scholarly journals Viscous Property of Toyoura Sand Over a Wide Range of Shear Deformation Rate and its Model Simulation

2009 ◽  
Vol 49 (2) ◽  
pp. 231-247 ◽  
Author(s):  
Antoine Duttine ◽  
Fumio Tatsuoka ◽  
Jina Lee ◽  
Warat Kongkitkul
Keyword(s):  
Shear Deformation ◽  
Deformation Rate ◽  
Model Simulation ◽  
Viscous Property ◽  
Wide Range ◽  
Toyoura Sand

Intercomparison of Phytoplankton functional types dynamics from satellite observations

2021 ◽  
Author(s):  
Marine Bretagnon ◽  
Séverine Alvain ◽  
Astrid Bracher ◽  
Philippe Garnesson ◽  
Svetlana losa ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Marine Environment ◽  
Model Simulation ◽  
Chlorophyll Concentration ◽  
Satellite Observations ◽  
Global Ocean ◽  
Ocean Colour ◽  
Marginal Seas ◽  
Functional Types ◽  
Wide Range

<p>Copernicus marine environment monitoring service (CMEMS) gives users access to a wide range of ocean descriptors. Both physics and biogeochemistry of the marine environment can be studied with complementary source of data, such as in situ data, modelling output and satellite observations at global scale and/or for European marginal seas. Among the ocean descriptors supplied as part of CMEMS, phytoplankton functional types (PFTs) describe the phytoplanktonic composition at global level or over European marginal seas. Studied phytoplankton assemblage is particularly important as it is the basis of the marine food-web. Composition of the first trophic level is a valuable indicator to infer the structure of the ecosystem and its health. Over the last decades, ocean colour remote sensing has been used to estimate the phytoplanktonic composition. The algorithms developed to estimate PFTs composition based on ocean colour observation can be classified in three categories: the spectral approaches, the abundance-based approaches (derived from the chlorophyll concentration) and the ecological approaches. The three approaches can lead to differences or, conversely, to similar patterns. Difference and similarity in PFTs estimation from remote sensing is a useful information for data assimilation or model simulation, as it provides indications on the uncertainties/variability associated to the PFT estimates. Indeed, PFT estimates from satellite observations are increasingly assimilated into ecological models to improve biogeochemical simulations, what highlights the importance to get an index or at least information describing the validity range of such PFTs estimates.</p><p>In this study, four algorithms (two abundance-based, and two spectral approaches) are compared. The aim of this study is to compare the related PFT products spatially and temporally, and to study the agreement of their derived PFT phenology. This study proposes also to compare PFT algorithms developed for the global ocean with those developed for specific regions in order to assess the potential strength and weakness of the different approaches. Once similarities and discrepancies between the different approaches are assessed, this information could be used by model to give an interval of confidence in model simulation.</p>

NNN-ISING MODEL SIMULATION OF NANODOMAIN TEXTURES IN RELAXOR-TYPE LEAD SCANDIUM TANTALATE

1993 ◽  
Vol 07 (26) ◽  
pp. 4353-4369 ◽  
Author(s):  
H. QIAN ◽  
J.L. PENG ◽  
L.A. BURSILL
Keyword(s):  
Statistical Physics ◽  
Nearest Neighbor ◽  
Model Simulation ◽  
Dark Field ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Wide Range ◽  
Transmission Electron Microscopic ◽  
Long Range Ordering ◽  
Perovskite Type

Chemical domain textures for lead scandium tantalate (PST) are modelled using Monte Carlo (MCS) and next-nearest-neighbor Ising (NNNI) models. A wide range of degrees of short- and long-range ordering of the (Ta, Sc) atoms occur in ceramic specimens, depending on processing routes. The simulations help us understand and quantify the chemical domain textures, chemical domain wall configurations and other chemical defects which may occur in certain relaxor-type perovskite-type oxides. The results are compared to dark-field transmission electron microscopic observations. Some new types of small defects were discovered. These are described and classified. The results provide a first step towards the development of a microscopic statistical physics framework for analytical theories of the dielectric response of relaxor-type ceramics, where the frequency and temperature variation of the permittivity are due essentially to dipolar-type fluctuations on nanometer scales.

