bluuebunny/crossref_metadata_2025 huggingface dataset:
Acquisition of Pig Latin: a case study
Authors: Cowan Nelson
Published: February 2009

A boy's acquisition of Pig Latin was monitored throughout the year preceding first grade. Abilities underlying this game include the identification of words, deletion of the first syllabic onset (i.e. prevocalic consonants) of each word, blending of this onset and the suffix [e1] onto the word's end, and short-term memory for speech units. Performance improved over time as the underlying abilities developed. Meanwhile, various informative errors were made. Throughout most of the study, onsets that were correctly removed from a word's beginning were often added to its end incorrectly; unstressed function words were repeated intact and not transformed; and the first syllabic onset was overlooked when the syllable was unstressed. Because speech games like this one depend upon basic language skills, they can clarify aspects of ordinary language development.
Theoretical implications of complement structure acquisition in Korean
Authors: Kim Young-Joo
Published: February 2009

The Acquisition Of Complement Phrasal Constructions In Korean Is Examined In Spontaneous Speech Data From Two Children, Who Were Observed From One And A Half To Three Years Of Age. In Spite Of Typological Differences Between English And Korean, Both Syntactic And Semantic Characteristics are found to be shared by children acquiring complement constructions in the two languages. however, certain language-specific features of korean complement structures make it possible to address theoretical points concerning the structure of infinitival complements which cannot be resolved with the acquisition data on English. The error pattern in the acquisition of certain ‘subject-equi’ verbs in Korean poses problems both for LEG and GB accounts of the constituent structure of infinitival complements and the acquisition of those constructions. On the basis of the Korean data, I propose that base-generated VP complements are acquired first, with semantically motivated reanalysis of previously acquired infinitival complement structures occurring at a later stage.
The argumentative connectivemêmein French: an experimental study in eight- to ten-year-old children
Authors: Bassano Dominique , Champaud Christian
Published: February 2009

This study examines how children understand the argumentative function of the French connectivemême(‘even’). Two completion tasks, related to the argumentative properties of the morpheme, were used: (1) to infer the conclusion of an ‘even’ sentence, and (2) to infer the argument position. Two main factors likely to influence the comprehension were investigated: the semantic context, and the syntactic form – affirmative vs negative. The argumentative function ofmêmewas globally mastered at the age of eight, but comprehension depends on semantic context. Performances were better for negative sentences, which suggests that negation plays a facilitating role; the specific properties of the negative expressionpas même/même pas(‘not even’) in discourse are discussed.
Fine-tuning of utterance length to preverbal infants: effects on later language development
Authors: Murray Ann D. , Johnson Jeanne , Peters Jo
Published: February 2009

The purpose of this study was to determine (1) whether mothers simplify their speech during the second half of the first year of development when infants begin to comprehend words and use gestures to communicate intentionally, and (2) whether individual differences in mothers' speech adjustments influence their infants' later language acquisition. The subjects for the study were 14 mother-infant pairs from a medically low risk sample who were followed longitudinally. Mothers' mean length of utterance (MLU) was calculated from transcripts of face-to-face interaction when the infants were 0;3, 0;6, and 0;9 in age. Mothers who provided responsive and stimulating environments, as indicated by HOME scores, also reduced their MLU over the age range studied. Moreover, mothers' MLU adjustments during the first year were more predictive than the HOME scale in forecasting receptive language development at 1; 6. In contrast, expressive language abilities at 1; 6 were unrelated to the environmental variables measured but were predicted by child characteristics such as the infant's sex. These results suggest that a mother's ability to ‘fine-tune’ her early linguistic input may be predictive of her child's later receptive language functioning. Precursors of fine-tuning, such as maternal beliefs in reciprocity and infant object orientation, are discussed.
Pointing and interaction initiation: the behaviour of young children with Down's syndrome when looking at books
Authors: Wootton Anthony J.
Published: February 2009

Data are derived from videotapes made in the homes of six Down's syndrome children with developmental ages varying between 1;1 and 2;1. The analysis concerns those sequences in which parent and child look at a book together, and more specifically those exchanges where the child initiates communication on a new target on the page. The design of these initiations is examined with respect to their various verbal and non-verbal components. The analysis of pointing, and in particular of point duration, reveals a possible developmental progression from a stage at which point and exchange duration are linked together to one in which the organization of pointing becomes more detached from the exchange as a unit of interaction.
Acquisition of passives: the role of patient animacy, salience, and lexical accessibility
Authors: Lempert Henrietta
Published: February 2009

