A tribute to John Stuart Gray (1941-2007)     

Richardson B  Wu R  Shin P  Lam P  Fleddum A  Elliott M  Sheppard C 《Marine pollution bulletin》2008,56(1):1-4

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Monitoring of toxic substances in the Hong Kong marine environment   总被引：1，自引：0，他引：1  

Kueh CS  Lam JY 《Marine pollution bulletin》2008,57(6-12):744-757

A long-term programme for monitoring toxic substances in the marine environment was established in Hong Kong in 2004, focusing on chemicals of potential ecological and health concern. The programme ran on 3-year cycles, with the first two years monitoring marine water, sediment, biota, and the third year monitoring pollution sources. Twenty-four priority chemicals were measured, including dioxins/furans, dioxin-like PCBs, total PCBs, PAHs, DDTs, HCHs, TBTs, phenol, nonylphenol (NP), NP ethoxylates, PBDEs and metals. Results from the first three years of monitoring indicate that toxic substances in the Hong Kong marine environment were within the range reported for the coastal waters in China and other regions, but generally lower than in the Pearl River Estuary. The levels met the standards for protecting aquatic life and human consumption. Sewage effluent, stormwater and river water were possible sources of phenolic compounds; whereas air deposition or regional pollution, rather than local discharges, may contribute to the dioxins/furans, PAHs and PCBs found in the marine environment.  相似文献   

The galaxy luminosity function in the LAMOST Complete Spectroscopic Survey of Pointing Area at the Southern Galactic Cap     

Pin-Song Zhao  Hong Wu  Cong Kevin Xu  Ming Yang  Fan Yang  Yi-Nan Zhu  Man I Lam  Jun-Jie Jin  Hai-Long Yuan  Hao-Tong Zhang  Shi-Yin Shen  Jian-Rong Shi  A-Li Luo  Xue-Bing Wu  Yong-Heng Zhao  Yi-Peng Jing 《天文和天体物理学研究(英文版)》2019,(8)

We present optical luminosity functions(LFs) of galaxies in the~(0.1) g,~(0.1) r,~(0.1) i bands, calculated using data in~40 deg~2 sky area of the LAMOST Complete Spectroscopic Survey of Pointing Area(LaCoSSPAr) in the Southern Galactic Cap. Redshifts for galaxies brighter than r = 18.1 were obtained mainly with LAMOST. In each band, LFs derived using both parametric and non-parametric maximum likelihood methods agree well with each other. In the0.1 r band, our fitting parameters of the Schechter function are φ_*=(1.65 ± 0.36) × 10~(-2) h~3 Mpc~(-3), M_*=-20.69 ± 0.06 mag and α =-1.12 ± 0.08,which agree with previous studies. Separate LFs are also derived for emission line galaxies and absorption line galaxies. The LFs of absorption line galaxies show a dip at~(0.1) r ~18.5 and can be fitted well by a double-Gaussian function, suggesting a bimodality in passive galaxies.  相似文献   

Three-dimensional fracture propagation under specified well-bore pressure     

K. Y. Lam  M. P. Cleary 《国际地质力学数值与分析法杂志》1988,12(6):583-598

Results are presented for three-dimensional planar fracture propagation in the presence of variations in confining stress, reservoir properties and frac-fluid viscosity when the well-bore pressure is constant throughout the frac-job. Solid rock deformation during the frac-job is described by the dislocation method with singular integral equations, and the fluid flow in the fracture is represented by the finite element method. A convergence study is undertaken on the three-dimensional numerical model, and good agreement is obtained with results from laboratory tests and from the simpler circular model.  相似文献   

Microbial ammonia oxidation and enhanced nitrogen cycling in the Endeavour hydrothermal plume   总被引：1，自引：0，他引：1  

Phyllis Lam  James P. Cowen  Ronald D. Jones 《Geochimica et cosmochimica acta》2008,72(9):2268-2286

Ammonium was injected from the subseafloor hydrothermal system at the Endeavour Segment, Juan de Fuca Ridge, into the deep-sea water column resulting in an -rich (?177 nM) neutrally buoyant hydrothermal plume. This was quickly removed by both autotrophic ammonia oxidation and assimilation. The former accounted for at least 93% of total net removal, with its maximum rate in the neutrally buoyant plume (?53 nM d⁻¹) up to 10-fold that in background deep water. Ammonia oxidation in this plume potentially added 26-130 mg into the deep-sea water column. This oxidation process was heavily influenced by the presence of organic-rich particles, with which ammonia-oxidizing bacteria (AOB) were often associated (40-68%). AOB contributed up to 10.8% of the total microbial communities within the plume, and might constitute a novel lineage of β-proteobacterial AOB based on 16S rRNA and amoA phylogenetic analyses. Meanwhile, assimilation rates were also substantially enhanced within the neutrally buoyant plume (?26.4 nM d⁻¹) and accounted for at least 47% of total net removal rates. The combined oxidation and assimilation rates always exceeded total net removal rates, suggesting active in situregeneration rates of at least an order of magnitude greater than the particulate nitrogen flux from the euphotic zone. Ammonia oxidation is responsible for turnover of 0.7-13 days and is probably the predominant in situ organic carbon production process (0.6-13 mg C m⁻² d⁻¹) at early stages of Endeavour neutrally buoyant plumes.  相似文献   

钢筋混凝土柱极限变形角的概率特性及其在有控结构大震可靠度分析中的应用     

吴波  郭安薪  林少书 《地震工程与工程振动》2001,21(3):36-40

通过对国外大量试验数据的整理和分析，统计给出了钢筋混凝土柱极限变形角的概率特性；在假设结构层间极限变形角近似等于柱子极限菜角的基础上，结合文献[1]的研究结果，初步建立了被动耗能减振结构大震可靠度的分析方法。  相似文献   

