• Title, Summary, Keyword: Diffusion mechanism

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First principles calculation of boron diffusion in fcc-Fe

  • Zhang, Xin;Li, Xianglong;Wu, Ping;Chen, Sen;Zhang, Shiping;Chen, Ning;Huai, Xiulan
    • Current Applied Physics
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    • v.18 no.10
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    • pp.1108-1112
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    • 2018
  • The diffusion mechanism of boron in fcc-Fe was studied by first-principles calculations. The sites where B atoms tend to occupy and the diffusion behavior were calculated. Results indicated that the main mechanism of boron diffusion in fcc-Fe was the B-monovacancy complex mechanism instead of the interstitial mechanism. The diffusion coefficient $D_1$ of the B-monovacancy complex mechanism was calculated without considering the backward jump of the B atoms. The calculated $D_1=1.26{\times}10^{-4}{\times}$ exp$({^-}2.01eV/k_BT)m^2{\cdot}s^{-1}$ is consistent with the reported results from experiments.

Numerical analysis of NOx formation characteristics in CH$_{4}$-air jet diffusion flame (CH$_{4}$-공기 분류 확산화염의 NOx 생성특성에 관한 수치해석)

  • O, Chang-Bo;Lee, Chang-Eon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.2
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    • pp.193-204
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    • 1998
  • Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymmetric 2-D CH$_{4}$ jet diffusion flame. Calculations were carried out twice with the $C_{2}$-Thermal Mechanism including $C_{2}$ and thermal NO reactions and the $C_{2}$-Full Mechanism including prompt NO reactions in addition to the above $C_{2}$-Thermal NO mechanism. The results show that the flame structures such as flame temperature, major and minor species concentration are indifferent to respective mechanisms. The production path of Thermal NO is dominant comparing with that of Prompt NO in total NO production of pure CH$_{4}$ jet diffusion flame. This is because thermal NO mechanism mainly contributes to positive formation of NO in the whole flame region, but Prompt NO mechanism contributes to negative formation in the fuel rich region. In addition, 0$_{2}$ penetration near the nozzle outlet affects the flame structures, especially N0$_{2}$ formation characteristics.

A Reliable Data Transfer Mechanism Using Directed Diffusion in Wireless Sensor Networks (무선 센서 네트워크에서 Directed Diffusion을 이용한 신뢰성 있는 데이터 전달 기법)

  • Choi Jae-Won;Lee Kwang-Hui
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.8
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    • pp.77-83
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    • 2006
  • In this paper, we have pesented a reliable data transfer mechanism using Directed Diffusion in WSNs (fireless Sensor Networks). This mechanism involves selecting a route with higher reachability and transferring data along the route chosen, which is based on the end-to-end reliability calculated by the dissemination procedure of Interest packets, while each node of a sensor network maintains the only information on its neighborhood. We performed various experiments changing the link error rates and the number of nodes and discovered that this proposed mechanism improves event-to-sink data transfer reliability in WSNs. We also found that this mechanism spreads traffic load over and reduces energy consumption, which in turn prolongs network lifetime.

Study of Driving and Thermal Stability of Anode-type Ion Beam Source by Charge Repulsion Mechanism

  • Huh, Yunsung;Hwang, Yunseok;Kim, Jeha
    • Applied Science and Convergence Technology
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    • v.27 no.3
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    • pp.47-51
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    • 2018
  • We fabricated an anode-type ion beam source and studied its driving characteristics of the initial extraction of ions using two driving mechanisms: a diffusion phenomenon and a charge repulsion phenomenon. For specimen exposed to the ion beam in two methods, the surface impurity element was investigated by using X-ray photoelectron spectroscopy. Upon Ar gas injection for plasma generation the ion beam source was operated for 48 hours. We found a Fe 2p peak 5.4 at. % in the initial ions by the diffusion mechanism while no indication of Fe in the ions released in the charge repulsion mechanism. As for a long operation of 200 min, the temperature of ion beam sources was measured to increase at the rate of ${\sim}0.1^{\circ}C/min$ and kept at the initial value of $27^{\circ}C$ for driving by diffusion and charge repulsion mechanism, respectively. In this study, we confirmed that the ion beam source driven by the charge repulsion mechanism was very efficient for a long operation as proved by little electrode damage and thermal stability.

Numerical Evaluation of Impurity Profile in Silicon (수치해법에 의한 실리콘에서의 불순물 분포의 산출)

  • 오형철;경종민
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.21 no.6
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    • pp.17-26
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    • 1984
  • A computer program (DIFSIM: Diffusion SIMulator) was written to calculate the impurity profile, specifically boron and phosphorus, due to three different diffusion processes-predeposition, drive-in in inert ambient, and drive-in in oxidizing ambient. The vacancy mechanism including Fair and Tsai's theory for phosphDrus diffusion was widely incorporated for modeling various diffusion processes. The concentrationtependent oxidation rate was also explained using the vacancy model, while the oxidation - enhanced diffusion was mo dolled using catkins replacement mochanlsm . The simulation results using DIFSIM showed a fairly good agreement with the experimental data by adjusting some of the empirical parameters in the program. The results obtained using DIFSIM were compared with the results from SUPREM II.

