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1.
The advective monthly mean transfer of water vapour in the layer below 700 mbar is investigated for India for the years 1962 to 1972 and for the months January to September. The average zonal and meridional components of the transfer of water vapour for India are obtained. They are further averaged for different combinations of the pre-monsoon months from January to May and are correlated with the summer monsoon rainfall. The correlation coefficients for zonal transfer of water vapour are either negative or small positive for different combinations of the months mentioned above. The correlation coefficients for the meridional transfer of water vapour are positive. The maximum value is 0.74 for the March to May combination and is statistically significant at the 1% level.An extensive investigation is, therefore, made for the March to May averages of water vapour transfer for four broad regions of India. The parameters of water vapour transfer for these regions are compared with the threshold values and the prediction category, normal or drought, for the subsequent summer monsoon season is determined for all years. The correlation coefficient between the index of drought, as determined from parameters of water vapour transport and rainfall departure, is statistically significant at the 2% level.  相似文献   

2.
An assessment of metal contamination in surface sediments of the Jiaozhou Bay, Qingdao, one of the rapidly developing coastal economic zones in China, is provided. Sediments were collected from 10 stations and a total of 15 heavy metals were analyzed. Concentrations of metals show significant variability and range from 210 to 620 ppm for Ti, 2.7 to 23 ppm for Ni, 4.2 to 28 ppm for Cu, 5.2 to 18 ppm for Pb, 12 to 58 ppm for Zn, 0.03 to 0.11 ppm for Cd, 5 to 51 ppm for Cr, 1.5 to 9.9 ppm for Co, 5.3 to 19 ppm for As, 12 to 32 ppm for Se, and 19 to 97 ppm for Sr. Based on concentration relationships and enrichment factor (EF) analyses, the results indicate that sediment grain size and organic matter played important roles in controlling the distribution of the heavy metals in surface sediments of the Jiaozhou Bay. The study shows that the sediment of the Jiaozhou Bay has been contaminated by heavy metals to various degrees, with prominent arsenic contributing the most to the contamination. The analysis suggests that the major sources of metal contamination in the Jiaozhou Bay are land‐based anthropogenic ones, such as discharge of industrial waste water and municipal sewage and run‐off. Notably, the elevated heavy metal concentrations of the Jiaozhou Bay sediments could have a significant impact on the bay's ecosystem. With the rapid economic development and urbanization around the Jiaozhou Bay, coastal management and pollution control should focus on these contaminant sources, as well as provide ongoing monitoring studies of heavy metal contamination within the bay.  相似文献   

3.
This work presents two software components aimed to relieve the costs of accessing high-performance parallel computing resources within a Python programming environment: MPI for Python and PETSc for Python.MPI for Python is a general-purpose Python package that provides bindings for the Message Passing Interface (MPI) standard using any back-end MPI implementation. Its facilities allow parallel Python programs to easily exploit multiple processors using the message passing paradigm. PETSc for Python provides access to the Portable, Extensible Toolkit for Scientific Computation (PETSc) libraries. Its facilities allow sequential and parallel Python applications to exploit state of the art algorithms and data structures readily available in PETSc for the solution of large-scale problems in science and engineering.MPI for Python and PETSc for Python are fully integrated to PETSc-FEM, an MPI and PETSc based parallel, multiphysics, finite elements code developed at CIMEC laboratory. This software infrastructure supports research activities related to simulation of fluid flows with applications ranging from the design of microfluidic devices for biochemical analysis to modeling of large-scale stream/aquifer interactions.  相似文献   

4.
Samples of raw water were collected in the St. Lawrence River during six sampling trips from August 1990 to April 1992. Water samples were analyzed for both dissolved and particulate phases for five trace metals. Partition coefficients (Kd) and metal fluxes were calculated in order to determine metal transport. A mass balance equation was used for the determination of the major metal sources to the St. Lawrence River and an estimation of metal loadings to the estuary was made. Average dissolved metal concentrations were found to be Cd 10 ng/L, Co 74 ng/L, Cu 64 ng/L, Fe 69 µg/L and Mn 700 ng/L. Particulate concentrations were (in µg/g) 1.68 for Cd, 31 for Co, 73 for Cu, 25 mg/g for Fe and 1.69 mg/g for Mn. Co, Fe and Mn were transported essentially in the particulate phase while Cd and Cu were predominantly found in the dissolved phase at 56% and 48% of the total metal concentration respectively. Log Kd values varied from 5.1 (for Cu) to 6.8 (for Mn). In the dissolved phase the major sources were found to be the Great Lakes and the Ottawa River whereas in the particulate phase Québec tributaries appear to be the most important. Industrial inputs are quite important in both the dissolved and the particulate phases for Cd, whereas other sources are very variable, especially for the dissolved phase.  相似文献   

