Fast Fourier Transform Filter Research Articles

LPI Sequences Optimization Method against Summation Detector Based on FFT Filter Bank

Waveform design is a crucial factor in electronic surveillance (ES) systems. In this paper, we introduce an algorithm that designs a low probability of intercept (LPI) radar waveform. Our approach directly minimizes the detection probability of summation detectors based on FFT filter banks. The algorithm is derived from the general quadratic optimization framework, which inherits the monotonic properties of such methods. To expedite overall convergence, we have integrated acceleration schemes based on the squared iterative method (SQUAREM). Additionally, the proposed algorithm can be executed through fast Fourier transform (FFT) operations, enhancing computational efficiency. With some modifications, the algorithm can be adjusted to incorporate spectral constraints, increasing its flexibility. Numerical experiments indicate that our proposed algorithm outperforms existing ones in terms of both intercept properties and computational complexity.

Effect of scattered megavoltage x-rays on markerless tumor tracking using dual energy kilovoltage imaging.

To determine the effect of megavoltage (MV) scatter on the accuracy of markerless tumor tracking (MTT) for lung tumors using dual energy (DE) imaging and to consider a post-processing technique to mitigate the effects of MV scatter on DE-MTT. A Varian TrueBeam linac was used to acquire a series of interleaved 60/120kVp images of a motion phantom with simulated tumors (10 and 15 mm diameter). Two sets of consecutive high/low energy projections were acquired, with and without MV beam delivery. The MV field sizes (FS) ranged from 2×2cm2 -6×6cm2 in steps of 1×1cm2 . Weighted logarithmic subtraction was performed on sequential images to produce soft-tissue images for kV only (DEkV ) and kV with MV beam on (DEkV+MV ). Wavelet and fast Fourier transformation filtering (wavelet-FFT) was used to remove stripe noise introduced by MV scatter in the DE images ( ). A template-based matching algorithm was then used to track the target on DEkV, DEkV+MV , and images. Tracking accuracy was evaluated using the tracking success rate (TSR) and mean absolute error (MAE). For the 10 and 15 mm targets, the TSR for DEkV images was 98.7% and 100%, and MAE was 0.53 and 0.42mm, respectively. For the 10mm target, the TSR, including the effects of MV scatter, ranged from 86.5% (2×2cm2 ) to 69.4% (6×6cm2 ), while the MAE ranged from 2.05mm to 4.04mm. The application of wavelet-FFT algorithm to remove stripe noise ( ) resulted in TSR values of 96.9% (2×2cm2 ) to 93.4% (6×6cm2 ) and subsequent MAE values were 0.89mm to 1.37mm. Similar trends were observed for the 15mm target. MV scatter significantly impacts the tracking accuracy of lung tumors using DE images. Wavelet-FFT filtering can improve the accuracy of DE-MTT during treatment.

Feature-Based Characterisation of Turned Surface Topography with Suppression of High-Frequency Measurement Errors.

Errors that occur when surface topography is measured and analysed can be classified depending on the type of surface studied. Many types of surface topographies are considered when frequency-based errors are studied. However, turned surface topography is not comprehensively studied when data processing errors caused by false estimation (definition and suppression) of selected surface features (form or noise) are analysed. In the present work, the effects of the application of various methods (regular Gaussian regression, robust Gaussian regression, and spline and fast Fourier Transform filters) for the suppression of high-frequency measurement noise from the raw measured data of turned surface topography are presented and compared. The influence and usage of commonly used available commercial software, e.g., autocorrelation function, power spectral density, and texture direction, which function on the values of areal surface topography parameters from selected (ISO 25178) standards, are also introduced. Analysed surfaces were measured with a stylus or via non-contact (optical-white light interferometry) methods. It was found that the characterisation of surface topography, based on the analysis of selected features, can be crucial in reducing measurement and data analysis errors when various filters are applied. Moreover, the application of common functions can be advantageous when feature-based studies are proposed for both profile and areal data processing.

