High Speed Visualization and Dynamic Measurement of Heat Driven Pumps

We provide the high speed flow visualization and dynamic measurement results for the U-shaped and the inverted U-shaped heat driven pumps. The U-shaped heat driven pumps at the high heating powers consist of a succession of tiny bubble nucleation, growth and coalescence process. Once the “larger” spherical bubble or the bubble slug forms, it expands quickly in both upstream and downstream directions. The increased pressure leads to the liquid discharge through the outlet check valve. When the advancing vapor/liquid interface reaches a higher position in the vertical discharge branch, the condensation heat transfer in the discharge branch shrinks the bubble slug, leading to the decreased pressure and initiating the open of the inlet check valve. Thus the fresh liquid can be sucked into the system. Heat driven pumps operating at the low heating powers display the similar process. However, two major differences are identified: (1) A full cycle includes a set of positive pressure pulses corresponding to a set of tiny bubble nucleation, growth and coalescence process in each substage. Only at the end of the cycle, an apparent negative pressure pulse is created. (2) For each substage in each cycle, when the newly formed bubble slug is chasing the ahead “old” bubble slug, the deformed liquid bridge is formed due to the gravity force effect. When the two bubble slugs are merging together, a wave vapor/liquid interface occurs along the bottom of the capillary tube. For the inverted U-shaped heat driven pumps, there are fewer positive pressure pulses included, corresponding to lesser number of new bubble nucleation, growth, and coalescence process. The bubble slug in the capillary tube is very standard with the smooth vapor/liquid interface. The cycle periods and the pumping flow rates are given versus the heating powers.     

高速动态非接触激光光学法测量光纤外径

光纤拉丝过程中必须对纤丝外径进行精密测控,但是通常用于圆柱形物体动态非接触测量的方法(如相关光通量比较法、电压鉴别法、补偿光通量法等等)精度太低,测量范围难适于光纤测量。本文介绍了四种测量高速运动的光纤外径很有效的非接触式激光光学测量方法:1.前向光散射法。它测量的是激光束射到光纤上的散射角和散射条纹;2.后向光散射法。它测量后向散射条纹的间隔; 3.直接衍射法。它测量激光束直射到光纤上产生的衍射图象;4.计量光脉冲法。它测量与光纤外径有关的光脉冲效。文中还对此四种方法进行了讨论。     

激光驱动高亮度电子束源

采用激光驱动光阴级和１００ｋＶ直流加速间隙可产生宽度为５０～１００ｐｓ的高亮度脉冲电子束．该装置主要由光阴极制备室和直流加速间隙组成．可以用化学气相沉积、离子注入和离子束增强沉积等方法制备光阴极．通过用ＥＧＵＮ和ＰＯＩＳＳＯＮ程序模拟,给出了直流加速间隙的物理设计．光源采用一台主被动双锁的Ｎｄ:ＹＡＧ激光器,可工作在１０６４、５３２和２６６ｎｍ三个波长,重复频率为１０Ｈｚ．此外,也论述了光阴极制备室与超与腔结合的超导高亮度注入器的有关问题. A DC high brigytness laser driven by photoemissive electron gun is being developed at Peking University,in order to produce 50～100ps electron bunches of high quality.The gun consists of a photocathode preparation chamber and a DC acceleration cavity.Different ways of fabricating photocathode,such as chemical vapor deposition,ion beam implantation and ion beam enhanced deposition,can be adopted.The acceleration gap is designed with the aid of simulation codes EGUN and POISSON,100kV DC high voltage is...     

Speed of Gamma Rays Emitted by High Speed Particles

Experiments alleged to confirm the absolute speed of light by Sadeh, Fillipas and Fox, and those done at CERN on the emission of gamma rays by high speed particles are shown to be inconclusive. These experiments have been interpreted quantitatively on the basis of an “extinction” hypothesis formulated by J. G. Fox for which there is no experimental confirmation or denial. Rather than confirming the absolute speed of light, these null result experiments can also be regarded as merely showing the obliteration of the relative speed of light as it propagates through various media.     

用光电传感器测量电机转速

基于传感器的转速测量方法较多,总体分为模拟式和数字式两种.本文重点研究数字式测量方法.针对光电传感器的原理进行简单介绍,并说明它是如何对电机转速进行测量的.通过实验得到的结果进行了数据分析,用最小二乘法拟合出了线性表达式.     

Noncontact characterization of glucose by a waveguide microwave probe

We investigate the electromagnetic field interaction with a glucose aqueous solution using a microwave dielectric waveguide probe to evaluate the glucose concentrations. A microwave dielectric waveguide probe allows observation of the small variation of the glucose concentration changes in the range of 0–300 mg/ml by measuring the change of the microwave reflection coefficient. We could observe the effect of concentration change of glucose with a detectable resolution up to 0.5 mg/ml at an operating frequency of about f = 2.0–2.5 GHz. The change of the glucose concentration is directly related to the change of the reflection coefficient due to the electromagnetic interaction between the dielectric waveguide resonator and the glucose aqueous solution. The operational principal is explained by a plane-wave solution model. A glucose biosensor using a microwave dielectric waveguide probe provides a unique approach for glucose monitoring.     

