17,318 research outputs found
Individual differences in human annoyance response to noise
Individual variations in annoyance and in susceptibility to noise were studied to establish a finer definition of the ingredients of the human annoyance response. The study involved interactions among a heterogeneous sample of human subjects, various noise stimuli, and different physical environments of exposure. Significant differences in annoyance ratings among the six noise stimuli, all equated for peak sound pressure level, were found
On the accuracy of retrieved wind information from Doppler lidar observations
A single pulsed Doppler lidar was successfully deployed to measure air flow and turbulence over the Malvern hills, Worcester, UK. The DERA Malvern lidar used was a CO2 µm pulsed Doppler lidar. The lidar pulse repetition rate was 120 Hz and had a pulse duration of 0.6 µs The system was set up to have 41 range gates with range resolution of 112 m. This gave a theoretical maximum range of approximately 4.6 km. The lidar site was 2 km east of the Malvern hill ridge which runs in a north-south direction and is approximately 6 km long. The maximum height of the ridge is 430 m. Two elevation scans (Range-Height Indicators) were carried out parallel and perpendicular to the mean surface flow. Since the surface wind was primarily westerly the scans were carried out perpendicular and parallel to the ridge of the Malvern hills.
The data were analysed and horizontal winds, vertical winds and turbulent fluxes were calculated for profiles throughout the boundary layer. As an aid to evaluating the errors associated with the derivation of velocity and turbulence profiles, data from a simple idealized profile was also analysed using the same method. The error analysis shows that wind velocity profiles can be derived to an accuracy of 0.24 m s-1 in the horizontal and 0.3 m s-1 in the vertical up to a height of 2500 m. The potential for lidars to make turbulence measurements, over a wide area, through the whole depth of the planetary boundary layer and over durations from seconds to hours is discussed
Effects of noise upon human information processing
Studies of noise effects upon human information processing are described which investigated whether or not effects of noise upon performance are dependent upon specific characteristics of noise stimulation and their interaction with task conditions. The difficulty of predicting noise effects was emphasized. Arousal theory was considered to have explanatory value in interpreting the findings of all the studies. Performance under noise was found to involve a psychophysiological cost, measured by vasoconstriction response, with the degree of response cost being related to scores on a noise annoyance sensitivity scale. Noise sensitive subjects showed a greater autonomic response under noise stimulation
Pressure Induced Changes in the Antiferromagnetic Superconductor YbPd2Sn
Low temperature ac magnetic susceptibility measurements of the coexistent
antiferromagnetic superconductor YbPd2Sn have been made in hydrostatic
pressures < 74 kbar in moissanite anvil cells. The superconducting transition
temperature is forced to T(SC) = 0 K at a pressure of 58 kbar. The initial
suppression of the superconducting transition temperature is corroborated by
lower hydrostatic pressure (p < 16 kbar) four point resisitivity measurements,
made in a piston cylinder pressure cell. At ambient pressure, in a modest
magnetic field of ~ 500 G, this compound displays reentrant superconducting
behaviour. This reentrant superconductivity is suppressed to lower temperature
and lower magnetic field as pressure is increased. The antiferromagnetic
ordering temperature, which was measured at T(N) = 0.12 K at ambient pressure
is enhanced, to reach T(N) = 0.58 K at p = 74 kbar. The reasons for the
coexistence of superconductivity and antiferromagnetism is discussed in the
light of these and previous findings. Also considered is why superconductivity
on the border of long range magnetic order is so much rarer in Yb compounds
than in Ce compounds. The presence of a new transition visible by ac magnetic
susceptibility under pressure and in magnetic fields greater than 1.5 kG is
suggested.Comment: 5 pages, 6 figure
Studies relating the individual characteristics of people with their responses to noise
Characteristic human responses to aviation and industrial noise stimul
Magnetism: the Driving Force of Order in CoPt. A First-Principles Study
CoPt or FePt equiatomic alloys order according to the tetragonal L10
structure which favors their strong magnetic anisotropy. Conversely magnetism
can influence chemical ordering. We present here {\it ab initio} calculations
of the stability of the L10 and L12 structures of Co-Pt alloys in their
paramagnetic and ferromagnetic states. They show that magnetism strongly
reinforces the ordering tendencies in this system. A simple tight-binding
analysis allows us to account for this behavior in terms of some pertinent
parameters
Morphological analysis of the cm-wave continuum in the dark cloud LDN1622
The spectral energy distribution of the dark cloud LDN1622, as measured by
Finkbeiner using WMAP data, drops above 30GHz and is suggestive of a Boltzmann
cutoff in grain rotation frequencies, characteristic of spinning dust emission.
