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Micromechanics, which can be used to relate the properties of a composite to the properties of individual constituents, is considered a good approach to understanding the fundamental mechanisms behind the behavior of asphalt materials. Compared with the semi-empirical and numerical micromechanical models, analytical micromechanical models do not need calibration factors. In addition, they can provide analytical solutions on the basis of a series of assumptions. Using these models, researchers have separated the effects of different stiffening mechanisms (i.e., the volume-filling reinforcement, the physicochemical reinforcement, and the particle-contact reinforcement) for mastic. However, similar research work has not been conducted for asphalt mixtures and, moreover, the characteristics of the particle-contact reinforcement have not been deeply analyzed by researchers. Therefore, this paper aims to understand the stiffness of asphalt mixture through micromechanics. The focus of this study was on porous asphalt mixture where particle-contact reinforcement plays an important role in its behavior. The stiffening effects of different mechanisms were separated using analytical micromechanical models. The effects of temperature/frequency and the properties of the matrix phase on the stiffening effect of the particle-contact reinforcement were analyzed.

Skid resistance is known to be affected by environmental conditions such as ambient temperature and pavement temperature. Finite element (FE) modeling has been an effective and efficient way to study the effects of temperature on skid resistance. However, existing FE models either are not able to incorporate the pavement surface characteristics or only perform heat transfer analysis per the two-dimensional (2-D) cross-section of the tire, which could lead to inaccurate predictions of skid resistance. Therefore, the aim of the current study was to develop a three-dimensional, coupled thermomechanical tire–pavement interaction model to investigate the variations in skid resistance as a function of ambient temperature and pavement temperature. The advantages and capability of the proposed model were highlighted by comparing the tire temperature profiles predicted by the proposed model and by the existing 2-D staggered model. Parametric studies of various factors that affect skid resistance were carried out. On the basis of the output results, a relationship between skid resistance and different parameters is proposed.

A non-destructive testing method suitable for network-level pavement structural evaluation is the traffic speed deflectometer (TSD) test. However, the analysis of TSD measurements still needs a proper parameter back-calculation procedure, which requires an accurate and efficient forward calculation model. As a first step to solving this issue, a nonlinear spectral element model which can simulate TSD tests of asphalt pavements is developed. The model is used to investigate the characteristics and parameter sensitivity of the response of asphalt pavements caused by the TSD loading. The results indicate that the vertical deflection curve along the direction of movement observed on the asphalt pavement surface is slightly asymmetric, and the maximum deflection appears behind the centre of the loading area. In addition, the slope curve of vertical deflection is highly sensitive to the magnitude of the applied force, the moduli of the base layer and subgrade, and the thicknesses of the asphalt layer and base layer. Furthermore, the slope curve is relatively sensitive to the glassy modulus of the asphalt layer. Because of its good predictive capability and high computational efficiency, the proposed model has the desired characteristics to be used as the computational kernel for parameter back-calculation procedures of TSD measurements.

Grasses have emerged as potential alternative raw materials which can replace wood for pulp and paper products. Various species of grasses have been explored previously for pulp and paper production. This study is aimed to investigate pulp and papermaking characteristics of a grass species namely Cymbopogon winterianus Jowitt which is commonly known as citronella grass. This grass was subjected to proximate chemical characterisation; fibre morphology analysis; soda, soda-AQ (soda-anthraquinone), and kraft pulping; elemental chlorine free bleaching using D0EPD1 (D = ClO2 in acidic medium; EP = alkaline extraction with addition of H2O2; 0 and 1 = initial and final stage) sequence; and evaluation of physical strength properties of paper hand sheets. The pulp and paper hand sheets were also examined through SEM (scanning electron microscope) and FTIR (Fourier-transform infrared) spectroscopy to observe the structural and functional group variations. The proximate chemical analysis of citronella grass was found superior in terms of α-cellulose (38.10%), pentosans (22.30%) and alkali solubility (28.20%) while inferior in terms of ash (8.20%), lignin (25.10%) and alcohol benzene solubility (6.31%) with respect to some other grass species used for pulp and papermaking. Fibre length (0.69–0.74 mm) and fibre width (13.8–15.1 μm) were also comparable to other grass species. Brown pulp characteristics such as screened yield (44.67%), brightness (~24 %ISO) and kappa number (~20) revealed superiority of soda-AQ pulping among all the pulping processes while the kraft pulp exhibited the highest brightness (83.05 %ISO) and intrinsic viscosity (17.6 cP) after D0EPD1 bleaching. Tear index, tensile index and burst index of paper hand sheets obtained from bleaching of soda-AQ and kraft pulps were almost similar but higher to that of bleached soda pulp. The citronella grass was found suitable for producing writing and printing grade paper based on processes and optimised parameters described in this study.

