Transient vibrations of an isotropic elastic sphere     

John P. Sheehan  Lokenath Debnath 《Pure and Applied Geophysics》1972,99(1):37-48

Summary An attempt is made to study the dynamic response of a thick, homogeneous isotropic elastic sphere under the action of uniformly distributed internal and external pressure distributions which vary sinusoidally with time. An exact solution of the problem is obtained with the aid of the Laplace transform method and the theory of residues. Some main properties of the radial vibration field are examined. The frequency equation for the free vibration is derived explicitly. Several limiting cases of interest are recovered.  相似文献   

Muscovite Reactions and Partial Melting in South-eastern Connecticut     

LUNDGREN  L. W.  JR. 《Journal of Petrology》1966,7(3):421-453

A sillimanite-orthoclase isograd mapped in south-eastern Connecticutcuts across the strike of the major Ordovician pelitic schistunit. This isograd separates a sillimanite muscovite zone froma sillimanite-orthoclase zone. Muscovite is not present in thesillimanite-orthoclase zone. Segments of all the Cambrian (?) and Ordovician units in south-easternConnecticut were affected by the reaction: muscovite_ssquartzsodicplagioclase_ss = sillimaniteorthoclase_ssless sodic plagioclase_sswater (Guidotti, 1963), and possibly by reactions such as muscovite_ssbiotite_ss3 quartz – orthoclase_ssgarnet_ssTi-rich biotite_sswater.This metamorphism was a post-Lower Devonian event. The sodiumcontent of orthoclases and data on stability boundaries formuscovite, anthophyllite, and cordierite suggest temperaturesof metamorphism in the sillimanite-orthoclase zone of more than650 C. Migmatites were formed during this metamorphic event,partly by isochemical elimination of muscovite to form 7 percent. orthoclase for every 10 per cent. modal muscovite initiallypresent. Most of the migmatites must have developed by partialmelting of rocks in which muscovite was being eliminated, andby the intrusion of melt from deeper zones in which biotitewas being eliminated. Melting in the lower-temperature partof the sillimanite-orthoclase zone must have been controlledby the amount of water released from muscovite; melting in thehigher temperature part may have been more extensive if thetemperature was sufficiently high to produce melts undersaturatedwith water.  相似文献   

VISCOSITY MEASUREMENTS OF AQUEOS CLAY SUSPENSIONS AS A TOOL FOR DETERMINING MINERALOGIC TYPE OF CLAYS     

JOHN O. ROBERTSON JR.    HERMAN H. RIEKE  GEORGE V. CHILINGAR 《Sedimentology》1965,4(3):181-187

  相似文献   

DEGREE OF HYDRATION OF CLAYS     

GEORGE V. CHILINGAR  HERMAN H. RIEKE  III  JOHN O. ROBERTSON JR. 《Sedimentology》1963,2(4):341-342

  相似文献   

The Rio Dell Formation: a Plio-Pleistocene basin slope deposit in Northern California     

DAVID J. W. PIPER  WILLIAM R. NORMARK  JAMES C. INGLE  JR 《Sedimentology》1976,23(3):309-328

The Rio Dell Formation (Pleistocene and Pliocene), exposed south of Eureka, California, is a prograded sequence of basinal turbidites overlain by basin slope and shelf deposits. The slope deposits studied in the Centerville Beach section accumulated in a steadily shallowing environment delineated by analysis of palaeobathymetrically significant benthonic foraminiferal biofacies in turn suggesting deposition at depths of 1000–100 m. Lower slope deposits interfinger with basinal turbidites derived from the Eel River delta to the north. Slumped blocks of silty mudstone, and associated silt and mud beds, are common. The middle slope deposits are mudstones; coarser sediments bypassed this zone. Mudstones and muddy siltstones alternate on the upper slope. Shallow depressions, probably slump scars, that have been rapidly filled by upper slope sediment are common. The transition to shelf deposits is marked by an increase in sediment grain size, in the degree of oxidation, and in the abundance of megafossils. High percentages of benthonic foraminifera displaced from shelf depths indicate that resedimentation processes are most important on the upper slope.  相似文献   

TEXTURAL DIFFERENTIATION ON THE SHORE FACE DURING EROSIONAL RETREAT OF AN UNCONSOLIDATED COAST, CAPE HENRY TO CAPE HATTERAS, WESTERN NORTH ATLANTIC SHELF     

