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Artykuły w czasopismach na temat "Locked up electromagnetic forces"
1
Teichrib, Sergey, i Richard Krimm. "Electromagnetic Material Feeder for High Speed Rates". Advanced Materials Research 769 (wrzesień 2013): 213–20. http://dx.doi.org/10.4028/www.scientific.net/amr.769.213.
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In sheet metal forming technology stamping machines are mainly used for an economical production of sheet metal workpieces. Apart from increasing the stroke rates of currently more than 3000 min-1, which can be achieved with modern high-performance stamping machines, the demands on the periphery of the plant are rising as well. In particular, this concerns the material feeding systems used for a reliable feed of the sheet metal. The current technology is based primarily on the roll and gripper feed. Here the sheet metal is clamped between the grippers or rollers with a high contact pressure, which is required for a slip-free operation. To avoid an external damage of the surface or a roll out of the sheet, the clamping forces may not be increased indefinitely. In addition, contamination of the sheet metal or the elements of the feeding system should be excluded in order to avoid a permanent damage of the system and related maintenance costs. This means that the feed rates of previous feeding systems, currently up to 2000 min-1, cannot be further increased, so that the performance potential of modern high-performance presses with large stroke rates cannot be exhausted. Thus the development of feeding systems in sheet metal processing with significantly higher forces is required.As part of a research project at the IFUM, facilitated by the German Machine Tools' Association (VDW), a novel method has been developed in which the sheet metal is fed completely without contact by means of electromagnetic forces. No mechanical elements are required for clamping the sheet metal, so that the inertia of the system can be reduced significantly. Thus higher dynamic properties of the feeder can be realized. The principle is based on the asynchronous linear motor with eddy current runner in a double cam arrangement. This feeder basically consists of two primary components, comprised of a laminated iron package and a three-phase winding. The primaries are symmetrically fixed positioned to compensate the forces of attraction in ferromagnetic materials as well as the repulsive forces in paramagnetic sheet metals such as aluminium or copper. The electrical conductive sheet metal acts as a secondary part and is located in the air gap between the two primary components. Thus the sheet is kept suspended in the air gap a damage to the sheet metal surface is prevented. Therefore surface-finished metal sheets can also be fed with high speed rates. The force initiation is performed entirely contactless to the sheet metal with the three-phase winding in the primaries which induce a sinusoidal magnetic traveling field in the air gap. During operation eddy currents are induced in the metal strip due to the speed of the traveling magnetic field relative to the sheet. By the interaction between the magnetic field and the eddy currents an advancing force is applied to the sheet metal according to the Lorentz law.For the design and optimization of the electromagnetic feeder extensive simulation-based studies have been performed using a parameterized finite element model. For this purpose the development of a three-dimensional model was necessary to represent the eddy currents in the sheet metal. The main subjects of the investigations were in particular the optimization of the iron core, the winding distribution and also to ensure an acceptable temperature in the primaries and the sheet metal during continuous operation. The studies show that, depending on the sheet material applied, very high feed forces can be achieved. For sheet metals with a width of about 100 mm more than 1000 N can be achieved by means of the electromagnetic feeding system. Compared to current mechanical feeders the forces can be more than doubled.To validate the simulation results and test the functional ability a demonstrator of the electromagnetic feeder was designed and manufactured. Due to the simulation-based optimization of the feeding system an external cooling is not required. The control of the feeder is realised via a conventional frequency converter, with which the voltage can be controlled in its amplitude and frequency, and thus indirectly the sheet metal position. The first experimental investigations were carried out on a specially designed force test bench. The results show a very good correlation obtained by simulation and the experimental measured feed forces. Future work objectives are to identify the feed characteristics and limitations as well as the implementation of a robust control algorithm for a reliable positioning of the sheet metal.
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Zeng, Chong, Song Huang, Yongming Yang i Guanghou Zhou. "Influence of End Structure on Electromagnetic Forces on End Winding of a 1550 MW Nuclear Generator". International Journal of Rotating Machinery 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/9545238.
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A 3D electromagnetic model of the end region of a 1550 MW nuclear generator is set up. The electromagnetic forces on the involute and nose parts of the end winding under a rated operation are obtained through the 3D time-step finite element method. The electromagnetic forces on different coils in the same phase are analyzed. By changing the rotor’s relative length and stator coil’s linear length in the 3D electromagnetic model, the electromagnetic force distributions on the end winding are obtained. The influence of each structure change on the electromagnetic force in different directions is studied in detail. Conclusions that can be helpful in decreasing the electromagnetic forces on the end winding through optimizing the end region design are presented.
3
Cheesewright, R., i C. Clark. "The Influence of Forces Due to Electromagnetic Pick-Ups on the Performance of Small Turbine Flowmeters". Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 210, nr 4 (listopad 1996): 243–47. http://dx.doi.org/10.1243/pime_proc_1996_210_463_02.
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An analysis is presented of the influence of forces due to an electromagnetic pick-up on the calibration of small turbine flowmeters. The analysis shows how the forces can produce high starting flows. A comparison between the theory and the experimental results of calibrating a meter both with and without the electromagnetic pick-up suggests that the dominant effect of the pick-up is to produce an additional resisting torque which is almost independent of the rotational speed of the meter.
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Suzuki, Nobuhisa, Toshiaki Murakami, Junichi Shibuya, Yasuhiro Furukawa, Satoru Asai i Shizuo Ohshima. "Structural Component Development of Three-Layer Cylinders for Superconducting Generators, Part 2: Development of Three-Layer Welding Techniques to Extend Axial Length and Evaluation of the Welds". Journal of Manufacturing Science and Engineering 119, nr 1 (1.02.1997): 78–87. http://dx.doi.org/10.1115/1.2836558.
