• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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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.

• Journal of the Korea Society of Computer and Information
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• v.17 no.11
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• pp.163-171
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• 2012

Many previous researches in the area of online games have been carried out about internet addiction by psychologist and about the development of related technologies by scientists. There are a few studies about the consumer satisfaction from the online business model. The purpose of this study is to examine the causal relationship between critical factors and consumer satisfaction of online game users. This study model used five themes(interactivity, enjoyment, challenge, feedback, design) in order to identify the effect of critical factors on consumer satisfaction. The result of this study identified that interactivity, enjoyment, challenge have a significant effect on consumer satisfaction of online game users. Future areas for studying on the Effect of Critical Factors on Consumer Satisfaction of Online Game Users are continuously discussed.

• Journal of Information Processing Systems
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• v.9 no.3
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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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• v.2 no.3
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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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.10
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• pp.2087-2092
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• 2011

In this paper, we use the earth's magnetic field is measured by the MR device. By analyzing the measured data to determine the direction to implement the system. The construction of the system to determine the direction of neural networks, using input data based on an analysis of the relationship between pattern formation and characteristics of study and related information through a pattern when it is remembered that the output feedback input to associative networks and proves its feasibility for implementation. The entire detection system with regional changes in the Earth's magnetic field to adapt to the environment should aim to build a system.

• Journal of Korea Society of Digital Industry and Information Management
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• v.7 no.3
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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.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.21 no.3
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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.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.6
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• pp.1177-1182
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• 2018

We designed a 500W zero voltage switching DC / DC converter operating at 100Mhz with phase shift topology using UCC3895 driver. The dead time of the UCC3895 driver is designed so that the leading and lagging leg of the full bridge can be driven separately. So, the dead time can be given between the two legs separately. The dead time, which is an asymmetrical relationship between the two legs, enables the implementation of zero voltage switching. This paper proposed a negative feedback circuit design method for stable output voltage. The maximum efficiency of the prototype was 95.5% at $500{\Omega}$ load.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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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.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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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.