Modeling and simulation of emissivity of silicon-related materials and structures

A brief review of the models that have been proposed in the literature to simulate the emissivity of silicon-related materials and structures is presented. The models discussed in this paper include ray tracing, numerical, phenomenological, and semi-quantitative approaches. A semi-empirical model, known as Multi-Rad, based on the matrix method of multilayers is used to evaluate the reflectance, transmittance, and emittance for Si, SiO₂/Si, Si₃N₄/SiO₂/Si/SiO₂/Si₃N₄ (Hotliner), and separation by implantation of oxygen (SIMOX) wafers. The influence of doping concentration and dopant type as well as the effect of the angle of incidence on the radiative properties of silicon is examined. The results of these simulations lead to the following conclusions: (1) at least within the limitations of the Multi-Rad model, near the absorption edge, the radiative properties of Si are not affected significantly by the angle of incidence unless the angle is very steep; (2) at low temperatures, the emissivity of silicon shows complex structure as a function of wavelength; (3) for SiO₂/Si, changes in emissivity are dominated by substrate effects; (4) Hotliner has peak transmittance at 1.25 μm, and its emissivity is almost temperature independent; and (5) SIMOX exhibits significant changes in emissivity in the wavelength range of 1–20 μm.     

Mechanisms and kinetics of vapor-phase etching of GaAs and GaP

Vapor-phase etching of (111), (111), (110) GaAs and (111), (111) GaP wafer in H₂ + HBr or H₂ + PBr₃ gas mixtures has been conducted. The results of two cases, with liquid-forming metal (gold) layers or without coatings, are compared. Etching rates as a function of temperature in the range of 600? to 950? C were measured in Arrhenius coordinates. For both materials and for different gas environments, low-, medium- and high-temperature regions are distinguished, the activation energies in the low-temperature region (below about 650?c) being quite different for the two cases. The kinetic results are correlated with morphological changes arising from temperature variations. Some conclusions are made about the mechanisms of chemical vaporization in various temperature regions. The vaporization mechanisms have much in common with those for A^II - B^VI compounds.     

红外靶船逼真度和可信度的检测与评估

将校核、验证与确认(Verification,Validation and Accreditation,VV&A)理念和测试与评估(Test and Evaluation,T&E)理念引入到了靶船的开发建设工作中,介绍了VV&A的发展历史、作用及其与T&E的关系,论述了红外靶船VV&A的原则、依据和过程。从逼真度的概念入手,分析了红外靶船的特点以及逼真度评估指标体系与评估方法。从技术体制和管理体制上为靶船建设提供了一条思路,解决了靶船逼真度和可信度的检测与评估难题。     

海森堡模型中概率及相应熵的计算分析

介绍海森堡模型的不同位型[N,n] （N为海森堡链总格点数, n为格点中自旋向下的电子数）中的体现本征值获取难易程度的本征值获取概率及其相应信息熵（香农所定义的）和体现模型体系关联程度的自旋向下电子发现概率、每一粒子的von Neumann及体系的平均von Neumann熵,可为量子计算与信息传递提供启示性信息。研究结果：(1)事件发生概率大于（小于）50%时,信息熵随概率增加而减小（增加）。(2)不同位型[N,n],当n（N）同, N（n）增加时：本征值获取概率减小,其相应的信息熵正确反映本征值获取的难易程度;模型参数一定时,格点中自旋向下电子发现概率与每一粒子的von Neumann及体系的平均von Neumann熵都分别减小（增加）。(3)位型[N,n]相同时, 每一粒子的von Neumann及体系的平均von Neumann熵随参数变化时出现拐点,显示体系发生量子相变的信息。(4)同位型[N,n]且同参数时处于海森堡链对称位置粒子的von Neumann熵相同。     

Capability and Limitations of Electrocardiography and Magnetocardiography

The capabilities and limitations of electrocardiography and magnetocardiography are discussed. Representing the electrical activity of the heart by an impressed current density ji, electrocardiography determines the spherical harmonic multipole expansion of its divergence (flux source), while magnetocardiography determines the spherical harmonic multipole expansion of the radial component of its curl (vortex source).     

