bluuebunny/crossref_metadata_2025 huggingface dataset:
A Critical Analysis of the Body of Work Method for Setting Cut-Scores
Authors: Radwan Nizam , Rogers W. Todd
Published: July 2024

The recent increase in the use of constructed-response items in educational assessment and the dissatisfaction with the nature of the decision that the judges must make using traditional standard-setting methods created a need to develop new and effective standard setting procedures for tests that include both multiple-choice and constructed-response items. The Body of Work (BoW) method is an examinee-centered method for setting cut-scores that applies a holistic approach to student work in order to estimate the cut-scores that differentiate examinees according to their level of performance in situations where both item formats are used. A detailed review of Version 1 and the recent modification, Version 2, are first presented followed by a critical evaluation of the two versions in terms of Berk’s (1986) 10 criteria for defensibility. The results reveal that the BoW method appears to be a promising method for setting cut-scores that could be used on a wider scale in Canada. However, as with other methods, the experience gained from using the BoW method in the field will probably lead to further modifications in an attempt to increase efficiency without sacrificing accuracy.
An Alternative Approach to Measuring Opportunity-to-Learn in High School Classes
Authors: Jaafar Sonia Ben
Published: July 2024

The Opportunity-to-Learn framework has provided policymakers and researchers a means to develop strategies to measure classroom practices. In particular, the measure of the delivered content has been shown to be a good predictor of student achievement on tests. The method presented in this article uses classroom artifacts as the main data source to determine the attention teachers give to various content in the curriculum. The number of treatments that address set learning outcomes was the unit of measurement employed in this method. The article illustrates how this method was used to describe content delivery and how content emphasis exposed the differences between two teachers following the same prescribed syllabus. This method is best applied at the secondary school level to measure one component of the delivered curriculum. Finally, the limitations and potential of this method are discussed for use in research and for school improvement.
Essential Elements in Teacher Education: Preservice Student Perspectives
Authors: Volante Louis
Published: July 2024

Using focus groups and individual interviews, student teachers’ perspectives on their program’s design and delivery were examined. Data analysis using constant comparison revealed a set of 10 essential elements for effective teacher education programs: diverse student bodies, effective program faculty, useful curricula and pedagogy, theory into practice orientation, program coherence, small class sizes, cohort class structure, supportive associate teachers, prolonged practicum experiences, and ongoing program review. The discussion underscores the value of studying student teachers’ perspectives, particularly when contemplating programmatic changes and reforms in teacher education.
A Game-Playing Approach to Interviewing Children About Loneliness: Negotiating Meaning, Distributing Power, and Establishing Trust
Authors: Kirova Anna
Published: July 2024

The new paradigm of studying childhood that has emerged in the past 15 years has significant implications for rethinking research with children. This article examines some methodological and ethical issues related to the role and responsibility of a researcher in the process of designing, structuring, and conducting research on childhood experiences and the role of children in such research. The main conceptual points are illustrated through examples from the process of developing and employing a game-playing approach to initiating conversations with young children about loneliness. Excerpts from a tape-recorded game-playing session with a 10-year-old child are used to illustrate how the approach facilitates negotiating meaning, distributing power, and establishing trust between the interviewer and the interviewee. The role of the game-playing approach as a research tool for involving children in the research process is examined.
Setting the Stage for a Narrative Inquiry: Negotiating Relationships and Understanding School Landscapes
Authors: Kitchen Julian D.
Published: July 2024

Narrative inquiry is a qualitative research approach that brings rigor and depth to the understanding of human experiences. It is important that the researcher become enmeshed in the school context in order to develop a heightened sense of the world view of participants. Critical to beginning a narrative inquiry are negotiating relationships and understanding the classroom and school landscape in which the inquiry takes place. Negotiating authentic relationships and understanding the school context set the stage for meaningful findings about teaching and learning in schools.
Mixed Methodology Research Design in Educational Technology
Authors: Kumar Muthu
Published: July 2024

In recent times many educational researchers have moved away from the traditional purist approach of strictly adopting either a qualitative or quantitative approach to conducting research. Instead they have attempted an eclectic mix of both methods in their research inquiry, combining aspects of both the traditions at various stages of their experimental study such as in the formulation of research questions/hypotheses, design of research methods, analysis of data, and discussion of research findings. Such integration harnesses the strengths of both traditions and underpins a methodologically sound research design. In this article the author recounts details of how a case study anchored to principles of mixed methodology research design was carried out.
Provincial Effects on Reading Achievement
Authors: Ma Xin , Crocker Robert
Published: July 2024

