<p>The current thesis investigated to which extent Korean heritage speakers (N = 20) maintain their L1 phonology by comparing their perceptual abilities with those of native speakers and English-speaking second language learners of Korean (N = 20) in an AX discrimination task. An AX discrimination task was implemented to measure perceptual accuracy of participants in discriminating the Korean lenis–aspirated stop contrast (aspirated stops: ‘ㅍ’ [p^h], ‘ㅌ’ [t^h], ‘ㅋ’ [k^h]; lenis stops: ‘ㅂ’ [p], ‘ㄷ’ [t], ‘ㄱ’ [k]) which is believed to be the most challenging among the Korean laryngeal categories to acquire not only for second language learners but also native speakers. To investigate whether linguistic factors known to be correlated with overall proficiency of heritage speakers can extend to Korean heritage speakers’ perceptual abilities, the current thesis examined the effects of language use and exposure, age of acquisition, and articulation rate on the perceptual accuracy in the AX discrimination task. Results of a mixed-effects logistic regression model showed that heritage speakers were as accurate as native speakers in discriminating the contrast while outperforming second language speakers. Another finding of the current study is that verbal fluency of heritage speakers measured by articulation rate was found to be a predictor for their perceptual accuracy. The results align with previous work suggesting that heritage speakers have the advantage of early language exposure and use that is sufficient to develop and maintain native-like phonological perceptual abilities later in life.</p>

Supersaturating formulations have become a popular approach for enhancing the oral bioavailability of poorly water-soluble drugs. These formulation strategies can increase the intraluminal concentration by generating and maintaining supersaturation, which provides an enhanced driving force for <i>in vivo</i> absorption. Due to their inherent metastability however, crystallization in these systems can occur, negatively impacting their bioperformance. Therefore, it is critical to characterize the phase behavior and crystallization tendency of supersaturated solutions under biorelevant conditions in order to assess their potential for maximized oral absorption. Biorelevant media are commonly employed to simulate the presence of bile salts and phospholipids found in the human intestinal fluids. Currently, there is little knowledge of how simulated and aspirated intestinal media can impact the complex phase behavior of supersaturated solutions. More importantly, commonly-used simulated media rely on oversimplified recipes in terms of bile salt composition. As a result, comprehensive understanding of how well simulated media correlate with aspirated media with respect to supersaturation stability and phase transition outcomes, is still lacking. The work presented within this thesis aims to address the knowledge gap by assessing the phase behavior of supersaturated solutions using complementary analytical approaches. Depending on the type of medium used to evaluate supersaturation, variations in solubility, supersaturation thermodynamics and crystallization kinetics can be observed. This understanding can aid future efforts to optimize simulated media, design supersaturating formulations and predict their <i>in vivo</i> performance.

送氣與非送氣的對比是台灣華語塞音及塞擦音之特性。為討論送氣的議題，本篇論文透過語音實驗，從兩方面來探討：其一為嗓音起始時間(voice onset time)，另一則為語誤的方向性(directionality)及標記 (markedness)。 本研究有兩個實驗，皆以四字非詞為實驗材料。實驗一為語誤實驗，此實驗結合繞口令以及立即回想的方法來誘發語誤；實驗二則為嗓音起始時間實驗，只讓受試者回想，並未結合繞口令。這兩個實驗的設計由於受到中文本身音韻限制及詞彙空缺的限制，韻母使用了單母音(V)及韻母(VG或GV)兩種形式，因此實驗二亦將母音對子音數值的影響之比較結果納入討論。 嗓音起始時間實驗的結果顯示，使用四字非詞並結合回想作為實驗內容所測量出的數值與前人使用實詞所測量出的數值並無太大不同，並支持送氣子音的數值較非送氣子音的大。此外，塞音的研究結果支持Cho & Ladefoged (1999)所提出的原則，也就是塞音除阻的位置若越後面，則其數值會越大；若將塞音的數值套用Cho & Ladefoged (1999)的分類，則中文的非送氣塞音確為非送氣子音，而送氣塞音的數值則介於稍微送氣及送氣子音之間。塞擦音的研究結果若如Lai (2013)般套用Cho & Ladefoged (1999)之原則，則會發現送氣塞擦音符合此原則，但非送氣塞擦音卻非如此。另外，子音後接的母音或韻母亦會影響子音之嗓音起始時間。研究結果顯示當大部份子音後接單母音時，子音之嗓音起始時間較長；研究結果亦指出當子音後接的為單母音[a]或以[a]開頭的韻母時，子音的嗓音起始時間會較接其他母音如[u], [i], [ow]時短。 語誤實驗的結果顯示，除了[k], [kh]有以有標送氣塞音取代無標非送氣塞音的情形外，其他組塞音及所有塞擦音皆無以有標送氣子音取代無標非送氣子音(反之亦然)的情形。就方向性而言，研究結果顯示語誤來源出現在語誤之前(perseveration)的方向性顯著最多。 / The contrast of aspiration is one of the characteristics of stops and affricates in Taiwan Mandarin. Through the conduction of two phonological experiments, we discuss the issue of aspiration from two aspects: one is from voice onset time (VOT), and the other one from directionality and markedness of speech errors. Non-word quadruple sets were used in both two experiments. The first experiment was speech errors, which combined tongue twister and immediate recall to induce speech errors; the second experiment was voice onset time, which only had the subjects to recall. Due to the limitation of phonological ill-form and lexical gaps, the rhymes of the two experiments had two forms, V and VG/GV; as a result, how vowels affected the VOT of stops and affricates were also discussed. The findings of the second experiment (voice onset time) showed that the VOT measured by using non-word quadruple set was similar to the VOT measured by using real words as stimuli, and the findings also indicated that the VOT of the aspirated consonants was longer than that of the unaspirated ones. In terms of the results of the stops, they supported the principle proposed by Cho & Ladefoged (1999) that the duration of VOT has a further back relationship with the closure; furthermore, the categories proposed by Cho & Ladefoged (1999) were applied onto the results, it showed that Mandarin unaspirated stops were indeed unaspirated consonants, and the aspirated stops fell between slightly aspirated and aspirated consonants. The findings of the aspirated stops, if applied the principle proposed by Cho & Ladefoged (1999) like Lai (2013), revealed that aspirated affricates supported the principle, yet the unaspirated ones did not. Regarding the influence of vowels on the VOT, it was found that when the succeeding vowel was a single vowel [a] or rhymes beginning with [a], the VOT of the stops and the affricates would be shorter. The findings of the first experiment (speech errors) indicated that with regard to the stops, the aspirated velar stop tended to replace the unaspirated counterpart, while for the other stops, the probability for marked aspirated stops to replace unmarked unaspirated ones or vice versa was of the same. With regard to the directionality of speech errors, the findings showed that perseverations significantly outnumbered anticipations and exchange.

Afin d’alléger les moteurs d’avions et diminuer la consommation de carburant, les industriels tendent à rendre plus compact le système de compression de leurs moteurs, qui représente environ 40% de la masse totale. Or, à taux de compression global égal, la réduction du nombre d’étages implique une charge aérodynamique plus élevée par étage. Cela augmente d’autant les risques de décollements sur les aubes et la dégradation des performances. L’aspiration de la couche limite sur les aubages s’est révélée très prometteuse pour supprimer ces décollements néfastes et satisfaire aux besoins de charge aérodynamique élevée. Cependant, l’aspiration modifie fortement la distribution de pression statique à la paroi des aubes, rendant les approches de conception traditionnelles inadaptées. L’objectif de ce travail de thèse est donc de proposer une nouvelle méthode et de nouveaux critères de conception d’aubages fortement chargés, intégrant l’aspiration de la couche limite. Cette méthode repose sur une stratégie d’aspiration en deux étapes. Dans un premier temps, un contrôle passif, par courbure et diffusion, de la position du point de décollement est effectué dans le but de la rendre insensible aux conditions de fonctionnement. Dans un second temps, un contrôle actif par aspiration vise à placer la fente d’aspiration par rapport au point de décollement de manière à minimiser le taux d’aspiration nécessaire au recollement de la couche limite. Afin de mettre en pratique cette stratégie, une technique de dessin d’aubages par prescription de la distribution de courbure de l’extrados et de la variation de section du canal inter-aubes, est ainsi développée. Associée à un outil de pré-dimensionnement rapide ainsi qu’une évaluation des pertes de pression totale incluant la présence d’aspiration, cette méthode permet ainsi de concevoir une grille de stator aspirée subsonique réalisant une déflexion fluide de 60 degrés, pour un nombre de Mach amont de 0,5, correspondant à un facteur de diffusion de 0,73. Cette performance au point nominal est obtenue avec un coefficient de pertes de pression totale de 2,5%, en aspirant 1,1% du débit entrant dans la grille. Ces valeurs peuvent néanmoins être réduites respectivement à 2,1% et 0,8% par l’emploi d’une fente d’aspiration à bords arrondis. Cette étude numérique bidimensionnelle est effectuée à l’aide du code de calcul elsA de l’ONERA. Afin de valider expérimentalement cette méthode de conception ainsi que les outils numériques associés, une grille d’aubes plane est construite et testée à basse vitesse au laboratoire de Mécanique de Fluides et d’Acoustique de l’Ecole Centrale de Lyon. A mi-envergure, les résultats issus de