Synchrotron-Based Capabilities for Studying Engineering Materials at PETRA-III

Scientists and engineers are increasingly using synchrotron radiation, largely due to its special characteristics, including high flux (intensity, high temporal resolution), low divergence (high spatial resolution, efficient focusing), linear polarization, and high penetration power. While surface-sensitive optical, electron microscopy and certain X-ray techniques (grazing incidence diffraction, reflectivity) tackle many problems, materials engineering largely relies on the volume properties of materials: residual strains and textures in the interior of building structures, overall phase composition, slip systems, etc.     

Scientific Review: A New Epithermal Neutron Diffractometer at KENS (EXCED)

Neutron scattering experiments on highly absorbing materials like boron (10B), cadmium (113Cd), rare earths (Sm, Eu, Gd, Dy), etc., are extremely difficult to perform and have so far discouraged research activities on relevant compounds. However, recent topical phenomena such as charge ordering and orbital ordering have highlighted the importance of studying 4f-electron systems and raised a large demand for neutron scattering studies. Unfortunately, the preparation of isotope enriched (weakly absorbing) samples are costly, and very often the large amount of sample required for experiments can not be produced. An alternative way consists of reducing the absorption cross-section _a by utilizing epithermal neutrons of the order of several eV.     

Scientific Review: ENGIN-X: A Fully Refined Diffractometer Designed Specifically for Measurement of Stress

Neutron stress measurement is a non-destructive technique that provides insights into strain and stress fields deep within engineering components and structures. As such, it has become an increasingly important tool within engineering, leading to improved manufacturing processes to reduce stress and distortion as well as to the definition of more precise structural integrity lifing procedures. Furthermore, it is often the only non-destructive means of measuring the stress state deep within engineering components and structures under conditions (temperature, stress, atmosphere, etc.) representative of those which might be experienced in service.     

The BEG Model in the Disordered Region and at the Antiquadrupolar-Disordered Line of Parameters

Journal of Statistical Physics - We analyse the d-dimensional BEG model with $$d\ge 2$$ and parameters in the disordered region and at the antiquadrupolar-disordered line. We obtain a subset of...     

Scientific Review: Spectroscopy at IPNS: Recent Instrumental Upgrade and Scientific Highlights

IPNS has four neutron spectrometers: two chopper spectrometers, HRMECS and LRMECS, and two crystal-analyzer spectrometers, QENS and CHEX. At the outset, HRMECS, LRMECS, and QENS (preceded by CAS in the 1980s) were fully users-dedicated instruments. CHEX was an add-on and has been a prototype for pilot experiments and for further development. Over the years, steady incremental improvements have been made on these spectrometers. Recently, QENS and HRMECS have undergone substantial upgrade both in hardware and software. Here, we describe the design and operation of QENS and HRMECS and illustrate their scientific capabilities by selected examples. Other details concerning IPNS' spectrometers are given elsewhere [1].     

The discrete-dipole-approximation code ADDA: Capabilities and known limitations

The open-source code ADDA is described, which implements the discrete dipole approximation (DDA), a method to simulate light scattering by finite 3D objects of arbitrary shape and composition. Besides standard sequential execution, ADDA can run on a multiprocessor distributed-memory system, parallelizing a single DDA calculation. Hence the size parameter of the scatterer is in principle limited only by total available memory and computational speed. ADDA is written in C99 and is highly portable. It provides full control over the scattering geometry (particle morphology and orientation, and incident beam) and allows one to calculate a wide variety of integral and angle-resolved scattering quantities (cross sections, the Mueller matrix, etc.). Moreover, ADDA incorporates a range of state-of-the-art DDA improvements, aimed at increasing the accuracy and computational speed of the method. We discuss both physical and computational aspects of the DDA simulations and provide a practical introduction into performing such simulations with the ADDA code. We also present several simulation results, in particular, for a sphere with size parameter 320 (100-wavelength diameter) and refractive index 1.05.     