Wind Force on Tall Structure: An Approach From SPH

2012 ◽  
Vol 2 (1) ◽  
Author(s):  
Ananna Ahmed ◽  
Abdullah Hil Baki ◽  
Munaz Ahmed Noor
Keyword(s):  
Structural Engineering ◽  
Model Simulation ◽  
Wind Load ◽  
Tall Building ◽  
Test Method ◽  
Wind Pressure ◽  
Wind Force ◽  
Wide Range ◽  
Particle Hydrodynamics ◽  
Tall Structure

Wind pressure calculation for tall building frame has always been an extensive job. Usual methods used to estimate wind load are Wind tunnel test method and Finite Element Method and specifications has been derived. In this research, with a view to eliminating drawbacks of these methods and providing a visual interpretation of wind flow a third method is introduced using Smooth Particle Hydrodynamics (SPH) Approach. A model simulation was performed by a SPH software named SPHysics to calculate the pressure exerted on the structure and to derive a graphical interpretation of flow pattern using Para View. Values of pressure at different elevation of the building that actually occurs when wind with certain velocity flows through a tall building are found. From the data found, height vs. pressure graphs are generated which clearly supports the proportional relationship between these two parameters even with triangular and parabolic variation. Again, velocity vs. pressure graphs are plotted which also justifies inter-relationship of proportionality. This is a qualitative comparison not a quantitative one as there is many limitations regarding technicality, computer capacity, and time. These values may be crosschecked with the values found from conventional methods when more precise and suitable boundary conditions can be used in simulation. In future, with intricate detailing and suitable three dimensional modeling, more accurate value of pressure can be found with wide range of applicability. The authors are expecting derivation of two equations as a function of height and velocity to calculate wind load to use in design if further proceeding is possible. This can offer a significant benefit of simplicity for users and can be beginning a new era of using SPH in structural engineering.   Keywords - Wind force, tall structure, Particle Hydrodynamics Approach

Performance evaluation of SBR treatment for nitrogen removal from tannery wastewater

2006 ◽  
Vol 53 (12) ◽  
pp. 275-284 ◽  
Author(s):  
S. Murat ◽  
G. Insel ◽  
N. Artan ◽  
D. Orhon
Keyword(s):  
Steady State ◽  
Nitrogen Removal ◽  
System Performance ◽  
Model Simulation ◽  
Pilot Scale ◽  
Simulation System ◽  
Nitrogen Compounds ◽  
Concentration Profiles ◽  
Steady State Operation ◽  
Wide Range

Performance of SBR treatment for nitrogen removal from tannery is evaluated for a wide range of wastewater temperature between 7 and 30 °C. A pilot-scale SBR unit fed with plain-settled wastewater is operated on site for this purpose. Effective nitrogen removal is sustained by adjustment of the sludge age from 28 to 5 days. Concentration profiles of nitrogen compounds within a selected complete SBR cycle during the steady state operation at different wastewater temperatures and sludge ages are evaluated by model simulation. System performance is also interpreted in terms of modeling and stoichiometric calculation. Additional nitrate loss was observed during aerobic period when the aeration intensity was reduced by the factor of 50%.

A Numerical Model for the Mist Dynamics and Heat Transfer at Various Ambient Pressures

2005 ◽  
Vol 127 (4) ◽  
pp. 631-639 ◽  
Author(s):  
Roy J. Issa ◽  
S. C. Yao
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Test Data ◽  
Model Simulation ◽  
Droplet Size Distribution ◽  
Atmospheric Conditions ◽  
Single Stream ◽  
Wide Range ◽  
Wall Interaction ◽  
Uniform Droplets

A numerical model is developed to simulate the dynamics of the droplet-wall interaction and heat transfer mechanisms at sub-atmospheric to elevated ambient pressures, and for surface temperatures ranging from nucleate to film boiling. This is the first time a general model is developed to study these phenomena over a wide range of ambient pressures. The model provides insight to the optimal flow conditions, and droplet size distribution for best heat transfer enhancement. Simulations are provided for single stream droplet impactions, and for full conical sprays using nozzles that dispense a spectrum of non-uniform droplets. The model simulation was compared against available test data for single stream of droplets at non-atmospheric conditions, and the simulation compared favorably well with the test data.

