• 열처리공학회지
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• 제31권6호
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• pp.269-274
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• 2018

Grain-oriented electrical steel sheets are mainly used as core materials for transformers and motors. They should have excellent magnetic properties such as low core loss, high magnetic flux density and high permeability. In order to improve the magnetic properties of the electrical steel sheet, it is important to form Goss oriented grains with a very strong {110}<001> orientation. Recently, efforts have been made to develop Goss grains by controlling processes such as hot rolling, cold rolling, and primary and secondary recrystallization. In this study, the sheets containing 3.2 and 3.4wt.% Si were used, which were rolled with 1 and 10 passes with total thickness reduction of 89%. Heating was carried out for primary recrystallization with different heating rates of $25^{\circ}C/s$ and $24^{\circ}C/min$ until $720^{\circ}C$. The behavior of Goss-, {411}<148>-, and {111}<112>-oriented grains were analyzed using X-ray diffraction(XRD) and electron back-scatter diffraction(EBSD) analysis. The area fraction of Goss-oriented grains increased with the number of rolling passes during cold rolling; however, after the primary recrystallization, the area fraction of the Goss grains was higher and exact Goss grains were found in the specimens subjected to rapid heating after one rolling pass.

• 한국식생활문화학회지
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• 제16권2호
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• pp.109-117
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• 2001

Judging from the studies carried out by Dr. Jo, Yong Jin on the Koreans' faces, Koreans divided into two constitutions according to their facial features and heritages. The one population is the Northern lineage whose ancestor migrated from Siberia in ice age. In order to survive in cold climate, they have developed a high level of metabolic heat production. Cold adaptation for preventing heat loss results in a reduction in the facial surface area with small eyes, nose and lips. The other population is the Southern lineage who is the descent of native in Korean peninsular. They have big eyes with double edged eyelids, broad nose and thick lips. It is generally believed that both genetic and environmetal factors influence eating behaviors. Although we can't recognized their heritage that may contribute to the metabolism and eating behavior, we commonly recognize their physiological heritage acceding to their facial features. In order to investigate the relationship among the size and shape of facial feature, the eating behavior, anthropometric measurement in female college students, the eating behaviors was measured during an instant-noodle lunch eaten in a laboratory setting at the ambient temperature of $23^{\circ}C$. The anterior surface area of left eye and length of right eye were positively correlated with the difference between the peak postprandial and the meal-start core temperature. The surface area of lower lip also negatively correlated with the meal-start core temperature and meal duration. In addition, the total lips' area was positively correlated with the difference between the peak postprandial and the meal-start core temperature and negatively correlated with the meal duration. However anthropometric measurements were not related with the size of facial features.

• 한국재난정보학회 논문집
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• 제7권4호
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• pp.286-293
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• 2011

최근 건축구조물은 초고층화, 대형화에 따라 고강도 및 고성능콘크리트의 사용이 증가하고 있는데, 고성능콘크리트는 화재 시 발생하는 폭렬현상에 취약한 문제가 있다. 폭렬은 화재 시 콘크리트 피복의 손실을 초래하여 내부콘크리트와 철근의 열전달률(rate of heat transmission)을 높여 콘크리트와 철근의 온도를 상승시키는 작용을 한다. 이러한 고강도콘크리트의 화재 시 폭렬을 막기 위하여 여러 가지 연구들이 진행되고 있으며 대표적으로 폴리프로필렌(Polypropylene)섬유, 강섬유를 사용한 연구들이 폭렬제어성능을 입증되었으나 유동성 저하에 따른 시공성 문제점이 제기되고 있다. 그러므로 본 연구에서는 위와 같은 문제를 에스테르계 윤활제 및 비이온성 계면활성제를 포함한 코팅액으로 코팅된 polyamide 섬유를 혼입하여 내화성능을 확보하였으며 강도영역별 최적 조건을 실험을 통하여 도출하였다. 13mm의 polyamide 섬유 적용시 강도영역별 적정 섬유 혼입량은 160MPa는 2.5kg이상에서 폭렬제어가 가능할 것으로 사료된다.

