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161.
162.
This paper summarizes information on geomorphology and physical resources as a part of the Jordan Badia Research and Development Program. The research focused on the issue of the environment in arid lands as an aid to providing practical options for sustainable development, for the benefit not only of the Hashemite Kingdom of Jordan but of other arid regions of the world. The research is significant in that there is a need to identify usable natural resources and establish a framework for their effective exploitation and management in a marginal, fragile environment, which is sensitive to change. Pressure for development of the Badia stems from the fact that the great majority of the population in Jordan is compressed into less than 10% of the country by environmental constraints. It is hoped that the Jordan Badia Research and Development Program will provide the required framework to ease current environmental pressures, encourage migration to the Badia, a sparsely populated region, and establish economically and ecologically self-supporting communities. This paper discusses the following areas that are related to the sustainable development of the Jordan Badia with special emphasis on the Safawi area in the northern Jordan Badia; geomorphology, including landform, processes, and hazards; geology and physical resources; hydrology; surface water and water engineering; and groundwater. 相似文献
163.
Camerlenghi Angelo Domack Eugene Rebesco Michele Gilbert Robert Ishman Scott Leventer Amy Brachfeld Stefanie Drake Allison 《Marine Geophysical Researches》2001,22(5-6):417-443
We present the results of a marine geophysical investigation of the northern Prince Gustav Channel. By comparative analysis of multibeam bathymetric data, single channel seismic reflection profiles, underway chirp sonar data, ADCP current data and sediment coring, we define the main morphological elements of the area. In particular we define the glacial morphogenesis in relation to the excavation of inner shelf basins and troughs along structural discontinuities and lithologic boundaries. We identify streamlined surfaces that testify to the grounding of ice and past ice flow directions. These glacial forms are found only on glacial tills preserved in the deepest part of the basins, while net erosion to bedrock has occurred elsewhere. Since the Last Glacial Maximum (LGM), the relict glacial morphology has been draped by hemipelagic and diatomaceous mud, and bottom currents have played a major role in focusing sedimentation within small depocentres, that we define as contouritic drifts. Based on shallow sediment architecture and supported by direct measurements, we propose that the direction of bottom water flow is from the outer shelf into the Prince Gustav channel as a result of a combination of tidal currents and ice shelf-related thermohaline circulation. 相似文献
164.
SummaryLow Frequency Sounding Technique for Predicting Progressive Failure of Rock The paper outlines the various techniques used for predicting failure of rock in open strip or underground mining operations. Changes occurring in mechanical parameters of rock on increase in stress and at failure are outlined. A new experimental technique is described, which is based upon detection of changes in the response of the rock mass to imposed very low frequency, low amplitude vibrations. The limitations of the existing equipment available for the purpose are outlined and the problems posed by the new technique discussed. The requirements of the system and the method of analysis are discussed. Results obtained on a gelatine model under laboratory conditions are described. These results clearly show that changes in the frequency and amplitude response of the model with developemnt of fractures can give advance indication of imminent failure.
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ZusammenfassungEin Niederfrequenz-Schallverfahren zur Vorausbestimmung des progressiven Gesteinbruches Die vorliegende Arbeit gibt in großen Zügen die verschiedenen Verfahren an, die zur Vorhersage des Versagens von Fels bei Obertage- und Untertagearbeiten Verwendung finden können. Die sich bei Spannungserhöhung sowie beim Zusammenbruch ergebenden Veränderungen der Gesteinsparameter werden im allgemeinen dargestellt. Ein neues, auf dem Nachweis der Veränderungen des Ansprechens von Fels auf induzierte Schwingungen sehr kleiner Frequenz und kleiner Amplitude beruhendes Prüfverfahren wird beschrieben. Die Grenzen der zur Zeit für diesen Zweck verfügbaren Apparatur werden angegeben, und die sich aus dem neuen Verfahren ergebenden Probleme werden besprochen. Die Voraussetzungen des Systems sowie der Analysenmethoden werden erörtert. Die an einem Gelatinemodell unter Laborbedingungen gewonnenen Ergebnisse werden beschrieben. Diese Ergebnisse zeigen deutlich, daß die bei der Bruchentwicklung vorkommenden Veränderungen des Frequenz- und Amplitudenansprechens des Modells einen vorläufigen Hinweis auf einen drohenden Gesteinszusammenbruch liefern können.
RésuméTechnique sonique à basse fréquence pour la prédiction de la fracture progressive de la roche Cet article expose à grands traits les diverses techniques employées pour prédire des avaries de roche dans les exploitations minières à ciel ouvert ou souterraines. Les changements des paramètres de la roche pendant l'augmentation des contraintes et au moment de l'avarie sont indiqués. Une nouvelle technique expérimentale est décrite, elle est basée sur les changements de la réponse d'une masse rocheuse à la surimposition de vibrations de basse amplitude et de très basse fréquence. Les limitations de l'appareillage disponible pour ce but sont indiquées et les problèmes posés par la nouvelle technique sont discutés. Les exigences du système et la méthode d'analyse sont discutées. Des résultats obtenus au laboratoire avec un modèle en gélatine sont décrits. Ces résultats montrent clairement que les changements de la réponse à la fréquence et à l'amplitude du modèle développant des fractures peuvent donner à l'avance des indications d'une avarie imminente.
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165.
Comparison of observed microstructures and deduced physical parameters of natural deformations with those encountered in superplastic metals permits identification of superplastic behaviour in rocks. From microstructural evidence, superplastic flow of feldspar is inferred to have occurred in the deformation of a granite from Miéville, Aiguilles-Rouges massif, Switzerland. The original igneous orthoclase and oligoclase phenocrysts have both recrystallised to fine-grained albite which has deformed by superplastic flow. This change in crystal chemistry was associated with a large negative change in free energy, enabling recrystallised grains of a very small size to be stable under the prevailing conditions, thereby producing the pre-requisite conditions for superplastic behaviour. 相似文献
166.
