16,459 research outputs found

    Key technologies for safe and autonomous drones

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    Drones/UAVs are able to perform air operations that are very difficult to be performed by manned aircrafts. In addition, drones' usage brings significant economic savings and environmental benefits, while reducing risks to human life. In this paper, we present key technologies that enable development of drone systems. The technologies are identified based on the usages of drones (driven by COMP4DRONES project use cases). These technologies are grouped into four categories: U-space capabilities, system functions, payloads, and tools. Also, we present the contributions of the COMP4DRONES project to improve existing technologies. These contributions aim to ease drones’ customization, and enable their safe operation.This project has received funding from the ECSEL Joint Undertaking (JU) under grant agreement No 826610. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and Spain, Austria, Belgium, Czech Republic, France, Italy, Latvia, Netherlands. The total project budget is 28,590,748.75 EUR (excluding ESIF partners), while the requested grant is 7,983,731.61 EUR to ECSEL JU, and 8,874,523.84 EUR of National and ESIF Funding. The project has been started on 1st October 2019

    Quantum dots based superluminescent diodes and photonic crystal surface emitting lasers

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    This thesis reports the design, fabrication, and electrical and optical characterisations of GaAs-based quantum dot (QD) photonic devices, specifically focusing on superluminescent diodes (SLDs) and photonic crystal surface-emitting lasers (PCSELs). The integration of QD active regions in these devices is advantageous due to their characteristics such as temperature insensitivity, feedback insensitivity, and ability to utilise the ground state (GS) and excited state (ES) of the dots. In an initial study concerning the fabrication of QD-SLDs, the influence of ridge waveguide etch depth on the electrical and optical properties of the devices are investigated. It is shown that the output power and modal gain from shallow etched ridge waveguide is higher than those of deep etched waveguides. Subsequently, the thermal performance of the devices is analysed. With increased temperature over 170 ÂșC, the spectral bandwidth is dramatically increased by thermally excited carrier transition in excited states of the dots. Following this, an investigation of a high dot density hybrid quantum well/ quantum dot (QW/QD) active structure for broadband, high-modal gain SLDs is presented. The influence of the number of QD layers on the modal gain of hybrid QW/QD structures is analysed. It is shown that higher number of dot layer provides higher modal gain value, however, there is lack of emission from QW due to the requirement of large number of carriers to saturate the QD. Additionally, a comparison is made between “unchirped QD” and “ chirped QD” of hybrid QW/QD structure in terms of modal gain and spectral bandwidth. It is showed that “chirped” of the QD can improve the “flatness” of the spectral bandwidth. Lastly, the use of self-assembled InAs QD as the active material in epitaxially regrown GaAs-based PCSELs is explored for the first time. Initially, it is shown that both GS and ES lasing can be achieved for QD-PCSELs by changing the grating period of the photonic crystal (PC). The careful design of these grating periods allows lasing from neighbouring devices at GS ( ~1230 nm) and ES (~1140 nm), 90 nm apart in wavelength. Following this, the effect of device area, PC etch depth, PC atom shape (circle or triangle or orientation) on lasing performance is presented. It is shown that lower threshold current density and higher slope efficiencies is achieved with increasing the device size. The deeper PC height device has higher output power due to more suitable height and minimal distance to active region. The triangular atom shape has slightly higher slope efficiency compared to triangular atom shape which is attributed to breaking in-plane symmetry and increase out-of-plane emission

    A direct-laser-written heart-on-a-chip platform for generation and stimulation of engineered heart tissues

