A general result on the uniform in bandwidth consistency of kernel-type function estimators

We develop a general theorem to prove the uniform in bandwidth consistency of kernel-type function estimators. This method unifies the approaches in some other recent papers. We show how to apply our results to kernel distribution function estimators and the smoothed empirical process. The results are applicable to establish strong uniform consistency of data-driven bandwidth kernel-type function estimators.     

Biofuel production from spent coffee grounds via lipase catalysis

Lipases namely Mucor miehei, Pseudomonas cepacia, Rhizopus delemar, Geotrichum candidum, Candida rugosa, Porcine pancreas-II, Pseudomonas fluorescence, and Candida antarctica lipase-B (Novozyme-435) were employed for biodiesel synthesis from spent coffee oil. Around 96% oil-to-biodiesel conversion was obtained using Novozyme-435 as a catalyst at 1:5 oil-to-methanol molar ratio and 40ºC. Total spent coffee grounds generated at the North-West University, Potchefstroom Campus (NWU PC) was estimated which could be used to produce 162 L of biodiesel. A waste valorization strategy was devised for converting organic wastes produced at the NWU PC to bioenergy.     

Bernstein estimation for a copula derivative with application to conditional distribution and regression functionals

Bernstein estimators attracted considerable attention as smooth nonparametric estimators for distribution functions, densities, copulas and copula densities. The present paper adds a parallel result for the first-order derivative of a copula function. This result then leads to Bernstein estimators for a conditional distribution function and its important functionals such as the regression and quantile functions. Results of independent interest have been derived such as an almost sure oscillation behavior of the empirical copula process and a Bahadur-type almost sure asymptotic representation for the Bernstein estimator of a regression quantile function. Simulations demonstrate the good performance of the proposed estimators.     

Structural analysis of CuInSe2 thin films prepared by selenization of Cu-In films

This study involves the characterization of thin films of copper indium diselenide (CuInSe₂) deposited on soda-lime glass substrates using a two-step process. In this technique electron-beam-evaporated Cu-In precursor layers were reacted with an atmosphere containing H₂Se gas. The morphological and structural aspects of the CuInSe₂ layers were studied (by scanning electron microscopy and X-ray diffraction) as a function of the Cu-In film morphology and the selenization temperature profile and exposure time. It was found that the Cu-In precursor morphology has a significant influence on the structural properties of the final CuInSe₂ film. Selenization of the Cu-In alloys (irrespective of the structure considered) directly at high temperature resulted in films with poor structural properties. However, a vast improvement in the adhesion properties and morphology of the CuInSe₂ films were observed when the Cu-In films were exposed to a reactive selenium atmosphere while ramping the temperature between 150 C and 400 C. Selenization of triple-layer structures (Cu/In/Cu and In/Cu/In) resulted in films with good structural properties and excellent compositional uniformity.     

Regeneration of barium carbonate from barium sulphide in a pilot-scale bubbling column reactor and utilization for acid mine drainage

Batch regeneration of barium carbonate (BaCO(3)) from barium sulphide (BaS) slurries by passing CO(2) gas into a pilot-scale bubbling column reactor under ambient conditions was used to assess the technical feasibility of BaCO(3) recovery in the Alkali Barium Calcium (ABC) desalination process and its use for sulphate removal from high sulphate Acid Mine Drainage (AMD). The effect of key process parameters, such as BaS slurry concentration and CO(2) flow rate on the carbonation, as well as the extent of sulphate removal from AMD using the recovered BaCO(3) were investigated. It was observed that the carbonation reaction rate for BaCO(3) regeneration in a bubbling column reactor significantly increased with increase in carbon dioxide (CO(2)) flow rate whereas the BaS slurry content within the range 5-10% slurry content did not significantly affect the carbonation rate. The CO(2) flow rate also had an impact on the BaCO(3) morphology. The BaCO(3) recovered from the pilot-scale bubbling column reactor demonstrated effective sulphate removal ability during AMD treatment compared with commercial BaCO(3).     

Analysis of a novel rotating disk cylinder engine concept for power generation

A new type of engine concept is proposed, namely a rotating disk cylinder engine. Unique secondary rotors with grooves act as guide vanes for a working fluid to power a main rotor with multiple cylindrical pistons. Currently, no literature exists on the proposed device and the modelling thereof. The aim of this paper is to determine the dynamic and thermodynamic behaviour of the machine so that recommendations can be made for further research work. A transient as well as a steady‐state thermodynamic model is developed for an adiabatic expansion process using first and second law analysis with air as ideal gas. The model is compared with experimental results of a piston engine driven by compressed air. Results show that the secondary rotor's angle of rotation is not a linear function of the main rotor's angle of rotation, which suggests a limitation in terms of operating speed. Furthermore, for constant power, the efficiency increases as the inlet pressure and speed decrease, while for constant efficiency, the power increases as the inlet pressure and speed increase. Results show the advantage of using three secondary rotors as it drastically decreases the pressure requirement for a constant torque output. The speed and inlet pressure of the device is, however, limited by the mass and material properties of the rotors as well as the effects of leakage. These limitations have not been considered in this initial analysis of the device and are recommended for future work.     

Dissolution properties of piroxicam powders and capsules as a function of particle size and the agglomeration of powders

The poor dissolution characteristics of relatively insoluble drugs have long been a problem to the pharmaceutical industry. An example is piroxicam, a highly potent anti-inflammatory agent. In many countries, a large number of generic piroxicam products are available to the prescriber. The aim of this study was to investigate the cause of the dissolution problems experienced by manufacturers of generic piroxicam capsules. Two raw material batches and the dissolution properties of several piroxicam capsules were studied. Differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) results showed that the two raw material samples were identical with respect to polymorphic modification. The particles of powder 1 were smaller than those of powder 2, but the dissolution of powder 1 was much slower than that of powder 2. The dissolution results for the capsules showed a marked difference among different brands, with capsule C not meeting the USP tolerance. Adding surfactant to the dissolution medium increased the dissolution of both powder 1 and capsule C. Failure of powder 1 or capsule C to meet USP dissolution criteria could result in differences in product efficacy, as well as in potential side effects. Such observations should be taken into account along with other relevant considerations when decisions regarding the generic substitution of oral piroxicam products are made.