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Potential Field (potential + field)
Selected AbstractsPotential field based geometric modelling using the method of fundamental solutionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2006Roman Tankelevich Abstract We propose a new geometric modelling method based on the so-called potential field (PF) modelling technique. The harmonic problem associated with this technique is solved numerically using the method of fundamental solutions (MFS). We investigate the applicability of the proposed approach to parametrically defined curves of varying complexity. Based on the MFS, we also provide definitions of the Boolean operations associated with the geometric modelling. Finally, we give practical applications of the method to computer-aided design and manufacturing problems. Copyright © 2006 John Wiley & Sons, Ltd. [source] Elastic Potential Grids: Accurate and Efficient Representation of Intermolecular Interactions for Fully Flexible DockingCHEMMEDCHEM, Issue 8 2009Sina Kazemi Potential fields represented by irregular, deformable 3D grids provide an accurate and efficient lookup table function for evaluating intermolecular interactions in docking algorithms that consider target flexibility. Target movements can be translated into appropriate displacements of grid intersection points in a binding site region if the irregular deformable 3D grid is modeled as a homogeneous linear elastic body. [source] Numerical modeling of the Joule heating effect on electrokinetic flow focusingELECTROPHORESIS, Issue 10 2006Kuan-Da Huang Abstract In electrokinetically driven microfluidic systems, the driving voltage applied during operation tends to induce a Joule heating effect in the buffer solution. This heat source alters the solution's characteristics and changes both the electrical potential field and the velocity field during the transport process. This study performs a series of numerical simulations to investigate the Joule heating effect and analyzes its influence on the electrokinetic focusing performance. The results indicate that the Joule heating effect causes the diffusion coefficient of the sample to increase, the potential distribution to change, and the flow velocity field to adopt a nonuniform profile. These variations are particularly pronounced under tighter focusing conditions and at higher applied electrical intensities. In numerical investigations, it is found that the focused bandwidth broadens because thermal diffusion effect is enhanced by Joule heating. The variation in the potential distribution induces a nonuniform flow field and causes the focused bandwidth to tighten and broaden alternately as a result of the convex and concave velocity flow profiles, respectively. The present results confirm that the Joule heating effect exerts a considerable influence on the electrokinetic focusing ratio. [source] Interpretation of observed fluid potential patterns in a deep sedimentary basin under tectonic compression: Hungarian Great Plain, Pannonian BasinGEOFLUIDS (ELECTRONIC), Issue 1 2001J. Tóth Abstract The , 40 000 km2 Hungarian Great Plain portion of the Pannonian Basin consists of a basin fill of 100 m to more than 7000 m thick semi- to unconsolidated marine, deltaic, lacustrine and fluviatile clastic sediments of Neogene age, resting on a strongly tectonized Pre-Neogene basement of horst-and-graben topography of a relief in excess of 5000 m. The basement is built of a great variety of brittle rocks, including flysch, carbonates and metamorphics. The relatively continuous Endr,d Aquitard, with a permeability of less than 1 md (10,15 m2) and a depth varying between 500 and 5000 m, divides the basin's rock framework into upper and lower sequences of highly permeable rock units, whose permeabilities range from a few tens to several thousands of millidarcy. Subsurface fluid potential and flow fields were inferred from 16 192 water level and pore pressure measurements using three methods of representation: pressure,elevation profiles; hydraulic head maps; and hydraulic cross-sections. Pressure,elevation profiles were constructed for eight areas. Typically, they start from the surface with a straight-line segment of a hydrostatic gradient (,st = 9.8067 MPa km,1) and extend to depths of 1400,2500 m. At high surface elevations, the gradient is slightly smaller than hydrostatic, while at low elevations it is slightly greater. At greater depths, both the pressures and their vertical gradients are uniformly superhydrostatic. The transition to the overpressured depths may be gradual, with a gradient of ,dyn = 10,15 MPa km,1 over a vertical distance of 400,1000 m, or abrupt, with a pressure jump of up to 10 MPa km,1 over less than 100 m and a gradient of ,dyn > 20 MPa km,1. According to the hydraulic head maps for 13 100,500 m thick horizontal slices of the rock framework, the fluid potential in the near-surface domains declines with depth beneath positive topographic features, but it increases beneath depressions. The approximate boundary between these hydraulically contrasting regions is the 100 m elevation contour line in the Duna,Tisza interfluve, and the 100,110 m contours in the Nyírség uplands. Below depths of ,,600 m, islets of superhydrostatic heads develop which grow in number, areal extent and height as the depth increases; hydraulic heads may exceed 3000 m locally. A hydraulic head ,escarpment' appears gradually in the elevation range of ,,1000 to ,,2800 m along an arcuate line which tracks a major regional fault zone striking NE,SW: heads drop stepwise by several hundred metres, at places 2000 m, from its north and west sides to the south and east. The