• Proceedings of the Korean Operations and Management Science Society Conference
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• 2001.10a
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• pp.213-217
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• 2001

This paper deals with the estimation of efficiency of Telecommunication Operators(TOs) using DEA (Data Envelopment Analysis). The measure of efficiency using DEA accomplishes next two steps. First, the efficient frontier is derived using the data of input and output. And then the efficiency of the decision making units are measured by the distances from this frontier To measure efficiency, we consider a one-output, three-input production function. We use the tangible assets, investment cost, the number of employees for input data and measure the output by the revenue. After measuring the efficiency, We can compare the domestic TOs with the international TOs and the wire TOs with wireless ones by average efficiency. After accomplishing the analysis of efficiency, the internal/external efficiency is measured simultaneously through correlation between efficiency and profitability, quality level.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.509-514
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• 2010

The purpose of this study is to analyze the technical efficiency and its determinants for Korean Apiculture farming by using from door to door and e-mail inquiry data. The analysis was implemented through the Cobb-Douglas stochastic frontier production function (SFPF) model including the technical inefficiency effect model for cross-sectional data. To measure the SFPF model, honey production was used for a dependent variable, and for input variables labor cost, preventive cost, material cost, feeding cost, depreciation cost were used. Farmer's age, farmer's career, farming scale, full-time or half-time firm and movement or fixed firm variables were used to measure the inefficiency effect model. The average technical efficiency on apiculture farming in Korea is estimated to be 0.8112. It means that there were technical inefficiency of about 18.88% in Korea apiculture farming. In this study there are some suggestions which could increase the technical efficiency of Korean apiculture farming.

• 한국초전도학회:학술대회논문집
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• 2009.07a
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• pp.6-6
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• 2009

• Journal of the Korean institute of surface engineering
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• v.39 no.5
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• pp.235-239
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• 2006

The aluminum nitride(AlN) layer on Al7075 substrate has been formed through nitrogen ion implantation process. The implantation process was performed under the conditions : 100 keV energy, total ion dose up to $2{\times}10^{18}\;ions/cm^2$. XRD analysis showed that aluminum nitride layers were formed by nitrogen implantation. The formation of Aluminum nitride enhanced surface hardness up to 265HK(0.02 N) from 150HK(0.02 N) for the unimplanted specimen. Micro-Knoop hardness test showed that wear resistance was improved about 2 times for nitrogen implanted specimens above $5\;{\times}\;10^{17}\;ions/cm^2$. The friction coefficient was measured by Ball-on-disc type wear tester and was decreased to 1/3 with increasing total nitrogen ion dose up to $1\;{\times}\;10^{18}ions/cm^2$. The enhancement of mechanical properties was observed to be closely associated with AlN formation. AES analysis showed that the maximum concentration of nitrogen increased as ion dose increased until $5\;{\times}\;10^{17}\;ions/cm^2$.

• Journal of The Korean Society of Grassland and Forage Science
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• v.14 no.4
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• pp.281-287
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• 1994

This experiment was canied out to determine the effects of 3cn1, 6cm, and lOcm of cutting height at harvest on the grass growth, dry matter(DM) yield, and weeds development in reed canarygrass(Phu1uris umndinacea L.) pasttire. The cultivars of reed canarygrass used in this study were Palaton. Veuture and Frontier(contro1). and the grass was harvested four times at soiling stage in 1992. The plant height at first harvest was 84, 96 and 94cm in Palaton, Venture and Frontier, respectively. The average regrowth height was same as 59cm in three cultivars. However, the regrowth height by cutting height was 61 -65cm in 6 and IOcm, and 51 -53cm in 3cm of low cutting height. Annual DM yield was not different in three cultivars of Palaton(l2.58lkg), Venture(l2,752kg), and Frontier (12,243kgIha). The yield at first harvmt wa5 significantly high in 3cm of height, however, the forage yields at second, third and fourth harvest were greatly high in 6cm of stubble height(P<0.05). Total yields by 3, 6 and lOcm of cutting height were 12.306. 14,094 and 11,342kg in Palaton, 12,794, 14,155 and 11,307kg in Venture, and 12,258, 12,940, and 11.535kglhg in Frontier, respectively. The highest yield was achieved in 6cm of stubble heigth(P<0.05). Daily DM production during grass regrowth was not affected by cultivars, and the best regrowth was observed by 6cm of cutting height. Development of weeds was high in 3cm of low stubble height, regradless of cultivars. The contents of crude protein, neutral detergent fiber, acid detergent fiber, and hemicellulose were not affected by cultivar and cutting height. In conclusion, it is suggested that the 6cm of cutting height is the most effective for grass regrowth, forage production, and weed control in reed canarygrass pasture. regradless of cultivm of Palaton, Venture and Frontier.

• Journal of The Korean Society of Grassland and Forage Science
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• v.15 no.2
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• pp.112-117
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• 1995

A field experiment was canied out to determine the effects of harvest time (grazing, soiling and hay stage) on the grass growth, dry matter (DM) yield, nutritive value, and weed development in reed canarygrass (Phalaris arundinacea L.) pasture. The cultivars of reed canarygrass used in this study were Palaton, Venture, Castor, and Frontier (control). The grass was harvested 3 times at hay stage, 4 times at soiling stage, and 6 times at grazing stage in 1992. The average plant height was 31-41cm at grazing, 47-59cm at soiling, and 76-86cm at hay stage. Similar DM yield was observed in Palaton(12,567 kglha), Venture(l2,435kg), and Frontier(12,762kg), and the yields of 3 cultivars were significantly higher than that of Castor(ll,025kg) (P<0.05). Total yields affected by harvest time were lO,O6 1, 1 1,832, and 14,699 kg/ha at grazing, soiling, and hay stage, respectively(P<0.05). The content of crude protein (CP) was not significantly different among cultivars. CP contents by harvest time were 21.6% at grazing, 19.3% at soiling, and 18.8% at hay stage, regardless of cultivm(P<0.05). The contents of neutral detergent fiber (NDF) and acid detergent fiber (ADF) were similar among cultivars and harvest time. However, slightly higher NDF and ADF contents were found in Frontier. The contents of Ca, P, K, and Mg were not affected by cultivars and harvest time. The appearance of weeds was high in Castor, and low in Frontier. The weeds at grazing stage(33.3-60.0%) were remarkably higher than those at soiling and hay astage (ca 10%). In conclusion, it is suggested that 3-4 times (soiling and hay stage) of harvest was recommended for grass production, nutritive value, and weed control in reed canarygrass pasture, regradless of cultivars of Palation, Venture and Frontier, except Castor.

• Carbon letters
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• v.28
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• pp.24-30
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• 2018

Coke aggregates and carbon artifacts were produced to investigate the interactions of coke and pitch during the kneading process. In addition, the kneading ratio of the coke and binder pitch for the coke aggregates was controlled to identify the formation of voids and pores during carbonization at $900^{\circ}C$. Experiments and thermogravimetric analysis revealed that carbon yields were improved over the theoretical yield calculated by the weight loss of the coke and binder pitch; the improvement was due to the binding interactions between the coke particles and binder pitch by the kneading process. The true, apparent, and bulk densities fluctuated according to the kneading ratio. This study confirmed that an excessive or insufficient kneading ratio decreases the density with degradation of the packing characteristics. The porosity analysis indicated that formation of voids and pores by the binder pitch increased the porosity after carbonization. Image analysis confirmed that the kneading ratio affected the formation of the coke domains and the voids and pores, which revealed the relations among the carbon yields, density, and porosity.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.10.2-10.2
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• 2007

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2004.05a
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• pp.41-44
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• 2004

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1671-1672
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• 2007