针对非同构分布式阵列无法使用旋转不变子空间算法(estimation of signal parameters via rotation invariant technique algorithm,ESPRIT),同时为了提高非同构分布式阵列的角度估计精度,提出基于求根降秩算法(root rank reduction est...针对非同构分布式阵列无法使用旋转不变子空间算法(estimation of signal parameters via rotation invariant technique algorithm,ESPRIT),同时为了提高非同构分布式阵列的角度估计精度,提出基于求根降秩算法(root rank reduction estimator,root-RARE)的目标波达方向估计方法。由于分布式阵列的基线长度远大于半波长,合成方向图出现栅瓣,导致测角模糊。算法以root-RARE与多重信号分类算法(multiple signal classification,MUSIC)联合解模糊,以root-RARE得到的粗估计为参考,解整个非同构分布式阵列MUSIC谱估计的模糊,从而得到高精度无模糊的估计。推导非同构分布式阵列方向估计的克拉美罗界,分析算法的波达方向估计性能,同时分析分布式阵列方向估计时的基线模糊门限与信噪比门限之间的关系。仿真结果验证所提算法方向估计的正确性及有效性。展开更多
为了解决当前的CMOS技术遇到"功耗墙"和"散热墙"等问题导致的很难通过提高主频来提升芯片性能的问题,文中提出了一种新型多态同构阵列处理器—PAAG(Polymorphic Array Architecture for Graphics)。该阵列机在一个...为了解决当前的CMOS技术遇到"功耗墙"和"散热墙"等问题导致的很难通过提高主频来提升芯片性能的问题,文中提出了一种新型多态同构阵列处理器—PAAG(Polymorphic Array Architecture for Graphics)。该阵列机在一个芯片上集成了多个处理器,能够通过将各种高性能复杂的算法合理分解映射到该平台上实现并行计算。通过结合使用数据并行、操作并行的计算方法,对固定渲染管线的图形算法以及由国际标准组织Khronos提出的计算视觉标准Open VX1.0中的Kernel函数图像算法进行了深入分析,并给出了基于这些算法在PAAG上的并行化设计。通过在PAAG硬件平台对应的仿真环境上进行各个算法的并行实现,得到了算法在多个处理单元上的运行时钟,由此计算出算法在多个处理单元上运行的加速比。实验结果表明,文中的并行化设计方法在PAAG上能够实现对图形图像算法的线性加速,与串行相比,效率更高。展开更多
It is well established that different sites within a protein evolve at different rates according to their role within the protein; identification of these correlated mutations can aid in tasks such as ab initio protei...It is well established that different sites within a protein evolve at different rates according to their role within the protein; identification of these correlated mutations can aid in tasks such as ab initio protein structure, structure function analysis or sequence alignment. Mutual Information is a standard measure for coevolution between two sites but its application is limited by signal to noise ratio. In this work we report a preliminary study to investigate whether larger sequence sets could circumvent this problem by calculating mutual information arrays for two sets of drug naive sequences from the HIV gpl20 protein for the B and C subtypes. Our results suggest that while the larger sequences sets can improve the signal to noise ratio, the gain is offset by the high mutation rate of the HIV virus which makes it more difficult to achieve consistent alignments. Nevertheless, we were able to predict a number of coevolving sites that were supported by previous experimental studies as well as a region close to the C terminal of the protein that was highly variable in the C subtype but highly conserved in the B subtype.展开更多
Silicon （Si） has the highest known theoretical specific capacity （3,590 mAh/g for Li1.5Si4, and 4,200 mAh/g for Li22Si4） as a lithium-ion battery anode, and has attracted extensive interest in the past few years. ...Silicon （Si） has the highest known theoretical specific capacity （3,590 mAh/g for Li1.5Si4, and 4,200 mAh/g for Li22Si4） as a lithium-ion battery anode, and has attracted extensive interest in the past few years. However, its application is limited by poor cyclability and early capacity fading due to significant volume changes during lithiation and delithiation processes. In this work, we report a coaxial silicon/anodic titanium oxide/silicon （Si-ATO--Si） nanotube array structure grown on a titanium substrate demonstrating excellent electrochemical cyclability. The ATO nanotube scaffold used for Si deposition has many desirable features, such as a rough surface for enhanced Si adhesion, and direct contact with the Ti substrate working as current collector. More importantly, our ATO scaffold provides a rather unique advantage in that Si can be loaded on both the inner and outer surfaces, and an inner pore can be retained to provide room for Si volume expansion. This coaxial structure shows a capacity above 1,500 mAh/g after 100 cycles, with less than 0.05% decay per cycle. Simulations show that this improved performance can be attributed to the lower stress induced on Si layers upon lithiation/delithiation compared with some other recently reported Si-based nanostructures.展开更多
文摘针对非同构分布式阵列无法使用旋转不变子空间算法(estimation of signal parameters via rotation invariant technique algorithm,ESPRIT),同时为了提高非同构分布式阵列的角度估计精度,提出基于求根降秩算法(root rank reduction estimator,root-RARE)的目标波达方向估计方法。由于分布式阵列的基线长度远大于半波长,合成方向图出现栅瓣,导致测角模糊。算法以root-RARE与多重信号分类算法(multiple signal classification,MUSIC)联合解模糊,以root-RARE得到的粗估计为参考,解整个非同构分布式阵列MUSIC谱估计的模糊,从而得到高精度无模糊的估计。推导非同构分布式阵列方向估计的克拉美罗界,分析算法的波达方向估计性能,同时分析分布式阵列方向估计时的基线模糊门限与信噪比门限之间的关系。仿真结果验证所提算法方向估计的正确性及有效性。
文摘It is well established that different sites within a protein evolve at different rates according to their role within the protein; identification of these correlated mutations can aid in tasks such as ab initio protein structure, structure function analysis or sequence alignment. Mutual Information is a standard measure for coevolution between two sites but its application is limited by signal to noise ratio. In this work we report a preliminary study to investigate whether larger sequence sets could circumvent this problem by calculating mutual information arrays for two sets of drug naive sequences from the HIV gpl20 protein for the B and C subtypes. Our results suggest that while the larger sequences sets can improve the signal to noise ratio, the gain is offset by the high mutation rate of the HIV virus which makes it more difficult to achieve consistent alignments. Nevertheless, we were able to predict a number of coevolving sites that were supported by previous experimental studies as well as a region close to the C terminal of the protein that was highly variable in the C subtype but highly conserved in the B subtype.
文摘Silicon （Si） has the highest known theoretical specific capacity （3,590 mAh/g for Li1.5Si4, and 4,200 mAh/g for Li22Si4） as a lithium-ion battery anode, and has attracted extensive interest in the past few years. However, its application is limited by poor cyclability and early capacity fading due to significant volume changes during lithiation and delithiation processes. In this work, we report a coaxial silicon/anodic titanium oxide/silicon （Si-ATO--Si） nanotube array structure grown on a titanium substrate demonstrating excellent electrochemical cyclability. The ATO nanotube scaffold used for Si deposition has many desirable features, such as a rough surface for enhanced Si adhesion, and direct contact with the Ti substrate working as current collector. More importantly, our ATO scaffold provides a rather unique advantage in that Si can be loaded on both the inner and outer surfaces, and an inner pore can be retained to provide room for Si volume expansion. This coaxial structure shows a capacity above 1,500 mAh/g after 100 cycles, with less than 0.05% decay per cycle. Simulations show that this improved performance can be attributed to the lower stress induced on Si layers upon lithiation/delithiation compared with some other recently reported Si-based nanostructures.
