Multistep processes in nuclear reactions

Recent applications of the theory of Feshbach, Kerman and Koonin to analyse multistep processes in nuclear reactions are described, and illustrated by detailed comparisons with a range of experimental data for neutron and proton reactions. The techniques used to distinguish between the multistep direct, multistep compound, compound and collective contributions to the cross-sections are described, and their effectiveness assessed. Particular attention is devoted to recent analyses that take into account the transitions from the multistep direct to the multistep compound chain and also to those that evaluate the collective contributions to the continuum region. The variation of the effective nucleonnucleon interaction with incident energy and target nucleus is studied, and the possibility of a parameter-free calculation is discussed. The extensions of the theory to include multiparticle emission from the direct chain and also to studies of alpha-particle emission are described.     

Evaluation of a contraceptive device with MR imaging.

The purpose of this investigation is to evaluate the positioning and to confirm the volume concept of the Lea's Shield diaphragm utilizing MR imaging. We evaluated the device in two women, one nulliparous and one multiparous. We were able to comprehensively evaluate the device in both patients and answer all questions regarding anatomical positioning and aspects pertaining to the morphology of the device relevant to its function. MRI may be effectively utilized to evaluate contraceptive devices and their relationship to adjacent anatomical structures. This may enhance the gynecologist's clinical assessment of its correct positioning and efficacy.     

Dissipative relativistic fluid dynamics for nuclear collisions

In the context of the Müller-Israel-Stewart second-order theory for dissipative fluids due to Grad, we analyze the effects of thermal conduction and viscosity in heavy ion collisions. We contrast the results to those of the first-order theory due to Eckart and to Landau and Lifshitz and to those of perfect (ideal) fluid due to Euler. We study the energy density and entropy density evolution of a pion gas produced in the heavy ion collisions. The truncated version of the second-order theory is used to find the dissipative quantities.     

圆柱螺旋弹簧迟滞的检测和补偿

介绍一种利用微电容测量技术检测圆柱螺旋压缩弹簧迟滞和利用单片机技术对迟滞进行补偿的实验方法,该方法涉及螺旋机构、电子秤和拟合曲线的求法等.通过这一实验,能帮助学生理解真实材料在一定程度上存在迟滞现象,掌握变极距电容传感器的概念,提高知识的综合应用能力和设计动手能力.     

Simulating coupled dynamics of a rigid-flexible multibody system and compressible fluid

As a subsequent work of previous studies of authors, a new parallel computation approach is proposed to simulate the coupled dynamics of a rigid-flexible multibody system and compressible fluid. In this approach, the smoothed particle hydrodynamics (SPH) method is used to model the compressible fluid, the natural coordinate formulation (NCF) and absolute nodal coordinate formulation (ANCF) are used to model the rigid and flexible bodies, respectively. In order to model the compressible fluid properly and efficiently via SPH method, three measures are taken as follows. The first is to use the Riemann solver to cope with the fluid compressibility, the second is to define virtual particles of SPH to model the dynamic interaction between the fluid and the multibody system, and the third is to impose the boundary conditions of periodical inflow and outflow to reduce the number of SPH particles involved in the computation process. Afterwards, a parallel computation strategy is proposed based on the graphics processing unit (GPU) to detect the neighboring SPH particles and to solve the dynamic equations of SPH particles in order to improve the computation efficiency. Meanwhile, the generalized-alpha algorithm is used to solve the dynamic equations of the multibody system. Finally, four case studies are given to validate the proposed parallel computation approach.     

Refinement and design of rare earth doped photonic crystal fibre amplifier using an ANN approach

A number of numerical and analytical methods with different complexity can be exploited to analyse fibre amplifiers. Conventional approaches make the refinement and design of the devices extremely time consuming, especially when several design parameters have to be simultaneously optimised to obtain the desired performance in terms of gain and noise figure.In order to tackle this issue, a method based on an artificial neural network to perform the refinement and design of erbium doped photonic crystal fibre amplifiers is proposed in this paper. The capability of the neural network to capture the nonlinear functional link among the physical and geometrical characteristics of the fibre amplifier and its gain and noise figure is exploited. In the refinement it is employed to determine the optimal values of the parameters maximising the gain. In the design, it is used to develop an inverse problem solver in order to determine the values of the parameters corresponding to the known values of gain.Numerical results show that the proposed approach finds the refinement/design parameters in good accordance with respect to the conventional one.     

