• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.458-465
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• 2007

Wireless Sensor Network(WSN) is a special network that collects measured data by sensor nodes in the predefined sensor field and forwards them to the base station in a distance using their own routing scheme. WSN requires routing techniques to maximize energy efficiency because sensor nodes have non-rechargeable and thus limited energy. Characteristics of WSN are various according to applications, many of routing algorithms have been proposed. This paper proposes an algorithm called A-PEGASIS that basically bases on PEGASIS and enhances in two aspects - an elegant chain generation algorithm and periodical update of chains. We compare performance of the previous algorithm of LEACH, PEGASIS, PEDAP and PEDAP-PA with ours through simulation. It confirms that the A-PEGASIS is most superior in terms of average WSN lifetime and high probability of node survival rate during WSN life time.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.621-628
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• 2009

Wireless sensor networks (WSNs) have been considered as a promising method for reliably monitoring both civil and military environments under hazardous or dangerous conditions. Due to the special property and difference from the traditional wireless network, the lifetime of the whole network is the most important aspect. The bottleneck nodes widely exist in WSNs and lead to decrease the lifetime of the whole network. In order to find out the bottleneck nodes, the traditional centralized bottleneck detection method MINCUT has been proposed as a solution for WSNs. However they are impractical for the networks that have a huge number of nodes. This paper first proposes a distributed algorithm called DBND (Distributed Bottleneck Node detection) that can reduce the time for location information collection, lower the algorithm complexity and find out the bottleneck nodes quickly. We also give two simple suggestions of how to solve the bottleneck problem. The simulation results and analysis show that our algorithm achieves much better performance and our solutions can relax the bottleneck problem, resulting in the prolonging of the network lifetime.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.583-588
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• 2009

Network intrusion detection system (NIDS) monitors all incoming packets in the network and detects packets that are malicious to internal system. The NIDS should also have ability to update detection rules because new attack patterns are unpredictable. Incorporating FPGAs into the NIDS is one of the best solutions that can provide both high performance and high flexibility comparing with other approaches such as software solutions. In this paper we propose and design a novel approach, prefix sharing parallel pattern matcher, that can not only minimize additional resources but also maximize the processing performance. Experimental results showed that the throughput for 16-bit input is twice larger than for 8-bit input but the used LEs/Char in FPGA increases only 1.07 times.

• The KIPS Transactions:PartC
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• v.15C no.3
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• pp.213-220
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• 2008

A MANET is an autonomous, infrastructureless system that consists of mobile nodes. In MANET, on-demand routing protocols are usually used because network topology changes frequently. The current approach in case of broken routes is to flag an error and re-initiate route discovery either at the source or at the intermediate node. Repairing these broken links is a costly affair in terms of routing overhead and delay involved. Therefore, this paper propose a NAODV(Neighbor-aware AODV) protocol that stands on the basis of an AODV. It sets up the route rapidly if it operates for setting the route directly by using sequence number of neighbor nodes without re-search the route when the route to destination node is broken. Also, it reduces loss of packets. We use NS-2 for the computer simulation and validate that the proposed scheme is better than general AODV in terms of packet delivery ratio and average end-to-end delay. Also, when the proposed protocol is applied to the large ad-hoc network with multiple nodes, the performance is more efficient.

• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.9-15
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• 2010

When designing the size of a heavy maintenance shop for rolling stock, it is required to arrange buildings and facilities in the minimum site so as to improve the maintenance efficiency. However, the fluctuation rate (hereinafter "allowance rate") on which factors such as service and maintenance fluctuation should be applied when estimating the size of the maintenance shop has been used without verification. The objective of the study is to calculate a reasonable allowance rate and to review its appropriateness through the analysis of the facilities layout and process simulation to absorb the above elements into the staying time in the heavy maintenance shop. Since the working time, in this study, is assumed to be average working time, 10~20% was given to the standard deviation of working time in consideration of difference between workers, and possible allowance rate was drawn by analysis of the simulation results. In the future, it is required to optimize the size of the shop by applying appropriate allowance rate through scientific review of such factors as O&M plan, R/S reserve rate, capability of the shop, outsourcing rate, standard work amount, and so on.

• Geophysics and Geophysical Exploration
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• v.16 no.4
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• pp.225-233
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• 2013

The accuracy of the automatic NMO velocity analysis, which is used for an effective and objective NMO velocity analysis, is highly affected by the velocity resolution of the velocity spectrum. In this study, we have developed an automatic NMO velocity algorithm, where the velocity spectra are created using high-resolution bootstrapped differential semblance (BDS), and the velocity analysis on CMP gathers is performed in parallel with MPI. We also compared the velocity models from the developed automatic NMO velocity algorithm with high-resolution BDS to those from BDS. To verify the developed automatic velocity analysis module we created synthetic seismic data from a velocity model including horizon layers. We confirmed that the developed automatic velocity analysis module estimated velocity more accurately. In addition, NMO velocity which yielded a CMP stacked section, where the coherency of the events were improved, was estimated when the developed module was applied to a marine field data set.

