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Статті в журналах з теми "Electric field modeling techniques"
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Mercadal, Borja, Ricardo Salvador, Maria Chiara Biagi, Fabrice Bartolomei, Fabrice Wendling, and Giulio Ruffini. "Modeling implanted metals in electrical stimulation applications." Journal of Neural Engineering 19, no. 2 (March 8, 2022): 026003. http://dx.doi.org/10.1088/1741-2552/ac55ae.
Повний текст джерелаАнотація:
Abstract Objective. Metal implants impact the dosimetry assessment in electrical stimulation techniques. Therefore, they need to be included in numerical models. While currents in the body are ionic, metals only allow electron transport. In fact, charge transfer between tissues and metals requires electric fields to drive electrochemical reactions at the interface. Thus, metal implants may act as insulators or as conductors depending on the scenario. The aim of this paper is to provide a theoretical argument that guides the choice of the correct representation of metal implants in electrical models while considering the electrochemical nature of the problem Approach. We built a simple model of a metal implant exposed to a homogeneous electric field of various magnitudes. The same geometry was solved using two different models: a purely electric one (with different conductivities for the implant), and an electrochemical one. As an example of application, we also modeled a transcranial electrical stimulation (tES) treatment in a realistic head model with a skull plate using a high and low conductivity value for the plate. Main results. Metal implants generally act as electric insulators when exposed to electric fields up to around 100 V m−1 and they only resemble a perfect conductor for fields in the order of 1000 V m−1 and above. The results are independent of the implant’s metal, but they depend on its geometry. tES modeling with implants incorrectly treated as conductors can lead to errors of 50% or more in the estimation of the induced fields Significance. Metal implants can be accurately represented by a simple electrical model of constant conductivity, but an incorrect model choice can lead to large errors in the dosimetry assessment. Our results can be used to guide the selection of the most appropriate model in each scenario.
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Akinsanmi, Olaitan, B. A. Adegboye, G. A. Olarinoye, and M. B. Soroyewun. "Neuro-Fuzzy Based Modeling of Electrostatic Fields for Harmattan Season in Zaria." International Journal of Engineering Research in Africa 4 (May 2011): 75–85. http://dx.doi.org/10.4028/www.scientific.net/jera.4.75.
Повний текст джерелаАнотація:
This paper presents a Neuro-Fuzzy based modeling of electrostatic fields for harmattan season in Zaria, Nigeria based on online based data capturing mechanism, which involved the use of a data acquisition system interfaced with a digital electrostatic field strength meter (model 257D) and a computer system. The acquired electric field data were captured by the computer using the Microsoft Office Excel Program for twenty-four months (February 2007 – February 2009). The focus of the analysis is determining the effect of environmental factors such as temperature, pressure and relative humidity on the static electric field during the harmattan season. The plots of the electrostatic field against the variation of the environmental factors were used as the qualitative analytical tools and yielded a non-linear relationship. The data was analyzed using Neuro-Fuzzy technique, which is a hybrid intelligent system combining the benefits of computational techniques of Fuzzy Logic and Artificial Neural Networks. The result of the analyses yielded good neural statistical values of Root Mean Square (RMS) of 0.32, Average Absolute Error of 0.18, and Pearson R value of 0.96 for the harmattan scenario, which are reflections of a good model. The result was further buttressed by the 3D plot of the Neuro-Fuzzy based modeling of the experimental parameters. With the insignificant values of the RMS and Average Absolute value, the empirical model gave a fairly good prediction which could be relied upon to predict the electrostatic fields during harmattan in Zaria, Nigeria.
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Tang, Zi Rong, M. Rizwan Malik, Tie Lin Shi, J. Gong, L. Nie, and Guang Lan Liao. "Modelling and Fabrication of 3-D Carbon-MEMS for Dielectrophoretic Manipulation of Micro/Nanoparticles in Fluids." Materials Science Forum 628-629 (August 2009): 435–40. http://dx.doi.org/10.4028/www.scientific.net/msf.628-629.435.
Повний текст джерелаАнотація:
Carbon-MEMS (C-MEMS) have emerged as a new category of devices for micro/nano technology with many potential applications. Dielectrophoretic manipulation of micro/nanoparticles with C-MEMS is studied in this paper. Through electric field distribution modeling in carbon electrode array, we analyze the strongest simulation effect results of electric field in three dimensional (3-D) surface plots depicting the magnitude of electric field in various cross sections at different heights above the channel floor for 2, 10, 30 and 50 μm high carbon electrodes. It is represented here that maximum intensity of electric field generates with the equality between the height above the channel floor and the height of the electrodes. Simulation parameters involved are for dielectrophoretic manipulation of micro/nano particles based on 3-D C-MEMS. The advantages of using 3-D C-MEMS electrodes over other techniques of creating high-throughput systems for dielectrophoretic manipulation environment surrounded by micro/nano horizons are: (i) complex microscale 3-D electrodes with high-aspect ratios can easily be shaped and patterned using conventional lithography (ii) carbon has a high window of stability thus allowing application of higher voltages (iii) there is no need for bulk micromachining or patterning electrodes on multiple planes (iv) the distance between electrodes can precisely be controlled through the lithography process. FEMLAB 3.4 Multiphysics Modeling software (COMSOL, Stockholm, Sweden) is used for the modeling of electric fields and one-layer C-MEMS microelectrode array was fabricated with SU-8 photoresist.
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Jörgens, Christoph, and Markus Clemens. "A Review about the Modeling and Simulation of Electro-Quasistatic Fields in HVDC Cable Systems." Energies 13, no. 19 (October 5, 2020): 5189. http://dx.doi.org/10.3390/en13195189.
Повний текст джерелаАнотація:
In comparison to high-voltage alternating current (HVAC) cable systems, high-voltage direct current (HVDC) systems have several advantages, e.g., the transmitted power or long-distance transmission. The insulating materials feature a non-linear dependency on the electric field and the temperature. Applying a constant voltage, space charges accumulate in the insulation and yield a slowly time-varying electric field. As a complement to measurements, numerical simulations are used to obtain the electric field distribution inside the insulation. The simulation results can be used to design HVDC cable components such that possible failure can be avoided. This work is a review about the simulation of the time-varying electric field in HVDC cable components, using conductivity-based cable models. The effective mechanisms and descriptions of charge movement result in different conductivity models. The corresponding simulation results of the models are compared against measurements and analytic approximations. Different numerical techniques show variations of the accuracy and the computation time that are compared. Coupled electro-thermal field simulations are applied to consider the environment and its effect on the resulting electric field distribution. A special case of an electro-quasistatic field describes the drying process of soil, resulting from the temperature and electric field. The effect of electro-osmosis at HVDC ground electrodes is considered within this model.
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Wijewardena Gamalath, K. A. I. L., and A. M. Samarakoon. "Modeling of Planar Plasma Diode." International Letters of Chemistry, Physics and Astronomy 13 (September 2013): 220–42. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.13.220.
Повний текст джерелаАнотація:
To investigate the dynamics of a planar plasma diode system (PDS), a model based on the current density equilibrium at the interface was developed. The current densities and plasma boundary variations with the potential fields were obtained by simulating a single square pulse. The variation of an observed overshoot current density with the applied voltage is presented. Planar plasma diode system was also simulated for periodic, sine, square, triangular and saw tooth voltage patterns by varying the amplitude and frequencies. A method to find the lower bound of the electron density of plasma for a specified PDS is presented. Particle-In-Cell simulation technique was used to investigate the plasma particles and electric field distributions over the anode cathode gap for different intensities of external electric fields. The system became stable after few time steps and this time depends upon the intensity and polarization of the external field.
