Degree Of Viscoelasticity Research Articles

Performance Evaluation of Multiple Aging-Regeneration of SBS-Modified Bitumen Regenerated by a Composite Rejuvenator

In this study, compound regeneration of SBS-modified bitumen (SMB) was carried out by a composite rejuvenator composed of furfural extraction oil (FEO) and 1,6-hexanediol diglycidyl ether (HDDGE) in the presence of catalyst triethanolamine (TEOA). SMB was subjected to three aging-regeneration cycles, and the physical and rheological properties, toughness and tenacity, and chemical structures of the SMB after each aging-regeneration cycle were tested to investigate the regeneration effect of the composite rejuvenator on SMB at different numbers of cycles. The ductility decreases and low-temperature properties deteriorate as the number of cycles increased, but the high-temperature properties of the SMB are improved. The complex modulus aging index and phase angle aging index indicate that the viscous behavior of SMB weakens after the second and third aging. The degree of viscoelasticity and toughness recovery decreases with the increase in the number of cycles, and the tenacity of SMB after the third aging-regeneration cycle is basically lost. The results of the Fourier transform infrared (FTIR) spectra tests prove that with the increase in the aging–regeneration cycles of SMB, the intensity of FTIR peaks of oxygen-containing functional groups is greater, and the recovery of aged SMB is gradually weakened.

Comparison of thermal, rheological properties of Finnish Pinus sp. and Brazilian Eucalyptus sp. black liquors and their impact on recovery units

Black liquor (BL) is the major bioproduct and biomass fuel in pulp mill processes. However, the high viscosity of BL makes it a challenging material to work with, resulting in issues with evaporators and heat exchangers during its transport and processing. The thermal and rheological properties of BLs from Pinus sp. (PBL) and Eucalyptus sp. (EBL) were studied. FTIR spectra revealed the presence of the characteristic functional groups and the chemical composition in liquors. TGA/DTG curves showed three characteristic degradation stages related to evaporation of water, pyrolysis of organic groups, and condensation of char. Rheologically, liquors are classified as non-Newtonian and with comportment pseudoplastic. Their rheological dynamic shear properties included a linear viscoelastic region up to 1% shear strain, while frequency sweeps showed that storage modulus (Gʹ) > loss modulus (Gʹʹ), thus confirming the solid-like behavior of both BLs. The rheological study demonstrated that increasing the temperature and oscillatory deformations of PBL and EBL decreased their degree of viscoelasticity, which could favor their pumping and handling within the pulp mill, as well as the droplet formation and swelling characteristics in the recovery furnace.

Enhancing heavy‐oil displacement efficiency through viscoelasticity of polymer solution by investigating the viscosity limit of crude oil: An experimental study

AbstractThe world is rich in ordinary heavy‐oil resources. Exploring the limit of the crude oil viscosity limits can further expand the application of polymer flooding technology in heavy‐oil reservoirs and improve the development efficiency of heavy‐oil reservoirs. On the basis of the polymer flooding that has been implemented in the Bohai offshore oilfield, this study characterized the in situ viscoelasticity of the polymer solution SNF3640C. We compared the polymer flooding and glycerol flooding performance in low‐viscous oil reservoirs (with a viscosity of 6.5 cp) and high‐viscous oil reservoirs (with a viscosity of 65 cp) by conducting microscopic dead‐end experiments and macroscopic core‐flooding experiments, and then analyzing the impact of polymer's viscoelasticity on the oil displacement efficiency of heavy oil. Finally, multiple crude oils with a wide range of viscosity were used to explore the crude oil viscosity limits under which the efficiency of heavy‐oil displacement could be improved through polymer viscoelasticity. The results demonstrate that: (1) the SNF3640C polymer solution can exhibit a certain degree of viscoelasticity in deep formation. At a distance of 140 m from the wellbore in the reservoir, a solution with a concentration of 1500 mg/L can still have a first normal stress difference of 2.5 Pa. Polymers can effectively improve the efficiency of heavy‐oil displacement through elastic action. (2) The viscosity limit that can improve the efficiency of heavy‐oil displacement under current experimental conditions does not exceed 5486 cp. The efficiency of polymer flooding for crude oil has decreased to 31.68%, and the contribution of elastic flooding is only 1.5%. The research method of using viscous glycerol as a comparison to demonstrate the contribution of polymer elasticity to oil displacement effectiveness effectively solves the problem of isolating the contribution by polymer solution's viscosity and elasticity, and clarifies the development direction of polymer flooding for developing heavy crude oil. Enhancing the elastic effect of polymer solution in porous media can increase the viscosity range of polymer flooding heavy oil.