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The warm damper is one of the multi-cylindrical rotor components, which is located at the outermost position in a rotor of the superconducting generator. The main function of the warm damper, in addition to bear rotor torque, is to shut off the magnetic fields of the armature. While maximum stresses in the warm damper are caused by electromagnetic forces in the event of a short-circuit fault, which cause large bending stresses, so it is required to have high conductivity and sufficient strength against bending stresses. A promising design for it is a three-layer cylindrical structure composed of a highly conductive Cu-Cr cylinder sandwiched between inner and outer stiffeners made of a high-strength nonmagnetic material (A286). To realize this structure, it is necessary first to select a suitable layer bonding method and then to research and develop the procedures to construct this large structure. The previous paper described selection of diffusion bonding as the suitable layer bonding method. The first step to fabricate this large structure was to prove the structural integrity of a diffusion-bonded mock-up model, which was 885 mm in diameter and 2800 mm in axial length [1]. This paper is a study on circumferential three-layer welding to extend the axial length allowing for the fabrication of a ever larger structure. Two A286/Cu-Cr/A286 three-layer rings, 625.5 mm in O.D. and 300 mm in axial length, were prepared by diffusion bonding the layers of each rings simultaneously by HIP. Then, the axial ends of their three-layers were butt welded with the filler wires, which were selected for each layers in advance. Subsequently, in accordance with the results of a study on the condition for aging treatment following diffusion bonding (800°C × 4 h) to obtain the proper mechanical properties of the alloy A286, which is a material for the major load bearing component, the rings were age-treated at 700°C for 10 h. The tensile test results of the welded joint and weld metal specimens cut out from the welded rings proved that both alloys A286 and Cu-Cr welded components had adequate mechanical properties. That is these properties were equivalent to those of the base metals, with no reductions of layer bonding strength due to weld heat input.
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Calabrese, Allegra, Djamal Gacemi, Mathieu Jeannin, Stéphan Suffit, Angela Vasanelli, Carlo Sirtori i Yanko Todorov. "Coulomb forces in THz electromechanical meta-atoms". Nanophotonics 8, nr 12 (25.10.2019): 2269–77. http://dx.doi.org/10.1515/nanoph-2019-0314.
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AbstractThanks to their large sensitivity to electromagnetic fields, microelectromechanical systems are becoming attractive for applications in the THz band (0.1–10 THz). However, up to date all THz electromechanical systems couple electromagnetic fields to mechanical motion only through photothermal dissipative forces: such mechanism allows for sensitive detection but prevents applications that require coherent transfer of information. In this work, we present a THz electromechanical meta-atom where the coupling between an electromagnetic mode and the displacement of a metallic micro-beam is substantially controlled by a conservative Coulomb force due to charge oscillations in the nanometric-size capacitive part of the meta-atom. We present experiments, performed at room temperature, which allow distinguishing and precisely quantifying the contributions of conservative and dissipative forces in the operation of our electromechanical resonator. Our analysis shows that the Coulomb force becomes the dominant contribution of the total driving force for high-order mechanical modes. Such system paves the way for the realization of coherent THz to optical transducers and allows the realization of fundamental optomechanical systems in the THz frequency range.
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Galin, Mikhail A., Vladimir M. Krasnov, Ilya A. Shereshevsky, Nadezhda K. Vdovicheva i Vladislav V. Kurin. "Coherent amplification of radiation from two phase-locked Josephson junction arrays". Beilstein Journal of Nanotechnology 13 (6.12.2022): 1445–57. http://dx.doi.org/10.3762/bjnano.13.119.
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We analyze experimentally and theoretically mutual phase locking and electromagnetic interaction between two linear arrays with a large number of Josephson junctions. Arrays with different separation, either on the same chip or on two separate substrates are studied. We observe a large coherent gain, up to a factor of three, of emitted power from two simultaneously biased arrays, compared to the sum of powers from two individually biased arrays. The phenomenon is attributed to the phase locking of junctions in different arrays via a common electromagnetic field. Remarkably, the gain can exceed the factor of two expected for a simple constructive interference of two oscillators. The larger gain is explained by an additional consequence of mutual interaction between two large arrays. Mutual phase locking of large arrays does not only result in constructive interference outside the arrays, but also improved synchronization of junctions inside each array. Our conclusion is supported by numerical modelling.
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Wilson, James H. "The quantum electrodynamics physical (QED-P) theory to complement quantum electrodynamics (QED)". Physics Essays 34, nr 1 (21.03.2021): 17–27. http://dx.doi.org/10.4006/0836-1398-34.1.17.
