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• The influence of non-linear soil properties on critical speed in railway lines is investigated for both slab and ballasted tracks. • Two models are used: a 3D FEM approach, and a novel dispersion curve technique. • The influence of the Plastic Index (PI), the soft soil thickness and train load magnitude are assessed. • The soil non-linear behaviour plays a very important role in ballasted tracks, while on slab tracks the influence is not so expressive. • For ballasted tracks, the relationship between the critical speed and shallow upper soil layer thickness can be weak. The design of high-speed railway lines involves geotechnical challenges, one of which is the risk of dynamic track amplification, for example on track sections where the train speed approaches the track-ground critical speed. In these cases, soil strains increase significantly with an increase in train speed, far exceeding the limits of linear elastic behaviour. This can result in a non-linear reduction of soil stiffness. To better understand this relationship, this paper studies the influence of soil non-linearity on the critical speed of concrete slab and ballasted tracks. To perform an in-depth analysis into non-linear critical speed, two models are used: a 3D FEM approach, and a novel dispersion curve technique. Using the models, the effect of soil plasticity on non-linearity is studied, with different ranges of plasticity found to play an important role. Secondly, the influence of soil thickness and loading magnitude are evaluated. It is shown that ballasted tracks are deeply affected by the non-linear soil behaviour, compared to a concrete slab track. Further, it is shown that for the ballasted tracks, the relationship between the critical speed and shallow upper soil layer thickness can be weak. [ABSTRACT FROM AUTHOR]

The studies related the deposition of the spoil piles, which is obtained by mining excavation in open pit mines, and the reclamation of the depositional areas are very important to overcome the induced destruction of the nature. A significant part of these studies is the investigation of the slope stability of spoil piles. In this study, slope stability analyses have been performed for the spoil piles of the Sekkö y open pit mine in Muğ la-Milas. Experimental results indicated that the spoil material includes nearly equal amount of coarse and fine grains, and has low plasticity index. With the purpose of determining the mobilized shear strength parameters at the time of failure, back analyses have been performed for the spoil pile failures observed in the study area. The comparison of data from the back analyses and the laboratory tests reveals that residual strength values were mobilized at the time of failure for the spoil material. By considering the data obtained and the field observations, one and multi-bench economical and safe slope design analyses have been performed for the spoil piles in the study area in accordance with the rules in the regulation on reclamation of the sites destructed by mining applications. According to the results of the analyses for 10, 20 and 30 m slope heights, 20-40° and 19° overall slope angle values were determined for one and multi-bench slopes, respectively. [ABSTRACT FROM AUTHOR]

A theoretical study of elastic-plastic contact of rough surfaces is considered based on n-point asperity model and accurate finite element analysis (FEA) of elastic-plastic deformation of single asperity contact. Kogut and Etsion (2003) formulations for intermediate elastic-plastic regimes of deformation are integrated with pure elastic model of Greenwood and Williamson (1966) and pure plastic model of Abbott and Firestone (1933) to obtain contact load and area in rough surface contact. Using practical values of material properties and surface roughness parameters, the load–separation and area-separation behaviour of surfaces are studied. [ABSTRACT FROM AUTHOR]

In this article, a study of elastic–plastic contact of statistical rough surfaces is presented. The contact behaviors of a single asperity with deformable substrate are studied by finite element method. The influences of material properties and substrate deformation on the single asperity contact behaviors are investigated. An elastic–plastic contact model of rough surfaces is established based on the proposed single asperity contact model and statistical rough surface contact model. The surface topography plasticity index and material plasticity index are defined to indicate the influences of surface topography and material properties on the contact behaviors of rough surfaces. Comparisons with some exiting models and finite element results show that the proposed formulations can model the single asperity contact behaviors well for a wide interference range. The rough surface contact model in this work is consistent with some existing models for small plasticity indices, and it is slightly different from the existing models for large plasticity indices. The increase of surface topography plasticity index and material plasticity index would result in larger contact area and contact load for given separations. [ABSTRACT FROM PUBLISHER]

