76 research outputs found
Flow Characterization over Biomimetic Fish Scale Arrays
The contributions of drag to energy consumption in the transportation sector are significant and often unavoidable. Biomimetic surfaces are promising as passive drag reduction mechanisms. Among them, fish scale arrays are beneficial in the laminar and transitional flow regimes but lack fundamental understanding. This research addressed this need and investigated the underlying flow mechanisms over fish scale arrays. Experimental measurements revealed the presence of flow recirculation, streamwise velocity streaks, spanwise velocity fluctuations, and wall normal vorticity streaks, all of which play a role in the near wall flow behaviour. Numerical simulations revealed the superior friction drag reduction capabilities of the diamond scale shape. The findings highlight how the surface variations contribute to the formation of flow behaviours which influence the skin friction and contribute to delaying the transition to turbulence. The improved understanding of underlying processes from this study will aid the optimization of scale shape to reduce drag
Investigation of the airflow instability in the print gap of inkjet printers
Inkjet printer manufacturers face the challenge of designing systems that operate at elevated print gap heights to enable new applications for inkjet technology. At large print gap heights, the print quality tends to be compromised due to an airflow instability that misdirects the ink droplets, misplacing them on the paper. This phenomenon can lead to the printing defect commonly referred to as tiger-stripes. To characterise this instability, simultaneous high-velocity planar PIV measurements and printing tests were performed, together with numerical simulations using the dispersed-phase continuum (DPC) and particle-in-cell (P-in-C) droplet modelling techniques. The DPC technique is based on a predifined temporally averaged number density field to model the droplets. The comparison between both techniques indicated that the DPC approximation effectively computed the mean flow field with a reduction of up to 1000x in processing time. The predicted and measured flow-fields showed a pair of counter-rotating vortices located near the injection-zone that became unstable with an increase in both print gap heights and number density of droplets. The increase in droplet number density or print gap height induced a supercritical pitchfork bifurcation, which was characterised by a transition from a steady and uniform flow field across the domain to a standing wave regime with deformed vortex cores in the spanwise direction. With further increases in number density and print gap height, the flow field became oscillatory. These different flow dynamics were linked to specific printing patterns. The uniform flow field produced a defect-free print, whereas the standing wave regime created a print with straight dark stripes, and the oscillatory flow regime produced the tiger-stripe printing defect. The PIV measurements also showed the existence of tip vortices at the edges of the print-zone that can lead to secondary droplet misplacement
Swan Songs: The muddy waters of affect
I was spawned within a fold of the Biokovo Mountains in the Dalmatian region of Croatia and born on the river’s edge in the Swan Valley of Western Australia.
When the Toscana sailed into Fremantle carrying my Mother, Father, Sister and I (in utero), it was 1958 and Dalmatian villagers dominated the Swan Valley landscape. Arriving in three waves and across two world wars, the Croatian diaspora community cultivated centuries-old traditions to help establish Western Australia's (WA) oldest wine/grape growing region. This cross-cultural story of family and community compels me to explore, via the lens of a practice-led PhD, how creative practice may uncover the different stories that exist in the liminal space. As well as textural preservation of a cultural group in transition, this project seeks to articulate the invisible and often excluded middle – liminal – of second-generation diasporic experience. The second-generation Croatian diaspora are unquestionably the ‘bridge’ generation. They straddle old-world affective inheritance steeped in tradition, imperialist domination, abject poverty, war, fear, loss, and memory on the one hand, in tension with new-world differences and translations on the other.
