Factor Graph Modeling of Rigid‐body Dynamics for Localization,Mapping, and Parameter Estimation of a Spinning Object in Space

This paper presents a new approach for solving the simultaneous localization and mapping problem for inspecting an unknown and uncooperative object that is spinning about an arbitrary axis in space. This approach probabilistically models the six degree‐of‐freedom rigid‐body dynamics in a factor graph formulation. Using the incremental smoothing and mapping system, this method estimates a feature‐based map of the target object, as well as this object's position, orientation, linear velocity, angular velocity, center of mass, principal axes, and ratios of inertia. This solves an important problem for spacecraft proximity operations. Additionally, it provides a generic framework for incorporating rigid‐body dynamics that may be applied to a number of other terrestrial‐based applications. To evaluate this approach, the Synchronized Position Hold Engage Reorient Experimental Satellites (SPHERES) were used as a testbed within the microgravity environment of the International Space Station. The SPHERES satellites, using body‐mounted stereo cameras, captured a dataset of a target object that was spinning at ten rotations per minute about its unstable, intermediate axis. This dataset was used to experimentally evaluate the approach described in this paper, and it showed that it was able to estimate a geometric map and the position, orientation, linear and angular velocities, center of mass, and ratios of inertia of the target object.     

Integrating scientific modeling and supporting dynamic hazard management with a GeoAgent-based representation of human–environment interactions: A drought example in Central Pennsylvania, USA

Recent natural disasters indicate that modern technologies for environmental monitoring, modeling, and forecasting are not well integrated with cross-level social responses in many hazard-management systems. This research addresses this problem through a Java-based multi-agent prototype system, GeoAgent-based Knowledge System (GeoAgentKS). This system allows: (1) computer representation of institutional regulations and behavioral rules used by multiple social institutions and individuals in cross-level human–environment interactions, (2) integration of this representation with scientific modeling of dynamic hazard development, and (3) application of automated reasoning that suggests to users the appropriate actions for supporting cooperative social responses. This paper demonstrates the software architecture of GeoAgentKS and presents such an integrated approach by modeling the drought management processes in Central Pennsylvania, USA. The results show that it is possible to use GeoAgentKS to represent multilevel human–environment interactions and to use those interactions as input to decision making in hazard management.     

Grid Resource Availability Prediction-Based Scheduling and Task Replication

The frequent and volatile unavailability of volunteer-based Grid computing resources challenges Grid schedulers to make effective job placements. The manner in which host resources become unavailable will have different effects on different jobs, depending on their runtime and their ability to be checkpointed or replicated. A multi-state availability model can help improve scheduling performance by capturing the various ways a resource may be available or unavailable to the Grid. This paper uses a multi-state model and analyzes a machine availability trace in terms of that model. Several prediction techniques then forecast resource transitions into the model’s states. We analyze the accuracy of our predictors, which outperform existing approaches. We also propose and study several classes of schedulers that utilize the predictions, and a method for combining scheduling factors. We characterize the inherent tradeoff between job makespan and the number of evictions due to failure, and demonstrate how our schedulers can navigate this tradeoff under various scenarios. Lastly, we propose job replication techniques, which our schedulers utilize to replicate those jobs that are most likely to fail. Our replication strategies outperform others, as measured by improved makespan and fewer redundant operations. In particular, we define a new metric for replication efficiency, and demonstrate that our multi-state availability predictor can provide information that allows our schedulers to be more efficient than others that blindly replicate all jobs or some static percentage of jobs.     

Boundary Spanning and Engineering: A Qualitative Systematic Review

Background

Engineers are often expected to span organizational, cultural, stakeholder, geographic, temporal, and other boundaries. Yet, few studies on boundary spanning have appeared in the engineering education literature, suggesting the need for improved theoretical and conceptual foundations to guide empirical studies of boundary spanning in engineering.

Purpose

To develop a more comprehensive understanding of boundary spanning, this study addresses five research questions: (a) What types of boundaries have been identified as topics of interest? (b) How are boundary spanners and boundary spanning defined? (c) What types of activities and behaviors comprise or have been linked to boundary spanning? (d) What individual competencies and characteristics have been proposed or studied as important for boundary spanning? and (e) What boundary spanning themes are most prominent in studies of engineers and other technical professionals?

Scope/Method

Using a qualitative systematic review process, we identified and analyzed 72 scholarly papers from multiple disciplines. Multiple reviewers coded each paper using a hybrid deductive‐inductive content analysis process to identify key themes related to boundary spanning.

Conclusions

The analysis resulted in a framework consisting of six boundary types, three types of roles and definitions, and five types of activities. Discussion of boundary spanning competencies was limited in the collected works, and only seven papers exclusively focused on engineers. We conclude by proposing boundary spanning as an important meta‐attribute for engineers and a promising lens for investigating engineering practice. We also relate our findings to the engineering education literature and suggest directions for future research.     

The privileged sensing framework: A principled approach to improved human-autonomy integration

ABSTRACT

A primary goal for human-autonomy integration (HAI) is to balance the strengths of human and autonomy in order to achieve performance objectives more efficiently and robustly than either the human or autonomous agents would independently. This paper proposes the Privileged Sensing Framework (PSF) as a novel approach to HAI. This approach is based on the concept of dynamically ‘privileging’ information during the process of integration by dynamically bestowing special rights based on the characteristics of each individual agent, the task context, and the performance goals. The proposed framework is tested through a series of simulation experiments that provide a clear demonstration of increased accuracy and throughput of human-autonomy performance. These proof-of-concept simulations provide initial evidence of the utility of the PSF. Continued development of this approach has the potential to revolutionise capabilities of multi-agent cooperative teams across a broad range of applications.     

