scispace - formally typeset
Search or ask a question
Institution

Sandia National Laboratories

FacilityLivermore, California, United States
About: Sandia National Laboratories is a facility organization based out in Livermore, California, United States. It is known for research contribution in the topics: Laser & Combustion. The organization has 21501 authors who have published 46724 publications receiving 1484388 citations. The organization is also known as: SNL & Sandia National Labs.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, a single layer of electrically controlled metamaterial was used to achieve active control of the phase of terahertz waves and demonstrated high-speed broadband modulation.
Abstract: Using a single layer of electrically controlled metamaterial, researchers have achieved active control of the phase of terahertz waves and demonstrated high-speed broadband modulation.

935 citations

Journal ArticleDOI
TL;DR: In this article, a large number of computer solutions of various types of resistor networks were presented, analogous to physical problems such as impurity conduction in lightly compensated semiconductors and variable-range hopping in amorphous semiconductor devices.
Abstract: In this paper we present a large number of computer solutions of various types of resistor networks. Some of these are analogous to physical problems such as impurity conduction in lightly compensated semiconductors and variable-range hopping in amorphous semiconductors. A significant extension of the standard relaxation techniques was required to implement these solutions. The results of these calculations are compared to percolation-model predictions based on concepts developed in the first paper of this series. A simple criterion is found for the applicability of the critical-percolation-path analysis to problems of this type and this is used to formulate an accurate prediction for the impurity-conduction case. Arguments based on percolation models are also given to show that the ${T}^{\ensuremath{-}\frac{1}{4}}$ and ${T}^{\ensuremath{-}\frac{1}{3}}$ dependence of ${log}_{10}\ensuremath{\sigma}$ often predicted for three-dimensional and two-dimensional variable-range hopping are indeed expected to be observed, and results on resistivity networks analogous to these problems are shown to be consistent with these arguments. Accurate empirical formulas are deduced from these computer calculations and we use them to analyze some recent data on films of $a$-Ge. Employing the results of the preceding paper, several experimental studies, and our computer models we have also examined the utility of the critical-volume-fraction rule of Sher and Zallen in solving various types of mixture conduction problems. We find that application of this rule is appropriate only in rather limited circumstances, and that in general a knowledge of the topological properties of these problems must be employed in finding the percolation threshold.

934 citations

Journal ArticleDOI
TL;DR: It is shown that for most situations relevant to microchip separations, the high‐ζ limit is most applicable, leading to the conclusion that the zeta potential on silica substrates is approximately proportional to the logarithm of the molar counterion concentration.
Abstract: This paper summarizes theory, experimental techniques, and the reported data pertaining to the zeta potential of silica and silicon with attention to use as microfluidic substrate materials, particularly for microchip chemical separations. Dependence on cation concentration, buffer and cation type, pH, cation valency, and temperature are discussed. The Debye-Huckel limit, which is often correctly treated as a good approximation for describing the ion concentration in the double layer, can lead to serious errors if it is extended to predict the dependence of zeta potential on the counterion concentration. For indifferent univalent electrolytes (e.g., sodium and potassium), two simple scalings for the dependence of zeta potential on counterion concentration can be derived in high- and low-z limits of the nonlinear Poisson-Boltzman equation solution in the double layer. It is shown that for most situations relevant to microchip separations, the high-z limit is most applicable, leading to the conclusion that the zeta potential on silica substrates is approximately proportional to the logarithm of the molar counterion concentration. The z vs. pH dependence measurements from several experiments are compared by normalizing the z based on concentration.

923 citations

Journal ArticleDOI
01 Jan 2009
TL;DR: The development of advanced compression-ignition (CI) engines can deliver both high efficiencies and very low NOX and particulate (PM) emissions, but unlike conventional diesel engines, the charge is highly dilute and premixed (or partially premixed) to achieve low emissions as mentioned in this paper.
Abstract: Advanced compression-ignition (CI) engines can deliver both high efficiencies and very low NOX and particulate (PM) emissions. Efficiencies are comparable to conventional diesel engines, but unlike conventional diesel engines, the charge is highly dilute and premixed (or partially premixed) to achieve low emissions. Dilution is accomplished by operating either lean or with large amounts of EGR. The development of these advanced CI engines has evolved mainly along two lines. First, for fuels other than diesel, a combustion process commonly known as homogeneous charge compression-ignition (HCCI) is generally used, in which the charge is premixed before being compression ignited. Although termed “homogeneous,” there are always some thermal or mixture inhomogeneities in real HCCI engines, and it is sometimes desirable to introduce additional stratification. Second, for diesel fuel (which autoignites easily but has low volatility) an alternative low-temperature combustion (LTC) approach is used, in which the autoignition is closely coupled to the fuel-injection event to provide control over ignition timing. To obtain dilute LTC, this approach relies on high levels of EGR, and injection timing is typically shifted 10–15° CA earlier or later than for conventional diesel combustion so temperatures are lower, which delays ignition and provides more time for premixing. Although these advanced CI combustion modes have important advantages, there are difficulties to implementing them in practical engines. In this article, the principles of HCCI and diesel LTC engines are reviewed along with the results of research on the in-cylinder processes. This research has resulted in substantial progress toward overcoming the main challenges facing these engines, including: improving low-load combustion efficiency, increasing the high-load limit, understanding fuel effects, and maintaining low NOX and PM emissions over the operating range.

919 citations

Book
19 Aug 2002
TL;DR: In this article, the authors present an approach for approximating the Stokes and Navier-Stokes equations for elliptic problems with respect to orthogonal polynomials and discrete transforms.
Abstract: Preface 1. Fluid mechanics and computation: an introduction 2. Approximation methods for elliptic problems 3. Parabolic and hyperbolic problems 4. Mutidimensional problems 5. Steady Stokes and Navier-Stokes equations 6. Unsteady Stokes and Navier-Stokes equations 7. Domain decomposition 8. Vector and parallel implementations Appendix A. Preliminary mathematical concepts Appendix B. Orthogonal polynomials and discrete transforms.

917 citations


Authors

Showing all 21652 results

NameH-indexPapersCitations
Lily Yeh Jan16246773655
Jongmin Lee1502257134772
Jun Liu13861677099
Gerbrand Ceder13768276398
Kevin M. Smith114171178470
Henry F. Schaefer111161168695
Thomas Bein10967742800
David Chandler10742452396
Stephen J. Pearton104191358669
Harold G. Craighead10156940357
Edward Ott10166944649
S. Das Sarma10095158803
Richard M. Crooks9741931105
David W. Murray9769943372
Alán Aspuru-Guzik9762844939
Network Information
Related Institutions (5)
Los Alamos National Laboratory
74.6K papers, 2.9M citations

94% related

Argonne National Laboratory
64.3K papers, 2.4M citations

94% related

Oak Ridge National Laboratory
73.7K papers, 2.6M citations

93% related

Georgia Institute of Technology
119K papers, 4.6M citations

93% related

École Polytechnique Fédérale de Lausanne
98.2K papers, 4.3M citations

91% related

Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202340
2022245
20211,510
20201,580
20191,535
20181,514