A laser Doppler anemometry technique for Reynolds stresses measurement

A technique is described for the measurement of all components of mean velocity and Reynolds stresses, in a complex turbulent flow where achieving coincidence data acquisition is difficult. The method is based on data recorded using four orientations of the laser probe. It is shown that the measurement errors are not the same for all the components of the Reynolds tensor, but they are sufficiently small to give a good accuracy. An application to a turbomachinery flow is given to illustrate the method.     

On the hysteresis of vortex shedding in a periodically-varying flow

Efforts are made to explore the hysteresis characteristics of vortex shedding in a pipe flow, whose velocity varies periodically in time. Results obtained show that during acceleration of the flow, the vortex strength tends to be stronger, whereas during deceleration of the flow, the situation is reversed. As reconstructed from the velocity signals measured at a point in the flow field, the shed vortex arrays appear to possess uneven vortex strengths in response to periodically-varying incoming flows. Furthermore, in the hysteresis range, the streamwise spacings between the vortices appear to be unequal.     

Nano-tribological study on a super-hydrophobic film formed on rough aluminium substrates

A novel super-hydrophobic stearic acid (STA) film with a water contact angle of 166^o was prepared by chemical adsorption on aluminum wafer coated with polyethyleneimine (PEI) film. The micro-tribological behavior of the super-hydrophobic STA monolayer was compared with that of the polished and PEI-coated Al surfaces. The effect of relative humidity on the adhesion and friction was investigated as well. It was found that the STA monolayer showed decreased friction, while the adhesive force was greatly decreased by increasing the surface roughness of the Al wafer to reduce the contact area between the atomic force microscope (AFM) tip and the sample surface to be tested. Thus the friction and adhesion of the Al wafer was effectively decreased by generating the STA monolayer, which indicated that it could be feasible and rational to prepare a surface with good adhesion resistance and lubricity by properly controlling the surface morphology and the chemical composition. Both the adhesion and friction decreased as the relative humidity was lowered from 65% to 10%, though the decrease extent became insignificant for the STA monolayer. The project supported by the National Natural Science Foundation of China (50375151, 50323007, 10225209) and the Chinese Academy of Sciences (KJCX-SW-L2)     

Photorefractive Four-Wave Mixing Switches Utilizing Pockels Effect -Longitudinal and Lateral Switches-

We carried out detailed calculations for photorefractive wave-mixing switches based on one of three crystals with high electro-optic coefficients, namely, BaTiO₃, Strontium Barium Niobate (SBN (0.75)), and Potasium Sodium Strontium Barium Niobate (KNSBN). A comparison of results for the three crystals shows that a 0_-cut BaTiO³ crystal is suitable for a longitudinal switch and requires a voltage of about 80 for a 2-mm-thick crystal to induce sufficient phase mismatch. The electrodes must be transparent for the incident and diffracted beams. A 45_-cut SBN (0.75) crystal, however, is suitable for a lateral switch and requires a voltage of about 150 for a 1-mm-wide crystal. The electrodes do not need to be transparent.     

Status of heavy element research using a gas-filled recoil separator at RIKEN

A gas-filled type of recoil separator for heavy element research was installed at an experimental hall of RIKEN Linear Accelerator facility to realize getting higher intensity of primary beam and long beam time. Performance of the separator was studied using target recoils and various nuclear reactions. The results show the high performance of the separator for heave element research. As an application of the GARIS, production and identification of an isotope of the 110th element ²⁷¹[110] have been performed using the ²⁰⁸Pb(⁶⁴Ni,1n)²⁷¹[110] reaction. Three decay chains coincide well both in decay times and energies with the ones reported by the group of SHIP experiment at GSI, Germany. Our results provide a confirmation of the synthesis of an isotope ²⁷¹[110] of element 110.     

Color Zone Map in Peripheral Vision at Various Illuminance Levels

We measured the entire region of mesopic and photopic vision to determine the color zone covering the visual field with unique red, yellow, green, and blue hue components. Eight kinds of test stimuli in the natural color system (NCS) color notation system were used. These stimuli were presented at horizontal and vertical meridians, and at meridians inclined at 45° angles. The illuminance level was set at six levels: 0.01 lx-1000 lx. The evaluation method measured chromatic, white, and black components as well as the hue component of the stimuli. Results show that the color zone of the retina extended further into the periphery with increasing illuminance; the response of opponent colors y-b was shown to be greater than that of the opponent colors r-g.     