Although Canadian students performed well on the 2000 Programme for International Student Assessment (PISA), there were considerable differences among provinces. Based on the Canadian sample of PISA 2000, our multilevel analysis examined the extent to which schools in various provinces produced differential effects on the reading achievement of their students. School characteristics that showed significant provincial effects on reading achievement included variables that described school context, school resources, and school climate, with most of these significant school-level variables being measures of school climate. Disciplinary climate and sense of belonging to school were the most important of significant school characteristics. They showed significant average effects by province on reading achievement, and their effects varied significantly across provinces. Results of our analysis suggest that provinces can use school effects to promote the reading achievement of their students.
Policy Trends and Tensions in Accountability for Educational Management and Services in Canada
Authors: Jaafar Sonia Ben , Anderson Stephen
Published: July 2024

Accountability structures and processes have become such an integral part of education policy development and implementation that Ranson (2003) argues, “accountability is no longer merely an important instrument or component within the system, but constitutes the system itself” (p. 459). This argument is supported by the growth of an orientation in public education reforms toward the premise that more accountable schools are better schools. Canada fits the global trend that levers educational reforms through accountability measures.
Critical Analysis of Problems Encountered in Incorporating Indigenous Knowledge in Science Teaching by Primary School Teachers in Zimbabwe
Authors: Shizha Edward
Published: July 2024

In Zimbabwe the need to incorporate indigenous knowledge in science education to reflect local cultural settings cannot be overemphasized. Current policies on science are situated in Western cultural definitions, thus marginalizing indigenous knowledge, which is misconceived as irrational and illogical. This study used qualitative research methods. Ten teachers were purposively selected and interviewed to gain their insights into problems faced in incorporating indigenous knowledge into science teaching. The study found that the problems were attitudinal, institutional, and systemic. Teachers were found to be conservative “gatekeepers” who exhibited negative attitudes toward indigenous science and supported maintaining the teaching of Western science. The study suggests reforming and transforming science curriculum, policymaking, and teacher education to promote cross-cultural science in Zimbabwean primary schools.
Knowledge, Power, and Social Policy: John M. MacEachran and Alberta’s 1928 Sexual Sterilization Act
Authors: Puplampu Korbla P.
Published: July 2024

This article examines how academic knowledge and power have shaped the discourse on human classification and how political authorities use academic knowledge producers to legitimize public policy. Specifically, the article draws on the role of John M. MacEachran, a former academic at the University of Alberta, in the implementation of the Alberta 1928 Sexual Sterilization Act. The article argues that political authorities use academics and their knowledge in social policy when there is consistency with the interests of broader sociopolitical forces. Drawing on critical pedagogy, the selective use of academic knowledge-producers and the implications are discussed with reference to the relationship between educators and learners and university-society relations in general.
Voices from the Field: School Leadership in Special Education
Authors: Zaretsky Lindy , Moreau Louise , Faircloth Susan
Published: July 2024

This study focuses on four key issues: the perception of the role played by principals in Ontario in the administration and supervision of special education programs and services; the extent to which the construct of the principal as the instructional leader accurately depicts the role of the principal in schools with high concentrations of students with special needs; the knowledge and skills needed by principals for them to assume responsibility for the administration and supervision of special education programs and services in school contexts of diversity and difference; and the [re]structuring of leadership preparation programs to bridge the gap between current knowledge and leadership/classroom practice.
Hidden Losses: How Demographics Can Encourage Incorrect Assumptions about ESL High School Students’ Success
Authors: Toohey Kelleen , Derwing Tracey M.
Published: July 2024

Data from ESL students’ records in Vancouver are examined in the light of the BC Ministry of Education’s claim that ESL high school students are more successful than students whose first language is English. We argue that the academic achievement of well-to-do students whose parents are skilled workers or entrepreneurs may mask the completion rates of students who entered BC through the family and refugee classes. The latter students, like their counterparts throughout Canada, are disappearing through the cracks in the education system. We maintain that it is time for provincial ministries, school boards, postsecondary institutions, and other stakeholders to work together to improve the current situation, which prevents many immigrant youths from achieving their educational aspirations.
Success in Writing and Attributions of 16-Year-Old French-Speaking Students in Minority and Majority Environments
Authors: Bouchamma Yamina , Lapointe Claire
Published: July 2024

This article examines causal attributions of writing performance made by 16-year-old French-speaking Canadian students (N=3,874). The students are from the French-speaking majority province (Quebec) and minority provinces in Canada (Manitoba, Ontario, New Brunswick, and Nova Scotia). The data came from the School Achievement Indicators Program (SAIP) Writing Assessment III (Council of Ministers of Education, 2002). A total of 15 variables are related to causal attributions of failure and success in writing. The interaction between these variables and the type of environment (i.e., minority vs. majority French environments) indicated that French-speaking students in a minority environment did not perform as well as those from a majority linguistic environment because they did not study hard enough, the teacher marked too severely, they had bad luck, and the course was not well taught. When they were successful, it was because they studied hard at home and attributed their good marks to working hard enough, the teacher being lenient marking, and having good luck. The majority group attributed their good marks to the ease of the course and their bad marks to its difficulty.
Integrating Computer Technology in Early Childhood Education Environments: Issues Raised by Early Childhood Educators
Authors: Wood Eileen , Specht Jacqueline , Willoughby Teena , Mueller Julie
Published: July 2024

