a p stable exponentially fitted method for the numerical integration of the schrodinger equation a p stable exponentially fitted method is developed in this paper for the numerical integration of the schrodinger equation an application to the resonance problem of the radial schrodinger equation indicates that the new method is generally more efficient than the previously developed exponentially fitted methods of the same kind

the equimaterial approach for the numerical solution of the one dimensional transient diffusion equation with zero flux boundary conditions abstract a new approach is proposed for the grid motion for the numerical solution of a general transient diffusion equation in one spatial dimension with zero flux boundary conditions the new criterion for grid motion is that the solute amount contained in each discretization section should be a pre described fraction of the total solute amount at each time step this requirement is not explicitly enforced to the solution technique but it is implicitly included in the equation through the appropriate variable transformation the results showed that although the technique leads to the required grid motion the numerical results are of pure quality due to the appearance of singularities during the variable transformation procedure nevertheless it is shown that by appropriate numerical handling of the solution at the singularity region the technique can lead to accurate results and potentially can replace the existing moving grid algorithms at least for the particular problem at hand

burst spectrum as a cue for the stop voicing contrast in american english voicing contrasts in stop consonants are expressed by a constellation of acoustic cues this study focused on a spectral cue present at burst onset in american english labial and coronal stops spectral shape was examined for word initial prevocalic stops of all three places of articulation in a laboratory production study and a large corpus of continuous read speech voiceless labial and coronal stops were found to have greater energy at higher frequencies in comparison to homorganic voiced stops a difference that could not be attributed to aspiration in the voiceless stops or modal phonation in the voiced while no consistent effect was found for dorsal stops this pattern was found with various methods of spectral estimation time averaged and multitaper spectra and measures of spectral energy concentration center of gravity and spectral peak for both linear and auditorily based frequency scales perceptual relevance of the spectral cue was tested in laboratory and online experiments with continua created by crossing burst shape and voice onset time a trading relation was observed such that voiceless identifications were more likely for tokens with higher frequency bursts goodness ratings indicated that burst spectrum influences category typicality for voiceless stops even when voice onset time is unambiguous

spectral dynamics of sibilant fricatives are contrastive and language specific previous research has extensively investigated the spectral properties of sibilant fricatives with little consideration to how these properties vary over time to investigate such spectro temporal variation productions of english s and and of japanese s and in word initial prevocalic position were elicited from adult native speakers the spectral dynamics of these productions were analyzed in terms of a psychoacoustic measure of peak frequency peak erbn number peak erbn number was computed at 17 evenly spaced points across each fricative production the resulting peak erbn number trajectories were analyzed with orthogonal polynomial growth curve models to determine how peak frequency varied temporally within each fricative three analyses compared 1 the english sibilants to each other 2 the japanese sibilants to each other and 3 english s to japanese s the results indicated that in both english and japanese the sibilant fricatives differ acoustically in terms of both static i e overall level and dynamic i e shape aspects of the peak erbn number trajectories furthermore english s and japanese s exhibited language specific differences in the shape but not overall level of peak erbn number trajectories

spectral moments versus bark cepstrum classification of children s voiceless stops spectral moments have been shown to be effective in deriving acoustic features for classifying voiceless stop release bursts k forrest g weismer p milenkovic and r n dougall j acoust soc am 84 115 123 1988 in this study we compared the classification of stops p t and k based on spectral moments with classification based on an equal number of bark cepstrum coefficients the speech tokens were 446 instances each of utterance initial p t and k sampled from utterances produced by 208 children 6 to 8 years old linear discriminant analysis lda was used to classify the three stops based on four analysis frames from the initial 40 ms of each token the best classification based on spectral moments used all four spectral moment features and all four time intervals and yielded 75 6 correct classification the best classification based on bark cepstrum yielded 83 4 correct also using four coefficients and four time frames differences between these results and previous classi

on the stability of mesh equidistribution strategies for time dependent partial differential equations abstract we study the stability of several mesh equidistribution schemes for time dependent partial differential equations in one space dimension the schemes move a finite difference or finite element mesh so that a given quantity is uniform over the domain we consider mesh moving methods that are based on solving a system of ordinary differential equations for the mesh velocities and show that some of these methods are unstable with respect to an equidistributing mesh when the partial differential system is dissipative using linear perturbation techniques we are able to develop simple criteria for determining the stability of a particular method and show how to construct stable differential systems for the mesh velocities several examples illustrating stable and unstable mesh motions are presented

