• 대한안전경영과학회지
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• 제3권3호
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• pp.77-86
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• 2001

An operational strategy for inventory control on finished goods in the distribution system has been given attention to many enterprises and many studies regarding this field have been done and is also on-going currently. Many of these studies represented a large scale distribution network with a unified formulation by using defined symbols. These methods have provided the systematic approach of the distribution network but they are impossible to applying the reality system due to not considering the service rate of demand and treating the shortage of inventory. In order to overcome these unrealistic problems, the novel safety stock policy of responding to customers' inventory distribution network is suggested. this paper explores the transportation between Central Distribution Center(CDC) and Regional Distribution Center(RDC). Especially, the relation of transportation cost between CDC and RDC and cost of inventory control according to safety inventory with service level are emphasized. We could obtain the good results of this study by determining the optimal safety stock considering the various variables and constraints.

• Structural Engineering and Mechanics
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• 제6권6호
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• pp.583-612
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• 1998

A unified third-order laminate plate theory that contains classical, first-order and third-order theories as special cases is presented. Analytical solutions using the Navier and L$\acute{e}$vy solution procedures are presented. The Navier solutions are limited to simply supported rectangular plates while the L$\acute{e}$vy solutions are restricted to rectangular plates with two parallel edges simply supported and other two edges having arbitrary combination of simply supported, clamped, and free boundary conditions. Numerical results of bending and vibration for a number of problems are discussed in the second part of the paper.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1992년도 봄 학술발표회 논문집
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• pp.79-84
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• 1992

An integrated design system has as its aim the incoporation of all the design processes, such as, planning, preliminary design, analysis, detailed design (mamber design), evaluation, and drafting into an unified software system. Successful implementation such a system could lead to major improvements in efficiency by eliminating duplication of data and efforts. reducing errors, saving design time, providing management support, and so on. This study presents a methodology for an computer-integrated design system for building structures, synthesizing algorithmic procedures and knowledge based expert systems on the network database. Network database, which was designed to store all information systematically during the design processes, provides centeral communication area between algorithms and expert systems. The conventional procedural codes automate the routine design phases such as structural analysis, whereas knowledge-based expert systems support designer's decisions at the creative design phases such as preliminary design etc. The user interface with interactive and batch modes controls the design phases and manages design information and activates the algorithms and the expert systems. The concept presented in this paper will contribute to the formulation of automated design systems for building structures.

• 한국통신학회논문지
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• 제17권11호
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• pp.1290-1298
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• 1992

본 논문은 fitting 파라미터를 배제하고 2차원적 Poisson 방정식을 도출해서 short-channel MOSFET의 model 식을 완전히 해석적으로 성립시켰다. 이로 인해 포화영역, 문턱전압, 강반전에 대한 것이 동시에 표현되는 정확한 드레인 전류가 유도되었다. 더욱이 이 model은 short-channel과 body효과, DIBL효과, 그리고 carrier운동에 대한 것도 설명할 수 있으며 온도와 $n^+$접합, 산화층에 관련되는 문턱전압도 표현할 수 있었다.

• 대한전자공학회논문지
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• 제11권2호
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• pp.12-21
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• 1974

전자력학적 근사해법인 섭운이론을 횡정식계를 가한 N형 Silicon 반도체로 충만된 거형도파관내의 마이크로로파의 정변특성에 적용해서 전력의 식을 구했다. 이는 전자파의 Maxwell 방정식을 연산자에 의한 고유치문제로 다루어 개발했다. 특히 2개의 Magic-Tee를 사용해서 x만에 의해서 변화하는 전자성분을 검출한 9.61GHz의 TE 파에 의한 실험결과는 제1차사치와 아주 잘 일치했다.

• Smart Structures and Systems
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• 제18권4호
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• pp.707-731
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• 2016

A unified mathematical model of the equations of generalized magneto-thermoelasticty based on fractional derivative heat transfer for isotropic perfect conducting media is given. Some essential theorems on the linear coupled and generalized theories of thermoelasticity e.g., the Lord- Shulman (LS) theory, Green-Lindsay (GL) theory and the coupled theory (CTE) as well as dual-phase-lag (DPL) heat conduction law are established. Laplace transform techniques are used. The method of the matrix exponential which constitutes the basis of the state-space approach of modern theory is applied to the non-dimensional equations. The resulting formulation is applied to a variety of one-dimensional problems. The solutions to a thermal shock problem and to a problem of a layer media are obtained in the present of a transverse uniform magnetic field. According to the numerical results and its graphs, conclusion about the new model has been constructed. The effects of the fractional derivative parameter on thermoelastic fields for different theories are discussed.

