The provenance of Australian uranium ore concentrates by elemental and isotopic analysis     

Elizabeth Keegan  Stephan Richter  Ian Kelly  Henri Wong  Patricia Gadd  Heinz Kuehn  Adolfo Alonso-Munoz 《Applied Geochemistry》2008

Elemental and isotopic ratio analyses of U ore concentrate samples, from the 3 operating U mining facilities in Australia, were carried out to determine if significant variations exist between their products, thereby allowing the U ore concentrate’s origin to be identified. Elemental analyses were conducted using inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence spectrometry (XRF). Lead isotope ratios were measured using ICP-MS and U isotope analyses were conducted using thermal ionisation mass spectrometry (TIMS). Minute quantities of sample, such as that obtained from a swipe, were also examined for elemental concentrations using secondary ion mass spectrometry (SIMS). The results of multivariate statistical analysis show clear patterns in the trace elemental composition of the processed U ores, indicating that it is possible to use this feature as a unique identifier of an Australian U ore concentrate’s source. Secondary ion mass spectrometry analyses also allow individual particles to be differentiated using this ‘fingerprinting’ technique. Isotope ratios determined using TIMS reveal that there is a significant difference in the n(²³⁴U)/n(²³⁸U) isotope ratio between the U ore concentrate from each mine.  相似文献   

Hydrographic surveys and sedimentation in Deep Bay,Hong Kong     

S. H. Wong  Y. S. Li 《Environmental Geology》1990,15(2):111-118

Three hydrographic surveys were carried out in Deep Bay, which is located in the eastern part of Pearl estuary between Shenzhen, the most successful special economic zone of PRC, and Hong Kong. Data on current, size distributions of bottom sediment, suspended solids, and some water quality parameters were obtained. This information is of value for mathematical modeling of tidal circulation and sediment transport in the bay, and also useful in the planning of further development in this area. The sedimentation rate in Deep Bay was estimated by two different approaches, viz. comparison of historical navigation maps and²¹⁰Pb dating. Information obtained from the maps indicated that average sedimentation rate between 1898 and 1949 was about 8 mm/yr, while a 15 mm/yr figure was obtained from the²¹⁰Pb dating for recent years.  相似文献   

1993年夏季低温及其对农业的影响   总被引：2，自引：0，他引：2  

吴金栋  太华杰 《气象》1995,21(2):19-22

从农业气候学和农业气象学基本原理出发,通过对１９９３年夏季气候特点的分析,试述“凉夏”天气对农业生产不利影响的一面,以期今后深入研究,达到减灾的目的。  相似文献   

Transgranular Crack Nucleation in Carrara Marble of Brittle Failure     

Yi Cheng  Louis Ngai Yuen Wong  Varun Maruvanchery 《Rock Mechanics and Rock Engineering》2016,49(8):3069-3082

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Size and Geometry Effects on the Mechanical Properties of Carrara Marble Under Dynamic Loadings     

Chunjiang Zou  Louis Ngai Yuen Wong 《Rock Mechanics and Rock Engineering》2016,49(5):1695-1708

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Numerical hindcasting of sea surface pCO₂ at Weathership Station Papa     

D. Archer  S. Emerson  T. Powell  C.S. Wong 《Progress in Oceanography》1993,32(1-4)

A one-dimensional model of temperature, salinity, nutrients, oxygen, carbon, and argon chemistry is used to hindcast the annual cycle of sea surface pCO₂ at weathership Station Papa in the subarctic Pacific (50°N, 145°W), based on recent biological and chemical measurements made in conjunction with the SUPER program. Heat fluxes are calculated from the meteorological time series data from the Canadian weathership program. The Price, Weller and Pinkle (1986) model is used for predicting mixed layer dynamics. The rate of new production in the model is based on sediment trap data (Welschmeyer, personal communication) and a comparison of model oxygen and argon concentrations with the recent data of Emerson, Quay, Stump, Wilbur and Knox (1991). The balances of nutrients and oxygen in the permanent halocline require isopycnal ventilation on a time frame of approximately 10 years; this estimate is consistent with estimate of Van Scoy, Fine and Ostlund (1991) based in tritium data from Geosecs and Long Lines programs. The model results are compared with the 5 year time series data presented by Wong and Chang (1990). The model appears to capture the mean sea surface pCO₂ and the magnitude and timing of the seasonal cycle. The data, howeber, contain much greater high frequency variation than the model results, which we believe is caused by patchiness in the horizontal distribution of NO₃. The model pCO₂ sensitivity to the chemistry of the upwelling water and the rate of biological new production are presented.Although the model simulation of pCO₂ is satisfactory, this study illustrates the limitations of modelling the chemistry of the upper ocean in one dimension. The slow currents and horizontally homogeneous sea surface in the subarctic Pacific make Papa one of the best available candidates for modelling in 1-D. In spite of this, a 1-D formulation is inadequate to address the chemistry of the halocline (a crucial lower boundary condition to the mixed layer) and does not constrain the transport of the nutrients by wind-driven currents in the mixed layer. We conclude that further progress in modelling the upper ocean nutrient and carbon cycles will requires simulation in three dimensions.  相似文献   

