Simulation and feedback control of the flow past the Ahmed body

This research investigates the turbulent flow past a blunt bluff body. The square-back Ahmed body is considered a canonical bluff body, representing a simplified road vehicle. Wall resolving Large Eddy Simulations (LES) were used to investigate the dynamics of the unforced flow and accordingly inform control strategies for drag reduction. The turbulent wake behind a square-back Ahmed body in close proximity to the ground exhibits bi-modal switching. This manifests as the centre of the wake switching between one of two asymmetric positions, either horizontally or vertically. Switches occur over random timescales, with the wake recovering symmetry in the long time-average. The present work investigates numerically feedback control for suppressing horizontal (lateral) wake bi-modality of a square-back Ahmed body at Re_H ∼ 3.3 × 10^4 based on the body height. Base-mounted pressure sensors are used to estimate the position of the wake as an input signal for the controller, while actuation targets the near-wake region via synthetic jets emanating from a gap around the perimeter of the Ahmed body base. A nonlinear feedback controller based on a Langevin model of the wake dynamics is synthesised. This successfully suppresses the wake lateral bi-modal switching. However, this switching is replaced by a time-periodic streamwise motion of the large coherent structure occupying the near-wake region. Further, the controller amplifies the higher frequency dynamical wake modes. The action of feedback control also leads to base pressure recovery and a reduction in pressure drag. A trade-off between the degree of bi-modality suppression and drag reduction is observed upon varying the controller parameters. A maximum drag reduction of 7.4% is achieved for a semi-symmetrised wake, with a fully symmetrised wake achieving a 2.5% reduction. Wake bi-modality is found to be sensitive to different parameters, including the free stream turbulent intensity, the underbody flow and the dynamics of the upstream boundary layers developed along the longitudinal surfaces. Boundary layers separate and reattach close to the body’s fore-end before reaching the base. Following this recently-established link by Hesse and Morgans (2021), the second part of this research investigates the effect of suppressing boundary layer separations on wake bi-modality. Hairpin vortices, formed at the reattachment points, grow along the surfaces before breaking down upstream of the base. The resultant smaller vortices from the top and side surfaces interact as they are convected downstream, which is suggested to be a trigger of the wake bi-modal switching. Suppressing boundary layer separations interrupts this interaction, which is found to have a damping effect on the fluctuations just upstream of the base. Steady suction was applied on the longitudinal surfaces of the body to suppress boundary layer separations. The results showed that horizontal bi-modality is completely suppressed by suppressing the separation of the boundary layers on the surfaces normal to the switching direction without affecting the vertical wake position. Different configurations for suppressing boundary layer separations affect the momentum and the turbulent kinetic energy of underbody flow. The wake can fully be symmetrised by reducing the momentum of the underbody flow with a reflected vertical symmetric position. The results of these cases open doors for using feed-forward controllers with actuation significantly upstream the base separation to reduce the drag rather than forcing the wake directly, which involves some trade-offs between different dynamics in the wake.Open Acces

Performance Evaluation of AODV and MDORA Protocols in Different Cases of Vehicles Movement

           Among the most important topics that have been under discussion are how to manage traffic at intersections and how to maintain road safety. Vehicular Network (VANETs) is one of the most important solutions to solve this problem. And to routing packets between vehicles, many protocols have been proposed. And from this protocols are the MDORA protocol and AODV protocol. This work provides a comparison between the two MDORA and AODV protocols in two cases at variable speed of vehicles, the first in the case of vehicles movement in several directions, and the second in the case of vehicles movement in one direction. The comparison results for the first case the MDORA protocol were worse than the AODV protocol in terms of (E2E end to end delay, PDR packet delivery ratio, communication overhead), while the comparison results in the second case of the MDORA protocol were better than the AODV protocol in terms of (E2E end to end delay , PDR packet delivery ratio, communication overhead), because in the MDORA algorithm there was a condition is choose the vehicles that moved with the same direction when to routing packets to the destination vehicle ,so negative results appeared in the first case

Size selectivity in antibiofilm activity of 3-(Diphenylphosphino)propanoic acid coated gold nanomaterials against Gram positive Staphylococcus aureus and Streptococcus mutans

