冷原子吸收法测定土壤中总汞

本文使用自制的汞原子化装置，与原子吸收仪联用，采用冷原子吸收法测定土壤中总汞，该法快速，简便，稳定性好，用于实际样品测试，结果令人满意。     

用短程飞行时间吸收谱对铯磁光阱中冷原子温度的测量

介绍采用短程飞行时间吸收谱测量铯原子磁光阱(MOT) 中冷原子温度的基本原理及实验实现.与通常的飞行时间方法不同，采用短程飞行时间吸收谱来测量MOT 中冷原子云的温度.在MOT 区域正下方若干毫米处入射一束圆柱状共振探测光束(实验中对于h=3mm，5mm，8mm的情况均作了研究)，释放冷原子云，在其膨胀和自由下落过程中穿过探测光束，即可由光电探测器测得飞行时间吸收谱，由此推得MOT中冷原子的温度. 关键词： 磁光阱 冷原子 飞行时间 短程飞行时间 铯原子     

国内外原子吸收分光光度计产品介绍及其技术发展动向

文章对国内外原子吸收分光光度计的产品结构及特点作了较为详尽的分析：国外产品重点介绍了PE、Varian、IL、PU、岛津等公司的仪器；国内部分则重点介绍了85年前后推出的微机化产品，叙述了国内原子吸收分光光度计的发展全过程。文章还以仪器的光源、原子化系统、扣背景方式三个方面全面综述了国外原子吸收仪器的技术发展动向，对发展我国原子吸收分光光度计亦提出了个人的一此看法。     

采用短程飞行时间吸收谱测量冷原子温度时参数误差的影响

详细介绍了短程飞行时间吸收谱测量冷原子温度的基本模型和实验方法.在对铯原子磁光阱中冷原子温度测量的基础上，分析了初始时刻冷原子云中心到探测光束中心的垂直距离、冷原子云初始半径、探测光束半径三个参数的误差分别对于通过短程飞行时间吸收谱测量冷原子温度时所带来的影响，并比较了这些参数各自的影响程度. 关键词： 冷原子温度 飞行时间 短程飞行时间吸收谱     

N型四能级系统的原子吸收

研究了在较强光低饱和限制下相干光场与N型四能级原子相互作用系统中原子的吸收性质。借助于数值计算,讨论了较强光失谐、探针光强、激发能级向低能级衰减的分配系数对原子吸收的影响。结果表明,抽运场失谐使原子吸收发生横向变化,信号场失谐使原子吸收发生纵向变化;探针光强影响非线性吸收,并通过它影响原子吸收,当探针光强远小于抽运和信号光强时,原子吸收与线性吸收一致,均表现为电磁感应透明特征,当信号光强增大,非线性吸收产生了增益,原子吸收也由透明变为增益;激发能级同时向两个低能级衰减,当对应探针光的原子衰减通道的衰减分配系数趋近零时,原子吸收随该系数变化非常强烈,当该分配系数等于零时,其增益在探针场共振处趋于无穷大。     

原子吸收法测定溶液中的钯含量

采用原子吸收法分析乙醛催化剂溶液中的钯含量，使分析工作者避免接触有毒试剂，改善了工作环境，又缩短了分析时间，通过准确度与精密度试验，证明了原子吸收法准确可靠，操作简便，适应性强，适用于各种含钯溶液的钯含量分析。     

100.8 km大动态零差相干微波光子传输链路

全同性原理要求电子波函数必须满足交换反对称性的条件，针对其对多电子系统的瞬态吸收谱产生的影响，运用Ritz变分法求出了具有全同反对称性的氦原子波函数。在此基础上，通过求解三能级模型并与不考虑电子交换作用的旧模型对比，在理论上研究了氦原子阿秒极紫外(XUV)光瞬态吸收谱。该研究突破传统所采用的单电子跃迁模型，重点考虑电子的交换作用对XUV光瞬态吸收谱的影响。研究发现该交换作用对该瞬态吸收谱的强度和吸收峰的位置等物理量都有重要的影响，该研究结果可为运用瞬态吸收谱探测原子内电子超快关联动力学提供参考。     