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Gavin, H. P., R. D. Hanson, and F. E. Filisko. "Electrorheological Dampers, Part II: Testing and Modeling." Journal of Applied Mechanics 63, no. 3 (September 1, 1996): 676–82. http://dx.doi.org/10.1115/1.2823349.
Повний текст джерелаАнотація:
Electrorheological (ER) materials develop yield stresses on the order of 5–10 kPa in the presence of strong electric fields. Viscoelastic and yielding material properties can be modulated within milli-seconds. An analysis of flowing ER materials in the limiting case of fully developed steady flow results in simple approximations for use in design. Small-scale experiments show that these design equations can be applied to designing devices in which the flow is unsteady. More exact models of ER device behavior can be determined using curve-fitting techniques in multiple dimensions. A previously known curve-fitting technique is extended to deal with variable electric fields. Experiments are described which illustrate the potential for ER devices in large-scale damping applications and the accuracy of the modeling technique.
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Kurbanismailov, Z. M., A. T. Tarlanov, and E. M. Akimov. "The technique of point visualization of the electric field in space and time." Russian Technological Journal 9, no. 3 (June 28, 2021): 58–65. http://dx.doi.org/10.32362/2500-316x-2021-9-3-58-65.
Повний текст джерелаАнотація:
Testing of electronic devices is an integral part of the technological process of any manufacturer of such equipment. In this case, an electronic device is understood as an energy-intensive unit such as a mobile phone, data center or spacecraft. One of the key stages of testing is to identify the effect of electric fields on various electronic components of the device. This stage often requires making a mock-up of some part of an unfinished device in order to fix interference with special equipment. This requires time, financial and human resource costs. In order to reduce these costs in the modern world, the use of mathematical modeling tools for testing noise immunity and electromagnetic compatibility is becoming popular. In this paper, it is proposed to use an algorithm for visualizing electric fields in three-dimensional space and time. The algorithm is easily embedded into applications as a component of a mathematical modeling system. The work considered three ways of visualizing the electric field strength: starting from a simple setting of points in space, on the basis of which the electric field will be built, around the source of electric field radiation, to the use of algorithms that make it possible to arrange points equidistantly based on a given number of points in space for the formation of an electric field. The performance and visual implications of these methods were analyzed. The proposed methodology will be useful to the developer community as an embedded solution for point visualization of the electric field in any project in any algorithmic language with the ability to animate in time.
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Brown, Thomas S., Tonatiuh Sánchez-Vizuet, and Francisco-Javier Sayas. "Evolution of a semidiscrete system modeling the scattering of acoustic waves by a piezoelectric solid." ESAIM: Mathematical Modelling and Numerical Analysis 52, no. 2 (March 2018): 423–55. http://dx.doi.org/10.1051/m2an/2017045.
Повний текст джерелаАнотація:
We consider a model problem of the scattering of linear acoustic waves in free homogeneous space by an elastic solid. The stress tensor in the solid combines the effect of a linear dependence of strains with the influence of an existing electric field. The system is closed using Gauss’s law for the associated electric displacement. Well-posedness of the system is studied by its reformulation as a first order in space and time differential system with help of an elliptic lifting operator. We then proceed to studying a semidiscrete formulation, corresponding to an abstract Finite Element discretization in the electric and elastic fields, combined with an abstract Boundary Element approximation of a retarded potential representation of the acoustic field. The results obtained with this approach improve estimates obtained with Laplace domain techniques. While numerical experiments illustrating convergence of a fully discrete version of this problem had already been published, we demonstrate some properties of the full model with some simulations for the two dimensional case.
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Poikonen, Ari, and Ilkka Suppala. "On modeling airborne very low‐frequency measurements." GEOPHYSICS 54, no. 12 (December 1989): 1596–606. http://dx.doi.org/10.1190/1.1442627.
Повний текст джерелаАнотація:
Numerical models employed in ground VLF modeling use a normally incident (homogeneous) plane wave as a primary field. We show that these models are not directly applicable to modeling the impedance and wavetilt in the air, quantities needed in the interpretation of airborne VLF resistivity measurements. Instead, the primary field must be replaced by an inhomogeneous plane wave incident on the ground at an angle close to 90 degrees in order to provide the correct behavior of the apparent resistivities in the air. VLF magnetic polarization parameters, however, can be modeled in the air using the normally incident plane wave as a primary field. We also show that the plane‐wave analysis provides the same attenuation characteristics for the wavetilt in the air that is predicted by the Norton’s surface wave obtained by using the vertical electric dipole as a source. Use of the inhomogeneous plane wave introduces the vertical component of the electric field in the model. A 2‐D modeling technique based on the network solution is used to demonstrate the effects of the vertical electric field in the H‐polarization case. The vertical electric field generates charge distributions on the horizontal boundaries of conductors. In the case of a vertical sheet‐like conductor, these charges cause a slight asymmetry in apparent‐resistivity anomalies. Attenuation characteristics of various VLF anomalies with altitude are also presented. The H‐polarization anomalies attenuate much more rapidly in the air than those for E‐polarization due to the difference in the dominating source of EM fields in each polarization.
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Shi, Yun Fei, and Jun Liu. "Multi-Physics Modeling and Simulation of Electro-Optical Sensing." Advanced Materials Research 1092-1093 (March 2015): 292–95. http://dx.doi.org/10.4028/www.scientific.net/amr.1092-1093.292.
Повний текст джерелаАнотація:
With the rapid development of UHV technology, Electric field measurement technique has attracted lots of people's attention.Electro-optical sensors for measuring the electric field to become the main method due to the crystal optical fiber preparation and mature technology. This article describes the basic principles that Mach - Zehnder of lithium niobate optical modulator for electric field measurements.Designing the Mach - Zehnder electro-optic sensors in the Comsol Multiphysics oftware, the calculation model for the simulation results of bending radius that the optical waveguide transmission power loss minimum, a 3dB directional coupler to determine the length of the arm and finally adding a signal voltage, the applied voltage is obtained a linear relationship between the output power.
Дисертації з теми "Electric field modeling techniques"
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Kumar, Akhilesh. "Leakage Power Modeling and Reduction Techniques for Field Programmable Gate Arrays." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/766.
Повний текст джерелаАнотація:
FPGAs have become quite popular for implementing digital circuits and systems because of reduced costs and fast design cycles. This has led to increased complexity of FPGAs, and with technology scaling, many new challenges have come up for the FPGA industry, leakage power being one of the key challenges. The current generation FPGAs are being implemented in 90nm technology, therefore, managing leakage power in deep-submicron FPGAs has become critical for the FPGA industry to remain competitive in the semiconductor market and to enter the mobile applications domain. In this work an analytical state dependent leakage power model for FPGAs is developed, followed by dual-Vt based designs of the FPGA architecture for reducing leakage power.
The leakage power model computes subthreshold and gate leakage in FPGAs, since these are the two dominant components of total leakage power in the scaled nanometer technologies. The leakage power model takes into account the dependency of gate and subthreshold leakage on the state of the circuit inputs. The leakage power model has two main components, one which computes the probability of a state for a particular FPGA circuit element, and the other which computes the leakage of the FPGA circuit element for a given input using analytical equations. This FPGA power model is particularly important for rapidly analyzing various FPGA architectures across different technology nodes.
