Enhancing the Performance of Power System under Abnormal Conditions Using Three Different FACTS Devices

In this paper, a comparison between Flexible Alternating Current Transmission System (FACTS) devices including Static Synchronous Compensator (STATCOM), Static Synchronous Series Compensator (SSSC) and Unified Power Flow Controller (UPFC) for providing a better adaptation to changing operating conditions and improving the usage of current systems. The power system using FACTS devices is presented under different conditions such as single phase fault and three phase fault. A digital simulation using Matlab/Simulink software package is carried out to demonstrate the better performance including the voltage and the current of the presented system using FACTS that located between buses B1 and B2 under different faults types. The results obtained investigate that the presented system gives better response with FACTS as compared to not using them under abnormal conditions besides, the UPFC gives better performance of power system under several faults as compared to STATCOM or SSSC as It can absorb reactive power in a manner which significantly reduced the fault current. It is demonstrated that UPFC can reduce the peak fault current at bus B1 ‎to 63.85% of its value without ‎using FACTS devices under line to ground fault and 79.18% under three line to ‎ground fault whereas STATCOM and SSSC reduce it ‎to (75.21, 94.35%) and (75.40, 94.68%), respectively

Medical Treatment of Cystoid Macular Edema with Topical Steroids and Topical Non-Steroidal Anti-Inflammatory Drugs

Aim: To provide knowledge that topical steroids and topical non-steroidal antiinflammatory drugs "NSAIDs";can cure cystoid macular edema "CME"; which iscurrently mostly treated by invasive procedures "i.e. intravitreal steroids and antiVEGF, laser and vitrectomy".Introduction: Through many years ever since the CME has been discovered by Irvin,invasive interventions were regarded as the most effective curative modalities oftreatment. Recently it was proved that there is an inflammatory reaction in the processof CME formation, based on that evidence many studies started aiming at evaluating therole of anti-inflammatory agents in the treatment of CME.Case presentation: A 60 years old gentleman presented with deterioration of vision inhis right eye over 45 days, he is on antiglaucoma medications and has undergone aglaucoma surgery two years back, there were no any associated systemic symptoms ordiseases. On examination: the left eye was diagnosed as end stage glaucoma and so itwas excluded from the examination; on examination of the right eye: best correctedvisual acuity was 6/36; intra ocular pressure "IOP" 10 mmHg, dilated fundusexamination: Optic disc: glaucomatous atrophy, Vessels: attenuated arterial system andcongested venous system, Macula: dull with irregular slit lamp light appearanceindicating microcysts formation; and Periphery: was non informative, Ocular CoherentTomography "OCT": showed marked increased thickness of the retinal layers with cystsformation at the macular area. Accordingly the patient was diagnosed as cystoid macularedema and hence the plan was to put him on topical steroids and topical NSAIDs eyedrops qid, a regular follow up and measurement of IOP.Results: OCT repeated after a month and there were no obvious changes, four monthslater OCT showed a remarkable improvement; i.e. the thickness is much lesser, anotherOCT after a further month showed complete resolution of the edema, and best correctedvisual acuity was 6/24.Discussion and Conclusion: CME is in part an inflammatory condition; so it couldpossibly be treated with anti-inflammatory agents, such as topical steroids and NSAIDs,as it is evident in this case CME can be totally cured without the need of invasiveprocedures

Electrical and Magnetic Properties of Mn-Bi-Sb Alloys

MnBi1-xSbx alloys were prepared by the conventional melt technique. The Seebeck coefficient (S), electrical resistivity (ρ), and magnetic susceptibility (c) were measured at various temperatures ranging from ~100 to 400 K. The electrical resistivity of x £ 0.15 shows both semiconducting and metallic behavior depending on temperature and Sb content, whereas samples x 3 0.2 have only semiconductor behavior in all the temperature range. The negative sign of the Seebeck coefficient increases, i.e., the positivity decreases with the increasing Sb content. The magnetic susceptibility (χ) shows that alloys undergo ferro-paramagnetic transition at a certain temperature (TC) and the TC values decrease with increasing Sb content. From thermoelectric measurements and electronic thermal conductivity calculated, it was observed that Sb doping increases the power factor (PF) and the figure of merit (ZT). Thus, Sb content plays an essential role in making these alloys applicable in the thermoelectric industry

Longitudinal Hierarchy Co3O4 Mesocrystals with High-dense Exposure Facets and Anisotropic Interfaces for Direct-Ethanol Fuel Cells

Novel electrodes are needed for direct ethanol fuel cells with improved quality. Hierarchical engineering can produce catalysts composed of mesocrystals with many exposed active planes and multi-diffused voids. Here we report a simple, one-pot, hydrothermal method for fabricating Co 3 O 4 /carbon/substrate electrodes that provides control over the catalyst mesocrystal morphology (i.e., corn tubercle pellets or banana clusters oriented along nanotube domains, or layered lamina or multiple cantilevered sheets). These morphologies afforded catalysts with a high density of exposed active facets, a diverse range of mesopores in the cage interior, a window architecture, and vertical alignment to the substrate, which improved efficiency in an ethanol electrooxidation reaction compared with a conventional platinum/carbon electrode. On the atomic scale, the longitudinally aligned architecture of the Co 3 O 4 mesocrystals resulted in exposed low- and high-index single and interface surfaces that had improved electron transport and diffusion compared with currently used electrodes

