• 기계와재료
• /
• v.22 no.4
• /
• pp.68-74
• /
• 2010

현장 운용조건하에서 사용자들이 요구하는 보증수명을 시험평가하기 위해서는 많은 시간과 비용이 소요된다. 이를 해결하기 위한 시험기술로써 흔히 가속시험이 운용되며 가속방법에는 연속적으로 사용하지 않는 제품을 연속적으로 가동시킴으로써 고장시간을 단축시키는 사용를 가속과 사용조건보다 높은 스트레스를 부과하여 제품의 수명을 단축시키는 고 스트레스 가속이 있다. 기계류 부품들에서 대부분 채택하고 있는 고 스트레스 가속방법을 적용한 무고장 가속시험의 전략은 크게 현장 운영조건하에서의 등가부하를 산출, 시험 운영조건하에서의 등가부하를 산출 그리고 보증수명에 의한 무고장 시험시간을 산출하는 3가지의 기술로 운영된다. 이러한 가속시험 전략은 기계류에 관련된 대부분의 부품 및 시스템에 적용 및 활용이 가능하다.

• Journal of the Korean Solar Energy Society
• /
• v.30 no.6
• /
• pp.95-101
• /
• 2010

This paper presents performance estimation approach of grid-connected photovoltaic(PV) system to predict energy yield from irradiance to PV system using normalized yield model for changing meteorological conditions. The accuracy and validity of proposed performance estimation method is identified by compared measured with estimated yield using monitored data. These results will indicate that it is useful to estimate various loss factors causing the system performance obstruction and enhance the lifetime yield of PV system.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.5
• /
• pp.18-23
• /
• 2013

This paper presents a simple but valid loss calculation method of grid-connected photovoltaic system based on normalized yield model. The proposed method can be represented as a quantitative value for five losses and performance of grid-connected photovoltaic system with three years monitored data. These results will indicate that it is useful to investigate various loss factors causing the performance obstruction, enhance the lifetime yield for changing meteorological conditions, and determine the optimal design and performance improvement of grid-connected photovoltaic system.

• Journal of the Korean Solar Energy Society
• /
• v.37 no.3
• /
• pp.23-32
• /
• 2017

This paper presents losses comparison and analysis results for different types of fault modes of grid-connected photovoltaic system generated for long-term operation. The approach of losses comparison and analysis by faults is to identify relationship between measured and estimated values of five loss factors which are quantified from irradiance to system output power. This paper presents the symptom results for faults such as snow, shading, sensor defect, blackout, soiling and so on from three years or more monitored data. These results will indicate that it is useful to develop fault detection and diagnosis tool to enhance capacity factor and save operation and maintenance cost of grid-connected photovoltaic system in the field.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.5
• /
• pp.89-94
• /
• 2013

This paper presents a simple but valid design factor calculation method of grid-connected photovoltaic system using normalized yield model. The proposed calculation method can be represented as a quantitative value about five design factors from irradiance to system output power. The validity of this method is identified by analyzing design factor with three years monitored data. These results will indicate that it is useful to determine the optimal design and selection of grid-connected photovoltaic system to meet different user purposes and enhance long-term reliability and stability of grid-connected photovoltaic system.

• Journal of the Korean Solar Energy Society
• /
• v.39 no.3
• /
• pp.29-45
• /
• 2019

As the solar energy market grows, the need to investigate the potential of photovoltaic system is being highlighted. However, due to the lack of plain field, the system on top of buildings is being exploited. This paper analyzes the potential to install PV systems on the rooftops. First of all, with the aid of a photovoltaic system simulation software, buildings were designed in a specific area based on the architectural data. And then, with the same software, the potential to install photovoltaic system was explored by placing PV modules on the buildings' rooftops. The installation potential was calculated and simulated with consideration for obstacles on the rooftops. The parameters are composed of available area for system installation, area utilization rate, PV system power capacity, operation yield hour per day and performance ratio. In the simulation, 5 sites were analyzed based on their architectural data. In the end, reliable data that can be utilized were collected for the potential to install the system with the photovoltaic system simulation software.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.17 no.3
• /
• pp.174-181
• /
• 2014

