Assessment Approach of Life Cycle of Vehicles Tyres on Egyptian Road Network

Recently the problem of used vehicle tires becomes in focus in Egypt. In this paper, the scope is to study life cycle of the yearly used tires by vehicles travelling on the Egyptian road network. For the first time, Life Cycle Assessment (LCA) approach is performed for tires used by the Egyptian road transportation fleet. Global Warming Potential (GWP), health toxicity, and Aquatic acidification are the main impact categories considered. The Life Cycle Impact Assessment Methodology (IMPACT2002+) is implemented for LCA analysis to encompass the transportation process of the yearly needed amount of tires, and the usage of the tires. At the nexus, data about transport demand and activity have been collected. Also, modal split ratios have been incorporated. It was found that, Egyptian road tires contributes mainly to GWP on the midpoint effect and also contributes mainly to the damage regarding terrestrial acidification and nitrification. Regarding the normalized effect, it was found that the highest contribution of used tyres on Egyptian road network is in respiratory effects on human health with 3.52*104(person year/kg) followed by terrestrial acidification of 3.1*104(person year/kg)

Mechanical Erosion Investigation Through the Solid Rocket Motor’s Nozzle

The solid rocket motor (SRM) is considered one of the essential engines that facilitatesaerospace research; thus, investigating the propellant burning process is vital. One of the challenges facing its growth is the oxidization of the aluminum into aluminum oxide at the exhaust’s high pressures and temperatures. The oxidized aluminum forms agglomerates, impinge on the exit nozzle walls, causing severe damage (erosion) to the nozzle material. Thus, the present work attempts to investigate and reduce this erosion. Two different approaches are followed in the current work, the first one aims to better understand the aluminum oxide agglomerates break-up mechanism and the factors affecting it experimentally (subsonic condition due to the safety purposes limitations), while the other establishes a numerical model to predict the nozzle mechanical erosion within the rocket’s combustion chamber severe conditions. The breakup process and some factors affecting it are investigated in three sections. Twophaseair-water flow experimental set-up is used, as a substitute for liquid aluminum agglomerates and exhaust combustion gases, in the three sections. The first section’s experimental results show that increasing the exhaust air velocity enhances the droplet\u27s break-up tendency to reduce the average diameter and increase droplet numbers per the testing channel volume. Numerical models were constructed and validated using the experimental results. The percentage error in the droplets’ average diameter and the number is between 6–15% and 8-18%. Furthermore, the effect of reducing the liquid surface tension was studied. The results showed that it facilitates water bodies’ separation from the interface surface, because of the reduced bounding forces between surface’s molecules, which enhances the break-up process (0.5-17% increase in the droplets’ average diameter and 4-100% increase in its number) and reduce the droplets impact on the nozzle walls, hence reduce the SRM nozzle erosion problem. While the second section investigated the breakup process at different water flow rates andconstant air velocity, where the results were used to validate a numerical model. The results revealed an excellent acceptance between the numerical, the experimental data (6-19%), and the effect of increasing the water flow rate on the break-up mechanism. The validated numerical model was further used to study the airflow acceleration impact on the break-up process. It was found that applying acceleration to the airflow subjects the water surface to rapid and sudden changes in the relative velocity between the gas and liquid, thus separating more water fragments from the primary liquid. In other words, it enhances the break-up process by reducing the average diameter with a range from 6.5% to 9% compared to the no-acceleration case and increasing the average droplets’ number [8.5-17%]. Finally, the third section investigated the submerged nozzle configuration on the breakupprocess under different air and water flow rates, in addition compared between the submerged nozzle and the external one. It was found that having a submerged nozzle enhances the droplets breakup in the nozzle convergent section due to the existence of the recirculation zones. However, the separated droplets will have higher velocity to hit the walls with, hence a supersonic model simulates the actual conditions within the rocket is essential to decisively conclude the submerged nozzle effect on the nozzle mechanical erosion. Erosion prediction of the solid propellent nozzle is vital for its design process. Thus, thesecond approach employing a multi-phase numerical model is established based on the Eulerian- Lagrangian approach to model the aluminum particles burning inside the combustion chamber, in addition to simulating the mechanical erosion of the nozzle. The numerical model is validated against numerical and experimental results from the literature. Then the validated model will be further used to investigate the SRM nozzle erosion at different boundary conditions, nozzle configurations, particles, and propellant properties. First the model was used to simulate the agglomerates\u27 break-up, in addition to predicting the mechanical erosion for aluminum particles with lower surface tension. The results showed that applying the Reitz-Diwakar breakup model reduces the erosion rate by 6.2% - 24% depending on the injected droplets. In addition, it was found that a decrease in the erosion rate by 1% to 4.5% can be achieved by reducing the aluminum additive\u27s surface tension by 15%. Then, an investigation of the effect of increasing the propellant aluminum content anddifferent particles’ injection velocity on the nozzle mechanical erosion was conducted and the results showed that having higher aluminum content increases the nozzle erosion by 4-10% compared to the 15% case. Furthermore, the aluminum particles will not fully burn within the combustion chamber and will participate in the nozzle erosion. In the end, having particles with higher initial velocity at the burning surface increases the nozzle mechanical erosion, despite of the incident mass flux decline. Finally, the submerged nozzle configuration effect on the mechanical erosion was studiedat seven particle diameters and was compared against the external nozzle results. And it was concluded that comparing the external nozzle and submerged nozzle configurations in terms of the predicted mechanical erosion, the external nozzle will perform better than the submerged one as lower mechanical erosion exists in its different sections

