5,526 research outputs found

    Securing NextG networks with physical-layer key generation: A survey

    Get PDF
    As the development of next-generation (NextG) communication networks continues, tremendous devices are accessing the network and the amount of information is exploding. However, with the increase of sensitive data that requires confidentiality to be transmitted and stored in the network, wireless network security risks are further amplified. Physical-layer key generation (PKG) has received extensive attention in security research due to its solid information-theoretic security proof, ease of implementation, and low cost. Nevertheless, the applications of PKG in the NextG networks are still in the preliminary exploration stage. Therefore, we survey existing research and discuss (1) the performance advantages of PKG compared to cryptography schemes, (2) the principles and processes of PKG, as well as research progresses in previous network environments, and (3) new application scenarios and development potential for PKG in NextG communication networks, particularly analyzing the effect and prospects of PKG in massive multiple-input multiple-output (MIMO), reconfigurable intelligent surfaces (RISs), artificial intelligence (AI) enabled networks, integrated space-air-ground network, and quantum communication. Moreover, we summarize open issues and provide new insights into the development trends of PKG in NextG networks

    Comparative analysis of energy transfer mechanisms for neural implants

    Get PDF
    As neural implant technologies advance rapidly, a nuanced understanding of their powering mechanisms becomes indispensable, especially given the long-term biocompatibility risks like oxidative stress and inflammation, which can be aggravated by recurrent surgeries, including battery replacements. This review delves into a comprehensive analysis, starting with biocompatibility considerations for both energy storage units and transfer methods. The review focuses on four main mechanisms for powering neural implants: Electromagnetic, Acoustic, Optical, and Direct Connection to the Body. Among these, Electromagnetic Methods include techniques such as Near-Field Communication (RF). Acoustic methods using high-frequency ultrasound offer advantages in power transmission efficiency and multi-node interrogation capabilities. Optical methods, although still in early development, show promising energy transmission efficiencies using Near-Infrared (NIR) light while avoiding electromagnetic interference. Direct connections, while efficient, pose substantial safety risks, including infection and micromotion disturbances within neural tissue. The review employs key metrics such as specific absorption rate (SAR) and energy transfer efficiency for a nuanced evaluation of these methods. It also discusses recent innovations like the Sectored-Multi Ring Ultrasonic Transducer (S-MRUT), Stentrode, and Neural Dust. Ultimately, this review aims to help researchers, clinicians, and engineers better understand the challenges of and potentially create new solutions for powering neural implants

    Broadband coherent Raman scattering spectroscopy at 50,000,000 spectra/s

    Full text link
    Raman scattering spectroscopy is widely used as an analytical technique in various fields, but its measurement process tends to be slow due to the low scattering cross-section. In the last decade, various broadband coherent Raman scattering spectroscopy techniques have been developed to address this limitation, achieving a measurement rate of about 100 kSpectra/s. Here, we present a significantly increased measurement rate of 50 MSpectra/s, which is 500 times higher than the previous state-of-the-art, by developing time-stretch coherent Raman scattering spectroscopy. Our newly-developed system, based on a mode-locked Yb fiber laser, enables highly-efficient broadband excitation of molecular vibrations via impulsive stimulated Raman scattering with an ultrashort femtosecond pulse and sensitive time-stretch detection with a picosecond probe pulse at a high repetition rate of the laser. As a proof-of-concept demonstration, we measure broadband coherent Stokes Raman scattering spectra of organic compounds covering the molecular fingerprint region from 200 to 1,200 cm-1. This high-speed broadband vibrational spectroscopy technique holds promise for unprecedented measurements of sub-microsecond dynamics of irreversible phenomena and extremely high-throughput measurements

