• Clean Technology
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• v.19 no.4
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• pp.423-429
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• 2013

This study aimed to develop flowable backfill material using oyster shell, coal ash, and surplus soil. The high temperature (> $800^{\circ}C$) reaction was required to convert $CaCO_3$ to CaO. The solid specimens formed by pozzlanic reaction between CaO and coal ash showed low unconfined compressive strength. The effect of kaolin and blast furnace slag was also examined. It was found that CaO and coal ash could not be utilized due to high cost and low performance. The use of oyster shell without calcination ($CaCO_3$) was evaluated. The specimens composing of oyster shell and cement showed the higher unconfined compressive strength than that composing of coal ash and cement. However, use of oyster shell is limited in mortar due to the presence of salt. Addition of soil into oyster shell-coal ash-cement mixture satisfied the specification of flowable backfill material by optimizing their ratio.

• Korea Journal of Hospital Management
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• v.4 no.1
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• pp.41-65
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• 1999

This study was attempted to identify the factors affecting profitability of general hospital in Kyung-In Region. Operating profit to gross revenues and net profit to gross revenues were used as a proxy indicator for profitability of hospitals. The unit of analysis was hospital, and the data were collected 5 years data from 20 hospitals. The major findings are as follows; (1) The average operating profit rate was 1.03% and the net profit rate was -5.00% in twenty hospitals in the Kyung-In Region for the last five years. In terms of maximum surplus, the operating profit rate was 14% and net profit rate was 3.40%. In terms of maximum loss revenue, the operating profit rate was -16.56% and the net profit rate was -22.83%. (2) Since the year 1993, which was the starting year of this study, the operating profits and the net profits consistently decreased. (3) Analyzing the difference in profits among various hospital groups, the tertiary hospital group and the 501-1000 beds group exhibited the highest in operating profit rate. Also, among the higher grade number of beds in hospital group, per 100 beds group, the 41-50 beds group exhibited the highest in operating profit rate. There is a statistically significant difference in those groups(p<0.05, p<0.01). (4) In the health care delivery system, the profit gain in the secondary hospital was 51.5% and in the tertiary hospital was 72.4%. Based on the number of beds in each hospital group, the highest profit gain was 75.0% in the over 1001 beds group, and 71.4% in the 501-1000 beds group. Also, among the higher grade number of beds in hospital group, per 100 beds group, the 41-50 beds group exhibited 88.6% surplus. (5) According to the surplus difference based on the analysis of health care utilization, a group with over 31 patients in bed turnover rate, a group with over 96% in bed occupancy rate and group with over 9% in emergency cases to outpatient visits exhibited the highest profit gains. In addition, a group with over 301 patients in daily outpatient visits per 100 beds and group with 11-12 days average length of stay exhibited the highest profit gains. These results are statistically significant(p<0.05, p<0.01). (6) According to a stepwise regression analysis, the variables measuring the bed turnover rate, number of licensed beds, and number of outpatient visits per specialist explain 34.1% of the variation in operating profits. In terms of net profits, the new outpatient visits, the bed turnover rates and the number of general bed variables explain 30.6%. These results are statistically significant(p<0.01).

• Journal of the Korean association of regional geographers
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• v.7 no.3
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• pp.44-58
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• 2001

The purpose of this study is to investigate the potential water condition of Honam region according to water budget analysis. For this purpose, the eight regions (Suncheon, Gwangju, Jhangheung, Damyang, Mokpo, Yosu, Huksando, Namwon) are selected as study area. The result is as follows. (1) The water surplus indicating the potential water condition is ordered as Yosu, Sunchon, Changhung, Namwon, Damyang, Huksando, Kwangju, Mokpo. So the potential water condition of Kwangju and Mokpo is worst among study regions. (2) The high water surplus region is corresponded to high precipitation and low actual evapotranspiration legions. (3) The potential water condition is to agree with several facts about the water resource condition of Honam region. For example, large scale dam of Honam region has been constructed for Kwangju and Mokpo city. This fact indicates that the potential water condition calculated by water budget analysis is corresponded to actual water resource condition. (4) Consequently, the water budget analysis is effective method for investigating the actual water condition and establishing the water resource management of specific regions.

