Journal articles: 'Compressive non-linearity'

1

Hammett, Stephen T., Mark A. Georgeson, Samantha Bedingham, and Gillian S. Barbieri-Hesse. "Motion sharpening and contrast: Gain control precedes compressive non-linearity?" Vision Research 43, no. 10 (May 2003): 1187–99. http://dx.doi.org/10.1016/s0042-6989(03)00071-3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Sun, C. T., and A. Wanki Jun. "Compressive strength of unidirectional fiber composites with matrix non-linearity." Composites Science and Technology 52, no. 4 (January 1994): 577–87. http://dx.doi.org/10.1016/0266-3538(94)90041-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Varma, R. Ramgopal, and G. Venkateswazra Rao. "Combined Effects of Geometric and Material Non—linearities on One Dimensional Structural Members." International Journal of Engineering Technology and Sciences 1, no. 1 (December 26, 2018): 5–8. http://dx.doi.org/10.15282/ijets.v1i1.1106.

Full text

Abstract:

Combined effects of geometric and material non-linearities on a uniform column subjected to an axial compressive load are presented in the present note. A simple, direct iterative numerical method has been proposed to study the geometric and material non-linear behavior of columns subjected to varying boundary conditions. Introduction of material non-linearity in the large deﬂection analysis of columns subjected to an axial compressive load reveals a reduction in Euler stress obtained when compared to the effect of geometric non-linear analysis and increase in the same when compared to the eﬂect of material non-linear analysis. A convergence study has been carried outfor the results obtained from the proposed iterative method to prove the efficacy.

APA, Harvard, Vancouver, ISO, and other styles

4

Korinets, A., and H. Alehossein. "Technical Note On the Initial Non-Linearity of Compressive Stress-Strain Curves for Intact Rock." Rock Mechanics and Rock Engineering 35, no. 4 (October 1, 2002): 319–28. http://dx.doi.org/10.1007/s00603-002-0030-4.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Sakaida, Yoshihisa, Keisuke Tanaka, and Shintaro Harada. "Measurement of Residual Stress Distribution of Ground Silicon Nitride by Glancing Incidence X-ray Diffraction Technique." Advances in X-ray Analysis 39 (1995): 331–38. http://dx.doi.org/10.1154/s0376030800022746.

Full text

Abstract:

A new method of X-ray stress measurement was proposed to estimate non-destructively the steep residual stress distribution in the surface layer of ground Si3N4. We assumed an exponential decrement of the residual stress near the ground surface, and derived a formula for the lattice strain as a function of sin2Ψ. In the experiments, the diffraction angles were measured on the ground surface for a widest possible range of sin2ѱ using an Ω-goniometer. In order to measure the diffraction angle at very high sin η values, a scintillation counter was located on the -η side and an incident X-ray beam impinged on the ground surface with a very low angle from the +η side using the glancing incidence X-ray diffraction technique. A strong non-linearity was found in the 20-sin2ѱ diagrams especially at very high ѱ -angles. From the analysis of non-linearity, the stress distribution in the surface layer was determined. Tine residual stress took the maximum compression of 2 GPa at a depth of about 0.5 μm from the surface, and then diminished to zero at about 25 μm in depth. In the close vicinity of the ground surface, the compressive residual stress was relieved because of both the surface roughness and microcracking induced during the grinding process.

APA, Harvard, Vancouver, ISO, and other styles

6

Stine, Wm Wren, and Natalie Khutoryansky. "An Investigation of the Venetian Blind Effect." Seeing and Perceiving 24, no. 3 (2011): 241–92. http://dx.doi.org/10.1163/187847511x580366.

Full text

Abstract:

AbstractWhen a rectangular wave grating is binocularly viewed with a neutral density filter over one eye, an illusory rotation resembling that of a partially opened Venetian blind is perceived (Cibis and Haber, 1951). Using a binary classification task, in the first experiment, the probability of perceiving a rotation in a given direction was measured as a function of a factorial combination of inter-ocular contrast (see Note 1) and luminance ratios. The probability of a rotation in a given direction decreased monotonically with the luminance of the brighter bars when the grating contains a less than unity contrast. This result is inconsistent with (i) the model of the Venetian blind effect proposed by Cibis and Haber (1951), (ii) a mechanism based on irradiation with a compressive non-linearity (von Helmholtz, 1911/1924, pp. 186–193) and (iii) contemporary stereo-energy/cross-correlation models of stereopsis. In the second and third experiments, we tested the prediction that irradiation combined with an early compressive non-linearity in response implies a positive relationship between both the threshold contrast or average luminance disparity to perceive rotation and the magnitude of perceived rotation, and the blur width at the bar's edge. No support was found for the prediction. We propose an intensity difference model of the probability of perceiving a rotation in a given direction as a function of the interocular difference in luminance or contrast.

APA, Harvard, Vancouver, ISO, and other styles

7

Jindal, Sumit Kumar, Ritobrita De, Ajay Kumar, and Sanjeev Kumar Raghuwanshi. "Novel MEMS Piezoresistive Sensor with Hair-Pin Structure to Enhance Tensile and Compressive Sensitivity and Correct Non-Linearity." Journal of Electronic Testing 36, no. 4 (July 16, 2020): 509–17. http://dx.doi.org/10.1007/s10836-020-05895-0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Fagan, M. J., S. Julian, D. J. Siddall, and A. M. Mohsen. "Patient-specific spine models. Part 1: Finite element analysis of the lumbar intervertebral disc—a material sensitivity study." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 216, no. 5 (May 1, 2002): 299–314. http://dx.doi.org/10.1243/09544110260216577.

Full text

Abstract:

If patient-specific finite element models of the spine could be developed, they would offer enormous opportunities in the diagnosis and management of back problems. Several generic models have been developed in the past, but there has been very little detailed examination of the sensitivity of these models' characteristics to the input parameters. This relationship must be thoroughly understood if representative patient-specific models are to be realized and used with confidence. In particular, the performance of the intervertebral discs are central to any spine model and need detailed investigation first. A generic non-linear model of an intervertebral disc was developed and subjected to compressive, flexion and torsional loading regimes. The effects of both material and geometric non-linearities were investigated for the three loading schemes and the results compared with experimental data. The basic material properties of the fibres, annulus and nucleus were then varied and the effects on the stiffness, annulus bulge and annulus stresses analysed. The results showed that the non-linear geometry assumption had a significant effect on the compression characteristics, whereas the non-linear material option did not. In contrast, the material non-linearity was more important for the flexural and torsional loading schemes. Thus, the inclusion of non-linear material and geometry analysis options in finite element models of intervertebral discs is necessary to predict in vivo load-deflection characteristics accurately. When the influence of the material properties was examined in detail, it was found that the fibre properties did not have a significant effect on the compressive stiffness of the disc but did affect the flexural and torsional stiffnesses by up to ±20 per cent. All loading modes were sensitive to the annulus properties with stiffnesses varying by up to ±16 per cent. The model also revealed that for a particular compressive deformation or flexural or torsional rotation, the disc bulge was not sensitive to any of the material properties over the range of properties considered. The annulus stresses did differ significantly as the material properties were varied (up to 70 per cent under a compressive load and 60 per cent during disc flexion).

APA, Harvard, Vancouver, ISO, and other styles

9

Balevičius, Robertas, and Eugedijus Dulinskas. "ON THE PREDICTION OF NON‐LINEAR CREEP STRAINS." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 16, no. 3 (September 30, 2010): 382–86. http://dx.doi.org/10.3846/jcem.2010.43.

