7,935 research outputs found
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
Designing carbon fibre-reinforced composites with improved structural retention on exposure to heat/fire
Carbon fibre-reinforced composites (CFRCs) are increasing in popularity due to their high
strength-to-weight ratio and resistance to corrosion. However, when exposed to temperatures
above 300Ā°C, the polymer matrix within CFRCs decomposes and then starts burning, exposing
carbon fibres to the surroundings. The residual carbon fibres being electrically conductive, may
pose a hazard to the surrounding electronics. Moreover, at over 550Ā°C the carbon fibres begin
to oxidise. This can lead to fibre defibrillation which also poses significant harm to human health
as broken fibres can be sharp enough to cut through human skin, and under 7Āµm these particles
are considered respirable where on inhalation they can causes damage to the trachea and lungs.
While considerable work has been carried out on assessing the effect of heat/fire on degradation
of the composite resin (matrix) and CFRCs themselves, there are limited studies on identifying
the damage to carbon fibres within CFRCs and the hazards posed by the exposed damaged
carbon fibres. This study examined the damage caused by high temperatures, radiant heat and
flames on carbon fibres and CFRCs, and the effects on their physical properties. A methodology
was developed to study and quantify the structural damage to carbon fibres and CFRCs after
exposure to a range of heat/fire conditions. These included thermogravimetric analysis (up to
900oC in nitrogen and air atmospheres), the tube furnace (450oCā900oC), cone calorimeter
(35kWm-2
to 75kWm-2
) and a propane burner (116kWm-2
) to simulate jet fuel fire conditions.
Residual fibres were removed from different parts of the CFRCs and the physical properties
were studied, such as fibre diameter reduction, change in electrical conductivity and decrease in
tensile strength. It was found that at heat fluxes ā„60kWm-2
oxidation of the carbon fibres
occurred. After 10min exposure to the propane flame, fibres in direct contact with the flame
showed signs of internal oxidation.The aim of this PhD project was to also improve the structural retention of CFRCs on exposure
to heat/fire so that the structural integrity is maintained and the carbon fibres are not exposed to
the environment. To address this, the following approaches were undertaken:
ā¢ Modification of the resin by adding flame retardants and nanoparticles in order to reduce the
flammability of CFRCs, improve the mechanical integrity of the char and its adherence to the fibre. Flame retardants included ammonium polyphosphate, resorcinol bis-(diphenyl
phosphate), 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide, and the nano-additives,
nano-clay, layered double hydroxide and carbon nano-tubes. Cone calorimeter testing at
75kWm-2 showed that the addition of 15wt% ammonium polyphosphate resulted in large char
formation and adherence to fibres in the underlying plies, which resulted in less oxidation to
these carbon fibres. The addition of layered double hydroxides and carbon nano-tubes on the
other hand caused pitting on fibres.
ā¢ Provide heat protection to carbon fibres within CFRCs by the inclusion of high performance
fibrous veils/woven fabrics of aramid, basalt, E-glass, polyphenylene sulphide and Kevlar.
The inclusion of the woven E-glass resulted in a notable reduction in the percentage of carbon
fibre oxidised. However, the volatiles produced during the decomposition of Kevlar and PPS
sensitised the carbon fibre to oxidation, causing it to occur more rapidly and at a lower
temperature.
ā¢ Using high temperature chemical coatings to individually coat carbon fibres prior to making
the CFRCs. Ceramic compounds (silica, alumina and zirconia), chosen as coating materials
because of their high thermal stability, were applied by different processes. The most
promising coatings included alumina and silica formed via sol-gel process and polysiloxane
deposited during plasma exposure. Tows coated in these chemicals underwent heat testing in
a tube furnace where those coated with alumina maintained the largest fibre diameters. While
polysiloxane coating provided oxidation protection up to 600Ā°C, after which cracks in the
coating were observed. This was attributed to the mechanical mismatch of the polysiloxane
coating and the carbon fibre
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Serial Biasing Technique for Rapid Single Flux Quantum Circuits
Superconductor electronics based on the Single Flux Quantum (SFQ) technology are considered a strong contender for the ābeyond CMOSā future of digital circuits because of the high speed and low power dissipation associated with them. In fact, digital operations beyond tens of GHz have been routinely demonstrated in the SFQ technology. These circuits have widespread applications such as high-speed analog-to-digital conversion, digital signal processing, high speed computing and in emerging topics such as control circuitry for superconducting quantum computing.