Dual-Vt based designs of the FPGA architecture are proposed, developed, and evaluated, for reducing the leakage power using a CAD framework. The logic and the routing resources of the FPGA are considered for dual-Vt assignment. The number of the logic elements that can be assigned high-Vt in the ideal case by using a dual-Vt assignment algorithm in the CAD framework is estimated. Based upon this estimate two kinds of architectures are developed and evaluated, homogeneous and heterogeneous architectures. Results indicate that leakage power savings of up to 50% can be obtained from these architectures. The analytical state dependent leakage power model developed has been used for estimating the leakage power savings from the dual-Vt FPGA architectures. The CAD framework that has been developed can also be used for developing and evaluating different dual-Vt FPGA architectures, other than the ones proposed in this work.
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Dastrup, Emily Joy. "Estimating the Discrepancy Between Computer Model Data and Field Data: Modeling Techniques for Deterministic and Stochastic Computer Simulators." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd986.pdf.
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Бойко, Антон Миколайович. "Діагностика полімерної ізоляції в процесі старіння кабелів під дією сильного електричного поля за трибоелектричним потенціалом". Thesis, НТУ "ХПІ", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/19647.
Повний текст джерелаАнотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.09.13 – техніка сильних електричних та магнітних полів. Національний технічний університет "Харківський політехнічний інститут", Харків, 2015. Дисертація присвячена розробці та обґрунтуванню діагностики за трибоелектричним потенціалом для виявлення зміни поверхневих властивостей полімерної ізоляції в процесі старіння кабелів під дією сильного електричного поля, підвищеної температури та іонізуючого випромінювання. В процесі старіння для двошарової ізоляції на основі застосування схеми заміщення встановлено появу струмів, що змінюються по експоненціальному закону, та отримано динаміку в часі накопичення, рекомбінації та релаксації поверхневого заряду на границі розділу. Встановлено розподіл густини поверхневого заряду по довжині симетричних ізольованих провідників при наявності між ними зазору та тонкого дефектного шару на поверхні полімерної ізоляції на основі отриманого аналітичного рішення. Показано, що окиснений прошарок на поверхні ізоляції призводить по появи сильного електричного поля. В залежності від конструктивного виконання і застосованих матеріалів експериментально визначено значення трибоелектричного потенціалу та встановлена динаміка його зміни в процесі прискореного терморадіаційного старіння кабелів. Встановлено вплив поверхневих та трибозарядів на результати діагностичних обстежень кабелів за опором ізоляції на високій напрузі. Запропонована діагностика за трибоелектричним потенціалом силових, контрольних та інформаційних кабелів дозволяє виявити зміну поверхневих властивостей полімерної ізоляції в процесі старіння кабелів.Thesis for granting Candidate of Technical sciences Degree in specialty 05.09.13 – Technics of Strong Electric and Magnetic Fields. – National Technical University "Kharkiv Polytechnic Institute", 2015. The thesis is devoted to development and diagnostic system for substantiation triboelectric potential to detect changes in surface properties of polymer isolation in aging cables under the strong electric field, high temperature and radiation. The distribution of surface charge density and voltage drop along the length of symmetrical insulated conductors in the presence of the gap between them and the defective thin layer on the surface of the polymer insulation was established based on the analytical solution. Experimentally determined the values of triboelectric potential and its dynamics of change in the process of accelerated termoradiation aging polymer cable insulation depending on the design of applied materials. There is a significant (threefold) increase in the maximum value of the contact potential difference and achieve maximum torque bias towards smaller values for single core power cables with cross-linked polyethylene insulation 6 kV after accelerated aging thermoradiation. This confirms the high sensitivity of triboelectric potential to aging and allows us to make a suggestion to use this parameter as an indicator of the polymeric insulation aging degree. Influence of surface charges and tribocharges on the results of diagnostic tests on the insulation resistance and stability during the measurement capacitance and dielectric loss tangent cables with polymer insulation was observed. Dynamics of changes in contact potential difference in the aging process power cables with different materials remains consistent with the results of diagnostic tests of capacity and dielectric loss tangent.
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Бойко, Антон Миколайович. "Діагностика полімерної ізоляції в процесі старіння кабелів під дією сильного електричного поля за трибоелектричним потенціалом". Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/19642.
Повний текст джерелаАнотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.09.13 – техніка сильних електричних та магнітних полів. Національний технічний університет "Харківський політехнічний інститут", Харків, 2015.
Дисертація присвячена розробці та обґрунтуванню діагностики за трибоелектричним потенціалом для виявлення зміни поверхневих властивостей полімерної ізоляції в процесі старіння кабелів під дією сильного електричного поля, підвищеної температури та іонізуючого випромінювання. В процесі старіння для двошарової ізоляції на основі застосування схеми заміщення встановлено появу струмів, що змінюються по експоненціальному закону, та отримано динаміку в часі накопичення, рекомбінації та релаксації поверхневого заряду на границі розділу. Встановлено розподіл густини поверхневого заряду по довжині симетричних ізольованих провідників при наявності між ними зазору та тонкого дефектного шару на поверхні полімерної ізоляції на основі отриманого аналітичного рішення. Показано, що окиснений прошарок на поверхні ізоляції призводить по появи сильного електричного поля. В залежності від конструктивного виконання і застосованих матеріалів експериментально визначено значення трибоелектричного потенціалу та встановлена динаміка його зміни в процесі прискореного терморадіаційного старіння кабелів. Встановлено вплив поверхневих та трибозарядів на результати діагностичних обстежень кабелів за опором ізоляції на високій напрузі. Запропонована діагностика за трибоелектричним потенціалом силових, контрольних та інформаційних кабелів дозволяє виявити зміну поверхневих властивостей полімерної ізоляції в процесі старіння кабелів.Thesis for granting Candidate of Technical sciences Degree in specialty 05.09.13 – Technics of Strong Electric and Magnetic Fields. – National Technical University "Kharkiv Polytechnic Institute", 2015. The thesis is devoted to development and diagnostic system for substantiation triboelectric potential to detect changes in surface properties of polymer isolation in aging cables under the strong electric field, high temperature and radiation. The distribution of surface charge density and voltage drop along the length of symmetrical insulated conductors in the presence of the gap between them and the defective thin layer on the surface of the polymer insulation was established based on the analytical solution. Experimentally determined the values of triboelectric potential and its dynamics of change in the process of accelerated termoradiation aging polymer cable insulation depending on the design of applied materials. There is a significant (threefold) increase in the maximum value of the contact potential difference and achieve maximum torque bias towards smaller values for single core power cables with cross-linked polyethylene insulation 6 kV after accelerated aging thermoradiation. This confirms the high sensitivity of triboelectric potential to aging and allows us to make a suggestion to use this parameter as an indicator of the polymeric insulation aging degree. Influence of surface charges and tribocharges on the results of diagnostic tests on the insulation resistance and stability during the measurement capacitance and dielectric loss tangent cables with polymer insulation was observed. Dynamics of changes in contact potential difference in the aging process power cables with different materials remains consistent with the results of diagnostic tests of capacity and dielectric loss tangent.
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Papalexopoulos, Alexis D. "Modeling techniques for power system grounding systems." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/13529.
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Babineau, David. "Modeling the electric field and natural environment of weakly electric fish." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27222.
