Dynamical optimization using reduced order models: A method to guarantee performance

Many methods employed for the modeling, analysis, and control of dynamical systems are based on underlying optimization schemes, e.g., parameter estimation and model predictive control. For the popular single and multiple shooting optimization approaches, in each optimization step one or more simulations of the commonly high-dimensional dynamical systems are required. This numerical simulation is frequently the biggest bottleneck concerning the computational effort.In this work, systems described by parameter dependent linear ordinary differential equations (ODEs) are considered. We propose a novel approach employing model order reduction, improved a posteriori bounds for the reduction error, and nonlinear optimization via vertex enumeration. By combining these methods an upper bound for the objective function value of the full order model can be computed efficiently by simulating only the reduced order model. Therefore, the reduced order model can be utilized to minimize an upper bound of the true objective function, ensuring a guaranteed objective function value while reducing the computational effort.The approach is illustrated by studying the parameter estimation problem for a model of an isothermal continuous tube reactor. For this system we derive an asymptotically stable reduction error estimator and analyze the speed-up of the optimization.     

ESC: an efficient error-based stopping criterion for kriging-based reliability analysis methods

The ever-increasing complexity of numerical models and associated computational demands have challenged classical reliability analysis methods. Surrogate model-based reliability analysis techniques, and in particular those using kriging meta-model, have gained considerable attention recently for their ability to achieve high accuracy and computational efficiency. However, existing stopping criteria, which are used to terminate the training of surrogate models, do not directly relate to the error in estimated failure probabilities. This limitation can lead to high computational demands because of unnecessary calls to costly performance functions (e.g., involving finite element models) or potentially inaccurate estimates of failure probability due to premature termination of the training process. Here, we propose the error-based stopping criterion (ESC) to address these limitations. First, it is shown that the total number of wrong sign estimation of the performance function for candidate design samples by kriging, S, follows a Poisson binomial distribution. This finding is subsequently used to estimate the lower and upper bounds of S for a given confidence level for sets of candidate design samples classified by kriging as safe and unsafe. An upper bound of error of the estimated failure probability is subsequently derived according to the probabilistic properties of Poisson binomial distribution. The proposed upper bound is implemented in the kriging-based reliability analysis method as the stopping criterion. The efficiency and robustness of ESC are investigated here using five benchmark reliability analysis problems. Results indicate that the proposed method achieves the set accuracy target and substantially reduces the computational demand, in some cases by over 50%.

     

Personness estimation for real-time human detection on mobile devices

One aim of detection proposal methods is to reduce the computational overhead of object detection. However, most of the existing methods have significant computational overhead for real-time detection on mobile devices. A fast and accurate proposal method of human detection called personness estimation is proposed, which facilitates real-time human detection on mobile devices and can be effectively integrated into part-based detection, achieving high detection performance at a low computational cost. Our work is based on two observations: (i) normed gradients, which are designed for generic objectness estimation, effectively generate high-quality detection proposals for the person category; (ii) fusing the normed gradients with color attributes improves the performance of proposal generation for human detection. Thus, the candidate windows generated by the personness estimation will very likely contain human subjects. The human detection is then guided by the candidate windows, offering high detection performance even when the detection task terminates prior to completion. This interruptible detection scheme, called anytime detection, enables real-time human detection on mobile devices. Furthermore, we introduce a new evaluation methodology called time-recall curves to practically evaluate our approach. The applicability of our proposed method is demonstrated in extensive experiments on a publicly available dataset and a real mobile device, facilitating acquisition and enhancement of portrait photographs (e.g. selfie) on widespread mobile platforms.     