Rapid Single Flux Quantum (RSFQ) circuits have emerged as a promising candidate within the SFQ technology, with information encoded in picosecond wide, milli-volt voltage pulses. As is the case with any integrated circuit technology, scalability of RSFQ circuits is essential to realizing their applications. These circuits, based on the Josephson junction, require a DC bias current for the correct operation. The DC bias current requirement increases with circuit complexity, and this has multiple implications on circuit operation. Large currents produce magnetic fields that can interfere with logic operation. Furthermore, the heat load delivered to the superconducting chip also increases with current which could result in the circuit becoming ānormalā and not superconducting. These problems make reduction of the bias current necessary.
Serial Biasing (SB) is a bias current reduction technique, that has been proposed in the past. In this technique, a digital circuit is partitioned into multiple identical islands and bias current is provided to each island in a serial manner. While this scheme is promising, there are multiple challenges such as design of the driver-receiver pair circuit resulting in robust and wide operating bias margins, current management on the floating islands, etc.
This thesis investigates SB in a systematic manner, focusing on the design and measurement of the fundamental components of this technique with an emphasis on reliability and scalability. It presents works on circuit techniques achieving high speed serially biased RSFQ circuits with robust operating margins and the experimental evidence to support the ideas. It develops a framework for serial biasing that could be used by electronic design tools to automate design and synthesis of complex RSFQ circuits. It also investigates Passive Transmission Lines (PTLs) for use as passive interconnects between library cells in a complex design, reducing the DC bias current required by the active circuitry
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Ensuring Access to Safe and Nutritious Food for All Through the Transformation of Food Systems
The development and applications of ceragenins and bone-binding antimicrobials to prevent osteomyelitis in orthopaedic patients
Bone infection remains a high-burden disease in orthopaedic and trauma patients with fractures and implantations. Osteomyelitis is difficult to cure in clinical settings, especially if antimicrobial resistance or biofilm is involved, which may prolong the treatments with antibiotics and require multiple surgeries, severely affecting the patients' quality of life and mobility. Osteomyelitis can lead to osteonecrosis, septicaemia, amputation, multi-organ dysfunction, and death in severe cases.
Preclinical models are essential for efficacy testing to develop new prophylactic and therapeutic interventions. Previously bone infection models in rats involved fractures and implantations, making it complicated to perform. In this study, we have developed and optimised murine models with a tibial drilled hole (TDH) and needle insertion surgery (NIS) that are reliable, reproducible, and cost-effective for studying implant- related and biofilm bone infections and efficacy testing.
Ceragenins (CSAs) are a novel class of broad-spectrum antimicrobials that mimic the activities of antimicrobial peptides. They are effective against bacterial, viral, fungal, and parasitic infections with low minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). CSAs can also penetrate biofilm and kill antimicrobial-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). In recent years, CSA-131 has been approved by the FDA for endotracheal tube coating to prevent infection in intubated and critical patients. In our study, we applied CSA-90 (which belongs to the same family as CSA-131) to implant coating and prevented osteomyelitis in a mouse model and demonstrated the osteogenic properties of CSA- 90, which promotes bone healing and reunion of the bone defects.
CSA-90 has been classified as a potential drug to prevent and treat osteomyelitis. However, conventional methods of antibiotic delivery to the bone are inefficient. To increase the bone-binding property of CSA-90, we invented a new molecule by attaching alendronate (bisphosphonate) to CSA-90 and named it bone-binding antimicrobial-1 (BBA-1). In vitro, we determined the bone-binding properties of BBA-1 and confirmed its antimicrobial activities against S. aureus. Later, we conducted a preclinical trial to test the in vivo efficacy of BBA-1 and showed that BBA-1 could prevent osteomyelitis in mice and has low cytotoxicity.
