首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
Finding interesting patterns from data is one of the most important problems in data mining and it has been studied actively for more than a decade. However, it is still largely open problem which patterns are interesting and which are not.The problem of detecting the interesting patterns (in a predefined class of patterns) has been attempted to solve by determining quality values for potentially interesting patterns and deciding a pattern to be interesting if its quality value (i.e., the interestingness of the pattern) is higher than a given threshold value. Again, it is very difficult to find a threshold value and a way to determine the quality values such that the collection of patterns with quality values greater than the threshold value would contain almost all truly interesting patterns and only few uninteresting ones.To enable more accurate characterization of interesting patterns, use of constraints to further prune the pattern collection has been proposed. However, most of the constrained pattern discovery research has been focused on structural constraints for the pattern collections and the patterns. We take a complementary approach and focus on constraining the quality values of the patterns.We propose quality value simplifications as a complementary approach to structural constraints on patterns. As a special case of the quality value simplifications, we consider discretizing the quality values. We analyze the worst-case error of certain discretization functions and give efficient discretization algorithms minimizing several loss functions. In addition to that, we show that the discretizations of the quality values can be used to obtain small approximate condensed representations for collections of interesting patterns. We evaluate the proposed condensation approach experimentally using frequent itemsets.  相似文献   

2.
目的 观察淋巴管透明质酸受体1(LYVE-1)的表达和癌周组织中淋巴管的生成情况在甲状腺恶性肿瘤的变化及转 移中的作用。方法 应用免疫组织化学和real-time PCR方法检测45 例甲状腺乳头状癌中央区、癌周边区和正常甲状腺组织中的LYVE-1及其mRNA 表达情况,并计算淋巴管密度(LVD)。结果 甲状腺乳头状癌周边区LVD 高于甲状腺乳头状癌中央区,而正常组织中很少见LYVE-1 阳性的微淋巴管;甲状腺乳头状癌周边区LVD 与淋巴结转移有密切关系(P<0.05)。结论 LYVE-1是一种特异性较高的淋巴管内皮特异性标志物,对淋巴管生成促进甲状腺乳头状癌的淋巴结转移。  相似文献   

3.
4.
Wiener Index of Trees: Theory and Applications   总被引:2,自引:0,他引:2  
The Wiener index W is the sum of distances between all pairs of vertices of a (connected) graph. The paper outlines the results known for W of trees: methods for computation of W and combinatorial expressions for W for various classes of trees, the isomorphism–discriminating power of W, connections between W and the center and centroid of a tree, as well as between W and the Laplacian eigenvalues, results on the Wiener indices of the line graphs of trees, on trees extremal w.r.t. W, and on integers which cannot be Wiener indices of trees. A few conjectures and open problems are mentioned, as well as the applications of W in chemistry, communication theory and elsewhere.  相似文献   

5.
目的对医院出院病人调查表普遍存在的数据缺失进行填补与分析,以保证统计调查表的质量,为医院以及上级卫生部门了解现状,进行预策和决策提供技术支持和质量保证。方法运用SAS9.1,采用多重填补方法Markov Chain Monte Carlo(MCMC)模型对缺失数据进行多次填补并综合分析。结果MCMC填补10次的结果最优。结论(Multiple Imputation)MI方法在解决医院出院病人调查表数据缺失时有优势,发挥空间较大,且填补效率较高。  相似文献   

6.
The effect of cyclone inlet dimensions on the flow pattern and performance   总被引:3,自引:0,他引:3  
The effect of the cyclone inlet dimensions on the performance and flow field pattern has been investigated computationally using the Reynolds stress turbulence model (RSM) for five cyclone separators. The results show that, the maximum tangential velocity in the cyclone decreases with increasing the cyclone inlet dimensions. No acceleration occurs in the cyclone space (the maximum tangential velocity is nearly constant throughout the cyclone). Increasing the cyclone inlet dimensions decreases the pressure drop. The cyclone cut-off diameter increases with increasing cyclone inlet dimension (consequently, the cyclone overall efficiency decreases due to weakness of the vortex strength). The effect of changing the inlet width is more significant than the inlet height especially for the cut-off diameter. The optimum ratio of inlet width to inlet height b/a is from 0.5 to 0.7.  相似文献   

