Coefficient Ke Research Articles

Research on Interaction between Asphalt and Filler Based on DSR Test

To explain the interactive effect between asphalt and fillers in the asphalt mastic, it is probably to start with an assessment of the rheology properties, since asphalt mastics are viscoelastic materials. In this study, firstly prepare the asphalt mastics with different dosage of limestone filler, and the volume fractions of fillers were 0, 14, 24, 32, 39 and 45%. And then, the same asphalt is mixed with different fillers, such as cement and hydrated lime, and the volume fractions of fillers were 18, 23, 28and 33%. DSR test was conducted on all of the asphalt mastic specimens to measure the complex shear modulus G* at different temperature. The volume filling effects and interaction between asphalt and filler are discussed on the analysis of complex shear modulus coefficient and Nielsens model model. It is obviously that G* of asphalt mastics decrease with the test temperature, but increase with the volume fraction of filler. A function relation between complex shear modulus coefficient and volume fraction of fillers is established, and the interaction coefficient α is proposed. For limestone, cement and hydrated lime filler, the interaction coefficient α values are 0.301, 0.317 and 0.429 respectively. Based on Nielsens model and DSR test data, the Einstein coefficient KE is calculated, and Einstein coefficients are 3.761, 5.09 and 7.44 for asphalt-limestone mastic, asphalt-cement mastic and asphalt-hydrated lime mastic respectively. Both the interaction coefficient α and Einstein coefficient KE can be used to represent the interaction between asphalt binder and filler. The bigger value means the better interaction.

Analysis of the kinetics of lead biosorption using native and chemically treated olive tree pruning

In this research, new biosorbents of olive tree biomass were obtained by acid and basic treatment of the raw material at 50°C and 1M of chemical agent concentration. A kinetic study of the biosorption of lead ions by olive tree pruning was analyzed according to six different kinetic models. The pseudo first, pseudo second, pseudo n-order, Elovich, solid diffusion and double exponential models were employed to study the kinetics. The biosorption kinetic data were successfully described with pseudo-nth order and double exponential models for all biosorbents. The double exponential model allowed estimating the values of external and internal mass transfer coefficients. The values of external mass transfer coefficient (ke) ranged from 16.2×10−6 to 1066×10−6mmin−1 and the internal mass transfer coefficient (ki) from 9×10−6 to 69.88×10−6mmin−1. On the other hand, the analysis of experimental data showed that chemical treatments of the biomass led to increase biosorption capacity of the raw biomass.

Bioaccumulation of perfluoroalkyl carboxylates (PFCAs) and perfluoroalkane sulfonates (PFSAs) by earthworms (Eisenia fetida) in soil

Earthworms were exposed to artificially contaminated soils with ten perfluoroalkyl substances (PFASs). PFASs with longer perfluorinated carbon chain displayed higher uptake rate coefficients (ku), longer half-life (t1/2) and time to steady-state (tss) but lower elimination rate coefficients (ke) than the shorter ones. Similarly, perfluorosulfonates acids (PFSAs) displayed higher ku, longer t1/2 and tss but lower ke than perflurocarboxylic acids (PFCAs) with the same perfluorinated chain length. All the studied PFASs, including those with seven or less perfluorinated carbons, were bioaccumulated in the earthworms and the biota-to-soil accumulation factors (BSAFs) increased with perfluorinated carbon chain length and were greater for PFSAs than for PFCAs of equal perfluoroalkyl chain length. The BSAFs were found to be dependent on the concentrations of PFASs in soil and decreased as the level of PFASs in soil increased.

Modeling constrained dendrite growth in rapidly directional solidification

Incorporating the effect of nonlinear liquidus and solidus, a constrained dendrite growth model was established for rapidly directional solidification, where both the interface and the bulk liquid are under local non-equilibrium conditions. The effect of nonlinear liquidus and solidus was first introduced into the interface kinetics, based on which the marginal stability criterion was then derived. By this way, not only the temperature dependent equilibrium partition coefficient ke, equilibrium liquidus slope ml and equilibrium solidus slope ms but also the derivation of ke with temperature are considered. The model is more physically realistic than the works in which the effect of nonlinear liquidus and solidus is not incorporated into the interface kinetics and hence the temperature dependent ms is not embodied. Applying the model to rapidly directional solidification of Ag–15 wt% Cu alloy, the effects of nonlinear liquidus and solidus and local non-equilibrium on the constrained dendrite growth were studied.

