Impact of integrating large-capacity hybrid renewable energy systems into Qatar's power grid.

The implementation of large-scale renewable energy systems (such as solar and wind) in the GCC is widely growing nowadays, particularly in remote areas generation applications where the grid extension is costly. The integration of renewable energy systems into the existing power grids, especially the hybrid ones like hybrid solar wind systems, not only provide a clean environmentally friendly supply of electricity but also provide a more reliable supply of electricity through the utilization of different energy sources

Numerical Simulation of Air Flow in Aeroengine Compressors

The performance of an aeroengine is influenced by the performance of the compressor system. A typical compressor consists of multistage axial compressors followed by a centrifugal stage. Here, a high-speed centrifugal and an axial stage are investigated in terms of turbulence modelling, flow blockage and rotor-stator (R-S) gap using the commercial software ANSYS CFX. The curvature corrected Shear stress transport (SST-CC) model of Smirnov and Menter is investigated for the first time in a high-speed centrifugal stage in terms of curvature and rotation effects. The SST-CC predictions are compared with the standard SST, Speziale, Sarkar, and Gatski Reynolds stress model (RSM-SSG) and the experimental data in terms of the global performance as well as the velocity profiles at the impeller-diffuser interface. The comparisons show that SST-CC has the best agreement with the experiments at choke condition while SST has better performance at the stall condition. The production term shows the expected sensitivity to the convex and concave curvatures. A new method to quantify blockage for both axial and centrifugal compressors is developed. Both steady and unsteady simulations are used to examine the flow blockage in the axial transonic stage. The variation of the rotor tip blockage with respect to the blade loading shows good agreement with previous studies. The total planar blockage indicates that stall might initiate at the stator trailing edge. The differences between the steady and unsteady predictions are mainly attributed to the local differences in the total pressure profiles at the inlet guide vanes–rotor interface. It was previously argued that reducing the R-S gap improves the efficiency of axial compressors due to reduced viscous mixing of the rotor wake. However, the current simulations show that the smallest R-S gap has the highest levels of total pressure losses within the stator passage and the highest levels of unsteady stator forces at reduced mass flow rates. The unsteadiness in the stator flow field is attributed to the larger stator suction surface boundary layer separation associated with the smallest gap. The smallest R-S gap reduces the viscous mixing of the wake at the expense of the efficiency

SPRAY DRIED LACTOSE BASED PRONIOSOMES AS STABLE PROVESICULAR DRUG DELIVERY CARRIERS: SCREENING, FORMULATION, AND PHYSICOCHEMICAL CHARACTERIZATION

Objective: In the present investigation efforts were considered to optimize the different conditions for the preparation of spray dried lactose based proniosomes. The aim of this research was to investigate the feasibility of proniosomes as stable precursors for the development of niosomes as oral drug delivery system for poorly water-soluble drugs. Methods: A total of twenty-eight plain proniosomal formulae were prepared with various surfactant-cholesterol loading ratios in each formula using spray dried lactose as a carrier. Span 20, 40, 60 and 80 were used in various molar ratios with cholesterol. Different evaluation techniques were performed to study the performance of the prepared proniosomes. The micromeritic properties of the prepared proniosomes were analyzed. The reconstituted niosomes were further evaluated for morphological characterization using transmission electron microscope (TEM), particle size analysis, zeta potential, and polydispersity index (PDI). Finally, selected proniosomal formulae were tested for stability study. Results: The proniosomal formulae prepared using span 40 and span 60 exhibited excellent flowability while those prepared with span 20 and span 80 showed poor flow properties. TEM photographs revealed that the vesicles were discrete, spherical without aggregation. The mean vesicle size of reconstituted niosomes was found to be in the range between (252.9±0.43–624.3±0.23 nm) with perfect PDI values (0.387±0.05–0.835±0.03). The negative values of zeta potential indicated that all prepared formulae were stabilized by electrostatic repulsion forces. Stability studies confirmed that proniosomes give a more stable system that could overcome the problems of standard niosomes. Formulae with the smallest particle size, higher surface charge values and best flow properties were selected to be loaded with poorly soluble drugs for further study. Conclusion: The obtained results offered evidence that spray-dried lactose based proniosomes are promising stable drug delivery carriers and ready to incorporate various poorly water-soluble drugs in order to improve their limited oral bioavailability

The effect of regular daily walking on adverse pregnancy outcomes among overweight primigravidas: a prospective cohort study

