• Title/Summary/Keyword: 에너지전달

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Asynchronous and Adaptive Massage Passing Scheme for Wireless Sensor Networks (무선 센서 네트워크를 위한 비동기 적응형 메시지 전달 기법)

  • Jeong, Jong-Kyun;Ra, In-Ho
    • Journal of the Korean Institute of Intelligent Systems
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    • v.23 no.3
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    • pp.196-201
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    • 2013
  • In this paper, we propose an asynchronous and adaptive message passing scheme based on S-MAC for handling with the problem on energy efficiency in wireless sensor networks. The proposed scheme consists of a policy that differentiate transmission errors caused by packet collision or radio interference from congestion errors caused by buffer overflow and a method that adaptively controls the size of a fragment according to the variance of traffic loads. Especially, it presents a method that highly reduce the energy consumption by keeping the size of fragment not being excessively smaller than the one that may result in rapid increment of the total transfer time. Finally, with the simulation results we show that network throughput and delay are improved by using the proposed message passing scheme.

An IDE based Hierarchical Node Authentication Protocol for Secure Data Transmission in WSN Environment (WSN 환경에서 안전한 데이터 전달을 위한 IDE 기반의 계층적 노드인증 프로토콜)

  • Cho, Young-Bok;Lee, Sang-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.3B
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    • pp.149-157
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    • 2012
  • In WSN environment, the sensor nodes collect sensed data, and transmit data to the BS. BS is difficult to trust the data from unauthenticated nodes. Therefore, many papers have been proposed about the node authentication and the safety of data. In the AM-E paper, data is delivered after node authentication. In this time, the sensor nodes are directly communicated to BS the AREQ/AREP message for authentication. Therefore, the sensor nodes consume more energy for authentication. Also, noes communicate directly with the BS for authentication will have problem due to the limited energy of nodes. In this paper, the same security with AM-E is supported, Furthermore, to minimize the energy consumption, IDE based hierarchical node authentication protocol is proposed. Compared with AM-E, the number of alive nodes is increased about 39%. Thus, the entire network life time is extended and energy efficiency is improved.

Perpendicular Spin-transfer Torque in Asymmetric Magnetic Tunnel Junctions: Material Parameter Dependence (비대칭 자기터널접합에서의 수직 스핀 전달 토크: 물질 변수에 대한 의존성)

  • Han, Jae-Ho;Lee, Hyun-Woo
    • Journal of the Korean Magnetics Society
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    • v.21 no.2
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    • pp.52-55
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    • 2011
  • Spin-transfer torque is a useful tool to control the magnetic state in nanostructures. In magnetic tunnel junctions, the spin-transfer torque has two components, the in-plane spin torque and the perpendicular spin torque. While properties of the in-plane spin-transfer torque are relatively well understood, properties of the perpendicular spin-transfer torque still remain controversial. A recent experiment demonstrated that in asymmetric magnetic tunnel junctions, the bias voltage dependence of the perpendicular spin-transfer torque contains both linear and quadratic terms in the bias. However it still remains unexplored how the bias voltage dependence changes as a function of material parameters. In this paper, we systematically investigate the perpendicular spin-transfer torque in asymmetric magnetic tunnel junction by varying spin splitting energy, work function difference, and Fermi energy of the ferromagnetic metal leads.

Polarized Light Emission of Liquid Crystalline Polymer Blends (액정성 고분자 블렌드의 편발광)

  • 김영철;조현남;김동영;홍재민;송남웅
    • Polymer(Korea)
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    • v.24 no.2
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    • pp.211-219
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    • 2000
  • Fluorene-based light emitting polymer blends with liquid crystalline characteristics were studied on effective energy transfer and dichroic characteristics. Incorporating 0.5 wt% of the non-liquid crystalline into the liquid crystalline polymer suppressed the PL emission at 420 nm on photoexcitation at 360 nm, but generated a new PL emission of the non-liquid crystalline polymer at 480 nm. The highest PL intensity at 480 nm, which was 13 times stronger than those of the two polymers before blending, was observed for a blend with 2.0 wt% of the non-liquid crystalline polymer. When the molecules of the blends were aligned on a rubbed polyimide surface by a heating-cooling process, the dichroic ratio and the order parameter were 2.0 and 0.25, respectively. Time-correlated single photon counting (TCSPC) study revealed that the time required for energy transfer between the two chromophores was shortened by 93 ps when the blends were aligned on the rubbed polyimide surface by the heating-cooling process. The thermal treatment also enhanced the energy transfer efficiency by 9%.

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Computation of Nonlinear Energy Transfer among Wind Seas (비선형 상호작용에 의한 풍파 성분간 에너지 전달의 계산)

  • 오병철;이길성
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.11 no.1
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    • pp.7-19
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    • 1999
  • The energy transfer between sea-wave components by way of nonlinear wave-wave interactions plays a central role in spectral evolution. Since huge calculation time is required to exact computation of the resulting Boltzmann integral, however, the exact nonlinear energy transfer has not been directly introduced into operational wave models. Thus, effective calculation methods were examined in the present study which exploit the scale property of a scattering coefficient and the detailed balance of interactions. The improved Webb's method (IWM) has inherent stability because singularities degenerate into a negligible point. The improved Masuda's method (IMM) makes a quasi-analytical treatment of the inherent singularities and requires only 1.3 seconds of computer time via Pentium 300MHz processor. The IMM is, therefore, projected to be very useful for theoretical researches in spectral evolution with fetch- or duration-limited situations.

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Pulse Energy Utilization in Space (우주에서의 펄스 에너지 활용)

  • Choi, Soo-Jin;Han, Tae-Hee;Lee, Hyun-Hee;Lee, Kyung-Cheol;Yoh, Jai-Ick
    • Journal of the Korean Society of Propulsion Engineers
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    • v.13 no.1
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    • pp.58-71
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    • 2009
  • The blast wave released during the initiation of energetic materials gives rise to pulse energy generation, characterized by a sudden increase of potential energy. A highly efficient energy source, sought from pulse-type lasers, may be utilized in various space propulsion and power applications. This paper introduces a scheme of utilizing the laser energy in 1) attitude control of a satellite requiring of a low thrust, 2) innovative laser-induced drug delivery, 3) implosion-based micro piston development, 4) deflecting and zapping of space debris for laser kill purpose, and 5) finally lunar detection using laser induced breakdown spectroscopy.