Showing papers by "University of Patras published in 1980"
TL;DR: In this article, the influence of a crack in a welded joint on the dynamic behavior of a structural member is discussed and the relation between the change in natural frequency of vibration of a cantilever beam and the crack depth that appears at the built-in edge which is clamped by way of a weld is investigated.
246 citations
106 citations
TL;DR: A survey of the work performed over the last two decades on the system reliability optimization, and a global view of the state of art of the field of optimal reliability design is provided.
Abstract: The paper provides a survey of the work performed over the last two decades on the system reliability optimization. The relevant system models are first given and a set of problems, covering most cases, are formulated. Then, the optimization techniques, used for solving these problems, are briefly described, and a number of representative illustrative examples are collected. It is hoped that the paper helps in obtaining a global view of the state of art of the field of optimal reliability design.
59 citations
TL;DR: Two chromatographical systems for the separation and determination of glucosamine and galactosamine are described and both determinations can be used when there are large differences in the relative amounts of the two hexosamines.
49 citations
TL;DR: In this article, two differentiation trends are recognized in the shoshonites. They were probably derived from partial melting of garnet peridotite enriched in LILE, with later fractionation controlled by anhydrous phases.
Abstract: Mid-Miocene shoshonitic volcanism in Lesbos is preceded and followed by minor calcalkaline activity that probably terminated in the Pliocene. Two differentiation trends are recognised in the shoshonites. The older shoshonites include voluminous acid rocks (mostly ignimbrites) and show normal shoshonite REE patterns. They were probably derived from partial melting of garnet peridotite enriched in LILE, with later fractionation controlled by anhydrous phases. Cooling units in the ignimbrites show upward increase in the K content of glass, suggesting K-feldspar fractionation in a high level magma chamber. Later shoshonites and the calc-alkali rocks have HREE enrichment and contain hydrous cognate xenoliths. Partial melting of a rising periodite diapir which had been relatively enriched in HREE within the garnet stability field and then entered the spinel stability field, would produce the observed HREE enrichment pattern. Later fractionation of these younger shoshonites and calc-alkali rocks was controlled largely by hydrous phases.
45 citations
TL;DR: In this article, the effects of a uniform transverse magnetic field on the free-convection flow of a viscous incompressible and electrically conductive fluid past an impulsively started, infinite, porous, vertical limiting surface (e.g., of a star) with a constant suction were analyzed.
Abstract: This paper provides a comprehensive analysis of the effects of a uniform transverse magnetic field on the free-convection flow of a viscous incompressible and electrically conductive fluid (e.g., of a stellar atmosphere) past an impulsively started, infinite, porous, vertical limiting surface (e.g., of a star) with a constant suction. The magnetic Reynolds number is assumed small so that the induced magnetic field is considered negligible. Exact solution of the equations governing the flow is obtained in closed form with the help of the Laplace transform technique when the Prandtl numberP=1. Expressions are given for the velocity field, for the temperature field and for their related quantities. The results thus obtained are discussed quantitatively in the last section of this paper.
27 citations
TL;DR: Feeding of the F1 larvae on a medium with BLM increased somatic crossing-over spots on female tergites and induced recombination in male germ cells, however, nonlinear dose-response curves were obtained.
Abstract: Bleomycin (BLM) is well known as an antibiotic as well as for its antineoplastic activity. A clinical preparation of BLM was tested for its recombinogenicity in a higher eukaryotic organism, Drosophila melanogaster . Feeding of the F 1 larvae on a medium with BLM increased somatic crossing-over spots on female tergites and induced recombination in male germ cells. However, nonlinear dose—response curves were obtained. Malformed tergites were also observed in females treated with BLM.
19 citations
TL;DR: The cytological analysis of the chromosomes of third-instar larvae deriving from appropriate crosses of the 31.1 MRF showed that the factor induced breaks in all major chromosomes (X, II, III), and that 51.81% of them occurred in sites showing late replication and/or ectopic pairing.
