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Showing papers by "University of the Aegean published in 1999"


Journal ArticleDOI
05 Nov 1999-Science
TL;DR: Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.
Abstract: At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.

1,870 citations


Journal ArticleDOI
TL;DR: In this paper, a computationally efficient and rigorous thermodynamic model (ISORROPIA) is presented to predict the physical state and composition of inorganic atmospheric aerosol.

318 citations


Journal ArticleDOI
TL;DR: An overview of existing work in the area of BPR is presented with the aim of highlighting the different categories of B PR methodologies identified in the literature, their focus on the redesign process and the general BPR principles that emerge from them.
Abstract: A plethora of BPR methodologies have appeared in the literature during recent years, however, most of them present serious limitations mainly due to the need for a multi‐disciplinary approach. In this paper we present an overview of existing work in the area of BPR with the aim of highlighting the different categories of BPR methodologies identified in the literature, their focus on the redesign process and the general BPR principles that emerge from them. We also present a BPR methodology called Agent Relationship Morphism Analysis (ARMA) that goes beyond the limitations of the existing BPR methodologies taking a holistic view of the organisation. In ARMA the modelling of the business environment is achieved with the use of three perspectives: the structural, behavioural and process. The use of these three perspectives provides insight to the relationship between organisational structure and organisational processes.

152 citations


Journal ArticleDOI
TL;DR: The results show that the mean competition strengths fall as assembly progresses and that most interactions in the communities formed are weak, implications for management and conservation of natural communities are substantial.
Abstract: Strength of interactions between species may be an important tool in our effort to understand community structure. Recent theoretical and empirical findings suggest that despite the presence of some strong interactions, weak interactions prevail in communities. Here, we examine how mean interaction strengths change as theoretical competition communities assemble and what the distribution of interaction coefficients is in the communities that are formed during the assembly process. Our results show that the mean competition strengths fall as assembly progresses and that most interactions in the communities formed are weak. Communities that are invulnerable to further invasions are those where interspecific interactions are weaker than the average interaction strength between species in the pool. If these results can be generalized to more than one trophic level, implications for management and conservation of natural communities are substantial.

131 citations


01 Jan 1999
TL;DR: In this article, a review summarizes factors affecting DBP formation and predictive equations proposed for it, physical and chemical properties, environmental fate, actual measurements of these compounds and technologies for controlling them, as well as regulation and currently proposed changes of their Maximum Contaminant Levels (MCLs) after evaluation by EPA of new data available.
Abstract: Chlorination of drinking water leads to the formation of a variety of Disinfection By-Products (DBPs) that may have adverse health effects on humans. Research on this subject has been continued and new epidemiological and toxicological studies have been conducted. This review summarizes factors affecting DBP formation and predictive equations proposed for it, physical and chemical properties, environmental fate, actual measurements of these compounds and technologies for controlling them, as well as regulation and currently proposed changes of their Maximum Contaminant Levels (MCLs) after evaluation by EPA of new data available.

86 citations


Journal ArticleDOI
TL;DR: The most commonly followed techniques for the application of formal methods for the ex-post analysis and verification of cryptographic protocols, as the analysis approach are reviewed, followed by the examination of robustness principles and application limitations.

82 citations


Journal ArticleDOI
Sergei Chekanov1, M. Derrick1, S. Magill1, B. Musgrave1  +333 moreInstitutions (47)
TL;DR: In this article, the production of forward jets has been measured in deep inelastic ep collisions at HERA in terms of single differential cross sections as a function of the Bjorken scaling variable (x_{Bj}) and as triple differential cross-sections d^3 \sigma / dx{Bj} dQ^2 dp_{t,jet}^2, where q is the four momentum transfer squared and p is the squared transverse momentum of the forward jet.
Abstract: The production of forward jets has been measured in deep inelastic ep collisions at HERA. The results are presented in terms of single differential cross sections as a function of the Bjorken scaling variable (x_{Bj}) and as triple differential cross sections d^3 \sigma / dx_{Bj} dQ^2 dp_{t,jet}^2, where Q^2 is the four momentum transfer squared and p_{t,jet}^2 is the squared transverse momentum of the forward jet. Also cross sections for events with a di-jet system in addition to the forward jet are measured as a function of the rapidity separation between the forward jet and the two additional jets. The measurements are compared with next-to-leading order QCD calculations and with the predictions of various QCD-based models.