Criteria of Acceptance for Constant Rate of Strain Consolidation Test for Tropical Cohesive Soil     

Khairul Anuar Kassim  Ahmad Safuan A. Rashid  Ahmad Beng Hong Kueh  Chong Siaw Yah  Lam Chee Siang 《Geotechnical and Geological Engineering》2016,34(4):931-947

In this study, the rapid consolidation equipment (RACE) was developed as an alternative device to the conventional consolidation test using Oedometer, consuming merely a few hours for the whole precedure to determine the consolidation characteristics of cohesive soil. RACE operates based on the constant rate of strain (CRS) consolidation theory, which is a continuous loading method of testing, requiring a good estimation of the loading rate such that it is ideal for the achievement of steady state condition during testing. The steady state condition is achieved when the c _v values from drained and undrained face of CRS converged with the c_v from Oedometer test. A slightly modification has been made on the normal constant rate of strain (CRS) test by proposing a direct back pressure system to the specimen using a tube to saturate the soil sample. This research has produced a set of criteria for determining the suitable rate for the rapid consolidation test based on the ratio of normalized strain rate, β, and proposed a new coefficient in terms of a ratio of β to clay fraction (CF), as a part of new criteria for testing a fine soil. Four types of sample were tested with different rates of strain using the RACE and their results were compared with those conducted using the Oedometer on the same soil type, from which fairly good agreements were evident in many specimens. It was found from the study that the minimum value of normalized strain rate, β, for the CRS test is 0.005 and for the u _a /σ _v ratio is suggested as 0.01. Also, the maximum β/CF for soils with clay friction lower and higher than 50 % are 0.008 and 0.001, respectively. The minimum β/CF value for both conditions is 0.0001.  相似文献   

Partitioning of metals among metal-binding proteins in the bay mussel, Mytilus edulis     

F.L. Harrison  J.R. Lam  J. Novacek 《Marine environmental research》1988,24(1-4)

Metabolism of metals was assessed in populations of Mytilus edulis exposed to metals in the laboratory and in the field. Chronic exposure to metals in both environments resulted in increased concentrations of metals in both the low molecular weight metal-binding protein fraction, which contains metallothioneins, and in the high molecular weight metal-binding protein fraction, which contains metalloenzymes. Our results from analysis of laboratory-exposed populations and from monitoring indigenous and transplanted populations indicate that the capacity for production of metallothioneins is limited and that the quantities present differ greatly with seasonal changes in the environment.  相似文献   

Numerical and experimental studies of pressure-controlled cavity expansion in completely decomposed granite soils of Hong Kong     

S.Y. Wang  D.H. Chan  K.C. Lam  S.K.A. AU 《Computers and Geotechnics》2010,37(7-8):977-990

Compaction grouting is the injection of a viscous grout into a soil under high pressure, which then densifies the surrounding soil by reducing void space. Laboratory and field tests of compaction grouting have been carried out. In this paper, a numerical model is used to simulate the compaction grouting process with the primary purpose of investigating relationships among various control parameters, such as injection pressure, void ratio and excess pore water pressure at various radial distances from the injection point. The compaction process is treated as a cavity expansion process in the numerical simulation. The soil is modelled with an elasto-plastic Mohr–Coulomb model using the commercial finite element program ABAQUS. In addition to numerical simulations, pressure-controlled cavity expansion laboratory tests were carried out on completely decomposed granite (CDG) soil specimens. Data collected from laboratory tests are compared with the finite element simulation to validate the finite element analyses. Factors that control the compaction process, such as the coefficient of earth pressure (K), initial void ratio, number of loading cycles and effective confining pressure, are explored in the numerical simulations.  相似文献   

Seasonal and event‐based drivers of runoff and phosphorus export through agricultural tile drains under sandy loam soil in a cool temperate region          下载免费PDF全文

W.V. Lam  M.L. Macrae  M.C. English  I. P. O'Halloran  J.M. Plach  Y. Wang 《水文研究》2016,30(15):2644-2656

Frequent algal blooms in surface water bodies caused by nutrient loading from agricultural lands are an ongoing problem in many regions globally. Tile drains beneath poorly and imperfectly drained agricultural soils have been identified as key pathways for phosphorus (P) transport. Two tile drains in an agricultural field with sandy loam soil in southern Ontario, Canada were monitored over a 28‐month period to quantify discharge and the concentrations and loads of dissolved reactive P (DRP) and total P (TP) in their effluent. This paper characterizes seasonal differences in runoff generation and P export in tile drain effluent and relates hydrologic and biogeochemical responses to precipitation inputs and antecedent soil moisture conditions. The generation of runoff in tile drains was only observed above a clear threshold soil moisture content (~0.49 m³·m^?3 in the top 10 cm of the soil; above field capacity and close to saturation), indicating that tile discharge responses to precipitation inputs were governed by the available soil‐water storage capacity of the soil. Soil moisture content approached this threshold throughout the non‐growing season (October – April), leading to runoff responses to most events. Concentrations of P in effluent were variable throughout the study but were not correlated with discharge (p > 0.05). However, there were significant relationships between discharge volume (mm) and DRP and TP loads (kg ha^?1) for events occurring over the study period (R² ≥ 0.49, p ≤ 0.001). This research has shown that the hydrologic and biogeochemical responses of tile drains in a sandy loam soil can be predicted to within an order of magnitude from simple hydrometric data such as precipitation and soil moisture once baseline conditions at a site have been determined. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献