• Fire Science and Engineering
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• v.33 no.1
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• pp.30-38
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• 2019

Mixing characteristics and backdraft dynamics were investigated using large eddy simulation for compartments initially filled with methane fuel. Four different opening geometries, i.e. conventional door opening case (Door) and the cases where horizontal door was implemented on the upper ($Slot_U$), middle ($Slot_M$) and lower part ($Slot_L$) of side wall, were considered in the simulations. For cases without ignition, the amounts of inflow oxygen and outflow fuel from the compartment opening were, from largest to smallest, Door > $Slot_U$ ~ $Slot_M$ > $Slot_L$. However, the fuel and oxygen were the best mixed for the $Slot_U$ case while the fuel and oxygen were not well mixed and in relatively separated two layers for the $Slot_L$ case. The global equivalence ratio defined by the amounts of fuel and oxygen in the compartment was not correlated reasonably with the peak pressure of backdraft. The peak pressure during backdraft was the highest for the $Slot_U$ case, a well mixed condition of fuel and air, and backdraft was not found for the $Slot_L$ where the pressure rise was not so high due to the mixing status. The peak pressures for the Door and $Slot_M$ cases were in between Door and $Slot_L$ cases. The peak pressure during backdraft was well correlated with the total amount of heat release until the instance of backdraft occurrence.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.254-254
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• 2017

수자원장기종합계획은 수자원의 안정적인 확보와 효율적인 이용 개발 및 보전을 위하여 "하천법" 제23조에 근거하여 수립되는 물 분야의 최상위 법정계획이다. 수자원장기종합계획은 20년 단위로 수립되며, 5년마다 그 타당성 여부를 검토하여 필요한 경우에는 계획을 변경하고 있다. 국토교통부는 지난 2016년 12월 수자원장기종합계획 제3차 수정계획(2016~2020년)을 수립 고시하였다. 그런데 수자원장기종합계획과 같이 상위 개념의 법정계획의 수립을 위해서는 관련 법정계획 및 부처 간의 수평적 수직적 연계가 중요한데, 현행 법체계는 이에 미흡한 측면이 있어 보인다. 우선적으로 수평적 연계를 위해서는 수자원장기종합계획 수립과정에 이수 치수 및 방재 분야의 업무를 담당하고 있는 관련 부처의 적극적인 참여를 독려할 필요가 있다. 현재 "하천법" 제23조제4항은 수자원장기종합계획을 수립하거나 변경할 경우, 중앙행정기관의 장과 협의하도록 규정하고 있다. 그러나 현행 규정에 따른 부처별 '협의'는 국토교통부가 수자원장기종합계획을 수립한 후 관련 부처의 의견을 수렴하는 소극적 형태의 협의라고 볼 수 있다. 효율적인 수자원장기종합계획 수립을 위해서는 "하천법" 소관 부처인 국토교통부가 수자원장기종합계획 수립을 위한 기본적인 지침을 수립하여 관련 중앙부처인 환경부(환경), 국민안전처(치수), 산업통상자원부(공업용수) 및 농림축산식품부(농업용수)에 시달하고, 각 부처는 담당 분야별 계획을 수립하여 국토교통부에 송달한 후, 국토교통부는 이를 취합 검토하여 수자원장기종합계획을 수립하는 적극적 형태의 연계를 고려할 필요가 있다. 수직적 연계를 위해서는 기존의 하향식(top-down)에서 벗어나 상향식(bottom-up)의 계획수립이 필요해 보인다. 즉 국토교통부의 수자원장기종합계획 수립에 따라 하위 개념의 유역종합치수계획("하천법" 제24조) 및 댐건설장기계획("댐건설 및 주변지역지원 등에 관한 법률" 제4조) 등을 수립하는 것이 아니라, 지역별 유역별로 수자원계획을 우선적으로 마련하도록 하고 이를 기초로 전 국토를 대상으로 하는 수자원장기종합계획을 수립하는 방안이 적절해 보인다. 이를 위해서는 수자원장기종합계획 수립하기 이전에 지역별 또는 유역별로 수자원계획을 수립할 수 있도록 "하천법"에 관련 규정을 신설할 필요가 있으며, 이수뿐만 아니라 환경, 방재 분야의 하위 법정계획의 수립 시기 및 주요 내용에 대한 종합적인 검토가 요구된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.15-15
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• 2023

