Use Of Physical Models Research Articles

Folding Sleeves — Variations on a Theme of the Earthworm

The earthworm is a pressurised fluid tube whose peristaltic locomotion is facilitated by distinct structural features. The envelope of the earthworm incorporates two primary morphological and structural systems: A skeletal system, formed by a helical network of collagen fibres, and a continuous system composed of a stretchable membrane. The two systems closely interact under internal fluid pressure to produce the peristaltic locomotion. The paper presents applications of foldable sleeves or tubes, simulating the morphological and kinematical aspects of the earthworm locomotion, focusing on the combination of skeletal and compatible stressed-skin systems to produce a functional envelope. Several skeletal and stressed-skin structural systems and their combinations are presented, making extensive use of physical models. These systems are characterised by helical morphological features, which preserve the main kinematical characteristics of earthworm locomotion.

Rapid prototyping in dentistry: technology and application

Medical imaging has been used to provide information for diagnostic and therapeutic purposes. The use of physical models provides added values in these applications. Rapid prototyping (RP) techniques have long been employed to build complex 3D models in medicine. However, publications regarding the dental application of RP technologies are still rare. This paper reviews and discusses the basics and applications of RP techniques in dentistry: (1) construction of a computer aided design (CAD) model, including data acquisition, data processing, and the corresponding machines and CAD packages, (2) typical RP systems and how to choose them, and (3) current and potential use of RP techniques in dentistry. Practical application examples of RP techniques in dentistry are provided.

Physical models enhance molecular three‐dimensional literacy in an introductory biochemistry course*

This article reports the results of a recent study to evaluate the usefulness of physical models of molecular structures as a new tool with which to teach concepts of molecular structure and function. Of seven different learning tools used by students in this introductory biochemistry class, the use of the physical models in a laboratory was rated as most useful. These results suggest that physical models can play an important role in capturing the interest of students in the subject of molecular structure and function. These physical models often stimulate more sophisticated questions in the minds of students, which can then be more appropriately explored using computer visualization tools.

Application of numerical analysis principles and key technology for high fidelity simulation to 3-D physical model tests for underground caverns

Numerical simulation and model testing are the main research methods of solving geo-technical and underground problems. In the 1980s, physical simulation (model testing) was one of the most popular methods to solve these types of problems, but since then, with the rapid development of IT technology, numerical simulations have rapidly become dominant. However, the complexity and uncertainty of geological conditions and geo-technical engineering problems represent a great challenge to the numerical method, leading some researchers to question how far numerical simulation can go. In this case, the physical simulations have begun to reappear in research and the use of physical models has seen valuable progress. In the past, problems have been solved either with physical simulation or numerical simulation, or just by comparing the results of these two methods simply. But very little attention has been paid to the question of how to combine the advantages of both and improve them. In the 3-D geo-mechanical model of the underground caverns of the Xiluodu hydropower station, the advantages of the two methods were combined and some of the primary principles of the numerical method were combined with the physical model process. Considering that the boundary condition has a great effect on the stress distribution, a larger test model was set up. The numerical discrete principle was also been used to simulate an initial geo-stress field. The basic principle of cavern excavation according to requires that loading comes first, followed by excavation. According to this idea, we developed a new technique, in which a high fidelity simulation of the excavation process and a very difficult cavern excavation were successfully achieved for the first time. The new method produced test results more satisfactory, and this simulation represents an obvious improvement of existing techniques. We also conducted a numerical simulation with almost the same conditions, and compared the results of the model test and the numerical simulation.

CFD ANALYSIS FOR SEA-CHEST DESIGN

ABSTRACT This paper presents a series of numerical simulations intended to determine whether the use of CFX, a commercially available computational fluid dynamics software may provide a viable alternative to the use of physical models for predicting the occurrence of vortices and swirl in pump intakes. Single pump sump experimental data are used for validating the CFX analysis. Experimental setup for the Sea-Chest model of scale 1:4 was fabricated and experiments are conducted for different parameters like baffle positions, suction pipe spacing and suction depths. Velocity measurements and dye injections were used to characterize the flow in the physical model. In experimental runs presence of the vortices were observed. Results from experimental investigation and from CFX simulations are compared to obtain optimal parameters. With these optimal parameters CFX analysis is made for the SEA-Chest prototype size.

