• 한국IT서비스학회지
• /
• 제6권1호
• /
• pp.141-149
• /
• 2007

Sensor node's mobility brings new challenges to data dissemination in large sensor networks. Frequent location updates of sensor nodes can lead to both excessive drain of sensor's limited battery supply and increased collisions in wireless transmissions. Conventional studies for routing protocols in wireless sensor networks are not enough to cover energy consumption and migration of sensor nodes. This study proposes a dynamic routing protocol based on the SPIN considering energy consumption and the migration, and also shows the effectiveness of the proposed routing protocol.

• Nuclear Engineering and Technology
• /
• 제44권1호
• /
• pp.79-88
• /
• 2012

Migration tests were performed with conservative tracers in a fractured zone that had a single fracture of about 2.5 m distance at the KURT. To interpret the migration of the tracers in the fractured rock, a solute transport model was developed. A two dimensional variable aperture channel model was adopted to describe the fractured path and hydrology, and a particle tracking method was used for solute transport. The simulation tried not only to develop a migration model of solutes for open flow environments but also to produce ideas for a better understanding of solute behaviours in indefinable fracture zones by comparing them to experimental results. The results of our simulations and experiments are described as elution and breakthrough curves, and are quantified by momentum analysis. The main retardation mechanism of nonsorbing tracers, including matrixdiffusion, was investigated.

• 한국콘텐츠학회논문지
• /
• 제6권5호
• /
• pp.35-41
• /
• 2006

기존의 무선 센서 네트워크에서의 라우팅 프로토콜로 사용되는 SPIN 프로토콜은 에너지 소모량 및 위치이동에 의한 동적 라우팅정책을 고려하지 않는 문제점이 있다. 본 논문은 기존의 SPIN 프로토콜보다 에너지 효율과 신뢰성이 높아 질 수 있도록 방향성과 에너지효율을 고려한 새로운 라우팅 프로토콜을 제안하고 효율성을 입증한다.

• 한국세라믹학회지
• /
• 제52권5호
• /
• pp.331-337
• /
• 2015

$LaBO_3$ (B = Cr, Mn, Fe, Co, and Ni) perovskites, the most common perovskite-type mixed ionic-electronic conductors (MIECs), are promising candidates for intermediate-temperature solid oxide fuel cell (IT-SOFC) cathodes. The catalytic activity on MIEC-based cathodes is closely related to the bulk ionic conductivity. Doping B-site cations with other metals may be one way to enhance the ionic conductivity, which would also be sensitively influenced by the chemical composition of the dopants. Here, using density functional theory (DFT) calculations, we quantitatively assess the activation energies of bulk oxide ion diffusion in $LaBO_3$ perovskites with a wide range of combinations of B-site cations by calculating the oxygen vacancy formation and migration energies. Our results show that bulk oxide ion diffusion dominantly depends on oxygen vacancy formation energy rather than on the migration energy. As a result, we suggest that the late transition metal-based perovskites have relatively low oxygen vacancy formation energies, and thereby exhibit low activation energy barriers. Our results will provide useful insight into the design of new cathode materials with better performance.

• 지구물리와물리탐사
• /
• 제5권1호
• /
• pp.18-22
• /
• 2002

단일 도달주시로서 최대에너지 도달주시는 카르히호프 구조보정을 위한 가장 적합한 연산자로 알려져 있다. 단순구조모델의 경우에 초동주시나 최대에너지 도달주시는 모두 정확한 카르히호프 구조보정 연산자로 사용될 수 있다. 그러나 구조가 복잡하고 속도대비가 큰 모델에 대해서 초동주시를 이용한 구조보정은 정확한 심도단면도를 얻을 수 없다. 즉 카르히호프 구조보정에서 요구되는 주시는 최대에너지 도달주시이지만 이 주시는 초동주시에 비해 상당히 많은 계산시간을 요한다. 본 논문에서는 일방향 파동방정식을 이용하여 최대에너지 도달주시에 근사한 주시를 계산하는 방법을 제안한다. 일방향 파동 방정식을 이용해 초동주시를 계산할 때 사용되는 WAS(Wrap Around Suppression, 두루마리현상억제)계수를 수평방향의 격자간격과 깊이에 대한 함수로 정의하고 음원 파형의 지연시간을 고려하여 최대 에너지 도달 시간에 근사한 주시를 구하였다. 이 주시의 타당성을 검증하고자 계산된 주시를 단순구조 및 복잡한 구조의 구조보정에 적용하고 그 심도단면도를 초동주시를 이용해 구한 심도단면도와 비교하였다.

