Identification of Viscoelastic Moduli of Composite Materials from the Plate Transmission Coefficients

A quick and accurate method of measuring elastic and viscoelastic constants of a material is the essential first step for characterizing the material. This is more challenging for composite materials because unlike homogeneous metals and ceramics the material properties change from specimen to specimen for composite materials as the volume fraction of fibers and their orientations change. Anisotropic properties of composite materials add another difficulty in the measurement technique, since anisotropy increases the number of independent material constants. Polymer composites exhibit a high degree of attenuation in the matrix material; as a result, these composite materials cannot be assumed to be pure elastic material, so they should be modeled as viscoelastic materials by making the material constants complex. The real part is associated with the elastic behavior and the imaginary part is associated with the viscoelastic or attenuative behavior of the material. The number of independent material constants for a unidirectional (UD) composite, which is transversely isotropic, is ten (five real and five imaginary). Naturally, it is not practical and almost impossible to measure all these material constants by the traditional engineering method of applying stresses and measuring strains in different directions. Because of the measurement difficulty the imaginary parts of the material constants are often ignored. However, it should be mentioned here that it is important to measure the imaginary components of material constants because porosity and microcracking in the matrix due to material fatigue and aging affect the attenuation more than the elastic properties. In other words, the imaginary components of the material constants are a better indicator of material aging compared to the real components. Hence, an efficient technique to measure both real and imaginary components of the material constants is warranted and developed in this paper.</p

Route planning with transportation network maps: an eye-tracking study.

Planning routes using transportation network maps is a common task that has received little attention in the literature. Here, we present a novel eye-tracking paradigm to investigate psychological processes and mechanisms involved in such a route planning. In the experiment, participants were first presented with an origin and destination pair before we presented them with fictitious public transportation maps. Their task was to find the connecting route that required the minimum number of transfers. Based on participants' gaze behaviour, each trial was split into two phases: (1) the search for origin and destination phase, i.e., the initial phase of the trial until participants gazed at both origin and destination at least once and (2) the route planning and selection phase. Comparisons of other eye-tracking measures between these phases and the time to complete them, which depended on the complexity of the planning task, suggest that these two phases are indeed distinct and supported by different cognitive processes. For example, participants spent more time attending the centre of the map during the initial search phase, before directing their attention to connecting stations, where transitions between lines were possible. Our results provide novel insights into the psychological processes involved in route planning from maps. The findings are discussed in relation to the current theories of route planning

Attention-deficit/hyperactivity disorder (ADHD) symptoms and academic entrepreneurial preference: is there an association?

Although commercialization of research activities has drawn some research attention, more studies are warranted to clearly understand the drivers behind academic entrepreneurship. The present paper investigates the association between attention-deficit/hyperactivity disorder (ADHD) symptoms and academic entrepreneurial preference. ADHD symptoms have typically been associated with impaired occupational functioning among wage employees. Recent studies, however, indicate that the same symptoms of ADHD that are a liability for wage employees may work out differently for entrepreneurs. Building on previous studies that link ADHD symptoms to entrepreneurship, and using the theoretical lens of person-environment fit, we hypothesize that ADHD symptoms (at the so-called subclinical level) are associated with academic entrepreneurial preference. Results of our data from academic researchers in France, Spain, and Italy (N = 534) show that there is a negative association between attention-deficit symptoms and academic entrepreneurial preference. However, there is no link between hyperactivity symptoms and academic entrepreneurial preference

Simultaneous Reconstruction of the Acoustic Properties of a Layered Medium: The Inverse Problem

In recent years, multi-layered metal materials have found increasing use in various disciplines, particularly in aerospace, electrical, automotive and pressure vessel industries. These applications utilize certain unique physical properties of the layered metals such as heat conductivity, electric conductivity or corrosion resistance. Thus, a nondestructive evaluation technique is essential for these advanced materials. In this work, we present a frequency domain nondestructive evaluation technique for these layered media and the results obtained when the technique is applied to the three-layer clad metal materials

Political integration, sustainability and environmental policy in Hong Kong

A technique for the accurate estimation of elastic constants in splid materials is described. Experimental waveforms generated in a plate by pulsed laser are compared with theoretical solutions for a point source. A non-linear fit makes it possible to obtain the longitudinal and shear velocities of the material

On the Efficiency of Generally Balanced Designs Analysed by Restricted Maximum Likelihood

International audienc

Can Design Choices for Language-Based Editors be Analysed with Keystroke-Level Models?

We have been concerned for some time with the lack of rigorous experimental evaluation of design options chosen for tools used by software engineers. In a series of studies using various evaluation techniques we built Keystroke-Level Models and conducted an empirical usability study of a design issue (choice of editing paradigm for language-based editors) that has reached a `subjective stalemate&apos; in the research community. The KLM analysis enabled us to predict usage differences and while this was useful we also noticed several problems, in particular we were concerned about the estimated value and placement of the memory operator. By utilising the same tasks in the usability study as in the KLM analysis, we were able to compare results from both evaluations and effectively validate the overall KLM estimates and the specific operator values involved. KEYWORDS: Keystroke-Level Model, model validation, language-based editors 1 Introduction Two basic paradigms for editing are commonly ..