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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The novel compounds Nd3Fe29−xTx (T=V and Cr) have been successfully synthesized. Their x-ray patterns can be indexed with a monoclinic symmetry and the A2/m space group. The Curie temperatures of Nd3Fe29−xTx are 455 and 413 K for T=V and Cr, the saturation magnetization at 4.2 K and room temperature are 54.7 and 46.8 μB/f.u. for T=V and 49.9 and 32.2 μB/f.u. for T=Cr, and the anisotropy fields at 4.2 K and room temperature are 12.8 and 2.4 T for T=V and 9.1 and 1.2 T for T=Cr, respectively. The spin reorientations of the easy magnetization direction of Nd3Fe29−xTx are observed at around 230 K for T=V and 135 K for T=Cr, respectively. After nitrogenation the relative volume expansion was about 6%, Curie temperature of each nitride increased about 50%, and the transition temperature Tsr of the spin reorientations of the nitride also increased 145 K for T=V and 250 K for T=Cr, respectively, compared with its parent compound. Nitrogenation resulted in remarkable improvements in the saturation magnetization and anisotropy fields at 4.2 K and room temperature. Magnetohistory effects for Nd3Fe29−xTx and Nd3Fe29−xTxN4 (T=V and Cr) in a low field have been observed. © 1997 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7450-7457 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic investigation of structure and intrinsic magnetic properties of the novel compounds R3(Fe, T)29 (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) has been performed. The lattice constants and unit cell volume decrease with increasing the rare-earth atomic number from R=Nd to Dy, except for Ce, reflecting the lanthanide contraction. The Curie temperature increases from R=Ce to Gd and decreases from Gd to Dy, respectively, with increasing atomic number and Gd3Fe29−xTx has the highest Curie temperature for each series of R3Fe29−xTx (T=V or Cr) compounds. The saturation magnetization of R3Fe29−xTx at 4.2 K decreases gradually from R=Nd to Dy with increasing atomic number, except for Ce, in each series of R3Fe29−xTx. It is suggested that the Ce ion in Ce3Fe29−xTx is valence fluctuated which leads to the unusual magnetic properties. The spin reorientations of the easy magnetization direction of R3Fe29−xTx are observed at around 230, 230, and 160 K for R=Nd, Sm, and Tb when T=V, and at around 230 and 180 K for R=Nd and Tb when T=Cr, respectively. First order magnetization processes are observed around 5.7 T for Sm3Fe26.7V2.3 and 4 T for Sm3Fe24.0Cr5.0 at 4.2 K, 2.0 T for Tb3Fe28.0V1.0, and 2.3 T for Tb3Fe28.0Cr1.0 at room temperature. A phenomenological analysis shows that the saturation magnetization of R3Fe29−xTx compounds with a low T concentration can be roughly calculated based on a combination of those of the 2:17R and 1:12 units in a ratio of 1:1. © 1997 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 4366-4372 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic investigation of crystallographic and magnetic properties of nitride R3Fe29−xCrxN4 (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed. The lattice constants and unit cell volume decrease with increasing rare earth atomic number from Nd to Dy, reflecting the lanthanide contraction. After nitrogenation the relative volume expansion of each nitride is around between 5% and 7%. The nitrogenation results in a good improvement in the Curie temperature, the saturation magnetization and anisotropy fields at 4.2 K, and room temperature for R3Fe29−xCrxN4. Magnetohistory effects of R3Fe29−xCrxN4 and R3Fe29−xCrx (R=Nd and Sm) are observed in a low field of 0.04 T. First order magnetization process occurs in Sm3Fe24.0Cr5.0N4 in magnetic fields of 2.8 T at 4.2 K. After nitrogenation, the easy magnetization direction of Sm3Fe24.0Cr5.0 is changed from the easy-cone structure to the uniaxial. The good intrinsic magnetic properties of Sm3Fe24.0Cr5.0N4 make this compound a hopeful candidate for new high-performance hard magnets. © 1998 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3248-3252 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic investigation of the structure and magnetic properties of novel compounds Tb3(Fe1−xVx)29 (x=0.033, 0.044, 0.056, and 0.061) has been performed. The lattice parameters and Curie temperatures are obtained. The saturation magnetization of Tb3(Fe1−xVx)29 decreases but the anisotropy field increases linearly with increasing V concentration at 4.2 K and room temperature. The spin reorientations of the easy magnetization direction of Tb3(Fe1−xVx)29 occur at around 160 K. A first order magnetization process of Tb3(Fe1−xVx)29 is observed with magnetic field in the range between 2.0 and 1.6 T at room temperature. The saturation magnetization of Tb3Fe29−yVy with a low V concentration at 4.2 K can be roughly calculated based on a combination of that of the Tb2Fe17 and TbFe12−yVy units in a ratio of 1:1. © 1997 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 32 (1999), S. 951-955 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The microdiffraction from a single translation domain boundary (TDB) in β-Ni3Nb has been recorded by using a Hitachi HF-2000 field emission gun transmission electron microscope, while high-resolution transmission electron microscopy images were used to assist the analysis. The diffraction splitting effect of a TDB is well explained by the kinematics and dynamic calculations, and complex diffraction characteristics have been studied by using dynamics simulation.