A new method for determination of satellite orbits by transfer

The original idea of a new method for determination of satellite orbits by transfer is from Two-Way Satellite Time and Frequency Transfer (TWSTFT). The original method is called “determination of satellite orbit by transfer”. The method is not only for determination of satellite orbit but also for the time transfer with high accuracy and precision. The advantage is that the accuracy and the precision for determination of satellite orbit are very high and the new method is favorable for various applications. The combination of various signals disseminated and received forms various modes of satellite orbit determinations. If receivers at stations receive the own station-disseminated signals via a satellite transponder, it forms an orbit determination mode called “receiving the own station-disseminated signals mode”. If receivers at all stations receive the signals disseminated from the master station via satellite transponders, it forms an orbit determination mode called “receiving the master station-disseminated signals mode”. If all of receivers at stations receive all stations-disseminated signals via satellite transponders, it forms an orbit determination mode called “receiving all stations-disseminated signals mode”. Also there are other combinations of signals for satellite orbit determination. For different orbit determination modes with different signal combinations, their rigorous formulae of processing are hereby presented in this paper. The accurate and the precise satellite orbit determination for both of the modes, “receiving the own station-disseminated signals mode” and “receiving the master station-disseminated signals mode” is attempted. It shows that the accuracy and precision for both of modes are nearly the same, the ranging accuracy is better than 1 cm, and the observation residuals of satellite orbit determination are better than 9 cm in the observation duration of 1 day. Supported by the National Basic Research and Development Program of China (Grant No. 2007CB815503100453001)     

The changing scenario of the atomic nucleus—from nucleons and mesons to quarks and gluons

The general characteristics of the transition from hadronic matter of nucleons, three quark bags, mesons of quark antiquark pairs to quark gluon plasma is discussed. The phenomenological approach essentially guided by the MIT bag model and general thermodynamic criteria of first-order phase transition is elaborated. The more realistic calculations using the QCD lattice renormalization quark are touched upon. Possible signals of quark-gluon plasma are discussed. The central issue of deciphering plasma signals from the signals of hot hadronic matter is discussed in detail. The signals of the quark-gluon plasma, a subject of considerable interest in contemporary literature are focussed only on (i) dileptons (ii) photon photon pairs and (iii)J/Ψ suppression (with special emphasis on CERN experiments). The lingering shadow of “EMC” effect is also mentioned. Relics of the very early universe microseconds after the big bang in today’s universe (∼ 15 billion years later) are discussed. Finally, the outlook of this very exciting field is presented, a purely personal viewpoint, generalized eventually to poetic signals of the creation of the universe.     

All-optical regeneration of polarization division multiplexing signals in polarization nonlinear loop mirror

All-optical regeneration of 2 × 10-Gb/s RZ-OOK polarization-division-multiplexed (PDM) signals is demonstrated through a single polarization nonlinear loop mirror configuration. PDM signals with orthogonal polarization states are regenerated simultaneously and reassembled automatically. Up to 3.0-dB eye-diagram-based signal-to-noise-ratio (SNR) improvement is achieved for both channels with the input SNR of 6.7 dB. Such scheme is also capable of mitigating the polarization-mode-dispersion (PMD) effect for PDM signals in the presence of up to 6.3-ps DGD.     

The time domain response of some systems for sound reproduction

The perception in a listener of the existence of a “virtual” source of sound at a prescribed spatial position can be produced by ensuring that the acoustic signals at the listener's ears faithfully replicate those that would be produced by a “real” source at the same position. When loudspeakers are used to transmit the signals, it is necessary to pass the signals intended for presentation at the listener's ears through a matrix of filters that provide the inverse of the matrix of transfer functions that relates the loudspeaker input signals to the listener's ear signals. The characteristics of such filter matrices are profoundly influenced by the conditioning of the matrix to be inverted. This filter design problem is reviewed here by representing the loudspeakers as simple point monopole sources the head of the listener as a rigid sphere. The case of a virtual acoustic imaging system that uses two loudspeakers in order to reproduce the signals at the two ears is first described in some detail and previous work is reviewed. It is confirmed that the time domain response of the reproduced field is of long duration at frequencies where the inversion problem is ill-conditioned. The influence of the presence of the listener's head on this time domain behaviour is also evaluated. The principle is then extended to four input-four output reproduction systems and the computational model is used to explain some previous experimental observations. Finally, the conditioning of five input-four output systems is also examined and shown to have some potentially desirable characteristics.     

