bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and properties of the system: poly(2,6-dimethylphenylene oxide) isotactic polystyrene. Small-angle x-ray studies
Authors: Wenig W. , Karasz F. E. , MacKnight W. J.
Published: February 2003

The superstructure of PPO/iPS blends, in which the iPS is partially crystallized from the glassy state by thermal treatment, is studied as a function of composition. A superstructure model, based on Hosemann’s treatment of a linear paracrystalline lattice, is used in order to calculate theoretical SAXS curves and fit them with experimental SAXS data. The model includes such superstructure parameters as lamellae thicknesses, thicknesses of amorphous regions, thickness distribution function, and size and shape of ’’ordered’’ regions. It is found that the lattice thickness distribution functions for both the crystalline lamellae and amorphous layers are best represented by symmetrical Gaussian functions. The thickness of the iPS crystal lamellae decreases with increasing PPO content. This explains, in part, the observed decrease of the melting point of the iPS in these blends.
Permanent polarization in poly(acrylonitrile)
Authors: Stupp S. I. , Carr S. H.
Published: February 2003

The dielectric behavior of poly(acrylonitrile) (PAN) has been investigated through the formation of electrically polarized films. The formation of films having a persistent electrical polarization has been achieved by the application of electric fields of the order 104 V cm−1 at temperatures ranging from 130 to 160 °C. The thermally stimulated discharge spectrum of PAN reveals at least three different peaks, two of which might be related to the relaxation of oriented nitrile side groups (90 and 145 °C). Intense current peaks observed above 160 °C are believed to be associated with backbone mobility in amorphous and paracrystalline regions. It is suggested that nitrile orientation with an applied electric field results in the formation of a highly developed level of intermolecular bonding.
Effects of defects on the longitudinal acoustic mode of n-alkane chains
Authors: Reneker D. H. , Fanconi B.
Published: February 2003

Normal mode calculations show that a single conformational defect in an otherwise all-trans n-alkane molecule disrupts the longitudinal acoustic mode (LAM) associated with the all-trans molecule. Similar calculations for a chain in the conformation produced by smoothly twisting a planar zigzag through 180 ° about the chain axis show that the LAM amplitudes and frequencies are unaffected by this gentle twist. These calculations indicate that the decrease in the LAM intensity observed in some polyethylene samples cannot be accounted for by smoothly twisted chains, but can be accounted for by defects which involve large localized departures from the all-trans conformation.
Physical properties of poly(vinyl chloride) -copolyester thermoplastic elastomer mixtures
Authors: Nishi T. , Kwei T. K. , Wang T. T.
Published: February 2003

A study has been made on the compatibility, thermal behavior, and mechanical properties of the system poly(vinyl chloride) and a copolyester thermoplastic elastomer (under the trade name of Hytrel by duPont). Results from NMR, linear thermal expansion, tensile test, and dynamic mechanical measurements indicate extensive mixing of PVC and the soft segments of the thermoplastic elastomer when the mixture is rapidly cooled from around 150 °C to ambient temperature. The hard segments of the elastomer crystallize under these conditions, as revealed by the calorimetric measurements. Upon isothermal annealing at 130 °C the mixture shows signs of phase separation in dynamic mechanical measurements. These observations suggest the existence of upper critical solution temperatures for the system. The associated miscibility gap encompasses room temperature and reaches a maximum temperature somewhere between 130 and 150 °C. The phase domains in the annealed sample are extremely fine and have been estimated to be no more than 100 Å in size from the pulsed NMR data.
NMR relaxation-time studies of poly(N-vinyl carbazole) and sorbed-O2 effects
Authors: Froix M. F. , Williams D. J. , Goedde A. O.
Published: February 2003

Proton spin-spin (T2) and spin-lattice (T1) relaxation times have been measured in order to elucidate the molecular dynamics in poly(N-vinylcarbazole) (PVK). Measurements were obtained on samples covering a broad range of molecular weights in air, O2, N2, and in vacuo. Correlation frequencies νc determined from NMR data were used in conjunction with dielectric data to construct transition maps. The α,β relaxations associated with main-chain and segmental motion exhibit temperature-dependent behavior very similar to that observed in polystyrene (PS). The γ relaxation in PVK is highly unusual in that it is dielectrically active and manifested in the T2 data only in the presence of O2. A detailed interpretation of this effect is provided, leading to the conclusion that O2 diffusion is severely restricted at low temperatures and that torsional oscillation of the carbazole group is responsible for the γ relaxation. It is proposed that the presence of O2 leads to relaxation by slow spin diffusion to the paramagnetic site at low temperatures but by direct paramagnetic relaxation by diffusing O2 molecules at high temperatures. This effect is related to the temperature-dependent lifetime of the O2-carbazole complex.
X-ray topographic examination of large paraffin single crystals
Authors: Green Robert E. , Farabaugh Edward N. , Crissman John M.
Published: February 2003

