Scale Effects in Media With Periodic and Nearly Periodic Microstructures, Part I: Macroscopic Properties

1997 ◽  
Vol 64 (4) ◽  
pp. 751-762 ◽  
Author(s):  
M. W. Schraad ◽  
N. Triantafyllidis
Keyword(s):  
Heterogeneous Media ◽  
Scale Effects ◽  
Relative Size ◽  
Macroscopic Strain ◽  
Planar Lattice ◽  
Analytical Approximations ◽  
Macroscopic Properties ◽  
Periodic Microstructures ◽  
The Difference ◽  
Nonlinearly Elastic

Traditional averaging and homogenization techniques, developed to predict the macroscopic properties of heterogeneous media, typically ignore microstructure related scale effects—that is, the influence of the size of the representative volume, relative to the size of the unit cell. This issue is presently investigated by exploring the behavior of a nonlinearly elastic, planar, lattice model, which is subjected to general macroscopic deformations. For these materials, scale effects may be due to nonuniformities in the macroscopic strain field throughout the specimen, or alternatively, to the presence of microstructural imperfections that may be either geometric or constitutive in nature. For the case of macroscopic strain nonuniformities, it is shown that the microstructure related scale effects can be accounted for by the presence of higher order gradient terms in the macroscopic strain energy density of the model. For the case of microstructural imperfections, the difference between the respective macroscopic properties of the perfect and imperfect models are shown to depend on the relative size of the specimen, and on the imperfection amplitude and wavelength, while being nearly insensitive to the imposed macroscopic strain. For all of the cases considered, several analytical approximations are proposed to predict the influence of scale on the macroscopic properties, and the accuracy of each method is examined.

Scale Effects in Media With Periodic and Nearly Periodic Microstructures, Part II: Failure Mechanisms

1997 ◽  
Vol 64 (4) ◽  
pp. 763-771 ◽  
Author(s):  
M. W. Schraad ◽  
N. Triantafyllidis
Keyword(s):  
Failure Modes ◽  
Scale Effects ◽  
Unit Cell ◽  
Equilibrium Path ◽  
Planar Lattice ◽  
Loss Of Ellipticity ◽  
Finite Models ◽  
Load Paths ◽  
Periodic Microstructures ◽  
Strain Space

Using the nonlinearly elastic planar lattice model presented in Part I, the influence of scale (i.e., the size of the representative volume, relative to the size of the unit cell) on the onset of failure in periodic and nearly periodic media is investigated. For this study, the concept of a microfailure surface is introduced—this surface being defined as the locus of first instability points found along radial load paths through macroscopic strain space. The influence of specimen size and microstructural imperfections (both geometric and constitutive) on these failure surfaces is investigated. The microfailure surface determined for the infinite model with perfectly periodic microstructure, is found to be a lower bound for the failure surfaces of perfectly periodic, finite models, and an upper bound for the failure surfaces of finite models with microstructural imperfections. The concept of a macrofailure surface is also introduced—this surface being defined as the locus of points corresponding to the loss of ellipticity in the macroscopic (homogenized) moduli of the model. The macrofailure surface is easier to construct than the microfailure surface, because it only requires calculation of the macroscopic properties for the unit cell, at each loading state along the principal equilibrium path. The relation between these two failure surfaces is explored in detail, with attention focused on their regions of coincidence, which are of particular interest due to the possible development of macroscopically localized failure modes.

Size Selectivity of Diamond and Square Mesh Codends in Pelagic Herring Trawls: Only Small Herring Will Notice the Difference

1992 ◽  
Vol 49 (10) ◽  
pp. 2104-2117 ◽  
Author(s):  
Petri Suuronen ◽  
Russell B. Millar
Keyword(s):  
Relative Size ◽  
Mesh Size ◽  
The Other ◽  
Size Selectivity ◽  
The Difference ◽  
Catch Rates ◽  
Two Sides ◽  
High Catch

A twin codend trawl was fished in the northern Baltic to study the size selectivity of square mesh and diamond mesh codends of 36-mm nominal mesh size. For each codend, 15 hauls were completed with a small mesh (20 mm) codend deployed on the other side of the trawl. The relative size of the catches in the two sides of the trawl varied considerably from haul to haul (the separator section was not operating properly) and selection curves were estimated from each individual haul using a method that incorporated the differences in catching efficiency of the two sides. The length of 50% retention decreased with increased catch for both the diamond and square mesh codends, although in neither case was this relationship statistically significant. Selection curves fitted to the combined haul data were asymmetric. The square mesh codend retained significantly less small herring than the diamond mesh codend, and for larger herring the two codends had similar selectivity. In both codends, most escapes occurred at the front of the catch bulge, from the upper side of the codend. At high catch rates, mesh blockage was observed for several metres ahead of the catch bulge during the later part of the tow.

