Showing papers by "University of Piraeus published in 1996"
TL;DR: This paper focuses on the interactions between the elements that constitute such a multi-echelon system, in order to determine several service measures (e.g. external customer service level and inventory holding costs).
190 citations
TL;DR: In this article, a fuzzy approach to a single machine scheduling problem is considered, where the system's variables are defined using linguistic terms and each of these variables may take values described via fuzzy triangular numbers.
73 citations
TL;DR: A set of jobs is scheduled using the SLK due-date determination method, according to which all the jobs are given the same flow allowance, and an analytical solution is given and an algorithm is presented, which provides optimal solutions.
Abstract: In this paper, a set of jobs is scheduled using the SLK due-date determination method, according to which all the jobs are given the same flow allowance. The single machine case is considered. The objective function is a cost function including three components, namely flow allowance and weighted earliness and tardiness. An analytical solution is given and an algorithm, which provides optimal solutions, is presented. Finally, the parallel machines case is discussed.
69 citations
TL;DR: In this article, an interactive model based system for the management of production in textile production systems focusing on the Master Production Scheduling problem is presented, which is also related to two well-known production control systems, namely MRP-II and Optimised Production Technology.
43 citations
TL;DR: This paper examined the trade-offs between size distortion and power that are implied by this approach to testing for unit roots, and proposed a general-to-specific approach for unit root regression.
34 citations
TL;DR: In this paper, the authors compared the average level of underpricing for pure primary offerings with that of mixed offerings for small firms in the over-the-counter (OTC) capital market.
Abstract: The existence of the phenomenon of “underpricing” has been well established for common stock initial public offerings (CSIPOs). However, the extent of underpricing varies from firm to firm. An examination of the prospectuses of different firms reveals that the motivation for going public varies, and that there are three types of offerings: pure primary offerings; pure secondary offerings; and mixed offerings. This study compares the average level of underpricing for pure primary offerings with that of mixed offerings for small firms in the over-the counter (OTC) capital market. The results of the study suggest that there are Implications of the type of offering for both the firm and the selling “harvesting” shareholders as well as the incoming investors.
27 citations
TL;DR: The proposed model for exponential smoothing methods using one, two and three smoothing parameters is described and the accuracy of the method is measured.
22 citations
TL;DR: A special minmax goal programming model with fractional goals is formulated and then used as the basis for developing two specific MCDM methods: a method to derive priorities for decision elements from pairwise comparison matrices in the AHP framework and an additive value function by analysing some preference information expressed over the set of alternatives on a ratio scale.
Abstract: A special minmax goal programming model with fractional goals is formulated and then used as the basis for developing two specific MCDM methods: (1) a method to derive priorities for decision elements from pairwise comparison matrices in the AHP framework; (2) a method to assess an additive value function by analysing some preference information expressed over the set of alternatives on a ratio scale For both methods a common iterative solution procedure is proposed by using a linear programming formulation
21 citations
TL;DR: In this paper, the permanence of the almost strong lifting property under finite and countable products of topological probability spaces has been studied, and the existence of liftings compatible with products of lifting topologies has been proved.
Abstract: Dealing with a problem posed by Kupka we give results concerning the permanence of the almost strong lifting property (respectively of the universal strong lifting property) under finite and countable products of topological probability spaces. As a basis we prove a theorem on the existence of liftings compatible with products for general probability spaces, and in addition we use this theorem for discussing finite products of lifting topologies.
16 citations
TL;DR: The single machine job scheduling problem, where due dates are assigned using the SLK due date determination method, is examined assuming different penalties for the early and tardy jobs.
12 citations
TL;DR: This article examined value creation as an alternative approach to measuring the performance of corporate entrepreneurship and found that value creation can provide an accurate picture of the firm's performance, while accounting measures may not provide a complete understanding of the company's performance.
Abstract: It has increasingly been recognized that appropriate theory based measures are required in entrepreneurial research (25) However, to date, the study of corporate entrepreneurship (CE) has principally used accounting measures which may not provide an accurate picture of the firm's performance This study examines value creation as an alternative approach to measuring the performance of corporate entrepreneurship
TL;DR: This paper examines the use of EDI in the healthcare administration sector and more specifically its application to the Medical Device Vigilance System.
Abstract: EDI is expected to be the dominant form of business communication between organizations moving to the Electronic Commerce era of 2000. The healthcare sector is already using EDI in the hospital supply function as well as in the clinical area and the reimbursement process. In this paper, we examine the use of EDI in the healthcare administration sector and more specifically its application to the Medical Device Vigilance System. Firstly, the potential of this approach is examined, followed by the definition of the EDI System Reference Model and the specification of the required system architecture. Each of the architecture's components are then explained in more detail, followed by the most important implementation options relating to them.
TL;DR: A general approach to a participative HIS development, where users are full members of the development team, and an application to the particular context of a Greek hospital is described.
Abstract: User participation in HIS development is considered essential for achieving systems implementation success. Realizing a participative HIS development, where users are full members of the development team, requires not only choosing an appropriate methodology but also organizing the participation process in a way that is tailored to the particular situation in order to achieve the desired results. A general approach to this problem is presented in this paper. An application of the approach to the particular context of a Greek hospital is described.
15 Dec 1996
TL;DR: This paper considers two models for provable security, one based on probabilistic encryption, the other on zero-knowledge, and proposes a variant of the Diffie-Hellman key agreement protocol which is provably secure and efficient.
