scholarly journals Reflection of an ultrasonic wave on the bone-implant interface: Comparison of two-dimensional and three-dimensional numerical models

2020 ◽  
Vol 147 (1) ◽  
pp. EL32-EL36 ◽  
Author(s):  
Yoann Hériveaux ◽  
Guillaume Haïat ◽  
Vu-Hieu Nguyen
Keyword(s):  
Ultrasonic Wave ◽  
Numerical Models ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Bone Implant

scholarly journals Experience of employment of computational models for water quality modelling

2019 ◽  
Vol 97 ◽  
pp. 05030 ◽  
Author(s):  
Anatoly Krutov ◽  
Dilshod Bazarov ◽  
Begzod Norkulov ◽  
Bakhtiyar Obidov ◽  
Bobur Nazarov
Keyword(s):  
Computational Models ◽  
Numerical Models ◽  
Qualitative Difference ◽  
Three Dimensional ◽  
Sufficient Conditions ◽  
Aral Sea ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Dimensional Model ◽  
Wind Currents

The purpose of the article is to develop the required and sufficient conditions under which numerical methods can be used for engineering calculations and for scientific research of hydrodynamic processes in solving practical problems related to predicting the spread of pollutants in water bodies and streams. The conducted studies consisted in comparing the results of laboratory experiments and mathematical modelling, in particular the distribution of heat in a stream with different temperature in water layers was studied. To check the adequacy of the proposed numerical models, calculations were performed and comparisons were made with the results of experimental data. The obtained results allowed to determine the boundaries of the qualitative difference in the flow behaviour for different numbers of Froude and Reynolds. The accuracy of the method was also studied. A number of additional requirements for numerical models were proposed in addition to approcsimation and stability, such as requirements of conservativeness (divergence), existence of trivial solutions on grids, possibility to calculate highly unsteady, quasi-stable, pulsating and stationary flows, requirement of invariance of linearized equations, as well as the requirement of a one-dimensional scheme to be a consequence of a two-dimensional scheme. Distribution of velocities of wind currents using a three-dimensional and two-dimensional model was studied for a real object. A shallow-water bay of the Aral Sea was chosen as the object for the research. Comparison of the calculation results for both models showed that the flow velocity fields, as well as the distribution of pollutants in shallow waters, can be performed using a two-dimensional model.

THREE-DIMENSIONAL ASPECTS OF RE-ENTRY IN EXPERIMENTAL AND NUMERICAL MODELS OF VENTRICULAR FIBRILLATION

1999 ◽  
Vol 09 (04) ◽  
pp. 695-704 ◽  
Author(s):  
V. N. BIKTASHEV ◽  
A. V. HOLDEN ◽  
S. F. MIRONOV ◽  
A. M. PERTSOV ◽  
A. V. ZAITSEV
Keyword(s):  
Ventricular Fibrillation ◽  
Numerical Simulations ◽  
Numerical Models ◽  
Three Dimensional ◽  
Spiral Waves ◽  
Excitable Media ◽  
Ventricular Wall ◽  
Two Dimensional ◽  
Key Features ◽  
Scroll Waves

Ventricular fibrillation is believed to be produced by the breakdown of re-entrant propagation waves of excitation into multiple re-entrant sources. These re-entrant waves may be idealized as spiral waves in two-dimensional, and scroll waves in three-dimensional excitable media. Optically monitored, simultaneously recorded endocardial and epicardial patterns of activation on the ventricular wall do not always show spiral waves. We show that numerical simulations, even with a simple homogeneous excitable medium, can reproduce the key features of the simultaneous endo- and epicardial visualizations of propagating activity, and so these recordings may be interpreted in terms of scroll waves within the ventricular wall.

Modelling the global sources and sinks of radiatively active gases

1995 ◽  
Vol 351 (1696) ◽  
pp. 397-411 ◽  
Keyword(s):  
Numerical Models ◽  
Stratospheric Ozone ◽  
Trace Gases ◽  
Three Dimensional ◽  
Relative Importance ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Sources And Sinks ◽  
Two Dimensional Model

The use of numerical models in understanding the budgets of atmospheric trace gases is discussed. The budget of methane is calculated in a two-dimensional model. The contrasting behaviour of the Northern and Southern Hemisphere reflects changes in the relative importance of emissions, transport and chemistry. Models can also be used to test hypotheses. An example of such a study is presented in which it is shown that changes in stratospheric ozone could have played a significant role in the dramatic change in methane trend observed in the early 1990s. Finally, use of a three-dimensional model to study tropospheric trace gases is introduced.

scholarly journals Hydrodynamic modelling of a regulated Mediterranean coastal lagoon, the Albufera of Valencia (Spain)

2014 ◽  
Vol 16 (5) ◽  
pp. 1062-1076 ◽  
Author(s):  
Javier García Alba ◽  
Aina G. Gómez ◽  
Pilar del Barrio Fernández ◽  
Andrés García Gómez ◽  
César Álvarez Díaz
Keyword(s):  
Coastal Lagoon ◽  
Sea Water ◽  
Numerical Models ◽  
Coastal Lagoons ◽  
Three Dimensional ◽  
Real Data ◽  
Two Dimensional ◽  
Shallow Water Models ◽  
Dimensional Models

