scholarly journals Physical modelling in biomechanics

2003 ◽  
Vol 358 (1437) ◽  
pp. 1589-1596 ◽  
Author(s):  
M. A. R. Koehl
Keyword(s):  
Mathematical Models ◽  
Parameter Space ◽  
Physical Modelling ◽  
Hydrodynamic Forces ◽  
Physical Models ◽  
Comparative Approach ◽  
Physical Measurements ◽  
Performance Consequences ◽  
Living Organisms ◽  
Sessile Organisms

Physical models, like mathematical models, are useful tools in biomechanical research. Physical models enable investigators to explore parameter space in a way that is not possible using a comparative approach with living organisms: parameters can be varied one at a time to measure the performance consequences of each, while values and combinations not found in nature can be tested. Experiments using physical models in the laboratory or field can circumvent problems posed by uncooperative or endangered organisms. Physical models also permit some aspects of the biomechanical performance of extinct organisms to be measured. Use of properly scaled physical models allows detailed physical measurements to be made for organisms that are too small or fast to be easily studied directly. The process of physical modelling and the advantages and limitations of this approach are illustrated using examples from our research on hydrodynamic forces on sessile organisms, mechanics of hydraulic skeletons, food capture by zooplankton and odour interception by olfactory antennules.

New evidence for the life habit of graptoloids from physical modelling

Paleobiology ◽  
1989 ◽  
Vol 15 (4) ◽  
pp. 402-413 ◽  
Author(s):  
Susan Rigby ◽  
Barrie Rickards
Keyword(s):  
Narrow Band ◽  
Physical Modelling ◽  
Physical Models ◽  
Life Habit ◽  
Passive Rotation ◽  
Directional Motion ◽  
Mode Of Life ◽  
The Individual ◽  
New Evidence ◽  
Colony Shape

Physical models of graptolites have been constructed for a range of morphologies, with emphasis on planar, multiramous forms. The models are life size and have the density of a living graptolite, based on the now-established collagenous nature of the periderm and unavoidable assumptions about the amount of extrathecal tissue present in the living colony. These models have been used to test the two main hypotheses of graptolite life habit developed by Bulman, Rickards, Kirk, and others. Testing of graptoloid models in water suggests that many rhabdosome shapes were designed for passive rotation within the water column. This is caused in the models by a variety of modifications, including changes in thecal and stipe orientation, alterations of colony shape and the addition of vanes and hooks. Rotation would only have been useful when the rhabdosome was in directional motion and the frequency of such modifications seems anomalous if no such movement occurred. Thus movement by some means is required, either passively, by changes in buoyancy, or by automobility. Spiralling action would increase the harvesting path of an individual living on a planar, multiramous colony, making this a theoretically advantageous mode of life for the morphology. It would prevent the individual zooids of scandent biserial and uniserial colonies from feeding from the same narrow band of water.

scholarly journals Modelling approaches in biomechanics

2003 ◽  
Vol 358 (1437) ◽  
pp. 1429-1435 ◽  
Author(s):  
R. McN Alexander
Keyword(s):  
Mathematical Models ◽  
Conceptual Models ◽  
Semicircular Canals ◽  
Physical Models ◽  
Anatomical Changes ◽  
Body Segments ◽  
Insect Wings ◽  
Calculated Effect ◽  
3D Assembly ◽  
Physical And Mathematical Models

Conceptual, physical and mathematical models have all proved useful in biomechanics. Conceptual models, which have been used only occasionally, clarify a point without having to be constructed physically or analysed mathematically. Some physical models are designed to demonstrate a proposed mechanism, for example the folding mechanisms of insect wings. Others have been used to check the conclusions of mathematical modelling. However, others facilitate observations that would be difficult to make on real organisms, for example on the flow of air around the wings of small insects. Mathematical models have been used more often than physical ones. Some of them are predictive, designed for example to calculate the effects of anatomical changes on jumping performance, or the pattern of flow in a 3D assembly of semicircular canals. Others seek an optimum, for example the best possible technique for a high jump. A few have been used in inverse optimization studies, which search for variables that are optimized by observed patterns of behaviour. Mathematical models range from the extreme simplicity of some models of walking and running, to the complexity of models that represent numerous body segments and muscles, or elaborate bone shapes. The simpler the model, the clearer it is which of its features is essential to the calculated effect.

scholarly journals ЦИФРОВІ ТЕХНОЛОГІЇ У ФОРМУВАННІ МОДЕЛЕЙ ПЕРЕХІДНИХ ПРОЦЕСІВ В ІНДУКТИВНОСТІ ТА ЄМНОСТІ

2021 ◽  
Vol 1 (2) ◽  
pp. 330-340
Author(s):  
G. O. SHYSHKIN ◽  
Keyword(s):  
Mathematical Models ◽  
Digital Technologies ◽  
Physical Experiment ◽  
Physical Models ◽  
Measuring System ◽  
Digital Measuring ◽  
Physics Teaching ◽  
Qualitative Level ◽  
Physical Quantities

