Physical Sciences and Mathematics Commons^™

Numerical Modeling Of Contaminant Transport In Fractured Porous Media Using Mixed Finite Element And Finite Volume Methods, Chen Dong

All Theses

A mathematical model for contaminant species passing through fractured porous media is presented. In the numerical model, we combine two locally conservative methods, i.e. mixed finite element (MFE) and the finite volume methods. Adaptive triangle mesh is used for effective treatment of the fractures. A hybrid MFE method is employed to provide an accurate approximation of velocities field for both the fractures and matrix which are crucial to the convection part of the transport equation. The finite volume method and the standard MFE method are used to approximate the convection and dispersion terms respectively. Numerical examples in different fractured media …

Computational Modeling Of Biological Neural Networks On Gpus: Strategies And Performance, Byron Galbraith

Master's Theses (2009 -)

Simulating biological neural networks is an important task for computational neuroscientists attempting to model and analyze brain activity and function. As these networks become larger and more complex, the computational power required grows significantly, often requiring the use of supercomputers or compute clusters. An emerging low-cost, highly accessible alternative to many of these resources is the Graphics Processing Unit (GPU) - specialized massively-parallel graphics hardware that has seen increasing use as a general purpose computational accelerator thanks largely due to NVIDIA's CUDA programming interface. We evaluated the relative benefits and limitations of GPU-based tools for large-scale neural network simulation and …

Stirring Up The Pot: Can Cooling Flows In Galaxy Clusters Be Quenched By Gas Sloshing?, J. A. A. Zuhone, M. Markevitch, R. E. Johnson

Dartmouth Scholarship

X-ray observations of clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as "cold fronts." In relaxed clusters with cool cores, these commonly observed edges have been interpreted as evidence for the "sloshing" of the core gas in the cluster's gravitational potential. Such sloshing may provide a source of heat to the cluster core by mixing hot gas from the cluster outskirts with the cool-core gas. Using high-resolution N-body/Eulerian hydrodynamic simulations, we model gas sloshing in galaxy clusters initiated by mergers with subclusters. The simulations include merger scenarios with gas-filled and gasless subclusters. The …

Low-Frequency Turbulence In A Linear Magnetized Plasma, B. N. Rogers, Paolo Ricci

Dartmouth Scholarship

Plasma turbulence in a linear device is explored for the first time with three-dimensional global two-fluid simulations, focusing on the plasma parameters of the Large Plasma Device. Three instabilities are present in the simulations: the Kelvin-Helmholtz instability, a sheath-driven instability, and a resistive drift wave instability. The Kelvin-Helmholtz mode is shown to dominate the transport of plasma across the magnetic field. Simple scaling laws are obtained for the plasma profiles.

On Simulating Univariate And Multivariate Burr Type Iii And Type Xii Distributions, Todd C. Headrick, Mohan D. Pant, Yanyan Sheng

Mohan Dev Pant

This paper describes a method for simulating univariate and multivariate Burr Type III and Type XII distributions with specified correlation matrices. The methodology is based on the derivation of the parametric forms of a pdf and cdf for this family of distributions. The paper shows how shape parameters can be computed for specified values of skew and kurtosis. It is also demonstrated how to compute percentage points and other measures of central tendency such as the mode, median, and trimmed mean. Examples are provided to demonstrate how this Burr family can be used in the context of distribution fitting using …

Cleaning Of Rivers Through The Application Of Advanced Technologies, Praveen Jha Dr

Praveen Jha Dr

Despite immense drain on our scarce resources, rivers remain polluted. Waste disposal into rivers on top of meager to absent infrastructural facilities, including treatment facilities, are the most important drivers of pollution. Unscientific development paradigm devoid of adequate environmental safeguards and failure of forestry sector to cope up with the challenge has led to the deteriorated condition of green cover and water. Several state-of-art geo-spatial programs developed by the author would be applied for generating optimum state-of-art plan. Three state-of-art geo-spatial programs - Multi-Algorithm Automation Program (MAAP), Data Automatic Modification Program (DAMP) and Multi-Stage Simulation Program (MUSSIP) - developed primarily …

Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman

Dartmouth Scholarship

We present an analysis of a 72 ks Chandra observation of the double cluster Abell 1644 (z = 0.047). The X-ray temperatures indicate that the masses are M ₅₀₀ = (2.6 ± 0.4) × 10¹⁴ h ^–1 M _☉ for the northern sub-cluster and M ₅₀₀ = (3.1 ± 0.4) × 10¹⁴ h ^–1 M _☉ for the southern, main cluster. We identify a sharp edge in the radial X-ray surface brightness of the main cluster, which we find to be a cold front, with a jump in temperature of a factor of ~3. This edge possesses …

Simulating The Fticr-Ms Signal Of A Decaying Beryllium-7 Ion Plasma In A 2d Electrostatic Pic Code, Michael Takeshi Nakata

Theses and Dissertations

Beryllium-7 (Be-7) only decays by electron capture into lithium-7 (Li-7) with a half life of 53 days. We study the effect of ionization on this decay rate. We do so by trapping a Be-7 ion plasma in a cylindrical Malmberg-Penning trap and measuring Be-7 and Li-7 concentrations as functions of time by using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). We have simulated these signals in a 2-dimensional electrostatic particle-in-cell (PIC) code. The two spectrum peaks merge at high ion densities whereas at low ion densities they can be resolved. The merged peak shifts linearly according to the relative …

Rfid-Enabled Inventory Control Optimization: A Proof Of Concept In A Small-To-Medium Retailer, H. Dane, Katina Michael, S. F. Wamba

Dr Samuel Fosso Wamba

This study examines the impact of radio-frequency identification (RFID) technology on the inventory control practices of a small-to-medium retailer using a proof of concept (PoC) approach. The exploratory study was conducted using a single case study of a hardware retailer stocking 5000 product lines provided by 110 active suppliers. To analyze the present mode of operation, procedural documents, semi-structured interviews and a participant observation was conducted. The basis for the proof of concept was a future mode of operation using a quasi-experimental design. Results indicate that in a small-to-medium retail environment, RFID technology could act as a loss prevention mechanism, …

Rfid-Enabled Inventory Control Optimization: A Proof Of Concept In A Small-To-Medium Retailer, H. Dane, Katina Michael, S. F. Wamba

Faculty of Informatics - Papers (Archive)

This study examines the impact of radio-frequency identification (RFID) technology on the inventory control practices of a small-to-medium retailer using a proof of concept (PoC) approach. The exploratory study was conducted using a single case study of a hardware retailer stocking 5000 product lines provided by 110 active suppliers. To analyze the present mode of operation, procedural documents, semi-structured interviews and a participant observation was conducted. The basis for the proof of concept was a future mode of operation using a quasi-experimental design. Results indicate that in a small-to-medium retail environment, RFID technology could act as a loss prevention mechanism, …

Simulating Multivariate G-And-H Distributions, Rhonda K. Kowalchuk, Todd C. Headrick

Todd Christopher Headrick

The Tukey family of g-and-h distributions is often used to model univariate real-world data. There is a paucity of research demonstrating appropriate multivariate data generation using the g-and-h family of distributions with specified correlations. Therefore, the methodology and algorithms are presented to extend the g-and-h family from univariate to multivariate data generation. An example is provided along with a Monte Carlo simulation demonstrating the methodology. In addition, algorithms written in Mathematica 7.0 are available from the authors for implementing the procedure.

