• 산업경영시스템학회지
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• 제44권2호
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• pp.15-23
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• 2021

Most of the open-source decision tree algorithms are based on three splitting criteria (Entropy, Gini Index, and Gain Ratio). Therefore, the advantages and disadvantages of these three popular algorithms need to be studied more thoroughly. Comparisons of the three algorithms were mainly performed with respect to the predictive performance. In this work, we conducted a comparative experiment on the splitting criteria of three decision trees, focusing on their interpretability. Depth, homogeneity, coverage, lift, and stability were used as indicators for measuring interpretability. To measure the stability of decision trees, we present a measure of the stability of the root node and the stability of the dominating rules based on a measure of the similarity of trees. Based on 10 data collected from UCI and Kaggle, we compare the interpretability of DT (Decision Tree) algorithms based on three splitting criteria. The results show that the GR (Gain Ratio) branch-based DT algorithm performs well in terms of lift and homogeneity, while the GINI (Gini Index) and ENT (Entropy) branch-based DT algorithms performs well in terms of coverage. With respect to stability, considering both the similarity of the dominating rule or the similarity of the root node, the DT algorithm according to the ENT splitting criterion shows the best results.

• Archives of Plastic Surgery
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• 제45권5호
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• pp.418-424
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• 2018

Background Complication rates after flap coverage for pressure ulcers have been high historically. These patients have multiple risk factors associated with poor wound healing and complications including marginal nutritional status, prolonged immobilization, and a high comorbidities index. This study utilizes the National Surgical Quality Improvement Program (NSQIP) to examine perioperative outcomes of flap coverage for pressure ulcers. Methods Data from the NSQIP database (2005-2015) for patient undergoing flap coverage for pressure ulcers was identified. Demographic, perioperative information, and complications were reviewed. One-way analysis of variance and Pearson chi-square were used to assess differences for continuous variables and nominal variables, respectively. Multivariate logistic regression was performed to identify independent risk factors for complications. Results There were 755 cases identified: 365 (48.3%) sacral ulcers, 321 (42.5%) ischial ulcers, and 69 (9.1%) trochanteric ulcers. Most patients were older male, with some degree of dependency, neurosensory impairment, high functional comorbidities score, and American Society of Anesthesiologists class 3 or above. The sacral ulcer group had the highest incidence of septic shock and bleeding, while the trochanteric ulcer group had the highest incidence of superficial surgical site infection. There was an overall complication rate of 25% at 30-day follow-up. There was no statistical difference in overall complication among groups. Total operating time, diabetes, and non-elective case were independent risk factors for overall complications. Conclusions Despite patients with poor baseline functional status, flap coverage for pressure ulcer patients is safe with acceptable postoperative complications. This type of treatment should be considered for properly selected patients.

• The Journal of Asian Finance, Economics and Business
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• 제8권3호
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• pp.1113-1119
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• 2021

This study aims to determine the impact of the news coverage of the COVID-19 pandemic on the composite stocks' movement (IHSG) in Indonesia. This study used secondary data of daily time series with an observation range of March 2020-June 2020. This study used three main variables, namely, COVID-19 news, the daily price of a composite stock market index (IHSG), and interest rate. This study clarifies pandemic news into two forms to facilitate quantitative analysis, namely, good news and bad news. Both pandemic news conditions, which have been clarified, are then processed into the index and reprocessed along with two other variables using vector autoregressive (VAR). The results showed that the good news have a dominant effect on developing the composite stock price index (IHSG) in Indonesia during the COVID-19 pandemic. Although the good news dominates the composite stock price index (IHSG) movement in Indonesia, the bad news must also be anticipated. By implementing a series of macroeconomic policies that follow the conditions of the composite stock price index (IHSG) movements on the stock exchange floor, the bad news response can decrease the potential for a decline in investor confidence, so that the financial system's macroeconomic stability is maintained.