Morphology and anatomy of pulp fibres are very crucial in determining the physical and strength properties of paper sheets prepared from them. This study reports the morphological and anatomical features of bleached soda, soda-AQ (Soda-anthraquinone) and kraft pulp fibres obtained from solid residues left after extraction of essential oil from Citronella grass (Cymbopogon winterianus Jowitt) using hydro-distillation. Their surface morphology and structural properties were also analyzed using SEM (Scanning electron microscope) and FTIR (Fourier transform infrared) spectroscope. The pulps exhibited mean length-weighted length ∼709–736 µm, average fibre width ∼13.5–14.4 µm, average fibre curl 8%, average fines length ∼49–51 µm and average fines area ∼1001–1058 µm. The parenchyma length, parenchyma width, vessels length, vessels width, lumen diameter and cell wall thickness of the bleached soda–AQ pulp were found to be 205.92 µm, 96.62 µm, 515.84 µm, 35.28 µm, 4.45 µm and 4.53 µm respectively. SEM analysis of paper hand sheets revealed a dense network of well bounded fibres within the matrix while FTIR analysis demonstrated presence of characteristic bands of cellulose, lignin and hemicellulose in pulp samples. Comparison of morphological and anatomical features of these pulps with those of other grasses and non-woody raw materials confirmed the suitability of essential oil isolated Citronella grass as potential raw material for pulp and paper industry.

Within the pavement engineering community, open graded mixes (OGM) are regarded as mixes capable of reducing noise and improving wet skid resistance. However, during their design life, these asphalt mixes are known to suffer from a particular distress type known as raveling. This results in a premature failure of a road network. In order to study the propensity of OGM to raveling, homogenization-based approaches are considered to be accessible and effective. One of the most widely accepted homogenization models for asphalt concrete is proposed by Christensen et al. Several studies related to homogenization techniques have been conducted in the past; however, to the best of the authors’ knowledge not a lot of attention has been paid to the study of OGM by means of homogenization models. The other limitation of the Christensen model is that some parameters are difficult to physically understand. Under the above realization, the objective of the paper is twofold: (1) to propose a modification of the Christensen model for OGM; and (2) to verify the modified model’s capability in predicting the mechanical properties of OGM. In general, it was found that once the proposed factor is calibrated for a given OGM by laboratory tests the obtained results are accurate.

The present study investigates the feasibility of synthesis of environmentally benign heterogeneous carbonaceous catalyst and biodiesel production from a single source i.e. Mesua ferrea Linn (MFL) seeds. The study primarily focuses on the optimisation of biodiesel synthesis process considering four parameters viz. reaction time, temperature, catalyst loading and methanol to oil ratio (M/O). The parametric influence on the free fatty acid (FFA) conversion has been studied to evaluate the most significant parameters. The contribution factor and analysis of variance results reveal that temperature is the most significant parameter influencing the FFA conversion followed by reaction time and catalyst content. The optimum conditions observed for maximum FFA conversion of 95.57% were: temperature 55 °C, time 2 h, catalyst content 10 wt% and M/O 6:1. The physico-chemical properties of the produced Mesua ferrea oil methyl ester (MFOME) were analysed following ASTM standard methods and found to be within limit; and compatible with the conventional diesel. Thus, the study suggests that the MFL seeds could be a promising source for the synthesis of an effective heterogeneous catalyst; and eco-friendly energy efficient sustainable fuel through the concept of green chemistry by converting waste into valuable commodity towards mitigation of increased energy demand.

