Blind Carrier Frequency Offset Estimation via Power Spectrum Analysis in MIMO OFDM Systems

As a generalization of orthogonal frequency-division multiplexing （OFDM） systems, multi-input multi-output （MIMO） OFDM systems are very sensitive to carrier frequency offset （CFO）. This paper proposes a blind CFO estimation method based on power spectrum analysis, which has high bandwidth efficiency and is much less complex. This method can be used to estimate the residual CFO, which is less than half of the subcarrier spacing. The method uses a cosine cost function to get a closed-form CFO estimate. Simulation results illustrate that the method is effective for MIMO OFDM systems.

Analysis of the common model error on velocity field under Colored noise model by GPS and InSAR: A case study in the Nepal and everest region

The accuracy of the velocity field will be affected by the noise model and common mode errors through GPS time series analysis.In order to analyze the influence of these two factors on the accuracy of the velocity field,two kinds of data are used,including the three-year observation from 20 permanent GPS stations with high spatial correlation in the Everest,which is about 650 km from north to south and 1068 km from east to west,and three-year 80 ascending images and 141 descending images from sentinel-1A,which are processed by GAMIT/GLOBK software and Small Baseline Subset-Interferometric Synthetic Aperture Radar method(SBAS-InSAR),respectively.The vertical deformation rate is solved by time series analysis through a self-made adaptive algorithm.In the analysis,the linear change rate,period,half period coefficient,and residual sequence of all stations are solved by using James L.Davis periodic model.The noise type of residual sequence is analyzed by the power spectrum model.The spatio-temporal correlated noise,Common Mode Error(CME),is extracted by the Principal Component Analysis(PCA)and Karhunen-Loeve(KLE)methods.The results show that noises can be best described by“flicker noise+white noise”model.After the removal of CME,the R^(2) estimates of all stations are above 0.8,with RMS value of velocity field decreasing from 1.428 mm/yr to 1.062 mm/yr and 1.063 mm/yr to 0.815 mm/yr,in N and E directions,respectively,indicating that the influence of CME can't be ignored in the extraction of the high-precision velocity field in the Nepal and Everest region.

A Numerical Fluid Analysis for Early Nonlinear Mode Evolution of Fast Electron Beams in Dense Plasmas

Nonlinear mode evolution for relativistic electrons in dense plasmas is analyzed in a three-dimensional fluid approach. Similar to the results previously obtained in particle-in-cell simulations, it is found that oblique modes dominate two-stream and filamentation modes in the linear stage. On the other hand a power spectrum analysis shows the nonlinear development of the high wavenumber modes.

Implications on Gravity Anomaly Measurements Associated with Different Lithologies in Turkana South Subcounty

The use of gravity data has demonstrated capability for monitoring lithological changes on a large scale as a consequence of differentiating basement and sedimentary of buried valleys. Gravity anomalies are associated with lateral contrasts in density and therefore deformation by faulting or folding will be manifested if accompanied by lateral density changes, otherwise, the vice versa is true. The study’s objective is to evaluate the effectiveness of gravity method in establishing different lithologies in an area. The study has revealed that regional anomaly gravity map presents high anomalies in the Northern region in the NW-SE trend and low anomalies in the southern trend in NW-SE, while the residual anomaly gravity map shows different trends for the low and high gravity anomalies. The gravity anomalies are well interpreted in line with the lithologies of the study area rather than the deformation of the same lithologies. There are observed high values of gravity anomaly values (ranging from -880.2 to -501.2 g.u.) where there are eolian unconsolidated rocks overlying the basement compared to low gravity anomaly values (ranging from -1338.9 to -1088.7 g.u.) where the andesites, trachytes and phonolites overly the basement. The different regional gravity anomalies relate well with different rock densities in the study area along the line profile for radially averaged power spectrum. The gravity highs are noted in the eastern point and are associated with andesites, trachytes, basalts and igneous rocks, while the gravity lows are associated with sandstone, greywacke, arkose, and eolian unconsolidated rock. The utilization of the information from the Power spectrum analysis demonstrates that the depth to the deepest basement rock is 12.8 km which is in the eastern flank, while the shallowest to the basement of 1.1 km to the western flank.

Synchronism of runoff response to climate change in Kaidu River Basin in Xinjiang,Northwest China

The runoff in alpine river basins where the runoff is formed in nearby mountainous areas is mainly affected by temperature and precipitation. Based on observed annual mean temperature, annual precipitation, and runoff time-series datasets during 1958-2012 within the Kaidu River Basin, the synchronism of runoff response to climate change was analyzed and iden- tified by applying several classic methods, including standardization methods, Kendall＇s W test, the sequential version of the Mann-Kendall test, wavelet power spectrum analysis, and the rescaled range （R/S） approach. The concordance of the nonlinear trend variations of the annual mean temperature, annual precipitation, and runoff was tested significantly at the 0.05 level by Kendall＇s W method. The sequential version of the Mann-Kendall test revealed that abrupt changes in annual runoff were synchronous with those of annual mean temperature. The periodic characteristics of annual runoff were mainly consistent with annual precipitation, having synchronous 3-year significant periods and the same 6-year, 10-year, and 38-year quasi-periodicities. While the periodic characteristics of annual runoff in the Kaidu River Basin tracked well with those of annual precipitation, the abrupt changes in annual runoff were synchronous with the annual mean temperature, which directly drives glacier- and snow-melt processes. R/S analysis indicated that the annual mean temperature, annual precipitation, and runoff will continue to increase and remain synchronously persistent in the future. This work can improve the understanding of runoff response to regional climate change to provide a viable reference in the management of water resources in the Kaidu River Basin, a regional sustainable socio-economie development.