The purpose of this study was to assess the educators’ perspectives on the introduction of computer technology in the early childhood education environment. Fifty early childhood educators completed a survey and participated in focus groups. Parallels existed between the individually completed survey data and the focus group discussions. The qualitative data provided a richer understanding of the issues faced by these educators. Thematic analyses of the focus group discussions revealed that many of the educators’ concerns involved the effect of technology on the educators themselves, with secondary emphasis on how computers affected the students and parents. Although educators generally supported the integration of computers, they also identified critical concerns and limitations.
Constructing My Cultural Identity: A Reflection on the Contradictions, Dilemmas, and Reality
Authors: Neegan Erica
Published: July 2024

This article provides a critical reflective analysis of my life growing up in Jamaica where I attended colonial school, to making the transition to high school in the Canadian context. I examine the elements that have influenced my cultural/racial identity as a person of African ancestry living in the diaspora. I ask questions such as how has colonial education influenced my cultural identity and how I see myself? I address the complexity of my racial and gender identity drawing on a Black feminist theoretical framework and anticolonial thought to inform this work.
Alignment of Scores on Large-Scale Assessments and Report-Card Grades
Authors: Ross John A. , Gray Peter
Published: July 2024

We examined how much agreement there was between scores from large-scale mandated assessments and report-card grades for 14,776 students in grades 3, 6, and 9 of a district in which conditions were conducive to alignment of assessments. We found significant mean differences between internal and external assessments: effect sizes were .29 to .63 in grades 3-6 and .10 to.30 in grade 9. Spearman correlations were in the .32-.59 range. Chance-adjusted agreement was low. Report-card grades were consistently higher than external assessments for grades 3 and 6 students and consistently lower for grade 9 students.
The Role of Value in Eclectic Inquiry
Authors: Bevan Ryan
Published: July 2024

Educational theorists have shown increasing concern over the need to ensure that citizens exercise values that consider the relevance of contributing even contradictory perspectives. Nussbaum (2004) has concentrated specifically on the contribution that literature provides in developing the moral imagination, a concept that is linked to the idea of cosmopolitan citizenship. This article reevaluates this particular position by examining the foundational role that value plays in Schwab’s (2004) vision of eclectic inquiry. An initial value attachment to a perspective or theory is seen by incorporating examples from outside the context of curriculum deliberation as a catalyst that stimulates effective eclectic inquiry in the face of criticism or contradiction. Following the recent work of Egan (1997), I argue that these value attachments can be initiated in an educational setting not simply by integrating more art classes, but by determining and isolating the essence of a value attachment to a novel and applying this interactive framework to all areas of study. Stimulating value attachments thus serves as a precursor to eclectic inquiry and contributes more significantly to the development of the moral imagination.
Specialist or Nonspecialist Physical Education Teachers in Ontario Elementary Schools: Examining Differences in Opportunities for Physical Activity
Authors: Faulkner Guy E.J. , Dwyer John J.M. , Irving Hyacinth , Allison Kenneth R. , Adlaf Edward M. , Goodman Jack
Published: July 2024

Research supports the position that specialists are the preferred providers of physical education in elementary (primary) school settings. We examined whether specialists delivered more physical education lessons and provided greater opportunities for moderate and vigorous physical activity and whether barriers to curricular and extracurricular physical activity opportunities in Ontario elementary schools differed for specialist and nonspecialist teachers. Using a cross-sectional design, a questionnaire was mailed to key informants in 599 randomly selected elementary schools in Ontario, yielding an 85% response rate. Most physical education in Ontario elementary schools is delivered by nonspecialists (63%). No self-reported differences were found between specialists and generalist teachers in the number of physical education lessons delivered per week, the minutes per physical education class, or in the amount of reported moderate or vigorous physical activity in lessons. Compared with specialists, respondents in schools in which generalist teachers taught PE perceived lack of training as a greater barrier to delivering physical education. Given the importance of subject knowledge in teaching effectively, there is still need to advocate for specialist physical education teaching in elementary schools. However, concerns about teaching specialism may be secondary to broader and more complex factors surrounding the delivery of physical education in elementary schools.
Analysis Of The Asymmetry Factor In Photophoresis Problems With Uniform Polychromatic Fields And Spherical Absorbers
Authors: Ambrosio Leonardo André , Sarro Jhonas Olivati De , Gouesbet Gérard , Wang Jiajie
Published: July 2024

