• 한국수소및신에너지학회논문집
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• 제24권1호
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• pp.44-49
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• 2013

Hydrogen penetration into a metal leads to damages and mechanical degradations and its content measurement is of importance. For a precise measurement, a sample preparation procedure must be optimized through a series of studies on sample washing and drying. In this study, two-step washing with organic solvents and thermal soaking in inert gas were tried with a rod-shaped, API X65 steel sample. The samples were machined from a steel plate and then washed in acetone and etyl-alcohol for 5 minute each and dried with compressed air. After then, the samples were thermally soaked in a home-made nitrogen gas chamber during 10 minute at different heat gun temperatures from 100 to $400^{\circ}C$ and corresponding temperature range in the soaking chamber was from 77 to $266^{\circ}C$ according to the temperature calibration. Hydrogen residue in the samples was measured with a hot extraction system after each soaking step; hydrogen residue of $0.70{\pm}0.12$ wppm after the thermal soaking at $77^{\circ}C$ decayed with increase of the soaking temperature. By adopting the heat transfer model, decay behavior of the hydrogen residue was fitted into an exponential decay function of the soaking temperature. Saturated value or lower bound of the hydrogen residue was 0.36 wppm and chamber temperature required to lower the hydrogen residue about 95% of the lower bound was $360^{\circ}C$. Furthermore, a thermal desorption spectroscopy was done for the fully soaked samples at $360^{\circ}C$. Weak hydrogen peak was observed for whole temperature range and it means that hydrogen-related contaminants of the sample surface are steadily removed by heating. In addition, a broad peak found around $400^{\circ}C$ means that parts of the hydrogen residue are irreversibly trapped in the steel microstructure.

• 한국세라믹학회지
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• 제37권5호
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• pp.425-431
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• 2000

Cobalt ferrite thin films on Corming glass substrate were fabricated by a sol-gel method. Cobalt ferrite thin films with the grain size of 20-35 nm and thickness of 50nm were obtained. Rapid thermal annealing (RTA) and Annealing processes were adopted for comparison of characteristics of the films. Coercivity values were changed with thermal condition and magnetization values were increased as a function of soaking time. With prolonged soaking time, however, it was decreased because of the diffusion of cations from the glass substrate. The RTA process in preparation of cobalt ferrite thin film was the effective way to prevent and to form a single spinel phase in reduced soaking time. The film heated at 600$^{\circ}C$ for 30 minutes by RTA had coercivity of 2,600 Oe, saturation magnetization 460 emu/㎤, and Mr$.$$\delta$ of 1.43 memu/$\textrm{cm}^2$.

• Korean Chemical Engineering Research
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• 제45권3호
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• pp.304-309
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• 2007

본 연구에서는 감압법 및 열자극법에 의한 메탄하이드레이트 생산실험을 수행하기 위해 고압의 다중공 평판형 셀기기를 설계 제작하였다. 이 실험장비를 이용하여 고투과성 미고결 시료 공극시스템에서 감압법과 열자극법에 의한 생산실험을 수행하여 생산메카니즘을 분석하였다. 감압법에 의한 생산실험 결과, 일반 가스전과는 달리 하이드레이트 해리에 의한 공극내에서의 소스효과로 인해 일시적으로 압력이 상승하고 또한 흡열반응으로 인해 온도가 하강함을 확인 하였으며, 열자극 생산실험을 수행한 결과에서는 감압법의 경우 열자극법에 비해 해리속도가 느리게 진행되어 가스생산이 낮은 상태로 지속되는 것으로 나타났다. 한편, 열자극법 중 열을 가한 후 곧바로 생산하는 경우, 주입지점 주변에서만 해리되고 또한 그 지역에서만 투과도가 커지는 것으로 나타났으며, 생산초반 이후 해리속도는 soaking까지 시행한 경우에 비해 해리가 느리게 진행됨을 알 수 있다. 한편, 본 연구의 낮은 하이드레이트 포화도를 갖는 미고 결시료 공극시스템에서 열자극법의 적정 soaking 시간 규명실험을 통해 압력과 생산거동을 고찰하였다. 그 결과, 6분간 soaking 한 경우, 온도 하강에 의한 하이드레이트의 재형성으로 2분 및 4분간 soaking한 경우보다 낮은 회수율을 보였다. 본 연구의 실험결과는 향후 높은 하이드레이트 포화도를 갖는 고결 시료 공극시스템에서의 실험을 통해 더욱 확연히 드러날 것으로 예상된다.

• 한국세라믹학회지
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• 제20권4호
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• pp.347-355
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• 1983

A batch mixture was prepared as 16mol% CaO-84mol% $ZrO_2$ of regeant-grade powder. The monoclinic Zirconia powder had an average particle size of $9.24 \mu\textrm{m}$ and calcium carbonate powder had a reported purity of 99.7 weight percent and mean particle size of TEX>$24, 37<\mu\textrm{m}$. The specimens were fired at 1400, 1500, 1650 and $1750^{\circ}C$ for 0. 3, 5 and 7 hours respectively. After fired the specimens were investigated using Scaning electron microscopy. Density Porosity Compressive strength Modulus of rupture and Thermal expansion were measured X-ray diffration analysis was also carried out. The results are as follows ; 1) As the firing temperature or soaking time was increased firing linear shrinkage apparent density compressive strength and modulus of rupture increased but apparent porosity decreased, 2) Cubic and monoclinic Zirconia was found at $1400^{\circ}C$ and cubic Ziconia found above $1500^{\circ}C$ 3) The specimens fired at 140$0^{\circ}C$ without soaking display thermal expansion curves by monoclinic〓tetragonal transformation and no tranformation was found at $1400^{\circ}C$ for 5hrs and above $1500^{\circ}C$. 4) The lattice parameter had constant value of 5.1345 $\AA$ through all the ranges of firing temperature 5) The higher the firing temperature was or the longer the soaking time was the larger the grain size was.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.397-400
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• 2008

A numerical analysis has been performed in this study to predict thermal behaviors of combined weapon systems in a large environmental tester. Also, temperature distributions of the materials of the system have been measured for the experimental conditions. The calculated thermal flow characteristics and the measured temperature distributions of the materials for the weapon systems have been analyzed to prepare for field tests in the environmental tester. The boundary conditions of the analysis are composed of inlet and outlet conditions of the environmental tester with various pressures and the limit of low temperature of -25$^{\circ}$C. The soaking time of the system in the environmental tester has been obtained by developed programs in this study to carry out the experiment in the predicted conditions.

