托福语法之独立主格
独立主格可以算是非谓语动词状语从句知识点的延伸，所以如果还没掌握非谓语动词及状语从句的省略的，请慎入，哈哈。
定义：非谓语动词作状语，其逻辑主语须与主句主语保持一致。若不一致，非谓语动词形式须另带主语，从而构成复合结构的形式作状语。这种结构称为“独立主格结构”。其中，非谓语动词主动用现在分词，被动用过去分词。
独立主格结构主要用于描绘性文字中，其作用相当于一个状语从句，常用来表示时间、原因、条件、行为方式或伴随情况等，如：
表示时间：
The meeting over, all of us went home.
Her work done, she sat down for a cup of tea.
表示条件：
The condition favorable, he may succeed.
表示原因：
He wrapped her up with great care, the night dark and frosty.
In the middle of February, the weather favorable for work, the workers began to repair and secure the dam of the river.
表示伴随情况：
Almost all metals are good conductors, silver the best of all.
所以其形式为：
1. 名词/主格代词 分词：
名词/主格代词 现在分词（表示主动和正在进行），
如：
The girl staring at him (= As the girl stared at him), he didn't know what to say.
Time permitting (= If time permits), we will go for an outing.
名词/主格代词 过去分词（表示被动和已完成），
如：
The problems solved (= As the problems were solved), the quality has been improved.
Her glasses broken (= Because her glasses were broken), she couldn't see the words on the blackboard.
2. 名词/主格代词 不定式：（表示将要发生的动作，主动关系）
如：
He is going to make a model plane, some old parts to help.
They said good-bye to each other, one to go home, the other to go to the bookstore.
3. 名词/主格代词 介词短语
如：
The boy goes to the classroom, book in hand.
Mary was sitting near the fire, her back towards the door.
4. 名词/主格代词 形容词
如：
An air accident happened to the plane, nobody alive.
So many people absent, the meeting had to be called off.
5. 名词/主格代词 副词
如：
He put on his sweater, wrong side out.
6. 名词/主格代词 名词
如：
His first shot failure，he fired again．
Two hundred people died in the accident, many of them children.
7. with引导的独立主格
与主句逻辑关系紧密，形式为with/without 宾语（名词/代词） 宾语补足语(分词/不定式/形容词/副词/介词短语)，宾语通常由名词或代词充当，但代词一定要用宾格。上文的独立主格结构的几种情况都适用于此结构，
如：
The girl hid her box without anyone knowing where it was.（分词）
Without a word more spoken, she left the meeting room. （分词）
The kid feels excited with so many places of interest to visit. （不定式）
With his son so handsome, the old man felt satisfied.（形容词）
The boy was walking, with his father ahead.（副词）
He stood at the door, with a computer in his hand.（介词短语）

8. each引导的强调型独立主格，形式为:句子 复数名词结尾 each 介词短语/形容词短语/名词短语/分词 如:
The huge organization that operates the company's basic businesses will be divided into five groups, each with its own executive.
注意：
1. 独立主格转换成状语从句，当状语从句的主语与主句的主语不是指同一个对象时，可用独立主格结构取代状语从句，但不再保留连词，
如：
After class was over (= Class being over / Class over), the students soon left the classroom.
2. 不能省略being (having been)的情形：
(1) 独立主格的逻辑主语是代词时，
如：
It being Sunday, we went to church.
(2)在There being 名词的结构中，
如：
There being no bus, we had to go home on foot.
3. 在“名词/主格代词 介词短语”构成的独立主格结构中，一般不用形容词性物主代词和冠词，体会与with引导的独立主格的区别，
如：
Miss Smith entered the classroom, book in hand.
Miss Smith entered the classroom with a book in her hand.
在with/without结构中，多数情况下with能省略，但without不能省略。
4. 独立主格结构的逻辑主语为名词时，没有所有格形式，
如：
The chief-editor arriving, we began the meeting.