• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1346-1351
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• 2003

There is few research about contact problem in SPH because it is primarily suitable to analyze the large deformation problem. However, an elasto-plastic problem with small deformation need to be considered about contact characteristics. The numerical formulating methods for SPH is induced to be able to obtain solutions based on a variational method in contact problem. The contact algorithm presented is applied to the elastic impact problem in 1D and 2D. The results show thai an imaginary tension and a numerical instability which happen in impacting between different materials can be removed and contact forces which could not have been calculated are able to obtain.

• 물과 미래
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• 제18권1호
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• pp.67-73
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• 1985

금강 감조구간의 조석전파현상을 장파, 중력파공식의 수치적분에 의한 통상적인 방법을 이용하여 조사하였다. 이용된 역학방정식은 비선형항을 포함하여 천해조를 산정할 수 있도록 하였다. 수립된 모델은 평균대, 중, 소조시의 감조구간의 조석전파를 산정하는데 이용되었으며 또한 상류홍수유출과 하구조석의 상호작용에 의한 감조구간의 수립분포를 산정하는데도 초기적용되었다. 이 연구의 목적은 하구의 체절공사가 시작되기 전의 금강감조구간의 조석역학을 조사하는데 있다.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.52-63
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• 2008

The side collision reconstruction algorithm is developed using three dimensional car crash analysis. Medium size passenger car is modeled for finite element analysis. Total 24 side collision configurations, four different speed and six different angle, are set up for making side collision database. Deformation index and degree index are built up for each collision case. Deformation index is a kind of deformation estimate averaging displacement of side door of crashed car from finite element analysis result. Angle index is constructed measuring deformed angle of crashing car. There are two kinds of angle index, one is measured at driver's side and the other is measured at passenger's side. Also a collision analysis information in side of cars is used for giving a basis for scientific and practical reason in a reconstruction of the car accident. The analysis program, LS-DYNA3D is utilized for finite element analysis program for a collision analysis. Those database are used for side collision reconstruction. Side collision reconstruction algorithm is developed, and applied to find the collision conditions before the accident occurs. Three example collision cases are tried to check the effectiveness of the algorithm. Deformation index and angle index is extracted for the case from the analysis result. Deformation index is compared to the established database, and estimated collision speed and angle are introduced by interpolation function. Angle index is used to select a specific collision condition from the several available conditions. The collision condition found by reconstruction algorithm shows good match with original condition within 10% error for speed and angle. As a result, the calculation from the reconstruction of the situation is reproducing the situation well. The performance in this study can be used in many ways for practical field using deformation index and degree index. Other different collision situations may be set up for extending the scope of this study in the future.

• 센서학회지
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• 제16권1호
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• pp.44-51
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• 2007

A hybridized simulator for generating blood pressure waveform is proposed to study the remedy and/or evaluation of the conventional sphygmomanometer utilizing the oscillometric method which is widely applied. The blood pressure of a flowing fluid was controlled for the blood vessel's condition caused by a rhythmical and periodical contraction/relaxation because of the special excitatory and conductive system of the heart. In this study, a hybridized controller composed of the PI feedback controller and the feedforward controller. The inverse dynamics function is proposed to operating the control valve while the pressure is applied in an oil pressure tank. The proposed hybrid simulator reproducing the blood pressure waveform in an artificial blood vessel has kept the control performance consistent over all range. Based on these results, the proposed simulators could be applied to the development and compensation of the non invasive sphygmomanometer type as well as to study the characteristics of the blood pressure and blood vessel.

• 한국해안·해양공학회논문집
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• 제31권4호
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• pp.199-208
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• 2019

2차원 조파수조에서 완전반사 조건의 규칙파 조파 실험을 수행하고, 세 가지 서로 다른 CFD 모델의 성능을 검증하였다. 사용된 CFD 모델은 CADMAS-SURF, olaFlow 및 KIOSTFOAM이었다. 쇄파가 발생하지 않는 조건, 중복파의 쇄파가 발생하는 조건, 입사파의 쇄파가 발생하는 조건에서 실험 및 모델링을 수행하였다. 그 결과 세 모델 중 KIOSTFOAM이 실험결과를 가장 잘 재현하는 것으로 나타났다. CADMAS-SURF는 KIOSTFOAM에 비해 계산 시간은 줄어들지만 계산 정확도가 상대적으로 더 낮았다. olaFlow는 계산은 가장 빠르지만 조파 경계에서 반사파 흡수가 만족스럽지 않고 쇄파 발생 시 파랑에너지를 과도하게 소산시키는 것으로 나타났다.

