340 research outputs found
Self-Learning Hot Data Prediction: Where Echo State Network Meets NAND Flash Memories
© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Well understanding the access behavior of hot data is significant for NAND flash memory due to its crucial impact on the efficiency of garbage collection (GC) and wear leveling (WL), which respectively dominate the performance and life span of SSD. Generally, both GC and WL rely greatly on the recognition accuracy of hot data identification (HDI). However, in this paper, the first time we propose a novel concept of hot data prediction (HDP), where the conventional HDI becomes unnecessary. First, we develop a hybrid optimized echo state network (HOESN), where sufficiently unbiased and continuously shrunk output weights are learnt by a sparse regression based on L2 and L1/2 regularization. Second, quantum-behaved particle swarm optimization (QPSO) is employed to compute reservoir parameters (i.e., global scaling factor, reservoir size, scaling coefficient and sparsity degree) for further improving prediction accuracy and reliability. Third, in the test on a chaotic benchmark (Rossler), the HOESN performs better than those of six recent state-of-the-art methods. Finally, simulation results about six typical metrics tested on five real disk workloads and on-chip experiment outcomes verified from an actual SSD prototype indicate that our HOESN-based HDP can reliably promote the access performance and endurance of NAND flash memories.Peer reviewe
2D :a stable direct-bandgap semiconductor with record-breaking carrier mobility,
The Moore's law in the semiconducting industry has faltered as the
three-dimensional (3D) Si-based transistors has approached their physical limit
with the downscaling. The carrier mobility , critical to the device's
performance, will be degraded when the thickness of Si is scaled into several
nanometers. In contrast to the bulk counterpart, two-dimensional (2D)
semiconductors can be scaled into atomic-layer thickness without dangling
bonds, maintaining its intrinsic carrier mobility and going beyond the limits
of Si-based electronics. Hence, the development of novel 2D semiconducting
materials with high carrier mobility is the market demand as well as the
scientific challenge. Here, we successfully designed 2D with planar hypercoordinate motif. It possesses the perfect
planar skeleton with both pentacoordinate carbon and hexacoordinate boron
moieties, which is the first reported material with such multi-hypercoordinate
centers. Density functional theory (DFT) calculations prove that the monolayer has excellent structural and thermal stabilities
as well as mechanical properties. Further investigations reveal that the monolayer has a strong ultrahigh Fermi velocity (), suitable direct bandgap (1.97 eV), and high optical
absorption coefficient (). As a result, an unprecedented ultrahigh
room-temperature carrier mobility ()
with strong anisotropy is discovered, making monolayer
a revolutionary candidate for future electronic and photovoltaic applications.Comment: 16 pages, 4 figures, 1 tabl
Surface Defect Classification for Hot-Rolled Steel Strips by Selectively Dominant Local Binary Patterns
Developments in defect descriptors and computer vision-based algorithms for automatic optical inspection (AOI) allows for further development in image-based measurements. Defect classification is a vital part of an optical-imaging-based surface quality measuring instrument. The high-speed production rhythm of hot continuous rolling requires an ultra-rapid response to every component as well as algorithms in AOI instrument. In this paper, a simple, fast, yet robust texture descriptor, namely selectively dominant local binary patterns (SDLBPs), is proposed for defect classification. First, an intelligent searching algorithm with a quantitative thresholding mechanism is built to excavate the dominant non-uniform patterns (DNUPs). Second, two convertible schemes of pattern code mapping are developed for binary encoding of all uniform patterns and DNUPs. Third, feature extraction is carried out under SDLBP framework. Finally, an adaptive region weighting method is built for further strengthening the original nearest neighbor classifier in the feature matching stage. The extensive experiments carried out on an open texture database (Outex) and an actual surface defect database (Dragon) indicates that our proposed SDLBP yields promising performance on both classification accuracy and time efficiencyPeer reviewe
Effect of chromatic dispersion induced chirp on the temporal coherence property of individual beam from spontaneous four wave mixing
Temporal coherence of individual signal or idler beam, determined by the
spectral correlation property of photon pairs, is important for realizing
quantum interference among independent sources. To understand the effect of
chirp on the temporal coherence property, two series of experiments are
investigated by introducing different amount of chirp into either the pulsed
pump or individual signal (idler) beam. In the first one, based on spontaneous
four wave mixing in a piece of optical fiber, the intensity correlation
function of the filtered individual signal beam, which characterizes the degree
of temporal coherence, is measured as a function of the chirp of pump. The
results demonstrate that the chirp of pump pulses decreases the degree of
temporal coherence. In the second one, a Hong-Ou-Mandel type two-photon
interference experiment with the signal beams generated in two different fibers
is carried out. The results illustrate that the chirp of individual beam does
not change the temporal coherence degree, but affect the temporal mode
matching. To achieve high visibility, apart from improving the coherence degree
by minimizing the chirp of pump, mode matching should be optimized by managing
the chirps of individual beams.Comment: 17pages, 4figure
An all fiber source of frequency entangled photon pairs
We present an all fiber source of frequency entangled photon pairs by using
four wave mixing in a Sagnac fiber loop. Special care is taken to suppress the
impurity of the frequency entanglement by cooling the fiber and by matching the
polarization modes of the photon pairs counter-propagating in the fiber loop.