In full passive sentences such as The cat was kicked by the dog, the patient (cat) is promoted to subject and the agent is demoted to the by-phrase. Children 2;10 to 4;7 years (mean 3;6) who were taught the form with animate patients and animate agents (The baby is being picked up by the girl) were better able to produce and comprehend passives than children taught with inanimate patients and animate agents (The flower is being picked up by the girl). The finding of comparable post-teaching performance in children taught with perceptually salient (coloured) VS. nonsalient patients argues against a salience explanation for the patient animacy effect. Moreover, equal access to word forms for animate and inanimate nouns did not reduce the effect. The animacy effect is consistent with claims that ‘perspective’ is the cognitive counterpart to the formal category of subject; and, conversely, inconsistent with attempts to understand language acquisition in terms of a language system that operates in isolation from other facets of human cognition.
Do children exploit the Maxim of Antecedent in order to interpret ambiguous descriptions?
Authors: Surian Luca
Published: February 2009

Twenty Italian six-year-olds and 20 eight-year-olds were asked to interpret eight ambiguous and eight clear definite descriptions. All ambiguous descriptions could refer to three drawings, one of which had been described by the subjects immediately before the comprehension task. In half of the trials with ambiguous messages the children's interlocutor was present while the children were describing the drawings; in the other half he was absent. In both conditions subjects showed a preference for the referents they had already described, indicating that they applied egocentrically a comprehension strategy based on the Maxim of Antecedent (Jackson & Jacobs, 1982). Children's failures to differentiate their responses in the two conditions are considered to be due to difficulties in taking account of the given-new distinction for relevant information.
The influence of linguistic context on young children's understanding of homophonic words
Authors: Beveridge Michael , Marsh Lesley
Published: February 2009

This study investigates young children's understanding of homophones in two different linguistic contexts. Research has shown that children interpret homophones according to their ‘primary’ sense even though this is inappropriate to the linguistic context. The present study investigates the influence of different contexts on their interpretations of homophones. A picture test, similar to the British Picture Vocabulary Scale (BPVS), was devised, depicting ten homophones in both their primary and secondary senses. Forty-eight children who were in matched pairs following the BPVS pre-test and whose ages ranged from three to six were asked to select the picture which showed the homophone, first when the homophone was in no linguistic context, and secondly following one of two conditions of the same story which differed according to the richness of context provided. Results showed that those children assigned to story B, the expanded version with full linguistic details and explanations of the words it contained, were more able to identify correctly the secondary meanings of the homophones intended than those children given story A, the unexpanded version. Analyses of variance showed both a significant age trend and a story-type effect. These results are interpreted as showing that the linguistic context is an important factor in young children's understanding of word meaning.
Introducing information in dialogues: forms of introduction chosen by young speakers and the responses elicited from young listeners
Authors: Anderson Anne H. , Clark Aileen , Mullin James
Published: February 2009

Young speakers in dialogue must establish mutual knowledge. Traditionally, researchers have focused on how children used indefinite and definite articles to signal novel and shared information. In this study of 170 children aged seven to thirteen, the form of introduction chosen, whether question or statement, is more significant than the type of article used. No developmental effects on article use emerge, with statement + indefinite always the least common choice. However, young speakers use question introductions significantly less than older children. There is also a developmental interaction between speakers' and listeners' behaviour. Question introduction elicit effective listener responses at all ages, but only twelve-year-olds respond reliably to statements. Unfortunately, young speakers prefer just those forms of introduction to which young listeners are least likely to provide informative feedback. Thus two separate developmental effects appear to combine to hamper young subjects' chances of achieving successful communication in dialogues.
Joint attention on actions: acquiring verbs in ostensive and non-ostensive contexts
Authors: Tomasello Michael , Kruger Ann Cale
Published: February 2009

Two studies of verb learning are reported. The focus of both studies was on children in their second year of life learning verbs in various pragmatic contexts. Of particular interest was the comparison of ostensive contexts – in which word and referent were simultaneously present in the child's perceptual field – to non-ostensive contexts. In a naturalistic study of 24 children at 1;3 and 1;9, it was found that mothers modelled verbs for their children most often BEFORE the referent action actually occurred. Over 60% of maternal verbs were used to refer to actions that mothers wished children to perform or that they were anticipating their performing (IMPENDING actions). Some verbs were also used to refer to current actions (ONGOING actions) or actions that had just been completed (COMPLETED actions). Children responded with comprehension most often to impending models. Impending and completed models, but not ongoing models, were correlated with children's verb vocabularies at 1;9. The second study was a lexical training study of 48 two-year-olds. Children learned to produce a novel verb best when it was modelled in the impending condition. They learned to comprehend it equally well in the impending and completed conditions. Children showed no signs of superior learning in the ostensive (ongoing) learning context. Results of the two studies are discussed in terms of the different learning processes involved in acquiring nouns and verbs, and, more broadly, in terms of a social-pragmatic view of language acquisition in which the ostensive teaching paradigm is but one of many contexts in which children learn to establish a joint attentional focus with mature language users.
Refining transcriptions: the significance of transcriber ‘errors’
Authors: Pye Clifton , Wilcox Kim A. , Siren Kathleen A.
Published: February 2009

