Showing papers by "Sandia National Laboratories published in 1979"

Basic Linear Algebra Subprograms for Fortran Usage

Abstract: A package of 38 low level subprograms for many of the basic operations of numerical linear algebra is presented. The package is intended to be used with FORTRAN. The operations in the package are dot products, elementary vector operations, Givens transformations, vector copy and swap, vector norms, vector scaling, and the indices of components of largest magnitude. The subprograms and a test driver are available in portable FORTRAN. Versions of the subprograms are also provided in assembly language for the IBM 360/67, the CDC 6600 and CDC 7600, and the Univac 1108.

The Use of the Rank Transform in Regression

Abstract: The rank transform is a simple procedure which involves replacing the data with their corresponding ranks. The rank transform has previously been shown by the authors to be useful in hypothesis testing with respect to experimental designs. This study shows the results of using the rank transform in regression. Two sets of data given by Daniel and Wood [8] are considered for purposes of illustrating the rank transform in simple and multiple regression. Also given are the results of a Monte Carlo study which compares regression on ranks with some published Monte Carlo results on isotonic regression. This Monte Carlo study is also modified to compare regression on ranks with robust regression. Another illustration gives the results of analyses on large computer codes by regression on ranks. The rank transform is a simple, repeatable process that compares favorably with other methods such as given by Andrews [1]. Our studies indicate the method works quite well on monotonic data.

Controllability/observability analysis of digital circuits

Abstract: The testability of a digital circuit is directly related to the difficulty of controlling and observing the logical values of internal nodes from circuit inputs and outputs, respectively. This paper presents a method for analyzing digital circuits in terms of six functions which characterize combinational and sequential controllability and observability.

A User’s View of Solving Stiff Ordinary Differential Equations

Abstract: This paper aims to assist the person who needs to solve stiff ordinary differential equations.First we identify the problem area and the basic difficulty by responding to some fundamental questions...

Preparation and Properties of Yttrium-Silicon-Aluminum Oxynitride Glasses

Abstract: Glasses containing up to 7 at. % nitrogen were prepared in the system Y-Si-Al-O-N. The glass transition temperature, hardness, and relative fracture toughness increase and the thermal expansion coefficient decreases with increasing nitrogen content. Weight losses after 350 h in 95/sup 0/C distilled water are not simply related to nitrogen content, but for some compositions they are half that reported for fused silica. The electrical conductivity at 548/sup 0/C and 10 kHz is 7.8 x 10/sup -10/ (..cap omega...cm)/sup -1/ for one composition. Fourier transform ir spectroscopic analysis indicates the presence of Si-N bonds in the glasses. The data suggest that nitrogen substitutes for oxygen in the glass network to produce a more highly cross-linked structure.

Application of the superposition principle to solar-cell analysis

Abstract: The principle of superposition is used to derive from fundamentals the widely used shifting approximation that the current-voltage characteristic of an illuminated solar cell is the dark current-voltage characteristic shifted by the short-circuit photocurrent. Thus the derivation requires the linearity of the boundary-value problems that underlie the electrical characteristics. This focus on linearity defines the conditions that must hold if the shifting approximation is to apply with good accuracy. In this regard, if considerable photocurrent and considerable dark thermal recombination current both occur within the junction space-charge region, then the shifting approximation is invalid. From a rigorous standpoint, it is invalid also if low-injection concentrations of holes and electrons are not maintained throughout the quasi-neutral regions. The presence of sizable series resistance also invalidates the shifting approximation. Methods of analysis are presented to treat these cases for which shifting is not strictly valid. These methods are based on an understanding of the physics of cell operation. This understanding is supported by laboratory experiments and by exact computer solution of the relevant boundary-value problems. For the case of high injection in the base region, the method of analysis employed accurately yields the dependence of the open-circuit voltage on the short-circuit current (or the illumination level).

Symmetric and Asymmetric Encryption

Abstract: All cryptosystems currently m use are symmetrm m the sense that they require the transmitter and receiver to share, m secret, either the same pmce of reformation (key) or one of a paLr of related keys easdy computed from each other, the key is used m the encryption process to introduce uncertainty to an unauthorized receiver. Not only is an asymmetric encryption system one in whmh the transmitter and receiver keys are different, but in addition it Is computatmnally mfeaslble to compute at least one from the other. Asymmetric systems make it possible to authent2cate messages whose contents must be revealed to an opponent or allow a transmitter whose key has been compromised to communmate m privacy to a receiver whose key has been kept secret--neither of which is possible using a symmetric cryptosystem. This paper opens with a brmf dmcussion of encryptmn principles and then proceeds to a comprehensive discussion of the asymmetric encryptmn/decryp tion channel and its application m secure communmations.

