The NLMS algorithm with time-variant optimum stepsize derived from a Bayesian network perspective

In this article, we derive a new stepsize adaptation for the normalized least mean square algorithm (NLMS) by describing the task of linear acoustic echo cancellation from a Bayesian network perspective. Similar to the well-known Kalman filter equations, we model the acoustic wave propagation from the loudspeaker to the microphone by a latent state vector and define a linear observation equation (to model the relation between the state vector and the observation) as well as a linear process equation (to model the temporal progress of the state vector). Based on additional assumptions on the statistics of the random variables in observation and process equation, we apply the expectation-maximization (EM) algorithm to derive an NLMS-like filter adaptation. By exploiting the conditional independence rules for Bayesian networks, we reveal that the resulting EM-NLMS algorithm has a stepsize update equivalent to the optimal-stepsize calculation proposed by Yamamoto and Kitayama in 1982, which has been adopted in many textbooks. As main difference, the instantaneous stepsize value is estimated in the M step of the EM algorithm (instead of being approximated by artificially extending the acoustic echo path). The EM-NLMS algorithm is experimentally verified for synthesized scenarios with both, white noise and male speech as input signal.Comment: 4 pages, 1 page of reference

A Bayesian Network View on Acoustic Model-Based Techniques for Robust Speech Recognition

This article provides a unifying Bayesian network view on various approaches for acoustic model adaptation, missing feature, and uncertainty decoding that are well-known in the literature of robust automatic speech recognition. The representatives of these classes can often be deduced from a Bayesian network that extends the conventional hidden Markov models used in speech recognition. These extensions, in turn, can in many cases be motivated from an underlying observation model that relates clean and distorted feature vectors. By converting the observation models into a Bayesian network representation, we formulate the corresponding compensation rules leading to a unified view on known derivations as well as to new formulations for certain approaches. The generic Bayesian perspective provided in this contribution thus highlights structural differences and similarities between the analyzed approaches

Spatial Diffuseness Features for DNN-Based Speech Recognition in Noisy and Reverberant Environments

We propose a spatial diffuseness feature for deep neural network (DNN)-based automatic speech recognition to improve recognition accuracy in reverberant and noisy environments. The feature is computed in real-time from multiple microphone signals without requiring knowledge or estimation of the direction of arrival, and represents the relative amount of diffuse noise in each time and frequency bin. It is shown that using the diffuseness feature as an additional input to a DNN-based acoustic model leads to a reduced word error rate for the REVERB challenge corpus, both compared to logmelspec features extracted from noisy signals, and features enhanced by spectral subtraction.Comment: accepted for ICASSP201

SHRIMP ion probe zircon geochronology and Sr and Nd isotope geochemistry for southern Longwood Range and Bluff Peninsula intrusive rocks of Southland, New Zealand

Permian–Jurassic ultramafic to felsic intrusive complexes at Bluff Peninsula and in the southern Longwood Range along the Southland coast represent a series of intraoceanic magmatic arcs with ages spanning a time interval of 110 m.y. New SHRIMP U-Pb zircon data for a quartz diorite from the Flat Hill complex, Bluff Peninsula, yield an age of 259 ± 4 Ma, consistent with other geochronological and paleontological evidence confirming a Late Permian age. The new data are consistent with an age of c. 260 Ma for the intrusive rocks of the Brook Street Terrane. SHRIMP U-Pb zircon ages for the southern Longwood Range confirm that intrusions become progressively younger from east to west across the complex. A gabbro at Oraka Point (eastern end of coastal section) has an age of 245 ± 4 Ma and shows virtually no evidence of zircon inheritance. The age is significantly different from that of the Brook Street Terrane intrusives. Zircon ages from the western parts of the section are younger and more varied (203–227 Ma), indicating more complex magmatic histories. A leucogabbro dike from Pahia Point gives the youngest emplacement age of 142 Ma, which is similar to published U-Pb zircon ages for the Anglem Complex and Paterson Group on Stewart Island

Les immigrants et les syndicats

La présente étude a pour objectif de dresser un portrait du rapport que la population immigrante du Luxembourg entretient avec les syndicats, leurs modes d?action et leurs revendications. Partant du constat que les immigrants adhèrent moins aux syndicats que ne le font les non-immigrants, elle cherche plus spécifiquement à savoir dans quelle mesure la plus faible propension des immigrants à se syndiquer traduit des attitudes plus négatives vis-à-vis des syndicats et des diverses formes d?action collective et examine jusqu?à quel point elle s?inscrit dans le cadre d?une moindre participation sociale générale des immigrants. Distinguant ensuite trois thèmes susceptibles d?être abordés par les syndicats ? à savoir les conditions de travail, l?avenir du système de pension luxembourgeois, ainsi que l?Union européenne et son élargissement ? l?étude tente de savoir si les immigrants se caractérisent par des revendications particulières. Les résultats rendent compte de différences importantes entre les immigrants et les nonimmigrants, mais également entre les groupes d?immigrants eux-mêmes. Ces différences sont largement attribuables aux caractéristiques sociodémographiques des groupes d?immigrants mais une part non négligeable d?entre elles semblent provenir d?autres facteurs restant encore à examiner. L?étude conclut par conséquent sur la nécessité d?investigations plus poussées pour mieux saisir les spécificités des relations que les groupes d?immigrants entretiennent à l?égard de la syndicalisation et de l?action collective.immigrants; syndicats; attitudes politiques; action collective; participation sociale; relations professionnelles