In this dissertation the methodology of ficto-criticism in collaboration with affect theory suspends a bridge across the liminal space supporting an inventory of traces that track the historical passage of ‘my peoples’ migration from Croatia to Western Australia. The thesis comprises two interlinked components. The creative artefact Swan Songs is a fluid multi-framed visual essay cinematically exploring the threshold of second-generation migration through the filtered lens of the first. The dissertation, The Muddy Waters of Affect expands on this, mapping histories of departure, arrival, and return, beginning at the turn of the twentieth century with Croatian diaspora on the Eastern Goldfields Wood-line before arriving to the Swan Valley Vineyards. This dissertation, as a work of creative research, is layered with past experience; artistic excursions supporting the notion that from the moment of birth deep knowing flows through the performing body as a living matrix
The Palgrave Handbook of International Energy Economics
This open access handbook is distinguished by its emphasis on international energy, rather than domestic energy policies or international geopolitic aspects. Addressing key topics such as energy production and distribution, renewables and corporate energy structures, alongside global energy trends, regional case studies and emerging areas such as the digitalization of energy and energy transition, this handbook provides a major new contribution to the field of international energy economics. Written by academics, practitioners and policy-makers, this handbook is a valuable and timely addition to the literature on international energy economics. This book was published open access with the support of Eni
Economics of Electricity Battery Storage
This chapter deals with the challenges and opportunities of energy storage, with a specific focus on the economics of batteries for storing electricity in the framework of the current energy transition. Storage technologies include a variety of solutions that have been used for different grid services, including frequency control, load following, and uninterrupted power supply. A recent interest is being triggered by the increasing grid balance requirements to integrate variable renewable sources and distributed generation. In parallel, lithium-ion batteries are experiencing a strong market expansion driven by an uptake of electric vehicles worldwide, which is leading to a strong decrease of production costs, making Li-ion batteries an attractive solution also for stationary storage applications
Aerodynamics of active and passive dispersal of miniature insects with bristled wings
Tiny insects with body lengths under 2 mm, such as thrips, use fringed/bristled wings for active flapping at Reynolds number (Re) on the order of 10. Even at such tiny scales these insects were found to fly effectively owing to significant variations in wing kinematics and bristled wing morphology. Very few data is available on these variations at such small scales. Morphological investigation on forewing images of bristled wings revealed large diversity in their wing design. This includes variations in gaping or spacing between pair of bristles (G), bristle diameter (D), number of bristles (n) and wing span (S). In the present study, we quantified these design parameters from forewing images of 59 species of thrips and fairyfly species from previously published data. Physical scaled-up bristled wing models were then fabricated based on these parameters and tested for aerodynamic force generation using a robotic model. Results revealed that tiny insects may experience less biological pressure to optimize n or G/D for a given wingspan. Thrips have been observed to use wing-wing interaction via the clap and fling mechanism to augment lift generation. However, drag was also found to significantly increase. We found that tiny insects use large rotation angle to reduce this drag and proposed that circulatory lift alone cannot explain lift force generation and other lift generating mechanisms such as pressure distribution in the flow field were discussed. Actively flying at such tiny scales demands lot of power and these miniature insects were found to employ two additional strategies that helps in overcoming large power demand. We found that pausing between upstroke and downstroke decrease power required during a cycle with small compromise in lift. In addition to active flight, these insects can intermittently parachute by spreading their bristled wings at a particular inter-wing angle (O). We found that a dense bristled wing maintains aerodynamic loading relative to leakiness through the bristles for O>/=100 degrees. Also, we developed a scaled up robotic flapping device that could mimic any flapping flight in a horizontal stroke plane and proposed that pitch rate significantly alters the aerodynamic force generation compared to wing revolution
American Cities in Post-Apocalyptic Science Fiction
Visions of the American city in post-apocalyptic ruin permeate literary and popular fiction, across print, visual, audio and digital media. American Cities in Post-Apocalyptic Science Fiction explores the prevalence of these representations in American culture, drawing from a wide range of primary and critical works from the early-twentieth century to today. Beginning with science fiction in literary magazines, before taking in radio dramas, film, video games and expansive transmedia franchises, Robert Yeates argues that post-apocalyptic representations of the American city are uniquely suited for explorations of contemporary urban issues. Examining how the post-apocalyptic American city has been repeatedly adapted and repurposed to new and developing media over the last century, this book reveals that the content and form of such texts work together to create vivid and immersive fictional spaces in ways that would otherwise not be possible. Chapters present media-specific analyses of these texts, situating them within their historical contexts and the broader history of representations of urban ruins in American fiction. Original in its scope and cross-media approach, American Cities in Post-Apocalyptic Science Fiction both illuminates little-studied texts and provides provocative new readings of familiar works such as Blade Runner and The Walking Dead, placing them within the larger historical context of imaginings of the American city in ruins
Holography
