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31.
Measurements of the dielectric constant and microwave conductivity are reported for the vanadium bronze Na0.33V2O5. The dielectric constant is highly anisotropic and very large parallel to the highly conducting direction, while the conductivity is strongly dispersive. The results can be consistently interpreted by considering Na0.33V2O5 as a quasi-one-dimensional conductor in which, at low temperatures, a pseudo-gap opens in the open-electron density of states due to inter-site correlations. 相似文献
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A theoretical investigation has been carried out of surface polaritons associated with surface magnetoplasmons coupled to surface optical phonons in polar semiconductors. The coupled mode frequencies are calculated for several orientations of the magnetic field relative to the surface and the direction of propagation in the large wave vector (unretarded) limit. Dispersion curves are calculated for the configuration in which the magnetic field is parallel to the surface and is perpendicular to the wave vector. Experimental possibilities for observing the interaction effects are discussed. 相似文献
35.
W.D Wallis 《Journal of Combinatorial Theory, Series A》1973,15(1):115-119
We show that the existence of a maximal arc in a finite projective plane implies the existence of certain block designs and partial geometries. The block designs obtained have interesting resolvability properties. 相似文献
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Jennifer Wallis 《Journal of Combinatorial Theory, Series A》1973,14(2):248-252
Recursive constructions are given which permit, under conditions described in the paper, a (v, b, r, k, λ)-configuration to be used to obtain a (v′, b′, r′, k, λ)-configuration. 相似文献
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The collisionless Boltzmann equation is solved by an iterative characteristic method to calculate temporal and spatial plasma wave echoes of arbitrary order neglecting self-consistent fields. Using this model the measured spatial echo amplitude dependence from the transmitter separation is explained. 相似文献
40.
A new echo type with free electrons in a slight inhomogeneous magnetic field excited by one electric and one magnetic pulse is calculated. Thus features of cyclotron echos and spin echoes are combined. The first electric pulse accelerates all (cold) particles to the same velocity as in the case of usual cyclotron echoes. The second magnetic pulse (at t = τ) rotates the plane of precession in phase space, quite in analogy to the motion of magnetic moments in the case of spin echoes. The echo arises at t = 2τ. The E-H echoes make relaxation and diffusion measurements in plasmas possible, using the methods proved useful in spin echo technique. There are no complications as in the case of E-E cyclotron echoes which are based on the fact that a velocity-dependent collision frequency is necessary for the nonlinearity of that echo mechanism. 相似文献