Electrostatic Forces and Stored Energy for Deformable Dielectric Materials

2004 ◽  
Vol 72 (4) ◽  
pp. 581-590 ◽  
Author(s):  
Robert M. McMeeking ◽  
Chad M. Landis
Keyword(s):  
Energy Balance ◽  
Electric Field ◽  
Conservative System ◽  
The Body ◽  
Material Behavior ◽  
Stored Energy ◽  
External Work ◽  
Special Cases ◽  
Surrounding Space ◽  
Electrostatic Stress

An isothermal energy balance is formulated for a system consisting of deformable dielectric bodies, electrodes, and the surrounding space. The formulation in this paper is obtained in the electrostatic limit but with the possibility of arbitrarily large deformations of polarizable material. The energy balance recognizes that charges may be driven onto or off of the electrodes, a process accompanied by external electrical work; mechanical loads may be applied to the bodies, thereby doing work through displacements; energy is stored in the material by such features as elasticity of the lattice, piezoelectricity, and dielectric and electrostatic interactions; and nonlinear reversible material behavior such as electrostriction may occur. Thus the external work is balanced by (1) internal energy consisting of stress doing work on strain increments, (2) the energy associated with permeating free space with an electric field, and (3) by the electric field doing work on increments of electric displacement or, equivalently, polarization. For a conservative system, the internal work is stored reversibly in the body and in the underlying and surrounding space. The resulting work statement for a conservative system is considered in the special cases of isotropic deformable dielectrics and piezoelectric materials. We identify the electrostatic stress, which provides measurable information quantifying the electrostatic effects within the system, and find that it is intimately tied to the constitutive formulation for the material and the associated stored energy and cannot be independent of them. The Maxwell stress, which is related to the force exerted by the electric field on charges in the system, cannot be automatically identified with the electrostatic stress and is difficult to measure. Two well-known and one novel formula for the electrostatic stress are identified and related to specific but differing constitutive assumptions for isotropic materials. The electrostatic stress is then obtained for a specific set of assumptions in regard to a piezoelectric material. An exploration of the behavior of an actuator composed of a deformable, electroactive polymer is presented based on the formulation of the paper.

scholarly journals Frictional internal work of damped limbs oscillation in human locomotion

2020 ◽  
Vol 287 (1931) ◽  
pp. 20201410 ◽  
Author(s):  
Alberto E. Minetti ◽  
Alex P. Moorhead ◽  
Gaspare Pavei
Keyword(s):  
Energy Balance ◽  
Time Course ◽  
Ex Vivo ◽  
Biological Tissues ◽  
The Body ◽  
Lower Limbs ◽  
Metabolic Energy ◽  
External Work ◽  
Internal Work

Joint friction has never previously been considered in the computation of mechanical and metabolic energy balance of human and animal (loco)motion, which heretofore included just muscle work to move the body centre of mass (external work) and body segments with respect to it. This happened mainly because, having been previously measured ex vivo , friction was considered to be almost negligible. Present evidences of in vivo damping of limb oscillations, motion captured and processed by a suited mathematical model, show that: (a) the time course is exponential, suggesting a viscous friction operated by the all biological tissues involved; (b) during the swing phase, upper limbs report a friction close to one-sixth of the lower limbs; (c) when lower limbs are loaded, in an upside-down body posture allowing to investigate the hip joint subjected to compressive forces as during the stance phase, friction is much higher and load dependent; and (d) the friction of the four limbs during locomotion leads to an additional internal work that is a remarkable fraction of the mechanical external work. These unprecedented results redefine the partitioning of the energy balance of locomotion, the internal work components, muscle and transmission efficiency, and potentially readjust the mechanical paradigm of the different gaits.

