Migration and global environmental change     

Richard Black  W. Neil Adger  Nigel W. Arnell  Stefan Dercon  Andrew Geddes  David Thomas 《Global Environmental Change》2011

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Evaluation of the controls affecting the quality of spatial data derived from historical aerial photographs     

Jan Walstra  Jim H. Chandler  Neil Dixon  Rene Wackrow 《地球表面变化过程与地形》2011,36(7):853-863

This paper is concerned with the fundamental controls affecting the quality of data derived from historical aerial photographs typically used in geomorphological studies. A short review is provided of error sources introduced into the photogrammetric workflow. Data‐sets from two case‐studies provided a variety of source data and hence a good opportunity to evaluate the influence of the quality of archival material on the accuracy of coordinated points. Based on the statistical weights assigned to the measurements, precision of the data was estimated a priori, while residuals of independent checkpoints provided an a posteriori measure of data accuracy. Systematic discrepancies between the two values indicated that the routinely used stochastic model was incorrect and overoptimistic. Optimized weighting factors appeared significantly larger than previously used (and accepted) values. A test of repeat measurements explained the large uncertainties associated with the use of natural objects for ground control. This showed that the random errors not only appeared to be much larger than values accepted for appropriately controlled and targeted photogrammetric networks, but also small undetected gross errors were induced through the ‘misidentification’ of points. It is suggested that the effects of such ‘misidentifications’ should be reflected in the stochastic model through selection of more realistic weighting factors of both image and ground measurements. Using the optimized weighting factors, the accuracy of derived data can now be more truly estimated, allowing the suitability of the imagery to be judged before purchase and processing. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

The effects of diagenesis on the reservoir characters in sandstones of the Late Cretaceous Pab Formation,Kirthar Fold Belt,southern Pakistan     

Muhammad Umar  Henrik Friis  Abdul Salam Khan  Akhtar Muhammad Kassi  Aimal Khan Kasi 《Journal of Asian Earth Sciences》2011,40(2):622-635

The Maastrichtian Pab Formation in the southern part of Pakistan is composed of fine- to very coarse-grained texturally mature quartz arenite and subordinate sublitharenite varieties. The sandstones have undergone intense and complex diagenetic episodes due to burial and uplift. Diagenetic modifications were dependent mainly on the clastic composition of sandstone, burial depth and thrust tectonics. Diagenetic events identified include compaction, precipitation of calcite, quartz, clay minerals and iron oxide/hydroxide, dissolution and alteration of unstable clastic grains as feldspar and volcaniclithic fragments as well as tectonically induced grain fracturing. The unstable clastic grains like feldspar and lithic volcanic fragments suffered considerable alteration to kaolinite and chlorite. Dissolution and alteration of feldspar and volcanic lithic fragments and pressure solution were the main sources of quartz cements. Mechanical compaction and authigenic cements like calcite, quartz and iron oxide/hydroxide reduced the primary porosity, whereas dissolution of clastic grains and cements has produced secondary porosity. Chlorite coatings on clastic grains have prevented quartz cementation. Coarse-grained, thick bedded packages of fluviodeltaic, shelf delta lobe and submarine channels facies have higher average porosity than fine-grained, thin bedded and bioturbated sandstone of deeper shelf and abyssal plain environments and these facies are concluded to be possible future hydrocarbon prospects.  相似文献   

Mineralogical, geochemical, and geotechnical evaluation of Al-Sowera soil for the building brick industry in Iraq     

Salih Muhammad Awadh  Hamed Hassan Abdullah 《Arabian Journal of Geosciences》2011,4(3-4):413-419