Objective: The study aims to evaluate the effect of regular daily walking on the occurrence of adverse pregnancy outcomes among overweight primigravidas. Materials and Methods: A prospective cohort study conducted at Aswan University Hospital from March 2015 to December 2016. The study included 360 overweight primigravidas, with singleton pregnancies, who were divided into two groups: Group I (control group) and Group II (study group) under supervised regular walking 5 times per week for 30 minutes, starting from 10-12 weeks of gestational age to 38-39 weeks of gestational age. The primary outcome of the study was the rate of gestational weight gain in participants in both groups. Secondary outcomes included the rate of gestational diabetes mellitus, gestational hypertension, preeclampsia, preterm labor ( 4 kg), excessive maternal weight gain (>11.5 kg), and the rate of cesarean delivery. Results: There were no significant differences between groups with regard to the basic criteria. The exercise program decreased the incidence of preeclampsia (OR=0.120; 95% CI=0.015-0.970; p=0.037), postdate (OR=0.274; 95% CI= 0.099-0.759); p=0.008), excessive weight gain (OR=0.220; 95% CI=0.114-0.424), p=0.000), and cesarean delivery (OR=0.519; 95% CI=0.316-0.841, p=0.007). Conclusion: Regular maternal walking throughout the pregnancy may be a preventive tool for preeclampsia, postdate pregnancy, excessive weight gain and may decrease the incidence of cesarean delivery in primigravidas

Does lidocaine gel produce an effective analgesia prior to copper IUD insertion? Randomized clinical trial

Background: IUD is a small contraceptive device, often containing either copper or levonorgestrel, which is inserted into the uterus. Objective of present study was to determine if lidocaine gel prior to intrauterine device (IUD) insertion decreases pain with the insertion procedure among multiparous women choosing the copper T380A-IUD.Methods: It is a randomized double-blind controlled trial carried out at Assiut Women's Health Hospital, Assiut, Egypt. Parous women eligible for Copper IUD insertion attended the Family Planning Clinic were recruited and randomized in a 1:1 ratio to lidocaine gel or placebo. Two ml of the study medications were topically placed on the cervix 3 minutes before IUD insertion. The primary outcome was the difference in pain scores using a 10-cm Visual Analogue Scale (VAS) during IUD insertion. We considered a 1.5 cm difference in VAS scores between study groups as clinically significant.Results: One hundred women consented to participate and randomized either to group I:  lidocaine group or group II: placebo group. Both groups were homogenous in baseline socio-demographic data. There was significant difference in mean pain scores for IUD placement between women who received lidocaine gel and placebo at two steps of insertion (at vulsellum application and at uterine sounding) while the rest of steps show no statistical significant difference (p=0.000). There were no statistical significant differences between both group as regard the ease of insertion, the duration of insertion and the satisfaction score after the procedure (p>0.05).Conclusions: This study depicts that the use of lidocaine gel prior to copper IUD insertion in multiparous women could partially reduce the pain during tenaculum placement and uterine sounding

Pregnancy outcome according to body mass index in primigravidas: a prospective cohort study

Objective: The study aims to evaluate the association between Body Mass Index (BMI), gestational weight gain (GWG) and adverse obstetric outcomes among primigravidas. Material and methods: This was a prospective cohort study conducted at a tertiary University Hospital between June 2015 and May 2017. The study included 480 primigravidas, with singleton pregnancies, who were divided into three groups: women with a healthy weight (BMI: 18.5–24.9 kg/m2) overweight (BMI: 25 – 29.9 kg/m2) and obese (BMI ≥ 30 kg/m2). The primary outcome of the study was the rate of GWG in the participants. Secondary outcomes included the rate of gestational diabetes mellitus (GDM), gestational hypertension, pre-eclampsia, preterm labor (PTL), postdate pregnancy, fetal macrosomia and the rate of birth by cesarean (CB). Results: There were no significant differences between groups regarding the socio-demographic criteria. The rate of GWG was significantly higher in obese women versus average weight women (11.4±1.73 vs. 10.49±1.09, p=0.0001). There was an increased incidence of GDM (p=0.008), gestational hypertension (p=0.001), pre-eclampsia (p=0.0001), PTL (p=0.002), postdate (p=0.0001) and macrosomia (p=0.0001) in women who were obese compared with women with a healthy weight. Additionally, there was an increased incidence of CB with increasing body mass (p=0.0001) Conclusions: Higher BMI in primigravidas is associated with increased GWG and with adverse pregnancy outcomes such as GDM, gestational hypertension, pre-eclampsia, PTL, postdate, fetal macrosomia and cesarean birth