Adsorption characteristics of nitrogen onto granular activated carbon for the wide range of temperature (303–323 K) and pressure (0.2027–2.0265 MPa) have been reported for a single bed pressure swing adsorption refrigeration system. The experimental data were fitted to Langmuir, Dubinin-Astakhov and Dubinin-Radushkevich (D-R) isotherms. The Langmuir and D-R isotherm models were found appropriate in correlating experimental adsorption data with an average relative error of ±2.0541% and ±0.6659% respectively. The isosteric heat of adsorption data were estimated as a function of surface coverage of nitrogen and temperature using D-R isotherm. The heat of adsorption was observed to decrease from 12.65 to 6.98 kJ.mol−1 with an increase in surface concentration at 303 K and it followed the same pattern for other temperatures. It was found that an increase in temperature enhances the magnitude of the heat of adsorption.

In the Netherlands, more than 80% of the highways are surfaced by porous asphalt (PA) mixes. The benefits of using PA mixes include, among others, the reduction of noise and the improvement of skid resistance. However, pavements with PA mixes are known to have a shorter lifetime and higher maintenance costs as compared with traditional dense asphalt mixes. Raveling is one of the most prominent distresses that occur on PA mix pavements. To analyze the raveling distress of a PA mix pavement, the stress and strain fields at the component level are required. Computational models based on finite element methods (FEM), discrete element methods (DEM), or both, can be used to compute local stress and strain fields. However, they require the development of large FEM meshes and large-scale computational facilities. As an alternative, the homogenization technique provides a way to calculate the stress and strain fields at the component level without the need for much computation power. This study aims to propose a new approach to analyze the raveling distress of a PA mix pavement by using the homogenization technique. To demonstrate the application of the proposed approach, a real field-like example was presented. In the real field-like example, the Mori–Tanaka model was used as a homogenization technique. The commonly available pavement analysis tool 3D-MOVE was used to compute the response of the analyzed pavement. In general, it was concluded that the homogenization technique could be a reliable and effective way to analyze the raveling distress of a PA mix pavement.

Asphalt mixtures with high porosities (known as porous asphalt (PA) mixes) are becoming a popular choice among road authorities as it provides better skid resistance while also reducing tire-pavement noises. Towards the design and manufacture of PA mix pavement, the evaluation of the mechanical properties of PA mixes is of great importance. To predict the mechanical properties of PA mixes, micromechanical models have been considered as an effective tool. In most research studies, continuum-based micromechanical models, i.e. the Self-consistent model, the Mori-Tanaka model, etc. are widely used to predict the stiffness of asphalt mixtures. However, the limitation of these models is that they cannot describe the characteristics of individual particles and thus they cannot provide accurate predictions. On the other hand, the discrete-based micromechanical model (DBMM) which simulates a granular material as an assembly of bonded particles seems to be a promising alternative. Limited research studies have focused on studying the utilization and the applicability of this model for asphalt mixes. Therefore, this paper aims to propose a framework to use DBMM and to evaluate its performance in estimating a PA mix’s stiffness. Based on the obtained results, both the merits and limitations of this model were highlighted.

Graphical abstract, The present investigation highlights the feasibility of a polymer grafting process to enhance the durability and flame retardancy of rice straw towards application as a low cost roofing material. The success of this grafting methodology was perceived to depend upon a bi-step pre-treatment process encompassing delignification and inorganic salts dispersion. Subsequently free radical polymer grafting of acrylonitrile onto rice straw was implemented by immersion mechanism initiated by oxalic acid-potassium permanganate initiator. The percentage of grafting, limiting oxygen index (LOI), biodegradability of the grafted rice straw and grafting yield percentage was estimated to be 57%, 27%, 0.02% and 136.67%, respectively. The weight loss of polymer grafted rice straw implied its less biodegradability over raw straw. Thus, the process of grafting contrived in the present analysis can be a promising and reliable technique for the efficient utilization of rice straw as an inexpensive roofing element through the augmentation of its durability and flame retardancy.

