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  • 1
    Electronic Resource
    Electronic Resource
    Magnetohydrodynamic flows sustaining stationary magnetic nulls (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3542-3550 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Exact solutions of the resistive magnetohydrodynamic equations are derived which describe a stationary incompressible flow near a generic null point of a three-dimensional magnetic field. The properties of the solutions depend on the topological skeleton of the corresponding magnetic field. This skeleton is formed by one-dimensional and two-dimensional invariant manifolds (so-called spine line and fan plane) of the magnetic field. It is shown that configurations of generic null points may always be sustained by stationary field-aligned flows of the stagnation type, where the null points of the magnetic and velocity fields have the same location. However, if the absolute value |j(parallel)| of the current density component parallel to the spine line exceeds a critical value jc, the solution is not unique—there is a second nontrivial solution describing spiral flows with the stagnation point at the magnetic null. The characteristic feature of these new flows is that they cross magnetic field lines but they do not cross the corresponding spine and fan of the magnetic null. Therefore these are nonideal but nonreconnecting flows. The critical value |j(parallel)|=jc coincides exactly with a threshold separating the topological distinct improper radial and spiral nulls. It is shown that this is not an accidental coincidence: the spiral field-crossing flows of the considered type are possible only due to the topological equivalence of the field lines forming the fan plane of the spiral magnetic null. The explicit expression for the pressure distribution of the solution is given and its iso-surfaces are found to be always ellipsoidal for the field-aligned flows, while for the field-crossing flows there are also cases with a hyperboloidal structure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1286862
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  • 2
    Electronic Resource
    Electronic Resource
    Absorptance of powder materials suitable for laser sintering (2000)
    Bingley : Emerald
    Rapid prototyping journal 6 (2000), S. 155-161 
    Details
    ISSN: 1355-2546
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The normal spectral absorptance of a number of metal, ceramic and polymer powders susceptible to be utilised for selective laser sintering (SLS) technique was experimentally determined. The measurements were performed with two laser wavelengths of 1.06µm and 10.6µm obtained by using two lasers - Nd-YAG and CO2 respectively. The change in the powder absorptance with time during laser processing was also investigated. The effect of the absorptance characteristics on the sintering process is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/13552540010337029
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanisms of selective laser sintering and heat transfer in Ti powder (2003)
    Bingley : Emerald
    Rapid prototyping journal 9 (2003), S. 314-326 
    Details
    ISSN: 1355-2546
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Coupled metallographic examination and heat transfer numerical simulation are applied to reveal the laser sintering mechanisms of Ti powder of 63-315?µm particle diameter. A Nd:YAG laser beam with a diameter of 2.7-5.3?mm and a power of 10-100?W is focused on a bed of loose Ti powder for 10?s in vacuum. The numerical simulation indicates that a nearly hemispherical temperature front propagates from the laser spot. In the region of a-Ti just behind the front, heat transfer is governed by thermal radiation. The balling effect, formation of melt droplets, is not observed because the temperature increases gradually and the melt appears inside initially sintered powder which resists the surface tension of the melt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/13552540310502211
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  • 4
    Electronic Resource
    Electronic Resource
    Narrow saturated absorption resonances in the transmission band of an active interferometer (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 127-131 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The shape of the transmission band of an active interferometer, a resonator with amplification and absorption cells excited by an external signal, is studied. Upon tuning the external signal frequency, the narrow saturated absorption resonances can be observed in the transmission band of the interferometer. It is shown that, by varying the gain, the resonance absorption amplitude can be compensated for one order of smallness in pressure. The effect of amplitude and frequency noises of the external signal on the results obtained is studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626759
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  • 5
    Electronic Resource
    Electronic Resource
    Measuring scanning acoustic microscope with a harmonic sounding signal (2000)
    Springer
    Acoustical physics 46 (2000), S. 523-529 
    Details
