• Corrosion Science and Technology
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• v.12 no.3
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• pp.142-148
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• 2013

Safety is a major concern in Nuclear Power Plants (NPPs). Piping systems in NPPs are very complex and composed of many components such as tees, elbows, expanders and straight pipes. The high pressure and high temperature water flows inside piping components. As high speed water flows inside piping, the pipe wall thinning occurs in various reasons such as FAC (Flow Accelerated Corrosion), LDIE (Liquid Droplet Impingement Erosion) and Flashing. To inspect the wall thinning phenomenon and protect the piping from damages, piping components are checked by UT measurement in every overhaul. During every overhaul, approximately 200~300 components (40,000~60,000 UT data) are examined in NPPs. There are some methods from EPRI for evaluating wear rate of components. However, only few studies have been conducted to find out the raw data reliability for the wear rate evaluation. Securing the reliable raw data is the key factor for a reasonable evaluation. This paper suggests the reliability analysis method for the repeatedly measured data for wear rate evaluation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.205-206
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• 2017

The purpose of this paper is to examine a reasonable share of cost in the apartment remodeling projects. Therefore, the case model of remodeling apartment was made up and then the rate of return by method of floor area change rate, method of proportion, method of investment earnings rate and method of proportion reflected business contribution were estimated. Consequently, the model by the method of proportion reflected business contribution presented 20.6% of rate in all apartment units.

• Bulletin of the Korean Chemical Society
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• v.11 no.4
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• pp.343-347
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• 1990

A thermal decomposition of the tert-butoxy radical has been studied in the gas phase over the pressure range of 1-200 torr at $413_{\circ}K$ using di-tert-butyl peroxide + trimethylsilane mixtures. The relative rate constants were obtained by studying the competitive reactions between tert-butoxy radical decomposition 4(t-BuO·→ CH_3COCH_3 + CH_3·)$ and hydrogen abstraction reaction from trimethylsilane $(t-BuO·+ HSi(CH_3)_3 → t-BuOH + Si(CH_3)_3)·).$ The conventional RRKM calculations were carried out to compare the observed fall-off behavior of the decomposition rate constant $({\kappa}_d)$ with the theoretical predictions using reasonable values of input parameters. In all cases the calculated half-rate pressure $(P_{1/2})$ were significantly higher than those observed. The failure of RRKM to reproduce the fall-off behavior led us to suggest that not all of vibrational modes contribute to excitation (leading to decomposition) on the same time scale.

• The Korean Journal of Applied Statistics
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• v.31 no.6
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• pp.677-692
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• 2018

The total fertility rate of Korea was 1.05 in 2017, showing a return to the 1.08 level in the year 2005. 1.05 is a very low fertility level that is far from replacement level fertility or safety zone 1.5. The number may indicate a low fertility trap. It is therefore important to predict fertility than at any other time. In the meantime, we have predicted the age-specific fertility rate and total fertility rate by various statistical methods. When the data trend is disconnected or fluctuating, it applied a nonparametric method applying the smoothness and weight. In addition, the Bayesian method of using the pre-distribution of fertility rates in advanced countries with reference to the three-stage transition phenomenon have been applied. This paper examines which method is reasonable in terms of precision and feasibility by applying estimation, forecasting, and comparing the results of the recent variability of the Korean fertility rate with parametric, non-parametric and Bayesian methods. The results of the analysis showed that the total fertility rate was in the order of KOSTAT's total fertility rate, Bayesian, parametric and non-parametric method outcomes. Given the level of TFR 1.05 in 2017, the predicted total fertility rate derived from the parametric and nonparametric models is most reasonable. In addition, if a fertility rate data is highly complete and a quality is good, the parametric model approach is superior to other methods in terms of parameter estimation, calculation efficiency and goodness-of-fit.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.30 no.2
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• pp.44-50
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• 2007

This paper deals with the problem of scheduling jobs and rate-modifying activities on parallel machines. A rate-modifying activity is an activity that changes the production rate of equipment such as maintenance and readjustment. If a job is scheduled after the rate-modifying activity, then the processing time varies depending on the modifying rate of the activity. In this study, we extend the single machine problem to parallel machines problem and propose algorithms is to schedule the rate-modifying activities and jobs to minimize the makespan on parallel machines which is NP-hard. We propose a branch and bound algorithm with three lower bounds to solve medium size problems optimally. Also we develop three heuristics, Modified Longest Processing Time, Modified MULTIFIT and Modified COMBINE algorithms to solve large size problems. The test results show that branch and bound algorithm finds the optimal solution in a reasonable time for medium size problems (up to 15 jobs and 5 machines). For large size problem, Modified COMBINE and Modified MULTIFIT algorithms outperform Modified LPT algorithm in terms of solution quality.

