Circular Polarisation Observations of SS433     

D.G. McCormick  R.E. Spencer  R.P. Fender 《Astrophysics and Space Science》2003,288(1-2):97-103

We present four epochs of observations of the Galactic X-ray binarySS433 using the Australian Telescope Compact Array (ATCA). These observations, taken on 4 February, 29 February, 23 March and 27 June 2000, at four frequencies ranging from 1–9 Ghz, are used to monitor the circular polarised emission from the source. We obtain circular polarisation spectra for the first three epochs with spectralindices α, (m _c ∝ν ^α), equal to 0.07±0.10, –1.07±0.09 and –0.18±0.05 and also observe a sign change in Stokes V. This change of handedness may indicate along-term restructuring of the magnetic field.  相似文献   

A modified linear analysis of a wave-energy conversion buoy     

Michael E. McCormick 《Ocean Engineering》1976,3(3):133-144

The analysis of a pneumatic-type wave-energy conversion buoy is developed assuming independence of the buoy heaving motion and the motion of the water column within the center pipe. Results of the analysis are then compared with experimental data in a study of the relative air velocity within the turbine passage. The results compare very well. The effect of the variation of the center pipe length is found to be significant for periods about the surge chamber resonance but is negligible in the neighborhood of the heaving resonance period. Further, the theory is applied to a prototype buoy study of the U.S. Coast Guard, and a dimensionless design curve is developed from the results of the prototype analysis.  相似文献   

On the occasion of the 65th birthday of Robert Maxwell     

Professor Michael E. McCormick  Co-Editor-in-Chief 《Ocean Engineering》1988,15(3)

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Control‐volume mixed finite element methods     

Z. Cai  J.E. Jones  S.F. McCormick  T.F. Russell 《Computational Geosciences》1997,1(3-4):289-315

A key ingredient in simulation of flow in porous media is accurate determination of the velocities that drive the flow. Large‐scale irregularities of the geology (faults, fractures, and layers) suggest the use of irregular grids in simulation. This paper presents a control‐volume mixed finite element method that provides a simple, systematic, easily implemented procedure for obtaining accurate velocity approximations on irregular (i.e., distorted logically rectangular) block‐centered quadrilateral grids. The control‐volume formulation of Darcy’s law can be viewed as a discretization into element‐sized “tanks” with imposed pressures at the ends, giving a local discrete Darcy law analogous to the block‐by‐block conservation in the usual mixed discretization of the mass‐conservation equation. Numerical results in two dimensions show second‐order convergence in the velocity, even with discontinuous anisotropic permeability on an irregular grid. The method extends readily to three dimensions.  相似文献   

Hydrodynamic coefficients of a monolithic circular offshore structure     

Michael E. McCormick 《地震工程与结构动力学》1989,18(2):199-216

Expressions for both the rectilinear and rotational inertial and damping coefficients for a circular monolithic tower of uniform radius are derived. The analysis matches the fluid velocity, derived from potential theory, with the structural velocity in sway. That is, the motions of the tower are assumed to be in a vertical plane. The analysis is then applied to a tower composed of (lumped-mass) elements, where the expressions for the added-mass and damping coefficients are shown to be functions of wave number. The added-mass is shown to be a product of two wave systems: a travelling wave system, which is responsible for the radiation damping, and a standing wave system, called the evanescent system, which is attached to the structure. The added-mass of the evanescent system is negative for small wave numbers, while that of the travelling waves is positive. The negative sign simply means that the inertial force of the evanescent waves is 180° out of phase with that of the travelling system. Furthermore, it is shown that the contributions of the two wave systems to the total added-mass of the structure counteract each other, resulting in a total added-mass which varies gradually with the wave number. Finally, the analysis is applied to an experiment, and results of the analysis and the experiment are found to agree rather well.  相似文献   

Partial recovery of Newark Bay,NJ, following pollution abatement     

J.M. McCormick  R.I. Hires  G.W. Luther  S.L. Cheng 《Marine pollution bulletin》1983,14(5):188-196

For the seven months terminating on 17 August 1980, primary sewage effluent was discharged into Newark Bay. From 22 July to 6 October 1980, we collected physical, chemical and biological data in the Newark Bay estuary from the lower Passaic River to New York Harbor. During the period of maximum discharge, the Passaic River and much of Newark Bay were anoxic or nearly so. Recovery of the Newark Bay water following sewage abatement took approximately 30 days. During most of the study period, a bloom of blue-green algae characterized the ‘Passaic River water’. This water was also characterized by chlorophyll-a values as high as 73 mg m^?3. Chlorophyll concentration almost always increased up the bay, along with decreasing salinity, increasing temperature, increasing phosphate-P and decreasing nitrate-N. The decrease in nitrate, however, was associated with an increase in ammonia-N and total N during the period of sewage discharge.  相似文献   

