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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
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Journal ArticleDOI
24 Feb 1989-Science
TL;DR: Concepts borrowed from polymer science have been applied to tailor the properties of inorganic materials, especially those derived from amorphous precursors, such as silica, to yield a variety of macromolecules.
Abstract: Concepts borrowed from polymer science have been applied to tailor the properties of inorganic materials, especially those derived from amorphous precursors. Fractal geometry can be used to characterize macromolecular precursors and to relate their structures to kinetic growth processes. Within the silica system, for example, it is possible to manipulate the conditions of solution polymerization to yield a variety of macromolecules from branched chains to smooth colloidal particles.

266 citations

Journal ArticleDOI
TL;DR: In this article, the potential of boosted HCCI for achieving high loads has been investigated for intake pressures (P in) from 100 kPa (naturally aspirated) to 325 kPa absolute.
Abstract: The potential of boosted HCCI for achieving high loads has been investigated for intake pressures (P in) from 100 kPa (naturally aspirated) to 325 kPa absolute. Experiments were conducted in a single-cylinder HCCI research engine (0.98 liters) equipped with a compression-ratio 14 piston at 1200 rpm. The intake charge was fully premixed well upstream of the intake, and the fuel was a research-grade (R+M)/2 = 87-octane gasoline with a composition typical of commercial gasolines. Beginning with P in = 100 kPa, the intake pressure was systematically increased in steps of 20 - 40 kPa, and for each P in, the fueling was incrementally increased up to the knock/stability limit, beyond which slight changes in combustion conditions can lead to strong knocking or misfire. A combination of reduced intake temperature and cooled EGR was used to compensate for the pressure-induced enhancement of autoignition and to provide sufficient combustion-phasing retard to control knock. The maximum attainable load increased progressively with boost from a gross indicated mean effective pressure (IMEP g) of about 5 bar for naturally aspirated conditions up to 16.34 bar for P in = 325 kPa. For this high-load point, combustion and indicated thermal efficiencies were 99% and 47%, respectively, and NOx emissions were < 0.1 g/kg-fuel. Maximum pressure-rise rates were kept sufficiently low to prevent knock, and the COV of the IMEP g was < 1.5%. Central to achieving these results was the ability to retard combustion phasing (CA50) as late as 19°after TDC with good stability under boosted conditions. Detailed examination of the heat release rates shows that this substantial CA50 retard was possible because intake boosting significantly enhances the early autoignition reactions, keeping the charge temperature rising toward the hot-ignition point despite the high rate of expansion at these late crank angles. Overall, the investigation showed that well-controlled boosted HCCI has a strong potential for achieving power levels close to those of turbo-charged diesel engines. Copyright © 2010 SAE International.

266 citations

Journal ArticleDOI
TL;DR: The most recent developments in digital microfluidics are discussed with particular attention to the potential benefits and outstanding challenges for applications in chemistry, biology, and medicine.
Abstract: Digital microfluidics (DMF) has recently emerged as a popular technology for a wide range of applications. In DMF, nanoliter to microliter droplets containing samples and reagents can be manipulated to carry out a range of discrete fluidic operations simply by applying a series of electrical potentials to an array of patterned electrodes coated with a hydrophobic insulator. DMF is distinct from microchannel-based fluidics as it allows for precise control over multiple reagent phases (liquids and solids) in heterogeneous systems with no need for complex networks of connections, microvalves, or pumps. In this review, we discuss the most recent developments in this technology with particular attention to the potential benefits and outstanding challenges for applications in chemistry, biology, and medicine.

266 citations

Journal ArticleDOI
TL;DR: In this paper, the relationship between the composition, structure, and properties of glasses in the Na 2 O.Al 2 O 3.P 2 O 5 (NAP) system is investigated.
Abstract: We have used 27 Al and 31 P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS) to describe quantitatively the relationships between the composition, structure, and properties of glasses in the Na 2 O.Al 2 O 3 .P 2 O 5 (NAP) system. In general, the glass properties (evaluated in part I) are most sensitive to changes in Al coordination. 27 Al MAS NMR spectra reveal that octahedrally coordinated Al is most abundant in glasses with O/P ratios less than 3.5, the pyrophosphate structural limit. Tetrahedrally coordinated Al is most abundant in glasses with O/P greater than 3.5. Decreasing Al(OP) 6 /Al(OP) 4 ratio generally correlates with decreasing glass transition temperature and refractive index

265 citations

Journal ArticleDOI
TL;DR: In this article, the nuclear magnetic resonance of hexagonal close-packed titanium metal in the temperature range of 12.5 MHz by pulsed nuclear resonance techniques was observed, and a partially resolved first-order quadrupole spectrum having a total width exceeding 8 kOe was observed.
Abstract: The nuclear magnetic resonance of $^{47}\mathrm{Ti}$ and $^{49}\mathrm{Ti}$ has been observed in hexagonal close-packed titanium metal in the temperature range $T=1\ensuremath{-}4\ifmmode^\circ\else\textdegree\fi{}$K. Measurements of the line profile and relaxation rates were carried out at 12.5 MHz by pulsed nuclear resonance techniques. Since the gyromagnetic ratios of $^{47}\mathrm{Ti}$ and $^{49}\mathrm{Ti}$ are nearly identical, the resonances of the two isotopes were superimposed. A partially resolved first-order quadrupole spectrum having a total width exceeding 8 kOe was observed, yielding a probable assignment ${h}^{\ensuremath{-}1}{e}^{2}q{Q}^{47}\ensuremath{\approx}{h}^{\ensuremath{-}1}{e}^{2}q{Q}^{49}\ensuremath{\approx}7.7$ MHz. The average Knight shift is estimated to be $K=(+0.4\ifmmode\pm\else\textpm\fi{}0.2)%$. The spin-lattice relaxation times ${T}_{1}$, which are quite long (${T}_{1}T=150\ifmmode\pm\else\textpm\fi{}20$ sec\ifmmode^\circ\else\textdegree\fi{}K), provide evidence that the conduction-electron states at the Fermi level are predominantly $d$-like. The theory of nuclear spin-lattice relaxation in hexagonal transition metals is treated in the tight-binding approximation. Contact, core-polarization, orbital, and dipolar hyperfine interactions are considered. The magnitudes of the orbital and dipolar contributions to the spin-lattice relaxation rate depend on the orientation of the magnetic field relative to the hexagonal $c$ axis. In the presence of $s\ensuremath{-}d$ mixing, the contact contribution is found to interfere destructively with one of the components of the core-polarization contribution. The predicted total relaxation rates are shown to depend more strongly on the orbital admixture coefficients than is the case in cubic transition metals. The relatively large number of parameters in the theory precludes a unique fit to the experimental results for titanium. In general, however, the calculated rates exceed the observed rate by a factor of 2-3 over a wide range of parameter values. The apparent discrepancy is attributed to the combined effects of (1) the electron-phonon enhancement of the electronic specific heat and (2) $s\ensuremath{-}d$ interference effects. The former effect causes the "bare" electron density of states to be overestimated, while the latter leads to an overestimate of the sum of contact and core-polarization contributions to the relaxation.

265 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
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202340
2022245
20211,510
20201,580
20191,535
20181,514