Fourier Transform Technique Research Articles

Efficient HEVC steganography approach based on audio compression and encryption in QFFT domain for secure multimedia communication

High-Efficiency Video Coding (HEVC) is the most recent video codec standard. It is substantial to analyze the HEVC steganography process due to its practical and academic significance. Thus, a secure HEVC steganography approach is introduced in this paper to study the possibility of hiding an encrypted secret audio message within a cover compressed video frame in a secure and complicated manner. In the preliminary stage, the secret audio message is compressed utilizing the Discrete Cosine Transform (DCT) to achieve a high capacity performance for the HEVC steganography process. After that, the suggested approach implies two-cascaded encryption layers to encrypt the compressed secret message before embedding it within a cover HEVC frame. In the first encryption layer, a novel encryption technique based on random projection and Legendre sequence in the Discrete Wavelet Transform (DWT) domain is introduced to cipher the compressed secret audio message. In the second encryption layer, the yielded encrypted audio message is represented in a form of quaternion numbers using the Quaternion Fast Fourier Transform (QFFT) technique. Each cover HEVC frame is also represented in a quaternion form. In the suggested approach, some straightforward quaternion mathematical operations are employed on the encrypted secret message and the cover HEVC frames to represent them in a quaternion form in the frequency domain, then the encrypted secret audio message is hidden within the cover HEVC frame. At the receiver, the secret message can be retrieved and extracted from the cover HEVC frame utilizing the same methodology of the employed quaternion mathematical operations. The major contributions of the suggested HEVC steganography scheme are: (1) it allows hiding of massive amount of secret information within cover video frames, and (2) it has higher robustness against multimedia attacks and steganalysis contrasted to the conventional and literature schemes. Furthermore, the proposed approach is evaluated utilizing different assessment metrics like Feature Similarity Index Measure (FSIM), Peak Signal-to-Noise Ratio (PSNR), correlation coefficient, and Structural Similarity Index Measure (SSIM) to evaluate the efficiency of the stego HEVC frames compared to the original ones. The achieved outcomes demonstrate that the suggested steganography scheme is straightforward to implement, more secure, and robust in the presence of steganalysis multimedia attacks compared to the literature approaches.

Non-Extra Pixel Interpolation

A non-extra pixel interpolation NPI is introduced for efficient image upscaling purposes. The NPI algorithm uses extended-triangular and linear scaling functions to match the pixel coordinates. The triangular function uses a modulo-operator with only two variables representing image pixels and scaling ratio. Every two variables of the linear scaling function represent the source/destination image pixels and scaling ratio. The traditional ceil function is used to round off non-integer pixel coordinates. The circshift and padarray functions are used to circularly shift the elements in array output by [Formula: see text]-amount in each dimension and pad elements of the [Formula: see text]th columns/rows by g-padsize in the shifted array, respectively. The [Formula: see text], [Formula: see text] and [Formula: see text] values are determined with respect to integer scaling ratios by a vector of [Formula: see text]-elements. The Exactness, Peak Signal-to-Noise Ratio, Signal-to-Noise Ratio and Discrete Fourier Transform techniques were used for objective evaluation purposes. Experiments demonstrated comparable results as well as the need for further researches.

Asteroseismology of twoKeplerdetached eclipsing binaries

The present work contains light curve, spectroscopic, and asteroseismic analyses for KIC 04851217 and KIC 10686876. These systems are detached eclipsing binaries hosting a pulsating component ofδScuti type and have been observed with the unprecedented accuracy of theKeplerspace telescope. Using ground-based spectroscopic observations, the spectral types of the primary components of the systems were estimated as A6V and A5V for KIC 04851217 and KIC 10686876, respectively, with an uncertainty of one subclass. The present spectral classification, together with literature radial velocity curves, were used to model the light curves of the systems and, therefore, to calculate the absolute parameters of their components with a higher degree of certainty. The photometric data were analysed using standard eclipsing binary modeling techniques, while their residuals were further analysed using Fourier transformation techniques to extract the pulsation frequencies of their hostδScuti stars. The oscillation modes of the independent frequencies were identified using theoretical models ofδScuti stars. The distances of the systems were calculated using the relation between the luminosity and the pulsation period forδScuti stars. Here, the physical and the oscillation properties of the pulsating components of these systems are discussed and compared with others of the same type. Moreover, using all the currently known cases ofδScuti stars in detached binaries, updated correlations between orbital and dominant pulsation periods and between loggand pulsation periods are derived. It can concluded that the proximity of the companion plays significant role in the evolution of the pulsational frequencies.

