Optimal mean-square performance for networked control systems with unreliable communication

In this work we study mean-square (MS) stability and mean-square (MS) performance for discrete-time, finite-dimensional linear time-varying systems with dynamics subject to i.i.d. random variation. We do so primarily in the context of networked control systems (NCS) where the network communication channels are unreliable and modeled as multiplicative stochastic uncertainties, e.g. wireless links subject to packet dropouts and modeled as Bernoulli processes. We first focus on the analysis problem in general. We derive a convex feasibility problem and associated convex optimization problem which can be used to determine the MS stability and MS performance respectively of a given system. Since this analysis theory is derived in terms of the feasibility of and optimization of a linear cost subject to linear matrix inequalities (LMIs), it serves as the foundation from which a solution methodology for numerous controller synthesis problems can be derived. Next we formulate the main synthesis problem we consider in this work: a networked control system where both the sensor measurements for the plant(s) and the commands from the controller are transmitted via unreliable communication channels. We treat the unreliable communication links as i.i.d. random processes. We assume that the plant(s) and links are subject to additive exogenous noise, and that we have access to a reliable but delayed acknowledgment of whether or not the controller commands were received by the plant(s) on the previous time step. Finally we restrict the controller to be finite-dimensional, linear, have no structural dependence on the particular path history of the random processes, and scale in size and complexity linearly with the number of random channels. We then show that this synthesis problem has a MS stabilizing solution if and only if two simpler convex problems have MS stabilizing solutions, and moreover that the optimal MS performance solution to this synthesis problem if it exists can be obtained by solving a sequence of these simpler convex problems. Additionally, we show that the overall optimal MS performance cost is the sum of two components which can be determined from the solutions to the special problems. That is, we derive a separation principle for our problem analogous to the classical H2 synthesis

Explorations in engagement for humans and robots

This paper explores the concept of engagement, the process by which individuals in an interaction start, maintain and end their perceived connection to one another. The paper reports on one aspect of engagement among human interactors--the effect of tracking faces during an interaction. It also describes the architecture of a robot that can participate in conversational, collaborative interactions with engagement gestures. Finally, the paper reports on findings of experiments with human participants who interacted with a robot when it either performed or did not perform engagement gestures. Results of the human-robot studies indicate that people become engaged with robots: they direct their attention to the robot more often in interactions where engagement gestures are present, and they find interactions more appropriate when engagement gestures are present than when they are not.Comment: 31 pages, 5 figures, 3 table

The coupling between pulsation and mass loss in massive stars

To what extent can pulsational instabilities resolve the mass-loss problem of massive stars? How important is pulsation in structuring and modulating the winds of these stars? What role does pulsation play in redistributing angular momentum in massive stars? Although I cannot offer answers to these questions, I hope at the very least to explain how they come to be asked.Comment: 12 pages, 1 figure, to appear in proceedings of "Unsolved Problems in Stellar Physics" conference (Cambridge, UK, July 2007

Paso del Norte Watershed Council Coordinated Water Resources Database Project

The Paso del Norte Watershed Council (PDNWC) is a quasi-governmental organization that serves in an advisory capacity to the New Mexico-Texas Water Commission regarding the selection, planning, and implementation of environmental enhancements and mitigations associated with the El Paso-Las Cruces Regional Sustainable Water Project. The Council recommends policies for cooperation, coordination, and the sharing of information concerning planning and management activities of projects affecting the Paso del Norte Watershed, this being defined as the Rio Grande Basin between Elephant Butte Dam/Reservoir in southern New Mexico and Fort Quitman, Texas. In the last several years, the Watershed Council has discussed the development of a regional cooperative database project that would provide streamlined access to a range of water resource data in the Paso del Norte region. In August of 2002, the El Paso Water Utilities provided initial funding to the Paso del Norte Watershed Council to develop a pilot cooperative database project, and efforts toward the development of such a project have been ongoing. This document is the final report for this effort. In this report, we detail the following elements of the project, as specified in the initial Scope of Work: 1. The background, motivation, and intended outcomes of the project, 2. The specific tasks that were undertaken in project development efforts, 3. The specific insights that we have gained in this pilot effort, 4. Specific recommendations for new water quality monitoring sites and equipment, and 5. An outline of tasks that should be undertaken in future phases of the project. All deliverables specified in the project have been completed, and we also note the following recommendations for future project work, as detailed in the latter part of this report: * Complete migration of the Project website and related databases to the ArcIMS software, * Installation of new monitoring stations and equipment as detailed above, and inclusion of these monitoring sites in future ArcIMS map products, * Enhanced levels of funding to be directed to support more active participation of regional volunteer data providers and to bring new providers into the project, * Exploration of scripting and automated FTP routines or a batch mode of data transfer to allow progress on the "user interface plateau" discussed in the report, * Inclusion of groundwater data into future phases of the project, * Linking the EPWU-funded project to USACE-supported database efforts, and * Additional funding to be provided to lend institutional support to the Watershed Council and also to fund future Cooperative Database Project activities

Repair and Strengthening of Bridges in Indiana Using Fiber Reinforced Polymer Systems: Volume 1–Review of Current FRP Repair Systems and Application Methodologies

