Observed spectrum in the South China Sea during storms     

Latheef  Mohamed  Abdullah  Mohd Nasir  Jupri  Mohd Faieez Mohd 《Ocean Dynamics》2020,70(3):353-364

Ocean Dynamics - The present work focuses on the measured wave spectrum in the South China Sea (scs) during storms. The measured spectra have been obtained from surface elevation measurements...  相似文献   

Current Status of Marine Pollution and Mitigation Strategies in Arid Region: A Detailed Review     

Chitrakar  Prerana  Baawain  Mahad Said  Sana  Ahmad  Al-Mamun  Abdullah 《Ocean Science Journal》2019,54(3):317-348

Ocean Science Journal - Coastal pollution is becoming a significant threat for both marine ecosystems and humans. Marine pollution and coastal degradation are severely exacerbated by anthropogenic...  相似文献   

Seasonal Shift in Community Structure of Periphytic Ciliates in Estuarine Waters in the Northern Bay of Bengal,Bangladesh     

Mamun?Abdullah Al  Rahman?Muhammed?Forruq  Aysha?Akhtar  Md.?Wahidul?Alam  Mohammad?Nurul?Azim?Sikder  Alan?Warren  Henglong?XuEmail author 《Ocean Science Journal》2018,53(4):707-718

To investigate the seasonal heterogeneity of the periphytic ciliate communities, a 1-year baseline survey was conducted in the Karnaphuli River estuary, northern Bay of Bengal, Bangladesh. A total of 54 ciliate species were recorded, including seven common and 14 dominant species. Maximum species number was in autumn whereas maximum abundance was in winter; the minimum for both occurred in summer. Multivariate analyses, i.e., canonical analysis of principal coordinates (CAP) and principal co-ordinates analysis (PCoA), revealed a clear seasonal heterogeneity of community structure and environmental variables. Multivariate correlation analysis (RELATE) demonstrated that the community structure of the periphytic ciliate communities was significantly correlated with environmental variables, and best matching analysis (BIOENV) indicated that heterogeneity of community patterns was mainly driven by water temperature, pH, dissolved oxygen, total dissolved solids and nutrients. Species richness and diversity peaked in autumn whereas species evenness peaked in summer. These results suggest that environmental conditions shape periphytic ciliate community structure, which is a potentially useful bio-indicator of estuarine water quality.  相似文献   

Circular restricted three-body problem when both the primaries are heterogeneous spheroid of three layers and infinitesimal body varies its mass     

Abdullah A. Ansari  Ziyad Ali Alhussain  Sada Nand Prasad 《Journal of Astrophysics and Astronomy》2018,39(5):57

The circular restricted three-body problem, where two primaries are taken as heterogeneous oblate spheroid with three layers of different densities and infinitesimal body varies its mass according to the Jeans law, has been studied. The system of equations of motion have been evaluated by using the Jeans law and hence the Jacobi integral has been determined. With the help of system of equations of motion, we have plotted the equilibrium points in different planes (in-plane and out-of planes), zero velocity curves, regions of possible motion, surfaces (zero-velocity surfaces with projections and Poincaré surfaces of section) and the basins of convergence with the variation of mass parameter. Finally, we have examined the stability of the equilibrium points with the help of Meshcherskii space–time inverse transformation of the above said model and revealed that all the equilibrium points are unstable.  相似文献   

Generalized Elliptic Restricted Four-Body Problem with Variable Mass     

Ansari  Abdullah A.  Prasad  Sada Nand 《Astronomy Letters》2020,46(4):275-288

Astronomy Letters - The elliptic case of restricted four-body problem with variable mass of infinitesimal body is studied here. The three primary bodies which are placed at the vertices of an...  相似文献   

Hydrocarbon Generation Potential of the Organic-Rich Naifa Formation,Say’un–Masila Rift Basin,Yemen: Insights from Geochemical and Palynofacies Analyses     

Hakimi  Mohammed Hail  Abdullah  Wan Hasiah  Lashin  Aref A.  Ibrahim  El-Khedr H.  Makeen  Yousif M. 《Natural Resources Research》2020,29(4):2687-2715

