The dual pump CARS technique is often used in the study of turbulent flames. Fast and accurate algorithms are needed for fitting dual-pump CARS spectra for temperature and multiple chemical species. This paper describes the development of such an algorithm. The algorithm employs sparse libraries, whose size grows much more slowly with number of species than a conventional library. The method was demonstrated by fitting synthetic "experimental" spectra containing 4 resonant species (N 2, Oz, H2 and CO2), both with noise and without it, and by fitting experimental spectra from a H 2-air flame produced by a Hencken burner. In both studies, wei ghted least squares fitting of signal, as opposed to least squares fitting signal or square-root signal, was shown to produce the least random error and nummize bias error in the fitted parameters.
Electronic conductivity of battery electrodes and the interfacial resistance at the current collector are key metrics affecting cell performance. However, in many cases they have not been properly quantified because of the lack of a suitably accurate and convenient non-destructive measurement method. There are also indications that conductivity across deposited films is not uniformly distributed. To characterize these variations, a micro-four-line probe has been developed for local mesoscale measurement of electronic conductivity of thin-film electrodes. The micro-four-line probe, coupled with a previously discussed mathematical model, overcomes key limitations of traditional point probes. This new approach allows pressure-controlled surface measurements to determine electronic conductivity without removal of the current collector. In addition, the probe allows one to measure the local interfacial contact resistance between the electrode film and the current collector. The method was validated by comparing to other conductivity sampling methods for a conductive test film. Three commercial-quality Li-ion battery porous electrodes were also tested and conductivity maps were produced. The results show significant local conductivity variation in such electrodes on a millimeter length scale. This method is of value to battery manufacturers and researchers to better quantify sources of resistance and heterogeneity and to improve electrode quality. A common electrode design for secondary batteries is a porous thin film of active material particles, conductive carbon particles, and polymeric binder. The film is coated on a metallic current collector. For commercially produced cells based on lithium-ion intercalation chemistry, the active materials are commonly a transition metal oxide on aluminum for the cathode and graphite on copper for the anode.Among the key properties determining electrode performance are the volume-averaged (effective or bulk) electronic conductivity of the film and the interfacial resistance at the current collector.1-4 These two quantities are surprisingly difficult to measure accurately for common thin-film electrodes because of the relatively large contact resistance between the sample and external probes, mechanical fragility of the sample, and the presence of the attached current collector. Lack of experimental data makes it hard to meet a longstanding need to be able to predict these parameters from knowledge of the composition and structure of the constituent materials.Commercial Li-ion battery electrodes are fabricated by first by making a slurry of the active material, carbon additive, binder, and a carrier solvent. This slurry is spread onto a metal foil current collector in a continuous process using a blade or slit to control deposition thickness, and then is immediately dried. Even in commercial coating processes it is difficult to achieve a uniform distribution of particles and porosity, leading to variability in the electronic conductivity of the electrodes.5 While this variability...
Self-activated movable flaps or pop-up feathers are used by a preponderance of feathered creatures as a means to modify foil characteristics during landing or incurred high angles of attack (gusts). When flow would normally separate, causing drastic decreases in lift, these pop-up feathers will activate, thus delaying the effects of stall. Although these flaps can almost entirely eliminate the stall region in a common UAV foil (NACA 2412), they have yet to be used commercially on any aircraft. The absence of these flaps is attributed mainly to the lack of understanding in their characteristics. This paper uses wind tunnel testing in an attempt to initially characterize the use of such flaps in low Reynolds number regions (1x10 5-5x10 5), including their placement, size and ideal material characteristics Nomenclature c = chord C d = coefficient of drag C l = coefficient of lift C m = coefficient of moment x = distance from leading edge, inches
An experiment has been conducted to acquire data for the validationof computationalfluicl dynamics codes used in the design of supersonic combustors. The flow in a supersonic combustor, consisting of a diverging duct with a single downstream-angled wail injector, is studied. Combustor entrance Mach number is 2 and enthalpy nominally corresponds to Mach 7 flight. The primary measurement technique is coherent anti-Stokes Raman spectroscopy, but surface pressures and temperatures have also been acquired. Modern design of experiment techniques have been used to nraximizethe quality of the data set (for the given level of effort) and to minimize systematic errors. Temperature maps are obtained at several pla nes in the flow fora case in which the combustor is piloted by injecting fuel upstream of the main injector and one case in which it is not piloted. Boundary conditions and uncertainties
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