An important role in the formation of qualitative knowledge of physics in the modern education system is played by students` ability to present the processes being studied at a qualitative level. Formation of students' abilities and skills to construct figurative physical models, finding mathematical dependences between physical quantities is one of the urgent problems of physics teaching methods. Our research is devoted to the problem of the formation of high-quality imaginary models of physical processes among physics students on the basis of an educational experiment and digital technologies. To improve the quality of teaching physics, the necessity of forming physical and mathematical models of the studied processes among future specialists is substantiated. On the example of experimental study of processes occurring in DC circuits, which contain inductors and capacitors, a method of forming their imaginary and mathematical models is proposed. A digital measuring system with a personal computer was used in the research. It is proved that conducting a physical experiment with simultaneous display of research results in the form of tables and graphs contributes to the formation of a qualitative level of physical models. To form students' skills of building mathematical models of the studied processes, it is proposed to use software that allows to analyze the results of the experiment. The analysis of graphs of the studied processes allows to select mathematical dependences and to calculate necessary coefficients. The use of digital technologies and related programs provides a quick finding of mathematical models. Changing the parameters of the studied objects while finding the corresponding mathematical dependencies allows students to establish relationships between mathematical symbols and physical quantities. This approach provides students with the ability to find mathematical models of these processes or objects. The results of the implementation of the proposed method showed that the use of digital measuring systems in the educational physical experiment significantly improves the quality of students' learning of new material. Key words: physical experiment, model, digital technologies, extra current, inductance, capacitance.

scholarly journals Implementation of Mathematical Models of Buck Converter using MatLab/Simulink

2021 ◽  
pp. 516-520
Author(s):  
S. Krishnaveni Krishnaveni
Keyword(s):  
Mathematical Model ◽  
Mathematical Models ◽  
State Space Model ◽  
Buck Converter ◽  
Physical Models ◽  
Transfer Function Model ◽  
Function Model ◽  
Space Model ◽  
Modeling Techniques ◽  
And Control

The study of the dynamic behavior, transient response and the characteristics of the converters require deep knowledge in mathematical models. Mathematical models have been adequately used in the design and control of DC-DC converters and also the mathematical models are more suitable than the physical models. This paper describes the four modeling techniques of a buck converter, circuit model, mathematical model, state space model and transfer function model, and their implementation in Simulink environment.

scholarly journals Super-resolution emulator of cosmological simulations using deep physical models

2020 ◽  
Vol 495 (4) ◽  
pp. 4227-4236 ◽  
Author(s):  
Doogesh Kodi Ramanah ◽  
Tom Charnock ◽  
Francisco Villaescusa-Navarro ◽  
Benjamin D Wandelt
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Computational Cost ◽  
Physical Modelling ◽  
Real Space ◽  
Physical Models ◽  
Small Scale ◽  
Cosmological Simulations ◽  
Scale Structures ◽  
Small Scale Structures

ABSTRACT We present an extension of our recently developed Wasserstein optimized model to emulate accurate high-resolution (HR) features from computationally cheaper low-resolution (LR) cosmological simulations. Our deep physical modelling technique relies on restricted neural networks to perform a mapping of the distribution of the LR cosmic density field to the space of the HR small-scale structures. We constrain our network using a single triplet of HR initial conditions and the corresponding LR and HR evolved dark matter simulations from the quijote suite of simulations. We exploit the information content of the HR initial conditions as a well-constructed prior distribution from which the network emulates the small-scale structures. Once fitted, our physical model yields emulated HR simulations at low computational cost, while also providing some insights about how the large-scale modes affect the small-scale structure in real space.

Physical modelling of forest fire spreading through heterogeneous fuel beds

2011 ◽  
Vol 20 (5) ◽  
pp. 625 ◽  
Author(s):  
Albert Simeoni ◽  
Pierre Salinesi ◽  
Frédéric Morandini
Keyword(s):  
Field Experiments ◽  
Heterogeneous Medium ◽  
Reaction Diffusion ◽  
Physical Modelling ◽  
Fire Spread ◽  
Physical Models ◽  
Fire Intensity ◽  
Fire Behaviour ◽  
Fire Front ◽  
Fire Spreading

Vegetation cover is a heterogeneous medium composed of different kinds of fuels and non-combustible parts. Some properties of real fires arise from this heterogeneity. Creating heterogeneous fuel areas may be useful both in land management and in firefighting by reducing fire intensity and fire rate of spread. The spreading of a fire through a heterogeneous medium was studied with a two-dimensional reaction–diffusion physical model of fire spread. Randomly distributed combustible and non-combustible square elements constituted the heterogeneous fuel. Two main characteristics of the fire were directly computed by the model: the size of the zone influenced by the heat transferred from the fire front and the ignition condition of vegetation. The model was able to provide rate of fire spread, temperature distribution and energy transfers. The influence on the fire properties of the ratio between the amount of combustible elements and the total amount of elements was studied. The results provided the same critical fire behaviour as described in both percolation theory and laboratory experiments but the results were quantitatively different because the neighbourhood computed by the model varied in time and space with the geometry of the fire front. The simulations also qualitatively reproduced fire behaviour for heterogeneous fuel layers as observed in field experiments. This study shows that physical models can be used to study fire spreading through heterogeneous fuels, and some potential applications are proposed about the use of heterogeneity as a complementary tool for fuel management and firefighting.

