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Enzymatic hydrolysis of corn stover was studied at agitation speeds from 50 to 500 rpm in a stirred tank bioreactor, at high solid concentrations (20% w/w dry solid/suspension), 50 °C and 15.5 mg protein ·g glucane −1 . Two empirical kinetic models have been fitted to empirical data, namely: a potential model and a fractal one. For the former case, the global order dramatically decreases from 13 to 2 as agitation speed increases, suggesting an increment in the access of enzymes to cellulose in terms of chemisorption followed by hydrolysis. For its part, the fractal kinetic model fits better to data, showing its kinetic constant a constant augmentation with increasing agitation speed up to a constant value at 250 rpm and above, when mass transfer limitations are overcome. In contrast, the fractal exponent decreases with rising agitation speed till circa 0.19, suggesting higher accessibility of enzymes to the substrate. [ABSTRACT FROM AUTHOR]

In this research work, an Intermingled Fractal Units' model (IFU's model) has been proposed with the aim of predicting water vapour permeability characteristics of porous rock, normally studied in gas reservoir field. IFU modelling approach commences with the reproduction of experimental pore size distribution with the help of diverse fractal base units mixed together. This procedure allows simulating the porous microstructure in terms of pore cumulative curve or pore size distribution. An analytical procedure is used for obtaining the permeability values. The studied rocks include limestone from South Sardinia quarries and have similar characteristics of those studied in gas reservoir field. They have been taken from four different parts (systems A, B, C and D) of the quarry for the assessment of the heterogeneity of this rock. From the experimental tests, the average water vapour permeability values are equal to 7.22 ± 1.22, 4.21 ± 1.51, 10.09 ± 1.11 and 10.12 ± 2.42 10 −12 kg m −1 s −1 Pa −1 respectively for systems A, B, C and D, whereas predictions by IFU are respectively equal to 7.15 ± 1.55, 4.25 ± 1.45, 10.12 ± 1.22 and 9.98 ± 2.18 10 −12 kg m −1 s −1 Pa −1 . The comparison shows a good capacity of IFU procedure to predict water vapour permeability values. [ABSTRACT FROM AUTHOR]

The Sorptivity is a coefficient very important to characterize porous materials. It is associated to principal properties such as mechanical durability, thermal and electrical conductivity, etc. In this work, the Sorptivity coefficient of several systems of porous ceramics has been measured following the experimental procedure. In different situations, this very simple test could be not performed; in cultural heritage or during an optimised industrial process. Major reasons for this inability include that it would demand great quantitates of materials impossible to withdraw from the protected building, as well as the experimental test can last for several days, which reduces the possibility to correct/improve the industrial production process. In this regards, being very useful to have analytical formulas in order to calculate Sorptivity coefficient, an Intermingled Fractal Units model has been proposed. Starting from its capability to reproduce entirely the pore size distributions of porous materials, IFU is used to simulate water absorption process and to estimate the Sorptivity coefficient. The obtained results are in good agreement with experimental data and others two models predictions. This fact allows considering IFU model as a future tool for design materials and to predict their service life. [ABSTRACT FROM AUTHOR]

Porous yittria-stabilized zirconia is an important advanced ceramic material for technological applications. One of the most important characteristics of this material is low thermal conductivity, which is greatly influenced by the presence of pores into the microstructure. In fact, air trapped in the pores represents a better thermal insulator. The role of the pore volume fraction on porous material characteristics has been extensively studied. On the other hand, the influence of the structure disorder, the pore size range and pore size distribution have been studied much less. In this study, an intermingled fractal model capable of relating thermal properties of ceramic materials and their pore microstructure has been proposed. Model predictions are found confirming the experimental data fairly well, even better than the others models available in the literature. [ABSTRACT FROM AUTHOR]