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The electronic and muonic hydrogen energy levels are calculated very accurately [M. L. Eides, H. Grotch, and V. Shelyuto, Phys. Rep. 342, 63 (2001)] in Quantum Electrodynamics (QED) by coupling the Dirac Equation four vector c(α, I) current covariantly with the external electromagnetic (EM) field four vector in QED’s Interactive Representation. While QED has been extraordinarily successful computationally, it presents no physical description of the electron, or other charged leptons. The QED-Physical (QED-P) theory presented in this paper is equivalent to QED in that it is based only on the four-current c(α, I) that is the reason that QED is so accurate computationally. However, QED-P describes the electron geometrically through the internal time/coordinate operators derived directly from c(α, I) with no assumptions. QED-P’s internal coordinate operators define an electron Center of Charge (CoC) point vibrating rapidly in space and time in its unique vacuum, creating the current that produces the electron’s magnetic moment and spin, and eliminating the need for “intrinsic” properties. QED-P also cuts off the photon propagator in a natural way so that the electron self-energy is finite and ad hoc renormalization procedures are not necessary. The c α-Non Exclusion Principle states that, if QED accepts c(α, I) as the electron current operator because of the very accurate hydrogen energy levels calculated, then one must also accept the QED-P electron internal spatial and time coordinate operators (ISaTCO) derived directly from c(α, I) without any other assumptions. QED-P shows the electron to be in both spin states simultaneously, and it is the external EM field that forces the electron’s spin state to be measured up or down. QED-P describes the bizarre, and very different, situation illustrated in Fig. 1 when the electron and muon are located “inside” the spatially extended proton with their CoCs orbiting the proton at the speed of light in S energy states of hydrogen, shedding some insight into the proton radius puzzle. The electron only appears to be a point particle with intrinsic properties when observed/measured from the far field. The Dirac‐Maxwell‐Wilson Equations are derived directly from the electron ISaTCO, and its EM fields “look” like they are from a point particle in far field scattering experiments in the same way the electric field from a sphere with evenly distributed charge “e” looks like a point charge with the same charge in the far field (Gauss Law). A physical basis for Quantum Entanglement is derived that can be measured experimentally.
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Kari, Tusong Jiang, Xi Wang Abuduwayiti i Ming Ma. "Numerical Calculation of Short Circuit Electromagnetic Force in Isolated Phase Bus". Advanced Materials Research 986-987 (lipiec 2014): 944–47. http://dx.doi.org/10.4028/www.scientific.net/amr.986-987.944.
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Short circuit electromagnetic forces are one of the most important factors in design and operation of buses. 2D infinite element models are set up with ANSOFT for isolated phase buses, simulating with transient method and calculating short circuit electromagnetic force taking eddy effect and proximity effect into account. The result reveals that the maximum electromagnetic force under short circuit condition is a periodic function of current phase angle.
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Böyük, Mustafa, Yakup Eroğlu, Günyaz Ablay i Kutay İçöz. "Feedback controller designs for an electromagnetic micromanipulator". Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 234, nr 6 (9.09.2019): 759–72. http://dx.doi.org/10.1177/0959651819871783.
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Magnetic micromanipulators are capable of generating wide range of magnetic forces to manipulate magnetic microparticles for biomedical applications. In this study, a multipole magnetic micromanipulator system including electromagnets, driver circuitry and control unit is designed, modeled and implemented. The micromanipulator can produce a broad range of magnetic forces up to 25 pN on a single magnetic microparticle (1–10 µm diameter) that is 5 mm away from the electromagnet core tip. Both linear and nonlinear controllers are designed and implemented, and the proposed nonlinear controller produces smooth control currents to assure closed-loop stability of the system with 1 s non-overshoot transient response and zero steady-state tracking error. The maximum output current of the driver circuitry is set to 1 A. The single particle at the center is moved at a speed of 5 mm/s. The fully automatic system can be utilized in applications related to single cell or microparticle manipulations.
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Lu, H., C. Wang i Yu M. Zabolotnov. "Using Sliding Mode Control to Set Up a Rotating Electrodynamic Space Tether System". Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, nr 2 (141) (czerwiec 2022): 4–19. http://dx.doi.org/10.18698/0236-3941-2022-2-4-19.
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The paper considers the process of imparting rotation at a given angular velocity to an electrodynamic space tether system in a near-Earth orbit. The tether system is a linear cluster of three microsatellites connected by insulated conductive cables. Initially the system is gravitationally stabilised in the approximate vertical direction. Electromagnetic forces generated in the conductive cables by the geomagnetic field impart rotation to the system. We stated the equations of motion for the system in the Earth-fixed coordinate system, taking into account distributed load produced by gravitational and electromagnetic forces. The system is moving in a fairly high, almost circular orbit, so aerodynamic forces are not taken into account. Adjusting the current will reduce the strain in the tethers. The model under consideration represents those as a set of material points connected by unilateral elastic links. We propose a feedback current controller based on sliding mode control. The system variables lie on a single surface, moving across which ensures asymptotic stability of the control process. We used a simplified system motion model to synthesise the controller parameters. We analysed the angular motion of microsatellites with respect to the tether direction while rotation is imparted to the system. Numerical examples confirm the efficiency of our approach to setting up a rotating space tether system
Rozprawy doktorskie na temat "Locked up electromagnetic forces"
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Coulter, John Edward. "Entropy Analysis of an Economic Activity: A Case Study of Simple Brickmaking in China". Thesis, Griffith University, 1993. http://hdl.handle.net/10072/367848.
