Alternative Forms of Enhanced Boussinesq Equations with Improved Nonlinearity

We propose alternative forms of the Boussinesq equations which extend the equations of Madsen and Schäffer by introducing extra nonlinear terms during enhancement. Theoretical analysis shows that nonlinear characteristics are considerably improved. A numerical implementation of one-dimensional equations is described. Three tests involving strongly nonlinear evolution, namely, regular waves propagating over an elevated bar feature in a tank with an otherwise constant depth, wave group transformation over constant water depth, and nonlinear shoaling of unsteady waves over a sloping beach, are simulated by the model. The model is found to be effective

Study of Histopathological and Molecular Changes of Rat Kidney under Simulated Weightlessness and Resistance Training Protective Effect

To explore the effects of long-term weightlessness on the renal tissue, we used the two months tail suspension model to simulate microgravity and investigated the simulated microgravity on the renal morphological damages and related molecular mechanisms. The microscopic examination of tissue structure and ultrastructure was carried out for histopathological changes of renal tissue morphology. The immunohistochemistry, real-time PCR and Western blot were performed to explore the molecular mechanisms associated the observations. Hematoxylin and eosin (HE) staining showed severe pathological kidney lesions including glomerular atrophy, degeneration and necrosis of renal tubular epithelial cells in two months tail-suspended rats. Ultrastructural studies of the renal tubular epithelial cells demonstrated that basal laminas of renal tubules were rough and incrassate with mitochondria swelling and vacuolation. Cell apoptosis in kidney monitored by the expression of Bax/Bcl-2 and caspase-3 accompanied these pathological damages caused by long-term microgravity. Analysis of the HSP70 protein expression illustrated that overexpression of HSP70 might play a crucial role in inducing those pathological damages. Glucose regulated protein 78 (GRP78), one of the endoplasmic reticulum (ER) chaperones, was up-regulated significantly in the kidney of tail suspension rat, which implied that ER-stress was associated with apoptosis. Furthermore, CHOP and caspase-12 pathways were activated in ER-stress induced apoptosis. Resistance training not only reduced kidney cell apoptosis and expression of HSP70 protein, it also can attenuate the kidney impairment imposed by weightlessness. The appropriate optimization might be needed for the long term application for space exploration

Estimate of Leaf Area Index in an Old-Growth Mixed Broadleaved-Korean Pine Forest in Northeastern China

Leaf area index (LAI) is an important variable in the study of forest ecosystem processes, but very few studies are designed to monitor LAI and the seasonal variability in a mixed forest using non-destructive sampling. In this study, first, true LAI from May 1st and November 15th was estimated by making several calibrations to LAI as measured from the WinSCANOPY 2006 Plant Canopy Analyzer. These calibrations include a foliage element (shoot, that is considered to be a collection of needles) clumping index measured directly from the optical instrument, TRAC (Tracing Radiation and Architecture of Canopies); a needle-to-shoot area ratio obtained from shoot samples; and a woody-to-total area ratio. Second, by periodically combining true LAI (May 1st) with the seasonality of LAI for deciduous and coniferous species throughout the leaf-expansion season (from May to August), we estimated LAI of each investigation period in the leaf-expansion season. Third, by combining true LAI (November 15th) with litter trap data (both deciduous and coniferous species), we estimated LAI of each investigation period during the leaf-fall season (from September to mid-November). Finally, LAI for the entire canopy then was derived from the initial leaf expansion to the leaf fall. The results showed that LAI reached its peak with a value of 6.53 m2 m−2 (a corresponding value of 3.83 m2 m−2 from optical instrument) in early August, and the mean LAI was 4.97 m2 m−2 from May to November using the proposed method. The optical instrument method underestimated LAI by an average of 41.64% (SD = 6.54) throughout the whole study period compared to that estimated by the proposed method. The result of the present work implied that our method would be suitable for measuring LAI, for detecting the seasonality of LAI in a mixed forest, and for measuring LAI seasonality for each species

Event-driven spiking neural network simulator based on FPGA

Recently, researchers have shown an increased interest in more biologically realistic neural networks. Spiking Neural Network (SNN) is one of the most widely used methodologies of mimic neural networks. It has been extensively used for Brain-Machine Interface (BMI), dynamic vision detection (DVS), image pattern recognition. From a biophysical point of view, neuron behaviors (action potentials) result from currents that pass through ion channels in the cell membrane. It is possible to simulate such a mimic network on circuit design by modeling the stimulus-voltage relationship. Compared with previous neuron networks, SNN can model a dynamical network in continuous real-time, significantly reducing its power consumption with the event-driven nature. In addition, more researchers participate in exploring the learning methodologies for SNN. As an unsupervised learning fashion, Spike Timing Dependent Plasticity (STDP) has achieved more than 94% accuracy on handwriting digits (MNIST dataset). Furthermore, researchers have migrated some excellent algorithms designed for conventional ANN, CNN to fit in the SNN environment and achieved higher accuracy, close to 99% in a supervised fashion. It has been solidly proved that SNN has the potential to catch up with other artificial neural networks. Keywords: Spiking Neuron Network, Machine Learning, Pattern Recognition, FPGA, Event-driven.Master of Science (Electronics

