New Estimates for the Rate of Convergence of the Method of Subspace Corrections

We discuss estimates for the rate of convergence of the method of successive subspace corrections in terms of condition number estimate for the method of parallel subspace corrections.We provide upper bounds and in a special case,a lower bound for preconditioners defined via the method of successive subspace corrections.

Dynamic inverse control of feedback linearization in ballistic correction based on nose cone swinging

It is a complicated nonlinear controlling problem to conduct a two-dimensional trajectory correction of rockets.By establishing the aerodynamic correction force mathematical model of rockets on nose cone swinging,the linear control is realized by the dynamic inverse nonlinear controlling theory and the three-time-scale separation method.The control ability and the simulation results are also tested and verified.The results show that the output responses of system track the expected curve well and the error is controlled in a given margin.The maximum correction is about±314 m in the lengthwise direction and±1 212 m in the crosswise direction from the moment of 5 s to the drop-point time when the angle of fire is 55°.Thus,based on the dynamic inverse control of feedback linearization,the trajectory correction capability of nose cone swinging can satisfy the requirements of two-dimensional ballistic correction,and the validity and effectiveness of the method are proved.

Near field 3-D imaging approach for joint high-resolution imaging and phase error correction

This paper combines compressed sensing (CS) imaging theory and range migration algorithm (RMA), and then proposes a near-field three-dimensional (3-D) imaging approach for joint high-resolution imaging and phase error correction. Firstly, a sparse measurement matrix construction method based on a logistic sequence is proposed, which conducts nonlinear transformation for the determined logistic sequence, making it obey uniform distribution, then conducts sign function mapping, and generates the pseudorandom sequence with Bernoulli distribution, thus leading to good signal recovery under down-sampling and easy availability for engineering realization. Secondly, in combination with the RMA imaging approach, the dictionary with all scene information and phase error correction is constructed for CS signal recovery and error correction. Finally, the non-quadratic solution model jointing imaging and phase error correction based on regularization is built, and it is solved by two steps - the separable surrogate functionals (SSF) iterative shrinkage algorithm is adopted to realize target scattering estimate; the iteration mode is adopted for the correction of the dictionary model, so as to achieve the goal of error correction and highly-focused imaging. The proposed approach proves to be effective through numerical simulation and real measurement in anechoic chamber. The results show that, the proposed approach can realize high-resolution imaging in the case of less data; the designed measurement matrix has better non-coherence and easy availability for engineering realization. The proposed approach can effectively correct the phase error, and achieve highly-focused target image. © 2017 Beijing Institute of Aerospace Information.

On the Computing of the Minimum Distance of Linear Block Codes by Heuristic Methods

The evaluation of the minimum distance of linear block codes remains an open problem in coding theory, and it is not easy to determine its true value by classical methods, for this reason the problem has been solved in the literature with heuristic techniques such as genetic algorithms and local search algorithms. In this paper we propose two approaches to attack the hardness of this problem. The first approach is based on genetic algorithms and it yield to good results comparing to another work based also on genetic algorithms. The second approach is based on a new randomized algorithm which we call 'Multiple Impulse Method (MIM)', where the principle is to search codewords locally around the all-zero codeword perturbed by a minimum level of noise, anticipating that the resultant nearest nonzero codewords will most likely contain the minimum Hamming-weight codeword whose Hamming weight is equal to the minimum distance of the linear code.

线性学术评价中权重扭曲危害、成因及对策研究——最小均值指标权重修正法

[目的/意义]在线性学术评价中,普遍存在初始权重与实际权重不一致问题。[方法/过程]文章以学术期刊评价为例,在对其产生机制进行理论分析的基础上,研究了其危害,并对现有的几种解决方法的不足进行了剖析,提出一种新的最小均值指标权重修正法,并进行了实证检验。[结果/结论]研究结果表明:最小均值指标权重修正法可以彻底解决自然权重问题;要重视自然权重问题对学术评价科学带来的影响;最小均值指标权重修正法也适用于所有的线性评价。

Arbitrary High-Order Fully-Decoupled Numerical Schemes for Phase-Field Models of Two-Phase Incompressible Flows