• 박물관보존과학
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• 제16권
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• pp.82-95
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• 2015

윤두서(尹斗緖)필 노승도(老僧圖)는 은지(銀紙)라는 독특한 바탕재료를 사용한 것으로 알려져 있다. 본 연구에서는 보존 환경에 따라 변색이 쉬운 은이 지금까지 안정적인 상태로 전해지는 원인을 알아보고자 하였다. 연구방법은 문헌 조사, 육안 관찰 및 광학적 조사, XRF 분석으로 표면가공 재료 및 원료 섬유를 분석하였고, 이를 근거로 재현 실험을 수행하여 윤두서필 노승도 바탕종이의 제작 재료와 표면가공 기법에 대해 접근하였다. 연구 결과 바탕 종이는 표면 평활성 및 밀도를 향상시키기 위하여 다각형의 결정을 가진 무기물에 의한 도침처리를 확인할 수 있었다. 그리고 XRF 분석 결과, 칼슘 함량이 높게 나타나 기존에 알려진 은(銀)이 아니라 전복 등의 패각류를 분쇄하여 표면 처리한 것으로 추정하였다. 따라서 칼슘 함량이 높은 재료인 패각류를 대상 재료로 한정하고, 그 중에서도 현재 가공되지 않은 패 상태의 전복을 대상 시료로 선정하여 재현 실험을 수행하였다. 전복패를 사용한 재현 실험을 통해 노승도 바탕 종이에 사용된 무기질은 패각류일 가능성이 높은 것으로 확인되었다. 다만 유물과 유사한 수준의 평활도와 광택을 재현하는 데는 한계가 있었으며 이에 대해 보다 세밀한 연구가 필요할 것으로 사료된다.

• 한국전산구조공학회논문집
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• 제27권1호
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• pp.1-8
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• 2014

레벨셋 기법과 무요소법을 결합한 위상 및 형상 최적설계 기법을 개발하여 선형 탄성문제에 적용하였다. 설계민감도는 애드조인트법을 사용하여 효율적으로 구하였다. 해밀턴-자코비 방정식을 업-윈드 기법을 이용하여 수치적으로 풀었으며, 구조물의 경계는 레벨셋 함수를 이용하여 암시적으로 표현하였다. 구조물의 응답과 설계민감도를 얻기 위하여 암시적 함수를 사용하여 명시적 경계를 생성하였다. 재생 커널 기법에 기초하여 얻어진 전역 절점 기저함수를 사용하여 연속체 지배방정식의 변위장을 이산화하였다. 따라서 질점들을 연속체 영역의 어느 곳이든 위치시킬 수 있으며, 이는 통해 명시적 경계를 생성하는 것이 가능하며, 결과적으로 정확한 설계를 얻을 수 있다. 개발된 방법은 제한 조건이 있는 최적설계 문제에 대하여 라그랑지안 범함수를 정의한다. 이는 경계의 변화를 통하여 허용 부피 제한조건을 만족시키면서 컴플라이언스를 최소화한다. 최적설계 과정 동안 라그랑지안 범함수의 최적화조건을 만족시킴으로써 해밀턴-자코비 방정식을 풀기 위한 속도장을 얻는다. 기존의 형상 최적설계 기법에 비하여, 본 방법론은 위상과 형상의 변화를 쉽게 얻어낼 수 있다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.671-679
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• 2008

