The influence of microform bed roughness elements on flow and sediment transport in gravel bed rivers     

Marwan A. Hassan  Ian Reid 《地球表面变化过程与地形》1990,15(8):739-750

Pebble clusters are reported widely as characteristic of gravel river beds and are known to influence the initial entrainment of bedload. A field assessment suggests that their distribution is not ubiquitous, favouring channel bars, but also reveals a tendency towards a preferred stream wise spacing. A series of laboratory flume experiments shows that flow resistance rises to, and falls from, a peak value as the longitudinal spacing of pebble clusters decreases, in a manner similar to that shown by others for strip roughness, isolated blocks, and simulated ripples and dunes. The experiments also reveal a strong inverse relationship between bedload flux rates and the flow resistance induced by the concentration of pebble clusters. It is concluded that pebble cluster spacing tends towards an equilibrium that is regulated by a feedback process involving sediment transport rates and that the spatial concentration of these microforms will adjust to the point where they induce maximum flow resistance.  相似文献   

Prediction of the collapsing risk of mining slopes based on geostatistical interpretation of geotechnical parameters     

Marzieh Shademan Khakestar  Hossein Hassani  Parvizz Moarefvand  Hassan Madani 《Journal of the Geological Society of India》2016,87(1):97-104

Almost all collapses of rock slopes especially in open pit mines are related to discontinuities such as bedding planes, faults and major joints.Geostatistical assessments can be used for understanding the distribution of regionalized variables in any spatial study. In this paper3D spatial dispersion of the fault planes in the Gole Gohar open pit iron mine, located in Kerman province, south east of Iran, is modeled. Then, regionalized variable theory is used to analyze and interpret spatial distribution of the following geotechnical parameters: Geological strength index (GSI), Rock quality designation (RQD), Cohesion (C) and angle of internal friction (f). In order to define regionalized variable distribution, variogram functions were determined for identifying the regional behavior. Structural analysis of variograms showed that the mentioned parameters have spatial structures that make it possible to set up a geostatistical model to predict their values for each non-sampled block on the pit wall. Results showed that there is a relation between the low values of geotechnical parameters and the existence of discontinuities around the pit area. The role of discontinuities in the occurrence of collapses in the area was clearly demonstrated by comparing the estimated parameters models and the model of discontinuities dispersion.  相似文献   

Comparison of different phases of bismuth silicate nanofibers for photodegradation of organic dyes     

S. S. Batool  S. Hassan  Z. Imran  K. Rasool  M. Ahmad  M. A. Rafiq 《International Journal of Environmental Science and Technology》2016,13(6):1497-1504

Two different phases of bismuth silicate nanofibers [Bi₂SiO₅ and Bi₄(SiO₄)₃] were synthesized using electrospinning technique. BS nanofibers were tested for the photocatalytic degradation of methyl orange and safranin O dyes. Different phases of BS affect the photodegradation efficiency of nanofibers. Impressive enhancement in photocatalytic efficiency and BET surface area of Bi₄(SiO₄)₃ was observed over Bi₂SiO₅. A speedy reduction in dyes concentration was attributed to the rapid formation of oxygenated radicals by the capture of electrons and holes, generated in the BS nanofiber by UV irradiation. Therefore, the photocatalytic mechanism was elucidated using impedance spectroscopy at room temperature. The lower impedance value of Bi₄(SiO₄)₃ nanofibers had improved high-efficiency charge transfer capability. The cycling efficiency (30 times) and recovery characteristics pointed out that Bi₄(SiO₄)₃ nanofibers photocatalysts had high constancy, resilience, and regeneration ability.  相似文献   

Role of ACC-deaminase and/or nitrogen fixing rhizobacteria in growth promotion of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) under cadmium pollution     

Waseem Hassan  Safdar Bashir  Farhan Ali  Muhammad Ijaz  Mubshar Hussain  Julie David 《Environmental Earth Sciences》2016,75(3):267

  相似文献   

Calcareous nannofossil biostratigraphy of the marine Oligocene and Miocene succession in some wells in Northern Egypt     

Mahmoud Faris  Hassan El Sheikh  Fatma Shaker 《Arabian Journal of Geosciences》2016,9(6):480

Twelve calcareous nannofossil biozones of Late Oligocene-Late Miocene in Northern Egypt were defined and correlated with their corresponding biozones in Egypt and other parts of the world. These are arranged from the top to base as Zone NN12, Zone NN11, Zone NN10, Zone NN8, Zone NN7, Zone NN6 Zone NN5, NN4, Zone NN3, Zone NN2 Zone NP25 and Zone NP24. In the present study (Boughaz-1 Well), the Late Miocene unconformably overlies the Middle Miocene. This unconformity surface is recognized by the missing of calcareous nannofossil zones NN7 to NN9. While, in North Sinai (Malha-1 Well), the Early/Middle Miocene boundary cannot be recognized, where the Middle Miocene unconformably overlies the topmost Oligocene, and it is defined by the missing calcareous nannofossil zones NN1 to NN4.  相似文献   

