• International Journal of Fluid Machinery and Systems
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• v.10 no.3
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• pp.287-295
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• 2017

The most detrimental pressure pulsations in high-head pump-turbines is caused by the rotor-stator interaction (RSI) between the guide vanes and runner blades. When the pump-turbine operates in the S-shaped region of the characteristic curves, the deteriorative flow structures may significantly strengthen RSI, causing larger pressure pulsations and stronger vibration with an increased risk of mechanical failure. CFD simulations were carried out to analyze the impacts of flow evolution on the pressure pulsations in the S-shaped region of a model pump-turbine. The results show that the reverse flow vortex structures (RFVS) at the runner inlet have regular development and transition patterns when discharge reduces from the best efficiency point (BEP). The RFVS first occur at the hub side, and then shift to the mid-span near the no-load point, which cause the strongest pressure pulsations. The locally distributed RFVS at hub side enhance the local RSI and makes the pressure fluctuations at the corresponding sections stronger than those at the rest sections along the spanwise direction. Under the condition of RFVS at the mid-span, the smaller flow rate make the smaller difference of pressure pulsation amplitudes in the spanwise direction. Moreover, the rotating stall, rotating at 35.7%-62.5% of the runner rotational frequency, make the low frequency components of pressure pulsations distribute unevenly along the circumference in the vaneless space. However, it have little influence on the distributions of high components.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.3
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• pp.3-15
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• 2001

The in situ observations and the seawater analyses were conducted for 3 years from August 1996 to August 1999 in order to elucidate and evaluate seasonal variations of marine water quality and trophic state in Mokpo harbour of Korea. Compared the seasonal seawater qualities of Mokpo harbour with the OECD standards of trophic classification in parameters such as Secchi depth, dissolved inorganic nitrogen, phosphate phosphorus and chlorophyll-a, the trophic level of seawater in Mokpo harbour was evaluated to be in mesotrophic or eutrophic state through all 4 seasons and to be in eutrophic state, particularly In summer. The estimation of pollution index by eutrophication showed the seawater quality of Mokpo harbour to deteriorate and fall under the regular grades through all 4 seasons, although the seawater quality of Mokpo harbour was evaluated to be equivalent to the second or third class of the Korean seawater quality standards in view of COD values. The results of eutrophication index estimation showed the high potentiality of red tide occurrence In Mokpo harbour, particularly in summer or fall. In the light of the average atomic ratio of N/P in seawater, the limiting nutrient factor against the growth of phytoplankton was concluded to be phosphorus rather than nitrogen in Mokpo Harbour.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.327-335
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• 2013

Purpose: The purpose of this study was to identify the factors related in an urban resident's drinking state and drinking problem. Methods: The data was collected from Oct. 2008 to Sep. 2009. Data were collected by questionaire from 359 urban resident over 20 years old and drinking experience residing. The instruments for this study were the alcohol use disorder identification test(AUDIT), the related factors of alcohol drinking. The data were analyzed using descriptive statistics, t-test, ANOVA, hierarchical multiple regression with the SPSS 18.0 program. Results: The problem drinking were 35.7% on AUDIT. (a) Male had significant effect on drinking problem; (b) If you drank alcohol for the first time prior to high school graduation had significant effect on drinking problem; (c) Permanent rental or unlicensed residential had significant effect on drinking problem; (d) Experience in drunk driving had significant effect on drinking problem. Conclusion: It is nessary to education at early childhood for the prevention of drinking problems and regular management for high risk.

• Korean Journal of Labor Studies
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• v.24 no.1
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• pp.229-260
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• 2018

Workaholism refers to a state in which work is the center of self, a state in which other life other than work is deemed worthless, and a state in which one feels that his or her life ends when things get lost. There are concerns that South Korea's work-centered institutions, cultures and long-time labor practices expose workers to workaholism. This study identifies the prevalence of workaholism and its risk factors among workers using a representative sample from Korean Labor and Income Panel Study. The results of empirical analysis of the wide range of workaholism showed that 7.0% of Korean workers were work-addicts. Male, workers working long hours, daily workers, employers, the self-employed were more likely to be work-addicts. Those who think that workload is high beyond regular working hours are more likely to be work-addicts. These results were also confirmed by regression analysis. It suggests that policies to shorten working hours and strengthen job and income stability can reduce the risk of workaholism and balance between work and life.

