An approach to normalization of coarticulation effects for vowels in connected speech

A method is proposed to reduce the ambiguity of vowels in connected speech by normalizing the coarticulation effects. The method is applied to vowels in phonetic environments where great ambiguity would be likely to occur, taking as their features the first and second formant trajectories. The separability between vowel clusters is found to be greatly improved for the vowel samples. In addition, distribution of the vowels on a feature plane characterized by this method seems to reflect their perceptual nature when presented to listeners without isolation from their phonetic environments. The results suggest that the method proposed here is useful for automatic speech recognition and help infer some possible mechanisms underlying dynamic aspects of human speech recognition.     

Suppression of slag foaming by a sound wave

The aim of this work was to study the effects of sound frequency, sound intensity and viscosity of slag on the slag foaming rate and the steady-state foam height. Experiments were carried out using two slags (BaO–B₂O₃) melted at a temperature of 1223 or 1273 K, as well as water–glycerin solutions at room temperature. Low frequency sound waves (<1.3 kHz) are found to be more effective in the slag foaming suppression than high frequency waves (1.3–12 kHz). The steady-state foam height decreases abruptly when the sound pressure reaches a threshold value that depends on sound frequency and liquid viscosity. The results can be explained in terms of enhancing the rates of liquid drainage and film rupture induced by sound.     

New fabrication method for anisotropic gratings formed in photocrosslinkable polymer liquid crystals

We present a new fabrication method, called two-step ultraviolet exposure, to prepare anisotropic gratings in photocrosslinkable polymer liquid crystal films. Using the controllability of the reorientation direction of mesogenic molecules, anisotropic phase gratings, in which the mesogenic molecules were periodically modulated in orthogonal directions, were prepared by the use of one grating photomask. The resultant gratings diffract the light and convert the polarization states at the same time, and have applications as diffraction optical devices. PACS 42.65.Hw; 42.70.Df; 42.70.Nq; 78.20.-e; 78.40.Me     

Fabrication and optical reflection behavior of a two-dimensional barium titanate ceramic photonic crystal

We demonstrate a method for fabricating a two-dimensional hexagonal array of nanoscale barium titanate ceramic pillars. A precursor array was prepared by introducing a sol solution into an electron-beam resist mold with air holes and subsequently dry etching the unnecessary gel layer formed on the mold. A ceramic array, consisting of barium titanate ceramic pillars with a radius of 85 nm, a lattice constant of 450 nm, and a height of 500 nm, was fabricated by sintering the precursor array at 1073 K. The reflection spectra for the ceramic array in the visible range revealed the underlying photonic band gaps, which were in good agreement with results calculated using a plane-wave method. PACS 77.84.-s; 42.70.-a; 42.70.Qs     

Reliability of mean transit time obtained using perfusion-weighted MR imaging; comparison with positron emission tomography

The purpose of this project was to assess the reliability of the cerebral mean transit time (MTT) obtained using perfusion-weighted MR imaging by comparing it with the MTT obtained when performing positron emission tomography (PET). Ten patients with chronic occlusive cerebrovascular disease were investigated. They had either unilateral internal carotid artery occlusion or middle cerebral artery occlusion. The regions-of-interest were placed in non-infarcted areas within the territory of the middle cerebral artery on the affected side. Control regions-of-interest were placed in mirrored regions of the contralateral side. Linear regression analyses were performed using the parameters of the MTT obtained with perfusion-weighted MR imaging and the MTT, cerebral blood flow, vascular reactivity, and oxygen extraction fraction obtained with PET. The respective MTTs of the affected and non-affected sides obtained with perfusion-weighted MR imaging versus those with PET were 7.3 +/- 2.2 s and 6.0 +/- 1.2 s versus 8.2 +/- 3.0 s and 6.4 +/- 1.7 s. The MTT obtained using perfusion-weighted MR imaging and PET demonstrated statistically significant correlation (r = 0.87, p < 0.0001). The MTT obtained with perfusion-weighted MR imaging correlated statistically with cerebral blood flow (r = -0.74, p < 0.001), vascular reactivity (r = -0.73, p < 0.001) and oxygen extraction fraction (r = 0.61, p < 0.01). Similarly, the MTT obtained using PET statistically correlated with cerebral blood flow (r = -0.78, p < 0.0001), vascular reactivity (r = -0.51, p < 0.05) and oxygen extraction fraction (r = 0.68, p < 0.01). The reliability of the MTT obtained using perfusion-weighted MR imaging appears to be approximately equal to that obtained with positron emission tomography.     

Enhanced effective mass in doped SrTiO3 and related perovskites

The effective mass is one of the main factors determining the Seebeck coefficient and electrical conductivity of thermo-electrics. In this ab-initio LDA-GGA study the effective mass is estimated from the curvature of electronic bands by one-band-approximation and is in excellent agreement with experimental data of Nb- and La-doped SrTiO₃. It is clarified that the deformation of SrTiO₃ crystals has a significant influence on the bandgap, effective electronic DOS-mass and band-mass, but the electronic effect due to the e_g-band flattening near the Γ-point due to Nb-doping up to 0.2 at% is the main factor for the effective mass increase. Doping of La shows a linear decrease of the effective mass; this can be explained by the different surroundings of A- and B-sites in perovskite. Substitution with other elements such as Ba on the A-site and V on the B-site in SrTiO₃ increases the effective mass as well.     

A new effect of ultrasonication on the formation of BaTiO3 nanoparticles

A new effect of ultrasonic irradiation on the formation of BaTiO₃ particles was identified. Ultrasonication caused the aggregation of the original 5–10 nm BaTiO₃ particles in the same crystal axis and accelerated the formation of BaTiO₃ particles significantly. Furthermore, narrow size distribution was obtained for the aggregated particles under ultrasonic irradiation.     

Pulse laser ablation at water–air interface

We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser pulse is focused through the transparent material. In this case, the ablation threshold fluence is reduced remarkably. In the present study, experiments were conducted in water and air in order to confirm this phenomenon for a combination of two fluid media with different refractive indices. This phenomenon was observed in detail by pulse laser shadowgraphy. A high-resolution film was used to record the phenomenon with a Nd:YAG pulse laser with 10-ns duration as a light source. The laser ablation phenomenon on the liquid surface layer caused by a focused Nd:YAG laser pulse with 1064-nm wavelength was found to be followed by the splashing of the liquid surface, inducing a liquid jet with many ligaments. The liquid jet extension velocity was around 1000 m/s in a typical case. The liquid jet decelerated drastically due to rapid atomization at the tips of the ligaments. The liquid jet phenomenon was found to depend on the pulse laser parameters such as the laser fluence on the liquid surface, laser energy, and laser beam pattern. The threshold laser fluence for the generation of a liquid jet was 20 J/cm². By increasing the incident laser energy with a fixed laser fluence, the laser focused area increased, which eventually led to an increase in the size of the plasma column. The larger the laser energy, the larger the jet size and the longer the temporal behavior. The laser beam pattern was found to have significant effects on the liquid jet’s velocity, shape, and history.     

Strong generators of the subregular $$\mathcal {W}$$W-algebra $$\mathcal {W}^{K-N}(\mathfrak {sl}_N,f_{sub})$$WK-N(slN,fsub) and combinatorial description at critical level

Letters in Mathematical Physics - We construct explicitly strong generators of the affine $$\mathcal {W}$$-algebra $$\mathcal {W}^{K_0-N}(\mathfrak {sl}_N, f_{sub})$$ of subregular type A....