Implementation of the classical plasma–fluid model for simulation of dielectric barrier discharge (DBD) actuators in OpenFOAM

To simulate the coupled plasma and fluid flow physics of dielectric-barrier discharge, a plasma–fluid model is utilized in conjunction with a compressible flow solver. The flow solver is responsible for determining the bulk flow kinetics of dominant neutral background species including mole fractions, gas temperature, pressure and velocity. The plasma solver determines the kinetics and energetics of the plasma species and accounts for finite rate chemistry. In order to achieve maximum reliability and best performance, we have utilized state-of-the-art numerical and theoretical approaches for the simulation of DBD plasma actuators. In this respect, to obtain a stable and accurate solution method, we tested and compared different existing numerical procedures, including operator-splitting algorithm, super-timestepping, and solution of the Poisson and transport equations in a semi-implicit manner. The implementation of the model is conducted in OpenFOAM. Four numerical test cases are considered in order to validate the solvers and to investigate the drawbacks/benefits of the solution approaches. The test problems include single DBD actuator driven by positive, negative and sinusoidal voltage waveforms, similar to the ones that could be found in literature. The accuracy of the results strongly depends to the choice of time step, grid size and discretization scheme. The results indicate that the super-time-stepping treatment improves the computational efficiency in comparison to explicit schemes. However, the semiimplicit treatment of the Poisson and transport equations showed better performance compared to the other tested approaches.info:eu-repo/semantics/publishedVersio

Saliva Secretion and Efficacy of Helicobacter Pylori Eradication in Peptic Ulcer Patients

Objective: It has been noted that the presence of Helicobacter pylori (H. pylori)in the oral cavity may affect the outcome of eradication therapy. This condition is associated with the recurrence of gastric infection. The optimum secretion of salivapromotes oral health consequently influencing H. pylori eradication. The purpose of this study was to investigate the relation between salivary secretion and the efficacy of H. pylori eradication from the stomach.Materials and Methods: Forty five patients with gastric H. pylori infection were enrolled in this study. Diagnosis of H. pylori infection was confirmed by endoscopy,biopsy, urease test and histological examination. Salivary secretion of all participants was determined under standard condition before the beginning of antibacterial treatment. Then the patients were treated with a 14-day course anti-H. pylori regimen consisting of amoxicillin, omeprazole, metronidazole and bismuth. The efficacy of eradication therapy was evaluated 4 weeks after the end of the treatment course. Mann-Whitney U test was used to analyze the variables.Results: The median of salivary secretion among successful and unsuccessful H. pylori eradication groups was 0.48 ml/min and 0.24 ml/min, respectively (p=0.005).Conclusion: Although the type of drug regimens is challenging, the efficacy of H. pylori eradication from the stomach might be reduced by lower salivary secretion

Self-regulated learning, metacognitive awareness, and argumentative writing: a structural equation modeling approach

This is the author accepted manuscript. The final version is available from Equinox Publishing via the DOI in this record The current study examined the relationships among self-regulated learning, metacognitive awareness, and EFL learners’ performance in argumentative writing. We collected data through two questionnaires (i.e., Motivated Strategies for Learning Questionnaire (MSLQ); Metacognitive Awareness Inventory (MAI)), and an argumentative writing task administered to 250 Iranian graduate students of TEFL in eleven universities across Iran. Using LISREL version 8.8, we ran structural equation modeling (SEM) to analyze the hypothesized relationships. The results revealed that although the SEM enjoyed a good fit on the hypothesized relationships among self-regulated learning, metacognitive awareness, and argumentative writing, the significant influence of metacognitive awareness and self-regulated learning on students’ argumentative writing performance could not be postulated. Finally, the pedagogical implications for writing instruction and research are discussed

Antibacterial and Antifungal Activities of Punica Granatum Peel Extracts Against Oral Pathogens