Natural Resources Research - The Say’un–Masila rift, one of the most important basins of Yemen, contains unconventional resources of organic-rich rocks. In the present work, geochemical...  相似文献   

Quantifying threats to groundwater resources in the Republic of Maldives Part II: Recovery from tsunami marine overwash events          下载免费PDF全文

Abdullah A. Alsumaiei  Ryan T. Bailey 《水文研究》2018,32(9):1154-1165

Marine overwash events are among the most serious short‐term threats to groundwater supply of small coral islands. During such events, seawater can inundate small islands partially or completely, causing salinization of the aquifer. A comprehensive knowledge of freshwater lens recovery is essential for water planners on these islands. In this study, a numerical modelling approach is used to quantify recovery of the freshwater lens on 4 islands of the Maldives after a tsunami‐induced overwash event similar to that experienced from the Indian Ocean earthquake in December 2004. The islands vary in size (0.2 to 10.1 km²) and span the climatic regions of the Maldives. A tested 3‐dimensional SEAWAT groundwater model for each island is used to simulate the recovery process. Recharge rates from historical rainfall data and from global climate models are imposed on each island during the post‐overwash recovery period. The effect of groundwater pumping on lens recovery also is examined. Results show abrupt decrease in fresh groundwater volumes for each island, followed by recovery that is significantly influenced by island size and recharge patterns. Overall, salinization is more widespread on small islands (<1 km²), but recovery is more rapid than for large islands. Between 50% and 90% of lens recovery occurs after 2 years for small islands (<1 km²) whereas only 35% and 55% for large islands. Imposing pumping rates required to sustain the local population lengthened the recovery time between 5% and 15%, with smaller islands having the higher percentage. However, the governing factor on recovery time is the spatial extent of land surface inundation by the overwash event, with wave height and duration of the event having a negligible impact. A strong relationship exists between required recovery time and island surface area, thereby providing a method to determine recovery time for other atoll islands not investigated in this study with similar geologic structure. Our results can be used to aid in managing water resources during the post‐overwash period.  相似文献   

Mineralogy, whole-rock and Sr-Nd isotope geochemistry of mafic microgranular enclaves in Cretaceous Dagbasi granitoids, Eastern Pontides, NE Turkey: Evidence of magma mixing, mingling and chemical equilibration   总被引：7，自引：0，他引：7  

Abdullah Kaygusuz  Emre Ayd?nçak?r 《Chemie der Erde / Geochemistry》2009,69(3):247-277

