27 research outputs found
Synthesis of a composite Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>/poly(SMA-co-BA-co-BZMA-co-DMC) and evaluation of its oil-water separation performance
No full textTo obtain a demulsification material with convenient recovery, high oil-water separation capacity, and excellent reusability, Fe3O4@SiO2 core-shell particles and hydrophilic DMC were introduced into the acrylic ester-based polymer system to prepare a magnetic amphiphilic composite demulsifier, Fe3O4@SiO2/poly(SMA-co-BA-co- BZMA-co-DMC) (Fe3O4@SiO2/PAMCs-P). The molecular structure of Fe3O4@SiO2/PAMCs-P was characterized using FT-IR and XPS, while the morphology was observed using SEM. Additionally, the effects of TEOS, Fe3O4@SiO2 core-shell particles, and DMC dosage on the demulsification performance of the composites were discussed in detail. Fe3O4@SiO2/PAMCs-P exhibited excellent demulsification, oil-water separation, and reusability properties for CTAB-toluene emulsions. Under magnetic field conditions, Fe3O4@SiO2/PAMCs-P achieved saturated separation within 2 h with a separation efficiency of 97.9%. After five consecutive separations, the separation efficiency decreased to 39.1%, but it could be restored to 91.5% of the initial separation efficiency after desorption. These results indicate that Fe3O4@SiO2/PAMCs-P has valuable application potential in emulsified wastewater treatment
mixture treatment
No full textTo acquire a material with simultaneous oil–water emulsion demulsification and oil-absorbing performance, SiO
2 nanoparticles were introduced into the acrylate polymerization system to prepare oil absorbent SiO
2/P (SMA-co-MMA-co-BA) (PSA-SiO
2). PSA-SiO
2 was synthesized from monomers and functional materials, including methyl methacrylate (MMA), butyl acrylate (BA), octadecyl methacrylate (SMA) and SiO
2 hydrophobically modified by vinyltrimethoxysilane. The molecular structure of PSA-SiO
2 was characterized by FT-IR, and its morphology was observed using scanning electron microscopy. In addition, the optimal synthesis conditions for the polymerization system, such as the monomer ratio, the amount of crosslinker and stabilizer and then the particle size and dose of SiO
2, were discussed in detail. PSA-SiO
2 had a decent oil absorbency for pure halogenated and aromatic hydrocarbons (49.10, 56.41, 47.32, 43.45, 36.22, and 30.14 g/g for CH
2Cl
2, CHCl
3, CCl
4, C
2Cl
4, toluene and styrene, respectively). Furthermore, SiO
2, as a functional material, makes composites that possess excellent demulsification properties for oil-in-water emulsions. The oil removal efficiency of CHCl
3 in Tween 80-stabilized and CTAB-stabilized emulsions were 94.88% and 98.11%, respectively. All results indicated that PSA-SiO
