• International Journal of Air-Conditioning and Refrigeration
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• 제6권
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• pp.136-147
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• 1998

An experimental facility consisting of two 3$\times$4.4$\times$2.8m rooms identical in construction is built. Each room has a control system and storage tank supplying hot water to the radiant floor heating system. The facility enables simultaneous comparison of two different control strategies each implemented in a separate room. The operating performance of three kinds of flow control scheme is tested and compared in this study: (ⅰ) conventional on-off control based on feedback from room air temperature (ⅱ) TPSC(two parameter switching control )(ⅲ) TPOC(two parameter on-off control). Results show that TPSC and TPOC using room air and surface temperature sequentially as feedback signal to control hot water supply is the better temperature regulation scheme than conventional control based on feedback from only room air temperature. They are good candidates for the room with radiant floor heating system under continuous and intermittent heating mode.

• 항공우주기술
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• 제5권2호
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• pp.85-89
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• 2006

우주비행체의 추진시스템은 주차 궤도에서 임무 궤도도의 진입을 위해 필요한 임펄스 및 궤도에서의 3축 자세제어에 요구되는 적절한 임펄스를 제공하는 역할을 수행한다. 새로운 저궤도위성 추진시스템은 용접으로 조립된 단일추진제 하이드라진 시스템으로 추력기, 추진제 템크, 압력변환기, 추진제 필터, 격리밸브 및 충전/배출 벨브 등의 주요부품들로 구성되며, 그외 각 부품들을 연결해주는 추진제 배관과 열제어 부품들이 추가된다. 이 논문에서는 저궤도위성 추진시스템의 예비 설계과정이 서술되었다.

• Journal of Electrical Engineering and Technology
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• 제6권6호
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• pp.842-848
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• 2011

The current study proposes the design of a hybrid series-parallel resonant converter (SPRC) and a three-stage Cockcroft-Walton voltage multiplier for precisely adjusting the power generated by a continuous wave (CW) $CO_2$ laser. The design of a hybrid SPRC, called LCC resonant converter, is described, and the fundamental approximation of a high-voltage and high-frequency (HVHF) transformer with a resonant tank is discussed. The results of the current study show that the voltage drop and ripple of a three-stage Cockcroft-Walton voltage multiplier depend on frequency. The power generated by a CW $CO_2$ laser can be precisely adjusted by a variable-frequency controller using a DSP (TMS320F2812) microprocessor. The proposed LCC converter could be used to obtain a maximum laser output power of 23 W. Moreover, it could precisely adjust the laser output power within 4.3 to 23 W at an operating frequency range of 187.5 to 370 kHz. The maximum efficiency of the $CO_2$ laser system is approximately 16.5%, and the minimum ripple of output voltage is about 1.62%.

• 수산해양기술연구
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• 제40권1호
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• pp.78-85
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• 2004

SSBL ${\circ}$ 핑거동기 바이오텔레메터리 방식과 시스템을 사용하여 핑거를 부착한 어류의 행동 추적실험을 실시하였다. 이상의 연구 성과를 정리하면 다음과 같다. 1) 수조의 추적실험에서는 어류의 대략적인 행동을 관측할 수 있기 때문에 어류의 이동경로의 계측치와 대체적인 관측치를 비교하면서 어류의 이동경로와 속도 등을 조사하였다. 계측한 잉어의 행동이 관측치와 대체적으로 일치하였으며, 3차원으로 추적이 가능하였다. 잉어의 평균 이동속도는 11.2cm/s로 거의 적당한 결과를 얻을 수 있었다. 2) 계류장의 추적실험에서는 상하, 좌우 방향으로 회전가능한 지지 파이프에 수파기를 설치하고 수파기를 회전시키며 자연상태에서 어류의 이동경로와 속도 등을 조사하였다. 방어의 행동이 상세하게 추적 가능함을 확인할 수 있었으며, 방어의 평균이동 속도는 439cm/s이었다. 이상에 의해 본 연구에서 개발한 SSBL ${\circ}$ 핑거동기 바이오텔레메터리 방식에 의하면 수신계의 고도화만으로도 핑거를 부착한 어류의 상세한 행동추적 이 가능함을 확인할 수 있었다.

• 농촌의학ㆍ지역보건
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• 제13권1호
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• pp.19-25
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• 1988

It is very important to supply safe drinking water for rural area not only a prevention of entric diseases but also a promotion of health life. It is estimated that 6,981,000 rural inhabitants were covered by the simple piped water supply system at the end of 1987 in Korea. The programme for improvement of water supply system in rural villages was initiated by the government since 1967. But most of these systems have been operated carelessly by the hands of villagers who have no proper knowledge and experience. Since most of water sources were located nearby farmland, there might be a possibility that the sources could be contaminated by pesticides and fertilizers. For this reason, it is recommended to take underground water as a water source rather than surface water such as a pond or streamwater in rural areas. However, the system is supplied from the surface water, its water quality can be improved by using of simple sand filter and simple chlorinator inexpensively. On the basis of an on-site study, conducted during 1986-87, in San-Buk Village, Keum-Sa-Myon, Yeju-Gun, Kyong-Gi-Do, the new simple piped water supply system was designed by the Institute for Environmental Research, Yonsei University, and constructed by the villagers themselves in September 1987. This simple system which is protected by metal fences consists of three main parts, pump house, vertical sand filter and water tank. The pumped water from underground flows into the upper part of the sand filter, through the sand, and out the water tank which is connected to the bottom of vertical filter. And the simple plastic-bottle chlorinator was installed in the water tank for chlorination. The water quality was remarkably improved after completion of construction. The total bacterial count was not detected from the tap water in households distributed by this simple piped water supply system. The construction cost of this system which was connected 34 households in San-Buk Village, was 4,851,000 won (approximately 6,020 U.S. dollars : 1$=805.8 won) in 1987,77% of expenses was supported by the Community Development Foundation in Korea. This case study for simple piped water supply projects will be applicable to other programme for improvement of water supply system in rural areas of Korea, and other developing countries.

