Spin squeezing in the presence of dissipation

The transfer of spin between photons and localized atomic levels, for a chain of two-level atoms, is studied. The Hamiltonian of the system is modelled by a radiation term and by atom-atom and radiation-atom interactions. Effects due to dissipation are accounted for by atom-photon exchange-interactions of complex strength. It is found that the spin-squeezing is suppressed by dissipation. Calculations are performed for arrays of Rb atoms excited by a GaAlAs laser.     

基于Labview的回波厚度测量系统

建立了基于Labview的回波厚度测量系统,用金属球撞击待测物体表面,产生脉冲声波,用换能器在待测物体表面接收物体内部多次反射的声波,用傅立叶变换计算出声波在物体内部的传输时间,就可得到待测物体的厚度。该测量方法具有成本低、设计新颖、物理思想清晰的特点,适合于发展为综合设计性大学物理实验项目。     

基于希尔伯特变换的干涉条纹相位解调新算法

提出了一种新的应用希尔伯特变换解调干涉条纹相位的算法,可以从单幅干涉条纹图中解调出全场相位分布.在实际应用中,常借助傅里叶变换实现希尔伯特变换算法,但是会忽略负频率成分,造成相位信息的丢失.对于相位分布非单调变化的干涉条纹,提出了一种判断函数,用来计算相位信息零频率点的分布.利用相位的零频率点分布构造了一个二元模板,使用该模板对本文提出的两次希尔伯特变换法产生的包裹相位图进行修正.对修正后的包裹相位图进行解包裹处理,可以得到连续的全场相位分布.对该方法用计算机模拟进行了验证.     

气液两相流速度及粒径分布激光干涉测量方法的研究

为了实现对气液两相流的粒子粒径、空间分布及其速度测量。对激光干涉气液两相流测量技术（ILIDS）进行了深入研究,该技术是一种应州于气液两相流测量的新技术,其主要优点是不干扰流场和颗粒粒径、位置测量精度高。基于该技术所开发的图像自动处理方法可以利用普通粒子成像测量技术系统拍摄气液两相流的激光散射干涉图像。并利用图像卷积定位、傅里叶变换频率分析及其图像互相关测速等图像处理手段从干涉图像中自动提取粒子的位置、直径和速度信息。为了验证该方法的测量精度,对喷嘴生成的气水两相流进行了测量实验,得到了喷嘴出口处不同区域的粒径、速度矢量的空间分布,并将测得的速度矢量与用粒子成像测量技术方法测得的结果进行对比,证明两种方法测量的平均速度差别仅为0．38％。     

Flux Induced by Multiplicative Dichotomous Noise

The transport of particles induced by multiplicative dichotomous noise for a system is investigated. The stationary probability current is derived. It is shown that, for the system studied by us, the spatial asymmetry is the ingredient for the nonzero stationary current.     

一种用于多叶准直器适形放疗的剂量算法研究

描述了一种用于多叶准直器适形放疗的剂量计算方法。 在不同大小的方野和非规则野照射情况下, 将此方法得到的剂量分布与微分卷积法计算得到的剂量分布进行了精度验证。 结果表明, 这种算法具有较高的剂量精度和较快的计算速度, 因此可在适形放疗中用作MLC适形野的自动生成。 A dose calculation algorithm for MLC based conformal radiotherapy is described in this paper. The algorithm is formulated by the coordinate of MLC leaves. Verification on the algorithm is made by comparing the dose distributions generated by this algorithm with that generated by a Differential Convolution Superposition algorithm for various regular and irregular fields. The results demonstrate that the present algorithm has suitable accuracy and high computational efficiency, thus it could be useful for the treatment planning process in MLC based conformal radiotherapy, where the workload for interactively or automatically designing the shapes of MLC is heavy.     