Sum Rules for the Quasi-Static and Visco-Elastic Response of Disordered Solids at Zero Temperature

We study exact results concerning the non-affine displacement fields observed by Tanguy et al. [Europhys. Lett. 57, 423 (2002), Phys. Rev. B 66, 174205 (2002)] and their contributions to elasticity. A normal mode analysis permits us to estimate the dominant contributions to the non-affine corrections to elasticity and relate these corrections to the correlator of a fluctuating force field. We extend this analysis to the visco-elastic dynamical response of the system.     

基于晶状体中微量元素与白内障关系的广义回归神经网络模式识别

选择微量元素Sr,Mg,Na,K,Mn,Cu,Fe和Zn在晶状体中的含量作为识别白内障患者的指标,建立了广义回归神经网络(GRNN)模式识别.选择20个样本为训练集,5个样本为预测集.结果表明,与BP神经网络相比,该种网络具有设计简单与收敛快的优点,对给定的数据能完全识别,预示着通过对晶状体中的微量元素含量的分析,可能作为白内障患者诊断的一种辅助手段.     

The Random Phase Property and the Lyapunov Spectrum for Disordered Multi-channel Systems

A random phase property establishing in the weak coupling limit a link between quasi-one-dimensional random Schrödinger operators and full random matrix theory is advocated. Briefly summarized it states that the random transfer matrices placed into a normal system of coordinates act on the isotropic frames and lead to a Markov process with a unique invariant measure which is of geometric nature. On the elliptic part of the transfer matrices, this measure is invariant under the unitaries in the hermitian symplectic group of the universality class under study. While the random phase property can up to now only be proved in special models or in a restricted sense, we provide strong numerical evidence that it holds in the Anderson model of localization. A main outcome of the random phase property is a perturbative calculation of the Lyapunov exponents which shows that the Lyapunov spectrum is equidistant and that the localization lengths for large systems in the unitary, orthogonal and symplectic ensemble differ by a factor 2 each. In an Anderson-Ando model on a tubular geometry with magnetic field and spin-orbit coupling, the normal system of coordinates is calculated and this is used to derive explicit energy dependent formulas for the Lyapunov spectrum.     

Correction to: The Density of States and Thermopower in Disordered Carbon Nanotubes

Russian Physics Journal - The name of the fourth author should read A. N. Ponomarev.     

Disordered heteropolymers: models for biomimetic polymers and polymers with frustrating quenched disorder

The ability to design and synthesize polymers that can perform functions with great specificity would impact advanced technologies in important ways. Biological macromolecules can self-assemble into motifs that allow them to perform very specific functions. Thus, in recent years, attention has been directed toward elucidating strategies that would allow synthetic polymers to perform biomimetic functions. In this article, we review recent research efforts exploring the possibility that heteropolymers with disordered sequence distributions (disordered heteropolymers) can mimic the ability of biological macromolecules to recognize patterns. Results of this body of work suggests that frustration due to competing interactions and quenched disorder may be the essential physics that can enable such biomimetic behavior. These results also show that recognition between disordered heteropolymers and multifunctional surfaces due to statistical pattern matching may be a good model to study kinetics in frustrated systems with quenched disorder. We also review work which demonstrates that disordered heteropolymers with branched architectures are good model systems to study the effects of quenched sequence disorder on microphase ordering of molten copolymers. The results we describe show that frustrating quenched disorder affects the way in which these materials form ordered nanostructures in ways which might be profitably exploited in applications. Although the focus of this review is on theoretical and computational research, we discuss connections with existing experimental work and suggest future experiments that are expected to yield further insights.     

Materials and reaction mechanisms at anode/electrolyte interfaces for SOFCs

The present paper reviews anodic reaction mechanisms of porous cermet and model anodes at metal/oxide interfaces in solid oxide fuel cells (SOFCs). Some analytical results, electrochemical methods, and reaction models were presented at Ni–YSZ cermets and well defined model anodes. Isotope labeling/secondary ion mass spectrometry (SIMS) analysis techniques were applied to determine the oxygen surface reactivity of oxide electrolytes in reducing atmospheres. The technique was also applied to determine the catalytic activity of metal/oxide interfaces for CH₄ decomposition and reactivity with the reformed gases at the mesh or stripe shaped anodes on different oxides. Observed SIMS images and the electrochemical analyses were compared at the model anode/electrolyte interfaces.     

