Circuit Techniques for Low-Power and Secure Internet-of-Things Systems

The coming of Internet of Things (IoT) is expected to connect the physical world to the cyber world through ubiquitous sensors, actuators and computers. The nature of these applications demand long battery life and strong data security. To connect billions of things in the world, the hardware platform for IoT systems must be optimized towards low power consumption, high energy efficiency and low cost. With these constraints, the security of IoT systems become a even more difficult problem compared to that of computer systems. A new holistic system design considering both hardware and software implementations is demanded to face these new challenges. In this work, highly robust and low-cost true random number generators (TRNGs) and physically unclonable functions (PUFs) are designed and implemented as security primitives for secret key management in IoT systems. They provide three critical functions for crypto systems including runtime secret key generation, secure key storage and lightweight device authentication. To achieve robustness and simplicity, the concept of frequency collapse in multi-mode oscillator is proposed, which can effectively amplify the desired random variable in CMOS devices (i.e. process variation or noise) and provide a runtime monitor of the output quality. A TRNG with self-tuning loop to achieve robust operation across -40 to 120 degree Celsius and 0.6 to 1V variations, a TRNG that can be fully synthesized with only standard cells and commercial placement and routing tools, and a PUF with runtime filtering to achieve robust authentication, are designed based upon this concept and verified in several CMOS technology nodes. In addition, a 2-transistor sub-threshold amplifier based "weak" PUF is also presented for chip identification and key storage. This PUF achieves state-of-the-art 1.65% native unstable bit, 1.5fJ per bit energy efficiency, and 3.16% flipping bits across -40 to 120 degree Celsius range at the same time, while occupying only 553 feature size square area in 180nm CMOS. Secondly, the potential security threats of hardware Trojan is investigated and a new Trojan attack using analog behavior of digital processors is proposed as the first stealthy and controllable fabrication-time hardware attack. Hardware Trojan is an emerging concern about globalization of semiconductor supply chain, which can result in catastrophic attacks that are extremely difficult to find and protect against. Hardware Trojans proposed in previous works are based on either design-time code injection to hardware description language or fabrication-time modification of processing steps. There have been defenses developed for both types of attacks. A third type of attack that combines the benefits of logical stealthy and controllability in design-time attacks and physical "invisibility" is proposed in this work that crosses the analog and digital domains. The attack eludes activation by a diverse set of benchmarks and evades known defenses. Lastly, in addition to security-related circuits, physical sensors are also studied as fundamental building blocks of IoT systems in this work. Temperature sensing is one of the most desired functions for a wide range of IoT applications. A sub-threshold oscillator based digital temperature sensor utilizing the exponential temperature dependence of sub-threshold current is proposed and implemented. In 180nm CMOS, it achieves 0.22/0.19K inaccuracy and 73mK noise-limited resolution with only 8865 square micrometer additional area and 75nW extra power consumption to an existing IoT system.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138779/1/kaiyuan_1.pd

Noncontact Seismocardiogram Signal Detection Using Microwave Doppler Radar

The objective of the research is to achieve non-contact detection of seismocardiogram (SCG), a representation of mechanical heart motion, using microwave Doppler radar system. The increase in demand for health monitoring requires robust, reliable, and accurate remote detection of cardiac signals. Due to its ability to penetrate non-metal obstacles, microwave Doppler radar is promising to provide a non-contact and unobtrusive measurement. In this dissertation, both the hardware system and the signal processing approaches are developed for providing an accurate and reliable measurement of cardiac signals using the microwave Doppler radar. First, a noise suppression scheme and a clutter removal strategy are investigated to improve the performance of a microwave Doppler radar system. Then, an investigation is conducted to demonstrate the effectiveness of using a radar signal to represent SCG, and a standalone method is developed to extract the SCG features from the radar signal without using a contact electrocardiogram (ECG) signal that the conventional methods rely on. With the development of the hardware system and signal processing approaches, the complete non-contact measurement and analysis of cardiac signals can be achieved.Ph.D

