• Structural Engineering and Mechanics
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• v.32 no.1
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• pp.167-178
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• 2009

Initial imperfections, such as initial deflection or remaining stress, cause deterioration of buckling strength of structures. The Koiter imperfection sensitivity law has been extended to describe the mechanism of reduction for structures. The extension is twofold: (1) a number of imperfections are considered, and (2) the second order (minor) imperfections are implemented, in addition to the first order (major) imperfections considered in the Koiter law. Yet, in reality, the variation of external loads is dominant over that of imperfection. In this research, probabilistic evaluation of buckling loads against external loads subjected to probabilistic variation is conducted by extending the concept of imperfection sensitivity. A truss arch subjected to dead and live loads is considered as a numerical example. The mechanism of probabilistic variation of buckling strength of this arch is described by the proposed method, and its reliability is evaluated.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.96.2-96.2
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• 2014

Using solar occultation data obtained by Cassini/Visual Infrared Mapping Spectrometer (VIMS), we were able to retrieve the 1 - 5 mm optical-depth spectra of the Titanian haze, for which only selected wavelength and altitudinal ranges were previously analyzed. We found that the gross 1 - 5 mm shapes of the retrieved haze spectra are significantly different from the spectra of tholin samples in the literature. We also derived the vertical variation of the spectral structure of the $3.3-3.4{\mu}m$ absorption feature of the Titan haze from the VIMS data recorded between 250 and 700 km altitude. We found a marked change between 480 and 580 km in the relative amplitudes of the 3.33 and $3.38{\mu}m$ features which are characteristic of aromatic (double C=Cchains or rings) or aliphatic (single C-C chains) structural groups, respectively. Dicussions on this spectral and altitudinal variation will be presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.258-259
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• 2009

Pipe wall thinning is one of severe problems on structural safety in nuclear power plants. A guided wave can be a proper tool for the fast evaluation or monitoring. As for gradual wall thinnings, however, low sensitivity caused by the low reflection coefficient limits the use of the guided wave. In this work, instead of the guided wave reflection at the wall thinning, the variation of dispersion characteristics is concerned. SH waves were employed due to several advantages and the magnetostrictive patch transducers were used for the excitation and sensing of the SH waves. The proposed method were verified with some experiments and showed the feasibility as an effective tool for the inspection of gradual wall thinning.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.1001-1020
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• 2016

The study is to investigate the free vibration of antisymmetric angle-ply conical shells having non-uniform sinusoidal thickness variation. The arbitrarily varying thickness is considered in the axial direction of the shell. The vibrational behavior of shear deformable conical shells is analyzed for three different support conditions. The coupled differential equations in terms displacement and rotational functions are obtained. These displacement and rotational functions are invariantly approximated using cubic spline. A generalized eigenvalue problem is obtained and solved numerically for an eigenfrequency parameter and an associated eigenvector of spline coefficients. The vibration characteristic of the shells is examined for cone angle, aspect ratio, sinusoidal thickness variation, layer number, stacking sequence, and boundary conditions.

• Structural Engineering and Mechanics
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• v.46 no.6
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• pp.843-852
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• 2013

This paper presents results of the effect of different bolt tightening sequences and methods on the performance of gasketed bolted flange joint using nonlinear finite element analysis. Bolt preload scatter due to elastic interactions, flange stress variation and bolt bending due to flange rotation and gasket contact stress variation is difficult to eliminate in torque control method i.e. tightening one bolt at a time. Although stretch control method (tightening more than one bolt at time) eradicates the bolt preload scatter, flange stress variation is relatively high. Flange joint's performance is compared to establish relative merits and demerits of both the methods and different bolt tightening sequences.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.2
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• pp.18-24
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• 1989

