• Advances in aircraft and spacecraft science
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• 제6권6호
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• pp.515-528
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• 2019

The structural vibrations of a flat plate induced by fluctuating wall pressures within wall-bounded transonic jet flow downstream of a high-aspect ratio rectangular nozzle are simulated. The wall pressures are calculated using Hybrid RANS/LES CFD, where LES models the large-scale turbulence in the shear layers downstream of the nozzle. The structural vibrations are computed using modes from a finite element model and a time-domain forced response calculation methodology. At low flow speeds, the convecting turbulence in the shear layers loads the plate in a manner similar to that of turbulent boundary layer flow. However, at high nozzle pressure ratio discharge conditions the flow over the panel becomes transonic, and the shear layer turbulence scatters from shock cells just downstream of the nozzle, generating backward traveling low frequency surface pressure loads that also drive the plate. The structural mode shapes and subsonic and transonic surface pressure fields are transformed to wavenumber space to better understand the nature of the loading distributions and individual modal responses. Modes with wavenumber distributions which align well with those of the pressure field respond strongly. Negative wavenumber loading components are clearly visible in the transforms of the supersonic flow wall pressures near the nozzle, indicating backward propagating pressure fields. In those cases the modal joint acceptances include significant contributions from negative wavenumber terms.

• 건축역사연구
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• 제25권6호
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• pp.35-44
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• 2016

The purpose of this study is to identify the aspect of expression about the form of Shwedagon Pagoda as well as to find out its meanings. The aesthetic value of Shwedagon Pagoda appears as the worship and infinite respect to Buddha realizing its beautiful sacred symbol. The meaning of Shwedagon Pagoda is to progress in keeping pace with the specific flexibility of Buddhism in Myanmar developing Buddhistic diversity and accepting its active changes. As time passes, Shwedagon Pagoda has been transformed. It is because that Myanmar's architecture was developed independently being affected by India with the introduction of Buddhism, and accepted it through autonomous reinterpretation. Then, the function of the worship space surrounding Shwedagon was extended and its annexes and statues of the Buddha were built; its scale became larger. This study shows the comparison between Shwezigon Pagoda and Shwedagon Pagoda. This method of investigation reveals that the formal changes of Shwedagon makes it transform to concise composition and develop aesthetical component giving the sense of vertical rise.

• Nuclear Engineering and Technology
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• 제46권5호
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• pp.633-640
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• 2014

In this research, the surface roughness affecting the pressure drop in a pipe used as the steam generator of a PWR was studied. Based on the CFD (Computational Fluid Dynamics) technique using a commercial code named ANSYS-FLUENT, a straight pipe was modeled to obtain the Darcy frictional coefficient, changed with a range of various surface roughness ratios as well as Reynolds numbers. The result is validated by the comparison with a Moody chart to set the appropriate size of grids at the wall for the correct consideration of surface roughness. The pressure drop in a full-scale U-shaped pipe is measured with the same code, correlated with the surface roughness ratio. In the next stage, we studied a reduced scale model of a U-shaped heat pipe with experiment and analysis of the investigation into fluid-structure interaction (FSI). The material of the pipe was cut from the real heat pipe of a material named Inconel 690 alloy, now used in steam generators. The accelerations at the fixed stations on the outer surface of the pipe model are measured in the series of time history, and Fourier transformed to the frequency domain. The natural frequency of three leading modes were traced from the FFT data, and compared with the result of a numerical analysis for unsteady, incompressible flow. The corresponding mode shapes and maximum displacement are obtained numerically from the FSI simulation with the coupling of the commercial codes, ANSYS-FLUENT and TRANSIENT_STRUCTURAL. The primary frequencies for the model system consist of three parts: structural vibration, BPF(blade pass frequency) of pump, and fluid-structure interaction.

• Interdisciplinary Bio Central
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• 제1권2호
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• pp.6.1-6.4
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• 2009

We stand at the brink of a fundamental change in how medicine will be practiced. Over the next 5-20 years medicine will move from being largely reactive to being predictive, personalized, preventive and participatory (P4). Technology and new scientific strategies have always been the drivers of revolutions and this is certainly the case for P4 medicine, where a systems approach to disease, new and emerging technologies and powerful computational tools will open new windows for the investigation of disease. Systems approaches are driving the emergence of fascinating new technologies that will permit billions of measurements on each individual patient. The challenge for health information technology will be how to reduce this enormous amount of data to simple hypotheses about health and disease. We predict that emerging technologies, together with the systems approaches to diagnosis, therapy and prevention will lead to a down turn in the escalating costs of healthcare. In time we will be able to export P4 medicine to the developing world and it will become the foundation of global medicine. The "democratization" of healthcare will come from P4 medicine. Its first real emergence will require the unprecedented integration of biology, medicine, technology and computation. as well as societal issues of major importance: ethical, regulatory, public policy, economic, and others. In order to effectively move the P4 scientific agenda forward new strategic partnerships are now being created with the large-scale integration of complementary skills, technologies, computational tools, patient records and samples and analysis of societal issues. It is evident that the business plans of every sector of the healthcare industry will need to be entirely transformed over the next 10 years.and the extent to which this will be done by existing companies as opposed to newly created companies is a fascinating question.

