Since the reform and opening-up, especially the 21th century, China has achieved the great progress on the transport construction. However, since the end of 20th century, especially in recent years, several problems on the transport construction became worse. Based on the investigation and discussion in 2009-2010, we complete the consulting report The Proposition to Avoid the Redundancy and Inappropriate Construction of China′s Transport Infrastructures. The report is submitted to the Chinese central government on in September, 2010. In this report we assess the progress of China′s transport construction and developing level of the transport industry. It shows that China had constructed one integrated transport system whose ability, structure and spatial distribution can ensure the rapid development of China′s socio-economy. And we reveal the existing serious problems on the transport construction in recent years on the whole China, such as over expansion, over-duplicated construction, unreasonable competition, etc. Now, several transport modes had produced the excessive capacities. Those problems resulted mainly from that the transport planning could not consider completely the China′s national conditions, and its developing stage, tendency. Then, we propose that China′s transport construction should step gradually one new stage to optimize the transport structure, construct the integrated transport system, and develop the transport infrastructures in the backward regions. The construction scale of express way, seaport, and express railway should be studied and verified more scientifically and comprehensively. Furthermore, we should strengthen the comprehensive study of transport industry in the long term. When the report is submit to the government it is in the upsurge of transport construction especially express railway, we are confronted the enormous pressure. To read the authentic report for the reader, we make no revision on this report.
The curves on the change of level of urbanization over time are called urbanization curves, which are in fact models of the progress of urbanization based on empirical evidences from developed countries and developing countries. There are two types of urbanization curves. One is S-shaped curve, and the other, J-shaped curve. The S-curve can be modeled with the logistic function, while the J-curve cannot be described by the logistic function. The former is applicable to the developed countries, whereas the latter is applicable to the developing countries. So far, there have been more studies on the S-shaped curve. However, fewer studies have been devoted to the J-shaped curve of urbanization. Consequently, we know little about the general principle on the J-shaped curve and its underlying rationale, which remain to be further explored in the future. In this paper, various studies on urbanization curves are systemized to form a framework of models on the level of urbanization. The logistic curve was once divided into three stages by Northam (1979): initial stage, acceleration stage, and terminal stage. However, the Northam's proposal is just a phenomenological theory with several defects: first, the definition of 'acceleration stage' is not correct; second, there are no theoretical basis and critical scale for the divisions. It can be proved that the logistic process falls into four phases. Taking half of urbanization level capacity as a tipping point, the logistic curve is divided into two stages: acceleration stage (urban majority) and deceleration stage (urban minority). The tipping point can be determined by two methods of elementary mathematics. Then the two stages are respectively divided into two sub-stages by means of the exponential law of urban-rural ratio with a parameter as characteristic length. Now, urbanization process can be divided into four stages: initial stage, acceleration stage, deceleration stage, and terminal stage. Also it can be divided into three stages: initial stage, celerity stage (including acceleration stage and deceleration stage), and terminal stage. Two methods are always applied to the research of urbanization curves and the related urbanization dynamics. One is phenomenological analysis, and the other, theoreticalogical analysis, which consists of three approaches: urban-rural allometric growth, urban-rural population replacement, and urban-rural population interaction dynamics. Urban-rural allometric growth analysis is a kind of scaling analysis. Urban-rural population replacement suggests a new dynamical analysis. Urban-rural interaction comprises linear dynamics and nonlinear dynamics. The linear dynamics is based on the well-known Keyfitz-Rogers model, whereas the nonlinear dynamical analysis can be employed to interpret the similarities and differences between the S-shaped and J-shaped curves. China’s urbanization process can be described with the J-shaped curve rather than the S-shaped curve. The studies on the urbanization curves will be significant for understanding the dynamical mechanism and essence of Chinese urbanization.
The research on identity is very important within cultural and social studies. Identity represents the roles that individuals or social groups play within a social and cultural structure. It is connected with self-recognition and self-definition. On the other hand, place identity means that the meanings of place are taken as part of self-definition. Through place identity, individuals or social groups understand themselves through the constructive nature of place as a reference. In this paper, place and identity are exploited as the main axes around which this discussion is embarked. Taking Guangzhou's "Artist Village"—Xiaozhou Village as an example, the evolution of identities of both the local villagers and the newcomer artists is to be understanded, under the context of Guangzhou′s urban spatial transformation. In particular, the coexistence, juxtaposition, collision and even conflict between the two groups′ place-based identities are interested in. The research results suggest that there is an apparent status of fragmentation between the place identities of the two social groups. There is no sound proof in support of any progressive sense of place in either group′s place imagination, in which sense it can be believed that there will still be a long process before the two social groups are fully integrated in, regard of the construction of their place-based identities.
