1,534 research outputs found
Antisite Disorder-induced Exchange Bias Effect in Multiferroic Y2CoMnO6
Exchange bias effect in the ferromagnetic double perovskite compound
YCoMnO, which is also a multiferroic, is reported. The exchange bias,
observed below 8~K, is explained as arising due to the interface effect between
the ferromagnetic and antiferromagnetic clusters created by {\it antisite}
disorder in this material. Below 8~K, prominent ferromagnetic hysteresis with
metamagnetic "steps" and significant coercive field, 10~kOe are
observed in this compound which has a 75~K. A model based on
growth of ferromagnetic domains overcoming the elastic energy of structurally
pinned magnetic interfaces, which closely resembles martensitic-like
transitions, is adapted to explain the observed effects. The role of {\it
antisite} disorder in creating the domain structure leading to exchange bias
effect is highlighted in the present work.Comment: 4 pages two-column, 4 figures, accepted to Appl. Phys. Let
Supersolid and solitonic phases in one-dimensional Extended Bose-Hubbard model
We report our findings on quantum phase transitions in cold bosonic atoms in
a one dimensional optical lattice using the finite size density matrix
renormalization group method in the framework of the extended Bose-Hubbard
model. We consider wide ranges of values for the filling factors and the
nearest neighbor interactions. At commensurate fillings, we obtain two
different types of charge density wave phases and a Mott insulator phase.
However, departure from commensurate fillings yield the exotic supersolid phase
where both the crystalline and the superfluid orders coexist. In addition, we
obtain signatures for solitary waves and also superfluidity.Comment: 7 pages, 11 figure
Geometric dimensioning and tolerancing a tool for concurrent engineering
The concept of Concurrent Engineering recognizes an immediate need for a new design environment and technology and so requires extensive interdisciplinary cooperation and integration of diverse functions of a manufacturing organization such as marketing, design, manufacturing and finance. One of the key factors to achieve successful integration among the departments is better communication and it becomes imperative in cases of varying levels of communication needs, especially in interdepartmental cases.
Concurrent Engineering is a philosophy which provides certain benefits. There are various tools and methods available for implementation of Concurrent Engineering concepts. One of the tools is Geometric Dimensioning & Tolerancing (GD & T), which can be used for indespensible communication of exact part design and its proper execution. Unlike other tools, GD & T concepts emphasize on the integration of various functions in a manufacturing organization.
This thesis discusses the applicability of Geometric Dimensioning and Tol-erancing as an integrating tool for related functional departments in the concurrent environment. It also establishes the synchronization between the objectives of the two concepts. Also, it discusses the effect of using GD & T on vendor lead time and manufacturing lead time. The effect on the product quality, the cost economics and the learning curve is also investigated.
Lastly, the thesis concludes that the implementation of GD & T concepts automatically attains the objectives of concurrent engineering. The use of GD & T in industries may lead to widespread implementation of the concurrent engineering concepts globally. Therefore, it can be considered as a medium or tool for Concurrent Engineering
Many-body approach to low-lying collective excitations in a BEC approaching collapse
An approximate many-body theory incorporating two-body correlations has been
employed to calculate low-lying collective multipole frequencies in a
Bose-Einstein condensate containing bosons, for different values of the
interaction parameter . Significant difference
from the variational estimate of the Gross-Pitaevskii equation has been found
near the collapse region. This is attributed to two-body correlations and
finite range attraction of the realistic interatomic interaction. A large
deviation from the hydrodynamic model is also seen for the second monopole
breathing mode and the quadrupole mode for large positive .Comment: 8 pages, 2 figure
Magnetic ordering in double perovskites RCoMnO (R= Y,Tb) investigated by high resolution neutron spectroscopy
We have investigated low energy nuclear spin excitations in double perovskite
compounds RCoMnO (R = Y,Tb) by inelastic neutron scattering with a
high-resolution back-scattering spectrometer. We observed inelastic signals at
about 2.1 eV for YCoMnO and also for TbCoMnO at T = 2 K in
both energy loss and energy gain sides. We interpret these inelastic peaks to
be due to the transitions between the hyperfine split nuclear levels of
Co nucleus. The inelastic peaks move towards the central elastic peak
and finally merge with it at the magnetic ordering temperature . The
energy of the low energy excitations decreases continuously and becomes zero at
K for YCoMnO and K for
TbCoMnO. For TbCoMnO, which contains magnetic rare-earth ions,
additional quasielastic scattering due presumably to the fluctuations of large
