111 research outputs found
A first Experimental Investigation of the Practical Efficiency of Battery Scheduling
Nowadays, mobile devices are used more and more, and their battery lifetime is a key concern. In this paper, we concentrate on a method called battery scheduling with the aim to optimize the battery lifetime of mobile devices. This technique has already been largely theoretically studied in other papers. It consists, for systems containing multiple batteries, in switching the load from one battery to the other. Then, while following a given scheduling sequence, advantage can be taken from the recovery and rate capacity effects. However, little studies with experimental data of battery scheduling have been found. In this paper we describe a simple setup for measuring the possible gain of battery scheduling, and give some exploratory results for two types of real batteries: a smart Li-Ion battery used in the Thales personal communication system and a more commonly used NiCd battery. The results, so far, show that system lifetime extension is not systematic, and generally can only reach less then 10%
Loading Stark-decelerated molecules into electrostatic quadrupole traps
Beams of neutral polar molecules in a low-field seeking quantum state can be
slowed down using a Stark decelerator, and can subsequently be loaded and
confined in electrostatic quadrupole traps. The efficiency of the trap loading
process is determined by the ability to couple the decelerated packet of
molecules into the trap without loss of molecules and without heating. We
discuss the inherent difficulties to obtain ideal trap loading, and describe
and compare different trap loading strategies. A new "split-endcap" quadrupole
trap design is presented that enables improved trap loading efficiencies. This
is experimentally verified by comparing the trapping of OH radicals using the
conventional and the new quadrupole trap designs
Throughput modeling of the IEEE MAC for sensor networks
In this paper we provide a model for analyzing the saturation throughput of the ieee 802.15.4 mac protocol, which is the de-facto standard for wireless sensor networks, ensuring fair access to the channel. To this end, we introduce the concept of a natural layer, which reflects the time that a sensor node typically has to wait prior to sending a packet. The model is simple and provides new insight how the throughput depends on the protocol parameters and the number of nodes in the network. Validation experiments with simulations demonstrate that the model is highly accurate for a wide range of parameter settings of the mac protocol, and applicable to both large and small networks. As a byproduct, we discuss fundamental differences in the protocol stack and corresponding throughput models of the popular 802.11 standard
Optical pumping of trapped neutral molecules by blackbody radiation
Optical pumping by blackbody radiation is a feature shared by all polar
molecules and fundamentally limits the time that these molecules can be kept in
a single quantum state in a trap. To demonstrate and quantify this, we have
monitored the optical pumping of electrostatically trapped OH and OD radicals
by room-temperature blackbody radiation. Transfer of these molecules to
rotationally excited states by blackbody radiation at 295 K limits the
trapping time for OH and OD in the state to
2.8 s and 7.1 s, respectively.Comment: corrected small mistakes; added journal reference
Reflection of OH molecules from magnetic mirrors
We have reflected a Stark-decelerated beam of OH molecules under normal
incidence from mirrors consisting of permanent magnets. Two different types of
magnetic mirrors have been demonstrated. A long-range flat mirror made from a
large disc magnet has been used to spatially focus the reflected beam in the
longitudinal direction ("bunching"). A short-range curved mirror composed of an
array of small cube magnets allows for transverse focusing of the reflected
beam.Comment: 10 pages, 5 figure
Electrostatic trapping of metastable NH molecules
We report on the Stark deceleration and electrostatic trapping of NH
() radicals. In the trap, the molecules are excited on the
spin-forbidden transition and detected via
their subsequent fluorescence to the ground state. The 1/e
trapping time is 1.4 0.1 s, from which a lower limit of 2.7 s for the
radiative lifetime of the state is deduced. The spectral
profile of the molecules in the trapping field is measured to probe their
spatial distribution. Electrostatic trapping of metastable NH followed by
optical pumping of the trapped molecules to the electronic ground state is an
important step towards accumulation of these radicals in a magnetic trap.Comment: replaced with final version, added journal referenc
Poster: Optimal dispatching policies for parallel processor sharing nodes with partial information
Production and deceleration of a pulsed beam of metastable NH () radicals
We report on the production of a pulsed molecular beam of metastable NH () radicals and present first results on the Stark deceleration of the
NH () radicals from 550 m/s to 330 m/s. The
decelerated molecules are excited on the spin-forbidden transition, and detected via their subsequent spontaneous
fluorescence to the ground-state. These experiments
demonstrate the feasibility of our recently proposed scheme [Phys. Rev. A 64
(2001) 041401] to accumulate ground-state NH radicals in a magnetic trap.Comment: 11 pages, 4 figures, v2: fixed author name for web-abstract, no
changes to manuscrip
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