• Steel and Composite Structures
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• v.33 no.4
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• pp.473-487
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• 2019

A shear-deformable finite element model (FEM) with five nodes and thirteen degrees of freedom (DOFs) for free vibrations of laminated composite beams with arbitrary lay-up is presented. This model can be capable of considering the elastic couplings among the extensional, bending and torsional deformations, and the Poisson's effect. Lagrange's principle is employed in derivation of the equations of motion, and thus the element matrices are obtained. Comparisons of the present element's results with those in experiment, available literature and the 3D finite element analysis software (ANSYS(R)) are made to show its accuracy. Some further results are given as referencing for the future studies in vibrations of laminated composite beamst.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.123-128
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• 2014

This paper analyzed the change of subthreshold current for channel dimension of double gate(DG) MOSFET. The nano-structured DGMOSFET to reduce the short channel effect had to be preciously analyze. Poisson's equation had been used to analyze the potential distribution in channel, and Gaussian function had been used as carrier distribution. The subthreshold current had been analyzed for device parameters such as channel dimension, and projected range and standard projected deviation of Gaussian function. Since this potential model was verified in the previous papers, we used this model to analyze the subthreshold current. Resultly, we know the subthreshold current was influenced on parameters of Gaussian function and channel dimension for DGMOSFET.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.2
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• pp.70-76
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• 2000

A numerical study on the viscous flow around a 2-dimensional circulation control foil is carried out for application on the field of naval architecture and ocean engineering. The governing equations are the RANS and the continuity equations. The equations are discretized by finite difference method and MAC method and the pressure poisson equation is calculate by a SOR method and an O-type non-staggered boundary fitted coordinate system which is overlapped near the slot is used to improve the numerical accuracy. Turbulence is approximated by a modified Baldwin-Lomax turbulence model. In the present paper, the Coanda effect on a 2-dimensional foil of a 20% thickness ellipse with modified rounded trailing edge has been numerically studied. The change in drag and lift of the foil with various jet momentums are calculated and compared to the experimental results to show good agreements.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.753-756
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• 2013

This paper analyzed the change of subthreshold current for channel dimension of double gate(DG) MOSFET. The nano-structured DGMOSFET to reduce the short channel effect had to be preciously analyze. Poisson's equation had been used to analyze the potential distribution in channel, and Gaussian function had been used as carrier distribution. The subthreshold current had been analyzed for device parameters such as channel dimension, and projected range and standard projected deviation of Gaussian function. Since this potential model was verified in the previous papers, we used this model to analyze the subthreshold current. Resultly, we know the subthreshold current was influenced on parameters of Gaussian function and channel dimension for DGMOSFET.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.3
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• pp.15-30
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• 2004

In this paper, an analytical modeling for the dark and photo-current characteristics of a buried-gate short- channel GaAs MESFET is presented. The presented model shows that the increase of drain current under illumination is largely due to not the increase of photo-conductivity in the neutral region but the narrowing effect of the depletion layer width. The carrier density profile within the neutral region is derived from solving the carrier continuity equation one-dimensionally. In deriving the photo-generated current, we assume that the photo-current is compensated with the thermionic emission current at the gate-channel interface. Moreover, the two-dimensional Poisson's equation is solved by taking into account the drain-induced longitudinal field effect. In conclusion, the proposed model seems to provide a reasonable explanation for the dark and photo current characteristics in a unified manner.

• Advances in concrete construction
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• v.14 no.2
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• pp.93-102
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• 2022

In this study, limestone powder (LS) and fly ash (FA) were used as powder materials in self-compacting concrete (SCC) in increasing quantities in addition to cement, so that the two powders commonly used in the production of SCC could be compared in the same study. Considering the reduction of the maximum aggregate size in SCC, 10 mm or 16 mm was selected as the coarse aggregate size. The properties of fresh concrete were determined by slump flow (including T₅₀₀ time), V-funnel and J-ring experiments. The experimental results showed that as the amount of both LS and FA increased, the slump flow also increased. The increase in powder material had a negative effect on V-funnel flow times, causing it to increase; however, the increase in FA concretes was smaller compared to LS ones. The increase in the powder content reduced the amount of blockage in the J-ring test for both aggregate sizes. As the hardened concrete properties, the compressive and splitting strengths as well as the modulus of elasticity were determined. Longitudinal and transverse deformations were measured by attaching a special frame to the cylindrical specimens and the values of Poisson's ratio, initiation and critical stresses were obtained. Despite having a similar W/C ratio, all SCC exhibited higher compressive strength than NVC. Compressive strength increased with increasing powder content for both LS and FA; however, the increase of the FA was higher than the LS due to the pozzolanic effect. SCC with a coarse aggregate size of 16 mm showed higher strength than 10 mm for both powders. Similarly, the modulus of elasticity increased with the amount of powder material. Inelastic properties, which are rarely found in the literature for SCC, were determined by measuring the initial and critical stresses. Crack formation in SCC begins under lower stresses (corresponding to lower initial stresses) than in normal concretes, while critical stresses indicate a more brittle behavior by taking higher values.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.95-102
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• 1996