2 had valuable potential for oil removal and emulsion treatment. Highlights: An organic–inorganic composite was synthesized by suspension polymerization. The composite was applied for absorbing pure oil or removing oil form water. By modification, the composite acquired the demulsification ability. The composite accomplished one-step demulsification and emulsion treatment. The oil absorption and emulsion treatment could achieve at room temperature.</p
Tonal Representations and Coarticulation in Ta-pu Hakka
No full text本研究主要研究兩個問題：(1)調查聲調在音韻學系統及其語音學上的表現之相關性; (2)調查聲調在一組連續發聲出來的雙字詞中，所產生的聲調聲學特徵的細微變化。
台灣目前有兩大客語系統：海陸腔及四縣腔，但除此之外，其實也還有許多其他的次方言。其中一種，是客家話大埔音，目前大約有六萬人會使用大埔客語，而這些人口目前主要分布在台灣的中部三鄉鎮：東勢，石岡及新社。不同的次方言是以不同的聲調系統或是用字來作區辨，然而，在之前文獻中所使用的大埔客語的聲調系統多是根據聽覺所標記出來的，而非根據聲學所計算出來的，最多只能呈現出一般人對此聲調系統的聽覺印象。
因此，本研究將從客觀之物理聲學角度來檢視大埔客語的聲調系統，透過單字詞與雙字詞，我們將分析大埔客語的本調調值及變調調值，另外，在雙字詞組中，我們也探索了本調調值在前字及後字的位置中，是否和在單字詞中所計算出來的調值有所不同。在重新檢視大埔客語的聲調系統之後，我們將緊接著探討聲調在一組連續發聲出來的雙字詞中，所產生的聲調聲學特徵的變化。「聲調連發」是指在一連串連續不斷的發音中，相鄰的聲調會因而產生的變化，這也是許多語音學家近幾年來研究的重點。而本研究將探討的是雙字詞的「聲調連發」現象，欲調查雙詞中的聲調在詞首及詞末會如何變化；此外，我們也將雙字詞組根據許毅(1994)的分類，將雙詞組的聲調組合分別歸類於調值相近或相斥的組合；接著，我們再細看調與調之間的相互作用。在探討「聲調連發」的過程中，我們也採用了許毅的「目標近似模型」，來看大埔客語中所發現的聲調變化現象。
為了回答我們所提出的兩個研究問題，本研究所量測的聲學特徵參數包含音節的起始點及終點的基頻，最大及最小基頻，以及整個音節包含子音部分的平均基頻、斜率及音長。而對於陽平調，我們也檢視了它「最小基頻」出現在「音節」部分的相對位置，因為這個參數將影響陽平調的調型。音節的起迄點及最小基頻將作為計算調值的參考點，而在探討「聲調連發」時，所有的參數都會用來調查聲調的聲學變化。在計算調值的公式上，我們將比較兩種不同的版本，一是馮怡蓁博士及江文瑜博士在1999年的研究中所採用的公式，另一方面，我們也採用了石鋒(1990)的對數公式來做比較。
透過公式的計算，我們發現，馮與江計算出來的調域是屬於非線性的，而石鋒的公式算出來的調域呈現接近線性的關係，因此，本研究中，我們將採計使用馮與江的版本所得到的結果。根據聲學觀察與計算的結果，大埔客語的聲調調值在單獨發音時應該修正為：陰平33，陽平313，上聲31，去聲53，超陰平34，陰入3，陽入4(底線表示促調)；而在雙字詞中，我們發現根據此組資料計算出來的調值不適宜當作大埔客語聲調的調值。至於變調的調值，我們發現採用石鋒的公式所計算出來的調值反而比較符合統計的結果，其計算出來的陰平變調為324，陽平變調為323，而去聲變調為44。然而，變調的調值實際上已經受到了其相鄰聲調的影響，因此在之後調查「聲調連發」的研究中，對於變調調值，我們還是會採用在原本文獻中所使用的調值來做分類，這三個變調原本的調值分別是35，33，55。透過聲學的參數，我們發現陽平調實際上並非真正的平調，而是先降後揚的凹型調。大埔客語的七個主調，加上三個變調，總共有十個聲調，這十個聲調大多可配成對，若其中一個是屬於高頻區，那另一個則屬於低頻區。其中我們注意到兩個入聲調的調值非常接近，但統計結果顯示4比3的基頻來得高，而3的斜率比4來的陡峭，這個結果與張月琴在1995年根據苗栗四縣客語所做的研究結果相同。
在針對第二個研究問題「聲調連發」進行多種面向的探討之後，我們發現，除了上聲及陰入之外，其餘所有聲調在詞尾都會有拉長的現象，而上聲及陰入反而是在詞首的調長比在詞尾時來得長。在斜率方面，這兩個調在詞尾的下降斜率都比較大，有一種「突如其來的下降」的現象；但超陰平這個揚調的斜率，反而是在詞首的位置時顯的較為陡峭。陽平調的調型則是在不同的位置，有不同的調型產生：在詞首，陽平調會較接近降調，而在詞尾，它仍會是個凹型調，只是音節的起迄點略較單字詞時降低。
而在採用許毅的調值相容與相斥的聲調環境的分類法時，我們發現大埔客與其實還存在有一種特殊的聲調環境──調型相容，所謂的調型相容是指降調加上揚調，或是揚調加上降調這樣的組合。雖然我們所定義的調型相容對許毅而言，是屬於調值相斥的環境，但我們研究的結果發現，大埔客語中的調型相容的環境其實是類似於調值相容的環境，兩者對聲調的影響是類似的。
另外，在我們分別看每一個聲調對其相鄰的聲調有何影響時，我們發現了三種聲調變化：(1)前字詞對後字詞造成目標近似的影響（持續保留的目標近似）；(2)後字詞對前字詞造成目標近似的影響（預期的目標近似）；及(3)後字詞對前字詞造成目標對比分化的影響（預期的目標對比）。第一類包含了陰平，陽平，去聲，及陽入調，第二類包含上聲，去聲及陰入調，而陽入調的聲調變化其實囊括這三類所有的變化。在第一及第二類的變化當中，我們發現了前字詞的迄點調值與後字詞的起點調值之間，有正比的關係存在，這現象也可以用許毅的「目標近似模型」來解釋，也就是相鄰兩點的調值會互相接近。然而，第三類的聲調變化卻無法用此模型來解釋，因為這種變化是一種相鄰兩點的調值互斥的結果，這個互斥現象是為了顯現出兩個調之間的反差與對比。這種調與調之間的互斥現象其實早就存在於大埔客語的變調系統中，例如：陰平後面若是跟著一個上聲，則陰平(33)會變成上揚調35，為的就是要拉開與後面上聲起點調值的距離以增強對比。我們相信，變調在音韻化之前，其實是長久以來的「聲調連發」的結果，當某個聲調因為連發時所造成的變化，已經大到可用聽覺直接歸類為另一個調時，音韻學上的變調便因此產生了。