Determination of sand dune characteristics through geomorphometry and wind data analysis in central Iran (Kashan Erg)   总被引：1，自引：0，他引：1  

Aliakbar Nazari Samani  Hassan Khosravi  Tayyebeh Mesbahzadeh  Maryam Azarakhshi  Mohammad Reza Rahdari 《Arabian Journal of Geosciences》2016,9(18):716

The combination of wind measurements and remotely sensed geomorphometry indices provides a valuable resource in the study of desert landforms, because arduous desert environments are difficult to access. In this research, we couple wind data and geomorphometry to separate and classify different sand dunes in Kashan Erg in central Iran. Additionally, the effect of sand-fixing projects on sand dune morphology was assessed using geomorphometry indices (roughness, curvature, surface area, dune spacing and dune height). Results showed that a Digital Elevation Model of the National Cartographic Center of Iran (NCC DEM) with 10-m resolution and accuracy of 54% could discriminate geomorphometry parameters better than the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data with 30-m resolution and Shuttle Radar Topography Mission (SRTM) data with 90-m resolution and 45.2 and 1.6% accuracy, respectively. Low classification of SRTM DEM was associated with too many non-value points found in the DEM. Accuracy assessment of comparison ground control points revealed that ASTER DEM (RMSE = 4.25) has higher accuracy than SRTM and NCC DEMs in this region. Study of curvature showed that transverse and linear sand dunes were formed in concave topography rather than convex. Reduced slopes in fixed sand dunes were established due to wind erosion control projects. Measurements of dune height and spacing show that there is significant correlation in compound dunes (R ² = 0.546), linear dunes (R ² = 0.228) and fixed dunes (R ² = 0.129). In general, the height of dunes in Kashan Erg increases from the margin of the field to the center of the field with a maximum height of 120 m in star dunes. Analysis of wind data showed that sand drift potential is in low-medium class in Kashan Erg. Linear sand dunes in Kashan Erg show that they are following a global trend in forming of these. Finally, established of geomorphometry method in dune classification will help researchers to identify priority of land management and performance assessment of sand dunes fixing projects in arid arduous environment.  相似文献   

Facies analysis of the Semanggol Formation,South Kedah,Malaysia: A possible Permian–Triassic boundary section     

Hassan Baioumy  Yuniarti Ulfa 《Arabian Journal of Geosciences》2016,9(8):530

Although the Permian–Triassic Semanggol Formation is widely distributed in northwestern Peninsula Malaysia and is made of various lithofacies, its sedimentology and possible relation with the Permian–Triassic boundary (PTB) were not considered before. In this study, detailed facies analysis was conducted for two sections of the Semanggol Formation at the Bukit Kukus and Baling areas, South Kedah to clarify its sedimentology and relation to the PTB. Four facies from the Permian part of the Semanggol Formation that were identified at the Bukit Kukus section include laminated black mudstone, interbedded mudstone and sandstone, volcanogenic sediments, and bedded chert. In Baling area, the Triassic part of the formation is classified into three members. The lower member comprises of claystone and bedded chert facies, while the middle member is composed of sandstone and claystone interbeds (rhythmite). On the other hand, the upper member is grouped into two main units. The lower unit is mainly claystone and includes two facies: the varve-like laminated silt and clay and massive black claystone. The upper unit is composed of various sandstone lithofacies ranging from hummocky cross stratified (HCS) sandstone to thinly laminated sandstone to burrowed sandstone facies. The HCS sandstones occur as two units of fine-grained poorly sorted sandstone with clay lenses as flaser structure and are separated by a hard iron crust. They also show coarse grains of lag deposits at their bases. The laminated black mudstone at the lowermost part of the Semanggol Formation represents a reducing and quite conditions, which is most probably below the fairweather wave base in offshore environment that changed upwards into a fining upward sequence of tide environment. Abundance of chert beds in the volcanogenic sediments suggests the deposition of tuffs and volcanic ashes in deep marine setting which continues to form the Permian pelagic bedded chert and claystone. The bedded chert in the lower member of the Triassic section suggests its formation in deep marine conditions. The rhythmic sandstone and claystone interbeds of the middle member are suggestive for its formation as a distal fan of a turbidite sequence. Lithology and primary sedimentary structure of the upper member suggest its deposition in environments range from deep marine represented by the varve-like laminated silt and clay to subtidal environment corresponds to the massive black claystone to coastal environment represented by the hummocky sandstone units and reaches the maximum regression at the hiatus surface. Another cycle of transgression can be indicated from the second hummocky unit with transgressive lag deposits that develops to relatively deeper conditions as indicated from the formation of relatively thick laminated sandstone and bioturbated massive sandstone facies that represent tidal and subtidal environment, respectively. Late Permian lithological variation from the radiolarian chert into early Triassic claystone probably resulted from a decrease in productivity of radiolarians and might represent a PTB in the Semanggol Formation. Volcanogenic sediments in the studied section can be used as an evidence for volcanic activities at the end of the Permian, which is probably connected to the nearby volcanic ash layers in the eastern China, the ultimate cause of the PTB in this area. Black mudstone in the Permian part of the studied section may be interrelated to the Latest Permian Anoxia that started to build in the deep ocean well before the event on shallow shelves.  相似文献   

