Mechanical Engineering Commons^™

Robust Techniques And Applications In Fuzzy Clustering, Amit Banerjee

Dissertations

This dissertation addresses issues central to frizzy classification. The issue of sensitivity to noise and outliers of least squares minimization based clustering techniques, such as Fuzzy c-Means (FCM) and its variants is addressed. In this work, two novel and robust clustering schemes are presented and analyzed in detail. They approach the problem of robustness from different perspectives. The first scheme scales down the FCM memberships of data points based on the distance of the points from the cluster centers. Scaling done on outliers reduces their membership in true clusters. This scheme, known as the Mega-clustering, defines a conceptual mega-cluster which …

A Gait Generation Mechanism For Leg Rehabilitation Therapy, Yazan Ahmad Manna

Theses

While most take their ability to walk for granted, some are unable to walk secondary to any number of pathologies, such as traumatic brain injury (TBI), spinal cord injury (SCI), cerebrovascular accidents (CVA), cerebral palsy (CP), multiple sclerosis (MS), Parkinson's disease, as well as various orthopedic conditions. Decreased activity has been shown to be associated with rapidly deconditioning and other co-morbidities. Rehabilitation techniques that afford patients the ability to begin reconditioning through walking sooner may ultimately enhance their return to a better quality of life.

The overall goal of this study is to design a gait generation mechanism for rehabilitation …

Evaporating Cross Flow Spray Jets In Gas-Solid Circulating Fluidized Bed, Tong Hoon Lee

Dissertations

Three-phase flow of solid-gas suspension with liquid spray is found in many industrial applications, including fluidized catalytic cracking in petroleum refinery process, and wet scrubbing process. This dissertation study is aimed to understand the gas-solid-liquid three-phase flow structure, phase interactions and transport in a gas-solid circulating fluidized bed where an evaporating cross-flow liquid spray jet from a rectangular nozzle with a fan angle is injected. The investigation is based on both numerical and experimental approaches. The numerical study is for detailed field descriptions of the flow structure, phase interaction and distributions whereas the experimental study is for simulation validations. The …

Direct Numerical Simulations And Experimental Investigation Of Dielectrophoresis, Arun Thankamony John-Kadaksham

Dissertations

This dissertation deals with the numerical and experimental studies of the phenomenon of dielectrophoresis, i.e., the motion of neutral particles in nonuniform electric fields. Dielectrophoresis is the translatory motion of neutral particles suspended in a dielectric medium when they are subjected to an external nonuniform electric field. The translatory motion occurs because a force called the dielectrophoretic force, which depends on the spatial variation of the electric field, acts on the particles. As the generation of force involves no moving parts and the particles can be moved without touching them, dielectrophoresis can be used in many applications, including manipulation and …

Simulation Of Creep In Nickel Based Single Crystal Superalloys, Yunhong Pang

Dissertations

Nickel based single crystal Superalloys are finding wide spread use in high temperature gas turbines and other similar applications because of their superior high-temperature strength and creep properties as compared to the other materials. This is due to two factors: solid solution and precipitation strengthening of the gamma (γ) and gamma prime (γ') phases, and the elimination of grain boundaries. Creep of Nickel based single crystal Superalloys are caused by two primary mechanisms, dislocation creep and diffusion creep. Several factors that affect the creep life of Nickel based single crystal Superalloys are the specific microstructure, stress, temperature and rafting. Also, …

Gas Fluidization Of Nanoparticles, Qun Yu

Dissertations

The primary objective of this study is to perform a systematic investigation on the gas fluidization of various nanoparticle agglomerates. Firstly, the gas fluidization characteristics and regime classifications without any additional external force fields are identified using both experimental measurements and modeling. Secondly, the effect of introducing certain external force fields on nanoparticle fluidization is experimentally investigated. Two external force fields were applied: sound waves from a loud speaker (acoustic assistance) and in-bed magnets that were excited by an external oscillating magnetic field (magnetic assistance). Thirdly, exploratory experimental research on the use of nanoparticle agglomerates as a granular filtration media …

Experimental Technique For Studying High-Temperature Phase Equilibria In Reactive Molten Metal Based Systems, Alexandre Ermoline

Dissertations

The general objective of this work is to develop an experimental technique for studying the high-temperature phase compositions and phase equilibria in molten metal-based binary and ternary systems, such as Zr-O-N, B-N-O, Al-O, and others. A specific material system of Zr-O-N was selected for studying and testing this technique.

The information about the high-temperature phase equilibria in reactive metal-based systems is scarce and their studying is difficult because of chemical reactions occurring between samples and essentially any container materials, and causing contamination of the system.

Containerless microgravity experiments for studying equilibria in molten metal-gas systems were designed to be conducted …

Computational Studies Of Viscoelastic Multiphase Flows, Shriram B. Pillapakkam

Dissertations

A finite element code based on the level set method is developed for performing two and three dimensional direct numerical simulations (DNS) of viscoelastic two-phase flow problems. The Oldroyd-B constitutive equation is used to model the viscoelastic liquid. The code is used to study transient and steady state shapes of Newtonian and viscoelastic drops in simple shear and buoyancy driven flows. The roles of the governing dimensionless parameters: Capillary number (Ca), Deborah Number (De) and the polymer concentration parameter c, in determining deformation of drops and bubbles, are also analyzed.

The numerical code permits us to vary Ca, De and …

Investigation Of Static And Dynamic Enhancement Of Laminar Natural Convection Cooling Of Electronics, Laurie Ann Florio

Dissertations

With the proliferation of consumer electronics devices and the increasingly demanding thermal control requirements for such devices, more effective and efficient means of cooling electronics are needed. The feasibility of three alternative approaches to enhancing pure natural convection cooling of electronics is investigated in the current research. The three static or dynamic methods investigated are alternate cross-flow passages, the strategic placement of transversely oscillating plates near the heat sources and a combined method using both the cross-flow passages and the strategically placed oscillating plates. These cooling methods are intended to operate in the regime for which natural convection cooling is …

Heat Transfer Model For The Ignition Of Metal Powder On A Heated Filament, Trent Stanton Ward

Theses

The thermal processes leading to ignition of metal powders in environments that experience rapid temperature changes are currently poorly understood. In this research, a methodology for studying and quantification of such processes is developed. In the experimental case study, the ignition temperature of Mg powder coated on the surface of an electrically heated filament is detected optically at different heating rates. To interpret the results, a heat transfer model has been developed for a multilayer powder coating on top of an electrically heated filament. The coating is modeled using a hexagonal close packed geometry and the heat transfer equations are …