The raw material soil of Al-Sowera factory quarry (quarry soil and mixture) used for building brick industry was tested mineralogically, geochemically and geotechnically. Mineral components of soil are characterized by Clay minerals (Palygoriskite and chlorite) and non-clay minerals like calcite, quratz, feldspar, gypsum and halite. The raw material is deficient in SiO₂, Al₂O₃, K₂O, Fe₂O₃ and MgO, while enriched in CaO. Loss on ignition and Na₂O are in suitable level and appear to be concordant with the standard. Grain size analyses show that the decreasing sand and clay, and increasing silt ratio in both quarry soil and mixture caused decreasing in strength of brick during molding and after firing. The quarry soil is characterized by high plasticity clayey soil of 30.49 plastic index (P.I), whereas the mixture considered a clayey soil has a low plasticity of 7.7 plastic index (P.I). To improve the chemical and physical properties of the raw material, alumina-silicate minerals rich in K₂O, Fe₂O₃ and MgO are recommended as additive materials to the main mixture.  相似文献   

Electrostatic solitons in rotating dusty plasmas with anisotropic ion pressure     

Muhammad Adnan  S. Mahmood  Anisa Qamar 《Astrophysics and Space Science》2012,341(2):551-558

The Zakharov-Kuznetsov (ZK) equation is derived for electrostatic wave in a rotating magnetoplasma with anisotropic ion pressure and in the presence of stationary charged dust particles. The anisotropic ion pressure is defined using double adiabatic Chew-Golberger-Low (CGL) theory. The reductive perturbation method is employed to study the dynamics of obliquely propagating low frequency ion acoustic wave with adiabatic ions. It is found that the ion pressure anisotropy, polarity, density of the dust particles and rotational frequency have significant effects on the formation nonlinear structures in rotating magnetized dusty plasmas. The numerical results are also presented for illustration.  相似文献   

Probabilistic seismic hazard analysis and spectral accelerations for United Arab Emirates     

Zahid Khan  Magdi El-Emam  Muhammad Irfan  Jamal Abdalla 《Natural Hazards》2013,67(2):569-589

In recent years, the United Arab Emirates (UAE) has experienced an unprecedented growth which is coupled with the increase in seismic activity in the surroundings. Previous studies presents significant variations in their results whereas some recent studies although very detailed focus on only few cities. This study reviews the results of previous studies and presents new findings for the whole of UAE based on the improved source model and use of next generation attenuation (NGA) equations. The peak ground accelerations, spectral accelerations and deaggregation of hazard for major cities are presented. Moreover, the breakdown of the range of mapped spectral accelerations (S _0.2 and S ₁) is proposed to form the basis for the development of site amplification factors in subsequent studies. The results of this study indicate almost similar values of ground motion compared to some recently published studies and smaller values compared to some earlier studies.  相似文献   

Noble gas and isotope geochemistry in western Canadian Arctic watersheds: tracing groundwater recharge in permafrost terrain     

Nicholas Utting  Bernard Lauriol  Neil Mochnacz  Werner Aeschbach-Hertig  Ian Clark 《Hydrogeology Journal》2013,21(1):79-91

In Canada’s western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems with features including the occurrence of year-round open water and the formation of icings, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. Stable isotopes (δ¹⁸O, δD, δ¹³C_DIC), and noble gases have proved useful to study groundwater recharge and flow of groundwater which discharges along rivers in Canada’s western Arctic. In these studies of six catchments, groundwater recharge was determined to be a mix of snowmelt and precipitation. All systems investigated show that groundwater has recharged through organic soils with elevated P_CO2, which suggests that recharge occurs largely during summer when biological activity is high. Noble gas concentrations show that the recharge temperature was between 0 and 5 °C, which when considered in the context of discharge temperatures, suggests that there is no significant imbalance of energy flux into the subsurface. Groundwater circulation times were found to be up to 31 years for non-thermal waters using the ³?H-³He method.  相似文献   

Mineralogy, geochemistry, and reserve estimation of the Euphrates limestone for Portland cement industry at Al-Najaf area, South Iraq   总被引：1，自引：1，他引：0  