Safe runway operations are an important consideration and challenge for airport authorities. Investigations have shown that runway friction is greatly reduced during wet weather operations. Any traction failure during high-speed landing and take off of an aircraft could lead to accidents and loss of human life. In practice, runway friction is estimated with a ground vehicle, such as continuous friction measuring equipment equipped with a Pavement International Association of Road Congress (PIARC) tire. Recommendations for safe runway friction are based on statistical correlations between such devices and aircraft tires. However, such correlations do not incorporate the variability of the field conditions to the test condition. This paper presents an approach that uses a three-dimensional finite element (FE) model capable of simulating a rolling aircraft tire at any given operating conditions. The highlight of the approach is the consideration of FE meshes of asphalt surfaces rather than artificial surfaces. The model was used to determine the effect of aircraft tire operating conditions on runway friction. The trends of results predicted by the model agree with the previous experimental studies on aircraft tires. It was also found that the computed wet friction of a PIARC tire and an aircraft tire are different, particularly for the extreme operating conditions of tire inflation pressure and water depth. This result indicates that an intrinsic variability exists between the friction coefficients of an aircraft tire and a PIARC tire.

Biochar fuel (CH0.50O0.19N0.06) was prepared from Leucaena leucocephala bark (CH2.80O0.53N0.03) through the slow pyrolysis process adopting design of experiments technique. Modelling and optimization of the slow pyrolysis process was respectively carried out implementing five level central composite design and numerical technique under response surface methodology. Pyrolysis temperature and time were taken as independent parameters while biochar fuel yield, bulk density, higher heating value, energy density and energy yield were chosen as dependent parameters. The optimal pyrolysis temperature and time were estimated to be 367.47 °C and 135.38 min respectively. These optimum values of temperature and time gave biochar yield 47.29%, bulk density 319.73 kg/m3, higher heating value 23.30 MJ/kg, energy density 1.21, and energy yield 56.55%. The developed quadratic models were checked using ANOVA (analysis of variance) technique for their validity and degree of fitness. The high values of ‘Adequate precision’,R2 and its negligible difference with ‘AdjustedR2’ as well as ‘PredictedR2’ for each model indicated that the fitted empirical models can be used for prediction with reasonable precision. The quadratic models revealed strong interaction between pyrolysis temperature and time towards preparation of biochar fuel. It was further observed that desirability of pyrolysis temperature (0.91) is more than pyrolysis time (0.63). Comparison of Van Krevelen diagram of present biochar fuel with several other biochar fuels and coals showed that prepared biochar has better fuel properties in comparison to raw bark.

A state-of-the-art review of key parameters that influence measurement and modeling of skid resistance of asphalt pavements is provided. Tire-pavement interaction/friction is discussed and the current harmonization method of friction measurements questioned. The latest developments on pavement surface texture measurement and characterization are highlighted. A critical review of aggregate properties affecting friction, the frictional properties of asphalt mixtures and the influence of environmental factors on skid resistance is presented. An overview of modeling efforts entailing different aspects of tire-pavement friction is also presented. The frictional performance of asphalt pavements largely depends on the type and quality of coarse aggregates used. The different hot mix asphalt (HMA) classifications generally have similar microtextures. Their frictional performance follows the same order as their macrotextures. There is need for experimentally-validated skid resistance prediction models, especially for warm surfaces. Such models should account for tire and pavement surface texture characteristics, and the influence of environmental factors. Some other research needs are also identified.

The mechanical properties of asphalt mixture are always required for the evaluation of the durability of pavements. In order to obtain these properties without conducting expensive laboratory tests and using calibrated empirical models, research studies have been carried out to develop micromechanics-based models. Continuum-based micromechanical models (CBMM), which are developed based on continuum mechanics, have increasingly been utilized to estimate the mechanical properties of asphalt materials based on the fundamental properties of individual constituents. These analytical models are expected to provide reliable predictions without the need for extensive computational facilities. Although the utilization of CBMM has been presented by several past studies, most of the studies do not provide a concise and critical review of these models. Therefore, in this paper, a complete review of CBMM was presented. Commonly used CBMM were introduced in detail and their advantages and disadvantages were discussed and compared. Comprehensive summaries and critical discussions about their current utilization and limitations for predicting the mechanical properties of asphalt materials were given. Further modifications and new development for addressing the limitations were extensively described and discussed. In the end, research challenges were highlighted and future recommendations from different perspectives were proposed.

