• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.9-9
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• 2008

일반적으로 섬광법으로 열전도율을 구하기 위해서는 섬광법으로 열확산계수를 측정하고, 시차주사열량계(Differential Scanning Calorimetry, DSC)로 비열측정을 하며 아르키메데스의 원리를 이용한 용적밀도를 구하여 이들 각각의 값을 사용하여 열전도율을 얻는다. 따라서 열전도율을 정밀하게 측정하기 위해서는 이 세 가지 물성치를 측정할 때 수반되는 오차요인을 종합적으로 검토하여 개선하는 것이 매우 중요하다. 섬광법으로 열확산계수를 측정할 때 시료의 전면에 조사되는 빛의 흡수율을 향상시키고 배면에서의 온도상승의 감지를 증대할 목적으로 시료 양면에 흑연코팅을 하게 된다. 이때 코팅된 흑연이 시료에 부가적으로 열저항을 증가시켜서 열확산계수를 측정하는데 가장 큰 오차요인이 되고 있다. 한편 비열은 대부분 DSC로 측정하는데, 시료와 용기의 열접촉 정도에 따라 큰 오차요인이 되기도 한다. 본 연구에서는 열확산계수를 정밀하게 측정하기 위해서 시료에 부가적인 열저항으로 작용하는 흑연코팅의 두께와 시료배면에서의 온도상승곡선 간의 상관관계를 실험식으로 도출하였으며 이방법은 열확산계수를 정밀하게 측정하는데 매우 유효한 방법임이 입증되었다. 또한 DSC의 접촉에서의 문제점을 해결하기 위해서 시료배면에서의 무차원 시간축(t/$t_{max}$)을 도입하였으며. 무차원 시간축에 따른 온도상승 곡선에서 표준시료와 측정시료의 half time($t_{1/2}$)의 0.5 배와 1.5배 사이 구간을 적분한 뒤 비교하여 열량계산으로부터 비열을 구하는 방법을 새롭게 개발하였으며 기존의 DSC에 비하여 정밀도를 향상시킬 수 있었다. 결론적으로 새롭게 제안된 측정기법들은 열확산계수 및 비열 혹정 시의 근본적인 오차요인을 혁신적으로 해결함으로써 정밀하고 신뢰성 있는 열전도율을 측정할 수 있음을 입증할 수 있었다.

• Korean Journal of Food Science and Technology
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• v.35 no.2
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• pp.211-216
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• 2003

Absorption characteristics of hot air-. vacuum-, and freeze-dried ginger powder were investigated. Monolayer moisture content as determined by GAB equation was $0.257{\sim}0.540\;H_2O/g$, showing higher significance than BET equation. Absorption enthalpy was calculated based on different drying methods and water activities. Absorption energy decreased with increasing water activity but was not affected by drying method. Isotherm curves showed a typical sigmoid form. Among models applied for predicting equilibrium moisture content, Caurie model was the best fit model for ginger powder, showing the lowest prediction deviation of $1.2{\sim}5.4%$, followed by Henderson then Bradley models. The prediction model equations for the moisture content were established by in(time), water activity, and temperature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1B
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• pp.29-39
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• 2012

Climate change has been obtained researchers' interest, especially in water resources engineering to adjust current conditions to the new circumstance influenced by climate change. In this study, WRF-ARW will be evaluated the capability to estimate distributed precipitation using global weather information instead of the data from rainfall observatory or radar. Cheongmi watershed is selected and adopted to generate a distributed rainfall-runoff model using ModClark. The results from the distributed model with precipitation data from WRF-ARW and the lumped model using observed precipitation data were compared to the observed discharge values. The final results showed that the distributed model, ModClark generated similar pattern of hydrograph to the observations in terms of the time and amount of peak discharge. In addition, the trend of hydrograph from the distributed model presented similar pattern to the observations.