Signal reconstruction from the undersampled signal samples

It is well-known from the celebrated Shannon sampling theorem for bandlimited signals that if the sampling rate is below the Nyquist rate, aliasing takes place and the original signal cannot be reconstructed back by simply passing the signal samples through an ideal lowpass filter. However, researchers such as Stern and Gori have shown the existence of some classes of signals for which the signals are sampled below the Nyquist rate but perfect signal reconstruction is still possible from the given signal samples. Here, we present a generalized lowpass sampling theorem and show that Stern’s and Gori’s lowpass sampling theorems are special cases of it. A sampling theorem for the bandpass signals in the linear canonical transform domains is also presented and its special cases are discussed. Using a modification of the conventional natural sampling waveform with a specific width of the pulses, it is shown that the sampling rate in our generalized lowpass sampling theorem and hence in the Stern’s and the classical Shannon sampling theorems can be further reduced by a factor of two, while for the bandpass signals, the reduction in the sampling rate by some factor is possible only under some restricted conditions.     

Studies of phase characteristics of various photon echoes with a phase sensitive detection method

Various optical coherent transient signals in ruby have been examined by using an optical phase sensitive detection (PSD) technique. The PSD is performed by comparing the phase of the heterodyne beat signals obtained by the Stark switching technique with that of a local oscillator whose frequency is equal to the heterodyne beat frequency. The optical FID, two-pulse photon echoes, radiation locked echoes and notched echoes have been detected as υ-mode signals with small u-mode signals probably due to the asymmetry of the inhomogeneous broadening. The dependence of the phase of the radiation locked and notched echoes upon the driving pulses is also examined. The experimental results are in good agreement with theoretical predictions based on Bloch equations.     

All-optical demultiplexing of 4-ASK optical signals with four-wave mixing optical gates

A new all-optical technique to demultiplex quaternary-amplitude-shift keying (4-ASK) signals into two on-off keying (OOK) signals is proposed. We show that such quaternary-to-binary conversion may be performed with two types of optical gates (OGs); a first one that implements an S-shaped optical power transfer function (TF), which is also the characteristic TF of optical pulse reshaping devices, and a second type that implements a U-shaped TF. Furthermore, we describe a heuristic approach to design such OGs by using the fiber four-wave mixing effect in highly non-linear dispersion-shifted fibers. The performance of the technique is evaluated by simulating the demultiplexing of 4-ASK signals with these OGs. Results indicate that the proposed devices are able to provide binary signals with acceptable BERs even after the 4-ASK signals are propagated through a cascade of eight fiber links of 50 km followed by optical amplifiers with a 4.5-dB noise figure.     

基于模糊近似熵的抑郁症患者静息态功能磁共振成像信号复杂度分析

提出采用模糊近似熵的方法对功能磁共振成像(functional magnetic resonance imaging,fMRI)复杂度量化分析,并与样本熵进行比较.采用的22个成年抑郁症患者中,11位男性,年龄在18—65岁之间.我们期望测量的静息态fMRI信号复杂度与Goldberger/Lipsitz模型一致,越健康、越稳健其生理表现的复杂度越大,且复杂度随年龄的增大而降低.全脑平均模糊近似熵与年龄之间差异性显著(r=-0.512,p0.001).相比之下,样本熵与年龄之间差异性不显著(r=-0.102,p=0.482).模糊近似熵同样与年龄相关脑区(额叶、顶叶、边缘系统、颞叶、小脑顶叶)之间差异性显著(p0.05),样本熵与年龄相关脑区之间差异性不显著性.这些结果与Goldberger/Lipsitz模型一致,说明采用模糊近似熵分析fMRI数据复杂度是一个有效的新方法.     