Dynamics of Ferroelectric and Nematic Liquid Crystals Confined in Porous Matrices

1994 ◽  
Vol 366 ◽  
Author(s):  
Fouad M. Aliev
Keyword(s):  
Liquid Crystals ◽  
Heterogeneous Media ◽  
Volume Fraction ◽  
Low Frequency ◽  
Pore Wall ◽  
Polar Molecules ◽  
Average Pore ◽  
Surface Polarization ◽  
The Difference ◽  
Frequency Relaxation

ABSTRACTWe performed dielectric spectroscopy measurements to study dynamics of collective modes of ferroelectric (FLC) and molecular motion of nematic (NLC) liquid crystals with polar molecules confined in silica macroporous and microporous glasses with average pore sizes of 1000 Å (volume fraction of pores 40%) and 100 Å (27%) respectively. For FLC the Goldstone and the soft modes are found in macropores. The rotational viscosity associated with the soft mode is about 10 times higher in pores than in the bulk. These modes are not detected in micropores although low frequency relaxation is present. The last one probably is not connected with the nature of liquid crystal but is associated with surface polarization effects typical for two component heterogeneous media. The difference between the dynamics of orientational motion of the polar molecules of NLC in confined geometries and in the bulk is qualitatively determined by the total energy Fs of the interaction between molecules and the surface of the pore wall, which is found Fs ≈ 102erg/cm2.

Statistical Approach to Radiative Transfer in the Heterogeneous Media of Thin-Wall Morphology—II: Applications

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
A. V. Gusarov
Keyword(s):  
Statistical Approach ◽  
Heterogeneous Media ◽  
Biological Tissues ◽  
Radiative Properties ◽  
Thin Wall ◽  
Porous Structures ◽  
Regular Arrangement ◽  
Mc Simulation ◽  
The Difference ◽  
Radiative Thermal Conductivity

The statistical multiphase approach (MPA) proposed in the first part of this work to evaluate radiative properties of composite materials is applied to porous structures of opaque material and biological tissues. Radiative thermal conductivity is calculated for the bundle of circular rods, packed pebble beds, and metal foams. The results generally agree with the reference calculations by other methods. The small difference can be explained by different approaches to scattering and assumptions about the temperature distribution. Attenuation of light in skin tissues is calculated by the diffusion approximation. The attenuation coefficient generally agrees with the reference Monte Carlo simulation (MC). The difference observed at certain combination of parameters can be due to the assumption of regular arrangement of vessels at the MC simulation.

Variations on a segmental theme: muscle receptor organs and extensor neuromusculature in the squat lobster Munida quadrispina (Anomura, Galatheidae)

1995 ◽  
Vol 198 (12) ◽  
pp. 2453-2463 ◽  
Author(s):  
E Wallis ◽  
D Paul ◽  
B Antonsen ◽  
R Hollenberg
Keyword(s):  
Relative Size ◽  
Extracellular Recording ◽  
Blue Staining ◽  
Squat Lobster ◽  
Muscle Receptor ◽  
Axial Muscles ◽  
Extensor Motoneurones ◽  
The Difference ◽  
Segmental Variation ◽  
Species Specific