Abstract: A cytological analysis was carried out on the salivary-gland chromosomes of third-instar larvae deriving from appropriate crosses of the 31.1/ CyL 4 strain with the dp b cn bw and dp b cn bw; ve strains. (1) The 31.1 MRF induced chromosomal rearrangements in both male and female germ cells. (2) The aberrations that occurred in the male germ cells were of three types — inversions, duplications and deficiencies — whereas those that occurred in the female germ cells were of all types. (3) The distributions of the break-points among the 4 major autosomal arms between the 1F 2 and 2AF 2 larvae were different. (4) The total distribution of the break-points along the polytene chromosomes showed that the factor induced breaks in all major chromosomes (X, II, III), and that 51.81% of them occurred in sites showing late replication and/or ectopic pairing. (5) A relationship existed between the frequencies of the second chromosomal aberrations and male recombination. A comparison of the break-points induced by the factor was made with those found in the rare endemic inversions of the same natural population from which the 31.1 MRF was isolated. The possibility that the factor acts in the natural population is discussed.
18 citations
TL;DR: In this paper, it was shown that low soluble calcium is a prerequisite for C 4 -photosynthetic carbon fixation, which is consistent with the hypothesis that low-soluble calcium is necessary and sufficient for carbon fixation.
18 citations
TL;DR: The fluidized bed system is a new method for the biological removal of carbonaceous BOD, nitrification, and denitrification of wastewaters as mentioned in this paper, which offers a much higher surface area per unit volume of reactor on which the microorganisms grow.
Abstract: The fluidized bed system is a new method for the biological removal of carbonaceous BOD, nitrification, and denitrification of wastewaters. The theory developed provides a method for determining the design and operating parameters of the fluidized bed process for the removal of carbonaceous BOD. The theory can be used to determine the optimal operational conditions of the system. The fluidized bed system offers a much higher surface area per unit volume of reactor on which the microorganisms grow, and, therefore, it can operate with much higher concentrations of biological mass than other systems. As a result, the fluidized bed system requires considerably less space and lower construction costs than others, and it should be considered as a welcome addition to the variety of wastewater treatment systems available.
17 citations
TL;DR: In this article, it was shown that minimum distance estimates enjoy the invariance property of maximum likelihood estimates, and that they enjoy the same invariance properties as maximum likelihood estimators.
Abstract: It is shown that minimum distance estimates enjoy the invariance property of maximum likelihood estimates
TL;DR: In this article, the properties of oxamic acid complexes with Zn(II), Cd(II) and Hg(II ) were investigated using analytical, conductometric and IR spectral data.
TL;DR: All C(4) plants examined kept their soluble calcium and interference with pyrophosphatase activity at very low levels, whereas the C(3) plants covered the whole range of soluble calcium concentration, and the hypothesis is advanced that low soluble calcium might be a prerequisite for high activity of pyroph phosphatase and the C4 pathway.
Abstract: Assays of alkaline pyrophosphatase activity in crude plant extracts are inhibited by soluble calcium coextracted with the enzyme from leaf tissues. Calcium concentrations in most extracts are high enough to interfere seriously with the assay. All C 4 plants examined kept their soluble calcium and interference with pyrophosphatase activity at very low levels, whereas the C 3 plants covered the whole range of soluble calcium concentration. The hypothesis is advanced that low soluble calcium might be a prerequisite for high activity of pyrophosphatase and the C 4 pathway.
TL;DR: Turbidimetric and viscometric results obtained with the ternary systems methanol/cyclohexane/poly(tetrahydrofuran) and water/butyl cellosolve/Poly(ethylene glycol) are reported in this paper.
Abstract: Turbidimetric and viscometric results obtained with the ternary systems methanol/cyclohexane/poly(tetrahydrofuran) and water/butyl cellosolve/poly(ethylene glycol) are reported. The turbidimetric results show that a small quantity of polymer changes extensively the coexistence curve of the solvent mixture, especially near the critical point of the two solvents. The viscometric results show that both polymers, poly(tetrahydrofuran) and poly(ethylene glycol) present abnormally high dimensions near the critical point of the two liquids.
TL;DR: In this paper, the reaction of 2-carboethoxyethyl-4,5-dimethoxybenzene sulfochloride with substituted pyridines leads to the corresponding sulfonamides.
TL;DR: In this article, the influence of the various parameters entering into the problem, especially of the magnetic parameter M, is extensively discussed and a comparative study with hydrodynamic case (M=0) is also made.
Abstract: Unsteady hydromagnetic boundary layer flow of a viscous incompressible and electrically conducting fluid past an infinite vertical non-conducting porous limiting surface in presence of a transverse magnetic field, is considered when the limiting surface is moving impulsively in its own plane and is subjected to a constant suction. The free stream oscillates in time about a constant mean value and the magnetic Reynolds number is taken to be small enough so that the induced magnetic field is negligible. As the mean steady flow has been presented in Part I, only the solutions for the transient velocity profiles, transient temperature profiles, the amplitude and the phase of the skin friction and the rate of the heat transfer are presented in this work. The influence of the various parameters entering into the problem, especially of the magnetic parameterM, is extensively discussed. A comparative study with hydrodynamic case (M=0) is also made.