Actuator and Sensor Fault Classification for Wind Turbine Systems Based on Fast Fourier Transform and Uncorrelated Multi-Linear Principal Component Analysis Techniques

In response to the high demand of the operation reliability and predictive maintenance, health monitoring and fault diagnosis and classification have been paramount for complex industrial systems (e.g., wind turbine energy systems). In this study, data-driven fault diagnosis and fault classification strategies are addressed for wind turbine energy systems under various faulty scenarios. A novel algorithm is addressed by integrating fast Fourier transform and uncorrelated multi-linear principal component analysis techniques in order to achieve effective three-dimensional space visualization for fault diagnosis and classification under a variety of actuator and sensor faulty scenarios in 4.8 MW wind turbine benchmark systems. Moreover, comparison studies are implemented by using multi-linear principal component analysis with and without fast Fourier transform, and uncorrelated multi-linear principal component analysis with and without fast Fourier transformation data pre-processing, respectively. The effectiveness of the proposed algorithm is demonstrated and validated via the wind turbine benchmark.

Buildup dynamics in an all-polarization-maintaining Yb-doped fiber laser mode-locked by nonlinear polarization evolution.

Soliton buildup dynamics in ultrafast fiber lasers are one of the most significant topics in both the fundamental and industrial fields. In this work, by using the dispersive Fourier transformation technique, the real-time spectral evolution of soliton buildup dynamics were investigated in the all-polarization-maintaining Yb-doped fiber laser, which is mode-locked by nonlinear polarization evolution technique through the cross splicing method. It was experimentally confirmed that the same stable soliton state could be achieved through different soliton starting processes because of the initial random noises. In one case, the maximum pulse energy during the soliton starting process could reach ∼15 times the stable pulse energy, which results in the spectral chaotic state and temporal shift. We also provide another soliton buildup case with the same cavity parameters, which illustrates more moderate evolution. It involves smaller energy variation and no complex transition state. These results would deepen our understanding of soliton buildup dynamics and be beneficial for the applications of ultrafast fiber lasers.

Seismic Edge Detection by Application of Cepstral Decomposition to Data Driven Modeled Geologic Channel Feature in Niger Delta.

Seismic edge detection algorithm unmasks blurred discontinuity in an image and its efficiency is dependent on the precession of the processing scheme adopted. Data-driven modeling is a ast machine learning scheme and a formal usually automatic version of the empirical approach in existence for long time and which can be used in many different contexts. Here, a desired algorithm that can identify masked connection and correlation from a set of observations is built and used.Geologic models of hydrocarbon reservoirs facilitate enhanced visualization, volumetric calculation, well planning and prediction of migration path for fluid. In order to obtain new insights and test the mappability of a geologic feature, spectral decomposition techniques i.e. Discrete Fourier Transform (DFT), etc and Cepstral decomposition techniques, i.e Complex Cepstral Transform (CCT), etc can be employed. Cepstral decomposition is a new approach that extends the widely used process of spectral decomposition which is rigorous when analyzing very subtle stratigraphic plays and fractured reservoirs. This paper presents the results of the application of DFT and CCT to a two dimensional, 50Hz low impedance Channel sand model, representing typical geologic environment around a prospective hydrocarbon zone largely trapped in various types of channel structures. While the DFT represents the frequency and phase spectra of a signal, assumes stationarity and highlights the average properties of its dominant portion, assuming analytical, the CCT represents the quefrency and saphe cepstra of a signal in quefrency domain. The transform filters the field data recorded in time domain, and recovers lost sub-seismic geologic information in quefrency domain by separating source and transmission path effects. Our algorithm is based on fast Fourier transform (FFT) techniques and the programming code was written within Matlab software. It was developed from first principles and outside oil industry’s interpretational platform using standard processing routines. The results of the algorithm, when implemented on both commercial and general platforms, were comparable. The cepstral properties of the channel model indicate that cepstral attributes can be utilized as powerful tool in exploration problems to enhance visualization of small scale anomalies and obtain reliable estimates of wavelet and stratigraphic parameters. The practical relevance of this investigation is illustrated by means of sample results of spectral and cepstral attribute plots and pseudo-sections of phase and saphe constructed from the model data. The cepstral attributes reveal more details in terms of quefrency required for clearer imaging and better interpretation of subtle edges/discontinuities, sand–shale interbedding, differences in lithology. These positively impact on production as they serve as basis for the interpretation of similar geologic situations in field data.

