A component-based parallel infrastructure for the simulation of fluid–structure interaction

The Uintah computational framework is a component-based infrastructure, designed for highly parallel simulations of complex fluid–structure interaction problems. Uintah utilizes an abstract representation of parallel computation and communication to express data dependencies between multiple physics components. These features allow parallelism to be integrated between multiple components while maintaining overall scalability. Uintah provides mechanisms for load-balancing, data communication, data I/O, and checkpoint/restart. The underlying infrastructure is designed to accommodate a range of PDE solution methods. The primary techniques described here, are the material point method (MPM) for structural mechanics and a multi-material fluid mechanics capability. MPM employs a particle-based representation of solid materials that interact through a semi-structured background grid. We describe a scalable infrastructure for problems with large deformation, high strain rates, and complex material behavior. Uintah is a product of the University of Utah Center for Accidental Fires and Explosions (C-SAFE), a DOE-funded Center of Excellence. This approach has been used to simulate numerous complex problems, including the response of energetic devices subject to harsh environments such as hydrocarbon pool fires. This scenario involves a wide range of length and time scales including a relatively slow heating phase punctuated by pressurization and rupture of the device.     

The relational self revealed: Integrative conceptualization and implications for interpersonal life.

The authors offer a new, integrative conceptualization of the relational self based on a synthesis of recent approaches to the self and significant others. This conceptualization provides a sharper and fuller definition of the relational self than does any existing approach alone and a common framework to interpret findings from separate literatures. The authors then present 5 propositions and evidence to support the thesis that relational selves exert a pervasive influence on interpersonal life. Specifically, relational selves (a) shape a wide range of psychological processes and outcomes, (b) exert their influence automatically, (c) serve basic orientation and meaning functions, (d) provide continuity and context-specific variability in personality, and (e) carry implications for psychological well-being. Discussion focuses on remaining issues and implications for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of a shortened center for epidemiological studies depression scale for assessment of depression in rheumatoid arthritis.

Objective: The purpose was to develop a short-form version of the Center for Epidemiologic Studies Depression Scale (CES-D) for the identification of persons with major depressive disorder (MDD) within a population with rheumatoid arthritis (RA). Study Design: Data were analyzed from 337 persons with RA. Forty-six participants met the diagnostic criteria for MDD; 291 participants were classified in the non-MDD category (including 21 participants with dysthymia and 18 participants with minor depressive disorder). A short-form version of the CES-D was developed, and multiple cutoff scores were examined. Results: A cutoff score of ≥5 from a 9-item, short-form CES-D was found to be generally as efficient as the more commonly used full-scale cutoff score of ≥16 for classifying participants with MDD within an RA population. Although the shortened CES-D scale (cutoff score ≥5) was slightly more sensitive, it also exhibited slightly less specificity than the full-scale cutoff score of ≥16. Conclusion: The results suggest that a short-form CES-D can be used to screen for MDD within an RA sample with a degree of efficiency that is generally comparable to that of the full-scale instrument. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of stress on mothers' memory of a natural disaster.

The effects of stress on mothers' recall for a major hurricane were studied. Stress was objectively defined as low, moderate, or high according to the severity of home damage. This study of 96 mothers was conducted concurrently with L. E. Bahrick, J. F. Parker, R. Fivush, and M. Levitt (1998), allowing the authors to compare child and adult recall as a function of the same stressor. There was a quadratic relationship between storm severity and total recall for adults, similar to their children. Mothers' recall increased from low to moderate severity, but recall at moderate severity did not differ from high severity. These findings help clarify the effects of stress on the amount and type of information adults recall in retrospective accounts of naturalistic, temporally extended events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Reinforcement Learning Algorithm in Cooperative Multi-Robot Domains

Reinforcement learning has been widely applied to solve a diverse set of learning tasks, from board games to robot behaviours. In some of them, results have been very successful, but some tasks present several characteristics that make the application of reinforcement learning harder to define. One of these areas is multi-robot learning, which has two important problems. The first is credit assignment, or how to define the reinforcement signal to each robot belonging to a cooperative team depending on the results achieved by the whole team. The second one is working with large domains, where the amount of data can be large and different in each moment of a learning step. This paper studies both issues in a multi-robot environment, showing that introducing domain knowledge and machine learning algorithms can be combined to achieve successful cooperative behaviours.     

