Abstract:
机械工程领域普遍存在正弦信号, 为提高频率估计精度, 提出了一种基于幅值-相角判据的修正Rife算法, 即A-P-Rife算法．针对Rife算法接近两相邻量化频率中心区域时估计精度接近克拉美-罗限(CRLB)的性能特点, 对信号进行FFT变换得到幅值和相角并计算出频移因子．通过设定门限值, 对频移因子进行判断, 满足门限值的信号采用Rife算法进行估计, 不满足门限值的信号则采用相角判据进行估计, 以获得更高的估计精度．仿真结果表明：在频率估计性能上, 所提算法优于原始Rife算法、相角判据算法和M-Rife算法, 其与I-Rife算法性能接近, 但计算量小于I-Rife算法．修正Rife算法可有效提高频率估计精度, 降低误判率并减少计算量, 可应用于工程中的实时频率估计． Sinusoidal signal is widely encountered in mechanical engineering. A modified algorithm called A-P-Rife algorithm is presented based on the amplitude and phase criterion to improve the estimation accuracy. The frequency estimation accuracy of Rife algorithm could reach Cramer-Rao lower bound(CRLB) when the signal frequency is close to the midpoint of two neighboring discrete frequencies. The amplitude and phase of the signal are obtained by the fast Fourier transform(FFT) in order to calculate the frequency-shifting operator. By setting a threshold value，the frequency-shifting operator is judged to determine which method to employ. If the frequency-shifting operator meets the threshold value，the signal is estimated by Rife algorithm; otherwise，it is estimated by phase criterion. The simulation results indicate that the new algorithm is superior to original Rife algorithm，phase criterion algorithm and M-Rife algorithm in frequency estimation performance，and has less computation than I-Rife algorithm with similar performance. The modified algorithm effectively improves the accuracy of frequency estimation and reduces misjudgment rate. It is proved that the new method can realize real-time frequency estimation of the signal

Abstract:
Rife算法是正弦波频率估计的一种经典算法，但其根本缺陷在于低信噪比且被估计频率接近量化频率点时估计性能差。本文通过分析Zoom-FFT的基本原理，验证了其具有可控的局部频谱放大功能，进而提出了一种改进的Rife频率估计算法。通过对信号进行Zoom-FFT处理实现以被估计频率为中心的较窄频段频谱的大幅度细化和放大，然后利用Rife算法进行精确频率估计。仿真结果表明，该算法具有高于传统Rife及其改进算法的估计精度和抗噪声性能，且对真实频率与量化频率点的位置关系不敏感，但计算复杂度有一定增加。 Rife algorithm is a classical algorithm for frequency estimation of sine wave. Its drawback is that the estimation performance is poor when the true frequency is close to the frequency quantization points or the SNR is low. After analyzing the theory of Zoom-FFT, its amplification function for spectrum is verified. Furthermore, an improved frequency estimation algorithm based on Zoom-FFT is proposed. After the Zoom-FFT process, spectrum of a narrowband centered on true frequency is amplified, and then Rife algorithm is used to finish the accurate estimation of signal frequency. Simulation results indicate that the improved Rife algorithm has higher estimation accuracy and better anti-noise performance than Rife algorithm and some other improved algorithms. Moreover, it is insensitive to the position of the true frequency in the spectrum. However, to a certain extent, the computation load is improved.

Abstract:
Mathieu equation is widely used to study several natural phenomenon. In this paper, we show that replacing the sinusoid in the Mathieu equation with a phasor can lead to solutions that behave in a totally different way. Solutions of Mathieu equation are either bounded or grow unboundedly at an exponential rate. Solutions of this new equation are always unbounded and grow linearly with time.

Abstract:
A frequency offset correcting algorithm is presented for frequency estimation of sinusoid signal, and a fast and accurate recursive algorithm for frequency estimation of sinusoid signal is investigated by associating the advantage of high accuracy of the M-Rife algorithm and the advantage of small computational load of the frequency offset correcting algorithm. Firstly, an initial estimation is obtained by the M-Rife algorithm for a truncated signal series which has a few points. Next, with the initial estimation result, a more accurate estimation is obtained by the frequency offset correcting algorithm for a longer truncated signal series. And then, deduce the rest by analogy. Finally, the ultimate estimation is obtained by the M-Rife algorithm for the entire signal series. The computational complexity of the recursive algorithm is lower than that of an FFT operation when the signal series is long. Simulation results show that the performance of this algorithm is stable, and the estimation variance is nearly the same as the M-Rife algorithm, approaching to CRLB(Cramer-Rao Lower Bound). The algorithm is convenient for realizing real-time frequency estimation accurately.