Crystal growth of high magnetostrictive polycrystalline Fe81Ga19 alloys

High magnetostrictive Fe81Ga19 alloy was prepared by induction heating zone melting method. The microstructure, solute partition behaviour, orientation evolution and magnetostriction are investigated. During the crystal growth process, the initial small grains gradually grow into large columnar crystals, and the solid–liquid interface shows slightly concave morphology. The equilibrium solute partition coefficient (k0), effective solute partition coefficient (ke) and solution diffusion coefficient (D) are calculated to be 0.74, 0.76 and 1.04×10−9m2/s, respectively. In the steady growth stage, the composition distribution of the FeGa rod is uniform with average level about 18.50at% Ga, which is close to the nominal composition. The deviation of the 〈001〉 orientation from the axial direction evolves from about 8° to 3° along the growth direction, and the corresponding magnetostriction increases from the initial 180ppm to the final 305ppm.

Relationship between streaming potential and compressive stress in bovine intervertebral tissue

The intervertebral disc is formed by the nucleus pulposus (NP) and annulus fibrosus (AF), and intervertebral tissue contains a large amount of negatively charged proteoglycan. When this tissue becomes deformed, a streaming potential is induced by liquid flow with positive ions. The anisotropic property of the AF tissue is caused by the structural anisotropy of the solid phase and the liquid phase flowing into the tissue with the streaming potential. This study investigated the relationship between the streaming potential and applied stress in bovine intervertebral tissue while focusing on the anisotropy and loading location. Column-shaped specimens, 5.5mm in diameter and 3mm thick, were prepared from the tissue of the AF, NP and the annulus–nucleus transition region (AN). The loading direction of each specimen was oriented in the spinal axial direction, as well as in the circumferential and radial directions of the spine considering the anisotropic properties of the AF tissue. The streaming potential changed linearly with stress in all specimens. The linear coefficients ke of the relationship between stress and streaming potential depended on the extracted positions. These coefficients were not affected by the anisotropy of the AF tissue. In addition, these coefficients were lower in AF than in NP specimens. Except in the NP specimen, the ke values were higher under faster compression rate conditions. In cyclic compression loading the streaming potential changed linearly with compressive stress, regardless of differences in the tissue and load frequency.

Viscoelastic Analysis of Asphalt Mastic Based on Micromechanics

In this study, the stiffening effect of fillers on asphalt binders was characterized through micromechanics and rheology methods. The dynamic shear rheometer (DSR) was used to measure viscoelastic properties of asphalt mastic. Mechanical volume filling effects and additional interacting mechanisms within mastic systems are discussed on the basis of micromechanics-rheology model to predict the complex shear modulus of asphalt mastic from the measured mastic data. It is observed that the phase angle ranges from 88.8o to 89.0o, does not significantly change due to limestone fillers addition. The analytical model prediction of complex shear modulus based on the dynamic shear modulus can be used. Using the nonlinear regression, the Einstein coefficient KE is 4.22, 5.09 and 7.44 for asphalt mixed with limestone, cement and hydrated lime, respectively. Beside, the SEM results explain why the mastic system with hydrated lime shows the highest KE. The behavior of hydrated lime fillers filled mastics is probably due to physico–chemical interaction, which can be validated by further research.

Experimental investigation of microsegregation in low frequency electromagnetic casting 7075 aluminum alloy

Abstract7075 aluminum alloy ingots were prepared by the process of low frequency electromagnetic casting (low frequency electromagnetic casting = LFEC) and conventional direct chill (direct chill = DC) casting, respectively. The effects of low frequency electromagnetic field on microsegregation were investigated from eutectic analysis and electro probe microanalysis (EPMA). It was found that the amount of the eutectic, which was composed of α‐Al (aluminum phase), T phase and MgZn2 was decreased markedly. In contrast, the solute concentration profiles which depend on solid fraction were increased to a certain extent with the presence of low frequency electromagnetic field. The effective distribution coefficient ke was calculated, and the values of ke for solutes in the LFEC sample were bigger than those in the DC sample. The LFEC process alleviated the microsegregation in 7075 aluminum alloy.

