Directions     

Lawrence J. Drew 《Natural Resources Research》1995,4(4):291-295

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An interview with James MacKenzie     

Lawrence J. Drew 《Natural Resources Research》1994,3(1):1-5

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A procedure to estimate the parent population of the size of oil and gas fields as revealed by a study of economic truncation     

John H. Schuenemeyer  Lawrence J. Drew 《Mathematical Geosciences》1983,15(1):145-161

An estimation technique has been derived to predict the number of small fields in a geologic play or basin. Historically, many small oil and gas fields went unreported because they were not economical. This led to an underestimation of the number of undiscovered small fields. A study of the distributions of reported oil and gas fields in well-explored areas suggests that the large fields when grouped into log base 2 size classes are geometrically distributed. Further, the number of small fields reported is a function of the cost of exploration and development. Thus, the population field-size distribution is conjectured to be log geometric in form.  相似文献   

Debris flow initiation and sediment recharge in gullies   总被引：2，自引：0，他引：2  

Drew Brayshaw  Marwan A. Hassan   《Geomorphology》2009,109(3-4):122-131

Landslides that enter gullied low-order drainages can either initiate debris flow or stop, depositing sediment in the channel. This process is one of the most common ways that debris flows initiate, but little attention to date has been paid to evaluating the factors that affect whether or not the initial landslide will become a debris flow or deposit sediment in the channel. Statistically significant parameters that determine whether slope failures become debris flows or act to recharge in-channel sediment are channel gradient, angle of entry of failure into the channel, initial failure volume, and the amount of in-channel stored sediment. Steeper channels, low angles of entry, lower volumes of in-channel sediment, and larger initial failures were more likely to result in debris flows. This study found that as the volume of in-channel stored sediment increased, the volume of initial failure required to initiate a debris flow also increased. This result calls into question the simple supply-limited model of cyclical debris recharge and debris flow in low-order gullied drainages and suggests a negative feedback mechanism between debris accumulation and debris flow susceptibility.  相似文献   

IPHAS discoveries of young stars towards Cyg OB2 and its southern periphery     

Jorick S. Vink  Janet E. Drew  Danny Steeghs  Nick J. Wright  Eduardo L. Martin  Boris T. Gänsicke  Robert Greimel  Jeremy Drake 《Monthly notices of the Royal Astronomical Society》2008,387(1):308-318

We report on the discovery of over 50 strong Hα emitting objects towards the large OB association Cyg OB2 and the H  ii region DR 15 on its southern periphery. This was achieved using the INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS), combined with follow-up spectroscopy using the MMT multi-object spectrometer HectoSpec. We present optical spectra, supplemented with optical r ',  i ' and H α photometry from IPHAS, and near-infrared J ,  H and K photometry from Two Micron All Sky Survey. The position of the objects in the ( J − H ) versus ( H − K ) diagram strongly suggests most of them are young. Many show Ca  ii infrared triplet emission indicating that they are in a pre-main-sequence phase of evolution of T Tauri and Herbig Ae nature. Among these, we have uncovered pronounced clustering of T Tauri stars roughly a degree south of the centre of Cyg OB2, in an arc close to the H  ii region DR 15, and the radio ring nebula G79.29+0.46, for which we discuss its candidacy as a luminous blue variable. The emission-line objects towards Cyg OB2 itself could be the brightest most prominent component of a population of lower mass pre-main-sequence stars that has yet to be uncovered. Finally, we discuss the nature of the ongoing star formation in Cyg OB2 and the possibility that the central OB stars have triggered star formation in the periphery.  相似文献   

Early-A stars from IPHAS, and their distribution in and around the Cyg OB2 association     

Janet E. Drew  R. Greimel  M. J. Irwin  S. E. Sale 《Monthly notices of the Royal Astronomical Society》2008,386(4):1761-1773

Stellar photometry derived from the INT/WFC Photometric Hα Survey (IPHAS) of the Northern Galactic plane can be used to identify large, reliable samples of A0–A5 stars. For every A-type star, so identified, it is also possible to derive individual reddening and distance estimates, under the assumption that most selected objects are on or near the main sequence, at a mean absolute r ' magnitude of 1.5–1.6. This study presents the method for obtaining such samples and shows that the known reddenings and distances to the open clusters NGC 7510 and NGC 7790 are successfully recovered. A sample of over 1000 A-type stars is then obtained from IPHAS data in the magnitude range  13.5 < r ' < 20  from the region of sky including the massive northern OB association Cyg OB2. An analysis of these data reveals a concentration of ∼200 A stars over an area about a degree across, offset mainly to the south of the known 1–3 Myr old OB stars in Cyg OB2: their dereddened r ' magnitudes fall in the range 11.8–12.5. These are consistent with a ∼7 Myr old stellar population at distance modulus DM = 10.8, or with an age of ∼5 Myr at DM = 11.2. The number of A-type stars found in this clustering alone is consistent with a lower limit to the cluster mass of  ∼10⁴ M_⊙  .  相似文献   

Wicked but worth it: student perspectives on socio‐hydrology          下载免费PDF全文

Morgan C. Levy  Margaret Garcia  Peter Blair  Xi Chen  Sharlene L. Gomes  Drew B. Gower  Johanna Grames  Linda Kuil  Ye Liu  Landon Marston  Paul F. McCord  Mahendran Roobavannan  Ruijie Zeng 《水文研究》2016,30(9):1467-1472

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Agriculturally induced environmental changes in the Burren Karst,Western Ireland     

D. Drew 《Environmental Geology》1996,28(3):137-144

 The Burren plateau of County Clare is a classic example of a plateau karst characterised by patchy, thin soils, a lack of defined surface drainage, and in the instance of the Burren, a rich floristic, archaeological and landscape heritage. Since accession to the European Union and, in particular, as a result of Common Agricultural Policy initiatives, attempts have been made to raise farm incomes and to modernise agriculture in areas such as the Burren. Due to the encouragement of land reclamation and silage production has largely replaced hay farming for winter fodder. These changes pose a threat to groundwater quality by enhancing the leaching of artificial fertilizers or of organic pollutants. The Burren is highly vulnerable to water pollution from silage effluent because of its thin or absent soils and its highly karstified aquifers. A full survey of silage clamps was made in the summers of 1991 and 1992. For each site data were collected to derive the following: mass of silage, effluent produced, hazard rating of site to groundwater, likely discharge of effluent to groundwater and groundwater dilution index. About 60% of clamps were considered to be high risk and 23% medium risk. About 92% of all sites probably allow some effluent to infiltrate groundwater. Received: 1 June 1995 · Accepted: 4 December 1995  相似文献   

Two-dimensional Monte Carlo simulations of H i line formation in massive young stellar object disc winds     

S. A. Sim  J. E. Drew  K. S. Long 《Monthly notices of the Royal Astronomical Society》2005,363(2):615-627

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The AAO/UKST SuperCOSMOS Hα survey     

Quentin A. Parker  S. Phillipps  M. J. Pierce  M. Hartley  N. C. Hambly  M. A. Read  H. T. MacGillivray  S. B. Tritton  C. P. Cass  R. D. Cannon  M. Cohen  J. E. Drew  D. J. Frew  E. Hopewell  S. Mader  D. F. Malin  M. R. W. Masheder  D. H. Morgan  R. A. H. Morris  D. Russeil  K. S. Russell  R. N. F. Walker 《Monthly notices of the Royal Astronomical Society》2005,362(2):689-710

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