• Journal of KIISE:Information Networking
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• v.32 no.5
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• pp.561-573
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• 2005

As the demand on ubiquitous communication increases, global roaming and vertical handover will be prevailing in the near future. Since this environment is accompanied by the frequent handovers at remote sites, a scalable and fast authentication becomes prerequisite for ubiquitous communication. In this paper, we suggest a framework for scalable and fast authentication, using hierarchical caching based on general trust relationship among domains. At the end, we show that the proposed scheme achieves reduced authentication delay and network overhead through an analytic method with fluid flow model.

• Journal of Internet Computing and Services
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• v.8 no.3
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• pp.1-7
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• 2007

Since the DirectTV started its digital broadcasting services in 1994 for the first time in the U.S., digital broadcasting widened its services in many areas. In korea, TIT(Transport Information Technology) based IP-TV services have been provided in Saemaeul trains and some sections of subway trains. But the software systems for the service performed in alternated fashions and suffered from many problems such as suspension, memory leaking and overflow. These problems increased playback loss time and resulted in bad reliabilities. In this paper, a software TIT monitor is designed and implemented for the TIT system in physically poor environments. The designed system formalized monitoring time intervals for effective monitoring. Through the real experiments, playback time is improved in 14% comparing to existing system.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.44.2-44.2
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• 2017

Multiple stellar systems composed of triple, double+double or double+triple, etc. are very rare and interesting objects for understanding the star formation and dynamical evolution. However, only six systems have been found to be a doubly eclipsing quadruple, which consists of two eclipsing binaries, and four systems to be a triply eclipsing hierarchical triple. Recently, the 15 doubly eclipsing multiple candidates located in the Large Magellanic Cloud (LMC) have been reported by the OGLE project. In order to examine whether these candidates are real multiple systems with eclipsing features, we performed a high-cadence time-series photometry for the LMC using the KMTNet (Korea Microlensing Telescope Network) 1.6 m telescopes in three site (CTIO, SAAO, and SSO) during 2016-2017. The KMTNet data will help reveal the photometric properties of the multiple-star candidates. In this paper, we present the VI light curves and their preliminarily analyses for 12 of the 15 eclipsing systems in the LMC, based on our KMTNet observations and the OGLE-III survey data from 2001-2009.

• Journal of Internet Computing and Services
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• v.8 no.2
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• pp.89-94
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• 2007

Even though lots of research have been doing about spam mail blocking technologies and their systems, the emergence of spam mails of new types causes the spam mail filtering rate to decrease and the occurrences of false-positive mails to increase. Therefore, existing spam mail filtering algorithms suffer from increasing load to be processed and decreasing reliability in spam mail blocking systems due to the shortage of newly developed algorithms and their research. This paper presents the Fit-FA Finder which is able to select appropriate algorithms to be applied and their procedures, and the development of the SMBC platform. The Fit-FA Finder is developed and implemented in the SMBC platform in which recovering process based on privacy information is employed for false-positive mails

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05c
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• pp.1961-1964
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• 2003

웹서비스에 대한 높은 관심과 함께 그 실현이 점차 가시화되고 XML로 이루어진 지원 기술들의 전폭적인 지지로 잠재력은 더욱 확대되고 있다. 웹서비스는 기존 웹 기반의 디스플레이에 그쳤던 단순정보 교환을 애플리케이션 차원에서 데이터를 통신할 수 있어 개발 가능성이 무한한 프레임워크로 각광받고 있다. 전자상거래 분야도 예외는 아니어서 웹서비스의 기본 개념을 이용하여 프레임워크를 구성하려는 노력이 진행되고 있다. 이에 따라 인증분야에서도 한계점이 드러나게 되었고 각 시스템마다 존재하는 많은 인증 정보관리 문제가 부각되고 있다. OASIS에서는 웹서비스의 등장과 함께 SAML이라는 표준 인증 방식을 제시하였다. SAML은 XML기반의 표준화된 인증방식을 취하여 안전성과 확장성 뿐만 아니라 인증 간 상호운용성을 제공하는 강력한 기능을 가지고 있다. 본 논문에서는 SAML을 이용한 SSO(Single Sign On)와 접근권한에 대한 적용개념을 소개하고 SAML인증서버를 이용한 Web Services인증 모델을 제시하고자 한다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.203.1-203.1
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• 2012

한국천문연구원에서는 2009년부터 외계행성 탐색시스템(KMTNet; Korea Microlensing Telescope Network) 개발 사업을 수행하고 있다. 이 사업에서는 중력렌즈 방법이나 별표면 통과(Transit) 방법으로 외계행성을 탐색하기 위하여, 1.6m 광학 망원경과 3.4억 화소의 모자이크 CCD 카메라로 구성된 2도x2도의 광시야 관측시스템을 제작하고 있다. 이 시스템은 2014년까지 남반구의 칠레 CTIO(1호기), 남아공화국 SAAO(2호기), 호주 SSO(3호기)에 설치될 예정이다. 우리은하 벌지 영역을 24시간 연속 모니터링 관측하여 외계행성과 변광천체를 탐색하는 것이 핵심연구주제이다. 광시야 망원경 1호기는 미국 Tucson에 건설된 관측시설 Prototype에 설치하여 공장시험을 수행하고 있다. 망원경의 지향(pointing) 정밀도와 Lucky Imaging 방법을 이용하여 얻은 광시야 광학계 성능 등 공장시험 결과를 보고할 것이다. 또한 핵심연구주제 이외의 관측시간을 활용할 2차 연구주제를 공모하여 심사한 결과를 제시할 것이다. 아울러 모자이크 CCD 카메라 제작, 남반구 관측소 설치 준비, 대용량 자료처리 시스템 개발, 남반구 관측소 운영 계획 등 전반적인 사업 현황과 계획을 발표할 것이다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.598-602
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• 2017