原子捕获—火焰原子吸收光度法测定火药烟晕中微量铅和锑

本文采用双缝式原子捕获石英管在火焰原子吸收分光光度计上测定火药烟晕中微量铅和锑，研究了捕获的时间及乙炔的流量等测试条件。实验表明，本文提高了原子吸收分光光度法的灵敏度，铅提高４倍，锑提高了９倍，方法的回收率铅为９８．６～１０４％，锑为９８～１１０％。     

高纯铯中痕量磷,砷的孔雀绿—磷（砷）酸钼浮膜分离及萃取—间接原子吸收…

本文提出一种测定金属铯中痕量磷，砷的方法－孔雀绿离子试剂分离，间接原子吸收测定法，该离子是由孔雀绿和磷（砷）酸钼生成薄膜，介于水相和乙醚相之间，分离后，用甲醇溶解，并用原子吸收法测定钼来确定磷，砷的含量。     

耦合场线宽：抑制电磁诱导吸收

原子相干对吸收的相长干涉导致电磁诱导吸收，这是一类新的相干效应. 以三个电偶极跃迁构成N型链，中间跃迁作为探测跃迁的四能级系统为例，揭示耦合场线宽抑制电磁诱导吸收的强度. 这并非与电磁诱导透明系统中耦合场线宽产生或者增强吸收的情形相矛盾，线宽仍然是抑制系统的相干性. 关键词： 电磁诱导吸收 耦合场线宽 原子相干 退相干     

Hysteretic behavior induced by an electroacoustic feedback loop in a thermo-acousto-electric generator

An active control method of the spatial distribution of the acoustic field is applied in a thermo-acousto-electric generator. An auxiliary acoustic source is used to force the self-sustained thermoacoustic oscillation in order to control the thermoacoustic amplification. The auxiliary source consists of a loudspeaker, located inside the loop-tube close to the main ambient heat exchanger, and supplied with a delayed signal through an electric feedback loop, comprising a phase-shifter and an amplifier, connected to a reference microphone. Experiments are performed on a prototype engine working with air at a static gauge pressure of 5 bars. Experimental results demonstrate how it is possible to tune the acoustic oscillations in order to increase the global performance of the generator, compared to the case without control, as well as the existence of a hysteretic behavior induced by the electroacoustic feedback loop itself, which leads to a discrepancy between the onset heat input and the offset one.     

采用选择激发研究光系统Ⅱ反应中心β-Car的物理特性

光系统Ⅱ反应中心包含有2个去镁叶绿素分子(Pheo),2个β胡萝卜素分子(β-Car)和6个叶绿素a分子(Chla).对反应中心的时间分辨荧光光谱表明,两个β-Car具有不同的吸收光谱,吸收峰分别为489 nm(Car489)和507 nm(Car507),Car489靠近吸收峰为667 nm和675 nm的叶绿素a(Chl a),它的主要功能是保护反应中心免受单态氧的破坏,而不能将激发能传递给光化学反应活性的色素分子P680;Car507靠近吸收峰为669 nm的Chl a分子;能够将激发能传递给P680,进行电荷分离.采用全局优化拟合的方法对荧光光谱进行处理,Car489在61 ps时间内将能量传递给Chl a672, 随后传给Chl a677,处于激发态的Chl a677在3 ns衰减到基态;Car507在274 ps时间内将能量传递给P680,P680＋Pheo-的电荷重组发生在3.8 ns和16 ns.     

Modelling of a novel high-impedance matching layer for high frequency (>30 MHz) ultrasonic transducers

This work describes a new approach to impedance matching for ultrasonic transducers. A single matching layer with high acoustic impedance of 16 MRayls is demonstrated to show a bandwidth of around 70%, compared with conventional single matching layer designs of around 50%. Although as a consequence of this improvement in bandwidth, there is a loss in sensitivity, this is found to be similar to an equivalent double matching layer design. Designs are calculated by using the KLM model and are then verified by FEA simulation, with very good agreement Considering the fabrication difficulties encountered in creating a high-frequency double matched design due to the requirement for materials with specific acoustic impedances, the need to accurately control the thickness of layers, and the relatively narrow bandwidths available for conventional single matched designs, the new approach shows advantages in that alternative (and perhaps more practical) materials become available, and offers a bandwidth close to that of a double layer design with the simplicity of a single layer design. The disadvantage is a trade-off in sensitivity. A typical example of a piezoceramic transducer matched to water can give a 70% fractional bandwidth (comparable to an ideal double matched design of 72%) with a 3 dB penalty in insertion loss.     