基于R-Tree的空间连接代价模型的改进

对基于R-Tree的空间连接代价模型进行了探讨，主要研究了HUANG Y W提出的空间连接代价模型。利用最优，最差选择策略降低该算法的时间复杂度，对基于缓冲区的代价模型提出了改进后的评估公式，通过实验验证了改进后的模型比原模型提高了评估的精确度。     

Makespan minimization on single batch-processing machine via ant colony optimization

This paper investigates the problem of minimizing makespan on a single batch-processing machine, and the machine can process multiple jobs simultaneously. Each job is characterized by release time, processing time, and job size. We established a mixed integer programming model and proposed a valid lower bound for this problem. By introducing a definition of waste and idle space (WIS), this problem is proven to be equivalent to minimizing the WIS for the schedule. Since the problem is NP-hard, we proposed a heuristic and an ant colony optimization (ACO) algorithm based on the theorems presented. A candidate list strategy and a new method to construct heuristic information were introduced for the ACO approach to achieve a satisfactory solution in a reasonable computational time. Through extensive computational experiments, appropriate ACO parameter values were chosen and the effectiveness of the proposed algorithms was evaluated by solution quality and run time. The results showed that the ACO algorithm combined with the candidate list was more robust and consistently outperformed genetic algorithm (GA), CPLEX, and the other two heuristics, especially for large job instances.     

Cooperative private searching in clouds

With the increasing popularity of cloud computing, there is increased motivation to outsource data services to the cloud to save money. An important problem in such an environment is to protect user privacy while querying data from the cloud. To address this problem, researchers have proposed several techniques. However, existing techniques incur heavy computational and bandwidth related costs, which will be unacceptable to users. In this paper, we propose a cooperative private searching (COPS) protocol that provides the same privacy protections as prior protocols, but with much lower overhead. Our protocol allows multiple users to combine their queries to reduce the querying cost while protecting their privacy. Extensive evaluations have been conducted on both analytical models and on a real cloud environment to examine the effectiveness of our protocol. Our simulation results show that the proposed protocol reduces computational costs by 80% and bandwidth cost by 37%, even when only five users query data.     

H.264/AVC中基于决策树的P帧快速模式选择（HHME2013第61号论文）

目的：H.264/AVC帧间预测编码需要对所有可能编码模式计算并比较率失真代价,众多的模式类型导致了P帧编码的计算复杂度非常高。本文提出了一种针对P帧的基于决策树的快速选择候选模式算法。方法：在对宏块进行16×16的帧间运动估计后,首先根据残差宏块中4×4全零系数块个数对部分宏块直接选择出候选模式;然后使用16个4×4块的SATD值,采用决策树分类方法对其余宏块选择候选模式。结果：由于只需对候选模式进行编码,因此有效降低了编码器的计算复杂度。实验结果表明,与原始全搜索编码算法相比,该算法对不同运动程度的视频序列获得了较一致的编码时间节省,同时平均峰值信噪比的损失和平均比特率的增加均较少。结论：本文提出了一种新的P帧帧间预测候选模式选择算法,根据帧间运动估计后的残差宏块信息,采用决策树方法对候选模式集进行分类。实验结果表明,该算法能在保证视频编码质量的前提下,有效地降低编码过程中的计算量,缩短编码时间。     

带宽受限下的基于一致性的分布式融合估计器

研究带宽受限下的基于一致性的分布式融合估计问题. 建立以一致性滤波增益为决策变量, 以所有传感器有限时域下融合估计误差协方差矩阵的迹的和为代价函数的优化问题. 在给定一致性权重的前提下, 给出使得系统融合估计误差在无噪声时渐近稳定的一致性滤波增益存在的充分条件, 并通过最小化代价函数的上界得到一组次优的一致性滤波增益. 最后通过算例仿真验证了所提出方法的有效性.     