Photophoresis with plane waves and spherical absorbers is traditionally investigated by considering monochromatic radiation. The asymmetry factor, which is proportional to the photophoretic force, can be expressed in using the Mie theory in terms of an infinite sum of terms depending on the wavelength of the impinging light. Here, we analyze an extension of the photophoresis problem for a polychromatic uniform optical field. Such an analysis demands the introduction of a spectrum which describes the weight of each plane wave for the total, polychromatic field. We expect that this work can find applications or pave the way for more advanced investigations in diverse areas of physics and engineering such as optical levitation, optical trap displays and spectroscopy.
Two-Photon Planar Laser-Induced Fluorescence Of Near-Wall CO During The Interaction Between A Flame And A Cooling Air Film
Authors: Blaise Antoine , Godard Gilles , Vandel Alexis , Grisch Frédéric , Xavier Pradip
Published: July 2024

Reducing the anthropogenic pollutant emissions is a major concern in the aeronautical community. Implementing high-power density core engines made of lighter materials would undoubtedly increase the thermal efficiency and reduce CO 2 emissions. Nevertheless, near-wall combustion processes will become significant, raising concerns regarding thermal management. As a result, walls in aero-engine combustors are commonly cooled, but it also introduces more complex physical phenomena associated to pollutant formation during flame-cooling air interaction (FCAI). This experimental study aims at elucidating the role of the cooling air film on CO emissions during FCAI. The experiments are conducted in an atmospheric pressure and optically-accessible lab-scale combustion test rig dedicated to near-wall combustion. It generates a lean premixed turbulent methane/air V-shaped flame, with one branch of the flame that interacts with an oil-cooled stainless-steel wall. A splash-cooling plate system enables to generate a momentum-controlled parietal cooling air film. The novelty of this study is to develop and implement planar laser-induced fluorescence of the CO molecule (CO-PLIF), complemented by planar laser-induced fluorescence of the OH radical (OH-PLIF) as well as global CO emissions in the exhaust gases. Results show that the excitation of the Hopfield-Birge system enables to detect the AN ngström bands and the third positive system. However, significant interferences with C 2 and CN emissions are highlighted, being more pronounced in rich combustion conditions, and originating from the incomplete fuel oxidation as well as the high energy density of the two-photon excitation process. A broadband collection strategy of the AN ngström bands is selected, since these interferences are limited in lean combustion regimes. The analysis of the flame dynamics indicates that the increase of the cooling air film momentum shifts the reactive flow away from the wall, but also controls the flame wrinkling through modified aerodynamics. As a result, the flame is not influenced anymore by thermal quenching processes, and can effectively burn further away from the wall. Global emission measurements indicate an increase in CO when the cooling air film momentum increases. While thermal quenching favors a faster oxidation downstream of the flame, the establishment of the cooling air film leads to a longer flame with more production areas. CO-PLIF imaging concurs this phenomenon, with a CO distribution all along the wall when the cooling air film is well established.
Particle Image Velocimetry And Scaling Of Mach 0.3 And 1.25 Axisymmetric Turbulent Jets
Authors: Hinh Kenneth Yi-Nian , Martinuzzi Robert , Johansen Craig
Published: July 2024

The influence of compressibility on the scaling of the Reynolds stress transport (RST) budgets is investigated for Mach 0.3 and Mach 1.25 free axisymmetric turbulent jets using particle image velocimetry (PIV). It is proposed that the RST equations can be shown in self-preserving form scaled by the local streamwise evolving spreading rate, b’. It is shown that b’ is a function of the local convective Mach number, M_c. Compressibility effects on the suppression of the Reynolds stresses and higher turbulence moments are detailed. From self-preservation principles, the budgets scaled by powers of b’. In this form, most terms in the budgets are scaled appropriately indicating self-preservation. Terms which are not properly scaled are isolated then which allows for insight on effects of compressibility on turbulence.
Picosecond Imaging Of Bubbly Flows
Authors: Hunter Daniel Andrew , Bardet Philippe M.
Published: July 2024

Despite their ubiquity, bubbly flows are notoriously challenging to instrument. In high-void fractions, most optical measurement techniques fail due to intense scattering and occlusion. Ultrafast imaging with picosecond exposure times offers an opportunity, allowing measurements before scattering obscures the field of view. Furthermore, detecting the time of arrival of photons allows measurement of bubble sizes, even for those partially occluded. Through implementing the Optical Kerr Effect (OKE), using a 70 fs 800 nm pulsed laser and a Carbon Disulfide cell, images are acquired with an exposure of 2.9 ps. Gating these images with an optical delay stage further allows the decomposition of scenes with 33 fs time increments. Proof of concept is demonstrated by applying this approach to static scenes of submerged bubbles at low and high void fractions. The experimental temporal decomposition shows the arrival of photons that travel through different media (air, water, and glass) and those scattered within the turbid media. A new visualization is presented to display this breakdown concisely, the Temporally Tagged Shadowgraph (TTS), presenting the time of arrival with the context of position and surroundings. Bubble sizes are measured using this temporal information and through edge detection, with good agreement for single unoccluded bubbles. With polydisperse bubble plumes, time delay-based measurements tend to overestimate bubble diameter; however, this could also be due to greater uncertainty in edge detection with occlusion. This demonstrates the potential of Ultrafast Imaging when it comes to probing high-void fraction flows. By further shortening exposure times and improving the robustness of processing algorithms, the scope of applicability of this technique can be widened.
Experimental Study On Bubble Pairs And Induced Flow Fields Using Tomographic Particle Image Velocimetry
Authors: Wang HanBin , Xu Yang , Wang Jinjun
Published: July 2024

