Three-dimensional,periodic, ‘halo’ orbits     

Kathleen Connor Howell 《Celestial Mechanics and Dynamical Astronomy》1984,32(1):53-71

A largely numerical study was made of families of three-dimensional, periodic, halo orbits near the collinear libration points in the restricted three-body problem. Families extend from each of the libration points to the nearest primary. They appear to exist for all values of the mass ratio , from 0 to 1. More importantly, most of the families contain a range of stable orbits. Only near L₁, the libration point between the two primaries, are there no stable orbits for certain values of . In that case the stable range decreases with increasing , until it disappears at =0.0573. Near the other libration points, stable orbits exist for all mass ratios investigated between 0 and 1. In addition, the orbits increase in size with increasing .  相似文献   

Piltdown Man's ‘Treasure Map’          下载免费PDF全文

Eric F. Freeman 《Geology Today》2017,33(3):108-113

The ‘Maresfield Map’ is a map that purports to show features pertinent to the old iron industry in the Sussex Weald of southern England in 1724. It first appeared in a journal published by the Sussex Archaeological Society in early 1913, at roughly the same time as the formal publication by the Geological Society of London of papers introducing the discovery of the ‘remains’ of what became known as ‘Piltdown Man’ to the world. Piltdown Man was eventually revealed as fraudulent in 1953, followed by the Maresfield Map in 1974. Experiments in replication now show that the Maresfield Map is a sort of ‘treasure map’ (in a negative sense), which points fairly accurately to the supposed find‐spot of Piltdown Man, along with a coded accusation against Charles Dawson. The map's compiler is thought to have been L.F. Salzmann, the editor of the journal in which the map appeared. As such, the map represents the only such denunciation to have been published in the open literature in Dawson's lifetime, albeit a cryptic one. Mr Salzmann's possible motives are explored.  相似文献   

Simulated water budget of a small forested watershed in the continental/maritime hydroclimatic region of the United States          下载免费PDF全文

Liang Wei  Timothy E. Link  Andrew T. Hudak  John D. Marshall  Kathleen L. Kavanagh  John T. Abatzoglou  Hang Zhou  Robert E. Pangle  Gerald N. Flerchinger 《水文研究》2016,30(13):2000-2013

Annual streamflows have decreased across mountain watersheds in the Pacific Northwest of the United States over the last ~70 years; however, in some watersheds, observed annual flows have increased. Physically based models are useful tools to reveal the combined effects of climate and vegetation on long‐term water balances by explicitly simulating the internal watershed hydrological fluxes that affect discharge. We used the physically based Simultaneous Heat and Water (SHAW) model to simulate the inter‐annual hydrological dynamics of a 4 km² watershed in northern Idaho. The model simulates seasonal and annual water balance components including evaporation, transpiration, storage changes, deep drainage, and trends in streamflow. Independent measurements were used to parameterize the model, including forest transpiration, stomatal feedback to vapour pressure, forest properties (height, leaf area index, and biomass), soil properties, soil moisture, snow depth, and snow water equivalent. No calibrations were applied to fit the simulated streamflow to observations. The model reasonably simulated the annual runoff variations during the evaluation period from water year 2004 to 2009, which verified the ability of SHAW to simulate the water budget in this small watershed. The simulations indicated that inter‐annual variations in streamflow were driven by variations in precipitation and soil water storage. One key parameterization issue was leaf area index, which strongly influenced interception across the catchment. This approach appears promising to help elucidate the mechanisms responsible for hydrological trends and variations resulting from climate and vegetation changes on small watersheds in the region. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Stretching in phase space and applications in general nonautonomous multi-body problems     

Cody R. Short  Daniel Blazevski  Kathleen C. Howell  George Haller 《Celestial Mechanics and Dynamical Astronomy》2015,122(3):213-238

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Welcome to Woodside: Inverbrackie Alternative Place of Detention and performances of belonging in Woodside,South Australia,and Australia     

Faith Curtis  Kathleen J. Mee 《The Australian geographer》2012,43(4):357-375

Alternative Places of Detention (APODs) are a new way of detaining asylum seekers in Australia. The establishment of APODs creates a new formal structure of belonging in Australia which challenges everyday practices of belonging and senses of belonging at the local and national scale. This paper examines practices of belonging which emerged following the establishment of the Inverbrackie APOD in Woodside, South Australia. Using a critical discourse analysis approach, informed by the insights of theories of performativity, this research explores the competing stories of two broadly defined groups (opponents and supporters of Inverbrackie) engaged in a dialogue about asylum seekers, refugees, immigration detention and belonging. While opposition to the APOD was vocal and frequent in the lead-up to the establishment of the detention centre, once the Inverbrackie APOD became operational opponents’ voices began to fade. On the other hand, supporters continued to say things—and more importantly continued to do things—to nurture belonging for asylum seekers in Inverbrackie, Woodside, and Australia.  相似文献   