• 대한조선학회논문집
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• 제60권6호
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• pp.450-459
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• 2023

According to Korea Maritime Safety Tribunal, there have been 14,100 maritime accidents from 2017 to 2021. Among those accidents, ship collision accidents have been up to 1,275 cases. But in the accidents relating to small ships like a fishing vessel, analyzing the causes of the accidents would depend on statements of the persons related because there is often no navigational data. But those statements can be incorrect and give rise to disagreements between them so that it causes conflicts with each other during the trial. So a replay system of ship collision accident (RESCA) has been developed in order to reproduce the ship collision accident by using AIS, V-PASS or radar data. But the reproduced trajectory of ship collision accident is needed to be verified because it can be unreasonable physically. So a method to verify the reproduced trajectory and collect the physical data on ship collision accident is newly designed by using free running test. In the RESCA, the accident is reproduced using the navigational data from the trajectory for a ship and measured from free running model test for the other ship at the same time. Through free running test, the behavior of the model ship is transformed from model scale into real scale. In order to check into the accuracy of the new method, free running model tests by using RESCA are carried out on the actual ship collision accidents.

• 한국재료학회지
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• 제8권6호
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• pp.505-512
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• 1998

플라즈마 용사법을이용하여 AISI 316 스테인레스 금속모재에 0.1mm 두께의 $NiCrAlCoY_{2}O_{3}$금속 결합층과 0.3mm 두께의 $ZrO_{2}(8wt%Y_{2}O_3$) 세라믹층으로 구성된 이층 단열코팅층을 제조하였다. 코팅층의 미세조직, 금속결합층의 산화를 고찰하였으며, $900^{\circ}C$에서 등은 시험과 열반복시험 후, 접합강도시험을 통하여 코팅층의 단사정 상은 열처리시간이 길어질수록 약간 증가하였다. 또한 비변태성 t'의 c/a는 용사상태에서 1.0099이였으며, 100시간 열처리 후에는 1.0115로 약간 증가하였다. 그리고 용사층의 접합강도는 열처리 시간이 길어질수록 감소하였다. 등온열처리 후에는 1.0115로 약간 증가하였다. 그리고 용사층 의 접합강도는 열처리 시간이 길어질수록 감소하였다. 등온열처리 후, 파괴는 주로 세라믹층에서 일어났으며, 반복 열처리되 시편에서는 10회 이후 대부분 금속결합층/세라믹층의 계면에서 일어났다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.440-440
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• 2012

Nanomaterials have emerged as new building blocks to construct light energy harvesting assemblies. Size dependent properties provide the basis for developing new and effective systems with semiconductor nanoparticles, quantized charging effects in metal nanoparticle or their combinations in 2 and 3 dimensions for expanding the possibility of developing new strategies for photovoltaic system. As top-down approach, we developed a simple and effective method for the large scale formation of self-assembled Cu(In,Ga)$Se_2$ (CIGS) nanostructures by ion beam irradiation. The compositional changes and morphological evolution were observed as a function of the irradiation time. As the ion irradiation time increased, the nano-dots were transformed into a nano-ridge structure due to the difference in the sputtering yields and diffusion rates of each element and the competition between sputtering and diffusion processes during irradiation. As bottom-up approach, we developed the growth of CIGS nanowires using thermal-chemical vapor deposition (CVD) method. Vapor-phase synthesis is probably the most extensively explored approach to the formation of 1D nanostructures such as whiskers, nanorods, and nanowires. However, unlike binary or ternary chalcogenides, the synthesis of quaternary CIGS nanostructures is challenging because of the difficulty in controlling the stoichiometry and phase structure. We introduced a method for synthesis of the single crystalline CIGS nanowires in the form of chalcopyrite using thermal-CVD without catalyst. It was confirmed that the CIGS nanowires are epitaxially grown on a sapphire substrate, having a length ranged from 3 to 100 micrometers and a diameter from 30 to 500 nm.