Within the pavement engineering community, porous asphalt (PA) mixes are regarded as mixes capable of reducing noise and improving wet skid resistance. However, these mixes are likely to have the distress of ravelling. In order to analyse the propensity of a given PA mix for ravelling, the homogenisation technique can be considered as an attractive method. Along the line of the homogenisation technique, micromechanical models have been used to predict the stiffness of asphalt mixes. However, it was found that the predicted results were not in good agreement with the experimental values due to the fact that the stiffness of interacted aggregates was not accurately accounted in the models. To deal with this issue, it is important for researchers to study the stiffness of the interacted aggregates network and its role in the behaviour of a given mix. Based on this realisation, this paper provided a methodology to estimate the stiffness of the stone-on-stone skeleton and its role in the overall response of PA mixes. The results showed that the predicted stiffness of the stone-on-stone skeleton is dependent on the loading frequency/temperature and the compaction effort. The frequency response of the stone-on-stone skeleton is similar to that of the mix.

In order to design high-performance roadways, a robust tool which can compute the structural response caused by moving vehicles is necessary. Therefore, this paper proposes a spectral element method-based model to accurately and effectively predict the 3D dynamic response of layered systems under a moving load. A layer spectral element and a semi-infinite spectral element are developed to respectively model a layer and a half-space, and the combinations of these two elements can simulate layered systems. The detailed mathematical derivation and numerical validation of the proposed model are included. Additionally, this model is used to investigate the dynamic characteristics of a pavement structure under a moving harmonic rectangular load. The results show that the proposed model can accurately predict the dynamic response of layered systems caused by a moving load. It is also found that the vertical displacement amplitude curves of surface points caused by a moving harmonic load are asymmetric along the moving direction, and this property is more dominant at higher velocities. In addition, the amplitudes of these vertical displacements are smaller if the loading frequency is higher or the loss factor is bigger. Finally, the loading area and Poisson's ratio only have effect on the displacement amplitudes of points in the close vicinity of the loading area. The proposed model is beneficial to the development of engineering methods for pavement design and is a promising parameter back-calculation engine for pavement quality evaluation.

This work presents the laboratory study conducted on fly ash and rice husk ash as soil stabilizers. Using these stabilizers, the deformation behaviors of subgrade soil-mixtures under repeated triaxial loading was conducted. Resilient strain, permanent strain and resilient modulus were ascertained at different deviator stress level and confining pressures at constant moisture content. Admixing of fly ash and rice husk ash reduces the maximum dry density but increase the water demands. The variations of elastic deformation and resilient modulus were significantly influenced by fly ash and rice husk ash contents. Better performances were observed for admixed soil irrespective of number of load applications. The results obtained from the laboratory confirm the potential use of subgrade soil admixed with fly ash and rice husk ash with respect to the permanent deformation.

Porous asphalt concrete (PAC) course is best known for its noise reduction and improved wet skid resistance characteristics. Nevertheless, the use of PAC is associated with reduced lifetimes and high maintenance costs, mainly owing to various distress mechanisms such as raveling. Therefore, it is necessary to have a better understanding of the stress states associated at the micromechanical level, that is, at the mastic–aggregate interfacial zone and the mastic itself. For this purpose, it is necessary to develop micromechanical finite element (FE) models that are composed of realistic asphalt mix meshes with different phases that are subjected to rolling wheel loads. A framework is presented to develop a three-dimensional FE model capable of simulating a rolling wide-base truck tire over an asphalt pavement surface. From results of FE simulations, the stress states at the mastic and mastic–aggregate interfacial layer were studied. For the analyzed surface of the PAC mix, it was observed that the mastic phase registered high stress states compared with the mastic–aggregate interfacial phase, suggesting that the sample may experience a cohesive failure in the long run. The developed methodology also provides a tool to analyze the influence of tire operating conditions such as tire inflation pressures and loads on the stress states of asphalt mixes. Finally, the micromechanical stress response of PAC mix was compared with that of other conventional asphalt mix designs, and it was found that the magnitude of stresses developed in the mastic of PAC are higher compared with the conventional asphalt mix designs.

