Jamali H.U.,University of Cardiff |
Jamali H.U.,Karbala University |
Sharif K.J.,University of Cardiff |
Evans H.P.,University of Cardiff |
Snidle R.W.,University of Cardiff
Tribology Transactions | Year: 2015
This article presents the results of a transient elastohydrodynamic analysis of the conditions at the contact of two pairs of helical gears operating with different gear ratios. The effects of the variation in contact geometry, kinematics, and tooth loading during the meshing cycle are taken into account together with both tip relief and axial crowning profile modifications. The results are compared with analyses under corresponding steady-state conditions for both point contact and equivalent line contact models. The comparisons show that, away from the ends of the contact lines, steady-state conditions can be used effectively to assess the film-forming capabilities of the gears. Conditions at the end of the contact lines are found to be more adverse with significant transient squeeze film effects. The form of tip relief profile adopted is shown to be highly influential in determining the peak contact pressures and thinnest oil films within the contacts. These conditions are experienced at all axial positions on the tooth flanks at the locations of the start of tip relief profile modifications. If the tip relief profile introduces a slope discontinuity to the gear profile, this can cause a significant stress concentration and very poor film-forming behavior. © 2015, Copyright © Society of Tribologists and Lubrication Engineers.
Ahmed L.M.,Karbala University |
Ivanova I.,Leibniz University of Hanover |
Hussein F.H.,University of Babylon |
Bahnemann D.W.,Leibniz University of Hanover
International Journal of Photoenergy | Year: 2014
Titania modified nanoparticles have been prepared by the photodeposition method employing platinum particles on the commercially available titanium dioxide (Hombikat UV 100). The properties of the prepared photocatalysts were investigated by means of the Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-visible diffuse spectrophotometry (UV-Vis). XRD was employed to determine the crystallographic phase and particle size of both bare and platinised titanium dioxide. The results indicated that the particle size was decreased with the increasing of platinum loading. AFM analysis showed that one particle consists of about 9 to 11 crystals. UV-vis absorbance analysis showed that the absorption edge shifted to longer wavelength for 0.5% Pt loading compared with bare titanium dioxide. The photocatalytic activity of pure and Pt-loaded TiO2 was investigated employing the photocatalytic oxidation and dehydrogenation of methanol. The results of the photocatalytic activity indicate that the platinized titanium dioxide samples are always more active than the corresponding bare TiO2 for both methanol oxidation and dehydrogenation processes. The loading with various platinum amounts resulted in a significant improvement of the photocatalytic activity of TiO2. This beneficial effect was attributed to an increased separation of the photogenerated electron-hole charge carriers. © 2014 Luma M. Ahmed et al.
Obaid H.A.,University of Technology Malaysia |
Shahid S.,University of Technology Malaysia |
Basim K.N.,Karbala University |
Chelliapan S.,University of Technology Malaysia
Water Science and Technology | Year: 2015
Water pollution during festival periods is a major problem in all festival cities across the world. Reliable prediction of water pollution is essential in festival cities for sewer and wastewater management in order to ensure public health and a clean environment. This article aims to model the biological oxygen demand (BOD5), and total suspended solids (TSS) parameters in wastewater in the sewer networks of Karbala city center during festival and rainy days using structural equation modeling and multiple linear regression analysis methods. For this purpose, 34 years (1980-2014) of rainfall, temperature and sewer flow data during festival periods in the study area were collected, processed, and employed. The results show that the TSS concentration increases by 26-46 mg/l while BOD5 concentration rises by 9-19 mg/l for an increase of rainfall by 1 mm during festival periods. It was also found that BOD5 concentration rises by 4-17 mg/l for each increase of 10,000 population. © 2015 IWA Publishing.
Al-Hamood A.,University of Cardiff |
Al-Hamood A.,Karbala University |
Clarke A.,University of Cardiff |
Evans H.,University of Cardiff
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology | Year: 2015
Experimental and theoretical analyses are reported to study the heat generation and partition in an elastohydrodynamic rolling/sliding point contact. Heat is generated within the lubricant in the Hertzian region by shearing and compression of the oil film. This heat is essentially conducted to the contacting surfaces as the amount convected from the Hertzian zone by the lubricant can be neglected due to the very low lubricant mass flowrate. A two-disk test rig was used for the experimental tests using crowned, superfinished 76.2 mm diameter disks fixed on parallel shafts. Each disk was fitted with six thermocouples in two rows of three located 3 mm and 6 mm below the surface to measure the temperature distribution of the disks during the tests. In addition, the disks were insulated on both plane sides by ceramic washers to minimise heat transfer to the surroundings over those surfaces. A numerical model was developed to calculate the circumferential mean disk temperature distribution in the outer 6 mm annular ring using the inner row of thermocouples to provide a boundary condition. The model was used to predict the temperature distribution for given values of the fraction of the total heat entering the fast disk, β, and the heat transfer coefficient, h, for the disk running surfaces. Minimisation of error between predicted and experimentally measured temperatures at the thermocouple positions, together with consideration of the physical relationship between fast and slow shaft heat transfer coefficients led to the conclusion that β lies in the range 0.71-0.77 for the experiments reported in the paper and that approximately 75% of the frictional heat dissipated within the lubricant film flows into the faster disk. This result indicates that the likely mechanism of heat dissipation within the lubricant film is by slip at or near the faster surface and that consideration of heat partition is a more discerning judge of lubricant rheological behaviour than the usual consideration of traction measurements alone. © IMechE 2014.
Abbas Z.H.,Karbala University |
Doosh K.S.,University of Baghdad |
Yaseen N.Y.,The University of Mustansiriyah
Pakistan Journal of Nutrition | Year: 2015
Lactoferrin is an important protein in many biological applications as a potential cancer treatment agent. In this study, lactoferrin was purified from goat colostrum by ion exchange chromatography through CM-Sephadex C-50 column and gel filtration chromatography through Sephadex G-200 column. The purification fold and yield were (20.83 time and 62.50%) respectively. The purity of lactoferrin to homogeneity was examined by polyacrylamide gel electrophoresis under denaturing conditions (SDS-PAGE) with single bond. Some biochemical characteristics of the purified Lactoferrin were determined, The molecular weight of LF were 80 and 79.50kDa as determined by gel filtration and SDS-PAGE respectively. The percentage of carbohydrate content in goat Lactoferrin was 10.4%, mean while the Iron percentage was 123 ppm and as a saturated percent 7.8%. © Asian Network for Scientific Information, 2015.