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 110 (1995), S. 73-94 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The influence of ellipsoidal inclusions and elliptic cracks on the overall effective moduli of a two-phase composite and of a cracked body, respectively, is investigated by means of Mori-Tanaka's theory for three types of inclusion and four types of crack arrangements: monotonically aligned, 2-D randomly oriented (two kinds for cracks), and 3-D randomly oriented. The effective moduli of the composite in the aligned case are known to coincide with Willis' orthotropic lower (or upper) bounds with a two-point ellipsoidal correlation function if the matrix is the softer (or harder) phase. With 2-D randomly oriented inclusions, the effective moduli are examined under Willis' transversely isotropic bounds with a two-point spheroidal correlation function, and it is found that, as the cross-sectional aspect ratio of the ellipsoidal inclusions flattens from circular shape to disc-shape, the two effective shear moduli and the plane-strain bulk modulus all lie on or within the bounds. The effective bulk and shear moduli of an isotropic composite containing randomly oriented ellipsoidal inclusions also fall on or within Hashin-Shtrikman's bounds as the shape of the ellipsoids changes. The obtained moduli are then extended to a cracked body containing elliptic cracks, which are generated by compressing the thickness of ellipsoidal voids to zero. It is found that only selected components of the effective moduli are dependent upon the crack density parameter η. Their dependence on η and the crack shape γ are explicitly established.
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  • 7
    ISSN: 1573-2754
    Keywords: fluid mechanics ; sloshing dynamics ; liquid-vapor interface ; microgravity ; spacecraft ; force moment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The mathematical formulation of sloshing dynamics for a partially liquid filled dewar container driven by the gravity jitter acceleration associated with slew motion is studied. Explicit mathematical expressions to manage jitter acceleration associated with slew motion which is acting on the fluid systems in microgravity are derived. The numerical computation of sloshing dynamics is based on the non-inertia frame container bound coordinate and the solution of time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions The numerical computation of fluid viscous stress forces and moment fluctuations exerted on the dewar container driven by jitter acceleration associated with slew motion is investigated.
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  • 8
    ISSN: 1573-1987
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The dynamical behavior of spacecraft propellant affected by the asymmetric combined gravity gradient and jitter acceleration are studied. In particular the effect of surface tension on partially-filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank has been investigated. Three different cases of orbital accelerations: (a) gravity gradient-dominated, (b) equally weighted between gravity gradients and jitter, and (c) gravity jitter-dominated accelerations are considered. Fluctuations of angular momentum, fluid moment and bubble mass center caused by slosh wave excitations driven by gravity gradient and jitter accelerations are also investigated.
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  • 9
    Publication Date: 1999-05-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 10
    Publication Date: 1995-07-01
    Description: High performance liquid chromatography (HPLC) analytical studies of inner bark extractives from a large number of silver birch (Betulapendula Roth) and hairy birch (Betulapubescens Ehrh.) trees revealed the diarylheptanoid glucoside platyphylloside to be present at high levels in B. pendula (20–60 mg/g dry bark) and at low levels in B. pubescens (≤ 0.5 mg/g dry bark). Based on these observations, a new simple and accurate precipitation method to distinguish between B. pendula and B. pubescens has been developed. In a solution of 2,4-dinitrophenylhydrazine, platyphylloside immediately forms an orange precipitate. A similar precipitate is also produced when a piece of B. pendula inner bark is kept for 1 h at room temperature in the same solution. However, no precipitate forms when a sample from B. pubescens is used. The diagnostic value of morphological characters was assessed by comparing the results of species determinations made on a large number of trees (〉 1600), both juvenile and mature, using the morphological and the new chemical method. For birches younger than 20 years there was 100% agreement between the two methods. However, in some mature birch stands with the two species mixed and ages over 40 years, up to 20–30% of the trees were incorrectly identified to species using morphological characters. Results from tests using the precipitation method on birch species, varieties, forms, and hybrids were reported.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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