Baseado nos conceitos da geometria fractal e nas leis de Laplace e de Poiseuille, foi criado um modelo geral para estimar a condutividade hidráulica de solos não saturados, utilizando a curva de retenção da água no solo, conforme representada por um modelo em potência. Considerando o fato de que este novo modelo da condutividade hidráulica introduz um parâmetro de interpolação ainda desconhecido, e que, por sua vez, depende das propriedades dos solos, a validação do modelo foi realizada, utilizando dois valores-limite fisicamente representativos. Para a aplicação do modelo, os parâmetros de forma da curva de retenção da água no solo foram escolhidos de maneira a se obter o modelo de van Genuchten. Com a finalidade de obter fórmulas algébricas da condutividade hidráulica, foram impostas relações entre seus parâmetros de forma. A comparação dos resultados obtidos com o modelo da condutividade e a curva experimental da condutividade dos dois solos, Latossolo Vermelho-Amarelo e Argissolo Amarelo, permitiu concluir que o modelo proposto é simples em sua utilização e é capaz de predizer satisfatoriamente a condutividade hidráulica dos solos não saturados.From a conceptual model based on fractal geometry and Laplace's and Poiseuille's laws, a versatile and general fractal model for the hydraulic conductivity to be used in the soils was developed. The soil-moisture retention curve is derived from a power model. Due to the fact that the proposed model of hydraulic conductivity introduces a still unknown interpolation parameter, which in turn is a function of soil properties, its limiting values were considered for the analysis. To apply the model in the soil, the form parameters of the soil-moisture retention curve were chosen so as to reproduce van Genuchten's equation. In order to obtain a closed-form equation for the hydraulic conductivity, relationships between the form parameters were imposed. The comparison between the predicted and experimental hydraulic conductivity from two soils, Oxisol and Yellow Utilsol, demonstrated that the proposed model is flexible and that it can be used to predict the unsaturated hydraulic conductivity of soils with good accuracy.

In this paper, we investigate the novel properties of the cluster interfacial nanolayer theory for a thermal conductivity-based model. Under the influence of magnetohydrodynamics, the interaction of nanomaterials aggregation of metallic oxide nanomaterials with base fluid is explored. This paper discusses a specific form of new low permeability Reynolds number connected with an injection/suction factor related to an absorbent channel. A numerical simulation of higher-order nonlinear differential equations reveals the momentum flow and energy fields predicted by single-phase nanofluid simulations. Shear stress and Nusselt numbers were used to determine the effect of nanoparticle radius and diameter. Insertion of the metallic nanoparticles volume fraction level from 1% to 8% enhances the thermal performance at lower and upper porous walls respectively. Injection/suction and MHD have to decrease and increase behavior respectively in the presence of spherical nanoparticles. Interfacial nanolayer formation has a substantial impact on thermal conductivity performance. Comparing calculated findings to published literature validates their correctness. Graphs are generated to analyze the impact of flow parameters on velocity and temperature profiles. In tabular and graphical style, the effects of all physical factors are explored on the skin friction coefficient and the local Nusselt number. [ABSTRACT FROM AUTHOR]

Autoclaved aerated concrete (AAC) has widely been utilized as a lightweight, porous insulation material for energy-efficient buildings. The knowledge on the thermal conductivity of AAC is required for thermal design of building envelopes. The effective thermal conductivity of AAC is strongly dependent on the moisture content. Such dependence, however, is not well documented in available literature. In this work, AAC bricks with three different bulk densities of 415, 520, and 630 kg/m 3 , were obtained as the raw materials, and the samples were prepared by humidification to a set of moisture content levels up to 100% by mass. The effective thermal conductivity of the moisturized samples was measured by means of the transient plane source technique. Meanwhile, fractal models for predicting the effective thermal conductivity were proposed based on construction of the porous structure of AAC by self-similar Sierpinski carpet. A two-phase fractal model was first proposed for dry AAC samples, and then an extension to a three-phase model was developed by considering the presence of water phase in the pores for unsaturated, moist samples. It was shown that the thermal conductivity increases with increasing the moisture content, by a factor up to 3.8 over the studied range of moisture content, following a two-section piecewise linear variation. A high-to-low slope change was found to be around a moisture content of 15% for all the AAC samples. A correlation was proposed for the measured thermal conductivity as a function of both moisture content and porosity. Appropriate parameters for the two-phase model were determined by comparing the predicted results to the measured data at dry state. The three-phase fractal model was exhibited to be able to predict the hygric dependence of thermal conductivity. The discrepancy among the predictions by the three-phase model with different geometric parameters was discussed in relation to the constructed pore structures. The predicted results by the two configurations of the three-phase model, i.e., with and without considering the presence of connected water bridges in the pores, were also presented. A reasonable elimination of the presence of connected bridges was shown to lead to better predictions in the low moisture content regime. [ABSTRACT FROM AUTHOR]

