• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.214-217
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• 2006

p-type 비정질 실리콘 에미터와 n-type 실리콘 기판의 계면에 intrinsic 비정질 실리콘을 증착함으로써 계면의 재결합을 억제하여 20%가 넘는 효율을 보이는 이종접합 태양전지가 Sanyo에 의해 처음 제시된 후 intrinsic layer에 대한 연구가 많이 진행되어 왔다. 하지만 p-type wafer의 경우는 n-type에 비해 intrinsic buffer의 효과가 미미하거나 오히려 특성을 저하시킨다는 보고가 있으며 그 이유로는 minority carrier에 대한 barrier가 상대적으로 낮다는 것과 partial epitaxy가 발생하기 때문으로 알려져 있다. 본 연구에서는 partial epitaxy를 억제하기 위한 방법으로 증착 온도를 낮추고 QSSPC를 사용하여 minority carrier lifetime을 측정함으로써 각 온도에 따른 passivation 특성을 평가하였다. 또한 SiH4에 H2를 섞어서 증착하였을 경우 각 dilution ratio(H2 flow/SiH4 flow)에서의 passivation 특성 또한 평가하였다. 기판 온도 $100^{\circ}C$에서 증착된 샘플의 lifetime이 가장 길었으며 그 이하와 이상에서는 lifetime이 감소하는 경향을 보였다 낮은 온도에서는 박막 자체의 결함이 증가하였기 때문이며 높은 온도에서는 partial epitaxy의 영향으로 추정된다. H2 dilution을 하여 증착한 샘플의 경우 SiH4만 가지고 증착한 샘플보다 훨씬 높은 lifetime을 가졌다 이 또한 박막 FT-IR결과로부터 H2 dilution을 한 경우 compact한 박막이 형성되는 것을 확인할 수 있었는데 radical mobility 증가에 의한 박막 특성 향상이 원인으로 생각된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.939-942
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• 2004

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors were Prepared by using the capacitively coupled RF magnetron sputtering method. In this paper the effect of RF discharge power on the electrical, optical and structural properties were investigated experimentally. The results show that the structural and electrical properties of the film are highly affected by the variation of RF discharge power. The optimum growth conditions were obtained for films doped with 2 wt% of $Al_2O_3$ and 200 W in RF discharge power, which exhibit a resistivity of $10.4{\times}10^{-4}{\Omega}-cm$ associated with a transmittance of 89.66 % for 1000nm in films thickness in the wavelength range of the visible spectrum.

• Journal of The Korean Astronomical Society
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• v.35 no.3
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• pp.131-141
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• 2002

We present Near-IR photometry of the Arches cluster, a young and massive stellar cluster near the Galactic center. We have analyzed the high resolution (FWHM $\~$ 0.2") Hand K' band images in the Galactic Center Demonstration Science Data Set, which were obtained with the Gemini/Hokupa's adaptive optics (AO) system. We present the color-magnitude diagram, the luminosity function and the initial mass function (IMF) of the stars in the Arches cluster in comparison with the HST/NICMOS data. The IMF slope for the range of 1.0 < log (M/M$\bigodot$) < 2.1 is estimated to be ${\Gamma} = -0.79 {\pm} 0.16$, in good agreements with the earlier result based on the HST/NICMOS data [Figer et al. 1999, ApJ, 525, 750]. These results strengthen the evidence that the IMF of the bright. stars close to the Galactic center is much flatter than that for the solar neighborhood. This is also consistent with a recent finding that the IMFs of the bright stars in young clusters in M33 get flatter as the galactocentric distance decreases [Lee et al. 2001, astro-ph 0109258]. It is found that the power of the Gemini/ AO system is comparable, with some limits, to that of the HST/NICMOS.

• Korean Journal of Remote Sensing
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• v.14 no.3
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• pp.307-314
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• 1998

To examine the detectability of the yellow sand and/or aerosol from China crossing over the Yellow Sea within the range of OSMI wavelengths(400-900 nm), we have investigated the optical characteristics of aerosols in yellow sand events observed on April, 1998 in Seoul. The spectral reflectance(%) and aerosol optical thickness in the range of Visible(VIS) and near Infrared (NIR) wavelengths were derived from the measurements of solar radiation using the GER-2600 spectroradiometer and sunphotometer during the April, 1798. The average spectral reflectance for the yellow sand events is over 40% and higher around 14:30 than 12:00 LST, but that for clear days is about 20% both at 12:00 and 14:30 LST in the range of 500-900 nm. The aerosol optical thickness at 501 nm varied from 0.25 on very clear day to 1.01 during a so-called "yellow-sand" episode and that for 673 nm varied from 0.14 to 0.92, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.49-55
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• 2013

This paper deals with the flight test of propulsion system of middle size electrically powered UAV (EAV2, Electric Aerial Vehicle 2) which is under development in KARI. EAV2 is low speed endurance type UAV whose wing span is 6.9 m, and weight is 18 kg. The UAV has flown for 22 hours in June of 2012. The flight test result showed that the propulsion system worked well suppling power for any circumstances during the test flight. Each power source worked according to the design purpose.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.689-709
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• 2010

