• 한국해양공학회지
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• 제11권3호
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• pp.39-47
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• 1997

Recently developed TMCP steels, which were manufactured by controlled rolling followed by accelerated cooling process, were examined to study their characteristics and weldability. Accelerated cooling type TMCP steel's hardness test result exhibited high value on weld zone. On the contrary, base metal and HAZ exhibited comparatively the similar value. On this experiment result Softening of HAZ is not occurred. in the-heat affected zone, grain size repression be caused by chemical composition properties which a small quantity Al-Ti-B-N. Changing stress ratio near-threshold fatigue crack propagation experiments were carried out. According to this result, crack propagation velocity of the HAZ exhibited slower than the base metal and near-threshold value had increased at the HAZ. Finally accelerated cooling type TMCP steels were exhibited excellent mechanical properties in both strength and toughness.

• 대한의용생체공학회:의공학회지
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• 제24권5호
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• pp.375-380
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• 2003

순수티타늄과 산화물계 주형재의 표변반응층을 제어하는 방법을 제시하기 위하여 치과용 인산염계 실리카·알루미나 주형재에 CP-Ti를 원심주조법으로 주조하고, 주조 후 냉각방법에 따른 치과용 티타늄 주조체의 표면반응층 및 기계적 특성에 미치는 영향을 조사하였다. 주조체는 주조 후 냉각방법에 관계없이 다층구조의 표면 반응층을 보였으며, 특히 수냉 방법이 공냉에 비해 표면반응층의 두께가 얇게 형성되었고, 강도는 약하고 연신율은 높게 나타나서, 치과용주조체로 만족할만한 기계적 성질을 얻을 수 있었다. 이러한 결과는, 용해분위기에서 산소의 침입과 주조시 주형재의 반응을 주도하는 냉각속도의 차이에 기인하는 것으로 판단된다.

• 설비공학논문집
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• 제17권4호
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• pp.370-376
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• 2005

For the purpose of investigating the effective removal of heating/cooling load from light-weighted building envelope, two air-conditioning systems, conventional parameter air-conditioning system and air-barrier system, are evaluated and compared by both experiment and simulation with six different cases during heating and cooling season. In addition, the characteristics of window-side building thermal load are assessed by varying supply air velocity in order to seek the optimal system operation condition. The results are as follows. 1) Air-barrier system is more effective to remove heating/cooling load at perimeter zone than conventional parameter air-conditioning system. Moreover, the better effectiveness appears during cooling season than during heating season. 2) The experiment during cooling season provides that indoor temperature of air-barrier system shows $1^{\circ}C$ less than that of the conventional system with similar outdoor air temperature profile, and indoor temperature distribution is more uniform throughout the experimented model space. It concludes that air-barrier system can achieve energy saving comparing to the conventional system. 3) The capturing efficiency of air-barrier system is 0.47 on heating season and 0.2 on cooling season with the same supply air volume. It results that the system performs effectively to remove building thermal load, moreover demonstrates high efficiency during cooling season. 4) The simulation results provide that capturing efficiency to evaluate the effective removal of building load from perimeter zone shows high value when supply air velocity is 1 m/s.

• 아시안잔디학회지
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• 제15권4호
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• pp.169-179
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• 2001

근권부의 온도를 대조구에 비하여 낮게 조절하고 토양조성을 달리하여 여름철 고온기에 Kentucky bluegrass (Poa pratensis L.‘Nuglade’), per-ennial ryegrass(Lolium perenne L.‘Accent’), tall fescue (Festuca arundinacea Schreb. ‘Pixie’), Japanese lawngrass (Zoysia japonica Steud.)를 재배하고 잔디의 품질, 병해발생 정도 엽록소 함량을 조사하고 아울러 예지물의 무기물 함량을 측정하여 다음과 같은 결과를 얻었다. 1. 여름철 근권부의 온도를 4~6$^{\circ}C$ 낮게 처리한 경우 한지형 잔디의 균일성을 현저히 높여주고 병의 발생률을 크게 억제시켰으며 그 효과는 perennial ryegrass에서 가장 큰 것으로 나타났다. 엽록소 함량은 토양조성에 따라 변화가 없었으나 냉온 처리구에서 대조구에 비하여 크게 증가되었다. 2. 여름철 근권부의 냉온처리는 Kentucky blue-grass와 perennial ryegrass는 대조구에 비하여 약 2배, tall fescue는 2.5배 이상의 clipping무게 증가를 나타냈다. 난지형 잔디인 들잔디에서도 냉온처리구에서 생육의 증진효과를 보였다. 한지형 잔디는 모래 ＋peat moss를 80 : 20(v/v)으로 혼합한 토양에 비하여 모래＋peat moss＋일반토양을 80：10 : 10 (v/v/v)으로 혼합한 토양에서 많은 생장을 보였다. 3. 근권부의 냉온처리는 공시된 세 종류의 한지형 잔디에서 N, P, K, Ca그리고 Mg의 흡수를 증가시켰으나 들잔디에서는 흡수차이를 보이지 않았다. 토양의 혼합비율에 따른 무기물함량의 차이는 인정되지 않았다. 이상의 결과로 미루어 근권부의 냉온처리는 고온 스트레스에 의한 잔디의 생육저하를 감소시키고 여름철 하고현상을 예방하여 줌으로써 고온다습한 기후조건에서도 경기장의 잔디 품질을 우수하게 유지할 수 있는 방안으로 판단된다.