• Journal of Astronomy and Space Sciences
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• 제36권4호
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• pp.225-234
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• 2019

We explore the associations between the total sunspot area, solar north-south asymmetry, and Southern Oscillation Index and the physical characteristics of clouds by calculating normalized cross-correlations, motivated by the idea that the galactic cosmic ray influx modulated by solar activity may cause changes in cloud coverage, and in turn the Earth's climate. Unlike previous studies based on the relative difference, we have employed cloud data as a whole time-series without detrending. We found that the coverage of high-level and low-level cloud is at a maximum when the solar north-south asymmetry is close to the minimum, and one or two years after the solar north-south asymmetry is at a maximum, respectively. The global surface air temperature is at a maximum five years after the solar north-south asymmetry is at a maximum, and the optical depth is at a minimum when the solar north-south asymmetry is at a maximum. We also found that during the descending period of solar activity, the coverage of low-level cloud is at a maximum, and global surface air temperature and cloud optical depth are at a minimum, and that the total column water vapor is at a maximum one or two years after the solar maximum.

• 아시안잔디학회지
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• 제16권1호
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• pp.41-47
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• 2002

본 연구는 녹지의 계층구조 등이 다양한 도시녹지를 대상으로 그 산출방법이 습도변화에 미치는 영향을 정량적으로 파악하기 위해 녹지내의 습도분포를 관측하였다. 그 데이터를 바탕으로 녹지의 토지피복현황과 습도분포, 식재의 산출방법과 습도, 식재의 계층구조의 산출방법과 습도와의 관련성을 회귀분석 등에 의해 해석하였다. 그 결과, 토지피복현황뿐만 아니라 녹지의 산출방법이 습도변화에 많은 영향을 미치고 있다. 또한, 식재율(평면적) 및 식재량(입체적)의 증가는 습도상승에 효과적이다. 더욱이 계층구조가 다양한 식재를 대상으로 그 산출방법과 습도상승과의 관계를 회귀계수와 상관계수를 통해 비교하면, 식재를 산출할 경우에는 평면적인 방법보다 입체적인 방법이 습도상승에 미치는 효과(수치)가 컸다. 앞으로 습도상승효과의 지표로서 식재의 산출은 입체적인 방법의 활용을 제안한다.

• 한국태양에너지학회 논문집
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• 제28권2호
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• pp.19-27
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• 2008

This study aims at examining the correlation between air temperature and urban structure such as land cover. For this, it measured summer air temperature by using data log type thermometer installed the inside of instrument screen, in the 9 points of elementary school in Haeundae, Busan. The accomplished results of this study are followings. 1) As altitude goes up 100m, air temperature drops to $0.6{\sim}1.0^{\circ}C$. 2) As building coverage ratio increases 10%, air temperature increases $0.3{\sim}0.4^{\circ}C$. 3) As floor space index increases 100%, air temperature increases $0.4{\sim}0.5^{\circ}C$. 4) As artificial coverage ratio increases 10%, air temperature increases $0.1{\sim}0.2^{\circ}C$. 5) As natural coverage ratio increases 10%, air temperature decreases $0.1{\sim}0.2^{\circ}C$.

• The Korean Journal of Ecology
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• 제21권5_3호
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• pp.665-673
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• 1998

This study was conducted to clarified the relationship between bird community and forest structure and present the counterplan for protection and management of bird community from February 1993 to July 1995 at deciduous and coniferous forest within Mt. Nam area, Seoul, Korea. DBH distribution has not significant differences in each study site. Deciduous forest had more foliage coverage in all layers than coniferous forest. Total 41 species of birds, which were 16 species of resident, 14 species of summer visitor, 4 species of winter visitor, and 7 species of passage migrant were recrded in two study sites. Leaf use rate of birds was increased the increase of coverage. The number of breeding species and pairs, breeding density, and diversity index were greater in deciduous forest than coniferous forest. The number of species and pairs on bush-nesting and foraging guild were greater than other guilds. And the nuber of species and pairs on hole nesting guild were the fewest in nesting guild. Use rate of artificial nests for improvement of habitat quality was greater in coniferous forest than deciduous forest. Maintenance of bush layer, increase of coverage and leaf layer diversity, supply of artificial nests, management of large trees, and control of natural enemy were necessary for protection and management of bird community in Mt. nam area.

