Unsteady Couette flows in a second grade fluid with variable material properties

Fluid solid mixtures are generally considered as second grade fluids and are modeled as fluids with variable physical parameters. Thus, an analysis is performed for a second grade fluid with space dependent viscosity, elasticity and density. Two types of time-dependent flows are investigated. An eigen function expansion method is used to find the velocity distribution. The obtained solutions satisfy the boundary and initial conditions and the governing equation. Remarkably some exact analytic solutions are possible for flows involving second grade fluid with variable material properties in terms of trigonometric and Chebyshev functions.     

Fission fragment energy correlation measurements for 229Th(nth,f)

Fission-fragment mass and kinetic energy distributions and their correlations have been measured for ²²⁹Th. The results are compared with those for the neighbouring nuclei. The ²²⁹Th yield data show a peak for the symmetric fission. The mass yield peak/valley ratio is 531 ± 49. The 〈E_K〉(μ_H ≈ 115?22) is flat and the dip ΔE_K at symmetry is 18.0 ± 1.1 MeV. In the yields for high kinetic energy selected events, the mass 144 dominates. A complete systematic for the μ_H≈ 144 structure as a function of the fissioning nuclei is presented and discussed.     

Study of some characteristics of the thermal-neutron-induced sub-barrier fission of 231Pa, 232Th and 237Np

Some characteristics of the thermal-neutron-induced fission of ²³¹Pa, ²³²Th and ²³⁷Np were studied using a highly pure thermal-neutron beam of the Grenoble High Flux Reactor. For the thermal-neutron-induced-fission cross section we obtained 20 ± 4 mb for ²³⁷Np, 19 ± 4 mb for ²³¹Pa and less than 2.5 μb for ²³²Th, in agreement with calculations based on a double humped fission barrier. We also determined a mean total fission fragment kinetic energy of 172.8 + 2.5 MeV for ²³⁷Np, which fits into the semi-empirical systematic of $\text{E}\text{?}{}_{\mathrm{<mtext>K</mtext>}}$ versus $\text{Z}{}^2\text{/A}{}^{\mathrm{<mtext>case1</mtext><mtext>3</mtext>}}$. Finally, we determined LRA/B ratios of (1.94±0.17) × 10^?3 for ²³⁷Np and (1.67±0.11) × 10^?3for ²³¹Pa, in disagreement with the theoretical predictions of Feather, but consistent with the semi-empirical systematic of Halpern.     

Search for the (n th, α) reaction on180Hf,181Ta and209Bi

The (n _th,α) reaction on¹⁸⁰Hf,¹⁸¹Ta and²⁰⁹Bi was studied at the thermal neutron guide of the Grenoble high flux reactor. Upper limits ofσ _α ≦13μb, ≦μb and ≦0.3μb, respectively, were obtained for the a branches to the ground states in contrast to the values of ≈100μb to ≈500 mb reported in the literature. Possible reasons for these discrepancies are discussed. Furthermore, the present upper limits of the cross sections are compared with the values calculated from the statistical model.     

A note on quantization in rotating co-ordinates

The quantization of scalar fields in a uniformly rotating frame is reconsidered. It is pointed out that the coordinates usually used do not represent a frame describing uniform circular motion and the metric in the correct coordinates has a singularity. The result obtained earlier with the wrong coordinates, that there is no radiation, nevertheless holds.

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Zusammenfassung Die Quantisierung skalarer Felder in einem gleichförmig rotierenden Koordinatensystem wird erneut betrachtet. Dabei wird hervorgehoben, daß die gewöhnlich verwendeten Koordinaten die gleichförmige Kreisbewegung nicht beschreiben und daß die Metrik in den richtigen Koordinaten eine Singularität aufweist. Trotzdem bleibt das früher mit den falschen Koordinaten abgeleitete Resultat erhalten, daß nämlich ein strahlungsfreier Zustand existiert.