矿山多源遥感图像像点位移测试系统设计

针对矿山地形的起伏变化影响对其进行分析研究的准确性,提出矿上多源遥感图像像点位移测试系统的设计方法。结合GPS定位原理,选取遥感图像上某一时刻点作为测试点,对拍摄得到的矿山图像和电子测试系统各触点之间的距离进行计算,进而得到测试点具体坐标位置,将其与测试点真实现场坐标相对比,实现矿山多源遥感图像像点位移的测试。通过实验证明,所设计的测试系统可以高精度实现对遥感图像像点位移的测试,有效减小了矿山地形变化带来的遥感图像研究误差。     

Stokes integral of economic growth: Calculus and the Solow model

Economic growth depends on capital and labor and two-dimensional calculus has been applied to economic theory. This leads to Riemann and Stokes integrals and to the first and second laws of production and growth. The mathematical structure is the same as in thermodynamics, economic properties may be related to physical terms: capital to energy, production to physical work, GDP per capita to temperature, production function to entropy. This is called econophysics. Production, trade and banking may be compared to motors, heat pumps or refrigerators. The Carnot process of the first law creates two levels in each system: cold and hot in physics; buyer and seller, investor and saver, rich and poor in economics. The efficiency rises with the income difference of rich and poor. The results of econophysics are compared to neoclassical theory.     

Modifications to functional and biological properties of proteins of cowpea pulse crop by ultrasound-assisted extraction

Natural resource depletion, negative environmental effects and the challenge to secure global food security led to the establishment of the Sustainable Development Goals (SDGs). In need to explore underutilized sustainable protein sources, this study aims at isolating protein from cowpea by ultrasound-assisted extraction (UAE), where the techno-functional characteristics of the protein isolates were studied at different sonication conditions i.e., 100 W and 200 W at processing times ranging from 5 to 20 min. The US at 200 W-10 min produced the optimal results for all properties. In this process combination, there was an increase in protein yield, solubility, water-holding capacity, foaming capacity and stability, emulsion activity and stability, zeta-potential, and in-vitro protein digestibility from 31.78% to 58.96%, 57.26% to 68.85%, 3.06 g/g to 3.68 g/g 70.64% to 83.74%, 30.76% to 60.01%, 47.48% to 64.26%, 56.59% to 87.71%, –32.9 mV to −44.2 mV and 88.27% to 89.99%, respectively and particle size dropped from 763 nm to 559 nm in comparison to control. The microstructure and secondary-structure alterations of proteins caused by sonication were validated by SEM images, SDS-PAGE, and FTIR analyses. Sonication leads to acoustic cavitation and penetrate the cell walls, improving extraction from the solid to liquid phase. After sonication, the hydrophobic protein groups were exposed and proteins were partially denatured which increased its functionality. The findings demonstrated that UAE of cowpea protein improved yield, modify characteristics to fit the needs of the food industry, and contribute to achieving SDGs 2, 3, 7, 12, and 13.     

Deflagration to detonation transition in fast flames and tracking with chemical explosive mode analysis