Aerodynamic measurement of a large aircraft model in hypersonic flow

Accurate aerodynamic measurements in the hypersonic flow of large aircraft models in tunnels have practical significance, but pose a significant challenge. Novel aerodynamic force measurement methods have been proposed,but lack theoretical support. The forms of the force signals techniques for signal processing and calculation of aerodynamics are especially problematic. A theoretical study is conducted to investigate the dynamic properties based on models of the draw-rod system and slender rods. The results indicate that the inertia item can be neglected in the rod governing equation;further, the solutions show that the signals of each rod are a combination of aerodynamic signals(with a constant value) and sine signals, which can be verified by experimental shock tunnel results. Signal processing and aerodynamics calculation techniques are also found to be achievable via the flat part of the signals.     

The influence of fiber dispersion on the code form of the optical mm-wave signal generated by single sideband intensity-modulation

We have theoretically investigated the transmission performance of the optical mm-wave generation by using an external modulator based on single sideband (SSB) intensity modulation. Though the SSB millimeter (mm)-wave can immune the fading effect, the baseband signals with a high bit rate are degraded greatly after transmission along fiber. The main reason is that the fiber dispersion causes the time shift of the code edges; therefore the maximum transmission distance of the baseband signals is limited. The experimental and simulation results agree well with our theoretical analysis. We also propose a novel scheme to extend the transmission distance. In this novel scheme, the data signals are modulated only onto one of the two optical carriers; hence the shift of the code edges in the down-converted signals after transmission is eliminated.     

基于改进MCA的干涉高光谱图像分解

干涉高光谱图像特殊的成像原理,使其帧内存在着大幅值且位置固定的干涉条纹,而帧间存在着水平移位的背景图像,这种特点会严重的破坏原始图像的固有结构,从而导致新兴的压缩感知理论与传统压缩算法的直接应用无法得到理想的效果。由于干涉条纹信息与背景图像信息的特征不同,能够对干涉条纹与背景图像进行稀疏表示的正交基也是不同的。基于这种思想,使用MCA(morphological component analysis)算法对干涉高光谱图像中干涉条纹信息与背景图像信息进行分离处理。由于干涉高光谱图像数据量庞大,传统的MCA算法对干涉高光谱数据的图像分解,迭代收敛速度慢,运算效率较低,故而针对干涉高光谱数据特点对传统MCA算法进行改进,改变其迭代收敛条件,当分离后的图像信号与原始图像信号的误差已经基本保持不变时,即终止迭代;并根据对应正交基能且仅能稀疏表示对应信号的思想,对阈值采用自适应的方式进行更新,在新的阈值更新模式中,图像信号在不同正交基下的映射系数被计算与比较。大量实验结果表明,对于LASIS数据与LAMIS数据,MCA算法都能够较完美的将干涉高光谱图像分解,改进的MCA算法更能在保持完美分解输出结果的同时,相对于传统MCA方法显著的减小迭代次数,更快的达到迭代收敛条件,从而有效的提高了算法的运算效率与实时性需求,也为新兴的压缩感知理论在干涉高光谱图像中的进一步应用提供了一种很好的解决方案。     

基于AD8232的心电实时监测及分析系统设计

为了方便对患者心电信号进行实时监测,实现对心脏疾病的及时预防及诊断,利用一款基于ATmega328p微控制器的Arduino开发板、一块心电监测前端模块AD8232及上位机软件LabVIEW开发出一套心电实时监测系统,并利用LabVIEW设计出多种软件滤波方法来抑制心电信号中的噪声。由于心电信号的时频特性能提供反映患者心脏活动动态行为的信息,该系统还包括基于LabVIEW设计出的多种用于心电信号实时分析的程序,使被试心电信号所包含的生理特性能够及时地被分析出来。利用所开发的心电实时监测分析系统对被试的心电信号进行采集和分析,发现系统能够非常灵敏、准确地检测心电信号,并对信号噪声有着很好的抑制能力。此外系统能够对信号进行各式的实时分析,且分析结果可靠,能够运用于临床诊断。利用该系统对心电信号进行实时采集和分析,其测量结果准确、去噪效果良好、分析结果可靠,为今后心电实时监测分析系统的设计提供了借鉴。     

