Shear Stress Distributions along the Cross Section in Smooth Open Channel Flow

Distributions of shear stress throughout the entire cross-section within the fully developedboundary layer region in a smooth and rectangular open channel flow setup areexperimentally determined with the help of a laser Doppler anemometer. Velocity measurements are taken for 24 different sub-critical flow conditions with Froude numbers inthe range: 0.13 Fr 0.78 and with aspect ratios within 1.5 B/H 12.0. For all the flow conditions created in the setup, the shear stress distribution is found to exhibit variations as afunction of the aspect ratio, B/H, which is caused by the flow cells originated by the secondary flows in opposite direction to the main flow. For the aspect ratio between 1.5 and5.0, the shear stress distributions are represented by a third degree polynomial function alongthe cross section. In this case, the maximum shear stress is 12% greater than the averagestress. For B/H≥ 5.0, the dimensionless shear stress distributions are represented by a seconddegree polynomial. Here, the maximum shear stress was 10% greater than the overall average shear stress throughout the entire cross-section

Turkish EFL Teachers’ Perceptions and Practices of Foreign Language Assessment in Primary Education

The present study aimed to investigate perceptions of EFL teachers working at state primary schools on core language skills, assessment types and question types used in assessing student’s foreign language development and proficiency during an academic year. Data were gathered from 56 EFL teachers working at 42 primary state schools in Turkey through a questionnaire comprising a variety of items to elicit their perceptions and applications of language assessment in the classes of 4th to 6th graders. Results obtained from frequency analyses indicated that the pen-and-paper tests, performance tasks, and in-class observation are the mostly used assessment tools, and that the selected response items are mostly employed question types in the tests, and that performance-based and communication-based assessment types are preferred more frequently than the traditional types in evaluating students’ success in learning EFL

Numerical simulation of a new type of cross flow tidal turbine using OpenFOAM - Part II: Investigation of turbine-to-turbine interaction

Copyright © 2013 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Renewable Energy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Renewable Energy, Volume 50 (2013), DOI: 10.1016/j.renene.2012.08.064Prediction of turbine-to-turbine interaction represents a significant challenge in determining the optimized power output from a tidal stream farm, and this is an active research area. This paper presents a detailed work which examines the influence of surrounding turbines on the performance of a base case (isolated turbine). The study was conducted using a new CFD based, Immersed Body Force (IBF) model, which was validated in the first paper, and an open source CFD software package OpenFOAM was used for the simulations. The influence of the surrounding turbines was investigated using randomly chosen initial lateral and longitudinal spacing among the turbines. The initial spacing was then varied to obtain four configurations to examine the relative effect that positioning can have on the performance of the base turbine

Dominant features in three-dimensional turbulence structure: comparison of non-uniform accelerating and decelerating flows

The results are presented from an experimental study to investigate three-dimensional turbulence structure profiles, including turbulence intensity and Reynolds stress, of different non-uniform open channel flows over smooth bed in subcritical flow regime. In the analysis, the uniform flow profiles have been used to compare with those of the non-uniform flows to investigate their time-averaged spatial flow turbulence structure characteristics. The measured non-uniform velocity profiles are used to verify the von Karman constant κ and to estimate sets of log-law integration constant B r and wake parameter П, where their findings are also compared with values from previous studies. From κ, B r and П findings, it has been found that the log-wake law can sufficiently represent the non-uniform flow in its non-modified form, and all κ, B r and П follow universal rules for different bed roughness conditions. The non-uniform flow experiments also show that both the turbulence intensity and Reynolds stress are governed well by exponential pressure gradient parameter β equations. Their exponential constants are described by quadratic functions in the investigated β range. Through this experimental study, it has been observed that the decelerating flow shows higher empirical constants, in both the turbulence intensity and Reynolds stress compared to the accelerating flow. The decelerating flow also has stronger dominance to determine the flow non-uniformity, because it presents higher Reynolds stress profile than uniform flow, whereas the accelerating flow does not

A compressible multiphase flow model for violent aerated wave impact problems

This paper focuses on the numerical modelling of wave impact events under air entrapment and aeration effects. The underlying flow model treats the dispersed water wave as a compressible mixture of air and water with homogeneous material properties. The corresponding mathematical equations are based on a multiphase flow model which builds on the conservation laws of mass, momentum and energy as well as the gas-phase volume fraction advection equation. A high-order finite volume scheme based on monotone upstream-centred schemes for conservation law reconstruction is used to discretize the integral form of the governing equations. The numerical flux across a mesh cell face is estimated by means of the HLLC approximate Riemann solver. A third-order total variation diminishing Runge–Kutta scheme is adopted to obtain a time-accurate solution. The present model provides an effective way to deal with the compressibility of air and water–air mixtures. Several test cases have been calculated using the present approach, including a gravity-induced liquid piston, free drop of a water column in a closed tank, water–air shock tubes, slamming of a flat plate into still pure and aerated water and a plunging wave impact at a vertical wall. The obtained results agree well with experiments, exact solutions and other numerical computations. This demonstrates the potential of the current method to tackle more general wave–air–structure interaction problems

