Modified Power Law Research Articles

Effect ­­­­­of ultrasonic irradiation treatment on rheological behaviour of extra heavy crude oil: A solution method for transportation improvement

AbstractThe highly viscous property of heavy oil often causes problems in its transportation in pipelines. Mixing heavy oil with light oil as well as ultrasound treatment are viable solutions to this problem. In this study, extra heavy crude oil samples were first diluted with 0, 0.05, 0.1, and 0.15 mL/mL (0, 5, 10, and 15 vol%) of a light crude oil; then the mixture was irradiated by ultrasonic waves for 0, 5, 10, 15, and 20 min; finally the viscous shear functions of all mixtures was measured at different values of shear rate at different temperature levels. The results revealed that the minimum viscosity of the diluted extra heavy crude oil samples was obtained at 10 min of ultrasonic irradiation. Moreover, the viscosity reduction rate in relation to temperature decreases as temperature increases. In other words, the maximum viscosity reduction rate occurred at 0.05 mL/mL (5 vol%) of light crude oil. Using the experimental data, the parameters of common rheological models were obtained and a new modified Power Law model was presented to calculate the effect of shear rate and temperature simultaneously.

A theory of scintillation for two‐component power law irregularity spectra: Overview and numerical results

AbstractWe extend the power law phase screen theory for ionospheric scintillation to account for the case where the refractive index irregularities follow a two‐component inverse power law spectrum. The two‐component model includes, as special cases, an unmodified power law and a modified power law with spectral break that may assume the role of an outer scale, intermediate break scale, or inner scale. As such, it provides a framework for investigating the effects of a spectral break on the scintillation statistics. Using this spectral model, we solve the fourth moment equation governing intensity variations following propagation through two‐dimensional field‐aligned irregularities in the ionosphere. A specific normalization is invoked that exploits self‐similar properties of the structure to achieve a universal scaling, such that different combinations of perturbation strength, propagation distance, and frequency produce the same results. The numerical algorithm is validated using new theoretical predictions for the behavior of the scintillation index and intensity correlation length under strong scatter conditions. A series of numerical experiments are conducted to investigate the morphologies of the intensity spectrum, scintillation index, and intensity correlation length as functions of the spectral indices and strength of scatter; retrieve phase screen parameters from intensity scintillation observations; explore the relative contributions to the scintillation due to large‐ and small‐scale ionospheric structures; and quantify the conditions under which a general spectral break will influence the scintillation statistics.

High Aspect Ratio Graphene Nanosheets Cause a Very Low Percolation Threshold for Polymer Nanocomposites

Liquid exfoliated, high aspect ratio (1272) graphene nanosheets (GNS) are dispersed in thermoplastic polyurethane (TPU) to prepare range of nanocomposites. A three fold increase in direct current conductivity is recorded at 0.0055 volume fraction (Vf) of GNS–TPU composites as compared to pristine TPU. It is suggested that the percolation threshold for conducting network achieved at low filler loadings is due to the high aspect ratio and homogeneous dispersion of GNS within the polymer. The experimental results are interpreted using interparticle distance model and modified power law. The two models predict threshold filler loading in 0.015–0.001 range volume fraction GNS based on the average values of mean length and no. of layers per nanosheet. The experimental results favor modified power law as it relies on aspect ratio of fillers. A slight deviation in our study from modified power law may be due to aggregation in as prepared GNS.

Stability of Audiometric Thresholds for Children with Hearing Aids Applying the American Academy of Audiology Pediatric Amplification Guideline: Implications for Safety.