Повний текст джерелаАнотація:
Weakly electric fish use a unique sensory modality in order to help them communicate, navigate and find prey. These fish emit electric discharges that are monitored by electroreceptors located in the fish's skin. Surrounding objects perturb these baseline transdermal potentials and create electric images. The study of these images has led to a better understanding of general sensory processing principles; however, many aspects of these fish's natural electrosensory environment remain unknown. To this end, a two-dimensional finite element model of Apteronotus leptorhynchus was created. Using this model, we suggest new ways by which electric fish are able to locate objects and propose that it is possible for these fish to extract useful information from their environment using their natural scanning behaviour. Our results also reveal important limitations in standard experimental paradigms that aim to mimic the effects of conspecifics. Alternative paradigms that will enable more realistic stimulation are suggested.
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Zhang, Minya. "Optoelectronic device modeling using field simulation techniques." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/NQ42892.pdf.
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Andersson, Helena. "Individualized mathematical modeling of neural activation in electric field." Thesis, Uppsala universitet, Avdelningen för systemteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-313150.
Повний текст джерелаАнотація:
Deep Brain Stimulation (DBS) is a treatment of movement disorders such as Parkinson's disease and essential tremor. Today it has been used in more than 80.000 patients. Electrical stimulation is administered by an implanted pulse generator through an electrode surgically placed in a target brain area specific to the treated disease. Opposed to alternative purely surgical treatment procedures, DBS is reversible and can be turned off. In this project, the aim is to individualise an already existing computational model of DBS, but also to look at optimisation of the treatment by developing a neuron model. It has been executed the following way. To localise the target area for the electrode, Magnetic Resonance Imaging (MRI) is used. An MRI image consists of volume elements called voxels. By analysing these voxels, it is possible to set up a coordinate system for the position of different parts of the brain. To build up an individualised model of the DBS, an MRI image is segmented into tissues of different conductivity thus resulting in a more accurate description of the electrical field around the electrode. To visualize the stimuli coverage for the medical staff, the MRI image of the target area, the electrode, and the electrical field produced by the stimuli are depicted in the same figure. From the results, we can draw the conclusion that this method works well for individualising the computational model of DBS, but it has only been used on one MRI scan so far so it needs further testing to obtain more data to compare with. The neuron model is a temporospatial mathematical model of a single neuron for the prediction of activation by a given electrically applied field generated by a DBS lead. The activation model is intended to be part of a patient-specific model of an already existing computational model of DBS. The model originate from a neuron model developed by Hodgkin and Huxley (HH). The original HH model only takes into account one compartment and, to make the neuron model more accurate, it is combined with a cable model. The simulation results obtained with the model have been validated against an established and widely accepted neuron model. The results correlated highly to each other with only minor differences. To see how position and orientation impact on activation, the developed HH model was tested for different pulse widths, distances from the lead, and rotations of the neuron relative to the lead. A larger pulse width makes activation more likely and so does a larger amplitude. Thicker neurons are more likely to get activated, neurons closer to the lead and also neurons perpendicular to the lead. From the results we can draw the conclusion that this method is a good way to stimulate neural activation of a single neuron. In future research, it might be possible to compare results from the neuron model with patient's response to treatment.
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De, Marco Tommaso <1980>. "Parallel modeling of the electric field distribution in the brain." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3618/.
Повний текст джерелаАнотація:
The term "Brain Imaging" identi�es a set of techniques to analyze the structure and/or functional behavior of the brain in normal and/or pathological situations. These techniques are largely used in the study of brain activity.
In addition to clinical usage, analysis of brain activity is gaining popularity in others recent �fields, i.e. Brain Computer Interfaces (BCI) and the study of cognitive processes. In this context, usage of classical solutions (e.g. f MRI, PET-CT) could be unfeasible, due to their low temporal resolution, high cost and limited portability. For these reasons alternative low cost techniques are object of research, typically based on simple recording hardware and on intensive data elaboration process. Typical examples are ElectroEncephaloGraphy (EEG) and Electrical Impedance Tomography (EIT), where electric potential at the patient's scalp is recorded by high impedance electrodes. In EEG potentials are directly generated from neuronal activity, while in EIT by the injection of small currents at the scalp. To retrieve meaningful insights on brain activity from measurements, EIT and EEG relies on detailed knowledge of the underlying electrical properties of the body. This is obtained from numerical models of the electric �field
distribution therein. The inhomogeneous and anisotropic electric properties of human tissues make accurate modeling and simulation very challenging, leading to a tradeo�ff between physical accuracy and technical feasibility,
which currently severely limits the capabilities of these techniques. Moreover elaboration of data recorded requires usage of regularization techniques computationally intensive, which influences the application with heavy temporal constraints (such as BCI).
This work focuses on the parallel implementation of a work-flow for EEG and EIT data processing. The resulting software is accelerated using multi-core GPUs, in order to provide solution in reasonable times and address requirements of real-time BCI systems, without over-simplifying the complexity and accuracy of the head models.
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Weinstein, Randall Kenneth. "Techniques for FPGA neural modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/26685.
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Thesis (Ph.D)--Bioengineering, Georgia Institute of Technology, 2007.Committee Chair: Lee, Robert; Committee Member: Butera, Robert; Committee Member: DeWeerth, Steve; Committee Member: Madisetti, Vijay; Committee Member: Voit, Eberhard. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Книги з теми "Electric field modeling techniques"
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Li, S. Z. Markov random field modeling in image analysis. 3rd ed. London: Springer, 2009.
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Najim, Mohamed. Modeling, estimation and optimal filtration in signal processing. Hoboken, NJ: ISTE ; J. Wiley & Sons, 2008.
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Gildenblat, Gennady Sh. Compact Modeling: Principles, Techniques and Applications. Dordrecht: Springer Science+Business Media B.V., 2010.
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RF and microwave modeling and measurement techniques for compound field effect transistors. Raleigh, NC: SciTech Pub., 2009.
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Burkov, Aleksey. Technical operation of electric ships. ru: INFRA-M Academic Publishing LLC., 2020. http://dx.doi.org/10.12737/1048423.
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The book investigates the issues related to improving the efficiency of technical operation of ship electric drives, developed their classification. Identified ship's drives, having low reliability, designed and implemented technical solutions to increase their reliability. The appropriateness of the integrated assessment within the tasks of a mathematical and physical modeling. Developed and implemented mathematical and physical models for studies of electric drives. The proposed method, an algorithmic software, and made payments of contactors for work in the proposed technical solutions.
Designed for those who specializiruetsya in the field of the theory and practice of ship electric drives. Useful for the learning process in the system of higher Maritime education.
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Lattman, Eaton E., Thomas D. Grant, and Edward H. Snell. Pushing the Envelope. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199670871.003.0014.
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Direct electron density determination from SAXS data opens up new opportunities. The ability to model density at high resolution and the implicit direct estimation of solvent terms such as the hydration shell may enable high-resolution wide angle scattering data to be used to calculate density when combined with additional structural information. Other diffraction methods that do not measure three-dimensional intensities, such as fiber diffraction, may also be able to take advantage of iterative structure factor retrieval. While the ability to reconstruct electron density ab initio is a major breakthrough in the field of solution scattering, the potential of the technique has yet to be fully uncovered. Additional structural information from techniques such as crystallography, NMR, and electron microscopy and density modification procedures can now be integrated to perform advanced modeling of the electron density function at high resolution, pushing the boundaries of solution scattering further than ever before.
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1934-, Zobrist George W., ed. VLSI fault modeling and testing techniques. Norwood, NJ: Ablex Pub. Corp., 1993.
