Application of Multi-Objective Evolutionary Optimization Algorithms to Reactive Power Planning Problem

This paper presents a new approach to treat reactive power (VAr) planning problem using multi-objective evolutionary algorithms. Specifically, Strength Pareto Evolutionary Algorithm (SPEA) and Multi-Objective Particle Swarm Optimization (MOPSO) approaches have been developed and successfully applied. The overall problem is formulated as a nonlinear constrained multi-objective optimization problem. Minimizing the total incurred cost and maximizing the amount of Available Transfer Capability (ATC) are defined as the main objective functions. The proposed approaches have been successfully tested on IEEE 14 bus system. As a result a wide set of optimal solutions known as Pareto set is obtained and encouraging results show the superiority of the proposed approaches and confirm their potential to solve such a large scale multi-objective optimization problem

Impact of high level of renewable energy penetration on inter-area oscillation

Many research projects have been focused on the impacts of each type of wind turbines on the stability of the power system. Due to the rapid increase in the penetration level of renewable energy and diverse power generation portfolios, it is vital to study the performance of the power system in presence of different renewable sources of energy. The focus of this paper is to study the small signal stability of a power system with high penetration level of wind and geothermal energy. The models of three commercially available wind turbines are used to investigate inter-area mode oscillations of a power system with renewable generators located in remote areas. Moreover, the performance of the power system with HVDC and HVAC interconnections is demonstrated. Simulations are carried out on a test power system using PSS/E software

The Applications of Cone-Beam Computed Tomography in Endodontics: A Review of Literature

By producing undistorted three-dimensional images of the area under examination, cone-beam computed tomography (CBCT) systems have met many of the limitations of conventional radiography. These systems produce images with small field of view at low radiation doses with adequate spatial resolution that are suitable for many applications in endodontics from diagnosis to treatment and follow-up. This review article comprehensively assembles all the data from literature regarding the potential applications of CBCT in endodontics

Comparison of Antibacterial Effects of Photodynamic Therapy, Modified Triple Antibiotic Paste and Calcium Hydroxide on Root Canals Infected with Enterococcus Faecalis: An In-Vitro Study

Background: A pivotal issue to achieve success in the treatment of the root canal is root canal disinfection. One of the most important bacteria that infect root canal is enterococcus faecalis. This study seeks to examine the effectiveness of three methods for disinfecting the root canal: photodynamic therapy, modified triple antibiotic paste (MTAP) and calcium hydroxide.Method and material: 62 single-rooted extracted anterior teeth were collectected.After cleaning and disinfection, crowns were cut at the CEJ point. The root canals were shaped to the working length up to file F3 protaper (F1, F2, F3). EDTA 17% and sodium hypochlorite 2.5% were used for 5 minutes to wash and remove the smear layer, and then the apical foramen was sealed using composite. After that, the teeth were sterilized in an autoclave at 121° C for 15 minutes. Then 10 samples were taken randomly as the negative control. The remaining samples were immersed and cultivated in a suspension containing enterococcus faecalis for 21 days. Then samples were divided into 5 groups: two positive control groups, one group treated with the antibiotic paste with the concentration of 1mg/ml, one group treated with calcium hydroxide, and one group treated with photodynamic therapy. Then, to collect the biofilm, the protaper file F4 was used. After that, the microbial suspension was provided and counting the colonies to compare the groups was carried out.Results: The findings indicated that the amount of CFU/mg of MTAP samples, including clindamycin, metronidazole and ciprofloxacin in the concentration of 1mg/ml and photodynamic therapy and calcium hydroxide was lower than that in the control group. Antibiotic paste, cleansed the root canal up to 99.9%. Photodynamic therapy reduced the amount of CFU/mg to 98.8%, and calcium hydroxide reduced the amount of CFU/mg to 94.13%.Conclusion: Using photodynamic therapy causes a reduction in biofilm and inhibits the growth of enterococcus faecalis bacterium. In addition, in this study MTAP with the concentration of 1mg/ml was used, which expunged the bacteria completely. Meanwhile, calcium hydroxide had the weakest effect of all on the enterococcus faecalis bacteriu

Accuracy Evaluation of Methods for Determining Jet Trajectory Characteristics in Flip Bucket

