Effect of gaunt factor correction in soft x-ray plasma diagnostics

The effect of Gaunt factor correction on temperature estimation over a range 100 to 1500 eV had been studied. Greene’s analytical expression for the quantum mechanical Gaunt factor averaged over Maxwellian distribution is used. Transmission ratios are calculated with and without Gaunt factor for various combinations of beryllium foils, taking into account x-ray emission due to free-free transitions. A significant difference (≳ 15%) is observed between the temperatures estimated from classical and quantum mechanical curves, above 600 eV. Selection of foil combinations useful for estimating higher temperatures is also discussed.     

Improvements in Carrier-to-Noise-Ratio (CNR) of Lightwave Amplitude Modulated Vestigial-Sideband (AM-VSB) Transmission Systems by the Use of Optical Isolators

In lightwave community antena television (CATV) systems as well as other optical fiber communication networks, a transmitted optical signal is known to be degraded by an intensity noise produced within the fiber due to the interference between the signal and doubly reflected light. We report on the improvements to the signal degradation due to the double Rayleigh backscattering by inserting optical isolators in the trunk lines of the systems. A carrier-to-noise ratio (CNR) has been calculated as a function of the number and the insertion loss of the isolators. The calculated results indicate that there is an optimum number of isolators, and if the insertion loss is less than 0.3 dB, the CNR degradation can be restored by more than 60%. To test the calculated results, we conducted experiments for the specific case of employing one isolator, and obtained good agreements between the two.     

板状非线性介质表面耦合波的反射和透射

本文详细分析了平面波激励非线性介质后介质的非线性极化、麦克斯专方程及其解、广义的反射和透射定律；导出了板状非线性介质表面任意阶耦合波的反射场和透射场；对介质满足相位匹配和泵浦波正入射下的场进行了深入的讨论；给了非线性介质表面的布儒斯特角。     

Metalorganic vapor phase epitaxial growth and structural characterization of GaAs/InP heterostructures

Highly mismatched GaAs epitaxial layers with thickness ranging from 15 nm to 7 μm have been grown on InP substrates by atomospheric pressure metalorganic vapor phase epitaxy. Layers thinner than 30 nm exhibited 3-D growth mechanism; in the thicker layers, the islands coalesced and then the growth followed the layer by layer mechanism. The elastic strain and the extended defects have been studied by high resolution x-ray diffraction and transmission electron microscopy, respectively. The common observation of planar defects, misfit, and threading dislocations in the layers has been confirmed. The results on the elastic strain release have been discussed on the basis of the equilibrium theory.     

一种适用于无线网络中多媒体传输的CDMA/RTDMA协议及性能分析

该文研究了一种在扩频分组无线网中适合2多媒体传输的MAC协议－－CDMA／RTDMA。它在RTDMA的基础上，将基站可分配的资源从时隙扩展为码字－时隙，从而增加了系统的容量，更有效地支持多媒体业务的传输。文章分别通过M／M/n/m排队模型和相位过程来分析话音的丢包率和数据的延迟。通过数值计算和计算机仿真，相对于原有的RTDMA方式，这种新的MAC协议在网络负载较重的情况下，仍能保证多种业务的QoS要求。     

传输/反射法测量复介电常数的若干问题

研究了传输／反射法测量线性材料复介电常数εr的厚度谐振、多值性等问题，得到了解决这些问题的有效方法。通过改进NRW传输／反射法，由散射参数直接得到了归一化特性阻抗与传播常数，从而可以把已有的三个确定复介电常数的方程用到NRW传输／反射法中。联合应用这三个方程解决了上述问题，这使得人们可以用传输／反射法对任意厚度的样品在任意频率上进行复介电常数的稳定测量。用波导取样器与同轴线取样器分别得到的实验结果证明了此方法的有效性与可实现性。     

Effects of aggregation on the electromagnetic resonance scattering of dielectric spherical objects

Summary The effects of aggregation on the electromagnetic resonance scattering by small, strongly reflecting spheres are studied. Two or more spheres are allowed to cluster together to form rather complicated anisotropic scatterers whose extinction cross-section is calculated as a function of the wave number of the incident field in the neighbourhood of the lowest resonance of the individual spheres. The macroscopic absorption coefficient of a low-density random dispersion of clusters is also calculated in the same range of wave number. The results for two-, three- and four-sphere clusters are discussed. Work supported in part by C.N.R. through the G.N.S.M. and in part by the U.S. Army European Research Office through grant DAJA45-84-C-0005 and contract DAJA37-81-C-0895.     

汽车尾气颗粒物的STXM和NEXAFS研究

为了研究汽车尾气颗粒物的结构和氮的种态,使用扫描透射X射线显微成像(STXM)技术研究了桑塔纳3000和高尔汽车尾气颗粒物.STXM表明单颗粒物的粒径为500nm,颗粒物质量分布不均匀,有中间空洞.比较汽车尾气颗粒物和(NH4)2SO4和NaNO3中N的1sX射线近边吸收精细结构谱(NEXAFS),铵盐在406eV有显著的σ*吸收峰,有肩部结构;汽车尾气颗粒物和NaNO3中N的近边吸收谱在412eV和418.5eV有明显的σ吸收峰;(NH4)2SO4中N的近边吸收谱在413.5eV和421.8eV更宽的σ吸收峰.硝酸盐是汽车尾气颗粒物中的N化学种态的主要存在形式.在395—418eV能量范围内对桑塔纳3000汽车尾气颗粒物进行堆栈扫描,经过主成分分析和聚类分析,发现其表层主要为硝酸盐,内部有少量铵盐.     

自支撑透射光栅的设计、制作和测试

采用标量衍射理论和严格耦合波理论分别计算和讨论了金自支撑透射光栅的衍射效率随波长和光栅周期变化的情况并设计了光栅的结构参数.制作了周期为300 nm、线宽/周期比为055、厚度为200 nm、总面积为1 mm×1 mm、有效面积比为65%的金自支撑透射光栅.在国家同步辐射实验室检测了该光栅在55—38 nm波长范围内的绝对衍射效率.检测结果表明所制作的光栅在8 nm附近具有接近10%的最大衍射效率,并且该光栅对于波长15—35 nm范围内的极紫外波段具有基本稳定的衍射效率. 关键词： 自支撑透射光栅 电子束光刻 电镀     

零势场中变质量粒子的束缚能谱

结合点正则变换(PCT)与分析转移矩阵(ATM)两种方法,得到了零势场中变质量粒子的束缚能谱.通过计算变质量粒子穿透零势场的概率,发现并解释了透射谱中共振峰与本征能量的一一对应关系.