• 콘크리트학회논문집
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• 제25권2호
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• pp.201-207
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• 2013

여름철 서중 콘크리트 타설시 높은 온도로 인하여 시멘트 수화반응이 촉진되어 수분의 증발 및 응결이 빨라지게 되며, 이로 인해 컨시스턴시(consistency)가 크게 저하되고, 콜드조인트(cold joint)가 발생한다. 이러한 문제 해결을 위하여 냉각 파이프, 얼음, 액체질소 등을 사용한 냉각 등의 방법이 사용되고 있으나, 사용상의 어려움과 에너지 소비에 따른 경제성 감소 등의 문제점을 가지고 있다. 이 중 지연제의 사용은 경제적이지만 첨가량을 과도하게 사용하면 콘크리트의 경화불량이 발생하기 쉽고, 응결시간 관리가 어려울 수 있다. 또한, 현재 지연제의 인력투입으로 인한 정확한 계량 및 투입이 어렵고 분진발생 등 작업성에 문제가 있다. 따라서 이 연구에서는 분말형 지연제를 의약분야에서 보편적으로 사용하는 정제화 방법을 이용하여 타블렛을 제작하였고, 모르타르의 플로우 테스트 및 응결 시험을 검토한 이 후 콘크리트의 물리적 특성 및 역학적 특성 시험을 실시하여 품질성능에 영향을 미치는지 확인 하였다. 그 결과 리그닌 설폰산염 지연제보다 글루코산염 지연제를 정제화 했을 때 보다 좋은 효과를 발휘 하는 것을 보여 주었다. 또한, 정제화 방법 적용으로 인해 콘크리트의 품질성능을 저하하지 않고 정확한 계량 및 분진발생 등과 같은 관리상의 어려움을 해결할 수 있는 가능성을 보여주었다.

• 원예과학기술지
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• 제32권1호
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• pp.53-59
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• 2014

본 실험은 고온기 근권 냉방 시간에 따른 배지 온도 하강과 파프리카(Capsicum annum L.) 'Orange glory'의 생리적 반응을 알아보고자 7월 16일부터 10월 15일까지 코이어 배지에서 수경 재배하였다. 배지의 일평균, 최고 및 최저 온도변화와 파프리카의 뿌리 활력, 수분 포텐셜, 개화시기 및 착과수 등을 측정하였다. $20{\pm}2^{\circ}C$의 냉수를 순환시키는 XL 파이프 근권부 냉방시간 처리는 전일(전일, 24시간), 야간(야간, 오후 5시-오전 3시), 및 냉방 무처리(대조구)로 7월 23일부터 9월 23일까지 처리하였다. 고온기(7월 23일-8월 31일) 동안 일평균 배지 온도가 전일 처리구에서는 $25.6^{\circ}C(22.7-28.2^{\circ}C)$, 야간 처리구에서는 $26.1^{\circ}C(22.9-29.2^{\circ}C)$로 대조구의 $29.1^{\circ}C(24.7-33.2^{\circ}C)$에 비해 $1.8-5^{\circ}C$ 낮아졌다. 하루 중(맑은 날, 8월 1일) 배지의 최고온도 도달 시간이 전일과 야간 처리구에서는 오후 4-5시였으며, 대조구는 오후 7-8시였다. 주간(오전 6시-오후 8시)과 야간(오후 8시-오전 6시) 시간의 배지 온도는 처리에 따라 차이를 보였다. 주간/야간의 배지 평균온도는 대조구보다 전일 처리구에서 $3.3^{\circ}C/4^{\circ}C$, 야간 처리구에서 $2.1^{\circ}C/3.4^{\circ}C$ 낮아졌다. 배지 깊이별 배지 온도 차(대조구 배지 온도 - 처리구 배지 온도)는 하부에서 가장 컸다. 전일 처리구의 배지 온도차 변화는 배지 상/중/하부에서 완만하였으나, 야간 처리구는 주간과 야간 시간대 배지 온도 차가 배지 중간, 하부에서 커졌다. 배지 평균 온도가 $25^{\circ}C$ 이상 계측된 날이 대조구에서는 40일, 전일 처리구에서는 23일, 야간 처리구에서는 27일로 대조구에 비해 각각 42.5%, 32.5% 배지온도 하강효과를 보였다. 전일 처리구의 파프리카 뿌리 활력과 수분 포텐셜은 야간 처리구보다 유의하게 높았다. 근권 냉방 처리의 첫 개화시기는 4-5일 앞당겨지고 착과수도 유의하게 증가하였다. 그러나 고온기 지상부가 고온(${\geq}30^{\circ}C$)으로 파프리카 착과는 늦어졌다. 이는 근권 냉방으로 배지 온도가 $1.8-5.0^{\circ}C$ 낮아졌으나, 고온기 파프리카 생육과 착과를 위해서는 근권 냉방뿐 아니라 지상부 온도를 낮추는 방식이 병행되어야 한다.

