132 research outputs found

    ELECTROHYDRODYNAMICS (EHD) PUMPING OF LIQUID NITROGEN APPLICATION TO SPOT CRYOGENIC COOLING OF SENSORS AND DETECTORS

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    Superconducting electronics require cryogenic conditions as well as certain conventional electronic applications exhibit better performance at low temperatures. A cryogenic operating environment ensures increased operating speeds and improves the signal-to-noise ratio and the bandwidth of analog devices and sensors, while also ensuring reduced aging effect. Most of these applications require modest power dissipation capabilities while having stricter requirements on the spatial and temporal temperature variations. Controlled surface cooling techniques ensure more stable and uniform temporal and spatial temperature distributions that allow better signal-to-noise ratios for sensors and elimination of hot spots for processors. EHD pumping is a promising technique that could provide pumping and mass flow rate control along the cooled surface. In this work, an ion-drag EHD pump is used to provide the pumping power necessary to ensure the cooling requirements. The present study contributes to two major areas which could provide significant improvement in electronics cooling applications. One direction concerns development of an EHD micropump, which could provide the pumping power for micro-cooling systems capable of providing more efficient and localized cooling. Using a 3M fluid, a micropump with a 50 mm gap between the emitter and collector and a saw-tooth emitter configuration at an applied voltage of about 250 V provided a pumping head of 650 Pa. For a more optimized design a combination of saw tooth emitters and a 3-D solder-bump structure should be used. The other major contribution involves the application, for the first time, of the EHD pumping technique to cryogenic liquids. Successful implementation of these cooling techniques could provide on-demand and on-location pumping power which would allow tight cryogenic temperature control on the cooling surface of sensors, detectors and other cold electronics. Pumping heads of up to 1 Pa with mass flow rates of 0.8 g/s were achieved using liquid nitrogen. Although the pressure head results seem relatively small, the corresponding liquid nitrogen mass flow rate meets the targeted heat removal requirements specific to superconducting sensors and detectors

    Quality by Design Approach to Advanced Particle Engineering, Process Optimisation and Upscaling of Electrohydrodynamic Atomisation Technology

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    Particle engineering for drug delivery (DD) has gained enormous research interests in recent years, with continuous development of new technological platforms and improvement of existing ones. Unlike most other technologies, the electrohydrodynamic atomisation (EHDA), has been shown to have more advantages in the fabrication of nano- and micro-sized drug particulates. With the advent of the recent pandemic and huge demand for large scale industrial application of nanotechnology, there is now more emphasis on the need for further advancement and upscaling of the EHDA technology. The research presented in this thesis employed the use of EHDA technologies in the engineering of drug particles and application of QbD technique in its optimisation and subsequent upscaling of the process. The work presented in this research is a proof-of-concept; demonstrating the capacity for upscaling of this promising technology. This was first achieved by the utilisation of the EHDA technique in the nanofabrication of indomethacin (INDO) crystal, with the intention of achieving nanocrystals with sustained or improved particle properties for DD. QbD technique was used in the optimisation of the process with an experimental model engendered using 23 full factorial screening design. This design of experiment (DoE) was achieved by carrying out a risk assessment (RA) of the critical quality attributes (CQAs) and critical process parameters (CPP) and using these to establish a quality target product profile (QTPP) yielding nanocrystals of desired particle properties with 395nm size. The nanonisation of crystal particles using this technology opens a new frontier in crystal engineering. Further modification and remodelling lead to the design of a quadrant nozzle system and 8-nozzle system with capabilities of large scale electrospraying of drug particles. Studies on the droplet dynamics showed the impact of the electric field from each nozzle on the spray pattern altering the spray projection of INDO in ethanol (EtOH). The voltage utility graph also demonstrated a higher energy requirement in the formation of stable cone-jets in the upscaled system. Hereafter, based on the result obtained from this work, QbD was subsequently employed in the optimisation of cone-jet formation of chloramphenicol (CAM) and polyvinyl pyrrolidone (PVP) using single nozzle, as well as spraying head designed for improved formulation flow such as multi-tip emitter (MTE) device and flute spraying head. Characterisation of the particles formed from the INDO in EtOH formulation showed stable, nano-sized particles while retaining the physico-chemical properties of INDO. Consequently, characterisation of the fabricated particulates yielded stable polymeric nanoparticles (NPs) which demonstrated a proper incorporation of the CAM in PVP with a steady release profile. This analysis shows a promising potential for the use of this novel upscaling designs in the pharmaceutical industries for the fabrication of both micro- and nano-sized composites, whilst requiring an in-depth exploration of the design functionality in different particle engineering remit