Road traffic is a major source of noise pollution. Road authorities and pavement researchers have been trying to reduce this noise pollution by laying quieter pavement surfaces. Poroelastic road surfaces (PERS) have been found to be the most effective solution because they are very porous and elastic in nature compared with conventional dense asphalt surfaces. However, the structural performance of PERS pavement under heavy traffic loads is still unknown. The aim of this study was to determine the critical stresses experienced by PERS pavement under heavy loads applied by a wide-base truck tire. For this purpose, finite element (FE) simulations of a wide-base truck tire rolling over a PERS pavement system were performed for various material properties of PERS and adhesive layers, speeds, tire loads, and inflation pressures. From the FE model results, the critical stress envelopes were constructed by using the concept of stress invariants. Stress invariants represent normal and shear stresses that might cause the PERS layer to fail under the critical combination of material, loading, and operating variables and therefore act as design indicators. The FE results showed that the higher contact pressures and the lower material stiffness resulted in higher stress invariants. It was also determined that the stiffness of the adhesive layer influenced the response of the PERS layer. The current study demonstrated a robust methodology for assessing the performance of a thin PERS layer pavement system under rolling–truck tire operating conditions.

The physical properties and performance of hot mix asphalt are governed by the properties of the aggregate, properties of the asphalt binder and asphalt–aggregate interactions. The study is aimed to compare the behaviour of bitumen containing various type of modifiers [styrene-butadiene-styrene (SBS) and ethylene-vinyl-acetate (EVA)] and aggregates (acidic and basic characters) for preparing hot mix asphalt on permanent deformation. Rutting and static creep tests were performed on various mixes to evaluate permanent deformation. Dynamic shear rheometer was used to determine the rheological properties and hence rutting parameter (G*/Sinδ). The results indicate that polymer modification increased rutting resistance. Moreover, samples prepared with EVA are more resistant to deformation compared to those prepared with SBS. Mixes consisting of quartzite aggregate are likely to deform more compared to marble mixes, both for modified and unmodified bituminous mixes, but the recovery of quartzite mixes on removal...

Pressure swing adsorption of nitrogen onto granular activated carbon in the single-bed adsorber–desorber chamber has been studied at six different pressures 6–18 kgf/cm2 to evaluate their performance as an alternative refrigeration technique. Refrigerating effect showed a linear rise with an increase in the operating pressure. However, the heat of adsorption and COP exhibited initial rise with the increasing operating pressure but decreased later after reaching a maximum value. The COP initially increases with operating pressures however, with the further rise of operating pressure it steadily decreased. The highest average refrigeration, maximum heat of adsorption and optimum coefficient of performance was evaluated to be 415.38 W at 18 kgf/cm2, 92756.35 J at 15 kgf/cm2 and 1.32 at 12 kgf/cm2, respectively. The system successfully produced chilled water at 1.7 °C from ambient water at 28.2 °C.

ZOAB (Zeer Open Asphalt Beton) is the most widely used asphalt mixture in the Netherlands. As a type of open asphalt mixture, it is known to suffer from raveling distress. In order to analyze the propensity of raveling, micromechanical models are considered effective. However, most of the research work about micromechanical models has focused on dense asphalt mixture and the application of these models on ZOAB mixes has not been paid adequate attention. Therefore, in this research study, the performance of various micromechanical models for predicting mechanical properties of ZOAB was evaluated. The predicted results were compared with the measured values from a dynamic uniaxial compression test. The analysis results showed that none of the applied micromechanical models could obtain acceptable predicted results of the dynamic Young’s modulus and phase angle of ZOAB. On one hand, the Dilute model, the Mori-Tanaka model, the generalized self-consistent model and the Lielens’ model provided lower values of dynamic Young’s modulus and higher values of phase angle, whereas, for the self-consistent model, the predicted results of dynamic Young’s modulus were higher, and the values of phase angle were lower. On the other hand, the shapes of the predicted master curves of both dynamic modulus and phase angle of ZOAB could not match well with the experimental results. The further research on the differential scheme method showed that at lower frequencies the predicted mechanical properties of ZOAB mixes by the applied micromechanical models could not be improved even by following this scheme.

