Identification of dynamic parameters of linear and non-linear structural models from experimental data

This paper reports on the study of microporous polydimethylsiloxane (PDMS) foams as a highly deformable dielectric material used in the composition of flexible capacitive pressure sensors dedicated to wearable use. A fabrication process allowing the porosity of the foams to be adjusted was proposed and the fabricated foams were characterized. Then, elementary capacitive pressure sensors (15 × 15 mm2 square shaped electrodes) were elaborated with fabricated foams (5 mm or 10 mm thick) and were electromechanically characterized. Since the sensor responses under load are strongly non-linear, a behavioral non-linear model (first order exponential) was proposed, adjusted to the experimental data, and used to objectively estimate the sensor performances in terms of sensitivity and measurement range. The main conclusions of this study are that the porosity of the PDMS foams can be adjusted through the sugar:PDMS volume ratio and the size of sugar crystals used to fabricate the foams. Additionally, the porosity of the foams significantly modified the sensor performances. Indeed, compared to bulk PDMS sensors of the same size, the sensitivity of porous PDMS sensors could be multiplied by a factor up to 100 (the sensitivity is 0.14 %.kPa−1 for a bulk PDMS sensor and up to 13.7 %.kPa−1 for a porous PDMS sensor of the same dimensions), while the measurement range was reduced from a factor of 2 to 3 (from 594 kPa for a bulk PDMS sensor down to between 255 and 177 kPa for a PDMS foam sensor of the same dimensions, according to the porosity). This study opens the way to the design and fabrication of wearable flexible pressure sensors with adjustable performances through the control of the porosity of the fabricated PDMS foams.

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Application of non-linear turbulence models in an engine-type flow configuration

International Journal of Engine Research ◽

10.1243/14680874jer00707 ◽

2007 ◽

Vol 8 (5) ◽

pp. 449-464 ◽

Cited By ~ 2

Author(s):

C. H. Son ◽

T. A. Shethaji ◽

C. J. Rutland ◽

H Barths ◽

A Lippert ◽

...

Keyword(s):

Experimental Data ◽

Renormalization Group ◽

Linear Models ◽

Combustion Engine ◽

Mean Flow ◽

Modest Improvement ◽

Non Linear ◽

Standard Linear ◽

Simple Flows ◽

Engine Type

Three non-linear k-ε models were implemented into the multi-dimensional computational fluid dynamics code GMTEC with the purpose of comparing them with existing linear k-ε models including renormalization group variations. The primary focus of the present study is to evaluate the potential of these non-linear models in engineering applications such as the internal combustion engine. The square duct flow and the backwards-facing step flow were two simple test cases chosen for which experimental data are available for comparison. Successful simulations for these cases were followed by simulations of an engine-type intake flow to evaluate the performance of the non-linear models in comparison with experimental data and the standard linear k-ε models as well as two renormalization group types. All the non-linear models are found to be an improvement over the standard linear model, but mostly in simple flows. For more complex flows, such as the engine-type case, only the cubic non-linear models appear to make a modest improvement in the mean flow but without any improvement in the root-mean-square values. These improvements are overshadowed by the stiffness of the cubic models and the requirements for smaller time steps. The contributions of each non-linear term to the Reynolds stress tensor are analysed in detail in order to identify the different characteristics of the different non-linear models for engine intake flows.

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Extracting real-crack properties from non-linear elastic behaviour of rocks: abundance of cracks with dominating normal compliance and rocks with negative Poisson ratios

Nonlinear Processes in Geophysics ◽

10.5194/npg-24-543-2017 ◽

2017 ◽

Vol 24 (3) ◽

pp. 543-551 ◽

Cited By ~ 9

Author(s):

Vladimir Y. Zaitsev ◽

Andrey V. Radostin ◽

Elena Pasternak ◽

Arcady Dyskin

Keyword(s):

Experimental Data ◽

Poisson Ratio ◽

A Priori ◽

Elastic Behaviour ◽

Crack Model ◽

Normal Compliance ◽

S Wave ◽

Linear Elastic ◽

Non Linear ◽

Linear Elastic Behaviour

Abstract. Results of examination of experimental data on non-linear elasticity of rocks using experimentally determined pressure dependences of P- and S-wave velocities from various literature sources are presented. Overall, over 90 rock samples are considered. Interpretation of the data is performed using an effective-medium description in which cracks are considered as compliant defects with explicitly introduced shear and normal compliances without specifying a particular crack model with an a priori given ratio of the compliances. Comparison with the experimental data indicated abundance (∼ 80 %) of cracks with the normal-to-shear compliance ratios that significantly exceed the values typical of conventionally used crack models (such as penny-shaped cuts or thin ellipsoidal cracks). Correspondingly, rocks with such cracks demonstrate a strongly decreased Poisson ratio including a significant (∼ 45 %) portion of rocks exhibiting negative Poisson ratios at lower pressures, for which the concentration of not yet closed cracks is maximal. The obtained results indicate the necessity for further development of crack models to account for the revealed numerous examples of cracks with strong domination of normal compliance. Discovering such a significant number of naturally auxetic rocks is in contrast to the conventional viewpoint that occurrence of a negative Poisson ratio is an exotic fact that is mostly discussed for artificial structures.

