• Korean Journal of Construction Engineering and Management
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• v.7 no.5
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• pp.115-127
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• 2006

Although the Korean government have made a plan of housing market with supply and concentrated on the welfare of the people, there are still a lot of problem in housing market for lack of a long-term vision and consistent policy of the government. The plan of 115% of housing diffusion in 2012 is in progress after its acquisition of 100% in 2002, but there are no changes in the rental housing rate of 43% in 2003. In addition, there are getting worse circumstances in the instability of housing market and the low-income bracket, because of the Korean construction firms' bankruptcy with an increase of unsold hosing and a rapid increase of housing prices. The government have made the strategy of revitalizing the economy and regional development by means of a million public rental housing plan for the low-income bracket and welfare. This paper introduces the basic information of the subjective strategy establishment with the analysis of the reciprocal action of influence factors for public rental housing by system dynamics theory and the effect of public rental housing in housing supply market which has a long-term dynamic form.

• Tribology and Lubricants
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• v.29 no.2
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• pp.111-116
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• 2013

This paper describes the adherence phenomenon, including the tribological characteristics, of a low-pressure fuel pump in a diesel engine for an excavator. Most fuel pumps of a diesel-engine excavator are of the fixed-quantity-gear type and have low pressure. However, the developed pumps develop problems in the pumping system owing to performance instability. Cavitation, which is the main obstacle to stable driving in the pump, occurs between an idle gear and the housing to produce a serious adherence problem. The present study not only examined how to suppress cavitation in a pump but also developed a simple method to improve pump performance through the early creation of a lubrication film with a phosphoric acid coating on the surface of the idle gear. The results showed that the coating successfully prevents breakage of the idle gear due to adherence.

• Journal of the Korea Convergence Society
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• v.10 no.5
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• pp.203-211
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• 2019

This study is to examine the impact of spatial characteristics of cities on homicide based on spatial econometric model. It selects housing types, racial heterogeneity, residential instability, overcrowding, commercial area, rate of 15 to 29 ages, and rate of the elderly as variables for spatial characteristics of cities. This study employs spatial regression analysis applying the spatial error model to analyze the data from 229 locals collected from Korean Statistical Information Service and Statistical Year Book of local governments. As a result, it shows that homicide has close relationships with apartment and multi-housing as housing types, racial heterogeneity, residential instability, and overcrowding, but not with the commercial area, rate of 15 to 29 ages, and rate of the elderly. The study contributes to expanding understanding and explanation on the causes of homicide focusing on social-structure approach for criminology by analyzing a more advanced model in applying variables than one of existing literature. This study suggests follow-up research on homicide based on both social-behavior approach and social-structure approach in the near future for the development of criminological theory.

• Land and Housing Review
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• v.5 no.4
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• pp.259-269
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• 2014

After global financial crisis, the ratio of household debt to GDP was decreasing in other advanced countries such as the U.S., and the U.K. and so on. But, in Korea, household debt (of which residential mortgage loan account for a large part) ratio is still increasing. This paper focuses on the scale and characteristics of households in negative housing equity (those are called House-poors in Korea), and also the socio-economic backgrounds of the formation process. In financial perspective, the problem of negative housing equity depends on financial debt repayment capability. We used DSR (Debt Service Ratio) and LTA (Loan to Asset ratio) as financial indicators to evaluate the debt repayment capability. The critical value of DSR is assumed as 40%, and LTA 100%. The socio-economic backgrounds of the House-poors are as follows : increasing households debt dependency, over lending competition of financial institutions and unreasonable loan in household economy, instability of real estate market, week regulation on mortgage loan. Finally, this paper suggests some implications about the range and the target of public intervention.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.51-57
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• 2022

In recent years, the government's urban housing expansion policy has resulted in increased construction and remodeling work of residential houses and apartments, causing more industrial accidents at elevator installation sites. Typically, accidents occur during the installation and dismantling of work scaffolds inside the hoistways or using non-standardized work scaffolds due to their structural instability. In view of this, the present study deals with the development of a standardized elevator system scaffolding that can be safely installed outside the hoistway, securing the work platform inside the hoistway. An improved version of the scaffolding system eliminates the need to enter the hoistway for the scaffolding installation, thereby preventing accidents.