Analysis of Pseudo-polymorphism Conversion of Theophylline During Wet Granulation and Drying Processes and Effect of Binder on Dehydration and Amorphization

We conducted a time-course analysis of the pseudo-polymorphism conversion (i.e., the hydration and dehydration) of the xanthine-related compound theophylline during wet granulation and drying processes, using terahertz spectroscopy. We also investigated the amorphization mechanism of theophylline hydrate during a drying process in a vacuum using terahertz, mid-infrared (mid-IR), and near-infrared (near-IR) spectroscopy. After a high-shear granulation process using a mixture of theophylline, hydroxypropyl cellulose (HPC), and water, the terahertz spectrum (which was similar to that of an anhydride) was changed to a spectrum that was quite similar to that of a monohydrate. This result suggests that (1) an anhydride was converted to a monohydrate during the wet granulation process and (2) the spectrum was changed to the original waveform after the drying process with heat. This phenomenon indicates that the theophylline monohydrate was reconverted to an anhydride during the drying process. When wet granules were dried in a vacuum, the terahertz absorption lessened and finally disappeared with the passage of time, suggesting that the theophylline monohydrate in the granules was converted to an amorphous state. During the drying process with heat, the dehydration progressed temperature dependently regardless of the presence/absence of HPC. In addition, the reconversion from a monohydrate to an anhydride was completed concurrently with the completion of dehydration. The conversion rate of theophylline from a monohydrate to an amorphous form in granules (with HPC) was faster than that without HPC. This observation suggests that HPC promotes the amorphization of theophylline.     

An Investigation of Microstructure and Microhardness of Sn-Cu and Sn-Ag Solders as Functions of Alloy Composition and Cooling Rate

The microstructure and microhardness of Sn-xAg and Sn-xCu solders were investigated as functions of alloy composition and cooling rate. The Ag compositions examined varied from 0.5 wt.% to 3.5 wt.%, while Cu varied from 0.5 wt.% to 2.0 wt.%. Three cooling rates were employed during solidification: 0.02°C/s (furnace cooling), about 10°C/s (air cooling), and 100°C/s or higher (rapid solidification). Sn grain size and orientation were observed by cross-polarization light microscopy and electron-backscattering diffraction (EBSD) techniques. The microhardness was measured to correlate the mechanical properties with alloy compositions and cooling rates. From this study, it was found that both alloy composition and cooling rate can significantly affect the Sn grain size and hardness in Sn-rich solders. The critical factors that affect the microstructure–property relationships of Sn-rich solders are discussed, including grain size, crystal orientation, dendrite cells, twin boundaries, and intermetallic compounds (IMC).     

Optical and photocatalytic properties of indium phosphide nanoneedles and nanotubes

Large scale indium phosphide (InP) nanoneedles and nanotubes were synthesized through a facile solvothermal reaction. The morphology and microstructure of the samples were analyzed by employing scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Ultraviolet-visible (UV–vis) spectroscopy. The room temperature photoluminescence (PL) measurements showed that the InP nanoneedles and nanotubes possessed a pronounced blue shift in contrast to the bulk counterpart, which was ascribed to the crystalline defects effect. Moreover, the InP nanotubes exhibited an enhanced photocatalytic performance as compared to the InP nanoneedles and nanoparticles.     

超宽带脉冲波形的收发特性分析

采用时域电场积分方程和互易原理相结合的方法,探讨了已知接收信号的情况下,脉冲发送信号的波形,并研究了视距和非视距两种传播路径对脉冲收发信号的影响.在分析中,脉冲波形和天线几何形状可以任意.分别以蝴蝶形天线和超宽带槽式天线为例,并将计算结果与已知接收脉冲信号进行了比较.它们之间良好的一致性说明了所提方法的正确性和有效性.     

The effects of PMD and PDL on the performance of OOK and DPSK systems

Using multiple importance sampling （MIS） technique, the optical communication system performance affected by polarization-mode dispersion （PMD） and polarization-dependent loss （PDL） is simulated numerically. The power penalties and system outage probabilities are obtained for optical communication systems with on-off keying （OOK） or differential phase shift keying （DPSK） modulation. The simulation results show that DPSK always performs better than OOK. When the system has moderate PDL （about 1.5 dB）, it is necessary to compensate effectively the fiber PMD in order to enhance the system tolerance to the PMD and PDL. However, the efficiency of PMD compensation will degrade rapidly when the PMD of the whole optical link drops into the low value.     

