The Transiometer: An Alternative Method of Soil Moisture Measurement in Slowly Permeable Soils     

Todd P. Trooien  Alan R. Bender  John H. Bischoff 《Ground Water Monitoring & Remediation》1986,6(2):99-105

The union of a piezoresistive pressure transducer and a porous ceramic cup was termed "transiometer." The transiometer was constructed from economical and readily available materials. It could be used to measure soil water potentials in both saturated and unsaturated conditions, and was well suited to continuous monitoring with data acquisition equipment.
Transiometer testing was conducted at two sites, one of moderate permeability and the other of slow permeability. The slowly permeable site was instrumented with four replications of the following: (1) transiometers installed at four depths, (2) a transi-ometerwithout the ceramic cup, (3) apiezometer, and (4) access tubes for monitoring soil moisture with a neutron probe. The moderately permeable site was instrumented with a transiometer, two piezometers, and an access tube for monitoring with a neutron probe.
In saturated conditions the transiometer had a faster response time after installation than the piezometer. Faster response makes the transiometer more desirable for use in slowly permeable soils, especially when monitoring dynamic soil water.
Calculated random error of the transiometer measuring system, including a digital voltmeter and a scanner, was typically 0.09 feet (2.8cm), with a maximum calculated to be 0.38 feet (11.5cm). The two most significant components were imprecision of the scanner card and calibration shift. The transiometer was sensitive to atmospheric pressure fluctuations, with sensitivity to atmospheric pressure change increasing with installation depth.  相似文献   

Shear diffusion and the spread of oil in the surface layers of the North Sea     

Dr. Alan J. Elliott 《Ocean Dynamics》1986,39(3):113-137

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Hydrodynamics and sedimentation in wave-dominated coastal environments,B. Greenwood and R. A. Davis,jr. (eds), developments in sedimentology, 39, Elsevier,Amsterdam, 1984. No. of Pages: 473     

Alan Carr 《地球表面变化过程与地形》1986,11(3):345-346

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Electron density and polarized absorption spectra of fayalite: A comment     

W. Alan Runciman 《Physics and Chemistry of Minerals》1987,14(4):387-387

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Diffusion of dissolved carbonate in magmas: Experimental results and applications     

E. Bruce Watson  Mark A. Sneeringer  Alan Ross 《Earth and Planetary Science Letters》1982,61(2):346-358

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The problem of current channelling: A critical review   总被引：1，自引：0，他引：1  

Alan G. Jones 《Surveys in Geophysics》1983,6(1-2):79-122

The notion that currents induced ‘elsewhere’, by external source fields, could wend their way in a frequency-independent ohmic-like manner through a region of interest has been the cause of many recent disputes within the geomagnetic induction community. In particular, two-dimensional (2D) models of the Rhinegraben, and of the region known as the ‘Eskdalemuir anomaly’ in southern Scotland, have been dismissed as erroneous by those who believe that the observations are more correctly interpreted as due to the effects of ‘channelled’ currents rather than ‘induced’ currents. In this review, attention is paid primarily to consider under what circumstances any perturbation of current flow, which may manifest itself as a ‘DC-like’ channelled current, could cause a ‘problem’ for those wishing to interpret their observations. Various concepts are introduced, particularly the ratio of 3D/2D current channelling numbers for the induction problem, which is shown to be the ratio of the length of the 3D body to the skin depth in the host medium. It is stressed that the worker must analyse his data by adequate statistical techniques, and that the simplest physical models possible, that describes the observations, must be sought. Finally, suggestions are made for further work to be undertaken.  相似文献   

Mineralogy and petrology of the Abee enstatite chondrite breccia and its dark inclusions     

Alan E. Rubin  Klaus Keil 《Earth and Planetary Science Letters》1983,62(1):118-131