• Annual Conference on Human and Language Technology
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• 2018.10a
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• pp.172-175
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• 2018

환자의 병력을 서술하는 임상문서에서 임상 개체명들은 그들 사이에 개체명이 아닌 단어들이 위치하기 때문에 거리상으로 서로 떨어져 있고, 임상 개체명인식에 많이 사용되는 조건부무작위장(conditional random fields; CRF) 모델은 Markov 속성을 따르기 때문에 서로 떨어져 있는 개체명 라벨 간의 전이 정보는 모델의 계산에서 무시된다. 본 논문에서는 라벨링 모델에 서로 떨어진 개체명 간 전이 관계를 표현하기 위하여 CRF 모델의 구조를 변경하는 방법론을 소개한다. 제안된 CRF 모델 디자인에서는 모델의 계산효율성을 빠르게 유지하기 위하여 Markov 속성을 유지하는 1차 모델 구조를 유지한다. 모델은 선행하는 개체명의 라벨 정보를 후행하는 개체명 엔터티에게 전달하기 위하여 선행 개체명의 라벨을 뒤 따르는 비개체명 라벨에 전이시키고 이를 통해 후행하는 개체명은 선행하는 개체명의 라벨 정보를 알 수 있게 된다. 라벨의 고차 전이 정보를 전달함에도 모델의 구조는 1차 전이 구조를 유지함으로 n차 구조의 모델보다 빠른 계산 속도를 유지할 수 있게 된다. 모델의 성능 평가를 위하여 서울대학교병원 류머티즘내과에서 퇴원한 환자들의 퇴원요약지에 병력과 관련된 엔터티가 태깅된 평가 데이터와 i2b2 2012/VA 임상자연어처리 shared task의 임상 개체명 추출 데이터를 사용하였고 기본 CRF 모델들(1차, 2차)과 비교하였다. 피처 조합에 따라 모델들을 평가한 결과 제안한 모델이 거의 모든 경우에서 기본 모델들에 비하여 F1-score의 성능을 향상시킴을 관찰할 수 있었다.

• Journal of the Korea Society for Simulation
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• v.15 no.3
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• pp.103-114
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• 2006

Now distribution centers include an ASRS (Automated Storage and Retrieving System) and automated transfer systems such as conveyors and AGV (Automated Guided Vehicle). These automated distribution centers have lots of parameters to be considered fur operating performance. The general basic parameters in the distribution centers are specifications of storage equipment, system operating rules, configuration of storage area and unit load features. In this paper, an approach using simulation and metamodeling with response Surface method to optimize the design parameters of an automated distribution center model is presented. The simulation based metamodel will constitute an efficient approximation of the system function, and the approximate function will be used to design rapid optimal parameters of the distribution center model. This paper provides a comprehensive framework for economical material flow system design using the simulation and metamodeling.

• Journal of the Korean Wood Science and Technology
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• v.29 no.2
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• pp.100-108
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• 2001

An understanding of potential lumber cutting yields may lead to increased utilization of the lower grades of lumber in wood industry. Computer simulations of rough-mill operations require a lumber database as input to give reasonable estimates of such yields. The lumber database must contain detailed information regarding the location and type of defects, and then all manufacturing sequences can be tested with the same raw material. However, no suitable lumber database with mapped defects exists for Korean wood industry. In this study lumber databases of Pinus densiflora S. et Z and Quercus acutissima which are the main Korean domestic species were developed to prepare for coming era of "utilization of domestic species" in the near future. These databases were put into lumber cut-up simulation model(gang-rip-first simulator) to investigate the part yields. Gang-rip first simulation showed average part yields of 44.75% and 63.10% for Quercus acutissima and Pinus densiflora lumber database developed, respectively. In most cases process set-up of fixed blade best feed showed the best part yields and the level of acceptable defects could not make significant differences in part yields.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.73-81
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• 2020

Today's massively multiplayer online games(MMOGs) can contain millions of synchronous players scattered across the world and participating with each other within a single shared game. The increase in the number of players in MMOGs has led to some issues with the demand of server which generates a significant increase in costs for the game industry and impacts to the quality of service offered to players. In dealing with a considerable scale of MMOGs, we propose a cloud computing and peer-to-peer(P2P) hybrid architecture in this paper. Given the two nearly independent functionalities of P2P and cloud architectures, we consider the possibility of fusing these two concepts and researching the application of the resultant amalgamation in MMOGs. With an efficient and effective provisioning of resources and mapping of load, the proposed hybrid architecture relieves a lot of computational power and network traffic, the load on the servers in the cloud while exploiting the capacity of the peers. The simulation results show that MMOGs based on the proposed hybrid architecture have better performance and lower traffic received compared with MMOGs based on traditional client-server system.