scholarly journals On the multi-fractal scaling properties of sea ice deformation

2019 ◽  
Author(s):  
Pierre Rampal ◽  
Véronique Dansereau ◽  
Einar Olason ◽  
Sylvain Bouillon ◽  
Timothy Williams ◽  
...  
Keyword(s):  
Sea Ice ◽  
Initial Conditions ◽  
Model Simulation ◽  
Winter Season ◽  
Scaling Properties ◽  
Scaling Invariance ◽  
Invariance Properties ◽  
Wide Range ◽  
Set Up ◽  
First Time

Abstract. In this paper, we evaluate the neXtSIM sea ice model with respect to the observed scaling invariance properties of sea ice deformation in the spatial and temporal domains. Using an Arctic set-up with realistic initial conditions, state-of-the-art atmospheric reanalysis forcing and geostrophic currents retrieved from satellite data, we show that the model is able to reproduce the observed properties of these scaling in both the spatial and temporal do- mains over a wide range of scales and, for the first time, their multi-fractality. The variability of these properties during the winter season are also captured by the model. We also show that the simulated scaling exhibit a space-time coupling, a suggested property of brittle deformation at geophysical scales. The ability to reproduce the multi-fractality of these scaling is crucial in the context of downscaling model simulation outputs to infer sea ice variables at the sub-grid scale, and also has implication in modeling the statistical properties of deformation-related quantities such as lead fractions, and heat and salt fluxes.

Viscoelastic-viscoplastic combined constitutive model for glassy amorphous polymers under loading/unloading/no-load states

2020 ◽  
Vol 37 (5) ◽  
pp. 1703-1735
Author(s):  
Seishiro Matsubara ◽  
Kenjiro Terada ◽  
Ryusei Maeda ◽  
Takaya Kobayashi ◽  
Masanobu Murata ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Deformation Rate ◽  
Amorphous Polymers ◽  
Elastic Behavior ◽  
Content Type ◽  
Rate Dependent ◽  
Proposed Model ◽  
Wide Range ◽  
In Series ◽  
Rheology Model

Purpose This study aims to propose a novel viscoelastic–viscoplastic combined constitutive model for glassy amorphous polymers within the framework of thermodynamics at finite strain that is capable of capturing their rate-dependent inelastic mechanical behavior in wide ranges of deformation rate and amount. Design/methodology/approach The rheology model whose viscoelastic and viscoplastic elements are connected in series is set in accordance with the multi-mechanism theory. Then, the constitutive functions are formulated on the basis of the multiplicative decomposition of the deformation gradient implicated by the rheology model within the framework of thermodynamics. Dynamic mechanical analysis (DMA) and loading/unloading/no-load tests for polycarbonate (PC) are conducted to identify the material parameters and demonstrate the capability of the proposed model. Findings The performance was validated in comparison with the series of the test results with different rates and amounts of deformation before unloading together. It has been confirmed that the proposed model can accommodate various material behaviors empirically observed, such as rate-dependent elasticity, elastic hysteresis, strain softening, orientation hardening and strain recovery. Originality/value This paper presents a novel rheological constitutive model in which the viscoelastic element connected in series with the viscoplastic one exclusively represents the elastic behavior, and each material response is formulated according to the multiplicatively decomposed deformation gradients. In particular, the yield strength followed by the isotropic hardening reflects the relaxation characteristics in the viscoelastic constitutive functions so that the glass transition temperature could be variant within the wide range of deformation rate. Consequently, the model enables us to properly represent the loading process up to large deformation regime followed by unloading and no-load processes.

scholarly journals Unified phase diagram of reversible–irreversible, jamming, and yielding transitions in cyclically sheared soft-sphere packings

2020 ◽  
Vol 117 (19) ◽  
pp. 10203-10209 ◽  
Author(s):  
Pallabi Das ◽  
H. A. Vinutha ◽  
Srikanth Sastry
Keyword(s):  
Phase Diagram ◽  
Shear Deformation ◽  
Soft Matter ◽  
Granular Matter ◽  
Colloidal Suspensions ◽  
Localized States ◽  
Sphere Packings ◽  
Cyclic Shear ◽  
Soft Sphere ◽  
Wide Range

