这是分词独立主格结构。关于该问题，请参考我曾给网友归纳的一个回答：

独立主格结构，是由“名词或代词+现在分词、过去分词、不定式、形容词短语、名词短语、介词短语或副词短语”构成的一种独立结构。在该结构中，名词或代词与其后的部分构成逻辑上的主谓关系，用来修饰谓语动词或整个句子。在句中作状语，表示“时间、条件、原因、伴随，方式或结果”等含义。其位置比较灵活，放于句首句末均可。

1. 名词（代词）+ 现在分词

The clock striking twelve, I went to bed. （表原因）

These women having produced works of the highest quality, any survey of the 19th century English literature must include them. （表原因）

2. 名词（代词）+ 过去分词

He lay there on his back, his teeth set, his right hand clenched on his breast. （表伴随）

Enough time given, she will surely do the job better. （表条件）

3. 名词（代词）+ 不定式

Here are the first three volumes, the fourth one to come out next month. （表伴随）

He proposed a picnic, he himself to pay for the railway tickets and John to provide the food. （表方式）

4. 名词（代词）+ 形容词短语

Her face pale with anger, she rose to go away. （表原因）

I saw a deep pond, the water blue like the sky. （表结果）

5. 名词（代词）+ 介词短语

Then, last night, I followed him here and climbed in, sword in hand. （表方式）

Child in arms, a few women stood there chatting. （表方式）

6. 名词（代词）+ 副词短语

Summer over, the students returned to school. （表原因）

7. 名词（代词）+ 名词短语

His first shot a failure, Tom fired again. （表原因）

8. with复合结构

“with复合结构”也是独立主格结构的一种，同样十分重要。在句中表示“原因，结果，伴随，方式”等情况。现把“with复合结构”的各种情况作一总结。

(1) with + 宾语 + 形容词

The children were listening to the teacher with their eyes wide open. （表伴随）

(2) with + 宾语 + 介词短语

The old man used to take a walk with a stick in his hand. （表方式）

(3) with + 宾语 + 副词

The proud girl walked away with her head up. （表方式）

(4) with + 宾语 + 现在分词

Mary felt very shy with so many eyes looking at her. （表原因）

(5) with + 宾语 + 过去分词

If you sit looking away from a person, or with your back turned, you are saying you are not interested in that person. （表方式）

(6) with + 宾语 + 不定式

With too much work to do the next day, he felt anxious and didn’t sleep well. （表原因）

一般说来，with 复合结构放在句末多表示伴随状况；若放在句首，则多表示“原因”或“条件”，例如：

With her mother away from home, the little girl felt lonely. 由于她妈妈不在家，这个女孩感到很孤单。

With the guide leading the way, I had no difficulty finding their village. 因为向导带路，我没怎么费事就找到了他们的村子。

【特别提示】从上面的各种例句中可以看出，独立主格结构本身不是一个完整的句子，它实际上是一个含有逻辑主语的某种短语，用来修饰其它一个句子的。

1. 独立主格结构的转换

独立主格结构可以根据其语法作用，进行句式转换。例如：The clock striking twelve, I went to bed.

①转换为状语从句：When the clock was striking twelve, I went to bed.

②也可以转换成一个并列句：The clock stuck twelve and I went to bed.

2. 独立主格结构与冠词

在“名词+ 介词短语”独立主格结构中，如果逻辑主语和介词短语中的名词都是可数名词单数，这些名词前不要用冠词，目的为了更加简练。

He was standing over there, pipe in mouth.

Flag on shoulder, the soldier rushed to the top of the building.

但若与with连用，名词前则要加冠词或物主代词。如：

Then, last night, I followed him here and climbed in, with a sword in his hand.

3. 独立主格结构中being 的省略

在下列句子中，being 可以省略，若不省略，则是现在分词短语。

Summer (being) over, the students returned to school.

His first shot (being) a failure, Tom fired again.

Her face (being) pale with anger, she rose to go away.