A Mathematical Model for Predicting Rotating Belt Filter Performance

Increased demand on wastewater treatment plants has motivated the development of new primary wastewater treatment techniques. Rotating belt filters (RBF) offer a spatially compact and lower cost solution. The goal of the present work is to develop a model that accurately predicts the flow rate capacity and removal efficiency of a generic RBF. Mesh resistance will be characterized using an idealized computational fluid dynamics (CFD) model of the mesh filter used in an RBF. To characterize the cake resistance, a gravity drainage column test was modeled and using the results from the CFD model, the cake resistance versus filtered volume was found. Removal efficiencies were calculated from sieve test data which characterized the effluent concentration of total suspended solids (TSS) for a given filtered volume. The RBF model is extended to include TSS scaling, a PID controller, and parameter optimization to accurately predict steady state and dynamic RBF pilot performance

A Numerical Approach for Determining the Resistance of Fine Mesh Filters

Characterizing the resistance of mesh filters, in terms of the pressure drop as a function of flow velocity, is an important part of modeling any filtration process. Most commonly, filters are characterized experimentally, which can be costly and time consuming. This motivates the need for a generalized numerical approach for characterizing the resistance of mesh filters based on the flow through a representative segment of the filter. There is uncertainty, however, in the correct specification of boundary conditions such that the numerical results for flow through the small segment match the overall behaviour of the filter. In this work, an experimentally validated numerical approach is developed by examining the velocity and turbulence intensity experienced across the filter. It has been shown that the flow resistance results are not sensitive to the turbulence intensity, but depend greatly on the imposed flow velocity. Specifying the peak velocity as the boundary condition in the filter simulations resulted in a good match with experiments, while using the bulk velocity was not able to reproduce the experimental results.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Human Visual Field and Navigational Strategies

In this study we use a particular virtual reality environment to investigate spatial navigation in human adults in two viewing conditions. In the first, participants could simultaneously see both landmarks of the virtual environment which inform about the location of the goal (simultaneous vision). In the second, participants could see only one landmark at a time (sequential vision). Basically, conditions differed with regard to the amplitude of the visual fields, which might influence the strategy adopted by the participant to navigate in the virtual space and locate the goal. When people have visual access to both landmarks, they can use all relevant information to navigate. However, when people see only one landmark at a time, they need to integrate the partial viewings of the environment in order to reconstruct the visual space. Consequently, simultaneous and sequential vision tasks involve different cognitive demands..

Computational Modelling of Resin Infiltration and Curing in High Pressure Resin Transfer Molding

Increased pressure on automotive manufactures to reduce overall greenhouse gas emissions from their vehicles has driven research into replacing conventional steel components with carbon fiber reinforced plastics (CFRP). This is due to their high weight specific properties and design freedom. High pressure resin transfer molding (HP-RTM), a derivative of resin transfer molding, is a manufacturing process for CFRP’s that offers high automation potential and low cycle times; critical properties of a manufacturing process for the automotive sector. The goal of the present work is to increase the accuracy and reduce the computational overhead of current RTM infiltration and curing models. These models allow for the reduction in development and testing costs, as they provide critical insight into the flow characteristics and cure development during said stages. First, a geometry dependent orientation calculator for the permeability tensor is proposed to quickly and accurately orient the fiber direction solely using the mold geometry and mesh required by the infiltration solver. The proposed calculator is verified against an 1D analytical solution of Darcy’s law and then validated against fiber orientation data generated from a constitutive draping simulation. Secondly, a local thermal non-equilibrium (LTNE) energy model is proposed. Due to the addition complexity and computational overhead, a non-dimensional analysis is performed to determine the appropriate operating conditions where the added accuracy of the LTNE model is required. Finally, the advancements in energy modelling approaches are highlight. A study is run on a complex, floor geometry where the three main energy modelling approaches are compared (i.e., isothermal, equilibrium, and LTNE). The results showcase the variability in the predicted cure degree development throughout both the infiltration and curing stage, depending on the energy model used. This highlights the importance of accurately capturing the temperature development, as it can lead to significant variations in the cure degree and cure degree rate development. To further reduce the computational cost an adaptive time step formulation, dependent on the maximum cure rate and minimum cure degree, is proposed. This formulation is shown to reduce the overall computational time of the curing simulation by up to 10 times