Analysis of Circular Saw Tooth Marks Profile on Material Machined Surface After Filtering with Fast Fourier Transform (FFT)

The article presents theoretical analysis of machined surface roughness after sawing on circular saw and implementation of fast Fourier transform (FFT) as a possible simple filtering method for filtering out just the saw blade and saw tooth influence on the surface roughness. Surface roughness profile is represented as a signal that can be obtained as a sum of complex periodic signals that represent theoretical profile of tooth marks and lateral movement of tooth due to saw lateral movement and signals that represent structural roughness of wood combined with machining roughness, represented as a Gaussian noise. The application of FFT based filtering on such a signal can be effectively used to extract the main frequency components due to tool influence on total surface signal and the time domain of filtered signals display can then be obtained by use of the inverse Fourier transform. In order to test the theoretical assumptions, the machining tests in sawing of solid oak wood (Quercus robur L.) and medium density fiberboard (MDF) was conducted. Machined surface roughness was measured and analyzed in accordance with theoretical assumptions. It was concluded that a combination of discrete Fourier transform of surface roughness profile and standard roughness parameters can give a more complete representation of machined surface roughness after sawing with circular saws and that filtering of surface roughness profile signal with FFT filter can be used as a simple and effective method in quantifying tool influence on machined surface roughness after sawing on circular saw in varying machining conditions and on different workpiece material.

Coupling Relationship Analysis of Gold Content Using Gaofen-5 (GF-5) Satellite Hyperspectral Remote Sensing Data: A Potential Method in Chahuazhai Gold Mining Area, Qiubei County, SW China

The gold (Au) geochemical anomaly is an important indicator of gold mineralization. While the traditional field geochemical exploration method is time-consuming and expensive, the hyperspectral remote sensing technique serves as a robust technique for the delineation and mapping of hydrothermally altered and weathered mineral deposits. Nonetheless, mineralization element anomaly detection was still seldomly used in previous hyperspectral remote sensing applications in mineralization. This study explored the coupling relationship between Gaofen-5 (GF-5) hyperspectral data and Au geochemical anomalies through several models. The Au geochemical anomalies in the Chahuazhai mining area, Qiubei County, Yunnan Province, SW China, was studied in detail. First, several noise reduction methods including radiometric calibration, Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH), Savitzky–Golay filter, and endmember choosing methods including Minimum Noise Fraction (MNF) transformation, matched filtering, and Fast Fourier Transform (FFT) transformation were applied to the Gaofen-5 (GF-5) hyperspectral data processing. The Spectrum-Area (S-A) method was introduced to build an FFT filter to highlight the spectral abnormal characteristics associated with Au geochemical anomaly information. Specifically, the Matched Filtering (MF) technique was applied to the dataset to find the Au geochemical anomaly abundances of endmembers with innovative large-sample learning. Then, Multiple Linear Regression (MLR), Partial Least Squares (PLS) regression, a Back Propagation (BP) network, and Geographically Weighted Regression (GWR) were used to reveal the coupling relationship between the spectra of the processed hyperspectral data and the Au geochemical anomalies. The results show that the GWR analysis has a much higher coefficient of determination, which implies that the Au geochemical anomalies and the spectral information are highly related to spatial locations. GWR works especially well for showing the regional Au geochemical anomaly trend and simulating the Au concentrated areas. The GWR model with application of the S-A method is applicable to the detection of Au geochemical anomalies, which could provide a potential method for Au deposit exploration using GF-5 hyperspectral data.

The use of filters based on the Fast Fourier Transform applied to DEMs for the objective mapping of karstic features

The suitability of Fast Fourier Transform (FFT) filters to delimit the objective location of geomorphic references is analysed for the case of karstic landscapes, where altitudes feature marked differences. From aerial images and a Light Detection and Ranging (LiDAR) derived high-resolution digital elevation model (DEM), a digital database was created, segregating two geomorphic domains according to scale: domain A (macroforms) and domain B (mesoforms), both subdivided in zones of positive and negative relief polarity. In order to minimise the producer error, the correspondence between the DEM morphology and the features mapped was generalised and certified in a test area, reducing ground truth uncertainty. The efficiency of FFT filters was compared against the most commonly referenced in the literature, such as convolution and openness, in terms of computation cost and geometric position. Two types of FFT filters were created modifying the radius of the high pass mask: short radius filters (appropriate to objectivise macroforms); and middle-large radius filters (appropriate for mesoforms) like convolution and openness. The FFT geomorphic reference obtained offers similar geometric patterns to other filters, but reduced computation times. Moreover, the filters reduce the positional uncertainty of geomorphic contacts, without changing the general altitude trend. The generation of FFT filtered references, combining short and middle-large radius, permits objective mapping of karstic landscapes using a DEM.

