• Membrane and Water Treatment
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• 제3권2호
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• pp.133-140
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• 2012

The overall performance of BNR-MBR, so-called Anoxic-Anaerobic-Aerobic Membrane Bioreactor ($A^3$-MBR), developed for nutrient removal was studied to determine the efficiencies and mechanisms under different solid retention time (SRT). The reactor was fed by synthetic high-rise building wastewater with a COD:N:P ratio of 100:10:2.5. The results showed that TKN, TN and phosphorus removal by the system was higher than 95%, 93% and 80%, respectively. Nitrogen removal in the system was related to the simultaneous nitrification-denitrification (SND) reaction which removed all nitrogen forms in aerobic condition. SND reaction in the system occurred because of the large floc size formation. Phosphorus removal in the system related to the high phosphorus content in bacterial cells and the little effects of nitrate nitrogen on phosphorus release in the anaerobic condition. Therefore, high quality of treated effluent could be achieved with the $A^3$-MBR system for various water reuse purposes.

• 환경위생공학
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• 제19권2호
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• pp.30-36
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• 2004

Dry decontamination technique is required for maintaining nuclear material handling equipment contaminated with highly radioactive material in a hot cell. In order to determine the optimum blasting conditions of dry ice pellet blasting device, the basic experiments have been conducted on the simulated test specimens of four types of metals. The removal efficiency of test piece was evaluated by the XRF analysis and the change of the surface condition before and after blasting. The removal efficiency of cesium on loose contamination was 100% under blasting pressure; 3 kg/$cm^2$, blasting distance; 10 cm, blasting time: 10 sec. In case of fixed contamination, the removal efficiency of cesium was almost 96% under blasting pressure; 4kg/$cm^2$, blasting distance; 10 cm, blasting time; 30 sec.

• 한국환경과학회지
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• 제19권1호
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• pp.105-114
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• 2010

The objective of the paper is to experimentally investigate the compressive strength of the concrete incorporating fly ash. Ordinary Portland cement(OPC). Water to binder ratio(W/B) ranging from 30% to 60% and curing temperature ranging from $-10^{\circ}{\sim}65^{\circ}C$ were also adopted for experimental parameters. Fly ash was replaced by 30% of cement contents. According to the results, strength development of concrete contained with fly ash is lower than that of plain concrete in low temperature at early age and maturity. In high curing temperature, the concrete with fly ash has higher strength development than that of low temperature regardless of the elapse of age and maturity. Fly ash can have much effect on the strength development of concrete at the condition of mass concrete, hot weather concreting and the concrete products for the steam curing.

• Advanced Composite Materials
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• 제16권4호
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• pp.361-376
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• 2007

Disposing of conventional fiber-reinforced polymers (FRPs) poses an environmentally challenging problem. Disposal of FRPs by combustion discharges carbon dioxide in the air because the resin of FRPs is made of fossil fuel. When they are disposed of in the ground, FRPs remain semipermanently without decomposing. In response to these problems, green composites are now being developed and are extensively studied as a material that produces a lower environmental burden. In this paper, green composites using kenaf fiber yarn bundles and PLA (poly(lactic acid)) are fabricated and their tensile properties are evaluated in the experiment. The tensile Young's modulus of all of the laminations is larger than that of PLA alone and the tensile strength of some laminations is larger than that of PLA alone. In particular, the value of UD composite of $0^{\circ$ shows double the tensile strength of PLA alone. Furthermore, the molding conditions for fabricating with a hot press are investigated and the heat resistant tensile properties of green composites are also reported.

• 화훼연구
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• 제16권1호
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• pp.17-22
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• 2008

엽연의 모양이 다른 4종류의 잎을 식물재료로 사용하고, 망사잎 제작을 위한 엽육제거시 sodium hydroxide(NaOH)의 농도와 처리시간의 최적 조건을 찾고자하였다. 중국단풍(장상열)은 NaOH 60% 용액에서 50분간, 호랑가시나무(예거치)는 NaOH 20% 용액에서 50분간, 신갈나무(천열)는 NaOH 20-60% 용액에서 70분간, 대왕참나무(전열)는 NaOH 20-40% 용액에서 70분간 열탕 처리하다 엽육제거율도 높고 관상가치가 높은 망사잎을 만들 수 있었다.

• 대한토목학회논문집
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• 제28권6A호
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• pp.881-891
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• 2008

국내 최초로 시공되는 롤러다짐 콘크리트 댐(RCD)의 온도균열 관리방안 수립하기 위하여 RCD 공법의 시공특성인 층(layer) 타설 방식을 고려하여, 댐체의 온도분포 및 온도응력 해석을 수행하였다. RCD 공법은 수 백 개의 시공단계로 구성되어 있고, 실제 타설 층을 시공단계로 해석하는 것과 6층을 한 시공단계로 시공하는 경우를 비교하여 해석 단계의 단순화 가능성을 검토하였으며, 단위시멘트량이 $130kg/m^3$ 내외로 발열량이 매우 작은 RCD 배합의 경우에도 여름철에는 온도균열 지수가 1.0 이하로 나타나 온도관리의 필요성을 확인하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.334-336
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• 2013

In this study, the temperature history was evaluated for the improved bubble sheets combining hot wires and PE films, which were developed under the extreme environmental condition of -10℃ and applied on the top surface of slab to prevent initial damage by freezing. Results can be summarized as follows. If improved bubble sheets combining hot wires with different capacity on double and quadruple bubble sheets are used, the temperature history for all materials decreased to 2~3℃ below zero but all test materials except Type 1 secured the accumulative temperature of 45° D·D at 7 days of material age, required for the prevention of initial freezing damage. This indicates the bubble sheets can prevent the initial damage by freezing.

