Solving a non-linear model: The importance of model specification for deriving a suitable solution

In this paper, we consider a macroeconomic model with alternative linear and non-linear specifications. One version of the model, expressed in levels, is highly non-linear and has at least two steady-state equilibria. One of these equilibria has an economically meaningful interpretation, while the other does not have a sensible economic interpretation. A second version of the model, expressed in logarithms, is linear and has a unique steady-state equilibrium, which corresponds to the economically meaningful equilibrium of the non-linear version of the model. The dynamic solution of each model version has a combination of stable and unstable eigenvalues so that any dynamic solution requires the calculation of appropriate “jumps” in endogenous variables. Attempts to solve these models, using forward-shooting and reverse-shooting algorithms, show that the forward-shooting algorithm chooses the “wrong” solution for the non-linear model, but the “right” solution for the linear model. The reverse-shooting algorithm chooses the “right” solution in both cases. We demonstrate how this result is driven by particular properties of the two versions of the model.     

Estimation of road frictional force and wheel slip for effective antilock braking system (ABS) control

The introduction of electric braking via brake‐by‐wire systems in electric vehicles) has reduced the high transportation delays usually involved in conventional friction braking systems. This has facilitated the design of more efficient and advanced control schemes for antilock braking systems (ABSs). However, accurate estimation of the tire‐road friction coefficient, which cannot be measured directly, is required. This paper presents a review of existing estimation methods, focusing on sliding‐mode techniques, followed by the development of a novel friction estimation technique, which is used to design an efficient ABS control system. This is a novel slip‐based estimation method, which accommodates the coupling between the vehicle dynamics, wheel dynamics, and suspension dynamics in a cascaded structure. A higher‐order sliding‐mode observer–based scheme is designed, considering the nonlinear relationship between friction and slip. A first‐order sliding‐mode observer is also designed based on a purely linear relationship. A key feature of the proposed estimation schemes is the inclusion of road slope and the effective radius of the tire as an estimated state. These parameters impact significantly on the accuracy of slip and friction estimation. The performance of the proposed estimation schemes are validated and benchmarked against a Kalman filter (KF) by a series of simulation tests. It is demonstrated that the sliding‐mode observer paradigm is an important tool in developing the next generation ABS systems for electric vehicles.     

Translating science to practice: Clinical Grand Rounds Series in Health Psychology.

In this issue of Health Psychology we launch an important new series focused on the implementation of evidence-based assessments and interventions in clinical settings. The series—Translating Science into Practice: Clinical Grand Rounds—is consistent with the journal’s emphasis on the practical significance of papers in Health Psychology and congruent with national and international trends in evidence-based care and translational science across all health disciplines. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Cognitive Science Approaches To Understanding Diagrammatic Representations

Through a wide variety of approaches cognitive sciencehas given us various important insights into thenature of diagrammatic representations. This papersurveys the findings, issues and approaches todiagrammatic representations in cognitive science. Important current issues that are highlighted include:the relation between the parts of the representationalsystem that are internal to the mind and in externalvisual media that presents the diagram; the use ofmultiple representations which is typical of realcontexts of diagram use; the benefits of diagrams interms of (i) computational offloading, (ii)re-representation and (iii) graphical constraining.     

Creep forming of high strength polyethylene fiber prepregs for the production of ballistic protection helmets

Production of highly three dimensionally curved composite products with continuous fibers so far is dependent on drapability of the fibrous precursor. Drapability depends on the in-plane shear compliance of the precursor and on its bending flexibility. Elongation of the fibers usually gives a negligible contribution to drapability because high performance fibers typically show small elongations to failure. However, high strength polyethylene fibers are an exception. They may accumulate considerable creep elongation, provided that the loading time is sufficiently long. Choosing a proper processing temperature, somewhat below the melting temperature, allows that this sufficiently long processing time is still within the limits that are acceptable for industrial production. This paper explores the technique for creep forming of high strength polyethylene fiber prepregs for the production of full scale ballistic protection helmet shells. Such helmets show a highly three dimensionally curvature. It was found that such helmets can be made by creep-forming indeed. The helmets were free of wrinkles and showed excellent protection against supersonic projectiles. It was found to be very important that a homogeneous temperature distribution is provided during creep forming. Very high fiber tensile stresses occur during creep forming. Control of these high creep stresses is necessary.     