Photogrammetric techniques for analyzing displacement, strain, and structural geometry in physical models: Application to the growth of monoclinal basement uplifts

ABSTRACTPhysical models have been widely used to study geological structures for more than one hundred years. The greatest benefi t of physical models is that with proper scal-ing of model dimensions and materials, researchers can directly observe structural or tectonic processes that take millions of years to occur naturally. Despite this ben-efi t, however, use of physical models is not widespread because their construction and analysis is commonly labor-intensive work that yields largely qualitative information on structural geometry and limited quantitative information on displacement and strain. This paper describes how close-range photogram-metry can be used to obtain quantitative information on the geometry, displacement, and strain patterns in an evolving physical model. The technique is an inexpensive, high-resolution, noninvasive, and effi cient method that uses standard commercial software and a digital camera to determine the x , y , z posi-tions of high-contrast markers placed on the model surface. The model geometry at any given time is defi ned by the positions of all the markers, whereas strain and displace-ment are obtained by comparing, or track-ing, the positions of the markers at different times during an experiment. We present as an example application of the technique, an analysis of scaled physical models of mono-clines that form above basement-involved reverse faults with differing displacement distributions. Using close-range photogram-metry, we are able to link fault displacement and lateral propagation history to unique, evolving, three-dimensional (3-D) geometries and deformation patterns that are unlikely to be revealed by other analysis techniques.Keywords: physical model, monocline, base-ment uplift, photogrammetry, strain.INTRODUCTION

Ballistic MOSFETs, the ultra scaled transistors

As the MOSFET dimensions are reduced further in the sub 50nm regime; ballistic transport would become a very important factor in governing the current characteristics. The maximum current a MOSFET can physically carry and the fastest it can operate is governed by the ballistic transport of the carriers in the channel. Therefore, we should fully understand this phenomenon, by the use of physical models, device simulations and if possible actual fabrication of devices. Also, the present gap between the results predicted by analytical models and rigorous simulations has to be bridged. To realize a device with 100% ballistic transport, efforts have to be directed to address the issues that impede the ballistic transport, like reducing the channel scattering, improving the Si-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface and use of double gate structures.

The physical scale modelling of braided alluvial architecture and estimation of subsurface permeability

ABSTRACTThe quantitative modelling of fluvial reservoirs, especially in the stages of enhanced oil recovery, requires detailed three‐dimensional data at both the scale of the channel belt and within‐channel. Although studies from core, analogue outcrop and modern environments may partially meet these needs, they often cannot provide detail on the smaller‐scale (i.e. channel‐scale) heterogeneity, frequently suffer from limited three‐dimensional exposure and cannot be used to examine the influence of different variables on the process–deposit relationship. Physical modelling offers a complementary technique that can address many of these quantitative requirements and holds great future potential for integration with reservoir modelling. Physical modelling provides the potential to upscale results and derive reservoir information on three‐dimensional facies geometry, connectivity and permeability.This paper describes the development and use of physical modelling, which employs generic Froude‐scaling principles, in an experimental basin that permits aggradation in order to model the morphology and subsurface depositional stratigraphy of coarse‐grained braided rivers. An example is presented of a 1:50 scale model based on the braided Ashburton River, Canterbury Plains, New Zealand and the adjacent late Quaternary braided alluvium exposed in the coastal cliffs. Critically, a full, bimodal grain size distribution (20% sand and 80% gravel) was used to replicate the prototype, which allows the realistic reproduction of the surface morphology and importantly permits grain size sorting during deposition. Uncertainties associated with the compression of time, sediment mass balance and the hydrodynamics of the finest particle sizes do not appear to affect the reproducibility of stratigraphy between experimental and natural environments.Sectioning of the preserved sedimentary sequence in the physical model allows quantification of the geometry, shape, spatial distribution and internal sedimentary structure of the coarse‐ and fine‐grained facies. A six‐fold facies scheme is proposed for the model braided alluvium and a direct link is established between the grain size distribution and facies type: this allows permeability to be estimated for each facies, which can be mapped onto two‐dimensional vertical cross‐sections of the preserved stratigraphy. Results demonstrate the dominance of four facies based on permeability that range over three orders of magnitude in hydraulic conductivity. Quantification of such variability, and linkage to both vertical proportion curves for facies distribution and connectivity presents significant advantages over other methodologies and offers great potential for the modelling of heterogeneous braided river sediments at the within channel‐belt scale. This paper outlines how physical models may be used to develop high‐resolution, geologically‐accurate, object‐based reservoir simulation models.

