1,005 research outputs found
Advanced composite aileron for L-1011 transport aircraft, task 1
Structural design and maintainability criteria were established and used as a guideline for evaluating a variety of configurations and materials for each of the major subcomponents. From this array of subcomponent designs, several aileron assemblies were formulated and analyzed. The selected design is a multirib configuration with sheet skin covers mechanically fastened to channel section ribs and spars. Qualitative analysis of currently available composite material systems led to the selection of three candidate materials on which comparative structural tests were conducted to measure the effects of environment and impact damage on mechanical property retention. In addition, each system was evaluated for producibility characteristics. From these tests, Thornel 300/5208 unidirectional tape was selected for the front spar and covers, and Thornel 300 fabric/5208 was chosen for the ribs
Study of advanced fuel system concepts for commercial aircraft and engines
The impact on a commercial transport aircraft of using fuels which have relaxed property limits relative to current commercial jet fuel was assessed. The methodology of the study is outlined, fuel properties are discussed, and the effect of the relaxation of fuel properties analyzed. Advanced fuel system component designs that permit the satisfactory use of fuel with the candidate relaxed properties in the subject aircraft are described. The two fuel properties considered in detail are freezing point and thermal stability. Three candidate fuel system concepts were selected and evaluated in terms of performance, cost, weight, safety, and maintainability. A fuel system that incorporates insulation and electrical heating elements on fuel tank lower surfaces was found to be most cost effective for the long term
Heterocyst placement strategies to maximize growth of cyanobacterial filaments
Under conditions of limited fixed-nitrogen, some filamentous cyanobacteria
develop a regular pattern of heterocyst cells that fix nitrogen for the
remaining vegetative cells. We examine three different heterocyst placement
strategies by quantitatively modelling filament growth while varying both
external fixed-nitrogen and leakage from the filament. We find that there is an
optimum heterocyst frequency which maximizes the growth rate of the filament;
the optimum frequency decreases as the external fixed-nitrogen concentration
increases but increases as the leakage increases. In the presence of leakage,
filaments implementing a local heterocyst placement strategy grow significantly
faster than filaments implementing random heterocyst placement strategies. With
no extracellular fixed-nitrogen, consistent with recent experimental studies of
Anabaena sp. PCC 7120, the modelled heterocyst spacing distribution using our
local heterocyst placement strategy is qualitatively similar to experimentally
observed patterns. As external fixed-nitrogen is increased, the spacing
distribution for our local placement strategy retains the same shape while the
average spacing between heterocysts continuously increases.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Physical Biology. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The definitive publisher-authenticated version
will be available onlin
Geometric representation of interval exchange maps over algebraic number fields
We consider the restriction of interval exchange transformations to algebraic
number fields, which leads to maps on lattices. We characterize
renormalizability arithmetically, and study its relationships with a
geometrical quantity that we call the drift vector. We exhibit some examples of
renormalizable interval exchange maps with zero and non-zero drift vector, and
carry out some investigations of their properties. In particular, we look for
evidence of the finite decomposition property: each lattice is the union of
finitely many orbits.Comment: 34 pages, 8 postscript figure
Making the user more efficient: Design for sustainable behaviour
User behaviour is a significant determinant of a productâs environmental impact; while engineering advances permit increased efficiency of product operation, the userâs decisions and habits ultimately have a major effect on the energy or other resources used by the product. There is thus a need to change usersâ behaviour. A range of design techniques developed in diverse contexts suggest opportunities for engineers, designers and other stakeholders working in the field of sustainable innovation to affect usersâ behaviour at the point of interaction with the product or system, in effect âmaking the user more efficientâ. Approaches to changing usersâ behaviour from a number of fields are reviewed and discussed, including: strategic design of affordances and behaviour-shaping constraints to control or affect energyor other resource-using interactions; the use of different kinds of feedback and persuasive technology techniques to encourage or guide users to reduce their environmental impact; and context-based systems which use feedback to adjust their behaviour to run at optimum efficiency and reduce the opportunity for user-affected inefficiency. Example implementations in the sustainable engineering and ecodesign field are suggested and discussed
The solvation and dissociation of 4-benzylaniline hydrochloride in chlorobenzene
A reaction scheme is proposed to account for the liberation of 4-benzylaniline from 4-benzylaniline hydrochloride, using chlorobenzene as a solvent at a temperature of 373 K. Two operational regimes are explored: âclosedâ reaction conditions correspond to the retention of evolved hydrogen chloride gas within the reaction medium, whereas an âopenâ system permits gaseous hydrogen chloride to be released from the reaction medium. The solution phase chemistry is analyzed by 1H NMR spectroscopy. Complete liberation of solvated 4-benzylaniline from solid 4-benzylaniline hydrochloride is possible under âopenâ conditions, with the entropically favored conversion of solvated hydrogen chloride to the gaseous phase thought to be the thermodynamic driver that effectively controls a series of interconnecting equilibria. A kinetic model is proposed to account for the observations of the open system
Effect of a magnetosphere compression on Jovian radio emissions: in situ case study using Juno data
During its 53-day polar orbit around Jupiter, Juno often crosses the
boundaries of the Jovian magnetosphere (namely the magnetopause and bow shock).
From the boundary locations, the upstream solar wind dynamic pressure can be
inferred, which in turn illustrates the state of compression or relaxation of
the system. The aim of this study is to examine Jovian radio emissions during
magnetospheric compressions, in order to determine the relationship between the
solar wind and Jovian radio emissions. In this paper, we give a complete list
of bow shock and magnetopause crossings (from June 2016 to August 2022), along
with some extra informations (e.g. solar wind dynamic pressure and position of
the standoff distances inferred from Joy et al. (2002)). We then select two
compression events that occur in succession (inferred from magnetopause
crossings) and we present a case study of the response of the Jovian radio
emissions. We demonstrate that magnetospheric compressions lead to the
activation of new radio sources. Newly activated broadband kilometric emissions
are observed almost simultaneously to compression of the magnetosphere, with
sources covering a large range of longitudes. Decametric emission sources are
seen to be activated more than one rotation later only at specific longitudes
and dusk local times. Finally, the activation of narrowband kilometric
radiation is not observed during the compression phase, but when the
magnetosphere is in its expansion phase
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