• 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.

• 대한조선학회논문집
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• 제56권3호
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• pp.187-199
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• 2019

In the case of gas carriers and oil tankers, pipes are installed on the upper deck as a moving passage to load LPG, LNG, crude oil, etc. Pipes used for loading or unloading liquid cargo in cargo holds are connected to the hull through support structures. However, many cases of hull damage have been reported where the various equipment and support structures are installed on the upper deck. It is assumed that not only the structural discontinuity where the hull and the pipe support structure meet, but also action due to the pipe loads and the hull girder bending moment are simultaneously affected. This paper deals with the design and strength evaluation of the support structure of pipes and cables installed on the upper deck of commercial ships and offshore structures. For these supporting structures, design conditions and working loads were defined. The design procedure was established through the structure analysis on the method of determining the member dimensions. A series of finite element analysis was performed on the factors to be considered in the design and the effects were discussed. The accuracy and design periods of the strength evaluation was improved and reduced by application of the automation program in the finite element analysis. It is also expected that the design reliability of the shipyard is improved.

• 소성∙가공
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• 제31권4호
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• pp.240-245
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• 2022

In this study, to achieve good electrical conductivity of a charging terminal component in electric vehicles, we investigated the microstructure evolution of pure-Cu subjected to metal injection molding by controlling the sintering variables, such as temperature and time. Thus, three samples were sintered at temperatures ranging from 1000 ℃ to 1050 ℃ near to the melting temperature of 1085 ℃ for 1 and 10 h after thermal evaporation of binder at 730 ℃. Both procedures were made using a unified furnace under Ar+H₂ gas with high purity. The structural observation displayed that the grain size as well as the compactness (a reciprocal of porosity) increased simultaneously as temperature and time increased. This gave rise to high thermal conductivity of 90% IACS together with high density, which was mainly attributed to decrease in fractions of grain boundaries and micro-pores working as effective scattering center for electron movement.

• 한국수소및신에너지학회논문집
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• 제33권4호
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• pp.337-342
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• 2022

In this study, a water electrolysis was studied to investigate the effect of ammonia on current density and H2 gas production. A H type cell with three electrodes was used and KOH solution was used as electrolyte. The conventional platinum foil was used for working electrode, whereas nickel foam was used for counter electrode. CV experiment was performed to see the activity of ammonia oxidation reaction. In addition, CP experiment was done to examine the dependence of Faraday efficiency of hydrogen on current density and NH3 concentration. The CV result shows the 0.5M NH3 concentration required for highest current density and reliable operation. The CP result shows the increased current density leads to higher H2 generation. The higher H2 production and subsequent energy efficiency was observed for 0.5M NH3 using a Pt/13%Rh coil for a cathode as compared to those in water electrolysis.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.580-586
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• 2023

Diversified fuel types such as methanol, hydrogen, liquefied natural gas, ammonia, biofuels, have been come to fore in consideration of the limitations, regulations, environmental perception and efficient use of resources on maritime sector. NE is described as a substantial alternative energy source on the marine vessels in the sense of de-carbonization and fuel efficiency activities carried out by IMO. Although NPVs have been constructed for the merchant, navy and supply fields over the years, their numbers are few and working ranges are quite limited. NE generation techniques, reactor types, safety and security issues in case of any leakage or radiation pollution are analyzed and comparisons are performed between fossil-based fueled and NP based on icebreakers. The comparison are conducted on the basis of dimensions, resistances and operational competences by the VIKOR. NP icebreakers operated in recent years occupy a notable position in the ranking, although fossil fueled ones are most prevalent. Consequently, refueling period and emissions are the principal benefits of NPVs. Nevertheless, the use of such systems on marine vessels especially for merchant ships may come to the fore when all concerns in terms of safety, security and society are resolved since the slightest mistake can have irreversible consequences.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.128-131
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• 2013

Energy losses through windows and doors are big problems in the construction industry. For glass only, it has takes the largest portion of mass from window assembly and it responsible for 24 ~ 45% of energy loss from total building energy loss. Insulating glass unit should maintain their basic functions during their working life in order to contribute positively for global warming issue. There have been many research works for improving insulating glass unit durability. But it is not easy job to fulfill the requirements because insulating glass units composed of many components. So, overall it is required to have right qualify control procedures starting from material selection to fabrication, shipping and installation to the customer site. In this report, we have reviewed the durability of insulating glass unit made from different grades of sealing materials based on globally accepted industry codes such as EN1279. ASTM E 2190 and Locally available code. KS L 2003. The result showed that there is a relationship between the mechanical properties of insulating glass 2nd sealant and the durability of the units.