• 열처리공학회지
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• 제5권2호
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• pp.122-132
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• 1992

This study has been performed to investigate into some effects of the power density and traverse speed of laser beam on the optical microstructure, hardness and wear characteristics of medium carbon low alloy steel treated by laser surface hardening technique. The results obtained from the experiment are summarized as follows : (1) Optical micrograph has shown that finer lath martensite is formed and the amount of undissolved complex carbides increases as the traverse speed increases under the condition of a given power density, whereas the coarsening of lath martensite and the reduction of undissolved complex carbides occur with increasing the power density at a given traverse speed. (2) Hardness measurements have revealed that as the traverse speed increases, hardness values of outermost surface layer more of less decrease under low power densities, but are uniformly distributed under high power densities, also showing that they are uniformly distributed at low traverse speeds and more or less decrease at high traverse speeds with increasing the power density. (3) The effective case depth has been found to decrease from 0.26 mm to 0.17 mm with increasing the traverse speed from 1.5 m/min to 3.0 m/min at a given power density of $25.48{\times}10^3w/cm^2$ and to increase from 0.20 mm to 0.36 mm with increasing the power density from $19.11{\times}10^3w/cm^2$ to $38.22{\times}10^3w/cm^2$ at a given traverse speed of 2.0 m/min. (4) Wear test has exhibited that the amount of weight loss of laser surface hardened specimen with respect to sliding distance at a given load increases with increasing traverse speed at a given power density and decreses with increasing power density at a given traverse speed.

• Macromolecular Research
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• 제12권4호
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• pp.399-406
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• 2004

Glass-like carbon precursors shrink significantly during curing and carbonization, which leads to crack formation and bending. Cured furan resin powder and ethanol were added to furan resin to diminish the weight loss, to suppress the shrinkage and bending, and to readily release the gases evolved during polymerization and curing. Curing and carbonization were controlled by pressure and slow heating to avoid damage to the samples. The effect of the filler and ethanol on the fabrication process was examined by measuring the properties of the glass-like carbon, such as the specific gravity, bending strength, electrical resistivity, and microstructural change. The specific gravities of the filler-added glass-like carbons were higher than those of the ethanol-added samples because of the formation of macropores from the vaporization of ethanol during the curing and polymerization processes. Although the ethanol-added glass-like carbons exhibited lower bending strengths after carbonization than did the filler-added samples, the opposite result was observed after aging at 2,600$^{\circ}C$. We found that the macropores created from ethanol were contracted and removed upon heat treatment. The electrical resistivity of the glass-like carbon aged at 2,600$^{\circ}C$ was lower than those of the samples carbonized at 1,000$^{\circ}C$. We attribute this phenomenon to the fact that aging at high temperature led to well-developed microstructures, the removal of macropores, and the reduction of the surface area.

• 한국컴퓨터정보학회논문지
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• 제28권1호
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• pp.121-127
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• 2023

본 연구에서는 질소화합물을 최적으로 줄일 수 있는 SCR에서 설계 조건과 CFD 해석 결과를 비교해 검토하고자 한다. 이를 위해 보일러의 쉘과 튜브 영역에 대해 설계 기준을 만족하고 있는지 CFD을 이용하여 해석하고 비교하였다. SCR 시스템에서 해석영역은 쉘 측은 가스·공기 열교환기 입구에서 출구까지이고, 튜브 측은 가스·공기 열교환기의 8개 튜브로 설정하였다. CFD 해석을 통해 SCR 시스템의 1차 촉매 면에서 가스의 속도 분포는 2.7%로 설계되었고, NH3/NOx 몰비 분포는 3.7%로 설계 기준을 만족하였다. 또한, 온도 분포의 균일성을 확인하였고 요구 조건인 260℃ 이상을 만족하였다. 촉매에 유입되는 가스의 각도는 2.9도로 설계 조건을 충족하였고, 그리고 발생하는 압력손실도 설계 요구조건을 만족하였다. 이러한 CFD 해석을 통해 각 영역별로 요구되는 설계조건을 만족하여 설계되어 최적으로 운전되고 있음을 확인하였다.