Abstract Biofilm formation by pathogenic bacteria is one of the major threats in hospital related infections, hence inhibiting and eradicating biofilms has become a primary target for developing new anti-infection approaches. The present study was aimed to develop novel antibiofilm agents against two Gram-positive bacteria; Staphylococcus aureus (ATCC 43300) and Streptococcus mutans (ATCC 25175) using gold nanomaterials conjugated with 3-(diphenylphosphino)propionic acid (Au-LPa). Gold nanomaterials with different sizes as 2–3 nm small and 9–90 nm (50 nm average size) large were stabilized by LPa via different chemical synthetic strategies. The nanomaterials were fully characterized using atomic force microscope (AFM), transmission electron microscope, ultraviolet–visible absorption spectroscopy, and Fourier transformation infrared spectroscopy. Antibiofilm activity of Au-LPa nanomaterials was tested using LPa alone, Au-LPa and unprotected gold nanomaterials against the both biofilm-producing bacteria. The results showed that LPa alone did not inhibit biofilm formation to a significant extent below 0.025 mM, while conjugation with gold nanomaterials displayed manifold enhanced antibiofilm potential against both strains. Moreover, it was also observed that the antibiofilm potency of the Au-LPa nanomaterials varies with size variations of nanomaterials. AFM analysis of biofilms further complemented the assay results and provided morphological aspects of the antibiofilm action of Au-LPa nanomaterials

Functional, cognitive and psychological outcomes, and recurrent vascular events in Pakistani stroke survivors: a cross sectional study

<p>Abstract</p> <p>Background</p> <p>There is little direct data describing the outcomes and recurrent vascular morbidity and mortality of stroke survivors from low and middle income countries like Pakistan. This study describes functional, cognitive and vascular morbidity and mortality of Pakistani stroke survivors discharged from a dedicated stroke center within a nonprofit tertiary care hospital based in a multiethnic city with a population of more than 20 million.</p> <p>Methods</p> <p>Patients with stroke, aged > 18 years, discharged alive from a tertiary care centre were contacted via telephone and a cross sectional study was conducted. All the discharges were contacted. Patients or their legal surrogate were interviewed regarding functional, cognitive and psychological outcomes and recurrent vascular events using standardized, pretested and translated scales. A verbal autopsy was carried out for patients who had died after discharge. Stroke subtype and risk factors data was collected from the medical records. Subdural hemorrhages, traumatic ICH, subarachnoid hemorrhage, iatrogenic stroke within hospital and all other diagnoses that presented like stroke but were subsequently found not to have stroke were also excluded. Composites were created for functional outcome variable and depression. Data were analyzed using logistic regression.</p> <p>Results</p> <p>309 subjects were interviewed at a median of 5.5 months post discharge. 12.3% of the patients had died, mostly from recurrent vascular events or stroke complications. Poor functional outcome defined as Modified Rankin Score (mRS) of > 2 and a Barthel Index (BI) score of < 90 was seen in 51%. Older age (Adj-OR-2.1, <it>p </it>= 0.01), moderate to severe dementia (Adj-OR-19.1, <it>p </it>< 0.001), Diabetes (Adj-OR-2.1, <it>p </it>= 0.02) and multiple post stroke complications (Adj-OR-3.6, <it>p </it>= 0.02) were independent predictors of poor functional outcome. Cognitive outcomes were poor in 42% and predictors of moderate to severe dementia were depression (Adj-OR-6.86, <it>p </it>< 0.001), multiple post stroke complications (Adj-OR-4.58, <it>p </it>= 0.01), presence of bed sores (Adj-OR-17.13, <it>p </it>= 0.01) and history of atrial fibrillation (Adj-OR-5.12, <it>p </it>< 0.001).</p> <p>Conclusions</p> <p>Pakistani stroke survivors have poor outcomes in the community, mostly from preventable complications. Despite advanced disability, the principal caretakers were family rarely supported by health care personnel, highlighting the need to develop robust home care support for caregivers in these challenging resource poor settings.</p

Does the Board Influence the Bank’s Performance? An Islamic & Commercial Banking Experience