Full text

Abstract:

In the short term, the Euorocode‐based techniques will be implemented as the main design specifications for structural engineers from the member‐states of the European Union instead of the national standards. Therefore, it is of primary importance draw attention to the observed inaccuracies, particularly, in predicting non‐linear creep strains according to EC‐2. The analysis performed was mainly focused on an inconsistency elimination observed in the original EC‐2 approach, when transition from the linear to non‐linear creep laws for a constant compressive stress is required. A recent CEN corrigendum eliminating the observed inconsistency was also discussed in detail. In this context, similar techniques which were reported in the literature for predicting the creep non‐linearity function were analysed to account for the results obtained. It was particularly demonstrated that the recent CEN amendment results in an extremely enhanced creep strain for low strength concrete. A comparison of the creep non‐linearity functions with experimental test results was also considered. Santrauka Artimiausiu metu nacionalines normas pakeis Europos normos, kurios taps privalomu normatyviniu dokumentu Europos Sajungos šaliu statybos inžinieriams. Todel labai svarbu konstatuoti ir patikslinti jose pastebetus netikslumus. Straipsnyje akcentuojamas normu EC2 metodikoje pastebetas valkšnumo deformaciju nesutapimas, kai reikalingas perejimas iš tiesiniu valkšnumo deformaciju prie netiesiniu. Pateikiama žinomu metodu ir eksperimentiniu tyrimu rezultatu lyginamoji analize, autoriu siūlymai bei detaliai nagrinejamas neseniai išleistas CEN komiteto taisymas. Atlikus analize nustatyta, kad CEN korektūra lemia nepaprastai dideles mažo stiprumo betonu netiesinio valkšnumo deformacijas.

APA, Harvard, Vancouver, ISO, and other styles

10

Pastor-Artigues, Ma-Magdalena, Francesc Roure-Fernández, Xavier Ayneto-Gubert, Jordi Bonada-Bo, Elsa Pérez-Guindal, and Irene Buj-Corral. "Elastic Asymmetry of PLA Material in FDM-Printed Parts: Considerations Concerning Experimental Characterisation for Use in Numerical Simulations." Materials 13, no. 1 (December 18, 2019): 15. http://dx.doi.org/10.3390/ma13010015.

Full text

Abstract:

The objective of this research is to characterise the material poly lactic acid (PLA), printed by fused deposition modelling (FDM) technology, under three loading conditions—tension, compression and bending—in order to get data that will allow to simulate structural components. In the absence of specific standards for materials manufactured in FDM technology, characterisation is carried out based on ASTM International standards D638, D695 and D790, respectively. Samples manufactured with the same printing parameters have been built and tested; and the tensile, compressive and flexural properties have been determined. The influences of the cross-sectional shape and the specimen length on the strength and elastic modulus of compression are addressed. By analysing the mechanical properties obtained in this way, the conclusion is that they are different, are not coherent with each other, and do not reflect the bimodular nature (different behaviour of material in tension and compression) of this material. A finite element (FE) model is used to verify these differences, including geometric non-linearity, to realistically reproduce conditions during physical tests. The main conclusion is that the test methods currently used do not guarantee a coherent set of mechanical properties useful for numerical simulation, which highlights the need to define new characterisation methods better adapted to the behaviour of FDM-printed PLA.

APA, Harvard, Vancouver, ISO, and other styles

11

LACERDA, B. M., M. C. V. LIMA, F. A. R. GESUALDO, and V. C. CASTILHO. "Numerical and experimental analysis of the behavior of structural elements composed of double lattice panels filled with cast-in-place concrete." Revista IBRACON de Estruturas e Materiais 8, no. 4 (August 2015): 467–78. http://dx.doi.org/10.1590/s1983-41952015000400003.

Full text

Abstract:

AbstractAn experimental and numerical investigation was conducted into the factors that interfere in the shear strength of the concrete-concrete interface in structures composed of double lattice panels subjected to direct shear stress. The experimental program consisted of testing 26 direct shear models with varying widths of concrete filling of 7 cm, 9 cm and 13 cm, with smooth and rough interfaces, as well as different concrete compressive strengths in the filled region. The numerical modeling, which was performed with ANSYS software, employed solid finite elements, bar elements and contact elements, taking into account the non-linearity of the materials involved. The analyses of the experimental results under direct shear indicated that the transfer of stresses at the interface occurred with loss of adhesion. The numerical simulations indicated that the higher the geometric ratio of reinforcement the higher the direct shear strength of the structural model. In general, the slip of the models with smooth interfaces was 2 or 3 times greater than the models with rough surfaces. Numerically, the models with smooth interfaces showed a 36.61% gain in shear strength when the compressive strength in the region filled with concrete increased from 20 MPa to 28.4 MPa.

APA, Harvard, Vancouver, ISO, and other styles

12

Vishwanath, K. S. "FEA of Circular Embedded Delamination with Variations in Temperature in a Composite Laminate using VCCT." International Journal for Research in Applied Science and Engineering Technology 9, no. VI (June 30, 2021): 5058–61. http://dx.doi.org/10.22214/ijraset.2021.36122.

Full text

Abstract:

The FRP laminates are widely implemented in aviation industry due to its advantages and applications other materials in terms of strength to weight ratio, design features and many more. The strength of the interface compared to longitudinal and lateral directions of the plies are comparatively less and give rise too poor transverse direction strength. Hence a failure mechanism called delamination will occur in case when tools are dropped or due to poor manufacturing which would give rise to interface delamination. In this paper, VCCT is employed at the interface between base and sub laminate to investigate for a circular shape delamination geometry of 60mm buckling driven delamination growth with variations in temperature for -20C, room temperature, 523C, 773C and 1273C. The computational prediction of delamination growth initiation is obtained by solving a CFRP specimen for geometric non linearity using SC8R continuum shell elements of Abaqus CAE and by plotting the required energy release rate versus inplane strains and inplane loads versus compressive strains.

APA, Harvard, Vancouver, ISO, and other styles

13

Favier, Philomène, David Bertrand, Nicolas Eckert, Isabelle Ousset, and Mohamed Naaim. "Assessing fragility of a reinforced concrete element to snow avalanches using a non-linear dynamic mass-spring model." Natural Hazards and Earth System Sciences 18, no. 9 (September 19, 2018): 2507–24. http://dx.doi.org/10.5194/nhess-18-2507-2018.

Full text

Abstract:

Abstract. This paper presents an assessment of the fragility of a reinforced concrete (RC) element subjected to avalanche loads, and more generally to dynamic pressure fields applied orthogonally to a wall, within a reliability framework. In order to obtain accurate numerical results with supportable computation times, a light and efficient Single-Degree-of-Freedom (SDOF) model describing the mechanical response of the RC element is proposed. The model represents its dynamic mechanical response up to failure. Material non-linearity is taken into account by a moment–curvature approach, which describes the overall bending response. The SDOF model is validated under quasi-static and dynamic loading conditions by comparing its results to alternative approaches based on finite element analysis and the yield line theory. Following this, the deterministic SDOF model is embedded within a reliability framework to evaluate the failure probability as a function of the maximal avalanche pressure reached during the loading. Several reliability methods are implemented and compared, suggesting that non-parametric methods provide significant results at a moderate level of computational burden. The sensitivity to material properties, such as tensile and compressive strengths, steel reinforcement ratio, and wall geometry is investigated. The effect of the avalanche loading rate is also underlined and discussed. Finally, the obtained fragility curves are compared with respect to the few proposals available in the snow avalanche engineering field. This approach is systematic and will prove useful in refining formal and practical risk assessments. It could be applied to other similar natural hazards, which induce dynamic pressure fields onto the element at risk (e.g., mudflows, floods) and where potential inertial effects are expected and for which fragility curves are also lacking.

APA, Harvard, Vancouver, ISO, and other styles

14

Hunt, D. G. "Linearity and non-linearity in mechano-sorptive creep of softwood in compression and bending." Wood Science and Technology 23, no. 4 (1989): 323–33. http://dx.doi.org/10.1007/bf00353248.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Kurashige, M., H. Sawaguchi, and K. Imai. "Compression Tests of a Fluid-Filled Poroelastic Sample and Apparent Non-Linearity." Proceedings of the JSME annual meeting 2004.1 (2004): 45–46. http://dx.doi.org/10.1299/jsmemecjo.2004.1.0_45.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Huang, Shi Zhao, Yong Feng Liu, and Zhe Wei. "The Realization of Random Frequency Modulation Pulse Compression Signal Based on AD9858." Applied Mechanics and Materials 427-429 (September 2013): 2022–24. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.2022.

Full text

Abstract:

A scheme producing non-linearity frequency-modulated signal which can be updated on-line based on AD9858 is mentioned. A method to design NLFM signal using immediate data update is introduced. Circuit structure is designed. Major factor that impacting data is analyzed and its solution is presented. Experiments certify that this method can generate broadband and narrow pulse width non-linearity frequency-modulated signal, whose frequency spectrum can be updated on-line in real time.

