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151.
针对正交时频空(Orthogonal Time Frequency Space, OTFS)调制系统采用矩形窗函数时,信道矩阵结构复杂导致的鲁棒性差的问题,提出了一种基于时域处理和酉近似消息传递的检测算法。该算法首先添加循环前缀,将时域信道转换为分块对角矩阵;然后应用酉变换和近似消息传递建立迭代检测算法。仿真结果表明,所提检测算法能够在不增加复杂度的条件下有效提升检测精度和鲁棒性,特别是存在信道编码的条件下表现出2 dB的性能增益,使得该算法更适用于杂散多径、高速移动等环境,具有较高的应用价值。 相似文献
152.
This paper proposes a method that can reduce the complexity of a system matrix by analyzing the characteristics of a pseudoinverse matrix to receive a binomial frequency division multiplexing (BFDM) signal and decode it using the least squares (LS) method. The system matrix of BFDM can be expressed as a band matrix, and as this matrix contains many zeros, its amount of calculation when generating a transmission signal is quite small. The LS solution can be obtained by multiplying the received signal by the pseudoinverse matrix of the system matrix. The singular value decomposition of the system matrix indicates that the pseudoinverse matrix is a band matrix. The signal-to-interference ratio is obtained from their eigenvalues. Meanwhile, entries that do not contribute to signal generation are erased to enhance calculation efficiency. We decode the received signal using the pseudoinverse matrix and the removed pseudoinverse matrix to obtain the bit error rate performance and to analyze the difference. 相似文献
153.
《Mechatronics》2022
Dynamic vibration absorber (DVA) is an effective device for suppressing resonant vibration of noisy machineries and structures. However, the optimum design of DVA requires precise tuning of the damping force in the DVA, which unfortunately is often not practical and prone to changes of working conditions. In this paper, a tunable electromagnetic shunt damper (EMSD) with different opposing magnet pairs configurations is tested for the optimum design of DVA. The optimum magnet pairs configuration is derived to provide the maximum damping force in the DVA. Both simulations and experiments are conducted to verify the damping coefficient variation with the number of magnet pairs in the EMSD. The experimental optimization procedure of the DVA is designed according to the fixed-points theory. The damping force generated by the EMSD can be readily adjusted by varying the external resistance of the EMSD. This is the first experimental implementation report of the optimization procedure described in the fixed-points theory. The proposed tunable EMSD can conveniently allow for onsite optimal tuning of DVA. The proposed design methodology provides fine tuning of the damping coefficient of EMSD to achieve robust optimal DVA performance, even when subject to changes of external parasitic damping. 相似文献
154.
“二选一”是我国平台经济领域较为常见的一种竞争策略,其实质是通过排他性交易限制第三方商家的多栖行为。我国平台经济中“二选一”现象的普及程度远超欧美发达国家,其原因包括立法与执法存在不足、线上线下深度融合、特殊的商业模式和市场环境等。从平台间竞争和平台内经营者间竞争两个维度分析了“二选一”行为对竞争的影响机理,提出跨边网络效应、用户转移成本、中小商家数量、平台双重角色等是影响竞争绩效的关键因素,并基于此,进一步提出了治理“二选一”行为的对策建议。 相似文献
155.
We simulate the classical diffusion of a particle of massM in an infinite one-dimensional system of hard point particles of massm in equilibrium. Each computer run corresponds to about 108 collisions of the diffusive particle. We find that (t) 1/t
fort large enough, and a crossover from an M m regime where=2 to=3 forM=m. The diffusion constant has a sharp maximum atM=m. We study moments x(t)2 and x(t)4, and examine the behavior ofq
2
(t)=x(t)4/3x(t)22. We find thatq(t)1 (consistent with a normal distribution) in theM limit (for all timest) and in the t limit for allM.
On sabbatical leave from IVIC-Instituto Venezolano de Investigaciones Cientificas. 相似文献
156.
L. A. Shundrin I. G. Irtegova A. D. Rogachev V. A. Reznikov 《Russian Chemical Bulletin》2005,54(5):1178-1184
The electrochemical reduction of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides (R = CF3, Me, Ph, But), which are cyclic dinitrons with conjugated C=C bond, in acetonitrile is an EE process producing stable radical anions and
dianions, whereas the electrochemical oxidation is an EEC (R = Me, Ph) or EE process (R = But) with formation of radical cations (except for the case of R = CF3) and dications (R = But) stable under standard conditions. Radical cations of the dioxides with R = Me, Ph, and But and radical anions of the whole series of the compounds studied, including R = CF3, were characterized by ESR spectroscopy combined with electrochemical measurements and quantum-chemical calculations. The
electrochemical behavior of the But-substituted dinitron is unique: the EE processes in the region of negative and positive potentials with formation of the
dianion, radical anion, radical cation, and dication stable at T = 298 K were observed for the first time within one cycle of potential sweep in the CV curve measured in MeCN.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1148–1154, May, 2005. 相似文献
157.
在金属和石墨基底电极上用恒电位沉积法制备出普鲁士蓝(PB)薄膜,研究了影响膜生长的多种因素;观察到PB膜的电化学活性。用红外光谱及电子能谱对膜的化学组成作了分析,结果表明,最初制备的膜为不溶性PB:Fe_4[Fe(CN)_6]_3,在含K~+的电解质溶液中经电化学反应后膜部分转变为可溶性PB:KFeFe(CN)_6,由此确定了PB膜的电化学反应式。 相似文献
158.
The vibration-rotational kinetic energy operators of four-particle system in various coordinates are derived using a new and simple angular momentum method. The operators are respectively suitable for studying the systems described by scattering coordinate, valence coordinate, Radau coordinate, Radau/Jacobi and Jacobi/valence hybrid coordinates and so on. Certain properties of these operators and their possible applications are discussed. 相似文献
159.
IntroductionTheadvantageofmacrocyclicoligomersasprecursorsforthepreparationofhighperformancepolymersviaring openingpolymerization (ROP)hassparkedmuchinterestintheareaofadvancedthermoplasticcomposites.1 3Andaseriesofcyclicoligomerssuchascarbonates,4 arylesters ,5,6 ethers,7amides8andsulfides9,10 hasbeensuccessfullysynthesized .Recently ,Nishikuboetal.11reportedakindofnovelmacro cyclicoligomerscontainingthioestergroupspreparedbycon densationofbis(4 mercaptophenyl)sulfidewitharomaticaciddichlo… 相似文献
160.