Cyprus Journal of Science and Technology Vol. 1.2 (1996)


List of Abstracts

Vlachos, G. and Tzannatos, E.

Ship Repair in the Eastern Mediterranean and the case of Greece

In this article, the past and future trends of the international shiprepair market are presented and analysed. In this analysis, it is acknowledged that new regional markets attract most of the attention. Therefore, the current status and prospects of the Eastern Mediterranean shiprepair industry due to its proximity with the emerging competition from East European yards attracted the attention of this work. The analysis of this regional shiprepair market concentrated on the Greek industry as being the regional leader. For the Greek shiprepair industry, its competitiveness was analysed on a regional and domestic basis, through reference to market shares, to areas (problems) of concern and improvement proposals.

Giziakis, K. and Giziaki, E.

Risk Assessment Methods in Shipping Safety

The ship losses are connected to safety. Reducing probable risks increases safety. Risk Analysis is distinguished in risk assessment and risk management. Risk assessment is a tool used for estimating the probability of being led to a failure as a result of the exposure to certain factors. Risk management uses the results of risk assessment to produce a decision about action to be taken.

This paper describes the statistical methodology that can be used in risk assessment to estimate the probability (risk) of failure and to quantify the effect of certain factors having a bearing on failure. It also includes an application of risk assessment for an effective port control.

Elena Vasseva, Evgeny Krustev

Theoretical Basis of European Code for Seismic Design of Structures - Eurocode 8

In the recent ten years the Commission of the European Communities (CEC) initiated the work of establishing of a set of harmonized technical rules for the design of building and civil engineering works, which would initially serve as an alternative to the different rules in force in the various Member States and would ultimately replace them. These technical rules became known as the “Structural Eurocode”. In this set of nine codes the code for earthquake resistant design of structures EUROCODE 8 is included. The Eurocode 8 was published in 1995 as a European Prestandards with an initial life of three years and is intended for experimental application and for the submission of comments.

This paper presents the overall philosophy and the theoretical basis of the current Prestandard EUROCODE 8 - ENV 1998, Part 1-1 and part 1-2 of May 1994. Particular attention is given to the basic spectrum analysis and to the recommended design procedures. The main tendency of EC8 is to emphasize the necessity of sound design of building - regularity of mass and stiffness distribution, and consequently to simplify the calculation as much as possible.

It is the main purpose of this paper to point out some basic problems, discussed in part 1-1, 1-2 of the Prestandard EUROCODE 8 and their connection with Bulgarian Code for seismic design of structures. Similar procedures can be applied to analyze the Cypriot Code and determine the necessary requirements for seismic building protection with respect to EUROCODE 8.

George Chrysostomou

Numerical Calculation of Bessel Functions by a Variational Method

A variational approach for calculating the first three zeros of the Bessel functions of the first kind and their derivatives for relatively small order not necessarily integer is presented. The trial functions used in the approach are simple polynomials which lead to closed form expressions for integrals involved in the method. A routine for solving generalized eigenvalue problems is used to calculate the estimates of the Bessel functions and their first three zeros as well as the first three zeros of their derivatives. The method was implemented on a VAX 11/750 machine using FORTRAN/IMSL routines. The accuracy of the estimates obtained is remarkable and the computational effort minimal.

Harry Papadopoulos

A Relationship between in situ void ratio and compression index of Sabkha

Sabkha is a material which is usually encountered at the surface in areas near the shoreline. This material when wet is amorphous and extremely soft and cohesion of less than 25KN/m2.

The development of an empirical relationship between in-situ void ratio and the compression index for saturated Sabkha soil material is presented here. These results will help the practising engineers to predict settlements with minimum and quick laboratory testing.

The relationship is applicable to Sabkha soils which consist mainly of calcium carbonate and have some sand and silty clay content. These or similar materials are encountered in the Eastern Province of Saudi Arabia. The Emirates, Israel, Egypt, Cyprus etc.

