Control of Networked Multiagent Systems with Uncertain Graph Topologies

Multiagent systems consist of agents that locally exchange information through a physical network subject to a graph topology. Current control methods for networked multiagent systems assume the knowledge of graph topologies in order to design distributed control laws for achieving desired global system behaviors. However, this assumption may not be valid for situations where graph topologies are subject to uncertainties either due to changes in the physical network or the presence of modeling errors especially for multiagent systems involving a large number of interacting agents. Motivating from this standpoint, this paper studies distributed control of networked multiagent systems with uncertain graph topologies. The proposed framework involves a controller architecture that has an ability to adapt its feed- back gains in response to system variations. Specifically, we analytically show that the proposed controller drives the trajectories of a networked multiagent system subject to a graph topology with time-varying uncertainties to a close neighborhood of the trajectories of a given reference model having a desired graph topology. As a special case, we also show that a networked multi-agent system subject to a graph topology with constant uncertainties asymptotically converges to the trajectories of a given reference model. Although the main result of this paper is presented in the context of average consensus problem, the proposed framework can be used for many other problems related to networked multiagent systems with uncertain graph topologies.Comment: 14 pages, 2 figure

Delivering Social Services through Faith-Based Organizations: Case of United Way of Massachusetts Bay

As deliverers of social services, faith-based organizations have been stereotyped as being inefficient and focused on spiritual outcomes alone, and have therefore been largely ignored by funding agencies. The United Way of Massachusetts Bay, realizing the importance of such organizations, particularly in communities of color, has actively sought to dispel these stereotypes and work with faith-based organizations to enhance service delivery to needy Black communities in Massachusetts. Through training and participatory research, faith-based organizations have begun to appreciate the importance of measurable outcomes

Examining the role of sea ice and meteorology in Arctic boundary layer halogen chemistry

Thesis (Ph.D.) University of Alaska Fairbanks, 2015Given the ubiquitous nature of ice, chemistry taking place on ice surfaces has a substantial effect on the environment, particularly in the polar regions. The return of sunlight to the polar regions releases halogen radicals (e.g. Br, Cl and their oxides, e.g. BrO) generated from salts on ice surfaces. These radicals fundamentally alter the chemistry of the Arctic boundary layer through processes such as boundary-layer ozone depletion events and mercury deposition events. Current understanding of the chemical processes involved in Arctic halogen chemistry is inhibited by a lack of knowledge about the ice surfaces on which this chemistry is thought to take place, as well as the sparsity of long-term field observations of this chemistry and its effects. This dissertation addresses both needs through a combination of laboratory experiments and long-term field studies. First, we use X-ray absorption computed micro-tomography at the Advanced Photon Source to image brine distributions within laboratory grown mimics of sea-ice features. These experiments showed that when brine is introduced to ice via wicking of brine from a saline surface, the resulting brine distribution is heterogeneous, with brine existing in distinct regions within the sample, rather than evenly spreading over the sample surface. To examine the horizontal and vertical extent of halogen chemistry in the Arctic boundary layer, we conducted long-term measurements of BrO at Barrow, Alaska using Multiple-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS). We developed a method to reduce these measurements to timeseries of near-surface and total column amounts of BrO. These measurements showed that the vertical distribution is highly variable, ranging from shallow layer events confined to the lowest 200 m, to distributed column events, which have lower mixing ratios of BrO, but are more distributed throughout approximately the lowest kilometer of the atmosphere. We find that the observed vertical distributions of BrO are influenced by atmospheric stability. We found minimal influence of wind speed on either lower-tropospheric bromine activation (LT-VCD) or the vertical distribution of BrO, while examination of seasonal trends and the temperature dependence of the vertical distribution support the finding that atmospheric stability affects the distribution of BrO. While shallow layer events have higher concentrations of halogens, distributed column events tend to have higher overall amounts of activation, implying that in situ near surface measurements may be insufficient to constrain the role of environmental parameters in the activation of halogens. Examination of multiple years of data at Barrow, Alaska shows that time spent in first year ice (FYI) areas is weakly linearly correlated (R=0.38) with the activation of BrO. However, examining annual averages of BrO shows that despite the non-linear relationship between time in FYI areas and BrO, time spent in FYI areas still influences the interannual variability of BrO

Demonstrating Advancements in Biotechnology to Ranchers in Southern Utah: Genetic Testing

This fact sheet describes genetic testing for beef cattle to identify which animals in a herd are the most productive or least productive and make some culling decisions based on the results of the tests

Single Camera, Three-Dimensional Particle Tracking Velocimetry.

This thesis presents the development of single-camera, three-dimensional particle-tracking velocimetry (SC3D-PTV), a method for measuring 3D air flow inside an optically-accessible combustion engine. The efficiency and pollutant formation of an internal combustion engine are strongly influenced by the air flow inside the engine cylinder, so understanding the flow is critical for improving engine operation. However, because 3D, volumetric results are needed to fully quantify these flows, and limited optical access is available, existing flow measurement techniques are ill-suited to engine measurements. To address this need, the SC3D-PTV method can perform high-speed, high-resolution 3D flow measurements with limited optical access, promote greater understanding of in-cylinder flow, and lead to improved engine operation. The optical element used for SC3D-PTV is similar to a stereo-microscope. A single large lens and two smaller lenses are used to create two parallel imaging sub-systems within a single housing. The two imaging sub-systems view the same measurement volume from different angles, but share a focal plane without perspective distortion. The positions of the object within the two images indicate the 3D position of the object, and 3D velocities are measured by taking images at successive points in time. A novel PTV algorithm relying on the similarity of the particle images corresponding to a single, physical particle produces 3-component, volumetric velocity fields without the reconstruction of an instantaneous 3D particle field. Validation of the SC3D-PTV method was obtained by analyzing a single experimental data set from a simple flow with both the SC3D-PTV algorithm and a stereoscopic PIV algorithm and comparing the results. After validation, the SC3D-PTV technique was applied to the air flow inside a motored engine. The three-component, 3D results provided by SC3D-PTV were shown to provide details of the flow that were lost when performing the planar, two- and three-component measurements commonly used to study engine flows. Because SC3D-PTV can fully quantify the 3D flow structures found within engines, even with very limited optical access, the development of SC3D-PTV significantly advances the study of engine flows and offers the chance to gain insights that would be impossible with existing measurement techniques.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91449/1/petersok_1.pd

A comparative molecular approach to mesodermal patterning in basal deuterostomes: the expression pattern of Brachyury in the enteropneust hemichordate Ptychodera flava

This work concerns the formation of mesoderm in the development of an enteropneust hemichordate, Ptychodera flava, and the expression of the Brachyury gene during this process. Brachyury expression occurs in two distinct phases. In the embryo, Brachyury is transcribed during gastrulation in the future oral and anal regions of the gut, but transcripts are no longer detected by 2 weeks of development. Brachyury expression is not detected during the 5 months of larval planktonic existence. During this time, the adult coeloms begin to develop, originating as coalescences of cells that appear to delaminate from the wall of the gut. Brachyury expression cannot be detected again until metamorphosis, when transcripts appear in the mesoderm of the adult proboscis, collar and the very posterior region of the trunk. It is also expressed in the posterior end of the gut. At no time is Brachyury expressed in the stomochord, the putative homologue of the chordate notochord. These observations illuminate the process of maximal indirect development in Ptychodera and, by comparison with patterns of Brachyury expression in the indirect development of echinoderms, their sister group, they reveal the evolutionary history of Brachyury utilization in deuterostomes