• Journal of Internet Computing and Services
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• v.17 no.2
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• pp.49-57
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• 2016

Ensemble classification involves combining multiple classifiers to obtain more accurate predictions than those obtained using individual models. Ensemble learning techniques are known to be very useful for improving prediction accuracy. Bagging is one of the most popular ensemble learning techniques. Bagging has been known to be successful in increasing the accuracy of prediction of the individual classifiers. Bagging draws bootstrap samples from the training sample, applies the classifier to each bootstrap sample, and then combines the predictions of these classifiers to get the final classification result. Bootstrap samples are simple random samples selected from the original training data, so not all bootstrap samples are equally informative, due to the randomness. In this study, we proposed a new method for improving the performance of the standard bagging ensemble by optimizing bootstrap samples. A genetic algorithm is used to optimize bootstrap samples of the ensemble for improving prediction accuracy of the ensemble model. The proposed model is applied to a bankruptcy prediction problem using a real dataset from Korean companies. The experimental results showed the effectiveness of the proposed model.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.241-242
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• 2011

유기물을 기반으로 하는 유기발광소자(OLED), 유기메모리(OBD) 및 유기 태양전지(organic solar cell) 등과 같은 차세대 전자 소자는 기존의 무기물 기반의 소자에 비해 가격이 싸고 제작방법이 간단하며 휘어지게 만들 수 있다는 장점을 갖기 때문에 많은 관심을 받고 있다. 유기물질을 기반으로 한 전자 소자의 효율을 향상시키기 위해서는 유기물 자체의 물리적인 특성을 고찰하는 연구가 중요하다. 특히, 유기물 내에서의 전하 전송 메카니즘을 이해하기 위해 유기물의 이동도에 대한 연구가 중요하나, 아직까지 유기물질을 기반으로 한 전자 소자의 전하이동도에 대한 이론적인 연구가 거의 없다. 본 연구에서는 온도 변화에 따른 유기물 내에서의 전자 이동도를 몬테카를로 방법을 이용하여 계산하였다. 시뮬레이션을 위한 기본 구조로 소자의 길이는 50~500 사이트로 하였으며, 이웃한 사이트간 거리는 3A로 결정하였다. 유기물 내에 존재하는 트랩의 분포는 가우시안 분포로 가정하였다. 유기물 내에서의 전자 이동도를 추출하기 위해 이웃한 트랩간의 천이 확률을 Miller and Abrahams 식을 이용하여 계산하고[1], 트랩간의 천이시간을 컴퓨터에서 발생시킨 난수를 통해 얻어 이들을 통계적으로 처리하여 유기물 내에서의 전자 이동도를 계산하였다. 시뮬레이션 결과, 전자 이동도는 전계가 증가함에 따라 일정하게 증가하다가 일정 전계에서 포화된 후, 다시 감소하는 현상을 갖는다. 초기의 전계영역에서는 전계의 증가에 따라 유기물 내 트랩간의 천이 확률이 증가하기 때문에 전자 이동도가 증가한다. 하지만, 일정 전계 이상의 큰 전계 영역에서는 전자의 이동 속도는 거의 변하지 않는 상태에서 전계는 계속 증가하기 때문에 상대적으로 전자 이동도는 줄어들게 된다. 다양한 길이를 갖는 벌크 상태의 유기소자에 대한 전자 이동도를 시뮬레이션 하였을 때, 소자의 크기와 상관없이 전자 이동도는 거의 일정 하였다. 이는 순수한 벌크 상태의 유기소자는 유기물 자체에서의 전자 움직임에 의해 전자 이동도가 결정되기 때문이다. 온도가 높아짐에 따라 유기물 내의 전자 이동도는 증가하였다. 이는 온도가 증가할수록 열적 여기에 의한 트랩간의 천이 확률이 증가하기 때문이다. 하지만, 트랩의 분산도가 30 meV로 작을 경우, 일정 온도 이상에서의 전자 이동도는 포화되어 일정한 값으로 유지한다. 유기물 내에 존재하는 트랩 분포에 따라 온도의 변화에 따른 전자 이동도 특성이 달라짐을 알 수 있다. 이러한 결과는 유기물질을 기반으로 한 전자소자에서의 전하 전송 메카니즘을 이해하고 소자의 제작 및 특성 향상에 도움이 된다고 생각한다.

