• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1995년도 한국우주과학회보 제4권1호
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• pp.21-21
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• 1995

The structures of 17GHz microwave burst for bipolar sunspots have investigated. which included the effects of the projected shapes of radio sources as they traverse across the solar disk using a magnetic loop employing a model of solenoid coils. An ensemble of high-energy electrons confined in the loop be assumed. The projected brightnesls distributions of gyrosynchrotron emission in x- and o-modes are computed and converted into total intensity and circular polarization difference at 17GHz for various heliocentric distances using numerical integration of the transfer equation along the line of sight. The results of computations at 17GHz for optical thin case will be presented. and the effects of the orientation of the loop will be discussed in detail, as well as the effect of size, position, Structure, and polarization of the emission. Also the results of the various physical P8lrameters such as the strength of magnetic field. high and low energy cut-off of accelerated electrons. spectral index and density of electrons will be preslmted. After comparing the results of model calculation with observations. we found that the observations can be well explained in terms of a loop model and its projection effect.effect.

• Advances in nano research
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• 제7권3호
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• pp.181-190
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• 2019

The thermal buckling temperature values of the graded carbon nanotube reinforced composite shell structure is explored using higher-order mid-plane kinematics and multiscale constituent modeling under two different thermal fields. The critical values of buckling temperature including the effect of in-plane thermal loading are computed numerically by minimizing the final energy expression through a linear isoparametric finite element technique. The governing equation of the multiscale nanocomposite is derived via the variational principle including the geometrical distortion through Green-Lagrange strain. Additionally, the model includes different grading patterns of nanotube through the panel thickness to improve the structural strength. The reliability and accuracy of the developed finite element model are varified by comparison and convergence studies. Finally, the applicability of present developed model was highlight by enlighten several numerical examples for various type shell geometries and design parameters.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.523-528
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• 2008

An open frame structure is fastened by bolt joints for strength and shock attenuation. Therefore the full finite element model of an open frame structure should be properly modeled including bolt joints for strength analysis of the frames and joint assemblies which are operated under multi-loading conditions such as driving, drop, inertia and torsional loads. Then the joints and frames must satisfy the specified allowable strength constraints. Because the full finite element model has a large number of elements to perform strength analysis, a detailed fine bolt analysis seems to be very expensive. Therefore bolts of the full finite element model are approximately modeled by constraints equations to constrain degree of freedoms between adjacent nodes. However, the constraints equation method can exaggerate stress results at the constrained nodes. Thus a detailed bolt analysis and a theoretical/experiential formula of bolts for a worst bolt joint are performed using reaction force applied both bolt and bolt joint. Finally, the results from the two methods are compared and discussed to verify the safety of the open frame structure.

• 전산구조공학
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• 제8권3호
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• pp.67-74
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• 1995

본 연구에서는 면진수조의 2차원 동적 해석기법을 개발하고 축소모델을 사용한 진동대실험을 통하여 해석기법의 타당성을 검증하였다. 수조의 벽체는 집중질량을 사용하여 모델링하였으며 유체의 부가질량을 벽체의 절점에 부가함으로써 유체의 동수역학적인 영향을 고려하였다. 면진수조의 운동방정식은 벽체와 유체로 구성된 상부구조의 운동방정식과 바닥슬래브와 면진장치로 구성된 하부구조의 운동방정식을 연계하여 구하였다. 진동대 실험에서는 투명한 아크릴로 제작한 모형수조를 사용하였으며 면진장치는 4개의 고감쇠 적층 고무베어링(High Damping Laminated Rubber Bearing)을 사용하였다. 축소모델에 의한 실험결과는 대체적으로 해석결과와 잘 일치하였으며 계산결과가 다소 보수적인 것으로 나타났다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2005년도 학술발표회 논문집
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• pp.405-412
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• 2005

In this study, a numerical method for soil-pile-structure interaction problems in multi-layered half-plane is developed. The total soil-pile-structure interaction system is divided into two parts namely, nonlinear structure part and linear soil-pile interaction parts. In the structure field, the general finite element method is introduced to solve the dynamic equation of motion for the structure. In the soil-pile structure interaction part, physical model consisting of lumped parameter, which is frequency dependent coefficient and determined by rigorous analysis method is introduced. Using proposed analysis procedure, the nonlinear behavior of structure considering soil-structure interaction can be efficiently determined in time domain and the analysis cost is dramatically reduced.

• 한국연소학회지
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• 제15권1호
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• pp.22-29
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• 2010

In this study, carbon conversion was measured using an electronic mass balance. In a lab scale furnace, each coal sample was pyrolyzed in a nitrogen environment and became coal char, which was then gasified with steam under isothermal conditions. The reactivity of coal char was investigated at various temperatures and steam concentrations. The VRM(volume reaction model), SCM(shrinking core model), and RPM(random pore model) were used to interpret experimental data. For each model the activation energy(Ea), pre-exponential factor (A), and reaction order(n) of the coal char-steam reaction were determined by applying the Arrhenius equation into the data obtained with thermo-gravimetric analysis(TGA). According to this study, it was found that experimental data agreed better with the VRM and SCM for 1,000 and $1,100^{\circ}C$, and the RPM for 1,200 and $1,300^{\circ}C$. The reactivity of chars increased with the increase of gasification temperature. The structure parameter(${\psi}$) of the surface area for the RPM was obtained.

