An experimental study of wall-injected flows in a rectangular cylinder

An experimental investigation of the flow inside a rectangular cylinder with air injected continuously along the wall is performed. This kind of flow is a two-dimensional approximation of what happens inside a solid rocket motor, where the lateral grain burns expelling exhaust gas or in processes with air filtration or devices to attain uniform flows. We propose a brief derivation of some analytical solutions and a comparison between these solutions and experimental data, which are obtained using the Particle Image Velocimetry (PIV) technique, in order to provide a global reconstruction of the flowfield. The flow, which enters orthogonal to the injecting wall, turns suddenly its direction being pushed towards the exit of the chamber. Under the incompressible and inviscid flow hypothesis, two analytical solutions are reported and compared. The first one, known as Hart-McClure solution, is irrotational and the injection velocity is non-perpendicular to the injecting wall. The other one, due to Taylor and Culick, has non-zero vorticity and constant, vertical injection velocity. The comparison with laminar solutions is useful to assess whether transition to turbulence is reached and how the disturbance thrown in by the porous injection influences and modifies those solutions

Scalar field dark energy and Cosmic Microwave Background

A dynamical scalar field represents the simplest generalization of a pure Cosmological Constant as a candidate to explain the recent evidence in favour of the accelerated cosmic expansion. We review the dynamical properties of such a component, and argue that, even if the background expectation value of this field is fixed and the equation of state is the same as a Cosmological Constant, scalar field fluctuations can still be used to distinguish the two components. We compare predicted spectra of Cosmic Microvave Background (CMB) anisotropies in tracking scalar field cosmologies with the present CMB data, in order to get constraints on the amount and equation of state of dark energy. High precision experiments like SNAP, {\sc Planck} and {\sc SNfactory}, together with the data on Large Scale Structure, are needed to probe this issue with the necessary accuracy. Here we show the intriguing result that, with a strong prior on the value of the Hubble constant today, the assumption of a flat universe, and consistency relations between amplitude and spectral index of primordial gravitational waves, the present CMB data at $1\sigma$ give indication of a dark energy equation of state larger than -1, while the ordinary Cosmological Constant is recovered at $2\sigma$.Comment: 4 pages including 2 figures, Dark Matter 2002 proceedings, Nucl.Phys.B in pres

Heavy particles in the near field of a turbulent jet

The behaviour of aluminium spherical particles of density ρp=2700 Kg/m3 dispersed in a turbulent round water jet, at Reynolds number Re≈15000 and exit Stokes number St0=0.013 is investigated via Particle Image Velocimetry up to x/D=16 from the nozzle exit. Average and fluctuating velocity fields are analysed and compared to the unladen jet condition. Generally, particles are reported not to behave like tracers, in particular outside the region of the jet potential core. Velocity fluctuations are reported to differ from the fluid fluctuations in particular at the jet centreline and shear layers. In particular, axial velocity fluctuations appear to be dominated by the fluid phase whereas a tendency towards an increase of radial fluctuations downstream of the jet exit is reported for particles. The complexity of this scenario suggests a selective particle response with respect to the flow dynamics

“I Hate History”: A Study of Student Engagement in Community College Undergraduate History Courses

Many instructors seek to improve student engagement, but determining how to achieve student engagement can be complex and complicated. The authors sought to explore how the implementation of active-learning strategies in undergraduate history courses at a metropolitan community college using graphic organizers and group discussion impacted student engagement. Surveys were distributed to students in five undergraduate history courses in order to elicit student perspectives on how active-learning strategies improved student engagement. The survey data revealed that some active-learning strategies improved student engagement, whereas others did not. The authors report that a combination of implementing lecture and active-learning strategies was effective in fostering student engagement in their undergraduate history courses

More than a feeling: Tracing the progressive era origins of historical empathy in the social studies curriculum, 1890–1940s

Understanding historical empathy is a bourgeoning subfield of social studies education research. Students demonstrate historical empathy by analyzing sources 1) to determine historical context, 2) identify perspectives of historical figures, and 3) make affective connections to historical content. Therefore, the purpose of this research is to examine primary sources from educational leaders and organizations during the Progressive Era in American public school education in order to trace the origins of historical empathy as an implicit goal in the social studies curriculum. Our guiding research question is “How does the work of Progressive Era organizations and educational leaders impact how Americans viewed historical empathy?” We purposefully selected documents from Progressive Era organizations and certain leaders whose work formed a strong foundation of social studies education history. We conclude with an examination of the importance of historical empathy today in order to demonstrate the importance of historical empathy as a curricular aim of social studies education

A Reflective Study of Online Faculty Teaching Experiences in Higher Education

Despite the popularity of online course and degree offerings in higher education, a lack of data persists on the unique challenges and opportunities online faculty face. Gaining insights about these experiences is important to ensure the quality of online teaching as colleges and universities continue expanding e-learning programs. Therefore, the purpose of this study is to examine the online teaching experiences of two faculty members through the implementation of reflective study methods. Major findings show that faculty access to professional development and mentoring, isolation and connectedness to the campus community, and academic freedom and curriculum control have significant implications for online teaching and student learning. In the wake of COVID-19 as colleges across the nation suddenly are faced with moving to exclusively online learning, this study is needed more than ever

Nineteenth Century Rosa Parks? Assessing Elizabeth Jennings\u27 Legacy as a Teacher and Civil Rights Pioneer in Antebellum America

Elizabeth Jennings should be recognized as more than a Rosa Parks figure in Antebellum New York City history. Both Jennings\u27 and Parks\u27 experiences with segregation on public transportation are similar, but they are not the same. Jennings\u27 ejection from a New York streetcar was not deliberately planned, nor did her removal from the streetcar lead to mass protests or boycotts in New York City or throughout the country. Similarly though, as many African Americans endured violence during the Civil Rights movement of the 1950s and 1960s, Elizabeth Jennings also survived the New York City Draft Riots in 1863. Overall, both women deserve their own respective place in United States history because they were emblematic of the socio-political issues of their time - Jennings in the Antebellum Era and Parks in the post-World War II civil rights movement