Showing papers by "University of Piraeus published in 1995"
TL;DR: In this article, the influence of product complexity on the purchasing structure within selected product types and phases of the purchasing process by using Analysis of Variance on data from Greek manufacturing and utility enterprises was examined.
Abstract: This article reports on the influence of product complexity on the purchasing structure within selected product types and phases of the purchasing process by using Analysis of Variance on data from Greek manufacturing and utility enterprises. Our study examined the influence of product complexity on four parameters of purchasing structure, across two different product types and four phases of the purchasing process. The results suggested that all but one parameter varied considerably among different degrees of product complexity and that their configuration depended on attributes such as product differentiation, technical complexity, specialized installation, and existence of after sale service.
67 citations
TL;DR: In this paper, a multivariate statistical analysis is applied to measure the banking performance on the basis of financial ratios that derive from the study of financial statements of a sample of Greek banks for the period 1989-1992.
Abstract: Ordinal regression analysis is proposed as a means for evaluating banking performance over multiple attributes in the presence of non-monotonic preferences. First, a multivariate statistical analysis is applied to measure the banking performance on the basis of financial ratios that derive from the study of financial statements of a sample of Greek banks for the period 1989-1992. Then, an additive utility model is assessed to obtain the final ranking of a representative sample of Greek banks
43 citations
TL;DR: The grade of similarity, LA.
31 citations
01 Jan 1995
TL;DR: The main model presented in this paper estimates an additive utility function with non-monotonic partial utilities by analysing some ordinal inter-alternative information provided by the decision maker by means of ordinal regression.
Abstract: Ordinal regression is used for modelling the problem of multiattribute choice in the presence of non-monotonic preferences. The main model presented in this paper estimates an additive utility function with non-monotonic partial utilities by analysing some ordinal inter-alternative information provided by the decision maker. Then the model is extended to fit in special conditions where intensity-of-preference information is available or concavity of the utility model is required.
23 citations
TL;DR: In this paper, the problem of estimating the number of production runs and the corresponding lot sizes in a batch type production system has been treated using fuzzy concepts in order to represent qualitative estimates that are expressed linguisticaly.
16 citations
TL;DR: It is shown that both algorithms lead to the same minimum value of the objective function, and that all the alternative optima of either method may be determined, if those optima derived from the other method are known.
Abstract: The optimal due date determination and sequencing problem of n jobs, on a single machine, with deterministic processing times is reviewed. An algorithm, using the SLK method, has been previously described by the authors, by means of which one optimal sequence as well as all the alternative optima are determined without resorting to the Complementary Pair and Exchange Principle concepts. In this paper, a similar algorithm using the CON method is proposed, the optimization criterion being the minimization of the total lateness penalty. It is shown that both algorithms lead to the same minimum value of the objective function. It is also shown that all the alternative optima of either method may be determined, if those optima derived from the other method are known.
6 citations
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TL;DR: In this paper, the causal negative influence from margin requirements to market participation in futures markets has been investigated, showing that as margin requirements increase, market participants leave the metal futures market affected by the margin increase and apparently move into similar metal markets unaffected by the increase.
Abstract: There is a clear causal negative influence from margin requirements to market participation in futures markets. As margin requirements increase, market participants leave the metal futures market affected by the margin increase and apparently move into similar metal markets unaffected by the increase. The behavioral differences between target and benchmark metals are not only economically important but also strongly statistically significant. We use a benchmark sample of other related contracts that do not undergo a similar margin change and, by comparing the behavior of target and benchmark metals, we assess more precisely the presence or absence of true causality from the change in margin requirements to the target contract. To our knowledge, this is the first study that uses a benchmark sample to explore the causal influence of futures margins.
5 citations
TL;DR: In this article, the current status of OR practice in Greece and the trends and challenges it faces are described, and the profile of OR in both public and private sectors and the specific role of the country's OR society are outlined.
5 citations
TL;DR: This work states that Boolean circuits are playing a more important role in the understanding of computation, and algebraic methods give a handle and allow for the first time to study complicated combinatorial structures.
