Magnetic fields in massive spirals: The role of feedback and initial conditions

Magnetic fields play a very important role in the evolution of galaxies through their direct impact on star formation and stellar feedback-induced turbulence. However, their co-evolution with these processes has still not been thoroughly investigated, and the possible effect of the initial conditions is largely unknown. This letter presents the first results from a series of high-resolution numerical models, aimed at deciphering the effect of the initial conditions and of stellar feedback on the evolution of the galactic magnetic field in isolated, Milky-Way-like galaxies. The models start with an ordered, either poloidal or toroidal, magnetic field of varying strength, and are evolved with and without supernova feedback. They include a dark matter halo, a stellar and a gaseous disk, as well as the appropriate cooling and heating processes for the interstellar medium. Independently of the initial conditions, the galaxies develop a turbulent velocity field and a random magnetic field component in under 15 Myrs. Supernova feedback is extremely efficient in building a random magnetic field component up to large galactic heights. However, a random magnetic field emerges even in runs without feedback, which points to an inherent instability of the ordered component. Supernova feedback greatly affects the velocity field of the galaxy up to large galactic heights, and helps restructure the magnetic field up to 10 kpc above the disk, independently of the initial magnetic field morphology. On the other hand, the initial morphology of the magnetic field can accelerate the development of a random component at large heights. These effects have important implications for the study of the magnetic field evolution in galaxy simulations.Comment: A&A Letters, accepte

Journeys in the City: Empathising With the Users of Transport Buildings

Accessibility is a considerable and growing issue in the design of many public buildings including vital high use buildings such as train stations. Yet research methods for these buildings are poor. This paper suggests that one new approach to design is to use immersive, auto-ethnographic methods to achieve an empathetic understanding of design needs. The paper asks: what can we learn about the mobility requirements of station users when we are immersed in a train station environment, and what mobile research methods can we use to begin to explore this? The paper reports on a study that used video diaries to explore Canary Wharf Station in a November evening rush hour in dry conditions, and specifically to study passenger behaviours on an island platform within the station. The analysis focused on how to improve mobility in the station from a user’s perspective. This use of auto-ethnography is discussed as part of a broader methodological debate about how to explore universal design issues from a user’s perspective, and in the context of empathetic desig

Video transmission over a relay channel with a compress-forward code design

There is an increasing demand to support high data rate multimedia applications over the current day wireless networks which are highly prone to errors. Relay channels, by virtue of their spatial diversity, play a vital role in meeting this demand without much change to the current day systems. A compress-forward relaying scheme is one of the exciting prospects in this regard owing to its ability to always outperform direct transmission. With regards to video transmission, there is a serious need to ensure higher protection for the source bits that are more important and sensitive. The objective of this thesis is to develop a practical scheme for transmitting video data over a relay channel using a compress-forward relaying scheme and compare it to direct and multi-hop transmissions. We also develop a novel scheme whereby the relay channel can be used as a means to provide the required unequal error protection among the MPEG-2 bit stream. The area of compress-forward (CF) relaying has not been developed much to date, with most of the research directed towards the decode-forward scheme. The fact that compress-forward relaying always ensures better results than direct transmission is an added advantage. This has motivated us to employ CF relaying in our implementation. Video transmission and streaming applications are being increasingly sought after in the current generation wireless systems. The fact that video applications are bandwidth demanding and error prone, and the wireless systems are band-limited and unreliable, makes this a challenging task. CF relaying, by virtue of their path diversity, can be considered to be a new means for video transmission. To exploit the above advantages, we propose an implementation for video transmission over relay channels using a CF relaying scheme. Practical gains in peak signal-to-noise ratio (PSNR) have been observed for our implementation compared to the simple binary-input additive white Gaussian noise (BIAWGN) and two-hop transmission scenarios

Decoding a Complex Visualization in a Science Museum -- An Empirical Study

This study describes a detailed analysis of museum visitors' decoding process as they used a visualization designed to support exploration of a large, complex dataset. Quantitative and qualitative analyses revealed that it took, on average, 43 seconds for visitors to decode enough of the visualization to see patterns and relationships in the underlying data represented, and 54 seconds to arrive at their first correct data interpretation. Furthermore, visitors decoded throughout and not only upon initial use of the visualization. The study analyzed think-aloud data to identify issues visitors had mapping the visual representations to their intended referents, examine why they occurred, and consider if and how these decoding issues were resolved. The paper also describes how multiple visual encodings both helped and hindered decoding and concludes with implications on the design and adaptation of visualizations for informal science learning venues.Comment: IEEE VIS (InfoVis/VAST/SciVis) 2019 ACM 2012 CCS - Human-centered computing, Visualization, Empirical studies in visualizatio

