On older ships, temperature maintenance can be made easier by increasing the __of recirculated to fresh air（）

A.quantity

B.ratio

C.percentage

D.permillage

答案

B、ratio

发布时间：2024-04-23

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第1题

Titanic: Sinking the Myths"Practically Unsinkable"As soon as the waves of the North Atlant

Titanic: Sinking the Myths

"Practically Unsinkable"

As soon as the waves of the North Atlantic closed over the stern of RMS Titanic on 15 April 1912, the myths began surrounding her design, construction and transatlantic voyage. The Titanic disaster today is a classic tale, a modern folk story, but like all folk stories our understanding of what really happened has been clouded by the way the disaster has been recounted over the years.

It was said that the builders and owners of Titanic claimed she was "unsinkable". The claim actually made was that she was "practically unsinkable" close enough, but nevertheless an unfortunate statement and one which would haunt both builder and owner for years.

Titanic, the largest vessel in the world when she entered service in 1912, was neither the finest nor the most technically advanced of her day. Size, seldom an indication that something is better, was the only record she held. The ships that Titanic, and her slightly older sister Olympic, were designed to compete with were the Cunard liners Lusitania and Mauretania, which entered service in 1907. Designed and built as record breakers, both held the coveted "Blue Riband" for the fastest Atlantic crossing. It was built principally from lessons learnt from advances in warship construction, but most importantly was powered by steam turbines driving quadruple screws, fitted with a large balanced rudder(方向舵), making them faster than the competition and easier to manoeuvre. This was a giant leap forward in marine engineering, comparable to the advances made in 1969 with the introduction of the Can corde supersonic aircraft.

Achille's Heel

Building ships this large led to inevitable compromises. Titanic adopted tried and trusted methods for her design and construction. No risks were taken with the choice of engines which were enlarged versions of the propulsion system first used experimentally in Laurentic, another White Star liner, in 1909. The triple screw vessel had proved that two expansion engines feeding exhaust steam into a low pressure turbine were more economical than vessels using expansion engines or turbines alone.

Titanic's hull(船体) and upper works were also enlarged versions of designs refined over several decades. Her stern(船尾),with its high graceful Counter and long thin rudder, was an exact copy of an 18th-century sailing ship, wrought in steel, a perfect example of the lack of technical development. Compared with the rudder design of the Cunarders, Titanic's was a fraction of the size. No account was made for advances in scale and little thought was given to how a ship, 852 feel in length, might turn in an emergency or avoid collision with an iceberg. This was Titanic's Achilles heel.

Speed

These design differences meant Titanic would never be able to challenge the speed or manoeuvrability of the Cunarders, but this did not matter. White Star had given up all thought of speed records more than a decade be- fore, in 1899, with the introduction of Oceanic, a ship given the title "Clowning Glory of the 19th Century". It was justly deserved, for her interiors were, the finest ever created by the Belfast shipbuilder of Harland & Wolff.

White Star could not afford to waste the same expense on their new ship Titanic, which was much larger than Oceanic. Titanic, nevertheless, was a fine, well-built vessel, with large public rooms and finely-appointed suites for those travelling in first class. However, there were many other ocean liners built in Britain, France and Germany which were technically superior and had stunning interiors.

Speed plays a major part in the continuing story of Titanic. It is often said she was trying to make a record on her maiden voyage, attempting to arrive ahead of schedule in New York. Not true. Not all of Titanic's boilers had been lit and besides this she was sailing on the l

A．Y

B．N

C．NG

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第2题

从串口接收缓冲器中将数据读入到变量temp中的C51语句是（)。

A.temp=SCON

B.temp=TCON

C.temp=DPTR

D.temp=SBUF

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第3题