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  • American Institute of Physics (AIP)  (31,708)
  • 1985-1989  (31,708)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3282-3294 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-consistent thermodynamics is developed for nonrelaxation hysteretic processes. This theory, nonequilibrium thermostatics, is based upon macroscopic empirical descriptions of hysteretic behavior and the laws of thermodynamics. It is shown that the empirical behavior of hysteretic systems does not satisfy the conditions required for application of either equilibrium or relaxation nonequilibrium thermodynamics. Therefore, modified thermodynamic assumptions are proposed which are consistent with empirical hysteretic behavior. The principal new assumptions are (1) that processes (energy dissipation permitted) consists of a differential sequence of nonequilibrium states; (2) that three new "state variables'' describe all of the "history dependence of a state;'' (3) that at least some "reversible'' processes exist; (4) that the time-independent "modified Gibbs relation'' can be used to describe the Second Law constraints. With these assumptions, it is shown that the thermodynamic relationships derived from the First Law are identical to those for standard equilibrium thermodynamics, but Second Law implications are significantly different, e.g., a new "dissipation'' state function is derived; it is proven that hysteretic behavior is a positive indication of a dissipative process and that dissipation always causes hysteresis. It is concluded that nonequilibrium thermostatics provides a self-consistent theory which extends the useful domain of thermodynamics to include nonrelaxation, hysteretic (dissipative)processes. A comparison of detailed predictions and experimental measurements of heat capacities, adiabatic paths, etc., for a hysteretic system is provided in a separate paper.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3314-3321 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quantum model of the single particle free-electron laser in a uniform magnetic field is given. Here the classical electron current due to electrons in helical orbits (caused by a uniform magnetic field) interacts with a quantized radiation in the interaction volume of finite extent. The description of this free-electron laser is through the S matrix which incorporates the quantum recoil completely and yields directly the full "quantum mechanical'' gain. Taking the relativistic electron factor γ to be approximately equal to 2.4 and the magnitude of the magnetic field in the range of 0.6–1.6 T, this free-electron laser should be capable of generating radiation in the far infrared-microwave spectral region. From the analysis of the asymptotic (classical limit) gain (a gain due to the "infinite'' number of photons in the interaction volume V), we conclude that it is generally easier to generate radiation in the forward, rather than backward, direction. We also discuss the dependence of the gain on the electron velocity in the z direction, the strength of the uniform magnetic field, and the fact that our (asymptotic) gain scales as L3, which is similar to the gain of the usual (wiggler) free-electron laser.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3333-3339 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic theoretical study of approximations to the Kirchhoff diffraction integral is presented, stressing the improved behavior at large angles. This work was motivated by consideration of diffraction in dual tilted dispersive interdigital transducers for surface acoustic wave generation, but the salient features are applicable to diffraction problems in general. Previous treatments of surface acoustic wave (SAW) propagation were limited to nearly forward directions perpendicular to transducer fingers, where the simple Fresnel diffraction theory was adopted. Improvement of the theory for nonforward angles is obtained in which both the Fraunhofer and Fresnel diffractions are correctly included. The conventional diffraction treatment used in optics (as in the textbook by Born and Wolf) is found inaccurate and a new form is presented.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3350-3355 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The energy distribution of positive ions incident on a grounded surface in a low-pressure argon planar rf glow discharge system has been measured as a function of excitation frequency from 70 kHz to 13.56 MHz for both capacitive and direct coupling of the rf power to the excitation electrode. The results are interpreted by taking into consideration both the transit time for the ion to traverse the sheath relative to the period of the rf excitation voltage, and the resistive or capacitive characteristics of the sheaths. The importance of system geometry and of the dc potential of the excitation electrode (as determined by external circuitry) on the maximum energy of ions incident on grounded surfaces is shown.