Interactions of "ultra-low" doses of naltrexone and morphine in mature and young male and female rats

Sex and age influence morphine analgesia in humans and animals. Mature rats show greater morphine analgesia in males than in females. Ultra-low doses of naltrexone enhance morphine analgesia. In mature rats (18-22 weeks), naltrexone (0.002-2.0 mg/kg)-morphine (2 mg/kg) cotreatment enhanced morphine analgesia in females, an effect inversely related to naltrexone dose. Conversely, in mature male rats, naltrexone tended to decrease morphine analgesia with increasing dose. In young rats (8-10 weeks), morphine analgesia was unrelated to sex and in both sexes the naltrexone-morphine interaction was negligible. These data show that dose, age, and sex alter the naltrexone-morphine interaction in rats.     

One-Order-Statistic Conditional Estimators of Shape Parameters of Limited and Pareto Distributions and Scale Parameters of Type II Asymptotic Distributions of Smallest and Largest Values

One-order-statistic estimators are derived for the shape parameter K of the limited distribution function F1(x, ?, K) = 1 - (? - x)K and the Pareto distribution function F2(y, ?, K) = 1 - (y - ?)-K, given the location parameters ? and ?, respectively. Similar estimators are derived for the scale parameters v1 and Vn, of the Type II asymptotic distributions of smallest and largest values, F3(w, v1, K) = 1 - exp[-(w/v1)-K] and F4(z, vn K) = exp [-(z/vn)-K], given the shape parameter K and assuming the location parameter is zero. The one-order-statistic estimators are K?|? = -1/Cmn 1n(? - xmn) for the limited distribution, K?|? = 1/Cmn 1n(ymn - ?) for the Pareto distribution, ?1|K = Cmn-1/K Wmn and ?n|K = Cmn-1/K Zn-m+1,n for the Type II distributions of smallest and largest values, where Xmn, Ymn, Wmn, Zmn are the mth order statistics of samples of size n from the respective distributions and Cmn is the coefficient for a one-order-statistic estimator of the scale parameter of an exponential distribution, which has been tabled in an earlier paper. It is shown that exact confidence bounds can be easily derived for these parameters using exact confidence bounds for the scale parameter of the exponential distribution. Use of the estimators is illustrated by numerical examples.     

Tridiagonal Commuting Matrices and Fractionalizations of DCT and DST Matrices of Types I, IV, V, and VIII

In this paper, we first establish new relationships in matrix forms among discrete Fourier transform (DFT), generalized DFT (GDFT), and various types of discrete cosine transform (DCT) and discrete sine transform (DST) matrices. Two new independent tridiagonal commuting matrices for each of DCT and DST matrices of types I, IV, V, and VIII are then derived from the existing commuting matrices of DFT and GDFT. With these new commuting matrices, the orthonormal sets of Hermite-like eigenvectors for DCT and DST matrices can be determined and the discrete fractional cosine transform (DFRCT) and the discrete fractional sine transform (DFRST) are defined. The relationships among the discrete fractional Fourier transform (DFRFT), fractional GDFT, and various types of DFRCT and DFRST are developed to reduce computations for DFRFT and fractional GDFT.     

超宽带定位研究与应用:回顾和展望

 超宽带(Ultra-Wideband,UWB)技术能获得比现有无线定位技术更高的测距定位精度.本文主要讨论UWB定位技术的研究和应用,包括TOA/TDOA(Time/Time Difference of Arrival)等UWB定位方法、多径时延估计理论、非视距定位和协作式定位、多带OFDM(Orthogonal Frequency Division Multiplexing)定位和其他超宽带信号定位方式等方面,对其发展历程和现状进行了充分的叙述和分析,最后指出了仍存在的问题和值得进一步探讨的方向.     

