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Chinese Optics Letters 2022年第9期20卷 68-72页

作者：赖林权陈玥陈孔涛唐嘉乐尹楷文贾富强乔盾范元龙李康 Nigel Copner Fujian Key Laboratory of Ultrafast Laser Technology and Applications School of Electronic Science and TechnologyXiamen UniversityXiamen 361005China Wireless&Optoelectronics Research&Innovation Centre Faculty of ComputingEngineering&ScienceUniversity of South WalesWales CF371DLUK

Conventional wavelength modulation spectroscopy(WMS)is vulnerable to the influence of low-frequency noise.Accuracy of the method highly depends on the performance of the costly lock-in amplifier.In this article,we report a new and effective method for reconstructing second-harmonic signals through WMS based on fast fourier transform(FFT).This method is less disturbed by low-frequency noise because it does not use a low-frequency ramp wave.Formulation and detection procedures were presented.The discrete second-harmonic waveform can be obtained by continuously changing the DC signal and FFT analysis in this method.Second-harmonic waveforms acquired by the two means are generally consistent.The experimental study validates the obtained gas concentration from 5% to 30%,showing a good linear relationship by the proposed method.The maximum relative error on concentration extraction is 2.87%;as for conventional WMS,this value is 4.50%.The developed measurement method may have potential in computed tomography.

关键词： fast fourier transform wavelength modulation spectroscopy second-harmonic waveform

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fast fourier transform-based Support Vector Machine for Prediction of G-protein Coupled Receptor Subfamilies

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Acta Biochimica et Biophysica Sinica 2005年第11期37卷 759-766页

作者： Yan-Zhi GUO Meng-Long LI Ke-Long WANG Zhi-Ning WEN Min-Chun LU Li-Xia LIU Lin JIANG College of Chemistry,Sichuan University,Chengdu 610064,China College of Chemistry Sichuan UniversityChengdu 610064 China

Although the sequence information on G-protein coupled receptors(GPCRs)continues togrow,many GPCRs remain orphaned(i.***.ligand specificity unknown)or poorly characterized with littlestructural information available,so an automated and reliable method is badly needed to facilitate the identifi-cation of novel receptors.In this study,a method of fast fourier transform-based support vector machinehas been developed for predicting GPCR subfamilies according to protein’s hydrophobicity.In classifyingClass B,C,D and F subfamilies,the method achieved an overall Matthew’s correlation coefficient andaccuracy of 0.95 and 93.3%,respectively,when evaluated using the jackknife test.The method achieved anaccuracy of 100% on the Class B independent dataset.The results show that this method can classify GPCRsubfamilies as well as their functional classification with high accuracy.A web server implementing theprediction is available at http://***/blast/Pred-GPCR.

关键词： G-protein coupled receptor subfamily fast fourier transform support vector machine prediction

Exploring the correlation between temperature and crime:A case-crossover study of eight cities in America

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Journal of Safety Science and Resilience 2024年第1期5卷 13-36页

作者： Jinming Hu Xiaofeng Hu Xin’ge Han Yan Lin Huanggang Wu Bing Shen School of Information Technology and Cyber Security People’s Public Security University of ChinaBeijing 100038China Center for Capital Social Safety People’s Public Security University of ChinaBeijing 100038China China Association for Public Safety Beijing 100084China School of Emergency Management and Safety Engineering China University of Mining and TechnologyBeijing 100083China School of International Police Studies People’s Public Security University of ChinaBeijing 100038China

Recent years have seen increasing academic interest in exploring the correlation between temperature and crime.However,it is uncertain whether similar long-term trends or seasonality(rather than causal effect)of temper-ature and crime is the major reason for the observed correlation between them.To explore whether there is still a correlation between temperature and crime when long-term trends and seasonal cycles are filtered out,we use the Kalman filter to decompose the time series of temperature and crimes,and then the fast fourier transform is used to calculate the exact circle of their seasonality separately.Based on that,the box-plot method and linear regression are used to explore the correlation between temperature residuals and crime residuals.The results show that more than half of the crime types have similar seasonal cycles(approximately 1 year)to that of temperature.Moreover,the daily residual analyses show that temperature residuals have a positive correlation with assault and robbery residuals in all cities,whose average slopes are more than 0.1.The other four types of crimes vary greatly from case to case.The temperature residuals show a weak correlation with the residuals of some crime types.