Based on cases studies in three coastal areas of Southeast China, this paper proposes a "Double-Pull" conceptual model to examine the migration intention and behaviour of the rural labor force and their urbanization effects in the areas characterized by well developed in situ urbanization and little out-migration, using data from a questionnaire survey. The results show that migration frequency of the respondents was low, and short-distance moves were the dominant form of their mobility. At the same time, they demonstrated low migration intention, and for those who did indicate such intention, they tended to choose nearby middle- and small-towns as the destination. Under the framework of "Double Pull" Conceptual Model, the above migration intention and behaviou were the result of the balance of both the rural and the urban pull forces. The "rural pull forces" included employment opportunities, income, social insurance and the sentimental attachment to hometowns; while the "urban pull forces" included employ opportunities, income, residential environments, children′s education, etc.; and the former was much stronger than the latter. In order to achieve maximum benefits, local people tended to choose rural-urban transformation rather than out-migration, and this led to the phenomenon of in situ urbanization, which is different from the conventional urbanization patterns in the past of developed countries. The paper confirms local nature of the endogenous nature of the emergence and development of in situ urbanization and its inevitability, and contributes to a deeper understanding on the micro mechanism of in situ urbanization.
Analyzing mining heritages on the World Heritage List is an effective way to learn this type of heritage and understand the international trends in heritage conservation. This study extracts 24 mining heritages by analyzing "Industrial and technical heritage in the World Heritage List" issued by ICOMOS and brief description of heritage sites announced by World Heritage Committee. Results of the analysis indicate: 1) Most of mining heritages are inscribed into the World Heritage List according to the Cultural Criteria ii, iii and iv; 2) The imbalance on spatial distribution of mining heritages is more serious than that on World Heritage List in the whole. Europe and North America have 16 items; Latin America and Caribbean have 7 items; Asia-Pacific has 1 item; Africa and Arab States has not yet got mining heritage on the World Heritage List; 3) Mining heritages on the World Heritage List have been selected from a long time span and most properties have long production history. These mining heritages mainly reflect the information and history of mining between 16th century A D to 20th century A D, and mining heritages formed before 9th century A D are ignored; 4) Heritages related with metal mining have occupied the majority of mining heritages on the World Heritage List and mining heritage towns and architectures are the main form of these mining heritages. These results reveal that the Euro-centric heritage discourse is prevalent in the process of valuing mining heritages when they are submitted for inclusion in the World Heritage List, which has led to the imbalance of mining heritages in the World Heritage List. Those suggests that heritages with outstanding universal significance should be associated with properties having connections with Europe in history, presenting the characteristics of European arts and architecture styles, and illustrating significant stages or (and) events in European history. It has also undervalued the mining heritages in some non-European cultural regions when this Euro-centric heritage discourse is viewed as the advanced experience in the international level and accepted without reservation. Realizing the problem of Euro-centralism in the world heritage affairs, the World Heritage Committee put forward the "Global Strategy" in 1994. In addition, this study points out that China is abundant in its mining heritages from the perspective of officially protected site/entity announced by governments at all levels, but until now China has no mining heritage on the World Heritage List. With the background of the global strategy of world heritage and the diversification of heritage discourse in the international level, this study puts forward some measures for Chinese mining heritages, such as strengthening the theoretic research and building suitable heritage discourses from Chinese actual conditions; conserving mining heritages relying on Chinese officially protected site/entity; launching special mining heritage programs and enhancing public awareness.