Anisotropy of Acoustic Wave Velocities and Electromechanical Coupling Coefficients in the Crystals of Symmetry mm2 and 4mm

Results of the theoretical and numerical analysis of orientation dependences for velocities and electromechanical coupling coefficients (EMCC) KD and KE for the longitudinal and shear acoustic waves propagating in the (100), (010) and (001) crystallographic plane of the crystals with symmetry mm2 and 4mm are presented. We have obtained that the EMCC KE and KD are comparable to their value in every from these crystals. The optimal conditions for surface excitation of acoustic waves in these crystals were found.

745 脊髄組織の粘弾性変形と流動電位の関係(S01-1 細胞と組織のバイオメカニクス(1)-ミクロからマクロまで-,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

The purpose of this study is the elucidation of electro-mechanical response of spinal cord tissue. Spinal cord tissue is composed of white matter, gray matter, spinal meninges and water. The tissue has triphasic construction consisting of solid phase, fluid phase and electric reactions. Solid phase contains negative charged proteoglycan which enhance swelling pressure and exerts an influence on the tissue behavior. On the other hand, strain increases fixed charge density relating to electric potential gradient and streaming potential. We conducted the confined compression tests on spinal code specimens cut out from both white matter and gray matter. Ag/AgCl electrodes were used to measure the electric potential change on each specimen deforming in physiological saline. The streaming potential measurements were performed under compression, cyclic loading and ramp/stress-relaxation displacements. The measured potentials were correlated well with strain and stress. In the compression/stress-relaxation test, linear relation was confirmed between the stress and streaming potential with constant value of electrokinetic coefficient ke used in triphasic theory. Streaming potential was detected in each loading condition and the value varied in different tissue.

Through drying characteristic of oil palm empty fruit bunch (EFB) fibers using superheated steam

AbstractEmpty fruit bunches (EFB) of the oil palm have great potential to be used as industrial fibers in various industries, such as fiber board, mattress and cushion, erosion controller, thermoplastic filler, paper, acoustics control, sound insulator, and animal feed industries. A rotary drum dryer with a flue gas drying medium has been conventionally used to dry EFB fibers. However, this drying system tends to produce highly entangled and blackened fiber. Furthermore, the uneven contact between the flue gas and fiber in the rotary dryer may cause nonuniformity in the moisture content of the product. To overcome this problem, the present work uses superheated steam as the drying medium for EFB fiber drying. The drying experiments were carried out at the following conditions: atmospheric pressure; temperature range 112–172 °C; steam superficial velocity in the range 0.14‐4.3 m/s, distance from steam nozzle to EFB in the range 50–200 mm; and size of holes on plate in the range 10–200 mesh. The initial fiber moisture content was in the range 0.96‐1.46 kg/kg dry basis. The mass loss of EFB fiber during the drying process was periodically measured using an analytical balance connected directly to the wire mesh plate when the steam was diverted momentarily so that the effect of momentum transfer between the steam and the sample holder is minimized. In the temperature range 112–172 °C and at atmospheric pressure, the equilibrium moisture content isotherm is found to follow an exponential equation with coefficient ke = 15.365 kg/kg, ne = —0.001 °C−me and power index me = 1.869. It was found that for maximum moisture removal, the temperature and steam superficial velocity was 142 °C and 0.39 m/s, respectively. The effect of steam velocity is greater than that of steam temperature in decreasing the moisture content. The drying rate initially increases to a maximum and then falls off exponentially thereafter. A new drying model was developed for superheated steam for drying of EFB fiber, which is given by MR = 1 − atnexp(−ktm). The increasing drying rate is largely described by the exponential term with the coefficient k having values ranging from 1.945 to 5.351 s−n and the index m having values ranging from − 0.843 to 1.198. The falling drying rate is largely described by the power law term with the coefficient a ranging in value from 0.453 to 1.027 s−m and the power index n ranging in value from 0.0415 to 0.317. The drying is best carried out with the plate at a distance of 150 mm from the sample holder containing a 50 mesh plate. The superheated steam through the drying system can successfully reduce the moisture content by almost 100% in 15 min without steam condensation during the drying process. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

