In terms of formation mechanisms of linear dunes,there are open arguments for their widespread distribution and multi-morphological diversities.In order to clarify the formation mechanism of linear dunes of Qarhan Sal...In terms of formation mechanisms of linear dunes,there are open arguments for their widespread distribution and multi-morphological diversities.In order to clarify the formation mechanism of linear dunes of Qarhan Salt Lake,we used pattern analysis method to analyze the statistical characteristics and spatial variation of their pattern parameters.Except at the west-northwest margin,the pattern parameters showed regular spatial variation from the up-middle part towards the downwind end of the dune field.Based on the cumulative probability plots for inter-crest spacing and crest length,we divided the linear dunes into three groups,which corresponding to the three evolution stages of these dunes.The first group comprises erosional relics,with shorter crests,smaller inter-crest spacing and more random dune orientation.The second group comprises dunes whose sand supply is just sufficient to maintain stability and these dunes are approaching the net erosion stage.The crest length and inter-crest spacing of these dunes are much larger than those of the first group,and dune orientation is closer to the resultant drift direction （RDD） .The last group comprises linear dunes that are still undergoing vertical accretion and longitudinal elongation,which follows the RDD of the modern wind regime.The presence of regular spatial variation of pattern parameters and a similar geometry with the vegetated linear dunes suggest that deposition and erosion coexist in the development and evolution of linear dunes of Qarhan Salt Lake,i.e.deposition predominates at the downwind end of linear dunes in the vertical accretion and longitudinal elongation stage,whereas erosion mainly occurs at the upwind end of linear dunes in the degradation stage.Therefore,the formation mechanism of linear dunes in Qarhan Salt Lake can be reasonably explained by the combination of depositional and erosional theories.展开更多
A variational formulation of the synthesis problem for plane radiating systems according to the prescribed power directivity pattern (DP) is considered. The function representing the mean-square deviation of the presc...A variational formulation of the synthesis problem for plane radiating systems according to the prescribed power directivity pattern (DP) is considered. The function representing the mean-square deviation of the prescribed and synthesized power DPs and containing the additional term with squared norm of the current or field in the antenna aperture is considered as the criterion of optimization. Freedom to choose the phase DP is used to improve the proximity of the prescribed and synthesized DPs. In such formulation, the classes of non-linear problems, for which the non-uniqueness of solutions, their branching and bifurcation are characteristic, arise. The properties of solutions depend on the electric size of radiating system and prescribed power DP. From a practical point of view, the existence of different solutions creating the same or similar DPs, gives the opportunity to choose the solution that has a simpler implementation. The synthesis problems for plane radiating systems and plane arrays are considered.展开更多
The differences in satellite DNA methylation pattern of corn seedlings with various spontaneous chromosome aberration yields and changes in methylation pattern of these DNA sequences under different exposure modes of ...The differences in satellite DNA methylation pattern of corn seedlings with various spontaneous chromosome aberration yields and changes in methylation pattern of these DNA sequences under different exposure modes of acute UV-C and chronic gamma-irradiations have been investigated. The obtained experimental data and the conducted correlation analysis demonstrated the significant correlation between the satellite DNA methylation pattern varieties and chromosome aberration yields under various stress exposure modes. The role of satellite DNA methylation pattern variability and its changing in key responses to stress such as mobile elements’ activation, cell’s passage of checkpoints, and homological repair was discussed.展开更多
