• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.4
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• pp.301-306
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• 2011

The paper presents an analysis of the heating cycle and discusses a desalination cycle that uses lowtemperature seawater. The basic heating cycle model is the heat pump cycle, and seawater desalination is usually performed by the indirect freezing desalination method. The low temperature of the seawater (below $5^{\circ}C$) acts as the heat source of the evaporator. R-134a, R-1234yf, R-600a are used as working fluids. In the 2-stage compression cycle, the compressor's work decreased by about 15.6% from that in the 1-stage compression cycle. Further, the COP in the 2-stage cycle was 17.6% higher than that in the 1-stage cycle. In the indirect desalination cycle, the energy per unit fresh water productivity in the 2-stage cycle was 19.8% lower than that in the 1-stage cycle.

• Journal of Power System Engineering
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• v.20 no.1
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• pp.11-17
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• 2016

In this study, the simulation for performance comparison between basic single stage organic rankine cycle, multi stage reheater cycle and multi stage reheater & recuperator cycle was carried out. The multi stage reheater cycle and multi stage reheater & recuperator cycle was designed to improve the efficiency for organic rankine cycle using heat source from industrial waste heat and heat sink from deep ocean water. R245fa was selected as a refrigerant for the cycle and system efficiencies were simulated by the variation of the heat sink temperature and the cycle classification. Performance characteristics were simulated by using the Aspen HYSYS. It was confirmed that the system efficiency was decreased by the increase of heat sink temperature. These results can be considered to be applied as geo-ocean thermal energy conversion in where plenty of geothermal or ocean thermal resource exist.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.8
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• pp.1041-1048
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• 2018

Gartner's Hype Cycle model is widely used to describe technology maturity, acceptability, and commercialization. In the Hype Cycle model, the techniques go through five stages, those are Innovation Trigger(first stage), stage Peak of Inflated Expectations(second stage), Trough of Disillusionment(third stage), Slope of Enlightenment(fourth stage) and Plateau of Productivity(fifth stage). In many studies, Hype Cycle is widely used as a basis for future prediction of technology, but the verification is somewhat lacking. In this paper, we analyzed the technologies that appeared in the Hype Cycle for the emerging technologies from 1995 to 2017. Through this, we found technologies that appeared as non first stage when first appearing, and techniques that showed a reversal of the maturity stage. In addition, we found that none of the technologies from 1995 to 2017 had gone through stages 1-5.

• The Transactions of the Korean Institute of Power Electronics
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• v.28 no.1
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• pp.59-67
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• 2023

This paper explores the variation of DC-Link current ripple analysis in terms of duty cycle and phase angle of Multi-phase/Multi-stage boost converter. A 2-Stage/1-Stage boost converter DC-Link current is used to determine the difference between the 1st stage diode current and the 2nd stage inductor current. Each stage boost converter diode and inductor current is subordinate to the phase angle and duty cycle. The magnitude of the ripple current is variable according to phase angle and duty cycle. The analysis results are verified by variation of DC-Link current ripple using a 1kW typical 2-stage/1-stage boost converter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3327-3335
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• 2014

In this study, comparison works have been performed for single-stage and multi-stage refrigeration cycle using propane as a refrigerant in order to cool down the natural gas stream. A comparative analysis has been performed for a single, two, three and four stage refrigeration cycle using propane as a refrigerant for cooling the natural gas stream. For the simulation, natural gas feedstock properties supplied by KOGAS were utilized and Peng-Robinson equation of state model was used. As the number of compression stages increase, the condenser heat duty is decreased. The refrigeration heat duty for a four-stage refrigeration cycle is decreased by 20.36% compared to that for a single-stage refrigeration cycle. Moreover, the total refrigerant circulation rate for a four-stage refrigeration system is was reduced by 14.53% compared to the single stage refrigeration cycle. The total compression power for a four-stage compression was reduced by 41.61% compared to the single stage compression.