A series of stress-controlled and undrained cyclic triaxial tests were conducted on mine tailings to investigate their dynamic properties and the influence of clay mineral types on their cyclic strength. The tests were performed on specimens with a cyclic shear stress ratio ranging from 0.10 to 0.40 under the same confining pressure. It was observed that the axial strain, excess pore water pressure, and damping ratio increase with the number of loading cycles, whereas the effective stress and dynamic shear modulus decrease with increasing number of loading cycles. The effect of void ratio on shear modulus was significant in the small strain range, and thereafter, the effect was not significant among the tailings studied. It was also observed that the cyclic strength of the tailings varies with the type of dominant clay mineral present in them. Tailings containing montmorillonite showed higher resistance to cyclic loading than those containing kaolinite. [ABSTRACT FROM AUTHOR]

Abstract: Coatings of hydroxyapatite (HAP) nanorods onto titanium surfaces were synthesized with the aim to improve coatings’ mechanical properties and adhesion to the substrate. The coatings are consisting of HAP nanorods synthesized in the presence of a cationic fourth generation diaminobutane poly(propylene imine) dendrimer (DAB) bearing 32 amine end groups employing varying calcium: dendrimer ratios and varying hydrothermal treatments. The quality, surface morphology and structure of the coatings were characterized with X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and energy dispersive microanalysis. Wear resistance and adhesion properties of the coatings onto titanium substrates were studied through nanoindentation analysis. The experimental conditions, namely the calcium: dendrimer molar ratio and the hydrothermal treatment temperature were carefully selected; thus, it was possible to produce coatings of high hardness and elastic modulus values (ranging between 1–4.5GPa and 40–150GPa, respectively) and/or high wear resistance and plastic deformation values. [Copyright &y& Elsevier]

Abstract: Stabilization of soils is an effective method for improvement of soil properties and the pavement system performance. Plasticity Index is one of the important properties of soil to determine the behavior of soil in presence of water. The poorest soil among all is Black Cotton Soil (BC Soil). In Rajkot area this BC Soil is spread over southern part of District. Rich proportion of montmorillonite is found in BC Soil from mineralogical analysis. High percentage of montomorillonite renders high degree of expansiveness. These property results cracks in soil without any warning. These cracks have sometimes extent severe limit like 1/2 “to 12” deep. Use of this type of land may suffer severe damage to the construction with the change in atmospheric conditions. In this paper, BC Soil was tested using three different stabilizing agents - 1.Cement waste dust collected from the cement plant 2. Cement Dust + Lime Powder 3. Lime Powder. The cement waste dust was found best agent as a stabilizer to improve the Atterbergs’ Limit and hence Plasticity Index of BC Soil as well as the compressive strength of the same. Laboratory tests were performed with different percentages of three stages, each of them ranging from 1% to 9%. The behavior of BC Soil of Rajkot region was improved with stage no. 1, the percentage of Cement dust 7% of Cement dust in BC Soil is looking to be the appropriate mixing. Also in second stage, improvement is shown at 8% of combination of cement dust and Lime powder. Third stage was observed a best suited result at 9% of Lime powder in BC Soil. The results, thus obtained in laboratory under standard conditions provide satisfactory reason to use the Cement dust as a stabilizing agent for the purpose to improve Plasticity Index of BC Soil compare to other two combinations. After satisfying result of Plasticity Index, Cylindrical Samples of BC Soil with all three combinations were prepared to check the compressive strength of stabilized soil. Moisture content taken was the optimum percentage of plastic limit in each combination. The cylinders of size 50mm in diameter and 60mm height were tested after 3, 5, 7, 14, 21, 28 days. The relations for these periods were established among the use of all three different agents. Compressive strength of Cement dust stabilized BC Soil found more reliable. [Copyright &y& Elsevier]

