• Journal of Internet Computing and Services
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• v.14 no.1
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• pp.53-62
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• 2013

It is common among users to have multiple computing devices as well as to access their files or do work at different locations. To achieve file consistency as well as mobility in this scenario, an efficient approach for workspace synchronization should be used. However, file synchronization alone cannot guarantee the mobility of work environment which allows activities to be resumed at any place and time. This paper proposes a ubiquitous synchronization approach which provides cloud-based access to a user's workspace. Efficient synchronization is achieved by combining session monitoring with file system management. Experimental results show that the proposed mechanism outperforms Cloud Master-replica Synchronization in terms of number of I/O operations, CPU utilization, as well as the average and maximum latencies in responding to client requests.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.4
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• pp.37-46
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• 2011

Time synchronization plays an important role in mobile communication systems, particularly, when an accurate time-division mechanism among the communication entities is required. We present a new time synchronization algorithm for a wireless mobile ad-hoc network assuming that communication link is managed by a time-slot reservation-based medium access control protocol. The central idea is to reduce time synchronization packet collisions by exploiting the advantages found in reference broadcasting. In addition, we adopt a sophisticated clock updating scheme to ensure the time synchronization convergence. To verify the performance of our algorithm, a set of network simulations has been performed under various mobile ad-hoc network scenarios using the OPNET. The results obtained from the simulations show that the proposed method outperforms the conventional TSF method in terms of synchronization accuracy and convergence time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1619-1627
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• 2014

Wearable computer systems can use the wireless universal serial bus (WUSB) that refers to USB technology that is merged with WiMedia PHY/MAC technical specifications. In this paper, we focus on an integrated system of the wireless USB over the IEEE 802.15.6 wireless body area networks (WBAN) for wireless wearable computer systems supporting U-health services. And a communication structure that performs the time-synchronization is proposed for WUSB over IEEE 802.15.6 hierarchical protocol. Proposed time-synchronization mechanisms adopt the WBAN Polling Access and combine it with a time-synchronization middleware using time stamps. In our performance evaluations, time-synchronization performances with only WBAN Polling Access scheme are analyzed first. After that, performances combined with the time-synchronization middleware are analyzed to evaluate the effectiveness of proposed time-synchronization structure in WUSB over IEEE 802.15.6.

• Journal of Information Processing Systems
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• v.1 no.1 s.1
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• pp.70-74
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• 2005

Sensor networks have emerged as an interesting and important research area in the last few years. These networks require that time be synchronized more precisely than in traditional Internet applications. In this paper, we compared and analyzed the performance of the RBS and TDP mechanisms in the view of the number of generated messages and the synchronization accuracy. The reason that we chose be RBS ad the TDP mechanism to be compared is because the RES is an innovative method to achieve the high accurate synchronization. And TDP is a new method taking over the NTP method which has been used widely in the Internet. We simulated the performance of two methods assuming the IEEE 802.11 CSMA/CA MAC. As for the number of nodes in the sensor networks, two situations of 25 (for the small size network) and 100 (for the large size network) nodes are used. In the aspect of the number of messages generated for the synchronization, TDP is far better than RBS. But, the synchronization accuracy of RBS is far higher than that of TDP. We cm conclude that in a small size sensor networks requiring very high accuracy, such as an application of very high speed objects tracking in a confined space, the RBS is more proper than TDP even though the RBS may generate more traffic than TDP. But, in a wide range sensor networks with a large number of nodes, TDP is more realistic though the accuracy is somewhat worse than RBS because RBS may make so many synchronization messages, and then consume more energies at each node. So, two mechanisms may be used selectively according to the required environments, without saying that the one method is always better than the other.