Objective: Punica granatum has been used for many years in folk medicine due to several purposes. The aim of the present study was to evaluate the effect of methanolic extract of Punica granatum peel (MEPGP) against Streptococcus mutans, Staphylococcus aureus,Streptococcus salivarius, Streptococcus sanguinis, Staphylococcus epidermidis, Actynomyces viscosus, Lactobacillus acidophilus and Candida albicans.Materials and Methods: In this in vitro study, the mentioned oral organisms were cultured in blood agar and mueller-hinton media and then paper disks containing MEPGP at concentrations of 4 mg/ml, 8 mg/ml and 12 mg/ml were inserted on medias. The antimicrobialactivity was evaluated by agar disk diffusion method. The effects of three different concentrations of MEPGP against microorganisms were compared using one-way ANOVA and Tukey tests.Results: All concentrations of MEPGP had antibacterial activity against S. aureus and S.epidermidis. Only at concentration of 8 mg/ml and 12 mg/ml MEPGP was effective against L. acidophilus, S. mutans and S. salivarius. Furthermore; no concentrations ofMEPGP inhibited A. viscosus and C. albicans.Conclusion: This study suggests that MEPGP might be used as an antibacterial agent in controlling oral infections

The relationship between L2 motivation and transformative engagement in academic reading among EAP learners: Implications for reading self-regulation

This is the final version. Available on open access from Frontiers Media via the DOI in this recordData availability statement: The original contributions presented in this study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.This study examined the relationship between L2 motivation and engagement in academic reading skill from the lenses of L2 motivational self-system and transformative experience. More specifically, following the transformative experience (TE) framework, we investigated the level of students' engagement in academic reading skills inside and outside English classes. We also explored what motivational factors act as strong predictors of transformative experience and whether L2 motivation and engagement of students differ across different disciplines. Stratified purposive sampling was followed to recruit 419 undergraduate English for academic purposes (EAP) students studying in different majors. As such, we developed a questionnaire for measuring TE and utilized a pre-established questionnaire to operationalize L2 motivational self-system. We found that L2 motivation significantly covaried with students' level of engagement in English academic reading skill. Furthermore, the results of multiple regression analysis revealed that L2 learning experience and ideal L2 self were strong predictors of transformative engagement; ought-to L2 self played a marginal role in the occurrence of TE. Discipline-wise, Life Sciences students were considerably more motivated than those in Arts and Humanities. However, no significant difference was observed in the extent of transformative engagement among students across disciplinary groups. Implications for EAP instructors, educational authorities, and material and curricula developers are discussed

In-situ nanocomposite in friction stir welding of 6061-T6 aluminum alloy to AZ31 magnesium alloy

Prior to friction stir welding (FSW), silicon carbide (SiC) nanopowders were placed inside the groove on the adjacent side of magnesium sheet. In order to make a good distribution of these nanoparticles, first, friction stir processing (FSP) with a pinless tool was conducted on this side. Second, using a frustum pin tool, a combination of two travel speeds (25 and 35¿mm/min) and three rotation speeds (550, 600 and 650¿rpm) were employed to obtain the optimal conditions for FSW of AZ31 magnesium alloy to 6061 aluminum alloy. The joint fabricated at 35¿mm/min and 650¿rpm, exhibited improvement of 28% in tensile strength and enhancement about three times in elongation, compared with the joint without nanoparticles. SiC nanoparticles had an effective role on the grain refining of the stirred zone and improving the microstructural characteristics of the banded structure zone. Due to the decreased grain size and the presence of ceramic nanoparticles (SiC) with high value of hardness, the hardness level of the reinforced samples was greater than that of the non-reinforced samples. Fracture of the non-reinforced sample was completely brittle, while in the reinforced samples, fracture features changed to the ductile mode.Peer ReviewedPostprint (author's final draft

Barriopsis iraniana and Phaeobotryon cupressi: two new species of the Botryosphaeriaceae from trees in Iran

Species in the Botryosphaeriaceae are well known as pathogens and saprobes of woody hosts, but little is known about the species that occur in Iran. In a recent survey of this family in Iran two fungi with diplodia-like anamorphs were isolated from various tree hosts. These two fungi were fully characterised in terms of morphology of the anamorphs in culture, and sequences of the ITS1/ITS2 regions of the ribosomal DNA operon and partial sequences of the translation elongation factor 1-α. Phylogenetic analyses placed them within a clade consisting of Barriopsis and Phaeobotryon species, but they were clearly distinct from known species in these genera. Therefore, they are described here as two new species, namely Barriopsis iraniana on Citrus, Mangifera and Olea, and Phaeobotryon cupressi on Cupressus sempervirens