Abstract: We studied the phenotypic plasticity of physiological and growth traits in two distinct clones of common reed (Phragmites australis (Cav.) Trin. Ex Steud.). Replicates of a clone from Denmark (DK clone) belonging to the European temperate P. australis and a clone from Algeria (ALG clone) belonging to the African-Mediterranean gene pool of P. australis were grown in phytotrons in a factorial block design at 15°C or 25°C daytime temperature and high or low fertilization level. Plant growth, tissue nutrient concentrations, photosynthetic pigments and photosynthetic characteristics were measured. Phenotypic plasticity was quantified for the measured traits as plasticity indices in relation to temperature and fertilization. The plasticity index was calculated as the difference between the maximum and the minimum mean value divided by the maximum mean value of a parameter within a treatment. The functional significance of the plasticity and its contribution to plant fitness was assessed by correlation of the plant traits to plant biomass as a proxy for fitness. The DK clone responded much more to temperature than the ALG clone, which responded more to fertilization, and both clones responded to high fertilization with lower allocation of biomass to roots and rhizomes. The ALG clone had a higher nutrient demand due to its large and fast biomass development. Hence, for most traits, the calculated plasticity indices for fertilization were highest for the ALG clone, especially within photosynthetic parameters and pigments, and the plasticity indices for temperature were highest for the DK clone, especially within growth parameters. In both clones, photosynthetic pigments, biomass allocation to leaf blades and rhizomes, the shoot:root ratio as well as leaf and shoot production rates were highly correlated to fitness. These traits also had a relatively high degree of plasticity, indicating a functional significance of plasticity, but several traits that showed high plasticity did not correlate with fitness (e.g. P max). We conclude that the responses of the two contrasting P. australis genotypes to temperature and fertilization are genetically determined and related to the climatic conditions at the site of their origin. Although phenotypic plasticity per se is not a precondition for plant fitness, the genetically determined differences in the degree of phenotypic plasticity of distinct P. australis genotypes to temperature and nutrient availability affect fitness and may influence how the genotypes will respond to global environmental change. [Copyright &y& Elsevier]

Improvement and stabilization of soils are widely used as an alternative to substitute the lacking of suitable material on site. Soils may be stabilized to increase strength and durability or to prevent erosion and dust generation. The use of nontraditional chemical stabilizers in soil improvement is growing daily. A new stabilizing agent was developed to improve the mechanical performance and applicability of clayey soils. In this study a laboratory experiment is conducted to evaluate the effects of plasticity index and waterborne polymer on the Unconfined Compression Strength (UCS) of clayey soils. The laboratory tests include sieve analysis, hydrometer, Atterberg limits, modified compaction and unconfined compression tests. Three clayey soils with different plasticity indexes were mixed with various amounts of polymer (2, 3, 4 and 5%) and compacted at the optimum water content and maximum dry density. The unstabilized and stabilized samples were subjected to unconfined compression tests to determine their strength at different curing times. The results of the tests indicated that the waterborne polymer significantly improved the strength behavior of unsaturated clayey soils. Also, an increase in plasticity index causes a reduction in unconfined compression strength. [ABSTRACT FROM AUTHOR]

Abstract: The physical and mechanical properties of fine-grained soils, especially clay minerals, are greatly influenced by the specific surface area. Many investigations were conducted to examine the relationships between the specific surface area of soils and their engineering properties. We have previously shown that there were relationships between the external specific surface area of the soils and their Atterberg limits. These relationships, based on the test results from soils prepared artificially in the laboratory, were presented in a general analytical form. As Atterberg limits are the most distinctive and the easiest property of soils to measure, it would be a very convenient basis for estimating the specific surface area. The aim of these investigations was to identify the possibility of practical applications. Five heterogeneous soil samples were selected, the liquid and plastic limits were measured as well as the grain size distribution, the mineral and chemical compositions and the specific surface area. The external specific surface area of the soils measured by the BET method ranged between 17m2/g and 54m2/g. The estimated values using Atterberg limits were slightly higher. The calculated and measured values of the external specific surface area differed by 0.6–6m2/g. [Copyright &y& Elsevier]