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CURVAS DE SECAGEM E AVALIAÇÃO DA ATIVIDADE DE ÁGUA DA BANANA PASSA

Boletim do Centro de Pesquisa de Processamento de Alimentos ◽

10.5380/cep.v22i1.1184 ◽

2004 ◽

Vol 22 (1) ◽

Cited By ~ 3

Author(s):

MILTON CANO-CHAUCA ◽

AFONSO M. RAMOS ◽

PAULO C. STRINGHETA ◽

JOSÉ ANTONIO MARQUES ◽

POLLYANNA IBRAHIM SILVA

Keyword(s):

Experimental Data ◽

Linear Regression ◽

Moisture Content ◽

Water Activity ◽

Linear Regression Analysis ◽

Sorption Isotherms ◽

Exponential Model ◽

Drying Time ◽

Non Linear ◽

Drying Curves

Curvas de secagem de banana passa foram determinadas, utilizando-se três temperaturas do ar de secagem. Os resultados indicaram que para reduzir o teor de umidade do produto até 23,5% foram necessários tempos de secagem de 51, 36 e 30 horas paras as temperaturas de 50, 60 e 70ºC, respectivamente. O modelo exponencial U/Uo = exp(-kt) foi ajustado para os dados experimentais mediante análise de regressão não-linear, encontrandose alto coeficiente de regressão linear. Determinou-se a atividade de água do produto ao longo do processo de secagem para as três temperaturas testadas. Estudou-se a correlação entre a atividade de água e o teor de umidade do produto, determinando-se as isotermas de dessorção da banana passa a 25ºC. Observou-se que a atividade de água diminuiu em função do tempo de secagem e do teor de umidade para as três temperaturas de secagem. Os dados experimentais foram ajustados mediante regressão não-linear ao modelo polinomial e a seguinte equação foi obtida: U = -1844,93 + 7293,53Aa 9515,52Aa2 + 4157,196Aa3. O ajuste mostrou-se satisfatório (R2 > 0,90). DRYING CURVES AND WATER ACTIVITY EVALUATION OF THE BANANA-PASSES Abstract Banana drying curves were determined by utilizing three drying air temperatures. The results indicated that to reduce the moisture content of the product until 23.5% it were necessary drying times of 51, 36 and 30 hours for temperatures of 50, 60 and 70ºC, respectively. The exponential model U/Uo = exp(-kt) was adjusted for the experimental data by means of non linear regression analysis, and a high coefficient of linear regression was found. The water activity of the product was determined throughout the drying process for the three tested temperatures. The correlation between the water activity and moisture content of the product was studied, and the sorption isotherms were determined at 25º C. It was observed that the water activity decreased in function to the drying time and moisture content for the three drying temperatures. The experimental data were adjusted by means of non linear regression to the polynomial model and the following equation was obtained: U = - 1844.93 + 7293.53A a 9515.52 Aa 2 + 4157.196A a 3. The final adjust was satisfactory (R2 > 0.90).

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Numerical Simulations as a Reliable Alternative for Landmine Explosion Studies: The AUTODYN Approach

Volume 9: Mechanics of Solids, Structures and Fluids ◽

10.1115/imece2010-40435 ◽

2010 ◽

Author(s):

Stephanie Follett ◽

Amer Hameed ◽

S. Darina ◽

John G. Hetherington

Keyword(s):

Experimental Data ◽

Numerical Simulations ◽

Reasonable Agreement ◽

Specific Impulse ◽

Numerical Procedure ◽

Ground Surface ◽

Time Of Arrival ◽

Linear Dynamics ◽

Non Linear

In order to validate the numerical procedure, the explosion of a mine was recreated within the non-linear dynamics software, AUTODYN. Two models were created and analysed for the purposes of this study — buried and flush HE charge in sand. The explosion parameters — time of arrival, maximum overpressure and specific impulse were recorded at two stand-off distances above the ground surface. These parameters are then compared with LS-DYNA models and published experimental data. The results, presented in table format, are in reasonable agreement.

