Solar-Electric Propulsion Probes for Exploring the Solar System

Payload capability of unmanned interplanetary probes using solar electric propulsio

Constitutional Constraints on the Admissibility of Grand Jury Testimony: The Unavailable Witness, Confrontation, and Due Process

Defendants, however, have raised serious constitutional objections to the introduction of grand jury testimony when the witness is unavailable to testify at trial. These claims have focused on the confrontation clause of the sixth amendment and the due process clauses of the fifth and fourteenth amendments. Defendants have contended that the introduction of testimony from a grand jury proceeding which cannot be subjected to cross-examination fatally compromises the defendant\u27s right to a fair trial. Lower courts are split over admitting grand jury testimony in these circumstances, and the Supreme Court has yet to rule on the issue. As a result, trial judges are left with little guidance as they grapple with evidentiary disputes amidst the pressures of criminal prosecutions. This Note argues that the confrontation clause normally bars grand jury testimony, but that it may be admissible when a defendant has waived his confrontation rights and an independent standard of due process is satisfied. Part I discusses the framework for confrontation analysis established by the Supreme Court in the context of preliminary hearings and applies it to the grand jury setting. This section concludes that grand jury testimony does not meet the Court\u27s test for reliability and therefore should not, as a general matter, be admissible at a later trial. Part II goes beyond the issue of confrontation and examines the additional considerations important for due process analysis if a defendant waives the right to confront

Frustration and glassiness in spin models with cavity-mediated interactions

We show that the effective spin-spin interaction between three-level atoms confined in a multimode optical cavity is long-ranged and sign-changing, like the RKKY interaction; therefore, ensembles of such atoms subject to frozen-in positional randomness can realize spin systems having disordered and frustrated interactions. We argue that, whenever the atoms couple to sufficiently many cavity modes, the cavity-mediated interactions give rise to a spin glass. In addition, we show that the quantum dynamics of cavity-confined spin systems is that of a Bose-Hubbard model with strongly disordered hopping but no on-site disorder; this model exhibits a random-singlet glass phase, absent in conventional optical-lattice realizations. We briefly discuss experimental signatures of the realizable phases.Comment: 5 pages, 2 figure

Technology and benefits of aircraft counter rotation propellers

Results are reported of a NASA sponsored analytical investigation into the merits of advanced counter rotation propellers for Mach 0.80 commercial transport application. Propeller and gearbox performance, acoustics, vibration characteristics, weight, cost and maintenance requirements for a variety of design parameters and special features were considered. Fuel savings in the neighborhood of 8 percent relative to single rotation configurations are feasible through swirl recovery and lighter gearboxes. This is the net gain which includes a 5 percent acoustic treatment weight penalty to offset the broader frequency spectrum noise produced by counter rotation blading

The context paradox in attitude surveys: assimilation or contrast?

Die Autoren untersuchen mit Hilfe dreier Experimente, unter welchen Bedingungen Antworten auf eine allgemeiner formulierte Frage ähnlicher ('part-whole-assimilation') oder unähnlicher ('part-whole-contrast') in bezug zu den Antworten auf eine folgende spezifischer formulierte Frage werden. Als Experimente sind an der Universität Illinois und Mannheim Befragungen von Studenten zu studentischen Belangen durchgeführt worden. Es wurde vermutet, daß das Fragen mit einer spezifischen Fragestellung die kognitive Zugänglichkeit zur gefragten Information erhöht. Die Antwort auf die nachfolgende allgemeine Frage könnte danach teilweise auf derselben Information beruhen und zur ähnlichen Antwort führen. Es zeigte sich, daß in Übertragung von Prinzipien der Alltagskommunikation, nach denen der Kommunikator Redundanz vermeiden sollte, die spezifische Information oft nicht mitgeteilt wird. Daraus läßt sich folgern, daß, wenn beide Fragen als zusammen gehörend wahrgenommen werden, die Antworten uneinheitlich werden. Die Autoren beschreiben die Bedingungen, unter denen die Effekte identifiziert und experimentell manipuliert worden sind und diskutieren die Fragebogengestaltung. (HN2)'Three experiments were conducted to determine under which conditions responses to a general question become more similar to ('part-whole assimilation') or more dissimilar from ('part-whole contrast') responses to a preceding specific question. The results suggest that asking a specific question increases the cognitive accessibility of the information used to answer it. The answer to the subsequent general question will therefore be based in part on the same information, resulting in similar responses. The highly accessible specific information, however, will not always be used. Most importantly, central principles of conversation urge communicators to be informative and to avoid redundancy. Therefore, if both questions are perceived as belonging together, the previously activated will be disregarded, which results in dissimilar pesponses to the general question. The conditions under which these effects occur are identified and experimentally manipulated, and the implications for questionnaire design are discussed.' (author's abstract

Manned Mars landing missions using electric propulsion

Manned Mars landing missions using electric propulsion - evaluation of various mission profile

Ferromagnetism in Correlated Electron Systems: Generalization of Nagaoka's Theorem

Nagaoka's theorem on ferromagnetism in the Hubbard model with one electron less than half filling is generalized to the case where all possible nearest-neighbor Coulomb interactions (the density-density interaction $V$, bond-charge interaction $X$, exchange interaction $F$, and hopping of double occupancies $F'$) are included. It is shown that for ferromagnetic exchange coupling ($F>0$) ground states with maximum spin are stable already at finite Hubbard interaction $U>U_c$. For non-bipartite lattices this requires a hopping amplitude $t\leq0$. For vanishing $F$ one obtains $U_c\to\infty$ as in Nagaoka's theorem. This shows that the exchange interaction $F$ is important for stabilizing ferromagnetism at finite $U$. Only in the special case $X=t$ the ferromagnetic state is stable even for $F=0$, provided the lattice allows the hole to move around loops.Comment: 13 pages, uuencoded postscript, includes 1 table and 2 figure

Some Low-Temperature Properties of a Generalized Hubbard Model with Correlated Hopping

In the present paper we study some correlation effects in a generalized Hubbard model with correlated hopping within low-temperature region using a generalized mean-field approximation. It is shown that in a series of cases the model leads to consequences deviating essentially from those of the Hubbard model. We consider the possibility of applying the result to interpret the peculiarities of physical properties of systems with narrow energy bands.Comment: 2 pages, LaTex2e using Elsevier style, presented at LT22 Conference, Helsinki, August 199