Characterization of Machinability and Environmental Impact of Cryogenic Turning of Ti-6Al-4V

Abstract Titanium alloys are widely used in aerospace applications due to their physical and mechanical properties. However, their poor machinability remains the main challenge to improve the productivity and the surface quality. Cryogenic machining recently gained interest as a clean and economical cooling technique. It becomes a promising candidate for applications that involve aggressive metal removal, especially for hard-to-cut material. This research provides insight into the cryogenic machining performance compared to flood machining in terms of its effect on tool life, surface quality, cutting forces and environmental impact. For such analysis, turning tests of Ti-6Al-4V using cryogenic and flood technologies were conducted at different cutting conditions. Life cycle analysis was conducted using the Eco-indicator method to compare the environmental impact of each technology. The cryogenic technology significantly improved the process environmental performance in addition to enhancing the tool life and surface quality compared to flood, hence improved the process productivity

Therapeutic Potential of 25-Hydroxyvitamin D in Promoting Cardiovascular Health

Introduction: The primary focus on vitamin D therapy was to treat metabolic bone disease. Over the past decade, however, researchers have demonstrated that vitamin D may have a role in other disease processes, particularly cardiovascular diseases (CVDs). Review: Serum 25-hydroxyvitamin D (25(OH)D) deficiency is widespread, and is extremely common in kidney transplant recipients. In community surveys, lower levels of 25(OH)D were associated with significantly higher adjusted prevalence of cardiovascular risk factors and CVD. CVD patients have lower 25(OH)D levels than controls, which are associated with more severe disease and worse prognosis. 25(OH)D levels are inversely associated with insulin resistance and future risk of hyperglycemia in non-diabetic subjects. Low levels of 25(OH)D were found to be independent predictors of death and end stage renal disease (ESRD) in chronic kidney disease (CKD) patients. Supplementation with vitamin D was found to lower parathyroid hormone and increase anti-inflammatory cytokines in congestive heart failure patient. It was found to improve flow mediated vasodilatation of the brachial artery in asymptomatic vitamin D deficient subjects and diabetic patients. Vitamin D supplementation was found to reduce proteinuria, mortality and progression to dialysis in CKD patients and to reduce cardiovascular mortality in hemodialysis patients. Vitamin D and calcium supplementation was also found to reduce cancer risk in community dwelling healthy postmenopausal women. Conclusion: Low levels of vitamin D seem to have undesirable effects on health. Based on the results of recent research, the recommended lower value of serum 25(OH)D is likely to be elevated. Key Words: Vitamin D; Cardiovascular disease ; Chronic kidney diseas

Water status and yield response to deficit irrigation and fertilization of three olive oil cultivars under the semi-arid conditions of Tunisia

Sustainability of olive production is possible by adopting the modern techniques of irrigation and fertilization. In Tunisia, olive trees are usually cultivated in poor soils, under semi-arid conditions characterized by water scarcity. This study investigated the effects of different water supply and fertilization on leaf water status and crop yield of three different olive oil varieties cultivated in central Tunisia, during four experimental seasons (2014-2017). Three treatments were examined: trees conducted under rainfed conditions (TRF), which represented the control treatment, trees irrigated with 50% ETc (T50) and, finally, trees irrigated with 50% ETc and with additional fertilization (T50F). Leaf water content and potential, yield and water use efficiency have been monitored on three different varieties, Chetoui, Chemlali, and Koroneiki, which are quite typical in the considered region. For all the growing seasons, midday leaf water potentials were measured from April to September. Midday leaf water potentials (MLWP) were generally higher for the two irrigated treatments (T50 and T50F) than for non-irrigated trees (TRF). As the season proceeded, MLWPs tended to decrease during summer for all the treatments and varieties. The lowest values were observed for the non-irrigated trees, varying between -3.25 MPa to -4.75 MPa. Relative leaf water content followed the same trends of midday leaf water potentials. Chetoui showed the lowest yield, which did not exceed 1530 Kg/(ha year), even for irrigated and fertilized trees. On the other hand, the yields of Chemlali and Koroneiki, cumulated in the four years, reached the maximum value of about 20 tons/ha. For these two varieties, the cumulated yield obtained in the control treatment (TRF) resulted significantly lower than the corresponding of the other two treatments (T50 and T50F). The highest irrigation water use efficiency (WUE) was estimated for Chemlali (T50) and (TRF). WUE was equal to 1.22 Kg/m3 for Koroneiki under fertigated treatment (T50F). Application of the only water supply (50% ETc) or associated with fertilizer improved the tree water status and increased the productivity of Chemlali and Koroneiki varieties

Steady Flow over a Rotating Disk in Porous Medium with Heat Transfer

The steady flow of an incompressible viscous fluid above an infinite rotating disk in a porous medium is studied with heat transfer. Numerical solutions of the nonlinear governing equations which govern the hydrodynamics and energy transfer are obtained. The effect of the porosity of the medium on the velocity and temperature distributions is considered

Synthesis of green thermo-responsive amphoteric terpolymer functionalized silica nanocomposite derived from waste vegetable oil triglycerides for enhanced oil recovery (EOR)

