Spatial Spectrum Analysis Research Articles

Spectrum Analysis-Based Traffic Video Synopsis

Camera-based monitoring systems have a wide range of applications in traffic management, since they can collect more informative data in contrast to other sensors. An increasing number of traffic camera systems collect a large volume of traffic video data daily, forming the Big Data of traffic video. One of the challenges for traffic video processing is their high cost of resources and time, which seriously block the development of intelligent transportation systems. This paper proposes a spectrum analysis method for traffic video synopsis, including motion detection and tracking. Our method can largely remove the background noises and correctly extract motion information. Spatial and temporal spectrum analysis (Fourier transformation) are jointly used to detect objects and their motions in traffic videos. Further, the detected motions are tracked by the particle filter, generating trajectories of motions. Motion detection and tracking results given by our method can provide a synopsis for Big Data of traffic videos. The outperformance of our method is demonstrated comparing to the state of art video analysis methods.

Pollution Characteristics and Source Apportionment of Polycyclic Aromatic Hydrocarbons in Soils of Shenyang North New Area

Topsoil (0-20 cm) samples (n=101) in 5 different land use types in Shenyang North New Area (SNNA), Shenyang, China were collected using the uniform grid layout method to investigate the spatial distribution characteristics, composition spectrum, and source analysis of 16 polycyclic aromatic hydrocarbons (PAHs) listed as priority pollutants by the Environmental Protection Agency of the United States. Results showed that the total concentration of the 16 PAHs (ΣPAHs) in soils of SNNA ranged from 123.7 μg·kg-1 to 932.5 μg·kg-1. The PAH components were mainly dominated by 3-ring and 4-ring PAHs, of which the proportion of 3-ring PAHs was the highest. The spatial distribution of the ΣPAHs concentration was obvious, showing a decreasing tendency from south to north and from east to west. In the five soil types, the average concentrations of the ΣPAHs were relatively higher in the urban green space and the artificial forest, followed by the vegetable land, while the total PAH concentrations in paddy fields and corn fields were relatively lower and had no obvious spatial distribution differences. Source apportionment results studied using characteristic ratio analysis and factor analysis/multivariate linear regression showed that the main sources of PAHs in the topsoil of SNNA were mixed sources. Industrial coal combustion and motor vehicle exhaust were the main PAH contributors, with a combined contribution rate of 79.6%. The oil spill and coke oven contribution rate was about 16.2%, and the biomass fuel combustion was about 4.2%.

Raw Signal Simulator for SAR With Trajectory Deviation Based on Spatial Spectrum Analysis

This paper presents a whole new method for simulating a raw signal of synthetic aperture radar (SAR) with trajectory deviation. In this paper, a SAR raw signal is viewed as a spatial function in terms of radar location, at a fixed range frequency component of the radar signal. It is disclosed and verified that the SAR raw signals is band limited from the perspective of spatial spectrum analysis. Based on this finding, SAR raw signals under condition of trajectory deviation are obtained by interpolating the SAR raw signal along a set of ideally linear trajectories. The unprecedent performance achieved by the new method mainly includes the following. First, it provides a way to update existing simulators designed for ideally linear trajectory, giving them the capability to take trajectory deviation into consideration. Second, it is an efficient SAR raw signal simulator whose validity limit is greatly expanded compared with existing efficient simulators, as many constraints are eliminated without sacrificing computational efficiency or phase accuracy. Third, it is a uniform framework applicable for multiple SAR acquisition modes. Finally, the computational complexity of Monte Carlo experiment under various trajectory deviations is dramatically reduced, at the expense of storage memory requirement. Theoretical analyses are demonstrated by experimental results.

Using a complex optical orbital-angular-momentum spectrum to measure object parameters.