The internal microstructure of large melt-grown paraffin (n-eicosane, C20H42) single crystals was examined by the Lang x-ray diffraction projection topographic technique. Crystal selection was facilitated by use of an electro-optical system which permitted instantaneous display of Laue transmission x-ray diffraction patterns on a television monitor. The crystals were oriented and topographic diffraction planes were selected by the use of a standard (001) stereographic projection plotted from computed angles between crystallographic planes. A second electro-optical system which permitted direct viewing of the topographic images was use for rapid alignment of the Lang camera and ensured uniformly exposed topographs. X-ray topographs were obtained from crystals in the as-grown, plastically deformed, and γ-irradiated states. The results indicate that both plastic deformation and γ irradiation caused marked changes in the microstructure of the crystals, and that x-ray topography can be successfully exploited to determine such changes in hydrocarbon crystals.
Methyl branches in hydrocarbon crystals: Calculation of relaxation parameters
Authors: Farmer B. L. , Eby R. K.
Published: February 2003

A site model has been used in conjuction with potential-energy calculations to examine the role of isolated molecules with methyl branches in the mechanical relaxations of a linear hydrocarbon host crystal. The results indicate that there are two possible relaxation modes and that the one involving molecular rotation is energetically favorable over the one involving rotation and translation. For some modes of deformation, the calculated relaxation strengths are comparable to the experimentally measured ones. Furthermore, the barriers determined in this work yield calculated curves of the logarithmic decrement as a function of temperature which are comparable to the experimental ones. The relaxation is much weaker for unbranched chains in the planar zigzag conformation.
Thin-film interdiffusion. II. Ti-Rh, Ti-Pt, Ti-Rh-Au, and Ti-Au-Rh
Authors: DeBonte W. J. , Poate J. M. , Melliar-Smith C. M. , Levesque R. A.
Published: February 2003

Interdiffusion in the Ti/Rh/Au and Ti/Pt thin-film systems is measured using Rutherford backscattering. Extensive grain size measurements are used to interpret the data in terms of grain-boundary-assisted bulk diffusion. At room temperature, rapid grain-boundary diffusion of Au into the fine-grained Rh layer of the Ti-Rh-Au films occurs, characterized by a diffusion coefficient DB∼10−16 cm2/sec. The bulk diffusion of Au into the grains of the Rh film layer is examined using the grain-boundary-assisted bulk diffusion model, and the influence of surface segregation and size effects is discussed. It is found that interdiffusion in Ti-Rh and Ti-Pt couples is much slower than in Ti-Pd or Ti-Au. Methods are suggested by which the utility of Ti-Rh-Au as a conductor metallization might be improved.
Cobalt silicide layers on Si. II. Schottky barrier height and contact resistivity
Authors: van Gurp G. J.
Published: February 2003

Cobalt silicide layers have been grown by electron-beam vacuum deposition of Co onto Si wafers and subsequent thermal treatment. The barrier height φB and contact resistivity ρc of the Co-Si contacts were determined from current-voltage characteristics. The barrier height for Co on P-type Si decreases on annealing and reaches a value of 0.38 eV after annealing at 450 °C. The barrier height on N-type Si is then 0.68 eV. Presumably these are the values for a CoSi-Si contact. Annealing at higher temperatures results in a higher barrier (0.40 eV) on P-type Si and a lower barrier on N-type Si, probably by the formation of CoSi2. The values for the contact resistivity on P-type Si were determined using a transmission-line model and found to be comparable to those for Al-Si contacts. Annealing above 400 °C results in a decrease of the contact resistivity, mainly due to an increase in the boron concentration. By annealing above 500 °C the contact resistivity increases again, in agreement with the increased barrier height.
Harmonic generation in nonlinear dielectrics
Authors: Aşkar Attila
Published: February 2003

A method based on Poincaré perturbation is presented for finding the various order harmonics in a nonlinear dielectric. The method is an extension of the ideas utilized by this author for finding spatial and temporal periodic solutions for elastic waves in an anharmonic lattice. The method is applied here to find the generation of the first and second harmonics by a fundamental mode in a dielectric where the relationship between the electric field and electric displacement contains linear, quadratic, and cubic terms.
Generalized criterion for feasibility of D-T plasma fusion
Authors: Treglio James R.
Published: February 2003

A general criterion for a D-T–fueled plasma is derived. Calculations based on specific assumptions that are not necessarily applicable to all systems yield nτ values around 1015 sec/cm3 at temperatures near 60 keV, as compared to 5×1013 sec/cm3 at 30 keV obtained by Lawson. Moreover, nτ is not density independent, improving as the density increases. Additional conditions for controlled fusion indicated are a minimum heating efficiency of 2% and a minimum confinement efficiency of 99%.
Electromagnetic fields of a coaxial cable with an interrupted shield located in a circular tunnel
Authors: Hill David A. , Wait James R.
Published: February 2003

An expression for the gap admittance of a coaxial cable within a circular tunnel is derived using a quasistatic method. Coupling between the TEM mode within the cable and the monofilar mode within the tunnel is computed, and 25% of the cable power is typically transferred to the tunnel from a single cable gap. The results have application to the use of leaky coaxial cables for communication in mine tunnels.
Evidence of mechanical instabilities of electrets in electric fields
Authors: Dreyfus G. , Lewiner J.
Published: February 2003

Evidence of mechanical instabilities of an electret in an electric field is reported. It is shown, by a simple calculation of the forces acting on a surface-charged electret, that the electret may have monostable or bistable behaviors, depending on its charge densities and on the geometrical characteristics of the system. The threshold voltages allowing the switching are calculated. A comparison is made between theory and experiment.
Polarization dependence in EM scattering from Rayleigh scatterers embedded in a dielectric slab. I. Theory
Authors: Leader J. Carl
Published: February 2003

