• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1059-1066
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• 2005

This paper reports an application of Doherty amplifier for efficiency improvement of feedforward power amplifier(FPA). For performance analysis, we measured 15 W average output power using WCDMA 4FA input signal with a center frequency 2.14 GHz. The applied Doherty amplifier presents the characteristics of high efficiency and low linearity in comparison to the class AB amplifier, and it was used as main amplifier of FPA fir efficiency improvement. To analyze the change of characteristic, tow Doherty amplifiers whose linearity and efficiency are different were applied. The applied FPAs are improved about $2\%$ or more performance in efficiency, but decreased in linearity on 15 W average output power. We additionally modified the coupling factor(CF) of the error loop and the error amplifier capacity for linearity improvement. Aa a result, the efficiency improvement and high linearity resulted from the change of CF and error amplifier capacity. However, we think if the linearity of Doherty amplifier were more than 35 dBc, the FPA would improve the performance about $2\%$ or more efficiency and maintain enough linearity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.349-350
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• 2008

In the structure of ITO/N,N'-diphenyl-N,N' bis (3-methylphenyl)-1,1'-biphenyl-4,4'-diamine(TPD) /2,9-Dimethy 1-4,7-diphenyl-1,10-phenanthroline (BCP)/tris (8-hydroxyquinoline)aluminum$(Alq_3)$/Al device, we studied the efficiency improvement of organic light-emitting diodes due to thickness variation of BCP materials used for a electron breaking layer. The thickness of TPD and $Alq_3$ was manufactured 40 nm, 60 nm, respectively under a base pressure of $5\times10^{-6}$Torr using a thermal evaporation. The TPD and $Alq_3$ layer were evaporated to be at a deposition rate of 2.0 A/s. The BCP was evaporated to be at a deposition of 1.0 A/s. When the thickness of BCP increased from 5 to 30 nm, we found that the luminous efficiency and the external quantum efficiency is superior to the others when the thickness of BCP is 20 nm. Compared to the ones from the devices made without BCP, the luminous efficiency and the external quantum efficiency was improved by 57 %, 70%, respectively.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.22-27
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• 2020

In this paper, a generalized efficiency equation was proposed to estimate the internal loss of the SMPS (switched-mode power supply) with 3 variables. The first variable was an internal loss not related to the load current such as auxiliary power, the second was a loss proportional to the current such as diode loss, and the third was a loss proportional to square of the current such as conduction loss. Especially, theoretical internal losses of the totem pole bridgeless PFC which is widely used for high efficiency SMPS were expressed as output function to compare generalized efficiency equation. In addition, in order to reduce the conduction loss of the switch, when a multiple switch were paralleled, the correlation with the efficiency was analyzed and shown as a graph. In order to confirm the degree of the parallel switch structure on the efficiency improvement, a 2kW class totem pole bridgeless PFC was constructed and the effectiveness of the analysis was confirmed by comparing the generalized efficiency equation and theoretical loss analysis results with experimental data.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.3
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• pp.193-195
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• 2009

Purpose: The work flow of international hospital's laboratory consists of rapid test and result report at the present day. However, the frequent inquiry of sample, which cause affairs to delay and efficiency to Lower, affects medical examination. In order to promote work's efficiency, we should improve the problem and make work smooth between a laboratory, outs and ward. Materials and Methods: This study runs as follows. First, Investigating test result, test schedule, test receipt, quick result, etc through the activity required from September to November 2007 about the inquiry of sample. After analysis of the problem in December, remaking the test schedule for improvement solution and reporting it to outs and ward. When the result is retest and dilution, we directly fill in a result space with the result situation of the patient to let them know beforehand. We also, prevent the omission of the result through checking the sample list and discriminate in vivo from in vitro by changing the laboratory's telephone number. We have improved the problem about the inquiry of sample through valuation and analysis since the improvement activity from January to March 2008. Result: The case about the frequent inquiry of sample has reduced by 57.8%. this improvement activity indicated that p-value<0.05 was statistically significant through paired t-test. This activity make study smooth and we rapidly report the result. Conclusion: By reducing the case regarding the inquiry of sample, work discontinuation, and concentration reduction, the work efficiency was increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.5
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• pp.307-311
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• 2014

Because of a waveguiding effect and total internal reflection caused by a difference in refractive indices, only 20% of generated light is emitted to the air and the rest is trapped or absorbed in the device. An improvement of outcoupled efficiency of organic light-emitting diodes was studied using a microlens array. Mold of microlens array was fabricated by using photo-lithography with the AZ9260 photoresist, and the microlens array was formed onto the glass substrate using the UV curing agent named ZPU13-440. Device structure consists of microlens/glass/ITO/TPD/$Alq_3$/LiF/Al. It was found that there is an improvement of external quantum efficiency by about 20% at the same current density for the device with the microlens array compared to that of the reference one. Simulated outcoupled efficiency shows the improvement by about 20% for the device with the microlens array compared to that of the reference one. These results are consistent with the experimental ones.

