• Proceedings of the Korean Radioactive Waste Society Conference
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• 2010.10a
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• pp.407-408
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• 2010

• Journal of Aquaculture
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• v.7 no.3
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• pp.177-187
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• 1994

The objective of the present study were to evaluate nitrification characteristics and determine optimum treatment conditions of three phase fluidized bed reactor for recycling water treatment of aquaculture. When the loading rates were 2.739-0.086kg $COD/m^3/day$ and 1.575-0.128kg $NH_4\;^+-N/m^3/day$, COD and ammonia removal efficiencies were $56.3-94.7\%\;and\; 67.3­92.6\%$, respectively. The maximum removal rates of COD and ammonia were 1200mg/l/day and 488mg/l/day, respectively. Ammonia removal rates were more than $90\%$ beyond 1hr HRT. The ammoniaremoval efficiency was sensitive to the variation of media concentration and air flowrate.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.403-404
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• 2009

This study has investigated application of the industrial by-product of reject ash and recycled fine aggregate to consider the economical issue to high flowing CLSM(controled low-strength material). But this high flowing CLSM is required more binder, so it has been estimated the influence of reject ash content, use of recycled fine aggregate and crushed sand, and air content about properties of CLSM.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.12
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• pp.821-827
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• 2012

Air drying is a technology to dry sludge at the ejector and multi cyclone as intaking and blowing air from outside. So, this technology has a weak point that operating fluctuation is large according to an outside conditions as well as energy consumption is also large due to open loop structure. This is to develop the closed-loop air drying system to be built the dehumidifier consisted of condenser, cooler and compressor at rear side of separator of air dryer, as a way to solve some problem. Air is circulation by the method of blowing-drying-dehumidifying-blowing within this system. It is analyzed that an air circulated at closed-loop air drying equipment contains the energy of 50% more compared with open-loop air drying and is operated regularly because of quality maintenance of air to dry sludge. And also it is analyzed that the cost of drying sludge of 1 ton by closed-loop air drying equipment is lower about 35% than conventional equipment. Therefore, this is evaluated by useful drying technology to face an unexpected climatic conditions due to regular operation as well as low energy consumption.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.198-203
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• 2020

Cracking due to material behavior like drying shrinkage easily occurs since tensile strength in concrete is very low at initial curing stage. In this paper, workability such as air content and slump was evaluated on CFC(Cellulose Fiber Concrete) with 0.0 ~ 2.0% of fiber addition, and the tests for tensile/compressive strength were performed. With increasing addition ratio of fiber, air content and slump kept similar level to 1.0kg/㎥ of addition ratio, and this trend was effective to 2 hours after mixing. Strength was enhanced with increasing addition ratio, which showed 7.0 ~ 9.0% for compressive strength and 7.0 ~ 22.0% for tensile strength, respectively. The tensile strength increased relatively more, which show the addition of cellulose fiber was very effective to crack resistance. The workability in CFC can be guaranteed for 2 hours in the following conditions like 2 minutes of mixing period and 1.0kg/㎥ of addition ratio of fiber.

• Journal of the Society of Disaster Information
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• v.9 no.4
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• pp.469-475
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• 2013

The purpose of this experimental research is to estimate compressive strength and resistance to freezing and thawing of recycled aggregate concrete containing ground granulated blast furnace slag. For this purpose, concrete specimens according to substitution ratio of recycled aggregate were made for different replacement ratio of ground granulated blast furnace slag(GGBFS), and then compressive strength and resistance to freezing and thawing were evaluated for those. It was observed from the test results that compressive strength at 28 days of recycled aggregate concrete containing GGBFS of 20% was much more excellent than plain concrete and when air content of concrete was maintained 4 to 6%, influence of substitution ratio of recycled aggregate and replacement ratio of GGBFS on resistance to freezing and thawing was little up to 300 cycles of freezing and thawing.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.516-525
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• 1994

Since the TMI and Chernobyl accidents, many passive safety features are suggested in advanced reactors in order to enhance the safety in future nuclear power plants. In order to verify the effectiveness and provide the data for detailed design of passive cooling system, in the present work, the effects of air inlet position and external condition on the natural circulated air flow rate and the natural and forced convective heat transfer coefficient have been investigated for the one-side heated closed path such as the passive containment cooling system of the Westinghouse's AP-600. A series of experiments have been peformed with the 1/26th scaled segment type test facility of the AP-600 passive containment. Under natural and forced convection, the air velocities and temperatures are measured at several points of the air flow path. The experimental result are compared with a simple one-dimensional model and it shows a good agreement.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.01a
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• pp.241-242
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• 2019

본 논문에서는 기존의 드론의 문제점을 보완하기 위한 모델을 제안한다. 기존 드론들의 태생적인 프로펠러 사용으로 인해 안전사고의 위험성, 프로펠러 파손으로 인한 소모성, 비행을 위한 프로펠러의 소음 등의 한계를 근본적으로 제거하여 단점을 최소화하고 성능의 감소를 최소화하여 차세대 드론모델의 한 방법을 제시한다. Bladeless fan 의 원리를 이용하여 프로펠러를 내부로 이동시키고, 하나로 줄임으로써 상승하는 안정성, 소모성, 장소의 제약을 해소할 수 있게 한 후에, 터보 팬 엔진의 원리를 이용한 공기의 압축과 내부 유속의 상승을 이용하여 내부의 순환 바람으로 인한 서브 날개의 바람 출력 상승을 시켜, 기존 드론의 추력을 얻게 하고 단점을 보완하게 한다. 본 논문에서는 기존 드론의 단점을 보완한 모델로써, 기존 드론과 같은 역할을 수행할 수 있고 장소의 제약, 상해사고의 위험성, 프로펠러의 소모성 면에서 효과적으로 우수함을 보인다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.322-324
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• 2008

현재 배전용변전소 대용량변압기 냉각방식은 주로 유입자냉식, 유입풍냉식, 송유풍냉식 및 수냉각 방식이 채용되고 있다. 유입풍냉식의 경우는 대기 공기의 자연대류 또는 냉각팬에 의한 강제대류에 의해 방열기 내부로 유입된 절연유의 온도를 낮추는 방식이고 송유풍냉식은 변압기 내부 절연유를 강제순환 시키면서 냉각팬을 가동하는 방식이다. 도심지 복합건물내 주변압기 냉각은 수냉식을 채용하여 절연유를 강제로 순환시키면서 열교환기 2차측에 냉각수를 순환시켜 열교환기 내로 유입된 절연유의 온도를 낮추는 방식이다. 그러나 도심지 변전소의 냉각방식 채택에 있어 냉각성능, 소음, 설비의 건전성등 여러 가지 문제점이 드러나 새롭고 획기적인 냉각방식이 요구되고 있다.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.259-261
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• 2007

논문은 동해화력발전처의 이차공기송풍기를 가변 회전수 제어하여 소내 소비 전력을 절감하고 전동기의 직입기동에 의한 스트레스를 줄이기 위하여 실증 적용된 동해화력발전처 이차 공기 송풍기 구동용 H-브릿지 멀티레벨 인버터에 관한 것이다. H-브릿지 멀티레벨 인버터는 독립적으로 절연된 직류 부를 갖는 저압의 단상 인버터(셀 인버터)를 다수 직렬 접속하여 고압 3상 전압을 출력하는 Cascaded H-브릿지 전압형 인버터이다. 본 논문에서는 동해화력발전처에 실증 적용된 6.6kV, 1MVA급 인버터의 계통 병입 후 부하 변동 시험을 통하여 신뢰성을 입증하였다.