• Journal of computational fluids engineering
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• v.11 no.3 s.34
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• pp.59-63
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• 2006

Accurate prediction of a supersonic missile base drag continues to defy even well-rounded CFD codes. In an effort to address the accuracy and predictability of the base drags, the influence of grid system and competitive turbulence models on the base drag is analyzed. Characteristics of some turbulence models is reviewed through incompressible turbulent flow over a flat plate, and performance for the base drag prediction of several turbulence models such as Baldwin-Loman(B-L), Spalart-Allmaras(S-A), k-$\varepsilon$, k-$\omega$ model is assessed. When compressibility correction is injected into the S-A model, prediction accuracy of the base drag is enhanced. The NSWC wind tunnel test data are utilized for comparison of CFD and semi-empirical codes on the accuracy of base drag predictability: they are about equal, but CFD tends to perform better. It is also found that, as angle of attack of a missile with control fins increases, even the best CFD analysis tool we have lacks the accuracy needed for the base drag prediction.

• KIISE Transactions on Computing Practices
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• v.22 no.2
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• pp.101-106
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• 2016

A femtocell network has been attracting attention as a promising solution for providing high data rate transmission over the conventional cellular network in an indoor environment. In this paper, we propose a distributed power control algorithm considering both indoor coverage and data load balancing in the femtocell network. As data traffic varies by time and location according to user distribution, each femto base station suffers from an unbalanced data load, which may degrade network performance. To distribute the data load, the base stations are required to adjust their transmission power dynamically. Since there are a number of base stations in practice, we propose a distributed power control algorithm. In addition, we propose the simple algorithm to detect the faulty base station and to recover coverage. We also explain how to insert a new base station into a deployed network. We present the simulation results to evaluate the proposed algorithms.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.579-583
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• 1991

A fuzzy logic controller with rule modification capability is proposed to overcome the difficulty of obtaining control rules from the human operators. This new SOC algorithm modifies control rules by a fuzzy inference machine utilizing data base. Computer simulation results show good performances on both a linear system and a nonlinear system.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.407-412
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• 1989

Using the knowledge base which contains the patterns and data of the past experience of a plant, a learning control method is suggested. The knowledge for controlling a plant is stored to the knowledge base and continually modified after performance evaluation of an applied control input. The performance of the resultant knowledge based control system is examined by an application to process.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1589-1594
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• 2004

A numerical analysis has been performed to give an understanding of the physics of a compressible base flow with mass bleed in a Mach 2.47 freestream. Axisymmetric, compressible mass-averaged Navier-Stokes equations are computed using a two-equation turbulence model, standard ${\kappa}-{\omega}$, and a fully implicit finite volume scheme. The mass bleed is characterized by the change in the mass flow rate of the bleed jet non-dimensionalized by the product of the base area and freestream mass flux. The result showing that there is an optimum bleed condition with maximum base pressure, leading to a minimum base drag, is clearly predicted and the validation with experimental data shows reasonable agreement.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.1177-1190
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• 2009

In this paper, we propose a fuzzy proxy cache scheme for caching web documents in mobile base stations. In this scheme, a mobile cache model is used to facilitate data caching and data replication. Using the proposed cache scheme, the individual proxy in the base station makes cache decisions based solely on its local knowledge of the global cache state so that the entire wireless proxy cache system can be effectively managed without centralized control. To improve the performance of proxy caching, the proposed cache scheme predicts the direction of movement of mobile hosts, and uses various cache methods for neighboring proxy servers according to the fuzzy-logic-based control rules based on the membership degree of the mobile host. The performance of our cache scheme is evaluated analytically in terms of average response delay and average energy cost, and is compared with that of other mobile cache schemes.

• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.445-452
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• 2006

In this paper, the conceptual design of satellite digital base put which is based upon data interface between satellite on-board computer and remote devices like satellite sub-components is presented. This conceptual design shows the unification of the interface between on-board computer and satellite remote devices and the hierarchical results of the interface level. A comparison of different system and merits and demerits of digital base part coming from this conceptual design is performed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.6
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• pp.187-196
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• 2001

In this study, by using the natural language processing of the field of artificial intelligence, automated index was performed. And then, the Natural Language Processing Interface for knowledge representation(NALPI) has been developed. Furthermore, the DEsign KnOwledge DataBase(DEKODB) has been also developed, which is designed to interlock the knowledge base. The DEKODB processes both the documented design-data, like a concrete standard specification, and the design knowledge from an expert. The DEKODB is also simulates the design space of structures accordance with the production rule, and thus it is determined that DEKODB can be used as a engine to retrieve new knowledge and to implement knowledge base that is necessary to the development of automatic design system. The application field of the system, which has been developed in this study, can be expanded by supplement of the design knowledge at DEKODB and developing dictionaries for foreign languages. Furthermore, the perfect automation at the data accumulation and development of the automatic rule generator should benefit the unified design automation.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2002.11a
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• pp.172-176
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• 2002

본 연구는 감성 의류용 PET 직물 소재별 직물설계 조건의 DB 구축을 목적으로 하여 직물 소재 설계시 보다 합리적이고 체계적인 의류용 합섬 소재 설계 방향을 제시하고 이들을 의류용 합섬 직물 설계시 적용가능한 기존의 CAD System에 응용할 수 있는 기초 연구를 수행하고자 국내 현업에서 적용되고 있는 100여 종류의 합섬직물의 설계 조건을 Data Base 化하여 경사, 위사의 굵기와 밀도계수 그리고 조직에 따른 이들 직물의 설계조건을 조사분석하였다. 그 결과 경위사 번수별, 조직별로 다양한 경·위사밀도를 가짐으로서 최종용도에 따라 다양한 밀도계수 분포를 보임을 확인하였으며 경·위사 번수별로 다양한 직물 조직에 따른 밀도계수 값으로 경·위사의 밀도 분포를 도시화함으로서 현업의 직물설계시 밀도선정에 보다 용이한 기초 연구를 수행하였다. 향후 보다 많은 Data를 수집하고 분석하여 소재별 합섬 직물의 설계에 필요한 Data Base를 더 보완하고 기존의 직물 CAD 시스템에 접목시킴으로서 기존의 직물CAD의 효율적인 이용이 가능할 것으로 사료된다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.1
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• pp.88-97
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• 1989

A new system for three dimensional object recognition is proposed in an attempt to overcome the lack of accuracy and flexibility, the essential problem at which model-based recognition technique faces. Hierarchical data base was designed to manage a number of features efficiently which are extracted for the purpose of matching by the system and to provide information necessary to match systema6tically. The results of matching, in turn, is fed back to the data base, and stored in. The recognition is done by saving the results on higher level of hierachical data base.