18,013 research outputs found
Relating adults' lives and learning: participation and engagement in different settings
This report shows how an understanding of language, literacy andnumeracy as social practices can help practitioners to take account oflearners' lives. It demonstrates how people's histories, currentcircumstances and imagined futures can shape their learning andaffect their level of engagement. The study is based on the research ofthe Adult Learners' Lives project in community settings in Blackburn,Lancaster and Liverpool
Possibilities for pedagogy in Further Education: Harnessing the abundance of literacy
In this report, it is argued that the most salient factor in the contemporary communicative landscape is the sheer abundance and diversity of possibilities for literacy, and that the extent and nature of students' communicative resources is a central issue in education. The text outlines the conceptual underpinnings of the Literacies for Learning in Further Education project in a social view of literacy, and the associated research design, methodology and analytical framework. It elaborates on the notion of the abundance of literacies in students' everyday lives, and on the potential for harnessing these as resources for the enhancement of learning. It provides case studies of changes in practice that have been undertaken by further education staff in order to draw upon students' everyday literacy practices on Travel and Tourism and Multimedia courses. It ends with some of the broad implications for conceptualising learning that arise from researching through the lens of literacy practices
Saddle Points and Stark Ladders: Exact Calculations of Exciton Spectra in Superlattices
A new, exact method for calculating excitonic absorption in superlattices is
described. It is used to obtain high resolution spectra showing the saddle
point exciton feature near the top of the miniband. The evolution of this
feature is followed through a series of structures with increasing miniband
width. The Stark ladder of peaks produced by an axial electric field is
investigated, and it is shown that for weak fields the line shapes are strongly
modified by coupling to continuum states, taking the form of Fano resonances.
The calculated spectra, when suitably broadened, are found to be in good
agreement with experimental results.Comment: 9 pages Revtex v3.0, followed by 4 uuencoded postscript figures,
SISSA-CM-94-00
Study of shuttle imaging microwave system antenna. Volume 1: Conceptual design
A detailed preliminary design and complete performance evaluation are presented of an 11-channel large aperture scanning radiometer antenna for the shuttle imaging microwave system (SIMS) program. Provisions for interfacing the antenna with the space shuttle orbiter are presented and discussed. A program plan for hardware development and a rough order of magnitude (ROM) cost are also included. The conceptual design of the antenna is presented. It consists of a four-meter diameter parabolic torus main reflector, which is a graphite/epoxy shell supported by a graphite/epoxy truss. A rotating feed wheel assembly supports six Gregorian subreflectors covering the upper eight frequency channels from 6.6 GHz through 118.7 GHz, and two three-channel prime forms feed assemblies for 0.6, 1.4, and 2.7 GHz. The feed wheel assembly also holds the radiometers and power supplies, and a drive system using a 400 Hz synchronous motor is described. The RF analysis of the antenna is performed using physical optics procedures for both the dual reflector Gregorian concept and the single reflector prime focus concept. A unique aberration correcting feed for 2.7 GHz is analyzed. A structural analysis is also included. The analyses indicate that the antenna will meet system requirements
Modal Analysis of the Orion Capsule Two Parachute System
As discussed in Ref [1], it is apparent from flight tests that the system made up of two main parachutes and a capsule can undergo several distinct dynamical behaviors. The most significant and problematic of these is the pendulum mode in which the system develops a pronounced swinging motion with an amplitude of up to 24 deg. Large excursions away from vertical by the capsule could cause it to strike the ground at a large horizontal or vertical speed and jeopardize the safety of the astronauts during a crewed mission. In reference [1], Ali et al. summarized a series of efforts taken by the Capsule Parachute Assembly System (CPAS) Program to understand and mitigate the pendulum issue. The period of oscillation and location of the system's pivot point are determined from post-flight analysis. Other noticeable but benign modes include: 1) flyout (scissors) mode, where the parachutes move back and forth symmetrically with respect to the vertical axis similar to the motion of a pair of scissors; 2) maypole mode, where the two parachutes circle around the vertical axis at a nearly constant radius and period; and 3) breathing mode, in which deformation of the non-rigid canopies affects the axial acceleration of the system in an oscillatory manner. Because these modes are relatively harm- less, little effort has been devoted to analyzing them in comparison with the pendulum motion. Motions of the actual system made up of two parachutes and a capsule are extremely complicated due to nonlinearities and flexibility effects. Often it is difficult to obtain insight into the fundamental dynamics of the system by examining results from a multi-body simulation based on nonlinear equations of motion (EOMs). As a part of this study, the dynamics of each mode observed during flight is derived from first principles on an individual basis by making numerous simplifications along the way. The intent is to gain a better understanding into the behavior of the complex multi-body system by studying the reduced set of differential equations associated with each mode. This approach is analogous to the traditional modal analysis technique used to study airplane flight dynamics, in which the full nonlinear behavior of the airframe is decomposed into the phugoid and short period modes for the longitudinal dynamics and the spiral, roll-subsidence, and dutch-roll modes for the lateral dynamics. It is important to note that the study does not address the mechanisms that cause the system to transition from one mode to another, nor does it discuss motions during which two or more modes occur simultaneously
Elliptic Flow, Initial Eccentricity and Elliptic Flow fluctuations in Heavy Ion Collisions at RHIC
We present measurements of elliptic flow and event-by-event fluctuations
established by the PHOBOS experiment. Elliptic flow scaled by participant
eccentricity is found to be similar for both systems when collisions with the
same number of participants or the same particle area density are compared. The
agreement of elliptic flow between Au+Au and Cu+Cu collisions provides evidence
that the matter is created in the initial stage of relativistic heavy ion
collisions with transverse granularity similar to that of the participant
nucleons. The event-by-event fluctuation results reveal that the initial
collision geometry is translated into the final state azimuthal particle
distribution, leading to an event-by-event proportionality between the observed
elliptic flow and initial eccentricity.Comment: To appear in the proceedings of the Lake Louise Winter Institute
2007. The proceedings of the institute will be published by World Scientifi
Casimir-Polder forces, boundary conditions and fluctuations
We review different aspects of the atom-atom and atom-wall Casimir-Polder
forces. We first discuss the role of a boundary condition on the interatomic
Casimir-Polder potential between two ground-state atoms, and give a physically
transparent interpretation of the results in terms of vacuum fluctuations and
image atomic dipoles. We then discuss the known atom-wall Casimir-Polder force
for ground- and excited-state atoms, using a different method which is also
suited for extension to time-dependent situations. Finally, we consider the
fluctuation of the Casimir-Polder force between a ground-state atom and a
conducting wall, and discuss possible observation of this force fluctuation.Comment: 5 page
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Livestock production extension: Issues, case studies and policy options
As resources become more constrained, there is an increasing need to provide meaningful information on livestock production and the integration of crop and livestock farming systems, as well as on preventive medicine and general livestock health. It is vital that the information is delivered in such a way that it l.'ead1es, and can be understood by, farmers of all income groups. Although some national extension services are already in place, many are only readling the wealthier farmers who could afford to pay for the information Wlder a cost-recovery system. It is important to involve livestock producers in the development of any new extension system through participatory needs assessment. It is also necessary to improve linkages with research so that specific needs can be addressed. When the extension systems have been installed or suitably refined, their successes and failures should be regularly monitored and evaluated so that any adjustments can be made. The provision of livestock production extension is assessed with reference to case studies in Burkina Faso, Kenya and India. Existing systems are reviewed and their impact evaluated. In a final section, the roles of different institutions and methodologies are evaluated, and lessons for the future are discussed
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