材料专业英语论文

In flat vast Yudong

Al 合金包含高Zn 内容被应用作为结构材料在许多工业ap- 折襞由于他们的好castability 、机械性能, 和耐磨性[ 1 的优秀组合? 为A] Zn 合金的过饱和的坚实解答包含16.5 at.% 到59.0 at.% Zn, spinodal 分解首先发生在冷却期间的过程; 然后不连续的降雨雪(DP) 并且发生在2770C [ 5-7 之下] 。DP 形式多孔的nu- cleus 在原始的晶界, 然后吞下矩阵spinodal 由多孔的界限的迁移, 和最后显现出成美好的薄片状混合物富有AI 和富有Zn 的坚实solu- tions [ 8-10 ] 。这双重阶段微结构首先被发现了在钢里, 叫做pearlite [ 11 ] 。pearlite 在钢里改变到球状?crostructure 在随后heat-treatment 期间。但是, 它被发现了DP 美好的薄片状微结构在AI Zn 合金里被变换成coarsening 薄片状一个通过生核和成长mecha- nism 。DP 动能学的中坚力量被调查为了深深地了解DP 2 实验性做法实验性合金的耐热性由熔化做了纯净的Al (99.99%), 纯净的Zn (99.99%), 和纯净的Cu (99.999%) 在铝土坩埚在高纯度和然后熔铸成钢模子。锭的大量是300 g 。根据Al Zn 二进制相位图[ 6 ], AI Zn 合金的有名无实的构成和AI Zn Cu 合金是60A1-40Zn (at.%, 叫AIZn 合金) 并且59A1-39Zn-2Cu (at.%, 叫A1Zn-2Cu 合金) 。它被预计, 富有Al 和富有Zn 的阶段的容量分数由spinodal 分解在这些合金里是大约50%, 关于specuvely 。压缩的锭接受了3750C x 的同类的治疗24 h 和4000C x 120 h 。在解答对待以后在4000C 为2 h, 样品各自地变老了在150, 200, 2500C 有些时间和由混杂的酸的水溶液铭刻了(HF+HCl+HN03) 。微结构观察由使用执行了Versamet-2 光学显微镜和菲利普XL30 FEG 扫描电子显微镜。X-射线衍射被执行了在RI- D/Max 镭X-射线衍射计GAKU, 并且钾Cu 目标衍射光芒被采取了。DP 微结构3 个结果和讨论3.1 Coarsening 机制在合金轻微地是在eutectoid 温度之下; thenthe spinodal 微结构被变换成美好薄片状一个由DP DP 完全地结束了在30 分钟之内在AlZn 合金里, 当在20 分钟之内在AlZn-2Cu 合金里[ 5].However, 美好的larneflar 微结构是不稳定的。何时AlZn 合金样品被拿着在250? 为2 h, 不连续的coarsening (DC) 细胞形成了在原始界限和多孔的界限DP (图1(a)) 。以老化时间增量, 不连续的coarsening 细胞吞下美好的薄片状微结构由多孔的界限的mi- gration 以高角度, 并且样品然后成为了coarsening 多孔的双重阶段微结构。同时, 新不连续的coarsening 细胞连续地形成了在高角度晶界(图1(b)) 。用老化时间进一步增加, 美好的薄片状微结构由coarsening 薄片状一个替换了(图1(c)) 。当AlZn-2Cu 样品被保留了在250?, DP 美好的薄片状微结构相似地改变了到coarsening 薄片状一个通过不连续coarsening, 但变革速度比那慢的在AIZn 合金(图1(d)) 。样品的微结构演变变老了在200? 同那是样品一样变老在250 吗? 在AlZn-(Cu) 合金, 即由生核和growth.(2) 溶解不连续的coarsening mecha- nism 和spheroidization mechanism.In AI Zn (Cu) 合金变老了在150? 为5 h 在解答治疗以后, DP 变革有al- 准备好完成, 并且DP 美好的薄片状微结构被溶化了入短rod-shaped 一个, 大小是相对地大的在原始的界限和多孔的界限(图2(a)).The rod-shaped 微结构以大大小在和在界限增加了和gradu- 盟友附近被改变到球状一个以增量老化时间(图2(b)) 。以老化时间进一步引伸, rod-shaped 微结构在DP 细胞里面逐渐并且改变了到球状一个, 以便细Zn 微粒dispersedly 被分布在Al 矩阵(图2(c)) 。当AIZn-2Cu 合金样品被保留了在150?, 微结构演变与那是相似在AlZn 二进制合金, 但第三个阶段被观察了在三部组成的合金(图2(d)), 是亚稳的CuZn4 阶段由X-ray diffrac- tion 分析作证。与老化时间增量, CuZn4 阶段逐渐被变换成A14Cu3Zn 阶段和最后完全地被变换成A14Cu3Zn 阶段。

