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1

Free vibration studies on skew sandwich plates

Kumar Dhotre Pavan, Venkateshappa Chikko Srinivasa

Composites Theory and Practice

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2020

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R. 20, nr 3-4

118--127

EN

The present work focuses on determining the fundamental frequencies of skew sandwich plates with face sheets considered to be classical thin plates, which are made of a graphite-epoxy material and an orthotropic core made of glass reinforced- epoxy using different boundary conditions. The fundamental frequencies were obtained using finite elements, which are validated with available literature results. The effects of the skew angle, ratio of the length to total thickness of the sandwich plate, and ratio of the thickness of the core to the face sheet on the fundamental frequency of skew sandwich plates were obtained. In addition, the effect of parameters such as the number of layers in the face sheet, the laminate stacking sequence and the fiber orientation angle on the fundamental frequencies of laminated skew sandwich plates was also ascertained. It was found that the CQUAD8 element yields better results than the CQUAD4 element in the present study. The fundamental frequencies were found to increase with an increasing skew angle. The variation in the fundamental frequency is negligible when there are a large number of layers in the face sheet.

2

Numerical analysis for frequency and displacement improvement of a long span floor building

Supriyadi Bambang

Archives of Civil Engineering

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2020

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Vol. 66, nr 4

651--660

EN

In the last decade many buildings such as multipurpose buildings, malls, auditoriums, sports halls which have long-span building floor structure. Various research results indicate that in general long-span concrete floor structures have a fundamental frequency of less than 7 Hz. This will risk a resonance if this floor receives dynamic loads of people jogging to follow the song with a frequency of 2-3 Hz. This research was conducted to numerically analyze the long-span building floor model using SAP2000, to determine the fundamental frequency and maximum displacement of the floor structure model. It was also investigated how to increase its fundamental frequency and reduce the maximum displacement. The results have shown that the numerical analysis of the plate model long-span floor building using SAP2000 produces a fundamental frequency of 5.19 Hz. Model III with Reinforcing double equal angles (84x37x10x2.5) steel truss provides the best results, increases the fundamental frequency to be 7.93 Hz, and with a variety of static and dynamic loads, decreases the value of the displacement and far from the allowable displacement.

3

Transient analysis of transversely functionally graded Timoshenko beam (TFGTB) in conjunction with finite element method

Khafaji Salwan Obaid Waheed, Al-Shujairi Mohammed A., Aubad Mohammed Jawad

Archive of Mechanical Engineering

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2020

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LXVII, nr 3

299--321

EN

In this work, transient and free vibration analyses are illustrated for a functionally graded Timoshenko beam (FGM) using finite element method. The governing equilibrium equations and boundary conditions (B-Cs) are derived according to the principle of Hamilton. The materials constituents of the FG beam that vary smoothly along the thickness of the beam (along beam thickness) are evaluated using the rule of mixture method. Power law index, slenderness ratio, modulus of elasticity ratio, and boundary conditions effect of the cantilever and simply supported beams on the dynamic response of the beam are studied. Moreover, the influence of mass distribution and continuous stiffness of the FGM beam are deeply investigated. Comparisons between the current free vibration results (fundamental frequency) and other available studies are performed to check the formulation of the current mathematical model. Good results have been obtained. A significant effect is noticed in the transient response of both simply supported and cantilever beams at the smaller values of the power index and the modulus elasticity ratio.

4

The effect of material gradient on the static and dynamic response of layered functionally graded material plate using finite element method

Vasiraja N., Nagaraj P.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2019

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Vol. 67, nr 4

827--838

EN

This article focuses on the finite element analysis (FEA) of the nonlinear behavior of a layered functionally graded material (FGM) plate as concerns displacement, stresses, critical buckling load and fundamental frequency. The material properties of each layer in an FGM plate are assessed according to a ceramic based simple power law distribution and the rules of mixture. The finite element model of a layered FGM plate is developed using ANSYS®15.0 software. The developed finite element model is used to study the static and dynamic responses of an FGM plate. In this paper, the effects of power law distribution, thickness ratio, aspect ratio and boundary conditions are investigated for central displacement, transverse shear stress, transverse normal stress, critical buckling load and fundamental frequency, and the obtained FEA results are in sound agreement with the literature test data results. Since the FGM is used in a high temperature environment, the FE analysis is performed for the FGM plate under a thermal field and then correlated. Finally, the FGM plate is analyzed under a thermomechanical load by using the current FE concept.

