• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.114-120
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• 2005

Urethane is a high polymeric and elastic material useful in designing mechanic parts that cannot be molded with rubber or plastic material. In particular, urethane is high in mechanical strength and anti-abrasive. Hereby, a urethane coated aluminum wheel is used to support of the OHT vehicle moving back and forth to transport products. For the sake of verifying the safety of the vehicle, structural safety fur applied maximum dynamic load on a urethane wheel must be examined carefully while driving. Therefore, we performed a dynamic simulation on the OHT vehicle model and we determined the driving load. The area definition of applied load may be obtained from the previous study of Hertzian and Non-Hertzian contact force model having exact properties of contact material. But the static analysis is simulated after we have performed the actual contact area test for each load since the proper material properties of urethane have not been guaranteed. In this study, the method of distributing loads for each node is included. Finally, in coMParison with the results of analysis and load-displacement curve obtained from the compression test, we have defined the material properties of urethane. In the analysis, we verified the safety of the wheel. Finally, we performed a mode analysis using the obtained material properties. With these results, we presented a reliable finite element model.

• Archives of design research
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• v.15 no.1
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• pp.93-100
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• 2002

The University's web library is a form of library that enables to deal with information about searching loaning, returning of books or data housed in it through web. With the advent of the network and multimedia following the entrance to an information-oriented society, we are experiencing a big change in how to communicate and acquire information. Massive multimedia information transmitted by image and moving picture through the network, made it possible to overstep the limit of the physical gap between information suppliers and users. Despite this important role, it is accompanied by problems such as copyright, scarcity of recognition, paralysis of infra, technical matters and reliability which demand development. In this thesis, according to the State University Evaluation Standards, search node and user interface by system used in 20 different universities possessing web-based library sites were compared are analysed. On the basis of this, an experimental user interface for web-based University libraries was produced, and various questionnaires and data leer this produced interface were collected, classified and analyzed. With the application of the results for the work above to the general search system interface of the web-based library, we proposed a new user interface that contains the following functions, such as location and loan condition of books, search frequency and steps for purchasing books inside the web library.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9B
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• pp.857-866
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• 2009

Recently, IP mobility study of infra's common elements is undergoing processes to achieve FMC based on All-IP. Existing typical mobility technology based on IP is IETF's Mobile IP. However, it faced to limitations due to packet loss, delays when MN is moving on Mobile IP, also existing network infra - routers (FA)-needed to add/change the functions to support Mobile IP. In this paper, existing mobility problems based on IP and the suggested improvements for platforms which support mobility, quality, security are proposed. It discusses the performance on the current existing IP infrastructure derived from simulation analysis on mobility packet loss and delay. From the resulting data, improvements will also be outlined for optimal performance.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.1
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• pp.31-42
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• 2006

Context-awareness is a technology to facilitate information acquisition and execution by supporting interoperability between users and devices based on users' context. It is one of the most important technologies in ubiquitous computing. In this paper, we propose a middleware and a context server for dealing with context-awareness in ubiquitous Computing and implement an application system using them. The middleware proposed in our work plays an important role in recognizing a moving node with mobility by using a Bluetooth wireless communication technology as well as in executing an appropriate execution module according to the context acquired from a context server. In addition, the proposed context server functions as a manager that efficiently stores into a database server context information, such as user's current status, physical environment, and resources of a computing system. Finally, our application system implemented in our work one which provides a music playing service based on context information, and it verifies the usefulness of both the middleware and the context server developed in our work.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.300-308
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• 2012

Many indoor location tracking technologies have been proposed. Generally indoor location tracking using TOA signal is used, there is a weak point that it's difficult to track the location due to obstacles like a refraction, reflection and dispersion of radio wave. In this paper, we apply ETOA(Estimated-TOA) algorithm in NLOS(Non-Line-Of-Sight) environment to solve above problem. In NLOS environment, TOA value between Beacon and Mobile node is predicted by ETOA algorithm and the tracking of indoor location is also possible to identify using two NLOS beacons of three beacons by this algorithm. We show that the proposed algorithm is accurate location tracking is accomplished using the applying the proposed algorithm to indoor moving robot and the inertia sensor of robot and Kalman filter algorithm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.9-16
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• 2011

This paper represents an interworking architecture for keeping the VLC audio quality between Worldwide Interoperability for Microwave Access (WiMAX) and IEEE 802.11 Mobile Ad hoc Network (MANET) where both mobile routers and mobile nodes are moving dynamically. Systematic performance analysis on the interworking architecture has been conducted by using OPNET simulator to show the results such as Packet Delivery Ratio (PDR) and throughput. Based on simulation results, when the number of MANET nodes is small, PDR remains relatively stable even though data packets increase. However, with the many MANET nodes, PDR decreases as data traffic increases. Throughput is affected by the number of MANET nodes. Especially when the MANET node density has increased further, throughput is much higher, but it is not affected by the mobility speed. However, FTP download and upload response time is not affected much by both the number of MANET nodes and the mobility speed.

