The Q-gram method: Q from instantaneous phase     

Peter D. Bromirski  L. Neil Frazer  Fred K. Duennebier 《Geophysical Journal International》1995,120(1):73-86

  相似文献   

Vertical Seismic Profile Inversion With Genetic Algorithms     

B. Nolte  L. N. Frazer 《Geophysical Journal International》1994,117(1):162-178

  相似文献   

A comparison of gas dynamics in smooth particle hydrodynamics and semi-analytic models of galaxy formation     

John C. Helly  Shaun Cole  Carlos S. Frenk  Carlton M. Baugh  rew Benson  Cedric Lacey  Frazer R. Pearce 《Monthly notices of the Royal Astronomical Society》2003,338(4):913-925

  相似文献   

Doubling of coastal erosion under rising sea level by mid-century in Hawaii     

Tiffany R. Anderson  Charles H. Fletcher  Matthew M. Barbee  L. Neil Frazer  Bradley M. Romine 《Natural Hazards》2015,77(1):75-96

This study discusses the scaling properties of the spatial distribution of the December 26, 2004, Sumatra aftershocks. We estimate the spatial correlation dimension D ₂ of the epicentral distribution of aftershocks recorded by a local network operated by Geological Survey of India. We estimate the value of D ₂ for five blocks in the source area by using generalized correlation integral approach. We assess its bias due to finite data points, scaling range, effects of location errors, and boundary effects theoretically and apply it to real data sets. The correlation dimension was computed both for real as well as synthetic data sets that include randomly generated point sets obtained using uniform distributions and mimicking the number of events and outlines of the effective areas filled with epicenters. On comparing the results from the real data and random point sets from simulations, we found the lower limit of bias in D ₂ estimates from limited data sets to be 0.26. Thus, the spatial variation in correlation dimensions among different blocks using local data sets cannot be directly compared unless the influence of bias in the real aftershock data set is taken into account. They cannot also be used to infer the geometry of the faults. We also discuss the results in order to add constraints on the use of synthetic data and of different approaches for uncertainty analysis on spatial variation of D ₂. A difference in D ₂ values, rather than their absolute values, among small blocks is of interest to local data sets, which are correlated with their seismic b values. Taking into account the possible errors and biases, the average D ₂ values vary from 1.05 to 1.57 in the Andaman–Nicobar region. The relative change in D ₂ values can be interpreted in terms of clustering and diffuse seismic activity associated with the low and high D ₂ values, respectively. Overall, a relatively high D ₂ and low b value is consistent with high-magnitude, diffuse activity in space in the source region of the 2004 Sumatra earthquake.  相似文献   

Chemical and mineralogical investigations on deep sea manganese nodules from the Southern Ocean     

J. Ostwald  F. W. Frazer 《Mineralium Deposita》1973,8(4):303-311

Deep sea manganese nodules from the Southern Ocean have been studied using chemical analysis, X-ray diffraction, optical mineragraphic and electron probe microanalysis techniques. The nodules were lower in manganese, iron and associated elements than the average grade of manganese nodules from other localities. A number of chemical relationships have been observed. Nickel, copper, cobalt, barium, zinc, molybdenum, strontium, sulphur and phosphorus are associated with the manganese rich phases and titanium with the iron rich phases. X-ray diffraction analysis and electron probe microanalysis results indicate that the manganese phases are similar to the disordered -MnO₂ and manganite phases reported by other workers.

---

Zusammenfassung Tiefsee-Manganknollen aus dem südlichen Ozean wurden mit Hilfe von chemischen Analysen, Röntgenbeugung, mikroskopischer Untersuchung und Anwendung von Mikroelektronensonden untersucht. Die Knollen enthielten weniger Mangan, Eisen und Begleitelemente als das Durchschnittsquantum in Manganknollen aus anderen Gebieten. Eine Anzahl chemischer Ähnlichkeiten wurde beobachtet. Nickel, Kupfer, Kobalt, Barium, Zink, Molybdän, Strontium, Schwefel und Phosphor treten gemeinsam mit den manganreichen Erscheinungsformen, und Titan zusammen mit den eisenreichen auf. Ergebnisse der Röntgenbeugungsanalyse und Mikroelektronensondenuntersuchung ergaben, daß die Manganphasen Ähnlichkeit haben mit ungeordneten -MnO₂ und manganitischen Erscheinungsformen, über die andere Wissenschaftler berichtet haben.

