Imag(in)ing 'homeless places': using auto-photography to (re)examine the geographies of homelessness   总被引：1，自引：0，他引：1  

Sarah Johnsen  Jon May  Paul Cloke† 《Area》2008,40(2):194-207

Despite its growing popularity as a method across the social sciences, the methodological literature on auto-photography is remarkably sparse. In an effort to begin redressing this gap, this paper provides an account of the ways in which auto-photography was used to complement other research methods in a (re)examination of the geographies of homelessness. It describes how auto-photography illuminated 'hidden' spaces that do not typically feature in public (or academic) imaginations of homelessness, and provided more nuanced understandings of the use, meanings and dynamics associated with other, apparently already 'known' spaces. It concludes that whilst auto-photography presents a number of logistical and ethical challenges – particularly when used with such a vulnerable group – it is nevertheless a powerful heuristic tool.  相似文献   

Model‐based attenuation for scattered dispersive waves     

Claudio Strobbia  Alexander Zarkhidze  Roger May  Fatma Ibrahim 《Geophysical Prospecting》2014,62(5):1143-1161

Coherent noise in land seismic data primarily consists in source‐generated surface‐wave modes. The component that is traditionally considered most relevant is the so‐called ground roll, consisting in surface‐wave modes propagating directly from sources to receivers. In many geological situations, near?surface heterogeneities and discontinuities, as well as topography irregularities, diffract the surface waves and generate secondary events, which can heavily contaminate records. The diffracted and converted surface waves are often called scattered noise and can be a severe problem particularly in areas with shallow or outcropping hard lithological formations. Conventional noise attenuation techniques are not effective with scattering: they can usually address the tails but not the apices of the scattered events. Large source and receiver arrays can attenuate scattering but only in exchange for a compromise to signal fidelity and resolution. We present a model?based technique for the scattering attenuation, based on the estimation of surface‐wave properties and on the prediction of surface waves with a complex path involving diffractions. The properties are estimated first, to produce surface?consistent volumes of the propagation properties. Then, for all gathers to filter, we integrate the contributions of all possible diffractors, building a scattering model. The estimated scattered wavefield is then subtracted from the data. The method can work in different domains and copes with aliased surface waves. The benefits of the method are demonstrated with synthetic and real data.  相似文献   

Dynamics of grains falling on a sloping granular medium: application to the evolution of a talus          下载免费PDF全文

Fabio Vittorio De Blasio  May‐Britt Sæter 《地球表面变化过程与地形》2015,40(5):599-609

Numerous field surveys have provided quantitative information on the characteristics of talus deposits. Much less has been done to quantify the basic dynamics processes of blocks involved in talus evolution. In this work, we perform a set of experiments at the reduced scale of some metres using an inclined board covered with a loose granular medium. The complexity of the processes forming a talus is simplified by studying the interaction of only two kinds of grain sizes at a time. Grains of one class size are dropped from a fixed height onto the board covered by a layer of grains of a different class size, and their final distribution is recorded. We find that when small grains fall on large grains, the granular abundance decreases rapidly as a function of the distance from the fall point, which is explained by the effect of multiple bouncing on the irregular surface. In contrast, large grains falling on a bed of smaller grains lose much more energy at impact. They may stop at once, or roll down slope, often reaching the whole board length; as a consequence, their abundance peaks in the fall zone and at the change of slope. Experiments also show that grains travel longer with increasing fall height and sloping angle. The results clarify in a physical manner one mechanism that might explain why large blocks are typically found in the distal part of a talus slope, while smaller blocks remain near the fall zone. Based on these and previous experiments, a schematic view of talus evolution is discussed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Late Holocene tsunami traces on the western and southern coastlines of the Peloponnesus (Greece)   总被引：1，自引：0，他引：1  

Anja Scheffers  Dieter Kelletat  Andreas Vtt  Simon Matthias May  Sander Scheffers 《Earth and Planetary Science Letters》2008,269(1-2):271-279

Greece, in particular the western and southern parts close to the subduction zone of the Hellenic Trench, experiences strong earthquakes and subsequent tsunamis. Nevertheless, field evidence of tsunamis from the late Holocene is extremely rare. Our research along the coastlines of the western and southern Peloponnesus resulted in new findings of tsunami impacts in the form of clusters and ridges of large boulders and thick tsunamigenic sand layers encountered in vibracores. Many boulders contained attached marine organisms, which prove that they were transported from the foreshore environment against gravity by extreme wave events. The attached organisms, which have been dated by ¹⁴C-AMS, suggest that historical tsunami events of great energy occurred around 1300 cal AD. A wood fragment found at the base of tsunami deposits in a vibracore from Cape Punta was dated to ~ 250 cal AD.  相似文献   

Experimental study of a 45-MHz array for radio astronomy     

H. Alvarez  J. Aparici  J. May  F. Olmos 《Experimental Astronomy》1994,5(3-4):315-328

The University of Chile transit radiotelescope is a 528-dipole array operating at 45 MHz. We present a comparison of an experimental study of the antenna radiation pattern with the basic theoretical pattern in three dimensions. We concentrate in the meridian plane diagram since this is particularly difficult to measure for an array like ours. The comparison shows excellent agreement. We have measured several important antenna parameters like the effective area as a function of zenith distance, the orientation of the plane of the array and the pointing accuracy. We include a detailed treatment of these subjects since not much information related to low frequency arrays for radio astronomy can be found in the literature. We discuss the importance of knowing these parameters in the preparation of the 45-MHz Sky Survey under way at the University of Chile Radio Observatory.  相似文献   

The signature of ENSO in the Northern Hemisphere midlatitude seasonal mean flow and high-frequency intraseasonal variability     

Dr. W. May  L. Bengtsson 《Meteorology and Atmospheric Physics》1998,69(1-2):81-100