The linear viscoelastic fracture theory applies to soft solids better when they are…viscoelastic

Over the last half-century, linear viscoelastic models for crack growth in soft solids have flourished but their predictions have rarely been compared to experiments. In fact, most available models are either very approximate or cast in forms which are not quite suitable for the analysis of actual data. Here, we propose a linear viscoelastic approach which consistently exploits the dynamic mechanical analysis data. We apply this method to four sets of results documenting fracture or adhesion rupture in soft solids with various degrees of viscoelasticity. For elastomers, the results reproduce the well-known inconsistency of the process zone size. In more viscoelastic systems, however, the present approach is able to match the measured velocity dependence of the rupture energy with physically acceptable process zone sizes. Moreover, our predictions agree with the damage zone sizes measured by mechanoluminescence. Building on these results, we discuss various issues arising when evaluating the linear viscoelastic contribution to the rupture/adhesion energy in soft solids: data quality, physical interpretation of the parameters, validity of simpler approximations and limitations of the present approach.

Non-Newtonian Flow with Heat and Mass Transfer Over a Porous Stretching Sheet Under the Effects of Space Dependent and TGD Heat Sink, Non-Uniform Heat Source and Dissipation of Energy and CGD Mass Diffusion with Suction/Blowing

In the present paper, an analytical study of visco - elastic fluid flow with heat and mass transfer characteristics over a porous stretching sheet has been examined. Heat balance is maintained with space dependent and temperature gradient dependent heat sink/source, viscous dissipation, and non-uniform heat source on the non-Newtonian Walter’s liquid B' model. The mass balance is maintained with chemically reactive species of order I, variable mass diffusivity and concentration gradient dependent mass diffusion. Using similarity transformation technique on the highly non-linear differential equations, several closed form analytical solutions are obtained for non-dimensional temperature and concentration in both PST and PHF cases in the form of confluent hypergeometric (Kummar’s) functions. The effect of permeability parameter, viscoelastic parameter, suction parameter on velocity profiles and various physical fluid situations with different degrees of viscoelasticity, Prandtl number, Eckert number, heat source- sink strength, temperature field are discussed in detail and presented through graphs. Similarly in the mass transfer field the effects of Schmidt number, reaction rate parameters are discussed in detail and presented through graphs.

Viscoelastic Behaviour of Flexible Thermoplastic Polyurethane Additively Manufactured Parts: Influence of Inner-Structure Design Factors.

Material extrusion based additive manufacturing is used to make three dimensional parts by means of layer-upon-layer deposition. There is a growing variety of polymers that can be processed with material extrusion. Thermoplastic polyurethanes allow manufacturing flexible parts that can be used in soft robotics, wearables and flexible electronics applications. Moreover, these flexible materials also present a certain degree of viscoelasticity. One of the main drawbacks of material extrusion is that decisions related to specific manufacturing configurations, such as the inner-structure design, shall affect the final mechanical behaviour of the flexible part. In this study, the influence of inner-structure design factors upon the viscoelastic relaxation modulus, E(t), of polyurethane parts is firstly analysed. The obtained results indicate that wall thickness has a higher influence upon E(t) than other inner-design factors. Moreover, an inadequate combination of those factors could reduce E(t) to a small fraction of that expected for an equivalent moulded part. Next, a viscoelastic material model is proposed and implemented using finite element modelling. This model is based on a generalized Maxwell model and contemplates the inner-structure design. The results show the viability of this approach to model the mechanical behaviour of parts manufactured with material extrusion additive manufacturing.

