• Structural Engineering and Mechanics
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• 제80권6호
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• pp.701-709
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• 2021

The paper aims at improving the understanding and mitigating the effects of tunnel fires that may breakout due to the burning fuel and/or explosion within the tunnel. This study particularly focuses on the behavior of the commonly used horse shoe geometry of tunnel systems. The problem has been obtained using an adequate well-established program incorporating the Lagrangian approach. A transient-thermo-coupled static structural analysis is carried out. The effects of radiation and convection to the outer walls of the tunnel is studied. The paper also presents the impact of the hazard on the structural integrity of the tunnel. A methodology is proposed to study the tunnel fire using a model which uses equivalent steel sheet to represent the presence of reinforcements to improve the computational efficiency with adequate validation. A parametric study has been carried out and the effect of suitable lining property for mitigating the fire hazard is arrived at. Detailed analysis is done for the threshold limits of the properties of the lining material to check if it is acceptable in all aspects for the integrity of the tunnel. The study may prove useful for developing insights for ensuring tunnel fire safety. To conduct such studies experimentally are tremendously costly but are required to gain confidence. But, scaled models, as well as loading and testing conditions, cannot be studied by many trials experimentally as the cost will shoot up sharply. In this context, the results obtained from such computational studies with a feasible variation of various combinations of parameters may act as a set of guidelines to freeze the adequate combination of various parameters to conduct one or two costly experiments for confidence building.

• 대한기계학회논문집A
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• 제37권2호
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• pp.161-168
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• 2013

오늘날 자동차 산업에서 가장 대두되고 있는 충돌 안전성과 배기가스의 감축을 위해서 dual phase 강, ferrite bainite 강 등의 고강도 강판이 개발 되었다. 이러한 강재는 주로 차체 구조부에 적용되며, 적용시에 차체 구조부가 가져야 하는 강도와 디자인 적인 측면에서 사용자의 요구에 맞추기 위하여 홀 플랜징 가공이 자주 사용된다. 이때 재료의 성형성을 알아보기 위한 홀 확장성 평가가 수행된다. 홀 확장실험에서는 크랙 생성 전후의 하중의 차이가 매우 작기 때문에, 단축 인장 시험에서와 같이 하중의 변화로 크랙 발생 유무를 판단하기가 쉽지 않다. 따라서 본 연구에서는 기존의 홀 확장성 평가에서 사람의 눈으로 크랙의 발생 유무를 판단하는 방법의 부정확성을 보완하기 위해 CCD 카메라를 이용하여 크랙의 발생 유무를 판단하는 시스템을 개발하였다.

• 한국산업보건학회지
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• 제25권4호
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• pp.506-515
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• 2015

Objectives: This study was conducted to evaluate the status of hazard communication regarding dental materials among dental hygienists in the Daegu Metropolitan City and the North Gyeongsang-do Province area. Materials: A total of 310 dental hygienists were surveyed using self-administered questionnaires to investigate the status of hazard communication on dental materials and information needs. We collected instructions for use and material safety data sheets(MSDSs) for 67 dental materials frequently used at dental hospitals located in the Daegu Metropolitan City and the North Gyeongsang-do Province area. Results: The questionnaire surveys showed that only 11% of the 310 dental hygienists had knowledge of MSDS and 46.8% of respondents never read instructions for use before using materials. Just 7.4% of dental hygienists have undergone training on hazard information for dental materials. In particular, dental hygienists working at dental clinics had significantly lower response rates on knowledge of MSDS(p<0.001), reading of instructions for use(p=0.042) and training on the hazard information of dental materials(p=0.004) than those in dental hospitals or general hospitals. The essential information most desired by dental hygienists was hazard identification(82.3%) followed by first-aid measures(53.9%), handling and storage(51%), disposal considerations (49%) and toxicological information(47.1%). All dental materials were on foreign products which came from Japan(59.7%), the USA(26.9%) and Liechtenstein(13.7%). In terms of usage, 56.7% of dental materials were prosthetic, followed by conservation(31.3%), orthodontics(9%), and prevention(3%). We found that dental hygienists had accessed MSDSs for only five dental products among the 67 dental materials. The instructions for the use of the 67 dental materials provided hazard identification(64.2%), first-aid measures(83.6%), handling and storage(97%), disposal considerations(20.9%) and toxicological information(26.9%). Conclusions: Based on the results of this study, the hazard communication system for dental hygienists working at dental clinics should be improved.