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Najim, Mohamed. Modeling, Estimation and Optimal Filtration in Signal Processing. Wiley & Sons, Incorporated, John, 2010.
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Gao, Jianjun. RF and Microwave Modeling and Measurement Techniques for Field Effect Transistors. Institution of Engineering and Technology, 2010. http://dx.doi.org/10.1049/sbew027e.
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Duen, Ho Fat, and United States. National Aeronautics and Space Administration., eds. Modeling of metal-ferroelectric-semiconductor field effect transistors. [Washington, D.C: National Aeronautics and Space Administration, 1998.
Знайти повний текст джерелаЧастини книг з теми "Electric field modeling techniques"
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Wölken, Thies, Johannes Sailer, Francisco Daniel Maldonado-Parra, Tobias Horneber, and Cornelia Rauh. "Application of Numerical Simulation Techniques for Modeling Pulsed Electric Field Processing." In Handbook of Electroporation, 1–31. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-26779-1_42-1.
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Wölken, Thies, Johannes Sailer, Francisco Daniel Maldonado-Parra, Tobias Horneber, and Cornelia Rauh. "Application of Numerical Simulation Techniques for Modeling Pulsed Electric Field Processing." In Handbook of Electroporation, 1237–67. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-32886-7_42.
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Takahashi, Norio. "Some Key Techniques in Electromagnetic and Thermal Field Modeling." In Modeling and Application of Electromagnetic and Thermal Field in Electrical Engineering, 53–100. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0173-9_3.
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Callejón-Leblic, M. A., and Pedro C. Miranda. "A Computational Parcellated Brain Model for Electric Field Analysis in Transcranial Direct Current Stimulation." In Brain and Human Body Modeling 2020, 81–99. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45623-8_5.
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AbstractRecent years have seen the use of increasingly realistic electric field (EF) models to further our knowledge of the bioelectric basis of noninvasive brain techniques such as transcranial direct current stimulation (tDCS). Such models predict a poor spatial resolution of tDCS, showing a non-focal EF distribution with similar or even higher magnitude values far from the presumed targeted regions, thus bringing into doubt the classical criteria for electrode positioning. In addition to magnitude, the orientation of the EF over selected neural targets is thought to play a key role in the neuromodulation response. This chapter offers a summary of recent works which have studied the effect of simulated EF magnitude and orientation in tDCS, as well as providing new results derived from an anatomically representative parcellated brain model based on finite element method (FEM). The results include estimates of mean and peak tangential and normal EF values over different cortical regions and for various electrode montages typically used in clinical applications.
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Fernandes, Sofia Rita, Ricardo Salvador, Mamede de Carvalho, and Pedro Cavaleiro Miranda. "Modelling Studies of Non-invasive Electric and Magnetic Stimulation of the Spinal Cord." In Brain and Human Body Modeling 2020, 139–65. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45623-8_8.
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AbstractExperimental studies on transcutaneous spinal cord direct current and magnetic stimulation (tsDCS and tsMS, respectively) show promising results in the neuromodulation of spinal sensory and motor pathways, with possible clinical application in spinal functional rehabilitation. Modelling studies on the electric field (EF) distribution during tsDCS and tsMS can be powerful tools to understand the underlying biophysics and to guide stimulation protocols for a specific clinical target. In this chapter, we review modelling studies of tsDCS and report on our own modelling findings on tsDCS and tsMS. We discuss the main differences between the EF induced by these two stimulation techniques and the implications for clinical practice, addressing the relevance of modelling studies for more personalized target protocols and individualized dosing.
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Guo, Tianruo, David Tsai, Siwei Bai, Mohit Shivdasani, Madhuvanthi Muralidharan, Liming Li, Socrates Dokos, and Nigel H. Lovell. "Insights from Computational Modelling: Selective Stimulation of Retinal Ganglion Cells." In Brain and Human Body Modeling 2020, 233–47. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45623-8_13.
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AbstractImprovements to the efficacy of retinal neuroprostheses can be achieved by developing more sophisticated neural stimulation strategies to enable selective or differential activation of specific retinal ganglion cells (RGCs). Recent retinal studies have demonstrated the ability to differentially recruit ON and OFF RGCs – the two major information pathways of the retina – using high-frequency electrical stimulation (HFS). However, there remain many unknowns, since this is a relatively unexplored field. For example, can we achieve ON/OFF selectivity over a wide range of stimulus frequencies and amplitudes? Furthermore, existing demonstrations of HFS efficacy in retinal prostheses have been based on epiretinal placement of electrodes. Other clinically popular techniques include subretinal or suprachoroidal placement, where electrodes are located at the photoreceptor layer or in the suprachoroidal space, respectively, and these locations are quite distant from the RGC layer. Would HFS-based differential activation work from these locations? In this chapter, we conducted in silico investigations to explore the generalizability of HFS to differentially active ON and OFF RGCs. Computational models are particularly well suited for these investigations. The electric field can be accurately described by mathematical formulations, and simulated neurons can be “probed” at resolutions well beyond those achievable by today’s state-of-the-art experimental techniques.
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Gentilal, Nichal, Ricardo Salvador, and Pedro Cavaleiro Miranda. "A Thermal Study of Tumor-Treating Fields for Glioblastoma Therapy." In Brain and Human Body Modeling 2020, 37–62. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45623-8_3.
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AbstractTumor-treating fields (TTFields) is an antimitotic cancer treatment technique used for glioblastoma multiforme (GBM) and malignant pleural mesothelioma. Although the frequency used is not as high as in hyperthermia, temperature increases due to the Joule effect might be meaningful given the necessary time that these fields should be applied for. Post hoc analysis of the EF-11 clinical trial showed higher median overall survival in patients whose compliance was at least 18 h per day. To quantify these temperature increases and predict the thermal impact of TTFields delivery to the head, we used a realistic model created from MR images segmented in five tissues: scalp, skull, CSF, gray matter (GM), and white matter (WM). Through COMSOL Multiphysics, we solved Laplace’s equation for the electric field and Pennes’ equation for the temperature distribution. To mimic the therapy as realistically as possible, we also considered complete current shutdown whenever any transducer reached 41 °C to allow transducers and tissues’ temperature to decrease. Our results indicate an intermittent operation of Optune due to this necessary current shutdown. Localized temperature increases were seen, especially underneath the regions where the transducers were placed. Maximum temperature values were around 41.5 °C on the scalp and 38 °C on the brain. According to the literature, significant thermal impact is only predicted for the brain where the rise in temperature may lead to an increased BBB permeability and variation in the blood flow and neurotransmitter concentration. Additionally, our results showed that if the injected current is reduced by around 25% compared to Optune’s standard way of operating, then uninterrupted treatment might be attainable. These predictions might be used to improve TTFields delivery in real patients and to increase awareness regarding possible thermal effects not yet reported elsewhere.
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Hill, T. W. "Generation of the Magnetospheric Electric Field." In Quantitative Modeling of Magnetospheric Processes, 297–315. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm021p0297.
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Peleg, Micha. "Modeling Microbial Inactivation by Pulsed Electric Field." In Handbook of Electroporation, 1–18. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-26779-1_43-1.
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Peleg, Micha. "Modeling Microbial Inactivation by Pulsed Electric Field." In Handbook of Electroporation, 1269–86. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-32886-7_43.
