38,734 research outputs found
Thermal spin-transfer in Fe-MgO-Fe tunnel junctions
We compute thermal spin transfer torques (TST) in Fe-MgO-Fe tunnel junctions
using a first principles wave function-matching method. At room temperature,
the TST in a junction with 3 MgO monolayers amounts to 10^-7J/m^2/K, which is
estimated to cause magnetization reversal for temperature differences over the
barrier of the order of 10 K. The large TST can be explained by multiple
scattering between interface states through ultrathin barriers. The angular
dependence of the TST can be very skewed, possibly leading to thermally induced
high-frequency generation.Comment: 5 pages, 5 figure
Dynamic reconfiguration technologies based on FPGA in software defined radio system
Partial Reconfiguration (PR) is a method for Field Programmable Gate Array (FPGA) designs which allows multiple applications to time-share a portion of an FPGA while the rest of the device continues to operate unaffected. Using this strategy, the physical layer processing architecture in Software Defined Radio (SDR) systems can benefit from reduced complexity and increased design flexibility, as different waveform applications can be grouped into one part of a single FPGA. Waveform switching often means not only changing functionality, but also changing the FPGA clock frequency. However, that is beyond the current functionality of PR processes as the clock components (such as Digital Clock Managers (DCMs)) are excluded from the process of partial reconfiguration. In this paper, we present a novel architecture that combines another reconfigurable technology, Dynamic Reconfigurable Port (DRP), with PR based on a single FPGA in order to dynamically change both functionality and also the clock frequency. The architecture is demonstrated to reduce hardware utilization significantly compared with standard, static FPGA design
Shot noise in magnetic tunnel junctions from first principles
We compute the shot noise in ballistic and disordered Fe/MgO/Fe tunnel
junctions by a wave function-matching method. For tunnel barriers with no more
than 5 atomic layers we find a suppression of the Fano factor as a function of
the magnetic configuration. For thicker MgO barriers the shot noise is
suppressed up to a threshold bias indicating the onset of resonant tunneling.
We find excellent agreement with recent experiments when interface disorder is
taken into accountComment: 5 pages,5 figure
The infrared spectra of ABC-stacking tri- and tetra-layer graphenes studied by first-principles calculations
The infrared absorption spectra of ABC-stacking tri- and tetra-layer
graphenes are studied using the density functional theory. It is found that
they exhibit very different characteristic peaks compared with those of
AB-stacking ones, caused by the different stacking sequence and interlayer
coupling. The anisotropy of the spectra with respect to the direction of the
light electric field is significant. The spectra are more sensitive to the
stacking number when the electric field is perpendicular to the graphene plane
due to the interlayer polarization. The high sensitivities make it possible to
identify the stacking sequence and stacking number of samples by comparing
theory and experiment.Comment: 7 pages, 5 figure
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Scenarios of energy efficiency and CO2 emissions reduction potential in the buildings sector in China to year 2050
As China’s rapid urbanization continues and urban dwellers become more affluent, energy use in buildings is expected to grow. To understand how this growth can be slowed, we explore four scenarios for Chinese buildings, ranging from a high-energy-demand scenario with no new energy policies to lowest energy demand under a techno-economic-potential scenario that assumes full deployment of cost-effective efficient and renewable technologies by 2050. We show that, in the high energy demand scenario, building energy demand has an average annual growth rate of about 2.8%, with slower growth rates in the other three scenarios. In all scenarios, CO2 emissions grow slower than energy, with building CO2 peaking around 2045 in the high energy demand scenario, and as early as 2030 in the techno-economic-potential scenario. We show that although various technological solutions, systems and practices can be very effective in minimizing building energy use, rigorous policies are needed to overcome multiple implementation barriers
Telling the difference between deceiving and truth telling: An experiment in a public space
The behavioral experiment presented in this paper investigated deception tasks (both concealment and lying) undertaken in a public space. The degree of risk of deception detection and the demands of self-regulation when deceiving were manipulated. The results showed a significant interaction effect between veracity and risk of deception detection, emerged for the body movement of “hand(s) in pocket(s)”. The incidence of “hand(s) in pocket(s)” was found to increase from truth telling to deceiving conditions when the risk of deception detection was higher, and to decrease from truth telling to deceiving conditions when the risk was lower. Higher risk of deception detection was also found in magnifying the “overall negative and controlled impression” displayed by both deceivers and truth tellers, compared to the lower risk of detection condition. We also discussed the possible effects of risk of deception detection and depletion of self-regulation, on deception behavior. Further studies and the connection between this study and the research community of computer vision and multimodel interaction is also discussed
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