Extensor neuromusculature and the muscle receptor organs (MROs) associated with them have been conserved during the evolution of malacostracan crustaceans, despite species-specific differences between homologous segments in divergent taxa. Investigations of these differences could provide insight into how sensory and neuromuscular elements are modified to accommodate changing behavioural patterns. The most obvious differences between squat lobsters (galatheid anomurans) and macruran decapods, such as crayfish, are the greater dorso-ventral flattening of the galatheid abdomen and its flexed resting posture. To investigate whether the evolution of this altered posture affected extensor neuromusculature and MRO morphology and physiology, we used Methylene Blue staining, cobalt backfilling and extracellular recording techniques to describe these elements in the caudal thoracic and six abdominal segments of the squat lobster Munida quadrispina and compared our results with published descriptions of homologous elements in macrurans. In M. quadrispina, there is segmental variation both in the orientation of the MROs along the abdomen and in their physiological responses to stretch: apparent sensitivity is higher in caudal than rostral MROs. Homologues of three of the four accessory neurones found in crayfish occur, but AN#1 has a major dendrite not present in crayfish. Intersegmental differences in size and morphology of extensor motoneurones occur in M. quadrispina, as have been reported in crayfish, but are dissimilar in the two: abdominal ganglion 5 extensor motoneurones are the largest in M. quadrispina and the smallest in crayfish; this difference correlates with the difference in relative size of axial muscles along the abdomen reported previously for these species. M. quadrispina also differs from macrurans in having a single tonic, and no phasic, MRO on each side of the last abdominal segment. Together, these observations suggest that galatheids have evolved modified or additional neurobehavioural control(s) for the abdomen and tailfan.

scholarly journals The tax gap as a public management instrument: application to wealth taxes

2019 ◽  
Vol 27 (81) ◽  
pp. 207-225
Author(s):  
José M. Durán-Cabré ◽  
Alejandro Esteller Moré ◽  
Mariona Mas-Montserrat ◽  
Luca Salvadori
Keyword(s):  
Public Management ◽  
Design Methodology ◽  
Relative Size ◽  
Tax Compliance ◽  
Content Type ◽  
Tax Gap ◽  
Wealth Tax ◽  
The Difference ◽  
Gift Tax ◽  
Over Time

Purpose The purpose of this paper is to study the concept of tax gap, that is the difference between the total amount of taxes collected and the total tax revenues that would be collected under full tax compliance. Design/methodology/approach The authors also present the methodology to estimate the gap for two taxes levied on wealth: the wealth tax and the inheritance and gift tax; both are administered in Spain by the regional tax authorities. Findings The authors point out that its estimation offers useful information about the relative size and nature of non-compliance, as well as its evolution over time. Likewise, the tax gap is a valuable instrument not only to define enforcement strategies of the tax administration but also to enhance its accountability. Nonetheless, the methodology used to estimate the tax gap and, consequently, the interpretation of the results is subject to limitations that are discussed in the paper. Originality/value Finally, the paper provides the results of the estimations obtained from using microdata: 44.34 per cent gap in the wealth tax and 41.26 per cent in the inheritance and gift tax.

scholarly journals Boulder Pickup by Tsunami Surge

2019 ◽  
Vol 13 (05n06) ◽  
pp. 1941006
Author(s):  
Samuel Harry ◽  
Margaret Exton ◽  
Harry Yeh
Keyword(s):  
Pore Water Pressure ◽  
Initial Conditions ◽  
Scale Effects ◽  
Traditional Approach ◽  
Water Pressure ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Conditions ◽  
The Difference ◽  
The Impact

Study of boulder transport by tsunamis is challenging because boulder size, shape, and composition vary greatly; furthermore, flow conditions, topography, and initial conditions are generally unknown. To investigate the mechanism of boulder pickup, experiments of tsunami-like flow past spherical boulders partially buried in a sediment bed are conducted. The experiments are performed in a large centrifuge facility to reduce scale effects and the corresponding dynamic similitude is discussed. The traditional approach to determine boulder pickup is adapted for the case of a half-buried spherical boulder. The adapted model predicts that the boulders are transported, but does not accurately predict the timing of pick up. To investigate the difference in pickup timing, two physical phenomena are discussed: pore-water-pressure dissipation in the soil, and the impact of the free-surface flow on hydrodynamic forces. For a spherical shaped boulder, vertical forces (i.e. buoyant and lift forces) are critical for the initiation of boulder pickup. It was found that spherical boulders that are three-quarter buried in the soil are not transported, even when exposed to flow conditions that would otherwise predict transport.

