A study on the texture diversity of the Artisan Ranchero Cheese from Central Mexico

The objective of the present study was to determine the diversity and causative factors in the textural profile of the Artisan Ranchero Cheese (ARC), a popular soft cheese made with raw cow's milk, which is consumed fresh. These factors included climatic conditions, production zone, cheese supplies, cheesemaking procedure and chemical attributes. Texture attributes were determined using texture profile analysis method. The relationship between texture and chemical attributes of the ARC were determined by a Factor Analysis. An Agglomerative Hierarchical Clustering Analysis was used to differentiate the ARC manufactures into groups. Two groups were identified, production zone being the variable which explained the variation in the data. Finally, a Discriminant Analysis was performed to determine standardisation of the ARC attributes through the sampling periods. The 89% of cheese samples were correctly classified into their own cheese manufacture. This last analysis demonstrated that there was an important degree of standardisation of the cheesemaking procedure within each cheese manufacture, something that was not demonstrated before with artisan cheesemakers.     

Electrical Resistivity Behavior and VRH Transport Mechanism in Semiconducting La0.6Sr0.4Mn1−2x Fe x Cr x O3 (0.10≤x≤0.25) Manganites

The transport properties and conduction mechanism in La_0.6Sr_0.4Mn_1?2x Fe _x Cr _x O₃ (0≤x≤0.3) have been investigated. The undoped samples show metal–semiconductor transition with a peak of resistivity at a temperature T _P , whereas for all doped compounds the semiconducting behavior persists in the whole temperature range. The insertion of Cr³⁺ and Fe³⁺ ions leads to the increase of resistivity because the simultaneous substitution of Fe³⁺ and Cr³⁺ for Mn³⁺ reduces the number of available hopping sites for the Mn e _g↑ electron and suppresses the double-exchange mechanism. It was found that the transport mechanism for substituted samples is dominated by the variable range hopping of small polarons between localized states in a model where the various parameters estimated from Mott’s relation obey the variable range hopping (VRH) mechanism.     

Efficient recovery-based error estimation for the smoothed finite element method for smooth and singular linear elasticity

An error control technique aimed to assess the quality of smoothed finite element approximations is presented in this paper. Finite element techniques based on strain smoothing appeared in 2007 were shown to provide significant advantages compared to conventional finite element approximations. In particular, a widely cited strength of such methods is improved accuracy for the same computational cost. Yet, few attempts have been made to directly assess the quality of the results obtained during the simulation by evaluating an estimate of the discretization error. Here we propose a recovery type error estimator based on an enhanced recovery technique. The salient features of the recovery are: enforcement of local equilibrium and, for singular problems a “smooth + singular” decomposition of the recovered stress. We evaluate the proposed estimator on a number of test cases from linear elastic structural mechanics and obtain efficient error estimations whose effectivities, both at local and global levels, are improved compared to recovery procedures not implementing these features.     

Demonstration of photon Bloch oscillations and Wannier-Stark ladders in dual-periodical multilayer structures based on porous silicon

ABSTRACT: : Theoretical demonstration and experimental evidence of photon Bloch oscillations and Wannier-Stark ladders (WSLs) in dual-periodical (DP) multilayers, based on porous silicon, are presented. An introduction of the linear gradient in refractive indices in DP structure, which is composed by stacking two different periodic substructures N times, resulted in the appearance of WSLs. Theoretical time-resolved reflection spectrum shows the photon Bloch oscillations with a period of 130 fs. Depending on the values of the structural parameters, one can observe the WSLs in the near infrared or visible region which may allow the generation of terahertz radiation with a potential applications in several fields like imaging.     

