Probing antiferromagnetic order with heat capacity in exchange-biased structures

We explore the magnetic heat capacity in exchange-biased ferromagnet/antiferromagnet bilayers theoretically. We show that changes in the antiferromagnetic structure due to the reversal of the ferromagnet layer can be detected by distinct features in the heat capacity. This offers a method for probing antiferromagnetic domains in exchange-biased systems.     

Adaptive‐numerical‐bias metadynamics

A metadynamics scheme is presented in which the free energy surface is filled with progressively adding adaptive biasing potentials, obtained from the accumulated probability distribution of the collective variables. Instead of adding Gaussians with assigned height and width in conventional metadynamics method, here we add a more realistic adaptive biasing potential to the Hamiltonian of the system. The shape of the adaptive biasing potential is adjusted on the fly by sampling over the visited states. As the top of the barrier is approached, the biasing potentials become wider. This decreases the problem of trapping the system in the niches, introduced by the addition of Gaussians of fixed height in metadynamics. Our results for the free energy profiles of three test systems show that this method is more accurate and converges more quickly than the conventional metadynamics, and is quite comparable (in accuracy and convergence rate) with the well‐tempered metadynamics method. © 2017 Wiley Periodicals, Inc.     

机抖激光陀螺的磁电拾振技术

经分析指出,磁电拾振技术应用在机抖激光陀螺抖动反馈方案中,其工作原理属于速度型传感器,直接反映抖动偏频量。给出了磁电拾振器的误差因素和结构特点,并测试了磁电拾振器方案与压电陶瓷反馈方案的输出特性。对同一机抖陀螺分别使用以上两种抖动反馈方案;在静态测试零偏稳定性、抗振动和冲击能力中,前者皆好于后者。研究表明磁电拾振方案比压电陶瓷反馈或光电反馈方案更适合作为抖动反馈。     

Ferromagnetic resonance study of interface anisotropies in exchange-biased Fe(0 0 1)/KNiF3 bilayers

Magnetic anisotropies at epitaxial Fe/KNiF₃ interfaces were probed by ferromagnetic resonance. Fe(0 0 1) films coupled to single crystal KNiF₃ exhibit four-fold in-plane anisotropy and a unidirectional bias upon field-cooling. In Fe(0 0 1) with polycrystalline KNiF₃, the bias direction deviates from the field-cooling direction. Lattice mismatch strain due to polycrystalline KNiF₃ also induces uniaxial anisotropy in Fe.     

Runaway electron generation decrease during a major disruption by limiter biasing in tokamaks

The high-energy current of runaway electrons during a major disruption in tokamak reactors can cause serious damage to the first wall of the reactors and reduce their life time. Therefore, finding a method to minimize runaway electron generation during a major disruption is much needed. Tokamak limiter biasing is one of the methods that can be used for controlling the radial electric field and can induce a transition to an improved confinement state. This paper attempts to examine the effect of limiter biasing on the generation of runaway electrons during a major disruption. To do so, a horizontal biased limiter placed on the tokamak was used. Main parameters such as plasma current, loop voltage, emitted hard X-ray intensity, magnetohydrodynamic (MHD) oscillation and H_α radiation and spectrum of hard X-rays, in the presence and absence of negative and positive limiter biasing, were measured. The results show that the application of limiter biasing during a major disruption can reduce runaway electron generation.     

模拟核测井工具响应的一种MC方法

描述了模拟双源距中子孔隙度测井工具响应的一种MC方法。在这个专用MC程序中,使用了几种有效方差降低技巧,如:隐吸收、权截断、能量截断、几何分裂和赌、方向偏倚等。针对这种核测井工具,将这些技巧作些改进;通过在程序中分别加上这几种方差降低技巧,对各自运行结果、精度、计算时间的分析和讨论,指出这些技巧的优缺点,亦证明了这些技巧确实有效;同时在某种程度上将此专用程序与通用程序做了比较。     

A PRESSURE-BASED ALGORITHM FOR HIGH-SPEED TURBOMACHINERY FLOWS

The steady state Navier–Stokes equations are solved in transonic flows using an elliptic formulation. A segregated solution algorithm is established in which the pressure correction equation is utilized to enforce the divergence-free mass flux constraint. The momentum equations are solved in terms of the primitive variables, while the pressure correction field is used to update both the convecting mass flux components and the pressure itself. The velocity components are deduced from the corrected mass fluxes on the basis of an upwind-biased density, which is a mechanism capable of overcoming the ellipticity of the system of equations, in the transonic flow regime. An incomplete LU decomposition is used for the solution of the transport-type equations and a globally minimized residual method resolves the pressure correction equation. Turbulence is resolved through the k–ε model. Dealing with turbomachinery applications, results are presented in two-dimensional compressor and turbine cascades under design and off-design conditions. © 1997 John Wiley & Sons, Ltd.     

偏压电场对压电板中Lamb波相速度的影响

本文研究了偏压电场作用下,Lamb波在压电板中的传播行为，首先给出了偏压电场作用时压电板中的应力场及电位移场，然后通过求解含初应力及初电位移的小幅波动问题的耦合方程，分别给出了Lamb波的对称模态和反对称模态的相速度方程，以典型的PZT－5H压电陶瓷板为例进行了数值计算,并讨论了偏压电场对Lamb波相速度及频散曲线的影响，结果表明，偏压电场可以显著地改变Lamb波的传播速度，借此可使声波器件获得延时效果。     

Some optimal bounds in the central limit theorem using zero biasing

The convergence rate in the central limit theorem (CLT) is investigated in terms of a wide class of probability metrics. Namely, optimal estimates for the proximity between a probability distribution and its zero bias transformation are derived. These new inequalities allow one to establish optimal rates of convergence in the CLT for sums of independent random variables with finite moments of order s, s∈(2,3], in terms of ideal metrics introduced by V.M. Zolotarev.     

电弹性体力学中的偏场方法及其应用

主要综述了当前有关叠加于偏场之上的电弹性体小位移问题的求解方法,即偏场方法.首先介绍了作为偏场方法理论基础的非线性电弹性力学理论,接着总结了偏场方法的研究进展以及受偏场作用后,电弹性梁、板、壳结构的分析方法,随后综述了偏场方法的诸多应用:其中,包括在薄壁电弹性结构屈曲分析中的应用、在记时与通信压电谐振器和基于频率漂移原理所设计的声波传感器的频率稳定性分析方面的应用、在非线性电弹性材料系数的测定以及偏场作用下电致伸缩陶瓷特征的分析等方面的应用.最后给出了该领域当前和未来的一些可能的研究课题.全文参考文献166篇.