• Journal of Adhesion and Interface
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• v.3 no.2
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• pp.9-16
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• 2002

In the synthesis of water-based polyurethane using self-emulsification process, after being neutralized, polyurethane pre-polymers containing ionic pendant groups are dispersed by simple convective mixing. Preparation of dispersion is followed by chain extension reaction, which is considered as important step for growth of the molecular weight of polyurethane. In this work, pH variations in the aqueous phase were monitored during the chain extension process in the presence of water-soluble diamines. The optimum degree of chain extension and the average particle size in the polyurethane dispersions were examined with varying ionic pendent group contents, type of chain extenders, and feed rate of chain extenders, The initial pH value in the aqueous phase linearly increased and the optimum chain extension point could be obtained from the intersection of two linear lines having different slopes, All average particle sizes before chain extension reaction were almost same, however, the final average particle size increased as feed rates of chain extenders increased, In addition, as the ionic pendant group contents increased, the particle size decreased since the hydrophilicity and hydrodynamic volume increased. As carbon numbers of the chain extenders increased, the final particle size increased significantly. From the results, it was concluded that the chain extension reaction took place among the particles not only in a particle.

• Korean Journal of Construction Engineering and Management
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• v.8 no.3
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• pp.125-133
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• 2007

If project time extension were required in the construction projects, either liquidated damages or extension costs should be applied according to causation of the schedule delays. However, in actual cases it is not applied so far according to the contract conditions. The reason why this situation happened Is that function of the present planning and scheduling is not working feasibly. The CPM schedule could not provide a proper solution for apportioning responsibility for the schedule delays. This situation could be considered as breach of contract and will cause potential disputes for schedule delay. Therefore, in this research process based contract administration model for construction delay claim is proposed to prevent schedule delay and solve the claims. The model is based on pro-active management for causation of delay to provide apportionment of responsibility and written evidences.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.305-310
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• 2001

The purpose of this study is to calculate delay damages for contractors. The study has been performed by investigation of delay cost occurrence status and the analysis of subway construction cases. The results of this study are as follows: 1. Delay cost( 1day) equivalent to $0.005\%$ of total construction cost by analysis case studies. 2. Including bank interest, dealy cost is analysed as the following; $1.1\~9.2\%$ of total construction cost in part extension period, $3.3\~11.0\%$ of total construction cost in total extension period. 3. In comparison between liquidated damages and delay cost, liquidated damages account for average 20.1 times of delay costs. 4. Acceleration cost will be calculate on the basis of delay cost calculation method. In the result of this method, acceleration cost is equal to delay cost at least or must be large than delay cost

• Nuclear industry
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• v.15 no.3 s.145
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• pp.62-68
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• 1995

NPT는 25년이 경과한 이후에 이 조약이 무기한으로 효력을 지속할 것인지, 아니면 추가적으로 1회 또는 수 차례에 걸쳐 일정기간 연장될 것인가를 결정하도록 규정하고 있어, 오는 4월 17일$\~$5월 12일로 예정된 연장 및 검토회의를 앞두고 어떠한 방법으로 연장될 것인가에 대한 관심이 고조되고 있다.

• Korean Journal of Construction Engineering and Management
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• v.8 no.1 s.35
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• pp.78-86
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• 2007

Top priority to manage construction projects is given to the planning and scheduling in order to keep the project duration, which is one of the most important factors in construction management. However, recently most of public construction projects especially for civil projects are delays and preventive research, many efforts were made concerning construction delays and preventive management methods. But analysis of delay causation, which is a main key to solve the problems is not done, yet. Therefore, in this research causation delays are analyzed by characteristics of construction projects, which are type of projects, type of contracts, project participants, and general condition. As a result of the analysis, delay causation are proved to be different by characteristics of the projects. The research results will be used for prevention of time extension and dispute resolution.

• Korean Journal of Construction Engineering and Management
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• v.19 no.4
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• pp.61-69
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• 2018

Research on additional indirect cost due to construction period extension in general contracts has continuously been active whereas the same for the subcontract operations has not been. In this research, we review previous research on evaluation methods for additional indirect costs which are widely being used on construction sites as well as previously proposed methods altogether, applying them to analyze model-cases for comparison. We acknowledge that this pattern for construction cost fluctuation over the construction period demonstrates an S-curve. This S-curve shaped indirect cost occurrence is then used to generate model-cases that are used throughout the research which models we applied previous evaluation methods on. Finally in pursuit of finding out some problems of evaluation methods, we came to derive a conclusion that the "Average Actual Cost Evaluation Method on Extended Duration," which, in turn, were proved to be valid for application on general contracts, was also valid for general application on subcontractor operations.

• Korean Journal of Construction Engineering and Management
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• v.13 no.6
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• pp.33-44
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• 2012

This study is as to payment improvement method of additional incidental cost to be occurred upon extension of public construction time. According to the result of analysis about the cause of non-payment of additional incidental cost of construction time extension through site examples, it was found that difficulties exist in disputes & proofing over the scope of actual cost recognition, and in this regard the result of experts opinion indicated that a construction extension pre-agreement system can be executed which agrees the scope of recognition of additional incidental cost of construction time extension once the statistical standard is clear and accurate. Accordingly, in this study, by totalling multiple sites data, calculations were implemented in terms of type of construction projects, amount of constructions, period of constructions. According to the result of calculation, the element of type of construction project and construction period appears to have none direct effect to the occurrence of additional cost of construction time extension, but direct relationship was indicated related to the contract amount element. In view of above, in this study a standard additional incidental cost of construction time extension was proposed, and presented a system improvement plan to implement the construction extension pre-agreement system.

• Journal of the Korean Data and Information Science Society
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• v.23 no.6
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• pp.1195-1202
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• 2012

In this paper, we determine the expected total cost from the user's perspective for the replacement model with the extended warranty when minimal repair cost is a function of failure time. To do so, we define the extended warranty and assume the replacement model following the expiration of extended warranty from the user's perspective. Especially, we propose the criterion to buy the extended warranty and the numerical examples are presented to illustrate the purpose when the failure time of the system has a Weibull distribution.

• 건강소식
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• v.37 no.6
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• pp.40-41
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• 2013

인류의 오랜 꿈, 수명연장을 향한 연구는 언제나 활발히 '진행 중'이다. 연구 방항도 세분화되어 세포, 유전자 호르몬 등을 다방면에 걸쳐 다루고 있다, 수명연장을 항한 연구로는 어떤 것들이 있고 어느 정도의 실현 가능성이 있을까.

• Korean Journal of Childcare and Education
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• v.9 no.4
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• pp.259-276
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• 2013

The purpose of this study was to investigate factors related to parental satisfaction of the Time-Extended Daycare. The subjects of this study were 1,000 parents(mothers or fathers) or caregivers whose child range in age from 0 to 5. The questionnaire was comprised of Quality of Time-Extended Daycare, Parental Satisfaction of Time-Extended Daycare, and a demographic questionnaire. The data analyses used SPSS 20.0 which employs basic statistics, ANOVA, Pearson's correlation and multiple regression analyses. The results of this study indicated a correlation between parental satisfaction and program(r=$.60^{***}$), safekeeping(r=$.56^{**}$), nutritious meals and health care(r=$.63^{**}$). Specifically, nutritious meals and health care could predict Parental satisfaction of the time-extented daycare.