沟槽型发射极SiGe异质结双极化晶体管新结构研究

提出了一种沟槽型发射极SiGe异质结双极化晶体管新结构. 详细分析了新结构中沟槽型发射极的引入对器件性能的影响,并对其机理进行研究. 新型发射极结构通过改变发射极电流路径使电阻分区并联,在不增大结电容的前提下,有效减小发射极电阻,提高器件的频率特性. 结果表明,新结构器件的截止频率和最大振荡频率分别增加至100.2 GHz和134.4 GHz,更重要的是沟槽型发射极结构的引入,在提高器件频率特性的同时,不会降低器件的电流增益,也不会增加结电容,很好实现了频率特性、电流增益和结电容之间的折中. 对沟槽型发射极进行优化设计,改变侧墙高度和侧墙宽度. 沟槽型发射极电阻不受侧墙高度改变的影响,频率性能不变;侧墙宽度增加,频率性能降低. 关键词： SiGe 异质结双极化晶体管 沟槽型发射极 发射极电阻     

五棱镜转动时出射光角度的变化

为了对大口径平面镜面形轮廓的五棱镜扫描法测试进行误差分析和修正,对五棱镜转动时出射光角度的变化进行了分析与精确计算。首先建立了合适的坐标系并规定了角度的正负,然后由入射光的偏摆角和俯仰角计算入射光向量,接着介绍了五棱镜的作用矩阵与坐标转换矩阵,在此基础上详细分析了五棱镜转动的整个过程并且计算了出射光向量。然后计算出射光的偏摆角和俯仰角,再计算当五棱镜没有转动时出射光的偏摆角和俯仰角。最后计算出射光偏摆角和俯仰角的变化。特别分析了当入射光垂直入射五棱镜的情况。随后进行了实际计算与实验,总结了出射光角度变化的一些规律。将计算数据与实验数据进行了比较,结果最大偏差为1"。最大偏差在实验精度范围内,证明了计算方法是正确的。     

强流激光离子源中的等离子体参数诊断

强流激光离子源是最有希望为重离子聚变直线感应加速器提供离子的离子源之一。离子源内等离子体决定了离子源性能和引出品质,为了了解强流激光离子源内等离子体参数,采用发射光谱和ICCD成像的方法对该离子源中的等离子体进行了诊断。该离子源由一台四倍频的266 nm Nd:YAG激光器和Cu靶组成,激光束经过透镜聚焦后照射在Cu靶上产生等离子体,激光打靶能量密度约为108 W/cm2,持续时间15 ns。ICCD相机拍摄了激光照射后等离子体的膨胀过程,初始时刻等离子体垂直表面喷射,膨胀速度约为1 cm/s。光谱仪测量了离子发射光谱,谱线主要由Cu原子的Cu Ⅰ谱线和Cu+离子的Cu Ⅱ谱线组成。采用Boltzmann图法得到膨胀等离子体电子激发温度约为1 eV,采用Stark展宽法得到电子密度约为1016 cm-3。     

Energetics of the Einstein–Rosen Spacetime

A study covering some aspects of the Einstein–Rosen metric is presented. The electric and magnetic parts of the Weyl tensor are calculated. It is shown that there are no purely magnetic E-R spacetimes, and also that a purely electric E-R spacetime is necessarily static. The geodesics equations are found and circular ones are analyzed in detail. The super-Poynting and the “Lagrangian” Poynting vectors are calculated and their expressions are found for two specific examples. It is shown that for a pulse-type solution, both expressions describe an inward radially directed flow of energy, far behind the wave front. The physical significance of such an effect is discussed.     

Angle Compensation and Asymmetry Effect of Light Diffracted by Millimeter Liquid Surface Slosh Wave

The angle compensation method is adopted to detect sloshing waves by laser diffraction,in the case that the wavelength of the sloshing waves is much greater than that of the incident light.The clear diffraction pattern is observed to be of asymmetry,involving orders,position and interval of the diffraction spots that are discovered during the light grazing incidence.It is found that the larger the angle of incidence is,the more obvious the asymmetry is.The higher the negative diffraction orders are,the smaller the intervals between spots are.On the contrary,in the positive region,the higher the diffraction orders are,the larger the spot intervals are.The positive interval is larger than that of the same negative diffraction order.If the incident angle reaches 1.558 rad in the experiment,all positive diffraction orders completely vanish.Based on the mechanism of phase modulation and with the Fourier transform method,the relations between the incident angle and position,interval spaces,and orders of diffraction spots are derived theoretically.The theoretical calculations are compared with the experimental data,and the comparison shows that the theoretical calculations are in good agreement with the experimental measurement.     

