• Journal of applied mathematics & informatics
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• v.23 no.1_2
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• pp.571-579
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• 2007

Finite difference schemes are considered for a generalization of the Cahn-Hilliard equation with Neumann boundary conditions and the Kuramoto-Sivashinsky equation with a periodic boundary condition, which is of the type $ut+\frac{{\partial}^2} {{\partial}x^2}\;g\;(u,\;u_x,\;u_{xx})=f(u,\;u_x,\;u_{xx})$. Stability and $L^{\infty}$ error estimates of approximate solutions for the corresponding schemes are obtained using the extended Lax-Richtmyer equivalence theorem.

• Communications of the Korean Mathematical Society
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• v.13 no.4
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• pp.889-901
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• 1998

Numerical approximations by pseudospectral method are obtained for the damped Boussinesq equation which is a modification of the good Boussinesq equation. The consistency and stability of the method are obtained using the extended Lax-Richtmyer equivalence theorem, which imply the convergence of the method. We obtain error estimates of O(h$^{s}$ ＋ k$^2$) for a fully discrete pseudospectral method.

• Phonetics and Speech Sciences
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• v.9 no.3
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• pp.25-32
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• 2017

Besides their effect on the f0 contour of the following vowel, Korean stops are undergoing a sound change in which a partial or complete consonantal merger on voice onset time (VOT) is taking place between aspirated and lax stops. Many previous studies on sound change have mainly focused on group-normative effects, that is, effects that are representative of the population as a whole. Few systematic quantitative studies of change in adult individuals have been carried out. The current study examines whether the sound change holds for individual speakers. It focuses on inter-speaker and intra-speaker variability on sound change in contemporary Korean. Speech data were collected for thirteen Seoul Korean speakers studying abroad in America. In order to minimize the possible effects of speech production, socio-phonetic factors such as age, gender, dialect, speech rate, and L2 exposure period were controlled when recruiting participants. The results showed that, for nine out of thirteen speakers, the consonantal merger is taking place between the aspirated and lax stop in terms of VOT. There were also intra-speaker variations on the merger in three aspects: First, is the consonantal (VOT) merger between the two stops is in progress or not? Second, are VOTs for aspirated stops getting shorter or not (i.e., the aspirated-shortening process)? Third, are VOTs for lax stops getting longer or not (i.e., the lax-lengthening process)? The results of remarkable inter-speaker and intra-speaker variability indicate a synchronous speech sound change of the stop system in contemporary Korean. Some speakers are early adopters or active propagators of sound change whereas others are not. Further study is necessary to see whether the inter-speaker differences exceed intra-speaker differences in sound change.

• Speech Sciences
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• v.11 no.2
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• pp.71-87
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• 2004

Korean has a pair of voiceless fricatives, whose laryngeal manifestation comes in parallel to stops and affricates with a three-way lexical contrast. Prior phonetic studies by Kagaya (1974), Iverson (1983), and Kang (1999, 2000) point out /s/ is associated with multiple characteristics of the larynx shared with not only the lax but also the aspirated series, whereas /s' / carries a laryngeal distinction typical of the tense consonants. The complex dual nature of /s/ is again supported by a psycholinguistic study by Kang (2004), as /s/ was found to interact with /$c^h$/ (17% of the time) as well as /c/ (57%) in speech errors. In addition, a recent work by Cho and Lee (2003) notes an interesting chain shift case in the acquisition of the fricatives. Although they observed a significant phonological pattern between child English and Korean, Cho and Lee's description of acquiring fricatives is far from being precise from the perspective of phonetics. From a longitudinal study of recorded tapes by two children at 1;7-3;8 and 1;7-2;1 respectively, I found that /s' / was usually substituted into tense noncontinuants in young children's early production as predicted, whereas /s/ having both lax and aspirated-like glottal properties revealed a complicated pattern of substitutions into lax, tense, and aspirated noncontinuants with a varying degree of preference relative to the subjects. The current acquisition study supports the previous claims concerning fricatives in other languages, showing that their acquisition comes after stops. Besides, it also notes that Korean fricatives are subject to a series of phonological processes called stopping, affricating, tensifying and palatalizing during the transitional period of phonological development by young children. Moreover, between the two voiceless types, /s/ was acquired earlier than /s'/ as the unmarked segment.

