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排序方式: 共有404条查询结果,搜索用时 390 毫秒
1.
Sei‐ichiro Kawase 《International Journal of Satellite Communications and Networking》2005,23(1):67-76
This paper proposes a technique for monitoring the longitudinal motion of geosynchronous satellites. A two‐antenna interferometer is used, with the baseline orientation adjusted to a particular horizontal azimuth. The interferometer then becomes insensitive to the north–south motion of the satellite, and this enables direct measurement of the satellite's longitudinal motion. Longitudes are monitored continuously, with no delay when orbital manoeuvres occur. The proposed technique is particularly useful when two or more satellites are operating in close proximity and their longitudes must be precisely monitored for safety control. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
2.
基于多信道预约可冲突避免的多址接入协议 总被引:3,自引:0,他引:3
本文为多跳分布多无线网络提出了一套灵活而有效的自适应获取冲突避免(AACA)的多址接入协议。在该协议中,各节点竞争公共信道,利用RTS/CTS对话形式来预约各业务信道,成功预约后的分组传输不会受到其他节点的干扰。它使用任意确定数目信道,以异步方式工作,并且使得各节点利用半双工无线电台就可以灵活、简便地实现资源预约。分析和比较结果说明,所提出的多信道预约协议可以有效地解决隐藏终端、暴露终端以及侵入终端的问题。 相似文献
3.
对拟线性椭圆变分不等式的障碍最优控制问题(即以障碍为控制变量)进行了研究.指标泛函为Lagrange型,其中含有控制变量二阶导数的p次幂,这使得最优性条件的推导颇为不易.对所考虑的问题给出了最优控制的存在性定理以及必要条件. 相似文献
4.
A horizontal translation of a function is the focus of this study. We examine the explanations provided by secondary school students and secondary school teachers to a translation of a function, focusing on the example of the parabola y=(x−3)2 and its relationship to y=x2. The participants’ explanations focused on attending to patterns, locating the zero of the function, and the point-wise calculation of function values. The results confirm that the horizontal shift of the parabola is, at least initially, inconsistent with expectations and counterintuitive to most participants. We articulate possible sources of this perceived inconsistency and describe a pedagogical approach aimed at resolving it. 相似文献
5.
In this paper we consider an obstacle control problem where the state satisfies a quasilinear elliptic variational inequality and the control function is the obstacle. The state is chosen to be close to the desire profile while the H2 norms of the obstacle is not too large. Existence and necessary conditions for the optimal control are established. 相似文献
6.
Maria A. Tikhonova Nadezhda G. Tikhonova Michael V. Tenditnik Marina V. Ovsyukova Anna A. Akopyan Nina I. Dubrovina Tamara G. Amstislavskaya Elena K. Khlestkina 《Molecules (Basel, Switzerland)》2020,25(22)
Functional nutrition is a valuable supplementation to dietary therapy. Functional foods are enriched with biologically active substances. Plant polyphenols attract particular attention due to multiple beneficial properties attributed to their high antioxidant and other biological activities. We assessed the effect of grape polyphenols on the life span of C57BL/6 mice and on behavioral and neuroinflammatory alterations in a transgenic mouse model of Parkinson disease (PD) with overexpression of the A53T-mutant human α-synuclein. C57BL/6 mice were given a dietary supplement containing grape polyphenol concentrate (GPC—1.5 mL/kg/day) with drinking water from the age of 6–8 weeks for life. Transgenic PD mice received GPC beginning at the age of 10 weeks for four months. GPC significantly influenced the cumulative proportion of surviving and substantially augmented the average life span in mice. In the transgenic PD model, the grape polyphenol (GP) diet enhanced memory reconsolidation and diminished memory extinction in a passive avoidance test. Behavioral effects of GP treatment were accompanied by a decrease in α-synuclein accumulation in the frontal cortex and a reduction in the expression of neuroinflammatory markers (IBA1 and CD54) in the frontal cortex and hippocampus. Thus, a GP-rich diet is recommended as promising functional nutrition for aging people and patients with neurodegenerative disorders. 相似文献
7.
基于MMSE准则实现多址干扰避免的信号设计 总被引:1,自引:0,他引:1
本文基于最小均方误差准则(MMSE),在发端对系统中多个用户的发送信号样式进行了设计优化,最大限度地避免用户间的相互干扰,使检测器输出与发送符号之间的最小均方误差达到理论下限。在最佳信号设计过程中,本文利用矩阵分块理论简化了算法、降低了运算复杂度。并且设计的信号在加性高斯白噪声信道条件下所获得的系统容量要优于Rose等人(2002)采用特征值迭代算法(Eigen Algorithm)设计的信号集合,文章最后通过仿真给予证实。 相似文献
8.
Functional load (FL) quantifies the contributions by phonological contrasts to distinctions made across the lexicon. Previous research has linked particularly low values of FL to sound change. Here, we broaden the scope of enquiry into FL to its evolution at higher values also. We apply phylogenetic methods to examine the diachronic evolution of FL across 90 languages of the Pama–Nyungan (PN) family of Australia. We find a high degree of phylogenetic signal in FL, indicating that FL values covary closely with genealogical structure across the family. Though phylogenetic signals have been reported for phonological structures, such as phonotactics, their detection in measures of phonological function is novel. We also find a significant, negative correlation between the FL of vowel length and of the following consonant—that is, a time-depth historical trade-off dynamic, which we relate to known allophony in modern PN languages and compensatory sound changes in their past. The findings reveal a historical dynamic, similar to transphonologization, which we characterize as a flow of contrastiveness between subsystems of the phonology. Recurring across a language family that spans a whole continent and many millennia of time depth, our findings provide one of the most compelling examples yet of Sapir’s ‘drift’ hypothesis of non-accidental parallel development in historically related languages. 相似文献
9.
Through-silicon via (TSV) is a key enabling technology for the emerging 3-dimension (3D) integrated circuits
(ICs). However, the crosstalk between the neighboring TSVs is one of the important sources of the soft faults. To
suppress the crosstalk, the Fibonacci-numeral-system-based crosstalk avoidance code ( FNS-CAC) is an effective
scheme. Meanwhile, the self-repair schemes are often used to deal with the hard faults, but the repaired results
may change the mapping between signals to TSVs, thus may reduce the crosstalk suppression ability of FNS-CAC.
A TSV self-repair technique with an improved FNS-CAC codec is proposed in this work. The codec is designed
based on the improved Fibonacci numeral system (FNS) adders, which are adaptive to the health states of TSVs.
The proposed self-repair technique is able to suppress the crosstalk and repair the faulty TSVs simultaneously. The
simulation and analysis results show that the proposed scheme keeps the crosstalk suppression ability of the original
FNS-CAC, and it has higher reparability than the local self-repair schemes, such as the signal-switching-based and
the signal-shifting-based counterparts. 相似文献
10.
We study pattern avoidance in the context of partial words. The problem of classifying the avoidable binary patterns has been solved, so we move on to ternary and more general patterns. Our results, which are based on morphisms (iterated or not), determine all the ternary patternsʼ avoidability indices or at least give bounds for them. 相似文献