Field studies of reptile thermoregulation: how well do physical models predict operative temperatures?

Abstract1. Field‐based studies on reptile thermoregulation increasingly rely upon physical models to estimate operative temperatures. Some investigators use models that mimic the size, shape, colour and posture of their study species, but such details may have little influence on thermal regimes (and hence, complex models may be a waste of time and money).2. Temperatures were measured at 10‐min intervals inside 48 hollow copper‐pipe models exposed to natural weather conditions over a 27‐day period, in a factorial design to examine the effects of model attributes on thermal profiles.3. These data clarify the ways in which model size, colour (reflectance), orientation and degree of contact with the substrate affect (a) mean, minimum and maximum temperatures, and (b) the number of hours per day that the models exceed specified thermal thresholds. Also examined are (c) interactions between model attributes in these respects, and (d) the ways in which such effects depend upon local weather conditions.4. Model temperatures were affected by all of the attributes tested, but with few interactions between these effects. Although statistically significant, the effects of model attributes upon operative temperature regimes were generally minor (&lt;5% of mean values).5. Guidelines for the use of physical models in future research are provided.

PRECIPITATION ONSET AND PHYSICAL MODELS OF ASPHALTENE SOLUTION BEHAVIOR

The onset of asphaltene precipitation provides important information about the thermodynamic state of the asphaltene solute in a given hydrocarbon system (a stock tank oil, a residue, or an asphaltenic solution). Such measurements are carried out by titrating the system with an asphaltene anti-solvent (an n-paraffin) while measuring some physical property (e.g., light absorbance, electrical conductivity, viscosity) that displays a distinctive discontinuity at the onset of phase separation. The quantity of anti-solvent required to attain this condition is expressed in most cases as mass (or volume) of anti-solvent per unit mass of oil. In the present work, the empirical models that have been proposed to account for asphaltene behavior in the titration experiments are described and compared critically. It is shown that they can all be reduced to a single general form that identifies a peculiar behavior of these systems: the onset conditions for precipitation are independent of the asphaltene concentration. This behavior cannot represented by most of the theoretical models proposed in literature. It is argued that the discordance between the observed behavior and the attempted mathematical descriptions derives, in large part, from an uncritical use of physical models of the asphaltenes. A tentative, new physical interpretation of asphaltene phase behavior is offered together with a simple mathematical model for predicting the onset conditions based on the results of titration experiments.

Automotive engine diagnosis and control via nonlinear estimation

The aim of this article is to explore a possible approach to the problem of designing control and diagnostic strategies for future generations of automotive engines. The work described focuses on the use of physical models to estimate unmeasured or unmeasurable variables and parameters, to be used for control and diagnostic purposes. We introduce the mean value engine model used, present a conceptual strategy for combined control and diagnosis focusing mainly on the problem of air fuel ratio control, review basic concepts related to estimation in nonlinear systems, and propose various forms of the estimators that serve different objectives. We illustrate estimation problems in the context of a simplified engine model, assuming both linear and nonlinear measurement of oxygen concentration in the exhaust. Some simulation and experimental results related to estimation-based control and diagnosis are shown.