• Structural Engineering and Mechanics
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• 제59권3호
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• pp.475-502
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• 2016

Nanobeams are widely used as a structural element for nanodevices and nanomachines. The development of nano-sized machines depends on proper understanding of mechanical behavior of these nano-sized beam elements. Small length scales such as lattice spacing between atoms, surface properties, grain size etc. are need to be considered when applying any classical continuum model. In this study, Eringen's nonlocal elasticity theory is incorporated into classical beam model considering the effects of axial extension and the shear deformation to capture unique static behavior of the nanobeams under continuum mechanics theory. The governing differential equations are obtained for curved beams and solved exactly by using the initial value method. Circular uniform beam with concentrated loads are considered. The displacements, slopes and the stress resultants are obtained analytically. A detailed parametric study is conducted to examine the effect of the nonlocal parameter, mechanical loadings, opening angle, boundary conditions, and slenderness ratio on the static behavior of the nanobeam.

• Structural Engineering and Mechanics
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• 제66권3호
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• pp.369-377
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• 2018

In this article, buckling and free vibration of functionally graded (FG) nanobeams resting on elastic foundation are investigated by developing various higher order beam theories which capture shear deformation influences through the thickness of the beam without the need for shear correction factors. The elastic foundation is modeled as linear Winkler springs as well as Pasternak shear layer. The material properties of FG nanobeam are supposed to change gradually along the thickness through the Mori-Tanaka model. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. From Hamilton's principle, the nonlocal governing equations of motion are derived and then solved applying analytical solution. To verify the validity of the developed theories, the results of the present work are compared with those available in literature. The effects of shear deformation, elastic foundation, gradient index, nonlocal parameter and slenderness ratio on the buckling and free vibration behavior of FG nanobeams are studied.

• 대한전자공학회논문지SD
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• 제41권2호
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• pp.9-15
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• 2004

본 논문에서는 부분공핍(partially-depleted : PD) 영역과 완전공핍(fully-depleted : FD) 영역을 나누는 임계 전면 게이트 전압 V/sub c/의 해석적 표현을 이용해서 PD 영역과 FD 영역의 천이를 정확히 설명하는 해석적 표면전위 모델(analytical surface potential model)을 소개한다. 이 모델은 모든 동작영역(subthreshold에서 strong inversion까지)에서 유효하고 반복 계산 절차 (iteration procedure)인 수치 해석적 방법보다 훨씬 짧은 계산시간이 걸린다. 이 모델에 기초한 charge sheet 모델이 모는 동작영역에 유효한 드레인 전류의 단일 공식을 유도하는데 사용된다. 대부분의 secondary 효과들이 charge sheet 모델에 쉽게 포함되고 그 모델의 결과들은 수치해석 결과와 실험 결과를 비교적 정확히 일치한다. 세 가지의 smoothing 함수가 사용될지 라도 표면전위 미분 값은 연속이다 더욱 중요한 점은 smoothing 함수에 사용된 파라미터들은 공정 파라미터들에 크게 의존하지 않는다.

• Coupled systems mechanics
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• 제7권6호
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• pp.649-668
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• 2018

In this paper, we present a numerical model for fluid-structure interaction between structure built of porous media and acoustic fluid, which provides both pore pressure inside porous media and hydrodynamic pressures and hydrodynamic forces exerted on the upstream face of the structure in an unified manner and simplifies fluid-structure interaction problems. The first original feature of the proposed model concerns the structure built of saturated porous medium whose response is obtained with coupled discrete beam lattice model, which is based on Voronoi cell representation with cohesive links as linear elastic Timoshenko beam finite elements. The motion of the pore fluid is governed by Darcy's law, and the coupling between the solid phase and the pore fluid is introduced in the model through Biot's porous media theory. The pore pressure field is discretized with CST (Constant Strain Triangle) finite elements, which coincide with Delaunay triangles. By exploiting Hammer quadrature rule for numerical integration on CST elements, and duality property between Voronoi diagram and Delaunay triangulation, the numerical implementation of the coupling results with an additional pore pressure degree of freedom placed at each node of a Timoshenko beam finite element. The second original point of the model concerns the motion of the outside fluid which is modeled with mixed displacement/pressure based formulation. The chosen finite element representations of the structure response and the outside fluid motion ensures for the structure and fluid finite elements to be connected directly at the common nodes at the fluid-structure interface, because they share both the displacement and the pressure degrees of freedom. Numerical simulations presented in this paper show an excellent agreement between the numerically obtained results and the analytical solutions.