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41.
Stephen R. Piotrowicz Robert A. Duce James L. Fasching Clifford P. Weisel 《Marine Chemistry》1979,7(4):307-324
The effects of the bubble breaking process on the atmospheric geochemical cycles of the elements Fe, Cu and Zn were investigated, in situ, in the estuarine waters of Narragansett Bay, Rhode Island. Enrichment, as defined by the metal-to-sodium ratios in the aerosols produced compared to their ratio in bulk water, occurred for the three metals investigated. The extent and potential geochemical importance of the process were different for each element. Iron enrichment was quite low (enrichment factor (EF) <100) and constant, and scavenging of iron from the water column and subsequent enrichment on the aerosols produced did not appear to occur. Copper enrichment on the aerosols was 200 and appeared to be influenced by both microlayer and scavenging effects. In addition, copper enrichment appears to be correlated to biological processes. Zinc enrichment was approximately the same as Cu; however, a strong scavening effect appeared to occur, suggesting scavenging of Zn by rising bubbles. Scavenging effects suggest that open-ocean enrichments for Cu may be slightly higher than observed here and a great deal higher for Zn.Geochemical implications of the data, together with other existing data, indicate that the sea is an insignificant source of Fe to the atmosphere. The sea may be a significant source (contributing on the order of 10% or more) of the total annual quantity of Cu and Zn to the atmosphere. 相似文献
42.
Stephen R. Piotrowicz George R. Harvey Deborah A. Boran Clifford P. Weisel M. Springer-Young 《Marine Chemistry》1984,14(4):333-346
The interactions in seawater of cadmium, copper, and zinc with natural levels of marine humus (fulvic and humic acids) were studied using differential pulse anodic stripping voltammetry (DPASV). Interactions with Cu were also examined by ultraviolet spectrophotometry. The degree of interaction relates to the structure of the particular fulvic or humic acid tested. Marine fulvic and humic acids with different equivalent weights and varying degrees of aromaticity and heteroatom substitution were tested to assess the relative importance of these fundamental structural features in determining the degree of interaction. An index of heteroatom substitution, derived from proton magnetic resonance spectra of these materials, when combined with equivalent weights correlated with the nature and degree of metal interaction. Both marine fulvic and humic acids appreciably interacted with Zn. In contrast, the extent of interaction of fulvic acids with Cu appears to be related to their structure while humic acids appear to interact with Cu regardless of structure. Cadmium interacts only with mature, highly crosslinked humic acids. 相似文献
43.
Nicholas J. Clifford Philip J. Soar Oliver P. Harmar Angela M. Gurnell Geoffrey E. Petts Joanne C. Emery 《水文研究》2005,19(18):3631-3648
Output from a three‐dimensional numerical flow model (SSIIM) is used in conjunction with high‐resolution topographic and velocity data to assess such models for eco‐hydraulic applications in river channel design and habitat appraisal. A new methodology for the comparison between field measurement and model output is detailed. This involves a comparison between conventional goodness‐of‐fit approaches applied to a spatially structured (riffle and pool) sample of model and field data, and a ‘relaxation’ method based upon the spatial semivariance of model/field departures. Conventional assessment indicates that the model predicts point‐by‐point velocity characteristics on a 0·45 m mesh to within ±0·1 m s−1 over 80% of the channel area at low flow, and 50% of the area at high in‐bank flow. When a relative criterion of model fit is used, however, the model appears to perform less well: 60–70% of channel area has predicted velocities that depart from observed velocities by more than 10%. Regression analysis of observed and predicted velocities gives more cause for optimism, but all of these conventional indicators of goodness of fit neglect important spatial characteristics of model performance. Spatial semivariance is a means of supplementing model appraisal in this respect. In particular, using the relaxation approach, results are greatly improved: at a high in‐bank flow, the model results match field measurements to within 0·1 m s−1 for more than 95% of the total channel area, provided that model and field comparisons are allowed within a radius of approximately 1 m from the original point of measurement. It is suggested that this revised form of model assessment is of particular relevance to eco‐hydraulic applications, where some degree of spatial and temporal dynamism (or uncertainty) is a characteristic. The approach may also be generalized to other environmental science modelling applications where the spatial attributes of model fits are of interest. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
44.
Grana Dario Parsekian Andrew D. Flinchum Brady A. Callahan Russell P. Smeltz Natalie Y. Li Ang Hayes Jorden L. Carr Brad J. Singha Kamini Riebe Clifford S. Holbrook W. Steven 《Mathematical Geosciences》2022,54(8):1315-1345
Mathematical Geosciences - Understanding the subsurface structure and function in the near-surface groundwater system, including fluid flow, geomechanical, and weathering processes, requires... 相似文献
45.
