• 한국항공운항학회지
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• 제23권3호
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• pp.1-7
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• 2015

In the present study, we conducted the research on the high efficiency propulsion system for the development of long-endurance UAV with an electric propulsion system. For the long endurance UAV, fair aerodynamic characteristics with the high efficiency of the propulsion system is required because the flight power and the duration time of the long-endurance UAV vary greatly depending on the efficiency of the propulsion system. Therefore, in this study, the tracking program which records the performance of motor, propeller was developed because of their wide variation in the efficiency depending on the using condition, and records from the existing flight test program were utilized to check the accuracy of the program we had developed. For the development of future long-endurance solar UAV, we confirmed the applied voltage of motor, the optimal rotation of propeller and the gear ratio of reduction gear in order to get the highest efficiency on the propulsion system at the optimal flying condition.

• 한국입자에어로졸학회지
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• 제11권2호
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• pp.47-55
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• 2015

This study compares the results of collection efficiency of difference gas temperature in cyclone dust collector. The previous researcher's experiment results were used to confirm the reliability of CFD(Computational Fluid Dynamics) model. Based on this verified CFD model, we extended the analysis on the cyclone dust collectors. In CFD study, we used RNG k-epsilon model for analysis of turbulence flow, fluid is air, the velocity at inlet is 10 m/s, the temperature of air is $20^{\circ}C$, $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, $600^{\circ}C$ and $1000^{\circ}C$. As the temperature decreases, the average velocity of outer vortex and collection efficiency is increased, showed the highest collection efficiency at $20^{\circ}C$. It can be inferred smooth flow in cyclone dust collector is difficult because air viscosity increases as temperature increases. The power required at $1000^{\circ}C$ is almost 18 times greater than that of $20^{\circ}C$ to get the similar collection efficiency.

• 반도체디스플레이기술학회지
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• 제8권3호
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• pp.1-5
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• 2009

In this study, we have shown the power conversion efficiency of organic thin film photovoltaic devices utilizing a conjugated polymer/fullerene bulk-hetero junction structure. We use MDMO-PPV(Poly[2-methoxy-5-(3,7-dimethyloctyloxy -1,4-phenylenevinylene) as an electron donor, PCBM([6,6]-Phenyl C61 butyric acid methyl ester) as an electron accepter, and PEDOT:PSS used as a HTL(Hole Transport Layer). We have fabricated OPV(Organic Photovoltaic) devices as a function of the MDMO-PPV/PCBM concentration from 1:1 to 1:5. The electrical characteristics of the fabricated devices were investigated by means of I-V, P-V, F·F(Fill Factor) and PCE(power conversion efficiency). The power conversion efficiency was gradually increased until 1:4 ratio, also the highest efficiency of 0.4996% was obtained at the ratio.

• 한방안이비인후피부과학회지
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• 제12권2호
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• pp.182-188
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• 1999

Tinnitus is a symptom frequently encountered in the E.N.T. clinic and variously described as buzzing, ringing and thumping sound, etc., but the cause, pathogenesis, specific treatment remains to be established through close investigation. In fact, it is not easy to evaluate the treatment efficiency of tinnitus reasonably. However, in this study. we clinically investigated 47 patients who visited E.N.T. department of Kyung Won University Hospital from May. 1996 to May. 1999 and belonged to specific bianzheng(辨證) types of tinnitus classified by bianzheng(辨證), a kind of diagnostic method in order to estimate efficiency of the treatment and give aids to establishing more effective and recognizable treatment method. The result is as follows: 1) In bianzheng(辨證) types of tinnitus, Piweixuruo(脾胃虛弱) was most frequently found, in descending order, Shenjingkuisun(腎精虧損), Ganhuoshangra(肝火上擾), Tanhuoyongjie(痰火壅結). 2) In the treatment efficiency, the type of Piweixuruo(脾胃虛弱) showed the highest, in descending order, Ganhuoshangrao(肝火上擾), Tanhuoyongjie(痰火壅結) and Shenjingkuisun(腎精虧損). 3) The treatment efficiency is shown higher in patients with tinnitus included in other sysmptoms than those with a simple symptom of tinnitus. especially in case of tinnitus accompanied by vertigo, we could get much higher treatment efficiency more than we had expected.