Research on magnetic levitation absolute vibration measurement method in vehicles

This paper presents a design for a magnetic levitation absolute- vibration test system which can be used by vehicles to measure the road surface roughness. The relationship between the vibration test system output voltage and measured speed of the object was obtained through testing,the power spectrum of the measured signal was obtained by virtual instrument analysis,the vibration waveforms of the vehicle over gentle and steep slopes were measured respectively and the road surface roughness was obtained by waveform analysis. Data was saved where the waveforms exceeded threshold. Finally,the steep slope was located using a GPS system. Experimental results show that the magnetic levitation absolute- vibration measurement method has characteristics of high sensitivity and a wide frequency range. This lays the foundation for research into multi- dimensional vibration measurements through magnetic levitation vibration test systems in vehicles.

ASSESSMENT OF THE POEM2 MODEL FOR SIMULATING TROPICAL INTRASEASONAL OSCILLATION

The intraseasonal oscillation(ISO)of the atmosphere is closely related to weather and climate systems and is also an important aspect of extended numerical weather forecast research.This phenomenon is significant in tropical regions and is one of the key indices for assessing the simulation capability of a climate model.To better evaluate numerical model simulations of the tropical ISO using the 10-year historic data calculated by the POEM2 climate system model developed by the University of Hawaii in the U.S.,we utilized the methods of variance and power spectral analysis to compare and assess the simulation ability of this model for the ISO in tropical regions.Our results showed that the simulated variance results for the 850 h Pa zonal wind and outgoing long-wave radiation(OLR)by POEM2 are overall consistent with the observed distribution pattern,and the simulated variance is relatively larger than the observed in the North Indian Ocean and West Pacific regions.With respect to the summer model,the winter model can better simulate the eastward propagation motion of the Madden-Julian oscillation(MJO)and the 850 h Pa zonal wind.In comparison,the summer model can better simulate the northward propagation motion of MJO and atmospheric precipitation than the winter model.The eastward propagation speed of the simulated MJO signal is faster in the model than in the observation,and the high frequency region for the power spectra of meteorological element anomalies are concentrated in wavenumber 2-3 in the simulation and in wavenumber 1-2 in the observation.The multivariate combined empirical orthogonal function(EOF)results showed that this model can simulate the relationship between high-low level wind distributions and precipitation over the East Indian Ocean and the West Pacific,but the simulated signal is weaker than the observed.The lagging correlation of time coefficients between the first two EOFs from observation and simulation shows a similar cycle.Thus,these results indicate that in the future,the POEM2 climate system model needs to optimize the involved physical processes and parameterization scheme,strengthen the dynamic description of the mixed Rossby gravity wave,and improve the simulated ability of wavenumber 1.

Interpretations of gravity and Songliao Basin with Wavelet magnetic anomalies in the Multi-scale Decomposition

In this paper, we introduce the method of Wavelet Multi-scale Decomposition （WMD） combined with Power Spectrum Analysis （PSA） for the separation of regional gravity and magnetic anomalies. The Songliao Basin is situated between the Siberian Plate and the North China Plate, and its main structural trend of gravity and magnetic anomaly fields is NNE. The study area shows a significant feature of deep collage-type construction. According to the feature of gravity field, the region was divided into five sub-regions. The gravity and magnetic fields of the Songliao Basin were separated using WMD with a 4th order separation. The apparent depth of anomalies in each order was determined by Logarithmic PSA. Then, the shallow high-frequency anomalies were removed and the 2nd-4th order wavelet detail anomalies were used to study the basin＇s major faults. Twenty-six faults within the basement were recognized. The 4th order wavelet approximate anomalies were used for the inversion of the Moho discontinuity and the Curie isothermal surface.

CORRELATION BETWEEN ASO AND AAO

Using a 34 years database consisting of sea level pressure and sea iceconcentration, the relationship between Antarctic Oscillation (AAO) and Antarctic Sea-iceOscillation (ASO) was investigated. Firstly, Empirical Orthogonal Function (EOF) analysis depictsthe spatial variability of AAO and ASO and Antarctic Sea-ice Oscillation Index (ASOI) was definedfor the first time. Secondly, power spectrum and head-lag correlation analysis show that ASO and AAOhave the same periods of quasi-three years, quasi-one year and quasi-half a year. Corresponding toAAO, ASO has an evident anti-oscillation after one and half a year.