• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.41-41
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• 2018

하천과 저수지의 수질을 예측하고 관리하는데 수리 수질예측모형이 널리 활용되고 있다. 수질예측모형은 유역이나 수체 내의 오염물질 이동경로나 농도를 수치해석 방법으로 계산하여 사용자가 필요로 하는 지점과 시점에서의 수질자료 생산하는데 활용되고 있다. 수질예측모형은 검 보정을 통해 정확도를 확보하며, 정확도의 확보를 위해서는 높은 수준의 전문성을 필요로 한다. 특히 시행착오법으로 모형을 보정하는 경우 많은 시간과 노력을 필요로 하게 되며, 보정계수를 과대 혹은 과소로 모형에 적용하는 오류를 범하기 쉽고 모델러의 주관이 관여되기 쉽다. 그래서 본 연구에서는 CE-QUAL-W2모형의 조류항목에 대한 모형 보정을 위하여 Chl-a와 남조류세포수에서 주로 활용되고 있는 보정계수에 대한 민감도 분석 결과를 토대로 매개변수별 모의결과 변화율을 산정하였으며, 시기적 경향성을 재현하기 위해 Ensemble-Bagging 기법과 머신 러닝 기법을 적용하여 모형 구동횟수를 최소화 할 수 있는 방법으로 구성하였다. Chl-a를 보정하기 위한 매개변수는 9개를 선정하였으며, 규조류, 남조류, 녹조류에 총 27개 매개 변수를 민감도 분석으로 도출 한 후 예상 변화율 대비 이벤트별 모의치와 실측치 간 %difference가 유사하도록 매개변수를 조정하였다. 또한 각 이벤트 조합의 매개변수 빈도수와 매개변수별 예상변화율, 시기적 조류특성을 고려하여 가중치를 도출하였으며, 1회 보정에 맞춰 Chl-a 모델 실행결과를 %difference로 평가한 후 "good"등급을 만족할 때까지 반복 적용하였다. 남조류세포수의 경우 Chl-a에 맞춰 매개변수 최적화 이후 남조류세포수 농도를 세포수로 환산하기 위한 CACEL에 대해 머신러닝 기법을 적용하였으며, CACEL 추정변화율 회귀식에 따라 평가 한 후 %difference "good"등급 이상을 만족할 때까지 반복 수행하는 방법을 적용하였다. 본 연구에서는 수질예측모형의 정확도를 확보하기 위하여 최적화 기법을 적용하였으며, 이를 통해 모형을 보정하는 과정에서 요구되는 시간과 노력을 줄일 수 있도록 하였으며, Ensemble기법과 머신러닝 기법을 적용하여 모형보정계수 적용에 객관성을 확보할 수 있도록 하였다.

• The Journal of the Korea Contents Association
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• v.22 no.6
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• pp.56-68
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• 2022

Recently, as the demand for real-time processing increases, studies on a dynamic graph that changes over time has been actively done. There is a connected components processing algorithm as one of the algorithms for analyzing dynamic graphs. GPUs are suitable for large-scale graph calculations due to their high memory bandwidth and computational performance. However, when computing the connected components of a dynamic graph using the GPU, frequent data exchange occurs between the CPU and the GPU during real graph processing due to the limited memory of the GPU. The proposed scheme utilizes the Weighted-Quick-Union algorithm to process large-scale graphs on the GPU. It supports fast connected components computation by applying the size to the connected component label. It computes the connected component by determining the parts to be recalculated and minimizing the data to be transmitted to the GPU. In addition, we propose a processing structure in which the GPU and the CPU execute asynchronously to reduce the data transfer time between GPU and CPU. We show the excellence of the proposed scheme through performance evaluation using real dataset.

• Journal of the Korea Society of Computer and Information
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• v.27 no.5
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• pp.149-156
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• 2022

Recently, there have been many reports of document-type malicious code injecting malicious code into Microsoft Office files. Document-type malicious code is often hidden by encoding the malicious code in the document. Therefore, document-type malware can easily bypass anti-virus programs. We found that malicious code was inserted into the Visual Basic for Applications (VBA) macro, a function supported by Microsoft Office. Malicious codes such as shellcodes that run external programs and URL-related codes that download files from external URLs were identified. We selected 354 keywords repeatedly appearing in malicious Microsoft Office files and defined the number of times each keyword appears in the body of the document as a feature. We performed machine learning with SVM, naïve Bayes, logistic regression, and random forest algorithms. As a result, each algorithm showed accuracies of 0.994, 0.659, 0.995, and 0.998, respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.314-314
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• 2020