Statistical Simulation: Power Method Polynomials And Other Transformations, Todd C. Headrick

Todd Christopher Headrick

Although power method polynomials based on the standard normal distributions have been used in many different contexts for the past 30 years, it was not until recently that the probability density function (pdf) and cumulative distribution function (cdf) were derived and made available. Focusing on both univariate and multivariate nonnormal data generation, Statistical Simulation: Power Method Polynomials and Other Transformations presents techniques for conducting a Monte Carlo simulation study. It shows how to use power method polynomials for simulating univariate and multivariate nonnormal distributions with specified cumulants and correlation matrices. The book first explores the methodology underlying the power method, …

Accounting For Response Misclassification And Covariate Measurement Error Improves Powers And Reduces Bias In Epidemiologic Studies, Dunlei Cheng, Adam J. Branscum, James D. Stamey

Dunlei Cheng

Purpose: To quantify the impact of ignoring misclassification of a response variable and measurement error in a covariate on statistical power, and to develop software for sample size and power analysis that accounts for these flaws in epidemiologic data. Methods: A Monte Carlo simulation-based procedure is developed to illustrate the differences in design requirements and inferences between analytic methods that properly account for misclassification and measurement error to those that do not in regression models for cross-sectional and cohort data. Results: We found that failure to account for these flaws in epidemiologic data can lead to a substantial reduction in …

A Bayesian Approach To Sample Size Determination For Studies Designed To Evaluate Continuous Medical Tests, Dunlei Cheng, Adam J. Branscum, James D. Stamey

Dunlei Cheng

We develop a Bayesian approach to sample size and power calculations for cross-sectional studies that are designed to evaluate and compare continuous medical tests. For studies that involve one test or two conditionally independent or dependent tests, we present methods that are applicable when the true disease status of sampled individuals will be available and when it will not. Within a hypothesis testing framework, we consider the goal of demonstrating that a medical test has area under the receiver operating characteristic (ROC) curve that exceeds a minimum acceptable level or another relevant threshold, and the goals of establishing the superiority …

Creation Of Synthetic Discrete Response Regression Models, Joseph Hilbe

Joseph M Hilbe

The development and use of synthetic regression models has proven to assist statisticians in better understanding bias in data, as well as how to best interpret various statistics associated with a modeling situation. In this article I present code that can be easily amended for the creation of synthetic binomial, count, and categorical response models. Parameters may be assigned to any number of predictors (which are shown as continuous, binary, or categorical), negative binomial heterogeneity parameters may be assigned, and the number of levels or cut points and values may be specified for ordered and unordered categorical response models. I …

Model Based Analysis Of Some High Speed Network Issues, Suman Kumar

LSU Doctoral Dissertations

The study of complex problems in science and engineering today typically involves large scale data, huge number of large-scale scientific breakthroughs critically depends on large multi-disciplinary and geographically-dispersed research teams, where the high speed network becomes the integral part. To serve the ongoing bandwidth requirement and scalability of these networks, there has been a continuous evolution of different TCPs for high speed networks. Testing these protocols on a real network would be expensive, time consuming and more over not easily available to the researchers worldwide. Network simulation is well accepted and widely used method for performance evaluation, it is well …

Generalized Curvilinear Advection Formalism For Finite Volume Codes Doing Relativistic Hydrodynamics, Jay Michael Call

LSU Doctoral Dissertations

While it is possible to numerically evolve the relativistic fluid equations using any chosen coordinate mesh, typically there are distinct computational advantages associated with different types of candidate grids. For example, astrophysical flows that are governed by rotation tend to give rise to advection variables that are naturally conserved when a cylindrical mesh is used. On the other hand, Cartesian-like coordinates afford a more straightforward implementation of adaptive mesh refinement (AMR) and avoid the appearance of coordinate singularities. Here it is shown that it should be possible to reap the benefits associated with multiple types of coordinate systems simultaneously in …

Dynamic Multivariate Simplex Splines For Volume Representation And Modeling, Yunhao Tan

Wayne State University Dissertations

Volume representation and modeling of heterogeneous objects acquired from real world are very challenging research tasks and playing fundamental roles in many potential applications, e.g., volume reconstruction, volume simulation and volume registration. In order to accurately and efficiently represent and model the real-world objects, this dissertation proposes an integrated computational framework based on dynamic multivariate simplex splines (DMSS) that can greatly improve the accuracy and efficacy of modeling and simulation of heterogenous objects. The framework can not only reconstruct with high accuracy geometric, material, and other quantities associated with heterogeneous real-world models, but also simulate the complicated dynamics precisely by …