• 연구논문집
• /
• 통권25호
• /
• pp.185-192
• /
• 1995

The solid/liquid interface migration in Nb-doped $SrTiO_3$ and its effect on dielectric properties have been investigated. The specimen sintered in air shows no migration during oxide infiltration treatment in air, whereas the specimen sintered in $5H_2-95N_2$ shows appreciable migration during similar infiltration. In the migrated layers of the specimen sintered in a reducing atmosphere, no cations of the infiltrants are detected by wavelength dispersive spectroscopy. These results show that nonstoichiometry due to the atmosphere change can induce the interface migration as in the case of frequently observed migrations due to solute concentration change. The driving force for the migration is discussed in terms of the coherency strain energy in a thin diffusional oxidized layer of the receding grain. The interface migration caused by nonstoichiometry could be suppressed by preoxidizing grain surfaces before oxide infiltration treatment. The suppression of migration increased the effective dielectric constant of the material.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
• /
• 제4권9호
• /
• pp.315-320
• /
• 2015

클라우드 컴퓨팅에서 서버 가상화는 한 대의 물리적인 서버를 다수의 가상머신으로 분할하여 다양한 운영체제 및 애플리케이션을 구동하는 기술이다. 가상머신의 마이그레이션은 현재 실행 중인 가상머신을 소스 호스트에서 다른 물리적인 장치인 타깃 호스트로 이동하는 것이다. 가상머신의 라이브 마이그레이션은 작업 수행 성능의 최적화와 저전력 지원 및 에너지 절감, 결함포용, 노드들 간의 부하 균형을 제공하기 위한 필수적인 요소이다. 본 논문에서는 오픈소스 기반의 적응적 VM 라이브 마이그레이션 기법을 제안한다. 이를 위해 적응적 VM 마이그레이션 시점을 결정하는 VM 모니터링 모듈을 제안하고 오픈소스 기반 전가상화를 지원하는 하이퍼바이저를 설계하였다.

• Journal of Electrochemical Science and Technology
• /
• 제13권1호
• /
• pp.71-77
• /
• 2022

Metal halide perovskites are promising photovoltaic materials, but they still have some issues that need to be solved. Hysteresis is a phenomenon that strongly is correlated with ion migration; thus, a fast, easy, and low-temperature method for measuring ion migration is required. Through selective blocking, ion migration can be measured separately, apart from electron migration. In this study, ion migration in metal halide perovskites was measured using a vertical device. At different temperatures, ionic activation energies were obtained for a range of perovskite compositions such as MAPbI₃, FAPbI₃, CsPbI₃, and MAPbBr₃. By comparing the measured ionic activation energies with the theoretical values, we conclude that among other possibilities, I^- is the migrating ion in MAPbI₃, FAPbI₃, CsPbI₃, and Br- is the migrating in MAPbBr₃.

• 한국세라믹학회지
• /
• 제48권2호
• /
• pp.195-199
• /
• 2011

The effect of copper oxide on migration and interaction of protons in barium zirconate was investigated using density functional theory. One copper atom was substituted for a zirconium atom site, and a proton was added to a $3{\times}3{\times}3$ barium zirconate superstructure. An energy barrier of 0.89 eV for proton migration was the highest among several energy barriers. To investigate the interaction between multiple protons and a copper atom, two protons were added to the superstructure. Various proton positions were determined by the interaction between the two protons and the copper atom.

• 한국방사성폐기물학회:학술대회논문집
• /
• 한국방사성폐기물학회 2019년도 춘계학술논문요약집
• /
• pp.153-154
• /
• 2019