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[en] A device is presented allowing the calibration of various types of calorimeters by Joule effect
[fr]On presente un appareil permettant de realiser les etalonnages par effet Joule sur differents calorimetres
[en] The spin-coupled interface (SI) resistance plays a crucial role in the interpretation of the giant magnetoresistance with current perpendicular to the plane. Recently, a theoretical work showed that its Joule heat also equals the total spin-dependent heat generation in a conceptual spin valve. Here we reexamine this conclusion in a practical spin valve with a finite nonmagnetic spacer layer and spin-selective interfaces. It turns out that this conclusion does not hold except for some special segments. The SI resistance has a more serious limitation: it may be negative in certain situation. In-depth analysis shows that its “Joule heating” should be interpreted actually as the extra energy supplied only in the ferromagnetic layers and at the interfaces. This extra energy is stored in the chemical-potential splitting due to spin accumulation and only part of it converts into heat locally. The rest flows to other layers, especially the nonmagnetic layer, in which the inflowing energy compensates exactly for the spin-dependent heat generation. In essence, this kind of energy transport makes the SI resistance unsuitable for a simple description of the heat generation, and thus we propose a new effective resistance as an alternative to it.
[en] We present calculations of thermal evolution of hot Jupiters with various masses and effective temperatures under ohmic dissipation. The resulting evolutionary sequences show a clear tendency toward inflated radii for effective temperatures that give rise to significant ionization of alkali metals in the atmosphere, compatible with the trend of the data. The degree of inflation shows that ohmic dissipation along with the likely variability in heavy element content can account for all of the currently detected radius anomalies. Furthermore, we find that in the absence of a massive core, low-mass hot Jupiters can overflow their Roche lobes and evaporate on Gyr timescales, possibly leaving behind small rocky cores.
[en] Peristaltic transport of magneto nanofluid in a symmetric channel is numerically discussed. Carreau–Yasuda model is used to explore the shear thickening and shear thinning characteristics. Joule heating and viscous dissipation effects are included in the energy equation. Effects of slip velocity, temperature jump and zero mass flux boundary conditions for channel walls are further considered. Entropy generation and Bejan number are studied. This research has been carried out employing lubrication approximation. Solutions are numerically developed and described. (paper)
[en] For a certain order of frequencies defined here we give the derivation and general solution of the 4th order differential equation obeyed by the radial MHD displacement of a cylindrical, resistive and incompressible plasma column. By means of a flux function the expressions of the elctromagnetic field and the current density in the resistive layer are obtained the power dissipated in this layer by an external wave and its limit when the resistivity disappears are then discussed
[fr]Pour un certain ordre de frequences que nous definissons, nous donnons la derivation et la solution generale de l'equation differentielle du 4eme ordre a laquelle obeit le deplacement radial MHD une colonne de plasma cylindrique, resistif et incompressible. Au moyen d'une fonction de flux nous en tirons les expressions du champ electromagnetique et de la densite du courant dans la couche resistive. Nous discutons ensuite la puissance dissipee dans celle-ci par une onde externe et sa limite lorsque la resistivite devient nulle
[en] OHTE is expected to be an improvement over the reversed field pinch in that the stabilizing reversal of edge toroidal field is augmented by external helical windings rather than totally relying on a dynamo effect. Reactors should be characterized by high power density, small size, moderate magnetic fields, room temperature coils, and ohmic heating to ignition. Five reactors have been studied self-consistently using a comprehensive systems code developed at General Atomic. It is shown that the development increments requird for OHTE commercialization are smaller and lower plants cost than for tokamaks, and that commerical plants should be economically and technically attractive
[en] This paper describes a technique for fabricating a free-standing micro-ring on an electrode chip using a cutting and welding technique which utilizes Joule heating. A thin Pt wire with a diameter of about 650 nm was prepared on a Cu electrode chip, and mechanical deformation of the thin wire was induced by twisting it around an Ag core using a nano-manipulator. One end of the thin Pt wire was then welded by Joule heating onto another Pt wire that was located on the same electrode chip, but the Pt wire was electrically isolated from the thin Pt wire. The diameters of the micro-rings fabricated were 11 and 30 µm. The micro-ring supported by simple beams was then positioned above a permanent magnet, and the ring structure was deflected vertically by supplying a current to the ring. It was found from the experimental results that the deflection of the simply supported micro-ring was proportional to the amount of current that was supplied. The linear behavior of the deflection of the ring structure can be explained by the electromagnetic force between a micro-ring and a magnet which is proportional to the current supplied to the micro-ring
[en] For /ω/ approximately equal to epsilonsup(1/3)tausub(A)sup(-1), we obtain the general solution of the resistive differential equation for the radial M.H.D. displacement in cylindrical geometry, under the assumption of incompressibility. Here: ω is the wave frequency, Tausub(A) = r0 Vsub(Atheta)sup(-1), r = r0 is the surface at which q(r) = 1, Vsub(Atheta) = Btheta0/√4πrho[r0 dq0/dr] (subscript zero indicates evaluation at r0), epsilon = tausub(A) tausub(R)sup(-1) and tausub(R) is the resistive diffusion time. By using a flux function, we write the expression of the electromagnetic field and current density in the resistive layer. Finally, we discuss power dissipated in this layer by an external wave and the limit when the resistivity vanishes