Know by a handful the whole sack: efficient sampling for top-k influential user identification in large graphs

Influence Maximization aims to find the top-K influential individuals to maximize the influence spread within a social network, which remains an important yet challenging problem. Most existing greedy algorithms mainly focus on computing the exact influence spread, leading to low computational efficiency and limiting their application to real-world social networks. While in this paper we show that through supervised sampling, we can efficiently estimate the influence spread at only negligible cost of precision, thus significantly reducing the execution time. Motivated by this, we propose ESMCE, a power-law exponent supervised Monte Carlo estimation method. In particular, ESMCE exploits the power-law exponent of the social network to guide the sampling, and employs multiple iterative steps to guarantee the estimation accuracy. Moreover, ESMCE shows excellent scalability and well suits large-scale social networks. Extensive experiments on six real-world social networks demonstrate that, compared with state-of-the-art greedy algorithms, ESMCE is able to achieve almost two orders of magnitude speedup in execution time with only negligible error (2.21 % on average) in influence spread.     

A hybrid recommendation algorithm adapted in e-learning environments

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.     

Everything-as-a-service platform for on-demand virtual enterprises

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.     

Algebraic operations in fuzzy object-oriented databases

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.     

A comparative analysis of evolutionary and memetic algorithms for community detection from signed social networks

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.     

运动与减肥

通过分析肥胖的病因学、运动减肥原理得出,非药物性的适量运动具有经济、有效、无副作用等优点,有利于各年龄段的人降脂减重,并能抑制体重反弹。     

光学镜头调制传递函数的测试

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。     

用顶空-气相色谱法检测水中一氯苯

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。     

浅谈当前环境保护工作现状及对策

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。     

浅析10 kV配网的线损与降损

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.