Optimal detection of discontinuous changes of signal parameters in discrete time

The problem of optimal detection (discrimination) of signals with random discontinuous parameter changes in discrete time is examined. A recursion algorithm for calculation of the likelihood ratio in real time is obtained. As an example, the problem of optimal detection of a rectangular pulse signal with a random time of appearance, duration, and amplitude is solved. Computer simulation results are presented.     

Parametric linear programming techniques for the indefnite quadratic programming problem

In this paper, we discuss a multiparametric technique for findinga global minimum for an indefinite quadratic programming problembased on the spectral decomposition of the matrix of the quadraticform. Special attention is given to the case where this matrixhas only rank 1, where the multiparametric linear program turnsout to be a single-parameter linear program. An extension ofthe traditional linear parametric procedure is introduced whichin general solves this problem efficiently. However, an exampleis presented showing that this technique may take an exponentialnumber of steps.     

Reduction of tympanic membrane displacement during vocalization of the arboreal frog, Eleutherodactylus coqui.

Tympanic membrane (TM) velocities of vocalizing male frogs, Eleutherodactylus coqui, were measured in the field using laser vibrometry. The animal's call produced levels of 114-120 dB SPL measured at distances of 12-20 mm from the eardrum and mean TM displacements in response to the two notes of the male's own advertisement call were 1.84 and 2.08 nm, respectively. These values are close to the TM displacements obtained in response to playback of the two-note call at much lower sound levels. Thus TM vibrations are attenuated during phonation in the frog, and several candidate mechanisms for auditory sensitivity reduction are discussed.     

Smectic liquid-crystalline phases of F(CF2)7(CHOH)(CH2)8H and F(CF2)9(CHOH)(CH2)10H Comparison with other partially fluorinated molecules

Partially fluorinated alcohols F(CF₂)_m(CHOH)(CH₂)_nH (where m = 7, n = 8 and m = 9, n = 10) exhibit highly ordered smectic liquid-crystalline phases, as confirmed by optical microscopy and differential scanning calorimetry. Miscibility studies show that the smectic phases of the two alcohols are not of the same type. The related partially fluorinated ketones F(CF₂)_mCO(CH₂)_nH do not form a detectable mesophase. This is rather surprising since the (more polar) corresponding alcohols and the (less polar) analogous iodides and n-alkanes do. A brief discussion of the results and a comparison among partially fluorinated alkanes with various functional groups are presented.     

On the localization of topological invariants

The approach of formal differential geometry to the topological invariants which can be localized is developed. The universal space and universal characteristic forms are constructed. They give rise to primary and secondary characteristic forms.     

Influence of concentration on the activation energy for diffusion in polymer-solvent systems

The self-diffusion of benzene, toluene, and ethylbenzene in polystyrene have been analyzed using the Vrentas/Duda free-volume diffusion model. Diffusion coefficient predictions suggest an exponential concentration dependence of the activation energy required to overcome attractive forces, E. Without the use of any diffusion data approximating E as zero over the entire concentration range yields self-diffusion coefficient predictions which are in good agreement with experimental data. © 1992 John Wiley & Sons, Inc.     

The effect of crystallinity on chain mobility and free volume in the amorphous regions of a miscible polycarbonate/polyester blend

Homopolymers and blends of polycarbonate/ThermX have been investigated by differential scanning calorimetry, dynamic mechanical analysis, density measurements, and positron annihilation lifetime spectroscopy. The study focuses on the chain mobility and free volume in the amorphous miscible regions of the blends and how this mobility and free volume are affected by increasing crystallinity. It is proposed that judicious annealing, which results in increasing crystallinity (while avoiding ageing or transesterification), induces a constraint on the amorphous region leading to an increase in T_g and coalescence of free volume sites. © 1994 John Wiley & Sons, Inc.