Children who wear hearing aids may be at risk for further damage to their hearing from overamplification. Previous research on amplification-induced hearing loss has included children using linear amplification or simulations of predicted threshold shifts based on nonlinear amplification formulae. A relationship between threshold shifts and the use of nonlinear hearing aids in children has not been empirically verified. The purpose of the study was to compare predicted threshold shifts from amplification to longitudinal behavioral thresholds in a large group of children who wear hearing aids to determine the likelihood of amplification-induced hearing loss. An accelerated longitudinal design was used to collect behavioral threshold and amplification data prospectively. Two-hundred and thirteen children with mild-to-profound hearing loss who wore hearing aids were included in the analysis. Behavioral audiometric thresholds, hearing aid outputs, and hearing aid use data were collected for each participant across four study visits. Individual ear- and frequency-specific safety limits were derived based on the Modified Power Law to determine the level at which increased amplification could result in permanent threshold shifts. Behavioral thresholds were used to estimate which children would be above the safety limit at 500, 1000, 2000, and 4000 Hz using thresholds in dB HL and then in dB SPL in the ear canal. Changes in thresholds across visits were compared for children who were above and below the safety limits. Behavioral thresholds decreased across study visits for all children, regardless of whether their amplification was above the safety limits. The magnitude of threshold change across time corresponded with changes in ear canal acoustics as measured by the real-ear-to-coupler difference. Predictions of threshold changes due to amplification for children with hearing loss did not correspond with observed changes in threshold over across 2-4 yr of monitoring amplification. Use of dB HL thresholds and predictions of hearing aid output to set the safety limit resulted in a larger number of children being classified as above the safety limit than when safety limits were based on dB SPL thresholds and measured hearing aid output. Children above the safety limit for the dB SPL criteria tended to be fit above prescriptive targets. Additional research should seek to explain how the Modified Power Law predictions of threshold shift overestimated risk for children who wear hearing aids.

A Brief Review of High Entropy Alloys and Serration Behavior and Flow Units

Multicomponent alloys with high entropy of mixing, e.g., high entropy alloys (HEAs) and/or multiprincipal-element alloys (MEAs), are attracting increasing attentions, because the materials with novel properties are being developed, based on the design strategy of the equiatomic ratio, multicomponent, and high entropy of mixing in their liquid or random solution state. Recently, HEAs with the ultrahigh strength and fracture toughness, excellent magnetic properties, high fatigue, wear and corrosion resistance, great phase stability/high resistance to heat-softening behavior, sluggish diffusion effects, and potential superconductivity, etc., were developed. The HEAs can even have very high irradiation resistance and may have some self-healing effects, and can potentially be used as the first wall and nuclear fuel cladding materials. Serration behaviors and flow units are powerful methods to understand the plastic deformation or fracture of materials. The methods have been successfully used to study the plasticity of amorphous alloys (also bulk metallic glasses, BMGs). The flow units are proposed as: free volumes, shear transition zones (STZs), tension-transition zones (TTZs), liquid-like regions, soft regions or soft spots, etc. The flow units in the crystalline alloys are usually dislocations, which may interact with the solute atoms, interstitial types, or substitution types. Moreover, the flow units often change with the testing temperatures and loading strain rates, e.g., at the low temperature and high strain rate, plastic deformation will be carried out by the flow unit of twinning, and at high temperatures, the grain boundary will be the weak area, and play as the flow unit. The serration shapes are related to the types of flow units, and the serration behavior can be analyzed using the power law and modified power law.

Near-exponential relationship between effective stress and permeability of porous rocks revealed in Gangi's phenomenological models and application to gas shales

A number of theoretical models, as well as empirical equations obtained by fitting specific experimental data, have been developed to describe the relationship between effective stress and permeability of intact and fractured porous rocks. It has been found that most experimental data can be fitted using exponential equations. In this study the modified power law equations by Gangi for intact and fractured rocks are revisited to evaluate their applicability for modeling experimental permeability data which display exponential or near-exponential effective stress dependency. It has been shown that Gangi's power law equations for both intact and fractured rocks can be approximated, over the range of effective stresses of practical interest, by exponential equations with compressibilities that are related to the physical properties of the rock. The significance of this work is that it has provided further theoretical evidence for the apparent exponential relationship between effective stress and permeability. Moreover, it allows for more vigorous theoretical equations to be applied with the easiness of empirical exponential equations. This is demonstrated by applying the models to the experimental permeability data for six gas shales reported recently.