APA, Harvard, Vancouver, ISO, and other styles

17

Ferrero, J. F., I. Tawk, S. Rivallant, J. J. Barrau, and M. Sudre. "Fibre Orientation Effects on High Strain Rate of Carbon/Epoxy Composites." Advanced Composites Letters 16, no. 1 (January 2007): 096369350701600. http://dx.doi.org/10.1177/096369350701600103.

Full text

Abstract:

Specific mechanical properties of composites make them particularly attractive. Dynamic loads are of prime interest for their applications. Laminated structures’ impact modelling implies prior material dynamic characterisation. This study suggests an analysis of split Hopkinson bar compression testing on T300/914 carbon/epoxy composite material. First, the effect of fibre orientation and stratification on compression dynamic behaviour is studied. Results show a high non-linearity for +/-45° laminates testing. This non-linearity is not observed when the laminates are reinforced with 0° and 90° plies. Analytical modelling is in agreement with the experimental results. Secondly, experiments are performed on pre-cracked specimens to show the influence of cracking on dynamic behaviour.

APA, Harvard, Vancouver, ISO, and other styles

18

Burrascano, Pietro, Giulia Di Capua, Nicola Femia, Stefano Laureti, and Marco Ricci. "A Pulse Compression procedure for power inductors modeling up to moderate non-linearity." Integration 66 (May 2019): 16–23. http://dx.doi.org/10.1016/j.vlsi.2019.01.010.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Rizov, Victor. "Delamination analysis of a layered elastic-plastic beam." International Journal of Structural Integrity 8, no. 5 (October 2, 2017): 516–29. http://dx.doi.org/10.1108/ijsi-11-2016-0035.

Full text

Abstract:

Purpose The purpose of this paper is to perform a theoretical analysis of delamination fracture behaviour of the Crack Lap Shear layered beam configuration taking into account the material non-linearity. A delamination crack located arbitrarily along the beam height was considered in this study. Design/methodology/approach The beam mechanical behaviour was described by using the Ramberg-Osgood stress-strain relation. Fracture was analysed by applying the J-integral approach. Besides by using symmetric Ramberg-Osgood stress-strain curve, fracture was investigated also by Ramberg-Osgood stress-strain curve that is not symmetric with respect to tension and compression. The J-integral solutions were verified by performing elastic-plastic analyses of the strain energy release rate. Findings The effects of crack location and material properties on the non-linear fracture behaviour were evaluated. It was found that the material non-linearity leads to increase of the J-integral values. Therefore, the material non-linearity has to be taken into account in fracture mechanics based safety design of structural members composed by layered materials. The analytical solutions derived are very useful for parametric investigations of delamination fracture with considering the material non-linearity. The results obtained can be applied for optimisation of the beam structure with respect to fracture performance. Originality/value The present study contributes for the understanding of delamination fracture in layered beams that exhibit non-linear material behaviour.

APA, Harvard, Vancouver, ISO, and other styles

20

Juozapaitis, Algirdas. "KOMBINUOTŲJŲ STOGO KONSTRUKCIJŲ LENKIAMOJO STRYPO RACIONALUS PROJEKTAVIMAS/RATIONAL DESIGN OF FLEXURAL ROD IN COMBINED ROOF STRUCTURES." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 2, no. 8 (December 31, 1996): 21–25. http://dx.doi.org/10.3846/13921525.1996.10590168.

Full text

Abstract:

The paper discusses a calculation of rational parameters of main flexural rod used in combined roof structures. Geometrical non-linearity can be discussed separately when the member is subjected either to tension or compression. It has been established that rational parameters for rods subjected to compression-bending or tension-bending have to be determined from the non-linear analysis calculation of the parameters using the slender- ness parameter, i.e. when kl ≤ 1. Also combined roof structures with a non-continuous main member are discussed. The rational parameters were calculated from the geometrically non-linear analysis. Numerical testing has shown that the non-continuous main members of the combined structures are more effective than the continuous ones.

APA, Harvard, Vancouver, ISO, and other styles

21

Baral, Biswajit, Sudhansu Mohan Biswal, Debashis De, and Angsuman Sarkar. "Radio frequency/analog and linearity performance of a junctionless double gate metal–oxide–semiconductor field-effect transistor." SIMULATION 93, no. 11 (April 20, 2017): 985–93. http://dx.doi.org/10.1177/0037549717704308.

Full text

Abstract:

The analog/radio frequency (RF) and linearity performance of a junctionless double gate metal–oxide–semiconductor field-effect transistor (JL DGMOS) is investigated using the numerical TCAD device simulator. JL DGMOSs have shown great promise for high-performance digital applications due to their superior short channel effect performance and ease of fabrication. In analog and RF circuit applications, linearity testing and RF performance is a major issue that is encountered due to non-linear behavior of the devices. Therefore, in this paper, different RF/analog and linearity performance figures of merits such as transconductance, intrinsic gain, the transconductance generation factor, the cut off frequency, the maximum frequency of oscillation, the gain bandwidth product, the variable intercept point of second order, the variable intercept point of third order, inter modulation distortion, the third-order intercept point, and 1-dB compression have been presented. Moreover, the effect of gate-length downscaling on these performance parameters has been carried out. The results indicate that the down scaled JL DGMOS shows great promise to become a competitive contender for analog/mixed signal system on chip applications by demonstrating a significant improvement in its RF performance with gate-length downscaling.

APA, Harvard, Vancouver, ISO, and other styles

22

Dambrosio, L., G. Pascazio, and B. Fortunato. "Fuzzy logic controller applied to a variable geometry turbine turbocharger." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 219, no. 11 (November 1, 2005): 1347–60. http://dx.doi.org/10.1243/095440705x35008.

Full text

Abstract:

This paper provides an adaptive technique for the control of a variable geometry turbine (VGT) in a turbocharged compression ignition engine. The adaptive control is based on a fuzzy logic control scheme and a least-squares parameter estimator algorithm. In order to test the performance of the proposed control technique, a numerical model of the engine has been used, which employs a thermodynamic (zero-dimensional) approach. The paper will show that the fuzzy logic control technique is able to take into account the non-linearity of the controlled system and to reject white noise affecting the measurement chain.

APA, Harvard, Vancouver, ISO, and other styles

23

Aminanda, Yulfian, Agus Geter Edy Sutjipto, Erry Yulian Triblas Adesta, and Bruno Castanie. "Simulation of Compression and Spring-Back Phenomena of Sandwich Structure with Honeycomb Core Subjected to Low Energy and Low Velocity Impact." Key Engineering Materials 462-463 (January 2011): 1296–301. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.1296.

Full text

Abstract:

The paper proposes first to study the behavior of honeycomb alone under uniform cyclic compression-relaxation loading. It is found that the behavior is linear until it reaches the maximum force following by a sudden drop of force and at the end following by a constant force during the compression. This force-displacement behavior is observed to be similar for all material of honeycomb such as; Nomex (with different densities and cell dimensions), fiber-glass and aluminum. From experimental study, the behavior becomes significantly non-linear in the area of constant force (flat zone) especially the spring-back behavior. A mathematical model is proposed to simulate completely compression-spring-back behavior of honeycomb. This mathematical model describes the behavior of honeycomb in compression and spring-back loading only in function of the maximum depth due to impact. The proposed mathematical model is then integrated to FEA model to simulate the spring-back behavior of sandwich structure with metallic skins and honeycomb core. After integrating the influence of skin-honeycomb interaction, a complete mathematical model which includes non-linearity of compression-spring-back behavior and rotation due to skin-honeycomb interaction is proposed to simulate the behavior of sandwich structure subjected to low energy/ low velocity impact (indentation) loading using spherical impactor. Some simulations of indentation and relaxation on sandwich structure with nomex honeycomb using different diameters of spherical indenter and different thickness of metallic skin are obtained with a good comparison with experimental results.

APA, Harvard, Vancouver, ISO, and other styles

24

Bayona Roa, Camilo Andrés, Joan Baiges, and R. Codina. "Variational multi-scale finite element approximation of the compressible Navier-Stokes equations." International Journal of Numerical Methods for Heat & Fluid Flow 26, no. 3/4 (May 3, 2016): 1240–71. http://dx.doi.org/10.1108/hff-11-2015-0483.

