Quantifying entanglement of two relativistic particles using optimal entanglement witness

In a recent paper, it was shown that the projections of a relativistic spin operator (RSO) massive spin- \frac12{\frac{1}{2}} particle on a world-vector which can be in timelike or null tetrad direction are proportional to the helicity or Bargman-Wigner (BW) qubit, respectively. Here we consider Lorentz transformations of two-particle states, which have been constructed both in helicity basis. For convenience, instead of using the superposition of momenta we use only two momentum eigenstates (p ₁ and p ₂) for each particle. Consequently, in 2D momentum subspace we describe the structure of one particle in terms of the four-qubit system. We present a new approach to quantification of relativistic entanglement based on entanglement witness (EW), which is obtained by a new method of convex optimization. In addition, Lorentz invariance of entanglement using BW qubit is also studied.     

Tripartite entanglements seen from a relativistically moving frame

In the rest frame of an observer, a moving system of three spin -\frac12{-\frac{1}{2}} massive particles described by a Gaussian momentum distributed wave packet, is considered. The spin part is assumed be maximally entangled as the Greenberger-Horne-Zeilinger (GHZ) or the W state. In a boosted frame the spin entanglements change as a result of the Wigner rotation produced by the Lorentz transformation. As a measure for these tripartite entanglements, the logarithmic negativity is calculated for the corresponding reduced density matrix viewed in the boosted frame. For a specific Lorentz boost, when the momentum part of the system is separable, the logarithmic negativity for both the spin states desend uniformly to nonzero asymptotic values depending on the width of the momentum distribution. However, when the momentum part is perfectly correlated, there exist boosts with determined speed that completely remove the GHZ spin entanglement. Also, there exist boosts leading to minimal destruction of the GHZ entanglement, provided that the width of the momentum distribution is large enough. Interestingly, the W spin entanglement in this case is Lorentz invariant.     

Spin-Orbit Entanglement in Time Evolution of Radial Wave Packets in Hydrogenic Systems

Time evolution of radial wave packets built from the eigenstates of Dirac equation for a hydrogenic system is considered. Radial wave packets are constructed from the states of different n quantum numbers and the same lowest angular momentum. In general they exhibit a kind of breathing motion with dispersion and (partial) revivals. Calculations show that for some particular preparations of the wave packet one can observe interesting effects in spin motion, coming from inherent entanglement of spin and orbital degrees of freedom. These effects manifest themselves through some oscillations in the mean values of spin operators and through changes of spatial probability density carried by upper and lower components of the wave function. It is also shown that the characteristic time scale of predicted effects (called T_ls) is much smaller for radial wave packets than in other cases, reaching values comparable to (or even less than) the time scale for the wave packet revival.Presented at the 36th Symposium on Mathematical Physics, ‘Open Systems & Quantum Information’, Toruń, Poland, June 9-12, 2004.     

基于布里渊散射的结构应力光纤测试技术研究

作者通过分析一定功率的脉冲光射入光纤中的布里渊散射规律,介绍了分布式光纤测量测量轴向应力的基本原理;制作实验装置,测量单独的应变模型,分析散射回来的波形图,初步了解应力在光纤布里渊散射波谱上的图像特征;将应力作用于光纤的不同位置,对比它们与无应力作用诗所得到的散射波形之间的图像差异,研究其对光脉冲在光纤传输过程中的影响规律;结果表明,应力的作用大小,作用位置的不同都会对脉冲光的传播造成影响,主要在于影响布里渊散射的斯托克斯光和反斯托克斯光;本次研究所得可以为分布式光纤测量提供参考,为分布式光纤在测量微型形变的应用中有一定的促进作用;本次研究的创新点在于使用滑轮的方法,解决同等应力在分布光纤的不同位置作用效果。     

Analysis of offshore structures with ADINA

The paper describes a developed version of the ADINA program, suitable for analysis of slender structures exposed to wave, current and wind action. The forces are calculated up to instantaneous water level using the non-linear Morison equation. The program includes several different current and wave theories, with arbitrary flow-directions.

