Abstract In this paper, we propose a low-rank minimum mean-square error (OLR-MMSE) channel estimator for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. We evaluate the performance of the proposed low-rank channel estimator for slowly fading channel environments in terms of the symbol error rate (SER) by computer simulations. It is shown that the proposed channel estimator gives the best tradeoff... In this paper, we propose a low-rank minimum mean-square error (OLR-MMSE) channel estimator for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. We evaluate the performance of the proposed low-rank channel estimator for slowly fading channel environments in terms of the symbol error rate (SER) by computer simulations. It is shown that the proposed channel estimator gives the best tradeoff between performance and complexity. Read More Read Less

Abstract In the present days, business applications are still designed for human consumption, which does not allow machines to understand the information contained in them, particularly preventing the correlation between concepts from different fields, in the generation and submission of new information for the handling of large data sets. The increasing complexity of applications, increases the attention in the construction of... In the present days, business applications are still designed for human consumption, which does not allow machines to understand the information contained in them, particularly preventing the correlation between concepts from different fields, in the generation and submission of new information for the handling of large data sets. The increasing complexity of applications, increases the attention in the construction of knowledgeable systems that can be understood and shared by all (application / machines / people). Using the concept of Ontology as a tool for knowledge representation has been effective, in order to develop applications with these said characteristics, since the semantic models have the ability to map and integrate different concepts from the same domain or different domains of knowledge, related to each other, therefore providing conditions for understanding the information contained herewith. Presently, there are different proposals for the aforesaid mapping, considering the semantics and ontological integrations, as well as interoperability of the information systems. This study presents a conceptual modeling in domain knowledge, about the potential vulnerabilities in environments, IaaS, in the public cloud, as a scenario using ontology reasoning. The purpose this modeling, is to provide an effective mechanism, capable of handling two major security issues, such as: providing a common vocabulary to describe vulnerabilities unambiguously and resolving the issue of semantic interoperability between the databases of vulnerabilities maintained by various entities. Read More Read Less

Abstract In recent years, user generated content services have become popular. The authors are interested in user generated online novel services. Classification of online novels is difficult because keywords and genre are assigned by the author of the novel without control. In order to overcome the problem in classifying seaching online novels, faceted views were introduced and a cross tabulation search... In recent years, user generated content services have become popular. The authors are interested in user generated online novel services. Classification of online novels is difficult because keywords and genre are assigned by the author of the novel without control. In order to overcome the problem in classifying seaching online novels, faceted views were introduced and a cross tabulation search and analysis system was developed. This system can discover relations between novel genres and keywords, and can find the author’s preference. Read More Read Less

Abstract In the last decade, researchers have developed a number of RBAC extensions such as Spatio-Temporal Role Based Access Control (STRBAC) that takes into consideration the location of users and the time of access. These models that incorporate time and location information into the basic model RBAC are mainly proposed to support many mobile applications and wireless networks. However by doing... In the last decade, researchers have developed a number of RBAC extensions such as Spatio-Temporal Role Based Access Control (STRBAC) that takes into consideration the location of users and the time of access. These models that incorporate time and location information into the basic model RBAC are mainly proposed to support many mobile applications and wireless networks. However by doing so, it further increases the complexity of an already complex Access Control model. As a result, this increases the possibility of having contradictory statements in the Access Control specification. Such statements are commonly known as inconsistencies. In this study, we provide a formal definition of inconsistency in Spatio- Temporal Role Based Access Control (STRBAC) and then define several examples of inconsistencies in STRBAC specification. To achieve this, we shall first present formal algebraic notations of STRBAC model. In addition, the paper introduces the concept of “semi-consistency” in STRBAC and presents several scenarios that are involving semi-consistencies. A semiconsistency is a special case where the inconsistency can be avoided if the assignment of user to role is controlled. Finally, the paper presents an eclipse application called AC2Alloy that transforms STRBAC specification into Alloy. The produced Alloy models can be analysed using Alloy Analyser in order to detect inconsistencies and semi-consistencies in the STRBAC specification. With the help of an example, we show how AC2Alloy converts the STRBAC model to the Alloy model and verifies the resulting model using the Alloy analyser to identify inconsistencies and semi-consistencies. Read More Read Less