Study of the effects of structural uncertainties on a fractional system of the first kind – application in vibration isolation with the CRONE suspension

In this paper, we deal with the effects of the uncertainties on a fractional system of the first kind, mainly on the frequency-domain and the time-domain responses. For the structural uncertainties, two main aspects are studied: the nonlinearities of the physical components used to realize the fractional system and the consideration of the previously neglected dynamics of the system. Both uncertainties are introduced for the hydropneumatic CRONE suspension, previously synthesized and realized without taking into consideration these uncertainties. So, the novel approach treated in this work is to find whether the uncertainties, which were previously neglected in the synthesis and the realization phases, alter the behaviour of the system or not. The results show that the fractional order system behaviour is not affected.     

The effect of radiopacifiers agents on pH,calcium release,radiopacity, and antimicrobial properties of different calcium hydroxide dressings

The aim of this study was to evaluate the antimicrobial activity, pH level, calcium ion release, and radiopacity of calcium hydroxide pastes associated with three radiopacifying agents (iodoform, zinc oxide, and barium sulfate). For the pH and calcium release tests, 45 acrylic teeth were utilized and immersed in ultrapure water. After 24 h, 72 h, and 7 days the solution was analyzed by using a pH meter and an atomic absorption spectrophotometer. Polyethylene tubes filled with the pastes were used to perform the radiopacity test. For the antimicrobial test, 25 dentin specimens were infected intraorally in order to induce the biofilm colonization and treated with the pastes for 7 days. The Live/Dead technique and a confocal microscope were used to obtain the ratio of live cells. Parametric and nonparametric statistical tests were performed to show differences among the groups (P < 0.05). The pH analysis at 7 days showed significant differences (P < 0.05) among the groups. No differences among the pastes were found in the calcium release test on the 7th day (P > 0.05). The calcium hydroxide/iodoform samples had the highest radiopacity and antimicrobial activity against the biofilm‐infected dentin in comparison to the other pastes (P < 0.05). Calcium hydroxide mixed with 17% iodoform and 35% propylene glycol into a paste had the highest pH, calcium ion release, radiopacity, and the greatest antimicrobial action versus similar samples mixed with BaSO4 or ZnO. Microsc. Res. Tech. 78:620–625, 2015. © 2015 Wiley Periodicals, Inc.     

Brazing of UNS S32101 and UNS S32304 lean duplex stainless steels and UNS S32750 super duplex with AWS A5.3 BNi-7 (Ni–Cr–P) filler metal

Summary

Weld metals solidified in the ferritic-austenitic solidification mode (FA mode) have dual phases of ferrite and austenite in their as-solidified condition, where ferrite exhibits different morphologies depending on the chemical composition and welding conditions. This paper describes an investigation of the effect of the solidification and transformation sequence on the formation of final ferrite morphologies. Austenite is formed through either a eutectic reaction or peritectic reaction at the dendrite boundaries after the primary formation of ferrite. During the eutectic formation of austenite, the <100>_δ direction of the primary ferrite and the <100>_γ direction of the eutectic austenite are parallel to each other and lie along the growth direction of the primary dendrites. However, any specific lattice plane relationship between the two phases is not identified. During cooling after solidification, the austenite extends into the primary ferrite via solid-state transformation, and the final morphology of the ferrite is vermicular without any coherent orientation relationship between the primary ferrite and eutectic austenite. During peritectic formation of austenite, the Kurdjumov-Sachs orientation relationship is established between the primary ferrite and peritectic austenite, and the <100>_γ direction of the peritectic austenite is not parallel to the growth direction of the primary dendrites. During cooling after solidification, the primary ferrite transforms into austenite, and the final morphology of the ferrite is lathy, since the primary ferrite and peritectic austenite have a favourable coherent orientation.     

Modeling the physical processes relevant during hot pressing of wood-based composites. Part II. Rheology

A rheological model to describe the development of the vertical density profile and of internal stresses within wood-furnish mats during hot pressing is presented in this paper. The rheological model is part of a comprehensive three-dimensional simulation model that accounts for those mechanisms most important during the pressing process, including heat and mass transfer inside the mat and adhesive cure. To model the rheological behavior of the mat, the four-element Burgers model commonly used to describe visco-elastic material behavior has been expanded with the addition of a fifth element that represents plastic and micro-fracture related deformation. The coefficients of the non-linear model are highly dependent on the material conditions. Equations of the coefficients as a function of temperature, moisture content and density, as well as a mathematical formulation of the five-element model is presented in this paper. Furthermore, model predictions for both a batch and a continuous press are given. A comparison with experimental results shows that the expanded Burgers model is suitable to predict typical features of the vertical density profile, such as the development of density maxima near the surfaces, shoulders or side maxima as a consequence of intermediate or final densification steps, and differences in the density profile between the mat center and the edges in the horizontal plane. Such agreement provides the basis for a wide range of industrial and research applications.     

A C<Superscript><Emphasis Type="Italic">k</Emphasis></Superscript> continuous generalized finite element formulation applied to laminated Kirchhoff plate model

A generalized finite element method based on a partition of unity (POU) with smooth approximation functions is investigated in this paper for modeling laminated plates under Kirchhoff hypothesis. The shape functions are built from the product of a Shepard POU and enrichment functions. The Shepard functions have a smoothness degree directly related to the weight functions adopted for their evaluation. The weight functions at a point are built as products of C ^∞ edge functions of the distance of such a point to each of the cloud boundaries. Different edge functions are investigated to generate C ^k functions. The POU together with polynomial global enrichment functions build the approximation subspace. The formulation implemented in this paper is aimed at the general case of laminated plates composed of anisotropic layers. A detailed convergence analysis is presented and the integrability of these functions is also discussed.     

Search directions for interior linear-programming methods

Since Karmarkar published his algorithm for linear programming, several different interior directions have been proposed and much effort was spent on the problem transformations needed to apply these new techniques. This paper examines several search directions in a common framework that does not need any problem transformation. These directions prove to be combinations of two problem-dependent vectors, and can all be improved by a bidirectional search procedure. We conclude that there are essentially two polynomial algorithms: Karmarkar's method and the algorithm that follows a central trajectory, and they differ only in a choice of parameters (respectively lower bound and penalty multiplier).     

Robust B-spline Snakes For Ultrasound Image Segmentation

Snake-based methods are commonly used to segment ultrasound images. However, their performance is generally limited because of the specific properties of this kind of images. This paper addresses the sensitivity of parametric active contours to speckle within ultrasound images. We propose a new B-spline snake model, founded on two original external energies specifically tailored for the segmentation of biomedical speckled images. First, the curve is attracted from a wide capture range with an expansion energy that facilitates the snake initialization. Then, it is accurately fitted on the region boundaries with an energy that allows precise positioning of the curve along edges in ultrasound images. A mutual inhibition function is designed to control the two energies. Results on real ultrasound images are presented and quantitatively compared to the boundaries manually outlined by experts. Our method improves the precision of heart cavities segmentation.