• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.41-50
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• 2013

Economic feasibility study using weighted average variable Jeju System Marginal Price, SMP, was conducted for Gasiri wind farm of Jeju Island. To predict the variable Jeju SMP, generator share ratio for SMP was calculated from the real time wind power production and the power demand data for years. Also, sensitivity analysis on Net Present Value, NPV, and Benefit/Cost Ratio, B/C ratio, were performed to clarify which factors are more important in assessing economic feasibility. The result shows that the Gasiri wind farm has a minimum of 110 billion won and a maximum of 132 billion won difference between fixed and variable SMP. Also, Capacity Factor, C.F., had the highest sensitivity for NPV, followed by SMP. Accordingly, when economic analysis for a potential wind farm site is carried out, the variable SMP as well as C.F. should be considered for more accurate assessment of the wind farm.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.688-698
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• 2016

In this paper, we investigate the achievable sum rate and energy efficiency of downlink massive multiple-input multiple-output antenna systems with zero-forcing precoding, by taking into account the randomness of user locations. Specifically, we propose two types of non-uniform user distributions, namely, center-intensive user distribution and edge-intensive user distribution. Based on these user distributions, we derive novel tight lower and upper bounds on the average sum rate. In addition, the impact of user distributions on the optimal number of users maximizing the sum rate is characterized. Moreover, by adopting a realistic power consumption model which accounts for the transmit power, circuit power and signal processing power, the energy efficiency of the system is studied. In particular, closed-form solutions for the key system parameters, such as the number of antennas and the optimal transmit signal-to-noise ratio maximizing the energy efficiency, are obtained. The findings of the paper suggest that user distribution has a significant impact on the system performance: for instance, the highest average sum rate is achieved with the center-intensive user distribution, while the lowest average sum rate is obtained with the edge-intensive user distribution. Also, more users can be served with the center-intensive user distribution.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.1
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• pp.35-37
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• 1998

This study was performed to investigate lipid content, melting point, refractive index, fatty acid composition and energy intake from lipid of commercial fried instant noodles. Sixty five samples were collected in Seoul area, and analyzed. The average of lipid content was 16.7%, melting point and refractive index were 29$^{\circ}C$ and 1.46, respectively. The fatty acid composition mainly consisted of C16:0, C18:1 and C18:2. The ratio of P/M/S in fried instant noodles was 0.19 : 0.77 : 1.00. The average energy intake from lipid of 100g fried instant noodles was 150.3kcal.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.2
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• pp.209-217
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• 2014

To enhance the performance of SEWGS system by holding the WGS catalyst in a SEWGS reactor, a spring type bed insert was developed. In this study, effects of operating variables such as steam/CO ratio, gas velocity, syngas concentration on CO conversion were investigated in a fluidized bed reactor using the spring type bed insert to hold the WGS catalyst as tablet shape. CO conversion increased initially as the steam/CO ratio increased. But further increment of the steam/CO ratio caused decreasing of CO conversion because of increment of gas velocity and decrement of syngas concentration. Moreover, CO conversion decreased as the gas velocity increased and the syngas concentration decreased at the same steam/CO ratio. Continuous operation up to 48 hours (2 days) was carried out to check reactivity decay of WGS catalyst supported by spring type bed insert. The average CO conversion was 99.04% and we could conclude that the WGS reactivity at those conditions was maintained up to 48 hours.

• Korean Journal of Community Nutrition
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• v.9 no.3
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• pp.263-273
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• 2004

The purpose of this study was to investigate the pattern of individual fatty acid intake and to compare serum lipid levels and total serum fatty acid composition of high school students in Seoul (total : 234 ; male : 91 ; female : 143) In serum lipid levels, total cholesterol (Chol.), HDL-Chol. and LDL-Chol. levels of female students were significantly higher than those of male students and there was no significant difference between High Fish ＆ Low Meat intake (HFLM) and Low Fish ＆ High Meat intake (LFHM) groups. The average fat intake was 22-25 energy % of total subjects and especially, that of LFHM group was 29%, which were over the recommendation level. Although the average P/M/S ratio of dietary fat was 1.1/1.2/1.0, the average range of $\omega6/\omega3$ fatty acid ratio of dietary fat was found to be 17.9-20.7, which was far beyond the suggested range, 4-10. The average intake of cholesterol of total subjects was 360mg. LFHM group had more meats and beverages such as carbonated drinks and tended to have less beans, vegetables and mushrooms. In addition, LFHM group had more energy and fat intake than those of HFLM group, the P/S ratio of dietary fat (0.73) was lower than the recommended ratio. Serum C16 : 0 composition of LFHM group was significantly higher than that of HFLM group, and EPA and DHA composition of HFLM was significantly lower than that of LFHM. Therefore, in HFLM group, the P/S ratio of serum fatty acids was significantly higher and the $\omega6/\omega3$ ratio was lower. Dietary C18 : 0 was negatively correlated with serum EPA and DHA composition. Individual PUFA intake was negatively correlated with serum C16 : 0 and sum of SFA, and positively correlated with serum C18 : $2\omega6(LA)\;,\;sum\;o;\omega6$ and sum of PUFA. Serum C18 : 1, C18 : $3\omega3\; and\; C20\;:\;4\omega6$ (AA) compositions were not correlated with dietary fatty acid. Only serum triglyceride (TG) levels were significantly correlated with serum fatty acid compositions. Sum of SFA, C14 : 0, C16 : 0, sum of MUFA and C18 : 1 compositions were positively correlated with serum TG levels, but LA, AA, sum of PUFA and P/S ratio were negatively correlated with it.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.329-333
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• 2001