5.
Through time people have been mobile, for a variety of complex reasons at a range of scales from local through regional and continental to intercontinental. Some are voluntary, others are made under pressure and the force of various circumstances, with environmental, socio-economic and political factors often interrelating to cause movements. We are now more mobile than at any time in the past, there are more people to move, the means to move are greater, and political boundaries are either open or often crossed without great difficulty. These movements have considerable consequences for human health, for disease transmission and diffusion and for measures for health improvement. They are viewed at a global scale, and then for two major regions in more detail to illustrate their significance for one old and one new disease, for malaria in Southeast Asia and for HIV/AIDS in West Africa. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

6.
We study wave propagation through isotropic and anisotropic scatterer distributions in order to observe azimuthal variations in velocity and apparent attenuation. Using thin aluminum plates as physical models, we obtained seismograms for compressional and shear wave propagation through heterogeneous media. Three random distributions of scatterers are studied: circular scatterers in isotropic distributions (modeling circular scatterers), elongated scatterers in isotropic distributions (modeling randomly oriented elliptical scatterers), and elongated scatterers in anisotropic distributions (modeling aligned elliptical scatterers). All scatterers had approximately the same cross-sectional area and were filled with epoxy in order to reduce the impedance contrast. In addition to seismograms recorded for no scatterers, seismograms were recorded for several scatterer volume fractions. Azimuths were measured relative to the long axis of the aligned elongated scatterers. Velocities were calculated using travel times and phase shifts at low frequencies. The velocities measured from the data were compared to simple low-frequency average-velocity theories based on thin lamellae or on distributions of penny-shaped cracks. The apparent attenuation for different scatterer distributions was computed using spectral ratios.Comparisons of the results for circular and randomly oriented elongated scatterers were made to determine the effects of scatterer shape. As expected, the circular and randomly oriented elongated scatterers showed no systematic azimuthal variation in velocity. The velocity anomalies were systematically larger for the randomly oriented elongated scatterers than for the circular scatterers. Both methods of theoretical estimation for the isotropic velocities produced velocities significantly larger than those measured. The spectral ratios showed more apparent attenuation for the randomly oriented elongated scatterers than for the circular scatterers.Comparisons of the results for the randomly oriented and aligned elongated scatterers were made to determine the effects of anisotropy in the scatterer distribution. Compressional waves for the aligned elongated scatterers with wave propagation parallel to the scatterers had larger velocities than for the aligned elongated scatterers with wave propagation perpendicular to the scatterers for all velocity calculations. Shear wave velocities were complicated by an anomalous phase change in the shear wave seismograms for azimuths less than 40° and were not as conclusive. The general trend of the theoretical velocities is similar to the velocities calculated from the data. There are, however, what appear to be significant differences. The spectral ratios showed more apparent attenuation for the randomly oriented elongated scatterers than for the aligned elongated scatterers with wave propagation parallel to the scatterers, and less attenuation than for the aligned elongated scatterers with wave propagation perpendicular to the scatterers.  相似文献   

7.
The expressions for second (SOE) and third order elastic (TOE) constants for rare gas solids are derived for comparative study of elastic behavior within the framework of many body potentials including the effect of pressure. The derived expressions are used to obtain the relations for pressure derivatives of bulk and shear moduli of RGS solids. The values of SOE, TOE constants and pressure derivative of bulk and shear modulus for Ne up to 100 GPa, Ar up to 75 GPa, for Kr up to 136 GPa and Xe up to 53.4 GPa...  相似文献   

