• 한국태양에너지학회 논문집
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• 제40권5호
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• pp.23-34
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• 2020

Concentrator photovoltaic (CPV) system consists of high-quality complex optical elements, mechanical devices, and electronics components and can have the advantages of high integration and high-efficiency energy sources. III-V compound semiconductor cells have proven performance based on high reliability in the aerospace field, but have characteristics that require absolute support of the balance of systems (BOS) such as solar position trackers, receivers with heat sinks, and housing instruments. To determine the optimum parameters of secondary optical elements (SOEs) design for CPV systems, we designed three types of CPV modules, classified as non-SOEs type, reflective mirror type, and CPC lens type. We measured the I-V and P-V characteristics of the prototype CPV modules with the angle of inclination varying from 0° to 12° and with a 500-magnification Fresnel lens. The experimental results assumed misalignment of the solar position tracker or module design of pinpoint accuracy. As a result, at the 0° tilt angle, the CPC lens produced lower power due to the quartz transmittance ratio compared to that by other SOEs. However, for tilt angles greater than 3°, the CPC lens type module achieved high efficiency and stability. This study is expected to help design high-performance CPV systems.

• 한국산학기술학회논문지
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• 제13권1호
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• pp.329-332
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• 2012

LED는 저 전력, 긴 수명, 고 휘도, 빠른 응답, 친환경적인 특성의 여러 장점을 갖고 있기 때문에 청색과 녹색 LED는 교통신호, 옥외 디스플레이, 백색 LED는 LCD 후면광 등의 응용 제품에 사용되고 있다. 여기서 LED의 성능을 향상하기 위하여 출력전력과 소자의 신뢰성을 높이고, 동작전압을 낮추어야 LED 칩의 고효율화가 이루어져야 하는데, 이는 에피택셜층, 표면요철, 패턴이 있는 사파이어 기판, 칩 설계의 최적화, 특수 공정의 개선 등의 기술이 우수해야 한다. 본 연구에서는 측면 에칭 기술과 절연층 삽입기술을 이용하여 사파이어 에피 웨이퍼 위에 GaN-기반 백색 LED 칩을 제작하여 그 성능을 조사하였다. LED 칩의 성능을 개선하기 위한 최적화 설계와 CBL(current blocking layer) 삽입 기술의 개선된 공정을 통하여 LED 칩 성능의 향상을 확인할 수 있었으며, 출력 전력은 광 출력 7cd, 순방향 인가전압 3.2V의 값을 얻었다. 현재의 LCD 후면광원으로 사용되고 있는 LED 칩의 출력에 비하여 성능이 개선되었으며, 의료기기 및 LCD LED TV의 후면광원으로 사용할 수 있을 것으로 기대된다.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.245-256
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• 2019

The experimentally determined mechanical behavior of the material under the prescribed service conditions is the basis of advanced engineering optimum design. To allow experimental data on the behavior of the material considered, uniaxial stress tests were made. The aforementioned tests have enabled the determination of mechanical properties of material at different temperatures, then, the material's resistance to creep at various temperatures and stress levels, and finally, insight into the uniaxial high cyclic fatigue of the material under different applied stresses for prescribed stress ratio. Based on fatigue tests, using modified staircase method, fatigue limit was determined. All these data contributes the reliability of the use of material in mechanical structures. Data representing mechanical properties are shown in the form of engineering stress-strain diagrams; creep behavior is displayed in the form of creep curves while fatigue of the material is presented in the form of S-N (maximum applied stress versus number of the cycles to failure) curve. Material under consideration was 18CrNi8 (1.5920) steel. Ultimate tensile strength and yield strength at room temperature and at temperature of $600^{\circ}C$: [${\sigma}_{m,20/600}=(613/156)MPa$; ${\sigma}_{0.2,20/600}=(458/141)MPa$], as well as endurance (fatigue) limit at room temperature and stress ratio of R = -1 : (${\sigma}_{f,20,R=-1}=285.1MPa$).

