96 research outputs found
Algorithm and Architecture for Path Metric Aided Bit-Flipping Decoding of Polar Codes
Polar codes attract more and more attention of researchers in recent years,
since its capacity achieving property. However, their error-correction
performance under successive cancellation (SC) decoding is inferior to other
modern channel codes at short or moderate blocklengths. SC-Flip (SCF) decoding
algorithm shows higher performance than SC decoding by identifying possibly
erroneous decisions made in initial SC decoding and flipping them in the
sequential decoding attempts. However, it performs not well when there are more
than one erroneous decisions in a codeword. In this paper, we propose a path
metric aided bit-flipping decoding algorithm to identify and correct more
errors efficiently. In this algorithm, the bit-flipping list is generated based
on both log likelihood ratio (LLR) based path metric and bit-flipping metric.
The path metric is used to verify the effectiveness of bit-flipping. In order
to reduce the decoding latency and computational complexity, its corresponding
pipeline architecture is designed. By applying these decoding algorithms and
pipeline architecture, an improvement on error-correction performance can be
got up to 0.25dB compared with SCF decoding at the frame error rate of
, with low average decoding latency.Comment: 6 pages, 6 figures, IEEE Wireless Communications and Networking
Conference (2019 WCNC
Immersion/Electroless Deposition of Cu on Ta
Continuous Cu films are deposited on Ta by a two-step process; galvanic displacement of Ta by Cu from ammonium fluoride solutions and subsequent electroless Cu deposition from a formaldehyde-containing bath. The conditions necessary for good adhesion are discussed. The extent of oxide film removal in the HF pretreatment solution is studied by electrochemical impedance spectroscopy. The charge-transfer resistance of about 57 Ω-cm2 is several orders of magnitude lower than that measured for the Ta native oxide. These results are consistent with the removal of the Ta2O5 portion of the native oxide
Australian universities engaging international students during the COVID-19 pandemic: A study of multimodal public communications with students.
Amidst the ongoing COVID-19 pandemic, university public communication channels have become unprecedentedly crucial in higher education settings. It is useful to consider how they have been used by universities as platforms for engaging international students. We collected data from three Australian universities: The University of Sydney, Curtin University and the University of New England. This data included COVID-19 information webpages, international student webpages, news/events webpages, and/or vice chancellor's video and text messages. Through an analysis of the data in terms of communicative acts and dimensions of engagement, we were able to identify the different constructions of roles and responsibilities at the three universities when engaging international students during the pandemic. These findings were interpreted in relation to the roles of universities in engaging with international students, and the value of a multimodal approach to researching engagement
Thickness dependence of superconductivity and superconductor-insulator transition in ultrathin FeSe films on SrTiO3(001) substrate
Interface-enhanced high-temperature superconductivity in one unit-cell (UC)
FeSe film on SrTiO3(001) (STO) substrate has recently attracted much attention
in condensed matter physics and material science. Here, by ex situ transport
measurements, we report on the superconductivity in FeSe ultra-thin films with
different thickness on STO substrate. We find that the onset superconducting
transition temperature (Tc) decreases with increasing film thickness of FeSe,
which is opposite to the behavior usually observed in traditional
superconductor films. By systematic post-annealing of 5 UC FeSe films, we
observe an insulator to superconductor transition, which is accompanied with a
sign change of the dominated charge carriers from holes to electrons at low
temperatures according to the corresponding Hall measurement
Chloride-induced alterations of the passive film on 316L stainless steel and blocking effect of pre-passivation
International audienceElectrochemical polarization measurements were combined with surface analysis by Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), X-Ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) to study the alterations of the passive film on 316L austenitic stainless steel induced by the presence of chlorides in sulfuric acid electrolyte. The work was performed at a stage of initiation of localized corrosion preceding metastable pitting at the micrometer scale as verified by current transient analysis and AFM. The results show that Cl-ions enter the bilayer structure of the surface oxide already formed in the native oxide-covered initial surface state at concentrations below the detection limit of XPS (< 0.5 at%), mostly in the hydroxide outer layer where Fe(III) and Mo(IV,VI) species are concentrated but barely in the oxide inner layer enriched in Cr(III). Their main effect is to produce a less resistive passive state by poisoning dehydroxylation and further Cr(III) and Mo(IV,VI) enrichments obtained in the absence of chlorides. This detrimental effect can be suppressed by pre-passivation in a Cl-free electrolyte, which blocks the entry of chlorides in the passive film, including in the outer exchange layer, and enables the beneficial aging-induced variations of the composition to take place despite the presence of chlorides in the environment
Simultaneous electrical-field-effect modulation of both top and bottom Dirac surface states of epitaxial thin films of three-dimensional topological insulators
It is crucial for the studies of the transport properties and quantum effects
related to Dirac surface states of three-dimensional topological insulators (3D
TIs) to be able to simultaneously tune the chemical potentials of both top and
bottom surfaces of a 3D TI thin film. We have realized this in molecular beam
epitaxy-grown thin films of 3D TIs, as well as magnetic 3D TIs, by fabricating
dual-gate structures on them. The films could be tuned between n-type and
p-type by each gate alone. Combined application of two gates can reduce the
carrier density of a TI film to a much lower level than with only one of them
and enhance the film resistance by 10000 %, implying that Fermi level is tuned
very close to the Dirac points of both top and bottom surface states without
crossing any bulk band. The result promises applications of 3D TIs in field
effect devices.Comment: 19 pages, 4 figures, accepted by Nano Letters, forthcomin
Passivation-Induced Physicochemical Alterations of the Native Surface Oxide Film on 316L Austenitic Stainless Steel
International audienceTime of Flight Secondary Ion Mass Spectroscopy, X-Ray Photoelectron Spectroscopy, in situ Photo-Current Spectroscopy and electrochemical analysis were combined to characterize the physicochemical alterations induced by electrochemical passivation of the surface oxide film providing corrosion resistance to 316L stainless steel. The as-prepared surface is covered by a ∼2 nm thick, mixed (Cr(III)-Fe(III)) and bi-layered hydroxylated oxide. The inner layer is highly enriched in Cr(III) and the outer layer less so. Molybdenum is concentrated, mostly as Mo(VI), in the outer layer. Nickel is only present at trace level. These inner and outer layers have bandgap values of 3.0 and 2.6−2.7 eV, respectively, and the oxide film would behave as an insulator. Electrochemical passivation in sulfuric acid solution causes the preferential dissolution of Fe(III) resulting in the thickness decrease of the outer layer and its increased enrichment in Cr(III) and Mo(IV-VI). The further Cr(III) enrichment of the inner layer causes loss of photoactivity and improved corrosion protection with the anodic shift of the corrosion potential and the increase of the polarization resistance by a factor of ∼4. Aging in the passive state promotes the Cr enrichment in the inner barrier layer of the passive film
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