• Cross-Cultural Studies
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• v.27
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• pp.497-523
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• 2012

Characteristics of the Listening and Pronunciation of Korean Obstruents of Chinese Learners -Based on the Phonetic Experiments Using Kalvin and Praat- This study aims at investigating the characteristics of confrontation in three ways, lax/ fortis/ aspirated consonants, in Korean obstruents through experimental phonetic analysis for the Chinese Korean language learners. On one hand, as a result of comparing Korean and Chinese obstruent systems, there is no big difference regarding the articulatory location. On the other hand, in regards to the articulatory method there is a difference. In a Korean obstruent system, the confrontation presented in three ways by the strength of aspiration. On the contrary, the Chinese obstruent system showed confrontation in two ways by the existence of aspiration. To examine the difficulty of the learners caused by the above-mentioned reason objectively, this paper studied the relationship between input and output of sound through the experimental phonetic analysis such as Kalvin and Praat. To research the input of sound, the listening ability of the learners was examined by 'Choosing Consonant' among the Menu of Kalvin. As a result of that experiment, many errors were shown. They recognized the fortis as lax in the area of affricates and plosives. In the area of fricatives, they recognized affricatives as fricatives. To investigate the output of sound, the section of aspiration and the section of friction of a plosive, an affricate and a fricative in Praat, were expressed numerically. The learners' VOT of lax and affricate represented that lax was pronounced close to the fortis, and the VOT of fricatives was not shown the section of aspiration and friction clearly, and also the result showed that they pronounced a fricative like affricative-aspirated one. The result shows that the learners' pronunciation is related to the listening ability. The consequence is caused by the characteristics of the difference between Korean obstruents and Chinese ones. If the training pronunciation is conducted based on above result, it would be a better methodology in teaching Korean.

• Phonetics and Speech Sciences
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• v.14 no.3
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• pp.1-9
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• 2022

The current study examined English-speaking adult learners' production and perception of L2 Korean stops (/t/ or /t'/ or /t^h/) to investigate whether the two modalities are linked in utilizing voice onset time (VOT) and fundamental frequency (F0) for the L2 sound distinction and how the learners' L2 proficiency mediates the relationship. Twenty-two English-speaking learners of Korean living in Seoul participated in the word-reading task of producing stop-initial words and the identification task of labelling CV stimuli synthesized to vary VOT and F0. Using logistic mixed-effects regression models, we quantified group- and individual-level weights of the VOT and F0 cues in differentiating the tense-lax, lax-aspirated, and tense-aspirated stops in Korean. The results showed that the learners as a group relied on VOT more than F0 both in production and perception (except the tense-lax pair), reflecting the dominant role of VOT in their L1 stop distinction. Individual-level analyses further revealed that the learners' L2 proficiency was related to their use of F0 in L2 production and their use of VOT in L2 perception. With this effect of L2 proficiency controlled in the partial correlation tests, we found a significant correlation between production and perception in using VOT and F0 for the lax-aspirated stop contrast. However, the same correlation was absent for the other stop pairs. We discuss a contrast-specific role of acoustic cues to address the non-uniform patterns of the production-perception link in the L2 sound learning context.

• Phonetics and Speech Sciences
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• v.1 no.1
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• pp.41-46
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• 2009

Duration of the preceding vowel is known to vary as a function of the (phonological or phonetic) voicing feature of the following consonant. This study raises a question against this general belief. A spectrographic experiment using 14 Korean obstruents (three sets of stops: /p, p', $p^h$/, /t, t', $t^h$/, /k, k', $k^h$/; one set of affricates: /c, c', $c^h$/; one set of fricatives: /s, s'/) reveals that (1) phonetic voicing in the intervocalic lax consonants /p, t, k, c, s/ has nothing to do with the duration of the preceding vowel; (2) vowel length is significantly shorter before tense consonants than before their lax cognates while tense consonants are significantly longer than their lax cognates. Importantly, Korean obstruents are all phonologically voiceless. Therefore, the voicing feature is rejected as the cause of preconsonantal vowel shortening in Korean both phonetically and phonologically. It is suggested that the temporal phenomenon is basically a kind of physiologically-motivated coarticulation though it is restricted by the phonology of a given language. To meet this assumption, the feature voicing should be replaced with the feature tenseness as the cause, which will enable us to explain the temporal phenomenon on the same basis irrespective of language.

