Distributed adaptive signal processing for frequency estimation

It is widely recognised that future smart grids will heavily rely upon intelligent communication and signal processing as enabling technologies for their operation. Traditional tools for power system analysis, which have been built from a circuit theory perspective, are a good match for balanced system conditions. However, the unprecedented changes that are imposed by smart grid requirements, are pushing the limits of these old paradigms. To this end, we provide new signal processing perspectives to address some fundamental operations in power systems such as frequency estimation, regulation and fault detection. Firstly, motivated by our finding that any excursion from nominal power system conditions results in a degree of non-circularity in the measured variables, we cast the frequency estimation problem into a distributed estimation framework for noncircular complex random variables. Next, we derive the required next generation widely linear, frequency estimators which incorporate the so-called augmented data statistics and cater for the noncircularity and a widely linear nature of system functions. Uniquely, we also show that by virtue of augmented complex statistics, it is possible to treat frequency tracking and fault detection in a unified way. To address the ever shortening time-scales in future frequency regulation tasks, the developed distributed widely linear frequency estimators are equipped with the ability to compensate for the fewer available temporal voltage data by exploiting spatial diversity in wide area measurements. This contribution is further supported by new physically meaningful theoretical results on the statistical behavior of distributed adaptive filters. Our approach avoids the current restrictive assumptions routinely employed to simplify the analysis by making use of the collaborative learning strategies of distributed agents. The efficacy of the proposed distributed frequency estimators over standard strictly linear and stand-alone algorithms is illustrated in case studies over synthetic and real-world three-phase measurements. An overarching theme in this thesis is the elucidation of underlying commonalities between different methodologies employed in classical power engineering and signal processing. By revisiting fundamental power system ideas within the framework of augmented complex statistics, we provide a physically meaningful signal processing perspective of three-phase transforms and reveal their intimate connections with spatial discrete Fourier transform (DFT), optimal dimensionality reduction and frequency demodulation techniques. Moreover, under the widely linear framework, we also show that the two most widely used frequency estimators in the power grid are in fact special cases of frequency demodulation techniques. Finally, revisiting classic estimation problems in power engineering through the lens of non-circular complex estimation has made it possible to develop a new self-stabilising adaptive three-phase transformation which enables algorithms designed for balanced operating conditions to be straightforwardly implemented in a variety of real-world unbalanced operating conditions. This thesis therefore aims to help bridge the gap between signal processing and power communities by providing power system designers with advanced estimation algorithms and modern physically meaningful interpretations of key power engineering paradigms in order to match the dynamic and decentralised nature of the smart grid.Open Acces

Kinematic analysis of the super-extended HI disk of the nearby spiral galaxy M 83

Funding: CE, FB, AB, IB, JdB and JP acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No.726384/Empire). TGW acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 694343). JMDK gratefully acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme via the ERC Starting Grant MUSTANG (grant agreement number 714907). SCOG acknowledges funding from the European Research Council via the ERC Synergy Grant “ECOGAL – Understanding our Galactic ecosystem: From the disk of the Milky Way to the formation sites of stars and planets” (project ID 855130). WJGdB received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 882793 ‘MeerGas’).We present new HI observations of the nearby massive spiral galaxy M83, taken with the VLA at 21″ angular resolution (≈500 pc) of an extended (1.5 deg2) 10-point mosaic combined with GBT single dish data. We study the super-extended HI disk of M83 (∼50 kpc in radius), in particular disc kinematics, rotation and the turbulent nature of the atomic interstellar medium. We define distinct regions in the outer disk (rgal > central optical disk), including ring, southern area, and southern and northern arm. We examine HI gas surface density, velocity dispersion and non-circular motions in the outskirts, which we compare to the inner optical disk. We find an increase of velocity dispersion (σv) towards the pronounced HI ring, indicative of more turbulent HI gas. Additionally, we report over a large galactocentric radius range (until rgal ∼ 50 kpc) that σv is slightly larger than thermal (i.e. > 8 km s-1). We find that a higher star formation rate (as traced by FUV emission) is not always necessarily associated with a higher HI velocity dispersion, suggesting that radial transport could be a dominant driver for the enhanced velocity dispersion. We further find a possible branch that connects the extended HI disk to the dwarf irregular galaxy UGCA365, that deviates from the general direction of the northern arm. Lastly, we compare mass flow rate profiles (based on 2D and 3D tilted ring models) and find evidence for outflowing gas at rgal ∼ 2 kpc, inflowing gas at rgal ~ 5.5 kpc and outflowing gas at rgal ~ 14 kpc. We caution that mass flow rates are highly sensitive to the assumed kinematic disk parameters, in particular, to the inclination.Publisher PDFPeer reviewe

