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Caltech Authors (93,451 recursos)
Repository of works by Caltech published authors.

Type = Conference or Workshop Item

Mostrando recursos 1 - 20 de 448

1. Shock-induced void collapse mechanisms in detonation initiation - Parker, M. D.; Austin, J. M.

2. Characterizing the fluctuations in gaseous detonation - Austin, J. M.; Shepherd, J. E.

3. Direct observations of reaction zone structure in propagating detonations - Pintgen, F.; Eckett, C. A.; Austin, J. M.; Shepherd, J. E.

4. Carbon monoxide detonations - Austin, J. M.; Shepherd, J. E.

5. Visualizations of reaction zones in highly unstable detonations - Austin, J. M.; Pintgen, F.; Shepherd, J. E.

6. Application of a laser induced fluorescence model to the numerical simulation of detonation waves - Mével, Rémy; Davidenko, Dmitry; Pintgen, Florian; Austin, Joanna; Shepherd, Joseph
Although numerical simulations have become an essential tool for detonation dynamics understanding, most of the physical constraints that exist within experiments are not accounted for which makes difficult a comparison. In the present study, a simple laser induced fluorescence model has been implemented and used to post-treat detonation wave numerical simulation results and allow a direct comparison with previous experimental visualizations of detonations in hydrogen-oxygen-diluent mixtures. The model is first applied to steady one-dimensional simulation results obtained with detailed chemistry. The effects on the fluorescence intensity of the model parameters are examined to underline the dominant processes. The model is then applied to unsteady two-dimensional simulation...

7. Shock induced detonations in composite heterogeneous energetic materials - Shukla, R. K.; Pantano, C.; Jackson, T. L.; Austin, J. M.; Freund, J. B.

8. On network coding and routing in dynamic wireless multicast networks - Ho, Tracey; Jin, Jia-Qi
We compare multicast network coding and routing for a time-varying wireless network model with interference- determined link capacities. We use dynamic back pressure algorithms that are optimal for intra-session network coding and routing respectively. Our results suggest that under such conditions, the gap in multicast capacity between network coding and routing can decrease relative to a collision-based wireless model with fixed link capacities.

9. Dry deposition of nitrogen containing species - McRae, Gregory J.; Russell, Armistead G.
Nitrogen oxides (NO_x) emissions and the oxidation products formed by photochemical interactions in the atmosphere are responsible for a significant fraction of both dry and wet acid deposition fluxes. In his paper a vertically-resolved, Lagrangian trajectory model is used to predict the diurnal variation of: NO, NO_2, NO_3, HONO, HONO_2, HO_2NO_2, RONO, RONO_2, RO_2NO_2, N_2O_5 and PAN over an urban airshed. Particular attention is given to the fate of nitric acid and its reaction with gaseous ammonia to form, aerosol phase, ammonium nitrate. A simple model for estimating the deposition fluxes of these species is also presented. A study of...

10. Stresses in Ytterbium Silicate Multilayer Environmental Barrier Coatings - Stolzenburg, F.; Almer, J.; Lee, K. N.; Harder, B. J.; Faber, K. T.
The internal stresses of plasma-sprayed multilayer ytterbium disilicate environmental barrier coatings were measured using microfocused high-energy X-rays in a transmission geometry. Stresses were measured for as-sprayed and ex-situ heat-treated ytterbium disilicate topcoats at room temperature and during in-situ heating and cooling experiments. In-situ loading experiments were also performed on the topcoat in order to establish its elastic constants. The ytterbium disilicate was found to have a relatively low coefficient of thermal expansion resulting in compressive stresses of approximately 100 MPa throughout the topcoat. In-situ heating experiments revealed a statistically significant stress relaxation in the ytterbium disilicate topcoat upon thermal cycling to temperatures above 1300°C, indicating the onset of...

11. Turbulence and Diffusion as Factors in Sediment Transportation - Vanoni, Vito A.; Hsu, En-Yun
The importance of turbulence in the transportation of sediment has long been recognized by hydraulic engineers and research workers in fluid flow. The turbulence contains the cross components of flow that transport or diffuse sediment from the bed into the main body of the stream. Without this turbulent motion no sediment could be picked up from the bed and there would be no muddy streams. Transport would be limited to the small amount resulting from the rolling and sliding of particles at the bed under the action of viscous shear.

12. Speed faults in computation by chemical reaction networks - Chen, Ho-Lin; Cummings, Rachel; Doty, David; Soloveichik, David
Chemical reaction networks (CRNs) formally model chemistry in a well-mixed solution. Assuming a fixed molecular population size and bimolecular reactions, CRNs are formally equivalent to population protocols, a model of distributed computing introduced by Angluin, Aspnes, Diamadi, Fischer, and Peralta (PODC 2004). The challenge of fast computation by CRNs (or population protocols) is to ensure that there is never a bottleneck "slow" reaction that requires two molecules (agent states) to react (communicate), both of which are present in low (O(1)) counts. It is known that CRNs can be fast in expectation by avoiding slow reactions with high probability. However, states may be...