Research on the heat transfer in hydrogen-fuelled spark ignition engines indicates that the two most common heat transfer correlations, namely the Annand correlation and the Woschni correlation, cannot perfectly predict the heat flux during the engine cycle. This questions the accuracy of thermodynamic hydrogen engine models because the heat transfer is one of the important submodels in the development of a thermodynamic model. In addition, the Hohenberg correlation and the Shudo–Suzuki correlation have not been evaluated for hydrogen engines. In this study, a thermodynamic model of the closed cycle of a spark ignition engine is developed with a multi-zone combustion submodel to predict the pressure and the heat flux traces and to compare the predicted values with the available experimental results. The effects of implementing different heat transfer correlations in the prediction of the maximum pressure of the cycle, the total heat transfer and the work are presented for two different compression ratios and two equivalence ratios with different ignition timings. The results indicated that, although the implemented heat transfer correlations predicted the heat flux and the heat transfer with a large percentage error, the fractal-based combustion model implementing the Annand correlation and the Shudo–Suzuki correlations predicted the maximum pressure and the total work with less than 10% error. Finally, a modified version of the Hohenberg correlation for predicting the total heat transfer in a hydrogen spark ignition engine was presented. [ABSTRACT FROM AUTHOR]

In the present paper, the fractal analysis on silica aerogel is performed based on the statistical self-similarity of porous media. A fractal model for the effective thermal conductivity of silica aerogel is proposed in consideration of the tortuosity of heat transfer path and the microstructure of secondary particle. The proposed model assumes that silica aerogel consists of two levels of microstructures: the secondary particles symbolized by improved 2-level Menger sponge and the cluster formed by secondary particles, which can be expressed as a function of density, the contact ratio, and the fractal dimensions. Validation with experimental data and predictions of other theoretical models shows that the present fractal model is reliable and accurate. [ABSTRACT FROM AUTHOR]

The mechanical properties of the cortical bone of fresh bovine femora along three different directions are tested through four-point bending experiments. It is indicated that the fracture energy along the transversal direction of the bone is distinctly larger than those of the longitudinal and radial directions. The fracture surfaces of the three different directions are observed by scanning electron microscope (SEM). It is shown that the roughness of the fracture surface of the transversal direction is obviously larger than those of the fracture surfaces of the longitudinal and radial directions. It is also revealed that the osteons in the bone are perpendicular to the fracture surface of the transversal direction and parallel to the fracture surfaces of the longitudinal and radial directions. Based on these experimental results, the fractal dimensions of the fracture surfaces of different directions are calculated by box-counting method in MATLAB. The calculated results show that the fractal dimension of the fracture surface of the transversal direction is remarkably larger than those of the fracture surfaces of the longitudinal and radial directions. The fracture energies of different directions are also calculated based on their fractal models. It is denoted that the fracture energy of the transversal direction is remarkably larger than those of the longitudinal and radial directions. The calculated results are in good agreement with the tested results. [ABSTRACT FROM AUTHOR]

This work studies the permeability of power-law fluids in porous fibrous media with electrokinetic effects. By solving the linearized Poisson–Boltzmann and Navier–Stokes equations, we get the analytical solutions of pressure driven flow of power-law fluids in a microcapillary with electric double layer (EDL). The flow rate in a single capillary, combining with the fractal model of pore distribution of fractures in naturally fractured porous media, deduces the total flow rate. Then the analytical result of effective permeability for power-law fluids with EDL effects is derived as a function of the porosity, the flow behavior index and a dimensionless number derived from the solid surface zeta potential and maximum pore radius. The present results show that the EDL effects as well as other variable parameters may greatly influence the effective permeability of the power-law fluids in porous fibrous media: the larger the porosity, the higher the effective permeability; the larger the maximum pore radius, the higher the effective permeability; the higher the solid surface zeta potential, the more the EDL effects; the more the EDL effects, the lower the effective permeability. Comparing the effective permeability produced by different flow behavior indexes, we further illustrate that the EDL has virtually no effects when the flow behavior index is great than 1, moderate effects when equal to 1, and very significant effects when less than 1. Therefore the EDL effects may provide strong constraints on evaluation of the effective permeability of the shear thinning fluids rather than the shear thickening and Newtonian fluids. [ABSTRACT FROM AUTHOR]