• Polymer(Korea)
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• v.27 no.2
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• pp.106-112
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• 2003

Poly(trimethylene terephthalate)(PTT) fibers were treated by passing on the plate heater to study the annealing effect on the change of morphological structure and physical properties. In the X-ray diffraction curves of PTT annealed, a sharp peak at 2$\theta$=15.6$^{\circ}$ appeared and the peak intensity became stronger with the increase of annealing temperature and time. This peak was based on the (010) plane of PTT crystals. The crystallinity determined by density measurement was also increased by annealing. With the increases of temperature and time, the dynamic viscoelastic behaviors were shown to be a large reduction in T(tan $\delta$$_{max}$). The birefringence and $T_g$ were also reduced, but the melting temperature was the same. These results mean that the molecular chains in armorphous region are transfered into the crystalline legion, making the remained chains relaxed during annealing at tensionless state.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.95-105
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• 2014

Reinforced concrete (RC) shield tunnel lining must be designed for fireproof performance because the lining is sometimes exposed to very high temperature due to traffic accidents. Both experimental and numerical studies are carried out to evaluate fire resistance performance of precast RC tunnel lining systems. In the experimental studies, six full-scale precast RC tunnel segments are exposed to fire in order to examine the influence of various parameters on the fire resistance performance of precast RC tunnel lining. We used the temperature curve of the RABT criteria, which are severe conditions of fire temperatures. The fire test showed that the explosive spalling was not observed by substituting concrete to PP fiber reinforced concrete. A transient heat flow analysis was carried out in consideration of the material properties that change with temperature, and the results showed good agreement with the test results.

• Food Science of Animal Resources
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• v.33 no.6
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• pp.772-780
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• 2013

The aim of this study was to investigate the effect of season and location on activities of enzyme produced by psychrotrophic bacteria isolated from raw milk located in Kyunggi region of South Korea. Agar diffusion and colorimetric methods were used for the lipase and protease activities of psychrotrophic bacteria. Intensities of dark blue and transparent ring around colony were compared for activity measurement. Nutrient agar with 1% skim milk added was employed for measuing protease activity. 14 strains of Arthrobacter russicus with lipase activity and 19 strains of Chryserobacterium shigense with protease activities were found to be present. It was found that Acinetobacter genomospecies 10 (match %: 99.90) isolated from B region in fall was the most lipolytic species, whereas Serratia liquefaciens (match %: 99.39) isolated from the same region in spring was the most proteolytic species. Growth curve of Acinetobacte and Serratia liquefaciens was a typical sigmoidal form. Lipase activity increased with incubation time, but its activity began to drop at stationary to motality phase. Optimum condition for incubation time, pH and temperature for extracellular lipase from Acinetobacter genomospecies 10 (match %: 99.90) was 12 h, 8.5, and $45^{\circ}C$, respectively. Extracellular protease from Serratia liquefaciens (match %:99.39) had the same optimum incubation time and pH as extracellular lipase, but optimum temperature was $35^{\circ}C$.

• Applied Biological Chemistry
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• v.32 no.4
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• pp.332-337
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• 1989

Rheological properties of rehydrated freeze dried instant rice were investigated in comparison with that of cooked rice. The time changes in reciprocal hardness of instant rice grains at various rehydration temperatures$(60{\sim}90^{\circ}C)$ could be expressed by the first order reaction rate equation regardless of rehydration temperature and reaction rate constant increased as the rehydration temperature increased. Activation energy for rehydrating instant rice was 6.1 kcal/g-mol. Analysis of compressive stress relaxation test showed that the viscoelastic properties of both rehydrated instant rice and cooked rice grains could be expressed by 6-elements generalized Maxwell model. Rehydrated instant rice revealed higher relaxation decay than that of cooked rice and showed the elastic property increased by increasing the rehydration temperature.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.42-42
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• 2003

