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排序方式: 共有200条查询结果,搜索用时 15 毫秒
191.
Nasr Yousef M. J. Omar M. Radzi Bin Abas Noorsaadah A. Rahman Norhayati Mohd. Tahir Ahmed I. Rushdi Bernd R. T. Simoneit 《Environmental Geology》2007,52(8):1485-1500
The concentrations of n-alkanes, unresolved complex mixture (UCM), petroleum molecular markers, other tracers of cooking and burning emissions, and
natural background in atmospheric particles and roadside dust particles were measured at eight locations in the city center
and the suburbs of Kuala Lumpur, Malaysia. Atmospheric particles were collected using high-volume filtration (PM-10, GFF)
over 24 h average periods. Road dusts were swept up, dried and sieved. Both types of samples were extracted with dichloromethane/methanol
mixture (3:1 v/v) by ultrasonic agitation. The extracts were then fractionated by column chromatography and the alkanes subjected
to gas chromatography–mass spectrometry (GC–MS). Total extracts were also analyzed directly by GC–MS after silylation. The
molecular distributions of compounds as well as diagnostic geochemical ratios were determined in order to identify the sources
of the organic compounds. Samples collected from a rural area and lubricating oils were also analyzed for comparisons. Anthropogenic
and biogenic sources such as vehicular emissions, waxes of higher plants, food cooking operations, and biomass and domestic
refuse burning processes contributed to the organic matter content of atmospheric and to lesser extent, roadside dust particles. 相似文献
192.
Zamri Zainal Abidin Zainol Abidin IbrahimZulfazli Rosli Siti Fatin Fathinah MalimNorsuzian Mohd Anim Noorkhallaf Noorazlan 《New Astronomy》2012,17(2):61-64
In this paper, we investigated the radio frequency interference (RFI) that future Very Long Baseline Interferometer (VLBI) observations in Malaysia may encounter. Four frequency windows below 2.8 GHz were chosen for this study and their spectra were measured at four sites. The frequency windows are 322-328 MHz, 608-614 MHz, 1660-1660.5 MHz and 1660.5-1668.4 MHz. The measured averaged RFI floor noise levels in these windows are −99.992 (±0.570) dBm, −99.907 (±0.639) dBm, −100.220 (±0.4941) dBm and −100.359 (±0.110) dBm, respectively. We found that only two bands below 2.8 GHz are permitted for the purpose of radio astronomy in Malaysia. They are 608-614 MHz and 1660-1660.5 MHz. The RFI levels in these permissible bands at the best site (Langkawi) were also measured and concluded to be relatively low. Main sources of RFI in these bands in Malaysia were identified. We also reviewed several current VLBI observations in these two bands. 相似文献
193.
In a preliminary investigation, Random Amplified Polymorphie DNA (RAPD) analysis and partial mitochon-drial ND2 gene sequencing were conducted to study the genetic variation of the Indian mackerel, Rastrelliger kanagurta along a 450 km stretch of its distribution on the west coast of Peninsular Malaysia. A total of 53 individuals from 6 popu-lations were analyzed using 4 RAPD primers and a sub-sample of 15 individuals was chosen for sequencing of partial ND2 gene. Comparison between the 2 markers revealed genetic structuring in the RAPD results but genetic homogeneity for ND2 gene. Based on the former there may be at least 2 genetically differentiated groups of Rastrelliger kanagurta a-long this stretch. 相似文献
194.
Mohamad Nasir Mohamad Ibrahim Wan Saime Wan Ngah Mohd Salleh Norliyana Wan Rosli Wan Daud 《洁净——土壤、空气、水》2009,37(1):80-85
The adsorption of Cu(II) ions from aqueous solutions by soda lignin as an absorbent using a batch adsorption system is presented in this paper. The soda lignin used in this study was extracted from black liquor derived from oil palm empty fruit bunches (EFB) using 20% v/v sulfuric acid. The effects of varying experimental parameters such as pH value, adsorbent dosage, different concentrations of Cu(II) ions, and agitation period were investigated. The results revealed that the optimum adsorption of Cu(II) onto soda lignin was recorded at a pH of 5.0 at an adsorbent dosage of 0.5 g soda lignin and an agitation period of 40 min. The adsorption capacities and rates of Cu(II) ions onto soda lignin was evaluated. The Langmuir and Freundlich adsorption models were applied to calculate the isotherm constants. It was found that the adsorption isothermal data could be well interpreted by the Freundlich model. The kinetic experimental data properly correlated with the pseudo‐second‐order kinetic model, which implies that chemical sorption is the rate‐limiting step. 相似文献
195.
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197.
