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A banked wide-angle diffuser with application to electrostatic precipitators
Barratt, Dylan,Kim, Tongbeum SAGE Publications 2015 Proceedings of the Institution of Mechanical Engin Vol.229 No.1
<P>This article introduces a simple and robust method of achieving low-velocity, uniform flow in a wide-angle diffuser upstream of an electrostatic precipitator used to control particulate emissions. A diffuser is inherently vulnerable to boundary layer separation, which greatly deteriorates flow uniformity, adversely affecting electrostatic precipitator performance. Conventionally, two different approaches are used to prevent separation in a diffuser: either reduce the adverse pressure gradient inside the diffuser or increase near-wall fluid momentum to overcome the existing adverse pressure gradient. The present alternative simultaneously incorporates both approaches through the use of an ultra-high porosity cylinder bank and outperforms the predominant technology in terms of flow uniformity.</P>
Barratt, Dylan,Lee, Jaehyoung,Atkins, Michael D.,Song, Seung Jin,Kim, Tongbeum Elsevier 2018 Experimental thermal and fluid science Vol.99 No.-
<P><B>Abstract</B></P> <P>We experimentally examine the impingement of a fully turbulent round jet (with diameter <I>D<SUB>j</SUB> </I>) on a long circular cylinder (with diameter <I>D</I>) in the crossflow plane coinciding with the jet axis for <I>D</I>/<I>D<SUB>j</SUB> </I> = 2.5 and <I>Re<SUB>Dj</SUB> </I> = 20,000. Particular focus is placed on the kinematics of boundary layer transition that occurs and subsequently leads to a second thermal peak on the cylinder surface downstream of the primary thermal peak near the stagnation point when placed inside the jet’s potential core. To this end, spectral analyses of wall shear stress data and time-resolved velocity data within both laminar and turbulent boundary layers have been performed. The present study demonstrates that the root mean square (rms) fluctuation of the stream-wise velocity component increases along both boundary layers due to the propagation of external perturbations from coherent structures that are shed from the jet exit, which incites the transition of the laminar boundary layer. The transition causes the local heat transfer elevation that interrupts the monotonic decrease from the primary thermal peak whereas it plays no direct part in forming the second thermal peak. Instead, the second thermal peak occurs at a delayed downstream azimuth angle from the transition where the rms velocity fluctuations of the boundary layer flow reach their peak at the dominant frequency, equivalent to that of the coherent structures of the jet.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The propagation of perturbations from the jet incites the transition. </LI> <LI> The rms fluctuation of the boundary layer flow increases. </LI> <LI> The transition plays no direct part in forming the second thermal peak. </LI> <LI> The second thermal peak occurs at a delayed downstream azimuth angle from the transition. </LI> <LI> The rms fluctuation of the boundary layer flow reaches a peak causing the second thermal peak. </LI> </UL> </P>
D. Barratt,M. Atkins,A. Juggernarth,T. Kim,S.J. Song 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
In cooling circular components, it is often questioned whether uniform flow or localized flow, e.g., an impinging jet, is more effective. In terms of average cooling performance, the former seems to be an intuitive choice but in terms of coolant consumption, the latter appears to be more attractive. The present study systematically tackles this issue by directly comparing the two specific flow configurations in a crossflow plane at a fixed Reynolds number. Based on detailed local heat transfer mechanisms and the average heat transfer associated with each configuration, some suggestions are provided, which are limited to the two-dimensional analysis.
Puji Astuti,Leslie Barratt 아시아테플 2018 The Journal of Asia TEFL Vol.15 No.1
Research shows that cooperative learning (CL) supports foreign language learning (e.g., Almuslimi, 2016; Wei & Tang, 2015). However, there is little research demonstrating how CL works and, specifically, how it promotes learning, particularly individual accountability, which is a principle in CL. This article reports on part of a larger study that aimed to fill this gap by exploring the roles of individual accountability in CL in enhancing EFL learning. The study involved two secondary school EFL teachers, with 77 students in their classrooms, and four focus students. Analysis of data from participant observations, in-depth interviews, and document analysis shows that individual accountability manifests itself in a series of activities from individual, group, and class presentations as well as other peer interactions. The findings also showed that the learners had more opportunities to interact and had more interactions with their peers during CL than during conventional group work (i.e., students simply completing non-CL activities in groups). Opportunities for student-student interactions in CL activities, absent in the conventional group work, may have contributed to the EFL learners’ communicative competence. However, teachers new to CL should follow the preset procedures for CL strategies to promote individual accountability and understand how these activities benefit students.
Nicholas Sevey,Michelle Barratt,Emma Omoruyi 한국보건의료인국가시험원 2020 보건의료교육평가 Vol.17 No.-
Purpose: According to the entrustable professional activities (EPA) for entering residency by the Association of American MedicalColleges, incoming residents are expected to independently obtain informed consent for procedures they are likely to perform. This requires residents to not only inform their patients but to ensure comprehension of that information. We assessed the communicationskills demonstrated by 372 incoming pediatric interns between 2007 and 2018 at the University of Texas Health Science Center atHouston, obtaining informed consent for a lumbar puncture. Methods: During a simulated case in which interns were tasked with obtaining informed consent for a lumbar puncture, a standardizedpatient evaluated interns by rating 7 communication-based survey items using 5-point Likert scale from “poor” to “excellent.” We thenconverted the scale to a numerical system and calculated intern proficiency scores (sum of ratings for each resident) and average itemperformance (average item rating across all interns). Results: Interns received an average rating of 21.6 per 28 maximum score, of which 227 interns (61.0%) achieved proficiency by scoring 21 or better. Notable differences were observed when comparing groups before and after EPA implementation (76.97% vs. 47.0%proficient, respectively). Item-level analysis showed that interns struggled most to conduct the encounter in a warm and friendly manner and encourage patients to ask questions (average ratings of 2.97/4 and 2.98/4, respectively). Interns excelled at treating the patientwith respect and actively listening to questions (average ratings of 3.16, each). Both average intern proficiency scores and each averageitem ratings were significantly lower following EPA implementation (P<0.001). Conclusion: Interns demonstrated moderate proficiency in communicating informed consent, though clear opportunities for improvement exist such as demonstrating warmth and encouraging questions.
Oxide Cathodes for Reliable Electron Sources
Weon, Byung-Mook,Je, Jung-Ho,Park, Gong-Seog,Koh, Nam-Je,Barratt, David S.,Saito, Tsunenari The Korean Infomation Display Society 2005 Journal of information display Vol.6 No.4
In this paper, we investigate the oxide cathodes for the development of reliable electron sources. Poisoning in oxide cathodes is one of the serious problems in achieving reliable electron emission. In particular, early poisoning induces poor life performance as will be demonstrated herein. The survivability of electron emission sources is significantly improved by high doping of high-speed activator. The robust oxide cathodes with 0.17 % Mg operating at about 1,050 K are expected to work for very long times (>100,000 hours). We suggest that this key idea will contribute to solving the basic problems in oxide cathodes such as poisoning or ion bombardment for high power or high frequency applications of electron sources.