Light beams can be characterized by their complex spatial profiles in both intensity and phase. Analogous to time signals, which can be decomposed into multiple orthogonal frequency functions, a light beam can also be decomposed into a set of spatial modes that are taken from an orthogonal basis. Such decomposition can potentially provide a tool for spatial spectrum analysis, which may enable stable, accurate, and robust extraction of physical object information that may not be readily achievable using traditional approaches. As a proof-of-concept example, we measure an object's opening angle using orbital-angular-momentum (OAM) -based complex spectrum, achieving a >15 dB signal-to-noise ratio. Moreover, the dip (i.e., notch) positions of the OAM intensity spectrum are dependent on an object's opening angle but independent of the opening's angular orientation, whereas the slope of the OAM phase spectrum is dependent on the opening's orientation but independent of the opening angle.

The Characteristics of Significant Wave Height and Sea Surface Temperature In The Sunda Strait

Sunda Strait has an important role in the water mass exchange from the Pacific Ocean and the Indian Ocean so that the oceanographic condition is strongly affected by seasonal factors. The purpose of this study is to observe the relationship and the characteristics of significant wave height (SWH) and sea surface temperature (SST) in the Sunda strait and its relationship with IOD. The method employed is spatial analysis, low-pass filter, and spectrum analysis by S-Transform, beside that the correlation between SST and SWH is analyzed by wavelet coherency. The period of SWH and SST is dominantly semiannual, at the time of winter monsoon (the Northeast Monsoon), the SWH was reaching up to 2,11 m, while at the summer monsoon, the SWH was reaching up to 3.62 m. Reversely, the SST increased during the winter monsoon. At the time of 2016 had been detecting by the negative IOD with the IOD index of -0.65 and it caused the SWH increased by 0.3 m than its average. Based on the wavelet coherence, the SWH and the SST have the coherence in the period of 8 to 16 days, especially in March to April, and June to August.

Application of the longitudinal chromatic aberration effect for distances measurement on the basis of a single photo

Subject of Research. We propose a method for measuring the distances to the surfaces of photographed objects based on the effect of longitudinal chromatic aberration. According to this effect, the focal length of lens depends on the wavelength of refracted light, thus the defocus of image formed by lens depends not only on the distance from image plane to lens, but also on the wavelength of light the picture was taken for (red, green or blue color ranges). Method. The proposed method of distance measurement is based on comparison of image defocus for different wavelengths (e.g., red and blue). The comparison is performed in the spatial frequency domain and is based on analysis of image complex spectrograms (the Fourier spectrum calculated locally within a window scanning the image).The distance to each point of photographed surface is calculated in closed form by the analysis of local spatial spectrum with the use of Gaussian model of point spread function. Main Results. The working capacity of distance measurement technique is partially verified on the basis of image defocus imitation by different displacement of objective lens with respect to sensor matrix of camera. The presented analysis of chromatic parameters of traditionally applied optical materials also proves the physical realizability of proposed technique. A technology is also proposed for distance measuring based on really differing image defocus in different color channels applying a special calibration of electro-optical system. Practical Relevance. The proposed distance measurement technique could be practically useful in the cases where any active illumination of objects being photographed is prohibited. It is also worth to be applied in the inexpensive low-sized optical measuring devices like Kinect for Xbox-360.

Analysis of the Beam Aberration and Transmission Coefficient’s Variation of Frequency Selective Surfaces in Quasi-Optical Feed System

Full-wave simulation is widely adopted for the calculation of the frequency response of frequency selective surfaces (FSSs). Generally, uniform plane wave excitation and an infinite FSS array are assumed, and the simulation results have good agreement with the measurement data. However, the simulation cannot provide accurate determination of the transmission coefficient in the optical path in a quasi-optical system because the incidence wave is Gaussian instead of the uniform plane wave. In the conventional simulation, the mode conversion loss is ignored, and the reflection loss is less than the one for Gaussian beam. It is related to the sensitivity of the FSS to the incidence angle, which results in the beam's aberration and converts the mode of the transmitted beam from the fundamental Gaussian beam mode to higher order of Gauss-Hermite mode. In this letter, the Spatial Spectrum Analysis (SSA) method is applied to calculate beam's aberration, transmission coefficient, and conversion of the transmission beam's mode. The influences of the beam waist radius on the transmission coefficient are analytically discussed. The transmission coefficient and the conversion of the transmission beam's mode in different beam waist radius are measured, which agrees well with the results by Spatial Spectrum Analysis.