• International Journal of Computer Science & Network Security
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• v.22 no.11
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• pp.222-228
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• 2022

In today's era of digital technologies, the problem of religious communication in the cyberspace is being actualized, since the globality and accessibility of the WWW makes it one of the most effective and promising channels for transmitting various kinds of messages, including those of a religious nature. Today, religious organizations and movements pay the closest attention to the virtual media space, not only using it to attract new followers, but also for religious PR, image-making and branding, informing the world about themselves through news from the life of the organization and its followers. An equally important form of electronic communication in the online sphere is currently the interaction of various religious movements and religious cultures in general, or the dialogue of confessions in particular. Research in the digital space makes it possible to identify important trends in religious spheres based on the analysis of the flow of information on the Internet, to demonstrate the specifics of individual media outlets and the consequences of their activities for interreligious dialogue, to study the role of the Internet in changing religious beliefs, the possibility of changing religious identity, retrospective development of religious enlightenment at the turn of the century, to determine the vectors of possible interreligious interaction and discuss the role of digital technologies in the work of religious structures, to state the need to continue an active dialogue between representatives of religious movements, to hold expert seminars on interreligious dialogue on a regular basis, and to record the risks generated by the digital space. Thus, the coronavirus pandemic served as a background and context, a litmus test and a catalyst for accelerating and intensifying interreligious, interfaith dialogue and dialogue between religious organizations and society.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1860-1871
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• 2011

Presently, The Regular Block System(Automatic, Interlocking block system) is usually used during the operation of block section. However, In case that the regular block system fails because of the failure of the fixed signals and block equipment or in case of the unexpected emergent situation which should drive on the single-track due to the accidents in the double-track section or the repair work of the one-track, the Substitute Block System to make use of the driving permission license(mapping ticket, mapping paper) is used. In case of the operation of the opposite line and the temporary one-track, the safety gets worse and the SBS may cause the fatal accidents such as a head-on & a rear-end collision. Also, the unmanned railroad stations has recently increased owing to the effective operation of the stations, for it is difficult to execute the SBS in their absence. As a result, the increase of the operation time made the train delayed. Being on the rise of these problems, in this study, we analyzed the problems and difficulties of the SBS on the single line which is lacking stability and safety and on the sections combined between maned and unmaned railroad stations. And we proposed the method to improve the existing drive permission license used for 50 years into the brand-new one with state-of-the art technology and scientific way. In the era of the 21th century, Carrying out the new SBS equipped with stability and safety, we will contribute to the effective operation of trains and the satisfaction of our customers in the future.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.178-185
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• 2006

This paper investigates the steady-state combustion characteristics of the Homogeneous charge compression ignition(HCCI) engine with variable valve timing(VVT) and dimethyl ether(DME) direct injection, to find out its benefits in exhaust gas emissions. HCCI combustion is an attractive way to lower carbon dioxide($CO_2$), nitrogen oxides(NOx) emission and to allow higher fuel conversion efficiency. However, HCCI engine has inherent problem of narrow operating range at high load due to high in-cylinder peak pressure and consequent noise. To overcome this problem, the control of combustion start and heat release rate is required. It is difficult to control the start of combustion because HCCI combustion phase is closely linked to chemical reaction during a compression stroke. The combination of VVT and DME direct injection was chosen as the most promising strategy to control the HCCI combustion phase in this study. Regular gasoline was injected at intake port as main fuel, while small amount of DME was also injected directly into the cylinder as an ignition promoter for the control of ignition timing. Different intake valve timings were tested for combustion phase control. Regular gasoline was tested for HCCI operation and emission characteristics with various engine conditions. With HCCI operation, ignition delay and rapid burning angle were successfully controlled by the amount of internal EGR that was determined with VVT. For best IMEP and low HC emission, DME should be injected during early compression stroke. IMEP was mainly affected by the DME injection timing, and quantities of fuel DME and gasoline. HC emission was mainly affected by both the amount of gasoline and the DME injection timing. NOx emission was lower than conventional SI engine at gasoline lean region. However, NOx emission was similar to that in the conventional SI engine at gasoline rich region. CO emission was affected by the amount of gasoline and DME.

