【Abstract】Beijing-Tianjin-Hebei regional cities has achieved stronger increase in speed and scale than ever before， but its bearing capacity has been difficult to load. In this paper， a basic model is used to evaluate the carrying capacity of urban infrastructure，We take three indicators like the infrastructure of transport， the Infrastructure of knowledge spillovers， the infrastructure of public Service， and each indicator contains three different secondary indicators. The infrastructure of transport include the number of transport hubs， the turnover of passengers ，the turnover of goods three index， and the number of transport hubs is the most import index over these index. The infrastructure of knowledge spillovers include three index： the over turnover of local technical market， the proportion of college students and the proportion of primary school teachers and students， and the over turnover of local technical market occupy the highest weight. The infrastructure of public service include the number of wastewaters treatment facilities for every people ， the medical and health institutions for every people and the number of waste-gass treatment facilities for every people. The medical and health institutions for every people occupy the highest weight. According to the regular of the weight of these indicators， we can take corresponding measures to release the pressure of Beijing-Tianjin-Hebei cities， improve the carrying capacity of infrastructure.

【Key words】Beijing-Tianjin-Hebei； Urban carrying capacity； AHP modle

【作者簡(jiǎn)介】苗童欣（1992.3- ），女，漢族，天津商業(yè)大學(xué)，公共管理專業(yè)，研究方向：公共基礎(chǔ)設(shè)施運(yùn)營(yíng)與管理。

1. Introduction

There are two types of based infrastructure commonly used by most of our researchers： the first one is classified by area， which can be divided into rural infrastructure and urban infrastructure. The other one is divided into three categories by their different natures： the nature of the public product， the nature of the private product and the nature of the mixed product. Infrastructure with a public product nature is noncompetitive and non-exclusive in the consumption process， such as rural roads. Such infrastructure can not be provided by the market because the provision of the market is based on a paid purchase and should be provided by the government； the infrastructure with a private product nature is competitive and exclusive， such as electricity and communication network， should be provided by the market， because the market is more efficient in this product； product in the market with a mixed natures of both the nature of public goods and private goods should also be provided by the market.

In this paper， the basic infrastructure is divided into three categories： the first one is the transportation infrastructure， such as： high-speed railway， highway， airport， port， etc. ； the second one is knowledge spillovers infrastructure， such as： universities， technology exchanges and other information highway network and information integration agencies； the last one is the public service infrastructure， such as： sewage treatment facilities， hospitals， kindergartens， primary and secondary schools， oil transport facilities and leisure facilities. Because the public effect of public goods provided by public service infrastructure is similar to that of knowledge spillovers， this paper focuses only on the role of transport infrastructure and knowledge spillovers in the regional economic carrying capacity of Beijing， Tianjin and Hebei.

This paper will study the carrying capacity of infrastructure in Beijing， Tianjin and Hebei from the following aspects. In the second chapter， we will introduce the present situation of urban carrying capacity in Beijing-Tianjin-Hebei region. Chapter 3 will use AHP to establish the evaluation model of urban carrying capacity. The fourth chapter puts forward the countermeasures to improve the carrying capacity of cities in Beijing， Tianjin and Hebei.

2. The Status of Infrastructure Carrying Capacity of Beijing， Tianjin and Hebei

The overall economic and social development of Beijing， Tianjin and Hebei is relatively high， but the regional differences are relatively large， which is not conducive to the harmonious development of Beijing， Tianjin and Hebei regional economic society. From the three levels of education development level， Beijing has the highest per capita education financial investment， followed by Tianjin， while the lowest level is Hebei Province， its per capita education finance investment less than 30% of Beijing， less than 40% of Tianjin， mainly shows in the relatively low level in schools hardware and software basic education facilities， so that unreasonable educational resources led to a large number of students in Hebei want to move to Beijing and Tianjin to seek higher educational resources， which may increase the pressure of education and teaching in thBeijing and Tianjin directly. In addition， the basic social insurance coverage and level of residents in Hebei Province is also lower than that of Beijing and Tianjin， and the basic medical facilities and conditions are relatively poor， increasing the economic and social carrying pressure in Beijing and Tianjin.