The matrix doubling method developed by Twomey, Jacobowitz, and Howell for calculating radiation transfer from a medium has been extended to permit calculations of the polarization components of the light intensity scattered from a slab medium illuminated with polarized light. Calculations have been performed for scattering in the incident plane from a Rayleigh scattering medium for various albedos and optical thicknesses. Expressions were also developed that permit calculations in terms of the same variables if the scattering centers are embedded in a dielectric slab medium. The results calculated from these expressions differ significantly from those obtained from simple refraction of the medium’s multiple scattering angular distribution. Calculated results indicate that the dielectric interface amplifies the scattering from the medium over that obtained without the interface. This amplification is most significant for the scattered depolarized components, which result exclusively from multiple scattering.
Correlation of stress-wave profiles and the dynamics of the plasma produced by laser irradiation of plane solid targets
Authors: Krehl P. , Schwirzke F. , Cooper A. W.
Published: February 2003

The interaction of 20-nsec 300-MW pulses of 1.06-μm laser radiation with thick aluminum targets in vacuum has been studied. The time history of the target impulse has been measured with a Sandia quartz gauge. A time sequence of plasma density maps constructed from floating double-probe data has been used with measured expansion velocities to estimate the plasma momentum. The results show that the stress wave is predominantly produced by about 10% of the evaporated target material which is ionized and expands from the surface in the form of a hot plasma during and shortly after the laser pulse. The estimated momentum of the plasma and neutral emitted particles is 5.6 g cm/sec for a typical case compared with the measured target impulse of 6.1 g cm/sec.
Method of solving potential field problems with complicated geometries
Authors: Yeh Hsu-Chieh
Published: February 2003

The method of solving potential field problems by dividing the potential field into an appropriate number of regions, expressing the solution in each region by eigenfunction expansion, and determining the expansion coefficients from the matching conditions at the dividing surfaces is commonly used. However, the existing solution is limited to the cases where the eigenfunctions are the same for all regions. This paper presents a method of determining the coefficients of expansion when the eigenfunctions are different for each region, which is the case for problems with complicated geometries. The method greatly increases the analytical power of solving potential fields such as electric or magnetic field, potential flow, heat conduction, and neutron diffusion, etc. The method is illustrated by solving (i) potential flow in a channel with a sudden change in cross-section area; (ii) conduction of heat in a cylinder with a sudden change in cross-section area; (iii) potential flow in a rectangular container with an inlet pipe and an outlet pipe.
Two-photon fluorescence in attenuating media and laser pulse duration measurements
Authors: Bechtel J. H. , Smith W. L.
Published: February 2003

Analytical and numerical results are obtained for two-photon fluorescence in an attenuating medium. Cases of one- and/or two-photon attenuation are considered. These results are interpreted with respect to the measurement of ultrashort laser pulses.
Comments on ’’Effects of spatially inhomogeneous oxide charge distribution on the MOS capacitance-voltage characteristics’’
Authors: McNutt M. J. , Sah C. T. , Van Overstraeten R. , Declerck G. , Muls P.
Published: February 2003

Clarifying distinctions are made concerning the models employed to describe the spatial oxide charge inhomogeneity in MOS capacitors.
Pulse propagation on a superconductive neuristor
Authors: Reible Stanley A. , Scott Alwyn C.
Published: February 2003

Both analytic study and experimental investigations on an electronic analog are presented which indicate the unstable nature of Parmentier’s traveling-wave pulse on a superconductive neuristor. In the vicinity of a critical bias level, the pulse is almost stable in the sense that pulse distortion over a finite distance can be made arbitrarily small by adjusting the bias to be sufficiently close to the critical value. It is also shown that the strength-duration curve for threshold excitation can be obtained by equating input magnetic flux to that of Parmentier’s pulse. Finally an R-T junction has been realized by resistive coupling of two neuristor lines and used to introduce a circulating pulse onto a storage ring.
Electromagnetic propagation in a ferrite-filled transversely magnetized waveguide
Authors: Sawado E.
Published: February 2003

The exact transcendental equation is obtained for a ferrite-filled transversely magnetized waveguide. It is shown that the transcendental equation leads to the magnetostatic wave dispersion relation when the propagation constant becomes very large compared with the wave number of ordinary electromagnetic waves. Transition from the exact solution to the magnetostatic limit is the main object of these investigations. At the same time numerical computations have been made and compared with magnetostatic calculations.
Magnetic properties of RMn2Ge2 compounds (R=La, Ce, Pr, Nd, Cd, Tb, Dy, Ho, Er, and Th)
Authors: Narasimhan K. S. V. L. , Rao V. U. S. , Bergner R. L. , Wallace W. E.
Published: February 2003