Stratigraphy of Quaternary inner-shelf sediments in Tai O Bay, Hong Kong, based on ground-truthed seismic profiles     

A. Bahr  H. K. Wong  W. W.-S. Yim  G. Huang  T. Lüdmann  L. S. Chan  W. N. Ridley Thomas 《Geo-Marine Letters》2005,25(1):20-33

High-resolution boomer profiles from Tai O Bay, Hong Kong SAR, were ground-truthed using ten discontinuously sampled boreholes penetrating bedrock with a maximum length of 82.1 m. The relationship between depth below seabed and seismic profiles was established through the measurement of two borehole compressional-wave velocity profiles. In departure from previous interpretations, nine Quaternary seismic units were identified, which can be divided into eight systems tracts formed by cycles of fourth-order sea-level fluctuations dating back at least to marine isotope stage (MIS) 7 (ca. 190–245 ka). These consist of two lowstand systems tracts, two transgressive systems tracts, and four highstand systems tracts. Secondary unconformities within the highstand deposits are interpreted to document fifth-order sea-level fluctuations. Lowstand deposits are less common because, as soon as the sea level drops by a few metres, Tai O Bay becomes sub-aerially exposed, leading to widespread non-deposition or erosion. At the same time, extensive fluvial erosion and channel incision take place. Filling of the fluvial channels occurs during rising sea level. Lowstand sediments (if present) are generally landslide deposits laid down on a basal alluvial plain. Uncorrected accelerator mass spectrometry (AMS) radiocarbon dates of mollusc shells show that the depositional environment was marine since 6.2 ka, becoming gradually more brackish as a result of progradation of the Pearl River delta. The computed average sedimentation rate for the period 6.2–4.1 ka is 4.4 m/1,000 year, and approximately 1 m/1,000 year since 4.1 ka.  相似文献   

The free vibration analysis of submerged cantilever plates   总被引：3，自引：0，他引：3  

Cho-Chung Liang  Ching-Chao Liao  Yuh-Shiou Tai  Wen-Hao Lai 《Ocean Engineering》2001,28(9):1487

Based on empirical added mass formulation, this work presents a simple procedure to determine the vibration frequencies and mode shapes of submerged cantilever plates. Once the added mass formulation is derived, the procedure can be used to analyze free vibration response easily. An analytical and numerical study is also performed for the vibrations of cantilever plates in air and in water, with these results compared with experimental and numerical data from pertinent literature. Besides, the frequency parameters of the submerged plate for various aspect ratios and thickness ratios are given in design data sheet form and are appropriate for engineering design applications.  相似文献   

Changes in topography and vegetation near gaps in a protective foredune     

Karl F. Nordstrom  JeanMarie Hartman  Amy L. Freestone  Mark Wong  Nancy L. Jackson 《Ocean & Coastal Management》2007,50(11-12):945-959

Data gathered on a foredune on a nourished beach reveal the relationships between topography and plant communities at gaps in the dune crest. Sand inundation at gaps allows plants in some portions of the dune to rejuvenate to earlier successional stages, while an increase in richness occurs in other portions. Ammophila breviligulata can create an initial dune ridge, colonize new areas of bare sand within the dune field, facilitate growth of other species, and provide a natural alternative to fencing in managing gaps. Foredune mobility can be considered a positive factor if beach width and dune volume provide adequate protection.  相似文献   

The distribution of suspended particles in the Southern Beaufort Sea     

Eiji Matsumoto  C. S. Wong 《Journal of Oceanography》1977,33(4):227-233

The Mackenzie River estuary serves as an avenue for suspended particles to pass seaward. The horizontal distribution of surface suspended particles is compartible with the distribution of low-salinity surface waters. The water structure in the shelf area is highly stratified in summer due to a thin upper layer of low-salinity which has a high concentration of suspended particles. The concentration of suspended particles decreases with depth, but near the bottom a turbid layer had often been observed. It is likely that bottom current energy high enough to erode and maintain in suspension the bottom sediments below 15m in diameter does occur over this shelf area.  相似文献