Abstract: Morphological, anatomical and physiological summer and winter leaf traits of Cistus incanus subsp. incanus, C. salvifolius and C. monspeliensis growing at the Botanical garden of Rome were analyzed. With regard to differences between summer and winter leaves of the considered species, leaf thickness (L) was 21% higher in summer than in winter leaves (mean of the considered species) and this increase was mostly the result of the increased palisade parenchyma thickness over the spongy parenchyma one (24 and 16% higher in summer than in winter leaves, respectively). Leaf mass area (LMA) and leaf tissue density (LTD) were 38% and 17% higher in summer than in winter leaves, respectively (mean of the considered species). The photosynthetic rate (P N), stomatal conductance (g s) and chlorophyll content (Chl) of summer leaves were 54%, 17% and 14% lower, respectively, than in winter leaves. C. monspeliensis summer leaves had the highest LMA, LTD, adaxial cuticle thickness (14.6±1.8mgcm−2, 1091±94mgcm−3, and 5.8±1.7μm, respectively) and the lowest mesophyll intercellular spaces (f ias 38±3%). Moreover, C. monspeliensis had the highest P N in summer (2.6±0.1μmolm−2 s−1) and C. incanus the highest P N and WUE (84% and 59% higher than the other species) in the favorable period, associated to a higher f ias (42±2%). C. salvifolius had the highest P N (54% higher than the other species) in winter. The plasticity index could allow a better interpretation of the habitat preference of the considered species. The physiological plasticity (PIp =0.39, mean value of the considered species) was higher than the morphological (PIm =0.22, mean value) and anatomical (PIa =0.13, mean value) plasticity. Moreover, among the considered species, C. salvifolius and C. incanus are characterized by a larger PIa (0.14, mean value) which seems to be correlated with their wider ecological distribution and the more favorable conditions of the environments where they naturally occur. The highest PIm (0.29) of C. monspeliensis indicates that it can play a high adaptive role in highly stressed environments, like fire degraded Mediterranean areas in which it occurs. [Copyright &y& Elsevier]

Abstract: Shear strength parameters such as friction angle and cohesion are of the most important soil''s parameters which are used for design and practice in engineering works. The main aim of this paper is investigation of artificial neural networks (ANNs) and multivariate regression (MR) potential for estimation of soil shear strength parameters. For this reason, two types of ANNs including multilayer perceptron (MLP) and radial basis function (RBF), and MR including multivariate non-linear regression (MNR) as well as multivariate linear regression (MLR), have been used. Five different ANN and MR models comprising various combinations of soil''s physical parameters, i.e.: percentages of passing the No. 200 (≠200), 40 (≠40) and 4 (≠4) sieves, plasticity index (PI), and density (ρ) have been developed to evaluate the effect degrees of these variables on shear strength parameters. In addition to correlation coefficient (r), root mean square error (RMSE), mean absolute error (MAE) and t-test have been also used for evaluation of prediction accuracy on both ANNs and ML methods. The results of this study indicated that MLP–ANN shows better performance rather than RBF–ANN. These results also indicated that the Levenberg–Marquardt learning rule and Sigmoid activation function were found to be appropriate for this problem. Furthermore, MLR shows better performance in prediction of shear strength parameters rather than MNR models. [Copyright &y& Elsevier]

Morphological and physiological traits of Crepis pygmaea L. subsp. pygmaea and Isatis apennina Ten. ex Grande growing at different altitudes in the Gran Sasso Massif (Abruzzo, Italy) were analyzed. The two populations of C. pygmaea and I. apennina growing at the highest altitude ( C and I at 2,310 m a.s.l. and 2,350 m a.s.l., respectively) had a lower leaf mass area (LMA) than the two populations growing at the lowest altitude ( C and I at 2,250 m a.s.l. and 2,310 m a.s.l., respectively). Leaf tissue density (LTD) had the same LMA trend, decreasing 23 and 10% in C. pygmaea and I. apennina, respectively, from the highest to the lowest altitude. C. pygmaea and I. apennina had the highest photosynthetic rates ( P) in July decreasing on an average 17 and 30%, respectively, in August and 50 and 38%, respectively, in September. Leaf respiration ( R) in I and I had the same trend as C and C, showing the highest rates in September. Global warming could drive C. pygmaea and I. apennina toward higher altitudes in the Gran Sasso Massif. Nevertheless, C. pygmaea with the higher plasticity index (PI) both at physiological and at morphological levels (0.50 and 0.35, respectively) might have a competitive advantage over I. apennina over the long term. [ABSTRACT FROM AUTHOR]

