Approximate analysis of surface wave-structure interaction

Surface wave-structure interaction is studied starting from a specialised approximate formulation involving a hyperbolic equation for the Rayleigh wave along with pseudostatic elliptic equations over the interior of an elastic half-space. The validity of the proposed approach for modelling a point contact is analysed. Explicit dispersion relations are derived for smooth contact stresses arising from averaging the effect of a regular array of spring-mass oscillators and also of elastic rods attached to the surface. Comparison with the exact solution of the associated plane time-harmonic problem in elasticity for the array of rods demonstrates a high efficiency of the developed methodology

The Effect of Occupational Groups and Use of Alcohol and Smoking in Thrace on Semen Parameters

DergiPark: 378981tmsjAims: Research of the effect of alcohol and smoking of the male spouses of infertile couples and their occupational groups on sperm quality. Methods: 686 male cases who have applied to Trakya University, Faculty of Medicine, Department of Assisted Reproductive Techniques, Infertility Polyclinic were included in the assessment. As a result of the spermiogram test, every patient’s sperm count, motility and morphology were assessed. Occupational groups, usage of alcohol and smoking were enquired to each case. Mann Whitney U, Willcoxon Test was employed in the statistical analyses and the risk ratios were calculated.Results: Out of the 686 people, 353 were smokers (51.4%) and 333 were non-smokers (48.6%). The number of people who smoked and also consumed alcohol was 59 (8.6%). In terms of occupation, 132 people were unemployed (%19.2), 23 were being exposed to heat (%3.3), 256 had to stand while working (%37.3), 31 were being exposed to radiation and chemicals (%4.5), 199 had to be both stand and sitting while working (%29) and 45 had to sit while working (%6.5). As a result of our study, while no correlation between smoking and the sperm count and morphology could be observed, the sperm motility of the smoking group has been observed to be lower. However, no significant difference in terms of semen analysis could be observed between, just drinkers, both drinker and smokers and non-smokers and drinkers groups. Smokers and those who both smoke and have a job where they have to be sitting have a significantly lower sperm motility. When the sperm quality is observed amongst occupational groups in terms of alcohol, the sperm motility of the people who were only exposed to radiation and chemicals have significantly increased in the alcohol consumers.Conclusion: Semen quality is affected by numerous genetic and environmental factors. Smoking, alcohol consumption and being employed in certain occupational groups are just a few of many risk factor

Hareketli Dağilimli Yük Etkisi Altinda Kaplamali Bir Elastik Yari Uzayin Yüzey Yer Değiştirme Alani

1 Department of Mathematics, )DFXOW\RI6FLHQFHDQGUWGiresun University, Giresun, Turkey2 Department of Mathematics, )DFXOW\RI6FLHQFHAnadolu University, Eskişehir, TurkeyABSTRACTAn analysis of the distributed moving load along the surface of a coated half space is presented. The formulation of the problemdepends on the hyperbolic-elliptic asymptotic model developed earlier by the authors. The integral solution of the longitudinaland transverse displacements along the surface for the sub and super-Rayleigh cases are obtained by using the uniformstationary phase method. Numerical comparisons of the exact and asymptotic solutions of the longitudinal displacement areillustrated for the certain cross-sections of the profile.Kaplamalı elastik bir yarı uzayın yüzeyi boyunca dağılımlı hareketli yükün bir analizi sunulmuştur. Problemin formülasyonuyazarlar tarafından önceden geliştirilmiş hiperbolik-eliptik modele dayanmaktadır. Sub ve süper Rayleigh durumları için yüzeyboyunca boyuna ve enine yer değiştirmelerin integral çözümleri düzgün durağan faz metodu kullanılarak elde edilmiştir.Boyuna yer değiştirmenin tam ve asimptotik çözümlerinin nümerik karşılaştırmaları profilin belirli kesitleri için grafikler ilegösterilmiştir

Bounded Motions of the Dynamical Systems Described by Differential Inclusions

The boundedness of the motions of the dynamical system described by a differential inclusion with control vector is studied. It is assumed that the right-hand side of the differential inclusion is upper semicontinuous. Using positionally weakly invariant sets, sufficient conditions for boundedness of the motions of a dynamical system are given. These conditions have infinitesimal form and are expressed by the Hamiltonian of the dynamical system

Response of a 3D elastic half-space to a distributed moving load

The dynamic eect of an out of plane distributed moving load on thesurface of an elastic half-space is considered. The problem is formulatedin terms of a hyperbolic-elliptic asymptotic model for a movingload where the trajectory and the distribution of the load are taken tobe orthogonal. Steady-state equations are written in terms of a movingcoordinate system. The near-resonant solutions are, then, obtained forsub and super-Rayleigh cases taking into account the causality principle.Numerical results of displacement components are presented forvarious values of the distribution parameter

Low-frequency vibrations of a thin-walled functionally graded cylinder (plane strain problem)

Low frequency vibrations of a thin walled functionally graded cylinder are considered within the plane strain framework. The dynamic relations in elasticity are subject to asymptotic analysis over cylinder cross section resulting in a consistent approximate equation of motion on the mid-surface. A simple explicit formula for natural frequencies emerging from the derived equation is validated by comparison with previous numerical predictions. The formula demonstrates that the ratio of the natural frequencies for functionally graded and homogeneous cylinders does not depend upon the mode number. Useful expressions for the variation of all stress components across the thickness are also obtained

A revisit to the plane problem for low-frequency acoustic scattering by an elastic cylindrical shell

The proposed revisit to a classical problem in fluid–structure interaction is due to an interest in the analysis of the narrow resonances corresponding to a low-frequency fluid-borne wave, inspired by modeling and design of metamaterials. In this case, numerical implementations would greatly benefit from preliminary asymptotic predictions. The normal incidence of an acoustic wave is studied for a circular cylindrical shell governed by plane strain equations in elasticity. A novel high-order asymptotic procedure is established considering for the first time all the peculiarities of the low-frequency behavior of a thin fluid-loaded cylinder. The obtained results are exposed in the form suggested by the Resonance Scattering Theory. It is shown that the pressure scattered by rigid cylinder is the best choice for a background component. Simple explicit formulae for resonant frequencies, amplitudes, and widths are presented. They support various important observations, including comparison between widths and the error of the asymptotic expansion for frequencies