72 citations


Journal ArticleDOI
TL;DR: A risk analysis is performed on a typical small enterprise and a home‐office set‐up to identify the risks associated with availability, confidentiality, and integrity requirements.
Abstract: The pervasive use of information technology in enterprises of every size and the emergence of widely deployed ubiquitous networking technologies have brought with them a widening need for security. Information system security policy development must begin with a thorough analysis of sensitivity and criticality. Risk analysis methodologies, like CRAMM, provide the ability to analyse and manage the associated risks. By performing a risk analysis on a typical small enterprise and a home‐office set‐up the article identifies the risks associated with availability, confidentiality, and integrity requirements. Although both environments share weaknesses and security requirements with larger enterprises, the risk management approaches required are different in nature and scale. Their implementation requires co‐operation between end users, network service providers, and software vendors.

69 citations


Journal ArticleDOI
TL;DR: In this article, the concepts of semistrict quasimonotonicity and strict quasiconvexity for multivalued maps are introduced. And an existence result for the corresponding variational inequality problem is obtained.
Abstract: New concepts of semistrict quasimonotonicity and strict quasimonotonicity for multivalued maps are introduced. It is shown that a locally Lipschitz map is (semi)strictly quasiconvex if and only if its Clarke subdifferential is (semi)strictly quasimonotone. Finally, an existence result for the corresponding variational inequality problem is obtained.

65 citations


Journal ArticleDOI
TL;DR: The notion of proper quasimonotonicity is introduced in this paper, which is related to the KKM property of multivalued maps and makes it more useful in applications to variational inequalities.

55 citations


Journal ArticleDOI
TL;DR: In this paper, a preliminary analysis of the influence of informal activities on the sustainability of development, as well as their policy and planning implications, is presented, based on a survey of the most sustainable developm...
Abstract: This article offers a preliminary analysis of the influence of informal activities on the sustainability of development, as well as their policy and planning implications. Most sustainable developm...

Journal ArticleDOI
TL;DR: The existence of conserved currents in completely integrable classical models, including chiral and Toda models as well as the KP and self-dual Yang-Mills equations, is traced back to a simple construction of an infinite chain of closed (respectively, covariantly constant) 1-forms in a (gauged) bi-differential calculus as mentioned in this paper.
Abstract: The existence of an infinite set of conserved currents in completely integrable classical models, including chiral and Toda models as well as the KP and self-dual Yang-Mills equations, is traced back to a simple construction of an infinite chain of closed (respectively, covariantly constant) 1-forms in a (gauged) bi-differential calculus The latter consists of a differential algebra on which two differential maps act In a gauged bi-differential calculus these maps are extended to flat covariant derivatives

Journal ArticleDOI
TL;DR: In this paper, five different approaches for the estimation of the regional flux of sensible and/or latent heat over the NOPEX area have been evaluated: (1) Direct aggregation, mixed layer evolution method, weighted averages of (a) aircraft measurements in the boundary layer and of (b) mast measurements, (3) Numerical models (e.g., ECOMAG), a distributed hydrological model and MIUU), a mesoscale meteorological model.

Journal ArticleDOI
TL;DR: In this article, the authors present measurements of Thermoluminescence (TL) from Greek marble quarried at Paros, Naxos, Pendeli, Hymitos, Thassos, which have been known since ancient times.
Abstract: We present measurements of Thermoluminescence (TL) from Greek marble quarried at Paros, Naxos, Pendeli, Hymitos, Thassos, which have been known since ancient times. The results concern i) the solar bleaching of TL, ii) the solar transmission through marble thicknesses up to 16 mm, and iii) the implications for potential dating of ancient carved marble monuments/objects. The bleaching rate for marbles is very fast during the first hour of exposure. The solar penetration is at least 35 mm for long exposures. Beyond the 2 mm marble slab for exposure times 90–120 hours of sunshine, the residual bleached TL level is not reached. The bleached TL reaches a plateau which serves as the “zero time” upon which the archaeological TL dose subsequently builds up and gives the age of a marble monument.

