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排序方式: 共有1018条查询结果,搜索用时 15 毫秒
81.
A. Z. Aris M. H. Abdullah B.Sc. M.Sc. Ph.D. A. Ahmed B.Sc. M.Sc. Ph.D. K. K. Woong B.Sc. M.Sc. Ph.D. 《International Journal of Environmental Science and Technology》2007,4(4):441-450
Factor analysis was applied to the hydrochemical data set of Manukan Island in order to extract the principal factors corresponding to the different sources of variation in the hydrochemistry. The application of varimax rotation was to ensure the clear definition of the main sources of variation in the hydrochemistry. The geochemical data of dissolved major, minor and trace constituents in the groundwater samples indicates the main processes responsible for the geochemistry evolution. By using Kaiser normalization, principal factors were extracted from the data for each location. The analysis reveals that there are four sources of solutes: (1) seawater intrusion; (2) leaching process of underlying rock mediated by pH; (3) minerals weathering process and (4) dissolution of carbonate minerals characterized by high loadings of Ca, Zn and Mg. Such processes are dominated by the significant role of anthropogenic impact from the over abstraction of fresh water from the aquifer. Those factors contributed to the changes of the groundwater geochemistry behavior explain the effect of rising extraction of freshwater from the aquifer. 相似文献
82.
R. Saravanathamizhan N. Mohan N. Balasubramanian V. Ramamurthi C. Ahmed Basha 《洁净——土壤、空气、水》2007,35(4):355-361
In the present investigation, treatment of textile effluent using an electrochemical technique was designed and analyzed using the Box-Behnken method. The influence of individual parameters on electro-oxidation of textile effluent has been critically examined using the response surface method (RSM), and a quadratic model for chemical oxygen demand (COD) reduction has been developed. It has been observed from the present analysis that the predicted values are in good agreement with experimental data with a correlation coefficient of 0.945. 相似文献
83.
Two-dimensional analytical elastic models are developed for evaluating dynamic characteristics, namely natural frequencies and modes of vibration of a wide class of earth dams in a direction parallel to the dam axis. In these models the non-homogeneity of the dam materials is taken into account by assuming a specific variation of the stiffness properties along the depth (due to the continuous increase in confining pressure). In addition, both shear and normal (axial) deformations are considered. Cases having constant elastic moduli, linear and trapezoidal variations of elastic moduli, and elastic moduli increasing as the one-half, one-third, two fifths, and a general (l/m)th powers of the depth are studied. Dynamic properties of three real earth dams in a seismically active area (Southern California) estimated from their earthquake records (input ground motion and crest response in the longitudinal direction) as well as results from full-scale dynamic tests on one of these dams (including ambient and forced vibration tests) are compared with those from the suggested models. It was found that the models in which the shear modulus and the modulus of elasticity of the dam material vary along the depth are the most appropriate representations for predicting the dynamic characteristics. The agreement between the experimental and earthquake data and the theoretical results from some of the models is reasonably good. 相似文献
84.
S.M. Ahmed 《International Journal of Mineral Processing》1978,5(2):163-174
The electrocatalytic activity of galena, pyrite and Co3S4 for oxygen reduction has been studied by potentiostatic methods. Open circuit potentials of the sulphide electrodes have also been measured as a function of pH in nitrogen, air and oxygen atmospheres and also in the presence of H2O2 and ethyl xanthate. The adsorption of xanthate on sulphides was followed by observing bubble attachment to the electrodes.The catalytic activity for oxygen (or H2O2) reduction (the cathodic currents), the electrode potentials and the xanthate adsorption as shown by bubble attachment within certain pH limits, all varied as indicating considerable dependence of the redox processes in flotation on the d - electron character of the sulphides.In the absence of oxygen, xanthate is probably bonded to the water structure of the surface through hydrogen-bonding, thus keeping the surface hydrophilic. Such adsorption reduces the electrode potential and inhibits oxygen reduction. 相似文献
85.
Fe-Cr-Ni particles and veinlets have been discovered in the top 15 m of the compressed zone with abundant shatter cones below the bottom of the Ries crater. The metallic particles are less than a few microns across. They occur in various minerals along healed intergranular and locally in intragranular microfractures in quartz diorite, amphibolite and chloritized granite of the basement crystalline rocks.The particles consist of major Fe, Cr, and Ni with minor Si and Ca. Origin due to contamination is absolutely ruled out. We believe that these Fe-Cr-Ni particles are probably condensed from the vaporized impacting body which produced the Ries crater. These particles were injected with high velocity into microfractures near the top of the compressed zone, implanted in and across various minerals before these microfractures were resealed. The presence of Si and Ca as well as the fact that the Cr content is nearly twice that of Ni, led us to conclude that the Ries impacting body is very likely not an iron meteorite but a stony meteorite. 相似文献
86.
87.
