Unsteadiness of Flow Separation and End-Effects Regime in a Thrust-Optimized Contour Rocket Nozzle

Turbulent flow separation in over-expanded rocket nozzles is investigated experimentally in a sub-scale model nozzle fed with cold air and having a thrust-optimized contour. Depending upon the pressure ratio either a free shock separation (FSS) or a restricted shock separation (RSS) is observed with a significant hysteresis between these two flow regimes. It is shown that the RSS configuration may involve several separated regions. Analysis of wall pressure fluctuations give quantitative information on the fluctuating pressure field directly connected with the occurrence of significant side loads. Direct measurements of the evolution of the side loads with respect to the pressure ratio show the occurrence of three distinct peaks which are explained by the wall pressure fluctuations measurements.     

Physical and chemical analysis of elemental sulfur formation during galena surface oxidation

The surface oxidation of sulfide minerals, such as galena (PbS), in aqueous solutions is of critical importance in a number of applications. A comprehensive understanding of the formation of oxidation species at the galena surface is still lacking. Much controversy over the nature of these oxidation products exists. A number of oxidation pathways have been proposed, and experimental evidence for the formation of elemental sulfur, metal polysulfides, and metal-deficient lead sulfides in acidic conditions has been shown and argued. This paper provides further insight into the electrochemical behavior of galena at pH 4.5. Utilizing a novel experimental system that combines in situ electrochemical control and AC mode atomic force microscopy (AFM) surface imaging, the formation and growth of nanoscopic domains on the galena surface are detected and examined at anodic potentials. AFM phase images indicate that these domains have different material properties to the underlying galena. Continued oxidation results in nanoscopic pitting and the formation of microscopic surface domains, which are confirmed to be elemental sulfur by Raman spectroscopy. Further clarification of the presence of elemental sulfur is provided by Cryo-XPS. Polysulfide and metal-deficient sulfide could not be detected within this system.     

Oleanolic triterpene saponins from the roots of Panax bipinnatifidus

Ten oleanane-type saponins (1-10), including three new compounds, namely bifinosides A-C (1-3), were isolated from the roots of Panax bipinnatifidus SEEM. Their structures were elucidated on the basis of chemical and spectroscopic methods.     

Optical stark spectroscopy of the D1Π-X1Σ+(0,0) band of scandium monohydride

The laser induced fluorescence (LIF) spectra of the D(1)Π-X(1)Σ(+)(0,0) band of a rotationally cold (<20 K) molecular beam sample of scandium monohydride, ScH, and scandium monodeuteride, ScD, were recorded without and in the presence of a static electric field. The fine and magnetic hyperfine parameters for the X(1)Σ(+)(v=0) and D(1)Π(v=0) states of ScH and ScD were determined from the analysis of the field-free spectra. An unexpected isotopic dependence of the (45)Sc(I=7/2) magnetic hyperfine interaction was observed. The lowest J-levels of the D(1)Π( v=0) state of ScH are not perturbed, but the corresponding levels for ScD are strongly perturbed. The observed electric field induced splitting, broadenings, and shifts were analyzed to produce permanent electric dipole moments, μ(e), of 1.74 ± 0.15 and 2.177 ± 0.006 D for the X(1)Σ(+)(v=0) and D(1)Π(v=0) states, respectively. The trend in μ(e) for the 3d-metal monohydrides is discussed.     

A novel implicit finite difference method for the one-dimensional fractional percolation equation

In this paper, a novel implicit finite difference method for the one-dimensional fractional percolation equation is proposed. Consistency, stability and convergence of the method are established. Some numerical examples are given. The numerical results demonstrate the effectiveness of theoretical analysis.     

Spitzen,Doppelpunkte und vertikale Tangenten in der Diskriminante verseller Deformationen von vollständigen Durchschnitten

Ohne Zusammenfassung     

Using the Banach Contraction Principle to Implement the Proximal Point Method for Multivalued Monotone Variational Inequalities

We apply the Banach contraction-mapping fixed-point principle for solving multivalued strongly monotone variational inequalities. Then, we couple this algorithm with the proximal-point method for solving monotone multivalued variational inequalities. We prove the convergence rate of this algorithm and report some computational results.This work was completed during the stay of the second author at the Department of Mathematics, University of Namur, Namur, Belgium, 2003.