Quantitative analyses of topography and elasticity of living and fixed astrocytes

The topography and elasticity of living and fixed astrocytes cultured from the rat cerebra were studied quantitatively by atomic force microscopy (AFM). Ridge-like structures reflecting F-actin beneath the cell membrane were prominent in the contact-mode images of living astrocytes. Many of these ridges became unclear after fixation (2% glutaraldehyde). In addition, the ridge-like structures were invisible in the topography of living cells observed at zero-loading force in the force mapping mode, which is considered to show the real cell surface not pressed down by an AFM tip. The topography of fixed cells observed both in the contact mode and at zero-loading force in the force mapping mode was similar to that of living cells observed at zero-loading force in the force mapping mode, although some deformed areas were detected in the fixed cells. The elasticity map images of living astrocytes showed that the cell membrane above the nucleus was softer (2-3 kPa) than the surroundings, and that the cell membrane above F-actin was stiffer (10-20 kPa) than the surroundings. In the elasticity map images of fixed astrocytes, on the other hand, the elasticity of the cells was found to be relatively uniform (200-700 kPa) irrespective of the inner structures of cells. These results show that images observed by AFM should be carefully examined in consideration of the force introduced to specimens and the elasticity of specimens to find out the real surface topography.     

矿区专用铁路调度监督系统的研制

介绍一种矿区专用铁路调度监督系统.该系统以AT89C系列单片机作为中央处理芯片,通过普通双绞电话线和调制解调芯片等实现了上千路开关量信号的实时采集、远距离接力式传输和调度中心大屏幕模拟车站现场显示.实际运行结果表明该系统工作稳定,实时性较好,给铁路调度指挥工作带来很大的方便.     

Characterization and Comparison of High Blocking Voltage IGBTs and IEGTs Under Hard- and Soft-Switching Conditions

The market of converters connected to transmission lines continues to require insulated gate bipolar transistors (IGBTs) with higher blocking voltages to reduce the number of IGBTs connected in series in high-voltage converters. To cope with these demands, semiconductor manufactures have developed several technologies. Nowadays, IGBTs up to 6.5-kV blocking voltage and IEGTs up to 4.5-kV blocking voltage are on the market. However, these IGBTs and injection-enhanced gate transistors (IEGTs) still have very high switching losses compared to low-voltage devices, leading to a realistic switching frequency of up to 1 kHz. To reduce switching losses in high-power applications, the auxiliary resonant commutated pole inverter (ARCPI) is a possible alternative. In this paper, switching losses and on-state voltages of NPT-IGBT (3.3 kV-1200 A), FS-IGBT (6.5 kV-600 A), SPT-IGBT (2.5 kV-1200 A, 3.3 kV-1200 A and 6.5 kV-600 A) and IEGT (3.3 kV-1200 A) are measured under hard-switching and zero-voltage switching (ZVS) conditions. The aim of this selection is to evaluate the impact of ZVS on various devices of the same voltage ranges. In addition, the difference in ZVS effects among the devices with various blocking voltage levels is evaluated.     

电子显微镜的现状与展望

本文扼要介绍了电子显微镜的现状与展望，透射电子显微镜方面主要有：高分辨电子显微学及原子像的观察，像差校正电子显微镜，原子尺度电子全息学，表面的高分辨电子显微正面成像，超高压电子显微镜，中等电压电镜，１２０ｋＶ，１００ｋＶ分析电镜，场发射枪扫描透射电镜及能量选择电镜等，透射电镜将又一次面临新的重大突破，扫描电子显微镜方面主要有：分析扫描电镜和Ｘ射线能谱仪，Ｘ射线波谱仪和电子探针仪，场发射枪扫描电镜和     

半导体设备与工艺技术的现状及新技术

简要介绍了半导体的有关工艺技术和生产设备的发展动向。首先对光刻技术、干蚀刻技术、清洗技术、氧化?扩散技术、快速高温处理(RTP)技术、离子注入技术、化学气相沉积(CVD)技术、物理气相沉积(PVD)技术以及化学机械研磨(CMP)技术等分别加以介绍,然后对未来的发展动向提出一些建议。     

Synthesis and characterization of porphyrin electrochromic and photovoltaic electropolymers

New asymmetric porphyrins, with electroactive functionalities were synthesized. 5,15-Bis[4(-N,N-diphenylamino)phenyl]-10,20-bis[3-(N-ethylcarbazoyl)]porphyrin and its Zn(II) derivative allow the electrochemical formation of conjugated, conducting and stable polymeric films over semitransparent indium-tin oxide surface. The spectral changes observed upon oxidation of the films produced different colorations. The polymeric materials showed the generation of photoinduced charge separation states and charge migration upon porphyrin excitation, making them promising candidates for application in optoelectronics devices.