The Abee E4 enstatite chondrite breccia consists of clasts (many rimmed by metallic Fe, Ni), dark inclusions and matrix. The clasts and matrix were well equilibrated by thermal metamorphism, as evidenced by uniform mineral compositions, recrystallized chondrules, low MnO content of enstatite and high abundance of orthoenstatite. The clasts acquired their metal-rich rims prior to this metamorphic episode. The occurrence in Abee of relatively unmetamorphosed dark inclusions, clasts with nearly random magnetic orientations and a matrix with a uniform magnetic orientation [18,19] indicates that clast and matrix metamorphism occurred prior to the agglomeration of the breccia.The dark inclusions are an unusual kind of enstatite chondritic material, distinguished from the clasts and matrix by their relative enrichments in REE [21–23], low relative abundances of kamacite, total metallic Fe, Ni and silica, lower niningerite/(total sulfide) ratios, high relative abundances of oldhamite and martensite, smaller euhedral enstatite, more heterogeneous enstatite and metallic Fe, Ni, more calcic enstatite and more nickeliferous schreibersite.We propose the following model for the petrogenesis of the Abee breccia: The maximum metamorphic temperature of breccia parent material was?- 840°C (the minimum temperature of formation of Abee niningerite) and perhaps near 950–1000°C (the Fe-Ni-S eutectic temperature). Euhedral enstatite crystals in metallic Fe, Ni- and sulfide-rich areas grew at these metamorphic temperatures into pliable metal and sulfide. Breccia parent material was impact-excavated from depth, admixed with dark inclusions and rapidly cooled (700 to 200°C in about 2 hours) [15]. During this cooling, clast and matrix material acquired thermal remanent magnetization. Random conglomeration of clasts and unconsolidated matrix materials caused the clasts to have random magnetic orientations and the matrix areas to have net magnetic intensities of zero (due to the cancellation of numerous randomly oriented magnetic vectors of equal intensity in the matrix). A subsequent ambient magnetic field imparted a uniform net magnetic orientation to the matrix and caused the magnetic orientations of the clasts to be somewhat less random. The Abee breccia was later consolidated, possibly by shock or by shallow burial and very long-period/low-temperature (< 215°C) metamorphism.  相似文献   

A new technique for determining the surface level of salt marshes and other uncompacted sedimentary environments     

Alan P. Carr 《地球表面变化过程与地形》1983,8(3):293-296

The method described involves the use of an electro-optical distance measurer mounted on a theodolite. Observations are taken onto a series of acrylic reflectors, aligned at right angles to the line of sight, and slope distances and vertical and horizontal angles are recorded. From these data it is possible to obtain surface heights to an accuracy of ±0·5 cm at 200 m and to avoid any direct disturbance of the site under investigation.  相似文献   

The development of warehousing in England     

Alan C. McKinnon 《Geoforum》1983,14(4):389-399

Over the past decade there has been a growing recognition by the business community, central government and local planners of the economic importance of warehousing. This importance can be measured in terms of the value of stock held in warehouses, their very rapid growth relative to other types of commercial property and the employment they create. This article reviews changes in business and planning attitudes to warehousing, accounts for the recent growth of warehouse floorspace in England and examines the spatial distribution of this growth.  相似文献   

Detection Time for Plausible Changes in Annual Precipitation, Evapotranspiration, and Streamflow in Three Mississippi River Sub-Basins     

Alan D. Ziegler  Edwin P. Maurer  Justin Sheffield  Bart Nijssen  Eric F. Wood  Dennis P. Lettenmaier 《Climatic change》2005,72(1-2):17-36

We use diagnostic studies of off-line variable infiltration capacity (VIC) model simulations of terrestrial water budgets and 21st-century climate change simulations using the parallel climate model (PCM) to estimate the time required to detect predicted changes in annual precipitation (P), evapotranspiration (E), and discharge (Q) in three sub-basins of the Mississippi River Basin. Time series lengths on the order of 50–350 years are required to detect plausible P, E, and Q trends in the Missouri, Ohio, and Upper Mississippi River basins. Approximately 80–160, 50, and 140–350 years, respectively, are needed to detect the predicted P, E, and Q trends with a high degree of statistical confidence. These detection time estimates are based on conservative statistical criteria (α = 0.05 and β = 0.10) associated with low probability of both detecting a trend when it is not occurring (Type I error) and not detecting a trend when it is occurring (Type II error). The long detection times suggest that global-warming-induced changes in annual basin-wide hydro-climatic variables that may already be occurring in the three basins probably cannot yet be detected at this level of confidence. Furthermore, changes for some variables that may occur within the 21st century might not be detectable for many decades or until the following century – this may or may not be the case for individual recording station data. The long detection times for streamflow result from comparatively low signal-to-noise ratios in the annual time series. Finally, initial estimates suggest that faster detection of acceleration in the hydrological cycle may be possible using seasonal time series of appropriate hydro-climatic variables, rather than annual time series.  相似文献