Geographic types are relative stability region units, which are formed in the certain geographical environment and a long history process, and composed by many special areas or units that have similar features in development conditions, production structure, development characteristics, development direction, and etc. The valley economy, as a new model of mountain development, is playing a more and more important role in gathering and effective linking in the mountainous traffic, villages, population and resources, which meets the requirements of mountainous space optimization development. By now, there are a little of achievements in the study of valley economy′s geographic type. From the perspective of Geography, valley economy′s geographic type identification has a great theory significance and practical value, which can provide some references for mountainous areas′ development. Mentougou, in the west of Beijing, is situated in the transitional mountainous areas of Mongolian plateau and North China plain, the intersection of platform anteclise in Shanxi Provinceand Yanshan fold belt. The mountainous areas occupy 98.5% of the study area, approximately 300 valleys here, thus it can be regarded as the pure mountainous area in Beijing. Mentougou possess the typical characteristics of valley economy development. Taking villages in Mentougou as the basic units, combined with dates from field research and village-level statistics, valley economy materials of 18 typical valleys in Mentougou district are gained. Based on the division of valley economy geographical zone, this paper identified its geographic type, and probed the spatial structure of different valley economy geographic types. According to the identification model, based on entropy weight theory and AHP method, combined with field research dates, expert advices and village-level statistical materials, this study obtained that, valley average elevation is the dominant factor to identificate valley economy geographic type. In geographic type, combined with analysis on the topographic profile, the Mentougou valley economy can be divided into piedmont type (≤400 m), shallow mountain type (≤600 m), appro-alpine type (≤1000 m) and far-alpine type (>1000 m). In spatial structure, the 4 valley economy geographic types have their own features: piedmont type valley possesses a network spatial structure (piedmont network type), shallow mountain type valley possesses a point-axis type spatial structure (shallow mountain point-axis type), appro-alpine type valley possesses a base type spatial structure (appro-alpine base type), and far-alpine type valley possesses a relative balanced type spatial structure (far-alpine relative balanced type).
The authors performed a quantitative study on characteristics of urban expansion in the Suzhou, Wuxi and Changzhou cities (SWC) by means of quadrant analysis and buffer analysis with Landsat MSS/TM/ETM images acquired in 1979, 1991, 2001and 2006. The results indicated that the spatial pattern of urban growth behaved certain regularity in the last 30 years. Expansion intensity index of the three cities showed a highly coherence with circle radius, and the peak of expansion intensity moved gradually from the inside out with time. Combined with experimental analysis for major growth axis, it is suggested that SWC region might present incomplete filling and axial development. The expansion pattern exhibited an alternating process that the complete cycle of diffusion-aggregate-diffusion was not observed in the whole city in 1976-2006. It was also found that urban expansion intensity index was quite different in different directions at different time. Various development zones which were initiated and located by the government played an important role in driving new urban growth. In Suzhou city, the eastern industrial park and southern districts lead the whole expansion process. In Wuxi, the expansion of all directions was relatively balanced.owing to the private economy development. In contrast, the urban expansion of Changzhou showed a multi-polarization trend which flocked to northern high-tech industrial zones and eastern industrial zones. A number of alternating development axes emerged as a result of the top-to-bottom control on urban development in the city.
This paper analyzes the ceramic workshops in Jingdezhen, Jiangxi, according to the inter-association of nature-economy-culture and the conversion between substance and energy from the angle of cultural geography. After field investigation of ecological environment in Jingdezhen and the large ceramic workshop, this article analyzes the manual mapping, measured data, the relative historical documents and archaeological materials. It points out the fact that the construction of ceramic workshops should follow strictly natural laws: it needs to choose the measures to suit for different conditions, the fabricationent to suit for different materials, and use the resource cyclically. In addition, it needs to study the building materials, the structure and the function, the production processes, the layout of the craft, which all have a basis in science, rationality, and rigor. This paper also points out that the ceramic craftsmen of Jingdezhen created the production environment which had proper lighting, ventilation, temperature and humidity. The construction, function, efficiency and the style of ceramic workshops achieve perfectly unification, which are the classic work of the human and nature getting along with each other harmoniously. All these explain the formation mechanism of the workshop landscape.