Tb magnetic moments was observed. The present study reveals the magnetic
ordering of the Co sublattice. The results of this investigation along with
that obtained by us for other compounds indicate the presence of unquenched
orbital moments in some of the Co compounds
Type I singularities and the Phantom Menace
We consider the future dynamics of a transient phantom dominated phase of the
universe in LQC and in the RS braneworld, which both have a non-standard
Friedmann equation. We find that for a certain class of potentials, the Hubble
parameter oscillates with simple harmonic motion in the LQC case and therefore
avoids any future singularity. For more general potentials we find that damping
effects eventually lead to the Hubble parameter becoming constant. On the other
hand in the braneworld case we find that although the type I singularity can be
avoided, the scale factor still diverges at late times.Comment: More references added. Final PRD versio
Live Soap: Order, Fluctuations and Instabilities in Active Smectics
We construct a hydrodynamic theory of noisy, apolar active smectics, in bulk
suspension or on a substrate. Our predictions include: quasi-long-ranged
smectic order in dimension d = 2, and long- ranged in d = 3, extending
previously published results to all dynamical regimes; Kosterlitz-Thouless
melting to an active nematic at high and low concentrations in d = 2; nonzero
second-sound speed parallel to the layers; the suppression of giant number
fluctuations by smectic elasticity; instability to spontaneous undulation and
flow in bulk contractile smectics; a layer spacing instability, possibly
oscillatory, for large enough extensile active stresses.Comment: 5 pages, 1 figure, submitted to Phys Rev Let
Photonuclear reactions of actinides in the giant dipole resonance region
Photonuclear reactions at energies covering the giant dipole resonance (GDR)
region are analyzed with an approach based on nuclear photoabsorption followed
by the process of competition between light particle evaporation and fission
for the excited nucleus. The photoabsorption cross section at energies covering
the GDR region is contributed by both the Lorentz type GDR cross section and
the quasideuteron cross section. The evaporation-fission process of the
compound nucleus is simulated in a Monte-Carlo framework. Photofission reaction
cross sections are analyzed in a systematic manner in the energy range of
10-20 MeV for the actinides Th, U and Np.
Photonuclear cross sections for the medium-mass nuclei Cu and Zn,
for which there are no fission events, are also presented. The study reproduces
satisfactorily the available experimental data of photofission cross sections
at GDR energy region and the increasing trend of nuclear fissility with the
fissility parameter for the actinides.Comment: 4 pages including 2 tables and 1 figur
Multiphysics modelling of a hybrid magnetic bearing (HMB) for calculating power loss and temperature with different loss minimization strategies
This paper represents a multiphysics modelling for calculating loss and temperature of a hybrid magnetic bearing (HMB) using finite element method (FEM). It also addresses the different loss minimization strategies for the HMB. The main sources of losses are identified as eddy current loss in permanent magnets, flywheel and copper loss in electromagnet. Due to these losses, the temperature distribution in different portions of HMB is computed using coupled field analysis. To minimize the eddy current loss, slits are fabricated in flywheel plate instead of a solid flywheel. The improvement of the control current is investigated by providing a coating of different metal, like copper, brass and stainless steel on the flywheel. A zero bias current (ZBC) scheme has been introduced where no bias current is required to levitate the rotor or to avoid singularity due to external disturbances, thus reducing the copper loss
A new HPTLC method for estimation of Bamifylline: Development and validation consideration
A new and rapid high-performance thin-layer chromatographic (HPTLC) method was developed and validated for quantitative determination of Bamifylline. The HPTLC separation was achieved on an aluminum-backed layer of silica gel 60F 254 using methanol : toluene (2.5 + 7.5 v/v) as mobile phase. Quantitation was achieved by densitometric analysis at 277 nm over the concentration range of 100600 ng/spot. The method was found to give compact spot for the drug ( R f = 0.51 0.01). The linear regression analysis data for the calibration plots showed good linear relationship with r 2 = 0.9995. The method was validated for precision, recovery, repeatability, and robustness as per the International Conference on Harmonization guidelines. The minimum detectable amount was found to be 7.65 ng/spot, whereas the limit of quantitation was found to be 23.19 ng/spot. Statistical analysis of the data showed that the method is precise, accurate, reproducible, sensitive and selective for the analysis of Bamifylline. The method was successfully employed for the estimation of Bamifylline as a bulk drug and in commercially available tablet formulation
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