The maximum scour of the flip-bucket occurs at the jet landing site, so it is important to know the exact path of the jet. In this research, by building two laboratory models of different sizes, the ability to exist relationships in predicting the jet path, length, and coordinates of the jet peak was evaluated. According to the results, Kawakami's relation had better accuracy in predicting the jet path. The average error percentage of the jet trajectory length prediction in USBR and Attari relationships was less than 10% and other relationships were more than 20%. USBR, Attari, and Kawakami relationships had a good estimate of the jet trajectory length along the edge. The error of other relationships in estimating this characteristic was more than 30%. In predicting the horizontal distance of the high point of the jet trajectory, the theoretical relationship and the profile of Kawakami and USBR had an average error of less than 10%. Theoretical relationships, Kawakami and USBR in estimating the maximum height of the jet, have an estimate with an error of 23.7, 33.9, and 21.4% and according to the Nash-Sutcliffe criterion, none of these relationships have been able to get a very good category

The Effect of Mineral Trioxide Aggregate Mixed with Chlorhexidine as Direct Pulp Capping Agent in Dogs Teeth: A Histologic Study

Introduction: The aim of the present investigation was to compare the efficacy of mineral trioxide aggregate (MTA) and 0.2% chlorhexidine (CHX) mixture to pure MTA, as a pulp capping material. Methods and Materials: The pulp of 24 lateral incisors and canines from four dogs were exposed and capped either with MTA or MTA+0.2% CHX. After 2 months the animals were sacrificed and the teeth were prepared for histological evaluation in terms of calcified bridge formation, the degree of inflammation and presence of necrosis. The Fisher’s exact test was used for data analysis. Results: The results showed that formation of complete calcified bridge in MTA specimens was significantly more than MTA+CHX (P<0.05). No significant difference was found in the degree of inflammation and necrosis between MTA and MTA+CHX groups (P>0.05). Conclusion: Mixing MTA with CHX as pulp capping agent had a significant negative impact on formation of calcified bridge on directly capped dog’s teeth.Keywords: Chlorhexidine; Mineral Trioxide Aggregate; Pulp Capping; Vital Pulp Therap

Probabilistic calculus in power system analysis and design

The increasing uncertainties grid operator have to face in their every-day work lead to the necessity for fast and accurate information about the probability of certain operational states of their network. Algorithms traditionally used in grid operation and planning are only able to determine a discrete operational state of the power grid. An inclusion of probabilistic data is usually done by analysis of selected discrete states with traditional power flow calculation techniques, followed by an interpolation of the results. In this paper the authors want to highlight the principle features of a novel class of probabilistic calculation algorithms, presently being researched and evalualted

Modelling demand response aggregator behavior in wind power offering strategies

This paper proposes a new wind offering strategy in which a wind power producer employs demand response (DR) to cope with the power production uncertainty and market violations. To this end, the wind power producer sets demand response (DR) contracts with a DR aggregator. The DR aggregator behavior is modeled through a revenue function. In this way the aggregator aims to maximize its revenue through trading DR with the wind power producer, other market players and the day-ahead market. The problem is formulated in bilevel programming in which the upper level represents wind power producer decisions and the lower level models the DR aggregator behavior. The given bilevel problem is then transformed into a single-level mathematical program with equilibrium constraints (MPEC) and linearized using proper techniques. The feasibility of the given strategy is assessed on a case of the Nordic market

Wind offering strategy in the Australian National Electricity Market: A two-step plan considering demand response

This paper proposes an energy offering strategy for wind power producers. A new trading plan is presented through which a wind power producer can employ demand response (DR) to maximize its profit. To consider DR, a new DR scheme is' developed here. The proposed plan includes two steps: The first step takes place on a day-ahead basis. The corresponding decisions involve an initial offering schedule and preliminary DR arrangements for the following day. The second step coincides with the day of the energy delivery. A consecutive approach is proposed in which the wind power producer determines its final energy offer during each trading interval. Simultaneously, the required DR agreements for that interval are also confirmed. This approach is repeated until all periods of the day are covered. The proposed plan is formulated as a stochastic programming approach, where its feasibility is evaluated on a case of the Australian National Electricity Market (NEM). (C) 2014 Elsevier B.V. All rights reserved