Evaluation of throughflow interceptors for controlling secondary soil and water salinity in dryland agricultural areas of southwestern Australia: I. Questionnaire surveys     

A.J. Conacher  P.L. Combes  P.A. Smith  R.C. McLellan 《Applied geography (Sevenoaks, England)》1983,3(1):29-44

Increasing soil and water salinity in southwestern Australia is a major social, economic and environmental problem. Hydrological imbalances following extensive clearing of the natural vegetation for agriculture have redistributed soluble salts into soils and streams. Interceptors have been designed by farmers to control the throughflow component of this hydrological imbalance, to reduce waterlogging of low-lying areas, and thus to ameliorate salinity problems.Farmer interviews show that, to date, interceptors have only partly achieved these objectives. Many interceptor systems are insufficiently comprehensive and leakages are common. Further, too short a period of time has elapsed since interceptor construction to have reversed the severe deterioration of soil properties.  相似文献   

Study and suppression of anomalous fast events in inorganic scintillators for dark matter searches     

V. A. Kudryavtsev  N. J. C. Spooner  P. K. Lightfoot  J. W. Roberts  M. J. Lehner  T. Gamble  M. J. Carson  T. B. Lawson  R. Lüscher  J. E. McMillan  B. Morgan  S. M. Paling  M. Robinson  D. R. Tovey  N. J. T. Smith  P. F. Smith  G. J. Alner  S. P. Hart  J. D. Lewin  R. M. Preece  T. J. Sumner  W. G. Jones  J. J. Quenby  B. Ahmed  A. Bewick  D. Davidge  J. V. Dawson  A. S. Howard  I. Ivaniouchenkov  M. K. Joshi  V. Lebedenko  I. Liubarsky  J. C. Barton  G. Gerbier  J. Mallet  L. Mosca  C. Tao 《Astroparticle Physics》2002,17(4):79-408

The status of dark matter searches with inorganic scintillator detectors at Boulby mine is reviewed and the results of tests with a CsI(Tl) crystal are presented. The objectives of the latter experiment were to study anomalous fast events previously observed and to identify ways to remove this background. Clear indications were found that these events were due to surface contamination of crystals by alphas, probably from radon decay. A new array of unencapsulated NaI(Tl) crystals immersed either in liquid paraffin or pure nitrogen atmosphere is under construction at Boulby. Such an approach allows complete control of the surface of the crystals and the ability to remove any surface contamination. First data from the unencapsulated NaI(Tl) do not show the presence of anomalous fast events.  相似文献   

Where Non-academic Geographers are Employed     

Bruce W. Smith  John Hiltner 《The Professional geographer》1983,35(2):210-213

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200-Mpc-sized structure in the 2dF QSO Redshift survey     

L. Miller †  S. M. Croom  B. J. Boyle  N. S. Loaring  R. J. Smith  T. Shanks  P. Outram 《Monthly notices of the Royal Astronomical Society》2004,355(2):385-394

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Volcanic hazard assessment incorporating expert knowledge: Application to the yucca mountain region, Nevada, USA     

Chih-Hsiang Ho  Eugene I. Smith 《Mathematical Geology》1997,29(5):615-627

Multiple-expert hazard/risk assessments have considerable precedent, particularly in the Yucca Mountain site characterization studies. A certain amount of expert knowledge is needed to interpret the geological data used in a probabilistic data analysis. As may be the situation in science, experts disagree on crucial points. Consequently, lack of consensus in some studies is a sure outcome. In this paper, we present a Bayesian approach to statistical modeling in volcanic hazard assessment for the Yucca Mountain site. Specifically, we show that the expert opinion on the site disruption parameterp is incorporated into the prior distribution, π(p), based on geological information that is available. Moreover, π(p) can combine all available geological information motivated by conflicting but realistic arguments (e.g., simulation, cluster analysis, structural control, ..., etc.). The incorporated uncertainties about the probability of repository disruptionp eventually will be averaged out by taking the expectation over π(p). We use the following priors in the analysis: (1) priors selected for mathematical convenience: Beta (r,s) for (r,s) = (2, 2), (3, 3), (5, 5), (2, 1),(2, 8), (8, 2), and (1, 1);and (2) three priors motivated by expert knowledge. Sensitivity analysis is performed for each prior distribution. Our study concludes that estimated values of hazard based on the priors selected for mathematical simplicity are uniformly higher than those obtained based on the priors motivated by expert knowledge. And, the model using the prior, Beta (8, 2), yields the highest hazard (=2.97 × 10^-2 . The minimum hazard is produced by the “three-expert prior” (i.e., values of p are equally likely for p = 10^-3, 10^-2,and 10^-1 . The estimate of the hazard is 1.39 × 10^-3, which is only about one order of magnitude smaller than the maximum value. The term, “hazard, ” is defined as the probability of at least one disruption of a repository at the Yucca Mountain site by basaltic volcanism for the next 10,000 years.  相似文献   