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A Study on the Solid State Diffusion Bonding of Ti-6Al-4V Alloy (Ti-6Al-4V합금의 고상 확산접합에 관한 연구)

  • 강호정;강춘식
    • Journal of Welding and Joining
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    • v.15 no.6
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    • pp.32-40
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    • 1997
  • Solid state diffusion bonding is the joining process performed by creep and diffusion, which is accelerated by heating below melting temperature and proper pressing, in vacuum or shielding gas atmosphere. By this process we can obtain sufficient joint which can't be expected from the fusion welding. For Ti-6Al-4V alloy, the optimum solid state diffusion bonding condition and mechanical properties of the joint were found, and micro void morphology at bond interface was observed by SEM. The results of tensile test showed sufficient joint, whose mechanical properties are similar to that of base metal. 850$^{\circ}$C, 3MPa is considered as the optimum bonding condition. Void morphology at interface is long and flat at the initial stage. As the percentage of bonded area increases, however, small and round voids are found. Variation of void shape can be explained as follows. As for the void shrinkage mechanism, at the initial stage, power law creep is the dominant, but diffusion mechanism is dominant when the percentage of bonded area is increased.

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NOx Formation Characteristics in Diffusion, Partial Premixed and Premixed Jet flame (가스 연료의 연소 방식에 따른 NOx 생성 특성)

  • Choi, Young-Ho;Lee, Chang-Eon
    • 한국연소학회:학술대회논문집
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    • pp.155-164
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    • 1998
  • Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymetric 2-D CH4 jet diffusion, partial premixed, premixed flame. Calculations were carried out twice with C2-Full Mechanism including prompt NO reaction in addition to the above C2-Thermal NO Mechanism. The role of thermal NO mechanism and prompt NO mechanism on each flame's NO production is investigated by using the numerical result. The NOx production of each flame were evaluated Quantitatively in terms of the NOx emission index

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Melting induced diffusion bonding of Rene 80 superalloys using boron doping method (Ren380 超合金의 보론 塗布法을 이용한 液化誘導擴散接合法의 硏究)

  • 정재필;강춘식;이보영
    • Journal of Welding and Joining
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    • v.9 no.3
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    • pp.26-33
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    • 1991
  • As it takes very long time for the Transient Liquid Phase(TLP) bonding, we tried to reduce the bonding time by changing insert material for the high diffusivity element. On this study boron powder was doped as a insert material on the bonding surface of Rene 80 superalloy, and diffusion treated at 1150.deg.C under vacuum. On this method differently from the TLP bonding the insert material was not melted during bonding but only the base metal reacted with the boron was inducedly melted. Therefore, as this bonding mechanism is different from the existing ones, it is suggested as a Melting Induced Diffusion Bonding. When this process was used for the diffusion bonding, the bonding time including homogenization decreased greatly compared to the conventional TLP bonding.

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Deformation Mechanism Map for Creep and Superplastic Deformation in $YBa_2Cu_3O_{7-x}$ Ceramic Superconductors ($YBa_2Cu_3O_{7-x}$ 세라믹 초전도체의 크리프와 초소성변형에 대한 변형기관도)

  • 윤존도;초우예
    • Journal of the Korean Ceramic Society
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    • v.33 no.6
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    • pp.718-724
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    • 1996
  • Deformation mechanism map of Langdon-Mohammed type for YBa2Cu3O7-x superconducting ceramic was constructed by considering mechanisms of Nabarro-Herring Coble and powder-law creep and grain boundary sliding (GBS) with an accommodation by grain boundary diffusion. The map was found consistent with experi-mental results not only of the creep the also of the superplastic deformation. It showed the transition from interface reaction-controlled to the grain boundary diffusion-controlled GBS mechanism at about 1 ${\mu}{\textrm}{m}$ grain size and 100 MPa flow stress in agreement with the experimental results.

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Characteristics of Critical Pressure for a Beam Shape of the Anode Type ion Beam Source

  • Huh, Yunsung;Hwang, Yunseok;Kim, Jeha
    • Applied Science and Convergence Technology
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    • v.27 no.4
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    • pp.61-65
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    • 2018
  • We studied the critical pressure characteristics of an anode type ion beam source driven by both charge repulsion and diffusion mechanism. The critical pressure $P_{crit}$ of the diffusion type ion beam source was linearly decreased from 2.5 mTorr to 0.5 mTorr when the gas injection was varied in 3~10 sccm, while the $P_{crit}$ of the charge repulsion ion beam source was remained at 3.5 mTorr. At the gas injection of 10 sccm, the range of having normal beam shape in the charge repulsion ion beam source was about 6.4 times wider than that in the diffusion type ion beam source. An impurity of Fe 2p (KE = 776.68 eV) of 12.88 at. % was observed from the glass surface treated with the abnormal beam of the charge repulsion type ion beam source. The body temperature of the diffusion type ion beam source was observed to increase rapidly at the rate of $1.9^{\circ}C/min$ for 30 minutes and to vary slowly at the rate of $0.1^{\circ}C/min$ for 200 minutes for an abnormal beam and normal beam, respectively.