Journal ArticleDOI
TL;DR: It was found that, as the underlying technologies mature, a Web-based trusted third party architecture provides a viable solution for delivering secure telemedical applications.

Journal ArticleDOI
TL;DR: This paper demonstrates how TTPs can be used effectively in order to develop medical applications that run securely over the World Wide Web.
Abstract: The EUROMED-ETS pilot system offers a number of security functionalities using off-the-shelf available products, in order to protect Web-based medical applications. The basic concept used by the proposed security architecture is the Trusted Third Party (TTP). A TTP is used in order to generate, distribute and revoke digital certificates to medical practitioners and healthcare organizations that wish to communicate securely. Digital certificates and digital signatures are used to provide peer and data origin authentication and access control. The paper demonstrates how TTPs can be used effectively in order to develop medical applications that run securely over the World Wide Web.

Journal ArticleDOI
TL;DR: In this paper, the optimal buffer allocation in short μ -balanced production lines consisting of machines that are subject to breakdown is investigated, where repair times and times to failure are assumed exponential, whereas service times are allowed to follow the Erlang- k distribution.

Journal ArticleDOI
TL;DR: In this paper, the relationship between the reduction of order through point symmetries and integration is explored with particular emphasis on the loss and gain of point (contact for third order) symmets to and from non-local symmets.

Journal ArticleDOI
TL;DR: In this paper, the uniqueness of the Schwarzian from a group theoretic point of view was investigated and the Kummer-Schwarz equation was analyzed for its group properties.

Journal ArticleDOI
TL;DR: In this work an integrated and distributed ES is developed which supervises the control system of the whole treatment plant and has the capability to learn from the correct or wrong solutions given to previous cases.
Abstract: The activated sludge process is a commonly used method for treating wastewater. Due to the biological nature of the process it is characterized by poorly understood basic biological behavior mechanisms, a lack of reliable on-line instrumentation, and by control goals that are not always clearly stated. It is generally recognized that an Expert System (ES) can cope with many of the common problems relative with the operation and control of the activated sludge process. In this work an integrated and distributed ES is developed which supervises the control system of the whole treatment plant. The system has the capability to learn from the correct or wrong solutions given to previous cases. The structure of the suggested ES is analyzed and the supervision of the local controllers is described. In this way, the main problems of conventional control strategies and individual knowledge-based systems are overcome.

Journal ArticleDOI
TL;DR: This paper presents the application of ARMA in a petrochemical industry, and presents the verification of the ARM and ALC/OLC models in order to secure that the resulting formal models are logically consistent.

01 Jan 1999
TL;DR: The objective is to specify an abstract reference model for the PKI as a combination of the results of various European projects, which is scaleable, based on standards and flexible across different domains, geographical areas and business sectors.
Abstract: We review the Public Key Infrastructure in Europe as outlined in various INFOSEC and ACTS projects. The objective is to specify an abstract reference model for the PKI as a combination of the results of various European projects, which is scaleable, based on standards and flexible across different domains, geographical areas and business sectors. The user requirements in various business domains, such as health, transport and public information systems are extracted and highlighted. The user needs are then used as the reference for the development of the services that a Trusted Third Party must offer to its users and consequently they will be the base for # In Simone Fisher-Hübner, Gerald Quirchmayr, and Louise Yngström, editors, User Identification & Privacy Protection: Applications in Public Administration & Electronic Commerce, pages 229-242, Kista, Sweden, June 1999. IFIP WG 8.5 and WS 9.6. This is a machine-readable rendering of a working paper draft that led to a publication. The publication should always be cited in preference to this draft using the reference in the previous footnote. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. 2 Dimitrios Lekkas et al the construction of an abstract reference model. This model outlines in general terms the entities involved in the provision of TTP services and the functions supporting their interactions.

