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1 Apr 1973

Volume 44, Issue 4, pp. 1417-1943

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Coherent phonon generation by optical mixing in a one‐dimensional superlattice

K. H. Yang, P. L. Richards, and Y. R. Shen

J. Appl. Phys. 44, 1417 (1973); http://dx.doi.org/10.1063/1.1662386 (3 pages) | Cited 8 times

Online Publication Date: 9 October 2003

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With the help of the lattice momentum, phase‐matched optical generation of coherent phonons with frequencies higher than 50 GHz appears feasible. We have considered two cases: (i) direct conversion of millimeter or submillimeter photons in a piezoelectric superlattice, (ii) optical mixing of two laser beams in a nonpiezoelectric superlattice.

Thermal diffusivity measuring technique for hazardous materials

R. C. Murray and T. E. Cooper

J. Appl. Phys. 44, 1420 (1973); http://dx.doi.org/10.1063/1.1662387 (6 pages)

Online Publication Date: 9 October 2003

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A technique is presented for measuring the thermal diffusivity of solids. This technique differs from others in that boundary conditions are obtained by use of a well‐stirred constant‐temperature bath. By varying the bath temperature and the initial temperature of the specimen, thermal diffusivity values may be determined as a function of temperature. Accuracies within ±5% may be obtained and the major sources of error in the technique may be isolated and controlled. The method lends itself to remote‐control testing of hazardous materials such as high explosives and solid propellants. In the present studies thermal diffusivities ranging from 0.005 to 0.010 ft2∕h were measured between −65 and 165°F on a typical high explosive material.

Nonlinear heat flow in anisotropic media with property variations and nonlinear heat generation

A. Campo and H. S. Wolko

J. Appl. Phys. 44, 1426 (1973); http://dx.doi.org/10.1063/1.1662388 (2 pages)

Online Publication Date: 9 October 2003

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See Also: Erratum

Show Abstract
A method based upon the use of two algebraic transformations is applied to the equation of heat conduction in anisotropic media having nonlinear generation. The feasibility of the method is manifested when the principal conductivities together with the volumetric heat capacity vary with temperature in a power fashion. Also, the conductivities are taken parallel to the principal axes. Except for the unsteady term, the transformed equation reduces to its counterpart in isotropic media with constant properties. Applicable boundary and initial conditions of general type are analyzed.

Growth of boron‐doped diamond seed crystals by vapor deposition

David J. Poferl, Nelson C. Gardner, and John C. Angus

J. Appl. Phys. 44, 1428 (1973); http://dx.doi.org/10.1063/1.1662389 (7 pages) | Cited 32 times

Online Publication Date: 9 October 2003

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p‐type semiconducting diamond was grown by vapor deposition from a 0.83% diborane in methane gas mixture at 1050°C and 0.2 Torr on 0 to 1‐μ nominal size natural type‐I diamond powder. Total mass increases of about 9% were achieved which correspond to average linear growth rates of less than 10−3 μ∕day. Evidence showing the growth was boron‐doped diamond included chemical etching, x‐ray and electron diffraction, density measurements, Seebeck and resistivity measurements, chemical analysis, optical measurements, induced electron emission spectroscopy, and scanning electron microscopy. The crystalline quality of the new diamond has not been established; it may be highly defective. A distinct change in color of the diamond seed crystals from an off‐white or gray for virgin crystals to light blue after growth was observed. The results are further confirmation that diamond may be grown at low pressures where it is thermodynamically metastable with respect to graphite. It is also further evidence that boron is the element responsible for blue p‐type diamonds.

Dislocation line kinetics as affected by high‐temperature pulse irradiations

H.M. Simpson, A. Sosin, and D.F. Johnson

J. Appl. Phys. 44, 1435 (1973); http://dx.doi.org/10.1063/1.1662390 (6 pages) | Cited 10 times

Online Publication Date: 9 October 2003

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Pulse experiments are described in which a pure copper sample was bombarded for 20 sec with 1‐MeV electrons at temperatures between 293 and 430°K, then the continuing increase in accumulation of point defects at dislocations was monitored at temperature by internal friction and elastic modulus data. No discontinuity in the rate of arrival is found at the moment that the irradiation is discontinued, indicating that the arriving point defect must be characterized in its motion by an energy of 0.6 eV. The postirradiation kinetics are analyzed to show that the energy of migration of this defect along dislocations is ∼ 0.2 eV less than the energy for motion in the lattice, away from the dislocations. The above kinetic analyses are carried out with the aid of the recently formulated ``defect dragging'' theory of Simpson and Sosin and constitute further verification of this theory.

