Method and apparatus for destroying organic compounds in fluid

An apparatus for the photocatalytic oxidation of organic contaminants in fluid includes a reactor and a photocatalyst affixed to support material. Preferably, the outer wall of the reactor is constructed of material transmissive of ultraviolet radiation. The support material preferably is transmissive of ultraviolet radiation. The support material can also be an adsorbent material. Also, a method for photocatalytic oxidation of organic contaminants in fluid. Also, a method for preparation of a supported photocatalyst. Also, a supported photocatalyst adapted for the photocatalytic oxidation of organic contaminants in fluid. Also, a method for preparing a photocatalyst adapted for the photocatalytic oxidation of organic contaminants in fluid.https://digitalcommons.mtu.edu/patents/1071/thumbnail.jp

Regeneration of adsorbents using advanced oxidation

The present invention is a method of purifying fluid having organic material. The method comprises two operational steps. The first step includes passing the fluid through an adsorbent such that the organic material is substantially adsorbed by the adsorbent and the fluid is substantially purified. The second step includes destroying the adsorbed organic material on the adsorbent and regenerating the adsorbent in a form substantially free of adsorbed organic material.https://digitalcommons.mtu.edu/patents/1115/thumbnail.jp

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In this paper we generalize previous work in which the fixed points of dynamical systems were used to construct obstacle-avoiding, goalattracting trajectories for robots to more complex attractors such as limit cycles in the form of closed planar curves. Following the development of a formalism for dealing with a mechanical system, some of whose coordinates are constrained to follow the trajectories of a set of coupled differential equations, we discuss how to construct, analyze, and solve a planar dynamical system whose limit set is one or more user-specified closed curves or limit cycles. This work finds its relevance in a wide range of applications. Our focus has mainly been on planning tool trajectories for industrial robot manipulators with applications such as welding and painting. However, the generalization from fixed points to limit cycles is also applicable when controlling automatic guided vehicles. KEY WORDS—trajectory planning constraint mechanics, dynamical systems, limit cycles 1

A Dynamical system for action potentials in the giant axon of the squid

We introduce a novel quantitative approach to describe ionic gating and use the Kramers equation for electrodiffusion of ions through membrane channels to construct a simple dynamical system for transient action potentials and resting potentials in giant axons of the squid on a better physicochemical basis than the Hodgkin−Huxley (HH) model and the Goldman−Hodgkin−Katz (GHK) model. Like the HH dynamical system, our present model describes many features of excitable membranes such as sharp firing thresholds, latency, refractory periods, repetitive firings with a sustained stimulating current, excitation blocking, and propagating action potentials. It differs from the HH dynamical system in having three fixed points, the first of which corresponds to the electrodiffusive resting potential. The second fixed (or saddle) point corresponds to the threshold for generation of local action potentials. It predicts monotonic rather than oscillatory decay of the membrane potential following subthreshold stimulation by microelectrodes. The ratio of sodium to potassium currents in the resting state of the membrane is set at 3:2. In the electrodiffusive “resting” state, all potassium and sodium activation gates are postulated to be closed, whereas, according to the HH model, about 32% of the potassium gates and 5.3% of the sodium activation gates are open. As our electrodiffusive “resting” state, described by a generalization of the GHK model, emerges as the stable fixed point of our dynamical system, our new model provides a unified treatment of both transient action potentials and electrodiffusive “resting” potentials in perfused axons.12 page(s