The Aerodynamic Interaction of Stator Shroud Leakage and Mainstream Flows in Compressors

2000 ◽  
Author(s):  
A. A. J. Demargne ◽  
J. P. Longley
Keyword(s):  
Mass Flow ◽  
Large Scale ◽  
Scale Effects ◽  
Tangential Velocity ◽  
Blade Loading ◽  
Vortical Structures ◽  
Low Leakage ◽  
Aerodynamic Interaction ◽  
Flow Interactions ◽  
The Difference

The aerodynamics of stator shroud leakage and mainstream flow interactions have been investigated using a linear cascade in which leakage mass flow and tangential velocity could be varied independently. Experimental measurements confirm the detrimental effect of increasing leakage mass flow rate, but also show clearly that increasing cavity tangential velocity improves the performance of the blade row. Shroud leakage is also found to modify significantly the spanwise distribution of blockage, flow turning and loss at exit of the stator passage. The mechanisms behind these large-scale effects are identified and a description of the interaction process based on momentum thickness arguments is proposed. Experimental and numerical results show that the amount of leakage is a linear function of the difference between cavity pressure and average pressure on the hub upstream of the stator. This result is shown to be an axisymmetric result, and thus largely independent of the pitchwise variation in blade loading. Departures from linearity at low leakage fractions are associated to the blade loading inducing pitchwise non-uniformities in the structure of the flow at the interface between the shroud cavity and the mainstream. These non-uniformities involve vortical structures, which participate in the exchange of fluid and momentum between the cavity and the mainstream, even at zero net leakage. Experiments also show that these non-uniformities in flow structure contribute to the generation of loss.

scholarly journals Single-stage prediction models do not explain the magnitude of syntactic disambiguation difficulty

2020 ◽  
Author(s):  
Marten van Schijndel ◽  
Tal Linzen
Keyword(s):  
Neural Network ◽  
Prediction Models ◽  
Relative Size ◽  
Language Models ◽  
Ambiguous Sentence ◽  
Linear Effect ◽  
Garden Path ◽  
Recovery Mechanisms ◽  
The Difference ◽  
Network Language

The disambiguation of a syntactically ambiguous sentence in favor of dispreferred parse can lead to slower reading at the disambiguation point. This phenomenon, referred to as a garden path effect, has motivated models in which readers only maintain a subset of the possible parses of the sentence; reverting to a discarded parse requires costly reanalysis. More recently, it has been proposed that the garden path effect can be reduced to surprisal arising in a fully parallel parser: words consistent with the initially dispreferred but ultimately correct parse are simply less predictable than those consistent with the incorrect parse. The surprisal account is more parsimonious since predictability has pervasive effects in reading far beyond garden path sentences. Crucially, this account predicts a linear effect of surprisal: the difficulty experienced by readers should be proportional to the difference in word surprisal between the ultimately correct and ultimately incorrect interpretations. To test this prediction, we estimated word-by-word surprisal using recurrent neural network language models, comparing those estimates to self-paced reading times for three garden path constructions. While surprisal successfully predicted the existence of garden path responses, it severely underpredicted the magnitude of all of the garden path effects. Further, the relative size of the predicted effects was inconsistent with the relative size of the responses in humans, indicating that a differently scaled linking function would not be able to predict the response magnitudes either. These results support two-stage processing models in which recovery mechanisms beyond predictability are involved in processing garden path sentences.

Effects of Framed Embankment for High-Grade Expressway in Permafrost Regions

2014 ◽  
Vol 505-506 ◽  
pp. 139-148 ◽  
Author(s):  
Wan Sheng Pei ◽  
Yuan Ming Lai ◽  
Ming Yi Zhang ◽  
Wen Bing Yu ◽  
Shuang Yang Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Thermal Stability ◽  
Global Warming ◽  
Scale Effects ◽  
Simulation Method ◽  
High Grade ◽  
Permafrost Table ◽  
The Difference ◽  
Thermal Stability Of ◽  
Permafrost Regions

Construction of high-grade highways is an important action to meet the requirement of communication and transportation in permafrost regions. Frame embankment is proposed to reduce the scale effects caused by wide pavement. Numerical simulation method is employed to analyze the improvement of frame embankment for thermal stability of roadbed, with the consideration of global warming. Compared the response of permafrost at symmetric position of each embankment to construction, the consistency degree of response is taken as decision fundament. Two indexes are selected, that is, the difference of permafrost table between the embankment and that at natural side, and the change of mean annual geothermal under the embankment. Additionally, the convenient for construction and wind-blown sand hazard are considered to determine reasonable frame space. So, numerical simulation of flow field of wind around embankments is carried out. It is concluded that the minimum space between two embankment is 6 m. The aim of this study is to provide scientific guidelines on construction of major permafrost engineering in the future.

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