Optimal Cantilever Dynamic Vibration Absorbers

This work considers the use of a double-ended cantilever beam as a distributed parameter dynamic vibration absorber applied to a single-degree-of-freedom system in the presence of sinusoidal forces. The problem is analyzed exactly and by an energy approach using a single mode approximation for the cantilever beam. The results for both techniques compare favorably and damping is introduced in the form of a complex beam modulus. Optimal tuning and optimal damping parameters are found for a given ratio of absorber mass to main mass. © 1977 by ASME

Low density instability in a nuclear Fermi liquid drop

The instability of a Fermi-liquid drop with respect to bulk density distortions is considered. It is shown that the presence of the surface strongly reduces the growth rate of the bulk instability of the finite Fermi-liquid drop because of the anomalous dispersion term in the dispersion relation. The instability growth rate is reduced due to the Fermi surface distortions and the relaxation processes. The dependence of the bulk instability on the multipolarity of the particle density fluctuations is demonstrated for two nuclei $^{40}Ca$ and $^{208}Pb$.Comment: 12 pages, latex, 3 ps-figures, submitted to Phys. Rev.

ICRF wave field measurements in the presence of scrape off layer turbulence on the ASDEX Upgrade tokamak (invited)

A new array of B-dot probes was installed on ASDEX Upgrade. The purpose of the new diagnostic is to study Ion Cyclotron Range-off Frequencies (ICRF) wave field distributions in the evanescent scrape-off layer (SOL) plasma region on the low field side of ASDEX Upgrade. The vacuum measurements (no gas, B-T = 0 T) reveal ICRF wave field measurements consistent with the profiles expected from the newly installed 3-strap ICRF antennas outside the antenna box: the shape of the toroidal distribution of both the amplitude and the phase is the same for the case of only the central straps being active, as for the case of only the side straps being active. These profiles become strongly modified during plasma operations. The modifications can be separated into two types: " Inter-edge localized mode (ELM)" and " During-ELM" periods. The phase distribution of the ICRF wave fields remains well-defined during the Inter-ELM period; however, it becomes more spread out over the entire 360. range during ELMs. The observed modulations cannot be explained by the observed changes in the ICRF power, as monitored in the transmission line. However, they are consistent with ICRF coupling changes introduced by plasma filaments: the plasma density perturbations due to the filaments are high enough to change the nature of the fast ICRF wave field from evanescent to propagating. The coverage of the present diagnostic is being expanded to include both the low field side and the high field side probes. Additionally, a manipulator probe head is being developed to measure ICRF wave field radial profiles across the SOL region. Published by AIP Publishing

Integrating Power Engineering Topics and Applications in Non-Power Courses

This paper investigates integrating power engineering material over the breadth of an electrical engineering curriculum. Electrical engineering curricula have a large number of required courses and many subareas for students to study. By introducing power concepts in a variety of courses, students may be motivated to take additional courses in the power area and are better prepared for the diverse background which will be required of them as practising power engineers. The important interrelationships between subareas of electrical engineering are better understood by students when cross discipline applications are discussed. This paper describes the introduction of power concepts and applications in courses such as linear systems, digital systems, microprocessors, digital signal processing, electronic system design and electrical materials

Continuous non-perturbative regularization of QED

We regularize in a continuous manner the path integral of QED by construction of a non-local version of its action by means of a regularized form of Dirac's $\delta$ functions. Since the action and the measure are both invariant under the gauge group, this regularization scheme is intrinsically non-perturbative. Despite the fact that the non-local action converges formally to the local one as the cutoff goes to infinity, the regularized theory keeps trace of the non-locality through the appearance of a quadratic divergence in the transverse part of the polarization operator. This term which is uniquely defined by the choice of the cutoff functions can be removed by a redefinition of the regularized action. We notice that as for chiral fermions on the lattice, there is an obstruction to construct a continuous and non ambiguous regularization in four dimensions. With the help of the regularized equations of motion, we calculate the one particle irreducible functions which are known to be divergent by naive power counting at the one loop order.Comment: 23 pages, LaTeX, 5 Encapsulated Postscript figures. Improved and revised version, to appear in Phys. Rev.

Evidence for Spinodal Decomposition in Nuclear Multifragmentation

Multifragmentation of a ``fused system'' was observed for central collisions between 32 MeV/nucleon 129Xe and natSn. Most of the resulting charged products were well identified thanks to the high performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments show a weak but non ambiguous enhancement of events with nearly equal-sized fragments. Supported by dynamical calculations in which spinodal decomposition is simulated, this observed enhancement is interpreted as a ``fossil'' signal of spinodal instabilities in finite nuclear systems.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Letter

Modern Rutherford experiment: Tunneling of the most neutron-rich nucleus

Expérience GANIL/SPIRALA modern variation of the Rutherford experiment to probe the tunneling of exotic nuclear matter from the measurement of the residues formed in the bombardment of 197Au by extremely neutronrich 8He nuclei is presented. Using a novel off-beam technique the most precise and accurate measurements of fusion and neutron transfer involving re-accelerated unstable beams are reported. The results show unusual behavior of the tunneling of 8He compared to that for lighter helium isotopes, highlighting the role of the intrinsic structure of composite many-body quantum systems and pairing correlations