Mautaz Al-Dabbas  Salih Muhammad Awadh  Ayad Abed Zaid 《Arabian Journal of Geosciences》2013,6(2):491-503

This study deals with the mineralogical and geochemistry of the Euphrates Formation (Lower Miocene) in Bahr Al-Najaf area in order to assess the lithofacies of the Euphrates Formation for Portland cement manufacturing. Petrographic and mineralogical studies were carried out on 210 core samples, collected from 21 boreholes, and showed that calcite is the dominant mineral with few amounts of quartz, gypsum, feldspar, and a rare amount of dolomite. Clay mineral suites (palygorskite, kaolinite, montmorillonite, and illite) formed about 5% from the total mineral composition. Palygorskite precipitated directly in alkali shallow water rich with Si and Mg ions. Chemical weathering of feldspar under acidic conditions participated in formation of Kaolinite. Geochemistry showed that there is no high variation in chemical constituents with depth, and the average of CaO (51.5), MgO (0.83), SO₃ (0.54), SiO₂ (4.3), Fe₂O₃ (0.45), Al₂O₃ (0.93), L.O.I (40.7), Na₂O₃ (0.08), K₂O (0.14), and Cl^- (0.1) qualified the lithofacies of Euphrates Formation to be raw materials suitable for manufacturing the Portland cement. Triangle Block method is applied to estimate the reserve on square area (2?×?2 km²) which is computed to be 63 million tons of medium-tough limestone as potential probable reserve.  相似文献   

Forecasting flood risk in the Indus River system using hydrological parameters and its damage assessment   总被引：1，自引：1，他引：0  

Bushra Khan  Muhammad Jawed Iqbal 《Arabian Journal of Geosciences》2013,6(10):4069-4078

Hydrological parameters are among the widely used parameters in assessing flood risk. On the other hand, anticipated flood damages, in case of flooding, are estimated with the help of expected losses in areas nearer to the watercourse. The major source of almost every-year flooding in Pakistan is the Indus River system that comprises the major rivers of Pakistan. We first use observed data to construct simulated data models based on various probability distributions namely normal, lognormal, Weibull, largest extreme value, gamma-3, and log-Pearson type-3 distributions and thereby compute probable maximum flood. Secondly, we perform log-Pearson type-3 analysis with and without historic adjustment on the observed data series of 17 years to forecast floods with return periods T of 2, 5, 10, 25, 50, 100, and 200 years. We also categorize the river structures based on the risk of flooding. Lastly, we estimate risk of flood damages in terms of expected losses based on observed data. The present study reveals that the log-Pearson type-3 distribution is relatively better for estimating probable maximum flood. We use exceedence probability to assess the risk of flooding in the various structures of the said rivers. The analysis shows that flood damages in Pakistan may be reduced by increasing the design capacity of the structures and also by giving awareness to people about the flood-generating factors.  相似文献   

The disposal of radioactive wastes underground     

Neil Chapman  Alan Hooper 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(1):46-63

Nuclear power is strategically and quantitatively an important contributor to global electricity generation capacity and produces a small amount of potentially highly hazardous wastes that require careful management. The accepted solution for disposing of higher activity and longer-lived radioactive wastes from the nuclear power industry and other sources is engineered emplacement in deep geological disposal facilities (GDFs), situated many hundreds of metres underground. The first purpose-built GDFs for the most active of these wastes (used nuclear fuel and high-level wastes) will be operational in about ten years time in a few countries, with most other countries (including the UK) developing such facilities during coming decades. This article reviews the conceptual basis for geological disposal, examines how long-term safety is provided, considers the geological challenges to developing GDFs and the uncertainties that have to be managed, and looks in more detail at some of the most advanced design concepts. Because the issue of forecasting GDF evolution and behaviour over very long time periods lies at the core of geological disposal, particular emphasis is placed on matching containment requirements with diminishing hazard potential over many thousands of years. The article concludes with a commentary on current developments in the UK geological disposal programme.  相似文献