• Korean Journal of Food Science and Technology
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• v.22 no.1
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• pp.1-6
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• 1990

The thermal diffusivity of defatted and nondefatted starches were measured on the basis of one dimensional semi-infinitive theory. Differential scanning calorymetry was used to study the effects of cooling rate, fat and water contents on the enthalpy and entropy changes with the cooling rate of $-2.5{\sim}10^{\circ}C/min$. Thermal diffusivity of defatted and nondefatted straches were determined to be $4.14{\times}10^{-4}{\sim}4.96{\times}10^{-4}(m^2/h),\;4.09{\times}10^{-4}{\sim}4.81{\times}10^{-4}(m^2/h)$ in unfrozen state, and $2.78{\times}10^{-3}{\sim}3.91{\times}10^{-3}(m^2/h),\;2.26{\times}10^{-3}{\sim}3.57{\times}1-^{-3}(m^2/h)$ in frozen state respectively. On decreasing temperatures in frozen state, thermal diffusivities of starches were increased and entropy and enthalpy were decreased, and more rapid cooling rates resulted in a decrease in entropy. A linear relation was observed between enthropy, enthaly and water content. Thermal diffusivity was decreased, and entropy was increasing fat content. With water content ranging from 35 to 90%, enthalpy and entropy of straches were found to be $107{\sim}216 (kcal /moi),\;0.45{\sim}0.94(kcal/mol.\;K)$, respectively.

• Journal of the Korean Chemical Society
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• v.50 no.1
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• pp.14-22
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• 2006

the basic model of chemical reactor using glow discharge, we used cathode discharge cell with vacant cavity in the middle. Currently glow discharge is widely studied as a radiation source or atomization device in atomic spectroscopy and remarkable technological achievements are made through the graft with other analysis devices such as microanalysis and steel analysis.1 Additionally, as the characteristics of basic glow discharge and radiation have been reviewed many times, those results could be used in this experiment.2-3 In 1993, an article regarding the treatment of poisonous gas in the air using low temperature plasma was published. According to this article, if DC Glow Discharge is used under continuous atmospheric flow, poisonous gases such as SO2 and NO can be removed.4 Based on those findings, we designed highly efficient reactor where stable air plasma is composed and all air flow pass the negative glow area passing through the tube. It was observed that the cathode tube type glow discharge developed in this study would be economical, easy to use and could be used as radiation source as well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.306-306
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• 2008