This work describes the importance of the transcription process in studies of speech and language acquisition. Using data collected from a hearing child of deaf parents, the three authors derived independent transcriptions of the same speech sample and systematically compared their transcripts with each other and with the best estimate of the speaker's actual productions. The resultant transcripts were used to produce two descriptions of this child's phonological system, one based on a liberal estimate and one on a conservative estimate of the potential error in the transcripts. Discussion includes suggestions for deriving percentages of inter-transcriber agreement and the utility of such figures as a metric of transcription difficulty as well as transcriber ability.
The semantic development of negation: a cross-linguistic longitudinal study
Authors: Choi Soonja
Published: February 2009

Negative utterances were collected longitudinally from two English-, five French- and four Korean-speaking children between 1;7 and 3;4. An analysis focusing on both non-verbal context and linguistic form led to the distinction of nine semantic/pragmatic categories which could capture cognitive and linguistic development in some detail: non-existence, prohibition, rejection, failure, denial, inability, epis-temic negation, normative and inferential negation. The nine categories were found in all three languages and their developmental order was similar across the languages. Different patterns were shown concerning the form-function relationship for different categories; for some categories, the distinct form emerged gradually after the function was acquired, while for others, the distinct form emerged simultaneously with the new function. Thus new forms emerged to subdivide an old category or to express a new function. This pattern was most typical for categories developed at later periods. It is suggested that whereas cognitive development precedes language development at an early period, at later periods cognitive and language development interact with each other.
The effect of animacy on children's noun order in verb-final sequences
Authors: Lempert Henrietta
Published: February 2009

This study examined whether pragmatic ordering factors account for the apparent preference for ANIMATE-INANIMATE (AI) order in passive and active sentences. If so, learning noun order relations in NNV sequences with an INANIMATE PATIENT + ANIMATE AGENT (It's the drum the boy plays) should be more difficult than with an ANIMATE PATIENT + ANIMATE AGENT (It's the girl the boy chases). Seventy children aged 3;0 to 5;3 were trained with either AAV or IAV exemplars, and then tested for their noun order in NNV utterances when describing animate agent + animate patient and animate agent + inanimate patient pictures. As judged by post-training performance, AAV and AIV training had comparable effects at age three, but IAV resulted in better learning at ages four and five. It was argued that the latter benefited from the correlation between animacy and subject in English sentences.
Local and topological processing in sentence comprehension by French and Spanish children
Authors: Kail Michèle , Charvillat Agnès
Published: February 2009

This cross-linguistic study investigates the relative importance of validity in terms of the strengths of syntactic cues and cue processing cost in sentence comprehension by French and Spanish children (4; 6–6; 6). The notion of cue cost refers to the distinction between local and topological processing types. Choices of the agent (cue strength) and latencies (cue cost) were collected through the acting out of sentences containing different syntactic cues. These cues (word order, clitic pronoun, verbal agreement plus accusative prepositionain Spanish) are ordered on a continuum from the most topological (word order) to the most local (prepositiona). The analysis of cue strengths reveals that, while for French children a linguistic cue is all the stronger the more topological it is (verbal agreement < clitic pronoun < word order), for Spanish children a cue is all the stronger the more local it is (word order < clitic pronoun < verbal agreement < prepositiona). The fact that Spanish children's latencies are always shorter (2150 msec) than those of French children (3110 msec) must be related to the effect of the prepositionawhich permits efficient role assignments with minimal cost. These results stress the importance of locality in sentence processing. On the other hand, a comparison with our similar adult cross-linguistic data demonstrates that the impact of cue cost changes over time.
The influence of dialectal variation on phonological acquisition: a case study on the acquisition of Cantonese
Authors: Tse Sou-Mee , Ingram David
Published: February 2009

The phonological acquisition of a young girl whose parents spoke two dialects of Cantonese was examined. The father's dialect had a phonological distinction between initial /l/ and /n/ which was merged into /l/ in the mother's dialect. The child was followed bi-weekly for approximately one year. The results indicate that she acquired neither the mother's nor the father's dialect. Instead, she acquired [l] and [n] as freely varying allophones of a single phoneme. In the first months, [n] was the most frequent realization of the phoneme, with [l] becoming the most frequent one in later sessions. The results are interpreted as supporting the claim that children use all available input in acquiring language rather than limiting themselves to a primary language model.
The comprehension of metaphor by preschool children
Authors: Pearson Barbara Zurer
Published: February 2009

