A multi-document summarization system based on statistics and linguistic treatment

The massive quantity of data available today in the Internet has reached such a huge volume that it has become humanly unfeasible to efficiently sieve useful information from it. One solution to this problem is offered by using text summarization techniques. Text summarization, the process of automatically creating a shorter version of one or more text documents, is an important way of finding relevant information in large text libraries or in the Internet. This paper presents a multi-document summarization system that concisely extracts the main aspects of a set of documents, trying to avoid the typical problems of this type of summarization: information redundancy and diversity. Such a purpose is achieved through a new sentence clustering algorithm based on a graph model that makes use of statistic similarities and linguistic treatment. The DUC 2002 dataset was used to assess the performance of the proposed system, surpassing DUC competitors by a 50% margin of f-measure, in the best case.     

Hybrid genetic algorithm with adaptive local search scheme

This paper proposes a hybrid genetic algorithm (a-hGA) with adaptive local search scheme. For designing the a-hGA, a local search technique is incorporated in the loop of genetic algorithm (GA), and whether or not the local search technique is used in the GA is automatically determined by the adaptive local search scheme. Two modes of adaptive local search schemes are developed in this paper. First mode is to use the conditional local search method that can measure the average fitness values obtained from the continuous two generations of the a-hGA, while second one is to apply the similarity coefficient method that can measure a similarity among the individuals of the population of the a-hGA. These two adaptive local search schemes are included in the a-hGA loop, respectively. Therefore, the a-hGA can be divided into two types: a-hGA1 and a-hGA2. To prove the efficiency of the a-hGA1 and a-hGA2, a canonical GA (cGA) and a hybrid GA (hGA) with local search technique and without any adaptive local search scheme are also presented. In numerical example, all the algorithms (cGA, hGA, a-hGA1 and a-hGA2) are tested and analyzed. Finally, the efficiency of the proposed a-hGA1 and a-hGA2 is proved by various measures of performance.     

基于局部搜索和遗传算法的激光切割路径优化

为了缩短激光加工时间,提高加工效率,提出了一种新的局部搜索法与遗传算法相结合的激光切割路径优化算法。该算法从加工轮廓中提取节点,通过局部搜索法对节点进行局部路径优化,再运用的遗传算法求得近似最优解,遗传算法中的选择算子改进为基于相对适应度的轮盘赌选择算子。详细介绍了算法的原理及实现,通过编程仿真证明该算法与传统的遗传算法相比具有良好的优化效果,可明显缩短加工路径,减少加工时间,提高加工效率。     

一种结合Tabu 搜索的非线性遗传算法研究

利用Tabu搜索的强大局部搜索性能,提出一种新的非线性遗传算法．该方法将Tabu搜索技术内嵌于遗传算子中,构造了基于Tabu搜索的非线性杂交及变异算子,它能有效地提高算子的局部搜索能力,通过实例仿真证明了该算法的有效性;同时,以“平均截止代数”和“平均截止代数分布熵”作为评价指标,对该方法的优化效率进行研究,定量评价了该方法的优化效率,通过与实数遗传算法进行比较,说明了该方法的优化效率高于实数遗传算法．     

Superior solution guided particle swarm optimization combined with local search techniques

Particle swarm optimization (PSO) is an evolutionary algorithm known for its simplicity and effectiveness in solving various optimization problems. PSO should have strong yet balanced exploration and exploitation capabilities to enhance its performance. A superior solution guided PSO (SSG-PSO) framework integrated with an individual level based mutation operator and different local search techniques is proposed in this study. In SSG-PSO, a collection of superior solutions is maintained and updated with the evolutionary process, such that each particle can comprehensively learn from the recorded superior solutions. In addition, to maintain the diversity of the particle swarm, SSG-PSO is combined with an individual level based mutation operator, which will be invoked when a particle is trapped in a local optimum (determined by the fitness and position states of the particle), thereby improving the adaptation and flexibility of each individual particle. Moreover, two gradient-based local search techniques, namely, the Broyden–Fletcher–Goldfarb–Shanno (BFGS) and Davidon–Fletcher–Powell (DFP) Quasi–Newton methods, and two derivative-free local search techniques, namely, pattern search and Nelder–Mead simplex search, are incorporated into SSG-PSO. The performances of SSG-PSO and that of its local search enhanced variants are extensively and comparatively studied on a suit of benchmark optimization functions.     

