Modeling Sediment Transport Dynamics in Thompson Island Pool,Upper Hudson River     

Ziegler  C. Kirk  Israelsson  Peter H.  Connolly  John P. 《Water Quality and Ecosystems Modeling》2000,1(1-4):193-222

Two-dimensional, vertically-averaged hydrodynamic and sediment transport models were developed and applied as part of a PCB fate and transport modeling study of Thompson Island Pool (TIP), Upper Hudson River. Mechanistic formulations were used to simulate cohesive and non-cohesive suspended load transport; site-specific data were extensively used to determine model inputs. This modeling approach is compared and contrasted to non-mechanistic solids transport sub-models used in other contaminant fate studies. A minimum number of model parameters were adjusted to calibrate the sediment transport model using data collected during the 1994 spring flood. The model was validated during the 1997 spring flood and for a 22-year (1977–1998) period. Successful calibration and validation of the model showed that: (1) deposition and resuspension processes were realistically and accurately formulated in the model; (2) the model is an effective diagnostic tool for quantitatively evaluating net deposition and erosion from various areas of TIP; and (3) sediment transport results can be coupled with a PCB fate model with a high degree of confidence.  相似文献   

Toward a greenhouse equivalence index: The total exposure analogy   总被引：1，自引：0，他引：1  

Kirk R. Smith  Dilip R. Ahuja 《Climatic change》1990,17(1):1-7

Work supported by Office of Policy Analysis, U.S.E.P.A.  相似文献   

Curvature and surface distribution of the polar rays in the solar corona on 12 November 1966     

J. G. Kirk  J. S. Newby 《Solar physics》1974,35(2):377-384

Following a technique developed by Saito, the positions and orientations of the polar rays visible in a photograph of the total solar eclipse of 12 November 1966 were examined to infer the length of an equivalent bar magnet representing the Sun's external magnetic field and the true distribution of polar rays from the two-dimensional projection seen in the photograph. In spite of the strong asymmetry in solar activity between the northern and southern solar hemispheres at the time of the eclipse, it was found that the magnetic field as delineated by the polar rays could be well represented by an extended dipole whose poles were each 0.43 R from the center of the Sun and on the axis of rotation. The polar rays are distributed mainly in a circular zone 9° away from the pole and about 8° wide, with this zone bounded by empty regions at the pole and 15° to 20° away from it, beyond which there are again some rays, but not so many. These results are in good accord with expectation from Saito's analysis.Operated by the Association of Universities for Research in Astronomy Inc. under contract with the National Science Foundation.  相似文献   

Harbour entrance morphology and sediments at a river mouth port,Westport, New Zealand     

R. M. Kirk  W. J. Hastie  J. L. Lumsden 《新西兰海洋与淡水研究杂志》2013,47(4):689-697

Entrance morphologies and sediment characteristics were studied at Westport Harbour, a river mouth port located on the Buller River, New Zealand. The most frequent morphology found was that in which two submarine bars were present off the river mouth. When present, these bars were separated by a transverse channel running east from Carters Beach and terminating in the principal inlet channel. Sediment samples were collected and analysed for grain size, reliability (grain shape), and, in a few instances, mineralogy. The data collected suggested that longshore sediment transport is predominantly west to east and that river derived sediment is deflected to the east. The inner bar is predominantly a littoral drift related event whereas the outer bar, which is composed mainly of littoral drifted sediment, forms as a submarine extension of Carters Beach. Both bars can be modified by floods in the river, although modification of the outer bar is much less frequent because of the very high river flows required. Sediment can bypass directly across the river mouth only when the inner bar is present. On other occasions bypassing can only occur by transport through the transverse channel or over the outer bar, into the river channel and then onshore.  相似文献   

Erupted upper teeth in a male sperm whale,Physeter macrocephalus     

Nadine J. Gibbs  Edwin J. Kirk 《新西兰海洋与淡水研究杂志》2013,47(2):325-327

An adult male sperm whale (Physeter macrocephalus L.) which stranded in Hawke's Bay, New Zealand, was found to have seven erupted teeth in its upper jaw—six on the left side, and one on the right side. Each upper tooth lay in the side of the pit into which the corresponding lower tooth fitted, and two bore a groove consistent with contact with a lower tooth.  相似文献   

Seasonal Prevalence of Hematodinium sp. Infections of Blue Crabs in Three South Carolina (USA) Rivers     

Kirk J. Parmenter  Patrick A. Vigueira  C. Kaighn Morlok  Jennifer A. Micklewright  Kylie M. Smith  Kimberly S. Paul  Michael J. Childress 《Estuaries and Coasts》2013,36(1):174-191

