Soil erosion and land degradation are global problems and pose major issues in many countries. Both soil erosion and mass movement are two forms of land degradation and humans play important roles in these geomorpholo...Soil erosion and land degradation are global problems and pose major issues in many countries. Both soil erosion and mass movement are two forms of land degradation and humans play important roles in these geomorphological processes. This paper reviews slope processes associated with mass movement and soil erosion and contributory factors, including physical and human agents. Acting together, these cause diverse geomorphological features. Slope processes are illustrated by reference to case studies from Brazil and UK. The causes and impacts of erosion are discussed, along with appropriate remedial bioengineering methods and the potential of the measures to prevent these types of environmental degradation. Although there are several agents of erosion, water is the most important one. Cultivation can promote soil erosion, due to ploughing and harvesting, which moves soil down slopes. Soil erosion and mass movement data would inform the viability of soil conservation practices. Integrated management of drainage basins offers a Dromising way forward for effective soil conservation and soil remedial bioengineering in Brazil and UK.展开更多
The multivariate extension of the Cox model proposed by Wei,Lin and Weissfeld in 1989 has been widely used for analyzing multivariate survival data.Under the model assumption,failure times from an individual are assum...The multivariate extension of the Cox model proposed by Wei,Lin and Weissfeld in 1989 has been widely used for analyzing multivariate survival data.Under the model assumption,failure times from an individual are assumed to marginally follow their respective proportional hazards regression relation,leaving the joint distribution completely unspecified.This paper presents a simple approach to efficiency improvement through segmentation of stochastic integrals in the marginal estimating equations and incorporation of the limiting covariance structure.It is shown that when partition of the time interval is done at a suitable rate,the resulting estimator is consistent and asymptotically normal.Through the reproducing kernel Hilbert space arising from the covariance function of the limiting Gaussian process,it is also shown that the proposed estimator is asymptotically optimal within a reasonable class of estimators under marginal specification.Simulations are conducted to assess the finite-sample performance of the proposed method.展开更多
Hazards and risks assessment of dangerous geocryological processes is an actual problem in connection with climate change.Permafrost is widespread in Russia,Canada,the USA(Alaska),China,Mongolia and in mountain region...Hazards and risks assessment of dangerous geocryological processes is an actual problem in connection with climate change.Permafrost is widespread in Russia,Canada,the USA(Alaska),China,Mongolia and in mountain regions.Currently there are many papers concerning permafrost-related hazards,but the conceptual and basic techniques are not available. Different approaches for solving this problem are considered in the paper.The generally accessible techniques of geocryological processes quantitative risk assessment are not available.The problem lies展开更多
Hazards and risks assessment of dangerous geocryological processes is actual problem in connection with climate change.Permafrost is widespread in Russia,Canada,the USA(Alaska), China,Mongolia and in mountain regions....Hazards and risks assessment of dangerous geocryological processes is actual problem in connection with climate change.Permafrost is widespread in Russia,Canada,the USA(Alaska), China,Mongolia and in mountain regions.Currently there are many papers concerning permafrost-related hazards,but the conceptual and based techniques are not available.Different approaches for solving this problem are considered in the paper.The generally accessible techniques of geocryological processes quantitative risk assessment are not available.The problem lies in uncertainty appearing from展开更多
基金the financial support of the Brazilian Research Council(CNPq)
文摘Soil erosion and land degradation are global problems and pose major issues in many countries. Both soil erosion and mass movement are two forms of land degradation and humans play important roles in these geomorphological processes. This paper reviews slope processes associated with mass movement and soil erosion and contributory factors, including physical and human agents. Acting together, these cause diverse geomorphological features. Slope processes are illustrated by reference to case studies from Brazil and UK. The causes and impacts of erosion are discussed, along with appropriate remedial bioengineering methods and the potential of the measures to prevent these types of environmental degradation. Although there are several agents of erosion, water is the most important one. Cultivation can promote soil erosion, due to ploughing and harvesting, which moves soil down slopes. Soil erosion and mass movement data would inform the viability of soil conservation practices. Integrated management of drainage basins offers a Dromising way forward for effective soil conservation and soil remedial bioengineering in Brazil and UK.
基金supported by National Natural Science Foundation of China (Grant Nos.10471136 and 10971210)the Knowledge Innovation Program of Chinese Academy of Sciences (Grant No.KJCX3-SYW-S02)
文摘The multivariate extension of the Cox model proposed by Wei,Lin and Weissfeld in 1989 has been widely used for analyzing multivariate survival data.Under the model assumption,failure times from an individual are assumed to marginally follow their respective proportional hazards regression relation,leaving the joint distribution completely unspecified.This paper presents a simple approach to efficiency improvement through segmentation of stochastic integrals in the marginal estimating equations and incorporation of the limiting covariance structure.It is shown that when partition of the time interval is done at a suitable rate,the resulting estimator is consistent and asymptotically normal.Through the reproducing kernel Hilbert space arising from the covariance function of the limiting Gaussian process,it is also shown that the proposed estimator is asymptotically optimal within a reasonable class of estimators under marginal specification.Simulations are conducted to assess the finite-sample performance of the proposed method.
文摘Hazards and risks assessment of dangerous geocryological processes is an actual problem in connection with climate change.Permafrost is widespread in Russia,Canada,the USA(Alaska),China,Mongolia and in mountain regions.Currently there are many papers concerning permafrost-related hazards,but the conceptual and basic techniques are not available. Different approaches for solving this problem are considered in the paper.The generally accessible techniques of geocryological processes quantitative risk assessment are not available.The problem lies
文摘Hazards and risks assessment of dangerous geocryological processes is actual problem in connection with climate change.Permafrost is widespread in Russia,Canada,the USA(Alaska), China,Mongolia and in mountain regions.Currently there are many papers concerning permafrost-related hazards,but the conceptual and based techniques are not available.Different approaches for solving this problem are considered in the paper.The generally accessible techniques of geocryological processes quantitative risk assessment are not available.The problem lies in uncertainty appearing from
