• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.3
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• pp.220-227
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• 2019

The satellites in orbit use a sun reference vector from solar model based the ephemeris. To get the ephemeris, we use DE-Series, an ephemeris developed by the Jet Propulsion Laboratory (JPL), or the reference vector generation formula proposed by Vallado. The DE-Series provides the numerical coefficients of Chebyshev polynomials, which have the advantage of high precision, but there is a computational burden on the satellite. The Vallado's method has low accuracy, although the sun vector can be easily obtained through the sun vector generation equation. In this paper, we have developed a program to provide the Chebyshev polynomial coefficients to obtain the sun position coordinates in the inertial coordinate system. The proposed method can improve the accuracy compared to the conventional method and can be used for high - performance, high - precision nano satellite missions.

• Korean Journal of Construction Engineering and Management
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• v.24 no.5
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• pp.35-43
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• 2023

Along with the increase in Multi-unit housing defect disputes, the importance of defect management is also increased. However, previous studies have mostly focused on the Multi-unit housing's 'common part'. In addition, there is a lack of research on the system for the 'management office', which is a part of the subject of defect management. These resulted in the lack of defect management capability of the management office and the deterioration of management quality. Therefore, this paper proposes a machine learning-based defect data management system for management offices. The goal is to solve the inconvenience of management by using Optical Character Recognition (OCR) and Natural Language Processing (NLP) modules. This system converts handwritten defect information into online text via OCR. By using the language model, the defect information is regenerated along with the form specified by the user. Eventually, the generated text is stored in a database and statistical analysis is performed. Through this chain of system, management office is expected to improve its defect management capabilities and support decision-making.

• Journal of dental hygiene science
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• v.9 no.4
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• pp.419-426
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• 2009

The occurrence of toothache signals the malfunction in oral health, which allows the detection of any abnormal condition in the oral cavity at an early stage to prevent the condition from worsening, and thus can act as a preventive measure. This study has looked into the status of oral health management in relation to toothache through the structured survey administered to 235 college students. Based on the survey results, this study aimed at comparing the toothache occurrence prediction between regression analysis and CART model in order to clarify the relationship between the factors of oral health management habits that contribute to toothache occurrence. According to the result, there was a difference between the present health status and the health status of the past year depending on the presence or non-presence of toothache occurrence (p<0.05). There was a difference in the regularity of meal time depending on the presence non-presence of toothache occurrence from the dietary habits of the research subjects (p<0.05). As for the presence or non-presence of toothache occurrence from the oral hygiene habits of the research subject, there was a difference between the occurrence and nonoccurrence of bleeding during brushing or flossing (p<0.05). According to the results of regression analysis, no factors were signifiant in the relationship with the presence or non-presence of toothache occurrence from the status of life habits and oral hygiene habits. 70% of the researched group was randomly selected as the sample for generating an analytical model and the remaining 30% was used as the sample for generating an evaluation model. According to the results of CART model, the occurrence of toothache was higher in the case of irregular meal time and poor current health condition than the case of average or satisfactory health condition. The above results imply that CART model is very useful technique in predicting toothache occurrence compared to regression analysis, and suggests that CART model could be very useful in predicting other oral diseases including toothache.

• Journal of the Korea Convergence Society
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• v.11 no.9
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• pp.1-6
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• 2020

In this study, we propose an association inference model based on data bias optimization for road hazard detection. This is a mining model based on association analysis to collect user's personal characteristics and surrounding environment data and provide traffic accident prevention services. This creates transaction data composed of various context variables. Based on the generated information, a meaningful correlation of variables in each transaction is derived through correlation pattern analysis. Considering the bias of classified categorical data, pruning is performed with optimized support and reliability values. Based on the extracted high-level association rules, a risk detection model for personal characteristics and driving road conditions is provided to users. This enables traffic services that overcome the data bias problem and prevent potential road accidents by considering the association between data. In the performance evaluation, the proposed method is excellently evaluated as 0.778 in accuracy and 0.743 in the Kappa coefficient.

• Journal of Korean Society of Steel Construction
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• v.23 no.2
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• pp.199-210
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• 2011

The cables in cable-stayed bridges are under high stress and are very sensitive to vibration due to their small section areas compared with other members. Therefore, it is reasonable to evaluate the cable impact factor by taking into account the dynamic effect due to moving-vehicle motion. In this study, the cable impact factors were evaluated via moving-vehicle-load analysis, considering the design parameters, i.e., vehicle weight, cable model, road surface roughness, vehicle speed, longitudinal distance between vehicles. For this purpose, two steel composite cable-stayed bridges with 230- and 540-m main spans were selected. The results of the analysis were then compared with those of the influence line method that is currently being used in design practice. The road surface roughness was randomly generated based on ISO 8608, and the convergence of impact factors according to the number of generated road surfaces was evaluated to improve the reliability of the results. A9-d.o.f. tractor-trailer vehicle was used, and the vehicle motion was derived from Lagrange's equation. 3D finite element models for the selected cable-stayed bridges were constructed with truss elements having equivalent moduli for the cables, and with beam elements for the girders and the pylons. The direct integration method was used for the analysis of the bridge-vehicle interaction, and the analysis was conducted iteratively until the displacement error rate of the bridge was within the specified tolerance. It was acknowledged that the influence line method, which cannot consider the dynamic effect due to moving-vehicle motion, could underestimate the impact factors of the end-cables at the side spans, unlike moving-vehicle-load analysis.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.164-175
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• 2009

