13,859 research outputs found
Tensor-Scalar Torsion
A theory of gravity with torsion is examined in which the torsion tensor is
constructed from the exterior derivative of an antisymmetric rank two potential
plus the dual of the gradient of a scalar field. Field equations for the theory
are derived by demanding that the action be stationary under variations with
respect to the metric, the antisymmetric potential, and the scalar field. A
material action is introduced and the equations of motion are derived. The
correct conservation law for rotational angular momentum plus spin is observed
to hold in this theory.Comment: 10 pages, LaTeX, Mod. Phys. Lett. A accepte
Journalism Studies: A Critical Introduction
As the world of politics and public affairs has gradually changed beyond recognition over the past two decades, journalism too has been transformed... yet the study of news and journalism often seems stuck with ideas and debates which have lost much of their critical purchase. Journalism is at a crossroads: it needs to reaffirm core values and rediscover key activities, almost certainly in new forms, or it risks losing its distinctive character as well as its commercial basis.
Journalism Studies is a polemical textbook that rethinks the field of journalism studies for the contemporary era.
Organised around three central themes – ownership, objectivity and the public – Journalism Studies addresses the contexts in which journalism is produced, practised and disseminated. It outlines key issues and debates, reviewing established lines of critique in relation to the state of contemporary journalism, then offering alternative ways of approaching these issues, seeking to reconceptualise them in order to suggest an agenda for change and development in both journalism studies and journalism itself.
Journalism Studies is a concise and accessible introduction to contemporary journalism studies, and will be highly useful to undergraduate and postgraduate students on a range of Journalism, Media and Communications courses
Establishing a support service for educational technology within a university
This paper covers some of the issues associated with the support of learning technology within an institution. It describes the activities of a working support service, and highlights approaches to some of the academic, technological, political and management issues that have helped it perform effectively over a four‐year period
Strings in gravity with torsion
A theory of gravitation in 4D is presented with strings used in the material
action in spacetime. It is shown that the string naturally gives rise to
torsion. It is also shown that the equation of motion a string follows from the
Bianchi identity, gives the identical result as the Noether conservation laws,
and follows a geodesic only in the lowest order approximation. In addition, the
conservation laws show that strings naturally have spin, which arises not from
their motion but from their one dimensional structure.Comment: 16 page
Ride quality systems for commuter aircraft
The state-of-the-art in Active Ride Augmentation, specifically in terms of its feasibility for commuter aircraft applications. A literature survey was done, and the principal results are presented here through discussion of different Ride Quality Augmentation System (RQAS) designs and advances in related technologies. Recommended follow-on research areas are discussed, and a preliminary RQAS configuration for detailed design and development is proposed
Experimental and numerical study of error fields in the CNT stellarator
Sources of error fields were indirectly inferred in a stellarator by
reconciling computed and numerical flux surfaces. Sources considered so far
include the displacements and tilts (but not the deformations, yet) of the four
circular coils featured in the simple CNT stellarator. The flux surfaces were
measured by means of an electron beam and phosphor rod, and were computed by
means of a Biot-Savart field-line tracing code. If the ideal coil locations and
orientations are used in the computation, agreement with measurements is poor.
Discrepancies are ascribed to errors in the positioning and orientation of the
in-vessel interlocked coils. To that end, an iterative numerical method was
developed. A Newton-Raphson algorithm searches for the coils' displacements and
tilts that minimize the discrepancy between the measured and computed flux
surfaces. This method was verified by misplacing and tilting the coils in a
numerical model of CNT, calculating the flux surfaces that they generated, and
testing the algorithm's ability to deduce the coils' displacements and tilts.
Subsequently, the numerical method was applied to the experimental data,
arriving at a set of coil displacements whose resulting field errors exhibited
significantly improved quantitative and qualitative agreement with experimental
results.Comment: Special Issue on the 20th International Stellarator-Heliotron
Worksho
Spinless Matter in Transposed-Equi-Affine Theory of Gravity
We derive and discus the equations of motion for spinless matter:
relativistic spinless scalar fields, particles and fluids in the recently
proposed by A. Saa model of gravity with covariantly constant volume with
respect to the transposed connection in Einstein-Cartan spaces.
A new interpretation of this theory as a theory with variable Plank
"constant" is suggested.
We show that the consistency of the semiclassical limit of the wave equation
and classical motion dictates a new definite universal interaction of torsion
with massive fields.Comment: 29 pages, latex, no figures. New Section on semiclassical limit of
wave equation added; old references rearranged; new references, remarks,
comments, and acknowledgments added; typos correcte
Moment bounds for the Smoluchowski equation and their consequences
We prove uniform bounds on moments X_a = \sum_{m}{m^a f_m(x,t)} of the
Smoluchowski coagulation equations with diffusion, valid in any dimension. If
the collision propensities \alpha(n,m) of mass n and mass m particles grow more
slowly than (n+m)(d(n) + d(m)), and the diffusion rate d(\cdot) is
non-increasing and satisfies m^{-b_1} \leq d(m) \leq m^{-b_2} for some b_1 and
b_2 satisfying 0 \leq b_2 < b_1 < \infty, then any weak solution satisfies X_a
\in L^{\infty}(\mathbb{R}^d \times [0,T]) \cap L^1(\mathbb{R}^d \times [0,T])
for every a \in \mathbb{N} and T \in (0,\infty), (provided that certain moments
of the initial data are finite). As a consequence, we infer that these
conditions are sufficient to ensure uniqueness of a weak solution and its
conservation of mass.Comment: 30 page
Design of a digital ride quality augmentation system for commuter aircraft
Commuter aircraft typically have low wing loadings, and fly at low altitudes, and so they are susceptible to undesirable accelerations caused by random atmospheric turbulence. Larger commercial aircraft typically have higher wing loadings and fly at altitudes where the turbulence level is lower, and so they provide smoother rides. This project was initiated based on the goal of making the ride of the commuter aircraft as smooth as the ride experienced on the major commercial airliners. The objectives of this project were to design a digital, longitudinal mode ride quality augmentation system (RQAS) for a commuter aircraft, and to investigate the effect of selected parameters on those designs
Onion gene expression in response to ethylene and 1-MCP
Onion is regarded as a non-climacteric vegetable. In onions, however,
ethylene can suppress sprouting while the ethylene binding inhibitor, 1-MCP (1-
methylcyclopropene) can also suppress sprout growth yet, it is unknown how ethylene
and 1-MCP elicit the same response. In this study, onions were treated with 10 μL L-1
ethylene or 1 μL L-1 1-MCP individually or in combination for 24 h at 20°C before or
after curing (six weeks) at 20 or 28°C then stored at 1°C. Following curing, a subset
of these same onions was stored separately under continuous air or ethylene (10 μL L-
1) at 1°C
Onions treated with ethylene and 1-MCP in combination after curing for 24 h
had reduced sprout growth as compared with the control 25 weeks after harvest.
Sprout growth following storage beyond 25 weeks was only reduced through
continuous ethylene treatment. This observation was supported by a higher proportion
of down-regulated genes characterised as being involved in photosynthesis measured
using a newly developed onion microarray. Physiological and biochemical data
suggested that ethylene was being perceived in the presence of 1-MCP since sprout
growth was reduced in onions treated with 1-MCP and ethylene applied in
combination but not when applied individually. A cluster of probes representing
transcripts up-regulated by 1-MCP alone but down-regulated by ethylene alone or in
the presence of 1-MCP support this suggestion. Ethylene and 1-MCP both down52
regulated a probe tentatively annotated as an ethylene receptor as well as EIN3,
suggesting that both treatments down-regulate the perception and signalling events of
ethylene
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