• 한국의류산업학회지
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• 제3권5호
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• pp.466-472
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• 2001

To find a suitable condition in this process examined, we investigated the main control factors, such as, the NaOH concentrations, such as, the NaOH concentrations, the heat treating times, and the heating temperatures. The resulting mechanical properties of the fabrics also studied. The samples used were Nylon/Co-PET sea-island type composite microfiber (Co-PET content: 35%) non-woven fabric. The conclusions obtained were as follows. 1. For the complete extraction of Co-PET from the sample non-woven fabric in the dry hot air process, $160^{\circ}C$ of air temperature, 15 min. of treatment time, and around 30% of NaOH concentration were required. On the other hand, in the wet hot air process, $140^{\circ}C$ of air temperature, 3.5 min. of treatment time, and around 30% of NaOH concentration were required. 2. The mechanical properties of the continuous processed samples showed that the WT, B, and WC increased with increasing the weight reduction ratio. However, the G, decreased with increasing the weight loss ratio. Note that, particularly in B, it increased drastically when the weight deduction ratios exceeded 30%. 3. As increasing the wet hot air temperature from 130 to $140^{\circ}C$, B appeared to increase, however, WT, G, and WC appeared to decrease. 4. The best condition found in this continuous process to extract Co-PET is the wet hot air temperature of 140, NaOH concentration of 28% or above, and the treatment time 2-4 min.

• KIEAE Journal
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• 제17권2호
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• pp.29-34
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• 2017

Purpose: Recently, significant heat loss through the window takes place in buildings. Nevertheless, there exists little literature concerning the exterior horizontal shading devices and the design criteria are not clearly settled yet. Applying the exterior horizontal shading devices is more efficient as compared to the interior shading devices in that solar radiation can be directly blocked before passing through the window or the envelope. The purpose of this study is to reduce the internal load by designing the exterior horizontal shading devices and verify the degree of reduction in energy consumption. Method: This study aims to reduce energy consumption in cooling and heating through proposing proper length and shape of the exterior horizontal shading devices in public buildings. In the process, actual energy data and the Design Builder simulation program are utilized. In addition, economic aspect is considered to figure out the optimal length of the exterior horizontal shading devices that maximizes efficiency. Result: As a result, the proper length and shape of the exterior horizontal shading devices are provided as follows: 1) Energy consumption in cooling and heating is minimized when the exterior horizontal shading devices are designed as 0.5m*2. 2) Electricity bill is the lowest when the exterior horizontal shading devices are designed as 3.3m*2. The gap between maximum and minimum electricity bill is about 7.8~14%.

• 한국결정성장학회지
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• 제13권3호
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• pp.139-144
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• 2003

유기용매로서 에탄올을 함유한 염화니켈 수용액으로부터 니켈 미분말을 제조하고 이들의 산화특성을 검토하였다. 에탄올을 함유한 염화니켈 수용액에서 히드라진의 환원반응은 반응온도에 크게 의존하였다. 히드라진에 의한 환원반응시간은 반응온도가 증가함에 따라 감소하였다. 반응온도를 제어함으로써 입경이 0.1 $\mu\textrm{m}$-1.0 $\mu\textrm{m}$ 범위를 갖는 구형 분말을 얻을 수 있었다. 또한, 반응온도가 증가함에 따라 입경은 다소 증가하였고 조대한 입자들의 존재로 인하여 넓은 입도 분포를 나타내었다. $60^{\circ}C$에서 합성된 니켈 분말의 평균 입경과 비표면적은 각각 0.3 $\mu\textrm{m}$와 31.8 $m^2$/g이었다. $300^{\circ}C$에서 니켈 분말의 중량감소는 $Ni(OH)_2$의 분해반응에 기인한 것이다. $200^{\circ}C$ 공기중에서 가열처리한 경우 내산화성은 합성 분말보다 현저하였다

• 자원리싸이클링
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• 제26권5호
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• pp.61-66
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• 2017

이산화바나듐은 적외선 투과를 차단하거나 창을 통해 건물 내부열 손실을 막아주는 광선택적 유리코팅 소재로 알려졌는데, 본 연구에서 이와 같은 열변색 특성을 가진 이산화바나듐을 수소와의 환원반응을 통하여 제조하는 방법에 대해 연구하였다. 환원반응에 의한 이산화바나듐의 제조는 반응이 쉽게 진행되고, 스퍼터, 빔 증발기 등과 같은 반도체 장비가 필요 없이 공정이 단순하고 대량생산에 용이한 장점을 갖고 있는데, 본 연구에서 수소와의 환원반응에 대한 반응온도, 반응시간, 환원가스의 농도 및 사후 열처리 조건, 첨가제로서 텅스텐의 첨가 등에 대해 실험을 수행하였으며, 최적조건을 도출하여 제조된 이산화바나듐 분말의 특성과 열변색 특성에 대해 조사하였다. 본 연구를 통해 개발된 이산화바나듐이 전자소재 및 에너지 저감 소재로서 많이 활용될 것으로 기대되고 있다.