Oblique surface cracking and crack closure in an orthotropic medium under contact loading

This article presents analytical methods for analysis of an inclined surface crack in an orthotropic medium subjected to contact loading. Governing partial differential equations are derived in accordance with plane theory of orthotropic elasticity. Contact and crack problems are formulated separately utilizing Fourier transformation techniques. The contact problem consists of a rigid flat punch pressing upon an orthotropic half-plane, and is reduced to a singular integral equation of the second kind. The surface crack is assumed to be tilted at an arbitrary angle with respect to the normal of the half-plane surface. Three different crack configurations are considered, which are completely closed, partially-closed, and fully-open cracks. Frictional contact between the crack faces is implemented in the cases of completely closed, and partially-closed cracks. A single singular integral equation is derived for the completely closed crack, whereas each of the problems of partially- and fully-open cracks requires derivation of a set of two singular integral equations. The contact problem and each of the crack problems are solved numerically by means of the expansion-collocation technique. A flowchart is developed and implemented to detect the type of crack closure configuration under a given contact loading. The parametric analyses carried out illustrate the influences of factors such as crack inclination angle, crack face and contact surface friction coefficients, material orthotropy, and relative punch location on crack face contact stresses, degree of crack closure, and mode I and II stress intensity factors.

Antibacterial applications and Comparative Study for Adsorption Phenol Red Dye Using Spinel Co1-xMxFe2O4 Nano Composites (M= Cd, Ag)

This work concerned with the study of adsorption of phenol red dye by using spinel Co1-xMxFe2O4 was prepare by Co-precipitation method at different ratios of (0.2:0.8, 0.5:0.5, 0.8:0.2) and calcinations at temperature 600 C0 for three hours. The conclusion showed that (0.5:0.5) percentage has high activity than other ratio at different temperature. The prepared powder was differentiated by X-ray diffraction, Fourier Transform Technique (FT-IR), UV-Visible Spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Atomic Force Microscope (AFM), high performance liquid chromatography (HPLC) were also studied for all spinel. X-ray and Electron Microscopy studies showed the average size of the granules prepared for the composite in this manner (17.44 for Cd and 37.55 for Ag)

Evaluation electromagnetic contactor magnetic core temperature and dynamic strain using fiber Bragg gratings

This paper presents the results obtained from the fiber Bragg grating (FBG) sensors installed on the fixed magnetic core of an electromagnetic AC contactor for temperature and dynamic strain measurements. Using the results analysis, it is possible to apply the sensor system as a preventive maintenance tool, since the deformation experienced is proportional to the electromagnetic force in the contactor. The temperature variation is 76 °C and reaches thermal stability at t = 160 min on the contactor magnetic core. For the dynamic strain sensing four measurements were carried out with the contactor: intact, with voltage sag, with an air gap obstacle and without shading ring. The electromagnetic force has a fundamental frequency of 120 Hz, which is twice the frequency of the main supply power for the intact and with voltage sag contactor. This fundamental frequency is obtained by using a Fast Fourier Transform (FFT) technique of the steady-state dynamic strain measured wavelength. For the contactor with air gap obstacle and without a shading ring, the FBG wavelength variation is very noisy and the electromagnetic force is not sinusoidal.