In this paper, a low cost, low power but multifunctional wireless sensor node is presented for the impedance-based SHM using piezoelectric sensors. Firstly, a miniaturized impedance measuring chip device is utilized for low cost and low power structural excitation/sensing. Then, structural damage detection/sensor self-diagnosis algorithms are embedded on the on-board microcontroller. This sensor node uses the power harvested from the solar energy to measure and analyze the impedance data. Simultaneously it monitors temperature on the structure near the piezoelectric sensor and battery power consumption. The wireless sensor node is based on the TinyOS platform for operation, and users can take MATLAB$^{(R)}$ interface for the control of the sensor node through serial communication. In order to validate the performance of this multifunctional wireless impedance sensor node, a series of experimental studies have been carried out for detecting loose bolts and crack damages on lab-scale steel structural members as well as on real steel bridge and building structures. It has been found that the proposed sensor nodes can be effectively used for local wireless health monitoring of structural components and for constructing a low-cost and multifunctional SHM system as "place and forget" wireless sensors.

• Psychiatry investigation
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• v.15 no.12
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• pp.1121-1129
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• 2018

Objective Categorical syndrome such as schizophrenia could be the complex of many continuous mental structure phenotypes including several personality development/degeneration dimensions. This is the study to search heritability and familiality of MMPI personality dimensions in the Korean schizophrenic LD (Linkage Disequilibrium) families. Methods We have recruited 204 probands (with schizophrenia) with their parents and siblings whenever possible. We have used MMPI questionnaires for measuring personality and symptomatic dimensions. Heritabilities of personality dimensions in total 543 family members were estimated using Sequential Oligogenic Linkage Analysis Routines (SOLAR). Personality dimensions in total family members were compared with those in 307 healthy unrelated controls for measuring the familialities using ANOVA analysis. Results Seven of the 10 MMPI variables were significantly heritable and were included in the subsequent analyses. The three groups (control, unaffected 1st degree relative, case) were found to be significantly different with the expected order of average group scores for all heritable dimensions. Conclusion Our results show that the aberrations in several personality dimensions could form the complexity of schizophrenic syndrome as a result of genetic-environment coactions or interactions in spite of some limitations (recruited family, phenotyping).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.561-564
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• 2014

In this paper a photovoltaic energy harvesting charger with battery management circuit is proposed. The proposed circuit harvests maximum power from a solar cell by employing MPPT(Maximum Power Point Tracking) control and charges an external capacitor battery with the harvested energy. The charging state of the battery is controlled according to the signals from the battery management circuit. The proposed circuit is designed in a 0.35um CMOS process technology and its functionality has been verified through extensive simulations. The maximum efficiency of the designed entire system is 84.8%, and the chip area including pads is $1350um{\times}1200um$.

• Environmental Engineering Research
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• v.24 no.3
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• pp.404-411
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• 2019

In this study, we designed a data-driven model to predict chlorophyll-a using M5P model tree and extreme learning machine (ELM). The Juksan weir in the Youngsan River has high chlorophyll-a, which is the primary indicator of algal bloom every year. Short-term algal bloom prediction is important for environmental management and ecological assessment. Two models were developed and evaluated for short-term algal bloom prediction. M5P is a classification and regression-analysis-based method, and ELM is a feed-forward neural network with fast learning using the least square estimate for regression. The dataset used in this study includes water temperature, rainfall, solar radiation, total nitrogen, total phosphorus, N/P ratio, and chlorophyll-a, which were collected on a daily basis from January 2013 to December 2016. The M5P model showed that the prediction model after one day had the highest performance power and dropped off rapidly starting with predictions after three days. Comparing the performance power of the ELM model with the M5P model, it was found that the performance power of the 1-7 d chlorophyll-a prediction model was higher. Moreover, in a period of rapidly increasing algal blooms, the ELM model showed higher accuracy than the M5P model.

• Smart Media Journal
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• v.8 no.1
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• pp.82-91
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• 2019

This study provides the analysis and prediction of fruits diseases related to weather conditions (temperature, wind speed, solar power, rainfall and humidity) using Linear Model and Poisson Regression. The main goal of the research is to control the method of fruits diseases and also to prevent diseases using less agricultural pesticides. So, it is needed to predict the fruits diseases with weather data. Initially, fruit data is used to detect the fruit diseases. If diseases are found, we move to the next process and verify the condition of the fruits including their size. We identify the growth of fruit and evidence of diseases with Linear Model. Then, Poisson Regression used in this study to fit the model of fruits diseases with weather conditions as an input provides the predicted diseases as an output. Finally, the residuals plot, Q-Q plot and other plots help to validate the fitness of Linear Model and provide correlation between the actual and the predicted diseases as a result of the conducted experiment in this study.