• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.859-866
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• 2003

In this paper, we designed the bandwidth allocation scheme with priority consideration for upstream channel access of EthernetPON. The objective of our scheme is to control the multi services in more effective way according to their CoS(Class of Service) or QoS(Quality of Service). The designed scheme considers transmission priority in the both side of OLT and ONU. In the OLT's view, the Two-step scheduling algorithm is applied with which we can support multiple bandwidth allocation policies simultaneously, i.e. SBA for the time-sensitive, constant rate transmission services and DBA for the best-effort services. This Two-step scheduling algorithm reduces the scheduling complexity by separating the process of transmission start time decision from the process of grant generation. In the ONU's view, the proposed scheme controls 8 priority queues of the 802.1d recommended 8 service classes. Higher priority queue is serviced in prior during the allowed GATE time from OLT. The OPNET modeling and simulation result compares the performance of each bandwidth allocation policy with SBA or DBA only approach.

• The KIPS Transactions:PartC
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• v.16C no.6
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• pp.707-716
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• 2009

Wireless Sensor Networks are consisted of sensor nodes that communicated with each other to transmit information. Because sensor nodes have physically many limits, wireless sensor networks are hard to adopt for traditional networks. Transmissions are consumed most energy of sensor nodes. That's why energy-efficient transmission techniques and QoS support techniques for different kind of data are most important in wireless sensor networks. The thesis proposes the agent based framework for energy distribution and QoS in wireless sensor networks. Agents have its own behavior policy by means of a gene, which is optimized by genetic operations. Agents behavior to distribute energy consumption over sensor nodes. Simulation results show that the enhanced framework extends the lifetime of sensor nodes. Successful transmission ratios of emergency data and non emergency data are increased by 27% and 14%, respectively. Also, the results demonstrate that Qos of networks are improved.

• Journal of Digital Convergence
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• v.11 no.8
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• pp.199-204
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• 2013

Computational fluid dynamics (CFD) is used to reduce number of experiments. The CFD tools are widely used for engine design and flow pattern analysis to reduce experiments. In this study the performance of a PEMFC single cell was analyzed by using STAR-CD, product of CD-ADAPCO. The effect of cell design and flow pattern on the performance of a PEMFC was analyzed with the 3-D simulation. As a result the performance of rectangular cell was the higher than that of square cell, while the flow direction scarcely affected on the performance of a PEMFC. Also the current density according to different excess ratio of air flow rate was compared and analyzed. The difference between maximum and minimum current density of flip-flow was lower than that of co-flow.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.1992-1998
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• 2014

This paper aims to understand the meaning of balanced development among regional economies and its importance in the s0-called knowledge-based economy. It is shown that the balanced allocation of human capital is necessary to achieve the efficient allocation of physical capital among regional economies, which makes the equality of marginal product of capital. And a simulation experiment is conducted to calculate the cost of unbalanced growth. It is shown that balanced growth among regional economies may increase the growth rate of whole national economy while unbalanced growth among them reduce it. The policy implication is that for an any economy to grow at a higher rate, the efficient allocation of physical and human capital both are necessary to have the balanced growth of regional economies in knowledge-based economy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2433-2438
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• 2011

Bus system consists of several masters, slaves, arbiter and decoder in a bus. Master means the processor that performs data command like CPU, DMA, DSP and slave means the memory that responds the data command like SRAM, SDRAM and register. Furthermore, as multiple masters can't use a bus concurrently, arbiter plays an role in bus arbitration. In compliance with the selection of arbitration method, bus system performance can be changed definitely. Fixed priority and round-robin are used in general arbitration method and TDMA and Lottery bus methods are proposed currently as the improved arbitration schemes. In this study, we proposed the score arbitration method and synthesized it using Hynix 0.18um technology, after design of RTL. Also we analyze the performance compared with general arbitration methods through simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.198-204
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• 2012

Generally, the clustering of sensor nodes in WSN is a useful mechanism that helps to cope with scalability problem and, if combined with network data aggregation, may increase the energy efficiency of the network. The Hierarchical clustering routing algorithm is a typical algorithm for enhancing overall energy efficiency of network, which selects cluster-head in order to send the aggregated data arriving from the node in cluster to a base station. In this paper, we propose the improved-LEACH that uses comparably simple and light-weighted policy to select cluster-head nodes, which results in reduction of the clustering overhead and overall power consumption of network. By using fine-grained power model, the simulation results show that i-LEACH can reduce clustering overhead compared with the well-known previous works such as LEACH. As result, i-LEACH algorithm and LEACH algorithm was compared, network power-consumption of i-LEACH algorithm was improved than LEACH algorithm with 25%, and network-traffic was improved 16%.

• Journal of Digital Convergence
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• v.11 no.12
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• pp.367-380
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• 2013

A secure data gathering in a Wireless Sensor Network(WSN) has given attention to one of security issues. In general, the process of secure data gathering causes difficulties: one process is exchanging the secured data and the other is constructing secured data path. The previous studies have been resolving the difficulties in terms of two problems: security and data gathering in WSNs. However, a WSN requires a protocol that has to guarantee a security of path between sensors and sink, or a cluster head. Thus how to gather data securely is an important issue. In this paper, we propose a secure data gathering protocol over WSNs, which consists of hierarchical key settlement and secure path construction, and aims at tackling two problems. The proposed protocol causes little overhead to sensor nodes for secured key settlement and path construction. This work provides security analysis focused on the key settlement protocol and evaluates network performance for the proposed data gathering protocol through simulation.

• Journal of Digital Convergence
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• v.11 no.12
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• pp.417-422
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• 2013

In this paper, the implementation of a null-steering antenna array using GPS patch antennas is suggested. The antenna array consists of five patch antenna elements fabricated on the ceramic substrate. The antenna element proposed here is a typical circular polarization patch and a prototype patch array antenna is manufactured on the PCB. The antenna has one reference element located at the center and other four elements are placed at the corners. A null in the direction of the jamming signal can be produced by changing the phases of 4-elements. Simulation results of the array antenna by CST MWS are presented and discussed. The basic performances are measured and the results are shown. The results show that the antenna presented here can be used to remove the signals from the directions of any jammers.

• Journal of Digital Convergence
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• v.10 no.10
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• pp.447-456
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• 2012

In space design or form design step, recognized necessity of digital design practical use. Also, deduced systematized analysis method that can use various function of CAD system actively. These method can promote the practical use because third dimensional digital design escapes plan and design process in concept that get presentation result after is completed, establishes role of effective and systematic digital design at planning and design of space or form. This uses by a design tool that ease designer's judgment and space and form analysis in architectural planning and design process that third dimension digital design is not part by a simplicity design tool. Share and takes advantage of digital design process method that is deduced in this study, need continuance of connection study for more effective and systematic digital design methodology deduction. Need public ownership of teaching material development and teaching method that can deliver extended third dimension digital design process.

• Journal of Digital Convergence
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• v.10 no.10
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• pp.97-106
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• 2012

In the past, executive managers made a decision based on personal experience and knowledge due to lack of the appropriate and timely information. With the development of information systems and technologies, efficiency and productivity of business operation has been enhanced. In this study, we propose a system design and architecture blue-print related to strategic decision making support system. The proposed system consists of 3 key parts; individual business feasibility test, business portfolio feasibility test, business portfolio management. The three key parts are comprised of 11 components to generate information and knowledge based on various data input from inside and outside of firm. This system is expected to provide objective and reliable output to users. In addition, the proposed strategic decision support system would help respond to a rapidly changing business environment.