• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.506-512
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• 2018

The fine dust generated in the home and restaurant business occupies a low ratio of about 4% of the total fine dust emissions. However, at the foodservice business, the rate of change of the pollutant concentration is very high, so that the temporary fine dust concentration can be measured up to 60 times. The pollutants generated from non-industrial combustion plants consist of particulate fine dust and gaseous organic compounds. To remove these pollutants, cleaning dust collection system, which is an effective system for simultaneous removal of gaseous and particulate matter, is applied. This is a method of increasing the probability of diffusion capture of the Brownian motion by pressurized liquid injection method using the atomizing nozzle. The dust removal efficiency of the fine dust collecting system was analyzed by nozzle spraying air pressure condition and angle using the manufactured fine dust removing system. As a result, it was confirmed that the efficiency of removal of fine dust and gaseous organic compounds was more than 90%. The developed system is expected to be highly usable in the future because it can remove particulate dust from the existing plant hood system without any installation cost.

• Journal of the Korean GEO-environmental Society
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• v.20 no.7
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• pp.5-10
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• 2019

In recent Gyeongju and Pohang earthquakes, motions that exceed the design ground motion were recorded. This has led to adjustments to the design earthquake intensity in selected design guidelines. An increment in the design intensity requires reevaluation of all associated facilities, requiring extensive time and cost. Firstly, the seismic factor of safety of built concrete retaining walls are calculated. Secondly, the seismic margin of concrete retaining walls is evaluated. The design sections of concrete walls built at power plants and available site investigation reports are utilized. Widely used pseudo-static analysis method is used to evaluate the seismic performance. It is shown that all concrete walls are safe against the adjusted design ground motion. To determine the seismic margin of concrete walls, the critical accelerations, which is defined as the acceleration that causes the seismic factor of safety to exceed the allowable value, are calculated. The critical acceleration is calculated as 0.36g~0.8g. The limit accelerations are significantly higher than the design intensity and are demonstrated to have sufficient seismic margin. Therefore, it is concluded that the concrete retaining walls do not need to be reevaluated even if the design demand is increased up to 0.3g.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.256-262
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• 2018

A great amount of fly ash, which is a waste from a thermal power plant, has not been appropriately recycled until now. Landfill of flay ash causes environmental pollution and enormous economic costs. In this study, manufacturing of architectural ceramic tile was investigated replacing fly ash with clay raw material. The properties of porcelain tile was analyzed after manufacturing porcelain tile with mineral based glaze and fast firing process. In particular, the effect of the fly ash addition on the properties of ceramic tile was investigated by increasing the amount of limestone addition. Porcelain tile with fly ash showed excellent bending strength, water absorption, warping and abrasion resistance. However, a significant decrease in durability was observed through the autoclave test. Addition of limestone increased the water absorption, twisting and hydration expansion of the ceramic tile, but it was confirmed that the durability of the ceramic tile with fly ash was greatly improved. In conclusion, recycled architectural ceramic tiles, which can meet domestic construction standards, could be manufactured with the addition of fly ash and limestone.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.215-217
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• 2014

A system architecture design relying only on the experience of its designer varies in quality in line with the designer's personal experience and knowledge ability. Likewise, a wrong estimation of hardware capacity ends up in waste of resources. In practice, a range of post-hoc monitoring tools are in operation, without providing any method for estimating and reflecting the performance at an early stage of architecture design. Provided capacity requirement is estimated in advance with simulation at the stage of design, the system capacity ends up in waste of resources. In practice, a range of post-hoc monitoring tools are in operation, without providing any method for estimating and reflecting the performance at an early stage of architecture design. Provided capacity requirement is estimated in advance with simulation at the stage of design, the system performance requirement can be met with a minimal cost while the waste of resources can be reduced to a great extent. In this context, the present study develops a pilot simulation model for hardware architecture design and then verifies its validity in an experiment. If the error rate falls within a permissible range in the experiment, the simulation model may be considered to reflect well the characteristics of real-life information system architecture.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.725-733
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• 2018

With urbanization projects involving trunk roads progressing, many simple interchanges, which separate passing traffic into the main traffic and access subtraffic, are being constructed to maximize the traffic capacity. Under the current Road Connection Rule, the access-prohibited section in an interchange is determined based on the access lane and limit distance in the complete interchange road, but separate criteria for the simple interchange are not defined. This may cause confusion in the Road Management Office's determination of the access-prohibited section in the simple interchange, or lead to the application of the criteria for the access-prohibited section in the complete interchange without considering the features of such interchange. This study conducted a comparative analysis of the domestic and overseas systems related to the installation of access section in trunk roads, such as general national roads. This paper presents a survey of the methods for applying the access-prohibited section in the interchange along with the actual cases and proposes improvement measures for a rational calculation of the access prohibited installation section in the simple interchange to minimize the downsides associated with the application of the extremely strict criteria. The proposed road connection rule improvement measures based on the consideration of the purpose of installing the simple interchange and on the consideration the features of the simple interchange are expected to prevent administration confusion by the field road management offices as well as the waste of unnecessary efforts and costs by petitioners so they can boost the service satisfaction for people and the administrative reliability.

