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

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 <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 >28 weeks (Group 1) and 8 patients with GA <28 weeks (Group 2). Delivery was planned before bypass in Group 1. Measures of fetal protection during surgery included: >2.7 L/m2/min high flow normothermic bypass maintaining mean perfusion pressure > 70mm Hg and keeping hematocrit >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<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 <28 weeks, calls for applying more safety bypass measures. Controlled randomized trials are equally needed to evaluate the alternative fibrinolytic therapy

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

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030