SWAT (Soil and Water Assessment Tool)은 미국 농무성 농업연구소에서 개발된 준분포형(semi-distributed) 수문 모형으로 복합토지이용유역에서 장기간에 걸친 다양한 종류의 토양, 토지이용 및 토지관리 상태의 변화에 따른 유역의 유출량, 유사량 및 영양물질의 영향을 예측하기 위해 개발되었다. SWAT은 기본적으로 다양한 매개변수에 대한 수동 보정 기능을 제공하고 있지만 매개변수 보정에 따른 모의결과의 불확실성을 수반하게 된다. 이러한 문제를 해결하기 위해 자동보정 기능을 제공하는 SWAT-CUP (Calibration and Uncertainty Program)이 개발되었다. SWAT-CUP에서 제공하는 매개변수의 최적화 과정에서 유사한 모의 결과를 산출하는 수천 개의 매개변수조합이 존재하기 때문에 보정기법의 선택에 따라 최종 매개변수의 값이 달라질 수 있다. 불확실성을 발생시키는 요인으로 (1) 매개변수의 선택, (2) 보정 기법, (3) 목적함수, (4) 매개변수의 초기 범위, (5) 모의(simulation)의 실행(run) 및 반복(iteration) 횟수, (6) 위치, 개수 등 보정 자료의 선택 등이 주로 지목된다. 이러한 요인으로 발생하는 불확실성은 SWAT 모형의 구조 및 입력 자료에서 기인하는 것으로, 사용자의 설정에 따라 크게 좌우된다. 본 연구에서는 SWAT 매개변수 보정 과정에서 발생할 수 있는 불확실성을 평가하고, 효율적인 보정 방안을 제시하기 위해 수행되었다. 낙동강 권역의 내성천 유역을 대상으로 SWAT 모형을 구축하였으며, 내성천 본류에 위치한 수위(유량) 관측소의 자료를 활용하여 검·보정을 수행하였다. 모의 결과는 유량의 크기 뿐 아니라 유량의 발생 시기, 유역의 반응 및 증가·감소 경향성을 함께 고려하여 평가하였다. 그 결과 모형 구조에 따른 불확실성의 전이과정을 정확하게 파악하는 것은 불가능하지만 SWAT 모형의 비고유성(non-uniqueness)에 의한 불확실성을 정량화하여 나타내었다.

• Information Systems Review
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• v.21 no.2
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• pp.91-115
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• 2019

The updates in the mobile application market have been widely used as strategic marketing tools. It has been used to (i) improve the visibility of an application, (ii) enhance the value of an applicationand strengthen the loyalty of current users, and (iii) expand the market by adding additional features or functions. A number of studies and anecdotal evidence have highlighted the importance of these updates in the mobile application market. However, not all updates in the mobile application market have been successful. Snapchat, for instance, lost 3 million users in three months after it rolled out a major update in November 2017. In this study, we investigate the impact of updates on the usage patterns of users in the mobile application market using MAU (Monthly Active Users), usage frequency, and usage time that we collected from a company that provides mobile application usage statistics.

• Journal of Korean Society of Transportation
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• v.34 no.1
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• pp.1-14
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• 2016

In the recent years, the internet has become accessible without limitation of time and location to anyone with smartphones. It resulted in more convenient travel information access both on the pre-trip and en-route phase. The main objective of this study is to conduct a stationary test for traffic information web/mobile application access indexes from TCS (Toll Collection System); and analyzing the relationship between the web/mobile application access indexes and actual traffic volume on expressways, in order to analyze searching behavior of expressway related travel information. The key findings of this study are as follows: first, the results of ADF-test and PP-test confirm that the web/mobile application access indexes by time periods satisfy stationary conditions even without log or differential transformation. Second, the Pearson correlation test showed that there is a strong and positive correlation between the web/mobile application access indexes and expressway entry and exit traffic volume. In contrast, truck entry traffic volume from TCS has no significant correlation with the web/mobile application access indexes. Third, the time gap relationship between time-series variables (i.e., concurrent, leading and lagging) was analyzed by cross-correlation tests. The results indicated that the mobile application access leads web access, and the number of mobile application execution is concurrent with all web access indexes. Lastly, there was no web/mobile application access indexes leading expressway entry traffic volumes on expressways, and the highest correlation was observed between webpage view/visitor/new visitor/repeat visitor/application execution counts and expressway entry volume with a lag of one hour. It is expected that specific individual travel behavior can be predicted such as route conversion time and ratio if the data are subdivided by time periods and areas and utilizing traffic information users' location.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.286-298
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• 2002

The Remote Procedure Call(RPC) has been traditionally used for Inter Process Communication(IPC) among precesses in distributed computing environment. As distributed applications have been complicated more and more, the Mobile Agent paradigm for IPC is emerged. Because there are some paradigms for IPC, researches to evaluate and compare the performance of each paradigm are issued recently. But the performance models used in the previous research did not reflect real distributed computing environment correctly, because they did not consider the evacuation elements for providing security services. Since real distributed environment is open, it is very vulnerable to a variety of attacks. In order to execute applications securely in distributed computing environment, security services which protect applications and information against the attacks must be considered. In this paper, we evaluate and compare the performance of the Remote Procedure Call with that of the Mobile Agent in IPC paradigms. We examine security services to execute applications securely, and propose new performance models considering those services. We design performance models, which describe information retrieval system through N database services, using Petri Net. We compare the performance of two paradigms by assigning numerical values to parameters and measuring the execution time of two paradigms. In this paper, the comparison of two performance models with security services for secure communication shows the results that the execution time of the Remote Procedure Call performance model is sharply increased because of many communications with the high cryptography mechanism between hosts, and that the execution time of the Mobile Agent model is gradually increased because the Mobile Agent paradigm can reduce the quantity of the communications between hosts.