Pattern Detection Model Using a Deep Learning Algorithm for Power Data Analysis in Abnormal Conditions

Building a pattern detection model using a deep learning algorithm for data collected from manufacturing sites is an effective way for to perform decision-making and assess business feasibility for enterprises, by providing the results and implications of the patterns analysis of big data occurring at manufacturing sites. To identify the threshold of the abnormal pattern requires collaboration between data analysts and manufacturing process experts, but it is practically difficult and time-consuming. This paper suggests how to derive the threshold setting of the abnormal pattern without manual labelling by process experts, and offers a prediction algorithm to predict the potentials of future failures in advance by using the hybrid Convolutional Neural Networks (CNN)–Long Short-Term Memory (LSTM) algorithm, and the Fast Fourier Transform (FFT) technique. We found that it is easier to detect abnormal patterns that cannot be found in the existing time domain after preprocessing the data set through FFT. Our study shows that both train loss and test loss were well developed, with near zero convergence with the lowest loss rate compared to existing models such as LSTM. Our proposition for the model and our method of preprocessing the data greatly helps in understanding the abnormal pattern of unlabeled big data produced at the manufacturing site, and can be a strong foundation for detecting the threshold of the abnormal pattern of big data occurring at manufacturing sites.

COMPARISON OF CLTD AND TETD COOLING LOAD CALCULATION METHODS FOR DIFFERENT BUILDING ENVELOPES

The estimation of the cooling load through the building envelope is an essential task in the selection of proper HVAC system components that influences the building’s performance. For this task, ASHRAE has presented several methods to calculate the building cooling load due to heat gain, such as the total equivalent temperature difference method (TETD), the cooling load temperature difference method (CLTD), and the radiant time series method (RTS). The present study aims to explore the accuracies of those calculation methods in terms of energy efficiency. In this regard, an analytical solution method utilizing Complex Finite Fourier Transform Technique (CFFT) was developed for the calculation of cooling load due to heat gain to compare the temperature differences obtained from the TETD and CLTD methods. Then, a computer program was prepared in MATLAB to perform the calculations based on an analytical methodology. Besides, the estimated CLTD and TETD values by the CFFT were compared with those values presented in the Handbook of the ASHRAE. The calculation results revealed there is a good agreement between the analytical and presented results in the ASHRAE Manual for the selected building envelopes. However, several differences were found between the estimated TETD and CLTD cooling load values and those presented in the Handbook of ASHRAE.

Ab initio potential energy surface and microwave spectrum of the NH3-N2 van der Waals complex.

We present a five-dimensional intermolecular potential energy surface (PES) of the NH3-N2 complex, bound state calculations, and new microwave (MW) measurements that provide information on the structure of this complex and a critical test of the potential. Ab initio calculations were carried out using the explicitly correlated coupled cluster [CCSD(T)-F12a] approach with the augmented correlation-consistent aug-cc-pVTZ basis set. The global minimum of the PES corresponds to a configuration in which the angle between the NH3 symmetry axis and the intermolecular axis is 58.7° with the N atom of the NH3 unit closest to the N2 unit, which is nearly parallel to the NH3 symmetry axis. The intermolecular distance is 7.01 a0, and the binding energy De is 250.6 cm-1. The bound rovibrational levels of the four nuclear spin isomers of the complex, which are formed when ortho/para (o/p)-NH3 combines with (o/p)-N2, were calculated on this intermolecular potential surface. The computed dissociation energies D0 are 144.91 cm-1, 146.50 cm-1, 152.29 cm-1, and 154.64 cm-1 for (o)-NH3-(o)-N2, (o)-NH3-(p)-N2, (p)-NH3-(o)-N2, and (p)-NH3-(p)-N2, respectively. Guided by these calculations, the pure rotational transitions of the NH3-N2 van der Waals complex were observed in the frequency range of 13-27 GHz using the chirped-pulse Fourier-transform MW technique. A complicated hyperfine structure due to three quadrupole 14N nuclei was partly resolved and examined for all four nuclear spin isomers of the complex. Newly obtained data definitively established the K values (the projection of the angular momentum J on the intermolecular axis) for the lowest states of the different NH3-N2 nuclear spin isomers.

