Co-propagation of maser emission at 1720 and 4765 MHz     

M. D. Gray  R. J. Cohen  A. M. S. Richards  J. A. Yates  D. Field 《Monthly notices of the Royal Astronomical Society》2001,324(3):643-647

MERLIN observations are presented of OH 4765-MHz and OH 1720-MHz masers in the massive star-forming region W3(OH). Two of the three intense spots of maser emission at 4765 MHz are spatially coincident with two similar spots at 1720 MHz in both left-hand circular (LHC) and right-hand circular (RHC) polarizations, to an accuracy of 15 mas. The spots also overlap in velocity when allowance is made for Zeeman splitting of the 1720-MHz line. We conclude that we have found two examples of masers in different rotational levels of OH which are co-propagating through the same column of gas and experiencing competitive gain effects. The third 4765-MHz maser spot was found to have no overlapping counterpart amongst the 1720-MHz masers.  相似文献   

Assessing stone degradation using an integrated database and geographical information system (GIS)     

Rob Inkpen  Bill Duane  John Burdett  Tim Yates 《Environmental Geology》2008,56(3-4):789-801

An integrated database and geographical information system (GIS) for the recording and monitoring of stone degradation are outlined. GIS requirements for stone degradation are summarized and a simple classification system for weathering forms identified and applied. The potential use of the system for identifying change in weathering forms using historic imagery is illustrated using an example from Oxford. Combining information from imagery of different buildings at different time periods, it is possible to put forward a possible scenario of weathering form evolution.  相似文献   

Geographic characteristics of a network interdiction problem     

Irene Casas  Eric Delmelle  Justin Yates 《GeoJournal》2016,81(1):37-53

The protection of critical infrastructure from natural and intentional events is a key component of any national security agenda. Protection schemes need to be readily identifiable and adaptable to complex changing environments. In this paper, we identify strategic geographic characteristics that impact the location of detection resources (e.g. sensors) towards the defense of regional critical infrastructure. Specifically, we seek to estimate the relationship between the results of a variation of the traditional shortest path network interdiction problem and geographical characteristics of the transportation infrastructure and the urban environment. Experiments conducted on three distinct transportation networks of different shapes and granularities (New York City—grid, Houston—radial, Boston—hybrid) underline the importance of geographic characteristics such as the proximity to resource location, attacker entry points as well as network coverage. Insights gained from this work are relevant to policy and decision makers to facilitate the development of analytical and decision-support tools capable of identifying resource allocation strategies. We discuss a heuristic-based framework that prioritizes the selection of detection resources, reflecting the importance of geographic characteristics. The findings underline the importance of geographical characteristics for the allocation of resources in a regional setting.  相似文献   

The JCMT Legacy Survey of the Gould Belt: a first look at Orion B with HARP     

J. V. Buckle  E. I. Curtis  J. F. Roberts  G. J. White  J. Hatchell  C. Brunt  H. M. Butner  B. Cavanagh  A. Chrysostomou  C. J. Davis  A. Duarte-Cabral  M. Etxaluze  J. Di Francesco  P. Friberg  R. Friesen  G. A. Fuller  S. Graves  J. S. Greaves  M. R. Hogerheijde  D. Johnstone  B. Matthews  H. Matthews  D. Nutter  J. M. C. Rawlings  J. S. Richer  S. Sadavoy  R. J. Simpson  N. F. H. Tothill  Y. G. Tsamis  S. Viti  D. Ward-Thompson  J. G. A. Wouterloot  J. Yates 《Monthly notices of the Royal Astronomical Society》2010,401(1):204-222

The Gould Belt Legacy Survey will survey nearby star-forming regions (within 500 pc), using Heterodyne Array Receiver Programme (HARP), Submillimetre Common-User Bolometer Array 2 and Polarimeter 2 on the James Clerk Maxwell Telescope. This paper describes the initial data obtained using HARP to observe ¹²CO, ¹³CO and C¹⁸O   J = 3 → 2  towards two regions in Orion B, NGC 2024 and NGC 2071. We describe the physical characteristics of the two clouds, calculating temperatures and opacities utilizing all the three isotopologues. We find good agreement between temperatures calculated from CO and from dust emission in the dense, energetic regions. We determine the mass and energetics of the clouds, and of the high-velocity material seen in ¹²CO emission, and compare the relative energetics of the high- and low-velocity material in the two clouds. We present a clumpfind analysis of the ¹³CO condensations. The slope of the condensation mass functions, at the high-mass ends, is similar to the slope of the initial mass function.  相似文献   

Power systems for autonomous underwater vehicles     

Bradley  A.M. Feezor  M.D. Singh  H. Yates Sorrell  F. 《Oceanic Engineering, IEEE Journal of》2001,26(4):526-538

In this paper, we examine the issues involved in designing battery systems and power-transfer (charging) techniques for Autonomous Underwater Vehicles (AUVs) operating within an Autonomous Ocean Sampling Network (AOSN). We focus on three different aspects of the problem, battery chemistry, pack management and in situ charging. We look at a number of choices for battery chemistry and evaluate these based on the requirements of maximizing power density and low temperature operation particular to AUVs. We look at the issues involved in combining individual cells into large battery packs and at the problems associated with battery monitoring, and the charging and discharging of packs in a typical AUV application. Finally, we present a methodology for charging an AUV battery pack in situ in support of long term deployments at remote sites  相似文献   

