How to understand the characteristics of blockchain decentraliza

7. Due to the use of Distributed Accounting and storage, there is no centralized hardware or management organization, the rights and obligations of any node are equal, and the data blocks in the system are jointly maintained by the nodes with maintenance function in the whole system
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8. Research on corridor effect in urban landscape ecological planning -- a case study of Beijing urban area Zong Yueguang (Department of resources and environmental science, Beijing Normal University, Beijing 100875) abstract urban corridor can be divided into two types: artificial corridor and natural corridor. Through the displacement of corridor benefit dividing point and corridor model, the deformation process of natural corridor apex and front is analyzed. Driven by pure economic interests, cities have a tendency to spread the pie in nature. According to the principle of corridor effect, it is proposed that in the process of Beijing's development towards an international metropolis, we should seize the favorable opportunity of building expressways, light rail lines and subway trunk lines, and transform the traditional decentralized group urban landscape into a star decentralized group urban landscape, that is, the urban built-up area expands outward along the main traffic trunk lines like the tentacles of starfish, On these axes, a series of discontinuous scattered groups, enclaves, sub cities or satellite cities are generated by the division of green space, and wedge-shaped green space inserted into the center of the city is formed between the long axis of the star, which constitutes the landscape pattern of alternate distribution and organic dispersion of artificial corridors and natural corridors. Key words: corridor effect, urban landscape structure, ecological planning. THE CO RR I R EFFECTS IN URBAN ECOLO G ICAL DO LAND SCAPE PLANN ING ——A CASE STUDY O N BE IJ ING ZON G Yue 2Guang ( T he D ep a rtm en t of R esou rces and E nv ironm en ta l S cience, B eij ing N orm a l U n iversity , B eij ing , 100875, Ch ina ) AbstractTw o typ es of u rban co rrido r, a rt ifit ia l co rrido r and na tu ra l co rrido r, is stud ied. T he co rrido r effect concep t is exam ined in the u rban land scap e st ructu re. T he ana lysis is . cep t“co rrido r benefit ”T he dem a rca t ion line betw een a rt ificia l co rrido r and na tu ra l co rri2 do r is the syn thet ic benefit po in t from the theo ry ana lysis. It is suggested tha t there a re . a na tu ra l co Two a rtifit ia l Co rrido RS in p a rticu La R, it is necessary to avo id a ra l Co rrido rs. t he sp a t ia l g row of 8 Co rrico RS is eximed in the cen t ra La rea of Beijing. Two sun their IC benefit Po in t s on the Cu rves of d istance 2 ecay function s fo r the ex istence of D, Date of receipt of the revised version: 1997212210. m u lt ip le fo rm to a sta r shap ed m u lt ip le fo rm in o rder to avo id the m a ssive g row th of the bu ilt 2up a rea. of na tu ra l co rrido r effect s. Idea s of hum an and na tu ra l in p erfect ha rm ony is u sed in the u r2 ban eco log ica l land scap e p lann ing. T he land scap e st ructu re of B eijing shou ld change from a ? 1994-2009 China Academic Journal Electronic Publishing House. All rights reserved. undertaken by u sing a D istance 2 ecay Funct ion, w h ich is ba sed on idea concern ing the con 2 D h igh den sity of a rt ificia l co rrido rs and to im p rove socia l and econom ic benefit s in the na tu 2 T h is inner city study a t tem p t s to rep lica te severa l find ing s of g reen a rea and w a ter system a s a fram ew o rk a roud and th rough the cen ter of the city com b ined w ith th This paper is supported by the Fulbright foundation and the National Ecation Commission fund for returned students. I sincerely thank the Graate School of urban design of Harvard University for its support. http://www.cnki.net  In the next few decades, the shock wave of China's urbanization will exceed any period in human history. Due to the huge population base and the acceleration of urbanization, the impact of floating population on cities, especially mega cities, will be more intense and lasting, The resulting series of urban problems may be more advanced and severe than people expected. Taking Beijing as an example, since the founding of the people's Republic of China, Beijing's urban planning has adopted the decentralized group layout. The overall layout principle of "one center, ten groups" was further determined in the urban master plan of 1992. Due to the rapid expansion of the central urban area of Beijing since the reform and opening up, the green isolation area between the central and peripheral areas has been constantly eroded. According to the relevant literature [1], the total area of green isolated area in 1958 was 314km2, and only 244km2 was left in 1993. If we subtract 120km2 from the planned land for urban and rural construction in the future, the area of green isolated area including farmland, vegetable land, water surface and forest land is less than 130km2, of which only 20km2 is really used for park green space. By 1997, more than half of the 10 scattered groups had been connected to the urban area more or less, and some of them had only a few hundred meters of green belt. If we continue to develop in this way, the "decentralized group" will exist in name only, and it is inevitable for the central urban area to spread the pie. In the face of the above grim reality, this paper discusses the way to realize the sustainable development of metropolitan area from the perspective of urban landscape structure optimization by using the principle of urban corridor effect to understand and master the law of metropolitan spatial expansion. In the 1970s, berry studied the relationship between air pollution and urban form, and found that in concentric circle, belt, grid, ring and star urban form, star urban landscape had the best effect on eliminating air pollution [3]. Since the 1980s, New York, London, Tokyo, Paris, San Francisco and other cities have developed into international metropolises e to the integration of international economy, the rection of transportation cost and the development of information superhighway. Many scholars put forward the concept of metropolitan ecotone, diffusion and backwave effect, corridor effect and so on. Among them, Jeff et al. Took Russia as an example to analyze the population diffusion, backwave and corridor effect in metropolitan ecotone. It is found that the population fluctuation in metropolitan ecotone points to the growth center and growth axis under the effect of central city and corridor effect, The intensity of corridor effect changes with the level of corridor, and corridor determines the urban landscape structure and population spatial distribution pattern, which provides a new idea for the optimization of metropolitan landscape structure [4]. Forman, a famous American landscape architect, divides the corridor structure into three types: linear corridor, belt corridor and river corridor. The functions of corridor mainly include transportation, material and energy exchange, environmental protection and aesthetic value [5]. On the basis of previous work, this paper divides urban landscape corridors into two categories: artificial corridor and natural corridor (AC and natu). 