7,788 research outputs found
Hybrid Geometric Reduction of Hybrid Systems
This paper presents a unifying framework in
which to carry out the hybrid geometric reduction of hybrid
systems, generalizing classical reduction to a hybrid setting
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Transient analysis and synthesis of linear circuits using constraint logic programming
In this paper describes the design of a transient analysis program for linear circuits and its implementation
in a Constraint Logic Programming language, CLP(R). The transient analysis program parses the input
circuit description into a network graph, analyses its semantic correctness and then performs the transient
analysis. The test results show that the program is at least 97% accurate when run at two decimal
places. We have also compared the performance of our program with a commercial package implemented
in an imperative language. The advantages of implementing the analysis program in a CLP language
include: quick construction and ease of maintenance. We also report on the synthesis of generation of a
circuit with given transient characteristics
A computational model for three-dimensional incompressible wall jets with large cross flow
A computational model for the flow field of three dimensional incompressible wall jets prototypic of thrust augmenting ejectors with large cross flow is presented. The formulation employs boundary layer equations in an orthogonal curvilinear coordinate system. Simulation of laminar as well as turbulen wall jets is reported. Quantification of jet spreading, jet growth, nominal separation, and jet shrink effects due to corss flow are discussed
Sufficient conditions for the existence of Zeno behavior in a class of nonlinear hybrid systems via constant approximations
The existence of Zeno behavior in hybrid systems
is related to a certain type of equilibria, termed Zeno equilibria,
that are invariant under the discrete, but not the continuous,
dynamics of a hybrid system. In analogy to the standard
procedure of linearizing a vector field at an equilibrium point to
determine its stability, in this paper we study the local behavior
of a hybrid system near a Zeno equilibrium point by considering
the value of the vector field on each domain at this point, i.e., we
consider constant approximations of nonlinear hybrid systems.
By means of these constant approximations, we are able to
derive conditions that simultaneously imply both the existence
of Zeno behavior and the local exponential stability of a Zeno
equilibrium point. Moreover, since these conditions are in terms
of the value of the vector field on each domain at a point, they
are remarkably easy to verify
The Hydrodynamical Limit of Quantum Hall system
We study the current algebra of FQHE systems in the hydrodynamical limit of
small amplitude, long-wavelength fluctuations. We show that the algebra
simplifies considerably in this limit. The hamiltonian is expressed in a
current-current form and the operators creating inter-Landau level and lowest
Landau level collective excitations are identified.Comment: Revtex, 16 page
Magnetotransport of Dirac Fermions on the surface of a topological insulator
We study the properties of Dirac fermions on the surface of a topological
insulator in the presence of crossed electric and magnetic fields. We provide
an exact solution to this problem and demonstrate that, in contrast to their
counterparts in graphene, these Dirac fermions allow relative tuning of the
orbital and Zeeman effects of an applied magnetic field by a crossed electric
field along the surface. We also elaborate and extend our earlier results on
normal metal-magnetic film-normal metal (NMN) and normal metal-barrier-magnetic
film (NBM) junctions of topological insulators [Phys. Rev. Lett. {\bf 104},
046403 (2010)]. For NMN junctions, we show that for Dirac fermions with Fermi
velocity , the transport can be controlled using the exchange field
of a ferromagnetic film over a region of width . The
conductance of such a junction changes from oscillatory to a monotonically
decreasing function of beyond a critical which leads to the
possible realization of magnetic switches using these junctions. For NBM
junctions with a potential barrier of width and potential , we find
that beyond a critical , the criteria of conductance maxima
changes from to for
integer . Finally, we compute the subgap tunneling conductance of a normal
metal-magnetic film-superconductor (NMS) junctions on the surface of a
topological insulator and show that the position of the peaks of the zero-bias
tunneling conductance can be tuned using the magnetization of the ferromagnetic
film. We point out that these phenomena have no analogs in either conventional
two-dimensional materials or Dirac electrons in graphene and suggest
experiments to test our theory.Comment: 11 pages, 12 figures; v
Tuning the conductance of Dirac fermions on the surface of a topological insulator
We study the transport properties of the Dirac fermions with Fermi velocity
on the surface of a topological insulator across a ferromagnetic strip
providing an exchange field over a region of width . We show
that the conductance of such a junction changes from oscillatory to a
monotonically decreasing function of beyond a critical . This
leads to the possible realization of a magnetic switch using these junctions.
We also study the conductance of these Dirac fermions across a potential
barrier of width and potential in the presence of such a
ferromagnetic strip and show that beyond a critical , the
criteria of conductance maxima changes from
to for integer . We point out that these novel phenomena
have no analogs in graphene and suggest experiments which can probe them.Comment: v1 4 pages 5 fig
Anharmonic quantum contribution to vibrational dephasing
Based on a quantum Langevin equation and its corresponding Hamiltonian within
a c-number formalism we calculate the vibrational dephasing rate of a cubic
oscillator. It is shown that leading order quantum correction due to
anharmonicity of the potential makes a significant contribution to the rate and
the frequency shift. We compare our theoretical estimates with those obtained
from experiments for small diatomics , and .Comment: 21 pages, 1 figure and 1 tabl
A consistent design procedure for supercritical airfoils in free air and a wind tunnel
A computational inverse procedure for transonic airfoils in which shapes are determined supporting prescribed pressure distributions is presented. The method uses the small disturbance equation and a consistent analysis-design differencing procedure at the airfoil surface. This avoids the intermediate analysis-design-analysis iterations. The effect of any openness at the trailing edge is taken onto account by adding an effective source term in the far field. The final results from a systematic expansion procedure which models the far field for solid, ideal slotted, and free jet tunnel walls are presented along with some design results for the associated boundary conditions and those for a free flight
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