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11.
A model for the air–sea interface, based on the coupled pair of similarity relations for “aerodynamically” rough flow in both
fluids, is presented, which is applied to fetch-limited and high wind speed conditions which occur, for example, in hurricanes.
It is shown that the specification of the maximum 10-m drag coefficient and the 10-m wind speed and the peak wave speed at
which it occurs are sufficient to uniquely determine the drag law, which asymptotes at low wind speeds to a Charnock constant
similar to that for the fully developed wind wave sea and is almost independent of the peak wave speed at the maximum in drag
coefficient. A feature of the drag law is that it is of Charnock form, almost independent of the wave age, consistent with
the transfer of momentum to the wave spectrum being due to the smaller rather than the dominant wavelengths. The analysis
is also applied to a variable sea state in which either the surface wind or the surface Stokes drift vary, but the peak wave
speed is kept constant. The corresponding variability in the Charnock constant is in general accord with observations. 相似文献
12.
Two long term microclimate measurement stations with Bowen ratio capability have been used to study water cycling in a closed desert basin. Microclimate variables including the temperature and vapor pressure gradients were monitored continuously and were used to estimate the Bowen ratio, sensible and latent heat fluxes during 1986 and 1987. Despite having a water table that varied between the surface and 30 cm below the surface, the playa had little evaporation except after rainfall events. The very high osmotic pressure of the soil and salt crust caused most of the absorbed radiation to be partitioned to sensible heat. In contrast, along the margin the thin grass and brush cover transpired water freely, with the latent heat flux exceeding 60% of available energy for much of the season. The higher air temperatures above the playa raised potential evapotranspiration (ET) significantly higher than along the margin throughout the summer. The annual average actual ET of the playa was only 36% of the margin. During the drier summer period (May–October), this ratio decreased to < 28%. Immediately after a rainfall event, evaporation rates of the two sites were similar, but the playa rate was quickly reduced as the osmotic potential increased. During this study, the playa lost < 229 mm of subsurface water to evaporation annually, while > 638 mm were lost from the margin groundwater supply.
The 24-h solar and net radiation correlations were 0.80 and 0.94 for the playa and margin, respectively. The lower correlation for the playa resulted from the wide variation of albedo with surface moisture changes. The annual average albedo values for the playa and margin were 0.64 and 0.46, respectively. 相似文献
13.
Comparison of the Bowen ratio-energy balance and stability-corrected aerodynamic methods for measurement of evapotranspiration 总被引：2，自引：0，他引：2
E. Malek 《Theoretical and Applied Climatology》1993,48(2-3):167-178
Summary The Bowen ratio-energy balance (BREB) and the stability-corrected aerodynamic method were used to estimate turbulent fluxes of sensible and latent heat at an irrigated alfalfa site in a semi-arid valley in northern Utah, U.S.A., during August and September of 1991. Despite inclusion of a generalized stability factor, the aerodynamic method underestimated the daytime (sunrise-sunset) sensible and latent heat fluxes by approximately 30% in comparison with the BREB method. The sum of the aerodynamic estimates of sensible and latent heat seldom balanced the energy avaiable from net radiation and change in storage. Wind speed was low during the experiment (averaging 1.6 m s–1), and so a second analysis was run for data from daytime, non-rainy, turbulent conditions (wind > 1.5 m s–1). This showed that sensible and latent heat were still underestimated by approximately 30% in comparison with the BREB approach. This suggests that underestimation of sensible and latent heat fluxes by the aerodynamic method was not related to the wind speed conditions during the experiment. These results show that the stability-corrected aerodynamic model did not agree with the Bowen ratio method in this experiment. It appears unlikely that the discrepancies resulted from measurement errors. Perhaps the theoretical foundation of the similarity parameters (stability functions) in the aerodynamic model are not sufficiently generalized. The discrepancies found here confirm the necessity of calibration checks on the validity of aerodynamic estimates of the turbulent fluxes.With 7 Figures 相似文献
14.