关键词： Time series decomposition Crime Temperature Kalman filter fast fourier transform

fast fourier transform:A Niche,but Critical Strategy in Optimizing Impression Evidence

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Journal of Forensic Science and Medicine 2018年第4期4卷 192-196页

作者： Brian Dalrymple Department of Forensic Science Laurentian UniversitySudburyCanada

The evolution from film to digital as the recording medium for forensic imaging has extended the reach of forensic photographers,both in original capture and postphotography processing.Images of fingermarks and footwear impressions are routinely obstructed by substrates displaying intrusive color and pattern.Such backgrounds are frequently sufficiently intrusive as to prevent the analysis and comparison of the images to known exemplars.Digital techniques such as fast fourier transform(FFT)in postphotography processing can optimize the signal-to-noise ratio to a greater degree than was ever possible when film was the recording standard.Occasionally,unwanted backgrounds can be removed or diminished in Photoshop with techniques such as background subtraction and channel blending.These strategies,however,are dependent on either physical removal of the evidence impression to obtain a second image of the obstructive pattern or on differences in color between the impression and the offending substrate.FFT is unique in its ability to optimize the image signal to noise ratio by suppressing the obstructive background,in that it is not reliant on color,and is not applied in the spatial domain.

关键词： fast fourier transform image pro premier postphotography digital optimization

A Deepfake Detection Algorithm Based on fourier transform of Biological Signal

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Computers, Materials & Continua 2024年第6期79卷 5295-5312页

作者： Yin Ni Wu Zeng Peng Xia Guang Stanley Yang Ruochen Tan School of Electrical and Electronic Engineering Wuhan Polytechnic UniversityWuhan430023China School of Mathematics and Computer Science Wuhan Polytechnic UniversityWuhan430048China Paul G.Allen School of Computer Science and Engineering University ofWashingtonSeattleWA98195USA School of Computer Science and Engineering University of CaliforniaSanDiegoCA92093USA

Deepfake-generated fake faces,commonly utilized in identity-related activities such as political propaganda,celebrity impersonations,evidence forgery,and familiar fraud,pose new societal threats.Although current deepfake generators strive for high realism in visual effects,they do not replicate biometric signals indicative of cardiac activity.Addressing this gap,many researchers have developed detection methods focusing on biometric characteristics.These methods utilize classification networks to analyze both temporal and spectral domain features of the remote photoplethysmography(rPPG)signal,resulting in high detection accuracy.However,in the spectral analysis,existing approaches often only consider the power spectral density and neglect the amplitude spectrum—both crucial for assessing cardiac activity.We introduce a novel method that extracts rPPG signals from multiple regions of interest through remote photoplethysmography and processes them using fast fourier transform(FFT).The resultant time-frequency domain signal samples are organized into matrices to create Matrix Visualization Heatmaps(MVHM),which are then utilized to train an image classification network.Additionally,we explored various combinations of time-frequency domain representations of rPPG signals and the impact of attention mechanisms.Our experimental results show that our algorithm achieves a remarkable detection accuracy of 99.22%in identifying fake videos,significantly outperforming mainstream algorithms and demonstrating the effectiveness of fourier transform and attention mechanisms in detecting fake faces.

关键词： Deepfake detector remote photoplethysmography fast fourier transform spatial attention mechanism

Identification of faults through wavelet transform vis-a-vis fast fourier transform of noisy vibration signals emanated from defective rolling element bearings

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Frontiers of Mechanical Engineering 2014年第2期9卷 130-141页

作者： Deepak PALIWAL Achintya CHOUDHURY T. GOVANDHAN Department of Mechanical Engineering Sir Padampat Singhania University Udaipur 313601 Rajasthan India

Fault diagnosis of rolling element bearings requires efficient signal processing techniques. For this purpose, the performances of envelope detection with fast fourier transform （FFT） and continuous wavelet transform （CWT） of vibration signals produced from a bearing with defects on inner race and rolling element, have been examined at low signal to noise ratio. Both simulated and experimental signals from identical bearings have been considered for the purpose of analysis. The bearings have been modeled as spring-mass-dashpot systems and the simulated signals have been obtained considering transfer functions for the bearing systems subjected to impulsive loads due to the defects. Frequency B spline wavelets have been applied for CWT and a discussion on wavelet selection has been presented for better effectiveness. Results show that use of CWT with the proposed wavelets overcomes the short coming of FFT while processing a noisy vibration signals for defect detection of bearings.