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    In this dissertation, we first develop a versatile microfluidic heart-on-a-chip model to generate 3D-engineered human cardiac microtissues in highly-controlled microenvironments. The platform, which is enabled by direct laser writing (DLW), has tailor-made attachment sites for cardiac microtissues and comes with integrated strain actuators and force sensors. Application of external pressure waves to the platform results in controllable time-dependent forces on the microtissues. Conversely, oscillatory forces generated by the microtissues are transduced into measurable electrical outputs. After characterization of the responsivity of the transducers, we demonstrate the capabilities of this platform by studying the response of cardiac microtissues to prescribed mechanical loading and pacing. Next, we tune the geometry and mechanical properties of the platform to enable parametric studies on engineered heart tissues. We explore two geometries: a rectangular seeding well with two attachment sites, and a stadium-like seeding well with six attachment sites. The attachment sites are placed symmetrically in the longitudinal direction. The former geometry promotes uniaxial contraction of the tissues; the latter additionally induces diagonal fiber alignment. We systematically increase the length for both configurations and observe a positive correlation between fiber alignment at the center of the microtissues and tissue length. However, progressive thinning and “necking” is also observed, leading to the failure of longer tissues over time. We use the DLW technique to improve the platform, softening the mechanical environment and optimizing the attachment sites for generation of stable microtissues at each length and geometry. Furthermore, electrical pacing is incorporated into the platform to evaluate the functional dynamics of stable microtissues over the entire range of physiological heart rates. Here, we typically observe a decrease in active force and contraction duration as a function of frequency. Lastly, we use a more traditional ?TUG platform to demonstrate the effects of subthreshold electrical pacing on the rhythm of the spontaneously contracting cardiac microtissues. Here, we observe periodic M:N patterns, in which there are ? cycles of stimulation for every ? tissue contractions. Using electric field amplitude, pacing frequency, and homeostatic beating frequencies of the tissues, we provide an empirical map for predicting the emergence of these rhythms

    Review of Methodologies to Assess Bridge Safety During and After Floods

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    This report summarizes a review of technologies used to monitor bridge scour with an emphasis on techniques appropriate for testing during and immediately after design flood conditions. The goal of this study is to identify potential technologies and strategies for Illinois Department of Transportation that may be used to enhance the reliability of bridge safety monitoring during floods from local to state levels. The research team conducted a literature review of technologies that have been explored by state departments of transportation (DOTs) and national agencies as well as state-of-the-art technologies that have not been extensively employed by DOTs. This review included informational interviews with representatives from DOTs and relevant industry organizations. Recommendations include considering (1) acquisition of tethered kneeboard or surf ski-mounted single-beam sonars for rapid deployment by local agencies, (2) acquisition of remote-controlled vessels mounted with single-beam and side-scan sonars for statewide deployment, (3) development of large-scale particle image velocimetry systems using remote-controlled drones for stream velocity and direction measurement during floods, (4) physical modeling to develop Illinois-specific hydrodynamic loading coefficients for Illinois bridges during flood conditions, and (5) development of holistic risk-based bridge assessment tools that incorporate structural, geotechnical, hydraulic, and scour measurements to provide rapid feedback for bridge closure decisions.IDOT-R27-SP50Ope

    Investigation of microparticle behavior in Newtonian, viscoelastic, and shear-thickening flows in straight microchannels

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    Sorting and separation of small substances such as cells, microorganisms, and micro- and nano-particles from a heterogeneous mixture is a common sample preparation step in many areas of biology, biotechnology, and medicine. Portability and inexpensive design of microfluidic-based sorting systems have benefited many of these biomedical applications. Accordingly, we have investigated microparticle hydrodynamics in fluids with various rheological behaviors (i.e., Newtonian, shear-thinning viscoelastic and shear-thickening non-Newtonian) flowing in straight microchannels. Numerical models were developed to simulate particles trajectories in Newtonian water and shear-thinning polyethylene oxide (PEO) solutions. The validated models were then used to perform numerical parametric studies and non-dimensional analysis on the Newtonian inertia-magnetic and shear-thinning elasto-inertal focusing regimes. Finally, the straight microfluidic device that was tested for Newtonian water and shear-thinning viscoelastic PEO solution, were adopted to experimentally study microparticle behavior in SiO2/Water shear-thickening nanofluid

    Underwater optical wireless communications in turbulent conditions: from simulation to experimentation