A Phase-Locked Loop in High-Temperature Silicon Carbide and General Design Methods for Silicon Carbide Integrated Circuits

Silicon carbide (SiC) has long been considered for integrated circuits (ICs). It offers several advantages, including wider temperature range, larger critical electric field, and greater radiation immunity with respect to Silicon (Si). At the same time, it suffers from challenges in fabrication consistency and lower transconductance which the designer must overcome. One of the recent SiC IC processes developed is the Raytheon High-Temperature Silicon Carbide (HTSiC) complementary MOSFET process. This process is one of the first to offer P channel MOSFETs and, as a result, a greater variety of circuits can be built in it. The behavior of SiC MOSFETs has some important differences with Si MOSFETs. Models such as the Shichman-Hodges, EKV, and Short-channel models have been developed over time to address the important behaviors observed in Si MOSFETs, but none of these captures all of the important effects in SiC. In this work, an improved Shichman-Hodges model that incorporates the body-charge effect, mobility reduction, and a nonlinear channel modulation is developed for SiC CMOS IC devices. The importance of considering these effects is demonstrated with a simple design exercise. This dissertation also describes the design and testing of the first-ever phase-locked loop (PLL) in SiC. This PLL is suitable for use as a general circuit building block such as in a clock recovery circuit. The fabricated circuit operates between 600 kHz and 1.5 MHz, and at temperatures up to 300 ℃. Testing results also show that output jitter and locking are negatively impacted at higher temperatures, and an improved design is proposed and analyzed

Convolutional Analysis Operator Learning: Acceleration and Convergence

Convolutional operator learning is gaining attention in many signal processing and computer vision applications. Learning kernels has mostly relied on so-called patch-domain approaches that extract and store many overlapping patches across training signals. Due to memory demands, patch-domain methods have limitations when learning kernels from large datasets -- particularly with multi-layered structures, e.g., convolutional neural networks -- or when applying the learned kernels to high-dimensional signal recovery problems. The so-called convolution approach does not store many overlapping patches, and thus overcomes the memory problems particularly with careful algorithmic designs; it has been studied within the "synthesis" signal model, e.g., convolutional dictionary learning. This paper proposes a new convolutional analysis operator learning (CAOL) framework that learns an analysis sparsifying regularizer with the convolution perspective, and develops a new convergent Block Proximal Extrapolated Gradient method using a Majorizer (BPEG-M) to solve the corresponding block multi-nonconvex problems. To learn diverse filters within the CAOL framework, this paper introduces an orthogonality constraint that enforces a tight-frame filter condition, and a regularizer that promotes diversity between filters. Numerical experiments show that, with sharp majorizers, BPEG-M significantly accelerates the CAOL convergence rate compared to the state-of-the-art block proximal gradient (BPG) method. Numerical experiments for sparse-view computational tomography show that a convolutional sparsifying regularizer learned via CAOL significantly improves reconstruction quality compared to a conventional edge-preserving regularizer. Using more and wider kernels in a learned regularizer better preserves edges in reconstructed images.Comment: 22 pages, 11 figures, fixed incorrect math theorem numbers in fig.

Radiation Hardened by Design Methodologies for Soft-Error Mitigated Digital Architectures

