Dynamic Assignment of Gaussian Components in Modelling Speech Spectra

In this paper, we describe a parametric mixture model for modelling the resonant characteristics of the vocal tract where Gaussian distributions are used to model spectral frequency regions. A mixtures of Gaussian (MoG) based parametrisation scheme is used for modelling a smoothed representation of the spectra. This smoothing procedure removes all signal periodicity from the spectra allowing highly natural analysis, manipulation and synthesis of speech. The goal of this parametrisation scheme is to ease the correspondence between the resonant characteristics of the vocal tract and the parametric distributions and modelling the spectrum with an appropriate number of parameters. Previously, a maximum likelihood (ML) approach to this parametrisation scheme was introduced. However, this approach has inherent local optima problems. Noting that, a relatively small class of Gaussian densities can approximate a large class of distributions, we propose a new scheme whereby starting with a large number of distributions in the mixture, we systematically reduce their number and re-approximate the densities in the mixture based on a distance criterion. The Kullback-Leibler (KL) distance was found to allow optimal MoG solutions to the spectra. Furthermore, a fitness measure based on KL information is used to provide a figure for estimating the model order in representing formant-like features. The proposed model is subjectively evaluated and is shown to reduce the number of Gaussian with an appreciable loss in the quality of the re-synthesised speech.     

“Pulsed field losses and coupling current loop in a large‐current superconductor”, Electrical Engineering in Japan Volume 142, Number 4, 2003, pages 27–33

The original article to which this Erratum refers was published in Electrical Engineering in Japan, Volume 142, Number 4, 2003, pages 27–33 An error appeared in the above article. The affiliations are correct as here. We apologize for any inconvenience this error may have caused.     

Oxygen radical density measurement in O2–N2 gas mixture plasma by means of a thin platinum wire

The oxygen radical density was measured in a weakly ionized plasma in an O₂–N₂ gas mixture by using a simple platinum thin‐wire sensor. The increased temperatures of the platinum wire caused by the energy released in the recombination of two oxygen radicals on the platinum surface were measured by varying the nitrogen gas mixture ratio and were compared with the oxygen radical densities theoretically calculated under the same plasma conditions. The relation between the wire temperature and the oxygen radical densities was cross‐checked by quantitative measurement of oxygen radical densities with a quadrupole mass spectrometer. All of these results made it possible to determine the oxygen radical density experimentally from the platinum wire temperature alone. The influence of the ambient gas temperature on the radical density measurement is also discussed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 14–20, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20018     

Structure of a replication-terminator protein complexed with DNA

The crystal structure of the Escherichia coli replication-terminator protein (Tus) bound to terminus-site (Ter) DNA has been determined at 2.7 A resolution. The Tus protein folds into a previously undescribed architecture divided into two domains by a central basic cleft. This cleft accommodates locally deformed B-form Ter DNA and makes extensive contacts with the major groove, mainly through two interdomain beta-strands. The unusual structural features of this complex may explain how the replication fork is halted in only one direction.     

Reduction method for residual stress of welded joint using random vibration

Welded joints are used for construction of many structures. Residual stress is induced near the bead caused by locally given heat. Tensile residual stress on the surface may reduce fatigue strength. In this paper, a new method for reduction of residual stress using vibration during welding is proposed. As vibrational load, random vibration, white noise and filtered white noise are used. Two thin plates are butt-welded. Residual stress is measured with a paralleled beam X-ray diffractometer with scintillation counter after removing quenched scale chemically. It is concluded that tensile residual stress near the bead is reduced by using random vibration during welding.     

Discriminative training via minimization of risk estimates based on Parzen smoothing

We describe a new approach to estimating classification risk in the domain of a suitably defined transformation that can be used as the basis for optimization of generic pattern recognition systems, including hidden Markov models and Multi-Layer Perceptrons. The two formulations of risk estimate described here are closely tied to the Minimum Classification Error/Generalized Probabilistic Descent (MCE/GPD) framework for discriminative training that is well-known to the speech recognition community. In the new approach, high-dimensional and possibly variable-length training tokens are mapped to the centers of Parzen kernels which are then easily integrated to find the risk estimate. The utility of such risk estimates lies in the fact that they are explicit functions of the system parameters and hence suitable for use in practical optimization methods. The use of Parzen estimation makes it possible to establish convergence of the risk estimate to the true theoretical classification risk, a result that formally expresses the benefit of linking the degree of smoothing to the training set size. Convergence of the minimized risk estimate is also analyzed. The new approach establishes a more general theoretical foundation for discriminative training than existed before, supporting previous work and suggesting new variations for future work.     

Humidity dependence of microwear characteristics of amorphous carbon films on silicon substrates

Influences of environmental humidity on various scanning-scratched wear characteristics, such as long-term stability of wear resistance and load dependence, scratch number dependence and scratch velocity dependence of wear depth, are evaluated by using an atomic force microscope and diamond tips. Amorphous carbon (a-C) films are deposited on silicon substrates by the electron cyclotron resonance plasma (ECR) sputtering method and the RF sputtering method combined with CVD using argon gas containing methane (CH₄) as a sputtering gas. In carbon samples with a higher hydrogen content, clear influences of the humidity on various wear characteristics are observed and their wear resistances decrease with increase of the humidity. In the ECR sputtered carbon film with low hydrogen content, wear resistance is stable during long-term exposure to an environment of high temperature and high humidity. In this film, the influences of humidity on the wear resistance and adhesion forces between the films and the substrates are not observed, since it is highly wear resistant and the wear depths are shallow in each test. Thus, amorphous carbon films with low hydrogen content are suitable as wear resistant protective overcoats from the point of view of the wear resistance, in particular the influence of the humidity on the wear resistance including its long-term stability.     

Investigation of micro-phase separation of the additive,cyclotriphosphazene, in lubricant films of hard disk media

The micro-phase separation of the additive, cyclotriphosphazene (X-1P), in perfluoropolyether (PFPE) lubricant films on hard disk media was studied. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) indicated that the small spots appearing on the disk surface consisted predominantly of X-1P. Observation using an atomic force microscope (AFM) revealed the micro-phase separation process to be the sudden, continuous appearance of new spots some time after coating the film. Some spots grew over previous ones, while some spots dissolved. Finally, they stopped growing and the number of spots became saturated. The solubility of X-1P in the lubricant film increased in the order of ZDIAC, ZDOL2000, ZDOL4000 and Z03, and that in bulk lubricant increased in the order of Z03, ZDOL4000, ZDOL2000 and ZDIAC. The order of solubility of X-1P in the film did not correspond to that in the bulk.     

Highly precise and stable displacement-measuring laser interferometer with differential optical paths

To achieve sub-nm precision of a displacement-measuring laser interferometer, its optical systematic error should be made as small as possible. In this paper, methods to reduce the optical path length changes and stray light reflections, as well as materials appropriate for main optical elements in the optical layout and the holders, are discussed. As a solution, a complete differential interferometer using a quartz plate inclined 45° to the optic axis is presented. This interferometer has null dead path length, fewer and smaller optical elements, and fewer boundary surfaces with air than conventional differential interferometers. Adopting the athermal glass (Ultran30) for interferometric prisms and aluminum alloy (A5056) for the interferometric prism holder was effective in reducing the drift of measurement caused by thermal changes. The interferometer made of Ultran30 glass with a A5056 holder achieved 0.31 nm/K thermal drift in the displacement measurement.