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    15 July 1999, Volume 54 Issue 4 Previous Issue    Next Issue
    Constrained Cellular Automata for Modelling Sustainable Urban Forms
    LI Xia, YEH A GO
    1999, 54 (4):  289-298.  doi: 10.11821/xb199904001
    Abstract ( )   PDF (7621KB) ( )   Save
    Cellular Automata (CA) have attracted growing attention in urban simulation because of their capability in spatial modelling which is not fully developed in GIS. This paper discusses how cellular automata (CA) which is increasingly used in urban simulation can be extended and integrated with GIS to help planners in the search for sustainable urban forms. A constrained cellular automaton is developed to produce optimal development patterns and thus reduce wasteful use of land resources. The cellular automaton is built within a grid GIS system to facilitate easy access to GIS databases for constructing the constraints. The essence of the model is that constraint space is used to regulate cellular space. Local, regional and global constraints play equally important roles in affecting the modelling results. Agricultural suitability, available land resource and economic and population growth could be used as key constraints. The paper discusses how to combine these constraints in CA modelling to enhance the efficiency in using land resources. In addition, ‘grey’ cells are defined to represent the continuous degrees or percentages of urban land development during the iterations of modelling for more accurate results. The model can be easily controlled by the parameter k using a power transformation function for calculating constraint scores. The CA model can be used as a useful planning tool to test the effects of different scenarios of urban development. The protection of valuable agricultural land is important in many developing countries where cities are growing rapidly. In China, some cities are expanding without properly considering land suitability and environmental impacts. Recent rapid land development has been accompanied by the loss of large amount of agricultural land. This study demonstrates that CA can be used to simulate urban development based on constraints that reflect our environmental concerns. The objective is to produce sustainable urban forms as alternatives to the existing development patterns. The study has suggested that CA can be used as a useful planning tool to model urban development under complicated and changeable environmental factors.
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    Changes of the Basic Nonbasic Economic Activities in Guangzhou A Re consideration of the Economic Base Theory of Urban Development
    YAN Xiao pei, XU Xue qiang
    1999, 54 (4):  299-308.  doi: 10.11821/xb199904002
    Abstract ( )   PDF (421KB) ( )   Save
    This paper focuses on the changes of the basic nonbasic economic activities in Guangzhou since the middle of 1980s. The attention is initially paid to the composition and change of urban basic nonbasic economic activities. Four research findings have been achieved. ① The general change tendency was that the scale of urban basic economic activities was smaller than that of nonbasic ones and showed the tendency of becoming smaller with time. The secondary sector showed the shrinking scale of basic activities but the tertiary sector had a reverse change. ② The scale of the basic economic activities of industry shrank and experienced a shift of the basic part being bigger than nonbasic part towards smaller than nonbasic, but industry was still the major economic basis of Guangzhou. ③ The proportions of basic and nonbasic parts of many tertiary trades changed, i.e. as the former rose, the latter fell, or the basic part had a relatively high proportion all the time, which strenghthened the status of the basic activities in urban economic development. ④ The fact, the basic employment (basic population) of producer services increased with a faster speed than the total employment and accounted for nearly 10% in the total employment, indicated that the producer services were becoming one of the important components in the urban economic basis and had the huge potential and possibility of occupying the regional market. Then the analysis was turned to the external function of the producer services based on questionnaires. The results showed that: ① In the producer services of Guangzhou, there indeed existed basic economic activities of exporting services to its surrounding regions (Guangdong Province, the whole country and the overseas). ② The differences of the external functions among the trades of producer services were obvious. The finance and insurance sectors had smaller proportions of providing services for the areas outside of the city than other sectors like information consultant, computer application, and scientific research and technological services. ③ The producer services in Guangzhou serviced mainly for Guangdong Province, which showed that the development level and scale of producer services were limited and their international market was narrow. Thirdly, the economic base theory of urban development was discussed. The research results showed that services not only provided services for cities themselves but also export services to the areas outside cities. And producer services mainly provided services for the areas outside cities (i.e. mainly being basic economic activities) which indicated that producer services have the function of engineering economic growth. The substance of development of basic economic activities lies in the tradability of services. Several factors, information technology, transnational enterprises of services and transformation of government function, have resulted in the services’ tradability. All these changes made the relationship between basic economic activities and urban development more complicated than before. A re explanation to the traditional economic base theory, paying more attention to interaction between urban economic activities and the location significance of the theory, was made. With the technological progress, the impacts of basic economic activities on urban development by stages have been identified. All these imply that the classic theories have not well explained the urban development in the post industrial society and it is very necessary to make the re explanation to the classic theories and build new theories.
