Imaging the domain pattern of the canted magnetization state in Co/Pt multilayer films

The exact magnetization pattern of magnetic films close to a spin-reorientation transition is difficult to analyze due to the intrinsically three-dimensional (3d) variation of the orientation of the local magnetization. We present a technique how this can be performed, based on the analysis of high quality 2d polarization maps from a single scanning electron microscope with polarization analysis (SEMPA) measurement with tilted sample. The key tool is the statistical distribution of all occurring polarization doublets, visualized in a 2d histogram plot. From the shape of the distribution the type of transition—canted-phase, or coexisting phases—can be inferred. For the canted-phase state, the canting angle can be accurately determined from geometrical considerations. With help of the histogram the image data can be analyzed and the three components of the magnetization can be calculated for most points of the image. For a Co/Pt multilayer film we found a cone state. The magnetization forms a complex pattern consisting of out-of-plane domains while the in-plane magnetization shows a maze pattern.     

Extremal optimization vs. learning automata: Strategies for spin selection in portfolio selection problems

Nowadays, various imitations of natural processes are used to solve challenging optimization problems faster and more accurately. Spin glass based optimization, specifically, has shown strong local search capability and parallel processing. But, spin glasses have a low rate of convergence since they use Monte Carlo simulation techniques such as simulated annealing (SA). Here, we propose two algorithms that combine the long range effect in spin glasses with extremal optimization (EO-SA) and learning automata (LA-SA). Instead of arbitrarily flipping spins at each step, these two strategies aim to choose the next spin and selectively exploiting the optimization landscape. As shown in this paper, this selection strategy can lead to faster rate of convergence and improved performance. The resulting two algorithms are then used to solve portfolio selection problem that is a non-polynomial (NP) complete problem. Comparison of test results indicates that the two algorithms, while being very different in strategy, provide similar performance and reach comparable probability distributions for spin selection. Furthermore, experiments show there is no difference in speed of LA-SA or EO-SA for glasses with fewer spins, but EO-SA responds much better than LA-SA for large glasses. This is confirmed by tests results of five of the world's major stock markets. In the last, the convergence speed is compared to other heuristic methods such as Neural Network (NN), Tabu Search (TS), and Genetic Algorithm (GA) to approve the truthfulness of proposed methods.     

旋转固体火箭发动机统一流场计算

为了进一步研究旋转对固体火箭发动机工作的影响,采用RSM湍流模型对内孔燃烧、内孔与端面同时燃烧管状装药旋转固体火箭发动机统一流场进行了仿真。采用UDF编程给出质量入口边界,获得了旋转条件下发动机内流场结构参数特点,并给予理论说明。计算结果表明,内孔燃烧装药发动机切向速度流场类似于典型的Rankine涡,端面和内孔同时燃烧装药发动机切向速度流场呈现出Rankine涡和由端面燃烧引起的强迫涡的复杂组合涡;在发动机前封头和喷管喉部涡核切向速度峰值非常大,使燃烧室前封头和喷管喉部工作环境显著恶化;旋转使发动机燃烧室压力沿径向逐渐增大,强迫涡附近的压力梯度远大于推进剂表面的压力梯度。     

基于自旋图和ICP算法的3D实体签名算法

针对已有的3D实体真实性认证方法中实体的标识不与实体自身绑定且难以验证的问题,提出了一种面向3D实体的签名算法。给出了3D实体签名算法的设计思想、签名产生算法以及签名验证算法。在粗配准和精匹配阶段分别通过自旋图(Spin Image)和ICP(Iterative Closest Point)算法对签名表面和待测表面进行匹配,从而提高了验证的准确率。对所设计的签名算法进行了实验仿真,所获得的迭代误差和匹配率表明该算法可以区分原始和伪造的签名表面,进而证明了算法的有效性。     

Spin dynamics and implications for superconductivity: some problems with thed-wave scenario

We review the spin dynamics of the normal state of the cuprates with special emphasis on neutron data in both the YBa₂Cu₃O_7– and La_2–x Sr _x CuO₄ systems. When realistic models of the Fermi surface shapes are incorporated, along with a moderate degree of spin fluctuations, we find good semiquantitative agreement with experiment for both cuprates. Building on the success of this Fermi-liquid-based scheme, we explore the implications ford-wave pairing from a number of vantage points. We conclude that our present experimental and theoretical understanding is inadequate to confirm or refute thed-wave scenario.     

一种新型高速动态液压加载装置

介绍了一种自行设计的用于高速齿轮试验台的新型液压加载装置,阐明了该装置的结构及工作原理．对影响加载装置的转矩和效率的几个主要参数进行了公式推导和分析．     

#BIS-hardness for 2-spin systems on bipartite bounded degree graphs in the tree non-uniqueness region

Counting independent sets on bipartite graphs (#BIS) is considered a canonical counting problem of intermediate approximation complexity. It is conjectured that #BIS neither has an FPRAS nor is as hard as #Sat to approximate. We study #BIS in the general framework of two-state spin systems on bipartite graphs. We define two notions, nearly-independent phase-correlated spins and unary symmetry breaking. We prove that it is #BIS-hard to approximate the partition function of any 2-spin system on bipartite graphs supporting these two notions. Consequently, we classify the complexity of approximating the partition function of antiferromagnetic 2-spin systems on bounded-degree bipartite graphs.     

Controlling Spin Qubits in Quantum Dots

We review progress on the spintronics proposal for quantum computing where the quantum bits (qubits) are implemented with electron spins. We calculate the exchange interaction of coupled quantum dots and present experiments, where the exchange coupling is measured via transport. Then, experiments on single spins on dots are described, where long spin relaxation times, on the order of a millisecond, are observed. We consider spin-orbit interaction as sources of spin decoherence and find theoretically that also long decoherence times are expected. Further, we describe the concept of spin filtering using quantum dots and show data of successful experiments. We also show an implementation of a read out scheme for spin qubits and define how qubits can be measured with high precision. Then, we propose new experiments, where the spin decoherence time and the Rabi oscillations of single electrons can be measured via charge transport through quantum dots. Finally, all these achievements have promising applications both in conventional and quantum information processing. PACS: 03.67.Lx, 03.67.Mn, 73.23.Hk, 85.35.Be     

A computer simulation of LiKSO4

Molecular-dynamics computer-simulation of an ionic molecular solid LiKSO₄ has been carried out at 300 and 1000 K using the atom-atom potentials obtained from lattice dynamical studies. We observe hopping of lithium ions to interstitial positions which is related to reorientations of sulphate tetrahedra.     

耐热铝合金的致密化工艺与材料性能

本文对多层喷射沉积耐热铝合金管坯经过挤压、旋压、轧制后的密度、显微结构及力学性能进行了检测和分析。在致密化加工过程中 ,材料的密度和力学性能明显提高 ,沉积坯中的界面和孔洞明显愈合 ,材料的显微组织趋于均匀。采用挤压 +旋压或挤压 +轧制致密化成型工艺可以获得高性能多层喷射沉积耐热铝合金材料。