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941.
由于器件的快速退化,101.5小时似乎成了Znse基蓝绿色半导体激光器难于逾越的寿命极限。分析退化机制,发现在强电流注入的半导体激光器中,热退化具有重要影响。研究表明,用作载流子限制层的宽带Ⅱ-Ⅵ族四元合金(如ZnMgSSe)只能对ZnSe中的电子有效地限制,无法对空穴很好地限制;而对BeTe,却只能对空穴进行有效的限制,无法对电子很好地限制。这导致ZnSe(或BeTe)活性层空穴(或电子)漏电发热,引起退化。本文提出以ZnSe/BeTe超晶格为蓝绿发光层,并用包络函数理论具体计算了阱宽、垒宽对载流子能级的不同影响,考察了ZnSe、BeTe厚度比和超晶格周期对带隙、载流子限制能力的调节。为研制新型长寿命蓝绿色半导体激光器提供了一条新的途径。 相似文献
942.
943.
The bicycle industry is an interesting case where East Asian firms have made a considerable impact, but where Taiwan has outperformed Korea. In the Korean sector, none of the well-known chaebol such as Samsung have become involved, and the incumbent firms experienced slow growth until there was government intervention in the 1980s. In Taiwan, small dynamic firms responded to large export orders in the early 1970s, and established a lasting lead which has been regenerated through technological upgrading. The paper argues that both countries’ bicycle industries have a vertically non-integrated structure, with extensive internal sub-contracting, and that the differences between the countries can be attributed to the timing and effcacy of industrial policy interventions. 相似文献
944.
大型复杂高精度波导钎焊设备的研制:简介ZHS—132型真空钎焊炉 总被引:1,自引:0,他引:1
应军事电子装备,特别是军用雷达预研和生产的急需,电子工业部第二研究所近期研制的成功大型、复杂、高精度波导钎焊设备ZHS-132型真空钎焊炉。文中主要介绍了该设备的开发背景和对波导钎焊工艺的影响,该设备的设计构思、结构和技术特征,使用功能和效果,以及推广应用前景。 相似文献
945.
The association of congenital heart block (CHB) with maternal autoantibodies to the Ro and La ribonucleoprotein antigens may be due to cross-reactions between maternal anti-La antibodies and fetal cardiac specific antigens. One of the major components of cardiac myocytes, laminin, is accessible for binding by maternal autoantibodies and we have previously reported cross-reactivity of mouse laminin with anti-La antibodies affinity purified from the sera of patients with primary Sj?gren's syndrome. Affinity purified anti-La antibodies from ten women who had at some time given birth to a child with CHB were examined for cross-reactivity with human placental laminin, which shares structural similarities with cardiac laminin. All ten anti-La antibodies bound to the surface of cryosections of normal full term placental trophoblasts. Binding could be inhibited by pre-incubation of antibodies with either La or placental laminin. Eight anti-La antibodies also reacted with placental laminin by ELISA and La inhibited up to 82% of binding to laminin while laminin inhibited up to 85% of binding to La in a dose dependent manner. Eight anti-La antibodies also bound to the surface of fetal cardiac myocytes at 10.3 weeks of gestation and five showed lower levels of reactivity with the surface of fetal cardiac myocytes at 16.5 weeks of gestation. None showed any surface staining of normal adult heart. These data confirm the cross-reactivity of anti-La antibodies with laminin and may support a placental role in preventing the majority of potentially pathogenic antibodies from reaching the fetal circulation. 相似文献
946.
介绍了低旋流进气直喷燃烧系统应用于195柴油机的试验结果,着重探讨了燃烧室结构尺寸和供油系统主要参数对柴油机性能和燃烧放热规律的影响。研究表明,这种燃烧系统应用于小缸径直喷柴油机具有良好的推广前景。 相似文献
947.
Haining Yang Mingyuan Gu Weiji Jiang Guoding Zhang 《Journal of Materials Science》1996,31(7):1903-1907
The interface structure in Gr/Al composites fabricated with liquid metal infiltration has been studied using transmission electron microscopy (TEM). Morphologies of interfacial reaction product, aluminium carbide Al4C3, formed at different manufacturing parameters were compared and, the growth mechanism of the carbide was studied by means of high resolution electron microscopy (HREM). It has been shown that the morphology of the carbide is intimately related to the processing parameters with which the composites were produced. There are two kinds of interfaces between the carbide and the aluminium matrix. They have different growth mechanisms and relative growth rates under different growth driving forces. Several crystal orientation relationships between the carbide and the aluminium matrix have been observed. 相似文献
948.
Airborne scatterometers: investigating ocean backscatter under low and high-wind conditions 总被引:1,自引:0,他引:1
Carswell J.R. Carson S.C. McIntosh R.E. Li F.K. Neumann G. McLaughlin D.J. Wilkerson J.C. Black P.G. Nghiem S.V. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1994,82(12):1835-1860
Attempting to understand and predict weather on a local and global basis has challenged both the scientific and engineering communities. One key parameter in understanding the weather is the ocean surface wind vector because of its role in the energy exchange at the air-sea surface. scatterometers, radars that measure the reflectivity of a target offer a tool with which to remotely monitor these winds from tower-, aircraft-, and satellite-based platforms. This paper introduces three current airborne scatterometer systems, and presents data collected by these instruments under low-, moderate-, and high-wind conditions. The paper focuses on airborne scatterometers because of their ability to resolve submesoscale variations in wind fields. Discrepancies between existing theory and the observations are noted and the concerns in measuring low-wind speeds discussed. Finally, the application of using this technology for estimating the surface-wind vector during a hurricane is demonstrated 相似文献
949.
950.