• Journal of Applied Biological Chemistry
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• v.59 no.2
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• pp.129-132
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• 2016

This study was conducted to evaluate the attraction effects of Sitophilus zeamais and Tribolium castaneum to light emitting diode (LED) trap in granary and compared with the black light bulb (BLB) trap, which is typical used in commercial trap. The red LED trap showed more attractive to S. zeamais and T. castaneum than that of the BLB. Moreover, the external condition of granary was about 1.5 times more attractive to S. zeamais and T. castaneum than the internal condition of granary. These results suggested that red LED trap could be useful to control S. zeamais and T. castaneum in granary.

• Korean journal of applied entomology
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• v.53 no.4
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• pp.375-380
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• 2014

The sweetpotato whitefly (SPW), Bemisia tabaci Gennadius, is a major pest in tomato greenhouses on Jeju Island because they transmit viral diseases. To develop practical sampling methods for adult SPWs, yellow-color sticky traps were used in commercial tomato greenhouses throughout the western part of Jeju Island in 2011 and 2012. On the basis of the size and growing conditions in the tomato greenhouses, 20 to 30 traps were installed in each greenhouse for developing a sampling plan. Adult SPWs were more attracted to horizontal traps placed 60 cm above the ground than to vertical trap placed 10 cm above the plant canopy. The spatial patterns of the adult SPWs were evaluated using Taylor's power law (TPL) and Iwao's patchiness regression (IPR). The results showed that adult SPWs were aggregated in each surveyed greenhouse. In this study, TPL showed better performance because of the coefficient of determination ($r^2$). On the basis of the fixed-precision level sampling plan using TPL parameters, more traps were required for higher precision in lower SPW densities per trap. A sequential sampling stop line was constructed using TPL parameters. If the treatment threshold was greater than 10 maximum adult SPWs on a trap, the required traps numbered 15 at a fixed-precision level of 0.25. In estimating the mean density per trap, the proportion of traps with two or more adult SPWs was more efficient than whole counting: ${\ln}(m)=1.19+0.90{\ln}(-{\ln}(1-p_T))$. The results of this study could be used to prevent the dissemination of SPW as a viral disease vector by using accurate control decision in SPW management programs.

• Korean journal of applied entomology
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• v.52 no.4
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• pp.341-348
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• 2013

We desinged and evaluated a remote-sensing sex pheromone trap for real-time monitoring of Mythimna separata (Lepidoptera: Noctuidae), a migratory insect in Korea. The system consisted of a modified cone-trap with a sex pheromone lure, a sensing module based on light interruption, a signal transmission module based on code division multiple access, a main electronic board for system control, a power supply based on a solar collector, a stainless steel-pole supporting the system, and a signal collection and display system based on an internet web page. The ratio (>92%) of the actual number of insects to the signal number in the remote-sensing trap was improved by sensing only within a limited period at night on the basis of the insect's circadian rhythm, control of signal sensitivity on the basis of sensing software programming, 1-h interval for signal transmission, and adjustment of the signal transmission program. The signal occurrence pattern in the remote-sensing trap was conclusively similar (correlation coefficient, >0.98) to the actual pattern of adult occurrence in the trap. The result indicated that the remote-sensing trap based on the attraction of the sex pheromone lure for M. separata has a promising potential for practical use. Occurrence of M. separata adults was observed several times in 2011 and 2012, and the peaks were sharp.

• Korean Journal of Organic Agriculture
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• v.26 no.3
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• pp.381-391
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• 2018

This study was carried out to determine whether cage traps can be used to capture wild boars successfully, and to assess their response to different bait materials and the number of wild boars caught. Steel cage-traps ($4.0m{\times}1.5m{\times}1.2m$, $L{\times}W{\times}H$) were installed at two sites in Damyang County and at one site in Sunchang County, South Korea. To identify preferred bait-diet, baits were prepared with dry corn and fermented sour corn and placed in equal amounts at the sites close to wild boar pads at 200 m intervals. Before selecting trap locations where sufficient activity was observed, pre-baiting was undertaken and steel-framed traps were installed with gates open. Preference for bait materials was not clearly defined. After providing the bait for the first time, the number of days until wild boars ate all the food were counted. In the Damyang and Youngam areas, where hunting was allowed, total bait consumption took 6 to 12 days; in contrast, in the Sunchang area, where no hunting took place, total food consumption took only 5 days. In addition, after pre-baiting with the mixture of dry and sour corn for diet for about 8.7 days and then opening the trap gates for 3 more days, 13.7 days were necessary to catch 4.3 wild boars per trap. These results suggest that hunting intensity around trapping places was an important factor in determining the success of the traps.