Comprehension of metaphor in preschoolers was studied through an elicited repetition task. Subjects were 52 children aged 3;0 to 5;2. Repetition performance on metaphors was compared to repetitions of semantically well-formed literal sentences as well as semantically anomalous sentences, all matched for length, vocabulary and sentence structure. Accuracy on literal and metaphoric stimuli was comparable, and both were significantly better than performance on anomalous sentences. There were no effects for age or sex. It was shown that the metaphors were not semantically anomalous to the children and that they were processed on a par with literal language. The argument is advanced from a review of the literature that imitation implicates understanding of the material imitated. If metaphor is thus shown to emerge early in the child's linguistic repertory, figurative language, it may be argued, occupies a more central position in linguistic theory than it has been accorded.
Development of forms and functions of negation in the early stages of language acquisition: a study in Tamil
Authors: Vaidyanathan R.
Published: February 2009

The development of forms and functions of negation in parent–child interactions in the early stages of language acquisition is discussed with illustrative examples from field data relating to two Tamil-speaking children and their parents. An attempt is made to provide a scheme for analysing the negatives in children's speech, maintaining the three basic functions of Bloom (1970) unaltered. Subcategories of these functions are introduced, taking into consideration the interactional situations as they are perceived by the parents and children. Children, it is observed, acquire the forms and functions of negation in a clear developmental sequence. They acquire and use the free forms naanaa (veeṇḍaam) ‘No, I don't want’ first, followed by negatives involving bound forms. Certain forms like maaṭṭeen ‘I won't’, muḍiyaadi' I can't’ and even veeṇḍaam are used in isolation (as free forms) first. Only later are they used with verb infinitives. The development of functions of negation follows the sequence: rejection, non-existence, prohibition and denial. Thus the children of this study show preference for rejection over non-existence as observed by earlier scholars.
A crosslinguistic investigation of vowel formants in babbling
Authors: de Boysson-Bardies Bénédicte , Halle Pierre , Sagart Laurent , Durand Catherine
Published: February 2009

A cross-cultural investigation of the influence of target-language in babbling was carried out. 1047 vowels produced by twenty 10-month-old infants from Parisian French, London English, Hong Kong Cantonese and Algiers Arabic language backgrounds were recorded in the cities of origin and spectrally analysed. F1-F2 plots of these vowels were obtained for each subject and each language group. Statistical analyses provide evidence of differences between infants across language backgrounds. These differences parallel those found in adult speech in the corresponding languages. Implications of an early build-up of target-language-oriented production skills are discussed.
Induction and the acquisition of English auxiliaries: the effects of differentially enriched input
Authors: Shatz Marilyn , Hoff-Ginsberg Erika , Maciver Douglas
Published: February 2009

Children aged 2;0 to 2;6 participated in a longitudinal study examining their acquisition of the English auxiliary system following a six-week period in which they were exposed to additional auxiliary input in varying sentence contexts. Groups of children received enrichment utterances with the auxiliarycouldeither in first position in the sentence, in middle position, or in both positions. Children in the front position group were significantly advanced over the other experimental groups in acquiring modal auxiliaries but not non-modals. However, none of the experimental groups differed significantly from a baseline group which received no additionalcouldinput. The implications of these findings for understanding the mechanisms of auxiliary acquisition and the nature of children's grammatical categories are discussed.
Canonical and non-canonical syllable discrimination by two-day-old infants
Authors: Moon Christine , Bever Thomas G. , Fifer William P.
Published: February 2009

Canonical syllables may be important units in early speech perception as well as production. Twenty infants (mean age 51 hours) (and twenty controls) were tested for their ability to discriminate between members of syllable pairs which were either canonical (pæt and tæp) or non-canonical (pst and tsp). A discrimination learning method was used in which syllables signalled the availability of either a recording of the mother's voice or silence – one of which was presented if the infant began a sucking burst. Infants in the canonical condition changed sucking patterns during signals over an 18-minute experimental session and activated their mother's voice more than silence, consistent with previous experiments using mother's voice as a reinforcer. In the non-canonical condition, infants also changed sucking patterns but sucked more during the signal for quiet than mother's voice, contrary to previous findings. Differential sucking during the syllables indicated discrimination in both conditions, but infants responded differently depending upon whether the syllables were canonical or non-canonical. The activation of silence in the non-canonical condition may be the result of a preference for quiet, but it is better explained as a failure to progress to a level of differential responding that was reached by the canonical group.
How referential are ‘referential’ children? Relationships between maternal-report and observational measures of vocabulary composition and usage
Authors: Pine Julian M.
Published: February 2009

This study examines the relationship between maternal-report measures of referential vocabulary and observational measures of referential vocabulary and usage in eight first-born middle-class children at 50 and loo words. The results indicate that although maternal-report measures of vocabulary composition can be reasonably reliable, provided some attempt is made to restrict variation in the number of vocabulary items upon which they are based, such measures tend to exaggerate the relative importance of common nouns for the child in two ways; firstly, in the sense that they reflect differential maternal sensitivity to such word-types in comparison with other less-‘referential’ items; and, secondly, in the sense that they overestimate the extent to which such word-types actually occur in the child's spontaneous speech.
Incidence of verbal comparisons in beginners' books and in metaphor comprehension research: a search for ecological validity
Authors: Broderick Victor
Published: February 2009