總而言之，本研究透過聲調的聲學研究結果，發現了大埔客語聲調系統的兩個重要特性：亦即「和諧共存」與「反差對比」，這兩個特性也展現在客家人的「硬頸」精神中。This present study aims (1) to investigate the correlation of phonological representations and phonetic realizations of Ta-pu Hakka tones, and (2) to explore the tonal coarticulation in different kinds of contexts.
There are two major Hakka sub-dialects spoken in Taiwan, the Hai-lu and the Suu-hsien systems. Another sub-dialect, Ta-pu Hakka, is spoken mainly in some townships in central Taiwan by about 60,000 people. Different sub-dialects of Hakka have their own tonal systems that have been described in detail in previous literature. However, most of the tonal representations used in the literature with regard to tones were based on auditive perception and phonological description. As a result, those phonological tonal representations were more impressionistic.
This study first investigated the correlation between phonological representations and phonetic realizations of the Ta-pu Hakka tones by taking acoustic and statistical approaches. Six informants, including three males and three females, were recruited in this study. Two sets of inventories were adopted as the test stimuli: the first was a set of monosyllabic words, and the other was a set of disyllabic words. The monosyllabic words were used to verify the citation tones, while the disyllabic words were used to verify the sandhi tones. Meanwhile, the tonal representations in different prosodic positions, i.e., in word-initial (WI) and in word-final (WF) positions were also investigated.
The second research question in this study was to explore tonal coarticulation in disyllabic words in Ta-pu Hakka. Tonal coarticulation refers to tonal variations in consecutive speech, which has been a great concern to many phoneticians (Xu, 1994, 1997, 1999, 2001, 2004; Gandour et al., 1994 & 1999; Peng, 1997; Shen, 1990 & 1992). In this study, we investigated tonal variations in different prosodic positions, tonal contexts, and in a context with different neighboring tones. Target Approximation model (Chen & Xu, 2006; Xu, 1997, 1999, 2004; Xu & Wang, 2001) was used to help explain the tonal variations found in this language.
To answer the above two research questions, we measured the average pitch height (F0) of the beginning point (BP), the ending point (EP), the maximum pitch (F0_Peak), the minimum pitch (F0_valley), and the average pitch of the syllable (Mean_F0). Besides, we also calculated the mean slope and the mean duration of the whole syllable. For Yang-Ping tone, the F0 valley alignment was calculated. As for falling tones and checked tones, the F0 peak alignment was calculated instead.