5

Speech Emotion Recognition Based on Voice Fundamental Frequency

Dimitrova-Grekow Teodora, Klis Aneta, Igras-Cybulska Magdalena

Archives of Acoustics

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2019

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Vol. 44, No. 2

277--286

EN

The human voice is one of the basic means of communication, thanks to which one also can easily convey the emotional state. This paper presents experiments on emotion recognition in human speech based on the fundamental frequency. AGH Emotional Speech Corpus was used. This database consists of audio samples of seven emotions acted by 12 different speakers (6 female and 6 male). We explored phrases of all the emotions – all together and in various combinations. Fast Fourier Transformation and magnitude spectrum analysis were applied to extract the fundamental tone out of the speech audio samples. After extraction of several statistical features of the fundamental frequency, we studied if they carry information on the emotional state of the speaker applying different AI methods. Analysis of the outcome data was conducted with classifiers: K-Nearest Neighbours with local induction, Random Forest, Bagging, JRip, and Random Subspace Method from algorithms collection for data mining WEKA. The results prove that the fundamental frequency is a prospective choice for further experiments.

6

Assessment of power frequency estimation methods in distributed generation in islanding condition

Sanca H. S., Campos J. T. L. S., Souza F. C., Costa F. B., Souza B. A.

Przegląd Elektrotechniczny

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2018

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R. 94, nr 5

1--6

EN

In this paper, a method for evaluation of power frequency estimation during transient operation in distributed generation (DG) in islanding conditions is presented. For this end, five methods of fundamental frequency estimation are evaluated in a distribution system with distributed generation in islanding operation, such as: (a) zero crossing, (b) adjustment of points to a pure sinusoidal waveform, (c) hybrid method, (d) discrete Fourier transform method based, and (e) Prony-Fourier-based algorithm. The estimators are compared and evaluated in two different ways, using two analytical functions, and in an electric power distributed system with DG in islanding condition. The evaluation methodology for the frequency estimators are based in statistical errors, taking into account mean, mean square error. The zero-crossing and discrete Fourier transform based estimator presented better results in comparison with the other evaluated algorithms. However, the discrete Fourier transform presented good results in the estimated frequency in the three evaluated cases.

PL

W artykule oceniono metody badania częstotliwości w stanach przejściowych rozproszonych sieci energetycznych w warunkach tworzenia się wysp. Zbadano pięć metod: zero crossing, APPSW, hybrydową, DFT iProny. Najlepszy wyniki osiągnięto przy stosowaniu metody zero-crossing (Przeciecia osi zero) I DFT.

7

Emotion Analysis from Speech of Different Age Groups

Palo Hemanta Kumar, Mohanty Mihir Narayan, Chandra Mahesh

Annals of Computer Science and Information Systems

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2017

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Vol. 10

283--287

EN

This Recognition of speech emotion based on suitable features provides age information that helps the society in different ways. As the length and shape of human vocal tract and vocal folds vary with age of the speaker, the area remains a challenge. Emotion recognition system based on speaker's age will help criminal investigators, psychologists and law enforcement agencies in dealing with different segments of the society. Particularly child psychologists, counselors can take timely preventive measures based on such recognition system. The area remains further complex since the recognition system trained for adult users performs poorer when it involves children. This has motivated the authors to move in this direction. A novel effort is made in this work to determine the age of speaker based on emotional speech prosody and clustering them using fuzzy c-means algorithm. The results are promising and we are able to demarcate the emotional utterances based on age.

8

Finite element studies on free vibration of laminated composite cylindrical skew panels

Srinivasa C. V., Suresh Y. J., Prema Kumar W. P.

International Journal of Applied Mechanics and Engineering

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2014

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Vol. 19, no. 1

165--180

EN

This paper presents the finite element studies on free vibration of isotropic and laminated composite cylindrical skew panels. The analysis is performed using CQUAD4 and CQUAD8 elements of MSC/NASTRAN. The effects of the panel angle, skew angle, aspect ratio and length-to-thickness-ratio on fundamental frequency of isotropic cylindrical skew panels are studied. The effects of additional parameters such as the fiber orientation angle, numbers of layers and stacking sequence on the fundamental frequency of antisymmetric composite laminates are also studied. It is found that the CQUAD8 element yields better results than the CQUAD4 element in the validation and convergence studies. The CQUAD8 element is employed for the remaining part of the studies. The fundamental frequencies are found to increase with the panel angle and skew angle. When the number of layers in the laminate is large, the variation of the fundamental frequency with the number of layers is not appreciable. The boundary conditions are found to have a significant influence on the fundamental frequency.

