Condensation of a Strongly Interacting Parton Plasma into a Hadron Gas in High Energy Nuclear Collisions

We examine the effects of color screening on the transition of a parton plasma into a hadron gas at RHIC energies. It is found that as expected, color screening posed itself as a significant barrier for hadronization. Parton-hadron conversion would therefore be delayed and prolonged when compared to that occuring in a vacuum. Due to the on-going expansion, the resulting hadron densities are lowered. Parton equilibration is also shown to be seriously disrupted in the process.Comment: 4 pages, 2 embedded EPS figures, talk presented at Quark Matter'99, Torino, Ital

Secret Sharing LDPC Codes for the BPSK-constrained Gaussian Wiretap Channel

The problem of secret sharing over the Gaussian wiretap channel is considered. A source and a destination intend to share secret information over a Gaussian channel in the presence of a wiretapper who observes the transmission through another Gaussian channel. Two constraints are imposed on the source-to-destination channel; namely, the source can transmit only binary phase shift keyed (BPSK) symbols, and symbol-by-symbol hard-decision quantization is applied to the received symbols of the destination. An error-free public channel is also available for the source and destination to exchange messages in order to help the secret sharing process. The wiretapper can perfectly observe all messages in the public channel. It is shown that a secret sharing scheme that employs a random ensemble of regular low density parity check (LDPC) codes can achieve the key capacity of the BPSK-constrained Gaussian wiretap channel asymptotically with increasing block length. To accommodate practical constraints of finite block length and limited decoding complexity, fixed irregular LDPC codes are also designed to replace the regular LDPC code ensemble in the proposed secret sharing scheme.Comment: submitted to IEEE Trans. on Information Forensics and Security, special issues on using the physical layer for securing the next generation of communication system

An Implementation, Empirical Evaluation and Proposed Improvement for Bidirectional Splitting Method for Argumentation Frameworks under Stable Semantics

Abstract argumentation frameworks are formal systems that facilitate obtaining conclusions from non-monotonic knowledge systems. Within such a system, an argumentation semantics is defined as a set of arguments with some desired qualities, for example, that the elements are not in conflict with each other. Splitting an argumentation framework can efficiently speed up the computation of argumentation semantics. With respect to stable semantics, two methods have been proposed to split an argumentation framework either in a unidirectional or bidirectional fashion. The advantage of bidirectional splitting is that it is not structure-dependent and, unlike unidirectional splitting, it can be used for frameworks consisting of a single strongly connected component. Bidirectional splitting makes use of a minimum cut. In this paper, we implement and test the performance of the bidirectional splitting method, along with two types of graph cut algorithms. Experimental data suggest that using a minimum cut will not improve the performance of computing stable semantics in most cases. Hence, instead of a minimum cut, we propose to use a balanced cut, where the framework is split into two sub-frameworks of equal size. Experimental results conducted on bidirectional splitting using the balanced cut show a significant improvement in the performance of computing semantics.Comment: 19 page

Of, By, and For the Community: The Story of PUENTE Learning Center

Reviews the 20-year development of the learning centers, located in East and South Los Angeles. Examines the impact of the center's preschool, kindergarten, and after-school programs for youth, and education and job training programs for adults

Data protection: the future of privacy

The Art. 29 Working Party (hereinafter “Art. 29 WP”) is an influential body comprised of representatives from the Member State Data Protection Authorities2 established under the Data Protection Directive 95/46/EC, has recently issued an opinion with the Working Party on Police and Justice. This is quite significant, since the opinion sets out some of the issues that will need to be addressed in the lead up to the revision of the Data Protection Directive 95/46/EC.3 This comes at a time, when there have been discussions on the current application of the European Data Protection Directive to the internet,4 (such as social networking) and the recent European Commission’s consultation on the legal framework for the fundamental right to protection of personal data. Not least, there have been a number of cases brought before the European Court of Justice dealing with the partial implementation of the Data Protection Directive 95/46/EC.5. The aim of this paper is to consider in detail the issues set out by the Art. 29 WP and the likely challenges in revising the Data Protection Directive 95/46/EC