Analysis of pore shrinkage by volume diffusion during final stage sintering

J. H. Rosolowski and C. Greskovich

J. Appl. Phys. 44, 1441 (1973); http://dx.doi.org/10.1063/1.1662391 (10 pages) | Cited 5 times

Online Publication Date: 9 October 2003

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The steady‐state flows of gas atoms and vacancies leaving a pore that is either on the surface, or at various positions inside of a spherical grain have been calculated by approximation methods for the conditions that exist during the final stage of sintering. Gas and vacancies were assumed to leave pores by volume diffusion only. It was found that the position of a pore in a grain should have little effect on its shrinkage rate—a result that appears to be in general accord with previous experimental observations on various materials. The rate of shrinkage of pores on grain boundaries in the one material investigated appears to be many times greater than that predicted by the calculations, implying that shrinkage of such pores was not controlled by volume diffusion. Pore‐to‐pore diffusion and removal of porosity by grain‐boundary migration are also discussed.

Estimation of Debye temperatures by averaging elastic coefficients

H. M. Ledbetter

J. Appl. Phys. 44, 1451 (1973); http://dx.doi.org/10.1063/1.1662392 (4 pages) | Cited 33 times

Online Publication Date: 9 October 2003

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Elastic Debye temperatures θ were calculated by averaging elastic stiffness coefficients. For cubic symmetry, eight averaging methods were evaluated with respect to a computationally exact θ. Reuss's θ, corresponding to uniform stress, gave better agreement than Voigt's θ, corresponding to uniform strain. Hill's geometrical θ gave the best agreement.

Finite pulse‐time and heat‐loss effects in pulse thermal diffusivity measurements

R. C. Heckman

J. Appl. Phys. 44, 1455 (1973); http://dx.doi.org/10.1063/1.1662393 (6 pages) | Cited 81 times

Online Publication Date: 9 October 2003

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The heat transfer problem associated with pulse thermal diffusivity measurements is analyzed for the cases of (i) triangular pulses whose widths are comparable with the transit time of temperature fronts across a sample (finite pulse width effects), (ii) heat losses from sample faces, and (iii) the simultaneous occurrence of heat losses and finite pulse‐width effects. Methods for the analysis of experimental results which are affected by these conditions are discussed. Tabular and graphical data which facilitate the analysis are given.

Low‐temperature resistivity of two‐phase Al☒Al3Ni alloys

R. Simoneau and G. Bégin

J. Appl. Phys. 44, 1461 (1973); http://dx.doi.org/10.1063/1.1662394 (7 pages) | Cited 8 times

Online Publication Date: 9 October 2003

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The electrical resistivity of Al☒Ni alloys in the composition range 2–28 wt% Ni was investigated. The eddy‐current decay method was used and the measurements were made at three temperatures: 297, 77, and 4.2 K. The results are explained in term of a series and parallel resistor model which takes into account the existence of different regions in the alloy (i.e., the continuous eutectic mixture, and the dispersed proeutectic constituents). This model permitted the resistivity curve to be fitted at the three temperatures and resistivity value for Al3Ni to be computed. The sharp maximum of resistivity at the eutectic composition, appearing at low temperature, has been attributed to the scattering of electrons on precipitate boundaries and to peculiar morphological features.

High‐velocity dislocation damping in aluminum

C. K. H. Dharan and F. E. Hauser

J. Appl. Phys. 44, 1468 (1973); http://dx.doi.org/10.1063/1.1662395 (7 pages) | Cited 2 times

Online Publication Date: 9 October 2003

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High‐velocity compression tests were conducted on pure polycrystalline aluminum. Data obtained at compressive strain rates ranging from 0.4×104 to 12×104 sec−1 could be divided into two regions of interest. For strain rates from 0.7×104 to 1.4×104 sec−1 a linear relationship was found to exist between the applied stress and the strain rate, indicating that the moving dislocations are viscously damped in this region. The values of the damping constant B obtained in this region ranged from 1.9×10−4 to 3.0×104 dyn sec∕cm2 and showed good agreement with B determined by other investigators. Beyond these strain rates, the damping reduced at first and then increased, with very high stresses being obtained at the highest strain rates reached. The drop in the damping has been attributed to the reduction in the volume around the cores of the moving dislocations that can exchange energy with the lattice phonons. The rise in the damping at the higher strain rates may be due to relativistic effects as the moving dislocations approach the velocity of sound. Using the expression for the strain field around a fast‐moving dislocation in the phonon viscosity theory and the general expression for dislocation damping due to phonon scattering, an expression for the damping constant was obtained embodying these effects. This was found to show good agreement with the data.