The Planetary Nebula Spectrograph elliptical galaxy survey: the dark matter in NGC 4494     

N. R. Napolitano †  A. J. Romanowsky  L. Coccato  M. Capaccioli †  N. G. Douglas  E. Noordermeer  O. Gerhard  M. Arnaboldi  F. De Lorenzi  K. Kuijken  M. R. Merrifield  E. O'Sullivan  A. Cortesi  P. Das  K. C. Freeman 《Monthly notices of the Royal Astronomical Society》2009,393(2):329-353

We present new Planetary Nebula Spectrograph observations of the ordinary elliptical galaxy NGC 4494, resulting in positions and velocities of 255 planetary nebulae out to seven effective radii (25 kpc). We also present new wide-field surface photometry from MMT/Megacam, and long-slit stellar kinematics from VLT/FORS2. The spatial and kinematical distributions of the planetary nebulae agree with the field stars in the region of overlap. The mean rotation is relatively low, with a possible kinematic axis twist outside  1 R _e  . The velocity dispersion profile declines with radius, though not very steeply, down to  ∼70 km s⁻¹  at the last data point.
We have constructed spherical dynamical models of the system, including Jeans analyses with multi-component Λ cold dark matter (CDM) motivated galaxies as well as logarithmic potentials. These models include special attention to orbital anisotropy, which we constrain using fourth-order velocity moments. Given several different sets of modelling methods and assumptions, we find consistent results for the mass profile within the radial range constrained by the data. Some dark matter (DM) is required by the data; our best-fitting solution has a radially anisotropic stellar halo, a plausible stellar mass-to-light ratio and a DM halo with an unexpectedly low central density. We find that this result does not substantially change with a flattened axisymmetric model.
Taken together with other results for galaxy halo masses, we find suggestions for a puzzling pattern wherein most intermediate-luminosity galaxies have very low concentration haloes, while some high-mass ellipticals have very high concentrations. We discuss some possible implications of these results for DM and galaxy formation.  相似文献   

Tornado warning dissemination and response at a university campus   总被引：1，自引：1，他引：0  

Kathleen Sherman-Morris 《Natural Hazards》2010,52(3):623-638

An online survey was completed by 2,921 students and employees at a large university following a tornado near-miss that required taking shelter. During this event, the university’s emergency alert messaging system was tested. The first alert message was received by over 66% of the sample within 15 min, and cell phones were the most common means of receiving this message—especially for students. Employees relied more on computer instant messaging than did students. Interpersonal communication was also important. The majority could correctly define tornado watch, tornado warning and shelter in place. Age and frequency of use of weather information were of mixed significance as predictors. Finally, over three quarters of respondents reported taking shelter during the event. Being female and being an employee made a respondent more likely to take shelter.  相似文献   

The effect of global warming on mortality     

Jean Calleja-Agius  Kathleen England  Neville Calleja 《Chemie der Erde / Geochemistry》2010

There is a significant relationship between ambient temperature and mortality. In healthy individuals with no underlying co-morbid conditions, there is an efficient heat regulation system which enables the body to effectively handle thermal stress. However, in vulnerable groups, especially in elderly over the age of 65 years, infants and individuals with co-morbid cardiovascular and/or respiratory conditions, there is a deficiency in thermoregulation. When temperatures exceed a certain limit, being cold winter spells or heat waves, there is an increase in the number of deaths. In particular, it has been shown that at temperatures above 27 °C, the daily mortality rate increases more rapidly per degree rise compared to when it drops below 27 °C.This is especially of relevance with the current emergency of global warming. Besides the direct effect of temperature rises on human health, global warming will have a negative impact on primary producers and livestock, leading to malnutrition, which will in turn lead to a myriad of health related issues. This is further exacerbated by environmental pollution.Public health measures that countries should follow should include not only health-related information strategies aiming to reduce the exposure to heat for vulnerable individuals and the community, but improved urban planning and reduction in energy consumption, among many others. This will reduce the carbon footprint and help avert global warming, thus reducing mortality.  相似文献   

The RAVE survey: constraining the local Galactic escape speed     

Martin C. Smith  Gregory R. Ruchti  Amina Helmi  Rosemary F. G. Wyse  J. P. Fulbright  K. C. Freeman  J. F. Navarro  G. M. Seabroke  M. Steinmetz  M. Williams  O. Bienaymé  J. Binney  J. Bland-Hawthorn  W. Dehnen  B. K. Gibson  G. Gilmore  E. K. Grebel  U. Munari  Q. A. Parker  R.-D. Scholz  A. Siebert  F. G. Watson  T. Zwitter 《Monthly notices of the Royal Astronomical Society》2007,379(2):755-772

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THE GEOGRAPHY OF GEOGRAPHERS     

T. W. Freeman 《The Professional geographer》1977,29(2):218-220

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