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31.
Cinthya Toro Nicolás D. Gómez Norberto G. Boggio Jorge Codnia M. Laura Azcárate Carlos Rinaldi 《Applied Physics A: Materials Science & Processing》2014,117(1):43-47
In this article, we present an experimental study of the effect of conical section nozzles coupled to solid targets on laser ablation propulsion. The impulse produced on the target by laser ablation was measured in terms of the coupling coefficient C m using a piezoelectric (PZT) sensor. The standard deviation of the PZT signal was used as an estimator of the transferred impulse. The ablation was performed with a TEA CO2 laser at room temperature and atmospheric pressure. The targets were pellets of 90/10 % w/w Zn/CaCO3 concentration ratio. Aluminum nozzles with conical section were coupled to these propellant pellets. A comparative study of the variation of C m using nozzles of different inlet and outlet diameters of the ejected material as well as of different heights was made. The results demonstrate that for the pellet composition analyzed, as the nozzle’s height increases and its diameter decreases improvements up to 250 % respect to the target without nozzle are obtained. These are promising results for the potential development of laser ablation microthrusters. 相似文献
32.
L. Gordillo T. Sauma Y. Zárate I. Espinoza M.G. Clerc N. Mujica 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,62(1):39-49
Development of technologies based on localized states depends on our ability to
manipulate and control these nonlinear structures. In order to achieve this, the
interactions between localized states and control tools should be well modelled and
understood. We present a theoretical and experimental study for handling
non-propagating hydrodynamic solitons in a vertically driven rectangular water
basin, based on the inclination of the system. Experiments show that tilting the basin
induces non-propagating solitons to drift towards an equilibrium position through a
relaxation process. Our theoretical approach is derived from the parametrically driven
damped nonlinear Schr?dinger equationwhich models the system. The basin tilting effect is
modelled by promoting the parameters that characterize the system, e.g. dissipation,
forcing and frequency detuning, as space dependent functions. A motion law for these
hydrodynamic solitons can be deduced from these assumptions. The model equation, which
includes a constant speed and a linear relaxation term, nicely reproduces the motion
observed experimentally. 相似文献
33.
A TEA CO2 laser was used to study the infrared multiple-photon absorption (IRMPA) and dissociation (IRMPD) spectra of CDCl3 in the fluence ranges 0.01–1.4 and 7–45 J/cm2, respectively, for different sample pressures. Experimental results were modeled with a master equation formulation which includes rotational and anharmonic bottlenecks and collisional effects. Experimental and calculated results show that CDCl3 has great rotational and anharmonic restrictions at the first stages of excitation. The IRMPD spectrum falls more slowly than the linear absorption spectrum at the blue wing due to intramolecular vibrational relaxation at the quasi-continuum level of excitation. 相似文献
34.
Ortiz de Zárate JM Sengers JV Bedeaux D Kjelstrup S 《The Journal of chemical physics》2007,127(3):034501
In this paper a simple reaction-diffusion system, namely a binary fluid mixture with an association-dissociation reaction between the two components, is considered. Fluctuations at hydrodynamic spatiotemporal scales when a temperature gradient is present in this chemically reacting system are studied. First, fluctuating hydrodynamics when the system is in global equilibrium (isothermal) is reviewed. Comparing the two cases, an enhancement of the intensity of concentration fluctuations in the presence of a temperature gradient is predicted. The nonequilibrium concentration fluctuations are spatially long ranged, with an intensity depending on the wave number q. The intensity exhibits a crossover from a proportional, variantq(-4) to a proportional, variantq(-2) behavior depending on whether the corresponding wavelength is smaller or larger than the penetration depth of the reacting mixture. This opens a possibility to distinguish between diffusion- or activation-controlled regimes of the reaction by measuring these fluctuations. In addition, the possible observation of these fluctuations in nonequilibrium molecular dynamics simulations is considered. 相似文献
35.
This paper deals with mean-value for the square of certain functionF(s) which has some characteristic properties of the Riemann zeta-function and its powers.Work supported by the University of the Basque Country. 相似文献
36.
J. Pons-Prats G. Bugeda F. Zárate E. Oñate 《Revista Internacional de Métodos Numéricos para Cálculo y Dise?o en Ingeniería》2012,28(1):18-32
Uncertainties are a daily issue to deal with in aerospace engineering and applications. Robust optimization methods commonly use a random generation of the inputs and take advantage of multi-point criteria to look for robust solutions accounting with uncertainty definition. From the computational point of view, the application to coupled problems, like fluid-dynamics (CFD) or fluid-structure interaction (FSI), can be extremely expensive. This work presents a coupling between stochastic analysis techniques and evolutionary optimization algorithms for the definition of a stochastic robust optimization procedure. At first, a stochastic procedure is proposed to be applied into optimization problems. The proposed method has been applied to both CFD and FSI problems for the reduction of drag and flutter, respectively. 相似文献
37.
N Zárate E Irazu A N Araújo M C B S M Montenegro R Pérez-Olmos 《Analytical sciences》2008,24(6):803-807
Two methods for the determination of potassium nitrate in mouthwashes, used against dentin hypersensitivity, have been simultaneously implemented in an sequence injection analysis (SIA) system. In addition to in-line dilution of the samples, the equipment simultaneously detected potassium and nitrate using two tubular potentiometric detectors, selective to each ion, providing a real-time assessment of the quality of the results. Both determinations were shown to be precise and accurate and the obtained results do not statistically differ from those furnished by applying the AES and HPLC reference methods. 相似文献
38.
The O3 absorption coefficients for the rotational lines P(12)–P(28) of the 9.4 μm emission band of the CO2 laser are presented. Measurements were made in O3–air dilute mixtures (20–600 ppm) at 25°C and a total pressure of 1013.25 h Pa using a frequency stabilized cw CO2 laser and values have been determined with greater precision than in previously reported studies. 相似文献
39.
The development of a sequential injection analysis manifold for the colorimetric determination of lead in water samples is described The concentration of lead was assessed from its catalytic effect on the reaction of resazurine reduction caused by sulfide in an alkali medium. To that effect, the reaction zone was stopped at the detector, and the time interval required for the attainment of an absorbance decrease of 0.800 at the wavelength of 610 nm was estimated. Interference of other transition metals of the samples was minimized by adding potassium iodide to the sample and retaining the iodocomplexes formed in an on-line anionic resin (AGI X8). Elution was made with a 2 mol/L sodium hydroxide solution. The relationship [SIA] microg/L = 0.99 (+/- 0.11) x [ETAAS] microg/L + 0 (+/- 4) was obtained upon comparing the results given by the proposed system and by electrothermal atomization atomic absorption spectrometry (ETAAS) after the analysis of ten water samples. 相似文献
40.
Eduardo Zárate M J. Gómez-Lara Rubén A. Toscano G. Negrón A. Campero 《Journal of chemical crystallography》1992,22(3):281-289
Crystal and molecular structures by X-ray diffraction analysis of Co, Cu and Zn complexes of 2,2-diacetoamidopropionic acid are reported. The results show that an uncommon bond from metal ion to a carbonyl-O-of-peptide atom is formed. The structures are isomorphic (Monoclinic,P21/c, with two formula units in the cell). The metal ion lies on a center of symmetry and it is six-oxygen coordinated in an octahedral-type configuration by pairs of water molecules, carboxylic (monodentate) groups and two carbonyl-O-of-peptide atoms. Ligand molecules bridge metal ions, so that the structure consists of a two-dimensional (sheet-type) polymer. Sheets are held together by a hydrogen-bond network making efficient use of the solvent water molecules. 相似文献