    The 2023 terahertz science and technology roadmap

    Get PDF
    Terahertz (THz) radiation encompasses a wide spectral range within the electromagnetic spectrum that extends from microwaves to the far infrared (100 GHz–∌30 THz). Within its frequency boundaries exist a broad variety of scientific disciplines that have presented, and continue to present, technical challenges to researchers. During the past 50 years, for instance, the demands of the scientific community have substantially evolved and with a need for advanced instrumentation to support radio astronomy, Earth observation, weather forecasting, security imaging, telecommunications, non-destructive device testing and much more. Furthermore, applications have required an emergence of technology from the laboratory environment to production-scale supply and in-the-field deployments ranging from harsh ground-based locations to deep space. In addressing these requirements, the research and development community has advanced related technology and bridged the transition between electronics and photonics that high frequency operation demands. The multidisciplinary nature of THz work was our stimulus for creating the 2017 THz Science and Technology Roadmap (Dhillon et al 2017 J. Phys. D: Appl. Phys. 50 043001). As one might envisage, though, there remains much to explore both scientifically and technically and the field has continued to develop and expand rapidly. It is timely, therefore, to revise our previous roadmap and in this 2023 version we both provide an update on key developments in established technical areas that have important scientific and public benefit, and highlight new and emerging areas that show particular promise. The developments that we describe thus span from fundamental scientific research, such as THz astronomy and the emergent area of THz quantum optics, to highly applied and commercially and societally impactful subjects that include 6G THz communications, medical imaging, and climate monitoring and prediction. Our Roadmap vision draws upon the expertise and perspective of multiple international specialists that together provide an overview of past developments and the likely challenges facing the field of THz science and technology in future decades. The document is written in a form that is accessible to policy makers who wish to gain an overview of the current state of the THz art, and for the non-specialist and curious who wish to understand available technology and challenges. A such, our experts deliver a 'snapshot' introduction to the current status of the field and provide suggestions for exciting future technical development directions. Ultimately, we intend the Roadmap to portray the advantages and benefits of the THz domain and to stimulate further exploration of the field in support of scientific research and commercial realisation

    Anaerobic Digestion and Pretreatment Techniques that Enhance the Digestibility of Lignocellulosic Biomass

    Get PDF
    To improve biological digestibility, lignocellulose was pretreated by shock, alkali, and combinations thereof. Shock is most effective when it precedes alkaline pretreatment, presumably because it opens the biomass structure and enhances diffusion of pretreatment chemicals. Lignocellulose digestibility from calcium hydroxide treatment improves significantly with oxygen addition. In contrast, sodium hydroxide is a more potent alkali, and thereby eliminates the need for oxygen to enhance pretreatment. For animal feed, Ca(OH)₂ treatment is recommended because residual calcium ions are valuable nutrients. However, for methane-arrested, anaerobic digestion (MAAD), NaOH treatment is preferred because sodium is a better buffer. The effect of shock is most pronounced when the no-shock control employed the same soaking-and-drying procedure as the shock treatment. MAAD is a more accurate assessment technique when lignocellulose is employed in the carboxylate platform, a promising approach that utilizes nearly all biomass components. Using recommended pretreatment conditions identified from a previous study, three corn stover pretreatments were compared using MAAD: (1) shock-only, (2) NaOH-only, and (3) shock + NaOH. Air-dried sewage sludge was used as nutrient source. At 100 g/L initial substrate concentration, compared to untreated corn stover, shock-only decreased conversion (amount of biomass digested) by 14%, NaOH-only increased conversion by 82%, and shock + NaOH increased conversion by 104%. To sustainably produce carboxylic acids, paper and chicken manure were co-digested through semi-continuous countercurrent (MAAD) using a mixed culture of marine microorganisms grown at mesophilic conditions (40 °C). During the digestion, anion-exchange resin (Amberlite IRA-67) adsorption was applied to simultaneously recover inhibitory acid products from the digestion medium. The adsorption efficiency was enhanced by supplying CO₂ during in-situ adsorption. Compared with stand-alone digestion (control), integrating adsorption with MAAD significantly increased biomass conversion and acid yield by 2.28 and 2.09 times, respectively. The effects of frozen (fresh), air-dried, and baked nutrients (chicken manure, sewage sludge) on MAAD was studied. Continuum particle distribution (CPDM) maps show the impact of liquid residence time (LRT) and volatile solids loading rate (VSLR) on conversion and product concentration. Baked chicken manure reduced conversion and acid concentration, which suggests that oven-drying damages nutrients. At high VSLR, air-dried nutrients have higher acid concentrations than fresh nutrients, but conversion is low; thus, fresh nutrients are preferred. At the same conditions, fresh chicken manure and sewage sludge have similar acid concentration; however, sewage sludge yields a larger proportion of caproic acid. Most biomass sources require expensive pretreatment to remove lignin, a component that makes biomass less reactive. However, prickly pear cladodes have low lignin content and high sugar content. Batch MAADs of prickly pear cladodes were performed and CPDM maps were generated. With a product yield of ~50% and biomass conversion of ~70%, prickly pear performed better than previously studied lignocellulosic feedstocks. At 100 g solids/L liquid, the CPDM map predicts that high acid concentrations (93 g/L) and conversions (93%) are obtained at VSLR of 6 g/(Lliq·day) and LRT of 35 days. The high sugar content and low lignin content of prickly pear makes it a suitable feedstock for the carboxylate platform

