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81.
Based on the analytical solutions for wave-induced soil response in an unsaturated anisotropic seabed of finite thickness, an elliptical, i.e., noncircular rotation stress path is proven to be a more common state in a soil element with the cyclic shear stresses due to the traveling linear wave. The influence of an elliptical stress path on the characterization of failure strength is analyzed using three new parameters representing the shape, size, and the orientation of the ellipse. A series of cyclic rotational shear tests on the reconstituted specimens of Chinese Fujian Standard Sand have been performed to investigate the effect of elliptical stress path. A strength function in term of failure cycles is derived to quantify the failure strength of a given sand within a seabed subjected to regular wave loading. The results provide a basis for the evaluation of liquefaction potential of seabed but also point to a unique backbone cycle shear strength curve for soil under principal stress rotation. 相似文献
82.
This paper presents a constitutive model for describing the stress-strain response of sands under cyclic loading. The model, formulated using the critical state theory within the bounding surface plasticity framework, is an upgraded version of an existing model developed for monotonic behaviour of cohesionless sands. With modification of the hardening law, plastic volumetric strain increment and unloading plastic modulus, the original model was modified to simulate cyclic loading. The proposed model was validated against triaxial cyclic loading tests for Fuji River sand, Toyoura sand and Nigata sand. Comparison between the measured and predicted results suggests that the proposed modified model can capture the main features of cohesionless sands under drained and undrained cyclic loading. 相似文献
83.
Hypoxia associated with eutrophication is a potential threat to the Chinese horseshoe crab Tachypleus tridentatus which inhabits intertidal sand flats in Asia. This study investigated the effect of dissolved oxygen level (DO) (6, 4 and 2 mg O2 l−1) on the physiological energetics in the juvenile T. tridentatus. They were exposed to various oxygen levels for three days and then transferred to normoxia for three days to examine the recovery from low oxygen stress. Feeding rate, respiration rate and scope for growth were reduced at lower DO levels while absorption efficiency and excretion rate were independent of DO levels. Although full recovery of the physiological responses and scope for growth from hypoxis stress was observed when normoxia resumed, their long term survival in suboptimal habitats with frequent occurrence of hypoxia deserves a close monitoring as hypoxia may be even more common in future in a warming world. 相似文献
84.
C.C. Fong Y.F. Shi W.K. Yu F. Wei J.P. van de Merwe Alice K.Y. Chan R. Ye Doris W.T. Au Rudolf S.S. Wu M.S. Yang 《Marine pollution bulletin》2014
A recent study demonstrated that 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) may have an adverse effect on the reproduction in marine medaka (Oryzias melastigma), but the molecular mechanisms remain largely unknown. In this study, we investigated the protein expression profiles of male and female gonads of O. melastigma exposed to dietary BDE-47 at two dosages (0.65 and 1.30 μg/g/day, respectively) for 21 days. Extracted proteins were labeled with iTRAQ and analyzed on a MALDI TOF/TOF analyzer, as results, 133 and 144 unique proteins were identified in testis and ovary, respective, and they exerted dose- and sex-dependent expression patterns. In testis, among the 42 differentially expressed proteins; down-regulation of histone variants and parvalbumins implicated BDE-47 may disrupt the spermatogenesis and induce sterility in fishes. In ovary, 38 proteins were differentially expressed; the elevation of vitellogenins and apolipoprotein A–I expression indicated BDE-47 acts as an estrogen-mimicking compound and led to reproductive impairment in O. melastigma. 相似文献
85.