• Journal of the Korean Applied Science and Technology
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• v.37 no.3
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• pp.463-472
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• 2020

The purpose of this study is to identify the BMI, diet perception and diet behavior of female university students. A descriptive survey design was used 165 students from October 29 to November 9, 2018. Data were analyzed using mean, t-test, ANOVA, cross analysis with SPSS 21.0. Total diet perception was 3.44 points, highest sub category was 'practice' with 4.00 points, followed by 'information and education' with 3.58 points, 'necessity' with 3.32 points and lowest category was 'self-recognition' with 2.84. 65 students(43.0%) were 'less than three times' in 'Number of diets' and diet methods was 65(43.0%) for 'food control' and 62(41.1%) for 'exercise'. During in a week, 98 students(84.9%) exercised within three hours, followed by 33(21.9%) who did not exercised at all. 22 students(14.6%) said they experienced damage from dieting, while the types included gastrointestinal disease, menstrual irregularity and hair loss. The total score of diet perception according to BMI was lower in the underweight group than in the normal and overweight groups(p<.001). In diet 'practice' category, low weight group scored lower than normal weight and overweight groups(p<.05). In 'information and education' category, overweight group scored the highest, followed by normal and underweight groups(p<.001). In diet 'necessity' and 'self-recognition' categories, low weight group scored lower than normal weight and overweight groups(p<.001). Diet behavior by diet perception was different in number and method of diet(p<.001). Based on the results, it is thought that attention and education are needed to form a proper diet perception and maintain healthy living for female university students.

• Journal of dental hygiene science
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• v.12 no.3
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• pp.189-195
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• 2012

The subjects in this study were 281 elderly people in some regions. After they were respectively interviewed, the following findings were given: The group of elderly people who brushed their teeth three times or more and who did toothbrushing in an arbitrary way were more concerned about oral health, and the gap between them and the others (p<.05). The group who paid a regular visit to dental clinics had more interest in oral health than the other (p<.01). The group who brushed their teeth in an arbitrary way had more remaining teeth, and the gap between them and the others(p<.05). The group who did toothbrushing for about two minutes had more remaining teeth, and more edentulous jaws were found in the group who brushed their teeth once (p<.01). The group who did toothbrushing three times or more scored higher in oral health knowledge, and the gap between them and the others(p<.01). And the group who paid a regular visit to dental clinics scored higher in oral health knowledge, and the gap between them and the other (p<.01). In the future, the development of a wide variety of oral health programs and prolonged oral health education are both required. Diverse oral health programs and education are expected to stir up elderly people's interest in oral health, to improve their oral health knowledge and to give a positive change to their oral health behavior.

• Journal of Nutrition and Health
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• v.41 no.8
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• pp.870-886
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• 2008

The purposes of this study were to (a) analyze school foodservice employees' knowledge and performance degree of HACCP system and (b) provide the basic data for planning the strategies which can be performed for systematic HACCP system in school foodservice. For these purposes, the subjects included 91 dieticians (a response rate 98.9%) and 270 foodservice employees (a response rate 98.2%) at school in Jeju city and they were surveyed from October 21 to November 4, 2006. The data were analyzed by descriptive analysis, reliability analysis, t-test, ANOVA (Duncan multiple range test) and Pearson's correlation coefficients using the SPSS Win Program (version 12.0). In terms of the number of training practice, the result of sanitary training indicated that the dieticians who trained the employees more than once per a week (48.6%) or everyday (36.3%) were 84.7%. And the dieticians who were higher age, full-time job, and working at middle school implemented significantly more training the employees. In the training methods, 40.7% of dieticians used the oral presentation and 37.4 % utilized the printed matters. Also, most of employees (98.1%) have experienced for the training, 39.6% of them did not have regular training experience and 40.7% of them responded that they were understanding the HACCP system well. The result of employees' knowledge level of HACCP system reported that the items of the personal hygiene scored the highest (92.3 points) whereas the items of CCP3 scored the lowest (58.3 points) as the average being 84.2 points (out of 100 scale). In terms of the performance degree of HACCP system, the average was 4.40 (out of 5 scale), the items of the personal hygiene scored the highest as 4.51 whereas the items of CCP2 scored the lowest as 4.31 points. The dieticians' perception degree of employees' performance degree in HACCP system showed that the average was 4.13 (out of 5 scale), so it was significantly lower than actual performance degree as average 4.40 (out of 5 scale). Additionally the employees' knowledge level was positively correlated to performance degree and employees' knowledge level of CCP3, CCP4, and the personal hygiene significantly influenced to the HACCP performance degree. Finally, the dieticians have to recognize correctly the employees' performance degree and on the basis of it must plan the sanitary training which has a proper contents and methods to enhance the employees' knowledge level and achieve more systematic HACCP system in school foodservice.