• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.2
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• pp.168-180
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• 1992

Commumication technology has been continuously developed to overcome the distance and time for the transmission of information to the human society. Wireless mobile communication, which had been used mostly in the military and police is widely used these days for enterprise and individuals. Therefore the domestic usage of the advanced mobile phone service are progressively gaining wide popularity. The modulation techniques used usually in mobile communications were the analog techniques such as AM and FM, but they are getting replaced by the digital techniques, However, the major disadvantage of the digital communications is the increase of the transmission bandwidth. Therefore, it is very important to use efficiently the limited frequency bandwidth. The domestic research and development on the subject seems quite limited and in order to establish the technology of the digital mobile communications. This thesis presents the design of the frequency hopping synthesizer providing 124 channels with a channel spcing of 200KHz. VCD used in the synthesizer employs a semi-rigid cable for higher purity of signal spectrum, and a hybrid pgase detector is realized with a sample hold phase detector in conjuction with a tri-state phase detedctor.

• Journal of Internet Computing and Services
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• v.4 no.4
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• pp.65-74
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• 2003

Recently, It is required that multimedia data display on not only PC but also the Mobile device such as cellar phone, PDA. Mobile divieces has not sufficient of storage space or main memory and has slow network speed. So we can't process the multimedia data with the existing way on PC. This paper presents various methods for MultimediaPresentation which are able to display on the mobile device with the low-bandwidth and small storage. There Is an analysis that Is playable on the mobile device using presentation area devision method and replayable analysis method. If the display of multimedia presentation is impossible from this analysis, to apply prefetch techniques a using EPOB apoint and as User QoS of multimedia data through prefetch techniques have keep, do so that playable. Then, it is proposed to playable smooth multimedia presentation as that each of the presentations through prefetch Scheduling techniques point and quantity of data which are prefetch.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.11 no.1
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• pp.49-53
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• 2011

Path following of the mobile robot is one research hot for the mobile robot navigation. For the control system of the wheeled mobile robot(WMR) being in nonhonolomic system and the complex relations among the control parameters, it is difficult to solve the problem based on traditional mathematics model. In this paper, we presents a simple and effective way of implementing an adaptive following controller based on the PID for mobile robot path following. The method uses a non-linear model of mobile robot kinematics and thus allows an accurate prediction of the future trajectories. The proposed controller has a parallel structure that consists of PID controller with a fixed gain. The control law is constructed on the basis of Lyapunov stability theory. Computer simulation for a differentially driven nonholonomic mobile robot is carried out in the velocity and orientation tracking control of the nonholonomic WMR. The simulation results of wheel type mobile robot platform are given to show the effectiveness of the proposed algorithm.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.560-562
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• 2006

In this paper, Correct problem in dead reckoning system and proposed about position error revision techniques of mobile robot to use RFID tag for position awareness. With the dead reckoning system, as the accumulation of error are unavoidable because of accumulation of informations as the time passage, so it is impossible to get correct information about posture, including torrent direction, movement distance, etc. As one of compensation method, the suggested method is that after selecting special area (corridor), compensate absolute location information by arranging two line of RFID tag along two side of corridor. Through this suggested method, it could be used when robot wants to move in limited areas.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.5
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• pp.1871-1890
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• 2021

The transition toward a contactless society has been rapidly progressing owing to the recent COVID-19 pandemic. As a result, the IT environment of organizations and enterprises is changing rapidly; in particular, data security is expanding to the private sector. To adapt to these changes, organizations and companies have started to securely transfer confidential data to residential PCs and personally owned devices of employees working from home or from other locations. Therefore, organizations and companies are introducing streaming data services, such as the virtual desktop infrastructure (VDI) or cloud services, to securely connect internal and external networks. These methods have the advantage of providing data without the need to download to a third terminal; however, while the data are being streamed, attacks such as screen shooting or capturing are performed. Therefore, there is an increasing interest in prevention techniques against screen capture threats that may occur in a contactless environment. In this study, we analyze possible screen capture methods in a PC and a mobile phone environment and present techniques that can protect the screens against specific attack methods. The detection and defense for screen capture of PC applications on Windows OS and Mac OS could be solved with a single agent using our proposed techniques. Screen capture of mobile devices can be prevented by applying our proposed techniques on Android and iOS.

