Delay Estimator and Improved Proportionate Multi-Delay Adaptive Filtering Algorithm

This paper pertains to speech and acoustic signal processing, and particularly to a determination of echo path delay and operation of echo cancellers. To cancel long echoes, the number of weights in a conventional adaptive filter must be large. The length of the adaptive filter will directly affect both the degree of accuracy and the convergence speed of the adaptation process. We present a new adaptive structure which is capable to deal with multiple dispersive echo paths. An adaptive filter according to the present invention includes means for storing an impulse response in a memory, the impulse response being indicative of the characteristics of a transmission line. It also includes a delay estimator for detecting ranges of samples within the impulse response having relatively large distribution of echo energy. These ranges of samples are being indicative of echoes on the transmission line. An adaptive filter has a plurality of weighted taps, each of the weighted taps having an associated tap weight value. A tap allocation/control circuit establishes the tap weight values in response to said detecting means so that only taps within the regions of relatively large distributions of echo energy are turned on. Thus, the convergence speed and the degree of estimation in the adaptation process can be improved

Temperature dependent effective potential method for accurate free energy calculations of solids

We have developed a thorough and accurate method of determining anharmonic free energies, the temperature dependent effective potential technique (TDEP). It is based on \emph{ab initio} molecular dynamics followed by a mapping onto a model Hamiltonian that describes the lattice dynamics. The formalism and the numerical aspects of the technique are described in details. A number of practical examples are given, and results are presented, which confirm the usefulness of TDEP within \emph{ab initio} and classical molecular dynamics frameworks. In particular, we examine from first-principles the behavior of force constants upon the dynamical stabilization of body centered phase of Zr, and show that they become more localized. We also calculate phase diagram for $^4$He modeled with the Aziz \emph{et al.} potential and obtain results which are in favorable agreement both with respect to experiment and established techniques

Configurational order-disorder induced metal-nonmetal transition in B13_{13}C2_{2} studied with first-principles superatom-special quasirandom structure method

Due to a large discrepancy between theory and experiment, the electronic character of crystalline boron carbide B$_{13}$C$_{2}$ has been a controversial topic in the field of icosahedral boron-rich solids. We demonstrate that this discrepancy is removed when configurational disorder is accurately considered in the theoretical calculations. We find that while ordered ground state B$_{13}$C$_{2}$ is metallic, configurationally disordered B$_{13}$C$_{2}$, modeled with a superatom-special quasirandom structure method, goes through a metal to non-metal transition as the degree of disorder is increased with increasing temperature. Specifically, one of the chain-end carbon atoms in the CBC chains substitutes a neighboring equatorial boron atom in a B$_{12}$ icosahedron bonded to it, giving rise to a B$_{11}$C$^{e}$(BBC) unit. The atomic configuration of the substitutionally disordered B$_{13}$C$_{2}$ thus tends to be dominated by a mixture between B$_{12}$(CBC) and B$_{11}$C$^{e}$(BBC). Due to splitting of valence states in B$_{11}$C$^{e}$(BBC), the electron deficiency in B$_{12}$(CBC) is gradually compensated

On Experimental Designs for Derivative Random Fields

Es werden differenzierbare zufällige Felder zweiter Ordnung untersucht und Vorschläge zur Versuchsplanung von Beobachtungen der abgeleiteten Felder unterbreitet. Von einem gewissen Standpunkt aus werden die folgenden Fragen beantwortet: Wie viele Informationen liefern Beobachtungen von Ableitungen für die Vorhersage des zugrunde liegenden Stochastischen Feldes? Wie beeinflusst eine a priori Wahl der Kovarianzfunktion das Informationsverhältnis zwischen verschiedenen abgeleiteten Feldern im Hinblick auf die Vorhersage? Als Zielfunktion wird das so genannte "imse-update" für den besten linearen Prädiktor betrachtet. Den zentralen Teil stellt die Untersuchung von Versuchsplänen mit (asymptotisch) verschwindenden Korrelationen dar. Hier wird insbesondere der Einfluss der Maternschen Klasse und J-Besselschen Klassen von Kovarianzfuntionen untersucht. Ferner wird der Einfluss gleichzeitiger Beobachtung von verschiedenen Ableitungen untersucht. Schließlich werden einige empirische Studien durchgeführt, aus denen einige praktische Ratschläge abgeleitet werden