Design of Observer-Based Robust Power System Stabilizers

Power systems are subject to undesirable small oscillations that might grow to cause system shutdown and consequently great loss of national economy. The present manuscript  proposes two  designs for observer-based robust power system stabilizer (PSS) using Linear Matrix Inequality (LMI) approach to damp such oscillations. A model to describe power system dynamics for different loads is derived in the norm-bounded form. The first controller design is based on the derived model to achieve  robust stability against load variation. The design is based on a new Bilinear matrix inequality (BMI) condition. The BMI optimization  is solved interatively in terms of Linear Matrix Inequality (LMI) framework. The condition contains a symmetric positive definite full matrix to be obtained, rather than the commonly used block diagonal form. The difficulty in finding a feasible solution is thus alleviated. The resulting LMI is of small size, easy to solve. The second PSS design shifts the closed loop poles in a desired region so as to achieve a favorite  settling time and damping ratio via a non-iterative solution to a set of LMIs.  The approach provides a systematic way to design a robust output feedback PSS which  guarantees good dynamic performance for different loads. Simulation results based on single-machine and multi-machine power system models verify the ability of the proposed PSS to satisfy control objectives for a wide range of load conditions

Hydrophilic nanosilica as a new larvicidal and molluscicidal agent for controlling of major infectious diseases in Egypt

Aim: This research was conducted to evaluate the molluscicidal and mosquitocidal efficacy of silica nanoparticles in the eradication of the larvae and pupa of malaria and filariasis vector as well as vectors of rift-valley fever virus (Culex pipiens); Schistosoma mansoni vector (Biomphlaria alexandrina (snail and egg masses)). Materials and Methods: Hydrophilic nanosilica particles (NSPs) were characterized using transmission electron microscope during the preliminary part of the study; the stages were exposed to upgrade concentrations of NSP from 50 to 1200 ppm each for 24-36 h exposure time. The highly effective concentrations were re-evaluated at lower exposure time as 3, 6, and 12 h. Results: Lethal concentration (LC50) and LC90 versus mosquito larvae were (350 ppm/24 h and 1400 ppm/24 h, respectively). C. pipiens pupae proved slight high tolerance versus the effect of these nanoparticles as the two previous doses increased to 680 ppm/6 h and 1300 ppm/24 h. The LC50 and LC90 versus B. alexandrina were increased to 590 ppm/6 h and 980 ppm/48 h, respectively. Moreover, the embryonated snail egg masses appear more susceptible to the toxic effect of these nanoparticles than the non-embryonated eggs as the LC50 and LC90 were increased to 1450 ppm/12 h and 1250 ppm/48 h, respectively, for embryonated eggs, and it was 1400 ppm/24 h and 1890 ppm/48 h, respectively, for non-embryonated one. Conclusion: The results open a new field for controlling the infectious diseases through eradication of their vectors by the way that avoids the resistance recorded from the successive chemical application in this field

ACUTE TOXICITY OF DIFFERENT SIZES OF SILVER NANOPARTICLES INTRAPERITONALLY INJECTED IN BALB/C MICE USING TWO TOXICOLOGICAL METHODS

Objective: This study aimed to evaluate the acute toxicity of intraperitoneally administrated silver nanoparticles (AgNPs) with different particle sizes in BALB/c mice.Methods: Citrate-capped AgNPs were prepared by citrate reduction method and isolated into small particles (average size 20 nm) and large particles (average size 50 nm). The median lethal dose (LD50) of 20 nm and 50 nm AgNPs was estimated using two toxicological methods, classical Dixon's up-and-down method and AOT425statPgm method for up-and-down procedure.Results: The LD50 was evaluated at the dosage level of 169 and 213.8 mg/kg, respectively for 20 nm AgNPs and at the dosage level of 354 and 391.5 mg/kg, respectively for 50 nm AgNPs. The results showed that LD50 obtained by the AOT425statPgm method was in accord with that of the Dixon's method and no significant differences between them (P = 0.06). The size 20 nm AgNPs were more toxic than the size 50 nm AgNPs. The behavioural responses and deviations were dose dependent, increasing by increasing the dose. The anatomical examinations showed that AgNPs were mainly accumulated in liver and spleen of dosed mice.Conclusion: The results suggested that the AOT425statPgm method was an efficient tool and a good alternative method for use in future acute toxicity studies.Â