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    Monthly Mean Surface Albedo Estimated From NCEP/NCAR Reanalysis Radiation Data
    ZHANG Qiong, QIAN Yong fu
    1999, 54 (4):  309-317.  doi: 10.11821/xb199904003
    Abstract ( )   PDF (259KB) ( )   Save
    The 17 years mean (1979~1995) NCEP/NCAR reanalysis radiation data are used to estimate the global monthly mean surface albedo. For clear sky conditions, the monthly mean surface albedo can be obtained by the ration of monthly mean reflected radiant flux and monthly mean total radiant flux at surface, and a correction is applied which takes account of the effect of solar zenith angle. The results show that the seasonal cycle and the spatial distribution of global surface albedo are correspondent to the characteristics and variations of the earth’s different underlying surface. The zonally averaged surface albedo shows an apparent annual variation. A comparison of the results of present method with other studies indicates that the values of sea surface albedo at high latitudes in this work tend to be slightly higher than the others. While the distribution of surface albedo in other regions are basically consistent to the others. The surface albedo in China also well represents the characteristics and seasonal cycle of complex underlying surface. Compared to the other similar works carried by Chinese scientists, the time and spatial distribution are accordant but the values in some regions are slightly higher. Verified by observation data of Qinghai Xizang (Tibetan) Plateau Meteorological Scientific Experiment in 1979, it is found that the surface albedo in the Qinghai Xizang (Tibetan) Plateau region obtained from the NCEP/NCAR data is closer to the observation data than the others. From the above results, it is suggested that the global monthly mean albedo estimated from the NCEP/NCAR can be applied into the global climate model, further correction for the albedo will depend on the sensitivity numerical experiment of the climate model.
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    Physico Geographical Factors for the Formation of Hyperconcentrated Flows in the Loess Plateau of China
    XU Jiong xin
    1999, 54 (4):  318-326.  doi: 10.11821/xb199904004
    Abstract ( )   PDF (267KB) ( )   Save
    Semi arid climate, poor vegetation cover and highly erodible loess can be regarded as the main natural factors responsible for the formation of hyperconcentrated flows in the Loess Plateau, China. The degree, to which the hyperconcentrated flows develop, especially their extreme suspended concentration, shows a significant areal differentiation. This is closely related to the grain size composition of suspended sediment. To study the relation between hyperconcentrated flows and the surface material, the mean annual suspended concentration C mean and C max suspended concentration C max have been plotted against the >0 05 mm and <0 01 mm percentages ( R >0 05 mm, R <0 01 mm) in suspended load, respectively. For each curve obtained, there is a peak value. The peak value appears where R >0 05 mm is around 40% or R <0 01 mm is around 20%. This fact means that there exists an optimal grain size composition of suspended load, which makes suspended concentration reach the highest value. The formative mechanism for this optimal grainsize composition can be explained by the special physical and mechanical properties of hyperconcentrated flow as a solid liquid two phase flow. When the fine sediment is much more but the coarse particles are not sufficient, the flow may enter a laminar state; when the coarse particles are much more but the fine sediment is not sufficient, the coarse particles can not be set in suspension effectively. In these two cases, suspended concentration cannot reach very high. Obviously, between the two ends, an optimal grainsize composition exists at which the suspended concentration may be the highest. This optimal composition is related to the combination of three surface material types, i.e. loess, wind blown sand and weathered material of bedrock, and it occurs as a result of seasonally alternating wind and water processes operating in this area. It was found that in the middle Huanghe River basin, suspended sediment is coarser than that of the loess in the basin, but finer than the wind blown sand and bedrock weathered material. So, it is some proper combination of materials supplied from these sources that forms the optimal grainsize composition. During winter and spring, wind carries coarse aeolian sand to gullies and river channels. It has been observed in the field that, driven by strong wind, aeolian sand dunes on floodplains may approach the river bank and then collapses into the channel. This process is enhanced by bank erosion. When floods occur in summer, the aeolian sand previously supplied to the channel may be carried downstream by stream flow. During the floods that come from loess covered areas and lack of coarse sediment, the previously stored coarse aeolian sand may be set suspension by the fine sediment rich water flow and thereby its suspended concentration increases sharply, leading to the formation of hyperconcentrated flows.