• 한국식품영양학회지
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• 제31권5호
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• pp.737-750
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• 2018

Effects of acid soaking (AS) and thermal sterilization (TS) on the shape and quality characteristics of Tteokbokki rice cake (TRC) were investigated. The F-value of a sequential process (SP) of the combination of AS and TS was quantitatively determined with a reference microorganism of Bacillus cereus. F-values were evaluated according to the minimum and the maximum D-value of B. cereus and the reduction exponent (m=12). The heat penetration curves at cold point (CP) of TRC (400 g) were used to estimate the TS time at 121, 100, and $95^{\circ}C$. F-values of the SP were revised according to the adjusted m values after AS at different pH. The non-uniformity parameters (NUP) of TRC had no significant changes during AS but it dramatically increased after applying TS at a low pH by AS. The result of solubilized starch contents (SSC) demonstrated that the shape changes during SP are related to SSC. The texture characteristics and the whiteness were significantly influenced by a low pH condition (3.5) (p<0.05). Sensory analysis showed that a lower pH and a longer thermal processing time influenced negatively on the acceptability. This study showed that pH 4.0 and $95^{\circ}C$ was an optimum condition for the SP.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.115-123
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• 2010

Cool-down performance after soaking is important because it affects passenger's thermal comfort. The cooling capacity of HVAC system determines initial cool down performance in most cases, the performance is also affected by location, and shape of panel vent, indoor seat arrangement. Therefore, optimal indoor designs are required in developing a new car. In this paper, initial cool down performance is predicted by CFD(computational fluid dynamics) analysis. Experimental time-averaging temperature data are used as inlet boundary condition. For more reliable analysis, real vehicle model and human FE model are used in grid generation procedure. Thermal and aerodynamic characteristics on re-circulation cool vent mode are investigated using CFX 12.0. Thermal comfort represented by PMV(predicted mean vote) is evaluated using acquired numerical data. Temperature and velocity fields show that flow in passenger's compartment after soaking is considerably unstable at the view point of thermodynamics. Volume-averaged temperature is decreased exponentially during overall cool down process. However, temperature monitored at different 16 spots in CFX-Solver shows local variation in head, chest, knee, foot. The cooling speed at the head and chest nearby panel vent are relatively faster than at the knee and foot. Horizontal temperature contour shows asymmetric distribution because of the location of exhaust vent. By evaluating the passenger's thermal comfort, slowest cooling region is found at the driver's seat.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3144-3149
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• 2007

A numerical analysis for temperature distribution of four different materials such as iron, silicon, aluminum and PVC has been performed in this study to predict thermal behaviors of combined weapon systems in a large environmental tester. Thus, experimental conditions have been proposed using a calculating software (SolidWorks 2007 COSMOS FloWorks) to prepare for field tests and analyze heat flow inside the environmental tester and temperature distributions of materials. The boundary conditions of the analysis are composed of inlet and outlet conditions of the environmental tester with different pressures and the limit of low temperature of -30$^{\circ}C$. The soaking time of the system in the environmental tester has been calculated by this commercial program in this study to carry out the experiment.

• KIEAE Journal
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• 제17권3호
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• pp.107-112
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• 2017

Purpose: Both silica gel and activated carbon black particles were adopted for use as PCM absorbed porous media applicable as construction materials. To investigate usable methods for absorbing PCM into the media, they were soaked into PCM and also tested for enhancement of PCM absorption into them. Method: To test PCM absorption into some porous media such as both ${\varphi}1{\sim}2mm$ and $10{\mu}m$ silica gels, and $50{\mu}m$ activated carbon black, $43^{\circ}C$ PCM was used as a laten heat material. The method, soaking into PCM was applied to this study, and the media were moderately rotated by centrifuge to have the extra PCM flow out. DSC analysis was conducted to investigate the melting and solidifying of the PCM absorbed into the porous media. Result: It was found that PCM was absorbed into the porous media by over 85 wt% of all particles. In addition, it was noted that the ultrasonic vibrator was accelerating the PCM absorption into the particles to three times higher speed than simple soaking. Centrifuge was adopted to remove extra PCM sticking on the particle surfaces and extra PCM was moderately removed from the surfaces of the particles. DSC analysis indicated that the latent heat of the absorbed PCM particles was 160 J/g, and the melting temperature was approximately $40^{\circ}C{\sim}50^{\circ}C$.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.24-28
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• 2002

Composite reinforced fiber materials are used in lots of fields such as a part of aeronautic space, ship, machinery and so on because can make structure wished for necessary condition by control fiber direction and laminated sequence. As the use of advanced composites increase, specific techniques have been developed to repair changed composite structures. In order to repair the damaged part production high quality composite reinforced fiber are completed by control the surrounding temperature and press in autoclave. The quality is influenced heat exposure degree by chemical reaction for precessing. This study considerated influence limit of using by repair structure part and change of properties according to heat exposure degree for repairing.