l’expérience et de simulations numériques 3D confirment la pertinence de la stratégie d’aspiration et la démarche de conception adoptée. Cette confrontation met alors en évidence l’impact de la distribution du taux d’aspiration suivant l’envergure sur l’efficacité de l’aspiration. Etant donné l’importance des écoulements tridimensionnels rencontrés, une généralisation en trois dimensions de la stratégie d’aspiration est proposée et est appliquée numériquement sur cette même grille d’aubes. En contrôlant simultanément les couches limites se développant sur l’aube et sur les parois latérales du canal de compression, il est alors possible de supprimer presque totalement les décollements de coins présents dans celui-ci. En contrepartie, le taux d’aspiration voit sa valeur augmenter très fortement, tempérant ce bénéfice. L’épaisseur des couches limites entrantes se révèle alors également être un facteur déterminant pour le succès du contrôle des couches limites par aspiration, dans un cadre tridimensionnel. / In order to reduce the mass of aircraft jet engines as well as their fuel consumption, manufacturers tend to make the compression system of their engines more compact, since this component represents approximately 40% of the total mass. However, for a given overall pressure ratio, decreasing the number of stages implies increasing the aerodynamic load per stage. This all the more increases the risk of flow separation on the blades ultimately resulting in a decrease in performance. Boundary layer suction on the blade has proven to be very promising to suppress this deleterious flow separation and meet the needs of high aerodynamic loads. Nevertheless, boundary layer suction significantly modifies the static pressure distribution on the blades, making traditional design approaches unsuitable. Therefore, the objective of this Ph.D. work is to develop a new method and new criteria for the design of highly loaded compressor blades, integrating boundary layer suction into the design process. This design method relies on a two-step aspiration strategy. First, passive control of the separation point location is applied via curvature and diffusion in order to make it insensitive to operating conditions. Second, active control through boundary layer suction aims at placing the suction slot with respect to the separation point location, in order to minimize the necessary suction mass flow rate required to reattach the flow. To put this strategy into practice, a blading technique that consists of prescribing the curvature distribution on the suction side of the blade and the cross-section distribution of the blade passage is developed. In association with a fast pre-design tool, as well as an overall total pressure loss coefficient including aspiration, this method allows the design of a subsonic aspirated stator cascade with flow turning of 60 degrees, for an inlet Mach number of 0.5,giving a Diffusion Factor of 0.73. This performance at the design point is obtained for an overall total pressure loss coefficient of 2.5%, aspirating 1.1% of the inlet mass flow rate. Nevertheless, these two values can be respectively reduced to 2.1% and 0.8% by rounding the edges of the suction slot. This bi-dimensional numerical study has been carried out with the elsA solver from ONERA. To experimentally validate this design method and the associated numerical tools, a planar cascade is built and tested at low speed at the Laboratoire de Mécanique de Fluides et d’Acoustique at the Ecole Centrale de Lyon. At mid-span, results from the experiment and from tri-dimensional numerical simulations confirm the relevance of the design approach. This comparison then discloses the impact of the suction mass flow rate distribution along the span, on the efficiency of aspiration. Given the importance of tri-dimensional flows encountered in the experiment and simulations, a generalization in three dimensions of the aspiration strategy is proposed and numerically applied on the same cascade. By simultaneously controlling the boundary layers developing on the blades and on the endwalls,it is possible to almost entirely suppress the corner separations present in the blade passage. However, one disadvantage is that the suction mass flow rate undergoes a strong increase, moderating this benefit. The thickness of the inlet boundary layers appears to be also a key factor in the success of boundary layer control by aspiration, in a tri-dimensional context.

Naturally aspirated petrol engine, pressure losses, EGR, low-pressure EGR, water injection, power increasing, BSFC, GT-Power, thermodynamic model, engine knock