• Journal of the Korean Geotechnical Society
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• v.30 no.8
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• pp.13-24
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• 2014

A series of trapdoor model tests was systematically performed in order to investigate soil arching. The mobilized soil arching was clearly observed by change of the vertical earth pressure loaded on trapdoor of soil container box. A slow decent of the loading plate at the trapdoor results in loosening zone over the trapdoor and the stress in this loosening zone was transferred to the stationary zone in the vicinity of the trapdoor. In particular, it was observed that the vertical earth pressure rapidly decreased in the loosening zone and increased in the stationary zone at the trapdoor. Both the maximum decreasing rate of the vertical earth pressure in the loosening zone and the increasing rate of the vertical earth pressure in the stationary zone were not influenced by the ground density, but affected by the size of the trapdoor. The loosening zone could be defined by the elliptical configuration, in which the major axis was twice as long as the height of the loosening zone at the center of trapdoor and the minor axis was the same as the width of trapdoor. The height of loosening zone at the center of trapdoor was one and a half times as long as the width of trapdoor loading plate.

• Korean journal of applied entomology
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• v.54 no.4
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• pp.289-294
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• 2015

Striped flea beetle, Phyllotreta striolata (SFB) and turnip sawfly, Athalia rosae ruficornis (TSF) are two economically important sporadic pests in radish fields on Jeju island. The response of adult SFB and TSF to a mixture of aggregation pheromone, (+)-(6R,7S)-himachala-9,11-diene and host plant volatile, allyl isothiocyanate (HAI), as well as to yellow and blue sticky traps was examined in radish fields. Adult SFB was more attracted to the sticky trap with HAI, regardless of the color of the sticky trap; however, adult TSF was more attracted on the yellow sticky trap than blue, and no effect of HAI was observed. The adult SFB and TSF can be effectively monitored using yellow sticky traps placed 10 cm above the plant canopy. SFB and TSF had 3 and 5 peak times in a year, respectively. The first peak occurred in the middle of March for SFB and mid-late of April for TSF. We expect that the results of the present study can facilitate minimizing the damage caused by the two important pests in commercial radish fields.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.5
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• pp.17-17
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• 2001

고유전 (Ba, Sr)TiO₃ (BST) 박막을 이용한 DRAM storage capacitor의 저전계 영역에서의 전하손실을 발생시키는 커패시터의 누설전류는 유전완화전류와 진성 누설전류로 이루진다고 알려져 있다. 특히, 기가급 DRAM의 동작 전압(~IV)에서 유전완화전류가 진성 누설전류에 비해 훨씬 크기 때문에 이에 대한 심도 있는 연구가 필요하다. 본 연구에서는 thermally stimulated current (TSC) 측정법을 BST 박막에 처음으로 적용하여 트랩의 에너지 level 및 공정변화에 따른 트랩 밀도의 상대적 평가를 하였다. 그리고, 기존에 사용되던 전류-전압(I-V) 측정이나 전류-시간(I-t) 측정과 비교 및 분석함으로써 유전완화 전류의 원인을 규명하고 TSC 측정법의 신뢰성을 살펴보았다. 먼저 안정적인 TSC 측정을 위해 전계, 시간, 온도 및 승온속도에 따른 polarization condition을 알아보았다 이 조건을 이용한 TSC 측정으로부터 BST 박막에서의 트랩의 energy level이 0.20(±0.01) eV와 0.45(±0.02) eV임을 알 수 있었다. Rapid thermal annealing (RTA)을 이용한 후속 열처리에 따른 TSC 측정을 통하여 이 트랩들이 산소결핍(oxygen vacancy)에 기인함을 확인할 수 있었다. MIM BST 커패시터의 열처리에 대한 TSC 특성은 전류-전압(I-V) 및 전류-시간(I-t) 특성과 같은 경향성을 보인다. 이것은 TSC 측정이 BST 박막내의 트랩을 평가하는데 있어서 매우 효과적인 방법이라는 것을 보여준다.

• The Korean Journal of Applied Statistics
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• v.19 no.3
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• pp.535-544
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• 2006

We consider use of Bootstrap calibration in the problem of setting a confidence interval for a linear combination of variance components. Based on the the modified large sample(MLS) method by Graybill and Wang(1980), Bootstrap Calibration is applied to improve the coverage probability of the MLS confidence bound when the experiment is balanced and coefficients of a linear combination are positive. Performance of the proposed confidence bound in small sample is investigated by simulation studies.