• 국제초고층학회논문집
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• 제3권2호
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• pp.99-106
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• 2014

This paper presents the determination of the structural system of the Changsha IFC T1 tower with 452 m in architectural height and 440.45 m in structural height. Sensitivity analyses are carried out by varying the location of belt trusses and outriggers. The enhancement of seismic capacity of the outer frame by reasonably adjusting the column size is confirmed based on parametric studies. The results from construction simulation including the non-load effect of structures demonstrate that the deformation of vertical members has little effect on the load-bearing capacity of belt trusses and outriggers. The elastoplastic time-history analysis shows that the overall structure under rare earthquake load remains in an elastic state. The influence of the frame shear ratio and frame overturning moment ratio on the proposed model and equivalent mega column model is investigated. It is found that the frame overturning moment ratio is more applicable for judging the resistance of the outer frame against lateral loads. Comparison is made on the variation of these two effects between a classical frame-core tube-outrigger structure and a structure with diagonal braces between super columns under rare earthquakes. The results indicate that plasticity development of the top core cube of the braced structure may be significantly improved.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.160-176
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• 2017

The interaction of focused wave groups with a vertical wall is investigated based on the second order potential theory. The NewWave theory, which represents the most probable surface elevation under a large crest, is adopted. The analytical solutions of the surface elevation, velocity potential and wave force exerted on the vertical wall are derived, up to the second order. Then, a parametric study is made on the interaction between nonlinear focused wave groups and a vertical wall by considering the effects of angles of incidence, wave steepness, focal positions, water depth, frequency bandwidth and the peak lifting factor. Results show that the wave force on the vertical wall for obliquely-incident wave groups is larger than that for normally-incident waves. The normalized peak crest of wave forces reduces with the increase of wave steepness. With the increase of the distance of focal positions from the vertical wall, the peak crest of surface elevation, although fluctuates, decreases gradually. Both the normalized peak crest and adjacent crest and trough of wave forces become larger for shallower water depth. For focused wave groups reflected by a vertical wall, the frequency bandwidth has little effects on the peak crest of wave elevation or forces, but the adjacent crest and trough become smaller for larger frequency bandwidth. There is no significant change of the peak crest and adjacent trough of surface elevation and wave forces for variation of the peak lifting factor. However, the adjacent crest increases with the increase of the peak lifting factor.

• International Journal of Automotive Technology
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• 제7권1호
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• pp.1-7
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• 2006

The ignition delay of a dual fuel system has been numerically investigated by adopting a constant volume chamber as a model problem simulating diesel engine relevant conditions. A detailed chemical kinetic mechanism, consisting of 28 species and 135 elementary reactions, of dimethyl ether (DME) with methane ($CH_{4}$) sub-mechanism has been used in conjunction with the multi-dimensional reactive flow KIVA-3V code to simulate the autoignition process. The start of ignition was defined as the moment when the maximum temperature in the combustion vessel reached to 1900 K with which a best agreement with existing experiment was achieved. Ignition delays of liquid DME injected into air at various high pressures and temperatures compared well with the existing experimental results in a combustion bomb. When a small quantity of liquid DME was injected into premixtures of $CH_{4}$/air, the ignition delay times of the dual fuel system are longer than that observed with DME only, especially at higher initial temperatures. The variation in the ignition delay between DME only and dual fuel case tend to be constant for lower initial temperatures. It was also found that the predicted values of the ignition delay in dual fuel operation are dependent on the concentration of the gaseous $CH_{4}$ in the chamber charge and less dependent on the injected mass of DME. Temperature and equivalence ratio contours of the combustion process showed that the ignition commonly starts in the boundary at which near stoichiometric mixtures could exists. Parametric studies are also conducted to show the effect of additive such as hydrogen peroxide in the ignition delay. Apart from accurate predictions of ignition delay, the coupling between multi-dimensional flow and multi-step chemistry is essential to reveal detailed features of the ignition process.

