Measuring the activity of a <Superscript>51</Superscript>Cr neutrino source based on the gamma-radiation spectrum

A technique for the measurement of activities of intense β sources by measuring the continuous gamma-radiation (internal bremsstrahlung) spectra is developed. A method for reconstructing the spectrum recorded by a germanium semiconductor detector is described. A method for the absolute measurement of the internal bremsstrahlung spectrum of ⁵¹Cr is presented.     

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.     

Surface green function matching approach to the surface dynamics of ionic crystals: II. Theoretical analysis of the inelastic scattering of He from NaF(001) in the eikonal approximation

A theoretical analysis of recent scattering time of flight (TOF) data for NaF(001)/He is done by means of a new version of the eikonal approximation to the inelastic processes, which allows for the use of atom-surface potentials obtained by summing over two-body potentials. A Morse potential for He-ion interactions is adopted in the present work. A good agreement between theory and experiment is found with the present scheme.     

一种陡脉冲高电压电阻分压器的补偿方法

在对实用分压器构型进行分析比较的基础上提出了一种补偿法。其特点是,采用高阻高压臂一级分压构型,利用低阻低压臂自身电感对分压器的对地分布电容进行抵偿。按这种方法设计的兆估级纳秒脉冲电阻分压器自身的方法响应上升时间约为1ns。     

基于小波概率估计的图像融合方法研究

在研究了已有的图像融合方法后,提出基于小波变换和最大似然概率估计(MLE)相综合的融合方法,利用概率估计融合模型,首先对不同的传感器图像进行小波分解,然后对相应的子带求解仿射变换参数,根据Bayes规则进行最大后验概率似然估计,得到估计子带系数,最后通过小波反变换得到融合图像.在仿射变换的假设条件下定义融合规则,更适合传感器图像具有局部相反对比度的情况,采用此方法对航空可见光图像和红外图像进行融合实验,其结果与采用其它方法进行了对比,表明该方法的有效性.     

60 A GeV16O原子核在核乳胶中的电磁离解

对60 A GeV¹⁶O在原子核乳胶中的电磁离解现象首次进行了高统计的研究,得到电磁离解截面随束流能量的增加而增加,射弹碎片电荷分布和200 A GeV¹⁶O在 乳胶中电磁离解的电荷分布一致,但电荷为3≤Z≤5的射弹碎片的发射概率低于200 A GeV能 区,这些特点和Weiszacker和Williams的经典电磁理论模型计算结果一致.60 A GeV¹⁶ O电磁离解下各反应道出现的概率和200 A GeV能区结果基本一致,但同14.6 关键词： 电磁离解 射弹碎片 碎裂     

Optical vidicon based on a layered semiconductor structure: Image reading and storage

A simple device for image scanning and storage based on a semiconductor structure is proposed. The scanning and storage involve laser-beam reading. A video signal is represented by the photoelectromotive force generated by the structure. Simple experiments demonstrating that the structure proposed works as a vidicon and a storage device capable of the data storage for at least two hours are presented. A physical interpretation of the effects observed is proposed.     

Correlation mechanism of negative differential resistance for tunneling through a molecule

A model for electron transport through a single molecule with two electronic states, one of which is strongly hybridized with contacts and the other is localized, has been investigated. A solution for this model in the limit of strong intramolecular Coulomb interaction is found. A mechanism of negative differential resistance caused by strong intramolecular correlations is revealed.     

Stability of A15 type phases

Previous works dealing with the stability of the A15 phases are reviewed. Data for over 60 known A15 phases are used to develop criteria for stability which may be applied to hypothetical A15 phases. Occurrence of these phases is examined in terms of the valence bond concepts of the Engel-Brewer correlation and in its frequency with changes in electronic density of states. A15 is most favored when the “A” elements are V, Nb or Cr, when radii of the constituent atoms differ by no more than 8 per cent, at compositions determined by electron concentration, and at relatively low temperatures. Composition and temperature of formation are predicted for several likely hypothetical A15 phases.     

The Δ- Method for the Boltzmann Equation

A new numerical method is proposed to solve the Boltzmann equation. A frame is set up by using a discrete velocity approximation in the infinite velocity space, but by considering only those distribution function points which are not too small. The distribution function points may occur anywhere in the infinite discrete velocity space and are not constrained to a pre-specified region. A fourth-order finite difference is used for the convection terms. A Monte Carlo-like method is applied to the discrete velocity model of the collision integral. The effort of the method is proportional to the number of discrete points. Numerical examples are given for the full Boltzmann equation and results for some benchmark problems are compared with analytical or prior solutions.     