Temperature Sensing Characteristics of an MKR in a Microfiber Taper Based on Mechanisms of Interference and Resonance with Vernier Effect

In this work, spectral characteristics and temperature sensing characteristics of an in-line microfiber Mach-Zehnder interferometer (MZI) with an embedded microfiber knot resonator (MKR) is investigated. The microfiber MZI with an MKR (MZIKR) has a dual-effect composite spectrum with comb-like spectrum of the MKR loaded on the dominant interference spectrum. Vernier effect is generated by the MKR via superposition of resonant spectra with three resonant modes circulating in the MKR. This is the first time that Vernier effect is generated in a single MKR, which has advantages of easy fabrication and compact structure compared to the traditional resonant structures with Vernier effect such as two cascaded MKRs. Fast Fourier transform (FFT) and FFT filter are used to analyze and extract the different components of the transmission spectrum of the MZIKR. Temperature sensing characteristics of the different components of the polydimethylsiloxane-coated MZIKR are studied, showing that the interference dip of the MZI spectrum and the envelope dip of the MKR Vernier spectrum achieve a high temperature sensitivity of about -1.8 nm/ °C and about -3.5 nm/ °C, respectively. The proposed sensor has the advantages of easy fabrication, robust structure, and high sensitivity in temperature measurement. The MZIKR with dual-effect composite spectrum may have potential in two-parameter measurement and narrow-band filtering.

A filtering-based bridge weigh-in-motion system on a continuous multi-girder bridge considering the influence lines of different lanes

A real-time vehicle monitoring is crucial for effective bridge maintenance and traffic management because overloaded vehicles can cause damage to bridges, and in some extreme cases, it will directly lead to a bridge failure. Bridge weigh-in-motion (BWIM) system as a high performance and cost-effective technology has been extensively used to monitor vehicle speed and weight on highways. However, the dynamic effect and data noise may have an adverse impact on the bridge responses during and immediately following the vehicles pass the bridge. The fast Fourier transform (FFT) method, which can significantly purify the collected structural responses (dynamic strains) received from sensors or transducers, was used in axle counting, detection, and axle weighing technology in this study. To further improve the accuracy of the BWIM system, the field-calibrated influence lines (ILs) of a continuous multi-girder bridge were regarded as a reference to identify the vehicle weight based on the modified Moses algorithm and the least squares method. In situ experimental results indicated that the signals treated with FFT filter were far better than the original ones, the efficiency and the accuracy of axle detection were significantly improved by introducing the FFT method to the BWIM system. Moreover, the lateral load distribution effect on bridges should be considered by using the calculated average ILs of the specific lane individually for vehicle weight calculation of this lane.

Mid-term periodicities in sunspot area of the Sun during solar cycles 22–24

We have studied a monthly variation of the total sunspot areas during solar cycles 22 to 24 (1986–2016). The ∼6 month smoothed variation (FFT filter technique) of the total sunspot areas shows double peaks (solar maximum) with the ascending phase in each cycle for the periods 1989, 1991, 2000, 2002, 2011, and 2014. We have observed mid-term periodicity (intermediate-term) such as the Rieger-type period (∼120 to ∼190 days), quasi-period (∼200 to ∼380 days), and quasi-biennial period (∼1.20 to ∼3.83 years) of the sunspot areas (total sunspot area, and northern and southern hemisphere of the Sun) for the combined solar cycles 22 to 24; using fast Fourier transform (FFT) and Morlet wavelet transformation (WT) techniques (wavelet power spectra and contour plot). The period ∼1.33 year of the southern hemisphere and total sunspot areas have shown the rotation rates on the basis of the convection zone. The quasi-annual period ∼356 days is observed as an important period for the total sunspot area and the southern hemisphere and are absent in the northern hemisphere of the Sun. The periodicities of the total sunspot areas, and southern and northern hemisphere constitute the fifth, sixth and seventh subharmonic of the solar synodic rotation of ∼27 days in the range of the Rieger-type periodicity. The 24th subharmonic of the solar synodic rotation of ∼27 days is highly significant in the total sunspot area and the southern hemisphere of the Sun during the period of our study (1986–2016).

