• Journal of Aerospace System Engineering
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• v.16 no.5
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• pp.1-7
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• 2022

Recently, satellites equipped with high-performance electronics have required higher power consumption because of the advancement of satellite missions. For this reason, the size of the solar panel is gradually increasing to meet the required power budget. Increasing the size and weight of the solar panel is one of the factors that induce the elastic vibration of the flexible solar panel during the highly agile maneuvering of the satellite or the mode of vibration coupling to the satellite or the mode of vibration coupling to the micro-jitter from the on-board appendages. Previously, an additional damper system was applied to reduce the elastic vibration of the solar panel, but the increase in size and mass of system was inevitable. In this study, to overcome the abovementioned limitations, we proposed a high -damping yoke structure consisting of a superplastic SMA(Shape Memory Alloy) laminating a thin FR4 layer with viscoelastic tape on both sides. Therefore, this advantage contributes to system simplicity by reducing vibrations with small volume and mass without additional system. The effectiveness of the proposed superelastic SMA multilayer solar panel yoke was validated through free vibration testing and temperature testing using a solar panel dummy.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.567-570
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• 2006

A numerical study has been carried out for a solar water heater which consists of double skin solar vacuum tubes. Water is heated as it flows through the coaxial fluid conduit inserted in each tube. The space between the exterior of the fluid conduit and the glass tube is tilled with antifreeze solution. This is to facilitate heat transfer from the solar heated absorber surface to water and to prevent the functional problems due to freezing in frigid weather conditions. A one-dimensional steady state model is fully described which will be used to develop three-dimensional model using STAR-CD. These models could be used efficiently in designing double skin solar collector tubes with different geometrical parameters other than those considered in the present analysis. Results show a good agreement when compared with other experimental data demonstrating the reliability of the one-dimensional model employed.

• Science of Emotion and Sensibility
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• v.26 no.2
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• pp.129-140
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• 2023

Following ISO 20471, in this study, first, two sets of safety clothes and safety vests were made by designing and attaching animal and bird patterns preferred by children to retroreflective films and black fabrics on those fluorescent fabrics and retroreflective materials prescribed by international standards. Second, by mounting a smart photonic device on the safety clothing so that the body can be recognized from a distance even without an ambient light source at night, children can emit three types of light depending on the situation with just one-touch of the button. From a result of comparison with visibility a day and night by dressing a mannequin in the made smart safety clothing, the difference in visibility was evident at night, it was confirmed that we can see the figure of a person even at a distance of approximately 70 m. Therefore, it is expected to contribute to the prevention of traffic and other accidents on the road, as the drivers driving at night or in bad weather can recognize a person from a distance. Third, in case of the energy is exhausted and cannot maintain the stability of the light-emitting function of the optical faber, we can use energy harvesting device, and the light-emitting time will be extended. As a result it comes up to emit light stably for a long time. And this prove that smart photonic safety clothing can also be used for night workers. Therefore, optical fiber safety clothing is expected to be highly wearable not only in real life but also in dark industrial sites due to stable charging by applying the energy harvesting provided by solar cells.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.179-184
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• 2018

To lessen oxygen concentrations in a wafer through modifying the length of graphite heaters, we investigated the influence of relative distance from heater to quartz crucible on temperature profile of hot-zone in Czochralski silicon-crystal growth by simulation. In particular, ATC temperature and power profiles as a function of different ingot body positions were investigated for five different heater designs; (a) typical side heater (SH), (b) short side heater-up (SSH-up), (c) short side heater-low (SSH-low), (d) bottom heater without side heater (Only-BH), and (e) side heater with bottom heater (SH + BH). It was confirmed that lower short side heater exhibited the highest ATC temperature, which was attributed to the longest distance from triple point to heater center. In addition, for the viewpoint of energy efficiency, it was observed that the typical side heater showed the lowest power because it heated more area of quartz crucible than that of others. This result provides the possibility to predict the feed-forward delta temperature profile as a function of various heater designs.

• Journal of the Korean Society for Railway
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• v.17 no.2
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• pp.94-99
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• 2014

Recently, trends in new transportation system development have been primarily focused on sustainable and ecofriendly mobility solutions. The personal rapid transit (PRT) system has been considered a promising candidate in this category; its competitiveness is being improved through convergence with cutting-edge electric vehicle (EV) technologies. However, battery-powered vehicles pose difficult technical challenges in attempts to achieve reliable and efficient operation. In this study, a design approach for a solar-power assisted PRT system is presented with small-scale demonstrations aimed at circumventing challenges facing its adoption, as well as helping speed the transition to electric-powered ground transportation. From the results, it is expected that flexible photovoltaic (PV) cells will be able to supply 11% of the power required by the service equipment installed in a prototype vehicle. In particular, flexible photovoltaic (PV) cells are advantageous in terms of cost, weight, and design considerations. Most importantly, the cells' flexibility and attach-ability are expected to give them great potential for extended application in various areas.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.4
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• pp.156-172
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• 2020