Ahmed Abdel-Latif 《Climate Policy》2015,15(1):103-126
The role of intellectual property rights (IPRs) in the development and transfer of climate change technologies has been a contentious issue in negotiations under the United Nations Framework Convention on Climate Change (UNFCCC). Irreconcilable differences seem to oppose those who believe IPRs are an inherent barrier to the transfer of climate change technologies and those who argue they are an essential incentive to innovation. After providing an overview of the polarized debate on this issue, this article reviews the existing literature and empirical evidence and looks into some practical initiatives and recent developments. Finally, it seeks to identify a way forward that could help overcome the current stalemate in international deliberations by suggesting a number of parameters to structure the discussion on this complex issue. 相似文献
88.
89.
Anja SZYMANSKI Frank E. BRENKER Herbert PALME Ahmed EL GORESY 《Meteoritics & planetary science》2010,45(1):21-31
Abstract– The oxygen fugacities recorded in the nakhlites Nakhla, Yamato‐000593 (Y‐000593), Lafayette, and NWA998 were studied by applying the Fe,Ti‐oxide oxybarometer. Oxygen fugacities obtained cluster closely around the FMQ (Fayalite–Magnetite–Quartz) buffer (NWA998 = FMQ ? 0.8; Y‐000593 = FMQ ? 0.7; Nakhla = FMQ; Lafayette = FMQ + 0.1). The corresponding equilibration temperatures are 810 °C for Nakhla and Y‐000593, 780 °C for Lafayette and 710 °C for NWA998. All nakhlites record oxygen fugacities significantly higher and with a tighter range than those determined for Martian basalts, i.e., shergottites whose oxygen fugacities vary from FMQ ? 1 to FMQ ? 4. It has been known for some time that nakhlites are different from other Martian meteorites in chemistry, mineralogy, and crystallization age. The present study adds oxygen fugacity to this list of differences. The comparatively large variation in fO2 recorded by shergottites was interpreted by Herd et al. (2002) as reflecting variable degrees of contamination with crustal fluids that would also carry a light rare earth element (REE)‐enriched component. The high oxygen fugacities and the large light REE enrichment of nakhlites fit qualitatively in this model. In detail, however, it is found that the inferred contaminating phase in nakhlites must have been different from those in shergottites. This is supported by unique 182W/184W and 142Nd/144Nd ratios in nakhlites, which are distinct from other Martian meteorites. It is likely that the differences in fO2 between nakhlites and other Martian meteorites were established very early in the history of Mars. Parental trace element rich and trace element poor regions (reservoirs) of Mars mantle ( Brandon et al. 2000 ) must have been kept isolated throughout Martian history. Our results further show significant differences in closure temperature among the different nakhlites. The observed range in equilibration temperatures together with similar fO2 values is attributable to crystallization of nakhlites in the same cumulate pile or lava layer at different burial depths from 0.5 to 30 m below the Martian surface in agreement with Mikouchi et al. (2003) and is further confirmed by similar crystallization ages of about 1.3 Ga ago (e.g., Misawa et al. 2003 ). 相似文献
90.
Petrology and geochemistry of greywackes from Goa-Dharwar sector,western Dharwar Craton: Implications for volcanoclastic origin 总被引:1,自引:0,他引:1
T. C. Devaraju T. L. Sudhakara R. J. Kaukonen R. P. Viljoen T. T. Alapieti S. A. Ahmed S. Sivakumar 《Journal of the Geological Society of India》2010,75(3):465-487
Late Archaean Supracrustals of the Goa-Dharwar sector (GDS) are composed of a thick sequence of greywacke sequence with narrow
intercalations of quartzite, BIF and carbonates. Mafic volcanics occupy the base of the sequence. The greywackes are predominantly
tuffacious containing chlorite-sericite and hornblende. Arkosic variations containing biotite dominate the western part of
the sector. Fine-grained variations occur as isolated narrow lenses within other types of greywackes. The conglomeratic greywackes
are localized along the western and the eastern margins of the sector. All of the greywackes are all typically immature containing
coarser clasts of mostly plagioclase (18–23%) and quartz (32–34%). Lithic fragments of felsic volcanic rocks are common. The
matrix is dominated by mafic material. Biotite and amphibole are related to metamorphic recrystallization. Chlorite, sericite,
epidote, carbonate and chert are products of the interplay of diagenesis and low-grade metamorphism. Fe-Ti oxide, sphene,
apatite and zircon are usual accessories. But for slight enrichment in K2O, the major element chemistry of the GDS greywackes is similar to the chemistry of Late Archaean greywackes. They also compare
in respect of V, Co, Hf contents, K2O/Na2O, SiO2/Al2O3, Na2O/Al2O3, Ba/Rb, Th/U, La/Th, Sm/Nd ratios, steep REE patterns with distinct LREE enrichment and HREE depletion. The GDS greywackes
however are distinctly enriched in Rb, Ba, Sr, Th, U, Cu, Zr, Ce/Ce* and depleted in Cr, Ni, and Zn. The conglomeritic and
biotite bearing verities contain considerable proportions of clasts derived from the basement tonalitic/granitic terrain.
The common tuffacious greywackes containing hornblende and biotite-sericite however include only volcanic clasts and bear
evidence of derivation from submarine weathering of predominantly felsic volcanics erupted on a large scale to form a magmatic
arc in the later stages of geosynclinal deposition. Geochemical data suggest that the GDS greywackes were laid down in progressively
changing basin geometry from a passive to active continental margin and island arc setting. 相似文献