The vertical distribution of morphologically different drifting invertebrates (mayfly and dipteran larvae) in a small salmon river was studied. Drifting invertebrates were caught with the Astakhov’s sampler equipped ...The vertical distribution of morphologically different drifting invertebrates (mayfly and dipteran larvae) in a small salmon river was studied. Drifting invertebrates were caught with the Astakhov’s sampler equipped with three driftnets placed one above another. The average annual drift rate in different levels of a water column was practically the same, while the drift density decreased from the bottom to the surface. Over the course of 24 hours, the drifting organisms did not show clear preference for a particular water layer. Invertebrates were constantly redistributed between the upper and lower levels at approximately 30 - 90 min intervals. This redistribution appears to be linked to the fact that invertebrates of the same taxa, which entered into water column from different bottom sites become active at different times.展开更多
Recent observation of oscillating the two stream instability (TSI) in a solar type III radio bursts and spatial damping of Langmuir oscillations has made this instability as an important candidate to understand the co...Recent observation of oscillating the two stream instability (TSI) in a solar type III radio bursts and spatial damping of Langmuir oscillations has made this instability as an important candidate to understand the coronal heating problem. This instability has been studied by several authors for cold plasma found to be stable for high frequencies (greater than plasma frequency ωp). In this paper, we prove that this instability is unstable for warm plasma for higher frequencies (greater than plasma frequency ωp) and much suitable to study the solar coronal heating problem. We have derived a general dispersion relation for warm plasma and discussed the various methods analyzing the instability conditions. Also, we derived an expression for the growth rate of TSI and analyzed the growth rate for photospheric and coronal plasmas. A very promising result is that the ion temperature is the source of this instability and shifts the growth rate to high frequency region, while the electron temperature does the reverse. TSI shows a high growth rate for a wide frequency range for photosphere plasma, suggesting that the electron precipitation by magnetic reconnection current, acceleration by flares, may be source of TSI in the photosphere. But for corona, these waves are damped to accelerate the ions and further growing of such instability is prohibited due to the high conductivity in coronal plasma. The TSI is a common instability;the theory can be easily modifiable for multi-ion plasmas and will be a useful tool to analyze all the astrophysical problems and industrial devices, too.展开更多
传统数据流聚类方法缺乏对高维数据的在线降维能力,导致其聚类性能受限。为解决此问题,提出了一种基于可扩展子空间学习的数据流聚类方法(Scalable Subspace Learning for Clustering Data Streams,S2LCStream)。首先,通过可扩展子空间...传统数据流聚类方法缺乏对高维数据的在线降维能力,导致其聚类性能受限。为解决此问题,提出了一种基于可扩展子空间学习的数据流聚类方法(Scalable Subspace Learning for Clustering Data Streams,S2LCStream)。首先,通过可扩展子空间学习建立历史数据与新增数据之间的投影关系,将新增数据投影至历史数据张成的子空间中,以实时获取其聚类划分。其次,为保持不同时刻聚类划分的准确性,对持续到达的数据流进行数据分布的一致性检测,捕获其中存在的概念漂移,并结合回溯机制对聚类划分进行调整以适应动态变化的数据分布。最后,通过在多个真实数据集上进行测试,验证了所提方法在处理高维数据流的效能。所提方法在保持较高聚类性能的同时,能够高效处理数据流中的概念漂移。展开更多
文摘The vertical distribution of morphologically different drifting invertebrates (mayfly and dipteran larvae) in a small salmon river was studied. Drifting invertebrates were caught with the Astakhov’s sampler equipped with three driftnets placed one above another. The average annual drift rate in different levels of a water column was practically the same, while the drift density decreased from the bottom to the surface. Over the course of 24 hours, the drifting organisms did not show clear preference for a particular water layer. Invertebrates were constantly redistributed between the upper and lower levels at approximately 30 - 90 min intervals. This redistribution appears to be linked to the fact that invertebrates of the same taxa, which entered into water column from different bottom sites become active at different times.
文摘Recent observation of oscillating the two stream instability (TSI) in a solar type III radio bursts and spatial damping of Langmuir oscillations has made this instability as an important candidate to understand the coronal heating problem. This instability has been studied by several authors for cold plasma found to be stable for high frequencies (greater than plasma frequency ωp). In this paper, we prove that this instability is unstable for warm plasma for higher frequencies (greater than plasma frequency ωp) and much suitable to study the solar coronal heating problem. We have derived a general dispersion relation for warm plasma and discussed the various methods analyzing the instability conditions. Also, we derived an expression for the growth rate of TSI and analyzed the growth rate for photospheric and coronal plasmas. A very promising result is that the ion temperature is the source of this instability and shifts the growth rate to high frequency region, while the electron temperature does the reverse. TSI shows a high growth rate for a wide frequency range for photosphere plasma, suggesting that the electron precipitation by magnetic reconnection current, acceleration by flares, may be source of TSI in the photosphere. But for corona, these waves are damped to accelerate the ions and further growing of such instability is prohibited due to the high conductivity in coronal plasma. The TSI is a common instability;the theory can be easily modifiable for multi-ion plasmas and will be a useful tool to analyze all the astrophysical problems and industrial devices, too.
文摘传统数据流聚类方法缺乏对高维数据的在线降维能力,导致其聚类性能受限。为解决此问题,提出了一种基于可扩展子空间学习的数据流聚类方法(Scalable Subspace Learning for Clustering Data Streams,S2LCStream)。首先,通过可扩展子空间学习建立历史数据与新增数据之间的投影关系,将新增数据投影至历史数据张成的子空间中,以实时获取其聚类划分。其次,为保持不同时刻聚类划分的准确性,对持续到达的数据流进行数据分布的一致性检测,捕获其中存在的概念漂移,并结合回溯机制对聚类划分进行调整以适应动态变化的数据分布。最后,通过在多个真实数据集上进行测试,验证了所提方法在处理高维数据流的效能。所提方法在保持较高聚类性能的同时,能够高效处理数据流中的概念漂移。