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    Features and Neotectonic Significance of River Valley Landforms in Mt. Daqingshan
    MA Bao qi, LI Ke, WU Wei min, NIE Zong sheng, YANG Fa, GUO Wen sheng, HE Fu li
    1999, 54 (4):  327-334.  doi: 10.11821/xb199904005
    Abstract ( )   PDF (239KB) ( )   Save
    There are 6 major rivers, named Wudanggou, Shuijiangou, Meidaigou, Dashuigou, Shuimogou and Halagou, from west to east, in Mt. Daqingshan, the upthrown block of the Daqingshan Piedmont Fault, which is an active normal fault. Based on paleoearthquakes having occurred along it, the Piedmont Fault can be divided into 5 segments, one of which has undergone unique faulting history. Accordingly, the 6 rivers, Crossing different segments of the Piedmont Fault, have differences in their landforms. The features of river valley landforms in Mt. Daqingshan reveal that the 3 middle segments are more active than the other 2 segments of the fault. In the river valleys, 2~5 terraces, having developed since 23 ka BP of Late Pleistocene, are identified. In the 4 west rivers’ valleys, the number of terraces is 4~5; the highest terrace is 80~120 m above the current river bed; all of the terraces have been displaced by the Daqingshan Piedmont Fault. But in the 2 east rivers’ valleys, the number of terraces is fewer, only 2~4; the highest terrace is 20~45 m; the latest terrace, formed in Holocene, has not been displaced yet. The model diagram of longitudinal profiles of the 6 rivers’ valleys is a parabolic pattern: h=aln . The longitudinal profile of the 4 west rivers’ valleys has a convex parabolic pattern, n<1; but that of the 2 east rivers’ valleys has a concave pattern, n>1. The more active a segment of the Fault is, the more convex the parabolic pattern of the river’s valley crossing the segment is. From west to east, Vf value of the river mouth at the Piedmont Fault becomes higher. Based on the detailed landforms and their formation ages of the rivers’ valleys, we can drive some conclusions on the activities of the Daqingshan Piedmont Fault. Since 23 ka BP, the uplift amount of Mt. Daqingshan is the same as the elevation of terrace Ⅴ near the Fault, 80~120 m for the 3 middle parts, and 20~45 m for the east part. During Holocene, the uplift amount is about 17~18 m for the 3 middle parts and less than 6 m for the east part. Obviously, the slip rate of the Daqingshan Fault can be calculated.
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    Endemic Goiterfoe in Historic China: Its Geographic Distribution
    GONG Sheng sheng
    1999, 54 (4):  335-346.  doi: 10.11821/xb199904006
    Abstract ( )   PDF (517KB) ( )   Save
    Endemic goiter, a worldwide endemic disease which relates to geo chemical environmental factors, has a very long prevalent history in China. This thesis discusses the below four issues by analyzing a large amount of Chinese historical document. 1. Ancient Chinese descriptions on endemic goiter’s symptoms As early as 2 500 years before present, Chinese knew the facts that endemic goiter distributes mostly in mountainous areas and prevails mainly in female population. In Chinese historical documents, goiter was called “Ying” (goiter) at first, and then “big neck”. According to modern medicine, “Ying” is the third or fourth degree of endemic goiter, “big neck” is the first or second degree of endemic goiter. Chinese character “Ying” is composed of words “disease”, “ornament” and “female”, its initial meaning might relate to the thought of antiquity people of goiter as the ornament surrounding female’s neck. The fact shows ancient Chinese very early knew that female falls endemic goiter easier than male. By the Southern Dynasties (A.D.420~589), Chinese were able to distinguish between diffuse goiter and nodular goiter. Unfortunately, after the Southern Song Dynasty (A.D.1 127~1 279), goiter was mixed with tumor by many doctors. 2. Ancient Chinese knowledge on the links between goiter and environment Ancient Chinese believed that the prevalence of endemic goiter in some area related closely to the natural environment of this area and pointed out that water quality and landscape were important pathogenic factors of endemic goiter. About 2 000 years ago, they discovered that mountainous areas were main goiter’s epidemic areas so that they wrongly believed endemic goiter resulted from drinking rushing, sandy water and living in precipitous place. Although then doctors knew how to treat goiter sufferers with rich in iodine drugs, until the early of the 20th century, Chinese don’t knew that the real reason for endemic goiter’s prevalence is iodine deficiency. 