• Journal of the Korean Mathematical Society
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• v.41 no.5
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• pp.875-882
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• 2004

Let (M,g) be a compact m dimensional Einstein manifold with smooth boundary. Let $\Delta$$_{p}$,B be the realization of the p form valued Laplacian with a suitable boundary condition B. Let Spec($\Delta$$_{p}$,B) be the spectrum where each eigenvalue is repeated according to multiplicity. We show that certain geometric properties of the boundary may be spectrally characterized in terms of this data where we fix the Einstein constant.ant.

• Steel and Composite Structures
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• v.38 no.5
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• pp.583-597
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• 2021

This article develops a nonclassical model to analyze bending response of squared perforated microbeams considering the coupled effect of microstructure and surface stress under different loading and boundary conditions, those are not be studied before. The corresponding material and geometrical characteristics of regularly squared perforated beams relative to fully filled beam are obtained analytically. The modified couple stress and the modified Gurtin-Murdoch surface elasticity models are adopted to incorporate the microstructure as well as the surface energy effects. The differential equations of equilibrium including the Poisson's effect are derived based on minimum potential energy. Exact closed form solution is obtained for bending behavior of the proposed model considering the classical and nonclassical boundary conditions for both uniformly distributed and concentrated loads. The proposed model is verified with results available in the literature. Influences of the microstructure length scale parameter, surface energy, beam thickness, boundary and loading conditions on the bending behavior of perforated microbeams are investigated. It is observed that microstructure and surface parameters are vital in investigation of the bending behavior of perforated microbeams. The obtained results are supportive for the design, analysis and manufacturing of perforated nanobeams that commonly used in nanoactuators, nanoswitches, MEMS and NEMS systems.

• International Journal of Aeronautical and Space Sciences
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• v.4 no.2
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• pp.1-8
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• 2003

Satellite formation flying is the placing micro-satellites with the same mission into nearby orbits to form a cluster. Clohessy-Wiltshire equations are used to describe the relative motion and control strategies between satellites within a cluster, which are known as Hill's equations. Even though Hill's equations are powerful in determining initial conditions for the satellite formation flying, they can not accurately express the relative motion under J2 perturbation. Some methods have been developed for the determination of initial conditions to avoid limits of Hill's equation. This paper gives a new method of determining initial conditions using mean elements. For this research mean elements were transformed to osculating elements using Brouwer's theory and the orbit was propaeated with the consideration of J2-J8 to get a relative position. The results show that satellites within a cluster are maintained in the desired boundary for long period and the method is effective on a fuel saving for satellite formation flying.

• International Journal of High-Rise Buildings
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• v.7 no.4
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• pp.313-325
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• 2018

Concrete-filled steel tubular (CFST) members are commonly used as composite columns in modern construction. However, the current guidelines for members' fire design (EN1994-1-2) have been proved to be unsafe in case the relative slenderness is higher than 0.5. In addition, the simplified design methods of Eurocode 4 are limited to circular and square CFST columns, while in practice columns with rectangular and elliptical hollow sections are being increasingly used because of their architectural aesthetics. In the last years a large experimental research has been carried out at Coimbra University on the topic. They have been tested concrete filled circular, square, rectangular and elliptical hollow columns with restrained thermal elongation. Some parameters such as the slenderness, the type of cross-section geometry as well as the axial and rotational restraint of the surrounding structure to the column have been tested in order to evaluate their influence on the fire resistance of such columns. In this paper it is evaluated the influence of the boundary conditions (pin-ended and semi-rigid end-support conditions) on the behavior of the columns in case of fire. In these tests it could not be seen a marked effect of the tested boundary conditions but it is believed that the increasing of rotational stiffness increases the fire resistance of the columns.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.311-316
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• 2001