Assessing the performance of normal-based and REML-based confidence intervals for the intraclass correlation coefficient

Using normal distribution assumptions, one can obtain confidence intervals for variance components in a variety of applications. A normal-based interval, which has exact coverage probability under normality, is usually constructed from a pivot so that the endpoints of the interval depend on the data as well as the distribution of the pivotal quantity. Alternatively, one can employ a point estimation technique to form a large-sample (or approximate) confidence interval. A commonly used approach to estimate variance components is the restricted maximum likelihood (REML) method. The endpoints of a REML-based confidence interval depend on the data and the asymptotic distribution of the REML estimator. In this paper, simulation studies are conducted to evaluate the performance of the normal-based and the REML-based intervals for the intraclass correlation coefficient under non-normal distribution assumptions. Simulated coverage probabilities and expected lengths provide guidance as to which interval procedure is favored for a particular scenario. Estimating the kurtosis of the underlying distribution plays a central role in implementing the REML-based procedure. An empirical example is given to illustrate the usefulness of the REML-based confidence intervals under non-normality.     

Optimising Reliability: Portfolio Modeling of Contract Types for Retail Water Providers

This paper considers the retail water provider’s purchasing decision of a portfolio of permanent contracts from wholesalers with multiple volatile water sources. We consider the reliability of two contract types: (1) fixed annual quantities, and (2) an inflow harvest function with storage. Our four-reservoir case in Sydney (Australia) has cross-correlated inflow data. To accommodate multi-reservoir cross-correlation we adapt Portfolio Theory from finance to lognormal reservoir inflows, re-framing traditional storage theory from the wholesaler’s optimal operating policy to the retailer’s optimal purchasing policy. We find that Reliability improves with access to a source pool (cf. fixed quantities from separate sources), demonstrating the ‘insurance effect’, and the portfolio that minimises lognormal variance also minimises harvest (and thus environmental impact). Reform direction in Australian (and other international) water markets is towards multi-provider vertical disintegration, which may reduce pool opportunities and negate the insurance effect. We consider diminishing reliability returns as reservoir harvesting increases, and conclude a retail portfolio of permanent contracts from reservoirs, plus short-term contracts from alternative sources (either independently or negatively cross-correlated) efficiently secures high reliability. The challenge in incomplete water markets remains in encouraging and sustaining supply diversification that may only be needed aperiodically during extreme droughts.     

The changing face of bullying: An empirical comparison between traditional and internet bullying and victimization

Electronic aggression, or cyberbullying, is a relatively new phenomenon. As such, consistency in how the construct is defined and operationalized has not yet been achieved, inhibiting a thorough understanding of the construct and how it relates to developmental outcomes. In a series of two studies, exploratory and confirmatory factor analyses (EFAs and CFAs respectively) were used to examine whether electronic aggression can be measured using items similar to that used for measuring traditional bullying, and whether adolescents respond to questions about electronic aggression in the same way they do for traditional bullying. For Study I (n = 17 551; 49% female), adolescents in grades 8-12 were asked to what extent they had experience with physical, verbal, social, and cyberbullying as a bully and victim. EFA and CFA results revealed that adolescents distinguished between the roles they play (bully, victim) in a bullying situation but not forms of bullying (physical, verbal, social, cyber). To examine this further, Study II (n = 733; 62% female), asked adolescents between the ages of 11 and 18 to respond to questions about their experience sending (bully), receiving (victim), and/or seeing (witness) specific online aggressive acts. EFA and CFA results revealed that adolescents did not differentiate between bullies, victims, and witnesses; rather, they made distinctions among the methods used for the aggressive act (i.e. sending mean messages or posting embarrassing pictures). In general, it appears that adolescents differentiated themselves as individuals who participated in specific mode of online aggression, rather than as individuals who played a particular role in online aggression. This distinction is discussed in terms of policy and educational implications.     

Modelling the activity of I in the primary coolant of a CANDU reactor

A mathematical treatment has been developed to describe the activity levels of ¹²⁹I as a function of time in the primary heat transport system during constant power operation and for a reactor shutdown situation. The model accounts for a release of fission-product iodine from defective fuel rods and tramp uranium contamination on in-core surfaces. The physical transport constants of the model are derived from a coolant activity analysis of the short-lived radioiodine species. An estimate of 3×10⁻⁹ has been determined for the coolant activity ratio of ¹²⁹I/¹³¹I in a CANDU Nuclear Generating Station (NGS), which is in reasonable agreement with that observed in the primary coolant and for plant test resin columns from pressurized and boiling water reactor plants. The model has been further applied to a CANDU NGS, by fitting it to the observed short-lived iodine and long-lived cesium data, to yield a coolant activity ratio of ∼2×10⁻⁸ for ¹²⁹I/¹³⁷Cs. This ratio can be used to estimate the levels of ¹²⁹I in reactor waste based on a measurement of the activity of ¹³⁷Cs.     

Reexamining the Vocabulary Spurt.

The authors asked whether there is evidence to support the existence of the vocabulary spurt, an increase in the rate of word learning that is thought to occur during the 2nd year of life. Using longitudinal data from 38 children, they modeled the rate of word learning with two functions, one with an inflection point (logistic), which would indicate a spurt, and one without an inflection point (quadratic). Comparing the fits of these two functions using likelihood ratios, they found that just 5 children had a better logistic fit, which indicated that these children underwent a spurt. The implications for theories of cognitive and language development are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)