Online-Lehre im Einsatz

Das im Rahmen des vom BMBF geförderten Projektes PORTIKO (Multimediale Lehr- und Lernplattform für den Studiengang Bauingenieurwesen) umfasst 10 Bauingenieurinstitute in Braunschweig und Dresden und das Fernstudium an der TU Dresden. Daneben sind drei Stabsprojekte für Didaktik, Teleteaching und Multimedia-Plattform als Dienstleister und Koordinatoren für die anderen Teilprojekte tätig. An der TU Braunschweig ist das Institut für Baustoffe, Massivbau und Brandschutz unter anderem für die Grundfachausbildung des Massivbau (5. + 6. Semester) und für eine spezielle Vertiefungsrichtung, den Brand- und Katastrophenschutz (7. bis 9. Semester), zuständig. In diesem Beitrag wird zunächst ein Überblick über die verwendete Plattform sowie die eingesetzten Hardware- und Softwaretechniken gegeben. Anschließend wird von ersten Erfahrungen über den Einsatz der Online-Lehre und die daraus gewonnen unterschiedlichen strategischen Ansätze für das weiter Vorgehen nach Projektende im Massivbau und im Brandschutz vorgestellt. Um den Praxisbezug zu vertiefen, wurden in PORTIKO zwei Projektbereiche gebildet, die auf Grund der engen Beziehung zwischen den Fächern gezielt zusammenarbeiten sollen. Dabei handelt es sich um die Bereiche >Virtuelles HausVirtuelle Infrastruktur<. Am Beispiel des Virtuellen Hauses soll gezeigt werden, wie die einzelnen Fächer mit Hilfe abgestimmter Übungsbeispiele den Studierenden die Notwendigkeit der Teamarbeit und Interaktion verschiedener Disziplinen vor Augen führen. Den Studenten stehen durch die Online-Plattform eine Vielzahl von Möglichkeiten zur Verfügung, z. B. mit Videoclips und Fotos über Versuche und Baustellen angereicherte Skripte, audio-kommentierte Vorlesungsfolien, alte Klausuren mit Musterlösungen, Aufgabenstellungen für Hausübungen, usw.. Den Studierenden können in der Online-Lehre interaktive Anwendungen zur Verfügung gestellt werden, die ein spielerisches Erproben und Beobachten von Parametereinflüssen ermöglichen. Solche interaktiven Übungen werden mit Java, Flash und Authorware erstellt. Hierzu werden Beispiele vorgestellt

An O(M(n) log n) algorithm for the Jacobi symbol

The best known algorithm to compute the Jacobi symbol of two n-bit integers runs in time O(M(n) log n), using Sch\"onhage's fast continued fraction algorithm combined with an identity due to Gauss. We give a different O(M(n) log n) algorithm based on the binary recursive gcd algorithm of Stehl\'e and Zimmermann. Our implementation - which to our knowledge is the first to run in time O(M(n) log n) - is faster than GMP's quadratic implementation for inputs larger than about 10000 decimal digits.Comment: Submitted to ANTS IX (Nancy, July 2010

Cryogenic Heat Transfer System

Disclosed herein is a cryogenic heat transfer system capable of transferring 50 W or more at cryogenic temperatures of 100.degree. K or less for use with cryocooler systems. In an embodiment, a cryogenic heat transfer system comprises a refrigerant contained within an inner chamber bound by a condenser in fluid communication with an evaporator through at least one flexible conduit, the condenser in thermal communication with the cold station of a cryocooler, and the evaporator positionable in thermal communication with a heat source, typically a radiation shield of a cryogenic chamber. A process to remove heat from a cryogenic chamber is also disclosed

Can a charged ring levitate a neutral, polarizable object? Can Earnshaw's Theorem be extended to such objects?

Stable electrostatic levitation and trapping of a neutral, polarizable object by a charged ring is shown to be theoretically impossible. Earnshaw's Theorem precludes the existence of such a stable, neutral particle trap.Comment: 11 pages, 1 figur

Heterodyne Interferometer Angle Metrology

A compact, high-resolution angle measurement instrument has been developed that is based on a heterodyne interferometer. The common-path heterodyne interferometer metrology is used to measure displacements of a reflective target surface. In the interferometer setup, an optical mask is used to sample the measurement laser beam reflecting back from a target surface. Angular rotations, around two orthogonal axes in a plane perpendicular to the measurement- beam propagation direction, are determined simultaneously from the relative displacement measurement of the target surface. The device is used in a tracking telescope system where pitch and yaw measurements of a flat mirror were simultaneously performed with a sensitivity of 0.1 nrad, per second, and a measuring range of 0.15 mrad at a working distance of an order of a meter. The nonlinearity of the device is also measured less than one percent over the measurement range