Explicit verbal comparisons in 53 popular children's books were syntactically and semantically classified. Comparison types found in these books were contrasted with comparisons used as comprehension stimuli in extant developmental research. Although noun-phrase metaphor has been a popular syntactic form in research, it is a rare form in children's literature. Implications for the design of future stimulus sets are discussed.
Can children use a verb without exposure to its argument structure?
Authors: Braine Martin D. S. , Brody Ruth E. , Fisch Shalom M. , Weisberger Mara J. , Blum Monica
Published: February 2009

We hypothesize that canonical sentence schemas (e.g. Agent—verb-Patient) can sometimes assign argument structure to verbs. In particular, they provide a default argument structure early in learning when a verb's lexical entry may record the nature of the action but lack a specific argument structure. To test the theory and its application to causative verb errors (e.g. stay it there), novel action verbs were modelled, some as causative, some as intransitive, and some unmarked for transitivity. Spontaneous usage was recorded, along with responses to agent-questions (‘What is the [Agent] doing?’) and patient-questions (‘What is the [Patient] doing?’). Comparable data were obtained for familiar English verbs, some of fixed and some of optional transitivity. Subjects were willing to use all novel verbs both transitively and intransitively, although adults respected assigned transitivity more than children. All subjects largely respected the transitivity of familiar verbs. The discourse pressure of the agent- and patient-questions greatly affected observed transitivity. No evidence was found for the intransitive-to-causative derivational process postulated by Bowerman. We propose that the kind of causativity error observed by Bowerman is due to assignment of argument structure from canonical sentence schemas, especially under pressure of a need to make a sentence with a particular argument (Agent or Patient) as subject. The theory has the advantage of explaining errors without postulating the acquisition of erroneous lexical entries that have to be unlearned, and it can be extended to other kinds of errors in the choice and placement of arguments.
Children use syntax to learn verb meanings
Authors: Naigles Letitia
Published: February 2009

Verb learning is clearly a function of observation of real-world contingencies; however, it is argued that such observational information is insufficient to account fully for vocabulary acquisition. This paper provides an experimental validation of Landau & Gleitman's (1985) syntactic bootstrapping procedure; namely, that children may use syntactic information to learn new verbs. Pairs of actions were presented simultaneously with a nonsense verb in one of two syntactic structures. The actions were subsequently separated, and the children (MA = 2;1) were asked to select which action was the referent for the verb. The children's choice of referent was found to be a function of the syntactic structure in which the verb had appeared.
How to measure development in corpora? An association strength approach
Authors: STOLL SABINE , GRIES STEFAN TH.
Published: February 2009

In this paper we propose a method for characterizing development in large longitudinal corpora. The method has the following three features: (i) it suggests how to represent development without assuming predefined stages; (ii) it includes caregiver speech/child-directed speech; (iii) it uses statistical association measures for investigating co-occurrence data. We exemplify the implementation of these proposals with data on the acquisition of the patterning of tense and grammatical aspect of four Russian children. The method, however, is suitable for a wide range of other acquisition questions as well.
On representations of a generalized method of field quantization
Authors: Kleeman R.
Published: February 2009

A new method of field quantization, in which the number operator has the form a*a, is proposed. Representations of this method are considered, particularly in reference to what conditions unique-vacuum state representations are required to satisfy.
Exact solution of a difference approximation to Duffing's equation
Authors: Potts Renfrey B.
Published: February 2009

Duffing's equation, in its simplest form, can be approximated by various non-linear difference equations. It is shown that a particular choice can be solved in closed form giving periodic solutions.
Dynamics of rapid extinction in a lumped system with Arrhenius chemistry
Authors: Do D. D. , Weiland R. H.
Published: February 2009

Reacting systems with Arrhenius chemistry can exhibit multiple steady states for γ > 4(1 + β)/β where γ is activation energy and β is the heat of reaction. We give a detailed analysis of the extremely rapid jump which takes place as catalyst activity slowly decays through criticality. Previous analyses are asymptotic in the limit γ → ∞; here we relax the large γ assumption and only require that passage through criticality is slow.
Three dimensional similarity solutions of the nonlinear diffusion equation from optimization and first integrals
Authors: Parlange J.-Y. , Braddock R. D. , Sander G. , Stagnitti F.
Published: February 2009