Pair potentials for fcc metals

Abstract: Long-range pair potentials are presented for the fcc metals Ni, Au, Ag, Pt, Pd, Cu, and Al. Experimental data considered in deriving the potentials include the sublimination energies and stacking-fault energies as well as the lattice parameters, elastic constants, and vacancy-formation and -migration energies. A volume-dependent energy term has been included in the potentials. By scaling the potentials with respect to lattice spacing and a characteristic binding energy, a striking similarity can be seen between the various potentials. These potentials have been used to calculate a variety of point-defect properties including self-interstitial geometries and migration energies. In addition the migration energy of helium and its binding energy to a vacancy have been calculated.

Effects on Photoemission of the Spatially Varying Photon Field at a Metal Surface

Abstract: Enhancement of photoionization cross sections due to spatially varying photon fields at a metal surface has been observed in the normal-emission cross sections for the surface state and Fermi level of A1(100) at photon energies between 9 eV and 23 eV. The data for Fermi-level photoexcitation are in excellent agreement with theoretical results for jellium. Below $\ensuremath{\hbar}{\ensuremath{\omega}}_{p}$, the predominant contribution to the photoionization matrix element comes from the spatially varying fields, which provide the momentum required for photoexcitation.

Techniques for reducing thermal conduction and natural convection heat losses in annular receiver geometries

Abstract: An effective device for the collection of solar energy which has received widespread attention is the so called parabolic-cylindrical solar collector. In this design a circular receiver tube, with a suitable selective coating, is enclosed by a concentric glass envelope and situated along the focal line of a parabolic trough reflector. The heat transfer processes which occur in the annular space between the receiver tube and the glass envelope are important in determining the overall heat loss from the receiver tube. In typical high temperature receiver tube designs the rate of energy loss by combined thermal conduction and natural convection is of the same order of magnitude as that due to thermal radiation, and can amount to approximately 6 percent of the total rate at which energy is absorbed by the solar collector. The elimination of conduction and natural convection losses can significantly improve the performance of a large collector field. Several techniques useful for the reduction of energy loss by thermal conduction and natural convection are considered. The receiver configuration chosen for study is typical of those used in the Solar Total Energy System at Sandia Laboratories. The receiver tube has a ''black chrome'' selective coating and is 2.54 more » cm in outside diameter. The inside diameter of the glass envelope is approximately 4.4 cm. Typical operating temperatures of the receiver tube and glass envelope are approximately 300/sup 0/C and 100/sup 0/C, respectively. « less

Bound, odd-parity J = 1 spectra of the alkaline earths: Ca, Sr, and Ba

Abstract: We have used multiphoton excitation via selected intermediate states to observe and identify triplet Rydberg series of the type msnp3P0 up to high n in Ca, Sr, and Ba. Previous efforts have failed to identify these series beyond n = 7. We present details of our experimental method, give tables of the newly determined energy levels, and describe their analysis by multi-channel quantum defect theory (MQDT). For the most part, the msnp3P0 series in Ca and Sr can be described by a nearly constant quantum defect δ with δCa = 19.7 and δSr = 2.90. The 6s n p3P0 series in Ba is more heavily affected by the configuration interaction, but to a reasonable approximation has δBa ≈ 3.81. For all three elements, we find that the msnp¹P10 series are much more strongly perturbed than the ³P10 series. Most of this paper treats Ba. In addition to the 3P0 states, 3F2 and 1G4 states are measured and tabulated. Further results in Ba include new and/or revised values for some ¹P10 states a revised ionization limit, evidence for an energy-dependent configuration interaction, and an MQDT prediction of the photoabsorption cross section at the ionization limit. This prediction agrees with the most recent experimental cross section. The MQDT analysis of Ba is described in great detail to make it useful as a guide to the reader who wishes to become a user of MQDT.

Small-Polaronic Diffusion of Light Interstitials in bcc Metals

Abstract: The small-polaronic diffusion associated with simple models of light interstitials in bcc metals has been investigated. By transcending the simplifications which are often introduced in studying electronic small-polaron transport, we calculate diffusion coefficients which are reasonably consistent with available data. In particular, an explanation of the ''anamalous'' isotope dependence observed for hydrogen diffusion in bcc metals emerges from these studies.