Full text

Abstract:

Purpose – The purpose of this paper is to apply the variational multi-scale framework to the finite element approximation of the compressible Navier-Stokes equations written in conservation form. Even though this formulation is relatively well known, some particular features that have been applied with great success in other flow problems are incorporated. Design/methodology/approach – The orthogonal subgrid scales, the non-linear tracking of these subscales, and their time evolution are applied. Moreover, a systematic way to design the matrix of algorithmic parameters from the perspective of a Fourier analysis is given, and the adjoint of the non-linear operator including the volumetric part of the convective term is defined. Because the subgrid stabilization method works in the streamline direction, an anisotropic shock capturing method that keeps the diffusion unaltered in the direction of the streamlines, but modifies the crosswind diffusion is implemented. The artificial shock capturing diffusivity is calculated by using the orthogonal projection onto the finite element space of the gradient of the solution, instead of the common residual definition. Temporal derivatives are integrated in an explicit fashion. Findings – Subsonic and supersonic numerical experiments show that including the orthogonal, dynamic, and the non-linear subscales improve the accuracy of the compressible formulation. The non-linearity introduced by the anisotropic shock capturing method has less effect in the convergence behavior to the steady state. Originality/value – A complete investigation of the stabilized formulation of the compressible problem is addressed.

APA, Harvard, Vancouver, ISO, and other styles

25

Chen, Cheng, and Zheng Ming Zhou. "A New Nonlinear Stress-Strain Model for Soils at Various Strain Levels." Advanced Materials Research 631-632 (January 2013): 782–88. http://dx.doi.org/10.4028/www.scientific.net/amr.631-632.782.

Full text

Abstract:

Soils have nonlinear stiffness and develops irrecoverable strains even at very small strain levels. Accurate modeling of stress-strain behaviour at various strain levels is very important for predicting the deformation of soils. Some existing stress-strain models are reviewed and evaluated firstly. And then a new simple non-linear stress-strain model is proposed. Four undetermined parameters involved in the proposed model can be obtained through maximum Young’s module, deformation module, and limit deviator stress and linearity index of soils that can be measured from experiment directly or calculated by empirical formulas indirectly. The effectiveness of the proposed stress-strain model is examined by predicting stress-strain curves measured in plane-strain compression test on Toyota sand and undrained triaxial compression test on London clay. The fitting results of the proposed model are in good agreement with experimental data, which verify the effectiveness of the model.

APA, Harvard, Vancouver, ISO, and other styles

26

Filanova, Yevgeniya, Johannes Hauptmann, Frank Längler, and Konstantin Naumenko. "Inelastic Behavior of Polyoxymethylene for Wide Strain Rate and Temperature Ranges: Constitutive Modeling and Identification." Materials 14, no. 13 (July 1, 2021): 3667. http://dx.doi.org/10.3390/ma14133667.

Full text

Abstract:

The aim of this paper is to present experimental data and the constitutive model for the inelastic behavior of polyoxymethylene in wide strain rate and temperature ranges. To capture the non-linearity of the stress responses for both loading and unloading regimes, the composite model of inelastic deformation is utilized and further developed. The equivalent inelastic strain rate is described by the Prandtl–Eyring law, while the temperature dependence is characterized by the modified Arrhenius-type law. Generalized equivalent stress and the flow rule are formulated to capture pressure sensitivity, transverse strain and volumetric strain responses. The results obtained by the constitutive law are compared with experimental data for stress vs. axial strain from standard tension tests as well as with axial and transverse strains measured by digital image correlation. The developed composite model is able to capture the non-linearity of stress–strain curves for complex loading paths within the small strain regime. For higher strains, apart from geometrically non-linear theory, evolution laws for the volume fraction of the constituents should be modified and calibrated. For the small strain regime, the inelastic dilatation is negligible. For higher axial strain values, a decrease in Poisson’s ratio under tension and increase in it under compression are observed. The Drucker–Prager-type equivalent stress and the developed flow rule provide a better description of both the transverse and volumetric strains than that of the classical von Mises–Odqvist flow rules.

APA, Harvard, Vancouver, ISO, and other styles

27

Lewis, D. D., S. Rigaud, G. B. Mackinzie, A. J. Rapoff, and A. R. Cross. "Effects of wire tension on the biomechanics of asymmetric four-ring circular external skeletal fixator constructs." Veterinary and Comparative Orthopaedics and Traumatology 15, no. 01 (2002): 44–50. http://dx.doi.org/10.1055/s-0038-1632712.

Full text

Abstract:

SummaryThis study evaluated the effects of fixation wire tension (0 kg, 30 kg, 60 kg, and 90 kg) on the biomechanics of a four ring asymmetric circular external fixator construct in four testing modes (axial compression, medio-lateral bending, craniocaudal bending, and torsional loading) using a gap fracture model. Wire tension had a significant direct effect on gap stiffness in all of the testing modes. Axial compression load-deformation curves exhibited non-linearity, characteristic of the self-tensioning effect observed with fine wire fixation. Bending loaddeformation curves had two discrete linear segments, attributable to slipping of the bone models on the fixation wires, once a critical bending moment was exceeded. Torsional loading caused a gradual ‘windup’ of the construct which was followed by a linear load-displacement curve. Increasing wire tension had a small but significant effect on gap stiffness, which generally diminished as higher tensions were applied, thus demonstrating the need for adequate initial construct design to achieve sufficient stability during fracture healing.

APA, Harvard, Vancouver, ISO, and other styles

28

Groen, S. S., D. Sinkeviciute, C. Thudium, P. Önnerfjord, M. Karsdal, A. C. Bay-Jensen, and S. Holm Nielsen. "THU0057 A NEO-EPITOPE FRAGMENT OF CARTILAGE DEGRADATION GENERATED FROM TYPE II COLLAGEN PROCESSING: A NOVEL SERUM BIOMARKER TO ACCESS TYPE II COLLAGEN DEGRADATION IN JOINT DEGENERATIVE DISEASES." Annals of the Rheumatic Diseases 79, Suppl 1 (June 2020): 240. http://dx.doi.org/10.1136/annrheumdis-2020-eular.5642.

Full text

Abstract:

Background:Altered extracellular matrix (ECM) remodelling is an important part of the pathology seen in joint degenerative diseases. Type II collagen is the most abundant ECM protein in the cartilage and provides the tissue with essential tensile strength in order to withstand high compressive loading. During cartilage erosion, type II collagen is cleaved by matrix metallopeptidases (MMPs) which generates new protein fragments called neo-epitopes. These fragments are released into circulation and may potentially serve as biomarkers by indicating the degree of cartilage destruction.Objectives:The aim of this study is to develop a highly specific immunoassay targeting a neo-epitope fragment of type II collagen cleaved, named T2CM. Moreover, we investigated the assays potential to evaluate type II collagen degradation in anex vivobovine full-depth cartilage explants model (BEX) with catabolic treatment and in healthy controls and osteoarthritis (OA) patients.Methods:A monoclonal antibody was raised in mouse against the C-terminus from protease cleavage site of type II collagen and a direct competitive ELISA was developed and technically validated. The assay specificity was evaluated for the standard peptide excluding cross-reactivity with elongated and truncated peptides, and a non-sense coating peptide. Human OA cartilage was cleaved with MMP-1, -2, -9 and -13 and measured with the T2CM-assay to investigate which MMPs generated the neo-epitope. T2CM levels were measured in supernatant from BEX explants cultured for 21 days in serum free DMEM/F12 medium with six different doses of OSM+TNF-α (O+T) treatment (20/10, 20/20, 20/40, 10/10, 10/20, 10/40 ng/mL) including a control group without (w/o) treatment. The supernatant was harvested 3 times weekly and replaced with new culture medium with O+T treatment. Biomarker results were confirmed by western blot, where T2CM was measured in supernatant from explants with O+T treatment 20/20 ng/mL and 20/40 ng/mL harvested on day 14 and day 21. To confirm the preclinical data, serum samples from 23 healthy controls (age range from 44-59 years with mean 51.4 ± SD 5.1, gender distribution was 56% female and 44% male, and 100% Caucasian) and 23 OA patients (age range from 41-77 years with mean 57.7 ± SD 13.7, gender distribution was 61% female and 39% male, and 100% Caucasian) were measured by T2CM.Results:A technically robust and T2CM-specific assay was developed. The assay linearity and spike-recovery were accepted with percentage of 99.69% and 93.15%. The assay showed no cross-reaction with the elongated, truncated or non-sense coating peptide. In addition, it was demonstrated that the T2CM neo-epitope was derived from MMP-1 and MMP-13 cleavage of type II collagen. O+T treatment induced the T2CM release in BEX compared to the untreated (Figure 1-2). Moreover, the western blot confirmed the T2CM results by the presence of two T2CM bands on day 21 from O+T treated explant compared to day 14 where no bands appeared. T2CM showed to be significantly elevated in patients with OA compared to controls (p=0.036; mean 3.262 ng/mL ± SD 1.065 vs 2.698 ng/mL ± SD 1.118).Conclusion:The newly developed assay was specific for the T2CM neo-epitope and was determined to be generated by MMP-1 and MMP-13. Additionally, the assay detected elevated levels of T2CM in supernatant from explants treated with O+T after 19 days of treatment compared to untreated. This was further confirmed in human OA patients, where the level of T2CM was elevated compared to healthy controls. This suggests that T2CM may have potential as biomarker for type II collagen degradation. Future preclinical and clinical studies are needed to validate these findings.Figure 1-2.T2CM measurements in BEX model. OSM + TNF-a (O+T) ng/mL.Disclosure of Interests:Solveig Skovlund Groen Employee of: Nordic Bioscience, Dovile Sinkeviciute Grant/research support from: Industrial PhD Student, Employee of: Industrial PhD Student, Christian Thudium Employee of: Employee at Nordic Bioscience A/S., Patrik Önnerfjord: None declared, Morten Karsdal Shareholder of: Nordic Bioscience A/S., Employee of: Full time employee at Nordic Bioscience A/S., Anne-Christine Bay-Jensen Shareholder of: Nordic Bioscience A/S, Employee of: Full time employee at Nordic Bioscience A/S., Signe Holm Nielsen Employee of: Full time employee at Nordic Bioscience