Mathematical modelling with experimental validation of viscoelastic properties in non-Newtonian fluids

The paper proposes a mathematical framework for the use of fractional-order impedance models to capture fluid mechanics properties in frequency-domain experimental datasets. An overview of non-Newtonian (NN) fluid classification is given as to motivate the use of fractional-order models as natural solutions to capture fluid dynamics. Four classes of fluids are tested: oil, sugar, detergent and liquid soap. Three nonlinear identification methods are used to fit the model: nonlinear least squares, genetic algorithms and particle swarm optimization. The model identification results obtained from experimental datasets suggest the proposed model is useful to characterize various degree of viscoelasticity in NN fluids. The advantage of the proposed model is that it is compact, while capturing the fluid properties and can be identified in real-time for further use in prediction or control applications.This article is part of the theme issue ‘Advanced materials modelling via fractional calculus: challenges and perspectives’.

Study on the Free Vibration of a Rubber Band Oscillator

Through theoretical analysis and experimental verification of the motion of a rubber band oscillator, this paper proves that the new model for describing the mechanical properties of rubber is effective. It is pointed out that there are both elasticforce related to deformation and viscoelastic force related to deformation process in rubber. Within a certain range of deformation, elastic force satisfies Hooke’s theorem, and viscoelastic force is proportional to fractional derivative of elongation with time. The mechanical properties of rubber materials can be described by static elastic modulus (elastic coefficient), viscoelastic degree and viscoelastic coefficient.

Mechanical characteristics of tunable uniaxial aligned carbon nanotubes induced by robotic extrusion technique for hydrogel nanocomposite

The utilisation of additive manufacturing technique for producing soft hydrogel nanocomposites could enable extraordinary advances in controlling of the material’s structure at microscale. A soft gel-printing based on 2-hydroxyethyl methacrylate (HEMA)-based gelation system with embedded uniaxial aligned carbon nanotubes (CNTs), was proposed in this paper. Shear-induced alignment determines the uniform orientation of CNTs during the gel-printing process, thereby introducing tunable mechanical anisotropy into the printed nanocomposite products. Herein, mechanical characterisation in terms of uniaxial tension, dynamic cyclic tension, and numerical simulations have been implemented on the printed samples. The numerical modelling findings, verified by the experimental observations, confidently confirm that the orientation of CNTs significantly impacts the mechanical properties of the nanocomposite, i.e. the ultimate strength, degree of viscoelasticity and strain-rate-sensitivity. Both the gel-printing technique and the anisotropic PHEMA-CNTs nanocomposite will ultimately assist to the rapid manufacture of diverse applications such as flexible electronics or tissue engineering.

Investigating the micro-rheology of the vitreous humor using an optically trapped local probe

We demonstrate that an optically trapped silica bead can be used as a local probe to measure the micro-rheology of the vitreous humor. The Brownian motion of the bead was observed using a fast camera and the micro-rheology determined by analysis of the time-dependent mean-square displacement of the bead. We observed regions of the vitreous that showed different degrees of viscoelasticity, along with the homogeneous and inhomogeneous nature of different regions. The motivation behind this study is to understand the vitreous structure, in particular changes due to aging, allowing more confident prediction of pharmaceutical drug behavior and delivery within the vitreous humor.