escarpment forms a ,fluid potential bank' between a ,fluid potential highland' (500,2500 m) to the north and west, and a ,fluid potential basin' (100,500 m) to the south and east. A ,potential island' rises 1000 m high above this basin further south. According to four vertical hydraulic sections, groundwater flow is controlled by the topography in the upper 200,1700 m of the basin; the driving force is orientated downwards beneath the highlands and upwards beneath the lowlands. However, it is directed uniformly upwards at greater depths. The transition between the two regimes may be gradual or abrupt, as indicated by wide or dense spacing of the hydraulic head contours, respectively. Pressure ,plumes' or ,ridges' may protrude to shallow depths along faults originating in the basement. The basement horsts appear to be overpressured relative to the intervening grabens. The principal thesis of this paper is that the two main driving forces of fluid flow in the basin are gravitation, due to elevation differences of the topographic relief, and tectonic compression. The flow field is unconfined in the gravitational regime, whereas it is confined in the compressional regime. The nature and geometry of the fluid potential field between the two regimes are controlled by the sedimentary and structural features of the rock units in that domain, characterized by highly permeable and localized sedimentary windows, conductive faults and fracture zones. The transition between the two potential fields can be gradual or abrupt in the vertical, and island-like or ridge-like in plan view. The depth of the boundary zone can vary between 400 and 2000 m. Recharge to the gravitational regime is inferred to occur from infiltrating precipitation water, whereas that to the confined regime is from pore volume reduction due to the basement's tectonic compression. [source] Interpretation of regional aeromagnetic data by the scaling function method: the case of Southern Apennines (Italy)GEOPHYSICAL PROSPECTING, Issue 4 2009G. Florio ABSTRACT A complex aeromagnetic anomaly in Southern Apennines (Italy) is analysed and interpreted by a multiscale method based on the scaling function. We use multiscale methods allowing analysis of a potential field along ridges, which are lines defined by the position of the extrema of the field at the considered scales. The method developed and applied in this paper is based on the study of the scaling function of the total magnetic field. It allows recovering of source parameters such as depth and structural index. The studied area includes a Pleistocene volcanic structure (Mt. Vulture) whose intense dipolar anomaly is superimposed on a longer wavelength regional anomaly. The interpretation of ridges of the modulus of the analytic signal at different altitude ranges allows recognition of at least three distinct sources between about 5 km and 20 km depth. Their interpretation is discussed in light of borehole data and other geophysical constraints. A reasonable geological model for these sources indicates the presence of intrusions, probably linked to the past activity of Mt. Vulture. [source] Potential field based geometric modelling using the method of fundamental solutionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2006Roman Tankelevich Abstract We propose a new geometric modelling method based on the so-called potential field (PF) modelling technique. The harmonic problem associated with this technique is solved numerically using the method of fundamental solutions (MFS). We investigate the applicability of the proposed approach to parametrically defined curves of varying complexity. Based on the MFS, we also provide definitions of the Boolean operations associated with the geometric modelling. Finally, we give practical applications of the method to computer-aided design and manufacturing problems. Copyright © 2006 John Wiley & Sons, Ltd. [source] Study of non-Fickian diffusion problems with the potential field in the cylindrical co-ordinate systemINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2003Han-Taw Chen Abstract The present study applies a hybrid numerical scheme of the Laplace transform technique and the control volume method in conjunction with the hyperbolic shape functions to investigate the effect of a potential field on the one-dimensional non-Fickian diffusion problems in the cylindrical co-ordinate system. The Laplace transform method is used to remove the time-dependent terms in the governing differential equation and the boundary conditions, and then the resulting equations are discretized by the control volume scheme. The primary difficulty in dealing with the present problem is the suppression of numerical oscillations in the vicinity of sharp discontinuities. Results show that the present numerical results do not exhibit numerical oscillations and the potential field plays an important role in the present problem. The strength of the jump discontinuity can be reduced by increasing the value of the potential gradient. The propagation speed of mass wave is independent of the potential gradient and the boundary condition. Copyright © 2003 John Wiley & Sons, Ltd. [source] A hindrance to communication: the use of difficult and incomprehensible languageINTERNATIONAL JOURNAL OF APPLIED LINGUISTICS, Issue 2 2002Karol Janicki This paper gives a brief theoretical background to and reports on three empirical studies carried out within the theoretical framework of folk linguistics, using questionnaire data. The paper is concerned with the layperson's reactions to the use of difficult and incomprehensible language. In study 1, subjects from Norway, Poland, Germany, and the USA were asked to