The use of solid physical models for the study of macromolecular assembly

The use of modern technology in the construction of accurate solid macromolecular models based on atomic coordinates and electron density functions has led us to re-examine the usefulness of physical models as tools for understanding molecular assembly and for designing detailed experimental and computational studies of the assembly process. Recent developments include the construction of new models, which have provided insights into the assembly of viruses and light harvesting complexes.

The Divisibility of xn − yn by x − y: A Constructive Example

The divisibility of xa − yn by x − y, where n is a positive integer and x # y, offers a rare opportunity to investigate and construct an inductive proof. I have used the following example to help my students better understand the nature of inductive reasoning and inductive proofs, since the expression can be investigated, hypothesized, tesLed, and modeled both physically and pictorially, at least to three dimensions. My students consisted of middle school and high school teachers in an in-service setting. Most were unfamHiar with the use of physical models and manipulatives, the applications of which were the purpose of the in-service sessions. In the application that follows, they were asked to humor their teacher and pretend that they were high school students. They good-naturedly agreed.

5725655 Method for new concrete from old concrete

Current urban washoff models still rely on empirical catchment-scale functions, that have not been substantially updated during the last 40 years. This paper introduce a new approach using the physical model FullSWOF to evaluate urban washoff process. The modelling approach is performed for a Parisian road catchment. Water flow simulation is validated by outlet discharge measurements and local observations of water depth. Water quality modelling of three classes of particles (d50 = 7 μm, 70 μm, and 250 μm) is applied using the Hairsine-Rose model. Analysis of the washoff process at the catchment scale indicates that most (> 90%) of the finest particles are removed at the beginning of a rainfall event, about 10%–20% of medium-sized particles are moved over the latest part of the event, and almost no coarse particles can be transferred into the sewer inlet. Spatial analysis of washoff process reveals that the concentration of suspended solids on road and sidewalk surface is more sensitive to rainfall intensities than that on gutter surface, while coarser particles tend to accumulate in the gutter over the later part of a rainfall event. Investigation of the driving force behind the detachment process indicates that rainfall-driven effects are two orders of magnitude higher than flow-driven effects. Moreover, it is observed that rainfall-driven detachment is considerably decreased with the rising water depth, while flow-driven detachment occurs only in gutter areas. Finally, several controversial arguments on the use of physical models for assessing the washoff process, and perspectives on development of physical urban washoff models are discussed.

Complex permittivity of a film of poly[4-(acryloxy)phenyl-(4-chlorophenyl)methanone] containing free ion impurities and the separation of the contributions from interfacial polarization, Maxwell–Wagner–Sillars effects and dielectric relaxations of the polymer chains

The previous theoretical study of measured complex permittivities of the amorphous copolymer of vinylidene cyanide and vinyl acetate (T. S. Sorensen and V. Compan, J. Chem. Soc., Faraday Trans., 1995, 91, 4235) is refined and used to explain measurements of the complex permittivity of the amorphous polymer poly[4-(acryloxy)phenyl(4-chlorophenyl)methanone] at different temperatures and frequencies. Throughout the paper we stress the use of physical models rather than the traditional use of equivalent circuits without much informational content. The data exhibit a maximum in the loss tangent at low frequencies (below 0.1 Hz) which can be explained by interfacial polarization near the two condensor plates, and from which information concerning the diffusion and the concentration of free charge (mobile ion) carriers may be estimated. The diffusion coefficient for the fast ion varies from 1.9 × 10–14 m2 s–1 at 120 °C to 1.8 × 10–13 m2 s–1 at 140 °C. The activation energy for diffusion is Ea/R≈ 12 800 K. At frequencies in the range 0.1–10 Hz, the Maxwell–Wagner–Sillars contribution dominates. This contribution is due to the bulk conductivity of the free charge carriers. From the value of this conductivity and the information obtained from the interfacial polarization, the value of the static permittivity of the polymer may be found. Experimentally, this value is completely obscured by the effects of the free charge carriers. At higher frequencies, the dielectric relaxations connected with the motion of segments of the polymer chains are seen if corrections are made for conductivity. Two dielectric loss peaks are observed moving towards higher frequencies when the temperature increases. The low frequency relaxation has an activation energy Ea/R≈ 11 200 K. For the high frequency relaxation Ea/R≈ 24 500 K. The approximate identity of the activation energy of the low frequency relaxation and the activation energy of diffusion might indicate that the same molecular reorientation is involved in both cases.

