bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupled Molecular Flow and Surface Diffusion. Application to Cesium Transport
Authors: Bates T. R. , Forrester A. T. 
Published: January 2005

The mechanisms of cesium transport through a cylindrical tungsten tube are now understood to consist of surface diffusion, molecular flow and ionic flow under the influence of electric fields which exist in the tube. In this paper an exact transport equation is developed for the idealized case of pure molecular flow coupled with surface diffusion. This takes the intractable form of a nonlinear integrodifferential equation of second degree. This is analytically reduced to a nonlinear form of Fredholm's integral equation suitable for solution by numerical iteration.
The Langmuir adsorption and diffusion data for cesium on tungsten are introduced and the approximate domain of convergence for the integral equation is found by the use of an appropriate existence theorem. Sample solutions are shown including one which satisfies required boundary conditions at the orifices.
Intrinsic Brittle Strength of Magnesium Oxide Bicrystals
Authors: Lange F. F. , Buessem W. R. 
Published: January 2005

The intrinsic brittle strength (i.e., without dislocation motion) was obtained for MgO bicrystals of various misorientations. Bicrystal fracture always occurred at the grain boundary. Strength values ranged between 70 000 psi and 370 000 psi. Two modes of fracture were observed: intergranular and intragranular fracture. The latter occurred only at high strain energies. Secondary cracks, believed to originate from flaws on the grain-boundary surface, were observed for all bicrystal specimens that fractured in a brittle manner.
Tensile stresses as high as 400 000 psi were obtained on single crystals of MgO before ductile fracture occurred.
Dislocation Pile-Ups against a Locked Dislocation of a Different Burgers Vector
Authors: Chou Y. T. 
Published: January 2005

The classical analysis of Eshelby, Frank, and Nabarro of a linear dislocation pile-up is generalized to include the case in which the locked dislocation may have a Burgers vector of mb, where b is the Burgers vector of free dislocations and m is a positive real number. The equilibrium positions of (n−1) free dislocations piled up against the locked dislocation under a uniform applied stress are given by the roots of the Laguerre polynomial Ln−1(2m−1). Simple expressions for the distance between the locked and nearest free dislocation, x1, the length of the pile-up, L, and the stress at its tip, σtip, are obtained. Increasing m will increase x1 and decrease σtip, while L is only slightly extended. For large n the stress field within a certain distance range around the tip is found to be independent of m.
Based on the Petch model of yielding it is shown that increasing m increases the Hall-Petch slope by a factor of (m)1/2. The effect of m on the coalescence of leading dislocations leads to a higher-fracture stress if m is increased.
Effect of Alloying on Aluminum K and Copper L X-Ray Emission Spectra in the Aluminum-Copper System
Authors: Baun William L. , Fischer David W. 
Published: January 2005

Data for the Al K emission band, Al Kα satellites and Cu LIII band in Al-Cu alloys (10%–100% Al) are presented. Significant changes in the spectra are noted with changes in composition. The Al K emission band is split and the long-wavelength component shifts to longer wavelengths and becomes dominant with a decrease in Al concentration. The short-wavelength component shifts only slightly and maintains the typical sharp, short wavelength-emission edge seen in pure aluminum. Separation between high- and low-energy components in the Al K band is as much as 4 eV (10% Al) and extrapolates to about 4.5 eV for very dilute alloys, which is nearly the calculated excitation energy of 3s2→3s3p in Al+. The Al K satellites Kα3 and Kα4 show corresponding intensity changes with alloy composition. The intensity ratio Kα4/Kα3 changes linearly (for 6-kV excitation) from 0.48 in Al to 0.70 in 10 Al-90 Cu.
The Cu LIII band also shows changes in shape with alloying but the changes are not as large as observed for the Al K band. The copper band shifts linearly to lower energy as more and more aluminum is added.
Wave Interactions with Moving Boundaries
Authors: Tsai C. S. , Auld B. A. 
Published: January 2005

The general theory of the double Doppler effect is reviewed for both vacuum and material media. Frequency and amplitude changes in the reflected and transmitted waves at a partially reflecting moving interface are calculated for cases in which the medium behind the interface: (a) moves at a different velocity than the interface; (b) moves at the interface velocity; (c) is stationary. The advantages of case (c) for practical frequency conversion are discussed.
Multiple moving interfaces in a stationary medium are also considered. On the basis of this theory, Doppler shifts at moving, tapered transition regions are analyzed as a series of discrete, closely spaced steps. This shows that the frequency conversion of the transmitted wave is independent of the slope of the taper. By use of a transmission line model, a simple physical explanation is given for the double Doppler effect in a moving taper.
Ultrasonic Attenuation in Aluminum Ammonium Alum and Aluminum Potassium Alum
Authors: Marshall B. J. , Pederson D. O. , Bailey W. E. 
Published: January 2005

