问题 解答题

制20节底面半径为5厘米、长为40厘米的圆柱形铁皮通风管,至少要用多大面积的铁皮?

答案

(3.14×5×2×40)×20,

=(3.14×400)×20,

=3.14×8000,

=25120(平方厘米);

答:至少要用25120平方厘米的铁皮.

单项选择题

 在数据库系统中,“事务”是访问数据库并可能更新各种数据项的一个程序执行单元。为了保证数据完整性,要求数据库系统维护事务的原子性、一致性、隔离性和持久性。针对事务的这4种特性,考虑以下的架构设计场景: 假设在某一个时刻只有一个活动的事务,为了保证事务的原于性,对于要执行写操作的数据项,数据库系统在磁盘上维护数据库的一个副本,所有的写操作都在数据库副本上执行,而保持原始数据库不变,如果在任一时刻操作不得不中止,系统仅需要删除副本,原数据库没有受到任何影响。这种设计策略称为()。 事务的一致性要求在没有其他事务并发执行的情况下,事务的执行应该保证数据库的一致性。数据库系统通常采用()机制保证单个事务的一致性。 事务的隔离性保证操作并发执行后的系统状态与这些操作以某种次序J顿序执行(即可串行化执行)后的状态是等价的。两阶段锁协议是实现隔离性的常见方案,该协议()。 持久性保证一旦事务完成,该事务对数据库所做的所有更新都是永久的,如果事务完成后系统出现故障,则需要通过恢复机制保证事务的持久性。假设在日志中记录所有对数据库的修改操作,将一个事务的所有写操作延迟到事务提交后才执行,则在日志中(),当系统发生故障时,如果某个事务已经开始,但没有提交,则该事务应该()。

假设在某一个时刻只有一个活动的事务,为了保证事务的原于性,对于要执行写操作的数据项,数据库系统在磁盘上维护数据库的一个副本,所有的写操作都在数据库副本上执行,而保持原始数据库不变,如果在任一时刻操作不得不中止,系统仅需要删除副本,原数据库没有受到任何影响。这种设计策略称为()。

A.主动冗余

B.影子拷贝

C.热备份

D.多版本编程

阅读理解

.

Facing the threat of the Internet, the traditional newspaper is thinking about what it can do to meet the challenge. To make teens get into the habit of reading, the French government is considering what kind of efforts it should pursue.  It seems that the two questions have nothing to do with each other, but a recent announcement made by French President Nicolas Sarkozy has connected these two issues together. The announcement gives an answer to both of them.

.  President Nicolas Sarkozy announced a rescue plan for France' s ailing print media, including measures to save printing and distribution costs. The plan also gives French teenagers a surprise as their 18-year-old birthday gift: France will offer all 18-year-olds a free daily copy of the newspaper of their choice.

"The habit of reading the press should start at a very young age," Sarkozy said, presenting the conclusion after talking to a group of journalists and officials in Paris. The President said the newspapers themselves would provide free copies for 18-year-olds, while the state would cover the cost of delivering them to many thousands of homes.       

The plan is an attempt to introduce teenagers, who frequently only get their news online, to the delights of the printed world.  A similar idea has been tested by L'Ouest-France (法兰西部报) over the past few years.  It offered some 18 to 24-year-olds a free paper once a week for a year.  L' Ouest-France reported that 15% of young people wanted to continue with a paid subscription after the year was over.

People in France welcomed the plan which should get more kids interested in current affairs and make reading be a pastime, as well as rescue the newspaper industry.

63. What does the underlined word " ailing" (in Paragraph 2) probably mean?

A. newly established       B. in difficult situations

C. most popular             D. warm-hearted

64. It can be inferred from the passage that           .

A. the government will pay for the delivery of newspapers to 18 -year-olds

B. the government will buy newspapers for 18-year-olds for one day

C.  some of the government officials are against the plan

D. President Nicolas Sarkozy would like to help the government

65. What is people' s reaction to the plan in France?

A,  They think it a waste of money.

B. They will buy newspapers themselves for 18-year-olds.

C.  They think highly of it and support it:.

D. They are worried the young will leave the Internet.

66. Which of the following can serve as the best for the passage?

A. A surprising plan from the President

B.  Help rescue the newspaper industry

C. Form the reading habit for the young

D. Free newspapers fly to teens