Multiple myeloma (MM) is an aggressive cancer of plasma cells. Although chemotherapy, corticosteroids, and radiation therapy manage multiple myeloma, MM has no cure. Most MM patients (>90%) suffer myeloma-skeletal disease, including local osteolytic lesions and osteomyelitis. Thus, we dedicate the clinical application of BBA-1 to MM patients. To pursue clinical trials, preclinical trials must be conducted. In our attempts, we proposed a feasible murine model that can induce bone infections in MM mice and elucidated how MM patients will benefit from BBA-1
CITIES: Energetic Efficiency, Sustainability; Infrastructures, Energy and the Environment; Mobility and IoT; Governance and Citizenship
This book collects important contributions on smart cities. This book was created in collaboration with the ICSC-CITIES2020, held in San JosƩ (Costa Rica) in 2020. This book collects articles on: energetic efficiency and sustainability; infrastructures, energy and the environment; mobility and IoT; governance and citizenship
Technologies and Applications for Big Data Value
This open access book explores cutting-edge solutions and best practices for big data and data-driven AI applications for the data-driven economy. It provides the reader with a basis for understanding how technical issues can be overcome to offer real-world solutions to major industrial areas. The book starts with an introductory chapter that provides an overview of the book by positioning the following chapters in terms of their contributions to technology frameworks which are key elements of the Big Data Value Public-Private Partnership and the upcoming Partnership on AI, Data and Robotics. The remainder of the book is then arranged in two parts. The first part āTechnologies and Methodsā contains horizontal contributions of technologies and methods that enable data value chains to be applied in any sector. The second part āProcesses and Applicationsā details experience reports and lessons from using big data and data-driven approaches in processes and applications. Its chapters are co-authored with industry experts and cover domains including health, law, finance, retail, manufacturing, mobility, and smart cities. Contributions emanate from the Big Data Value Public-Private Partnership and the Big Data Value Association, which have acted as the European data community's nucleus to bring together businesses with leading researchers to harness the value of data to benefit society, business, science, and industry. The book is of interest to two primary audiences, first, undergraduate and postgraduate students and researchers in various fields, including big data, data science, data engineering, and machine learning and AI. Second, practitioners and industry experts engaged in data-driven systems, software design and deployment projects who are interested in employing these advanced methods to address real-world problems
Electromembrane Processes: Experiments and Modelling
Electromembrane processes offer a multitude of applications, allowing for the recovery of water, other products, and energy. This book is a collection of contributions on recent advancements in electromembrane processes attained via experiments and/or models. The first paper is a comprehensive review article on the applications of electrodialysis for wastewater treatment, highlighting current status, technical challenges, and key points for future perspectives. The second paper focuses on ZSM-5 zeolite/PVA mixed matrix CEMs with high monovalent permselectivity for recovering either acid or Li+. The third paper regards direct numerical simulations of electroconvection in an electrodialysis dilute channel with forced flow under potentiodynamic and galvanodynamic regimes. The fourth paper investigates the reasons for the formation and properties of soliton-like charge waves in overlimiting conditions. The fifth paper focuses on the characterization of AEMs functionalized by surface modification via poly(acrylic) acid yielding monovalent permselectivity for reverse electrodialysis. In the sixth paper, CFD simulations of reverse electrodialysis systems are performed. The seventh paper proposes an integrated membrane process, including electrochemical intercalationādeintercalation, for the preparation of Li2CO3 from brine with a high Mg2+/Li+ mass ratio. Finally, the eighth paper is a perspective article devoted to the acidābase flow battery with monopolar and bipolar membranes
Advanced Modeling, Control, and Optimization Methods in Power Hybrid Systems - 2021
The climate changes that are becoming visible today are a challenge for the global research community. In this context, renewable energy sources, fuel cell systems and other energy generating sources must be optimally combined and connected to the grid system using advanced energy transaction methods. As this reprint presents the latest solutions in the implementation of fuel cell and renewable energy in mobile and stationary applications such as hybrid and microgrid power systems based on the Energy Internet, blockchain technology and smart contracts, we hope that they will be of interest to readers working in the related fields mentioned above
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