基于指针网络的抽取生成式摘要生成模型

作为自然语言处理中的热点问题,摘要生成具有重要的研究意义。基于Seq2Seq模型的生成式摘要模型取得了良好的效果,然而抽取式的方法具有挖掘有效特征并抽取文章重要句子的潜力,因此如何利用抽取式方法来改进生成式方法是一个较好的研究方向。鉴于此,提出了融合生成式和抽取式方法的模型。首先,使用TextRank算法并融合主题相似度来抽取文章中有重要意义的句子。然后,设计了融合抽取信息语义的基于Seq2Seq模型的生成式框架来实现摘要生成任务;同时,引入指针网络解决模型训练中的未登录词（OOV）问题。综合以上步骤得到最终摘要,并在CNN/Daily Mail数据集上进行验证。结果表明在ROUGE-1、ROUGE-2和ROUGE-L三个指标上所提模型比传统TextRank算法均有所提升,同时也验证了融合抽取式和生成式方法在摘要生成领域中的有效性。     

Iterated local search based on multi-type perturbation for single-machine earliness/tardiness scheduling

We propose an iterated local search based on a multi-type perturbation (ILS-MP) approach for single-machine scheduling to minimize the sum of linear earliness and quadratic tardiness penalties. The multi-type perturbation mechanism in ILS-MP probabilistically combines three types of perturbation strategies, namely tabu-based perturbation, construction-based perturbation, and random perturbation. Despite its simplicity, experimental results on a wide set of commonly used benchmark instances show that ILS-MP performs favourably in comparison with the current best approaches in the literature.     

具有混沌局部搜索策略的双种群遗传算法*

为提高遗传算法的局部和全局搜索能力,提出了一种具有混沌局部搜索策略的双种群遗传算法（CLSDPGA）。CLSDPGA中,一个作为探测种群,另一个作为开发种群。两个种群按照不同交叉概率和变异概率进行进化,每个种群每进化一代后就对其最优解进行混沌局部搜索。若搜索到更优的解,则取代原最优解直至搜索到预设的混沌次数,同时两个种群之间每10代进行一次移民操作。六个Benchmark函数的实验结果证明,CLSDPGA比另一种自适应局部搜索策略的遗传算法（a-hGA2）具有更好的寻优能力。     

Memetic Algorithm based on Improved Inver-over operator and Lin-Kernighan local search for the Euclidean traveling salesman problem

In this study, an Improved Inver-over operator is proposed to solve the Euclidean traveling salesman problem (TSP) problem. The Improved Inver-over operator is tested on 14 different TSP examples selected from TSPLIB. The application of the Improved Inver-over operator gives much more effective results regarding to the best and average error values than the Basic Inver-over operator. Then an effective Memetic Algorithm based on Improved Inver-over operator and Lin-Kernighan local search is implemented. To speed up the convergence capability of the presented algorithm, a restart technique is employed. We evaluate the proposed algorithm based on standard TSP test problems and show that the proposed algorithm performs better than other Memetic Algorithm in terms of solution quality and computational effort.     

