Participatory design to lower the threshold for intelligent support authoring

One of the fundamental aims of authoring tools is to provide teachers with opportunities to configure, modify and generally appropriate the content and pedagogical strategies of intelligent systems. Despite some progress in the field, there is still a need for tools that have low thresholds in terms of the users’ technical expertise. Here, we demonstrate that designing systems with lower entry barrier can potentially be achieved through co-design activities with non-programmers and carefully observing novices. Following an iterative participatory co-design cycle with teachers who have little or no programming expertise, we reflect on their proposed enhancements. Our investigations focus on Authelo, an authoring tool that has been designed primarily for Exploratory Learning Objects, but we conclude the paper by providing transferable lessons, particularly the strong preference for visual interfaces and high-level pedagogical predicates for authoring analysis and feedback rules

CREVICULAR FLUID LEVEL OF ELASTASE IN TYPE I AND TYPE II DIABETES MELLITUS PATIENTS

ABSTRAC

Thermodynamic principles and implementations of quantum machines

The efficiency of cyclic heat engines is limited by the Carnot bound. This bound follows from the second law of thermodynamics and is attained by engines that operate between two thermal baths under the reversibility condition whereby the total entropy does not increase. By contrast, the efficiency of engines powered by quantum non-thermal baths has been claimed to surpass the thermodynamic Carnot bound. The key to understanding the performance of such engines is a proper division of the energy supplied by the bath to the system into heat and work, depending on the associated change in the system entropy and ergotropy. Due to their hybrid character, the efficiency bound for quantum engines powered by a non-thermal bath does not solely follow from the laws of thermodynamics. Hence, the thermodynamic Carnot bound is inapplicable to such hybrid engines. Yet, they do not violate the principles of thermodynamics. An alternative means of boosting machine performance is the concept of heat-to-work conversion catalysis by quantum non-linear (squeezed) pumping of the piston mode. This enhancement is due to the increased ability of the squeezed piston to store ergotropy. Since the catalyzed machine is fueled by thermal baths, it adheres to the Carnot bound. We conclude by arguing that it is not quantumness per se that improves the machine performance, but rather the properties of the baths, the working fluid and the piston that boost the ergotropy and minimize the wasted heat in both the input and the output.Comment: As a chapter of: F. Binder, L. A. Correa, C. Gogolin, J. Anders, and G. Adesso (eds.), "Thermodynamics in the quantum regime - Recent Progress and Outlook", (Springer International Publishing

Three dimensional fracture analysis of FGM coatings

In this study the three - dimensional surface cracking of a graded coating bonded to a homogeneous substrate is considered. The main objective is to model the subcritical crack growth process in the coated medium under a cyclic mechanical or thermal loading. Because of symmetry, along the crack front conditions of mode I fracture and plane strain deformations are assumed to be satisfied. Thus, at a given location on the crack front the crack propagation rate would be a function of the mode I stress intensity factor. A three - dimensional finite element technique for nonhomogeneous elastic solids is used to solve the problem and the displacement correlation technique is used to calculate the stress intensity factor

Interface crack problems in graded orthotropic media: Analytical and computational approaches

Interface crack problems in graded orthotropic media are considered using analytical and computational techniques. In the analytical formulation an interface crack between a graded orthotropic coating and a homogeneous orthotropic substrate is considered. The principal axes of orthotropy are assumed to be parallel and perpendicular to the crack plane. Mechanical properties of the medium are assumed to be continuous with discontinuous derivatives at the interface. The problem is formulated in terms of the averaged constants of plane orthotropic elasticity and reduced to a pair of singular integral equations which are solved numerically to compute the mixed mode stress intensity factors and the energy release rate. In the second part of the study, enriched finite elements are formulated and implemented for graded orthotropic materials. Comparisons of the finite element and analytical results show that enriched finite element technique is capable of producing highly accurate results for crack problems in graded orthotropic media. Finally, periodic interface cracking and the four point bending test for graded orthotropic solids are modeled using enriched finite elements and the results are briefly discussed

The frictional contact problem of sliding rigid parabolic stamps on graded materials

This study presents an analytical procedure to determine the contact stress distribution at the surface of an FGM coating perfectly bonded to a homogeneous substrate. The coating is assumed to be loaded by a rigid stamp of a semi-circular or circular profile. Using Fourier transformations, the contact mechanics problems are reduced to a singular integral equation of the second kind. Singular behavior of the unknown contact stress distribution at the end points is determined by following a function theoretic method. The singular integral equation is solved numerically using an expansion-col location technique. Main results of the study are the normal and lateral contact stress components and required contact forces as functions of material parameters. It is shown that a substrate that is softer than the FGM coating could be useful in decreasing the magnitude of the positive lateral stress at the trailing end of the contact

Mixed-mode stress intensity factors for an embedded crack in an orthotropic FGM coating

Analytical and computational methods are developed to examine mixed-mode fracture behaviour of an orthotropic FGM coating bonded to a homogeneous substrate through a layer of a bond-coat. The coating is assumed to contain an embedded crack perpendicular to the direction of the material property gradation. First, an analytical solution is developed considering a perturbation problem. Using Fourier transform, the problem is reduced to a system of singular integral equations which are solved by means of an expansion-collocation technique. Then, finite element method is utilized to investigate the same problem using the displacement correlation technique (DCT). By using the developed finite element method, mixed-mode stress intensity factors are also evaluated for an FGM coating-bond coat-substrate structure that is subjected to thermal stresses