Engineering Commons^™

Parameter Estimation For Mechanical Systems Via An Explicit Representation Of Uncertainty, Emmanuel Blanchard, Adrian Sandu, Corina Sandu

Emmanuel Blanchard

Purpose – The purpose of this paper is to propose a new computational approach for parameter estimation in the Bayesian framework. A posteriori probability density functions are obtained using the polynomial chaos theory for propagating uncertainties through system dynamics. The new method has the advantage of being able to deal with large parametric uncertainties, non-Gaussian probability densities and nonlinear dynamics. Design/methodology/approach – The maximum likelihood estimates are obtained by minimizing a cost function derived from the Bayesian theorem. Direct stochastic collocation is used as a less computationally expensive alternative to the traditional Galerkin approach to propagate the uncertainties through the …

Structural Applications Of Metal Foams Considering Material And Geometrical Uncertainty, Mohammadreza Moradi

Open Access Dissertations

Metal foam is a relatively new and potentially revolutionary material that allows for components to be replaced with elements capable of large energy dissipation, or components to be stiffened with elements which will generate significant supplementary energy dissipation when buckling occurs. Metal foams provide a means to explore reconfiguring steel structures to mitigate cross-section buckling in many cases and dramatically increase energy dissipation in all cases. The microstructure of metal foams consists of solid and void phases. These voids have random shape and size. Therefore, randomness ,which is introduced into metal foams during the manufacturing processes, creating more uncertainty in …

Materials For Presentation: Water Banks: Voluntary And Flexible Water Supplies For The Colorado River's Uncertain Future [Outline], Robert Wigington

Navigating the Future of the Colorado River (Martz Summer Conference, June 8-10)

4 pages.

"Robert Wigington, The Nature Conservancy"

Adaptive Decision Support For Structured Organizations: A Case For Orgpomdps, Pradeep Reddy Varakantham, Nathan Schurr, Alan Carlin, Christopher Amato

Research Collection School Of Computing and Information Systems

In today's world, organizations are faced with increasingly large and complex problems that require decision-making under uncertainty. Current methods for optimizing such decisions fall short of handling the problem scale and time constraints. We argue that this is due to existing methods not exploiting the inherent structure of the organizations which solve these problems. We propose a new model called the OrgPOMDP (Organizational POMDP), which is based on the partially observable Markov decision process (POMDP). This new model combines two powerful representations for modeling large scale problems: hierarchical modeling and factored representations. In this paper we make three key contributions: …

Distributed Model Shaping For Scaling To Decentralized Pomdps With Hundreds Of Agents, Prasanna Velagapudi, Pradeep Reddy Varakantham, Katia Sycara, Paul Scerri

Research Collection School Of Computing and Information Systems

The use of distributed POMDPs for cooperative teams has been severely limited by the incredibly large joint policy- space that results from combining the policy-spaces of the individual agents. However, much of the computational cost of exploring the entire joint policy space can be avoided by observing that in many domains important interactions between agents occur in a relatively small set of scenarios, previously defined as coordination locales (CLs) [11]. Moreover, even when numerous interactions might occur, given a set of individual policies there are relatively few actual interactions. Exploiting this observation and building on an existing model shaping algorithm, …

Decentralized Decision Support For An Agent Population In Dynamic And Uncertain Domains, Pradeep Reddy Varakantham, Shih-Fen Cheng, Thi Duong Nguyen

Research Collection School Of Computing and Information Systems

This research is motivated by problems in urban transportation and labor mobility, where the agent flow is dynamic, non-deterministic and on a large scale. In such domains, even though the individual agents do not have an identity of their own and do not explicitly impact other agents, they have implicit interactions with other agents. While there has been much research in handling such implicit effects, it has primarily assumed controlled movements of agents in static environments. We address the issue of decision support for individual agents having involuntary movements in dynamic environments . For instance, in a taxi fleet serving …

Automatic Particle Image Velocimetry Uncertainty Quantification, Benjamin H. Timmins

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The uncertainty of any measurement is the interval in which one believes the actual error lies. Particle Image Velocimetry (PIV) measurement error depends on the PIV algorithm used, a wide range of user inputs, flow characteristics, and the experimental setup. Since these factors vary in time and space, they lead to nonuniform error throughout the flow field. As such, a universal PIV uncertainty estimate is not adequate and can be misleading. This is of particular interest when PIV data are used for comparison with computational or experimental data.

A method to estimate the uncertainty due to the PIV calculation of …

The Shifting Terrain Of Risk And Uncertainty On The Liability Insurance Field, Tom Baker

All Faculty Scholarship

Recent sociological and historical work suggests that insurance risks often are not reliably calculable, except in hindsight. Insurance is “an uncertain business,” characterized by competition for premiums that pushes insurers into the unknown. This essay takes some preliminary steps that extend this insight into the liability insurance field. The essay first provides a simple quantitative comparison of U.S. property and liability insurance premiums over the last sixty years, setting the stage to make three points: (1) liability insurance premiums have grown at a similar rate as property insurance premiums and GDP over this period, providing yet another piece of evidence …

Emergy As A Life Cycle Impact Assessment Indicator A Gold Mining Case Study, Wesley W. Ingwesen

United States Environmental Protection Agency: Staff Publications

Founded in thermodynamics and systems ecology, emergy evaluation is a method to associate a product with its dependencies on all upstream environmental and resource flows using a common unit of energy. Emergy is thus proposed as an indicator of aggregate resource use for life cycle assessment (LCA). An LCA of gold mining, based on an original life cycle inventory of a large gold mine in Peru, is used to demonstrate how emergy can be incorporated as an impact indicator into a process-based LCA model. The results demonstrate the usefulness of emergy in the LCA context. The adaptation of emergy evaluation, …

Long Term Resource Planning For Electric Power Systems Under Uncertainty, Sarah M. Ryan, James D. Mccalley, David L. Woodruff

Sarah M. Ryan

Electric power systems are subject to uncertainties of many types and at many levels. In addition to the uncertain fuel prices, demand growth, and equipment outages included in traditional models, current trends portend increasing uncertainty due to such factors as the growth in generation from renewable sources which may be intermittent, the possibility of regulations to control carbon emissions, and the increasing price responsiveness of demand encouraged by smart grid technologies. This paper begins by discussing issues that confront electric system planners and explains the requirements for useful tools. We continue with a description of academic and commercial planning models …

An Overview Of The Low-Cost Carrier Model In The Russian Market, Tamilla Curtis, Dawna L. Rhoades

Publications

This study provides an overview of the low-cost carrier (LCC) model in the Russian market. The LCC model seeks to achieve a competitive advantage through the reduction of operating costs, below the traditional airline model. Since Russia is an emerging and developing economy, airlines face a high level of uncertainty. Despite the fact that the Russian aviation market is dominated by a few large carriers, Russian lowcost airlines such as SkyExpress and Avianova have been growing rapidly since starting their operations. While Russian LCCs follow the traditional LCC model, some differences are apparent as a result of the specifics of …