9

Computation of ground motion amplification in Kolkata megacity (India) using finite-difference method for seismic microzonation

Shiuly A, Kumar V, Narayan J.P.

Acta Geophysica

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2014

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Vol. 62, no. 3

425--450

EN

This paper presents the ground motion amplification scenario along with fundamental frequency (F0) of sedimentary deposit for the seismic microzonation of Kolkata City, situated on the world’s largest delta island with very soft soil deposit. A 4th order accurate SH-wave viscoelastic finite-difference algorithm is used for computation of response of 1D model for each borehole location. Different maps, such as for F0, amplification at F0, average spectral amplification (ASA) in the different frequency bandwidth of earthquake engineering interest are developed for a variety of end-users communities. The obtained ASA of the order of 3-6 at most of the borehole locations in a frequency range of 0.2510.0 Hz reveals that Kolkata City may suffer severe damage even during a moderate earthquake. Further, unexpected severe damage to collapse of multi-storey buildings may occur in localities near Hoogly River and Salt Lake area due to double resonance effects during distant large earthquakes.

10

Estimation of the Fundamental Frequency of the Speech Signal Compressed by MP3 Algorithm

Milivojević Z. N., Brodić D.

Archives of Acoustics

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2013

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Vol. 38, No. 3

363--373

EN

The paper analyzes the estimation of the fundamental frequency from the real speech signal which is obtained by recording the speaker in the real acoustic environment modeled by the MP3 method. The estimation was performed by the Picking-Peaks algorithm with implemented parametric cubic convolution (PCC) interpolation. The efficiency of PCC was tested for Catmull-Rom, Greville, and Greville two- parametric kernel. Depending on MSE, a window that gives optimal results was chosen.

11

Perceptually Correlated Parameters of Musical Instrument Tones

Beauchamp J. W.

Archives of Acoustics

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2011

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Vol. 36, No. 2

225-238

EN

In Western music culture instruments have been developed according to unique instrument acoustical features based on types of excitation, resonance, and radiation. These include the woodwind, brass, bowed and plucked string, and percussion families of instruments. On the other hand, instrument performance depends on musical training, and music listening depends on perception of instrument output. Since musical signals are easier to understand in the frequency domain than the time domain, much effort has been made to perform spectral analysis and extract salient parameters, such as spectral centroids, in order to create simplified synthesis models for musical instrument sound synthesis. Moreover, perceptual tests have been made to determine the relative importance of various parameters, such as spectral centroid variation, spectral incoherence, and spectral irregularity. It turns out that the importance of particular parameters depends on both their strengths within musical sounds as well as the robustness of their effect on perception. Methods that the author and his colleagues have used to explore timbre perception are: 1) discrimination of parameter reduction or elimination; 2) dissimilarity judgments together with multidimensional scaling; 3) informal listening to sound morphing examples. This paper discusses ramifications of this work for sound synthesis and timbre transposition.

12

Diagnostic significance of phase spectrum in acoustic analysis of pathological voice

Samborska-Owczarek A.

Pomiary Automatyka Kontrola

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2010

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R. 56, nr 12

1547-1550

EN

The paper regards the possibility of using new numerical features extracted from the phase spectrum of a speech signal for voice quality estimation in acoustic analysis for medical purposes. This novel approach does not require detection or estimation of the fundamental frequency and works on all types of speech signal: euphonic, dysphonic and aphonic as well. The experiment results presented in the paper are very promising: the developed F0-independant voice features are strongly correlated with two voice quality indicators: grade of hoarseness G (r>0.8) and roughness R (r>0.75) from GIRBAS scale, and exceed the standard voice parameters: jitter and shimmer.

