A near real-time algorithm for flood detection in urban and rural areas using high resolution Synthetic Aperture Radar images

A near real-time flood detection algorithm giving a synoptic overview of the extent of flooding in both urban and rural areas, and capable of working during night-time and day-time even if cloud was present, could be a useful tool for operational flood relief management and flood forecasting. The paper describes an automatic algorithm using high resolution Synthetic Aperture Radar (SAR) satellite data that assumes that high resolution topographic height data are available for at least the urban areas of the scene, in order that a SAR simulator may be used to estimate areas of radar shadow and layover. The algorithm proved capable of detecting flooding in rural areas using TerraSAR-X with good accuracy, and in urban areas with reasonable accuracy

The Nature of Lyman Break Galaxies in Cosmological Hydrodynamic Simulations

What type of objects are being detected as $z\sim 3$ "Lyman break galaxies"? Are they predominantly the most massive galaxies at that epoch, or are many of them smaller galaxies undergoing a short-lived burst of merger-induced star formation? We attempt to address this question using high-resolution cosmological hydrodynamic simulations including star formation and feedback. Our $\Lambda$CDM simulation, together with Bruzual-Charlot population synthesis models, reproduces the observed number density and luminosity function of Lyman break galaxies when dust is incorporated. The inclusion of dust is crucial for this agreement. In our simulation, these galaxies are predominantly the most massive objects at this epoch, and have a significant population of older stars. Nevertheless, it is possible that our simulations lack the resolution and requisite physics to produce starbursts, despite having a physical resolution of \la 700 pc at z=3. Thus we cannot rule out merger-induced starburst galaxies also contributing to the observed population of high-redshift objects.Comment: 5 pages, contribution to the Proceedings of Rencontres Internationales de l'IGRAP, Clustering at High Redshift, Marseille 199

Developing a complete system architecture for sensor networking

Wireless sensor networking is the result of interdisciplinary research involving aspects of computer science and electrical engineering. By creating large wireless networks of computational devices that can sense many types of phenomena, it is possible to gather information in ways that were previously not feasible. Currently the main applications of sensor networking are for biological and environmental data gathering, security and military sensing systems, location tracking and the development of smart spaces; however, as the field continues to advance these networks are consistently being applied to varying scenarios that call for new features and include unique constraints. As new applications for sensor networking arise it is clear that researchers are in need of a highly expandable platform for prototyping both hardware and software technologies. Although it is also important to design specialized systems for specific applications, we believe that at this point in the evolution of sensor networking a general purpose platform with maximum expandability and ease of use would be a more valuable commodity

Stability of adversarial Markov chains, with an application to adaptive MCMC algorithms

We consider whether ergodic Markov chains with bounded step size remain bounded in probability when their transitions are modified by an adversary on a bounded subset. We provide counterexamples to show that the answer is no in general, and prove theorems to show that the answer is yes under various additional assumptions. We then use our results to prove convergence of various adaptive Markov chain Monte Carlo algorithms.Comment: Published at http://dx.doi.org/10.1214/14-AAP1083 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Theoretical Modeling of the High Redshift Galaxy Population

We review theoretical approaches to the study of galaxy formation, with emphasis on the role of hydrodynamic simulations in modeling the high redshift galaxy population. We present new predictions for the abundance of star-forming galaxies in the Lambda + cold dark matter model (Omega_m=0.4, Omega_L=0.6), combining results from several simulations to probe a wide range of redshift. At a threshold density of one object per arcmin^2 per unit z, these simulations predict galaxies with star formation rates of 2 msun/yr (z=10), 5 msun/yr (z=8), 20 msun/yr (z=6), 70-100 msun/yr (z=4-2), and 30 msun/yr (z=0.5). For galaxies selected at a fixed comoving space density n=0.003 h^3 Mpc^{-3], a (50 Mpc/h)^3 simulation predicts a galaxy correlation function (r/5 Mpc/h)^{-1.8} in comoving coordinates, essentially independent of redshift from z=4 to z=0.5. Different cosmological models predict global histories of star formation that reflect their overall histories of mass clustering, but robust numerical predictions of the comoving space density of star formation are difficult because the simulations miss the contribution from galaxies below their resolution limit. The LCDM model appears to predict a star formation history with roughly the shape inferred from observations, but it produces too many stars at low redshift, predicting Omega_* ~ 0.015 at z=0. We conclude with a brief discussion of this discrepancy and three others that suggest gaps in our current theory of galaxy formation: small disks, steep central halo profiles, and an excess of low mass dark halos. While these problems could fade as the simulations or observations improve, they could also guide us towards a new understanding of galactic scale star formation, the spectrum of primordial fluctuations, or the nature of dark matter.Comment: 12 pages, 3 figs. To be published in "Photometric Redshifts and High Redshift Galaxies", eds. R. Weymann, L. Storrie-Lombardi, M. Sawicki & R. Brunner, (San Francisco: ASP Conference Series