With the establish of Beijing-Tianjin-Hebei regional integration of economic and social development planning. The population of Beijing， Tianjin and Hebei is gradually increasing. the regional population of Beijing continues to expand. Population aggregation is relatively large IN Tianjins core region and the economic opening new areas. The concentration of the core city population is relatively high， but the rational distribution of urbanization has not really formed. Therefore， it is necessary to re-establish a new system of urban regional development， re-adjust the regional development policies and effective easing of the population.

3. Construction of Evaluation System for Infrastructure Carrying Capacity of Beijing， Tianjin and Hebei

We would like to use the AHP model to evaluate the urban infrastructure carrying capacity of Beijing， Tianjin and Hebei in this article.

3. 1 Introduction to Analytic Hierarchy Process

When we use AHP model to analyze the basic infrastructures carrying capacity. we need to evaluate the overall goal clearly， the entire evaluation system should be considered seriously. The complex overall goal should be divided into primary indicators and secondary indicators， in order to analyze it easier. When researchers use AHP model， they often divide it in to three levels：

The highest level： the highest level is our overall goal of the article， which only contains only one indicator in this level， when we consider the highest level during the evaluation progress， we need to determine the target and think about the possible results clearly， which may help us avoid simple mistakes.

The middle layer： The middle layer includes the intermediate goals that can be manipulated by researchers， An AHP model often include many intermediate layers， each of which needs to be re-measured on the next layer of indicators.

The bottom layer： the bottom layer is used to measure the target and also need to measure the various indicators， this layer is the most direct way to measure the indicators linked with our goals， so the last layer is also known as the measures layer or program layer， which is necessary in AHP models.

3. 2 Construction of Evaluation System Index

In this paper， the introduction of the basic evaluation of Beijing-Tianjin-Hebei infrastructure system is in Table 1， in order to reflect the meaning of carrying capacity more accurately， we selected three indicators to evolution the basic infrastructure capacity from famous researchers in this paper： the first-level only has one indicator： infrastructure； the second level have 3 indicators， which include transport infrastructure， the infrastructure of knowledge spillovers and the public service infrastructure； these three indicators are classified as follows： The third level indicators under the transport infrastructure are the number of transport hubs， the turnover of passengers， the turnover of goods， The third level indicators under the infrastructure of knowledge spillovers include the over turnover of local technical market， the proportion of college students， the proportion of primary school teachers and students； The third level indicators under the public service infrastructure include the number of wastewaters treatment facilities for every people， the medical and health institutions for every people， the number of waste-gass treatment facilities for every people.

3. 3 Develop AHP Model

When we use the analytic hierarchy model， the first step is need to build a comparison matrix that compares the metrics at each level to determine the relative importance of each indicator， we usually use numbers 1-9 to indicate the relative importance， and each number represents a different degree of importance， which is given in Table 2 below.

According to the above comparative analysis progress， we can get a judgment matrix. We use an expert questionnaire to collect the opinions of professionals on the importance of the indicators above， and collect their suggestions about the importance of the relevant indicators when evaluate the urban basic infrastructure capacity. By collecting the score data and take the average， we can get the judgment matrix.

For example， the judgment score and judgment matrix of the target layer is as follows：

By averaging the above data， we obtain the evaluation matrix of the importance of the target layer， as shown in Table 4 below.

Similarly， the following three judgment matrices are available. Judgment matrix for the infrastructure of transport， the infrastructure of knowledge spillovers and the infrastructure of public service are in Table 5， Table 6， Table 7.

Judgment matrix for the infrastructure of knowledge spillovers include the over turnover of local technical market， the proportion of college students， the proportion of primary school teachers and students are in Table6.

Judgment matrix for the infrastructure of public service include the number of wastewaters treatment facilities for every people， the medical and health institutions for every people， the number of waste-gass treatment facilities for every people are in Table7.