The attenuation of 10-Mc/sec sound waves in AlNH4(SO4)2·12H2O and AlK (SO4)2·12H2O over a temperature range of 300° to 4.2°K has been measured. Results, which are available for both longitudinal and transverse waves propagated in the [111], [110], and [100] directions show that there are some very large absorption peaks occurring in the temperature range between 80° and 120°K.
The complex dielectric constants of these alums have also been measured using the same frequency and directional dependence as that used in the ultrasonic attenuation measurements. The results, presented in this paper, show that the real and imaginary parts exhibit peaks in the same temperature region as that for the ultrasonic attenuation peaks.
It is believed that these results might be associated with a Debye type of relaxation in solids.
Behavior of Passing Dislocations in Superlattices
Authors: Marcinkowski M. J. , Lakso G. 
Published: January 2005

A detailed computer analysis has been made of the behavior associated with the passage of pairs of superlattice dislocations on neighboring parallel slip planes for the specific case of the Fe3Si alloy. The treatment has been carried out for superlattice screw and edge dislocations of like and unlike sign for a series of vertical passing distances. In particular, the equilibrium separation between the individual ordinary dislocations constituting the superlattice dislocation has been determined as a function of distance between the pair of superlattice dislocations. In addition, the passing forces as well as the cross slip and climb forces associated with the dislocations have been calculated.
It has been found that cross slip of superlattice screw dislocations with mutual annihilation, if they are of unlike sign, will occur for passing separations of 100 Å or less. Superlattice edge dislocations can, however, be passed by one another at much closer distances, which results in the uncoupling of the superlattice dislocation. Furthermore, the extension of the superlattice dislocations oscillates strongly as they pass one another. All of these results are in general agreement with observations obtained with the Fe3Si superlattice.
Ionization Waves in Semiconductors and Gaseous Plasmas
Authors: Weissglas Peter , Andersson Bengt 
Published: January 2005

A theory for ionization waves in plasmas is developed. If the ionization rate depends strongly on carrier temperature such waves may propagate and an instability, which in some cases is absolute, can occur. The wave has a phase velocity opposite the electron drift and can have either positive or negative group velocity. The theory agrees qualitatively, but not in detail with that previously developed by Pekarek for striations in gasous discharges.
In particular, the theory is applied to InSb, which is a favorable solid-state material for observations of ionization waves. Instabilities are predicted for thin layers of intrinsic material.
It is also shown that the temperature dependence of the ambipolar diffusion coefficient can give rise to an instability which is independent of the ionization phenomena.
Behavior of Ultrathin Zirconium Films upon Exposure to Oxygen
Authors: Fehlner Francis P. 
Published: January 2005

Discontinuous films of zirconium, having surface resistivities between 104 and 106 Ω sq−1, were deposited on glass substrates in ultrahigh vacuum and then exposed to oxygen pressures in the range of 5×10−7 to 4×10−8 Torr at temperatures of 25° and −196°C. The change in film resistance with time was monitored and a plot of logR vs logt was constructed. This graph was initially concave upwards, but became linear after a time which was characteristic of monolayer formation.
An interpretation of the film behavior was based on the transport of electrons by tunneling through gaps separating the metal islands. The initial change in film resistance was caused by an increase in the zirconium work function. This increase was due to oxygen monolayer formation. The subsequent linear log-log behavior was caused by an increase in the tunneling distance which resulted from oxidation of the metal islands.
Values for both the interisland spacing and the room-temperature oxidation rate constant have been calculated from the experimental data. Both impurities and the heat of adsorption interfered with determining a value for the interisland spacing, but when these interferences were eliminated, a distance of 6.9 Å was found for a 104 Ω sq−1 film. The oxidation rate constant for a comparable film at 25°C was 4×10−9 cm with an activation energy of 0.3 kcal mole−1.
Pumping speeds also were determined. Zirconium initially pumped oxygen at ≈1500 ml·sec−1·cm−2. The sticking coefficient for oxygen on a partially oxygen covered zirconium surface was approximately 0.05.
Method for Pulsewidth Measurement of Ultrashort Light Pulses Generated by Phase-Locked Lasers using Nonlinear Optics
Authors: Weber H. P. 
Published: January 2005