Contactless Liquid Height and Property Estimation Using Surface Acoustic Waves

The propagation of surface acoustic waves over a solid plate is highly influenced by the presence of liquid media on the surface. At the solid–liquid interface, a leaky Rayleigh wave radiates energy into the liquid, causing a signification attenuation of the surface acoustic wave amplitude. In this study, we take advantage of this spurious wave mode to predict the characteristics of the media, including the volume or height. In this study, the surface acoustic waves were generated on a thick 1018 steel surface via a 5 MHz transducer coupled through an angle beam wedge. A 3D-printed container was inserted on the propagation path. The pulse-echo time-domain responses of the signal were recorded at five different volumes (0, 400, 600, 1000, and 1800 µL). With the aid of parametric CAD analysis, both the position and distance of the entire traveling wave in the liquid layer were modeled and verified with experimental studies. The results indicated that the average drop in the reflected wave amplitude due to liquid loading is −62.5% compared to the empty container, with a percentage of error within 10% for all cases. The localized-time frequency components of the reflected wave were obtained via a Short-Time Fourier Transform technique. Up to 10% reduction (500 KHz) in the central frequency was observed due to the liquid volume increasing. The method discussed herein could be useful for many applications, where some of the liquid’s parameters or the ultrasonic wave behavior in the liquid need to be assessed.

An experimental investigation of the effect of thermophysical properties on time lag and decrement factor for building elements

The time lag (TL) and decrement factor (DF) are essential for the heat storage capabilities of building elements, which strictly depend on the thermophysical properties of the elements. Many investigations are presented in literature arguing to find the influence of each thermophysical property on TL and DF by keeping the other properties constant. This study aims to investigate the effect of each property on TL and DF, utilizing relationships between the measurement values of the thermophysical properties of wall materials. Therefore, first, 132 new concrete wall samples were produced, and their thermophysical properties were tested. Secondly, TL and DF values for each building element are computed from the solution of the problem by Complex Finite Fourier Transform (CFFT) technique. Finally, a multivariate regression analysis has been performed, and the variations of each thermophysical property versus TL and DF are presented, and also the findings are compared with literature. The results show that each property alone (keeping the other properties constant) is not adequate to identify the thermal inertia and thermal performance of a wall element. Besides, 87.3 % decrease in thermal diffusivity corresponds to 6.03 h increase in the value of TL and 88.8 % decrease in value of DF; respectively, for W1 wall assembly.

Application of aeromagnetic data to map subsurface structural features in Ewekoro, Southwestern Nigeria

In this study, aeromagnetic data were interpreted and analyzed in order to map the subsurface geological structures at Ewekoro, southwestern, Nigeria. To accomplish this goal, some image enhancement techniques were applied to the magnetic data by which concealed subsurface structures were revealed. The total magnetic intensity data were reduced to the magnetic pole using Fourier transformation technique. The results of these filtering techniques were displayed with a number of maps. From the interpreted maps, a number of lineaments majorly trending in NE–SW direction were identified. These lineaments were indications of faults or fractures due to the displacements that might have arisen from tectonic events in the area. The estimated depths from the power spectrum technique suggest the presence of two magnetic sources the shallow and deep sources at depth of 0.02–0.75 km, respectively. The deep source indicates the basement rocks underlying the sedimentary cover in the area.

Hybrid frequency-time spectrograph for the spectral measurement of the two-photon state.

In this Letter, a hybrid frequency-time spectrograph combining a tunable optical filter and a dispersive element is presented for measurement of the spectral properties of the two-photon state. In comparison with the previous single-photon spectrograph utilizing the dispersive Fourier transformation (DFT) technique, this method is advanced since it avoids the need for additional wavelength calibration and the electronic laser trigger for coincidence measurement; therefore, its application is extended to continuous wave (CW) pumped two-photon sources. The achievable precision of the spectrum measurement has also been discussed in theory and demonstrated experimentally with a CW pumped periodically poled lithium niobate (PPLN) waveguide-based spontaneous parametric down-conversion photon source. Such a device is expected to be a versatile tool for the characterization of the frequency entangled two-photon state.