Holography - Basic Principles and Contemporary Applications is a collection of fifteen chapters, describing the basic principles of holography and some recent innovative developments in the field. The book is divided into three sections. The first, Understanding Holography, presents the principles of hologram recording illustrated with practical examples. A comprehensive review of diffraction in volume gratings and holograms is also presented. The second section, Contemporary Holographic Applications, is concerned with advanced applications of holography including sensors, holographic gratings, white-light viewable holographic stereograms. The third section of the book Digital Holography is devoted to digital hologram coding and digital holographic microscopy
Deformability-induced effects of red blood cells in flow
To ensure a proper health state in the human body, a steady transport of blood is necessary. As the main cellular constituent in the blood suspension, red blood cells (RBCs) are governing the physical properties of the entire blood flow. Remarkably, these RBCs can adapt their shape to the prevailing surrounding flow conditions, ultimately allowing them to pass through narrow capillaries smaller than their equilibrium diameter. However, several diseases such as diabetes mellitus or malaria are linked to an alteration of the deformability. In this work, we investigate the shapes of RBCs in microcapillary flow in vitro, culminating in a shape phase diagram of two distinct, hydrodynamically induced shapes, the croissant and the slipper. Due to the simplicity of the RBC structure, the obtained phase diagram leads to further insights into the complex interaction between deformable objects in general, such as vesicles, and the surrounding fluid. Furthermore, the phase diagram is highly correlated to the deformability of the RBCs and represents thus a cornerstone of a potential diagnostic tool to detect pathological blood parameters. To further promote this idea, we train a convolutional neural network (CNN) to classify the distinct RBC shapes. The benchmark of the CNN is validated by manual classification of the cellular shapes and yields very good performance. In the second part, we investigate an effect that is associated with the deformability of RBCs, the lingering phenomenon. Lingering events may occur at bifurcation apices and are characterized by a straddling of RBCs at an apex, which have been shown in silico to cause a piling up of subsequent RBCs. Here, we provide insight into the dynamics of such lingering events in vivo, which we consequently relate to the partitioning of RBCs at bifurcating vessels in the microvasculature. Specifically, the lingering of RBCs causes an increased intercellular distance to RBCs further downstream, and thus, a reduced hematocrit.Um die biologischen Funktionen im menschlichen Körper aufrechtzuerhalten ist eine stetige Versorgung mit Blut notwendig. Rote Blutzellen bilden den Hauptanteil aller zellulären Komponenten im Blut und beeinflussen somit maßgeblich dessen Fließeigenschaften. Eine bemerkenswerte Eigenschaft dieser roten Blutzellen ist ihre Deformierbarkeit, die es ihnen ermöglicht, ihre Form den vorherrschenden Strömungsbedingungen anzupassen und sogar durch Kapillaren zu strömen, deren Durchmesser kleiner ist als der Gleichgewichtsdurchmesser einer roten Blutzelle. Zahlreiche Erkrankungen wie beispielsweise Diabetes mellitus oder Malaria sind jedoch mit einer Veränderung dieser Deformierbarkeit verbunden. In der vorliegenden Arbeit untersuchen wir die hydrodynamisch induzierten Formen der roten Blutzellen in mikrokapillarer Strömung in vitro systematisch für verschiedene Fließgeschwindigkeiten. Aus diesen Daten erzeugen wir ein Phasendiagramm zweier charakteristischer auftretender Formen: dem Croissant und dem Slipper. Aufgrund der Einfachheit der Struktur der roten Blutzellen führt das erhaltene Phasendiagramm zu weiteren Erkenntnissen über die komplexe Interaktion zwischen deformierbaren Objekten im Allgemeinen, wie z.B. Vesikeln, und des sie umgebenden Fluids. Darüber hinaus ist das Phasendiagramm korreliert mit der Deformierbarkeit der Erythrozyten und stellt somit einen Eckpfeiler eines potentiellen Diagnosewerkzeugs zur Erkennung pathologischer Blutparameter dar. Um diese Idee weiter voranzutreiben, trainieren wir ein künstliches neuronales Netz, um die auftretenden Formen der Erythrozyten zu klassifizieren. Die Ausgabe dieses künstlichen neuronalen Netzes wird durch manuelle Klassifizierung der Zellformen validiert und weist eine sehr hohe Übereinstimmung mit dieser manuellen Klassifikation auf. Im zweiten Teil der Arbeit untersuchen wir einen Effekt, der sich direkt aus der Deformierbarkeit der roten Blutzellen ergibt, das Lingering-Phänomen. Diese Lingering-Ereignisse können an Bifurkationsscheiteln zweier benachbarter Kapillaren auftreten und sind durch ein längeres Verweilen von Erythrozyten an einem Scheitelpunkt gekennzeichnet. In Simulationen hat sich gezeigt, dass diese Dynamik eine Anhäufung von nachfolgenden roten Blutzellen verursacht. Wir analysieren die Dynamik solcher Verweilereignisse in vivo, die wir folglich mit der Aufteilung von Erythrozyten an sich gabelnden Gefäßen in der Mikrovaskulatur in Verbindung bringen. Insbesondere verursacht das Verweilen von Erythrozyten einen erhöhten interzellulären Abstand zu weiter stromabwärts liegenden Erythrozyten und damit einen reduzierten Hämatokrit
Neurovascular Surgery
This open access book presents the diagnosis, investigation and treatment of neurovascular diseases, and offers expert opinions and advice on avoiding complications in neurovascular surgery. It also covers complication management and post-operative follow-up care. The book is divided in to three parts; the first part discusses common approaches in neurovascular surgery, describing the steps, indications for and limitations of the approach, as well as the associated complications and how to avoid them. The second part addresses surgical treatment based on pathology, taking the different locations of lesions into consideration. The third part focuses on the technological developments that support neurovascular surgery, which may not be available everywhere, but have been included to help vascular surgeon understand the principles. This book is a guide for young neurosurgeons, neurosurgery residents and neurosurgery fellows, as well as for medical students and nurses who are interested in neurosurgery or are associated with this field in any way. It is also a useful teaching aid for senior neurosurgeons
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