8.
This paper presents a procedure for computing inelastic design spectra in terms of yield displacement. The procedure results in substantial computational savings as compared to the current procedures for computing the inelastic spectra in terms of displacement ductility. The proposed method is used to obtain inelastic design spectra for alluvium and rock. The results for alluvium are compared to those from the Newmark and Hall,10 Riddell and Newmark12 and Lai and Biggs4 studies. The findings indicate that for given ductility and frequency one may de-amplify the elastic response or reduce the elastic forces more for a structure on rock than for a structure on alluvium. A technique is presented so that the inelastic design spectrum can be scaled to any desired yield displacement and acceleration. An example is presented to illustrate how the proposed inelastic spectra can be used to compute the required ductility for a given system.  相似文献   

9.
Summary The probability of occurrences of thundery weather over Gauhati airport has been investigated. During the pre-monsoon thunderstorm period, the months of April and May have higher probabilities for the occurrences of thundery weather and the month of March has, on average, medium probabilities. The probability for thundery weather, during the months of March and April, is the highest during >18 to 24 h and then decreases successively during 00 to 06 h, >12 to 18 h and >06 to 12 h in order. The month of May, being the transition season for sharp decrease of nor' westers, is an exception. The months June to September, during monsoon season, have high probabilities for a day being thundery; but the month of October, during which monsoon virtually withdraws, shows decreasing trend in probabilities for successive date-groups. During the whole of the monsoon months, the time-groups >12 to 18 h, >18 to 24 h, 00 to 06 h and >06 to 12 h rank first, second, third and fourth in the order of probability for a day being thundery.In April and May, the probabilities for the occurrences of thundery weather of MLL, LL and VLL groups are higher, but in the month of March, the probabilities for the occurrences of first two groups are higher and the third group has medium probability. During the months June to September, in the monsoon season, the probability for thundery weather of MLL and LL groups are higher but that of VLL group has the medium probability; during the month of October — the last month for monsoon season — MLL and LL have higher and medium probabilities for the occurrences of thundery weather.  相似文献   

10.
Pacific oyster (Crassostrea gigas Thunberg) embryos, bay mussel (Mytilus edulis Linnaeus) embryos, and Dungeness crab (Cancer magister Dana) zoea I stage larvae were exposed to arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, and zinc salts. The two bivalve species were exposed through the completion of embryogenesis (48 h), and the effects of the metals upon abnormal development were monitored. The crab larval stages were exposed to the metal solutions for 96 h. Concentrations (μg l.?1 as metal) which caused 50% abnormal development in the two species of bivalve larvae and which were fatal to 50% of the crab larvae ranged from 5.3 (oyster) to 49 (crab) for copper; 5.8 (mussel) to 8.2 (crab) for mercury; 14 (mussel) to 55 (crab) for silver; 119 (oyster) to 456 (crab) for zinc; 232 (crab) to 3000 (mussel) for arsenic; 247 (crab) to 1200 (mussel) for cadmium; 349 (oyster) to 4360 (crab) for nickel; 476 (mussel) to 758 (oyster) for lead; 3440 (crab) to 4538 (oyster) for hexavalent chromium; and selenium greater than 10 000 for the three species. The acute toxicity testing of C. gigas embryo together with two California native species confirmed its usefulness for predicting toxicity to the latter species.  相似文献   

11.
Hydrogen isotopic compositions in seven carbonaceous chondrites lie in the range ?70 to +771‰ relative to SMOW. These values decrease, to a range from ?145 to +219‰, after low-temperature oxidation in an oxygen plasma. Deuterium enrichment is therefore concentrated in the organic matter, the hydrous silicates probably lying close to the terrestrial range for such material. Calculated values for δD of the organic fraction are +450 ‰ for Orgueil and Ivuna and up to +1600‰ for Renazzo. These enrichments, at least for Orgueil and Ivuna, suggest equilibration with protosolar hydrogen at very low temperatures. Assuming a value of 2.5 × 10?5 for the protosolar D/H ratio, nominal equilibration temperatures of 230°K for silicates and 180°K for organic matter may be derived.  相似文献   

