Removal of boron from aqueous solution by using neutralized red mud

The adsorptive removal of boron from aqueous solution by using the neutralized red mud was studied in batch equilibration technique. The effects of pH, adsorbent dosage, initial boron concentration and contact time on the adsorption were investigated. The experiments demonstrated that boron removal was of a little fluctuation in pH range of 2-7 and it takes 20 min to attain equilibrium. The adsorption data was analyzed using the Langmuir and the Freundlich isotherm models and it was found that the Freundlich isotherm model represented the measured sorption data well.     

Effect of ZrSiO4 on the Friction Performance of Automotive Brake Friction Materials

Friction-wear properties of the ZrSiO4 reinforced samples were measured and compared with those of plain bronze based ones. For this purpose, density, hardness, friction coefficient wear behaviour of the samples were tested. Microstructures of samples before and after sintering and worn surfaces were also investigated by scanning electron microscopy （SEM）, and the wear types were determined. The optimum friction-wear behaviour was obtained in the sample compacted at 500 MPa and sintered at 820℃. Density of the final samples decreased with increasing the amount of reinforcing elements （ZrSiO4） before pre-sintering. However after sintering, there is no change in density of the samples including reinforcing elements （ZrSiO4）. With increasing friction surface temperature, a reduction in the friction coefficient of the samples was observed. However, the highest reductions in the friction coefficients were observed in the as-received samples containing 0. 5% reinforced ZrSiO4. The SEM images of the sample indicated that while bronze-based break lining material without ZrSiO4 showed abrasive wear behaviour, increasing the amount of ZrSiO4 resulted a change in abrasive to adhesive wear mechanism. All samples exhibited friction-wear values, which were within the values shown in SAE-J661 standard. With increasing the amount of reinforcing ZrSiO4, wear resistance of the samples was increased. However samples reinforced with 5% and 6% ZrSiO4 showed the best results.     

The application of solar distillation technique as a mean for olive mill wastewater management

The present study was conducted on a pilot scale level using a solar still unit to separate olive mill wastewater (OMW) into condensate and solid residue. The prevailing conditions inside the solar still, rates of distillation and a number of quality parameters for condensate [pH, electrical conductivity (EC), turbidity, chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN) and total‐phenols] were evaluated to assess the system performance. The solid residue was evaluated as well for its utility as a potential biofuel. The condensate is acidic (pH 3.8), colourless, transparent and free of suspended solids. The turbidity and EC were reduced in the condensate by 100 and 99%, respectively, while the loads of COD, TOC, TN and T‐phenols were reduced by 90, 98, 99.9 and 99.96%, respectively. Almost 0.04% of initial total phenols found in OMW were recovered in the condensate. High calorific value (23.5 kJ/g) and combustible portion (84%) of solid residue suggests its applicability as a potential biofuel     

Kinetics of plasma paste boronized AISI 8620 steel in borax paste mixtures

In the present study, AISI 8620 steel was plasma paste boronized by using various borax paste mixtures. The plasma paste boronizing process was carried out in a dc plasma system at a temperature of 973, 1023 and 1073 K for 2, 5 and 7 h respectively in a gas mixture of 70% H₂-30% Ar under a constant pressure of 10 mbar. The properties of the boride layer were evaluated by optical microscopy, X-ray diffraction, the micro-Vickers hardness tester and the growth kinetics of the boride layers. The thickness of the boride layers varied from 14 to 91 μm depending on the boronizing time and temperature. X-ray diffraction analysis of boride layers on the surface of the steel revealed the formation of FeB and Fe₂B phases. Depending on the temperature and layer thickness, the activation energies of boron in steel were found to be 99.773 kJ/mol for 100% borax paste.     

An Experimental Investigation on the Chemical Stability of Selected Formation and Determination of the Proper Type of Water-Base Drilling Fluids. Part 2. Test Results

The objective of this study was to select the proper drilling fluid type and composition for drilling stable holes through the problems of the selected formations. This study was performed on shale samples taken from 10 wells in which hole instability was encountered to various extents during drilling the Germav formation. Both ionic and polymer inhibitions were utilized in formulating the proper drilling for the Germav formation. Ionic inhibition was obtained using KCl and NaCl. Polyanionic polymer (Pac-L) was used for providing the polymer encapsulation. Experimental results indicated that KCl is superior to NaCl in providing ionic inhibition. Both salts lowered the interaction between the drilling fluid and Germav formation, but better results were obtained with KCl. Minimum salt concentration up to 15% yields more inhibitive environment. Polymer inhibition tests indicated that minimum Pac-L concentration required for maintaining the polymer inhibition was about 2 lb/bbl for both systems. In conclusion, KCl/encapsulating polymer system seems to be the most proper water: base drilling fluid available for Germav formation achieving the required wellbore stability. The fluid loss and suspending properties of the proposed system must be controlled using the modified starch and XC polymer.     