    Analytical Models and Artificial Intelligence for Open and Partially Disaggregated Optical Networks

    Get PDF
    L'abstract Ăš presente nell'allegato / the abstract is in the attachmen

    Comparative evaluation of acoustic and electric signals of partial discharges

    Get PDF
    Failures of power electric components such as transformers and outages can lead to a huge economical loss in the electric power grid. One of the main parts of a power electric components is the insulation system, namely, insulation oil, impregnated pressboard and paper. Several methods exist for diagnostics of these insulation materials. Partial discharge (PD) measurement known as one of the main non-destructive monitoring systems of the insulation materials. However, it has been mainly done off-line in maintenance periods, and the existing on-line methods generally provide less information due to environment electric noises. In contrast to electric PD measurement system, the acoustic emission (AE) measurement system is well known for its immunity against environment electrical noises. In this thesis comparative evaluation of acoustic and electric signals of PD events generated in oil impregnated pressboard and papers is investigated. The thesis is focused on the characteristic of PD activity and the consequence of that on the electric and AE signal. PD classification is defined by using the relation between acoustic and electric signals of PD events. Although the sensitivity of the AE sensors has been improved over the years, but the detection of the acoustic signals from PD activity in power equipment mainly transformers remain the main challenge of acoustic measurement. Lack of information regarding evaluation of electric PD signals and AE signals beside the mechanical attenuation are two main disadvantages of AE measurement method. Due to mechanical and electrical mechanism of waves generated during PD activities, the mechanical and electrical behaviour of the waves is discussed in more detail to have better understanding about the electric and acoustic signals. PD sources were generated at different electrode configurations such as needle-plane and electrode ball arrangement within a sample in the tank to investigate different types of PD. Electric characteristics of PD and different PD measuring technics such as electric, UHF and acoustic beside the mechanical behaviour of the acoustic waves are also discussed. The corona in oil results regarding the relation between AE and electric PD signals shows the correlated behaviour between AE and PD apparent charge magnitude. However, in surface discharges these behaviours are uncorrelated. In this regards the surface discharge is studied in more detail, leading to the first results of PD with very low acoustic (no acoustic) activity. Regarding these results two different categories in term of AE signals of PDs are defined, silent PD and non-silent PD. Silent PDs are those PD activities without or with very low acoustic signal and non-silent PDs are with acoustic signal. The existence of the silent PD is validated via oscilloscope and digital signal processing (DSP) devices. Also, with different innovative methods and arrangements such as needle plane and ball electrodes with and without oil gap, the probable reasons of creation this phenomenon (silent PD) is investigated. It is found that the carbonization patterns start with non-silent PD and remain the same during silent PD activities even with very high electric apparent charges. It means the development in carbonization traces produce electric and AE signals and in contrast no changes in carbonization traces produce only electric signals with no AE signal. These results verify the advantages of using acoustic technics and electric measurement in terms of PD classification and localization.AusfĂ€lle von Komponenten in elektrischen Energiesystemen wie Transformatoren können zu einem enormen