Digital TV processing system

Two digital video data compression systems directly applicable to the Space Shuttle TV Communication System were described: (1) For the uplink, a low rate monochrome data compressor is used. The compression is achieved by using a motion detection technique in the Hadamard domain. To transform the variable source rate into a fixed rate, an adaptive rate buffer is provided. (2) For the downlink, a color data compressor is considered. The compression is achieved first by intra-color transformation of the original signal vector, into a vector which has lower information entropy. Then two-dimensional data compression techniques are applied to the Hadamard transformed components of this last vector. Mathematical models and data reliability analyses were also provided for the above video data compression techniques transmitted over a channel encoded Gaussian channel. It was shown that substantial gains can be achieved by the combination of video source and channel coding

Methods for Determining Aircraft Surface State at Lesser-Equipped Airports

Tactical departure scheduling within a terminal airspace must accommodate a wide spectrum of surveillance and communication capabilities at multiple airports. The success of such a scheduler is highly dependent upon the knowledge of a departure's state while it is still on the surface. Airports within a common Terminal RAdar CONtrol (TRACON) airspace possess varying levels of surface surveillance infrastructure which directly impacts uncertainties in wheels-off times. Large airports have access to surface surveillance data, which is shared with the TRACON, while lesser-equipped airports still rely solely on controllers in Air Traffic Control Towers (Towers). Coordination between TRACON and Towers can be greatly enhanced when the TRACON controller has access to the surface surveillance and the associated decision-support tools at well-equipped airports. Similar coordination at lesser-equipped airports is still based on verbal communications. This paper investigates possible methods to reduce the uncertainty in wheels-off time predictions at the lesser-equipped airports through the novel use of Over-the-Air (OTA) data transmissions. We also discuss the methods and equipment used to collect sample data at lesser-equipped airports within a large US TRACON, as well as the data evaluation to determine if meaningful information can be extracted from it

The role of implicit memory in visual word recognition: Principles and processes of long- and short-term repetition priming

This review examines the role of long- and short-term repetition priming research in the theoretical debate between episodic and abstractionist accounts of implicit memory. The empirical research and theoretical accounts of priming reviewed indicate that neither episodic or abstractionist theories alone can successfully account for the processes of long- and short-term repetition priming. The major variations between studies in experimental methods used to measure repetition priming are also examined, providing a possible explanation for contrasting results obtained within repetition priming research and a reason for why the episodic versus abstractionist debate persists. Finally, research examining the underlying mechanisms responsible for priming is also discussed, indicating that it still has not been determined whether or not long- and short-term priming rely upon the same underlying mechanism. One method proposed for providing further clarification to this issue is to examine whether fluctuations in long-term priming levels result in changes in the magnitude of short-term priming. Previous models of word recognition assume the presence of only a single underlying mechanism in repetition priming. Recent research has, however, suggested that priming may be generated by two distinct processes; namely a long-term priming component and a short-term priming component. An experiment was conducted in order to examine the relationship between long- and short-term priming in order to determine whether or not these two processes can be attributed to a single underlying process. A total of 60 people (45 females, 15 males) participated in a computer-based lexical decision task designed to measure levels of short-term priming at varying levels of long-term priming. It was anticipated that if the priming components represented two distinctly different processes, a change in the level of long-term priming should not influence the obtainable level of short-term priming when other factors are held constant. The results demonstrated that changes in long-term priming were typically accompanied by changes in short-term priming (p \u3c .05). Results were interpreted as support for existing single-process models of priming

Advanced Techniques for the Decipherment of Ancient Scripts

This contribution explores modern and traditional approaches to the decipherment of ancient writing systems. It surveys methods used by paleographers and epigraphers and state-of-the art applications of computational linguistics, such as models based on neural networks. It frames the contextual problems scholars encounter in dealing with ancient codes, the situations and preconditions of the unknown codes, their idiosyncrasies and peculiarities, and the potential solutions afforded by both traditional and novel methods of investigation