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E Motion Electrodynamique

Electrodynamic tethers (EDTs) are long conducting wires, such as one deployed from a tether satellite, which can operate on electromagnetic principles as generators, by converting their kinetic energy to electrical energy, or as motors, converting electrical energy to kinetic energy.[1] Electric potential is generated across a conductive tether by its motion through a planet's magnetic field.

E Motion Electrodynamique

In self-powered mode (deorbit mode), this EMF can be used by the tether system to drive the current through the tether and other electrical loads (e.g. resistors, batteries), emit electrons at the emitting end, or collect electrons at the opposite. In boost mode, on-board power supplies must overcome this motional EMF to drive current in the opposite direction, thus creating a force in the opposite direction, as seen in below figure, and boosting the system.

An electrodynamic tether is attached to an object, the tether being oriented at an angle to the local vertical between the object and a planet with a magnetic field. The tether's far end can be left bare, making electrical contact with the ionosphere. When the tether intersects the planet's magnetic field, it generates a current, and thereby converts some of the orbiting body's kinetic energy to electrical energy. Functionally, electrons flow from the space plasma into the conductive tether, are passed through a resistive load in a control unit and are emitted into the space plasma by an electron emitter as free electrons. As a result of this process, an electrodynamic force acts on the tether and attached object, slowing their orbital motion. In a loose sense, the process can be likened to a conventional windmill- the drag force of a resistive medium (air or, in this case, the magnetosphere) is used to convert the kinetic energy of relative motion (wind, or the satellite's momentum) into electricity. In principle, compact high-current tether power generators are possible and, with basic hardware, tens, hundreds, and thousands of kilowatts appears to be attainable.[10]

The primary passive processes that control the electron and ion collection on an EDT system are thermal current collection, ion ram collection effects, electron photoemission, and possibly secondary electron and ion emission. In addition, the collection along a thin bare tether is described using orbital motion limited (OML) theory as well as theoretical derivations from this model depending on the physical size with respect to the plasma Debye length. These processes take place all along the exposed conducting material of the entire system. Environmental and orbital parameters can significantly influence the amount collected current. Some important parameters include plasma density, electron and ion temperature, ion molecular weight, magnetic field strength and orbital velocity relative to the surrounding plasma.

The concept of current collection to a bare conducting tether was first formalized by Sanmartin and Martinez-Sanchez.[9] They note that the most area efficient current collecting cylindrical surface is one that has an effective radius less than 1 Debye Length where current collection physics is known as orbital motion limited (OML) in a collisionless plasma. As the effective radius of the bare conductive tether increases past this point then there are predictable reductions in collection efficiency compared to OML theory. In addition to this theory (which has been derived for a non-flowing plasma), current collection in space occurs in a flowing plasma, which introduces another collection affect. These issues are explored in greater detail below.

For use in EDT system modeling, each of the passive electron collection and emission theory models has been verified by reproducing previously published equations and results. These plots include: orbital motion limited theory,[15] Ram collection, and thermal collection,[58] photoemission,[59] secondary electron emission,[60] and secondary ion emission.[61][62][63][64]

Realistically, the transverse electrodynamic forces cause the tether to bow and to swing away from the local vertical. Gravity gradient forces then produce a restoring force that pulls the tether back towards the local vertical; however, this results in a pendulum-like motion (Gravity gradient forces also result in pendulous motions without ED forces). The B direction changes as the tether orbits the Earth, and thus the direction and magnitude of the ED forces also change. This pendulum motion can develop into complex librations in both the in-plane and out-of-plane directions. Then, due to coupling between the in-plane motion and longitudinal elastic oscillations, as well as coupling between in-plane and out-of-plane motions, an electrodynamic tether operated at a constant current can continually add energy to the libration motions. This effect then has a chance to cause the libration amplitudes to grow and eventually cause wild oscillations, including one such as the 'skip-rope effect',[69] but that is beyond the scope of this derivation. In a non-rotating EDT system (A rotating system, called Momentum Exchange Electrodynamic Reboost [MXER]), the tether is predominantly in the z-direction due to the natural gravity gradient alignment with the Earth.