• Journal of Navigation and Port Research
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• v.43 no.1
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• pp.72-78
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• 2019

The second-hand ship market provides immediate access to the freight market for shipping investors. When introducing second-hand vessels, the precise estimate of the price is crucial to the decision-making process because it directly affects the burden of capital cost to investors in the future. Previous studies on the second-hand market have mainly focused on the market efficiency. The number of papers on the estimation of second-hand vessel values is very limited. This study proposes an artificial neural network model that has not been attempted in previous studies. Six factors, freight, new-building price, orderbook, scrap price, age and vessel size, that affect the second-hand ship price were identified through literature review. The employed data is 366 real trading records of Panamax second-hand vessels reported to Clarkson between January 2016 and December 2018. Statistical filtering was carried out through correlation analysis and stepwise regression analysis, and three parameters, which are freight, age and size, were selected. Ten-fold cross validation was used to estimate the hyper-parameters of the artificial neural network model. The result of this study confirmed that the performance of the artificial neural network model is better than that of simple stepwise regression analysis. The application of the statistical verification process and artificial neural network model differentiates this paper from others. In addition, it is expected that a scientific model that satisfies both statistical rationality and accuracy of the results will make a contribution to real-life practices.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.607-612
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• 2019

The softness of the crashpad part is one of the important factors which affect the interior perceived quality of the vehicle interior. And while improving the softness of the crashpad part, every effort to lower the production cost has been going on. The PU foaming process for the crashpad part depends on the understanding of a lot of processes, tools and material properties. Therefore, to achieve the requirement of the customer for the interior part's visual quality, the integrated design techniques are investigated to correlate the processes, tool design, material design and the computer aided analysis. In this paper, IMG (In Mold Grain) designed concept is firstly developed to integrate the skin preforming, plastic injection molding of the substrate and the foaming process in a tool within reduced processes. Through the application of this technology, softness of crashpad is improved by 40% compared to the conventional vacuum molding method, and the existing process is reduced by 50% by integrating the injection process and the manufacturing process. And by integrating the injection mold and the skin mold and removing the foaming mold, the number of molds are reduced from 3 to 1, resulting in 20% reduction in the cost of applying a medium-sized passenger car.

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.73-82
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• 2011

Coal ash of industial by-products was not recycled about 30% in total emissions. Moreover, it caused environmental pollution as well as wasted unnecessary expenses and time. Currently, fly ash(FA) is recycled as construction material however ponded ash(PA) is mostly buried. Lightweight foamed Controlled Low-Strength Materials(CLSM) evaluated in this study reduces unit weight by mixing foam in the traditional Controlled Low-Strength Material and has lightweight and flowability to be available for backfill materials in construction. Flow test, unconfined compressive strength test, and foamed-slurry unit weight test were performed in this study and the applicability of lightweight foamed CLSM for construction materials was evaluated. The results indicate that the mixture ratio(PA:FA) ranging from 70:30 to 50:50, cement of 7%, foam of 2~3%, and water content of 26.5~29.5% were required to satisfy the following standards such as flow value(i.e., 20cm), unconfined compressive strength(i.e., 0.8~1.2MPa), and foamed-slurry unit weight(i.e., $12{\sim}15kN/m^3$).

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.113-118
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• 2021

The International Maritime Organization (IMO) has confirmed a global limit of 0.5 % for sulfur in fuel oil used on board ships with effect from January 1, 2020. Among various alternatives to respond to these regulations on sulfur content in fuel oil, such as LNG ships, SOx scrubbers, and very-low-sulfur fuel oil (VLSFO). VLSFO is preferred owing to its low investment costs. As more ships are expected to use VLSFO, VLSFO spills are expected to increase. In particular, when the seawater temperature is below the pour point of VLSFO, VLSFO solidifies when it is spilled, which makes controlling spills difficult. In this study, six types of VLSFO produced in Korea and one type of high-sulfur fuel oil (MF380) were compared in terms of the dispersibility of dispersants according to the seawater temperature conditions. The results confirmed that the six type of VLSFO did not satisfy the domestic standards for dispersant rate (60 % or more for 0.5 min, 20 % or more for 10 min). Morever, the dispersant rate of the six types of VLSFO was low compared with that of the high-sulfur fuel oil. The results of this study are expected to be used to set the direction of dispersant control in the case of VLSFO spills.