• 아태비즈니스연구
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• 제9권3호
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• pp.51-69
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• 2018

This study intends to investigate the management efficiency of social enterprises according to types based on the portion of the budget for employing disadvantaged social groups, in the region of Gyeonggi-do. Based on the performance list disclosed at Korea Social Enterprise Promotion Agency's website, 126 social enterprises certified during a period of five years from 2013 to 2017, 126 enterprises were analyzed by using data envelopment analysis (DEA) models comparing five types of the enterprises. The types was mainly identified by the job security of disadvantaged social groups. As for measurement variables, the input components included average wage, support fund, and the number of non-vulnerable employees and the number of vulnerable employees, sales, and net income were selected as output variables. In conclusion, the efficiency of Gyeonggi-do social enterprises decreased every year, and thus it is urgent to improve their efficiency, and priority should be given to the employment of vulnerable social groups, which both the job opportunity providing-type and the social service providing-type showed the highest performance.

• Steel and Composite Structures
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• 제44권1호
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• pp.105-117
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• 2022

Impact resistance efficiency of the newly designed sandwich beam with a laterally arched core as bio-inspired by the woodpecker is numerically investigated. The principal components of the beam comprise a dual-core system sandwiched by the top and bottom laminated CFRP skins. Different materials, including hot melt adhesive, high-density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS), epoxy resin (EPON862), aluminum (Al6061), and mild carbon steel (AISI1018), are considered for the side-arched core layer of the beam for impact efficiency assessment. The aluminum honeycomb takes the role of the second core. Contact force, stress, damage formation, and impact energy for beams equipped with different materials are examined. A diversity in performance superiority is noticed in each of these indicators for different core materials. Therefore, for overall performance appraisal, the impact resistance efficiency index, which covers several chief impact performance parameters, of each sandwich beam is computed and compared. The impact resistance efficiency index of the structure equipped with the AISI1018 core is found to be the highest, about 3-10 times greater than other specimens, thus demonstrating its efficacy as the optimal material for the bio-inspired dual-core sandwich beam system.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2023년도 춘계학술대회
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• pp.118-120
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• 2023

Increasing port competition driven by the containerisation has motivated ports and terminals to focus on their performance to efficiently utilise the available resources and to make strategic decisions in port development and expansion. With both inter-port andintra-port competition increasing in the port of Colombo, this study aims to measure the efficiency of the container terminals in Colombo comparing to terminals in the port of Busan using the DEA window analysis to determine their operational efficiency and to provide suggestions for future port development activities. Multiple window analyses were conducted using CCR and BCC models with different orientations and window lengths to compare the efficiencies of 11 DMUs in both ports during the period from 2015-2019 to measure the efficiencies prior to the COVID-19 pandemic. Results revealed the largest terminal operator, PNC in Busan, to be the most efficient overall, while the second highest efficiency was recorded by one of the smallest terminal operators, SAGT in Colombo, among the sample. Although use of DEA in port performance measurement has been popular for many years, efficiency measurements in the port of Colombo, the main hub port in the South Asian region, has not been comprehensively studied so far.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 1999년도 추계학술대회
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• pp.543-563
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• 1999

본 연구에서는 특수 설계된 연면방전(Surface discharge induced Plasma Chemical Process, SPCP) 반응기로부터 발생하는 플라스마에 의하여 일산화질소(NO)와 이산화질소($NO_2$)등 유해 환경오염 가스를 주파수, 유량, 농도, 전극재질 및 감은 횟수 등의 공정변수 변화에 따른 분해율, 소비전력 및 소비전압 등을 측정하여 최적의 공정조건과 최대의 분해효율을 얻고자 하였다. 표준시료로서 일산화질소와 이산화질소를 고전압발생기의 주파수(5~50kHz), 유해가스의 체류시간(1~10.5 초)과 초기농도(100~1000 ppm), 전극의 재질(W, Cu, Al), 전극의 굵기(1, 2, 3 mm)및 감은횟수(7회, 9회, 11회)에 대하여 플라스마 연면방전 반응기를 이용하여 분해효율을 구하였다. 유해가스(NO, $NO_2$)의 분해제거 실험결과, 10 kHz의 주파수와 각각 19.8와 20 W의 소비전력에서 각각 94.3, 84.7 %로 가장 높은 분해제거율을 나타내었고, 20 kHz이상에서는 주파수가 커질수록 분해율이 감소하였다. 또한 연면방전 반응기에서 유해가스의 체류시간이 길수록, 그리고 초기농도가 작을수록 분해율은 증가하였다. 방전전극에 대한 영향은 전극의 굵기가 굵을수록 분해율이 증가하여 본 실험의 경우 3 mm의 전극을 사용하였을 때 가장 높은 분해율을 나타내었고, 전극의 재질은 텅스텐을 사용하여 방전한 경우에 가장 높은 분해율을 보였으며 구리, 알루미늄의 순으로 낮아졌다. 방전전극의 감은 횟수에 대한 영향은 7회, 9회, 11회의 순으로 감은 횟수가 많을수록 분해율이 높아짐을 알 수 있었다.

