PARAMETRIC SENSITIVITY ANALYSIS FOR THE PERFORMANCE OF STEAM JET EJECTOR

The paper aims for parametric sensitivity analysis for the performance of the steam jet ejector in a steam power plant. This paper contains a one-dimensional mathematical model for the steam jet ejector major components; the chest chamber, the mixing chamber and the diffuser. It presents the entrainment ratio as a function of operating parameters. The developed equations were solved iteratively for parametric evaluation and latter, for studying the effect of the operating parameters on the efficiency of the steam jet ejector. The efficiency of the ejector will reach its maximum when the compression ratio and the driving pressure are kept at minimum. In case of a positive incremental increase of the driving pressure, a larger size of ejector is required. More over, an optimum temperature ratio of a slight fraction over one needed to be maintained for best working conditions. With these deductions, this research paper will provide a temporary optimization for the efficiency of a setup ejector in case of off-design parameters

PARAMETRIC SENSITIVITY ANALYSIS FOR THE PERFORMANCE OF STEAM JET EJECTOR

The paper aims for parametric sensitivity analysis for the performance of the steam jet ejector in a steam power plant. This paper contains a one-dimensional mathematical model for the steam jet ejector major components; the chest chamber, the mixing chamber and the diffuser. It presents the entrainment ratio as a function of operating parameters. The developed equations were solved iteratively for parametric evaluation and latter, for studying the effect of the operating parameters on the efficiency of the steam jet ejector. The efficiency of the ejector will reach its maximum when the compression ratio and the driving pressure are kept at minimum. In case of a positive incremental increase of the driving pressure, a larger size of ejector is required. More over, an optimum temperature ratio of a slight fraction over one needed to be maintained for best working conditions. With these deductions, this research paper will provide a temporary optimization for the efficiency of a setup ejector in case of off-design parameters

Hydraulic performance of sluice gate with unloaded upstream rotor

This study presents video analysis of the hydraulic performance of a sluice gate with an unloaded upstream built-in rotor. A number of laboratory experiments were  conducted using two unloaded rotor shapes. The first was the cross-shaped rotor and the second was the Savonius-like rotor. A new video analysis technique was  introduced for measuring rotor angular speed and its perturbation. Swift speed  cameras and Tracker software were used to measure the upstream backwater depth and to estimate the instantaneous variation of the rotor speed. The study shows that adding a rotor upstream of the gate caused the upstream water level to increase  such that the averaged normalized afflux increased to 1.72 and 0.9 for the cross-shaped and the Savonius rotors, respectively. Lab experiments indicated that the water flow–structure interaction for the sluice-rotor is quite complex and nonlinear. Two main flow regimes were distinguished. The flow regimes are: the flow through a rotor with possible weir flow conditions and the orifice flow conditions. The  time-averaged angular speed of the tested Savonius-like rotor ranged between 0 and 300 r/min. As the upstream backwater depth increased, the angular speed  increased; however, the rate was significantly lower for the orifice flow condition compared to the flow under rotor and weir flow conditions. The video analysis also indicated that significant perturbation exists for the rotor angular speed. The  normalized perturbation intensity varied from a minimum of 8% to a maximum of 60%.Keywords: sluice gate, rotor, angular speed, video analysis, hydropowe

Relationship Between Alexithymia, Smartphone Addiction, and Psychological Distress Among University Students: A Multi-country Study

Objectives: Increasing dependence on smartphones results in the appearance of psychological problems, especially among young people. This study aims to determine the rates of alexithymia and its relationship with smartphone addiction and psychological distress in university students. Methods: A total of 2616 students (mean age = 22.5±3.5 years; 73.1% female) from universities in Egypt, Oman, and Pakistan were included in a cross-sectional and comparative study conducted through a web survey during the COVID-19 pandemic from October to December 2021. The following scales were used: Toronto Alexithymia Scale (TAS-20), Depression Anxiety Stress Scale (DASS-21), and Smartphone Addiction Scale-Short Version (SAS-SV). The survey also included questions related to sociodemographic and smartphone usage patterns.Results: Students scoring above the TAS-20 cutoff point were significantly more likely to have smartphone addiction (χ2(1) = 45.41; p < 0.001) and psychological distress (χ2(1) = 246.31; p < 0.001). Likewise, smartphone addiction was significantly associated with psychological distress (χ2(1) = 57.46; p < 0.001). However, at each of the TAS-20, SAS-SV, and DASS-21 variables, there were significant differences between the students of the three countries (p < 0.050, p < 0.010, and p < 0.010, respectively); smartphone addiction was highest in Oman, while alexithymia and psychological distress were most severe in Egypt. Women scored higher than men on SAS and TAS scales (p < 0.001). Students who used social media frequently were more prone to smartphone addiction. Conclusions: Understanding cultural and socioeconomic factors (such as living standards, technology accessibility, and social interaction patterns) is crucial for generating strategies to improve the psychological well-being of the youth of different regions and countries. Further, this study confirms the findings of recent studies indicating the heightened university students’ psychological vulnerability during the COVID-19 pandemic

