Exploiting array manipulation habits to optimize garbage collection and type flow analysis

A widespread practice to implement a flexible array is to consider the storage area into two parts: the used area, which is already available for read/write operations, and the supply area, which is used in case of enlargement of the array. The main purpose of the supply area is to avoid as much as possible the reallocation of the whole storage area in case of enlargement. As the supply area is not used by the application, the main idea of the paper is to convey the information to the garbage collector, making it possible to avoid completely the marking of the supply area. We also present a simple method to analyze the types of objects, which are stored in an array as well as the possible presence of NULL values within the array. This allows us to better specialize the work of the garbage collector when marking the used area, and also, by transitivity, to improve overall results for type analysis of all expressions of the source code. After introducing several abstract data types, which represent the main arrays concerned by our technique (i.e., zero or variable indexing, circular arrays and hash maps), we measure its impact during the bootstrap of two compilers whose libraries are equipped with these abstract data types. We then measure, on various software products we have not written, the frequency of certain habits of manipulation of arrays, to assess the validity of our approach. Copyright © 2014 John Wiley & Sons, Ltd.     

On a method for solving a local boundary problem for a nonlinear stationary system with perturbations in the class of piecewise constant controls

The wide class of nonlinear stationary systems of ordinary differential equations taking into account restrictions on control and external perturbation is considered. An algorithm for constructing a discrete control function that guarantees the transfer of the systems from the initial state to the origin and an arbitrary neighborhood of the origin is proposed. A constructive sufficient condition of the Kalman type, in which the specified translation is possible, is obtained. The problem of robot‐manipulator control is considered and its numerical simulation is carried out.     

A Magnifying Glass for Virtual Imaging of Subwavelength Resolution by Transformation Optics

Traditional magnifying glasses can give magnified virtual images with diffraction‐limited resolution, that is, detailed information is lost. Here, a novel magnifying glass by transformation optics, referred to as a “superresolution magnifying glass” (SMG) is designed, which can produce magnified virtual images with a predetermined magnification factor and resolve subwavelength details (i.e., light sources with subwavelength distances can be resolved). Based on theoretical calculations and reductions, a metallic plate structure to produce the reduced SMG in microwave frequencies, which gives good performance verified by both numerical simulations and experimental results, is proposed and realized. The function of SMG is to create a superresolution virtual image, unlike traditional superresolution imaging devices that create real images. The proposed SMG will create a new branch of superresolution imaging technology.     

电力系统电压稳定性分析的实用算法

阐述了用于电压稳定性分析的一种实用计算方法。这种方法通过参数变换,解决了最大负荷点处病态潮流方程不收敛的问题,从而可以获得精确的电压稳定极限,并且通过引进预估校正技术更好地考虑了发电机无功越限及系统其它限制因素的影响。算法计算简单快捷,结果更具有理论依据。     

Self-corrected unsupervised domain adaptation

Unsupervised domain adaptation (UDA), which aims to use knowledge from a label-rich source domain to help learn unlabeled target domain, has recently attracted much attention. UDA methods mainly concentrate on source classification and distribution alignment between domains to expect the correct target prediction. While in this paper, we attempt to learn the target prediction end to end directly, and develop a Self-corrected unsupervised domain adaptation (SCUDA) method with probabilistic label correction. SCUDA adopts a probabilistic label corrector to learn and correct the target labels directly. Specifically, besides model parameters, those target pseudo-labels are also updated in learning and corrected by the anchor-variable, which preserves the class candidates for samples. Experiments on real datasets show the competitiveness of SCUDA.     

多体系统动力学方程的基于离散零空间理论的Newmark积分算法

考虑到多体系统动力学方程的数值计算方法是系统动力学分析的基础,提出一种基于离散零空间理论的Newmark积分算法。应用Newmark积分框架对多体系统动力学方程在时域上进行离散,通过离散零空间矩阵消去动力学方程中的拉格朗日乘子项,建立离散的达朗贝尔动力学方程,采用局部结点参数化进一步获得降维的达朗贝尔动力学方程。以空间双摆为算例,数值结果表明:该算法能够在实现系统降维、提高计算效率的同时,进行有效的数值分析,约束违约很小。     

修正值和类似区域在砌体墙板中的应用

对面外水平均布荷载下的砌体墙板考虑了砌体的变异和边界条件这两个重要因素,引入了修正值和类似区域的概念,然后根据新板在基础板对应的类似区域,将基础板的修正值应用到新板中,对新板的不同区域的弹性模量进行修正,再结合传统的有限元分析技术计算出新板的破坏荷载。将用该方法计算的破坏荷载值与试验值进行对比。     

改进G-S零点控制算法在雷达中的应用

针对目前对Gram-Schmidt(G-S)自适应零点控制算法的研究大多只停留在理论研究阶段,还没有将其应用于低截获概率(LPI,Low Probability of Intercept)雷达设计,提出一种改进的G-S自适应零点控制算法应用于连续波(CW,Continuous Wave)体制LPI雷达。该算法可以把接收信号中的目标信息去除,只留下干扰信号,进而进行正交化处理,从而防止目标信息被当作干扰抑制掉。阵列方向图、零陷深度和误差分析等仿真结果表明:该算法在保证较快的收敛速度和较好的稳定性的基础上,相对于传统的G-S正交法有10 dB以上的零陷加深,从而验证了该算法能有效提升雷达的LPI性能。