• Korea journal of population studies
• /
• v.10 no.2
• /
• pp.17-45
• /
• 1987

This study contributes to understanding women's labor market behavior by focusing on a particular set of labor force transitions - labor force withdrawal and entry during the period surrounding the first birth of a child. In particular, this study provides a dynamic analyses, using longitudinal data and event history analysis, to conceptualize labor force behaviors in a straightforward way. The main research question addresses which factors increase or decrease the hazard rates of leaving and entering the labor market. This study used piecewise Gompertz model, following the guide of the non-parametric analysis on the hazard rates, which allowed relatively detailed description on the distribution of timing of leave and entry to the labor market as parameters of interest. The results show that preferences and structural variables, as well as economic considerations, are very important factors to explain the labor market behavior of women in the period surrounding childbirth.

• The Journal of Society for e-Business Studies
• /
• v.21 no.3
• /
• pp.101-128
• /
• 2016

To improve competitiveness & performance for salesmen of small & medium IT company, this study aims not only to inspect how value orientation, leadership & justice make effects for Organizational Citizenship Behavior & Business Corporate Performance & but also to explore the role of adaptive selling practices as parameter. To support the study, the data collected from 314 employees in sales roles at more than 200 IT companies was processed via. regression analysis method. The research model of study lies at identification of 'the Effects of Value Orientation, Leadership, & Justice of/Posed by the Salesmen of a IT Company on Organizational Citizenship Behavior & Corporate Performance' based on the phenomena of unfair sales strategies rampantly being taken for short-term profits & survivals despite of the value of upholding business ethics to realize long-term, sustainable growth of a business of company. The hypotheses of this study are formulated as follows. First, value orientation, leadership, & justice shall have effects on organizational citizenship behavior & Corporate performance. Second, adaptive selling practices shall function as the parameters between the independent & dependent variables. The analysis results on the research, undertaken with verification of parametric effects, confirm the following: 1. Value orientation imposes positive (+) effects on adaptive selling practices which impose positive (+) impacts on organizational citizenship behavior & Corporate performance. 2. Adaptive selling practices function as a full parameter between value orientation & organizational citizenship behavior whilst functioning as a partial parameter between value orientation & Corporate performance. 3. Leadership imposes positive (+) effects on adaptive selling practices which impose positive (+) effects on organizational citizenship behavior & Corporate performance. 4. Adaptive selling practices function as a partial parameter between leadership & organizational citizenship behavior whilst functioning as a full parameter between leadership & Corporate performance. Therefore, this study is concluded that establishing & executing sales strategies in consideration of value orientation & fairness is of extreme importance for IT companies to realize & maintain their sustainable corporate management, & last but not least, it is necessary for IT companies to proactively introduce & provide educational systems for their salesmen thus to help them to uphold & sustain ethics & values of the business.

• Fire Science and Engineering
• /
• v.17 no.4
• /
• pp.76-85
• /
• 2003

In this study, we write down the definitions, their causes and the techniques of analysis as a theoretical consideration of common cause failures, and investigate the limitation and the importance of the common cause failures by applying to the analysis on the fire protection as a representative safety facility. As you can know in the reliability analysis, most impressive cause is the malfunctions of pumping operations; especially the common cause failure of two pumps is dominant. In other words, it is possible to assess system-reliability as twice as actual without CCF From these, CCF is extraordinarily important and the results are highly dependent on the CCF factor. And although it would increase with multiple installations, the reliability are not defined as linear with those multiplications. In addition, the differences in results due to the models for analysis are not significant, whereas the various sources of data produce highly different results. Therefore, we conclude that the reliabilities are dependent on the quality of the usable data much better than the variety of models. As a result, the basic and engineering device for the preventions of CCF of the multiple facilities is to design it as reliably as to design the fire-water pump. That is to say, we must assess those reliabilities using PFD whether they are appropriate to SIL (Safety Integrity Level) which is required for the reliability in SIS (Safety Instrumented System). The result of the analysis on the reliability of the fire-water supply with CCF shows that PFD is 3.80E-3, so that it cannot be said to be designed as safely as in the level of SIL5. However, without CCF, PFD is 1.82E-3 which means that they are designed as unsafely as before.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.2
• /
• pp.165-174
• /
• 2010

The numerical modeling of a coal gasification reaction occurring in an entrained flow coal gasifier is presented in this study. The purposes of this study are to develop a reliable evaluation method of coal gasifier not only for the basic design but also further system operation optimization using a CFD(Computational Fluid Dynamics) method. The coal gasification reaction consists of a series of reaction processes such as water evaporation, coal devolatilization, heterogeneous char reactions, and coal-off gaseous reaction in two-phase, turbulent and radiation participating media. Both numerical and experimental studies are made for the 1.0 ton/day entrained flow coal gasifier installed in the Korea Institute of Energy Research (KIER). The comprehensive computer program in this study is made basically using commercial CFD program by implementing several subroutines necessary for gasification process, which include Eddy-Breakup model together with the harmonic mean approach for turbulent reaction. Further Lagrangian approach in particle trajectory is adopted with the consideration of turbulent effect caused by the non-linearity of drag force, etc. The program developed is successfully evaluated against experimental data such as profiles of temperature and gaseous species concentration together with the cold gas efficiency. Further intensive investigation has been made in terms of the size distribution of pulverized coal particle, the slurry concentration, and the design parameters of gasifier. These parameters considered in this study are compared and evaluated each other through the calculated syngas production rate and cold gas efficiency, appearing to directly affect gasification performance. Considering the complexity of entrained coal gasification, even if the results of this study looks physically reasonable and consistent in parametric study, more efforts of elaborating modeling together with the systematic evaluation against experimental data are necessary for the development of an reliable design tool using CFD method.

• KEPCO Journal on Electric Power and Energy
• /
• v.5 no.3
• /
• pp.173-179
• /
• 2019

Cryogenic air separation unit produces various gases such as $N_2$, $O_2$, and Ar by liquefying air. The process also varies with diverse production conditions. The one for SNG production among them has lower efficiency compared to other air separation unit because it requires ultrapure $O_2$ with purity not lower than 99.5%. Among factors that reduce the efficiency of air separation unit, power consumption due to compress air and heat duty of double column were representatives. In this study, simulation of the air separation unit for SNG production was carry out by using ASEPN PLUS. In the results of the simulation, 18.21 kg/s of at least 99.5% pure $O_2$ was produced and 33.26 MW of power was consumed. To improve the energy efficiency of air separation unit for SNG production, the sensitivity analysis for power consumption, purities and flow rate of $N_2$, $O_2$ production in the air separation unit was performed by change of air boosting ratios. The simulated model has three types of air with different pressure levels and two air boosting ratio. The air boosting ratio means flow rate ratio of air by recompressing in the process. As increasing the first air boosting ratio, $N_2$ flow rate which has purity of 99.9 mol% over increase and $O_2$ flow rate and purity decrease. As increasing the second air boosting ratio, $N_2$ flow rate which has purity of 99.9 mol% over decreases and $O_2$ flow rate increases but the purity of $O_2$ decreases. In addition, power consumption of compressing to increase in the two cases but results of heat duty in double column were different. The heat duty in double column decreases as increasing the first air boosting ratio but increases as increasing the second air boosting ratio. According to the results of the sensitivity analysis, the optimum air boosting ratios were 0.48 and 0.50 respectively and after adjusting the air boosting ratios, power consumption decreased by approximately 7% from $0.51kWh/O_2kg$ to $0.47kWh/O_2kg$.