Probabilistic Damage Characterization Using the Computationally-Efficient Bayesian Approach

This work presents a computationally-ecient approach for damage determination that quanti es uncertainty in the provided diagnosis. Given strain sensor data that are polluted with measurement errors, Bayesian inference is used to estimate the location, size, and orientation of damage. This approach uses Bayes' Theorem to combine any prior knowledge an analyst may have about the nature of the damage with information provided implicitly by the strain sensor data to form a posterior probability distribution over possible damage states. The unknown damage parameters are then estimated based on samples drawn numerically from this distribution using a Markov Chain Monte Carlo (MCMC) sampling algorithm. Several modi cations are made to the traditional Bayesian inference approach to provide signi cant computational speedup. First, an ecient surrogate model is constructed using sparse grid interpolation to replace a costly nite element model that must otherwise be evaluated for each sample drawn with MCMC. Next, the standard Bayesian posterior distribution is modi ed using a weighted likelihood formulation, which is shown to improve the convergence of the sampling process. Finally, a robust MCMC algorithm, Delayed Rejection Adaptive Metropolis (DRAM), is adopted to sample the probability distribution more eciently. Numerical examples demonstrate that the proposed framework e ectively provides damage estimates with uncertainty quanti cation and can yield orders of magnitude speedup over standard Bayesian approaches

Mediated Communication and Customer Service Experiences: Psychological and Demographic Predictors of User Evaluations in the United States

People around the world who seek to interact with large organisations increasingly find they must do so via mediated and automated communication. Organisations often deploy both mediated and automated platforms, such as instant messaging and interactive voice response systems (IVRs), for efficiency and cost-savings. Customer and client responses to these systems range from delight to frustration. To better understand the factors affecting people's satisfaction with these systems, we conducted a representative U.S. national survey (N = 1321). We found that people overwhelmingly like and trust in-person customer service compared to mediated and automated modalities. As to demographic attitude predictors, age was important (older respondents liked mediated systems less), but income and education were not strong attitude predictors. For personality variables, innovativeness was positively associated with mediated system satisfaction. However, communication apprehensiveness, which we expected to be related to satisfaction, was not. We conclude by discussing implications for the burgeoning field of human-machine communication, as well as social policy, equity, and the pullulating digital services divide

Paper Session III-A - Next Generation Reusable Launch Systems Site Selection Trade Study: An Application of the Analytic Hierarchy Process

This paper focuses on site selection trade studies associated with Next Generation Reusable Launch Vehicle concepts. During site selection trade studies the need to utilize a decision making tool enabling tradeoffs between competing objectives while minimizing intuitive bias was recognized. In order to meet established goals of the next generation reusable launch vehicle concepts, a comprehensive site selection trade study must be performed. Estimates for both non-recurring and recurring costs associated with each candidate site must be evaluated. The systems’ operations concept, environmental constraints, logistics, range support, and weather are other important factors which must also be considered. Based on this, the Analytic Hierarchy Process (AHP) was implemented, allowing for systematic evaluation and measurement of each of the identified criteria in the site selection process. AHP is a multi-criterion decision support methodology allowing study participants (engineers and program management) to deal consistently with comparisons between both tangible and intangible criteria. Using this tool, participants in the site selection process can integrate their collective judgment, experience and understanding concerning the relevant importance of identified criteria as they relate to one another. The resulting process is organized in a logical hierarchical structure which can be easily tested for sensitivities to changes in assumptions and judgments