High Temperature Expansion for a Driven Bilayer System

Based directly on the microscopic lattice dynamics, a simple high temperature expansion can be devised for non-equilibrium steady states. We apply this technique to investigate the disordered phase and the phase diagram for a driven bilayer lattice gas at half filling. Our approximation captures the phases first observed in simulations, provides estimates for the transition lines, and allows us to compute signature observables of non-equilibrium dynamics, namely, particle and energy currents. Its focus on non-universal quantities offers a useful analytic complement to field-theoretic approaches.     

A Diffusive System Driven by a Battery or by a Smoothly Varying Field

We consider the steady state of a one dimensional diffusive system, such as the symmetric simple exclusion process (SSEP) on a ring, driven by a battery at the origin or by a smoothly varying field along the ring. The battery appears as the limiting case of a smoothly varying field, when the field becomes a delta function at the origin. We find that in the scaling limit the long range pair correlation functions of the system driven by a battery are very different from the ones known in the steady state of the SSEP maintained out of equilibrium by contact with two reservoirs, even when the steady state density profiles are identical in both models.     

高速CCD图像数据存储技术

介绍了一种高速CCD图像数据的实时存储方法利用FIFO缓存器使CCD输出的高速数据流和低速存储介质二者的速度匹配,将多路高速大容量图像数据实时记录到了存储介质中,为后期的图像恢复和图像处理提供了原始数据该图像数据存储的方法对各种数据采集以及存储系统的设计具有很好的参考意义.     

Coherent Control of High Harmonic Generation Driven by Metal Nanotip Photoemission

Steering ultrafast electron dynamics with well-controlled laser fields is very important for generation of intense supercontinuum radiation. It can be achieved through coherent control of the symmetry of the interaction between strong-field laser fields and a metal nanotip. We employ a scheme of two-color laser pulses combined with a weak static field to realize the control of a single quantum path to generate high harmonic generation from a single solid-state nanoemitter. Moreover, a smooth and ultrabroad supercontinuum in the extreme ultraviolet region is obtained, which can produce a single attosecond pulse. Our findings are beneficial for efficient generation of isolated sub-100 as XUV pulses from solid-state sources.     

High Speed Demultiplexer Based on a Three-Wavelength SLA

By using a semiconductor laser amplifier (SLA) with a three-wavelength configuration, which works as a nonlinear element in an optical loop mirror, a demultiplexer device for ultra-fast processing is presented. The simulation shows that its switching time can be less than 10 ps at the holding beam power of 1 W, therefore it has the ability of demultiplexing one bit data from 100 Gb/s Optical Time Division Multiplexing (OTDM) pulse trains at the control power of 1 W.     

Noncontact temperature measurement by means of CCD cameras in a participating medium

An original technique was presented for noncontact three-dimensional temperature field measurement in a participating medium using radiative information captured by a CCD camera. This technique was based on the backward Monte Carlo method and was faster and more efficient than traditional techniques based on the forward Monte Carlo method. A numerical simulation case was adopted to validate the technique. It was found that the technique was capable of reconstructing the three-dimensional temperature field well, even with noisy input data.     

一种基于光纤阵列的高速电光开关系统

提出了一种基于光纤阵列的新型电光开关,设计了高速电光选通电路.经实验测得,高压选通电路可获得电压幅度6 000 V可调,前、后沿小于30 ns,触发晃动小于1 ns,脉冲宽度为100 ns可调的高压矩形脉冲.用小口径电光晶体实现了大的通光口径、快的开关速度的惯性约束核聚变驱动系统光开关.选出了在100 ns标称开关速度内所关心的光信息,满足了惯性约束核聚变驱动系统中大的通光口径和均匀性的要求.     

70mm间歇式同步高速摄影机系统的研究

70 mm同步高速摄影机系统主要是用于拍摄激光制导炸弹、火箭、导弹的三维飞行姿态和空间参数的测试设备,具有画幅大、速度高、机动灵活的特点.简要介绍了该摄影机系统的总体组成与各部分的工作原理,并着重描述了摄影机系统的设计及性能指标.鉴于该系统已成功应用,因而可为其他摄影机系统的设计提供一定参考.     

High Speed Demultiplexer Based on a Three-Wavelength SLA

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Noncontact photoacoustic imaging achieved by using a low-coherence interferometer as the acoustic detector

We report on a noncontact photoacoustic imaging (PAI) technique in which a low-coherence interferometer [(LCI), optical coherence tomography (OCT) hardware] is utilized as the acoustic detector. A synchronization approach is used to lock the LCI system at its highly sensitive region for photoacoustic detection. The technique is experimentally verified by the imaging of a scattering phantom embedded with hairs and the blood vessels within a mouse ear in vitro. The system's axial and lateral resolutions are evaluated at 60 and 30?μm, respectively. The experimental results indicate that PAI in a noncontact detection mode is possible with high resolution and high bandwidth. The proposed approach lends itself to a natural integration of PAI with OCT, rather than a combination of two separate and independent systems.     

基于数值模拟的飞行员高速气流吹袭损伤分析

研究飞行员高速气流吹袭的损伤机理,应用尺度适应模型对人椅系统外流场进行数值模拟.在马赫数为0.6,迎角为-90°~90°条件下的数值计算结果与风洞试验结果吻合较好.对不同马赫数、不同迎角的无防护状态下的人椅系统进行数值模拟,研究发现高速气流吹袭下飞行员面颈部、胸腹部、上臂内侧、小腿迎风侧压力较大;增大人椅系统的迎角可以改善飞行员身体各部分的受力情况.