• Title/Summary/Keyword: MoM matrix elements

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Numerical Evaluation of MoM Diagonal and Off-diagonal Elements for the Analysis of a General Microstrip Structures (마이크로스트립 구조의 해석을 위한 MoM 대각 및 비대각 행렬요소들의 수치계산)

  • 김의중;오병희;이영순;조영기
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.13 no.1
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    • pp.26-32
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    • 2002
  • When a spatial method of moments(MoM) is used in conjunction with closed-form Greens functions for the analysis of a general microstrip structures of thin or thick substrate, an efficient technique fur the evaluation of MeM off-diagonal matrix elements as well as diagonal elements is proposed. In order to check the validity of the present method, performance is demonstrated for the example of a coaxially-fed microstrip antenna and the present results are compared with the previous results.

Numerical Evaluation of MoM Matrix for a General Microstrip Structures (일반적인 마이크로스트립 구조에 관한 MoM 행렬의 수치계산)

  • 이영순;김의중;오병희;조영기
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2001.11a
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    • pp.3-6
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    • 2001
  • In case that a closed-form Green's functions are used for the numerically efficient analysis of a general microstrip structures of thin or thick substrate, an efficient technique for the evaluation of MoM off-diagonal matrix elements as well as diagonal elements is proposed. In order to check the validity of the present method, performance is demonstrated for the example of a coaxially-fed microstrip antenna and the present results are compared with the previous results.

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Analytical Evaluation of MoM Matrix Elements Based upon a New Closed-Form Greenos Functions (새로운 Closed-Form 그린함수에 근거를 둔 MoM 행렬 요소의 해석적 계산)

  • 김의중;이상준;이영순
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.5
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    • pp.499-508
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    • 2004
  • An efficient method of moments(MoM), which can lead to the analytical evaluation of the matrix elements, is proposed to analyze microstrip structures. The present method is formulated in conjunction with use of a new closed-form spatial-domain Green's functions which are derived by use of the integral formula for semi-infinite integrals of Bessel functions. It is observed that the computational efficiency such as the amount of calculation and computation speed has been improved due to the present MoM scheme by a factor of about 4 in comparison with the previous method. To validate the proposed method, several numerical examples are presented.

Depletion of Solid Solution Elements and Change of Carbides in Artificially Aging Heat Treated 2.25CrMo Steel (인공 경년열화 열처리된 2.25CrMo 강에서의 고용원소 고갈 및 탄화물 변화)

  • Byeon, Jal Won;Pyo, S.W.;Kwun, S.I.
    • Journal of the Korean Society for Heat Treatment
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    • v.15 no.2
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    • pp.70-75
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    • 2002
  • The depletion of solid solution elements from matrix and the change of carbides during artificial aging of 2.25CrMo steel at $630^{\circ}C$ were investigated. The Mo and Cr elements were found to be depleted drastically in the early stage of aging. The change of carbides was confirmed by analyzing the XRD patterns of electrolytically extracted carbides. Four type of carbides, $M_{23}C_6$, $M_3C$, $M_2C$ and $M_6C$, were found to exist in the specimen before aging. The amount of $M_6C$ carbides increased with aging time, while that of $M_3C$ carbides diminished after short aging time.

Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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As-Cast and Solidification Structures of Fe-3%C-x%Cr-y%V-w%Mo-z%W Multi- Component White Cast Irons (Fe-3%C-x%Cr-y%V-w%Mo-z%W 다합금계백주철의 주방상태 및 급냉조직)

  • Yu, sung-Kon;Shin, Sang-Woo
    • Korean Journal of Materials Research
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    • v.12 no.5
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    • pp.414-422
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    • 2002
  • Three different multi-component white cast irons alloyed with Cr, V, Mo and W were prepared in order to study their as-cast and solidification structures. Three combinations of the alloying elements were selected so as to obtain the different types of carbides and matrix structures : 3%C-10%Cr-5%Mo-5%W(alloy No.1), 3%C-10%V-5% Mo-5%W(alloy No. 2) and 3%C-17%Cr-3% V(alloy No.3). The as-cast microstructures were investigated with optical and scanning electron microscopes. There existed two different types of carbides, $M_7C_3$ carbide with rod-like morphology and $M_6C$ carbide with fishbone-like one, and matrix in the alloy No. 1. The alloy No. 2 consisted of MC carbide with chunky and flaky type and needle-like $M_2C$ carbide, and matrix. The chunky type referred to primary MC carbide and the flaky one to eutectic MC carbide. The morphology of the alloy No. 3 represented a typical hypo-eutectic high chromium white cast iron composed of rod-like $M_7C_3$ carbide which is very sensitive to heat flow direction and matrix. To clarify the solidification sequence, each iron(50g) was remelted at 1723K in an alumina crucible using a silicon carbide resistance furnace under argon atmosphere. The molten iron was cooled at the rate of 10K/min and quenched into water at several temperatures during thermal analysis. The solidification structures of the specimen were found to consist of austenite dendrite(${\gamma}$), $ ({\gamma}+ M_7C_3)$ eutectic and $({\gamma}+ M_6C)$ eutectic in the alloy No. 1, proeutectic MC, austenite dendrite(${\gamma}$), (${\gamma}$+MC) eutectic and $({\gamma}+ M_2C)$ eutectic in the alloy No. 2, and proeutectic $M_7C_3$ and $ ({\gamma}+ M_7C_3)$ eutectic in the alloy No 3. respectively.

