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Mathematical modeling -- what is mathematical modeling
2022-07-07 15:04:00 【WangLanguager】
This paper mainly introduces two examples of data modeling : Make dumplings 、 Roadblock
Introduce the whole process of data modeling
Introduce the basic methods and steps of mathematical modeling
One 、 introduction
mathematics : The foundation of each discipline , A tool for social progress
Solve any practical problem with mathematical methods , We must build a bridge between practice and Mathematics .
To solve the process : Practical problems are transformed into mathematical problems ; Solving mathematical problems ; Mathematical solutions return to practical problems .
This process of solving is called mathematical modeling , That is to establish a mathematical model for practical problems .
Two 、 Examples of mathematical modeling 1: Make dumplings
Usually ,1kg Noodles ,1kg Stuffing , package 100 A dumpling ( Or Tangyuan ), today 1kg The face does not change , But the stuffing ratio 1kg More , ask : It should be more packages ( Each is smaller ), It's better to pack a few less ( Each is bigger )?
1、 problem : Round area A skin of , Pack into volume
Dumplings ; It is divided into n Skin , The area of each small circle is :
, The wrapped volume is :
Dumplings .
and
Who is big ? 【 qualitative analysis 】
Than
How much larger ? 【 quantitative analysis 】
2、 hypothesis (1)、 The thickness of dumpling skin is the same (2)、 The shape of dumplings is the same
modeling :=
(1)
,
, among
For the radius of dumplings , be
(2)
,
, among
For the radius of small dumplings , be
(3)
from (1)、(2)、(3) Available :
application :,
yes
Of
times .
if 100 A dumpling can be made 1kg Stuffing , be 50 A dumpling can be made kg Stuffing
3、 The basic key steps of dumpling modeling process
(1) In mathematical language ( Volume and surface area ) Indicates a real phenomenon ( Stuffing and skin ).
(2) Make simplified and reasonable assumptions ( Same thickness , Same shape ).
(3) Use the inherent law contained in the problem ( Volume 、 Geometric relationship between surface area and radius )
The results of this model can be used to explain many phenomena in daily life .
Over time, the unit price of large package goods is cheaper than that of small package goods .
3、 ... and 、 Examples of mathematical modeling 2: Car barricade
1、 background : campus 、 In the middle of the road in the residential area , Roadblocks are often set up to limit the speed of cars .
2、 problem : If you want to limit the speed to no more than 40km/h, How far away should a barricade be set ?
3、 analysis : The speed of the car passing the barrier is close to zero , Accelerate after passing the barrier , The car accelerated to 40km/h when , Slow down because there is the next roadblock ahead , The speed at the barricade is close to zero .
So fast 、 The deceleration cycle alternates to achieve the purpose of speed limit .
4、 hypothesis : The car performs equal acceleration and equal deceleration between two adjacent roadblocks .
You need to get the acceleration and deceleration of the car .
Method 1 : Access to information , Method 2 : To test
(1) Test data of accelerating car
Speed (km/h) | 0 | 10 | 20 | 30 | 40 |
Time (s) | 0 | 1.6 | 3.0 | 4.2 | 5 |
(2) Test data of vehicle deceleration
Speed (km/h) | 40 | 30 | 20 | 10 | 0 |
Time (s) | 0 | 2.2 | 4.0 | 5.5 | 6.8 |
5、 modeling : The distance the car accelerates S1, Time t1, The acceleration a1
The distance the car slows down S2, Time t2, deceleration a2, The speed limit is :
be :,
,
,
Total distance traveled between adjacent roadblocks :
Given , From the test data a1 and a2, You can figure it out S.
The total distance traveled by vehicles between two adjacent roadblocks is designed as the distance between roadblocks .
Parameter estimation : The relationship between speed and time during design driving is :, Test data , Then use the least square method to calculate :
be :
The distance between roadblocks is 65 rice
6、 The basic key steps of barrier spacing modeling
(1) Make simplified and reasonable assumptions ( Wait for acceleration, wait for deceleration ).
(2) Use the inherent law contained in the problem ( Time 、 distance 、 Speed 、 The physical relationship between accelerations )
(3) Estimate the parameters of the model according to the test data ( Acceleration and deceleration )
Mathematical modeling used in barricade design can also be used to solve other problems , for example : Design the height of the barricade 、 The shape of the barricade .
Four 、 What is a mathematical model (Mathematical Model) And mathematical modeling (Mathematical Modeling)?
1、 mathematical model : For a real object , For a specific purpose , According to its inherent law , Make the necessary simplifying assumptions , Use appropriate mathematical tools , Get a mathematical structure .
2、 mathematical modeling : The whole process of establishing mathematical model
3、 The whole process of mathematical modeling :
Information of real objects ——>【 describe 】——> mathematical model ——>【 solve 】——> Solutions to mathematical models ——>【 explain 】——> Solutions to real objects
two “ translation process ”: Real phenomena are translated into Mathematics Model , The solution of mathematical model is translated into the solution of real phenomenon .
practice ——> theory ——> practice
5、 ... and 、 The basic analysis method of mathematical modeling
(1) Mechanism analysis : Understanding of the characteristics of objective things , The quantitative law of internal mechanism .【 White box model 】
(2) Test and analysis : Statistical analysis of measured data , The model that best fits the data .【 Black box model 】
(3) Mechanism analysis 、 Test and analyze the combination of the two : Mechanism analysis and establishment of model mechanism , Test and analyze to determine the model parameters .【 Grey box model 】
Mechanism analysis is mainly learned from case studies , Modeling mainly refers to mechanism analysis .
6、 ... and 、 Basic steps of mathematical modeling
Model preparation ——> The model assumes ——> Model composition ——> Model solving ——> model analysis ——> Model test ——> Model application
If the model test finds that the model is not suitable , The model assumptions need to be corrected again
7、 ... and 、 Summary of content
Have a preliminary understanding of what mathematical modeling is
(1) Mathematical modeling refers to transforming practical problems into mathematical problems , Then solve the mathematical problem , The whole process of returning to practical problems after solving mathematical problems and constantly revising mathematical models .
(2) Mathematical modeling widely exists in all fields of social life .
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