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This chapter presents an overview of what is currently known about phonetic and phonological first language (L1) attrition and drift in bilingual speech and introduces a new theory of bilingual speech, Attrition & Drift in Access, Production, and Perception Theory (ADAPPT). Attrition and drift are defined and differentiated along several dimensions, including duration of change, source in second language (L2) experience, consciousness, agency, and scope. We address why findings of attrition and drift are important for our overall understanding of bilingual speech and draw links between ADAPPT and well-known theories of L2 speech, such as the revised Speech Learning Model (SLM-r), the Perceptual Assimilation Model-L2 (PAM-L2), and the Second Language Linguistic Perception model (L2LP). The significance of findings revealing attrition and drift is discussed in relation to different linguistic subfields. The chapter raises the question of how attrition and drift potentially interact to influence speech production and perception in the bilingual’s L1 over the life span; additional directions for future research are pointed out as well.
This chapter takes an individual-differences perspective on the dual sound systems of American heritage speakers (HSs) of Mandarin Chinese. Based on detailed socio-demographic data and production data on segmentals and suprasegmentals, we build holistic demographic and phonetic profiles for HSs, as well as native speakers and late learners, to explore how different aspects of their two languages (i.e., Mandarin, English) may develop in relation to each other and how individual variation in production may be related to socio-demographic factors. Using multiple factor analysis (MFA), we describe the range of these profiles, identify clusters of variation defined by different socio-demographic factors, and argue that some factors (e.g., age of arrival, language(s) spoken at home) have more predictive power for phonetic profiles than others. Overall, our results suggest a significant, if limited, link between socio-demographic factors and production, but only in Mandarin. We conclude by discussing the advantages and disadvantages of group-based and individual-centered approaches.
This chapter provides an overview of research on heritage language (HL) sound systems, with a focus on areas of convergence and divergence among heritage speakers (HSs), native speakers (NSs) who continue to be dominant in the language, and second language learners (L2ers) who acquired the language later in life. Drawing on data from a wide range of HLs, the chapter addresses both phonetic (articulatory, acoustic, perceptual) and phonological (phonemic, distributional, phonotactic) aspects of the HL sound system, as well as that of the majority language, in light of theories of bilingual speech and variables previously studied as predictors of HSs’ linguistic behavior. Despite the diversity of results reviewed, several recurring themes emerge, including intermediate patterning between NSs and L2ers, a higher level of performance in perception than production, and individual variability. In particular, the depth and the accessibility of HSs’ knowledge of the HL sound system show considerable variation related to structural linguistic factors, demographic and sociolinguistic factors, input and usage-based factors, and methodological factors. In addition to summarizing the areas in which there is an emerging consensus, the chapter points out a number of remaining questions that pave the way for future research on HL sound systems.
Research on the linguistic knowledge of heritage speakers has been concerned primarily with the advantages conferred by heritage language experience in production, perception, and (re)learning of the heritage language. Meanwhile, second-language speech research has begun to investigate potential benefits of first-language transfer in second-language performance. Bridging these two bodies of work, the current study examined the perceptual benefits of heritage language experience for heritage speakers of Korean in both the heritage language (Korean) and the dominant language (American English). It was hypothesized that, due to their early bilingual experience and the different nature of unreleased stops in Korean and American English, heritage speakers of Korean would show not only native-like perception of Korean unreleased stops, but also better-than-native perception of American English unreleased stops. Results of three perception experiments were consistent with this hypothesis, suggesting that benefits of early heritage language experience can extend well beyond the heritage language.
BaxSr1−xTiO3 (BST, x=0.5 and 0.6) thin films have been deposited onto (100) MgO single crystal substrates by pulsed laser deposition (PLD). The room temperature capacitance and dielectric quality factor (Q=1/tanδ have been measured as a function of electric field (≤ 100 kV/cm) at microwave frequencies (1 to 20 GHz) using silver interdigitated electrodes deposited on top of the BST film. It has been observed that the dielectric constant of the film and its change with electric field are closely related to film phase (amorphous to crystalline phase) and film strain which affects the ionic polarization of the film. Amorphous BST films show high dielectric Q (> 100) with low dielectric constant (∼30–200) and low dielectric tuning (< 1%), presumably due to small ionic polarization. Crystalline films have a higher dielectric constant (∼1000–3000) and a higher dielectric tuning (∼ 65%) but a lower dielectric Q (∼20). As an optimal microstructure of the film for tunable microwave applications, strain-relieved large-grained (∼5000 Å) randomly oriented polycrystalline films were deposited using a thin amorphous buffer layer of BST (∼50 Å). Very large grains (size up to a few microns) were observed in BST films prepared using a thicker amorphous buffer layer (∼500 Å). We will present results on how careful control of microstructure can lead to films with optimal dielectric properties for the tunable microwave devices.
Single phase BaxSr1−xTiO3 (BST) films (∼0.5-7 μm thick) have been deposited onto single crystal substrates (MgO, LaAlO3, SrTiO3) by pulsed laser deposition. Silver interdigitated electrodes were deposited on top of the ferroelectric film. The room temperature capacitance and dielectric Q (1/tanδ) of the film have been measured as a function of electric field (≤80 kV/cm) at 1 - 20 GHz. The dielectric properties of the film are observed to strongly depend on substrate type and post-deposition processing. After annealing (≤1000° C), it was observed that the dielectric constant and % tuning decreased and the dielectric Q increased for films deposited onto MgO, and the opposite effect was observed for films deposited onto LaA1O3. Presumably, this change in dielectric properties is due to the changes in film stress. Very thin (∼50 Å) amorphous BST films were successfully used as a stress-relief layer for the subsequently deposited crystalline BST (∼5000 Å) films to maximize % tuning and dielectric Q. Films have been deposited from stoichiometric targets and targets that have excess Ba and Sr. The additional Ba and Sr has been added to the target to compensate for deficiencies in Ba and Sr observed in the deposited BST (x=0.5) films. Films deposited from compensated targets have higher dielectric constants than films deposited from stoichiometric targets. Donor/acceptor dopants have also been added to the BST target (Mn, W, Fe ≤4 mol.%) to further improve the dielectric properties. The relationship between the dielectric constant, the dielectric Q, the change in dielectric constant with electric field is discussed.
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