Due to the coupling between the hydrodynamic equation and the phase-field equation in two-phase incompressible flows,it is desirable to develop efficient and high-order accurate numerical schemes that can decouple these two equations.One popular and efficient strategy is to add an explicit stabilizing term to the convective velocity in the phase-field equation to decouple them.The resulting schemes are only first-order accurate in time,and it seems extremely difficult to generalize the idea of stabilization to the second-order or higher version.In this paper,we employ the spectral deferred correction method to improve the temporal accuracy,based on the first-order decoupled and energy-stable scheme constructed by the stabilization idea.The novelty lies in how the decoupling and linear implicit properties are maintained to improve the efficiency.Within the framework of the spatially discretized local discontinuous Galerkin method,the resulting numerical schemes are fully decoupled,efficient,and high-order accurate in both time and space.Numerical experiments are performed to validate the high-order accuracy and efficiency of the methods for solving phase-field models of two-phase incompressible flows.

一类带线性约束的变分不等式的预测校正方法的收敛率分析

考虑一类带线性约束的变分不等式问题:寻找x^(*)∈Ω满足F(x^(*))^(T)(x-x^(*))≥0,■x∈Ω,其中Ω={x∈R^(n)|Ax≤b,x∈K},A∈R^(m×n),b∈R^(m),K是R^(n)上的一个简单的非空闭凸子集,F是R^(n)到R^(n)的连续未知算子且满足强单调.对此类问题,本文研究了一种新的预测校正方法.根据已有的收敛性结果,利用误差界条件进一步分析了该方法的线性收敛性.最后,通过交通均衡问题中两个带线性约束例子的数值结果展示了算法的有效性.

抛物型积分微分方程的全离散界面修正直接间断有限元法

针对线性抛物型积分微分方程,首先利用带界面修正的直接间断有限元(DDGIC)法对空间离散,分析半离散格式的稳定性;然后在时间方向应用Crank-Nicolson法,建立全离散的Crank-Nicolson/DDGIC格式,对全离散格式的收敛性进行了详细讨论;最后给出数值算例验证方法的有效性和理论结果.

基于ESO和分数阶PID的改进P&O控制策略

为了提高光伏电池转换效率、降低能量损失,有必要研究最大功率点跟踪(maximum power point tracking,MPPT)方法。针对传统扰动观察法(perturbation observation method,P&O)存在无法兼顾跟踪速度与稳态精度、在光照度发生较大变化时会产生误判现象的问题,文中提出一种能适应环境变化的变步长P&O控制策略。首先,利用光伏电池刚启动时类似恒流源的特性获取当前光照度下的短路电流,通过固定电流法推导出最大功率点(maximum power point,MPP)的参考电压;其次,当光照度突变时,提出功率修正方法,并给出突变时的变步长调整策略;最后,设计基于线性扩张状态观测器(linear extended state observer,LESO)的分数阶比例积分微分(fractional order proportion integration differentiation,FOPID)控制器,可以对算法输出的参考电压进一步进行跟踪补偿。仿真结果表明,所提控制策略可以提高稳态精度和跟踪速度,有效提高光伏电池的输出功率。

Study of Different Attenuation Correction Methods in Association with Rainfall Estimation for X-Band Polarimetric Radars

Different attenuation correction methods for the X-band dual linear polarimetric radar are analyzed in this paper.The specific differential phase shift KDP is always considered as an effective factor in radar signal attenuation correction.However,the values of KDP for light rains are too small,which results in unstable quality and large errors of rainfall estimation.Therefore,radar horizontal reflectivity ZH and specific differential phase shift are combined together in the ZH-KDP method to correct the attenuation error.Based on the similar consideration,a ZH-KDP-R combined technique is also proposed to estimate rainfall（R）.During the development and set-up of the synchronous transmitting and receiving dual polaximetric Doppler weather radar with 3.2 cm wave length,a set of observational data were obtained in the field experiment in Pingliang,Gansu Province in August 2005.Some continuous measurements with 5-12-minute intervals were gained in the time period from 1508 to 2205（Beijing Time）11 August 2005.Using the data,the performance of the combined attenuation correction and rainfall estimation methods is examined.The results indicate that the ZH-KDP combined method is effective and the correction speed meets the requirement of real-time operations.The analysis of the precipitation process shows that the ZH-KDP-R combined technique is more suitable for rainfall estimation than single factor methods such as the KDP-R or Z-R relation,and the estimated results are in good agreement with automatic rain gauge records.As to the Z-R relation,the deviation between the precipitation estimation and the available gauge measurement decreases obviously when the corrected ZH is used,indicating that the radar data quality has been obviously improved after the attenuation correction.