Medical image reconstruction using a multi-objective genetic local search algorithm

Image reconstruction from projections is a key problem in medical image analysis. In this paper, we cast image reconstruction from projections as a multi-objective problem. It is essential to choose some proper objective functions of the problem. We choose the square error, smoothness of the reconstructed image, and the maximum entropy as our objective functions of the problem. Then we introduce a hybrid algorithm comprising of multi-objective genetic and local search algorithms to reconstruct the image. Our algorithm has remarkable global performance. Our experiments show that we can get different results when we give different weights to different objective functions. We can also control the noise by giving different weights on different objective function. At the same time, we can adjust the parameter to let it have good local performance. Though the computation demands of the hybrid algorithm tends to be larger because of the random search of the GA, it is really a common feature of the global optimization method. Our results show that the hybrid algorithm is a more effective than the conventional method. We think our method is very promising for the medical imaging field.     

基于Powell局部搜索策略的全局优化布谷鸟算法

为了解决布谷鸟搜索算法后期收敛速度慢、求解精度不高、易陷入局部最优等缺陷,提出了一种基于Powell局部搜索策略的全局优化布谷鸟搜索算法.算法将布谷鸟全局搜索能力与Powell方法的局部寻优性能有机地结合,并根据适应度值逐步构建精英种群候选解池在迭代后期牵引Powell搜索的局部优化,在保证求解速度、尽可能找到全局极值点的同时提高算法的求解精度.对52个典型测试函数实验结果表明,该算法相比于传统的布谷鸟搜索算法不仅寻优精度和寻优率有所提高,并且适应能力强、鲁棒性好,与最新提出的其他改进算法相比也具有一定的竞争优势.     

一种混合局部搜索算法的嵌套分区算法

提出了一种混合多种局部搜索算法的嵌套分区算法用于求解中小规模旅行商问题.该算法使用加权抽样法产生初始最可能域,用带约束的3-opt局部搜索算法搜索每个子域的最优解,然后对Lin-Kemighan算法进行了改进,并且用改进的Lin-Kemighan算法搜索每个裙域的最优解,最后通过实验分析法确定了子域和裙域最优的抽样个数及初始最可能域的长度.对TSPLIB中15个问题实例的仿真结果表明,所提出的混合局部搜索算法的改进嵌套分区算法在求解旅行商问题时可以获得高质量的解.     

基于混沌局部搜索算子的人工蜂群算法

在求解函数优化问题时,为了提升人工蜂群算法局部搜索能力,提出了一种新颖的混沌蜂群算法。新算法设计了一种混沌局部搜索算子,并将其嵌入蜂群算法框架中;该算子不仅能够实现在最优食物源周围局部搜索,还能够随着进化代数增加使搜索范围不断缩小。仿真实验结果表明,与人工蜂群算法相比,新算法在Rosenbrock函数上,求解精度和收敛速度明显占优;此外新算法在多模函数Griewank和Rastrigin上,收敛速度明显占优。     

Model-driven visualizations of constraint-based local search

Visualization is often invaluable to understand the behavior of optimization algorithms, identify their bottlenecks or pathological behaviors, and suggest remedial techniques. Yet developing visualizations is often a tedious activity requiring significant time and expertise. This paper presents a framework for the visualization of constraint-based local search (CBLS) algorithms. Given a high-level model and a declarative visualization specification, the CBLS visualizer systematically produces animations to visualize constraints and objectives, violations, and conflicts, as well as the temporal behavior of these measures. The visualization specification is declarative and typically composed of a triple (what,where,how) indicating what to display, where, and with which graphical objects. The visualizer architecture is compositional and extensible. It provides building blocks which can be assembled freely by the user and focuses almost exclusively on static aspects, the dynamic aspects being automated by the use of invariants. The paper highlights various functionalities of the visualizer and describes a blueprint for its implementation.     

