3,136 research outputs found
High Intensity Laser Power Beaming for Wireless Power Transmission
This paper describes work supporting the development of a high intensity laser power beaming (HILPB) system for the purpose of wireless power transmission. The main contribution of this research is utilizing high intensity lasers to illuminate vertical multi-junction (VMJ) solar cells developed by NASA-GRC. Several HILPB receivers are designed, constructed and evaluated with various lasers to assess the performance of the VMJ cells and the receiver under a variety of conditions. Several matters such as parallel cell back-feeding, optimal receiver geometry, laser wavelength, non-uniform illumination and thermal effects at high intensities are investigated. Substantial power densities are achieved, and suggestions are made to improve the performance of the system in future iterations. Thus far, the highest amount of energy obtained from a receiver during these tests was 23.7778 watts. In addition, one VMJ cell was able to achieve a power density of 13.6 watts per cm2, at a conversion efficiency of 24 . These experiments confirm that the VMJ technology can withstand and utilize the high intensity laser energy without damage and/or significant reduction in the conversion efficienc
High Intensity Laser Power Beaming for Wireless Power Transmission
This paper describes work supporting the development of a high intensity laser power beaming (HILPB) system for the purpose of wireless power transmission. The main contribution of this research is utilizing high intensity lasers to illuminate vertical multi-junction (VMJ) solar cells developed by NASA-GRC. Several HILPB receivers are designed, constructed and evaluated with various lasers to assess the performance of the VMJ cells and the receiver under a variety of conditions. Several matters such as parallel cell back-feeding, optimal receiver geometry, laser wavelength, non-uniform illumination and thermal effects at high intensities are investigated. Substantial power densities are achieved, and suggestions are made to improve the performance of the system in future iterations. Thus far, the highest amount of energy obtained from a receiver during these tests was 23.7778 watts. In addition, one VMJ cell was able to achieve a power density of 13.6 watts per cm2, at a conversion efficiency of 24 . These experiments confirm that the VMJ technology can withstand and utilize the high intensity laser energy without damage and/or significant reduction in the conversion efficienc
A Bag-of-Tasks Scheduler Tolerant to Temporal Failures in Clouds
Cloud platforms have emerged as a prominent environment to execute high
performance computing (HPC) applications providing on-demand resources as well
as scalability. They usually offer different classes of Virtual Machines (VMs)
which ensure different guarantees in terms of availability and volatility,
provisioning the same resource through multiple pricing models. For instance,
in Amazon EC2 cloud, the user pays per hour for on-demand VMs while spot VMs
are unused instances available for lower price. Despite the monetary
advantages, a spot VM can be terminated, stopped, or hibernated by EC2 at any
moment.
Using both hibernation-prone spot VMs (for cost sake) and on-demand VMs, we
propose in this paper a static scheduling for HPC applications which are
composed by independent tasks (bag-of-task) with deadline constraints. However,
if a spot VM hibernates and it does not resume within a time which guarantees
the application's deadline, a temporal failure takes place. Our scheduling,
thus, aims at minimizing monetary costs of bag-of-tasks applications in EC2
cloud, respecting its deadline and avoiding temporal failures. To this end, our
algorithm statically creates two scheduling maps: (i) the first one contains,
for each task, its starting time and on which VM (i.e., an available spot or
on-demand VM with the current lowest price) the task should execute; (ii) the
second one contains, for each task allocated on a VM spot in the first map, its
starting time and on which on-demand VM it should be executed to meet the
application deadline in order to avoid temporal failures. The latter will be
used whenever the hibernation period of a spot VM exceeds a time limit.
Performance results from simulation with task execution traces, configuration
of Amazon EC2 VM classes, and VMs market history confirms the effectiveness of
our scheduling and that it tolerates temporal failures
Operator Positivity and Analytic Models of Commuting Tuples of Operators
We study analytic models of operators of class with natural
positivity assumptions. In particular, we prove that for an
-hypercontraction on a Hilbert space ,
there exists a Hilbert space and a partially isometric multiplier
such that
\mathcal{H} \cong \mathcal{Q}_{\theta} = A^2_m(\mathcal{H}) \ominus \theta
H^2(\mathcal{E}), \quad \quad \mbox{and} \quad \quad T \cong
P_{\mathcal{Q}_{\theta}} M_z|_{\mathcal{Q}_{\theta}},where is the
weighted Bergman space and is the Hardy space over the unit disc
. We then proceed to study and develop analytic models for doubly
commuting -tuples of operators and investigate their applications to joint
shift co-invariant subspaces of reproducing kernel Hilbert spaces over
polydisc. In particular, we completely analyze doubly commuting quotient
modules of a large class of reproducing kernel Hilbert modules, in the sense of
Arazy and Englis, over the unit polydisc .Comment: Revised. 16 pages. To appear in Studia Mathematic
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