Evolution and significance of an overfilled alluvial foreland basin: Burnside Formation (1.9 Ga), Kilohigok Basin, N.W.T., Canada     

DAVID S. McCormick  JOHN P. Grotzinger 《Basin Research》1992,4(3-4):253-278

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Spatially explicit measures of production of young alewives in Lake Michigan: Linkage between essential fish habitat and recruitment     

Tomas?O.?H??kEmail author  Edward?S.?Rutherford  Shannon?J.?Brines  Doran?M.?Mason  David?J.?Schwab  Michael?J.?McCormick  Timothy?J.?DeSorcie 《Estuaries and Coasts》2003,26(1):21-29

The identification and protection of essential habitats for early life stages of fishes are necessary to sustain fish stocks. Essential fish habitat for early life stages may be defined as areas where fish densities, growth, survival, or production rates are relatively high. To identify critical habitats for young-of-year (YOY) alewives (Alosa pseud oharengus) in Lake Michigan, we integrated bioenergetics models with GIS (Geographic Information Systems) to generate spatially explicit estimates of potential population production (an index of habitat quality). These estimates were based upon YOY alewife bioenergetic growth rate potential and their salmonine predators’ consumptive demand. We compared estimates of potential population production to YOY alewife yield (an index of habitat importance). Our analysis suggested that during 1994–1995, YOY alewife habitat quality and yield varied widely throughout Lake Michigan. Spatial patterns of alewife yield were not significantly correlated to habitat quality. Various mechanisms (e.g., predator migrations, lake circulation patterns, alternative strategies) may preclude YOY alewives from concentrating in areas of high habitat quality in Lake Michigan.  相似文献   

Phytoplankton diversity and chlorophyll-A in a polluted estuary     

J. Michael McCormick  Patricia T. Quinn 《Marine pollution bulletin》1975,6(7):105-106

The quantity of phytoplankton in Newark Bay, New Jersey as indicated by chlorophyll-a content of the water, is low in the winter and early spring, and fluctuates greatly during the spring and summer. Chlorophyll-a concentrations are generally less than 20 μg/l until April. Between April and August, three phytoplankton blooms were indicated by chlorophyll-a concentrations as high as 81.4 μg/l. Net phytoplankton diversity values indicated generally eutrophic conditions; however, there was no significant correlation between diversity and chlorophyll-a concentrations. A role of nannoplankton in blooms is indicated.  相似文献   

<Emphasis Type="Italic">Phragmites australis</Emphasis> (Common Reed) Invasion in the Rhode River Subestuary of the Chesapeake Bay: Disentangling the Effects of Foliar Nutrients,Genetic Diversity,Patch Size,and Seed Viability     

Karin M. Kettenring  Melissa K. McCormick  Heather M. Baron  Dennis F. Whigham 《Estuaries and Coasts》2010,33(1):118-126

The invasion and expansion of the introduced haplotype of Phragmites australis across North America is of growing concern. Previous studies in the Chesapeake Bay region found that Phragmites was more abundant, had higher foliar nitrogen, and produced more viable seeds in brackish wetland subestuaries with more anthropogenic development of the watershed. Here, we focus on a different scale and address issues related to the invasion of Phragmites within a single subestuary, the Rhode River. We evaluated patterns in seed viability, foliar nutrient concentrations, patch size, and genetic variation in ten Phragmites patches in wetlands that occur in the side of the subestuary that is surrounded by forest and 10 patches in wetlands that are in the side of the subestuary that has extensive anthropogenic development. Seed viability varied from 0–60% among the 20 patches but did not differ significantly between patches on the developed vs. forested sides of the Rhode River. Foliar nutrients also did not differ between patches on the two sides of the Rhode River. Seed viability, however, was negatively related to foliar nutrients. Most Phragmites patches consisted of >1 genotype. Larger patches had multiple genotypes, and patches with more genotypes produced more viable seeds. Our study indicates that the Rhode River subestuary behaves as one system with no differences in the measured Phragmites variables between the forested vs. developed sides of the watershed. Our findings also suggest a cyclical process by which Phragmites can spread: larger patches contain more genetic diversity, which increases the chances for cross-fertilization. The subsequent increased production of viable seeds can increase local levels of genetic diversity, which can further facilitate the spread of Phragmites by seed.  相似文献