두개의 다른 고상이 동시에 액상으로부터 응고되는 공정합금에 일방향응고를 적용함에 따라 응고방향으로 규칙적으로 잘 배열된 복합재료를 만들 수 있다. 이렇게 방향성을 가지고 응고된 공정조직은 여러 가지 기계적, 전기적, 자기적 특수분야에 이용될 수 있다. 그런데 공정조직의 상간격은 재료의 기계적, 물리적 성질과 밀접한 관계를 가지며 응고속도, 온도기울기와 같은 일방향응고의 변수에 따라 결정된다. 그래서 본 연구에서는 금속합금계와 유사한 섬유상 공정조직을 보이는 NaNO$_3$-NaCl계를 이용하여 공정조직의 미세구조와 일방향응고 변수와의 관계를 조사하였다. 또한 액상으로부터 시간에 따른 냉각곡선으로부터 공정온도와 공정조성부근의 부분상태도를 구하였다. 그리고 응고녹도(V)에 따른 섬유상간격(λ$_{E}$ )의 실험적 관계식을 두가지의 온도기울기에 대하여 구하여 금속재료의 결과식과 비교, 검토하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.5-8
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• 2006

수소 station에서 수소분리정제를 위한 compact형 PSA 공정 설계를 위하여 활성탄으로 충진된 dual bed의 흡착동특성을 연구하였다. 기존 PSA 공정의 흡착탑이 차지하는 시스템의 공간을 줄이기 위하여 하나의 흡착탑 안에 다른 흡착탑을 넣어 흡착탑이 차지하는 공간을 최소화하고, 흡착탑 간의 열교환을 효과적으로 할 수 있도록 고안하였다. 수소 혼합물에 대한 dual bed에서의 흡착, 탈착 실험 실시하였으며, 시간에 따른 농도와 온도의 변화를 측정하였다. 수소 혼합물로는 $H_2/CO/CH_4/CO_2$ (69:2:3:26vol.%)를 사용하였으며, 흡착유량은 7LPM, 흡착압력은 9atm 조건에서 운전하였다. Inner bed와 outer bed의 수소 농도 파과곡선의 형태에 있어 차이를 보였으며, 이는 각 탑에서 열교환 효과로 인한 내부 온도 차이에 기인하여 발생하였다.

• The korean journal of orthodontics
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• v.36 no.5
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• pp.349-359
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• 2006

Objective: Nickel-titanium alloy wire possesses excellent spring-back properties, shape memory and super-elasticity. In order to adapt this wire to clinical use, it is necessary to bend as well as to control its super-elastic force. The purpose of this study is to evaluate the effects of heat treatment on the load-deflection properties and transitional temperature range (TTR) of nickel-titanium wires. Methods: Nickel-titanium wires of different diameters ($0.016"\;{\times}\;0.022"$, $0.018"\;{\times}\;0.025"$ and $0.0215"\;{\times}\;0.028"$) were used. The samples were divided into 4 groups as follows: group 4, posterior segment of archwire (24 mm) without heat treatment; group 2, posterior segment of archwire (24 mm) with heat treatment only; group 3, anterior segment with bending and heat treatment; group 4, anterior segment with bending and 1 sec over heat treatment. Three point bending test was used to evaluate the change in load-deflection curve and obtained DSC (different scanning calorimetry) to check changes in $A_f$ temperature. Results: In the three point bending test, nickel-titanium wires with heat treatment only had higher load-deflection curve and loading and unloading plateau than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment had lower Af temperature than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment and bending had higher load-deflection curve than nickel- titanium wires with heat treatment and nickel-titanium wires without heat treatment. Nickel-titanium with heat treatment of over 1 sec and bending had the highest load-deflection curve. Nickel-titanium wires with heat treatment and bending had lower Af temperature, Nickel-titanium wires with heat treatment of over Af sec and bending had the lowest Af temperature. Conclusion: From the results of this study, it can be stated that heat treatment for bending of Nickel-titanium wires does not deprive the superelastic property but can cause increased force magnitude due to a higher load-deflection curve.