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1. There is a crisis in economics. The discipline evolved in nineteenth century Europe and is difficult to adapt to modern conditions, even in the West, and particularly in alien cultures. Application of conventional economic analysis to economic activity in a culture as alien as traditional China highlights the biases in assumptions of the paradigm. 2. The concepts, models and vocabulary evolved over one hundred years ago predate important developments in the natural sciences. It is now necessary for economists to concede no goods can ever be 'produced', and they are not 'consumed' either. In clear terms matter is transformed, but is not created or destroyed (First Law of Thermodynamics). 3. When people transform matter, in lay language we say energy is 'used'. In a simple cottage industry, 'raw material' is transformed into a commodity in front of our eyes by the use of human energy and the release of energy from a 'fuel'. In modem complex economic activity, it is difficult or impossible to keep track of the processes from raw matter to transformed 'product' although the principle is the same. 4. The Second Law of Thermodynamics states that in any transformation, energy is not created or destroyed, but becomes 'less available'. In short, entropy increases. This appears to work well for pure physics and chemistry, but its application to analysis of economic activity has only been notional. 5. There is a reason why economists borrowing terms from hard science experience difficulty. It is because physicists and chemists have addressed specific laboratory and engineering problems, but not the broader economic issues. The hypothesis gradually evolved in this research program that not only economic concepts and terms needed reworking, but those in physics as well. The definitions of energy as 'ability to do works and of entropy as 'unavailable energy' jar the logic of our commonsense. 6. The notion of 'available energy' was traced back to the phenomenon in physical chemistry known as exothermicity, or the release of energy during a chemical reaction. It was reasoned that while scientists had focussed on this phenomenon and measured it carefully they saw no need to ask where the energy came from, or to measure its transformation. From the perspective of analysing economic activity, the question was important. 7. It was hypothesised that the energy released from a fuel as electromagnetic radiation (mainly heat) was the residual of the set of coulombic forces within atoms that maintain the structure of shells of electrons around the protons. This idea in turn came from the presumption that molecular bonding is a residual of vectors of the set of coulombic forces within atoms, and the likelihood that in an exothermic reaction, after the reactants are said (by scientists) to 'seek equilibrium', product molecules have a portion of the coulombic forces 'left over' and not required to maintain their structures. An estimate was made of the coulombic forces extant in various fuels, and compared with the known data for their release of energy. 8. The idea was developed in detail. The concept we call in economics, 'production', and should call 'transformation' can only occur when forces locked within atoms are released as electromagnetic forces. (Gravitational forces exist because matter has been put 'there' by electromagnetic radiation). When 100 grams of dry grass fuel is burnt, about 2 megajoules of electromagnetic radiation are released. It was estimated that the coulombic forces between each electron and proton in that amount dry grass total 150 gigajoules (or giganewtons, since the reference is to forces). 9. Within the boundary of a simple economic activity, the ratio of aggregated coulombic forces locked up within atoms to the electromagnetic forces radiated out was estimated at the beginning of the activity, and then after a duration. The ratio of forces always tends towards 'evening out'. This measurement captures the entropy phenomenon which has been said by Georgescu-Roegen to be the basis of all economic activity. 10. At the roots of the economic paradigm founded by Adam Smith is the premise that the material world, as a set of substances, is a stage on which economic actors 'add value', bid prices up and down, and by their rational perception manage their livelihoods and surroundings well. From the findings of this research program it is contended that the surroundings of economic actors can be classed into two categories: locked up (coulombic) electromagnetic forces, and radiated electromagnetic forces. The former has a tendency to convert to the latter. All action, including all economic activity, and all life can be traced to a point in space and time where this conversion is (naturally) occurring. The phenomenon is analogous to a slope where water cascades, and gravitational potential energy converts to other (either useless or useful) forms of energy. To appreciate the nature of this phenomena, and to attempt to fathom its dimensions, sets our perceptions of ourselves as economic actors in a quite different and very humbling context.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Division of Asian and International Studies
Full Text
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Coulter, John Edward, i n/a. "Entropy Analysis of an Economic Activity: A Case Study of Simple Brickmaking in China". Griffith University. Division of Asian and International Studies, 1993. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20070410.170509.
Pełny tekst źródłaStreszczenie:
1. There is a crisis in economics. The discipline evolved in nineteenth century Europe and is difficult to adapt to modern conditions, even in the West, and particularly in alien cultures. Application of conventional economic analysis to economic activity in a culture as alien as traditional China highlights the biases in assumptions of the paradigm. 2. The concepts, models and vocabulary evolved over one hundred years ago predate important developments in the natural sciences. It is now necessary for economists to concede no goods can ever be 'produced', and they are not 'consumed' either. In clear terms matter is transformed, but is not created or destroyed (First Law of Thermodynamics). 3. When people transform matter, in lay language we say energy is 'used'. In a simple cottage industry, 'raw material' is transformed into a commodity in front of our eyes by the use of human energy and the release of energy from a 'fuel'. In modem complex economic activity, it is difficult or impossible to keep track of the processes from raw matter to transformed 'product' although the principle is the same. 4. The Second Law of Thermodynamics states that in any transformation, energy is not created or destroyed, but becomes 'less available'. In short, entropy increases. This appears to work well for pure physics and chemistry, but its application to analysis of economic activity has only been notional. 5. There is a reason why economists borrowing terms from hard science experience difficulty. It is because physicists and chemists have addressed specific laboratory and engineering problems, but not the broader economic issues. The hypothesis gradually evolved in this research program that not only economic concepts and terms needed reworking, but those in physics as well. The definitions of energy as 'ability to do works and of entropy as 'unavailable energy' jar the logic of our commonsense. 6. The notion of 'available energy' was traced back to the phenomenon in physical chemistry known as exothermicity, or the release of energy during a chemical reaction. It was reasoned that while scientists had focussed on this phenomenon and measured it carefully they saw no need to ask where the energy came from, or to measure its transformation. From the perspective of analysing economic activity, the question was important. 