Electrical switching of the vortex core in a magnetic disk

A magnetic vortex is a curling magnetic structure realized in a ferromagnetic disk, which is a promising candidate for a memory cell for future non-volatile data-storage devices. Thus, an understanding of the stability and dynamical behaviour of the magnetic vortex is a major requirement for developing magnetic data-storage technology. Since the publication of experimental proof for the existence of a nanometre-scale core with out-of-plane magnetization in a magnetic vortex, the dynamics of vortices have been investigated intensively. However, a way to electrically control the core magnetization, which is a key for constructing a vortex-core memory, has been lacking. Here, we demonstrate the electrical switching of the core magnetization by using the current-driven resonant dynamics of the vortex; the core switching is triggered by a strong dynamic field that is produced locally by a rotational core motion at a high speed of several hundred metres per second. Efficient switching of the vortex core without magnetic-field application is achieved owing to resonance. This opens up the potentiality of a simple magnetic disk as a building block for spintronic devices such as a memory cell where the bit data is stored as the direction of the nanometre-scale core magnetization.     

A case-based reasoning approach toward developing a belief about the cost of concept

It is generally acknowledged that product development involves a sequence of decision making under uncertainty, including setting target requirements for a new product, selecting product concept, and developing conceptual and detailed design of a chosen concept. To select a product concept, engineers need to assess the uncertainty of a future market share, market size, and a cost of concept (cost of the final product developed from a concept). This paper proposes a case-based reasoning (CBR) approach to model beliefs about the uncertainty of a cost of concept. The proposed CBR approach consists of storing information about various products in a knowledge-base, defining a new product concept, retrieving a cluster of products in the knowledge-base that are highly similar to the concept, and adapting the cost of the retrieved product to construct a distribution of the cost of concept. This paper illustrates the proposed approach using printers as an example.     

Fabry–Perot interferometer in pulsed illumination: a new approach and capabilities

An analysis of the spectral-time characteristics of a Fabry–Perot interferometer (FPI) in pulsed illumination is given. Processes that occur in the transit of light pulses of different widths through a FPI are considered in detail. A relationship between the baseline of a FPI and the width of the incident light pulse is established. The time structure of a pulse that has traversed a FPI is analyzed. The theoretical difference in the transit of a light pulse through a FPI and of a regular sequence of synchronized laser pulses is found. The maximum time resolution of a FPI is determined. A model that describes the transit of a regular sequence of synchronized laser pulses through a FPI functioning in the mode of an optical filter is determined.     

六边形孔蜂窝梁和蜂窝组合梁抗剪性能分析

该文对不同参数下的正六边形孔蜂窝梁和蜂窝组合梁抗剪性能进行了试验与有限元分析研究。以试验研究为基础,基于有限元软件ABAQUS 建立非线性有限元模型,对不同开孔率、不同翼缘宽度和厚度的蜂窝梁和蜂窝组合梁进行分析比较,发现蜂窝梁和蜂窝组合梁抗剪承载力大小与翼缘厚度、开孔率和连接程度均有关。结果表明:蜂窝梁翼缘厚度变化对其抗剪承载力影响较大,而蜂窝组合梁中翼缘厚度的变化对其抗剪性能影响相对较小;混凝土板提高了蜂窝梁的抗剪极限承载能力;最后,给出蜂窝梁和蜂窝组合梁抗剪计算公式。     

Unstable resonator with reduced output coupling

The properties of a laser beam coupled out of a standard unstable laser resonator are heavily dependent on the chosen resonator magnification. A higher magnification results in a higher output coupling and a better beam quality. But in some configurations, an unstable resonator with a low output coupling in combination with a good beam quality is desirable. In order to reduce the output coupling for a particular resonator, magnification fractions of the outcoupled radiation are reflected back into the cavity. In the confocal case, the output mirror consists of a spherical inner section with a high reflectivity and a flat outer section with a partial reflectivity coating. With the application of the unstable resonator with reduced output coupling (URROC), magnification and output coupling can be adjusted independently from each other and it is possible to get a good beam quality and a high power extraction for lasers with a large low gain medium. The feasibility of this resonator design is examined numerically and experimentally with the help of a chemical oxygen iodine laser.     

Extraordinary magneto-optical effect of transmitted wave phase change in periodic diffraction structures

Based on the results of electromagnetic simulations for a dielectric structure comprising a grating over a homogeneous layer, a new magnetooptical effect is predicted according to which the phase of the transmitted zeroth order of diffraction must exhibit resonant variation during a change in the magnetization of the material. The structure is magnetized in the plane of the grating, in a direction perpendicular to its grooves. Since the magnitude of this effect is greater by several orders than that of the analogous effect for a homogeneous magnetized layer, the new effect is called extraordinary. The phenomenon is given a theoretical explanation based on a resonance excitation of an eigenmodes in the structure and the dependence of the mode frequency on the magnetization. It is shown that a large change in the phase of the transmitted order of diffraction is achieved at a certain ratio of the resonant and nonresonant diffraction processes.     