3. 4 Single Level Sort and Consistency Test

The first step： Calculate each row of elements of A：Mi

The second step： Calculate the mth root of the Mi

The third step： normalize the vector a = （a1， a2，. . . ， am） T，

The last step： Find the maximum eigenvalue of A

As shown in Table 8 below， this is the relationship between the consistency index R. I and the matrix order in the analytic hierarchy process.

While in our calculation， all the matrix order is 3， we can see R. I as 0. 52.

（1）Verify the consistency of the target layer matrix A

We can see that

The maximum eigenvalue of the target layer matrix A can be calculated as below：

Thus， the target layer matrix A satisfies the consistency check.

（2）Test the consistency of first order index matrix B1

At this point， the largest eigenvector of the infrastructure of transport index is 3. 063， and we can make a consistency judgment.

At this point， the matric B1 through the consistency test， we can know that the determine of the importance of the three secondary indicator under the infrastructure of transport index is right.

（3）Test the consistency of first order index matrix B2

By calculating the maximum eigenvalue of the infrastructure of knowledge spillovers matric B2 and making a consistent judgment， we can obtain that：

Therefore， the matric B2 of the infrastructure of knowledge spillovers passes the consistency check.

（4）Test the consistency of first order index matrix B3

By calculating the maximum eigenvalue of the infrastructure of public services matric B3 and making a consistent judgment， we can obtain that：

Therefore， the matric B3 of the infrastructure of public service s passes the consistency check.

（5）Calculate the weight of the indicator

Through the calculation of the weight index， we get the weight value of each index， among which the index about the infrastructure of transport is the most important， occupies the weight of 0. 45， the index about the infrastructure of knowledge spillovers occupies the weight of 0. 29， and the index about the infrastructure of public service only occupies a weight of 0. 26. It can be seen that the infrastructure of transport is the most important influencing factors when we want to evaluate the basic urban infrastructure carrying capacity of Beijing， Tianjin and Hebei. It is undeniable that traffic often occupies an important position in a city. A convenient city can provide its residents with a better living environment， make it easier for people to go out， and it also may help a city to attract more investment and create a favorable environment for its longer development. Good traffic is one of the basic requirements for a city， which also should be considered first when we want to evaluate an urban infrastructure carrying capacity.

3. 5 Total Level Sort and Consistency Test

Through the calculation in Table 9， we get the corresponding weight of the first-level index and its corresponding secondary index， and the weight of the secondary index is the weight of the secondary index multiplied by the weight of the corresponding first- The overall ranking of the hierarchy is shown in Table 10 below.

Through the calculation of urban Infrastructure carrying capacity by using Analytic Hierarchy Process， the number of transport hubs is one of the most important indicator when we calculate cities basic instruction carrying ability， This indicator can reflect a citys traffic infrastructure clearly， involving the road design， bus routes， subway routes， high-speed rail， trains and aircraft and other means of transport， a city can get development only when it have good transportation capacity， In addition， the assessment of basic medical equipment is also very important， with the improvement of peoples living standards， good medical facilities can provide a platform for people to have better treatment when they are ill. The number and quality of the universities owned by a city is also an important indicator of the carrying capacity of basic infrastructure of this area， which occupy a weight of 0. 18， we all know that good universities can cultivate more talents for the society and promote the development and progress of the society.

4. Advice on Improving the Capacity of Urban Infrastructure

4.1 Actively Introducing International and Private Capital

The experience of the developed countries shows that infrastructure construction should not be monopolized by the government， because monopoly is the last efficient way of resource allocation； but it also can not be completely improved by the market， which will lead to inadequate supply of public goods. The optimal investment and financing of infrastructure construction is the way of government-led， international capital and private capital. The government should do the following things： first， make the relevant laws clearly， protect the legitimate rights and interests of the private sector and international investors and the state-owned enterprises equal investment environment；， Second， give tax incentives to private capital， the international capital investment toward infrastructure construction， Third， arrange a preferential lending rates； Fourth， the Ministry of Railways should release high-speed rail ticket pricing， and give it to market； Fifth， for profits generated by the Ministry of Railways， the Ministry of Railways， Infrastructure operations should reinvest in new infrastructure projects.