• Current Optics and Photonics
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• 제5권6호
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• pp.606-616
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• 2021

A photonic integrated interferometric imaging system possesses the characteristics of small-scale, low weight, low power consumption, and better image quality. It has potential application for replacing conventional large space telescopes. In this paper, the principle of photonic integrated interferometric imaging is investigated. A novel lenslet array arrangement and lenslet pairing approach are proposed, which are helpful in improving spatial frequency coverage. For the novel lenslet array arrangement, two short interference arms were evenly distributed between two adjacent long interference arms. Each lenslet in the array would be paired twice through the novel lenslet pairing approach. Moreover, the image reconstruction model for optical interferometric imaging based on compressed sensing was established. Image simulation results show that the peak signal to noise ratio (PSNR) of the reconstructed image based on compressive sensing is about 10 dB higher than that of the direct restored image. Meanwhile, the normalized mean square error (NMSE) of the direct restored image is approximately 0.38 higher than that of the reconstructed image. Structural similarity index measure (SSIM) of the reconstructed image based on compressed sensing is about 0.33 higher than that of the direct restored image. The increased spatial frequency coverage and image reconstruction approach jointly contribute to better image quality of the photonic integrated interferometric imaging system.

• 대한원격탐사학회지
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• 제37권6_1호
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• pp.1757-1766
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• 2021

녹피율은 행정구역면적 대비 녹지가 피복된 면적의 비율로, 실질적인 도시녹화 지표로 활용되고 있다. 현재 녹피율은 토지피복지도를 기반하여 산출되는데, 토지피복지도의 낮은 공간해상도와 일정하지 않은 제작시기는 정확한 녹피율 산출과 정밀한 녹피분석을 어렵게 한다. 따라서 본 연구는 새로운 녹피율 산출방안으로 항공영상과 심층학습을 활용한 방안을 제안한다. 항공영상은 높은 해상도와 비교적 일정한 주기로 정밀한 분석을 가능하게 하며 심층 학습은 항공영상 내 녹지를 자동으로 탐지할 수 있다. 지자체는 매년 다양한 목적을 위해 유인항공영상을 취득하여 이를 활용해 신속하게 녹피율을 산출한다. 하지만 미리 취득된 유인항공영상은 취득 시기와 해상도, 센서와 같은 세부사항을 선택할 수 없어 정밀한 분석이 어려울 수 있다. 이러한 한계점은 다양한 센서의 탑재가 가능하고 낮은 고도의 비행으로 인해 고해상도 영상을 취득할 수 있는 무인항공기를 활용하여 보완될 수 있다. 이에 두 가지 항공영상으로부터 녹피율을 산출하였고 그 결과, 모든 녹지 유형으로 부터 높은 정확도로 녹피율을 산출할 수 있었다. 하지만 유인항공영상으로부터 산출된 녹피율은 복잡한 환경에서 한계가 있었다. 이를 보완하고자 활용한 무인항공영상은 복잡한 환경에서도 높은 정확도의 녹피율을 산출할 수 있었고 추가밴드 영상을 통해 더 정밀한 녹지 영역 탐지가 가능했다. 추후 기존 유인항공영상에 새로 취득한 무인항공영상을 보완적으로 사용해 녹피율을 효과적으로 산출할 수 있을 것이라 기대된다.

• 한국정밀공학회지
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• 제26권7호
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• pp.73-80
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• 2009

This paper describes a path planning algorithm, which is the minimal turning path based on the shape and size of the cell to clean up the whole area with two cleaning robots. Our method divides the whole cleaning area with each cell by cellular decomposition, and then provides some path plans among of the robots to reduce the rate of energy consumption and cleaning time of it. In addition we suggest how to plan between the robots especially when they are cleaning in the same cell. Finally simulation results demonstrate the effectiveness of the algorithm in an unknown area with multiple robots. And then we compare the performance index of two algorithms such as total of turn, total of time.