Dynamic stress intensity factors analysis of interface crack using line-spring model

In this study, a new method for calculating the dynamic stress intensity factors of a bimaterial bending specimen with an interface crack is proposed by making use of a line-spring model. A pre-cracked bending specimen is modeled by one-dimensional beam finite elements and a line-spring representing the stiffness or compliance of a cracked part. The proposed method enables the one-dimensional analysis of a two-dimensional crack problem; thus the time variations of the dynamic stress intensity factors of a bimaterial bending specimen with an interface crack can be obtained by making use of a personal computer within a few minutes. The results obtained by the proposed method agree reasonably well with those obtained by the two-dimensional finite element method, although a slight difference in period can be found. The proposed method enables rapid evaluation of dynamic stress intensity factors. So a rapid evaluation system of the dynamic fracture toughness of a bimaterial with an interface crack can be achieved by combining an instrumented impact test apparatus with a computer program based on the proposed method which runs on a personal computer.     

Pd-C高温共晶点复现装置研制

主要针对Pd-C高温共晶点复现装置的组成进行介绍,其中包括复现用高温均热炉炉体、温度控制系统、真空泵、充气保护装置、水冷系统、复现用的石墨坩埚、二等B型标准热电偶和Pt-Pd热电偶等。针对石墨坩埚的灌注和共晶点复现过程进行了描述,根据复现的试验数据进行了相应的分析。     

Image segmentation of a color-blindness plate

One way of testing color vision is with a color-blindness plate (CBP) consisting of a set of brilliant colored dots to form a pattern (a figure) and a set of other colored dots to form a background. Classification of such a type of color image into a pattern and a background with a traditional technique is difficult. Based on a self-organizing feature map and a labeling process as well as spatial distance computation, an effective approach to the segmentation of a CBP image is presented. We describe the principle of a CBP segmentation and then introduce the CBP. The proposed approach is described, and its experimental results are presented. We conclude that the method can segment the CBP image into a pattern and a background successfully.     

Reusable platforms for high-throughput on-chip temperature gradient assays

This paper describes a reusable platform that can apply a linear temperature gradient to a lab-on-a-chip device. When a planar microfluidic device with a series of microchannels is placed on top of the platform with the channels perpendicular to the gradient, each channel is held at a discrete temperature. This allows temperature-dependent data for chemical or biochemical species flowed into the device to be obtained in a concurrent fashion. As a demonstration, a melting curve for dsDNA is performed by collecting all the data simultaneously. The gradient is stable enough to easily distinguish between 30-mers where the complement strand contains a single C-A mismatch or a single T-G mismatch or is a perfect match. On the other hand, a temperature gradient can be formed parallel to the direction of flow of the microchannels. This allows the temperature in each channel to vary continuously as the liquid flows downstream. If each microchannel in the array contains a distinct pH value, ionic strength, species concentration, or chemical composition, then a high-throughput two-variable experiment can be performed. We demonstrate this mode of data collection by measuring the fluorescence yield of fluorescein dye molecules in aqueous solution simultaneously as a function of concentration and temperature.     

Fluctuational electromagnetic interaction between a moving particle and a flat surface covered with a thin adsorbed film

The effect of a thin adsorbed film on the fluctuational electromagnetic tangential force of interaction between a moving nanoparticle and a flat solid surface was theoretically studied for the first time in a nonrelativistic approximation. Particular calculations were performed for a metal film on a dielectric and for a dielectric film on a metal. In both cases, the nanoparticle is assumed to be made of a nonmagnetic metal. It is shown that, at a normal temperature, the presence of an adsorbed film may lead to an increase in the tangential friction force by one or two orders of magnitude for a certain relation between the particle distance from the surface and the film thickness. In the case of a dielectric film on a metal substrate, a decrease in the temperature is accompanied by exponential decrease in the viscous friction. For a metal film on a dielectric substrate, the tangential force exhibits a quadratic dependence on the temperature.     

Mutation-periodic quivers, integrable maps and associated Poisson algebras

We consider a class of map, recently derived in the context of cluster mutation. In this paper, we start with a brief review of the quiver context, but then move onto a discussion of a related Poisson bracket, along with the Poisson algebra of a special family of functions associated with these maps. A bi-Hamiltonian structure is derived and used to construct a sequence of Poisson-commuting functions and hence show complete integrability. Canonical coordinates are derived, with the map now being a canonical transformation with a sequence of commuting invariant functions. Compatibility of a pair of these functions gives rise to Liouville's equation and the map plays the role of a B?cklund transformation.     

Optimal bandwidth for topographical differential absorption lidar detection

A detected laser signal backscattered from a tilted target is modeled with a laser-pulse shape as a response of a high-pass filter to an exponential input that describes the gain buildup within the laser cavity before a laser pulse is emitted and a single-pole low-pass RC filter for the electronic amplifier. The model is used to maximize the signal-to-noise ratio of the detected peak signal with a proper choice of the integration time constant τ as a function of the laser-pulse shape and the tilt angle of the backscattering target.     