On suprasegmental features Introduction So far we havebeen talking about phonetic features as they apply to single phonetic segments,or phones. Phonetic features can also apply to a string of severalsounds, such as a syllable, or an entire word or utterance. The study ofphonological features which applies to groups larger than the single segment,are known as suprasegmentalfeatures, such as the syllable or the word. The study of these features is knownas prosody. It mainly includessyllable, stress, pitch, tone, and intonation. In this paper, I will talk aboutthe suprasegmental features ingreat detail. Key words: phonetic, suprasegmental. Syllable The most obvious prosodic feature in languageis the syllable. Let's briefly discuss the notion of syllables. Like all of our other basic linguistic concepts,although everyone knows what a syllable is, the concept "syllable" isdifficult to define in absolute terms. A syllable can be divided into threeparts, that is, onset, nucleus, and coda, of which nucleus is a must. Asyllable that has no coda is called an open syllable while a syllable with codais called a closed syllable. In English only long vowels and diphthongs canoccur in open syllables. The onset may be empty or filled by a cluster of asmany as three consonants, while the coda position may be filled as many as fourconsonants. The maximal onset principle states that when there is a choice asto where to place a consonant, it is put into the onset rather than the coda.In some languages, syllables are always open,that is, they always end in a vowel, never a consonant. (Hawaiian) On the other hand, every Hawaiian syllable must begin with a consonant. (Aloha spoken as a single word beginsin a glottal stop.) In other languages, syllables are always closed; they mustend in a consonant (Navaho): Háá'ishah dididiljah. Let's build a fire. Táá diné 'ooljéé'go naaskai' Three men went to the moon. (LikeHawaiian, they must also begin in a consonant.)Stress The nature of stress The word stress is used differently bydifferent authors, and the relationship between stress, emphasis, accent andprominence is also defined differently. Robins has defined it as “a genericterm for the relatively greater force exerted in the articulation of part ofutterance”. The nature of stress is simple enough—practically everyone wouldagree that the first syllable of words like“father”, “open” is stressed, thatthe middle syllable is stressed in “potato”, “apartment” and the final syllableis stressed in “about”, “perhaps”, and most people feel they have some sort ofidea of what the difference is between stressed and unstressed syllables,though they might explain it in many different ways.The production of stress is generallybelieved to depend on the speaker using more muscular energy than is used forunstressed syllables. From the perceptual point of view, all stressed syllableshave one characteristic in common, and that is “prominence”. Roach hasmanifested that at least four different factors are important to make asyllable prominent:i) Loudness: Most people seem to feelthat stressed syllables are louder than unstressed ones; in other words,loudness is a component of prominence.ii) Length: The length of syllables hasan important part to play in prominence; the syllables which are made longerthan the others will be heard as stressed.iii) Pitch: Pitch in speech is closelyrelated to the frequency of vibration of the vocal folds and to the musicalnotion of low-pitched and high-pitched notes; if one syllable is said with apitch that is noticeably different from that of the others, this will have astrong tendency to produce the effect of prominence.iv) Quality: a syllable will tend to be prominentif it contains a vowel that is different in quality from neighboring vowels. Languages differ in how they use stress.1) In some languages, eachsyllable is equally stressed or unstressed,as in Cambodian2) the syllable in eachword is more stressed. Theplace of stress is fixed on acertain syllable:1) initial. Finnish,Hungarian and other Finno-Ugric languages2) penultimate. Polish,3) final. French.4) Complex set ofrules. In Bulgarian nouns and verbs have separate sets of rules forstress placement. Hopi (phonetic: first syllable of a two syllableword: síkwi meat; inwords of three or more syllables, accent falls on the first long vowel: máamatsi to recognize; or onthe first short vowel before a consonant cluster: péntani to write; otherwise it falls on thenext to last syllable: wunúvtu standup)The place of stress is random.1) In Russian the stress iscompletely random: xoroshó, xoróshi.2) In English the stress ismore predictable but still random. Usually a middle syllable of a longerword receives the stress. In two syllable words stress is rando and oftenrenders differences in meaning: project/toproject, produce/produce, and insult/ to insult. Some languages have more than one stress perword: English is such a language. In English, words of foursyllables or more have a primaryand a secondary stress. SomeEnglish compounds have phrasal stress on the first element of thecompound. Phrasal stress often distinguishes meaning in adjective/nouncombinations. Sentence stress in English According to He Shanfen (1992), Englishsentence stress has two main functions:⑴ to indicate the important words in thesentence; ⑵ to serve as thebasis for the rhythmic structure of the sentence. Consequently, in connected English speech,sentence stress usually falls on content ( or lexical) words, which carry thebasic meaning of a sentence, e.g. nouns, adjectives, adverbs etc. Those whichare usually unstressed in sentences are form (or structural) words, which showgrammatical relationships, such as articles, auxiliary and modal verbs,monosyllabic prepositions, etc.Pitch Another prosodic feature is pitch, defined as the frequency ofvibration of vocal cords. Pitch is measured in hertzes. Physiologically, pitch tends to be higher inwoman than in men and higher before puberty than after puberty. Also, thepitch of women's voices tends to lower with old age; the pitch of men's voicestends to get higher with age. Despite these physiological, non-linguisticuniversal, each language uses pitch distinctions for linguisticallymeaningful purposes. Startingfrom the lowest pitch on the initial syllable, the pitch of each subsequentsyllable raises until the word reaches the "peak". From that point,pitch either remains at the same level for the remainder of the word or itdrops again. The choice between maintenance of high pitch or allowing it todrop is a matter of formality: pitch is maintained in formal or careful speech,but dropped in colloquial usage.七．ConclusionBeing the most important part, suprasegmental features can not be despised in phonology research.From the whole passage, we can understand that suprasegmentalfeatures not only has its phonology significance, but also the practicaluse as well. We can not say this person is a good language user just by his orher vocabulary, as well as the grammar. Spoken language is also very useful. Ido hope that the paper will be sufficient to prove that suprasegmental features is an efficient way for our studies and encouragemore and more students to pay attention to using it.