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In this paper,we use the a-plane InGaN interlayer to improve the property of a-plane GaN.Based on the a-InGaN interlayer,a template exhibits that a regular,porous structure,which acts as a compliant effect,can be obtained to release the strain caused by the lattice and thermal mismatch between a-GaN and r-sapphire.We find that the thickness of InGaN has a great influence on the growth of a-GaN.The surface morphology and crystalline quality both are first improved and then deteriorated with increasing the thickness of the InGaN interlayer.When the InGaN thickness exceeds a critical point,the a-GaN epilayer peels off in the process of cooling down to room temperature.This is an attractive way of lifting off a-GaN films from the sapphire substrate.  相似文献   
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The effects of V/Ill growth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated. The surface morphology, crystalline quality, strain states, and density of basal stacking faults were found to depend heavily upon the V/III ratio. With decreasing V/III ratio, the surface morphology and crystal quality first improved and then deteriorated, and the density of the basal-plane stacking faults also first decreased and then increased. The optimal V/III ratio growth condition for the best surface morphology and crystalline quality and the smallest basal-plane stacking fault density of a-GaN films are found. We also found that the formation of basal-plane stacking faults is an effective way to release strain.  相似文献   
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本文根据全息学基本原理,应用光的干涉,衍射理论详细描述了曲面全息元件的成象特性。用位相比较法导出了一套曲面全息光学元件的成象公式及焦距和各项放大倍率计算公式。  相似文献   
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The electron mobility limited by the interface and surface roughness scatterings of the two-dimensional electron gas in AlxGa1-xN/GaN quantum wells is studied. The newly proposed surface roughness scattering in the AlGaN/GaN quantum wells becomes effective when an electric field exists in the AlxGa1-xN barrier. For the AlGaN/GaN potential well, the ground subband energy is governed by the spontaneous and the piezoelectric polarization fields which are determined by the barrier and the well thicknesses. The thickness fluctuation of the AlGaN barrier and the GaN well due to the roughnesses cause the local fluctuation of the ground subband energy, which will reduce the 2DEG mobility.  相似文献   
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武器红外传感器系统实时仿真概述   总被引:2,自引:0,他引:2  
王建霞 《应用光学》2000,21(Z1):33-37
红外传感器系统的性能取决于系统操作时的环境,如复杂的地形、背景环境和大气条件等,用传统的飞行试验方法来作为系统性能的测试手段已不适应.采用半物理闭环仿真方法,在实验室建目标模拟器,可实时产生动态逼真的交战时所观察到的红外场景,为具有红外探测能力武器系统在研制、集成、测试、系统性能有效评价、武器系统的开发等方面提供精确可重复的实验途径.仿真系统包括目标特性及与红外场景有关的数据库、图像生成计算机、红外目标发生器、红外场景投影光学系统、飞行模拟器、仿真计算机.目前目标发生器产生的红外图像分辨率已达到512×512,帧频100Hz,辐射波段3~5μm、8~12μm,适用于目前红外制导系统制导过程的分析和评价.  相似文献   
6.
疲劳驾驶检测中人脸检测的算法有很多,其中相对成熟的是Gentle-Adaboost,此算法虽然识别率较高,但是识别时间较长,研究在识别过程中使用均值哈希算法进行算法优化,并引入缓存的概念来缩短识别时间.首先,根据Gentle-Adaboost算法和Haar特征来提取基本特征点,然后通过对比前后两帧图像的哈希指纹来减少人脸检测次数,最后通过缓存数据库来存储相似图片的哈希指纹,运行一段时间后仅需通过对比哈希指纹就能精准的找到人脸区域.通过实验,可以证明改进后的平均识别时间可减少原时间的80%.  相似文献   
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The effects of V/Ⅲgrowth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated.The surface morphology,crystalline quality,strain states,and density of basal stacking faults were found to depend heavily upon the V/Ⅲratio.With decreasing V/Ⅲratio,the surface morphology and crystal quality first improved and then deteriorated,and the density of the basal-plane stacking faults also first decreased and then increased.The optimal V/Ⅲratio growth condition for the best surface morphology and crystalline quality and the smallest basalplane stacking fault density of a-GaN films are found.We also found that the formation of basal-plane stacking faults is an effective way to release strain.  相似文献   
8.
疵点图像的特征提取是识别织物疵点的重要依据,它直接影响疵点识别的效率和准确率.基于特征参数应具有灵敏度高、独立性强、运算快的特点,提取出疵点的区域面积、边界周长、中心点坐标、长短轴长度、形状参数F和离心率E作为疵点的特征参数.实验证明它能够识别出大部分常见疵点,并为疵点定位标识提供充分依据.  相似文献   
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