CFD is used to analyze gas flow characteristics, power absorption, electron temperature, electron density and chemical species profile of an internal antenna type inductively coupled plasma system. An optimized grid generation technology is used for a complex real-scale models for industry. A bare metal antenna shows concentrated power absorption around rf a feeding line. Skin depth of power absorption for a system is modeled to 50 mm, which is reported 53 mm by experiments. For an application of bipolar plates for hydrogen fuel cells, multi-sheet loading ICP nitriding system is proposed using an internal ICP antenna. It shows higher atomic nitrogen density than reported simple pulsed dc nitriding systems. Minimum gap between sheets for uniform nitriding is modeled to be 39 mm.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.363-367
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• 2009

We propose Cubical User Interface(CUI) for toy block composition in Augmented Reality. The creation of new object by composing virtual object is able to construct various AR contents effectively. However, existing GUI method requires learning time or is lacking of intuitiveness between act of user and offered interface. In case of AR interfaces, they mainly have been supported one handed operation and it did not consider composition property well. Therefore, the CUI provide tangible cube as the manipulation tool for virtual toy block composition in AR. The tangible cube which is attached multi-markers, magnets, and buttons supports free rotation, combination, and button input. Also, we propose two kinds of two-handed composing interactions based on CUI. First is Screw Driving(SD) method which is possible to free 3-D positioning and second is Block Assembly(BA) method which support visual guidance and is fast and intuitive. We expected that proposed interface can apply as the authoring system for content such as education, entertainment, Digilogbook.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.75-75
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• 2011

본 논문에서는 진동중인 교량 거더에 작용하는 풍하중을 산정하고 그에 따른 플러터 발생풍속을 예측하기 위하여 분산형 전산환경을 활용한 수치해석 연구를 수행하였다. 분산형 전산환경은 웹 포탈을 기반으로 수치해석 환경을 제공하는 수치풍동 시스템으로서, 전산유체역학(CFD : Computational Fluid Dynamics)에 대한 전문지식이 부족한 사용자들도 격자생성, 수치해석자를 이용한 계산, 가시화 등의 전 과정을 편리하게 수행할 수 있는 차세대 토목분야 연구 환경이다. 본 시스템은 그리드스피어(GfidSphere)를 기반으로 구성되었으며, 기본적으로 사용자 관리, 세션 관리, 그룹 관리, 레이아웃 관리 등을 제공하여 사용자가 포탈을 통해서 다양한 서비스를 쉽게 사용할 수 있는 환경을 구축하도록 도와준다. 수치해석을 위한 유체 지배방정식은 2차원 비정상 비압축성 RANS(Reynolds-Averaged Navier-Stokes) 방정식이며, pseudo compressibility 방법을 적용하였다. 비정상 유동장을 해석하기 위하여 이중시간 전진법(dual time stepping)을 사용하였으며, 수렴가속화를 위해 Multi-grid 기법을 적용하였다. 또한 난류 유동장 해석을 위해서 $k-{\omega}$ SST 난류 모델을 사용하였으며, 난류 천이 과정에서의 유동을 모사하기 위하여 Total stress limitation 방법을 적용하였다. 교량 거더의 연직과 회전방향의 2자유도 움직임을 모사하기 위하여 동적격자 기법을 도입하였다. 교량 거더 주변의 비정상 유동해석 결과를 통해, 거더 표면에서 떨어져나가는 크고 작은 와류의 영향으로 양력 및 모멘트 계수 그래프가 중첩된 진폭과 주기를 갖고 주기적으로 나타나는 것을 확인할 수 있었다. 또한 계산된 비정상 공기력을 적용한 2자유도 플러터 방정식을 통하여 플러터 발생풍속을 산정하였다. 최종적으로 본 연구에서 계산된 결과의 타당성을 검증하기 위하여 수치적으로 구한 플러터 발생풍속과 기존의 실험 및 수치해석 결과를 비교하였으며, 결과는 잘 일치하였다.

• Journal of KIISE:Software and Applications
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• v.34 no.3
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• pp.235-245
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• 2007

UUV(Unmanned Underwater Vehicle) should possess an intelligent control software performing intellectual faculties such as cognition, decision and action which are parts of domain expert's ability, because unmanned underwater robot navigates in the hazardous environment where human being can not access directly. In this paper, we suggest a RVC intelligent system architecture which is generally available for unmanned vehicle and develope an autonomous navigation system for UUV, which consists of collision avoidance system, path planning system, and collision-risk computation system. We present an obstacle avoidance algorithm using fuzzy relational products for the collision avoidance system, which guarantees the safety and optimality in view of traversing path. Also, we present a new path-planning algorithm using poly-line for the path planning system. In order to verify the performance of suggested autonomous navigation system, we develop a simulation system, which consists of environment manager, object, and 3-D viewer.

• The KIPS Transactions:PartB
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• v.14B no.3 s.113
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• pp.199-214
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• 2007

Recently, there have been a lot of works trying to realize automated composition of semantic web services though application of AI planning techniques. The traditional AI planning techniques, however, have some limitations: it is not easy to represent a web service process with complex control constructs as an action or a plan; it is hardly possible to consider enough the rich information contained in domain ontologies during the planning process; it is impossible to model directly the data flow from the outputs of a web service to the inputs of another web service; it is difficult to predict and deal with uncertainty and dynamics of the environment because the plan generation phase is supposed to be separated from the plan execution phase. In order to overcome some of these limitations, this paper suggests a reactive planning approach to automated composition of semantic web services. Through some experiments using several e-commerce web services, we found that the reactive planning is an effective way to realize automated composition of semantic web services.