Geochemistry and Genesis of Iron-apatite Ore in the Khanlogh Deposit, Eastern Cenozoic Quchan-Sabzevar Magmatic Arc, NE Iran     

Arezo ZAREI  Azadeh Malekzadeh SHAFAROUDI  Mohammad Hassan KARIMPOUR 《《地质学报》英文版》2016,90(1):121-137

The Khanlogh deposit in the Cenozoic Quchan-Sabzevar magmatic belt, NE Iran, is hosted by Oligocene granodioritic rock. The Khanlogh intrusive body is I-type granitoid of the calc-alkaline series. The orebodies are vein, veinlet, massive, and breccia in shape and occur along the fault zones and fractures within the host rock. Ore minerals dominantly comprise magnetite and apatite associated with epidote, clinopyroxene, calcite, quartz, and chlorite. Apatites of the Khanlogh deposit have a high concentration of REE, and show a strong LREE/HREE ratio with a pronounced negative Eu anomaly. Magnetites have a high concentration of REE and show weak to moderate LREE/HREE fractionation. They are comparable to the REE patterns in Kiruna-type iron ores and show an affinity to calc-alkaline magmas. The Khanlogh deposit is similar in the aspects of host rock lithology, alteration, mineralogy, and mineral chemistry to the Kiruna-type deposits. Field observations, hydrothermal alteration halos, style of mineralization, and the geochemical characteristics of apatite, magnetite, and host rock indicate that these magnetite veins have hydrothermal origin similar to Cenozoic Kiruna-type deposits within the Tarom subzone, NW Iran, and are not related to silica-iron oxide immiscibility, as are the major Precambrian magnetite deposits in central Iran.  相似文献   

A harmonic approach to global ocean tide analysis based on TOPEX/Poseidon satellite     

Alireza Azmoudeh Ardalan  Hassan Hashemi-Farahani 《Marine Geophysical Researches》2007,28(3):235-255

The constant and harmonic parts of the global ocean tide are modeled by up to nine major tidal constituents, namely, S2, M2, N2, K1, P1, O1, Mf, Mm, and Ssa. Our computations start with the Fourier sine and cosine series expansion for the tidal constituents, including the constant Mean Sea Level (MSL). Although the frequencies of the tidal constituents are considered known, the coefficients of the sine and cosine functions are assumed to be unknown. Subsequently, the coefficients of the sine and cosine functions, as well as the constant part of the Fourier expansion, were expanded into spherical harmonics up to degree and order n, where n corresponds to the number of linearly independent spherical harmonic base functions needed to model the tidal constituents, determined via independent columns of the Gram matrix. The unknown coefficients of the spherical harmonic expansions are computed using sea level observations within cycles #1–#350 of the TOPEX/Poseidon satellite altimetry over 11 years of its mission. A set of orthonormal base functions was generated for the marine areas covered by TOPEX/Poseidon observations from the spherical harmonics using a Gram-Schmidt orthogonalization process. These were used for modeling the dominant tidal constituents. The computed models based on orthonormal base functions for the nine tidal constituents and the constant part of the Fourier expansion, were tested numerically for their validity and accuracy, proving centimeter accuracy.  相似文献   

World-views of Arab Geographers     

Hassan Hanafi 《GeoJournal》1992,26(2):153-156

This paper describes the fundamental attitudes toward nature, land, and human existence which characterize Koranic teachings. Created by God of Heavens and Earth, Land is a substratum of life and resource for human welfare, subject to Divine Will and the fulfillment of human vocations through belief and right action. No land is the eternal or unequivocal possession of any group and the abuse or destruction of the land is due to pride and arrogance which leads to violence, oppression, and the division of mankind between Greeks and barbarians. Arab geography, while drawing on pre-Islamic sources and constantly adapting to new environments and challenges, was a unified science incorporating astronomy, geology, botanics, metallurgy, ethnology, mathematics and metaphysics. Travel accounts provided empirical foundations for mathematical, commercial, economic, and maritime geography, the Portolan charts and other maps providing guides for Spanish and Portuguese sailors and the geographical discoveries of European explorers.  相似文献