Protection Schemes for Contemporary Power Systems: FPGA-Based Design and Development

Concurrently functioning relays using FPGA technology are the primary focus of the project. The suggested FPGA-based relays are much faster than microprocessor- or microcontroller-based relays because they use continuous sense-process communicate cycles. The Xilinx Virtex-II FPGA Board's implementation of overcurrent, impedance, reactance, and mho was evaluated using the 400 kv line transmission hardware simulator. Fault currents in power systems may contain a component of direct current (DC) that decays exponentially in the case of transient failures. Extracting the fundamental frequency element is essential for avoiding false tripping. To do this, we make use from the VHDL FFT IP core. A Fast Fourier Transform (FFT) filter is used to implement overcurrent, impedance, reactance, and mho dependence. The FFT filter is also used to evaluate the DC decaying portion.

Development on the reconstruction of photothermal imaging method for subsurface structure

The photothermal imaging technique is a nondestructive inspection technique that visualizes the inside of a metal by utilizing the photothermal effect. Although the concept of photothermal imaging techniques has been proposed, systematic research on the characteristics thereof has not been conducted. This study attempts to enhance the measurement and reconstruction process for a photothermal imaging method. To detect the edge of a subsurface pattern more accurate, low-pass FFT (fast Fourier transform) filter for noise reduction of measured data, and derivative detectors are adopted for the reconstruction of photothermal imaging. The adopted methods are applied to and visualize 20 mm × 25 mm × 1.5 mm copper block including radius 5 mm, height 1 mm cylindrical resin as a subsurface pattern. The results show that the developed method can detect the edge of the resin subsurface 50% more accurately than the previous reconstruction method for photothermal imaging.

Analysis of the pressure fluctuation in the flow field of a large-scale cyclone separator

Flow field in a cyclone separator is not stable and show complex dynamic properties. Dynamic pressure signals were measured at different positions in a large-scale gas-solid cyclone separator such as the vortex finder, outer vortex and inner vortex, using a micro-differential pressure transmitter with different inlet gas velocities and inlet particle concentrations. Power spectral density (PSD) and fast Fourier transform (FFT) were used to analyze the characteristics of these dynamic pressure signals. The results showed that the PSD of the outer vortex was divided into two parts: part 1 in a low frequency region (0–n Hz) with high magnitude and part 2 in a high frequency region (n–50 Hz) with low magnitude. The dominant frequency region was related to outer vortex, and its range and magnitude increased with increased inlet gas velocity. There was a dominant frequency in the vortex finder of the cyclone separator, which was related to inner vortex rotation. The dominant frequency increased with increased inlet gas velocity and decreased with increased particle concentration. Using data processing methods, including an FFT filter and standard deviation, particle effects were found to be focused in lower frequency region parts, while the effects were not linearly depend on the particle concentration. Furthermore, there were special pressure transfer characteristics in the cyclone separator, which resulted in forming the pressure fluctuation. Through PSDs and the coherence analysis of the dynamic pressure in two positions in the vortex space of the cyclone separator, the outer vortex was found to induce a low frequency range pressure fluctuation with high magnitude and the inner vortex induced a new main frequency because of the periodically-rotating flow behavior. Considering the resonance phenomenon, the natural frequency of cyclone separator should be kept away from the frequency of pressure fluctuation, which concentrated below 50 Hz.

Analysis of a Multiple Supply Voltage Floorplan Considering Voltage Drop and Electron Migration Risk

In Contemporary Integrated Circuits (IC), the Voltage drop in the power rails and Electron migration risk (EM) due to high current densities are the most important factors degrading the reliability of the chip. The effect of these factors leads to an imbalance in the flow of charge carriers and voids in interconnects. This paper resolves the above issues, through analyzing and predetermining it in a Multiple Supply Voltage (MSV) design during the floorplanning stage. Simulations were carried out in Cadence digital Encounter system with 180nm technology for the circuit net list of 8 point FFT (Fast Fourier Transform) and FIR filter. Results show that floorplanning scheme is powerful in reducing 100% of voltage drop and 50% of EM risk in the chip as compared to previous works.