Повний текст джерелаТези доповідей конференцій з теми "Electric field modeling techniques"
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Zhang, Chunhua, Bing Li, Ning Gao, Wenbin Zhao, and Song Li. "Analytical Expressions of the Magnetic Field Generated by Horizontal Time-harmonic Electric Dipole in Sea-air Model." In Proceedings of the 2019 International Conference on Modeling, Simulation, Optimization and Numerical Techniques (SMONT 2019). Paris, France: Atlantis Press, 2019. http://dx.doi.org/10.2991/smont-19.2019.41.
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Smekal, Thomas, Cindy Briscoe, Tony Chan, Yung Chang, Seth Dobrin, Sean Gallagher, Heidi Groninger, et al. "Modeling, Design and Fabrication of a Microdevice for E-Field Cell Lysis." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0273.
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Abstract The development of an electric field cell lysis device for microfluidic applications will be presented. Detailed modeling of the electrode configuration for the optimization of the electric field has been performed. Device design and fabrication has been accomplished using traditional integrated circuit (IC) manufacturing techniques. As a result, murine lymphocytes have been lysed using several electrode configurations. The requisite electric field strength and pulse parameters for cell lysis were determined. The non-specific adsorption of the released DNA to the materials used in the fabrication of the device was observed. Surface passivation of the fabrication materials was effected through the use of silanization compounds.
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Datta, Brajagopal, and Saibal Chatteijee. "Modelling of hybrid electric field for parallel operation of HVDC and HVAC transmission lines using COMSOL multiphysics." In 2017 3rd International Conference on Condition Assessment Techniques in Electrical Systems (CATCON). IEEE, 2017. http://dx.doi.org/10.1109/catcon.2017.8280217.
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Teimoori, Khashayar, Ali M. Sadegh, and Bhaskar Paneri. "Novel Electro-FSI Model of Trabecular Network in the Brain Sub Arachnoid Space." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10529.
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Abstract The brain is encased in the skull and suspended and supported by a series of three fibrous tissue layers: Dura mater, Arachnoid and Pia matter, known as the Meninges. Arachnoid trabeculae are strands of collagen tissues located in a space between the arachnoid and the pia matter known as the subarachnoid space (SAS). The SAS trabeculae play an important role in damping and reducing the relative movement of the brain with respect to the skull. The SAS is filled with cerebrospinal fluid (CSF), which is a colorless fluid that surrounds all over the brain inside the subarachnoid spaces. This fluid stabilizes the shape and position of the brain during head movements. To address normal and pathological SAS functions, under conditions where an electrical stimulation is applied, this study proposes a novel fully-coupled electro-Fluid-Structure Interaction (eFSI) modeling approach to investigate the response of the system of SAS-CSF under the applied electric current, which is provided by the transcranial Direct Current Stimulation (tDCS) technique according to the following steps. First, a two-dimensional channel model of the brain SAS with several trabecular morphologies is numerically simulated using the finite element (FE) method. The channel model is then subjected to a specific electric field intensity by applying a 1∼2mA direct current. COMSOL Multiphysics v. 5.3a software is used to perform the coupled eFSI numerical simulation in order to investigate the effects of the applied electric field on the flow of the CSF, thereby showing the deflection of the trabeculae inside the channel model. The results of this study demonstrate that the induced electric field causes less deflection of the trabeculae by exacerbating the velocity profile of the cerebrospinal fluid flow and decreasing the flow pressure applied on each trabecula inside the trabecular SAS channel. This electro-mechanostructural modeling approach is significant because of the applied current on the channel walls that can directly affect the CSF flow. In fact, the results of this study can open up a new horizon for future research on disorders like hydrocephalus, which involves an unusual production rate of the CSF inside the brain. This disorder may be controlled by applying an electric current in the brain, using one of the available brain stimulation techniques, i.e. tDCS. By using an electrical stimulation technique, one might control the dynamics of brain function and, therefore, regulate dysfunctionality through the first eFSI multiphysics modeling approach proposed in this study. Briefly, the brain SAS may be considered as a novel region for electrotherapeutic and electromechanical neuromodulation.
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Sahoo, Seshadev, and Kevin Chou. "Review on Phase-Field Modeling of Microstructure Evolutions: Application to Electron Beam Additive Manufacturing." In ASME 2014 International Manufacturing Science and Engineering Conference collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/msec2014-3901.
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Powder-bed electron beam additive manufacturing (EBAM) is a relatively new technology to produce metallic parts in a layer by layer fashion by melting and fusing metallic powders. EBAM is a rapid solidification process and the properties of the parts depend on the solidification behavior as well as the microstructure of the build material. Thus, the prediction of part microstructures during the process may be an important factor for process optimization. Nowadays, the increase in computational power allows for direct simulations of microstructures during materials processing for specific manufacturing conditions. Among different methods, phase-field modeling (PFM) has recently emerged as a powerful computational technique for simulating microstructure evolutions at the mesoscale during a rapid solidification process. PFM describes microstructures using a set of conserved and non-conserved field variables and the evolution of the field variables are governed by Cahn-Hilliard and Allen-Cahn equations. By using the thermodynamics and kinetic parameters as input parameters in the model, PFM is able to simulate the evolution of complex microstructures during materials processing. The objective of this study is to achieve a thorough review of PFM techniques used in various processes, attempted for an application to microstructure evolutions during EBAM. The concept of diffuse interfaces, phase field variables, thermodynamic driving forces for microstructure evolutions and the kinetic phase-field equations are described in this paper.
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Neal, Robert E., Helen Kavnoudias, Franklin Rosenfeldt, Ruchong Ou, James Marron, Rafael V. Davalos, and Kenneth R. Thomson. "In Vivo Validation of Irreversible Electroporation Electric Field Threshold for Prostate Tissue." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14425.
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Irreversible electroporation (IRE) is a non-thermal focal ablation technique that uses needle electrodes to deliver a series of brief (100μs duration) electric pulses into the targeted region. These alter cellular transmembrane potentials, destabilizing the membranes in a manner that kills the cells while sparing major vasculature and other sensitive structures. IRE can therefore be used in regions ineligible for surgical resection or thermal ablation. Treatments result in rapid lesion creation and resolution [1], are unaffected by the blood perfusion “heat sink”, can be planned with numerical modeling [2], and its effects can be readily monitored with various imaging modalities [3]. Therapeutic ire has proven effective in the treatment of experimental [4] and clinical tumors. A human safety study attained complete regression in 46 of 69 tumors ineligible or unresponsive to conventional treatment [5], and veterinary case studies convey its utility in large difficult tumors [6, 7].
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Lapizco-Encinas, Blanca H. "Microscale Electrokinetics: Dielectrophoretic Manipulation of Particles." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63911.
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Miniaturization is a rapidly growing field, with great potential for many applications, from cell and clinical analysis, medical diagnostics, food and water safety, and environmental monitoring. Working on the microscale offers significant advantages, such as shorter time, reduced sample requirement, higher resolution and sensitivity. There are important research efforts devoted to the development of separation and analytical techniques that can be employed on the microscale. Dielectrophoresis (DEP) is the motion of particles due to polarization effects when exposed to nonuniform electric fields; this electrokinetic transport mechanism has a great potential for the manipulation of a wide array of particles. DEP offers great flexibility, since it can be carried out employing DC and AC electric fields, and neutral and charged particles can be manipulated. Insulator-based dielectrophoresis (iDEP) is novel technique where insulating structures, instead of electrodes, are used to create nonuniform electric fields. This presentation is focused on the use of AC-iDEP and DC-iDEP for the manipulation, concentration y separation of different types of particles. Experimental and modeling results obtained with COMSOL will be presented and discussed, demonstrating the versatility and great potential of iDEP as a microscale technique for effective and highly controlled particle manipulation.
