• 새물리
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• 제69권10호
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• pp.1107-1114
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• 2019

다양한 기능의 새로운 물질을 합성하고 정적 및 동적 특성을 조사하기 위해서는 매우 안정된 고온 및 고압 조건을 만드는 것이 중요하다. 새로운 물질을 제조하는 데 필요한 다이아몬드 엔빌 셀 (DAC)을 사용하여 Mbar 범위의 고압 조건은 이미 확보되었다. 이 연구에서는 DAC와 결합된 레이저 가열 시스템을 설계하였으며, DAC의 양쪽 방향에서 시료를 가열하기 위해 2 대의 1064 nm, 100 W 파이버 레이저를 사용했을 뿐만 아니라 3 대의 분광기를 사용하여 온도, 압력 및 라만 스펙트럼을 측정하였다. 고압 실험에서 시료를 가두는 구멍으로 일반적으로 사용되는 스테인리스 강 개스킷을 가열하여 열 방사선원을 만들고, 이 방사선원으로부터 방출되는 복사 스펙트럼을 획득하여 가열된 개스킷의 온도를 측정하였다. 이 기술을 적용하여 다양한 물질들을 만들고 극한 조건에서 물리적 특성을 조사 할 수 있다.

• 대한기계학회논문집B
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• 제23권8호
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• pp.1040-1047
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• 1999

The characteristics of flame propagation in inert particle-laden $H_2$/Air premixed gas are numerically investigated on this study. The 2nd order TVD scheme is applied to numerical analysis of governing equations and multi-step chemical reaction model and detailed transport properties are sued to solve chemical reaction terms. Radiation heat transfer is computed by applying the finite volume method to a radiative transfer equation. The burning velocities against the mole fractions of hydrogen agree well with results performed by different workers. The inert particles play significant roles in the flame propagation on account of momentum and heat transfer between gas and particles. Gas temperature, pressure and flame propagation speed are decreased as the loading ratio of particle is increased. Also the products behind flame zone contain lots of water vapor whose absorption coefficient is much larger than that of unburned gas. Thus, the radiation effect of gas and particles must be considered simultaneously for the flame propagation in a mixture of $H_2$/Air and inert particles. As a result, it is founded that because the water vapor emits much radiation and this emitted radiation is released at boundaries as radiant heat loss as well as reabsorbed by gas and particles, flame propagation speed and flame structure are altered with radiation effect.

• Applied Science and Convergence Technology
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• 제23권6호
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• pp.309-316
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• 2014

A large particle accelerator requires an ultrahigh vacuum (UHV) system of average pressure under $1{\times}10^{-7}$ Pa for mitigating the impact of beam scattering from the residual gas molecules. The surface inside the beam ducts should be controlled with an extremely low thermal outgassing rate under $1{\times}10^{-9}Pa{\cdot}m^3/(s{\cdot}m^2)$ for the sake of the insufficient pumping speed. To fulfil the requirements, the aluminum alloys were adopted as the materials of the beam ducts for large accelerator that thanks to the good features of higher thermal conductivity, non-radioactivity, non-magnetism, precise machining capability, et al. To put the aluminum into the large accelerator vacuum systems, several key technologies have been developed will be introduced. The concepts contain the precise computer numerical control (CNC) machining process for the large aluminum ducts and parts in pure alcohol and in an oil-free environment, surface cleaning with ozonized water, stringent welding process control manually or automatically to form a large sector of aluminum ducts, ex-situ baking process to reach UHV and sealed for transportation and installation, UHV pumping with the sputtering ion pumps and the non-evaporable getters (NEG), et al. The developed UHV technologies have been applied to the 3 GeV Taiwan Photon Source (TPS) and revealed good results as the expectation. The problems of leakage encountered during the assembling were most associated with the vacuum baking which result in the consequent trouble shootings and more times of baking. Then the installation of the well-sealed UHV systems is recommended.

• 방사선산업학회지
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• 제9권3호
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• pp.119-126
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• 2015

In Shinjeong-dong of Jeongeup, there are three government-supported research institutes and an RFT industrial complex which is currently being established. Increased human activities can affect flora and fauna as a man-made pressure onto the region. As a baseline study, status of exotic plants was investigated prior to a full operation of the RFT industrial complex. A total of 54 species and 1 variety of naturalized or introduced plants were found in the study area. Among them, three species (Ambrosia artemisifolia var. elatior, Rumex acetocella and Aster pilosus) belong to 'nuisance species', and four species(Phytolacca americana, Iopomoea hederacea, Ereechtites hieracifolia and Rudbeckia laciniata) to 'monitor species' designated by the ministry of Environment. Some of naturalized trees and plants were intentionally introduced in this area, while others naturally immigrated. Physalis angulata seemes to immigrate in the study area in the form of mixture with animal feeds as its distribution coincided with the transportation route of the animal feeds. Liquidambar styraciflua is amenable to the ecological investigation on the possible expansion of the species to the nearby Naejang National Park as its leave shape and autumn color are very similar to those of maple trees. The number of naturalized plants around the RFT industrial complex will increase with an increase in floating population, in human activities in association with constructions of factories and operations of the complex. The result of this study provides baseline data for assessing the ecological change of the region according to the operation of the RFT industrial complex.