2022年5月,欧亚大陆中高纬度地区出现了“三极子”型的异常表面气温(Surface air temperature,SAT),东欧和东北亚偏冷,欧亚大陆中北部偏暖,是2000年以来5月最明显的一次气温异常。基于多种资料和方法,本文探讨了此次“三极子”型异常气...2022年5月,欧亚大陆中高纬度地区出现了“三极子”型的异常表面气温(Surface air temperature,SAT),东欧和东北亚偏冷,欧亚大陆中北部偏暖,是2000年以来5月最明显的一次气温异常。基于多种资料和方法,本文探讨了此次“三极子”型异常气温的特点和成因。结果表明:“三极子”型异常SAT在5月15—27日期间最显著,与“三极子”型的异常大气环流密切相关,偏暖(冷)处受到了异常高(低)压和异常偏南(北)风的影响,欧亚大陆中北部(东欧)还受到了异常下沉(上升)运动和净热通量正(负)异常的影响,东北亚较弱的异常环流可能是该处SAT异常较弱的原因。比较不同物理过程对三极子各区域SAT异常的贡献,发现异常温度平流(异常经向风对气候态温度的平流)在“三极子”型异常SAT的形成中贡献最大,贡献率分别为40.5%、18.7%和17.7%。“三极子”型异常环流与两支波列有关。里海以北和中纬度北大西洋东部分别在5月9—10日和15—17日期间有与低层辐合异常和高层辐散异常相关的异常上升运动,导致降水异常偏多。线性斜压模式结果证明,降水导致的潜热释放在对流层形成的异常热源可以激发出欧亚大陆上的“三极子”型环流。展开更多
基金funded by the National Basic Research Program of China (2013CB956000)the National Natural Science Foundation of China (41171010,41371102,41301003)
文摘In terms of formation mechanisms of linear dunes,there are open arguments for their widespread distribution and multi-morphological diversities.In order to clarify the formation mechanism of linear dunes of Qarhan Salt Lake,we used pattern analysis method to analyze the statistical characteristics and spatial variation of their pattern parameters.Except at the west-northwest margin,the pattern parameters showed regular spatial variation from the up-middle part towards the downwind end of the dune field.Based on the cumulative probability plots for inter-crest spacing and crest length,we divided the linear dunes into three groups,which corresponding to the three evolution stages of these dunes.The first group comprises erosional relics,with shorter crests,smaller inter-crest spacing and more random dune orientation.The second group comprises dunes whose sand supply is just sufficient to maintain stability and these dunes are approaching the net erosion stage.The crest length and inter-crest spacing of these dunes are much larger than those of the first group,and dune orientation is closer to the resultant drift direction （RDD） .The last group comprises linear dunes that are still undergoing vertical accretion and longitudinal elongation,which follows the RDD of the modern wind regime.The presence of regular spatial variation of pattern parameters and a similar geometry with the vegetated linear dunes suggest that deposition and erosion coexist in the development and evolution of linear dunes of Qarhan Salt Lake,i.e.deposition predominates at the downwind end of linear dunes in the vertical accretion and longitudinal elongation stage,whereas erosion mainly occurs at the upwind end of linear dunes in the degradation stage.Therefore,the formation mechanism of linear dunes in Qarhan Salt Lake can be reasonably explained by the combination of depositional and erosional theories.
文摘A variational formulation of the synthesis problem for plane radiating systems according to the prescribed power directivity pattern (DP) is considered. The function representing the mean-square deviation of the prescribed and synthesized power DPs and containing the additional term with squared norm of the current or field in the antenna aperture is considered as the criterion of optimization. Freedom to choose the phase DP is used to improve the proximity of the prescribed and synthesized DPs. In such formulation, the classes of non-linear problems, for which the non-uniqueness of solutions, their branching and bifurcation are characteristic, arise. The properties of solutions depend on the electric size of radiating system and prescribed power DP. From a practical point of view, the existence of different solutions creating the same or similar DPs, gives the opportunity to choose the solution that has a simpler implementation. The synthesis problems for plane radiating systems and plane arrays are considered.
文摘The differences in satellite DNA methylation pattern of corn seedlings with various spontaneous chromosome aberration yields and changes in methylation pattern of these DNA sequences under different exposure modes of acute UV-C and chronic gamma-irradiations have been investigated. The obtained experimental data and the conducted correlation analysis demonstrated the significant correlation between the satellite DNA methylation pattern varieties and chromosome aberration yields under various stress exposure modes. The role of satellite DNA methylation pattern variability and its changing in key responses to stress such as mobile elements’ activation, cell’s passage of checkpoints, and homological repair was discussed.
文摘2022年5月,欧亚大陆中高纬度地区出现了“三极子”型的异常表面气温(Surface air temperature,SAT),东欧和东北亚偏冷,欧亚大陆中北部偏暖,是2000年以来5月最明显的一次气温异常。基于多种资料和方法,本文探讨了此次“三极子”型异常气温的特点和成因。结果表明:“三极子”型异常SAT在5月15—27日期间最显著,与“三极子”型的异常大气环流密切相关,偏暖(冷)处受到了异常高(低)压和异常偏南(北)风的影响,欧亚大陆中北部(东欧)还受到了异常下沉(上升)运动和净热通量正(负)异常的影响,东北亚较弱的异常环流可能是该处SAT异常较弱的原因。比较不同物理过程对三极子各区域SAT异常的贡献,发现异常温度平流(异常经向风对气候态温度的平流)在“三极子”型异常SAT的形成中贡献最大,贡献率分别为40.5%、18.7%和17.7%。“三极子”型异常环流与两支波列有关。里海以北和中纬度北大西洋东部分别在5月9—10日和15—17日期间有与低层辐合异常和高层辐散异常相关的异常上升运动,导致降水异常偏多。线性斜压模式结果证明,降水导致的潜热释放在对流层形成的异常热源可以激发出欧亚大陆上的“三极子”型环流。
