Virtual audio reproduced in a headrest

When virtual audio reproduction is simultaneously required in many seats, such as in aircraft or cinemas, it may be convenient to use loudspeakers mounted inside each seat's headrest. In this preliminary study, the feasibility of virtual audio reproduction in the headrest of a single seat is explored using an inversion technique to compensate for crosstalk and the synthesis of head related transfer functions. Although large changes in the magnitude of the signals reproduced at the listener's ears are observed as the listener moves their head within the headrest, informal listening tests indicate that the reproduced acoustic images are surprisingly stable in about an eighth of an arc either side of the loudspeaker positions. Not surprisingly, frontal images are more difficult to reproduce with headrest loudspeakers

Attractor Metadynamics in Adapting Neural Networks

Slow adaption processes, like synaptic and intrinsic plasticity, abound in the brain and shape the landscape for the neural dynamics occurring on substantially faster timescales. At any given time the network is characterized by a set of internal parameters, which are adapting continuously, albeit slowly. This set of parameters defines the number and the location of the respective adiabatic attractors. The slow evolution of network parameters hence induces an evolving attractor landscape, a process which we term attractor metadynamics. We study the nature of the metadynamics of the attractor landscape for several continuous-time autonomous model networks. We find both first- and second-order changes in the location of adiabatic attractors and argue that the study of the continuously evolving attractor landscape constitutes a powerful tool for understanding the overall development of the neural dynamics

The light curve of the companion to PSR B1957+20

We present a new analysis of the light curve for the secondary star in the eclipsing binary millisecond pulsar system PSR B1957+20. Combining previous data and new data points at minimum from the Hubble Space Telescope, we have 100% coverage in the R-band. We also have a number of new K_s-band data points, which we use to constrain the infrared magnitude of the system. We model this with the Eclipsing Light Curve code (ELC). From the modelling with the ELC code we obtain colour information about the secondary at minimum light in BVRI and K. For our best fit model we are able to constrain the system inclination to 65 +/- 2 degrees for pulsar masses ranging from 1.3 -- 1.9 M_sun. The pulsar mass is unconstrained. We also find that the secondary star is not filling its Roche lobe. The temperature of the un-irradiated side of the companion is in agreement with previous estimates and we find that the observed temperature gradient across the secondary star is physically sustainable.Comment: 6 pages, 4 figures & 3tables. Accepted for publication in MNRA

Direct neutron capture cross sections of 62Ni in the s-process energy range

Direct neutron capture on 62Ni is calculated in the DWBA and the cross sections in the energy range relevant for s-process nucleosynthesis are given. It is confirmed that the thermal value of the capture cross section contains a subthreshold resonance contribution. Contrary to previous investigations it is found that the capture at higher energies is dominated by p-waves, thus leading to a considerably increased cross section at s-process energies and a modified energy dependence.Comment: 10 pages, 1 figure, corrected typos in Eq. 6 and subsequent paragrap

Excitons in Electrostatic Traps

We consider in-plane electrostatic traps for indirect excitons in coupled quantum wells, where the traps are formed by a laterally modulated gate voltage. An intrinsic obstacle for exciton confinement in electrostatic traps is an in-plane electric field that can lead to exciton dissociation. We propose a design to suppress the in-plane electric field and, at the same time, to effectively confine excitons in the electrostatic traps. We present calculations for various classes of electrostatic traps and experimental proof of principle for trapping of indirect excitons in electrostatic traps.Comment: 4 pages, 3 figure

Secondary atomization of coal-water fuels for gas turbine applications

The main research objective is to determine the effect of coal-water fuel (CWF) treatment on atomization quality when applied to an ultrafine coal water fuel (solids loading - 50%) and at elevated pressures. The fuel treatment techniques are expected to produce secondary atomization, i.e., disruptive shattering of CWF droplets subsequent to their leaving the atomizing nozzle. Upon combustion, the finer fuel droplets would then yield better burnout and finer fly ash size distribution, which in turn could reduce problems of turbine blade erosion. The parallel objective was to present quantitative information on the spray characteristics of CWF (average droplet size and spray shape and angle) with and without fuel treatment for purposes of application to the design of CWF-burning gas turbine combustors. The experiments include laser diffraction droplet size measurements and high speed photographic studies of CWF sprays in the MIT Spray Test Facility to determine mean droplet size (mass median diameter), droplet size distribution, and spray shape and angle. For the spray tests at elevated pressures, pressure vessels were constructed and installed in the spray test rig. For support of data analyses, a capillary tube viscometer was used to measure the CWF viscosity at the high shear rate that occurs in an atomizer (> 104 sec' ). A semi-empirical relationship was developed giving the CWF spray droplet size as a function of the characteristic dimensionless parameters of twin-fluid atomization, including the Weber number, the Reynolds number, and the air-to-fuel mass flow ratio. The correlation was tested experimentally and good agreement was found between calculated and measured drop sizes when the high shear viscosity of the CWF was used in the semi-empirical equation. Water and CWF spray tests at elevated pressure were made. Average droplet sizes measured as a function of atomizing air-to-fuel ratios (AFRs) at various chamber pressures show that the droplet mass median diameter (MMD) decreases with increasing AFR at a given chamber pressure and increases with increasing chamber pressure at a given AFR. In particular, the results show that droplet sizes of CWF sprays decrease with increasing chamber pressure if the atomizing air velocity is held constant. Of the fuel treatment techniques investigated, the heating of CWF (flash-atomization) was found to be very effective in reducing droplet size, not only at atmospheric pressure but also at elevated pressure. Secondary atomization by C02 absorption (used in a previous study) had given favorable results on CWF combustion, but in this present case this fuel treatment did not seem to have any observable effect on the drop size distribution of the CWF spray at room temperature. The spray angle was observed to reduce with increasing chamber pressure for given atomizing conditions (AFR, fuel flow rate, fuel temperature). The decreasing entrainment rate per unit length of spray with increasing chamber pressure was mainly responsible for the reduction of the spray angle. The heating of the CWF increased the spray angle, both at atmospheric and elevated pressures. A model was developed to predict spray angle change for the effects of the flash-atomization as a function of AFR, fuel flow rate, and the superheat of the water