wirtschaftlichen Verlust im Energiesystem fĂŒhren. Einer der Hauptbestandteile der Komponenten in elektrischen Energiesystemen ist das Isoliersystem, nĂ€mlich Öl, imprĂ€gniert Pressboard und Papier. Es gibt mehrere Methoden zur Diagnose dieser Isoliermaterialien. Die Messung der Teilentladung (TE) ist als eines der wichtigsten zerstörungsfreien Überwachungssysteme fĂŒr Isoliermaterialien bekannt. Jedoch wird dies in Wartungsperioden hauptsĂ€chlich offline durchgefĂŒhrt, und die existierenden Online-Verfahren liefern im Allgemeinen weniger Informationen aufgrund von elektromagnetischen Störungen. Im Gegensatz zum elektrischen TE-Messsystem ist das Schallemissionsmesssystem fĂŒr seine ImmunitĂ€t gegen elektrische UmgebungsgerĂ€usche bekannt. In dieser Arbeit wird die vergleichende Auswertung von akustischen und elektrischen Signalen von TE-Ereignissen untersucht, die in ölimprĂ€gnierten Pressboard und Papieren erzeugt werden. Sie konzentriert sich auf die Charakteristik der TE-AktivitĂ€t und deren Einfluss auf akustische Signale. Die TE-Klassifizierung wird definiert, indem die Beziehung zwischen akustischen und elektrischen Signalen von TE-Ereignissen verwendet wird. Obwohl die Empfindlichkeit der akustischen Sensoren im Laufe der Jahre verbessert wurde, bleibt die Erkennung der akustischen Signale von TE-AktivitĂ€t das Hauptproblem bei Komponenten in elektrischen Energiesystemen, hauptsĂ€chlich Transformatoren. Fehlende Informationen zur Auswertung von elektrischen TE-Signalen und akustischen Signalen sind neben der mechanischen DĂ€mpfung zwei Hauptnachteile der akustischen Messung. Wegen der mechanischen und elektrischen Mechanismen von Wellen, die wĂ€hrend der TE-AktivitĂ€ten erzeugt werden, wird deren Verhalten ausfĂŒhrlicher diskutiert, um ein besseres VerstĂ€ndnis ĂŒber die elektrischen und akustischen Signale zu erhalten. An verschiedenen Elektrodenkonfigurationen innerhalb einer Probe im Öltank werden TE-Quellen an verschiedenen Elektrodenkonfigurationen wie Spitze-Platte und Elektrodenkugelanordnung innerhalb einer Probe im Tank erzeugt, um verschiedene Arten von TE zu untersuchen. Neben dem mechanischen Verhalten der akustischen Wellen werden auch elektrische Eigenschaften von TE und verschiedene TE-Messtechniken wie elektrisch, UHF und akustisch behandelt. Die Ergebnisse bezĂŒglich des VerhĂ€ltnisses zwischen AE- und elektrischen TE-Signalen fĂŒr Korona im Öl zeigen das korrelierte Verhalten zwischen AE- und TE-Signalen. Bei OberflĂ€chenentladungen sind diese Verhaltensweisen jedoch unkorreliert. Die OberflĂ€chenentladung wird genauer untersucht, was zu den ersten Ergebnissen von TE mit sehr geringer akustischer (keine akustischen Signale) AktivitĂ€t fĂŒhrt. In Bezug auf diese Ergebnisse werden zwei verschiedene Kategorien in Bezug auf elektrische und AE-Signale von TE definiert, stille TE und nicht-stille TE. Stille TE sind elektrische TE-Signale ohne oder mit sehr geringer akustischer AktivitĂ€t, und nicht-stille TE sind elektrische TE-Signale mit akustischer AktivitĂ€t. Die Existenz der stillen PD wird ĂŒber Oszilloskope und digitale SignalverarbeitungsgerĂ€te (DSP) validiert. Auch mit verschiedenen innovativen Methoden und Anordnungen wie Nadel und Kugelelektroden mit und ohne Ölspalt werden die wahrscheinlichen Entstehungsursachen dieses PhĂ€nomens (Silent TE) untersucht. Es wurde festgestellt, dass die Karbonisierungsmuster mit nicht-stiller TE beginnen und wĂ€hrend stiller TE-AktivitĂ€ten selbst bei sehr hohen scheinbaren elektrischen Ladungen unverĂ€ndert bleiben. Dies bedeutet, dass bei der Entwicklung der Karbonisierungsspuren elektrische und AE-Signale erzeugt werden und im Gegensatz dazu ohne Änderungen der Karbonisierungsspuren nur elektrische Signale (ohne AE-Signale) erzeugt werden. Diese Differenzierung ist nur möglich bei gleichzeitigem Einsatz der akustischen Technik und elektrischen Messung im Hinblick auf die TE-Klassifizierung und Lokalisierung