鲁棒最小二乘支持向量回归机

针对最小二乘支持向量回归机(LS-SVR)对异常值较敏感的问题,通过设置异常值所造成的损失上界,提出一种非凸的Ramp损失函数。该损失函数导致相应的优化问题的非凸性,利用凹凸过程(CCCP)将非凸优化问题转化为凸优化问题。给出Newton算法进行求解并分析了算法的计算复杂度。数据集测试的结果表明,与最小二乘支持向量回归机相比,该算法对异常值具有较强的鲁棒性,获得了更优的泛化能力,同时在运行时间上也具有明显优势。     

Reliable LQ fuzzy control for continuous-time nonlinear systems with actuator faults

This paper deals with the reliable linear quadratic (LQ) fuzzy control problem for continuous-time nonlinear systems with actuator faults. The Takagi-Sugeno (T-S) fuzzy model is employed to represent a nonlinear system. By using multiple Lyapunov functions, an improved linear matrix inequality (LMI) method for the design of reliable LQ fuzzy controllers is investigated, which reduces the conservatism of using a single Lyapunov function. The different upper bounds on the LQ performance cost function for the normal and different actuator fault cases are provided. A suboptimal reliable LQ fuzzy controller is given by means of an LMI optimization procedure, which can not only guarantee the stability of the closed-loop overall fuzzy system for all cases, but also provide an optimized upper bound on a weighted average LQ performance cost function. Finally, numerical simulations on the chaotic Lorenz system are given to illustrate the application of the proposed design method.     

具有传感器增益退化的不确定系统融合估计器

研究具有传感器增益退化、模型不确定性的多传感器融合估计问题, 其中传感器增益退化现象描述为统计特性已知的随机变量, 模型的不确定性描述为系统矩阵受到随机扰动. 设计一种局部无偏估计器结构, 并建立以局部估计器增益为决策变量、以有限时域下融合估计误差为代价函数的优化问题. 在给出标量融合权重时, 考虑到求得最优的局部估计器增益的解析形式较为困难, 通过最小化代价函数的上界得到一组次优的局部估计器增益. 最后通过算例仿真表明了所设计融合估计器的有效性.

     

An efficient multi-label support vector machine with a zero label

Existing multi-label support vector machine (Rank-SVM) has an extremely high computational complexity and lacks an intrinsic zero point to determine relevant labels. In this paper, we propose a novel support vector machine for multi-label classification through both simplifying Rank-SVM and adding a zero label, resulting into a quadratic programming problem in which each class has an independent equality constraint. When Frank-Wolfe method is used to solve our quadratic programming problem iteratively, our entire linear programming problem of each step is divided into a series of sub-problems, which dramatically reduces computational cost. It is illustrated that for famous Yeast data set our training procedure runs about 12 times faster than Rank-SVM does under C++ environment. Experiments from five benchmark data sets show that our method is a powerful candidate for multi-label classification, compared with five state-of-the-art multi-label classification techniques.     

多种群伪正态分布估计算法

为了提高基于正态分布模型的分布估计算法子代候选解的质量,防止早熟收敛,文中提出多种群伪正态分布估计算法.首先,采用佳点集方法进行种群初始化,将种群分为3个子群.然后,采用样本重心取代样本均值的方式,获得伪正态分布模型.最后,融合种群与子群伪正态分布模型,得到子群进化的概率模型.23个基准函数的对比测试表明,文中算法在求解质量和收敛速度上较优.针对多约束条件下的并行装配优化问题,提出工序池、员工池、罚函数等措施,将具有工序约束和人员约束的离散组合优化问题转化为无约束的多种群伪正态分布估计优化问题.工程应用结果表明,只需要将候选解的无限集合修正为有限集合,文中算法可方便地用于离散组合优化问题的快速求解.     