Journal ArticleDOI
TL;DR: A peephole optimiser is designed that operates using a declarative specification of the optimisations to be performed to convert target machine instruction sequences containing conditional execution of instructions inside loop bodies into code that adaptively executes the optimum branch instructions according to the program's branch behaviour.
Abstract: Peephole optimisation as a last step of a compilation sequence capitalises on significant opportunities for removing low level code slackness left over by the code generation process. We have designed a peephole optimiser that operates using a declarative specification of the optimisations to be performed. The optimiser's implementation is based on string pattern matching using regular expressions. We used this approach to prototype an optimiser to convert target machine instruction sequences containing conditional execution of instructions inside loop bodies into code that adaptively executes the optimum branch instructions according to the program's branch behaviour.

Journal ArticleDOI
TL;DR: In this article, the authors used the soil-gas method to compare geochemical data with the geological and structural information on Lesbos Island (NE Aegean) in particular in the Aghia Paraskevi-Kalloni region, the epicentral area of an earthquake in 1867.

Journal ArticleDOI
01 Jan 1999
TL;DR: In this paper, the existence of periodic solutions for differential inclusions with nonconvex-valued orientor fields was proved based on degree-theoretic arguments, and the results were generalized to the case of continuous orientors.
Abstract: In this paper we prove the existence of periodic solutions for differential inclusions with nonconvex-valued orientor field. Our proof is based on degree theoretic arguments.

Journal ArticleDOI
TL;DR: The structure of the transition matrices of these specific type of production lines is examined and a recursive algorithm is developed for generating them, which allows one to obtain the exact solution of a sparse linear system by the use of the Gauss–Seidel method.

Journal ArticleDOI
01 Sep 1999-Ethos
TL;DR: In this article, the authors argue that the imaginary body as flesh may be as much painfully or pleasantly experienced as the non-imaginary one, and that prospective donation as a culturally elaborated, somatic, intersubjective practice does not guarantee the material immediacy of self presence.
Abstract: Several body theorists focus on the precultural materiality of the body as flesh to argue against the discursively constructed, supposedly fleshless or imagined bodies of postmodernity. This article is about body perceptions of 24 people sharing an exceptionally fleshly and seemingly imagined experience: their determination to donate their organs or bodies after their death. Approaching prospective donation as a culturally elaborated, somatic, intersubjective practice, I argue, first, that flesh in itself does not guarantee the material immediacy of one's self presence. Second, that the imaginary body as flesh may be as much painfully or pleasantly experienced as the non-imaginary one.


Journal ArticleDOI
TL;DR: In this paper, a variational approach is used to derive a theory of elastic dielectrics with polarization gradient, quadrupole polarization and polarization inertia, and the relation of the present theory with existing ones is extensively discussed.
Abstract: In the present work a variational approach is used to derive a theory of elastic dielectrics with polarization gradient, quadrupole polarization and polarization inertia. The results (field equations, jump conditions and constitutive relations) are favorably compared with those of the approach followed in part I of this work. Finally, the relation of the present theory with existing ones is extensively discussed.

Proceedings ArticleDOI
05 Jan 1999
TL;DR: The identification, design and implementation of a user interface to a brokerage system and the conceptual architecture and functional behaviour of an intelligent interaction agent that supports and enhances the interaction between the user and the system are presented.
Abstract: This paper presents the identification, design and implementation of a user interface to a brokerage system and the conceptual architecture and functional behaviour of an intelligent interaction agent that supports and enhances the interaction between the user and the system. The term interaction agent is used in order to describe a particular class of interface agents that function as intelligent personal assistants to users of a computer based system. The interaction agent provides assistance to the user in two contexts. On the user interface level it assists users to comprehend and manipulate the user interface. On the domain of application level, it provides users with information and advice according to their preferences. This work is being carried out in the context of an ACTS (AC 221) project GAIA (Generic Architecture for Information Availability).