• 열처리공학회지
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• 제11권1호
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• pp.46-53
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• 1998

The variation of the mechanical properties, microstructures and the formation of retained austenite with heat treatment conditions in austempered ductile cast iron has been investigated. In the case of austempered ductile cast iron below 25mm diameter, it has been found that a pearlite structure are not obtained under a super cooled condition at range of $0.05^{\circ}C/sec{\sim}10^{\circ}C/sec$, and the matrix is precipitated in graphite, bainite and retained austenite. After austempering treatment the retained austenite is increased with decreasing cooling rate. The elongation increases with decreasing super cooling rate, and the optimum result has been shown to be the elongation of 15.6% at super cooling rate of $0.05^{\circ}C/sec$. The optimum result has been shown to be the tensile strength-elongation balance of $1656kgf/mm^2.%$ and it is more than doubled to as the casting state and continuous cooling condition.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.110-113
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• 2004

ZnO varistor ceramics which were fabricated with variation of added of $0.5{\sim}1.0mol%\;Co_3O_4$ sintered at $1150^{\circ}C$. In the specimen added $0.7mol%\;Co_3O_4$, sintered density was $6.03g/cm^3$ and electrical peoperties were superior to any other components. The nonlinear coefficient a was 83, and clamping voltage ratio was 1.35. But, endurence surge current in the specimen added $0.5mol%\;Co_3O_4$ was $7000A/cm^2$, and deviation of varistor voltage was ${\Delta}-3.23%$. As P.C.T and T.C.T environment test were succeed in all specimens, and deviation of varistor voltage in the specimen added $0.6mol%\;Co_3O_4$ was ${\Delta}-0.81%$. All specimens showed a good leakage current property in the High Temperature Continuous Load Test for 1000hr, at $85^{\circ}C$, and variation rate of the varistor voltage was ${\Delta}-2%$.

• 한국축산식품학회지
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• 제29권3호
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• pp.310-316
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• 2009

In this study, the influence of pressure assisted mild thermal inactivation (PAMTI) on E. coli ATCC 10536 was examined at 200 MPa and temperature range of $20-50^{\circ}C$. Inactivation rate significantly increased (p<0.05) as temperature and time increased at 200 MPa. The maximum inactivation (7.91 log reduction) was obtained at $50^{\circ}C$ for 30 min under 200 MPa, which meant the complete inactivation of E. coli ATCC 10536. Inactivation kinetics were evaluated with the first order inactivation rate (k), activation energy ($E_a$), thermal death time (TDT), and z value. Kinetic parameters were significantly (p<0.05) influenced by variation temperature of PAMTI. In this study, the synergistic effect of pressure and temperature were found in the inactivation of E. coli ATCC 10536 through PAMTI.

• 한국입자에어로졸학회지
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• 제8권4호
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• pp.173-180
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• 2012

SiC particles, 8.3 ${\mu}m$ in volume average diameter, were chlorinated in an alumina tubular reactor, 2.4 cm in diameter and 32 cm in length, with reactor temperature varied from 100 to $1200^{\circ}C$. The flow rate of the gas admitted to the reactor was held constant at 300 cc/min, the mole fraction of chlorine in the gas at 0.1 and the reaction time at 4 h. The chlorination was negligibly small up to the temperature of $500^{\circ}C$. Thereafter, the degree of chlorination increased remarkably with increasing temperature until $900^{\circ}C$. As the temperature was increased further from 900 to $1200^{\circ}C$, the increments in chlorination degree were rather small. At $1200^{\circ}C$, the chlorination has nearly been completed. The surface area of the residual carbon varied with chlorination temperature in a manner similar to that with the variation of chlorination degree with temperature. The surface area at $1200^{\circ}C$ was 912 $m^{2}/g$. A simple model was developed to predict the conversion of a SiC under various conditions. A Langmuir-Hinshelwood type rate law with two rate constants was employed in the model. Assuming that the two rate constants, $k_{1}$ and $k_{2}$, can be expressed as $A_{1e}^{-E_{1}/RT}$ and $A_{2e}^{-E_{2}/RT}$, the four parameters, $A_{1}$, $E_{1}$, $A_{2}$, and $E_{2}$ were determined to be 32.0 m/min, 103,071 J/mol, 2.24 $m^{3}/mol$ and 39,526 J/mol, respectively, through regression to best fit experimental data.

