Incidence of Auroras and Their North-South Motions in the Northern Auroral Zone

Studies of the incidence of auroral forms and their north and south motions are made by using a close-spaced array of all-sky cameras located in the northern auroral zone at the approximate geomagnetic longitude 250°E. It is found that during the observing season 1957-58 the peak of the average auroral zone occurred at 66-67° geomagnetic latitude. Although the southern extent of auroras retreats northward after local magnetic midnight, the southward motion of the individual forms, observed at the southern edge of the auroral zone, predominates over the northward motion throughout most of the night. The data indicate the existence on any given night of a latitude position near which many auroral forms occur. The first motion of auroras incident north of this position tends to be northward, and the first motion of auroras incident south of this position tends to be southward. A curve showing the occurrence of auroral forms peaks at, and is nearly symmetrical about, local geographic midnight, but the intensity of auroral emissions measured over the celestial hemisphere remains at a high level after midnight.NSP Grant No. Y/22.6/327Ye

Perspective distortion modeling for image measurements

A perspective distortion modelling for monocular view that is based on the fundamentals of perspective projection is presented in this work. Perspective projection is considered to be the most ideal and realistic model among others, which depicts image formation in monocular vision. There are many approaches trying to model and estimate the perspective effects in images. Some approaches try to learn and model the distortion parameters from a set of training data that work only for a predefined structure. None of the existing methods provide deep understanding of the nature of perspective problems. Perspective distortions, in fact, can be described by three different perspective effects. These effects are pose, distance and foreshortening. They are the cause of the aberrant appearance of object shapes in images. Understanding these phenomena have long been an interesting topic for artists, designers and scientists. In many cases, this problem has to be necessarily taken into consideration when dealing with image diagnostics, high and accurate image measurement, as well as accurate pose estimation from images. In this work, a perspective distortion model for every effect is developed while elaborating the nature of perspective effects. A distortion factor for every effect is derived, then followed by proposed methods, which allows extracting the true target pose and distance, and correcting image measurements

An evaluation of auroral all-sky camera observations

From photometric, all-sky camera, and visual observations of a moderate auroral display, it is found that the all-sky camera compares favorably with the visual observer in detecting and recording auroral forms. The visual observer can make instantaneous observations and so can detect rapid changes and auroral forms lasting only a few seconds, whereas the poorer time resolution of the all-sky camera prevents it from recording very short-lived phenonema. However, the ability of the all-sky camera to accurately record the shape and intensity of the majority of auroral forms allows it to yield more precise and complete information about these aspects of auroral morphology than is normally obtained through visual observation.Ye

Improved space radiation shielding methods

The computing software that was used to perform the charged particle radiation transport analysis and shielding design for the Mariner Jupiter/Saturn 1977 spacecraft is described. Electron fluences, energy spectra and dose rates obtained with this software are presented and compared with independent computer calculations

Chiral Vortons and Cosmological Constraints on Particle Physics

We investigate the cosmological consequences of particle physics theories that admit stable loops of current-carrying string - vortons. In particular, we consider chiral theories where a single fermion zero mode is excited in the string core, such as those arising in supersymmetric theories with a D-term. The resulting vortons formed in such theories are expected to be more stable than their non-chiral cousins. General symmetry breaking schemes are considered in which strings formed at one symmetry breaking scale become current-carrying at a subsequent phase transition. The vorton abundance is estimated and constraints placed on the underlying particle physics theories from cosmological observations. Our constraints on the chiral theory are considerably more stringent than the previous estimates for more general theories.Comment: minor corrections made. This version will appear in PR

Titanium honeycomb structure

A brazed titanium honeycomb sandwich system for supersonic transport wing cover panels provides the most efficient structure spanwise, chordwise, and loadwise. Flutter testing shows that high wing stiffness is most efficient in a sandwich structure. This structure also provides good thermal insulation if liquid fuel is carried in direct contact with the wing structure in integral fuel tanks

What makes a 'good group'? Exploring the characteristics and performance of undergraduate student groups

Group work forms the foundation for much of student learning within higher education, and has many educational, social and professional benefits. This study aimed to explore the determinants of success or failure for undergraduate student teams and to define a ‘good group’ through considering three aspects of group success: the task, the individuals, and the team. We employed a mixed methodology, combining demographic data with qualitative observations and task and peer evaluation scores. We determined associations between group dynamic and behaviour, demographic composition, member personalities and attitudes towards one another, and task success. We also employed a cluster analysis to create a model outlining the attributes of a good small group learning team in veterinary education. This model highlights that student groups differ in measures of their effectiveness as teams, independent of their task performance. On the basis of this, we suggest that groups who achieve high marks in tasks cannot be assumed to have acquired team working skills, and therefore if these are important as a learning outcome, they must be assessed directly alongside the task output

ASCA observations of massive medium-distant clusters of galaxies. II

We have selected seven medium-distant clusters of galaxies (z ~ 0.1 - 0.3) for multi-wavelength observations with the goal of investigating their dynamical state. Following Paper I (Pierre et al. 1999) which reported the ASCA results about two of them, we present here the analysis of the ASCA observations of the other five clusters; RXJ1023.8-2715 (A3444), RXJ1031.6-2607, RXJ1050.5-0236 (A1111), RXJ1203.2-2131(A1451), and RXJ1314.5-2517. Except for RXJ1031.6, whose X-ray emission turned out to be dominated by an AGN, the ASCA spectra are well fitted by a one-temperature thin thermal plasma model. We compare the temperature-luminosity relation of our clusters with that of nearby ones (z<0.1). Two clusters, RXJ1050.5 and RXJ1023.8, show larger luminosities than the bulk of clusters at similar temperatures, which suggests the presence of a cooling flow. The temperature vs. iron-abundance relationship of our sample is consistent with that of nearby clusters.Comment: 9 pages, 20 figures, A&AS in pres

Magnetoresistance in the superconducting state at the (111) LaAlO3_3/SrTiO3_3 interface

Condensed matter systems that simultaneously exhibit superconductivity and ferromagnetism are rare due the antagonistic relationship between conventional spin-singlet superconductivity and ferromagnetic order. In materials in which superconductivity and magnetic order is known to coexist (such as some heavy-fermion materials), the superconductivity is thought to be of an unconventional nature. Recently, the conducting gas that lives at the interface between the perovskite band insulators LaAlO$_3$ (LAO) and SrTiO$_3$ (STO) has also been shown to host both superconductivity and magnetism. Most previous research has focused on LAO/STO samples in which the interface is in the (001) crystal plane. Relatively little work has focused on the (111) crystal orientation, which has hexagonal symmetry at the interface, and has been predicted to have potentially interesting topological properties, including unconventional superconducting pairing states. Here we report measurements of the magnetoresistance of (111) LAO/STO heterostructures at temperatures at which they are also superconducting. As with the (001) structures, the magnetoresistance is hysteretic, indicating the coexistence of magnetism and superconductivity, but in addition, we find that this magnetoresistance is anisotropic. Such an anisotropic response is completely unexpected in the superconducting state, and suggests that (111) LAO/STO heterostructures may support unconventional superconductivity.Comment: 6 Pages 4 figure