• Smart Structures and Systems
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• 제30권5호
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• pp.433-446
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• 2022

Despite efforts to reduce unexpected accidents at confined construction sites, choking accidents continue to occur. Because of the poorly ventilated atmosphere, particularly in long, confined underground spaces, workers are subject to dangerous working conditions despite the use of artificial ventilation. Moreover, the traditional monitoring methods of using portable gas detectors place safety inspectors in direct contact with hazardous conditions. In this study, a long-range (LoRa)-based wireless safety monitoring system that features the network organization, fault-tolerant, power management, and a graphical user interface (GUI) was developed for underground construction sites. The LoRa wireless data communication system was adopted to detect hazardous gases and oxygen deficiency within a confined underground space with adjustable communication range and low power consumption. Fault tolerance based on the mapping information of the entire wireless sensor network was particularly implemented to ensure the reliable operation of the monitoring system. Moreover, a sleep mode was implemented for the efficient power management. The GUI was also developed to control the entire safety-monitoring system and to manage the measured data. The developed safety-monitoring system was validated in an indoor testing and at two full-scale water pipeline construction sites.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 추계학술대회
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• pp.160-161
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• 2022

Hydrogen is bridge fuel with high energy content and environmentally friendly to satisfy the stringent IMO regulation relating to greenhouse gas (GHG) emissions. There is growing interest in hydrogen in numerous nations and regions illustrated by an extensive range of research and development in technology. Regarding maritime applications, researchers have recognized the utilization of hydrogen as a fuel for fuel cells, a device that converts the chemical energy of the fuel to electrical energy. Solid oxide fuel cell (SOFC), with high working temperature, is easy to combine with the waste heat recovery cycles/devices to increase output power and thermodynamic performances as well. Furthermore, the cold energy from liquid hydrogen supplied to SOFC can also be used to generate more power. In this study, we proposed a SOFC integrated system with the idea of combining the waste heat recovery from the SOFC exhaust stream and cold energy utilization from LH₂. The designation is aimed to target small-scale vessel which uses electric propulsion for short distances voyage.

• Advances in aircraft and spacecraft science
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• 제10권3호
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• pp.245-256
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• 2023

In order to improve aerodynamic performance of multi-stage axial flow turbines used in aircraft engines, a one-dimensional aerodynamic design and optimization framework is constructed. In the method, flow path is generated by solving mass continuation and energy conservation with loss computed by the Craig & Cox model; Also real gas properties has been taken into consideration. To obtain an optimal result, a multi-objective genetic algorithm is used to optimize the efficiencies and determine values of various design variables; Final design can be selected from obtained Pareto optimal solution sets. A three-stage axial turbine is used to verify the effectiveness of the developed optimization framework, and designs are checked by three-dimensional CFD simulation. Results show that the aerodynamic performance of the optimized turbine has been significantly improved at design point, with the total-to-total efficiency increased by 1.17% and the total-to-static efficiency increased by 1.48%. As for the off-design performance, the optimized one is improved at all working points except those at small mass flow.

• 항공우주시스템공학회지
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• 제18권2호
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• pp.95-103
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• 2024

무인기에 적용되는 다양한 추진기관 기술은 항공의 중요한 개발 방향 중의 하나인 무인기의 비행 성능에 크게 관련이 있다. 본 논문에서는 무인기의 내연기관(왕복엔진, 로타리엔진, 가스터빈엔진), 하이브리드 및 순수한 전기 추진시스템에 대하여 조사를 수행하였다. 특히 이러한 추진기관들의 분류, 작동사이클, 특성 및 주요 기술들에 대하여 제시하였다. 그러므로 미래의 무인기 추진시스템의 개발 틀, 종합적인 예측 및 다양한 비교를 정립하는데 도움을 줄 것으로 판단된다.