The Pedagogical Agents (PAs) for Mobile Learning (m-learning) must be able not only to adapt the teaching to the learner knowledge level and profile but also to ensure the pedagogical efficiency within unpredictable changing runtime contexts. Therefore, to deal with this issue, this paper proposes a Context-aware Self-Adaptive Fractal Component based Generalized Pedagogical Agent (CASA FBGPA) framework for Mobile Learning. The proposed framework allows for the construction of PA that self-reconfigures its structure, the functional part, to conform to the unpredictable changing runtime context. To carry out the context-awareness, the PA embeds a distinct Search based Adapting Engine that dynamically monitors and assembles the appropriate linear combination of Fractal components. In addition, to avoid the rules associated conceptual holes, to deal with the conflicting objectives and to reduce the substantial overhead, the components selection is formulated as a multiobjective problem and it is tackled using a metaheuristic search method. Furthermore, to evaluate the design and the feasibility of the proposed framework, a use case and a discussion are provided. [ABSTRACT FROM AUTHOR]

Detecting anomaly in data streams attracts great attention in both academic and industry communities due to its wide range application in venture analysis, network monitoring, trend analysis and so on. However, existing methods on anomaly detection suffer three problems. 1) A large number of false positive results are generated. 2) Training data are needed to build the detection model, and an appropriate time window size along with corresponding threshold has to be set empirically. 3) Both time and space overhead is usually very high. To address these limitations. We propose a fractal-model-based approach to detection of anomalies that change underlying data distribution in this paper. Both a history-based algorithm and a parameter-free algorithm are introduced. We show that the later method consumes only limited memory and does not involve any training process. Theoretical analyses of the algorithm are presented. The experimental results on real life data sets indicate that, compared with existing anomaly detection methods, our algorithm can achieve higher precision with less space and time complexity. [ABSTRACT FROM AUTHOR]

In order to improve the spatial resolution of 3d numerical simulation of lightning shielding fractal discharging, this paper proposes an improved fractal model， which is the three - dimensional numerical simulation of lightning discharge with resolution of 50 m on the basis of the fractal theory and with resolution of 1m in the protection zone. On the basis of the improved model, the application of the method to estimate the lightning shielding performance of UHVDC transmission lines could be obtained. Moreover, through the combination of the lightning current space probability with the lightning shielding failure probability from the fractal model, the lightning shielding failure rate of the transmission lines could be obtained. Taking the ±500 kV UHVDC transmission lines in Inner Mongolia as an example, the rationality of the numerical simulation is verified by comparing the statistical values of parameters of natural lightning discharges and simulation results. [ABSTRACT FROM AUTHOR]

This is the second part of the special issue on fractal geometry and its applications to the modeling of flow and transport in porous media, in which 10 original research articles and one review article are included. Combining to the first part of 11 original research articles, these two issues summarized current research on fractal models applied to porous media that will help to further advance this multidisciplinary development. This whole special issue is published also to celebrate the 70th birthday of Professor Boming Yu for his distinguished researches on fractal geometry and its application to transport physics of porous media. [ABSTRACT FROM AUTHOR]

Based on the contact fractal theory and MB model, considering the elastic contact deformation, the plastic contact deformation and two different regimes of elastoplastic contact deformation, a fractal model of normal contact stiffness of joint interfaces was proposed. Numerical simulation results of this model show that the elastoplastic contact deformation mechanism has an obvious effect on the normal contact stiffness, and the dimensionless normal contact stiffness of this model is much more than that considering only elastic and plastic regime, respectively. It also shows that the dimensionless normal contact stiffness increases with the increase of the dimensionless normal load but the varying tendency is strongly nonlinear! when fractal dimension D= 1.1 ~ 1.4 ) or near linear! when fractal dimension D = 1.4 ~ 1.9), and it increases!when fractal dimension D = 1.1 ~ 1. 6) with the increase of the fractal dimension or decreases!when fractal dimension D=1.6 ~ 1.9) with the increase of the fractal dimension. It decreases with the increase of normal fractal roughness, and increases with the increase of plastic index. The validity of the model was verified with an experimental example. [ABSTRACT FROM AUTHOR]

The authors substantiate the objectives for the prospective research program dedicated to the destruction of the traditional informal institutions - the TII. TII is considered by many experts as one of the most significant obstacles for modernization of all systems of Russian socio-political institutions. The article contains a description of the social problems associated with the presence of the TII, also literature analysis on this issue and the statement of the suggested methodology. Creating fractal computer models is a new and highly promising research tool, not only in the natural sciences, but also in the socio-humanitarian disciplines. In the article it is talked about the approaches of construction of a fractal model that imitate, in particular, the transformation of the socio-political institutions (General fractal transition model - GFTM). Also we provide some most interesting - qualitative interpretation of experiments on the simulation of institutional modernization. Hypothetical variants of forced institutional modernization are constructed. Some non-linear effects that arise during the transformation of the "sedimentary" social structures are found. The whole set of such effects authors call "turbulent" accelerated modernization.DOI: http://dx.doi.org/10.12731/2218-7405-2013-7-12