Failure behavior of asphalt mixture is the process of local deformation accumulation, therefore, local deformation investigation is the base work of failure behavior. Digital image correlation (DIC) method is an optical method which can calculate the local deformation in the failure process. This paper aims to evaluate the precision, select the optimal test parameters for DIC deformation measurement based on natural speckle image, and investigate the local deformation characteristic in the failure process for different mixtures. The results show the image quality of AC with smaller normal maximum aggregate size (NMAS) is better for DIC deformation calculation, the relative deviation of virtual translation and shear test can satisfy the precision requirement, the optimal subset size is 31. Based on the strain distribution, the optimal local deformation measure length for indirect tensile test is set as 50 mm, the critical steady strain is proposed based on R2 obtained by the least squares fitting method, according to local deformation characteristic, the results show SMA can bear more deformation before unstable deformation stage and failure.

A three-layered feed-forward artificial neural network (ANN) model has been designed to predict the adsorption efficiency and adsorption capacity for the adsorptive removal of chromium (VI) from synthetic wastewater. The adsorbent dose, wastewater pH, initial pollutant concentration and contact time were used to develop the network. The data used to train and test the model were obtained from several batch experiments. Various algorithms and transfer functions for hidden layer were tested to find the most reliable network. Broyden–Fletcher–Goldfarb–Shanno (BFGS) quasi-Newton backpropagation algorithm gave the most satisfactory results for adsorption efficiency. Resilient and BFGS quasi-Newton backpropagation were the most suitable algorithm for adsorption capacity. The best combination of training algorithm and transfer function for adsorption efficiency was found to be trainrp and poslin, while poslin produced simulated results within 10% deviation for adsorption capacity. Eight to eleven neurons...

Stopping distance includes driver thinking distance and braking distance. Braking distance is one of the basic standards for road design and maintenance practices. Adequate tire–pavement skid resistance plays a significant role in reducing braking distance and consequently enhancing road safety. With technology such as the antilock braking system, the friction force is maximized by applying the brakes repeatedly, in an on-and-off pattern, such that the braking distance is shortened. Several studies have shown the effect that some parameters, such as water film thickness, tire inflation pressure, and wheel load, have on braking distance. Less discussed is the effect of slip ratio, temperature, and pavement surface characteristics. Measuring the braking distance in the field is energy-consuming and time-consuming, and there are uncertainties in the environmental conditions as well. General approaches to calculating braking distance are based on basic mechanics principles. To the authors’ knowledge, a model that can simulate the whole braking process is not available. The presented study proposes a way to predict braking distance by means of finite element modeling only. A model that can include the effect of parameters such as temperature, slip ratio, and pavement surface characteristics on the braking distance is introduced.

The surface texture of the pavement plays a very important role in driving the frictional properties at the tire rubber-pavement interface. Particularly, the hysteretic friction due to viscoelastic deformations of rubber depends mainly on the pavement surface texture. In the present paper, the effect of micromechanical pavement surface morphology on rubber block friction was brought in by comparing the friction results for three different asphalt mix morphological surfaces, named stone mastic asphalt (SMA), ultra-thin surfacing (UTS) and porous asphalt (PA). The asphalt surface morphologies of these mixes were captured by using an X-ray tomographer, from which the resulting images micromechanical finite element (FE) meshes for SMA, UTS and PA pavements were developed by means of the SimpleWare software. In the FE model, the rubber and asphalt binder were modeled as viscoelastic (VE) materials and the formulation was given in the large deformation framework. FE simulations were then carried out by using contact algorithm between rubber and the road surface. It was observed that the rubber friction inversely varies with the sliding speed and positively varies with the pressure for all the pavement morphological and stiffness conditions. Furthermore, it was observed that the highly porous pavement surface results in large dissipation of energy, hence, large rubber friction which shows that the mix characteristics of pavements have a significant effect on rubber friction.