Magnetic properties RMn2Ge2 compounds where R is La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, and Th have been investigated from 4.2 to 500 K. LaMn2Ge2, CeMn2Ge2, PrMn2Ge2, and NdMn2Ge2 are ferromagnetic with Curie temperatures of 306, 316, 334, and 334 K, respectively. The heavy rare-earth compounds do not order ferromagnetically until low temperatures. GdMn2Ge2 shows a sharp magnetic transition at 97 K both in the magnetization-vs-temperature and resistivity-vs-temperature data. For this compound, it is proposed that above 97 K the Mn moments order antiferromagnetically among themselves while the Gd moments are disordered. Below 97 K the Mn moments couple ferromagnetically with each other but are opposed to the ordered Gd sublattice. Magnetic moment obtained at 4.2 K can be explained for all the compounds on the basis of an antiferromagnetic coupling between Mn and rare-earth spins.
Eddy currents and paramagnetic resonance in anisotropic conductors with application to TTF-TCNQ
Authors: Kahn Arnold H.
Published: February 2003

A theoretical analysis of the eddy currents in an anisotropically conducting solid is given. The geometry considered is that of a long rectangular prism with the applied rf field parallel to the length. The solution for the rf field in the solid has been found in terms of a Fourier series, and the dissipated power and average energy stored have been calculated. The changes in resonant frequency and quality factor of a microwave cavity into which a sample has been introduced are expressed in terms of the stored energy and dissipated power. Application is also made to the EPR absorption due to spins uniformly distributed throughout the sample, as outlined by Bloembergen. The asymmetric resonance line is similar to that of the infinite plate, but the peak line anisotropy is reduced as sample dimensions are decreased. The analysis is applied to samples of TTF-TCNQ and the results tabulated for varied sample sizes.
Self-heating effects in thin-film type-I superconductors
Authors: Huebener R. P.
Published: February 2003

We have investigated the current-induced electrical resistance for zero applied magnetic field in long superconducting strips of tin 100–200 μm wide and up to a few μm thick. We observe self-heating effects similar to those reported recently by Skocpol, Beasley, and Tinkham (SBT) for ’’one-dimensional’’ tin microbridges with dimensions much smaller than those of our samples. Our results agree well with the one-dimensional SBT hotspot model for long microbridges. In the presence of an inductive load, relaxation oscillations can be observed resulting from the negative differential resistance region in the V-I characteristic.
Origin of 1/f noise—Part III: A source of magnetically generated 1/f noise
Authors: Stephany Joseph F.
Published: February 2003

An interaction between noise-generating mechanisms and a uniformly moving magnetic field is derived and the conditions under which it may be observed are discussed. It is found that the effect of a uniform field generating a force in the direction of the conduction electrons is to create a new noise source which is linear with the current flowing in a conductor and which possesses a 1/f frequency dependence. The observation of this magnetically generated noise source has the theoretical interest of testing a theory of 1/f noise previously published, as well as providing a means of reducing ordinary 1/f noise to zero.
Separation of nonmagnetic metals from solid waste by permanent magnets. I. Theory
Authors: Schlömann Ernst
Published: February 2003

A new method of separating nonmagnetic metlas from solid waste is described. The process makes use of the much higher electrical conductivity of metals as compared to that of glass, ceramics, and wood. The separation is achieved by means of a ramp, which has permanent magnets embedded in its surface. The magnets are arranged in stripes of alternating polarity at 45° to the ramp axis. Nonconducting particles will slide straight down the ramp, whereas conducting particles will be deflected laterally. The amount of deflection has been calculated as a function of the length and inclination of the ramp, the period and strength of the magnets at the ramp surface, the conductivity, density, shape, size, and initial velocity of the particles and the coefficient of sliding friction between particles and ramp. The deflection is proportional to the ratio of electrical conductivity to mass density and varies substantially as the 3/2 power of the ramp length. If the particle diameter is small compared to the magnet period, the deflection varies as the square of the diameter. In the deflection is substantially independent of the particle size.
Separation of nonmagnetic metals from solid waste by permanent magnets. II. Experiments on circular disks
Authors: Schlömann Ernst
Published: February 2003

A metal separator using an inclined ramp containing a periodic array of permanent magnets is described. Measurements of the magnetic flux density near the ramp surface are in good agreement with theoretical expectations. The lateral deflection of circular disks of aluminum, copper, zinc, brass, lead, and stainless steel has been measured as a function of the ramp inclination, disk thickness, disk diameter, distance of the disks to the magnet face, and initial velocity. Good agreement with theoretical predicitons is observed in all cases. The ratio of electrical conductivity to mass density inferred from these experiments agrees well with published data for copper, zinc, and lead but is somewhat smaller (37%) for aluminum. This is attributed to the fact that the disks are made from an aluminum alloy with a smaller conductivity than pure aluminum.
Temperature dependence for carbon monoxide optical broadening cross sections
Authors: Greene A. E. , Harris R. A.
Published: February 2003

A temperature dependence for CO optical broadening cross sections is derived and shown to agree with values determined from experimentally measured CO self-broadened half-widths. It is emphasized that accurate cross sections are essential in computer modeling of CO laser performance.
Direct measurement of the absorption coefficient for the P1(7) transition in HF
Authors: Laguna Glenn A. , Storm Erik
Published: February 2003

The absorption coefficient for the P1(7) transition in pure HF gas has been measured using resonant radiation from an HF laser. It was found that the Doppler-broadened absorption coefficient is equal to the pressure-broadened absorption coefficient at a pressure of 16 Torr.
Kinetic processes in a laser-heated helium-nitrogen plasma for use as a uv laser medium
Authors: Brown Robert T.
Published: February 2003