The program is general and flexible. Comparisons are made with a number of special written programs. Future development is outlined.     

On the role of anxiety in decisions under possiblistic uncertainty.

We focus on situations in which we must decide on what time to take an action. The action is not in question it is the time of action. We call these "time for action decisions," a prototypical example being deciding when to leave on a journey. We point out that during this type of decision process, the decision-maker recognizes two groups of forces acting on him: one that pushes him to act now and other that pushes him act later. We note that the strength of these forces depends on the information available about various uncertainties associated with the situation. It also strongly depends upon the personality of the decision-maker. We observe that as time passes these conflicting forces tend to build up an anxiety in the decision-maker resulting in an action being taken at a time of most intense anxiety. In this paper using the ideas of possibility and necessity measures to enable different interpretations of uncertain information we investigate the temporal profile of the decision-maker's anxiety as a function of their decision attitude. We investigate the role of maximization of anxiety as decision paradigm. One of our goals here is to try to understand role of the nature and the quality information plays in these types of decisions as well as its interaction with anxiety.     

Entangled spin states in geodesic motion around massive body

We discuss the effect of the gravitational field of a massive body on the spin entanglement of a two-qubit system in the singlet and triplet spin states in circular geodesic motion. We study the entanglement transport using Wootters concurrence, which depends on the momentum state of the system. We describe the behavior of the concurrence as a function of the orbital radius and show that the spin entanglement is more robust against changes caused by motion in the singlet state than in the triplet state. Furthermore, for the singlet (triplet) state, momentum correlation increases (decreases) the concurrence.     

The effectiveness of office information systems: a social action perspective

Abstract. The purpose of this paper is to show that a number of basic issues have not been adequately addressed in existing office information systems research. Prominent among these are the nature and role of offices, the goals of office information systems development, and the nature of its organizational and managerial consequences. It is proposed that office information systems should be analysed as social action systems the behaviour of which is strongly affected by socially determined forces and constraints such as the behaviour-channelling influences of authority, norms, customs, habits and precedence. Four types of social action are discussed: instrumental, strategic, communicative and discursive. Three contexts for perceiving and analysing the effects of social action in offices are introduced: technology, language and organization. Office information systems changes affect elements and relationships in these three contexts in different ways. By cross-relating social action types and contexts, nine classes of object systems are identified. Each object system class implies a different category of effectiveness concerns which in turn implies different office information system design requirements. The paper notes that the existing research literature has primarily been concerned with only three of the nine object systems. For more effective office information systems development, however, the other systems also need to be considered. The paper concludes by exploring how this may be done.     

Effects of submersion depth on wave uplift force acting on Biloxi Bay Bridge decks during Hurricane Katrina

A large portion of the Biloxi Bay Bridge was submerged and destroyed by surface waves and storm surge associated with Hurricane Katrina in 2005. In this paper, the time history of wave forces exerted on the Biloxi Bay Bridge during Hurricane Katrina was investigated by a wave-loading model. The Volume of Fluid (VOF) method was adopted in the model to track the variations of water surface levels. In order to obtain wave parameters and storm-surge elevation at the bridge site during Hurricane Katrina, a storm surge model and a wave propagation model were coupled to hindcast the hydrodynamic conditions. Outputs of the coupled wave-surge models were imported to the wave-loading model to simulate the dynamic wave forces acting on the bridge deck. In order to evaluate the maximum uplift wave force, five different bridge deck elevations submerged at different water depths were investigated. The processes of wave-bridge interaction were simulated by the wave-loading model. The wave profiles, velocity field in the vicinity of the bridge, and dynamic wave forces on the decks were analyzed. Results indicate that the uplift force on the submerged bridge deck span exceeded its own weight under the extreme wave and storm surge conditions during Hurricane Katrina. Moreover, the numerical simulations suggest that the maximum uplift wave force occurred when the storm surge water level reached the top of the bridge deck.     