abstract: Digital architectures for data encryption, processing, clock synthesis, data transfer, etc. are susceptible to radiation induced soft errors due to charge collection in complementary metal oxide semiconductor (CMOS) integrated circuits (ICs). Radiation hardening by design (RHBD) techniques such as double modular redundancy (DMR) and triple modular redundancy (TMR) are used for error detection and correction respectively in such architectures. Multiple node charge collection (MNCC) causes domain crossing errors (DCE) which can render the redundancy ineffectual. This dissertation describes techniques to ensure DCE mitigation with statistical confidence for various designs. Both sequential and combinatorial logic are separated using these custom and computer aided design (CAD) methodologies. Radiation vulnerability and design overhead are studied on VLSI sub-systems including an advanced encryption standard (AES) which is DCE mitigated using module level coarse separation on a 90-nm process with 99.999% DCE mitigation. A radiation hardened microprocessor (HERMES2) is implemented in both 90-nm and 55-nm technologies with an interleaved separation methodology with 99.99% DCE mitigation while achieving 4.9% increased cell density, 28.5 % reduced routing and 5.6% reduced power dissipation over the module fences implementation. A DMR register-file (RF) is implemented in 55 nm process and used in the HERMES2 microprocessor. The RF array custom design and the decoders APR designed are explored with a focus on design cycle time. Quality of results (QOR) is studied from power, performance, area and reliability (PPAR) perspective to ascertain the improvement over other design techniques. A radiation hardened all-digital multiplying pulsed digital delay line (DDL) is designed for double data rate (DDR2/3) applications for data eye centering during high speed off-chip data transfer. The effect of noise, radiation particle strikes and statistical variation on the designed DDL are studied in detail. The design achieves the best in class 22.4 ps peak-to-peak jitter, 100-850 MHz range at 14 pJ/cycle energy consumption. Vulnerability of the non-hardened design is characterized and portions of the redundant DDL are separated in custom and auto-place and route (APR). Thus, a range of designs for mission critical applications are implemented using methodologies proposed in this work and their potential PPAR benefits explored in detail.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Biology of the razor clam (Ensis magnus Schacher, 1817), in the Ría de Pontevedra (NW Spais): application to fishery management