Sum-frequency vibrational spectroscopy of a monolayer self-assembled on gold: interference between resonant and nonresonant contributions of nonlinear polarization

zzz ^(R) is dominant in the observed resonant signals, whereas all of the ijk components contribute to the nonresonant signal. The transition frequencies and the relative amplitude of resonant signals are also determined for the CH₃ vibrational modes of ODT on gold. Received: 21 August 1998 / Revised version: 16 September 1998 / Published online: 24 February 1999     

Multiscale Permutation Lempel–Ziv Complexity Measure for Biomedical Signal Analysis: Interpretation and Application to Focal EEG Signals

This paper analyses the complexity of electroencephalogram (EEG) signals in different temporal scales for the analysis and classification of focal and non-focal EEG signals. Futures from an original multiscale permutation Lempel–Ziv complexity measure (MPLZC) were obtained. MPLZC measure combines a multiscale structure, ordinal analysis, and permutation Lempel–Ziv complexity for quantifying the dynamic changes of an electroencephalogram (EEG). We also show the dependency of MPLZC on several straight-forward signal processing concepts, which appear in biomedical EEG activity via a set of synthetic signals. The main material of the study consists of EEG signals, which were obtained from the Bern-Barcelona EEG database. The signals were divided into two groups: focal EEG signals (n = 100) and non-focal EEG signals (n = 100); statistical analysis was performed by means of non-parametric Mann–Whitney test. The mean value of MPLZC results in the non-focal group are significantly higher than those in the focal group for scales above 1 (p < 0.05). The result indicates that the non-focal EEG signals are more complex. MPLZC feature sets are used for the least squares support vector machine (LS-SVM) classifier to classify into the focal and non-focal EEG signals. Our experimental results confirmed the usefulness of the MPLZC method for distinguishing focal and non-focal EEG signals with a classification accuracy of 86%.     

FDMR of Carotenoid and Chlorophyll triplets in light-harvesting complex LHCII of spinach

Fluorescence detected magnetic resonance (FDMR) of the light-harvesting complex LHCII of the spinach photosynthetic machinery revealed triplet contributions both from Carotenoids and Chlorophylls. All three carotenoids present in the complex (lutein, neoxanthin and violaxanthin) are evidenced as triplet states in the FDMR signals obtained as variation of the emission intensity of the Chlorophylls in the 680 nm region. The triplets show ?D? values of 0.0401, 0.0388 and 0.0382 cm^?1. A comparison with the results obtained by ADMR (Absorption Detected Magnetic Resonance) is made and discussed. An interesting concentration effect is discovered and discussed in terms of specific interactions between carotenoids and chlorophyll molecules. Signals are also obtained by microwave sweeping in the Chlorophyll regions and one triplet is detected (?D?=0.028?0.029 cm^?1). The polarization of the carotenoid signals is discussed in terms of singlet-singlet and triplet-triplet energy transfer between carotenoids and chlorophylls, also with the help of double resonance experiments. Double resonance experiments involving both carotenoids and chlorophylls signals gave negative results. It is not possible as a consequence to assess that the chlorophyll whose triplets levels are scanned in the FDMR spectra are functionally connected to the carotenoids.     

S波段宽带光纤喇曼放大器研究

在PTDS(Photonic Transmission Design Suite)仿真平台上,用3个泵浦源的RFA实现了S波段的增益平坦,同时对泵浦光与信号光,信号光与信号光,泵浦光与泵浦光之间的相互作用以及RFA的噪声特性进行了研究.     

