电能质量数据的DCT压缩方法研究

变换编码对于电能质量数据压缩的提高是一项很重要的技术。文章首先介绍了离散余弦变换（DCT）的基本概念,然后对电能质量数据进行映射变换,并利用MATLAB进行仿真研究,利用离散余弦变换将原始电能质量数据映射到离散余弦空间,产生了更有效更紧凑的系数,但是直接对采样数据进行DCT处理,压缩比与精度成反比。提出数据复制组合方法进行改进,实验证明此方法有利于熵编码压缩码率和数据精度的提高。     

Theoretical analysis of polarization properties for tilted fiber Bragg gratings

The polarization properties for tilted fiber Bragg gratings (TFBGs) are investigated theoretically based on coupled-mode theory and Mueller matrix method. The expression of wavelength-related polarizationdependent loss (PDL) for TFBGs with different tilt angles is derived and calculated. Simulation results are compared, and the results indicate that the polarization capability of TFBGs with 45° angle is stronger than other TFBGs with smaller angles. The degree of polarization for unpolarized light passing T...     

Understanding buyers' loyalty to a C2C platform: the roles of social capital,satisfaction and perceived effectiveness of e‐commerce institutional mechanisms

Drawing upon social capital theory, this study aims to investigate how different dimensions of social capital affect online buyers' satisfaction and ultimately boost their loyalty to a Consumer‐to‐Consumer (C2C) platform. Specifically, we propose that three dimensions of social capital (i.e., cognitive, structural and relational capital) contribute positively to the two types of online buyers' satisfaction (i.e., economic and social satisfaction). In addition, we posit that perceived effectiveness of e‐commerce institutional mechanisms (PEEIM) moderates the relationships between economic and social satisfaction and buyers' loyalty to the platform. Three hundred buyers on the Consumer‐to‐Consumer platform, TaoBao, were surveyed to test the proposed model. The results suggest that buyers' evaluation of social capital with the community of sellers can enhance their satisfaction with the sellers, which subsequently affect their loyalty to the platform. Furthermore, perceived effectiveness of e‐commerce institutional mechanisms negatively moderates the effect of economic satisfaction and positively moderates the effect of social satisfaction on buyers' loyalty to the platform. The theoretical contributions and practical implications are discussed.     

Efficient image colorization based on seed pixel selection

Colorization is a technique to automatically produce color components for monochrome images and videos based on a few input colors. Generally, image colorization is initialized from a number of seed pixels whose colors are specified by users, and then the colors are gradually prorogating to the monochrome surroundings under a given optimization constraint. So, the performance of colorization is highly dependent on the selection of seed pixels. However, little attention has been paid to the selection of seed pixels, and how to improve the effectiveness of manual input remains a challenging task. To address this, an improved colorization method using seed pixel selection is proposed to assist the users in determining which pixels are highly required to be colorized for a high-quality colorized image. Specifically, the gray-scale image is first divided into non-overlapped blocks, and then, for each block, two pixels that approximate the average luminance of block are selected as the seeds. After the seed pixels are colored by users, an optimization that minimizes the difference between the seeds and their adjacent pixels is employed to propagate the colors to the other pixels. The experimental results demonstrate that, for a given amount of inputs, the proposed method can achieve a higher PSNR than the conventional colorization methods.     

无线局域网非授权用户入侵行为分析及检测*

针对当前流行的破解有线等效加密无线局域网密钥进而盗用上网资源的现象,研究了相关产品的攻击手段.对其提供的交互式重放攻击、ARP注入攻击、chopchop攻击和分片攻击四种攻击方式,通过跟踪记录攻击过程,分析了它们的攻击原理.在借鉴KDD99等特征提取方法的基础上,提取了9个用于识别攻击的流量统计特征,并利用支持向量机设...     