Compression of Ag and phase transformation of NaCl

Lin‐gun Liu and William A. Bassett

J. Appl. Phys. 44, 1475 (1973); http://dx.doi.org/10.1063/1.1662396 (5 pages) | Cited 53 times

Online Publication Date: 9 October 2003

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The isothermal compression of silver up to 309 kbar has been measured at 23±3°C by high‐pressure x‐ray diffraction employing a diamond‐anvil cell. The B1 phase of NaCl mixed with the silver was used both as a pressure transmitting medium and as an internal pressure calibrant. The data fitted to two forms of the Birch equation yield K0=1180±50 kbar, K0′=3.8±0.5, and K0=1105±95 kbar, K0′=4.6±0.8. When the pressure exceeded 300 kbar, the NaCl underwent a phase transformation to the B2 phase. Increasing the load did not result in the complete disappearance of the B1 phase up to a pressure of 311 and 334 kbar based on the extrapolation of the Ag and Re compression data, respectively. The average volume change measured for the B1‐B2 transformation is −0.83±0.11 cm3∕mole, which is 17% smaller than the value reported by Bassett et al. This smaller volume change improves the agreement of NaCl with the linear relationship between volume change and entropy change proposed by Bassett et al. for the B1‐B2 transformation in the alkali halides.

Theory of interdigital couplers on nonpiezoelectric substrates

G. S. Kino and R. S. Wagers

J. Appl. Phys. 44, 1480 (1973); http://dx.doi.org/10.1063/1.1662397 (9 pages) | Cited 76 times

Online Publication Date: 9 October 2003

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This paper is concerned with the theory of excitation of surface acoustic waves on a nonpiezoelectric material, by using an interdigital electrode structure overlaid with a piezoelectric film. The impedance and capacity of such transducers have been worked out. The results are given in terms of Δv∕v, the perturbation in acoustic wave velocity when a perfect conductor is placed in the position of the transducer. A computer program which calculates surface wave propagation on a layered medium consisting of a film on a substrate, with arbitrary elastic and piezoelectric properties for both media, has been used to determine Δv∕v, and hence the coupling coefficients and radiation resistance of the interdigital transducer. As a function of piezoelectric film thickness, two peaks in coupling are observed. The results for the interdigital couplers are in quantitative agreement with experiments employing single‐crystal materials. Data for experiments using sputtered piezoelectric films also give qualitative agreement with the theory. If high‐quality crystalline layers are used, the theory suggests that interdigital couplers on nonpiezoelectric delay lines with properties comparable to or better than the present piezoelectric delay lines may be achievable.

Study of ion‐nitriding

Martin Hudis

J. Appl. Phys. 44, 1489 (1973); http://dx.doi.org/10.1063/1.1662398 (8 pages) | Cited 97 times

Online Publication Date: 9 October 2003

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A study of ion nitriding has been conducted in a nitrogen‐hydrogen‐argon gas mixture with emphasis on the mechanism and the active plasma ingredients which cause nitriding. The study is based on mass and energy data of ions sampled through a 4‐mil hole in the cathode, metallurgical data, and gas‐absorption data. The results of the experiment demonstrate that ion nitriding is not a gas‐absorption process. Ion nitriding requires ionic bombardment. Nitrogen ions and nitrogen‐hydrogen molecular ions are the active plasma ingredients. Nitrogen‐hydrogen molecular ions are responsible for the superior nitriding properties produced by a nitrogen‐hydrogen plasma compared to the properties produced by a nitrogen or nitrogen‐noble gas mixture.

Parametric excitaiton of ultrasonic waves in piezoelectric semiconductors

Predhiman K. Kaw

J. Appl. Phys. 44, 1497 (1973); http://dx.doi.org/10.1063/1.1662399 (2 pages) | Cited 20 times

Online Publication Date: 9 October 2003

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We have investigated the parametric excitation of ultrasonic waves in piezoelectric semiconductors by the application of a high‐frequency electric field, near the electron‐plasma frequency. The high‐frequency field produces a nonlinear coupling between the ultrasonic waves and electron‐plasma waves and leads to an instability when a critical value is exceeded.

Dielectric behavior of ceramic grain boundaries by electron‐beam scanning

A. J. Mountvala and H. R. Marks

J. Appl. Phys. 44, 1499 (1973); http://dx.doi.org/10.1063/1.1662400 (5 pages)

Online Publication Date: 9 October 2003

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The use of the electron‐beam‐scanning technique to study the dielectric properties of material interfaces, such as grain boundaries is described and results obtained on potassium chloride and barium titanate boundaries discussed. The results indicate that grain boundaries in ionic materials such as KCl have electrical conductivities differing from those of the grain depending upon their misorientation and degree of hydration. For twist boundaries, the grain‐boundary conductivity is higher than that of the grains and this difference increases with increasing twist. No such conductivity difference was evident for a high‐angle tilt boundary. In BaTiO3 ceramics, the permittivity values in the grain‐boundary regions were specifically different from those in the grains.