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    Underwater optical wireless communication (UOWC) is a technology that aims to apply high speed optical wireless communication (OWC) techniques to the underwater channel. UOWC has the potential to provide high speed links over relatively short distances as part of a hybrid underwater network, along with radio frequency (RF) and underwater acoustic communications (UAC) technologies. However, there are some difficulties involved in developing a reliable UOWC link, namely, the complexity of the channel. The main focus throughout this thesis is to develop a greater understanding of the effects of the UOWC channel, especially underwater turbulence. This understanding is developed from basic theory through to simulation and experimental studies in order to gain a holistic understanding of turbulence in the UOWC channel. This thesis first presents a method of modelling optical underwater turbulence through simulation that allows it to be examined in conjunction with absorption and scattering. In a stationary channel, this turbulence induced scattering is shown to cause and increase both spatial and temporal spreading at the receiver plane. It is also demonstrated using the technique presented that the relative impact of turbulence on a received signal is lower in a highly scattering channel, showing an in-built resilience of these channels. Received intensity distributions are presented confirming that fluctuations in received power from this method follow the commonly used Log-Normal fading model. The impact of turbulence - as measured using this new modelling framework - on link performance, in terms of maximum achievable data rate and bit error rate is equally investigated. Following that, experimental studies comparing both the relative impact of turbulence induced scattering on coherent and non-coherent light propagating through water and the relative impact of turbulence in different water conditions are presented. It is shown that the scintillation index increases with increasing temperature inhomogeneity in the underwater channel. These results indicate that a light beam from a non-coherent source has a greater resilience to temperature inhomogeneity induced turbulence effect in an underwater channel. These results will help researchers in simulating realistic channel conditions when modelling a light emitting diode (LED) based intensity modulation with direct detection (IM/DD) UOWC link. Finally, a comparison of different modulation schemes in still and turbulent water conditions is presented. Using an underwater channel emulator, it is shown that pulse position modulation (PPM) and subcarrier intensity modulation (SIM) have an inherent resilience to turbulence induced fading with SIM achieving higher data rates under all conditions. The signal processing technique termed pair-wise coding (PWC) is applied to SIM in underwater optical wireless communications for the first time. The performance of PWC is compared with the, state-of-the-art, bit and power loading optimisation algorithm. Using PWC, a maximum data rate of 5.2 Gbps is achieved in still water conditions

    Cost-effective non-destructive testing of biomedical components fabricated using additive manufacturing

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    Biocompatible titanium-alloys can be used to fabricate patient-specific medical components using additive manufacturing (AM). These novel components have the potential to improve clinical outcomes in various medical scenarios. However, AM introduces stability and repeatability concerns, which are potential roadblocks for its widespread use in the medical sector. Micro-CT imaging for non-destructive testing (NDT) is an effective solution for post-manufacturing quality control of these components. Unfortunately, current micro-CT NDT scanners require expensive infrastructure and hardware, which translates into prohibitively expensive routine NDT. Furthermore, the limited dynamic-range of these scanners can cause severe image artifacts that may compromise the diagnostic value of the non-destructive test. Finally, the cone-beam geometry of these scanners makes them susceptible to the adverse effects of scattered radiation, which is another source of artifacts in micro-CT imaging. In this work, we describe the design, fabrication, and implementation of a dedicated, cost-effective micro-CT scanner for NDT of AM-fabricated biomedical components. Our scanner reduces the limitations of costly image-based NDT by optimizing the scanner\u27s geometry and the image acquisition hardware (i.e., X-ray source and detector). Additionally, we describe two novel techniques to reduce image artifacts caused by photon-starvation and scatter radiation in cone-beam micro-CT imaging. Our cost-effective scanner was designed to match the image requirements of medium-size titanium-alloy medical components. We optimized the image acquisition hardware by using an 80 kVp low-cost portable X-ray unit and developing a low-cost lens-coupled X-ray detector. Image artifacts caused by photon-starvation were reduced by implementing dual-exposure high-dynamic-range radiography. For scatter mitigation, we describe the design, manufacturing, and testing of a large-area, highly-focused, two-dimensional, anti-scatter grid. Our results demonstrate that cost-effective NDT using low-cost equipment is feasible for medium-sized, titanium-alloy, AM-fabricated medical components. Our proposed high-dynamic-range strategy improved by 37% the penetration capabilities of an 80 kVp micro-CT imaging system for a total x-ray path length of 19.8 mm. Finally, our novel anti-scatter grid provided a 65% improvement in CT number accuracy and a 48% improvement in low-contrast visualization. Our proposed cost-effective scanner and artifact reduction strategies have the potential to improve patient care by accelerating the widespread use of patient-specific, bio-compatible, AM-manufactured, medical components