In this study, a stochastic finite element model is proposed with a view to consider the uncertainty of physical properties of discontinuous rock mass in the analysis of structural behavior on underground caverns. In so doing, the LHS(Latin Hypercube sampling) technique has been applied to make up weak points of the Crude Monte Carlo technique. Concerning the effect of discontinuities, a joint finite element model is used that is known to be superior in explaining faults, cleavage, things of that nature. To reflect the uncertainty of material properties, the variables such as the the elastic modulus, the poisson's ratio, the joint shear stiffness, and the joint normal stiffness have been used, all of which can be applicable through normal distribution, log-normal distribution, and rectangulary uniform distribution. The validity of the newly developed computer program has been confirmed in terms of verification examples. And, the applicability of the program has been tested in terms of the analysis of the circular cavern in discontinuous rock mass.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.398-403
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• 2017

본 연구에서는 gate-all-around(GAA) 수직 나노선 Field-Effect Transistor(FET)의 소스/드레인 반도체/실리사이드 접합에 존재하는 Schottky 장벽이 트랜지스터의 DC특성에 미치는 영향에 대하여 조사하였다. Non-Equilibrium Green's Function와 Poisson 방정식 기반의 시뮬레이터를 사용하여, Schottky 장벽의 위치와 높이, 그리고 채널 단면적의 크기에 따른 전류-전압 특성 곡선과 에너지 밴드 다이어그램을 통해 분석을 수행하였다. 그 결과, 드레인 단의 Schottky 장벽은 드레인 전압에 의해 장벽의 높이가 낮아져 전류에 주는 영향이 작지만, 소스 단의 Schottky 장벽은 드레인 전압과 게이트 전압으로 제어가 불가능하여 외부에서 소스 단으로 들어오는 캐리어의 이동을 방해하여 큰 DC성능 저하를 일으킨다. 채널 단면적 크기에 따른 DC특성 분석 결과로는 동작상태의 전류밀도는 채널의 폭이 5 nm 일 때까지는 유지되고, 2 nm가 되면 그 크기가 매우 작아지지만, 채널 단면적은 Schottky 장벽에 영향을 끼치지 못하였다. 본 논문의 분석 결과로 향후 7 nm technology node 에 적용될 GAA 수직 나노선 FET의 소자 구조 설계에 도움이 되고자 한다.

• Smart Structures and Systems
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• v.15 no.5
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• pp.1345-1362
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• 2015

The present paper deals with the free vibration analysis of the functionally graded solid and annular circular plates with two functionally graded piezoelectric layers at top and bottom subjected to an electric field. Classical plate theory (CPT) is used for description of the all deformation components based on a symmetric distribution. All the mechanical and electrical properties except Poisson's ratio can vary continuously along the thickness direction of the plate. The properties of plate core can vary from metal at bottom to ceramic at top. The effect of non homogeneous index of functionally graded and functionally graded piezoelectric sections can be considered on the results of the system. $1^{st}$ and $2^{nd}$ modes of natural frequencies of the system have been evaluated for both solid and annular circular plates, individually.

• JSTS:Journal of Semiconductor Technology and Science
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• v.10 no.2
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• pp.130-133
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• 2010

This paper presents a study of the influence of variation of counter doping thickness on short channel effect in symmetric double-gate (DG) nano MOSFETs. Short channel effects are estimated from the computed values of current-voltage (I-V) characteristics. Two dimensional Quantum transport equations and Poisson equations are used to compute DG MOSFET characteristics. We found that the transconductance ($g_m$) and the drain conductance ($g_d$) increase with an increase in p-type counter-doping thickness ($T_c$). Very high value of transconductance ($g_m=38\;mS/{\mu}m$) is observed at 2.2 nm channel thickness. We have established that the threshold voltage of DG MOSFETs can be tuned by selecting the thickness of counter-doping in such device.