Black Holes Are One-Dimensional

The holographic principle has revealed that phyical systems in 3-D space, black holes included, are basically two-dimensional as far as their information content is concerned. This conclusion is complemented by one sketched here: as far as entropy or information flow is concerned, a black hole behaves as a one-dimensional channel. We define a channel in flat spacetime in thermodynamic terms, and contrast it with common entropy emitting systems. A black hole is more like the former: its entropy output is related to the emitted power as it would be for a one-dimensional channel, and disposal of an information stream down a black hole is limited by the power invested in the same way as for a one-dimensional channel.     

激光测距仪信噪比与激光发散角最佳值的选取

研讨激光测距仪的信噪比和激光发散角如何选取最佳值的问题。如果信噪比为SNR，激光发散角为θt，则取SNR θt^2最小时的信噪比和激光发散角为最佳值。     

红外目标仿真光学机构

论述了目标仿真机构的用途、仿真的光学原理以及实现原理的光学系统。对其中的两个光学问题的研究作了详细地论述 ,即干扰光路 2倍于目标光路的视场角以及如何由摆镜的摆动实现。由于析光镜与光轴成 45°角 ,使像点在子午方向被拉长约为弧矢方向的 10倍。为了减少子午像差 ,将两块析光镜作成略带楔角的楔形镜。结果表明 ,由于该机构的尾焰、尾喷管用的是同一条光路 ,所以使结构大为简化 ,这对降低转动惯量非常有利 ;由于有干扰弹仿真 ,使机构的功能得到了扩大     

Texture formation in polycrystalline diamond vapour growth under the influence of a pulsed supersonic beam

Polycrystalline diamond film deposition is studied under the influence of a pulsed supersonic beam. The beam is formed by a high-pressure value which is used as gas inlet in an otherwise conventional hot-filament reactor. The growth rate of the films as well as the typical size of the microcrystallites are independent of the stagnation pressure behind the nozzle of the valve as long as the background pressure and the gas flow through the chamber are kept constant. In contrast, a drastic change in texture formation is found.     

Stochastic resonance in a stochastic bistable system subject to additive white noise and dichotomous noise

The stochastic resonance (SR) in a stochastic stable system driven by a static force and a periodic square-wave signal as well as by additive white noise and dichotomous noise is considered from the point of view of the signal-to-noise ratio (SNR). It is found that the SNR exhibits SR behavior when it is plotted as a function of the noise strength of the white noise and dichotomous noise, as well as when plotted as a function of the static force. Moreover, the influence of the strength of the stochastic potential force and the correlation rate of the dichotomous noise is investigated.     

Multiple pure tone noise prediction

This paper presents a fully numerical method for predicting multiple pure tones, also known as “Buzzsaw” noise. It consists of three steps that account for noise source generation, nonlinear acoustic propagation with hard as well as lined walls inside the nacelle, and linear acoustic propagation outside the engine. Noise generation is modeled by steady, part-annulus computational fluid dynamics (CFD) simulations. A linear superposition algorithm is used to construct full-annulus shock/pressure pattern just upstream of the fan from part-annulus CFD results. Nonlinear wave propagation is carried out inside the duct using a pseudo-two-dimensional solution of Burgers? equation. Scattering from nacelle lip as well as radiation to farfield is performed using the commercial solver ACTRAN/TM. The proposed prediction process is verified by comparing against full-annulus CFD simulations as well as against static engine test data for a typical high bypass ratio aircraft engine with hardwall as well as lined inlets. Comparisons are drawn against nacelle unsteady pressure transducer measurements at two axial locations as well as against near- and far-field microphone array measurements outside the duct.     

Propulsion of a molecular machine by asymmetric distribution of reaction products

A simple model for the reaction-driven propulsion of a small device is proposed as a model for (part of) a molecular machine in aqueous media. The motion of the device is driven by an asymmetric distribution of reaction products. The propulsive velocity of the device is calculated as well as the scale of the velocity fluctuations. The effects of hydrodynamic flow as well as a number of different scenarios for the kinetics of the reaction are addressed.     

Exploding wires in air and vacuum

An apparatus for studies of wire explosions in air at atmospheric as well as reduced pressures is described. A theoretical treatment of the discharge circuit is presented. In this treatment the external resistance and inductance as well as the wire inductance (all as functions of time) have been taken into consideration. It is then possible to calculate the wire variables — current, resistance, resistive voltage drop, effect, and energy input — as functions of time from thedI/dt waveform experimentally obtained. Wire variables of Ni- and W-wires exploded both in air and vacuum are presented as well as a discussion of these.     