Laminar MHD flow and heat transfer of power-law fluids in square microchannels

The steady fully developed laminar flow and heat transfer of electrically conducting non-Newtonian fluids through square microchannels at the presence of transverse magnetic field are investigated with emphasis on viscous dissipation and joule heating effects. The governing continuity, momentum and energy equations are being discretized using a finite difference approach using Modified Power-Law (MPL) model and have been solved iteratively, through Alternating Direction Implicit (ADI) scheme with successive over-relaxation under the classical boundary conditions of no-slip velocity and uniform constant heat flux for flow and thermal fields.The velocity, temperature profiles, product of friction factor–Reynolds number and Nusselt number are computed for various values of flow index and dimensionless shear rate parameter of modified power-law fluids. Also, the effect of Hartmann number and Brinkman number on velocity, temperature distributions and Nusselt number are discussed. It is shown that the results are in good agreement with the previous studies.

Interpreting the electrophysiological power spectrum.

Recent experimental findings suggest that there may be rich physiological information embedded within the power spectrum of neurophysiological recordings, which, in addition to power in specific oscillatory frequencies, can be extracted with the appropriate model. This article reviews previous empirical and modeling results, as well as the canonical power law model that is often used to describe the power spectrum. In addition, a modified power law model with parameters estimating synaptic and spiking contributions is proposed.

Sustained immunogenicity of the HPV-16/18 AS04-adjuvanted vaccine administered as a two-dose schedule in adolescent girls: Five-year clinical data and modeling predictions from a randomized study

In this randomized, partially-blind study (clinicaltrials.gov; NCT00541970), the licensed formulation of the human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine (20 μg each of HPV-16/18 antigens) was found highly immunogenic up to 4 y after first vaccination, whether administered as a 2-dose (2D) schedule in girls 9–14 y or 3-dose (3D) schedule in women 15–25 y. This end-of-study analysis extends immunogenicity and safety data until Month (M) 60, and presents antibody persistence predictions estimated by piecewise and modified power law models. Healthy females (age stratified: 9–14, 15–19, 20–25 y) were randomized to receive 2D at M0,6 (N = 240 ) or 3D at M0,1,6 (N = 239). Here, results are reported for girls 9–14 y (2D) and women 15–25 y (3D). Seropositivity rates, geometric mean titers (by enzyme-linked immunosorbent assay) and geometric mean titer ratios (GMRs; 3D/2D; post-hoc exploratory analysis) were calculated. All subjects seronegative pre-vaccination in the according-to-protocol immunogenicity cohort were seropositive for anti-HPV-16 and −18 at M60. Antibody responses elicited by the 2D and 3D schedules were comparable at M60, with GMRs close to 1 (anti-HPV-16: 1.13 [95% confidence interval: 0.82–1.54]; anti-HPV-18: 1.06 [0.74–1.51]). Statistical modeling predicted that in 95% of subjects, antibodies induced by 2D and 3D schedules could persist above natural infection levels for ≥ 21 y post-vaccination. The vaccine had a clinically acceptable safety profile in both groups. In conclusion, a 2D M0,6 schedule of the HPV-16/18 AS04-adjuvanted vaccine was immunogenic for up to 5 y in 9–14 y-old girls. Statistical modeling predicted that 2D-induced antibodies could persist for longer than 20 y.

An investigation of different fitting functions to accurately model the compressive relaxation modulus master curve of asphalt mixes

This research was carried out to rank the different fitting functions utilised to construct the compressive relaxation modulus master curve of asphalt mixes. To this end, 72 cylindrical dense-graded asphalt mixture specimens containing crushed stone aggregates with 60/70 penetration asphalt binder were fabricated using two aggregate gradations, two binder contents, two air void levels, and three ageing conditions with three replicates for each experimental combination. Uniaxial compressive relaxation modulus tests were conducted on the specimens at four temperatures using the trapezoidal loading pattern at a low level of input strain. Different functions, that is, Pure Power Law (PPL), Generalised Power Law (GPL), Modified Power Law (MPL), Modified Power Law Series (MPLS), Standard Sigmoid (SS), Generalised Logistic Sigmoid (GLS), and Prony Series (PS), were utilised as the fitting models, and the compressive relaxation modulus master curves of all the experimental combinations were constructed using the numerical shifting technique. The compressive relaxation modulus values resulted by the mentioned fitting functions were graphically and statistically compared to each other, and PS was found to be the most accurate function, followed by MPLS, GLS, MPL, SS, GPL, and PPL, respectively. Finally, the rankings determined in compression were compared to those previously obtained in tension for the same experimental combinations.

