Abstract:Recently, the study of phonetics and phonology has become one of the hot issuesin the field of second language acquisition. Nevertheless, this aroused the interest ofthe researchers both in China and abroad. Many researches, theories and advancedmethods have sprung up and made great contributions to the development ofphonetics and phonology. The present researcher also has great interest in thephonetics and still applies myself to the teaching and linguistic studies. The currentthesis is the witness of the scientific research of the researcher and it will give a greatguidance of the fliture teaching as well. They usually ignore the importance and take it for granted that they have noproblems in the acquisition of them. The reason is that many of the ECS are similar tothe Chinese consonants in the pronunciation. Therefore, Chinese EFL learners thinkit's easy for them to pronounce the ECS and ECCS correctly. As a matter of fact, thepronunciation of many ECS has many differences from that of the Chinese consonantsno matter in the place of articulation, rules of articulation, and voiceless and voicedsounds. It simply means that the Chinese EFL learners often rely on the Chinesearticulation rules and habits to guide the pronunciation of the ECS and ECCS. 
關鍵詞：優選論 制約條件 二語語音 英語輔音 輔音群 降級排列

Chapter 1 Introduction

1.1 Origin of the research topic
In the process of teaching phonetics, I found many students have more or lesspronouncing mistakes, most of which are mistakes in English consonants (CESS,hereafter)and English consonant clusters(ECCS, hereafter),such as great to etc. No matter how many times I corrected them, I can only see atemporary effect. This phenomenon makes both the students and teachers frustrated.Therefore, I decided to look through the related reference. After a brief review ofliteratures, native language transfer has been researched by many scholars. TheContrastive Analysis of hypothesis (CAH, hereafter) is the main theory on nativelanguage transfer. However, there exist many problems. If the elements in L2 aremuch more similar to those in LI, it will be easier for the learners to acquire theconnect pronunciation. This is because LI plays a positive transfer. While, on theother hand，the elements in L2 are much different from those in LI, it will be muchmore difficult for the learners to acquire and even to correct. The reason is that the LIplays a stronger role of negative transfer than positive one. Therefore, native languagetransfer can only explain a certain amount of the errors and it isn't able to solve all theproblems thoroughly and completely. For the research, some serendipitous factorsexist. Up to now, so many scholars still hold native language transfer to explain L2phonology.
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1.2 Theoretical and Pedagogical Significance
Until now, OT has been widely applied in the field of L2 phonology abroad, suchresearchers as Radwanska-Williams and Yam, 2001; Broselow and Xu, 2004; Cardoso，2007. While, the domestic development of OT framework is not as systematic andthorough as abroad, only a few scholars making their researches under the frameworkof OT, such as Yan, 2004; Fan, 2008.The research of ECS and ECCS by CLES withinthe powerful framework of OT will absolutely help the scholars find a more scientificand complete pattern to explain the problems in L2 phonology. More significantly, thepresent research is different from the previous ones. It is the first time that the presentresearch combines both and ECS and ECCS as a whole in the field of L2 phonology.And it will further improve the development of L2 consonant acquisition.Pedagogically, most of the L2 phonological researches still rely on the nativelanguage transfer as the theoretical basis. As mentioned above, there are someserendipitous elements in the native language transfer in that it can only explain partof the errors. While, OT is an extremely different theory from the native transferlanguage. In daily teaching, teachers can outbreak the teaching model of perceptuallyblind error correction, start with the analysis of mistakes in final ESC and ECCS,rationally help the students reduce pronouncing mistakes in the perspective ofdifferent re-ranking of constraint hierarchy inChinese and English Syllable structure, and consequently, improve the self-awareness of CLES.