For diffusion problems, the boundary conditions are specified at two distinct points, yielding a two end-point boundary value problem which normally requires iterative techniques. For spherical geometry, it is possible to specify the boundary conditions at the same points, approximately, by using an optimization principle for arbitrary diffusivity. When the diffusivity obeys a power or an exponential law, a first integral exists and iteration can be avoided. For those two exact cases, it is shown that the general optimization result is extremely accurate when diffusivity increases rapidly with concentration.
Stiff systems of ordinary differential equations. III. Partially stiff systems
Authors: Mahony J. J. , Shepherd J. J.
Published: February 2009

The partially stiff system of ordinary differential equations

is studied by the methods developed in the earlier papers in this series. Here e is a small positive parameter, x and y are n- and m-vectors respectively, and A is nonsingular. A useful basis for the solution space of the homogeneous system is constructed and the method of variation of parameters is used to obtain useful representations of all solutions. Sufficient conditions are derived under which the formal approximation

is close to the actual solution. it is found that purely imaginary eigenvalues for A require more stringent requirements for the formal technique to be valid. A brief discussion of the case when A is singular shows that there are a great number of possibilities requiring consideration for a general theory. it is suggested that local computation of such cases is likely to be the most effective weapon for any specific system.
Input retrieval in finite dimensional linear systems
Authors: Howlett P. G.
Published: February 2009

For finite dimensional linear systems it is known that in certain circumstances the input can be retrieved from a knowledge of the output only. The main aim of this paper is to produce explicit formulae for input retrieval in systems which do not possess direct linkage from input to output. Although two different procedures are suggested the fundamental idea in both cases is to find an expression for the inverse transfer function of the system. In the first case this is achieved using a general method of power series inversion and in the second case by a sequence of elementary operations on a Rosenbrock type system matrix.
Double conductor line above a two-layered cylinder with varying properties
Authors: Kolyshkin A. A. , Vaillancourt Rémi
Published: February 2009

The change of impedance per unit length in a single or double conductor line situated parallel to an infinitely long two-layered metallic circular cylinder is found (within the quasistatic approximation) in the form of an infinite series. The cylinder consists of an inner core and an outer annulus. The properties of the inner core are assumed to be constant. The relative magnetic permeability, μ(r) = rα and the conductivity, σ(r) = σ(0)rκ, of the outer annulus vary with respect to the radial coordinate, r, and α and κ are arbitrary real numbers. Numerical results are presented in the form of figures and tables.
Oscillations of Interconnected Systems withC0Nonlinearities
Authors: He Xiangjian
Published: February 2009

In this paper we establish conditions which ensure the existence of self-excited oscillations in complex dynamical systems with nondifferentiable nonlinearities, by considering those types of systems which can be viewed as an interconnection of several simpler subsystems. We find that the nonlinear terms of the system in which we are interested do not need to satisfy the Lipschitz condition.
Global attractivity in time-delayed predator-prey systems
Authors: Cao Yulin , Freedman H. I.
Published: February 2009

For a predator-prey model with time-delay due to gestation, criteria are obtained for persistence and global attractivity. The global attractivity criteria apply only to models with a decreasing prey isocline.
Generalized multi-peg tower of hanoi problem
Authors: Majumdar A. A. K.
Published: February 2009

This paper treats the multi-peg generalization of the Tower of Hanoi problem with n(≥ 1) disks and p(≥ 3) pegs, P1, P2,…, Pp. Denoting by M(n, p) the presumed minimum number of moves required to transfer the tower of n disks from the source peg, P1, to the destination peg, Pp, under the condition that each move transfers the topmost disk from one peg to another such that no disk is ever placed on top of a smaller one, the Dynamic Programming technique has been employed to find the optimality equation satisfied by M(n, p). Though an explicit expression for M(n, p) is given, no explicit expressions for the partition numbers (at which M(n, p) is attained) are available in the literature for p ≥ 5. The values of the partition numbers have been given in this paper.
The fractional fourier transform and the wigner distribution
Authors: Mustard David
Published: February 2009

The Wigner distribution and many other members of the Cohen class of generalized phase-space distributions of a signal all share certain translation properties and the property that their two marginal distributions of energy density along the time and along the frequency axes equal the signal power and the spectral energy density. A natural generalization of this last property is shown to be a certain relationship through the Radon transform between the distribution and the signal's fractional Fourier transform. It is shown that the Wigner distribution is now distinguished by being the only member of the Cohen class that has this generalized property as well as a generalized translation property. The inversion theorem for the Wigner distribution is then extended to yield the fractional Fourier transforms.
Adaptive boundary-element methods for transmission problems
Authors: Carstensen Carsten , Stephan Ernst P.
Published: February 2009

