A Comparison of Matched-Field and Pseudo-Inverse Methods for Source Identification on a Frame Structure

1999 ◽  
Author(s):  
Matthew A. Craun ◽  
David Feit

Abstract The combined use of pseudo-inverse and matched-field processing methods is investigated for localizing and characterizing a broad-band random vibration source on a lightly-damped finite frame structure. The low-frequency range where global modes of the frame are dominant in the response is considered. Experimental results for two different sensor array geometries are compared. Also, the use of numerically-derived transfer functions is demonstrated for each of the processing methods. The results indicate that a combined use of matched-field and pseudo-inverse methods allows for a more complete characterization of the frame excitation than either method used exclusively.

2021 ◽  
pp. 107754632110337
Author(s):  
Arup Maji ◽  
Fernando Moreu ◽  
James Woodall ◽  
Maimuna Hossain

Multi-Input-Multi-Output vibration testing typically requires the determination of inputs to achieve desired response at multiple locations. First, the responses due to each input are quantified in terms of complex transfer functions in the frequency domain. In this study, two Inputs and five Responses were used leading to a 5 × 2 transfer function matrix. Inputs corresponding to the desired Responses are then computed by inversion of the rectangular matrix using Pseudo-Inverse techniques that involve least-squared solutions. It is important to understand and quantify the various sources of errors in this process toward improved implementation of Multi-Input-Multi-Output testing. In this article, tests on a cantilever beam with two actuators (input controlled smart shakers) were used as Inputs while acceleration Responses were measured at five locations including the two input locations. Variation among tests was quantified including its impact on transfer functions across the relevant frequency domain. Accuracy of linear superposition of the influence of two actuators was quantified to investigate the influence of relative phase information. Finally, the accuracy of the Multi-Input-Multi-Output inversion process was investigated while varying the number of Responses from 2 (square transfer function matrix) to 5 (full-rectangular transfer function matrix). Results were examined in the context of the resonances and anti-resonances of the system as well as the ability of the actuators to provide actuation energy across the domain. Improved understanding of the sources of uncertainty from this study can be used for more complex Multi-Input-Multi-Output experiments.


Author(s):  
Rajeev Vishwakarma ◽  
Dennis Turner ◽  
Andrew Lewis ◽  
Yongkang Chen ◽  
Yigeng Xu

2015 ◽  
Vol 58 (2) ◽  
Author(s):  
Ujjal K. Borah ◽  
Prasanta K. Patro ◽  
Vaddeboina Suresh

<p>Rolling array pattern broad band magnetotelluric (MT) data was acquired in the Koyna-Warna (Maharashtra, India) seismic zone during 2012-14 field campaigns. The main objective of this study is to identify the thickness of the Deccan trap in and around the Koyna-Warna seismic zone and to delineate the electrical nature of the sub-basalt. The MT data at many places got contaminated with high tension power line noise due to Koyna hydroelectric power project. So, in the present study an attempt has been made to tackle this problem due to 50 Hz noise and their harmonics and other cultural noise using commercially available processing software MAPROS. Remote site was running during the entire field period to stand against the cultural noise problem. This study is based on Fast Fourier Transform (FFT) and mainly focuses on the behaviour of different processing parameters, their interrelations and the influences of different processing methods concerning improvement of the S/N ratio of noisy data. Our study suggests that no single processing approach can give desirable transfer functions, however combination of different processing approaches may be adopted while processing culturally affected noisy data.</p>


Author(s):  
Yichi Zhang ◽  
Bingen Yang

Abstract Transient vibrations of flexible structures at mid- and high-frequencies have important applications in aerospace, civil, auto and ship engineering. In this paper, a new method is developed for the determination of the transient vibration solutions of two-dimensional beam frames in mid- and high-frequency regions. In the development, the governing equations of a beam frame structure are formulated by an augmented Distributed Transfer Function Method (DTFM), without the need for discretization and approximation. The augmented DTFM differs from the traditional DTFM in that it does not contain the singularities of subsystem transfer functions, which is crucially important in a mid- or high-frequency analysis. The proposed method delivers exact eigensolutions of a beam structure from low- to high-frequencies without numerical instability. With the platform provided by the augmented DTFM, the transient response of a beam structure can be conveniently estimated by either modal expansion or the residue formula for inverse Laplace transform. A highlight of the augmented DTFM lies in that detailed information at mid- and high-frequencies, such as local displacement, slope, bending moment and shear force at any point, can be obtained, which otherwise may be difficult with conventional methods for mid- and high-frequency analysis. The proposed method is illustrated on several examples and is computationally efficient and stable from low- to high-frequency regions. In the numerical simulation, the augmented DTFM is shown to produce more accurate results than traditional finite element analysis (FEA). The proposed method is extensible to three-dimensional beam structures.