Litter fall, litter stocks and decomposition rates in rainforest and agroforestry sites in central Amazonia

The sustainability of agroforestry systems in Amazonia was assessed from their litter dynamics and decomposition. Litter fall and litter stocks were determined from July 1997 to March 1999 in four sites in central Amazonia: a primary rainforest, a 13-year-old secondary forest, and two sites of a polyculture forestry system which consisted of four planted tree species of commercial use amidst upcoming secondary growth. The average annual litter fall in the undisturbed primary rainforest (FLO) was 8.4 t ha−1 year−1, which is within the range of litter fall in other rainforests in the region. It was similar in one of the two polyculture sites (8.3 t ha−1 year−1), but lower in the secondary forest and in the second polyculture site. In the litter fall in secondary forest and agroforestry sites, the leaf portion was higher (76–82% of total litter fall) than in FLO, due to reduced fine matter and wood fall. Leaf litter fall variability was much lower in the plantation sites than in the forests, which is explained by the much more homogeneous stand structure of the plantations. The quality of the produced litter, measured as C/N ratio, differed significantly between the primary forest site and one polyculture and the secondary forest site. The cumulative input of nitrogen through litter fall was 144 kg ha−1 year−1 in FLO, and 91–112 kg ha−1 year−1 in the polycultures and the secondary forest. Litter fall was not correlated with soil parameters, but had a significant linear regression with canopy closure. For the primary rainforest, litter fall was also (inversely) correlated with monthly rainfall. Litter fall was higher in the first year (1997–1998; an El Nino period) than in 1998–1999. Litter stocks on the forest floor were highest in the secondary forest (24.7 t ha−1), and much lower in the polyculture sites (15.1–16.2 t ha−1) and the primary forest (12.0 t ha−1). There were no differences in the relative N content (C/N ratio) of the litter stocks between the sites, but the larger stocks led to higher absolute N contents in the litter layer in the secondary forest. From the monthly values of litter stocks (S) and litter fall (P), the decomposition coefficient k e=P/S was calculated, which was, on average, highest for the primary forest (0.059), followed by the polyculture systems (0.040–0.042), and by the secondary forest (0.024). Thus, due to low decomposition rates, the secondary forest site showed large litter accumulations in spite of a relatively low litter fall. In contrast, the primary forest showed high litter fall but low stocks, due to high decomposition rates. The decomposition coefficients of the polyculture systems ranged between the primary and the secondary forest. The reduced decomposition rates in the man-managed agroecosystems indicate quantitative and/or qualitative changes in the decomposer communities of these systems that lead to a higher build-up of litter stocks on the forest floor. However, the decomposer systems in the polyculture sites still were more functional than in the site of non-managed secondary growth. Thus, from a soil biological viewpoint, ecologically sustainable low-input agroforestry in Amazonia will benefit from the application of these polyculture systems.

Accounting For Corrosion Of Hlw Glasses By Humid Air In TSPA

ABSTRACTThis paper describes how the results of vapor hydration tests (VHTs) are used to model the corrosion of waste glasses exposed to humid air in the glass degradation model for total system performance assessment (TSPA) calculations for the proposed Yucca Mountain disposal system. Corrosion rates measured in VHTs conducted at 125, 150, 175, and 200°C are compared with the rate equation for aqueous dissolution to determine parameter values that are applicable to glass degradation in humid air. These will be used to determine the minimum for the range and distribution of parameter values in calculations for the Yucca Mountain disposal system license application (TSPA-LA). The rate equation for glass dissolution is rate = kE • 10 η • pH • exp(–Ea/RT). Uncertainties in the calculated rate due to the range of waste glass compositions and water exposure conditions are taken into account by using a range of values for the rate coefficient kE. The parameter values for the pH dependence (η) and temperature dependence (Ea) and the upper limit for kE are being determined with other tests. Using the values of η and Ea from the site recommendation model, the VHT results described in this paper provide a value of log kE = 5.1 as the minimum value for the rate expression. This value will change slightly if different pH-and temperature-dependencies are used for the TSPA-LA model.