Pressure drop predictions for laminar pipe flow of carreau and modified power law fluids

Fluids used in many chemical and petroleum industrial processes are often described as complex systems that exhibit non‐Newtonian character. Due to the complex nature of non‐Newtonian fluids, universally accepted flow equations are unavailable. This paper uses the Carreau and modified power law–Cross (MPL‐Cross) rheological models to derive pressure drop–flow rate relationships under laminar flow condition. The aim is to develop simple but effective equations that enable accurate estimation of pressure drop for flow in any pipe size using viscometric data. The new relationships compare favourably with experimental data. Furthermore, new Reynolds number and generalized Reynolds number expressions have been defined.

A Modification of Murray's Law for Shear-Thinning Rheology

This study reformulates Murray's well-known principle of minimum work as applied to the cardiovascular system to include the effects of the shear-thinning rheology of blood. The viscous behavior is described using the extended modified power law (EMPL), which is a time-independent, but shear-thinning rheological constitutive equation. The resulting minimization problem is solved numerically for typical parameter ranges. The non-Newtonian analysis still predicts the classical cubic diameter dependence of the volume flow rate and the cubic branching law. The current analysis also predicts a constant wall shear stress throughout the vascular tree, albeit with a numerical value about 15-25% higher than the Newtonian analysis. Thus, experimentally observed deviations from the cubic branching law or the predicted constant wall shear stress in the vasculature cannot likely be attributed to blood's shear-thinning behavior. Further differences between the predictions of the non-Newtonian and the Newtonian analyses are highlighted, and the limitations of the Newtonian analysis are discussed. Finally, the range and limits of applicability of the current results as applied to the human arterial tree are also discussed.

Water flooding performance prediction by multi-layer capacitance-resistive models combined with the ensemble Kalman filter

In this study, a system of multi-layer capacitance resistive models (MLCRMs) is established for water flooding performance prediction in a layered reservoir. Three different types of observation data are considered for a layered reservoir: (1) both injection and production rates of each layer; (2) only production rates of each layer; and (3) only injection rates of each layer. The cross flow among layers and the bottom-hole pressure are considered in the models. A modified power law model is used to describe the ratio of water to oil production. The ensemble Kalman filter (EnKF) method is applied to estimate the connectivity coefficients for each layer and the well index numbers in the MLCRMs. Synthetic examples of a layered reservoir with different types of observation data are performed to validate the proposed models. The results show a good match of historical data and a reasonable prediction for future oil and liquid production. • We establish a system of multi-layer capacitance resistive models (MLCRMs) for water flooding performance prediction in a layered reservoir. • Three different types of observation data of a layered reservoir are considered for the MLCRMs. • Both the effects of cross flow across the layers and bottom-hole pressure are taken into consideration. • The MLCRMs combined with the EnKF can assist us in characterizing the inter-well connectivity of a layered reservoir.

Initial Inoculum and Spatial Dispersal of Colletotrichum gloeosporioides, the Causal Agent of Strawberry Anthracnose Crown Rot.

Anthracnose crown rot (ACR), caused by Colletotrichum gloeosporioides, is a serious disease of strawberry (Fragaria × ananassa) in nurseries and fruiting fields in the southeastern United States. This study was conducted to determine the potential of alternative hosts for initial inoculum source and spread that causes ACR in strawberry nurseries. Results indicated that Parthenocissus quinquefolia is a noncultivated host of C. gloeosporioides in North Carolina and may serve as an initial inoculum source for planting material. Sources of inoculum data were complemented with a 2-year study of disease incidence and spread in simulated nursery production experiments. Sixty days after inoculation of the mother plants in the nursery, three different inoculation levels showed a significant positive correlation (r = 0.78, P < 0.004) with the quiescent infection (QI) incidence on the runner or daughter plants at the end of the nursery production cycle. Runner plant counts from different proportion of mother plants' inoculation treatments indicated that runner plant production was negatively and significantly (P < 0.001) affected by C. gloeosporioides. Infected tips used to produce transplants destined for fruit production resulted in 29.3 and 16.8% mortality in plug trays in 2007 and 2008, respectively. Tracking foliar QI incidence that resulted from dispersal of inoculum from an introduced point source in the nursery showed a sharp decline at 1 m and beyond from the inoculation focus. Although the exponential model (R2 = 0.92 to 0.94) had slightly higher coefficients of determination than the modified power law (R2 = 0.89 to 0.90), residual plots indicated that the modified power law model fit the disease gradient data better than the exponential model in both years. Results from our dispersal study indicated that rogueing of infected plants within a 4-m radius of infection foci would reduce the risk of transferring infected runner plants from the nursery to the fruiting field.