    Accurate quantum transport modelling and epitaxial structure design of high-speed and high-power In0.53Ga0.47As/AlAs double-barrier resonant tunnelling diodes for 300-GHz oscillator sources

    Get PDF
    Terahertz (THz) wave technology is envisioned as an appealing and conceivable solution in the context of several potential high-impact applications, including sixth generation (6G) and beyond consumer-oriented ultra-broadband multi-gigabit wireless data-links, as well as highresolution imaging, radar, and spectroscopy apparatuses employable in biomedicine, industrial processes, security/defence, and material science. Despite the technological challenges posed by the THz gap, recent scientific advancements suggest the practical viability of THz systems. However, the development of transmitters (Tx) and receivers (Rx) based on compact semiconductor devices operating at THz frequencies is urgently demanded to meet the performance requirements calling from emerging THz applications. Although several are the promising candidates, including high-speed III-V transistors and photo-diodes, resonant tunnelling diode (RTD) technology offers a compact and high performance option in many practical scenarios. However, the main weakness of the technology is currently represented by the low output power capability of RTD THz Tx, which is mainly caused by the underdeveloped and non-optimal device, as well as circuit, design implementation approaches. Indeed, indium phosphide (InP) RTD devices can nowadays deliver only up to around 1 mW of radio-frequency (RF) power at around 300 GHz. In the context of THz wireless data-links, this severely impacts the Tx performance, limiting communication distance and data transfer capabilities which, at the current time, are of the order of few tens of gigabit per second below around 1 m. However, recent research studies suggest that several milliwatt of output power are required to achieve bit-rate capabilities of several tens of gigabits per second and beyond, and to reach several metres of communication distance in common operating conditions. Currently, the shortterm target is set to 5−10 mW of output power at around 300 GHz carrier waves, which would allow bit-rates in excess of 100 Gb/s, as well as wireless communications well above 5 m distance, in first-stage short-range scenarios. In order to reach it, maximisation of the RTD highfrequency RF power capability is of utmost importance. Despite that, reliable epitaxial structure design approaches, as well as accurate physical-based numerical simulation tools, aimed at RF power maximisation in the 300 GHz-band are lacking at the current time. This work aims at proposing practical solutions to address the aforementioned issues. First, a physical-based simulation methodology was developed to accurately and reliably simulate the static current-voltage (IV ) characteristic of indium gallium arsenide/aluminium arsenide (In-GaAs/AlAs) double-barrier RTD devices. The approach relies on the non-equilibrium Green’s function (NEGF) formalism implemented in Silvaco Atlas technology computer-aided design (TCAD) simulation package, requires low computational budget, and allows to correctly model In0.53Ga0.47As/AlAs RTD devices, which are pseudomorphically-grown on lattice-matched to InP substrates, and are commonly employed in oscillators working at around 300 GHz. By selecting the appropriate physical models, and by retrieving the correct materials parameters, together with a suitable discretisation of the associated heterostructure spatial domain through finite-elements, it is shown, by comparing simulation data with experimental results, that the developed numerical approach can reliably compute several quantities of interest that characterise the DC IV curve negative differential resistance (NDR) region, including peak current, peak voltage, and voltage swing, all of which are key parameters in RTD oscillator design. The demonstrated simulation approach was then used to study the impact of epitaxial structure design parameters, including those characterising the double-barrier quantum well, as well as emitter and collector regions, on the electrical properties of the RTD device. In particular, a comprehensive simulation analysis was conducted, and the retrieved output trends discussed based on the heterostructure band diagram, transmission coefficient energy spectrum, charge distribution, and DC current-density voltage (JV) curve. General design guidelines aimed at enhancing the RTD device maximum RF power gain capability are then deduced and discussed. To validate the proposed epitaxial design approach, an In0.53Ga0.47As/AlAs double-barrier RTD epitaxial structure providing several milliwatt of RF power was designed by employing the developed simulation methodology, and experimentally-investigated through the microfabrication of RTD devices and subsequent high-frequency characterisation up to 110 GHz. The analysis, which included fabrication optimisation, reveals an expected RF power performance of up to around 5 mW and 10 mW at 300 GHz for 25 ÎŒm2 and 49 ÎŒm2-large RTD devices, respectively, which is up to five times higher compared to the current state-of-the-art. Finally, in order to prove the practical employability of the proposed RTDs in oscillator circuits realised employing low-cost photo-lithography, both coplanar waveguide and microstrip inductive stubs are designed through a full three-dimensional electromagnetic simulation analysis. In summary, this work makes and important contribution to the rapidly evolving field of THz RTD technology, and demonstrates the practical feasibility of 300-GHz high-power RTD devices realisation, which will underpin the future development of Tx systems capable of the power levels required in the forthcoming THz applications