12.
Worldwide experience repeatedly shows that damages in structures caused by earthquakes are highly dependent on site condition and epicentral distance. In this paper, a 21-storey shear wall-structure built in the 1960s in Hong Kong is selected as an example to investigate these two effects. Under various design earthquake intensities and for various site conditions, the fragility curves or damage probability matrix of such building is quantified in terms of the ductility factor, which is estimated from the ratio of storey yield shear to the inter-storey seismic shear. For high-rise buildings, a higher probability of damage is obtained for a softer site condition, and damage is more severe for far field earthquakes than for near field earthquakes. For earthquake intensity of VIII, the probability of complete collapse (P) increases from 1 to 24% for near field earthquakes and from 1 to 41% for far field earthquakes if the building is moved form a rock site to a site consisting a 80 m thick soft clay. For intensity IX, P increases from 6 to 69% for near field earthquake and from 14 to 79% for far field earthquake if the building is again moved form rock site to soft soil site. Therefore, site effect is very important and not to be neglected. Similar site and epicentral effects should also be expected for other types of high-rise structures.  相似文献   

13.
Design parameters for borehole strain instrumentation   总被引：3，自引：0，他引：3  
The response of a borehole strain meter to hydrostatic and shear deformations in an isotropic medium is calculated to facilitate optimum instrument design and produce instrument response factors for parameters typically encountered in installed instruments. Results for an empty borehole are first compared with results for an instrument in intimate contact with the surrounding rock. The effects of the grout used to install the instrument are then examined. Where possible, analytic forms for the response factors are given. Results for typical installations are then presented in graphical form for optimizing instrument design in an environment of known elastic parameters. Alternatively, the results may be applied in the measurement of unknown strain signals, to correct for instrument response or to provide in-situ estimates of the elastic properties of the environment by examination of observed strain response to known strain signals.  相似文献   

14.
Temporal and spatial moment analysis of one-dimensional equations governing fate and transport of parent compounds along with their transformation products is useful for parameter estimation of model parameters, and for understanding the average attributes of contaminant behavior. The objective of this paper is to present analytical expressions for the lower order moments of members in a sequential chain reaction, where members undergo first-order decay to produce the next member in the chain. Specifically, moments up to second order are discussed for the first two members. For the case of purely advective transport (Peclet number tending to infinity), temporal moment expressions are provided for more members of the chain. The sensitivity of temporal moments is examined with respect to Peclet number and transformation rates. Spatial moments are derived by two methods—one using Fourier transforms and another using moment generating differential equations. The behavior of lower order moments for the first few members of a chain can be elucidated from their mathematical expressions. However, expressions for higher order moments tend to be very complicated especially for members further down the chain.  相似文献   

15.
Confinement of concrete in circular spiral steel binders imparts to it considerable ductility and also some increase in strength. This property can be utilized in designing concrete structures to withstand seismic forces where the members are required to possess not only strength but also energy absorbing capacity. Assuming the stress-strain behaviour of confined concrete as elastic-plastic, the ductility factor for strain and the strength factor (denoting increase in strength) have been determined for concrete confined to different degrees. Similarly, assuming the moment-curvature behaviour of reinforced concrete sections with confined compression concrete to be elastic-plastic, the ductility factor for curvature has been determined for such beams. The computed moment-curvature plots have been found to compare satisfactorily with tests on 18 beams. Ductility factors for curvature of singly and doubly reinforced concrete sections with compression concrete confined to different degrees have been determined and presented for certain typical cases. Such plots would be of use in designing reinforced concrete beam sections for required ductility.  相似文献   

16.
We develop a probabilistic model for estimating the tsunami hazard along the coast of New Zealand due to plate-interface earthquakes along the South American subduction zone. To do this we develop statistical and physical models for several stages in the process of tsunami generation and propagation, and develop a method for combining these models to produce hazard estimates using a Monte-Carlo technique. This process is largely analogous to that used for seismic hazard modelling, but is distinguished from it by the use of a physical model to represent the tsunami propagation, as opposed to the use of empirical attenuation models for probabilistic seismic hazard analysis.  相似文献   

17.
This study is an attempt to underline the lack of preparedness and the nature of immediate further measures to be taken for facing a moderate earthquake in Indian subcontinents. Surprisingly, moderate to severe damage was noticed in structures located in hundreds of kilometres away from epicentre during last Gorkha earthquake. In this context, the present study makes an effort to validate a proposed modified rapid visual screening schemes for low cost houses frequently available in India. This may be used extensively for quick vulnerability assessment of a locality. Examples of retrofitting measures for typical buildings presented in this study may be useful for upgrading the valuable structures. Thus this study may be helpful for quick vulnerability assessment and adopting retrofitting measures for identified structures for earthquake prone developing countries.  相似文献   