In this paper we present an adaptive boundary-element method for a transmission prob-lem for the Laplacian in a two-dimensional Lipschitz domain. We are concerned with an equivalent system of boundary-integral equations of the first kind (on the transmission boundary) involving weakly-singular, singular and hypersingular integral operators. For the h-version boundary-element (Galerkin) discretization we derive an a posteriori error estimate which guarantees a given bound for the error in the energy norm (up to a multiplicative constant). Then, following Eriksson and Johnson this yields an adaptive algorithm steering the mesh refinement. Numerical examples confirm that our adaptive algorithms yield automatically good triangulations and are efficient.
Analytical and numerical studies of the Bonhoeffer van der Pol system
Authors: Barnes Belinda , Grimshaw Roger
Published: February 2009

The Bonhoeffer Van der Pol system is a planar autonomous nonlinear system of differential equations which has been invoked as a qualitative model of physiological states in a nerve membrane. It contains three independent parameters and previous work has only studied a small portion of the parameter space, that part which is thought to be of physiological relevance. Here we give a complete study of the full parameter space, using both theoretical results and numerical solutions.
Second method of Lyapunov and comparison principle for impulsive differential–difference equations
Authors: Bainov D. D. , Stamova I. M.
Published: February 2009

In the present paper questions related to stability and boundedness with respect to manifolds of solutions of impulsive differential-difference equations are considered. The investigations are carried out by means of piecewise-continuous functions which are analogues of the classical Lyapunov's functions. By means of a vectorial comparison equation and differential inequalities for piecewise-continuous functions, theorems are proved on stability and boundedness with respect to manifolds of solutions of impulsive differential-difference equations with impulse effect at fixed moments.
A programming model for student enrolment planning
Authors: Campbell L. H.
Published: February 2009

The problem of planning the annual intakes to a university course, in which there are capacity constraints on the total enrolment, so as to produce a steady transition into an eventual no-growth situation is formulated as a linear program. The special structure of the problem is exploited to find a particular, optimal solution and to show that the addition of integrality constraints on the intakes poses no additional difficulty. The usefulness of the proposed methods is illustrated with an example from the University of Adelaide.
Heat transfer in the thermal entrance region of a flat duct
Authors: Jones A. S.
Published: February 2009

The problem of heat transfer in a duct or tube for large values of the Péclet number has traditionally been solved by assuming that diffusion in the axial direction is negligible. This approach was used by Graetz [2] for the circular tube and by Prins et al [5] for the flat duct to obtain a series solution for downstream temperature field.

Since these series converge very slowly in the neighbourhood of the origin, some other approach is necessary in the thermal entrance region. This was supplied by Lévêque [3] and extended by Mercer [4] who matched the Lévêque solution to the eigenfunction expansion.

In all these solutions it was assumed that the axial diffusion of heat was negligible, but this assumption is invalid close to the discontinuity, since in this region the axial temperature gradient is large and the fluid velocity is small, so that axial diffusion plays an important role.

In this paper, the assumptions implicit in Lévêque's solution are re-examined, and the correct approximation in the neighbourhood of the discontinuity as well as the solution which matches this into Lévêque's solution are presented. In the first of these solutions, diffusion is the only heat-transfer mechanism, while in the matching solution diffusion and convection are in balance.

The corresponding solutions for the case of prescribed flux on the boundary are also considered.
A note on stress concentration around an elliptic hole in micropolar elasticity
Authors: Basu Animesh
Published: February 2009

Within the scope of Eringen's linearised micropolar theory, this note outlines a solution for the stress concentration around an elliptic hole in an infinite plate under axial tension.
Optimal control with a cost of switching control
Authors: Blatt John M.
Published: February 2009

The Pontryagin theory of optimal control is modified by assuming a positive cost associated with switching control from one discrete value to another. The resulting new theory permits a general existence theorem. Pontryagin's maximum principle is replaced by an “indifference principle”.
On finite anti-plane shear for imcompressible elastic materials
Authors: Knowles James K.
Published: February 2009

This paper is concerned with deformations corresponding to antiplane shear in finite elastostatics. The principal result is a necessary and sufficient condition for a homogeneous, isotropic, incompressible material to admit nontrivial states of anti-plane shear. The condition is given in terms of the strain energy density characteristic of the material and is illustrated by means of special examples.
Control systems with time lags
Authors: Blatt John M.
Published: February 2009

Necessary conditions for optimal controls are given for non-linear systems with time delayed effects in both control and state variables.
A note on anti-plane shear for compressible materials in finite elastostatics
Authors: Knowles James K.
Published: February 2009

This note gives a necessary and sufficient condition that a compressible, isotropic elastic material should admit non-trivial states of finite anti-plane shear.
The initial dispersion of soluble matter in three-dimensional flow
Authors: Barton N. G.
Published: February 2009

The dispersion of a passive solute in three-dimensional flow is examined for short times after the injection of solute. If the diffusivity is constant, the solute at first diffuses isotropically about the fluid particle originally coincident with the injection point whilst, at longer times, the effect of diffusion across a velocity shear becomes more important. An asymptotic expansion is derived for the concentration of solute at small times after its injection into the fluid flow and the use of the theory is illustrated for three representative flows. Some critical remarks on the applicability and limitations of the results conclude the note.
Characterizations of optimality for continuous convex mathematical programs. Part I. Linear constraints
Authors: Scott C. H. , Jefferson T. R.
Published: February 2009