Recycled Aggregate Self-curing High-strength Concrete

The use of recycled aggregates from demolished constructions as coarse aggregates for concrete becomes a need to reduce the negative effects on the environment. Internal curing is a technique that can be used to provide additional moisture in concrete for more effective hydration of cement to reduce the water evaporation from concrete, increase the water retention capacity of concrete compared to the conventionally cured concrete. High strength concrete as a special concrete type has a high strength with extra properties compared to conventional concrete. In this research, the combination of previous three concrete types to obtain self-curing high-strength concrete cast using coarse recycled aggregates is studied. The effect of varying water reducer admixture and curing agent dosages on both the fresh and hardened concrete properties is studied. The fresh properties are discussed in terms of slump values. The hardened concrete properties are discussed in terms of compressive, splitting tensile, flexure and bond strengths. The obtained results show that, the using of water reducer admixture enhances the main fresh and hardened properties of self-curing high-strength concrete cast using recycled aggregate. Also, using the suggested chemical curing agent increased the strength compared to conventional concrete without curing

New 1.5V CMOS current feedback operational amplifier

Abstract-a novel CMOS low-voltage current feedback operational amplifier (CFOA) is presented. The proposed CFOA based on a new positive second-generation current conveyor (CCII+). The new circuit allows almost a rail-to-rail input and output operation; also, it reduces the offset voltage and provides high driving current capabilities. The CFOA is operating at supply voltages of ±0.75 V with a total standby current of 338 µA. The circuit exhibits better than 10 MHz bandwidth and ±1mA current drive capability. PSpice simulation results are given using 0.35µm technology for the proposed CFOA

Capability of the Invasive Tree Prosopis glandulosa Torr. to Remediate Soil Treated with Sewage Sludge

Sewage sludge improves agricultural soil and plant growth, but there are hazards associated with its use, including high metal(loid) contents. An experimental study was conducted under greenhouse conditions to examine the effects of sewage sludge on growth of the invasive tree Prosopis glandulosa, as well as to determine its phytoremediation capacity. Plants were established and grown for seven months along a gradient of sewage sludge content. Plant traits, soil properties, and plant and soil concentrations of N, P, K, Cd, Pb, Cu, Ni, Zn, Cr, Co, As, and Fe were recorded. The addition of sewage sludge led to a significant decrease in soil pH, and Ni, Co, and As concentrations, as well as an increase in soil organic matter and the concentrations of N, P, Cu, Zn, and Cr. Increasing sewage sludge content in the growth medium raised the total uptake of most metals by P. glandulosa plants due to higher biomass accumulation (taller plants with more leaves) and higher metal concentrations in the plant tissues. P. glandulosa concentrated more Cd, Pb, Cu, Zn, and Fe in its below-ground biomass (BGB) than in its above-ground biomass (AGB). P. glandulosa concentrated Ni, Co, and As in both BGB and AGB. P. glandulosa has potential as a biotool for the phytoremediation of sewage sludges and sewage-amended soils in arid and semi-arid environments, with a potential accumulation capability for As in plant leaves

Dual buoyant/mucoadhesive macroporous polypropylene microparticles for gastric delivery of repaglinide

