STATCOM Optimal Allocation in Transmission Grids Considering Contingency Analysis in OPF Using BF-PSO Algorithm

In this paper, a combinational optimization algorithm is introduced to obtain the best size and location of Static Compensator (STATCOM) in power systems. Its main contribution is considering contingency analysis where lines outages may lead to infeasible solutions especially at peak loads and it commonly can be vanished by load-shedding. The objective of the proposed algorithm is firstly to prevent infeasible power flow solutions without undesired load-shedding, which is critical in contingency analysis; and secondly to mitigate overall power losses and costs. Moreover, active and reactive powers generation costs are considered in the proposed objective function. Since there are various constraints such as lines outages number, cost and their duration that must be taken to account, Bacterial Foraging oriented by Particle Swarm Optimization (BF-PSO) algorithm combined with Optimal Power Flow (OPF) is used to solve and overcome the complexity of this combinational nonlinear problem. In order to validate the accuracy of the proposed method, two test systems, including IEEE 30 bus standard system and Azarbaijan regional power system of Iran, are applied in simulation studies. All obtained optimization results show the effectiveness of the suggested combinational method in loss and cost reduction and preventing load-shedding

Characterization and Separation Performance of a Novel Polyethersulfone Membrane Blended with Acacia Gum

Novel polyethersulfone (PES) membranes blended with 0.1–3.0 wt. % of Acacia gum (AG) as a pore-former and antifouling agent were fabricated using phase inversion technique. The effect of AG on the pore-size, porosity, surface morphology, surface charge, hydrophilicity, and mechanical properties of PES/AG membranes was studied by scanning electron microscopy (SEM), Raman spectroscopy, contact angle and zeta potential measurements. The antifouling -properties of PES/AG membranes were evaluated using Escherichia coli bacteria and bovine serum albumine (BSA). The use of AG as an additive to PES membranes was found to increase the surface charge, hydrophilicity (by 20%), porosity (by 77%) and permeate flux (by about 130%). Moreover, PES/AG membranes demonstrated higher antifouling and tensile stress (by 31%) when compared to pure PES membranes. It was shown that the prepared PES/AG membranes efficiently removed lead ions from aqueous solutions. Both the sieving mechanism of the membrane and chelation of lead with AG macromolecules incorporated in the membrane matrix contributed to lead removal. The obtained results indicated that AG can be used as a novel pore-former, hydrophilizing and antifouling agent, as well as an enhancer to the mechanical and rejection properties of the PES membranes

Preparation and characterization of emulsion poly(vinyl chloride) (EPVC)/TiO(2) nanocomposite ultrafiltration membrane

Emulsion poly(vinyl chloride)/titanium dioxide (EPVC/TiO2) nanocomposite ultrafiltration membranes were prepared using the phase inversion method with different TiO2 contents. Pure water flux through the membranes was investigated at a operating pressure of 2 bar and its antifouling properties were studied using bovine serum albumin (BSA) as a foulant. The results showed an increment in pure water flux with increasing content of TiO2 up to 2 wt%, and then it slightly decreased by addition of 4 wt% TiO2 due to agglomeration of the nanoparticles at this content. The static water contact angle test showed improvement in membrane hydrophilicity, due to hydrophilic behavior of the nanoparticles, which led to higher water flux. SEM and EDAX analyses were applied to investigate membrane morphological changes. EDAX analysis indicated that the nanoparticles are homogeneously dispersed in membrane structure at low concentrations. However, at high loading, the nanoparticles have a propensity to aggregate. SEM images showed that with TiO2 addition, initially finger-like structures change to macro-voids and after 1 wt% TiO2 loading, they return to finger-like construction with elongated finger-like pores. TiO2 addition also enhanced BSA rejection properties. BSA ultrafiltration experiments showed that the antifouling ability of nano-TiO2 embedded membranes was better than the unfilled EPVC membrane.Hesamoddin Rabiee, Mohammad Hossein Davood Abadi Farahani, Vahid Vatanpou

Study of the Knowledge of Elementary School Health Teachers of Tehran City on How to Control Students’ Teeth Injuries at School in

Background and Aim: Dental injuries are one of the common problems in children. Considering that nowadays, more attention is being paid to dental health and that school health teachers play a key role in the management of dental injuries, this research was designed with the aim of determining the extent of the knowledge of elementary school health teachers of Tehran city on how to control students’ teeth injuries at school. Materials and Methods: This research is a cross-sectional study. The questionnaires were given to 280 elementary school health teachers in Tehran city. Of the 280 questionnaires, 216 were answered (77.14%). Data were collected and statistical analysis was performed using descriptive statistics methods and inferential statistics test in two study populations, chi-square independence and Spearman correlation coefficient with 95% confidence interval (CI). Results: Receiving medical emergency training courses affected the responses to the questions regarding the maximum time to restore the teeth to their location (p = 0.001), and the most appropriate action in case of altered consciousness (p = 0.05). Receiving dental emergency training courses had no impact on the responses to any of the other questions (p = 0.231). According to Spearman correlation test results, there was a weak reverse significant correlation between age and the question regarding the most appropriate way to reposition the teeth in this case (p = 0.031 and correlation coefficient = - 0.157), and between work experience and the question regarding distinguishing the tooth type (p = 0.042 and correlation coefficient = - 0. 153). Conclusion: the results indicated that the knowledge of these teachers is not adequate, and that there is a need for education regarding the management of dental injuries. Furthermore, there is no significant correlation between the responses to the questionnaire and receiving dental emergency training courses

The influence of torque and manual glide path on the defect or separation rate of NiTi rotary instruments in root canal therapy

