Publications with Abstracts by Alfred Hübler (1997)

1. T. Ritz, A. Hübler, Controlling Complex Systems and First Principles of Complex Systems Research, Proc. of the 1996 International Workshop, (Las Cruces, New Mexico), Control Mechanisms for Complex Systems: Issues of Measurement and Semiotic Analysis, 51-66 (1997)
   Abstract: Complex systems are high dimensional, nonlinear systems far from equilibrium. In this article, we present new principles and methodologies that may help to understand and control the dynamics of such systems. The dynamics of a high dimensional complex system can in many cases be estimated from simple models such as coupled maps dynamics, low dimensional systems of ODEs, singular motions, or genetic algorithms. The reduction of dimensionality means that a few order parameters govern the dynamics of the complex system.
   While the mentioned models are simple, they still may contain a large number of parameters. These parameters can be determined from experiments if the experimental dynamics is complex, e.g. aperiodic or chaotic. However, if the experimental dynamics is simple, e.g. a fixed point dynamics, it is necessary to perturb it in order to reconstruct the model. Of course, perturbations are also necessary to control a system. The problem with these perturbations is that they may activate additional variables which are not included in the simple model. Thus, the simple model is in general no longer valid for the perturbed system.
   For a driven anharmonic oscillator a special class of aperiodic forcing functions that overcome this problem can be derived from a variational principle. The intuitive generalization of the variational principle is captured by the principle of the dynamical key which we propose as a "first principle" for complex systems. Aperiodic forcing functions that act as a dynamical key can be used for system identification purposes and for controlling complex systems.

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2. * A. Hübler, U. Kuhl, R. Wittmann, T. Nagata, Sharp Diffraction Peaks from Chaotic Structures, CHAOS 7, 577-589 (1997)
   Abstract: Spectroscopy is, in general, a powerful approach to examining a system. A wide range of techniques may be used for such diverse purposes as determining molecular configurations, measuring concentrations and distributions of species, and probing nuclear structures. Spectroscopic methods typically exploit a resonance of the system. If the system under investigation is linear or has a periodic structure, then certain periodic forcing functions are in resonance with the system. However, if the system is nonlinear or has an aperiodic structure with only short-range order, it resonates with chaotic forcing functions. Currently, virtually all spectroscopic techniques use only periodic forcing functions, which makes it difficult to study aperiodic structures such as amorphous solids and the dynamics of large molecules. As we present here, the theory of optimal open-loop controls can be used to develop novel spectroscopic methods which are based on chaotic forcing functions.

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3. * D. Raineri, A. Hübler, B. Mertens, Cyberprof^TM: An Intelligent Human-Computer Interface for Interactive Instruction on the World Wide Web, JALN 1, 20 (1997)
   Abstract: Advances in computer technology and the human-computer interface have created a wealth of new opportunities for the development of computer-based instruction and intelligent tutoring systems. Unfortunately, much of the material currently available amounts to little more than "electronic books", in which learning is still accomplished by reading text and viewing two-dimensional pages. This paper describes the features of CyberProf - an interactive, World Wide Web-based teaching system developed at the University of Illinois. Using CyberProf, instructors can create on-line lecture notes that include equations, animations, and graphics; write on-line interactive homework problems; communicate with students using CyberProf's Web-based conferencing system; survey students in order to receive feedback on course material; and record student grades in CyberProf's online grade book. Students can review lecture notes 24 hours a day; complete homework problems on the Web and receive immediate intelligent feedback to their answers; use the conferencing system to post questions to their instructor, teaching assistants, and peers; and review their grades in the class at any time.

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4. H. Higuraskh, A. Toriumi, F. Yamaguchi, K. Kawamura, A. Hübler, Correlation Tunnel Device, U. S. Patent # 5,679,961 (1997)
   Abstract: According to the present invention, there is provided a correlation tunnel device capable of achieving a low power consumption without decreasing a drive force when a large-scale-integrated circuit is constituted. A correlation tunnel device according to the present invention comprises a first quantum dot structure including a first carrier confinement region having at least two discrete energy levels, a carrier conduction region adjacent to the first carrier confinement region, and a tunnel barrier arranged only between the first carrier confinement region and the conduction region, and a second quantum dot structure including a second carrier confinement region having at least two discrete energy levels, a carrier conduction region adjacent to the second carrier confinement region, and a tunnel barrier arranged only between the second carrier confinement region and the conduction region, wherein an energy level occupied by the carrier in the first carrier confinement region and an energy level occupied by the carrier in the second carrier confinement region have a correlation.

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