Modeling of the refractive index and extinction coefficient of binary composite films

Southwell's analysis of optical multilayers within the limits of very thin films has been extended to include absorption in the multilayer for predicting the effective values of the refractive index n(e) and extinction coefficient k(e) of mixed-composition binary homogeneous films over a wide spectral region, including the high-absorption (k > 10(-2)) region. It has been found that n(e) in general is a complicated function of the optical parameters (n(1), k(1), n(2), k(2)) and volume fractions (f(1), f(2)) of the component materials in a homogeneous layer, and the expression for n(e) becomes the same as that predicted by the Drude model in the spectral region where the layers are transparent. Moreover, according to the present analysis, the volume fractions of the product of the refractive index and the extinction coefficient of the component materials of a binary composite film are additive and the sum equals the product of the effective refractive index and extinction coefficient of the composite film.

Dissociative electron attachment to dipolarmolecules at low energies with meV resolution: CFCl3,1,1,1-C2Cl3F3, and HI

Using the laser photoelectron attachment method we investigateddissociative electron attachment e-(E) + XY→X + Y-(DEA, shortnotation Y-/XY) to three molecules XY with a permanent electricdipolemoment in the electron energy range 0<E/meV ⩽ 173 with veryhighresolution (energy width ΔE⩽1 meV). With reference toreliable thermal attachment rate coefficients absolute DEA cross sectionsσe(E) have been derived for the processes Cl-/CFCl3,Cl-/1,1,1-C2Cl3F3 and I-/HI. Atthresholdsfor vibrational excitation of the neutral molecule, the cross sectionsexhibit a pronounced cusp structure (in most cases of a downward stepcharacter) due to coupling of the attachment process with scatteringchannels. At low energies (from about 0.8 meV to the first vibrationalcuspstructure) the cross sections are well described by the simple analyticalexpressionσe(E) = (σ0/E)[1-exp (-βE1/2)] (withβ falling in the range from 0.88 to 1.6 (meV)-1/2),indicating an energy dependence of between E-1/2 and E-1, inessential agreement with predictions of an extended Vogt-Wannier (EVW)capture model which includes the long-range electron-dipole interactionin addition to the polarization force. Comparisons are made with crosssections derived from previous photoelectron attachment work (TPSA) andfrom experiments involving electron beams, electron swarms and Rydbergatoms. Based on our experimental results for σe(E), wecalculate and report for all investigated processes the energy dependenceof the rate coefficients ke(E) for monoenergetic free-electronattachment as well as for Rydberg electron attachment knl (n≈30-150,l<<n) and the electron temperature dependenceof the rate coefficients ke(Te) for free-electronattachmentinvolving a Maxwellian electron ensemble and a gas at room temperature(TG = 300 K).

Estimation of the TEOS dissociation coefficient by electron impact

SiO2-like films are deposited in a low-pressure rf helicon reactor using oxygen-rich O2/TEOS (tetraethoxysilane) mixtures. A model based on the deposition rate variation with the distance to the TEOS injection is used to estimate the TEOS electron-impact dissociation coefficient ke and the effective sticking coefficient of reactive fragments s. In the helicon diffusion chamber where the electron temperature and density are about 4 eV and 1010 cm−3, respectively, ke and s are found to be 1.82×10−7 cm3 s−1 and 0.035, respectively. Under these low-pressure plasma conditions, the TEOS dissociation by electron impact is dominant over dissociation by oxygen atoms.