• 한국지반공학회논문집
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• 제28권9호
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• pp.31-45
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• 2012

본 연구에서는 월파시 해안안벽에 작용하는 지진과 지진해일의 영향에 대하여 한계평형상태해석법을 적용하여 안정성을 검토하였다. 지진해일파력에 대하여 TWOPM-3D를 적용하였으며, 특히 안벽의 뒷채움재를 투과성재료로 가정하여 지진해일파가 월파 후에 안벽배후에 작용하는 파력을 산정하였다. 그리고, 수동상태와 주동상태 조건에서 해안안벽의 안정성에 영향을 주는 요인인 지진해일파고, 뒷채움재의 수위, 수평 수직지진가속도계수, 내부마찰각, 벽마찰각, 간극수압비 등을 변화하여 활동과 전도에 대한 안벽 안전율의 변화특성을 시간에 따라 검토하였다. 이로부터 지진과 지진해일파의 작용하에 지진해일파가 안벽을 월파하는 경우 수동상태에 대한 안전율은 결과적으로 안전율을 증가시키는 요인으로 작용하는 반면, 주동상태에 대하여 결과적으로 안전율을 감소시키는 요인으로 작용함을 확인할 수 있었다.

• 천문학회보
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• 제36권1호
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• pp.27.2-27.2
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• 2011

The Kepler(NASA) and CoRoT(ESA) space telescopes are surveying thousands of exoplanet for finding Earth-like exoplanets with similar environments of the Earth. Then the TPF(NASA), DARWIN(ESA) and many large-aperture ground telescopes have plan for spectroscopic observations of these earth-like exoplanets in next decades. Now, it has been started to simulate the disk averaged spectra of the earthlike exoplanets for comparing the observed spectra and suggesting solutions of environment of these planets. Previous research, the simulations are based on radiative transfer method, but these are limited by optical models of Earth system and instruments. We introduce a new simulation method, IRT(Integrated Ray Tracing) to overcome limitations of previous method. The 3 components are defined in IRT; 1)Sun model, 2)Earth system model (Atmosphere, Land and Ocean), 3)Instrument model. The ray tracing in IRT is simulated in composed 3D real scale space from inside the sun model to the detector of instrument. The Sun model has hemisphere structure with Lambertian scattering optical model. Atmosphere is composed of 16 distributed structures and each optical model includes BSDF with using 6SV radiative transfer code. Coastline and 5 kinds of vegetation distribution data are used to land model structure, and its non-Lambertian scattering optical model is defined with the semi-empirical "parametric kernel method" used for MODIS(NASA) and POLDER(CNES) missions. The ocean model includes sea ice cap structure with the monthly sea ice area variation, and sea water optical model which is considering non-lambertian sun-glint scattering. Computation of spectral imaging and radiative transfer performance of Earth system model is tested with hypothetical space instrument in IRT model. Then we calculated the disk averaged spectra of the Earth system model in IRT computation model for 8 cases; 4 viewing orientation cases with full illuminated phase, and 4 illuminated phase cases in a viewing orientation. Finally the DAS results are compared with previous researching results of radiative transfer method.

• Steel and Composite Structures
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• 제22권6호
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• pp.1417-1443
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• 2016

Cellular and castellated steel beams are used to obtain higher stiffness and bending capacity using the same weight of steel. In addition, the beam openings may be used as a pass for different mechanical fixtures such as ducts and pipes. The aim of this study is to investigate the effect of different parameters on both elastic and inelastic critical buckling stresses of steel web plates with openings. These parameters are plate aspect ratio; opening shape (circular or rectangular); end distance to the first opening; opening spacing; opening size; plate slenderness ratio; steel grade; and initial web imperfection. The web/flange interaction has been simplified by web edge restraints representing simply supported boundary conditions. A numerical parametric study has been performed through linear and nonlinear finite element (FE) models, where the FE results have been verified against both experimental and numerical results in the literature. The web plates are subject to in-plane linearly varying compression with different loading patterns, ranging from uniform compression to pure bending. A buckling stress modification factor (${\beta}$-factor) has been introduced as a ratio of buckling stress of web plate with openings to buckling stress of the corresponding solid web plate. The variation of ${\beta}$-factor against the aforementioned parameters has been reported. Furthermore, the critical plate slenderness ratio separating elastic buckling and yielding has been identified and discussed for two steel grades of DIN-17100, namely: ST-37/2 and ST-52/3. The FE results revealed that the minimum ${\beta}$-factor is 0.9 for web plates under uniform compression and 0.7 for those under both compression and tension.

