Measurement by wake momentum surveys at Mach 1.61 and 2.01 of turbulent boundary-layer skin friction on five swept wings

Measurement by wake momentum surveys at Mach 1.61 and 2.01 of turbulent boundary layer skin friction on five swept wing

The study of comets, part 2

Flyby missions and systematic observations of comets are projected for studying comet nuclei and cometary dust tail structures

The study of comets, part 1

Papers are presented dealing with observations of comets. Topic discussed include: photometry, polarimetry, and astrometry of comets; detection of water and molecular transitions in comets; ion motions in comet tails; determination of comet brightness and luminosity; and evolution of cometary orbits. Emphasis is placed on analysis of observations of comet Kohoutek

A survey of polarization in the JVAS/CLASS flat-spectrum radio source surveys: I. The data and catalogue production

We have used the very large JVAS/CLASS 8.4-GHz surveys of flat-spectrum radio sources to obtain a large, uniformly observed and calibrated, sample of radio source polarizations. These are useful for many investigations of the properties of radio sources and the interstellar medium. We discuss comparisons with polarization measurements from this survey and from other large-scale surveys of polarization in flat-spectrum sources.Comment: Accepted by MNRAS. 8 pages, 5 figures. Full version of Table 2 available at http://www.jb.man.ac.uk/~njj/classqu_po

Transistor and Diode Studies

Contains reports on two research projects.Lincoln Laboratory (Purchase Order DDL-B187)Department of the ArmyDepartment of the NavyDepartment of the Air Force under Contract AF19(122)-45

Vortex signatures in annular Bose-Einstein condensates

We consider a Bose-Einstein condensate confined in a ``Mexican hat'' potential, with a quartic minus quadratic radial dependence. We find conditions under which the ground state is annular in shape, with a hole in the center of the condensate. Rotation leads to the appearance of stable multiply-quantized vortices, giving rise to a superfluid flow around the ring. The collective modes of the system are explored both numerically and analytically using the Gross-Pitaevskii and hydrodynamic equations. Potential experimental schemes to detect vorticity are proposed and evaluated, which include measuring the splitting of collective mode frequencies, observing expansion following release from the trap, and probing the momentum distribution of the condensate.Comment: 11 pages, 7 figure

An analysis of the far-field response to external forcing of a suspension in Stokes flow in a parallel-wall channel

The leading-order far-field scattered flow produced by a particle in a parallel-wall channel under creeping flow conditions has a form of the parabolic velocity field driven by a 2D dipolar pressure distribution. We show that in a system of hydrodynamically interacting particles, the pressure dipoles contribute to the macroscopic suspension flow in a similar way as the induced electric dipoles contribute to the electrostatic displacement field. Using this result we derive macroscopic equations governing suspension transport under the action of a lateral force, a lateral torque or a macroscopic pressure gradient in the channel. The matrix of linear transport coefficients in the constitutive relations linking the external forcing to the particle and fluid fluxes satisfies the Onsager reciprocal relation. The transport coefficients are evaluated for square and hexagonal periodic arrays of fixed and freely suspended particles, and a simple approximation in a Clausius-Mossotti form is proposed for the channel permeability coefficient. We also find explicit expressions for evaluating the periodic Green's functions for Stokes flow between two parallel walls.Comment: 23 pages, 12 figure

Hysteresis effects in rotating Bose-Einstein condensates

We study the formation of vortices in a dilute Bose-Einstein condensate confined in a rotating anisotropic trap. We find that the number of vortices and angular momentum attained by the condensate depends upon the rotation history of the trap and on the number of vortices present in the condensate initially. A simplified model based on hydrodynamic equations is developed, and used to explain this effect in terms of a shift in the resonance frequency of the quadrupole mode of the condensate in the presence of a vortex lattice. Differences between the spin-up and spin-down response of the condensate are found, demonstrating hysteresis phenomena in this system.Comment: 16 pages, 7 figures; revised after referees' report

<i>‘What retention’ means to me</i>: the position of the adult learner in student retention

Studies of student retention and progression overwhelmingly appear adopt definitions that place the institution, rather than the student, at the centre. Retention is most often conceived in terms of linear and continuous progress between institutionally identified start and end points. This paper reports on research that considered data from 38 in-depth interviews conducted with individuals who had characteristics often associated with non-traditional engagement in higher education who between 2006 and 2010 had studied an ‘Introduction to HE’ module at one distance higher education institution, some of whom had progressed to further study at that institution, some of whom had not. The research deployed a life histories approach to seek a finer grained understanding of how individuals conceptualise their own learning journey and experience, in order to reflect on institutional conceptions of student retention. The findings highlight potential anomalies hidden within institutional retention rates – large proportions of the interview participants who were not ‘retained’ by the institution reported successful progression to and in other learning institutions and environments, both formal and informal. Nearly all described positive perspectives on lifelong learning which were either engendered or improved by the learning undertaken. This attests to the complexity of individuals’ lives and provides clear evidence that institution-centric definitions of retention and progression are insufficient to create truly meaningful understanding of successful individual learning journeys and experiences. It is argued that only through careful consideration of the lived experience of students and a re-conception of measures of retention, will we be able to offer real insight into improving student retention

Fiscal year 1976 progress report on a feasibility study evaluating the use of surface penetrators for planetary exploration

The feasibility of employing penetrators for exploring Mars was examined. Eight areas of interest for key scientific experiments were identified. These include: seismic activity, imaging, geochemistry, water measurement, heatflow, meteorology, magnetometry, and biochemistry. In seven of the eight potential experiment categories this year's progress included: conceptual design, instrument fabrication, instrument performance evaluation, and shock loading of important components. Most of the components survived deceleration testing with negligible performance changes. Components intended to be placed inside the penetrator forebody were tested up to 3,500 g and components intended to be placed on the afterbody were tested up to 21,000 g. A field test program was conducted using tentative Mars penetrator mission constraints. Drop tests were performed at two selected terrestrial analog sites to determine the range of penetration depths for anticipated common Martian materials. Minimum penetration occurred in basalt at Amboy, California. Three full-scale penetrators penetrated 0.4 to 0.9 m into the basalt after passing through 0.3 to 0.5 m of alluvial overburden. Maximum penetration occurred in unconsolidated sediments at McCook, Nebraska. Two full-scale penetrators penetrated 2.5 to 8.5 m of sediment. Impact occurred in two kinds of sediment: loess and layered clay. Deceleration g loads of nominally 2,000 for the forebody and 20,000 for the afterbody did not present serious design problems for potential experiments. Penetrators have successfully impacted into terrestrial analogs of the probable extremes of potential Martian sites