Near real-time flood detection in urban and rural areas using high resolution Synthetic Aperture Radar images

A near real-time flood detection algorithm giving a synoptic overview of the extent of flooding in both urban and rural areas, and capable of working during night-time and day-time even if cloud was present, could be a useful tool for operational flood relief management. The paper describes an automatic algorithm using high resolution Synthetic Aperture Radar (SAR) satellite data that builds on existing approaches, including the use of image segmentation techniques prior to object classification to cope with the very large number of pixels in these scenes. Flood detection in urban areas is guided by the flood extent derived in adjacent rural areas. The algorithm assumes that high resolution topographic height data are available for at least the urban areas of the scene, in order that a SAR simulator may be used to estimate areas of radar shadow and layover. The algorithm proved capable of detecting flooding in rural areas using TerraSAR-X with good accuracy, classifying 89% of flooded pixels correctly, with an associated false positive rate of 6%. Of the urban water pixels visible to TerraSAR-X, 75% were correctly detected, with a false positive rate of 24%. If all urban water pixels were considered, including those in shadow and layover regions, these figures fell to 57% and 18% respectively

The effects of spatial resolution and dimensionality on modeling regional-scale hydraulics in a multichannel river

As modeling capabilities at regional and global scales improve, questions remain regarding the appropriate process representation required to accurately simulate multichannel river hydraulics. This study uses the hydrodynamic model LISFLOOD-FP to simulate patterns of water surface elevation (WSE), depth, and inundation extent across a ∼90 km, anabranching reach of the Tanana River, Alaska. To provide boundary conditions, we collected field observations of bathymetry and WSE during a 2 week field campaign in summer 2013. For the first time at this scale, we test a simple, raster-based model's capabilities to simulate 2-D, in-channel patterns of WSE and inundation extent. Additionally, we compare finer resolution (≤25 m) 2-D models to four other models of lower dimensionality and coarser resolution (100–500 m) to determine the effects of simplifying process representation. Results indicate that simple, raster-based models can accurately simulate 2-D, in-channel hydraulics in the Tanana. Also, the fine-resolution, 2-D models produce lower errors in spatiotemporal outputs of WSE and inundation extent compared to coarse-resolution, 1-D models: 22.6 cm versus 56.4 cm RMSE for WSE, and 90% versus 41% Critical Success Index values for simulating inundation extent. Incorporating the anabranching channel network using subgrid representations for smaller channels is important for simulating accurate hydraulics and lowers RMSE in spatially distributed WSE by at least 16%. As a result, better representation of the converging and diverging multichannel network by using subgrid solvers or downscaling techniques in multichannel rivers is needed to improve errors in regional to global-scale models