01 Jan 1980
TL;DR: In this paper, a certain class of continuous time parameter Markov processes is considered, whose probability law depends on a k-dimensional parameter, and under suitable regularity conditions, several asymptotic results are devived.
Abstract: In this paper, a certain class of continuous time parameter Markov processes is considered, whose probability law depends on a k-dimensional parameter. Then, under suitable regularity conditions, several asymptotic results are devived. These results are sufficient to allow us to draw statistical inferences about the stochastic processes in question.
TL;DR: In this article, the properties of pyridine and aniline complexes are described. But the preparation, for the first time, and properties of the title compounds are described only in terms of their X-ray powder spectra.
Abstract: The preparation, for the first time, and the properties of the title compounds are described. Analytical conductometric, spectral (infrared and ultraviolet) and data from X-ray powder spectra yield information about the probable structure of the complexes in the solid state. The existence of metal-nitrogen bond for all pyridine and aniline complexes, except H2CdI4·4An (An=aniline), is adduced from infrared and far infrared spectral studies.
TL;DR: In this article, the authors studied the problem of quantum friction in the Wigner representation for quadratic Hamiltonians and showed that for these distributions the product of the standard deviations of p and q is greater or equal to,NU>◑ 2 so that the uncertainty principle of Heisenberg holds.
Abstract: In this paper we shall study the problem of quantum friction in the Wigner representation. For quadratic Hamiltonians the Wigner equation coincides with the classical Liouville equation although there are distribution functions which depend on the Planck constant. For these distributions the product of the standard deviations of p and q is greater or equal to ,NU>◑ 2 so that the uncertainty principle of Heisenberg holds.
TL;DR: In this article, the effects of mass transfer on free convection flow of an electrically conducting viscous fluid past an impulsively started infinite vertical limiting surface (e.g., of a star) in presence of a transverse magnetic field is considered.
Abstract: The effects of the mass transfer on free convection flow of an electrically conducting viscous fluid (e.g., of a stellar atmosphere) past an impulsively started infinite vertical limiting surface (e.g., of a star) in presence of a transverse magnetic field is considered. Solutions for the velocity and skin-friction, in closed form are obtained with the help of the Laplace transform technique and the results obtained for various values of the parametersSc (Schmidt number),P (Prandtl number) andM (Hartmann number) are given in graphical form. The paper is concluded with a discussion of the results obtained.
TL;DR: In this article, a useful approach for implementing such an approximation is presented, which makes use of double Walsh series expansions and is based on finited output measurements at a specified set of spatial points.
TL;DR: In this paper, the possibility of treating a wormlike polymer as a random coiled polymer is examined, taking from the literature intrinsic viscosity data concerning several wormlike polymers, using two graphical methods which have been proposed for flexible polymers.
TL;DR: In this paper, the authors analyzed the temperature fluctuations in a mercury turbulent-free convection layer in the presence and absence of a magnetic field, and the statistical quantities obtained from the analysis were the flatness, skewness and intermittency factors.
TL;DR: In this paper, an experimental procedure was developed for the determination of pad bearing performance by means of nonlinear stiffness pad functions, which describe the pad reaction for each location of the journal.
Abstract: An experimental procedure was developed for the determination of pad bearing performance by means of nonlinear stiffness pad functions. These functions describe the pad reaction for each location of the journal. The performance of the complete bearing is then computed from the assembly of the individual pad functions. This yields a complete static nonlinear description of the bearing forces. The same method, that is by using nonlinear damping pad functions, can as well be used for investigating the dynamic behavior of tilting pad bearings. This procedure can be used in two ways: (a) To tabulate the functions for an adequate constellation of the design parameters of the pads and from them compute the performance parameters of the bearing such as load carrying capacity and linear coefficients, (b) To incorporate these functions into a nonlinear numerical analysis of the dynamic response of the rotor-bearing system. Comparison of the static state results with previous investigations on complete bearings shows a good agreement while existing numerical solutions give unacceptable results for wide areas of bearings operation.
TL;DR: A modification of the differentialfile approach in that the differential file only stores record additions, and is concerned with the selection of the optimum reorganization points for both the original and the modified differential file approaches.