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2001년도 정기학술대회
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• pp.277-278
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• 2001

The successful operation of a product In service depends upon the effective provision of logistic support in order to achieve and maintain the required levels of performance and customer satisfaction. Logistic support encompasses the activities and facilities required to maintain a product (hardware and software) in service. Logistic support covers maintenance, manpower and personnel, training, spares, technical documentation and packaging handling, storage and transportation and support facilities.The cost of logistic support is often a major contributor to the Life Cycle Cost (LCC) of a product and increasingly customers are making purchase decisions based on lifecycle cost rather than initial purchase price alone. Logistic support considerations can therefore have a major impact on product sales by ensuring that the product can be easily maintained at a reasonable cost and that all the necessary facilities have been provided to fully support the product in the field so that it meets the required availability. Quantification of support costs allows the manufacturer to estimate the support cost elements and evaluate possible warranty costs. This reduces risk and allows support costs to be set at competitive rates.Integrated Logistic Support (ILS) is a management method by which all the logistic support services required by a customer can be brought together in a structured way and In harmony with a product. In essence the application of ILS:- causes logistic support considerations to be integrated into product design;- develops logistic support arrangements that are consistently related to the design and to each other;- provides the necessary logistic support at the beginning and during customer use at optimum cost.The method by which ILS achieves much of the above is through the application of Logistic Support Analysis (LSA). This is a series of support analysis tasks that are performed throughout the design process in order to ensure that the product can be supported efficiently In accordance with the requirements of the customer.The successful application of ILS will result in a number of customer and supplier benefits. These should include some or all of the following:- greater product uptime;- fewer product modifications due to supportability deficiencies and hence less supplier rework;- better adherence to production schedules in process plants through reduced maintenance, better support;- lower supplier product costs;- Bower customer support costs;- better visibility of support costs;- reduced product LCC;- a better and more saleable product;- Improved safety;- increased overall customer satisfaction;- increased product purchases;- potential for purchase or upgrade of the product sooner through customer savings on support of current product.ILS should be an integral part of the total management process with an on-going improvement activity using monitoring of achieved performance to tailor existing support and influence future design activities. For many years, ILS was predominantly applied to military procurement, primarily using standards generated by the US Government Department of Defense (DoD). The military standards refer to specialized government infrastructures and are too complex for commercial application. The methods and benefits of ILS, however, have potential for much wider application in commercial and civilian use. The concept of ILS is simple and depends on a structured procedure that assures that logistic aspects are fully considered throughout the design and development phases of a product, in close cooperation with the designers. The ability to effectively support the product is given equal weight to performance and is fully considered in relation to its cost.The application of ILS provides improvements in availability, maintenance support and longterm 3ogistic cost savings. Logistic costs are significant through the life of a system and can often amount to many times the initial purchase cost of the system.This study provides guidance on the minimum activities necessary to Implement effective ILS for a wide range of commercial suppliers. The guide supplements IEC60106-4, Guide on maintainability of equipment Part 4: Section Eight maintenance and maintenance support planning, which emphasizes the maintenance aspects of the support requirements and refers to other existing standards where appropriate. The use of Reliability and Maintainability studies is also mentioned in this study, as R&M is an important interface area to ILS.

• 드라이브 ㆍ 컨트롤
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• 제12권3호
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• pp.52-59
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• 2015

An electro hydraulic poppet valve (EHPV) and a variable orifice poppet are assembled in a single block, which is referred to as a RHINO but is also generally called a pilot-operated flow control valve. In this study, we analyzed the structure and the operating principle for a RHINO applied in a 21-ton electric excavator system. The RHINO was experimentally tested to measure the dynamic responses and the pressure energy loss. In this test, we investigated the variation in the conductance coefficient according to the increase in the supply pressure under a constant current and a variation in the flow rate according to the increase in the current. Then, the geometrical shapes and the spring stiffness of the RHINO were considered to develop an analysis model. The characteristics (current-force and hysteresis) for the solenoid based on the experimental data were reflected in the analysis model that was developed, and the reliability of the analysis model was also verified by comparing the experimental and analytical results. The developed model is thus considered to be reliable for use in a wide range of applications, including optimum design, sensitivity analysis, parameter tuning, etc.