THE LANDSCAPE: A GOOD OF CULTURE, IDENTIFICATION AND RICHNESS

The adoption of a systematic in geography has helped to "revolutionize" and in the same time to complete the notion of landscape that, until the half '900, has mastered the international geographic research. We are passed from definitions of the landscape like complex of the sensible features of a region of landscape like theatre etc. to that of landscape as structured system, where the natural and anthropic component are melt in a system which complexity is given by the inextricability of their relations as seen in a historical perspective. Already L. Gambi, however, in 1964 had adopted a first interpretative approach to the complexity of the landscape, looking no more at the man in the nature, according to Biasutti's point of view, but putting the "man in history" near the nature who, exploiting his kind of life contributes at the constitution of the "Anthropogeographic landscape". The centrality of the history in the processes of complexification of the landscape has been put, most recently, in evidence by Paola Sereno (2001): the landscape is composed of elements that belong to the various processes of territorialization, then at more territorial systems that the history produces, transmit some components that, changing even meaning and function, are reunited in a new system, establish new connections with other elements inside of new processes of territorialization. Not exist however a true "past" of the landscape if not in the whole of the continuous morphogenetic processes that had characterized it. In this perspective the landscape's tutelage not is immediately connected at the tutelage of a cultural, architectonic or monumental good that would be, because the same landscape configure itself as the historical - geographical context that the single object inside it get meaning; a context complex, however, because not only the simple union of elements, but the architecture of the nexus that tie them. The landscape configure itself as a whole of signs imprinted by the community to the own territory; it become then expression of belonging that consents to the men of recognize and identify themselves in the "places". Every landscape then has strong individualizing characters that consent the emersion of the deep roots of the realities that constitute the identity of the human groups that in time have established themselves in the territory. (Mautone, 1999). It is uncovered then an ambivalence that, according to M.C. Zerbi (1999) constitute the very essence of the complexity of the notion of landscape: from a side the landscape as visible, external, objective reality, that the observer can see, on the other side the mental image that the observer build for himself, the subjective dimension that is more strictly connect to the notion of cultural landscape. In particular Zerbi see how in the contemporary geographic research, the notion of landscape is seen in three different aspects that presuppose various uses. The first aspect concern The notion of cultural landscape, to whom geography has dedicate much time, as landscape modified by human work. Is derived a large meaning of this term, because the human work -directly or indirectly- manifests itself in a great number of landscapes. Is, however, according Zerbi, a good starting point to pick the past and present dynamics through an approach at the same time ecologic and historical - geographical. When then some elements of the cultural landscape stand out which are particularly appraised or are perceived as menaced in their own existence, it comes out the concept of landscape as patrimonial heritage. Is a more selective concept than previous, which concerns a reality full of values: archaeological sites, traditional agrarian cultivations, ancient houses become a heritage to protect and maintain more than to hand down. The historical gardens and parks too find place in this concept, becoming a planning object. There is even, according M.C. Zerbi, a third notion of cultural landscape that, this time, consider the landscape not only a objective reality, but a subjective interpretation of elements held in the ambient to which various human groups attribute different meanings and values. 228 Landscape then as way to see that surrounds us. At first sight it could seem an abstract approach, less responding to reality; is, instead, an approach that has validity even on the operative plane when is needed to know the values of the insiders, to make them aware of the planning of their complex of life

Is clopidogrel better than aspirin following breakthrough strokes while on aspirin? A retrospective cohort study.

ObjectiveThere is insufficient evidence on which to base a recommendation for optimal antiplatelet therapy following a stroke while on aspirin. The objective was to compare clopidogrel initiation vs aspirin reinitiation for vascular risk reduction among patients with ischaemic stroke on aspirin at the time of their index stroke.DesignRetrospective.SettingWe conducted a nationwide cohort study by retrieving all hospitalised patients (≥18 years) with a primary diagnosis of ischaemic stroke between 2003 and 2009 from Taiwan National Health Insurance Research Database.ParticipantsAmong 3862 patients receiving aspirin before the index ischaemic stroke and receiving either aspirin or clopidogrel after index stroke during follow-up period, 1623 were excluded due to a medication possession ratio <80%. Also, 355 were excluded due to history of atrial fibrillation, valvular heart disease or coagulopathy. Therefore, 1884 patients were included in our final analysis.InterventionsPatients were categorised into two groups based on whether clopidogrel or aspirin was prescribed during the follow-up period. Follow-up was from time of the index stroke to admission for recurrent stroke or myocardial infarction, death or the end of 2010.Primary and secondary outcome measuresThe primary end point was hospitalisation due to a new-onset major adverse cardiovascular event (MACE: composite of any stroke or myocardial infarction). The leading secondary end point was any recurrent stroke.ResultsCompared to aspirin, clopidogrel was associated with a lower occurrence of future MACE (HR=0.54, 95% CI 0.43 to 0.68, p<0.001, number needed to treat: 8) and recurrent stroke (HR=0.54, 95% CI 0.42 to 0.69, p<0.001, number needed to treat: 9) after adjustment of relevant covariates.ConclusionsAmong patients with an ischaemic stroke while taking aspirin, clopidogrel initiation was associated with fewer recurrent vascular events than aspirin reinitiation