• Journal of Navigation and Port Research
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• v.38 no.5
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• pp.457-462
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• 2014

Indoor-positioning systems are useful to various applications. Navigation system is one of the most popular applications, which needs the information of directions of nodes' movements. Specifically the applications should get the information in real-time to properly show the current moving position of a node. In this paper, simple vector-based algorithms are proposed to compute amount and direction of changes of azimuth of mobile nodes' heading directions using existing indoor positioning systems in indoor environments where azimuth sensors do not work properly. Previous algorithms calculate the azimuth changes by too many steps of topology-based formula. The algorithms proposed in this paper get the amount of changes of azimuth by simple formula based on vector, and determine the direction of changes by the sign of value of simple formula based on the previous movement of nodes. The algorithms are much simpler and less error-prone than previous ones, and then they can detect changes in many location-based applications as well. The performance of the algorithms is proved logically and mathematically.

• Journal of Information Processing Systems
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• v.10 no.1
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• pp.103-118
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• 2014

Over the last couple of years, traditional VANET (Vehicular Ad Hoc NETwork) evolved into VANET-based clouds. From the VANET standpoint, applications became richer by virtue of the boom in automotive telematics and infotainment technologies. Nevertheless, the research community and industries are concerned about the under-utilization of rich computation, communication, and storage resources in middle and high-end vehicles. This phenomenon became the driving force for the birth of VANET-based clouds. In this paper, we envision a novel application layer of VANET-based clouds based on the cooperation of the moving cars on the road, called CaaS (Cooperation as a Service). CaaS is divided into TIaaS (Traffic Information as a Service), WaaS (Warning as a Service), and IfaaS (Infotainment as a Service). Note, however, that this work focuses only on TIaaS and WaaS. TIaaS provides vehicular nodes, more precisely subscribers, with the fine-grained traffic information constructed by CDM (Cloud Decision Module) as a result of the cooperation of the vehicles on the roads in the form of mobility vectors. On the other hand, WaaS provides subscribers with potential warning messages in case of hazard situations on the road. Communication between the cloud infrastructure and the vehicles is done through GTs (Gateway Terminals), whereas GTs are physically realized through RSUs (Road-Side Units) and vehicles with 4G Internet access. These GTs forward the coarse-grained cooperation from vehicles to cloud and fine-grained traffic information and warnings from cloud to vehicles (subscribers) in a secure, privacy-aware fashion. In our proposed scheme, privacy is conditionally preserved wherein the location and the identity of the cooperators are preserved by leveraging the modified location-based encryption and, in case of any dispute, the node is subject to revocation. To the best of our knowledge, our proposed scheme is the first effort to offshore the extended traffic view construction function and warning messages dissemination function to the cloud.

• Journal of KIISE:Information Networking
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• v.30 no.5
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• pp.595-603
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• 2003

To provide mobile nodes with continuous communication services, it is important to reduce the packet losses during handoffs. The handoffs of mobile nodes cause packet losses and decrease of TCP throughput on account of a variety of factors. One of those is the congestion in the new cell. Due to the congestion, not only the node moving into the cell but also the already existing nodes that were successfully communicating in the cell suffer the performance degradation. In this paper we propose a new handoff mechanism called‘packet freeze control’, which avoids the congestion caused by handoffs by regulating the influx of traffic burst into the new cell. Packet freeze control is applicable to a wireless network domain in which FAs(Foreign Agents) are connected hierarchically and constitute a logical tree. It gradually increases the number of packets transferred to the new cell by buffering packets in the FAs on the packet delivery path over the wireless network domain. The simulation results show that the proposed mechanism not only reduces the packet losses but also enhances the TCP throughput of other mobile nodes in the cell.

• Journal of Internet Computing and Services
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• v.10 no.6
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• pp.1-6
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• 2009

In this paper, we propose an energy efficient index scheme for Nearest Neighbor queries, specially designed for mobile P2P environments. we propose a PMBR (P2P Minimum Boundary Rectangle) index that provides the client with the ability of selective contacting and tuning from other nodes. The mobile client is able to identify whether or not the neighbor nodes have the desired information by accessing PMBR. Thus, the client immediately switches to change to another node's broadcast channel if the index does not contain the desired information. Furthermore, the client is able to predict the arrival time of the desired data items and only needs to tune into the broadcast channel when the requested data items arrives, by first accessing PMBR. Thus, the mobile client can stay in power save mode most of time, and tune into the broadcast channel only when the requested data items arrive. Experiments are conducted to evaluate the performance of the proposed scheme. Comprehensive experiments illustrate that the proposed scheme is more efficient than the previous techniques in terms of energy consumption.