• Journal of the Korean Institute of Gas
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• v.16 no.1
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• pp.8-14
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• 2012

Hydrogen is considered to be the most important future energy carrier in many applications reducing significantly greenhouse gas emissions, but the explosion safety issues associated with hydrogen applications need to be investigated and fully understood to be applicable as the carrier. The risk associated with a explosion depends on an understanding of the impacts of the explosion, particularly the pressure-time history during the explosion. This work provides the effects of explosion parameters, such as specific heat ratio of burned and unburned gas, equilibrium maximum explosion pressure, and burning velocity, on the pressure-time history with flame growth model. The pressure-time history is dominantly depending on the burning velocity and equilibrium maximum explosion pressure of hydrogen-air mixture. The pressure rise rate increase with the burning velocity and equilibrium maximum explosion pressure. The specific heat ratio of unburned gas has more effect on the final explosion pressure increase rate than initial explosion pressure increase rate. However, the specific heat ratio of burned gas has more influence on initial explosion pressure increase rate. The flame speeds are obtained by fitting the experimental data sets. The flame speeds for hydrogen in air based on our experimental data is very low, making a transition from deflagration to detonation in a confined space unlikely under these conditions.

• Journal of the Ergonomics Society of Korea
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• v.32 no.1
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• pp.145-152
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• 2013

Objective: The aim of this study is to develop an ergonomic office chair that has an alarm function for the unbalanced sitting postures. Background: Contrary to expectation, it is reported that office workers sit on their chairs much more in unbalanced postures during daily work. Even though an office worker uses an ergonomically good-designed chair and begins their work in a good sitting posture, his/her posture is likely to shift to the unbalanced bad posture. Therefore, a posture alarm system would be very helpful in keeping office workers' good postures. Method: We developed a prototype chair with four load cells under a seat pan and one load cell beneath a backrest. Through some experiments, we set the criteria for unbalanced bad postures then implemented the criteria into the alarm system of the prototype chair. The chair called e-BASE chair could detect unbalance postures and show alarms for chair users. We also enhanced back support by developing a step-wised folding backrest. Results: The e-BASE chair showed better performance in interface pressure distributions and balanced posture ratio in VDT work. Conclusion: The ergonomic chair with posture alarm function(e-BASE chair) was developed. It showed better performance in seat pressure distribution and in keeping good posture during office work. Application: The posture alarm system and folding backrest can be applied to the new models of office chair.

• Journal of Community Nutrition
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• v.7 no.3
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• pp.135-140
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• 2005

This study was conducted to evaluate the health status of staff by medical examination data according to the work classification as professional, office worker and laborer in K University in Seoul, Korea. Two thousand four hundred and eighty-four staff (men : 1154, female: 1330) from the university were studied for this report. The anthropometric (height, weight and BMI) and blood pressure (systolic, diastolic) and biochemical parameters (hemoglobin, glucose, cholesterol, AST, ALT) were measured. All groups were calculated using GLM multivariate analysis for three groups after adjustment for age. The average BMI was significantly higher in laborers than professionals and officers after adjustment for age. In blood pressure, especially in SBP, the significant difference was found in females according to the job classification. Blood glucose levels of female laborers were significantly higher than those of officers and professionals. The level of blood total cholesterol of male professionals was significantly higher than those of laborers. The level of blood total cholesterol of female laborers was significantly higher than officers or professionals. Importantly, significant differences were found in BMI, SBP, blood glucose level and cholesterol level of female staff after adjustment for age. These results showed that there were differences in health subjects of staff according to the work classification. This study would provide basic data to prepare the program of health promotion for the college staff according to work classification. Further research is required to discover factors influencing health promotion of staff in colleges.

• The Korean Journal of Community Living Science
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• v.22 no.4
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• pp.599-613
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• 2011

This study aimed to provide an efficient time management scheme for farmers by analysing how they experience time constraints in spending their time and understand time management. Firstly, farmers found that they didn't have enough time for farm keeping as a result of house work obligations. It was caused by excessive time for agricultural work. Thus, 93.7% of respondents recognized that ‘they were pressed for time' because there is relatively less time to spend for socio-cultural and physiological matters. In addition, 83.0% responded that they felt the pressure of something. Respondents who were in forties reduced their sleeping hours due to lack of time. The majority of people who were in the farmhouse doing controlled horticulture cannot enjoy their own time for leisure owing to a lack of time. Secondly, respondents under thirty-nine years of age were solving the problems of time constraints as prioritizing matters, planning handling time and utilizing household instruments. On the other hand, respondents who were in forties found the solution by reflecting on their conduct toward a time consumption plan, self-evaluation and received help from their family and/or neighbors. A group of respondents who had already graduated from college or higher education often reflected on their conduct and self-evaluated. Respondants who participatied in farmhouse controlled horticulture, generally took turns in managing their house work. For reducing farmers' time constraints and managing their time efficiently, they should standardize matters done repeatedly and also manage time by dividing work among family members. Furthermore, if a long-term time scheme such as more than a month is established and practiced, time constraints may be somewhat solved.