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Shooshtari, A., S. Chowdhury, and M. Ohadi. "Numerical Modeling of Dissociation-Injection Process for the Electrohydrodynamic Pumping." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81391.
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In recent decades, the phenomenon of electrohydrodynamics (EHD) has gained prominence due to its potential applications in microsystems. One such application is pumping and transport of dielectric fluids in micropumps meant for cooling or other such purposes. Electrohydrodynamics can be defined as a direct coupling between the electric and hydrodynamic fields, where the electric field produces fluid motion. The motion of the fluid can occur due to an electrical body force being exerted on the fluid. In single-phase liquid flows, the electrophoretic (Coulombic) component of the electrical body force is the main driving force that acts on the free charge carriers. There are different physico-chemical processes that result in production of free charge carriers inside fluids; among these processes, the ion-injection and conduction/dissociation of ionic pairs are typical and hence worth mentioning. So far, several different numerical methods have been developed to model the EHD pumping effect due to the ion-injection process and the process of dissociation of ionic pairs. This paper presents a numerical model of the electrophoretic force in dielectric liquids that combines both the aspects of dissociation of ionic pairs and ion-injection processes. In this modeling, it is assumed that the ion injection process is unipolar. However, the dissociation process generates both positive and negative ions. Therefore, modeling of this process involves determining the concentration of both types of ions. The present modeling procedure is used to simulate a mesoscale electrohydrodynamic pump where the numerical and experimental results are compared and found to be in agreement within acceptable limits. This modeling technique serves as an effective tool for prediction and optimization of the electrohydrodynamic pumps.
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Arzpeyma, Alborz, Ali Dolatabadi, and Paula Wood-Adams. "A 3-D Numerical Modeling of Droplet Actuation via Electrowetting in Microchannels." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37581.
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Numerical investigation is performed to study the droplet behavior under electrowetting actuation inside microchannels. Volume of Fluid (VOF) technique is employed to track the interface while the electric field is solved inside the whole domain in each time step simultaneously. The equations are solved in three dimensions for water as the liquid phase. Droplet morphology under the application of an electric field is investigated. Droplet velocity studied under different actuation voltages and compared to the experiments. Contact angle hysteresis and its effects on the threshold voltage are discussed.
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Dogruoz, M. Baris, and Gokul Shankaran. "Advances in Fan Modeling: Issues and Effects on Thermal Design of Electronics." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89857.
Повний текст джерелаАнотація:
Forced convection air-cooled electronic systems consist of fans to provide fluid flow through the enclosure. Typically axial flow fans, radial impellers, and centrifugal blowers fall into this category. In numerical computations of flow fields in electronic enclosures, axial fans have most commonly been abstracted as planar (2-D) rectangular or circular surfaces. In some cases, these abstract or lumped models may be used to mimic impellers and centrifugal blowers as well. All of these models rely on an experimentally derived “pressure head-flow rate” (P-Q) curve (also called “fan curve”). The experiments to obtain the fan curve should conform to the test codes published by ASME and/or AMCA. Convenience and accuracy of abstract fan models are dependent on the specific application/cooling method and the acceptable error margin. The latter for the thermal design of electronics has recently diminished considerably which led to the need of using more accurate and robust fan modeling techniques such as Multiple Reference Frame (MRF) model. The authors validated this method for different types of fans against relevant experimental data previously [1,2]. As a continuation of this earlier effort, an attempt is made to examine the thermal field computed by various fan modeling techniques including MRF for air-cooled enclosures in the present work. The results show that the temperature values obtained from lumped fan model and the MRF technique differ considerably.
Звіти організацій з теми "Electric field modeling techniques"
1
Thorne, Colin R. Field Assessment Techniques for Bank Erosion Modeling. Fort Belvoir, VA: Defense Technical Information Center, February 1992. http://dx.doi.org/10.21236/ada250806.
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Thorne, Colin R. Field Assessment Techniques for Bank Erosion Modeling. Fort Belvoir, VA: Defense Technical Information Center, November 1990. http://dx.doi.org/10.21236/ada230453.
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Hutchinson, S. A., L. A. Romero, and C. F. Diegert. Advanced computer techniques for inverse modeling of electric current in cardiac tissue. Office of Scientific and Technical Information (OSTI), August 1996. http://dx.doi.org/10.2172/367252.
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Modlo, Yevhenii O., Serhiy O. Semerikov, Stanislav L. Bondarevskyi, Stanislav T. Tolmachev, Oksana M. Markova, and Pavlo P. Nechypurenko. Methods of using mobile Internet devices in the formation of the general scientific component of bachelor in electromechanics competency in modeling of technical objects. [б. в.], February 2020. http://dx.doi.org/10.31812/123456789/3677.
Повний текст джерелаАнотація:
An analysis of the experience of professional training bachelors of electromechanics in Ukraine and abroad made it possible to determine that one of the leading trends in its modernization is the synergistic integration of various engineering branches (mechanical, electrical, electronic engineering and automation) in mechatronics for the purpose of design, manufacture, operation and maintenance electromechanical equipment. Teaching mechatronics provides for the meaningful integration of various disciplines of professional and practical training bachelors of electromechanics based on the concept of modeling and technological integration of various organizational forms and teaching methods based on the concept of mobility. Within this approach, the leading learning tools of bachelors of electromechanics are mobile Internet devices (MID) – a multimedia mobile devices that provide wireless access to information and communication Internet services for collecting, organizing, storing, processing, transmitting, presenting all kinds of messages and data. The authors reveals the main possibilities of using MID in learning to ensure equal access to education, personalized learning, instant feedback and evaluating learning outcomes, mobile learning, productive use of time spent in classrooms, creating mobile learning communities, support situated learning, development of continuous seamless learning, ensuring the gap between formal and informal learning, minimize educational disruption in conflict and disaster areas, assist learners with disabilities, improve the quality of the communication and the management of institution, and maximize the cost-efficiency. Bachelor of electromechanics competency in modeling of technical objects is a personal and vocational ability, which includes a system of knowledge, skills, experience in learning and research activities on modeling mechatronic systems and a positive value attitude towards it; bachelor of electromechanics should be ready and able to use methods and software/hardware modeling tools for processes analyzes, systems synthesis, evaluating their reliability and effectiveness for solving practical problems in professional field. The competency structure of the bachelor of electromechanics in the modeling of technical objects is reflected in three groups of competencies: general scientific, general professional and specialized professional. The implementation of the technique of using MID in learning bachelors of electromechanics in modeling of technical objects is the appropriate methodic of using, the component of which is partial methods for using MID in the formation of the general scientific component of the bachelor of electromechanics competency in modeling of technical objects, are disclosed by example academic disciplines “Higher mathematics”, “Computers and programming”, “Engineering mechanics”, “Electrical machines”. The leading tools of formation of the general scientific component of bachelor in electromechanics competency in modeling of technical objects are augmented reality mobile tools (to visualize the objects’ structure and modeling results), mobile computer mathematical systems (universal tools used at all stages of modeling learning), cloud based spreadsheets (as modeling tools) and text editors (to make the program description of model), mobile computer-aided design systems (to create and view the physical properties of models of technical objects) and mobile communication tools (to organize a joint activity in modeling).
