Identifying Typesof Semiconductors
Which of the following elements, if doped into silicon, would yield an n-type semiconductor: Ga, As, or C?
Compound semiconductors can be doped to make n-type and p-type materials, but the scientist has to make sure that the proper atoms are substituted. For example, if Ge were doped into GaAs, Ge could substitute for Ga, making an n-type semiconductor, but if Ge substituted for As, the material would be p-type. Suggest a way to dope CdSe to create a p-type material.
LING 202 2/8 Lecture 1 – Nature of Human Language A grammar is a speaker’s knowledge of 5 kinds of properties of language: 1. Phonetics – basic speech sounds 2. Phonology – how those sounds are represented and combined 3. Morphology – words; basic units of phrases and of meaning 4. Syntax – how phrases are built from those basic units 5. Semantics – how the meaning of linguistic units and complexes is determined 4 key properties… 1. Productivity – every human language has an unlimited number of sentences. a. Is there a longest sentence i. No – more words can always be added (in various ways) ii. Recursion (“bolder than bolder than bold”) b. How common are new sentences in speech i. We can always understand sentences we have never heard before ii. Frequency and rank of words in an Alice in Wonderland: 1. Words like “the,” “and,” “to,” etc. iii. Zipf’s law – graphed rank and frequency of a million words of writing in English (from the Wall Street Journal) 1. Bell curve shape – a few words that are very frequent, 44% of words only appear once 2. In the same corpus, 89% of the 3-word sequences only occur once 3. So: most sentences you hear, you only hear once. a. You’ve heard all the individual words themselves, and more than once, but that’s because you’ve heard many more than a million words 2. Compositionality – new sentences are understood by recognizing the meanings of their basic parts and how they are combined. a. It’s the explanation for productivity John believes Mary. John believed Mary. John believed you. i. Meaning of the parts determines the meaning of the whole – analyzing small changes in the sentence about John allows us to comprehend a change in meaning b. Our ability to understand so many sentences is analogous to the simpler mathematical talk of putting small numbers or sets together to get larger ones. i. You do not understand a sentence because you have heard it and figured it out before. c. The meanings of the limitless number of sentences of a productive language can be finitely specified, if the meanings of longer sentences are composed in regular ways from the meanings of their parts. d. We analyze language as having basic units and some number of ways for putting these units together i. Grammar allows us to handle a language that is essentially unlimited LING 202 1. Regarded as a cognitive structure – the system we use to “decode” language 3. Creativity – the distinctively human ability to express new thoughts and to understand entirely new expressions of thought, within the framework of an “instituted” language a. We are creative with respect to how we use language, but this creative use of language is something that we know no more about than philosophers did in the 1600’s. b. Language use is appropriate to the situation, but it is not determined by it. c. It remains a deep mystery why we say what we say when we say it. i. Difficult to study 4. Flexibility – we are inventing the language all the time. a. Languages change over time – they can be extended in some ways, but not in others i. Conventional aspects of each language are constantly changing (new names, new terms, new idioms) ii. But according to Stabler: You can name your new dog almost anything you want, but could you give it a name like –ry were this must be part of another word, like the plural marker –s… 1. Fido eats tennis balls. 2. Eats-ry tennis balls. 3. Eats tennis balls-ry. iii. There are some significant limitations What are words 1. Some have parts a. John believes Mary b. John believe –s Mary 2. A word can contain a root with 0 or more affixes a. believe-s, quick-ly,… 3. A morpheme is the smallest meaningful part a. Some can occur freely like John or dog or believe, but others cannot (tense markers like –s and –d) i. Bound morphemes are those that cannot occur freely b. Roots and affixes are morphemes c. Variant pronunciations of the morpheme are sometimes called allomorphs 4. A compound is a word that has other words as parts 5. A word is a morpheme, or complex of morphemes, which occurs freely a. Can be composed of a root with 0 or more affixes (prefix or suffix) b. Not the smallest units of meaning, but meaningful units that can “stand on their own” Irregular forms – are they complex 1. Many English verbs have irregular past tense forms that are not root + suffix combinations a. In many cases, forming past tense involves changing the vowel i. Should the vowel be regarded as a kind of morpheme 1. i.e. grew = grow + PAST where the PAST is pronounces as a vowel change LING 202 b. In other verbs, nothing gets added to form the past (hit, slit, quit, knit, let, set, cut, shut) i. All end in [t] or [d] 2. The irregular past tense forms, like the regular ones, never allow an additional affix: a. * He was promis-ed-ing everything b. * He was knew-ing everything c. * He was found-ing everything d. * He was taught-ing everything 3. Also true with irregular plurals: a. * He looks mice-y b. * He looks mouse-y 4. Forming a yes-no question seems to involve splitting the tense away from the verb (for both regular and irregular forms): a. You promis-ed Bianca. i. Di-d you promise Bianca b. You knew Bianca. i. Di-d you know Bianca c. You found Bianca. i. Di-d you find Bianca d. You taught Bianca. i. Di-d you teach Bianca 5. Similar phenomenon when using do emphatically: a. I never promised Bianca, but you di-d promise her. b. (Same with knew, found, taught) 6. So, when the past tense is expressed on do, the verb takes its usual bare form, whether it is regular or not a. Suggests that both regular and irregular forms are complex, with a verb morpheme and a PAST morpheme Lecture 1 Summary 1. How can human languages be (1) learned and (2) used as they are 2. Languages are productive – no human language has a longest sentence a. Zipf’s law – stronger claim, that though the most frequent words are very frequent, the frequencies of other words drop off exponentially 3. Language is compositional – has basic parts and certain ways in which those parts can be combined a. A language user must know this – called grammar