Experimental and theoretical studies of an optically pumped electric discharge laser in helium-nitrogen mixtures are described. While the inherent efficiency of this system is rather low, these studies illustrate the basic parameters controlling the dynamics and efficiency of such a laser. In the experiments, intense diffuse discharges were obtained at pressures up to 12 atm and amplified spontaneous emission along the axis of the discharge was observed. The numerical modeling studies showed qualitative agreement with the experimental data and gave an optimized value of the kinetic coupling efficiency (absorbed 10.6-μ power to uv laser power) of 1.6% and of the total efficiency (energy stored in the TEA laser supply to uv output energy) of 0.1–0.2%.
Enhanced diffusion of Zn in Al under high-flux heavy-ion irradiation
Authors: Myers S. M. , Picraux S. T.
Published: February 2003

Zinc diffusion in Al has been enhanced by factors ∼102-106 under 80−keV Ne and 160-keV Ar irradiation at damage rates ≲1 dpa/sec (dpa=displacements per atom). The Ne bombardment was varied in flux in the range (1.4–70) ×1013 atoms/cm2 sec, and in temperature in the range 50–130 °C. The enhanced diffusion coefficient is linear in Ne flux and nearly independent of temperature, both consistent with annihilation of mobile defects at fixed sites. Analysis indicates that the average diffusion distance to annihilation for mobile defects is ∼1000 Å, and that one mobile defect is created for ∼102 atomic displacements.
Cathodoluminescence of GaAs1−xPx alloys
Authors: Marciniak H. C. , Wittry D. B.
Published: February 2003

Temperature dependence of cathodoluminescence was studied for GaAs, GaP, and GaAs1−xPx alloys. Specimens were investigated at temperatures from 30 to 300 °K using a beam voltage of 50 kV and a spot size of 10–15 μm. The change in the band gap, from direct to indirect, was observed by the variation of the wavelength of the maximum cathodoluminescence intensity and a crossover composition of ∼0.51 mole% GaP was obtained for both 30 and 300 °K. The relative peak intensities and half-widths of the recombination radiation was also studied for compositions on both sides of this crossover point.
Heterojunction laser operation of GaAs1−xPx : N on NN-pair (ENN) and A-line (EN) transitions near the direct (Γ) band edge
Authors: Coleman J. J. , Holonyak N. , Ludowise M. J. , Nelson R. J. , Wright P. D. , Groves W. O. , Keune D. L. , Craford M. G.
Published: February 2003

Single heterojunction diodes constructed by the LPE growth of In1−yGayP1−zAsz on otherwise identical N-free and N-doped VPE GaAs1−xPx substrates permit the examination of laser operation on NN-pair (ENN) and A-line (EN) recombination transitions near the direct (Γ) band edge of GaAs1−xPx. Data are presented on the effect of NN-pair states on laser operation in the region ‖EΓ−ENN‖≲50 meV (ENN<EΓ, x?0.32), where NN-pair states are degenerate with a large donor band tail (nd?1.6×1018/cm3). The NN-pair states cause increased laser threshold current density, increased laser photon energy, and a large effective index [n−λ (dn/dλ)]≳5 that is free of structure. Photoexcitation data on thin p-type platelets prepared from the same substrate crystal are described confirming this behavior. Data are presented also for the case of single N atom (A-line) states lying below EΓ and degenerate with donor tail states in GaAs1−xPx : N (x?0.40). The laser threshold current is increased because of the N doping, as for NN-pair states, but recombination on the A line occurs at lower energy (EN<EΓ) than for otherwise identical N-free diodes, which automatically operate as lasers at high thresholds and photon energies hν∼EΓ. In addition, the presence of N-trap states in the region of donor tail states results in the observation of structure (4.2 °K) in the index dispersion [n-λ (dn/dλ)] in the spectral region of the A line. This behavior is attributed to the resonant-antiresonant properties of a narrow autoionizing trap state (N trap) located in the donor tail state ’’continuum’’.
Spectral efficiency of pulsed high-current flashlamps
Authors: Gusinow M. A.
Published: February 2003

The spectral efficiency of flashlamps is considered as a function of xenon gas pressure, discharge current, and flashlamp bore. A detailed discussion is given concerning the optimum choice of flashlamp bore.
Optical absorption and dispersion in rf-sputtered α-HgS films
Authors: Nakada Tokio
Published: February 2003

The refractive index and the absorption coefficient for sputtered α-HgS films several μm thick were determined in the wavelength region from 0.5 to 2.5 μm by the analysis of transmission and reflection spectra. The results showed that the refractive index for as-deposited films decreased with increasing rf power density; however, after annealing approached the bulk value for the ordinary ray. Optical gap energy for films deposited above 0.8 W/cm2 was determined to be 2.02±0.05 eV, but became smaller with decreasing rf power density. Microprobe analysis showed that the variation in optical properties may well be related to differences in film composition. Edge absorption spectra for stoichiometric films were also measured between 77 and 330 K, and these results were compared with single-crystal data.
CuInS2 thin films: Preparation and properties
Authors: Kazmerski L. L. , Ayyagari M. S. , Sanborn G. A.
Published: February 2003