Semi-Implicit Spectral Deferred Correction Method Based on the Invariant Energy Quadratization Approach for Phase Field Problems

This paper presents a high order time discretization method by combining the semi-implicit spectral deferred correction method with energy stable linear schemes to simulate a series of phase field problems.We start with the linear scheme,which is based on the invariant energy quadratization approach and is proved to be linear unconditionally energy stable.The scheme also takes advantage of avoiding nonlinear iteration and the restriction of time step to guarantee the nonlinear system uniquely solvable.Moreover,the scheme leads to linear algebraic system to solve at each iteration,and we employ the multigrid solver to solve it efficiently.Numerical re-sults are given to illustrate that the combination of local discontinuous Galerkin(LDG)spatial discretization and the high order temporal scheme is a practical,accurate and efficient simulation tool when solving phase field problems.Namely,we can obtain high order accuracy in both time and space by solving some simple linear algebraic equations.

A Linear-correction Least-squares Approach for Geolocation Using FDOA Measurements Only

A linear-correction least-squares（LCLS） estimation procedure is proposed for geolocation using frequency difference of arrival （FDOA） measurements only. We first analyze the measurements of FDOA, and further derive the Cramer-Rao lower bound （CRLB） of geoloeation using FDOA measurements. For the localization model is a nonlinear least squares（LS） estimator with a nonlinear constrained, a linearizing method is used to convert the model to a linear least squares estimator with a nonlinear con- strained. The Gauss-Newton iteration method is developed to conquer the source localization problem. From the analysis of solving Lagrange multiplier, the algorithm is a generalization of linear-correction least squares estimation procedure under the condition of geolocation using FDOA measurements only. The algorithm is compared with common least squares estimation. Comparisons of their estimation accuracy and the CRLB are made, and the proposed method attains the CRLB. Simulation re- sults are included to corroborate the theoretical development.

基于线阵相机的铁路列车变流器超温故障检测方法

由于铁路列车变流器超温故障检测过程受到谐波影响,存在故障电流、电压数据检测结果不精准的问题。为了提高故障检测精度,研究了一种基于线阵相机的铁路列车变流器超温故障检测方法。采用改进区域生长-消除法,分割变流器红外热图像,区分发热区域和不发热区域。结合最小二乘法多项式曲线拟合方法,拟合变流器内部结温,通过温度定标算法计算变流器温度。充分考虑线阵相机镜头本身的非线性畸变,构建线阵相机畸变校正数学模型,采用积分波形修复算法,划分变流器定子电流波形的前半周期和后半周期,并修复电流波形,消除谐波。构建三相六阶段输出变流器电路图,定位变流器超温故障位置。由实验结果可知,该方法检测的故障电流、电压波动范围分别为[(-1.5~1.5)A]、[(-2~2)V],与实验数据一致,且波动曲线平滑,有效解决了谐波问题,具有精准检测的效果。

红外焦平面器件二点多段非均匀性校正算法研究

分析了红外焦平面探测器的非均匀性机理和各种非均匀性校正算法 ,提出两点多段非均匀性校正算法 ,该算法避免了二点校正算法的低精度和多点校正算法的大运算量 .在红外多谱段相机上的应用结果表明二点多段非均匀性校正算法具有运算量小、精度高、实用性强的优点 .