Investigation of guided surface acoustic wave sensors by analytical modeling and perturbation analysis

In this paper, shear horizontal polarized guided surface acoustic wave propagation was investigated with analytical modeling and perturbation analysis for biosensing applications. The model was also verified experimentally. The analytical model was developed for multilayer systems taking viscoelasticity into consideration. Detailed parametric investigation of dispersion curves was conducted using various substrate materials and guiding layers. The effects of frequency and degree of viscoelasticity were also studied. Perturbation equations were developed with first order approximations by relating the dispersion curve slopes to sensitivity. Among the guiding layers investigated, Parylene C showed the highest sensitivity followed by gold, chrome and silicon dioxide. The perturbation investigations were also extended to protein layers for immunosensing applications. It was observed that viscous behavior resulted in slightly higher sensitivity, and protein layers showed almost identical sensitivity similar to polymers investigated (SU-8, Parylene, etc.). The optimum configuration is found to be Parylene-C guiding layer on a ST-cut quartz substrate for protein layer sensing and this configuration has 40 times the sensitivity of gold guiding layer on quartz substrate. Our results indicate that chrome and silicon dioxide have low sensitivity when used as guiding layers. Also, lithium tantalate substrate with gold and Parylene-C guiding layers results in ∼10% lower sensitivity as compared to quartz substrate.

Correlation between the characteristics of acceleration and visco elasticity of artery wall under pulsatile flow conditions (physical meaning of I* as a parameter of progressive behaviors of atherosclerosis and arteriosclerosis)

Previously, I* parameter has been proposed to diagnose noninvasively the progressive degree of atherosclerosis which is considered to concern the discrimination of the progressive degree of visco elasticity of blood vessel wall. However, the detailed physical meaning of this parameter has not yet been clarified. In this paper, the theoretical analysis and experiments were conducted and the detailed physical meaning of I* parameter was clarified. The following results were obtained. I* parameter was found to well correlate with the progressive degree of visco elasticity of blood vessel wall characterized by the Ith* parameter derived based on the analysis of visco elasticity in this paper. That is, I* was found to have the physical meaning of representing the progressive degree of visco elasticity of blood vessel wall. On the basis of this results, using clinical data, two dimensional representation between the progressive degree of visco elasticity of blood vessel wall by I* and the decrease in the rigidity of blood vessel wall by PWV was found to be useful to conduct much more detailed diagnosis of atherosclerosis.

Evidence for alternative trapping strategies in two forms of the pitcher plant, Nepenthes rafflesiana.

Nepenthes pitchers are specialized leaves that function as insect traps. Several pitcher components may contribute to trapping, including the pitcher fluid, slippery wax crystals and downward-pointing epidermal cells on the inner pitcher wall, and the wetness-dependent pitcher rim (peristome), but the relative importance of these traits is unclear. Mechanisms of prey capture and retention in the field were investigated by quantifying the effect of ‘knock-out’ manipulations of individual pitcher structures, and by testing the ability of pitcher fluids and water to retain insects. Two forms of Nepenthes rafflesiana Jack (‘elongate’ and ‘typical’) with contrasting combinations of pitcher traits were compared. Wax crystals on the inner pitcher wall were found to be the most important trapping structure in the elongate form, whereas the typical form relied primarily on the peristome. The pitcher fluids of both forms, differing markedly in the degree of viscoelasticity, retained significantly more ants than water. The present results show that pitcher plants utilize several mechanisms for prey capture and retention, varying in efficiency and relative importance between forms. It is proposed that these differences represent alternative prey capture strategies that may provide a mechanism to reduce competition and facilitate species co-existence in nutrient-limited habitats.

Experimental study of atomization patterns produced by the oblique collision of two viscoelastic liquid jets