• Human Ecology Research
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• v.52 no.5
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• pp.457-471
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• 2014

Family instability has a negative effect on not only an individual household but also the society. The government continues to operate family support centers as a countermeasure to family instability issues. A healthy and multicultural family support center is considered an effective support system that extends from a family unit to the local community. In this study, the satisfaction and demand levels of each center, located in Seoul and Incheon, were examined with respect to items such as operation contents, physical space, and organizational structure. The results showed that various efforts for creating a family-friendly community were implemented in healthy family support centers and multicultural family support centers. It was found that the center organizers and operators focused more on software and programs than on the physical environment. There was mostly a shortage of physical and environmental space. This space shortage limited the planned and ongoing activities in terms of the residents' self-directed participation and space formation for a family-friendly educational culture. Therefore, it was necessary to set up the space-related criteria for each center in order to solve this environmental issue. We identified the baseline data of the criteria for a center's physical and spatial design and size. In particular, it was suggested that a more strategic physical and spatial design is needed to achieve an integral and effective operation for the connection of the family with the local society.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.8
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• pp.843-849
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• 2009

The reliable operation of a swing check valve in the main feed water system of a power plant is most essential for successful shout-down process. A failure to close the valve at proper time often leads to the instability of the main feed water system, or even to an emergency stop of the power plant. In reality it is a very difficult task to monitor the behavior of a swing check valve. Furthermore it is impossible to see the motion of the valve. In this work two measurements were carried out simultaneously to determine the precise valve closure time. The dynamic pressure measurements were made at the inlet and outlet regions of the swing check valve. The transient vibration of the valve housing in the direction of water flow was also measured, which enabled the measurement of the transient vibration of the valve housing near valve closure. By comparing the results produced from these measurements the precise valve closure time could be determined. By carrying out order tracking technique using the dynamic pressure signals and pump rpm signal, the complicated dynamic problems inside the main feed water system can be more easily dealt with. This measurement scheme might be implemented in a power plant on a real-time basis without much difficulty. If this could be implemented, valuable information essential for shut-down operations can readily be passed on to the main control room. The feasibility of this implementation was demonstrated by this experimental work.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.1-7
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• 2010

The paper proposes a multi-body dynamic simulation to numerically evaluate the generated axial force(G.A.F) and plunging resistant force(P.R.F) practically related to the shudder and idling vibration of an automobile. A numerical analysis of two plunging types of CV joints, tripod joint(TJ) and very low axial tripod joint(VTJ), is conducted using the commercial program DAFUL. User-defined subroutines of a friction model illustrating the contacted parts of the outboard and inboard joint are subsequently developed to overcome the numerical instability and improve the solution performance. The Coulomb friction effect is applied to describe the contact models of the lubricated parts in the rolling and sliding mechanisms. The numerical results, in accordance with the joint articulation angle variation, are validated with experimentation. The offset between spider and tulip housing is demonstrated to be the critical role in producing the 3rd order component of the axial force that potentially causes the noise and vibration in vehicle. The VTJ shows an excellent behavior for the shudder when compared with TJ. In addition, a flexible nonlinear contact analysis coupled with rigid multi-body dynamics is also performed to show the dynamic strength characteristics of the rollers, housing, and spider.

• Journal of IKEEE
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• v.24 no.3
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• pp.766-776
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• 2020

Recently, as interest in machine learning (ML) has increased and research using ML has become active, it is becoming more important to find an optimal hyperparameter combination for various ML models. In this paper, among various hyperparameters, we focused on ML optimizers, and measured and compared the performance of major optimizers using various datasets. In particular, we compared the performance of nine optimizers ranging from SGD, which is the most basic, to Momentum, NAG, AdaGrad, RMSProp, AdaDelta, Adam, AdaMax, and Nadam, using the MNIST, CIFAR-10, IRIS, TITANIC, and Boston Housing Price datasets. Experimental results showed that when Adam or Nadam was used, the loss of various ML models decreased most rapidly and their F1 score was also increased. Meanwhile, AdaMax showed a lot of instability during training and AdaDelta showed slower convergence speed and lower performance than other optimizers.

• Journal of Families and Better Life
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• v.20 no.6
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• pp.151-162
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• 2002

The instability in the current financial market caused consumers a lot of difficulties in their financial decision making. The purpose of this study is to classify the changes in household portfolios during the economic crisis under IMF-trusteeship (IMF Crisis hereafter), and to examine the characteristics of the households according to the types of household portfolio changes. The data were taken from 1996 and 1999 Korean Household Panel Studies, and 1,293 households were selected for the final analysis. Methods of analysis included frequencies, percentages, Chi-square tests, F-tests, and t-tests. Major findings are as follows: 1. In the midst of the financial market changes during the period of the IMF crisis, consumers tended to manage their household portfolio differently according to their household characteristics. 2. The changes of household portfolio can be classified into two different types: the changed type (44.4%) and the unchanged type(55.6%). There are significant differences in the level of wealth, family life cycle stage, housing tenure, and the household head's job, between the changed type and the unchanged type. The family members of the unchanged type are more likely to be older and relatively wealthy compared with the families in the changed type. 3. The changes of household portfolio can be further classified into six different types: the unchanged-liquidity type (21%), the unchanged-multiplication type (24.6%), the unchanged-insurance type (9.8%), the changed-to-liquidity type (13.9%), the changed-to-multiplication type (13.0%), and the changed-to-insurance type (17.5%). There are significant differences in income level, wealth level, family life cycle stage, housing tenure, and the job of household head among the six types of changes.