• Asian Journal of Turfgrass Science
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• v.1 no.1
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• pp.7-17
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• 1987

The experiment with two levels of nitrogen (0. and 300kg / ha / year) and two levels of clipping height (1.5cm and 4cm) was conducted on the field during the period 3 June to 23 October 1985. Clonal lines of korean lawngrass ( Zoysia japonica Steud.) and manilagrass ( Zoysia matrella ( L.) Merr.)of Daejon origin were established in June, as individual clone in rows 30cm apart with a 40cm spacing between clones, actually 4 clones each plot. The results obtained were as follows : 1. When no nitrogen was applied to korean lawngrass, leaf blade which appeared during the August / early September period remained green for a period of about 10 weeks and even leaves emerged in late September lived for 42 days. However, leaf longevity did not exceed 8 weeks as nitrogen was applied. In contrast the leaf longevity of manilagrass which emerged during the mid - August / early September period was 11 weeks and, under the nitrogen applied, 9 weeks, indicating that the life - saen of individual leaf of manilagrass may be longer than that of korean lawngrass. Meanwhile, clipping height had no effect on the leaf longevity in both grasses. 2. During the July / August period, tiller number, green leaf number and DM weight of korean lawngrass were increased significantly with fertilizer nitrogen, but were not with two levels of clipping height. This trend was reversed after late September : no effect of nitrogen was appeared. Instead, lax clipping increased tiller number, green leaf number and DM weight. Green leaves stimulated by lax clipping resulted in the occurrance of more dead leaves in late October. 3. The increase of tiller number, green leaf number, and DM weight of korean lawngrass due to nitrogen application appeared to be of significance in early September. Unlike korean lawngrass, however, this significant increase was maintained to late October when new green leaves still emerge. Clipping height had little effect on the growth of manilagrass by early September, but since then, lax clipping stimulated leaf appearance, possibly resulting in a remained green color of manilagrass turf. 4. Among the stolons outgrown until early September, the primary stolon was not influenced by nitrogen and clipping treatments to produce only 2 - 3 stolons. However, 1st branch stolon as affected by nitrogen increased significantly, so most of stolons which occurred consisted of 1st branch stolon. 5. Until early September, stolon length obtained at nil nitrogen level was chiefly caused by lengthening the primary stolons. By applying nitrogen the primary stolons of korean lawngrass was longer than 1st branch stolons when severe clipping was involved and in turn, shorter than 1st branch stolons when lax clipping was concerned. In manilagrass, 1st branch stolons were much longer than the primary stolons when turf was clipped severely but in conditions of lax clipping, there was little difference in length between primary and 1st branch stolons. 6. Stolon nodes of both korean lawngrass and manilagrass were positively influenced by nitrogen, but no particular increases by imposing clipping height treatment was marked in manilagrass. Although the stolon of korean lawngrass was grown until late october, the growth stimulated by nitrogen was not so remarkable as to exceed that a by nil N. 7. The thickness of korean lawngrass and manilagrass was greatest in late September, but that of manilagrass did not differ significantly from that in late October. 8. The response of stolon length of korean lawngrass to lax clippings was not so great in late October as to that to severe clippings. On the other hand, the positive effect of lax clippings to stolon length in m anilagrass was confirmed even in late October.

• MALSORI
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• no.spc1
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• pp.13-23
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• 2002

• ETRI Journal
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• v.23 no.1
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• pp.9-15
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• 2001

We suggest a generalized Lax pair on a Hermitian symmetric space to generate a new coupled higher-order nonlinear $Schr{\ddot{o}}dinger$ equation of a dual type which contains both bright and dark soliton equations depending on parameters in the Lax pair. Through the generalized ways of reduction and the scaling transformation for the coupled higher-order nonlinear $Schr{\ddot{o}}dinger$ equation, two integrable types of higher-order dark soliton equations and their extensions to vector equations are newly derived in addition to the corresponding equations of the known higher-order bright solitons. Analytical discussion on a general scalar solution of the higher-order dark soliton equation is then made in detail.