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Flow through rough fractures is investigated numerically in order to assess the validity of the local cubic law for different fracture geometries. Two‐dimensional channels with sinusoidal walls having different geometrical properties defined by the aperture, the amplitude, and the wavelength of the walls' corrugations, the corrugations asymmetry, and the phase shift between the two walls are considered to represent different fracture geometries. First, it is analytically shown that the hydraulic aperture clearly deviates from the mean aperture when the walls' roughness, the phase shift, and/or the asymmetry between the fracture walls are relatively high. The continuity and the Navier–Stokes equations are then solved by means of the finite element method and the numerical solutions compared to the theoretical predictions of the local cubic law. Reynolds numbers ranging from 0.066 to 66.66 are investigated so as to focus more particularly on the effect of flow inertial effects on the validity of the local cubic law. For low Reynolds number, typically less than 15, the local cubic law properly describes the fracture flow, especially when the fracture walls have small corrugation amplitudes. For Reynolds numbers higher than 15, the local cubic law is valid under the conditions that the fracture presents a low aspect ratio, small corrugation amplitudes, and a moderate phase lag between its walls.  相似文献   
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The self‐centering rocking steel frame is a seismic force resisting system in which a gap is allowed to form between a concentrically braced steel frame and the foundation. Downward vertical force applied to the rocking frame by post‐tensioning acts to close the uplifting gap and thus produces a restoring force. A key feature of the system is replaceable energy‐dissipating devices that act as structural fuses by producing high initial system stiffness and then yielding to dissipate energy from the input loading and protect the remaining portions of the structure from damage. In this research, a series of large‐scale hybrid simulation tests were performed to investigate the seismic performance of the self‐centering rocking steel frame and in particular, the ability of the controlled rocking system to self‐center the entire building. The hybrid simulation experiments were conducted in conjunction with computational modules, one that simulated the destabilizing P‐Δ effect and another module that simulated the hysteretic behavior of the rest of the building including simple composite steel/concrete shear beam‐to‐column connections and partition walls. These tests complement a series of quasi‐static cyclic and dynamic shake table tests that have been conducted on this system in prior work. The hybrid simulation tests validated the expected seismic performance as the system was subjected to ground motions in excess of the maximum considered earthquake, produced virtually no residual drift after every ground motion, did not produce inelasticity in the steel frame or post‐tensioning, and concentrated the inelasticity in fuse elements that were easily replaced. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
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The indiscriminate use of antimicrobials especially in developing countries has evoked serious bacterial resistance and led to the emergence of new and highly resistant strains of bacteria to commonly used antimicrobials. In Lebanon, pollution levels and bacterial infections are increasing at a high rate as a result of inadequate control measures to limit untreated effluent discharges into the sea or freshwater resources. The aim of this study was to isolate and molecularly characterize various Staphylococcus strains isolated from sea water, fresh water, sediments, and crab samples collected from representative communities along the coast of Lebanon. The results on the antimicrobial resistance indicated that the level of resistance of Staphylococcus aureus varied with various antimicrobials tested. The resistance patterns ranged between 45% in freshwater isolates and 54.8% in seawater ones. Fifty one percent of the tested isolates have shown resistance to at least one of the five tested antimicrobials; with seawater isolates exhibiting the highest rates of antimicrobial resistance.  相似文献   
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Three hundred and twenty‐two samples of desalinated household water were collected from 99 sampling locations that covered 95% of Kuwaiti's residential areas. Seventy‐one brands of bottled water were collected from Kuwaiti markets. The water quality parameters that were studied included pH, electrical conductivity (EC), total dissolved solids (TDS), F?, Cl?, Br?, , , , , , , , and the major macronutrients Na+, K+, Ca2+, and Mg2+. The analysis yielded a large range of results for most of these parameters, with differences in some cases exceeding 10‐fold. With a few exceptions, the results were found to comply with US‐EPA and WHO standards. Only the water in two brands of bottled water was acidic (pH < 6.5). The TDS was found to be higher than the US‐EPA regulated value in 4 and 3% of the household samples and bottled water brands, respectively. The fluoride levels were generally higher in bottled water than in household water. However, the household water that was produced by the Doha desalination plant and some of the European brands of bottled water were the best samples studied in terms of their quantity of Ca2+, Mg2+, and Na+ compared with the DRI values for those substances. EC and TDS were positively correlated with , , Na+, K+, Ca2+, and Mg2+ for household water but only with Ca2+ and Mg2+ for bottled water.  相似文献   