• 한국주조공학회지
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• 제11권5호
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• pp.398-405
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• 1991

Al-Li alloy has a high strength with low density. Practically this alloy should use by the material which made from the rapid solidification. Therefore we examine the solidification structures of alloy with cooling rate. According to cooling rate increased, grain size and secondary dendrite arm spacing were smaller. Also grain size was further smaller by Zr added. To obtain more fine solidification structure, rapid solidification by single roll melt spinning was performed. According to higher wheel speed, cooling rate increased and cell size was smaller. Because of locally different cooling rate, different cell size was obtained in same specimen. More than cooling rate $10^6^{\circ}C$ /sec, zone A(insensible zone to corrosion)was obtained.

• 설비공학논문집
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• 제17권5호
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• pp.477-486
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• 2005

In this study, indoor thermal environment, resident behavior of operating cooling device, and thermal comfort vote are investigated at the living room of apartment during summertime in Seoul. Based on the results of the investigation, indoor air temperatures that residents turn air conditioners (especially for cooling load in this research) on and off were found out. The relationships between outdoor weather condition and the number of days using air conditioner, and whether operating patterns of the devices were also found out. The acceptable thermal comfort zone is figured out from these results, and this research is expected to contribute to the development of household air conditioner. The results can be summarized as the followings; Residents turned the air conditioner on at $29.76^{\circ}C$ of indoor air temperature, and $28.89^{\circ}C$ of $SET^\ast$. And turned the air conditioner off at $27.31^{\circ}C$ of indoor air temperature, and $23.70^{\circ}C$ $SET^\ast$. Therefore, acceptable thermal comfort zone could be lied between these temperatures. If comfortable indoor thermal environment can be obtained with various architectural passive cooling techniques based on the results, energy consumption of cooling devices will be reduced.

• 설비공학논문집
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• 제18권4호
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• pp.304-311
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• 2006

Experiments on evaporative spray cooling on the square plate heaters with plain or micro-porous coated surfaces were performed in this study. Micro-porous coated surfaces were made by using DOM [Diamond particle, Omegabond 101, Methyl-Ethyl-Keton] method. In case of purely air-jet cooling, the micro-porous coating doesn't affect the cooling capacity. In spray cooling three different flow patterns (complete wetting, evaporative wetting, dryout) are observed on both plain and micro-porous coated surfaces. The effects of various operating conditions, such as water flow rate, particle size, and coating thickness were investigated on the micro-porous coated surfaces. It is found that the level of surface wetting is an important factor to determine the performance of spray cooling. It depends on the balance between absorbed liquid amount by capillary force over porosity and the evaporative amount. The micro-porous coated surface has largest cooling capacity, especially in the evaporative wetting zone. It is found that the effects of liquid flow rate and coating thickness are significant in evaporative wetting zone, but are not in complete wetting and dryout zones.

• 대한조선학회지
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• 제9권2호
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• pp.49-55
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• 1972

The temperature distribution and cooling rate play an important role in the investigation of heat affected zone of weldment. All the problems such as metallurgical changes, welding thermal stress, welding residual stress and welding deformation in the heat affected zone of welded joint are due to the temperature distribution and cooling rate. In this paper, one dimensional temperature distribution and cooling rate due to transient arc welding heat in the heat affected zone of the base metal are studied. Heat transfer equation for one dimensional heat flow is formed, and solution is obtained. Weld heat input formula is also formed and used. Computed numerical results show a good agreement with the experimented temper color.

• 생물환경조절학회지
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• 제3권1호
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• pp.36-41
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• 1994

본 시험의 목적은 온실의 주년계획이용을 위해서 하기주간 냉방의 방법으로 heat pump를 이용한 냉수냉방과세무냉방의 효율성을 검사했고 하기 토마토 배꼽썩음병 발생을 억제하기 위하여 냉방과 함께 과실에 송풍처리와 식물체 전체의 공기유동을 촉진시켜주는 처리를 했다. 시험결과는 다음과 같다. 1) 냉수냉방구간 기온은 13시경 온실내 기온보다 약 1$0^{\circ}C$이상 낮았고, 세무냉방구간 하부의 기온은 13시경 온실내 기온보다 약 5$^{\circ}C$ 낮았다. 2) 과실에 송풍처리는 냉방방법에 상관없이 배꼽썩음병이 방지됐고, 냉수냉방 무송풍구의 배꼽썩음병 발생율은 34.5%, 세무냉방 무송풍구는 54.5%, 세무순환냉방구는 78%였다. 냉방효율면에서는 냉수냉방 방법이 충분히 생육한계온도 이하로 냉각되었고, 배꼽썩음병 발생율에서도 세무냉방보다 낮았다. 세무냉방은 재배구간의 공기를 유동시킴으로서 약 24%증가했다. 그러므로 토마토 배꼽썩음병 발생에 관한 환경요인은 온도보다는 습도가 밀접한 관계가 있는 것으로 생각되어진다.

• 설비공학논문집
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• 제14권10호
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• pp.854-862
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• 2002

In the previous research, a simplified correlation method was developed as an easy prediction tool for comparing energy use of cooling plants. The purpose of this paper is to test the applicability of this method for economic evaluation with two zones of a 20-story commercial building in Seoul. The results of this method were compared with the DOE-2 simulation and actual measured data. Then, Comparisons of life cycle cost were carried out for three types of cooling plants. Testing of one zone showed good agreement of within 10% error in cooling energy use and within 2% error in LCC. But testing of the other zone indicated that the use of this method were invalid when input variables were used beyond its valid range.