multiscale fourier descriptors for classifying semivowels in spectrograms abstract fourier descriptors fds have been used successfully to characterize the boundary of objects in images it is demonstrated that fds are appropriate for characterizing objects in speech spectrograms consisting of 40 sounds representing 10 speaker dependent words containing the english semivowels w y l r with 10 fds a 97 5 recognition rate is attained different sounds are misclassified by wide and narrow band methods suggesting that multiscaling and fd changes differences may be appropriate features with a fd difference approach recognition rates equaled or exceeded those obtained with a conventional linear predictive coding lpc classifier as well as those obtained with wide and narrow band fd methods alone

subelliptic estimates for some systems of complex vector fields quasihomogeneous case for about twenty five years it was a kind of folk theorem that complex vector fields defined on x r t with open set in r n by l j t j i t j t x j 1 n t x r with analytic were subelliptic as soon as they were hypoelliptic this was the case when n 1 but in the case n 1 an inaccurate reading of the proof given by maire see also treves of the hypoellipticity of such systems under the condition that does not admit any local maximum or minimum through a nonstandard subelliptic estimate was supporting the belief for this folk theorem quite recently j l journe and j m trepreau show by examples that there are very simple systems with polynomial s which are hypoelliptic but not subelliptic in the standard l 2 sense so it is natural to analyze this problem of subellipticity which is in some sense intermediate at least when is c between the maximal hypoellipticity which was analyzed by helffer nourrigat and nourrigat and the simple local hypoellipticity or local microhypoellipticity and to start first with the easiest nontrivial examples the analysis presented here is a continuation of a previous work by the first author and is devoted to the case of quasihomogeneous functions

articulatory acoustic kinematics the production of american english s due to its aerodynamic articulatory and acoustic complexities the fricative s is known to require high precision in its control and to be highly resistant to coarticulation this study documents in detail how jaw tongue front tongue back lips and the first spectral moment covary during the production of s to establish how coarticulation affects this segment data were obtained from 24 speakers in the wisconsin x ray microbeam database producing s in prevocalic and pre obstruent sequences analysis of the data showed that certain aspects of jaw and tongue motion had specific kinematic trajectories regardless of context and the first spectral moment trajectory corresponded to these in some aspects in particular contexts variability due to jaw motion is compensated for by tongue tip motion and bracing against the palate to maintain an invariant articulatory aerodynamic goal constriction degree the change in the first spectral moment which rises to a peak at the midpoint of the fricativ

high order closed newton cotes trigonometrically fitted formulae for the numerical solution of the schrodinger equation abstract in this paper we investigate the connection between closed newton cotes formulae trigonometrically fitted methods symplectic integrators and efficient integration of the schrodinger equation the study of multistep symplectic integrators is very poor although in the last decades several one step symplectic integrators have been produced based on symplectic geometry see the relevant literature and the references here in this paper we study the closed newton cotes formulae and we write them as symplectic multilayer structures based on the closed newton cotes formulae we also develop trigonometrically fitted symplectic methods an error analysis for the one dimensional schrodinger equation of the new developed methods and a comparison with previous developed methods is also given we apply the new symplectic schemes to the well known radial schrodinger equation in order to investigate the efficiency of the proposed method to these type of problems

hypoellipticity and loss of derivatives let x1 xp be complex valued vector fields in rn and assume that they satisfy the bracket condition i e that their lie algebra spans all vector fields our object is to study the operator e x i xi where x i is the l2 adjoint of xi a result of hi ormander is that when the xi are real then e is hypoelliptic and furthemore it is subelliptic the restriction of a destribution u to an open set u is i smootheri then the restriction of eu to u when the xi are complex valued if the bracket condition of order one is satisfied i e if the xi xi xj span then we prove that the operator e is still subelliptic this is no longer true if brackets of higher order are needed to span for each k ia 1 we give an example of two complex valued vector fields x1 and x2 such that the bracket condition of order k 1 is satisfied and we prove that the operator e x 1x1 x 2x2 is hypoelliptic but that it is not subelliptic in fact it i losesi k derivatives in the sense that for each m there exists a distribution u whose restriction to an open set u has the property that the d aeu are bounded on u whenever a i m and for some with m k 1 the restriction of d u to u is not locally bounded