Blue crab, Callinectes sapidus, commercial landings in the USA have been declining at an alarming rate. In South Carolina, these declines are significantly correlated with years of decreased rainfall and elevated salt marsh salinity. Previous studies suggest that higher salinity increases the risk of infection by Hematodinium sp., a dinoflagellate parasite of blue crabs, C. sapidus. A 4-year survey (June 2008 to March 2012) of blue crabs in the ACE Basin National Estuarine Research Reserve documented (1) the temporal and spatial patterns of Hematodinium sp. infection in relation to salinity, (2) some environmental correlates of disease prevalence, and (3) the characteristics of infected blue crabs. Sampling was conducted four times a year in March, June, September, and December in the South Edisto, Ashepoo, and Combahee rivers beginning in June 2008. Crab hemolymph samples were collected and preserved and DNA was successfully amplified for 2,303 individuals. Hematodinium sp. infection was evaluated by PCR amplification of its 18S rRNA gene and adjacent regions. Prevalence was highest in December 2008 in the Combahee River at sites closest to St. Helena Sound. The spatial and temporal pattern of Hematodinium sp. infection was correlated with several environmental parameters. Infected crabs exhibited differences in carapace shape and body condition compared to uninfected crabs. Overall, these results suggest that blue crabs in regions of higher salinity are at greater risk of infection by Hematodinium sp. and infected individuals exhibit sub-lethal effects of the disease.  相似文献   

Perspectives of Taiwan Tectonics from TAIGER Project     

Francis T Wu  Hao Kuo-Chen  Kirk McIntosh  Luc Lavier 《地质学报》2013,87(Z1):84-85

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Models,validation, and applied geochemistry: Issues in science,communication, and philosophy     

D. Kirk Nordstrom 《Applied Geochemistry》2012

Models have become so fashionable that many scientists and engineers cannot imagine working without them. The predominant use of computer codes to execute model calculations has blurred the distinction between code and model. The recent controversy regarding model validation has brought into question what we mean by a ‘model’ and by ‘validation.’ It has become apparent that the usual meaning of validation may be common in engineering practice and seems useful in legal practice but it is contrary to scientific practice and brings into question our understanding of science and how it can best be applied to such problems as hazardous waste characterization, remediation, and aqueous geochemistry in general. This review summarizes arguments against using the phrase model validation and examines efforts to validate models for high-level radioactive waste management and for permitting and monitoring open-pit mines. Part of the controversy comes from a misunderstanding of ‘prediction’ and the need to distinguish logical from temporal prediction. Another problem stems from the difference in the engineering approach contrasted with the scientific approach. The reductionist influence on the way we approach environmental investigations also limits our ability to model the interconnected nature of reality. Guidelines are proposed to improve our perceptions and proper utilization of models. Use of the word ‘validation’ is strongly discouraged when discussing model reliability.  相似文献   

Numerical models of thermally and mechanically coupled two-layer convection of highly viscous fluids     

Kirk Ellsworth  Gerald Schubert 《Geophysical Journal International》1988,93(2):347-363

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Monte Carlo evaluation of microbial-mediated contaminant reactions in heterogeneous aquifers     

Mohamed M.A. Mohamed  Kirk Hatfield  Ahmed E. Hassan 《Advances in water resources》2006

Monte Carlo simulations are conducted to evaluate microbial-mediated contaminant reactions in an aquifer comprised of spatially variable microbial biomass concentrations, aquifer hydraulic conductivities, and initial electron donor/acceptor concentrations. A finite element simulation model is used that incorporates advection, dispersion, and Monod kinetic expressions to describe biological processes. Comparisons between Monte Carlo simulations of heterogeneous systems and simulations using homogeneous formulation of the same two-dimensional transport problem are presented. For the assumed set of parameters, physical aquifer heterogeneity is found to have a minor effect on the mass of contaminant biodegraded/transformed when compared to a homogeneous system; however, it noticeably changes the dispersion, skewness, and peakness of contaminant concentration distributions. Similarly, for low microbial growth rate, given favorable microbial growth characteristics, biological heterogeneity has minor effect on the mass of contaminant biodegraded/transformed when compared to a homogeneous system. On the other hand, when higher effective growth rates are assumed, biological heterogeneity and spatial heterogeneities in essential electron donor/acceptors reduce the efficiency of biotic contaminant reactions; consequently, model simulations derived from heterogeneous biomass distributions predict remediation time scales that are longer than those simulated for homogeneous systems. When correlations between physical aquifer and biological heterogeneities are considered, the assumed correlation affects predicted mean and variance of contaminant concentration and biomass distributions. For example, an assumed negative correlation between hydraulic conductivity and the initial biomass distribution produces a plume where less efficient biotic contaminant reactions occur at the leading edge of the plume; this is consistent with less degradation/transformation occurring over regions of higher groundwater velocities. However, the presence and absence of these correlations do not appear to affect the efficiency of microbial-mediated contaminant attenuation.  相似文献