Millimeter-Wave Signal Generation and Harmonic Upconversion Through PM-IM Conversion in Chirped Fiber Gratings

A novel technique for generating millimeter-wave signals through phase-to-intensity modulation conversion in chirped fiber gratings is proposed and demonstrated. Experimental results on generating a 28 G Hz signal using harmonics orders from 7th to 10th are provided. Excellent phase-noise performance (87 dBc Hz @ 10KHz) is demonstrated. It is also demonstrated that this technique may be efficiently used for harmonically upconverting intermediate frequency signals to the millimeter-wave band. Bit-error-rate measurements for different modulation format (QPSK MQAM) signals, which were upconverted employing the PM-IM conversion technique, show very good performance (&lt; 10 ^{- 9}) and transparency to the modulation format.     

Strategies for reliable automatic onset time picking of acoustic emissions and of ultrasound signals in concrete

Determining the onset of transient signals like seismograms, acoustic emissions or ultrasound signals is very time consuming if the onset is picked manually. Therefore, different approaches exist, especially in seismology. The concepts of the most popular approaches are summarized. An own approach adapted to ultrasound signals and acoustic emissions, based on the Akaike Information Criterion (AIC), is presented. The AIC-picker is compared to an automatic onset detection algorithm based on the Hinkley criterion and also adapted to acoustic emissions. Manual picks performed by an analyst are used as reference values. Both automatic onset detection algorithms are applied to ultrasound signals which are used to monitor the setting and hardening of concrete. They are also applied to acoustic emissions recorded during a pull-out test. The AIC-picker produces sufficient reliable results for ultrasound signals where the deviation from the manual picks varies between 2% and 4%. Concerning acoustic emissions, only 10% of the events result in a mislocation vector greater than 5mm. It can be shown that our AIC-picker is a reliable tool for automatic onset detection for ultrasound signals and acoustic emissions of varying signal to noise ratio.     

Analysis of 90° pulsed magnetization signals of ferrite-garnet films with easy plane-type anisotropy

The results from a numerical analysis of 90° pulsed magnetization signals of ferrite-garnet films with easy plane-type anisotropy are discussed. The possibility of nonlinear magnetization oscillations occurring at a magnetizing pulse front several times greater than the oscillation period is shown. The results from the calculations describe the actual shape of the longitudinal and transverse signals quite well. The calculated values of the oscillation frequency (∼500 MHz) are also in good agreement with the experimental data.     

基于1–10GHz空地链路信号的雨强监测方法可行性研究

空地链路上的微波信号受降雨影响, 会产生功率衰减和去极化效应. 基于这些物理特性, 本文提出利用1–10 GHz空地链路信号的降雨干扰项获取雨强的方法, 并开展了相关理论研究. 根据空地链路信号与雨滴复杂的相互作用, 研究了空地链路信号频率为1–10 GHz时, 雨强 (rain rate, R) 对衰减 (attenuation, A) 和交叉极化分辨率 (cross-polarization discrimination, XPD)的影响, 分别建立了A-R和XPD-R关系模型. 通过数值模拟, 分别分析了利用上述两个关系模型估测雨强的可行性, 并系统研究了不同频率、极化方式和仰角条件下的适用性. 研究结果表明, 对于水平极化或圆极化, 且频率较高的空地链路信号, 利用A-R关系反演强降雨具有理论上的可行性; 对于不同频率和极化方式的信号, XPD-R关系模型都可以用于反演雨强, 并且对于1–50 mm·h^-1范围内的雨强, XPD较为敏感; 不同仰角条件下, A-R和XPD-R 模型都适用. 在4–10 GHz时, 本文的XPD-R模型和国际电信联盟ITU-R中XPD预测模型的结果非常接近. 所得出的结论对于下一步开展相关的验证实验, 拓展卫星系统的气象应用, 实时估测降雨强度, 实现全球降雨观测具有重要的参考价值. 关键词： 空地链路信号 雨强 衰减特性 交叉极化分辨率(XPD)