2020년 기준 국내 상수도 보급률은 99.1% 차지하고 있으며(환경부, 2019), 수도관리차원에서 수돗물은 먹는 물로 시판되어질 만큼 우수한 관리체계를 유지하고 있다. 그 반면에 지하수는 생활용수, 식품가공, 농·축산, 양어, 군부대를 비롯한 전국지역에서 연간 10억 8천만톤 용수를 소비하고 있음에도 (환겨례 신문, 2013; 환경부, 2019) 사용되는 지하수의 약 65%가 음용수 불가판정을 받았으며, 최근 지하수의 오염비율은 급격히 증가하는 추세이다. 특히, 지하수관정의 관리부주의에 의한 수질오염 및 수인성 다제내성균(슈퍼박테리아) 등에 의한 오염사례가 국내는 물론, 국제적으로 다수 보고되고 있는 실정이다 (환경부, 2013). 현재 지하수 수질관리는 공공기관 및 지자체 지정기관을 통해 진행되고 있으며, 검사기간은 수질채취로부터 통상 7~15일정도 소요되어 수질 관리 및 기준, 검사주기에 대한 애로가 많다. 현장 지하수관정에서 실시간 수질을 모니터링하고 이에 연동된 자동 수처리 시스템의 개발 및 도입은 나날이 심각해지는 환경오염 상황에서 선제적 예방과 해결방법으로 중요한 요소기술이다. 현재 지하수오염 및 부적합 음용의 수질처리는 화학약품, 필터여과, UV살균, O₃ (플라즈마)을 이용하는 것이 대표적이나, 화학약품의 경우 2차 오염이나 식품 세척 및 가공에 있어 부적합성의 한계점이 있다. 필터여과의 대표적인 RO필터의 경우 약 50% 순손실이 발생하고, UV 살균의 경우 UV에 의한 사용관리자의 위험 및 장비의 광부식 문제, O₃ 의 경우 고압전류 사용에 따른 위험성 등의 한계점이 나타나고 있다. 지하수 수질정화를 위한 광유도 활성산소(¹O₂, ·O^-₂)는 광감응제에 가시광의 빛 조사를 통해 생성되는 활성산소로의 에너지 및 전자 전이가 동시 진행되어 단일항 산소(¹O₂)와 슈퍼옥사이드 이온(·O^-₂)을 생성하게 된다. 생성된 활성산소는 유해미생물 또는 유기화학물과 개열, 제거, 치환 반응 등을 통해 미생물사멸 및 유해화학물질들이 분해 가능하다. 이를 이용한 지하수 유해미생물 사멸기술, 장비, 실시간 지하수의 분석기술 및 정수처리, 지하수 물순환 시스템 개발뿐만 아니라 지하수 음용수 및 오염개선, 지하수 기저유출에 의한 오염원 저감으로부터 지류·지천, 하천 본류 수질개선 등의 대상지역에 활용 가능하다. 또한 광유도 활성산소는 기존 상수도 수처리에 있어 오존(O₃) 처리와 이산화티탄을 이용한 AOP과정을 단일처리 공정으로, 기존 O₃ 의 특성상 확산 거리가 매우 길어 사람을 포함한 생체 내에 유입 시 다양한 부작용 발생과 O₃ 차폐시설 요구의 문제점 극복의 대안으로 환경 및 인체에 무해한 광유도 활성산소 시스템을 적극적으로 도입 및 적용해야 한다. 본 연구 목적은 정류상태 흡광분광기술을 이용한 실시간 수질 모니터링과 광유도 활성산소를 이용한 유해 미생물의 멸균효능 및 지하수 수질관리 기술로의 적용 가능성을 제시하고자 한다.

• Journal of the Korea Institute of Building Construction
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• v.23 no.4
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• pp.465-476
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• 2023

This study introduces the development of a precast concrete double-wall, applicable to basement construction in apartment buildings. Unlike traditional precast concrete double walls, the developed double-wall doesn't require specialized manufacturing equipment such as a lathe. The constructability of these advanced technologies was validated through a full-scale mock-up test using the precast concrete double wall. The test specimens were constructed to represent a structural wall with a thickness of 250mm. It was observed that the quality of the in-situ concrete, filled between two single panels of 110mm thickness each, was excellent. The construction efficiency of the developed double-wall system for basement construction in an apartment building was also examined. Expert interviews about installation times of precast concrete elements were conducted to evaluate the speed of the basement floor's installation. The results showed that installation of precast concrete elements, including the proposed double walls, could be completed within 20 to 29 days for a basement in an apartment building. This indicates a three-fold increase in construction efficiency compared to traditional methods relying on in-situ casting.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.269-281
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• 2008