기계적 에너지를 전기적 에너지로 변환하는 에너지 변환소자인 압전 세라믹스는 액추에이터, 변압기, 초음파모터, 초음파 소자 및 각종 센서로 응용되고 있으며, 그 응용분야는 크게 증가하고 있다. 최근에는 이러한 압전 소자를 앞으로 도래하는 ubiquitous, 무선 모바일 시대의 휴대용 전자제품, robotics, MEMS 분야 등의 대체 에너지원으로 응용하기 위한 연구가 진행되고 있다. 특히 인간의 걷기 운동 등과 같은 일상적인 동작으로 필요한 전력을 얻을 수 있고, 세라믹 소자를 이용하기 때문에 전자노이즈가 발생되지 않을 뿐 아니라 반영구적으로 사용할 수 가 있어서, 기존 이차전지를 대체 또는 보완 할 수 있는 방안도 검토되고 있다. PZT계 세라믹스는 높은 유전상수와 우수한 압전특성으로 전자세라믹스 분야에서 가장 널리 사용되어지고 있지만 $1200^{\circ}C$ 이상의 높은 소결온도 때문에 $1000^{\circ}C$ 부근에서 급격히 휘발되는 PbO로 인한 환경오염과 기본조성의 변화로 인한 압전 특성의 저하가 문제시 되고 있다. 또한 적층 세라믹스의 제작 시 구조적 특성상 내부전극이 도포된 상태에서 동시 소결이 필요한데, 융점이 낮은 Ag전극 대신 값비싼 Pd나 Pt가 다량 함유된 Ag/Pd, Ag/Pt 전극이 사용되고 있어 경제성이 떨어지는 단점을 갖게 된다. 순수 Ag 전극을 사용하거나 Ag의 비율이 높은 내부전극을 사용하기 위해서는 $900^{\circ}C$ 이하에서 소결되고 우수한 전기적 특성을 보이는 압전 세라믹스를 개발 하는 것이 필요하다. 따라서 본 연구에서는 압전특성이 우수한 $(Pb_{1-x}Cd_x)(Ni_{1/3}/Nb_{2/3})_{0.25}(Zr_{0.35}/Ti_{0.4})O_3$ 계의 조성을 설계하고, 소걸온도를 낮추기 위해서 2 단계 하소법을 이용하였다. 또한 $MnCO_3$, $SiO_2$, $Pb_3O_4$ 등을 소량 첨가하여 액상 소결 특성을 부여하여 소결 온도를 감소시키려는 시도도 하였다. 분말을 볼 밀링 (ball milling)을 통해 24시간 동안 혼합하고, 혼합된 분말은 $800^{\circ}C$에서 2시간 동안 하소하였다. 하소한 분말을 다시 72시간 동안 볼 밀링 하여 최종 분말을 얻었다. 최종 분말에 PVB를 첨가하여 직경 15mm의 디스크 형태로 성형한 후, 850~$975^{\circ}C$ 범위에서 온도를 변화시키면서 소결을 하였다. 최종 분말 및 소결된 시편을 XRD분석을 통하여 상을 확인하였고, SEM을 이용하여 미세조직을 관찰 하였다. 전기적 특성을 평가하기 위하여 두께를 1mm로 연마한 시편에 Ag 전극을 도포하여 $650^{\circ}C$에서 열처리한 후, 분극처리 하였다. 압전특성은 $d_{33}$-meter로 측정하였고, impedance analyzer를 이용하여 압전 특성 (전기기계결합계수 및 기계적품질계수)을 측정 하였다. 또한 강유전체 특성 평가 장치 (Precision-LC)를 이용하여 분극-전계 특성을 평가하였다. 이상의 연구를 통하여 소결 온도가 $900^{\circ}C$인 경우에서도 양호한 압전 특성을 확보 할 수 있었다.

• Journal of the Korea Society of Computer and Information
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• v.17 no.6
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• pp.1-11
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• 2012

As the process technology scales down, multi-core processors cause serious problems such as increased interconnection delay, high power consumption and thermal problems. To solve the problems in 2D multi-core processors, researchers have focused on the 3D multi-core processor architecture. Compared to the 2D multi-core processor, the 3D multi-core processor decreases interconnection delay by reducing wire length significantly, since each core on different layers is connected using vertical through-silicon via(TSV). However, the power density in the 3D multi-core processor is increased dramatically compared to that in the 2D multi-core processor, because multiple cores are stacked vertically. Unfortunately, increased power density causes thermal problems, resulting in high cooling cost, negative impact on the reliability. Therefore, temperature should be considered together with performance in designing 3D multi-core processors. In this work, we analyze the temperature of the cache in quad-core processors varying cache organization. Then, we propose the low-temperature cache organization to overcome the thermal problems. Our evaluation shows that peak temperature of the instruction cache is lower than threshold. The peak temperature of the data cache is higher than threshold when the cache is composed of many ways. According to the results, our proposed cache organization not only efficiently reduces the peak temperature but also reduces the performance degradation for 3D quad-core processors.

• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.135-143
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• 2017

The domestic unique research reactor, HANARO (Hi-flux Advanced Neutron Application ReactOr), has been constructed with the open-pool, the core is submerged in, for the multi-purpose neutron application. The reactor has a primary cooling system to remove the fission heat from the core and its connected fluidic systems. Since the works are required at the reactor pool top as a characteristic of the research reactor, the radiation shall be minimized with the operation of the hot water layer system to avoid unnecessary radiation exposure on the workers during work at the pool top. Moreover, the pool water management system is connected to the reactor pool to maintain the pool temperature below $50^{\circ}C$ to minimize the uprising radioactive gas or impurity from the colder pool bottom. For the efficient flow rate of the PWMS, the thermal capacity of heat exchanger is selected with 260 kW in the normal operation condition. In this paper, the modeling is formulated to figure out whether or not each pool temperature maintains below the temperature limit and the calculation results show that the designed PWMS heat exchanger has enough capacity with the design margin regardless of the reactor operation mode.

