Effect of Droplet Size and Atomization on Spray Formation: A Priori Study Using Large-Eddy Simulation

The paper is mainly focused to the vast number of researchers who work within direct injection (DI) engine fuel spray simulations. The most common simulation framework today within the community is the Reynolds Averaged Navier Stokes (RANS) approach together with the Lagrangian Particle Tracking (LPT) method. In fact, this study is one of the first studies where high resolution LES/LPT diesel spray modeling is considered. The potential of LES to deepen the present day multidimensional LPT fuel spray simulations is discussed. Spray evolution is studied far from an injector by modeling a spray as a particle laden jet (PLJ). The effect of d on mixing in non-atomizing and atomizing sprays is thoroughly investigated at jet inlet Reynolds number Re?=?10⁴ and Mach number Ma?=?0.3. Based on and justified by rather recent and also quite old ideas, novel and compact views on droplet breakup in turbulent flows are pointed out from the literature. We use LES/LPT to illustrate that even in a low Weber number flow (We?<?13) the droplet breakup modeling may need considerable attention in contrast to what is typically assumed in the present-day breakup models. LES and LPT techniques are first applied to essentially confirm certain expected droplet size effects on spray shape in non-atomizing monodisperse sprays. In the simulations LES e.g. produces an expected turbulent dispersion pattern that depends on droplet diameter (d) without a droplet dispersion model in contrast to RANS. A new compact droplet breakup model is formulated and tested for droplets that break with a natural resonance time rate according to the Poisson process. As a result of the study: 1) the analysis gives a rigorous and enriching proof of currently existing views on droplet size effects on mixing, and 2) the presented a priori analysis points out the importance of modeling the resonance breakup even at a low We.     

How the dynamics of an ablation plume is affected by ambient gas ionisation

The influence of inert gas ionisation on the expansion dynamics of a laser ablation plume propagating through an inert gas is studied. Charge transfer reactions between ionised ablated species and gas neutrals lead to the formation of a charged layer of ionised gas atoms in contact with the plume expansion front. The energy lost by fast ablated ions when the plume is slowed down is calculated. For the exemplary carbon ablation in helium and argon atmospheres, where background gas ionisation plays a different role, model predictions agree with the observed microstructural differences of deposited films.     

Resonant Raman Scattering in the Polyacetylene System

The amplitude mode approach for describing the resonant raman scattering in dimerized chains is reviewed and applied to the polyacetylene system. trans-(CH)_x is disordered with a variable electron-phonon coupling constant. cis-(CH) _x is ordered with an extrinsic gap of ～ 5% of the full gap. A distribution of extrinsic gaps is shown to exist In trans-(CH) _x chains in partially isomerized polyacetylene.     

SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

The deposition power dependence of visible transmittance and refractive index of room temperature-deposited ZnO:Al thin films by RF magnetron sputtering has been studied. All films exhibited high visible transmittance and near-complete UV absorption. The refractive index of the films decreased continuously with an increase in the RF power at all photon energies in the visible and near-IR region, which has been partially attributed to the decreased packing density of the films. For each film, the refractive index exhibited strong frequency dispersion in the weak-absorption region. The origin of optical dispersion at different RF power has been discussed in the light of a single-oscillator model.     

Retardation effects on the Peierls phase

The mean field theory of the Peierls instability is extended to include the small momentum transfer interaction, which is shown to be a retarded interaction. The Peierls transition temperature is shown to depend significantly on the bare phonon frequency. A positive isotope shift parameter is predicted, with values in the range 0–0.5.It is also argued that the ratio of the zero temperature gap to the transition temperature is larger than the BCS value of 3.5.     

Medical genetic services in the state of Rio de Janeiro, Brazil

Rio de Janeiro is a state with close to 15 million inhabitants and approximately 250,000 births per year. The state counts nine clinical genetic units in public institutions, providing for 9,400 outpatient consultations yearly, which is insufficient to cover the estimated needs. Laboratory tests such as cytogenetics, inborn errors of metabolism and molecular studies are available on a limited basis. Newborn screening in the public health system is being performed for phenylketonuria, congenital hypothyroidism and sickle cell disease. In the state there are also special treatment programs for osteogenesis imperfecta and Gaucher's disease, subsidized by the Brazilian Ministry of Health. Presently, efforts of medical geneticists are concentrated on highlighting the practical relevance of clinical genetics, and the need to integrate the specialty into the public health system in a functional network of genetic services.     

Infrared Absorption of Doped Polyacetylene

The frequency dependent conductivity of added charge (e.g. solitons) to a dimerized Peieres condensate with N coupled phonons is studied. The electron-Phonon system, with electron -electron interactions and pinning effects, yields in the adiabatic and continuum limits an infrared absprption whose structure is independent of the charge configuration. The kinetic mass of the charge affects only the pinning parameter and the over-all magnitude of the absorption. This mass is es timated from experimental data and compared with theoretical soliton and polaron masses.     

Raman Spectroscopy-Based Assessment of the Liquid Water Content in Snow

In snow, water coexists in solid, liquid and vapor states. The relative abundance of the three phases drives snow grain metamorphism and affects the physical properties of the snowpack. Knowledge of the content of the liquid phase in snow is critical to estimate the snowmelt runoff and to forecast the release of wet avalanches. Liquid water does not spread homogeneously through a snowpack because different snow layers have different permeabilities; therefore, it is important to track sudden changes in the amount of liquid water within a specific layer. We reproduced water percolation in the laboratory, and used Raman spectroscopy to detect the presence of the liquid phase in controlled snow samples. We performed experiments on both fine- and coarse-grained snow. The obtained snow spectra are well fitted by a linear combination of the spectra typical of liquid water and ice. We progressively charged snow with liquid water from dry snow up to soaked snow. As a result, we exploited continuous, qualitative monitoring of the evolution of the liquid water content as reflected by the fitting coefficient c.     

Radioaktivit?t, radiometrische Mikroanalyse

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Über die Umlagerung von Chinin durch Schwefelsäure

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