Real-time color holographic interferometry devoted to 2D unsteady wake flows

A new optical technique based on real time holographic interferometry in true colors has been implemented around the transonic wind tunnel of the ONERA-Lille center to analyze 2D unsteady wake flows. Tests realized in color interferometry, real time and double exposure, use simultaneously three wavelengths of a continuous waves laser (argon and krypton mixed) and holograms are recorded on silver-halide single-layer panchromatic Slavich PFG03c plates. The very principle of real-time true color holographic interferometry uses three primary wavelengths (red, green and blue) to record, under no-flow conditions, the interference among the three measurement beams and the three reference beams simultaneously on a single reference hologram. After the holographic plate is developed, it is placed on the test setup again in the position it occupied during exposure and the hologram is illuminated again by the three reference beams and three measurement beams. A flat, uniform color can then be observed behind the hologram. So a horizontal, vertical, or even circular fringe pattern can be formed and the achromatic central fringe can be made out very clearly. The single color is used to determine the path difference zero on the interferograms. The flow studied was the unsteady flow downstream of a cylinder placed crosswise in the test section. A sequence of hundred interferograms was recorded on the flow around the cylinder at Mach 0.37. The vortex formation and dissipation phases can be seen very clearly, along with the fringe beat to either side of the cylinder.     

Sulfonated poly(aryl ether ketone)s containing naphthalene moieties obtained by direct copolymerization as novel polymers for proton exchange membranes

A series of sulfonated poly(aryl ether ketone)s (SPAEKs) were prepared by aromatic nucleophilic polycondensation of 2,6‐dihydroxynaphthalene with 5,5′‐carbonyl‐bis(2‐fluorobenzenesulfonate) and 4,4′‐difluorobenzophenone. The structure and degree of sulfonation (DS) of the SPAEKs were characterized using ¹H NMR spectroscopy. The experimentally observed DS values were close to the expected values derived from the starting material ratios. The thermal stabilities of the SPAEKs were characterized by thermogravimetric analysis, which showed that in acid and sodium salt forms they were thermally stable in air up to about 240 and 380 °C, respectively. Transparent membranes cast from the directly polymerized SPAEKs exhibited good mechanical properties in both dry and hydrated states. The dependence of water uptake and of membrane swelling on the DS at different temperatures was studied. SPAEK membranes with a DS from 0.72 to 1.60 maintained adequate mechanical properties after immersion in water at 80 °C for 24 h. The proton conductivity of SPAEK membranes with different degrees of sulfonation was measured as a function of temperature. The proton conductivity of the SPAEK films increased with increased DS, and the highest room temperature conductivity (4.2 × 10^?2 S/cm) was recorded for a SPAEK membrane with a DS of 1.60, which further increased to 1.1 × 10^?1 S/cm at 80 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2866–2876, 2004     

Living polymerization of styrene initiated by mercaptan/ε‐caprolactam

The bulk polymerization of styrene initiated by ?‐caprolactam (CL) and n‐dodecyl mercaptan (RSH) has been explored. This novel polymerization system shows living characteristics. For example, the molecular weight of the resulting polymers increases with conversion, and the system has the ability to form diblock copolymers and so forth. The polymer chain end contains thiol and lactam structures, which we have investigated with Fourier transform infrared, ¹H NMR, and ¹³C NMR techniques. Electron spin resonance spectra and theoretical calculations by the Hartree–Fock methods have been used to examine the mechanism. The results reveal that the initial polymerization starts from thiol via a chain‐transfer reaction, and the propagation proceeds by the insertion of a monomer between the terminal group and the intermediate structure of lactam. Finally, the polymerization kinetics have been examined. The polymerization rate varies linearly with the concentration of CL and RSH, and this confirms the mechanism. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4976–4993, 2004     

Soluble,saturated‐red‐light‐emitting poly(p‐phenylenevinylene) containing triphenylamine units and cyano groups

A conjugated poly(p‐CN‐phenylenevinylene) (PCNPV) containing both electron‐donating triphenylamine units and electron‐withdrawing cyano groups was prepared via Knoevenagel condensation in a good yield. Gel permeation chromatography suggested that the soluble polymer had a very high weight‐average molecular weight of 309,000. A bright and saturated red emission was observed under UV excitation in solution and film. Cyclic voltammetry showed that the polymer presented quasi‐reversible oxidation with a relatively low potential because of the triphenylamine unit. A single‐layer indium tin oxide/PCNPV/Mg–Ag device emitted a bright red light (633 nm). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3947–3953, 2004