• Proceedings of the Safety Management and Science Conference
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• 2002.05a
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• pp.121-127
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• 2002

In this paper, we propose traffic management support and evaluate the performance through simulation. We suggest traffic management routing protocol that can guarantee reliance according to not only reduction of the Network traffic congestion but also distribution of the network load that prevents data transmission. For performance evaluation, we analyzed the average data reception rate and network load, considering the node mobility. We found that in the mobile Ad Hoc networks, the traffic management service increased the average data reception rate and reduced the network traffic congestion and network load in Mobile Ad Hoc Networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.5
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• pp.874-887
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• 2011

Compared to nomadic and fixed relay stations, vehicle-mounted mobile relay stations show different characteristics caused by the time-variant topology, due to their mobility. Especially, a relay mounted in a vehicle is differentiated from nomadic or fixed relay by the restricted distance between the relay and associated mobile station and the variable density of relay deployment in a cell. In this paper, we identify the characteristics of vehicle-mounted mobile relay stations and provide some parameters that highly influence the performance of vehicle-mounted relay. Through simulation, we measure the effect of relay density, zone ratio, relay transmission power, and frame transmission mode on the performance of vehicle-mounted relay. The results show that the performance of vehicle-mounted relay is highly susceptible to the above vehicle-mounted relay-specific parameters.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1131-1143
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• 2016

Differential detection schemes do not require any channel estimation, which can be employed under user mobility with low computational complexity. In this work, a soft-input soft-output (SISO) differential detection algorithm is proposed for amplify-and-forward (AF) over time-varying relaying channels based cooperative communications system. Furthermore, maximum-likelihood (ML) detector for M-ary differential Phase-shift keying (DPSK) is derived to calculate a posteriori probabilities (APP) of information bits. In addition, when the SISO is exploited in conjunction with channel decoding, iterative detection and decoding approach by exchanging extrinsic information with outer code is obtained. Finally, simulation results show that the proposed non-coherent approach improves detection performance significantly. In particular, the system can obtain greater performance gain under fast-fading channels.

• Journal of KSNVE
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• v.9 no.3
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• pp.587-592
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• 1999

Piston slap is one of the sources producing engine block surface vibration and mechanical noise. To analyze piston slap-induced vibration, a realistic but simple model is proposed and verified experimentally. A piston is modeled by 3 degree of freedom system and an impact point between piston skirt and cylinder wall by 2 degree of freedom system. Numerical simulation estimates impact forces of piston in cylinder, and the engine block surface vibration response is predicted by the convoluton of the impact forces with measured impulse responses. Experimental verification on the predicted response has been also performed by using a commercial 4-cylinder diesel engine. the predicted and experimental vibration responses confirm that the suggested model is practically useful.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.5
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• pp.405-411
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• 2015

In this paper, we propose routing protocol for mobile wireless sensor networks with a mobile sink in cluster configuration. The proposed protocol extends LEACH-ME by introducing a mobile sink. The mobile sink moves to the cluster head with the highest number of member nodes to collect sensed data from cluster heads within its vicinity, which results in reducing energy consumption in forwarding packets to the sink. The simulation results show that the proposed protocol outperform LEACH-ME in terms of energy efficiency.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1124-1125
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• 2015

밴드-갭이 큰 반도체는 실리콘에 비하여 다양한 전기 물성 장점을 가져 고주파수 증폭 소자나 차세대 전력 반도체 소자로 각광을 받고 있다. 다양한 와이드 밴드-갭 반도체 중 AlGaN/GaN 이종접합 반도체는 채널의 높은 전도성과 높은 임계 전계로 인하여 우수한 전기적 특성을 가진다. 최근 발전된 수치해석 시뮬레이션을 이용하여 AlGaN/GaN 고전자 이동도 트랜지스터 (high-electron-mobility transistor, HEMT)의 설계연구를 진행하였다. AlGaN 장벽층의 두께가 증가할수록 채널의 전자 면 농도가 증가하도록 설계하였다. 또한 게이트 필드 플레이트 설계를 통하여 AlGaN/GaN HEMT의 역방향 전계 피크를 1개에서 2개로 증가시켜 항복전압을 368 V에서 최대 822 V로 개선하였다. 수렴문제를 개선한 수치해석 시뮬레이션은 RF power AlGaN/GaN HEMT의 설계에 유용하다.

• Journal of Computing Science and Engineering
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• v.4 no.2
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• pp.153-172
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• 2010

Wireless mobile multimedia communications have been greatly increased in the number of users, diversity of applications and interface technologies. Wireless mobile networks are being evolved and integrated into IP based core network, so it is necessary to provide sufficient QoS (Quality of Service) mechanism to provide enhanced user's satisfaction. In this paper, we propose a new adaptive QoS mechanism based on utility function borrowed from the field of microeconomics, call setup and handover signaling mechanism integrating QoS and mobility management. Through a simulation, we show that adaptive resource allocation based on user preferences can be realized in the wireless mobile network with some considerations.

• Journal of Information Display
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• v.10 no.2
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• pp.80-86
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• 2009

The variation of the electrical characteristics of thin-film transistors (TFTs) causes a non-uniform image quality problem, and the differential aging of organic light-emitting diode (OLED) devices causes an image-sticking problem. A video data correction method is proposed herein as an effective solution to the non-uniform electro-optical characteristics of the pixels in activematrix organic light-emitting diode (AMOLED) displays. The results of the simulation that was conducted show that the proposed method successfully senses the electrical characteristics of TFTs and the degradation of OLEDs and effectively compensates for them.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.238-242
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• 2001

In this paper, the current-voltage characteristics of a 4H-SiC MESFET is simulated by using the Atlas Simulation tool. we are able to use the simulator to extract more information about the new material 4H-SiC, including the mobility, velocity-field Curve and the Schottky barrier height. We have enabled and used the new simulator to investigate breakdown Voltage and thus predict operation limitiations of 4H-SiC device. Modeling results indicate that the Breakdown Voltage is 197 V and Current is 100 mA

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.385-385
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• 2011

Ion beam Sputtering (IBS)를 이용한 물질 표면의 pattern 형성은 물리적 변수 조절로 손쉽게 nano structure의 크기와 형태를 조절할 수 있어 관심을 받고 있다. 본 연구발표에서는 massless Dirac Fermion behavior로 인한 highly carrier mobility와 같은 특성으로 인해 차세대 device material로 각광받고 있는 Graphene의 layered compound (층상구조) 형태인 HOPG (Highly Ordered Pyrolysis Graphite)에 IBS (Ion beam Sputtering)를 이용해 nano structure가 형성 가능함을 보이고 그 특징에 대해 소개하려 한다. HOPG(0001)를 Sputter 했을 때, 표면에 잘 정렬된 nano ripple pattern이 형성 가능함을 확인하였으며 sputter하는 시간을 변화하면 약 10 nm에서 80 nm까지 wavelength를 조절할 수 있다. 또한 이전의 IBS를 이용한 연구들에서 확인할 수 있는 다른 물질의 곧게 뻗은 nano ripple과는 다르게 ripple의 끝에 nano swab이 생기는 것을 AFM (Atomic Force Microscope)으로 확인할 수 있었다. 이러한 Graphite에서만 나타나는 Sputter에 의한 표면의 변화의 원인을 규명하고자 Sputter가 지속됨에 따라 나타나는 mopology의 roughness와 wavelength의 시간에 따른 dynamic scaling behavior를 확인하였고 그 얼개를 알기 위해 simulation을 수행 하였다.