Microstructure Evolution Across Interfaces of Heterogeneous Metal Systems Under Ultrasonic Impact

2004 ◽  
Vol 854 ◽  
Author(s):  
Youhong Li ◽  
Yinon Ashkenazy ◽  
Robert S. Averback
Keyword(s):  
Large Scale ◽  
Shock Loading ◽  
Interfacial Strength ◽  
Interface Layer ◽  
Structural Defects ◽  
Interfacial Region ◽  
Heterogeneous Model ◽  
Interfacial Defects ◽  
Temperature And Pressure ◽  
Pressure Changes

ABSTRACTLarge-scale Molecular Dynamics (MD) studies on heterogeneous, model metal systems subjected to intense shock loading by a flyer plate were carried out. Of interest here is the effect of structural defects on interfacial strength under these extreme conditions. The metal target and flyer were essentially single crystals of Cu, but an interface layer was created by varying the mass of the Cu atoms in part of the sample. Interfacial defects in the form of vacancies, and at different concentrations, were introduced into the interfacial region. In addition to microstructural evolution of damage in this system, the shock induced temperature and pressure changes were also analyzed.

Shock Loading of Bone-Inspired Metallic Nanocomposites

2008 ◽  
Vol 139 ◽  
pp. 11-22 ◽  
Author(s):  
Dipanjan Sen ◽  
Markus J. Buehler
Keyword(s):  
Large Scale ◽  
Shock Loading ◽  
Interatomic Potential ◽  
Tensile Load ◽  
Interfacial Strength ◽  
Structural Features ◽  
Valuable Insight ◽  
Length Scales ◽  
Design Elements ◽  
Interfacial Sliding

Nanostructured composites inspired by structural biomaterials such as bone and nacre form intriguing design templates for biomimetic materials. Here we use large scale molecular dynamics to study the shock response of nanocomposites with similar nanoscopic structural features as bone, to determine whether bioinspired nanostructures provide an improved shock mitigating performance. The utilization of these nanostructures is motivated by the toughness of bone under tensile load, which is far greater than its constituent phases and greater than most synthetic materials. To facilitate the computational experiments, we develop a modified version of an Embedded Atom Method (EAM) alloy multi-body interatomic potential to model the mechanical and physical properties of dissimilar phases of the biomimetic bone nanostructure. We find that the geometric arrangement and the specific length scales of design elements at nanoscale does not have a significant effect on shock dissipation, in contrast to the case of tensile loading where the nanostructural length scales strongly influence the mechanical properties. We find that interfacial sliding between the composite’s constituents is a major source of plasticity under shock loading. Based on this finding, we conclude that controlling the interfacial strength can be used to design a material with larger shock absorption. These observations provide valuable insight towards improving the design of nanostructures in shock-absorbing applications, and suggest that by tuning the interfacial properties in the nanocomposite may provide a path to design materials with enhanced shock absorbing capability.

scholarly journals Assessment of Piezoelectric Sensors for the Acquisition of Steady Melt Pressures in Polymer Extrusion

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 66
Author(s):  
Sónia Costa ◽  
Paulo Teixeira ◽  
José Covas ◽  
Loic Hilliou
Keyword(s):  
Polymer Processing ◽  
Piezoelectric Transducers ◽  
Piezoelectric Sensors ◽  
Flow Curves ◽  
Signal Drift ◽  
Temperature And Pressure ◽  
Pressure Independent ◽  
Pressure Changes ◽  
Different Levels ◽  
Slit Die

Piezoelectric sensors have made their way into polymer processing and rheometry applications, in particular when small pressure changes with very fast dynamics are to be measured. However, no validation of their use for steady shear rheometry is available in the literature. Here, a rheological slit die was designed and constructed to allow for the direct comparison of pressure data measured with conventional and piezoelectric transducers. The calibration of piezoelectric sensors is presented together with a methodology to correct the data from the inherent signal drift, which is shown to be temperature and pressure independent. Flow curves are measured for polymers showing different levels of viscoelasticity. Piezoelectric slit rheometry is validated and its advantage for the rheology of thermodegradable materials with viscosity below 100 Pa·s is highlighted.

