Retrieving documents by plausible inference: An experimental study

Choosing an appropriate document representation and search strategy for document retrieval has been largely guided by achieving good average performance instead of optimizing the results for each individual query. A model of retrieval based on plausible inference gives us a different perspective and suggests that techniques should be found for combining multiple sources of evidence (or search strategies) into an overall assessment of a document's relevance, rather than attempting to pick a single strategy. In this paper, we outline our approach to plausible inference for retrieval and describe some experiments designed to test this approach. The experiments use a simple spreading activation search to implement the plausible inference process. The results show that combining term-based, nearest-neighbor, and citation evidence can give significant effectiveness improvements.     

一类广义隐马尔科夫模型的建模与参数估计

隐马尔科夫模型在很多方面已有广泛应用.讨论了一类更为一般的模型,这类模型由Wojciech Pieczynski首次提出,并且给出了在图像识别中的应用.这里首次给出在离散观测和离散状态下该模型的精确数学描述,其中包括建模、状态估计和参数估计,这些算法都是首次被提出的.     

Fuzzy-logic adaptive variable structure multiple-model algorithm for tracking a high maneuvering target

The conventional interacting multiple model (IMM) algorithm will increase the computational load when applying a large number of models, meanwhile, it cannot yield accurate estimation results with a small number of models. Furthermore, the unknown target acceleration is regarded as an additional process noise to the target model, and its time-varying variance is hard to be approximated. The paper proposes a fuzzy-logic adaptive variable structure multiple model (FAVSMM) algorithm for tracking a high maneuvering target. The algorithm can optimize the model parameters using the model probability and construct an optimal model set quickly, and the fuzzy-logic IMM algorithm included in the FAVSMM algorithm is adopted for states estimation. The simulation results show that the proposed algorithm can match well with the actual target trajectory with less computational complexity and better accuracy.     

Observer-based mean square consensus of nonlinear networked systems under Markov switching communication topologies

This paper aims to investigate the mean square consensus (MSC) problem of a class of nonlinear networked systems subject to directed and stochastic switching communication topologies, where the switching law is determined by an ergodic continuous-time Markov process. The cooperative consensus controller is designed by using an observer-based method. Firstly, for the case with Lur’e nonlinear dynamics, by developing a stochastic Lyapunov function, we show that the MSC under consideration can be realized if the union of the underlying network graphs has a directed spanning tree. It is worth noting that none of the network graphs is required to contain a directed spanning tree. Moreover, we study the MSC problem for networked systems with Lipschitz-type nonlinear dynamics. Finally, a numerical simulation is conducted on multiple Chua’s circuit systems to illustrate the effectiveness of the proposed controllers.     

生境片断化对遗传多样性的影响

由于人类活动造成的生境破碎,对生态系统的影响很大,使片断状生境中的生物因子和非生物因子都发生了一系列变化,生境片断化将物种种群分割为若干个小种群,影响物种的迁入和迁出,基因的流动受阻,遗传变异丧失,加之小种群易于灭绝,结果使种群遗传多样性减少,从而加速物种灭绝的进程。     

Beyond direct neighbourhood effects: higher-order interactions improve modelling and predicting tree survival and growth

It is known that biotic interactions are the key to species coexistence and maintenance of species diversity. Traditional studies focus overwhelmingly on pairwise interactions between organisms, ignoring complex higher-order interactions (HOIs). In this study, we present a novel method of calculating individual-level HOIs for trees, and use this method to test the importance of size- and distance-dependent individual-level HOIs to tree performance in a 25-ha temperate forest dynamic plot. We found that full HOI-inclusive models improved our ability to model and predict the survival and growth of trees, providing empirical evidence that HOIs strongly influence tree performance in this temperate forest. Specifically, assessed HOIs mitigate the competitive direct effects of neighbours on survival and growth of focal trees. Our study lays a foundation for future investigations of the prevalence and relative importance of HOIs in global forests and their impact on species diversity.     

企业负面新闻事件下社交媒体多类型信息竞争演化研究

研究企业负面新闻爆发后社交媒体平台产生的多类型信息的竞争传播规律有助于企业负面新闻的应对。企业负面新闻爆发后社交媒体平台随之产生虚假新闻、不确定性新闻信息及真实新闻信息。以生态学种群理论为基础,引入生物种群竞争Lotka-Volterra模型来刻画三者之间的动态竞争过程,并进行仿真和实证分析。不确定性新闻信息及真实新闻信息对虚假新闻的竞争系数影响虚假新闻的生存状态;三种新闻信息达到平衡状态只与三者之间的竞争系数有关;三种信息传播的拐点受竞争系数、信息扩散率及信息初始值的影响。     

State and unknown input estimation for discrete time multiple model

This paper deals with the state estimation of nonlinear discrete systems described by a multiple model with unknown inputs. The main goal concerns the simultaneous estimation of the system's state and the unknown inputs. This goal is achieved through the design of a multiple observer based on the elimination of the unknown inputs. It is shown that the observer gains are solutions of a set of linear matrix inequalities. After that, an unknown input estimation method is proposed. An academic example and an application dealing with message decoding illustrate the effectiveness of the proposed multiple observer.     