• 수산해양기술연구
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• 제43권1호
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• pp.1-11
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• 2007

It is the basic studies for productivity improvement and laborsaving of purse seine fishery. Because the seine shape is apt to be transformed in seine shooting process due to the effect of tide, this study is intended to establish 4 steps, whose flow velocity are 0, 2, 4 and 6cm/sec, in flume tank and perform the experiment to review the character. We used two model seines designed on the scale of 1 to 180 based on the power block seine, which is the mackerel purse seine generally used in the near sea of Jeju Island and triplex seine, which is the mackerel purse seine of one boat system fishing expected in the future, for the experiment, analyzed of the sinking movements on the two seines and its results are as follows. In the setting over the flow velocity 6cm/sec, experiment was impossible because of flying and transformation of seine were severe. The sinking movements of P seine and T seine generally showed linear phenomenon and the sinking speed showed gentle curve shape. Sinking tendency was distinguished by existence of flow velocity. When there is flow velocity, it showed the phenomenon that it sinking by similar type. Although sinking depth and sinking speed did not show distinguished classification, P seine shows bigger than T seine. When there was in flow velocity, the elapsed time(Et) and sinking depth (PDp, TDp) of P seine and T seine can be shown such experimental equations as PDp=(0.21V+4.96)Et-(0.62V-0.10) and TDp=(0.19V+4.95)Et-(0.72V+0.34). When there was in flow velocity, the elapsed time and siking speed (PSp, TSp) of P seine and T seine can be shown such experimental equations as $PSp=-0.11Et^2+1.42Et+1.75\;and\;TSp=-0.11Et^2+1.41Et+1.37$.

• 문화기술의 융합
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• 제8권5호
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• pp.641-651
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• 2022

이 연구는 숙박시설이 있는 특정소방대상물 수용인원의 산정 방법에 따라 피난가능시간을 기준으로 피난시뮬레이션을 실시하여 고시원 화재 발생 시 계단 폭의 변화에 따른 피난소요시간을 비교·분석하였다. 현재 숙박시설로 분류하는 고시원(바닥면적 합계 500m² 이상)은 소방시설법, 건축법, 주차장법이 정하는 맹점을 이용, 적은 면적의 대지 위에 고층으로 건축물을 신축하여, 적지 않은 양의 호실을 만들어 대다수의 고시원이 학생과 고시생을 위한 곳이 아닌 변형된 숙박시설의 형태로 변질되어가고 있다. 이는 건축주의 영업이익에 부합하므로 지속적인 증가 추세를 보일 것으로 예상된다. 고시원 피난 시간의 골든타임 확보는 우리 사회의 경제적 약자에 속하는 고시원 재실자의 최후의 보루로 본 연구가 사회적 안전망 구축을 위한 관계법령의 개정 논의에 시발점이 되길 바라며, 피난시뮬레이션 분석의 결과 피난훈련이 실행된 집단과 피난계단의 폭을 200cm로 확장한 경우에 피난소요시간이 가장 적게 나타났으며, 기존 건물의 계단 폭의 변화 없이 피난시뮬레이션을 실시한 피난소요시간이 648.4초와 시나리오 6을 비교하면 최대166.3초가 단축되는 결과를 보였다. 이와 같은 분석 결과를 통하여 고시원의 피난안전성 개선을 위해 피난계단의 폭을 다중이용업소의 안전관리에 관한 특별법의 안전시설 등 종류에 추가하여 관련 법령의 개정에 활용할 수 있는 근거를 마련했다는 점에서 의의가 있다.

• 한국화재소방학회논문지
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• 제33권6호
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• pp.120-125
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• 2019

본 연구에서는 구획된 공간에 비닐장판을 깔고, 인화성 액체 50 ml를 뿌리고 실물 연소 실험을 실시하였다. 연소가 진행될 때의 연소 거동을 실시간 분석하였으며, 탄화된 비닐장판의 표면 및 단면의 탄화 패턴을 해석하였다. 휘발유에 착화되어 화염이 최성기에 도달하면 지속적으로 화염이 일어나는 영역, 간헐적으로 화염이 일어나는 영역, 플룸 영역 등이 형성되는 것을 알 수 있었다. 50 ml의 휘발유가 비닐장판 위에서 연소되는데 약 26 s가 소요되었으며, 달무리 패턴이 형성되는 것을 확인할 수 있었다. 등유를 비닐 장판 위에 동일하게 뿌리고, 가스 토치를 이용하여 착화를 시도하였으나 실패하였다. 연소가 완료된 후의 비닐장판의 탄화 범위는 가로 600 mm, 세로 380 mm이며, 탄화 면적은 1,000 ㎟로 분석되었다. 탄화된 비닐장판의 표면은 열에 의해 코팅층이 탄화층으로 변형되어 더욱 딱딱한 것을 알 수 있었다. 그리고 탄화된 비닐장판의 경계면을 실체현미경을 이용하여 단면을 분석한 결과 부풀림 현상이 확인되었고, 코팅층 하부의 흰색 경계층이 없어지는 것을 알 수 있었다.