Behaviors Of Real-Time Schedulers Under Resource Modification And A Steady Scheme With Bounded Utilization, Refi̇k Samet, Orhan Fi̇kret Duman

Turkish Journal of Electrical Engineering and Computer Sciences

In this article we present an analysis for task models having random resource needs and different arrival patterns. In hard real-time environments like avionic systems or nuclear reactors, the inputs to the system are obtained from real world by using sensors. And it is highly possible for a task to have different resource needs for each period according to these changing conditions of real world. We made an analysis of schedulers for task models having random resources in each period. Since feasibility tests for usual task models are just limited to some specific schedulers and arrival patterns, we made our …

Biological Simulations And Biologically Inspired Adaptive Systems, Edgar Alfredo Duenez-Guzman

Doctoral Dissertations

Many of the most challenging problems in modern science lie at the interface of several fields. To study these problems, there is a pressing need for trans-disciplinary research incorporating computational and mathematical models. This dissertation presents a selection of new computational and mathematical techniques applied to biological simulations and problem solving: (i) The dynamics of alliance formation in primates are studied using a continuous time individual-based model. It is observed that increasing the cognitive abilities of individuals stabilizes alliances in a phase transition-like manner. Moreover, with strong cultural transmission an egalitarian regime is established in a few generations. (ii) A …

Comparing Cognitive Decision Models Of Iowa Gambling Task In Indivituals Following Temporal Lobectomy, Jenny Vennukkah Jeyarajah

Mathematics Theses

This study examined the theoretical basis for decision making behavior of patients with right or left temporal lobectomy and a control group when they participated in the Iowa Gambling Task. Two cognitive decision models, Expectancy Valence Model and Strategy Switching Heuristic Choice Model, were compared for best fit. The best fitting model was then chosen to provide the basis for parameter estimation (sources of decision making, i.e. cognitive, motivational, and response processes) and interpretation. Both models outperformed the baseline model. However comparison of G2 means between the two cognitive decision models showed the expectancy valence model having a higher mean …

Assessing Trends: Monte Carlo Trials With Four Different Regression Methods, Daniel R. Thompson

Journal of Modern Applied Statistical Methods

Ordinary Least Squares (OLS), Poisson, Negative Binomial, and Quasi-Poisson Regression methods were assessed for testing the statistical significance of a trend by performing 10,000 simulations. The Poisson method should be used when data follow a Poisson distribution. The other methods should be used when data follow a normal distribution.

Application Of The Truncated Skew Laplace Probability Distribution In Maintenance System, Gokarna R. Aryal, Chris P. Tsokos

Journal of Modern Applied Statistical Methods

A random variable X is said to have the skew-Laplace probability distribution if its pdf is given by f(x) = 2g(x)G(λx), where g (.) and G (.), respectively, denote the pdf and the cdf of the Laplace distribution. When the skew Laplace distribution is truncated on the left at 0 it is called it the truncated skew Laplace (TSL) distribution. This article provides a comparison of TSL distribution with twoparameter gamma model and the hypoexponential model, and an application of the subject model in maintenance system is studied.

Dynamic Load Balancing For I/O-Intensive Applications On Clusters, Xiao Qin, Hong Jiang, Adam Manzanares, Xiaojun Ruan, Shu Yin

School of Computing: Faculty Publications

Load balancing for clusters has been investigated extensively, mainly focusing on the effective usage of global CPU and memory resources. However, previous CPU- or memory-centric load balancing schemes suffer significant performance drop under I/O-intensive workloads due to the imbalance of I/O load. To solve this problem, we propose two simple yet effective I/O-aware load-balancing schemes for two types of clusters: (1) homogeneous clusters where nodes are identical and (2) heterogeneous clusters, which are comprised of a variety of nodes with different performance characteristics in computing power, memory capacity, and disk speed. In addition to assigning I/O-intensive sequential and parallel jobs …