强流激光离子源中的等离子体参数诊断

强流激光离子源是最有希望为重离子聚变直线感应加速器提供离子的离子源之一。离子源内等离子体决定了离子源性能和引出品质,为了了解强流激光离子源内等离子体参数,采用发射光谱和ICCD成像的方法对该离子源中的等离子体进行了诊断。该离子源由一台四倍频的266 nm Nd:YAG激光器和Cu靶组成,激光束经过透镜聚焦后照射在Cu靶上产生等离子体,激光打靶能量密度约为108 W/cm2,持续时间15 ns。ICCD相机拍摄了激光照射后等离子体的膨胀过程,初始时刻等离子体垂直表面喷射,膨胀速度约为1 cm/s。光谱仪测量了离子发射光谱,谱线主要由Cu原子的Cu Ⅰ谱线和Cu+离子的Cu Ⅱ谱线组成。采用Boltzmann图法得到膨胀等离子体电子激发温度约为1 eV,采用Stark展宽法得到电子密度约为1016 cm-3。     

Generalized measure theory

It is argued that a reformulation of classical measure theory is necessary if the theory is to accurately describe measurements of physical phenomena. The postulates of a generalized measure theory are given and the fundamentals of this theory are developed, and the reader is introduced to some open questions and possible applications. Specifically, generalized measure spaces and integration theory are considered, the partial order structure is studied, and applications to hidden variables and the logic of quantum mechanics are given.     

复杂分光仪器中的像差研究

为提高分光仪器的性能,采用两个椭球面镜和一个椭球面消像差光栅分光。光源发出的光线被第一个椭球面镜反射,产生特定的波前,经过光栅衍射以后,不同波长的光波被第二个椭球面镜汇聚到探测器的不同位置上。系统具有复杂的像差特性和成像特性,根据费马原理,参考第二代全息变线距光栅的制作光路和理论,建立坐标系,定义两个椭球面上的入射角和反射角,确定各元件的位置变量,确立基本几何关系,将光程函数分为两部分:由衍射引起的光程变化和几何位置引起的光程变化,将两部分都按级数展开,给出了高阶像差的解析形式。对于平面、柱面、球面光栅和反射镜也可以使用这些公式。像差的解析式和光路也可以用于各种分光仪器中。     

双折射滤波片的优化参量

研究了双折射滤波片的滤波和调谐性质。利用矩阵方法和反射、透射系数,给出了波片两个界面的菲涅耳系数。利用相移公式和光线轨迹公式,由入射角和光轴方位角可计算波片精确的相移公式。将上述系数和这一波片的相移公式用于琼斯矩阵,得到透射率的本征矩阵。该矩阵的本征值即为波片的透射系数。由此,给出了波片的主要性质(特别是透射宽度),讨论了波片参量(入射角、方位角和厚度)对波片性质的影响。利用相移公式,讨论了波片的调谐性质,并给出了选择参量的最佳范围。对石英波片,最佳参量为:厚度约在1500~2000μm,方位角大于45°,循环系数r尽可能大。在激光器增益较大时,选择较小的入射角。     

Relativistic decay theory: Corrections to the Weisskopf-Wigner approximation

An analysis is undertaken of the corrections to the Wigner-Weisskopf approximation for relativistic decay processes. It is shown that difficulties with relativistic invariance are encountered. A proposal is made for a Lorentz invariant approximation, which preserves as much of the original expression as possible. The effects of measurements are discussed, and it is noted that, indeed, a watched pot cannot boil. Curves are presented for a hypothetical σ→ππ decay process, and the deviations from exponentiality are discussed when measurements both are and are not being made.     