So we see that we cannot attach any absolutesignification to the concept of simultaneity, but that two eventswhich, viewed from a system of co-ordinates, are simultaneous, canno longer be looked upon as simultaneous events when envisaged froma system which is in motion relatively to that system.

For this purpose we introduce a third system of co-ordinates, which relatively to thesystem k is in a state of parallel translatory motionparallel to the axis of ,*1 suchthat the origin of co-ordinates of system , moves with velocity -v on the axis of. At the time t=0 let all threeorigins coincide, and when t=x=y=z=0let the time t' of the system be zero. We call the co-ordinates, measured in thesystem , x', y',z', and by a twofold application of our equations oftransformation we obtain

Without affecting the general character of our considerations,we may and will assume that the electron, at the moment when wegive it our attention, is at the origin of the co-ordinates, andmoves with the velocity v along the axis of X of the systemK. It is then clear that at the given moment (t=0) theelectron is at rest relatively to a system of co-ordinates which isin parallel motion with velocity v along the axis of X.

With a different definition of force and acceleration we shouldnaturally obtain other values for the masses. This shows us that incomparing different theories of the motion of the electron we mustproceed very cautiously.

We will now determine the kinetic energy of the electron. If anelectron moves from rest at the origin of co-ordinates of thesystem K along the axis of X under the action of an electrostaticforce X, it is clear that the energy withdrawn from theelectrostatic field has the value . As the electron is to be slowlyaccelerated, and consequently may not give off any energy in theform of radiation, the energy withdrawn from the electrostaticfield must be put down as equal to the energy of motion W of theelectron. Bearing in mind that during the whole process of motionwhich we are considering, the first of the equations (A)applies, we therefore obtain

Objectives: In this paper, we present a unified electrodynamic heart model that permits simulations of the body surface potentials generated by the heart in motion. The inclusion of motion in the heart model significantly improves the accuracy of the simulated body surface potentials and therefore also the 12-lead ECG.

Methods: The key step is to construct an electromechanical heart model. The cardiac excitation propagation is simulated by an electrical heart model, and the resulting cardiac active forces are used to calculate the ventricular wall motion based on a mechanical model. The source-field point relative position changes during heart systole and diastole. These can be obtained, and then used to calculate body surface ECG based on the electrical heart-torso model.

While classical and quantum electrodynamics present the existence of dipole-dipole long-range electrodynamics forces, they remain to be experimentally observed. The discovery of completely new and unanticipated forces that are present between biomolecules have considerable impact to understand the dynamics of molecular machines at work within living organisms. In a new report now published in Science Advances, Mathias Lechelon and a research team at the French National Centre for Scientific Research (CNRS) France conducted two independent experiments based on different physical effects, which they detected via fluorescence correlation spectroscopy and terahertz spectroscopy, respectively, to demonstrate experimental activation of resonant electrodynamic intermolecular forces. The outcomes provided unprecedented experimental proof-of-principle of a physical phenomenon with importance in biology. According to the study, aside from thermal fluctuations that randomly drove molecular motion, resonant and selective electrodynamic forces contributed to molecular encounters in crowded cellular spaces. googletag.cmd.push(function() googletag.display('div-gpt-ad-1449240174198-2'); ); Electrodynamic (ED) forces

We present a quantum-mechanical model for a four-wave-mixing Josephson traveling-wave parametric amplifier including substrate losses and associated thermal fluctuations. Under the assumption of a strong undepleted classical pump tone, we derive an analytic solution for the bosonic annihilation operator of the weak signal photon field using temporal equations of motion in a reference timeframe, including chromatic dispersion. From this result, we can predict the asymmetric gain spectrum of a Josephson traveling-wave parametric amplifier due to nonzero substrate losses. We also predict the equivalent added input noise including quantum fluctuations as well as thermal noise contributions. Our results are in excellent agreement with recently published experimental data. 041b061a72

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