Experimental observations and analysis are presented for the formation and atomization of the fluid sheet created by obliquely colliding jets of viscoelastic fluids. Solutions of mono-disperse polystyrene (PS) in diethylphthalate and of poly-disperse polyethylene oxide (PEO) in glycerol/water mixtures were used to investigate the effects of fluid elasticity on the break-up patterns generated by the impact of two jets ejected from nozzles with an internal diameter of 0.85 mm. Various regimes of behaviour were identified which depend on the jet speed. The structures observed for these elastic fluids differ somewhat from those previously reported for Newtonian viscous fluids, and also show different behaviours depending on the degree of viscoelasticity. This study focuses on the periodic atomization, the so-called fishbone pattern, which occurs when the impinging jets form a liquid sheet which breaks up into a regular succession of ligaments and droplets. High-speed flash photography reveals that low concentrations of polymers significantly affect the evolution of the sheet and its fragmentation, the shapes of the ligaments, and the final drop sizes. The maximum fishbone angle is defined and shown to be a useful tool to describe the variation of the atomization pattern with polymer concentration. For the PS solutions the variation of maximum fishbone angle with reduced polymer concentration ( c/c * ) follows a single master curve, but although the same is true for PEO with high molecular weights, the curves remain separate for low molecular weights. Observation of the fishbone patterns formed by the oblique impact of jets may provide a useful tool to observe and characterize inter-chain interaction in high speed extensional flow of polymer solutions.

Rheology of Non-Newtonian Fluids Containing Glass Fibers: A Review of Experimental Literature

The objective of this review is to elucidate the rheological behavior of glass fiber suspensions whose suspending mediums are non-Newtonian fluids. In particular, this review focuses on determining the impact of fiber concentration, aspect ratio, orientation distribution, interaction with the suspending medium, and suspending medium viscoelasticity on the rheology of glass fiber composite fluids. The presence of glass fiber can induce a yieldlike behavior, causing shear thinning to occur at reduced shear rates. Glass fiber can impede the elastic properties of the suspending medium but enhance the first normal stress function. Large stress overshoots in both the shear and normal stress growth functions are observed that are associated with changes in fiber orientation. Upon cessation of flow, stress relaxation follows that of the suspending medium but fibers retain their orientation. The presence of glass fiber can induce extension rate thinning and suppress the strain thickening behavior of the suspending medium. 1. Introduction Glass fibers have been used for decades to improve the mechanical, thermal, and insulative properties of polymers. 1 These property improvements are highly dependent on the orientation distribution of the glass fiber. This makes it desirable to be able to predict not only the rheological behavior of the composite fluid but also the orientation of the fiber generated during processing. Understanding the rheological behavior of polymeric fluids containing glass fibers is essential to model development. With respect to the fiber, it is of interest to understand the role of concentration and aspect ratio and their relation to the degree of interparticle interaction (fiber -fiber) as well as orientation distribution and interaction with the suspending medium. With respect to the suspending medium, it is of interest to understand the role of viscoelasticity and how it is affected by the presence of the fibers. The rheological properties of glass fiber suspensions in Newtonian suspending mediums has been reviewed in detail by Ganani and Powell 2 and Zirnsak et al. 3 and will be referred to in this review for comparison purposes only. The primary focus of this review is to elucidate the rheological properties of glass fiber suspensions in non-Newtonian fluids of various degrees of viscoelasticity with an emphasis on composite fluids. Before reviewing the rheology, it is imperative to have a basic understanding of glass fiber suspensions, the rheometers used to characterize them, and any extra forces that can lead to mechanisms for changes in the fiber microstructure. For this reason, subsequently, we will briefly discuss the use of surface treatments to increase the interaction with the matrix. We then classify fiber suspensions by their concentration and length. This is followed by a review of the different rheometers and rheometer geometries used to characterize glass fiber suspensions, including a discussion of their strengths and weaknesses with respect to obtaining accurate measurements of rheological material functions. Last, we discuss and estimate the contribution of Brownian motion and gravity (relating to particle sedimentation) to changes in fiber orientation within the suspension. 1.1. Surface Modifications. The surface of a glass fiber is typically modified for two reasons: to minimize the selfdestructive abrasive contact between the fibers and to increase the fiber-matrix interaction of the melt and the adhesive strength of the composite. The use of “sizing” as a surface treatment has become an industrial standard and addresses both the abrasive contact and the surface interaction. Sizing is a functional coating that acts as an abrasive barrier that is tailored

Papain‐induced Gelation of Soy Glycinin (11S)