This paper presents a preliminary work to evaluate the thermal conductivity performance in pure and blended cement pastes with fly ash, slag and silica fume. The thermal conductivity of cement pastes cured in saturated and dry status with different hydration ages are also measured and predicted by quick thermal conductivity meter (QTM) and innovative non-contact impedance measurement (NCIM) based on a newly proposed fractal model. Besides, a corresponding simulation of fractal-like network is developed to evaluate the influences of pore structure parameters, intrinsic thermal conductivity coefficients of solid and water or gas phase on thermal conductivity performance of cement pastes. [ABSTRACT FROM AUTHOR]

We used the fractal theory based on a single variable Weierstrass-Mandelbrot function to obtain the normal contact stiffness if rough and smooth isotropic surfaces are pressed against each other. Because in the original fractal theory the distribution of contact area is assumed geometrically, we propose the method in which the actual deformation of asperities and a correction due to asperity coupling (interaction) will be taken into account. This correction is equivalent to an increase of the effective separation by a quantity proportional to the nominal pressure and it has a significant effect on contact stiffness at larger normal loads (low separations). The numerical results demonstrate a nonlinear evolution of the contact stiffness with the normal load in particular in the first stage of loading at low squeezing pressures. We have compared the results of the theoretical contact stiffness using the fractal method with the experimental ultrasonic measurements. Experimental results made on real surfaces agree remarkably well with the theoretical predictions. [ABSTRACT FROM AUTHOR]

The present study proposes a technological transfer from modern mining prospection to the field of archaeology, providing a methodology to facilitate the discovery of ancient mining sites. This method takes advantage of the thousands of geochemical analyses of streambed sediments, performed by national geological surveys to inventory mineral substances. In order to delineate geochemical anomalies, the datasets are treated following two different approaches: Exploratory Data Analysis and a fractal-based method often recognised as more powerful. Mineral prospectivity maps are then obtained by combining the results with a geographical information system. The surroundings of the Celtic oppidum of Bibracte, French Massif Central, known to have been mined at least since the Late Bronze Age until Modern Times, have been chosen to exemplify the method's potential in archaeology. First, an exhaustive record of the mining sites was undertaken over a pilot area by pedestrian prospection. If mineral prospectivity maps had been used as guidelines, ~70% of these mines would have been discovered by prospecting only ~15-20% of the whole area whatever the method used to treat the dataset. At least for our specific case, the multifractal approach is as powerful as EDA. Besides saving a significant amount of time and effort, the methods described here may supply clues for determining the nature of mineral substances exploited in the past, when such information cannot be straightforwardly obtained from the field or from textual archives. It should however be noticed that this approach is proposed as a first step before peer archaeological investigation following more conventional methods. Technically, there is no real obstacle to the application of the methodology proposed here, because ( i ) software and associated packages are freely available from the web, as well as original geochemical datasets (at least in France), and ( ii ) minimal mathematical skills are required. [ABSTRACT FROM AUTHOR]

This special issue gathers together a number of recent papers on fractal geometry and its applications to the modeling of flow and transport in porous media. The aim is to provide a systematic approach for analyzing the statics and dynamics of fluids in fractal porous media by means of theory, modeling and experimentation. The topics covered include lacunarity analyses of multifractal and natural grayscale patterns, random packing's of self-similar pore/particle size distributions, Darcian and non-Darcian hydraulic flows, diffusion within fractals, models for the permeability and thermal conductivity of fractal porous media and hydrophobicity and surface erosion properties of fractal structures. [ABSTRACT FROM AUTHOR]

The complex structure and surface property of porous media have significant impact on its accumulation and adsorption capacity. Based on the fractal theory, this paper presents a fractal pore structure model for shales. The effect of different pore structures on fractal dimension is discussed, and the influence of fractal dimension and pore size distribution on porosity is also analyzed. It is shown that the fractal dimension D decreases with the increase of structure parameter q/m for a certain pore diameter ratio, and porosity has positive relationship with fractal dimension. This paper also presents a multilayer fractal adsorption model which takes into account the roughness of adsorption surface by using fractal theory. With the introduction of pseudo-saturated vapor pressure in the supercritical temperature condition, the proposed adsorption model can be applied into a wider range of temperature. Based on the low-pressure nitrogen adsorption and methane isothermal adsorption experiments, the effect of fractal dimension on the adsorption behavior of shales is discussed. Fractal dimension has significant impact on the surface adsorption property and adsorption layer number n. The monolayer saturated adsorption volume Vm increases with the increase of D, while parameter C has the opposite variation trend. Finally, the optimal combination of fractal parameters for describing pore structure of shale samples is selected. [ABSTRACT FROM AUTHOR]

