Further generalization of the theory of concentration depolarization of photoluminescence

The theory of concentration depolarization is generalized to include the effects of non-luminescent dimers which belong to the centres. The theory is applied to Na-fluoresceine and to rhodamine 6G.     

Dynamic measurement of beam divergence angle of different fields of view of scanning lidar

The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted over a long distance,but also objectively evaluate the performance of the laser system.At present,lidar has received a lot of attention as a core component of environment awareness technology.Micro-electromechanical system(MEMS)micromirror has become the first choice for three-dimensional imaging lidar because of its small size and fast scanning speed.However,due to the small size of the MEMS micromirror,the lidar scanning system has a small field of view(FOV).In order to achieve a wide range of scanning imaging,collimating optical system and wide-angle optical system are generally added to the system.However,due to the inherent properties of the optical lens,it is impossible to perfect the imaging,so the effects of collimating and expanding the beam will be different at different angles.This article aims to propose a measurement system that dynamically measures the divergence angles of MEMS scanning lidar beams in different fields of view to objectively evaluate the performances of scanning lidar systems.     

Pitch of components of complex tones

Subjects made pitch matches to individual components in complex tones consisting of either the 4th to 7th or the 1st to 7th harmonics of a 200-Hz fundamental. All components were at equal levels (either 31-, 51-, or 71-dB SPL per component) and the matching pure tone was equal in level to the component being matched. Attention was drawn to the component to be matched either by giving the matching tone an initial frequency close to that of the component (standard condition) or by suppressing and then introducing the component (emergent condition). The pitch matches did not differ significantly for the two conditions, and did not change with overall level. For two subjects, matches to components in the context of the complexes were very close to matches obtained for the components presented in isolation. For a third subject, matches in context were shifted slightly upwards for the lowest component, and downwards for the highest component. A control condition showed that subjects were able accurately to match a small shift in frequency of one component in a four-tone complex. An adaptive forced-choice method described by Jesteadt [Percept. Psychophys. 28, 85-88 (1980)] was also used to estimate the pitches of the components. A very slight bias was apparent in the results, but the pitches of components in context were again found to be very close to those of components in isolation.     

傅里叶望远镜外场实验性能改进和结果分析

为了实现对傅里叶望远镜成像系统更接近实际的仿真,改进了外场实验系统结构。采用反射式目标,利用准直扩束镜替代空间滤波器和准直透镜,使用大靶面电荷耦合器件作为监视器。在无大气和包含200m水平大气两种情况下,分别对2.5mm的4种不同空间频谱分布目标进行实验。实验选用9×9,17×17,33×33和65×65傅里叶分量分别进行重构。最高成像角分辨率为3.5″。结果表明含大气与无大气重构结果的Strehl比值相近,从而证明傅里叶望远镜成像系统能够克服下行链路低阶大气扰动的影响。     

BSA-SDS-Ag聚合物纳米微粒的制备及其水凝胶性质的研究（Ⅰ）

报道了BSA－SDS－Ag聚合物纳米微粒的制备及水凝胶的性质,用X射线衍射（XRD）、透射电镜（TEM）、傅里叶变换红外（FT－IR）光谱考察了这种聚合物微粒的结构,微粒粒径32nm左右,用UV／Vis光谱及SEM考察了冰凝胶的性,表明Ag^ 离子先与BSA产生化学键合,再学原了Ag粒,进行聚合成网状结构的聚合物。     

测量棱镜色散规律的方法改进

对目前实验教科书中研究棱镜色散规律常用的方法具有数据多、用时长及技巧性强的不足,提出了一种比较简洁直观的测量棱镜折射率的方法,即直接测量光线的入射角和不同频率光的出射角,用折射定律即可算得各色光的折射率.通过与传统的实验方法相比较,结果表明在准确度上二者是一致的.最后用Matlab拟合出棱镜的色散曲线及公式.     

旋转波片偏振仪波片方位误差研究

旋转波片Stokes偏振仪是最常用的测量光束偏振态的仪器。波片快轴方位误差是影响旋转波片Stokes偏振仪的主要误差源之一。为了研究波片方位偏差对测量精度的影响,提出了一种描述波片快轴方位误差向最终的偏振测量误差传递的数学模型,并引入协方差矩阵法表征偏振测量误差。根据这一模型,获得最优的偏振仪配置参数。在推导过程中,假设波片方位误差服从同一高斯分布。基于此误差模型,得到如下结论：(1)由波片方位误差引入的测量误差与光强测量次数N成反比;(2)测量误差独立于入射光强度,但是依赖于入射光偏振态(s₁, s₂, s₃)和波片的位相延迟量δ;(3)波片位相延迟量在(103.22°, 116.13°)范围内时波片方位误差引入的测量误差最小。最后,经过仿真实验证明,所得解析结果与仿真模拟结果相一致。     