2007 ◽  
Vol 190 (1-4) ◽  
pp. 73-91 ◽  
Author(s):  
S. Ghosh ◽  
B. Talukdar ◽  
P. Sarkar ◽  
U. Das

Author(s):  
Manuel Duarte Ortigueira ◽  
Duarte Vale´rio ◽  
Jose´ Sa´ da Costa

In this paper, the classic Levy identification method is reviewed and reformulated using a complex representation. This new formulation is able to solve the well known bias of the classic method at low frequencies. The formulation is generic, addressing both integer order and fractional order transfer functions. A new algorithm based on a stacked matrix and its pseudo-inverse is proposed to accommodate the data over a wide range of frequencies. Several simulation results are presented, together with a real system identification. This system is the Archimedes Wave Swing, a prototype of a device to convert the energy of sea waves into electricity.


2021 ◽  
Author(s):  
Joaquin Garcia-Suarez

The effect of ``velocity reversals'' (soft soil layers confined between stiffer ones) over 1D Site Response calculations has been studied for many years now, but a complete characterization of their influence is still pending. In a recent article titled \textit{Never Fear Velocity Reversals}, Yagoda-Biran, Kerpel and Kamai analyzed a set of three-layer systems with different properties. Their study was focused on numerical calculations leading to insights concerning the influence of the reversal over the fundamental resonant mode. The same systems are analyzed in this note, yet from a theoretical standpoint in this case, working directly with the analytical transfer functions. A new interpretation of their results is provided, along with a reasoning that evinces difficulties when it comes to extrapolating insights to more complex layerings.


Author(s):  
P.A. Probeigolova ◽  
E.V. Ostroukhova

В настоящей публикации представлены результаты аналитических и органолептических исследований ароматобразующего комплекса и профиля аромата красных столовых сухих вин, полученных из винограда разных сортов, произрастающего в Крыму, 2013-2017 годов урожая, в условиях микровиноделия при варьировании технологических приемов переработки и параметров сульфитации мезги. На основании статистической обработки (критерий Mann-Whitney) и обобщения экспериментальных данных установлены значимые (р 0,05) различия количественного содержания аро-матобразующих компонентов в винах, полученных по различным схемам, и определены технологические приемы, позволяющие получать вина с ароматом заданного направления. Показано, что брожение сульфитированной до 60-80 мг общего диоксида серы на 1 кг мезги до 1/3 остаточных сахаров от их исходного количества приводит к наименьшему накоплению терпеновых спиртов в винах: вина (при 80 мг общего SO2 на 1 кг мезги) характеризуются выраженным ягодно-фруктовым ароматом. Внесение в мезгу до брожения препарата конденсированного танина или увеличение дозы сульфитации мезги до 100 5 мг общего SO2 на 1 кг мезги, а также брожение сусла после настаивания мезги способствуют усилению цветочных оттенков в аромате вин, в том числе за счет увеличения концентрации терпеновых спиртов в винах в 1,6-1,9 раза. Внесение в мезгу до брожения ферментного препарата пектолитического действия и снижение дозы сульфитации мезги до 605 мг/кг приводит к усилению пряных оттенков. Совместное использование препаратов пектолитического действия и конденсированного танина приводит к формированию сложного аромата с яркими пряными и цветочными оттенками.The paper summarizes analytical and organoleptic data on the aroma-building complex and aroma profile of red table dry wines produced from different cultivars of Crimean grapevines of the 2013-2017 vintages under conditions of micro-vinification using various technological processing methods and must sulfitation param-eters. Based on statistically processed (Mann-Whitney test) and consolidated experimental data, the study established significant variations (p 0.05) in the quantitative content of the aroma-building components of wines produced by different processing schemes. Processing methods were determined that make it possible to obtain wines with pre-determined aroma. The study demonstrates that fermentation of must sulfited to 60-80 mg of total SO2 per 1 kg of must to 1/3 of residual sugars from the original amount decreases terpene alcohols accumulation in wines: wines (sulfited to 80 mg/kg) demonstrate pronounced berry-fruit aroma. Introduction of condensed tannin preparation into the must before fermentation or increasing must sulfitation dose to 1005 mg of total SO2 per 1 kg of after must maceration enhances flowery overtones in the wine aroma, which includes a 1.6-1.9 increase in the concentration of terpene alcohols in wines. Introduction of pectolytic enzyme preparation into the must before fermentation and decreasing must sulfitation to 605 mg/kg strengthens spicy overtones. The combined use of pectolytic enzyme preparation and condensed tannin produces complex aroma with pronounced spicy and flowery notes.


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