Digital Commons Network^™

Biped Dynamic Walking Using Reinforcement Learning, Hamid Benbrahim

Doctoral Dissertations

This thesis presents a study of biped dynamic walking using reinforcement learning. A hardware biped robot was built. It uses low gear ratio DC motors in order to provide free leg movements. The Self Scaling Reinforcement learning algorithm was developed in order to deal with the problem of reinforcement learning in continuous action domains. A new learning architecture was designed to solve complex control problems. It uses different modules that consist of simple controllers and small neural networks. The architecture allows for easy incorporation of modules that represent new knowledge, or new requirements for the desired task. Control experiments were …

Use Of Geographic Information System Technology To Assess Vulnerability To Shallow Groundwater Contamination., Brenda G. Bruner

LSU Historical Dissertations and Theses

Geographic Information System (GIS) technology was used to develop a local scale screening procedure for assessing shallow ground water's vulnerability to nitrate contamination. The procedure was based on the spatial distribution of ten key physical and chemical properties of soils. Both flow characteristics and attenuation capabilities of soils were incorporated into the assessment. Land surface areas were classified by the GIS to show the level of vulnerability present at a site as a result of existing natural conditions. The procedure produced a Vulnerability Index (VI), and resulted in VI ranging from 4.98 to 6.72 for the study area (with ten …

Experimental Investigation Of Wall And Inertial Effects On A Disk Sedimenting At Low Reynolds Number., Joe Wade Pulley

LSU Historical Dissertations and Theses

Measurements have been made of the drag on a thin disk of diameter d moving broadside through a liquid of viscosity $\mu$ and density $\rho$. The liquid is bounded on the outside by a cylindrical tube, diameter D, which is coaxial with the disk. The geometrical parameter $\xi$ = d/D ranges from 0.0189 to 0.112. The Reynolds number Re = $\rho$Ud/$\mu$ ranges from 0.0167 to 6.89. When the measured values are extrapolated to Re = 0, the results agree with the calculations of Shail and Norton. When extrapolated to $\xi$ = 0, the results agree with the matched-asymptotic series solution …

Communication Network Design And Evaluation Using Shadow Prices., Cesar Vargas-Rosales

LSU Historical Dissertations and Theses

We use shadow prices to measure the rate of change of performance functions of a communications network with respect to incremental changes in one or more of the design parameters such as capacity, anticipated demand, reservation levels, routing proportions, etc. The ability to evaluate such shadow prices allows us to introduce designs that optimize network performance according to network-wide criteria. We present models for the evaluation of shadow prices for different cases of networks: single-rate circuit-switched networks, wireless networks, multi-rate circuit-switched networks. For these cases, we demonstrate the wide applicability of shadow price methods. We formulate the new and very …

The Increase In Shaft Capacity With Time For Friction Piles Driven Into Saturated Clay., Hani Hasan Titi

LSU Historical Dissertations and Theses

A general method for predicting pile setup, or the increase in the load carrying capacity of friction piles driven into saturated clay, was developed. The solution is based on the HiSS modeling approach, the strain path method, and the theory of nonlinear porous media. The ability of this method was demonstrated by predicting the field behavior of pile segment models during driving, subsequent consolidation, and load testing. Numerical simulations were performed on pile segment models because of the availability of field experimental tests necessary for verification and evaluation schemes. The method was also applied to investigate the behavior of full-scale …

Analysis And Design Of Ac Induction Motors With Squirrel Cage Rotors, Shine Ho

Doctoral Dissertations

The traditional approach to modelling the AC induction motor revolves around the well-known equivalent "T" circuit model. In this approach, the direct connection from geometry to performance is suppressed. For better understanding of magnetic, electrical, and thermal behaviors, three lumped models based on the actual geometry are developed in this dissertation. Based on these lumped models, an iterative design model is also developed.