Highlights: [•] The permeability of young cement pastes is evaluated using new impedance system. [•] A fractal permeability model based on this measurement is proposed. [•] The permeability value of cement pastes can be measured continuously. [•] A fractal permeability simulation is conducted. [ABSTRACT FROM AUTHOR]

Highlights: [•] We present a physically-based theoretical model of a fractal porous medium. [•] The model describes porosity, permeability, saturation, and diffusion coefficient. [•] The model calculates the evolution of these properties during rock dissolution. [•] Under simplifying conditions the expressions are equivalent to empirical relations. [ABSTRACT FROM AUTHOR]

To study the dynamic characteristics of joint surfaces from the perspective of combination of macroscale and microscale, first of all, a fractal model is established for the contact stiffness of the joint surface with the friction factor considered. Moreover, as an instance study, the substructures and their joint surface of a composite beam are reconstructed as a solid- generalized clearance-solid system. Thus, the joint surface is regarded as the generalized clearance, and its material constants are obtained by making equal of the fractal model of the contact stiffness and the strain energy of the material. The finite element analysis of the composite beam is conducted based on the derived material constants and the modal test is conducted as comparison. The comparison results show the validity of the fractal model of the contact stiffness and the rightness of equivalence method. [ABSTRACT FROM AUTHOR]

Tight sandstone has relatively low permeability, with various mineral pores. Hemiwicking on micro-nano pore walls is special, which will finally influence the imbibition behavior. Commonly, in traditional strongly water-wet-matrix-based imbibition model ignored the important influence of hemiwicking on imbibition process. In this work, intermingled fractal method is introduced to represent the tight sandstone based on the experiment data. Then a novel imbibition model is built considering hemiwicking, main meniscus imbibition and dynamic wetting in matrix. The model is verified by experiment data. Finally, the mechanisms of hemiwicking is discussed. It shows that hemiwicking is very important when investigating the special imbibition behavior in tight sandstone. This work provides a novel revised imbibition model for gas-liquid spontaneous imbibition, which may be helpful for imbibition analysis within shut-in period after hydraulic fracturing in tight formation in field. • Provided a novel way to investigate the influence of hemiwicking on spontaneous imbibition process in tight matrix. • Provided a new model to analysis the influencing mechanisms of hemiwicking on special imbibition behavior. • Analyzed micro imbibition mechanism based on this model. [ABSTRACT FROM AUTHOR]

Soil water retention curves (SWRCs) can be predicted by fractal models with soil pore fractal dimensions, which can be derived from either particle size distribution (PSD) or image analysis. The PSD curve is first converted to a pore size distribution, and fractal dimensions are then calculated to estimate the water retention function. The current study compares SWRC predicted by conventional PSD to the results of image analysis in three different textural fluvo-aquic soil samples. Images of soil pores were obtained using nondestructive computerized tomography (CT). The Brooks–Corey, Rieu–Sposito, Tyler–Wheatcraft and van Genuchten models were applied to estimate SWRC. The results indicated that image analysis improved the estimated results of the fractal models except for the Rieu–Sposito model, indicating significantly greater quantitative information provided by CT technique compared to the PSD approach. The Brooks–Corey model produced more acceptable results for all three soil samples than the Rieu–Sposito, Tyler–Wheatcraft and van Genuchten models. Thus, the Brooks–Corey model is preferable for accurate prediction of water retention characteristics. [ABSTRACT FROM PUBLISHER]

Abstract: The traditional Richards’ equation implies that the wetting front in unsaturated soil follows Boltzmann scaling, with travel distance growing as the square root of time. This study proposes a fractal Richards’ equation (FRE), replacing the integer-order time derivative of water content by a fractal derivative, using a power law ruler in time. FRE solutions exhibit anomalous non-Boltzmann scaling, attributed to the fractal nature of heterogeneous media. Several applications are presented, fitting the FRE to water content curves from previous literature. [Copyright &y& Elsevier]

