1,067 research outputs found

    Effects of Changes in Surface Water Regime and/or Land Use on the Vertical Distribution of Water Available for Wetland Vegetation: Dynamic Model of the Zone of Aeration (Part 1 of Completion Report for Project A-023-ARK)

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    A mathematical model by Green, simulating one-dimensional vertical ground-water movement in unsaturated soils of the prairie region of Kansas, has been adapted for use in a wetlands environment typified by the wetlands forest of Eastern Arkansas. The model consists of two second-order, non-linear, partial differential equations and an algorithm for their numerical solution. The original model was extended to include functions for seasonal changes in transpiration and for drainage of excess precipitation. Before the addition of the two functions, the model reliability was limited to one growth season

    Forecasting and Conditional Projection Using Realistic Prior Distributions

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    This paper develops a forecasting procedure based on a Bayesian method for estimating vector autoregressions. The procedure is applied to ten macroeconomic variables and is shown to improve out-of-sample forecasts relative to univariate equations. Although cross-variables responses are damped by the prior, considerable interaction among the variables is shown to be captured by the estimates.We provide unconditional forecasts as of 1982:12 and 1983:3.We also describe how a model such as this can be used to make conditional projections and to analyze policy alternatives. As an example, we analyze a Congressional Budget Office forecast made in 1982:12.While no automatic causal interpretations arise from models like ours, they provide a detailed characterization of the dynamic statistical interdependence of a set of economic variables, which may help inevaluating causal hypotheses, without containing any such hypotheses themselves.

    Simulation Video Electric Single Particle Aerodynamic Relaxation Time Analyzers

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    The simulation of physical parameters provides a virtual environment for the design and optimization of instrumentation. applying physical laws and theorems to natural phenomena defines the behavior of analytical processes. Simulation provides means for the adjustment of specific operating parameters while maintaining the repeatability of constant parameters. The video Electric Single Particle Aerodynamic Relaxation Time Analyzer (VESPART) is an instrument that provides the diameter and charge-to-mass (q/m) ratio of particles. The simulation of the VESPART requires the modeling of the physical environment and application of modeling to simulations. Simulation includes characterization of the various natural forces that feet particle motion within the instrument. These natural forces can be modified to determine the impact each has on particle motion. The graphical user interface is created in MS Visual Basic providing an MS Windows compatible simulating environment. The output of the simulator is a virtual, illuminated particle track similar to the actual particle track acquired by le VESPART. This paper presents the parameters of simulation as well as the output virtual particle track. Also, the benefits simulation are presented relative to research and development projects

    Modeling of Electrofusion Coils for Performance Optimization

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    Modeling physical parameters provides a virtual design environment allowing the confirmation and optimization of electrofusion characteristics. Finite element incorporate physical parameters and their interactions along common boundaries defined within a model geometry. The electrofusion of polymeric piping is a widely accepted means of assembling piping systems with zero-leakage integrity. The key parameters in the fusion process are the coil resistance, the current passing through the coil and the time the current is applied. Modeling the coil and applying current to the model is accomplished using the MATLABpartial differential equations (PDE) toolbox. This paper presents the method of modeling and the results from changing the various fusion parameters such as time and current. Both the parameters and outputs are illustrated in various configurations

    Differences in transmission properties and susceptibility to long-term depression reveal functional specialization of ascending axon and parallel fiber synapses to Purkinje cells

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    An understanding of the patterns of mossy fiber transmission to Purkinje cells, via granule cell axons, is fundamental to models of cerebellar cortical signaling and processing. Early theories assumed that mossy fiber input is widely disseminated across the cerebellar cortex along beams of parallel fibers, which spread for several millimeters across the cerebellar cortex. Direct evidence for this has, however, proved controversial, leading to the development of an alternative hypothesis that mossy fiber inputs to the cerebral cortex are in fact vertically organized such that the ascending segment of the granule axon carries a greater synaptic weight than the parallel fiber segment. Here, we report that ascending axon synapses are selectively resistant to cerebellar long-term depression and that they release transmitter with higher mean release probabilities and mean quantal amplitudes than parallel fiber synapses. This novel specialization of synapses formed by different segments of the same axon not only explains the reported patterns of granule cell→ Purkinje cell transmission across the cerebellar cortex but also reveals an additional level of functionality and complexity of cerebellar processing. Consequently, ascending axon synapses represent a new element of cortical signal processing that should be distinguished from parallel fiber synapses in future experimental and theoretical studies of cerebellar function

    Portable Environmental Data Logger and Sensor

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    An instrumentation and recording package and several transducers were constructed and used to collect data on the environmental parameters thought to affect wetland vegetation growth and reproduction. These parameters were temperature, humidity, wind velocity, depth of water table, and amount of surface water. The data were collected four times a day and recorded on a magnetic cassette tape that could record for as long as 90 days. The tapes were read and the data were converted to engineering units by a microcomputer-based instrument constructed for that purpose

    Effects of Changes in Surface Water Regime and/or Land Use on the Vertical Distribution of Water Available for Wetland Vegetation: Portable Environmental Data Logger and Sensors (Part II of Completion Report for Project A-023-ARK)

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    An instrumentation and recording package and several transducers were constructed and used to collect data on the environmental parameters thought to affect wetland vegetation growth and reproduction. These parameters were temperature, humidity, wind velocity, depth of water table, and amount of surface water. The data were collected four times a day and recorded on a magnetic cassette tape that could record for as long as 90 days. The tapes were read and the data were converted to engineering units by a microcomputer-based instrument constructed for that purpose

    Dynamic Model of the Zone of Aeration

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    A mathematical model by Green (1), simulating one-dimensional vertical ground-water movement in unsaturated soils of the prairie region of Kansas, has been adapted for use in a wetlands environment typified by the wetlands forest of Eastern Arkansas. The model consists of two second-order, non-linear, partial differential equations and an algorithm for their numerical solution. The original model was extended to include functions for seasonal changes in transpiration and for drainage of excess precipitation. Before the addition of the two functions, the model reliability was limited to one growth season. With the mathematical model presented in this work it is possible to study interactions between hydrologic changes and the long term vegetative changes. The model potentially is a versatile management tool which could be used to help predict the environmental impact of proposed flood control projects

    Modification of Surface Properties of Polymeric Materials

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    Polymeric materials are successfully used in virtually all industries ranging from semiconductors, and coatings, to household appliances, automotive, and biomedical implants. Polymers generally have excellent bulk physical and chemical properties. However, certain properties of polymers such as low surface energy, low wettability, and high electrical resistivity sometimes limit their applications. Changing the bulk formulation of the polymers can alter some of these properties, but in general this is not acceptable as it can affect desirable bulk properties. Surface modification techniques have been used to alter polymer surfaces without affecting the bulk properties of the material. Most polymers have very high surface and bulk resistivity, which causes static charge problems in many applications. One such application is powder coating where the accumulation of excess charge causes an adverse impact on the appearance of the powder layer. Similarly the buildup of static charge during processing and application of polymer films in packaging industries is often harmful to sensitive electronic components such as those used in the computer industry. Charge buildup may be reduced by surface modification to control the surface resistivity. In this work, atmospheric plasma treatment was used to modify the surface resistivity of polymers. The surface resistivity of polyethylene film decreased from 1.28x1O16 Q/D to 5.73x1O15 Q/U at 18% RH
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