Solute transport and geochemical modeling of the coastal quaternary aquifer, Delta Dahab Basin, South Sinai, Egypt

The wadi dahab delta is in a dry, arid coastal zone within Egypt’s south Sinai Peninsula’s eastern portion. The primary water source is the Quaternary coastal alluvial aquifer. The groundwater salinity varies from 890to 8213 mg/L, with a mean value of 3417 mg/L. The dissolved major ions have been used to calculate the seawater mixing index(SWMI) using a linear equation that discriminates the groundwater mostly affected by water–rock interaction(SWMI 1>) and other samples mixed with Seawater(SWMI < 1). The isotopic composition of groundwater for specifically chosen groundwater samples ranges from-0.645‰ to +5.212‰ for δ^(18)O and from-9.582‰ to + 22.778‰ for δ^(2)H, where the seawater represented by a Red Sea water sample(δ^(18)O + 1.64‰-δ^(2)H + 9.80‰) and reject brine water are considerably enriched the isotopic groundwater values. The geochemical NETPATH model constrained by the dissolved significant ions, isotopes, and the rock aquifer forming minerals as phases indicate the mixing percent with the seawater ranges from 9% to 97% of seawater from 91% to 3% of original recharge water. According to the SEAWAT 3-D flow models, seawater has penetrated the Northeastern Dahab delta aquifer, with the intrusion zone extending1500 m inland. The salt dissolution, upwelling of saline water, recharge from the upstream mountain block, and seawater encroachment are the primary aspects contributing to the deterioration of groundwater quality. These findings may have significance for effective groundwater withdrawal management in arid locations worldwide with similar hydrogeological systems.

Modeling impact of culture facilities on hydrodynamics and solute transport in marine aquaculture waters of North Yellow Sea

An increasing number of marine aquaculture facilities have been placed in shallow bays and open sea,which might significantly affect hydrodynamic and solute transport processes in marine aquaculture waters.In this study,a coupled hydrodynamic and solute transport model was developed with high-resolution schemes in marine aquaculture waters based on depth-averaged shallow water equations.A new expression of drag force was incorporated into the momentum equations to express the resistance of suspended culture cages.The coupled model was used to simulate the effect of suspended structures on tidal currents and the movement of a contaminant cloud in the marine aquaculture of the North Yellow Sea,China.The simulation results showed a low-velocity area appearing inside the aquaculture cage area,with a maximum reduction rate of velocity close to 45%under high-density culture.The results also showed that tidal currents were sensitive to the density of suspended cages,the length of cages,and the drag coefficients of cages.The transport processes of pollutants inside aquaculture facilities were inhibited away from the vicinity of the culture cage area because of the diminished tidal currents.Therefore,the suspended cages significantly affected the transport processes of pollutants in the coastal aquaculture waters.Furthermore,the reduced horizontal velocity significantly decreased the food supply for the aquaculture areas from the surrounding sea.

Impact of normal stress-induced closure on laboratory-scale solute transport in a natural rock fracture

The impact of normal stress-induced closure on fluid flow and solute transport in a single rock fracture is demonstrated in this study.The fracture is created from a measured surface of a granite rock sample.The Bandis model is used to calculate the fracture closure due to normal stress,and the fluid flow is simulated by solving the Reynold equation.The Lagrangian particle tracking method is applied to modeling the advective transport in the fracture.The results show that the normal stress significantly affects fluid flow and solute transport in rock fractures.It causes fracture closure and creates asperity contact areas,which significantly reduces the effective hydraulic aperture and enhances flow channeling.Consequently,the reduced aperture and enhanced channeling affect travel time distributions.In particular,the enhanced channeling results in enhanced first arriving and tailing behaviors for solute transport.The fracture normal stiffness correlates linearly with the 5th and 95th percentiles of the normalized travel time.The finding from this study may help to better understand the stress-dependent solute transport processes in natural rock fractures.

