637 research outputs found
An Evaluation of Georgia HOPE Scholarship Program: Effects of HOPE on Grade Inflation, Academic Performance and College Enrollment
Abstract pending
The Socially Constructive Aspects of Outside Agents in Community Decision-Making in a Rural Area
The outside-change agent is dangerous, something to be feared (based on past experiences, long since blurred by boredom and powerlessness) and not taken into the community. The outsider offers few, if any, tangible immediately useable resources -- only promises and fancy talk. Limited experience has taught the Appalachian that promises fade into misery and fancy talk to poverty. The self-fulfilling prophesy of inhospitality and disbelief in oneself, turn the Appalachian against the change agent and challenge the agent to leave the area out of self-felt persistent futility
A first-principles study of bilayer 1T'-WTe2/CrI3: A candidate topological spin filter
The ability to manipulate electronic spin channels in 2D materials is crucial
for realizing next-generation spintronics. Spin filters are spintronic
components that polarize spins using external electromagnetic fields or
intrinsic material properties like magnetism. Recently, topological protection
from backscattering has emerged as an enticing feature through which the
robustness of 2D spin filters might be enhanced. In this work, we propose and
then characterize one of the first 2D topological spin filters: bilayer
CrI3/1T'-WTe2. To do so, we use a combination of Density Functional Theory and
maximally localized Wannier functions to demonstrate that the bilayer (BL)
satisfies the principal criteria for being a topological spin filter; namely
that it is gapless, exhibits charge transfer from WTe2 to CrI3 that renders the
BL metallic despite the CrI3 retaining its monolayer ferromagnetism, and does
not retain the topological character of monolayer 1T'-WTe2. In particular, we
observe that the atomic magnetic moments on Cr from DFT are approximately 3.2
mB/Cr in the BL compared to 2.9 mB/Cr with small negative ferromagnetic (FM)
moments induced on the W atoms in freestanding monolayer CrI3. Subtracting the
charge and spin densities of the constituent monolayers from those of the BL
further reveals spin-polarized charge transfer from WTe2 to CrI3. We find that
the BL is topologically trivial by showing that its Chern number is zero.
Altogether, this evidence indicates that BL 1T'-WTe2/CrI3 is gapless, magnetic,
and topologically trivial, meaning that a terraced WTe2/CrI3 BL heterostructure
in which only a portion of a WTe2 monolayer is topped with CrI3 is a promising
candidate for a 2D topological spin filter. Our results further suggest that 1D
chiral edge states may be realized by stacking strongly hybridized FM
monolayers, like CrI3, atop 2D nonmagnetic Weyl semimetals like 1T'-WTe2
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Throughput and Fairness in Random Access Networks
This paper present an throughput analysis of log-utility and max-min fairness. Assuming all nodes interfere with each other, completely or partially, log-utility fairness significantly enhances the total throughput compared to max-min fairness since the nodes should have the same throughput in max-min fairness. The improvement is enlarged especially when the effect of cumulated interference from multiple senders cannot be ignored
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PBS: A Unified Priority-Based CPU Scheduler
A novel CPU scheduling policy is designed and implemented. It is a configurable policy in the sense that a tunable parameter is provided to change its behavior. With different settings of the parameter, this policy can emulate the first-come first-serve, the processing sharing, or the feedback policies, as well as different levels of their mixtures. This policy is implemented in the Linux kernel as a replacement of the default scheduler. The drastic changes of behaviors as the parameter changes are analyzed and simulated. Its performance is measured with the real systems by the workload generators and benchmarks
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Linear Approximation of Optimal Attempt Rate in Random Access Networks
While packet capture has been observed in real implementations of wireless devices randomly accessing shared channels, fair rate control algorithms based on accurate channel models that describe the phenomenon have not been developed. In this paper, using a general physical channel model, we develop the equation for the optimal attemp rate to maximize the aggregate log utility. We use the least squares method to approximate the equation to a linear function of the attempt rate. Our analysis on the approximation error shows that the linear function obtained is close enough to the original with the square of the residuals more than 0.9
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The PBS Policy: Some Properties and Their Proofs
In this report we analyze a configurable blind scheduler containing a continuous, tunable parameter. After the definition of this policy, we prove the property of no surprising interruption, the property of no permanent starvation, and two theorems about monotonicity of this policy. This technical report contains supplemental materials for the following publication: Hanhua Feng, Vishal Misra, and Dan Rubenstein, 'PBS: A unified priority-based scheduler', Proceedings of ACM SIGMETRICS '07, 2007
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