Interpretation of ultrasonic measurements of hot‐pressed polycrystalline specimens of MgO

D. L. Fancher and H. A. Spetzler

J. Appl. Phys. 44, 1504 (1973); http://dx.doi.org/10.1063/1.1662401 (4 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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A model has been developed to interpret the anomalous behavior in the elastic properties of hot‐pressed MgO samples as observed by ultrasonic measurements. The present model, by including distortion of individual crystallites within the polycrystalline samples, extends the Kröner theory which calculates longitudinal and shear moduli and their pressure derivatives. In this ``distorted'' Kröner theory, a distortion factor proportional to Young's modulus is used. The results obtained from the present theory agree quite well with the observed change in the shear and longitudinal moduli in polycrystalline MgO samples which have been simultaneously subjected to pressure and temperature changes subsequent to hot pressing.

Long‐range elastic interaction between a dislocation and an ellipsoidal inclusion in cubic crystals

S. C. Lin and T. Mura

J. Appl. Phys. 44, 1508 (1973); http://dx.doi.org/10.1063/1.1662402 (7 pages) | Cited 1 time

Online Publication Date: 9 October 2003

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By using the stress field of 〈110〉 dislocation in cubic crystals and the solutions of eigen‐strain problem in anisotropic media, the long‐range interaction energy between 〈110〉 dislocation and an ellipsoidal inclusion in cubic crystals is derived. Also, the Peach‐Koehler force on the dislocation is calculated. The explicit expressions of the interaction are shown for spherical, disk‐shaped, and rod‐shaped inclusions interacting with screw, glide‐edge, and climb‐edge dislocations. When the material is isotropic and the inclusion is spherical, the results agree with the result obtained by Comninou and Dundurs, and Weeks, Pati, Ashby, and Barrand. The numerical results are shown for the void interacting with a screw dislocation. It can be seen that the results are qualitatively the same as those of the isotropic case, but quantitatively different, due to anisotropy of the materials.

Evaluation of some transport integrals. IV. Nonparabolic bands

Van E. Wood

J. Appl. Phys. 44, 1515 (1973); http://dx.doi.org/10.1063/1.1662403 (3 pages) | Cited 1 time

Online Publication Date: 9 October 2003

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Formulas are presented for the practical evaluation of transport and related integrals for conduction in a single nonparabolic band of the simplest type: k ∝(ϵ+ϵ2∕ϵg)1∕2. It is shown that when Maxwell‐Boltzmann statistics apply, these integrals may be evaluated in terms of modified Bessel functions plus a single additional function. For the Fermi‐Dirac region, approximation formulas for small ϵg are given, complementing those for large ϵg found in the literature. It is shown how further approximations may be found using the Laplace transform technique. As an example, the Faraday rotation due to free carriers is considered. It is pointed out that nondegeneracy of the carriers does not mean that effects of nonparabolicity are negligible.

A lattice‐dynamics approach to the acoustic signal by a uniformly moving dislocation

G. Cortellazzi, S. Boffi, G. Caglioti, and F. Rossitto

J. Appl. Phys. 44, 1518 (1973); http://dx.doi.org/10.1063/1.1662404 (6 pages) | Cited 5 times

Online Publication Date: 9 October 2003

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The acoustic signal generated by a uniformly moving edge dislocation is interpreted as the linear response of the crystal to the excitation produced by this motion. The proposed approach is based on the atomistic model of Frenkel and Kontorova, but the rigidity of the substrate is here removed. The expectation value of the atomic displacement induced in the crystal is thus directly evaluated in terms of lattice dynamics via a normal mode expansion. Numerical predictions are presented for several selected dislocation velocities in a specific case. These model calculations could help in interpreting experimental results.

Effect of a metallic thin film on the propagation of Rayleigh waves

Jean Pouliquen and Guy Vaesken

J. Appl. Phys. 44, 1524 (1973); http://dx.doi.org/10.1063/1.1662405 (3 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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An oscillator built with a thermostated Rayleigh‐wave delay line can be shifted in frequency by a metallic (Au, Cu, Al) thin film evaporated in a vacuum on the ultrasonic wave path. For very thin films (<100 Å) there is a rapid decrease in frequency of the oscillator and electrical resistance of the metal. This phenomenon is due to the short circuiting of the electric field to the interface and gives a good method for measuring the value of electromechanical coupling constant. For thicker film (from 200 to 3000 Å) the variations are much slower. The slope of the frequency‐vs thickness curve is propotional to the mass of deposited metal.