Gas-liquid two-phase flows, such as bubbly flows, are widely used across various engineering and military applications due to their distinctive fluid dynamics. This study utilizes advanced imaging techniques, including shadowgraphy and laser-induced fluorescence tomographic particle image velocimetry (LIF-TPIV), to provide a quantitative analysis of bubble motions and the resulting flow fields. We systematically investigate the effects of orifice distances (s) set at 10, 15, 20, and 25 mm to assess the impact of spacing on bubble behavior and interactions. Our findings indicate that at orifice distances of 20 mm or less, the proximity of bubbles facilitates interactions, promoting dynamic bubble behaviors. In contrast, at distances greater than 25 mm, interactions become markedly weaker, leading to increased separation between bubbles during their free oscillation stages. This weak interaction directly influences the characteristics of bubble-induced flow fields. As orifice spacing increases, there is a noticeable decrease in the velocity of the flow field between bubbles, particularly noticeable at spacings of 20 mm and above. At these larger spacings, a low-velocity zone develops between the bubbles at higher heights, which, according to Bernoulli's principle, corresponds to a high-pressure area. This high pressure contributes to a reduction in bubble volume with increasing orifice spacing. Furthermore, the intensity of wake vortices between two bubbles is observed to be highest at the smallest spacing of 10 mm, closely resembling the flow structure characteristic of a single rising bubble. For spacings of 15 and 20 mm, the induced flow fields of the bubbles continue to interact significantly. However, at a spacing of 25 mm, the flow fields appear to function independently, suggesting a threshold beyond which bubble interactions stop to significantly affect their surrounding fluid environments. These findings are helpful for comprehending the two-phase flow dynamics, particularly in multi-orifices bubbly flow.
Three-Dimensional Measurements Of Deformable Oil Droplets In Turbulence
Authors: Beckedorff Leonel Edward , Caridi Giuseppe Carlo Alp , Soldati Alfredo
Published: July 2024

This work introduces an experimental facility designed to generate turbulence with a high energy dissipation rate of up to 0.3 m^2/s^3 , sufficient to induce deformation and fragmentation of oil droplets. The turbulence is produced by opposing arrays consisting of 24 jet streams in total, each with Reynolds numbers ranging from 12,000 to 50,000. Flow regimes are determined using 3D Particle Tracking Velocimetry (PTV) conducted in the center of the octagonal test section. The statistical analysis of the turbulence reveals a nearly homogeneous and isotropic nature. A 3D imaging system, equipped with six high-speed cameras, allows for the reconstruction of droplets using the multiple algebraic reconstruction technique algorithm, fostering both visualization and quantification of interface deformation. Additionally, the system enables the tracking of the breakup process. The presented setup is able to couple the measurements of the droplet shapes with surrounding turbulence in 3D dproplet topology reconstruction coupled with surrounding flow measurements. We demonstrate the capability of our imaging system and reconstruction methods for multiphase flow studies with an example of full 3D droplet topology reconstruction coupled with surrounding flow measurements.
Multiple-Exposure PTV With Variable Time Steps
Authors: Scarano Fulvio , Hysa Ilda , Guerra Adrian Grille , Tuinstra Marthijn , Sciacchitano Andrea
Published: July 2024

Recording multiple exposures of the tracer particles onto a single digital image has the potential to simplify the hardware needed for 3D PTV measurements. A sequence with equal time intervals leads to the well-known directional ambiguity problem. Instead, a sequence with irregular time-intervals (two or more) allows resolving the ambiguity. Two fundamental criteria are introduced that determine whether a set of particle samples corresponds to a physical trace for a given neighborhood: the kinematic similarity criterion imposes similarity (i.e. proportionality) between the length travelled by the particle and time elapsed. Additionally, the trace regularity criterion favors sets with minimum fluctuations of the velocity vector. A numerical algorithm, based on combinatorial analysis is presented, whereby all possible sets are scrutinized and the set of particles yielding the minimum disparity from the above criteria corresponds to the physical trace. The algorithm is demonstrated using 3D experimental data and results are benchmarked against the state-of-the-art time-resolved analysis Shakethe-Box (single-frame, single-exposure).
Microfiber Rotational Dynamics In Turbulence
Authors: Giurgiu Vlad , Caridi Giuseppe Carlo Alp , Paoli Marco De , Soldati Alfredo
Published: July 2024