Custodiol versus Cold Blood Cardioloplegia in Minimally Invasive Aortic Valve Surgery: A Comparative Study

Background: Myocardial protection is a critical concern during aortic valve replacement. Custodiol cardioplegia and cold blood cardioplegia represent two primary strategies for myocardial preservation. This study sought to compare Custodiol and blood cardioplegia results for myocardial protection in aortic valve replacement. Methods: This prospective study included 200 patients who were evenly divided into two groups based on the cardioplegia solution used: the Custodiol group (Group A) and the cold blood cardioplegia group (Group B). The study evaluated postoperative mechanical ventilation duration, ICU and overall hospital stay lengths, and echocardiographic findings at three and six months postoperatively. Results: Compared with Group B, Group A had significantly shorter ventilation times (min-max: 6-9 vs. 9-15 hours), ICU stays (3-3 vs. 4-5 days), and hospital stays (7-9 vs. 10-20 days) (p<0.001 for all). Group A exhibited shorter cardiopulmonary bypass times (179 ± 9 minutes vs. 216 ± 14 minutes, p<0.001) and cross-clamp times (137 ± 8 minutes vs. 176 ± 18 minutes, p<0.001). Postoperative atrial fibrillation was more common in Group A (66% vs. 20%, p<0.001), while ventricular tachycardia and nodal rhythm post-defibrillation were greater in Group B. Mortality was lower in Group A (2% vs. 9%, p=0.03). However, at three and six months postoperatively, echocardiographic findings were significantly different in terms of left atrial diameter and left ventricular end-systolic diameter between Group A and Group B (p<0.001). Conclusion: Custodiol cardioplegia could be associated with superior postoperative outcomes, including shorter ventilation times, ICU and hospital stays, and lower mortality rates, compared to cold blood cardioplegia in minimally invasive aortic valve replacement surgery

Numerical modelling of a high temperature borehole thermal energy storage system: Norway case study

Global warming is threatening life on earth. Utilising renewable energy is considered as the most effective measure to minimise anthropogenic CO2 emissions. High-temperature borehole thermal energy storage (BTES) systems have a world-wide potential to reduce energy consumption, increase energy utilisation of waste heat and provide efficient seasonal heat storage. Hybrid application of BTES and solar energy leads to net zero emissions. In this study HT-BTES is evaluated for seasonal thermal heat storage and recovery. To this end, a CMG STARS model was built and validated using the existing 100-wells BTES system in Norway. Then, the model was used to evaluate BTES thermal performance and thermal recovery efficiency. Sensitivity analysis was also conducted to study the dynamics of storage temperature in the BTES under different operating conditions, such as heat carrier flow rate, injection temperature, and charging period. Results of this case study show that the model-predicted temperatures during charging and discharging are in good agreement with the existing BTES system. In 5 years of operation, 35.5% of the heat injected into the BTES system was recovered, while the significant heat remained in the borehole region and lost to surrounding rock (64.5%). BTES was found very sensitive to flow rate, the charging period and injection temperature. Borehole depth has a minimal effect on BTES storage temperature at constant studied injection temperature.publishedVersio

Doppler Flowmeter Is a Valuable Tool for Prevention of Early Postoperative Myocardial Infarction