• Journal of the Korean Home Economics Association
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• v.30 no.1
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• pp.199-217
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• 1992

The purpose of this study was to examine changes in the household investment planning according to the family life cycle, to improve the household investment planning process, and to develop research model. The results were as follows : Household investment planning varied with stages of the family life cycle because the stock of resources shifted and financial goals changed as the family life cycle stage changed. The main financial goals of family in each stage of the life cycle were the purchasing of house in the establishing stage, children's education and marriage in the extending stage, and the elderly's economic welfare in the diminishing stage. Also, in the Ⅰ & Ⅱ stage the most important investment goals were the purchasing of house, children's education in the Ⅲ stage, children's marriage in the Ⅳ stage, and the elderly's economic welfare in the Ⅴ stage. Therefore, the financial goals were recognized as the important goals underlain the investment-planning goals, and alternatives for the accomplishment of investment-planning goals were determined. The results of this study can contribute to establish the long-run investment planning process and improve the level of household's financial well-being.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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• pp.835-841
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• 2006

A $CO_2$ system using the two-stage compression cycle was tested by varying $1^{st}-2^{nd}$ compressor frequencies in the cooling mode. To improve the cooling performance of the two-stage compression $CO_2$ cycle, the following cycle options were applied: a basic cycle, a cycle with an intercooler, a cycle with an IHX (internal heat exchanger), and a cycle with an intercooler and IHX. The cycle with the intercooler-IHX showed the highest cooling capacity improvement among the cycle options at all compressor frequencies. The cycle with the intercooler, the cycle with the IHX, and the cycle with the intercooler-IHX improved the cooling COP by 7, 12, and 15%, respectively, over the basic $CO_2$ cycle when the compressor frequencies for the first and second compressors were 50 Hz and 30 Hz, respectively. In addition, the applications of the selected cycle options enhanced system reliability.

• The Korean Journal of Food And Nutrition
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• v.25 no.1
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• pp.205-213
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• 2012

This study investigated the life cycle of menus and made suggestions on the appropriate time for when new menus should be developed. For this purpose, a total of 636 customers who visited 'T' Restaurant more than 25 times in the past three years were used for analysis. After estimating product life cycles based on sales and selling period, an empirical study was conducted. In terms of product life cycle, a growth stage was observed in the category of pasta and pizza in both stores A and B, whereas sales in the rice category stayed constant. Regarding trend in seasonal sales, a big difference was detected between the two stores. While store A was already in the decline stage of the life cycle in all menu categories, store B remained in the growth stage. In terms of menu life cycle, the product life cycle of long-lived products was observed in the pasta category in both stores A and B. While the pizza category was in the growth stage, the product life cycle of long-lived products was observed in the rice category. It is expected that the results of this study could be useful in development of new menus and product life cycle management to fulfill diverse customer needs in the dining-out business.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.398-403
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• 2005

The cooling performance of a transcritical $CO_2$ cycle varies significantly with a variation of refrigerant charge amount. In this study, the performance of the $CO_2$ system was measured and analyzed by varying refrigerant charge amount with a change of cycle option. The applied cycle options are the single-stage compression system, two-stage compression with 1-EEV system, and two-stage compression with 2- EEV system. The optimum normalized charge were 0.363, 0.297, and 0.282 for the two-stage compression with 2-EEV system, two-stage compression with 1-EEV system, and single-stage compression system, respectively.

• Fisheries and Aquatic Sciences
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• v.2 no.1
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• pp.78-84
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• 1999

Ultrastructural changes in the cuticle of Paleamon serrifer associated with the intermolt cycle were examined and quantified as changes in the cuticular thickness. The cuticular thickness in each zoea stage increased with time elapsed after molting. The cuticle in the premolt stage was about 1.5 and 3 times thicker than that in the postmolt and intermolt stage, respectively. The cuticle in the premolt stage, including the molting space, was more than 5 times as thick as in the postmolt stage. In addition, newly hatched larvae were individually reared in the laboratory and body length for each specimen was measured frequently until the end of zoea VI. An average increase in body length between one zoea stage and the next is about $10\%$ of the length of the previous stage. Within individual zoea stages, the premolt stage had a body length some 0.3% longer than that of the postmolt stage, indicating a growth rate of about 0.03 mm/d.