• Corrosion Science and Technology
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• 제14권2호
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• pp.47-53
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• 2015

Recently, the bending process is greatly applied to fabricate the pipe line. Bending process can reduce welding joints and then decrease the number of inspection. Thus, the maintenance cost will be reduced. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. By this thermal process, corrosion properties and microstructure can be affected. This work focused on the effect of induction heating bending process on the properties of ASME SA106 Gr. C low carbon steel pipes. Microstructure analysis, hardness measurements, and immersion corrosion test were performed for base metal and bended area including extrados, intrados, crown up, and down parts. Microstructure was analyzed using an optical microscope and SEM. Hardness was measured using a Rockwell B scale. Induction heat bending process has influenced upon the size and distribution of ferrite and pearlite phases which were transformed into finer structure than those of base metal. Even though the fine microstructure, every bent area showed a little lower hardness than that of base metal. It is considered that softening by the bending process may be arisen. Except of I2, intrados area, the others showed a similar corrosion rate to that of base metal. But even relatively high rate of intrados area was very low and acceptable. Therefore, it is judged that induction heat bending process didn't affect boric acid corrosion behaviour of carbon steel.

• Corrosion Science and Technology
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• 제14권3호
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• pp.120-126
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• 2015

The usage of bending products recently have increased since many industries such as automobile, aerospace, shipbuilding, and chemical plants need the application of pipings. Bending process is one of the inevitable steps to fabricate the facilities. Induction heat bending is composed of compressive bending process by local heating and cooling. This work focused on the effect of induction heat bending process on the properties of ASME SA312 Gr. TP304 stainless steel pipes. Tests were performed for base metal and bended area including extrados, intrados, crown up, and down parts. Microstructure was analyzed using an optical microscope and SEM. In order to determine intergranular corrosion resistance, Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) test and ASTM A262 practice A and C tests were done. Every specimen revealed non-metallic inclusion free under the criteria of 1.5i of the standard and the induction heat bending process did not affect the non-metallic inclusion in the alloys. Also, all the bended specimens had finer grain size than ASTM grain size number 5 corresponding to the grain sizes of the base metal and thus the grain size of the pipe bended by induction heat bending process is acceptable. Hardness of transition start, bend, and transition end areas of ASME SA312 TP304 stainless steel was a little higher than that of base metal. Intergranular corrosion behavior was determined by ASTM A262 practice A and C and DL-EPR test, and respectively step structure, corrosion rate under 0.3 mm/y, and Degree of Sensitization (DOS) of 0.001~0.075% were obtained. That is, the induction heat bending process didn't affect the intergranular corrosion behavior of ASME SA312 TP304 stainless steel.

• 조명전기설비학회논문지
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• 제30권2호
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• pp.71-77
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• 2016

The dielectric barrier discharge (DBD) has low efficiency due to about 70% input power is consumed as thermal energy in the discharge space. However, because of the usage of DBD ozone generator is easier than other methods. The DBD ozone generator has been widely applied for high concentration ozone generation in the industrial application. But, the low-capacity compact DBD ozone generator is not applied so far. Therefore, the DBD ozone generator is necessary to improve ozone production efficiency and reduce the capacity. In this paper, the stainless steel pipe inner electrode was designed with hall type and screw type to improve the ozone production yield. The manufactured two inner electrodes were experimented with normal type for comparison of the discharge characteristics and the ozone generating characteristics. As the experimental results, the discharge current effective value of designed inner electrodes with hall type and screw type are higher than the normal type, due to unequal electric field is formed at the boundary. However, the difference of designed and original electrodes is less than 0.1mA that has no effect on the discharge characteristic. On the other hand, the screw type inner electrode increased higher than original model about 7 times when the flow rate of the oxygen source gas was increased from $0.6{\ell}/min$ to $1.0{\ell}/min$ The reason was assumed by the flow rate of the raw gas through the inner electrode was became fast that has a cooling effect. The designed hall type and screw type inner electrodes have shown good performances in ozone generation and ozone production that better than normal type in the same electrode surface area.

• 지질공학
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• 제26권4호
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• pp.461-471
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• 2016

수주지열정의 지하수 유동 및 지열 이동 현상을 모사할 수 있는 수치 모델링 기법을 제시하기 위하여 열-수리학적 모델인 TOUGH2를 기반으로 한 모듈을 개발하였고 두 유형의 수주지열정에서의 냉방 및 난방 운영을 수치 모의하였다. 수치 모델링 결과들은 수주지열정의 냉난방 운영이 주변 지층 및 지하수와의 열교환 및 유체 혼합에 크게 영향을 받으며, 특히 PVC 또는 PE 파이프 내부와 수주지열정 내부에서 서로 반대방향으로 유동하는 유입수와 유출수 간의 열교환이 중요한 요소임을 보여준다. 또한 본 연구에서 개발 및 제안된 수치 모델링 기법이 수주지열정의 내부 구조 및 유체 유동과 열 이동 현상을 합리적으로 모사할 수 있음을 보여준다. 이러한 수치 모델링 기법은 수주지열정의 설계, 시공 및 운영 단계에서 열교환 성능을 정량적으로 분석할 때 유용하게 활용될 수 있을 것으로 기대된다.