Intervention and strategy analysis for web group-learning

Abstract Owing to the lack of face-to-face interactions, students using a web-based learning system are likely to study alone and with relatively little classmate support and pressure. Teachers in a web-based learning system may apply a group-learning model to overcome this problem. Teachers first need to organise, manage and monitor the group learning and they must take appropriate actions based on teaching strategies to improve the learning achievements of the students. To perform these tasks effectively, teachers must obtain relevant information by analysing the huge volume of web-access logs or by monitoring web interactions. This paper presents novel methodologies for developing instruments to assist teachers in performing intervention and strategy analysis. The proposed methodologies apply data mining tools provided by existing database management systems. Database techniques, including the multi-dimensional cube, are then applied to make student web logs meaningful and helpful to teachers in managing group learning. The associate rule mining tool is finally employed to assist teachers in analysing their pedagogical strategies. These tools relieve teachers of tedious data collection and analysis, allowing them to focus on managing the groups to promote students' learning achievement.     

A MODIFIED METHOD FOR SUPERVISOR SPECIFICATION AND SYNTHESIS OF A CLASS OF DISCRETE EVENT SYSTEMS

In this paper, a model‐refining method is proposed to alleviate the complexity involved in specification interpretation of DES control problems. The legal constraint language is defined in terms of illegal states and events in contrast with constructing the automaton of the specification language. This method could provide a more intuitive view of the DES control problem and would be suitable for practical implementation. Two examples, which have commonly been used in the literature, are employed to show the efficiency of the proposed method. Further, under this framework, it is shown that the supremal controllable sublanguage can take a simpler form based on the concept of an illegal state set. A state‐based supervisor synthesis procedure is presented, and a simple example is provided.     

路堑高边坡三维监控体系监测效果分析

边坡稳定是一个空间的、复杂的、多参数的岩土力学问题,进行动态监测是保证边坡稳定的重要措施之一.结合某高速公路K58+ 800.00～ K59+ 030.00 m段路堑高边坡开挖与加固防护施工过程,通过对边坡深层水平位移、锚杆拉力和锚索预应力损失的监测与分析,分析潜在滑动面位置,并将监测分析潜在滑动面与设计潜在滑动面进行对比分析,提出优化监控体系和加固设计方案.利用动态监测手段可以更加有效的指导施工和确保现场施工安全.     

Numerical analysis of seepage flow characteristic of collapse column under the influence of mining

Based on the importance of fractured rock mass seepage research, in order to analyze seepage flow characteristics of collapse column under the influence of mining, a method by embedding fractured rock mass flow solid coupling relationship into FLAC^3D internal flow models is presented according to fluid–solid coupling theory and strength criterion. A calculation model of numerical analysis was established, and the influences of mining pressure and plastic damage to pore water pressure and seepage vector change rule were studied. The results show that collapse column is the main channel of confined water seepage upward. The impact is not big when the workface is away from the collapse column. But when the workface is nearing a collapse column, there will be a seepage channel on a side near the workface, in which seepage vector and head are comparatively large. With workface pushing through collapse column, the seepage channel transfers to the other side of the column. In addition, when the plastic damage area within the collapse column breaks through, a “pipeline flow” will be formed within the column, and seepage field will change remarkably and the possibility of water bursting will be greater.     

Multi-product economic lot scheduling problem with manufacturing and remanufacturing using a basic period policy

In this research we study the multi-product Economic Lot Scheduling Problem (ELSP) with manufacturing and remanufacturing opportunities. Manufacturing and remanufacturing operations are performed on the same production line. Both manufactured and remanufactured products have the same quality thus they fulfil the same demand stream. Tang and Teunter (2006) firstly studied this type of Economic Lot Scheduling Problem with Returns (ELSPR) and presented a complex algorithm for the optimal solution. More recently Teunter, Tang, and Kaparis (2009) proposed several heuristics to deal with the same problem using more computational efficient approaches. However, both studies have limited the attention to the common cycle policy with the assumption that a single (re)manufacturing lot is used for each item in each cycle. Relaxing the constraint of common cycle time and a single (re)manufacturing lot for each item in each cycle, we propose a simple, easy to implement algorithm, based on Segerstedt (1999), to solve the model using a basic period policy. Several numerical examples show the applicability of the algorithm and the cost savings.