采用时空互代法，以不同年限坡改梯田为研究对象，分析了陇东黄土丘陵区梯田土壤有机碳（SOC）的时空分布特征。结果表明，1）陇东黄土丘陵区黄绵土在坡改梯后近50 a内，农田0—60 cm土层土壤有机碳处于持续累积状态，20—40 cm与40—60...采用时空互代法，以不同年限坡改梯田为研究对象，分析了陇东黄土丘陵区梯田土壤有机碳（SOC）的时空分布特征。结果表明，1）陇东黄土丘陵区黄绵土在坡改梯后近50 a内，农田0—60 cm土层土壤有机碳处于持续累积状态，20—40 cm与40—60 cm土层SOC较坡耕地的增幅分别为54.6%和52.4%，大于表层增幅 （33.7%）（P〈0.05）；各土层SOC随梯田年限的变化趋势基本一致，在修建初期（0~8 a）累积较快并超过坡耕地SOC水平（P〈0.01），24 a 后有了显著提高（P〈0.05），后期SOC累积变化不显著。2）不同土壤类型及地形下SOC含量及累积速率有所差异，0—20 cm 土层的SOC在黄绵土中累积最为明显，20—40 cm与40—60 cm 两个土层SOC在红粘土中的累积量最为显著（P〈0.05）；阴坡表层SOC大于阳坡，梯田修建25 a 后阴坡平均SOC较阳坡高22.1%。3）梯田土壤有机碳的时空变异受土壤类型的影响最大，其贡献率达62.0%，海拔和坡向影响次之，两者可解释20.4%的有机碳的变异；梯田年限和施用有机肥可分别解释11.7%和5.8%的变异。陇东黄土丘陵区坡改梯田土壤在当前经营状况下表现出较弱的碳汇效应。展开更多
Based on the slice method of the non-circular slip surface for the calculation of integral stability of slope, an improved genetic algorithm was proposed, which can freely search for the most dangerous slip surface of...Based on the slice method of the non-circular slip surface for the calculation of integral stability of slope, an improved genetic algorithm was proposed, which can freely search for the most dangerous slip surface of slope and the corresponding minimum safety factor without supposing the geometric shape of the most dangerous slip surface. This improved genetic algorithm can simulate the genetic evolution process of organisms and avoid the local minimum value compared with the classical methods. The results of engineering cases show that it is a global optimal algorithm and has many advantages, such as higher efficiency and shorter time than the simple genetic algorithm.展开更多
De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau.There are different views about the defarming method,and also various...De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau.There are different views about the defarming method,and also various de-farming patterns have been put into practice.This paper takes the Yangou Watershed in Shaanxi Province of China as a case for studying the comprehensive benefits of transforming slope farmland to terraces.Based on the day-by-day meteorological data of the Yan'an station in 2005 and the data of terrain features,soil and land use data of the Yangou Watershed,the impact of transforming slope farmland on terraces were simulated and analyzed in aspects of yield increase and water-soil conservation under different topographic conditions with the aid of software WIN-YIELD.Furthermore,an empirical analysis was applied to study the effects of transforming slope farmland to terraces in the Yangou Watershed.The results show that:(1) The bigger the topographic gradient is,the more remarkable benefits it has in yield increase and water-soil conservation.(2) Farmland with slope below 5° could be retained,but farmland with slope above 15° should be converted to forest or grassland as soon as possible.(3) Transforming slope farmland to terraces has the same remarkable effects as the current policy of "Relieving and de-farming" in improving agricultural production conditions,safeguarding food security,raising permanent vegetation coverage rate,and preventing soil and water loss.Besides,it is more cost-effective than the policy of "Relieving and de-farming".It's strongly suggested that the policy of transforming slope farmland to terraces be carried out on the Loess Plateau without delay.展开更多
Magnetically modified palygorskite composites were synthesized with γ-Fe2O3 dispersing on the external surface of clay mineral. The magnetic clay was characterized with Fourier transform infrared, X-ray diffrac- tion...Magnetically modified palygorskite composites were synthesized with γ-Fe2O3 dispersing on the external surface of clay mineral. The magnetic clay was characterized with Fourier transform infrared, X-ray diffrac- tion, transmission electron microscopy, and vibrating sample magnetometer. Candida sp. 99-125 lipase was immobilized on magnetic palygorskite composites by physical adsorption with enzyme loading of 41.5 mg· g^-1 support and enzyme activity of 2631.6 U· （g support）^-1. The immobilized lipase exhibit better thermal and broader pH stability and excellent reusabilitV compared with free lipase.展开更多
A new image enhancement algorithm based on Retinex theory is proposed to solve the problem of bad visual effect of an image in low-light conditions. First, an image is converted from the RGB color space to the HSV col...A new image enhancement algorithm based on Retinex theory is proposed to solve the problem of bad visual effect of an image in low-light conditions. First, an image is converted from the RGB color space to the HSV color space to get the V channel. Next, the illuminations are respectively estimated by the guided filtering and the variational framework on the V channel and combined into a new illumination by average gradient. The new reflectance is calculated using V channel and the new illumination. Then a new V channel obtained by multiplying the new illumination and reflectance is processed with contrast limited adaptive histogram equalization(CLAHE). Finally, the new image in HSV space is converted back to RGB space to obtain the enhanced image. Experimental results show that the proposed method has better subjective quality and objective quality than existing methods.展开更多