• Korean Journal of Labor Studies
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• v.24 no.3
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• pp.35-71
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• 2018

The purpose of this study is to examine which job-related factors are associated with presenteeism, which is defined as attending work while ill. Although presenteeism is a relatively new concept in academic research, it should be regarded as an important social issue in that presenteeism threatens employees' job prospects and quality of life as well as it causes loss of work productivity. I analyzed a cross-sectional survey of 24,571 wage workers over 15 from the fourth wave of the Korean Working Conditions Survey in 2014. Five logistic regression models were analyzed on experience of presenteeism, and work hours and private life, occupational environment, job insecurity, rewards and welfare were assessed as key predictors of presenteeism. I found that 1) work hours with bad fit with private life, 2) high level of work time-pressure, and low job satisfaction 3) job insecurity, and 4) low benefits are associated with experience of presenteeism. The findings are fairly consistent with the theory of job-person mismatch, which explains that workers tend to preserve their personal resources by going to work while ill (presenteeism) when job demands or work conditions do not match with their level of personal expectation and, thus, workers are afraid of loss of personal resources. Presenteeism influences worker's long-term health and quality of life negatively as well as causes serious social costs. Therefore, we need organizational efforts to prevent the negative effects of presenteeism on society as well as workers.

• Safety and Health at Work
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• v.12 no.2
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• pp.147-153
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• 2021

Background: In this study, the association of work and demographic characteristics with different traffic offenses committed by food delivery riders in Greece was examined. Previous research has identified various factors related to risky driving however, there is a need for exploring the complex interrelationship of work-related factors underlying risky driving behavior. Materials and Methods: A 2-items uestionnaire was used exploring delivery riders demographic characteristics, terms of employment, issues of concern during work and type of traffic offenses committed. In total, uestionnaires were analyzed using logistic regression in order to identify characteristics independently associated with serious traffic offenses, namely, red-light running and helmet non-use. Results: The analysis showed that: (i) typical health and safety measures had no effect on serious traffic offenses, (ii) young age was related to both offenses however (iii) different sets of work conditions were associated with reports of red-light running (i.e. low work experience, use of personal vehicle for work, and payment by hour) and helmet non-use respectively (i.e. intense work pace, high tip income per day and low concern about vehicle condition). Conclusion: The above findings provide evidence that serious traffic offenses are manifestations of underlying conflict experienced by the riders between safety and various performance criteria. Each one of the two offenses is related to different rider profiles aiming to satisfy different goals, namely, those mainly trying to maximize profit non-helmet users and those, mostly inexperienced ones, trying to cope with work pressure red light runners. Potential regulatory measures to alleviate risky practices are discussed.

• Journal of computational fluids engineering
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• v.17 no.1
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• pp.36-43
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• 2012

When a high-speed train passes an underground station, large pressure waves are generated due to the piston effect. These pressure waves can cause the problems of vibration and noise as well as the ear discomfort of passengers at the underground station. This work numerically analyzed the pressure wave generation and propagation in an high-speed railway underground station, and the optimal location for vent shafts was studied to improve the passenger comfort by reducing the magnitude of the pressure wave and its rate of change. The evolution of pressure field in the underground station was calculated using a CFD(Computational Fluid Dynamics) software(Fluent), where the axis-symmetric two-dimensional model verified by Wu was used. And this study is applied to modelling of the underground station and the tunnel from Daegok station A-line of GTX(Great Train Express). From the result, we can have a conclusion that the role of vent shafts respectively were different according to the position in and out the underground station. Also Vent shaft in the underground station widely reduced pressure magnitude. And vent shaft out underground station reduced initial pressure peak value. Double vent shafts installed at tunnel toward station entrance and inside of the tunnel are the most efficient to reduce pressure. and pressure reduction increases according to the number of vent shaft.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.441-442
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• 2002

Chemical mechanical polishing (CMP) is a manufacturing process that uses controlled wear to planarize dielectric and metallic layers on silicon wafers. CMP experiments revealed that a sub-ambient film pressure developed at the wafer/pad interface. Additionally, dishing occurs in CMP processes when the copper-in-trench lines are removed at a rate higher than the barrier layer. In order to study dishing across a stationary wafer during polishing, dishing maps were created. Since dishing is a function of the total contact pressure resulting from the applied load and the fluid pressure, the hydrodynamic pressure model was refined and used in an existing model to study copper dishing. Density maps, highlighting varying levels of dishing across the wafer face at different radial positions, were developed. This work will present the results.

• Wind and Structures
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• v.12 no.4
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• pp.299-312
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• 2009

It has long been studied about the flow around bluff bodies, but the effect of aspect ratio on the sharp-edged bodies in thick turbulent boundary layers is still argued. The author investigates the flow characteristics around a series of rectangular bodies ($40^d{\times}80^w{\times}80^h$, $80^d{\times}80^w{\times}80^h$ and $160^d{\times}80^w{\times}80^h$ in mm) placed in a deep turbulent boundary layer. The study is aiming to identify the extant Reynolds number independence of the rectangular bodies and furthermore understand the surface pressure distribution around the bodies such as the suction pressure in the leading edge, when the shape of bodies is changed, responsible for producing extreme suction pressures around the bluff bodies. The experiments are carried out at three different Reynolds numbers, based on the velocity U at the body height h, of 24,000, 46,000 and 67,000, and large enough that the mean boundary layer flow is effectively Reynolds number independent. The experiment includes wind tunnel work with the velocity and surface pressure measurements. The results show that the generation of the deep turbulent boundary layer in the wind tunnel and the surface pressure around the bodies were all independent of Reynolds number and the longitudinal length, but highly dependent of the transverse width.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1024-1029
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• 2012

As DME (Dimethyl ether) is the one of the future possible massive energy sources synthesized from natural gas, KOGAS has been doing to obtain overseas resources to meet the domestic needs. and tried to build new DME FPSO ship. This paper presents that it can help for the DME storage tank designers and storage management engineers doing proper work by understood the evaporation phenomena and pressure change of DME by thermal intake in storage tank. The experimental result shows that the evaporation rate and pressure are increased with higher liquid filling level. The proper DME liquid filling level in tank is obtained as lower than full 98% volume of tank in case of storing longer than a day, because the pressure is increased rapidly with full 98% filled level of storage tank.