• Magazine of the Korean Society of Agricultural Engineers
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• v.27 no.2
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• pp.38-46
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• 1985

The reinforced concrete farm silos on the elastic foundatin are widely used in agricultural engineering because of their superior structural performance, economy and attractive appearance. Various methods for the analysis and design of farm silo, such as the analytical method, the finite difference method, and the finite element methods, can be used. But the analytical procedure can not be applied for the intricate conditions in practice. Therefore lately the finite element method has been become in the structural mechanics. In this paper, a method of finite element analysis for the cylindrical farm silo on ffness matrix for the elastic foundation governed by winkler's assumption. A complete computer programs have been developed in this paper can be applicable not only to the shell structures on elastic foundation but also to the arbitrary three dimensional structures. Assuming the small deflection theory, the membrane and plate bending behaviours of flat plate element can be assumed mutually uncoupled. In this case, the element has 5 degrees of freedom per node when defined in the local coordinate system. However, when the element properties are transformed to the global coordinates for assembly, the 6th degree of freedom should be considered. A problem arises in this procedure the resultant stiffness in the 6th degree of freedom at this node will be zero. But this singularity of the stiffness matrix can be eliminated easily by merely replacing the zero diagonal by dummy stiffness.

• Advances in Computational Design
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• v.9 no.1
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• pp.39-52
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• 2024

If the governing differential equation arising from engineering problems is treated as an analytic, continuous and derivable function, it can be expanded by one point as a series of finite numbers. For the function to be zero for each value of its domain, the coefficients of each term of the same power must be zero. This results in a recursive relationship which, after applying the natural conditions or the boundary conditions, makes it possible to obtain the values of the derivatives of the function with acceptable accuracy. The elastoplastic analysis of an inhomogeneous thick sphere of metallic materials with linear variation of the modulus of elasticity, yield stress and Poisson's ratio as a function of radius subjected to internal pressure is presented. The Beltrami-Michell equation is established by combining equilibrium, compatibility and constitutive equations. Assuming axisymmetric conditions, the spherical coordinate parameters can be used as principal stress axes. Since there is no analytical solution, the natural boundary conditions are applied and the governing equations are solved using a proposed new method. The maximum effective stress of the von Mises yield criterion occurs at the inner surface; therefore, the negative sign of the linear yield stress gradation parameter should be considered to calculate the optimal yield pressure. The numerical examples are performed and the plots of the numerical results are presented. The validation of the numerical results is observed by modeling the elastoplastic heterogeneous thick sphere as a pressurized multilayer composite reservoir in Abaqus software. The subroutine USDFLD was additionally written to model the continuous gradation of the material.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.28 no.3
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• pp.96-107
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• 2024

We consider the bifocusing method (BFM) for a fast identification of small objects in microwave imaging. In many researches, it was very hard to measure the scattering parameter data if the location of the transmitter and the receiver is the same. Due to this reason, the imaging function of BFM has mainly been designed by converting unknown measurement data into the zero constant; this approach has yielded reliable imaging results, but the theoretical reason for this conversion has not been investigated yet. In this study, we converted unknown measurement data to a fixed constant and applied the BFM to retrieve small objects. To demonstrate the effect of the converted constant, we show that the imaging function of the BFM can be represented in terms of an infinite series of the Bessel functions of an integer order, antenna setting, material properties, and applied constant. Based on the theoretical result, we concluded that converting unknown measurement data to constant zero guarantees good imaging results, including the unique determination of the objects. Simulation results obtained with synthetic and real data support the theoretical result.

• Journal of the Korean GEO-environmental Society
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• v.18 no.3
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• pp.31-38
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• 2017

The purpose of this study is to propose a chart that can easily estimate the seismic failure probability of small and medium sized earthfill dams with little geotechnical information. By considering the existing method and procedure for estimating the seismic failure probability of a dam, the zero seismic failure probability curve, on which the seismic probability is zero regardless of the geotechnical properties of the dam, was determined in the form of hyperbola in the dam height and freeboard ratio plane. It was confirmed that the dam height-freeboard ratio distribution pattern of the Korean small and medium sized dams was shaped like a hyperbola like the zero seismic failure probability curve. Therefore, a estimation chart was constructed in which a number of seismic failure probability contours are represented by a number of hyperbolas at regular intervals in the dam height-freeboard ratio plane. The proposed chart was applied to the calculation of the seismic failure probability of two small and midium sized dams with relatively well-managed geotechnical properties and the validity of the chart was confirmed by comparison with the results obtained by the existing procedures and methods. In the future, the proposed chart is expected to be useful in considering investment priorities for maintenance and reinforcement of small and medium sized dams in preparation for earthquakes.