Diagnosing Power Quality-Related Computer Problems

Abstract: Total reliance on sensitive electronic systems for such important functions as data processing, communications, and process control is now a way of life in our commercial, industrial, and governmental activities. This development has necessitated a new concern toward the quality of the electric power supply. Intermittent power disturbances, capable of disrupting electronic equipment are inherent to both commercial and industrial power systems. Any disruption causing downtime and financial loss, power-related or otherwise, is likely to precipitate a study to determine appropriate corrective actions. Unfortunately, analyzing the cause and effect of power disturbances can be difficult, particularly when sophisticated computer systems are involved. The ultimate purpose is to assist the electronic equipment users in reducing power-related downtime.

Stability of high-temperature polymers

Abstract: Thermal stability of aromatic-heterocyclic organic polymers is surveyed. Highest stabilities were observed with step ladder (SL) and ladder (L) type polymers. Aliphatics were the most stable. Crosslinking generally results in enhanced stability. The stability of polymers containing fused rings appears to decrease as the number of fused chain segments increases. The effect of pendant groups depends on the nature of the group as well as the polymer to which it is bonded. (FS)

Algorithm 539: Basic Linear Algebra Subprograms for Fortran Usage [F1]

Abstract: Received 13 July 1977. Perm~sion to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. The work of the fast and fourth authors was supported by the National Aeronautics and Space Administration under Contract NAS 7-100. The work of the second author was supported by the U.S Energy Research and Development Administration (ERDA) under Contract AT (29-1)-789 and (at Washington State University) by the Office of Naval Research under Contract NR 044-457. Authors' addresses: C.L Lawson, Jet Propulsion Laboratory, M/S 125-128, 4800 Oak Grove Drive, Pasadena, CA 91103; R.J. Hanson, Numerical Mathematics, I :~. 5122, Sandia Laboratories, Albuquerque, NM 87115; D.R. Kincaid, Center for Numerical Analysis, The University of Texas at Austin, Austin, TX 78712; F.T. Krogh, Jet Propulsion Laboratory, M/S 125-128, 4800 Oak Grove Drive, Pasadena, CA 91103. © 1979 ACM 0098-3500/79/0900-0324 $00.75

Correlation effects in hopping transport

Abstract: The effects of intersite Coulomb interactions on transport in a system of localized states is examined. Correlation effects are seen to inhibit the DC conduction but to enhance the AC conduction. It is shown that the interactions lead to a Coulomb gap in the one-electron excitation spectrum for DC conduction of width E g ∝ E c (E c /W) 1 2 , where E c is the average intersite Coulomb energy and W is the random potential. The need to excite across the Coulomb gap can be alleviated by multi-electron hopping, which can lead to a non-activated T − 1 4 -like behavior as transport becomes collective in nature. Examples of systems where correlations effects have been observed are given. The possibility of a many-electron delocalization is also discussed.

Numerical Simulation of Turbulent Mixing Layers via Vortex Dynamics

Abstract: The simple concept of effective transport coefficients for turbulent flows is starting to be replaced with the realization that turbulent flows consist of structures which are created and destroyed, and it is their interactions that produce the transport of mass, momentum, and energy. The bursting phenomena in boundary layers is one aspect of that structure, and vorticity (or eddy) pairing is the structure of the turbulent mixing layer. This paper describes numerical experiments using discrete vortices in order to determine to what detail they can simulate the planar turbulent mixing layer. Calculations involving several thousand vortices have duplicated the mixing layer growth, eddy pairing, turbulent shear-stress profile, and root mean square velocity fluctuations of moderate Reynolds number flows. With the exception of the normal rms velocity fluctuation, good agreement is also found at high Reynolds number.

Thermal expansion of amorphous metals

Abstract: The thermal expansion of three commercial amorphous metals has been measured from room temperature to above the crystallization temperature. The results clearly demonstrated the glassy nature of these materials and show the reduction in volume which results from crystallization. The glass transformation temperature is more evident here than on the usual differential scanning calorimeter curves. The activation energies associated with the glass transformation and crystallization are derived from data taken as a function of heating rate. The measured temperatures for the glass transformation and crystallization from the thermal expansion measurements are the same as those obtained from DSC measurements at the same heating rate.