• Ocean and Polar Research
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• v.40 no.4
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• pp.237-247
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• 2018

This study aims to estimate optimal harvests, fishing efforts, and stock levels of hairtail harvested by the large pair bottom trawl, the large otter trawl, the large purse seine, the offshore long line, and the offshore angling fisheries by using the surplus production models and the current value Hamiltonian method. Processes of this study are as follows. First of all, this study estimates the standardized fishing efforts regarding the harvesting of the hairtail by the above five fishing gears based on the general linear model developed by Gavaris. Secondly, this study estimates environmental carrying capacity (k), intrinsic growth rate (r), and catchability coefficient (q) by applying the Clarke Yoshimoto Pooley (CY&P) model among various surplus production models. Thirdly, this study estimates the optimal harvests, fishing efforts, and stock levels regarding the hairtail by the current value Hamiltonian method, including the average landing price, the average unit cost, and the social discount rate. Finally, this study attempts a sensitivity analysis to figure out changes in optimal harvests, fishing efforts, and stock levels due to changes in the average landing price and the average unit cost. As results induced by the current value Hamiltonian method, the optimal harvests, fishing efforts, and stock levels regarding the hairtail caught by several fishing gears were estimated as 33,133 tons, 901,080 horse power, and 79,877 tons, respectively. In addition, from the results of the sensitivity analysis, first of all, if the average landing price of the hairtail constantly increases, the optimal harvests of it increase at a decreasing rate, and then harvests finally slightly decrease as a result of decreases in stock levels. Secondly, if the average unit cost of fishing efforts continuously increases, the optimal fishing efforts decreases, but optimal stock levels increase. Optimal harvests start climbing and then decrease continuously due to increases in the average unit cost. In summary, this study suggests that the optimal harvests (33,133 tons) were larger than actual harvests (25,133 tons), but the optimal fishing efforts (901,080 horse power) were much less than estimated standardized fishing efforts (1,277,284 horse power), corresponding to the average of the recent three years (2014-2016). This result implies that the hairtail has been inefficiently harvested and recently overfished due to excessive fishing efforts. Efficient management and conservation policies on stock levels need to be urgently implemented. Some appropriate strategies would be to include the hairtail in the Korean TAC species or to extend the closed fishing season for this species.

• ETRI Journal
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• v.15 no.2
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• pp.69-74
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• 1993

The consumer surplus under the open economy is greater than that under the closed economy from the viewpoint of social welfare. This indication has been proved when only the product market is considered. This article is to show how this result is changed if the R&D market as well as the product market is considered. We find the possibility that the closed economy is preferred to the open economy in case of the (international) R&D joint venture.

• New & Renewable Energy
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• v.4 no.2
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• pp.31-38
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• 2008

Using a surplus head in presented water supply pipes, we have studied to improve the operating efficiency of small hydro generator, which was chosen for a test model with 00 hydro power plant. With regard to power control and countermeasure of water hammer impact, Finally we have represented the optimal control method through the synthetical analysis of existing system symptoms, operation efficiency, the effect of water hammer impact and system configuration.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.9
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• pp.994-1002
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• 1992

With regard to price elasticity and cross elasticity of electricity, optimal generation expansion planning method including load management effect is suggested. In addition, optimal peak time price can be determined simultaneously, and we adopt peak time tariff as load management strategy. Instead of using hourly marginal demand curves where we can get customer surplus, we used chronological load curve with constraints to preserve social welfare. This method is proved useful in short-term generation expansion planning.

• Journal of Korean Society for Quality Management
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• v.17 no.2
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• pp.149-157
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• 1989

A one-upper warehouse n-lower retailer inventory model is discussed. The probability distribution of demand for a given perod is independent. The inventory holding cost is proportional to the number of unsold units and the cost of shortages is proportional to the number of shortages. In the event of a shortage, units are redistributed with a cost proportional to the number of units from the retailers which are a surplus at the end of the period. The optimum stock levels are obtained and the effects of redistribution are analized.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1342-1343
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• 2011

댐체를 통해 하류 관개용수로 무효방류되는 수자원을 활용한 초소수력 발전가능성에 관한 고찰을 통해 개발 가능한 신재생 에너지 발굴 및 경제성과 타당성에 대하여 검증해 보고자 한다.

• Bulletin of the Korean Mathematical Society
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• v.48 no.2
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• pp.325-334
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• 2011

In this paper we consider the discrete time delayed renewal risk model. We investigate what will happen when the distribution function of the discounted proper deficit is asymptotic in the initial surplus. In doing this we establish several lemmas regarding some related ruin quantities in the discrete time delayed renewal risk model, which are of significance on their own right.