问题 阅读理解

第三部分阅读理解(共20小题;每小题2分,满分40分)

阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

  Many people will remember the flight of the space shuttle(航天飞机)challenger,in June,1983. The achievement of Sally Ride,America’s first woman astronaut to fly into space,made this flight especially memorable. Students from two Camden, New Jersey, high schools, however, are probably to remember Norma rather than Sally whenever they think about the flight.

  Norma didn’t travel alone. She brought about 100 companions along with her. Norma was an ant,a queen ant who,with her subject,made up the first ant colony(群体)to travel into space. The ants were part of a science experiment designed by students to test the effects of weightlessness on insects.

  The equipment designed by the students for their colony functioned perfectly throughout the long space trip. The young scientists and their teachers were very sad to find that their insect astronauts had all died at some point before the container was returned to the school and opened. The problem didn’t occur in space,but on the ground after challenger had landed. The container remained in the desert for nearly a week before the ant colony was moved. The hot,dry desert air dried out the colony’s container and the ants died from lack of moisture(水分).

  The project was termed success because it did provide useful information. Students will continue their efforts to pinpoint(精确找到)what went wrong. They will try to prevent the same difficulties from reoccurring on future missions. They don’t want to be discouraged either by the demise of the ants or by the $ 10,000 shuttle fare they will have to pay to send the next colony of ants into space.

51.What does the passage mainly tell us?

A.Sally Ride,America’s first woman astronaut.

B.How to keep ants alive in space.

C.How to make equipment for insects in space.

D.An experiment with ants in space.

52.According to the passage, we know that the underlined word“demise”is another word for“_____”.

A.death               B.colony

C.insect              D.moisture

53.We don’t think the project was a failure. This is because_____.

A.everything went as smoothly as expected

B.the students had pinpointed exactly the reason

C.something important had been learned

D.the students had succeeded in the experiment

54.We can conclude that ants _____ on the next space trip.

A.will have to be kept alive in a container full of water

B.will have to be sent into space with the first woman astronaut

C.should be put into a container where there is enough food

D.should be put into a container which is not too dry

答案

小题1:D

小题2:A

小题3:C

小题4:D

         

选择题
问答题 案例分析题

实时系统

博学公司承担了一项嵌入式系统软件开发项目。该项目主要用于车载电子系统中监视发动机及燃油系统等系统工作状况,并通过综合仪表显示给驾驶员。经过多次与用户沟通,形成以下技术要求:

(1)本项目的硬件平台由主处理机模块和多种接口模块组成,底板采用标准VME总线(硬件结构图见图12-8),具体硬件模块配置如下:

①主处理机模块(CPM)采用PowerPC755,主频266MHz,配有SDRAM存储器和FLASH存储器;提供一个定时/计数器;支持16级中断和二级Cache。

②输入输出模块(IOC)支持16路RS422接口信号,传输速率不低于115.2kbps,IOC模块与CPM模块的数据交换采用64KB双端口存储器。

③离散量接口模块(DAM)支持64路开关型离散量输入输出接口;2路频率量输入;12位A/D转换器和12位D/A转换器。

④图形处理模块(GPM)用于显示图形,支持OpenGL标准接口软件。

⑤MBI模块主要提供1553B外总线接口,PSM为电源支持模块。

(2)本项目软件主要工作在CPM模块中,完成对外部设备的数据采集、分析和相应的控制,将监视结果以图形方式显示给驾驶员。该系统的软件主要包括外部接口驱动软件、VME数据传输软件、处理软件、图形显示和外总线(1553B)数据交换软件。要求数据的采集必须确保每帧数据无丢失,并在本帧内完成数据的处理工作,本帧信息显示给驾驶员的时刻最晚不能超过下一帧。详细的技术要求如下:

①16路RS422接口主要完成对汽车燃油系统、动力系统和驾驶员命令的数据采集与控制。RS422数据传输格式将以32B为基本数据块,分别以20ms、40ms、60ms、1s这4个不同周期交换数据。

②64路离散量数据主要监控发动机工作状态,要求每10ms采集一次,并在下一个10ms周期内将发动机状况显示到驾驶员座舱。

③多路模拟量数据主要采集发动机转速、油量及汽车的其他数据,为驾驶员监控汽车状态提供必要的量化数据。模拟量数据的刷新频率为1s。

④外总线(1553B)主要完成该系统与汽车其他电子系统的数据交换。

公司将本项目交给项目主管李工实施,要求李工按技术要求完成本项目的软件设计工作,公司根据合同关于"数据的采集必须确保每帧数据无丢失,并在本帧内完成数据的处理工作,本帧信息显示给驾驶员的时刻最晚不能超过下一帧"的要求,提醒李工设计中重点考虑整个系统的实时性问题。李工完成设计后,提交公司评审,会上就李工设计中存在的缺陷展开了激烈讨论,最终达成一致。

如果CPM模块中采用了嵌入式实时操作系统,请根据本项目的需求,用300字以内的文字说明CPM模块中数据采集任务应如何划分?系统对任务调度的最小调度周期如何计算?各个任务周期及优先级如何定义?