Core ionization potentials in carbon monoxide

Conflicting values have been reported for the core ionization potentials in carbon monoxide. We have remeasured these and find 296.24 ± 0.03 for the carbon 1s ionization potential and 542.57 ? 0.03 for oxygen 1s. The carbon value is close to previously reported values; that for oxygen is higher by ～ 0.5 eV. These results are compared with ionization potentials calculated from molecular orbital theory. The value predicted by near-Hartree-Fock calculations for oxygen is too low by ～ 1eV and that for carbon is too high by ～ 0.5 eV.     

Fourier transform moiré tomography for high-sensitivity mapping asymmetric 3-D temperature field

Fourier transform evaluation for moiré deflectogram is proposed to automatically map the temperature field. The moiré deflectogram is generated by conventional deflectometer and is analyzed by means of Fourier transform algorithm. The convolution backprojection algorithm is used for the optical tomography. Asymmetric 3-D gas temperature distribution for a given layer is reconstructed.     

强非局域非线性介质中强光导引的弱光呼吸子传输规律研究

研究了强光导引的弱光呼吸子传输问题. 尽管弱光本身的非线性效应可以忽略, 但强光通过强非局域非线性效应会对弱光形成约束并与弱光本身的衍射效应达到动态平衡, 从而形成呼吸子. 得到了弱光呼吸子的解析表达式, 在此基础上分析了其束宽的呼吸演化规律, 并对弱光呼吸子整体轨迹的形状、方位、旋向等性质进行了系统的研究.     

含Laplace-Gauss型混合噪声图像二阶正则化重建方法

假设观测数据含Laplace-Gauss型混合噪声条件下,提出求解数据重建反问题的一种新型一阶二阶混合正则化模型,阐述该模型在断层重建和流体动力学实验定量诊断中的应用.建模过程采用贝叶斯推断理论和期望极大方法,将空间自适应函数引入经典的增广拉格朗日方法得到模型数值算法.所提出的模型及其算法进行图像复原和客体重建实验.结果表明模型算法的可靠性.     

基于图像方法模拟尾流气泡分布特性的研究

舰船尾流中气泡对尾流特性研究起着重要的作用,研究气泡数密度分布对于追踪舰船有着重要意义.用图像方法来研究气泡,具有直观、简便的优点.采用激光片光源限定采样区域,利用数学形态学的方法对气泡图像进行了处理.通过剪切、变灰度、调整照明和亮度、填充、膨胀、腐蚀等操作获得理想的图像并进行统计.用上述方法对记录气泡消散过程的图片进行处理,可以看出气泡的消散过程基本符合指数衰减的规律.     

Control of the vortex flow in microchannel arrays produced in YBCO films by heavy-ion lithography

High-energy heavy-ion lithography is a powerful tool for tuning both structural and electromagnetic properties of high temperature superconductors by inducing nanometer scale defects confined in micron scale patterns. We show how the vortex dynamics in YBCO thin films patterned by heavy-ion lithography can be controlled and potentially exploited for device applications. Both local critical temperature and local critical currents are effectively tailored by the imposed irradiation geometry. The direct visualization of the real-time dynamics of the magnetic pattern is achieved by the magneto-optical imaging technique, while confined vortex flow is revealed by the simultaneous measurement of the electrical resistance both along and perpendicular (Hall resistance) to the direction of the applied current. It is shown that, for microchannel arrays inclined with respect to the transport current flow, the direction of vortex motion is solely determined by the imposed irradiation pattern geometry, in a well-defined temperature range, for a given applied current.     

土壤中铅、砷、铬、铜和锌含量的连续快速测定

建立了土壤中铅、砷、铬、铜和锌含量的连续快速测定方法。土壤样品经微波消解,用同一份消解液,分别连续测定土壤中的铅、砷、铬、铜和锌含量,铬、铜和锌采用火焰原子吸收光谱法,铅和砷采用氢化物发生-原子荧光光谱法。采用本方法,对环境土壤标准样品ESS-1黑钙土(GSBZ50011)和ESS-3红壤(GSBZ50013)进行多次测定,检测结果与标样的推荐值吻合。经统计计算,回收率为95.2%—103.6%,精密度RSD均小于7%。本法操作简单快速,光谱测定结果已成功地用于无公害水果和蔬菜生产基地的土壤环境质量评价。     

小波分析在全息图信息压缩中的应用

全息图信息压缩是实现全息图通讯的首要工作.本文提出将小波分析方法应用于全息图的信息压缩,并以二维人象与三维球体为例表明这一方法的有效性和灵活性.     