Filter method and silicon detectors to measure the temperature of a hot dense thermal deuterium plasma from its quantum bremsstrahlung

B.V. Robouch and J.P. Rager

J. Appl. Phys. 44, 1527 (1973); http://dx.doi.org/10.1063/1.1662406 (7 pages) | Cited 4 times

Online Publication Date: 9 October 2003

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The filter method, used to measure the temperature of a hot (T> 1 keV) deuterium plasma through its bremsstrahlung emission, is studied taking into account two new features: (i) the bremsstrahlung emission (accounted for, up until now, by its classical approximation) is described by its quantum expression, (ii) real solid‐state silicon detectors are considered, instead of ideal ones. Deductions are made concerning the best choice of the detector and the corresponding adequate filter for different temperature ranges; the limits of the temperature ranges are established considering the minimum number of points necessary to identify the shape of the spectrum curve, as well as the loss of efficiency of the detectors at high energies. An upper bound is set to the measurable temperature. Neutron radiation damages to the Si detectors, at current and foreseen levels, are considered and shown to impose no serious limitation to the practical applicability of the method.

Escape length of Auger electrons

M.L. Tarng and G.K. Wehner

J. Appl. Phys. 44, 1534 (1973); http://dx.doi.org/10.1063/1.1662407 (7 pages) | Cited 60 times

Online Publication Date: 9 October 2003

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Sputter deposition of Mo atoms on W substrates (and vice versa) was shown to form uniform overlayers. Such overlayers are ideally suited for studies of the escape length of Auger electrons. The results show that the escape length increases with Auger electron energy as expected. In both Mo and W the escape length of 48‐eV Auger electrons is about 5 Å. For 1736‐eV Auger electrons it increases to 24 Å in Mo and 17 Å in W. For a Mo overlayer on W, the Mo signal can reach an intensity 1.2 times that of the bulk Mo signal due to the higher backscattering coefficient of W. For a W overlayer on Mo, a corresponding reduction in the W signal compared to bulk W, i.e., an increase in the apparent escape depth was observed. With a model in which the backscattering effect is incorporated, one obtains satisfactory agreement with the experimental results. In addition the result indicates that while high‐energy Auger peaks are generated by the primary beam alone, a substantial fraction of observed low‐energy Auger electrons are generated by backscattered electrons. For the case of the Mo (120‐eV) Auger signal with 3‐keV primary beam energy, this fraction amounts to approximately 40%.

Observation of radially propagating collisionless‐drift‐wave instability

Y. Nishida, T. Dodo, T. Kuroda, and G. Horikoshi

J. Appl. Phys. 44, 1541 (1973); http://dx.doi.org/10.1063/1.1662408 (2 pages) | Cited 1 time

Online Publication Date: 9 October 2003

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The radially traveling drift‐wave instability is observed in a fully ionized collisionless plasma. The observed radial wave number is larger than the azimuthal wave number. The observed frequency, in the frame of ErBz plasma rotation, is in good agreement with the calculated frequency of the drift instability after the correction of finite ion inertia including the radial wave number, where Er is a radial electric field and Bz is an axial magnetic field.

Electric field, transfer, and spread functions in xerographic image studies

Cheng C. Kao

J. Appl. Phys. 44, 1543 (1973); http://dx.doi.org/10.1063/1.1662409 (9 pages) | Cited 11 times

Online Publication Date: 9 October 2003

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The general solution to the problem of computing the electric field associated with any charge distribution on the surface of a photoconductor has been solved. The model includes the case where an interposition film is present. Use of the concept of the point spread function and the transfer function in the modeling of this step of the xerographic process is discussed with reference to particular examples.

Theory of the constant property arc

Alan M. Whitman and Ira M. Cohen

J. Appl. Phys. 44, 1552 (1973); http://dx.doi.org/10.1063/1.1662410 (5 pages) | Cited 5 times

Online Publication Date: 9 October 2003

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The canal model for arc discharges is examined and shown to yield a unique consistent solution when the canal boundary temperature T* is specified as a gas property. Electrical and thermal conductivities are taken as constants appropriate to T*. Solutions are obtained for both cylindrical and planar arc columns. Both are qualitatively similar and show a distinct minimum in the current‐electric field characteristic. This is attributed to the competition between the growing arc diameter with current and the increasing conduction to the wall of the dissipated energy. Favorable comparison is shown between this simple model and more exact calculations for arc discharges.
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