• Communications of the Korean Mathematical Society
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• v.26 no.1
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• pp.135-149
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• 2011

Using (r, s)-preopen sets [14] and pre-${\omega}_t$-closures [6], a new kind of covering property $P^t_{({\omega}_r,s)}$-closedness is introduced in a bitopological space and several characterizations via filter bases, nets and grills [30] along with various properties of such concept are investigated. Two new types of cluster sets, namely pre-(${\omega}_r$, s)t-${\theta}_f$-cluster sets and (r, s)t-${\theta}_f$-precluster sets of functions and multifunctions between two bitopological spaces are introduced. Several properties of pre-(${\omega}_r$, s)t-${\theta}_f$-cluster sets are investigated and using the degeneracy of such cluster sets, some new characterizations of some separation axioms in topological spaces or in bitopological spaces are obtained. A sufficient condition for $P^t_{({\omega}_r,s)}$-closedness has also been established in terms of pre-(${\omega}_r$, s)t-${\theta}_f$-cluster sets.

• The Journal of Korean Physical Therapy
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• v.13 no.3
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• pp.727-734
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• 2001

The purpose of this study was to obtain the information of the home treatment state for children with delayed development and to identify stress and coping pattern in mothers of the children. Data were collected from 211 mothers of delayed developmental children(DDC) by means of structured questionnaires. The results of this study were that in the home treatment mothers had technical insufficiencies to treat their children. so they had a difficulties in treating their children at home. But the home treatment were effective and mothers were assisted by their family and others in their treatment. The mothers had stress by anxiety of prognosis. hurts, responsibility, technical insufficiencies and negligent in housework. And acquisition of home treatment technique, the existence of assistant, and emotion in treatment also influenced on stress in the mother. The coping pattern in the stress were regular medical examination. communication with medical team and other mothers with DDC, faith of recovery and treatment. confidence in home treatment, family coorperation. and leisure time without concern for treatment. The younger mother received the more help from other mothers with DDC. And the mothers with severe, complex DDC had the more help from faith of recovery. Regular medical examination and faith of recovery were helpful coping pattern in mothers who had no treatment skill. Confidence in family coorperation and leisure time without concern for treatment were particularly helpful in mothers whose treatment duration is longer, and home treatment was not effective.

• Health Policy and Management
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• v.26 no.1
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• pp.24-29
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• 2016

Background: Socio-economical status, represented by poverty, is a potent factor in predicting health status, because preventable illness and death occurs due to poverty and socio-economical situation. This study aims to provide information towards on the correlation between poverty and self-rated health in consideration of elements of health behaviors and family and friend support in Philippines. Methods: Data was collected on 15th to 28th of February 2011 by using structured questionnaire through interview method. Study area is Antipolo and Tondo in Manila, Philippines. Sample size was 1,100 but only 658 cases was analyzed due to incomplete questionnaire. Results: Results show that the poverty has direct negative influence on self-rated health, while the presence of family and friend support decreased negative influence. And through the analysis of mediated moderation model, similarly poverty has also indirect negative effect on self-rated health by health behaviors and family and friend support. Especially, regular exercise was found to be a major variable that mediates poverty and self-rated health. Conclusion: In conclusion, to improve the self-rated health state of respondents need to provide emotional support especially from family and friends. Also regular exercise should be encouraged by raising health awareness through continuous health education and promotion for the residents in order to develop health behaviors.