Digital Commons Network^™

Steam Reheat In Nuclear Power Plants, Paul John Marotta

Doctoral Dissertations

In this work, reheating steam from a commercial nuclear power plant is explored in order to increase efficiency and power output. A thermal source in the form of a High Temperature Gas Reactor (HTGR) is considered. Engineering challenges include proof-of-principle, reactor sizing, evaluation, and feasibility.

The proposed thermodynamic process modifications have been evaluated for a range of inlet steam quality conditions. The evaluation of the steam tube dimensions and number of optimal tubes have been calculated utilizing the so-called Log Mean Temperature Difference method. Subsequently, the performance of the steam tubes was further analyzed within a water vapor and liquid …

Passive Control Architectures For Collaborative Virtual Haptic Interaction And Bilateral Teleoperation Over Unreliable Packet-Switched Digital Network, Ke Huang

Doctoral Dissertations

This PhD dissertation consists of two major parts: collaborative haptic interaction (CHI) and bilateral teleoperation over the Internet. For the CHI, we propose a novel hybrid peer-to-peer (P2P) architecture including the shared virtual environment (SVE) simulation, coupling between the haptic device and VE, and P2P synchronization control among all VE copies. This framework guarantees the interaction stability for all users with general unreliable packet-switched communication network which is the most challenging problem for CHI control framework design. This is achieved by enforcing our novel \emph{passivity condition} which fully considers time-varying non-uniform communication delays, random packet loss/swapping/duplication for each communication channel. …

Parametric Instability Investigation And Stability Based Design For Transmission Systems Containing Face-Gear Drives, Meng Peng

Doctoral Dissertations

The objective of this dissertation is to provide a novel design methodology for face-gear transmissions based on system stability - a dynamics viewpoint. The structural dynamics models of transverse and torsional vibrations are developed for face-gear drives with spur pinions to investigate the parametric instability behavior in great depth. The unique face-gear meshing kinematics and the fluctuation of mesh stiffness due to a nonunity contact-ratio are considered in these models. Since the system is periodically timevarying, Floquet theory is utilized to solve the Mathieu-Hill system equations and determine the system stability numerically. To avoid complex numerical computations, Treglod’s approximation is …

Measurement Of Power-Law Creep Parameters By Instrumented Indentation Methods, Caijun Su

Doctoral Dissertations

New experimental methods have been developed to measure the uniaxial power-law creep parameters α [alpha] and n in the relation έ[epsilon dot]=α[alpha]σⁿ[sigma] (έ [epsilon dot] is the creep strain rate and σ [sigma] is the creep stress) from the load, time, displacement and stiffness data recorded during an instrumented indentation experiment performed with a conical or pyramidal indenter. The methods are based on an analysis of Bower et al., which relates the indentation creep rate to the uniaxial creep parameters based on simple assumptions about the constitutive behavior (Bower et al., 1993 …

Nonlinear Vibration Control And Limit-Cycle Analysis Of Rotor/Autobalancer Systems Equipped With Hydrodynamic And Active Magnetic Bearing Supports, Daeyi Jung

Doctoral Dissertations

In recent years, there has been much interest in the use of automatic balancing devices (ABDs) in rotating machinery. Autobalancers consists of several freely moving eccentric balancing masses mounted on the rotor, which, at certain operating speeds, act to cancel rotor imbalance. This “automatic balancing” phenomena occurs as a result of nonlinear dynamic interactions between the balancer and rotor wherein the balancer masses naturally synchronize with the rotor with appropriate phase to cancel the imbalance. However, due to inherent nonlinearity of the autobalancer, the potential for other undesirable non-synchronous limit-cycle behavior exists. In such situations, the balancer masses do not …

Vision-Based Robot Control In The Context Of Human-Machine Interactions, Andrzej Nycz

Doctoral Dissertations

This research has explored motion control based on visual servoing – in the context of complex human-machine interactions and operations in realistic environments. Two classes of intelligent robotic systems were studied in this context: operator assistance with a high dexterity telerobotic manipulator performing remote tooling-centric tasks, and a bio-robot for X-ray imaging of lower extremity human skeletal joints during natural walking. The combination of human-machine interactions and practical application scenarios has led to the following fundamental contributions: 1) exploration and evaluation of a new concept of acquiring fluoroscope images of musculoskeletal features of interest during natural human motion, 2) creation …

The Search For An Optimal Means Of Determining The Minmax Control Parameter Using Sensitivity Analysis, John Teye Brown

Doctoral Dissertations

The use of computational methods for design and simulation of control systems allows for a cost-effective trial and error approach. In this work, we are concerned with the robust, real-time control of physical systems whose state space is infinite-dimensional. Such systems are known as Distributed Parameter Systems (DPS). A body whose state is heterogeneous is a distributed parameter. In particular, this work focuses on DPS systems that are governed by linear Partial Differential Equations, such as the heat equation. We specifically focus on the MinMax controller, which is regarded as being a very robust controller. The mathematical formulation of the …

Mathematical Modeling Of Pipeline Features For Robotic Inspection, Yang Gao

Doctoral Dissertations

Underground pipeline systems play an indispensable role in transporting liquids in both developed and developing countries. The associated social and economic cost to repair a pipe upon abrupt failure is often unacceptable. Regular inspection is a preventative action that aims to monitor pipe conditions, catch abnormalities and reduce the chance of undesirable surprises. Robots with CCTV video cameras have been used for decades to inspect pipelines, yielding only qualitative information. It is becoming necessary and preferable for municipalities, project managers and engineers to also quantify the 3-D geometry of underground pipe networks. Existing robots equipped specialized hardware and software algorithms …

Manufacturing And Characterization Of Soy-Based Polyurethane Composites, Rama Bhadra Raju Vuppalapati

Doctoral Dissertations

"The major cost drivers for composites are raw materials and manufacturing process. Automated manufacturing processes like pultrusion and low cost bio-based raw materials can significantly lower the cost of composites. Polyurethane (PU) resin systems are being introduced in the pultrusion industry as they have higher performance characteristics and manufacturing feasibility when compared to conventional resin systems such as polyester and vinyl ester. PU resin systems are generally characterized as aromatic and aliphatic. Aliphatic PU has lower mechanical properties than the aromatic resin system due to its chemical structure. Nano materials can be used to increase the mechanical properties of aliphatic …

The Risk Mitigation Strategy Taxonomy And Generated Risk Event Effect Neutralization Method, Daniel A. Krus

Doctoral Dissertations

"In the design of new products and systems, the mitigation of potential failures is very important. The sooner in a product's design mitigation can be performed, the lower the cost and easier to implement those mitigations become. However, currently, most mitigations strategies rely on the expertise of the engineers designing a product, and while models and for failure modes do exist to help, there are no guidelines for performing product changes to reduce risk. To help alleviate this, the risk mitigation strategy taxonomy is created from an empirical collection of mitigation strategies used in industry for failure mitigation, creating a …