A nonlinear optics experimental arrangement is proposed for the measurement of the pulsewidth of ultrashort light pulses. The experiment consists of a Michelson-like arrangement in which each light pulse is split into two pulses which are delayed and polarized orthogonally to one another. The two pulses are propagated as ordinary and extraordinary rays through a nonlinear crystal whose orientation is chosen so that the second harmonic is only generated by the interaction arising from the superposition of these two pulses. The pulsewidth is obtained from the dependence of the intensity of the second harmonic upon the relative delay of the pulses. This method suggests itself for coincidence measurements of pulse delays including those due to optical path variations.
The experimental arrangement is given and an analysis for light pulses from an ideal phase locked laser is carried out. The resolution time of the coincidence method as limited by phase matching considerations is calculated. For the example of a phase-locked Nd laser and a 1-mm-thick KDP crystal the numerical value of the resolution time is about 1 psec.
Generation of Giant Pulses from a Neodymium Laser with an Organic-Dye Saturable Filter
Authors: Cross Lee A. , Cheng Charles K. 
Published: January 2005

There has been much recent interest in the production of high-peak power laser pulses by regeneration switching. Organic dyes have been used as saturable filters for both the ruby (cyanine dyes) and neodymium (a polymethine dye) to produce single high-power spikes.
The cyanine dye, in suitable concentration and path length, can also be used to produce a long train of slightly enhanced (gain about 10) regular Q-switched spikes from the ruby laser, but the neodymium laser can apparently only be operated in the single-pike mode. This paper reports the discovery of saturable filter action in a common dye, rose bengal, a derivative of fluorescein, which permits the production of an extremely regular sequence of enhanced spikes from the neodymium laser. Unlike the previous dyes, the transition corresponding to the saturable absorption occurs between two excited states, not between the ground state and an excited state. The population of the lower excited state is achieved by optical pumping of the dye solution, and, by varying the intensity of the pumping flash lamp, the optical density of the filter may be altered thus changing the spacing between light spikes as well as their height.
Nature of the Electrical Conduction Transients Observed in CeO2 and Ca-Doped CeO2
Authors: Blumenthal R. N. , Pinz B. A. 
Published: January 2005

The electrical conduction transients of CeO2 and ca-doped CeO2 were investigated by employing a constant-current dc power source and a six-probe high-resistance input-isolated recording system.
In contrast to the observations made by Kevane et al. neither voltage-time transients nor non-Ohmic behavior were observed when high-purity CeO2 (99.9% min.) was investigated in the temperature range 300° to 1000°C.
Transients were observed for the high-purity CeO2 specimen when loading due to the instrumentation occurred or when high current densities due to a small contact area were used at the contacts. A model based on electrolysis was used to explain these results.
Voltage transients at constant current were observed on a CeO2 specimen doped with 1 wt% CaO in argon but not in oxygen. These transients increased with increasing temperature in contrast to the observations made by Kevane.
At 960°C in argon potential distribution curves at several different times showed that the electrical conductivity increases with time and was larger at the negative end of the sample than at the positive end where the conductivity decreases with time initially. After longer periods of time the conductivity increased over the entire specimen. In addition the specimen exhibited a discolored region; the intensity of the discoloration decreased with increasing distance from the cathode. After reoxidation at 1000°C in air the discolored region disappeared and the weight of the specimen increased. These results were explained in terms of a model that assumed blocking of the oxygen vacancies and oxygen ions at the cathode and anode, respectively. The electrons were then distributed so that electroneutrality was preserved. Thus the electrical conductivity was dependent upon the distribution of the oxygen vacancies and the oxygen ions. After longer times the voltage transients were controlled by electrolysis.
Longitudinal Magnetoresistance and Hall Mobility of n-Type Germanium at High Electric Fields
Authors: Nag B. R. , Paria H. , Guha S. 
Published: January 2005

The longitudinal magnetoresistance and Hall mobility of 5-Ω·cm n-type germanium have been measured for electric fields applied in the (111) direction up to 4 kV/cm. It has been found that (i) longitudinal magnetoresistance at a particular electric field decreases with an increase in the magnetic field, (ii) for small magnetic fields the longitudinal magnetoresistance decreases with an increase in the electric field, and (iii) the Hall mobility and the ratio of Hall mobility to the conductivity mobility decrease with an increase in the electric field.
The experimental value for fields above 1 kV/cm are found to agree with the theoretical values calculated with the assumptions that (i) the scattering is due to the acoustic, optical, and intervalley phonons, (ii) the average energy of the electrons is much larger than that of the optical phonons, (iii) the intervalley phonons affect only the carrier repopulation in the different valleys, and (iv) the value of the optical-phonon deformation potential constant is 0.8×109 eV/cm.
Nature of Electrical Contact between Tarnished Surfaces
Authors: Tripp J. H. , Snowball R. F. , Williamson J. B. P. 
Published: January 2005