3. The geographical distribution of endemic goiter in ancient China Because ancient historians and literature writer intentionally evaded recording diseases, the records on endemic goiter in China’s historical document are seldom seen and very fragmentary. But this paper yet collects enough historical data to recover the distribution image of endemic goiter in ancient China’s hinterland. By analyzing a lots of historical records, the author finds the serious prevalent areas of endemic goiter in ancient China mainly include: the Qinba mountainous areas in Shaanxi Province, the western mountainous areas of Henan Province, the west northern mountainous areas of Hubei Province, the Zhongtiao mountainous areas in Shanxi Province, the Taihang mountainous areas in Hebei Province, the Yimeng mountainous areas in Shandong Province, the Three Gorges area, the Minshan mountainous areas in the northwestern of Sichuan Province, the Dieshan and Liupan mountainous areas in Gansu Province, and so on. These areas are situated in the central part of China, so are earlier exploited and are more recorded. But it is not mean other areas without the records are not the prevalence areas of endemic goiter. 4. The causes of distribution change and the socio economic harm of endemic goiter Endemic goiter is a geo chemical environmental disease. Owing to only a little change of geo chemical environment in the past 2 000 years, the spatial distribution of endemic goiter in China remained relatively stability so that the serious prevalent areas of endemic goiter in the historical times was generally coincident with the distribution areas of endemic cretinism in the early of 1980s. But, by comparing and analyzing, we could still find, because of the improvement of translation condition and dietary composition, the distribution scope of endemic goiter reduced and its harm is alleviated and even eliminated in some areas. For example, the western part of Three Gorges area, the eastern foot plain of the Taihang Mountain.
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    Theoretical Analysis and Experimental Study on the Critical Slope of Erosion
    HU Shi xiong, JIN Chang xing
    1999, 54 (4):  347-356.  doi: 10.11821/xb199904007
    Abstract ( )   PDF (238KB) ( )   Save
    The overland flow is defined as the flow of water over the land surface toward a stream channel and is the initial phase of surface runoff. The sediment yielding from overland flow erosion increases with the increasing slope if the slope is smaller than a critical value, and reduces following further increase of the slope if the slope is larger than the critical slope. With Energy Theory, Sediment Transportation Mechanism and data from laboratory and field experiments, the critical slope of overland flow erosion was studied in detail. Firstly, from the viewpoint of energy analysis, the detachment capacity of overland flow is directly proportional to the flow shear stress, and the shear stress is directly proportional to the kinetic energy of overland flow. A theoretical formula is derived which indicated that the energy of overland flow is closely related to the flow rate per unit width, composition of soil particle size, runoff depth and slope gradient. The maximum flow shear stress occurs if the slope is between 22° and 26°. Therefore, the conclusion from the energy analysis is obtained that the critical slope of overland flow erosion is about 22°~26°. Secondly, the analysis from dimensionless shear ratio and sediment transportation mechanism shows that the capacity of overland flow carrying sediment reach its maximum at the slope gradient approximate to the frictions angle of sediment under water. The sediment carried by overland flow is mainly composed by the silt and fine sand, whose friction angle under water is measured at 22°~27°. This means that critical slope of over land erosion is between 22°~27°, which is coincident with the critical slope derived from energy analysis. Thirdly, simulation experiment in laboratory shows that the maximum sediment yield is obtained at the slope of 23°~27°, which verified the result induced from the theoretical analysis. Finally, it is concluded that the critical slope gradient of sheet erosion and rill erosion is about 22°~27°, and that of rainsplash transportation is below 22°, and critical slope gradient of gully and gravitational erosion will be bigger than that of sheet erosion and rill erosion. Another conclusion of this paper is that the critical slope gradient is not a fixed value, but a range of values, and discussion of the critical slope of erosion should refer to concrete erosion way and boundary conditions.
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    Spatial Structure of Tourist Source Areas for the Naturally Scenic Sightseeing Places:A Case Study of Jiuzhaigou
    ZHANG Jie, DU Jin kang, ZHOU Yin kang, ZHANG Si yan, PAN Bing
    1999, 54 (4):  357-364.  doi: 10.11821/xb199904008
    Abstract ( )   PDF (383KB) ( )   Save
    The spatial structure of the source or market areas of tourists is basic to tourist geography. Although there are case studies on such issues as mathematical modeling of distance decay of tourists from a tourist site, its market potential and actual market structure, many questions remain. Take tourist distance decay for example. Whereas hypothetical theoretical curves have been suggested, no basic mathematical model based on case studies exists. In addition, the application of distance cumulative curve in tourist research is still limited to descriptions of the actual distribution of tourists, which is ineffective in analyzing the spatial structure of tourist market potential. Jiuzhaigou Conservation District, one of China’s most picturesque tourist areas with numerous colorful lakes and waterfalls, is recognized by UNESCO as one of the world’s natural heritage sites. Distance decay model is used to reveal the characteristics of its market area structure. Several types of distance cumulative curve are also used to reveal its market structure at varying distances from the site. A sample of more than 16 000 tourists was obtained from entrance registration which shows the they come from 235 cities and counties. Through regression analysis we calculated the main coefficients of the distance decay model and found that the best fit model is the Pareto model with a distance decay exponent of 0 48. The next best are the lognormal model and square root exponential model, while the normal model is unfit. As the relative coefficients of these models are not high enough, we used the gravity model to analyze distance decay versus the influence of population and economic growth. The result shows a distance decay exponent of 1.84 and a clear increase in relative coefficient to 0 70. Gravity model was also used to better understand how the sampled tourists declined proportionally with increasing distance from the site. The result shows the distance decay exponents range between 1 74 and 1 92. When per capita industrial and agricultural output is replaced with total industrial and agricultural output of cities and counties, the exponents range between 2 5 and 3 0. This study demonstrates that the several distance cumulative curves of the market areas of the site and the population of the market areas can be effectively used to analyze the spatial structure of the site’s ultimate market area potentials.
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    Humanism, the Rise of Postmodernism and the Development of New Regional Geography in the West
    Laurence J. C. Ma
    1999, 54 (4):  365-372.  doi: 10.11821/xb199904009
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    In the last four decades, human geography in the West has experienced major changes in both theoretical and empirical orientations. These changes began with the appearance of the quantitative revolution in the late 1950s and the 1960s which greatly enhanced the position of theory in geographic scholarship. Adopting logical positivism as its theoretical foundation, early quantitative geographers clearly displayed epistemological arrogance who considered views of knowledge other than their own as either invalid or insignificant. However, by the late 1960s, both the revolutionaries and the bystanders had become disillusioned about the revolution’s future as it had failed to achieve what it had set out to do earlier: the development of geographic laws and metatheories. This set the stage for the emergence of a host of competing schools of thought in human geography, ranging from behavioralism, Marxism and humanism. Postmodernism made its appearance in American human geography in 1984. It rejects any narrow epistemological stance that sees the complex world through only one predetermined lens. It argues that no metatheory is capable of accounting for the complex reality, and it does not favor any one type of represented world over others. It emphasizes the importance of difference, heteorogeneity, context and human agency, which have since found their way in a new regional geography centered on the study of localities. Local conditions in China since the 1978 reforms have varied greatly, with places in different regions acquiring unque place identities. Such a condition is suitable for the use of postmodern perspectives for place based studies.
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    Data Logic Study for the Resources and Environment Information System Design in a Feature based Approach
    CHEN Chang song, HE Jian bang
    1999, 54 (4):  373-381.  doi: 10.11821/xb199904010
    Abstract ( )   PDF (226KB) ( )   Save
    The category theory is a dominant methodology in the designs of the resources and environment information systems (REIS) and information coding. This approach, however, proves to meet only thematic REIS designs. A new method must be used in the designs of the comprehensive REIS to get a stable performance and more easy sharable system. The paper proposes a feature based approach to be an improvement of the category method in the designs of an integrated REIS. The feature based GIS model is a semantics model from the point of abstractive levels. It has a higher abstractive level than some spatial data models such as the vector or raster GIS data models. The concept of geographic feature, the key concept in the feature based model, has the following characteristics: (1) It is applicable directly but application-independent. (2) Application schemas can be formed by the integration of a standard feature schema and some different descriptive data. In allusion to the shortcomings of the category approach in the REIS designs: term instabilities, meaning instabilities and classification position instabilities, the paper argues that the integration of standard feature schema and descriptive data can be utilized to form different resources and environment application schemas.
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