APA, Harvard, Vancouver, ISO, and other styles

29

Mitrofanov, O. V., and M. V. Klesareva. "Design of cylindrical composite panels with mild camber for biaxial compression taking into account geometrical non-linearity with uniform heating and rigid support." IOP Conference Series: Materials Science and Engineering 684 (November 25, 2019): 012019. http://dx.doi.org/10.1088/1757-899x/684/1/012019.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Vouvaris, Petros, and Dimitris Tasoudis. "B(l)ending time, (de)compressing identity: Creative thought and meaning construction in Copy Shop (2001)." Musicae Scientiae 22, no. 1 (February 21, 2018): 88–107. http://dx.doi.org/10.1177/1029864917719940.

Full text

Abstract:

According to the critics of Conceptual Blending Theory (CBT), most of its creativity-related applications tend to conflate the role of producer and consumer, implicitly proposing the deduction of the former’s creative perspective from the finished product through a process of reverse-engineering the latter’s meaning-making strategies. However, given the non-linearity and multi-directionality of the actual creative praxis, the relation between these two roles as heuristic categories need not be considered so much oppositional, as dialectical. Investigating the cognitive mechanisms involved in the ongoing creative process within the context of this dialectical relationship can help us gain some insight into both perspectives, while eschewing the elusiveness of their precise demarcation. The case study presented in this article constitutes such an attempt. By adopting a CBT approach, it offers an interpretation of the creative thinking behind the 2001 short film Copy Shop, informed by the documented insights of its creators. The article proposes a shift in primary focus from the mechanics of conceptual blending to its consequences in reference to the compression and decompression of vital relations and, more particularly, Time and Identity. On the one hand, it aims at examining how the particular ways of populating and interrelating the mental spaces that input to the blend at selected time points in the film occasion Time compressions and shape temporal experience. On the other hand, it concentrates on demonstrating how Copy Shop narrativizes the same processes of (de)compressing Identity that inform the conceptual blends it proposes.

APA, Harvard, Vancouver, ISO, and other styles

31

Siddique, Abrar, Tahesin Samira Delwar, Prangyadarsini Behera, Manas Ranjan Biswal, Amir Haider, and Jee-Youl Ryu. "Design and Analysis of a Novel 24 GHz Up-Conversion Mixer with Improved Derivative Super-Position Linearizer Technique for 5G Applications." Sensors 21, no. 18 (September 12, 2021): 6118. http://dx.doi.org/10.3390/s21186118.

Full text

Abstract:

A 24 GHz high linear, high-gain up-conversion mixer is realized for fifth-generation (5G) applications in the 65 nm CMOS process. The mixer’s linearity is increased by applying an Improved Derivative Super-Position (I-DS) technique cascaded between the mixer’s transconductance and switching stage. The high gain and stability of amplifiers in the transconductance stage of the mixer are achieved using novel tunable capacitive cross-coupled common source (TCC-CS) transistors. Using the I-DS, the third-order non-linear coefficient of current is closed to zero, enhancing the linearity. Additionally, a TCC-CS, which is realized by varactors, neutralizes the gate-to-drain parasitic capacitance (Cgd) of transistors in the transconductance stage of the mixer and contributes to the improvement of the gain and stability of the mixer. The measured 1 dB compression point OP1dB of the designed mixer is 4.1 dBm and IP1dB is 0.67 dBm at 24 GHz. The conversion gain of 4.1 dB at 24 GHz and 3.2 ± 0.9 dB, from 20 to 30 GHz is achieved in the designed mixer. Furthermore, a noise figure of 3.8 dB is noted at 24 GHz. The power consumption of the mixer is 4.9 mW at 1.2 V, while the chip area of the designed mixer is 0.4 mm2.

APA, Harvard, Vancouver, ISO, and other styles

32

Roy, Krishanu, Tina Chui Huon Ting, Lau Hieng Ho, Shashank Bhatnagar, and James B. P. Lim. "Finite Element Modeling of Back-to-Back Built-Up CFS Un-Lipped Channels under Axial Compression." Materials Science Forum 969 (August 2019): 819–27. http://dx.doi.org/10.4028/www.scientific.net/msf.969.819.

Full text

Abstract:

A finite element model is described in this paper, which investigates the behavior of CFS built-up un-lipped channel sections, connected back to back with the help of intermediate web fasteners, subjected to axial load. Finite element package ABAQUS was used to develop the model for built-up columns, which were validated against the test results reported by the authors recently on another paper. Material non-linearity and initial imperfections were included in the FEA model. A parametric study was conducted using the validated FEA model to investigate the effect of screw spacing on axial strength. Axial strengths obtained from the FEA model were compared against the AISI&AS/NZS design strengths; obtained comparisons showed that the AISI&AS/NZS standards were un-conservative for stub and short columns which failed by local buckling whereas the standards were over-conservative for columns failed through overall buckling.

APA, Harvard, Vancouver, ISO, and other styles

33

Li, Xiaoxiao, Paolo Colantonio, Franco Giannini, Hongxi Yu, and Chenchen Lin. "S-Band Class-C-F Power Amplifier with 2nd Harmonic Control at the Input." Applied Sciences 10, no. 1 (December 29, 2019): 259. http://dx.doi.org/10.3390/app10010259.

Full text

Abstract:

Power amplifiers (PAs) are the most power-consuming devices in a transmitter. Their performance in efficiency is crucial to the efficiency of the whole system. Therefore, the issue of high efficiency PA has remained hot over the years. This paper presents an approach to design an S-band single stage class-F PA biased in class-C condition. Through the manipulation of the 2nd harmonic at the input, shaping the voltage waveform at the gate node, a class-F PA with proper output matching network (OMN) is realized. The proposed class-C-F PA achieved 60% drain efficiency (DE) and 36.3 dBm of output power around the 3 dB compression point. The methodology of taking the input non-linearity into consideration is also presented. Its feasibility has been verified through both the design and measurements.

APA, Harvard, Vancouver, ISO, and other styles

34

Hernoune, Houria, Benchaa Benabed, Antonios Kanellopoulos, Alaa Hussein Al-Zuhairi, and Abdelhamid Guettala. "Experimental and Numerical Study of Behaviour of Reinforced Masonry Walls with NSM CFRP Strips Subjected to Combined Loads." Buildings 10, no. 6 (May 31, 2020): 103. http://dx.doi.org/10.3390/buildings10060103.