Under natural conditions the overlapping of multiple stressors may initiate coordinated ecophysiological responses in Mediterranean species. Seasonal plasticity may enable plants to better cope with adverse environmental conditions and/or resource variability. In this article, we study the seasonal responses of 12 woody species in two sites of differing water availability, in a Mediterranean-type climate. Plants were measured for water potential, photochemical efficiency, photosynthetic pigments and leaf proline content throughout the year. The results revealed that species presented different ecophysiological strategies, even when sharing the same area. In the xerophytic site, some species suffered severe water stress (−12 MPa and F/ F lower than 0.3), while others exhibited optimal values of F/ F and only moderate water stress. All the plants recovered after the first autumn rains. In the hygrophytic site, some sclerophyll species did not exhibit signs of water stress, but did suffer photoinhibition in clear winter days. A plasticity index was calculated to provide an integrated value of species plasticity. In summer, plasticity was higher in the xerophytic site, while in winter it was higher in the hygrophytic site. Ordination analysis of the physiological traits supports the traditional gradient of Mediterranean strategies from drought semideciduous to evergreen sclerophyll species, although spiny legume species formed an independent functional group. The functional responses of species clearly differ among plant communities according to the prevailing site stressors, but no unique pattern emerges. Species combine traits in broader strategies according to previous evolutionary story exhibiting a certain amount of trade among traits, each contributing to alleviate a part of the plant stress. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the behavior of cohesive soil reinforced with a geotextile, 144 unconfined and 72 unconsolidated–undrained (UU) triaxial compression tests were conducted. The moisture content of soil during remolding, relative compaction, soil type, confining pressure, type and number of geotextile layers were all varied so that the behavior of the sample could be examined. The results provide evidence that as the moisture content increases, the peak strength of both the reinforced and unreinforced samples decreases and the axial strain at failure increases. Moreover, with increasing relative compaction the peak strength of the sample and axial strain at failure increases, whereas the peak strength ratio decreases. The peak strength ratio is the ratio of the peak strength of the reinforced samples to that of the unreinforced samples. For soils with low plasticity indices the main cause of the increase in the strength is the increase in the cohesion of the reinforced sample. However, in soils of higher plasticity index, as the number of geotextile layers increases, the internal friction angle of the reinforced samples increases. [Copyright &y& Elsevier]

A model for the contact area and static friction of nominally flat rough surfaces and rough spherical surfaces is presented. The model extends previously published models, which are limited to plasticity index values below 8, to higher plasticity index values by accounting for fully plastically deformed asperities based on finite element results by Jackson and Green [2005, "A Finite Element Study of Elasto-Plastic Hemispherical Contact Against a Rigid Flat," Trans. ASME, J. Tribol., 127, pp. 343-354]. The present model also corrects some deficiencies of the earlier models at very small plasticity index values below 0.5. [ABSTRACT FROM AUTHOR]

Abstract: In soil mechanics, the plasticity of fine-grained soils is expressed using the plasticity index. This represents the difference between the water content at the liquid and plastic limits, which are often collectively referred to as the Atterberg (or consistency) limits. They are of key importance in soil mechanics because they determine, in a simple way, the interaction between the solid and liquid phases in soils, and thus provide the possibility to classify soils into groups with similar mechanical properties. As the Atterberg limits are the most distinctive and the easiest property of fine-grained soils to measure, several researchers have tried to use them to predict various mechanical properties, such as the normalized, undrained shear strength of fine-grained soils. The most widely used expression for predicting this value from the plasticity index was suggested by Skempton. Since then, there have been several studies to examine the validity of his relation. A lot of the data agree with this relation; however, there is an equally large volume of data that contradicts it. The present study shows that the correlation between the normalized undrained shear strength of cohesive soils and the plasticity index really exists, but it is not as simple as was suggested by previous studies. By considering the mineralogical properties of clay minerals and their impact on the quantity and state of water in soils, it was found that there is no uniform criterion to determine the normalized undrained shear strength from the plasticity index for all fine-grained soils. [Copyright &y& Elsevier]

Abstract: The low nutrient availability of the acidic and sandy soils of Galicia (Northwest Spain) is probably the main environmental factor limiting forest primary productivity in the area. These particular edaphic conditions could have imposed selective pressures on maritime pine populations leading to specific local adaptations. We first assessed the nutritional status of 22 young contemporary Pinus pinaster plantations in Northwest Spain, and then analysed the response to fertilization in three family×fertilization trials, and how this response varied across sites and genotypes. Growth of P. pinaster in Northwest Spain appeared to be largely limited by nutrient availability, where most of the plantations showed severe nutrient deficiencies, especially in P and Mg. According to these deficiencies, a strong positive response to nutrient additions was observed in the three trials, with height increments of up to 30% compared with the unfertilized control. However, the response to fertilizers was very variable from site to site, and in some cases did not agree with the foliar nutritional diagnosis. The response to fertilization was also significantly affected by pine genotype, suggesting that the plastic response to nutrient additions within each environment was under genetic control. However, the family response to nutrient availability was not consistent across sites, and no significant differences among families were observed for the RDPI plasticity index – a single index that summarizes the phenotypic change in multiple environments – when analysed across environments. The strong environmental component modulating phenotypic responses to fertilization could impose an important obstacle to evolve specific adaptations to the local edaphic conditions, as well as to artificially select genotypes adapted to different environments and silviculture regimes. [Copyright &y& Elsevier]