Risky driving behavior among university students and staff in the Sultanate of Oman

Background

There is a well developed literature on research investigating the relationship between various driving behaviors and road crash involvement. However, this research has predominantly been conducted in developed economies dominated by western types of cultural environments. To date no research has been published that has empirically investigated this relationship within the context of the emerging economies such as Oman.

Objective

The present study aims to investigate driving behavior as indexed in the driving behavior questionnaire (DBQ) among a group of Omani university students and staff.

Methods

A convenience non-probability self-selection sampling approach was utilized with Omani university students and staff.

Results

A total of 1003 Omani students (n = 632) and staff (n = 371) participated in the survey. Factor analysis of the BDQ revealed four main factors that were errors, speeding violation, lapses and aggressive violation. In the multivariate logistic backward regression analysis, the following factors were identified as significant predictors of being involved in causing at least one crash: driving experience, history of offenses and two DBQ components, i.e., errors and aggressive violation.

Conclusion

This study indicates that errors and aggressive violation of the traffic regulations as well as history of having traffic offenses are major risk factors for road traffic crashes among the sample. While previous international research has demonstrated that speeding is a primary cause of crashing, in the current context, the results indicate that an array of factors is associated with crashes. Further research using more rigorous methodology is warranted to inform the development of road safety countermeasures in Oman that improves overall Traffic Safety Culture.     

A strategic decision framework for a value added supply chain

Supply chains are becoming increasingly complex. The structure of the supply chain and the suppliers who participate in it are critical decisions for managers. The supply chain is no longer simply a source of inputs or services but an integral source of value added. It is clear that in some cases strategic supply chain objectives may require trade-offs, for example, between cost and innovation capability or between managing risk and maximising flexibility. These decisions balancing trade-offs between desirable partner characteristics are critical and can make a significant contribution to business performance. A framework is outlined, based on the foundation of extant literature, within which firms can make strategic decisions on supply chain structure by categorising the characteristics they prioritise in their supply chain strategy. There is also a strong foundation in the literature on developing mathematical models that provide insight into the decision-making process. A mixed integer programming model is specified that incorporates the opportunity for diversification and provides a demand allocation decision. The model is robust enough to allow for single or diversified supplier strategies based not only on capacity constraints but also on risk pooling and minimum performance requirements for key characteristics that form the basis of the strategy. A Lagrangian relaxation is proposed and satisfactory performance results are provided.     

Evolution of the mosaic structure in InGaN layer grown on a thick GaN template and sapphire substrate

The In_xGa_1?xN epitaxial layers, with indium (x) concentration changes between 0.16 and 1.00 (InN), were grown on GaN template/(0001) Al₂O₃ substrate by metal organic chemical vapour deposition. The indium content (x), lattice parameters and strain values in the InGaN layers were calculated from the reciprocal lattice mapping around symmetric (0002) and asymmetric (10–15) reflection of the GaN and InGaN layers. The characteristics of mosaic structures, such as lateral and vertical coherence lengths, tilt and twist angle and heterogeneous strain and dislocation densities (edge and screw dislocations) of the InGaN epilayers and GaN template layers were investigated by using high-resolution X-ray diffraction (HR-XRD) measurements. With a combination of Williamson–Hall (W-H) measurements and the fitting of twist angles, it was found that the indium content in the InGaN epilayers did not strongly effect the mosaic structures’ parameters, lateral and vertical coherence lengths, tilt and twist angle, or heterogeneous strain of the InGaN epilayers.     

Investigation of Rubber-to-Metal Bonding on Solid Rubber Tires

The knowledge on rubber-to-metal adhesion, which is an important issue in manufacturing processes of some automotive and aircraft parts and solid rubber tires, is generally confined within the patented information. This study investigates the factors contributing to the ability to produce strong and permanent rubber-to-metal bonds. Consideration is given to the material factors and methods of surface preparation, for which the quantitative data available in the open literature are very limited. Bonding strengths achieved by two different surface preparation methods are compared. Also discussed are percent elongation, bonding strength, and tensile strength measurements on the samples prepared in accordance with the solid tire recipe and cured at 140°, 150°, 160°, and 170°C. The effect of molding forces on rubber-to-metal bonding is established by applying different force values. The use of “cushion gum” as adhesion medium is proposed as a new way of obtaining successful rubber-to-metal bonding. The effect of the thickness of cushion gum layer on bond strength is presented.