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Biodiesel wastewater contained residual of alkali catalyst, soap and glycerol which causing in high chemical oxygen demand (COD). The optimum conditions of aluminium sulphate (alum), poly-aluminium chloride (PAC) and laterite soil (silifloc) in the coagulation of biodiesel wastewater for COD reduction were explored through a sequence of studies including the effects of pH and dosage of coagulants. Coagulation process were conducted in the fixed conditions of mixing rate, mixing time, settling time and anionic polymer aid as flocculant. Silifloc could treat acidified biodiesel wastewater with 32.35 % at pH 2 and dosage of 4000ppm, the highest among these three coagulants. This was due to the silifloc rich in silica component had a higher rate law at sufficient dosage and had an effective range of at around pH 2. Whereas, PAC had a highest efficiency with 61.58% at pH 6 and dosage of 1100ppm in coagulation of raw biodiesel wastewater due to its solubility and elements of higher ions content. On other hand, alum had a moderate performance in acidified and raw wastewater with 26.42 % at pH 6 and 57.63 % at pH 4, respectively.

Ascorbic acid is the most abundant antioxidant present in guava (Psidiumguajava L.). There had only been few studies concerning the determination of diffusion coefficient and antioxidant activity of ascorbic acid in guava juice using cyclic voltammetry specifically at varying temperatures. Thus, this study on the effect of temperature on diffusion coefficient and antioxidant activity on ascorbic acid found in guava was done using cyclic voltammetry. The temperatures tested were at 15°C, 25°C, 36°C, and 45°C. Electrodes used in the experiment were glassy carbon as the working electrode, platinum wire as the counter electrode, and Ag/AgCl electrode as the reference electrode. The results showed that the peak currents of ascorbic acid in guava juice at 15°C, 25°C, 36°C, and 45°C were -0.5720, -0.5380, -0.5000, and -0.4760 μA, respectively. The diffusion coefficients of the ascorbic acid were obtained using the Randles-Sevcik equation at all given temperatures and the values were 2.1489 x10−5, 2.1711 x10−5, 2.2070 x10−5, and 2.2250 x10−5 cm2/s, respectively. The antioxidant activities, in terms of concentration, at the said temperatures were found to be 0.3374, 0.3212, 0.3015, and 0.2899 mM, respectively. It is concluded that at higher temperature, ascorbic acid in guava juice has a higher diffusion coefficient but lower antioxidant activity. The present results can be used by other researchers doing similar work on fate and transport of the studied system.

It was observed that the polyurethane shape memory polymer (SMP) loses its shape fixing capability after being exposed in the air at room temperature for several days. A significant indication for this change is the continuous decrease of the glass transition temperature (Tg) of polyurethane. Accompanying the decrease of Tg, the uniaxial tensile behaviour also changes. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) tests were carried out to find the cause behind this phenomenon. Moisture was concluded as the main reason. A mathematical expression was obtained for the relationship between Tg and the moisture. Moreover, the polyurethane shape memory polymer can fully regain its original properties after being heated at temperatures above 180 °C, which is the melting temperature of this SMP.

MgB2 bulk samples were synthesized by the usual solid-state reaction method. AC losses of the MgB2 bulk sample were measured using the ac susceptibility system (ACS) in external dc magnetic fields up to 7 T. The dependence of losses of the sample on temperature (T), frequency (f) and magnitude of ac field (Bac) was experimentally obtained. A comparison is made between the properties of losses of MgB2 and that of high-Tc superconductor Ag-Bi2223 and low-Tc superconductor NbTi. It is found that the mechanism of losses in the MgB2 sample may still be the same as that of high-Tc superconductors and can be explained by the flux creep models.

We investigate magnetic and crystalline microstructures of melt-spun (Fe0.675Pt0.325)(100-x)B-x (x = 12, 14, 16, 18, 20) nanocomposite ribbons after optimal thermal treatment using a magnetic force microscope. The magnetic microstructures are characterized by darker spots adjacent to brighter ones in a sub-micro scale and in random distribution. It is found that the strength of the exchange coupling interaction between the crystals in the 10-100nm scale, implied by the maximum value (delta M)(max) of the Henkel plot, could be roughly described by the ratio of the average width of the magnetic spots (w) over bar to the average crystal size (D) over bar for the ribbons. Moreover, we find that the intrinsic coercivity H-j(c) of the ribbons is sensitive to their crystal sizes, and the smaller (D) over bar, the higher jHc. Finally, by using roughness analysis, the curve of the root mean square values of the phase shift of the magnetic force images versus the boron content x is obtained, which is qualitatively consistent with that of the magnetization sigma(12)kOe of the ribbons versus x.

The bipolaronic system model of an infinite quantum well, in which two electrons or holes are weakly or intermediately coupled with both longitudinal optical (LO) and surface optical (SO) phonons, may be applied to layer-type high- superconductivity. A double unitary transformation of the Hamiltonian is carried out. The numerical results show that when the thickness of the polar slab increases the LO phonon contribution to the binding energy increases but that from the SO phonon decreases. On taking the Coulombic repulsion into account, the binding energy of the bipolaron is found to depend on the distance between the two electrons or holes. It is shown that the potential energy of the effective interaction of the two holes that form the stable bipolaron in a relatively thin polar slab of YBCO has a distinct equilibrium position at its minimum. The magnitude of the binding energy of these two holes becomes larger as the bipolaron size, taken as the equilibrium distance between the holes, becomes smaller.

In this paper, we study the low-lying energy spectra of a two-dimensional (2D) graphene-based magnetic dot in a perpendicular and radially inhomogeneous magnetic field with the use of the massless Dirac-Weyl equation. Numerical calculations are performed using 2D harmonic basis states for direct diagonalization. Effects of both the dot size and the magnetic field on the low-lying energy spectra are discussed.

The analytic behaviour of the ordinary (f) and exchange (g) amplitudes appearing in the dispersion relation for e--H(1s) scattering is examined via comparatively simple configuration-space arguments. It is found that the quantity f-fB is everywhere analytic in the energy (E) plane at energies where the total Green's function G(E) is analytic, in agreement with assumptions made by Gerjuoy and Krall (1960, 1962) in deriving dispersion relations for e--H(1s) scattering; here the subscript B denotes the first Born approximation. However, the amplitude g-gB is found to be singular at certain negative real energies, in disagreement with Gerjuoy and Krall's assumptions, but consistent with the recent conclusions of several groups.

Simpler theories for the shapes of bremsstrahlung cross sections differential in photon energy and angle are examined using numerical data obtained with the partialwave method for incident electrons of kinetic energy from 1 keV to 500 keV, under the assumption the process is described as a single electron transition in an atomic central potential. For low-Z elements the Born approximation or the Elwert-Haug approach, modified with form-factor screening, give good predictions for the shape of the angular distributions except at forward and backward angles, i.e., the results are good in the main region which contributed to the energy spectrum. While for high-Z elements, such predictions are accurate within about 15%. Analytic properties of the shape of the angular distribution from simpler theories suggest a simple way to paramaterize the results.