Hydroacoustic Analysis of the Effects of a Tidal Power Turbine on Fishes

Tidal currents help shape coastal marine environments and are essential in life cycles of many fish species. Areas with strong tidal currents are also targeted by humans for energy extraction via tidal energy turbines. The effects of these devices on fishes are difficult to predict because fish behavior within fast tidal currents is largely unstudied. Based at a tidal energy site in Cobscook Bay, Maine, this work sought to describe fish reactions to a tidal energy device, to understand the natural presence of fish at the site, and to provide guidance for future monitoring of tidal energy device effects in these difficult environments. A bottom-mounted echosounder was used to monitor the behavior of fish 7-18 m away from a stationary MHK device for several weeks. Fish moved with the current, but those approaching the device showed signs of avoiding it by adjusting their direction. The same echosounder was used to collect a two-year record of hourly fish passage rate at the depth of the turbine, after it had been removed. Fish passage rate, and therefore potential encounter rate with the turbine, changed dramatically over time with the dominant environmental patterns (tidal, daily, lunar, and seasonal cycles). By timing surveys of fish abundance at tidal energy sites with these cycles (e.g., carrying out 24-hr surveys at the same lunar stage throughout the year), the quality of results can be improved. Using this approach at tidal energy sites could therefore increase our ability to detect device effects without requiring expensive continuous sampling over a long time. Monitoring costs may be further reduced by using single beam echosounders, rather than the typical split beam systems, as statistical methods (deconvolution) were found to make certain single beam data comparable to that from the split beam. Depending on monitoring goals, the use of single beam echosounders could substantially reduce costs while supplying sufficient information on device effects for use in management decisions. Results from Cobscook Bay are likely to be useful at other tidal energy sites, but study designs and results need to be considered in the context of fish species and life stages present

Hydrokinetic Turbine Effects on Fish Swimming Behaviour

Hydrokinetic turbines, targeting the kinetic energy of fast-flowing currents, are under development with some turbines already deployed at ocean sites around the world. It remains virtually unknown as to how these technologies affect fish, and rotor collisions have been postulated as a major concern. In this study the effects of a vertical axis hydrokinetic rotor with rotational speeds up to 70 rpm were tested on the swimming patterns of naturally occurring fish in a subtropical tidal channel. Fish movements were recorded with and without the rotor in place. Results showed that no fish collided with the rotor and only a few specimens passed through rotor blades. Overall, fish reduced their movements through the area when the rotor was present. This deterrent effect on fish increased with current speed. Fish that passed the rotor avoided the near-field, about 0.3 m from the rotor for benthic reef fish. Large predatory fish were particularly cautious of the rotor and never moved closer than 1.7 m in current speeds above 0.6 ms-1. The effects of the rotor differed among taxa and feeding guilds and it is suggested that fish boldness and body shape influenced responses. In conclusion, the tested hydrokinetic turbine rotor proved non-hazardous to fish during the investigated conditions. However, the results indicate that arrays comprising multiple turbines may restrict fish movements, particularly for large species, with possible effects on habitat connectivity if migration routes are exploited. Arrays of the investigated turbine type and comparable systems should therefore be designed with gaps of several metres width to allow large fish to pass through. In combination with further research the insights from this study can be used for guiding the design of hydrokinetic turbine arrays where needed, so preventing ecological impacts

Effects of propulsion system operation on military aircraft survivability

The recent advances in infrared (IR) weapon technology have dramatically altered the rules of air combat, leading to a consistent departure from “traditional” energy-maneuverability philosophy in aircraft design, prioritizing stealth and sophisticated armament instead. In this modern aerial warfare environment, it is obvious that new techniques need to be applied to properly assess aircraft survivability and produce successful designs for aircraft propulsion systems. The present study focuses on the development of such a methodology, which contrary to related work in the field includes considerations for both aircraft IR signature and missile/aircraft kinematic performance. An aircraft IR signature model is constructed using a collection of methods for area and temperature estimation and exhaust plume modeling; the latter is combined with missile-vs-aircraft and aircraft-vs-aircraft simulations to quantify aircraft survivability in the form of missile and aircraft lethal zones. The proposed methodology is applied to a study on propulsion system effects on aircraft survivability, in which a comparison between different engine configurations is performed: In the scenarios examined, IR signature at cruise conditions and maximum-power thrust performance are identified as key parameters for aircraft combat performance

