Robustly stable feedback min-max model predictive control

Published versio

Local stable and unstable manifolds and their control in nonautonomous finite-time flows

It is well-known that stable and unstable manifolds strongly influence fluid motion in unsteady flows. These emanate from hyperbolic trajectories, with the structures moving nonautonomously in time. The local directions of emanation at each instance in time is the focus of this article. Within a nearly autonomous setting, it is shown that these time-varying directions can be characterised through the accumulated effect of velocity shear. Connections to Oseledets spaces and projection operators in exponential dichotomies are established. Availability of data for both infinite and finite time-intervals is considered. With microfluidic flow control in mind, a methodology for manipulating these directions in any prescribed time-varying fashion by applying a local velocity shear is developed. The results are verified for both smoothly and discontinuously time-varying directions using finite-time Lyapunov exponent fields, and excellent agreement is obtained.Comment: Under consideration for publication in the Journal of Nonlinear Science

Durkheim's imperative: The role of Humanities faculty in the information technologies revolution

The arrival of powerful information technologies in the traditional humanistic disciplines has done far more than simply add to the tools available for research and instruction. Those who have embraced these technologies have also experienced a significant disruption of their traditional roles within the academy, producing confusion and disorientation as well as excitement and innovation. Some of the reasons for this confusion are discussed, and one example of two "restabilized" roles for humanities faculty the work of the Advanced Information Technologies Group at the University of Illinois is described. The conclusion explores some of the advantages of this new kind of division of intellectual labor.published or submitted for publicatio

What Attracts Women to the IT Field? The First Process of Occupational Socialization

Socialization in an occupation differs in important ways from organizational socialization. Entering a defined occupation is apt to involve a lifelong commitment, yet it is one that individuals often drift into gradually. Entering occupations involves five different, but overlapping processes: attraction, access, adjustment, identification and commitment (Trice & Beyer, 1993). The first of these five processes refers to the specific features of the occupation that get individuals attention and attract them to the occupation. Such features include specific members of the occupation to whom newcomers get attracted such as successful heroes and mentors. It could also be the activities distinctive of the occupational culture or the kinds of extrinsic and intrinsic rewards that the occupation appears to offer. This research study focuses on the attraction process of occupational socialization to the information technology (Ahuja, 2002) field of female students in order to understand women’s experiences and initial perceptions of the IT occupation. This study gathers empirical evidence from current female students in IT-related majors based on a qualitative approach and the use of focus groups as the elicitation technique. The goal of our research study is to contribute to a better understanding of the initial process of occupational socialization of female students in IT majors. The findings of this study, we believe, can help in improving and customizing recruitment strategies for female students that would emphasize the most attractive features of the IT occupation as perceived by women. In this research in progress we present the findings of our study based on eight focus groups conducted with students of three IT related academic majors in two academic institutions in the United States

Intermediary LEO propagation including higher order zonal harmonics

Two new intermediary orbits of the artificial satellite problem are proposed. The analytical solutions include higher order effects of the Geopotential, and are obtained by means of a torsion transformation applied to the quasi-Keplerian system resulting after the elimination of the parallax simplification, for the first intermediary, and after the elimination of the parallax and perigee simplifications, for the second one. The new intermediaries perform notably well for low earth orbits propagation, are free from special functions, and result advantageous, both in accuracy and efficiency, when compared to the standard Cowell integration of the J2 problem, thus providing appealing alternatives for onboard, short-term, orbit propagation under limited computational resources.Comment: Celestial Mechanics and Dynamical Astronomy: Accepted September 25, 201

Static Interaction of Black Holes in 1+1 Dimensions

We consider a version of general relativity in two spacetime dimensions, and study a solution describing two static black holes in the presence of a cosmological constant. We first analytically find an embedding diagram to visualize the geometry outside the black holes. We then examine how the two black holes must be interacting to remain static. Our main result is to show how the black holes behave effectively like two electric charges. This charge model exhibits both attraction and repulsion, which evidently balance and moreover are localized in different regions of space. We also begin an investigation of the black holes’ interaction in terms of the gravitational energy localized in a region (similar to a Gauss’s law approach). One application of these static black holes is to construct a static wormhole, which was started in a previous thesis. Here we finish this construction by verifying the wormhole’s smoothness where the two black hole horizons are matched together