• The KSFM Journal of Fluid Machinery
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• v.17 no.4
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• pp.30-39
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• 2014

The cross flow turbine is economical because of its simple structure. For remote rural region, there are needs for a more simple structure and very low head cross flow turbines. However, in this kind of locations, the water from upstream always flows into the turbine with some other materials such as sand and pebble. These materials will be damage to the runner blade and shorten the turbine lifespan. Therefore, there is a need to develop a new type of cross flow turbine for the remote rural region where there is availability of abundant resources. The new design of the cross flow turbine has an inlet open duct, without guide vane and nozzle to simplify the structure. However, the turbine with inlet open duct and very low head shows relatively low efficiency. Therefore, the purpose of this study is to optimize the shape of the turbine inlet to improve the efficiency, and investigate the internal flow of a very low head cross flow turbine. There are two steps to optimize the turbine inlet shape. Firstly, by changing the turbine open angle along with changing the turbine inlet open duct bottom line (IODBL) location to investigate the internal flow. Secondly, keeping the turbine IODBL location at the maximum efficiency achieved at the first step, and changing the turbine IODBL angle to improve the performance. The result shows that there is a 7.4% of efficiency improvement by optimizing turbine IODBL location (open angle), and there is 0.3% of efficiency improvement by optimizing the turbine IODBL angle.

• Plant Journal
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• v.17 no.1
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• pp.58-66
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• 2021

The government has recently come up with a policy to tighten regulations on air pollutant emissions due to public concerns over the emission of pollutants such as fine dust. The coal-fired power plant is speeding up the improvement of the performance of environmental facilities, and this paper deals with the cases of performance improvement by adding a catalyst to the 500 MW standard coal-fired power DeNox system, and examines the change in the performance factors according to the addition of catalysts and the efficiency of NOx removal. The DeNOx efficiency before and after improvement increased from 80% to 88%, and the conversion rate of SO2/SO3, ammonia slip which are performance factors satisfied the design assurance value, but exceeded the design assurance value for differential pressure. At the same time, the ammonia slip concentration and differential pressure items increased as the NOx removal efficiency increased, resulting in the need for management and improvement.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.320-331
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• 2012

A combination system of catch canal and constructed wetland was designed and suggested to improve water quality in gagricultural region of lower Dong-jin river basin. In order to evaluate an water quality improvement efficiency of the designed combination system, the NPS-WET model was applied in this study. Simulation result of the NPS-WET shown that the nutrient load removal rate of constructed wetland was BOD, T-N, T-P and SS was 30.7~39.0%, 46~60%, 40.7~57.0% and 68.2~74.7%, respectively. Nutrients reduction of constructed wetland was higher in growing season than winter season because vital activity of microorganism, macrophyte and algae was augmented with high air and water temperature. Effluents from constructed wetland can affect water-quality of catch canal drains, especially, water-quality on junction point to Dong-jin river. Water-quality improvement in low-flowed catch canal (Un-san) was more significant than in high-flowed catch canal (Won-pyeong). In conclusion, a feasible design of constructed wetland is necessary to treat large quantity of receiving water. The NPS-WET is useful tool for assessing water-quality improvement efficiency using constructed wetland.

• The Journal of Information Systems
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• v.26 no.2
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• pp.143-164
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• 2017

Purpose The purpose of this study is to investigate to investigate the effects of cloud system on the efficiency improvement and cost-saving of production processes. It also tries to provide small- and medium-sized companies and IT practitioners with a practical guideline for a successful implementation of could systems. Design/methodology/approach This study was conducted by observing and analyzing a case of implementing a cloud system at a small-sized company having multiple job sites in terms of the improvement in data-sharing efficiency and cost-saving of production processes. Findings This study found that cloud system was an effective way of sharing data between and among production processes of geographically scattered job sites and thus, helped the company to remedy problems of work schedule and load-balance along sequential production processes. Cloud system also allowed the company to reduce the number of visits made by 3-inspectors to four job sites by 75% and the personnel cost related to inspectors' site visit.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.373-382
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• 2007

In the vertical drain method, discharge capacity is generally one of the most important factor which affect on the estimation of the drain efficiency. However, adopting the drain considering discharge capacity only is not sufficiently considered method so that systematic criteria for adoption is necessary to choose the most suitable drain. Therefore, this study represents the application method considering behavior of the ground and vertical drain which is coupled together and ground improvement efficiency analyzing various cases of discharge capacity test performed in the recent soft ground improvement projects. According to the analysis, most drains tend to satisfy the required discharge capacity. It presents that deformed shape of the drains and well resistance estimation along the ground settlement, improvement efficiency by water content ratio along the depth and shear strength obtained after ground improvement should be considered altogether with the discharge capacity to select the proper drain. Also, appropriate adoption of drain material considering the ground condition is vital through analyzing the field measured data and comparing the result of the discharge capacity test as various vertical drain materials are being constructed continuously.