    Dual-Use Space Technology Transfer Conference and Exhibition

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    This document contains papers presented at the Dual-Use Space Technology Transfer Conference and Exhibition held at the Johnson Space Center February 1-3, 1994. Possible technology transfers covered during the conference were in the areas of information access; innovative microwave and optical applications; materials and structures; marketing and barriers; intelligent systems; human factors and habitation; communications and data systems; business process and technology transfer; software engineering; biotechnology and advanced bioinstrumentation; communications signal processing and analysis; new ways of doing business; medical care; applications derived from control center data systems; human performance evaluation; technology transfer methods; mathematics, modeling, and simulation; propulsion; software analysis and decision tools systems/processes in human support technology; networks, control centers, and distributed systems; power; rapid development perception and vision technologies; integrated vehicle health management; automation technologies; advanced avionics; ans robotics technologies. More than 77 papers, 20 presentations, and 20 exhibits covering various disciplines were presented b experts from NASA, universities, and industry

    Tribology of Machine Elements

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    Tribology is a branch of science that deals with machine elements and their friction, wear, and lubrication. Tribology of Machine Elements - Fundamentals and Applications presents the fundamentals of tribology, with chapters on its applications in engines, metal forming, seals, blasting, sintering, laser texture, biomaterials, and grinding

    Lubrication & efficiency of rear wheel drive axles in road vehicles

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    The automotive rear axle is a part of the final drive for front engine, rear wheel drive, road vehicles. The axle is an important component in vehicle dynamics. The task of the axle is to transfer drive to the road surface as efficiently and with as low a mechanical loss as possible. Usually, the rear axle consists of a hypoid bevel geared transmission and a differential. A thermally coupled mathematical model of a hypoid axle is developed to calculate the total power loss in the rear axle. The drive cycle and gear and bearing details along with operating conditions are used as input data. The model also considers gradient, tyre pressure, aerodynamics and external temperature for a given drive cycle. The heat liberated due to mechanical losses at each time step and removed by convection is found, leading to the temperature of the bulk oil and components. Buckingham’s approximate analysis is used to define contact conditions for the hypoid gear pair. Elastohydrodynamic theory is applied to calculate film thickness and traction at the gear and bearing contacts. A tribometer (MTM) is used to obtain lubricant rheological parameters. Empirical formulae are used to find churning, seal and bearing losses. The efficiency of the axle is derived for different lubricants for the specified drive cycle. The prediction of the axle power loss is validated through comparisons with extensive experiments performed on the Ford F150 2010 model and a separate axle test rig, over a wide range of operating conditions. The comparisons between modelling results and test measurements demonstrate that the thermally coupled model is indeed capable of predicting the axle efficiency or temperatures reasonably well. The findings showed that the intended use of the vehicle greatly affected the temperature in the axle and hence determines the ranking order of lubricants. Lubricant rheology strongly influenced the overall efficiency of the axle. A lubricant boundary friction additive was only effective for the most severe drive cycle giving a significant reduction in the axle temperature. A simple test rig was built up to study churning losses of a partly immersed spur gear. This is similar to dip lubrication used in the axle. The influence of variation in air pressure within a cylindrical enclosure was investigated. This test was used to investigate the effect of the gear speed, air density and fluid properties, and used as a lubricant ranking method for churning losses. Lubricant base oils, water and aqueous glycerol solutions were tested using the inertia rundown method. The findings showed that the principal effects are those due to inertia and weight of the oil on the churning power loss. High viscosity lubricants impede gravitational reflow reducing overall losses. When air pressure varied, vacuum (0 bar) in the enclosure increased the power loss by up to 4.5 times, while Compressed air (2 bar) reduced the power loss by up to 2.2 times, compared to atmospheric pressure, for the more viscous oils. Glycerol aqueous solutions give similar trend curve for the losses comparable to oils but an effect of surface tension is predominant. Adding a surfactant to water led to a reduction in the power loss possibly resulting from the effect of the surface tension of the fluid.Open Acces

    Microfluidics and Nanofluidics Handbook

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    The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals

    Crude Oil

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    Petroleum crude oil is the main energy source worldwide. However, global fossil fuel resources and reservoirs are rapidly and disturbingly being depleted. Thus, it is particularly important to shed light on new techniques developed for economic production and better utilization of crude oil. In addition, the processes involved in the production, refining, and transportation of crude oil are environmentally hazardous. It is essential to develop cleaner technologies and to find innovative solutions to overcome these problems. Over four sections, this book discusses materials used in cracking crude oil and improving its specifications, methods for reducing or eliminating the hazardous effects of petroleum pollution, and the environmental effects of crude oil, as well as presents case studies from different countries

    Second Microgravity Fluid Physics Conference

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    The conference's purpose was to inform the fluid physics community of research opportunities in reduced-gravity fluid physics, present the status of the existing and planned reduced gravity fluid physics research programs, and inform participants of the upcoming NASA Research Announcement in this area. The plenary sessions provided an overview of the Microgravity Fluid Physics Program information on NASA's ground-based and space-based flight research facilities. An international forum offered participants an opportunity to hear from French, German, and Russian speakers about the microgravity research programs in their respective countries. Two keynote speakers provided broad technical overviews on multiphase flow and complex fluids research. Presenters briefed their peers on the scientific results of their ground-based and flight research. Fifty-eight of the sixty-two technical papers are included here

    Digital Holography Microscopy at Lab-on-a-Chip scale: novel algorithms and recording strategies

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    Il lavoro presentato è mirato allo sviluppo di nuove tecniche di microscopia olografica digitale (Digital Holography Microscopy, DHM), e di opportuni algoritmi numerici per lo studio di biomateriali in ambiente microfluidico. Nello specifico vengono affrontate due problematiche di imaging particolarmente rilevanti nello studio di sistemi Lab-on-a-Chip (LoC). Dapprima è stato studiato il problema della microscopia quantitativa di oggetti biologici osservati attraverso mezzi complessi, come soluzioni torbide e substrati diffondenti, dove la formazione dell’immagine è ostacolata da processi di scattering. Lo studio condotto è stato mirato all’analisi di processi di diffusione da layer statico e da mezzo liquido di tipo colloidale, in regime quasi-statico e dinamico. Sono stati sviluppati a tale scopo dei metodi di registrazione e nuovi algoritmi di ricostruzione dell’immagine olografica (Multi-Look Digital Holography, MLDH) che consentono di fornire un imaging quantitativo dei campioni in esame. Di particolare interesse è il caso di volumi di liquido costituiti da globuli rossi: nel lavoro presentato viene dimostrata la possibilità di studiare, mediante MLDH, processi di adesione cellulare di materiale biologico situato in presenza di flussi di globuli rossi ad alta concentrazione. La possibilità di visualizzare e analizzare quantitativamente materiale biologico all’interno di un capillare o una vena, compensando l’effetto di diffusione del sangue, potrebbe in futuro consentire di studiare la formazione all’interno del vaso di coaguli e placche di colesterolo, sintomatici dell’insorgere di malattie cardiache. La stessa tecnica è in grado di recuperare l’informazione distorta a causa della presenza all’interno del canale di ostacoli statici o quasi-statici (dovuti alla formazione di bio-film o sospensioni batteriche, o causata da processi di fabbricazione del canale microfluidico), aumentando così notevolmente la varietà dei processi biologici analizzabili su piattaforme LoC. Nel lavoro viene anche dimostrato come la presenza di un mezzo torbido possa essere sfruttata vantaggiosamente al fine di migliorare la qualità dell’immagine in sistemi di imaging basati su luce coerente. Parallelamente è stata messa a punto una tecnica interferometrica che, sfruttando il movimento dei campioni nei canali microfluidici, consente di sostituire un sensore convenzionale 2D con un sensore lineare, più compatto e integrabile a bordo del chip, e capace di fornire prestazioni superiori in termini di velocità di acquisizione. Il lavoro presentato descrive il processo di sintesi di un nuovo tipo di ologramma (Space-Time Digital Hologram, STDH), che consente di ottenere un Field-of-View (FoV) illimitato nella direzione del flusso e, quindi, di superare il trade-off esistente tra fattore di ingrandimento e FoV, comune ad ogni tecnica di microscopia convenzionale. Viene inoltre dimostrato che un STDH mantiene le caratteristiche e i vantaggi di un ologramma digitale standard, quali la focalizzazione numerica flessibile, che permette di analizzare contemporaneamente tutti gli oggetti presenti in un volume di liquido, e la possibilità di estrarre la segnatura di fase degli stessi
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