On the origin of extrusion instabilities: Linear stability analysis of the viscoelastic die swell

It is well-known that, increasing the flow rate in polymer extrusion, the flow becomes unstable and the smooth extrudate surface becomes wavy and disordered to an increasing degree. In order to investigate the mechanisms responsible for these instabilities we perform a linear stability analysis of the steady extrusion of a viscoelastic fluid flowing through a planar die under creeping flow conditions. We consider the Phan-Thien-Tanner (PTT) model to account for the viscoelasticity of the material. We employ the mixed finite element method combined with an elliptic grid generator to account for the deformable shape of the interface. The generalized eigenvalue problem is solved using Arnoldi’s algorithm. We perform a thorough parametric study in order to determine the effects of all material properties and rheological parameters. We investigate in detail the effect of the interfacial tension and the presence of a deformable interface. It is found that the presence of a finite surface tension destabilizes the flow as compared to the case of the stick-slip flow. We recognize two modes, which become unstable beyond a critical value of the Weissenberg number and perform an energy analysis to examine the mechanisms responsible for the destabilization of the flow and compare against the mechanisms that have been suggested in the literature

Presence of Hypertension Is Reduced by Mediterranean Diet Adherence in All Individuals with a More Pronounced Effect in the Obese: The Hellenic National Nutrition and Health Survey (HNNHS)

Hypertension is a major risk of cardiovascular diseases. This study's aim was to examine associations between hypertension and a priori known lifestyle risk factors, including weight status and Mediterranean diet adherence. The study included a representative sample of the adult population (N = 3775 (40.8% males)), from the Hellenic National Nutrition and Health Survey (HNNHS), which took place from September 2013 to May 2015. Demographic and anthropometric data were collected using validated questionnaires, and blood pressure (BP) measurements were performed for the two main metropolitan areas (N = 1040; 41.1%). Hypertension diagnosis was according to the International Classification of Diseases (ICD-10) guidelines. Weighted proportions, extended Mantel-Haenszel (M-H) analyses, and multiple logistic regressions (for the survey data) were performed. Mean systolic BP (SBP) and diastolic BP (DBP) were 118.6 mmHg and 72.2 mmHg respectively, with both values being higher in males compared to females in all age groups (p < 0.001). Study participants with hyperlipidemia or diabetes, and those overweight, were almost twice as likely to be hypertensives, with the odds increasing to 4 for those obese (p for all, < 0.05). Stricter Mediterranean diet adherence significantly decreased the likelihood of hypertension by 36% (OR: 0.64; 95% CI: 0.439, 0.943), and a significant interaction was found between Mediterranean diet adherence and weight status on hypertension. The presence of hypertension is clustered with comorbidities, but is significantly associated with modifiable risk factors, including Mediterranean diet and weight status, underlining the need for personalized medical nutritional treatment

Interface design and evaluation of a personal information space for mobile learners

In response to the market penetration of mobile phones, educational institutions will soon focus on delivering information to mobile phones. This paper presents the design and evaluation of a prototype mobile application for lifelong learning. The application is a personal information space for mobile learners to access, compose and manage their learning in a variety of settings. As a result of the evaluation, a revised set of design guidelines is produced that can potentially feed into other attempts to develop a framework for designing applications for mobile learners

An architecture for a personalised mobile environment to facilitate contextual lifelong learning

In response to the ever-increasing need of private and public organizations for lifelong learning, research in technology-enhanced learning has been geared towards the provision of systems that will better support those who pursue education at a number of different stages in their life, move between institutions while pursuing a course of study, or make use of resources and facilities from more than one institution/ organization. The new generation of mobile phones can support applications that would facilitate contextual learning through life. This chapter presents our approach to designing a mobile application for contextual lifelong learning and the prototype created. The application assists learners to access, compose and manage their learning in a range of institutional, informal and work-based settings by keeping them connected with content that is relevant to their studies, and its use is demonstrated in three lifelong learning scenarios

Designing Personalised Information Access to Structured Information Spaces

Abstract. The paper presents an approach to personalisation of structured information spaces that builds around a set of services. Structured information representation is increasingly being used to improve the organisation, search, and analysis of information spaces provided on the Web and is very popular in digital libraries, classification-based search engines, information directories, and subject gateways. In a service-oriented approach, the application behaviours contained in the various systems are defined as services which are “open ” and can be consumed by other applications. The paper identifies relevant personalisation services, discusses their expected behaviours, and explores the dimensions of individual differences that should be included in a user model specification to meet personalisation services requirements and create personalised information access

A flexible interface design for web directories to accommodate different cognitive styles

Search engines are very popular tools for collecting information from distributed resources. They provide not only search facilities, but they also offer directories for users to browse content divided into groups. In this paper, we've adopted an individual differences approach to explore user's attitudes towards various interface features provided by existing Web directories. Among a variety of individual differences, cognitive style is a particularly important characteristic that influences the effectiveness of information seeking. Empirical results indicate that users' cognitive styles influence their reactions to the organization of subject categories, presentation of the results, and screen layout. We developed a set of design guidelines on the basis of these results, and propose a flexible interface that adopts these guidelines to accommodate the preferences of different cognitive style groups

ABSTRACT A PERSONALISED MOBILE ENVIRONMENT FOR LIFELONG LEARNERS

With the new generation of mobile phones that are always online, can handle multimedia and connect to local networks using bluetooth technology, an application that will facilitate learning for lifelong learners can be accomplished. To this end, this paper presents a design approach and an architecture for a prototype personalised environment that aims to facilitate contextual lifelong learning by making accessible learning services and opportunities provided by the university or by remote personalised servers that are available in the vicinity of the user