Development of an operational rainfall data quality-control scheme based on radar-raingauge co-kriging analysis 总被引:1,自引:0,他引:1
AbstractAutomatic raingauge data often serve as an important input to hydrological and weather warning operations. They are not only fundamental in quantitative rainfall analysis, but also act as the ground truth in warning operation and forecast validation. Quality control is required before the data can be used quantitatively due to systematic and random errors. Extremely large random errors and unreasonably small or false zero values can hamper effective monitoring of heavy rain. Yet both are difficult to detect in real-time by objective means. In an attempt to address these problems, a rainfall data quality-control scheme based on radar-raingauge co-kriging analysis was developed. The important threshold values required in the data quality control of 60-min raingauge rainfall were determined from a detailed analysis of the distributions of rainfall residuals defined as the arithmetic difference and the logarithm of the ratio between a raingauge measurement and its co-kriging estimate. The scheme has been developed and is in real-time use in Hong Kong, a coastal city of about 1100 km2 area with more than 150 raingauges installed. Geographically, it is located in the subtropics and dominated by heavy convective rainfall in the summer. As a basis of the quality-control scheme, the co-kriging rainfall analysis was shown through a verification exercise to be superior to those obtained by the Barnes analysis and ordinary kriging of raingauge data. The performance of the quality-control algorithm was assessed using selected cases and controlled tests, and was found to be satisfactory, with a high error detection rate for the two targeted types of error. Limitations and operational issues identified during a real-time trial of the quality-control scheme are also discussed.
Citation Yeung, H.Y., Man, C., Chan, S.T., and Seed, A., 2014. Development of an operational rainfall data quality-control scheme based on radar-raingauge co-kriging analysis. Hydrological Sciences Journal, 59 (7), 1285–1299. http://dx.doi.org/10.1080/02626667.2013.839873 相似文献
86.
A deep geologic repository (DGR) situated on the Canadian Shield will be subject to long-term climate change that will markedly
alter surface conditions as a result of glaciation and permafrost penetration. Systematic, two-dimensional and three-dimensional
coupled thermal–hydraulic–mechanical finite-element simulations with varying degrees of coupling, including depth-dependent
salinity (represented as a change in groundwater density) and temperature-dependent density and viscosity, were undertaken
to address the implications of glaciation on groundwater flow system dynamics as it could affect DGR performance. The modelling
domain consisted of a 1.6-km deep sub-regional scale (≈100 km2) fractured Shield flow system. Initial and transient thermal, hydraulic and mechanical boundary conditions were developed
from two realizations of the University of Toronto Glacial Systems Model of the last Laurentide glaciation. Results indicate
that during the glacial loading/unloading cycle, for this particular conceptual model, there is limited penetration of glacial
meltwaters to depth and small residual anomalous hydraulic head. During glacial coverage, the mechanical factor of safety
increases in the moderately fractured and sparsely fractured rock mass, but principal effective stress reorientation also
occurs. Given the assumed nonglacial in situ state of stress and mechanical properties, the fracture zones were predicted
to be less stable under glacial conditions.
相似文献
Tin ChanEmail: |
87.
We quantify and compare different measures of potential propagule pressure (PPP) of aquatic invasive species (AIS) from commercial vessels in Canada. We used ship arrivals and ballast water discharge volumes as proxies for PPP from ballast water organisms, and wetted surface area (WSA) as a proxy for hull fouling PPP, to determine their relative contributions to total PPP. For three regions studied, PPP proxies correlated significantly across ports and some vessel categories. Relative contributions of ship arrivals, ballast discharge, and WSAs to PPP, evidenced by non-significant correlations across these measures, varied across regions, ports, vessel types, and seasons. Flow-through (dominant on east and west coasts) and empty-refill (in Great Lakes-St. Lawrence region) were the major ballast water exchange methods employed by the vessels surveyed. These methods have different biological efficacy for AIS removal, influencing PPP. Our study illustrates benefits and limitations of using different PPP proxies to estimate invasion risk. 相似文献
88.
Hong Kong has undergone substantial economic transformations and developed into a sophisticated business and financial center in the Asia-Pacific region,since the return of sovereignty to China as a Special Administrative Region under the One Country Two Systems (OCTS) in 1997.This paper discusses and analyzes the industrial structural changes of Hong Kong in recent decades as well as its future challenges and opportunities.The data and finding reveal that even though Hong Kong will face fierce competition from the Mainland’s cities as the rise of China,the important role as a bridge between China and the rest of the world will brace Hong Kong itself under the OCTS for developing into a service hub for business and trade in the Asia-Pacific region. 相似文献
89.
90.
Silva Vinicius Oliveira de Mello Carlos Rogério Chou Sin Chan 《Theoretical and Applied Climatology》2022,148(3-4):1289-1302
Theoretical and Applied Climatology - South of Minas Gerais state, in Southeast Brazil, is known for the coffee crop production (more than 30% of country’s production) and hydroelectricity... 相似文献