Abstract: The protein concentration dependence on the rheological properties of acid-induced gels formed with unheated and heated soy protein-stabilized emulsions (UHSPE and HSPE) was investigated at different acidification temperatures. Pre-heat treatment on soy protein solutions resulted in a higher storage modulus (G′) and a shorter gelation time (t gel) of acid-induced emulsion gels. A maximum in tan δ was observed in the UHSPE gels but no maximum was detected in the HSPE gels. Increasing the acidification temperature decreased the G′ and t gel. The dependence of the G′ on the protein concentration (c) can be scaled with a power law: G′ ∼ c A. The exponent (A) increased with pre-heat treatment and acidification temperature. The experimental data.fitted the fractal scaling model (G′ ∼ φ A) and the simple time- scaling model above very well for the acid-induced soy protein-stabilized HSPE gels with varying oil volume fraction. The large deformation and fracture properties were significantly affected by soy protein concentration, pre-heat treatment, acidification temperature and volume fraction of oil droplets (p < 0.05). [Copyright &y& Elsevier]

In this work, the effects of nanoparticle size, particle volume fraction and pH on the viscosity of silicon dioxide nanocolloidal dispersions are investigated. Both size and pH are found to significantly affect nanocolloid viscosity. Two models are used to study the effect of aggregate structure on the viscosity of the nanocolloidal dispersion. The fractal concept is introduced to describe the irregular and dynamic aggregate structure. The structure of aggregates, which is considered to play an important role in viscosity, is affected by both intermolecular and electrostatic forces. The particle interaction is primarily affected by particle distance and becomes stronger with decreasing particle size and increasing volume fraction. The aggregate structure is also affected by the pH of the solution. Studying the relationship between pH and zeta-potential shows that with the neutralization of charges on the particle surface and decreasing electrical repulsion force, the particle interaction becomes dominated by attractive forces and the aggregates form a more compact structure. [ABSTRACT FROM AUTHOR]

In simulations of light propagation in soft biomedical tissues, the tissue is generally modeled as a turbid medium. In one such model, suspended scatterers are assumed to be homogeneous spheres of size following a fractal size distribution law. In this paper, we examine, within the framework of this model, the accuracy of a well-known approximation known as the anomalous diffraction approximation. The deployment of this approximation allows the tissue scattering coefficient to be expressed in a closed analytic form. It is demonstrated that use of the anomalous diffraction approximation yields reasonably good results for the tissue scattering coefficient, the phase function and the asymmetry parameter. It is also shown that the experimentally observed wavelength dependence of the scattering coefficient follows analytically from the formulas obtained using this approximation. The results are important from the point of view of constructing more realistic tissue models which may include non-spherical scatterers. [ABSTRACT FROM AUTHOR]

Abstract: Flow behavior in porous fibrous media with consideration of electrokinetic phenomena is investigated based on a linearized Poisson–Boltzmann equation and Navier–Stokes equation. An analytical solution of effective permeability of porous fibrous media as functions of porosity, dimensionless local averaging net charge density and dimensionless electric resistance number is derived in this paper. The influences of the electrokinetic phenomena can be measured by the dimensionless electric resistance number, which is proportional to the square of the liquid dielectric constant, the solid surface Zeta potential and inversely proportional to the liquid dynamic viscosity, electric conductivity and the square of the maximum pore radius. The analytical results show that when the dimensionless electric resistance number is small and the porosity is large, the dimensionless total flow rate shows a nearly uniform distribution. When the dimensionless electric resistance number is large, the resistant effects of the electrical double layer (EDL) become so significant that the superficial velocity decreases. The effective permeability of the porous fibrous media decreases correspondingly. Furthermore, the theoretical predicted effective permeability values are compared with experimental data, and good agreement is observed between the two. It shows that the mathematical model for the effective permeability of porous fibrous media with consideration of electrokinetic phenomena is satisfactory. [Copyright &y& Elsevier]