indicate which professional groups exhibit the use of difficult language. They were also asked to suggest reasons for that use. In study 2, subjects from Norway, Poland, Germany, and the UK were asked to answer questions concerning the use of incomprehensible language in the academic community. Study 3 was similar to study 2, but in this case only highly comparable subjects from the USA and Poland were recruited. The three studies show that the use of difficult and incomprehensible language is perceived by the layperson as a serious sociolinguistic problem. They point to lawyers, politicians, computer specialists, academics and medical doctors as the heaviest users of such language. They also show that such language exerts much negative impact on the educational process and that the educational domain is a huge potential field for future research in this respect. [source] Obstacle Avoidance for Spatial Hyper-Redundant Manipulators Using Harmonic Potential Functions and the Mode Shape TechniqueJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 1 2003F. Fahimi This paper deals with the obstacle avoidance problem for spatial hyper-redundant manipulators in known environments. The manipulator is divided into two sections, a proximal section that has not entered the space among the obstacles and a distal section among the obstacles. Harmonic potential functions are employed to achieve obstacle avoidance for the distal section in three-dimensional space in order to avoid local minima in cluttered environments. A modified panel method is used to generate the potential of any arbitrary shaped obstacle in three-dimensional space. An alternative backbone curve concept and an efficient fitting method are introduced to control the trajectory of proximal links. The fitting method is recursive and avoids the complications involved with solving large systems of nonlinear algebraic equations. The combination of a three-dimensional safe path derived from the harmonic potential field and the backbone curve concept leads to an elegant kinematic control strategy that guarantees obstacle avoidance. © 2003 Wiley Periodicals, Inc. [source] Interpretation of observed fluid potential patterns in a deep sedimentary basin under tectonic compression: Hungarian Great Plain, Pannonian BasinGEOFLUIDS (ELECTRONIC), Issue 1 2001J. Tóth Abstract The , 40 000 km2 Hungarian Great Plain portion of the Pannonian Basin consists of a basin fill of 100 m to more than 7000 m thick semi- to unconsolidated marine, deltaic, lacustrine and fluviatile clastic sediments of Neogene age, resting on a strongly tectonized Pre-Neogene basement of horst-and-graben topography of a relief in excess of 5000 m. The basement is built of a great variety of brittle rocks, including flysch, carbonates and metamorphics. The relatively continuous Endr,d Aquitard, with a permeability of less than 1 md (10,15 m2) and a depth varying between 500 and 5000 m, divides the basin's rock framework into upper and lower sequences of highly permeable rock units, whose permeabilities range from a few tens to several thousands of millidarcy. Subsurface fluid potential and flow fields were inferred from 16 192 water level and pore pressure measurements using three methods of representation: pressure,elevation profiles; hydraulic head maps; and hydraulic cross-sections. Pressure,elevation profiles were constructed for eight areas. Typically, they start from the surface with a straight-line segment of a hydrostatic gradient (,st = 9.8067 MPa km,1) and extend to depths of 1400,2500 m. At high surface elevations, the gradient is slightly smaller than hydrostatic, while at low elevations it is slightly greater. At greater depths, both the pressures and their vertical gradients are uniformly superhydrostatic. The transition to the overpressured depths may be gradual, with a gradient of ,dyn = 10,15 MPa km,1 over a vertical distance of 400,1000 m, or abrupt, with a pressure jump of up to 10 MPa km,1 over less than 100 m and a gradient of ,dyn > 20 MPa km,1. According to the hydraulic head maps for 13 100,500 m thick horizontal slices of the rock framework, the fluid potential in the near-surface domains declines with depth beneath positive topographic features, but it increases beneath depressions. The approximate boundary between these hydraulically contrasting regions is the 100 m elevation contour line in the Duna,Tisza interfluve, and the 100,110 m contours in the Nyírség uplands. Below depths of ,,600 m, islets of superhydrostatic heads develop which grow in number, areal extent and height as the depth increases; hydraulic heads may exceed 3000 m locally. A hydraulic head ,escarpment' appears gradually in the elevation range of ,,1000 to ,,2800 m along an arcuate line which tracks a major regional fault zone striking NE,SW: heads drop stepwise by several hundred metres, at places 2000 m, from its north and west sides to the south and east. The escarpment forms a ,fluid potential bank' between a ,fluid potential highland' (500,2500 m) to the north and west, and a ,fluid potential basin' (100,500 m) to the south and east. A ,potential island' rises 1000 m high above this basin further south. According to four vertical hydraulic sections, groundwater flow is controlled by the topography in the upper 200,1700 m of the basin; the driving force is orientated downwards beneath the highlands and upwards beneath the lowlands. However, it is directed uniformly upwards at greater depths. The transition between the two regimes may be gradual or abrupt, as indicated by wide or dense spacing of the hydraulic head contours, respectively. Pressure ,plumes' or ,ridges' may protrude to shallow depths along faults