In investigating tonal representations, we adopted Fon and Chiang’s (1999) postulated formulae and Shi’s (1990) logarithmic function. In the first section with regard to verifying the tonal representations in Ta-pu Hakka, the revised T-scales (5-scaled tonal system) of the seven citation tones were suggested as follows: Yin-Ping as [33], Yang-Ping as [313], Shang as [31], Chü as [53], Yin-Ju as [3], Yang-Ju as [4], and Supra-Yin-Ping as [34], based on the data from monosyllabic words.
As for the tones in disyllabic words, the T-scales showed great incongruence between the results obtained via the two calculation methods. The results suggested that tonal representations in disyllabic words should not be considered as the norms of tonal representations. As for the three sandhi tones (ST), we found that the revised T-scales via Shi’s function were more appropriate to show their phonetic realizations. The three sandhi tones were suggested as ST-Yin-Ping as [324], ST-Yang-Ping as [323], and ST-Chü as [44], respectively. However, the revised T-scales in fact represented the phonetic realizations of the sandhi tones under the influence of tonal coarticulation, so we would still adopt the original T-scales, ST-Yin-Ping as [35], ST-Yang-Ping as [33], and ST-Chü as [55], when sandhi tones were involved in investigating tonal coarticulation effect.
The phonetic realizations of tones in Ta-pu Hakka showed that the seven citation tones included one level tone, two falling tones, two checked tones, one rising tone, and one concave tone. The tones in this language could be paired off, one belonged to the lower register, whereas the other belonged to the higher register. Note that the T-scales of the two checked tones were very close to each other. The statistical results of comparing means of the measured parameters in the two checked tones indicated that not only the pitch height but also the falling slope served as the criterion of distinguishing one from the other, within which the lower checked tone, Yin-Ju [3], had a steeper falling F0 slope.
As for tonal coarticulation, we explored the tonal variations from different aspects. First we investigated the tonal variations of tones according to their position in disyllabic words, namely in WI and WF positions. Afterward, Xu’s (1994) classification of different tonal combinations into a compatible or a conflicting context was examined and modified based on the tonal combinations in Ta-pu Hakka. We proposed a third type of tonal context, which was termed as a contour compatible context, referring to a context where a rising tone followed by a falling tone, or a falling tone followed by a rising tone. Then the influence of adjacent tones on their preceding or following tone was compared and discussed.
The results of tonal coarticulation in Ta-pu Hakka were summarized as follows. First, in regard with the position effect, final-lengthening was found in all the non-falling tones and the Yang-Ju [4]. However, the duration of Yin-Ju [3] and Shang [31] was longer in WI rather than in WF. Furthermore, the mean F0 slope of these two tones was steeper in WF position, indicating an abrupt fall at the end of the utterance. As for Supra-Yin-Ping [34], however, the mean slope was steeper when it was in SI than in SF. The most interesting finding was that the F0 valley alignment of Yang-Ping [313] was closer to the onset in WI, and it became closer to the middle of a syllable when in WF.
With regard to the tonal variations in a compatible or conflicting context, we found that Shang [31] showed a steeper slope in a contour compatible context than in a conflicting context. The result also suggested that a contour compatible context was very similar to a compatible context. As for Supra-Yin-Ping [34], the slope was even steeper in a contour compatible context than in a compatible context.
As for the results of the influence of adjacent tones on each other, carryover assimilation effect was found in Yin-Ping [33], Yang-Ping [313], Supra-Yin-Ping [34], Chü [53] and Yang-Ju [4]. Anticipatory assimilation was found in Shang [31], Chü [53] and Yin-Ju [3]. For Yang-Ju [4], anticipatory effect was also found, but the influence of its following tones on its tonal variations showed both assimilation and dissimilation effect. Furthermore, we also found a positive correlation between the offset F0 in syllable 1 (WI) and the onset F0 in syllable 2 (WF).
