Thermal-Boundary-Layer Response to Convected Far-Field Fluid Temperature Changes

Fluid flows of varying temperature occur in heat exchangers, nuclear reactors, nonsteady-flow devices, and combustion engines, among other applications with heat transfer processes that influence energy conversion efficiency. A general numerical method was developed with the capability to predict the transient laminar thermal-boundary-layer response for similar or nonsimilar flow and thermal behaviors. The method was tested for the step change in the far-field flow temperature of a two-dimensional semi-infinite flat plate with steady hydrodynamic boundary layer and constant wall temperature assumptions. Changes in the magnitude and sign of the fluid-wall temperature difference were considered, including flow with no initial temperature difference and built-up thermal boundary layer. The equations for momentum and energy were solved based on the Keller-box finite-difference method. The accuracy of the method was verified by comparing with related transient solutions, the steady-state solution, and by grid independence tests. The existence of a similarity solution is shown for a step change in the far-field temperature and is verified by the computed general solution. Transient heat transfer correlations are presented, which indicate that both magnitude and direction of heat transfer can be significantly different from predictions by quasisteady models commonly used. The deviation is greater and lasts longer for large Prandtl number fluids

Nemo phosphorylates Eyes absent and enhances output from the Eya-Sine oculis transcriptional complex during Drosophila retinal determination

AbstractThe retinal determination gene network comprises a collection of transcription factors that respond to multiple signaling inputs to direct Drosophila eye development. Previous genetic studies have shown that nemo (nmo), a gene encoding a proline-directed serine/threonine kinase, can promote retinal specification through interactions with the retinal determination gene network, although the molecular point of cross-talk was not defined. Here, we report that the Nemo kinase positively and directly regulates Eyes absent (Eya). Genetic assays show that Nmo catalytic activity enhances Eya-mediated ectopic eye formation and potentiates induction of the Eya-Sine oculis (So) transcriptional targets dachshund and lozenge. Biochemical analyses demonstrate that Nmo forms a complex with and phosphorylates Eya at two consensus mitogen-activated protein kinase (MAPK) phosphorylation sites. These same sites appear crucial for Nmo-mediated activation of Eya function in vivo. Thus, we propose that Nmo phosphorylation of Eya potentiates its transactivation function to enhance transcription of Eya-So target genes during eye specification and development

Archaeology at the Danube using non-invasive ground and aerial prospection methods to document prehistoric settlement traces at the Bisamberg near Vienna, Austria

To link prehistoric settlement activities with a modern mapping of existing monuments on the site, non-invasive aerial and terrestrial prospection methods are used. The LiDAR data catches the course of the presumed prehistoric rampart. The geomagnetic measurements display, among other things, the course of a 250 m long prehistoric ditch. Furthermore, ERT measurements reveal the rampart’s inner construction

The Cotoncello Shear Zone (Elba Island, Italy): The deep root of a fossil oceanic detachment fault in the Ligurian ophiolites

The ophiolite sequences in the western Elba Island are classically interpreted as a well-exposed ocean-floor section emplaced during the Apennines orogeny at the top of the tectonic nappe-stack. Stratigraphic, petrological and geochemical features indicate that these ophiolite sequences are remnants of slow-ultraslow spreading oceanic lithosphere analogous to the present-day Mid-Atlantic Ridge and Southwest Indian Ridge. Within the oceanward section of Tethyan lithosphere exposed in the Elba Island,we investigated for the first time a 10s of meters-thick structure, the Cotoncello Shear Zone (CSZ), that records high-temperature ductile deformation. We used a multidisciplinary approach to document the tectono-metamorphic evolution of the shear zone and its role during spreading of the western Tethys. In addition, we used zircon U–Pb ages to date formation of the gabbroic lower crust in this sector of the Apennines. Our results indicate that the CSZ rooted below the brittle–ductile transition at temperature above 800 °C. A high-temperature ductile fabric was overprinted by fabrics recorded during progressive exhumation up to shallower levers under temperature b500 °C.Wesuggest that the CSZ may represent the deep root of a detachment fault that accomplished exhumation of an ancient oceanic core complex (OCC) in between two stages of magmatic accretion.We suggest that the CSZ represents an excellent on-land example enabling to assess relationships between magmatism and deformation when extensional oceanic detachments are at work

Fluid rock interactions as recorded by Cl-rich amphiboles from continental and oceanic crust of Italian orogenic belts