13. Real Fluid Effects on an Accelerated Sphere Before Boundary-Layer Separation - Mellsen, S. B.; Waugh, J. G.; Ellis, A. T.
Studies were made on the apparent increase in mass on acceleration (added mass) of a sphere accelerated from rest and before boundary-layer separation, in cylinders of various diameters filled with water or oil. From a comparison of theoretical and experimentally obtained added masses, the following conclusions were drawn: In the absence of wall effects on the boundary layer, the wall shear stress over elements of the sphere can be approximated by the solution for the flat plate moving parallel to itself and the potential flow over the elements outside the boundary layer. The impulse on the elements is obtained by integration with...

14. Note on the Application of Cascade Theory to Design of Axial-Flow Pumps - Linhardt, H. D.; Acosta, A. J.
Theoretical and experimental results are presented which reassure the usefulness of two-dimensional cascade theories to the design of axial flow pumps. For this purpose it is necessary to include the effect of the blade thickness upon the impeller flow which has been found to be responsible for reported discrepancies between predictions of thin airfoil theories and the performance of axial-flow pumps characterized by high stagger angle and low aspect ratio.

15. Measured Performance of Pump Impellers - Osborne, William C.; Morelli, Dino A.

16. Laboratory Developments for Study of Flow in Rotating Channels - Knapp, R. T.; Hollander, A.; Acosta, A. J.; Osborne, W. C.
[no abstract]

17. Effects of anodic potential and chloride ion on overall reactivity in semiconductor electrochemical reactors - Hoffmann, Michael R.; Cho, Kangwoo
We have investigated electrochem. treatment of real domestic wastewater coupled with simultaneous prodn. of mol. H2 as useful byproduct. The electrolysis cells employ multi-layer semiconductor anodes with electro-active bismuth-doped TiO2 functionalities and stainless steel cathodes. DC-powered Lab.-scale electrolysis expts. were performed under static anodic potentials (+2.2 or +3.0 V NHE) using domestic wastewater samples, with added chloride ion in variable concns. Greater than 95% redns. in COD (COD) and ammonium ion were achieved within 6 h. In addn., we exptl. detd. a decreasing overall reactivity of reactive chlorine species towards COD with an increasing chloride ion concn. under chlorine radicals...

18. Selective formation of olefins using olefin metathesis - Grubbs, Robert H.
Olefin metathesis catalysts have become one of the tools for the efficient synthesis of complex mols. Until recently, the catalysts demonstrated poor catalyst controlled selectivity of the product double bond. Over the past several years, complexes based on molybdenum, tungsten and ruthenium have been discovered that will produce olefins good to excellent selectivity for the generation of Z olefins both in cross and in ring closing metathesis. New ligands have been developed that result in different selectivities and open new applications of metathesis in the synthesis of an array of complex mols. These catalysts are developed through design, computation and...

19. Multi-​scale simulation of electrode interfaces - Miller, Thomas F.
The computational modeling of chem. reactions at electrode interfaces presents extraordinary challenges from the perspective of electronic structure theory. Target applications include electrolyte redn. in formation of the solid-electrolyte interphase (SEI) and the nucleation and growth of metal dendrites. These problems combine large system sizes with subtle interactions, multiple dynamical timescales, and electronically non-adiabatic eects. The development of new methods to perform reliable, on-the-fly electronic structure calcns. at a computational cost that makes feasible the simulation of long-timescale dynamics in large systems remains a central theor. challenge. We describe recent progress towards the development of accurate, scalable treatments for describing...

20. Accurate and systematically improvable density functional theory embedding for correlated wavefunctions - Miller, Thomas F.
We will describe quantum embedding methods for performing accurate and scalable electronic structure theory calcns. in large mol. systems, with application to clusters, liqs., transition metal complexes, and chem. reactions.[1] "Exact non-additive kinetic potentials for embedded d. functional theory. Goodpaster JD, Ananth N, Manby FR, and Miller TF, JCP, 133, 084103 (2010).[2] "A simple, exact d.-functional-theory embedding scheme. Manby FR, Stella M, Goodpaster JD, and Miller TF, JCTC, 8, 2564 (2012).[3] "Accurate and systematically improvable d. functional theory embedding for correlated wavefunctions. Goodpaster JD, Barnes TA, Manby FR, and Miller TF, JCP, 140, 18A507 (2014).

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