• 한국식품과학회지
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• 제12권1호
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• pp.18-23
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• 1980

회전 점도계를 사용하여 온도 $25{\sim}55^{\circ}C$에서 시판고추장의 유동학적 거동을 조사하고 다음의 결과를 얻었다. 1. 고추장은 전단 속도 $0.323{\sim}1.653\;sec^{-1}$에서 의가소성을 나타내며 항복치를 가지며 시간 의존성을 나타내는 thixotropic 식품이었다. 2. 전단 속도 0.978 $sec^{-1}$에서 유동 지수, 조밀도 지수, 항복치는 각각 0.597, 192.3 dyne $sec^s/cm^{2}$, 91 dyne/$cm^{2}$ 이었다. 3. 고추장의 시간 경과에 따른 겉보기 점도 변화는 초기 20분 동안에는 2차 반응 속도식에 따라 붕괴되었으나 그 이후는 시간에 거의 무관하였다. 4. 고추장의 온도 변화에 따른 겉보기 점도 변화는 Andrade 식에 따랐으며 이 식으로부터 구한 유동에 대한 활성화 에너지는 1.03 kcal/$g{\cdot}mole$이었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.322-327
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• 2007

Dedicated outdoor air-conditioning(DOA) system that utilizes pre-cooling and desiccant dehumidification can be superior to conventional cooling and reheating system with respect to energy consumption and indoor thermal comfort. In this work, simulation has been conducted to study various factors that affect the performance of DOA. Dynamic simulation shows the transient variation of temperature and humidity as the on/off control logic is imposed. Exit humidity of process air and flow rate are varied to study the effect on exit temperature of process air, dehumidification quantity, required regeneration temperature and exit humidity of regeneration air. For an outdoor air condition of $28.5^{\circ}C$ temperature, 16 g/kg humidity ratio and 2000 cmh flow rate, the dehumidification efficiency is increased by 4.6% as the flow rate is doubled.

• 생명과학회지
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• 제20권4호
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• pp.481-486
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• 2010

유럽마가목에서 핵 및 엽록체 유전자의 서열을 이용하여 동의 및 비동의치환율을 산출하였다. 유럽마가목 엽록체 유전자의 서열은 핵 유전자에 비해 평균적으로 움진화가 느리게 일어나고 있음을 나타내었으며 다른 쌍자엽식물과 유사하였다. 핵에서 동의치환율(Ks)은 2.45-2.60이었으며 비동의치환율(Ka=1.15-1.30)보다 약 2배 정도 높았다. 엽록체에서 Ks는 1.20-1.26이었으며 엽록체에서 Ka (0.26-0.42) 보다 약 6배 높았다. 유럽마가목에서 핵 및 엽록체 Ka/Ks은 각각 0.178과 0.056이었다. 이 Ka/Ks의 비율이 1보다 작다는 것은 음의 도태에 있다는 것을 나타낸다. 엽록체 유전자는 유효유전자코돈(ENC)이 22.4-32.2로 핵의 값(35.8-38.7)에 비해 낮았다. G+C 함량 분석에서 엽록체 유전자는 동의코돈 A와 T에 대해 높은 선호성(G+C 함량은 28.4-29.1%에 불과)을 나타낸 반면 핵에서는 G와 C가 더 선호성을 나타내었다(G+C 함량은 63.2-64.2%).