• 한국농공학회논문집
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• 제47권3호
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• pp.29-37
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• 2005

This study was carried out to file up structural design data for optimizing Pleurotus eryngii growing houses. Design data are including current farm status of Pleurotus eryngii growing houses in the aspect of structural configuration as well as environmental conditions to be controlled and maintained inside. A structural analysis was performed for the on-farm structures as well as some structures modified and suggested through field survey and analysis. The results are summarized as follows. According to the results of status analysis, Pleurotus eryngii growing houses were categorized as arch-roofed simple type and sandwich panel type. Though the size of Pleurotus eryngii cultivation facilities were considerably diverse, the basic dimensions of Pleurotus eryngii cultivation facilities showed relatively similar pattern: more or less of 20m of length, $6.6\~7.0m$ of width, $4.6\~5.0m$ of peak height, $1.2\~1.6m$ of bed width, and 4 layers of bed. In the aspect of spatial use of cultivation facilities, suggested models were shown to be mostly reasonable in the aspect of heating and cooling, micro-meteorological stability, land use efficiency per unit floor area, etc.. Especially, the standard models suggested so far were thought to be not efficient in its surface area and spatial volume per unit floor area as well as its uneffective structural design in the area around ceiling. In the results of structural analysis for the models suggested through this study by using those section frames to be found on farms, the panel type structures of both single span and double span were estimated to be over designed, whereas arch-roofed pipe houses were mostly found to be under-designed.

• 접착 및 계면
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• 제7권3호
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• pp.16-25
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• 2006

내열성 및 투습방수기능을 가진 신발용 직물 및 부직포를 제조하기 위하여 스크린 방식으로 공정조건을 검토하고 투습방수 필름을 라미네이팅 한 후, 최종제품의 물성을 평가하였다. 결과는 다음과 같다. 열가소성 핫 멜트와는 달리 반응형 폴리우레탄 핫 멜트는 작업 이후에 적정한 내열성을 보유하는 것으로 나타났다. 최적의 용융접착 공정조건은 다음과 같다 ; 드럼 온도 $95^{\circ}C$, 호스 온도 $97^{\circ}C$, 공급파이프 온도 $100^{\circ}C$, 스크린 온도 $105^{\circ}C$이고, opposite roller의 압력은 $1kgf/cm^2$, laminating roller의 압력은 $3kgf/cm^2$이며, 가공속도는 15 m/min이다. 투습도는 필름의 두께가 증가함에 따라 투습도는 감소하였으나, 내수도는 증가하였고, 공기투과도는 필름의 영향이 지배적이었다.

• 상하수도학회지
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• 제26권3호
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• pp.409-421
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• 2012

Ethanolamine (ETA) is mainly used to prevent corrosion of pipe in secondary cooling system of nuclear power plant. Condensed ETA in wastewater could increase COD and T-N when it was emitted to natural water system. Compared to conventional treatments, electrochemical oxidation process using packed bed bipolar electrodes was adopted to treat COD and T-N. According to arrangement of feeder electrode, single packed bed bipolar electrode reactor and multi-paired packed bed bipolar reactor were developed and conventional zero-valent iron (ZVI) was selected as conducting bipolar electrode. Bipolar electrodes were coordinated three-dimensionally in the reactor. The experimental results showed that COD and T-N was little removed in unit system at different pH condition (pH 8 and 11) on 100V. However, in multi-paired system that applied 600V, COD was eliminated 80.85% (anode-cathode-anode, A-C-A) and 85.11% (cathode-anode-cathode, C-A-C), respectively. T-N was also removed 96.88% (A-C-A) and 90.63% (C-A-C), simultaneously. Current efficiency was estimated both single and multi-paired system. At unit bipolar packed bed reactor, current efficiency was almost zero, however in multi-paired system, current efficiency was 300~500% at A-C-A and 250~350% at C-A-C. Current efficiency was over 100% hence it was confirmed that this system is more effective than conventional electrochemical oxidation system.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.57-60
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• 2008

According to the recent tendency that the buildings in the downtown concerning rising land prices and efficient use of building are gradually Manhattanized mainly the grand scaled residential buildings, structure of the buildings relates to safety and so the very thick mat concrete is selected as the foundation of architectures. Because mat concretes can not be simultaneously pour in a great quantity due to the circumstance at the field, not only the questions on the unification between the concretes pour on the upper layer and the lower layer are presented but also the cracks by the internal force from the difference of hydration exothermic period are occurred because of the time lag. Thus, this study checked the efficiency to apply "The hydration heat controlling method of mass concrete for horizontal partition pouring construction" to the skyscraper sites under construction at Haiundai in Busan. After applying this method, the result of observation that the cracks by hydration heat in all over the placement surface did never be founded. Also, in case of the economic analysis that the hydration heat reduction method using super retarding agent by difference of setting time is approximately 80% cheaper than the hydration heat reduction method by pipe cooling in the construction expenses.