• Resources Recycling
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• v.19 no.6
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• pp.36-42
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• 2010

Researches on resources recycling in the field of construction have made an extensive progress such as recycled aggregate of waste concrete and recycling of asphalt. On the other hand, there are almost never researches on pavement method with used waste frying oil. In South Korea, 0.2 million ton used waste frying oil is discharged every year. It is guessed that about 0.1 million ton used waste frying oil can be collected. If used waste frying oil is recycled, it is expected that disuse cost will be reduced and water pollution of rivers will be prevented. Therefore, the purpose of the study was to evaluate on mechanical features (strength, water resistance, chemical resistance, abrasion resistance, freezing and thawing resistance and permeable coefficient) whether dense graded permeable concrete mixing silica sand with flexible alkyd resin manufactured by making ester reaction with collected used waste frying oil to make alkyd resin could be applied to road pavement for non-roadway. The results of the study were as follows. In flexural strength, it had 1.6 times as much as road design standard 4.5MPa. In water resistance, chemistry resistance and freezing and thawing resistance, they had lack of strength in early age. As age went by, they didn't have large changes. And curing temperature had phenomenon of increase in strength at rather low temperature than high temperature by glass transition temperature of resin. Therefore, considering workability, strength and durability when it was applied to road pavement, it was reasonable that the mixing ratio of flexible alkyd resin was 10~15% in comparison with silica sand weight.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.295-295
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• 2007

기계적 에너지를 전기적 에너지로 변화하는 에너지 변환소자인 압전 세라믹스는 액츄에이터, 변압기, 초음파모터, 초음파 소자 및 각종 센서로 응용되고 있으며, 그 응용분야는 크게 증가하고 있다. 최근 이러한 에너지 변화 소자는 앞으로 도래하는 ubiquitous, 무선 모바일 시대의 휴대용 전자제품, robotics, 항공우주, 자동차, 의료, 건축, MEMS 분야 등의 대체 에너지원으로 응용하기 위한 연구가 진행되고 있다. 특히 인간의 동작 등과 같은 일상적인 동작으로 필요한 전력을 얻을 수 있고, 세라믹 소자를 이용하기 때문에 전자노이즈가 발생되지 않을 뿐 아니라 반영구적으로 사용할 수가 있어서, 기존 이차전지, 연료전지를 대체 또는 보완 할 수 있는 방안도 검토되고 있다. PZT계 세라믹스는 높은 유전상수와 압전특성으로 전자세라믹스분야에서 가장 널리 사용되어지고 있지만 $1200^{\circ}C$이상의 높은 소결온도 때문에 $1000^{\circ}C$ 부근에서 급격히 휘발되는 PbO로 인한 환경오염과 기본조성의 변화로 인한 압전 특성의 저하가 문제시되고 있다. 또한, 적층 세라믹스의 제작 시 구조적 특성상 내부 전극이 도포된 상태에서 동시 소결이 필요한데, 융점이 낮은 Ag전극 대신 값비싼 Pd나 Pt가 다량 함유된 Ag/Pd, Ag/Pt 전극이 사용되고 있어 경제적인 문제가 발생하게 된다. 따라서 순수 Ag 전극을 사용하거나, Ag의 비율이 높은 내부 전극을 사용하기 위해서는 $950^{\circ}C$ 이하에서 소결되는 압전 세라믹스를 개발 하는 것이 필요하다. 따라서 본 연구에서는 압전특성이 우수한 $(Pb_{1-x}Cd_x)\;[(Ni_{1/3}/Nb_{2/3})_{0.25}Zr_{0.35}Ti_{0.4}]O_3$계의 조성을 설계하여, 소결온도를 낮추기 위해서 2단계 하소법을 이용하였다. 분말을 ball milling을 통해 24시간 동안 혼합하였다. 혼합된 분말은 $800^{\circ}C$에서 2시간 동안 하소하였다. 하소한 분말을 72시간 동안 ball milling 하여 최종 분말을 얻었다. 최종 분말에 PVB를 첨가하여 ${\Phi}21$ disk 형태로 성형한 후, $800{\sim}950^{\circ}C$ 소결을 하였다. 최종 분말 및 소결된 시편을 XRD분석을 통하여 상을 확인하였고, SEM을 이용하여 미세조직을 관찰하였다. 전기적 특성을 확인하기 위하여 두께 1mm로 연마한 시편에 Ag 전극을 도포하여 열처리한 후, 분극 처리하였다. 압전특성은 $d_{33}$ 미터로 측정하였고, impedance analyzer를 이용하여 주파수 및 impedance 특성을 측정하였다. 그 결과 $900^{\circ}C$에서 우수한 압전 특성 및 전기적 특성을 확보 할 수 있었다.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.89-94
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• 2008