scholarly journals Compensation of phase drifts caused by ambient humidity, temperature and pressure changes for continuously operating interferometers

2019 ◽  
Vol 14 (11) ◽  
pp. P11016-P11016
Author(s):  
K.J. Brunner ◽  
J. Knauer ◽  
J. Meineke ◽  
M. Stern ◽  
M. Hirsch ◽  
...  
Keyword(s):  
Ambient Humidity ◽  
Temperature And Pressure ◽  
Pressure Changes

DECOMPOSITION PRESSURES OF FERRIC SULPHATE AND ALUMINUM SULPHATE

1960 ◽  
Vol 38 (11) ◽  
pp. 2196-2202 ◽  
Author(s):  
N. A. Warner ◽  
T. R. Ingraham
Keyword(s):  
Gas Phase ◽  
Static System ◽  
Ferric Sulphate ◽  
Kcal Mole ◽  
Aluminum Sulphate ◽  
Temperature And Pressure ◽  
Pressure Changes ◽  
Mercury Manometer ◽  
Decomposition Pressure ◽  
Gas Pressures

The gas pressures over samples of anhydrous ferric sulphate and anhydrous aluminum sulphate have been measured in a static system, using a mercury manometer in which the exposed surface was covered with a flexible Pyrex bellows. The calculated ΔH for the decomposition of Fe2(SO4)3 was +135.4 kcal/mole. It was not possible to calculate the ΔH for the Al2(SO4)3 decomposition, because a discrete aluminum oxide with singular thermodynamic properties was not obtained.In the Fe2(SO4)3 system, the fraction of SO3 in the gas phase was found to be almost constant over the range of temperature and pressure changes used in the study.At any given temperature, the decomposition pressure over a ferric sulphate sample is greater than that over an aluminum sulphate sample, thus indicating that preferential decomposition of ferric sulphate should be thermodynamically feasible in mixtures of ferric sulphate and aluminum sulphate.

Micro-Photoluminescence Mapping of Defect Structures in SiC Wafers

2007 ◽  
Vol 556-557 ◽  
pp. 383-386 ◽  
Author(s):  
John Hennessy ◽  
Tom Ryan
Keyword(s):  
Carrier Lifetime ◽  
Deep Level ◽  
Complex Function ◽  
Band Edge ◽  
Structural Defects ◽  
Band Edge Emission ◽  
Interfacial Defects ◽  
Pl Mapping ◽  
Boron Acceptor ◽  
Excitation Conditions

Micro-photoluminescence can be used to image electrically active structural defects in SiC. Under suitable excitation conditions it is possible to observe both band-edge PL and near bandedge PL from recombination via a shallow boron acceptor. The intensity of the band-edge emission is related to the carrier lifetime – and is reduced by the presence of structural or interfacial defects. The intensity of the deep level PL is a complex function of the number of radiative centers and the number of centers limiting carrier lifetime. Micro-PL mapping can provide information on the spatial distribution of electrically active defects in SiC.

Experiments on vertical transverse mixing in a large-scale heterogeneous model aquifer

2005 ◽  
Vol 80 (3-4) ◽  
pp. 130-148 ◽  
Author(s):  
Md. Arifur Rahman ◽  
Surabhin C. Jose ◽  
Wolfgang Nowak ◽  
Olaf A. Cirpka
Keyword(s):  
Large Scale ◽  
Heterogeneous Model ◽  
Transverse Mixing

A landscape-ontology scale MTInSAR deformation monitoring solution for the sustainable conservation of architectural heritage sites