500.8 nmNd∶YAG青光激光器光学薄膜的设计与制备

从双波长激光运转及和频的机理出发，对LD泵浦Nd∶YAG，LBO腔内和频500.8 nm〖JP2〗青光激光器所使用的光学薄膜进行了设计和制备.在激光反射镜的设计上，为了达到最佳的和频输出，对膜系要求进行了深入分析.采用对谐振腔一端面反射率固定不变并通过对另一腔镜基频光的透射率进行调谐的方法, 在给出合理初始结构后，利用计算机对膜厚进行了优化.并采用双离子束溅射沉积的方法，通过时间监控膜厚法成功制备出青光激光器所使用的全介质激光反射膜, 在室温下实现946 nm和1064 nm双波长连续运转，并通过Ⅰ类临界相位匹配LBO晶体腔内和频在国内首次实现500.8 nm青色激光连续输出.当泵浦注入功率为1.4 W时和频青光最大输出达20 mW.     

1700 线/mm镀金光栅的拼接理论和实验研究

提出了一个能够实时地监控拼接光栅状态的方案；理论上论证了氦氖光不能用来实时监控1740线衍射光栅的光栅拼接实验；提出了一种选择监控光波长的方法，使得拼接光栅的各种误差对于主光束和监控光的影响是一致的，并且通过实验进行了验证. 关键词： 拼接光栅 刻线密度误差 实时监控 光栅对压缩池     

准等熵压缩的数值模拟研究

 就阻抗递变的多层组合飞片对靶样品的冲击压缩过程进行了一维平面应变数值模拟计算,其中,等熵线采用逐步递推法计算。以水和钽为靶的计算结果显示,这种多层组合飞片对水和钽均产生了很好的准等熵压缩效果。其中,对水的计算结果与国外文献报道的结果一致;计算的钽/氟化锂窗口界面速度历史与实验结果十分吻合。因此,用适当匹配的多层组合飞片对靶样品产生准等熵压缩是可行的,提出的准等熵压缩的数值模拟方法是可靠的。     

任意折射率分布光纤的一种有效的近似分析方法

本文讨论了一种任意折射率分布光纤的有效的数值分析方法。光纤折射率分布被多层结构所模拟，矢量波动方程用矩阵来代替，传播常数用４×４矩阵的选代相乘来计算。若光纤的折射率变化是缓慢的，可以进一步简化成２×２矩阵的简单运算。     

Highly sensitive optical sensor system for blood leakage detection

A highly sensitive method for the detection of blood leakage has been developed, and a practical sensor system for blood concentration measurement has been constructed. The present method is based on the attenuation of laser light by blood cells. The effects of the fluctuations of the incident laser light power are eliminated by normalizing the attenuated light intensity by the incident light intensity. A part of the incident laser light is reflected by a beam splitter mounted at the entrance of the test cell, of which the power is measured to provide base data for normalization. The optical path is extended to enhance sensitivity by using a pair of side mirrors. This multi-reflection method is very effective to increase sensitivity; the maximum sensitivity obtained for blood concentration is about 4 X 10^-6 by volume, which is significantly higher than that of the conventional sensors.     

Convergence of the Godunov scheme for a simplified one-dimensional hydrodynamic model for semiconductor devices

Convergence of approximate solutions derived by the Godunov scheme for a simplified one-dimensional hydrodynamic model for semiconductor devices is established by using the compensated compactness method. A global existence theorem is shown; and a numerical method for the computation of the physical global solution of this model is provided by this approach.