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991.
考场手机屏蔽器电磁辐射的研究   总被引:1,自引:1,他引:0  
目前考场普遍使用手机屏蔽器,许多家长产生了手机屏蔽器对考生电磁辐射影响的忧虑,文中对高考考场普遍使用的手机屏蔽器进行了分析研究,利用时域有限差分法计算了其在考场内的场强分布,进行了实地测量,两者结果符合的比较好,并且依据国家标准对该手机屏蔽器的电磁辐射影响给出了定量分析。  相似文献   
992.
基于听觉掩蔽效应的小波包语音增强   总被引:1,自引:0,他引:1  
冯流保 《通信技术》2010,43(3):139-141
在分析传统阈值函数小波去噪方法的基础上,提出一种根据人耳掩蔽效应设计的阈值函数去噪方法。该方法利用小波包的多分辨率的优点,把语音分解到反映人耳听觉特性的小波子带中,再使用根据人耳听觉掩蔽原理设计的噪声掩蔽阈值函数对带噪的小波系数进行处理,最后反变换得到增强语音。仿真实验表明:输出的信噪比与听觉评测(PESQ)均取得较好结果。  相似文献   
993.
ICP power/RF power, operating pressure, and Cl2/BCl3 gas mixing ratio are altered to investigate the effect of input process parameters on the etch characteristics of GaN films. The etch selectivity of GaN over SiO2 and photoresist is studied. Although higher ICP/RF power can obtain higher GaN/photoresist etch selectivity, it can result in faceting of sidewall and weird sidewall profile due to photoresist mask erosion. Etch rates of GaN and SiO2 decrease with the increase of operating pressure, and etch selectivity of GaN over SiO2 increases with the increasing operating pressure at fixed ICP/RF power and mixture component. The highest etch selectivity of GaN over SiO2 is 7.92, and an almost vertical etch profile having an etch rate of GaN close to 845.3 nm/min can be achieved. The surface morphology and root-mean-square roughness of the etched GaN under different etching conditions are evaluated by atomic force microscopy. The plasma-induced damage of GaN is analyzed using photoluminescence (PL) measurements. The optimized etching process, used for mesa formation during the LED fabrication, is presented. The periodic pattern can be transferred into GaN using a combination of Cl2/BCl3 plasma chemistry and hard mask SiO2. Patterning of the sapphire substrate for fabricating LED with improved extraction efficiency is also possible using the same plasma chemistry.  相似文献   
994.
The technique details for measuring radiation dose are expounded. The results of gamma and neutron radiation levels are presented and the corresponding radiation shielding is discussed based on the simplified estimation. In addition, the photon radiation level move as background for future experiments is measured by a NaI(T1) detector.  相似文献   
995.
菲波纳契准周期超结构光纤光栅   总被引:1,自引:0,他引:1  
采用相位掩模板扫描法,在单模光敏光纤中制备了中心波长为1 541.86 nm,菲波纳契序数为0~9的准周期超结构光栅.通过模拟引入相移过程中纤芯折射率的改变对制作参量进行了优化.传输矩阵分析与实验结果均表明,该超结构光纤光栅的透射谱呈现分形结构,在中心波长附近有六循环和自相似特性.所制备超结构光栅可作为C波段分形结构滤波器件在光通信和全光集成领域得到应用.  相似文献   
996.
将一种可旋转的双棱镜引入到相位掩模技术中以改变光栅的写入Bragg波长.在该系统中,光纤光栅是由来自可旋转双棱镜所形成的波长为248 nm的紫外干涉条纹写入的,其中,相位掩模被用作 1级衍射光的分束器,通过双棱镜的旋转可改变两写入光束的交叉角.为了初始化Bragg波长的参考值,双光栅的顶角由相位掩模的 1级衍射角和双棱镜的折射率确定.因为在~100 nm范围内两光束的非对称旋转对光栅周期的改变是5×10~(-4) nm,双棱镜引入的光栅的闪耀可忽略.当Bragg波长的移位为1 nm时,棱镜最大的旋转角为~1 degree,最小的旋转角是~2.4 min.与Talbot干涉仪中平面镜的旋转角~23 s/nm相比,该相位干涉仪中棱镜的旋转精度降低了2~3个数量级.  相似文献   
997.
Using quantum chemistry methods we have evaluated the solvent effects on the 14N NMR chemical shifts in five oxa- and oxadiazoles dissolved in twelve solvents. These solvents differ in their polarity with the dielectric constants varying from 2 to 80. Moreover, three of them have a hydrogen-bond donor character. All possible hydrogen-bonding in the water solution with the oxygen and nitrogen (hydrogen-acceptor) centers in oxazoles (2) and oxadiazoles (3) have been considered in our studies. It has been shown that both the pure solvent and hydrogen-bonding effects are significant and result in 14N magnetic shielding increase. In water solutions the pure solvent effect is larger than the hydrogen-bonding effect. In addition, the solvent effect has been analyzed in terms of its direct and indirect contributions. It should be emphasized that our theoretical results for 14N chemical shifts in oxa- and oxadiazoles remain in a very good agreement with the accurate experimental data.  相似文献   
998.
The most annoying problem relating to the sensitivity of mask inspection systems is the encountering of false signals arising from nuisance defects. In order to overcome this problem, we have previously proposed a new algorithm for die-to-wafer-like image (D-to-WI) in real time. This paper describes the optimum mask inspection optics for the D-to-WI mask inspection. We examine the optimum mask inspection optics with numerical simulation for various numerical apertures (NAs) and partial coherence factors (σ) in these optics. The simulated result shows that the optimum mask inspection optics for the D-to-WI mask inspection has NA 0.9 and σ = 0.95 for an ArF-6%-phase shift mask (PSM) 260/260 nm line/space pattern on the mask plane, in which the 193 nm-ArF scanner has NA 0.93, σ = 0.92 − 0.92/0.3 annular illumination, reduction factor of ×4, and circular polarization incident light.  相似文献   
999.
The European Commission has funded within its 6th Framework Programme a three-year project (2005–2007) called CONRAD, COordinated Network for RAdiation Dosimetry. A major task of the CONRAD Work Package “complex mixed radiation fields at workplaces” was to organise a benchmark exercise in a workplace field at a high-energy particle accelerator where neutrons are the dominant radiation component. The CONRAD benchmark exercise took place at the Gesellschaft für Schwerionenforschung mbH (GSI) in Darmstadt, Germany in July 2006. In this paper, the results of the spectrometry using four extended -range Bonner sphere spectrometers of four different institutes are reported. Outside Cave A the neutron spectra were measured with three spectrometers at six selected positions and ambient dose equivalent values were derived for use in the intercomparison with other area monitors and dosemeters. At a common position all three spectrometers were used to allow a direct comparison of their results which acts as an internal quality assurance. The comparison of the neutron spectra measured by the different groups shows very good agreement. A detailed analysis presents some differences between the shapes of the spectra and possible sources of these differences are discussed. However, the ability of Bonner sphere spectrometers to provide reliable integral quantities like fluence and ambient dose equivalent is well demonstrated in this exercise. The fluence and dose results derived by the three groups agree very well within the given uncertainties, not only with respect to the total energy region present in this environment but also for selected energy regions which contribute in certain strength to the total values. In addition to the positions outside Cave A one spectrometer was used to measure the neutron spectrum at one position in the entry maze of Cave A. In this case a comparison was possible to earlier measurements.  相似文献   
1000.
A simple analytical formula for the spectrum of spatial harmonic components of a diffracted field is derived. It is used for construction of an effective algorithm of image calculation in photolithography.  相似文献   
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