Spatiotemporal structure of a laser beam at a path length of 144 km: comparative analysis of spatial and temporal spectra.

We present an analysis of spatial and temporal spectra of the observations of scintillations in a laser beam (532nm, ∼200 mW power) traveling along a 144km path at an altitude of 2-2.4km above sea level, just above the atmospheric boundary layer, between the islands of La Palma and Tenerife. The observations were performed during nighttime on July 18 and 21, 2011, by means of a telescope with an aperture diameter of 1m. Strong scintillations were observed. We compared the temporal and spatial spectra of the scintillations. For the temporal spectra, we performed the correction for the aliasing effect due to the low frame rate. The 2D spatial spectra of the scintillations in the observation plane were found to be close to isotropic. This allowed for transforming them into 1D spectra. We found a good agreement between the temporal and 1D spatial spectra. This corroborates the applicability of the Taylor hypothesis of frozen turbulence for finite-size laser beams and strong scintillations.

Study on Vector Hydrophone Array DOA Estimation

Vector hydrophone is composed of acoustic pressure sensor and particle velocity sensor, which can simultaneously measure acoustic pressure and orthogonal components of particle velocity. MUSIC (Multiple Signal Classification) algorithm is a high resolution spatial spectrum analysis method based on subspace decomposition. This paper introduces the operation principles of this algorithm in detail and investigates the application of MUSIC algorithm to the DOA estimation of acoustic sources by a vector-hydrophone ULA (Uniform Linear Array) output model. Simulation results indicate that the resolution capability of MUSIC algorithm under larger SNRs is excellent.

Morphological analysis of stylolites for paleostress estimation in limestones

We develop and test a methodology to infer paleostress from the morphology of stylolites within borehole cores. This non-destructive method is based on the analysis of the stylolite trace along the outer cylindrical surface of the cores. It relies on an automatic digitisation of high-resolution photographs and on the spatial Fourier spectrum analysis of the stylolite traces. We test and show, on both synthetic and natural examples, that the information from this outer cylindrical surface is equivalent to the one obtained from the destructive planar sections traditionally used. The assessment of paleostress from the stylolite morphology analysis is made using a recent theoretical model, which links the morphological properties to the physical processes acting during stylolite evolution. This model shows that two scaling regimes are to be expected for the stylolite height power spectrum, separated by a cross-over length that depends on the magnitude of the paleostress during formation. We develop a non linear fit method to automatically extract the cross-over lengths from the digitised stylolite profiles. Results on cores from boreholes drilled in the surroundings of the Andra Underground Research Laboratory located at Bure, France, show that different groups of sedimentary stylolites can be distinguished, and correspond to different estimated vertical paleostress values. For the Oxfordian formation, one group of stylolites indicates a paleostress of around 10MPa, while another group yields 15MPa. For the Dogger formation, two stylolites indicate a paleostress of around 10MPa, while others appear to have stopped growing at paleostresses between 30 and 22MPa, starting at an erosion phase that initiated in the late Cretaceous and continues today. This method has a high potential for further applications on reservoirs or other geological contexts where stylolites are present.

Analysis of spatial and temporal spectra of liquid film surface in annular gas–liquid flow

Wavy structure of liquid film in annular gas–liquid flow without liquid entrainment consists of fast long-living primary waves and slow short-living secondary waves. In present paper, results of spectral analysis of this wavy structure are presented. Application of high-speed LIF technique allowed us to perform such analysis in both spatial and temporal domains. Power spectra in both domains are characterized by one-humped shape with long exponential tail. Influence of gas velocity, liquid Reynolds number, liquid viscosity and pipe diameter on frequency of the waves is investigated. When gravity effect is much lesser than the shear stress, similarity of power spectra at different gas velocities is observed. Using combination of spectral analysis and identification of characteristic lines of primary waves, frequency of generation of secondary waves by primary waves is measured.