铁电液晶光寻址空间光调制器响应速度的宏模型研究

将铁电液晶(FLC)的本征电路模型扩展到以FLC为调制层,a Si∶H为光敏层的光寻址空间光调制器(OASLM),建立了FLC OASLM的宏模型。用电路方法模拟了控制光强度以及外部激励信号的特征参数对FLC OASLM响应速度的影响。模拟结果表明,FLC OASLM的响应速度随写入光强度和激励信号幅度的增大而加快,随擦除光强度和激励信号频率的提高而减慢。同时,激励信号存在一个上界频率,当频率参数取值超过界值时,响应峰值迅速下降。     

Dynamic speckle effect induced by an acousto-optic deflector for fast range sensing

A technique for fast distance measurements based on continuous frequency measurements of the power modulation of spatially filtered scattered light is proposed. For what is to our knowledge the first time, it is shown that the technique works when laser beam scanning is performed with an acousto-optic deflector. The most impressive feature of the proposed technique is that it works at very high scanning speed, providing an extremely fast response time. Experimental verification of the technique is demonstrated at a scanning speed as as high as 130 m/s. The proposed method of range sensing allows the design of a distance sensor possessing a response time as fast as 80 ns.     

Improved Uncertainty of Optical Frequency Domain Reflectometry Based Length Measurement by Linearizing the Frequency Chirping of a Laser Diode

Length resolution of optical-frequency-domain-reflectometry (OFDR) is improved by reducing the chirping fluctuation of a laser diode. The fluctuation is detected as the frequency deviation of a beat signal from a reference interferometer, which is used as the control signal for servo-control of the laser diode (LD) drive current. As a result of the effective chirping stabilization, chirping span limited-resolution is achieved. In addition, use of a block gauge as the path difference of the reference interferometer enables the OFDR system to improve accuracy of the length as well as the resolution.     

低能反质子的核散射与Glauber理论

运用Glauber多次散射理论,分析低能量反质子与⁴He核的弹性散射微分截面的实验结果.看到反质子能量低到19.6MeV时,多次碰撞的特征仍然是主要的.用光学模型的计算和比较,也得到相同的结论.     

Universal record statistics of random walks and Lévy flights

It is shown that statistics of records for time series generated by random walks are independent of the details of the jump distribution, as long as the latter is continuous and symmetric. In N steps, the mean of the record distribution grows as the sqrt[4N/pi] while the standard deviation grows as sqrt[(2-4/pi)N], so the distribution is non-self-averaging. The mean shortest and longest duration records grow as sqrt[N/pi] and 0.626 508...N, respectively. The case of a discrete random walker is also studied, and similar asymptotic behavior is found.     

Monte-Carlo algorithm for line-by-line calculations of thermal radiation in multiple scattering layered atmospheres

An algorithm for calculations of the longwave radiation in cloudy and aerosol slab atmospheres is described. It is based on the line-by-line and Monte-Carlo methods and is suitable for accurate treatment of both the gaseous absorption and the particulate multiple scattering in any spectral regions; other published algorithms as accurate as this can only make calculations in narrow spectral regions. It is recommended that this algorithm is well suited for radiation code validations as well as for theoretical investigations of radiative transfer in clouds and aerosols and satellite signal simulations.     

Thermal modelling of laser welding and related processes: a literature review

The main emphasis of this review is on thermal modelling and prediction of laser welding in metals. However as similar techniques are employed to model conventional welding processes such as arc, resistance and friction, as well as related processes such as alloying, cladding and surface hardening, part of this review is given over to the modelling of these processes where appropriate. The time frame of the review is up to the year 2002.     

Hypergeometric solution of the Stark-ladder effect in crystals

The motion of electrons in a crystal subjected to a linear electric field is studied by means of the molecular orbital method. The field perturbation of the resonance integrals, as well as the Coulomb ones, results in the Schroedinger equation being expressed as a hypergeometric difference equation, whose solution gives rise to the well-known Stark-ladder picture of the tilted energy band. It is found that the part played by the resonance integral perturbation is just as important as that of the Coulomb integral perturbation and, therefore, cannot be neglected as in earlier investigations.     

ZnS衬底上GeC/GaP增透保护膜系的制备及红外光学性质

把GeC/GaP双层膜用作ZnS衬底的长波红外(8~11.5μm波段)增透保护膜系。采用射频磁控溅射法,以高纯Ar为工作气体、单晶GaP圆片为靶制备了GaP薄膜;用射频磁控反应溅射法在高纯Ar和CH4的混合气体中,以单晶Ge圆片为靶制备了GeC薄膜。分别用柯西(Cauchy)公式和乌尔巴赫(Urbach)公式表示折射率和吸收系数,对薄膜的红外透射率曲线进行最小二乘法拟合,得到了它们的厚度及折射率、吸收系数等光学常数。GaP膜的折射率与块体材料的相近,在波长10μm处约为2.9;GeC膜的折射率较小,在波长10μm处约为1.78。用所得到的薄膜折射率,通过计算机膜系自动设计软件在ZnS衬底上设计并制备出了GeC/GaP双层增透保护膜系,当GaP膜厚较大时,由于吸收增大膜系增透效果较差;当GaP膜厚较小时,膜系有较好的增透效果。     

极性超晶格中电子—声子的相互作用

本文在Wendler、潘金声研究双层极性晶体时得出的声子振动极化场所满足的微分、积分方程及归一化条件的基础上,讨论周期性排列的层状极性晶体中声子振动极化场所满足的微分、积分方程,得到了SO声子的色散关系,SO声子和LO声子极化强度矢量.用声子产生、湮灭算符表出了声子振动能量及电子—声子的相互作用哈密顿量.