    Development of spectroscopic assays for rapid monitoring of estrogen biodegradation

    Get PDF
    Estrogen hormones are well-established environmental micropollutants which have been linked to endocrine disruption in aquatic organisms in wastewater discharge sites. Biological degradation is the primary wastewater treatment mechanism for estrogen removal. However, treatment efficacy is highly variable and difficult to engineer due to the “black box” nature of biological treatment. Microbial strain selection is a critical impediment towards engineering estrogen biodegradation, since isolating endogenous strains with specific metabolic traits requires lengthy enrichment cultures and is limited to culturable organisms. Furthermore, the highly sensitive and selective chemical trace analysis techniques used to measure estrogen removal are relatively expensive and inefficient. In this thesis, we developed rapid, high-throughput spectroscopic methods designed to monitor estrogen biodegradation. The spectroscopic methods include a fluorometric assay based on the uptake of a fluorescently-labelled estrogen and a colorimetric biosensor using gold nanoparticles (AuNPs) and an aptamer bioreceptor. A synthetic microbial community comprised of characterised estrogen-degrading reference strains was used to evaluate the fitness for purpose of the developed methods. A trace analysis method using conventional chromatography was developed to validate the use of the fluorescent probes with the synthetic microbial community. The biochemical fate and distribution of the BODIPY-estrogen in the estrogen-degrading bacteria – specifically, the biotransformation of BODIPY-estradiol to BODIPY-estrone by Caenibius tardaugens – was used to inform the design of the fluorometric assay. The fluorometric assay utilises a cell impermeable halide quencher to suppress the extracellular fluorescence, and thus, the obtained fluorescence response was attributed to the selective internalisation of BODIPY-estrogen by C. tardaugens. While the fluorometric assay was developed to screen for estrogen-degrading bacteria, the colorimetric aptasensor, which was adapted from published AuNP biosensors and aptamers for this application, was developed to quantify 17ÎČ-estradiol (E2) in buffered culture media. The developed aptasensor was evaluated against industry guidelines for ligand-binding assays. While the analytical performance of the aptasensor satisfied the majority of the guidelines’ acceptance criteria, the method suffered from biological interferences by the estrogen-degrading bacteria. The work in this thesis contributes towards expanding the available bioanalytical methods in environmental biotechnology
    • 

    corecore