originating in the basement. The basement horsts appear to be overpressured relative to the intervening grabens. The principal thesis of this paper is that the two main driving forces of fluid flow in the basin are gravitation, due to elevation differences of the topographic relief, and tectonic compression. The flow field is unconfined in the gravitational regime, whereas it is confined in the compressional regime. The nature and geometry of the fluid potential field between the two regimes are controlled by the sedimentary and structural features of the rock units in that domain, characterized by highly permeable and localized sedimentary windows, conductive faults and fracture zones. The transition between the two potential fields can be gradual or abrupt in the vertical, and island-like or ridge-like in plan view. The depth of the boundary zone can vary between 400 and 2000 m. Recharge to the gravitational regime is inferred to occur from infiltrating precipitation water, whereas that to the confined regime is from pore volume reduction due to the basement's tectonic compression. [source] Active control of FGM shells subjected to a temperature gradient via piezoelectric sensor/actuator patchesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2002K. M. Liew Abstract A generic static and dynamic finite element formulation is derived for the modelling and control of piezoelectric shell laminates under coupled displacement, temperature and electric potential fields. The base shell is of functionally graded material (FGM) type, which consists of combined ceramic,metal materials with different mixing ratios of the ceramic and metal constituents. A multi-input,multi-output (MIMO) system is applied to provide active feedback control of the laminated shell using self-monitoring sensors and self-controlling actuators through a close loop. Numerical studies clearly show the influence of the positional configurations of sensor/actuator pairs on the effectiveness of static and dynamic control for the shell laminates. The effects of the constituent volume fractions on the static and dynamic responses of the shell laminate are also elucidated. Copyright © 2002 John Wiley & Sons, Ltd. [source] Inverse design of directional solidification processes in the presence of a strong external magnetic fieldINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2001Rajiv Sampath Abstract A computational method for the design of directional alloy solidification processes is addressed such that a desired growth velocity ,f under stable growth conditions is achieved. An externally imposed magnetic field is introduced to facilitate the design process and to reduce macrosegregation by the damping of melt flow. The design problem is posed as a functional optimization problem. The unknowns of the design problem are the thermal boundary conditions. The cost functional is taken as the square of the L2 norm of an expression representing the deviation of the freezing interface thermal conditions from the conditions corresponding to local thermodynamic equilibrium. The adjoint method for the inverse design of continuum processes is adopted in this work. A continuum adjoint system is derived to calculate the adjoint temperature, concentration, velocity and electric potential fields such that the gradient of the L2 cost functional can be expressed analytically. The cost functional minimization process is realized by the conjugate gradient method via the FE solutions of the continuum direct, sensitivity and adjoint problems. The developed formulation is demonstrated with an example of designing the boundary thermal fluxes for the directional growth of a germanium melt with dopant impurities in the presence of an externally applied magnetic field. The design is shown to achieve a stable interface growth at a prescribed desired growth rate. Copyright © 2001 John Wiley & Sons, Ltd. [source] Building and navigating a network of local minimaJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 8 2001Seung-Woo Kim We present a novel method that constructs and navigates a network of local minima of potential fields defined over multidimensional spaces. Though motivated by problems of motion planning for robotic manipulators, similar techniques have been proposed for use in other domains such as molecular chemistry and drug design. The method is based on building a roadmap of paths connecting local minima of a potential function. The novel approach consists of an up-hill search strategy used to climb out of local minima and find new nearby local minima, without doubling back on previous local minima. With this up-hill search strategy, one can find local minima otherwise difficult to encounter, and one can focus the search to specific local minima and specific directions from those local minima. The construction of the roadmap can be done in parallel with very little communication. We present extensive simulation results. © 2001 John Wiley & Sons, Inc. [source] Production of Inorganic Nanoparticles by MicroorganismsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2009N. Krumov Abstract A promising new dimension in the field of biotechnology is the use of microorganisms for the production of inorganic nanoscale particles. The interest in nanotechnology is provoked by the unique properties of nanostructured materials and their potential fields of application ranging from medicine to electronics. This review article presents a systematic overview of the microorganisms capable of producing nanoparticles, and describes cellular mechanisms and outlines cultivation conditions that turn this process into a successful synthetic pathway. [source] | ||||||||||||||||