Discrete quantum theory

This paper is concerned with tracing the implications of two ideas as they affect quantum theory. One, which descends from Leibniz and Mach, is that there is no space-time continuum, but that which are involved are spacial and temporal relations involving the distant matter of the universe. The other is that our universe is finite. The picture of the world to which we are led is that of an enormous space-time Feynman diagram whose vertices are events. A consequence of finiteness is that between each pair of events, along a world line, there can be only finitely many intermediate events. A further change is that we are no longer required to believe that particles need be anywhere between events. The paper takes up nonrelativistic quantum theory in a way that is consistent with these ideas. By considering analogies between the Wiener and the Feynman integrals, and between the Wiener process and related discrete processes, there is obtained a straightforward theory for the Feynman integral. Propagators are worked out for many of the cases relevant to the nonrelativistic theory.The paper shows that, even when there are, along each world-line, no more than one event per Compton wavelength, agreement is good with the usual Schrödinger theory.Research supported in part by the NSF.     

高速CCD成像电路抗串扰技术

为了解决高速CCD成像电路串扰问题,分析了产生串扰的原因,建立了CCD成像电路的串扰模型,提出了有效的抗串扰技术。对多通道的CCD视频信号采用带状线而非微带线并使用防护布线进行隔离。对多通道的电源供电进行了隔离,设计并采取有效的去耦电容布线方法,降低了寄生电感,避免了由电源公共阻抗引起的串扰。采用统一的地平面,对模拟电路和数字电路进行分区布局,避免了地弹对信号的影响。针对一个串扰较严重的CCD成像电路进行了实验,结果表明：采取上述抗串扰技术后,通道隔离度大于60 dB,有效降低了串扰,提高了图像质量。     

Multiple-quantum polarization-transfer coherence pathways in liquids

Polarization-transfer processes in liquid-state NMR are discussed in terms of a simplified operator formalism. The operator model is introduced and the various transformation rules are tabulated. The idea of a coherence pathway is also introduced and the various coherence pathways for the SPT, INEPT, and DEPT polarization-transfer experiments are discussed briefly. The bulk of the paper is devoted to the POMMIE family of pulse sequences and a detailed analysis is made of the extensive phase cycling possible with this pulse train. General expressions are derived for the signal acquired as the phase of the various pulses is changed. Subspectral editing using the POMMIE procedure is discussed in detail and it is shown to be superior to all other polarization-transfer techniques. Edited proton-decoupled carbon-13 spectra of cholesterol are generated using the POMMIE procedure.     

Modeling and Performance Optimization of an Irreversible Two-Stage Combined Thermal Brownian Heat Engine

Based on finite time thermodynamics, an irreversible combined thermal Brownian heat engine model is established in this paper. The model consists of two thermal Brownian heat engines which are operating in tandem with thermal contact with three heat reservoirs. The rates of heat transfer are finite between the heat engine and the reservoir. Considering the heat leakage and the losses caused by kinetic energy change of particles, the formulas of steady current, power output and efficiency are derived. The power output and efficiency of combined heat engine are smaller than that of single heat engine operating between reservoirs with same temperatures. When the potential filed is free from external load, the effects of asymmetry of the potential, barrier height and heat leakage on the performance of the combined heat engine are analyzed. When the potential field is free from external load, the effects of basic design parameters on the performance of the combined heat engine are analyzed. The optimal power and efficiency are obtained by optimizing the barrier heights of two heat engines. The optimal working regions are obtained. There is optimal temperature ratio which maximize the overall power output or efficiency. When the potential filed is subjected to external load, effect of external load is analyzed. The steady current decreases versus external load; the power output and efficiency are monotonically increasing versus external load.     

一种新型的两镜三反射光学系统设计

 结合反射系统中双反射和三反射各自的优缺点,提出一种特殊的两镜三反光学系统,给出其初始结构的确定方法。对其结构优化过程中,在系统次镜后加平面反射镜,将系统进行折轴处理,然后在折轴反射镜后加透镜来校正剩余像差。该系统初始结构中两反射镜组成的是一个无焦系统,在主镜发生2次反射后成像。分析该初始系统的缺陷,对补偿该缺陷并使其成像质量达到衍射极限的后续补偿系统进行了设计。应用该方法设计了焦距f=5000mm,F数均为5,全视场角分别为0.4°和1°的2个系统,从像质评价结果可以看出,系统成像质量接近衍射极限,具有长焦距、小尺寸等特点。     