Comparing various fitting models to construct the tensile relaxation modulus master curve of asphalt mixes

This study was to compare the relative ability of seven common fitting models, i.e. Pure Power Law (PPL), Generalized Power Law (GPL), Modified Power Law (MPL), Modified Power Law Series (MPLS), Standard Sigmoid (SS), Generalized Logistic Sigmoid (GLS) and Prony Series (PS), to construct the tensile relaxation modulus master curve of dense graded asphalt mixes. To this end, cylindrical asphalt mixture specimens containing crushed stone aggregates with 60/70 penetration asphalt binder were fabricated using two aggregate gradations, two binder contents, two air void levels and three ageing conditions with three replicates. Direct tension relaxation modulus tests were conducted on the specimens at four different temperatures using the trapezoidal loading pattern at a low level of input strain. Tensile relaxation modulus master curves were constructed using all the fitting models together with the numerical shifting technique. Finally, both the graphical and statistical comparisons were made among the fitting models, and the best one was found to be PS, followed by MPLS, GLS, MPL, SS, GPL and PPL.

Predicting the establishment and spread of plant disease from regulatory sampling

Invasive plant diseases can have devastating consequences on the local plant populations, in both agricultural and natural landscapes. Knowledge of the spatial patterns of pathogen spread can be used to guide more time- and cost-effective disease management strategies. Based on disease dispersal principles and consideration of host pattern, an improved plant disease epidemiological model was developed and tested for plant disease mapping. The model is able to characterize the disease dispersal gradient and predict infection risk, with indication of uncertainty, through heterogeneous environments without reference to the source of infection. As a result, sampling methods can be informed by the predicted prevalence map of the disease. In order to better describe the shapes of the dispersal gradients, three different dispersal functions (Exponential, Modified power law, and Cauchy distribution) were considered in the model. Two data sets of disease observations of Huanglongbing (HLB) of citrus in different landscapes (Southern Garden and Devils Garden plantation) in Florida were used to evaluate the performance of the improved method for disease mapping. The results showed that the improved model provided estimates of greater precision for unsampled hosts. With all different dispersal models compared, the exponential dispersal gradient gave the most satisfactory performance. All the determined information can help decision makers understand the spatial aspects of disease processes, and formulate decisions about disease control accordingly.

Vibration characteristics of stepped beams made of FGM using differential transformation method

The present paper is given to investigate free vibration analysis of stepped beams produced from functionally graded materials (FGMs). The differential transformation method is employed to solve the governing differential equations of the beams to obtain their natural frequencies and mode shapes. The power law distribution is used and modified for describing material compositions across the thickness of the stepped beams made of FGM. Two main types of the stepped FGM beams in which their material compositions can be described by the modified power law distribution are selected to investigate the free vibration behaviour. The significant parametric studies such as step ratio, step location, boundary conditions and material volume fraction are also covered in this paper.