Small-scale or artisanal fisheries produce nearly half of the world¿s catch and employ 50 million of the 51 million people engaged in fisheries (FAO 2008). However, most scientific studies have focused on the analysis of industrial fisheries, and little attention has been given to small-scale fisheries. Bivalves are among the most important resources in S-fisheries (Small-Scale and Spatially Structured fisheries targeting Sedentary resources with artisanal gears, Orensanz et al., 2005a) worldwide (landings around 3 million t, FAO 2013) and some species have high commercial value in international markets, represent substantial food resources and play important economic and social roles. Razor clams (Bivalvia, Solenoidea) are distributed throughout the world, in the Pacific, the Atlantic and the Mediterranean Sea ranging from tropical to temperate areas inhabiting fine sand, silt or sandy-mud ocean floors (Hayward and Ryland, 1998). These species represent a substantial food resource that has experienced a considerable economic valuation development during the last decade. The species most commonly commercialized are Ensis magnus Schumacher, 1817 [syn. E. arcuatus (Jeffreys, 1865)], E. siliqua (Linnaeus, 1758) and E. directus (Conrad, 1843). The sword razor E. magnus is the razor clam with the highest commercial value in European markets (according to the Eurostat information database) and the most important commercial species of razor clam in Spain. Within Spain E. magnus is mainly exploited in Galicia (NW Spain). The increasing demand and the new capture methods introduced in some regions during the last decades (hydraulic and suction dredging or electrical fishing) leaded to sudden increases of landings and subsequently several razor clams beds showed signs of overexploitation (Hall et al., 1990; Fahy and Carroll, 2007; Hauton et al., 2007; Espinoza et al., 2010, FAO 2015). This situation is enhanced by the recruitment variability (del Piero and Dacaprile, 1998; Szarzi et al., 1995) and the slow turnover of the species (Fahy and Carroll, 2007). Although the Galician razor clams beds are harvested manually by diving with a very selective method, they have also been more heavily exploited in the last years, being their maximum sustainable fishing rate still unknown though. Moreover, in winter, coinciding with reproductive season (Darriba et al., 2004) up to 40% of sword razor specimens break at the foot when harvested, and must be discarded, as they are not marketable. To avoid the sword razor discards, the harvest is totally closed for one-two months during winter. This market shortage is overcome by the importation of razor clams mainly from Argentina and Chile, which are less than a third of the price of the local product. Together with the Spanish economic crisis, this has generated a 50% fall in the market price of the local product. Knowledge of marine resources biology is essential for fisheries management. Although a great effort has been conducted to study E. magnus biology during the last two decades (e.g. Robinson and Richardson, 1998; Fahy et al., 2002; Darriba et al., 2004, 2005a, 2010; da Costa et al., 2008, 2011, 2013; Varela et al., 2009; Ruiz et al., 2011, 2012), some important biological information for fisheries management such as growth parameters or size at first maturity has been little studied. Indeed, none of these features were previously described for the species in the Iberian Peninsula. Moreover, razor clams, which like many other benthic organisms are sedentary, inhabit spatially heterogeneous environments and are distributed in dispersed beds, which generate a spatial variability in their population dynamics between near areas (eg. Robinson and Richardson, 1998; Rabaoui et al., 2007). This variability could even happen within a small spatial range like the Galician rias. This fact complicates the assessment, as reported for other S-fisheries (Cochrane, 1999; Walters and Pearse, 1996; Wilson et al., 2010). Thus, biological studies of the population dynamics need to take into account the spatial variability of this species. Many authors have pointed out that simple assessment and management procedures are needed for small-scale fisheries management. These procedures should be based on indicators determined directly by the catch/landings data or by simple surveys by actively involving fishers (e.g. Orensanz et al., 2005a,b; Prince, 2010). Moreover, S-fisheries need simple local tools to enable adaptive and flexible management that takes into account biological and social aspects (Parada et al., 2012; Prince, 2010; Macho et al., 2013). In Galicia, S-fisheries operate under a co-management system, based on territorial user rights for fishing (TURFs) between cofradías (local fishers¿ guilds) and the fisheries administration (Molares and Freire 2003, Macho et al 2013). These entities cooperate for developing and implementing the annual management plans with the help of a Technical Assistant, an on-site fisheries advisor who design the fisheries management plans according to the status of the resources (Macho et al, 2013). The adaptive character of the management plans allows including the aforementioned simple tools and procedures in daily harvesting strategies (Molares and Freire, 2003; Macho et al., 2013; Parada and Molares, 2013). Of the 26 razor clam harvesting plans in Galicia, which involve a total of 35 cofradías, we have selected as case of study the one developed for E. magnus in the Ría de Pontevedra as a result of the fishers and Technical Assistant demand for biological methods and simple management tools that contributes to the fishery sustainability. Moreover, this razor clam harvesting plan is one of the most productive in Galicia, with landings that accounted for 78 t in 2014, worth ~ 0.52 million € (www.pescadegalicia.com). The Ría de Pontevedra is a partially mixed estuary with a mesotidal and semidiurnal regime located NW of the Iberian Peninsula, at the northern limit of the North Atlantic upwelling system (Wooster et al., 1976). It is a large (25 km long) V-shaped indentation in the coast that gradually widen from the innermost area to the open sea (4 - 12 km wide). According to many studies (e.g. Dale and Prego, 2002) the ria is divided into three well defined zones determined by the presence of the Lérez River, water stratification and topography: the innermost zone, strongly influenced by the Lérez River; the outer zone which has a strong oceanic influence, and the intermediate zone. The sword razor fishery of the Ría de Pontevedra is managed as a joint harvesting plan agreed between seven cofradías of