• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.197-197
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• 2011

최근 들어 전력 사용량의 증가로 인한 화력발전소의 부산물인 석탄회 중 바텀애시와 각종 공공사업과 관련하여 해마다 현장발생토의 발생량이 지속적으로 증가하고 있는 추세이다. 바텀애시와 현장발생토사를 효과적으로 재활용하는 방법 중 유동성 뒤채움재를 개발하여 활용하는 방안을 모색하기 위한 연구이다. SP로 분류된 흙 현장발생토와 서천 화력발전소에서 발생하는 석탄회 중 입경이 0.9~1.5mm의 바텀애시만을 선별하여 현장발생토와 바텀애시의 비율을 7 : 3으로 변환한 최적배합을 선정하여 강재로 제작된 가로 80cm, 세로 60cm, 높이 90cm의 모형토조를 이용하여 실험을 진행하였으며, 사용상 지하 매설이 되는 관의 거동 특성은 확인하기 위하여 내경 30cm, 두께 8mm의 연선관 중 하나인 PVC관을 원형지하매설관으로 선정하여 배합을 타설하는 과정과 타설 후 7일간의 양생기간을 거친 후 차량하중으로 가정할 수 있는 하중을 가하여 원형지하매설관의 관외부에서 수직방향과 수평방향의 토압과 관내부의 수직 수평방향 변위 그리고 관 자체의 횡 종단 변형을 측정하여 원형지하매설관의 거동특성을 파악하였다. 타설시 지하매설관은 유동성 뒤채움재의 특성으로 인하여 시간이 지남에 따라 안정화되는 것을 확인할 수 있었으며, 최대하중을 3300kgf로 하여 하중 재하 후 지하매설관의 거동특성은 대체적으로 일반 모래를 사용하여 실험한 값보다 적은 변형 특성을 보이고 있으나 수평토압의 경우 일반적인 흙의 변형과 전혀 상이한 결과값을 보이는 경우도 있어 추가적인 실험 및 고찰의 필요하다. 본 실험에서 사용한 최적배합비 이외의 배합으로 같은 실험을 수행하여 바텀애시 량의 가감 및 재활용 재료인 폐타이어 고무칩등을 첨가한 실험을 계획하고 있으며 추후 실내시험과 모형실험을 토대로 유한요소해석을 추가로 시행하여 실험값과 해석값의 비교를 할 예정이다.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.661-669
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• 2000

This research was carried out to evaluate effect of metallic release and change of water corrosive indices by the pH and alkalinity adjustment using the SDLS (Simulated Distribution Loop System) which consist of six types of pipe loop with DCIP, PVC, PE, STS304, CP, GSP, respectively, and its effects on water quality changes which were microbes quality(SPC), residual chlorine. THMs and other parameters. And it was to propose optimal criteria of water quality control for the field application. According to the results, water control system by pH and alkalinity adjustment showed the changing of corrosive water and reducing of metallic release rate and it was not affects of THMs formation, microbes regrowth and variation of other parameters. Water quality stability and corrosion control were due to calcium carbonate precipitation film formation of pipe inner by water quality control. Therefore, corrosive water control system by pH and alkalinity adjustment can be attributed to effective water quality management in water distribution system according to water quality stability of pH and TIC(Total Inorganic Carbonate concentration) that affect the precipitation and dissolution of solids.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.98.1-98.1
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• 2015