文摘采用时空互代法，以不同年限坡改梯田为研究对象，分析了陇东黄土丘陵区梯田土壤有机碳（SOC）的时空分布特征。结果表明，1）陇东黄土丘陵区黄绵土在坡改梯后近50 a内，农田0—60 cm土层土壤有机碳处于持续累积状态，20—40 cm与40—60 cm土层SOC较坡耕地的增幅分别为54.6%和52.4%，大于表层增幅 （33.7%）（P〈0.05）；各土层SOC随梯田年限的变化趋势基本一致，在修建初期（0~8 a）累积较快并超过坡耕地SOC水平（P〈0.01），24 a 后有了显著提高（P〈0.05），后期SOC累积变化不显著。2）不同土壤类型及地形下SOC含量及累积速率有所差异，0—20 cm 土层的SOC在黄绵土中累积最为明显，20—40 cm与40—60 cm 两个土层SOC在红粘土中的累积量最为显著（P〈0.05）；阴坡表层SOC大于阳坡，梯田修建25 a 后阴坡平均SOC较阳坡高22.1%。3）梯田土壤有机碳的时空变异受土壤类型的影响最大，其贡献率达62.0%，海拔和坡向影响次之，两者可解释20.4%的有机碳的变异；梯田年限和施用有机肥可分别解释11.7%和5.8%的变异。陇东黄土丘陵区坡改梯田土壤在当前经营状况下表现出较弱的碳汇效应。
文摘Based on the slice method of the non-circular slip surface for the calculation of integral stability of slope, an improved genetic algorithm was proposed, which can freely search for the most dangerous slip surface of slope and the corresponding minimum safety factor without supposing the geometric shape of the most dangerous slip surface. This improved genetic algorithm can simulate the genetic evolution process of organisms and avoid the local minimum value compared with the classical methods. The results of engineering cases show that it is a global optimal algorithm and has many advantages, such as higher efficiency and shorter time than the simple genetic algorithm.
基金the National Natural Science Foundation of China(No.40771086)National Key Technology R&D Program of China (No.2006BAD09B10)Knowledge Innovation Project of Chinese Academy of Sciences (No.KZCX2-XB2-05-01)
文摘De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau.There are different views about the defarming method,and also various de-farming patterns have been put into practice.This paper takes the Yangou Watershed in Shaanxi Province of China as a case for studying the comprehensive benefits of transforming slope farmland to terraces.Based on the day-by-day meteorological data of the Yan'an station in 2005 and the data of terrain features,soil and land use data of the Yangou Watershed,the impact of transforming slope farmland on terraces were simulated and analyzed in aspects of yield increase and water-soil conservation under different topographic conditions with the aid of software WIN-YIELD.Furthermore,an empirical analysis was applied to study the effects of transforming slope farmland to terraces in the Yangou Watershed.The results show that:(1) The bigger the topographic gradient is,the more remarkable benefits it has in yield increase and water-soil conservation.(2) Farmland with slope below 5° could be retained,but farmland with slope above 15° should be converted to forest or grassland as soon as possible.(3) Transforming slope farmland to terraces has the same remarkable effects as the current policy of "Relieving and de-farming" in improving agricultural production conditions,safeguarding food security,raising permanent vegetation coverage rate,and preventing soil and water loss.Besides,it is more cost-effective than the policy of "Relieving and de-farming".It's strongly suggested that the policy of transforming slope farmland to terraces be carried out on the Loess Plateau without delay.
基金the National Basic Research Program of China(2009CB724700)the Foundation of Jiangsu Province of China for College Postgraduate Students in Innovation Engineering(CXZZ12_0440)
文摘Magnetically modified palygorskite composites were synthesized with γ-Fe2O3 dispersing on the external surface of clay mineral. The magnetic clay was characterized with Fourier transform infrared, X-ray diffrac- tion, transmission electron microscopy, and vibrating sample magnetometer. Candida sp. 99-125 lipase was immobilized on magnetic palygorskite composites by physical adsorption with enzyme loading of 41.5 mg· g^-1 support and enzyme activity of 2631.6 U· （g support）^-1. The immobilized lipase exhibit better thermal and broader pH stability and excellent reusabilitV compared with free lipase.
基金supported by the China Scholarship CouncilPostgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX17_0776)the Natural Science Foundation of NUPT(No.NY214039)
文摘A new image enhancement algorithm based on Retinex theory is proposed to solve the problem of bad visual effect of an image in low-light conditions. First, an image is converted from the RGB color space to the HSV color space to get the V channel. Next, the illuminations are respectively estimated by the guided filtering and the variational framework on the V channel and combined into a new illumination by average gradient. The new reflectance is calculated using V channel and the new illumination. Then a new V channel obtained by multiplying the new illumination and reflectance is processed with contrast limited adaptive histogram equalization(CLAHE). Finally, the new image in HSV space is converted back to RGB space to obtain the enhanced image. Experimental results show that the proposed method has better subjective quality and objective quality than existing methods.