Despite the high efficiency of polymer flooding as a chemical enhanced oil recovery (CEOR) technique, the low thermal stability and poor salt resistance of widely applied partially hydrolyzed polyacrylamide (HPAM) limited the application of this technique in oil reservoirs at harsh reservoir conditions of high–temperature and high–salinity (HTHS). These inadequacies of HPAM, result in the urge for an environmentally friendly polymer with good viscosifying properties and a substantial effect on mobility ratio at HTHS reservoir conditions. In this research, a high oleic acid waste vegetable oil (WVO) is utilized to synthesize a novel environmentally benign, thermo-responsive amphoteric nanocomposite for EOR applications at HTHS reservoir conditions. A green route transesterification reaction has been utilized to synthesize a novel thermo-sensitive monomer from WVO. The existence of unsaturated fatty acids isolated double bonds and acryloyl functional groups in the synthesized monomer has been confirmed using different characterization methods. The reactive acryloyl double bond in the synthesized monomer has been copolymerized with acrylamide, acrylacyloxyethyltrimethyl ammonium chloride, and 2-acrylamide-2-methylpropane sulfonic acid in presence of dimethylphenylvinylsilane via free radical emulsion polymerization. The synthesized nanocomposite has been characterized by FTIR, 1H NMR, SEM, EDX, TEM, and DLS. The thermal stability of the nanocomposite has been evaluated by TGA and DTA analysis. The results indicated that nanocomposite solution exhibited a pouncing thermo-thickening behaviour and superior viscosifying properties even at an ultra-low polymer concentration of 0.04 wt.% as the temperature increased from 25 to 100 °C, with increasing salinity from 10,000 to 230,000 ppm as well as salt-free solutions. Flooding experiments demonstrated that the oil recovery factor reached 15.4 ± 0.1% using low nanocomposite concentrations of 0.04 wt.%, 22.6 ± 0.3% using nanocomposite concentrations of 0.06 wt.% and 25 ± 0.2% using 0.1 wt.% nanocomposite concentrations evaluated under hostile conditions of 100 °C and salinity of about 230,000 ppm. This research offers a new direction for the synthesis of a novel green, high molecular weight thermo-responsive nanocomposite for EOR application at extremely harsh reservoir conditions via WVO valorization

Halophytes as Forages

It is the chemical composition of the halophyte forages and the digestion process of these forages that matter. As the science gets more advanced and the information about these two points becomes clearer, the view of this information might modify our understanding to these processes. Then, some topics might be dropped, and others might be raised or become more obvious. However, the feeding of halophyte forages as per se has several drawbacks and therefore, they have to be fed in mixed rations, fortifying these rations with energy supplements

A Study on the Factors Influencing the Intention of Blog Usage: A Case of UUM Postgraduate Students

Nowadays, there has been a dramatic proliferation in the number of blogs and several social networks; however, little is published about what factor (s) motivates universities students to participate in blog activities. The remarkable growth and use of a social networking website such as "Facebook", "Hi5", and "Friendster" among UUM international postgraduate students is more challenging for a researcher to investigate the extent to which a new media channel affects people’s lives, relationships, and wellbeing, how and why it is used, and who is using it. Based on the Theory of Reasoned Action (TRA), a model was developed relating technology acceptance (TAM) and social influences. a combination of convenience and purposive sampling was used to collect the data from UUM Postgraduate students that used different blogs and Facebook regularly. A survey of 112 of UUM postgraduate students found strong support for the model. One of the major finding of this research illustrated that perceived usefulness, ease of use and social norms were positively related to attitude toward blogging and accounted for a higher variance. On the other hand, perceived enjoyment and attitude toward blogging did not significantly influence UUM postgraduate students’ intention to continue to use Facebook as their favorite blogging site

Aeroelastic Investigation of Long Span Suspension Bridge Decks by Numerical CFD and FSI Analyses

CFD (Computational Fluid Dynamics) simulations appear to be strong competitor of the wind tunnel test which required scaled model and it is really expensive and time consuming tool in designing bridges therefore there is a strong claim to replace them with CFD. Analyses carried out for different deck cross sections by secondary development of commercial computational fluid dynamics software ANSYS FLUENT, establishing two dimensional bending and torsional fluid-structure interaction (FSI) numerical model to calculate flutter critical wind speed. The flutter motion belongs to a sharp growth of amplitude (heave or rotation) as a function of the wind speed can be detected by performing the FSI at different wind speeds set in FLUENT model as a velocity inlet. By using the two neighboring wind speeds the critical wind speed can be obtained once a decay motion oscillation observed. Steady and unsteady simulations have been computed in order to judge the feasibility of CFD simulations in the early design stage of long span bridges. Additionally realizable (κ-ε) model with enhanced wall treatment and (κ-ω SST) turbulence models have been considered to verify their performance in bridge aerodynamics problems. It has been found that static aerodynamic coefficients have been correctly modeled using a steady simulation, while flutter critical wind speed is judged from time histories of unsteady simulations for stationary deck sections. The validity of the simulation method was verified by comparison of simulation results with the work done by other researchers. Keywords: CFD, critical flutter wind speed, bridge aeroelasticity, suspension bridges