Purpose: This study investigates to explore the impact of corporate governance and the performance of the banking Industry of Bahrain for the period of 2012–2020.   Theoretical framework: This research is to take a look at corporate governance actions and how it affects the actual bank performance, there are four chosen banks for this particular purpose that are listed under the Stock exchange of Bahrain (SEB) and the Central bank of Bahrain (CBB).   Design/methodology/approach: The methodology for the study is based on pooled data collection from Islamic and commercial banks of Bahrain. All the data will be extracted from the chosen banks’ audited annual financial statements for 9 years ranging from 2012 to 2020. To go ahead with this research two kinds of dependent variables also called performance measures are (ROA, and ROE), and six kinds of independent variables were selected (CEO duality, the board size, board independence, female directorship, number of BOD meetings, and lastly board members expertise) for us to understand the bank performance better.   Findings: The results showed good connections between the (BS) and bank performance as well as the (NBDM), while the (BDI) and (FD) displayed a negative link, and (BDME) and (CEOD) showed no signs of a relationship because all banks had separate people holding those positions instead of one. And even though (BDME) is proven and is logically impactful some analyses failed to show the true linkage.   Research, Practical &amp; Social implications: These results of the study will help the banking industry, regulators, investors, and government to understand the board’s influence on the firm performance.    Originality/value: Original Research Article

Automated brain tumour identification using magnetic resonance imaging:a systematic review and meta-analysis

BACKGROUND: Automated brain tumor identification facilitates diagnosis and treatment planning. We evaluate the performance of traditional machine learning (TML) and deep learning (DL) in brain tumor detection and segmentation, using MRI. METHODS: A systematic literature search from January 2000 to May 8, 2021 was conducted. Study quality was assessed using the Checklist for Artificial Intelligence in Medical Imaging (CLAIM). Detection meta-analysis was performed using a unified hierarchical model. Segmentation studies were evaluated using a random effects model. Sensitivity analysis was performed for externally validated studies. RESULTS: Of 224 studies included in the systematic review, 46 segmentation and 38 detection studies were eligible for meta-analysis. In detection, DL achieved a lower false positive rate compared to TML; 0.018 (95% CI, 0.011 to 0.028) and 0.048 (0.032 to 0.072) (P < .001), respectively. In segmentation, DL had a higher dice similarity coefficient (DSC), particularly for tumor core (TC); 0.80 (0.77 to 0.83) and 0.63 (0.56 to 0.71) (P < .001), persisting on sensitivity analysis. Both manual and automated whole tumor (WT) segmentation had “good” (DSC ≥ 0.70) performance. Manual TC segmentation was superior to automated; 0.78 (0.69 to 0.86) and 0.64 (0.53 to 0.74) (P = .014), respectively. Only 30% of studies reported external validation. CONCLUSIONS: The comparable performance of automated to manual WT segmentation supports its integration into clinical practice. However, manual outperformance for sub-compartmental segmentation highlights the need for further development of automated methods in this area. Compared to TML, DL provided superior performance for detection and sub-compartmental segmentation. Improvements in the quality and design of studies, including external validation, are required for the interpretability and generalizability of automated models

Impact of CSR, innovation, and green investment on sales growth: new evidence from manufacturing industries of China and Saudi Arabia

Environmental concerns have got supreme interest from the researchers and policy makers for which experts have revealed their organizational impacts too. At the same time, corporate social responsibility is observed as a key determinant of financial performance both in developed and developing economies. Recognize the same, this study aims to examine the impact of corporate social responsibilities, economic innovation, green credit, and green investment on the sales growth of manufacturing industries of China and Saudi Arabia. This study has selected top twelve trading manufacturing companies registered in the Shanghai stock exchange and Saudi stock exchange during the period of 2016 to 2020. For data estimation, panel regression estimations like fixed and random effect models have been used. The results indicate that corporate social responsibility, economic innovation, green credit, and green investment are significantly and positively associated with sales growth of manufacturing industries in China and Saudi Arabia. However, their coefficient’s magnitude varies due to distinct features of both countries. These findings offer valuable policy recommendations for all stakeholders

Awareness and attitude toward using dental magnification among dental students and residents at King Abdulaziz University, Faculty of Dentistry

