• 에너지공학
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• 제11권3호
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• pp.237-246
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• 2002

한국형차세대원자로 APR-1400의 안전감압계통이 작동하면 물, 공기 및 증기가 sparger를 통해 격납건물 내 핵연료재장전 수조로 차례로 방출된다. 방출 과정 중 생기는 여러 현상 중에서 수조 내의 공기 기포군은 저주파, 고진폭의 진동 하중을 발생하며, 주파수가 침수 구조물의 고유 주파수와 거의 같은 경우에는 구조물에 심각한 영향을 줄 수 있다. 이러한 현상은 복잡하기 때문에 주파수와 하중에 대한 규명은 주로 실험에 의존해 왔으며 수치해석적 연구는 이루어지지 않았다. 본 연구에서는 sparger를 통해 수조 내로 방출되는 공기 기포군의 거동에 대한 수치해석을 상용 열수력 해석 코드인 FLUENT Version 4.5를 사용하여 수행하였다. 다상유동 해석모델중 VOF(Volume Of Fluid)모델을 사용하여 물, 공기 및 증기 등의 다상유동을 모의하였다. 해석결과를 sparger 개발을 위해 ABB-Atom이 수행하였던 실험결과와 비교하여 만족할만한 결과를 얻었다.

• 한국산업융합학회 논문집
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• 제20권5호
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• pp.359-364
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• 2017

A machine such as bean crusher machine is subjected to different loads and vibration. Due to this vibration there will be certain deformations which affect the performance of the machine in adverse manner. This paper proposed a vibration analysis of bean crusher machine using ANSYS. The Finite Element Method (FEM) analysis is carried out to study the effect of vibration on the structure in order to ensure the safety. This work helps the machine developer make a better product at the early design stage with lower cost and faster development time. To do this, firstly, using Inventor, a CAD model is prepared. Secondly, the analysis is to be carried out using ANSYS 15. The modal analysis and random vibration analysis of the structure was conducted. The analysis shows that the proposed design was successfully shows the minimum deformation when the vibration was applied in normal condition.

• Tribology and Lubricants
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• 제23권3호
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• pp.130-133
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• 2007

Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube and support. The fretting wear of tube and support can threaten the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of tube-support is required. The fretting wear tests were performed with supporting grids and cladding tubes, especially after corrosion treatment on tubes, in water. The tests were done using various applied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tube materials can be predictable by obtaining the wear coefficient using the work rate model. Due to stick phenomena the wear depth was changed as increasing load and temperature. The maximum wear depth was decreased as increasing the water temperatures. At high temperatures there are the regions of some severe adhesion due to stick phenomena.

• Tribology and Lubricants
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• 제24권3호
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• pp.129-132
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• 2008

Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube and support. The fretting wear of tube and support can threaten the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of tube-support is required. The fretting wear tests were performed with supporting grids and cladding tubes, especially after corrosion treatment on tubes, in water. The tests were done using various applied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tube materials can be predictable by obtaining the wear coefficient using the work rate model. Due to stick phenomena the wear depth was changed as increasing load and temperature. The maximum wear depth was decreased as increasing the water temperatures. At high temperatures there are the regions of some severe adhesion due to stick phenomena.

• 한국산학기술학회논문지
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• 제19권3호
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• pp.61-68
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• 2018

공동주택 하자는 유지보수에 막대한 비용이 들어가게 되며, 발주자, 시공자 그리고 입주자 등에게 심각한 피해를 입힌다. 이에 따라 하자분쟁을 최소화하고 철저한 품질관리를 통한 체계적이고 효율적인 하자관리를 위한 토대를 마련할 필요가 있다. 본 연구에서는 하자분쟁사례를 활용하여 공동주택의 공종/부위/현상에 따른 하자분류체계를 도출하고, 이를 기반으로 하자유형별 하자위험을 평가할 수 있는 방안을 제시하였다. 이를 위하여 본 논문에서는 경과년수 10년 이상 공동주택 하자분쟁사례 34건, 약 6000여개의 하자항목 자료를 토대로 분석을 실시하였다. 분석 결과를 정리하면, 하자분류체계는 하자 공종, 하자부위 및 하자현상으로 크게 분류한 후 세부적으로 총 157개 항목으로 세분화하였다. 하자분류체계를 토대로 하자 빈도, 하자비용 및 하자위험을 분석한 결과, RC공사 및 마감공사에 하자위험이 상당히 집중되어 있는 것으로 확인되었다. 이에 따라 이러한 하자위험에 대한 하자예방 활동이 우선적으로 고려되어야 할 것으로 판단된다. 본 연구를 토대로 하자위험을 관리할 수 있는 방안에 대한 추가적인 연구가 필요할 것으로 판단된다.

• Geomechanics and Engineering
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• 제11권4호
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• pp.571-585
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• 2016

The crest of the Pubugou central core rockfill dam (CCRD) cracked in the first and second impounding periods. To evaluate the safety of the Pubugou CCRD, an inversion analysis of the constitutive model parameters for rockfill materials is performed based on the in situ deformation monitoring data. The aim of this work is to truly reflect the deformation state of the Pubugou CCRD and determine the causes of the dam crest cracks. A novel real-coded genetic algorithm based upon the differences in gene fragments (DGFX) is proposed. It is used in combination with the radial based function neural network (RBFNN) to perform the parameters back analysis. The simulated settlements show good agreements with the monitoring data, illustrating that the back analysis is reasonable and accurate. Furthermore, the deformation gradient of the dam crest has been analysed. The dam crest has a great possibility of cracking due to the uncoordinated deformation, which agrees well with the field investigation. The deformation gradient decreases to the value lower than the critical one and reaches a stable state after the second full reservoir.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.509-516
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• 2004