Abstract: Data security in computer networks is becoming increasingly important due to the expanding role of distributed computation, distributed databases and tele-communication applications such as electronic mail and electronic funds transfer. For privacy, information which may be highly sensitive or privileged must be encrypted with secret keys which are shared by the communicating parties. These keys are generated by key agreement protocols. Traditionally such protocols were designed by trial and error. History has proven this method to be unreliable: many protocols were broken or serious flaws were exposed. In this paper we discuss the security aspects of key agreement protocols. In particular, we consider two models for provable security, one based on probabilistic encryption, the other on zero-knowledge. We propose a variant of the Diffie-Hellman key agreement protocol which is provably secure and efficient.
TL;DR: This paper describes a front end authorization mechanism that has been developed in an attempt to enhance the security features of an existing HIS without extensive modifications to the system structure.
Abstract: Authorization is an important functionality that every hospital information system (HIS) should provide. An authorization mechanism permits information to be accessed only by properly authorized users. Authorization models and mechanisms have been widely investigated within the framework of HISs. However, their implementation into existing systems, that do not any longer meet increased authorization requirements, requires a major redesign effort. This paper describes a front end authorization mechanism that has been developed in an attempt to enhance the security features of an existing HIS without extensive modifications to the system structure.
Posted Content•
TL;DR: The prices of Greek closed-end funds behave similarly to the prices of US funds: they deviate substantially from their net asset values (NAVs); they are more volatile than their NAVs; and they are overly sensitive to the movements of the domestic stock market index as discussed by the authors.
Abstract: The prices of Greek closed-end funds behave similarly to the prices of US funds: they deviate substantially from their net asset values (NAVs); they are more volatile than their NAVs; and they are overly-sensitive to the movements of the domestic stock market index. Furthermore, their premia are: (i) positively correlated cross-sectionally; (ii) positively correlated with the future NAV returns; and (iii) negatively correlated with the future returns on the funds. Yet most Greek funds are subsidiaries of banks that have considerable influence on their pricing, whereas US funds are owned mainly by small investors. Future explanations to the closed-end fund puzzle should, therefore, transcend the narrow institutional characteristics of asset composition and ownership of US closed-end funds.
TL;DR: This article explored the nature of this problem with a theoretical model for consumption and demonstrates how severe the problem can be with US data and also recommends a reexamination of the evidence in cases where the ECM appears to be insignificant or to display the "wrong" sign.
Abstract: Reflecting the nature of economic decisions, the error correction mechanism (ECM) in the error-correction representation of a system of co-integrated variables may arise from forward-looking behavior In such a case, the estimated ECM coefficients may misleadingly appear to be insignificant or to have the opposite-than-expected sign if the variables in the error-correction representation do not adequately capture short-run expectations This paper explores the nature of this problem with a theoretical model for consumption and demonstrates how severe the problem can be with US data Because the conditions for similar erroneous inferences are likely to apply to many other settings, the paper also recommends a reexamination of the evidence in cases where the ECM appears to be insignificant or to display the "wrong" sign
15 Dec 1996
TL;DR: A communication protocol is proposed that is provably secure and practical for implementation of the medical device vigilance system and a scenario for the operation of the MDVS network based on this protocol is presented.
Abstract: The medical device vigilance system (MDVS) is a Europe-wide system concerned with the exchange of information, generated from the process of investigating a medical device incident, among various authorized parties. Due to the sensitivity of the exchanged information, security is of primary importance. In order to address the security requirements of the MDVS, a communication protocol is proposed that is provably secure and practical for implementation. In addition, a scenario for the operation of the MDVS network based on this protocol is presented.
Posted Content•
TL;DR: In this paper, the authors evaluate the ability of the empirical model of asset pricing of Campbell (1993a,b) to explain the time-series and cross-sectional variation of expected returns of portfolios of stocks.
Abstract: This paper evaluates the ability of the empirical model of asset pricing of Campbell (1993a,b) to explain the time-series and cross-sectional variation of expected returns of portfolios of stocks. In Campbell's model, an alternative risk-return relationship is derived by substituting consumption out of the linearized first-order condition of the representative agent. We compare this methodology to models that use actual consumption data, such as the model of Epstein and Zin, 1989, 1991, and the standard consumption-based CAPM. Although we find that Campbell's model fits the data slightly better than models which explicitly price consumption risk, and provides reasonable estimates of the representative agent's preference parameters, the parameter restrictions of the Campbell model, as well as its over-identifying orthogonality conditions, are generally rejected. The parameter restrictions of the Campbell model, and the over-identifying conditions, are marginally not rejected when the empirical model is augmented to account for the "size effect".
Journal Article•
TL;DR: This paper describes a conceptual data model that has been derived within the scope of the EUROMEDIES project and accepted by project participants as a meaningful representation of data requirements on medical device vigilance.
Abstract: Effective and efficient medical device vigilance information exchange requires addressing several organizational and technical issues in a harmonized way. This paper describes a conceptual data model that has been derived within the scope of the EUROMEDIES project and accepted by project participants as a meaningful representation of data requirements on medical device vigilance. A possible scenario of a distributed implementation of the model is also discussed.
01 Sep 1996
TL;DR: Morphological filters are introduced in the matching approach with which to overcome inherent problems of correlation based techniques in the performance of optical flow computation at the first early level.
Abstract: Local information in not always enough for efficient motion analysis. Additive processing is required to get accurate results. This has been formulated as the aperture problem. Block matching algorithms are applied between successive images for motion estimation, assuming conservation of local intensity distribution. Matching approaches provide good results when the aperture problem does not exist. However, in regions when the aperture problem exists, additional constraints are required in order to recover the displacement of pixels between consecutive images. In this paper we present a way to improve the performance of optical flow computation at the first early level. Morphological filters are introduced in the matching approach with which we overcome inherent problems of correlation based techniques.
Proceedings Article•
01 Jan 1996