Ghrelin and Obesity-An Update

2017 ◽  
Vol 9 (1) ◽  
Author(s):  
Gandhi M. ◽  
Swaminathan S.
Keyword(s):  
Diabetes Mellitus ◽  
Cardiac Output ◽  
Energy Balance ◽  
Vascular Resistance ◽  
The Body ◽  
Ghrelin Receptor ◽  
Type2 Diabetes ◽  
Type2 Diabetes Mellitus ◽  
Natural Hormones

Ghrelin as human natural hormones is involved in fundamental regulatory process of eating and energy balance. It is a stomach derived hormone that acts as at the ghrelin receptor in multiple tissues throughout to the body. Its properties includes increasing appetite, decreasing systemic inflammation, decreasing vascular resistance ,increasing cardiac output, increasing glucose and IGF-1 levels, Hence it may play a significant role in Diabetes mellitus. Many studies have linked ghrelin to obesity and this paper is an attempt to bring out recent findings on the role of ghrelin in Diabetes Mellitus, particularly type2 Diabetes mellitus.

scholarly journals Electrochemotherapy Effectiveness Loss due to Electric Field Indentation between Needle Electrodes: A Numerical Study

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
José Alvim Berkenbrock ◽  
Rafaela Grecco Machado ◽  
Daniela Ota Hisayasu Suzuki
Keyword(s):  
Electric Field ◽  
In Silico ◽  
Treatment Effectiveness ◽  
Numerical Study ◽  
Specific Treatment ◽  
The Body ◽  
Membrane Selectivity ◽  
Chemotherapy Drugs ◽  
Mast Cell Tumor ◽  
Anticancer Treatment

Electrochemotherapy is an anticancer treatment based on applying electric field pulses that reduce cell membrane selectivity, allowing chemotherapy drugs to enter the cells. In parallel to electrochemotherapy clinical tests, in silico experiments have helped scientists and clinicians to understand the electric field distribution through anatomically complex regions of the body. In particular, these in silico experiments allow clinicians to predict problems that may arise in treatment effectiveness. The current work presents a metastatic case of a mast cell tumor in a dog. In this specific treatment planning study, we show that using needle electrodes has a possible pitfall. The macroscopic consequence of the electroporation was assessed through a mathematical model of tissue electrical conductivity. Considering the electrical and geometrical characteristics of the case under study, we modeled an ellipsoidal tumor. Initial simulations were based on the European Standard Operating Procedures for electrochemotherapy suggestions, and then different electrodes’ arrangements were evaluated. To avoid blind spots, multiple applications are usually required for large tumors, demanding electrode repositioning. An effective treatment electroporates all the tumor cells. Partially and slightly overlapping the areas increases the session’s duration but also likely increases the treatment’s effectiveness. It is worth noting that for a single application, the needles should not be placed close to the tumor’s borders because effectiveness is highly likely to be lost.

Stresses and Displacements in a Rotating Conical Shell

1943 ◽  
Vol 10 (2) ◽  
pp. A53-A61
Author(s):  
J. L. Meriam
Keyword(s):  
Conical Shell ◽  
Body Force ◽  
Theory Of Elasticity ◽  
Common Type ◽  
The Body ◽  
Surface Loading ◽  
Thin Walled Structures ◽  
Special Cases ◽  
Engineering Problems ◽  
Rotating Conical Shell

Abstract The analysis of shells is an important subdivision of the general theory of elasticity, and its application is useful in the solution of engineering problems involving thin-walled structures. A common type of shell is one which possesses symmetry with respect to an axis of revolution. A theory for such shells has been developed by various investigators (1, 2, 3, 6) and applied to a few simple cases such as the cylindrical, spherical, and conical shapes. Boundary conditions, for the most part, have been simple static ones, and conditions of surface loading have been included in certain special cases. This paper extends the theory of axially symmetrical shells by including the body force of rotation about the axis and applies the results to the rotating conical shell. The analysis follows a pattern established by several investigators (1, 2, 3, 6) and for this reason is abbreviated to a considerable extent. Only where the inclusion of the body force makes elucidation advisable or where a slightly different method of approach is used are the steps presented in more detail.

External work in level and grade walking on a motor-driven treadmill

1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
Author(s):  
J. W. Snellen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Total Energy Expenditure ◽  
The Body ◽  
External Work ◽  
Thermal Exchange ◽  
Level Walking ◽  
The Subject ◽  
Set Up ◽  
Physical Laws

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960

scholarly journals Interpreting Neuronal Population Activity by Reconstruction: Unified Framework With Application to Hippocampal Place Cells