一种非球面测量的新方法

提出一种基于光镊技术测量非球面面形的新方法.用光镊将直径为微米级的高分子小球移动到被测表面上,小球折射产生的球面波与平面波干涉,形成牛顿环.在相互垂直的二维标尺上分别测量两组牛顿环中心位置,得到小球的三维坐标.光镊对小球只产生亚皮牛量级的作用力,小球对被测表面的弹性变形可以忽略.通过测量若干小球坐标后,可拟合出三维曲面.     

A metaheuristic approach for optical network optimization problems

Two of the most complex optimization problems encountered in the design of third generation optical networks are the dynamic routing and wavelength assignment (DRWA) problem under the assumptions of ideal and non-ideal physical layers. Both these problems are NP-complete in nature. These are challenging due to the presence of multiple local optima in the search space. Even heuristics-based algorithms fail to solve these problems efficiently as the search space is non-convex. This paper reports the performance of a metaheuristic, that is, an evolutionary programming algorithm in solving different optical network optimization problems. The primary motivation behind adopting this approach is to reduce the algorithm execution time. It is demonstrated that the same basic approach can be used to solve different optimization problems by designing problem-specific fitness functions. Also, it is shown how the algorithm performance can be improved by integrating suitable soft constraints with the original constraints. Exhaustive simulation studies are carried out assuming the presence of different levels of linear impairments such as switch and demultiplexer crosstalk and non-linear impairments like four wave mixing to illustrate the superiority of the proposed algorithms.     

Experimental study of a momentum-based method for identifying the inertia barycentric parameters of a human body

Physical modeling, simulation and analysis of an individual human body require inertia properties of the body segments of the human. Such subject-specific inertia data can be obtained only by measuring the individual human body as opposed to be derived from statistically generated anthropometric database. This paper presents experimental validation of a momentum-based approach for identifying the barycentric parameters of an individual human body which fully describes the inertia properties of the human. The identification algorithm is derived from the impulse–momentum equations of the human body which is assumed to be a multibody system with tree-type topology. Since the impulse–momentum equations are linear in terms of the unknown barycentric parameters, these parameters can be solved from the equations using a least-squares method. The approach does not require measuring or estimating accelerations and joint forces/torques because they do not appear in the impulse–momentum equations, and thus, the resulting identification procedure is less demanding on measurement data than the methods derived from the equations of motion. In this paper the test results of the identification method are validated by comparing the identified inertia parameters against the statistically established anthropometric data. Additionally, the identification results are also confirmed by comparing the contact forces using inverse dynamics to those obtained by forces plates.     

自旋卫星喷气姿态控制动力学

本文讨论了自旋卫星向任意目标姿态机动的动力学问题.文中导出了一组受一串脉冲控 制力矩作用的卫星姿态运动的解析表达式.这些公式描述了角动量、章动角和姿态相位角与 控制力矩、控制次数之间的变化规律,可以直接应用于卫星姿控系统和姿态确定设计. 必须指出的是:关于将卫星自旋轴控制到垂直于轨道平面或将自旋轴控制到指向太阳, 都是本文所得结果的两个特例.     

A wideband transmission metasurface for generating Bessel beam carrying orbital angular momentum

Orbital angular momentum (OAM) microwave waves have received increasing research interest because of their potential to improve communication capacity and radar resolution. However, the traditional orbital angular momentum wave has the problem of diffraction divergence. The ideal Bessel beam with orbital angular momentum has the property of nondiffraction. Hence, the Bessel beam carrying orbital angular momentum has great research potential. In this work, a wideband transmission metasurface for generating Bessel beam carrying OAM is designed, fabricated, and measured. And it is the first experimental to show that the Bessel beam carrying OAM has higher gain and lower crosstalk than the traditional OAM wave in far field transmission.     

