Application of a modified quasilinearization technique to totally singular optimal control problems†

This paper presents an algorithm for the computation of totally singular optimal control problems. The algorithm is an extension of a modified quasilinearization technique which was originally developed for the solution of non-linear two-point boundary-value problems. A numerical example is included for illustration.     

Modelling and identification of offshore towers with general damping

The modelling problem of offshore towers is considered. A model is proposed which includes viscous and hydrodynamic drag damping and takes into account the stochastic nature of the problem. The model is decoupled into a set of modal equations by using the complex mode theory. A technique is developed to identify the modal parameters and the complex mode shapes by using the noisy excitation and response measurements. This technique is computationally efficient and accurate in the sense of minimizing a criterion function of the estimates variance. A simulation example is presented to demonstrate the results.     

Extraction of Niobium and Tantalum from Nitrate and Sulfate Media by Using MIBK

Abstract

The niobium-tantalum ore material obtained from Ras Baroud locality in the central Eastern Desert of Egypt, consists mainly of two minerals namely: columbite and alvarolite. The extractive separation of niobium(V) and tantalum(V) from the acid media HF-HNO₃or HF-H₂SO₄ have been worked out using methyl isobutyl ketone (MIBK) as an extractant.

The extraction system HF-H₂SO₄-MIBK proved to have the most promising separation effect with the highest purity of each niobium and tantalum oxides.

The optimum loading conditions in HF-H₂SO₄-MIBK system were: O/A = 10/1.15 minutes contact time, 100% MIBK. while the feed solution assayed 4.3 N HF and 5.7 N H₂SO₄. Moreover, the stripping process was performed with 1.0 N HF and distilled water in subsequent steps.     

Feasible design for electricity generation from <i>Chlorella vulgaris</i> using convenient photosynthetic conditions

Many recent studies are concerned with low cost, easy to handle and alternative renewable energy as a feasible solution for the upcoming crisis of energy shortage. Microalgae are unicellular entities the can only depend on CO2, water and solar power to cover their nutritional needs. The current study is concerned with using algal cells in a polymeric hydrogel, as a cheap source of energy for electricity generation. Chlorella vulgaris has been proved to be a promising algal species for electricity generation, as compared with Micractinium reisseri. PVA hydrogel has been used for the immobilization of both algal species in order to protect them from the adverse surrounding conditions in addition to its ability to slowly release the required water molecules according to needs. Under these conditions, C. vulgaris showed the ability to generate 60 mV compared with 15 mV generated by M. reisseri. Scanning electron micrographs showed nano-threads that bind the C. vulgaris cells to each other, indicating the ability of algae to create nanowires that facilitate the electron transfer among algal cells and from cells to the nearest electrode. However, we would expect an increase in the produced potential with simultaneous amendment of environmentally polluted water, such as sewage or waste water. Both of FTIR and raman spectroscopy proved the presence of the characteristic groups of PVA hydrogel and proved the proper integration of the algal cells inside the hydrogel cavities     

Hydrothermal preparation of TiO₂-Ag nanoparticles and its antimicrobial performance against human pathogenic microbial cells in water

Water contaminated with pathogenic microbes is considered as one of the most common routes for transmitting diseases in human beings. Different methods have been applied for the decontamination of microbes in contaminated water. In the current study, an easy to do hydrothermal method has been used for the preparation of TiO₂-Ag nanoparticles. The obtained material was characterised using a scanning electron microscope (SEM) and fourier transform infra-red spectroscopy (FTIR). The morphological appearance of the obtained nanoparticles was in the shape of a sphere with a size range of 60-90 nm. The antimicrobial activity of the prepared nanoparticles was tested against several pathogenic bacteria and fungi. The obtained results proved that the nanoparticles succeeded to affect all the tested microbes in the following order: Bacillus cereus ATCC6633>Pseudomonas aeruginosa ATCC9027= Klebsiella pneumoniae ATCC13883>Vibrio cholera ATCC700=Candida albicans ATCC 700=Escherichia coli NCTC10418>Staphylococcus aureus ATCC6538. The minimum inhibitory concentration (MIC) of the prepared nanoparticles varied among the tested microbes at range of 12 mg/ml and 25 mg/ml. These results encourage the application of prepared TiO₂-Ag nanoparticles for treatment of microbe-contaminated waters.     

Libyan Date Syrup (Rub Al-Tamr)

Representative samples of date syrup were obtained from the local market and analysed. The chemical composition and some characteristics of these samples were investigated. The reducing sugars of the syrup comprised about 95% of its total sugars content. The major sugars present were glucose—48.70%, fructose-45.21%, and sucrose—6.09%. Furthermore, the coloring matters of date syrup were isolated, separated and further investigated. It was concluded that the color groups, degradation products of reducing sugars, melanoidines, and iron-polyphenolic complexes, contributed to the color of date syrup. The melanoidine-type compounds, which comprised the major part of syrup colorants, showed a low selective adsorption tendency on both charcoal and anion resins. An efficient clarification of date syrup has been achieved by the use of calcium phosphate precipitation. The results obtained may be of help in devising industrial processes for the utilization of dates, abundantly grown in Libya, in the production of “Total invert liquid sugar” with multiple commercial uses of its own.     

MUTAGENICITY OF HEATED COTTONSEED FRYING OIL

A control experiment showed that cottonseed oil used in frying falafel developed significant mutagenic activity. As a result, one hundred samples of fresh and used cottonseed oil employed commercially for frying falafel were collected from restaurants in thirteen major cities of Egypt. Samples were examined for mutagenic activity using the Salmonella typhimurium assay with and without S9. Six of the heated oil samples showed significant mutagenic activity. None of the fresh unheated oil samples were mutagenic. Salmonella typhimurium TA 102 gave a higher response than did either TA 100 or TA 98.
Peroxide, hydroxyl, acid and conjugated diene values were much higher for mutagenic samples. Iodine values, however, were lower. Liquid chromatography fractionation revealed that the mutagenicity was concentrated in the polar fraction. The column fraction having the highest mutagenic activity was further examined by chromatographic and spectroscopic techniques.     

A New Approach for Manufacturing a High Porosity Ti-6Al-4V Scaffolds for Biomedical Applications

Titanium and its alloys are currently considered as one of the most important metallic materials used in the biomedical applications, due to their excellent mechanical properties and superior biocompatibility. In the present study, a new effective method for fabricating high porosity titanium alloy scaffolds was developed. Porous Ti-6Al-4V scaffolds are successfully fabricated with porosities ranging from 30% to 70% using spaceholder and powder sintering technique. Based on its acceptable properties, spherical carbamide particles with different diameters （0.56, 0.8, and 1mm） were used as the space-holder material in the present investigation. The Ti-6Al-4V scaffolds porosity is characterized by using scanning electron microscopy. The results show that the scaffolds spherical-shaped pores are depending on the shape, size and distribution of the space-holder particles. This investigation shows that the present new manufacturing technique is promising to fabricate a controlled high porosity and high purity Ti-6Al-4V scaffolds for hard tissue replacement.