The growth and electrical properties of CuInS2 thin films are described. Two deposition schemes, single- and double-source methods, are reported. Data are presented indicating the effects of film and substrate temperature on the electrical characteristics (mobility, resistivity, and carrier concentration) of the films. Both n- and p-type films are reported, and the effects of sulfur concentrations are discussed. Some postdeposition annealing effects are also detailed.
Observation of dynamic thermal processes induced by α-particle impact on sapphire
Authors: Shepard Kenneth W. , Lai W. Y. , Mercereau J. E.
Published: February 2003

An aluminum thin-film superconducting microstrip was used to measure, in real time, the local temperature perturbation caused by single 6–8-MeV α particles striking a sapphire substrate at about 2 °K. The microstrip monitored temperature changes from a few m °K to a few hundred m °K with a spatial resolution of ∼5 μ and a time resolution of ∼3 nsec. Results indicate that the initial energy transfer in the substrate lattice is via a thermal shock wave propagating outward from the point of α impact with a velocity of 3×103 m/sec to a distance of 20–40 μ followed by a diffusionlike cooling process which appears to be of a highly nonequilibrium nature.
Fracture of graphite composites under shock loading
Authors: Goeke Elizabeth C. , McClintock Frank A.
Published: February 2003

A previously obtained set of experimental data on the failure of three-dimensional graphite composites under shock loading was examined. The critical event was determined to be fracture in the fiber bundles parallel to the shock direction. Physical considerations, as well as a simple approximate equation and a computer model of the fiber bundle fracture, show rather definitely that for pulse widths less than 0.5 μsec the variability in the strength of the individual fibers is the primary cause of the observed stress–pulse-width relationship. The assumptions of the computer model include a static stress concentration around the broken fibers and a fiber strength described by an extreme value distribution.
Nonlinear scattering of a Gaussian laser beam from a turbulent plasma
Authors: Sodha M. S. , Sharma R. P. , Kaushik S. C.
Published: February 2003

The propagation of a high-power Gaussian laser beam in a turbulent plasma has been studied by taking the effect of the redistribution of electrons into account. The redistribution of electrons is caused by the ponderomotive force and the nonuniform heating of the electrons by the Gaussian beam. The redistribution of the electrons changes the density correlation function considerably, and the scattered power from the plasma is reduced. When the power of the beam is sufficient to cause the self-focusing of the beam, the scattered power is further reduced. The scattered power at intermediate angles is greatly affected by the nonlinearity.
Measurement of anode surface temperature during a high-current vacuum arc
Authors: Boxman Raymond L.
Published: February 2003

Anode surface temperature was measured during a 3.8-kA-peak-current 7.2-ms-duration discharge between 2.5-cm-diam Ni electrodes spaced 9 mm apart. The temperature was determined by measurements of the spectral radiance of the anode in the 0.6–1.0-μm spectral region by means of a Si photovoltaic detector and narrow-band interference filters. The spectral radiance was related to anode surface temperature through the Planck radiation law. The major uncertainty in the measurement was the uncertainty of the emissivity. The actual temperature could be bracketed, however, by assuming alternatively the lowest published emissivity and unity emissivity. Prior to high-voltage arcing onset at 2.7 kA, the anode surface temperature was below 1500 °K. After high-voltage arcing onset the surface temperature rose very rapidly, reaching an equilibrium temperature of approximately 2900 °K.
A model of contact activation and the long-term behavior of R
C protected contacts
Authors: Uhrig Thomas A.
Published: February 2003

The long-term arcing behavior of resistor-capacitor protected contacts is important for many telephone relay applications; and the surrounding organic vapors and the contact surface conditions (rather than the electrical circuit) are chiefly responsible for determining the arc duration, erosion, and life of these contacts. A model of this contact activation process is developed based upon rate equations using averaged variables to characterize the contact surface conditions. Two limiting cases of the general steady-state and transient solutions are discussed. Experimental transient average arc time observations corroborate the model and show a single exponential variation of the average arc time with the number of operations. Other results imply that the adsorption of organic vapors occurs over periods of time comparable to, or greater than, the open time of the contacts which was approximately 0.1 sec. Therefore, the slow adsorption limit of the model is the most appropriate for experimental analysis. In addition to the transient average arc time observations, individual and average arc times per operation are presented for contacts in the laboratory for periods up to 2 weeks. It is observed that while the arc durations per operation are quite unpredictable, they are not truly random. There is a positive autocorrelation in the arc durations for 60 operations followed by a slight negative autocorrelation out to about 150 operations. Even after 150 operations, the arc durations are still not a random sampling of the arc time distribution since the accuracy of the average arc time does not increase as n−1/2.
Thermal conductivity of Cr-doped GaAs at low temperature
Authors: Vuillermoz P. L. , Laugier A. , Mai C.
Published: February 2003

Below 50 °K, phonon scattering by stacking faults and by very small precipitates (diameter typically 20 Å) is shown to be an important mechanism of the thermal conductivity of Cr : GaAs. The stacking faults are directly observed by x-ray topography. They appear as the dominant large structural defect. Their association with precipitates is ascribed to the large chromium concentration and to a precipitation which takes place during the growth procedure. The residual optical absorption at 10.6 μ can be attributed to these defects.
Approximate analysis of the reflection of surface acoustic waves by steps
Authors: Curtis R. G. , Redwood M.
Published: February 2003