Solute trapping and solute drag in a phase-field model of rapid solidification

During rapid solidification, solute may be incorporated into the solid phase at a concentration significantly different from that predicted by equilibrium thermodynamics. This process, known as solute trapping, leads to a progressive reduction in the concentration change across the interface as the solidification rate increases. Theoretical treatments of rapid solidification using traditional sharp-interface descriptions require the introduction of separately derived nonequilibrium models for the behavior of the interfacial temperature and solute concentrations. In contrast, phase-field models employ a diffuse-interface description and eliminate the need to specify interfacial conditions separately. While at low solidification rates equilibrium behavior is recovered, at high solidification rates nonequilibrium effects naturally emerge from these models. In particular, in a previous study we proposed a phase-field model of a binary alloy [A. A. Wheeler et al., Phys. Rev. E 47, 1893 (1993)] in which we demonstrated solute trapping. Here we show that solute trapping is also possible in a simpler diffuse interface model. We show that solute trapping occurs when the solute diffusion length DI/V is comparable to the diffuse interface thickness. Here V is the interface velocity and DI characterizes the solute diffusivity in the interfacial region. We characterize the dependence of the critical speed for solute trapping on the equilibrium partition coefficient kE that shows good agreement with experiments by Aziz and co-workers [see M. J. Aziz, Metall. Mater. Trans. A 27, 671 (1996)]. We also show that in the phase-field model, there is a dissipation of energy in the interface region resulting in a solute drag, which we quantify by determining the relationship between the interface temperature and velocity.

Segregation behavior during silicon single-crystal growth from the melt

The dependence of the effective segregation coefficient (ke) on the growth rate (R) has been investigated by the necking method using phosphorous as an impurity in the silicon melt growth process. The investigations were carried out for two different growth orientations of the silicon crystal, 〈100〉 and 〈111〉. The coefficient increased with increasing growth rate for both crystal orientations. The behavior in the relatively lower growth rate region is explained by the BPS model. However, the coefficient in the higher growth rate region is larger than that expected by the BPS theory. Additionally, the critical growth rate (R*), where the value of the coefficient deviates from the theory, depends on the growing crystal orientation. The R* in the 〈111〉 crystal is lower (∼0.5 mm/min) than that in the 〈100〉 crystal (∼3.0 mm/min).

Electromechanical coupling coefficients and far-field radiation patterns of lithium niobate bars (Y-cut) used in high-frequency acoustical imaging and nondestructive testing

For high-frequency applications in ultrasonic imaging and nondestructive testing, lithium niobate (LiNbO3) can be used when cut under the shape of long bars with proper orientation and width to thickness ratio W/T. However, due to a strong material anisotropy, the modeling of such elementary bar transducers, for the sake of optimization, is quite difficult. In this paper, the use of the finite element method, with the help of the ATILA code, is proposed to compute resonance frequencies, coupling coefficients, electrical impedances and in-water far-field directivity patterns. (YZw)36° and (YXl)36° cuts with different W/T ratios have been analyzed and numerical results have been carefully and successfully compared with measurements. Main results concern the (YZw)36° cut for which symmetrical directivity patterns are obtained. In this case, a quite constant value is found for the thickness mode coupling coefficient ke in the ranges W/T&amp;lt;0.8 (ke≊50%) and 1.2&amp;lt;W/T&amp;lt;1.7 (ke≊40%). For the (YXl)36° cut, the directivity pattern is nonsymmetrical. In all the cases, a clear physical interpretation of transducer radiation characteristics is provided in terms of vibration modes. This analysis is the first application of new damping finite elements developed together with a specific extrapolation method and presented in a previous, companion paper [Assaad et al., J. Acoust. Soc. Am. 94, 562–573 (1993)].

157 nm F2 laser ablation of polyethylene terephthalate

The ablation of polyethylene terephthalate (PET) by pulsed 157 nm radiation from a fluorine laser has been studied. Etch depth measurements give an effective absorption coefficient (ke) of (1.1-0.4+0.5)*105 cm-1 corresponding to a threshold fluence for ablation (FT) of (29+or-6) mJ cm-2. The gaseous products of the ablation are CO, CO2, CH4, C2H2, C2H4, C4H2, C4H4, benzene and CH3CHO, similar to those found in the XeCl laser and the ArF laser ablation. The ablation threshold is lower than a value predicted on the basis of thermal decomposition alone, suggesting that there is a significant photochemical contribution to the ablation mechanism.