On the Elastic Coupling Through the Flux Lines and Magnetic Interaction

It is defined the magnetic interaction energy between two superconductor pieces situated in a magnetic field by using the elastic coupling through the flux lines. On this basis, it is shown that a force between a superconducting material and a source of magnetic field is always repulsive, the force between a ferromagnetic material and a source of magnetic field is always attractive and a force between a normal metal and a source of time-varying magnetic field is always repulsive.     

Filling the Radon domain in computed tomography by local convex combination

Radon data interpolation is a necessary procedure in computed tomography (CT), especially for reconstruction from divergent beam scanning. In a polar-grid representation, the Radon data of a fanbeam projection are populated on an arc, rather on a radial line. Collectively, the Radon data generated from a fanbeam CT system are unevenly populated: The population becomes sparser as the polar distance increases. In CT reconstruction, the Fourier central slice theorem requires a radial scanline full of Radon data. Therefore the vacant entries of a scanline must be filled by interpolation. In addition, interpolation is also required in polar-to-Cartesian conversion. In this paper we propose a practical interpolation technique for filling the vacant entries by local convex combination. It is a linear interpolant that generates a value for a grid point from the available data lying in its neighborhood, by a weighted average, with the weights corresponding to the inverse distances. In fact, the linear convex combination serves as a general flat-smoothing operation in filling a vacancy. Specifically, this technique realizes a variety of linear interpolations, including nearest-neighbor replication, two-point collinear, three-point triangulation, and four-point quadrilateral, and local extrapolation, in a unified framework. Algorithms and a simulation demonstration are provided.     

Formation of a Nanophase Wetting Layer and Metal Growth on a Semiconductor

Based on the data on the atomic density of a film and degree of its homogeneity during the formation of the interface between 3d transition metals (Cr, Co, Fe, or Cu) and silicon, a new concept of forming a contact between a reactive metal and a semiconductor has been justified. According to this concept, the low-temperature vapor-phase deposition of a metal onto a semiconductor is accompanied by the formation of a two-dimensional nanophase wetting layer of a metal or its mixture with silicon with a thickness of several monolayers, which significantly affects the interface formation and structure. This concept changes a perspective of forming a contact between a metal and a semiconductor substrate: it is necessary to take into account not only the formation of surface phases and clusters and/or the mixing process, but also the effect of elastic wetting of a substrate by the forming phases.     

Optical radiation flux illuminating a circular disk from an off-axis point source separated by a homogeneous plane-parallel plate

In a number of techniques that measure weak fluxes of optical radiation, it is frequently necessary to keep a detector in a medium different from that of the radiating source by separating it from the source with a planar transparent window. However, sources such as systems of light-emitting diodes, large-fiber illuminators, and microscopic living objects that emit biological luminescence may sometimes be regarded as multiple-point sources. To estimate the fluxes of optical radiation illuminating a surface from a nonuniformly distributed multiple-point source, a method for calculating fluxes from a single off-axis point source is needed. A formula is derived to estimate a flux of temporally incoherent optical radiation incident on a circular disk from a single off-axis point source separated by a plane-parallel plate (PPP). This formula is expressed by a series of single integrals of some superposed elementary functions. These functions depend on the variables that characterize the point-source-plane-parallel-plate-circular-disk geometry and on the optical properties of the media that separate the source from the PPP and the PPP from the disk. The solution was obtained for isotropic media. For illustrative purposes some examples of the use of the formula are presented. The selected results are illustrated by three-dimensional surface plots and compared with the values of the fluxes calculated for radiation incident on the disk from a point source not separated by a PPP.     

Effect of a Multimode Laser Field on Multichannel Multiphoton Ionization of Hydrogen

Abstract

The effect of the multimode structure of a laser field on multichannel multiphoton ionization is investigated, taking the hydrogen atom as a study case. It is found that at moderately high laser intensity the ionization rate into a given channel is changed by varying the number of modes in a similar way to the single-channel multiphoton ionization. At higher intensities the ionization rates saturate, reaching a maximum which is almost independent of the number of modes. In the saturation regime a peaking approximation is performed which gives the ionization rate in a given channel as a simple analytical function of the number of modes and the laser intensity, and provides a useful insight into the characteristic features of the process.     

摩擦调节剂抑制钢轨波磨的机理研究

基于轮轨之间的摩擦耦合自激振动引起钢轨波磨的观点,论文建立了车辆稳态通过小半径曲线时由轮对－钢轨－轨枕组成的轮轨系统有限元弹性振动摩擦自激振动有限元模型,用ABAQUS软件对该模型的运动稳定性进行了分析,重点研究了轮轨摩擦系数和蠕滑力-蠕滑率曲线负斜率对轮轨系统摩擦自激振动的影响。计算结果显示,轮轨摩擦系数对轮轨摩擦自激振动有重要影响,当控制摩擦系数 时可以消除钢轨磨耗型波磨,蠕滑力-蠕滑率曲线负斜率对钢轨波磨有显著影响。