Background: Early postoperative myocardial infarction (MI) remains a critical complication following coronary artery bypass grafting (CABG). The intraoperative use of Doppler flowmetry could improve outcomes by ensuring optimal graft patency and flow. This study evaluated the effect of Doppler flowmetry on early postoperative MI in patients undergoing CABG. Methods: This double-blinded, randomized controlled study included 120 patients who underwent elective CABG. Patients were divided into two equal groups: Group A underwent CABG with Doppler flowmetry, and Group B underwent CABG without Doppler flowmetry. The patients' ages ranged between 45 and 60 years old, with no difference in gender distribution between groups. The primary outcomes were early postoperative arrhythmias and echocardiographic parameters. Secondary outcomes included mechanical ventilation duration, ICU stay, and complication rates. Results: There was no difference in postoperative arrhythmias between groups (P= 0.142). Postoperative regional wall motion abnormalities occurred in 90% of Group B versus 5% of Group A (P < 0.001). Difficult weaning (10 (16.7%) vs. 25 (41.7%); P= 0.003), longer ventilation time (8 ±3 vs. 17 ±7 h; P<0.001), and prolonged ICU stay (3 (3 – 10) vs. 5 (2 – 9) days; P<0.001) were all significantly higher in Group B than that of group A. Infection and re-exploration rates were significantly higher in Group B (13.3% and 25%) than in Group A (1.7% and 6.7%) (P = 0.032 and P = 0.006, respectively). The cross-clamp time and total circulatory time were shorter in Group A (55 ± 6 minutes and 87 ± 12 minutes) than in Group B (89 ± 12 minutes and 110 ± 17 minutes) (P < 0.001). Multivariable logistic regression indicated that using Doppler flowmetry reduced the risk of reexploration by 81% (OR: 0.189, 95% CI:0.054 – 0.663, P= 0.009). There was no early mortality in both groups Conclusion: Using Doppler flowmetry during CABG could improve intraoperative and postoperative outcomes, reducing perioperative myocardial infarction and related complications. This technique could be valuable to standard CABG procedures, enhancing patient recovery and reducing hospital stay duration

Finger-joint optimization of spruce lumber using finite element and statistical modelling

The primary objective of this thesis was to investigate and explore the feasibility of using a numerical 3-D finite element analysis (FEA) and statistical design of experiment methodology (DOE) to optimize finger-joint (FJ) configuration. This thesis provides guidelines to achieve structural behaviour of finger-joined elements that approaches non-finger-joined (NFJ) lumber. The optimum configurations will improve strength, save time, and money. A numerical 3-D finite element model was established using Abaqus FEA to simulate the interface between the two FJ adherent parts. The model was verified with experimental tests of actual FJ samples which showed a close agreement with the corresponding numerical model. An optimization of FJ lumber in horizontal, vertical and slope orientations were carried out to obtain the FJ geometry that achieves maximum structural performance of such lumber. A Reduced Quadratic Response Surface Model (RSM) and a Modified Two-Factor Interaction (2FI) experimental design were then used for both Normal and Inclined FJ categories, respectively. The statistical model were set up to assess the effect of the main factors: FJ-length, FJ-pitch, and FJ-tip width (tip thickness) and their interactions values on the stiffnesses. One additional parameter, FJ-Slope of three-levels was added with the Inclined FJ category. The obtained results showed clearly the potential of increasing FJ resistance by optimizing its geometry. In addition, it was observed that FJ in vertical orientation achieved higher structural performance close to the NFJ lumber comparing to the FJ in the horizontal orientation. Regression analysis was used to develop a design equations per each joint orientation (horizontal and vertical). The predicted equations will be useful to determine the optimum FJ geometry directly without the need to use a trial and error approach to achieve structural behaviours close to the NFJ lumber. Finally, enhancing these properties impact the behaviour and capacity of finger-joined elements at the serviceability and ultimate limit states

Development and validation of a correction equation for Corvis tonometry.

Primary objectiveThis study uses numerical analysis and validation against clinical data to develop a method to correct intraocular pressure (IOP) measurements obtained using the Corvis Tonometer for the effects of central corneal thickness (CCT), and age.Materials and methodsFinite element analysis was conducted to simulate the effect of tonometric air pressure on the intact eye globe. The analyses considered eyes with wide variations in IOP (10-30 mm Hg), CCT (445-645 microns), R (7.2-8.4 mm), shape factor, P (0.6-1) and age (30-90 years). In each case, corneal deformation was predicted and used to estimate the IOP measurement by Corvis (CVS-IOP). Analysis of the results led to an algorithm relating estimates of true IOP as a function of CVS-IOP, CCT and age. All other parameters had negligible effect on CVS-IOP and have therefore been omitted from the algorithm. Predictions of corrected CVS-IOP, as obtained by applying the algorithm to a clinical data-set involving 634 eyes, were assessed for their association with the cornea stiffness parameters; CCT and age.ResultsAnalysis of CVS-IOP measurements within the 634-large clinical data-set showed strong correlation with CCT (3.06 mm Hg/100 microns, r(2) = 0.204) and weaker correlation with age (0.24 mm Hg/decade, r(2) = 0.009). Applying the algorithm to IOP measurements resulted in IOP estimations that became less correlated with both CCT (0.04 mm Hg/100 microns, r(2) = 0.005) and age (0.09 mm Hg/decade, r(2) = 0.002).ConclusionsThe IOP correction process developed in this study was successful in reducing reliance of IOP measurements on both corneal thickness and age in a healthy European population