The effect of Pre-cooled Turbojet Engine installation and nozzle exhaust jet on Hypersonic Turbojet EXperimental aircraft(HYTEX aircraft) were investigated by three-dimensional numerical analyses to obtain aerodynamic characteristics of the aircraft during its in-flight condition. First, simulations of wind tunnel experiment using small scale model of the aircraft with and without the rectangular duct reproducing engine was performed at M=5.1 condition in order to validate the calculation code. Here, good agreements with experimental data were obtained regarding centerline wall pressures on the aircraft and aerodynamic coefficients of forces and moments acting on the aircraft. Next, full scale integrated analysis of the aircraft and the engine were conducted for flight Mach numbers of M=5.0, 4.0, 3.5, 3.0, and 2.0. Increasing the angle of attack $\alpha$ of the aircraft in M=5.0 flight increased the mass flow rate of the air captured at the intake due to pre-compression effect of the nose shockwave, also increasing the thrust obtained at the engine plug nozzle. Sufficient thrust for acceleration were obtained at $\alpha=3$ and 5 degrees. Increase of flight Mach number at $\alpha=0$ degrees resulted in decrease of mass flow rate captured at the engine intake, and thus decrease in thrust at the nozzle. The thrust was sufficient for acceleration at M=3.5 and lower cases. Lift force on the aircraft was increased by the integration of engine on the aircraft for all varying angles of attack or flight Mach numbers. However, the slope of lift increase when increasing flight Mach number showed decrease as flight Mach number reach to M=5.0, due to the separation shockwave at the upper surface of the aircraft. Pitch moment of the aircraft was not affected by the installation of the engines for all angles of attack at M=5.0 condition. In low Mach number cases at $\alpha=0$ degrees, installation of the engines increased the pitch moment compared to no engine configuration. Installation of the engines increased the frictional drag on the aircraft, and its percentage to the total drag ranged between 30-50% for varying angle of attack in M=5.0 flight.

• 한국환경복원기술학회지
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• 제16권4호
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• pp.1-14
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• 2013

A species restoration plan requires a process where the first is to thoroughly study the target species, second is to provide them with an onsite reproduction and adaptation period, and finally, third is to release them to their natural habitat. This study focuses on the space planning for target species' successful onsite reproduction and adaptation. For the study, a site planning near Sobaeksan National Park was implemented with Red Fox's behavior and habitat characteristics in mind for its recovery, reproduction, and natural adaptation. During site selection and planning, the basic aim was to incorporate the existing site as much as possible thus reducing the impact on the environment from the recovery plan. In addition, for a stable recovery of the Red Fox population, the site was classified into three different areas : core area, buffer zone, and transition area. Then, the facilities that help Red Fox's reproduction and adaptation such as reproduction center, foraging site, adaptation training center were planned. Under the condition that the site will be off limit to the public, a limited number of paths for monitoring was provided. For the site's vegetation, the existing species were planted as much as possible with the addition of plants that the Red Fox consume. The facilities included as Red Fox's habitat were fox burrows for hiding and ecological ponds for drinking. From this study, the recovery of the endangered fox species is expected as well as the contribution to an effort to increase of awareness toward the biological resources in Korea through Nagoya protocol. Furthermore, it has the potential to change the public's attitude toward endangered species recovery projects through publicizing and providing experience to the national park visitors.

• Geomechanics and Engineering
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• 제19권2호
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• pp.153-165
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• 2019

A case study of monitoring and analysis of surface settlement induced by tunneling of Tabriz metro line 2 (TML2) is presented in this paper. The TML2 single tunnel has been excavated using earth pressure balanced TBM with a cutting-wheel diameter of 9.49 m since 2015. Presented measurements of surface settlements, were collected during the construction of western part of the project (between west depot and S02 station) where the tunnel was being excavated in sand and silt, below the water table and at an average axis depth of about 16 m. Settlement readings were back-analyzed using Gaussian formula, both in longitudinal and transversal directions, in order to estimate volume loss and settlement trough width factor. In addition to settlements, face support and tail grouting pressures were monitored, providing a comprehensive description of the EPB performance. Using the gap model, volume loss prediction was carried out. Also, COB empirical method for determination of the face pressure was employed in order to compare with field monitored data. Likewise, FE simulation was used in various sections employing the code Simulia ABAQUS, to investigate the efficiency of numerical modelling for the estimating of the tunneling induced-surface settlements under such a geotechnical condition. In this regard, the main aspects of a mechanized excavation were simulated. For the studied sections, numerical simulation is not capable of reproducing the high values of in-situ-measured surface settlements, applying Mohr-Coulomb constitutive law for soil. Based on results, for the mentioned case study, the range of estimated volume loss mostly varies from 0.2% to 0.7%, having an average value of 0.45%.