Improving frequency response for AC interconnected microgrids containing renewable energy resources

Interconnecting two or more microgrids can help improve power system performance under changing operational circumstances by providing mutual and bidirectional power assistance. This study proposes two interconnected AC microgrids based on three renewable energy sources (wind, solar, and biogas). The wind turbine powers a permanent magnet synchronous generator. A solar photovoltaic system with an appropriate inverter has been installed. In the biogas generator, a biogas engine is connected to a synchronous generator. M1 and M2, two interconnected AC microgrids, are investigated in this study. M2 is connected to a hydro turbine, which provides constant power. The distribution power loss, frequency, and voltage of interconnected AC microgrids are modeled as a multi-objective function (OF). Minimizing this OF will result in optimal power flow and frequency enhancement in interconnected AC microgrids. This research is different from the rest of the research works that talk about the virtual inertia control (VIC) method, as it not only improves frequency using an optimal controller but also achieves optimal power flow in microgrids. In this paper, the following five controllers have been studied: proportional integral controller (PI), fractional-order PI controller (FOPI), fuzzy PI controller (FPI), fuzzy fractional-order PI controller (FFOPI), and VIC based on FFOPI controller. The five controllers are tuned using particle swarm optimization (PSO) to minimize the (OF). The main contribution of this paper is the comprehensive study of the performance of interconnected AC microgrids under step load disturbances, the eventual grid following/forming contingencies, and the virtual inertia control of renewable energy resources used in the structure of the microgrids, and simulation results are recorded using the MATLAB™ platform. The voltages and frequencies of both microgrids settle with zero steady-state error following a disturbance within 0.5 s with less overshoots/undershoots (3.7e-5/-0.12e-3) using VIC. Moreover, the total power losses of two interconnected microgrids must be considered for the different controllers to identify which one provides the best optimal power flow

Prediabetes management in the Middle East, Africa and Russia: Current status and call for action:

Most data on the burden of diabetes and prediabetes are from countries where local infrastructure can support reliable estimates of the burden of non-communicable diseases. Countries in the Middle ..

Outcome of surgery in critically ill patients presenting with mechanical mitral valve thrombosis during pregnancy

Objectives: Prosthetic valve thrombosis during pregnancy is associated with serious maternal complications and considerable fetal loss. We report and analyze the outcome of surgery in critically ill patients referred to our tertiary center between January 2009 and January 2015.Methods: Twenty-eight pregnant patients with median age of 28 years (range: 20-40 years) presented with thrombosed bileaflet mechanical mitral valve prostheses, 48 (15-192) months after implantation. Twenty-two patients (78.6%) were on fixed dose LMWH (1 mg/kg twice daily) and six patients were on warfarin, with an INR &lt;1.4 in four cases (66.6%).  Patients were reported as being critically ill since 4 (1-12) days and presented in NYHA class IV (III-IV), with median gestational age (GA) of 31 (8-40) weeks. We had six cases of confirmed stillbirth (21.4%) on admission. The remaining were 14 patients presenting with GA &gt;28 weeks (Group 1) and 8 patients with GA &lt;28 weeks (Group 2). Delivery was planned before bypass in Group 1. Measures of fetal protection during surgery included: &gt;2.7 L/m2/min high flow normothermic bypass maintaining mean perfusion pressure &gt; 70mm Hg and keeping hematocrit &gt;28%.Results: All mitral prostheses were emergency replaced with same-sized mechanical valves. Median aortic cross clamp and bypass times were 57 (34-106) and 93 (48-140) minutes. We had two maternal mortalities (7.1%) and one preoperative regressive stroke (3.6%). Thirteen fetuses (59.1%) were successfully delivered before surgery (92.8% of Group 1) and nine were submitted to bypass: one rapidly deteriorating Group 1 patient and all eight patients in Group 2. Only three fetuses (GA =10, 21 and 31 weeks) survived bypass (33.3%) and were delivered at term. Outcome of the 22 live fetuses on admission was: 14 live births in Group 1 (100%; 9 healthy babies and 5 prematures) versus two in Group 2 (25%; P&lt;0.001), with a total fetal loss of 27.3%.Conclusion: Maternal outcomes are comparable to those of non-pregnant subjects. Unless the fetus is delivered before bypass, the heavy fetal loss, especially in patients presenting with GA &lt;28 weeks, calls for applying more safety bypass measures. Controlled randomized trials are equally needed to evaluate the alternative fibrinolytic therapy

Exposure to urban green spaces and mental health during the COVID-19 pandemic: evidence from two low and lower-middle-income countries