    ISSN: 1562-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A concept of a scanning acoustic microscope with a harmonic sounding signal for measuring the parameters of local homogeneous regions of flat samples is proposed. The distinctive feature of the device is the utilization of the Doppler effect that occurs in the sounding wave reflected from the sample surface when the sample is uniformly moved relative to the focusing ultrasonic transducer of the microscope. It is theoretically demonstrated that the spectrum of the received signal is determined by the product of the reflection coefficient and the transfer function of the transducer. The errors of the measurement technique are considered, and the sources of signal distortions are analyzed. High sensitivity of the measurement results to the errors of the scanning system is demonstrated. The developed measuring microscope is described, in which an acoustic interferometer is used to provide the necessary precision of the scanning coordinate measurement. The microscope transfer function is measured for the frequency of the sounding signal 65 MHz, and the values of density and bulk wave velocities are determined for a homogeneous sample by the measured phase of the reflection coefficient using the technique of nonlinear estimation of parameters. With fused quartz used as an example, it is shown that the measurement error is 7.2% for density and 2.3 and 0.7% for the velocities of longitudinal and transverse waves, respectively. In addition, the velocity of a leaky surface wave (SAW) is determined by two methods. One method is based on measuring the position of the inflexion point for the experimental phase of the reflection coefficient, and the other is based on calculating the SAW velocity corresponding to the measured values of density and bulk wave velocities. The errors of these methods are found to be equal to 0.42 and 0.17%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1310375
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  • 6
    Electronic Resource
    Electronic Resource
    Short-distance wavefunction statistics in one-dimensional Anderson localization (2003)
    Springer
    The European physical journal 35 (2003), S. 421-427 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We investigate the short-distance statistics of the local density of states $\nu$ in long one-dimensional disordered systems, which display Anderson localization. It is shown that the probability distribution function $P(\nu)$ can be recovered from the long-distance wavefunction statistics, if one also uses parameters that are irrelevant from the perspective of two-parameter scaling theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00294-0
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  • 7
    Electronic Resource
    Electronic Resource
    Spin filters with Fano dots (2003)
    Springer
    The European physical journal 37 (2003), S. 399-403 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We compute the zero bias conductance of electrons through a single ballistic channel weakly coupled to a side quantum dot with Coulomb interaction. In contrast to the standard setup which is designed to measure the transport through the dot, the channel conductance reveals Coulomb blockade dips rather then peaks due to the Fano-like backscattering. At zero temperature the Kondo effect leads to the formation of broad valleys of small conductance corresponding to an odd number of electrons on the dot. By applying a magnetic field in the dot region we find two dips corresponding to a total suppression in the conductance of spins up and down separated by an energy of the order of the Coulomb interaction. This provides a possibility of a perfect spin filter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00072-6
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  • 8
    Electronic Resource
    Electronic Resource
    Features of the structure and ferroelectric properties of the solid solutions of lead titanate with rare-earth metals (2000)
    Springer
    Technical physics letters 26 (2000), S. 799-802 
    Details
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A secondary periodicity in variation of the properties of ferroelectric solid solutions of lead titanate with rare-earth metals is established. It is demonstrated that this behavior is related both to the modifying cations belonging to two natural subgroups and to the energetic features of their 4f levels. The extrema of the structural and ferroelectric characteristics correspond to the domains of electron instability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1315499
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  • 9
    Electronic Resource
    Electronic Resource
    New One and Two-Coordinate Detectors in SSRC (2000)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 321-324 (Jan. 2000), p. 320-325 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/04/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.321-324.320.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Structure clusterization preceding concentration phase transitions (2000)
    Springer
    Technical physics letters 26 (2000), S. 810-813 
    Details
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The formation and development of bulk crystallochemical defects—mesoscopic clusters representing the nuclei of new phases—was studied in systems exhibiting concentration phase transitions. When a solid solution approaches a morphotropic region, the clusters exhibit a stepwise evolution involving several stages manifested by corresponding changes in macroscopic properties. The role of clusters in the development of the extreme electrophysical properties of the objects studied is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1315502
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