Clifford E. Singer T. S. Gopi Rethinaraj Samuel Addy David Durham Murat Isik Madhu Khanna Brandon Kuehl Jianding Luo Wilma Quimio Kothavari Rajendran Donna Ramirez Ji Qiang Jürgen Scheffran T. Nedjla Tiouririne Junli Zhang 《Climatic change》2008,88(3-4):309-342
Probability distributions for carbon burning, atmospheric CO2, and global average temperature are produced by time series calibration of models of utility optimization and carbon and heat balance using log-linear production functions. Population growth is used to calibrate a logistically evolving index of development that influences production efficiency. Energy production efficiency also includes a coefficient that decreases linearly with decreasing carbon intensity of energy production. This carbon intensity is a piecewise linear function of fossil carbon depletion. That function is calibrated against historical data and extrapolated by sampling a set of hypotheses about the impact on the carbon intensity of energy production of depleting fluid fossil fuel resources and increasing cumulative carbon emissions. Atmospheric carbon balance is determined by a first order differential equation with carbon use rates and cumulative carbon use as drivers. Atmospheric CO2 is a driver in a similar heat balance. Periodic corrections are included where required to make residuals between data and model results indistinguishable from independently and identically distributed normal distributions according to statistical tests on finite Fourier power spectrum amplitudes and nearest neighbor correlations. Asymptotic approach to a sustainable non-fossil energy production is followed for a global disaggregation into a tropical/developing and temperate/more-developed region. The increase in the uncertainty of global average temperature increases nearly quadratically with the increase in the temperature from the present through the next two centuries. 相似文献
46.
47.
N. J. Clifford 《地球表面变化过程与地形》1993,18(9):845-854
The theoretical basis and use of statistical and correlation approaches for the analysis of turbulence time series are described. In particular, the analysis of data from high frequency current meter measurements using MINITAB is presented and the data files and analytical routines are included on the software disk. 相似文献
48.
Edward D. Ghent Philip S. Simony Clifford C. Knitter 《Contributions to Mineralogy and Petrology》1980,74(1):67-73
Late Precambrian and Lower Paleozoic metapelitic rocks near Mica Creek, British Columbia, range in metamorphic grade from biotite zone to sillimanite zone. The kyanite-sillimanite isograd was established after phase 2 folding but was deformed by phase 3 folding. Topographic relief of about 2 km, combined with phase 3 folding, permits reasonably precise determination of the geometry of the isogradic surfaces. The effects of phase 3 folding have been accounted for and the isobaric surfaces at the time of metamorphism are inferred to have been dipping gently. Using the kyanite-sillimanite experimental phase diagram, intersection of the isobars and the isograd permits estimates of differences in temperature and pressure along a cross section. These estimates are about 400 bars and 20° C. Mineral geothermometry (garnet-biotite) and geobarometry (garnetplagioclase-Al 2SiO5-quartz) does not provide a fine enough resolution to detect these predicted differences. 相似文献
49.
Single stage magmatic fractionation processes result in igneous rock suites in which correlation coefficients between pairs of elements are generally high. The Tertiary lavas of E. Iceland are used as an illustration of this type of behaviour. When a second process such as fractionation at a different pressure, wall-rock assimilation, or mixing with a different magma, occurs, correlation coefficients are altered in a predictable way if the process and the chemical characteristics of the participating rocks, minerals and liquids are known. A computer program has been devised to simulate complete correlation coefficient matrices for any desired two- or multi-stage process e.g. fractional crystallisation coupled with contamination. Basaltic suites from Mahabaleshwar, India and the Rooi Rand, southern Africa show correlation coefficient patterns characteristic of multi-stage evolution, and these are interpreted with the aid of computer simulation. The Mahabaleshwar suite shows clear evidence of contamination by a granitic component. The Rooi Rand rocks however remain problematic. 相似文献
50.
CPT Clifford W. Greve 《Journal of Geodesy》1972,46(1):31-45
This paper discusses theory and results of an attempt to use non-linear programming methods to arrive at an optimal, in the
sense of least cost, solution to the design of a survey system to meet specified accuracy. In other words, the method determines
the combination of various types of observations which will yield the required accuracy of control points for a minimum cost.
The theoretical background of the procedure is discussed, and methods of extension to photo-grammetry and other sciences are
presented. Much of the paper is concerned with discussing results of numerical solutions for the optimal design of several
small, but typical, mapping problems.
It is believed that this research is original with the author, as extensive literature searches and correspondence has produced
no knowledge of prior research into this application of nonlinear programming. The method at its current state of development
appears to be capable of yielding significant improvements to the present concepts of survey network design. 相似文献