Design procedure of LEG(Linear Electric Generator) is introduced by performing the time-domain analysis for the heaving motion of a floating buoy coupled with LEG. A vertical truncated buoy is selected as a point absorber and a double-sided Halbach array mover and cored slotless stator is adopted as a linear electric generator. LEG with a double-sided Halbach array mover and cored slotless stator is designed with the input data such as the heave motion velocity and wave exciting forces in time-domain. The validity of designed LEG is confirmed by performing generating-characteristic-analysis under the sinusoidal motion of a buoy, based on the numerical techniques such as FE(Finite Element) analysis. In particular, an ECM(Equivalent Circuit Method) is employed as the design tool for the prediction of generating characteristics under irregular wave conditions. Finally, we confirm that the ECM gives reasonable and fast results without sacrifice of accuracy.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.1049-1061
• /
• 2013

In this paper, a relative heat exchange rate is numerically compared for cast-in-place concrete energy piles with different heat exchange pipe configurations, and a new design method for energy piles is proposed. An equivalent heat exchange rate was estimated for the W-type (one series loop), multiple U-type (four parallel loops), and coil-type heat exchanger installed in the same large-diameter drilled shaft. In order to simulate a cooling operation in summer by a CFD analysis, the LWT (leaving water temperature) into a energy pile was fixed at $35^{\circ}C$ and then the EWT (entering water temperature) into a heat pump was monitored. In case of continuously applying the artificial maximum cooling load for 100 hours, all of the three types of heat exchangers show the marginally similar heat exchange rate. However, in case of intermittently applying the cooling load with a cycle of 8 hours operation-16 hours off for 7 consecutive days, the coil type heat exchanger exhibits a heat exchange rate only 86 % of the multiple U-type due to measurable thermal interference between pipe loops in the energy pile. On the other hand, the W-type possesses the similar heat exchange rate to the multiple U-type. The equivalent heat exchange rates for each configuration of heat exchangers obtained from the CFD analysis were adopted for implementing the commercial design program (PILESIM2). Finally, a design method for cast-in-place concrete energy piles is proposed along with a design chart in consideration of typical design factors.

• Radiation Oncology Journal
• /
• v.8 no.1
• /
• pp.7-15
• /
• 1990

The ultimate objective of our experiment is to obtain the precise distribution of temperature in malignant tumors occurring in cerebral parenchyme of human beings when we will carry out interstitial hyperthermia in the near future. To achieve this purpose, first of all, it is necessary to make an attempt at performing interstitial hyperthermia in vivo under the similar condition of human beings. Therefore, we chose cats as materials much alike tissue characteristics of human beings. Moreover, it is also necessary to get the basic data from dynamic phantom in order to standardize and compare results obtained from interstitial hyperthermia carried out in cats. By having performed these experiments we got the following results. 1) On doing interstitial hyperthermia with 915 MHz microwave, the possible treated volume was 2 cm by 2 cm by 6 cm according to $50\%$ specific absorption rate (SAR). 2) The distribution of temperature within non-circulated static phantom was much the same as power density in air, but we observed that the temperature, within $5\~10$ minutes, rose to more higher than $55^{\circ}C$ not measured with Ga-As fiberoptic thermistor which was not impeded by microwave after performing interstitial hyperthermia. 3) Within dynamic phantom in which normal saline was circulating, temperature reached steady state which was maintained for more than 45 minutes through transit period in 5 minutes after starting interstitial hyperthermia. 4) When we interrupted circulation in the dynamic phantom, we observed that temperature rose to the same level as in the static phantom. 5) We could carry out interstitial hyperthermia safely when we used the generating power below 5 watts. Abrupt interruption of circulation caused a rapid increase in temperature. Times taking to rise to maximum $55^{\circ}C$ were 15.2 minutes (SE 0.4),9.7 minutes (SE 0.3), and 6.3 min-utes (SE 0.4) respectively with generating powers of 5,10, and 15 watts.