Acoustic portrait of herring in Vestfjord, january 1996, with geostatistical analysis

In January 1996 the stock of Norwegian spring-spawning herring (Clupea harengus) was acoustically surveyed in the wintering area. Both immature and mature fish were present. Because of the comparative lateness of the survey, the spawning migration had already begun, and the total survey area extended from the inner reaches of Ofotfjord and Tysfjord to the sea area southwest of Vestfjord, well over 200 nautical miles from end to end. Coverage of the Vestfjord area alone occupied three days, thus also including diurnal vertical migration. The evident complex of dynamics is described in two ways: (1) by acoustic images of herring distribution in vertical sections of Vestfjord, and (2) through variograms computed for strata identified by the visual presentation. Speculation is offered on the use of such an analysis in stratification

PRM-RL: Long-range Robotic Navigation Tasks by Combining Reinforcement Learning and Sampling-based Planning

We present PRM-RL, a hierarchical method for long-range navigation task completion that combines sampling based path planning with reinforcement learning (RL). The RL agents learn short-range, point-to-point navigation policies that capture robot dynamics and task constraints without knowledge of the large-scale topology. Next, the sampling-based planners provide roadmaps which connect robot configurations that can be successfully navigated by the RL agent. The same RL agents are used to control the robot under the direction of the planning, enabling long-range navigation. We use the Probabilistic Roadmaps (PRMs) for the sampling-based planner. The RL agents are constructed using feature-based and deep neural net policies in continuous state and action spaces. We evaluate PRM-RL, both in simulation and on-robot, on two navigation tasks with non-trivial robot dynamics: end-to-end differential drive indoor navigation in office environments, and aerial cargo delivery in urban environments with load displacement constraints. Our results show improvement in task completion over both RL agents on their own and traditional sampling-based planners. In the indoor navigation task, PRM-RL successfully completes up to 215 m long trajectories under noisy sensor conditions, and the aerial cargo delivery completes flights over 1000 m without violating the task constraints in an environment 63 million times larger than used in training.Comment: 9 pages, 7 figure

Dynamics of wintering Norwegian spring-spawning herring at the entrance to Tysfjorden, December 1996

The entrance region to Tysfjorden was acoustically surveyed a total of eleven times during the December 1996 abundance survey of the spawning stock of Norwegian spring-spawning herring (Clupea harengus). The observations are summarized through maps of the distribution, vertical sections, and statistical measures of acoustic density in each of two strata. Experimental variograms are modeled, yielding parameter values that summarize the major properties of aggregation. The collective measures of density and aggregation portray a highly dynamic situation with strong diel variation but a general persistence of the fish distribution over the eleven days of its repeated observation

The modeling and use of syntactic foams for passive control of fluid-borne noise

Syntactic foams-composite materials consisting of hollow particles embedded in a host matrix-have many applications for manufactured products, including weight reduction, thermal insulation, and noise reduction. In this thesis, a certain variety of syntactic foam is investigated with regards to reducing fluid borne noise in hydraulic systems. Such a foam maintains stiffness at low hydrostatic pressures and becomes compressible as pressure increases. With this compressibility, the foam is potentially useful as a liner for a reactive noise control device, much like compressed gas style devices currently in use; but the syntactic foam additionally adds significant damping to the system. In order to predict device performance, a linear multimodal model is developed of a hydraulic suppressor, constructed as an expansion chamber lined with a syntactic foam insert. Material models are developed for various compositions of the foam liners, based on an inverse analysis matching the model to experimental results. Two model simplifications are considered, and it is found that a simplified bulk modulus model gives sufficiently accurate results to make approximate predictions of suppressor performance. Several optimizations are performed to predict the optimal material composition for hydraulic excavator work cycles. To help compare the prototype suppressor against commercially available bladder style suppressors, a model is developed for the bladder style silencer and is validated experimentally. Overall, this work both demonstrates the current and potential utility of syntactic foam as a device lining material, and contributes new models to the hydraulics noise control community.Ph.D

Interactive Audio Content: An Approach to Audio Content for a Dynamic Museum Experience through Augmented Audio Reality and Adaptive Information Retrieval

ec(h)o is an “audio augmented reality interface” utilizing spatialized soundscapes and a semantic web approach to information. The paper discusses our approach to conceptualizing museum content and its creation as audio objects in order to satisfy the requirements of the ec(h)o system. This includes, the conceptualizing of information relevant to an existing exhibition design (an exhibition from the Canadian Museum of Nature in Ottawa). We will discuss the process of acquiring, designing and developing information relevant to the exhibition and its mapping to the requirements of adaptive information retrieval and the interaction model. The development of the audio objects is based on an audio display model that addresses issues of psychoacoustics, composition and cognition. The paper will outline the challenges and identify the limitations of our approach

The caring self within a context of increasing rationalisation: The enduring importance of clients for home care aides

The current political economy imposes cost-saving rationalisation within home care work. In this context, a key question is whether home care aides act with indifference to clients or whether home care aides continue to espouse and act out of the caring self, which centres on the desire to give meaningful care to clients. This article assesses the thesis of the caring self within a context of rationalisation in relation to home care aides in three organisations. The article brings qualitative and quantitative research to bear on this question. It finds that despite the processes of rationalisation occurring in home care work, home care aides’ overall satisfaction with client relations, and their ability to satisfy clients continue to have significant links to their job satisfaction, and discretionary effort. This offers support for the thesis of the caring self within the context of rationalisation

Directed Search and the Futility of Cheap Talk

Abstract We study directed search in a frictional two-sided matching market in which each seller can communicate with buyers prior to matching via costless public messages that entail no obligation regarding post-matching behavior (cheap talk). We establish that messages cannot contain payoff-relevant information in any equilibrium