Assessment of a New Three-Group Software Quality Classification Technique: An Empirical Case Study

The primary aim of risk-based software quality classification models is to detect, prior to testing or operations, components that are most-likely to be of high-risk. Their practical usage as quality assurance tools is gauged by the prediction-accuracy and cost-effective aspects of the models. Classifying modules into two risk groups is the more commonly practiced trend. Such models assume that all modules predicted as high-risk will be subjected to quality improvements. Due to the always-limited reliability improvement resources and the variability of the quality risk-factor, a more focused classification model may be desired to achieve cost-effective software quality assurance goals. In such cases, calibrating a three-group (high-risk, medium-risk, and low-risk) classification model is more rewarding. We present an innovative method that circumvents the complexities, computational overhead, and difficulties involved in calibrating pure or direct three-group classification models. With the application of the proposed method, practitioners can utilize an existing two-group classification algorithm thrice in order to yield the three risk-based classes. An empirical approach is taken to investigate the effectiveness and validity of the proposed technique. Some commonly used classification techniques are studied to demonstrate the proposed methodology. They include, the C4.5 decision tree algorithm, discriminant analysis, and case-based reasoning. For the first two, we compare the three-group model calibrated using the respective techniques with the one built by applying the proposed method. Any two-group classification technique can be employed by the proposed method, including those that do not provide a direct three-group classification model, e.x., logistic regression and certain binary classification trees, such as CART. Based on a case study of a large-scale industrial software system, it is observed that the proposed method yielded promising results. For a given classification technique, the expected cost of misclassification of the proposed three-group models were significantly better (generally) when compared to the techniques direct three-group model. In addition, the proposed method is also evaluated against an alternate indirect three-group classification method.     

A data mining approach to dynamic multiple responses in Taguchi experimental design

To simultaneously optimize the parameter robust design of dynamic multiple responses is difficult due to product complexity; however, the design is what determines most of the production time, cost, and quality. Although several methods tackling this problem have been published, they have proven unable to effectively resolve the situation if a system has continuous control factors. This work proposes a data mining approach, consisting of four stages based on artificial neural networks (ANN), desirability functions, and a simulated annealing (SA) algorithm to resolve the problems of dynamic parameter design with multiple responses. An ANN is employed to build a system’s response function model. Desirability functions are used to evaluate the performance measures of multiple responses. A SA algorithm is applied to obtain the best factor settings through the response function model. By using the proposed approach, the obtained best factor settings can be any values within their upper and lower bounds so that the system’s multiple responses have the least sensitivity to noise factors along the magnitude of the signal factor. An example from the literature is illustrated to confirm the feasibility and effectiveness of the proposed approach.     

基于轻量型卷积神经网络的交通标志识别方法

交通标志识别设备的功耗和硬件性能较低,而现有卷积神经网络模型内存占用高、训练速度慢、计算开销大,无法应用于识别设备.针对此问题,为降低模型存储,提升训练速度,引入深度可分离卷积和混洗分组卷积并与极限学习机相结合,提出两种轻量型卷积神经网络模型:DSC-ELM模型和SGC-ELM模型.模型使用轻量化卷积神经网络提取特征后,将特征送入极限学习机进行分类,解决了卷积神经网络全连接层参数训练慢的问题.新模型结合了轻量型卷积神经网络模型内存占用低、提取特征质量好以及ELM的泛化性好、训练速度快的优点.实验结果表明.与其他模型相比,该混合模型能够更加快速准确地完成交通标志识别任务.     

An extended one-versus-rest support vector machine for multi-label classification

Hybrid strategy, which generalizes a specific single-label algorithm while one or two data decomposition tricks are applied implicitly or explicitly, has become an effective and efficient tool to design and implement various multi-label classification algorithms. In this paper, we extend traditional binary support vector machine by introducing an approximate ranking loss as its empirical loss term to build a novel support vector machine for multi-label classification, resulting into a quadratic programming problem with different upper bounds of variables to characterize label correlation of individual instance. Further, our optimization problem can be solved via combining one-versus-rest data decomposition trick with modified binary support vector machine, which dramatically reduces computational cost. Experimental study on ten multi-label data sets illustrates that our method is a powerful candidate for multi-label classification, compared with four state-of-the-art multi-label classification approaches.     