Eulerian Description of Wave-Induced Stokes Drift Effect on Tracer Transport

The wave-induced Stokes drift plays a significant role on mass/tracer transport in the ocean and the evolution of coastal morphology. The tracer advection diffusion equation needs to be modified for Eulerian ocean models to properly account for the surface wave effects. The Eulerian description of Stokes drift effect on the tracer transport is derived in this study to show that this effect can be accounted for automatically in the wave-averaged advection-diffusion equation. The advection term in this equation is the wave-averaged concentration flux produced by the interaction between fluctuations of linear wave orbital velocity and tracer concentration, and the advection velocity is the same as the Stokes drift velocity. Thus, the effective dispersion of tracers by surface gravity waves is calculated due to the Stokes drift effect and the corresponding dispersion coefficient in the depth-integrated equation is then derived. The Eulerian description of Stokes drift effect of tracer concentration is illustrated by the direct numerical simulation of the advection–diffusion equation under simple linear waves. The equivalence between both the Eulerian and Lagrangian descriptions is also verified by particle tracking method. The theoretical analysis is found to agree well with the wave-induced dye drift velocity observed outside the surf zone in a longshore current experiment

A Computation Model for Coast Wave Motions with Multiple Breakings

This paper presents a computational model for coast wave motions with multiple wave breakings. In the Boussinesq model, the wave breaking judgment method is combined with the wave recovery judgment condition, which stops the wave breaking process when triggered. The energy dissipation of wave breaking is corrected, and the dissipation of wave energy is maintained at about 10% during the wave recovery stage, so that the dissipation caused by the residual turbulent motion of wave breaking and the increase in wave height caused by the shallowing of waves due to the water bottom slope are offset. By comparing the calculation results with the experimental results, it is proved that this model can be used to calculate multiple wave breakings. This model is applied to discuss the influence of wave incident angle and wave period on wave height and longshore current and gives the distribution characteristics of wave height and longshore current under multiple wave breakings

A Set of Accurate Dispersive Nonlinear Wave Equations

In this study, a set of accurate dispersive nonlinear wave equations is established, using the wave velocity and free surface elevation as variables. These equations improve upon previous equations in which the velocity potential is used as a variable by considering the rotational wave motion and by adding a second-order bottom slope term that applies to general situations, allowing the equations to consider the influence of rapidly changing, horizontal, two-dimensional bottom topographies. The problem of the inaccuracy of the integral calculations used in previous equations in nearshore areas is solved by approximating the integral calculations into differential calculations, and a set of coupled wave equations is established by keeping the free surface elevation and the horizontal velocity constant, thus allowing the calculation of nearshore wave-generated currents. The benefits of the current model are confirmed through comparisons with corresponding laboratory experimental findings and are illustrated through a comparison with the numerical outcomes of other pertinent models

Longshore Current Profiles and Instabilities on Plane Beaches with Mild Slopes

The accurate determination of cross-shore longshore current profiles in the surf zone is essentially important in understanding of coastal physical processes and modelling of longshore sediment transport. In this study, a comprehensive laboratory study was undertaken to directly measure longshore current profiles over plane beaches with two mild slopes, 1:40 and 1:100, in a wave basin 55 m long, 34 m wide, and 0.7 m deep. Different wave conditions with an incidence angle of 30° were generated by piston-type wave makers consisting of 70 individual paddles, and two arrays of 29 Acoustic Doppler Velocimeters (ADVs) were used to measure longshore currents in the surf zone. Based on the experimental data collected in this study, three types of cross-shore longshore current profiles were found on the two plane beaches under different testing wave conditions, namely quasi-Rayleigh, quasi-Gaussian, and M-shape profiles. The quasi-Rayleigh profile was found on the beach slope of 1:40, and the other two types were found on the beach slope of 1:100. Analytical formulae were proposed to describe these profiles and agreed well with the laboratory data. The fluctuations of longshore currents observed in this study were attributed to their shear instabilities based on linear instability analysis. The results of the linear instability analysis and the spectra of measured velocities also showed that the three types of velocity profiles led to different instability characteristics

Vertical Distribution of Rip Currents Generated by Intersecting Waves in a Sandbar–Groin Systems

To analyze the impacts of groins, sandbars, and channels on the three-dimensional features of rip currents, we conducted experimental investigations on the vertical distribution of rip currents under intersecting waves along barred beaches with channels. This study employed ADV flow velocity measurements at two distinct locations: within channel and on a sandbar. The results indicate that in nodal sections within channel and on a sandbar, the rip head region manifests surface flow characteristics, characterized by high velocities near water surface. In a rip neck location, the vertical distribution of rip currents on a sandbar exhibits greater variability, whereas within channel, the distribution is more homogeneous. The vertical distribution of rip currents in nodal sections within channel aligns with the logarithmic distribution law. The vertical distributions of the alongshore velocity of rip currents display a consistent pattern of higher at the top and lower at the bottom. However, this pattern varies slightly depending on the wave period. The presence of groins influences the fluctuation characteristics of the alongshore velocity of rip currents by regulating the nearshore circulation system. This results in the alongshore velocity of rip currents in channel pointing towards the groin. In contrast, the alongshore velocity of rip currents on sandbar, situated farther away from groin, exerts a weaker effect on the alongshore velocity of a rip current

Azo dye wastewater treatment in a novel three-dimensional electrode reactor

A novel three-dimensional electrode reactor (3DER) was designed to treat the dye wastewater. The performance of 3DER was evaluated via methyl orange (MO) removal efficiency. For comparison, the performance of the two-dimensional electrode reactor (2DER) was also assessed. Furthermore, the effects of electrolyte and aeration on treatment performance were preliminarily evaluated to further optimize the operation on 3DER. A repeatable and stable MO treatment efficiency was obtained in the 3DER. The MO removal rate reached 79.5% at the applied voltage of 1.0 V, electrode spacing of 2 cm and initial MO concentration of 60 mg/dm3, significantly higher than that in the 2DER (58.8%), suggesting the obvious improvement of particle electrodes on MO removal. Both adding electrolyte and air sparging into the 3DER contributed to the enhancement of the MO removal rate. These results obtained here suggest that the 3DER may provide an effective alternative for the treatment of azo dye wastewater and/or non-biodegradable industrial wastewaters