We measure the effect of turbulence on spinning and tumbling rates of microfibers in wall-bounded turbulence. The measurements are performed in a turbulent water channel at Reτ 720. Fibres are 1.2 mm long and 10 m in diameter (aspect ratio 120). Their length ranges from 4 to 12 Kolmogorov length scales. They are neutrally buoyant, inertial-less, and rigid in these flow conditions. Six high-speed cameras image the fibres at the channel centre and in a near-wall region. We employ and further refine a technique of tomographic fibre reconstruction and tracking. Their curved shape is used to define a fibre-fixed reference frame and measure its time-resolved orientation. Thus measurements of tumbling and spinning rates are enabled. We provide a discussion about the uncertainty on the rotation rates based on their shape and angular displacement between time-steps. Based on converged statistics, we observed that the mean and mean square spinning are higher than tumbling rates at both channel centre and near-wall region. In addition, our study reveals that slender, curved fibres behave akin to straight rods, yet their curved shape provides a unique advantage: this curvature allows us to measure all rotational components.
Unbalanced Optimal Transport For Stochastic Particle Tracking
Authors: Hao Kairui , Hans Atharva , Vlachos Pavlos , Bilionis Ilias
Published: July 2024

Non-invasive ﬂow measurement techniques, such as particle tracking velocimetry, resolve 3D velocity ﬁelds by pairing tracer particle positions in successive time steps. These trajectories are crucial for evaluating physical quantities like vorticity, shear stress, pressure, and coherent structures. Traditional approaches deterministically reconstruct particle positions and extract particle tracks using tracking algorithms. However, reliable track estimation is challenging due to measurement noise caused by high particle density, particle image overlap, and falsely reconstructed 3D particle positions. To overcome this challenge, probabilistic approaches quantify the epistemic uncertainty in particle positions, typically using a Gaussian probability distribution. However, the standard deterministic tracking algorithms relying on nearest-neighbor search do not directly extend to the probabilistic setting. Moreover, such algorithms do not necessarily ﬁnd globally consistent solutions robust to reconstruction errors. This paper aims to develop a globally consistent nearest-neighborhood algorithm that robustly extracts stochastic particle tracks from the reconstructed Gaussian particle distributions in all frames. Our tracking algorithm relies on the unbalanced optimal transport theory in the metric space of Gaussian measures. Speciﬁcally, we optimize a binary transport plan for efﬁciently moving the Gaussian distributions of reconstructed particle positions between time frames. We achieve this by computing the partial Wasserstein distance in the metric space of Gaussian measures. Our tracking algorithm is robust to position reconstruction errors since it automatically detects the number of particles that should be matched through hyperparameter optimization. Notably, our tracking algorithm also readily applies to the standard deterministic PTV case. Finally, we validate our method using an in vitro ﬂow experiment using a 3D-printed cerebral aneurysm.
Erosion Characterization Of Gas-Solid Jets Impinging Onto Inclined Surfaces
Authors: Loureiro Juliana Braga Rodrigues , Freire Atila Pantaleão Silva
Published: July 2024

Erosion caused by solid particles is an important phenomenon in many industrial applications.  Wear modelling is a complex phenomenon due to the many relevant variables. In any event, the dynamics of the fluid flow and particles need to be characterized so that their interrelations are well understood and models can be advanced. Depending on their sizes, particles immersed in solid-gas flows may deviate from the fluid stream, meaning that any deployed measuring technique must take this into account. The work describes through PIV and PTV the flow and particle dynamics of a round air-jet loaded with carbon silicate particles (SiO2) impinging onto an inclined surface. Flow conditions are set for two different Reynolds numbers and four impinging angles. The experimental results are compared with numerical simulations furnished by a two-way coupling scheme. The results show that erosion wear is highly dependent on the kinetic energy of the particle at impact. The larger the size of the particle or the larger its velocity, the larger is the damage it causes. A correlation between the thickness of removed material with particle size distribution and flow rate is presented. For low flow rates, the distinction between the damage caused by particles of various sizes is small.
Turbulent Thermal Convection At A Rough Surface
Authors: Puits Ronald Du
Published: July 2024

We present measurements of the near-wall velocity field in highly turbulent Rayleigh-Bénard(RB) convection with rough horizontal surfaces. The measurements have been undertaken in a large-scale RB experiment which is called "Barrel of Ilmenau". We used the technique of stereoscopic Particle Image Velocimetry to measure the three components of the velocity field in horizontal planes parallel to the heated bottom plate. The measurements reported here comprise two Rayleigh numbers Ra=8.6×10^{10} and Ra=6.3×10^{11}. The Prandtl number of the working fluid was Pr=0.7. We used a chess board-like pattern of cuboids with a base area of 30 mm by 30 mm and a height of h=12 mm. Our measurements confirm the observation from previous experiments that the relation Nu=f(Ra) remains unchanged with respect to RB convection with smooth surfaces as long as the thickness of the thermal boundary layer \delta_{th}=H/(2Nu) exceeds the height of the roughness elements h. If \delta_{th} falls below h, Nu becomes larger and grows faster with increasing Ra then it does in RB convection with smooth plates. We also could identify the valleys in between the cuboids as the main contribution for the increase of Nu
Near-Wall Flow Measurements Using Frequency-Modulating Filtered Rayleigh Scattering (FM-FRS)
Authors: Byun Gwibo , Lowe K. Todd , Ellery Michael , Sole Joshua
Published: July 2024