Clonal diversity and detection of carbapenem resistance encoding genes among multidrug-resistant Acinetobacter baumannii isolates recovered from patients and environment in two intensive care units in a Moroccan hospital

Background Carbapenem-resistant Acinetobacter baumannii has recently been defined by the World Health Organization as a critical pathogen. The aim of this study was to compare clonal diversity and carbapenemase-encoding genes of A. baumannii isolates collected from colonized or infected patients and hospital environment in two intensive care units (ICUs) in Morocco. Methods The patient and environmental sampling was carried out in the medical and surgical ICUs of Mohammed V Military teaching hospital from March to August 2015. All A. baumannii isolates recovered from clinical and environmental samples, were identified using routine microbiological techniques and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry. Antimicrobial susceptibility testing was performed using disc diffusion method. The carbapenemase-encoding genes were screened for by PCR. Clonal relatedness was analyzed by digestion of the DNA with low frequency restriction enzymes and pulsed field gel electrophoresis (PFGE) and the multi locus sequence typing (MLST) was performed on two selected isolates from two major pulsotypes. Results A total of 83 multidrug-resistant A. baumannii isolates were collected: 47 clinical isolates and 36 environmental isolates. All isolates were positive for the bla OXA51-like and bla OXA23-like genes. The coexistence of bla NDM-1 /bla OXA-23-like and bla OXA 24-like /bla OXA-23-like were detected in 27 (32.5%) and 2 (2.4%) of A. baumannii isolates, respectively. The environmental samples and the fecally-colonized patients were significantly identified (p < 0.05) as the most common sites of isolation of NDM-1-harboring isolates. PFGE grouped all isolates into 9 distinct clusters with two major groups (0007 and 0008) containing up to 59% of the isolates. The pulsotype 0008 corresponds to sequence type (ST) 195 while pulsotype 0007 corresponds to ST 1089.The genetic similarity between the clinical and environmental isolates was observed in 80/83 = 96.4% of all isolates, belonging to 7 pulsotypes. Conclusion This study shows that the clonal spread of environmental A. baumannii isolates is related to that of clinical isolates recovered from colonized or infected patients, being both associated with a high prevalence of the bla OXA23-like and bla NDM-1genes. These findings emphasize the need for prioritizing the bio-cleaning of the hospital environment to control and prevent the dissemination of A. baumannii clonal lineages

TURBULENT VELOCITY PROFILES FOR SMOOTH AND ROUGH OPEN CHANNELS - CLOSURE

WOS: A1991GD59100013

Fostering young learners' listening and speaking skills

WOS: 000462458200012

Exploring the impact of the fulbright foreign language teaching assistant program on grantees’ educational and cultural beliefs and practices

Educational exchanges like the Fulbright scholarship programs are viewed positively at a number of levels, from promoting personal growth to helping build cooperative relations between nations. This study reported in this chapter examined the experiences of eight Turkish Fulbright Foreign Language Teaching Assistant (FLTA) grantees in the years after their exchange program, to investigate the reported impacts that the Fulbright experience had on the grantees’ subsequent understandings of education, democracy and intercultural issues. The study utilized a survey instrument, follow up interviews and e-mail correspondence, and drew on Mezirow’s transformative learning theory to explore the participants’ changing perspectives. It was found that various transformations did occur in the grantees’ perspectives as a result of their international experience. Suggestions are offered for future research. © The Editor(s) (if applicable) and The Author(s) 2017

PRESERVICE EFL TEACHERS' PERCEPTIONS AND THEIR REFLECTED EXPERIENCES IN A SERVICE-LEARNING COURSE

WOS: 000475723500013Service-learning is a teaching and learning strategy that integrates meaningful community service with instruction and reflection to enrich the learning experience, to teach civic responsibility, and to strengthen communities. This study describes Turkish preservice English as a Foreign Language (EFL) teachers' perceptions and their reflected experiences in a service-learning course which required student teachers to participate, in teams, in various community service activities and to reflect upon their experiences. The study employs a multiple-case study research design incorporating qualitative data from three sources: focus-group interviews, written reflections, and course projects. The three sets of service-learning projects produced by the teacher candidates focused on visiting the rest homes, teaching the disabled, and teaching English in a school. Qualitative analysis of data suggests that service-learning can be an effective pedagogical tool to help promote teacher candidates' empowerment, increase their awareness of community issues, as well as their confidence in meeting community needs. Suggestions are offered to give insights into service-learning programs in local and global contexts