    Interference mitigation in LiFi networks

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    Due to the increasing demand for wireless data, the radio frequency (RF) spectrum has become a very limited resource. Alternative approaches are under investigation to support the future growth in data traffic and next-generation high-speed wireless communication systems. Techniques such as massive multiple-input multiple-output (MIMO), millimeter wave (mmWave) communications and light-fidelity (LiFi) are being explored. Among these technologies, LiFi is a novel bi-directional, high-speed and fully networked wireless communication technology. However, inter-cell interference (ICI) can significantly restrict the system performance of LiFi attocell networks. This thesis focuses on interference mitigation in LiFi attocell networks. The angle diversity receiver (ADR) is one solution to address the issue of ICI as well as frequency reuse in LiFi attocell networks. With the property of high concentration gain and narrow field of view (FOV), the ADR is very beneficial for interference mitigation. However, the optimum structure of the ADR has not been investigated. This motivates us to propose the optimum structures for the ADRs in order to fully exploit the performance gain. The impact of random device orientation and diffuse link signal propagation are taken into consideration. The performance comparison between the select best combining (SBC) and maximum ratio combining (MRC) is carried out under different noise levels. In addition, the double source (DS) system, where each LiFi access point (AP) consists of two sources transmitting the same information signals but with opposite polarity, is proven to outperform the single source (SS) system under certain conditions. Then, to overcome issues around ICI, random device orientation and link blockage, hybrid LiFi/WiFi networks (HLWNs) are considered. In this thesis, dynamic load balancing (LB) considering handover in HLWNs is studied. The orientation-based random waypoint (ORWP) mobility model is considered to provide a more realistic framework to evaluate the performance of HLWNs. Based on the low-pass filtering effect of the LiFi channel, we firstly propose an orthogonal frequency division multiple access (OFDMA)-based resource allocation (RA) method in LiFi systems. Also, an enhanced evolutionary game theory (EGT)-based LB scheme with handover in HLWNs is proposed. Finally, due to the characteristic of high directivity and narrow beams, a vertical-cavity surface-emitting laser (VCSEL) array transmission system has been proposed to mitigate ICI. In order to support mobile users, two beam activation methods are proposed. The beam activation based on the corner-cube retroreflector (CCR) can achieve low power consumption and almost-zero delay, allowing real-time beam activation for high-speed users. The mechanism based on the omnidirectional transmitter (ODTx) is suitable for low-speed users and very robust to random orientation

    Statistical Learning for Gene Expression Biomarker Detection in Neurodegenerative Diseases

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    In this work, statistical learning approaches are used to detect biomarkers for neurodegenerative diseases (NDs). NDs are becoming increasingly prevalent as populations age, making understanding of disease and identification of biomarkers progressively important for facilitating early diagnosis and the screening of individuals for clinical trials. Advancements in gene expression profiling has enabled the exploration of disease biomarkers at an unprecedented scale. The work presented here demonstrates the value of gene expression data in understanding the underlying processes and detection of biomarkers of NDs. The value of novel approaches to previously collected -omics data is shown and it is demonstrated that new therapeutic targets can be identified. Additionally, the importance of meta-analysis to improve power of multiple small studies is demonstrated. The value of blood transcriptomics data is shown in applications to researching NDs to understand underlying processes using network analysis and a novel hub detection method. Finally, after demonstrating the value of blood gene expression data for investigating NDs, a combination of feature selection and classification algorithms were used to identify novel accurate biomarker signatures for the diagnosis and prognosis of Parkinson’s disease (PD) and Alzheimer’s disease (AD). Additionally, the use of feature pools based on previous knowledge of disease and the viability of neural networks in dimensionality reduction and biomarker detection is demonstrated and discussed. In summary, gene expression data is shown to be valuable for the investigation of ND and novel gene biomarker signatures for the diagnosis and prognosis of PD and AD
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