Multidimensional Particle Codes: Their Capabilities and Limitations for Modeling Space and Laboratory Plasmas

Increasing the number of dimensions calls for significant changes in simulation techniques. Demand on computer time and space increases by orders of magnitude, and hardware development affects the feasibility. Gridless and Fokker-Planck codes are possible in one dimension but one needs grids and PIC codes in two and three dimensions. This imposes limits on Debye lengths, particle size and spacing, and resolution. Nonspectral (local) electromagnetic (EM) codes also suffer a Courant restriction on ?t, in addition to the usual ?p?t restriction. Spectral methods therefore have an advantage: they also permit convenient filtering, particle shaping, and control of resolution. Two-dimensional and 2?D codes are well advanced and documented [4], [5]. Three-dimensional codes are in their infancy. Data management, rather than physics or numerical analysis, becomes the major problem [10]. Machine-independent 3D codes are too limited in resolution and speed. Parallelism helps greatly but makes the 3D codes machine dependent. A present-day limit is attempted in a 2*128**3 grid code for CRAY's which processes ~5 million particles in ~2 min per time step. Layering is employed to break up the 3D problem into many 2D problems. Fields and particles are packed and buffered in and out of core. Diagnostics are limited by the large volume of information accumulated in a run. Results of runs with 3D codes have tended to show that the third dimension, treated as "ignorable" in 2D simulations, should not have been ignored.     

液体中溶解气体的普适分析方法-声致发光法

液体中溶解气体的量的分析一直是分析化学中的难题。迄今为止,只是发展了水体中溶解氧的化学分析与仪器分析方法,而其他的气体如N2,CO2,CH4的分析方法至今仍很缺乏,特别是液体中溶解的稀有气体,如：Ar,He,Ke的分析方法至今仍然是空白,文章介绍了声致发光分析气体溶解于液体（包括非水溶液）的新方法。     

Wave Fronts for Hamilton-Jacobi Equations:¶The General Theory for Riemann Solutions in

The Hamilton-Jacobi equation describes the dynamics of a hypersurface in . This equation is a nonlinear conservation law and thus has discontinuous solutions. The dependent variable is a surface gradient and the discontinuity is a surface cusp. Here we investigate the intersection of cusp hypersurfaces. These intersections define (n-1)-dimensional Riemann problems for the Hamilton-Jacobi equation. We propose the class of Hamilton-Jacobi equations as a natural higher-dimensional generalization of scalar equations which allow a satisfactory theory of higher-dimensional Riemann problems. The fist main result of this paper is a general framwork for the study of higher-dimensional Riemann problems for Hamilton-Jacobi equations. The purpose of the framwork ist to unterstand the structure of Hamilton-Jacobi wave interactions in an explicit and constructive manner. Specialized to two-dimensional Riemann problems (i.e., the intersection of cusp curves on surfaces embedded in ), this framework provides explicit solutions to a number of cases of interest. We are specifically interested in models of deposition and etching, important processes for the manufacture of semiconductor chips. We also define elementary waves as Riemann solutions which possess a common group velocity. Our second main result, for elementary waves, is a complete characterization in terms of algebraic constraints on the data. When satisfied, these constraints allow a consistently defined closed form expression for the solution. We also give a computable characterization for the admissibility of an elementary wave which is inductive in the codimension of the wave, and which generalizes the classical Oleinik condition for scalar conservation laws in one dimension. Received: 9 September 1996 / Accepted: 22 April 1997     

Nanoindentation and Mechanical Properties of Materials at Submicro- and Nanoscale Levels: Recent Results and Achievements

Physics of the Solid State - The review is dedicated to characteristics of the mechanical behavior of various materials at submicro- and nanoscale levels. To a large extent, progress in this area...     

Scientific and Technical Basis of Application of Nanostructured Materials Science and Nanoelectronics in Systems of Electromechanical Energy Converters for Special Purposes

Technical Physics - We consider the current state of a completely new area of science; microsystem electromechanics. Тhe wide spectra of its practical applications and prospects for further...