Equilibrium and Kinetic Studies on the Removal of Reactive Red 2 Dye from an Aqueous Solution Using a Positively Charged Functional Group of the Nymphaea rubra Biosorbent

Nymphaea rubra stem was used as a low cost and easily available biosorbent for the removal of Reactive Red 2 dye from an aqueous solution. Initially, the effects of biosorbent dosage (0.2–1.0 g L^–1), pH (1–6), and dye concentration (30–110 mg L^–1) on dye removal were studied. Batch experiments were carried out for biosorption kinetics and isotherm studies. The results showed that dye uptake capacity was found to increase with a decrease in biosorbent dosage. Equilibrium uptake capacity was found to be greatest at a pH value of 2.0, when compared to all other pH values studied. The equilibrium biosorption isotherms were analyzed by the Freundlich and Langmuir models. The equilibrium data was found to fit very well with the Freundlich isotherm model when compared to the Langmuir isotherm model. The kinetic data was analyzed using pseudo-first order and pseudo-second order kinetic models. From the results, it was observed that the kinetic data was found to fit the pseudo-second order kinetic model very well. The surface morphology of the stem of the N. rubra biosorbent was exemplified by scanning electron microscopy. Fourier transform infrared analysis was employed to confirm the existence of an amine group in the stem of N. rubra.     

Removal of Basic Textile Dyes in Single and Multi‐Dye Solutions by Adsorption: Statistical Optimization and Equilibrium Isotherm Studies

The removal of three basic dyes by adsorption onto bentonite was investigated for single, binary, and ternary solutions in a batch system. Before and after dye adsorption, bentonite samples were analyzed by using X‐ray fluorescence spectrometer, SEM, and Fourier transform IR spectrometry. The D‐optimal design and response surface methodology were applied in designing the experiments for evaluating the interactive effects of each initial concentrations variable of the dyes in binary systems. Predicted values were found to be in good agreement with experimental values, which defined propriety of the model and the achievement of D‐optimal in optimization of adsorption of binary dye systems. The competitive adsorption results showed that the adsorption amount of a dye was suppressed in the presence and increasing concentrations of second or third dye. For mono‐component isotherm modeling, Langmuir and Freundlich models were applied to equilibrium data of single, binary, and ternary dye solutions, while modified Langmuir, Sheindrof–Rebhun–Sheintuch and modified extended Freundlich models were also applied to equilibrium data of binary dye solutions for multi‐component isotherm modeling. The results showed that the Langmuir was the more suitable model for single dye systems while extended Freundlich model fitted best to the experimental data with the lowest error values for multi‐dye systems.     

Effects of seismic isolation on the seismic response of a California high‐speed rail prototype bridge with soil‐structure and track‐structure interactions

With the launch of the high‐speed train project in California, the seismic risk is a crucial concern to the stakeholders. To investigate the seismic behavior of future California High‐Speed Rail (CHSR) bridge structures, a 3D nonlinear finite‐element model of a CHSR prototype bridge is developed. Soil‐structure and track‐structure interactions are accounted for in this comprehensive numerical model used to simulate the seismic response of the bridge and track system. This paper focuses on examining potential benefits and possible drawbacks of the a priori promising application of seismic isolation in CHSR bridges. Nonlinear time history analyses are performed for this prototype bridge subjected to two bidirectional horizontal historical earthquake ground motions each scaled to two different seismic hazard levels. The effect of seismic isolation on the seismic performance of the bridge is investigated through a detailed comparison of the seismic response of the bridge with and without seismic isolation. It is found that seismic isolation significantly reduces the deck acceleration and the force demand in the bridge substructure (i.e., piers and foundations), especially for high‐intensity earthquakes. However, seismic isolation increases the deck displacement (relative to the pile cap) and the stresses in the rails. These findings imply that seismic isolation can be promisingly applied to CHSR bridges with due consideration of balancing its beneficial and detrimental effects through using appropriate isolators design. The optimum seismic isolator properties can be sought by solving a performance‐based optimum seismic design problem using the nonlinear finite‐element model presented herein. Copyright © 2016 John Wiley & Sons, Ltd.     