• 한국지반신소재학회논문집
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• 제19권4호
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• pp.21-32
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• 2020

세계적으로 대규모 인프라 구조 건설 시장이 확대됨에 따라 극한지 및 극서지와 같은 극한 환경에서의 토목 구조물 시공이 계획 혹은 시공 중에 있다. 이에 따라 구조물의 지지력 확보를 위한 말뚝 기초의 시공이 필수적이나 극한지 및 극서지의 지반 변형 가능성으로 인해 말뚝 기초의 안정성 및 기능 상실이 우려된다. 따라서 본 연구에서는 새로운 형식의 말뚝 기초를 개발함으로써 지반 변형에 대응하고자 하며, 극한지 및 극서지에서 발생 가능한 지반 변형을 크게 융기 및 침하로 구분하였다. 지반 변형 대응형 말뚝은 강관 말뚝 내부에 수축 및 팽창이 가능한 실린더가 삽입된 형태로 융기 및 침하 과정에서 실린더의 거동에 따른 말뚝 영향을 수치해석적으로 분석하였다. 수치해석 결과 지반 융기는 말뚝의 과도한 인장응력을 발생시켰으며, 실린더의 팽창 조건은 말뚝에 작용하는 인장 응력을 분담해 주어 전체적으로 말뚝에 작용하는 축 응력을 감소시켰다. 지반 침하는 부주면 마찰력 발생에 따른 말뚝의 압축응력을 증가시켜 주었는데, 실린더는 중립점 이하에 위치하여 수축 거동 시 최적의 효율을 보여주었다. 하지만 지반 변형 대응형 말뚝 시공 시 수축 및 팽창량은 상부 구조체의 허용 변위 범위를 준수하여야 하며, 설계 시 이에 따른 고려가 필요할 것으로 판단된다.

• 한국농촌생활과학회지
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• 제5권1호
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• pp.1-8
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• 1994

온랭 열 자극에 대하여 인체의 말초 혈류량과 심박수가 어떻게 반응하는가를 관찰하기 위하여 건강한 성인 여자 4명을 피험자로 실험군과 비교군으로 나누어 실험을 실시하였다. 실험군은 온랭열 자극의 단기 훈련을 12회 실시하고 비교군은 실험군의 초기와 말기 2회 실시하여 얻은 결과를 비교ㆍ검토하여 다음과 같은 결과를 얻었다. $\circled1$ 실험군에서의 손가락 혈류량의 초기 반응은 훈련 후에 민감해졌다. $\circled2$ 심박수는 냉수 노출시보다 온수 노출시 증가하였다. $\circled3$ 실험군과 비교군간에는 혈류량의 변화 형태와 심박수에 차이가 있었다. 이상에서 E-군과 C-군의 혈류량과 심박수에서 차이를 나타낸 것은 단기 훈련 효과에 의한 것으로 추정된다.

• 한국환경보건학회지
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• 제27권4호
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• pp.107-114
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• 2001

The number of covered carts selling snack foods along the streets are increasing in Korea and people enjoy eating foods at these carts. However there are only a few reports on the contamination or sanitary condition of the food carts. This study was performed to investigate the sanitary condition of food and water at the street food carts in the eight major areas of a city. Water and several kinds of food, kimbop(laver rollers) ddeokbokki(stir fried rice cake in hot pepper paste) oemuk(fish cakes) fish cake soup, and soy sauce were collected from four street carts from each of the 8 areas from June to August in 2001 The standard plate counts(SPCs) and coliform groups were examined according to the Food Code of Korea. The nufitness rates of SPCs of the samples were 0~15.6%: 15.6% in kimbop:6.3% in fish cake soup; and 3.1% in water samples SPCs were not detected in some samples. of ddeokbokki, oemuk and soy sauce. The unfitness rates of coliform groups were 0~62.5%; 46.9% in kimbop; 6.3% in ddeokbokki,;22.9% in oemuk 62.5% in fish cake soup; and 3.1% in soy sauce. Coliform groups were not detected in water sample The numbers and unfitness rates of SPCs and coliform groups showed increasing tendencies over time within a day. The higher the air temperature was the more increase of bacteriological growth was observed These results indicate that the level of bacteriological contamination of foods and water in the street carts should be monitored and strict inspection is necessary. There should be legal consequences for serving contaminated food to the public.