INTRODUCTION: The COVID-19 pandemic has had a significant impact on mental health globally, with limited access to mental health care affecting low- and middle-income countries (LMICs) the most. In response, alternative strategies to support mental health have been necessary, with access to green spaces being a potential solution. While studies have highlighted the role of green spaces in promoting mental health during pandemic lockdowns, few studies have focused on the role of green spaces in mental health recovery after lockdowns. This study investigated changes in green space access and associations with mental health recovery in Bangladesh and Egypt across the pandemic. METHODS: An online survey was conducted between January and April 2021 after the first lockdown was lifted in Bangladesh (n = 556) and Egypt (n = 660). We evaluated indoor and outdoor greenery, including the number of household plants, window views, and duration of outdoor visits. The quantity of greenness was estimated using the normalized difference vegetation index (NDVI). This index was estimated using satellite images with a resolution of 10x10m during the survey period (January-April 2021) with Sentinel-2 satellite in the Google Earth Engine platform. We calculated averages within 250m, 300m, 500m and 1000m buffers of the survey check-in locations using ArcGIS 10.3. Multiple linear regression models were used to evaluate relationships between changes in natural exposure and changes in mental health. RESULTS: The results showed that mental health improved in both countries after the lockdown period. People in both countries increased their time spent outdoors in green spaces after the lockdown period, and these increases in time outdoors were associated with improved mental health. Unexpectedly, changes in the number of indoor plants after the lockdown period were associated with contrasting mental health outcomes; more plants translated to increased anxiety and decreased depression. Refocusing lives after the pandemic on areas other than maintaining indoor plants may assist with worrying and feeling panicked. Still, indoor plants may assist with depressive symptoms for people remaining isolated. CONCLUSION: These findings have important implications for policymakers and urban planners in LMICs, highlighting the need to increase access to natural environments in urban areas to improve mental health and well-being in public health emergencies

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10&nbsp;years; 78.2% included were male with a median age of 37&nbsp;years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Effects of a high-dose 24-h infusion of tranexamic acid on death and thromboembolic events in patients with acute gastrointestinal bleeding (HALT-IT): an international randomised, double-blind, placebo-controlled trial

Background: Tranexamic acid reduces surgical bleeding and reduces death due to bleeding in patients with trauma. Meta-analyses of small trials show that tranexamic acid might decrease deaths from gastrointestinal bleeding. We aimed to assess the effects of tranexamic acid in patients with gastrointestinal bleeding. Methods: We did an international, multicentre, randomised, placebo-controlled trial in 164 hospitals in 15 countries. Patients were enrolled if the responsible clinician was uncertain whether to use tranexamic acid, were aged above the minimum age considered an adult in their country (either aged 16 years and older or aged 18 years and older), and had significant (defined as at risk of bleeding to death) upper or lower gastrointestinal bleeding. Patients were randomly assigned by selection of a numbered treatment pack from a box containing eight packs that were identical apart from the pack number. Patients received either a loading dose of 1 g tranexamic acid, which was added to 100 mL infusion bag of 0·9% sodium chloride and infused by slow intravenous injection over 10 min, followed by a maintenance dose of 3 g tranexamic acid added to 1 L of any isotonic intravenous solution and infused at 125 mg/h for 24 h, or placebo (sodium chloride 0·9%). Patients, caregivers, and those assessing outcomes were masked to allocation. The primary outcome was death due to bleeding within 5 days of randomisation; analysis excluded patients who received neither dose of the allocated treatment and those for whom outcome data on death were unavailable. This trial was registered with Current Controlled Trials, ISRCTN11225767, and ClinicalTrials.gov, NCT01658124. Findings: Between July 4, 2013, and June 21, 2019, we randomly allocated 12 009 patients to receive tranexamic acid (5994, 49·9%) or matching placebo (6015, 50·1%), of whom 11 952 (99·5%) received the first dose of the allocated treatment. Death due to bleeding within 5 days of randomisation occurred in 222 (4%) of 5956 patients in the tranexamic acid group and in 226 (4%) of 5981 patients in the placebo group (risk ratio [RR] 0·99, 95% CI 0·82–1·18). Arterial thromboembolic events (myocardial infarction or stroke) were similar in the tranexamic acid group and placebo group (42 [0·7%] of 5952 vs 46 [0·8%] of 5977; 0·92; 0·60 to 1·39). Venous thromboembolic events (deep vein thrombosis or pulmonary embolism) were higher in tranexamic acid group than in the placebo group (48 [0·8%] of 5952 vs 26 [0·4%] of 5977; RR 1·85; 95% CI 1·15 to 2·98). Interpretation: We found that tranexamic acid did not reduce death from gastrointestinal bleeding. On the basis of our results, tranexamic acid should not be used for the treatment of gastrointestinal bleeding outside the context of a randomised trial