基于云计算的应急决策知识匹配研究

文章基于云模型和云计算原理提出了一种在历史经验数据基础上进行高精度知识匹配的方法,利用知识概念的定性值与经验数据的定量值之间的自然转换,把应急决策知识的匹配过程变成基于云计算的定性规则推理过程,这个推理过程可以得到一定的输出,输出结果即为应急决策知识匹配值。这种应急决策知识匹配方法为应急辅助决策中知识获取过程探索了一条有效的新途径。     

贷款组合中的一个破产模型

本文针对银行贷款组合中的信用风险,提出了贷款组合的盈余过程,得到了有限离散时间下的一个破产模型;并且利用该破产模型推导出单一贷款额结构和多个贷款额结构下的破产概率及其递归公式。此外,本文还探讨了破产概率与风险价值VaR的关系。     

Microfluidic study of the chemotactic response of Escherichia coli to amino acids,signaling molecules and secondary metabolites

Quorum sensing and chemotaxis both affect bacterial behavior on the population level. Chemotaxis shapes the spatial distribution of cells, while quorum sensing realizes a cell-density dependent gene regulation. An interesting question is if these mechanisms interact on some level: Does quorum sensing, a density dependent process, affect cell density itself via chemotaxis? Since quorum sensing often spans across species, such a feedback mechanism may also exist between multiple species. We constructed a microfluidic platform to study these questions. A flow-free, stable linear chemical gradient is formed in our device within a few minutes that makes it suitable for sensitive testing of chemoeffectors: we showed that the amino acid lysine is a weak chemoattractant for Escherichia coli, while arginine is neutral. We studied the effect of quorum sensing signal molecules of Pseudomonas aeruginosa on E. coli chemotaxis. Our results show that N-(3-oxododecanoyl)-homoserine lactone (oxo-C12-HSL) and N-(butryl)-homoserine lactone (C4-HSL) are attractants. Furthermore, we tested the chemoeffector potential of pyocyanin and pyoverdine, secondary metabolites under a quorum sensing control. Pyocyanin is proved to be a weak attractant while pyoverdine are repellent. We demonstrated the usability of the device in co-culturing experiments, where we showed that various factors released by P. aeruginosa affect the dynamic spatial rearrangement of a neighboring E. coli population, while surface adhesion of the cells is also modulated.     

基于分形的树木生长建模方法

针对树木生长建模的复杂性和挑战性,采用分形的方法对树木的生长过程进行建模。根据树木枝干和叶片的自然生长特点,模拟叶片的生长过程,采用分形的算法生成树木的主要枝干,并采用Logistic模型模拟树木的生长过程。通过改变树叶的大小、树的深度、弯曲度以及树的大小等参数实现交互式动态生长模型,能够较为逼真地展现树的生长过程。     

生物文化多样性与西部大开发(英)

中国是世界上生物多样性资源丰富的国家之一。作为全球性生物 巨大多样性"国家,中国具有多种多样的生态系统、植被类型、物种和遗传多样性。中国的植物尤其丰富,30,0 0 0种高等植物产于中国,其中乔、灌木 7,5 0 0种;中国的动物区系同样丰富。据统计已发现有 6,347种脊椎动物(包括 1,2 4 4种鸟类和 3,862种鱼类),特有植物物种多达 1 7,30 0种;特有脊椎动物 667种;中国西部 1 2个省、市、自治区,包括甘肃、贵州、陕西、四川、青海、云南 6省,广西壮族自治区、内蒙古自治区、宁夏回族自治区、新疆维吾尔族自治区和西藏自治区等 5个自治区以及重庆市。土地面积 6 98万km2 ,约占国土总面积的70 %;有全国 75 %的植物物种数和动物物种数。中国西部省区人口总数为 4 0 5亿,其中少数民族人口占相当比重。多民族文化状态造就了中国西部省区成为独特的生物 文化多样性地区;另一方面,中国西部省区面临农村贫困、自然资源与环境的退化和少数民族依然处于边缘状态的现实。本文讨论了中国西部省区的生物与文化多样性及其在经济发展方面的潜力。急需保护该地区的自然和文化,以达到可持续发展的目的。     

生物文化多样性与西部大开发

中国是世界上生物多样性资源丰富的国家之一.作为全球性生物"巨大多样性"国家,中国具有多种多样的生态系统、植被类型、物种和遗传多样性.中国的植物尤其丰富,30,000种高等植物产于中国,其中乔、灌木7,500种;中国的动物区系同样丰富.据统计已发现有6,347种脊椎动物(包括1,244种鸟类和3,862种鱼类),特有植物物种多达17,300种;特有脊椎动物667种;中国西部12个省、市、自治区,包括甘肃、贵州、陕西、四川、青海、云南6省,广西壮族自治区、内蒙古自治区、宁夏回族自治区、新疆维吾尔族自治区和西藏自治区等5个自治区以及重庆市. 土地面积6.98万km2, 约占国土总面积的70%; 有全国75%的植物物种数和动物物种数.中国西部省区人口总数为4.05亿,其中少数民族人口占相当比重.多民族文化状态造就了中国西部省区成为独特的生物-文化多样性地区;另一方面,中国西部省区面临农村贫困、自然资源与环境的退化和少数民族依然处于边缘状态的现实.本文讨论了中国西部省区的生物与文化多样性及其在经济发展方面的潜力.急需保护该地区的自然和文化,以达到可持续发展的目的.     