• 한국정보통신학회논문지
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• 제16권2호
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• pp.325-330
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• 2012

본 연구에서는 차세대 나노소자인 이중게이트(Double gate; DG) MOSFET에서 발생하는 단채널효과 중 하나인 드레인유기장벽감소(Drain Induced Barrier Lowering; DIBL)에 대하여 분석하였다. 포아송방정식을 풀어 전위분포에 대한 분석학적 해를 구할 때 전하분포함수에 대하여 가우시안 함수를 사용함으로써 보다 실험값에 가깝게 해석하였으며 이때 가우시안 함수의 변수인 이온주입범위 및 분포편차 그리고 소자 파라미터인 채널의 크기, 도핑강도 등에 대하여 드레인유기장벽감소의 변화를 관찰하고자 한다. 본 연구의 모델에 대한 타당성은 이미 기존에 발표된 논문에서 입증하였으므로 본 연구에서는 이 모델을 이용하여 드레인유기장벽감소에 대하여 분석한 결과 드레인유기장벽감소 현상은 채널의 구조 및 도핑강도에 따라 매우 급격히 변화하는 것을 알 수 있었다.

• 대한토목학회논문집
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• 제12권2호
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• pp.1-10
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• 1992

이 논문에서는 철근 콘크리트 부재의 전단 해석을 위한 트러스 유사법이 발전된 형태인 '빗 구조' 해석 모델을 부분 프리스트레스트 콘크리트 부재의 전단 해석을 위해 수정하여 제안 하였다. 제안된 '빗 구조' 모델은 콘크리트 압축대의 위치와 경사 및 사압축대의 경사가 하중과 프리스트레스의 크기에 따라서 변하는 것이다. 역학적 모델의 구성을 위하여 비선형 보, 트러스 요소를 사용하였으며, 사압축대의 경사를 결정하기 위한 식을 '압축대' 이론을 수정하여 유도하였다. '빗구조' 모델에 의한 해석 결과를 부분 프리스트레스트 콘크리트 부재의 재하 실험 결과와 비교하였다. 이에 따르면 '빗 구조' 해석 결과에 의한 전단 철근의 응력은 수정 M$\ddot{o}$rsch이론과 고전 M$\ddot{o}$rsch 이론에 의한 계산치의 중간 정도의 값이다. 처짐과 전단철근의 응력값을 비교한 결과, 본 논문에서 제안된 '빗 구조' 모델이 부분 프리스트페스트 콘크리트 부재의 전단 해석에 사용될 수 있음을 알 수 있었다.

• 대한간호학회지
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• 제45권1호
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• pp.97-106
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• 2015

Purpose: This study was done to develop and test a structural model for caregiving experience including caregiving satisfaction and caregiving strain in families providing care for family members with a mental disorder. Methods: The Stress-appraisal-coping model was used as the conceptual framework and the structural equation model to confirm the path that explains what and how variables affect caregiving experience in these families. In this hypothesis model, exogenous variables were optimism, severity of illness and uncertainty. The endogenous variables were self efficacy, social support, caregiving satisfaction and caregiving strain. Data were collected using structured questionnaires. Results: Optimism and caregiving self-efficacy had significant direct and indirect effects on caregiving satisfaction. Optimism, severity of illness and uncertainty had significant direct and indirect effects on caregiving strain. The modified path model explained effects of optimism on caregiving self-efficacy with social support in the path structure as a mediator. Also, there were direct and indirect effects of optimism and uncertainty on caregiving satisfaction with social support and caregiving self-efficacy in the path structure as a mediators. Conclusion: Results suggest the need to improve caregiving self-efficacy of these families, establish support systems such as a mental health professional support programs for caregiving self-efficacy. Optimism, severity of illness and uncertainty perceived by families need to be considered in the development of support programs in order to increase their effectiveness.

• 한국해양공학회지
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• 제17권5호
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• pp.57-65
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• 2003

This paper proposes an optimum design method of structural and control systems, using a 2-D truss structure as an example. The structure is subjected to initial static loads and disturbances. For the structure, a FEM model is formed. Using modal transformation, the equation of motion is transformed into modal coordinates, in order to decrease D.O.F. of the FEM model. To suppress the effect of the disturbances, the structure is controlled by an output feedback $H_{\infty}$ controller. The design variables of the combined optimal design of the control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the $H_{\infty}$ norm, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been perform. Through the consideration of structural weight and $H_{\infty}$ norm, an advantage of the combined optimum design of structural and control systems is shown. Moreover, since the performance index of control is almost nearly optimiz, we can acquire better design of structural strength.