Paper Session I-A - Space Shuttle to Reusable Launch Vehicle

The National Space Transportation Policy establishes national policy, guidelines, and implementing actions for the conduct of National space transportation programs that will sustain and revitalize U.S. space transportation capabilities... . The direction to the National Aeronautics and Space Administration (NASA) is to provide for the improvement of the Space Shuttle system focusing on reliability, safety, and cost effectiveness. as well as be the lead agency for technology development and demonstration for next generation reusable space transportation systems, such as the single-stage-to-orbit concept. With this vision, NASA has initiated Cooperative Agreement Notices between NASA and the private sector for X-33 (Reusable Launch Vehicle-Advanced Technology Demonstrator) and X-34 (Reusable Launch Vehicle-Small Reusable Booster) which would provide insight to a decision by December 1996 to proceed with sub-scale flight demonstration to prove the single-stage-to-orbit (SSTO) concept. This paper deals with operational issues which must be dealt with in order to achieve SSTO goals of reliable low cost space transportation and order of magnitude reductions in operating costs

Personal Power and Agency When Dealing with Interactive Voice Response Systems and Alternative Modalities

In summer 2015, we conducted an exploratory study of how people in the U.S. use and respond to robot-like systems in order to achieve their needs through mediated customer service interfaces. To understand this process, we carried out three focus groups sessions along with 50 in-depth interviews. Strikingly we found that people perceive (correctly or not) that interactive voice response customer service technology is set up to deter them from pursuing further contact. And yet, for the most part, people were unwilling to simply give up on the goals that motivated their initial contact. Consequently, they had to innovate ways to communicate with the automated systems that essentially serve as gatekeepers to their desired ends. These results have implications for communication theory and system design, especially since these systems will be increasingly presented to consumers as social media affordances evolve

A Volcanic Origin for Sinuous and Branching Channels on Mars: Evidence from Hawaiian Analogs

Observations of sinuous and branching channels on planets have long driven a debate about their origin, fluvial or volcanic processes. In some cases planetary conditions rule out fluvial activity (e.g. the Moon, Venus, Mercury). However, the geology of Mars leads to suggestions that liquid water existed on the surface in the past. As a result, some sinuous and branching channels on Mars are cited as evidence of fluvial erosion. Evidence for a fluvial history often focuses on channel morphologies that are unique from a typical lava channel, for instance, a lack of detectable flow margins and levees, islands and terraces. Although these features are typical, they are not necessarily diagnostic of a fluvial system. We conducted field studies in Hawaii to characterize similar features in lava flows to better define which characteristics might be diagnostic of fluvial or volcanic processes. Our martian example is a channel system that originates in the Ascraeus Mons SW rift zone from a fissure. The channel extends for approx.300 km to the SE/E. The proximal channel displays multiple branches, islands, terraces, and has no detectable levees or margins. We conducted field work on the 1859 and 1907 Mauna Loa flows, and the Pohue Bay flow. The 51-km-long 1859 Flow originates from a fissure and is an example of a paired a a and pahoehoe lava flow. We collected DGPS data across a 500 m long island. Here, the channel diverted around a pre-existing obstruction in the channel, building vertical walls up to 9 m in height above the current channel floor. The complicated emplacement history along this channel section, including an initial a a stage partially covered by pahoehoe overflows, resulted in an appearance of terraced channel walls, no levees and diffuse flow margins. The 1907 Mauna Loa flow extends > 20 km from the SW rift zone. The distal flow formed an a a channel. However the proximal flow field comprises a sheet that experienced drainage and sagging of the crust following the eruption. The lateral margins of the proximal sheet, past which all lava flowed to feed the extensive channel, currently display a thickness of < 20 cm. Were this area covered by a dust layer, as is the Tharsis region on Mars, the margins would be difficult to identify. The Pohue Bay flow forms a lava tube. Open roof sections experienced episodes of overflow and spill out. In several places the resultant surface flows appear to have moved as sheet flows that inundated the preexisting meter scale features. Here the flows developed pathways around topographic highs, and in so doing accreted lava onto those features. The results are small islands within the multiple branched channels that display steep, sometimes overhanging walls. None of these features alone proves that the martian channel networks are the result of volcanic processes, but analog studies such as these are the first step towards identifying which morphologies are truly diagnostic of fluvial and volcanic channels