A robust method for derivation of the new closed-form Green관s functions for microstrip structures and its application to a fast MoM (마이크로스트립 구조에 관한 새로운 closed-form 그린함수 유도를 위한 견실한 방법과 빠른 모멘트법으로의 응용)

  • Kim, Eui-Joong
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2002.11a
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    • pp.423-433
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    • 2002
  • A very fast method of moments(MoM) for the analysis of microstrip structure is considered based upon the use of rooftop basis and razor test functions in conjunction with a new closed-form Green's functions. The present method presents a robust approach to obtain the Green's functions which can be derived by use of only one set of approximation parameters independently of operating frequency range. Moreover, using the present MoM scheme, the MoM matrix elements can be analytically evaluated with few number of terms in comparison with the previous method. So, the computational efficiency can be improved significantly without loss of the precision. In order to check the validity of the present method, performance is demonstrated for the example of a coaxially-fed microstrip transmission line and the present results are compared with the previous results.

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COMPARATIVE ANALYSIS OF STRUCTURAL CHANGES IN U-MO DISPERSED FUEL OF FULL-SIZE FUEL ELEMENTS AND MINI-RODS IRRADIATED IN THE MIR REACTOR

  • Izhutov, Aleksey.L.;Iakovlev, Valeriy.V.;Novoselov, Andrey.E.;Starkov, Vladimir.A.;Sheldyakov, Aleksey.A.;Shishin, Valeriy.Yu.;Kosenkov, Vladimir.M.;Vatulin, Aleksandr.V.;Dobrikova, Irina.V.;Suprun, Vladimir.B.;Kulakov, Gennadiy.V.
    • Nuclear Engineering and Technology
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    • v.45 no.7
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    • pp.859-870
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    • 2013
  • The paper summarizes the irradiation test and post-irradiation examination (PIE) data for the U-Mo low-enriched fuel that was irradiated in the MIR reactor under the RERTR Program. The PIE data were analyzed for both full-size fuel rods and mini-rods with atomized powder dispersed in Al matrix as well as with additions of 2%, 5% and 13% of silicon in the matrix and ZrN protective coating on the fuel particles. The full-size fuel rods were irradiated up to an average burnup of ${\sim}60%^{235}U$; the mini-rods were irradiated to an average burnup of ${\sim}85%^{235}U$. The presented data show a significant increase of the void fraction in the U-Mo alloy as the U-235 burnup rises from ~ 40% up to ~ 85%. The effect of irradiation test conditions and U-235 burnup were analyzed with regard to the formation of an interaction layer between the matrix and fuel particles as well as generation of porosity in the U-Mo alloy. Shown here are changes in distribution of U fission products as the U-235 burnup increases from ~ 40% up to ~ 85%.

Magnetic Hardening of Rapidly Solidified $SmFe_{7+x}M_{x}(M=Mo,\;V,\;Ti)$ Compounds (급속냉각된 $SmFe_{7+x}M_{x}(M=Mo,\;V,\;Ti)$ 화합물에서 생성된 신 강자성상)

  • Choong-Jin Yang;E. B. Park;S. D. Choi
    • Journal of the Korean Magnetics Society
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    • v.4 no.3
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    • pp.226-232
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    • 1994
  • Rapidly solidified $SmFe_{7+x}M_{x}(M=Mo,\;V,\;Ti)$ compound were found to crystallize in the ${Sm(Fe,\;M)}_{7}$ based stable magnetic phase by introducing a second transition element into the Sm-Fe binary system. The ${Sm(Fe,\;M)}_{7}$ phase exhibits the highest Curie temperatuer ($T_{c}=355^{\circ}C$) ever Known in the Sm-Fe magnetic systems with a quite high intrinsic coercivity($_{i}H_{c}=3~6\;kOe $). The ${Sm(Fe,\;M)}_{7}$ phase remains stable even after annealing if once form during the rapid solidification. The primary reason for the high coercive force is due to the fine grain size($2000~8000\;{\AA}$)of the magnetic ${Sm(Fe,\;M)}_{7}$ matrix phase, and the enhanced Curie temperature is attributed to the extended solid-solubility of the additive transition elements in Fe matrix, which leads to volume expansion of the ${Sm(Fe,\;M)}_{7}$ cell causing an enhanced coupling constant of Fe atoms.

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Analysis of Electromagnetic Characteristics of a Grounded Slab and a Parallel-Plate Structure Using the SDDI Technique

  • Choi, Jae-Hoon;Kahng, Sung-Tek
    • ETRI Journal
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    • v.23 no.2
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    • pp.71-76
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    • 2001
  • In this paper, the electromagnetic characteristics of a grounded slab and a parallel-plate structure are analyzed by the Spline-type Divided-Difference Interpolation (SDDI) technique. The technique efficiently evaluates the MoM impedance matrix elements of the multifold spectral or spatial domain integrals or summation in integro differential equations. The numerical results of the proposed method agree well with those of the corresponding literatures.

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