• 한국산림과학회지
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• 제99권2호
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• pp.163-171
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• 2010

Forest fires have potentials to change the structure and function of forest ecosystems and significantly influence on atmosphere and biogeochemical cycles. Forest fire also affects the quality of public benefits such as carbon sequestration, soil fertility, grazing value, biodiversity, or tourism. The prediction of fire occurrence and its spread is critical to the forest managers for allocating resources and developing the forest fire danger rating system. Most of fires were human-caused fires in Korea, but meteorological factors are also big contributors to fire behaviors and its spread. Thus, meteorological factors as well as social factors were considered in the fire danger rating systems. A total of 298 forest fires occurred during the fall season from 2002 to 2006 in South Korea were considered for developing a logistic model of forest fire occurrence. The results of statistical analysis show that only effective humidity and temperature significantly affected the logistic models (p<0.05). The results of ROC curve analysis showed that the probability of randomly selected fires ranges from 0.739 to 0.876, which represent a relatively high accuracy of the developed model. These findings would be necessary for the policy makers in South Korea for the prevention of forest fires.

• 한국구조물진단유지관리공학회 논문집
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• 제7권2호
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• pp.135-140
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• 2003

As a construction technique is developed recently, the construction space and construction period are considered to important matters. Especially, in case of construction period, several method is proposed for strength control in the construction field. However there are very little strength control models for application of internal condition. The purpose of this study is to develop a strength control model for application of variety internal condition at construction field. The results are as follows ; 1) According to the results of compressive strength of concrete evaluated by logistic curve and proposed curve, proposed curve is applicable of construction field because there is similar relation with logistic curve. 2) It is shown that the construction period is shortened by reduction of the formwork removal time, because a predicted compressive strength of using the new curve is higher than the proposed compressive strength of standard.

• Journal of the Optical Society of Korea
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• 제20권3호
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• pp.341-357
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• 2016

A novel asymmetric multiple-image encryption method using an octonion Fresnel transform (OFST) and a two-dimensional Sine Logistic modulation map (2D-SLMM) is presented. First, a new multiple-image information processing tool termed the octonion Fresneltransform is proposed, and then an efficient method to calculate the OFST of an octonion matrix is developed. Subsequently this tool is applied to process multiple plaintext images, which are represented by octonion algebra, holistically in a vector manner. The complex amplitude, formed from the components of the OFST-transformed original images and modulated by a random phase mask (RPM), is used to derive the ciphertext image by employing an amplitude- and phase-truncation approach in the Fresnel domain. To avoid sending whole RPMs to the receiver side for decryption, a random phase mask generation method based on SLMM, in which only the initial parameters of the chaotic function are needed to generate the RPMs, is designed. To enhance security, the ciphertext and two decryption keys produced in the encryption procedure are permuted by the proposed SLMM-based scrambling method. Numerical simulations have been carried out to demonstrate the proposed scheme's validity, high security, and high resistance to various attacks.

• 보건의료산업학회지
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• 제13권1호
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• pp.67-78
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• 2019

Objectives: To identify the factors affecting the cognitive function according to the education level of people aged 65 or older. Methods: This study used the data from the 2014 survey of living conditions and welfare needs of Korean older adults. A total of 10,248 people were analyzed in the final analysis, not including those who responded by proxy and those who did not participate in cognitive function tests. Cognitive function was measured by Mini Mental State Examination -Dementia Screening(MMSE-DS), and logistic regression was performed using the SPSS/WIN 24.0 program. Results: There were differences in factors affecting cognitive function depending on the education level. Overall, regular exercise had a positive effect on maintaining cognitive function, and the higher the education level, the more important it was to maintain the Instrumental Activities of Daily Living(IADL). In addition, for lower education levels, improving the life satisfaction was important to prevent the decline of cognitive function. Conclusions: Based on the results of this research, it is suggested that customized approaches shoud be taken according to education level when developing and implementing programs to prevent the decline of cognitive function.

• 한국항행학회논문지
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• 제17권3호
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• pp.292-297
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• 2013

본 논문에서는 혼돈 스트림 발생기에 사용되는 혼돈합성함수의 디지털 회로설계를 연구 하였다. 혼돈키 스트림 발생기의 수학적 모델에 기인하는 전반적인 설계 개념과 절차를 자세히 설명하였다. 또한 혼돈 함수에 대한 이진화 2진 진리표를 보였다. 결과로서 1차원과 2차원 두 종류의 혼돈맵들-텐트맵과 삐뚤어진 로지스틱 맵-을 연결시켜 합성맵으로 사용하는 합성상태머신의 설계를 제시하였다.