Fatigue or overload can result in mechanical problems of implant components. The mechanical strength in the implant system is dependent on several factors, such as screw and fixture diameters, material, and design of the fixture-abutment connection and abutment. In these factors, the last rules the strength and stability of the fixture-abutment assembly. There have been some previous reports on the mechanical strength of the fixture-abutment assembly with the compressive bending test or short-term cyclic loading test. However, it is restrictive to predict the long-term stability of the implant system with them. The purpose of this study was to evaluate the influence of the design of the fixture-abutment connection and abutment on the mechanical strength and failure mode by conducting the endurance limit test as well as the compressive bending strength test. Tests were performed according to a specified test(ISO/FDIS 14801) in 4 fixture-abutment assemblies of the Osstem implant system: an external butt joint with Cemented abutment (group BJT), an external butt joint with Safe abutment (group BJS), an internal conical joint with Solid abutment (group CJO), and an internal conical joint with ComOcta abutment (group CJT). The following conclusions were drawn within the limitation of this study. Compressive bending strengths were decreased in order of group BJS(1392.0N), group CJO(1261.8N), group BJT(1153.2N), and group CJT(1110.2N). There were no significant differences in compressive bending strengths between group BJT and group CJT(P>.05). Endurance limits were decreased in order of group CJO(600N), group CJT(453N), group BJS(360N), and group BJT(300N). 3. Compressive bending strengths were influenced by the connection and abutment design of the implant system, however endurance limits were affected more considerably by the connection design.

• Geotechnical Engineering
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• v.1 no.2
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• pp.27-40
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• 1985

This study aims at the development of computer Program for the deformation analysis of soft clay layers, and using this computer program, study the constraint effect of deformation- heaving, lateral displacement-of the soft clay layers reinforced with sheet pile at the tip of banking or improvement of soft clay layer up to hard strata, under intact state (natural) and the state of vertical drain respectively. For this study, Biot's consolidation theories and modified Cam-clay theory for constitutive equation for FEMI were selected and coupled governing equation, and christian-Boehmer's technique was applied to solve the coupled relationship. The following results are obtained. 1. Sheet pile or improvement of soft clay layer to the hard strata work well against the settlement of neighboring ground. B. In view of restriction of heaving or lateral displacement, sheet pile is not supposed to be of use. 3. Sheet pile is of effect only when vertical drain is constructed for acceleration of consolidation and load increases gradually. B. The larger the rigidity of improvement of layer to hard strata is, the less settlement occurs.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.191-197
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• 2016

The shaft system of a vessel becomes stiffer because of larger engine power, whereas the hull structure becomes more flexible because of scantling optimization conducted by using high-tensile thick steel plates. The draught-dependent deformation of the hull affects each bearing offset and reaction force comprising the subsequent shaft system. This is the reason that more sophisticated shaft alignments are required. In this study, an FE analysis performed under the expected operating conditions of two (2) vessels, as maximum draught change and to analyze the shaft alignment using the relative bearing offset change, which was derived from an FE analysis of the 50,000 DWT oil/chemical tanker, which has become an eco-friendly vessel in recent years. Based on this, the influence of the hull deflection on the bearing offset was reviewed against results for shaft alignment conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.249-255
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• 2014

This paper deals with measurement on the economic impact of tax-free oil for Agriculture in Korea. According to increasing of world oil price, the supply policy of agricultural tax-free oil, which specified to support farmers since 1986, are required to expand by farmers. But the supply quantity of tax-free oil is deceased continuously and Korean Ministry of Trade, Industry, and Energy(MOTIE) present stance of sundown policy of tax-free oil for agriculture. In this context, It is necessary and important to measure the economic impact of the supply policy of tax-free oil for agriculture. This study address a econometric method for measurement the economic impact of the supply policy of tax-free oil and suggest several policy implements. Our results show that when the supply policy of tax-free oil for agriculture is annihilated in phases over the five years. the agricultural GDP is decreased by about 3,195 billion korean won and the agricultural price level is increased by 26.6 points after 5 years.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.281-289
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• 2015

This study investigated the conversion of oil products from polypropylene by using dispersed Co and Mo catalyst on reaction time and concentration change for knowledging liquefation characteristics at low-temperature (425, 450 and $475^{\circ}C$) pyrolysis in a batch reactor. The reaction time was set in 20~80 minutes and the oil products formed during pyrolysis were classfied into gas, gasoline, kero, diesel and heavy oil according to the domestic specification of petroleum products. The pyrolysis conversion rate was showed as Mo catalyst > Co catalyst > Thermal in all reaction time at reaction temperature $450^{\circ}C$. The conversion rate and yields of the pyrolysis products were the most height when Co and Mo Catalyst ratio was 50:50.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.551-558
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• 2015

Lateral displacement in the most complex-shaped tall buildings is caused by eccentric gravity loads which are induced by the difference in location between a center of mass and a center of stiffness. The lateral displacements obtained from analysis, using conventional procedures, are prone to overestimate the actual values because much of realignment efforts made during construction phase are ignored. In construction sequence analysis, the self-leveling of slab and the verticality of columns/walls could be considered at each construction stage. Moreover, the displacement compensation can be achieved by manual process such as re-centering - locating to global coordinates through surveying. Because the lateral displacement increases with the building height, it is necessary to set up adjustment plan through construction stage analysis in advance in order to result in displacements less than the allowable limits. Because analytical solution includes lots of assumptions, the pre-adjusting displacement should be reasonably controlled with considerations for the uncertainty due to these assumptions.