Modelling of dielectric barrier discharge plasma actuators for direct numerical simulations

In recent years the development of devices known as plasma actuators has advanced the promise of controlling flows in new ways that increase lift, reduce drag and improve aerodynamic efficiencies; advances that may lead to safer, more efficient and quieter aircraft. The large number of parameters (location of the actuator, orientation, size, relative placement of the embedded and exposed electrodes, materials, applied voltage, frequency) affecting the performance of plasma actuators makes their development, testing and optimisation a very complicated task. Several approaches have been proposed for developing numerical models for plasma actuators. The discharge can be modelled by physics-based kinetic methods based on first principles, by semi-empirical phenomenological approaches and by PIV-based methods where the discharge is replaced by a steady-state body force. The latter approach receives a recent interest for its easy implementation in RANS and U-RANS solvers. Here, a forcing term extracted from experiments is implemented into our high-order Navier-Stokes solver (DNS) in order to evaluate its robustness and ability to mimic the effects of a surface dielectric barrier discharge. This experimental forcing term is compared to the numerical forcing term developed by Suzen & Huang (1, 2) with an emphasis on the importance of the wall-normal component of each model

Heat generation mechanisms of DBD plasma actuators

During the last twenty years DBD plasma actuators have been known by their ability for boundary layer flow control applications. However, their usefulness is not limited to this application field, they also present great utility for applications within the field of heat transfer, such as a way to improve the aerodynamic efficiency of film cooling of gas turbine blades, or de-icing and ice formation prevention. Nevertheless, there is a relative lack of information about DBD’s thermal characteristics and its heat generation mechanisms. This happens due to the extremely high electric fields in the plasma region and consequent impossibility of applying intrusive measurement techniques. Against this background, this work describes the physical mechanisms behind the generation of heat associated to the DBD plasma actuators operation. An experimental technique, based on calorimetric principles, was devised in order to quantify the heat energy generated during the plasma actuators operation. The influence of the dielectric thickness, as well as the dielectric material, were also evaluated during this work. The results were exposed and discussed with the purpose of a better understanding of the heat generation mechanisms behind the operation of DBD plasma actuators

Information Retrieval on the World Wide Web and Active Logic: A Survey and Problem Definition

As more information becomes available on the World Wide Web (there are currently over 4 billion pages covering most areas of human endeavor), it becomes more difficult to provide effective search tools for information access. Today, people access web information through two main kinds of search interfaces: Browsers (clicking and following hyperlinks) and Query Engines (queries in the form of a set of keywords showing the topic of interest). The first process is tentative and time consuming and the second may not satisfy the user because of many inaccurate and irrelevant results. Better support is needed for expressing one's information need and returning high quality search results by web search tools. There appears to be a need for systems that do reasoning under uncertainty and are flexible enough to recover from the contradictions, inconsistencies, and irregularities that such reasoning involves. Active Logic is a formalism that has been developed with real-world applications and their challenges in mind. Motivating its design is the thought that one of the factors that supports the flexibility of human reasoning is that it takes place step-wise, in time. Active Logic is one of a family of inference engines (step-logics) that explicitly reason in time, and incorporate a history of their reasoning as they run. This characteristic makes Active Logic systems more flexible than traditional AI systems and therefore more suitable for commonsense, real-world reasoning. In this report we mainly will survey recent advances in machine learning and crawling problems related to the web. We will review the continuum of supervised to semi-supervised to unsupervised learning problems, highlight the specific challenges which distinguish information retrieval in the hypertext domain and will summarize the key areas of recent and ongoing research. We will concentrate on topic-specific search engines, focused crawling, and finally will propose an Information Integration Environment, based on the Active Logic framework. Keywords: Web Information Retrieval, Web Crawling, Focused Crawling, Machine Learning, Active Logic (Also UMIACS-TR-2001-69