Rocks of the Late Cretaceous Dagbasi Pluton (88-83 Ma), located in the eastern Pontides, include mafic microgranular enclaves (MMEs) ranging from a few centimetres to metres in size, and from ellipsoidal to ovoid in shape. The MMEs are composed of gabbroic diorite, diorite and tonalite, whereas the felsic host rocks comprise mainly tonalite, granodiorite and monzogranite based on both mineralogical and chemical compositions. MMEs are characterized by a fine-grained, equigranular and hypidiomorphic texture. The common texture of felsic host rocks is equigranular and also reveals some special types of microscopic textures, e.g., oscillatory-zoned plagioclase, poikilitic K-feldspar, small lath-shaped plagioclase in large plagioclase, blade-shaped biotite, acicular apatite, spike zones in plagioclase and spongy-cellular plagioclase textures and rounded plagioclase megacrysts in MMEs. Compositions of plagioclases (An₃₃-An₆₀), hornblendes (Mg#=0.77-1.0) and biotites (Mg#=0.61-0.63) of MMEs are slightly distinct or similar to those of host rocks (An_12-57; hbl Mg#=0.63-1.0; Bi Mg#=0.50-0.69), which suggest partial to complete equilibration during mafic-felsic magma interactions.The felsic host rocks have SiO₂ between 60 and 76 wt% and display low to slightly medium-K tholeiitic to calc-alkaline and peraluminous to slightly metaluminous characteristics. Chondrite-normalized rare-earth element (REE) patterns are fractionated (La_cn/Lu_cn=1.5-7.3) with pronounced negative Eu anomalies (Eu/Eu*=0.46-1.1). Initial ε_Nd(i) values vary between −3.1 and 1.6, initial ⁸⁷Sr/⁸⁶Sr values between 0.7056 and 0.7067.Compared with the host rocks, the MMEs are characterized by relatively high Mg-number of 22-52, low contents of SiO₂ (53-63 wt%), low ASI (0.7-1.1) and low to medium-K tholeiitic to calc-alkaline, metaluminous to peraluminous composition. Chondrite-normalized REE patterns are relatively flat [(La/Yb)_cn=1.4-3.9; (Tb/Yb)_cn=0.9-1.5] and show small negative Eu anomalies (Eu/Eu*=0.63-1.01). Isotope signatures of these rocks (⁸⁷Sr/⁸⁶Sr_(i)=0.7054-0.7055; ε_Nd(i)=-1.0 to 1.9) are largely similar to the host rocks. Gabbroic diorite enclaves have relatively low contents of SiO₂, ASI; high Mg#, CaO, Al₂O₃, TiO₂, P₂O₅, Sr and Nb concentrations compared to dioritic and tonalitic enclaves.The geochemical and isotopic similarities between the MMEs and their host rocks indicate that the enclaves are of mixed origin and are most probably formed by the interaction between the lower crust- and mantle-derived magmas. All the geochemical data suggest that a basic magma derived from an enriched subcontinental lithospheric mantle, interacted with a crustal melt that originated from dehydration melting of the mafic lower crust at deep crustal levels. The existence of compositional and textural disequilibrium and the nature of chemical and isotopic variation in these rock types indicate that magma mixing/mingling between an evolved mafic and a granitic magma was involved in their genesis. Microgranular enclaves are thus interpreted to be globules of a more mafic magma probably from an enriched lithospheric mantle source. Al-in-amphibole estimates the pluton emplacement at ca. 0.3-3.8 kbar, and therefore, magma mixing and mingling must have occurred at 3.8 kbar or below this level.  相似文献   

The March 11, 2002 Masafi, United Arab Emirates earthquake: Insights into the seismotectonics of the northern Oman Mountains   总被引：2，自引：1，他引：1  

Arthur Rodgers  Abdel-Rahman Fowler  Abdullah M.S. Al-Amri  Abdullah Al-Enezi 《Tectonophysics》2006,415(1-4):57-64

A moderate (M 5) earthquake struck the northeastern United Arab Emirates (UAE) and northern Oman on March 11, 2002. The event was felt over a wide area of the northern Emirates and was accompanied by smaller (felt) events before and after the March 11 main shock. The event was large enough to be detected and located by global networks at teleseismic distances. We estimated focal mechanism and depth from broadband complete regional waveform modeling. We report a normal mechanism with a slight right-lateral strike-slip component consistent with the large-scale tectonics. The normal component suggests relaxation of obducted crust of the Semail ophiolite (specifically, the Khor Fakkan Block) while the right-lateral strike-slip component of the mechanism is consistent with shear across the Oman Line. Felt earthquakes are rare in the region, however no regional seismic network exists in the UAE to determine local seismicity. This event offers a unique opportunity to study the active tectonics of the region as well as inform future studies of seismic hazard in the UAE and northern Oman.  相似文献   

Analysis of South Asian Monsoons within the Context of Increasing Regional Black Carbon Aerosols          下载免费PDF全文

Rashed MAHMOOD  LI Shuanglin  YAO Jin-Feng 《大气和海洋科学快报》2010,3(4):224-231

South Asian monsoons were analyzed within the context of increasing emissions of black carbon(BC) aerosols using a global atmospheric general circulation model.The BC aerosols were allowed to increase only over the south Asian domain to analyze the impacts of regional black carbon over the climatological patterns of monsoons.The black carbon significantly absorbed the incoming short wave radiation in the atmosphere,a result that is consistent with previous studies.Pre-monsoon(March-April-May) rainfall showed positive anomalies,particularly for some coastal regions of India.The summer(June-July-August) rainfall anomalies were negative over the northern Himalayas,Myanmar,southern China,and most of the regions below 20°N due to the decrease in temperature gradients induced by the absorption of radiation by BC aerosols.The vertical wind speed anomalies indicated that these regions experienced less convection,which reduces the precipitation efficiency of the monsoon system in South Asia.  相似文献