Changsha, Zhuzhou and Xiangtan, the key components of Changsha-Zhuzhou-Xiangtan urban agglomeration and the core growth pole of economic development in Hunan province, have been accelerating their economic and social development and their urbanization in recent years. Their high-speed urbanization is the main reason for the significant changes in the land use structures and functions in Changsha-Zhuzhou-Xiangtan core area. Therefore, research of regional land use change will exert a positive and significant influence on enhancing the harmony among land use, urban environment, economic and social development, and helping satisfy the requirements both the human living and ecological protection. Wavelet analysis, which emerged in the 1990s, is a mathematical tool for multi-scale analysis. It specializes in land use pattern analysis from frequency and scale, linking spatio-temporal pattern with scale and location. This analysis, though widely applied in ecology, has never been adopted in exploring scale characteristics of land use change in urban agglomeration. It must be a significant attempt to adopt wavelet analysis in exploring the scale characteristics of land use change in the core area of Changsha-Zhuzhou-Xiangtan, for its results will help to explain the spatial heterogeneity and scale sensitivity and further, the driving mechanism in regional land use change, and provide an important basis for response analysis of the scale of landscape change. The research is carried on the relationship between time and location and land use change characteristics scale from a wavelet analysis on typical transect line of the belt along the Xiangjiang River as the typical land use region based on the data of land use change extracted from the remote sensing image data in four periods from 1989 to 2008. The result shows that the different degrees of sensitivity of each quarter of the Changsha-Zhuzhou-Xiangtan core area to scale change determine their selection in land use characteristic scale, which is supported by 1) The quarter around the city centre, which is of a relatively single land use type, is the least sensitive to scale change, thus about 3 300 m parcel analysis being the most appropriate; 2) The urban fringe quarter is the most sensitive to scale change, thus about 2 000 m parcel analysis being the most appropriate; and 3) The green heart of Changsha-Zhuzhou-Xiangtan, the combination quarter of the three cities, is moderately sensitive to scale change, thus about 3 000 m parcel analysis being the most appropriate.
Based on listing systematically the historical records of the Chaohu Lake Basin’s drought and flood, and integrating the data of 7 counties (cities) on watershed flood and drought indexes and its grades, a graded series of dryness/wetness during the past 600 years has been rebuilt to calculated the drought and flood frequency. The results of continuous power spectrum analysis reveal the rules and cycles of dryness/wetness change within the Basin. In comparison with the dryness/wetness series of mid-downstream basin of the Changjiang River and the watershed climatic change in temperature, then the impacts on environment change by natural factor and human exploitation can be indicated. The main conclusions are as follows: 1) In past 600 years, the disaster of flood and drought usually occurred within the Chaohu Lake Basin, and its average frequency was once-in-1.88 years. The frequency of flood was nearly equivalent to that of drought, but the frequency of heavy and great flood was higher than that of heavy and great drought. From the time perspective, the frequency of drought was higher than that of flood before the 19th century; flood was more serious than drought in the 19th century. But to the 20th century, this trend reversed. Moreover, it is a remarkable character that the great drought and great flood appeared 2 to 3 years continuously within the Chaohu Lake Basin in this period. 2) The result of continuous power spectrum analysis demonstrates that there were the 2 or 3-year and 7-10-year fluctuations among them within the Chaohu Lake Basin. The period from the 1920s to the 1960s was the worst drought period within the Chaohu Lake Basin over 600 years. In contrast, the period from the 1820s to the 1860s was the most serious flood period. By the dryness/wetness disaster time series’ fitting on the Chaohu Lake Basin and the Changjiang River mid-downstream Basin, it is found that there was an approximate synchronous variation of disaster occurrence between them. It is also proved that the Chaohu Lake Basin is the commendable indicator of dryness/wetness variation within the Changjiang River mid-downstream Basin. With the advent of agriculture, and the large-scale developing of industry, especially during the past 2 hundred years, the number and activity of the human species increase sharply, so that the mankind intervenes more strongly to environment. Some estimate that the impacts on environment of human activity has been the same degree as that of natural evolutionary process, but so far there is no conclusion on which is more important. Precious curve-fitting illustrated that the environmental evolution within the Chaohu Lake Basin is mainly limited by climate change. Although the degree of human intervention is deepening, it is just one inducement to environmental evolution. 3) There is a certain relationship existing between the occurrence of drought/flood and the regional climatic change in temperature. Before the 1830s, drought often happened in the cool periods, while flood often happened in the warm periods. But the relationship had broken down after the 1830s, and it was characterized by flooding and drought coming by turns, which is the direct result caused by deepening human activity. These viewpoints need to be proved by further research work.
A runoff sequence is classified into several sub-runoff sequences with cluster analysis and practical application, and local dynamic neural network for each sub-runoff sequence is performed separately. An Elman recurrent neural network model (ENN) is constructed and applied for the daily runoff forecast in the Linyi sub-catchment of the upper Yishu river basin in this paper. In order to further evaluate the performance of local Elman neural network (LENN), global Elman neural network (GENN) is applied as a comparison at the same time in the study region. Based on analysis indexes such as Nash-Sutcliffe coefficient, correlation coefficient, mean relative error and root mean relative square error, the results of daily runoff and flooding processes are attained. It suggested that Elman recurrent neural network model has a high accuracy of forecast on the rainfall-runoff dynamic process and the maximum peak flow and peak occurrence time, whether it is configuration samples or evaluation samples. However, local Elman neural network based on runoff classification is more suitable and efficient to daily runoff forecasting than global Elman neural network, especially during the period of arid season and semi-humid season. The simulation precision of different periods decreases in the order of arid season, semi-humid season and humid season. Elman recurrent neural network model is feasible to effectively simulate the hydrological dynamic characteristic of the daily runoff and to reflect the complex nonlinear runoff regular pattern in the basin as a promising and efficient method. In order to further evaluate superiority of this method, longer series of data, more regions and hydrology model are need to study and analysis because of the highly nonlinear, spatial and temporal heterogeneity and dynamic uncertainty of rainfall-runoff process.
Based on collecting, reorganizing and analyzing the history data about the Guanzhong Plain during the Ming Dynasty, the grade series, stage changes and different grades' periodicity of the frost and snow disaster are studied in this study. The statistical results show that, frost and snow disaster of the Ming Dynasty had 22 times altogether, and occurred averagely one time per 12.6 years. The Guanzhong Plain's frost and snow disaster grade may be divided into mild, moderate and severe disaster in the Ming Dynasty, and their occurrence probabilities are 26%, 52% and 22%. The disaster has been divided into four uneven periods in the Guanzhong Plain. The first period (1368-1448), and the third one (1508-1568) had the fewer disasters in the Guanzhong Plain, and there were the more disasters during the second period (1449-1507), and the fourth one (1569-1644). The frequency of frost and snow disasters was obvious upward in the Guanzhong Plain. Wavelets analysis has the characteristics of multi-resolution analysis and ability of expressing local features of signal in both time and frequency domains, which is a local analysis method. This novel method is suitable for complex natural disaster systematic. The spatial distribution, temporal evolution and multi-scale period of the frost and snow disaster are studied from the year of 1368 to 1644, applying wavelet analysis method and the history data about the Guanzhong Plain during the Ming Dynasty. The result of wavelet analysis shows, the mild, moderate, severe disaster occurrence periodicity is respectively 11, 8 and 44 years. The change of frost and snow disaster in the Guanzhong Plain during the Ming Dynasty is significant. This phenomenon can indicate climate change of the Ming Dynasty. On the basis degree of the frost and snow disaster, mean annual temperature can be reconstructed. There was one cold climatic event in the Guanzhong Plain in Ming Dynasty, occurring between 1618 and 1631, and the temperature was obviously lower than the other time of Ming Dynasty and the modern. There are six disasters in the period, including one-time moderate frost and snow disaster, 5-times severe frost and snow disasters. The frost and snow disaster occurred averagely one time per 2.3 year during the period. The degree and frequency frost and snow disaster is greater than that of the other time of Ming Dynasty. The result can indicate that there is the little ice age of Ming Dynasty. The results mentioned above indicate that the primary cause of the frequency of frost and snow disasters in the Guanzhong Plain was sudden drop of air temperature caused by sustainable snowfall, accumulated snow and cold snap.
Environmental pollution degradation and water purification are the major function of wetland. This article analyzes the water field characteristics and researches the water quality by field investigation and water quality monitoring. based on the theory of chemical thermodynamics and systematic analytic method,analyzes the relationship between water purification mechanism of Zhalong Wetland and the formation of water chemistry. The result indicates that the major mechanism of water purification of Zhalong Wetland is adsorption precipitation, plant uptake, biodegradation and denitrification, and the purification ability is highly related to chemical condition of solution, geological characteristics of wetland, chemical cycle and biological effect. And the NH4+ entered in the wetland was removed by the adsorption of clay, which reduced the concentration of TN and NO3- in the center of wetland. The concentration of Ca2+, NH4+ in the peripheral of wetland decreased with the direction of runoff, while the concentration of Na+ increased with the runoff direction. Carbonate balance play an important role in the formation and characteristics of pollutant migration. Stable pH value controlled the existence formation of pollutants and the direction and strength of its migration, and controlled the existence formation, migration and transformation of inorganic phosphorus. The existence formation of phosphorus in the low content of neutral and alkaline water was HPO42- and H2PO4-. The content of organic nitrogen is higher in sewage. The main transformation mechanism is biochemical effect and the reaction product is NH4+. Due to NH4+ is susceptible to be adsorption or absorbed by soil and biology, so it is lower in the water. Zhalong Wetland purified TP, NH4-N, CODcr and suspended matter with the rates higher than 90% and purified TN, NO3-N with the rates higher than 75%. The water purification function restores the natural ecosystem remarkably. The regulation of condition of water environment can extremely improved the ability of the wetland’s water purification, and the power of water environment control.
Climate change and regional development under the background of water resource decreased over the Yellow River basin, which is under the monsoon climate control. The runoffs during flood season in the Yellow River is about 60%-70%. Rain-fed agriculture is the most important ecnomy part of China during the past thousands of years, while rainy summer and autumn leads to rivers flood, so in history Chinese government must predominate the flood to avoid the agricultural loss. According to the historical records of water level in the Wanjintan during 1766-1911 A D, the reconstruction of the flood flow (R) of Sanmenxia section sequences, and the start time of 115-year flood. Its multi-year average runoffs are R=51.06×109 m3/yr, and the average flood conditions for the start time T is in the early July. Wavelet shows the a 50-year cycle in the runoff series. The results show that: the runoffs in the middle reaches of the Huanghe River has inter-annual and inter-decadal oscillations like 6-8 years, quasi-22 years and 50 years. The determination of the quasi-22 years is link to the changing of Wolf Sunspot Numbers. The solar activity was significant during the 1830s. ENSO event is negative with the changing of natural runoff at the inter-annual scale. There was a low-flow period in the last 4 eras of LIA, and it has been the longest low-flow period since 1766 A D. The summer is the key reason of the changing of flood season beginning time for the unstable rainband moving from the middle and lower reaches of the Changjiang River to the middle reaches of the Huanghe River. Based on water level of Wanjintan in the middle reach of Yellow River（Sanmenxia, Henan）in the 1766-1911s were recorded the time of rising water. Under the 5-days scale, establishing the beginning time of flood season in Sanmenxia in the study period. The results show that: 1766-1840s is the start time of flood season in the middle reaches of the average level; in 1840-1860s the beginning time of flood season come late; in 1860~1890s the beginning time of flood season advance again. In the study period, the average beginning time of flood season in the middle reaches of Yellow River is in the early July, the end time of rainy in the middle reach of Changjiang River have a good correspondence. However, summer wind rain-band moving is the main driving factors of changing of flood season beginning. The delay of flood season to about one pentad in the middle reaches of the Yellow River from 1870 to 1900 is in accordance with the relative low temperature of the Loess Plateau in summer, while the early flood season of the middle reaches of the Yellow River and Qin River is correspondent with the relative high temperature of summer in the Loess Plateau.
Choosing scientific method to extract and express relief amplitude has become the critical factor to improve the effectiveness and practicality in relief research. Based on SRTM3-DEM, the relief amplitude with increasing grid window method in the Tibetan Plateau was extracted, and then the best window area by the mean change point method was calculated. The result shows that 1.17km2 could be the best window area, the relief amplitude can be divided into eight classes, and the most widely distributed class is low rolling mountain. The relief amplitude is generally more violent at the edge of the plateau. It is mainly due to the intensive tectonic movement and river headward erosion. While the terrain is relatively flat in hinterland of the plateau, the erosion and removal caused by glaciation and unfreezing may be the greater impact on the relief amplitude.
Based on the DEM data of Jiuyuangou wateshed in Suide County, Shaanxi of China, with a spatial resolution of 5 m, employing the digital terrain analysis, multivariate statistics and data mining methods, multiple indexes of multi-azimuth DEM shaded relief and slope are established. The solutions of extraction positive and negative terrain of loess plateau by Principle Components Analysis, and Logistic regression model is proposed. The result indicates that: the extracting model has better consistency and accuracy, of which the accuracy is 82.1% and Kappa statistics is 0.6298. Tested on 6 samples of different valley by this model, the mean accuracy of positive and negative terrain are at 77.6% and 84.9%, and weighed mean accuracy is 81.3%. It is suitable to extract positive and negative terrain of loess plateau by PCA and Logistic regression model.
Sand hills distributed along shores of the Poyang Lake are composed of alternate eolian sand layers and silt layers. The Shaling sand hill, about 2 km in width and 5 km in length, is located in Liaohua Town of Xingzi County. On its north and west margins, three sections (SS1, SS2 and SS3) were investigated. Vermiculated mottles in this hill can be divided into three types. Vermiculated mottles of type Ⅰ are thick and dense and only occur in the lower part (layer 1) of section SS1. Vermiculated mottles of type Ⅱ are relatively thin and sparsely scattered and occur in the beds (layer 2) above type Ⅰ. Vermiculated mottles of type Ⅲ are indistinctly shaped and occur in the upper part (layer 5) of the section SS1and the upper part (layer 2) of the section SS2. A sand bed (layer 4) separates the vermiculated mottles of type Ⅲ from that of type I and type Ⅱ in section SS1. Vermiculated mottles of type Ⅲ cover a sand bed (layer 1) in section SS2. The section SS3 only comprises one sand bed (layer 1) and develops no vermiculated mottle. Vermiculated mottles of types I and type II are mature vermiculated mottles, whereas type Ⅲ are immature. OSL samples were collected from each sand bed. 125-250 μm quartz grains were separated from sand samples following the sequences of the standard pretreatment. The equivalent dose was measured using the Single Aliquot Regeneration protocol in the Laboratory of Surface Process of Nanjing University. The annual dose was determined by contents of U, Th and K measured using the neutron activation method in China Institute of Atomic Energy. In OSL dating of sand samples, no evidence indicates that the samples show OSL saturation signals and the annual dose of the samples was affected by weathering. So, the OSL ages can be interpreted as the deposition ages. The sand layers of Section SS1 and SS2 were deposited about 80 ka and 71 ka ago respectively and the sand layer of Section SS3 has been accumulated since 29 ka. From these OSL ages, it can be thought that the age of the layers with mature vermiculated mottles is older than 80 ka and the age of the layers with immature vermiculated mottles ranges from 71 ka to 29 ka. The top boundary age of vermiculated beds can be inferred to be 80-29 ka if the layers with immature vermiculated mottles are taken as the vermiculated beds. The top boundary age of vermiculated beds is older than 80 ka if the layers with mature vermiculated mottles are taken as the vermiculated beds. Both inferred top boundary ages are much younger than 400 ka, which was previously reported as the formation age of the vermiculated beds. However, this conclusion is drawn on three OSL ages in Shaling area and should be validated by other studies in the future.
In Gansu-Qinghai Region, compared with the previous Majiayao culture, the distribution of Qijia culture’s northern boundary trended south and the overall elevation lowered, which is the response to 4 200 a B.P. extreme events of arid climate and temperature drop. Distribution of Qijia culture sites are sparser than Majiayao, the shortest distance between sites become larger and the dependence on the river reduced, which shows that animal husbandry came into being during the period of Qijia culture. Density analysis showed that Majiayao single-core condensed settlement model evolved into Qijia′s multi-core model around 4 ka B.P.,and it implies that Qijia community splited into several tribal groups .Extreme weather events caused the agricultural productivity decrease , resource deterioration and frequent inter-tribal war, which stimulated the formation of patriarchy and progress of smelting technology. So extreme weather events around 4 200 a B.P. promoted the production of animal husbandry, the establishment of patriarchy and the generation of smelting technology, eventually make the Gansu-Qinghai prehistoric society complicated and organized.
Using the MUGCM simulations, the variation features of stable isotopes in precipitation, amount effect and relationship between δD and δ18O, on the diurnal, monthly and yearly time scales in Yunnan Province, China, are analyzed. There is significant amount effect for the isotopes in precipitation, whether on the diurnal time scale or on the monthly or the yearly time scales. Compared with the measured values, the simulated δ18O in precipitation shows the stronger correlation with precipitation. For the single station, the local meteoric water line (LMWL) is simulated well at Mengzi and Tengchong, however at Simao and Kunming, the simulated results do not reproduce truly the measured relationship between δD and δ18O in precipitation with the higher LMWL slopes, which implies that the model may overestimate the depletion of the HDO over such a particular areas like Yunnan.