• 공업화학
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• 제32권3호
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• pp.320-325
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• 2021

본 연구에서는 밀배아유에 항산화 물질이 다량 함유되어있는 밀싹 추출물을 첨가한 후 O/W 유화액을 제조하는 최적화 공정을 설계하였다. 최적화 공정 설계는 반응표면분석법의 중심합성계획모델을 사용하였다. 기초실험을 통하여 유화제 첨가량, 유화시간, 밀싹 추출물의 첨가량을 독립변수로 설정하였다. 그리고 반응치는 평균입자크기, 점도, 유화안정도지수를 설정하여 유화액의 안정성을 평가하였다. 각 독립변수에 대해 최적화하여 P-value와 결정계수를 평가하여 실험 신뢰도를 확인하였다. 모든 독립변수를 만족하는 최적화 조건은 유화제 첨가량 = 7.7 wt.%, 유화시간 = 23.6 min, 밀싹 추출물의 첨가량 = 3.9 wt.%에서 평균입자크기 = 252.3 nm, 유화액의 점도 = 616.7 cP, ESI = 88.7%로 나타났다. 종합만족도가 0.9137으로 실험의 타당성을 뒷받침하였고, 실제실험을 진행하여 오차율이 0.5 %이하로 측정되었다. 따라서 중심합성계획모델을 통해 밀싹 추출물을 첨가하여 유화액을 제조하는 최적화 과정을 설계하였다.

• 대한환경공학회지
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• 제32권1호
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• pp.33-46
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• 2010

본 연구는 광분해 산화공정으로 난분해성 물질인 N-Nitrosodimethylamine (NDMA)인 제거 및 부산물 생성 특성을 파악하기 위한 3개의 독립변수 (자외선 강도($X_1:\;1.5{\sim}4.5\;mW/cm^2$, 초기 NDMA 농도($X_2:\;100{\sim}300\;uM$), pH(X3:3~9))와 4개의 종속변수(NDMA 제거율($Y_1$), dimethylamine (DMA) 생성농도($Y_2$), dimethylformamide (DMF) 생성농도($Y_3$) 및 $NO_2$-N 생성농도($Y_4$))로 구성된 박스-벤켄 설계를 이용한 실험계획을 적용시켜 예측 모델과 광분해 산화 최적조건을 수립하였다. 실험결과 2시간 광분해 후 NDMA는 거의 완전히 제거되었으며 DMA, DMF와 $NO_2$-N은 NDMA 광분해와 동시에 부산물로 생성되었다. 광분해 최적의 조건을 얻기 위해 정준분석을 수행하여 최적 점 (반응값, 독립변수 조건)과 예측반응모델을 수립한 결과, 다음과 같은 결과를 얻었다 ($Y_1=117+21X_1-0.3X_2-17.2X_3+{2.43X_1}^2+{0.001X_2}^2+{3.2X_3}^2-0.08X_1X_2-1.6X_1X_3-0.05X_2X_3$ ($R^2$ = 96%, Adjusted $R^2$ = 88%)와 99.3% ($X_1:\;4.5\;mW/cm^2$, $X_2:\;190\;uM$, $X_3:\;3.2$), $Y_2=-101+18.5X_1+0.4X_2+21X_3-{3.3X_1}^2-{0.01X_2}^2-{1.5X_3}^2-0.01X_1X_2-0.07X_1X_3-0.01X_2X_3$ ($R^2$= 99.4%, 수정 $R^2$ = 95.7%)와 35.2 uM ($X_1:\;3\;mW/cm^2$, $X_2:\;220\;uM$, $X_3:\;6.3$), $Y_3=-6.2+0.2X_1+0.02X_2+2X_3-{0.26X_1}^2-{0.01X_2}^2-{0.2X_3}^2-0.004X_1X_2+0.1X_1X_3-0.02X_2X_3$ ($R^2$= 98%, 수정 $R^2$ = 94.4%)와 3.7 uM ($X_1:\;4.5\;mW/cm^2$, $X_2:\;290\;uM$, $X_3:\;6.2$), $Y_4=-25+12.2X_1+0.15X_2+7.8X_3+{1.1X_1}^2+{0.001X_2}^2-{0.34X_3}^2+0.01X_1X_2+0.08X_1X_3-3.4X_2X_3$ ($R^2$= 98.5%, 수정 $R^2$ = 95.7%)와 74.5 uM ($X_1:\;4.5\;mW/cm^2$, $X_2:\;220\;uM$, $X_3:\;3.1$). 반응표면분석법 중 하나인 박스-벤켄법은 UV 광분해에 의한 NDMA 분해 및 부산물 생성에 대한 통계학적 및 수학적인 결과 및 최적의 운전조건을 제시하였다. 예측모델의 검정을 통하여 박스-벤켄법은 매우 높은 신뢰성을 보였다.