Furthermore, the tonal variations found in Ta-pu Hakka could be explored via Xu’s Target Approximation model. Both anticipatory assimilation and carryover assimilation phenomena supported Xu’s claim that “when two pitch targets occur next to each other, if the offset of the first one is different from the onset of the second one, the second one will appear as if it has been assimilated or partially assimilated to the second” (Xu and Wang 2001, p. 329). As for the anticipatory dissimilation, the effect could be found in Yin-Ping sandhi rule ([33] turning [35]) and Yang-Ping sandhi rule ([313] turning [33]). On the other hand, the anticipatory assimilation could also be seen in Chü sandhi rule ([53] turning [43]).
We stipulate that tone sandhi rules are in fact the historical products of tonal coarticulation, and the phonological aspect of tone sandhi rules is either to show greater contrast between adjacent tones or to ease the effort of articulation.
To sum up, both the phonetic realizations of tonal representations and tonal coarticulation effect in Ta-pu Hakka aim to show either harmony or contrast. The phonetic realizations of tonal representations and coarticulation in this language also help group all the tones into different natural classes: such as non-falling vs. falling, and non-checked vs. checked.Table of Contents
Acknowledgement……………………………………………………………………….i
English Abstract………………………………………………………………………...iii
Chinese Abstract………………………………………………………………………..vi
List of Tables…………………………………………………………………………...xii
List of Figures………………………………………………………………………….xv
Chapter 1 Introduction
1.1 Introduction …………………………………………………...…………..…1
1.1.1 First Research Question:
Tonal Representations and Phonetic Realizations………………..……...1
1.1.2 Second Research Question:
Tonal Coarticulation Effects......................................................................7
1.2 Introduction to Ta-pu Hakka…………………………………..………………..8
1.2.1 Tones in Ta-pu Hakka………………………….……………………...9
1.2.2 Syllable Structure of Ta-pu Hakka…………………………………...13
1.2.3 Consonants and Vowels in Ta-pu Hakka…………………………….16
1.2.4 Tone Sandhi Rules of Disyllabic Words……………………………..18
1.3 Contributions of the Two Studies on Phonological Theory………...….……...20
1.4 Organization of this Thesis……………………………………….….………..22
Chapter 2 Methodology
2.1 Word Inventories ………………………………………….……….…………26
2.2 Calculation of T-scales via Two Versions………………….……….….….…..28
2.2.1 Fon and Chiang’s Version…….……….……….……………..…..….28
2.2.2 Shi’s Logarithmic Function...……..………………………….…..….32
2.3 Effects of Tonal Coarticulation…………………………………………….….33
2.3.1 Prosodic Contextual Effect……………………………………….….34
2.3.2 Tonal Contextual Effect………………………………………….…..35
2.3.3 Adjacent Tone Effect…………………………………………….…..36
2.3.4 Xu’s Target Approximation model…………………………….…….37
2.4 Subjects and Recording……………………………………….…………..…..39
2.5 Parameters Measurement…………………………………………………..….41
2.6 Definitions of Various Parameters…………………………………..……..….44
Chapter 3 Tonal Representations Revised via Acoustic Data
3.1 Tonal Representations Revised via Monosyllabic Words…………………….48
3.1.1 Fon and Chiang’s Formulae……………………………….………...50
3.1.2 Shi’s Logarithmic Function……...……………………...……….…..54
3.1.3 Discussion of the Two Revised T-scales……………………………..57
3.2 Tonal Representations Revised via Disyllabic Words………………………...63
3.2.1 Tonal Representations of Disyllabic Words………………………….63
3.2.2 Sandhi Tones in Word-Initial Position……………………………….69
3.2.2.1 Tone1[33] Sandhi Rule…………………………………………70
3.2.2.2 Tone2[313] Sandhi Rule………………………………………..72
3.2.2.3 Tone4[53] Sandhi Rule…………………………………………73
3.2.3 Discussion of the Two Revised T-scales……………………………..75
3.2.4 Interim Summary…………………………………………………….78
3.3 Checked Tones Comparison…………………………………………………..79
3.4 Intensity Comparison Among Monosyllabic Words…………..……….……...83
3.5 Discussion and Summary of Tonal Representations……………...……….….86