An Investigation into the Use of Physical Modeling for the Prediction of Various Feature Types Visible from Different Viewpoints

Given that aspect graph and viewsphere-based object recognition systems provide a valid mechanism for 3D object recognition of man-made objects, this paper provides a flexible, automated, and general purpose technique for generating the view information for each viewpoint. An advantage of the work is that the technique is unaffected by object complexity because each step makes no assumptions about object shape. The only limitation is that the object can be described by a boundary representation. A second advantage is that the technique can include other feature types such as specularity. The reason for this is that raytracing techniques are used to simulate the physical process of image generation. Hence it is extendible to visible features resulting from effects due to lighting, surface texture, color, transparency, etc. The work described in this paper shows how occluding and nonoccluding edge-based features can be extracted using image processing techniques and then parametrized and also how regions of specularity can be predicted and described. The use of physical modeling enables situations to be simulated and predicted that are intractable for CAD-based methods (e.g., multiscale feature prediction). An advantage of the method is that the interface between the technique and the raytracing module is a rendered image. Should better physics-based image formation algorithms become available, then they could replace the raytracing module with little modification to the rest of the method.

Some physical model studies of gas-induced flows in aluminum cells

It is possible to make use of simple low-temperature models to elucidate the transport processes that occur in a Hall-Heroult cell. While the models differ from the actual processes in terms of temperature and physical properties, the relationship between the model and the actual process may be related via a study of the principle of similarity. The following gives a brief description of the relevance of dimensionless groups in the use of physical models, followed by some experience with the use of physical models in the study of gas-induced fluid flow and heat/mass transfer in a Hall-Heroult cell.

A spectral approach for analyzing the rill structure over hillslopes. Part 2. Application

This paper deals with examining the bandwidth of the spectral density functions of rill profiles from transect measurements at three cross-slope locations over decomposed granite hillslopes in Northern California. Parameter estimation for the probabilistic description of rill heights under the narrow-banded spectrum assumption was then considered. The theoretical predictions of the rill structure agree fairly well with the corresponding observed results. Estimation of extreme-valued rills and significant rill heights is addressed to quantify the severity of the rilled hillslope surface. It is concluded that the spectral approach is a valid method for quantifying the rill structure for use in physical models of water flow and sediment transport over rilled hillslope surfaces.

Statistics of CRack Initiation and Propagation

ABSTRACTStatistics of fracture fatigue are derived based on essentially general models of crack propagation and initiation. In fact, the form of the distribution is invariant with respect to the crack propagation law, however, the parameters do depend on the details of the phenomena. When this dependence is known, i.e. extracted from experimental data, our results can be applied even in the case of changing environments. Thus, such problems as projections to use conditions and the efficiency of burn in procedures can be precisely formulated and resolved, often without the requirements of further testing. These advantages derive from our use of physical models in deriving the failure distribution. This was not previously the case where for the almost universally used log-normal distribution each new situation requires the establishment of new rules. In fact, the log-normal is usually pessimistic and requires ad-hoc rectification to account for curvature when plotted on log-normal paper!, and generally does not relate to the fatigue process.

A mental model for early arithmetic.

The authors examined young children's ability to solve nonverbal calculation problems in which they must determine how many items are in a hidden array after items have been added into or taken away from it. Earlier work showed that an ability to reliably solve such problems emerges earlier than verbal calculation ability but did not examine when it first appears. The authors propose that the ability to solve such problems involves domain-general symbolic processes similar to those involved in symbolic play and the use of physical models. Hence the ability to calculate should appear at about 2 years and should be related to overall level of intellectual competence. The authors show that the ability to reliably solve nonverbal calculation tasks emerges only after 2 years of age and that performance on nonverbal calculation problems is highly related to overall level of intellectual competence in children between 3 and 4 years of age.