发布时间 : 星期一 文章2016美赛E题参考答案更新完毕开始阅读9f36d621ba0d4a7303763aaa
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Figure 4: Annual average growth rate of population
The fitting results could give us the fact that the annual average growth rate of population
Presented a negative correlation with time, on the other hand, the growth of the population in North China will be more slower, even there is zero growth at some time. This has a great relationship with the long-term family planning in China.
Put a??0.000734,b?0.017604into the complex model (4), we get the model of population growth in the North China.
2??????0.000734t0?0.000734t2?N(t)?N0?exp???0.017604t0????exp?0.017604t??22?????? Choose the initial conditionN(17)?147010, therefore
??0.000734t2?N(t)?147010?exp(1.043)?exp?0.017604t??2??
Sincea??0.000734?0,b?0.017604?0, we obtain the max value of N(t)b?24. This represents that the population of the North China will reach azero growth in 2032. Using the software Matlab to draw the curve of the population growth of the North China. See Figure 5:
whent??
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Figure 5:The curve of the population growth in the North China
According to the Figure 5, the data will reach zero growth in 2032 and turn to run downward. At the same time, the current growth rate of population is decreasing. After analyzing the in-depth causes, the conclusion has been drawn in two aspects. Culture is the first cause. With the development of scientific and educational standard, people receive a lengthened education which results in the postponing of average marriage age. More attention will be paid to the development of all qualities one should have and the next generation as well. Lowering the growth rate and uplifting educational quality. Raising only one child rather than raising too many with the limited money. These are why the population growth did not see effective and profound change when China lifted the restriction on one-child policy in 2014. The disconcerted population construction of northern China is another cause such as the aging population. According to the statistics, the old over 60 years take up 9.5 percent of the population in northern China which leads to the increasing of the local death rate, another cause affecting the natural increasing of population.
According to the average volume-36.5 cubic meters[5]-of water using in northern China, we can get the water using model:
??0.000734t2?A(t)?5.3659?exp(1.043)?exp?0.017604t??2??
A(t)unit: billion cubic meter
According to the analysis of the model in task one with the data of Table 5, we
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can get industrial water using model through Matlab programming
B(t)?0.1199t?4.4068
The approximate coefficient is 0.9735 which close to 1, Model fits well. The agricultural water using model
C(t)?0.1681t?19.8899
The approximate coefficient is 0.9522which close to 1, Model fits well. The ecological water using model
D(t)?0.1642t?0.585
The approximate coefficient is 0.9648 which close to 1, Model fits well.
The statistics of the water usage in northern China from 2008 to 2014 are displayed in diagram 1
The industrial, agricultural and ecological water usages are displayed,see Figure 6:
Table 5:the water usage in the North China from 2008 to 2014
Unit: billion cubic meter
year 2008 2009 2010 2011 2012 2013 2014 industry 4.77 4.38 4.56 5.11 5.02 5.12 5.25 usage agriculture ecology 20.05 0.78 20.25 0.87 20.37 1.07 20.57 1.26 20.73 1.41 20.90 1.57 21.06 1.73
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Figure 6:industrial, agricultural and ecological water usage
According to Figure 6, the agricultural water usage is on the rise much more than industrial and ecological water usage. Also, the growth rate is extremely high in accordance with the demand of agricultural production. The development of science and technology improves the output of agriculture and increase the demand of water as well. The low growth rate of industrial and ecological water usage comes from the intensive efforts put in environmental protection. The control on industrial sewage lowers the demand of water in this sector. The rise of the proportion of ecological water usage explains that the government in the North China put increasing emphasis on ecological water-supplying project. This is of great significance in improving local environment.
We can get the water consumption model in the North China from population, industrial, agricultural and ecological water using models.
??0.000734t2?E(t)?5.3659?exp(1.043)?exp?0.017604t???0.4522t?24.88172??
7.2Water supplymodel in the North China