On the nature of liquid junction and membrane potentials

Whenever a spatially inhomogeneous electrolyte, composed of ions with different mobilities, is allowed to diffuse, charge separation and an electric potential difference is created. Such potential differences across very thin membranes (e.g. biomembranes) are often interpreted using the steady state Goldman equation, which is usually derived by assuming a spatially constant electric field. Through the fundamental Poisson equation of electrostatics, this implies the absence of free charge density that must provide the source of any such field. A similarly paradoxical situation is encountered for thick membranes (e.g. in ion-selective electrodes) for which the diffusion potential is normally interpreted using the Henderson equation. Standard derivations of the Henderson equation appeal to local electroneutrality, which is also incompatible with sources of electric fields, as these require separated charges. We analyse self-consistent solutions of the Nernst–Planck–Poisson equations for a 1 : 1-univalent electrolyte to show that the Goldman and Henderson steady-state membrane potentials are artefacts of extraneous charges created in the reservoirs of electrolyte solution on either side of the membrane, due to the unphysical nature of the usual (Dirichlet) boundary conditions assumed to apply at the membrane–electrolyte interfaces. We also show, with the aid of numerical simulations, that a transient electric potential difference develops in any confined, but initially non-uniform, electrolyte solution. This potential difference ultimately decays to zero in the real steady state of the electrolyte, which corresponds to thermodynamic equilibrium. We explain the surprising fact that such transient potential differences are well described by the Henderson equation by using a computer algebra system to extend previous steady-state singular perturbation theories to the time-dependent case. Our work therefore accounts for the success of the Henderson equation in analysing experimental liquidjunction potentials.14 page(s

Efficient Algorithms for Simulating Complex Mechanical Systems Using Constraint Dynamics

The constrained Lagrangian and constrained Hamiltonian equations of motion for a general nonrelativistic classical mechanical system subject to rheonomous holonomic constraints are derived in an easy and straightforward manner. The numerical integration of the constrained equations of motion are discussed. It is shown how constraint errors introduced by the numerical integration can be avoided by introducing simple constraint correction schemes. As an example, the developed constrained methods are applied to the periodically driven inverted n-linked pendulum. It is demonstrated how the constrained methods leads to very efficient numerical algorithms. In the case of the n-linked pendulum the computational complexity using the constrained methods is O(n) compared to O(n³) using the conventional unconstrained approach

Pendula as Constrained Dynamical Systems

Two algorithms for deriving the constrained Lagrangian and Hamiltonian equations of motion are presented. They are used to derive the constrained equations of motion for various pendulum systems in an easy and straightforward manner. The advantages of the algorithms are discussed. Computer experiments are performed by solving numerically the constrained equations of motion

Fixed-Bed Photocatalysts for Solar Decontamination of Water

A solar decontamination process for water was developed using TiO2 photocatalysts supported on silica-based material. The supported catalysts were systematically optimized with respect to catalyst type, catalyst dosage, silica-based support material, particle size, catalyst/support bonding, and calcination temperature. The optimized supported catalysts outperformed an optimized slurry catalyst under identical operational conditions and had a reaction rate four times that of the slurry catalyst. Trichloroethylene (TCE) as a model compound was also used to investigate the impact of solar irradiance, influent concentration, pH value, and hydraulic loading. Supported photocatalysts displayed high light efficiencies over a wide range of weather conditions, an apparent quantum yield of 40% was obtained in a rainy late-afternoon experiment. The complete mineralization of TCE was achieved, and in addition, background natural organic matter (BNOM) in a local surface water did not interfere with the degradation significantly. © 1994, American Chemical Society. All rights reserved

Photocatalytic oxidation of chlorinated hydrocarbons in water

The impact of surface modification on the photocatalytic activity of two different commercial TiO2 catalysts is studied using different impregnation methods with platinum, silver and iron oxide. The Degussa P-25 TiO2 as received is more active than Aldrich TiO2, but the photocatalytic activity of Aldrich TiO2 can be greatly increased by surface modification with platinum or silver. No improvement in the photocatalytic activity has been observed for the Degussa P-25 TiO2 impregnated with platinum. The most active photocatalyst for the trichloroethylene (TCE) destruction is Aldrich TiO2 loaded with 1.0 wt% platinum using a photoreduction method. Similar destruction efficiency was obtained for the destruction of para-Dichlorobenzene (p-DCB) using platinized Aldrich TiO2 as catalyst. A kinetic model developed in this study can quantitatively describe the effect of light intensity and catalyst dosage on the photocatalytic oxidation of TCE. The reaction rate is proportional to the half-order of incident light intensity for the light intensity within the range studied (83.2-743.3 mW/L). The optimum catalyst dosage increases as the incident light intensity increases