134 research outputs found
On critical Fujita exponents for the porous medium equation with a nonlinear boundary condition
AbstractWe establish the critical Fujita exponents for the solution of the porous medium equation ut=Δum, x∈R+N, t>0, subject to the nonlinear boundary condition −∂um/∂x1=up, x1=0, t>0, in multi-dimension
The role of tool offset on the microstructure and mechanical properties of Al/Cu friction stir welded joints
In this study, dissimilar butt joining of 6061 aluminum alloy and commercially pure copper via friction stir welding was performed with varying tool offset value. The mechanical properties were compared using transverse tensile testing. It was found that as the tool offset decreased from a position of 2 mm–0 mm, the ultimate tensile strength of the welded joint increased, and then decreased drastically when the offset was more than 1.6 mm. X-ray tomography results showed that an effective mechanical interlocking structure was formed with a chaotic interface along the joint line. In addition, in-situ tool temperatures measurement showed that the stir zone peak temperature was highly dependent on tool offset
OHQ: On-chip Hardware-aware Quantization
Quantization emerges as one of the most promising approaches for deploying
advanced deep models on resource-constrained hardware. Mixed-precision
quantization leverages multiple bit-width architectures to unleash the accuracy
and efficiency potential of quantized models. However, existing mixed-precision
quantization suffers exhaustive search space that causes immense computational
overhead. The quantization process thus relies on separate high-performance
devices rather than locally, which also leads to a significant gap between the
considered hardware metrics and the real deployment.In this paper, we propose
an On-chip Hardware-aware Quantization (OHQ) framework that performs
hardware-aware mixed-precision quantization without accessing online devices.
First, we construct the On-chip Quantization Awareness (OQA) pipeline, enabling
perceive the actual efficiency metrics of the quantization operator on the
hardware.Second, we propose Mask-guided Quantization Estimation (MQE) technique
to efficiently estimate the accuracy metrics of operators under the constraints
of on-chip-level computing power.By synthesizing network and hardware insights
through linear programming, we obtain optimized bit-width configurations.
Notably, the quantization process occurs on-chip entirely without any
additional computing devices and data access. We demonstrate accelerated
inference after quantization for various architectures and compression ratios,
achieving 70% and 73% accuracy for ResNet-18 and MobileNetV3, respectively. OHQ
improves latency by 15~30% compared to INT8 on deployment.Comment: 10 pages, 6 figure
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Electron irradiation-induced defects for reliability improvement in monolayer MoS2-based conductive-point memory devices
Monolayer molybdenum disulfide has been previously discovered to exhibit non-volatile resistive switching behavior in a vertical
metal-insulator-metal structure, featuring ultra-thin sub-nanometer active layer thickness. However, the reliability of these nascent
2D-based memory devices was not previously investigated for practical applications. Here, we employ an electron irradiation
treatment on monolayer MoS2 film to modify the defect properties. Raman, photoluminescence, and X-ray photoelectron
spectroscopy measurements have been performed to confirm the increasing amount of sulfur vacancies introduced by the e-beam
irradiation process. The statistical electrical studies reveal the reliability can be improved by up to 1.5× for yield and 11× for average
DC cycling endurance in the devices with a moderate radiation dose compared to unirradiated devices. Based on our previously
proposed virtual conductive-point model with the metal ion substitution into sulfur vacancy, Monte Carlo simulations have been
performed to illustrate the irradiation effect on device reliability, elucidating a clustering failure mechanism. This work provides an
approach by electron irradiation to enhance the reliability of 2D memory devices and inspires further research in defect
engineering to precisely control the switching properties for a wide range of applications from memory computing to radio-
frequency switches.This work was supported in part by the National Science Foundation (NSF) grant
#1809017, and an NSF MRSEC under Cooperative Agreement No. DMR-1720595. The
authors acknowledge use of Texas Nanofabrication Facilities supported by the NSF
NNCI award #1542159. D.A. acknowledges the Presidential Early Career Award for
Scientists and Engineers (PECASE) through the Army Research Office (W911NF-16-1-
0277).Center for Dynamics and Control of Material
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Sulfurization Engineering of One-Step Low-Temperature MoS2 and WS2 Thin Films for Memristor Device Applications
2D materials have been of considerable interest as new materials for device applications. Non-volatile resistive switching applications of MoS2 and WS2 have been previously demonstrated; however, these applications are dramatically limited by high temperatures and extended times needed for the large-area synthesis of 2D materials on crystalline substrates. The experimental results demonstrate a one-step sulfurization method to synthesize MoS2 and WS2 at 550 °C in 15 min on sapphire wafers. Furthermore, a large area transfer of the synthesized thin films to SiO2/Si substrates is achieved. Following this, MoS2 and WS2 memristors are fabricated that exhibit stable non-volatile switching and a satisfactory large on/off current ratio (103–105) with good uniformity. Tuning the sulfurization parameters (temperature and metal precursor thickness) is found to be a straightforward and effective strategy to improve the performance of the memristors. The demonstration of large-scale MoS2 and WS2 memristors with a one-step low-temperature sulfurization method with simple strategy to tuning can lead to potential applications such as flexible memory and neuromorphic computing.This research was
primarily supported by the National Science Foundation through
the Center for Dynamics and Control of Materials: an NSF MRSEC
under Cooperative Agreement No. DMR-1720595. The work was partly
done at the Texas Nanofabrication Facility supported by NSF grant
NNCI-2025227. This work was performed in part at the Center for
Integrated Nanotechnologies, an Office of Science User Facility operated
for the U.S. Department of Energy (DOE) Office of Science. Los Alamos
National Laboratory, an affirmative action equal opportunity employer,
is managed by Triad National Security, LLC for the U.S. Department
of Energy’s NNSA, under contract 89233218CNA000001.Center for Dynamics and Control of Material
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