• 한국전기전자재료학회논문지
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• 제13권9호
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• pp.735-744
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• 2000

The electrical procerties and stability of ZnO-Pr$_{6}$O$_{11}$-CoO-Cr$_2$O$_3$-Er$_2$O$_3$ (ZPCCE) based varistors were investigated in the Er$_2$O$_3$content range of 0.0 to 4.0 mol%. ZPCCE ceramics containing 2.0 mol% Er$_2$O$_3$ exhibited the highest density of 5.74 g/㎤ corresponding to 99.3% of theoretical density. The varistors with 0.5 mol% and 2.0 mol% Er$_2$O$_3$exhibited a relatively satisfying nonlinearity, which the nonlinear exponent is 40.50 and 47.15, respectively and the leakage current is 2.66 $mutextrm{A}$, respectively. Under more severe d.c. stress, such as (0.80 V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85 V$_{1mA}$115$^{\circ}C$/12h)+(0.90 V$_{1mA}$12$0^{\circ}C$/12h)+(0.95 V$_{1mA}$1$25^{\circ}C$12h), they showed a very excellent stability, which the variation rate of the variator voltage is -0.89% and -0.15%, the variation rate of the nonlinear coefficient is -4.67% and -3.56%, and the variation rate of leakage current is -6.02% and -19.56%, respectively. It is surely bellived that ZnO-0.5 mol% Pr$_{6}$O$_{11}$-1.0 mol% CoO-0.5 mol% Cr$_2$O$_3$-x mol% Er$_2$O$_3$(x=0.5, 2.0) based varistors will be greatly contributed to develop the advanced Pr$_{6}$O$_{11}$-based ZnO varistors in future.uture. future.uture.

• Carbon letters
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• 제10권3호
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• pp.181-189
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• 2009

Activated carbon spheres (ACS) were prepared at different heating rates by carbonization of the resole-type phenolic beads (PB) at $950^{\circ}C$ in $N_2$ atmosphere followed by activation of the resultant char at different temperatures for 5 h in $CO_2$ atmosphere. Influence of heating rate on porosity and temperature on carbon structure and porosity of ACS were investigated. Effect of heating rate and temperature on porosity of ACS was also studied from adsorption isotherms of nitrogen at 77 K using BET method. The results revealed that ACS have exhibited a BET surface area and pore volume greater than $2260\;m^2/g$ and $1.63\;cm^3/g$ respectively. The structural characteristics variation of ACS with different temperature was studied using Raman spectroscopy. The results exhibited that amount of disorganized carbon affects both the pore structure and adsorption properties of ACS. ACS were also evaluated for structural information using Fourier Transform Infrared (FTIR) Spectroscopy. ACS were evaluated for chemical composition using CHNS analysis. The ACS prepared different temperatures became more carbonaceous material compared to carbonized material. ACS have possessed well-developed pores structure which were verified by Scanning Electron Microscopy (SEM). SEM micrographs also exhibited that ACS have possessed well-developed micro- and meso-pores structure and the pore size of ACS increased with increasing activation temperature.

• Composites Research
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• 제19권4호
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• pp.1-6
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• 2006

PSF/AS4 복합재 적층구조의 가속노화가 피로강도에 미치는 영향을 변분이론을 이용한 에너지 발산율(energy release rate) 분석을 이용하여 연구하였다. 변분이론 분석은 수지미소균열에 대한 파괴역학을 해석하는데 사용되어 왔으며 이 논문에서는 피로하중 하에서 가속노화 시간에 따르는 파괴인성이 어떻게 변하는가를 설명하였다. 수정된 Paris 법칙에 의한 선도는 각 재료마다. 미소균열이 형성되는 특성을 나타낸다. PSF/AS4 $[0/902]_s$ 적층구조가 60일 동안 유리천이온도에 근거를 두고 세분한 4개의 각기 다른 온도로 가속노화를 하였다. 모든 온도에서 파괴인성은 가속노화 시간에 따라 감소하였다. 높은 온도에서의 파괴인성의 감소는 낮은 온도에서의 감소보다 빠르게 진전되었다. 가속노화가 피로강도에 미치는 영향을 파악하기 위해 유리 천이온도인 섭씨 180도에 가까운 170도에서 60일 동안 노화한 것과 노화하지 않은 것을 비교하였다. 노화된 시편에 대하여 파괴인성의 변화(${\Delta}G_m$)가 낮은 값에서 미소균열이 형성되는 것을 알 수 있었다.