The measurement of abnormal change of temperature(temperature anomaly) will help determine the safety of various engineering constructions, as the measurement in body often used to diagnose one's health. Temperature anomaly can be occurred in leakage or seepage of water flow in rocks, and in ground water table etc. Grouting materials injected in fractured rocks generate heat during hardening process. The degree of temperature change is associated directly with heat flow characteristics, that is, thermal conductivity, specific heat capacity. density of the surrounding rocks and can afford to assess the grouting efficiency. However, in practice, the use of traditional temperature measuring technique composed of only one single thermal sensor has been fundamentally limited to acquire thermal data sufficient to use for that, partly due to the time-consuming measuring work, partly due to the non-consecutive quality of data. Thus, in this paper, a new concept of temperature measuring technique, what we call, thermal line sensor technique is introduced. In this, the sensors with an accuracy of $0.02^{\circ}$ are inserted at regular intervals in one line cable and addressed by a control device, which enables to fundamentally enhance the capability of data acquisition in time and space. This new technology has been demonstrated on diverse field model experiments. The results were simply meant to be illustrative of a potential to be used for various kinds of temperature measurements encountered in grouting and leakage problems.

• 보건교육건강증진학회지
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• 제13권2호
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• pp.167-183
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• 1996

Human teeth vary widely in color. Practitioner and patients are concerned with preventing and correcting discolored or dark teeth to achieve and maintain stain-free, white teeth. Tooth brushing cannot alter tooth color but it can remove adhering films and stains. The esthetics of natural dentition can be improved by bleaching and this process can be applied to intrinsically and extrinsically stained teeth. The need for a brighter, more attractive smile has made rapid growth in the market for tooth whiteners. There is no doubt these products work as whiteners, at least on mild to moderate stains, but the safety of these products are unclear. In this experiment, the effect of tooth whitener application on the color and microhardness of extracted human enamel was measured. RMS, RMT and NWT were used as tooth whiteners, and tooth paste(ETQ) and hydrogen peroxide solution(HPO) were used as controls. 35 caries-free extracted human molars were embedded and polished with the exposed enamel diameter of 4 mm. The tooth whiteners and control agents were applied according to the manufacturers' instructions or clinically simulated procedures for eight weeks, and measurements were repeated every two weeks. Value(L＊) difference was measured using Differential Colorimeter(Model TC-6FX, Denshoku Co., Japan), and microhardness was measured using microhardness tester(Mitsuzawa Seiki Co., Japan). The results were as follows; 1. After application of agents for eight weeks, the Vickers hardness increased significantly in the ETQ, RMS and RMT application group(p〈0.01), and that decreased significantly in NWT application group(p〈0.01), but in HPO application group there was no significant change. The change in microhardness was greatest in NWT application group(p〈0.01). 2. After application of tooth whiteners and controls for eight weeks, the value change of toothpaste application group was significantly lower than those of other agents groups(p〈0.01), and there was no significant difference in value(L＊) change among tooth whitener groups(p〉0.01). 3. The application of tooth paste and paste type tooth whitener made gradual value change, but hydrogen peroxide gel type tooth whitener and hydrogen peroxide solution made rapid value change during initial application period.

• 한국BIM학회 논문집
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• 제5권3호
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• pp.19-32
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• 2015

For decades, the productivity issue has been a primary concern for the all stake-holders who participate in domestic construction industry. Especially, between a whole life cycle of building, the construction phase's productivity problem makes or break the entire project. In this respect, the general construction company, who accept the order and construct the building(so called General Contractor), should consider various strategies, such as schedule management, cost management, quality management, inner-crew management, etc., for the productivity improvement., and almost of these management methods have been studied for a long time. But, the researches and studies about the specialty contractor, who construct the building directly in construction site were not sufficiently complete yet. This research begins as an idea which tries to apply the BIM(Building Information Modeling) into the tasks of Specialty contractors for their productivity improvement. And for the effective application of construction BIM to specialty contractors, establish of the BIM project execution plan for them, not the fragmentary adoption of BIM. Therefore, in this paper, we develop the BIM project execution plan for the reinforced concrete companies who conduct the framework construction which located on CP(Critical Path) Especially, we model the "Construction BIM Use List for the RC Work", "BIM Application Master Process" and "BIM Application Detailed Process", and general contractor who use these BIM uses list and process models can manage various specialty contractors about schedule, cost, earned value, quality, safety and environment management systematically.

• 대한토목학회논문집
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• 제33권3호
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• pp.1191-1202
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• 2013

기존의 토공 자동화 연구들은 주로 GPS와 센서의 응용, 작업환경 모델링, 장비 진로계획, 작업 정보관리, 원격조정 등과 같은 주제에 관심을 두었다. 최근에는 건설자동화 연구분야에서 $CO_2$ 감축이 주요 관심사의 하나로 대두되었다. 토공작업의 경우에는 많은 종류의 건설장비나 로봇들이 관여되므로 건설현장에서 많은 양의 $CO_2$를 배출하는 작업이 되고 있다. 효과적인 토공계획과 건설장비 운영은 생산성 및 안전성을 증가시킬 뿐만 아니라 $CO_2$ 배출량도 줄일 수 있다. 본 연구에서는 3D 토공현장 모델, 2가지 시공법에 의한 3D 토량배분 방법, 토공작업 패키지 구성방법과 같은 그린 토공을 위한 몇 가지 자동화 개념을 제시하고 있다. 엑셀로 작성된 시뮬레이터를 개발을 통하여 주어진 토공작업에 대하여 3D 토량배분 계획을 수립하였고 $CO_2$ 배출량을 추정하였다.