Recently we have developed a completely symmetric duality theory for mathematical programming problems involving convex functionals. Here we set our theory within the framework of a Lagrangian formalism which is significantly different to the conventional Lagrangian. This allows various new characterizations of optimality.
A-topology for Minkowski space
Authors: Nanda Sribatsa
Published: February 2009

We consider in this paper a topology (which we call the A-topology) on Minkowski space, the four-dimensional space–time continuum of special relativity and derive its group of homeomorphisms. We define the A-topology to be the finest topology on Minkowski space with respect to which the induced topology on time-like and light-like lines is one-dimensional Euclidean and the induced topology on space-like hyperplanes is three- dimensional Euclidean. It is then shown that the group of homeomorphisms of this topology is precisely the one generated by the inhomogeneous Lorentz group and the dilatations.
Propagation properties in scattering theory
Authors: Robinson Derek W.
Published: February 2009

Generalizations of the Green-Lanford-Dollard theorem on scattering into cones and Ruelle-Amerin-Georgescu theorem characterizing bound states and scattering states are derived. The first is shown to be an easy consequence of the Kato-Trotter theorem on semi-group convergence whilst the latter is corollary of Wiener's version of the mean ergodic theorem.
Coherent states of para-Bose oscillators
Authors: Biswas S. N. , Santhanam T. S.
Published: February 2009

Para-Bose coherent states, defined as “displaced” ground states, are obtained using the differential operator representation for the annihilation operator.
Asymmetric bifurcation
Authors: Rosenblat S.
Published: February 2009

A study is made of a non-linear diffusion equation which admits bifurcating solutions in the case where the bifurcation is asymmetric. An analysis of the initial-value problem is made using the method of multiple scales, and the bifurcation and stability characteristics are determined. It is shown that a suitable interpretation of the results can lead to determination of the choice of the bifurcating solution adopted by the system.
The diffraction of elastic waves by small cylindrical cavities
Authors: Buchwald V. T.
Published: February 2009

The note added in proof on p. 495 should read:

The author has discovered that R. P. Kanwal (J. Math. Phys. 44 (1965), 273–283) proposed a technique similar to the one in this paper. Unfortunately, Kanwal's scheme implies that the elastostatic problem can be reduced generally to the solution of Laplace's equation, a result which is well-known to be incorrect.
On the implementation of a subset selection algorithm for the restricted least squares problem
Authors: Clark D. I. , Osborne M. R.
Published: February 2009

By noting that it is possible to interchange the roles of the solution vector x and the vector of Lagrange multipliers λ in the restricted least squares problem we are able to give a very efficient implementation of Clark's subset selection algorithm. Numerical results are presented for several selection heuristics.
The complete symmetry group of a forced harmonic oscillator
Authors: Leach P. G. L.
Published: February 2009

The complete symmetry group of a forced harmonic oscillator is shown to be Sl(3, R) in the one-dimensional case. Approaching the problem through the Hamiltonian invariants and the method of extended Lie groups, the method used is that of time-dependent point transformations. The result applies equally well to the forced repulsive oscillator and a particle moving under the influence of a coordinate-free force. The generalization to na-dimensional systems is discussed.
A “constant of the motion” for the geodesic deviation equation
Authors: Dolan P. , Choudhury P. , Safko J. L.
Published: February 2009

In this short paper, it is shown that the geodesic deviation equation admits a “constant of the motion” and so can be solved exactly. We also derive an expression for the energy E of relative motion between two freely falling test particles. We can infer that, in general, E will not be a linear superposition of kinetic and potential energies.
A discrete random walk model for diffusion in media with double diffusivity
Authors: Hill James M.
Published: February 2009

Diffusion in the presence of high-diffusivity paths is an important issue of current technology. In metals, high-diffusivity paths are identified with dislocations, grain boundaries, free surfaces and internal microcracks. In pourous media such as rocks, fissures provide a system of high-flow paths. Recently, based on a continuum approach, these phenomena have been modelled, resulting in coupled systems of partial differential equations of parabolic type for the concentrations in bulk and in the high-diffusivity paths. This theory assumes that each point of the medium is simultaneously occupied by more than one diffusion or flow path. Here a simple discrete random walk model of diffusion in a medium with double diffusivity is given.
Exact solutions of two nonlinear equations and hypercircle estimates
Authors: Hart V. G.
Published: February 2009

In a recent paper estimates of the solutions of two nonlinear differential equations were made by use of the hypercircie method. Here exact solutions are given which are compared with those estimates.