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排序方式: 共有483条查询结果,搜索用时 219 毫秒
31.
32.
G. Sharaf H. Hassan 《International Journal of Environmental Science and Technology》2014,11(6):1581-1590
The batch removal of copper(II) ions from aqueous solution under different experimental conditions using alkali-leached silica and activated charcoal was investigated in this study. The copper(II) uptake was dependent on varying time, pH, copper concentration and temperature. Copper sorption was found fast reaching equilibrium within 1 h with better performance for alkali-leached silica than charcoal. Copper sorption was low at low pH values and increased with rise in initial pH-value until 6.7. Sorption fits well the Langmuir and Freundlich equations with higher uptake by increasing temperature. According to Langmuir equation, the maximum uptake of Cu(II) ions by alkali-leached SiO2 and charcoal was found to be 242.5 and 94.4 mmol/g at temperature 60 °C and pH 6. Thermodynamic studies confirm that the process was spontaneous and endothermic nature. Kinetic data for Cu(II) sorption was found to follow pseudo-second-order model. 相似文献
33.
Muhammad Hassan Agheem Mohammad Tahir Shah Tahseenullah Khan Mamoru Murata Muhammad Arif Humaira Dars 《Arabian Journal of Geosciences》2014,7(9):3801-3814
A variety of gemstones is being mined in the Shigar valley, Skardu, Pakistan. These include beryl (goshenite and aquamarine), tourmaline (schorl), garnet (almandine–spessartine), apatite, topaz, fluorite, zoisite, clinozoisite, and axinite, mostly occurring in complex or zoned pegmatites and metamorphic rocks. These have been analyzed using electron probe micro-analyzer and X-ray diffractometer. The mineral chemistry of each gemstone is similar to its respective typical gemstone variety with homogenous chemical composition. Field and chemical characteristics suggest that beryl, tourmaline, garnet, apatite, topaz, and fluorite are occurring in zoned pegmatites which are largely formed by magmatic hydrothermal fluids in the cavities and vugs within the intermediate zone. However, zoisite, clinozoisite, and axinite may have a metamorphic and/or metasomatic origin. 相似文献
34.
Lithological, chemical, and stable isotope data are used to characterize lacustrine tufas dating back to pre-late Miocene and later unknown times, capping different surfaces of a Tertiary carbonate (Sinn el-Kedab) plateau in Dungul region in the currently hyperarid south-western Egypt. These deposits are composed mostly of calcium carbonate, some magnesium carbonate and clastic particles plus minor amounts of organic matter. They have a wide range of (Mg/Ca)molar ratios, from 0.03 to 0.3. The bulk-tufa carbonate has characteristic isotope compositions: (δ13Cmean = −2.49 ± 0.99‰; δ18Omean = −9.43 ± 1.40‰). The δ13C values are consistent with a small input from C4 vegetation or thinner soils in the recharge area of the tufa-depositing systems. The δ18O values are typical of fresh water carbonates. Covariation between δ13C and δ18O values probably is a reflection of climatic conditions such as aridity. The tufas studied are isotopically similar to the underlying diagenetic marine chalks, marls and limestones (δ13Cmean = −2.06 ± 0.84‰; δ18Omean = −10.06 ± 1.39‰). The similarity has been attributed to common meteoric water signatures. This raises large uncertainties in using tufas (Mg/Ca)molar, δ13C and δ18O records as proxies of paleoclimatic change and suggests that intrinsic compositional differences in material sources within the plateau may mask climatic changes in the records. 相似文献
35.
Hassan Abdel Kader Saleh 《GeoJournal》1995,37(1):125-132
In spite of Jordan's insignificant natural resources and geopolitical problems, industrial development is being emphasized in Jordan since 1972. Industries are now the second largest sector of economy. Industries contributed 10% of the GDP in 1972, 19.5% in 1989 and 17.4% in 1993. This is remarkable as the national investment in industries is declining. The investments for industrial development was 30% of the total national investment in five year development plans (1976–1980), 23% in the next plan (1981–1985), and 13% in the following plan (1986–1990).The number of; industries has increased from 2500 in 1959 to 4684 in 1974, to 8533 in 1984, and 18600 in 1992. The employment or labor force also increased from 10,000 in 1959 to 70,000 in 1988, and to 110,000 in 1992. It represents about 16.4% of the total labor force in Jordan, the index number of industrial production also increased from (100) in 1979 which was the same base year, to (151) in 1983 to (205) in 1987 and to (215) in 1993. The study was based on three hypotheses: (i) the magnitude varies from one industry to another at the national (Jordan) and local (governorate levels), (ii) temporal change in the magnitude of industries has taken place during the period 1979–1992, (iii) the temporal change in the magnitude of industries was positive in some industries and negative in others. 相似文献
36.
37.
Eskandari Damaneh Hadi Khosravi Hassan Habashi Khalil Eskandari Damaneh Hamed Tiefenbacher John P. 《Natural Hazards》2022,110(3):2185-2205
Natural Hazards - Analysis of long-term land use and land cover (LULC) changes requires up-to-date remotely sensed data to assess their effects on erosion. This is a particularly important... 相似文献
38.
Reza Jamshidi Chenari Hassan Kamyab Farahbakhsh 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2015,9(2):96-108
This paper emphasises the true realisation of Cone Penetration Test (CPT) profiles considering non-stationary nature of the data. Formulation of stationary random field theory has been modified and adapted to non-stationary state in order to take into account the mean and variance variability for soil properties. Multi-variance correlation matrix along with the Cholesky decomposition technique was employed to produce realisations of non-homogenous and non-stationary random fields of CPT profiles. A piecewise and segmental data realisation according to the lithology and site class specifications acquired directly from CPT data is adopted in this study so as to render an accurate data simulation. For validation of proposed method 8 CPT test profiles collected from Urmia Lake site have been introduced and simulated by the stationary and non-stationary algorithms. The mean correlation coefficient between the actual CPT data profiles and related realisations along with some other important statistical parameters and their coefficients of variation strongly demonstrate that non-stationary random field generation technique gives quite better accuracy, by comparison to the conventional stationary random field generation scheme. 相似文献
39.
Although current navigation services provide significant benefits to people's mobility, the turn‐by‐turn instructions they provide are sometimes ineffective. These instructions require people to maintain a high level of attention and cognitive workload while performing distance or angle measurements on their own mental map. To overcome this problem, landmarks have been identified as playing a major role in turn‐by‐turn instructions. This requires the availability of landmarks in navigation databases. Landmarks are commonly selected manually, which involves time‐consuming and tedious tasks. Automatic selection of landmarks has recently gained the attention of researchers but currently there are only a few techniques that can select appropriate landmarks. In this article, we present a technique based on a neural network model, where both static and dynamic features are used for selecting landmarks automatically. To train and test this model, two labeling approaches, manual labeling and rule‐based labeling, are also discussed. Experiments on the developed technique were conducted and the results show that rule‐based labeling has a precision of approximately 90%, which makes the technique suitable and reliable for automatic selection of landmarks. 相似文献
40.
Hassan M. El Shaer 《寒旱区科学》2015,7(1):0016-0022
Environmental degradation resulting from current climate changes, including prolonged drought, land degradation, desertification, and loss of biodiversity, is presenting enormous challenges to achieve ... 相似文献