2021 ◽  
Author(s):  
Hang Xu ◽  
FuLong Chen
Keyword(s):  
Large Scale ◽  
Anthropogenic Activities ◽  
Deformation Monitoring ◽  
Global Navigation Satellite Systems ◽  
Structural Defects ◽  
Spatial Density ◽  
Architectural Heritage ◽  
Heritage Sites ◽  
Sustainable Conservation ◽  
Great Wall

<p>Architectural heritage is cultural and spiritual symbol of our predecessors with immeasurable historical, artistic, and technological value. However, these heritages are exposed to long-term degradation due to the combination impacts from the natural erosion and anthropogenic activities. Consequently, it is important to establish an effective deformation monitoring system to support the sustainable conservation of those properties. In order to make complementary to conventional geodetic measurements such as global navigation satellite systems (GNSS) and leveling in terms of spatial density, we propose a landscape-ontology scale multi-temporal InSAR (MTInSAR) solution for the preventive deformation monitoring of large-scale architectural heritage sites through the adaption of current MTInSAR approaches. We apply different solutions in Shanhaiguan section of the Great Wall in China and the Angkor Wat in Cambodia based on their onsite characteristics. At the cultural landscape scale, we improve the small baseline subset (SBAS) approach by the induced pseudo-baseline strategy in order to avoid the errors caused by inaccurate external DEM, resulting in a robust deformation estimation in mountainous areas where the architecture heritage of the Great Wall located; at the ontology scale, we integrate the differential SAR tomography (DTomoSAR) with the finite element method (FEM) for the structural instability detection of the Angkor Wat Temple, pinpointing the structural defects from the 3D deformation measurements and simulation. This study demonstrates the capability of adaptive MTInSAR approaches for the preventive monitoring the deformation of large-scale architectural heritage sites.</p><p><strong>Keywords</strong>: Architectural heritage; two-scale; deformation; MTInSAR</p>

Epidural versus subdural spinal cord cooling: cerebrospinal fluid temperature and pressure changes

2000 ◽  
Vol 70 (1) ◽  
pp. 222-227 ◽  
Author(s):  
Sven A Meylaerts ◽  
Cor J Kalkman ◽  
Peter de Haan ◽  
Marjolein Porsius ◽  
Michael J.H.M Jacobs
Keyword(s):  
Spinal Cord ◽  
Cerebrospinal Fluid ◽  
Fluid Temperature ◽  
Temperature And Pressure ◽  
Pressure Changes

Heterogeneous model of schistosomiasis transmission and long-term control: the combined influence of spatial variation and age-dependent factors on optimal allocation of drug therapy

Parasitology ◽  
2004 ◽  
Vol 130 (1) ◽  
pp. 49-65 ◽  
Author(s):  
D. GURARIE ◽  
C. H. KING
Keyword(s):  
Large Scale ◽  
Optimal Allocation ◽  
Field Studies ◽  
Human Populations ◽  
Infection Prevalence ◽  
Snail Population ◽  
Extended Model ◽  
Heterogeneous Model ◽  
Age Dependent

Prior field studies and modelling analyses have individually highlighted the importance of age-specific and spatial heterogeneities on the risk for schistosomiasis in human populations. As long-term, large-scale drug treatment programs for schistosomiasis are initiated in subSaharan Africa and elsewhere, optimal strategies for timing and distribution of therapy have yet to be fully defined on the working, district-level scale, where strong heterogeneities are often observed among sublocations. Based on transmission estimates from recent field studies, we develop an extended model of heterogeneous schistosome transmission for distributed human and snail population clusters and age-dependent behaviour, based on a ‘mean worm burden+snail infection prevalence’ formulation. We analyse its equilibria and basic reproduction patterns and their dependence on the underlying transmission parameters. Our model allows the exploration of chemotherapy-based control strategies targeted at high-risk behavioural groups and localities, and the approach to an optimal design in terms of cost. Efficacy of the approach is demonstrated for a model environment having linked, but spatially-distributed, populations and transmission sites.

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