The variation of contact resistance with temperature has been measured on clean and tarnished silver contacts between 77° and 420°K. It is shown that the temperature coefficient of resistance provides a direct method of distinguishing film conduction from metallic conduction in contacts, and conversely that a single measurement at room temperature cannot reliably yield this information. Clean contacts have the positive temperature coefficient of resistance of the conductor metal. A film-covered contact on the other hand exhibits either of two distinct types of temperature dependence: one with a large negative temperature coefficient, and one that is metallic. It is suggested that these occur according to whether mechanical contact is made on the film or through a small fissure in it. If the contact is mechanically disturbed, the nature of the conduction fluctuates randomly between these two modes.
Further, the temperature coefficient of resistance provides a means for distinguishing between semiconducting and tunneling contacts. The experimental observations on silver sulfide tarnish film suggest that electron tunneling is dominant at cryogenic temperatures, but that at normal temperatures the film is an n-type semiconductor.
Elastic Moduli of Single-Crystal Spinel at 25°C and to 2 kbar
Authors: Schreiber Edward 
Published: January 2005

The elastic properties of a synthetic single-crystal spinel with a composition of MgO·2.6Al2O3 have been determined at 25°C and up to 2 kbar by measuring propagational velocities of ultrasonic waves using the method of pulse superposition. The isotropic moduli and Poisson's ratio were computed from the single-crystal values using the Voigt-Reuss-Hill approximation.
Values of the adiabatic elastic moduli at 1 bar and 2 kbar and at 25°C are c11c12c441 bar2985.71537.21575.8(kbar)2 kbar2995.51545.01577.5(kbar).
The adiabatic bulk modulus was computed to be 2019.9 kbar, and the pressure derivative of the adiabatic bulk modulus was found to be 4.18.
Thick Cylindrical Coil Systems for Strong Magnetic Fields with Field or Gradient Homogeneities of the 6th to 20th Order
Authors: Garrett Milan Wayne 
Published: January 2005

For strong homogeneous fields the ideal loop and solenoid elements of a prototype system may be expanded into thick cylindrical coils whose current density is (a) uniform or (b) inversely proportional to the cylindrical radius. Error coefficients of the zonal harmonic series for field or gradient that are cancelled in any given prototype continue to vanish as the elements are expanded, even to fusion, if at each stage the coil boundaries are adjusted by an iterative method. This involves the use of (a) the harmonic source functions Un* or (b) the Legendre functions Pn; either set is best computed by a recursion formula. An alternative method based on Lyle's principle requires no iterations and only trivial calculations. Though it also is valid for systems of any order, it can only expand a set of loops into coils with square cross sections of limited area. Also, the true null coefficients are replaced by small residues proportional to 4th and higher powers of the section dimensions when the second method is used.
The number of tabulated prototype systems of the 6th and 8th orders is increased to more than 200. Since multiply infinite sets of prototypes can be computed for every order higher than the 8th, univariate tables would be inadequate and only a few illustrative examples of such systems are given. Some 150 thick-walled systems of the 6th or 8th order are listed in several tables, but such a selection can only suggest the wide range of possibilities. These systems have more degrees of freedom than do the corresponding prototypes, and even the 6th order is multivariant. At the 8th order and beyond, the growing redundancy of variables permits the design of systems with a common current density in all coils and with all section dimensions proportional to a set of small integers. Systems of order 4n have paired coils with gaps for lateral access, an advantage that is lacking in the 6th-order designs.
Efficient computer programs have been written to design systems of all the types so far enumerated, including multiple sets of both prototypes and fully adjusted systems of thick coils for orders from 8 to 20 in steps of 4. Since adequate tabulation of results is ruled out by their diversity and sheer bulk, in view of the wide range of potential applications the programs themselves must be considered the basic research tool. They will be described in detail elsewhere.
As a measure of field inhomogeneity, including contributions from all orders and from both axial and radial field components, the concept of total vector error is developed. The tables include error limits for all systems, and some 40 systems or their error contours are shown in the figures.
Effect of Stacking Faults and Twins on the Coercive Force of Thin Magnetic Films
Authors: Walker G. A. , Larson H. W. 
Published: January 2005

The effects of fairly high densities of extrinsic stacking faults (α approximately as large as 0.3) and twins (β approximately as large as 0.15) on the coercive force, Hc, of thin (less than 700 Å) ferromagnetic Fe-Co-Ni films are studied.
Once the effects of strain and small crystallite size on Hc are eliminated, it can be shown that stacking faults and twins increase the Hc, stacking faults having a larger effect than the twins. The introduction of the faults was achieved by sputtering onto ``unclean'' substrates, which gave an initial small-crystallite-size layer of about 100 Å, where the crystallite size gradually increased to that found on ``clean'' substrates. At the intersection of the two layers, there was a layer of faults extending about 200 Å into the larger-crystallite-size film. The x-ray technique used to evaluate thickness variation of faults is described.