New Identity of the Kimberlite Melt: Constraints from Unaltered Diamondiferous Udachnaya –East Pipe Kimberlite, Russia

Kimberlite magmas are in many aspects unusual compared to other terrestrial magmatic liquids. They are very rare and occur in small volumes, but their intimate relationships with diamonds make them invaluable to the scientific and exploration communities. The association of kimberlite rocks with diamonds and deep-seated mantle xenoliths links the origin of parental kimberlite magmas to the highest known depths (> 150 km) of magma derivation (e.g. Dawson, 1980; Eggler, 1989; Girnis & Ryabchikov, 2005; Mitchell, 1986; Mitchell, 1995; Pasteris, 1984). Kimberlite magmas would have one of the lowest viscosities and highest buoyancies that enable exceptionally rapid transport from the source region (Canil & Fedortchouk, 1999; Eggler, 1989; Haggerty, 1999; Kelley & Wartho, 2000; Sparks et al., 2006) and preservation of diamonds. Despite significant research efforts, there is still uncertainty about the true chemical identity of kimberlite parental melts and their derivates. Kimberlite magmas are always contaminated by large quantities of lithic fragments and crystals, unrelated to the evolution of the parental melt. In most cases kimberlites are severely modified by syn- and post-magmatic changes that have altered the original alkali and volatile element abundances. These problems are reflected in the definition of the kimberlite rock as “both a contaminated and altered sample of its parent melt” (Pasteris, 1984). Numerous other definitions of the kimberlite commonly reflect on ultramafic compositions and enrichment in volatiles (CO2 and H2O; Clement et al., 1984; Kjarsgaard et al., 2009; Kopylova et al., 2007; Mitchell, 1986; Mitchell, 2008; Patterson et al., 2009; Skinner & Clement, 1979) which are supposedly inherited from parental magmas. The physical properties of a kimberlite magma directly, and occurrence of diamonds indirectly, relate to the enrichment in carbonate components which are represented in common kimberlites by calcite and dolomite. The abundant carbonate component in kimberlite rocks is counter-balanced by a more abundant olivine (ultramafic) component, represented by olivine fragments and crystals that are commonly affected by serpentinisation. The ultramafic silicate compositions of kimberlites are ascribed to abundant olivine macrocrysts and phenocrysts, whereas significant CO2 and H2O contents are attributed respectively to carbonate minerals (calcite and dolomite) and serpentine (+ other H2O-bearing magnesian silicates). Unfortunately, the masking effects of deuteric and post-magmatic alteration do not permit routine recognition of olivine generations, and so the olivine component originally dissolved in the kimberlite parental melt remains controversial (Brett et al., 2009; Francis & Patterson, 2009; Mitchell & Tappe, 2010; Patterson et al., 2009). Similarly, the original magmatic abundances of volatile and fluid-mobile alkali elements are disturbed by syn- and post-emplacement modifications, thus complicating complicating quantification of the parental melt composition if inferred from bulk kimberlite analyses. The existing dogma about correspondence between compositions of whole rock kimberlites and their parental melt has been recently challenged by the newcomers to the kimberlite scientific community (e.g., Kamenetsky et al., 2004; Kamenetsky et al., 2007a; Kamenetsky et al., 2007b; Kamenetsky et al., 2008; Kamenetsky et al., 2009a; Kamenetsky et al., 2009b; Kamenetsky et al., 2009c; Maas et al., 2005). A breakthrough into understanding of the kimberlite magma chemical and physical characteristics was made possible by detailed studies of the diamondiferous Udachnaya-East kimberlite pipe in Siberia. Unlike other kimberlites worldwide, severely modified by syn- and post-magmatic changes, the Udachnaya-East kimberlite is the only known fresh rock of this type, and thus it is invaluable source of information on the composition and temperature of primary melt, its mantle source, rheological properties of ascending kimberlite magma. This kimberlite preserved unequivocal evidence for olivine populations, olivine paragenetic assemblages and olivine-hosted melt inclusions, and the role of mantle-derived alkali carbonate and alkali chloride components in the parental melt.