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GD/J0303-2010《数字电视广播条件接收系统技术要求及测量方法》是数字条件接收系统进行入网检测的指导性文件,该检测方法较之前标准在测试环境及测试方法方面均进行了较大改变。本文中,作者根据实际工作经验,对数字电视广播条件接收系统测试进行了全面介绍并对其中难点进行了重点解析。 相似文献
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Gallium nitride (GaN) based light emitting diodes (LEDs) with a thick and high quality ZnO film as a current spreading layer grown by metal-source vapor phase epitaxy (MVPE) are fabricated successfully. Compared with GaN-based LEDs employing a Ni/Au or an indium tin oxide transparent current spreading layer, these LEDs show an enhancement of the external quantum efficiency of 93% and 35% at a forward current of 20 mA, respectively. The full width at half maximum of the ZnO (002) ω-scan rocking curve is 93 arcsec, which corresponds to a high crystal quality of the ZnO film. Optical microscopy and atomic force microscopy are used to observe the surface morphology of the ZnO film, and many regular hexagonal features are found. A spectrophotometer is used to study the different absorption properties between the ZnO film and the indium tin oxide film of the GaN LED. The mechanisms of the extraction quantum efficiency increase and the series resistance change of the GaN-based LEDs with ZnO transparent current spreading layers are analyzed. 相似文献
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An 8 μ m thick Ga-doped ZnO (GZO) film grown by metal-source vapor phase epitaxy was deposited on a GaN-based light-emitting diode (LED) to substitute for the conventional ITO as a transparent conduct layer (TCL). Electroluminescence spectra exhibited that the intensity value of LED emission with a GZO TCL is markedly improved by 23.6% as compared to an LED with an ITO TCL at 20 mA. In addition, the forward voltage of the LED with a GZO TCL at 20 mA is higher than that of the conventional LED. To investigate the reason for the increase of the forward voltage, X-ray photoelectron spectroscopy was performed to analyze the interface properties of the GZO/p-GaN heterojunction. The large valence band offset (2.24± 0.21 eV) resulting from the formation of Ga2O3 in the GZO/p-GaN interface was attributed to the increase of the forward voltage. 相似文献
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采用化学气相沉积(CVD)方法在Si(001)衬底上分别制备了有金属Au缓冲层以及无Au缓冲层的ZnO薄膜。其中Au缓冲层在物理气相沉积(PVD)设备中蒸发,厚度大约为300nm。有Au缓冲层的ZnO薄膜晶体质量比直接在Si衬底上生长有了显著提高。利用X射线衍射(XRD)研究了所生长ZnO薄膜的结晶质量,有Au缓冲层的ZnO薄膜虽然仍为多晶,但显示出明显的择优取向。用光学显微镜研究了ZnO薄膜的表面特征,金属Au缓冲层显著地提高了在Si衬底上生长的ZnO薄膜的晶粒尺寸及平整度。同时利用室温光致发光(PL)谱研究了ZnO薄膜的光学性质,并分析了有Au缓冲层的ZnO薄膜NEB发光峰强度反而弱的可能原因。 相似文献
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移动多媒体广播电视作为新媒体既有同传统媒体的相通性又存在一定的特殊性。由于CMMB在大城市采用多点单频网发射,这样就对发射机监测造成了一定的难度,而且CMMB接收未采用有效的安全防范机制,这样就对非法干扰的监测带来了前所未有的挑战。本文提出对CMMB监测设备部署方式的一些观点,为CMMB监测网的建设提供了一些参考。 相似文献
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随着广播电视信息化程度的提高,各信息系统安全性问题已经成为各大制作、播出及管理单位关注的焦点,怎样对系统进行加固是摆在各管理者及网络维护人员面前的重要课题。本文中,作者从网络、设备、应用等多方面对影响信息安全的因素进行了解析。 相似文献