渐进多焦点眼用镜片的子午线设计研究

介绍渐进多焦点眼用镜片的构造,论述镜片的设计思想,阐述渐进多焦点眼用镜片子午线设计的基本原理,构建子午线多项式,给出子午线设计需满足的准则.在子午线设计的基础上,设计渐进多焦点眼用镜片等屈光度轮廓线,确定镜片面形,并求出镜片平均球面度与像散.比较3种不同子午线设计的渐进多焦点眼用镜片,并进行实际加工与检测.研究结果表明,子午线设计是渐进多焦点眼用镜片设计的关键之一,不同的子午线屈光度分布,对应的渐进多焦点眼用镜片的球面度、像散以及畸变等差别较大.依据实际设计与检测结果,给出适用于不同个性化需求的渐进多焦点眼用镜片子午线屈光度分布的规律.     

两种谐振腔长度的微腔有机电致发光器件模拟

微腔的谐振腔长度直接影响微腔有机电致发光器件(MOLED)的发光特性,根据微腔器件的相关计算公式运用传输矩阵法,分别对微腔长度L=λ/2和L=λ(λ:中心波长)时,在微腔内不同位置激子复合发光的电致发光谱(EL)进行模拟计算和比较。发现:微腔长度为L=λ/2时,峰值均为520nm,半峰全宽均为17nm,激子处在微腔的中心位置时,峰值强度和积分强度均为最大。L=λ时,激子在腔内不同位置时,峰值均为520nm,半峰全宽均12nm,在腔的中心区域时,与L=λ/2时正好相反,峰值强度和积分强度最小。分析后判断是因为两种长度的微腔内电场强度分布不同,激子位于腔内电场的最大值处发光性能最好。说明要制作出高效率的MOLED,要区别不同谐振腔长度,并使激子处于腔内电场最大处。     

Free vibration analysis of magneto-electro-elastic microbeams subjected to magneto-electric loads

Different types of actuating and sensing mechanisms are used in new micro and nanoscale devices. Therefore, a new challenge is modeling electromechanical systems that use these mechanisms. In this paper, free vibration of a magnetoelectroelastic (MEE) microbeam is investigated in order to obtain its natural frequencies and buckling loads. The beam is simply supported at both ends. External electric and magnetic potentials are applied to the beam. By using the Hamilton's principle, the governing equations and boundary conditions are derived based on the Euler–Bernoulli beam theory. The equations are solved, analytically to obtain the natural frequencies of the MEE microbeam. Furthermore, the effects of external electric and magnetic potentials on the buckling of the beam are analyzed and the critical values of the potentials are obtained. Finally, a numerical study is conducted. It is found that the natural frequency can be tuned directly by changing the magnetic and electric potentials. Additionally, a closed form solution for the normalized natural frequency is derived, and buckling loads are calculated in a numerical example.     

Stochastically excited waves in a 1D random medium - the mean field and power spectrum

Scalar wave propagation is examined when both the wave source and the propagation speed are random. Results are derived for the mean field and the power spectrum using the second-order Born approximation. The results depend on whether the source S(x, t) and the propagation speed c(x, t) are correlated or not. When they are uncorrelated, the mean field is zero. When they are correlated, the mean field is non-zero only when the source is non-stationary. The power spectrum is incoherent to leading order. There is a transfer of energy from lower to higher frequencies owing to wave scattering. The corresponding frequency upshift of the power profile in the (k, ω) domain is mainly caused by the cross power between the direct and the twice scattered field, which represents a second-order incoherent power contribution. The results are confirmed using a numerical solution of the wave equation where the scattered field is expanded to fifth order.     

光纤陀螺中一种光相位差跟踪方法

对光纤陀螺中相位差的检测是得到所需角速度的基础。简要分析了陀螺输出信号的特点：噪声大、非线性、周期性,以及这些特点对检测有效信号的影响。提出了一种单通通光相位差跟踪的方法。这种方法采用正弦调制,通过对信号（包括输出信号和跟踪信号）的三角和乘法运算,并在必要的环节进行滤波得到光相位差。它能够解决光纤陀螺动态范围和刻度因子线性度问题,并具有简明、成本低、易实现的特点。最后进行了相位跟踪的计算机模拟和电路的实现,并给出了实验结果。