Purpose: To observe the high temperature creep test and the fracture surface of the samples of 9% Ni alloy steel generally used for all kinds of mahine parts and predict the durability of that by determining a constant of C with a Larson-Miller variable. Methods: The equipment of this test was made into lever-beam style designed by Andrade and F. Garofalo et al.. The condition of creep test was set under 16 kinds of conditions after fixing 4 kinds of temperature condition and 4 kinds of stress condition to check how it effects the samples. Results: The temperature of creep test was increased, the stress index (n) of creep deformation was gradually decreased from 3.97 to 3.55. The activation energy of creep deformation was decreased from 90.39 to 83.64 kcal/mol when the stress was increased. A constant of C value by calculation of larson-Miller variable was about 22 and if temperature for use is suggested, the durability could be calculated. Conclusions: By analyzing the fracture phenomenon and suggesting the observation result of the fracture surface of the samples and creep test of 9% Ni alloy steel, the basic design data for the practical use of accessories in the field of equipment could be constructed and used to predict the durability of the equipment.

• Food Engineering Progress
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• v.13 no.4
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• pp.308-313
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• 2009

This study was conducted to design and fabricate a heat pump that can produce some weather conditions similar to those of the dry season of the rough rice in Korea, and to investigate basic performances of the apparatus. During the drying test, the amount of energy consumption and drying characteristics were measured at four different temperature levels ranging between 20$^{\circ}C$ and 50${^{\circ}C}$. In the psychrometric chart, the freezing capacity and refrigerant circulation ratio of the heat pump were 173 kJ/kg and 49.6 kg/hr, respectively. Therefore, coefficient of performance was 5.5, which was superior to that of refrigerant R-22 (4.0) in standard refrigeration cycle. In addition, the time to reach target drying temperature (30${^{\circ}C}$) and relative humidity (40%) were 6 minutes and 7 minutes, respectively. Temperature differences between the drying temperature and the rice were 1.5${^{\circ}C}$ and 8.5${^{\circ}C}$ at the drying temperatures of 21.9${^{\circ}C}$ and 48.7${^{\circ}C}$, respectively. This result demonstrated that the increased temperature of the rice in the drying section decreased sufficiently in the tempering section. At the drying temperatures of 21.9, 30.7 38.8, and 48.7${^{\circ}C}$, drying rates were 0.29, 0.61, 0.85, and 1.26%/hr, respectively, which were similar to those of commercial dryer. In addition, the amounts of energy consumption were 325, 667, 692, and 776 kJ/kg, respectively. These results showed that this dryer saved up to 86% of energy consumption compared with the commercial dryer, which uses 4,000-5,000 kJ/kg of fossil fuel.

• Journal of the Korean Society of Radiology
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• v.12 no.6
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• pp.713-718
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• 2018

In many previous studies, monte carlo simulation is used to produce lead-free shielding sheet, and the possibility of radiation shielding capability and weight reduction is presented. But it is difficult to simulation for binder and micro-pores because of In fact it does not provide sufficient information necessary for the commercialization process. Therefore, in this paper, the results of radiation shielding capability corresponding to filling factor was presented by using the screen printing method to provide information on gel-paste required for the commercialization process. In this study, the geometric setup for evaluate of radiation shielding ability was designed to comply with IEC 61331-1:2014 and KS A 4025. In addition, radiation irradiation conditions were 100 kVp filtered with 2.0 mmAl total filtration was applied according to KS A 4021 standard. In this study, Pb $1270{\mu}m$, $BaSO_4$ $3035{\mu}m$, $Bi_2O_3$ $1849{\mu}m$ and $WO_3$ $2631{\mu}m$ were analyzed based on ten value layer. Additionally, the filling factor was analyzed as $BaSO_4$ 38.6%, $Bi_2O_3$ 27.1%, $WO_3$ 30.15%. However, in the case of applying low-temperature high-pressure molding in the future, it is expected that the radiation shielding capability can be sufficiently improved by reducing the porosity while increasing the filling factor.