On the detection of dispersion in the head-related transfer function

Because of dispersion in head-related transfer functions (HRTFs), the interaural time difference (ITD) varies with frequency. This physical effect ought to have consequences for the size or shape of the auditory image of broadband noise because different frequency regions of the noise have different ITDs. However, virtual reality experiments suggest that human listeners are insensitive to head-related dispersion. The experiments of this article test that suggestion by experiments that isolate dispersion from amplitude effects in the HRTF and attempt to optimize the opportunity for detecting it. Nevertheless, the experiments find that the only effect of dispersion is to shift the lateralization of the auditory image. This negative result is explained in terms of the cross-correlation function for head-dispersed noise. Although the broad-band cross-correlation function differs considerably from 1.0, the cross-correlation functions within bands characteristic of auditory filters do not. A detailed study of the lateralization shifts show that the experimental shifts can be successfully calculated as an average of stimulus ITDs as weighted by Raatgever's frequency-weighting function (Thesis, Delft, The Netherlands, 1980).     

Sustainable production technologies which take into account environmental constraints

We formulate and study a multiobjective programming approach for production processes which implements suitable constraints on pollutant emissions. We consider two alternative optimization problems: (a) minimum pollution risk; (b) maximum expected return. For each pollutant, we define three different contamination levels: (a) the desirable or the target pollution level, (b) the alarm (warning or critical) level and (c) the maximum admissible (acceptable) level, and introduce penalties proportional to the amounts of pollutants that exceed these levels. The objective function of the minimum pollution risk problem is not smooth since it contains positive parts of some affine functions, resulting in mathematical difficulties, which can be solved by formulating an alternative linear programming model, which makes use of additional variables and has the same solutions as the initial problem. We investigate various particular cases and analyze a numerical example for a textile plant.     

BCS Theory of Hadronic Matter at High Densities

The equilibrium between the so-called 2SC and CFL phases of strange quark matter at high densities is investigated in the framework of a simple schematic model of the NJL type. Equal densities are assumed for quarks u,d and s. The 2SC phase is here described by a color-flavor symmetric state, in which the quark numbers are independent of the color-flavor combination. In the CFL phase the quark numbers depend on the color-flavor combination, that is, the number of quarks associated with the color-flavor combinations ur,dg,sb is different from the number of quarks associated with the color flavor combinations ug,ub,dr,db,sr,sg. We find that the 2SC phase is stable for a chemical potential μ below μ _c ?=?0.505 GeV, while the CFL phase is stable above, the equilibrium pressure being P _c ?=?0.003 GeV⁴. We have used a 3-momentum regularizing cutoff Λ?=?0.8 GeV, which is somewhat larger than is usual in NJL type models. This should be adequate if the relevant chemical potential does not exceed 0.6 GeV.     

Symmetry Energy, Neutron Star Crust and Neutron Skin Thickness

We analyze the correlations of the slope and curvature parameters of the symmetry energy with the neutron skin thickness of neutron-rich isotopes, and the crust-core transition density in neutron stars. The results are obtained within the microscopic Brueckner?CHartree?CFock approach, and are compared with those obtained with several Skyrme and relativistic mean field models.     

The influence of the powders synthesis method on the microstructure of lanthanum-stabilized β-alumina ceramics

The theoretically predicted capacity of La³⁺ to act as stabilizer and microstructure controller in β-alumina ceramics has been tested. Precursor powders were synthesised by nitrate decomposition and alcoholate hydrolysis, and by the classical ceramic method. The formation mechanism of the crystalline phases up to 1600°C has been determined. The influence of the powders synthesis method on the reaction course is quite important. Marked differences were noted in the microstructure of sintered products in connection with the precursor powder type. The powders prepared from alcoholates exhibit a better grain size distribution. Introduction of La³⁺ results in the expected stabilizing and microstructure controlling effects.     

Magnetization of High Density Hadronic Fluid

In the present paper the magnetization of a high density relativistic fluid of elementary particles is studied. At very high densities, such as may be found in the interior of a neutron star, when the external magnetic field is gradually increased, the energy of the normal phase of the fluid remains practically constant before extremely high magnetic fields are reached. However, if pion condensation occurs, the energy decreases linearly while the magnetic field strength increases, so that a non vanishing magnetization, independent of the magnetic field, is present. The expression of the magnetization is derived by first considering and solving the Dirac equation of a fermion in interaction with a magnetic field and with a chiral sigma-pion pair. The solution provides the energies of single-particle states. The energy of the system is found by summing up contributions from all particles in the particle fluid. For nuclear densities above 2 to 3ρ ₀, where ρ ₀ is the equilibrium nuclear density, the resulting magnetic field turns out to be rather huge, of the order of 10¹⁷ Gauss.