A failure probability model based on Von-Mises failure criterion and the standard normal probability function is proposed. The effects of varying boundary conditions such as internal fluid pressure, external soil, traffic loads, temperature change and corrosion on failure probability of the buried pipes are systematically investigated. To allow for the uncertainties of the design variables, a reliability analysis technique has been adopted; this also allows calculation of the relative contribution of the random variables and the sensitivity of the failure probability.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.4
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• pp.204-213
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• 2003

A survey for finding corrosion examples was performed on the underground steel piles buried for 19 years in the area of iron and steel making factory near Young-il bay. A failure probability model, which can be used to check the reliability of the corrosive mechanical element, based on Von-Mises failure criterion and the standard normal probability function is proposed. The effects of varying boundary conditions such as temperature change, soil-friction, internal pressure, earthquake, loading of soil, traffic loads and corrosion on failure probability of the buried steel piles are systematically investigated. To allow for the uncertainties of the design variables, a reliability analysis technique has been adopted; this also allows calculation of the relative contribution of the random variables and the sensitivity of the failure probability.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.37-49
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• 1997

The buckling behavior of the web of steel girders are largely dependent on the size and the location of stiffeners and the restraining effect of top and bottom flanges. Elastic and inelastic buckling analyses based or the Spline Finite Strip Method were executed to study the stiffening effect of the longitudinal stiffener on the web of box girders and to find how the top and bottom flanges had effects on the web, where geometric boundary conditions were limited by both hinged, both fixed and the flange sections. The basic assumption for the longitudinal end boundary conditions was that the vertical stiffeners had the rigidity enough to force nil deflection line on the web panel so that the junction line between web and vertical stiffener was assumed to be hinged boundary conditions. The provisions on the longitudinal stiffener of the plate and box girders of the Korean Standard Highway Bridge Specifications(1995) and AASHTO Specifications(1994 LRFD) were compared with the results obtained numerically for the various longitudinal stiffener size of box girders. Simple equations and design curves for the longitudinal stiffener of the web were proposed for the practical use.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.258-264
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• 1999

In this study, a computer program was developed for analysis of the orthotropic curved ring sector plates. In the developing program , the thin-plate theory and multi-base coordinate system was adopted. The effect of design factors-boundary conditions, loading conditions, steel ratio, open angle, radius of curvature and relative flexural rigidity between slab and edge-beam-on the behavior of the circular ring sector plates were discussed. Also, the practical limitations was proposed to replace the problem of the orthotropic sector plate by equivalent rectangular plage.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.1
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• pp.49-54
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• 2021

In this paper, n this paper, E-polarized electromagnetic scattering problems by a resistive strip grating between a double dielectric layer are analyzed by applying the PMM(Point Matching Method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, and the resistive boundary condition is applied to analysis of the resistive strip. The numerical results for the normalized reflected and transmitted power are analyzed by according as the relative permittivity and thickness of the double dielectric layers, and the resistivity of resistive strip. Overall, when the resistivity of the resistive strip decreased or the relative permittivity of the dielectric layer increased, the reflected power increased, and as the reflected power increased, the transmitted power decreased relatively. Especially, as the relative permittivity of double dielectric layer increases, the minimum value of the variation curve of the reflected power shifted in the direction that the grating period decreased. The numerical results for the presented structure of this paper are shown in good agreement compared to those of the existing papers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.5
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• pp.429-435
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• 2007

The present study proposed a method fer simulating reflective boundary conditions in Boussinesq wave propagation model by lining lateral boundaries like breakwaters and seawalls with artificial sponge layers. In order to find out the reflective characteristics of sponge layers, 1D numerical experiments were performed varying the relative sponge width (sponge width/wave length). The results showed that the reflection coefficient can be effectively realized from no reflection to full reflection simply by adjusting the relative sponge width. Based on the results, a multiple regression formula was proposed to delineate the relationship among the reflection coefficient and other dimensionless variables. Finally, the reflective sponge layer was applied to a semi-infinite breakwater, demonstrating that it can also be successfully employed in 2D applications.