问题 单项选择题

人们需要用观测或测量得到的原始数据建立数学模型来解决实际问题,这种方法称为数据建模法。在建模过程中,下面关于原始数据作用的叙述,不正确的是()

A.原始数据能够对构建什么样的模型给予提示

B.原始数据可以帮助对模型的参数给出估计

C.模型的合理性取决于原始数据的精确性和完整性

D.原始数据可以帮助检验模型、优化模型

答案

参考答案:C

解析:从实际问题中观察或测量得到的原始数据,通常是不太精确的,也难以完整。需要透过现象看本质,去伪存真,建立比较合理的模型,并求解。建模的过程通常是个渐进的过程。首先,要根据原始数据初步判断应架构什么样的模型。例如,将一批二维数据画在平面坐标系内,观察它们的分布趋势,初步判断采用什么样的曲线进行拟合比较合适。写出大致的曲线函数表达式,其中必然带有待定的参数。然后,通过原始数据来估计模型中的参数。算出了参数后,初步的模型就已经建立。但是,该模型是否符合实际,还需要用原始数据来检验。如果发现有些偏差,则需要调整模型或调整参数。一般的建模过程往往要反复多次经历上述过程,逐步优化得到比较合理、适用的模型,然后再选用适当的数值方法进行求解。针对不太精确、不大完整的原始数据建立起比较合理的数学模型,并获得满意的(不一定最优的)解答,是应用数学工作者能力、水平和经验的体现。

单项选择题 A1/A2型题
阅读理解

阅读理解。

     Eating too much fatty food, exercising too little and smoking can raise your future risk of heart disease. But there is

another factor that can cause your heart problems more immediately: the air you breathe.

     Previous studies have linked high exposure (暴露)to environmental pollution to an increased risk of heart problem,

but two analyses now show that poor air quality can lead to heart attack or stroke (中风)within as little as a few hours

after exposure. In one review of the research, scientists found that people exposed to high levels of pollutants (污染物)were up to 5% more likely to suffer a heart attack within days of exposure than those with lower exposure. A separate

study of stroke patients showed that even air that the U. S. Environmental Protection Agency (EPA) considers to be of "moderate" (良好)quality and relatively safe for our health can raise the risk of stroke as much as 34% within 12 to 14

hours of exposure.

     The authors of both studies stress that these risks are relatively small for healthy people and certainly modest

compared with other risk factors such as smoking and high blood pressure. However, it is important to be aware

of these dangers because everyone is exposed to air pollution regardless of lifestyle choices. So stricter regulation

by the EPA of pollutants may not only improve environmental air quality but could also become necessary to

protect public health.

1. The text mainly discusses the relationship between          .

A. heart problems and air quality

B. heart problems and exercising

C. heart problems and smoking

D. heart problems and fatty food

2. The underlined word "modest" in Paragraph 3 most probably means         .

A. relatively high

B. extremely low

C. relatively low

D. extremely high

3. What can we learn from the text?

A. Eating fatty food has immediate effects on your heart.

B. The EPA conducted many studies on air quality.

C. Moderate air quality is more harmful than smoking,

D. Stricter regulations on pollutants should be made.

4. The author's purpose of writing the text is most likely to       .

A. inform

B. persuade

C. describe

D. entertain