of this paper is to present the subject of wavelets from a filter-theory perspective, which is quite familiar to electrical engineers. Such a presentation provides both physical and mathematical insights into the problem. It is shown that taking the discrete wavelet transform of a function is equivalent to filtering it by a bank of constant-Q filters, the non-overlapping bandwidths of which differ by an octave. The discrete wavelets are presented, and a recipe is provided for generating such entities. One of the goals of this tutorial is to illustrate how the wavelet decomposition is carried out, starting from the fundamentals, and how the scaling functions and wavelets are generated from the filter-theory perspective. Examples (including image compression) are presented to illustrate the class of problems for which the discrete wavelet techniques are ideally suited. It is interesting to note that it is not necessary to generate the wavelets or the scaling functions in order to implement the discrete wavelet transform. Finally, it is shown how wavelet techniques can be used to solve operator/matrix equations. It is shown that the “orthogonal-transform property” of the discrete wavelet techniques does not hold in numerical computations 相似文献
65.
利用修正的非线性Schrodinger方程研究了单模光纤最小群速度色散波长附近的调制不稳定性,发现了一个新的由光纤四色散导致的调制不稳定性区域,该区域的调制范围与初始入射脉冲的功率和四阶色散有关。 相似文献
66.
67.
短模型上的明渠非恒定流试验 总被引:1,自引:0,他引:1
水工整体模型试验中,明渠非恒定流至今大多被简化为恒定流,而效果有时并不理想。本文指出,只要设置固定式曲线尾门,并有必要的动态量测设备,便可模拟原型非恒定流;即使模型偏短,也能得出比恒定流试验更接近原型的成果。在同一模型上,既做恒定流试验,又进行必要的非恒定流试验,二者相辅相成,必将有助于试验水平的提高。作为例证,本文介绍了泄洪调度导致航道水面波动的一项试验成果,并以岩基冲刷、通航水流条件、围堰过水、河床冲淤等研究课题为例,讨论了采用“短模型非恒定流试验方式”的必要性与可行性。 相似文献
68.
The purpose of this paper is to study the relationship between the oxygen concentration and brightness degradation in ZnS:TbOF green thin-film electroluminescent (EL) devices. The characteristics including crystallinity, optical, and electrical properties were discussed. The brightness-voltage (B-V) measurement results shelved that with higher oxygen-content in ZnS:TbOF phosphor layer, lower brightness was measured. It was consistent with the poor crystallinity, worse photoluminescent intensity, and easier to get moisture in the oxygen-rich (O/Tb>1) phosphor film. Furthermore, deep level transient spectroscopy (DLTS) measurements identified that when the O/Tb ratio was greater than 1, the oxygen-related deep hole traps EH1 and/or EH2 could be detected in the ZnS:TbOF phosphor layer. These E H1 and/or EH2 traps were believed to be the main killers for the brightness of the device since they capture most of the holes from the generated electron-hole pairs. This evidence strongly supports that the modified energy transfer model is more dominant than direct impact excitation during the luminescent process 相似文献
69.
M Pan J Suárez de Lezo A Medina M Romero E Hernández J Segura F Melian F Wangüemert M Landin F Benítez M Amat F Velasco A Torres 《Canadian Metallurgical Quarterly》1997,80(10):1336-1338
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation. 相似文献
70.
气—液式热管换热器在硫酸工业中的应用研究 总被引:4,自引:0,他引:4
本文研制的气-液式热管换热器应用于硫酸生产中SO3气体的余热回收。它具有传热性能好、流动阻力小、寿命长、体积小、节能效果显著和易清垢等优点。 相似文献