acoustic cue weighting in the singleton vs geminate contrast in lebanese arabic the case of fricative consonants this paper is the first reported investigation of the role of non temporal acoustic cues in the singleton geminate contrast in lebanese arabic alongside the more frequently reported temporal cues the aim is to explore the extent to which singleton and geminate consonants show qualitative differences in a language where phonological length is prominent and where moraic structure governs segment timing and syllable weight twenty speakers ten male ten female were recorded producing trochaic disyllables with medial singleton and geminate fricatives preceded by phonologically short and long vowels the following acoustic measures were applied on the medial fricative and surrounding vowels absolute duration intensity fundamental frequency spectral peak and shape dynamic amplitude and voicing patterns of medial fricatives and vowel quality and voice quality correlates of surrounding vowels discriminant analysis and receiver operating characteristics roc curves were used to assess each acoustic cue s contribution to the singleton geminate contrast classification rates of 89 and roc curves with an area under the curve rate of 96 confirmed the major role played by temporal cues with non temporal cues contributing to the contrast but to a much lesser extent these results confirm that the underlying contrast for gemination in arabic is temporal but highlight tense fortis as a secondary feature

statistical analysis of word initial voiceless obstruents preliminary data a statistical procedure for classifying word initial voiceless obstruents is described the data set to which the analysis was applied consisted of monosyllabic words starting with a voiceless obstruent each word was repeated six times in the carrier phrase i can say again by each of ten speakers fast fourier transforms ffts using a 20 ms hamming window were calculated every 10 ms from the onset of the obstruent through the third cycle of the following vowel each fft was treated as a random probability distribution from which the first four moments mean variance skewness and kurtosis were computed moments were calculated from linear and bark transformed spectra data were pooled across vowel contexts for speakers of a given gender and input to a discriminant analysis using the moments calculated from the linear spectra 92 of the voiceless stops were classified correctly when dynamic aspects of the stop were included even more important the model constructed from the males data correctly classified about 94 of the voiceless stops produced by the female speakers classification of the voiceless fricatives when all places of articulation were included in the analysis did not exceed 80 correct when the moments from either the linear or bark transformed scales were used however classification of only the voiceless sibilants was 98 correct when the moments from the bark transformed spectra were used as with the stops the classification model held across gender

unbiased adaptive estimations of the fourth order cumulant for real random zero mean signal in this paper a consistent efficient estimator of the fourth order cumulant for real discrete time random i i d at least up to order 8 zero mean signal is proposed in both batch and adaptive versions in batch version the proposed estimator is not only consistent but also unbiased and efficient the systematical theoretical and experimental studies with comparisons between the proposed estimator and three other estimators of the fourth order cumulant the natural or the traditional one the trivial unbiased estimator for the known power case and the fourth k statistics are undertaken for both normal and uniform processes then the adaptive versions of the estimators all except the fourth k statistics are given and studied in detail the convergence in mean and the convergence in mean square analyses are performed for them first theoretically then empirically finally the whole set of analyses carried out for both batch and adaptive versions shows that from many points of view the proposed estimator is interesting for use in versatile signal processing applications especially in real time and short term ones

method for the location of burst onset spectra in the auditory perceptual space a study of place of articulation in voiceless stop consonants a method for distinguishing burst onsets of voiceless stop consonants in terms of place of articulation is described four speakers produced the voiceless stops in word initial position in six vowel contexts a metric was devised to extract the characteristic burst friction components at burst onset the burst friction components derived from the metric as sensory formants were then transformed into log frequency ratios and plotted as points in an auditory perceptual space aps in the aps each place of articulation was seen to be associated with a distinct region or target zone the metric was then applied to a test set of words with voiceless stops preceding ten different vowel contexts as produced by eight new speakers the present method of analyzing voiceless stops in english enabled us to distinguish place of articulation in these new stimuli with 70 accuracy

acoustic characteristics of english fricatives this study constitutes a large scale comparative analysis of acoustic cues for classification of place of articulation in fricatives to date no single metric has been found to classify fricative place of articulation with a high degree of accuracy this study presents spectral amplitudinal and temporal measurements that involve both static properties spectral peak location spectral moments noise duration normalized amplitude and f2 onset frequency and dynamic properties relative amplitude and locus equations while all cues except locus equations consistently serve to distinguish sibilant from nonsibilant fricatives the present results indicate that spectral peak location spectral moments and both normalized and relative amplitude serve to distinguish all four places of fricative articulation these findings suggest that these static and dynamic acoustic properties can provide robust and unique information about all four places of articulation despite variation in speaker vowel context and voicing

a family of trigonometrically fitted partitioned runge kutta symplectic methods abstract we are presenting a family of trigonometrically fitted partitioned runge kutta symplectic methods of fourth order with six stages the solution of the one dimensional time independent schrodinger equation is considered by trigonometrically fitted symplectic integrators the schrodinger equation is first transformed into a hamiltonian canonical equation numerical results are obtained for the one dimensional harmonic oscillator and the exponential potential