RSS feeds behavior analysis, structure and vocabulary

Purpose – The purpose of this paper is to present a thorough analysis of three complementary features of real-scale really simple syndication (RSS)/Atom feeds, namely, publication activity, items characteristics and their textual vocabulary, that the authors believe are crucial for emerging Web 2.0 applications. Previous works on RSS/Atom statistical characteristics do not provide a precise and updated characterization of feeds’ behavior and content, characterization that can be used to successfully benchmark the effectiveness and efficiency of various Web syndication processing/analysis techniques. Design/methodology/approach – The authors empirical study relies on a large-scale testbed acquired over an eight-month campaign from 2010. They collected a total number of 10,794,285 items originating from 8,155 productive feeds. The authors deeply analyze feeds productivity (types and bandwidth), content (XML, text and duplicates) and textual content (vocabulary and buzz-words). Findings – The findings of the study are as follows: 17 per cent of feeds produce 97 per cent of the items; a formal characterization of feeds publication rate conducted by using a modified power law; most popular textual elements are the title and description, with the average size of 52 terms; cumulative item size follows a lognormal distribution, varying greatly with feeds type; 47 per cent of the feed-published items share the same description; the vocabulary does not belong to Wordnet terms (4 per cent); characterization of vocabulary growth using Heaps’ laws and the number of occurrences by a stretched exponential distribution conducted; and ranking of terms does not significantly vary for frequent terms. Research limitations/implications – Modeling dedicated Web applications capacities, Defining benchmarks, optimizing Publish/Subscribe index structures. Practical implications – It especially opens many possibilities for tuning Web applications, like an RSS crawler designed with a resource allocator and a refreshing strategy based on the Gini values and evolution to predict bursts for each feed, according to their category and class for targeted feeds; an indexing structure which matches textual items’ content, which takes into account item size according to targeted feeds, size of the vocabulary and term occurrences, updates of the vocabulary and evolution of term ranks, typos and misspelling correction; filtering by pruning items for content duplicates of different feeds and correlation of terms to easily detect replicates. Originality/value – A content-oriented analysis of dynamic Web information.

Flux growth and effect of cobalt doping on dielectric, conductivity and relaxation behaviour of 0.91Pb[Zn1/3Nb2/3]O3–0.09PbTiO3crystals

Crystals of 1 mol% cobalt-doped Pb(Zn1/3Nb2/3)O3–0.09PbTiO3 (PZNCT) have been grown using a high-temperature self-flux method. A pure perovskite phase with mixed symmetry at room temperature was observed using X-ray diffraction analysis. Their electrical properties were further investigated by measuring temperature- and frequency-dependent dielectric constant (e) and loss (tan δ) behaviour of as-grown crystals. To study the degree of dielectric relaxation, modified power law fitting and Lorentz-type quadratic fitting were performed. The as-grown PZNCT crystals showed a low Curie temperature (Tc ~131 °C) with a rhombohedral–tetragonal phase transition temperature (Trt) of 104 °C. The piezoelectric coefficient (d33) value at the optimized poling field was found to be ~1000 pC N−1. Complete electrical characterization revealed the growth of high-performance PZNCT crystals with enhanced remnant polarization (34.23 μC cm−2) and low coercive field (6.97 kV cm−1) with cobalt doping. The conduction and relaxation mechanisms of grown PZNCT crystals have been discussed in detail.

Drug release mechanisms of chemically cross-linked albumin microparticles: Effect of the matrix erosion

Albumin (BSA) microparticles were developed as a biotechnological alternative for drug delivery. Vitamin B12 (Vit-B12) was used as a model drug. The microparticles were obtained from maleic anhydride-functionalized BSA and N′,N′-dimethylacrylamide (DMAAm) in a W/O emulsion without and with PVA. The microparticles produced at 15min of stirring without PVA showed the best results in terms of size, homogeneity, and sphericity. In such a case, BSA played a role as a surface active agent, replacing PVA. For longer stirring times, BSA was unable to act as an emulsifier.These microparticles showed an uncommon release profile, consisting of a two-step release mechanism, at the pH range studied. Considering that a two-step release mechanism is occurring, the experimental data were adjusted by applying modified power law and Weibull equations in order to describe release mechanism n and release rate constant k, respectively. Each one of the release stages was related to a specific value of n and k. The second stage was driven by a super case II transport mechanism, as a result of diffusion, macromolecular relaxation, and erosion. A third model, described by Hixson–Crowell, confirmed the erosion mechanism.Vit-B12 diffusion kinetics in aqueous solutions (i.e., without the microparticles) follows a one-step process, being k dependent on the pH, confirming that the two-step release mechanism is a characteristic profile of the developed microparticles. The microparticles released only 2.70% of their initial drug load at pH 2, and 58.53% at pH 10.