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991.
Steady free convection boundary layer about a truncated cone embedded in a porous medium saturated with pure or saline water at low temperatures has been studied in this paper. The governing coupled partial differential equations are solved numerically using a very efficient finite-difference method. Several new parameters arise and the results are given for some specific values of these parameters. The obtained results for a Boussinesq fluid are compared with known results from the open literature and it is shown that the agreement between these results is very good. 相似文献
992.
993.
本文提出了一种码率不高于22Mb/s的基于MPEG-2标准的数字高清晰度电视视频编解码实验系统,重点研究了帧/场自适应DCT变换及相应的帧/场扫描方式、量化器设计、码率控制及缓存器控制策略、数据流层结构等关键技术。 相似文献
994.
基于DirectDraw的动画设计技术 总被引:3,自引:0,他引:3
DirectDraw是Microsoft公司发行的软件开发工具包,由于他能产生快速,平稳的图形,而被广泛用于游戏软件及动画设计中,本文结合一个开发实例提出了一种切实可行的动画程序开发方法。 相似文献
995.
In an in-home digital network it may be expected that several data streams (audio, video) run simultaneously over a shared
communication device, e.g., a bus. The burstiness of a data stream can be reduced by buffering data at the sending and receiving
side, thereby allowing a lower bus share allocation for the stream. In this paper we present an algorithm that determines
how much of the bus capacity and buffer space should be allocated to each stream, in order to have a feasible transmission
schedule for each stream. Furthermore, the algorithm determines a transmission schedule for each stream, indicating how much
data is transmitted over time. We show how this multiple-stream problem can be solved by repeatedly solving single-stream
problems. We present efficient algorithms to solve these single-stream problems. Furthermore, we present some experimental
results.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
996.
997.
K. Ramamoorthy M. Jayachandran K. Sankaranarayanan Pankaj Misra L. M. Kukreja C. Sanjeeviraja 《Current Applied Physics》2004,4(6):679-684
Intrinsic epitaxial zinc oxide (epi-ZnO) thin films were grown by laser-molecular beam epitaxy (L-MBE), i.e., pulsed laser deposition (PLD) technique using Johnson Matthey “specpure”-grade ZnO pellets. The effects of substrate temperatures on ZnO thin film growth, electrical conductivity (σ), mobility (μ) and carrier concentration (n) were studied. As well as the feasibility of developing high quality conducting oxide thin films was also studied simultaneously. The highest conductivity was found for optimized epi-ZnO thin films is σ=0.06×103 ohm−1 cm−1 (n-type) (which is almost at the edge of semiconductivity range), carrier density n=0.316×1019 cm−3 and mobility μ=98 cm2/V s. The electrical studies further confirmed the semiconductor characteristics of epi-n-ZnO thin films. The relationship between the optical and electrical properties were also graphically enumerated. The electrical parameter values for the films were calculated, graphically enumerated and tabulated. As a novelty point of view, we have concluded that without doping and annealing, we have obtained optimum electrical conductivity with high optical transparency (95%) for as deposited ZnO thin films using PLD. Also, this is the first time that we have applied PLD made ZnO thin films to iso-, hetero-semiconductor–insulator–semiconductor (SIS) type solar cells as transparent conducting oxide (TCO) window layer. We hope that surely these data be helpful either as a scientific or technical basis in the semiconductor processing. 相似文献
998.
从理论上研究缓冲层的厚度和特性对多量子阱材料 (GaAs/Ga1-xAlxAs)中的共振态的影响 ,利用界面响应理论的格林函数方法 ,计算了局域和总电子态密度以及电子对结的穿透率 ,展示了缓冲层特性对态密度特征峰、穿透率的影响。结果表明 ,缓冲层具有控制共振隧穿电子和影响系统电子态的作用 相似文献
999.
汪波 《光纤与电缆及其应用技术》2004,(4):20-22
简要介绍了光纤不锈钢松套管的两种结构以及相关制造工艺。对生产原理、关键技术进行了对比分析,对一些有争议的问题进行了探讨。 相似文献
1000.
SiC MESFETs with a narrow channel layer are proposed to alleviate the short-channel effects, in particular the drain-induced barrier lowering (DIBL) effect that results in threshold voltage that is dependent on the gate length and the drain voltage applied. Such narrow channel layer 4H-SiC MESFETs were fabricated and characterized. The thickness and doping concentration of the channel layer are 0.08 μm and 8.0 × 1017 cm−3, respectively. The measurement results showed that the threshold voltage of the MESFETs is about −1.1 V and is independent of the gate length from 1 to 3 μm, and the drain voltage applied up to 40 V. Good saturation behavior with fairly low output conductance was also achieved, which is desirable for small signal applications. The results obtained for the narrow channel layer MESFETs are also compared with those measured for conventional devices with thicker channel layer of 0.20 μm and doping concentration of 2.5 × 1017 cm−3. 相似文献