Chapter 4 Tonal Coarticulation in Disyllabic Words
4.1 Material……………………………………………………………….……….91
4.2 Subjects, Recording and Measurement………………….………….………...93
4.3 Prosodic Contextual Effect on Tonal Coarticulation………………………….93
4.3.1 Level, Concave, and Rising Tones: Tone1, Tone2, and Tone7………94
4.3.2 Falling Tones: Tone3[31] and Tone4[53]…………………………...101
4.3.3 Checked Tones: Tone5[3] and Tone6[4]……………………………107
4.3.4 Discussion and Interim Summary…………………………………..109
4.4 Tonal Contextual Effect on Tonal Coarticulation……..….………………….110
4.4.1 Introduction to Tonal Contexts and Definitions Modified……….…111
4.4.2 Falling Tones: Tone3[31] and Tone4[53]…………………………...114
4.4.3 Tone7[34]…………………………………………………………...118
4.4.4 Tone2[313]………………………………………………………….120
4.4.5 Discussion and Interim Summary…………………………………..122
4.5 Adjacent Tone Effect on Tonal Coarticulation……………..………………..124
4.5.1 Carryover Effect……………………………………………………124
4.5.1.1 Tone1[33]……………………………………………………...124
4.5.1.2 Tone2[313]…………………………………………………… 126
4.5.1.3 ST-Tone1[35] vs. Tone7[34]…………………………………..132
4.5.1.4 Tone4[53]……………………………………………………...135
4.5.1.5 Tone6[4]……………………………………………………….138
4.5.2 Discussion and Interim Summary of Carryover Effect...........……..142
4.5.3 Anticipatory Effect…………………………………………………143
4.5.3.1 Tone3[31]……………………………………………………..143
4.5.3.2 Tone4[53]……………………………………………………..146
4.5.3.3 ST-Tone4[55]-OTR…………………………………………...149
4.5.3.4 Checked Tones………………………………………………..152
4.5.4 Discussion and Interim Summary………………………………….156
4.5.5 Conclusion of Adjacent Tone Effects………………………………158
4.6 Summary of Tonal Coarticulation…………..………………….................…158
Chapter 5 General Discussion and Conclusion
5.1 Phonological Representations vs. Phonetic Realizations.………..………….162
5.2 Tonal Coarticulation…………………………………………………………165
5.3 Contributions of This Study…………………………….……………...……168
5.4 Limitations of the Study and Suggestions for Future Study………...…...… 170
References………………………………………………………………….……171
Appendix I……………………………………………………………….………174
Appendix II………………………………………………………………………17
Author response image 1. Author response
No full textAnkyrin adaptors together with their spectrin partners coordinate diverse ion channels and cell adhesion molecules within plasma membrane domains and thereby promote physiological activities including fast signaling in the heart and nervous system. Ankyrins specifically bind to numerous membrane targets through their 24 ankyrin repeats (ANK repeats), although the mechanism for the facile and independent evolution of these interactions has not been resolved. Here we report the structures of ANK repeats in complex with an inhibitory segment from the C-terminal regulatory domain and with a sodium channel Nav1.2 peptide, respectively, showing that the extended, extremely conserved inner groove spanning the entire ANK repeat solenoid contains multiple target binding sites capable of accommodating target proteins with very diverse sequences via combinatorial usage of these sites. These structures establish a framework for understanding the evolution of ankyrins' membrane targets, with implications for other proteins containing extended ANK repeat domains.</p
Ji yu jin chang sheng xue xuan fu de zi yun xing he zi fu dong er wei zhi dong qi
No full textM.Phil.Acoustic radiation force in the near-field of a vibrating source can be utilized to lift and transport objects, which provides a non-contact driving technology in addition to maglev. This research presents a novel self-running planar motion stage utilizing near-field acoustic transportation phenomenon and coupled resonant vibration of the device.Finite element analysis models have been established to find the needed resonant modes and optimize the design of the structure. The first longitudinal and the second bending modes are designed to have an identical