the ria. Exploitation is organized through a rotational harvesting strategy in which six areas are exploited, with a close season of two months during the peak reproductive season (February-March, Darriba et al., 2004) (www.pescadegalicia.com). We selected our sampling sites taking into account the oceanographic divisions of the ria and the exploitation areas of the management plan. In this context, this PhD dissertation aims to support the E. magnus fishery management by studying the spatial heterogeneity in reproduction and growth of the species in the Ría de Pontevedra in order to promote a biologically informed harvesting strategy. We have focused in the main biological aspects that determine the dynamic of the species and that represent the most important features for fishery management: 1) reproduction, essential for the establishment of the close season or the commercial size, and 2) growth, necessary to know the age at which individuals become part of the exploited biomass or to determine how populations respond to exploitation. Both biological features are also fundamental for stablishing the harvesting rotational scheme, a key factor in the management of this fishery. This work was done in close collaboration with the TA and the fishers involved in the management plan. The main objective of the reproductive cycle study is to adapt the rotational harvesting strategy and the close season to the differences of the gonadal cycle development along the ria. This would avoid the foot breakage if its relationship with gonad maturation is confirmed. The study also aims to investigate the relation of the reproductive cycle to the main environmental variables and to estimate the size at first maturity (defined as the length at which 50% of the population is mature, L50). Gametogenic development of E. magnus was studied in six shellfish beds of the Ría de Pontevedra (one in each exploitation area) during two years. Study sites were distributed from the innermost to the outermost part of the ria being separated from each other no more than 15 km. To determine L50, additional razor clams were collected at the innermost part of the ria, where the smallest individuals were found. Results showed that the sword razor started to mature between 60 and 70 mm, reaching L50 at 79.5 mm and L95 at 110 mm, although the observed data confirmed that 100% of the sampled individuals were mature between 100 and 105 mm. This result is in accordance with that obtained in Scotland (Muir and Moore, 2003). The reproductive cycle was characterized by a resting stage during summer and early autumn, initiation of gametogenesis in autumn and a period of successive spawning interspersed with gonad recovery during winter and spring, as previously observed in the Ría de Vigo (Darriba et al., 2004). However, a 15-day to one-month delay in advanced stages of gametogenesis and maturation was observed between the inner and the outermost site of the ria, as well as an extended spawning period in the outermost area. Lower bottom seawater temperatures at the outermost sites appeared to delay maturation and to prolong the spawning periods, whereas salinity fluctuations at the innermost sites appeared to reduce the length of the cycle. Both results are in agreement with the previously reported for E. magnus (Darriba et al., 2004, 2005a) and other species of the Superfamily Solenoidea (Cross et al., 2014; López et al., 2005). Finally, the highest foot breakage was observed throughout winter, during maturity, postspawning and gonad recovery stages, confirming the relationship between foot breakage and gonadal development. In view of these results, and after explaining them to the sector, the razor clam fishery in the Ría de Pontevedra adapted the rotation harvesting scheme and the close period to the gonadal cycle. Nevertheless, the gametogenic cycle may differ from year to year influenced by environmental factors, making impossible to apply the same schemes every year. In order to provide a simple tool that enables adaptation of the exploitation to the gonadal stage of the resource, we develop two rapid, simple and inexpensive methods that provide accurate information about the gonadal stage of E. magnus: percentage coverage of the gonad on and over the digestive gland (gonad coverage hereinafter) and examination of the gonad smear. Although similar gonad coverage scales were established before for other razor clams (Aracena et al., 2003; Remacha-Triviño and Anadón, 2006), no gonad smear scale was previously developed for razor clams. Both methods were validated with most accurate and precise histological and gonadal index methods, to construct a correspondence table between all methods. The correspondence table constitutes a simple tool that can be used in any razor clam fishery to monitor the gonad development stage in order to minimize the discards by foot breakage, caused by extension of the gonad into the foot during maturity and the spawning period, and to allow higher numbers of spawning individuals in the bed. This table can be also used to shorten the close season in the fishery by adapting the rotational scheme, thus helping to avoid market shortages and reduce the need to import razor clams. Modelling growth is required in many ecological studies and stock assessment applications (Quinn and Deriso, 1999). The age estimation method and the growth model used should be chosen with caution since uncertainties in age estimates lead to uncertainties in management. From the different methods that can be used to estimate the age of razor clams (measurement of growth during culture, length-frequency distribution analyses, examination of shell cross sections by light microscopy, counting surface growth rings, analysis of the internal growth rings by acetate peels, etc.) we selected the culture method to follow the growth of E. magnus early stages (from larvae to juveniles of ~1.5 years old) and the analysis of internal growth rings by the acetate peel method (Richardson et al. 1979) to determine the age and growth of E. magnus population, as it has been described as the most suitable method to ageing razor clams (e.g. Gaspar et al. 1994). We also used the simplest one (counting of surface growth rings by the naked eye and under binocular microscope) to test the possibility of using it as an easy management tool in other exploitation areas. Most marine bivalves exhibit different growth patterns depending on the stage of their life history (Urban, 2002) and consequently different mathematical models must be used. To our knowledge, larval and postlarval growth was never modelled for any razor clam