• 한국주거학회논문집
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• 제25권2호
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• pp.19-26
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• 2014

The number of elderly who wants to access to Nursing Homes (NH) will increase due to the rapid aging society and domestic changes. Those who move into NH expect 24/7 care service in safe environment. Providing space free from danger, especially from fall, for the frail elderly is essential. The purpose of this study is to categorize performance needs of flooring materials in the aspect of safety, and analyze materials so that adequate ones for each space in NH can be suggested. Performance needs are as follows; slip resistance (dry/wet), fire resistance, resilience, water resistance, soil retardant, anti-bacterial, gloss, sound absorbtion. maintenance, durability, ease replacement, color and pattern variety, visual and tactual texture, tactile warmth, IAQ, sustainable material (before use), impact to nature (after use). They are categorized under function, economy, sensibility and sustainability. It was found that there are better materials than common ones that has been used repeatedly in NHs, such as vinyl sheets and VCT. In overall, Cork flooring and nylon carpet met all four categories, followed by wool carpet, rubber and linoleum. For bedroom, wood flooring, Cork, rubber, wool carpet, nylon carpets were suggested. In bathroom with shower, rubber, vinyl sheet and porcelain tiles were safe materials. As living/dining room and corridor floors, wool carpet, nylon carpet, cork flooring would be excellent as they are resilient and durable. The result of this paper can be used by both NH managers and material companies, resulting better quality of life of the elderly by providing safe environment.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.215-221
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• 2017

An electromagnetic (EM) wave absorber reduces the possibility of radar detection by minimizing the radar cross section (RCS) of structures. In this study, a radar absorbing structure (RAS) was applied to the leading edge of a blended wing body aircraft to reduce RCS in X-band (8.2~12.4GHz) radar. The RAS was composed of a periodic pattern resistive sheet with conductive lossy material and glass-fiber/epoxy composite as a spacer. The applied RAS is a multifunctional composite structure which has both electromagnetic (EM) wave absorbing ability and load-bearing ability. A two dimensional unit absorber was designed first in a flat-plate shape, and then the fabricated leading edge structure incorporating the above RAS was investigated, using simulated and free-space measured reflection loss data from the flat-plate absorber. The leading edge was implemented on the aircraft, and its RCS was measured with respect to various azimuth angles in both polarizations (VV and HH). The RCS reduction effect of the RAS was evaluated in comparison with a leading edge of carbon fabric reinforced plastics (CFRP). The designed leading edge structure was examined through static structural analysis for various aircraft load cases to check structural integrity in terms of margin of safety. The mechanical and structural characteristics of CFRP, RAS and CFRP with RAM structures were also discussed in terms of their weight.

• 한국화재소방학회논문지
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• 제21권3호
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• pp.56-60
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• 2007

세계적으로 GHS와 REACH의 도입으로 위험물의 위험성평가를 위한 기존의 MSDS 이용이 증가하여 MSDS의 정확도를 알아보기 위하여 n-Decanol의 인화점을 Tag closed tester, Seta-flash closed tester, Pensky-Martens closed tester, Cleveland open tester 기기를 이용하여 국내와 일본에서 각각 측정하였다. 실험은 국내와 일본에서 각각 다른 제조사에서 구입한 시약으로 인화점을 측정하였으며 인화점 값은 국내와 일본에서 유사한 값을 얻었으나 기존의 MSDS와 문헌의 인화점 값과 비교하여 차이가 크다는 것이 발견되었다. 본 연구에서는 국내와 일본에서 측정된 시험값의 타당성을 제시하고 제조업체가 MSDS를 작성할 시는 신중을 기하여 작성하여야 하며 GHS와 REACH를 위한 위험물분류시는 신뢰성 있는 기관에서 발행한 레포트를 참고로 할 것을 제시하였다.