Children’s sensitivity to speaker accuracy and explanatory competence with biological concepts

This thesis investigated children’s selective trust in contexts that extend beyond a direct comparison of a distinctly accurate labeller with a distinctly inaccurate labeller in the domain of artifacts. First, it was examined whether children’s evaluations of informant trustworthiness is similar across the biological domain and the domain of artifacts. Second, it was investigated how children interpret novel labellers when compared to accurate and inaccurate labellers. Finally, children were presented with informants who provided functional or surface information for body parts to determine whether they prefer learning from informants who provided functional explanations. Across five experiments, children aged between 3 and 8 years of age (N = 379) were tested. The main findings were as follows: (a) 4- and 5-year-olds knew more about external body parts than internal organs; (b) 5-year-olds began to appreciate that speakers offering novel information were more trustworthy than those offering inaccurate information; (c) 4- to 8-year-olds had difficulty with distinguishing between informants who provided either functional explanations or obvious descriptions for highly unfamiliar organs; (d) however, when presented with informants who provided either functional or obvious information for highly familiar body parts, 8-year-olds (and to some extent, 5-year-olds) showed better recall of which informant provided a particular type of explanation, but they did not consider either informant to be a more trustworthy source. These findings indicate that children demonstrate selective trust in the biological domain, as well as in contexts that go beyond comparing accurate and inaccurate labellers. It is apparent that children are balanced in their evaluations of informants who provide new information, as well as those provide information that varies in explanatory depth. However, they are yet to fully consider functional explanations to be superior to superficial descriptions

Children’s sensitivity to speaker accuracy and explanatory competence with biological concepts

This thesis investigated children’s selective trust in contexts that extend beyond a direct comparison of a distinctly accurate labeller with a distinctly inaccurate labeller in the domain of artifacts. First, it was examined whether children’s evaluations of informant trustworthiness is similar across the biological domain and the domain of artifacts. Second, it was investigated how children interpret novel labellers when compared to accurate and inaccurate labellers. Finally, children were presented with informants who provided functional or surface information for body parts to determine whether they prefer learning from informants who provided functional explanations. Across five experiments, children aged between 3 and 8 years of age (N = 379) were tested. The main findings were as follows: (a) 4- and 5-year-olds knew more about external body parts than internal organs; (b) 5-year-olds began to appreciate that speakers offering novel information were more trustworthy than those offering inaccurate information; (c) 4- to 8-year-olds had difficulty with distinguishing between informants who provided either functional explanations or obvious descriptions for highly unfamiliar organs; (d) however, when presented with informants who provided either functional or obvious information for highly familiar body parts, 8-year-olds (and to some extent, 5-year-olds) showed better recall of which informant provided a particular type of explanation, but they did not consider either informant to be a more trustworthy source. These findings indicate that children demonstrate selective trust in the biological domain, as well as in contexts that go beyond comparing accurate and inaccurate labellers. It is apparent that children are balanced in their evaluations of informants who provide new information, as well as those provide information that varies in explanatory depth. However, they are yet to fully consider functional explanations to be superior to superficial descriptions