• 한국정밀공학회지
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• 제14권3호
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• pp.66-74
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• 1997

In a high speed and high precision vertical machining center, chatter vibration is easily generated due to unbalanced masses in rotating parts and changtes of cutting forces. In this paper, modal test is performed to obtain modal parameters of the vertical machining center. In order to predit the cutting force of endmilling process for various cutting conditions, a mathematical model is given and this model is based on chip load, cutting geometry, and relationship between cutting forces and the chip load. Specific cutting constants of the model are obtained by averaging forces of cutting tests. The interactions between the dy- namic characteristics and cutting dynamics of the vertical machining center make the primary and the secondary feedback loops, and we make use of the equations of system to predict the chatter vibration. The chatter prediction is formulated as linear differential-differene equations, and simulated for several cases. Trends of vibration as radial and axial depths of cut are changed are shown and compared.

• 한국컴퓨터정보학회논문지
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• 제17권11호
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• pp.163-171
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• 2012

온라인게임에 관한 대다수의 연구들은 주로 심리학자들에 의한 인터넷 중독과 과학자들에 의한 관련기술의 개발에 관해 수행되어왔다. 온라인 비즈니스 모델의 관점에서 고객만족을 연구한 논문은 드문 편이다. 본 연구의 목적은 온라인게임 이용자들을 대상으로 고객만족과 주요 요인들 간의 인과관계를 조사하는 것이다. 이를 위해 연구모델은 고객만족에 영향을 미치는 주요 요인들을 규명하기 위해 상호작용, 즐거움, 도전, 보상, 디자인의 개념을 이용하였다. 연구결과 상호작용, 즐거움, 도전 요인이 온라인게임 이용자들의 고객만족에 유의한 영향을 미치는 요인으로 규명되었다. 온라인게임 이용자들의 만족도에 영향을 미치는 주요 요인에 관한 연구는 지속적으로 논의되고 있다.

• Journal of Information Processing Systems
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• 제9권3호
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• pp.349-364
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• 2013

The big challenge in current content-based image retrieval systems is to reduce the semantic gap between the low level-features and high-level concepts. In this paper, we have proposed a novel framework for efficient image retrieval to improve the retrieval results significantly as a means to addressing this problem. In our proposed method, we first extracted a strong set of image features by using the dual-tree rotated complex wavelet filters (DT-RCWF) and dual tree-complex wavelet transform (DT-CWT) jointly, which obtains features in 12 different directions. Second, we presented a relevance feedback (RF) framework for efficient image retrieval by employing a support vector machine (SVM), which learns the semantic relationship among images using the knowledge, based on the user interaction. Extensive experiments show that there is a significant improvement in retrieval performance with the proposed method using SVMRF compared with the retrieval performance without RF. The proposed method improves retrieval performance from 78.5% to 92.29% on the texture database in terms of retrieval accuracy and from 57.20% to 94.2% on the Corel image database, in terms of precision in a much lower number of iterations.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제2권3호
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• pp.204-209
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• 2002

The interest of data mining in artificial intelligence with fuzzy logic has been increased. Data mining is a process of extracting desirable knowledge and interesting pattern ken large data set. Because of expansion of WWW, web data is more and more huge. Besides mining web contents and web structures, another important task for web mining is web usage mining which mines web log data to discover user access pattern. The goal of web usage mining in this paper is to find interesting user pattern in the web with user feedback. It is very important to find user's characteristic fer e-business environment. In Customer Relationship Management, recommending product and sending e-mail to user by extracted users characteristics are needed. Using our method, we extract user profile from the result of web usage mining. In this research, we concentrate on finding association rules and verify validity of them. The proposed procedure can integrate fuzzy set concept and association rule. Fuzzy association rule uses given server log file and performs several preprocessing tasks. Extracted transaction files are used to find rules by fuzzy web usage mining. To verify the validity of user's feedback, the web log data from our laboratory web server.

• 한국정보통신학회논문지
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• 제15권10호
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• pp.2087-2092
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• 2011

본 논문에서는 지구 자기장을 측정하여 방향을 인식하는 시스템 구현에 있어 하드웨어적으로 회로를 부가하는 방식 보다는 소프트웨어적인 알고리즘을 추가하여 지구 자기장의 지역적 변화와 주변 환경에 적응력을 갖는 측정 시스템을 구축한다. 소프트웨어적인 알고리즘에는 뉴럴 네트워크(neural network)를 사용하여, 입력 패턴에 따른 패턴간의 관련성을 형성하고 학습을 통해 패턴들의 특징과 관련 정보가 기억 되었을 때 출력이 입력에 feedback하는 연상회로망을 구성하여 방향 인식에 사용할 수 있는 소프트웨어를 구현하고 그 실효성에 대해 입증한다.

