• 제목/요약/키워드: Confined

검색결과 2,265건 처리시간 0.03초

Chain Length Dependence of Confined Liquid Crystals Configuration

  • Finotello, Daniele;Jin, Tao
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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    • pp.256-259
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    • 2003
  • The study of confined liquid crystals flourished in the decade of the nineties. Liquid crystals properties have been probed after confinement in well-defined or interconnected geometries as those available in porous media and in polymer networks. In this work we emphasized the power of the nuclear magnetic resonance technique to determine the confined liquid crystal structures. We also present unexpected results on the dependence of the confined liquid crystal configuration on the chain length.

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횡방향철근에 의하여 구속된 콘크리트 기둥의 거동해석 (Analysis of Concrete Columns Confined with Lateral Reinforcement)

  • 송하원;최동휴;변근주
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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    • pp.493-499
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    • 1997
  • Objectives of this study is to investigate the behaviors of the confined concrete columns having different core sizes, lateral reinforcement ratios and spacing ratios by using the 3-dimensional analysis of confined concrete columns. In this paper, analyses are done by 3-D nonlinear finite element analysis considering continuum fracture and plasticity and then analysis results are compared with those of model tests. From the comparison, it is shown that the technique in this paper can be used effectively for the analysis of confined concrete columns.

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밀폐공간작업을 하는 산업의 관리와 실태조사 (Control and status of Industries with Confined Space)

  • 양홍석;방상수;강경식
    • 대한안전경영과학회:학술대회논문집
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    • 대한안전경영과학회 2003년도 추계학술대회
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    • pp.65-69
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    • 2003
  • The study was purposed to know the status of prevention on health obstacle in industries with confined space. The results were as follows: 1. It was found 38% of respondents established health-work program in confined space. The percentage of respondents with instrument of oxygen sampling and equipment of ventilation, operation of safety and health education, posting of watching man and operation of head count were 42%, 35%, 75%, 46% and 56%, respectively. 2. The percentage of awakening of risk, confirm of air condition and operation of emergency training were 36%, 25% and 10%, respectively.

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Chain Length Dependence of Confined Liquid Crystals Configuration

  • Finotello, Daniele;Jin, Tao
    • Journal of Information Display
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    • 제4권1호
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    • pp.14-16
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    • 2003
  • The study of confined liquid crystals flourished in the decade of the nineties. Liquid crystals properties have been probed after confinement in well-defined or interconnected geometries as those available in porous media and in polymer networks. In this work we emphasized the power of the nuclear magnetic resonance technique to determine the confined liquid crystal structures. We also present unexpected results on the dependence of the confined liquid crystal configuration on the chain length.

밀폐공간 종류별 유해가스 발생 농도 평가 (Exposure Assessment of Hazardous gases in Confined Spaces)

  • 박현희;유계묵;함승헌;정광재;신민아;이구용;장경조;윤충식
    • 한국산업보건학회지
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    • 제19권4호
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    • pp.381-389
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    • 2009
  • Confined spaces are inherently dangerous workplace and many fatal and nonfatal accidents have been reported. Even though these accidents occur in various kinds of confined spaces, there has rarely been reported on the health hazard agent, i.e., the types of gases and their concentration ranges. Therefore in this study, we evaluated several toxic and asphyxiating gas concentrations in various confined spaces. We surveyed 57 manholes, 3 sewage treatment plants, 2 yellow radish manufacturing companies and 7 barges to measure the concentrations of oxygen($O_2$), hydrogen sulfide($H_2S$), carbon monoxide(CO), ammonia($NH_3$). Lower Explosion Limits(LEL) and Volatile Organic Compounds (VOCs). Those four types of confined spaces occupies 56% of accidents during last 9 years in Korea. In 57 manholes, the concentration varied according to the types of manholes; rainfall and sewage, and by location; residential and industrial areas. Sewage manhole in industrial area was evaluated as the most hazardous than other types of manhole like rainfall manholes, residential sewage manholes. The highest $H_2S$ concentration and the lowest $O_2$ concentration at sewage manhole in industrial area were 300 ppm, 8.7% respectively. In 3 sewage treatment plants, $H_2S$ and $NH_3$ concentrations were reached up to the 500 ppm and 200 ppm respectively. Two yellow radish manufacturing companies showed the concentrations of 316 ppm, 505.2 ppm, 90 ppm and 15.7% for $H_2S$, CO, VOCs and $O_2$, respectively. Seven barges showed 15.9%~20.9% oxygen concentration. Gas species and concentration ranges varied by the types and location of confined spaces; CO, $H_2S$, $O_2$ could be hazardous in manhole, especially manhole connected to sewage plants. CO, $H_2S$, LEL, $O_2$, $NH_3$ should be controlled in sludge silo and sluge pumping confined spaces in sewage treatment plant. The activity of lifting out radish from the storage tank was evaluated more hazardous rather than the other activities in yellow radish manufacturing industry. The employers must conduct the survey to identify all possible confined spaces in their local workplace prior to performing the tasks. At the national level to reduce the accidents in the confined spaces, we suggest that systemic approach and active education program including possible hazards, standard operation procedures, ventilation plan, and personal protective equipment in confined spaces should be implemented.

