Day-ahead allocation of operation reserve in composite power systems with large-scale centralized wind farms

This paper focuses on the day-ahead allocation of operation reserve considering wind power prediction error and network transmission constraints in a composite power system. A two-level model that solves the allocation problem is presented. The upper model allocates operation reserve among subsystems from the economic point of view. In the upper model, transmission constraints of tielines are formulated to represent limited reserve support from the neighboring system due to wind power fluctuation. The lower model evaluates the system on the reserve schedule from the reliability point of view. In the lower model, the reliability evaluation of composite power system is performed by using Monte Carlo simulation in a multi-area system. Wind power prediction errors and tieline constraints are incorporated. The reserve requirements in the upper model are iteratively adjusted by the resulting reliability indices from the lower model. Thus, the reserve allocation is gradually optimized until the system achieves the balance between reliability and economy. A modified two-area reliability test system (RTS) is analyzed to demonstrate the validity of the method.This work was supported by National Natural Science Foundation of China (No. 51277141) and National High Technology Research and Development Program of China (863 Program) (No. 2011AA05A103)

Junior parkrun pilot in Australia: A real world evaluation.

ISSUE ADDRESSED: Regular physical activity is important for children's health. Parkrun supports communities to deliver free, weekly, 5 km events in 22 countries around the world and is the largest physical activity model delivered at scale in the world. Junior parkrun aims to encourage children aged 4-14 years to be active outdoors through providing safe, cost-free and non-competitive weekly timed walk, run or jog over a 2-km distance. The aim of this study is to evaluate the junior parkrun pilot in Australia. METHODS: A process evaluation was conducted using routinely collected data of junior parkrun participants, as well as a self-completed questionnaire. RESULTS: A total of 1827 children had registered and participated in at least one junior parkrun over the course of the pilot period. Participants had, on average, attended 10% of the junior parkrun events including and subsequent to their first participation by the end of the study period. Majority of parents (61%) said that junior parkrun had increased their child's physical activity either a little or a lot, and most agreed or strongly agreed that junior parkrun was fun (90%), enjoyable (91%), energising (85%) and challenging (70%). CONCLUSION: The junior parkrun pilot appears to show promise in Australia for enabling children to engage in physical activity, in their local communities in a fun and inclusive way. SO WHAT: Parkrun junior can co-exist with other organised sports programs; however, it can also specifically target those not participating in any sports, given the high levels of enjoyment in a non-competitive, non-team environment

Size constancy in bat biosonar?

Perception and encoding of object size is an important feature of sensory systems. In the visual system object size is encoded by the visual angle (visual aperture) on the retina, but the aperture depends on the distance of the object. As object distance is not unambiguously encoded in the visual system, higher computational mechanisms are needed. This phenomenon is termed "size constancy". It is assumed to reflect an automatic re-scaling of visual aperture with perceived object distance. Recently, it was found that in echolocating bats, the 'sonar aperture', i.e., the range of angles from which sound is reflected from an object back to the bat, is unambiguously perceived and neurally encoded. Moreover, it is well known that object distance is accurately perceived and explicitly encoded in bat sonar. Here, we addressed size constancy in bat biosonar, recruiting virtual-object techniques. Bats of the species Phyllostomus discolor learned to discriminate two simple virtual objects that only differed in sonar aperture. Upon successful discrimination, test trials were randomly interspersed using virtual objects that differed in both aperture and distance. It was tested whether the bats spontaneously assigned absolute width information to these objects by combining distance and aperture. The results showed that while the isolated perceptual cues encoding object width, aperture, and distance were all perceptually well resolved by the bats, the animals did not assign absolute width information to the test objects. This lack of sonar size constancy may result from the bats relying on different modalities to extract size information at different distances. Alternatively, it is conceivable that familiarity with a behaviorally relevant, conspicuous object is required for sonar size constancy, as it has been argued for visual size constancy. Based on the current data, it appears that size constancy is not necessarily an essential feature of sonar perception in bats

New energy geographies : a case study of yoga, meditation and healthfulness

Beginning with a routine day in the life of a practitioner of yoga and meditation and emphasising the importance of nurturing, maintaining and preventing the dissipation of diverse ‘energies’, this paper explores the possibilities for geographical health studies which take seriously ‘new energy geographies’. It is explained how this account is derived from in-depth fieldwork tracing how practitioners of yoga and meditation find times and spaces for these practices, often in the face of busy urban lifestyles. Attention is paid to the ‘energy talk’ featuring heavily in how practitioners describe the benefits that they perceive themselves to derive from these practices, and to claims made about ‘energies’ generated during the time-spaces of these practices which seemingly flow, usually with positive effects, into other domains of their lives. The paper then discusses the implications of this energy talk in the context of: (a) critically reviewing conventional approaches to studying ‘energy geographies’; (b) identifying an alertness to the likes of ‘affective energies’ surfacing in recent theoretically-attuned works of human geography (and cognate disciplines); and (c) exploring differing understandings of energy/energies extant in geographical studies of health and in step with the empirical research materials presented about yoga, meditation and healthfulness. While orientated towards explicitly geographical inquiries, the paper is intended as a statement of interest to the wider medical humanities

The Evolution of Compact Binary Star Systems

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure

Plant ecology meets animal cognition: impacts of animal memory on seed dispersal

We propose that an understanding of animal learning and memory is critical to predicting the impacts of animals on plant populations through processes such as seed dispersal, pollination and herbivory. Focussing on endozoochory, we review the evidence that animal memory plays a role in seed dispersal, and present a model which allows us to explore the fundamental consequences of memory for this process. We demonstrate that decision-making by animals based on their previous experiences has the potential to determine which plants are visited, which fruits are selected to be eaten from the plant and where seeds are subsequently deposited, as well as being an important determinant of animal survival. Collectively, these results suggest that the impact of animal learning and memory on seed dispersal is likely to be extremely important, although to date our understanding of these processes suffers from a conspicuous lack of empirical support. This is partly because of the difficulty of conducting appropriate experiments but is also the result of limited interaction between plant ecologists and those who work on animal cognition

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Characterizing the non-linear growth of large-scale structure in the Universe

The local Universe displays a rich hierarchical pattern of galaxy clusters and superclusters. The early Universe, however, was almost smooth, with only slight 'ripples' seen in the cosmic microwave background radiation. Models of the evolution of structure link these observations through the effect of gravity, because the small initially overdense fluctuations attract additional mass as the Universe expands. During the early stages, the ripples evolve independently, like linear waves on the surface of deep water. As the structures grow in mass, they interact with other in non-linear ways, more like waves breaking in shallow water. We have recently shown how cosmic structure can be characterized by phase correlations associated with these non-linear interactions, but hitherto there was no way to use that information to reach quantitative insights into the growth of structures. Here we report a method of revealing phase information, and quantify how this relates to the formation of a filaments, sheets and clusters of galaxies by non-linear collapse. We use a new statistic based on information entropy to separate linear from non-linear effects and thereby are able to disentangle those aspects of galaxy clustering that arise from initial conditions (the ripples) from the subsequent dynamical evolution.Comment: Accepted for publication in Nature. For high-resolution Figure 3, please see http://www.nottingham.ac.uk/~ppzpc/phases/n0colorphase.html, For the animations and the idea of this paper please see http://www.nottingham.ac.uk/~ppzpc/phases/index.htm