DONALD J. P. SWIFT  ROBERT B. SANFORD  CHARLES E. DILL JR  NICHOLAS F. AVIGNONE 《Sedimentology》1971,16(3-4):221-250

  相似文献   

Oxygen and Carbon Isotope Studies of Contact Metamorphism of Carbonate Rocks     

SHIEH  Y. N.; TAYLOR  H. P.  JR. 《Journal of Petrology》1969,10(2):307-331

O¹⁸/O¹⁶ and C¹²/C¹³ ratios have been determined for carbonaterocks and coexisting minerals from two contact metamorphic aureolesat Birch Creek, California and Marble Canyon, Texas. The peliticmetasediments and granitic intrusions of the Birth Creek localitywere also analyzed for their O¹⁸/¹⁶ and D/H ratios. Oxygen andcarbon isotope fractionations in coexisting dolomite and calciteare interrelated but show no obvious correlation with sampledistance from the intrusive contact. Small-scale oxygen isotopicexchange effects between rock units are observed within a fewfeet of the intrusive-country rock contacts and the marble-schistcontacts at Birch Creek. Oxygen isotopic temperatures obtainedfrom quartz—biotite fractionations in the biotite schistsof Birch Creek show a systematic decrease with increasing distanceaway from the intrusive contact; the isotopic contact temperatureis calculated to be 535–45°C. Low O¹⁸/¹⁶ and C¹³/¹²ratiosof the contact metamorphic marbles generally correlate wellwith presence of calc-silicate minerals, indicating that theCO₂ liberated during metamorphic decarbonation reactions isenriched in both O¹⁸and C¹² relative to the carbonates. Materialbalance calculations indicate that the liberated CO₂ is about5 per mille richer in O¹⁸ and about 6 per mille richer in C¹³than coexisting calcite.  相似文献   

Size Selective Predation by the Asteroid Pisaster ochraceus on the Bivalve Mytilus calif ornianus: A Cost-Benefit Analysis     

James B.  Mcclintock Truman J.  Robnett JR. 《Marine Ecology》1986,7(4):321-332

Abstract. When simultaneously presented with equal numbers of four sizes of clumped Mytilus californianus (20, 35, 55 and 85 mm shell length), Pisaster ochraceus (arm length of 70-110mm R) showed a preference for the medium sizes (35 and 55mm length). Prey-size preference was positively correlated with predator size. Mean prey-digestion times (insertion of the stomach, opening of the valves and digestive period) decreased significantly following fiiing of an artificial gape between the valves of mussels. When presented with different sizes of clumped filed mussels, starfish still chose medium mussels, indicating that stomach insertion, valve opening, and digestion rate may not be important constraints determining size selective predation. Measurements of the force required to dislodge mussels from the substratum and conspecifics showed an increasing exponential relationship with mussel size. Size selective feeding may be an energy maximizing and time minimizing strategy, where energy gained from choosing larger mussels is balanced against disproportionately increased costs in energy and time of removing large mussels from the substratum.  相似文献   

THE DRIVING FORCES OF LAND CHANGE IN THE NORTHERN PIEDMONT OF THE UNITED STATES     

ROGER F. AUCH  DARRELL E. NAPTON  STEVEN KAMBLY  THOMAS R. MORELAND JR.  KRISTI L. SAYLER 《Geographical review》2012,102(1):53-75

Driving forces facilitate or inhibit land‐use / land‐cover change. Human driving forces include political, economic, cultural, and social attributes that often change across time and space. Remotely sensed imagery provides regional land‐change data for the Northern Piedmont, an ecoregion of the United States that continued to urbanize after 1970 through conversion of agricultural and forest land covers to developed uses. Eight major driving forces facilitated most of the land conversion; other drivers inhibited or slowed change. A synergistic web of drivers may be more important in understanding land change than individual drivers by themselves.  相似文献   

Nonlinear bend stiffener analysis using a simple formulation and finite element method     

LOW Ying Min  SHEEHAN John M 《中国海洋工程》2011,25(4):577-590

Flexible marine risers are commonly used in deepwater floating systems.Bend stiffeners are designed to protect flexible risers against excessive bending at the connection with the hull.The structure is usually analyzed as a cantilever beam subjected to an inclined point load.As deflections are large and the bend stiffener material exhibits nonlinear stress-strain characteristics,geometric and material nonlinearities are important considerations.A new approach has been developed to solve this nonlinear problem.Its main advantage is its simplicity;in fact the present method can be easily implemented on a spreadsheet.Finite element analysis using ABAQUS is performed to validate the method.Solid elements are used for the bend stiffener and flexible pipe.To simulate the near inextensibility of flexible risers,a simple and original idea of using truss elements is proposed.Through a set of validation studies,the present method is found to be in a good agreement with the finite element analysis.Further,parametric studies are performed by using both methods to identify the key parameters and phenomena that are most critical in design.The most important finding is that the common practice of neglecting the internal steel sleeve in the bend stiffener analysis is non-conservative and therefore needs to be reassessed.  相似文献