Self-organization, and transitions from reversible to irreversible behavior, of interacting particle assemblies driven by externally imposed stresses or deformation is of interest in comprehending diverse phenomena in soft matter. They have been investigated in a wide range of systems, such as colloidal suspensions, glasses, and granular matter. In different density and driving regimes, such behavior is related to yielding of amorphous solids, jamming, memory formation, etc. How these phenomena are related to each other has not, however, been much studied. In order to obtain a unified view of the different regimes of behavior, and transitions between them, we investigate computationally the response of soft-sphere assemblies to athermal cyclic-shear deformation over a wide range of densities and amplitudes of shear deformation. Cyclic-shear deformation induces transitions from reversible to irreversible behavior in both unjammed and jammed soft-sphere packings. Well above the minimum isotropic jamming density (ϕJ), this transition corresponds to yielding. In the vicinity of the jamming point, up to a higher-density limit, we designate ϕJcyc, an unjammed phase emerges between a localized, absorbing phase and a diffusive, irreversible, phase. The emergence of the unjammed phase signals the shifting of the jamming point to higher densities as a result of annealing and opens a window where shear jamming becomes possible for frictionless packings. Below ϕJ, two distinct localized states, termed point- and loop-reversible, are observed. We characterize in detail the different regimes and transitions between them and obtain a unified density-shear amplitude phase diagram.

scholarly journals The role of annealing in determining the yielding behavior of glasses under cyclic shear deformation

2021 ◽  
Vol 118 (16) ◽  
pp. e2100227118
Author(s):  
Himangsu Bhaumik ◽  
Giuseppe Foffi ◽  
Srikanth Sastry
Keyword(s):  
Shear Deformation ◽  
Strain Amplitude ◽  
Threshold Energy ◽  
Cyclic Shear ◽  
Annealing Regime ◽  
Uniform Shear ◽  
High Annealing ◽  
Wide Range ◽  
Yielding Behavior

Yielding behavior in amorphous solids has been investigated in computer simulations using uniform and cyclic shear deformation. Recent results characterize yielding as a discontinuous transition, with the degree of annealing of glasses being a significant parameter. Under uniform shear, discontinuous changes in stresses at yielding occur in the high annealing regime, separated from the poor annealing regime in which yielding is gradual. In cyclic shear simulations, relatively poorly annealed glasses become progressively better annealed as the yielding point is approached, with a relatively modest but clear discontinuous change at yielding. To understand better the role of annealing on yielding characteristics, we perform athermal quasistatic cyclic shear simulations of glasses prepared with a wide range of annealing in two qualitatively different systems—a model of silica (a network glass) and an atomic binary mixture glass. Two strikingly different regimes of behavior emerge. Energies of poorly annealed samples evolve toward a unique threshold energy as the strain amplitude increases, before yielding takes place. Well-annealed samples, in contrast, show no significant energy change with strain amplitude until they yield, accompanied by discontinuous energy changes that increase with the degree of annealing. Significantly, the threshold energy for both systems corresponds to dynamical cross-over temperatures associated with changes in the character of the energy landscape sampled by glass-forming liquids.

A Parametric Study on the Free Vibration of Noncylindrical Helical Springs

1998 ◽  
Vol 65 (1) ◽  
pp. 157-163 ◽  
Author(s):  
V. Yıldırım
Keyword(s):  
Free Vibration ◽  
Shear Deformation ◽  
Parametric Study ◽  
Natural Frequencies ◽  
Rotary Inertia ◽  
Helical Springs ◽  
Wide Range ◽  
Stiffness Method

In the work based on the stiffness method reported in this paper, considering the rotary inertia, the axial and shear deformation terms, the natural frequencies of conical, barrel and hyperboloidal-type helical springs fixed at both ends are calculated. The results are presented in dimensionless graphical forms for the six lowest natural frequencies of all types of noncylindrical helices for a wide range of vibrational parameters which influence the natural frequencies. A discussion about the effects of vibrational parameters on the natural frequencies is also presented.

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