PL

Artykuł dotyczy możliwości ekstrakcji cech numerycznych z widma fazowego sygnału mowy w celu wykorzystania w analizie akustycznej na potrzeby medyczne. Podejście to umożliwia uzależnienie analizy akustycznej od zawodnych metod wykrywania/wyznaczania częstotliwości podstawowej (tonu krtaniowego) i dzięki temu przeznaczone jest do badania wszystkich typów sygnału mowy (również afonicznych). Wyniki eksperymentu są bardzo obiecujące - proponowane cechy Ph1 i Ph2 są silnie skorelowane z dwoma kategoriami percepcyjnymi: stopniem chrypki (r>0.8) oraz szorstkością głosu (r>0.75) ze skali GIRBAS, wykazując silniejsze znaczenie diagnostyczne niż znane i stosowane od dawna wskaźniki jitter i shimmer. Proponowane podejście oprócz skuteczności charakteryzuje się szeregiem dodatkowych korzyści: algorytm metody z powodu niskiej złożoności jest szybki i niekosztowny, interpretacja matematyczna jest prosta i jednoznaczna oraz spójna z obserwowanym obrazem widma fazowego głosu. Ponadto uniezależnienie od detekcji częstotliwości podstawowej sprawia, że algorytm jest deterministyczny oraz efektywny dla każdego typu sygnału mowy.

13

Hydrodynamic resonation through-flow system as acoustic circuit

Kusnerova M., Valicek J., Hloch S., Sadilek M., Cep R.

Archiwum Technologii Maszyn i Automatyzacji

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2008

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Vol. 28, nr 4

43-52

EN

The paper proposes a derivation of general characteristic acoustic parameters of the hydrodynamic resonation system elements. The acoustic parameters of the system are the acoustic compliance and acoustic mass as primary parameters for calculation of the theoretical resonation fundamental frequency for turbulent water-flow. Frequency model (5 kHz to 25 kHz) refers to the interpolation for the liquid pressure range from 5 MPa to 25 MPa. The analysis travels in a direction of a value comparison of concrete acoustic characteristic parameters for any element of the system and has been contrasted with theoretical conditions about an acoustic mass for tubes and an acoustic compliance for chambers. This system generates a modulate liquid jet as a result of resonation chamber implantation. The theoretical model was built on the basis of knowledge of primarily geometric dimensions of the system and the pressures of the liquid to predict values of fundamental frequencies of oscillations. Predicted oscillation frequencies were verified by laboratory measurements.

PL

W artykule zaproponowano ogólną charakterystykę parametrów akustycznych hydrodynamicznego systemu rezonansowego. Podstawowymi parametrami akustycznymi systemu, wykorzystywanymi do obliczeń podstawowej częstotliwości teoretycznego rezonansu przepływu turbu-lentnego wody, są odkształcalność akustyczna i masa akustyczna. Model częstotliwościowy (od 5 kHz do 25 kHz) dotyczy interpolacji dla ciśnienia płynu od 5 MPa do 25 MPa. Analiza zmierza w kierunku porównania wartości konkretnych parametrów charakterystyk akustycznych każdego elementu systemu i została zestawiona z warunkami teoretycznymi dotyczącymi masy akustycznej rur i akustycznej odkształcalności komór. System ten tworzy modulowany strumień płynu jako wynik zastosowania rezonansu komory. Model teoretyczny był zbudowany na podstawie wiedzy o pierwotnych wymiarach geometrycznych systemu i ciśnień płynu po to, aby przewidzieć wartości podstawowych częstotliwości drgań. Przewidywane częstotliwości drgań były sprawdzane przez pomiary laboratoryjne.

14

Feature space reduction and classification in automatic voice quality estimation

Samborska A.

Image Processing & Communications

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2005

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Vol. 10, no 2

93-102

EN

The paper presents an approach to solve a problem of feature space reduction applied to a voice quality estimation system. In order to reduce symptom space dimensionality, a method based on of decision tree and Fisher Linear Discriminant has been introduced. On the basis of 3 discrimination tests, the patient's voice is being classified into one of 3 groups - healthy, ill or risk, obtaining 90% of correct results. The experiment involved voice recordings of 70 patients who were diagnosed by the specialist. The method has been applied to a system of automatic voice quality estimation - the SpeechAnalyser, which was designed to be a supportive tool in laryngologica. l screening tests and treatment progress monitoring. There have been also briefly introduced the algorithms of feature extraction from a voice sample and also diagnostic significance of the symptoms has been discussed. Author proposed a new approach to cepstral analysis that allows objective measuring of harmonic and subharmonic content is spectrum.