Abstract: Hydraulic conductivity is one of the important, basic engineering properties of soils. However, as a soil parameter it is difficult to measure and can be highly variable, necessitating the investigation of a large number of samples. For these reasons several researchers have proposed various indirect methods for predicting the hydraulic conductivity of soils from easily measured and routinely obtainable data. As plasticity is the most distinctive and the easiest property of clays to measure, it would be a very convenient basis for predicting the hydraulic conductivity. This paper focuses on an investigation of the relationship between the hydraulic conductivity of clays and their Atterberg limits. For this purpose five samples of expanding and non-expanding clays were used. The results of laboratory tests showed that the hydraulic conductivity of a clay at a selected void ratio could be adequately determined when the external surface area of the clay grains was considered. The finding that there exists an exactly defined relationship between the Atterberg limits of clays and their external specific surfaces helped us to express the hydraulic conductivity in terms of the void ratio and the plasticity value. [Copyright &y& Elsevier]

Abstract: The main objective of this study was to look into the phenotypic plasticity of the semi-deciduous Mediterranean shrub, Halimium halimifolium. We studied morphological, allocation and physiological traits to determine which characters were more plastic and contribute in a greater extent to the acclimation ability of the species. We present a phenotypic plasticity index for morphological, physiological and allocation traits, which we have applied in the most contrasted plant communities where the species grows naturally. Data published by Díaz Barradas, M.C., García Novo, F. [1987. The vertical structure of Mediterranean scrub in Doñana National Park (SW Spain). Folia Geobotanica Phytotaxonomica 22, 415–433; 1988. Modificación y extinción de la luz a través de la copa en cuatro especies de matorral en el Parque Nacional de Doñana. Monografias Instituto Pirenaico de Ecologia 4, 503–516; 1990. Seasonal changes in canopy structure in two mediterranean dune shrubs. Journal of Vegetation Science 1, 31–40.], Díaz Barradas, M.C., Zunzunegui, M., García Novo, F. [1999a. Autoecological traits of Halimium halimifolium in contrasted habitats under Mediterranean type climate. Folia Geobotanica 34, 189–208.] and Zunzunegui et al. [Zunzunegui, M., Díaz Barradas, M.C., García Novo, F. 1997. Autoecological notes of Halimium halimifolium. Lagascalia 19, 725–736. Sevilla, Spain; Zunzunegui, M., Díaz Barradas, M.C., Fernández Baco, L., García Novo, F. 1999. Seasonal changes in photochemical efficiency in leaves of Halimium halimifolium a Mediterranean semideciduous shrub. Photosynthetica 36, 17–31; Zunzunegui, M., Díaz Barradas, M.C., García Novo, F. 2000. Different phenotypic response of Halimium halimifolium in relation to groundwater availability. Plant Ecology 148, 165–174; Zunzunegui, M., Díaz Barradas, M.C., Aguilar, F., Ain-Lhout, F., Clavijo, A., García Novo, F. 2002. Growth response of Halimium halimifolium at four sites with different soil water availability regimes in two contrasted hydrological cycles. Plant and Soil 247, 271–28.] have been re-appraised and combined with original data. Phenotypic plasticity index showed that the highest plasticity of the species was physiological, and especially for the traits related with water control. This high physiological plasticity appears mainly between seasons (September–November) rather than between sites. Plasticity in allocation traits showed intermediate values between physiological and morphological traits. [Copyright &y& Elsevier]