     

Thermal neutron induced charged particle reactions in radioactive targets of37Ar,109Cd,125Xe,127Xe,and132Cs

Thermal neutron induced charged particle reactions in a radioactive target of³⁷Ar have been studied. Upper limits of the cross-sections for the (n, α) reaction in radioactive targets of¹⁰⁹Cd,^{125, 127}Xe, and¹³²Cs have been obtained. The isotopically pure targets were produced at the ISOLDE facility at CERN and irradiated with thermal neutrons at the high flux reactor of the Institute Laue-Langevin in Grenoble. Charged particles from (n, p) and (n, α) reactions in³⁷Ar were observed with cross-sections of 69±14b and 1970 ±330b, respectively. TheQ-values for these reactions were determined to be 1600 ±12 keV and 4630±7 keV, in agreement with existing mass data. The branching ratio Γ_α/Γ_p of the³⁷Ar capturing state was found to be 28.5±2.7. An upper limit of the cross-section for the (n, γα) reaction in³⁷Ar was obtained.     

Effect of preparation methods of graphene oxide on permeability of free-standing membranes against polar and nonpolar species

ABSTRACT

In this study, graphene oxide (GO) was synthesized using Hummers, modified Hummers and improved Hummers methods, and then freestanding membranes were prepared based on these materials. Effects of different GO preparation methods on C/O ratio and interlayer spacing of freestanding membranes were studied. Structure of these membranes was studied by X-ray diffraction, contact angle, XRF, FT-IR, and FESEM methods. Also, permeability of ammonia, dichloromethane, and water vapor was investigated through these membranes. Results showed that, the sample prepared by the Hummers method had lower C/O ratio, smoother surface and lower permeability for polar species, such as water and ammonia vapors, than nonpolar materials. Membranes prepared using Improved Hummers method showed the least permeability against nonpolar vapors such as dichloromethane.     

Effect of potassium permanganate on morphological,structural and electro-optical properties of graphene oxide thin films

This work investigated the effect of Potassium Permanganate (KMnO₄) on graphene oxide (GO) properties, especially on electrical properties. The GO thin films were deposited on a glass substrate using drop casting technique and were analysed by using various type of spectroscopy (e.g. Scanning Electron Microscopy (SEM), Ultra- Violet Visible (UV–VIS), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), optical band gap, Raman Spectroscopy). Furthermore, the electrical experiments were carried out by using current–voltage (I-V) characteristic. The GO thin film with 4.5 g of KMnO₄ resulted in higher conductivity which is 3.11 × 10^?4 S/cm while GO with 2.5 g and 3.5 g of KMnO₄ achieve 2.47 × 10^?9 S/cm and 1.07 × 10^?7 S/cm, respectively. This further affects the morphological (SEM), optical (band gap, UV–Vis, FTIR, and Raman), and crystalline structural (XRD) properties of the GO thin films. The morphological, elemental, optical, and structural data confirmed that the properties of GO is affected by different amount of KMnO₄ oxidizing agent, which revealed that GO can potentially be implemented for electrical and electronic devices.     

Excess molar volume and isentropic compressibility of monoethanolamine in aqueous system at temperatures from 298.15 to 318.15 K

Densities and sound velocities for aqueous monoethanolamine (MEA) system are reported over the entire composition range at different temperatures (298.15, 303.15, 313.15 and 318.15 K). These experimental data have been further used in calculating the excess molar volume, partial molar volumes, isobaric thermal expansion coefficients and the deviation in isentropic compressibility. The excess molar volumes data were fitted to the Redlich–Kister polynomial equation to obtain their coefficients and standard deviations. The partial molar volume at infinite dilution of both water in MEA and MEA in water and have been determined using two different methods. Knowledge of the above properties of these mixtures is a basis for understanding some of the molecular interactions in these systems. From the analysis of the results, the type of interactions between the MEA and water is discussed in terms of the number and size of the alkyl groups attached to the nitrogen atom of MEA.     

Ultrasound-mediated efficient synthesis of dihydrothiopyrano[2,3-<Emphasis Type="Italic">b</Emphasis>]indole-3-carbonitrile derivatives

An efficient one-pot synthesis of fused dihydrothiopyrano[2,3-b]indole-3-carbonitriles has been developed through ultrasound mediated reaction by simply combining malononitrile and various aldehydes with two indoline-2(3H)-thiones. The method has the advantages of high yields, short reaction time, good functional group tolerance and green reaction conditions.