• Journal of Photoscience
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• v.11 no.1
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• pp.19-23
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• 2004

The sharp-line absorption spectrum of microcrystalline samples of cis-[Cr(cycb)$Cl_2$]Cl (cycb=rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) has been measured between 13000 and $16000 cm^{-1}$ at temperatures down to 5K. The 77K emission and excitation spectra, and 298 K infrared and visible absorption spectra have also been measured. The nine electronic bands due to spin-allowed and spin-forbidden transitions were assigned. Using the observed transitions, a ligand field analysis has been performed to probe the ligand field properties of coordinated atoms in the title chromium(III) complex. The zero-phonon line in the sharp-line absorption spectrum splits into two components by $240 cm^{-1}$ , and the $large ^2$$_E{g}$ splitting can be reproduced by the modem ligand field theory. It is confirmed that nitrogen atoms of the macrocyclic cycb ligand have a strong $\sigma$-donor character, but chloride ligand has weak $\sigma$- nd $\pi$-donor properties toward chromium(III) ion.n.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.340-345
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• 2003

B $i_2$ $O_3$-Ti $O_2$ composite dielectric ceramics have been prepared by a conventional solid state ceramic route. The composite ceramics were prepared with starting materials of different origin and the microwave dielectric properties were investigated. The sintered ceramics were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, Raman and microwave methods. Structural and microstructural analyses identified two separate phases: Ti $O_2$(rutile) and B $i_2$ $Ti_4$0$_{11}$. The separate grains of titania and bismuth titanate were distributed uniformly in the ceramic matrix. The composition 0.88Ti $O_2$-0.12B $i_2$ $Ti_4$ $O_{11}$ was found to have a Q$\times$f of 9300 GHz (measured at a frequency of 3.9 GHz), a temperature coefficient of frequency, $\tau$$_{cf}$ near zero and a high relative permittivity, $\varepsilon$r of 83. The microwave dielectric properties were measured down to 20$^{\circ}$K K. The quality factor increased on cooling the ceramic samples.les.

• Geomechanics and Engineering
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• v.8 no.3
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• pp.305-321
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• 2015

In this paper, a new hyperbolic shear deformation plate theory based on neutral surface position is developed for the static analysis of functionally graded plates (FGPs). The theory accounts for hyperbolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. The neutral surface position for a functionally graded plate which its material properties vary in the thickness direction is determined. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Based on the present new hyperbolic shear deformation plate theory and the neutral surface concept, the governing equations of equilibrium are derived from the principle of virtual displacements. Numerical illustrations concern flexural behavior of FG plates with Metal-Ceramic composition. Parametric studies are performed for varying ceramic volume fraction, volume fraction profiles, aspect ratios and length to thickness ratios. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions.

• Bulletin of the Korean Mathematical Society
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• v.29 no.1
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• pp.65-72
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• 1992

All rings are commutative, Noetherian with identity and of prime characteristic p, unless otherwise specified. First, we describe the definition of tight closure of an ideal and the properties about the tight closure used frequently. The technique used here for the tight closure was introduced by M. Hochster and C. Huneke [4,5, or 6]. Using the concepts of the tight closure and its properties, we will prove that if R is a complete local domain and F-rational, then R is Cohen-Macaulay. Next, we study the properties of R$^{+}$, the integral closure of a domain in an algebraic closure of its field of fractions. In fact, if R is a complete local domain of characteristic p>0, then R$^{+}$ is Cohen-Macaulay [8]. But we do not know this fact is true or not if the characteristic of R is zero. For the special case we can show that if R is a non-Cohen-Macaulay normal domain containing the rationals Q, then R$^{+}$ is not Cohen-Macaulay. Finally we will prove that if R is an excellent local domain of characteristic p and F-ratiional, then R is Cohen-Macaulay.aulay.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.617-620
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• 2008

When fresh concrete is exposed to the cold weather, the concrete may happen frost damage because of freezing at early ages and the strength development may be go down. Therefore, this paper is intend to investigate the properties and availabilities of cold weather concrete using anti-freeze based formate-acetate for ensure of excellent concrete quality on cold temperature. According to test result for concrete in anti-freeze agent, strength properties in sub-zero temperature increases in comparison with concrete of non anti-freeze agent without decline of strength until later age. When anti-freezing agent is added by 3.0% to binder, it gives good effects on the performance of the fresh and harden concrete.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.150-151
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• 2003

In the past years, a giant magnetoresistance (GMR) effect found in perovskite-like structured materials has attracted considerable attention among scientists and manufacturers, since, a practical point of view, the capacity of producing magnetic and sensing sensors. In a stream of this interest, further efforts to understand the underlying mechanism that leads to the GMR effect relative to the correlation between transport and magnetic properties, have been extensively devoted. In these cases, spin-glass-like behaviors are ascribed to the frustration of random competing exchange interactions, namely the ferromagnetic double-exchange interaction between Co$\^$3+/ (or Mn$\^$3+/) and Co$\^$4+/(or Mn$\^$4+/) and the antiferromagnetic one like spins. Noticeably, the distinction of spin-glass region from cluster-glass one, involved in the remarkable changes in transport and magnetic properties at a critical value of doping concentration, was observed. Magnetic anomalies in zero-field-cooled (ZFC) magnetization as well as ac magnetic susceptibility below Curie temperature T$\sub$c/ and the charge/orbital fluctuation were also realized. In this work, we present a study of magnetic properties of a deficient manganese perovskites system of La$\sub$0.6/Sr$\sub$x/MnTi$\sub$y/O$_3$, and particularly provide its new magnetic phase diagram.