2,505 research outputs found
An Investigation of the Use of Bandwidth Criteria for Rotorcraft Handling-Qualities Specifications
The objective of this study was to investigate bandwidth concepts for deriving rotorcraft handling-qualities criteria from data obtained in two simulator experiments conducted at the Aeromechanics Laboratory. The first experiment was an investigation of the effects of helicopter vertical-thrust-response characteristics on handling qualities; the second experiment investigated the effects of helicopter yaw-control-response characteristics. In both experiments, emphasis was on low-speed Nap-of-the-Earth (NOE) tasks
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Investigating Dielectric Properties of Sintered Polymers for Rapid Manufacturing
Selective Laser Sintering (SLS) of polymers is the leading technology in the growing field of
Rapid Manufacturing. High Speed Sintering (HSS) is a process that offers the potential to reduce
costs and processing times and thus open significant new markets for Rapid Manufactured parts.
Much academic research has been performed with respect to mechanical properties of Rapid
Manufactured parts, however the area of electrical properties has received little attention to date.
Electrical properties are obviously important in applications that will involve embedding of
circuits with Rapid Manufactured 3D objects. However electrical properties are also important
for a wide variety of electrical products where Rapid Manufactured parts can be used as housings
etc.
This paper focuses on the dielectric properties of parts made by SLS and HSS and compares
properties with those for conventionally processed polymers. Dielectric strength results show
that SLS parts are comparable with injection moulded parts, while HSS parts are inferior to SLS
parts. Dielectric constant and dissipation factor results show that HSS parts are comparable with
injection moulded parts, whilst SLS parts have superior properties. The presence of porosity
(SLS and HSS) and the presence of carbon (HSS) are suggested as reasons behind the variation in
dielectric properties when compared with injection moulded parts.Mechanical Engineerin
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A functional model of similarity
In the first chapters, the prevalent conception of the nature of similarity is shown to be too narrow, and the argument is developed that models of similarity must encompass both analytic and synthetic components. Some general problems of measurement and the testing of psychological models are also discussed.A review of the philosophical treatment of the concept of similarity is made in order to understand the origins of the models found in the present psychological literature. These are then analysed in terms of their implicit object representations and cognitive processes. The distinction between the'class inclusion' and 'distance relation' models of similarity is shown tobe qualitative in nature, and to correspond to the analytic-synthetic distinction in terms of cognitive process.A functional model of the psychological processes and object representations involved in similarity judgements is then proposed. The fundamental idea involved in this model is that the global properties of referents are synthetically evaluated in terms of their contextual relations, whilst an analytic 'pattern matching' of local properties is made. Various theoretical aspects of the model are examined experimentally, and its general applicability is indicated in a series of applied studies.The scope of the argument is finally broadened to encompass a development of Torgerson's (196.5) conception of the nature of the dimensions resulting from MDS analysis. Dimensions may be considered as 'virtual' artifacts of the experimental task and the individual's conception of it. This possibility allows the methodology to escape the dominating influence of its psychophysical tradition, and become a conceptually deeper tool for cognitive psychology
Electronics and Chemistry: Varying Single Molecule Junction Conductance Using Chemical Substituents
We measure the low bias conductance of a series of substituted benzene
diamine molecules while breaking a gold point contact in a solution of the
molecules. Transport through these substituted benzenes is by means of
nonresonant tunneling or superexchange, with the molecular junction conductance
depending on the alignment of the metal Fermi level to the closest molecular
level. Electron-donating substituents, which drive the occupied molecular
orbitals up, increase the junction conductance, while electron-withdrawing
substituents have the opposite effect. Thus for the measured series,
conductance varies inversely with the calculated ionization potential of the
molecules. These results reveal that the occupied states are closest to the
gold Fermi energy, indicating that the tunneling transport through these
molecules is analogous to hole tunneling through an insulating film.Comment: 14 pages, 4 figure
Formation and Evolution of Single Molecule Junctions
We analyze the formation and evolution statistics of single molecule
junctions bonded to gold electrodes using amine, methyl sulfide and dimethyl
phosphine link groups by measuring conductance as a function of junction
elongation. For each link, maximum elongation and formation probability
increase with molecular length, strongly suggesting that processes other than
just metal-molecule bond breakage play a key role in junction evolution under
stress. Density functional theory calculations of adiabatic trajectories show
sequences of atomic-scale changes in junction structure, including shifts in
attachment point, that account for the long conductance plateau lengths
observed.Comment: 10 pages, 4 figures, submitte
Cannabinol and cannabidiol exert opposing effects on rat feeding patterns
Rationale: Increased food consumption following Δ9-
tetrahydrocannabinol-induced cannabinoid type 1 receptor
agonism is well documented. However, possible non-Δ9-
tetrahydrocannabinol phytocannabinoid-induced feeding
effects have yet to be fully investigated. Therefore, we
have assessed the effects of the individual phytocannabinoids, cannabigerol, cannabidiol and cannabinol, upon feeding behaviors.
Methods: Adult male rats were treated (p.o.) with cannabigerol, cannabidiol, cannabinol or cannabinol plus the CB1R antagonist, SR141716A. Prior to treatment, rats were satiated and food intake recorded following drug administration. Data were analyzed for hourly intake and meal microstructure.
Results: Cannabinol induced a CB1R-mediated increase in
appetitive behaviors via significant reductions in the latency to feed and increases in consummatory behaviors via
increases in meal 1 size and duration. Cannabinol also
significantly increased the intake during hour 1 and total
chow consumed during the test. Conversely, cannabidiol
significantly reduced total chow consumption over the test
period. Cannabigerol administration induced no changes to
feeding behavior.
Conclusion: This is the first time cannabinol has been shown to increase feeding. Therefore, cannabinol could, in the future, provide an alternative to the currently used and
psychotropic Δ9-tetrahydrocannabinol-based medicines since
cannabinol is currently considered to be non-psychotropic.
Furthermore, cannabidiol reduced food intake in line with
some existing reports, supporting the need for further mechanistic and behavioral work examining possible anti-obesity effects of cannabidiol
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