Modelling of a micro Coriolis mass flow sensor for sensitivity improvement

We have developed a multi-axis flexible body model with which we can investigate the behavior of (micro) Coriolis mass flow sensors with arbitrary channel geometry. The model has been verified by measurements on five different designs of micro Coriolis mass flow sensors. The model predicts the Eigen frequency of the first two modes within 10% when the sensor tube is filled with air, water or iso-propyl alcohol. The complex shape and high aspect ratio of the micro channels do not allow conventional FEM modelling. Instead the Matlab package SPACAR is used, which allows to model the sensor with a limited number of elements, providing fast and accurate numerical computations. This allows optimization of channel geometry and positioning of the sensing structures. The model can also be applied to other resonating structures

Changing from batch to flow assembly in the production of emergency lighting devices.

Current assembly enterprises are under a lot of pressure, as they are faced with increasing volume demands and product variations, needs for shorter delivery times and cost reduction. This pressure is likely to increase the pressure on individual workers. In many small to medium-sized enterprises (SMEs), we observe that traditional assembly concepts are no longer fulfilled. These are challenged to find other concepts to meet today's demands. In a company where emergency lighting devices are assembled in batches (large series of products are assembled step by step), we applied a participatory and integrative approach to set up a mixed flow assembly system including ergonomically designed work stations. In this paper, we describe the approach and the effects which were studied by a within-subject design. We observed an increase of 44% in productivity and a reduction in order lead time of 46%. The time that workers spent to added-value activities increased significantly from 74% to 92%, without any increase in postural and experienced loads. Instead, the workers experienced significantly less overall fatigue at the end of the day in the new situation. The results show the potential benefits of the approach for the many SMEs where products are assembled in batches and faced with the problem of meeting current production demands. © 2005 Taylor & Francis Group Ltd

Seat design in the context of knowledge work

Performing knowledge work often involves prolonged sitting in a limited number of positions with little physical effort. This can lead to discomfort in the neck and shoulder region, and health problems in the back and neck. Subsequently, it can affect job performance adversely. In this PhD project is the influence of different seat design variables investigated, combined with posture and movement behavior in several tasks, on comfort and discomfort. The research was carried out in various office environments and in the train. In addition, a prototype lounge chair has been studied, whereby watching a monitor screen was central. The results of these studies contribute to the scientific debate on optimal seating support for knowledge work, but also to practical applications for functional chair design and evaluation.Applied Ergonomics and DesignIndustrial Design Engineerin

Kies de ideale kantoorstoel : draaiend, kantelend of roterend

Het uitkiezen van een bureaustoel is niet eenvoudig: er is een enorme keus in gezondheidsstoelen zoals roterende stoelen, pendelstoelen en skippybalstoelen. Belangrijk is dat de stoel past bij het werk. Bij al deze gezondheidsstoelen is het idee dat meer beweging betere doorbloeding geeft, dat de tussenwervelschijf beter van voedingsstoffen wordt voorzien en het gehele bewegingsapparaat niet stijf wordt. Dit zou klachten aan rug en nek voorkomen en het zitcomfort bevorderen. In dit artikel wordt nagegaan of deze stoelen ook leiden tot een meetbaar effect op de werknemer, of er verschillen in spierspanning meetbaar zijn en of gebruikers zich comfortabel voelen. Vakmedi

One set of pliers for more tasks in installation work: The effects on (dis)comfort and productivity

In installation work, the physical workload is high. Awkward postures, heavy lifting and repetitive movements are often seen. To improve aspects of the work situation, frequently used pliers were redesigned to make them suitable for more cutting tasks. In this study these multitask pliers are evaluated in comparison to the originally used pliers in a field study and a laboratory study. For the field study 26 subjects participated divided into two groups according to their type of work. Ten subjects participated in the laboratory study. The multitask plier appeared to result in more comfort during working, more relaxed working and more satisfaction. No differences in productivity were found. In conclusion, the multitask pliers can replace the originally used pliers and are suitable for more tasks than the original pliers. The installation workers have to carry less pliers by using the multitask pliers. © 2004 Elsevier Ltd. All rights reserved

Effects of differences in office chair controls, seat and backrest angle design in relation to tasks

In this study the influence of chair characteristics on comfort, discomfort, adjustment time and seat interface pressure is investigated during VDU and non-VDU tasks: The two investigated office chairs, both designed according to European and Dutch standards are different regarding: 1) seat cushioning and shape, 2) backrest angle and 3) controls. Thirty subjects in total, both male and female, participated in two experiments: twenty in the first and ten in the second. Significant differences are found for ease of adjustment and adjustment time of controls, independent of the tasks. Related to tasks, a significant difference was found for the backrest range of motion. For non-VDU tasks a larger range of backrest motion was preferred by 70% of the subjects. The chair design differences were most clear for comfort and adjustment time of controls, followed by comfort of backrest angle. No differences are found between seat pan comfort and discomfort, first impressions and peak interface pressure. © 2008 Elsevier Ltd. All rights reserved