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Chapter 2 Theoretical Background and Literature Review

2.1 Theoretical Background
Optimality Theory was first put forward by the phonological linguist Alan Princeand the Cognitive scientist Paul Smolensky in 1993, and it has become a newphonological theory. OT not only denies some important hypotheses in traditionalgenerative phonology, but challenges some fundamental theories in GenerativeLinguistics. And more than that, OT provides a new perspective for the languageanalysis, so that it attracts extensive attention worldwide. The basic principles of OTby McCarthy & Prince (1994) are summarized as follows: Violability. Constraints are violable, but the degree of violable must be minimal.Specifically speaking, in particular language constraints, those front positions(higher ranking) are inviolable; those in middle positions (inter mediate rankings)are either inviolable or not; those in back positions (lower rankings) are alwaysviolable. It is because OT restricts ranks of constraints that can establish theevaluator system to justify the optimal candidate.  Ranking. Constraints are ranked on a basis of a particular language. The idea ofminimal violation (satisfaction) is defined with regard to the ranking principle.Among the 3 basic principles, violability & ranking are the most crucial. Onelanguage form cannot satisfy all the constraints. T
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2.2 Literature Review
The development of SLA of phonology abroad experienced from languagetransfer initially, universal principles continuously to optimality Theory at present.The theoretical and empirical hypotheses prove that OT is more comprehensive,encompassing model in andyzing in the phenomenon of phonology, in both LI andL2.Before the application of OT，most of the L2 phonological researches still rely onnative language transfer as the theoretical basis. The contrastive Analysis ofHypothesis (CAH, hereafter) is the main theory to guide native language transfer.Some linguistics divide the native language transfer into two branches: positivetransfer refers to the active or positive function or role played by native language totarget language, and negative transfer, which is also called cross-linguistic influenceprefers to its passive or negative fianction on target language. If native language hasmuch more similarities in segments with target language, then positive transfer willwork, and it will be more beneficial to the L2 learners. Otherwise，if there are fewersimilarities or more differences between native and target language, then negativetransfer must carryout. And it will absolutely become the main obstacle in L2 learners'acquisition of pronunciation. Furthermore, L2 learners have to appeal to some specialstrategies to deal with their problems in pronunciation, such as simplificationstrategies, e-map-guide strategies. 

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Chapter 3 Research Design......... 21
3.1 Research Questions and Hypotheses ........   21
3.2 Subject ........21
3.3 Instruments and Materials........ 23
3.4 Research Procedures ........24
Chapter 4 Results and Discussions........ 27
4.1 Pilot Study ........27
4.2 The Research Project........ 31
Chapter 5 Conclusion........ 48
5.1 Main Findings ........48
5.2 Innovations ........50
5.2.1 Theoretical Improvement........ 50
5.2.2 Empirical Improvement........ 51
5.3 Limitations ........51
5.4 Suggestions for the Future Teaching........ 52

Chapter 4 Results and Discussions

4.1 Pilot Study
In this subsection, the results of the pilot study will be presented from thefollowing two aspects: general tendency and individual difference in OT account. Tableau 4.1 describes the general acquisition of ECS and ECCS by CLES. As itshows, the error rate of the pronunciation is still much higher than imagined. Whaithe subjects meet difficult sound segments, they are intended to adopt silence to avoidreading. As tableau 4.2 shows, there are four main error types in the wrong pronunciationof ECS and ECCS. Epenthesis errors (Wl) are the most frequent one in the total(48.5%)，and the second common errors are Deletion errors (W2)，taking up 39.7%,the last type Substitution errors (W3) are also commonly made (11.8%). In the pilotstudy, there are no other mistakes, thus the present research will not take them intoconsideration.It can be concluded clearly that the problems in the acquisition of ECS and ECCSby CLES are not only very common, but the CLES mainly used such simplificationstrategies as epenthesis, deletion and substitution.

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Conclusion

Recently, the study of phonetics and phonology has become one of the hot issuesin the field of second language acquisition. Nevertheless, this aroused the interest ofthe researchers both in China and abroad. Many researches, theories and advancedmethods have sprung up and made great contributions to the development ofphonetics and phonology. The present researcher also has great interest in thephonetics and still applies myself to the teaching and linguistic studies. The currentthesis is the witness of the scientific research of the researcher and it will give a greatguidance of the fliture teaching as well. They usually ignore the importance and take it for granted that they have noproblems in the acquisition of them. The reason is that many of the ECS are similar tothe Chinese consonants in the pronunciation. Therefore, Chinese EFL learners thinkit's easy for them to pronounce the ECS and ECCS correctly. As a matter of fact, thepronunciation of many ECS has many differences from that of the Chinese consonantsno matter in the place of articulation, rules of articulation, and voiceless and voicedsounds. It simply means that the Chinese EFL learners often rely on the Chinesearticulation rules and habits to guide the pronunciation of the ECS and ECCS.