Ultralong Fatty Acyl Derivatives As Occlusive Structure Lipids for Cosmetic Applications: Synthesis and Characterization

Finding sustainable and commercially viable sources of occlusive materials, as an alternative to petroleum, is of great interest. Inspired by the fundamental role of long chain fatty acids in maintaining skin barrier, ultralong fatty acyl derivatives with diverse structures (varied acyl chain length and different polar head; i.e. glycerol, ethylene glycol, and diethylene glycol) were synthesized. These molecules can be feasibly obtained via enzymatic esterification of fatty acids or fractionated from commercial glycerides mixture via short path distillation. The molecular packing behaviors of compounds were characterized via differential scanning calorimetry, Fourier transform infrared, and Langmuir isotherm measurements. The structure–property relationship study reveals that a glycerol molecule monoacylated with an ultralong fatty acyl is the derivative which entails the most occlusive properties of the series of ultralong chain fatty acid derivatives. Fast Fourier transform filtering (FFTF) analysis of ...

Approaches towards Implementation of Multi-bit Digital Receiver using Fast Fourier Transform

This paper compares different digital receiver signal processing schemes as applied to current ESM/RWR systems. The schemes include fast fourier transform (FFT)-based, FIR filter-based and mixed architectures. Use of polyphase FFT and IIR filters is also discussed. The specifications and signal processing requirements of a modern digital electronic warfare (EW) receiver are discussed. The design procedures and architectures for all the schemes are brought out. The tradeoffs involved in selection of different parameters for these schemes are also discussed. The digital receiver schemes are modeled and analyzed for different metrics such as, Parameter measurement accuracies, Pulse handling capability, Frequency separation capability, Number of multipliers required for implementation etc. The analysis is done for a 500 MHz BW digital receiver and assumes 8 bit ADC in the front end. The results obtained for the comparison are discussed in the paper. Limited simulations show that overlapped FFT scheme is a better approach for digital receiver processing. Defence Science Journal, 2013, 63(2), pp.198 -203 , DOI:http://dx.doi.org/10.14429/dsj. 63.4264

Performance Analysis of FFT Filter to Measure Displacement Signal in Road Roughness Profiler

 Abstract—In the application of pavement roughness test, accelerometer sensors are used to measure vertical acceleration of a vehicle body. The displacement of that object is then determined by using double integrating acceleration data from the accelerometer sensor. High pass filters are used to remove DC components to avoid integrated errors. Fast Fourier Transform (FFT) Filter is known to provide a higher accuracy compared to Infinite Impulse Response (IIR) Filter and Finite Impulse Response (FIR) Filter. In this research, we analyze the performance of FFT Filter with experiment in MATLAB. The results show that FFT filters give results more accurate than do FIR and IIR not only for single frequency signal but also for multi-frequency signal. The standard error and peak error of FFT Filter are less than those of FIR and IIR Filter. Moreover the error of FFT Filter can be reduced when increasing the cut frequency of FFT filter but it is remained less than the frequency of acceleration signal.

Cutting force analysis in reaming of ZL102 aluminium cast alloys by PCD reamer

The cutting forces are studied for the reaming of casting aluminium alloy ZL102 (ZAlSi12) using a four-flute PCD reamer on DMG DMU 50 linear five-axis CNC machine. Kistler Dynamometer is used to measure the cutting force (X-, Y- and Z-axes) and torque. Three-coordinate measuring machine is used for measuring cylindricity of machined hole. The cutting force signatures are diagnosed by using Fast Fourier Transform (FFT) algorithm. FFT analysis suggests that fundamental frequency is only determined by cutting speed. The frequency for the thrust signal of cutting force is zero which illustrates that the thrust is constant when cutting speed and cutting feed are fixed. The relationship between the cutting force and cutting parameter are investigated by using FFT filtering. High value of cutting feed and the low cutting speed provide the higher thrust. The optimized machining parameters are provided relative to cutting force (Fx and Fy) and the cylindricity of reamed holes.