Monte Carlo Simulations for Tomlinson Sliding Models for Non-Sinusoidal Periodic Potentials

It is shown that the velocity dependence of a tungsten tip sliding against a mica surface cannot be fit to a semi-empirical analytical solution of the Tomlinson/Prandtl model using a simple sinusoidal sliding potential. This could be due to invalid assumptions in the model itself. However, if it is assumed that the periodic sliding potential is much sharper than a simple sinusoid, quantitative agreement between the experimental velocity dependence of the sliding force and theory is obtained using a single variable parameter, the height of the surface potential. Sliding is modeled in this case using Monte Carlo theory, and it is found that the height of the potential varies linearly with the normal load.     

Carbon black‐filled PET/HDPE blends: Effect of the CB structure on rheological and electric properties

The rheological and electric properties of blends of poly(ethylene terephthalate) (PET) and high‐density polyethylene (HDPE) filled with various types of carbon black (CB) were analyzed in detail in this project. Four types of CB samples with available values of surface area, particle size, porosity, density, and maximum packing fraction were considered. Blends were prepared using an internal mixing chamber at two different rotational speeds, prior to mold compression of the samples. The rheological properties of the blends with varying polymer composition and a constant amount of CB were recorded in terms of torque variation with time for two shear rates (in terms of rotational speed). Rheological data were related to the resistivity of blends. Results show that the CB structure (porosity, surface area, apparent bulk density, and particle size) largely determine the resulting equilibrium torque and electrical properties. Furthermore, since CB is preferentially located in the HDPE phase, higher conductivity is observed as the PET content decreases, since the relative CB content in this phase increases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 562–569, 2001     

Averaging model for cuttings transport in horizontal wellbores

This paper presents a theoretical analysis of the problem of cuttings transport for a two-region system composed of a fluid bed (ω-region) and a stationary bed of drill cuttings, which is considered as a porous medium (η-region) in the two-phase system. The ω-region is made up of a solid phase (σ-phase) dispersed in a continuos fluid phase (β-phase), while the η-region consists of a stationary solid phase (σ-phase) and a fluid phase (β-phase). The volume averaging method was applied in this study. Volume-averaged transport equations were derived for both the fluid bed and the porous medium regions. These equations are based on the non-local form of the volume-averaged momentum transport equation that is valid within the bounded region. Outside this region, the non-local form reduces to the classic volume-averaged transport equation. From these equations, a one-equation model was obtained, and the constraints that the one-equation model must satisfy were applied. For estimating the averaged pressure drop and the averaged velocity, the one-equation model was solved numerically by using the finite-difference technique in the implicit scheme. Numerical results are in agreement with experimental data and theoretical results reported in the literature.     

Rheological characterization of 4,4′-bis (diethylamino)benzophenone-functionalized polybutadienes with low and medium vinyl content

In this article a mechnical spectroscopic study of a series of low (?8%) and medium (? 70%) vinyl-content polybutadiences, some of them functionalized with 4,4′-bis(diethylamino)-benzophenone, is presented. Characterization of polymers with well-known structure by small-amplitude oscillatory shear flow enabled investigation of the effect of the vinyl content and functional groups on the rheological behavior of the samples in the linear viscoelastic region. The Doi–Edwards viscolastic model, without any adjustable parameter, proved to be adequate to describe the relationship between the macro/micro structure of the polymers and their viscoelastic properties. Results indicate that the vinyl content and functional groups modify the rheological behavior extensively. © 1995 John Wiley & Sons, Inc.     

On predicting self-diffusion coefficients from viscosity in gases and liquids

The relations between self-diffusion and viscosity for compressed liquids and gases have been reviewed, and a new equation for correlating viscosities over wide ranges of temperature and pressure is proposed. This formula is inspired by the Lennard-Jones Chain model of Yu and Gao for self-diffusion, and represents the viscosities of 15 compounds (1046 data points) with an average absolute deviation of 6.95%. Moreover, as the presented equation and the Yu-Gao model require the same fitting parameters, the ability to calculate self-diffusion coefficients from the viscosity parameter is studied. Some of the classic reviewed relations, such as the Stokes-Einstein formula, are also contrasted with the available experimental data of both transport properties.