Determination of groundwater solute transport parameters in finite element modelling using tracer injection and withdrawal testing data

The groundwater tracer injection and withdrawal tests are often carried out for the determination of aquifer solute transport parameters.However,the parameter analyses encounter a great difficulty due to the radial flow nature and the variability of the temporal boundary conditions.An adaptive methodology for the determination of groundwater solute transport parameters using tracer injection and withdrawal test data had been developed and illustrated through an actual case.The methodology includes the treatment of the tracer boundary condition at the tracer injection well,the normalization of tracer concentration,the groundwater solute transport finite element modelling and the method of least squares to optimize the parameters.An application of this methodology was carried out in a field test in the South of Hanoi city.The tested aquifer is Pleistocene aquifer,which is a main aquifer and has been providing domestic water supply to the city since the French time.Effective porosity of 0.31,longitudinal dispersivity of 2.2 m,and hydrodynamic dispersion coefficients from D=220 m^(2)/d right outside the pumping well screen to D=15.8 m^(2)/d right outside the tracer injection well screen have been obtained for the aquifer at the test site.The minimal sum of squares of the differences between the observed and model normalized tracer concentration is 0.00119,which is corresponding to the average absolute difference between observed and model normalized concentrations of 0.0355(while 1 is the worst and 0 is the best fit).

A multiscale 3D finite element analysis of fluid/solute transport in mechanically loaded bone

The transport of fluid, nutrients, and signaling molecules in the bone lacunar–canalicular system(LCS) is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching(FRAP) approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30–50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis(FEA)approach. An intact murine tibia was first re-constructed from micro CT images into a three-dimensional(3D)linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform(FEBio) to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex.Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces(shear and drag forces) for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.

A Discontinuous Galerkin Method for Blood Flow and Solute Transport in One-Dimensional Vessel Networks

This paper formulates an efficient numerical method for solving the convection diffusion solute transport equations coupled to blood flow equations in vessel networks.The reduced coupled model describes the variations of vessel cross-sectional area,radially averaged blood momentum and solute concentration in large vessel networks.For the discretization of the reduced transport equation,we combine an interior penalty discontinuous Galerkin method in space with a novel locally implicit time stepping scheme.The stability and the convergence are proved.Numerical results show the impact of the choice for the steady-state axial velocity profile on the numerical solutions in a fifty-five vessel network with physiological boundary data.

Hyper-gravity experiment of solute transport in fractured rock and evaluation method for long-term barrier performance

Hyper-gravity experiment enable the acceleration of the long-term transport of contaminants through fractured geological barriers.However,the hyper-gravity effect of the solute transport in fractures are not well understood.In this study,the sealed control apparatus and the 3D printed fracture models were used to carry out 1 g and N g hyper-gravity experiments.The results show that the breakthrough curves for the 1 g and N g experiments were almost the same.The differences in the flow velocity and the fitted hydrodynamic dispersion coefficient were 0.97–3.12%and 9.09–20.4%,indicating that the internal fractures of the 3D printed fracture models remained stable under hyper-gravity,and the differences in the flow and solute transport characteristics were acceptable.A method for evaluating the long-term barrier performance of low-permeability fractured rocks was proposed based on the hyper-gravity experiment.The solute transport processes in the 1 g prototype,1 g scaled model,and N g scaled model were simulated by the OpenGeoSys(OGS)software.The results show that the N g scaled model can reproduce the flow and solute transport processes in the 1 g prototype without considering the micro-scale heterogeneity if the Reynolds number(Re)
critical Reynolds number(Recr)and the Peclet number(Pe)
the critical Peclet number(Pecr).This insight is valuable for carrying out hyper-gravity experiments to evaluate the long-term barrier performance of low-permeability fractured porous rock.

Effect of nozzle type on fluid flow, solidification, and solute transport in mold with mold electromagnetic stirring

The mathematical model of coupling fluid flow,heat transfer,solidification,solute transport,and the electromagnetic field of the bloom in the upper part of the strand was established with three nozzle types.Then,the flow field,distribution of the temperature,solidification,and macrosegregation of carbon were investigated and compared by numerical modeling.In the case of the straight submerged entry nozzle(SEN),the molten steel flows down deep into the liquid pool,and the depth of the jet flow reaches about 1.0 m beneath the meniscus.The jetting zone is the high-temperature zone.In the case of two-port SEN and four-port SEN,the flow patterns and distribution of temperature in the central longitudinal section are similar.The jet flow impinges directly on the initially solidified shell and then it is divided into two longitudinal circulations.The heat of molten steel is dissipated along with the longitudinal circulations.The negative segregation band was generated near the bloom surface due to the washing effect by the rotating flow at the solidification front with three nozzle types.The negative segregation deteriorates gradually with the number of ports decreasing.

