• Journal of Energy Engineering
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• v.11 no.4
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• pp.291-298
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• 2002

This paper presents a practical methodology that can analysis power flow and marginal factors based on optimal power flow (OPF) of power systems under restructuring environment. First of all, to evaluate useful marginal factors, nonlinear optimization problems of minimum fuel cost and minimum transmission loss are formulated and solved by nonlinear primal-dual interior point method. Here, physical constraints considered in the optimization problems are the limits of bus voltage. line overloading, and real & reactive power generation. Also, an evaluation method of marginal price and marginal transmission loss is presented based on sensitivities calculated by the two OPF problems. Especially, to reflect the cost related to transmission losses in the competitive electricity market, an analysis method of MLF (marginal loss factor) is pro-posed. Numerical results on IEEE RTS 24 show that the proposed algorithm is effective and useful for analysis of power market price.

• Korean Journal of Social Welfare
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• v.63 no.1
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• pp.113-135
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• 2011

As intense economic competition has led to more flexibility in the labor market, marginal or atypical employment has rapidly grown. Although marginal work represents an important proportion of whole employment, it is still characterized by insecure and unfavorable working conditions. Therefore employees in marginal jobs are highly likely to be subject to social exclusion. In turn, social exclusion puts marginal workers in a high risk of mental health problems. One of major mental health symptoms has been depression. So far, however, little attention has been paid to the effect of social exclusion of marginal employees on mental health problems including depression. Hence this study examines empirically the effect of social exclusion of casual workers in the construction industry, a protype of marginal employees, on depression. Its results indicate that social exclusion has influence upon depression of marginal workers. This study is the first one to delve into the relationships between temporary employment, social exclusion, and depression of marginal employees. Yet much more empirical researches are needed in order to shed brighter light on these relationships.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.6
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• pp.760-768
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• 2007

Statement of problem. Conventional denture treatment for totally edentulous patients is associated with a variety of functional and psychosocial problems. The placement of implants in the anterior region of the maxilla and mandible and the fabrication of an implant-retained overdenture might solve these problems. Purpose. This study compared the marginal bone loss around the implant and evaluated the implant survival rate and complications in patients treated with overdentures retained by implants for 2 years. Material and methods. Patients who had received implant-retained overdentures using a Dolder bar at Samsung Medical Center from January 1999 to June 2005 and had participated in the annual recall programs for two years were selected for this study. A total of 18 patients and 56 $Br{\aa}ne-mark\;system^{(R)}$ implants were used, and their data were reviewed. Evaluations of the survival rate, bone quality, marginal bone loss, and complications were performed. The data on the Dolder bar length and clip length were measured. The change in marginal bone loss and the correlation between the marginal bone loss and bar length, clip length, or bone quality were investigated. Results. Implants placed in this study showed a 100% survival rate. The average annual bone loss was 1.12mm in the first year and 0.27mm in the second year in the maxilla, and 0.58mm in the first year and 0.22mm in the second year in the mandible. The marginal bone loss in the maxilla showed no significant association with those in the mandible. (P>.05). There was no significant difference in marginal bone loss around implants between the first and second year. (P>.05) There was no statistically significant relationship (P>.05) between the marginal bone loss and bone quality, clip length, or Dolder bar length. The Dolder bar length showed a high correlation with the clip length. (P<.05) Various complications were noted. Conclusion. These results confirmed the favorable outcome for patients treated with implant-retained overdentures.

• Korean System Dynamics Review
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• v.17 no.1
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• pp.107-134
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• 2016

Accelerated ageing with low fertility is one of the most critical problems in Korea. Because of ageing via low fertility, Korea will face a serious demographic cliff. This research primarily focus on the analyzing the dynamics of the marginal ageing state and decreasing population especially in Eup and Myeon region. This study based on the system dynamics approaches for finding causal loop structure of marginal ageing and critical mass of population disappearing. The results of this study are summarized as follows. First, demographic marginalization trends have already begun in the Eups and Myons of Gun. Second, marginal aging speed in Eup/Myeon areas is causing an population disappearing in the near future. Third, critical mass of population disappearing will begin when the rate of marginal aging is exceed 82% after 2023.

• Journal of Korean Society of Rural Planning
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• v.12 no.4 s.33
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• pp.33-42
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• 2006

Recently, Korean government has been initiating various schemes for reactivation of the marginal farmland use. However, although about ten years have passed from the introduction of the marginal farmland redevelopment projects in 1995, there have been very few research works on their systematic and objective appraisal. Therefore, this study checked the statutory concept and development schemes of the marginal farmland, firstly. Ant through case studies on 5 completed project sites and questionnaire/interview surveys on local government officers/private developers, problems and suggestions on project implementation were analysed. Finally, in consideration with analysed results and suggestions together, tentative project directions and reaction schemes on marginal farmland development were proposed.

