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A bounding surface elasto‐viscoplastic constitutive model for non‐isothermal cyclic analysis of asphaltic materials 下载免费PDF全文
An elasto‐viscoplastic constitutive model for asphaltic materials is presented within the context of bounding surface plasticity theory, taking into account the effects of the stress state, void binder degree of saturation, temperature and strain rate on the material behaviour. A stress state dependent non‐linear elasticity model is introduced to represent time‐independent recoverable portion of the deformation. The consistent visco‐plasticity framework is utilised to capture the rate‐dependent, non‐recoverable strain components. The material parameters introduced in the model are identified, and their determination from conventional laboratory tests is discussed. The capability of the model to reproduce experimentally observed response of asphaltic materials is demonstrated through numerical simulations of several laboratory test data from the literature. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Majid Shayegan Abolghasem Esmaeili Fereidouni Naser Agh Khosrow Jani Khalili 《中国海洋湖沼学报》2016,34(4):709-718
The effects of salinity on the copepod, Acartia tonsa in terms of daily egg production rate (EPR), hatching success, fecal pellet production rate (FPR), naupliar development time and survival, sex ratio, and total life span were determined in laboratory conditions through three experiments. In experiment 1, EPR, hatching success, and FPR of individual females were monitored at salinities of 13, 20, 35 and 45 during short-periods (seven consecutive days). Results show EPR was affected by salinity with the highest outputs recorded at 20 and 35, respectively, which were considerably higher than those at 13 and 45. Mean FPR was also higher in 35 and 20. In experiment 2, the same parameters were evaluated over total life span of females (long-term study). The best EPR and FPR were observed in 35, which was statistically higher than at 13 and 20. In experiment 3, survival rates of early nauplii until adult stage were lowest at a salinity of 13. The development time increased with increasing of salinity. Female percentage clearly decreased with increasing salinity. Higher female percentages (56.7% and 52.2%, respectively) were significantly observed at two salinities of 13 and 20 compared to that at 35 (25%). Total longevity of females was not affected by salinity increment. Based on our results, for mass culture we recommend that a salinity of 35 be adopted due to higher reproductive performances, better feeding, and faster development of A. tonsa. 相似文献
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The problem of drained cavity expansion in soils of finite radial extent is investigated. Cylindrical and spherical cavities expanded from zero radius subjected to either constant stress or zero displacement at the finite boundary are considered. The generalised analytical solution procedure presented enables more advanced constitutive models to be implemented than have been possible in previous studies. Results generated for Sydney quartz sand highlight substantial differences between cavity limit pressures for the two boundary conditions and for boundaries of finite and infinite radial extent. This is of significance in accounting for boundary effects when interpreting cone penetration tests conducted in calibration chambers. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Summary The impact of the Arctic Oscillation (AO) on the winter surface air temperature (SAT) over Iran is demonstrated. Winter SAT
data for 50 years (1951–2000) are analyzed for the negative and the positive AO phases. Using the Median Sequential Correlation
Analysis (MSCA) technique it is shown that the winter SAT is negatively correlated to the winter AO index for most parts of
Iran. The winter AO index accounts for about 14% to 46% of the winter SAT variance. The positive (negative) SAT anomaly is
found to be associated with the onset of the negative (positive) phase. The overall probability of below long-term mean temperature
during the positive and the negative phases are estimated to be around 70% and 25%, respectively. For the negative phase,
westerly winds that originate from the warm Atlantic regions increase over Iran and consequently positive temperature anomalies
are found across the country. The positive AO phase is accompanied by northerly winds that allow continental polar and arctic
air masses to move into Iran, producing below normal temperatures. The summer AO is found to explain about 25–32% of the winter
SAT variance in Iran. The reason for this is explained by the significant correlation (+0.38) between the summer and the following
winter AO indices. These results indicate that the summer climate is linked to changes in atmospheric circulation which persist
through to the following autumn and winter. 相似文献