Dynamic investigation of Georges phenomenon related to three-phase wound-rotor induction motor

The aim of this paper is to analyze the performance of a three-phase wound-rotor induction motor (WRIM) under rotor windings asymmetry. The dynamic performance of the WRIM under healthy and rotor windings asymmetry with one-open-phase fault conditions is analyzed using a dynamic model in the ABC frame. Under opening one phase of the rotor windings, the WRIM suffers from operation at a speed near to the half of its synchronous speed, which is known as the Georges phenomenon. The behavior of the WRIM is simulated and investigated experimentally under faulty conditions for four different possible connections of rotor windings. The stator and rotor currents are analyzed using fast Fourier transformation technique to identify the fault signatures. The results prove that under opening one phase of the rotor windings the WRIM suffers from pulsating electromagnetic torque, high oscillatory stator currents and high unbalanced rotor currents. Also the results prove that the performance of the motor under rotor windings asymmetry conditions and the occurrence of Georges phenomenon depend on the type of connection of the rotor windings and fault location. Therefore, the authors suggest a special delta connection for the rotor winding to reduce the effects of this phenomenon. The simulation and experimental results show good agreement and prove the validity of the suggested delta connection.

A novel FFT-based phase field model for damage and cracking behavior of heterogeneous materials

A novel numerical method is developed for three-dimensional modeling of damage and cracking in heterogeneous rock-like materials. Two key issues are addressed. For the first issue, influences of materials heterogeneities such as pores and inclusions on damage evolution and cracking processes are investigated by a homogenization approach with Fast Fourier Transform technique. For the second issue, the nucleation and propagation of cracks from diffuse damage evolution are formulated in Fourier space and described by a phase-field method. To do this, an efficient numerical procedure is developed for the stress–strain relationships and crack phase field propagation. A new elastic degradation function is proposed in order to describe a large range of cracking processes. A range of heterogeneous materials with different microstructure are generated and performed numerically to study effects of pores and inclusions on the damage evolution and cracking process in heterogeneous materials.

Comparative Analysis among Discrete Fourier Transform, K-Means and Artificial Neural Networks Image Processing Techniques Oriented on Quality Control of Assembled Tires

The present paper discusses a comparative application of image processing techniques, i.e., Discrete Fourier Transform, K-Means clustering and Artificial Neural Network, for the detection of defects in the industrial context of assembled tires. The used Artificial Neural Network technique is based on Long Short-Term Memory and Fully Connected neural networks. The investigations focus on the monitoring and quality control of defects, which may appear on the external surface of tires after being assembled. Those defects are caused from tires which are not properly assembled to their respective metallic wheel rim, generating deformations and scrapes which are not desired. The proposed image processing techniques are applied on raw high-resolution images, which are acquired by in-line imaging and optical instruments. All the described techniques, i.e., Discrete Fourier Transform, K-Means clustering and Long Short-Term Memory, were able to determine defected and acceptable external tire surfaces. The proposed research is taken in the context of an industrial project which focuses on the development of automated quality control and monitoring methodologies, within the field of Industry 4.0 facilities. The image processing techniques are thus meant to be adopted into production processes, giving a strong support to the in-line quality control phase.

Autosetting Mode-Locked Laser Using an Evolutionary Algorithm and Time-Stretch Spectral Characterization

There is an increased research effort on the development of smart ultrafast laser systems with the intended goal of converting the high parameter sensitivity of the complex laser dynamics from a practical challenge to an opportunity. Evolutionary algorithms have the potential to find suitable mode-locking parameters and optimize the laser output according to the user specifications. In this article, we present the auto setting of optimized self-starting ultrafast pulse regimes at the optical telecom wavelength. We implement an evolutionary algorithm on a normal-dispersion fiber laser cavity mode-locked through a 4-parameter nonlinear polarization evolution. By using a consistent scheme of intracavity liquid-crystal retarders for polarization control, and the time-stretch dispersive Fourier-transform technique for real-time spectral output analysis, we show that we can achieve an efficient and fast optimization of the mode-locked state, with the ability to tune its spectral width.