Forced wave motion in an unbouded space surrounding a lined,spherical cavity     

Herbert Reismann  John Gideon 《Pure and Applied Geophysics》1971,85(1):189-213

Summary This investigation considers the point-symmetric response of an unbounded, elastic medium. A spherical cavity in the unbounded medium is lined by an elastic, spherical shell attached to the surrounding medium. The shell liner is subjected to specified time-varying surface stress acting upon its internal surface. A detailed evaluation of the shell liner shielding characteristics is presented.  相似文献   

Advection and removal of Pb and stable Pb isotopes in the oceans: a general circulation model study     

Gideon M. Henderson  Ernst Maier-Reimer 《Geochimica et cosmochimica acta》2002,66(2):257-272

Natural Pb-isotope variability in the oceans encodes information about the sources of continental material to the oceans, about ocean circulation, and about Pb removal. In order to use this information, we must understand the natural cycle of Pb in the oceans, which is overprinted by large anthropogenic input. In this study we use ²¹⁰Pb, which has not been significantly anthropogenically perturbed, to investigate oceanic Pb. GEOSECS ²²⁶Ra and model-derived atmospheric fluxes of ²¹⁰Pb are used to input ²¹⁰Pb into an ocean general circulation model. Irreversible scavenging of this ²¹⁰Pb onto settling biogenic particles and at the seafloor are tuned so that the model replicates the observed pattern of ²¹⁰Pb in the oceans. The best-fit model run provides a map of the variability of residence time for Pb. The global average residence time of Pb in this model is 48 yr, but there is over an order of magnitude variation between areas of high and low productivity. This is expected to enhance provinciality of Pb isotope ratios in the oceans. Because stable Pb isotopes are expected to behave in seawater in a similar fashion to ²¹⁰Pb, the pattern of removal of ²¹⁰Pb derived by the model can be used to investigate the behavior of stable Pb isotopes. We use a simplified input of Pb consisting of five point sources representing major rivers and a disseminated dust input. Although this simplified input scheme does not allow precise reconstruction of Pb concentration and isotopes in the oceans, it allows us to answer some first-order questions about the behavior of Pb as an ocean tracer. With a total Pb input of 6.3 × 10⁷ mol/yr (Chow T. J. and Patterson C. C., “The occurrence and significance of Pb isotopes in pelagic sediments,” Geochim. Cosmochim. Acta26, 263-308, 1962), the model predicts natural seawater Pb concentrations averaging 2.2 pmol/kg. Even in the absence of anthropogenic input, the model ocean exhibits a near-surface maximum in Pb concentration. And the model suggests natural Pb concentrations in the Northern Hemisphere an order of magnitude higher than in the Southern Hemisphere. A point source of Pb is suggested to dominate the seawater Pb inventory close to the source but is reduced to typically less than 10% of the inventory by the time that Pb is advected out of the originating ocean. This length scale of advection for Pb isotope signals confirms their potential as tracers of ocean circulation. Assuming an 8% dissolution of dust, their input to the open ocean are seen to be a significant portion of Pb inventory throughout the oceans and make up >50% of the Pb inventory in the model’s Southern Ocean. Finally, a preliminary investigation of the response of Pb-isotope distributions to changes in boundary conditions between glacial and interglacial times illustrates that significant variation in the Pb isotopes are expected in some regions, even for reasonably small changes in climate conditions.  相似文献   

Marginal-water application in arid zones     

Dr. Gideon Oron 《GeoJournal》1987,15(3):259-266

The intensified efforts to improve agricultural economy in arid zones is associated with increased demand for water. Scarcity of potable water has hightened the importance of marginal water in dry regions. Marginal water includes saline water, wastewater, and runoff water. These water sources differ in location in regards to the application site, quality, quantity, and stability of supply. Previous experience proved that each of the above alternative water sources can be used separately or in combination, for the economic benefit of the farmers.  相似文献   

Marine geotechnical studies at continental margins: a review—Part II     

Gideon Almagor 《Applied Ocean Research》1982,4(3):130-150

  相似文献   

Marine Sand Resources Offshore Israel     

Gideon Almagor  Dan Gill  Ithamar Perath 《Marine Georesources & Geotechnology》2000,18(1):1-42