Superconductor-normal metal quantum phase transition in dissipative and non-equilibrium systems

Abstract

In physical systems, coupling to the environment gives rise to dissipation and decoherence. For nanoscopic materials, this may be a determining factor of their physical behaviour. However, even for macroscopic many-body systems, if the strength of this coupling is sufficiently strong, their ground-state properties and phase diagram may be severely modified. Also dissipation is essential to allow a system in the presence of a time-dependent perturbation to attain a steady, time-independent state. In this case, the non-equilibrium phase diagram depends on the intensity of the perturbation and on the strength of the coupling of the system to the outside world. In this paper, we investigate the effects of both dissipation and time-dependent external sources in the phase diagram of a many-body system at zero and finite temperatures. For concreteness, we consider the specific case of a superconducting layer under the action of an electric field and coupled to a metallic substrate. The former arises from a time dependent vector potential minimally coupled to the electrons in the layer. We introduce a Keldysh approach that allows to obtain the time dependence of the superconducting order parameter in an adiabatic regime. We study the phase diagram of this system as a function of the electric field, the coupling to the metallic substrate and temperature.     

The shape gradient of the least-squares objective functional in optimal shape design problems of radiative heat transfer

Optimal shape design problems of steady-state radiative heat transfer are considered. The optimal shape design problem (in the three-dimensional space) is formulated as an inverse one, i.e., in the form of an operator equation of the first kind with respect to a surface to be optimized. The operator equation is reduced to a minimization problem via a least-squares objective functional. The minimization problem has to be solved numerically. Gradient minimization methods need the gradient of a functional to be minimized. In this paper the shape gradient of the least-squares objective functional is derived with the help of the shape sensitivity analysis and adjoint problem method. In practice a surface to be optimized may be (or, most likely, is to be) given in a parametric form by a finite number of parameters. In this case the objective functional is, in fact, a function in a finite-dimensional space and the shape gradient becomes an ordinary gradient. The gradient of the objective functional, in the case that the surface to be optimized is given in a finite-parametric form, is derived from the shape gradient. A particular case, that a surface to be optimized is a “two-dimensional” polyhedral one, is considered. The technique, developed in the paper, is applied to a synthetic problem of designing a “two-dimensional” radiant enclosure.     

Three-dimensional finite element simulation of closed delaminations in composite materials

Early stage delaminations in composite materials tend to be closed at rest. Inspection with traditional linear ultrasonic techniques generally fails to diagnose and locate such imperfections. However, if undetected and left untreated, incipient defects may gradually grow within the material and eventually lead to failure of the component. Kissing bonds or clapping contacts inherently demand a non-linear diagnostic method, applying a finite excitation amplitude that is able to overcome an activation threshold to open and close the contact. In order to obtain a better understanding and analysis of the macroscopic non-linear behavior that can be observed at the component level, we developed and investigated the results of a finite element model for a composite material containing a single circular delamination. The model makes use of local node splitting and the non-linear constitutive behavior is implemented by means of spring-damper elements at the delamination interface. The results of this parametric study allow a better insight in the behavior of the excited delamination in experimental conditions, including the appearance of localized subharmonics and harmonics of the excitation frequency. Based on the developed model, two different detection and localization techniques (using either a single frequency or a sweep excitation) were demonstrated to determine position, shape, depth and orientation of one or multiple delaminations.     