Computer-aided high frequency ultrasonic is applied to aluminum oxide(85w%, 94w%, 96w%, and 99w%) MOR(modulus of rupture) samples to evaluate mechanical properties such as density variation, pore content, elastic modulus, shear modulus, and poisson's ratio. Ultrasonic wave velocity and attenuation measurement techniques were used as an evaluator of such properties. Pulse-echo C-Scan images with different fate setting method using 50MHz center frequency 1 inch focal length transducer allows evaluation of density variation and pore content. Elastic modulus calculated with the relation of density and ultrasonic velocity. It shows good reliability as compared with resonance method. Sintered density variation of $0.025g/cm^{3}$, that is 0.6% of theoretical density in $Al_{2}O_{3}$ samples can be observed by ultrasonic velocity measurement. Attenuation measurement method qualitatively agree with 4-point fracture testing result concerning of porosity content.

• ETRI Journal
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• v.28 no.3
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• pp.347-354
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• 2006

The characteristic variation of 3-dimensional (3-D) solenoid-type embedded inductors is investigated. Four different structures of a 3-D inductor are fabricated by using a low-temperature co-fired ceramic (LTCC) process, and their s-parameters are measured between 50 MHz and 5 GHz. The circuit model parameters of each building block are optimized and extracted using the partial element equivalent circuit method and an HSPICE circuit simulator. Based on the model parameters, the characteristics of the test structures such as self-resonant frequency, inductance, and quality (Q) factor are analyzed, and predictive modeling is applied to the structures composed of a combination of the modeled building blocks. In addition, characteristic variations of the 3-D inductors with different structures using extracted building blocks are also investigated. This approach can provide a characteristic estimation of 3-D solenoid embedded inductors for structural variations.

• Journal of Plant Biology
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• v.33 no.3
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• pp.189-196
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• 1990

Suspension cell lines have been newly established from the calli derived from the immuature embryo culture of hexapolid (Triticum aestivum var. sicco), tetrapolid (T. durum) and diploid (T. tauchii or Aegilops squarrosa) wheat species. The chromosomal variation in suspension cultured cell lines was examined and old cell line, C82d, established from T. aestivum var. copain was also used. New method using 1-bromonaphthalene for metaphase rapping of suspension cells was developed. Variation in chromosome number was observed among all the suspension lines. Cells with doubled chromosome number and deleted chromosome were also observed. Extensive structural changes in chromosome were found in C82d line. Chromosome aberrations showed loss of chromosome arms and chromosome segment. The mean chromosome number in suspension cells of T. aestivum var. sicco was 40, in C82d line 33, in T. durum 28 and in T. tauchii 14. The stability of chromosome in suspension cells of diploid and tetrapolid wheats was higher than that of hexaploid wheat.

• Journal of Sensor Science and Technology
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• v.13 no.1
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• pp.66-71
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• 2004

Pt-doped zinc oxide (ZnO:Pt) films were deposited by ultrasonic spray pyrolysis. Resistivity variation with Pt concentration was measured. The Pt distribution in ZnO:Pt films was studied through Auger Electron Spectroscopy (AES). The ZnO:Pt films were annealed in the ambient of air, water vapor and ozone, respectively. The variation in crystallographic properties and surface morphologies with respect to the annealing condition was observed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The resistivity variation of the films with the annealing condition was measured. Finally, Atomic Force Microscopy (AFM) measurements were carried out to study the effects of the annealing on the roughness of ZnO:Pt films.

• Structural Engineering and Mechanics
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• v.35 no.3
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• pp.365-377
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• 2010

In the present article, effect of non-uniform excitation due to spatially variation of seismic input on nonlinear response of concrete gravity dams is considered. The reservoir is assumed compressible. Isotropic damage mechanics approach is used to model static and dynamic nonlinear behavior of mass concrete in 2D space. The validity of utilized nonlinear model is considered using available theoretical results under static and dynamic conditions. The tallest monolith of Pine Flat dam is selected as a case study. Two cases are analyzed for considering the effect of limited wave propagation velocity on seismic behavior of the dam-reservoir system in which travelling velocities are chosen as 2000 m/s and infinity. It is found that tensile damage in neck and toe regions and also, in the vicinity of the base increase when the system is excited non-uniformly.