2,632 research outputs found
Dynamics of the triple contact line on a non-isothermal heater at partial wetting
The dynamics of the triple gas-liquid-solid contact line is analysed for the
case where the gas is the saturated vapour corresponding to the liquid, like in
the vapour bubble in boiling. It is shown that even small superheating (with
respect to the saturation temperature) causes evaporation of the adsorption
liquid film and the true triple contact is established. It is shown that the
hydrodynamic contact line singularity cannot be relaxed with the Navier slip
condition under such circumstances. Augmented with the second derivative slip
condition is proposed to be applied. For the partial wetting conditions, a
non-stationary contact line problem where the contact line motion is caused by
evaporation or condensation is treated in the lubrication approximation in the
vicinity of the contact line. High heat fluxes in this region require the
transient heat conduction inside the heater to be accounted for. Two 2D
problems, those of drop retraction with no phase change and of drop evaporation
are solved and analysed as illustrations of the proposed approach
Low-speed aerodynamic characteristics of a 0.08-scale YF-17 airplane model at high angles of attack and sideslip
Data were obtained with and without the nose boom and with several strake configurations; also, data were obtained for various control surface deflections. Analysis of the results revealed that selected strake configurations adequately provided low Reynolds number simulation of the high Reynolds number characteristics. The addition of the boom in general tended to reduce the Reynolds number effects
Low speed aerodynamic characteristics of an 0.075-scale F-15 airplane model at high angles of attack and sideslip
An 0.075 scale model representative of the F-15 airplane was tested in the Ames 12 foot pressure wind tunnel at a Mach number of 0.16 to determine static longitudinal and lateral directional characteristics at spin attitudes for Reynolds numbers from 1.48 to 16.4 million per meter (0.45 to 5.0 million per foot). Angles of attack ranged from 0 to +90 deg and from -40 deg to -80 deg while angles of sideslip were varied from -20 deg to +30 deg. Data were obtained for nacelle inlet ramp angles of 0 to 11 deg with the left and right stabilators deflected 0, -25 deg, and differentially 5 deg and -5 deg. The normal pointed nose and two alternate nose shapes were also tested along with several configurations of external stores. Analysis of the results indicate that at higher Reynolds numbers there is a slightly greater tendency to spin inverted than at lower Reynolds numbers. Use of a hemispherical nose in place of the normal pointed nose provided an over correction in simulating yawing moment effects at high Reynolds numbers
Schooling of hearing-impaired children and benefit of early diagnosis
AbstractObjectiveTo assess the impact of moderate-to-severe bilateral hearing loss on schooling and the factors influencing this impact, and to evaluate special schooling needs in addition to speech therapy.Material and methodsRetrospective study including children with moderate-to-severe bilateral hearing loss, born between 1992 and 2006, diagnosed and managed in our institution. The age and degree of hearing loss in the better ear, the type of schooling and the level of schooling at the time of the last visit were recorded for each patient.ResultsTwo hundred and twenty-five hearing-impaired children were included: 161 attended a regular school (58% of the 55Â children with severe hearing loss and 76% of the 170Â children with moderate hearing loss). The percentage of children with moderate hearing loss attending a regular school increased over time. This study did not demonstrate any difference in terms of grade retention according to the age at diagnosis for children with moderate hearing loss. No child with comorbidity affecting intellectual capacities attended a regular school.ConclusionThis study confirms that moderate-to-severe congenital bilateral hearing loss has an impact on the child's schooling, with grade retention that depends, but not exclusively, on the degree of hearing loss. A growing number of children with moderate bilateral hearing loss fitted with a hearing aid now attend a regular school
Radiative cascade from quantum dot metastable spin-blockaded biexciton
We detect a novel radiative cascade from a neutral semiconductor quantum dot.