7. It was hypothesised that the energy released from a fuel as electromagnetic radiation (mainly heat) was the residual of the set of coulombic forces within atoms that maintain the structure of shells of electrons around the protons. This idea in turn came from the presumption that molecular bonding is a residual of vectors of the set of coulombic forces within atoms, and the likelihood that in an exothermic reaction, after the reactants are said (by scientists) to 'seek equilibrium', product molecules have a portion of the coulombic forces 'left over' and not required to maintain their structures. An estimate was made of the coulombic forces extant in various fuels, and compared with the known data for their release of energy. 8. The idea was developed in detail. The concept we call in economics, 'production', and should call 'transformation' can only occur when forces locked within atoms are released as electromagnetic forces. (Gravitational forces exist because matter has been put 'there' by electromagnetic radiation). When 100 grams of dry grass fuel is burnt, about 2 megajoules of electromagnetic radiation are released. It was estimated that the coulombic forces between each electron and proton in that amount dry grass total 150 gigajoules (or giganewtons, since the reference is to forces). 9. Within the boundary of a simple economic activity, the ratio of aggregated coulombic forces locked up within atoms to the electromagnetic forces radiated out was estimated at the beginning of the activity, and then after a duration. The ratio of forces always tends towards 'evening out'. This measurement captures the entropy phenomenon which has been said by Georgescu-Roegen to be the basis of all economic activity. 10. At the roots of the economic paradigm founded by Adam Smith is the premise that the material world, as a set of substances, is a stage on which economic actors 'add value', bid prices up and down, and by their rational perception manage their livelihoods and surroundings well. From the findings of this research program it is contended that the surroundings of economic actors can be classed into two categories: locked up (coulombic) electromagnetic forces, and radiated electromagnetic forces. The former has a tendency to convert to the latter. All action, including all economic activity, and all life can be traced to a point in space and time where this conversion is (naturally) occurring. The phenomenon is analogous to a slope where water cascades, and gravitational potential energy converts to other (either useless or useful) forms of energy. To appreciate the nature of this phenomena, and to attempt to fathom its dimensions, sets our perceptions of ourselves as economic actors in a quite different and very humbling context.
Części książek na temat "Locked up electromagnetic forces"
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Satz, Helmut. "The Nature of Forces". W More than the Sum of the Parts, 27–39. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192864178.003.0004.
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Abstract We introduce gravity and electromagnetic interactions, discuss the origin of dark matter, of dark energy, and obtain the entropy of black holes. Dark matter is seen to arise from the velocity distribution of outlying stars in galaxies, deviating from Kepler’s law. Up to today, the form and nature of such matter is not understood. We discuss the entropy of black holes and note the specific form of the force of gravity.
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Lacey, James. "Adrianople’s Aftermath". W Rome, 327—C18.P16. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780190937706.003.0019.
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Abstract The true consequence of the Battle of Adrianople was that it locked in place the separation that had arisen when Constantine’s sons decided to divide the Empire between them and then fought a series of civil wars to bring it back together. In the meantime, they had done little to assist each other against outside threats. It had, of course, been long understood that the Empire was too big to be entirely run by just one man. This realization had been the basis for the tetrarchy, but even the tetrarchy had a single senior emperor to rule the others. There were always centrifugal forces trying to break up the Empire or tear parts of it away. After Adrianople, the Empire was for all practical purposes permanently divided, although not in any manifestly political way, as there remained two Augusti who were communicating with each other. What changed was that only rarely would either half of the Empire be willing to help one another. And even when they were, the help was rarely of meaningful size or long maintained. When Gratian’s army marched to help Valens, it marked the last time an eastern or western Roman field army marched to the assistance of the other. When his army marched back west, it heralded a break that doomed the consolidated Empire, which had existed since the reign of Augustus.
3
Gross, Alan G. "Steven Weinberg: The Conjectural Sublime". W The Scientific Sublime. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190637774.003.0007.
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Steven Weinberg had been working for some time on the problem of the strong force that holds together the components of an atom’s nucleus. He was getting nowhere. “Suddenly,” while driving home in his red Camaro, insight arrived. He did not have the wrong answer to the problem of the strong force but the right answer to a different, equally interesting problem: …And I realized the massless particle in this theory that had given me so much trouble had nothing to do with the heavy particles that feel the strong interaction; it was the photon, the particle of which light was composed, that is responsible for electric and magnetic forces and that indeed has zero mass. I realized that what I had cooked up was an approach not just to understanding the weak interaction but to unifying the theories of the weak and electromagnetic forces into what has since come to be called the electroweak theory… “A Model of Leptons” is a paper of which he is justly proud. It has garnered 4,503 citations; a copy has been offered for sale at $950. This is the physicist at his mathematical best, a language he speaks as if it were his native tongue. Another incident confirms Weinberg’s extraordinary talent. Physicist Rich Muller has a bright idea. After several tries, however, the mathematics continues to defeat him. Despondent, he walks down the hall to an office where Steven Weinberg is chatting with Freeman Dyson. The two agree to help: …Weinberg went to the blackboard, wrote down the first equation. “And then he did some manipulations on it,” said Muller, “and stood back.” Dyson said, “I think if you make a substitution of variables now— .” Weinberg said, “Oh, yes, of course,” and wrote several more lines. “I was taking notes,” Muller said, “but I wasn’t sure what he was doing.” Weinberg paused in his writing, and Dyson said, “Now evaluate the delta function,” and Weinberg said, “Oh, okay.” Weinberg wrote down a few more lines, and Dyson said, “Good. You’ve proven it.”
Streszczenia konferencji na temat "Locked up electromagnetic forces"
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Bucenieks, I. "Perspectives of Increasing Efficiency and Productivity of Electromagnetic Induction Pumps for Mercury Basing on Permanent Magnets". W 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89193.
