2,121 research outputs found
Oxidation-induced changes in mechanical properties of silicon nitride ceramics
The effect of oxidation on the room-temperature mechanical properties of four different silicon
nitride ceramics is investigated. The strength and the elastic modulus of the whole material and
the hardness, the fracture toughness and the elastic modulus of the internal region (without
surface oxide layer) are determined for the materials oxidized at temperatures up to 1400°C. It
is found that the fracture toughness decreases during oxidation at 1000°C. Reduction of the
elastic modulus of the materials oxidized at 1400°C is also observed. A part of the changes in
the mechanical properties is interpreted by the changes in the phase composition
Fe-substituted mullite powders for the in situ synthesis of carbon nanotubes by catalytic chemical vapor deposition
Powders of iron-substituted mullite were prepared by combustion and further calcination in air at different temperatures. A detailed study involving notably Mo¨ssbauer spectroscopy showed that the Fe3+ ions are distributed between the mullite phase and a corundum phase that progressively dissolves into mullite upon the increase in calcination temperature. Carbon nanotube-Fe-mullite nanocomposites were prepared for the first time by a direct method involving a reduction of these powders in H2-CH4 and without any mechanical mixing step. The carbon nanotubes formed by the catalytic decomposition of CH4 on the smallest metal particles are mostly double-walled and multiwalled, although some carbon nanofibers are also observed
Effect of fly ash washing conditions on the properties of coupling agent modified polypropylene/fly ash composites
Two fly ash samples (one from UK, UKFA, and another from South Africa, SAFA) were washed with water and 1 M hydrochloric acid (followed by water) prior to incorporation (at 65% wt) into polypropylene homopolymer, containing an unsaturated carboxylic acid coupling agent (Lubrizol Solplus® C800) with dicumyl peroxide free radical initiator. Melt blending was achieved using a Haake Rheomix 600 mixing chamber, and composite test plaques were compression moulded. Flexural and impact testing was then carried out. Unwashed and water washed fly ash-based composites responded well to C800 modification, and flow microcalorimetry (FMC) and diffuse reflectance Fourier transform infrared spectroscopy studies confirmed strong interaction between C800 and fly ash. However, washing the fly ash with HCl led to a reduction in composite flexural and impact properties. Scanning electron microscopy imaging of the latter composite fracture surfaces revealed poor filler-matrix adhesion, which was thought to be due to reduced interaction between C800 and HCl washed fly ash. The latter was confirmed using FMC. Reduction of C800/fly ash interaction led to a reduction in the nucleation of polypropylene (PP) crystallization and a decrease in melt flow rate. The latter may be due to a shift in locus of PP-C800 addition reactions from the interfacial region to the bulk matrix. © 2013 Society of Plastics Engineers
Progressive Label Distillation: Learning Input-Efficient Deep Neural Networks
Much of the focus in the area of knowledge distillation has been on
distilling knowledge from a larger teacher network to a smaller student
network. However, there has been little research on how the concept of
distillation can be leveraged to distill the knowledge encapsulated in the
training data itself into a reduced form. In this study, we explore the concept
of progressive label distillation, where we leverage a series of
teacher-student network pairs to progressively generate distilled training data
for learning deep neural networks with greatly reduced input dimensions. To
investigate the efficacy of the proposed progressive label distillation
approach, we experimented with learning a deep limited vocabulary speech
recognition network based on generated 500ms input utterances distilled
progressively from 1000ms source training data, and demonstrated a significant
increase in test accuracy of almost 78% compared to direct learning.Comment: 9 page
The mobility of H2 Adsorbed in Mo2C Derived Carbon Materials with Different Porous Structures Studied with Quasi-Elastic Neutron Scattering
1969 July, Memphis State University bulletin
Vol. 58, No. 5 of the Memphis State University bulletin containing the schedule of classes for fall semester 1969, 1969 July.https://digitalcommons.memphis.edu/speccoll-ua-pub-bulletins/1321/thumbnail.jp
On Comon's and Strassen's conjectures
Comon's conjecture on the equality of the rank and the symmetric rank of a
symmetric tensor, and Strassen's conjecture on the additivity of the rank of
tensors are two of the most challenging and guiding problems in the area of
tensor decomposition. We survey the main known results on these conjectures,
and, under suitable bounds on the rank, we prove them, building on classical
techniques used in the case of symmetric tensors, for mixed tensors. Finally,
we improve the bound for Comon's conjecture given by flattenings by producing
new equations for secant varieties of Veronese and Segre varieties.Comment: 12 page
Water and small organic molecules as probes for geometric confinement in well- ordered mesoporous carbon material
Mesoporous carbon materials were synthesized employing polymers and silica
gels as structure directing templates. The basic physico-chemical properties
of the synthetic mesoporous materials were characterized by 1H and 13C MAS
solid-state NMR, X-ray diffraction, transmission electron microscopy (TEM) and
nitrogen adsorption measurements. The confinement effects on small guest
molecules such as water, benzene and pyridine and their interactions with the
pore surface were probed by a combination of variable temperature 1H-MAS NMR
and quantum chemical calculations of the magnetic shielding effect of the
surface on the solvent molecules. The interactions of the guest molecules
depend strongly on the carbonization temperature and the pathway of the
synthesis. All the guest-molecules, water, benzene and pyridine, exhibited
high-field shifts by the interaction with the surface of carbon materials. The
geometric confinement imposed by the surface causes a strong depression of the
melting point of the surface phase of water and benzene. The theoretical
calculation of 1H NICS maps shows that the observed proton chemical shifts
towards high-field values can be explained as the result of electronic ring
currents localized in aromatic groups on the surface. The dependence on the
distance between the proton and the aromatic surface can be exploited to
estimate the average diameter of the confinement structures
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