In order to analyze and design induction motors, the relationships of basic motor variables to motor performance must be known. For determining the relationships, three new mathematical lumped models are developed. The magnetic model describes flux behavior. …

Fume Generation In Gas Metal Arc Welding, Robert V. Albert

Doctoral Dissertations

This investigation studied fume generated from Gas Metal Arc Welding (GMAW). Through an extensive literature review, experimental measurements and analytical reasoning this dissertation answers four questions. Why and how does oxygen content of the shield gas effect fume generation? Why is more fume generated with helium than with argon as a shield gas? Why and how does welding mode affect fume rate? Why and how does pulsing the current lower fume generation rate?

An extensive literature survey was conducted. The current view of GMAW indicates that four modes exist in metal transfer across the arc. Each mode selects from several …

Longitudinal Dispersion And Interstitial Velocity Relationship In Subsurface Flow Constructed Wetlands., Gianna M. Cothren

LSU Historical Dissertations and Theses

Treatment of municipal and rural wastewater using subsurface flow constructed wetlands (SFCW's) is growing in popularity. These systems often consist of an excavated cell containing 2-3 in. rock with the wastewater level maintained below the media surface. A SFCW is a natural form of wastewater treatment which removes organics and nutrients based on the attached growth of microorganisms on crushed rocks where biological reactions take place. The currently accepted design procedure is based on the first order plug flow model, although tracer studies have shown that flow conditions are not well represented by the plug flow condition. This design rationale …

Design And Analysis Of Reduced-Connection Multiple Bus Systems: A Probabilistic Approach., Najmul Karim

LSU Historical Dissertations and Theses

In the dissertation we have proposed the first systematic and formal approach to reduce connectivity of general purpose multiple bus systems. The approach is based on a probabilistic technique. The hypothesis on which this dissertation is based stipulates that bus connectivity in multiple bus systems can be much reduced by removing connections which are only needed for highly improbable request patterns. With this approach, performance comparable to that of the original multiple bus system could be achieved while significantly reducing memory bus connectivity. The new architecture thus obtained (Probabilistically load reduced connection multiple bus system, or PRMB in short) might …

Low Temperature Silicon Oxide And Fluorinated Silicon Oxide Films Prepared By Plasma-Enhanced Chemical Vapor Deposition Using Disilane As Silicon Precursor., Juho Song

LSU Historical Dissertations and Theses

The deposition and characterization of the silicon oxide and fluorinated silicon oxide films, as interlevel dielectrics in microelectronics devices, prepared by plasma enhanced chemical vapor deposition at low substrate temperature using $\rm Si\sb2H\sb6$ as silicon precursor are studied. The film deposition is limited by the mass transport regime, resulting in nearly temperature independent deposition rate. The characteristics for the silicon oxide films deposited at 120$\sp\circ$C show that the film etch rate is comparable to that obtained by TEOS-based PECVD at 400$\sp\circ$C and the leakage current is comparable to that of the films deposited at 350$\sp\circ$C with conventional SiH$\sb4$ precursor. It …

Dendrite And Silicon Particle Refinement Using Aluminum-Insoluble Elements In Hypoeutectic Aluminum Silicon Alloys., Yunsong. Wen

Electronic Theses and Dissertations

For hypoeutectic Al-Si alloy castings, minimizing dendrite arm spacing and modification of the secondary Si particles is the most effective means for maximizing strength and ductility. Dendrite refinement can be affected by microalloying with selective elements that promote interfacial instability through constitutional and thermal supercooling. The microalloying elements used in commercial Al alloys A319 and A356 are 0.5 to 1.0 wt% of Sb, Bi, In and Sn, which have little or no solubility in Al, i.e. they have extremely low distribution coefficients. Significant refinement of the dendrite structures (decreasing DAS) and the modification of eutectic Si particles were obtained with …

Adaptive Non-Linear Predictive Control, Edward Katende

Digitized Theses

Most predictive control algorithms, including the Generalized Predictive Control (GPC) (Clarke et al. 1987) are based on linear dynamics. Many processes are severely non-linear and would require high order linear approximations. Another approach, which is presented here, is to extend the basic adaptive GPC algorithm to a non-linear form. This provides a non-linear predictive controller which is shown to be very effective in the control of processes with non-linearities that can be suitably modelled using general Volterra, Hammerstein and bilinear models. In developing this algorithm, the process dynamics are not restricted to a particular order as is the case with …