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In the next generation neutron sources the HLM (heavy liquid metals) such as lead, lead based eutectic alloys and mercury will be used both as spallation target material and simultaneously as the cooling liquid. In this aspect the design of safe and effective pumps for HLM recirculation at high pressure heads and big flow rates becomes important. For this purpose electromagnetic inductions pumps having no problems of hydraulic seals being in contact with liquid metal (electromagnetic forces in the liquid metal are induced by magnetic system located outside of the channel of pump) are more perspective from the point of view of their safety for operation at high temperature and radiation conditions in comparison with mechanical pumps. At the Institute of Physics of University of Latvia (IPUL) the design concept of electromagnetic induction pumps basing on the principle of rotating permanent magnets (PMP) have been developed. Such design concept of electromagnetic induction pumps has many advantages in comparison with traditionally used electromagnetic induction pumps basing on 3-phase linear flat or cylindrical inductors. The estimations of parameters of powerful pumps (such as overall dimensions of the active magnetic system, power of motor needed for pump drive, the efficiency of pump) for mercury for the developed by pump pressure heads in the range up to 10.0 bar and provided flow rates in the range up to 20 litres per second are demonstrated.
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Singh, Maniesh, Parmanand Dhermeshwar Thakur, Mariam N. M. Al Baloushi, Haitham Ali Al Saadi, Maisoon M. Al Mansoori, Ahmed S. Al Mesafri, Saif Al Arfi i in. "Real-Time 3D Ultra Deep Directional Electromagnetic LWD Inversions: An Innovative Approach for Geosteering and Geomapping Water Slumping Movement Around Sub-Seismic Fault, Onshore Abu Dhabi". W Abu Dhabi International Petroleum Exhibition & Conference. SPE, 2021. http://dx.doi.org/10.2118/207478-ms.
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Abstract An Ultra-Deep Directional Electromagnetic LWD Resistivity (UDDE) tool was deployed in a mature Lower Cretaceous carbonate reservoir to map injection water movement. These thick carbonate reservoirs experience injection water preferentially travelling laterally at the top of the reservoir. The water held above oil by negative capillary forces slumps quickly, leading to increasing water cut, eventually killing the natural lift horizontal producing well. Real time 3D and 1D inversions provided important accurate mapping of the non-uniform water fronts and reservoir boundaries, providing insights into reservoir architecture and water movement. The candidate well is located in an area of significant uncertainty regarding fluid distribution and structural elements like sub-seismic faults etc. Pre-well 1D inversion results indicated that the water slumping front away from wellbore can be mapped within a vertical radius of 60-100 ft TVD. However, 1D inversion is not accurate where steeply dipping or discontinuous formations exist due to the presence of faults and is expected to impact well placement, mapping water fronts / formation boundaries and long-term oil recovery. Therefore in the real time, full 3D and 1D inversions of the Ultra-Deep EM data were run to provide high quality reservoir imaging in this complex geometrical setting and deliver improved reservoir fluid distribution and structure mapping. The pre-well inversion modeling optimized the frequency and transmitter-receiver spacing of the UDDE tool. The bottom hole assembly (BHA) configuration also included conventional LWD tools such as Neutron-Density, propagation Resistivity and Gamma Ray. Multiple 3D inversion datasets were processed in real-time using different depths of inversion ranging from 50 ft up to 120 ft depth. The 3D inversion results during the real-time drilling operation detected the non-uniform waterfront boundaries and water slumping up to 80 ft TVD above the wellbore using a slimhole (4¾″) tool. An interpreted sub-seismic down-thrown fault was mapped which controlled the non-uniform slumping fluid distribution, causing the water front to approach closest to the wellbore in this location. This suggests that the fault zone is open and provides a degree of increased permeability around the plane of the fault. The real-time 3D inversion, 1D shallow and 1D deep inversion results showed comparable structural imaging despite being inverted independently of each other. These results permitted updates to the static / dynamic reservoir models and an optimization of the completion design, to delay the water influx and thereby sustain oil production for a longer period of time. Field wide implementation of the UDDE tool and its advanced technology with improved 1D and 3D inversion results will enhance the quality of realtime geosteering, mapping and updating of reservoir models which have challenging water slumping fronts and structural variations. This will enable improvment in well locations, their spacing and finally allowing the proactive design of smart completions for enhanced oil production and improved recovery factors.
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Mohiuddin, Mohammad W., Alan B. Palazzolo, Randy P. Tucker, Desireddy V. Reddy, Andrew J. Provenza i Albert F. Kascak. "High Temperature Magnetic Thrust Bearing: Theory and Experiment". W ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91544.
