2,472 research outputs found
Study of Trajectory of Spin-Stabilised Artillery Projectiles
Equations of motion for conventional spin-stabilised artillery projectile have been derived using a pseudo-stability axes system in addition to body-fixed and space-fixed axes systems. The aerodynamic forces and moments have been represented by their respective coefficients and the effects of Mach number and Reynolds number have been suitably accounted. The magnus terms which are significant at high rates of spin are estimated using a simple model. The set of equations have been partly linearised and solved numerically for a typical projectile using NAG system routines. Various trajectory parameters are computed and compared with the range-table data for the projectile. A parametric study had been carried out varying the aerodynamic coefficients to understand the sensitivity of the results obtained
3D Dirac semimetal Cd3As2: A review of material properties
Cadmium arsenide (Cd3As2) - a time-honored and widely explored material in
solid-state physics - has recently attracted considerable attention. This was
triggered by a theoretical prediction concerning the presence of 3D
symmetry-protected massless Dirac electrons, which could turn Cd3As2 into a 3D
analogue of graphene. Subsequent extended experimental studies have provided us
with compelling experimental evidence of conical bands in this system, and
revealed a number of interesting properties and phenomena. At the same time,
some of the material properties remain the subject of vast discussions despite
recent intensive experimental and theoretical efforts, which may hinder the
progress in understanding and applications of this appealing material. In this
review, we focus on the basic material parameters and properties of Cd3As2, in
particular those which are directly related to the conical features in the
electronic band structure of this material. The outcome of experimental
investigations, performed on Cd3As2 using various spectroscopic and transport
techniques within the past sixty years, is compared with theoretical studies.
These theoretical works gave us not only simplified effective models, but more
recently, also the electronic band structure calculated numerically using ab
initio methods.Comment: 16 pages, 16 figure
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Interaction of Phonons and Dirac Fermions on the Surface of Bi2Se3: A Strong Kohn Anomaly
We report the first measurements of phonon dispersion curves on the (001)
surface of the strong three-dimensional topological insulator Bi2Se3. The
surface phonon measurements were carried out with the aid of coherent helium
beam surface scattering techniques. The results reveal a prominent signature of
the exotic metallic Dirac fermion quasi-particles, including a strong Kohn
anomaly. The signature is manifest in a low energy isotropic convex dispersive
surface phonon branch with a frequency maximum of 1.8 THz, and having a
V-shaped minimum at approximately 2kF that defines the Kohn anomaly.
Theoretical analysis attributes this dispersive profile to the renormalization
of the surface phonon excitations by the surface Dirac fermions. The
contribution of the Dirac fermions to this renormalization is derived in terms
of a Coulomb-type perturbation model
One pion events by atmospheric neutrinos: A three flavor analysis
We study the one-pion events produced via neutral current (NC) and charged
current (CC) interactions by the atmospheric neutrinos. We analyze the ratios
of these events in the framework of oscillations between three neutrino
flavors. The ratios of the CC events induced by to that of the NC
events and a similar ratio defined with help us in distinguishing the
different regions of the neutrino parameter space.Comment: 14 pages, 4 figures (separate postscript files
Quantum nondemolition detection of a propagating microwave photon
The ability to nondestructively detect the presence of a single, traveling
photon has been a long-standing goal in optics, with applications in quantum
information and measurement. Realising such a detector is complicated by the
fact that photon-photon interactions are typically very weak. At microwave
frequencies, very strong effective photon-photon interactions in a waveguide
have recently been demonstrated. Here we show how this type of interaction can
be used to realize a quantum nondemolition measurement of a single propagating
microwave photon. The scheme we propose uses a chain of solid-state 3-level
systems (transmons), cascaded through circulators which suppress photon
backscattering. Our theoretical analysis shows that microwave-photon detection
with fidelity around 90% can be realized with existing technologies
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