whereas adult growth was always modelled assuming annual growth rings. Besides, usually bivalve growth studies do not evaluate different growth models but they use the von Bertalanffy growth model as default without testing their fitness, which has long been criticized (e.g. Cailliet et al., 2006; Katsanevakis, 2007). Even more, these studies neither consider the growth seasonal variation nor incorporate the influence of environmental variables on growth. The objectives of the growth study in the present PhD dissertation are: to describe with precision the early stages of E. magnus growth cultured on its optimal habitat; to provide sword razor growth parameters; to evaluate the growth variability at mesoscale and the influence of environmental variables on growth and, finally, to test the fitness of different growth models (Logistic, Gompertz, von Bertalanffy and Richards) for each developmental stage. Larval and postlarval culture was conducted in the Estación de Ciencias Mariñas de Toralla (ECIMAT, Universidade de Vigo) while juvenile growth were carried out in a subtidal bed of E. magnus in the Ría de Vigo (SW Galicia) because of the proximity to the ECIMAT. The growth and age study was conducted in three fishing beds of the Ría de Pontevedra in each oceanographic zone of the ria. E. magnus larval and postlarval growth results agreed with those reported by da Costa et al. (2008, 2011). Thus, larvae grew linearly at 10 µm day-1 reaching 250 µm 20 days after fertilisation, when settlement started, while postlarvae grew slowly (length increment, ¿L = 0.04 mm day-1) during the first 10 days after settlement, fast during the next month (¿L = 0.34 µm day-1) and finally declined (¿L = 0.21 µm day-1) in the last month of culture, reaching 750 µm after one month of fertilisation, 10.5 mm at two months old and 25 mm at three months old. Larval growth followed a linear function while postlarval growth was sigmoidal and thereby adequately represented by the Richards model. By contrast, E. magnus juveniles seeded on subtidal bed of the Ría de Vigo showed a higher growth rate than other razor clam culture experiences which used intertidal or suspended culture methods (da Costa and Martínez-Patiño, 2009; da Costa et al., 2011, 2013). Thus, E. magnus was 50 mm at six months old, 67 mm at 1 year old and 82 mm when the experiment finished, 1.5 years after fertilisation. During winter, a growth cessation period was observed probably caused by a combination of downwelling conditions and low seawater temperature values. To model juvenile growth and incorporate the seasonal oscillation we used temperature-dependents growth models previously described on literature (Otterlei et al., 1999; Kielbasa et al., 2010) and developed two upwelling-dependent growth models. Juvenile growth was better described when using growth models that incorporate environmental variables in their functions, especially the von Bertalanffy growth model that included temperature, as the estimated curves reflected better the winter growth cessation period. Optimum temperature for growth was estimated on 15ºC. These results provide important information for aquaculture techniques and confirm that each growth ring is laid down annually, which is crucial to apply indirect ageing methods such as the ones used in the adult growth study. Examination of adult individuals¿ internal shell microgrowth patterns (acetate peel method) proved to be the most suitable method for growth estimate, as observed in other studies (e.g. Gaspar et al. 1994). Similarly to other bivalves, the growth of E. magnus is faster during the first three years of life, declines at about four¿six years old and almost ceases in subsequent years, with the organisms entering into an asymptotic phase around the age of eight-nine years. The mean population length is attained at four-five years. Within this general pattern, there was significant variation among study sites. Sword razor growth was slower in the intermediate zone (L¿ = 140.4, k = 0.40) followed by the innermost zone (L¿ = 151.91, k = 0.40) and the outermost zone (L¿ = 172.7, k = 0.33). As a result, razor clams reached commercial size in 1.7, 2.3 and 2.8 years in the outer, innermost and intermediate zones of the ria, respectively. The growth pattern obtained for the sword razor population in the Ría de Pontevedra is consistent with the one of the sword razor individuals reared in the Ría de Vigo and the growth parameters are similar to those obtained for other Ensis spp. populations by the same ageing technique (e.g. Gaspar et al., 1994; Henderson and Richardson, 1994; Robinson and Richardson, 1998). The influence of environmental factors on the growth of E. magnus in the Ría de Pontevedra is difficult to determine because of the synergistic interactions among environmental factors in highly dynamic systems such as the rias. However, our results indicate that growth is negatively correlated with mud content at all of the sites under study. In addition, we suggest that growth is positively correlated with current speed and negatively correlated with salinity oscillations. The present PhD dissertation provides the first estimation of the size and age at which E. magnus reaches sexual maturity in the Iberian Peninsula (L50 = 79.5 mm, attained between the first and second year of life) and confirmed that the European legal commercial size for E. magnus (>100 mm) is consistent with the reproductive biology of the species. It is also the first work that determines the mesoscale variation in gonadal development of any species of the superfamily Solenoidea and the first that estimates growth parameters for the species in the Iberian Peninsula. The findings of the reproductive cycle study are being applied since 2011 in the rotation scheme of the fishery management plan of the Ría de Pontevedra, leading to a more efficient and sustainable exploitation, and have been also employed to determine the size at first maturity of other sword razor populations. Besides, the proposed management tool enables consideration of gonadal cycle differences between beds and years in the daily fishery management of any razor clam fishery. Finally, the growth rates estimated for each site enable to establish a rotational harvest strategy of subareas of the same exploited bed to allow individuals to grow to a certain size or orient fishing effort to areas of highest growth rate or productivity. The results highlight the importance of carrying out mesoscale studies of the biology in coastal fisheries resources and lay the foundation for further research in other Galician shellfisheries.Xunta de Galici