Recent measurements of aero-optical effects caused by subsonic boundary layers

Results of recent experimental measurements of aero-optical distortions caused by turbulent boundary layers at subsonic speeds M=0.4…0.6 are presented. Measurements were performed using a high-speed Shack-Hartmann sensor to collect instantaneous wavefronts with high spatial and temporal resolution, accompanied by wavefront measurements with a Malley probe. Effects of different aperture sizes on levels of aero-optical aberrations and detailed statistical analysis of spatial and temporal spectra of aero-optical distortions for both wavefront sensors are presented and discussed.

An evaluation of target irradiation uniformity based on spatial-spectrum analysis

The irradiation uniformity of target spots in high-power laser driver is evaluated based on spatial-spectrum analysis. Spatial spectrum can display the detailed spatial intensity structure of the spots and show the spatial frequency modes smoothed by the beam smoothing techniques. This evaluating model is applied to two kinds of typical target spots obtained with a lens array and a random phase plate, respectively, and its validity is found to be independent of the spot profile and the degree of intensity modulation. The uniformity evaluations based on this model are in good agreement with the fractional power above intensity.

Detection and analysis of diamond fingerprinting feature and its application

Before becoming a jewelry diamonds need to be carved artistically with some special geometric features as the structure of the polyhedron. There are subtle differences in the structure of this polyhedron in each diamond. With the spatial frequency spectrum analysis of diamond surface structure, we can obtain the diamond fingerprint information which represents the "Diamond ID" and has good specificity. Based on the optical Fourier Transform spatial spectrum analysis, the fingerprinting identification of surface structure of diamond in spatial frequency domain was studied in this paper. We constructed both the completely coherent diamond fingerprinting detection system illuminated by laser and the partially coherent diamond fingerprinting detection system illuminated by led, and analyzed the effect of the coherence of light source to the diamond fingerprinting feature. We studied rotation invariance and translation invariance of the diamond fingerprinting and verified the feasibility of real-time and accurate identification of diamond fingerprint. With the profit of this work, we can provide customs, jewelers and consumers with a real-time and reliable diamonds identification instrument, which will curb diamond smuggling, theft and other crimes, and ensure the healthy development of the diamond industry.

Spatial Variance Spectrum Analysis and Its Application to Unsupervised Detection of Systematic Wafer Spatial Variations

Investigation of wafer spatial variations is critical for semiconductor process/equipment optimization and circuit design. The objective of spatial variation study is to differentiate the systematic variation component from the random component. This is usually done by contrasting with a set of known systematic patterns based on engineering knowledge. However, there could exist unknown systematic components remaining in the unexplained residuals and overlooked by the conventional spatial variation study. In this paper, we develop a novel spatial variance spectrum (SVS) to analyze the systematic variations without any priori information of the systematic patterns. The SVS is a series of spatial variations over a range of spatial moving window sizes from the smallest spatial moving window consisting of only two metrology sites to the largest one covering all metrology sites of the entire wafer. The SVS can be used to characterize the wafer spatial variations and to detect existence of systematic variations by a proposed hypothesis test. We also propose an index to summarize from the SVS the systematic proportion of the spatial variation. The proposed test and index of systematic variations will be demonstrated and validated through both hypothetical examples and actual cases of wafer critical dimension (CD) metrology data.

