Chapter3

29
● 启发式搜索策略
假设初始状态、算符和目标状态的定义都是完全确定的，然后决定一
个搜索空间。因此，问题就在于如何有效地搜索这个给定空间。 启发信息按其用途可分为下列3种： (1) 用于决定要扩展的下一个节点，以免像在宽度优先或深度优先搜索 中那样盲目地扩展。 (2) 在扩展一个节点的过程中，用于决定要生成哪一个或哪几个后继节 点，以免盲目地同时生成所有可能的节点。
22ห้องสมุดไป่ตู้
有深度界限的深度优先搜索算法如下： (1) 把起始节点S放到未扩展节点OPEN表中。如果此节点为一目标节点，则得 到一个解。 (2) 如果OPEN为一空表，则失败退出。 (3) 把第一个节点(节点n)从OPEN表移到CLOSED表。 (4) 如果节点n的深度等于最大深度，则转向(2)。 (5) 扩展节点n，产生其全部后裔，并把它们放入OPEN表的前头。如果没有后 裔，则转向(2)。 (6) 如果后继节点中有任一个为目标节点，则求得一个解，成功退出；否则，
度依次扩展节点的，那么这种搜索就叫做宽度优先搜索(breadth-first search)。
从图可见，这种搜索是逐层进行的；在对下一层的任一节点进行搜索之前，必 须搜索完本层的所有节点。
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宽度优先搜索算法如下： (1) 把起始节点放到OPEN表中(如果该起始节点为一目标节点，则求得 一个解答)。 (2) 如果OPEN是个空表，则没有解，失败退出；否则继续。 (3) 把第一个节点(节点n)从OPEN表移出，并把它放入CLOSED扩展节
1
状态图的例子：
设有三枚钱币，其排列处在“正，正，反”状态，现允许每次 可翻动其中任意一个钱币，问只允许操作三次的情况下，如何 翻动钱币使其变成“正，正，正”或“反，反，反”状态。 若“正面”用“1”表示，“反面”用“0”表示，则问题化成求 解从初始状态（1,1,0）到目标状态（1，1，1）或(0,0,0)的路 径问题，且该路径的长度为3。 （1，1，0）--------->（1，1，1）或（1,1,0）--------->(0,0,0)

Allomorph: a member of a set of morphs which represent the same morpheme. Allomorphs are phonological or orthographic variants of the same morpheme.
河南大学外语学院 马应聪
英语语言学：第3章
Allomorph
Allomorphs are in complementary distribution.
{-s} (plurality) [-z]: meanings [-s]: maps [-iz]: watches [-ai-]: mice [-i:-]: feet [0]: deer
Inflectional morphemes manifest various grammatical relations or grammatical categories such as number, tense, degree and case.
河南大学外语学院 马应聪
英语语言学：第3章
河南大学外语学院 马应聪
英语语言学：第3章
Summary
Lexical morpheme
Free morpheme
morpheme
Functional morpheme
Derivational morpheme
Bound morpheme
Inflectional morpheme
河南大学外语学院 马应聪
Root: the basic element of a word that can stand by itself: talk, internationalism, work/shop, black/bird

What are his famous cartoon Mickey Mouse, Donald Duck characters? Goofy and Snow White Where was Disney born? in the USA sold newspapers What did he do after leaving delivered mail school? drawing cartoons for films What was his final job? What was Mickey Mouse based on? What did Mickey become? a real mouse a star
Post reading activity
Why& how ? Do they live now? Food& nature?
• What are dinosaurs?
When? Size?
where ……live?
Key words for dinosaurs
Chapter 3 Encyclopaedia
Reading
Fast-reading and word-guessing
Pre-reading
P30 What do you know about…?
b 1. Now you can find dinosaurs______.
a. in zoos b. in museums c. anywhere 2. The statement ______ is NOT true. b a. Dinosaurs once lived on Earth b. All dinosaurs were very big c. Some dinosaurs could fly

How to write to the company you wish to contact for the first time?
（1）the source of your information. ） （2）your intention ） （3）your business scope ） （ 4 ） the reference as to your firm’s financial position and integrity. （5）your expectation ）
Where to find the company you want to deal with?
（1）Overseas Chamber of Commerce ） 海外商会 （ 2 ） The Economic and Commercial Counselor’s Office of the Embassy of People’s Republic of China in Foreign Countries 中国驻外商务参赞处 （3） Your branch offices abroad ） （4） Directories ） 贸易行的行名录
CHAPTER 3
Establishing Business Relations 建立业务关系
INTRODUCING BUSINESS OPERATION
Dear Sirs, RE: TABLE-CLOTH We have your name and address from the Commercial Councilor's Office of Chinese Embassy in Pakistan. We take this opportunity to write to you with a view to set up friend business relations with you. We are a state-owned company dealing specially with the export of table-cloth. We are in a position to accept orders according to the customer's samples. In the customer's samples, request about the assorted pattern, specification and package of the needed goods can be indicated particularly.