A hybrid nine-arm modular multilevel converter for medium-voltage six-phase machine drives

The nine-arm modular multilevel converter (9A-MMC) has been recently proposed as a reduced MMC topology variation for six-phase drive applications, with 25% reduction in the number of employed arms and associated components, compared to a standard dual three-phase MMC, however with a limited output voltage amplitude. This paper proposes a hybrid 9A-MMC comprised of half-bridge submodules (SMs) in both the upper and lower arms, and full-bridge SMs in the middle arms. By employing the negative-voltage state of the full-bridge SMs, the hybrid 9A-MMC avoids the limitations imposed on the dc-link voltage utilization, while achieving further reduction in the component count, compared to a standard 9A-MMC with identical half-bridge SMs. The operating principles of the proposed hybrid 9A-MMC are illustrated with mathematical analysis, while its characteristics are verified through both simulation and experimentation. An assessment of the proposed topology quantifying its employed components is also provided, in comparison to other MMC-based six-phase machine drives

Parameters identification and optimization of photovoltaic panels under real conditions using Lambert W-function

This paper proposes a new approach based on Lambert W-function to extract the electrical parameters of photovoltaic (PV) panels. This approach can extract the optimal electrical characteristics of the PV panel under variable conditions of irradiation and temperature. Three benchmarking panels (shell SP70 monocrystalline silicon, shell ST40 thin film, and KC200GT Polycrystalline Silicon) are demonstrated and analyzed considering the electrical characteristics provided by the manufacturers. A comprehensive assessment is carried out under different weather condition to validate the capability and the robustness of the proposed approach. Furthermore, the simulated output characteristics of the three modules Photovoltaic are almost comparable and reproduce faithfully the manufacturer’s experimental data The novelty of this study is the using a new hybrid analytical and numerical method that straight forward and effective given value of Root mean square error less than those obtained by others methods that indicate the estimated results are very close to the experimental values provided by the manufacturers

The Effect of surface topographical changes of two different surface treatments rotary instrument

One of the major innovations in endodontics has been the introduction of nickel-titanium (NiTi) alloy. This study evaluated the surface topographical changes of two different surface treatments rotary instrument after instrumentation and sterilization. 240 Extracted teeth were included in this study. 90 new AlphaKite and Revo-S NiTi rotary instruments were selected and divided into two groups (Group A 45 AlphaKite and group B 45 Revo-S). Each group were divided into three subgroups: (A1, B1) n=5 files were used as a control, (A2,B2) n=20 files were used to prepare three root canals using endodontic rotary motor then sterilized by autoclave for one cycle under 121°C at 15 psi for 30 minutes and (A3,B3) n=20 files were used to prepare nine root canals using the same rotary system then sterilized by autoclave for three cycles under 121°C at 15 psi for 30 minutes. Files were examined under scanning electron microscopy. On examining the AlphaKite, A1 revealed gross machining grooves on their surface with no pits, A2 showed disruption of cutting and A3 showed microcracks and deepening of the machining grooves. B1 showed a smoother surface with few machining grooves, B2 showed dulling and blunting of the cutting edges was predominant and B3 files showed plastic deformation in the form of unwinding of the flutes. The defects were less distributed along the electropolished Revo-S files than the physical vapor deposition AlphaKite

Suitability of Treated Wastewater Produced in Sudan for Irrigation Plants

The aim of this study was to characterize the quality of treated wastewater of Soba treatment plant, in Khartoum state, in term of its potential to be used in irrigation for different plant products, as well as to study the temporal variations of its physicochemical and biological parameters. Sampling of the treated wastewater was performed during Dec. 2014 and November 2015. The parameters indicating the suitability of such wastewater for irrigation were estimated, these include pH, Total Suspended Solids (TSS), Electrical Conductivity (EC), Total Dissolved Solids (TDS), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Sulphate, Ammonia, Chloride as well as total count, coli from bacteria and parasites. Results showed that, significant variation in values of pH, EC. Chloride, sulphate, BOD, COD was observed throughout the months of year. In spite of variability throughout the year, the values of pH, EC, TDS chlorides and sulphate, in term of their suitability for use in irrigation, fall within the limits set by FAO for irrigation water. Concentration of total coliform and nematodes in treated wastewater, were more than the concentration limit set by WHO, for restricted irrigation, and less than the limit for unrestricted irrigation. The reuse of the treated wastewater in irrigation of non food crops could be carried out without restriction, however, regarding the use of restricted irrigation, it would be necessary to upgrade treatment processes for further reduction in some parameters, providing that, regular testing should be done regularly