• Journal of The Korean Astronomical Society
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• v.55 no.5
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• pp.173-194
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• 2022

We complete the survey for finite-source/point-lens (FSPL) giant-source events in 2016-2019 KMTNet microlensing data. The 30 FSPL events show a clear gap in Einstein radius, 9 𝜇as < 𝜃_E < 26 𝜇as, which is consistent with the gap in Einstein timescales near t_E ~ 0.5 days found by Mróz et al. (2017) in an independent sample of point-source/point-lens (PSPL) events. We demonstrate that the two surveys are consistent. We estimate that the 4 events below this gap are due to a power-law distribution of free-floating planet candidates (FFPs) dN_FFP/d log M = (0.4 ± 0.2) (M/38 M_⊕)^-p/star, with 0.9 ≲ p ≲ 1.2. There are substantially more FFPs than known bound planets, implying that the bound planet power-law index 𝛾 = 0.6 is likely shaped by the ejection process at least as much as by formation. The mass density per decade of FFPs in the Solar neighborhood is of the same order as that of 'Oumuamua-like objects. In particular, if we assume that 'Oumuamua is part of the same process that ejected the FFPs to very wide or unbound orbits, the power-law index is p = 0.89 ± 0.06. If the Solar System's endowment of Neptune-mass objects in Neptune-like orbits is typical, which is consistent with the results of Poleski et al. (2021), then these could account for a substantial fraction of the FFPs in the Neptune-mass range.

• Journal of Internet of Things and Convergence
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• v.8 no.1
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• pp.17-22
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• 2022

This paper is a study on the self-powered wireless bus information and disaster information system based on Internet of Things (IoT). The existing bus information system supplies power and communication by cable, which causes a problem of increased installation cost and limited installation site due to cable burial. To solve this problem, a self-powered wireless bus information and disaster information system was proposed. The proposed system provides bus arrival information. Furthermore, in the event of a disaster such as a natural disaster, it can also reduce confusion and damage by notifying the disaster information through the system's speaker. In this study, a self-powered system using a solar module was proposed. As data are transmitted and received through wireless WiFi or LTE, the installation cost can be reduced and the problem of installation location restrictions can be solved.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.494-506
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• 2010

On the crisis of international economy, the government is making an effort to seek economic growing motivation with the method of overcoming economic crisis and 'low carbon green growth'. Furthermore, to promote maritime vessel traffic service related inefficient energy wastage was revealed and eco-friendly alternative energy was accepted because of high price of oil in the beginning of 2008. In this situation, I'm going to discuss the possibility of eco-friendly energy system in maritime vessel traffic service with the way of cutting the budget and expansion of solar power generation system which was promoted to meet governmental 'energy saving plan for high price of oil'.

• The KSFM Journal of Fluid Machinery
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• v.19 no.6
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• pp.34-42
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• 2016

The organic Rankine cycle (ORC) has been used to convert thermal energy to mechanical energy or electricity. The available thermal energy could be waste heat, solar energy, geothermal energy, and so on. However, these kinds of thermal energies cannot be provided continuously. Hence, the ORC can be operated at the off-design point. In this case, the performance of the ORC could be worse because the components of the ORC system designed based on a design point can be mismatched with the output power obtained at the off-design point. In order to improve the performance at the off-design point, a few components were replaced including generator, bearing, load bank, shaft, pump and so on. Experiments were performed on the same facility without including other losses in the experiment. The experimental results were compared with the results obtained with the previous model, and they showed that the system efficiency of the ORC was greatly affected by the losses occurred on the components.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1384-1385
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• 2011

This paper presents the active maximum power point tracking(MPPT) control of the photovoltaic(PV) module integrated converter(MIC) system considering the shadow influence. Conventional perturbation and observation(PO) and incremental conductance(IC) are the method finding MPP by the continued self-excitation vibration. The MPPT control is unable to be performed by rapid output change affected by the shadow. To solve this problem, the active MPPT in which the step value changes by output change is presented. In case there are the solar radiation, a temperature and shadow influence, the presented algorithm treats and compares the conventional control algorithm and output error. In addition, the validity of the algorithm is proved through the output error response characteristics.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1590-1591
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• 2011