Finite element analysis of damage and failure of reinforced concrete members under earthquake loading 
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下载免费PDF全文 This paper presents a three‐dimensional analysis framework, based on the explicit finite element method, for the simulation of reinforced concrete components under cyclic static and dynamic loading. A recently developed triaxial constitutive model for concrete is combined with a material model for reinforcing steel which can account for rupture due to low‐cycle fatigue. The reinforcing bars are represented with geometrically nonlinear beam elements to account for buckling of the reinforcement. The strain penetration effect is also accounted for in the models. The modeling scheme is used in a commercial finite element program and validated with the results of experimental static and dynamic tests on reinforced concrete columns and walls. The analyses are supplemented with a parametric study to investigate the impact of several modeling assumptions on the obtained results. 相似文献
15.
Javad Saberian Mohammad Reza Malek Stephan Winter Majid Hamrah 《Transactions in GIS》2014,18(5):767-782
In this article we define inverse line graphs of directed graphs as a new framework for solving some classical network analysis problems. The extraction method and theories of inverse line graphs are explained in this article. It is shown that by changing the analysis space from the original directed graph to the inverse line graph, complex problems can be changed into simpler problems. We show the usefulness of the proposed framework in two particular applications: shortest path computations and the more general route planning. Considering the implementation result, we expect that this framework could be used in many more network analysis problems. 相似文献
16.
Mahdi Hasanipanah Danial Jahed Armaghani Hassan Bakhshandeh Amnieh Mohammadreza Koopialipoor Hossein Arab 《Geotechnical and Geological Engineering》2018,36(4):2247-2260
Flyrock is an adverse effect produced by blasting in open-pit mines and tunneling projects. So, it seems that the precise estimations and risk level assessment of flyrock are essential in minimizing environmental effects induced by blasting. The first aim of this research is to model the risk level associated with flyrock through rock engineering systems (RES) methodology. In this regard, 62 blasting were investigated in Ulu Tiram quarry, Malaysia, and the most effective parameters of flyrock were measured. Using the most influential parameters on flyrock, the overall risk of flyrock was obtained as 32.95 which is considered as low to medium degree of vulnerability. Moreover, the second aim of this research is to estimate flyrock based on RES and multiple linear regression (MLR). To evaluate performance prediction of the models, some statistical criteria such as coefficient of determination (R2) were computed. Comparing the values predicted by the models demonstrated that the RES has more suitable performance than MLR for predicting the flyrock and it could be introduced as a powerful technique in this field. 相似文献
17.
Mohammadreza Kavianpour Mohammadreza Seyedabadi Saber Moazami 《Environmental Earth Sciences》2018,77(22):769
Drought as a natural disaster impresses people living. The main tool in better management of such phenomena is to explain its characteristics, using drought indices. The indices use precipitation, temperature, streamflow, and other hydrological variables to explain such events. In this study, standardized precipitation index (SPI) and stream-flow drought index (SDI) were used to develop a new combined drought index (CDI) based on copula functions. The proposed index function was evaluated in Khuzestan, Yazd and Golestan provinces of Iran from 1982 to 2012. These areas introduce different climate conditions. The index was analyzed temporally and spatially. In the temporal analysis, CDI was calculated separately for each station and the finest index was chosen by Kolmogorov–Smirnov and Chi-squared tests. In the spatial analysis, CDI was computed for two main scenarios and twenty sub-scenarios for the whole area of Golestan Province. The optimum index was chosen based on comparison with initial SPI and SDI. The results showed that CDI is more meticulous than both singular SPI and SDI, as it can trace a drought onset earlier and drought duration more accurate than the two individual indices and obviously display extreme states. 相似文献
18.
