In view of the application importance of resistance network in modern science and technology, this paper presents the basic structure of a three terminals ladder shaped resistance network, for which, to study in- dept...In view of the application importance of resistance network in modern science and technology, this paper presents the basic structure of a three terminals ladder shaped resistance network, for which, to study in- depth the equivalent resistance, carry out network analysis by applying virtual current method and construct a model of two elements three orders differential equation. Based on different marginal conditions, two general adaptive rules for the three-terminal ladder shaped inlet resistance, as well as two ultimate rules for the equiva- lent resistance of three-terminal infinite ladder shaped were given.展开更多
A 2.4-m-long core was extracted from Diaojiao Lake (41?8′N, 112?1′E) at the foot of the northern part of Daqingshan Mts. High-resolution pollen analysis results of two sites showed 10 arboreal genera, including Pinu...A 2.4-m-long core was extracted from Diaojiao Lake (41?8′N, 112?1′E) at the foot of the northern part of Daqingshan Mts. High-resolution pollen analysis results of two sites showed 10 arboreal genera, including Pinus, Betula, Picea, Abies, Carpinus, Quercus, Ulmus and more than 20 non-arboreal genera, mainly of Artemisia, Labiatae, Nitraria, Polygonaceae, Ranunculus, Thalictrum, Umbelliferae, Caryophyllaceae and Cyperaceae dominating the record. Fern spores, aquatic pollen and algae were also observed in some sections of the cores. The sequence was divided stratigraphically into six pollen assemblage zones by a stratigraphically-constrained cluster analysis using an incremental sum of squares method. The vegetation underwent the following stage changes: steppe with sparse trees, steppe, forest, and steppe. During the middle Holocene, a mixed forest of Pinus, Betula and Quercus occurred on the mountainous areas, and Pinus forest dominated the frontal plains. Six climatic stages were inferred from total pollen flux and pollen percentage from the two sites using a transfer function: humid-cool (10000—7800 aBP), arid-cold (9200—7800 aBP), arid-warm (7800—7100 aBP), humid-warm (7100—4400 aBP), arid-warm (4400—3000 aBP), arid-cold (3000—2100 aBP) phases were identified.展开更多
Based on reviewing the problems in limnology and watershed sciences in meeting the national demands and the development of theories and methodology, this paper proposed some challeng-ing topics to the sciences, coveri...Based on reviewing the problems in limnology and watershed sciences in meeting the national demands and the development of theories and methodology, this paper proposed some challeng-ing topics to the sciences, covering the process of lake evolution and the quantitative analysis of hu-man impacts, in-lake nutrient cycling an biogeo-chemical process, the process and mechanisms of material flow in lake-watershed system, digital watershed and the modeling of the surface pro-cess of lake-watershed, and ecosystem health and scientific management of lake- watershed.展开更多
基金a project financed by Natural Science Fund of Education Department of Jiangsu Province (02KJB140008)
文摘In view of the application importance of resistance network in modern science and technology, this paper presents the basic structure of a three terminals ladder shaped resistance network, for which, to study in- depth the equivalent resistance, carry out network analysis by applying virtual current method and construct a model of two elements three orders differential equation. Based on different marginal conditions, two general adaptive rules for the three-terminal ladder shaped inlet resistance, as well as two ultimate rules for the equiva- lent resistance of three-terminal infinite ladder shaped were given.
基金supported by the National Key Basic Research Support Foundation Project(Grant No.G2000018604).
文摘A 2.4-m-long core was extracted from Diaojiao Lake (41?8′N, 112?1′E) at the foot of the northern part of Daqingshan Mts. High-resolution pollen analysis results of two sites showed 10 arboreal genera, including Pinus, Betula, Picea, Abies, Carpinus, Quercus, Ulmus and more than 20 non-arboreal genera, mainly of Artemisia, Labiatae, Nitraria, Polygonaceae, Ranunculus, Thalictrum, Umbelliferae, Caryophyllaceae and Cyperaceae dominating the record. Fern spores, aquatic pollen and algae were also observed in some sections of the cores. The sequence was divided stratigraphically into six pollen assemblage zones by a stratigraphically-constrained cluster analysis using an incremental sum of squares method. The vegetation underwent the following stage changes: steppe with sparse trees, steppe, forest, and steppe. During the middle Holocene, a mixed forest of Pinus, Betula and Quercus occurred on the mountainous areas, and Pinus forest dominated the frontal plains. Six climatic stages were inferred from total pollen flux and pollen percentage from the two sites using a transfer function: humid-cool (10000—7800 aBP), arid-cold (9200—7800 aBP), arid-warm (7800—7100 aBP), humid-warm (7100—4400 aBP), arid-warm (4400—3000 aBP), arid-cold (3000—2100 aBP) phases were identified.
文摘Based on reviewing the problems in limnology and watershed sciences in meeting the national demands and the development of theories and methodology, this paper proposed some challeng-ing topics to the sciences, covering the process of lake evolution and the quantitative analysis of hu-man impacts, in-lake nutrient cycling an biogeo-chemical process, the process and mechanisms of material flow in lake-watershed system, digital watershed and the modeling of the surface pro-cess of lake-watershed, and ecosystem health and scientific management of lake- watershed.