Amber fossils demonstrate deep-time stability of Caribbean lizard communities

Whether the structure of ecological communities can exhibit stability over macroevolutionary timescales has long been debated. The similarity of independently evolved Anolis lizard communities on environmentally similar Greater Antillean islands supports the notion that community evolution is deterministic. However, a dearth of Caribbean Anolis fossils—only three have been described to date—has precluded direct investigation of the stability of anole communities through time. Here we report on an additional 17 fossil anoles in Dominican amber dating to 15–20 My before the present. Using data collected primarily by X-ray microcomputed tomography (X-ray micro-CT), we demonstrate that the main elements of Hispaniolan anole ecomorphological diversity were in place in the Miocene. Phylogenetic analysis yields results consistent with the hypothesis that the ecomorphs that evolved in the Miocene are members of the same ecomorph clades extant today. The primary axes of ecomorphological diversity in the Hispaniolan anole fauna appear to have changed little between the Miocene and the present, providing evidence for the stability of ecological communities over macroevolutionary timescales

A wildland fire model with data assimilation

A wildfire model is formulated based on balance equations for energy and fuel, where the fuel loss due to combustion corresponds to the fuel reaction rate. The resulting coupled partial differential equations have coefficients that can be approximated from prior measurements of wildfires. An ensemble Kalman filter technique with regularization is then used to assimilate temperatures measured at selected points into running wildfire simulations. The assimilation technique is able to modify the simulations to track the measurements correctly even if the simulations were started with an erroneous ignition location that is quite far away from the correct one.Comment: 35 pages, 12 figures; minor revision January 2008. Original version available from http://www-math.cudenver.edu/ccm/report

The hypoxia imaging agent Cu ii(atsm) is neuroprotective and improves motor and cognitive functions in multiple animal models of Parkinson's disease

Parkinson's disease (PD) is a progressive, chronic disease characterized by dyskinesia, rigidity, instability, and tremors. The disease is defined by the presence of Lewy bodies, which primarily consist of aggregated α-synuclein protein, and is accompanied by the loss of monoaminergic neurons. Current therapeutic strategies only give symptomatic relief of motor impairment and do not address the underlying neurodegeneration. Hence, we have identified Cu II(atsm) as a potential therapeutic for PD. Drug administration to four different animal models of PD resulted in improved motor and cognition function, rescued nigral cell loss, and improved dopamine metabolism. In vitro, this compound is able to inhibit the effects of peroxynitrite-driven toxicity, including the formation of nitrated α-synuclein oligomers. Our results show that Cu II(atsm) is effective in reversing parkinsonian defects in animal models and has the potential to be a successful treatment of PD

Single-molecule imaging of DNA gyrase activity in living Escherichia coli

Bacterial DNA gyrase introduces negative supercoils into chromosomal DNA and relaxes positive supercoils introduced by replication and transiently by transcription. Removal of these positive supercoils is essential for replication fork progression and for the overall unlinking of the two duplex DNA strands, as well as for ongoing transcription. To address how gyrase copes with these topological challenges, we used high-speed single-molecule fluorescence imaging in live Escherichia coli cells. We demonstrate that at least 300 gyrase molecules are stably bound to the chromosome at any time, with ~12 enzymes enriched near each replication fork. Trapping of reaction intermediates with ciprofloxacin revealed complexes undergoing catalysis. Dwell times of ~2 s were observed for the dispersed gyrase molecules, which we propose maintain steady-state levels of negative supercoiling of the chromosome. In contrast, the dwell time of replisome-proximal molecules was ~8 s, consistent with these catalyzing processive positive supercoil relaxation in front of the progressing replisome