frequency to create elliptical vibration of the structure, which can provide vertical levitation force as well as the propulsion force. A dynamic model based on the Reynolds Equation has been established to study the levitation and driving mechanism of the proposed device. The levitation and driving forces are analyzed; and the relationship between the driving force and the input phase difference is investigated to optimize the following position control. A capacitance surface encoder is proposed to provide the levitation height and two dimensional position feedback for the stage. The encoder design is based on the measurement of capacitance change between the driving stage and the metal sensing plates embedded in the ground. The lateral position (in the XY plane) of the circular stage can be uniquely determined based on the capacitance values.A prototype including the stage, encoder, and controller is implemented and characterized to demonstrate the performance of the proposed design. Two motion characteristics of the stage are first tested: one is the influence of the excitation voltage amplitude on the levitation height, and the other is the influence of the amplitude and phase angles of the excitation signals on the velocity and thrust force. In the calibration of the encoder, the calculated coordinates are firstly compensated for the scaling and the misalignment of the encoder axis and the precision stage. And the systematic errors from the nonlinear features are identified and fitted to a third-order polynomial equation in each axis. In the control scheme, the capacitance encoder works as the feedback module, and a LabVIEW program is used for date acquisition and processing. The stage is tested and demonstrated to follow a circular trajectory with a radius of 3.5mm.This work investigates a novel self-floating and self-running two-dimensional actuator using near-field acoustic levitation and coupled resonant vibration of the device. Compared with the conventional designs based on near-field acoustic levitation, the proposed design eliminates any external component such as guide rail, which contributes to bigger working space. This design also has two-dimensional motion capability with higher load capacity and energy efficiency. A dynamic model based on the Reynolds Equation is established to study the driving mechanism. A capacitance surface encoder is proposed to provide the two dimensional position feedback for the stage. A prototype including the stage, encoder, and controller is implemented and characterized to demonstrate the capability of the proposed design.振動源在近場中產生的輻射力可以用於提升和運輸物體，這現象可用於非接觸驅動技術，並有別於磁懸浮技術。本研究提出了一種新型的自運行平面運動機構，該機構利用了近場聲學傳播現象和裝置的耦合諧振。通過有限元分析可以找到機構的共振模態，並且用於指導結構的優化設計。通過結構設計，使得一階縱向模態和二階橫向模態具有相同的振動頻率，以產生橢圓振動，橢圓振動同時提供懸浮立和前進驅動力。建立了基於雷諾方程的運動模型，來分析機構的懸浮和運動機制。通過分析懸浮力和驅動力，獲得驅動力與輸入信號相位差之間的關係，用於之後定位平臺的位置控制。基於表面電容的編碼器被用於定位平臺的位置反饋，這個反饋包括了平臺的懸浮高度以及它的二維平面位置。編碼器可以測量懸浮平臺和固定在地上的金屬感應板間的電容。基於測得的電容值，通過相應的計算，可以得出平臺在XY平面內的確定位置。建立了包括運動器，編碼器和控制器在內的實驗模型，用於驗證設計的性能。首先是關於驅動器運動性能的測定，第一個是電壓大小對懸浮高度的影響，第二個是電壓大小以及電壓相位角對於運動速度和驅動力的影響。在編碼器的校準過程中，首先補償了由於編碼器和精密平臺錯位以及縮放而引起的誤差， 然後運用三階多項式來擬合每個軸的非線性系統誤差。在控制方案中，電容式編碼器起反饋作用，一個LabVIEW程序用於對電信號的處理。在運動測試中，平臺行走了一個半徑為3.5mm的圓形軌跡。這項研究成功研發了一種新型的自懸浮和自運動的二維運動機構，這個機構運用了近場超聲懸浮和耦合共振效應。與傳統的近場超聲懸浮裝置相比，新的設計不需要導軌之類的任何外部部件，這有助於提供更大的工作空間。該設計具有二維運動能力，並有更高的負載能力和能量效率。建立了基於雷諾方程的運動模型來研究其運動機制。用電容編碼器來當作二維定位平臺的位置反饋。包括運動機構，編碼器和控制器在內的實驗模型被建立，用於驗證設計的性能。Chen, Keyu.Thesis M.Phil. Chinese University of Hong Kong 2017.Includes bibliographical references (leaves 56-60).Abstracts also in Chinese.Title from PDF title page (viewed on 06, February, 2020).Chen, Keyu
A Mean Field Game Approach to Relative Investment-Consumption Games with Habit Formation
No full textThis paper studies an optimal investment-consumption problem for competitive
agents with exponential or power utilities and a common finite time horizon.