Full text

Abstract:

Near surface mounted (NSM) carbon fibers reinforced polymer (CFRP) reinforcement is one of the techniques for reinforcing masonry structures and is considered to provide significant advantages. This paper is composed of two parts. The first part presents the experimental study of brick masonry walls reinforced with NSM CFRP strips under combined shear-compression loads. Masonry walls have been tested under vertical compression, with different bed joint orientations 90° and 45° relative to the loading direction. Different reinforcement orientations were used including vertical, horizontal, and a combination of both sides of the wall. The second part of this paper comprises a numerical analysis of unreinforced brick masonry (URM) walls using the detailed micro-modelling approach (DMM) by means of ABAQUS software. In this analysis, the non-linearity behavior of brick and mortar was simulated using the concrete damaged plasticity (CDP) constitutive laws. The results proved that the application of the NSM-CFRP strips on the masonry wall influences significantly strength, ductility, and post-peak behavior, as well as changing the failure modes. The adopted DMM model provides a good interface to predict the post peak behavior and failure mode of unreinforced brick masonry walls.

APA, Harvard, Vancouver, ISO, and other styles

35

GILLIE, M., J. M. F. G. HOLST, M. MÜNCH, and J. M. ROTTER. "BEHAVIOUR OF SILOS SUPPORTED ON DISCRETE BRACKETS." International Journal of Structural Stability and Dynamics 02, no. 01 (March 2002): 45–62. http://dx.doi.org/10.1142/s0219455402000415.

Full text

Abstract:

The controlling design condition in thin metal silos is generally buckling under axial compression. This compression is often assumed to be uniform but in many practical cases several failure modes interact as a result of a rather more complex pattern of stresses. Small silos are often supported on several columns with local brackets attached to the sides of the shell. Failure occurs with an interaction between buckling and yielding under a stress regime involving a combination of membrane and bending stresses developed by the applied loads. This paper firstly reviews the literature relevant to bracket supported silos and exposes the limitations in the available design guidance. The results of a series of finite element analyses are then presented to describe the underlying structural behaviour. It is shown that material and geometric non-linearity both play an important role in the behaviour of discretely supported silos. It is also established that the degree of bracket eccentricity is an important factor in determining the mechanism of failure and the associated strength of the silo. Finally, comparison is made between the numerical results and existing design guidelines.

APA, Harvard, Vancouver, ISO, and other styles

36

Niemelä, Tanja, Markku Leppänen, Minna Päivinen, and Markku Mattila. "Evaluation of an Experimental Testing System for Non-Powered Hand Tools." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 44, no. 22 (July 2000): 643–46. http://dx.doi.org/10.1177/154193120004402239.

Full text

Abstract:

During the Eurohandtool Project an experimental testing system for non-powered hand tools was developed for laboratory testing. With this system, it is possible to measure simultaneously (1) the EMG activity of two muscles, (2) the opening angle of hand tool blades by means of a potentiometer and, (3) by means of strain gages, the force transmitted to the handle. The first part of evaluation of the system was to determine its time of warming-up, reliability, linearity and repeatability. This paper concentrates on the second part, during which the aim was to test the measurement system by comparing the forces needed to cut wood of a certain diameter, and the actual force required, as measured by a material-testing system. The correlation between forearm flexor muscle activity and the compression force created by the user was investigated. The evaluation of experimental testing system for non-powered hand tools has shown that there are methods to measure force demand, opening angle and EMG-activity simultaneously. However, it is recommended to make some improvements before this measurement system can be taken into widespread use.

APA, Harvard, Vancouver, ISO, and other styles

37

Chaudhuri, Reaz A. "Localization, delocalization and compression fracture in externally pressurized thick cross-ply (very) long cylindrical shells with material non-linearity: A multi-scale and multi-physics analysis." International Journal of Non-Linear Mechanics 84 (September 2016): 68–81. http://dx.doi.org/10.1016/j.ijnonlinmec.2016.02.004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Bhusal, Bikram, Satish Paudel, and Tek Bahadur Katuwal. "Investigation of Confinement Effects for Determining Moment Curvature and Interaction Diagram of Reinforced Concrete Column." Technical Journal 2, no. 1 (November 11, 2020): 81–88. http://dx.doi.org/10.3126/tj.v2i1.32844.

Full text

Abstract:

This paper presents the relevance of using various material models to represent the inherent material non-linearity of the cross-section in generating moment curvature relationship. Further, confinement effects are imposed on geometry and P-M diagram is constructed of typical cross-section of column adopted in Nepal. Also, the modelling capability and user defined modelling aspects in terms of section, material behavior is assessed and suitability of modelling criteria to depict the actual displacement capacity is studied. It was observed the ultimate curvature of the un-confined concrete section considered was obtained approximately to be 0.16 per m while for studied confined material models the curvature was obtained approximately to be 0.66 per m. This increase in curvature is due to the confinement effect of the lateral ties. It was observed that the loss of strength of concrete in cover is compensated by use of the confinement since gain in axial and bending capacity of the confined concrete in comparison to unconfined one in compression control region. Hence, it is suggested to adopt the confined material model as user-defined for generating hinge property for non-linear analysis of the structures.

APA, Harvard, Vancouver, ISO, and other styles

39

CARDOSO, M. T. S. A., and M. C. V. LIMA. "Physical and geometrical non-linear behavior of precast beams on elastomeric supports." Revista IBRACON de Estruturas e Materiais 11, no. 1 (February 2018): 183–202. http://dx.doi.org/10.1590/s1983-41952018000100010.

Full text

Abstract:

Abstract The stability of long and slender precast beams has been associated with structural collapse during the transitory phase of construction. The inevitable deviations regarding the execution between the support cross-section and midspan aggravate the instability problem, thus causing the beams to become even more susceptible to its effects. The focal point of this study is the numerical and behavioral evaluation of concrete beams that present geometric imperfections on elastomeric supports and analyze the influence exerted by the variables of: strength characteristics of concrete, physical non-linearity of the concrete and the compression stiffness of the bearing pad. The numerical analyses were developed on a computer program based on the finite element method (FEM). Among the principle conclusions drawn from the study, one finds that the increase in the characteristic strength of the concrete provides the beam with a higher degree of stability, and the consideration of the physical non-linear behavior of the material did not allow the equilibrium point on the numerical model to be found in some of the cases that were evaluated. The rotational stiffness of the pad decreases as the skew angle increases. Therefore, one needs to remember that in very critical situations, it may not be possible to find the point of equilibrium, thus leading to collapse.

APA, Harvard, Vancouver, ISO, and other styles

40

Ventini, Roberta, Alessandro Flora, Stefania Lirer, and Claudio Mancuso. "Magnetic measurement system of sandy gravel specimens shape during tests in a large triaxial apparatus." E3S Web of Conferences 92 (2019): 02004. http://dx.doi.org/10.1051/e3sconf/20199202004.

Full text

Abstract:

As well known, rockfill behaviour is strongly influenced by both intrinsic (mineralogy and size of particles, grain shapes, soil grading etc.) and state parameters (relative density, stress state, relative humidity). To investigate their mechanical response to stresses and relative humidity (RH) loadings, a large size triaxial device (H = 410 mm, D = 200 mm) has been developed at the University of Naples Federico II (Italy), including modifications required to impose partially saturated conditions in the specimen by means of the vapour equilibrium technique. In order to evaluate local axial and radial strains and global volumetric strains in partially saturated conditions, a magnetic shape detector device has been designed and installed. The accuracy of this system has been evaluated in some isotropic compression triaxial tests on compacted sandy-gravel specimens. The experimental data clearly show the effectiveness of the magnetic system in the measurement of axial displacements while the measurement in radial direction appear to be strongly affected by the non-linearity of the complex magnetic field generated during the test and requires further checking tests.

APA, Harvard, Vancouver, ISO, and other styles

41

Nishimura, Satoshi, Shota Okajima, Jinyuan Wang, and Bhakta Raj Joshi. "Small-strain deformation behaviour of a clay at frozen and unfrozen states: A comparative study." E3S Web of Conferences 92 (2019): 04001. http://dx.doi.org/10.1051/e3sconf/20199204001.