Rainfall and wine samples have been analysed for tritium in order to obtain a record of tritium fallout since 1950 for use in hydrologic studies in southern Australia.The tritium concentrations of rainfall have been estimated for years when no samples are available by using measured values of the tritium concentration of wine samples together with Roether's (1967) exchange model and and a simple model for predicting the age of soil water used by vines.As expected, the tritium fallout pattern is similar to that obtained for Kaitoke in New Zealand and Pretoria in southern Africa. 相似文献
167.
Isotopes have often been used to discern riverine subsidies to coastal food chains, but there are few direct measurements of nutritional quality of riverine particulates. We tested for nutritionally enriched organic matter in the Mississippi River suspended sediment and evidence for its delivery to Louisiana coastal sediments by measuring enzymatically hydrolysable amino acids (EHAA). Riverine suspended sediments contained EHAA concentrations of up to 5 mg g?1, higher than reported in any coastal sediment. Pigment concentrations indicated that EHAA in some river samples were dominated by phytoplankton, but many samples contained significant non-algal EHAA. Coastal sediments showed EHAA concentrations lower than riverine sediments but still higher than most reported shelf values. Incubation of riverine sediment showed losses of 28–34% of their EHAA over 6 days, similar to differences found between riverine and coastal sediments. EHAA concentrations decreased more rapidly than total nitrogen, indicating the relative lability of this pool of material in the studied region. These EHAA-enriched materials provide fuel for various coastal biota whose composition likely depends on factors such as disturbance regimes. 相似文献
168.
Peter F. Sale Tundi Agardy Cameron H. Ainsworth Blake E. Feist Johann D. Bell Patrick Christie Ove Hoegh-Guldberg Peter J. Mumby David A. Feary Megan I. Saunders Tim M. Daw Simon J. Foale Phillip S. Levin Kenyon C. Lindeman Kai Lorenzen Robert S. Pomeroy Edward H. Allison R.H. Bradbury Jennifer Corrin Alasdair J. Edwards David O. Obura Yvonne J. Sadovy de Mitcheson Melita A. Samoilys Charles R.C. Sheppard 《Marine pollution bulletin》2014
Over 1.3 billion people live on tropical coasts, primarily in developing countries. Many depend on adjacent coastal seas for food, and livelihoods. We show how trends in demography and in several local and global anthropogenic stressors are progressively degrading capacity of coastal waters to sustain these people. Far more effective approaches to environmental management are needed if the loss in provision of ecosystem goods and services is to be stemmed. We propose expanded use of marine spatial planning as a framework for more effective, pragmatic management based on ocean zones to accommodate conflicting uses. This would force the holistic, regional-scale reconciliation of food security, livelihoods, and conservation that is needed. Transforming how countries manage coastal resources will require major change in policy and politics, implemented with sufficient flexibility to accommodate societal variations. Achieving this change is a major challenge – one that affects the lives of one fifth of humanity. 相似文献
169.
Allen H. Reed Richard W. Faas Mead A. Allison Lauro J. Calliari K.T. Holland S.E. O’Reilly W.C. Vaughan A. Alves 《Continental Shelf Research》2009
Rapid deposition of mud on the beach along the shoreface of Rio Grande do Sul, Brazil dramatically influences the normal operations in the littoral zone. In the surf zone, fluid and suspended mud opposes water-wave movement and dissipates water-wave energy; on the beach, mud limits trafficability. As part of a multinational, multidisciplinary program to evaluate the influence of mud strength, density and viscosity on water-wave attenuation, sediments were evaluated in situ or collected for evaluation from an area offshore of Cassino Beach, slightly south of the Patos Lagoon mouth. Shear strength of deposited sediments ranged from 0.6 kPa at the seafloor to 3.4 kPa at ∼1 m below the seafloor. Mud sediments were also collected to simulate the in situ response of fluid mud to shear stresses. For this determination, rheological evaluations were made using a strain-controlled Couette viscometer on numerous remixed samples that ranged in density from 1.05 to 1.30 g/cm3. It was determined that this mud is a non-ideal Bingham material in that it has a true initial yield stress as well as a upper Bingham yield stress. Initial yield stress ranged from 0.59 to 2.62 Pa, upper Bingham yield stress ranged from 1.05 to 7.6 Pa. Apparent viscosity ranged from 0.02 to 4.7 Pa s with the highest viscosities occurring between the two yield stresses. Sediment strength in the remixed samples is 2 to 3 orders of magnitude lower than the horizontal shear strength of the sediment bed as determined by shear vane or predicted from penetrometer measurements. This difference is partially due to the fact that rheological evaluations are made on fully remixed sediments, whereas horizontal shear strength is determined within relatively undisturbed sediments. Similar values of viscosity and shear strength are comparable to those determined for mud in other coastal areas where fluid mud deposits occur. 相似文献
170.
Although coral reefs worldwide are subject to increasing global threats, humans also impact coral reefs directly through localized activities such as snorkeling, kayaking and fishing. We investigated five sites on the northern shore of Moorea, French Polynesia, and quantified the number of visitors on the beach and in shallow water. In field surveys, we measured total coral cover and colony sizes of two common genera, Porites and Acropora, a massive and branching morphology, respectively. One site, which hosted over an order of magnitude more people than the other four, had significantly less total coral cover and supported very little branching Acropora. In addition, size frequency distributions of both the branching and massive genera were skewed toward smaller colony sizes at the high use site. Our results demonstrated that the use of tropical beaches may result in less coral cover, with branching colonies rare and small. 相似文献