Coincidence detection of signal and idler photons, which are created in pair
and in different spatial modes of the fiber loop, shows the quantum
interference in the form of spatial beating, while the single counts of the
individual signal (idler) photons keep constant. When the production rate of
photon pairs is about 0.013 pairs/pulse, the envelope of the quantum
interference reveals a visibility of , which is close to the
calculated theoretical limit 97.4%Comment: 11 pages, 6 figures, to appear in Phys. Rev.
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A wafer-scale two-dimensional platinum monosulfide ultrathin film via metal sulfurization for high performance photoelectronics
2D nonlayered materials have attracted enormous research interests due to their novel physical and chemical properties with confined dimensions. Platinum monosulfide as one of the most common platinum-group minerals has been less studied due to either the low purity in the natural product or the extremely high-pressure conditions for synthesis. Recently, platinum monosulfide (PtS) 2D membranes have emerged as rising-star materials for fundamental Raman and X-ray photoelectron spectral analysis as well as device exploration. However, a large-area homogeneous synthesis route has not yet been proposed and released. In this communication, we report a facile metal sulfurization strategy for the synthesis of a 4-inch wafer-scale PtS film. Enhanced characterization tools have been employed for thorough analysis of the crystal structure, chemical environment, vibrational modes, and atomic configuration. Furthermore, through theoretical calculations the phase diagram of the Pt–S compound has been plotted for showing the successful formation of PtS in our synthesis conditions. Eventually, a high-quality PtS film has been reflected in device demonstration by a photodetector. Our approach may shed light on the mass production of PtS films with precise control of their thickness and homogeneity as well as van der Waals heterostructures and related electronic devices
Quantum efficiency measurement of single photon detectors using photon pairs generated in optical fibers
Using the correlated signal and idler photon pairs generated in a dispersion
shifted fiber by a pulsed pump, we measure the quantum efficiency of a
InGaAs/InP avalanche photodiode-based single photon detector. Since the
collection efficiency of photon pairs is a key parameter to correctly deduce
the quantum efficiency, we carefully characterize the collection efficiency by
studying correlation dependence of photon pairs upon the spectra of pump,
signal and idler photons. This study allows us to obtain quantum efficiency of
the single photon detector by using photon pairs with various kinds of
bandwidths.Comment: 21pages, 6figures, 4tables, accepted for publication in J. Opt. Soc.
Am.
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Multilayered Epithelium in a Rat Model and Human Barrett's Esophagus: Similar Expression Patterns of Transcription Factors and Differentiation Markers
Background: In rats, esophagogastroduodenal anastomosis (EGDA) without concomitant chemical carcinogen treatment leads to gastroesophageal reflux disease, multilayered epithelium (MLE, a presumed precursor in intestinal metaplasia), columnar-lined esophagus, dysplasia, and esophageal adenocarcinoma. Previously we have shown that columnar-lined esophagus in EGDA rats resembled human Barrett's esophagus (BE) in its morphology, mucin features and expression of differentiation markers (Lab. Invest. 2004;84:753–765). The purpose of this study was to compare the phenotype of rat MLE with human MLE, in order to gain insight into the nature of MLE and its potential role in the development of BE. Methods: Serial sectioning was performed on tissue samples from 32 EGDA rats and 13 patients with established BE. Tissue sections were immunohistochemically stained for a variety of transcription factors and differentiation markers of esophageal squamous epithelium and intestinal columnar epithelium. Results: We detected MLE in 56.3% (18/32) of EGDA rats, and in all human samples. As expected, both rat and human squamous epithelium, but not intestinal metaplasia, expressed squamous transcription factors and differentiation markers (p63, Sox2, CK14 and CK4) in all cases. Both rat and human intestinal metaplasia, but not squamous epithelium, expressed intestinal transcription factors and differentiation markers (Cdx2, GATA4, HNF1α, villin and Muc2) in all cases. Rat MLE shared expression patterns of Sox2, CK4, Cdx2, GATA4, villin and Muc2 with human MLE. However, p63 and CK14 were expressed in a higher proportion of rat MLE compared to humans. Conclusion: These data indicate that rat MLE shares similar properties to human MLE in its expression pattern of these markers, not withstanding small differences, and support the concept that MLE may be a transitional stage in the metaplastic conversion of squamous to columnar epithelium in BE
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