HgCdTe electron avalanche photodiodes

Exponential-gain values well in excess of 1,000 have been obtained in HgCdTe high-density, vertically integrated photodiode (HDVIP) avalanche photodiodes (APDs) with essentially zero excess noise. This phenomenon has been observed at temperatures in the range of 77–260 K for a variety of cutoff wavelengths in the mid-wavelength infrared (MWIR) band, with evidence of similar behavior in other IR bands. A theory for electron avalanche multiplication has been developed using density of states and electron-interaction matrix elements associated with the unique band structure of HgCdTe, with allowances being made for the relevant scattering mechanisms of both electrons and holes at these temperatures. This theory is used to develop an empirical model to fit the experimental data obtained at DRS Infrared Technologies. The functional dependence of gain on applied bias voltage is obtained by the use of one adjustable parameter relating electron energy to applied voltage. A more quantitative physical theory requires the use of Monte Carlo techniques incorporating the preceding scattering rates and ionization probabilities. This has been performed at the University of Texas at Austin, and preliminary data indicate good agreement with DRS models for both avalanche gain and excess noise as a function of applied bias. These data are discussed with a view to applications at a variety of wavelengths.     

应用光生物反应器高密度培养等鞭藻

在经济型 10L气升式光生物反应器上进行了等鞭藻 (Isochrysisgalbana)高密度培养的研究 .结果表明 :一次性培养 12d ,藻细胞由最初的接种密度 1.9× 10 5/mL ,9d后上升到最高值 1.4 1× 10 7/mL ;定时补充营养盐试验过程中 ,经过 12d培养 ,藻细胞密度由最初接种密度 1.8× 10 5/mL上升到最高值 6.0 5× 10 7/mL ,是一次性培养试验相同接种密度、相同培养时间内最高密度 1.4 1× 10 7/mL的4 .2 9倍 .定时补充营养盐试验的第 12天 ,放去 2 /3体积的藻液 ,加回新鲜培养液继续培养 ,2d后 ,藻细胞密度由 1.5 6× 10 7/mL升高到 3.5× 10 7/mL ,这对于快速培养饵料生物具有重要意义     

可擦重写相变光盘的研究进展

文章综述了可擦重写相变光盘的研究进展，简单介绍了其记录原理、记录性能和记录材料，重点叙述了相变光盘今后的发展趋势。     

On the Asymptotics of Trimmed Best k-Nets

Trimmed best k-nets were introduced in J. A. Cuesta-Albertos, A. Gordaliza and C. Matrán (1998, Statist. Probab. Lett.36, 401–413) as a robustified L_∞-based quantization procedure. This paper focuses on the asymptotics of this procedure. Also, some possible applications are briefly sketched to motivate the interest of this technique. Consistency and weak limit law are obtained in the multivariate setting. Consistency holds for absolutely continuous distributions without the (artificial) requirement of a trimming level varying with the sample size as in J. A. Cuesta-Albertos, A. Gordaliza and C. Matrán (1998, Statist. Probab. Lett.36, 401–413). The weak convergence will be stated toward a non-normal limit law at a O_P(n^−1/3) rate of convergence. An algorithm for computing trimmed best k-nets is proposed. Also a procedure is given in order to choose an appropriate number of centers, k, for a given data set.     

快速开关CO2激光钻孔技术

我们必须为高密度导通孔的形成开发一些新颖的钻孔技术。这样一种新技术,即快速开关射频激励波导CO2激光器,可望凭借其高脉冲重复频率的性能提高导通孔钻孔能力。     

一种高密度多输出T/R组件供电模块的研制

为适应未来雷达天线阵面向轻量化、高效率方向发展的需求,研制了一种为T/R组件供电的高密度、高效率、三路输出的电源模块。文中提出一种结合变压器辅助绕组的供电方式,解决了模块内部的所有控制电路的供电问题;采用同步整流技术,有效提高转换效率;介绍了多路输出互锁保护的设计方法,有效提高模块的可靠性。最后给出了样机的实验数据和波形,验证了该设计方案的正确性和有效性。     

利用声衰减反演气泡群分布的方法研究

通过测量含气泡水的声衰减反演气泡群参数是获取水中气泡分布的重要方法,但是经典方法忽略了较高浓度气泡水中的强频散特性和气泡振动参数的改变,导致反演较高浓度气泡群分布时会产生巨大误差.为解决这个问题,本文基于等效媒质理论建立起了声衰减和相速度的联系,并考虑了含气泡水平均量对气泡阻尼系数和共振频率的影响.在此基础上,通过将反演气泡分布和修正相速度及气泡振动参数交替迭代的方法,有效地消除了高浓度气泡水中由频散和气泡振动特性改变引起的误差.与实验数据对比发现,气泡群孔隙率达到10^-5时,考虑含气泡水的频散特性会显著降低反演误差;而当气泡群孔隙率达到10^-3时,气泡阻尼系数和共振频率的修正会对反演结果变得重要.本文方法在反演孔隙率为10^-3-10^-2的高浓度气泡群时,仍有较好效果,这可为获取水下较高浓度气泡群分布提供方法借鉴.     

Carbon nanotubes periodically decorated by high-density polyethylene crystalline using solution crystallization

The carbon nanotubes (CNTs) periodically decorated by high-density polyethylene (HDPE) composites with nanohybrid shish kebabs (NHSK) structures were prepared by CNTs-initiated solution crystallization. The disc-shaped HDPE crystalline lamellae were periodically located on the surface of CNTs in the direction perpendicular to the nanotube axis. Observations from scanning electron microscopy and transmission electron microscopy showed that with the increasing of crystallization temperature, the lateral dimension of the lamellae was decreased and the distance between two neighboring lamellae was increased. However, the thickness of the lamellae did not vary with the crystallization temperature. The formation mechanism of the NHSK structures was also explained. The one-dimensional structure and the ultra-high curved surface of CNTs lead to strong geometry confinement, which plays a main role in the formation of the NHSKs. Supported by the National Natural Science Foundation of China (Grant No. 50772031), the Chinese Program for New Century Excellent Talents in University (Grant No. NCET-05-0678), the Scientific Research Foundation for the Returned Overseas Chinese Scholars of Ministry of Education, Hubei Provincial Department of Education (Grant No. Q200610005), and Hubei Provincial Science & Technology Department (Grant No. 2006ABA020)     

大型场馆WLAN高密度组网关键问题研究

无线局域网已成为高速无线宽带数据业务广泛使用的技术手段,但是在开阔环境下的高密度组网,国内外还缺乏成熟的组网方案。分析了在该环境下组网面临的技术难点和问题,提出了应对措施,给出了高密度环境下的WLAN组网方案,并在实际环境下进行了测试,验证了解决方案的可行性。     

高密度电法在工程岩溶勘探中的应用

高密度电法是一种直流电法勘探技术,具有测点密度高,信息量大,对探测对象不造成损伤,成果直观、准确、高效等特点而被广泛应用于岩溶勘察中。论述了其原理、技术方法并通过桥梁基础勘察和隧道工程两个应用实例,论述了高密度电法在桥基灰岩地层中圈定溶洞和在隧道内确认破碎带的应用,最后通过后期打钻证实高密度电法是岩溶勘探中一种可行有效的勘察方法。