LDN1622 is conspicuous in the 31 GHz image we obtained with the Cosmic
Background Imager, which is the first cm-wave resolved image of a dark cloud.
The 31GHz emission follows the emission traced by the four IRAS bands. The
normalised cross-correlation of the 31 GHz image with the IRAS images is higher
by 6.6sigma for the 12um and 25um bands than for the 60um and 100um bands:
C(12+25) = 0.76+/-0.02 and C(60+100) = 0.64+/-0.01.
The mid-IR -- cm-wave correlation in LDN 1622 is evidence for very small
grain (VSG) or continuum emission at 26-36GHz from a hot molecular phase. In
dark clouds and their photon-dominated regions (PDRs) the 12um and 25um
emission is attributed to stochastic heating of the VSGs. The mid-IR and
cm-wave dust emissions arise in a limb-brightened shell coincident with the PDR
of LDN1622, where the incident UV radiation from the Ori OB1b association heats
and charges the grains, as required for spinning dust.Comment: accepted for publication in ApJ - the complete article with
uncompressed figures may be downloaded from
http://www.das.uchile.cl/~simon/ftp/l1622.pd
A shrinking Compact Symmetric Object: J11584+2450?
We present multi-frequency multi-epoch Very Long Baseline Array (VLBA)
observations of J11584+2450. These observations clearly show this source,
previously classified as a core-jet, to be a compact symmetric object (CSO).
Comparisons between these new data and data taken over the last 9 years shows
the edge brightened hot spots retreating towards the core (and slightly to the
west) at approximately 0.3c. Whether this motion is strictly apparent or
actually physical in nature is discussed, as well as possible explanations, and
what implications a physical contraction of J11584+2450 would have for current
CSO models.Comment: 16 pages, 6 figures, 5 tables. Accepted for publication in Ap
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Simulation and Measurement of Transient Fluid Phenomena within Diesel Injection
Rail pressures of modern diesel fuel injection systems have increased significantly over recent years, greatly improving atomisation of the main fuel injection event and air utilisation of the combustion process. Continued improvement in controlling the process of introducing fuel into the cylinder has led to focussing on fluid phenomena related to transient response. High-speed microscopy has been employed to visualise the detailed fluid dynamics around the near nozzle region of an automotive diesel fuel injector, during the opening, closing and post injection events. Complementary computational fluid dynamic (CFD) simulations have been undertaken to elucidate the interaction of the liquid and gas phases during these highly transient events, including an assessment of close-coupled injections. Microscopic imaging shows the development of a plug flow in the initial stages of injection, with rapid transition into a primary breakup regime, transitioning to a finely atomised spray and subsequent vaporisation of the fuel. During closuring of the injector the spray collapses, with evidence of swirling breakup structures together with unstable ligaments of fuel breaking into large slow-moving droplets. This leads to sub-optimal combustion in the developing flame fronts established by the earlier, more fully-developed spray. The simulation results predict these observed phenomena, including injector surface wetting as a result of large slow-moving droplets and post-injection discharge of liquid fuel. This work suggests that post-injection discharges of fuel play a part in the mechanism of the initial formation, and subsequent accumulation of deposits on the exterior surface of the injector. For multiple injections, opening events are influenced by the dynamics of the previous injection closure; these phenomena have been investigated within the simulations
Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers
Spin pumping is a mechanism that generates spin currents from ferromagnetic
resonance (FMR) over macroscopic interfacial areas, thereby enabling sensitive
detection of the inverse spin Hall effect that transforms spin into charge
currents in non-magnetic conductors. Here we study the spin-pumping-induced
voltages due to the inverse spin Hall effect in permalloy/normal metal bilayers
integrated into coplanar waveguides for different normal metals and as a
function of angle of the applied magnetic field direction, as well as microwave
frequency and power. We find good agreement between experimental data and a
theoretical model that includes contributions from anisotropic
magnetoresistance (AMR) and inverse spin Hall effect (ISHE). The analysis
provides consistent results over a wide range of experimental conditions as
long as the precise magnetization trajectory is taken into account. The spin
Hall angles for Pt, Pd, Au and Mo were determined with high precision to be
, , and ,
respectively.Comment: 11 page
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