Autonomous Collision avoidance for Unmanned aerial systems

Unmanned Aerial System (UAS) applications are growing day by day and this will lead Unmanned Aerial Vehicle (UAV) in the close future to share the same airspace of manned aircraft.This implies the need for UAS to define precise safety standards compatible with operations standards for manned aviation. Among these standards the need for a Sense And Avoid (S&A) system to support and, when necessary, sub¬stitute the pilot in the detection and avoidance of hazardous situations (e.g. midair collision, controlled flight into terrain, flight path obstacles, and clouds). This thesis presents the work come out in the development of a S&A system taking into account collision risks scenarios with multiple moving and fixed threats. The conflict prediction is based on a straight projection of the threats state in the future. The approximations introduced by this approach have the advantage of high update frequency (1 Hz) of the estimated conflict geometry. This solution allows the algorithm to capture the trajectory changes of the threat or ownship. The resolution manoeuvre evaluation is based on a optimisation approach considering step command applied to the heading and altitude autopilots. The optimisation problem takes into account the UAV performances and aims to keep a predefined minimum separation distance between UAV and threats during the resolution manouvre. The Human-Machine Interface (HMI) of this algorithm is then embedded in a partial Ground Control Station (GCS) mock-up with some original concepts for the indication of the flight condition parameters and the indication of the resolution manoeuvre constraints. Simulations of the S&A algorithm in different critical scenarios are moreover in-cluded to show the algorithm capabilities. Finally, methodology and results of the tests and interviews with pilots regarding the proposed GCS partial layout are covered

Application of advanced on-board processing concepts to future satellite communications systems

An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development