ABSTRACT: The gelation of soy peptides produced by the action of papain enzymes on soy glycinin (11S) dispersions (4.7% w/v) was investigated. Cation‐exchange chromatography was used to fractionate crude papain. The nonbinding fraction showed no gel‐forming activity on the 11S dispersion. Two binding fractions showed gel‐forming activity, and the gel strength of both 11S gels was similar. The activity of the crude papain on 11S dispersions produced a slightly stronger gel than one formed with either of the 2 binding fractions. With the crude papain, the rate of gel formation appeared to be strongly influenced by the enzyme concentration, but the maximum gel strength was independent of enzyme concentration. When the temperature was increased, the papain treatment of 11S soy protein produced weaker gels when the measurement was made at the temperature of formation. This dependence of maximum gel strength on temperature was found to be a function of only the measurement temperature and not the gel formation temperature. The degree of protein hydrolysis at maximum gel strength was similar (∼6%) for the gels formed at different temperatures. When the temperature was increased, the elastic modulus G′, the viscous modulus G″, and the degree of viscoelasticity (G″/G′) decreased. This suggested that the gels were formed the by hydrophobic interactions among the peptides. This observation was supported by particle size measurements on samples of gels which were mixed with reagents known for their ability to disrupt hydrophilic/electrostatic, hydrophobic, or disulfide interactions.

Nano-mechanical exploration of the surface and sub-surface of hydrated cells of Staphylococcus epidermidis

The surface of hydrated cells of Staphylococcus epidermidis has been probed using an atomic force microscope. While local force measurements over the surface of bacteria reveal a heterogeneous chemical surface, with heterogeneous mechanical properties, different kinds of force curves appear with high frequency, and are thought to provide information on features contributing strongly to the overall mechanical and surface behaviour of the cell. Force curves often present two different mechanical regimes, being the first one (outer) of about 48 nm thick, and presenting a local relative elasticity of about 0.08 N/m, which is about a third of the relative elasticity of the inner part of the cell wall, harder, with a relative elasticity of about 0.24 N/m, in water. Both regimes appears as straight lines in the force versus distance curves (the 'corresponding' stress-strain curves in contact mechanics), but hysteresis is observed between the approach and the retraction line in the inner regime, indicating a degree of viscoelasticity. No viscoelasticity is observed in the outer regime, however, which presents quite linear and juxtaposed approach-retraction lines. These kinds of force curves do not present measurable pull-off forces nor snap-in forces, which indicates an almost null interaction between tip and bacterial surface, which could be in agreement with the measured very high hydrophobicity of this strain. Another kind of force curve has been observed recurrently, showing peaks in the retraction curves. Adhesive pull-off forces were measured giving an average of about 2 nN. Interestingly, however, these force curves appear only when quite irregular and wavy retraction curves are present, from the very beginning of its trace (maximum indentation). This leads us to think that these pull-off forces measured by our AFM do not give information on surface forces-unbinding events at the surface of the bacteria, but could be related to events at the sub-surface of the cell surface. Oscillations seen in the retraction curve in the portion corresponding to the contact with the bacteria surface could be due to rupture phenomena within the multilayered cell wall architecture expected in Gram-positive bacteria as Staphylococcus epidermidis, which could result in local irreversible deformations of the cell surface. Imaging with a sharp tip in contact mode sometimes leads to surface damage. Force curves recorded over damaged parts of the cell surface showed a completely different behaviour, in many cases with two well-defined high-adhesion peaks, and also interestingly, with snap-in forces of about 0-2 nN, which seems to indicate a completely different electrical/hydrophobicity state only a few nanometers down from the surface. Similar indentation effects can occur in the contact of a bacterial cell with a solid surface, even when showing only atomic-molecular-scale roughness, thus interacting not only with the very surface of the cell, especially when soft layers are present in the outer. Our results highlight the importance of the cell surface mechanical properties and their interplay with purely surface properties when analyzing cell-material interaction, and show the AFM as a useful method for investigating this.