The Effects of Different Substrates on Ammonium Removal in Constructed Wetlands: A Comparison of Their Physicochemical Characteristics and Ammonium‐Oxidizing Prokaryotic Communities

A vertical flow constructed wetland (VFCW) filled with natural zeolite had higher ammonium removal (82.4–94.0%) than another VFCW filled with volcanic rock (51.3–69.4%) treating piggery wastewater under any of three recirculation ratios. To reveal the underling reasons, physicochemical characteristics and ammonium‐oxidizing prokaryotes (AOPs) of two substrates were determined. The calculated maximum ammonium adsorption of zeolite (11.6 mg g^?1) was remarkably higher than that of volcanic rock (0.21 mg g^?1), mainly because the former contains two cationic binding crystalline species, and montmorillonite. Quantitative analyses indicated that ammonium‐oxidizing archaea (AOA) are the dominant AOP of zeolite and ammonium‐oxidizing bacteria (AOB) are the dominant AOP of volcanic rock respectively. Diversity and phylogenetic analysis further showed that both AOB and AOA communities were significantly different between two substrates. Nitrosospira‐like AOB (92.6%) and sediment/soil clade AOA (71.4%) were the main components of AOB and AOA in natural zeolite, whereas Nitrosomonas‐like AOB (76.1%) and water/sediment clade AOA (77.1%) dominated the AOB and AOA in volcanic rock. These results suggest that the substrates show high selectivity to AOP community. Thus, in addition to physicochemical characteristics, the AOP of substrates is very likely to affect ammonium removal in VFCWs.     

Effects of mid‐twenty‐first century climate and land cover change on the hydrology of the Puget Sound basin,Washington

The distributed hydrology–soil–vegetation model (DHSVM) was used to study the potential impacts of projected future land cover and climate change on the hydrology of the Puget Sound basin, Washington, in the mid‐twenty‐first century. A 60‐year climate model output, archived for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), was statistically downscaled and used as input to DHSVM. From the DHSVM output, we extracted multi‐decadal averages of seasonal streamflow, annual maximum flow, snow water equivalent (SWE), and evapotranspiration centred around 2030 and 2050. Future land cover was represented by a 2027 projection, which was extended to 2050, and DHSVM was run (with current climate) for these future land cover projections. In general, the climate change signal alone on sub‐basin streamflow was evidenced primarily through changes in the timing of winter and spring runoff, and slight increases in the annual runoff. Runoff changes in the uplands were attributable both to climate (increased winter precipitation, less snow) and land cover change (mostly reduced vegetation maturity). The most climatically sensitive parts of the uplands were in areas where the current winter precipitation is in the rain–snow transition zone. Changes in land cover were generally more important than climate change in the lowlands, where a substantial change to more urbanized land use and increased runoff was predicted. Both the annual total and seasonal distribution of freshwater flux to Puget Sound are more sensitive to climate change impacts than to land cover change, primarily because most of the runoff originates in the uplands. Both climate and land cover change slightly increase the annual freshwater flux to Puget Sound. Changes in the seasonal distribution of freshwater flux are mostly related to climate change, and consist of double‐digit increases in winter flows and decreases in summer and fall flows. Copyright © 2010 John Wiley & Sons, Ltd.     

Effects of infill walls and floor diaphragms on the dynamic characteristics of a narrow‐rectangle building

Most buildings in Singapore are lightly reinforced concrete structures, which are mainly designed for gravity loading only, because Singapore is an island country located in a low‐to‐moderate seismic region. The dynamic properties of a typical high‐rise residential building with a long, narrow rectangular floor plan are studied using both experimental and numerical methods. The effects of the brick infill walls and the flexible diaphragms on the dynamic characteristics of the building are discussed in detail. The results from the ambient vibration tests are correlated with the numerical results of three different finite element models with different levels of sophistication. They include a bare frame model, a frame model with brick infill walls, and a frame model with both brick infill walls and flexible diaphragms. The dynamic properties of the third model match very well with the measured results in terms of both the natural frequencies and the mode shapes. The correlation results demonstrate the respective effects of the brick infill walls and the flexible diaphragms on the dynamic characteristics of the narrow‐rectangle building structure. Copyright © 2006 John Wiley & Sons, Ltd.     

Effects of the geometry of two‐dimensional fractures on their hydraulic aperture and on the validity of the local cubic law

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.     

Hydrogeomorphic processes of thermokarst lakes with grounded‐ice and floating‐ice regimes on the Arctic coastal plain,Alaska

Thermokarst lakes cover > 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded ice) and deeper lakes maintaining perennial liquid water (floating ice). Thus, lake depth relative to maximum ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum ice thickness by analysing remotely sensed, water quality, and climatic data over a 35‐year period. Shoreline erosion rates due to permafrost degradation ranged from < 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P ? E_L) with periods of full and nearly dry basins. Shorter‐term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long‐term record for only shallow lakes. Our analysis suggests that grounded‐ice lakes are ice‐free on average 37 days longer than floating‐ice lakes resulting in a longer period of evaporative loss and more frequent negative P ? E_L. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum ice thickness in ACP lakes. Copyright © 2011 John Wiley & Sons, Ltd.     