• 보건의료산업학회지
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• 제10권3호
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• pp.147-158
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• 2016

Objectives : The aim of this study was to investigate predictors of cognitive function decline among community dwelling elderly. Methods : Data were analyzed from the Survey of Living Condition of Elderly panel study. Cognitive function was measured with the MMSE-KC at baseline and year 3. The study subjects were 5,464 community dwelling people aged 65 years or older who had no disability at baseline. Logistic regression analysis was used to predict cognitive function decline. Results : From 2008-2011, 4,417(80.8%) elderly people had no cognitive decline, and 1,074(19.2%) showed cognitive function decline measured by the MMSE-KC. After adjusting for demographics and baseline MMSE-KC score, the best predictors for cognitive function decline at 36 months were diabetes mellitus, smoking, low intensity physical activity, relationship with relatives and friends. Conclusions : Health promotion programs that are focused on the elderly are essential in preventing cognitive function decline. Promoting regular physical activity, and social relationships should be included in health promotion for elderly. When treating patients with diabetes, preventing cognitive impairment should be considered through education and counseling.

• 한국국방경영분석학회지
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• 제6권2호
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• pp.129-149
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• 1980

In medical follow-up, equipment lifetesting, various military situations, and other fields, one often desires to calculate survival probability as a function of time, p(t). If the observer is able to record the time of occurrence of the event of interest (called a 'death'), then an empirical, non-parametric estimate may simply by obtained from the fraction of survivors after various elapsed times. The estimation is more complicated when the data are truncated, i.e., when the observer loses track of some individuals before death occurs. The product-limit method of Kaplan and Meier is one way of estimating p(t) when the mechanism causing truncation is independent of the mechanism causing death. This paper proposes jackknife estimators of logistic trans-formation and compares it to the product-limit method. A computer simulation is used to generate the times of death and truncation from a variety of assumed distributions.

• 환경정책연구
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• 제2권1호
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• pp.77-86
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• 2003

입도분포는 토양의 수리특성을 추정하는 데 많이 사용되고 있다. 본 연구는 다양한 가정조건을 가진 9개의 입도분포모형을 가지고 한국토양을 대상으로 어떤 모형이 가장 잘 입도분포를 모사하는지를 조사하였다. 4개의 추정변수를 가진 Fredlund모형, 로지스틱성장곡선, 그리고 Weibull분포가 다른 모형에 비해 PSD를 잘 모사하였다. 특히 추정변수가 없는 로지스틱 성장곡선 함수가 좋은 모사를 나타낸 것이 흥미로웠다.

• Journal of Information Processing Systems
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• 제11권2호
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• pp.310-324
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• 2015

The stream cipher Salsa20 and its reduced versions are among the fastest stream ciphers available today. However, Salsa20/7 is broken and Salsa20/12 is not as safe as before. Therefore, Salsa20 must completely perform all of the four rounds of encryption to achieve a good diffusion in order to resist the known attacks. In this paper, a new variant of Salsa20 that uses the chaos theory and that can achieve diffusion faster than the original Salsa20 is presented. The method has been tested and benchmarked with the original Salsa20 with a series of tests. Most of the tests show that the proposed chaotic Salsa of two rounds is faster than the original four rounds of Salsa20/4, but it offers the same diffusion level.

• Industrial Engineering and Management Systems
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• 제13권4호
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• pp.421-431
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• 2014

The market basket data in the form of a binary user-item matrix or a binary item-user matrix can be modelled as a binary classification problem. The binary logistic regression approach tackles the binary classification problem, where principal components are predictor variables. If users or items are sparse in the training data, the binary classification problem can be considered as a cold-start problem. The binary logistic regression approach may not function appropriately if the principal components are inefficient for the cold-start problem. Assuming that the market basket data can also be considered as a special regression problem whose response is either 0 or 1, we propose three supervised learning approaches: random forest regression, random forest classification, and elastic net to tackle the cold-start problem, comparing the performance in a variety of experimental settings. The experimental results show that the proposed supervised learning approaches outperform the conventional approaches.