Liquid densities of THF and excess volumes for the mixture with water in a wide temperature and pressure range

In this paper densities for THF (tetrahydrofuran) and THF + water mixtures measured with the help of the Anton Paar DMA HPM vibrating tube densimeter are reported. The pure component densities of tetrahydrofuran measured in the temperature range from 278 to 437 K and pressures up to 130 MPa were correlated with the TRIDEN-System. Additionally densities of the binary mixture tetrahydrofuran + water were measured for 6 different concentrations in a temperature range from 288 to 338 K and up to 130 MPa. Excess volumes (vE)$(v^E)$ of the mixture were determined using the own correlation of the tetrahydrofuran densities and the equation of state (EoS) for water by Wagner and Pruß. Redlich–Kister polynomials were used to fit the vE-data$v^E\text{-data}$. Additionally in this work it was checked if the vibrating tube densimeter allows the determination of the miscibility gap for the system THF–water as a function of temperature and pressure.     

Transition from the ballistic to the diffusive regime in a turbid medium

By varying the absorption coefficient and width of an intralipid-India ink solution in a quasi-one-dimensional experiment, we investigate the transition between the ballistic and the diffusive regimes. The medium's attenuation coefficient changes abruptly between two different values within a single mean free path. This problem is analyzed both experimentally and theoretically, and it is demonstrated that the transition location depends on the scattering coefficient as well as on the measuring solid angle.     

An entropy-based approach to automatic image segmentation of satellite images

An entropy-based image segmentation approach is introduced and applied to color images obtained from Google Earth. Segmentation refers to the process of partitioning a digital image in order to locate different objects and regions of interest. The application to satellite images paves the way to automated monitoring of ecological catastrophes, urban growth, agricultural activity, maritime pollution, climate changing and general surveillance. Regions representing aquatic, rural and urban areas are identified and the accuracy of the proposed segmentation methodology is evaluated. The comparison with gray level images revealed that the color information is fundamental to obtain an accurate segmentation.     

BDD-based heuristics for binary optimization

In this paper we introduce a new method for generating heuristic solutions to binary optimization problems. We develop a technique based on binary decision diagrams. We use these structures to provide an under-approximation to the set of feasible solutions. We show that the proposed algorithm delivers comparable solutions to a state-of-the-art general-purpose optimization solver on randomly generated set covering and set packing problems.     

Spheroidally deformed sodium clusters in the selfconsistent jellium model

We present the first systematic study of potential energy curves and prolate-oblate shape transitions of sodium clusters with 8 < N < 40 atoms. The Kohn-Sham equations are solved in the local density approximation for the jellium model with spheroidal deformations. The ionic background density is taken to have a diffuse surface of Woods-Saxon type. The quadrupole and hexadecupole moments of the electron and jellium densities are investigated, revealing a strong hexadecupole dependence for selected clusters. Collective dipole resonances are described in the simple surface plasmon model. Shape transitions are found to occur at particle numbers 12–14 (prolate-oblate), 18–20–22 (oblate-spherical-prolate) and 30–32 (prolate-oblate), which are in good agreement with experimental results; triaxiality is predicted for Na-36. Comparing our results with those of molecular dynamics calculations, we confirm the scheme of Kohn-Sham levels and the gross behaviour of potentials and densities.     

New Crystalline Lasers on the Base of Monoclinic KR(W04)2:Ln3+ Tungstates (R=Y and Ln)

Monoclinic KY(WO₄)₂:Pr₃₊, Tm₃₊:KY(WO₄)₂:Er₃₊, Yb₃₊ single crystals are grown by low-gradient Czochralski technique. Stimulated emission at 1.0223μm wavelength in the new lasing ¹D₂→³F₃ channel of Pr³⁺ ions in KY(WO₄)₂ at room temperature under Xe-flashlamp pumping is excited. Full sets of Stark-level energies for Pr₃₊ ions in KY(WO₄)2 and KGd(WO₄)₂ crystals at 77 K are determined. 4f²-4f² intensity-transitions for the KY(WO₄)₂:Pr³⁺ are analyzed preliminarily. All observed at present and earlier one-micron Pr³⁺-ion, induced transitions in the ¹D₂→³F₃ and ¹D₂→³F₄ channels are identified. In yttrium and gadolinium sensitized-tungstates a two-micron (³H₄→³H₆) low-threshold generation of Tm³⁺ ions at cryogenic temperatures is achieved.All authors cooperate with the Joint Open Laboratory for Laser Crystals and Precise Laser Systems at the Institute of Crystallography and Institute of Laser Physics, Russian Academy of Sciences.     

Additive global noise delays Turing bifurcations

We apply a stochastic center manifold method to the calculation of noise-induced phase transitions in the stochastic Swift-Hohenberg equation. This analysis is applied to the reduced mode equations that result from Fourier decomposition of the field variable and of the temporal noise. The method shows a pitchfork bifurcation at lower perturbation order, but reveals a novel additive-noise-induced postponement of the Turing bifurcation at higher order. Good agreement is found between the theory and the numerics for both the reduced and the full system. The results are generalizable to a broad class of nonlinear spatial systems.