13,844 research outputs found
Polar cap observations of thermospheric winds and temperatures at Sondre Stromfjord, Greenland
An agreement of averaged temperatures with mass spectrometer incoherent scatter radar looked reasonable for several nights, but for many nights there are differences: (1) midnight period of cooling, and (2) temperature increases associated with overhead crossings of the auroral belt. The observed rise of the temperature before dawn in conjunction with the high 6300A intensities suggests a connection between the two effects: soft particle precipitation most likely candidate but frictional heating perhaps also a possibility. A comparison with the thermospheric general circulation model calculations also needed. The technique for formulating neutral wind vectors performs well in most cases. The observed patterns show evidence for abatement in the midnight sector in the meridional wind component at the separatix between the two cells with a frequency of the order of 20 to 25%, also observed in radar observations at Sondre Stromfjord. The observed patterns for magnetically quiet conditions show flow characteristic of the auroral belt, westward in evening followed by the midnight surge. The observed patterns for active conditions show dominance either by the evening cell or the morning cell, but most often the former
Dynamic Arrival Rate Estimation for Campus Mobility on Demand Network Graphs
Mobility On Demand (MOD) systems are revolutionizing transportation in urban
settings by improving vehicle utilization and reducing parking congestion. A
key factor in the success of an MOD system is the ability to measure and
respond to real-time customer arrival data. Real time traffic arrival rate data
is traditionally difficult to obtain due to the need to install fixed sensors
throughout the MOD network. This paper presents a framework for measuring
pedestrian traffic arrival rates using sensors onboard the vehicles that make
up the MOD fleet. A novel distributed fusion algorithm is presented which
combines onboard LIDAR and camera sensor measurements to detect trajectories of
pedestrians with a 90% detection hit rate with 1.5 false positives per minute.
A novel moving observer method is introduced to estimate pedestrian arrival
rates from pedestrian trajectories collected from mobile sensors. The moving
observer method is evaluated in both simulation and hardware and is shown to
achieve arrival rate estimates comparable to those that would be obtained with
multiple stationary sensors.Comment: Appears in 2016 IEEE/RSJ International Conference on Intelligent
Robots and Systems (IROS).
http://ieeexplore.ieee.org/abstract/document/7759357
Dyon Spectrum in CHL Models
We propose a formula for the degeneracy of quarter BPS dyons in a class of
CHL models. The formula uses a modular form of a subgroup of the genus two
modular group Sp(2,Z). Our proposal is S-duality invariant and reproduces
correctly the entropy of a dyonic black hole to first non-leading order for
large values of the charges.Comment: LaTeX file, 38 pages, minor changes in section 3.3(v2), minor changes
in introduction, appendix A and C(v3
Quantum interference by two temporally distinguishable pulses
We report a two-photon interference effect, in which the entangled photon
pairs are generated from two laser pulses well-separated in time. In a single
pump pulse case, interference effects did not occur in our experimental scheme.
However, by introducing a second pump pulse delayed in time, quantum
interference was then observed. The visibility of the interference fringes
shows dependence on the delay time between two laser pulses. The results are
explained in terms of indistinguishability of biphoton amplitudes which
originated from two temporally separated laser pulses.Comment: two-column, 4pages, submitted to PRA, minor change
GRID3D-v2: An updated version of the GRID2D/3D computer program for generating grid systems in complex-shaped three-dimensional spatial domains
In order to generate good quality systems for complicated three-dimensional spatial domains, the grid-generation method used must be able to exert rather precise controls over grid-point distributions. Several techniques are presented that enhance control of grid-point distribution for a class of algebraic grid-generation methods known as the two-, four-, and six-boundary methods. These techniques include variable stretching functions from bilinear interpolation, interpolating functions based on tension splines, and normalized K-factors. The techniques developed in this study were incorporated into a new version of GRID3D called GRID3D-v2. The usefulness of GRID3D-v2 was demonstrated by using it to generate a three-dimensional grid system in the coolent passage of a radial turbine blade with serpentine channels and pin fins
Visualizing Quantum Well State Perturbations of Metallic Thin Films near Stacking Fault Defects
We demonstrate that quantum well states (QWS) of thin Pb films are highly
perturbed within the proximity of intrinsic film defects. Scanning Tunneling
Spectroscopy (STM/STS) measurements indicate that the energy of these states
have a strong distance dependence within 4 nm of the defect with the strongest
energetic fluctuations equaling up to 100 meV. These localized perturbations
show large spatially-dependent asymmetries in the LDOS around the defect site
for each corresponding quantum well state. These energetic fluctuations can be
described by a simple model which accounts for fluctuations in the confinement
potential induced by topographic changes.Comment: Updated Versio
Pseudomoduli Dark Matter
We point out that pseudomoduli -- tree-level flat directions that often
accompany dynamical supersymmetry breaking -- can be natural candidates for
TeV-scale dark matter in models of gauge mediation. The idea is general and can
be applied to different dark matter scenarios, including (but not limited to)
those of potential relevance to recent cosmic ray anomalies. We describe the
requirements for a viable model of pseudomoduli dark matter, and we analyze two
example models to illustrate the general mechanism -- one where the
pseudomoduli carry Higgsino-like quantum numbers, and another where they are SM
singlets but are charged under a hidden-sector gauge group.Comment: 20 pages, refs adde
Simulation of valveless micropump and mode analysis
In this work, a 3-D simulation is performed to study for the solid-fluid
coupling effect driven by piezoelectric materials and utilizes asymmetric
obstacles to control the flow direction. The result of simulation is also
verified. For a micropump, it is crucial to find the optimal working frequency
which produce maximum net flow rate. The PZT plate vibrates under the first
mode, which is symmetric. Adjusting the working frequency, the maximum flow
rate can be obtained. For the micrpump we studied, the optimal working
frequency is 3.2K Hz. At higher working frequency, say 20K Hz, the fluid-solid
membrane may come out a intermediate mode, which is different from the first
mode and the second mode. It is observed that the center of the mode drifts.
Meanwhile, the result shows that a phase shift lagging when the excitation
force exists in the vibration response. Finally, at even higher working
frequency, say 30K Hz, a second vibration mode is observed.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
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