The continental margin of northern Sinai and Israel, up to Haifa Bay, is the northeastern limb of the submarine Nile Delta Cone. It is made up predominantly of clastics from the Nile and its predecessors. The continental shelf and coastal plain of Israel are built of a series of shore-parallel ridges composed of carbonate-cemented quartz sandstone (locally named kurkar), a lithification product of windblown sands that were piled up into dunes during the Pleistocene. The drop in global sea level and regression during the last glacial period exposed the continental shelf to subaerial erosion and created a widespread regional erosional unconformity which is expressed as a prominent seismic reflector at the top of the kurkar layers. The subsequent Holocene transgression abraded much of the westernmost kurkar ridges, drowned their cores, and covered the previous lowstand deposits with marine sands, which were in turn covered by a sequence of sub-Recent clayey silts. The Mediterranean coasts of Sinai and Israel are part of the Nile littoral cell. Since the building of the Aswan dams the sand supplied to Israel's coastal system is derived mainly from erosion of the Nile Delta and from sands offshore Egypt that are stirred up by storm waves. The sands are transported by longshore and offshore currents along the coasts of northern Sinai and Israel. Their volume gradually declines northward with distance from their Nile source. The longshore transport terminates in Haifa Bay where some sand is trapped, and the test escapes to deeper water by bottom currents and through submarine canyons, thus denying Nile-derived sand supply to the 40-km-long 'Akko-Rosh Haniqra shelf. The sand balance along Israel's coastal zone is a product of natural processes and human intervention. Losses due to the outgoing longshore transport, seaward escape, and landward wind transport exceed the natural gains from the incoming longshore transport and the abrasion of the coastal cliffs. The deficit is aggravated by the construction of (1) seaward-projecting structures that trap sands on the upstream side and (2) offshore detached breakwaters that trap sands between themselves and the coast. The negative sand balance is manifested by the removal of sand from the seabed and the consequent exposure of archaeological remains that were hitherto protected by it. The sediments that escape seaward from the longshore transport system form a 2.5- to 4-km-wide sandy apron adjacent to the shore that extends to where the water is 30 - 40 m deep. The apron's slope (0.5 - 0.8) is steeper than the theoretical equilibrium slope for the median grain-size diameter in this zone (0.1 - 0.3 mm). The beach sands and the apron's surficial sands are well sorted. Their grain size decreases with distance from shore, from 0.2 - 0.3 mm nearshore to 0.11 - 0.16 mm by the drowned ridge. The coarse-grained fraction consists of skeletal debris (commonly 5 - 12% carbonate matter) and wave-milled kurkar grains (locally named zifzif). In deeper water, the basal sands underlying the fine-grained sediment cover consist of 1- to 30-cm layers whose composition ranges from silty sands to various types of sands (fine, medium, coarse, and gravelly) to zifzif. For the most part, they contain large amounts of skeletal debris (20 - 60%) and small fragments of kurkar. Two types of kurkar rock were encountered offshore: a well-sorted, fine- to medium-grained (0.074 - 0.300 mm) lithified dune sand with variable amounts of carbonate cement, ranging from hard rock of low permeability to loose sand; and a porous sandstone made up predominantly of algal grains and skeletal debris (calcarenite).  相似文献   

Assessment of the Intake and the Pretreatment Design in Existing Seawater Reverse Osmosis (SWRO) Plants by Hasse Diagram Technique (HDT)     

Amos Bick  Rainer Bruggemann  Gideon Oron 《洁净——土壤、空气、水》2011,39(11):933-940

Seawater desalination is a rising technology intended to overcome water scarcity and is increasingly being used for the production of drinking water. A good quality pretreatment process is prominent to the successful operation of a Seawater Reverse Osmosis (SWRO) plant. The tasks of the intake and the pretreatment modules are to prevent fouling and to extend the lifetime of the reverse osmosis membranes. To practice the method of assessment design, 19 seawater plants with 11 different design strategies have been evaluated. The assessed strategies consist of: (i) Intake treatment, (ii) pretreatment aid (coagulation, flocculation, clarification), and (iii) pretreatment unit. Every possible combination of the design elements has been evaluated by a set of 15 attributes. The comparative evaluation has been conducted by Hasse diagram technique (HDT) using PyHasse software. The result of the HDT application includes 7 favorable incomparable design strategies. In order to solve the incomparability, the Condorcet–Kemeny–Young–Levenglick (C–K–Y–L) ranking procedure was additionally used and rendered the optimal design that is based on subsurface intake and membrane (ultrafiltration) pretreatment facilities. According to the results, both mathematical methods, i.e., the HDT in combination with the C–K–Y–L, procedure can be powerful and helpful tools to assist decisions concerning design strategies.  相似文献   

CyberShake: A Physics-Based Seismic Hazard Model for Southern California   总被引：2，自引：0，他引：2  

Robert Graves  Thomas H. Jordan  Scott Callaghan  Ewa Deelman  Edward Field  Gideon Juve  Carl Kesselman  Philip Maechling  Gaurang Mehta  Kevin Milner  David Okaya  Patrick Small  Karan Vahi 《Pure and Applied Geophysics》2011,168(3-4):367-381