RÉSUMÉDes sondages électriques verticaux, des enregistrements diagraphiques et des données de forages sont utilisés pour identifier et caractériser les aquifères de la région de Bou Salem (Nord-Ouest de la Tunisie). Les données de résistivité apparente mesurées à chaque sondage électrique vertical pour les différentes distances AB sont interprétées unidimensionnellement. Les enregistrements diagraphiques ont permis la restitution précise des colonnes lithologiques des forages préexistants et par conséquent l’étalonnage des sondages électriques. L’analyse et l’interprétation des données révèlent que les alluvions quaternaires perméables se limitent aux zones proximales des oueds Kasseb et Bouhertma. Cette distribution est contrôlée par les mécanismes de sédimentation dans les plaines d’inondation et par la réactivation des accidents N–S en failles normales durant le Quaternaire récent. Il ressort aussi que les calcaires éocènes et crétacés correspondant au substratum des alluvions quaternaires et caractérisés par des fortes résistivités peuvent constituer d’intéressants aquifères. 相似文献
19.
M.J. Rospondek M. Szczerba K. Malek M. Gra L. Marynowski 《Organic Geochemistry》2008,39(12):1800-1815
Evaluation of the relative thermodynamic stabilities of phenyldibenzothiophenes, by means of molecular modelling, has led to the prediction of their equilibrium mixture composition. The calculated equilibrium composition shifts towards that obtained in a laboratory maturation experiment and encountered in mature geological samples (mean vitrinite reflectance Rr 1.2%). Close inspection of a suite of samples, having in common hydrothermal oxidation of organic matter, but varying in maturity, suggests that phenyldibenzothiophenes can isomerise and also cyclise to triphenyleno[1,12-bcd]thiophene. Both reactions are thermodynamically possible as a result of the relative decrease in enthalpy along the reaction paths and the resulting competition for the precursor 1-phenyldibenzothiophene. Changes in the phenyldibenzothiophene positional isomer distributions from kinetically to thermodynamically controlled mixtures are likely to be achieved with an acid catalysed 1,2-phenyl shift, as suggested from our maturation experiment. To validate this hypothesis, ab initio quantum chemical calculations (DFT) were performed, leading to the localisation of potential transition states as well as the determination of activation energies in gas phase and aqueous solution. The isomerisation barriers are significantly lowered by acid catalysis. They are in the range from ΔE(aq) 20.5 to 28.7 kcal/mol, consistent with the early beginning of the isomerisation observed for our samples. With increasing maturity, 1-PhDBT decays rapidly. At very advanced maturity stages the process is often accompanied by the appearance of triphenyleno[1,12-bcd]thiophene, suggesting its simultaneous formation by cyclisation/oxidation. The oxidation is most likely associated in nature via thermochemical sulfate reduction (TSR). The modelling of such a reaction with thiosulfates yielded an energy barrier ΔE(aq) of ca. 64.7 kcal/mol, only when the initial step involved protonation. This energy seems relevant to very advanced stages of diagenesis/catagenesis. The modelled barrier can be lowered by 2–3 kcal/mol at significantly elevated fluid temperatures as a result of changes in the physical properties of water. 相似文献
20.
Noor Azlinda Ahmad M. Fernando Z.A. Baharudin V. Cooray H. Ahmad Z. Abdul Malek 《Journal of Atmospheric and Solar》2010,72(5-6):534-540
Narrow bipolar pulses (NBPs) are considered as isolated intracloud events with higher peak amplitude and strong high frequency emission compared to the first return strokes and other intracloud discharges. From 182 NBPs recorded in Malaysia in the tropic, 75 were narrow negative bipolar pulses (NNBPs) while 107 were narrow positive bipolar pulses (NPBPs). The mean duration of NNBPs was 24.6±17.1 μs, while 30.2±12.3 μs was observed for NPBPs. The mean full-width at half-maximum (FWHM) was 2.2±0.7 and 2.4±1.4 μs for NNBPs and NPBPs, respectively. The mean peak amplitude of NPBPs normalized to 100 km was 22.7 V/m, a factor of 1.3 higher than that of NNBPs which is 17.6 V/m. In contrast to the previous studies, it was observed that the electric field change was characterized by a bipolar pulse with a significant amount of fine structures separated by a few tens of nanoseconds intervals, embedded on it. 相似文献