• 상하수도학회지
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• 제16권6호
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• pp.670-678
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• 2002

Since Korean government imposed a stricter regulation on effluent T-N and T-P concentrations from wastewater treatment plant, a new process has to be developed to meet these rules and this process should remove T-N and T-P, economically, from weak wastewater that is typical for Korea's combined sewer system sewage. In this study, a computer simulator, BioWin from EnviroSim, Inc. was used. Three processes - A2/O, Modified Johannesburg, UCT- had been simulated under same operational conditions and a new process - Parallel BNR Process - had been developed based on these simulation results. The Parallel BNR process consists of two rows of reactors: One row has anaerobic and aerobic reactors in series, and the other row has RAS anoxic1 and RAS anoxic2 reactors in series. In order to ensure anaerobic state in anaerobic tank, a part of influent is fed to RAS anoxic1 tank in second row. This process had been simulated under same conditions of other three processes and the simulation results were compared. The results showed that three existing processes could not perform biological phosphorus removal when the average influent was fed at any operation temperatures. However, the Parallel BNR process was found that biological phosphorus removal could be performed when both design and average influent were fed at any operation temperatures. This process showed the T-N concentration in effluent had a maximum value of 15mg/L when design influent was fed at $13^{\circ}C$ and a minimum value of 14mg/L when average influent was fed at $20^{\circ}C$. Also, T-P concentrations had a maximum value of 1.3mg/L when average influent was fed at $20^{\circ}C$ and a minimum value of 1.1mg/L when design influent was fed at $13^{\circ}C$. Based on these results, we found that this process can remove nitrogen and phosphorus biologically under any operational conditions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.260-265
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• 2001

This paper describes total flow control of an ice slurry system for pump energy saving. Similar turbo machinery has a characteristic that input power ratio is proportional to the three time of revolution speed ratio. To reduce the energy cost of brine pump in ice slurry storage systems, inverter is adapted instead of 3-way valve to control the speed of brine pump motor. One type of cooling load profile was used as driving load of the system, generated by a boiler and warm water storage tank. As results of the laboratory test, energy consumption and cost of the pump were reduced by 11.4%.

• 생태와환경
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• 제42권2호
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• pp.153-160
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• 2009

비점오염원으로부터 오염된 소하천에서 영양염류를 제거하기 위하여 식물플랑크톤 배양 장치를 설치하고 운영하였다. 식물플랑크톤 배양조에서 식물플랑크톤 정치배양 결과, 식물플랑크톤의 연속배양을 위한 배양조의 체류 시간을 3일로 결정하였으며 TP는 70%, TN은 44%가 제거됨을 확인하였다. 연속배양 결과 45일 동안 배양조에 유입된 TP의 53.9%, TN의 53.1%가 식물플랑크톤에 의한 흡수와 슬러지로 제거되었다. 식물플랑크톤이 성장하면서 배양조의 pH와 용존산소농도는 각각 평균 10.8, 16mg $L^{-1}$이었다. 결국 비점오염원에 오염된 하천수의 영양 염류는 식물플랑크톤의 사체와 화학반응으로 생성된 침전물로 제거되었다. 비교적 설치가 간단하고 경제성이 높은 식물플랑크톤 배양법의 높은 현장적용 가능성을 확인하였다.

• 한국농공학회지
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• 제35권3호
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• pp.23-35
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• 1993

The objectives of this paper were to validate the proposed network flow model using field data and to demonstrate the model applicability for various purposes. The model was tested with data from the Banweol watershed, where an intentive streamflow gauging system has been established. Model parameters were not calibrated with field data so that it can be validated as ungaged conditions. Three different schemes were employed to represent the drainage system of the tested watershed : a single, complex, and detailed network. The single network assumed the watershed as a cell, while complex and detailed networks considered several cells. The results from different schemes were individually compared satisfactorily to the observed daily stages at the Banweol reservoir located at the outlet of the watershed. The results from three schemes were in close agreement with each other, Justifying that the model performs very well for different network schemes being used. Daily streamflow from three network schemes was compared for a selected reach within the watershed. The results were very close to each other regardless of network formulation. And the model was applied to simulate daily streamflow before and after the construction of a reservoir at a reach. The differences were discussed, which reflected the influences of the dam construction upon the downstream hydrology. Similar appliocations may be possible to identify the effects of hydraulic structures on streamflow.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.237.2-237.2
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• 2010

Although oscillating water column type wave energy devices are nearing the stage of commercial exploitation, there is still much to be learnt about many facets of their hydrodynamic performance. The techniques of Computational Fluid Dynamics (CFD) are applied to simulate a wave energy conversion device in free surface such as waves. This research uses the commercially available ANSYS CFX computational fluid dynamics flow solver to model a complete oscillating water column system with savonius turbine incorporated at the rear bottom of the OWC chamber in a three dimensional numerical wave tank. The purpose of the present study is to investigate the effect of an average wave condition on the performance and internal flow of a newly developed direct drive turbine (DDT) model for wave energy conversion numerically. The effects of blade angle and front lip shape on the hydrodynamic efficiency are investigated. The results indicated that the developed models are suitable to analyze the water flow characteristics both in the chamber and in the turbine. For the turbine, the numerical results of torque were compared for the all cases. The results of the testing have also illustrated that simple changes to the front wall aperture shape can provide marked improvements in the efficiency of energy capture for OWC type devices.