Application of new methods of interpretation of meteor observations at the Institute of Astrophysics of Tajikistan

New methods of interpretation of meteor observations were developed and published in [1?C9]. The interpretation of ground-based observations of meteors and bolides available today in the scientific literature all over the world suffers from serious contradictions. Observers use the so-called photometric approach for determination of extra-atmospheric masses of meteoric bodies. This approach is based on the formula proposed in 1933 [10] and very simple ideas of how to describe the interaction between the atmospheric air and the surface of a meteoric body. These ideas are provisionally suitable to describe the flow around a body in a free molecular regime. Subsequently, the photometric approach was applied to all the meteor events including bolides. The main effort aimed to elaborate the approach included a choice of new formulas for the radiative efficiency.     

国家同步辐射实验室速调管走廊泄漏电磁场的计算

国家同步辐射实验室速调管走廊内的高频微波泄漏,严重影响着速调管走廊内的微波通讯.为了降低速调管走廊的电磁辐射场,抑制走廊的电磁噪声,必须要确定噪声源的位置,而对于空间复杂的泄漏场,噪声源的位置很难确定,我们可以通过测定空间的泄漏场,经过计算,反过来确定噪声源的位置,进而研究抑制走廊电磁噪声的办法.给出了速调管走廊泄漏电磁场的计算方法、计算公式及现场的对比测试.     

Laser cooling of internal degrees of freedom of molecules

Optical pumping techniques using laser fields combined with photo-association of ultracold atoms leads to control of the vibrational and/or rotational population of molecules. In this study, we review the basic concepts and main steps that should be followed, including the excitation schemes and detection techniques used to achieve ro-vibrational cooling of Cs₂ molecules. We also discuss the extension of this technique to other molecules. In addition, we present a theoretical model used to support the experiment. These simulations can be widely used for the preparation of various experiments because they allow the optimization of several important experimental parameters.     

Improvement of accuracy of interferometric measurement of wedge angle of plates

A method is proposed for improving the accuracy of measuring the wedge angle of transparent plates using a lateral-shear holographic interferometer. Consecutive processing of a pair of interferograms with doubled number of interference fringes leads to reduction of the observational error by a factor of two compared to traditional interferometric methods. Data on the experimental validation of the method are presented.     

Applicability of the approximation of equivalent photons for interference of diagrams of different orders

A study is made of the influence of the Coulomb field of a nucleus on a process that also occurs in the absence of interaction with the nucleus. It is shown that the approximation of equivalent photons applies to the interference between the diagram without interaction with the nucleus and the diagram of two-photon exchange with the nucleus, which contributes to the cross section of the process to the same order in the fine structure constant as the square of the diagram of single-photon exchange. As an example, the method of equivalent photons is used to calculate the cross section of the decay π → μ +ν on a nucleus.     

Evaluation of the Realizability of Algorithms of Utilization of Spent GNSS Objects

Russian Physics Journal - This paper presents estimates of the time and energy costs required to transfer spent navigation satellites to orbit disposal using a thruster. Orbits located...     

The Characterisation of the Products of Reduction of Chinkombe Ilmenite

The characterisation of iron-containing species in Chinkombe ilmenite and its reduction products was undertaken using Mössbauer Spectroscopic techniques. The ore was reduced by graphite in an inert atmosphere. The effects of such variables as quantity of reductant, temperature and preoxidation were investigated. The ore was completely reduced to alpha-iron and titanium dioxide with 20% carbon for a period of one hour at 1373 K. Chemical mechanisms are proposed for the reduction and oxidation of Chinkombe ilmenite. In the processing of ilmenite to obtain synthetic rutile, the ultimate desire is to separate the Fe phase from the TiO₂. Mössbauer Spectroscopy has unambiguously confirmed the desired transformation of the iron phase according to thermodynamic predictions. The information gained would be used to choose the conditions of the reduction process. The alpha-iron could be separated physically or chemically from the completely reduced product mass to obtain synthetic titanium dioxide suitable for the paint industry.     