Each agent regards the average of habit formation and wealth from all peers as
benchmarks to evaluate the performance of her decision. We formulate the
n-agent game problems and the corresponding mean field game problems under the
two utilities. One mean field equilibrium is derived in a closed form in each
problem. In each problem with n agents, an approximate Nash equilibrium is then
constructed using the obtained mean field equilibrium when n is sufficiently
large. The explicit convergence order in each problem can also be obtained. In
addition, we provide some numerical illustrations of our results.Comment: arXiv admin note: substantial text overlap with arXiv:2206.13341 by
other author
Dual Benefits in Yield Enhancement and Grain Desiccation: Irrigation Coupled with Husk Removal Modulates Grain Moisture Dynamics in Maize
No full textGrain moisture influences grain number formation during the critical period as well as determining the final grain weight during the grain-filling period in maize (Zea mays L.). To clarify the relationships between grain number, grain weight, and grain moisture dynamics, a 2–year field experiment in a split-plot design was conducted with two irrigation treatments, well irrigation (WI) and no irrigation (NI), and with four husk removal treatments, including no husk removal as control (H0) and removal of 1/4 (H1/4), 2/4 (H2/4), 3/4 (H3/4), and 4/4 (H4/4) of the husk layers, respectively. Husk removal reduced the maize grain number, grain dry weight, and yield, and the reductions were larger under no irrigation (33.4–33.5%) than under well irrigation conditions (27.7–33.2%). By contrast, irrigation increased grain water content by 11.1–13.4% and grain dry weight by 6.5–10.4%, regardless of husk removal. Meanwhile, the interactive effects between irrigation and husk removal were significant in grain water content but not in grain yield, reflecting the larger negative effects of husk removal on maize grain yield. In conclusion, husk plays a crucial role in grain number formation during the critical period and grain weight during the grain-filling period, especially in drought conditions, in relation to the trade-offs between yield enhancement and grain desiccation in maize production
A Comparative Analysis of Multi-Scale and Rayleigh Approaches in Capturing Eigenfrequencies and Mode Shape Evaluation in Planetary Gear Transmission Systems of Medium and Heavy Trucks
No full textWithin planetary gear transmissions (PGTs), mode shapes and eigenfrequencies hold a crucial significance in operational reliability and efficacy. Mode shapes explain the unique motion patterns inherent in PGT systems. Conversely, eigenfrequencies describe the inherent frequencies at which PGT systems undergo vibration or oscillation upon exposure to external forces or disruptions. This research paper presents a comprehensive investigation into the dynamic behavior of a three-stage PGT utilized in medium and heavy trucks. This study introduces the Rayleigh energy method to assess system dynamics, revealing a bounded Rayleigh quotient related to the highest related eigenvalue. Then, this study delves into eigenfrequencies and the mode shape behavior of the adopted PGT model. The eigenfrequencies are identified as encompassing diverse vibrational modes of central components and planet gears. Moreover, a multi-scale analysis of the adopted PGT model is presented by deriving matrices for mass, bearing stiffness, and mesh stiffness. Comparisons with the Rayleigh energy method demonstrate the new approach’s efficiency, exhibiting a low margin of error in the determination of eigenfrequencies. This investigation also highlights the alignment of identified mode shapes with the established literature, detailing the multi-scale approach’s minor deviation in mode shape determination compared to the Rayleigh energy method