A graphics processing unit-based robust numerical model for solute transport driven by torrential flow condition

Solute transport simulations are important in water pollution events.This paper introduces a finite volume Godunovtype model for solving a 4×4 matrix form of the hyperbolic conservation laws consisting of 2D shallow water equations and transport equations.The model adopts the Harten-Lax-van Leer-contact(HLLC)-approximate Riemann solution to calculate the cell interface fluxes.It can deal well with the changes in the dry and wet interfaces in an actual complex terrain,and it has a strong shock-wave capturing ability.Using monotonic upstream-centred scheme for conservation laws(MUSCL)linear reconstruction with finite slope and the Runge-Kutta time integration method can achieve second-order accuracy.At the same time,the introduction of graphics processing unit(GPU)-accelerated computing technology greatly increases the computing speed.The model is validated against multiple benchmarks,and the results are in good agreement with analytical solutions and other published numerical predictions.The third test case uses the GPU and central processing unit(CPU)calculation models which take 3.865 s and 13.865 s,respectively,indicating that the GPU calculation model can increase the calculation speed by 3.6 times.In the fourth test case,comparing the numerical model calculated by GPU with the traditional numerical model calculated by CPU,the calculation efficiencies of the numerical model calculated by GPU under different resolution grids are 9.8–44.6 times higher than those by CPU.Therefore,it has better potential than previous models for large-scale simulation of solute transport in water pollution incidents.It can provide a reliable theoretical basis and strong data support in the rapid assessment and early warning of water pollution accidents.

A Well-Balanced and Non-Negative Numerical Scheme for Solving the Integrated Shallow Water and Solute Transport Equations

Based on the recent development in shallow flow modelling, this paperpresents a finite volume Godunov-type model for solving a 4×4 hyperbolic matrixsystem of conservation laws that comprise the shallow water and depth-averaged solute transport equations. The adopted governing equations are derived to preserveexactly the solution of lake at rest so that no special numerical technique is necessaryin order to construct a well-balanced scheme. The HLLC approximate Riemann solveris used to evaluate the interface fluxes. Second-order accuracy is achieved using theMUSCL slope limited linear reconstruction together with a Runge-Kutta time integration method. The model is validated against several benchmark tests and the resultsare in excellent agreement with analytical solutions or other published numerical predictions.

A Layer-IntegratedModel of Solute Transport in HeterogeneousMedia

This study presents a numerical solution to the three-dimensional solute transport in heterogeneous media by using a layer-integrated approach.Omitting vertical spatial variation of soil and hydraulic properties within each layer,a threedimensional solute transport can be simplified as a quasi-three-dimensional solute transport which couples a horizontal two-dimensional simulation and a vertical onedimensional computation.The finite analytic numericalmethod was used to discretize the derived two-dimensional governing equation.A quadratic function was used to approximate the vertical one-dimensional concentration distribution in the layer to ensure the continuity of concentration and flux at the interface between the adjacent layers.By integration over each layer,a set of system of equations can be generated for a single column of vertical cells and solved numerically to give the vertical solute concentration profile.The solute concentration field was then obtained by solving all columns of vertical cells to achieve convergence with the iterative solution procedure.The proposed model was verified through examples from the published literatures including four verifications in terms of analytical and experimental cases.Comparison of simulation results indicates that the proposed model satisfies the solute concentration profiles obtained from experiments in time and space.

Comparison of the performance of traditional advection-dispersion equation and mobile-immobile model for simulating solute transport in heterogeneous soils

The traditional advection-dispersion equation(ADE) and the mobile-immobile model(MIM) are widely used to describe solute transport in heterogeneous porous media. However, the fitness of the two models is casedependent. In this paper, the transport of conservative,adsorbing and degradable solutes through a 1 m heterogeneous soil column under steady flow condition was simulated by ADE and MIM, and sensitivity analysis was conducted. Results show that MIM tends to prolong the breakthrough process and decrease peak concentration for all three solutes, and tailing and skewness are more pronounced with increasing dispersivity. Breakthrough curves of the adsorbing solute simulated by MIM are less sensitive to the retardation factor compared with the results simulated by ADE. The breakthrough curves of degradable solute obtained by MIM and ADE nearly overlap with a high degradation rate coefficient, indicating that MIM and ADE perform similarly for simulating degradable solute transport when biochemical degradation prevails over the mass exchange between mobile and immobile zones. The results suggest that the physical significance of dispersivity should be carefully considered when MIM is applied to simulate the degradable solute transport and/or ADE is applied to simulate the adsorbing solute transport in highly dispersive soils.