In this paper, the UV corona camera was developed using the solar blind and Multi Channel Plate(MCP) technology for the target localization of UV camera. UV camera developed a $6.4^{\circ}{\times}4.8^{\circ}$ of the field of view as a conventional camera to diagnose a wide range of slightly enlarged, and power equipment to measure the distance between the camera and the distance meter has been attached. The UV camera was developed and measured using a UV image, as applied voltage increased ultraviolet images of the phenomenon could be obtained. And we investigated properties of UV corona image on insulator in salt water environments. From the results, the breakdown voltage was decreased and UV images were taken at low voltages and the UV image is rapidly increased with increasing High voltage.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.511-514
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• 2004

Proposed about new inverter that can use in PV system in this paper. Multi_level inverter that used inverter makes use of 4 transformers is basis, primary winding of each transformer voltage as can do step_up or step_down to appropriate voltage space tap lake. Put circuit that tap that turn in transformer connects properly according to inhibit signal that sense change of input voltage (output voltage of solar cell place) and transformer secondary voltage controls point of contact of relay so that get into fixed output voltage. As a result, can minimise relative harmonic content despite change width of input voltage are wide because number of output voltage level of multi_level inverter does not decrease. Because proposed circuit manufactures is easy and control is easy and is no burden of cost price rise economically, commercialization expected to do easily and this study examined propriety of action as that compose and experiments proposed circuit.

• Journal of Korean Association for Spatial Structures
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• v.8 no.6
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• pp.85-94
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• 2008

This paper is concerned with the domestic and foreign PV integrated projects in view of structural design. These projects are classified with public and display 6 facilities. The evaluated items are natural integration with building, engineering details and innovative new design. 6 domestic public and display facilities are frequently using isolated supporting system at roof, but show weakness in design integration. But the cases, using the PV panel in the stage of design some display facilities, are increasing. In the other hand, foreign public and display facilities are using the modul connection majorly and the structural and design integration are obtained.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.278.2-278.2
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• 2014

We have investigated the highly flexible and transparent Si-doped $In_2O_3$(ISO)/Ag/ISO multilayer grown on polyethylene terephthalate (PET) substrates using a roll-to-roll sputtering system. The electrical and optical properties of ISO/Ag/ISO multilayer electrodes depended on the insertion of a nano-size Ag layer. Due to the high conductivity of a nano-size Ag layer, the optimized ISO/Ag/ISO multilayer electrodes showed the lowest resistivity of $3.679{\times}10^{-5}Ohm-cm$, even though the ISO/Ag/ISO multilayer electrodes was sputtered at room temperature. Furthermore, the ISO/Ag/ISO multilayer electrodes exhibited a high transmittance of 86.33%, because of the anti-reflection effect, comparable to Sn-doped $In_2O_3$ (ITO) electrodes. In addition, the ISO/Ag/ISO multilayer electrodes had a very smooth surface morphology without surface defects and showed good flexibility. The flexible OSCs fabricated on ISO(30nm)/Ag(8nm)/ISO(30nm) multilayer electrode showed a power conversion efficiency of 3.272%. This result indicates that the ISO/Ag/ISO multilayer is a promising transparent conducting electrode for flexible OSCs.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.135.1-135.1
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• 2011

철도 선진국을 중심으로 신재생에너지의 철도 시스템 적용이 가속화 되고 있고, 국내에서도 철도 시스템에 신재생에너지를 적용하려는 시도가 이루어지고 있다. 이미 상당수의 신규 역사가 BIPV(building integrated photovoltaic) 시스템을 적용하고 있고, 단순히 유휴지를 이용한 풍력 발전 시스템을 넘어서 차량의 주행풍을 이용하거나 차량 외부에 풍력 발전기를 설치하는 등의 다양한 시도들이 이루어지고 있다. 수소 에너지를 연료로 하는 연로전지의 경우 기존 전기철도의 대체 연료로서 주목을 받으며 많은 연구가 이루어졌고 현재는 시험 운전 단계에 이르러 있다. 지열의 경우에는 벌써 오래전부터 승강장 또는 선로의 해빙장치의 에너지원으로 사용 되고 있다. 이밖에 수력 및 해양 에너지의 경우 전철전력의 청정 에너지 공급원으로 보고되고 있으며, 차량이나 역사 내에서 발생하는 운동 에너지를 수확하여 전기 에너지로 변환하는 에너지 하베스팅 기술이 새로운 신재생에너지 기술로서 많은 관심을 받고 있다. 에너지 문제와 온실가스 감축 의무 부담이 날로 가중되는 현 시점에서 신재생에너지의 전기철도 시스템 적용은 이 같은 문제를 해결할 수 있는 확실한 대안이 될 것이다. 본 논문에서는 국내외 전기철도 시스템의 신재생에너지 적용 기술과 적용 방안에 대해 고찰한다.