Summary The impact of pronounced positive and negative sea surface temperature (STT) anomalies in the tropical Pacific associated with the El Niño/Southern Oscillation (ENSO) phenomenon on the atmospheric circulation in the Northern Hemisphere extratropics during the boreal winter season is investigated. This includes both the impact on the seasonal mean flow and on the intraseasonal variability on synoptic time scales. Moreover, the interaction between the transient fluctuations on these times scales and the mean circulation is examined. Both data from an ensemble of five simulations with the ECHAM3 atmospheric general circulation model at a horizontal resolution of T42 each covering the period from 1979 through 1992 and operational analyses from ECMWF for the corresponding period are examined. In each of the simulations observed SSTs for the period of investigation are given as lower boundary forcing, but different atmospheric initial conditions are prescribed.The simulations with ECHAM3 reveal a distinct impact of the pronounced SST-anomalies in the tropical Pacific on the atmospheric circulation in the Northern Hemisphere extratropics during El Niño as well as during La Niña events. These changes in the atmospheric circulation, which are found to be highly significant in the Pacific/North American as well as in the Atlantic/European region, are consistent with the essential results obtained from the analyses. The pronounced SST-anomalies in the tropical Pacific lead to changes in the mean circulation, which are characterized by typical circulation patterns. These changes in the mean circulation are accompanied by marked variations of the activity of the transient fluctuations on synoptic time scales, that are changes in both the kinetic energy on these time scales and the atmospheric transports of momentum and heat accomplished by the short baroclinic waves. The synoptic disturbances, on the other hand, play also an important role in controlling the changes in the mean circulation associated with the ENSO phenomenon. They maintain these typical circulation patterns via barotropic, but counteract them via baroclinic processes.The hypothesis of an impact of the ENSO phenomenon in the Atlantic/European region can be supported. As the determining factor the intensification (reduction) of the Aleutian low and the simultaneous reduction (intensification) of the Icelandic low during El Niño and during La Niña events respectively, is identified. The changes in the intensity of the Aleutian low during the ENSO-events are accompanied by an alteration of the transport of momentum caused by the short baroclinic waves over the North American continent in such a way that the changes in the intensity of the Icelandic low during El Niño as well as during La Niña events are maintained.With 16 Figures  相似文献   

Reply to Comment on: Coarse clast ridge sequences as suitable archives for past storm events? Case study on the Houtman Abrolhos,Western Australia     

Anja M. Scheffers  Sander R. Scheffers  Dieter H. Kelletat  Peter Squire  Lindsay Collins  Yuexing Feng  Jian‐Xin Zhao  Renaud Joannes‐Boyau  Simon Matthias May  Gerhard Schellmann  Heather Freeman 《第四纪科学杂志》2013,28(2):213-215

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Towards semantic‐aware multiple‐aspect trajectory similarity measuring     

Lucas May Petry  Carlos Andres Ferrero  Luis Otavio Alvares  Chiara Renso  Vania Bogorny 《Transactions in GIS》2019,23(5):960-975

The large amount of semantically rich mobility data becoming available in the era of big data has led to a need for new trajectory similarity measures. In the context of multiple‐aspect trajectories, where mobility data are enriched with several semantic dimensions, current state‐of‐the‐art approaches present some limitations concerning the relationships between attributes and their semantics. Existing works are either too strict, requiring a match on all attributes, or too flexible, considering all attributes as independent. In this article we propose MUITAS, a novel similarity measure for a new type of trajectory data with heterogeneous semantic dimensions, which takes into account the semantic relationship between attributes, thus filling the gap of the current trajectory similarity methods. We evaluate MUITAS over two real datasets of multiple‐aspect social media and GPS trajectories. With precision at recall and clustering techniques, we show that MUITAS is the most robust measure for multiple‐aspect trajectories.  相似文献   

Embedding scale: new thinking of scale in machine learning and geographic representation     

Yuan  May  McKee  Arlo 《Journal of Geographical Systems》2022,24(3):501-524

Journal of Geographical Systems - Concepts of scale are at the heart of diverse scientific endeavors that seek to understand processes and how observations and analyses influence our understanding....  相似文献   

Geochemical,mineralogical and magnetic characteristics of vertical dust deposition in urban environment   总被引：1，自引：0，他引：1  

Péter Sipos  Emő Márton  Zoltán May  Tibor Németh  Viktória Kovács Kis 《Environmental Earth Sciences》2014,72(3):905-914

Studies on composition and distribution of dust deposition are necessary for the risk assessment of dust to atmospheric quality. We studied the vertical distribution pattern of dust and metal (Cu, Fe, Pb, Zn) deposition up to 33 m height in urban environment. Integrated geochemical, mineralogical and magnetic study of the seasonally sampled dust helped to specify our knowledge on the use of magnetic susceptibility for tracking its deposition. Harmful dust and metal deposition may occur even at great heights and at the low-traffic side of buildings. Re-suspension of local surface materials dominates the dust deposition primarily in summer and spring due to weather conditions, and it may overwrite the influence of recent anthropogenic activities on dust composition. The accepted air-flow models should be modified by taking the local conditions (weather, morphology, etc.) into account. All studied metals showed strong enrichment in the dust and could be characterized by similar vertical deposition pattern to dust. The total susceptibility was found to be much more useful proxy for tracking dust and metal deposition than mass-specific susceptibility. Using the former, potential errors arising from sampling practice of settled dust could be eliminated. The most important heavy-metal-bearing phases were iron oxides and clay minerals. Their different behavior during the dust deposition is reflected by the vertical metal distribution patterns. Clay minerals originate primarily from re-suspension and may be one of the most important sources of potentially mobile heavy metals in such materials.  相似文献