Direct measurement of electron emission from defect states at silicon grain boundaries

Abstract: The first direct measurements of charge emission from silicon grain-boundary defect states have been made by monitoring the recovery of the nonequilibrium grain-boundary barrier capacitance. The density of grain-boundary states obtained in this fashion is in excellent agreement with the values found from deconvoluting room-temperature $I\ensuremath{-}V$ data. These data are shown to suggest strongly that the double-depletion-layer/thermal-emission model gives a good description of silicon grain boundaries.

Vacancies and the Chemical Trapping of Hydrogen in Silicon

Abstract: The first evidence for Si${\mathrm{H}}_{1}$-like centers in crystalline Si ($c$-Si) is presented from infrared measurements of H (D) implanted at 80 K. In contrast to Si${\mathrm{H}}_{1}$ centers in amorphous Si ($a$-Si) which are stable to \ensuremath{\approx} 700 K, the crystalline band anneals below 300 K with an activation energy and illumination enhancement that are characteristic of the Si vacancy. These results relate specific defects for implanted H in $c$-Si to previous observations for H in $a$-Si.

Scaled electron ionization cross sections in the Born approximation for atoms with 55< or =Z< or =102

Abstract: Using the generalized oscillator-strength formulation of the Born approximation, the author calculated electron ionization cross sections for all significant subshells of every fourth atom with 58< or =Z< or =102, and for Hg. The calculations used approximate Herman-Skillman wave functions and eigenvalues. The cross sections were put in scaled form, depending essentially on ionization energy only. The scaled cross sections were used with experimental energies to calculate the cross sections for Cs, Cs/sup +/, Ba, Ba/sup +/, Au, Hg, Tl, Tl/sup +/, and Pb. The cross sections so calculated were in good agreement with the measurements. Both inner-shell ionization and excitation followed by autoionization were prominent contributors to the cross section. The scaling procedure was used to calculate the electron ionization cross section of the noble-gas metastable levels, and there is excellent agreement with measured values for Ne and A. The scaling procedure was used to calculate cross sections for the sequential ionization Ni/sup +1/--Ni/sup +14/ and Au/sup +3/--Au/sup +14/, which were compared with cross sections obtained from the semiempirical expression of Lotz. Good agreement was found for the Ni ions, but there was poor agreement for the Au ions. Lotz's expression is a factor of 3 smaller than ourmore » scaled cross section for the 4d, 4f, and 5d subshells. It is suggested that the absence of measurements on these subshells precluded correct parametrization in the semiempirical expression of Lotz.« less

Correlation of nosetip boundary-layer transition data measured in ballistics-range experiments

Abstract: Preablated nosetips of various carbonaceous materials were tested in a ballistics range. Surface-temperature contours, measured with image-converter cameras, were used to define boundary-layer transition-front contours. Measurements of surface roughness, surface temperature, average transition-front location, and freestream environment were combined with calculations of nosetip flowfields, and with calculations of laminar boundary-layer development in these flowfields, to transform all data into various dimensionless parameters. These parameters were defined by previous attempts to correlate existing wind-tunnel data for transition on rough/blunt bodies. Of the available correlating techniques, only one, based on the concept of a constant (critical) roughness Reynolds number for transition, was found to successfully describe both the wind-tunnel and ballistics-range data, thereby validating the extrapolation of this concept to actual re-entry vehicle materials and environments.

Generation, transport, and trapping of excess charge carriers in Czochralski-grown sapphire

Abstract: The transient x-ray-induced conductivity in high-purity Union Carbide ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ single crystals is reported. The mobility lifetime product for electrons is much greater than that for holes and consequently the transport properties of the holes remain obscured. The trapping and detrapping rates for four different electron traps were determined from the data, including the trapping parameters for substitutional ${\mathrm{Cr}}^{3+}$. Even though the transport is dominated by trapping and detrapping, the high-mobility transport of electrons was observed in the first few nanoseconds; the mobility was found to be 3 \ifmmode\pm\else\textpm\fi{} 1 ${\mathrm{cm}}^{2}$/V sec independent of temperature between 100 and 350 K. The magnitude and temperature dependence of the intrinsic mobility are not in agreement with simple large-polaron theory. It was found that one of the deep traps (not ${\mathrm{Cr}}^{3+}$) could be filled with an accumulated dose of 2000 rad at 300 K, and that the filling led to an increase of up to fivefold in the lifetime.