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Abstract Active magnetic bearings (AMBs) are being increasingly utilized in industrial applications due to their advantages over conventional bearings. They offer very low friction and wear, variable stiffness and damping, and greater tolerance of rotating mass imbalance. These unique features of AMBs have enabled design of robust rotating machinery at much higher speed with higher power concentration. The present work discusses the design of a high temperature magnetic bearing for operation at an axial thrust load of 4448N, speed 20000 rpm and temperature 538°C. Various disk profiles were considered to lower peak stresses due to centrifugal forces, including uniform (rectangular), linear tapered and hyperbolic. The predictions showed that the hyperbolic profile reduced stresses by 60% compared to the rectangular profile enabling rotor disks to operate at much higher speed. A test bearing was built with the hyperbolic disc profile. An Iron-Cobalt alloy, commercially known as Hyperco 27 was utilized for the thrust disc for its high yield strength 570MPa, high saturation flux density of 2.35T and high resistivity of 250μΩ-mm. Hyperco 50A was selected for the bearing stator, due to the lower load requirement and cost. Magnetic circuit design assumptions for the axial thrust AMB included (1) relative permeability of the magnetic material was nearly infinite, (2) fringing at gap edges as well as leakage flux were negligible, and (3) the field within the circuit was homogeneous. The initial circuit design was improved using finite element magnetic field analysis. The effective force acting on the hyperbolic rotor determined the required number of turns and current for the electromagnetic coils. Extensive structural finite element analyses suggested not to use an interference fit of the attached disk with the shaft. Rather, it was decided to utilize a sleeve and lock-nut mechanism. Inconel 718 was used for the shaft due to its slightly higher thermal expansion coefficient than Hyperco 27. The thrust AMB containment vessel included thermally-insulated radial and axial adjustment bolts to position and align the AMB inside the vessel. The AMB rotating assembly was spun using an electric motor. The magnetic force generated by the AMB at room temperature was similar to its predicted value, with a 0.85 derating factor. The magnetic force was temperature dependent and was reduced to 65% of its room temperature value, at 538°C. The maximum operating speed reached thus far in the experimental study was 5000 rpm. The magnetic bearing force was nearly invariant with rotational speed at any given temperature (e.g., room and high), while the electric current was held constant. The design indicates that the novel magnetic thrust bearing should perform well at the target operating conditions of 4448N axial load at 538°C (1000 lb-f at 1000°F), and 20,000 rpm. This has been achieved thus far only up to 5000 rpm. The force appears to be very insensitive to motion induced eddy currents up to the present maximum speed of 5000 rpm. Future work will focus on reaching the full speed target of 20,000 rpm at 538°C and 4,448 N loading.
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Bacon, J. L., D. G. Davis, R. J. Polizzi, R. L. Sledge, J. R. Uglum i R. C. Zowarka. "A New Electromagnetic Powder Deposition System". W ITSC 1997, redaktor C. C. Berndt. ASM International, 1997. http://dx.doi.org/10.31399/asm.cp.itsc1997p0393.
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Abstract Existing state of the art thermal spray processes (HVOF, D-Gun, Plasma Spraying) are limited to powder velocities of about 1 km/sec because they rely on the thermodynamic expansion of gases. A new thermal spray process using electromagnetic forces can accelerate powder particles to a final velocity of up to 2 km/sec. At this velocity powder particles have sufficient kinetic energy to melt their own mass and an equivalent substrate mass on impact. The process is based on railgun technology developed by the Department of Defense. A railgun is filled with argon gas and a high energy electrical pulse, provided by a capacitor bank, drives the gas down the railgun to a final velocity of up to 4 km/sec. This gas passes over a powder cloud and accelerates the powder through drag forces. The electrical and powder discharge frequency can be adjusted so that the deposition rate and thermal input to the substrate can be controlled.
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Xu, Jiankang, Youbai Xie i Junhong Mao. "Modeling and Dynamic Behaviors of a Rotor Suspended in Electromagnetic Bearings". W ASME 1991 Design Technical Conferences. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/detc1991-0366.
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Abstract A closed loop system composed of a rotor in electromagnetic bearings and a PID (proportion-integration-differentiation) controller is developed. With the active electromagnetic forces the rotor 50 millimeters in diameter can be fully suspended in two radial electromagnetic bearings and can be driven from zero up to 3000 rpm. This closed loop system is modeled and its dynamic behaviors are analized by digital simulation. The influence of controller parameters on motion of the rotor and the relation between controller parameters and dynamic stiffness of the electromagnetic bearings are presented.
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Nashine, B. K., S. K. Dash, K. Gurumurthy, M. Rajan i G. Vaidyanathan. "Design and Testing of D.C. Conduction Pump for Sodium Cooled Fast Reactor". W 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89123.
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DC Conduction pump immersed in sodium forms a part of Failed Fuel Location Module (FFLM) of 500 MWe Fast Breeder Reactor (PFBR) currently under construction. FFLM housed in control plug of the reactor, is used to locate the failed fuel sub-assembly due to clad rupture in the fuel pin. The DC conduction pump sucks the sodium from the top of fuel sub-assemblies through the selector valve and pumps the sodium to hold up for detecting the presence of delayed neutrons. Presence of delayed neutron is the indication of failure in the sampled fuel sub-assembly. The DC Conduction Pump was chosen because of its low voltage operation (2 V) where argon/alumina ceramic can provide required electrical insulation even at operating temperature of 560°C without much complication on the manufacturing front. Sampling of sodium from top of different sub-assemblies is achieved by operation of selector valve in-conjunction with the drive motor. FFLM requires the pump to be immersed in sodium pool at ∼560°C located above the fuel sub-assemblies in the reactor. The Pump of 0.36 m3/h capacity and developing 1.45 Kg/ cm2 pressure was designed, manufactured and tested. The DC Conduction Pump has a stainless steel duct filled with liquid sodium, which is to be pumped. The stainless steel duct is kept in magnetic field obtained by means of electromagnet. The electromagnet is made of soft iron and the coil made of copper conductor surrounds the yoke portion of electromagnet. The external DC source of 2000 Amps, 2 Volt is used to send current through sodium placed in the stainless steel duct and the same current is sent through copper coil of electromagnet for producing required magneto motive force, which in turn produces required magnetic field. The interaction of current in sodium (placed in stainless steel duct) and magnetic field produced by the electromagnet in the duct region produces pumping force in the sodium. Electromagnet, copper coil, stainless steel duct, copper bus bar etc. are encapsulated in stainless steel shell. Hydraulic characteristics, efficiency, cavitation free operation at operating temperatures was ascertained by conducting tests in sodium loop called Large Component Test Rig (LCTR). The pump was also endurance tested for 750 hrs. The performance tests on DC Conduction Pump indicate that the pump meets the target specification at reactor operating condition. This paper deals with design, construction and performance testing of DC Conduction Pump.