  相似文献   

The relationship between basicity and swelling on reduction of iron-ore pellets     

F.W. Frazer  H. Westenberger  K.H. Boss  W. Thumm 《International Journal of Mineral Processing》1975,2(4):353-365

The influence of gangue composition on swelling during reduction of iron-ore pellets is investigated for nine iron ores with a range of basicities. X-ray diffraction studies show that high swelling on reduction is accompanied by the formation of low-melting-point, calcium-substituted olivines. Recrystallisation of the hematite structure occurs on firing high-basicity pellets. An explanation is given for the existence of high swelling for fired pellets of basicities 0.2–0.8.  相似文献   

The orientation of galaxy dark matter haloes around cosmic voids     

Riccardo Brunino  Ignacio Trujillo  Frazer R. Pearce  Peter A. Thomas 《Monthly notices of the Royal Astronomical Society》2007,375(1):184-190

Using the Millennium N -body Simulation we explore how the shape and angular momentum of galaxy dark matter haloes surrounding the largest cosmological voids are oriented. We find that the major and intermediate axes of the haloes tend to lie parallel to the surface of the voids, whereas the minor axis points preferentially in the radial direction. We have quantified the strength of these alignments at different radial distances from the void centres. The effect of these orientations is still detected at distances as large as 2.2 R _void from the void centre. Taking a subsample of haloes expected to contain disc-dominated galaxies at their centres we detect, at the 99.9 per cent confidence level, a signal that the angular momentum of those haloes tends to lie parallel to the surface of the voids. Contrary to the alignments of the inertia axes, this signal is only detected in shells at the void surface  (1 < R < 1.07  R _void)  and disappears at larger distances. This signal, together with the similar alignment observed using real spiral galaxies, strongly supports the prediction of the Tidal Torque theory that both dark matter haloes and baryonic matter have acquired, conjointly, their angular momentum before the moment of turnaround.  相似文献   

Comparative patterns of occupancy by decapod crustaceans in seagrass,oyster, and marsh-edge habitats in a Northeast Gulf of Mexico estuary     

Thomas?P.?GlancyEmail author  Thomas?K.?Frazer  Charles?E.?Cichra  William?J.?Lindberg 《Estuaries and Coasts》2003,26(5):1291-1301

Decapod crustaceans occupying seagrass, salt marsh edge, and oyster habitats within the St. Martins Aquatic Preserve along the central Gulf coast of Florida were quantitatively sampled using a 1-m² throw trap during July–August 1999 and March–April 2000. Relative abundance and biomass were used as the primary measures to compare patterns of occupancy among the three habitat types. Representative assemblages of abundant and common species from each habitat were compared using Schoener's Percent Similarity Index (PSI). In all, 17,985 decapods were sampled, representing 14 families and 28 species. In the summer sampling period, mean decapod density did not differ between oyster and seagrass habitats, which both held greater densities of decapods than marsh-edge. In the spring sampling period oyster reef habitat supported greater mean decapod density than both seagrass and marsh-edge, which had similar densities of decapods. Habitat-specific comparisons of decapod density between the two sampling periods indicated no clear seasonal effect. In summer 1999, when seagrasses were well established, decapod biomass among the three habitats was not significantly different. During spring 2000, decapod biomass in oyster (41.40 gm⁻²) was greater than in marshedge (4.20 gm⁻²), but did not differ from that of seagrass (9.73 g m⁻²). There was no significant difference in decapod biomas between seagrass and marsh-edge habitats during the spring 2000 sampling period. The assemblage analysis using Schoener's PSI indicated that decapod assemblages associated with oyster were distinct from seagrass and marshedge habitats (which were similar). The results of this study suggest that in comparison to seagrass and marsh-edge habitats, oyster reef habitats and the distinct assemblage of decapod crustaceans that they support represent an ecologically important component of this estuarine system.  相似文献   

Two problems in WKBJ theory: the interpolation of sampled velocity profiles and the use of frequency-dependent, complex velocities     

L. Neil Frazer 《Geophysical Journal International》1983,72(1):193-211

  相似文献   

Kirchhoff–Helmholtz reflection seismograms in a laterally inhomogeneous multi-layered elastic medium – II. Computations     

Mrinal K. Sen  L. Neil Frazer 《Geophysical Journal International》1985,82(3):415-437

Summary. High-frequency reflection and refraction seismograms for laterally variable multi-layered elastic media are computed by using the frequency domain elastic Kirchhoff–Helmholtz (KH) theory of Frazer and Sen. Both source and receiver wavefields are expanded in series of generalized rays and then elastic (KH) theory is applied to determine the coupling between each source ray and each receiver ray at each interface. The motion at the receiver is given as a series of integrals, one for each generalized ray. We use geometrical optics and plane wave reflection and transmission coefficients for rapid evaluation of the integrand. When the source or the receiver ray field has caustics on the surface of integration geometrical ray theory breaks down and this gives rise to singularities in the KH integrand. We repair this using methods suggested by Frazer and Sen.
Examples of reflection seismograms for 2-D structures computed by elastic KH theory are shown. Those for a vertical fault scarp structure are compared with the seismograms obtained by physical modelling. Then OBS data obtained from the mid-America trench offshore Guatemala area are analysed by computing KH synthetics for a velocity model that has been proposed for that area. Our analysis indicates the existence of a small low-velocity zone off the trench axis.
No head wave arrivals are obtained in our KH synthetics since we do not consider multiple interactions of a ray with an interface. The nearly discontinuous behaviour of elastic R/T coefficients near the critical angle causes small spurious phases which arrive later than the correct arrivals.  相似文献