A tabu search based memetic algorithm for the max-mean dispersion problem

Given a set V of n elements and a distance matrix ${[d_{\mathit{ij}}]}_{n\times n}$ among elements, the max-mean dispersion problem (MaxMeanDP) consists in selecting a subset M from V such that the mean dispersion (or distance) among the selected elements is maximized. Being a useful model to formulate several relevant applications, MaxMeanDP is known to be NP-hard and thus computationally difficult. In this paper, we present a tabu search based memetic algorithm for MaxMeanDP which relies on solution recombination and local optimization to find high quality solutions. One key contribution is the identification of the fast neighborhood induced by the one-flip operator which takes linear time. Computational experiments on the set of 160 benchmark instances with up to 1000 elements commonly used in the literature show that the proposed algorithm improves or matches the published best known results for all instances in a short computing time, with only one exception, while achieving a high success rate of 100%. In particular, we improve 53 previous best results (new lower bounds) out of the 60 most challenging instances. Results on a set of 40 new large instances with 3000 and 5000 elements are also presented. The key ingredients of the proposed algorithm are investigated to shed light on how they affect the performance of the algorithm.     

局部搜索的音频数据检索

根据多媒体音频数据的特点,提出一种适用于快速音频数据检索的局部搜索数据结构,即局部搜索树(local search tree,LS-tree).在局部搜索树中,分别以音频数据小波变换系数的过零率和平均幅度作为主、次关键码,基于局部范围对作为索引的其他系数进行组织.其次,基于局部搜索树,提出采用小波包最好基小波塔型算法实现音频数据检索.最后,把采用局部搜索树的小波包最好基—小波塔型算法的搜索和基于小波不同级系数的检索方法相比较,结果表明,这种方法对音频数据检索的快速和有效性.     

基于遗传算法和禁忌搜索的混合优化策略

将禁忌搜索和遗传算法相结合,给出了一种求解优化问题的混合策略--禁忌遗传优化算法.该算法一方面为禁忌搜索找到了较好的初始点,减少了调用禁忌搜索的次数,另一方面也可以克服遗传算法爬山能力差的缺点,从而加快了收敛速度,提高了解的质量.通过实例验证了该优化算法的有效性和可靠性,并将其用于网络拥塞控制的研究中,为进一步实施网络拥塞控制提供了一种有效的途径.     

主题信息的中文多文档自动文摘系统

多文档自动文摘能够帮助人们自动、快速地获取信息,使用主题模型构建多文档自动文摘系统是一种新的尝试,其中主题模型采用浅层狄利赫雷分配（LDA）。该模型是一个多层的产生式概率模型,能够检测文档中的主题分布。使用LDA为多文档集合建模,通过计算句子在不同主题上的概率分布之间的相似度作为句子的重要度,并根据句子重要度进行文摘句的抽取。实验结果表明,该方法所得到的文摘性能优于传统的文摘方法。     

基于局部搜索的改进SPEA2算法

由于追求收敛速度与防止陷入局部最优,标准的改进强度Pareto算法(SPEA2)过于注重全局搜索能力,从而导致局部搜索能力不足.为了增强SPEA2算法的局部搜索性能,进而提高算法收敛速度,提出了一种基于局部搜索的改进SPEA2算法.该算法单独设置一个新外部存档集以保存局部搜索后的非支配集,并且改进了交叉算子,加入了部分个体更新策略.将该改进算法与SPEA2算法进行了收敛性能比较实验.仿真实验结果表明,相比于标准算法,改进SPEA2算法不仅可以保证收敛到多目标优化问题的Pareto最优边界,而且在收敛能力上也得到了较好的改善.     

Integrated optimization of inventory-distribution systems by random local search and a genetic algorithm

A new model and its solution procedure for the commodity distribution system consisting of distribution centers and consumer points are discussed. Demand is assumed to be a random variable that obeys a known, stationary probability distribution. An integrated optimization model is built where both the order-up-to-R policy, which is one of the typical inventory policies for periodic review models, and the transportation problem are considered simultaneously. The assignment of consumer points to distribution centers is not fixed. The problem is to determine the target inventory and the transportation quantity in order to minimize the expectation of the sum of inventory related costs and transportation costs. Simulation and linear programming are used to calculate the expected costs, and a random local search method is developed in order to determine the optimum target inventory. A genetic algorithm is also tested and compared with the proposed random local search method. The model and effectiveness of the proposed solution procedure are clarified by computational experiments.