Abstract:
A novel adaptive FIR filter for the estimation of a single-tone sinusoid corrupted by additive noise is described. The filter is based on an offline optimization procedure which, for a given notch frequency, computes the filter coefficients such that the frequency response is unity at that frequency and a weighted noise gain is minimized. A set of such coefficients is obtained for notch frequencies chosen at regular intervals in a given range. The filter coefficients corresponding to any frequency in the range are computed using an interpolation scheme. An adaptation algorithm is developed so that the filter tracks the sinusoid of unknown frequency. The algorithm first estimates the frequency of the sinusoid and then updates the filter coefficients using this estimate. An application of the algorithm to beamforming is included for angle-of-arrival estimation. Simulation results are presented for a sinusoid in correlated noise, and compared with those for the adaptive IIR notch filter.

Abstract:
Hepatic ischemia-reperfusion (I/R) activates Kupffer cells (KCs),which produce various inflammatory cytokines, causing adhesionof neutrophils to sinusoidal endothelium and microcirculatorydisturbance. These phenomena are well known as mechanisms ofhepatic I/R injury. Recently, in the early period of I/R, i.e., within120 min after reperfusion, it was proved that accumulation of plateletsto sinusoid is strongly associated with mechanism of the I/R.In this editorial, we describe the mechanism of I/R injury focusingon platelets and KCs in the early period of I/R. We successfullyobserved the dynamics of platelets and KCs in the hepatic sinusoidtime dependently using an intravital microscopy (IVM) system inrat. Platelets were isolated from the whole blood of syngeneic ratsand labeled with rhodamine-6G. KCs were labeled using the liposomeentrapment method. The observations revealed that plateletsattached to KCs and sinusoidal endothelial cells (SECs) duringthe early period of I/R. The number of platelets adhering to bothKCs and SECs increased in proportion to the duration of reperfusion.These interactions may be causally related to the downstreameffects of I/R and are important to characterize. The existence ofplatelets as well as KCs is indispensable for the I/R injury.

Abstract:
The recently published book, ``Lise Meitner and the Dawn of the Nuclear Age'', by Patricia Rife (Boston: Birkh\"{a}user, 1999) is reviewed in an essay for the lay audience. Meitner was a leading nuclear physicist at the time that the nucleus was the most exciting frontier of science. To establish her career, she had to overcome daunting prejudices against women in science and academia. Being of Jewish origin in Germany in the 1930's, she narrowly escaped certain disaster. Meitner was a crucial participant in the discovery of nuclear fission, yet did not share in the Nobel Prize that her collaborator, Otto Hahn, received in 1945. How these events came about, how they were intertwined with contemporary history and how they fit into the evolution of Meitner's social conscience and her abhorrence of war are some of the fascinating subjects discussed in the book and reviewed in this essay.

Abstract:
In this paper, an analytical expression is developed for the differential entropy of a sinusoid with a Beta-distributed phase angle. This particular signal model is prevalent in optical communications, however an expression for the associated differential entropy does not currently exist. The expression we derive is approximate as it relies on a series expansion for one of the key terms needed in the derivation. However, we are able to show that the approximation is accurate (error ≤ 5%) for a wide variety of Beta parameter choices.

Abstract:
This paper proposes a novel nano-sinusoid particle to be employed in enhanced localized surface plasmon resonance (LSPR) bio-sensing devices. Numerical investigations are carried out to demonstrate advantages offered by the proposed nano-particle on LSPR enhancement over other nano-particles including noble nano-triangles and nano-diamonds. Although nano-triangles exhibit high concentration of the electric field near their tips, when illuminated with a light polarized along the tip axis, they present only one hot spot at the vertex along the polarization direction. To create a structure with two hot spots, which is desired in bio-sensing applications, two nano-triangles can be put back-to-back. Therefore, a nano-diamond particle is obtained which exhibits two hot spots and presents higher enhancements than nano-triangles for the same resonant wavelength. The main drawback of the nano-diamonds is the fluctuation in their physical size-plasmon spectrum relationships, due to a high level of singularity as the result for their four sharp tip points. The proposed nano-sinusoid overcomes this disadvantage while maintaining the benefits of having two hot spots and high enhancements.