• Steel and Composite Structures
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• 제22권6호
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• pp.1359-1389
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• 2016

Buckling and free vibration behavior of a laminated cylindrical panel exposed to non-uniform thermal load is addressed in the present study. The approach comprises of three portions, in the first portion, heat transfer analysis is carried out to compute the non-uniform temperature fields, whereas second portion consists of static analysis wherein stress fields due to thermal load is obtained, and the last portion consists of buckling and prestressed modal analyzes to capture the critical buckling temperature as well as first five natural frequencies and associated mode shapes. Finite element is used to perform the numerical investigation. The detailed parametric study is carried out to analyze the effect of nature of temperature variation across the panel, laminate sequence and structural boundary constraints on the buckling and free vibration behavior. The relation between the buckling temperature of the panel under uniform temperature field and non-uniform temperature field is established using magnification factor. Among four cases considered in this study for position of heat sources, highest magnification factor is observed at the forefront curved edge of the panel where heat source is placed. It is also observed that thermal buckling strength and buckling mode shapes are highly sensitive to nature of temperature field and the effect is significant for the above-mentioned temperature field. Furthermore, it is also observed that the panel with antisymmetric laminate has better buckling strength. Free vibration frequencies and the associated mode shapes are significantly influenced by the non-uniform temperature variations.

• 방사성폐기물학회지
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• 제6권2호
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• pp.73-100
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• 2008

고준위 방사성폐기물 처분장으로부터 유출된 핵종에 의한 선량률을 계산하기 위한 생태계평가 코드 ACBIO를 일반적인 구획모델링도구인 AMBER를 이용하여 BIOMASS 방법론을 적용하여 개발하였다. ACBIO의 유용성을 보이고, 구획의 변화나 일부 파라미터값의 변화에 따른 구획 내 농도와 방사능, 그리고 구획간의 플럭스의 민감도도 검토하였다. 지하매질-생태계 경계(GBI)를 통해 넘어오는 핵종의 유출플럭스에 따른 선량환산인자를 각 핵종별로 구하여 결정집단내 개인의 최대피폭선량율을 선량환산인자로 얻는 계산을 수행하였다. 또한 생태계 요소의 구획모델링이나 가능한 피폭집단의 설정, 그리고 GBI의 인지 등이 생태계평가에 중요한 요소가 되는 것을 확인하였다.

• 한국산학기술학회논문지
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• 제15권10호
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• pp.6329-6335
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• 2014

스트럿-타이 모델에서 절점 폭은 해석과 설계에서 중요하다. 그것은 트러스 유사 시스템에서 힘의 분포에 영향을 준다. 또한, 설계 코드를 만족시키기 위한 모든 스트럿 및 절점의 검증에도 영향을 미친다. 여기서 코드는 ACI-318 코드를 의미한다. 절점 폭을 결정하는 4가지 방법이 있다. 즉 1)유효 깊이를 보 높이의 0.9배로 가정하는 방법 2)모멘트 평형을 이용하는 방법 3)절점 폭을 380mm로 가정하는 방법 그리고 4)본 연구에서 제안된 방법이다. 106개의 파라미터 연구를 분석하였다. 그 결과 필요로 하는 총 강재량이 4가지 방법 모두 크게 차이가 나지 않기 때문에 가장 쉬운 방법으로 선택하는 것이 시간 절약 측면에서 좋을 것으로 판단된다.

• 한국전기전자재료학회논문지
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• 제26권3호
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• pp.232-239
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• 2013

Thin light-active layers of the $CuInSe_2$ solar cell were prepared on Mo-coated sodalime glass substrates by one-step electrodeposition and post-annealing. The structure, morphology, and composition of $CuInSe_2$ film could be controlled by deposition parameters, such as the composition of metallic precursors, the concentration of complexing agents, and the temperature of post-annealing with elemental selenium. A dense and uniform Cu-poor $CuInSe_2$ film was successfully obtained in a range of parametric variation of electrodeposition with a constant voltage of -0.5 V vs. a Ag/AgCl reference electrode. The post-annealing of the film at high temperature above $500^{\circ}C$ induced crystallization of $CuInSe_2$ with well-developed grains. The KCN-treatment of the annealed $CuInSe_2$ films further induced Cu-poor $CuInSe_2$ films without secondary phases, such as $Cu_2Se$. The structure, morphology, and composition of $CuInSe_2$ films were compared with respect to the conditions of electrodeposition and post-annealing using SEM, XRD, Raman, AES and EDS analysis. And the conditions for preparing device-quality $CuInSe_2$ films by electrodeposition were proposed.