For bridges that are experiencing deterioration, action is needed to ensure the structural performance is adequate for the demands imposed. Innovate repair and strengthening techniques can provide a cost-effective means to extend the service lives of bridges efficiently and safely. The use of fiber reinforced polymer (FRP) systems for the repair and strengthening of concrete bridges is increasing in popularity. Recognizing the potential benefits of the widespread use of FRP, a research project was initiated to determine the most appropriate applications of FRP in Indiana and provide recommendations for the use of FRP in the state for the repair and strengthening of bridges. The details of the research are presented in two volumes. Volume 1 provides the details of a study conducted to (1) summarize the state-of-the-art methods for the application of FRP to concrete bridges, (2) identify successful examples of FRP implementation for concrete bridges in the literature and examine past applications of FRP in Indiana through case studies, and (3) better understand FRP usage and installation procedures in the Midwest and Indiana through industry surveys. Volume 2 presents two experimental programs that were conducted to develop and evaluate various repair and strengthening methodologies used to restore the performance of deteriorated concrete bridge beams. The first program investigated FRP flexural strengthening methods, with a focus on adjacent box beam bridges. The second experimental program examined potential techniques for repairing deteriorated end regions of prestressed concrete bridge girders. Externally bonded FRP and near-surface-mounted (NSM) FRP were considered in both programs

Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z

The classification of galaxy mergers and isolated disks is key for understanding the relative importance of galaxy interactions and secular evolution during the assembly of galaxies. The kinematic properties of galaxies as traced by emission lines have been used to suggest the existence of a significant population of high-z star-forming galaxies consistent with isolated rotating disks. However, recent studies have cautioned that post-coalescence mergers may also display disk-like kinematics. To further investigate the robustness of merger/disk classifications based on kinematic properties, we carry out a systematic classification of 24 local (U)LIRGs spanning a range of galaxy morphologies: from isolated spiral galaxies, ongoing interacting systems, to fully merged remnants. We artificially redshift the WiFeS observations of these local (U)LIRGs to z=1.5 to make a realistic comparison with observations at high-z, and also to ensure that all galaxies have the same spatial sampling of ~900 pc. Using both kinemetry-based and visual classifications, we find that the reliability of kinematic classification shows a strong trend with the interaction stage of galaxies. Mergers with two nuclei and tidal tails have the most distinct kinematic properties compared to isolated disks, whereas a significant population of the interacting disks and merger remnants are indistinguishable from isolated disks. The high fraction of late-stage mergers showing disk-like kinematics reflects the complexity of the dynamics during galaxy interactions. However, the exact fractions of misidentified disks and mergers depend on the definition of kinematic asymmetries and the classification threshold when using kinemetry-based classifications. Our results suggest that additional indicators such as morphologies traced by stars or molecular gas are required to further constrain the merger/disk classifications at high-z.Comment: 16 pages, 5 figures, ApJ accepte

Repair and Strengthening of Bridges in Indiana Using Fiber Reinforced Polymer Systems: Volume 2–FRP Flexural Strengthening and End Region Repair Experimental Programs

For bridges that are experiencing deterioration, action is needed to ensure the structural performance is adequate for the demands imposed. Innovate repair and strengthening techniques can provide a cost-effective means to efficiently and safely extend the service lives of bridges. The use of fiber reinforced polymer (FRP) systems for the repair and strengthening of concrete bridges is increasing in popularity. Recognizing the potential benefits of the widespread use of FRP, a research project was initiated to determine the most appropriate applications of FRP in Indiana and provide recommendations for the use of FRP in the state for the repair and strengthening of bridges. The details of the research are presented in two volumes. Volume 1 provides the details of a study conducted to (i) summarize the state-of-the-art for the application of FRP to concrete bridges, (ii) identify successful examples of FRP implementation for concrete bridges in the literature and examine past applications of FRP in Indiana through case studies, and (iii) better understand FRP usage and installation procedures in the Midwest and Indiana through industry surveys. Volume 2 presents two experimental programs that were conducted to develop and evaluate various repair and strengthening methodologies used to restore the performance of deteriorated concrete bridge beams. The first program investigated FRP flexural strengthening methods, with focus placed on adjacent box beam bridges. The second experimental program examined potential techniques for repairing deteriorated end regions of prestressed concrete bridge girders. Externally bonded FRP and near-surface-mounted (NSM) FRP were considered in both programs

The kinematics of ionized gas in lyman-break analogs at z ~ 0.2

We present results for 19 “Lyman-break analogs” observed with Keck/OSIRIS with an adaptive-optics-assisted spatial resolution of less than 200 pc. We detect satellites/companions, diffuse emission, and velocity shear, all with high signal-to-noise ratios. These galaxies present remarkably high velocity dispersion along the line of sight (~70 km s^(−1)), much higher than standard star-forming spirals in the low-redshift universe. We artificially redshift our data to z ~ 2.2 to allow for a direct comparison with observations of high-z Lyman-break galaxies and find striking similarities between both samples. This suggests that either similar physical processes are responsible for their observed properties, or, alternatively, that it is very difficult to distinguish between different mechanisms operating in the low- versus high-redshift starburst galaxies based on the available data. The comparison between morphologies in the UV/optical continuum and our kinemetry analysis often shows that neither is by itself sufficient to confirm or completely rule out the contribution from recent merger events. We find a correlation between the kinematic properties and stellar mass, in that more massive galaxies show stronger evidence for a disk-like structure. This suggests a co-evolutionary process between the stellar mass buildup and the formation of morphological and dynamical substructure within the galaxy