Filtration of clay suspensions through sand

Clay Minerals ◽  
1987 ◽  
Vol 22 (1) ◽  
pp. 49-61 ◽  
Author(s):  
K. J. Ives
Keyword(s):  
Drinking Water Treatment ◽  
Hydrodynamic Forces ◽  
Physical Models ◽  
Clear Water ◽  
Fluid Shear ◽  
Clay Particles ◽  
Video Recordings ◽  
Common Process ◽  
Clay Suspensions ◽  
Time Of Operation

AbstractThe filtration of suspensions containing clay and other particles in water is a common process in drinking water treatment. Such filtration processes are very efficient, producing clear water containing less than 1 mg/l from suspensions with particle concentrations of up to 100 mg/l. This filtration is not straining, but a process of collection of clay particles on the sand surfaces in the pores. The clays may range in size from sub-micron to ∼20 µm, and may be flocculated, and are retained in pores ∼200 µm in size within sand grains ∼500 µm in diameter. The collection process has three principal components (i) transport of clay particles across laminar water streamlines by diffusion, gravity and hydrodynamic forces, (ii) attachment by electrical or van der Waals' forces with hydrodynamic forces intervening, (iii) detachment by fluid shear or instabilities caused by arriving particles. Mathematical and physical models relate suspension concentration, quantity of deposit and permeability to depth in a filter, and time of operation. Fibre-optic endoscopes with CCTV enable video recordings to be made of the behaviour of clay particles in the filter pores, at magnifications up to 500 ×.

Automatic Reverse Engineering Based on Reconstructing Measurement Data in 3D-Lattice

2012 ◽  
Vol 523-524 ◽  
pp. 414-419
Author(s):  
Kiyomoto Tsushima ◽  
Hideki Aoyama
Keyword(s):  
Reverse Engineering ◽  
Mathematical Models ◽  
Measurement Data ◽  
Least Square Method ◽  
Lattice Points ◽  
Least Square ◽  
Physical Models ◽  
Engineering System ◽  
Surface Data ◽  
Data Density

Reverse engineering systems are used to construct mathematical models of physical models such as clay model based on measurement data. In this study, we proposed a reverse engineering method which can construct high quality surface data automatically. This method consists of the following steps; The first globally and regionally smooths measured data based on the target shape by fitting quadric surface to measurement data. The second defines quadric surfaces and converts measurement points into 3D lattice points to obtain uniform measurement data density. As the positions of measurement data are converted from coordinate values into 3D lattice points, it is easier to find neighboring points and clarify neighboring relations between surfaces. The third acquires segment measurement data based on maximum curvatures and normals at each point. The last defines NURBS surfaces for each segment using the least square method to average positional errors. In order to validate the effectiveness of the proposed method, we developed a reverse engineering system and constructed mathematical models through basic experiments using clay car model measurement data.

scholarly journals Cavitator Design for Straight-Running Supercavitating Torpedoes

2021 ◽  
Vol 11 (14) ◽  
pp. 6247
Author(s):  
Min-Jae Kim ◽  
Seon-Hong Kim ◽  
Kurn-Chul Lee ◽  
Bu-Geun Paik ◽  
Moon-Chan Kim
Keyword(s):  
Mathematical Models ◽  
Design Method ◽  
Design Procedure ◽  
Hydrodynamic Forces ◽  
Small Scale ◽  
Total Drag ◽  
Level Flight ◽  
Supercavitating Vehicle ◽  
Maximum Range ◽  
Design Requirements

A practical cavitator design method for straight-running-type supercavitating torpedoes was developed in this paper. Design requirements were first drawn in terms of torpedo performance characteristics, such as maximum range and motion stability. This method determines the optimum cavitator satisfying the design requirements that not only minimize the total drag of the torpedo, extending the maximum range, but also provide hydrodynamic forces required for straight level flight. The design procedure includes determining a design cavitation number and cavitator type (disk or cone) for obtaining the optimal cavitator that minimizes the total drag of a torpedo in straight level flight. To determine such an optimal cavitator, the equations of force and moment equilibrium for straight level flight were iteratively solved by the existing mathematical models that determine the cavity shapes generated by disk- and cone-shaped cavitators and hydrodynamic forces acting on the vehicle. For validation, model experiments on a small-scale supercavitating vehicle were conducted in a towing tank, and the results agree well with those of the mathematical models used in this study. A preliminary design based on the newly proposed method was also implemented for a realistic supercavitating vehicle. More precise computations using CFD should be conducted to investigate the physics in more detail in the near future.

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