28 research outputs found
Mesopore etching under supercritical conditions â A shortcut to hierarchically porous silica monoliths
Hierarchically porous silica monoliths are obtained in the two-step Nakanishi process, where formation of a macro microporous silica gel is followed by widening micropores to mesopores through surface etching. The latter step is carried out through hydrothermal treatment of the gel in alkaline solution and necessitates a lengthy solvent exchange of the aqueous pore fluid before the ripened gel can be dried and calcined into a mechanically stable macro mesoporous monolith. We show that using an ethanol water (95.6/4.4, v/v) azeotrope as supercritical fluid for mesopore etching eliminates the solvent exchange, ripening, and drying steps of the classic route and delivers silica monoliths that can withstand fast heating rates for calcination. The proposed shortcut decreases the overall preparation time from ca. one week to ca. one day. Porosity data show that the alkaline conditions for mesopore etching are crucial to obtain crack-free samples with a narrow mesopore size distribution. Physical reconstruction of selected samples by confocal laser scanning microscopy and subsequent morphological analysis confirms that monoliths prepared via the proposed shortcut possess the high homogeneity of silica skeleton and macropore space that is desirable in adsorbents for flow-through applications
Accelerating Neural Network Training with Distributed Asynchronous and Selective Optimization (DASO)
With increasing data and model complexities, the time required to train neural networks has become prohibitively large. To address the exponential rise in training time, users are turning to data parallel neural networks (DPNN) and large-scale distributed resources on computer clusters. Current DPNN approaches implement the network parameter updates by synchronizing and averaging gradients across all processes with blocking communication operations after each forward-backward pass. This synchronization is the central algorithmic bottleneck. We introduce the Distributed Asynchronous and Selective Optimization (DASO) method, which leverages multi-GPU compute node architectures to accelerate network training while maintaining accuracy. DASO uses a hierarchical and asynchronous communication scheme comprised of node-local and global networks while adjusting the global synchronization rate during the learning process. We show that DASO yields a reduction in training time of up to 34% on classical and state-of-the-art networks, as compared to current optimized data parallel training methods
Accelerating Neural Network Training with Distributed Asynchronous and Selective Optimization (DASO)
With increasing data and model complexities, the time required to train neural networks has become prohibitively large. To address the exponential rise in training time, users are turning to data parallel neural networks (DPNN) to utilize large-scale distributed resources on computer clusters. Current DPNN approaches implement the network parameter updates by synchronizing and averaging gradients across all processes with blocking communication operations. This synchronization is the central algorithmic bottleneck. To combat this, we introduce the Distributed Asynchronous and Selective Optimization (DASO) method which leverages multi-GPU compute node architectures to accelerate network training. DASO uses a hierarchical and asynchronous communication scheme comprised of node-local and global networks while adjusting the global synchronization rate during the learning process. We show that DASO yields a reduction in training time of up to 34% on classical and state-of-the-art networks, as compared to other existing data parallel training methods
Direct synthesis of carbide-derived carbon monoliths with hierarchical pore design by hard-templating
Carbide-derived carbon Monoliths (CDC-Ms) containing a multimodal arrangement with high volumes of micro- meso- and macropores are prepared by direct nanocasting of silica monoliths with polycarbosilane precursors. CDC-Ms show well-defined pore structures along with specific surface areas of more than 2600 m2 gâ1 and overall pore volumes as high as 3.14 cm3 gâ1. They exhibit advanced gas filtration properties compared to purely microporous materials due to enhanced storage capacities and kinetics as demonstrated by thermal response measurements based on InfraSORP technology
Direct synthesis of carbide-derived carbon monoliths with hierarchical pore design by hard-templating
Carbide-derived carbon Monoliths (CDC-Ms) containing a multimodal arrangement with high volumes of micro- meso- and macropores are prepared by direct nanocasting of silica monoliths with polycarbosilane precursors. CDC-Ms show well-defined pore structures along with specific surface areas of more than 2600 m2 gâ1 and overall pore volumes as high as 3.14 cm3 gâ1. They exhibit advanced gas filtration properties compared to purely microporous materials due to enhanced storage capacities and kinetics as demonstrated by thermal response measurements based on InfraSORP technology
Proton Conduction in Sulfonated OrganicâInorganic Hybrid Monoliths with Hierarchical Pore Structure
Porous
organicâinorganic hybrid monoliths with hierarchical porosity
exhibiting macro- and mesopores are prepared via solâgel process
under variation of the mesopore size. Organic moieties in the pore
walls are incorporated by substituting up to 10% of the silicon precursor
tetramethylorthosilicate with bisilylated benzene molecules. After
functionalization with sulfonic acid groups, the resulting sulfonated
hybrid monoliths featuring a bimodal pore structure are investigated
regarding proton conduction depending on temperature and relative
humidity. The hierarchical pore system and controlled mesopore design
turn out to be crucial for sulfonation and proton conduction. These
sulfonated hybrid hierarchical monoliths containing only 10% organic
precursor exhibit higher proton conduction at different relative humidities
than sulfonated periodic mesoporous organosilica made of 100% bisilylated
precursors exhibiting solely mesopores, even with a lower concentration
of sulfonic acid groups
Hierarchical Carbon with High Nitrogen Doping Level: A Versatile Anode and Cathode Host Material for Long-Life Lithium-Ion and LithiumâSulfur Batteries
Nitrogen-rich carbon with both a
turbostratic microstructure and meso/macroporosity was prepared by
hard templating through pyrolysis of a tricyanomethanide-based ionic
liquid in the voids of a silica monolith template. This multifunctional
carbon not only is a promising anode candidate for long-life lithium-ion
batteries but also shows favorable properties as anode and cathode
host material owing to a high nitrogen content (>8% after carbonization
at 900 °C). To demonstrate the latter, the hierarchical carbon
was melt-infiltrated with sulfur as well as coated by atomic layer
deposition (ALD) of anatase TiO<sub>2</sub>, both of which led to
high-quality nanocomposites. TiO<sub>2</sub> ALD increased the specific
capacity of the carbon while maintaining high Coulombic efficiency
and cycle life: the composite exhibited stable performance in lithium
half-cells, with excellent recovery of low rate capacities after thousands
of cycles at 5C. Lithiumâsulfur batteries using the sulfur/carbon
composite also showed good cyclability, with reversible capacities
of âŒ700 mA·h·g<sup>â1</sup> at C/5 and without
obvious decay over several hundred cycles. The present results demonstrate
that nitrogen-rich carbon with an interconnected multimodal pore structure
is very versatile and can be used as both active and inactive electrode
material in high-performance lithium-based batteries
helmholtz-analytics/heat: Heat 1.0: Data Parallel Neural Networks, and more
Release Notes Heat v1.0 comes with some major updates: new module nn for data-parallel neural networks Distributed Asynchronous and Selective Optimization (DASO) to accelerate network training on multi-GPU architectures support for complex numbers major documentation overhaul support channel on StackOverflow support PyTorch 1.8 stop supporting Python 3.6 many more updates and bug fixes, check out the CHANGELO