G-M극저온냉동기의 구동으로 인해 발생되는 크라이오 펌프의 진동 저감을 위해 각 요소에 해당하는 부품의 소재 및 모델 변경으로 설계에 반영하고자 한다. G-M극저온냉동기는 헬륨냉매를 사용하여 2개의 정압과정과 2개의 정적과정으로 구성되는 냉동사이클을 구성하는데, 구조적 특성상 내부 왕복기의 운동과 고저압변환에 따른 압력차이가 냉동기의 진동을 유발하므로 진공성능에 영향을 줄 수 있으므로, 이를 최소화하는 기술 개발이 필요하다. 헬륨냉매의 고압 유동에 따른 관로 압력증가로 인한 유동소음이 발생하는데, 이로 인한 소음을 줄이기 위해 관로의 최적화 설계/방진구조반영(DAMPER)으로 진동 안정화(Vibration Stabilization)설계를 수행 하고자 하며, 이에 따른 최적화 연구을 수행하고자 한다. 일차적으로, 기존 시스템의 진동측정을 통해 진동의 가진원을 밝히고 진동 전달경로를 파악하고자한다. 진동 가진원의 가진 최소화, 진동전달경로의 전달률 최소화, 고압유동에 따른 관로 설계 최적화를 진동해석, 탄성체 동역학해석, 그리고 유동해석을 통해 진동 및 소음의 최소화 방안을 도출하고자 한다. 해석결과를 토대로 진동가진원의 최소화를 위한 제품설계변경과 진동전달경로에 대한 방진을 위한 dmper 적용(전달률 최소화) 및 유동소음 최소화를 위한 damper나 관로 최적화 설계를 수행한다. 상기 기존시스템 측정/분석, CAE해석을 통한 진동/소음의 최적화방안도출 및 실제품 적용기술은 저진동 크라이오펌프 개발을 위한 기반 기술 확립에 크게 기여할것이며, 향후 크라이오펌프 고도화 및 최신 기술 제품 개발에 큰 기여가 기대된다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2010.04a
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• pp.231-237
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• 2010

소방방재로봇이 2009년 9월부터 대구시 산하 소방서에 배치되어 시범적으로 운용되고 있다. 운용자인 소방관을 대상으로 심층면담과 설문 등을 통해 각종 문제점들과 기능 개선사항을 분석함으로써 현장 적응성, 실효성 있는 로봇의 개발방향을 제시하고자 했다. 소방관 보조로봇은 조종 편의성을 높이고, 장애물 통과 및 이동성이 용이하도록 바퀴 성능을 우선적으로 개선하여야 하며, 소방 필드로봇은 조종 편의성을 높이고, 무게의 경량화와 아울러 제어 통신선 꼬임을 방지하기 위한 무선통신방식을 안정화할 필요가 있는 것으로 분석되었다. 현재 운용중인 로봇에 대한 기능 만족도는 전반적으로 낮으며, 보조로봇에 대해서는 현장 투입의사가 8.4% 수준으로 미미하였다. 이에 소방방재로봇의 조기 상용화를 이루기 위해서는 현장에서의 사용 활성화가 우선되어야 하며 이를 통해 국내 로봇산업의 성장과 경쟁력을 높일 수 있을 것이다.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.4
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• pp.284-290
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• 2017

For individuals with cleft lip and palate, the removable partial dentures (RPDs) have been an important treatment option. Some modifications from conventional prosthetic treatment may be necessary to achieve satisfactory functional and esthetic results in cleft patients. In case of cleft palate patient with periodontally compromised and only posterior few remaining teeth, removable partial prosthesis connected to telescopic crown can be the alternative treatment option. When connected to the RPD, telescopic crowns increase the prosthetic stability and retention, optimize favorable force transmission to the long dental axis, and improve esthetics. And the cross arch stabilization of double crown denture helps to stabilize both divided maxillary ridges in CLP patient. This case present one adult CLP patient using an RPD connected with hybrid telescopic crowns with friction pins to improve not only retention and stability but also aesthetics.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.3
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• pp.57-63
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• 2002

This paper describes a control algorithm for the buffer of a deep-sea mining system, in which the buffer is connected to a long slender pipe and then to a surface ship on one end, and to a collector on sea floor through a flexible hose on the other end. A mathematical modeling is established for designing the controller for buffer thrusters, in which the dynamic response of the long pipe is taken into account based on the mode superposition method. The fluid loading acting on the pipe is estimated by using Morison's formula. For simplicity, the surface ship is assumed to be kept stationary, the reaction from the flexible hose is ignored and only the lateral motions are considered. In order to guide the buffer to react only to the low-frequency motion of the surface vessel, the FIR digital filter is introduced to a PID-based controller It can be shown numerically that the high frequency component of the ship's motion can be effectively filtered out by using the FIR low pass filter.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.11
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• pp.916-923
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• 2009