• Journal of Korean Society of Rural Planning
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• v.24 no.1
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• pp.21-31
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• 2018

This study is a basic research for the development of 'Marginal Village Policy' in response to the hollowing-out of rural areas. For this purpose, the viewpoint of "Regeneration" & "Reconstruction" of the "Marginal Village Theory" and the recent "Rural Planning Theory of Evacuation" in Japan were reviewed. The background and trends of Marginal Village policy in Japan were also investigated. And based on this, the implications and future tasks for Korea were summarized as follows; (1)It is necessary to be interested in the disappearance of villages and marginal villages and to form positive discussions and social consensus. (2)Continuous field investigation and management of changes in population and village functions at regional and village level are required. (3)In addition to increasing the importance of depopulation problems, it is necessary to establish 'marginal villages' as a public policy target. (4)It is necessary to review and consider the viewpoint of reconstruction along with regeneration. (5)It is necessary to pay attention that the software project is expanded, and the regeneration & reconstruction policies of the rural villages are aimed at revitalizing the rural community. (6)It is necessary to consider the possibility of applying 'spacial construction' along with the expansion of the academic debate on the 'rural planning theory of evacuation'. On the basis of this, in this study, rural villages were classified into 'continuous villages', 'semi-marginal villages' and 'marginal villages' according to the degree of marginalization, and the basic framework of 'Marginal Village Policy' was proposed, which is to encourage the differentiated policies of 'continuous villages' by 'rural village policy', 'semi-marginal villages' and 'marginal villages' by 'marginal village policy'.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.1
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• pp.9-17
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• 1992

Proper resource allocation is also a very important topic in power system problems, especially in operation and planning. One such is optimal maintenance problem in operation and planning. Least cost and highest reliability should be the subjects to be pursued. A probabilistic operation simulation model developed recently by authors is applied to the proboem of optimal maintenance scheduling. Three different methods are compared, marginal maintenance cost, levelized risk and maintenance space. The method by the marginal maintenance costs shows the least cost, the highest reliability and the highest maintenance outage rates. This latter characteristics may considerably influence the results of genetation planning, because the usual maintenance outages obtained from the other methods have shown to be lower.

• Environmental and Resource Economics Review
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• v.30 no.1
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• pp.107-128
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• 2021

It has been recognized that implementing the marginal price mechanism to CBP is not acceptable due to the lack of revenue of the marginal generators. This study shows that it is not the problem of marginal price mechanism but the structural problems originated by the suspension of restructuring, the technical limits of RSC program and inaccuracy of the generation cost estimation method. This study explains the method to calculate the cost function in operating modes of the CC generators and proposes the modeling for the CC generators in RSC program. To implementing the cost function in operating modes could give an opportunity to change the price setting mechanism from average to marginal cost. The price setting mechanism based on the marginal cost will be one of the main points to provide the right price signals and to introduce a real-time and A/S markets to prepare the energy transition era.

• Journal of the Korean housing association
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• v.25 no.3
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• pp.35-43
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• 2014

Korea is the most rapidly aging country in the OECD countries, becoming 'an aging society' in 2010, when over 12% of the population had reached the age 65 and beyond. Along with the population aging, problems of the elderly have become a social issue. Also, the elderly population in most farming villages is increasing due to the cityward concentration of younger generation and the rapid urbanization centered around the capital area. Yet no definite success in revitalization of these villages has been reported despite the acknowledgement of the problems arising from such phenomena. Therefore, by examining "marginal villages" (communities whose joint social activities are difficult to maintain as over 50% of the population is 65 years or older) in Japan, which at this point has entered "the ultra-aged society" before Korea, this study intends to compare and analyze the countermeasure plans for the population decrease in these villages. The case study has been done with the focus on the literary references published in Japan such as papers, various reports, statistics, newspapers, and journals.

• Journal of the Korean Operations Research and Management Science Society
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• v.24 no.2
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• pp.109-119
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• 1999

The average shadow price is a substitute for the traditional marginal shadow price. It can serve as a standard for decision making problems about the economic resources where the marginal analysis gives no useful information. This paper treats the average shadow price in pure integer programming and shows some stability properties of it. This implies that the values of the average shadow prices once computed are reliable within some extent of the data perturbations of the integer programming model.