An algorithm for cooperative task allocation in scalable,constrained multiple robot systems

The current trends in the robotics field have led to the development of large-scale multiple robot systems, and they are deployed for complex missions. The robots in the system can communicate and interact with each other for resource sharing and task processing. Many of such systems fail despite the availability of necessary resources. The major reason for this is their poor coordination mechanism. Task planning, which involves task decomposition and task allocation, is paramount in the design of coordination and cooperation strategies of multiple robot systems. Task allocation mechanism allocates the task in a mission to the robots by maximizing the overall expected performance, and thereby reducing the total allocation cost for the team. In this paper, we formulate a heuristic search-based task allocation algorithm for the task processing in heterogeneous multiple robot system, by maximizing the efficiency in terms of both communication and processing cost. We assume a set of decomposed tasks of a mission, which needs to be allocated to the robots. The near-optimal allocation schemes are found using the proposed peer structure algorithm for the given problem, where the number of the tasks is more than the robots present in the system. The cost function is the summation of static overhead cost of robots, assignment cost, and the communication cost between the dependent tasks, if they are assigned to different robots. Experiments are performed to verify the effectiveness of the algorithm by comparing it with the existing methods in terms of computational time and quality of solution. The experimental results show that the proposed algorithm performs the best under different problem scales. This proves that the algorithm can be scaled for larger system and it can work for dynamic multiple robot system.     

An EM-like algorithm for the semiparametric accelerated failure time gamma frailty model

The frailty model is one of the most popular models used to analyze clustered failure time data, and the frailty term in the model is used to assess associations in each cluster. The frailty model based on the semiparametric accelerated failure time model attracts less attention than the one based on the proportional hazards model due to its computational difficulties. In this paper, we develop a new estimation method for the semiparametric accelerated failure time gamma frailty model based on the EM-like algorithm and the rank-like estimation method. The proposed method is compared with the existing EM algorithm, which incorporates the M-estimator in the M-step. From simulation studies, we show that the rank-like estimation method in the M-like step simplifies the estimation procedure and reduces the computational time by the linear programming approach. With respect to the accuracy of estimates and length of computational time, the proposed method outperforms the existing estimation methods. For illustration, we apply the proposed method to the data set of sublingual nitroglycerin and oral isosorbide dinitrate on angina pectoris of coronary heart disease patients.     

Block-matching algorithm based on harmony search optimization for motion estimation

Motion estimation is one of the major problems in developing video coding applications. Among all motion estimation approaches, Block-matching (BM) algorithms are the most popular methods due to their effectiveness and simplicity for both software and hardware implementations. A BM approach assumes that the movement of pixels within a defined region of the current frame can be modeled as a translation of pixels contained in the previous frame. In this procedure, the motion vector is obtained by minimizing a certain matching metric that is produced for the current frame over a determined search window from the previous frame. Unfortunately, the evaluation of such matching measurement is computationally expensive and represents the most consuming operation in the BM process. Therefore, BM motion estimation can be viewed as an optimization problem whose goal is to find the best-matching block within a search space. The simplest available BM method is the Full Search Algorithm (FSA) which finds the most accurate motion vector through an exhaustive computation of all the elements of the search space. Recently, several fast BM algorithms have been proposed to reduce the search positions by calculating only a fixed subset of motion vectors despite lowering its accuracy. On the other hand, the Harmony Search (HS) algorithm is a population-based optimization method that is inspired by the music improvisation process in which a musician searches for harmony and continues to polish the pitches to obtain a better harmony. In this paper, a new BM algorithm that combines HS with a fitness approximation model is proposed. The approach uses motion vectors belonging to the search window as potential solutions. A fitness function evaluates the matching quality of each motion vector candidate. In order to save computational time, the approach incorporates a fitness calculation strategy to decide which motion vectors can be only estimated or actually evaluated. Guided by the values of such fitness calculation strategy, the set of motion vectors is evolved through HS operators until the best possible motion vector is identified. The proposed method has been compared to other BM algorithms in terms of velocity and coding quality. Experimental results demonstrate that the proposed algorithm exhibits the best balance between coding efficiency and computational complexity.