The tectonic setting of the Fiordland region, south-west New Zealand     

F. J. Davey  Euan G. C. Smith 《Geophysical Journal International》1983,72(1):23-38

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The 2dF QSO Redshift Survey – XIII. A measurement of Λ from the quasi-stellar object power spectrum, P^S(k_∥, k_⊥)     

P. J. Outram  T. Shanks  B. J. Boyle  S. M. Croom  Fiona Hoyle  N. S. Loaring  L. Miller  R. J. Smith 《Monthly notices of the Royal Astronomical Society》2004,348(3):745-752

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Processes affecting transfer of sediment and colloids,with associated phosphorus,from intensively farmed grasslands: an overview of key issues     

P. M. Haygarth  G. S. Bilotta  R. Bol  R. E. Brazier  P. J. Butler  J. Freer  L. J. Gimbert  S. J. Granger  T. Krueger  C. J. A. Macleod  P. Naden  G. Old  J. N. Quinton  B. Smith  P. Worsfold 《水文研究》2006,20(20):4407-4413

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[Ti ii] and [Ni ii] emission from the strontium filament of η Carinae     

M. A. Bautista  H. Hartman  T. R. Gull  N. Smith  K. Lodders 《Monthly notices of the Royal Astronomical Society》2006,370(4):1991-2003

We study the nature of the [Ti  ii ] and [Ni  ii ] emission from the so-called strontium filament found in the ejecta of η Carinae. To this purpose, we employ multilevel models of the Ti  ii and Ni  ii systems, which are used to investigate the physical condition of the filament and the excitation mechanisms of the observed lines. For the Ti  ii ion, for which no atomic data were previously available, we carry out ab initio calculations of radiative transition rates and electron impact excitation rate coefficients. It is found that the observed spectrum is consistent with the lines being excited in a mostly neutral region with an electron density of the order of 10⁷ cm⁻³ and a temperature around 6000 K. In analysing three observations with different slit orientations recorded between 2000 March and 2001 November, we find line ratios that change among various observations, in a way consistent with changes of up to an order of magnitude in the strength of the continuum radiation field. These changes result from different samplings of the extended filament due to the different slit orientations used for each observation, and yield clues on the spatial extent and optical depth of the filament. The observed emission indicates a large Ti/Ni abundance ratio relative to solar abundances. It is suggested that the observed high Ti/Ni ratio in gas is caused by dust–gas fractionation processes and does not reflect the absolute Ti/Ni ratio in the ejecta of η Carinae. We study the condensation chemistry of Ti, Ni and Fe within the filament and suggest that the observed gas phase overabundance of Ti is likely the result of selective photoevaporation of Ti-bearing grains. Some mechanisms for such a scenario are proposed.  相似文献   

Solar Wind Statistics at 1 AU: Alfven Speed and Plasma Beta     

D. J. Mullan  C. W. Smith 《Solar physics》2006,234(2):325-338

The phenomenon of MHD wave refraction is useful in interpreting the properties of the magnetic fluctuations in certain parcels of solar wind. In the physics of MHD wave refraction, variations in the Alfvén speed V_Alf play a dominant role. Here, we compile statistics of the 1-min averages of V_Alf at the location of the ACE spacecraft during its first 5 years of operation. We find that monthly distributions of V_Alf are close to log-normal, with standard deviations σ_V as small as 0.11 in the logarithm. Variations in the monthly mean V_Alf are correlated significantly with sunspot number. We also compile monthly distributions of the plasma β parameter. The distributions of both V_Alf and β are significantly narrower than they would be if the various solar wind parameters were statistically independent. In the T_p–V_Alf plane, we find a zone of avoidance at low V_Alf: for V_Alf ≤10 – 15 km/s, there are no samples in the 1-min data that are cooler than T_p = 10 000 – 15 000 K. This feature can be understood in the context of MHD wave refraction, although other explanations are also possible.  相似文献