Informatica

Wireless communication techniques provide convenience for users to get desired information. Construction and management costs of information provision systems with low computational-ability devices, such as RFID devices, are low so lightweight authentication protocols are required for information security. In this paper, two lightweight authentication protocols are proposed for reliable information provision systems with low computational-ability devices. The first protocol is for public information, and the other ensures that only authorized users can get information.

The number of digital resources to be used and reused for learning (learning objects) is constantly increasing, therefore describing learning objects with metadata is important to enhance learning object search, retrieval, and usage. Learning objects can be considered not only as resources, providing learning content, but as methodological resources, including teachers' experiences, reflections, examples or instructions of usage of content objects, and descriptions of learning methods. However, existing standards and specifications for learning objects metadata are not intended for including methodological resources and learning method descriptions together with content objects. In this paper, we present the results of a study, carried among general school teachers, which present a view of teachers on methodological resources and their importance, and propose a new model of learning object metadata for the learning object repository to include methodological resources, descriptions of learning methods and their links with content objects.

The aim of the given paper is development of an approach based on reordering of observations to be processed for the extraction of an unmeasurable internal intermediate signal, that acts between linear dynamical and static nonlinear blocks of the Wiener system with hard-nonlinearity of the known structure. The technique based on the ordinary least squares (LS) and on data partition is used for the internal signal extraction. The results of numerical simulation and identification of a discrete-time Wiener system with five types of hard-nonlinearities, such as saturation, dead-zone, preload, backlash, and, discontinuous nonlinearity are given by computer.

Technological advances have allowed all conferees to hold a mobile conference via wireless communication. When designing a conference scheme for mobile communications it should be taken into account that the mobile users are typically using portable devices with limited computing capability. Moreover, wireless communications are more susceptible to eavesdropping and unauthorized access than conversations via wires. Based on elliptic curve cryptography, this article proposes a secure mobile conference scheme which allows a participant to join or quit a teleconference dynamically. Without any interactive protocol among participants are required to construct the common key. This can save on communication overhead.

The problem we address in this paper is the design of a quantizer that in comparison to the classical fixed-rate scalar quantizers provides more sophisticated bit rate reduction while restricting the class of quantizers to be scalar. We propose a switched variable-length code (VLC) optimal companding quantizer composed of two optimal companding scalar quantizers, the inner and the outer one, both designed for the memoryless Gaussian source of unit variance. Quantizers composing the proposed quantizer have a different codebook sizes and a different compressor functions. Particularly, we assume a smaller size of the inner quantizer's codebook in order to provide assignment of the shorter codewords to the high probability low amplitude speech samples belonging to the support region of the inner quantizer. We study the influence of codebook size of the inner and the outer quantizer on the Signal to Quantization Noise Ratio (SQNR). In such a manner the conclusion of the proposed quantizer significance in speech compression is distinctly shown in the paper. For the proposed quantizer model and its forward adaptive version the SQNR robustness analysis in a wide variance range is also presented in the paper. It is shown that our multi-resolution quantizer can satisfy G.712 Recommendation for high-quality quantization at the bit rate of 6.3 bit/sample achieving the compression of 1.7 bit/sample over the G.711 quantizer.

Frequent sequence mining is one of the main challenges in data mining and especially in large databases, which consist of millions of records. There is a number of different applications where frequent sequence mining is very important: medicine, finance, internet behavioural data, marketing data, etc. Exact frequent sequence mining methods make multiple passes over the database and if the database is large, then it is a time consuming and expensive task. Approximate methods for frequent sequence mining are faster than exact methods because instead of doing multiple passes over the original database, they analyze a much shorter sample of the original database formed in a specific way. This paper presents Markov Property Based Method (MPBM) – an approximate method for mining frequent sequences based on kth order Markov models, which makes only several passes over the original database. The method has been implemented and evaluated using real-world foreign exchange database and compared to exact and approximate frequent sequent mining algorithms.

This paper proposes a new multi-attribute ranking procedure based on distance from decision-maker preferences. This method has two phases. In the first phase, the decision maker is asked to define the preferred performance for each attribute. In the second phase, Weighted Sum method and new distance-based normalization procedure are used to determine the overall performance rating of alternatives.

Due to numerous public information sources and services, many methods to combine heterogeneous data were proposed recently. However, general end-to-end solutions are still rare, especially systems taking into account different context dimensions. Therefore, the techniques often prove insufficient or are limited to a certain domain. In this paper we briefly review and rigorously evaluate a general framework for data matching and merging. The framework employs collective entity resolution and redundancy elimination using three dimensions of context types. In order to achieve domain independent results, data is enriched with semantics and trust. However, the main contribution of the paper is evaluation on five public domain-incompatible datasets. Furthermore, we introduce additional attribute, relationship, semantic and trust metrics, which allow complete framework management. Besides overall results improvement within the framework, metrics could be of independent interest.

Grey numbers facilitate the representation of uncertainty not only for elements of a set, but also the set itself as a whole. This paper utilizes the notion of possibility degree from grey system theory coupled with the idea of dominance relation and partial order set (poset) from rough theory to represent uncertain information in a manner that maintains the degree of uncertainty of information for each tuple of the original data. Concept lattices of grey information system are constructed and a decision-making algorithm that combines with grey relational grade is described. A case study is used to demonstrate the supplier selection problem applying the proposed method. The research has concluded that the method is appropriate to use.