Perturbing and evaluating numerical programs without recompilation—the wonglediff way

wonglediff is a program that tests the sensitivity of arbitrary program executables or processes to changes that are introduced by a process that runs in parallel. On Unix and Linux kernels, wonglediff creates a supervisor process that runs applications and, on the fly, introduces desired changes to their process state. When execution terminates, it then summarizes the resulting changes in the output files. The technique employed has a variety of uses. This paper describes an implementation of wonglediff that checks the sensitivity of programs to random changes in the floating‐point rounding modes. It runs a program several times, ‘wongling’ it each time: randomly toggling the IEEE‐754 rounding mode of the program as it executes. By comparing the resulting output, one gets a poor man's numerical stability analysis for the program. Although the analysis does not give any kind of guarantee about a program's stability, it can reveal genuine instability, and it does serve as a particularly useful and revealing idiot light. In our implementation, differences among the output files from the program's multiple runs are summarized in a report. This report is in fact an HTML version of the output file, with inline mark‐up summarizing individual differences among the multiple instances. When viewed with a browser, the differences can be highlighted or rendered in many different ways. Copyright © 2004 John Wiley & Sons, Ltd.     

Frequency Domain Frequency Shift for Optimal Filtering of Cyclostationary Signals

Parker, G., Frequency Domain Frequency Shift for Optimal Filtering of Cyclostationary Signals, Digital Signal Processing12 (2002) 561–589Optimum reconstruction of corrupted cyclostationary signals is achieved using the filter class known as the frequency shift filter. This filter requires the received signal to be shifted by the frequencies of cyclostationarity of the signal and with a frequency domain implementation it will often be best to effect the frequency shifts directly in the frequency domain. This paper introduces techniques for exactly achieving these shifts as well as providing more computationally efficient approximate solutions.     

Design and analysis of a robust real-time engine control network

Increasing numbers of automotive control systems are being designed as distributed systems, with critical functions linked by electronic communications. This includes X-by-wire systems, which seek to replace mechanical or hydraulic linkages with electrical or communications links. These systems raise a number of new challenges: Safety is a function of the whole system rather than any one system feature. Thus, safety analysis and understanding must occur at the (complex) system level. A robust design process is essential to ensure that complex system issues and critical analysis occur at the right development stage and cover all appropriate parts of the system. This article provides a case study of a development project to show how these and other issues can be addressed. We describe the development of a communications network for a safety-related engine application that consists of a central electronic control unit (ECU) and a number of distributed actuators that are controlled via the network. We apply several techniques, such as hazard and scheduling analysis, to resolve safety and reliability issues     

Nonlinear adaptive filtering of stimulus artifact

Noninvasive measurements of somatosensory evoked potentials have both clinical and research applications. The electrical artifact which results from the stimulus is an interference which can distort the evoked signal, and introduce errors in response onset timing estimation. Given that this interference is synchronous with the evoked signal, it cannot be reduced by the conventional technique of ensemble averaging. The technique of adaptive noise cancelling has potential in this regard however, and has been used effectively in other similar problems. An adaptive noise cancelling filter which uses a neural network as the adaptive element is investigated in this application. The filter is implemented and performance determined in the cancelling of artifact for in vivo measurements on the median nerve. A technique of segmented neural network training is proposed in which the network is trained on that segment of the record time window which does not contain the evoked signal. The neural network is found to generalize well from this training to include the segment of the window containing the evoked signal. Both quantitative and qualitative measures show that significant stimulus artifact reduction is achieved.     

Children's attributions of intentions to an invisible agent.

Children ages 3-9 years were informed that an invisible agent (Princess Alice) would help them play a forced-choice game by "telling them, somehow, when they chose the wrong box," whereas a matched control group of children were not given this supernatural prime. On 2 unexpected event trials, an experimenter triggered a simulated unexpected event (i.e., a light turning on/off; a picture falling), and children's behavioral response to these events (i.e., moving their hand to the opposite box) was coded. Results showed a significant Age Group × Experimental Condition interaction; the only children to reliably alter their behavior in response to the unexpected events were the oldest children (M = 7 years 4 months), who were primed with the invisible agent concept. For children's posttest verbal explanations, also, only these children saw the unexpected events as being referential and declarative (e.g., "Princess Alice did it because I chose the wrong box"). Together, these data suggest that children may not regularly begin to see communicative signs as embedded in unexpected events until they are around 7 years of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)