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The paper presents a mechanical model for non‐isothermal behaviour of unsaturated soils. The model is based on an incrementally non‐linear hypoplastic model for saturated clays and can therefore tackle the non‐linear behaviour of overconsolidated soils. A hypoplastic model for non‐isothermal behaviour of saturated soils was developed and combined with the existing hypoplastic model for unsaturated soils based on the effective stress principle. Features of the soil behaviour that are included into the model, and those that are not, are clearly distinguished. The number of model parameters is kept to a minimum, and they all have a clear physical interpretation, to facilitate the model usefulness for practical applications. The step‐by‐step procedure used for the parameter calibration is described. The model is finally evaluated using a comprehensive set of experimental data for the thermo‐mechanical behaviour of an unsaturated compacted silt. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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AbstractGully erosion is considered to be one of the most important soil erosion processes in Mediterranean marly environments, but its actual contribution to total soil loss is still under discussion. The objectives of this paper are: (a) to acquire the distributed value of erosion rate in a permanent gully developed on a marly substratum in a Mediterranean environment; and (b) to quantify the key factors responsible for the spatial and temporal differences in erosion rates observed within the gully. A permanent gully located in Cap Bon (northeastern Tunisia) has been intensively and regularly monitored over a 7-year period with electronic survey equipment (total station) to give five field topographic surveys, as well as hydrological measurements at the gully outlet. The net soil loss for the 7-year period comprised a denudation of 51 m3 of sediment on the gully bank slopes, which corresponds to a mean soil loss of 61 m3 ha?1 year?1 or 6.1 mm year?1. Denudation was observed on bed units with a slope gradient greater than 20%, while the remainder showed deposition. By confirming the factors involved in gully evolution, and by refining the statistical link between factors and erosion rates within the gully, the results provide important information to predict gully erosion rates in Mediterranean marly environments.Editor Z.W. Kundzewicz; Associate editor G. MahéCitation El Khalili, A., Raclot, D., Habaieb, H., and Lamachère, J.M., 2013. Factors and processes of permanent gully evolution in a Mediterranean marly environment (Cape Bon, Tunisia). Hydrological Sciences Journal, 58 (7), 1519–1531. 相似文献
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Probabilistic analysis of extreme regional meteorological droughts by L-moments in a semi-arid environment 总被引:1,自引:1,他引:0
Regional extreme value analyses of drought characteristics provide information on probabilistic nature of drought occurrence, viewed as an essential tool in drought mitigation and planning. In this paper, L-moments are used to investigate the regional characteristics and probabilistic behavior of drought severity levels, represented by the Standardized Precipitation Index (SPI) annual minima (the minimum monthly SPI value). Rainfall data of 3, 6, 12, and 24 month time scales are investigated. A regional watershed in southwestern Iran is used as a case study area. The semi-arid nature of the study area requires appropriate selection of rainfall data. The boxplot approach is used to select those months with adequate data time series for the SPI analysis. Appropriateness of the suggested data time series is discussed in the context of the research by Wu et al. (2007). Based on the results, all of the suggested time scales are found appropriate for SPI investigations. For each time scale of interest regional homogeneity is evaluated and the best regional/sub-regional probability distribution function is selected. Regional quantiles are estimated for different time scales and their variability with respect to return period is discussed. 相似文献
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Summary This study attempts to find possible linkages between the NCP index and the winter temperature variability over Iran. The
investigation is based on statistical analysis of simple, partial and multiple correlations and also evaluation of composite
maps of the extreme NCP index and maps of correlation between atmospheric variables and the temperature time series.
Our results show that the NCP has a strong negative correlation with the winter temperature in Iran. Furthermore, combination
of both the NCP and the AO (Arctic Oscillation) indices improve the correlations in all stations, implying both NCP and AO
can be considered as major patterns for explaining the Iranian winter temperature variability. The results show that the positive
NCP is associated with enhanced precipitation and cloudy conditions, consequently causing below normal temperature over Iran.
The anomalies of OLR in this phase are also negative, implying a cloudy sky. For the negative NCP phase these results are
completely reversed. The correlation maps indicate that the NCP is negatively/positively correlated with winter Outgoing Long-wave
Radiation/precipitation over Iran. The results also show that the SLP and GPH patterns are quite different for the positive
and negative NCP phases over Iran. During the negative NCP a small cyclone is formed over the Arabian Sea causing a strong
easterly towards Iran. During the positive NCP this cyclone is removed. Our results show that for the positive NCP years an
upper-level trough is formed over northern Iran and the eastern Mediterranean. For the negative NCP years this trough becomes
weak and is located over central European regions. This trough is closely linked with the winter temperature over Iran. This
is expressed by a high correlation between 500-hPa geopotential height at this region and Iranian winter temperature.
Authors’ addresses: A. R. Ghasemi, Climate Research Center, Water Engineering Department, Agricultural Faculty, Shiraz University,
Shiraz, Iran; D. Khalili, Water Engineering Department, Agricultural Faculty, Shiraz University, Shiraz, Iran. 相似文献