The pulsed poser system has been widely used to many applications, such as E/P(Electrostatic Precipitator), DeNox/DeSOx power system, ozon generator, etc. A pulse energy efficiency for load depends on the rising time, peak value, pulse duration and impedance matching, etc. The pulse generator generally required for short pusle duration and high peak value was forced to consider its volume and economy. In this study, developing a compact pulse generator that applied for cascading method to be made of two pulse transformers, we compared cascading voltage with non cascading one by applying the pulse energy to load. Adopting cascading technique to pulse transformer, we found that average cascading voltage was about 60[%] of theoretical value. Maximum cascading ratio was calculated at 60 times compared with non cascading voltage.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.1009-1018
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• 1995

(Ti.Si)C composite powders were synthesized by SHS method using microwave energy. Compositional and structural characterization of the powder were carried out by using scanning electron microscopy and X-ray diffraction. The average particle size of the synthesized (Ti.Si)C composite powders was smaller than that of the starting materials. From the results of the temperature profile, combustion temperature and velocity were decreased with increasing Si molar ratio. With increasing C molar ratio combustion temperature and velocity did not change. (Ti.Si)C composite was sintered at 185$0^{\circ}C$ for 60 min by using hot-pressing with 30 MPa. The best properties were obtained from the sintered specimen whose composition was 1 : 1 : 1.9 molar ratio of Ti : Si : C. The sintering density, flexural strength and vickers hardness of the sintered body were 4.71 g/㎤, 423 MPa and 21 GPa, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.377-384
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• 2002

For economic evaluation of cooling plant equipments, it is necessary to simplify energy Prediction method, which should includes efficiency corrected by part-load ratio. This study proposed simplified method with regression equations of time-average partial loads and refrigerator capacity. DOE-2 Program was used to carry out a parametric study of twelve design variables. Five input variables were considered to be significant and were used in the regression equations. To test accuracy of simplified method, calculated results were compared with DOE-2 simulated results. Test result showes a good agreement with the simulation result with an error of 5.9∼7.6%. It is expected that this method can be used as an easy prediction tool for comparing energy use of different cooling plants during the early design stage.

• Journal of Powder Materials
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• v.17 no.4
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• pp.270-275
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• 2010

Ethylene glycol-based Cu nanofluids were prepared by pulsed wire evaporation (PWE) method. The structural properties of Cu nanoparticles were studied by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The average diameter and Brunauer Emmett Teller (BET) surface area of Cu nanoparticles were about 100 nm and $7.46\;m^2/g$, respectively. The thermal conductivity and viscosity of copper nanofluid were measured as functions of Cu concentration and temperature. As the volume fraction of Cu nanoparticles increased, both the enhanced ratios of thermal conductivity and viscosity of Cu nanofluids increased. As the temperature increased, the enhanced ratio of thermal conductivity increased, but that ratio of viscosity decreased.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2059-2065
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• 2008

In this paper, quasi-static crushing tests of composite circular tubes under axial compression load are conducted to investigate the energy absorption characteristics. Circular tubes used for this experiment are glass/epoxy (GFRP) composite tubes, which is fabricated by the filament winding method. One edge of the composite tube is chamfered to reduce the initial peak load and to prevent catastrophic failure during crushing process. Two suggested trigger mechanisms for the composite tubes are investigated. Crushing modes are mainly affected by thickness/diameter ratio, and average crushing loads are mainly affected by their cross-sections. Energy absorption characteristics vary significantly as a function of the tube geometry, trigger mechanism, t/D ratio and the cross-sectional shape.