Korea Aerospace Research Institute has been developing 3-stage launcher KSLV-II, which can inject 1.5-ton satellite into sun synchronous orbit (SSO). For development process, Test Launch Vehicle(TLV) adopting the $2^{nd}$ and $3^{rd}$ stage of KSLV-II will be scheduled to launch in 2018. The propulsion system of TLV is composed of $2^{nd}$ stage engine system (ground type) and propellant supply system including LOX, Kerosene tanks. Until now, system integration of engineering model of TLV and delivery of qualification model have been done. In this paper, the product assurance activities for propulsion system KSLV-II will be illustrated.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.28.3-28.3
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• 2010

위성이 궤도를 운용함에 있어서 원으로 운용되는 저궤도(LEO)에서는 대기저항(Drag)에 의한 섭동 영향이 가장 크게 미친다. 이 연구에서는 대기저항 섭동에 의해 감소되는 위성의 고도를 전기추력기를 이용하여 고도를 유지할 때 이를 해석적인 측면에 대해 살펴보고 지구 관측 위성에서 많이 쓰이는 태양 동기 궤도(SSO)에 적용하여 궤도를 유지하는 방법에 대해 알아보았다. 태양활동에 의한 대기의 밀도변화를 John kennewell의 모델을 통해 예측하여 대기저항에 의해 감소되는 고도량을 구하고 위성에서 추력(thrust)을 줄 때는 Gaussian Variation of Parameters식을 이용하여 해석적인 방법으로 궤도 장반경의 증가량을 구하였다. 위성에 추력을 줄때 이심률이 증가하게 되는 문제는 구속조건으로 이심률 값의 최대 허용치를 정하여 증가하는 것을 방지하도록 하였다. 또한 $J_2$ 섭동에 의해 가장 영향을 받는 승교점(Ascending Node)과 추력에 의해 변화할 수 있는 근지점(Perigee)을 살펴보고 궤도 유지를 위한 적절한 추력 방향을 구하였다. 각각의 궤도 요소의 변화를 살펴보고 일반적인 태양 동기 궤도 위성의 제원을 이용하여 궤도 유지에 적용하였다. 저궤도 위성의 궤도 유지에 대한 복잡한 수치적인 방법으로 궤도요소의 변화를 정확하게 구하지만 해석적인 방법으로도 위성의 궤도 유지를 위한 정보를 얻을 수 있었다. 이를 저궤도 위성의 궤도 운용과 변화 예측에 적용할 수 있다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.4
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• pp.215-219
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• 2019

Objectives: Postoperative paresthesia is a common complication after sagittal split osteotomy (SSO). This study aimed to compare paresthesia among different fixation methods one year postoperative. Materials and Methods: This prospective cohort study assessed subjects in four groups: class II with miniplate fixation (Group 1), class II with three-screw fixation (Group 2), class III with miniplate fixation (Group 3), and class III with three-screw fixation (Group 4). Paresthesia was evaluated one year postoperative based on a 0-10 visual analogue scale. Pearson correlation was used to evaluate associations of age and mandibular movement with paresthesia. ANOVA was used to compare paresthesia among groups. Results: A total of 80 subjects were enrolled, with 20 subjects in each of the four groups. The Pearson correlation test demonstrated a significant correlation between mandibular movement and paresthesia (P=0.001). Comparison of paresthesia among the groups showed significant differences among groups 1 and 2, 2 and 3, and 3 and 4 (P<0.05). Conclusion: The three-screw fixation method led to more paresthesia one year postoperative compared with miniplate fixation. In addition, the magnitude of mandibular movement had a positive correlation with paresthesia.

• Structural Engineering and Mechanics
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• v.81 no.1
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• pp.93-102
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• 2022

The optimum design of reinforced concrete cantilever retaining walls subjected to seismic loads is an extremely important challenge in structural and geotechnical engineering, especially in seismic zones. This study proposes an adaptive sperm swarm optimization algorithm (ASSO) for economic design of retaining structure under static and seismic loading. The proposed ASSO algorithm utilizes a time-varying velocity damping factor to provide a fine balance between the explorative and exploitative behavior of the original method. In addition, the new method considers a reasonable velocity limitation to avoid the divergence of the sperm movement. The proposed algorithm is benchmarked with a set of test functions and the results are compared with the standard sperm swarm optimization (SSO) and some other robust metaheuristic from the literature. For seismic optimization of retaining structures, Mononobe-Okabe method is employed for dynamic loading conditions and total construction cost of the structure is considered as the single objective function. The optimization constraints include both geotechnical and structural restrictions and the design variables are the geometrical dimensions of the wall and the amount of steel reinforcement. Finally, optimization of two benchmark retaining structures under static and seismic loads using the ASSO algorithm is presented. According to the numerical results, the ASSO may provide better optimal solutions, and the designs obtained by ASSO have a lower cost by up to 20% compared with some other methods from the literature.