1998 ◽  
Vol 79 (2) ◽  
pp. 1017-1044 ◽  
Author(s):  
Kechen Zhang ◽  
Iris Ginzburg ◽  
Bruce L. McNaughton ◽  
Terrence J. Sejnowski
Keyword(s):  
Bayesian Methods ◽  
Neuronal Population ◽  
Place Cells ◽  
The Body ◽  
Unified Framework ◽  
Population Activity ◽  
Reconstruction Methods ◽  
Special Cases ◽  
Physical Variables ◽  
The Brain

Zhang, Kechen, Iris Ginzburg, Bruce L. McNaughton, and Terrence J. Sejnowski. Interpreting neuronal population activity by reconstruction: unified framework with application to hippocampal place cells. J. Neurophysiol. 79: 1017–1044, 1998. Physical variables such as the orientation of a line in the visual field or the location of the body in space are coded as activity levels in populations of neurons. Reconstruction or decoding is an inverse problem in which the physical variables are estimated from observed neural activity. Reconstruction is useful first in quantifying how much information about the physical variables is present in the population and, second, in providing insight into how the brain might use distributed representations in solving related computational problems such as visual object recognition and spatial navigation. Two classes of reconstruction methods, namely, probabilistic or Bayesian methods and basis function methods, are discussed. They include important existing methods as special cases, such as population vector coding, optimal linear estimation, and template matching. As a representative example for the reconstruction problem, different methods were applied to multi-electrode spike train data from hippocampal place cells in freely moving rats. The reconstruction accuracy of the trajectories of the rats was compared for the different methods. Bayesian methods were especially accurate when a continuity constraint was enforced, and the best errors were within a factor of two of the information-theoretic limit on how accurate any reconstruction can be and were comparable with the intrinsic experimental errors in position tracking. In addition, the reconstruction analysis uncovered some interesting aspects of place cell activity, such as the tendency for erratic jumps of the reconstructed trajectory when the animal stopped running. In general, the theoretical values of the minimal achievable reconstruction errors quantify how accurately a physical variable is encoded in the neuronal population in the sense of mean square error, regardless of the method used for reading out the information. One related result is that the theoretical accuracy is independent of the width of the Gaussian tuning function only in two dimensions. Finally, all the reconstruction methods considered in this paper can be implemented by a unified neural network architecture, which the brain feasibly could use to solve related problems.

scholarly journals Modelo predictor de las conductas del balance energético corporal BEC (Predict model of the body energy balance BEB behaviors)

Retos ◽  
2021 ◽  
Vol 41 ◽  
pp. 653-663
Author(s):  
Andrés Gómez-Acosta ◽  
Constanza Londoño
Keyword(s):  
Energy Balance ◽  
Health Beliefs ◽  
Structural Equation ◽  
Contextual Factors ◽  
Equation Model ◽  
The Body ◽  
Sociocultural Factors ◽  
P Value ◽  
Cross Sectional ◽  
Body Energy

Hace falta evidencia acerca de la sinergia entre los factores psicológicos y contextuales que subyacen a la práctica simultánea de las conductas del balance energético corporal [BEC] (actividad física [AF], alimentación saludable [AS] y sueño de calidad [SC]). Por ello, se busca identificar si el optimismo disposicional [OD], flexibilidad en regulación emocional [RE], las creencias compensatorias en salud [CCS] y factores ambientales – socioculturales, predicen los dominios conductuales señalados en adultos, a través de un Modelo de Ecuaciones Estructurales [MEE]. Para ello, se dispuso de una investigación explicativa trasversal con una muestra de 300 participantes, que diligenciaron un cuadernillo compuesto por instrumentos psicométricos validados (uno por cada variable indagada). Los resultados establecieron que la tendencia a la realización de las conductas el BEC es predicha por los factores contextuales referidos y las variables psicológicas evaluadas (R=.54, valor p < .05). Se valida un modelo hipotético que incorpora el agregado conductual del sueño en la ecuación del BEC, susceptible de modificación e inclusión de nuevas variables.  Abstract. There is a lack of evidence about the synergy between the psychological and contextual factors that underlie the simultaneous practice of the behavioral domains of the Body Energy Balance [BEB] (Physical Activity [PA], Healthy Eating [HE] & Quality Sleep [QS]). Therefore, we seek to identify whether dispositional optimism [DO], emotion regulation [ER] flexibility, compensatory health beliefs [CHB], and environmental-sociocultural factors, predict behaviors of the body energy balance [BEB] in adults, through a Structural Equation Model [SEM]. To do this, cross-sectional explanatory research was available with a sample of 300 participants, who completed a booklet made up of validated psychometric instruments (one for each variable investigated). The results established that the tendency to perform the BEB behaviors is predicted by the contextual factors referred to, and the psychological variables were evaluated (R=.54, p-value < .05). A hypothetical model that incorporates the behavioral aggregate of sleep in the BEB equation is validated, subject to modification and inclusion of new variables.