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Lee, Youn M., and Bruce T. Benwell. Calibration Techniques and Procedures for Ground-Plane-Version Electric and Magnetic Field Sensors. Fort Belvoir, VA: Defense Technical Information Center, July 1989. http://dx.doi.org/10.21236/ada210131.
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Mock, Raymond Cecil. Radial electric field 3D modeling for wire arrays driving dynamic hohlraums on Z. Office of Scientific and Technical Information (OSTI), June 2007. http://dx.doi.org/10.2172/909913.
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WALL, FREDERICK D., MICHAEL A. MARTINEZ, CORBETT C. BATTAILE, and NANCY A. MISSERT. Quantifying Atmospheric Corrosion Processes Using Small Length-Scale Electrochemical Measurements and 3-D Electric Field Modeling. Office of Scientific and Technical Information (OSTI), November 2001. http://dx.doi.org/10.2172/789582.
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Tanny, Josef, Gabriel Katul, Shabtai Cohen, and Meir Teitel. Micrometeorological methods for inferring whole canopy evapotranspiration in large agricultural structures: measurements and modeling. United States Department of Agriculture, October 2015. http://dx.doi.org/10.32747/2015.7594402.bard.
Повний текст джерелаАнотація:
Original objectives and revisions The original objectives as stated in the approved proposal were: (1) To establish guidelines for the use of micrometeorological techniques as accurate, reliable and low-cost tools for continuous monitoring of whole canopy ET of common crops grown in large agricultural structures. (2) To adapt existing methods for protected cultivation environments. (3) To combine previously derived theoretical models of air flow and scalar fluxes in large agricultural structures (an outcome of our previous BARD project) with ET data derived from application of turbulent transport techniques for different crops and structure types. All the objectives have been successfully addressed. The study was focused on both screenhouses and naturally ventilated greenhouses, and all proposed methods were examined. Background to the topic Our previous BARD project established that the eddy covariance (EC) technique is suitable for whole canopy evapotranspiration measurements in large agricultural screenhouses. Nevertheless, the eddy covariance technique remains difficult to apply in the farm due to costs, operational complexity, and post-processing of data – thereby inviting alternative techniques to be developed. The subject of this project was: 1) the evaluation of four turbulent transport (TT) techniques, namely, Surface Renewal (SR), Flux-Variance (FV), Half-order Time Derivative (HTD) and Bowen Ratio (BR), whose instrumentation needs and operational demands are not as elaborate as the EC, to estimate evapotranspiration within large agricultural structures; and 2) the development of mathematical models able to predict water savings and account for the external environmental conditions, physiological properties of the plant, and structure properties as well as to evaluate the necessary micrometeorological conditions for utilizing the above turbulent transfer methods in such protected environments. Major conclusions and achievements The major conclusions are: (i) the SR and FV techniques were suitable for reliable estimates of ET in shading and insect-proof screenhouses; (ii) The BR technique was reliable in shading screenhouses; (iii) HTD provided reasonable results in the shading and insect proof screenhouses; (iv) Quality control analysis of the EC method showed that conditions in the shading and insect proof screenhouses were reasonable for flux measurements. However, in the plastic covered greenhouse energy balance closure was poor. Therefore, the alternative methods could not be analyzed in the greenhouse; (v) A multi-layered flux footprint model was developed for a ‘generic’ crop canopy situated within a protected environment such as a large screenhouse. The new model accounts for the vertically distributed sources and sinks within the canopy volume as well as for modifications introduced by the screen on the flow field and microenvironment. The effect of the screen on fetch as a function of its relative height above the canopy is then studied for the first time and compared to the case where the screen is absent. The model calculations agreed with field experiments based on EC measurements from two screenhouse experiments. Implications, both scientific and agricultural The study established for the first time, both experimentally and theoretically, the use of four simple TT techniques for ET estimates within large agricultural screenhouses. Such measurements, along with reliable theoretical models, will enable the future development of lowcost ET monitoring system which will be attainable for day-to-day use by growers in improving irrigation management.
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Heitman, Joshua L., Alon Ben-Gal, Thomas J. Sauer, Nurit Agam, and John Havlin. Separating Components of Evapotranspiration to Improve Efficiency in Vineyard Water Management. United States Department of Agriculture, March 2014. http://dx.doi.org/10.32747/2014.7594386.bard.
Повний текст джерелаАнотація:
Vineyards are found on six of seven continents, producing a crop of high economic value with much historic and cultural significance. Because of the wide range of conditions under which grapes are grown, management approaches are highly varied and must be adapted to local climatic constraints. Research has been conducted in the traditionally prominent grape growing regions of Europe, Australia, and the western USA, but far less information is available to guide production under more extreme growing conditions. The overarching goal of this project was to improve understanding of vineyard water management related to the critical inter-row zone. Experiments were conducted in moist temperate (North Carolina, USA) and arid (Negev, Israel) regions in order to address inter-row water use under high and low water availability conditions. Specific objectives were to: i) calibrate and verify a modeling technique to identify components of evapotranspiration (ET) in temperate and semiarid vineyard systems, ii) evaluate and refine strategies for excess water removal in vineyards for moist temperate regions of the Southeastern USA, and iii) evaluate and refine strategies for water conservation in vineyards for semi-arid regions of Israel. Several new measurement and modeling techniques were adapted and assessed in order to partition ET between favorable transpiration by the grapes and potentially detrimental water use within the vineyard inter-row. A micro Bowen ratio measurement system was developed to quantify ET from inter-rows. The approach was successful at the NC site, providing strong correlation with standard measurement approaches and adding capability for continuous, non-destructive measurement within a relatively small footprint. The environmental conditions in the Negev site were found to limit the applicability of the technique. Technical issues are yet to be solved to make this technique sufficiently robust. The HYDRUS 2D/3D modeling package was also adapted using data obtained in a series of intense field campaigns at the Negev site. The adapted model was able to account for spatial variation in surface boundary conditions, created by diurnal canopy shading, in order to accurately calculate the contribution of interrow evaporation (E) as a component of system ET. Experiments evaluated common practices in the southeastern USA: inter-row cover crops purported to reduce water availability and thereby favorably reduce grapevine vegetative growth; and southern Israel: drip irrigation applied to produce a high value crop with maximum water use efficiency. Results from the NC site indicated that water use by the cover crop contributed a significant portion of vineyard ET (up to 93% in May), but that with ample rainfall typical to the region, cover crop water use did little to limit water availability for the grape vines. A potential consequence, however, was elevated below canopy humidity owing to the increased inter-row evapotranspiration associated with the cover crops. This creates increased potential for fungal disease occurrence, which is a common problem in the region. Analysis from the Negev site reveals that, on average, E accounts for about10% of the total vineyard ET in an isolated dripirrigated vineyard. The proportion of ET contributed by E increased from May until just before harvest in July, which could be explained primarily by changes in weather conditions. While non-productive water loss as E is relatively small, experiments indicate that further improvements in irrigation efficiency may be possible by considering diurnal shading effects on below canopy potential ET. Overall, research provided both scientific and practical outcomes including new measurement and modeling techniques, and new insights for humid and arid vineyard systems. Research techniques developed through the project will be useful for other agricultural systems, and the successful synergistic cooperation amongst the research team offers opportunity for future collaboration.
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Computational Biology: Development in the Field of Medicine. Science Repository, April 2021. http://dx.doi.org/10.31487/sr.blog.31.
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Computational biology involves the development and application of analytical-data and theoretical methods, computational simulation techniques, and mathematical modeling to the study of biological, behavioral, ecological, and social systems.