A fast three-dimensional object recognition based on modulation analysis

A novel method of the 3-D object recognition based on modulation analysis is proposed. Two orthogonal gratings with a small interval are vertically projected on an object surface and the recognized object is placed between the imaging planes of the two gratings. Then the image of the object surface modulated by the orthogonal gratings can be obtained by a CCD camera from the same direction, and the object height information is encoded in the image. The image is processed by the operations consisting of performing the Fourier transform and spatial spectrum analysis. The fundamental frequency can be obtained in two different directions. Then we calculated the recognition parameter RP (the normalized energy of each fundamental frequency). According to the RP values, we can determine the object position in the 2-D orthogonal co-ordinate system. The RP values will vary for different objects, so the different objects will be shown in different positions of the co-ordinate system. The expressions of the recognition parameter in the space and spectrum region have been given in this work. There are some advantages of our method. Firstly, it can recognize the 3-D object by the fundamental frequency energy analysis in two directions of the frequency domain, which cannot be almost discerned from their 2-D intensity images. Secondly, it has the advantages of shift-invariance and rotation-invariance, and can avoid the influence of shadow on 3-D object recognition. Finally the method has noise resistance ability. Both the computer simulation and the experimental results are presented in support of the proposed idea.

Effect of smoothing by spectral dispersion on the spatial spectrum of focal spot

The model of laser spectrum used in the method of smoothing by spectral dispersion （SSD） affecting the beam smoothing was theoretically discussed based on the analysis of spatial frequency spectrum, and the response function to the spatial frequency modulation was put forward to describe the effects. With theoretical derivation and numerical simulation, it is concluded that the spatial frequency response function by SSD has periodical property and is determined by dispersion angle and spectrum shape. More generally, spectrum shape was related with the shape of response function, the dispersion angle affects the lowest spatial frequency, and color cycle number can modify the distribution of low and high spatial frequency to change the smoothing effect. Applied to multidimensional SSD, the response function characters can give the guiding principle for optimization.

PERIODICITY AND STOCHASTIC HIERARCHICAL ORDERS OF SOIL CUTTING FORCE DATA DETECTED BY AN “AUTO-REGRESSIVE ERROR DISTRIBUTION FUNCTION” (AREF)

In this article, we describe a methodology to estimate typical soil properties such as moisture content andcompactness using soil cutting force fluctuation information obtained by a conventional chisel. The data were obtained ina Yolo loam field under four different soil conditions: tilled dry (TD), tilled wet (TW), untilled dry (UD), and untilled wet (UW).In order to quantify the complexity of fluctuating patterns of soil cutting force and soil physical properties, we introduce anew time-series analysis technique, the auto-regressive error function (AREF). We found that the frequency distributionpattern of the modified time-series data with the time lag showed a very clear shift with change in the time lag. The AREFwas developed to detect this pattern shift. The soil cutting force time-series data obtained using an instrumented chisel wereanalyzed using power spectrum and AREF techniques. The spatial power spectrum analysis detected periodicity under drysoil conditions. On the other hand, the AREF showed a very clear hierarchical order, which was caused by the existence ofself-similarity in the fluctuating patterns of soil cutting forces under all four tested soil conditions. Two AREF parameterswere found to be related to soil moisture content and cone index, but not bulk density.

Spatial spectrum analysis of wave-front correction with a segmented mirror.

An expression is derived for the spatial power spectrum of wave-front errors after correction with a segmented mirror. This includes estimates of the spectral contributions of segment piston and tilt corrections and spatial aliasing by a regular array of segments. The approach allows rapid computation of wave-front error spectra in systems with highly segmented mirrors.

Measuring cosmological parameters with the SDSS QSO spatial power spectrum analysis to test the cosmological principle

In this paper we emphasize the importance of the Sloan Digital Sky Survey (SDSS) quasi-stellar object (QSO) clustering statistics as a unique probe of the Universe. Because the complete SDSS QSO sample covers a quarter of the observable Universe, cosmological parameters estimated from the clustering statistics have an implication as a test of the cosmological principle, by comparing with those from local galaxies and other cosmological observations. Using an analytical approach to the power spectrum for the QSO sample, we assess the accuracy with which the cosmological parameters can be determined. Arguments based on the Fisher matrix approach demonstrate that the SDSS QSO sample might have a potential to provide useful constraints on the density parameters as well as the cosmic equation of state.