• Journal of Engineering Education Research
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• v.17 no.3
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• pp.34-41
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• 2014

In distance education, use of proper software tools can greatly enhance student's attention and learning efficiency. In such software tools, offering diverse multimedia information is one of the most critical factors. However, integration and synchronization of the various media types has been relatively difficult parts of implementation. This paper proposes a prototype system that uses a metafile and event handling mechanism for the uniform treatment of various media types. This event-level integration and synchronization of multimedia makes the implementation relatively simple. With this approach, instructor's behaviors are automatically recorded, and the instructors can freely choose and show any type of multimedia contents while lecturing. Current commercial or non-commercial lecture management systems could incorporate this approach, so that the distance education market could be expanded with richer multimedia contents.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.12A
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• pp.1861-1868
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• 2000

실시간 응용 프로그램은 미디어 데이터간에 만족되어야 할 동기화 제약조건(synchronization constraints)을 가지고 있다. 이러한 제약조건을 프리젠테이션 되어야 할 미디어 데이터간의 지연시간 및 서비스 품질을 나타낸다. 미디어 데이터간의 지연시간 및 서비스 품질을 효율적으로 표현하기 위해서는 이에 적합한 새로운 동기화 기법이 요구된다. 동기화 기법은 미디어의 재생시 끊어짐이 없는 유연한 재생을 처리하는 기법이다. 제안된 기법은 사용자 측면에서 엄격한 재생을 위하여 프레임을 생략하는 것보다는 부드러운 영화를 볼 수 있도록 유연한 재생 처리를 한다. MMSM(MultiMedia Synchronization Model) 모델의 동기화 기법은 종 미디어 스트림을 부드럽게 재생하는 결과를 나타내었다.

• Journal of Internet Computing and Services
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• v.10 no.6
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• pp.37-50
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• 2009

In this paper, we proposed a mechanism for effective cooperation in sensor network. There are a few mechanism like RBS, TPSN, FPSN for sensor network. However these are supporting synchronization among nodes without global state. Therefore, we proposed SGSM(Simple Global State Management) to maintain global state among sensor nodes. As experimental results, we confirmed loss rate is within 1% as maintaining global state with SGSM mechanism. In this paper, we defined global state in sensor network and introduced SGSM for improving timming accuracy in sensor environment.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.5
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• pp.354-361
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• 2016

Parallel robots are usually used for performing pick-and-place motion to increase productivity in high-speed environments. The present study proposes a high-speed parallel robot and a control approach to improve the tracking performance for the purpose of handling a solar cell. However, the target processes are not limited to the solar cell-handling field. Therefore, a delta-type parallel manipulator is designed, and a ball joint structure is specifically proposed to increase the allowed angle that would meet the required workspace. A control algorithm considering the synchronization between multiple joints in a closed-chain mechanism is also suggested to improve the tracking performance, where the tracking and synchronization errors are simultaneously considered. In addition, a prototype machine with the proposed ball joint is implemented. A satisfactory tracking performance is achieved by applying the proposed control algorithm, with a cycle time of 0.3 s for a 0.1 kg payload.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.5
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• pp.485-495
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• 2000

The parallel computer system that uses parallel program on the application such as a large scale business or complex operation is required. One of crucial operation of parallel computer system is synchronization. A representative method of synchronization is barrier synchronization. A barrier forces all process to wait until all the process reach the barrier and then releases all of the processes. There are software schemes, hardware scheme, or combinations of these mechanism to achieve barrier synchronization which tends to use hardware scheme. Besides, barrier synchronization lets parallel computer system fast because it has fewer start-up overhead. In this paper, we propose a new switch module that can implement fast and fault-tolerant barrier synchronization in hardware scheme. A proposed barrier synchronization is operated not in full-switch-driven method but in processor-driven method. An effective barrier synchronization is executed with inexpensive hardware supports. Therefore, a new proposed hardware barrier synchronization is designed that it is operated in arbitrary network topology. In this paper, we only show comparison of barrier synchronization on Multistage Interconnection Network. This research results in 24.6-24.8% reduced average delay. Through this result, we can expect lower average delay in irregular network.

• The Transactions of the Korea Information Processing Society
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• v.3 no.2
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• pp.305-314
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• 1996

In the paper, we divide the ATM cells generated by multimedia systems that want to transmit multimedia informations over B-ISDN into two categories:i)a media cell with a media information and ii) a synchronization cell with a synchronization information. We induce a media cell loss equation and a synchroni- zation cell loss equation based on probability distribution functions with on-off source as an input traffic model. In order to meet the requirements of real-time and integrity of multimedia informations, multimedia synchronization cells should provide the delay-sensitive and the loss-sensitive requirements. A traffic control mechanism needs to satisfy above requirements. According to the performance evaluation by a traffic control model simulation, we describe both spatial priority for minimizing the synchronization cell loss and temporal priority for reducing the synchronization cell delay must be applied simultaneously.