Abstract: Atomic force microscopy (AFM) indentation technique is used for characterization of mechanical properties of fluorocarbon (CFx) thin films obtained from C4F8 gas by plasma enhanced chemical vapour deposition at low r.f. power (5–30 W) and d.c. bias potential (10–80 V). This particular deposition method renders films with good hydrophobic property and high plastic compliance. Commercially available AFM probes with stiff cantilevers (10–20 N/m) and silicon sharpened tips (tip radius <10 nm) are used for indentations and imaging of the resulted indentation imprints. Force depth curves and imprint characteristics are used for determination of film hardness, elasticity modulus and plasticity index. The measurements show that the decrease of the discharge power results in deposition of films with decreased hardness and stiffness and increased plasticity index. Nanolithography based on AFM indentation is demonstrated on thin films (thickness of 40 nm) with good plastic compliance. [Copyright &y& Elsevier]

This article presents the theoretical basis from which a sampling interval may be meaningfully determined in the surface roughness measurements for engineering tribology applications. Equations are derived that relate the measurement sampling interval to the material properties of the part and the RMS roughness of the surface. The feasibility of the roughness measurements is discussed. The study also reveals some insights into the surface characterization parameters and the quality of surface run-in processes. [ABSTRACT FROM AUTHOR]

This study explores the engineering characteristics of Black cotton soil (BCS) stabilized with natural lime, volcanic ash (VA), and their mixtures. Based on the available literature, the stabilization of VA-BCS is limited. Laboratory tests conducted on stabilized BCS include the Atterbeg limits, the proctor test, the swell percent test, and the California bearing ratio (CBR). The results showed that adding VA and lime greatly improves the engineering characteristics of BCS. BCS stabilized with a mixture of VA and lime showed superior results. Adding 3% lime with 20% VA increased natural CBR values 10.76 times, reduced plasticity by 29%, and reduced swell percent by 88%. Stabilized BCS with 3% lime + 20% VA meets the minimum swell, plasticity, and strength requirements; thus, it can be used as an alternative to cutting and filling. [ABSTRACT FROM AUTHOR]

Atterberg limits are broadly used for engineering and geology purposes as well as in agricultural and environmental applications. Laboratory methods used for their determination are, however, laborious, destructive and tool dependent. The aim of this study was to test the feasibility of using visible near-infrared spectroscopy (vis–NIRS) as a fast and accurate alternative to the conventional measurements of Atterberg limits (LL and PL) and the PI for 229 geographically diverse soil samples originating from 24 countries. Three types of calibration techniques including Partial Least Squares (PLS) regression, Artificial Neural Networks (ANN) and Support Vector Machines (SVM) were applied to the spectral data. The performance of the best vis–NIRS models was validated using 45 independent samples and compared with two existing and one newly developed pedotransfer functions (PTF). The application of SVM yielded marginally better predictive ability than PLS and ANN for all modelled properties. The SVM models estimated LL, PL, and PI with root mean squared error (RMSE) of 7%, 5% and 7%, respectively. The newly developed PTF gave slightly better estimations than the existing ones, with RMSE values of 8%, 6%, and 6%, respectively for LL, PL, and PI. Furthermore, in terms of the sample swelling class, the SVM model correctly classified 31 of the 45 samples, compared to 34 samples for the best PTF. The results indicate a great potential of vis–NIRS for reliable estimates of Atterberg limits for soil samples of large geographical and mineralogical diversity. [ABSTRACT FROM AUTHOR]

Abstract: Silicon carbonitride (Si:C:N) films produced by the remote microwave hydrogen plasma chemical vapor deposition (RP-CVD) using bis(dimethylamino)methylsilane as single-source precursor and hydrogen as an upstream gas for plasma generation, were examined in terms of their physical (density) and mechanical (hardness, elastic modulus, friction coefficient, and “plasticity index”) properties. The effect of substrate temperature (varied in the range of 30–400°C) on the properties of Si:C:N films is presented. A reasonable compositional and structural dependencies of film properties were determined using, respectively, the XPS atomic concentration ratios N/Si and C/Si, as well as the relative integrated intensities of the IR absorption bands from the Sice:glyph name="sbnd" />C bonds (controlled by deposition temperature), evaluated in the first part of this work. In view of their good mechanical properties, Si:C:N films seem to be useful coatings for improving surface mechanics of engineering materials. [Copyright &y& Elsevier]