In the context of vapour cloud explosion, the flame acceleration process can lead to conditions promoting deflagration to detonation transition (DDT), potentially leading to increased damages in accidental scenarios. This study focuses on this phenomenon by performing simulations of detonation reinitiation for fast flames in the Chapman–Jouguet deflagration regime. It is obtained experimentally by the attenuation of an incident detonation by an array of obstacles. A primary objective of the paper is to demonstrate the ability of the numerical model to reproduce the major experimental trends, namely the variation of the reinitiation propensity for different initial pressures and blockage ratios (BRs). Chemical explosive mode analysis (CEMA) is also adapted to the context of this study, in order to identify locally the propagation regime and to provide insights on the reinitiation mechanism. An a priori validation of the CEMA methodology is first performed on relevant canonical one-dimensional configurations. Subsequently, ensembles of five realizations are computed at different initial pressures and BRs and compared to experimental data. They are shown to reproduce the major observed trends in terms of detonation reinitiation length with respect to the operating conditions, with significant variability from one realization to another. In addition, the reinitiation mechanism is also found to be consistent with experimental observations and a previous numerical study of the same configuration. The CEMA methodology adapted to this context is able to identify locally the different propagation regimes, and to track the highly reactive zones that coherently couple with transverse pressure perturbations, leading to the formation of a strongly reacting kernel which eventually triggers the detonation reinitiation.     

Ohmic Contacts to ZnSe-Based Materials

The formation of ohmic contacts to n- and p-type ZnSe is reviewed. The mechanisms for forming reasonable low-resistance ohmic contacts to n-ZnSe are well understood. This results from the fact that the Fermi energy level of ZnSe is unpinned and metals with sufficiently large work functions can make contact to n-type material. However, the situation is reversed for p-ZnSe where a large band gap and large electron affinity make it impossible to find metals with sufficiently large work functions to create an ohmic contact. Instead, the use of HgSe to form low barrier height Schottky contacts and of ZnSe/ZnTe multiple quantum wells (MQWs) to form ohmic contacts is reviewed. Although the MQWs can be used to form ohmic contacts to p-ZnSe, they degrade at high temperatures and high current densities. This is reviewed and shown to be a serious problem for applications to laser diodes.     

On the forced response of waveguides using the wave and finite element method

The forced response of waveguides subjected to time harmonic loading is treated. The approach starts with the wave and finite element (WFE) method where a segment of the waveguide is modeled using traditional finite element methods. The mass and stiffness matrices of the segment are used to formulate an eigenvalue problem whose solution yields the wave properties of the waveguide. The WFE formulation is used to obtain the response of the waveguide to a convected harmonic pressure (CHP). Since the Fourier transform of the response to a general excitation is a linear combination of the responses to CHPs, the response to a general excitation can be obtained via an inverse Fourier transform process. This is evaluated analytically using contour integration and the residue theorem. Hence, the approach presented herein enables the response of a waveguide to general loading to be found by: (a) modeling a segment of the waveguide using finite element methods and post-processing it to obtain the wave characteristics, (b) using Fourier transform and contour integration to obtain the wave amplitudes and (c) using the wave amplitudes to find the response at any point in the waveguide. Numerical examples are presented.     

临界-燃耗耦合计算方法

基于蒙特卡罗模拟方法,采用MCNP的多群计算程序模拟中子输运方程,并与栅元均匀化程序WIMS耦合,实现了临界-燃耗耦合计算。具体过程是:首先扩展MCNP的多群功能,将其能群扩展为69群;然后,由接口程序将WIMS程序产生69群共振、自屏宏观中子截面转化为ACE格式的多群截面;其次,将新产生的多群截面提供给MCNP,完成临界-燃耗计算;最后,利用此耦合程序进行了基准题校核计算以及实验对比。计算结果表明,此耦合程序是可靠和正确的。     

微燃机气封装置的数值模拟

为了将旋转部件与静止部件之间不同压力的空间隔开,微燃机中采用了气封装置以减少泄流量。泄漏流量的大小,以及其对主流的干扰,微燃机设计时必须加以认真考虑。工作时通过间隙而泄漏的流量过大,必然会对其整体效率产生重大影响。通常,在间隙处采用特殊结构来控制泄流量的大小,减少间隙对微燃机总体效率的影响。本文采用三维数值模拟对微燃机压气机与透平之间的间隙流动进行模拟分析,通过不同工况的比较以及对其内部流场进行分析,研究了气封内部流动特性,使得微燃机总体计算可考虑间隙引起的泄流对微燃机总体效率的影响。     

A recursive approach to prony parameter estimation

The Prony series method of fitting a series of complex exponentials to a time series can be applied to many acoustic and vibration signals. For example, in the analysis of a structure's response to transient excitation the Prony series method can be used to find the natural frequencies, damping ratios, amplitudes and relative phases of the modes of the structure. One of the main problems with this method is the need to calculate and invert matrices. In this paper an algorithm that combines the Prony series method with the recursive least squares algorithm is described. This eliminates the need to invert any matrices and also requires only part of the data to be available at one particular time. The method is applied to analyze a simulated structure's response and also to analyze the response of a beam to transient excitation.     