Abstract Background The authors conducted a study aimed to assess the awareness and attitude among dental students and residents at King Abdulaziz University, Faculty of Dentistry (KAUFD) toward using dental magnification. Methods An e-questionnaire was formulated then sent to dental students and residents (n = 651). The questionnaire included questions that assessed both the awareness and attitude toward using dental magnification. Data were analyzed using IBM SPSS version 22. The chi-square test was used to establish relationships between categorical variables. Results The response rate was 69.7 % (n = 454). Of those, 78.1 % did not use magnification during dental procedures. However, 81.8 % agreed that dental magnification could enhance the accuracy and quality of their dental work. Thus, 91.6 % thought it would be useful in endodontics and 46.3 % voted for surgery. Of the 21.9 % that used magnification, dental loupes were mostly used, 55.9 %. The majority (59.4 %) of the participants believed that using dental magnification should be introduced by faculty beginning in Year I of dental school. Conclusions Among our respondents, most of the undergraduate students did not use dental magnification nor attended courses in the use of dental magnifications. However, most of the students were aware of its significance in improving the accuracy and quality of their work.http://deepblue.lib.umich.edu/bitstream/2027.42/134609/1/12903_2016_Article_254.pd

Evaluation of solar disinfection of water intervention delivered through lady health workers in reduction of diarrheal episodes in under five children

Background: Solar Water Disinfection (SODIS) is a simple, inexpensive and sustainable means of daily household treatment for drinking and storage of water. Globally, over a billion people lack access to safe drinking water. As many as half million under five children die annually due to diarrheal illnesses. Most of these deaths are concentrated in Africa and South Asia. Unsafe water is one of the most critical risk factors for diarrhoea. Systematic reviews indicate that interventions to improve the microbial quality of drinking water in households are effective at reducing diarrhoea illnesses and thereby contribute significantly in reducing deaths due to communicable diseases in children under 5 years. We evaluated the impact of the SODIS intervention on health outcomes and diarrheal episodes in two districts of Punjab province in Pakistan. Methods: A cross-sectional survey was undertaken to assess the impact of solar water disinfection (SODIS) program in two districts of Punjab province, Pakistan. The program was implemented by the Ministry of Health from April 2010- May 2011 in Faisalabad district. We selected Toba Tek Singh as a comparison district for the survey.Results: Analysis with regression models revealed that children had a lower risk of contracting diarrhoea when they consumed high percentages of safe drinks (SODIS), lived in households with good hygiene, washed hands, and belonged to the richest quintile. Diarrhoea prevalence was 10.1 episodes per child per year in the non-intervention area compared to 5.6 episodes per child per year (\u3c 0.0001) in the intervention area. Similarly the proportion of children with dysentery reported in the intervention was half compared to non-intervention area (6.1% vs. 13.9%). SODIS method for purifying drinking water is acceptable and effective in the developing countries. It should be a part of preventive strategies at health system level to control diarrheal illnesses and reduce under five mortalit

Readiness for antimicrobial resistance (AMR) surveillance in Pakistan; a model for laboratory strengthening

Background: Limited capacity of laboratories for antimicrobial susceptibility testing (AST) presents a critical diagnostic bottleneck in resource limited countries. This paper aims to identify such gaps and to explore whether laboratory networks could contribute towards improving AST in low resource settings. Methods: A self-assessment tool to assess antimicrobial susceptibility testing capacity was administered as a pre-workshop activity to participants from 30 microbiology laboratories in 3 cities in Pakistan. Data from public and private laboratories was analyzed and capacity of each scored in percentage terms. Laboratories from Karachi were invited to join a support network. A cohort of five laboratories that consented were provided additional training and updates sessions over a period of 15 months. Impact of training activities in these laboratories was evaluated using a point scoring (0-11) tool. Results: Results of self-assessment component identified a number of areas that required strengthening (scores of ≤60%). These included; readiness for AMR surveillance; 38 and 46%, quality assurance; 49 and 55%, and detection of specific organisms; 56 and 60% for public and private laboratories respectively. No significant difference was detected in AST capacity between public and private laboratories [ANOVA; p \u3e 0.05]. Scoring tool used to assess impact of training within the longitudinal cohort showed an increase from a baseline of 1-5.5 (August 2015) to improved post training scores of 7-11 (October 2016) for the 5 laboratories included. Moreover, statistical analysis using paired t-Test Analysis, assuming unequal variance, indicated that the increase in scored noted represents a statistically significant improvement in the components evaluated [p \u3c 0.05]. Conclusion: Strengthening of laboratory capacity for AMR surveillance is important. Our data shows that close mentoring and support can help enhance capacity for antimicrobial sensitivity testing in resource limited settings. Our study further presents a model wherein laboratory networks can be successfully established and used towards improving diagnostic capacity in such setting