Fission product diffusion in ig-110 graphite

The threat of global climate change and resultant disasters has never been higher. The promises made by many countries of carbon neutrality by 2050 will be impossible to achieve without nuclear technology. Global public support for nuclear energy is at its highest level in modern history but is still severely hampered by perceptions of safety and issues involving nuclear waste and proliferation. The Fukushima disaster of 2011 and the attack on Ukraine by the Russian Federation in 2022 only served to highlight the dangers of older reactor technology and the potential for large releases of radioactivity either by accident or intentional sabotage. For these reasons most countries have a keen interest in improved reactor technologies, particularly in regards to safety, as they plan to build, or continue building, their nuclear fleets. Generation-IV reactors are characterized by improved safety, economics, and proliferation resistance compared to current light water reactor designs. The hightemperature gas-cooled reactor (HTGR) exemplifies these characteristics with the additional benefit of process heat production capabilities. Past and current demonstration reactors have proved the technical feasibility of the design and several future reactors are set to enter demonstration phases as early as the late 2020s. Despite strong performance in past and present reactors, there remains several unknown variables, particularly in regards to fission product behavior and transport under differing reactor conditions. Due to the robust nature of the tristructural isotropic fuel particles used in HTGRs, as well as the large amount of graphite comprising the core, there is little risk of a reactor meltdown. Instead, the primary safety consideration of HTGRs is the release of radioactive materials from the core, either during normal operation or an off-normal event. Most fission and activation products will be completely retained in either the fuel particle or the surrounding matrix graphite; a few, however, have a demonstrated ability to migrate through all core structures and deposit onto cooling system components. This poses a danger to reactor workers and, if the closed coolant circuit were to be compromised, the public. With that in mind, it is essential to fully understand the transport parameters of these select radionuclides in every component of the reactor core, including the core structural graphite. This work has measured effective diffusion coefficients of Sr, Ag, Pd, Eu, and Cs in IG-110 structural graphite. A time-release method was utilized to measure these diffusion coefficients at temperatures up to 1973 K using an inductively-coupled plasma mass spectrometer. The effective diffusion coefficients here reported can be used to aid predictive fission product transport programs.Includes bibliographical references

The Application of Detrended Fluctuation Analysis and Adaptive Fractal Analysis on Center of Pressure Time Series in Parkinson's Disease

The long term goal of this thesis is to create quantitative, clinically significant measures that allow for early detection of Parkinson’s disease (PD) postural instability (PI), the progression of PI due to PD progression, and ultimately, fall risk in PD patients. Current clinical assessments in PD are not sufficiently sensitive to predict fall risk. Although biomechanical postural sway measures have provided quantitative characterization towards the progression of PI associated with PD progression, these methods are still not sufficiently sensitive to allow for early detection of PD and fall risk. Thus, a need arises for new quantitative methods to be established which can further describe PI progression in PD. This thesis had two overall goals: • Evaluate the appropriate selection of input parameters of detrended fluctuation analysis (DFA) and adaptive fractal analysis (AFA) in simulated signals. • Test the sensitivity of AFA, as compared to DFA, towards center of pressure velocity (COPv) time series towards characterization of postural instability (PI) progression in patients with Parkinson’s disease. Specific Aim 1 determined through iterative testing of input parameter combinations that both AFA and DFA are highly sensitive to input parameters when considering fractional Brownian motion (fBm) signals. Input parameter ranges for fBm-like signals in appropriately-large biological data should be examined at maximum window sizes (nmax) values between N/6 and N/10; minimum window sizes (nmin) values around 4 to 6 samples; and for fitted polynomial order (M) for AFA to remain first order. Specific Aim 2 showed that fractal analysis methods may be sensitive towards detecting the development and progression of PI in PD. AFA and DFA were tested on postural sway data collected in a previous study that used mild PD patients (Hoehn and Yahr stage (H&Y) 2, without postural deficits), moderate PD patients (H&Y 3, with postural deficits), and age-matched healthy controls (HC). AFA produced the most clinically significant measure, Hfast, which detected changes in COPv dynamics across smaller time scales than other parameters. These results suggest that components of fractal analysis on COPv time series could be used in concert with traditional quantitative and clinical measures to further enhance the sensitivity of clinical analysis, the understanding of PD PI dynamics and progression, and development of predictive computational simulations of motor and postural control in PD