Coastal lagoon hydrodynamics are strongly influenced by sea water exchange, especially when the connection between the lagoon and the sea is artificially regulated. These situations increase the complexity of the hydrodynamic regime, requiring the use of numerical models to understand their behaviour. Traditionally, one-dimensional models have been used, although in recent years, the development of two-dimensional shallow water models and advanced numerical techniques have increased notably. However, most of the existing bi-dimensional models consider the connection to the sea as a boundary condition, and they do not take into consideration the sea-lagoon exchange. In this paper, a fully two-dimensional hydrodynamic model of a heavily regulated coastal lagoon, which includes the artificial connection with the sea, is presented. The model allows the characterization of water level variation in the lagoon, taking into account the combined effect of different forcings. This model consists of two hydrodynamic modules: a long wave module (two-dimensional depth-averaged) which includes the analysis of a system of sluice gates, and a wind module (quasi three-dimensional). The model was successfully calibrated and validated with real data, showing its ability to accurately describe the hydraulic dynamics of regulated coastal lagoons.

scholarly journals Quick self-assembly of bio-inspired multi-dimensional well-ordered structures induced by ultrasonic wave energy

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246453
Author(s):  
Connor Murphy ◽  
Yunqi Cao ◽  
Nelson Sepúlveda ◽  
Wei Li
Keyword(s):  
Ultrasonic Wave ◽  
Wave Energy ◽  
Self Assembly ◽  
Mechanical Vibration ◽  
Water Environment ◽  
Three Dimensional ◽  
Building Blocks ◽  
Two Dimensional ◽  
Ordered Structures ◽  
Bottom Up

Bottom-up self-assembly of components, inspired by hierarchically self-regulating aggregation of small subunits observed in nature, provides a strategy for constructing two- or three-dimensional intriguing biomimetic materials via the spontaneous combination of discrete building blocks. Herein, we report the methods of ultrasonic wave energy-assisted, fast, two- and three-dimensional mesoscale well-ordered self-assembly of microfabricated building blocks (100 μm in size). Mechanical vibration energy-driven self-assembly of microplatelets at the water-air interface of inverted water droplets is demonstrated, and the real-time formation process of the patterned structure is dynamically explored. 40 kHz ultrasonic wave is transferred into microplatelets suspended in a water environment to drive the self-assembly of predesigned well-ordered structures. Two-dimensional self-assembly of microplatelets inside the water phase with a large patterned area is achieved. Stable three-dimensional multi-layered self-assembled structures are quickly formed at the air-water interface. These demonstrations aim to open distinctive and effective ways for new two-dimensional surface coating technology with autonomous organization strategy, and three-dimensional complex hierarchical architectures built by the bottom-up method and commonly found in nature (such as nacre, bone or enamel, etc.).

Effects of Varying the Shape of the Convective Heating Profile on Convectively Coupled Gravity Waves and Moisture Modes

2012 ◽  
Vol 69 (8) ◽  
pp. 2505-2519 ◽  
Author(s):  
Željka Fuchs ◽  
Saska Gjorgjievska ◽  
David J. Raymond
Keyword(s):  
Analytical Model ◽  
Gravity Waves ◽  
Numerical Models ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Convective Heating ◽  
Two Dimensional ◽  
Beta Plane ◽  
Gross Moist Stability ◽  
Heating Profiles

Abstract The analytical model of convectively coupled gravity waves and moisture modes of Raymond and Fuchs is extended to the case of top-heavy and bottom-heavy convective heating profiles. Top-heavy heating profiles favor gravity waves, while bottom-heavy profiles support moisture modes. The latter behavior results from the sensitivity of moisture modes to the gross moist stability, which is more negative with bottom-heavy heating. A numerical implementation of the analytical model allows calculations in the two-dimensional nonrotating case as well as on a three-dimensional equatorial beta plane. In the two-dimensional case the analytical and numerical models are mostly in agreement, although minor discrepancies occur. In three dimensions the gravity modes become equatorial Kelvin waves whereas the moisture modes are more complex and require further investigation.

A discussion on ocean currents and their dynamics - Ocean models

1971 ◽  
Vol 270 (1206) ◽  
pp. 391-413 ◽  
Keyword(s):  
Ocean Circulation ◽  
Nonlinear Models ◽  
Numerical Models ◽  
Bottom Topography ◽  
Three Dimensional ◽  
Drake Passage ◽  
Western Boundary ◽  
Two Dimensional ◽  
Equatorial Undercurrent ◽  
Oceanic Gyres

Over the past twenty years or so, a good qualitative description of the ocean circulation has been built up through the use of two-dimensional wind-driven models. These correctly predict the position and sense ot circulation of the major oceanic gyres, and explain the strong western boundary currents. However, the only direct measurements available for quantitative comparison with theory are those of the transport of the Gull Stream. Observed values are considerably larger than those predicted by linear theory, but can be explained by nonlinear models. . Two-dimensional models have their shortcomings, however, because they take no account ot vertical structure. They cannot properly model effects of nonlinearity, bottom topography, or of motions driven by thermohaline effects. They overlook important aspects of the circulation such as the equatorial undercurrent, and upwelling. Three-dimensional numerical models are designed to include these effects, and successfully reproduce, in a qualitative fashion, the major features of the ocean circulation. The models may be used for ‘experiments’ to find possible effects of changing parameters (such as the width and depth of Drake Passage), and to investigate the relative importance of different regions. With presentday computers, however, there are resolution and other problems which limit the degree to which the real ocean’s parameters may be matched.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

A linearity test for thick specimens imaged by HVEM over a 180° angular range

1991 ◽  
Vol 49 ◽  
pp. 552-553
Author(s):  
Yu Liu
Keyword(s):  
Phase Contrast ◽  
Three Dimensional ◽  
Angular Range ◽  
Two Dimensional ◽  
Back Projection ◽  
Line Integral ◽  
Exponential Law ◽  
Transmission Electron ◽  
Absorption Law ◽  
Linearity Test

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.

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