Test samples of the material specified above were taken from five different sites in the Eastern Province of Saudi Arabia. Samples from a sixth site were used to confirm the results of this study.

Christodoulos N. Christodoulou

Metallurgy techniques for the preparation of microcrystalline materials:  Sm2Fe17N3 permanent magnets

The Rapid Solidification (RS), Hydrogenation Decomposition Desorption Recombination (HDDR) and Powder Metallurgy (PM) processes in conjunction with nitrogenation have been employed to produce microcrystalline Sm2Fe17 - nitride-based permanent magnets. Depending on the alloy composition and quenching rate, the rapidly solidified alloys contained a mixture of the following phrase: α-Fe, metastable-SmFe7 Sm2Fe3, SmFe2 , Sm and an amorphous phase. In general, phases produced under low quenching rates (25m/sec) could also be produced in a combination of high quenching rates (55 m/sec) followed by flash-annealing (650°C for 10 min) under argon gas atmosphere. The HDDR process has been studied in terms of the reaction characteristics, phases present and development of the magnetic properties at the different stages involved in the process. On heating under hydrogen gas, the Sm2Fe17 phase begins to absorb hydrogen at the temperature of about 185°C and up to 250°C where the hydrogen concentration reaches a maximum value of about 2.4H atoms per mole of Sm2Fe17. Subsequently, interstitial hydrogen desorption occurs gradually up to the temperature of 510°C(Sm2Fe17H0.1), where a massive absorption of hydrogen takes place due to the decomposition of Sm2Fe17H0.1 into Sm-hydride + α-Fe. Additional heat-treatment of the ``Sm-hydrite + α-Fe'' mixture at temperatures of about 725°C or above under vacuum or argon gas flow, causes the simultaneous desorption of the Sm-hydride (forming Sm + H2 ) and recombination of Sm + α-Fe forming microcrystalline Sm2Fe17 phase. The powder metallurgy process involved a special preparation of sub-single grain powders, nitrogenation under N2 or N2 + H2 mixture and further pulverization. Magnets prepared by rapid solidification and HDDR processes exhibited iHc of 8.4 kOe and (BH)max of 36MGOe (assuming full density) were produced by using the powder metallurgy process. All of the produced magnets exhibit a Curie temperature of 470°C.

Andreas Poullikkas

A model for pumping two phase mixtures

We analyse the flow in a centrifugal pump when pumping two phase (gas/liquid) mixtures. A control volume method is employed to derive a model which combines the ideal (Eulers) two phase head of a centrifugal pump with additional losses due to compressibility and condensation of the gas phase. The results obtained are in close agreement with previous models and experimental investigations.

Vladimir A. Shikhin

Combined treatment of nonhomogeneous radar measurements

The objective of the paper is to present an effective method of combined statistical estimates for target parameters estimation under Automatic Object Recognition. The introduced algorithm can be used in any application dealing with different-accuracy measurements (possibly, optical or radar). It is also proven that it is possible to use in calculating the achieved low-accuracy data files. The proposed method of combined estimates gives final expression for calculating the unknown estimates, which are insensitive to considerable deviations in low-accuracy data files. Further, the paper discusses the problems of estimates accuracy controllability. In the case where estimates accuracy restrictions are given the available gains in the total number of needed measurements are analyzed. The experimental results are satisfactory and agree well with the reference solutions.

Ludmil Tzenov

Seismic Design of irregular structural systems

The paper proposes a formalism for seismic design of complex structural systems based on a generalization of the spectral method main concepts. It takes into consideration the nonuniform distribution of ground accelerations at the different points of the structure’s foundation, the existence of horizontal and vertical components of the seismic excitation and the most unfavorable or effective direction of the seismic excitation. A “loading function” is introduced in the suggested formulae for determining the design. It is shown that the well known formulae for determining the design seismic loading follow as a particular case of this formalism application for a particular value of the “loading function”. A numerical example of a 6 storey residential large panel building is here presented in order to illustrate the influence of the structure's length in planning its seismic design.