19,878 research outputs found
Quantum Goos-H\"{a}nchen shift and tunneling transmission at a curved step potential
We study the quantum Goos-H\"{a}nchen (GH) shift and the tunneling
transmission at a curved step potential by investigating the time evolution of
a wave packet. An initial wave packet is expanded in terms of the eigenmodes of
a circular step potential. Its time evolution is then given by the interference
of their simple eigenmode oscillations. We show that the GH shift along the
step boundary can be explained by the energy-dependent phase loss upon
reflection, which is defined by modifying the one-dimensional (1D) effective
potential derived from the 2D circular system. We also demonstrate that the
tunneling transmission of the wave packet is characterized by a free-space
image distant from the boundary. The tunneling transmission exhibits a rather
wide angle divergence and the direction of maximum tunneling is slightly
rotated from the tangent at the incident point, which is consistent with the
time delay of the tunneling wave packet computed in the 1D modified effective
potential
Rice monitoring using ENVISAT-ASAR data: preliminary results of a case study in the Mekong River Delta, Vietnam
Vietnam is one of the world’s largest rice exporting countries, and the fertile Mekong River Delta at the southern tip of Vietnam accounts for more than half of the country’s rice production. Unfortunately, a large part of rice crop growing time coincides with a rainy season, resulting in a limited number of cloud-free optical remote sensing images for rice monitoring. Synthetic aperture radar (SAR) data allows for observations independent of weather conditions and solar illumination, and is potentially well suited for rice crop monitoring.
The aim of the study was to apply new generation Envisat ASAR data with dual polarization (HH and VV) to rice cropping system mapping and monitoring in An Giang province, Mekong River Delta. Several sample areas were established on the ground, where selected rice parameters (e.g. rice height and biomass) are periodically being measured over a period of 12 months. A correlation analysis of rice parameters and radar imagery values is then being conducted to determine the significance and magnitude of the relationships.
This paper describes a review of the previous research studies on rice monitoring using SAR data, the context of this on-going study, and some preliminary results that provide insights on how ASAR imagery could be useful for rice crop monitoring. More work is being done to develop algorithms for mapping and monitoring rice cropping systems, and to validate a rice yield prediction model for one year cycle using time-series SAR imagery
HI-to-H2 Transitions in the Perseus Molecular Cloud
We use the Sternberg et al. (2014) theory for interstellar atomic to
molecular (HI-to-H) conversion to analyze HI-to-H transitions in five
(low-mass) star-forming and dark regions in the Perseus molecular cloud, B1,
B1E, B5, IC348, and NGC1333. The observed HI mass surface densities of 6.3 to
9.2 M pc are consistent with HI-to-H transitions dominated
by HI-dust shielding in predominantly atomic envelopes. For each source, we
constrain the dimensionless parameter , and the ratio ,
of the FUV intensity to hydrogen gas density. We find values from
5.0 to 26.1, implying characteristic atomic hydrogen densities 11.8 to 1.8
cm, for appropriate for Perseus. Our analysis
implies that the dusty HI shielding layers are probably multiphased, with
thermally unstable UNM gas in addition to cold CNM within the 21 cm kinematic
radius.Comment: 5 pages, 2 Figures. Minor improvements suggested by the referee.
Accepted for publication in the Astrophysical Journa
Quarkonium above deconfinement as an open quantum system
Quarkonium at temperatures above deconfinement is modeled as an open quantum
system, whose dynamics is determined not just by a potential energy and mass,
but also by a drag coefficient which characterizes its interaction with the
medium. The reduced density matrix for a heavy particle experiencing
dissipative forces is expressed as an integral over paths in imaginary time and
evaluated numerically. We demonstrate that dissipation could affect the
Euclidean heavy-heavy correlators calculated in lattice simulations at
temperatures just above deconfinement.Comment: 13 pages, 1 figur
Carnot rectifiability of sub-Riemannian manifolds with constant tangent
We show that if is a sub-Riemannian manifold and is a Carnot group
such that the nilpotentization of at almost every point is isomorphic to
, then there are subsets of of positive measure that embed into by
bilipschitz maps. Furthermore, is countably --rectifiable, i.e., all of
except for a null set can be covered by countably many such maps.Comment: 18 page
Avalanches in mean-field models and the Barkhausen noise in spin-glasses
We obtain a general formula for the distribution of sizes of "static
avalanches", or shocks, in generic mean-field glasses with
replica-symmetry-breaking saddle points. For the Sherrington-Kirkpatrick (SK)
spin-glass it yields the density rho(S) of the sizes of magnetization jumps S
along the equilibrium magnetization curve at zero temperature. Continuous
replica-symmetry breaking allows for a power-law behavior rho(S) ~ 1/(S)^tau
with exponent tau=1 for SK, related to the criticality (marginal stability) of
the spin-glass phase. All scales of the ultrametric phase space are implicated
in jump events. Similar results are obtained for the sizes S of static jumps of
pinned elastic systems, or of shocks in Burgers turbulence in large dimension.
In all cases with a one-step solution, rho(S) ~ S exp(-A S^2). A simple
interpretation relating droplets to shocks, and a scaling theory for the
equilibrium analog of Barkhausen noise in finite-dimensional spin glasses are
discussed.Comment: 6 pages, 1 figur
A New Powerful Nonparametric Rank Test for Ordered Alternative Problem
We propose a new nonparametric test for ordered alternative problem based on the rank difference between two observations from different groups. These groups are assumed to be independent from each other. The exact mean and variance of the test statistic under the null distribution are derived, and its asymptotic distribution is proven to be normal. Furthermore, an extensive power comparison between the new test and other commonly used tests shows that the new test is generally more powerful than others under various conditions, including the same type of distribution, and mixed distributions. A real example from an anti-hypertensive drug trial is provided to illustrate the application of the tests. The new test is therefore recommended for use in practice due to easy calculation and substantial power gain
Enabling Multi-Hop Remote Method Invocation in Device-To-Device Networks
To avoid shrinking down the performance and preserve energy, low-end mobile devices can collaborate with the nearby ones by offloading computation intensive code. However, despite the long research history, code offloading is dilatory and unfit for applications that require rapidly consecutive requests per short period. Even though Remote Procedure Call (RPC) is apparently one possible approach that can address this problem, the RPC-based or message queue-based techniques are obsolete or unwieldy for mobile platforms. Moreover, the need of accessibility beyond the limit reach of the device-to-device (D2D) networks originates another problem. This article introduces a new software framework to overcome these shortcomings by enabling routing RPC architecture on multiple group device-to-device networks. Our framework provides annotations for declaring distribution decision and out-of-box components that enable peer-to-peer offloading, even when a client app and the service provider do not have a direct network link or Internet connectivity. This article also discusses the two typical mobile applications that built on top of the framework for chatting and remote browsing services, as well as the empirical experiments with actual test-bed devices to unveil the low overhead conduct and similar performance as RPC in reality
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