The frequency-modulating filtered Rayleigh scattering (FM-FRS) technique has been developed and applied for the boundary layer measurements. The FM-FRS technique effectively extracts Rayleigh scattering information from noisy low SNR signals caused by intense wall glare. The boundary layer velocity profiles measured by FM-FRS show excellent agreement with an independent pressure probe measurement and the law-of-the-wall, including approximately 100 μ m above the wall. This technique is desirable for the practical applications of the Rayleigh scattering technique for flow diagnostics to regions that were limited due to strong background and low signal-to-noise ratio.
Three-Dimensional Visualization Of The Behavior Of Solid Particles Traveling In A Horizontal Gas Pipe Flow By Color PTV Using Discontinuously Changing Hue Illumination
Authors: Park Hyun Jin , Murai Yuichi
Published: July 2024

In a gas pipe, a lot of solid particles remained during its construction. They are called dust and gas supply companies have tried to remove them using filters because they cause various problems. To optimize the maintenance period of dust removal filters, it is required to understand the behaviors of particles in the pipe. However, we do not fully understand yet because of their very complex behaviors caused by dune accumulated in the pipe. Furthermore, it is hard to investigate their behaviors with a traditional volumetric PTV using multiple cameras. Normally, its calibration is difficult because of the curvature of the pipe and the plural number of cameras. Therefore, we developed a new volumetric color PTV algorithm with discontinuously changing color illumination in the camera shooting direction, i.e. the depth direction. Color PTV can determine particle positions in three dimensions using a single camera but has low depth accuracy. Our new PTV measures particle positions and velocity vectors in the plane of picture using the same algorithm used in the normal planar PTV. On the other hand, particle positions and velocity vectors in the camera shooting direction are measured by a pattern of color changing on particle scattering light, which is our original method. To adopt the new volumetric PTV in the pipe flow, a volumetric light changing color discontinuously in the flow direction was irradiated and the particles were visualized using a camera installed at the outlet of the pipe. When a dune exists, the particles are thrown to the top of the pipe and their advection velocity is increased by the wakes generated by the dune. As a result, the dune makes more particles to be advected to a longer distance.
Physics Of Two-Stage Evaporation Of Volatile Droplets Suspended In An Ultrasonic Levitator
Authors: Wang Tianyi , Hardalupas Yannis
Published: July 2024

The evaporation process of mono-component droplets in an ultrasonic levitator is experimentally monitored, focusing on three types of volatile liquids: methanol, ethanol, and 2-propanol. This investigation reveals a ‘two-stage’ evaporation process characterized by an initial rapid evaporation stage followed by a significantly slower evaporation stage; a pattern consistently observed across all three volatile liquids. However, for droplets of comparable size, methanol droplets evaporate faster in the rapid stage than ethanol and iso-propanol droplets and enter the slow evaporation stage earlier. On the other hand, during the slow evaporation stage, 2-propanol droplets exhibit the lowest evaporation rate compared to methanol and ethanol droplets. To explain the two-stage evaporation and the varying evaporation characteristics of mono-component droplets with different volatile components, the streaming patterns within the levitator, with and without a suspended droplet, are visualized and quantified using Particle Imaging Velocimetry (PIV). Two acoustic-induced jet flows, originating from the transducer and reflector of the levitator and considered as Eckart streaming, are observed within the empty levitator. These jet flows move toward the levitated droplet, influencing its evaporation process. Additionally, Stefan flow, carrying vapor away from the surface of the volatile droplet, is clearly observed due to rapid evaporation. The competition between Stefan flow and Eckart streaming ultimately determines the external streaming patterns around the investigated droplets. A theory combining the external streaming patterns and vapor enrichment is proposed to interpret the two-stage evaporation and the corresponding characteristics of the evaporating droplets suspended in the levitator. Furthermore, this study captures boundary-driven acoustic streaming near the droplet surface, known as Rayleigh–Schlichting streaming, whose dimensions and motion vary with the different liquid components and the properties of the corresponding vapor. In summary, the study highlights the presence of Eckart streaming in the ultrasonic levitator and Stefan flow outside an evaporating volatile droplet. Considering these flow patterns is essential for explaining the ‘two-stage’ evaporation and the relevant characteristics within the ultrasonic levitator.
An In-Vitro Study On The Carotid Bifurcation And Its Influence On Arterial Haemodynamics With Newtonian And Non-Newtonian Blood Analogs
Authors: Lowe Joshua Andrew , Barton Eleanor , Leslie Laura J , Souppez Jean-Baptiste R. G , Fratini Antonio , Ho Wei Hua , Yazdi Sina G , Geoghegan Patrick
Published: July 2024