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EXPLORATION OF INTERCALATED KAOLINITE CLAY FOR THE UPTAKE OF BASIC DYE BY ADSORPTION − EQUILIBRIUM, KINETICS AND THERMODYNAMIC STUDIES

Journal of Chemical Society of Nigeria ◽

10.46602/jcsn.v46i1.590 ◽

2021 ◽

Vol 46 (1) ◽

Author(s):

C. E. Chigbundu ◽

K. O. Adebowale

Keyword(s):

Experimental Data ◽

Linear Regression ◽

Goodness Of Fit ◽

Linear Regression Analysis ◽

Dye Adsorption ◽

Batch Adsorption ◽

Sem Images ◽

Kaolinite Clay ◽

Non Linear ◽

The Impact

Dyes are complex and sensitive organic chemicals which exposes microbial populations, aquatic lives and other living organisms to its toxic effects if their presence in water bodies or industrial effluents are not properly handled. This work therefore, comparatively studied the adsorption efficiencies of natural raw kaolinite (NRK) clay adsorbent and dimethyl sulphoxide (DMSO) faciley intercalated kaolinite clay (DIK) adsorbent for batch adsorption of Basis Red 2 (BR2) dye. The impact of varying the contact time, temperature and other operating variables on adsorption was also considered. The two adsorbents were characterized using SEM images, FTIR and XRD patterns. Linear and non-linear regression analysis of different isotherm and kinetic models were used to describe the appropriate fits to the experimental data. Error analysis equations were also used to measure the goodness-of-fit. Langmuir isotherm model best described the adsorption as being monolayer on homogenous surfaces while Kinetic studies showed that Elovich model provides the best fit to experimental data. The adsorption capacities of NRK and DIK adsorbents for the uptake of BR2 were 16.30 mg/g and 32.81 mg/g, respectively (linear regression) and 19.30 mg/g and 30.81 mg/g, respectively (non-linear regression). The thermodynamic parameter, ∆G showed that BR2 dye adsorption onto the adsorbents were spontaneous. DIK adsorbent was twice efficient compared with NRK for the uptake of BR2 dye.

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Research on Dynamic Alignment for Sophisticated System Based on ACP Technology

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.630.473 ◽

2012 ◽

Vol 630 ◽

pp. 473-478 ◽

Cited By ~ 2

Author(s):

Fei Wan ◽

Guo Xi Li ◽

Jing Zhong Gong ◽

Bao Zhong Wu

Keyword(s):

Experimental Data ◽

Dynamic Simulation ◽

Process Parameters ◽

Simulation Software ◽

Contact Theory ◽

Dynamic Parameters ◽

Agent Model ◽

The Status ◽

Alignment Process ◽

Dynamic Alignment

To change the status of time-consuming and over-reliance on technicians in mechanical system alignment process, the ACP technology is presented. The mapping between alignment process parameters and dynamic parameters was established through contact theory to build the agent model for parts. While the second mapping between dynamic parameters and machine dynamic characteristics is calculated by dynamic simulation software to conduct computational experiments. Experimental data is analyzed in order to implement data mine, optimize the alignment process, guide technician alignment, modify the theory mapping and improve the alignment efficiency.

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The predictability of the "Voyager" accident

Natural Hazards and Earth System Science ◽

10.5194/nhess-8-533-2008 ◽

2008 ◽

Vol 8 (3) ◽

pp. 533-537 ◽

Cited By ~ 3

Author(s):

L. Bertotti ◽

L. Cavaleri

Keyword(s):

Experimental Data ◽

Measured Data ◽

Balearic Islands ◽

Local Conditions ◽

Best Estimate ◽

Non Linear ◽

Local Wave ◽

Wave Heights ◽

Wave Conditions

Abstract. On 14 February 2005 a severe mistral storm caused substantial damage to the passenger cruiser "Voyager" between Balearic Islands and Sardinia. The storm had been well predicted. However, the ship was hit by one or more, apparently unexpected, large waves. Our aim was to understand if this was a freak event or it was within the expectable probability. At this aim we use our best estimate of the local wave conditions, obtained combining modelling and measured data. Starting from these we derive the probability of large waves, considering both linear and non-linear cases. Notwithstanding a correction towards the worse of the, otherwise inconsistent, available reports, on the basis of the data at disposal we conclude that, given the local conditions, the event was within the range of the potentially expectable wave heights. This turns out to be even more the case on the basis of recent results based on theoretical and experimental data.

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