The damping and structural properties of dragonfly and damselfly wings during dynamic movement

For flying insects, stability is essential to maintain the orientation and direction of motion in flight. Flight instability is caused by a variety of factors, such as intended abrupt flight manoeuvres and unwanted environmental disturbances. Although wings play a key role in insect flight stability, little is known about their oscillatory behaviour. Here we present the first systematic study of insect wing damping. We show that different wing regions have almost identical damping properties. The mean damping ratio of fresh wings is noticeably higher than that previously thought. Flight muscles and hemolymph have almost no ‘direct’ influence on the wing damping. In contrast, the involvement of the wing hinge can significantly increase damping. We also show that although desiccation reduces the wing damping ratio, rehydration leads to full recovery of damping properties after desiccation. Hence, we expect hemolymph to influence the wing damping indirectly, by continuously hydrating the wing system

Design issues in the British Household Panel Study

The British Household Panel Study is the largest single project ever funded by the UK Economic and Social Research Council. Housed in the ESRC's Centre on Micro-social Change in Britain at the University of Essex, the BHPS will comprise an initial 5000 households and 10000 individuals. This paper introduces the Study through an overview of its coverage and some key aspects of its design. A short discussion of some of the analytic advantages of panel data is complemented by three examples of substantive research issues where panel data can assist in our understanding of micro-social change. The BHPS is discussed as an instance of a dynamic approach to social change and its overall rationale is briefly examined. The Study's six substantive research areas - household organisation and dynamics; labour market behaviour and activity; income and wealth dynamics; housing; health; and socio-economic values - are described. The remainder of the paper is concerned with three key design issues for panel studies and explains how these have been tackled on the BHPS. The issues are (1) changing populations; (2) non-sampling errors (and especially non-response and panel conditioning); and (3) sample design. The paper is accompanied by a substantial bibliography on panel design and methodology