Effect of pressure work on free convection flow along a vertical circular cone with suction and variable surface temperature

Free convection laminar flow from a vertical circular cone maintained a variable surface temperature with suction and pressure work effects has been investigated. The governing boundary layer equations are transformed into a non-dimensional form and the resulting nonlinear system of partial differential equations are reduced to local non-similarity equations. The governing non-similarity equations are then solved numerically by implicit finite difference method together with Keller box scheme. Numerical results are presented in terms of velocity and temperature profiles of the fluid as well as the local skin-friction coefficients and the local heat transfer rate for different values of Prandtl number Pr, suction parameter ξ, temperature gradient parameter n and the pressure work parameter ∈. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Adsorption of acridine yellow G from aqueous solutions using functionalized graphene nanoplatelets/modified polybutadiene hybrid composite

This paper presents an analysis of adsorption of acridine yellow G (AYG) from aqueous solutions through the use of functionalized grapheme nanoplatelets/modified polybutadiene hybrid composite (FGNPs/MPB). The adsorption of AYG onto FGNPs/MPB was investigated based on the AYG concentration, pH, contact time, temperature, and adsorbent dose. A maximum adsorption capacity was obtained at a pH of 7 (23.7 mg/g), an adsorbent dose of 1.0 g/L (20.8 mg/g), and an initial AYG concentration of 28.5 mg/L (16.9 mg/g). The value of q_e of FGNPs/MPB increases with an increase in temperature from 293 to 323 K. Equilibrium isotherm data were analyzed using the Langmuir and Freundlich isotherm models. The Langmuir model best describes the adsorption processes of AYG, which showed that the monolayer adsorption capacity of FGNPs/MBP is 22.9 mg/g. The pseudofirst-order, pseudosecond-order, and intraparticle diffusion models were used to study the kinetics of the AYG adsorption onto FGNPs/MPB. The pseudosecond-order model better described kinetic data for the adsorption of AYG onto FGNPs/MPB. Thermodynamic parameters, such as the Gibbs free energy, enthalpy, and entropy, indicated that the AYG adsorption onto FGNPs/MPB was spontaneous feasible, and endothermic.     

Magnetic recyclable eggshell-based mesoporous catalyst for biodiesel production from crude neem oil: Process optimization by central composite design and artificial neural network

A magnetically recyclable eggshell-based catalyst (MKEC) was synthesized to circumvent saponification during the conversion of neem, Jatropha, and waste cooking oils (free fatty acid, 2.3–6.6%) to biodiesel. The characterization results indicated that MKEC had a mesoporous structure with the pore width of 3.24 nm, a specific surface area of 128 m²/g, and a pore volume of 0.045 cm³/g. The results confirmed that the MKEC is more tolerant to fatty acid poisoning than calcined eggshell. The effects of process parameters for maximum fatty acid methyl ester (FAME) content were evaluated by central composite design (CCD) and artificial neural network (ANN). The experimental FAME content of 94.5% was achieved for neem oil with a standard deviation (SD) of 0.68, which was in reasonable agreement with predicted values (CCD, 96.9%; ANN, 95.9%; SD, 0.73). The reusability studies showed that the mesoporous catalyst can be reused efficiently for five cycles without much deterioration in its activity.     

Synthesis of 2-(1-N-Methyl Piperazinyl) and (N-Morpholino)substituted Quinolines

Hitherto unknown seven 3,6,7 trisubstituted 2-(1-N-methyl piperazinyl) and 2-(N-morpholino)quinolines are synthesised by using 1:1 complex of piperazinyl and morpholino amides with phosphorous oxychloride and its condensation with O-formyl acetanilides.     

A semi-empirical method for calculation of true coincidence corrections for the case of a close-in detection in γ-ray spectrometry

In this paper, a semi-empirical method is proposed to determine true coincidence-summing (TCS) correction factors for high resolution γ-ray spectrometry. It needs the knowledge of both full energy peak (FEP) efficiency and total-to-peak (TTP) efficiency curves. The TTP efficiency curve is established from the measurements with a set of coincidence-free point sources. Whereas for a volume source, the coincidence-free FEP efficiency curve is obtained iteratively by using the peaks from almost the coincidence-free nuclides and those from the coincident nuclides in the mixed standard sources. Then the fitting parameters obtained for both TTP and FEP efficiency curves are combined in a freely-available TCS calculation program called TrueCoinc, which yields the TCS correction factors required for any nuclide. As an application, the TCS correction factors were determined for the particular peaks of ²³⁸U, ²²⁶Ra and ²³²Th in the reference materials, measured in the case of a close-in detection geometry using a well-type Ge detector. The present TCS correction method can be applied without difficulty to all Ge detectors for any coincident nuclide.     

Heavy ion–acoustic rogue waves in magnetized electron–positron multi-ion plasmas

Non-linear heavy ion-acoustic waves (HIAWs) are studied in a homogeneous magnetized four-component multi-ion plasma composed of inertial heavy negative ions, light positive ions, and inertia-less non-extensive electrons and positrons. The non-linear Schrödinger equation is derived in this model using the perturbation method. The criteria for modulational instability of HIAWs and the basic features of finite-amplitude heavy ion acoustic rogue waves (HIARWs) are investigated. The presence of the magnetic field was found to reduce the amplitude of HIARWs and enhances the stability. It is interesting to note that increasing positive ion mass causes decreases in the amplitude and width of rogue waves, which is opposite behaviour to that demonstrated in the previous study of these waves in an unmagnetized plasma. Furthermore, it is also shown that striking parameters, such as the non-extensive parameter, the positron number density, the electron number density, the electron temperature, and the magnetic field parameter, play an undeniable role on the stability of waves packets. The findings of the present investigation may be of wide relevance to some plasma environments, such as active galactic nuclei, pulsar magnetospheres, and other magnetic confinement systems.     

Analytical and numerical solutions of a generalized hyperbolic non-Newtonian fluid flow

Generalized hyperbolic non-Newtonian fluid model first proposed by Al-Zahrani [1] is considered. The model was successfully applied to some drilling fluids with better performance in relating shear stress and velocity gradient compared to power-law and Hershel-Bulkley model. Special flow geometries namely pipe flow, parallel plate flow and flow between two rotating cylinders are treated. For the first two cases, analytical solutions of velocity profiles in the form of integrals are presented. For the flow between two rotating cylinders, the differential equation is solved by Runge-Kutta method combined with shooting. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Intermediate Valence Behavior of Yb2Cu9Al8

Intermediate valence behavior is frequently observed in materials containing Ce, Yb, Eu, Sm, or Tm. In the current work, we report synthesis and characterization of Yb₂Cu₉Al₈ (Th₂Zn₁₇ structure type). Its intermediate valence behavior can be described by an excitation energy E_ex/k_B = 319 K and a spin fluctuation temperature T_sf = 60 K. The valence state of Yb is estimated to be close to 2.04 for the low-temperature region. The valence gradually evolves to the value of 2.80 at T = 400 K. The specific heat coefficient of γ_exp = 59 mJ · mol_Yb^–1 · K^–2 indicates a moderate effective mass enhancement, together with finite density of states at the Fermi level. The latter is also confirmed by the band structure calculations.