Drinking Water Optimum Supply System (Dwoss) Through The Application Of Advanced Technologies, Praveen Jha Dr

Praveen Jha Dr

Paradigm shift in the approach for planning regarding supply of drinking water is mandatory since the current DPRs are unscientific and expensive. Planning for an optimum Drinking Water Supply System (ODWSS) that includes - optimization of Water Source Point (WSP), Water Treatment System (WTS), Water Storage Systems (WSSs), Water Distribution Points (WDP) and Water Supply Network (WSN); scientific estimation of long term demand of drinking water; minimization of physical and financial resources required for the plan implementation; water conservation and sanitation – could be done by applying several state-of-art geo-spatial programs developed by the author. Three programs - Multi-Algorithm Automation …

Using Rfid To Overcome Inventory Control Challenges: A Proof Of Concept, Dane Hamilton, Katina Michael, Samuel Fosso Wamba

Dr Samuel Fosso Wamba

Using a Proof of Concept approach, this paper examines RFID’s impact on inventory control of a small-to-medium retailer. Results indicate that RFID technology can function effectively in a small-to-medium hardware environment. Also, the majority of the simulations recorded reasonable read rates even though the simulations were set up over a short period of time without a great deal of fine-tuning. Moreover, RFID could have a positive impact on the inventory-related processes of the organisation by either streamlining or formalizing them and facilitate the electronic storage of information captured in real-time, relating to the movement of stock and the amount of …

Using Rfid To Overcome Inventory Control Challenges: A Proof Of Concept, Dane Hamilton, Katina Michael, Samuel Fosso Wamba

Professor Katina Michael

Using a Proof of Concept approach, this paper examines RFID’s impact on inventory control of a small-to-medium retailer. Results indicate that RFID technology can function effectively in a small-to-medium hardware environment. Also, the majority of the simulations recorded reasonable read rates even though the simulations were set up over a short period of time without a great deal of fine-tuning. Moreover, RFID could have a positive impact on the inventory-related processes of the organisation by either streamlining or formalizing them and facilitate the electronic storage of information captured in real-time, relating to the movement of stock and the amount of …

Hydrodynamic Relaxation Of An Electron Plasma To A Near-Maximum Entropy State, D. J. Rodgers, S. Servidio, W. H. Matthaeus, D. C. Montgomery, T. B. Mitchell, T. Aziz

Dartmouth Scholarship

Dynamical relaxation of a pure electron plasma in a Malmberg-Penning trap is studied, comparing experiments, numerical simulations and statistical theories of weakly dissipative two-dimensional (2D) turbulence. Simulations confirm that the dynamics are approximated well by a 2D hydrodynamic model. Statistical analysis favors a theoretical picture of relaxation to a near-maximum entropy state with constrained energy, circulation, and angular momentum. This provides evidence that 2D electron fluid relaxation in a turbulent regime is governed by principles of maximum entropy.

Visualizing The Simulation Of 3-D Underwater Sensor Networks, Matthew T. Tran

Honors Scholar Theses

The majority of sensor network research deals with land-based networks, which are essentially two-dimensional, and thus the majority of simulation and animation tools also only handle such networks. Underwater sensor networks on the other hand, are essentially 3D networks because the depth at which a sensor node is located needs to be considered as well. Due to that additional dimension, specialized tools need to be used when conducting simulations for experimentation.

The School of Engineering’s Underwater Sensor Network (UWSN) lab is conducting research on underwater sensor networks and requires simulation tools for 3D networks. The lab has extended NS-2, a …

Least Absolute Value Vs. Least Squares Estimation And Inference Procedures In Regression Models With Asymmetric Error Distributions, Terry E. Dielman

Journal of Modern Applied Statistical Methods

A Monte Carlo simulation is used to compare estimation and inference procedures in least absolute value (LAV) and least squares (LS) regression models with asymmetric error distributions. Mean square errors (MSE) of coefficient estimates are used to assess the relative efficiency of the estimators. Hypothesis tests for coefficients are compared on the basis of empirical level of significance and power.