Early clinical outcome after right anterolateral thoracotomy as an alternative for median sternotomy for mitral valve replacement

Background: The advantages of the right anterolateral thoracotomy (RALT) approach for mitral valve surgery over standard median sternotomy (MS) are still debatable. The objective of this study was to evaluate and compare the postoperative clinical outcome after RALT and MS for mitral valve replacement. Methods: This prospective observational study included 40 patients who underwent mitral valve replacement between January 2016 and August 2018. Patients were assigned to two groups, the first group included 20 patients who had conventional median sternotomy approach and the second group included 20 patients who had right anterolateral thoracotomy with the complete cannulation and aortic cross-clamping conducted through the same incision. Results: In comparison to MS, RALT had significantly higher cross-clamp time (77.7±16.1 vs 45.8±8.7 minutes, P < 0.01), total bypass time (105.2±12.7 vs 72.2±10.4 minutes, P < 0.01), and total operative time (287±41 vs 231±36 min, P < 0.01), in addition to significantly lower ventilation time (4.2±1.51 vs 6.1±1.84 hours, P < 0.01), blood loss (229±85 vs 335±137 ml), amount of blood transfusion (1.41±0.6 vs 2.19±1.1 units, P < 0.01), ICU stay duration (2.11±0.49 vs 2.78±0.82 days, P < 0.01), pain scores at 1st and 2nd postoperative days (5.67±0.79 vs 7.81±0.53, p < 0.01), and total hospital stay duration (7.2±1.3 vs 8.4±1.6 days, P = 0.01). Patients' satisfaction about their wound was significantly higher in RALT group compared to MS group (95% vs 30%, P < 0.01). Conclusion: The RALT approach for mitral valve surgery could be a safe and effective approach when compared to median sternotomy. RALT could be associated with a reduction of blood loss, blood transfusion, wound infection, in addition to shorter ICU and hospital stay

Optimal Coordination of Directional Overcurrent Relays Using Hybrid Firefly–Genetic Algorithm

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/The application of directional overcurrent relays (DOCRs) plays an important role in protecting power systems and ensuring their safe, reliable, and efficient operation. However, coordinating DOCRs involves solving a highly constrained and nonlinear optimization problem. The primary objective of optimization is to minimize the total operating time of DOCRs by determining the optimal values for decision variables such as the time multiplier setting (TMS) and plug setting (PS). This article presents an efficient hybrid optimization algorithm that combines the modified firefly algorithm and genetic algorithm to achieve improved solutions. First, this study modifies the firefly algorithm to obtain a global solution by updating the firefly’s brightness and to prevent the distance between the individual fireflies from being too far. Additionally, the randomized movements are controlled to produce a high convergence rate. Second, the optimization problem is solved using the genetic algorithm. Finally, the solution obtained from the modified firefly algorithm is used as the initial population for the genetic algorithm. The proposed algorithms have been tested on the IEEE 3-bus, 8-bus, 9-bus and 15-bus networks. The results indicate the effectiveness and superiority of the proposed algorithms in minimizing the total operating time of DOCRs compared with other optimization methods presented in the literature.Peer reviewe

Advanced control strategy to maximize view and control discomforting glare: a complex adaptive façade

Increasing demands for full-glazed façades have motivated designers/researchers to propose advanced control strategies for dynamic shading systems to mitigate the negative impacts of excessive sunlight penetration into interior spaces. Nevertheless, in line with the latter, outside view is commonly obstructed as a result of utilizing conventional shading systems including Venetian blinds. This is primarily the consequence of conventional systems’ lack of flexibility to respond appropriately to occupants’ requirements and the sun's changing orientation. This paper presents the virtual prototype development of a Multi-layer blind system through a brute-force algorithm. It emphasizes proposing a customizable and affordable complex shading system with advanced control strategies for multiple building typologies. The research intends to improve visual comfort (daylight and glare) and maximize unblocked window view in a single office room located in Tehran. Furthermore, the control system was developed based on a combination of the cut-off and a glare protection control strategy. Concerning the cut-off control system, the slat angles change to block direct sun radiations, and then, if needed, the position of the front slat, named ‘View slat’, changes to avoid discomforting glare. In conclusion, the proposed prototype could improve daylight performance by up to 44% and maximize unobstructed outdoor view by approximately 47% in an almost glare-free zone. Finally, the usage of swarm intelligence could significantly improve the performance of the proposed prototype by determining which blind and how they should respond to environmental changes and occupants’ requirements