Organizational Unit:

George W. Woodruff School of Mechanical Engineering

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https://hdl.handle.net/1853/70728

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College of Engineering

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Advanced Mechanical Bipedal Experimental Robotics Lab

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Computational Reactor and Medical Physics Laboratory

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Cryo Lab

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Environmentally Conscious Design and Manufacturing

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Fusion Research Center

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https://finding-aids.library.gatech.edu/agents/corporate_entities/120

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Publication Search Results

Now showing 1 - 10 of 31

Test-Based Stabilizing Control of COVID-19 Transmission

(Georgia Institute of Technology, 2020-03) Sadegh, Nader ; Sadegh, Payman

The COVID-19 pandemic has confronted the world with a health and an economic crisis not seen since 1918. Appearing first in Wuhan, China, in late 2019, the virus has now spread to over 150 countries. At the time of this writing, hundreds of thousands have already been infected and tens of thousands have died as a result. Given the virus' high degree of contagion, a question that occupies everyone's mind is whether a strategy could be conceived to suppress or at least substantially slow the spread of the virus until a vaccine becomes widely available. Using an extended SEIR model with COVID-19's available epidemiological parameters, this paper studies a feedback control solution to stabilize the virus' transmission dynamic based on a test-and-isolate strategy. The derived theoretical results combined with simulation analyses are used to answer key questions around testing strategies that will be required for suppression of the virus.
Non-Diffusive Transport in the Tokamak Edge Pedestal

(Georgia Institute of Technology, 2012) Stacey, Weston M. ; Groebner, Rich J. ; Evans, T. E.

There are (at least) two classical mechanisms for non-diffusive transport in the edge plasma: i) particle “pinch” velocities due to forces such as VxB, and Er; and ii) outward drifts due to ion-orbit loss and X-transport. A theoretical development for the treatment of these non-diffusive transport mechanisms within the context of fluid theory is assembled and applied to several DIII-D discharges in order to investigate the importance of these non-diffusive transport mechanisms in the edge pedestal. Several interesting insights emerge from this investigation.
Biodynamic Feedthrough Compensation and Experimental Results Using a Backhoe

(Georgia Institute of Technology, 2011-03) Heather C. Humphreys ; Book, Wayne J. ; Huggins, James D.

In some operator-controlled machines, motion of the controlled machine excites motion of the human operator, which is fed back into the control device, causing unwanted input and sometimes instability; this phenomenon is termed biodynamic feedthrough. In operation of backhoes and excavators, biodynamic feedthrough causes control performance degradation. This work utilizes a previously developed advanced backhoe user interface which uses coordinated position control with haptic feedback, using a SensAble Omni six degree-of-freedom haptic display device. Backhoe user interface designers and our own experiments indicate that biodynamic feedthrough produces undesirable oscillations in output with conventionally controlled backhoes and excavators, and it is even more of a problem with this advanced user interface. Results indicate that the coordinated control provides more intuitive operation, and the haptic feedback relays meaningful information back to the user. But the biodynamic feedthrough problem must be overcome in order for this improved interface to be applicable. For the purposes of reducing model complexity, the system is limited to a single degree of freedom, using fore-aft motion only. This paper investigates what types of controller-based methods of compensation for biodynamic feedthrough are most effective in backhoe operation, and how they can be implemented and tested with human operators.
Evolution of the H-mode edge pedestal between ELMs

(Georgia Institute of Technology, 2010-08) Stacey, Weston M. ; Groebner, Rich J.

The evolution of edge pedestal parameters between edge-localized modes (ELMs) is analyzed for an H-mode DIII-D [J Luxon, Nucl. Fusion 42, 612 (2002)] discharge. Experimental data are averaged over the same sub-intervals between successive ELMs to develop data that characterize the evolution of density, temperature, rotation velocities, etc. over the interval between ELMs. These data are interpreted within the context of the constraints imposed by particle, momentum and energy balance, in particular in terms of the pinch-diffusion relation for radial particle flux that is required by momentum balance. It is found that in the edge pedestal there is an increase of both inward (pinch) electromagnetic and outward (diffusive) pressure gradient forces over the inter-ELM interval.
Designing Platforms for Customizable Produces and Processes in Markets of Non-Uniform Demand

(Georgia Institute of Technology, 2007) Williams, Christopher Bryant ; Rosen, David W. ; Mistree, Farrokh ; Allen, Janet K.

The foremost difficulty in making the transition to mass customization is how to offer product variety affordably. The answer to this quandary lies in the successful management of modularity and commonality in the development of products and their production processes. While several platform design techniques have emerged as a means to offer modularity and commonality, they are limited by an inability to handle multiple modes of offering variety for multiple design specifications. The Product Platform Constructal Theory Method (PPCTM) is a technique that enables a designer to develop platforms for customizable products while handling issues of multiple levels of commonality, multiple product specifications, and the inherent trade-offs between platform extent and performance. The method is limited, however, by its inability to handle multiple design objectives and its reliance on the assumption that demand in the market is uniform for each product variant. The authors address these limitations in this paper by infusing the utility-based compromise Decision Support Problem and demand modeling techniques. The authors further augment the PPCTM by extending it use to a new domain: the design of process parameter platforms. The augmented approach is illustrated through a tutorial example: the design of a product and a process parameter platform for the realization of a line of customizable cantilever beams.
Validating Behavioral Models For Reuse

(Georgia Institute of Technology, 2007) Paredis, Christiaan J. J. ; Malak, Richard J., Jr.