Full text

Abstract:

The small-strain deformation behaviour of frozen high-plasticity clay, and the factors influencing it were investigated through parallel tests at frozen and unfrozen states. The first and second series involved temperature-controlled triaxial compression tests on unfrozen and frozen samples, respectively, with accurate strain measurement with local displacement sensors, fully calibrated for cold environment. The small-strain loading was conducted at different axial strain rates and temperatures. At pre-yield small strains in order of 0.001%, Young's modulus was independent of the strain rate, in a same manner as in unfrozen soils. The strain rate only affected the onset of small-scale yielding and the degradation of stiffness after that. The elastic strain range was greater at lower temperature, but the degree of stress-strain non-linearity seen at small strains remained on the whole similar between frozen and unfrozen states. An interesting feature of the frozen clay's stiffness, also confirmed by third test series adopting bender elements, is that it decreases when the soil is frozen from higher effective stress. A simple model was proposed to explain this feature.

APA, Harvard, Vancouver, ISO, and other styles

42

Shen, Hui-Shen. "Post-buckling of internal-pressure-loaded laminated cylindrical shells surrounded by an elastic medium." Journal of Strain Analysis for Engineering Design 44, no. 6 (August 1, 2009): 439–58. http://dx.doi.org/10.1243/03093247jsa505.

Full text

Abstract:

This paper presents a study on the post-buckling response of an anisotropic laminated cylindrical shell of finite length embedded in a large outer elastic medium and subjected to internal pressure in thermal environments. The surrounding elastic medium is modelled as a tensionless Pasternak foundation reacting in compression only. The governing equations are based on higher-order shear deformation shell theory with von Kármán–Donnell kinematic non-linearity and including extension–twist, extension–flexural, and flexural–twist couplings. The thermal effects are also included, and the material properties are assumed to be temperature dependent. Non-linear prebuckling deformations and the initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the post-buckling response of the shells, and an iterative scheme is developed to obtain numerical results without using any assumption concerning the shape of the contact region between the shell and the elastic medium. Numerical illustrations concern the buckling and post-buckling response of cross-ply and symmetric angle-ply laminated shells surrounded by an elastic medium of tensionless foundation of the Pasternak type, from which results for conventional elastic foundations are obtained as comparators. The results reveal that unilateral constraints have a significant effect on the post-buckling response of shells subjected to internal pressure in thermal environments when the foundation stiffness is sufficiently large.

APA, Harvard, Vancouver, ISO, and other styles

43

Jivkov, A. P., M. Gunther, and K. P. Travis. "Site-bond modelling of porous quasi-brittle media." Mineralogical Magazine 76, no. 8 (December 2012): 2969–74. http://dx.doi.org/10.1180/minmag.2012.076.8.12.

Full text

Abstract:

AbstractGeological repository designs employ a multi-barrier approach. The materials, which include wasteforms, backfill and host rock, are typically porous quasi-brittle. Mechanical damage (e.g. nucleation and growth of microcracks) can result in significant changes in permeability. A knowledge of how the permeability is affected is critical to accurate modelling of radionuclide transport. This work proposes a novel 3D lattice-type model for the damage evolution in such materials, referred to as the site-bond model. Its advantages over previous models are that the shape of the lattice cell is physically realistic and that any macroscopic elastic response can be represented, including those of cementitious and geological materials. Damage accumulates as bonds fail upon reaching prescribed failure strengths. These are dictated by a predefined pore size distribution. Concrete is used as a study material. It is demonstrated that the model can predict the macroscopic stress–strain response under unconfined tension and compression with emergent non-linearity due to damage evolution. Ongoing work on the prediction of permeability changes with damage is discussed. This is based on the interaction between the model proposed here and a lattice model of the pore space.

APA, Harvard, Vancouver, ISO, and other styles

44

Gönüllü, Ü., P. Gürpınar, and M. Üner. "Double-layer Tablets of Lornoxicam: Validation of Quantification Method, In vitro Dissolution and Kinetic Modelling." Tropical Journal of Pharmaceutical Research 14, no. 9 (October 12, 2015): 1659–66. http://dx.doi.org/10.4314/tjpr.v14i9.16.

Full text

Abstract:

Purpose: To formulate double-layer tablets of lornoxicam (LRX) prepared by direct compression method and evaluate their physical and drug release characteristics.Methods: The outer layer of tablets, composed of microcrystalline cellulose (MCC), starch and lactose, incorporated tan initial or prompt dose of the drug (4 mg) for immediate release. Hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP K90) and carbomer, in varying concentrations, were used to prepare the tablet cores for sustained drug delivery. Weight variation, dimensions, hardness, tensile strength, friability and disintegration time of the tablets were evaluated. Drug release from double-layer tablets as well as kinetic models of drug release were determined after validating the method used for the quantification of the drug. The analytical method for quantification of LRX by UV spectroscopy was validated and verified for linearity, intra-day and inter-day precision, accuracy, recovery and specifity.Results: Tablet cores based on HPMC and HPMC:PVP K90 mixture displayed better compression and flow properties (good and fair to passable) than those formulated with PVP K90 and carbomer (poor). Satisfactory results were obtained from all the tablet formulations met compendial requirements. The slowest drug release rate was obtained with tablet cores based on PVP K90 (1.21 mg%.h-1). Drug release followed Higuchi kinetic model and the tablet cores released drug by diffusion/polymer relaxation or diffusion/erosion.Conclusion: Double-layer tablet formulation of lornoxicam based on HPMC or HPMC-PVP mixture is suitable for the treatment of inflammatory and painful conditions.Keywords: Lornoxicam, Controlled release, Double-layer tablets, Non-steroidal antiinflammatory drug, Oral delivery

APA, Harvard, Vancouver, ISO, and other styles

45

Bugaychuk, Svetlana, and Andrey Iljin. "Squeezing of laser pulses in nonlinear-optical LC cell." Photonics Letters of Poland 10, no. 4 (December 31, 2018): 112. http://dx.doi.org/10.4302/plp.v10i4.864.

Full text

Abstract:

Controllable compression of the temporal duration of light pulses takes place in a liquid crystal medium via self-action processes of beam mixing, namely, a dynamic Bragg grating formation by incoming light waves with their consequent self-diffraction on the same recorded grating. Wherein, the laser pulse duration should be comparable with the time relaxation constant of the medium while the extent of the temporal compression is controlled by the variation of the input pulse durations and the value of nonlocal response. Full Text: PDF ReferencesU. Bortolozzo, S. Residori and J. P. Huignard, "Beam coupling in photorefractive liquid crystal light valves", J. Phys. D: Appl. Phys. 41, 224007 (2008). CrossRef P. Guner and J.P. Huignard, Photorefractive Matrials and their Applications, 1, 2, and 3 (New York Springer) and references therein (2006). CrossRef S. Bugaychuk and E. Tobisch, "Single evolution equation in a light-matter pairing system", J. Phys. A: Math. Theor., 51 (12), 125201 (2018). CrossRef S. Bugaychuk and R. Conte, "Nonlinear amplification of coherent waves in media with soliton-type refractive index pattern", Phys. Rev. E 86, 026603 (2012). CrossRef A. Iljin, "Light-induced order modification – The way to speed up", Journal of Molecular Liquids 267, 38 (2018). CrossRef A. Iljin, "Transient Modulation of Order Parameter and Optical Non-Linearity in a Chiral Nematic Liquid Crystal", Mol. Cryst. Liq. Cryst. 543, 143 (2011). CrossRef D. Wei, A. Iljin, Z. Cai, S. Residori, and U. Bortolozzo, "Two-wave mixing in chiral dye-doped nematic liquid crystals", Opt. Lett. 37, 734 (2012). CrossRef S. Bugayhuk, A. Iljin, O. Lytvynenko, L. Tarakhan and L. Karachevtseva, Nanoscale Res. Lett., 12, 449 (2017). CrossRef

APA, Harvard, Vancouver, ISO, and other styles

46

Saucier, David, Tony Luczak, Phuoc Nguyen, Samaneh Davarzani, Preston Peranich, John E. Ball, Reuben F. Burch, et al. "Closing the Wearable Gap—Part II: Sensor Orientation and Placement for Foot and Ankle Joint Kinematic Measurements." Sensors 19, no. 16 (August 10, 2019): 3509. http://dx.doi.org/10.3390/s19163509.

