Using structured steiner trees for hierarchical global routing

The Steiner problem in a hierarchical graph model, the structured graph, is defined. The problem finds applications to hierarchical global routing. Properties of minimum-cost Steiner trees in structured graphs are investigated. A “top-down” approximate solution to the Steiner problem in structured graphs, called a top-down Steiner tree, is defined, and an algorithm is given to compute such solution. The top-down Steiner tree provides also an approximate solution to the Steiner problem in graphs admitting a structured representation. The properties of such solution are discussed and some experimental results on the quality of the approximation are presented. A reduction in time complexity is demonstrated with respect to both exact and heuristic algorithms applied to such graphs.     

Comparison of Skidding Performance of Small Track-type Experimental Prototype Skidder and J-50 Skidding Tractor

In this paper, field experimental comparison is made between a small track-type experimental prototype skidder and a J-50 skidding tractor. Experimental data, including skidding productivity, soil compaction on skidding trails, and damage rate of the residual trees, are analyzed. The results indicate that with the condition of scattered skidding area and low skidding volume per cycle, small track-type experimental prototype skidder has advantage on working and a higher skidding productivity. It makes lower soil compaction to the skidding trails in the depth of 0-5 cm, 5-10 cm, and 10-15 cm. Under the same work conditions, the damage rate of the residual trees made by small track-type experimental prototype skidder is only 1/5 of those made by J-50 type skidding tractor. The damage rate is reduced by 80%.     

基于Logistic模型的P2P资源流行程度分析

为了解决目标资源数量增多而带来的监管成本过高的问题,提出一种基于Logistic模型的资源流行程度分析方法.利用该方法估计目标资源的流行程度,剔除流行程度低的资源,以此缩小监控范围,减少节点的部署数量.在Kad中对不同资源进行追踪,统计资源的共享节点数量,估计Logistic模型的参数,并进行曲线拟合.通过决策树建模得出,资源的共享节点数量和资源大小是影响该方法准确性的关键因素.     

一种基于系数状态表的SPIHT图像编码算法

提出了一种新的基于系数状态表的SPIHT(LPS-SPIHT,list of p ixel stata-set partition ing in h ierarch icaltrees)图像压缩编码算法,该算法具有以下5个特点:第一,定义了一种扩展的空间方向树,使1个结点含有2×2相邻的4个系数,并将基本EZW(嵌入式小波零树)的符号定义应用于扩展树;第二,用1个廉价的系数状态表代替了SPIHT算法中的LIS(不重要集合表)、LIP(不重要像素表)、LSP(重要像素表)等3个数据表,节省了内存;第三,通过扫描系数状态表,可一次性完成对图像数据的编码,使分类过程与细化过程合二而一;第四,利用一种树指数避免了重复计算,提高了处理速度;第五,通过重新组织编码过程,省去了对大量可推知位的编码,提高了压缩效率。实践证明,与目前公认的最为有效的SPIHT算法相比,该算法不仅性能优越,而且计算简单,容易实现。     

Learning from examples with unspecified attribute values

A challenging problem within machine learning is how to make good inferences from data sets in which pieces of information are missing. While it is valuable to have algorithms that perform well for specific domains, to gain a fundamental understanding of the problem, one needs a “theory” about how to learn with incomplete data. The important contribution of such a theory is not so much the specific algorithmic results, but rather that it provides good ways of thinking about the problem formally. In this paper we introduce the unspecified attribute value (UAV) learning model as a first step towards a theoretical framework for studying the problem of learning from incomplete data in the exact learning framework.In the UAV learning model, an example x is classified positive (resp., negative) if all possible assignments for the unspecified attributes result in a positive (resp., negative) classification. Otherwise the classification given to x is “?” (for unknown). Given an example x in which some attributes are unspecified, the oracle UAV-MQ responds with the classification of x. Given a hypothesis h, the oracle UAV-EQ returns an example x (that could have unspecified attributes) for which h(x) is incorrect.We show that any class of functions learnable in Angluin’s exact model using the MQ and EQ oracles is also learnable in the UAV model using the MQ and UAV-EQ oracles as long as the counterexamples provided by the UAV-EQ oracle have a logarithmic number of unspecified attributes. We also show that any class learnable in the exact model using the MQ and EQ oracles is also learnable in the UAV model using the UAV-MQ and UAV-EQ oracles as well as an oracle to evaluate a given boolean formula on an example with unspecified attributes. (For some hypothesis classes such as decision trees and unate formulas the evaluation can be done in polynomial time without an oracle.) We also study the learnability of a universal class of decision trees under the UAV model and of DNF formulas under a representation-dependent variation of the UAV model.     

Barrier Trees on Poset-Valued Landscapes

Fitness landscapes have proved to be a valuable concept in evolutionary biology, combinatorial optimization, and the physics of disordered systems. Usually, a fitness landscape is considered as a mapping from a configuration space equipped with some notion of adjacency, nearness, distance, or accessibility, into the real numbers. In the context of multi-objective optimization problems this concept can be extended to poset-valued landscapes. In a geometric analysis of such a structure, local Pareto points take on the role of local minima. We show that the notion of saddle points, barriers, and basins can be extended to the poset-valued case in a meaningful way and describe an algorithm that efficiently extracts these features from an exhaustive enumeration of a given generalized landscape.     

通用数据访问技术分析

数据访问技术的发展对数据的访问方式有了更多的选择。对 ODBC、OL E DB、ADO、ADO.NET几种常用数据访问技术进行了系统的分析 ,并给出了其适于使用的环境     

钻铣镗类加工中心的概念设计与方案评估研究

提出一种基于多色集合理论的机械产品概念设计的推理算法．采用一个有效的多目标方案评估算法，综合应用了层次分析法、模糊规则和神经网络，对满足需求的方案集进行评估和优化选择，得出满足需求的最优方案．以钻铣镗类加工中心的方案设计为例，用文中方法进行概念设计，得到了能满足需求的方案集和最优方案。     

对合肥市郊县绿化造林的一点看法

对合肥市郊县的绿化造林现状作了分析，提出了切实可行的措施。     

嵌入式数据挖掘系统实现方法研究

文中分析了数据挖掘系统与数据库及数据仓库系统间的关系,提出了嵌入式数据挖掘系统的思想、实现方法,及其关键技术。并引用决策树算法对嵌入式数据挖掘系统的实现方法做了描述。文中对嵌入式数据挖掘系统的未来进行了展望,一旦数据挖掘过程变得简单易用,并且能够无缝地集成到商业过程和企业的通用数据和信息流中,将会有新的应用和协同作用使数据挖掘成为功能完备的数据仓库中一项重要的要求。