Towards a prototype of a spherical tippe top

Among spinning objects, the tippe top exhibits one of the most bizarre and counterintuitive behaviours. The commercially available tippe tops basically consist of a section of a sphere with a rod. After spinning on its rounded body, the top flips over and continues spinning on the stem. It is the friction with the bottom surface and the position of the center of mass below the centre of curvature that cause the tippe top to rise its centre of mass while continuing rotating around its symmetry axis (through the stem). The commonly used simplified mathematical model for the tippe top is a sphere whose mass distribution is axially but not spherically symmetric, spinning on a flat surface subject to a small friction force that is due to sliding. Adopting a bifurcation theory point of view we reach a global geometric understanding of the phase diagram of this dynamical system. According to the eccentricity of the sphere and the Jellet invariant (which includes information on the initial angular velocity) three main different dynamical behaviours are distinguished: tipping, non-tipping, hanging (i.e. the top rises but converges to an intermediate state instead of rising all the way to the vertical state). Subclasses according to the stability of relative equilibria can further be distinguished. Since our concern is the degree of confidence in the mathematical model predictions, we applied 3D-printing and rapid prototyping to manufacture a ’3-in-1 toy’ that could catch the three main characteristics defining the three main groups in the classification of spherical tippe tops as mentioned above. This ’toy’ is suitable to validate the mathematical model qualitatively and quantitatively

Prenatale diagnostiek en morele vooruitgang

status: publishe

Design for [every]one

“Design for [every]one” is an ergonomic design process appropriate for the assistive technology sector. User centered techniques are applied for an incremental personalization process involving design team members, patients and occupational therapists. By implementing active engagement with user experience prototypes and observational techniques, it is possible to reduce the stigmatization and augment the product affinity between patient and assistive tool. Basically, this approach works in two ways , personalized assistive products are fitted to the users and users become fitted to their products. In this paper we will sketch the framework of this design type and discuss some tools to gather and validate information during various phases of the iterative design process

The role of prototyping in developing assistive devices

Products in the healthcare context must put human relationships and social interactions central. Today, two main approaches are common when adopting assistive products for impaired users. Standard assistive devices offer either functionality that is not well-matched to the patient’s impairment. Or - in case a occupational therapist has physically hacked the product accordingly - it works stigmatizing for the patient, due to its unattractive design. “Design for [every]one” is a multidisciplinary design process appropriate for developing customized assistive devices. Prototyping is consecutively applied as design method and communication language for an incremen-tal personalization process involving design team members, patients and occupational therapists. By imple-menting active engagement with user experience prototypes and observational techniques, it is possible to re-duce stigmatization and augment the product affinity between patient and the assistive tool. The starting point of this personalized system are questions about what an individual needs in the broadest sense. Through an extended dialogue with prototypes, a person’s aspirations and needs can be made tangible to all the stakeholders in the design process. During this “design, implement- and evaluate” process, a wide range of prototyping techniques have to be adhered, due to the high functional demands and the different user-driven aspects of the actual product. A consensus has to be made where rapid prototyping techniques go hand in hand with manual prototyping tech-niques and the use of standard components in order to come up with a fully functional and esthetical prod-ucts. The development process is documented by allocating versions to the sequential prototypes and describing particularly the performed user tests. The developed method is verified and illustrated by real case-studies

A prototype of a spherical tippe top

Among spinning objects, the tippe top exhibits one of the most bizarre and counterintuitive behaviours. The commercially available tippe tops basically consist of a section of a sphere with a rod. After spinning on its rounded body, the top flips over and continues spinning on the stem. It is the friction with the bottom surface and the position of the center of mass below the centre of curvature that cause the tippe top to rise its centre of mass while continuing rotating around its symmetry axis (through the stem). The commonly used simplified mathematical model for the tippe top is a sphere whose mass distribution is axially but not spherically symmetric, spinning on a flat surface subject to a small friction force that is due to sliding. According to the eccentricity of the sphere and the Jellet invariant (which includes information on the initial angular velocity) three main different dynamical behaviours are distinguished: tipping, non-tipping, hanging (i.e. the top rises but converges to an intermediate state instead of rising all the way to the vertical state.). Subclasses according to the stability of relative equilibria can further be distinguished. Our concern is the quantitative verification of the mathematical model. We applied 3D-printing to manufacture a '3-in-1 toy' that could catch the three main characteristics defining the three main groups in the classification of spherical tippe tops as mentioned above. This 'toy' allows verification by experimentation

The role of prototyping in product development

Companies want to increase the innovation degree and shorten development time of products in order to remain competitive. To obtain this goal, prototyping has become a decisive tool. Traditionally, prototypes get produced in a workshop. With the emergence of rapid prototyping and virtual prototyping, the range of prototyping methods has expanded. Research/service centers provide technical knowledge in order to support designers during prototyping. Despite these efforts and promising expectations, many companies have not significantly improved their development process, because they apply prototyping randomly and do not have a systematic method in applying prototyping adequately in the different stages of the development process. The industrial design center of HOWEST has performed a research project, sponsored by Flanders in Shape, on a systematic approach to apply rapid, traditional and virtual prototyping in the design process. The project resulted in a roadmap based on four design stages. The obtained research results were validated by designers in several industrial cases

Zorg Proeftuinen Vlaanderen. Een inhoudelijke vergelijking van de platformen en projecten bij de start

nrpages: 195status: publishe

Second asymptomatic carotid surgery trial (ACST-2) : a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86-1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91-1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable