Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among ...Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among which the biggest altitude above river level is 401m and the formation age of the highest terrace is 1.57 Ma B.P. Based on comparative analysis of the Yellow River terraces located separately in the Mijiashan mountain, the Chemuxia gorge, the Heishanxia gorge and the other river terraces in the vast extent of the northern part of China, it has been found that the tectonic processes resulting in the formation of the terrace series is one of multi-gradational features, i.e., a terrace series can include the various terraces produced by tectonic uplifts of different scopes or scales and different ranks. The Yellow River terrace series in the study region can be divided into three grades. Among them, in the first grade there are 6 terraces which were formed separately at the same time in the vast extent of the northern part of China and represent the number and magnitude of uplift of the Qinghai-Xizang Plateau since 1.6 Ma B. P.; in the second grade there are 5 terraces which were separately and simultaneously developed within the Haiyuan-Tianjingshan tectonic region and represent the number and magnitude of uplift of this tectonic region itself since 1.6Ma B.P.; in the third grade there are 10 terraces which developed on the eastern slope of the Mijiashan mountain and represent the number and amplitude of uplift of the Haiyuan tectonic belt itself since 1.6Ma B.P. Comparison of the terrace ages with loess-paleosoil sequence has also showed that the first grade terraces reflecting the vast scope uplifts of the Qinghai-Xizang Plateau are very comparable with climatic changes and their formation ages all correspond to the interglacial epochs during which paleosoils were formed. This implies that the vast extent tectonic uplifts resulting in river down-cutting are closely related to the warm-humid climatic periods which can also result in river downward erosion after strong dry and cold climatic periods, and they have jointly formed the tectonic-climatic cycles. There exists no unanimous and specific relationship between the formation ages of the second and third grade terraces and climatic changes and it is shown that the formation of those terraces was most mainly controlled by tectonic uplifts of the Tianjingshan block and the Haiyuan belt. The river terraces in the study region, therefore, may belong to 2 kinds of formation cause. One is a tectonic-climatic cyclical terrace produced jointly by vast extent tectonic uplifts and climatic changes, and the terraces of this kind are extensively distributed and can be well compared with each other among regions. Another is a pulse-tectonic cyclical terrace produced by local tectonic uplifts as dominant elements, and their distribution is restricted within an active belt and can not be compared with among regions.展开更多
The objective of this study is to improve the statistical modeling for the ternary forecast of heavy snowfall in the Honam area in Korea. The ternary forecast of heavy snowfall consists of one of three values, 0 for l...The objective of this study is to improve the statistical modeling for the ternary forecast of heavy snowfall in the Honam area in Korea. The ternary forecast of heavy snowfall consists of one of three values, 0 for less than 50 mm, 1 for an advisory （50-150 ram）, and 2 for a warning （more than 150 mm）. For our study, the observed daily snow amounts and the numerical model outputs for 45 synoptic factors at 17 stations in the Honam area during 5 years （2001 to 2005） are used as observations and potential predictors respectively. For statistical modeling and validation, the data set is divided into training data and validation data by cluster analysis. A multi-grade logistic regression model and neural networks are separately applied to generate the probabilities of three categories based on the model output statistic （MOS） method. Two models are estimated by the training data and tested by the validation data. Based on the estimated probabilities, three thresholds are chosen to generate ternary forecasts. The results are summarized in 3 × 3 contingency tables and the results of the three-grade logistic regression model are compared to those of the neural networks model. According to the model training and model validation results, the estimated three-grade logistic regression model is recommended as a ternary forecast model for heavy snowfall in the Honam area.展开更多
Original ecotourism resources mainly refer to natural and human original ecotourism resources, and it＇s of fragility, rarity and irreversibility. As a valuable historic heritage and hnportant tourism resources, it pl...Original ecotourism resources mainly refer to natural and human original ecotourism resources, and it＇s of fragility, rarity and irreversibility. As a valuable historic heritage and hnportant tourism resources, it plays a significant role in developing tourism and economy in such areas as the underdeveloped areas, the mountain areas and mimority areas. The tourism resources in the western mountain areas of Guangxi owe ,superiorities and characteristics ＇o their original ecology, Yet, western Guangxi is an ethnic region with fragile karst eco-environment, so it is specialto exploit the tourism resources. The paper defines original eeotourism and analyses the specialties and advantages of the original ecotourism resources as well as thefrailty of the ecotourism resources of the region. The ways of thinking are put forward for safe preservation and sustainable development of the original ecotourism resources, i.e. carrying out measures for the multi-grade protection of heritage resources, setting up a ethnic eco-museum/ ethnic culture eco-park and a gene pool of ethnic cultures, etc.展开更多
This paper proposes an approach to calculate the head difference at two sides of suspended waterproof curtains during multi-grade dewatering.The seepage during the dewatering process can be subdivided into three regio...This paper proposes an approach to calculate the head difference at two sides of suspended waterproof curtains during multi-grade dewatering.The seepage during the dewatering process can be subdivided into three regions:(i)seepage in pit,(ii)seepage between cur-tains,and(iii)seepage outside the pit.The flow rate of the first region is equal to the pumping rate,and the flow rate of the second and third regions can be obtained by numerical analysis.A numerical model is established to simulate the seepage in the second and third regions and its performance is validated by using the measured data of a series of field tests.The flow rate of each region is then used to derive formulae for the head difference in conventional dewatering,which can be used to determine the head difference at two sides of each waterproof curtain during multi-grade dewatering.The proposed formula expresses the head difference as a function of the relative depth of the curtain inserted into the confined aquifer,the thickness of the aquifer,the distance between two curtains,and the anisotropy of the hydraulic conductivity of the aquifer.The proposed numerical approach is further validated by using data derived from numerical analysis.The validation results demonstrated that the predictions of the proposed approach are acceptable and convenient.展开更多