An overview of lidar imaging systems for autonomous vehicles

Lidar imaging systems are one of the hottest topics in the optronics industry. The need to sense the surroundings of every autonomous vehicle has pushed forward a race dedicated to deciding the final solution to be implemented. However, the diversity of state-of-the-art approaches to the solution brings a large uncertainty on the decision of the dominant final solution. Furthermore, the performance data of each approach often arise from different manufacturers and developers, which usually have some interest in the dispute. Within this paper, we intend to overcome the situation by providing an introductory, neutral overview of the technology linked to lidar imaging systems for autonomous vehicles, and its current state of development. We start with the main single-point measurement principles utilized, which then are combined with different imaging strategies, also described in the paper. An overview of the features of the light sources and photodetectors specific to lidar imaging systems most frequently used in practice is also presented. Finally, a brief section on pending issues for lidar development in autonomous vehicles has been included, in order to present some of the problems which still need to be solved before implementation may be considered as final. The reader is provided with a detailed bibliography containing both relevant books and state-of-the-art papers for further progress in the subject.Peer ReviewedPostprint (published version

Monitoring and Cordoning Wildfires with an Autonomous Swarm of Unmanned Aerial Vehicles

Unmanned aerial vehicles, or drones, are already an integral part of the equipment used by firefighters to monitor wildfires. They are, however, still typically used only as remotely operated, mobile sensing platforms under direct real-time control of a human pilot. Meanwhile, a substantial body of literature exists that emphasises the potential of autonomous drone swarms in various situational awareness missions, including in the context of environmental protection. In this paper, we present the results of a systematic investigation by means of numerical methods i.e., Monte Carlo simulation. We report our insights into the influence of key parameters such as fire propagation dynamics, surface area under observation and swarm size over the performance of an autonomous drone force operating without human supervision. We limit the use of drones to perform passive sensing operations with the goal to provide real-time situational awareness to the fire fighters on the ground. Therefore, the objective is defined as being able to locate, and then establish a continuous perimeter (cordon) around, a simulated fire event to provide live data feeds such as e.g., video or infra-red. Special emphasis was put on exclusively using simple, robust and realistically implementable distributed decision functions capable of supporting the self-organisation of the swarm in the pursuit of the collective goal. Our results confirm the presence of strong nonlinear effects in the interaction between the aforementioned parameters, which can be closely approximated using an empirical law. These findings could inform the mobilisation of adequate resources on a case-by-case basis, depending on known mission characteristics and acceptable odds (chances of success)

Multisensor acoustic tracking of fish and seabird behavior around tidal turbine structures in Scotland