Investigation on Peaming Process of PCD Tool when Reaming Aluminium Cast Alloys

An experimental investigation on the unique reaming behavior of aluminium cast alloys (AlSi12) by using PCD (polycrystalline diamond) tools has been studied. The torque has been monitored in real time during reaming process and the average values of torque were calculated by using FFT (Fast Fourier Transform) filtering. The optimized cutting parameters are provided in terms of analyzing the cutting torque, hole diameter and cylindricity. Results show that the torque initial increases with the rising cutting speed but subsequently decreases when the cutting speed reach to 6000r/min. It is also notable that the optimization of machining parameters basing on cylindricity are that when the cutting speed is under 6000r/min, smaller cutting feed is recommended, while when the cutting speed is over 6000r/min, higher cutting feed is appropriate.

Spatial and temporal changes in flooding and the affecting factors in China

Spatial and temporal changes in flood events in China are becoming increasingly important due to the rapid climate warming that is occurring. This study was conducted to consider changes in flood events and the factors affecting such changes. To accomplish this, China was divided into natural and social-economic flood regions: north China, northwest China, northeast China, southwest China, central China, east China, south China, and Taiwan, Hong Kong and Macau. Spatial and temporal changes in flood patterns were rebuilt during 1980–2009, and Fast Fourier Transform Filtering was then employed to stimulate the changes in floods during this period. The factors affecting flooding were then analyzed quantitatively. The results showed that, based on the time series for China as a whole, flooding was more serious during 1990–1999 than 1980–1989 and 2000–2009. However, in different regions, the trends in flooding differed greatly. Based on spatial changes, the areas hardest hit by floods were northeast China in the 1980s, northeast China, central China and east China in the 1990s, and central China after 2000. In China, the main flood-affecting factors were meteorological, ecological, population, water conservation facilities, and policy factors. However, the main affecting factors differed by region. Overall, the complex spatial and temporal features of flood variations and various affecting factors demand proper national and regional governmental action in the face of the changing flood patterns in China. The results of the present study provide valuable information to flood policymakers and flood disaster researchers.

놋치 필터 개선을 통한 인체 연속절단 영상 재현

현재 VK(Visible Korean) 프로젝트의 인체 연속절단 영상을 이용한 해부학 분야의 다양한 연구가 진행중이다. 이러한 관점에서 VK 영상 데이터의 정확한 인체 정보 재현이 날로 중요해지고 있다. 이와 관련하여 VK 영상의 시상면 및 관상면에 존재하는 절단무늬 제거를 위한 연구들이 있었다. 하지만, 진행 과정에서 급격한 주파수 변화에 따른 울림 현상이 공통으로 발생하였다. 또한, 절단무늬가 제거되지 않은 원본영상과의 병합으로 절단무늬가 다시 재현되는 문제가 있었다. 따라서 본 논문에서는 먼저 FFT 및 놋치필터 적용에 효과적인 색공간을 찾고자 하였다. 이를 위해, RGB, LAB, CMYK, HSV, HSL 색공간을 이용하였다. 다음으로, 놋치 필터 개선을 통해 울림 현상을 제거 및 완화하고자 하였다. 이를 검증하기 위해 원본 영상을 대상으로 하여 선행 연구와 제안 방법을 가시적인 접근과 객관적인 수치를 통해 비교하였다. 이러한 연구를 통해 더욱 실제 인체 정보를 유지한 데이터를 재현할 수 있어서 앞으로 VK 관련 연구에 긍정적으로 작용할 것으로 기대한다. Recently various anatomic researches by using serially sectioned images in VK(Visible Korean) project are in progress. In that sense, it is very important and necessary to represent images which keep information of the original anatomic images. In this regard, there are some studies to get rid of slice patterns in coronal and sagittal images. However, according to the rapid spatial frequency changes, the ringing effect occurred in common. In addition, because of merge with the original images which have splice patterns, those patterns appeared again. Therefore, in this study we found effective color space to apply to FFT(Fast Fourier Transform) and notch filter in getting rid of the slice patterns. To verify this, we used RGB, LAB, CMYK, HSV and HSL color space. Secondly we got rid of and alleviated the ringing effect by improving notch filter. To verify this, we compared proposed method with previous study on the basis of original images by visual method and objective values. These result images are expected to contribute to anatomy research in relation to VK project.