Implementation and stability analysis of prioritized whole-body compliant controllers on a wheeled humanoid robot in uneven terrains

In this work, we implement the floating base prioritized whole-body compliant control framework described in Sentis et al. (IEEE Transactions on Robotics 26(3):483–501, 2010) on a wheeled humanoid robot maneuvering in sloped terrains. We then test it for a variety of compliant whole-body behaviors including balance and kinesthetic mobility on irregular terrain, and Cartesian hand position tracking using the co-actuated (i.e. two joints are simultaneously actuated with one motor) robot’s upper body. The implementation serves as a hardware proof for a variety of whole-body control concepts that had previously been developed and tested in simulation. First, behaviors of two and three priority tasks are implemented and successfully executed on the humanoid hardware. In particular, first and second priority tasks are linearized in the task space through model feedback and then controlled through task accelerations. Postures, on the other hand, are shown to be asymptotically stable when using prioritized whole-body control structures and then successfully tested in the real hardware. To cope with irregular terrains, the base is modeled as a six degree of freedom floating system and the wheels are characterized through contact and rolling constraints. Finally, center of mass balance capabilities using whole-body compliant control and kinesthetic mobility are implemented and tested in the humanoid hardware to climb terrains with various slopes.     

Improving TLB performance on current chip multiprocessor architectures through demand‐driven superpaging

Translation Lookaside Buffers (TLBs) can play a critical role in improving the performance of emerging parallel workloads. Most current chip multiprocessor systems include multilevel TLBs and provide support for superpages both at the hardware and software level. Judicious use of superpages can significantly cut down the number of TLB misses and improve overall system performance. However, indiscriminate superpage allocation results in page fragmentation and increased application footprint, which often outweigh the benefits of reduced TLB misses. Previous research has explored policies for smart allocation of superpages from an operating system perspective. This paper presents a compiler‐based strategy for automatic and profitable memory allocation via superpages. A significant advantage of a compiler‐based approach is the availability of data‐reuse information within an application. Our strategy employs data‐locality analysis to estimate the TLB demands for both single‐threaded and multi‐threaded programs and uses this metric to apply selective superpage allocation. Apart from its obvious utility in improving TLB performance, this strategy can be used to improve the effectiveness of certain data‐layout transformations and can be a useful tool in benchmarking and automatic performance tuning. We demonstrate the effectiveness of this strategy with experiments on three multicore platforms on a workload that contains both sequential and parallel applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Bandit algorithms to personalize educational chatbots

Machine Learning - To emulate the interactivity of in-person math instruction, we developed MathBot, a rule-based chatbot that explains math concepts, provides practice questions, and offers...     

Boundary object efficacy: The mediating role of boundary objects on task conflict in global virtual project networks

As project-based industries such as Architecture, Engineering and Construction globalize, workers require strategies for managing conflict in virtual project networks. Our aim in this paper is to explore the efficacy of boundary objects as tools to mediate conflict in culturally-diverse, distributed networks. Based on annotated recordings for eight networks of graduate student engineers, we demonstrate that different interactional patterns between distributed engineers and boundary objects can lead to a reduction in conflict duration. We did not observe higher levels of conflict for global compared to domestic networks, but did discover that, regardless of network diversity, networks that interacted with the boundary objects in certain ways were able to identify and resolve conflicts more quickly. Our findings have important implications for theories of conflict management and boundary object efficacy in addition to practical applications to support conflict management in global virtual project networks.     

Effects of Postinoculation Talk on Resistance to Influence

Contemporary inoculation scholarship has focused on the process of resistance to persuasion, and recently begun to examine various incidental effects that may accompany inoculation treatments. This study considers how talk fits within both of these areas, not only as a byproduct of inoculation, but also as a potentially important contributor to the process of resistance. Results indicate inoculation not only enhances talk about the target issue, but such talk appears to bolsters resistance to subsequent counterattitudinal messages.     

Development of Test Methods for Assessing the Fire Hazards of Landscaping Mulch

Landscape mulches are widely used adjacent to buildings and represent a potential fire threat to the building. To date, relatively limited research has been conducted to characterize the ignition and flame spread potential of the various types of commercially available landscaping mulches. Consequently, ignition and flame spread test protocols were developed to evaluate candidate mulch products based upon the scientific research involving mulches and forest litters. The ignition protocol used brands from the ASTM E108 test to determine the minimum brand size required for reliable burning of the mulch to the border of the 0.6 m square mulch bed. The flame spread on mulches was assessed for a mulch bed 0.46 m wide by 1.8 m long. The initiating source for the flame spread testing was a gas-fired line burner with an intensity of 108 kW/m. The ability of the mulch bed to propagate flame remote from the initiation source was determined and the resulting flame spread rate was measured. The protocols were exercised in using various types of landscaping mulch (pine bark, hardwood, pine bark nugget, and pine straw mulch). The test protocol is found to be a viable method to provide quantitative measures of the hazards of landscape mulches. Further potential areas of test method development are identified.     

Effective Model for Prediction of N2O and NH3 Formation During the Regeneration of NO x Storage Catalyst

In this paper we propose an effective global kinetic model that allows prediction of N₂O and NH₃ formation during the reduction of stored NO _x in dependence on the composition of the rich mixture (H₂/CO/C₃H₆), actual operating temperature, and length of regeneration period. A bench flow reactor equipped with a high-speed FTIR was used to measure dynamic evolution of gas components during periodic lean/rich operation of a fully formulated NSRC catalyst (PtPdRh/Ba/Ce–Zr/Mg–Al/Al₂O₃).     

Ombudspersons or peers? The effect of third-party expertise and recommendations on negotiation.

Despite the prevalence of ombudspersons (also called "ombudsmen" or "ombuds") in organizations, little empirical research has examined their effectiveness in mediating workplace conflicts. In this laboratory study, the influence of these expert third parties was modeled. Specifically, the effects of mediator expertise and the content of the mediator's recommendations on disputants' perceptions and behavior were examined. Results showed that disputant offers remained inelastic when peers made recommendations, regardless of recommendation quality. However, the recommendations of expert third parties significantly influenced disputants' offers. Disputants reduced their offers when experts made unintegrative recommendations, and they kept their offers high when experts gave integrative-compromise recommendations. The implications of these findings for conflict-management research and organizational dispute resolution are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)