• 한국태양에너지학회 논문집
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• 제28권3호
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• pp.7-14
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• 2008

400RT geothermal system which is the biggest capacity among on-operations at present in Korea is measured and evaluated on 23rd${\sim}$26th Jan. 2008 during those days building is not allowed owners and/or tenants to move in. The geothermal system is consist with vertical-typed 112 geothermal heat exchangers which are installed circle-like 1 row with 4m interval, and has 16 units of 25USRT geothermal-source heat pump(GSHP)s. And each 5 units of circulation pump are running for geothermal heat exchangers and hot water supplies. The followings are the results. The temperatures at G.L. -70m of 2 boreholes are varied quite similarly. The average temperature difference between inlet and outlet of geothermal pipes is $4.1^{\circ}C$, and that of hot water supply is $3.2^{\circ}C$, of Zone 3's each 4 GSHPs when being operated. Despite temperature fluctuations by heating loads, the average temperature difference between main pipes of inlet and outlet of geothermal heat exchangers is measured as $4.1^{\circ}C$. This study propose "Geothermal System COP" which includes not only consumed electric power by compressor but also circulation pumps and auxiliary utilities. By comparing the geothermal system COP with GSHP's performance specification, it is clear that the performances of GHSPs of this site are satisfied with the specification.

• 대한금속재료학회지
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• 제48권10호
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• pp.901-906
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• 2010

The first stage blade of a gas turbine was operated under a severe environment which included both $1300^{\circ}C$ hot gas and thermal stress. To obtain high efficiency, a thermal barrier coating (TBC) and an internal cooling system were used to increase the firing temperature. The TBC consists of multi-layer coatings of a ceramic outer layer (top coating) and a metallic inner layer (bond coat) between the ceramic and the substrate. The top and bond coating layer respectively act as a thermal barrier against hot gas and a buffer against the thermal stress caused by the difference in the thermal expansion coefficient between the ceramic and the substrate. Particularly, the bondcoating layer improves the resistance against oxidation and corrosion. An inter-diffusion layer is generated between the bond coat and the substrate due to the exposure at a high temperature and the diffusion phenomenon. A thickness measurement result showed that the bond coat of the suction side was thicker than that of the pressure side. The thickest inter-diffusion zone was noted at SS1 (Suction Side point 1). A chemical composition analysis of the bond coat showed aluminum depletion around the inter-diffusion layer. In this study, we evaluated the properties of the bond coat and the degradation of the coating layer used on a $1300^{\circ}C$-class gas turbine blade. Moreover, the operation temperature of the blade was estimated using the Arrhenius equation and this was compared with the result of a thermal analysis.

• 대한가정학회지
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• 제43권2호
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• pp.19-31
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• 2005

The purpose of this study was to evaluate the microbiological quality and assure the hygienic safety of the Bibimbap production in elementary school foodservice in accordance with the HACCP(Hazzard Analysis Critical Control Point) program. The time-temperature relationship and the microbiological quality(total plate count and coliform bacteria count) were assessed to find the critical control point(CCP) during each of the production phase. In the pre-preparation phase, the risk factors of the raw ingredients exceeded the standard level suggested by Solberg et al. Mungbean starch jelly, egg and Kochujang were satisfactory in that no coliform groups were observed over the standard TPC level. In particular, there was a high the risk of beef from the early stages in terms of the coliform level. In the pre-preparation phase, green pumpkin had more coliform groups than the standard level even after washed, which calls for special attention to washing, sterilization, secondary infection of the handler, and the required time for pre-preparation of raw vegetables. In the cooking phase, the temperature of the soybean sprout and mungbean starch jelly decreased to 42$^{\circ}C$ and 26$^{\circ}C$, respectively, which was within the risk zone. In particular, mungbean starch jelly had a great risk factor even after boiling in hot water. During the storage stage before serving, a lot of ingredients were exposed to poor management of temperature and time and thus exceeded the standard level in the total plate counts. In particular, the microbiological count of beef was five times the standard level. Green pumpkins and soybean sprouts were left at 15-38$^{\circ}C$ that is within the risk zone for a long period of time after they were cooked. It is highly recommended that the time of the storage stage before consumption should be shortened and that proper devices should be used to prevent proliferation of bacteria. The number of TPC of the utensils was satisfactory enough, but the knife used exceeded the standard level and thus was a risk factor of bacteria proliferation.