The effects of configuration of fuel and air tubes on the flame stabilization were experimentally investigated in half-closed combustors. Flame behaviors and stabilities of methane, propane, and DME flames were compared by changing tube diameters and the locations of the fuel and air tubes. It was found that flammability limits are significantly affected by the outlet boundary condition, which disturbs compositions of burned and unburned mixtures near the flame base. And it was found that there exist critical inner tube heights, over which flame stability is determined only by the fuel flow rate. Conclusively, flame stabilization is governed by the flame propagation velocity in an ordinary mixing flow and the non-uniform mixture concentration in the combustion space which is affected by flow recirculation and the combustor configuration. The compositions of $NO_x$ and CO were compared to know basic characteristics of methane, propane, and DME flames.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.3
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• pp.23-33
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• 2016

The characteristics of ammonia generated from alkaline stabilization facilities was investigated which are for organic sewage sludge from wastewater treatment plants. The highest concentration of ammonia was found in mixing and curing process in alkaline stabilization facility and ammonia mainly showed a range of 87.78 ppm($66.62mg/m^3$) to 1,933 ppm($1,467.01mg/m^3$) by detection tube. This is presumed to occur because nitrogen oxides are converted into ammonia as the sewage sludge is mixed with lime. In some facilities, hydrogen sulfide and methyl mercaptan were detected in relatively high concentrations, but odor materials except ammonia were not detected in most of the facilities. The concentration of ammonia caused by process was generally high in the order of "mixing > curing > output > storage > drying > input." It was found that odor compounds are removed by wet absorption using sulfuric acid and sodium hypochlorite in the 5 alkaline stabilization facilities currently in operation. Each facility was designed to meet the concentration of after-treatment emission in 1 ppm($0.76mg/m^3$), 50 ppm($37.95mg/m^3$) or 100 ppm($75.89mg/m^3$), but no facility satisfied the design standard for their emssion limit. In case of ammonia, some workplaces in alkaline stabilization facilities exceeded the exposure limits established by the Ministry of Labor. It appears that proper ventilation should be provided for the safety of workers in future. No odor compound including ammonia was found by detection tubes in the border of the facilities, but trace amounts of odor compounds are expected to exist, given the current operational status of facilities.

• Korean Journal of Comparative Education
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• v.18 no.4
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• pp.113-139
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• 2008

The purpose of this study is to analyze the operating case of admission officer system of colleges and universities in USA, and to deduce its implications to Korean colleges and universities. In order to accomplish the purpose of this study, following methodologies were adopted: review on the related literatures, statistical data, and previous studies concerning admission officers of colleges and universities in USA, and in-depth interview with them. Historical and cultural background of university admission system of USA was analyzed. Case study on USA colleges and universities was divided with four parts such as determining factors of admission and admission methods, organization for admission affairs and its number of persons, work of admission officer and admission process, and cost of admission and salary. Implications to Korean colleges and universities were presented with three points such as overall implication, implication on materials for admission process, and implication on managing system of admission. Based on the analysis, discussion and implications, the conclusion and further suggestion of this study are as follows: First, actual authority of admission should be grant to admission officer. Second, not only non-curricular factors but also scholastic factors should be emphasized in role of admission officer. Third, education and training about work of admission officer and unification of criteria for admission should be held. Fourth, admission officers with various occupation background are needed. Fifth, work of admission officers should be extended to various work concerning university entrance. Sixth, cross-checking on marks of over two admission officers is needed. Seventh, in order to stabilize admission process, status of admission officer should be stabilized. Eighth, part-time admission officers are need to employ in season of admission. Ninth, authority of weighting high schools should be grant to admission officers in long term perspective.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.2
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• pp.18-24
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• 1999

Liquid ramjet combustor is closely connected with complex phenomena due to a series of processes such as intake air, spray, mixing, and combustion. The present numerical experiments were peformed to investigate these flow characteristics for two and three dimensional liquid ramjet combustor. Grid system was made with three domains: intake region where air is supplied and fuel is injected, combustor and nozzle region, and exit atmosphere region. The numerical results showed that two and three dimensional flow patterns in recirculation region of combustor were significantly different each other and spray model was necessary to predict correctly the chemical reaction flow characteristics. Numerically examined for two different location of fuel injector, one is located on the bottom position of curved intake and the other is located on the top position. We found that bottom position of fuel injector is better than top position because fuel influx to the recirculation region which is need to sustain chemical reaction is more than the latter.