2 artificial corridor is mainly traffic trunk, and natural corridor is mainly River and vegetation belt (including artificial natural landscape). Corridor effect (RA l Co rrido R, n c). There are circulation effect and field effect. This paper focuses on the field effect of the corridor. The corridor effect field includes the corridor itself and its radiation area, which is collectively referred to as the corridor area. 2 the basic characteristics of urban corridor effect 211 two kinds of corridor effects in urban landscape planning 212 the research on the decreasing rate and dividing point of corridor benefits shows that the landscape structure of many mature megacities in China and the world is an annular spider web structure, such as London, Paris, Moscow, Berlin, Tokyo, Shanghai, Beijing, Tianjin, etc. Urban landscape is the result of the development, construction and transformation of urban space under the comprehensive effect of natural, social and economic forces in a considerable period of time. In theory, it can be proved that from the perspective of simple economy, under the joint action of urban center and traffic trunk, the urban landscape structure is a polygon formed by the center and trunk, and the actual land price gradient field tends to the concentric circle ideal land price gradient field. The experience and lessons of Urbanization in developed countries or developing countries have shown that the landscape pattern of the city is a big pie, It not only seriously damages the urban ecosystem, but also forms in the same dynamic process, which is called artificial corridor effect [7]. Under the trend of simple economic interests, there is a tendency to spread the cake in cities. In many cities, there is a balance between man and nature, and because of the paralysis of the urban traffic arteries, the decline of the central area is accelerated, which makes the city further spread, resulting in a great waste of land resources. In order to avoid this situation, we must consider the use of natural corridor (river, vegetation belt, park green space, farmland, etc.) to limit this uncontrolled development. The existence of natural corridor is concive to absorb, discharge, rece and alleviate urban pollution, rece the population density and traffic flow in the central urban area, and improve the intensive and efficient land use, which is called natural corridor effect. These two kinds of corridor effects should be considered comprehensively in urban landscape planning. The essence of the corridor effect is that there is a benefit gradient field around the corridor in a certain range. The corridor benefit graally decays from the center to the outside, following the distance decay rate. In theory, it can be expressed by logarithmic decay function [8]: D = f (E) = a LN a ± The function graph of A2 E 2 a2 - E2 (1) is shown in Figure 1, where e is the benefit of gradient field, D is the distance, and a is a constant, indicating the maximum corridor benefit. It can be seen from Figure 1? 1994-2009 China Academic Journal Electronic Publishing House. All rights reserved. http://www.cnki.net  Issue 2 Zong Yueguang: the corridor effect research in urban landscape ecological planning 147 shows that when the distance is extended from D1 to D3, the corridor benefit is reced from E1 to E3, which causes the urban landscape structural units to be arranged in strips from the center to the outside. The similar benefit gradient field can be extended to the concentric circle gradient field in the city center, as shown by the dotted line at the bottom of Figure 1. In order to simplify the problem, this paper assumes that the artificial corridor mainly proces economic benefits V and the natural corridor proces environmental benefits e, and does not consider the superimposed benefits. The intersection F of the two kinds of corridor effects is the dividing point of corridor benefits. On the left side of point F, V & gt; E, which becomes the artificial corridor area, V & lt; on the right side of point F; Therefore, point d 1 determined by F is the best distance between the two kinds of corridor effects (Fig. 2). Fig. 1 the curve of distance attenuation function of urban corridor Fig. 2 the displacement of two kinds of benefit curve of artificial and natural corridor Fig. 2 tw o Cu rves of CO rrido r benefits, i.e. moving from F 1 to f 3, in urban landscape, the built-up area expands from D 1 to D 3. Its landscape significance is that the natural corridor is compressed by the field effect of the artificial corridor, and the frontal angle is shrinking. Finally, bab 'forms a strip or line, such as Tonghuihe and Xibahe corridors in Beijing; Secondly, assuming that the front is constant and B is a constant, the relationship between the corridor apex and the coefficient a, when a changes from a 1 to a 3, the corridor apex is far away from the city center, and its landscape significance is shown as the displacement of the corridor benefit dividing point of the natural corridor in the central field effect and the deformation of the natural corridor in the spatial expansion of the city, driven by the simple economic interests, There is a process of continuous strengthening of the artificial corridor and squeezing of the natural corridor. Figure 3 shows that the artificial corridor in a certain direction of the city is continuously strengthened, such as improving the road grade, compounding and three-dimensional of a variety of road trunk lines, which improves the effect of the artificial corridor and forms three equivalent benefit curves L 1, 2 and 3, which intersect with the natural benefit curve at F 1, 2 and 3 respectively, Therefore, the compression of the benefit dividing point LFF will inevitably lead to the deformation of the natural corridor in the urban-rural ecotone. In the ideal state, the end point of the natural corridor can be changed