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981.
With the rapid development of online learning technology, a huge amount of e-learning materials have been generated which are highly heterogeneous and in various media formats. Besides, e-learning environments are highly dynamic with the ever increasing number of learning resources that are naturally distributed over the network. On the other hand, in the online learning scenario, it is very difficult for users without sufficient background knowledge to choose suitable resources for their learning. In this paper, a hybrid recommender system is proposed to recommend learning items in users’ learning processes. The proposed method consists of two steps: (1) discovering content-related item sets using item-based collaborative filtering (CF), and (2) applying the item sets to sequential pattern mining (SPM) algorithm to filter items according to common learning sequences. The two approaches are combined to recommend potentially useful learning items to guide users in their current learning processes. We also apply the proposed approach to a peer-to-peer learning environment for resource pre-fetching where a central directory of learning items is not available. Experiments are conducted in a centralized and a P2P online learning systems for the evaluation of the proposed method and the results show good performance of it. 相似文献
982.
While constructing virtual enterprises, it is crucial to flexibly integrate heterogeneous business resources and processes of different business partners and make them collaborate dynamically. Keeping involved IT systems or components as autonomous and loose-coupled services, the “Everything as a Service” concept supports flexible integration of heterogeneous applications. We adopt this concept and analyze the challenges in virtual enterprise construction, then propose a service platform for on-demand virtual enterprises. The platform supports flexible integration of networked resources, and facilitates virtual enterprise construction with business process utility, trusted service composition and data service centric business collaborations. At the end of the paper, together with a case study, experimental evaluations in contexts of concurrent multi-users are presented, showing the effectiveness and performance of the platform. 相似文献
983.
The fuzzy object-oriented databases have been proposed to meet the need of dealing with fuzzy as well as complex objects. In this paper, we present a formal fuzzy object-oriented database model. Based on the semantic measure of fuzzy data, we first identify two kinds of fuzzy object redundancies, which are inclusion redundancy and equivalence redundancy, and then define three kinds of merging operation for redundancy removal. On the basis, we define some fuzzy algebraic operations for fuzzy classes and fuzzy objects. Finally, in the paper, we discuss fuzzy querying strategies and give the form of SQL-like fuzzy querying for the fuzzy object-oriented databases. 相似文献
984.
Yadong Li Jing Liu Chenlong Liu 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(2):329-348
To detect communities in signed networks consisting of both positive and negative links, two new evolutionary algorithms (EAs) and two new memetic algorithms (MAs) are proposed and compared. Furthermore, two measures, namely the improved modularity Q and the improved modularity density D-value, are used as the objective functions. The improved measures not only preserve all properties of the original ones, but also have the ability of dealing with negative links. Moreover, D-value can also control the partition to different resolutions. To fully investigate the performance of these four algorithms and the two objective functions, benchmark social networks and various large-scale randomly generated signed networks are used in the experiments. The experimental results not only show the capability and high efficiency of the four algorithms in successfully detecting communities from signed networks, but also indicate that the two MAs outperform the two EAs in terms of the solution quality and the computational cost. Moreover, by tuning the parameter in D-value, the four algorithms have the multi-resolution ability. 相似文献
985.
986.
为了定量、客观、全面地评价光学镜头的像质,介绍了光学镜头调制传递函数的测试。先简要叙述了测试的原理,并给出计算公式;然后介绍了测试步骤,其中包括固定、穿轴、测试中心视场和测试轴外视场;最后介绍了测试时的注意事项,包括对测试工装的要求、对测试平面的要求和正、负轴外视场测试值相差较大时的处理办法。 相似文献
987.
介绍了使用顶空-气相色谱法检测水中一氯苯的方法。该方法使氯苯分子在气液两相之间、在一定温度下达到了动态平衡。此时,一氯苯在气相中的浓度与它在液相中的浓度成正比。通过测定气相中一氯苯的浓度,即可计算出水样中氯苯的浓度。使用该方法可以直接测定水样,与国标方法相比,它无需琐碎的前处理过程,避免了实验人员与有毒有害溶剂的接触,而且测定结果稳定性较好,能够满足测定需求。 相似文献
988.
随着经济的飞速发展,我国的环境状况在不断恶化。就目前的环境现状、环境污染问题和环境保护工作现状进行了详细分析和阐述,并对环境保护工作提出参考和建议。 相似文献
989.
线损可在一定程度上体现一个城市电网的规划设计水平、生产管理水平,它还影响着供电企业的经济效益.因此,如何降低线损是每个供电企业关注的焦点.通过探讨当前线损过高的原因,从管理、技术等方面提出了相应的改善措施,以期为相关单位提供借鉴. 相似文献
990.
随着电力体制改革的不断推进,电力企业需要加强人力资源管理,以增强企业的核心竞争力.通过阐述电力企业人力资源管理工作面临的主要问题,提出了做好电力企业人力资源管理的对策. 相似文献