Full text

Abstract:

The linearity of soft robotic sensors (SRS) was recently validated for movement angle assessment using a rigid body structure that accurately depicted critical movements of the foot–ankle complex. The purpose of this study was to continue the validation of SRS for joint angle movement capture on 10 participants (five male and five female) performing ankle movements in a non-weight bearing, high-seated, sitting position. The four basic ankle movements—plantar flexion (PF), dorsiflexion (DF), inversion (INV), and eversion (EVR)—were assessed individually in order to select good placement and orientation configurations (POCs) for four SRS positioned to capture each movement type. PF, INV, and EVR each had three POCs identified based on bony landmarks of the foot and ankle while the DF location was only tested for one POC. Each participant wore a specialized compression sock where the SRS could be consistently tested from all POCs for each participant. The movement data collected from each sensor was then compared against 3D motion capture data. R-squared and root-mean-squared error averages were used to assess relative and absolute measures of fit to motion capture output. Participant robustness, opposing movements, and gender were also used to identify good SRS POC placement for foot–ankle movement capture.

APA, Harvard, Vancouver, ISO, and other styles

47

Pasa, Gourishyam, Prasanta Kumar Choudhury, and Ghanshyam Panigrahi. "FORMULATION DESIGN AND OPTIMIZATION OF ORAL FLOATING MATRIX TABLETS OF CIPROFLOXACIN HCL BY USING HPMC AND XANTHAN GUM WITH EXPERIMENTAL DESIGN." Asian Journal of Pharmaceutical Research and Development 6, no. 6 (December 8, 2018): 23–35. http://dx.doi.org/10.22270/ajprd.v6i6.430.

Full text

Abstract:

The oral floating matrix tablets of Ciprofloxacin Hydrochloride were formulated by Experimental design by using HPMC K100M and Xanthan gum as the retardant polymers each with three different levels with an approach to increase gastric residence and thereby improve drug bioavailability. From FTIR results confirm the absence of chemical interaction between the drug with the excipients used in tablet formulations. Also, there was no shift in the endotherm of in the drug- excipients mixtures indicating compatibility of drug with all the excipients. All the tablets were prepared by effervescent approach in which Sodium bicarbonate was added as a gas generating agent. Floating Matrix tablets were prepared by direct compression method and prepared tablets were evaluated for weight variation, percentage friability, hardness and drug content studies. All the formulations showed compliance with pharmacopeia standards. Floating lag times of all the formulations were within 1 minute and Total floating time of all the formulations were more than 12 hours. In vitro release studies revealed that the release rate decreased with increase polymer proportion of retarding polymers. The formulation CHX8 sustained release of drug for 12 hrs with 20% release of drug after 1hr and more than 97% at the end of 12 hrs. From the Kinetic model it was found that the optimized formulation CHX8 showed linearity in case of Zero order (R2: 0.952) and Higuchi model (R2: 0.948). By fitting data to Korsmeyer-Peppas model and ‘n’ value lying above 0.5 indicating non Fickian release.

APA, Harvard, Vancouver, ISO, and other styles

48

Newlands, Shawn D., and Min Wei. "Tests of linearity in the responses of eye-movement-sensitive vestibular neurons to sinusoidal yaw rotation." Journal of Neurophysiology 109, no. 10 (May 15, 2013): 2571–84. http://dx.doi.org/10.1152/jn.00930.2012.

Full text

Abstract:

The rotational vestibulo-ocular reflex in primates is linear and stabilizes gaze in space over a large range of head movements. Best evidence suggests that position-vestibular-pause (PVP) and eye-head velocity (EHV) neurons in the vestibular nuclei are the primary mediators of vestibulo-ocular reflexes for rotational head movements, yet the linearity of these neurons has not been extensively tested. The current study was undertaken to understand how varying magnitudes of yaw rotation are coded in these neurons. Sixty-six PVP and 41 EHV neurons in the rostral vestibular nuclei of 7 awake rhesus macaques were recorded over a range of frequencies (0.1 to 2 Hz) and peak velocities (7.5 to 210°/s at 0.5 Hz). The sensitivity (gain) of the neurons decreased with increasing peak velocity of rotation for all PVP neurons and EHV neurons sensitive to ipsilateral rotation (type I). The sensitivity of contralateral rotation-sensitive (type II) EHV neurons did not significantly decrease with increasing peak velocity. These data show that, like non-eye-movement-related vestibular nuclear neurons that are believed to mediate nonlinear vestibular functions, PVP neurons involved in the linear vestibulo-ocular reflex also behave in a nonlinear fashion. Similar to other sensory nuclei, the magnitude of the vestibular stimulus is not linearly coded by the responses of vestibular neurons; rather, amplitude compression extends the dynamic range of PVP and type I EHV vestibular neurons.

APA, Harvard, Vancouver, ISO, and other styles

49

Bietresato, Marco, Francesco Selmo, Massimiliano Renzi, and Fabrizio Mazzetto. "Torque Prediction Model of a CI Engine for Agricultural Purposes Based on Exhaust Gas Temperatures and CFD-FVM Methodologies Validated with Experimental Tests." Applied Sciences 11, no. 9 (April 25, 2021): 3892. http://dx.doi.org/10.3390/app11093892.

Full text

Abstract:

A truly universal system to optimize consumptions, monitor operation and predict maintenance interventions for internal combustion engines must be independent of onboard systems, if present. One of the least invasive methods of detecting engine performance involves the measurement of the exhaust gas temperature (EGT), which can be related to the instant torque through thermodynamic relations. The practical implementation of such a system requires great care since its torque-predictive capabilities are strongly influenced by the position chosen for the temperature-detection point(s) along the exhaust line, specific for each engine, the type of installation for the thermocouples, and the thermal characteristics of the interposed materials. After performing some preliminary tests at the dynamometric brake on a compression-ignition engine for agricultural purposes equipped with three thermocouples at different points in the exhaust duct, a novel procedure was developed to: (1) tune a CFD-FVM-model of the exhaust pipe and determine many unknown thermodynamic parameters concerning the engine (including the real EGT at the exhaust valve outlet in some engine operative conditions), (2) use the CFD-FVM results to considerably increase the predictive capability of an indirect torque-detection strategy based on the EGT. The joint use of the CFD-FVM software, Response Surface Method, and specific optimization algorithms was fundamental to these aims and granted the experimenters a full mastery of systems’ non-linearity and a maximum relative error on the torque estimations of 2.9%.

APA, Harvard, Vancouver, ISO, and other styles

50

Cardillo, M., N. Marchili, G. Piano, A. Giuliani, M. Tavani, and S. Molinari. "The Orion Region: Evidence of enhanced cosmic-ray density in a stellar wind forward shock interaction with a high density shell." Astronomy & Astrophysics 622 (January 28, 2019): A57. http://dx.doi.org/10.1051/0004-6361/201833651.

Full text

Abstract:

Context. In recent years, an in-depth γ-ray analysis of the Orion region has been carried out by the AGILE and Fermi/LAT (Large Area Telescope) teams with the aim of estimating the H2–CO conversion factor, XCO. The comparison of the data from both satellites with models of diffuse γ-ray Galactic emission unveiled an excess at (l, b)=[213.9, −19.5], in a region at a short angular distance from the OB star κ-Ori. Possible explanations of this excess are scattering of the so-called “dark gas”, non-linearity in the H2–CO relation, or cosmic-ray (CR) energization at the κ-Ori wind shock. Aims. Concerning this last hypothesis, we want to verify whether cosmic-ray acceleration or re-acceleration could be triggered at the κ-Ori forward shock, which we suppose to be interacting with a star-forming shell detected in several wavebands and probably triggered by high energy particles. Methods. Starting from the AGILE spectrum of the detected γ-ray excess, showed here for the first time, we developed a valid physical model for cosmic-ray energization, taking into account re-acceleration, acceleration, energy losses, and secondary electron contribution. Results. Despite the characteristic low velocity of an OB star forward shock during its “snowplow” expansion phase, we find that the Orion γ-ray excess could be explained by re-acceleration of pre-existing cosmic rays in the interaction between the forward shock of κ-Ori and the CO-detected, star-forming shell swept-up by the star expansion. According to our calculations, a possible contribution from freshly accelerated particles is sub-dominant with respect the re-acceleration contribution. However, a simple adiabatic compression of the shell could also explain the detected γ-ray emission. Futher GeV and TeV observations of this region are highly recommended in order to correctly identify the real physical scenario.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Compressive non-linearity'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles