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101.
Electrical resistivity studies of the charge transfer complex benzidine—TCNQ and its inclusion compound, have been carried
out up to pressures 8 GPa. Two types of behaviour were observed in these complexes under high pressure and this difference
is interpreted and discussed. 相似文献
102.
Different kinds of mean-field theories (MFT) of spin glasses (SG) are reviewed. A brief introductory review of major experimental results, which have to be explained theoretically, is presented in the beginning. Marshall-Klein-Brout type random local field theories are described qualitatively. Edwards-Anderson MFT of SG transition is introduced after defining the various relevant order parameters. Almost all the static and dynamic approaches to the solution of the Sherrington-Kirkpatrick model are reviewed in detail. The existence of mixed phase(s) in the MFT of vector SG is examined critically in the light of recent theories and experiments. The existence of macroscopic anisotropy energy in SG and their microscopic origin are mentioned. The upper and lower critical dimensionalities obtained by different authors are enlisted. The concept of frustration and its deeper connection with other branches of human knowledge are indicated. Nonlinear susceptibilities, spin wave and relaxational modes in SG are also reviewed. The two-level-system picture of SG, its physical basis and important consequences are presented. The Tholence-Tournier-Wohlfarth phenomenological cluster model of SG is discussed with a stress on the role of measurement time. SG transition has been described as percolation and localization-delocalization problems. Some special features of the local field distribution in SG are mentioned. Some results of computer simulation on the various models of SG are summarized. The theories of the transport properties of SG are enlisted. Recent trends in the theory of SG are indicated at the end. 相似文献
103.
104.
A.K. Bandyopadhyay F. Beuneu L. Zuppiroli M. Beauvy 《Journal of Physics and Chemistry of Solids》1984,45(2):207-214
Boron carbide is a ceramic which has a wide field of application because of its mechanical and nuclear properties. This material is difficult to characterise due to the presence of different levels of disorder and inhomogeneities which are found in the usual available samples. The transport and magnetic properties of several samples of boron carbide have been measured from liquid helium to room temperature as a function of temperature and composition. We have attempted to attribute the different features of these properties to the different levels of disorder. The role of free carbon, in form of thin layers of graphite within the disordered semi-conducting matrix, was investigated in particular details, because it was either ignored or neglected by others. Free carbon is found to dominate the D.C. transport when its concentration is larger than 5%; while the principal features of the electron spin resonance (E.S.R.) line show a dominance of free carbon when the concentration is larger than 3.5%. Below these concentrations conductivities as well as spin relaxation rates do not depend very much on free carbon; neither these have been found to be correlated in a simple way to the stoichiometry: the disorder in the boron sublattice is probably responsible for the electronic properties in this range of concentrations. 相似文献
105.
The problem of nonlinear optimization is encountered while fitting the observed response of certain radiation detectors. In
this paper the development of an optimizing technique based on quasi random search is described. The performance of this technique
is compared with other existing methods of gradient search and linear Taylor differential correction technique in the case
of fitting the photopeak responses of Nal(Tl) detectors. Our results are favourable especially when the observed data are
associated with poor statistics. 相似文献
106.
A study of effective implementation of threshold activation technique for neutron spectral analysis in the environment of
an alpha-cyclotron target is presented. The activation data are analysed using LOUHI-82 code. Optimal choices of the regularization
parameters of the code are studied and discussed. Energy distribution of neutrons emitted from thick targets of Be, C and
Ta irradiated by 40–45 MeV alphas is discussed. 相似文献
107.
Jorgen Rassing Saibal Bandyopadhyay Edward M. Eyring 《Journal of Molecular Liquids》1983,26(2):97-108
A new sample cell construction for a light diffraction method permits absolute measurements of the ultrasonic absorption coefficient for a strongly absorbing transparent gel. By means of this cell the absorption coefficient at 6.2 MHz has been measured as a function of the temperature in the gelling temperature range for a 25% (w/w) aqueous solution of the ABA polyoxyethylene-polyoxypropylene block copolymer PLURONICR F 127. The resonator method has been used under the same experimental conditions. The strongly absorbing gel causes overlapping of the resonance signals. A calibration based on resonance experiments compared with the absolute measurements yields a solution to that problem and thus makes the resonator method applicable to a strongly absorbing gel. 相似文献
108.
Pratul Bandyopadhyay Brahmananda Bhattacharya Harish Sarkar 《International Journal of Theoretical Physics》1983,22(8):677-689
In quantum neutrinodynamics (photon-neutrino weak coupling) all the renormalization constants vanish and therefore the field equations cannot be expressed in terms of unrenormalized field quantities. This helps us to formulate quantum neutrinodynamics as a convergent quantum field theory. It is also pointed out that from the viewpoint of the unified model of weak and electromagnetic interaction as developed on the basis of the photon-neutrino weak coupling by Bandyopadhyay, quantum electrodynamics also manifests itself as a convergent field theory. 相似文献
109.
Nibedita Bandyopadhyay Ananda Sen 《Annals of the Institute of Statistical Mathematics》2005,57(4):703-732
Nonhomogeneous Poisson process (NHPP) is a commonly used stochastic model that is utilized to describe the pattern of repeated
occurrence of certain events or conditions. Aninhomogeneous gamma process evolves as a generalization to NHPP, where the observed failure epochs correspond to every successive κ-th event of the underlying
Poisson process, κ being an unknown parameter to be estimated from the data. This article focuses on a special class of inhomogeneous
gamma process, calledmodulated power law process (MPLP) that assumes the Weibull form of the intensity function. The traditional power law process is a popular stochastic
formulation of certain empirical relationships between the time to failure and the cumulative number of failures, often observed
in industrial experiments. The MPLP retains this underlying physical basis and provides a more flexible modeling environment
potentially leading to a better fit to the failure data at hand. In this paper, we investigate inference issues related to
MPLP. The maximum likelihood estimators (MLE’s) of the model parameters are not in closed form and enjoy the curious property
that they are asymptotically normal with a singular variance-covariance matrix. Consequently, the derivation of the large-sample
results requires non-standard modifications of the usual arguments. We also propose a set of simple closed-form estimators
that are asymptotically equivalent to the MLE’s. Extensive simulation results are carried out to supplement the theoretical
findings. Finally, we implement our inference results to a failure dataset arising from a repairable system. 相似文献
110.