The purpose of this study was to predict road surface temperature using high-resolution solar radiation data. The road surface temperature prediction model (RSTPM) was applied to predict road surface temperature; this model was developed based on the heat-balance method. In addition, using SOLWEIG (SOlar and LongWave Environmental Irradiance Geometry-model), the shadow patterns caused by the terrain effects were analyzed, and high-resolution solar radiation data with 10 m spatial resolution were calculated. To increase the accuracy of the shadow patterns and solar radiation, the day that was modeled had minimal effects from fog, clouds, and precipitation. As a result, shadow areas lasted for a long time at the entrance and exit of a tunnel, and in a high-altitude area. Furthermore, solar radiation clearly decreased in areas affected by shadows, which was reflected in the predicted road surface temperatures. It was confirmed that the road surface temperature should be high at topographically open points and relatively low at higher altitude points. The results of this study could be used to forecast the freezing of sections of road surfaces in winter, and to inform decision making by road managers and drivers.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.190-195
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• 2009

Since the industrial revolution, the global environmental problems such as greenhouse gas accumulation and the average temperature increase have caused people's attention. 'Low Carbon, Green Growth' was presented to cope with these global concerns, as one of main policies of 2008 in Korea. The paradigm of a green urban development is started to concern the whole city's energy problems owing to realize 'Low Carbon, Green Growth' in the urban side. The government established a nation's basic energy plan for 20 years, and some local cities made efforts to develop new renewable energy such as the solar, wind and water energy which are suitable to each city's character. As a part of these efforts, the concept of U-Eco city is newly appeared to reflect upon ubiquitous technique, urban ecology and the next generation energy system. However, urban plan is difficult to adopt this next generation energy system with existing laws, regulations and technical systems. The new executive and systematic system is needed to realize the U-Eco city U-Eco for the management of an efficient city. In this study, the authors investigate the concept of the next generation energy system and U-Eco city to realize the energy-efficient city plan and analyze problems to occur during the application of them in an existing city plan. Then, the authors show the remedies to deal with occurred problems.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.66-71
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• 2016

Reducing the wafer breakage rate and sawing thinner wafers will decrease the cost of solar cells. This study was carried out in order to identify ways to achieve this goal. In this study, the cutting force characteristics using an ingot tilting-type diamond multi wire-sawing machine were analyzed. The cutting force was analyzed while varying the tilting angles and wire speed. The obtained data were analyzed by classifying the tangential cutting force and the normal cutting force. In this cutting force experiment, the difference between the forces was confirmed; it was found that it rises with increasing the tilting angles and decreases when the wire speed elevates. The resulting value can be utilized as basic data for the determination of an ideal cutting recipe.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.232-232
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• 2011

투명전도산화물에 대한 연구가 많이 이루어지고 있으며, 최근 Ga이 도핑된 ZnO의 연구가 많이 되고 있다. 투명전도산화물은 태양전지, 평면디스플레이와 같은 다양한 분야에 응용이 가능하다. 본 연구에서는 RF magnetron sputtering을 이용하여 Ar gas 유량 변화에 따른 GZO 박막을 연구하였다. 기판으로는 유리기판을 사용하였으며, 전기적, 광학적, 구조적인 특성을 조사하였다. 박막의 증착시 초기 압력은 $2.0{\times}10^{-6}$Torr 이하로 하였으며, 증착온도는 상온으로 고정하여 증착하였다. 기판은 Corning 1737 유리 기판을 사용하였고, GZO 타겟은 ZnO : Ga 분말이 각각 97 : 3 wt.%로 소결된 타겟을 사용하였다. Ar 유량변수는 20, 40, 60, 80 sccm으로 변화를 주었다. 유리기판에 증착된 모든 GZO박막은 약 200 nm의 두께로 증착되었으며 모든 GZO 박막에서 85%이상의 투과율을 나타내었다. Ar 유량이 적을수록 투과율을 증가하였으며, 광학적 밴드갭 또한 증가하였다. 공정별로 제작된 모든 GZO박막에서 (002)면의 배향성이 관찰되었고, Ar 유량이 적을수록 박막의 결정성은 향상되었다. Hall 측정 결과 Ar 유량이 20 sccm일 때 전기비저항 $3.46{\times}10^{-3}{\Omega}cm$, 전하의 농도 $3.832{\times}10^{-20}\;cm^{-3}$, 이동도 $4.7cm^2V^{-1}s^{-1}$로 전극으로서의 특성을 나타내었다. GZO 박막의 경우 Ar 유량이 적었을 때 결정성이 높아지고, 전극 특성이 더 우수한 것을 확인할 수 있었다.

• Journal of the Korean institute of surface engineering
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• v.50 no.4
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• pp.244-250
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• 2017

Effects of plating conditions (dispersant concentration, plating time, and ultrasonication) on electroless Cu plating on SiC fabric woven by crossing of SiC continuous fibers vertically were studied. The ultrasonic dispersion treatment not only did not improve the dispersion of the SiC fibers, but also did not change the plating thickness. The ultrasonication in the pretreatment step of electroless plating did not improve the dispersion of the fibers, while the ultrasonication in the plating step enhanced the dispersion of the fibers and decreased the thickness of the Cu films. It was possible to control the thickness of the Cu coating layer as well as the dispersion of the fibers in the fabric by changing the plating conditions such as dispersant concentration, plating time, and ultrasonication, but it was very difficult to coat copper on the intersection of vertical fibers in the fabric.