Despite rapid development of marine renewable energy, relatively little is known of the immediate and future impacts on the surrounding ecosystems. Quantifying the behavior and distribution of animals around marine renewable energy devices is crucial for understanding, predicting, and potentially mitigating any threats posed by these installations. The Flow and Benthic Ecology 4D (FLOWBEC) autonomous seabed platform integrated an Imagenex multibeam echosounder and a Simrad EK60 multi-frequency echosounder to monitor marine life in a 120◦ sector over ranges up to 50 m, seven to eight times per second. Established target detection algorithms fail within MRE sites, due to high levels of backscatter generated by the turbulent physical dynamics, limiting and biasing analysis to only periods of low current speed. This study presents novel algorithms to extract diving seabirds, fish, and fish schools from the intense backscatter caused by turbulent dynamics in flows of 4ms−1. Filtering, detection, and tracking using a modified nearest neighbor algorithm provide robust tracking of animal behavior using the multibeam echosounder. Independent multifrequency target detection is demonstrated using the EK60 with optimally calculated thresholds, scale-sensitive filters, morphological exclusion, and frequency-response characteristics. This provides sensitive and reliable detection throughout the entire water column and at all flow speeds. Dive profiles, depth preferences, predator–prey interactions, and fish schooling behavior can be analyzed, in conjunction with the hydrodynamic impacts of marine renewable energy devices. Coregistration of targets between the acoustic instruments increases the information available, providing quantitative measures including frequency response from the EK60, and target morphology and behavioral interactions from the multibeam echosounder. The analyses draw on deployments at a tidal energy site in Scotland to compare the presence and absence of renewable energy structures across a range of physical and trophic levels over complete spring-neap tidal cycles. These results can be used to inform how animals forage in these sites and whether individuals face collision risks. This quantitative information can de-risk the licensing process and, with a greater mechanistic understanding at demonstration scales, its predictive power could reduce the monitoring required at future arrays

The role and regulation of CD1d in normal and pathological B cells

This work provides novel insights into the intersection between two critical areas of immunology, the CD1d-invariant NKT (iNKT) axis and B cells. CD1d is a non-polymorphic, MHC class I-like molecule, which presents phospho- and glycosphingo-lipid antigens to a subset of CD1d-restricted T cells called iNKT cells. CD1d is expressed on a variety of antigen presenting cells and the CD1d-iNKT cell axis regulates nearly all aspects of the innate and adaptive immune response. Expression of CD1d on B cells allows these cells to form cognate interactions with iNKT cells. Emerging evidence suggests, however, that expression of CD1d on B cells is variable, both on “normal” B cells during humoral immune responses, and also on “pathological” B cells in certain B cell disorders. In this work, I investigate in detail the expression of CD1d on B cells across a range of conditions. Using both human and murine germinal centre (GC) B cells as a model for normal B cells, I show for the first time that CD1d expression changes dynamically, both at the surface protein and transcriptional level. CD1d falls to a nadir as a naïve B cell enters the GC, and subsequently rises again in post GC B cells. I then provide evidence that the loss of CD1d expression is paralleled in pathological B cells, specifically in Epstein-Barr Virus infection of B cells and the plasma cell disorder Multiple Myeloma. In these conditions, CD1d is again downregulated at both the surface and transcriptional level. Having established that CD1d expression is lost in certain scenarios, I attempt to elucidate the biological significance of this downregulation. I approach this aim by attempting to constitutively express CD1d in murine GC B cells, and subsequently assessing the GC reaction. Constitutive expression of CD1d is achieved by two distinct methods, either by using adoptive transfer of Cd1d1 transduced haematopoietic stem cells or by using a CD1d transgenic mouse model. I show that both of these approaches represent a feasible way to constitutively express CD1d in murine GC B cells, but cannot establish a definitive biological role for CD1d downregulation in murine GC B cells. Finally, I investigate the transcriptional mechanisms governing the downregulation of CD1d, in either normal or pathological B cells. By analysing GC and MM B cells, I provide the first evidence that both retinoic acid signalling and bivalent chromatin domains act as a dual regulatory mechanism of CD1d. These findings demonstrate a new concept in the field of MM biology, specifically that MM B cells (like lymphomas) are able to “hijack” physiological pathways for disease propagation. Although previous work has highlighted the ability of all-trans retinoic acid (ATRA) alone to increase CD1d expression, this uncovering of a dual mechanism provides the rationale to use both ATRA and the polycomb-repressive complex inhibitor GSK343 to restore CD1d expression. I show that this is a more effective strategy than ATRA alone in increasing CD1d expression. Although this will need to be validated in further in vivo models, this ability to further increase CD1d expression may be of great therapeutic importance in the emerging field of tumour immunotherapy.Open Acces