The effect of industrial food processing on potentially health-beneficial tomato antioxidants

Increasing desires from both consumers and producers to understand better which nutritive components are present in our food and how these are influenced by industrial processing strategies is resulting in extra research involving the use of state-of-the-art technologies to generate novel biochemical information. In this review, attention has been focused on tomato as this is a product eaten right across the world both as fresh produce and after having been processed in a wide variety of ways. There is a particular interest in tomato as it is a major component in the so-called "Mediterranean diet" which has recently been associated with a healthier lifestyle. Tomatoes are rich sources of a variety of nutritional compounds and especially some key antioxidant components such as the carotenoid lycopene, vitamin C, and a range of polyphenols. The potentially protective properties of these antioxidants are of great interest and the consumer has already become aware of their potential importance. Surveying the literature has revealed that much research has been done on the biochemical composition of tomato and its products. However, it remains difficult to make clear conclusions on optimizing the processing strategy. Many, apparently conflicting, findings have been reported and consequently, in this review, we have drawn attention to these and have attempted to clarify their cause. Finally, a range of recommendations has been made as to how future research might be performed in order to generate more concrete conclusions enabling recommendations towards more optimized processing strategies.     

On the use of adaptive refinement in isogeometric digitalimage correlation

A novel global digital image correlation method was developed using adaptive refinement of isogeometric shape functions. Non‐uniform rational B‐spline shape functions are used because of their flexibility and versatility, which enable them to capture a wide range of kinematics. The goal of this work was to explore the full potential of isogeometric shape functions for digital image correlation (DIC). This is reached by combining a global DIC method with an adaptive refinement algorithm: adaptive isogeometric GDIC. The shape functions are automatically adjusted to be able to describe the kinematics of the sought displacement field with an optimized number of degrees of freedom. This results in an accurate method without the need of making problem‐specific choices regarding the structure of the shape functions, which makes the method less user input dependent than regular global DIC methods, while keeping the number of degrees of freedom limited to realize optimum regularization of the ill‐posed DIC problem. The method's accuracy is demonstrated by a virtual experiment with a predefined, highly localized displacement field. Real experiments with a complex sample geometry demonstrate the effectiveness in practice. Copyright © 2015 John Wiley & Sons, Ltd.     

Challenges and solutions of environmental scanning electron microscopy characterisation of biomaterials: Application to hygro-expansion of paper

Most methodologies to measure the moisture-induced deformation (hygro-expansion) of paper microconstituents, including fibres and interfibre bonds, are low resolution or time-consuming. Hence, here, a novel method is proposed and validated to measure high-resolution full-field strain maps of paper microconstituents during hygro-expansion, based on environmental scanning electron microscopy (ESEM). To this end, a novel climate stage enables accurate control of the relative humidity (RH) near the specimen in the ESEM from 0%–100%. The fibre surface, which is decorated a priori with a microparticle pattern, is captured during RH change. Subsequently, correlating the fibre surface using a dedicated global digital image correlation algorithm enables high-resolution hygro-expansion strain maps. Method optimisation involved performing contrast enhancement, scan-correction to reduce ESEM artefacts and a background correction, resulting in a strain resolution of $6·10^{-4}$. Method validation revealed that the fibres' crystallinity is affected by the electron beam, even for minimal invasive electron beam settings. Interestingly, however, the fibres consistently exhibit conventional hygro-expansion behaviour during the drying slopes. Using the optimised procedure, hygro-expansion characterisation of two interfibre bonds and four interfibre bond cross-sections revealed the competition between the low longitudinal and large transverse fibre hygro-expansion in the bonded area.