CyberShake, as part of the Southern California Earthquake Center??s (SCEC) Community Modeling Environment, is developing a methodology that explicitly incorporates deterministic source and wave propagation effects within seismic hazard calculations through the use of physics-based 3D ground motion simulations. To calculate a waveform-based seismic hazard estimate for a site of interest, we begin with Uniform California Earthquake Rupture Forecast, Version 2.0 (UCERF2.0) and identify all ruptures within 200?km of the site of interest. We convert the UCERF2.0 rupture definition into multiple rupture variations with differing hypocenter locations and slip distributions, resulting in about 415,000 rupture variations per site. Strain Green Tensors are calculated for the site of interest using the SCEC Community Velocity Model, Version 4 (CVM4), and then, using reciprocity, we calculate synthetic seismograms for each rupture variation. Peak intensity measures are then extracted from these synthetics and combined with the original rupture probabilities to produce probabilistic seismic hazard curves for the site. Being explicitly site-based, CyberShake directly samples the ground motion variability at that site over many earthquake cycles (i.e., rupture scenarios) and alleviates the need for the ergodic assumption that is implicitly included in traditional empirically based calculations. Thus far, we have simulated ruptures at over 200 sites in the Los Angeles region for ground shaking periods of 2?s and longer, providing the basis for the first generation CyberShake hazard maps. Our results indicate that the combination of rupture directivity and basin response effects can lead to an increase in the hazard level for some sites, relative to that given by a conventional Ground Motion Prediction Equation (GMPE). Additionally, and perhaps more importantly, we find that the physics-based hazard results are much more sensitive to the assumed magnitude-area relations and magnitude uncertainty estimates used in the definition of the ruptures than is found in the traditional GMPE approach. This reinforces the need for continued development of a better understanding of earthquake source characterization and the constitutive relations that govern the earthquake rupture process.  相似文献   

Tectonic and magmatic responses to the subduction of high bathymetric relief     

Gideon Rosenbaum  Won Mo 《Gondwana Research》2011,19(3):571-582

Subduction of high bathymetric relief, such as aseismic ridges and magmatic plateaus, is considered to be responsible for dramatic changes in the dynamics and kinematics of the subduction zone. For example, the buoyancy of high bathymetric relief is thought to flatten the dip of the subducting slab, modifying the structural and magmatic evolution of the overriding plate and terminating arc volcanism. In addition, the effect of ridge subduction in retreating plate boundaries can inhibit subduction rollback, a process that could locally pin the subduction hinge and lead to the development of cusps and slab tearing. Here we discuss the tectonic response to subduction of high bathymetric relief using examples from the circum-Pacific subduction systems. We demonstrate that flattening of the subduction dip angle is only significant in the eastern Pacific, where the average slab dip angle is relatively shallow. In the western Pacific, in contrast, the average subduction dip angle is steeper and there is no significant flattening of the dip angle in areas of ridge subduction. Subduction of high bathymetric relief in the circum-Pacific is commonly associated with reduced arc volcanism, and in many cases, the area of ridge subduction coincides with a volcanic gap. In the overriding plate, ridge subduction is associated with pronounced changes in the style of deformation, involving uplift, reactivation of basement thrusts, development of orogen-perpendicular tear faults and block rotations leading to oroclinal bending. The discussed characteristic patterns associated with ridge subduction provide important guidelines for reconstructing past plate tectonic processes, and could help constraining the geodynamics of ancient subduction systems.  相似文献   

Effects of nitrogen nutritional stress on the morphological and yield parameters of tomato (Solanum lycopersicum L.)     

Gideon O. Okunlol  Olusanya A. Olatunji  Akinjide M. Afolabi  Kolade K. Gbadegesin 《寒旱区科学》2015,7(2):137-145

This investigation was carried out to better understand the effects of nitrogen stress on the growth and yield of tomato(Solanum lycopersicon L.). Seeds of S. lycopersicon(Ife No. 1 variety) were collected from the Osun–State Ministry of Agriculture, Oshogbo, Nigeria and planted in analyzed top soil. The plants were grown for a period of five weeks within which they were supplied with water and kept under optimum environmental conditions that enhanced normal growth. After this period, the plants were subjected to different levels of nitrogen stress which include: plants supplied with distilled water only(n), plants supplied with complete nutrient solution(N), plants supplied with nutrient solution in which nitrogen concentration sources was increased by a factor of 5(N5), and plants supplied with nutrient solution in which nitrogen concentration sources was increased by a factor of 10(N10). Analysis of Variance(ANOVA) results shows that there is no significant effect of stress on the growth and morphological parameters of tomato plants. However, there was a significant effect of nitrogen stress on the yield parameters. Nitrogen stress also caused an increase in the number and size of fruits produced in plants subjected with high nitrogen concentration.  相似文献   

Physical geography and law: The case of international river boundaries     

Gideon Biger Dr. 《GeoJournal》1988,17(3):341-347

The delimination of international boundaries in rivers and lakes are open to some unique questions. The natural, physical qualities of those geographical phenomena, which, as a part of state territory, in contrast to the definition of territory, is not immovable but movable and is even naturally a fluid element, gives it its unique characteristics. There are geographical, cartographical, even mathematical problems which the legal world had to deal with while dealing with boundaries in rivers and lakes. The two main problems are the exact location of the line and the changeable character of every river and lake, which could change the location of the line.Part of the Iraki-Iranian border runs along the Shatt al Arab river and its history reveals problems concerning the delimination of a boundary in rivers.  相似文献