A number of samples of Cl-rich amphiboles coming from oceanic and sub-continental gabbro bodies has been studied in order to compare their microstructural and compositional peculiarities and to investigate the fluid-rock interactions in different geodynamic contexts. The development of a first group of amphiboles outcropping in the Northern Apennines was the result of a hydration event that has been ascribed to oceanic metamorphism. The second group was found in a slice of continental crust subducted during Alpine collision, in a subcontinental metagabbro from the Sesia-Lanzo Zone of Italian Western Alps. Their development has been ascribed to a hydrothermal event that took place after the exhumation of the metagabbro during pre-Alpine lithospheric extension. The Cl-amphiboles are either found in veins, as granoblastic aggregates in different microstructures or as rims of zoned amphiboles, where brown-amphibole cores (sometimes Ti-rich), and successive green amphibole, are rimmed by the Cl-rich amphibole. All amphiboles show edembergite to pargasite compositions up to glaucophane and crossites when reequilibrated under HP conditions, with a direct correlation between Fe and Na(A) vs. Cl content, and inverse correlation of Mg and Na(M4) vs. Cl. A comparison with other Cl-amphiboles that have been observed both in oceanic and continental settings, allow discussing the role played by Clrich fluids infiltration both in oceanic and continental crust, during lithospheric extension. The large variations in Si, AlIV, AlVI, Fe, Mg, K and Cl may be related to the combination of different factors, such as Cl-content and related cristal-chemical constraints, whole rock composition, PT conditions of reequilibration, the microdomains where the amphibole grows and the variable aHCl/fluid/aH2O/fluid ratio of the fluid in equilibrium with the amphiboles at various stages of the metamorphic evolution. Amphiboles that locally contain extremely high Cl contents (up to 4% wt) could have been in equilibrium with a locally enriched Cl-fluid. As suggested by the fact that the Cl content of amphibole into the veins is generally lower than in amphibole rims far from the veins, these equilibrium conditions probably were reached at places where the system was locally closed. In addition, hydration reaction consumed the H2O component of the fluid, leading to a re-equilibration of the crystallising amphibole with the remaining Cl-enriched fluid. Equilibration temperatures up to 350 \ub0C can be attributed to the Northern Apennines amphiboles, and up to 550 \ub0C to the ones from the Sesia-Lanzo Zone

Flipped Learning in Computer Science for non-native English-speaking Students: Case Study

While flipped learning courses generally follow a basic concept (web-based technologies outside the classroom and instructor-student interaction during class time), the detailed design of the delivery builds on the instructor\u27s personal experience, knowledge, teaching philosophy and goals of the course. When designing such a course, it is very important to also take into consideration the teaching and learning environment and culture of the students. Flipped learning is not a fully grounded category in education literature; the area has been examined by a number of studies, but the methodology and its concept is not completely standardized [1, 2]. The flipped learning concept reached the Republic of Korea (RoK) over a decade ago as a result of challenges East Asian universities were facing: to enhance the quality of education, to keep up with international trends and to make education as cost-effective as possible [3]. Tham and Tham [4] reviewed blended learning practices in higher education across Asia and noted that while there are a number of challenges in delivering blended modules in general, in Korea, there was much interest and approval for such a format. As a new, and in Western countries highly praised, methodology, it requires careful consideration and examination. Keeping in mind that Korean education methodology and students\u27 school behavioural patterns are different from Western higher-education systems, this paper compares the recommendations made and features considered ideal by the literature, to the reality of a flipped learning course delivered in the RoK while acknowledging that there is no absolute recipe to a successful flipped learning course. It is also worth noting that this case study is also an intensive summery delivery of technical course material by a native English speaking lecturer to non-native English speaking students. The case study presented in this paper is the first flipped learning course examined in such a setting, with similar courses being developed for delivery in the near future. Therefore, lessons learned from this case study will help in designing and implementing courses in the future. Similarly, it is important to note that this case study pre-dates the Covid19 global pandemic (taking place in the Summer of 2019), meaning that social distancing and other related concerns were not relevant during delivery. However, knowing about the successes and challenges of such formats is of particular relevance to educators in more recent times, as we have become more reliant on blended/online teaching and learning. Based on our final findings presented in this case study it seems certain that the flipped learning methodology has a future in Korean higher education, as long as the course is designed for the specific setting: for example, emphasis should be put on student/teacher discourse in order to encourage naturally shy students to engage with the instructor, to increase constructive interaction throughout the course

Effect of Inclination of Twin Jets Impinging a Heated Wall

This study examines the interaction of twin oblique turbulent slot-jets of different directions (divergent, convergent or parallel) impinging a heated wall. A comparison of the results is done between the cases of perpendicular jets and three cases of twinned jets (parallel, convergent and divergent).The twin slot jets are located on a confining adiabatic wall at a distance of 8 slot jet width. Convective heat is investigated numerically examining the effect of Reynolds number (Re) and jet inclination angle (). This problem is relevant to a wide range of practical applications including nuclear engineering devices, manufacturing, material processing, electronic cooling, drying paper or textile, tempering of glass, etc. The numerical investigation is performed using two dimensional large eddy simulations (LES) approach with Smagorinsky sub-grid scale (SGS) models. The results show the presence of a complex flow resulting from the interaction of the two jets. When the impingement angle is reduced from 0° (perpendicular impingement) to 60°, the position of the stagnation points are modified and therefore the peaks of the Nusselt number locations on the impingement surface and their magnitude, vary. For largest Reynolds number Nusselt number is enhanced for all types of inclination. The averaged Nusselt number shows that the perpendicular impingement gives better heat transfer than that of the oblique jets. The poor heat transfer is obtained for the parallel oblique jets. For the same angle, divergent jets give smallest heat transfer than the convergent jets

Couplage conduction-convection en régime transitoire

Ce travail est réalisé dans le but de caractériser le transfert de chaleur couplé en régime transitoire à l'interface fluide-solide. Le problème étudié représente une plaque plane chauffée par un flux de chaleur variable dans le temps et refroidie par un écoulement d'air. Deux configurations sont étudiées : écoulement sur la même face que le chauffage et écoulement sur la face opposée. Une étude paramétrique a permis d'exprimer le coefficient d'échange en fonction du matériau de la plaque, de son épaisseur, de la vitesse d'air de refroidissement et de l'abscisse considérée