The carotid artery bifurcation is a region susceptible to atherosclerosis and cardiovascular diseases. The geometry of the bifurcation is individually unique and significant differences have been correlated to both age and gender. Identifying geometric features that produce adverse flow patterns could enable clinicians to make early assessment of an individual’s risk of developing the disease enabling proactive management. Consequently, this study aims to evaluate the influence of the carotid bifurcation angle on arterial haemodynamics using stereoscopic particle image velocimetry. Pulsatile flow conditions were applied to a Newtonian and non-Newtonian blood analog in three compliant, physiologically realistic carotid artery bifurcation phantoms with different bifurcation angles. Results indicate large bifurcation angles can produce adverse flow conditions, increasing size of stagnation regions and promoting plaque development. Additionally, an optimal bifurcation angle could exist that could be considered atheroprotective. Comparison of Newtonian and non-Newtonian blood analogs in one of the geometries show subtle yet significant differences between flow fields, suggesting the shear-thinning behaviour of blood should be carefully considered prior to adopting a Newtonian assumption, even in large vessels.
Turbulence Analysis From Long-Exposure-Time Acquisitions With Interferometric Rayleigh Scattering
Authors: Castelain Thomas , Kurek Igor , Lecomte Pierre , Bailly Christophe
Published: July 2024

This study focuses on the analysis of long-exposure-time interferograms obtained with an Interferometric Rayleigh Scattering (IRS) set-up pointing at a high subsonic isothermal jet ﬂow. The objectives are twofold: retrieve from seeding-free optical measurements the mean characteristics of this ﬂow - in particular the mean velocity proﬁle in the jet shear-layer - and determine higher order statistics for the ﬂow velocity in the shear layer. The results are compared to those obtained on the same test bench by use of hot wire anemometry, and conclusions about the relevancy of the approach together with potential improvements are deduced therefrom.
A Software Tool For Automated Analysis And Characterization Of Raw PIV Images
Authors: Bessa Guilherme M. , Saffar Yeganeh , Sabbagh Reza , Nobes David S.
Published: July 2024

The time to process large PIV data sets can be expensive and the resultant velocity fields are a strong function of the quality of the particle images used. For new and even experienced users of PIV, determination of the quality of a particle image data set can be challenging and time consuming especially for a large number of data sets. This is compounded with new high-speed camera systems that are capable of collecting terabytes of data quickly. A software tool is described here that allows the user to make informed decisions on the general quality of the data sets and what pre-processing image data steps are needed. The software provides statistical feedback on such parameters as particle count, particle size, particle intensity for not only a single image but also a complete data set. Using this software allows the user to make informed decisions and generate and document the quality of the data collected. Based on this, a robust PIV processing algorithm can be developed.
NGHIÊN CỨU GIÁ TRỊ CỦA CHUỖI XUNG TƯỚI MÁU VÀ CHUỖI XUNG PHỔ TRÊN CỘNG HƯỞNG TỪ 3 TESLA CHẨN ĐOÁN PHÂN BẬC U THẦN KINH ĐỆM
Authors: Ngô Đức Yên , Vũ Đăng Lưu , Đàm Thủy Trang , Nguyễn Công Tiến
Published: July 2024

Mục tiêu: Đánh giá giá trị của chuỗi xung phổ và chuỗi xung tưới máu trên máy cộng hưởng từ (CHT) 3 Tesla (T) trong chẩn đoán phân bậc u thần kinh đệm (UTKĐ).
Phương pháp: Bệnh nhân được chụp chuỗi xung phổ và tưới máu trên máy 3T với tiêu chuẩn vàng là giải phẫu bệnh. Dùng phần mềm tính toán các giá trị Ktrans, Ve, Cho/NAA, Cho/Cre. Sử dụng đường cong ROC để so sánh các thông số tưới máu và phổ để phân biệt UTKĐ bậc cao và UTKĐ bậc thấp.
Kết quả: Có 15 bệnh nhân UTKĐ, trong đó có 10 bệnh nhân UTKĐ bậc cao, 5 bệnh nhân UTKĐ bậc thấp. Có sự khác biệt có ý nghĩa thống kê của các thông số tưới máu (Ktrans, Ve) và phổ (Cho/NAA, Cho/Cre) trong phân bậc UTKĐ. Trong đó, Ktrans có giá trị cao nhất để phân bậc u thần kinh đệm (AUC 0.956).
Kết luận: Giá trị Ktrans, Ve của chuỗi xung tưới máu có khả năng phân biệt UTKĐ bậc cao và UTKĐ bậc thấp.