• 소성∙가공
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• 제24권3호
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• pp.176-180
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• 2015

The current study is concerned with the prediction of fracture strains for DP980 steel sheets over a wide range of loading paths. The use of DP980 steel is increasing significantly in automotive industries for enhanced safety and higher fuel efficiency. The material behavior of advanced high-strength steels (AHSSs) sheets sometimes show unpredictable and sudden fracture during sheet metal forming. A modified Lou-Huh ductile fracture criterion is utilized to predict the formability of AHSSs because the conventional forming limit diagram (FLD) constructed based on necking is unable to evaluate the formability of AHSSs sheets. Fracture loci were extracted from three dimensional fracture envelopes by assuming the plane-stress condition to evaluate equivalent plastic strains at the onset of fracture for a wide range of loading paths. Three different types of specimens -- pure shear, dog-bone and plane strain grooved -- were utilized for tensile testing to calibrate the fracture model of DP980 steel sheets. Fracture strains of each loading path were evaluated such that there shows little deviation between fracture strains predicted from the fracture model and the experimental measurements. From the comparison, it is clearly shown that the three dimensional fracture envelopes can accurately predict the onset of the fracture of DP980 steel sheets for complicated loading conditions from compressive loading to shear loading and to equibiaxial tensile loading.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.501-505
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• 2013

It is well known that monolithic glass has specific coincidence dip allowing transmittance of noise around the critical frequency. Laminated glass, made of a polyvinyle butyral(PVB) interlayer sandwiched by two panes of glass sheet, has long served for the advantage in noise attenuation properties as well as the safety purpose. More research on the improvement of sound insulation performance is needed, considering much of the noise is still transmitted through the glass. As a preliminary study, authors have made several test specimens, varied combinations of glass and interlayer film, to optimize the acoustic performance. Experimental investigation was carried out to study the sound transmission loss of test specimens in the reverberation chamber by using sound intensity method. Several new applications, instead of the existing PVB laminated glass, show better results in sound transmission loss and low temperature have a bad influence on the acoustic performance.

• Journal of Yeungnam Medical Science
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• 제36권1호
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• pp.20-25
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• 2019

Background: The aim of this study was to evaluate the awareness of occupational hazards and personal protective equipment use among dental hygienists (DHs). Methods: A total of 271 self-administered questionnaires were obtained from 280 DHs working at dental hospitals or clinics in Daegu and Gyeongsangbuk-do, Korea. Results: The occupational hazards included work involving dust (94.1%), volatile substances (86.0%), noise (97.0%), and light-curing units (96.7%). The proportion of dental hygiene tasks that participants perceived as harmful were 42.4%, 51.7%, 9.2%, and 31.4% in the same order as above. The proportion of participants who used dust-proof masks during work involving dust was 1.1%. Those who wore gas-proof masks and gloves for work using volatile substances were 0.7% and 31.2%, respectively. Participants who used goggles for work involving light-curing units were 31.0%. None of the participants used ear plugs for work involving noise. A total of 22.9% of the participants recognized the Material Safety Data Sheet, while 79.7% had never been educated about harmful work environments. Conclusion: When compared to exposure status and perception of occupational hazards, the level of protective equipment use was very low. Extra measures to increase DHs' use of personal protective equipment are necessary.

• 한국재난정보학회 논문집
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• 제15권4호
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• pp.634-647
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• 2019

연구목적: 현재 많은 화학물질들이 산업 및 실생활에서 사용하고 있고, 단일 물질의 상태로 사용하는 물질도 많으나, 대부분 혼합물의 형태로 사용되고 있고, 이러한 물질들의 위험성을 판단하는 기준이 필요한 실정이다. 연구방법: 따라서 본 연구에서는 기존의 "위험물안전관리법 위험물 판정 기준"에 대한 세부내용의 실효성확보 및 위험물 판정의 신뢰성 및 재현성 확보를 목적으로 인화성 혼합물에 대한 실험적연구를 통해서 혼합물에 대한 위험성 판단기준을 확인하고자 하였다. 연구결과: 실험결과를 살펴보면 먼저 알코올류 인화점의 경우 비가연성 액체인 물과 혼합되었을 때. 알콜 기준으로 60%를 전후로 비슷한 인화점 추이를 나타내었고, 또한 가연성-가연성 혼합물의 경우에 있어서는 두 물질의 인화점차이가 크지 않으면 인화점의 변화가 거의 없었고, 두 물질의 인화점차이가 낮으면 인화점이 높은 물질의 증가에 따라 인화점이 증가하는 경향을 보였다. 연구결과: 향후 본 실험결과는 소방현장에서 단속되는 인화성 액체 대한 실험적 판정 기준에 대한 참고적인 자료를 제공할 수 있을 것이다.