• Structural Engineering and Mechanics
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• v.80 no.6
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.161-168
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• 2013

Nowadays, one of the most interested area of automobile industry is the production of vehicle which has collision safety and ability to produce less amount of $CO_2$. The achievement of such a dual performance is done by choosing the materials like dual phase steel, ferrite bainite steel, etc. These steels have been used in automotive chassis and body parts, and also used to be formed by hole flanging to meet the goal of strength and design requirement. The formability of sheet material was experimented by hole expansion test and the judgement relies on human eye and his experience. This manual judgement involves many errors and large deviation. This paper develops the automatic crack recognition system which finds a crack based on CCD image to complement the problem of the current method depending on human's sense.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.4
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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.

• Journal of the Korean housing association
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• v.25 no.2
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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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• v.18 no.2
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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.

• Fire Science and Engineering
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• v.21 no.3
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• pp.56-60
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• 2007

The usage of MSDS (Material Safety Data Sheet) is increased world widely for the implementation of GHS and REACH. In order to know the accuracy of the data in MSDS the flash point of n-Decanol was measured by using a Tag closed tester, a Seta-flash closed tester, a Pensky-Martens closed tester and a Cleveland open tester in Japan and Korea, respectively. The test results of flash points of n-Decanol purchased different manufacturer were compared to the data of the references and MSDS. The flash points determined in Japan were similar to those in Korea but have shown much difference from those in MSDS and literatures. It is suggested that the results of flash points determined in this research have validity and manufacturers should be more careful when they make MSDS as well as for the classification of GHS and REACH.

• Transactions of Materials Processing
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• v.24 no.3
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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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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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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• v.36 no.1
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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.

• Journal of the Society of Disaster Information
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• v.15 no.4
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• pp.634-647
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• 2019

Purpose: Currently, many chemicals are used in industrial and real life, and many substances are used in the form of a single substance, but most of them are used in the form of a mixture, and there is a need for a criterion for judging the danger of these substances. Method: Therefore, this study aims to confirm the risk criteria of the mixture through experimental studies on flammable mixtures in order to secure the effectiveness of the details of the existing Dangerous Goods Safety Management Act angerous Goods Judgment Criteria and to ensure the reliability and reproducibility of the dangerous goods judgment. Result: Experimental results show that alcohol flash point is mixed with water, which is a non-flammable liquid. Similar flash point trends occurred around 60% on an alcohol basis. In addition, in the case of flammable-combustible mixtures, there was little change in flash point if the flash point difference of the two materials was not large, and if the flash point difference of the two materials was low, the flash point tended to increase with the increase of the high flash point material. Conclusion: In the future, the test results may provide reference data on the experimental criteria for the flammable liquids that are cracked at the fire site.