Private capital has the most obvious effect on knowledge spillovers in infrastructure construction， our country can learn from US to build a National Technical Information Service Center and other institutions， develop an information network. Private capital should act as the main force of science and technology transformation. Government should take a series of preferential measures in the administrative examination and approval procedures to simplify the tax relief and other aspects， to induce private technology information release platform， angel investment fund companies， technology incubators， management consulting， planning and design， research and development services， standard applications， entrepreneurship counseling agencies， Intellectual property agencies continue to germinate under our market mechanisms.

4.2 Pay Attention to Knowledge Spillover and Public Infrastructure Construction

As we all know that the basic public services should be equal to people in a city， Beijing is the capital of our country and has a large number of good education and medical services resource， government need to encourage and support the Beijings elite schools， hospitals spread to the surrounding cities， in the process of the promotion of industrial transfer and population easing， it may gradually narrow the gap between different levels of public services. Rational people pursue their own interests， and the maximization of their own welfare is an important part of the maximization of benefits. Only when a city can provide people good public service infrastructure， the population can spread， the central citys bearing capacity can be relieved. Thus， the spread of knowledge spillovers and public service infrastructures is a prerequisite for industrial transfer. Beijing， Tianjin and Hebei government should coordinate planning， coordination with relevant ministries， to guide the major colleges and universities in Beijing and Tianjin to establish a branch institution in Hebei Province， to encourage the major hospitals located in Beijing， Tianjin to establish a branch institution in Hebei Province.

4.3 Reconstructing the Population and Economic Structure System

Based on the consideration of economic and social benefits and ecological and environmental benefits， we need to balance the proportion of population， resources and environment， and implement the coordinated development strategy of Beijing-Tianjin-Hebei region. First of all， we need to take differentiated development measures according to the economic development strength scientific and technological innovation capacity of Beijing， Tianjin and Hebei， ； Secondly， we should strengthen the integration of Beijing-Tianjin-Hebei regional development strategy， such as the release of household registration management system； Thirdly， develop Beijing-Tianjin-Hebei regional economic development zone supported by innovation， regard Beijing and Tianjin as the economic development leader and the main line and Hebei Province as the economic development of the rear base； Finally， When we speed up the integration of Beijing-Tianjin-Hebei regional urbanization process， we should stand in the overall height from the population， ecological system， infrastructure and other aspects of planning and promotion. For the two core cities—— Beijing， Tianjin， government need change the mode of urban economic development and adjust their economic structure， focusing on cultivating new industries and technological innovation industries， and then promote it in Hebei Province.

5. Conclusion

With the development of modern life， Beijing-Tianjin-Hebei regional cities has achieved stronger increase in development speed and scale than ever before， while many of us may consider a question： whether these cities basic instruction can beer the development. This article aims to build a simple hierarchical analysis model to help the government and other researchers to estimation their urban carrying capacity better.

Three indicators are used as level 1 indicator， like the infrastructure of transport， the Infrastructure of knowledge spillovers and the infrastructure of public Service， and each indicator contains three different secondary indicators. The infrastructure of transport include the number of transport hubs， the turnover of passengers， the turnover of goods three index， and the number of transport hubs is the most import index over these index. The infrastructure of knowledge spillovers include three index： the over turnover of local technical market， the proportion of college students and the proportion of primary school teachers and students， and the over turnover of local technical market occupy the highest weight. The infrastructure of public service include the number of wastewaters treatment facilities for every people， the medical and health institutions for every people and the number of waste-gass treatment facilities for every people. The medical and health institutions for every people occupy the highest weight.

According to the regular of the weight of these indicators， we can take corresponding measures to release the pressure of Beijing-Tianjin-Hebei cities， introducing international and private capital， pay attention to knowledge spillover and public infrastructure construction and reconstructing the population and economic structure system to improve the carrying capacity of infrastructure.

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