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3368-3372 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Isochronal and isothermal annealing results for peroxy radical defects induced in Suprasil W1 by γ irradiation are reported. The activation energy for annealing is estimated to be ∼2 eV and argued to be due to OO bond dissociation rather than gaseous interstitial or network diffusion. The results are shown to be consistent with those obtained from annealing/reactivation studies on oxygen vacancy defect centers.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3388-3393 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase and microstructure of Ni, Co, and Fe impurities found in synthetic diamonds have been characterized in some detail using a combination of extended x-ray absorption fine structure (EXAFS) utilizing intense synchrotron radiation as a light source, and conventional transmission electron microscopy (TEM), x-ray diffraction, and fluorescence analyses. In all three cases, the metal impurity exists as an fcc metallic phase dispersed in the diamond matrix. The particles are submicron in size and not facetted. There was no evidence of a metal carbide phase in these systems. Quantitative simulations of the first-shell EXAFS signal showed that the Co and Ni particles contain, respectively, 2.3 and 1.5 at. % of carbon in solution.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3404-3408 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A light gas gun has been used to measure the unreacted Hugoniot of both pressed and cast Composition B-3. Transmitted stress and wave speeds were determined from quartz gauges placed on the rear surface of explosive disks. Both pressed and cast Composition B-3 exhibited elastic–plastic behavior. Good agreement was found between the elastic and plastic shock wave speeds and those determined ultrasonically. The elastic constants for pressed Composition B-3 were evaluated ultrasonically. Apparently, reaction in Composition B-3 has not occurred in the Hugoniot measurements described in this work.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3409-3414 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Refractory metallic coatings of (W0.6Re0.4)76B24 (WReB) have been deposited onto glass, quartz, and heat-treated AISI 52100 bearing steel substrates by dc magnetron sputtering. As-deposited WReB films are amorphous, as shown by their diffuse x-ray diffraction patterns; chemically homogeneous, according to secondary ion mass spectrometry (SIMS) analysis; and they exhibit a very high (∼ 1000 °C) crystallization temperature. Adhesion strength of these coatings on heat-treated AISI 52100 steel is in excess of ∼20, 000 psi and they possess high microhardness (∼ 2400 HV50). Unlubricated wear resistance of such hard and adherent amorphous metallic coatings on AISI 52100 steel is studied using the pin-on-disc method under various loading conditions. Amorphous metallic WReB coatings, about 4 μm thick, exhibit an improvement of more than two and a half orders of magnitude in the unlubricated wear resistance over that of the uncoated AISI 52100 steel.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3425-3429 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interdiffusion in the Ta-W system, a continuous body-centered-cubic solid solution, has been investigated in the temperature range 1300–2100 °C with single-phase diffusion couples prepared by chemical vapor deposition. Fine inclusions, presumably oxides or carbides, decorated the couple interfaces and served as Kirkendall markers. The diffusion annealing times ranged from 16 h to 220 days. The resulting concentration profiles were measured with the electron microprobe and analytical electron microscope. The chemical diffusion coefficient was determined by the classical Boltzmann–Matano technique. The intrinsic diffusivities were determined by the technique of Darken. In the composition range 20–80 at. % W, the activation energy Q for chemical diffusion was constant at 130.5±1.5 kcal/mole. The activation energies for the intrinsic diffusion coefficients at the composition of the Kirkendall marker plane, approximately 70 at. % W, were Q(Ta)=132.3±0.5 kcal/mole and Q(W)=122.0±0.5 kcal/mole.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3440-3443 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The reaction kinetics of Al with Ti22W78 alloys has been investigated under vacuum annealing conditions. In particular, the effects of Cu in Al and venting during deposition of TiW were studied. It was observed that Cu did not play any significant role in the kinetics of the interdiffusion of Al and TiW. During the reaction process at temperatures around 500 °C, Ti accumulated on the surface of the samples with or without Cu in Al. The Ti accumulation is diffusion limited with an activation energy of 2.4 eV. Interface oxides are believed to be primarily responsible for the stability of Al/TiW metallization.
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