汽车排气系统包络计算与运动干涉分析

汽车排气系统往往由于其设计不当而在某些工况下与车身或车身附件发生干涉,排气系统的运动包络面包含了汽车在极限工况下排气系统的运动轨迹,可得出排气系统与车身及其附件的干涉部位,从而作出改进。文章结合MSC/PATRAN和MSC/ADAMS,以某轿车排气系统为例,由PATRAN建立排气系统柔性体模型,再由ADAMS建立刚弹性耦合模型计算其运动轨迹,解决了该轿车排气系统与隔热板之间的运动干涉问题。     

Knowledge diffusion models – perspectives of gene evolution and population dynamics

Knowledge management has become a popular issue in both the practical and academic fields recently, and is concerned with the processes of knowledge creation, knowledge diffusion and knowledge usage of both intra-organization and inter-organizations. In this paper, we limit the topic of knowledge management to the process of knowledge diffusion. Two knowledge diffusion models distinguished by the degree of involvement of the organizational members are proposed according to the perspectives of gene evolution and population dynamics. These models of knowledge diffusion propose an organic view for realizing the process of knowledge diffusion and insights into how to improve the process of efficient knowledge diffusion based on the evolution of species.     

Distributed state estimation and fault diagnosis using reduced sensitivity to neighbor estimates with application to building control

This paper proposes solutions that reduce the inaccuracy of distributed state estimation and consequent performance deterioration of distributed model predictive control caused by faults and inaccurate models. A distributed state estimation method for large-scale systems is introduced. A local state estimation approach considers the uncertainty of neighbor estimates, which can improve the state estimation accuracy, whereas it keeps a low network communication burden. The method also incorporates the uncertainty of model parameters which improves the performance when using simplified models. The proposed method is extended with multiple models and estimates the probability of nominal and fault behavior models, which creates a distributed fault detection and diagnosis method. An example with application to the building heating control demonstrates that the proposed algorithm provides accurate state estimates to a controller and detects local or global faults while using simplified models.     

基于多主体的工程项目组合决策模型研究

为了保证工程项目组合决策流程的顺利实施,将多主体系统应用于决策流程中,构建了基于多主体的工程项目组合决策流程模型。将具有自适应能力的决策主体作为模型的核心单元,设计了决策主体的逻辑结构和行为推理算法,并将工程项目组合决策流程划分为企业战略评定、单个项目评价、项目组合选择优化、项目组合执行控制以及项目组合调整5个阶段,分析了每个阶段的具体功能。最后通过模型在某建筑企业的具体应用证明了其有效性。     

When humans are the exception: cross-species databases at the interface of biological and clinical research

Cross-species comparison has long been regarded as a stepping-stone for medical research, enabling the discovery and testing of prospective treatments before they undergo clinical trial on humans. Post-genomic medicine has made cross-species comparison crucial in another respect: the 'community databases' developed to collect and disseminate data on model organisms are now often used as a template for the dissemination of data on humans and as a tool for comparing results of medical significance across the human-animal boundary. This paper identifies and discusses four key problems encountered by database curators when integrating human and non-human data within the same database: (1) picking criteria for what counts as reliable evidence, (2) selecting metadata, (3) standardising and describing research materials and (4) choosing nomenclature to classify data. An analysis of these hurdles reveals epistemic disagreement and controversies underlying cross-species comparisons, which in turn highlight important differences in the experimental cultures of biologists and clinicians trying to make sense of these data. By considering database development through the eyes of curators, this study casts new light on the complex conjunctions of biological and clinical practice, model organisms and human subjects, and material and virtual sources of evidence--thus emphasizing the fragmented, localized and inherently translational nature of biomedicine.     

内容分析的概念框架新探

克里本道夫于上世纪60年代末提出内容分析的概念框架，概念框架从内容分析中提炼出文本、研究问题、情境、分析构念、推论、验证依据等重要因素，这些因素彼此间紧密联系，实现了内容分析从本文推论到文本外特征或现象的飞越。同时。克里本道夫的概念模型对情境的强调，对于认识内容分析的关键问题、论述内容分析中定量与定性的关系具有重要作用。对于从方法论的视角审视内容分析，克里本道夫的概念模型也奠定了内容分析理论方法论的基础。