Wide range instantaneous temperature measurements of convective fluid flows by using a schlieren system based in color images

In the schlieren method, the deflection of light by the presence of an inhomogeneous medium is proportional to the gradient of its refractive index. Such deflection, in a schlieren system, is represented by light intensity variations on the observation plane. Then, for a digital camera, the intensity level registered by each pixel depends mainly on the variation of the medium refractive index and the status of the digital camera settings. Therefore, in this study, we regulate the intensity value of each pixel by controlling the camera settings such as exposure time, gamma and gain values in order to calibrate the image obtained to the actual temperature values of a particular medium. In our approach, we use a color digital camera. The images obtained with a color digital camera can be separated on three different color-channels. Each channel corresponds to red, green, and blue color, moreover, each one has its own sensitivity. The differences in sensitivity allow us to obtain a range of temperature values for each color channel. Thus, high, medium and low sensitivity correspond to green, blue, and red color channel respectively. Therefore, by adding up the temperature contribution of each color channel we obtain a wide range of temperature values. Hence, the basic idea in our approach to measure temperature, using a schlieren system, is to relate the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the system. Our approach was applied to the measurement of instantaneous temperature fields of the air convection caused by a heated rectangular metal plate and a candle flame. We found that for the metal plate temperature measurements only the green and blue color-channels were required to sense the entire phenomena. On the other hand, for the candle case, the three color-channels were needed to obtain a complete measurement of temperature. In our study, the candle temperature was took as reference and it was found that the maximum temperature value obtained for green, blue and red color-channel was ∼275.6, ∼412.9, and ∼501.3 °C, respectively.     

Discreteness of space from GUP II: Relativistic wave equations

Various theories of Quantum Gravity predict modifications of the Heisenberg Uncertainty Principle near the Planck scale to a so-called Generalized Uncertainty Principle (GUP). In some recent papers, we showed that the GUP gives rise to corrections to the Schrödinger equation, which in turn affect all quantum mechanical Hamiltonians. In particular, by applying it to a particle in a one-dimensional box, we showed that the box length must be quantized in terms of a fundamental length (which could be the Planck length), which we interpreted as a signal of fundamental discreteness of space itself. In this Letter, we extend the above results to a relativistic particle in a rectangular as well as a spherical box, by solving the GUP-corrected Klein–Gordon and Dirac equations, and for the latter, to two and three dimensions. We again arrive at quantization of box length, area and volume and an indication of the fundamentally grainy nature of space. We discuss possible implications.     

Differential Replication for Credit Scoring in Regulated Environments

Differential replication is a method to adapt existing machine learning solutions to the demands of highly regulated environments by reusing knowledge from one generation to the next. Copying is a technique that allows differential replication by projecting a given classifier onto a new hypothesis space, in circumstances where access to both the original solution and its training data is limited. The resulting model replicates the original decision behavior while displaying new features and characteristics. In this paper, we apply this approach to a use case in the context of credit scoring. We use a private residential mortgage default dataset. We show that differential replication through copying can be exploited to adapt a given solution to the changing demands of a constrained environment such as that of the financial market. In particular, we show how copying can be used to replicate the decision behavior not only of a model, but also of a full pipeline. As a result, we can ensure the decomposability of the attributes used to provide explanations for credit scoring models and reduce the time-to-market delivery of these solutions.     

用于光电仪器和相关测量的自混合干涉技术（特邀）

回顾了一种全新结构的干涉仪—自混合干涉仪（SMI）的发展情况。SMI由于其在激光器外部无需任何光学元件且应用范围广泛而倍受关注。SMI可用于测量与光路长度有关的一些量（如位移、小幅度振动、速度）,也可用于测量弱光的回波（即回波损耗和隔离因子的测量）并可表征与介质相互作用特性相关的物理参数（如激光线宽、相干长度以及α因子等）。SMI是一种相干探测方法,其工作在靠近接收场的量子极限处,目前对散射目标物的最小探测幅值可达槡20 pm/（Hz）～（1/2）甚至更高,使用角锥棱镜使其计数步长为半波长,在动态范围为2 m时其分辨率约为0.5μm。另外,SMI结构紧凑、易于现场安装且可用于MEMS测试、旋转机械振动测试和生物运行测试等各种实验。