An approximate method of obtaining the surface-wave reflection coefficient of a step is developed. Numerical results are presented for Bleustein-Gulyaev and Rayleigh waves reflected at normal incidence from electrodes of aluminum and gold on a piezoelectric ceramic. The results show good agreement with results previously obtained using a more exact but much longer method. The method is easily extended to any crystal symmetry.
Theoretical transducer properties of piezoelectric insulator FET transducers
Authors: Greeneich E. W. , Muller R. S.
Published: February 2003

An oriented piezoelectric film incorporated in the insulator region of a silicon insulated-gated field-effect transistor (FET) results in a sensitive high-frequency strain transducer. Theory governing the transducer properties of the piezoelectric insulator FET transducer is presented. Equations are developed which relate the drain current of the device to induced polarizations of the piezoelectric layer. The highest frequency of surface strains to which the FET transducer can respond is determined by the FET frequency response—ultimately by the channel transit time. This frequency can extend to the GHz range. The low-frequency response to applied strain is determined by the dielectric relaxation frequency of the piezoelectric layer.
Photoconductivity of microcrystalline AgBr : I− emulsions
Authors: Beutel J.
Published: February 2003

It is experimentally demonstrated that the photoelectron trap depth of AgBr : I− is unaffected by I− addition. The trap density increases with both I− content and with the size of the crystal. It is likely that the traps are on the surface of the microcrystals. Photoelectron decay data indicate that, after saturation of a few deep traps, the decay rate for temperatures above 60 K is determined by diffusion of interstitial silver ions (Ag+i) to the sites of trapped electrons. The activation energy for Ag+i diffusion in AgBr : I− is higher than in AgBr, and the concentration of Ag+i increases with both crystal size and I− content. These results are explained in terms of a more uniform Ag+i distribution and a probable localization of Ag+i near the I− impurity.
Energy spreading and angular distribution of a beam of electrons in molecular hydrogen
Authors: Heaps M. G. , Green A. E. S.
Published: February 2003

A Monte Carlo approach is used to obtain the energy spreading and angular distribution of initially monoenergetic and monodirectional beams of electron incident on a gas of molecular hydrogen. Several beams of primary electrons and the resultant secondaries are degraded in a step-by-step procedure which utilizes a detailed set of cross sections, together with reasonable approximations for the creation of secondary electrons. Particular attention is paid to the initial angular distribution of secondary electrons. An analytic function which characterizes current experimental differential cross-section data is used to provide realistic inputs into our calculations. The results for energy distribution as a function of distance and angular distribution at selected energies and distances are illustrated.
Influence of anode composition on the electrical properties of relativistic electron-beam diodes
Authors: Kelly J. G. , Goldstein S. A. , Swain D. W.
Published: February 2003

Current, voltage, x-ray, and witness plate measurements of the diode characteristics of the Nereus accelerator (150 kV, 50 kA) have shown that the composition of the anode can have a profound effect on the properties of the electron beam. In particular, if the anode is heated to remove absorbed gases and volatile impurities, the diode impedance holds up longer than in the case of an anode having an unprepared surface or one that has been covered with an easily vaporized low-Z substance (which leads to very rapid diode shorting). The fact that the anode surface can influence the electron current less than 10 ns into the beam pulse, before space-charge-limited electron flow has been established, indicates that ions, plasmas, or photons are generated at the anode and cross the diode gap before the electron beam has deposited more than 1 cal/cm2 into the anode.
Effective collision frequency in the presence of an ion sound wave parametrically excited in Tonks-Dattner resonance
Authors: Ikezawa Shunjiro , Okuda Takayoshi
Published: February 2003

Effective collision frequency enhanced by an ion sound wave parametrically excited in Tonks-Dattner (T-D) resonance is evaluated from the Q value and the damping rate of a surface wave propagating along the axial direction as a test wave, which are observed in a mercury vapor discharge. The ion sound wave is produced by a three-wave process of the parametric excitation where the incident electromagnetic wave decays into two electrostatic waves, an ion sound wave, and a T-D resonance. The effective collision frequencies thus obtained as a function of the absorbed pumping power are nearly in agreement with those based on the perturbed orbit theory proposed by Weinstock et al. The ion density fluctuation level estimated from Dawson’s formula is found to be lower than that obtained in other turbulent experiments.
A theorem on the effective conductivity of a two-dimensional heterogeneous medium
Authors: Mendelson Kenneth S.
Published: February 2003

Consider a two-dimensional heterogeneous system with a conductivity of σ (x,y) =σ0η (x,y), where σ0 is a scalar constant and η (x,y) is a dimensionless tensor function. Then the effective conductivity has the form σ* (σ) =σ0η* (η), where the tensor η* is also dimensionless. In this paper we prove that η* satisfies the relation ηR* (ηR−1) η* (η) =1̂, where 1̂ is the unit tensor and the subscript R indicates the tensor obtained by rotating the coordinate system through 90°. If the system is locally, but not necessarily statistically, isotropic and x and y are the principal axes of the effective conductivity, then the above relation becomes ηx* (η) ηy* (η−1) =1.
Electrical resistivity of beryllium
Authors: Mitchell M. A.
Published: February 2003