文摘Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among which the biggest altitude above river level is 401m and the formation age of the highest terrace is 1.57 Ma B.P. Based on comparative analysis of the Yellow River terraces located separately in the Mijiashan mountain, the Chemuxia gorge, the Heishanxia gorge and the other river terraces in the vast extent of the northern part of China, it has been found that the tectonic processes resulting in the formation of the terrace series is one of multi-gradational features, i.e., a terrace series can include the various terraces produced by tectonic uplifts of different scopes or scales and different ranks. The Yellow River terrace series in the study region can be divided into three grades. Among them, in the first grade there are 6 terraces which were formed separately at the same time in the vast extent of the northern part of China and represent the number and magnitude of uplift of the Qinghai-Xizang Plateau since 1.6 Ma B. P.; in the second grade there are 5 terraces which were separately and simultaneously developed within the Haiyuan-Tianjingshan tectonic region and represent the number and magnitude of uplift of this tectonic region itself since 1.6Ma B.P.; in the third grade there are 10 terraces which developed on the eastern slope of the Mijiashan mountain and represent the number and amplitude of uplift of the Haiyuan tectonic belt itself since 1.6Ma B.P. Comparison of the terrace ages with loess-paleosoil sequence has also showed that the first grade terraces reflecting the vast scope uplifts of the Qinghai-Xizang Plateau are very comparable with climatic changes and their formation ages all correspond to the interglacial epochs during which paleosoils were formed. This implies that the vast extent tectonic uplifts resulting in river down-cutting are closely related to the warm-humid climatic periods which can also result in river downward erosion after strong dry and cold climatic periods, and they have jointly formed the tectonic-climatic cycles. There exists no unanimous and specific relationship between the formation ages of the second and third grade terraces and climatic changes and it is shown that the formation of those terraces was most mainly controlled by tectonic uplifts of the Tianjingshan block and the Haiyuan belt. The river terraces in the study region, therefore, may belong to 2 kinds of formation cause. One is a tectonic-climatic cyclical terrace produced jointly by vast extent tectonic uplifts and climatic changes, and the terraces of this kind are extensively distributed and can be well compared with each other among regions. Another is a pulse-tectonic cyclical terrace produced by local tectonic uplifts as dominant elements, and their distribution is restricted within an active belt and can not be compared with among regions.
基金This research was performed for the project "Development of technique for Local Prediction", one of the research and development projects on meteorology and seismology funded by the Korea Meteorological Administration (KMA), 2005.
文摘The objective of this study is to improve the statistical modeling for the ternary forecast of heavy snowfall in the Honam area in Korea. The ternary forecast of heavy snowfall consists of one of three values, 0 for less than 50 mm, 1 for an advisory （50-150 ram）, and 2 for a warning （more than 150 mm）. For our study, the observed daily snow amounts and the numerical model outputs for 45 synoptic factors at 17 stations in the Honam area during 5 years （2001 to 2005） are used as observations and potential predictors respectively. For statistical modeling and validation, the data set is divided into training data and validation data by cluster analysis. A multi-grade logistic regression model and neural networks are separately applied to generate the probabilities of three categories based on the model output statistic （MOS） method. Two models are estimated by the training data and tested by the validation data. Based on the estimated probabilities, three thresholds are chosen to generate ternary forecasts. The results are summarized in 3 × 3 contingency tables and the results of the three-grade logistic regression model are compared to those of the neural networks model. According to the model training and model validation results, the estimated three-grade logistic regression model is recommended as a ternary forecast model for heavy snowfall in the Honam area.
文摘Original ecotourism resources mainly refer to natural and human original ecotourism resources, and it＇s of fragility, rarity and irreversibility. As a valuable historic heritage and hnportant tourism resources, it plays a significant role in developing tourism and economy in such areas as the underdeveloped areas, the mountain areas and mimority areas. The tourism resources in the western mountain areas of Guangxi owe ,superiorities and characteristics ＇o their original ecology, Yet, western Guangxi is an ethnic region with fragile karst eco-environment, so it is specialto exploit the tourism resources. The paper defines original eeotourism and analyses the specialties and advantages of the original ecotourism resources as well as thefrailty of the ecotourism resources of the region. The ways of thinking are put forward for safe preservation and sustainable development of the original ecotourism resources, i.e. carrying out measures for the multi-grade protection of heritage resources, setting up a ethnic eco-museum/ ethnic culture eco-park and a gene pool of ethnic cultures, etc.
基金the National Natural Science Foundation for Surface Project of China(Grant Nos.51878157,41572273)the Jiangsu Natural Science Foundation,China(Grant No.BK20181282).
文摘This paper proposes an approach to calculate the head difference at two sides of suspended waterproof curtains during multi-grade dewatering.The seepage during the dewatering process can be subdivided into three regions:(i)seepage in pit,(ii)seepage between cur-tains,and(iii)seepage outside the pit.The flow rate of the first region is equal to the pumping rate,and the flow rate of the second and third regions can be obtained by numerical analysis.A numerical model is established to simulate the seepage in the second and third regions and its performance is validated by using the measured data of a series of field tests.The flow rate of each region is then used to derive formulae for the head difference in conventional dewatering,which can be used to determine the head difference at two sides of each waterproof curtain during multi-grade dewatering.The proposed formula expresses the head difference as a function of the relative depth of the curtain inserted into the confined aquifer,the thickness of the aquifer,the distance between two curtains,and the anisotropy of the hydraulic conductivity of the aquifer.The proposed numerical approach is further validated by using data derived from numerical analysis.The validation results demonstrated that the predictions of the proposed approach are acceptable and convenient.