关键词： Fault detection spline wavelet continuous wavelet transform fast fourier transform

fast fourier transform Approximation of Foreign Currency Option Pricing Based on Exponential Lévy Model

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Journal of Southwest Jiaotong University(English Edition) 2007年第3期15卷 261-270页

作者：陈旭万建平 Department of Mathematics Huazhong University of Science and Technology

To study the approximation of foreign currency option prices when the underlying assets＇ price dynamics are described by exponential Lévy processes, the convolution representations for option pricing formulas were given, and then the fast fourier transform （FFT） algorithm was used to get the approximate values of option prices. Finally, a numerical example was given to demonstrate the calculate steps to the option price by FFT.

关键词： Exponential Lévy model Bilateral Laplace transformation Measure change Foreign currency options fast fourier transform

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A sapphire fibre thermal probe based on fast fourier transform and phase-lock loop

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Chinese Physics B 2006年第5期15卷 975-979页

作者：王平田王冬生葛文谦崔立超 Department of Electrical Engineering Yanshan University Qinhuangdao 066004 China

A sapphire fibre thermal probe with Cr^3＋ ion-doped end is developed by using the laser heated pedestal growth method. The fluorescence thermal probe offers advantages of compact structure, high performance and ability to withstand high temperature in a detection range from room temperature to 450℃. Based on the fast fourier transform （FFT）, the fluorescence lifetime is obtained from the tangent function of phase angle of the non-zeroth terms in the FFT result. This method has advantages such as quick calculation, high accuracy and immunity to the background noise. This FFT method is compared with other traditional fitting methods, indicating that the standard deviation of the FFT method is about half of that of the Prony method and about 1/6 of that of the log-fit method. And the FFT method is immune to the background noise involved in a signal. So, the FFT method is an excellent way of processing signals. In addition, a phase-lock amplifier can effectively suppress the noise.

关键词： fluorescence thermometer fast fourier transform phase-lock loop sapphire optical fibre

A high performance fast-fourier-transform spectrum analyzer for measuring spin noise spectrums

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Chinese Physics B 2020年第9期29卷 259-266页

作者：仝煜王淋张闻哲朱明东秦熙江敏荣星杜江峰 Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics University of Science and Technology of ChinaHefei 230026China CAS Key Laboratory of Microscale Magnetic Resonance University of Science and Technology of ChinaHefei 230026China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of ChinaHefei 230026China

A high performance fast-fourier-transform (FFT) spectrum analyzer, which is developed for measure spin noise spectrums, is presented in this paper. The analyzer is implemented with a field-programmable-gate-arrays (FPGA) chip for data and command management. An analog-to-digital-convertor chip is integrated for analog signal acquisition. In order to meet the various requirements of measuring different types of spin noise spectrums, multiple operating modes are designed and realized using the reprogrammable FPGA logic resources. The FFT function is fully managed by the programmable resource inside the FPGA chip. A 1 GSa/s sampling rate and a 100 percent data coverage ratio with non-dead-time are obtained. 30534 FFT spectrums can be acquired per second, and the spectrums can be on-board accumulated and averaged. Digital filters, multi-stage reconfigurable data reconstruction modules, and frequency down conversion modules are also implemented in the FPGA to provide flexible real-time data processing capacity, thus the noise floor and signals aliasing can be suppressed effectively. An efficiency comparison between the FPGA-based FFT spectrum analyzer and the software-based FFT is demonstrated, and the high performance FFT spectrum analyzer has a significant advantage in obtaining high resolution spin noise spectrums with enhanced efficiency.

关键词： fast fourier transform spectrum analyzer field-programmable-gate-arrays(FPGA) spin noise spectrum

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Gait Recognition Based on the fast fourier transform and SVM

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Gait Recognition Based on the Fast Fourier Transform and SVM