• 한국안전학회지
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• 제31권3호
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• pp.42-46
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• 2016

In LCD Display or semiconductor manufacturing processes, the anti-static technology of glass substrates and wafers becomes one of the most difficult issues which influence the yield of the semiconductor manufacturing. In order to overcome the problems of wafer surface contamination various issues such as ionization in decompressed vacuum and inactive gas(i.e. $N_2$ gas, Ar gas, etc.) environment should be considered. Soft X ray radiation is adequate in air and $O_2$ gas at atmospheric pressure while UV radiation is effective in $N_2$ gas Ar gas and at reduced pressure. At this point of view, the "vacuum ultraviolet ray ionization" is one of the most suitable methods for static elimination. The vacuum ultraviolet can be categorized according to a short wavelength whose value is from 100nm to 200nm. this is also called as an Extreme Ultraviolet. Most of these vacuum ultraviolet is absorbed in various substances including the air in the atmosphere. It is absorbed substances become to transit or expose the electrons, then the ionization is initially activated. In this study, static eliminator based on the vacuum ultraviolet ray under the above mentioned environment was tested and the results show how the ionization performance based on vacuum ultraviolet ray can be optimized. These vacuum ultraviolet ray performs better in extreme atmosphere than an ordinary atmospheric environment. Neutralization capability, therefore, shows its maximum value at $10^{-1}{\sim}10^{-3}$ Torr pressure level, and than starts degrading as pressure is gradually reduced. Neutralization capability at this peak point is higher than that at reduced pressure about $10^4$ times on the atmospheric pressure and by about $10^3$ times on the inactive gas. The introductions of these technology make it possible to perfectly overcome problems caused by static electricity and to manufacture ULSI devices and LCD with high reliability.

• 한국가스학회지
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• 제14권1호
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• pp.37-41
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• 2010

공정내의 가연성 혹은 독성가스를 연소시켜 안전한 물질로 전환시키는 것을 목적으로 플레어시스템이 설치되어 있다. 플레어시스템은 공정의 안전성 향상을 위하여 폐가스의 안전한 연소가 가장 중요한 요소이다. 연소의 복사열이 공정의 위험요인이 되지 않도록 API 521 Code에 규정되어 있다. 플레어스택에서 발생하는 화염의 형상은 방출되는 가스의 압력과 질량유속에 의하여 jet fire의 형상을 하고 있으며, 이를 API 521 Code 방식이 아닌 Chamberlain Model을 이용하여 화염의 형상을 확인하고, 이로 인한 복사열을 분석하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1476-1481
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• 2007

Numerical investigation on radiation characteristics of discrete frequency noise from asymmetry aero-intakes was carried out. The near-field predictions were obtained by solving the linearized Euler equations with computational aeroacoustic techniques consisting of high order finite difference scheme, non-reflecting boundary conditions, oversetgrid techniques. For the prediction of far-field directivity pattern, the Kirchhoff integral method was applied. By comparing the directivities of noise radiating from the scarf and the scoop aero-intakes with that from an axisymmetric aero-intake, it is shown that noise reduction at downward peak radiation angle can be achieved. The scattering of the radiating acoustic wave by background mean flow shifts the peak lobe radiation angle toward ground and increases the amplitude of the acoustic pressure compared with the cases without mean flow effect.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.561-562
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• 2008

The numerical analysis of sound radiation by vibrating structure is a well known and mature technology used in many industries. Accurate methods based on the boundary or finite element method have been successfully developed over the last two decades and are now available in standard CAE tools. These methods are however known to require significant computational resources which, furthermore, very quickly increase with the frequency of interest. The low speed of most current methods is a main obstacle for a systematic use of acoustic CAE in industrial design processes. In this paper we are going to present a set of innovative techniques that significantly speed-up the calculation of acoustic radiation indicators (acoustic pressure, velocity, intensity and power; contribution vectors). The modeling is based on the well known combination of finite elements and infinite elements but also combines the following ingredients to obtain a very high performance: o a multi-frontal massively parallel sparse direct solver; o a multi-frequency solver based on the Krylov method; o the use of pellicular acoustic modes as a vector basis for representing acoustic excitations; o the numerical evaluation of Green functions related to the specific geometry of the problem under investigation. All these ingredients are embedded in the ACTRAN/AR CAE tool which provides unprecedented performance for acoustic radiation analysis. The method will be demonstrated on several applications taken from various industries.

• 한국습지학회지
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• 제10권1호
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• pp.21-30
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• 2008

증발산은 지표와 대기 사이에서 일어나는 에너지 상호작용에 기여하는 중요한 요소 중 하나이다. 갈대로 덮인 고흥만 간척지에서 현열, 토양열 그리고 순복사를 측정하여 증발산량을 조사하였다. 자동기상관측 자료로부터 산출된 증발산량은 구름과 바람의 연직경도가 $1s^{-1}$보다 미약한 경우를 제외하고 열수지 방정식으로 추정한 값과 잘 일치하였다. 토양열은 순복사의 약 10%로 평가되었다. 갈대로 구성된 식생캐노피 내에서 온도에 따른 포화수증기압의 변화율($${\Delta}{\sim_=}de_s/dT$$)이 약 1.5로 근사되었고, 증발산량은 순복사 에너지의 함수로 설명될 수 있다.

• 한국소음진동공학회논문집
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• 제18권4호
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• pp.439-447
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• 2008

One of the key elements in efforts to minimize noise radiation from a powertrain is the knowledge of the main radiating component and the relation between the surface vibration of a powertrain and the sound pressure. In this research, the powertrain model is developed based on FEM(finite element method). This model is applied to the prediction of the vibration of a powertrain by using ADAMS and the radiation noise by using BEM(boundary element method). According to this numerical analysis, the surface vibration of a powertrain is investigated as a source of radiated noise. This surface vibration is caused by the 1st order natural vibration of the cylinder block and its mode shape is the torsion mode. Therefore, this mode shape is modified to reduce the surface vibration of the powertrain. The radiation noise of the modified powertrain is also reduced to $5{\sim}12\;dB$. This modification is very successful for the noise reduction based on the CAE technology.