Simulation of flow and solute coupled 2‐D problems with velocity‐dependent dispersion coefficient based on the network method

The governing equations of coupled density‐driven flow and solute transport problems in porous media, with velocity‐dependent dispersion coefficient, are strongly nonlinear and must be solved numerically. This contribution presents a network model, based on the network simulation method, capable of simulating the transient solution to this kind of problem efficiently and with a relatively low computational time. The mathematical model is formulated using the stream function and concentration variables. Simulation of the network model is carried out in the standard electric circuit simulation code, Pspice. The present model is first applied to simulate the original benchmark Henry problem, and the solution is compared with those obtained by other authors. A study of the grid size is also carried out. In addition, the modified version of Simpson and Clement of the Henry problem, as well as the groundwater flow in the closed desert basin of Pilot Valley, is studied using the proposed model. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental–numerical investigation on the seismic behaviour of moment‐resisting timber frames with densified veneer wood‐reinforced timber joints and expanded tube fasteners

This paper investigates the seismic behaviour of moment‐resisting timber frames with beam‐column joints fastened with expanded tubes and reinforced with densified veneer wood. Laboratory experiments are carried out on single joints to investigate the cyclic behaviour and, more specifically, the impairment of strength, the ductility ratio and the equivalent viscous damping ratio. A phenomenological numerical model is proposed, where the beams and columns are schematized using linear‐elastic beam elements, and the joints with non‐linear hysteretic spring calibrated on the results of the experimental tests. The model is used to analyse some representative moment‐transmitting structures characterised by different number of bays and storeys. After an estimation of the lateral load‐carrying capacity using a pushover analysis, the numerical model is used to estimate the behaviour factor. An incremental dynamic analysis is performed using a set of accelerograms spectrum consistent with a chosen design spectrum. The analyses lead to an estimation of the behaviour factor of 3 and 6 for a portal frame and a five‐storey, three‐bay frame, respectively, which confirms the highly dissipative behaviour of this kind of moment connection. Copyright © 2017 John Wiley & Sons, Ltd.     

Effects of forestry on summertime low flows and physical fish habitat in snowmelt‐dominant headwater catchments of the Pacific Northwest

Periods of summertime low flows are often critical for fish. This study quantified the impacts of forest clear‐cutting on summertime low flows and fish habitat and how they evolved through time in two snowmelt‐dominant headwater catchments in the southern interior of British Columbia, Canada. A paired‐catchment analysis was applied to July–September water yield, the number of days each year with flow less than 10% of mean annual discharge, and daily streamflow for each calendar day. The postharvest time series were divided into treatment periods of approximately 6–10 years, which were analysed independently to evaluate how the effects of forestry changed through time. An instream flow assessment using a physical habitat simulation‐style approach was used to relate streamflow to the availability of physical habitat for resident rainbow trout. About two decades after the onset of logging and as the extent of logging increased to approximately 50% of the catchments, reductions in daily summertime low flows became more significant for the July–September yield (43%) and for the analysis by calendar day (11–68%). Reductions in summertime low flows were most pronounced in the catchment with the longest postharvest time series. On the basis of the temporal patterns of response, we hypothesize that the delayed reductions in late‐summer flow represent the combined effects of a persistent advance in snowmelt timing in combination with at least a partial recovery of transpiration and interception loss from the regenerating forests. These results indicate that asymptotic hydrological recovery as time progresses following logging is not suitable for understanding the impacts of forest harvesting on summertime low flows. Additionally, these reductions in streamflow corresponded to persistent decreases in modelled fish habitat availability that typically ranged from 20% to 50% during the summer low‐flow period in one of the catchments, suggesting that forest harvest may have substantial delayed effects on rearing salmonids in headwater streams.     

Pseudodynamic tests on rubber base isolators with numerical substructuring of the superstructure and strain‐rate effect compensation

A pseudodynamic testing procedure has been applied by which the seismic response of a base‐isolated building is obtained by using as specimen the isolators, while the superstructure is numerically simulated. The procedure also takes advantage of the continuous pseudodynamic testing capabilities of the ELSA laboratory, which increase the accuracy of the results and reduce the strain‐rate effect of the rubber bearings. A simple proportional correction of the measured forces compensates the remaining strain‐rate effect due to the unrealistic speed of the test. The correction factor is obtained by means of a characterizing test on the specific rubber isolators. The developed method has been successfully applied to the prediction of the seismic response of a base‐isolated four‐storey building submitted to several specified accelerograms. The results for those earthquakes as well as the effects of some changes of the parameters of the system are discussed. Copyright © 2002 John Wiley & Sons, Ltd.