• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.102-102
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• 2012

타이탄의 근적외선 영역 스펙트럼에서 나타나는 특유의 넓은 흡수밴드를 고체 탄화수소화합물과 질소화합물의 조합으로 설명하고자 한다. 이 흡수 밴드는 대기권의 하층부에 존재하는 연무(haze)에 의한 것으로, 3.3 - 3.4 micron 부근과 2.30 - 2.35 micron 부근에서 유사한 형태가 발견됐다. 두 파장대 모두 C-H 스트레칭 모드가 존재하는 영역이라는 공통점이 있으며, 그 형태가 넓은 흡수밴드로 나타나므로 대기 중에 고체상태의 탄화수소화합물이 존재하는 것으로 유추할 수 있으며, 관련 분자들의 실험값과 복사전달모델을 이용하여 이를 설명하고자 한다. 또한, 이 흡수밴드는 고도에 따라 그 형태와 세기가 달라지므로, 연무 입자들의 고도에 따른 수직분포 및 크기 등을 파악할 수 있다. 이 연구에서는 기존에 타이탄에서 발견된 $CH_4$, $C_2H_6$, $CH_3CN$의 고체 분광선과, 해당 영역에서 흡수선을 보이는 $C_5H_{12}$, $C_6H_{12}$, $C_6H_{14}$ 등의 고체 분광선을 이용한 모델을 Cassini 탐사선의 VIMS 관측자료로부터 유도한 파장 및 고도에 따른 광학적 깊이 변화량과 비교하여 보여주고자 한다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.245-253
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• 2020

In this study, natural frequencies are compared using several pile-soil interaction (PSI) models to evaluate the effects of each model on resonance safety checks for a monopile type of wind turbine structure. Base spring, distributed spring, and three-dimensional brick-shell models represented the PSIs in the finite element model. To analyze the effects of the PSI models on a natural frequency, after a stiffness matrix calculation and Winkler-based beam model for base spring and distributed spring models were presented, respectively; natural frequencies from these models were investigated for monopiles with different geometries and soil properties. These results were compared with those from the brick-shell model. The results show that differences in the first natural frequency of the monopiles from each model are small when the small diameter of monopile penetrates hard soil and rock, while the distributed spring model can over-estimate the natural frequency for large monopiles installed in weak soil. Thus, an appropriate PSI model for natural frequency analyses should be adopted by considering soil conditions and structure scale.

• Journal of the KSME
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• v.25 no.3
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• pp.209-215
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• 1985

충격파에 의해 폭말물에 일어나는 화학반응 진행현상을 Forest Fire 모델과 함께 고온 부위에 의한 점화와 표면연소자는 현상학적인 근거위에 개발한 모델 두가지(IAG, Sandia)를 설명하였고 이 위에 고온부위 개념에 물리적인 설명을 부여한 새로운 모델을 소개하였다. 나중 세가지 모 델들을 PBX-9404에 대한 여러 가지 실험결과와 비교하였는 바 화학반응 초기의 압력증가현상은 주로 점화항(고온 부위에 의한)에 기인하는 것으로써 모두 만족할만한 결과를 보여주고 있으며 후기의 현상은 실험치와 약간 달라지는것(크거나 혹은 작거나)이 보인다. 이 오차가 과연 어느 만큼 실험 오차이며, 또 어느만큼이 모델 오차인지에 대하여는 아직 자료의 불충분으로 확정지어 말할 수 없다. 예를 들어 그림 4에서는 실험결과가 이론결과 보다 압력을 더 큰 것으로 나타 내고 있으며 그림 5에서는 그 반대 현상을 보인다 앞으로 이 방면에 더 연구가 진행되어야 하 리라고 고려되며 연후에 이 모델들을 다른 폭발물에 적용시켜 일반화시키는 일이 남아 있다.

• Fire Science and Engineering
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• v.33 no.2
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• pp.47-55
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• 2019

The prediction performance of design fire curves was evaluated using a Fire dynamics simulator (FDS) for a solid fuel fire in a building space by comparing the results with experimental data. EDC 2-step mixing controlled combustion model was used in the FDS simulations and the previously suggested 2-stage design fire (TDF), Quadratic and Exponential design fire curves were used as the FDS inputs. The simulation results showed that smoke propagation in the building space was significantly affected by the design fire curves. The predictions of simulations using design fire curves for the experimental temperatures in the building space were reasonable, but the TDF was found to be the most acceptable for predicting temperature. The predictions with each design fire curve of species concentrations showed insufficient agreement with the experiments. This suggests that the combustion model used in this study was not optimized for the simulation of a solid fuel fire, and additional studies will be needed to examine the combustion model on the FDS prediction of solid fires.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.113-122
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• 1992

When predicting shipboard noise levees, the accuracy depends largely on the value of the structureborne noise transmission loss. Although empirical formulars are frequently used because of their simplicities, researches on the analytical methods to estimate the transmission loss of structureborne noise such as wave guide theory and SEA has long bean one of the major topics in shipboard acoustics to overcome the inherent limiations of empirical ones. This paper describes an application of SEA to predict the transmission loss of the structureborne noise of a simple shiplike structural mode1 consisted of 22 flats plates. The result shows trial discrepancies between experimental and theoretical transmission losses are less than 3 dB.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.72-79
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• 2003