• 디지털산업정보학회논문지
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• 제7권3호
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• pp.123-136
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• 2011

Arts gains a new relation as the new academic area that deals with living organisms and through this technology, it affects everything, such as the body, entity, consciousness and unconsciousness to bring an overall change. Based on this premise, arts require a different interpretation from the previous product-focused interpretation or the analysis focusing on the aesthetics. As the result of arts using the scientific methods, I examined the changes of the arts semantics and how it evolved with what kind of contents and characteristics. The net art with the internet base also form a close relationship with the social and cultural codes. In categorizing the social issues and the topical discussions with semantic factors that evolve from the digital biological perspective, it can be divided into four types of complex interaction, positive feedback negative feedback, and amplification of unsettledness. Based on the characteristics of the multimedia and the interactive reaction, the technique and the imagery amplify the message through a spatial and timely meeting in a mutual repletion. In other words, the emotional communication is used to attempt the messages from the products and the expression in various methods.

• 한국항공운항학회지
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• 제21권3호
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• pp.9-14
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• 2013

Continuous airworthiness system is comprised of regulations and procedures to assure the safety and reliability through the total stage of development, certification and operation of aircraft. The purpose of this system is not only to provide the guidelines that should be kept by manufacturers and operators, but also to evaluate the maintenance capability in every activity of safety related procedures. During the development process of the mid and large size aircraft, operational experience should be reflected systematically for a safer and more reliable product by using the meaningful data base from operation. The relationship of safety roles between manufacturer and operator is mutually complementary, and the roles of each function have an influence to the next step. Overall structure of the procedure contains the concept of continuous analysis and feedback to achieve highest degree of safety and reliability during the entire life of aircraft. Finally, this paper describes how the feedback is made and used for aircraft design from operational experience under the continuous analysis and surveillance system.

• 한국전자통신학회논문지
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• 제13권6호
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• pp.1177-1182
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• 2018

UCC3895 드라이버를 이용하여 위상천이방식의 100Mhz로 운용되는 500W급 영전압스위칭(Zero voltage switching) DC/DC 컨버터를 설계하였다. UCC3895 드라이버의 데드타임은 풀브리지의 리딩래그와 레깅래그가 별도로 구동 가능하도록 설계되어 있어 두 래그간에 데드타임을 별도로 부여하는 것이 가능하며, 이것은 두 래그간에 비대칭관계인 데드타임으로 영전압스위칭의 구현을 가능하게 하였다. 또한 본 논문에서는 안정된 출력전압을 위한 부귀환회로 설계방식이 제안되었다. 시제품의 최대 효율은 $500{\Omega}$의 부하에서 95.5% 정도를 나타냈다.

• 천문학회보
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• 제44권2호
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• pp.75.4-75.4
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• 2019

We present a quantitative analysis of the relationship between the gas dynamics and star formation history of DDO 210 which is an irregular dwarf galaxy in the local Universe. We perform profile analysis of an high-resolution neutral hydrogen (HI) data cube of the galaxy taken with the large Very Large Array (VLA) survey, LITTLE THINGS using newly developed algorithm based on a Bayesian Markov Chain Monte Carlo (MCMC) technique. The complex HI structure and kinematics of the galaxy are decomposed into multiple kinematic components in a quantitative way like 1) bulk motions which are most likely to follow the underlying circular rotation of the disk, 2) non-circular motions deviating from the bulk motions, and 3) kinematically cold and warm components with narrower and wider velocity dispersion. The decomposed kinematic components are then spatially correlated with the distribution of stellar populations obtained from the color-magnitude diagram (CMD) fitting method. The cold and warm gas components show negative and positive correlations between their velocity dispersions and the surface star formation rates of the populations with ages of < 40 Myr and 100~400 Myr, respectively. The cold gas is most likely to be associated with the young stellar populations. Then the stellar feedback of the young populations could influence the warm gas. The age difference between the populations which show the correlations indicates the time delay of the stellar feedback.

• 천문학회보
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• 제46권1호
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• pp.51.2-51.2
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• 2021

Nuclear rings are sites of intense star formation at the center of barred spiral galaxies. A straightforward but unanswered question is what controls star formation rate (SFR) in nuclear rings. To understand how the ring SFR is related to mass inflow rate, gas content, and background gravitational field, we run a series of semi-global hydrodynamic simulations of nuclear rings, adopting the TIGRESS framework to handle radiative heating and cooling as well as star formation and supernova feedback. We find: 1) when the mass inflow rate is constant, star formation proceeds in a remarkably steady fashion, without showing any burst-quench behavior suggested in the literature; 2) the steady state SFR has a simple linear relationship with the inflow rate rather than the ring gas mass; 3) the midplane pressure balances the weight of the overlying gas and the SFR surface density is linearly correlated with the midplane pressure, consistent with the self-regulated star formation theory. We suggest that the ring SFR is controlled by the mass inflow rate in the first place, while the gas mass adjusts to the resulting feedback in the course of achieving the vertical dynamical equilibrium.