Conserved quantities in discrete dynamics: what can be recovered from Noether’s theorem, how, and why?

The connections between symmetries and conserved quantities of a dynamical system brought to light by Noether??s theorem depend in an essential way on the symplectic nature of the underlying kinematics. In the discrete dynamics realm, a rather suggestive analogy for this structure is offered by second-order cellular automata. We ask to what extent the latter systems may enjoy properties analogous to those conferred, for continuous systems, by Noether??s theorem. For definiteness, as a second-order cellular automaton we use the Ising spin model with both ferromagnetic and antiferromagnetic bonds. We show that??and why??energy not only acts as a generator of the dynamics for this family of systems, but is also conserved when the dynamics is time-invariant. We then begin to explore the issue of whether, in these systems, it may hold as well that translation invariance entails momentum conservation.     

一个不能满足于牛顿第三定律的物理实验

受磁场对载流导线有力的作用和牛顿第三定律的启发 ,希望制造一种新型的直流电动机。然而失败了。在找寻失败原因的实验中发现了如下物理现象 :以电磁相互作用的两个物体 ,在发生相互作用时 ,作用在两物体等效作用点上的二力虽然大小相等方向相反 ,但是该二力可以不在一条直线上。     

Symplectic and multi-symplectic methods for coupled nonlinear Schrödinger equations with periodic solutions

We consider for the integration of coupled nonlinear Schrödinger equations with periodic plane wave solutions a splitting method from the class of symplectic integrators and the multi-symplectic six-point scheme which is equivalent to the Preissman scheme. The numerical experiments show that both methods preserve very well the mass, energy and momentum in long-time evolution. The local errors in the energy are computed according to the discretizations in time and space for both methods. Due to its local nature, the multi-symplectic six-point scheme preserves the local invariants more accurately than the symplectic splitting method, but the global errors for conservation laws are almost the same.     

改进的键基正交各向异性近场动力学模型

针对经典的键基近场动力学(bond-based peridynamic,BPD)模型受固定泊松比限制的问题,提出一种改进BPD模型。该模型可解除泊松比限制,并可用于分析正交各向异性单向板的变形和裂纹扩展问题。在改进BPD模型中,每根键受到轴向和横向成对力的作用,额外增加的节点转动可消除由横向力引起的附加弯矩,从而确保该模型满足角动量守恒条件。仿真结果验证所提出的改进BPD模型的精度,并展示其预测碳纤维复合材料变形和裂纹扩展的能力。     

Analytical and numerical procedures in the application of many-body green's function methods to electron-atom scattering problems

The analytical and numerical procedures used in calculation of e^?-He elastic scattering phase shifts in the Generalized Random Phase Approximation (GRPA) and e^?-He inelastic cross sections in the Random Phase Approximation (RPA) are presented. The pertinent equations are first written in general form and analyzed into spin and angular momentum variables. In both elastic and inelastic work the transition density matrix was represented on a basis. Finite basis sets were also used to construct the static-exchange and polarization parts of the optical potential. The elastic scattering phase shifts were then evaluated numerically. In the inelastic work all calculations were done numerically. As an illustration of the usefulness of these methods, some typical results and computational times are given.     

Generation of Bessel beams with 3D‐printed lens

In this article, the 3D‐printed dielectric lens is proposed to generate Bessel beam in millimeter‐wave band. The dielectric lens is made of many square unit cells with the side length of a half wavelength. The unit cells with different thicknesses generate different insertion phase shift to the transmitted millimeter wave. The insertion phase distribution of the lens is calculated by comparing the phase distributions of the incident Gaussian beam and the desired output Bessel beam. Three types of lenses are simulated and fabricated using 3D printing technology with Nylon. The measured magnitude and phase distributions of zero‐order Bessel beam agree with the simulated results very well and the measured phase distributions of the first‐order Bessel beam carry orbital angular momentum.