A numerical calculation was conducted to estimate and to elucidate the role of the radiative heat flux from metal particles(Al, $Al_2O_3$) on the dynamic extinction of solid propellant rocket where the rapid depressurization took place. Anon-linear flame modeling implemented by the residence time modeling for metalized propellant was adopted to evaluate conductive heat flux to the propellant surface. The radiative heat feed back was calculated with the aid of a modified comvustion-flow model as well. The calculation results with the propellant of AP:Al:CTPB=76:10:14 had revealed that the radiative heat flux is approximately 5~6% of total flux at the critical depressurization rate regardless of chamber geometry (open or confined chamber). It was also found that the dynamic extinction in open geometry could be predicted at the depressurization rate about 45% larger with radiative heat feedback than without radiation. Thus, it should be claimed that even a small amount of radiative flux 5~6% could produce a big error in predicting the critical depressurization rate of the metalized propellant combustion.

• Journal of the Korean Society of Safety
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• v.12 no.3
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• pp.178-184
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• 1997

Many mathematical techniques have been developed to determine the muscle forces and force distribution in biomechanical human model, because it is so important to understand internal forces resisting external loading. However, a three-dimensional mathematical model of wrist joint, which is essential to develop solid modeling and artificial wrist joint, has not been well developed. This study proposed to define three-dimensional mathematical model of distal radius and ulna of the human wrist and to develop a detailed two-dimensional finite element through comparisons to existing analytical models and experimental tests. This mathematical model were accurately recreated, allowing the internal tendon force as well as force transmission and distribution through the distal radios and ulna during dynamic loadings. The results found in this study indicate and support the findings of other investigator that cyclic loading condition results in higher compression force on distal radius and ulna and may be source of wrist disorder.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.2
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• pp.101-109
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• 1981

균일 인장하중하에 있는 고체 내부에 고립된 제 1형 탄소성 크랙의 반취성 파괴를 경사슬립밴드모델(inclined slip band model)로서 연속크랙전위(conticuum crack dislocation) 및 연속격자 전위(continum lattice dislocation)을 이용하여 이론적으로 연구하였다. 크랙전위 및 격자전위에 관한 힘평형을 나타애는 연립특이적분방정식의 해는크랙전위 및 격자전위에 관한 적정밀도함수를 가지고 특이함을 해소하는 조건을 부가하여 얻는다. 이특이항 해소조건의 타당성은 처음으로 소성영역의 크기를 그 판단기준으로 검토되었으며, 그결과 합당한 것으로 확인되었다. 또한 상기방법으로부터 산출된 COD는 소규모 성역을 넘어서도 선형적으로 .KAPPA.$^{2}$.EPSILON..sigma.$_{Y}$ 에 따라 변화함을 알게 된다. 상기모델에서 위축적분경로(Shrunk path) 상의 J 적분치를 J=.delta..sigma.$_{Y/}$sin2.theta.의 형태로 유도하였는데, 이것은 J 적분에 관한 Eshelby의 힘개념을 구체적으로 표현한다: J는 크랙전파방향으로 탄소성크랙정점에 작용하는 가상적인 힘이며, 1/2 J의 한 슬립편면상에서의 분력은 그 슬립정면사으이 보든 격자전위에 작용하는 전단력의 총화와 같다. 같다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.565-568
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• 2010

A pressure control law to regulate mass flow rate of gas generator is suggested. The governing equation is modeled by considering the burning rate of solid propellant and the conservation equation of gas generator. And then, a classical control law is applied after verifying the accuracy of dynamic model through comparing with ground test and internal ballistic results. The results show degradation of performance as shown in typical time varying system. To overcome this problem, an adaptive scheme is suggested and the performance is verified through numerical simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.595-600
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• 2020

The purpose of this paper was to prepare and evaluate solid dispersions (SD) that can increase the dissolution rate of dexibuprofen as a model drug with low solubility in water using saccharides and sugar alcohols as dispersion materials. DSC, XRD, content and content uniformity test, dissolution test, and disintegration test were conducted for physicochemical evaluation of the prepared SD. For the results, it was confirmed using differential scanning calorimetry that fructose, which has a melting point around 120 ℃ of the device operating temperature range, is a suitable excipient for the preparation of SD by the rotary hot-melt granulation (RHMG) method. X-ray diffraction analysis was conducted to confirm that the crystallinity of dexibuprofen was reduced. Disintegration test of the prepared tablet using SD-containing dexibuprofen and fructose confirmed a very fast disintegration time within 1~2 seconds and also showed that the dissolution rate was about 20% faster than that of the dexibuprofen raw material. Dexibuprofen with reduced crystallinity by SD confirmed through the RHMG method can be used to increase the dissolution rate of the drug and increase the disintegration time of the tablet. Thus, it can be used in the manufacturing of various solid preparations.