7.
基于MCLP的知识挖掘模型在项目管理中的应用   总被引:1,自引:0,他引:1  
针对项目管理中不同知识的分类和表达模式,提出了一种基于多目标线性规划的知识挖掘模型.该模型在对文本信息预处理的基础上,采用多目标线型规划方法,实现了对可量化信息和不可量化信息的同时挖掘,从而挖掘出更准确的项目知识模式,实现了项目管理中的知识的再利用,并就应用过程中遇到的具体问题进行了探讨.  相似文献   

8.
A dominant retailer will purchase a newsvendor-type product from a manufacturer, who incurs a unit manufacturing cost k. The expected retail demand is a function of the unit retail price p. How should the retailer design her purchase contract? For this increasingly prevalent but inadequately studied scenario, we propose plausible adaptations of several contract formats that have been widely studied in the dominant-manufacturer context. For both symmetric-k and asymmetric-k-knowledge situations, we present performance results of these contracts. Our results then reveal that the performance of these contract formats under our scenario differs considerably from what one would surmise from the well-known results published for closely related scenarios. For example, the widely studied buyback and revenue-sharing formats turn out to be largely ineffective when implemented by a dominant retailer. In contrast, the two-part tariff format performs well relative to the theoretically optimal “menu of contracts.” Our results highlight the need to study purchase contract formats designed specifically for dominant-retailer newsvendor-product channels.  相似文献   

9.
In this paper,we define a model of random dynamical systems(RDS)on graphs and prove that they are actually homogeneous discrete-time Markov chains.Moreover,a necessary and sufficient condition is obtained for that two state vectors can communicate with each other in a random dynamical system(RDS).  相似文献   

10.
A closed-loop supply chain (CLSC) network consists of both forward and reverse supply chains. In this paper, a CLSC network is investigated which includes multiple plants, collection centres, demand markets, and products. To this aim, a mixed-integer linear programming model is proposed that minimizes the total cost. Besides, two test problems are examined. The model is extended to consider environmental factors by weighed sums and ε-constraint methods. In addition, we investigate the impact of demand and return uncertainties on the network configuration by stochastic programming (scenario-based). Computational results show that the model can handle demand and return uncertainties, simultaneously.  相似文献   

11.
The main objective of this paper is to compare the classification accuracy provided by large, comprehensive collections of patterns (rules) derived from archives of past observations, with that provided by small, comprehensible collections of patterns. This comparison is carried out here on the basis of an empirical study, using several publicly available data sets. The results of this study show that the use of comprehensive collections allows a slight increase of classification accuracy, and that the “cost of comprehensibility” is small.  相似文献   

12.
13.
《Applied Mathematical Modelling》2014,38(21-22):5092-5112
One of the most complicated decision making problems for managers is the evaluation of supply chain (SC) performance which involves various criteria. Though vast studies have been recorded on supply chain efficiency evaluation via balanced scorecard (BSC) approach, these studies do not focus on the relationships between the four perspectives of BSC approach. The present paper is an attempt focusing on these relationships, especially the returnable ones. To do so, at first, all relationships between the four perspectives of BSC were determined and then the DEMATEL approach was employed to obtain a network structure. This network structure was then used to create a network DEA model. Since it was not possible to calculate the efficiency evaluation score by BSC, the data envelopment analysis (DEA) model was used for such an evaluation. Moreover, after reviewing different tools to evaluate the performance of supply chain, a new approach, relying on network DEA with BSC approach, was generated. Finally, this model was applied in the Iranian food industry to evaluate its supply chains efficiency and the results proved the high efficiency of the model designed. The findings could be used in various evaluation processes in different industries.  相似文献   

14.
服务大规模定制模式下的供应链调度优化   总被引:1,自引:0,他引:1       下载免费PDF全文
为了提升服务大规模定制(SMC)模式下供应链系统的运作柔性,应对客户较强的多样化需求特征,本文在对服务定制特征分析、服务阶段界定以及服务规模效应探讨的基础上,指出SCM模式下的供应链调度问题是一个典型的随机需求与随机资源约束的多目标动态优化问题。研究了SMC模式下供应链调度的优化目标与约束条件,建立了完整的随机多目标动态调度优化数学模型。基于SMC运作的特点,运用改进的蚁群算法对调度问题进行了求解。最后,通过实例分析了模型及算法的可行性、有效性及适用性。  相似文献   