Abstract: The interaction is quite complex between a ground object and an electromagnetic wave transmitted by synthetic aperture radar (SAR). In a ground resolution cell illuminated by a radar beam, there are many chaotic scatterers and the whole scattering echo has the chaotic characteristics which is usually described with the fractal theory, and the fractal dimension can be used to detect the change information for multitemporal SAR images. In order to improve the change detection effect with fractal model, this paper proposes a new multitemporal SAR image change detection algorithm based on the fractal model and wavelet transform (called FMWT algorithm). The FMWT algorithm has two advantages. One is insensitive to speckle noise; the other is that the change detection accuracy is improved, comparing with a general fractal change detection (GFCD) algorithm. Since the FMWT algorithm adopts the two-dimensional discrete stationary wavelet transform (TDDSWT) technique, it can obtain different direction sub-images and avoid down-sampling of the discrete wavelet transform (DWT). In the paper, not only the simulative data test has been carried out, but also the real natural disaster SAR images have been checked. Experimental results verify that the FMWT algorithm is feasible for multitemporal SAR image change detection, it is not sensitive to speckle noise of SAR images, and the performance of it is better than that of the GFCD algorithm. At the same time, the size of a sliding window will bring some affection in counting fractal dimensions. [Copyright &y& Elsevier]

Aiming at the time redundancy in the flat panel display (FPD) imaging process, the paper studied some problems for FPD gray scale controlling based on the fractal theory, dissertates the construction of the space-time mapping topology architecture, the proposition of optimal scanning structure for FPD's gray imaging, and the creation of the fractal theoretic model. Then the logic implementation and system application are presented based on the fractal model of the optimal scan architecture, and the application results achieved target of eliminating time redundancy and increasing the scanning availability. The novel control mode that the fractal scanning IP core described with Verilog language embedded in the FPGA hardware frame can efficiently increase the imaging gray scales and quality in the FPDs scanning controller and speed up the frame frequency of display system. [ABSTRACT FROM AUTHOR]

Fractal geometry theory has proved to be a powerful tool for the analysis of porous media with complicated microstructures. With the assumption that needle-punched nonwoven geotextile has the same porosity and pore size distribution in two and three dimensions, a fractal model was used to analyse the vertical permeability of needle-punched nonwoven geotextiles. The pore tortuosity fractal dimension, area fractal dimension and characteristic parameters of nonwoven geotextiles, such as mass per unit area, thickness, pore size, fibre diameter and density, were all represented in the model. The pore tortuosity fractal dimension and area dimension were determined by the box-counting and Sierpinski-type gasket methods, respectively. Four geotextile samples were selected to verify the validity of the fractal model used in present study and the good agreement between the theoretical and experimental results suggests that the fractal model was highly accurate. [ABSTRACT FROM AUTHOR]

Abstract: The wet agglomeration of durum wheat semolina is an important stage in couscous production which contributes to the final quality of the end products (couscous grains). There is still a lack of studies in investigating the agglomeration mechanisms of durum wheat semolina. The present study aims to investigate the agglomeration mechanisms occurring during the wetting/mixing process of durum wheat semolina. This process implies the mixing of semolina with different quantities of water in low shear mixers at fixed operating speed. The wet agglomeration mechanisms promote significant changes in size and textural parameters that have been investigated. The evolution in the diameter of the agglomerated structures (nuclei, agglomerates and dough pieces) composing the bed bulk, shows a continuous growth process associated to the expansion of their internal structure. Descriptions of the internal and the external structures of these elements are investigated by scanning electron microscopy. The evolution of solid volume fraction is depicted with respect to the water content at both bed bulk scale and agglomerate scale. At the bed bulk scale, a three-stage texturing phenomenon is identified. At the agglomerate scale, the evolution of solid volume fraction can be related to the evolution of the agglomerate size. The relation between the diameter and the solid volume fraction of the agglomerates can be modeled by a power law equation and could thus indicate that the agglomeration mechanism of durum wheat semolina is a fractal formation process. [Copyright &y& Elsevier]

Abstract: This paper developed a mathematical model for the coupled heat and mass transfer in porous media based on the fractal characters of the pore size distribution. According to Darcy’s law and Hagen–Poiseuille’s law for liquid flows, the diffusion coefficient of the liquid water, a function of fractal dimension, is obtained theoretically. The liquid flow affected by the surface tension and the gravity, the water vapor sorption/desorption by fibers, the diffusion of the water vapor and the phase changes are all taken into account in this model. With specification of initial and boundary conditions, distributions of water vapor concentration in void spaces, volume fraction of liquid water, distribution of water molecular content in fibers and temperature changes in porous fibrous media are obtained numerically. Effects of porosity of porous fibrous media on heat and mass transfer are analyzed. The theoretical predictions are compared with experimental data and good agreement is observed between the two, indicating that the fractal model is satisfactory. [ABSTRACT FROM AUTHOR]