When using a model to predict the behavior of a physical system of interest, engineers must be confident that, under the conditions of interest, the model is an adequate representation of the system. The process of building this confidence is called model validation. It requires that engineers have knowledge about the system and conditions of interest, properties of the model and their own tolerance for uncertainty in the predictions. To reduce time and costs, engineers often reuse preexisting models that other engineers have developed. However, if the user lacks critical parts of this knowledge, model validation can be as time consuming and costly as developing a similar model from scratch. In this article, we describe a general process for performing model validation for reused behavioral models that overcomes this problem by relying on the formalization and exchange of knowledge. We identify the critical elements of this knowledge, discuss how to represent it and demonstrate the overall process on a simple engineering example.
Multi-Attribute Utility Analysis in Set-Based Conceptual Design

(Georgia Institute of Technology, 2007) Paredis, Christiaan J. J. ; Malak, Richard J., Jr. ; Aughenbaugh, Jason Matthew

During conceptual design, engineers deal with incomplete product descriptions called design concepts. Engineers must compare these concepts in order to move towards the more desirable designs. However, comparisons are difficult because a single concept associates with numerous possible final design specifications, and any meaningful comparison of concepts must consider this range of possibilities. Consequently, the performance of a concept can only be characterized imprecisely. While standard multi-attribute utility theory is an accepted framework for making preference-based decisions between precisely characterized alternatives, it does not directly accommodate the analysis of imprecisely characterized alternatives. By extending uncertainty representations to model imprecision explicitly, it is possible to apply the principles of utility theory to such problems. However, this can lead to situations of indeterminacy, meaning that the decision maker is unable to identify a single concept as the most preferred. Under a set-based perspective and approach to design, a designer can work towards a single solution systematically despite indecision arising from imprecise characterizations of design concepts. Existing work in set-based design primarily focuses on feasibility conditions and single-attribute objectives, which are insufficient for most design problems. In this article, we combine the framework of multi-attribute utility theory, the perspective of set-based design, and the explicit mathematical representation of imprecision into a single approach to conceptual design. Each of the component theories are discussed, and their combined application developed. The approach is illustrated using the conceptual design of a fixed-ratio power transmission as an example. Additionally, important directions for future research are identified, with a particular focus on the process of modeling abstract design concepts.
Manufacturing Cellular Materials Via Three-Dimensional Printing of Spray-dried Metal Oxide Ceramic Powder

(Georgia Institute of Technology, 2007) Rosen, David W. ; Williams, Christopher Bryant

Cellular materials, metallic bodies with gaseous voids, are a promising class of materials that offer high strength accompanied by a relatively low mass. Unfortunately, existing manufacturing techniques constrain a designer to a predetermined part mesostructure, material type, and macrostructure. In this paper, the authors document their design rationale for the selection of the Three-Dimensional Printing (3DP) additive manufacturing process as a means to fabricate metallic cellular materials. This is achieved by selectively printing a solvent into a bed of spray-dried metal oxide ceramic powder. The resulting green part undergoes reduction and sintering post-production processes in order to chemically convert it to metal.
Higher Order Approximations of the TEP Method for Neutral Particle Transport in Edge Plasmas

(Georgia Institute of Technology, 2006) Stacey, Weston M. ; Zhang, Dingkang ; Mandrekas, John

Higher order approximations, which take into account the effects of angular anisotropy, spatial non-uniformity and energy dependence of the distribution of neutral particles, have been developed and implemented to extend the range of validity of the Transmission and Escape Probabilities (TEP) method for the calculation of neutral particle transport in plasmas. Comparisons with Monte Carlo calculations of model test problems and DIII-D L- and H- mode discharges show that these new extensions significantly improve the accuracy and extend the range of validity of the TEP methodology.
Empowering Students to Learn How to Learn: Mass Customization of Graduate Engineering Design Course

(Georgia Institute of Technology, 2006) Mistree, Farrokh ; Williams, Christopher Bryant

ME 6101: Engineering Design is a graduate level course offered through the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. To empower students to learn how to learn, the orchestrators of ME 6101 strive to offer an individual course in a group setting. In this paper, the techniques utilized to create this type of learning environment are described in terms parallel to those of the mass customization paradigm. Excerpts from students' essays are presented as anecdotal evidence that the concerted use of these methods aids and empowers students both in the internalization of course content and the development of critical analysis, abstraction, and synthesizing skills that will help them become lifelong learners.