Analysis of the Range of Applicability of Thermodynamic Calculations in the Engineering of Nitride Fuel Elements

The domains of applicability of thermodynamic calculations in the engineering of nitride fuel are analyzed. Characteristic values of the following parameters, which affect directly the concentration equilibration time, are estimated: nuclide production rate; characteristic times to local equilibrium in the considered temperature range; characteristic time needed for a stationary temperature profile to be established; characteristic time needed for a quasi-stationary concentration field to be established on a scale comparable to the size of a fuel pellet. It is demonstrated that equilibrium thermodynamic calculations are suitable for estimating the chemical and phase composition of fuel. However, a two-layer kinetic model should be developed in order to characterize the transport processes in condensed and gaseous phases. The process of diffusive transport needs to be taken into account in order to determine the composition in the hot region at the center of a fuel element.     

Control of the photodissociation of CsCl

A femtosecond UV laser pulse is used to resonantly excite CsCl molecules from the ionically bound ground state to the first excited repulsive state. The excitation leads to the dissociation of CsCl. After a certain time delay a visible (VIS) femtosecond laser pulse interrupts the dissociation process by resonantly de-exciting the molecule back to the ground state. According to the Tannor–Rice control scheme, the fraction of dissociated CsCl molecules is controlled by changing the delay time between the two fs laser pulses. The processes involved are investigated theoretically and experimentally. Based on the results, a self-learning system has been realized, which is able to control the dissociation without any a priori knowledge of the molecule. Received: 2 December 1999 / Published online: 24 July 2000     

Selective excitation of single lines of a multiplet for interpretation of spectra of complex multicomponent systems

The article discusses the most important aspects of the selective RF excitation of multiplet single lines, an approach that makes it possible to simplify the spectra of complex multicomponent systems, to measure the spin–spin coupling constant, and to determine molecular structure. Semi-selective and selective methods of recording spectra are considered and theoretically substantiated based on the product operator formalism. The results are verified using quantum-mechanical calculations within the framework of the density matrix formalism. The paper demonstrates that the proposed new method leads to a significant simplification of two-dimensional nuclear magnetic resonance spectra. This makes it possible to study chemical processes and spin state exchange by observing the dynamic behavior of the multiplet structure of bound nuclei.     

原卟啉（PP）、血卟啉（HP）和双卟啉醚、酯混合物（DHE）对蛋白质主链结构的光敏损伤特征─—兼论它们在Hala细胞死亡中的作用

原卟啉（ＰＰ）、血卟啉（ＨＰ）和双卟啉醚、酯混合物（ＤＨＥ）对蛋白质主链结构的光敏损伤特征─—兼论它们在Ｈａｌａ细胞死亡中的作用许以明，张志义，杨勇正（中国科学院生物物理研究所北京１００１０１）ＣｈａｒａｃｔｃｆｏｆＰｈｏｔｏｓｅｎｓｉｔｉｖｅＤａｍ...     

Effect of irradiation on the laws of annealing of impurity hardening of NaCl crystals

Studies were carried out on crystals containing various types of impurity: Ca²⁺, a hole-acceptor impurity, which dissolves well in NaCl; and Pb²⁺, an electronacceptor impurity, which dissolves poorly in NaCl. For the first time when doped crystals were annealed softening was observed to occur as a result of irradiation with soft x-rays prior to the annealing. The microhardness of irradiated doped NaCl crystals drops below the value that corresponds to the unannealed unirradiated sample. This effect is more pronounced in NaCl:Pb. It is postulated that the weakening effect is due to the breakup of impurity complexes. This assumption is supported by the results of studies on the laws governing the annealing of dislocation structures about the imprints of an indenter. These laws are shown to depend on the type of impurity: processes of dislocation polygonization were observed in NaCl:Ca crystals and the dislocation distribution was random in NaCl:Pb crystals. Pre-irradiation of the latter caused dislocations to be built in and polygonization to appear. Evidently, by breaking up impurity complexes in NaCl:Pb crystals x-ray irradiation brings the state of the impurity in them closer to that in NaCl:Ca.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 57–62, August, 1988.     

Chemisorption of oxygen to gold: AES study of catalytic effect of calcium

Surface-segregating calcium impurity is removed from a polycrystalline gold sample by heating, exposing to oxygen, and ion-bombarding over an extended period of time. The rate of oxygen chemisorption is found to decrease drastically from that at the beginning of the purification period where calcium segregation is substantial to that at the end where segregated calcium is nearly undetectable. The effect of calcium appears to involve dissociative chemisorption of molecular oxygen at the calcium sites followed by migration of oxygen atoms to gold sites, in a manner analogous to “hydrogen spillover” occurring on the surface of supported catalysts. It is also found that oxygen previously chemisorbed to a gold surface can promote the surface segregation of calcium even in the absence of gas-phase oxygen. Equations are presented to account for simultaneous catalysis of oxygen chemisorption to gold by calcium, and promotion of calcium surface-segregation by oxygen chemisorbed to gold.