Abstract: In this study we deal with the problem of normal contact between rough surfaces. A power spectral density of the asperity heights which obeys a power-law within a given range of wavelengths has been considered. Hence, the resolution dependence of the statistical parameters computed according to the random process theory, of the plasticity index and of the contact predictions provided by stochastic and fractal contact models is discussed and emphasized. It is demonstrated that the plasticity index diverges to infinity when the lower cut-off length of the system vanishes, whereas the slope of the real contact area versus normal load curve tends to zero. In this limit case stochastic and fractal approaches predict either a vanishing real contact area or an infinite normal pressure, regardless of the asperity deformation assumptions. On the other hand, when a non-zero lower cut-off length exists, finite contact predictions can be obtained by applying the contact models at that scale length. This possibility is numerically investigated and, comparing contact results of several models, it is shown that the plasticity index plays an important role for the characterization of the interface mechanical response. [Copyright &y& Elsevier]

Abstract: Nayak''s analysis of isotropic surface roughness as a random field has been extended to show that most summits are only mildly ell, the most common ratio of principal summit curvatures being near 2:1. Also from Nayak''s theory, the distribution of the geometric-mean summit curvature with height has been obtained. By using an approximate solution for elliptical Hertzian contacts based on the geometric-mean summit curvature, the full elliptical solution of Bush, Gibson and Thomas can be reproduced more conveniently. Their values for the area of contact are accurately reproduced, and it is argued that the present values for load and contact pressure are more plausible: unlike the original numerical values, the present values converge smoothly to the BGT asymptote . Once again, it is found that elastic contact models can explain the proportionality between contact area and load, although at realistic loads the proportionality is merely very good, not exact. The model shows that a plasticity index (closely related to Mikic''s index) can be used to predict the behaviour of surfaces in contact. [Copyright &y& Elsevier]

Abstract: This paper presents and analyses data obtained from the uniaxial compaction of pure pharmaceutical powders in terms of a number of mechanical properties, and correlates these data to some aspects of fracture mechanics. This includes seven different types of pharmaceutical drugs and excipients: alpha lactose, microcrystalline cellulose (Avicel PH 102), acetylsalicylic acid (Aspirin), dicalcium phosphate, magnesium carbonate, acetaminophen (Paracetamol) and starch. The powders were compacted to various ultimate normal stresses ranging between 25 and 246MPa in an instrumented (force/displacement) single-ended axial compression in cylindrical die with planar punches. The results clearly demonstrate that, to some extent, the toughness of a tablet may be interpreted directly from some mechanical characteristics of its compliance response, i.e., the plastic work and the plasticity index, during the compaction process. [Copyright &y& Elsevier]

In this paper a comparison among several micromechanical contact models is presented. The aim of the research is to provide a degree of confidence about the differences between the predictions of the contact behavior provided by the models. For this purpose some ideal microscopically rough surfaces with self-affine topography have been generated by means of a numerical algorithm. From such surfaces all the parameters needed to characterize them from the statistical viewpoint have been extracted. The predictions provided by the models with increasing normal load for the evolution of the real contact area, the number of contact points and other useful parameters have been outlined with diagrams, clearly showing the existing differences. [Copyright &y& Elsevier]

Site investigations of the soils are considered very important for evaluation of the site conditions, as well as the design and construction for the project built in it. Taihu tunnel is thus far the longest tunnel constructed in the lake in China, with an entire length of over 10 km. However, due to the very insufficient site data obtained for the lacustrine clay in the Taihu lake area, a series of self-boring pressuremeter (SBPM) field tests was therefore carried out. Undrained shear strengths were deduced from the SBPM test, with the results showing generally higher than those obtained from the laboratory tests, which may be attributed to the disturbance to the soil mass during the sampling process. Degradation characteristics of the soil shear modulus (Gs) were mainly investigated, via a thorough comparison between different soil layers, and generally, the shear modulus would cease its decreasing trends and become stable when the shear strain reaches over 1%. Meanwhile, it was found that a linear relationship between the plasticity index and the shear modulus, and between the decay rate of the shear modulus and the plasticity index as well, could be developed. Further statistical analysis over the undrained shear strength and shear modulus distribution of the soils shows that the undrained shear strength of the soils follows a normal distribution, while the shear modulus follows a log-normal distribution. More importantly, the spatial correlation length of the shear modulus is found much smaller than that of the undrained strength. [ABSTRACT FROM AUTHOR]