• 에너지공학
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• 제27권2호
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• pp.32-48
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• 2018

건물의 에너지사용량을 효율적으로 관리하기 위해서는 에너지의 사용에 대한 모니터링이 우선시 되어야 한다. 건물에서의 에너지사용량은 크게 에너지원별, 용도별, 구역별로 구분하여 관리할 수 있다. 에너지원별이란 건물의 설비를 가동하기 위해 공급되는 전기, 가스, 연료, 지역난방 등을 의미한다. 용도별이란 크게 냉방, 난방, 조명, 급탕, 환기와 같이 5대 용도로 구분할 수 있지만, 5대 용도 안에 포함시키기 어려운 엘리베이터나 전열기기 등은 별로도 분류하는 것을 의미한다. 이 외 구역별은 건물의 사용목적이나 사용용도가 비슷하거나 구분되는 지역을 묶어서 비교 관리 하거나 별도 관리 하는 것을 말한다. 이 밖에 에너지의 효율관리에서는 건물의 에너지사용량에 영향을 주는 온도, 습도와 재실자에 대한 관리가 필요하며, 최근 문제가 되는 미세먼지는 건물의 환기에 직접적인 영향을 주기 때문에 이에 대한 관리도 병행되어야 한다.

• 한국인터넷방송통신학회논문지
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• 제15권5호
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• pp.193-199
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• 2015

요즈음, 온도 및 습도, 조도 센서를 이용하여서, 식물 재배 환경 정보를 자동으로 수집하고 생장환경을 관리하는 지능형 온실 시스템이 많이 연구되고 있다. 본 논문에서는 조도, 온도 및 습도를 예측해서 인터넷 기반에서, 식물 재배의 최적 환경 조건을 추론하는 모의실험을 하였다. IOT 환경에서, 식물 재배 조건을 온도, 습도, 조도를 아두이노 센서에 실시간으로 온실 관리자에게 전송해서, 식물 재배에 필요한 최적의 온도, 습도 조건 값보다 크거나 적으면 자동으로 SMS 경고 문자를 실시간으로 전송해 주기 때문에, 급격한 기후 변화 (눈,비, 폭염)조건일 경우라도 최적의 화초 재배조건을 관리 할 수 있다. 본 논문에서는 퍼지논리와 WEKA TOOL을 이용하여서, 같은 온대 식물이라도, 그 지역에 필요한 최적의 온도, 습도, 조도(일사량) 수치를 산출하는 모의실험을 하였다.

• 한국공작기계학회논문집
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• 제16권4호
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• pp.1-12
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• 2007

S45C steel has been widely used in industrial applications, such as crank shafts, gears, main spindles of machine tools, connecting rods, etc., because of its distinguished mechanical property. In the convention arc welding of S45C plates without heat treatments, it is possible for welding defects to take place, such as a void or a hot-crack, due to a high carbon composition of S45C. Laser welding process is widely used in the industrial field due to its numerous advantages: a small heat affected zone(HAZ), deep penetration, high welding speed, single-pass thick section capability, and small distortion after welding. The objective of this research works is to investigate the influence of the process parameters, such as power of laser and welding speed, on the characteristics of laser welding for the case of nickel coated and nickel uncoated S45C steel. As the result of the experiment, in case of butt welding, nickel coated S45C steel has a uniform formation of welding zone and it was judged that the welding nature was better as inner defects and the quantity of spatter were formed relatively fewer than nickel uncoated S45C steel.

• 대한치과기공학회지
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• 제27권1호
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• pp.9-17
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• 2005