An efficient physical device-circuit simulator and its application to accurate design of millimeter wave oscillators

A rigorous one-dimensional physical device-circuit simulator is developed to accurately determine the transport properties and the electrical performance of semiconductor devices embedded into a passive circuit. The simulator is well suited to study the effects of device geometry, doping level, bias voltage, and mounting structure on the performance and to compare the accuracy and the computational efficiency of different physical models. The model is applied to determine the application limits of the drift-diffusion and hydrodynamic models when they are used to characterize the operation and to optimize the structure of cm- and mm-wave oscillators with two-terminal devices, and to produce a set of design curves which indicate the performance limits of different devices under various operating conditions.     

基于风洞的设备健康管理与数据有效性判定平台研究

低速增压风洞是满足我国航空工业科技发展而建设的一座气动力重大基础试验设施。为了保障该设施的高效率和可靠地运行,以各机电设备、电气测控设备、机械装置为对象,根据其故障模式和故障特点选取合适的监测点,获取实时工作状态数据,再以数据为基础,进行状态监测、故障诊断、故障预测,实现预先性决策和针对性快速维修。基于OSA-CBM 体系构建的风洞健康管理系统,根据设备的运行状态,实现对试验数据的有效性进行实时判定,并实现了风洞装备由事后维修向视情维修转变;实现了装备从使用、维护、管理模式由分散式管理向集约式管理的转变;实现了装备系统故障诊、预测及判读从人工智能向机器智能的转变。     

新教学体系下普通物理实验交叉教学模式的探讨

本文对分别执行传统教学体系和新教学体系实施教学的三个不同年级的教学效果进行比较和分析,发现实验交叉教学模式,既可以促使实验教师打破陈规、加强沟通.使所有实验项目的教学要求趋近,利于实现实验考核公平,又可以促进实验教师全面掌握每学期实验课程中的所有实验项目,提升自身业务水平,适应新的教学体系,以获得更佳的教学效果.     

Biospeckle numerical values over spectral image maps of activity

The image analysis presents itself as a powerful instrument applied to all sort of biological phenomena monitoring. The development of many optical approaches to carry out a feasible image assembling and analysis to different demands has been the main effort in this application area. A consequence of that effort is the adoption of the biospeckle laser technique as a potential alternative to pursue the optical metrology. Particularly, the monitoring of the biological activity under the laser illumination presents as a reliable tool to many applications in many areas, such as to identify the changes in the micro-blood flow in animal tissues, or even to monitor the vegetal and the animal tissues and their metabolism. However, one limitation of biospeckle is the access of graphical maps of activity with any numerical information linked to them. This work had the objective to present a protocol to separate different tissues in the same material by means of the frequency signature, and by means of the association of graphical and numerical results from the biospeckle laser images. In order to confirm the efficiency of the proposed protocol we applied it to separate embryo and endosperm in maize seed and as well to separate tumour cells and normal tissues in animals. The results showed the feasibility of the approach proposed offering results with graphical maps associated to numerical information.     

基于虚拟仪器的图像采集处理及仪器控制

针对激光测距机三光轴平行度调校,提出了由CCD摄像机摄取激光光斑图像,然后用图像采集与处理方法计算白光十字线中心与光斑中心偏差的方法,并对选用的图像处理算法进行了论述。此外,采用可变固定衰减片方法测量激光测距机接收系统的灵敏度。以LabVIEW为软件平台,开发出检测激光光轴中心及控制衰减器的虚拟仪器系统。该系统具有直观形象,使用方便,可移植性强等优点。