This study investigates the acquisition of English lexical stress by Cantonese-English bilingual children and compares the bilinguals with English monolingual children of the same age. The aim of this study is to find out how Cantonese-English bilingual children develop English lexical stress under the possible interaction of the two phonological systems. Two age groups were included: 2;06 and 3;0. Two acoustic correlates for lexical stress were measured: syllable duration and peak F0. Words in two language contexts were examined: disyllabic words in English speech and code-switched English words in Cantonese speech. / Data of eight bilingual children and seven monolingual children were used. All the bilingual data came from CHILDES database and monolingual data came from multiple sources. Disyllabic words were extracted from English utterances, and the stressed/unstressed syllable duration and peak F0 ratios were calculated to see how contrastive the stress patterns were. Results indicated that the monolingual children displayed a more contrastive stress pattern in both acoustic correlates, although syllable duration is found to be more reliable than peak F0 in stress distinction. Stress pattern in code-switched words were also analyzed. It was found that bilingual children displayed a stronger pitch difference in code-switched words, more contrastive than the patterns in their English speech. The results suggest that between 2;06 and 3;0, Cantonese-English bilingual children used less duration and pitch contrast for lexical stress than English monolingual children did, and they were slower in developing native-like lexical stress pattern during this period. On the other hand, Cantonese-English bilingual children used acoustic properties for lexical stress differently in the two language contexts, indicating that they possessed some kind of metalinguistic awareness at such an early age. / 本研究探索粵語和英語雙語兒童對英語詞重音的早期習得情況，並將雙語兒童與英語單語兒童進行對比討論。研究目的旨在探討雙語語音系統之間是否存在相互影響，以及此影響如何改變雙語兒童的語言韻律發展。研究對象包括處於2 歲6個月及3 歲這兩個年齡階段的粵英雙語及英語單語兒童。文章選取兒童自然對話中,位於句中位置的雙音節詞，對其音節時長和音高峰值進行測量。此外，本研究發現雙語兒童存在代碼轉換的現象，即在粵語表達中插入英語辭彙，因此本文同時也對被插入的英語辭彙的詞重音進行探究，以期對詞重音的雙語習得獲得更詳盡的瞭解。 / 本研究所用數據來自八名粵英雙語兒童和七名英語單語兒童。雙語兒童數據取自“兒童語言資料交換系統”（CHILDES）中的“香港雙語兒童語料庫”，單語兒童數據則來自多方資料。研究將所提取的雙音節詞的重音音節與非重音音節的時長及音高峰值分別測量之後，計算出重音音節與非重音音節的比值。比值越大表明兒童在產出中越能明顯區別重音音節與非重音音節，即對英語詞重音的掌握越好。 / 研究結果發現單語兒童的表現領先于雙語兒童，體現在單語兒童可以將重音與非重音音節的時長與音高明顯區分，而雙語兒童產出的雙音節詞中，重音音節和非重音音節在時長和音高方面的區別都不明顯。然而對於被插入粵語句子中的英語雙音節詞，雙語兒童卻能很好地區分開重音音節和非重音音節的音高 。 / 研究結果表明，在2 歲6 個月至3 歲之間的這段時間，粵語和英語雙語兒童對英語詞重音的習得逊於英語單語兒童。但另一方面，粵語和英語雙語兒童表現出對語言環境的敏感，可以根據語言環境和交流對象的不同改變對語音特徵的運用，展現出一定程度的元（後設）語言覺識。 / Li, Jingwen. / Thesis M.Phil. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 56-65). / Abstracts also in Chinese. / Title from PDF title page (viewed on 11, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

Induced strain actuators have been integrated with conventional structural materials to serve as energy input devices or actuating elements in many engineering applications implementing intelligent material systems and structures concepts. In order to use the actuation mechanism produced by the integrated induced strain actuators efficiently, the mechanics of the mechanical interaction between the actuator and the host substructure must be understood and modeled accurately. A refined analytical model has been developed based on the plane stress formulation of the theory of elasticity for a surfacebonded induced strain actuator/beam substructure system. Closed-form solutions of the induced stress field were obtained in an approximate manner using the principle of stationary complementary energy. The model has also been extended to include the presence of adhesive bonding layers and applied external loads. The results of the current model were compared with those obtained by finite element analysis and the pin-force and Euler-Bernoulli models. It was shown that the current model is capable of describing the edge effects of the actuator on actuation force/moment transfer and interfacial shear and peeling stress distributions that the existing analytical models fail to describe. Good agreement was obtained between the current model and the finite element analysis in terms of predicting actuation force/moment transfer. The interfacial shear stress distribution obtained by the current model satisfies stress-free boundary conditions at the ends of the actuator, which the finite element model is not able to satisfy. The current model correctly describes the transfer of the actuation mechanism and the resulting interfacial stress distributions; thus, it can be used in designing integrated induced strain actuator/substructure systems. Moreover, a new induced strain actuator configuration, which includes inactive edges on the ends of the actuators, has been proposed to alleviate the intensity of the interfacial stresses. The effectiveness of the actuator on the interfacial stress alleviation was verified by the current analytical model and finite element analysis. It was shown that the proposed actuator configuration can significantly alleviate intensive interfacial shear and peeling stresses without sacrificing the effectiveness of the actuation mechanism. The chances of interfacial failure of the integrated structural system, fatigue failure in particular, can thus be reduced. / Ph. D.