直接汞分析仪测定煤中汞含量不确定度评定

对直接汞分析仪测定煤炭中汞含量过程中可能引入的不确定度进行分析和评定。采用棋盘取样法确定样品均匀性不确定度分量,用较严密的密度修正法评估校准溶液质量浓度变化的不确定度分量,用一般的线性拟合法和较严密的非线性拟合法评估校准曲线拟合浓度的不确定度分量。

混合氯化石蜡中短链氯化石蜡定量分析方法的比较

分别采用总体响应因子校正法和多元线性回归法对混合氯化石蜡中短链氯化石蜡进行定量分析,结果表明:两种方法均能较好地排除中链氯化石蜡的干扰,从而提高了短链氯化石蜡的定量准确性;但是两种方法均对标准曲线的浓度范围存在一定的依赖性,在使用这两种方法进行定量分析时,应将样品稀释到标准曲线适用的浓度范围。另外,相对于总体响应因子校正法,多元线性回归法定量范围更广。

高层基础隔震建筑非平稳随机响应改进算法

利用虚拟激励法和等效线性化技术,计算了基础隔震高层建筑的非平稳随机响应。研究了高阶振型对高层隔震建筑响应的影响,提出了针对基础隔震结构随机响应分析的改进算法。计算中假定隔震建筑上部结构在大震作用下依然保持弹性状态,塑性变形集中在隔震层处,隔震层的恢复力-位移本构关系采用Bouc-Wen模型来描述。上部结构只需要提取前若干阶振型参与动力计算,剩余的高阶振型对结构响应的贡献按照静力校正技术求得。研究表明,改进的计算方法在没有显著增加计算量的同时,通过近似考虑高阶振型的影响,有效地提高了计算的精度。

X波段双线偏振雷达不同衰减订正方法对比及其对降水估测影响研究

文中分析了X波段双线偏振雷达衰减订正各种方法的特点,考虑到差传播相移率(KDP)作为衰减订正的一种有效途径,以及由于KDP值较小,数据质量不稳定,往往导致订正误差较大,因此提出了同时利用水平反射率因子ZH与KDP进行衰减订正的ZH-KDP综合法。基于同样的考虑,在随后利用ZH、KDP进行降水估测时,提出了ZH-KDP-R综合估测方法。利用中国科学院寒区旱区环境与工程研究所和成都锦江电子系统工程有限公司,在研制3.2cm波长同时收发式多普勒偏振天气雷达过程中,2005年8月在平凉外场试验取得的一批观测资料,对提出的衰减订正综合法及降水估测综合法的效果进行了分析检验,结果表明,ZH-KDP综合法对ZH、ZDR有稳定的订正效果,并且订正速度快,能够达到实时运行的要求。2005年8月11日15:08:03—22:05:46,间隔5—12min不等,雷达开机取得了连续的观测资料,通过对这次降水过程的对比分析表明,ZH-KDP-R综合估测法比单因子KDP-R法、Z-R关系法,适用估测的降水强度变化范围广,与自动雨量记的观测结果较为吻合。Z-R关系法中,利用订正后的ZH值,比利用订正前的ZH值,降水估测值与雨量记实测值的误差明显减小,说明衰减订正后的雷达数据质量有明显的改善。

基于信赖域内点法的最优潮流算法

在电力市场环境下 ,诸多问题 (例如实时电价、网络阻塞管理和可用传输能力的计算等 )都需要最优潮流 ( OPF)作为理想的工具。文中基于信赖域的思想提出了求解 OPF的新算法。该算法连续求解线性规划 ( LP)子问题 ,通过信赖域决定线性化步长的选取 ,由多步中心校正原—对偶内点法求解信赖域 LP子问题 ,并采用了一个物理策略以改善 OPF算法的稳定性。对国外一个 662节点实际电力系统进行了数值计算 ,结果表明该算法是快速、鲁棒的 。

二参数Weibull分布在风能资源参数长年代订正中的应用探讨

选择代表平原、丘陵和山区的6个气象站分别作为参证站和订正站,采用二参数Weibull分布法和线性回归法进行30 a订正效果检验,结果表明:短期资料进行风电场风能资源评估,误差较大;二参数Weibull分布法适宜不同地形风能资源参数长年代平均订正,年平均风功率密度的订正效果更好;线性回归法适宜于订正站和参证站线性相关性较好的长年代平均订正;使用2 a以上的观测资料,订正效果较1 a资料有所提高。