15.
This paper will discuss the case study conducted to evaluate a logistics related policy (time between successive collections of commodities) that optimizes the total shifting cost and minimizes the transportation cost by considering the problem as a Dynamic Multi Capacitated Vehicle Routing Problem (DMCVRP). The DMCVRP is formulated and solved for various policies using Mixed Integer Linear Programming (MILP) with an objective to minimize the cost associated with the distance traveled by the vehicles and the cost associated with unutilized capacity in the vehicles. Finally, we approximate the total shifting cost as a single variable function of transportation, inspection and inventory carrying cost, which possesses continuous derivatives at every order with the single variable as time between successive collections and derive the necessary and sufficient conditions in locating the optimum (minimum) total shifting cost.  相似文献   

16.
We investigate integral-type functionals of the first hitting times for continuous-time Markov chains. Recursive formulas and drift conditions for calculating or bounding integral-type functionals are obtained. The connection between the subexponential integral-type functionals and the subexponential ergodicity is established. Moreover, these results are applied to the birth-death processes. Polynomial integral-type functionals and polynomial ergodicity are studied, and a sufficient criterion for a central limit theorem is also presented.  相似文献   

17.
中国是世界上最大的电子产品生产国和需求国,现在面临着废旧电子产品数量急剧增长的严峻形势,日益对环境产生严重影响.引入绿色供应链管理理念,实施绿色供应链管理战略是中国电子产品行业主动挑战环境危机,提高国际市场竞争力以拓展企业生存发展空间的必由之路.给出了阻碍电子行业绿色供应链管理的16种因素,然后运用图论方法对电子生产企业构建绿色供应链的障碍进行了量化排序.结果表明制度法规是制约企业实施绿色供应链管理的最重要的因素,所以政府应从加强执法力度和推出恰当的激励机制两方面做出努力,以减少法制法规对绿色供应链管理的阻碍.这一方法便于管理者优先解决对绿色供应链管理阻碍较大的因素,确保在资源稀缺时代实现资源的最优利用.  相似文献   

18.
供应链网络道德风险演化与仿真研究   总被引:1,自引:0,他引:1       下载免费PDF全文
针对目前供应链网络存在的越来越严重的道德风险问题,利用演化博弈和系统动力学理论,从供应链网络结构入手,对其演化过程进行了研究。首先基于供应商之间合作过程中的诚信和败德行为,建立供应链网络同级企业间道德风险的演化博弈模型,并分析了其演化路径。其次通过对制造商和供应商之间博弈的动态性分析,建立供应链网络上下游企业间道德风险演化的SD模型,并对其演化过程进行了仿真分析。研究结果表明:供应链网络道德风险的演化结果取决于网络内败德企业获得的超额收益、收益调整程度、惩罚力度和惩罚机制。另外,罚款力度大小与供应链网络道德风险演化的动态性密切相关;动态惩罚机制在其演化的波动性控制方面,具有明显效果。  相似文献   

19.
Joint logistics and financial services by a 3PL firm   总被引:4,自引:0,他引:4  
Integrated logistics and financial services have been practiced by third party logistics (3PL) firms for years; however, the literature has been silent on the value of 3PL firms as credit providers in budget-constrained supply chains. This paper investigates an extended supply chain model with a supplier, a budget-constrained retailer, a bank, and a 3PL firm, in which the retailer has insufficient initial budget and may borrow or obtain trade credit from either a bank (traditional role) or a 3PL firm (control role). Our analysis indicates that the control role model yields higher profits not only for the 3PL firm but also for the supplier, the retailer, and the entire supply chain. In comparison with a supplier credit model where the supplier provides the trade credit, the control role model yields a better performance for the supply chain as long as the 3PL firm’s marginal profit is greater than that of the supplier. We further demonstrate that, for all players, both the control role and supplier credit models can outperform the classic newsvendor model without budget constraint.  相似文献   

20.
21世纪激烈的企业竞争以及企业经营的无国界化,迫使企业建立更加高效的管理方式,而供应链管理则是这种管理方式的典型代表,也必将是我国企业管理的发展方向。章介绍了企业供应链管理的由来,主要内容及运作方式,以及信息技术对供应链管理的决定性的作用。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号