ZTE Unveils Next Generation iCTN Transport Network Solution and Flagship Product ZXONE 5800 at MWC Barcelona 2009

ZTE Corporation (ZTE),a leading global provider of telecommunications equipment and network solutions,shined at the Mobile World Congress (MWC) 2009 by rolling out its next generation intelligent Converged

Evolution of Optical Transport Networks and Their Solution in 3G Networks

As new generation mobile networks, 3G networks focus on data services and integrate voice, data and multimedia services. However, traditional Optical Transport Networks (OTNs) cannot meet the requirements of 3G networks anymore, because of their complicated configuration, low bandwidth efficiency, high cost, and bad network and service scalability. The emerging of Multi-Service Transport Platform (MSTP), Wavelength Division Multiplexing (WDM), and Automatically Switched Optical Network (ASON) technologies for optical fiber communications makes up for these weaknesses. The leading solution to 3G access transport networks is the MSTP technology based on Synchronous Digital Hierarchy (SDH), while that to 3G core transport network is ASON+WDM.

Analysis of Anisotropic Nonlocal Diffusion Models:Well-Posedness of Fractional Problems for Anomalous Transport

We analyze the well-posedness of an anisotropic,nonlocal diffusion equation.Establishing an equivalence between weighted and unweighted anisotropic nonlocal diffusion operators in the vein of unified nonlocal vector calculus,we apply our analysis to a class of fractional-order operators and present rigorous estimates for the solution of the corresponding anisotropic anomalous diffusion equation.Furthermore,we extend our analysis to the anisotropic diffusion-advection equation and prove well-posedness for fractional orders s∈[0.5,1).We also present an application of the advection-diffusion equation to anomalous transport of solutes.

An update on placental drug transport and its relevance to fetal drug exposure

Pregnant women are often complicated with diseases that require treatment with medication.Most drugs administered to pregnant women are off-label without the necessary dose,efficacy,and safety information.Knowledge concerning drug transfer across the placental barrier is essential for understanding fetal drug exposure and hence drug safety and efficacy to the fetus.Transporters expressed in the placenta,including adenosine triphosphate(ATP)-binding cassette efflux transporters and solute carrier uptake transporters,play important roles in determining drug transfer across the placental barrier,leading to fetal exposure to the drugs.In this review,we provide an update on placental drug transport,including in vitro cell/tissue,ex vivo human placenta perfusion,and in vivo animal studies that can be used to determine the expression and function of drug transporters in the placenta as well as placental drug transfer and fetal drug exposure.We also describe how the knowledge of placental drug transfer through passive diffusion or active transport can be combined with physiologically based pharmacokinetic modeling and simulation to predict systemic fetal drug exposure.Finally,we highlight knowledge gaps in studying placental drug transport and predicting fetal drug exposure and discuss future research directions to fill these gaps.

Co-doping method used to improve the charge transport balance in solution processed OLEDs

In this paper, co-doping method is used to improve the current efficiency of solution-processed organic light-emitting diodes(OLEDs). By changing the ratio of two thermally activated delayed fluorescent(TADF) emitters, we studied the performance of device and its mechanism. A solution processed OLED with a structure of indium tin oxide(ITO, 150 nm)/PEDOT:PSS(30 nm)/CBP:4 Cz IPN-x%:4 Cz PN-y%(30 nm)/TPBi(40 nm)/Li F(1 nm)/Al(100 nm) was fabricated. The current efficiencies of 26.6 cd/A and 26.4 cd/A were achieved by the devices with dopant ratio of 6% 4 Cz IPN:2% 4 Cz PN and 2% 4 Cz IPN:6% 4 Cz PN in emitting material layer(EML), respectively. By investigating the tendency of current density change in devices with different doping ratio, we suggested that the enhancement of the current efficiency should be due to the charge transport balance improvement induced by assist dopant in EML.

SOLUTION TO A PARAMETRIC EQUATION IN TRANSPORT THEORY

In 1976, Ronen et al. raised the question of how to solve the new integrodifferential parameter equation with transport theory. So far there have only been some approximate calculations and numerical analyses about this question. Using functional analysis, this note discusses this question in a strict mathematical way, gives the parameter distribution in L^p space (1≤p≤+∞) with which the