Introduction: One of the effecting factors in prognosis of root canal therapy is accidental procedure as broken files that may be unpreventable. Many manufacturers have designed and marketed various electromotors that can control rotational speed and torque. On the other hand, some studies have recommended applying a manual glide path to diminish contact area between the file and canal walls. The purpose of this study was evaluation of the effect of torque and a manual glide path on defects as separation of Nickel-titanium (NiTi) rotary files. Materials and Methods: This ex vivo randomized controlled trial study was carried out on 160 canals of human′s matured molars with mild curvature (15-338). After initial preparation of samples and checking for inclusion criteria, in first group, preparation was carried out with air-driven handpiece, and in group two, Endo IT was used as electromotor. In both groups, Mtwo files with simultaneous technique were used for preparation. Then all data were collected and analyzed with Mann Whitny, Mantel Cox, and t-test. Results: No significant differences between two groups (P < 0.05) were observed. Based on survival analysis, safety probability of files after preparation of nine canals is 64% in group one and 69.9% in group two. There was no significant differences between this safety probability in two groups (P = 0.272). Conclusion: Usage of torque control handpiece is not an important factor, comparing instrumentation technique

Probabilistic and sensitivity analyses of effective geotechnical parameters on rock slope stability: A case study of an urban area in northeast Iran

Despite the development of cities, risk assessment of rock slope stability in urban areas seems not to be growing at the same time. Mashhad is a developed city in northeast of Iran with a population of over 2.4 million. Given the closeness of the southern part of Mashhad to the Binaloud mountain ridge, the stability of the residential complexes that are being constructed in this area is a critical issue. Based on the fundamental roles of discontinuity properties and geo-mechanical parameters of rock mass, in this study we evaluated the most influential parameters of the rock slope stability and the failure probability of the slope near the Negin residential complex built on this ridge. According to the deterministic and probabilistic analyses, the north trench that was excavated for this residential complex could potentially cause plane failure. Moreover, the relationship between effective parameters on instability and their impact on safety factors were determined by sensitivity analysis. Therefore, slope dip, pore water pressure, and joint set dip were highly influential on the safety factor. There was also a nonlinear relationship between different parameters and safety in the studied area. This study presents an approach for risk assessment of rock slope stability in urban areas. © 2013 Springer Science+Business Media Dordrecht

Improvement in flux and antifouling properties of PVC ultrafiltration membranes by incorporation of zinc oxide (ZnO) nanoparticles

In this study, modification of polyvinyl chloride (PVC) ultrafiltration membranes with zinc oxide (ZnO) nanoparticle addition was taken into consideration. The ZnO at five different weights was added to the polymeric solution, and the membranes were fabricated by the phase inversion method using water as a nonsolvent and PEG 6 kDa as a pore former additive. The results showed that the pure water flux of the modified membranes increased up to 3 wt% ZnO addition, which was the optimized amount of the nanoparticle addition in this study. Also, at 3 wt% ZnO addition, flux recovery ratio reached from 69% to above 90%, indicated that the nanocomposite membranes were less susceptible to be fouled. BSA rejection of the membranes also enhanced up to 97% by 3 wt% ZnO addition. The membranes were further characterized by SEM images and remarkable changes in their morphologies were observed, and they became more porous with higher interconnectivity between the pores. Furthermore, EDAX analysis was applied to study ZnO dispersion in the membrane structure and except for 4 wt% ZnO addition which particles aggregation was noticeable, ZnO was dispersed finely in the membrane structure. In addition, the modified membranes had higher hydrophilicity and lower contact angle that was effective to obtain higher water flux.Hesamoddin Rabiee, Vahid Vatanpour, Mohammad Hossein Davood Abadi Farahani, Hamed Zarrab

Evaluation of Multiple Choice Questions of Oral and Maxillofacial Medicine Courses 1, 2, and 3 in the First Semester of Academic Year 2014-2015

Background and aim: Lack of proper assessment of students' knowledge regarding theoretical contents leads to disappointment and negligence by weak students. This study assessed multiple-choice questions (MCQs) of oral and maxillofacial medicine courses in the first semester of the academic year 2014-2015. Materials and Methods: In this cross-sectional study, questions of theoretical oral medicine courses 1, 2, and 3 were assessed according to twelve items in Millman's checklist, including clearness of stem, negative option for stem, specific option, contrastive option, positive words in stem and options, writing structure of stem, duplicated option, the spelling of stem and options, vertically of options, positivity of stem and options, and use of "all of the above" and "none of the above" phrases in options. Difficulty and discrimination coefficients of each question and the rate of compliance with Millman's principles were evaluated using Excel 2007 and SPSS 16. Data were analyzed using descriptive statistics, analysis of variance (ANOVA), and Regression analysis. Results: The responses of 219 students to 113 MCQs were evaluated. In theoretical course 1 with 40 MCQs, discrimination coefficient was 0.36±0.2, difficulty coefficient was 73.2±15.02, and correlation coefficient was 0.58. In theoretical course 2 with 35 MCQs, discrimination coefficient was 0.2±0.04, difficulty coefficient was 70.91±25.13, and correlation coefficient was 0.47. In theoretical course 3 with 38 MCQs, discrimination coefficient was 0.3±0.19, difficulty coefficient was 68.73±26.89, and correlation coefficient was 0.5. The percentage of compliance with Millman's principles was 81.88%, 83.58%, and 84.42% in courses 1, 2, and 3, respectively. Conclusion: The weakest discrimination coefficient was noted in theoretical oral medicine 2. The high percentage of simple difficulty coefficient in the three theoretical courses indicates the necessity of training faculty members in designing questions