Visco-elastic MHD flow, heat and mass transfer over a porous stretching sheet with dissipation of energy and stress work

The present paper deals with the study of momentum, heat and mass transfer characteristics in a viso-elastic fluid flow over a porous sheet, where the flow is generated due to linear stretching of the sheet and influenced by a uniform magnetic field applied vertically and a continuous injection of the fluid through porous boundary. In the flow region, heat balance is maintained with a temperature dependent heat source/sink, viscous dissipation, dissipation due to elastic deformation and stress work produced as the result of magnetic field on the non-Newtonian fluid. In mass transfer analysis we have taken into account the loss of mass of the chemically reactive diffusive species by means of first order chemical conversion rate. Using suitable similarity transformations on the highly non-linear partial differential equations we derive several closed form analytical solutions for non-dimensional temperature, concentration, heat flux, mass flux profiles in the form of confluent hyper geometric (Kummer's) functions and some other elementary functions as its special form, for two different cases of the boundary conditions, namely, (i) wall with prescribed second order power law temperature (PST) and prescribed second order power law concentration (ii) wall with prescribed second order power law heat flux (PHF) and prescribed second order power law mass flux. The effect of the non-dimensional magnetic parameter on momentum, heat and mass transfer characteristics for non-isothermal boundary condition and different physical situations of the fluid, having various degrees of visco-elasticity, Prandtl number, heat source/sink strength and Schmidt number, are discussed in detail. Some of the several important findings reported in this paper are: (i) The combined effect of magnetic field, visco-elasticity and impermeability of the wall is to increase skin-friction largely at the wall; (ii) maximum enhancement of wall-temperature profile due to the application of transverse magnetic field occurs when the boundary heating is maintained with prescribed heat flux, boundary wall is porous and Prandtl number of the fluid is low; (iii) the effect of transverse uniform magnetic field is to increase concentration in the flow region, however, enhancement of concentration is higher when the stretching wall is porous and subjected to injection and (iv) the reduction of concentration due to chemical conversion is of significant order near the wall in PHF case when the wall is maintained with prescribed power low mass flux, in comparison with the PST case when the wall is maintained with prescribed power law surface concentration.

Theoretical Foundation on a Noninvasive Estimation for Viscoelastic Mechanical Property of Blood Vessels by Ultrasonic Doppler Effect

The method used in this paper is developed to estimate the degree of viscoelasticity of the blood vessel wall in a noninvasive mechanical method. In this proposed method, we can obtain an output waveform connected with mechanical behavior of blood vessels by using Ultrasonic Doppler Effect Sensory (UDES). Characterizing parameters on this waveform are established to estimate the mechanical properties of blood vessels. By analyzing the characteristics of these parameters, we attempt to estimate the viscoelastic property of blood vessels. Previously, it was found that these parameters are related to viscoelastic mechanical properties of materials. In this paper, we carried out computer analysis on the mechanical viscoelastic model and compared the theoretical behavior of blood vessels with the experimental output waveform by UDES. From these results, it was proved that values of these parameters connect with the change of the viscoelastic mechanical property of blood vessels. Therefore, the characterizing parameters of experimental output waveforms can be used to estimate the viscoelastic property of blood vessels in a noninvasive method.

Macroscopic Dynamic Equations for Nematic Liquid Crystalline Side-Chain Polymers

Abstract We present linear macroscopic dynamic equations for nematic liquid crystalline side-chain polymers. The visco-elastic degree of freedom of the polymeric backbone is taken into account by a strain field, which relaxes on a long but finite time scale. Besides the usual director field to describe the nematic ordering of the side-chains we also keep the nematic order parameter modulus as a variable, in order to describe the intrinsic connection of the polymeric and nematic aspects in nematic side-chain polymers. We discuss two experiments where our concept can be tested. PACS: 61.41. + e, 61.30.-v, 05.70.Ln