基于用户行为特征的P2P代理缓存的研究*

通过对BitTorrent用户一段时间内的行为统计分析,把握用户的行为特征.在此特征的基础上,提出一种BitTorrent缓存模式,更大程度地利用缓存空间,提高缓存命中率,减轻网络运营商的出口压力.     

基于非侵入式负荷监测的用户行为精细化分析

随着非侵入式电力负荷监测的发展,如何利用用户负荷用电细节信息,分析用户用电行为特征成为重要的研究方向。本文提出了基于非侵入式负荷监测的用户行为精细化分析方法,根据历史数据建立用户行为特性指标,提出基于因子分析与支持向量机的用户聚类方法。在此基础上,建立基于精细化负荷数据的用户需求响应潜力评估指标。算例结果表明,所研究内容可以准确分析用户行为,为电力公司施行需求侧管理提供科学指导。     

基于Stacking模型融合的专变用户电费回收风险识别方法

针对当前电力公司面临的专变用户电费回收风险,提出一种基于Stacking模型融合的专变用户电费回收风险识别方法。对专变用户数据进行特征处理、特征构造与特征筛选,从样本分布和特征属性上优化模型的泛化性能;利用Stacking模型融合多个基学习器,构建专变用户电费回收风险识别模型。实验结果表明,相较于其他常用的分类算法,所提方法具有更优的精确率、召回率、P-R调和均值、AUC值以及模型泛化性能,对专变风险用户的识别率也更高。     

大学生求学满意度实证研究--某高校学生个体特征对满意度单项要素的影响分析

求学满意度，又称为求学满意程度，它取决于教育需求主体对教育服务的预期同其实际所感知的教育服务水平的对比。教学计划、教学组织、教师教学、教学设施、校园环境、学生5知识技能等都是影响求学满意度的因素。本文在调查取得基本数据的基础上，使用相关的统计检验方法，分析了性别、生源地和不同年级这些学生个体地征对求学满意度单项要素的影响。主要结论有：学生性别差异对满意度单项要素的影响基本是随机的；不同生源地的学生对教学计划和管理制度两个要素的评价具有差异；不同年级的学生对教学设施和知识掌握程度的评价具有显著性差异；学生对学校服务评价单项因素差异很少，总体满意度在一定程度上反应学校的实际情况。     

Customer satisfaction and competitiveness in the Chinese E-retailing: Structural equation modeling (SEM) approach to identify the role of quality factors

This paper attempts to study the impact of customer satisfaction and the Chinese electronic retailers (E-retailers) competitiveness using quality factors. Two conceptual models based on asset-process-performance (APP) competitive theoretical framework have been proposed. The proposed models include E-retailers strategic factors such as logistics, quality and customer satisfaction equivalent to asset, process and performance entities of the APP framework. Using an empirical survey from a young population, this study, with the support of structural equation modeling (SEM) identifies reliability in service quality and purchasing experience in e-service quality as dominant customer satisfaction factors. This study uses both exploratory and confirmatory factor analysis and suggests that to be competitive Chinese E-retailers have to focus more on the delivery of products (logistics) compared to other intangible service quality factors. On theoretical front, this study is a novel attempt to validate the APP framework for E-retailers’ competitiveness. On the practical front, the outcome of the study would be highly beneficial to the Chinese E-retailers to fine tune their strategy to satisfy the growing demand. Furthermore, this study can supplement government policy makers to regulate the growing volatile market.     

Dynamics of fluid circulation in coupled free and heterogeneous porous domains

Fluid flow in coupled free and porous domain, particularly when the porous medium is heterogeneous, is encountered in many hydro-environmental conditions, e.g., leakage from underground pipe, combined groundwater lake-subsurface interactions. One of the most difficult problems in the study of coupled flow behaviour has been the development of a universally applicable modelling scheme for combining the flow regimes. This is because the free/porous interfacial properties (e.g., shear-stress; velocity slip) that govern the coupled flow behaviour are difficult to determine experimentally under hydro-environmental conditions. On the other hand, the implications of various forms of heterogeneity in the porous media properties can be very different on the fluid-flow behaviour. Difficulties may also arise in direct coupling of the model equations that govern the fluid flow in the individual regions (e.g., Navier-Stokes for free-flow region and the Darcy's equation for the porous flow region). Consequently, models of coupled free and porous flow for hydro-environmental conditions are not very well developed at the moment. While there are some indications that fluids in coupled free and porous domains may circulate (i.e., development of flow cells), there is a lack of appropriate 3D analysis on how heterogeneities in porous media may affect such flow patterns. In this paper, we aim to analyse how porous media heterogeneity affects the dynamics of flow circulation in the porous side of a coupled free and porous domain. For this purpose, we analyse flow patterns in several model domains made up of two porous layers with differing permeabilities. The governing model equations are discretised and solved using the standard finite volume method on a staggered cell-centred mesh. The temporal discretisation is done using the explicit method. An in-house graphical user interface (GUI) has been created specifically to aid in the visualisation of otherwise complex flow patterns. The GUI contains many post-processing options and provides a comprehensive tool for the analysis of hydrodynamics and contaminant motion (not discussed in this paper) in coupled free and porous flow domains. This GUI is described in this paper briefly. The effects of altering the aspect ratio (i.e., multi-scale) of the domain on the coupled flow pattern have also been discussed.     

Augment low-field intra-operative MRI with preoperative MRI using a hybrid non-rigid registration method

Background

Preoperatively acquired diffusion tensor image (DTI) and blood oxygen level dependent (BOLD) have been proved to be effective in providing more anatomical and functional information; however, the brain deformation induced by brain shift and tumor resection severely impairs the correspondence between the image space and the patient space in image-guided neurosurgery.

Method

To address the brain deformation, we developed a hybrid non-rigid registration method to register high-field preoperative MRI with low-field intra-operative MRI in order to recover the deformation induced by brain shift and tumor resection. The registered DTI and BOLD are fused with low-field intra-operative MRI for image-guided neurosurgery.

Results

The proposed hybrid registration method was evaluated by comparing the landmarks predicted by the hybrid registration method with the landmarks identified in the low-field intra-operative MRI for 10 patients. The prediction error of the hybrid method is 1.92 ± 0.54 mm, and the compensation accuracy is 74.3 ± 5.0%. Compared to the landmarks far from the resection region, those near the resection region demonstrated a higher compensation accuracy (P-value = .003) although these landmarks had larger initial displacements.

Conclusions

The proposed hybrid registration method is able to bring preoperatively acquired BOLD and DTI into the operating room and compensate for the deformation to augment low-field intra-operative MRI with rich anatomical and functional information.     

一种融合服务满意度的多因素感知云服务性能预测策略

提出了一种多因素感知的云服务性能预测策略,它基于综合权衡服务提供商的利益,通过合理定价和性能保障来量化和优化服务满意度,并以之驱动性能预测,并引入效用理论实现服务满意度的合理定价.最后通过模拟实验表明,它能够降低SLA破坏率,有效提高云服务的资源利用率.     

基于海量搜索历史数据的用户兴趣模型

针对互联网搜索引擎环境中,基于海量搜索历史数据分析用户兴趣的问题,提出一种改进的用户兴趣模型。该模型根据用户搜索的历史数据,结合向量空间模型（ VSM ）和TF-IDF算法,递归地回溯出用户兴趣权重列表。为解决用户兴趣变化和时间性能的问题,该模型引入时间遗忘机制进行动态更新,并在Hadoop分布式系统架构下利用MapReduce分布式编程模型进行实现。实验结果表明,改进的用户兴趣模型的查准率和召回率都能达到50',具有较好的可行性和可用性。     

基于遗忘曲线的微博用户兴趣模型

为解决微博用户兴趣漂移问题,以人类记忆学中遗忘曲线为基础,提出一种微博用户兴趣模型,利用用户历史信息预测当前兴趣。在预测过程中,用户关注某信息的时间距离当前时间越远,该信息越容易被遗忘,其对用户当前兴趣的影响越小;用户关注某一领域的信息越多,印象越深刻,对该领域的兴趣度越高。这两点与人类对知识逐渐遗忘和重复学习的过程具有高度相似性,因此该模型预测准确性更高。实验结果表明,该模型能较好地预测微博用户兴趣,召回率可达85.3％,实用性较强。