Mapping of induced polarization using natural fields

Geophysics ◽  
2001 ◽  
Vol 66 (1) ◽  
pp. 137-147 ◽  
Author(s):  
Erika Gasperikova ◽  
H. Frank Morrison
Keyword(s):  
Electric Field ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Induced Polarization ◽  
The Body ◽  
Electromagnetic Response ◽  
Frequency Dependent ◽  
Finite Body ◽  
Electric Field Profile ◽  
Measured Response

The observed electromagnetic response of a finite body is caused by induction and polarization currents in the body and by the distortion of the induction currents in the surrounding medium. At a sufficiently low frequency, there is negligible induction and the measured response is that of the body distorting the background currents just as it would distort a direct current (dc). Because this dc response is not inherently frequency dependent, any observed change in response of the body for frequencies low enough to be in this dc limit must result from frequency‐dependent conductivity. Profiles of low‐frequency natural electric (telluric) fields have spatial anomalies over finite bodies of fixed conductivity that are independent of frequency and have no associated phase anomaly. If the body is polarizable, the electric field profile over the body becomes frequency dependent and phase shifted with respect to a reference field. The technique was tested on data acquired in a standard continuous profiling magnetotelluric (MT) survey over a strong induced polarization (IP) anomaly previously mapped with a conventional pole‐dipole IP survey. The extracted IP response appears in both the apparent resistivity and the normalized electric field profiles.

Light Dance

Leonardo ◽  
2020 ◽  
Vol 53 (1) ◽  
pp. 90-91
Author(s):  
Seth Riskin
Keyword(s):  
Simple Approach ◽  
The Body ◽  
Speed Of Light ◽  
Body Movements ◽  
Room Light ◽  
Shared Space ◽  
Surrounding Space ◽  
The Individual ◽  
Individual Body ◽  
Movement Expression

The author discusses the origin and meaning of his Light Dance artwork. The simple approach—placing a source of light on the body and thereby manipulating the illumination of the surrounding space through body movements—alters the viewer’s perception of space and time. Architecture appears malleable as the performer affects the size, shape and speed of light forms that reach from the body to the boundaries of the room. Light, in this perceptual environment, is not a mere transmitter of information between the invariant material surroundings and the eye of the viewer; light is a space-defining extension of the performer’s body that transposes movement expression from the individual body to the shared space. An inversion of subjective and objective “spaces” is realized in the experience of Light Dance wherein the prevailing conceptual hierarchy of light and vision is overcome.

scholarly journals BEM Modelling of High Voltage ELF electric field applied to a 3D pregnant woman model

2010 ◽  
Vol 6 (1) ◽  
pp. 31 ◽  
Author(s):  
Cristina Peratta ◽  
Andres Peratta ◽  
Dragan Poljak
Keyword(s):  
Pregnant Woman ◽  
Electric Field ◽  
Electric Fields ◽  
High Voltage ◽  
Medical Information ◽  
Three Dimensional ◽  
Low Frequency ◽  
Element Model ◽  
The Body ◽  
Geometrical Properties

The paper introduces a three dimensional multidomainboundary element model of a pregnant woman and foetus for the analysis of exposure to high voltage extremely low frequency electric fields. The definition of the differentphysical and geometrical properties of the relevant tissues is established according to medical information available in existing literature. The model takes into account changes in geometry, body mass, body fat, and overall chemical composition in the body which influence the electrical properties, throughout the different gestational periods. The developed model is used to solve the case of exposure to overhead power transmission lines at different stages of pregnancy including weeks 8, 13, 26 and 38. The results obtained are in line with those published in the earlier works considering different approaches. In addition, a sensitivity analysis involving varying scenarios of conductivity, foetus postures and geometry for each stage is defined and solved. Finally, a correlation between the externally applied electric field and the current density inside the foetus is established and the zones of maximum exposure are identified.

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