• Journal of Information Processing Systems
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• v.15 no.5
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• pp.1192-1200
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• 2019

Recently, artificial intelligence techniques have been widely used in the computer science field, such as the Internet of Things, big data, cloud computing, and mobile computing. In particular, resource management is of utmost importance for maintaining the quality of services, service-level agreements, and the availability of the system. In this paper, we review and analyze various ways to meet the requirements of cloud resource management based on artificial intelligence. We divide cloud resource management techniques based on artificial intelligence into three categories: fog computing systems, edge-cloud systems, and intelligent cloud computing systems. The aim of the paper is to propose an intelligent resource management scheme that manages mobile resources by monitoring devices' statuses and predicting their future stability based on one of the artificial intelligence techniques. We explore how our proposed resource management scheme can be extended to various cloud-based systems.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.569-577
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• 2009

Mobile information retrieval is an evolving branch of information retrieval that is centered on mobile and ubiquitous environments. In general, mobile devices are characterized by lightweight, low power, small memory, small display, limited input/output, low bandwidth, and so on. Some of these characteristics make it impossible to apply general information retrieval to mobile environments without any modification. In order to relieve this problem, we design and implement an information retrieval system for mobile devices like wireless phones, PDA and handheld devices. We use document summarization techniques to alleviate the limitation of small display and user profiles to retrieve the most proper documents for each individual user for personalized search. Futhermore we use meta-search to lighten some burdens visiting several portal sites. In this paper, we have implemented and demonstrated the proposed mobile information retrieval system on the domain of travel and received good evaluation from users subjectively.

• Journal of the Korean Data and Information Science Society
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• v.17 no.4
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• pp.1261-1270
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• 2006

This paper proposes a mobile computing prefetching method providing the effective information about location change of mobile user or mobile computing in mobile information services. For mobile computing environments, there exist restrictions as like low bandwidth, latency and traffic. To solve those problems, a variety of techniques have been developed including caching and prefetching. In this paper we present a Statistical Poisson Prefetching Scheme using the reference count to provide a mobile user information that will be likely referenced in the near future. Comparing to existing methods in numerical results, the proposed method improves the prefetching performance to give the maximum effectiveness and reduces the failure rate of information searching.

• Journal of Communications and Networks
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• v.9 no.3
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• pp.254-264
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• 2007

A promising approach to improve the performance of mobile location system is the use of antenna arrays in both transmitter and receiver sides. Using advanced array signal processing techniques, such multiple-input multiple-output (MIMO) communication systems can offer more mobile location information by exploiting the spatial properties of the multipath channel. In this paper, we propose a novel approach to determine the position of mobile terminal based on estimated multipath signal parameters using only one base station in MIMO communication systems. This approach intends to minimize the error occurring from the estimation of multiple paths and gives an optimal estimation of the position of mobile terminal by simultaneously calculating a set of nonlinear location equations. This solution breaks the bottleneck of conventional mobile location systems which have to require multilateration of at least three base stations.

• Korean Journal of Remote Sensing
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• v.22 no.5
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• pp.351-356
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• 2006

Based on current practical needs for geo-spatial information on mobile platform, the main theme of this study is a design and implementation of dynamic 3D terrain rendering system using spaceborne imagery, as a kind of texture image for photo-realistic 3D scene generation on mobile environment. Image processing and 3D graphic techniques and algorithms, such as TIN-based vertex generation with regular spacing elevation data for generating 3D terrain surface, image tiling and image-vertex texturing in order to resolve limited resource of mobile devices, were applied and implemented by using graphic pipeline of OpenGL|ES (Embedded System) API. Through this implementation and its tested results with actual data sets of DEM and satellite imagery, we demonstrated the realizable possibility and adaptation of complex typed and large sized 3D geo-spatial information in mobile devices. This prototype system can be used to mobile 3D applications with DEM and satellite imagery in near future.