273,983 research outputs found
Invariant graphical method for electron-atom scattering coupled-channel equations
We present application examples of a graphical method for the efficient
construction of potential matrix elements in quantum physics or quantum
chemistry. The simplicity and power of this method are illustrated through
several examples. In particular, a complete set of potential matrix elements
for electron-Lithium scattering are derived for the first time using this
method, which removes the frozen core approximation adopted by previous
studies. This method can be readily adapted to study other many-body quantum
systems
Microwave induced elastic deformation of a metallic thin film
The microwave induced elastic deformation of a metallic thin film is computed
numerically and we found that the deformation can be significantly enhanced at
resonance. We show that an analytical transmission line model can reproduce the
numerical results almost quantitatively and at the same time reveal the
underlying physics.Comment: 8 pages,3 figure
Analytical Results For The Steady State Of Traffic Flow Models With Stochastic Delay
Exact mean field equations are derived analytically to give the fundamental
diagrams, i.e., the average speed - car density relations, for the
Fukui-Ishibashi one-dimensional traffic flow cellular automaton model of high
speed vehicles with stochastic delay. Starting with the basic
equation describing the time evolution of the number of empty sites in front of
each car, the concepts of inter-car spacings longer and shorter than are
introduced. The probabilities of having long and short spacings on the road are
calculated. For high car densities , it is shown that
inter-car spacings longer than will be shortened as the traffic flow
evolves in time, and any initial configurations approach a steady state in
which all the inter-car spacings are of the short type. Similarly for low car
densities , it can be shown that traffic flow approaches an
asymptotic steady state in which all the inter-car spacings are longer than
. The average traffic speed is then obtained analytically as a function of
car density in the asymptotic steady state. The fundamental diagram so obtained
is in excellent agreement with simulation data.Comment: 12 pages, latex, 2 figure
Paid Peering, Settlement-Free Peering, or Both?
With the rapid growth of congestion-sensitive and data-intensive
applications, traditional settlement-free peering agreements with best-effort
delivery often do not meet the QoS requirements of content providers (CPs).
Meanwhile, Internet access providers (IAPs) feel that revenues from end-users
are not sufficient to recoup the upgrade costs of network infrastructures.
Consequently, some IAPs have begun to offer CPs a new type of peering
agreement, called paid peering, under which they provide CPs with better data
delivery quality for a fee. In this paper, we model a network platform where an
IAP makes decisions on the peering types offered to CPs and the prices charged
to CPs and end-users. We study the optimal peering schemes for the IAP, i.e.,
to offer CPs both the paid and settlement-free peering to choose from or only
one of them, as the objective is profit or welfare maximization. Our results
show that 1) the IAP should always offer the paid and settlement-free peering
under the profit-optimal and welfare-optimal schemes, respectively, 2) whether
to simultaneously offer the other peering type is largely driven by the type of
data traffic, e.g., text or video, and 3) regulators might want to encourage
the IAP to allocate more network capacity to the settlement-free peering for
increasing user welfare
Optical spectroscopy study of the collapsed tetragonal phase of CaFe(AsP) single crystals
We present an optical spectroscopy study on P-doped CaFeAs which
experiences a structural phase transition from tetragonal to collapsed
tetragonal (cT) phase near 75 K. The measurement reveals a sudden reduction of
low frequency spectral weight and emergence of a new feature near 3200 \cm (0.4
eV) in optical conductivity across the transition, indicating an abrupt
reconstruction of band structure. The appearance of new feature is related to
the interband transition arising from the sinking of hole bands near
point below Fermi level in the cT phase, as expected from the density function
theory calculations in combination with the dynamical mean field theory.
However, the reduction of Drude spectral weight is at variance with those
calculations. The measurement also indicates an absence of the abnormal
spectral weight transfer at high energy (near 0.5-0.7 eV) in the cT phase,
suggesting a suppression of electron correlation effect.Comment: 6 pages, 4 figure
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