The use of titanium alloys as biomaterials is increasing due to their superior biocompatibility and enhanced corrosion resistance compared to conventional stainless steels and cobalt-based alloys. Ti-6Al-4V ($\alpha+\beta$type) alloy instead of pure titanium ($\alpha$type) is being widely used as biomaterials has some characteristics such as high fatigue strength, tensile strength and corrosion resistance. But it has been reported recently that the vanadium element expresses cytotoxicity and the aluminium element is related with dementia of Alzheimer type and neurotoxicity. In order to overcome their detrimental effects, $\beta$-phase stabilizer Nb was chosen in the present study. This paper was described the influence of phase changes of Ti-Nb alloys on mechanical properties. Ti-3wt.%Nb($\alpha$type),Ti-20wt.%Nb($\alpha+\beta$type) and Ti-40wt.%Nb($\beta$type) alloys were melted by vacuum arc furnace. The specimens were homogenized at 1050$^{\circ}C$ for 24hr and were then hot rolled to 50% reduction. Each alloys were solution heat treated at $\beta$ zone and $\alpha+\beta$ zone after homogenization and then were aged. The mechanical properties of Ti alloys were analysed by hardness test, tensile test, elongation test and SEM test. The results can be summarized as follows: 1) The higher hardness value of $\alpha+\beta$type alloy was obtained compared to the, $\alpha,\beta$type alloys. 2) The aged treated showed better hardness compared to the solution heat treated, homogenized. 3) In the case of solution and aging treatment at $\beta$region, the $\alpha+\beta$type alloy showed the most highest tensile strength and $\beta$type alloy showed the best elongation.

• Journal of Welding and Joining
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• 제31권3호
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• pp.31-38
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• 2013

The transition of serrated grain boundary and its effect on liquation behavior in the simulated weld heat-affected zone (HAZ) have been investigated in a wrought Ni-based superalloy Alloy 263. Recently, the present authors have found that grain boundary serration occurs in the absence of adjacent coarse ${\gamma}^{\prime}$ particles or $M_{23}C_6$ carbides when a specimen is direct-aged with a combination of slow cooling from solution treatment temperature to aging temperature. The present study was initiated to determine the interdependence of the serration and HAZ property with a consideration of this serration as a potential for the use of a hot-cracking resistant microstructure. A crystallographic study indicated that the serration led to a change in grain boundary character as special boundary with a lower interfacial energy as those terminated by low-index {111} boundary planes. It was found that the serrated grain boundaries are highly resistant to boron enrichment, and suppress effectively grain coarsening in HAZ. Furthermore, the serrated grain boundaries showed a higher resistance to susceptibility of liquation cracking. These results was discussed in terms of a significant decrease in interfacial energy of grain boundary by the serration.

• 한국산림과학회지
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• 제35권1호
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• pp.19-23
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• 1977

열대산(熱帶産) 광엽수재(廣葉樹材)에는 추출물(抽出物)이 많고, 특(特)히 온수추출물(溫水抽出物)이 많다. Lignin 함유량(含有量)은 Shorea속(屬)의 2수종(樹種)(Bangkirai, Red lauan)이 온대산(溫帶産) 침엽수재(針葉樹材)정도로 높고, Rhizophara속(屬)의 Mangrove재(材)는 온대산(溫帶産) 광엽수재(廣葉樹材)정도이며, Dipterocarpus속(屬)의 Keruing재(材)는 이것들의 중간(中間)정도이다. 당조성(糖組成)은 Xylose함유량(含有量)이 Shorca 속(屬)의 그 수종(樹種)이 온대산(溫帶産) 침엽수재(針葉樹材)정도로 낮고, Mangrove재(材)는 온대산(溫帶産) 광엽수재(廣葉樹材)정도이며, Kcruing재(材)는 이것들의 중간(中間)정도다. 황산(黃酸)과 무수초산(無水酢酸)에 의한 acctyl화(化)한 alditol acetate의 전수율(全收率)은 보정(補正)하여도 100%가 되지 않는다. Acetyl화(化)한 직후(直後)이면 분석(分析)에 지장이 없지만, 4~5일(日) 방치(放置)하면 분해(分解)가 일어난다. 그리고 Pyridine과 무수초산(無水酢酸)으로 acetyl환(化)한 것도 같은 경과(結果)였다.

• Journal of Welding and Joining
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• 제35권3호
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• pp.68-74
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• 2017

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E71T-1C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, Intragranular polygonal ferrite and grainboundary ferrite were formed only in first layer of weld metal. Another layers consisted of acicular ferrite and $Widmannst{\ddot{a}}tten$ ferrite. The amount of acicular ferrite was increased with decreasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered martensite and lower bainite. Lower and upper bainite were formed in heat affected zone of carbon steel. Tensile strengths of dissimilar metal welds decreased with increasing heat inputs. Dissimilar metal welds showed a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals welds showed that the weight loss rate by corrosion below 170 hours was decreased with increasing heat inputs due to the increase of the amount of acicular ferrite.