Preparation and characterization of dual buoyant/mucoadhesive polypropylene microparticles (MPs) loaded with repaglinide (REP) for gastric drug delivery in order to augment the weak mucoadhesion in the stomach.Porous foam powder MPs were prepared using coating polymers with variable permeability (Eudragit L100, Eudragit RSPO) alone or in combination by the soaking method. Thiolated Eudragit L100 (Eudragit L100-SH) was also synthesized and tried in an attempt to enhance the mucoadhesive properties of MPs. All formulae were characterized for their yield, flow properties, particle size, encapsulation efficiency (EE %), morphology, and drug release and its mechanistics. Possible interactions inside MPs matrix were also elucidated using FTIR study. The suitability of the selected formulae for gastroretention was evaluated by in vitro buoyancy and ex-vivo mucoadhesion studies.All REP-loaded MPs demonstrated a passable powder flow, high yield values, promising floatation and mucoadhesion. Encapsulation efficiency % values were nearly tripled upon addition of Eudragit polymers. Compared to the Eudragit free REP loaded foam powder, all formula showed more sustained release features. Eudragit L100-SH was synthesized and confirmed by FTIR. Furthermore, its incorporation, alone or in combination, exhibited a significant increase in mucoadhesion strength compared to the unmodified one.Dual buoyant/mucoadhesive MPs loaded with REP encourage planning for future in-vivo performance studies for the management of diabetes

Evaluation of the safety and antioxidant activities of Crocus sativus and Propolis ethanolic extracts

AbstractThe possible toxicological effects and in vitro antioxidant activity of the ethanolic extracts of Crocus sativus and Propolis were investigated. Both extracts did not cause any mortalities or signs of toxicity in mice when administered orally at doses up to 5g/kgb.wt. In the sub-chronic study; the tested extracts did not produce any significant change in liver and kidney functions of rats, following oral administration for 8 successive weeks at doses of 500mg/kgb.wt. of each. Propolis showed remarkable in vitro antioxidant activity at concentrations of (40–100mg/ml). In contrast, the ethanolic extract of C. sativus ethanolic extract showed weak antioxidant activity in concentrations of (1–10mg/ml) while at concentrations of (20–100mg/ml) failed to exhibit any antioxidant activity. It was concluded that: both extracts were non-toxic, as they did not cause any mortalities or signs of toxicity in mice when administered orally at doses up to 5g/kgb.wt. Daily oral administration of C. sativus, Propolis ethanolic extracts alone or in combination for 8 successive weeks to rats was quiet safe and didn't cause any toxic changes in liver and kidney. Antioxidant study showed that Propolis ethanolic extract was a more potent antioxidant than C. sativus extract

HEPATOPROTECTIVE AND HEPATOTHERAPUTIC EFFECTS OF PROPOLIS AGAINST D-GALACTOSAMINE/LIPOPOLYSACCHARIDE-INDUCED LIVER DAMAGE IN RATS

Objective: The aim of the present study was to investigate the potential hepatoprotective and hepatotherapeutic activities of propolis against D-galactosamine and lipopolysaccharide (D-GaIN/LPS)-induced hepatotoxicity in rats.Methods: Hepatotoxicity was induced in rats by intra peritoneal injection of GalN (300 mg/kg) and LPS (30 μg/kg). In the hepatoprotection experiment, propolis was administered orally for 10 days before induction of hepatoxicity. In another experiment (hepatotherapy), propolis was dosed immediately after GalN/LPS injection.Results: Injection of GalN/LPS to rats induced hepatic damage that was manifested by a significant increase in the activities of aminotransferases, alkaline phosphatase, lactate dehydrogenase and levels of tumor necrosis factor-alpha (TNF-α) and total bilirubin in serum. Liver homogenate of intoxicated animals had the lower content of reduced glutathione with increased levels of the hepatic malondialdehyde and caspase-3 enzyme. Histological data presented marked damage in liver sections of intoxicated rats. Oral dosing of propolis before or once immediately after intoxication reversed these altered parameters near to normal values.Conclusion: Liver apoptotic events such as DNA fragmentation and increased caspase-3 activity observed during intoxication were prevented by pre and post- propolis treatment. These results suggest that propolis could afford significant protection and therapy in alleviation of hepatotoxicity.Â