18.
Concentrations of selected heavy metals (Cu, Pb, Zn, Cd, Cr, Ni and Fe) in surface sediments from nine sites in western Xiamen Bay and its vicinity were studied in order to understand current metal contamination due to urbanization and economic development in Xiamen, China. The sediment samples were collected in December 2004 and July 2005 respectively in order to examine temporal variations. In this study, we found that heavy metal concentrations in surface sediments sampled in the western Xiamen Bay and adjacent Maluan Bay and Yuandang Lagoon varied from 19 to 97mg kg(-1) for Cu, 45 to 60mg kg(-1) for Pb, 65 to 223mg kg(-1) for Zn, 0.11 to 1.01mg kg(-1) for Cd, 37 to 134mg kg(-1) for Cr, 25 to 65mg kg(-1) for Ni and 3.08 to 4.81% for Fe. Although all metal concentrations in sediments meets Chinese National Standard Criteria for Marine Sediment Quality, both metal enrichment factors (EF) and geoaccumulation index (I(geo)) show that Pb contamination exists in the entire study area and contamination of other metals are also present in some locations depending on the sources, of which sewage outlets and commercial ports are the main sources of contaminants to the area. This study shows that using the sediment quality standard criteria only to assess sediments cannot properly reflect sediment contamination. A multiple approaches should be applied for the sediment quality assessment.  相似文献   

19.
Real‐time hybrid simulation is a viable experiment technique to evaluate the performance of structures equipped with rate‐dependent seismic devices when subject to dynamic loading. The integration algorithm used to solve the equations of motion has to be stable and accurate to achieve a successful real‐time hybrid simulation. The implicit HHT α‐algorithm is a popular integration algorithm for conducting structural dynamic time history analysis because of its desirable properties of unconditional stability for linear elastic structures and controllable numerical damping for high frequencies. The implicit form of the algorithm, however, requires iterations for nonlinear structures, which is undesirable for real‐time hybrid simulation. Consequently, the HHT α‐algorithm has been implemented for real‐time hybrid simulation using a fixed number of substep iterations. The resulting HHT α‐algorithm with a fixed number of substep iterations is believed to be unconditionally stable for linear elastic structures, but research on its stability and accuracy for nonlinear structures is quite limited. In this paper, a discrete transfer function approach is utilized to analyze the HHT α‐algorithm with a fixed number of substep iterations. The algorithm is shown to be unconditionally stable for linear elastic structures, but only conditionally stable for nonlinear softening or hardening structures. The equivalent damping of the algorithm is shown to be almost the same as that of the original HHT α‐algorithm, while the period elongation varies depending on the structural nonlinearity and the size of the integration time‐step. A modified form of the algorithm is proposed to improve its stability for use in nonlinear structures. The stability of the modified algorithm is demonstrated to be enhanced and have an accuracy that is comparable to that of the existing HHT α‐algorithm with a fixed number of substep iterations. Both numerical and real‐time hybrid simulations are conducted to verify the modified algorithm. The experimental results demonstrate the effectiveness of the modified algorithm for real‐time testing. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

20.
Improved knowledge of the effects of grass and shrub cover in overland flow can provide valuable information for soil and water conservation programs.Laboratory simulated rainfall studies were conducted to determine effects of grass and shrub on runoff and soil loss and to ascertain the relationship between the rate of soil loss and the unit stream power of runoff for a 20°slope subjected to rainfall intensities of 45,87,and 127 mm/h.The results indicated that the average runoff rates ranged from 4.2 to 73.1 mm/h for grass plots and from 9.3 to 58.2 mm/h for shrub plots.Runoff rates from shrub plots were less than those from grass plots for all but the 45 mm/h rainfall intensity regime. Average soil loss rates varied from 5.7 to 120.3 g/min.m~2 for grass plots and from 5.6 to 84.4 g/min.m~2 for shrub plots.Soil loss rates from shrub plots were generally lower than those from grass plots.Runoff and soil loss were strongly influenced by soil surface conditions due to the formation of erosion pits and rills.The rate of soil loss increased linearly with the unit stream power of runoff on both grass and shrub plots.Critical unit stream power values were 0.0127 m/s for grass plots and 0.0169 m/s for shrub plots.Shrub plots showed a greater stability to resist soil detachment and transport by surface flow than grass plots.  相似文献   

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