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Bougacha, Samir, Hongwei Cai, Jeffry Booher i Marshall Newlin. "Rational Analysis for Understanding Skewed Steel Bridge Cross-Frame Behavior". W IABSE Congress, New York, New York 2019: The Evolving Metropolis. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2019. http://dx.doi.org/10.2749/newyork.2019.1371.
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<p>The design of skewed I-girder steel bridges is common throughout the country. Such bridges have been fabricated and constructed and have generally performed well. Where issues have been encountered, they were primarily related to bridge construction and, quite often to the torsional behavior of the severely skewed bridge superstructure. Until recently, there have been few analysis and design guidelines available to the structural designer on the construction engineering of the skewed I-girder bridges. AASHTO [1] specifies that the contract documents should state the fit condition for which the cross frames are detailed for I-girder bridges. Recommendations are also provided for the estimation of the cross frame locked-in forces. This paper presents a case study in a fit-up analysis of multi-span skewed I-girder steel bridge using 3D finite element method modeling. Fit-up analysis was carried out to evaluate girder’s web distortions, determine the cross- frames locked-in forces and compare them to the recent AASHTO’s recommendations. The paper should provide designers with a more detailed understanding of a bridge’s behavior in this condition as compared with the more generalized recommendations from AASHTO guidelines.</p>
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Ároch, Rudolf, Michal Kováč, Tomáš Klas, Róbert Štecák i Michal Venglár. "Monitoring and Assessment of Bridge Cable Stays Consisting of Bundles of Fully Locked Coil Ropes". W IABSE Symposium, Prague 2022: Challenges for Existing and Oncoming Structures. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2022. http://dx.doi.org/10.2749/prague.2022.0338.
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<p>The paper describes the health monitoring of the cables of the largest cable-stayed bridge in Slovakia. The bridge spans the Danube River and is located in Bratislava. It was opened for traffic in 1972. The bridge is known for the restaurant at the top of its inclined pylon. The cables consist of bundles of fully locked coil ropes.</p><p>The vibration method was used to assess the forces and damping of the cables. The results were compared with the topographical measurement method. The distribution of the total force in the stays among the individual fully locked coil ropes was also investigated by the vibration method. The measurement was performed in the anchor chambers in the bridge beam where the bundles of ropes spread out. Due to the short lengths of the ropes, the influence of their bending stiffness had to be considered. A non-linear fitting procedure with minimising the sum of squares was used.</p><p>A set of up to nine accelerometers was used to measure the vibration of individual ropes. A study on the number of necessary considered mode shapes was also performed. Ambient vibrations were used for the operational modal analysis and impact loads coming from a hammer were used for excitation as well.</p>
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Hu, Wenhua, Wei Zhang, Qian Wang, Dongxing Cao i Xiaofeng Yang. "Nonlinear Dynamics of the Active Magnetic Bearings System Up to the Second-Order Time Scale". W ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/detc2013-12713.
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As techniques develop, the AMBs are more widely utilized in engineering fields than ever before. Their performance depends on the actively control strategies due to their complicated dynamical characteristics, which mainly arise from the electromagnetic forces. Those forces usually are nonlinear functions of the displacements of the rotor and the control current. An understanding of the dynamical characteristics of these structural systems is essential for the rules of their designing and controlling. Variations of a long time could be observed easier with a quicker time scale. In order to study the AMBs’ action during a very long time, we use the perturbation method to obtain the AMBs’ motion up to second-order time scale. In present work, the horizontal and vertical motions of a rotor-AMBs system with 8-pole legs and the time-varying stiffness are formulated. We use the multiple scales method to study the simultaneous resonance of a 1:2 sub-harmonic resonance and a primary parametric resonance for this system up to the second-order time scale. With numerical simulation, we focus on the nonlinear dynamics describing the system’s approximate solution with regard to the second-order time scale. It is found that the modulations of the amplitudes and phases of the rotor-AMBs system in higher time scale could be severely affected by changing some parameters in governing equations.
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Sharma, P., S. Gupta, A. S. Das i J. K. Dutt. "Active Vibration Control of Flexible Rotor-Shaft System Subject to Earthquake". W ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89298.
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This paper presents the results of a numerical simulation to actively control transverse vibration of a flexible rotor shaft subject to seismic base excitation. The active control force is applied over an air gap by an electromagnetic actuator. Equations of motion of the rotor-shaft-system have been drawn up after discretizing the rotor continuum with finite beam elements and taking into account rotor flexibility, internal friction forces due to rotor material damping, inertial forces due to base motion, gyroscopic forces and non-linear electromagnetic control forces from the actuator in addition to harmonic excitation due to unbalance in the steadily spinning rotor-disc. A MATLAB code in the SIMULINK domain has been created for this purpose and the equations developed are solved numerically in the time domain to get the response at each nodal point. Numerical simulation of vibration response of the disc in a single-disc rotor-shaft-system is compared with and without the control action when the rotor base is excited with the El-Centro earthquake data. The comparison shows a remarkable reduction of response amplitude and improvement of rotor-shaft-system stability in comparison with no control action. Hence the usefulness of an electromagnetic actuator is proposed for safe and sound operation of rotor-shaft systems even under the seismic base excitation.