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The present study reveals spatial variability of haloacetic acids and the basic physiochemical properties of drinking water samples through visualization based on the Kriging algorithm and hierarchical cluster analysis. Both projection and statistical method contributed to the logical classification of the indoor and outdoor water samples collected from various governorates covering more than 95% of the residential areas in Kuwait. Clustering of the variables led to the formation of several significant clusters corresponding to the effect of chlorine concentration and its residence time on the formation potential of chlorinated acetic acid derivatives in desalinated drinking water as well as to the total ionic composition of water samples and to the effect of the formation of brominated acetic acid derivatives. Clustering of samples, both indoor and outdoor, indicated that all of governorates located in the northern part of Kuwait are supplied with water containing high concentrations of chlorinated acetic acid derivatives, whereas significantly lower amounts of chlorinated or monobrominated acetic acids were found in water samples in the central and southern parts of the country.  相似文献   
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Tunnels constructed using New Austrian Tunnelling Method (NATM) are always based on certain round (unsupported) advance lengths, after which, the temporary lining is placed. The settlement of the ground surface resulting from such construction is of high significance in design and practice. The existing data in this respect, however, is scarce. It is the aim of this paper to propose a semi‐analytical procedure based on three‐dimensional finite element analyses to predict the maximum surface settlement of the ground in NATM tunnels under different combinations of tunnel diameter, overburden depth, round length and soil and lining properties. The comparison of the results with three case histories of real tunnels reveals reasonable accuracy of the present solution. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
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Neoproterozoic volcanic series are exposed in the northern edge of the Saghro massif (Eastern Anti-Atlas, Morocco). Four volcanic rock types (basalt, andesite, dacite, and rhyolite) were distinguished in the Boumalne inlier within the so-called Saghro volcanic sequences based on petrographic and geochemical observations. Boumalne volcanic rocks contain high Al2O3, Fe2O3, Ba, Sr, Zr, Rb, and Nb contents, including calc-alkaline affinity in composition. Boumalne volcanic rocks are similar to other lower-Neoproterozoic volcanic rocks such Agouiniy formation in Sirwa inlier and in other parts of Bou-Azzer inlier. Indeed, they indicate an active subduction signature. The geochemical data show a LREE enrichment compared to HREE. The fractional crystallization has played a major role during the evolution of the magma. The less-siliceous dacitic rocks could have been formed after a low degree of partial melting of mafic parental magma source, whereas the rich-siliceous rhyolite may have been derived from dacitic magma source by a higher degree of fractional crystallization.  相似文献   
9.
The levels of the trace elements aluminum (Al), arsenic (As), boron (B), barium (Ba), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), mercury (Hg), molybdenum (Mo), nickel (Ni), antimony (Sb), selenium (Se), strontium (Sr), titanium (Ti), vanadium (V), and zinc (Zn) were determined in 93 brands of non‐carbonated (BW) and carbonated (CBW) bottled water available in Kuwaiti markets and in 321 samples of desalinated household water (HW) collected from 99 sampling locations, which covered 95% of Kuwait's residential areas. The study yielded a large range of results for most of these elements, and the difference between the lowest and highest measured values exceeded three orders of magnitude for some elements in a number of the BW and CBW brands. With a few exceptions, the results for the HW and BW were found to comply with the United States‐Environmental Protection Agency and World Health Organization guideline values. The elements Fe, Pb, Hg, and Ni exceeded these GVs in 8.5, 0.3, 1.2, and 1% of the HW samples, respectively. One brand of BW exceeded the GV for B, while the levels of B, Ba, Be, Fe, and Mn exceeded the GVs in 35, 15, 5, 75, and 25% of the CBW brands, respectively. Correlations were found between the levels of some elements and either the desalination plant that produced the HW or the country of origin of the BW or CBW. The levels of the elements Al, Cu, Fe, and Zn in HW were higher in the summer than in the winter, with 14, 14, 42, and 18% increases, respectively. Nutritional evaluation revealed that significant percentages of the DRIs of Cr, Cu, Fe, and Se can be provided by drinking 2 L of HW, and significant percentages of the DRIs of B, Cr, Cu, and Mo can be provided by drinking 2 L of BW.  相似文献   
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Modern highway bridges in Illinois are often installed with economical elastomeric bearings that allow for thermal movement of the superstructure, and steel fixed bearings and transverse retainers that prevent excessive movement from service‐level loadings. In the event of an earthquake, the bearing system has the potential to provide a quasi‐isolated response where failure of sacrificial elements and sliding of the bearings can cause a period elongation and reduce or cap the force demands on the substructure. A computational model that has been calibrated for the expected nonlinear behaviors is used to carry out a parametric study to evaluate quasi‐isolated bridge behavior. The study investigates different superstructure types, substructure types, substructure heights, foundation types, and elastomeric bearing types. Overall, only a few bridge variants were noted to unseat for design‐level seismic input in the New Madrid Seismic Zone, indicating that most structures in Illinois would not experience severe damage during their typical design life. However, Type II bearing systems, which consist of an elastomeric bearing and a flat PTFE slider, would in some cases result in critical damage from unseating at moderate and high seismic input. The sequence of damage for many bridge cases indicates yielding of piers at low‐level seismic input. This is caused by the high strength of the fixed bearing element, which justifies further calibration of the quasi‐isolation design approach. Finally, the type of ground motion, pier height, and bearing type were noted to have significant influence on the global bridge response. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
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