Micellar Electrokinetic Remediation Of Tnt From Soil., Mohd Raihan Taha

LSU Historical Dissertations and Theses

An assessment of the feasibility of micellar electrokinetic (EK) remediation of TNT from soils is presented. Batch solubilization tests and bench scale EK tests were conducted to select the best candidate surfactant and to evaluate the efficiency of removal of TNT from a real world soil. From batch tests, it was found that SDS gave the best desorption results among a group of candidate surfactants, which includes DOWFAX 8390 (anionic), Tween 80 and Brij 35 (nonionic) and CTAB and CTAC (cationic). Unenhanced and surfactant enhanced EK tests was unable to move substantial amounts of TNT across the specimen to the …

A Cyclic Plasticity/Damage Model For Metal Matrix Composites., Ganesh Thiagarajan

LSU Historical Dissertations and Theses

A new six parameter general anisotropic yield surface using a fourth order anisotropic tensor $M\sb{ijkl}$ has been proposed. This form has been derived based on the physical behavior observed for the material under consideration--directionally reinforced metal matrix composites. Its validity has been shown by proving its convexity and form under coordinate transformation. This form of the anisotropic yield function is general in nature which can be used for either pressure dependent or independent cases. The proposed surface compares well with the extensive experimental data of Dvorak et al. (1988) and Nigam et al. (1993) performed on boron-aluminum metal matrix composite. …

Friction And Wear Of Nanocrystalline Materials And Nanolaminated Composites., Zoheir N. Farhat

Electronic Theses and Dissertations

In the search of new wear resistant coatings for applications such as cutting tools and turbine refurbishing, a wide range of coatings, belonging to emerging classes of materials, namely, nanocrystalline materials and nanolayered composites, have been produced and tested. These coatings were produced using an rf magnetron sputtering system and include monolithic nanocrystalline metals (Al,Ti,Cu), nanolaminated composites composed of alternating layers of metal/ceramic (Al/Al$\sb2$O$\sb3$, Ti/TiN) and metal/metal (Ti/Cu). The metal layer thickness in the as-sputtered films of Al/Al$\sb2$O$\sb3$ ranged from 70 to 500 nm, and 150 to 450 nm in Ti/TiN. The nonmetals (Al$\sb2$O$\sb3$,TiN) layer thicknesses ranged from 10 to …

A Hierarchical Approach To Equilibrium Cycle Nuclear Fuel Analysis., Jon Juneau

LSU Historical Dissertations and Theses

This research involved developing an expert system that allows a nuclear fuel engineer to quickly provide answers to strategic nuclear fuel management questions, which are typically broad based. Current nuclear fuel analysis research concentrates on getting more accurate and precise answers at the expense of using large computer programs to get answers that are too specific to answer the broad based questions. The expert system brings together several artificial intelligence techniques to allow a nuclear fuel engineer to consider several scenarios in a general way in order to quickly answer the fuel management questions asked. The expert system is based …

Simulation And Modelling Of Thin Film Phi(Rho-Z) Curves For Electron Probe Microanalysis, Ka Shing Chan

Digitized Theses

Quantitative analysis of homogeneous bulk unknowns using an electron probe microanalyzer requires the accurate knowledge of the depth distributions of x-ray production ({dollar}\phi{dollar}({dollar}\rho{dollar}z) curves). Straight line behaviour is observed in the plot of ln{dollar}\phi{dollar}({dollar}\rho{dollar}z) versus ({dollar}\rho{dollar}z){dollar}\sp2{dollar} for most experimentally measured data. Monte Carlo calculations can be used to simulate {dollar}\phi{dollar}({dollar}\rho{dollar}z) curves. However, ln {dollar}\phi{dollar}({dollar}\rho{dollar}z) versus ({dollar}\rho{dollar}z){dollar}\sp2{dollar} plots of these {dollar}\phi{dollar}({dollar}\rho{dollar}z) curves, in general, are nonlinear and concave downward. By introducing the concept of electron straggling into a multiple scattering Monte Carlo model, agreement with the behaviour of experimental curves is achieved.;Electron probe microanalysis can also be used for the characterization …