나선형 철근 및 섬유에 의하여 동시에 구속된 원형 콘크리트 실린더의 거동 (Behavior of Circular Concrete Cylinders Confined with Both Steel Spirals and Fiber Composites)

  • 이정윤;오영준;정훈식
    • 콘크리트학회논문집
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    • 제16권2호
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    • pp.175-184
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    • 2004
  • 횡방향철근에 의하여 구속된 기존의 철근콘크리트 부재를 섬유에 의하여 보수$\cdot$보강할 경우에 그 부재는 철근과 섬유에 의하여 동시에 구속된다. 이렇게 두 가지 재료에 의하여 복합구속된 콘크리트의 거동은 구속재료의 응력-변형률 곡선 및 구속압에 따라서 달라진다. 이 논문에서는 나선형철근과 섬유에 의하여 동시에 구속된 24개의 실린더 실험을 통하여 복합재료에 의하여 구속된 콘크리트의 거동을 분석하였다. 실험에 의하면 복합재료에 의하여 구속된 콘크리트의 거동은 한 가지 재료만에 의하여 구속된 콘크리트의 거동과 큰 차이를 나타냈다.

밀폐공간 질식재해 자료 분석을 통한 질식재해 요인 분석 (2005-2015) (Analysis of Suffocating Accidents in Confined Spaces in the Past 10 Years (2005-2015))

  • 이정완;김태형;하현철;박승욱;안광석
    • 한국산업보건학회지
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    • 제26권4호
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    • pp.436-444
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    • 2016
  • Objectives: Despite recent efforts to prevent suffocation disasters, a number of confined space accidents still happen and each year deaths continue to occur. There have been insufficient studies on the dangers of various potential disaster sites, such as manholes, septic tanks, reactors, and other tanks according to type, characteristics, task-specific disasters, equipment specific disasters, etc. The purpose of this study was to analyze recent suffocation disasters based on place and properties. Methods: In this study, we analyzed confined space accident cases from 2005 to 2015 in Korea and grouped them by type, size, monthly occurrence, continuous service period, accident location, person-specific group, age, employment, structural work and subcontracting work. We studied examples of accidents developed in other countries. Results: (1) We reviewed confined-space accident statistics, compared legal standards and analyzed cases of suffocation accidents in the United States and Japan. (2) Using a case study report from the Korea Occupational Safety & Health Agency, we specified confined-space accident statistics based on place, person-specific group, age, employment, structural work and subcontracting work. As a result we generated some precautions about confined-space accidents for the prevention of such accidents. Conclusions: Conclusions: Statistical analysis of recent suffocation disaster cases was performed to establish improvement measures, compare practices from developed countries, and develop precautionary measures accordingly. In this study, we presented the causes of disaster that occur in a confined space and proposed related preventive measures.

Study on bearing capacity of combined confined concrete arch in large-section tunnel

  • Jiang Bei;Xu Shuo;Wang Qi;Xin Zhong Xin;Wei Hua Yong;Ma Feng Lin
    • Steel and Composite Structures
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    • 제51권2호
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    • pp.117-126
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    • 2024
  • There are many challenges in the construction of large-section tunnels, such as extremely soft rock and fractured zones. In order to solve these problems, the confined concrete support technology is proposed to control the surrounding rocks. The large-scale laboratory test is carried out to clarify mechanical behaviours of the combined confined concrete and traditional I-steel arches. The test results show that the bearing capacity of combined confined concrete arch is 3217.5 kN, which is 3.12 times that of the combined I-steel arch. The optimum design method is proposed to select reasonable design parameters for confined concrete arch. The parametric finite element (FE) analysis is carried out to study the effect of the design factors via optimum design method. The steel pipe wall thickness and the longitudinal connection ring spacing have a significant effect on the bearing capacity of the combined confined concrete arch. Based on the above research, the confined concrete support technology is applied on site. The field monitoring results shows that the arch has an excellent control effect on the surrounding rock deformation. The results of this research provide a reference for the support design of surrounding rocks in large-section tunnels.

Uniaxial Compression Behavior of High-Strength Concrete Confined by Low-Volumetric Ratio Lateral Ties

  • Hong Ki-Nam;Han Sang-Hoon
    • 콘크리트학회논문집
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    • 제17권5호
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    • pp.843-852
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    • 2005
  • Presently, test results and stress-strain models for poorly confined high-strength columns, more specifically for columns with a tie volumetric ratio smaller than $2.0\%$, are scarce. This paper presents test results loaded in axial direction for square reinforced concrete columns confined by various volumetric ratio lateral ties including low-volumetric ratio. Test variables include concrete compressive strength, tie yield strength, tie arrangement type, and tie volumetric ratio. Local strains measured using strain gages bonded to an acryl rod. For square RC columns confined by lateral ties, the confinement effect was efficiently improved by changing tie arrangement type from Type-A to Type-B. A method to compute the stress in lateral ties at the concrete peak strength and a new stress-strain model for the confined concrete are proposed. Over a wide range of confinement parameters, the model shows good agreement with stress-strain relationships established experimentally.

복합재료에 의하여 구속된 콘크리트 기둥의 응력-변형률 관계에 대한 실험적 연구 (An Experimental Study on the Stress-Strain Relationship of Concrete Columns Confined with Composite Materials)

  • 오영준;황현복;이정윤
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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    • pp.194-197
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    • 2003
  • The stress-strain curve of concrete confined with both lateral ties and carbon fiber sheet(CFS) is different to that of concrete confined with only lateral ties or CFS. The objective of this study is to investigate the stress-strain relation of reinforced concrete columns confined by composite material. The main variable of the specimens was the content rate of lateral ties to CFS. In the test a total 24 rectangular specimens, which are all 148$\times$148$\times$300mm size. The test results indicated that while the compressive strength of specimens confined with both lateral ties and CFS increased proportionally to the aided amount of two materials, the maximum strain of specimens depended on the larger strain of lateral ties or CFS.

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