Measurements have been made of the electrical resistivity of two single crystals of beryllium parallel and perpendicular to the hexagonal c axis, respectively, between 4 and 800 °K. The resistance ratios were 10.0 and 15.5 for the parallel and perpendicular directions, respectively. The anisotropy of the temperature-dependent part of the resistivity was about 35% (ρi∥ being higher) at room temperature in contrast to 12% found by Grüneisen and Erfling. The anisotropy was approximately constant in temperature above 273 °K and decreased rapidly below. The Bloch-Grüneisen equation was fit to the data. The characteristic temperatures were ϑR=1246±1 and 1202±1 °K for the parallel and perpendicular directions, respectively.
Vacuum arc anode plasma. I. Spectroscopic investigation
Authors: Bacon F. M.
Published: February 2003

A spectroscopic investigation was made of the anode plasma of a pulsed vacuum arc with an aluminum anode and a molybdenum cathode. The arc was triggered by a third trigger electrode and was driven by a 150-A 10-μs current pulse. The average current density at the anode was sufficiently high that anode spots were formed; these spots are believed to be the source of the aluminum in the plasma investigated in this experiment. By simultaneously measuring spectral emission lines of Al I, Al II, and Al III, the plasma electron temperature was shown to decrease sequentially through the norm temperatures of Al III, Al II, and Al I as the arc was extinguished. The Boltzmann distribution temperature TD of four Al III excited levels was shown to be kTD/e=2.0±0.5 V, and the peak Al III 4D excited state density was shown to be about 5×1017 m−3. These data suggest a non-local-thermodynamic-equilibrium (non-LTE) model of the anode plasma when compared with the Al3+ production in the plasma. The plasma was theoretically shown to be optically thin to the observed Al III spectral lines.
Vacuum arc anode plasma. II. Collisional-radiative model and comparison with experiment
Authors: Bacon F. M. , Watts H. A.
Published: February 2003

A one-dimensional model describing the ionization and excitation of Al2+ ions in the anode plasma of a vacuum arc is developed using collisional-radiative ionization and recombination coefficients. The model is constructed so that local thermodynamic equilibrium (LTE) is approached in the collision-dominated limit; however, when the results of the model are compared with the experimental data, the anode plasma is shown not to be in LTE. The experimental and theoretical results are shown to be consistent for Ne?5×1020 m−3 and kTe/e?30 V within about 0.3 mm of the anode surface. At distances greater than 0.3 mm from the anode, kTe/e<15 V. The change in Te at Z=0.3 mm suggests that a potential ’’hump’’ exists in the anode plasma out to Z=0.3 mm. Theoretical Al2+ excited-state densities are shown to be related by a Boltzmann factor with a ’’temperature’’ that is considerably less than and independent of the electron temperature in the plasma.
Interfacial barrier height measurement from voltage dependence of the photocurrent
Authors: Gundlach K. H. , Kadlec J.
Published: February 2003

Powell’s method of barrier height determination which does not require knowledge of the absorbed light power is slightly modified for application to asymmetric MIM sandwich structures. An experimental result of this method is presented and compared with that of the conventional Fowler plot.
Three-mirror double-pass laser
Authors: Oettinger P. E.
Published: February 2003

A new laser configuration is conceived and tested, wherein intracavity quarter-wave plate and beam splitting polarizer produce laser oscillations between three mirrors. The main advantages of this configuration are to offer choice of polarization output from a single cavity and to increase the efficiency of specific lasers.
On the characteristics of a transversely magnetized parallel-plane waveguide containing moving plasma
Authors: Mukherjee Pradeep K.
Published: February 2003

Some properties of a transversely magnetized parallel-plane waveguide containing moving plasma have been studied. Expressions are obtained for the dispersion relations and the field components for the TE and the TM modes excited in the waveguide. Analytic expressions are also derived for the cutoff frequencies of these modes. It is found that the characteristics of a TE mode remain unaffected by the velocity of the moving medium and the presence of an ambient magnetic field.
Laser emission cross section of the system LiNd0.5M0.5P4 O12 (M=Gd, La)
Authors: Otsuka Kenju , Nakano Jun’ichi , Yamada Tomoaki
Published: February 2003

The laser-related spectroscopic parameters such as the laser transition cross section and fluorescence lifetime of the compositions LiNd0.5Gd0.5P4012 and LiNd0.5La0.5P4O12 were examined. The products of the measured emission cross section and fluorescence lifetime of the 4F3/2 manifold in the mixed crystals were estimated to be very close to the product in the pure LiNdP4012 crystal. The laser emission was linearly polarized along the pseudoorthorhombic c axis of the crystal in these mixed crystals, as was done for LNP.
The effect of ion-cyclotron motion on the transverse interactions in beam-plasma systems
Authors: Demokan O.
Published: February 2003

In this work the instability of the transverse modes with left-hand polarization and frequencies around the ion-cyclotron frequency, propagating parallel to an external magnetic field in an unbounded homogeneous electron beam-plasma system, is investigated. The beam velocity is assumed to be parallel to the magnetic field. The ion distribution is assumed to have a certain velocity spread perpendicular to the external magnetic field, as a result of a possible ion-cyclotron resonance interaction with the instability. It is shown that even for very small values of this average perpendicular velocity the instability ceases to exist, practically regardless of the value of the beam velocity.