4,964 research outputs found
Calculating groundwater response times for flow in heterogeneous porous media
Predicting the amount of time required for a transient groundwater response
to take place is a practical question that is of interest in many situations.
This time scale is often called the response time. In the groundwater hydrology
literature there are two main methods used to calculate the response time: (i)
both the transient and steady state groundwater flow equations are solved, and
the response time is taken to be amount of time required for the transient
solution to approach the steady solution within some tolerance; and (ii) simple
scaling arguments are adopted. Certain limitations restrict both of these
approaches. Here we outline a third method, based on the theory of mean action
time. We derive the governing boundary value problem for both the mean and
variance of action time for confined flow in two-dimensional heterogeneous
porous media. Importantly, we show that these boundary value problems can be
solved using widely available software. Applying these methods to a test case
reveals the advantages of the theory of mean action time relative to standard
methods.Comment: 15 pages, 2 Figure
Study of aerodynamic technology for single-cruise-engine V/STOL fighter/attack aircraft
A viable, single engine, supersonic V/STOL fighter/attack aircraft concept was defined. This vectored thrust, canard wing configuration utilizes an advanced technology separated flow engine with fan stream burning. The aerodynamic characteristics of this configuration were estimated and performance evaluated. Significant aerodynamic and aerodynamic propulsion interaction uncertainties requiring additional investigation were identified. A wind tunnel model concept and test program to resolve these uncertainties and validate the aerodynamic prediction methods were defined
Viscous fingering in miscible, immiscible and reactive fluids
With the Lattice Boltzmann method (using the BGK approximation) we
investigate the dynamics of Hele-Shaw flow under conditions corresponding to
various experimental systems. We discuss the onset of the instability
(dispersion relation), the static properties (characterization of the
interface) and the dynamic properties (growth of the mixing zone) of simulated
Hele-Shaw systems. We examine the role of reactive processes (between the two
fluids) and we show that they have a sharpening effect on the interface similar
to the effect of surface tension.Comment: 6 pages with 2 figure, to be published in J.Mod.Phys
Nonlinear diffusion model for Rayleigh-Taylor mixing
The complex evolution of turbulent mixing in Rayleigh-Taylor convection is
studied in terms of eddy diffusiviy models for the mean temperature profile. It
is found that a non-linear model, derived within the general framework of
Prandtl mixing theory, reproduces accurately the evolution of turbulent
profiles obtained from numerical simulations. Our model allows to give very
precise predictions for the turbulent heat flux and for the Nusselt number in
the ultimate state regime of thermal convection.Comment: 4 pages, 4 figure, PRL in pres
Unconditional convergence and optimal error estimates of a Galerkin-mixed FEM for incompressible miscible flow in porous media
In this paper, we study the unconditional convergence and error estimates of
a Galerkin-mixed FEM with the linearized semi-implicit Euler time-discrete
scheme for the equations of incompressible miscible flow in porous media. We
prove that the optimal error estimates hold without any time-step
(convergence) condition, while all previous works require certain time-step
condition. Our theoretical results provide a new understanding on commonly-used
linearized schemes for nonlinear parabolic equations. The proof is based on a
splitting of the error function into two parts: the error from the time
discretization of the PDEs and the error from the finite element discretization
of corresponding time-discrete PDEs. The approach used in this paper is
applicable for more general nonlinear parabolic systems and many other
linearized (semi)-implicit time discretizations
Statistics of precursors to fingering processes
We present an analysis of the statistical properties of hydrodynamic field
fluctuations which reveal the existence of precursors to fingering processes.
These precursors are found to exhibit power law distributions, and these power
laws are shown to follow from spatial -Gaussian structures which are
solutions to the generalized non-linear diffusion equation.Comment: 7 pages incl. 5 figs; tp appear in Europhysics Letter
Preventing sexual violence in New Mexico: what our communities have to say.
Presented at: 2015 Annual Conference of the New Mexico Public Health Association; March 31-April 1, 2015; Albuquerque, NM.https://digitalrepository.unm.edu/prc-posters-presentations/1036/thumbnail.jp
ADULT LEARNING ON THE INTERNET: ENGAGING THE eBAY AUCTION PROCESS
The current revolution of the Information Age is rapidly changing the complexion of many personal
and corporate societies. This revolution is changing the methods people use to communicate with
each other, research new information, solve problems, and transact business. The purpose of this
study was to describe the learning strategies that adults use in learning to engage in the eBay
auction process. The study used the following research questions: (a) what are the identified
learning strategy preferences of adult learners using eBay, (b) how do the learning strategy
preferences of eBay users compare to the norms for ATLAS, and (c) how do eBay users describe
their learning processes related to getting started on eBay, participating in eBay activities,communicating on eBay, learning through eBay, and experiencing eBay?
This study used a descriptive design along with the information and data gathering advantages of
the Internet to collect data about how adults learn using the Internet. An online questionnaire
which featured 19 qualitative questions and 11 quantitative Likert scale items was used to
determine the perceptions of eBay participants. Assessing The Learning Strategies of AdultS
(ATLAS) instrument was imbedded within the online questionnaire to determine the preferred
strategies of eBay users. The study involved a representative sample of 380 eBay users which
was identified by electronically downloading the e-mail addresses of participants in completed
auctions. The sample was stratified by the 13 categories of items listed on eBay. Within each of these categories, high-volume completed auctions were selected in which the final sale price was under 11 and 100
Prospectus, January 10, 2001
https://spark.parkland.edu/prospectus_2001/1000/thumbnail.jp
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