On the diffusion-driven growth: The perturbed sphere problem revisited

A growth process driven by stationary diffusion field is considered to be a consequence of the mass conservation law. A correct expression for the growth velocity is derived and applied to a specific model of the perturbed sphere. It is studied in the linear regime, for which all corrections are consequently taken into account and graphically demonstrated. A critical discussion and confrontation with some statements in the literature is carried out.The work was supported in part by the Committee of Scientific Research. The authors are indebted to the referee for remarks which allowed them to improve the presentation.     

Theory of frequency modulation spectroscopy of coherent dark resonances

The interaction of a three-level atom in the A configuration with a frequency-modulated (FM) field is analyzed theoretically for the first time. The two-frequency model for solving the problem of frequency modulation spectroscopy of coherent dark resonances is described and analyzed for a three-level A system. The effectiveness of the two-frequency model is demonstrated by comparing the results obtained using this model with the results of solving the exact problem of interaction of a A system with an FM field, which can be solved by the density matrix method. It is shown that the simple two-frequency model corresponds to the exact solution and is in qualitative agreement with experimental data.     

Grid-based photogrammetry system for large scale sheet metal strain measurement

This paper presents a new approach to fast strain measurement with high accuracy for large scale sheet metal based on the surface circular grid and digital close range photogrammetry. A multi-block measuring method of discretization is implemented to archive large scale measurement. The sheet metal is separated into several blocks for respective calculating and joined together by common reference points. A surface circular searching method is presented for fast and robust 3D grid generation. A flexible bundle adjustment method is proposed for large amount 3D grid nodes reconstruction, which employs the conception of sampling points and is proved to be efficient. Furthermore, a multi-stage grid registration method is introduced to improve the accuracy of strain field by correcting the true deformation gradient tensor. A novel system is developed and performances well in actual large scale sheet metal strain measurement. Two accuracy tests confirm that the system strain measurement error is less than 0.2%.     

一种新型迈克尔逊干涉仪条纹计数器的设计

设计了一种简便的能自动适应不同背景光强的新型迈克尔逊干涉仪条纹计数器。利用光敏电阻将条纹的变化转化为电信号,同时检测出背景光,并利用减法器去掉背景,经施密特触发器整形后,送入单片机计数并显示。实验证明,本计数器原理简单,可以适应不同的背景光强,具有精确度高、操作简便可靠等优点。     

Appell方程Mei对称性导致的一种新型守恒量

研究完整系统Appell方程Mei对称性导致的一种新型守恒量.首先,给出完整系统Appell方程Mei对称性的定义和判据.其次,得到用Appell函数表示的完整系统Appell方程Mei对称性导致的一种新型守恒量.最后,举例说明由所得结果可找到新的守恒量.     

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     

Meixner basis functions in the problem of diffraction by a disk

A basis to solve the problem of diffraction by a disk in the axisymmetric case is constructed. A set of functions that satisfy the well-known Meixner condition on an edge, admit of analytical calculation of encountered integrals, and exhibit the orthogonality property in corresponding Hilbert spaces is derived for the first time. A theory of integral equations of diffraction by a disk is developed.     

一种新型主动锁模光纤激光器腔长稳定技术研究

提出了一种全新的主动锁模光纤激光器的腔长稳定方案,通过波长的变化检测腔长的漂移,使用波长锁定器得到偏移误差信号补偿腔长变化.实验得到了脉宽为7.6 ps的近变换极限锁模脉冲,其超模抑制比达到60 dB,并且在近2 h的工作时间内工作稳定,波长漂移小于0.01 nm.与已有的方案相比较,不但输出脉冲质量高、并可长时间稳定工作,而且由于采用了低成本的稳定方案,更易于实现.     

Two-Band Model for High Tc Superconductivity

A two-band model is dealt with by the canonical perturbation theory of projection operators. An effective Hamiltonian with Cu-Cu, Cu-O and O-O couplings is obtained. A unified treatment for such a coupled system gives the variations of transition temperatures for Cu-Cu, Cu-O and O-O parings with the concentration of O-holes. A window of δ for superconductivity is obtaihed and compared with experimental data qualitatively and quantitatively.     

A bound for the pressure integral in a plasma equilibrium

An interpolation inequality for the total variation of the gradient of a composite function is derived by applying the coarea formula. A bound for the pressure integral is studied by establishing ana priori estimate for a solution of the Grad-Shafranov equation of plasma equilibrium. A weak formulation of the Grad-Shafranov equation is given to include singular current profiles.