The cascade initiates from a metastable biexciton state in which the holes form
a spin-triplet configuration, Pauli-blockaded from relaxation to the
spin-singlet ground state. The triplet biexciton has two photon-phonon-photon
decay paths. Unlike in the singlet-ground state biexciton radiative cascade, in
which the two photons are co-linearly polarized, in the triplet biexciton
cascade they are crosslinearly polarized. We measured the two-photon
polarization density matrix and show that the phonon emitted when the
intermediate exciton relaxes from excited to ground state, preserves the
exciton's spin. The phonon, thus, does not carry with it any which-path
information other than its energy. Nevertheless, entanglement distillation by
spectral filtering was found to be rather ineffective for this cascade. This
deficiency results from the opposite sign of the anisotropic electron-hole
exchange interaction in the excited exciton relative to that in the ground
exciton.Comment: 6 pages, 4 figure
Spin injection in a single metallic nanoparticle: a step towards nanospintronics
We have fabricated nanometer sized magnetic tunnel junctions using a new
nanoindentation technique in order to study the transport properties of a
single metallic nanoparticle. Coulomb blockade effects show clear evidence for
single electron tunneling through a single 2.5 nm Au cluster. The observed
magnetoresistance is the signature of spin conservation during the transport
process through a non magnetic cluster.Comment: 3 page
Polarization Gradient Study of Interstellar Medium Turbulence Using The Canadian Galactic Plane Survey
We have investigated the magneto-ionic turbulence in the interstellar medium
through spatial gradients of the complex radio polarization vector in the
Canadian Galactic Plane Survey (CGPS). The CGPS data cover 1300 square-degrees,
over the range ,
with an extension to
in the range , and arcminute
resolution at 1420 MHz. Previous studies found a correlation between the
skewness and kurtosis of the polarization gradient and the Mach number of the
turbulence, or assumed this correlation to deduce the Mach number of an
observed turbulent region. We present polarization gradient images of the
entire CGPS dataset, and analyze the dependence of these images on angular
resolution. The polarization gradients are filamentary, and the length of these
filaments is largest towards the Galactic anti-center, and smallest towards the
inner Galaxy. This may imply that small-scale turbulence is stronger in the
inner Galaxy, or that we observe more distant features at low Galactic
longitudes. For every resolution studied, the skewness of the polarization
gradient is influenced by the edges of bright polarization gradient regions,
which are not related to the turbulence revealed by the polarization gradients.
We also find that the skewness of the polarization gradient is sensitive to the
size of the box used to calculate the skewness, but insensitive to Galactic
longitude, implying that the skewness only probes the number and magnitude of
the inhomogeneities within the box. We conclude that the skewness and kurtosis
of the polarization gradient are not ideal statistics for probing natural
magneto-ionic turbulence.Comment: 21 pages, 15 figures, accepted by Ap
Screening nuclear field fluctuations in quantum dots for indistinguishable photon generation
A semiconductor quantum dot can generate highly coherent and
indistinguishable single photons. However, intrinsic semiconductor dephasing
mechanisms can reduce the visibility of two-photon interference. For an
electron in a quantum dot, a fundamental dephasing process is the hyperfine
interaction with the nuclear spin bath. Here we directly probe the consequence
of the fluctuating nuclear spins on the elastic and inelastic scattered photon
spectra from a resident electron in a single dot. We find the nuclear spin
fluctuations lead to detuned Raman scattered photons which are distinguishable
from both the elastic and incoherent components of the resonance fluorescence.
This significantly reduces two-photon interference visibility. However, we
demonstrate successful screening of the nuclear spin noise which enables the
generation of coherent single photons that exhibit high visibility two-photon
interference.Comment: 5 pages, 4 figures + Supplementary Informatio
Development of an electro-mechanically controlled hand orthosis for assisting finger extension in stroke survivors
Los accidentes cerebro-vasculares son una de las causas más comunes de discapacidad permanente en los Estados Unidos y el mundo. Esta condición causa déficits crónicos, como la hemiparesis, que es especialmente prevalente en las extremidades distales superiores. Se ha desarrollado una órtesis de mano controlada electromecánicamente para determinar el potencial uso terapéutico de este tipo de dispositivos en la rehabilitación funcional de la mano. Un pequeño motor de corriente directa es utilizado como el actuador principal, y un guante operado mecánicamente por el usuario por medio de un cable es el componte central del dispositivo. El control de la órtesis se logra por medio de un sistema automatizado utilizando un sensor de fuerza conectado al cable del guante. Adicionalmente se usa un microcontrolador para generar la señal de ancho de pulso modulada (PWM) y las señales de dirección requeridas para operar el motor, a una velocidad determinada por el ciclo de trabajo de la señal de PWM y en la dirección determinada por el estado de un bit bandera que es modificado por un interruptor que opera el usuario. El diseño es portátil y el dispositivo está listo para pruebas clÃnicas, ya que mostró un desempeño aceptable en pruebas iniciales con individuos sanos.Stroke is the leading cause of long-term disability in the world. It causes chronic deficits, such as hemiparesis, especially prevalent in the distal upper extremities. An electro-mechanically driven hand orthosis has been developed to assess the potential therapeutic use of such devices in rehabilitating hand function. A small Direct Current (DC) brushed motor is used as the main actuator, and a cable-driven glove connected to the motor shaft is the central component of the device. The orthosis control is achieved through a force feedback loop using a miniature load cell attached in series to the cable and control module. The later, generates Pulse Width Modulated (PWM) and direction signals required to drive the motor. The speed is determined by the duty cycle of the PWM signal while the direction by the status of a flag bit modified by a user-operated switch. A portable design was achieved by using a 6 V battery pack as the power supply. The device is ready for use in clinical trials with stroke survivor subjects as it has already been tested on healthy individuals with satisfactory performance
- …