Mohd Yunus Shah Kato K. Ayemi Prakash Kumar Shrivastava 《Journal of the Geological Society of India》2017,90(3):371-377
Sea ice formation in Quilty Bay, East Antarctica shows a strong relationship with climatic conditions and its spatial variation is established by GPR survey over the sea ice during the austral winters. The study also evaluates the variability of sea ice thickness and extent with local weather parameters between 2010 and 2014. Profiling on sea ice in Quilty Bay shows that sea ice thickness decreases gradually towards east. The overall thickness of sea ice is considerably less at the centre of the bay as compared to the coastal side. Two types of fast ice layers have been delineated from GPR surveys i.e. top layer fast ice which incorporates very low density surface snow and underlying high density fast ice i.e. with melt water pockets. Development of sea ice is influenced by persistent easterly winds, temperature fluctuations and ocean currents. Sea ice reveal average annual cyclic trend in Quilty Bay with maximum development in the year 2013 (157.54 cm) and the minimum development has been observed in the year 2010 (99.04 cm).The cyclic pattern of average sea ice accumulation data show perfect inverse correlation with surface air temperature, with measure of reliability R2 = 0.93. However, moderate (R2 = 0.52) and good (R2 = 0.69) degree of inverse relationship is observed with surface snow and overall sea ice (snow and ice) respectively. With 0.46 °C change in temperature, there is 33% change in sea ice condition in Quilty Bay which may remain same as far as ice extents in the region. Besides this easterly winds play a vital role in controlling the snow/ice distribution patterns as reflected by isopach maps. 相似文献
198.
Syamsidik Rina Suryani Oktari Khairul Munadi Suhada Arief Inayah Zhiaul Fajri 《Natural Hazards》2017,88(3):1503-1521
Ten years after the Indian Ocean tsunami in 2004 and following a long process of rehabilitation and reconstruction, Aceh has finally recovered. After the tsunami, Aceh experienced a dramatic migration of its coastal population away from the city; however, after 10 years, the population has mostly recovered. As new houses have been built and new economic activities commenced in the coastal areas, there is now concern regarding potential future tsunami risks for the city. The initial rehabilitation and reconstruction plan sought to prevent the construction of any new houses 500 m from the coastline; however, this failed to happen. This paper elucidates the reasons why these new coastal communities chose their new housing areas and examines the coastal land use changes around Banda Aceh 10 years after the Indian Ocean tsunami. Questionnaires were distributed to 457 respondents, and multiple logistic regressions were used to examine the reasons for household location selection and whether a possible future tsunami was a deciding factor. To examine the coastal land use changes, a series of aerial images from the Banda Aceh coastal area were digitised. It was found that tsunami history was not a major factor in new household selection; rather, rents and land prices, distance from work, and family connections were the top three reasons motivating households to select new living places. These changes and new settlements have given the city’s disaster management agency the challenge of building more emergency infrastructure in the coastal areas. 相似文献
199.
Mohd Yawar Ali Khan Khalid Muzamil Gani Govind Joseph Chakrapani 《Environmental Earth Sciences》2017,76(5):231
The River Ganges being the most sacred river and lifeline to millions of Indians in serving their water requirements is facing excessive threat of pollution. Under various river management and conservation strategies for its protection, the assessment of water quality of its main tributary Ramganga River is lacking. This study focuses on assessment of physicochemical and heavy metal pollution of the Ramganga River by application of multivariate statistical techniques. Sampling of Ramganga River at sixteen sampling sites was carried out in three seasons (summer, monsoon and winter) of 2014. The collected water samples were analyzed for physicochemical parameters and heavy metals. Results from cluster analysis (CA) of the data divided the whole stretch of the river into three clusters as elevation from 1304 to 259 m as less polluted, from 207 to 154 m as moderately polluted and from elevation 154 to 139 m as high-polluted stretches with anthropogenic as main sources of pollution in high-polluted stretch. Principal component analysis of the seasonal dataset resulted in three significant principal components (PC) in each season explaining 72–8% of total variance with strong loadings (>0.75) of PC1 on fluoride (F?), chloride (Cl?), sodium (Na+), calcium (Ca2+), magnesium (Mg2+), bicarbonate (HCO3 ?), total dissolved solids and electrical conductivity. Temporal variation by one-way ANOVA (Analysis of Variance) showed significant seasonal variation was in the pH, chemical oxygen demand, biochemical oxygen demand, turbidity, HCO3 ?, F?, Zn, cadmium (Cd) and Mn (p < 0.05). Turbidity showed approximately a twofold increase in monsoon season due to rainfall in the catchment area and subsequent flow of runoff into the river. Concentration of HCO3 ?, F? and pH also showed similar increase in monsoon. The concentration of Zn, Cd and Mn showed an increasing trend in summers compared to monsoon and winter season due to dilution effect in the monsoon season and its lasting effect in winters. 相似文献
200.
Sathish Twinkle Nazrin A. K. Thomas Lathika Cicily Padmakumar K. B. 《Journal of Oceanography》2022,78(5):397-408
Journal of Oceanography - To understand seasonal variations of the dinoflagellate community in the estuarine waters of Cochin (Southwest coast of India), the abundance and species composition, in... 相似文献