• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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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.

• 반도체디스플레이기술학회지
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• 제19권4호
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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.

• 한국전자파학회논문지
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• 제16권11호
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• pp.1059-1066
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• 2005

본 논문은 피드포워드 전력 증폭기의 효율 개선을 위한 도허티 증폭기의 적용에 관한 연구이다. 성능 분석을 위하여 중심 주파수 2.14 GHz의 WCDMA 4FA신호를 인가하여 평균 출력 전력 15 W에서 측정하였다. 적용한 도허티 증폭기는 동급 class AB 증폭기와 비교하여 고효율 저선형성의 특성을 나타내며 효율 개선을 위하여 피드포워드 전력 증폭기(FPA)의 주 증폭기로 사용되었다. 특성 변화를 분석하기 위해 선형성과 효율 특성이 다른 2가지 종류의 도허티 증폭기를 적용하였으며 각각의 FPA들은 평균 출력 15 W에서 효율은 $2\%$ 이상의 개선을 보였지만 선형성은 1.5 dBc 이상 저하되는 특성을 나타냈다. 저하된 선형성을 개선하기 위하여 부가적으로 오차 루프의 결합 계수(CF)와 오차 증폭기의 용량을 변화시켰다. CF와 오차 증폭기의 용량 변화로 효율 개선과 높은 선형성을 얻을 수 있었고 도허티 증폭기가 35 dBc 이상의 선형성을 유지하면 부가적인 변화 없이 평균 출력 전력 15 W에서 $2\%$ 이상의 효율 개선과 충분한 선형성을 얻을 수 있다.

• 핵의학기술
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• 제13권3호
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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.

• 한국전기전자재료학회논문지
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• 제27권5호
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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.

• 한국유체기계학회 논문집
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• 제17권4호
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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.

• 플랜트 저널
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• 제17권1호
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• pp.58-66
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• 2021

최근 미세먼지 등 대기오염물질 배출에 대한 전국민적 우려로 정부는 대기오염물질 배출규제 강화정책을 내놓고 있다. 국내 석탄화력발전소는 대기환경설비 성능개선에 박차를 가하고 있으며, 이 논문에는 500 MW급 표준석탄화력 탈질설비에 촉매단을 추가하는 성능개선사례를 다루고 있으며, 촉매단 추가 전·후 성능시험시험과 NOx제거효율에 따른 탈질설비 핵심성능 인자의 변화를 살펴보았다. 연구결과 촉매단 추가 전·후 탈질설비 효율은 80%에서 88%로 상승했고, 핵심성능인자인 미반응 암모니아, SO2/SO3 전환율은 설계보증치를 만족하였으나, 차압의 경우 설계보증치를 초과하였다. 동시에, NOx 제거효율에 따른 핵심성능인자 변화는, 미반응 암모니아 농도, 차압 항목은 NOx 제거효율이 증가에 따라 같이 증가하는 양상을 보여 관리 및 개선이 필요하다는 결과를 얻을 수 있었다.

• Geomechanics and Engineering
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• 제10권5호
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• pp.617-633
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• 2016

A numerical study has been conducted to examine the improvement achieved in the ultimate pullout capacity of horizontal circular anchor plates embedded in undrained clay, by constructing granular columns of varying diameter over the anchor plates. The analysis has been carried out by using lower bound theorem of limit analysis and finite elements in combination with linear programming. The improvement in uplifting capacity of anchor plate is expressed in terms of an efficiency factor (${\xi}$). The efficiency factor (${\xi}$) has been defined as the ratio of ultimate vertical pullout capacity of anchor plate having diameter D embedded in soft clay reinforced by granular column to the vertical pullout capacity of the anchor plate with same diameter D embedded in soft clay only. The variation of efficiency factor (${\xi}$) for different embedment ratios and different diameter of granular column has been studied considering a wide range of softness of clay and different value of soil internal friction angle (${\phi}$) of the granular material. It is observed that ${\xi}$ increases with an increase in diameter of the granular column ($D_t$) and increase in friction angle of granular material. Also, the effectiveness of the usage of granular column increases with decrease in cohesion of the clay.

• 한국전기전자재료학회논문지
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• 제26권10호
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• pp.745-753
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• 2013

Performance of organic light-emitting diodes incorporating microlens array was simulated using a Light Tools software. Use of microlens array can help the light to escape out of the device. We simulated a reference device that is consisted of reflection layer, emissive layer, and flat transparent substrate. And in this reference device, outcoupled efficiency of 22% was obtained. Several shapes of microlens were applied such as hemisphere, trapezoid, cone, and rectangular parallelepiped. The results showed the improvement of outcoupled efficiency of the device with microlens compared to that of the reference one. And from the analyses of the simulated data, the obtained appropriate shape of microlens is hemisphere, and the improvement of the device with hemispherical lens is 57% higher than that of the reference one.

• 한국정보시스템학회지:정보시스템연구
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• 제26권2호
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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.