• 동의생리병리학회지
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• 제16권3호
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• pp.464-471
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• 2002

Author applied several engineering methodologies to classical ultrasonic nebulizer to cope with it's demerits. After several trials and errors, we got the several meaningful results. To evaluate the modified ultrasonic nebulizer for inhalation toxicology of cadmium, author used light-scattering photometer. This paper is the one part of inhalation exposure systems for inhalation toxicology study of cadmium. According to the testing conditions, source temperature 50℃ and inlet-duct band temperature 150℃, aerosol generation results for sodium chloride and cadmium chloride were as followings: Coefficients of variation(CV) of sodium chloride and cadmium chloride for repeated trials were 3.38 and 4.77 for 10g, 2.47 and 5.02 for 5g, and 4.70 and 2.98 for 2.5g. All the CVs were within 10% of acceptance variability. Count Per Minute(CPM) changes of NaCl and CdCl₂ for 5 repeated trials were similar. CPM ratios of CdCl₂/NaCl were 1.13 for 10g, 0.76 for 5g, and 1.06 for 2.5g. Relative aerosol generation of cadmium chloride to sodium chloride was the highest in 10g. Efficiency increases of 24.50% for 5g NaCl, 14.91 % for 2.5g NaCl, and 16.48% for 2.5g CdCl₂ with respect to theoretical efficiency were observed but 0.04% efficiency decrease was observed in 5g CdC₂. According to the modifications of source temperature(20, 50, 70℃) and inlet-duct band temperature(20, 50, 100, 150, 200℃), aerosol generation results for NaCl and CdCl₂ were as followings: CPM trends for each quantity excepting 10g NaCl in inlet-duct band temperature 200℃ were similar, and the highest CPM was observed in source temperature 70℃ to each inlet-duct band temperature. The highest CPMs to 10, 5, and 2.5g NaCl were observed in source temperature 70℃ and inlet-duct band temperature 20℃. Aerosol generation of cadmium chloride was increased with the higher source temperature, excepting inlet-duct band temperature 200℃. The highest CPMs for 10, 5, and 2.5g CdCl₂ were observed in source temperature 70℃ and inlet-duct band temperature 20℃, and this trend was similar to NaCl aerosol generation The highest CPMs for 10, 5, and 2.5g CdCl₂ were observed in source temperature 70℃ and inlet-duct band temperature 20℃, and this result was similar to NaCl aerosol generation. Observed efficiencies of 5 and 2.5g NaCl were similar to ifs theoretical efficiency but -3.08% efficiency decrease of 5g CdCl₂, 17.47% efficiency increase of 2.5g CdCl₂ were observed. CPM ratio of CdCl₂/NaCl of 10g was different to 5 and 2.5g, and 2.5g ratio was higher than 5g ratio. In conclusion, to get maximum aerosol generation for NaCl and CdCl₂ will be the conditions that set the appropriate inlet-duct band temperature for each materials and increase the source temperature. Sodium chloride can be used to evaluate the performance and predict the concentration for cadmium aerosol in aerosol generator and inhalation exposure system.

• 디지털융복합연구
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• 제20권2호
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• pp.339-344
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• 2022

본 연구에서는 공장 및 대형 시설에서 사용되고 있는 전기집진장치에 대하여 미세분진이 효율적으로 얼마나 제거 될 수 있는지에 대한 내용이다. 미세분진 제거 효율을 평가한 결과는 다음과 같다. 10,000 V 에서는 Efficiency method I은 68.1 % 를 보였고, Efficiency method I는 58.6 %로 Efficiency method I의 효율 보다 낮은 효율을 보였다. 5,000 V 에서는 Efficiency method I은 57.6 %를 보였고, Efficiency method II는 51.6 %로 Efficiency method I보다 낮은 효율을 보였다. 2,500 V 에서는 Efficiency method I은 50.3 %를 보였고, Efficiency method II는 24.4 %로 Efficiency method I보다 낮은 효율을 보였다. Efficiency method I의 경우 전 분진농도와 필터 통과 후 분진농도을 활용하여 계산한 효율이다. Efficiency method II는 필터 후의 공기와 오염된 공기가 혼합되는 환경에서 조금 더 정확한 효율을 측정하기 위해 Efficiency method II를 계산하였다. Efficiency method II는 Efficiency method I보다 낮은 효율을 나타내었다. 전기집진장치 실험 결과 10,000 V에서 집진 성능이 가장 높게 나타났으며, 그 다음 5,000 V, 2,500 V의 순을 보였다.