Book reviews     

E. M. Yates  Raymond M. Rice 《GeoJournal》1978,2(1):90-90

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Storage diagenesis versus sulphide authigenesis: possible implications in environmental magnetism     

F. Oldfield  I. Darnley  G. Yates  D. E. France  J. Hilton 《Journal of Paleolimnology》1992,7(3):179-189

Experiments involving the gradual drying out of controlled mixtures of soil and organic lake sediment during storage at room temperature show that this leads to a loss of magnetic susceptibility and isothermal remanence greatly in excess of the initial values for the sediment components of the mixtures. We conclude that during storage in the moist state, soil-derived, fine-grained, ferrimagnetic iron oxides (magnetite and/or maghemite) are transformed to paramagnetic and/or imperfect antiferrimagnetic minerals. The imperfect anti-ferromagnetic component of the initial mixtures, which probably includes goethite, appears to survive and may even increase during storage. The experimental results compare well with the previously documented effects of storing wet sediment from the site, Peckforton Mere, Cheshire, U.K., over a comparable time interval. We conclude that transformation of fine grained ferrimagnets during storage diagenesis may be responsible for many of the examples of loss of magnetic susceptibility and remanence attributed by other authors solely to the oxidation of an iron sulphide such as greigite. Only where greigite is positively identified is it valid to infer a contribution from it to the magnetic properties of lake sediments: loss of susceptibility or remanence during storage is not alone a sufficient basis for such an inference. Early drying of samples will normally avoid the effects of storage diagenesis; and recent sediment samples so treated will, where greigite formation, bacterial magnetite and magnetite dissolution are insignificant, provide a valid basis for source identification on the basis of magnetic properties.  相似文献   

Testing the 'clump' model of SiO maser emission     

M. D. Gray  R. J. Ivison  E. M. L. Humphreys  & J. A. Yates 《Monthly notices of the Royal Astronomical Society》1998,295(4):970-976

Building on the detection of the J =7–6 SiO maser emission in both the v =1 and v =2 vibrational states towards the symbiotic Mira R Aquarii, we have used the James Clerk Maxwell Telescope to study the changes in the SiO maser features from R Aqr over a stellar pulsational period. The observations, complemented by contemporaneous data taken at 86 GHz, represent a test of the popular thermal-instability clump models of SiO masers. The 'clump' model of SiO maser emission considers the SiO masers to be discrete emitting regions which differ from their surroundings in the values of one or more physical variables (SiO abundance, for example). We find that our observational data are consistent with a clump model in which the appearance of maser emission in the J =7–6 transitions coincides with an outward-moving shock impinging on the inner edge of the maser zone.  相似文献   

Water resources for agriculture in a changing climate: international case studies   总被引：1，自引：0，他引：1  

Cynthia Rosenzweig  Kenneth M. Strzepek  David C. Major  Ana Iglesias  David N. Yates  Alyssa McCluskey  Daniel Hillel 《Global Environmental Change》2004,14(4):823

This integrated study examines the implications of changes in crop water demand and water availability for the reliability of irrigation, taking into account changes in competing municipal and industrial demands, and explores the effectiveness of adaptation options in maintaining reliability. It reports on methods of linking climate change scenarios with hydrologic, agricultural, and planning models to study water availability for agriculture under changing climate conditions, to estimate changes in ecosystem services, and to evaluate adaptation strategies for the water resources and agriculture sectors. The models are applied to major agricultural regions in Argentina, Brazil, China, Hungary, Romania, and the US, using projections of climate change, agricultural production, population, technology, and GDP growth.For most of the relatively water-rich areas studied, there appears to be sufficient water for agriculture given the climate change scenarios tested. Northeastern China suffers from the greatest lack of water availability for agriculture and ecosystem services both in the present and in the climate change projections. Projected runoff in the Danube Basin does not change substantially, although climate change causes shifts in environmental stresses within the region. Northern Argentina's occasional problems in water supply for agriculture under the current climate may be exacerbated and may require investments to relieve future tributary stress. In Southeastern Brazil, future water supply for agriculture appears to be plentiful. Water supply in most of the US Cornbelt is projected to increase in most climate change scenarios, but there is concern for tractability in the spring and water-logging in the summer.Adaptation tests imply that only the Brazil case study area can readily accommodate an expansion of irrigated land under climate change, while the other three areas would suffer decreases in system reliability if irrigation areas were to be expanded. Cultivars are available for agricultural adaptation to the projected changes, but their demand for water may be higher than currently adapted varieties. Thus, even in these relatively water-rich areas, changes in water demand due to climate change effects on agriculture and increased demand from urban growth will require timely improvements in crop cultivars, irrigation and drainage technology, and water management.  相似文献   

Multibeam maser survey of methanol and excited OH in the Magellanic Clouds: new detections and maser abundance estimates     

J. A. Green  J. L. Caswell  G. A. Fuller  S. L. Breen  K. Brooks  M. G. Burton  A. Chrysostomou  J. Cox  P. J. Diamond  S. P. Ellingsen  M. D. Gray  M. G. Hoare  M. R. W. Masheder  N. McClure-Griffiths  M. Pestalozzi  C. Phillips  L. Quinn  M. A. Thompson  M. Voronkov  A. Walsh  D. Ward-Thompson  D. Wong-McSweeney  J. A. Yates  R. J. Cohen † 《Monthly notices of the Royal Astronomical Society》2008,385(2):948-956

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