5 citations
TL;DR: Four algorithms are developed for the solution of scheduling jobs in a single machine using the CON method, the objective function is the total weighted lateness with different penalties, allocated to early and tardy jobs.
4 citations
01 Jan 1995
TL;DR: This work considers a variant of the Burmester-Desmedt conference key distribution system, based on public keys, that has a low communication and computation complexity and the security is based on the intractability of the Diffie-Hellman problem.
Abstract: We consider a variant of the Burmester-Desmedt conference key distribution system proposed at Eurocrypt ′94. Our system is also based on public keys and has a low communication and computation complexity. Each party exchanges only three messages, and only a few multiplications are required. The security is based on the intractability of the Diffie-Hellman problem.
TL;DR: In this article, the status of OR Societies, members of the EURO, is surveyed based on a questionnaire addressed to the societies, where the authors refer to membership, activities (publications, conferences, etc.) and objectives of societies, their views about EURO and their financial status.
19 Apr 1995
TL;DR: This paper analyzes the ability of several bounded degree networks to tolerate faults and shows that an N-node butterfly containing N/sup 1-/spl epsiv// worst-case faults can emulate a fault-free butterfly of the same size with only constant slowdown.
Abstract: This paper analyzes the ability of several bounded degree networks that are commonly used for parallel computation to tolerate faults. Among other things it is shown that an N-node butterfly containing N/sup 1-/spl epsiv// worst-case faults (for any constant /spl epsiv/>0) can emulate a fault-free butterfly of the same size with only constant slowdown. Similar results are proven for the shuffle-exchange graph. Hence, these networks become the first connected bounded-degree networks known to be able to sustain more than a constant number of worst-case faults without suffering more than a constant-factor slowdown in performance. >
TL;DR: In this article, two special cases of the generalized inverse problem, namely, given R and B find A such that A ° R = B, where R, B and A are fuzzy matrices, are considered.
19 Apr 1995
TL;DR: A queueing model is developed and evaluated, based on runtimes as obtained from measurements of the test system, and it is demonstrated that significant performance improvements can be achieved once the process scheduling strategy at the ISDN protocol testers is properly adjusted.
Abstract: Conformance testing of communication protocols has recently become a major issue in the context of OSI-based standardization of protocols. The aim of conformance testing is to assure that a protocol fulfils an OSI specification. A performance study is presented for a distributed protocol test system that has been installed for conformance testing of the ISDN D-channel signalling protocol. Using a general approach for performance measurements and evaluation in distributed systems, a queueing model is developed and evaluated, based on runtimes as obtained from measurements of the test system. It is demonstrated that significant performance improvements can be achieved once the process scheduling strategy at the ISDN protocol testers is properly adjusted. >
TL;DR: A set of deadlock free router functions relevant to the iWarp system configurations are described and proven to be correct and reveals the design options to deal with irregularities and shows how additional flexibility can be used to achieve better load balancing.
TL;DR: In this article, the authors introduce a category of (topological) measure spaces in which inductive limitis exist and where the Banach spaces are isometric for arbitrary inductive systems.
Abstract: We introduce a category of (topological) measure spaces in which inductive limitis exist and where the Banach spaces
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and
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(1≤p≤+∞) are isometric for arbitrary inductive systems
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of (topological) measure spaces.
01 Jan 1995
TL;DR: The need to improve performance, especially quality, at an unprecedented pace, has become a prerequisite for survival and growth for manufacturing or service companies as discussed by the authors, and it is also important in the public sector and non-profit organizations.
Abstract: The development of global markets and deregulation of many industries have intensified competition. Management in most companies must now address issues related to the definition and measurement of their performance. The need to improve performance, especially quality, at an unprecedented pace, has become a prerequisite for survival and growth for manufacturing or service companies. It is also important in the public sector and non-profit organizations.
TL;DR: This paper identifies the Operations Research problems from a systems view of information, knowledge and understanding as a basis for a developmental approach to problem solving and decision making processes.
Abstract: This paper identifies the Operations Research (O.R.) problems from a systems view of information, knowledge and understanding. This systems view is examined as a basis for a developmental approach to problem solving and decision making processes. O.R. wisdom lies in achieving a balance between short-and long-term goals through a process of participation and learning.