• Journal of the Korean Dietetic Association
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• v.3 no.1
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• pp.44-54
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• 1997

This survey was conducted to find out one serving size and waste rate of frequently consumed dishes in 37 Korean style restaurants. The range of one serving size and waste rate of Pab(boiled rice) were 180-290g and 0-21%, respectively. The mean intakes of Pab were varied according to the kind of dishes served. The waste rate of Yukgaejang(Hot meat soup) is low among Tangban(meat soups). The waste rate of Jeongol(stew with various foods) was higher than other menu items. The average one serving size per person of Pulgogi(grilled meat with sauce), Galbi gui(grilled beef ribs with sauce), Deongsim gui(grilled meat) were 270g, 360g, and 210g, respectively. The average waste rate of side dishes were varied according to dist served. The dish which has higher waste rate than other dishes were Samgaetang(boiled chicken with ginseng), Bokmaeuntang(stew with puffer), Naengmyeun(cold noodle), Pulgogi(grilled meat with sauce), Galbi gui(grilled beef ribs). The reasonable one serving size of dishes based on this survey results was suggested for serving in restaurants.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.53-60
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• 2008

In recent years, finite strain consolidation theories including a mechanical nonlinearity and a reasonable coordinate system have been proposed and used in educations and practical consolidation problems. However, despite their reasonable ability to predict the consolidation behavior, their failure in the field can be attributed to the complexity of estimating and selecting proper parameters for simulating the consolidation phenomenon. In this study, therefore, the application of a piecewise-linear method was proposed to solve such problems including the assumption of the uniqueness in compressibility. Especially, the concept of reference curve was introduced to define the effect of strain rate dependency of clay. The applicability of the methodology is verified by several tests. It was found that the proposed method is applicable in restrictive ranges of study carried out in the laboratory. Finally it is expected that the verification in field consolidation problem has to be carried out through future study.

• Journal of the Korean Society of Safety
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• v.33 no.5
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• pp.84-91
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• 2018

Despite the government 's efforts to reduce constructional disasters, it has been pointed out that the safety management cost of the Construction Technology Promotion Act does not reflect the actual site. Therefore, it is necessary to study the proper guideline of the safety management cost which can be used as the most fundamental measure to prevent construction accidents. Moreover for the securement of the reasonable safety management costs, it is important to calculate its appropriate rate. Thus, in this study, the appropriate rate of safety management cost was proposed by the construction cost & type based on the 111 execution plans of safety management cost, and the rate is analyzed to be 1/10 of the occupational safety and health management cost. The results of this study will be a guideline in improvement to the proper schedule rating system improvement and in implement of pilot projects.

• Korean Journal of Community Nutrition
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• v.17 no.2
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• pp.182-193
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• 2012

The purpose of this study was to investigate the current status of food service management in the restaurants participating in the government-funded children's meal program during summer vacation. A mail survey was conducted with individuals who worked in the restaurants participating in the government-funded children's meal program in Seoul during the summer vacation in 2010. A total of 600 questionnaires were distributed to 274 Chinese, 235 Bunsik and 91 Korean restaurants, which were selected using proportionate stratified sampling by regions and types of operations. A total of 138 usable questionnaires (23.0%) were returned and analyzed. The results showed that over half (57.2%) of the restaurants did not employ any certified cooks. Most of the restaurants (97.8%) provided side dishes; among them, only 42% planned menus for side dishes in advance and only a half changed side dish menus periodically. The suggested reasonable reimbursement rate per meal for children using restaurants differed by types of restaurants; the percentage of restaurants having responded 5,000 won or higher was the highest in Chinese restaurants. This study revealed that food service in the restaurants participating in the government-funded children's meal program was not properly managed during summer vacation, especially in terms of menu and food production. This study also showed that the suggested reasonable reimbursement rate of meals for children using restaurants differed by types of restaurants, implying that adjusting the reimbursement rate according to types of restaurants should be considered in the government-funded children's meal program.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1156-1167
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• 2010

The constant rate of strain (CRS) consolidation test has been widely used to evaluate consolidation characteristics of soils instead of the standard Incremental Loading Test. In practical problems, after the ground improvement, the condition of the soil is over-consolidated. Therefore, it is important to determine the recompression indices and the coefficient of consolidation(or the coefficient of swelling) of unloading-reloading cycle to predict the settlement behavior. However, since standard testing procedures or studies related with strain rate are insufficient especially in unloading-reloading cycle, it is difficult to predict the settlement field behavior accurately from the CRS consolidation test results in spite of its lots of strengths. The several CRS consolidation tests were performed changing the unloading strain rate from 0.2%/hr to 20%/hr with vertical drainage condition using the reconstituted kaolinite sample. For the reconstituted kaolinite sample in CRS consolidation test, the recompression indices are insensitive to the strain rate. It is revealed that the coefficient of consolidation of reloading is affected by the developed pore pressure during unloading. Additionally, the test should be conducted in the positive pore pressure ratio range (3~15%) to obtain the reasonable coefficient of consolidation in the whole range(loading, unloading and reloading).