Measurements of Solid Spheres Bouncing Off Flat Plates

Recent years have seen a substantial increase of interest in the flows of granular materials whose rheology is dominated by the physical contact between particles and between particles and the containing walls. Considerable advances in the theoretical understanding of rapid granular material flows have been made by the application of the statistical methods of molecular gas dynamics (e.g., Jenkins and Savage (1983), Lun et al. (1984)) and by the use of computers simulations of these flows (e.g., Campbell and Brennen (1985), Walton (1984)). Experimental studies aimed at measurements of the fundamental rheology properties are much less numerous and are understandably limited by the great difficulties involved in trying to measure velocity profiles, solid fraction profiles, and fluctuating velocities within a flowing granular material. Nevertheless, it has become clear that one of the most severe problems encountered when trying to compare experimental data with the theoretical models is the uncertainty in the material properties governing particle/particle or particle/wall collisions. Many of the theoretical models and computer simulations assume a constant coefficient of restitution (and, in some cases, a coefficient of friction). The purpose of the present project was to provide some documentation for particle/wall collisions by means of a set of relatively simple experiments in which solid spheres of various diameters and materials were bounced off plates of various thickness and material. The objective was to provide the kind of information on individual particle/wall collisions needed for the theoretical rheological models and computer simulations of granular material flows: in particular, to help resolve some of the issues associated with the boundary condition at a solid wall. For discussion of the complex issues associated with dynamic elastic or inelastic impact, reference is made to Goldsmith (1960) and the recent text by Johnson (1985)

Une bibliothèque de recherche face à l'édition électronique

Le développement des collections de périodiques a toujours constitué une composante majeure des politiques d'acquisition des bibliothèques de recherche. Aujourd'hui, les voilà confrontées simultanément, et de manière aiguë, à une difficulté certes récurrente : l'augmentation ininterrompue du coût des abonnements, et à une nouveauté radicale encore très difficile à maîtriser et qui engendre plutôt des surcoûts : la mise sur le marché de documents numérisés, principalement des périodiques. Organe d'un établissement pionnier en matière d'utilisation des réseaux informatiques pour la diffusion des résultats de la recherche, la bibliothèque du CERN a depuis plusieurs années déjà intégré cette nouvelle donne dans sa politique d'acquisition

Luxury fashion brands: factors influencing young female consumers' luxury fashion purchasing in Taiwan

Purpose - Against the background of increasing consumption of luxury fashion brands by young female consumers in Asian countries, this paper offers insights into the consumption motives and purchasing behaviour of that market segment in Taiwan. Design/methodology/approach - Analysis of data collected using face-to-face semi-structured interviews with twenty-three 18-32 year-old fashion-conscious females was completed and new empirical insights are offered. Findings - The study found a high level of involvement in the world of luxury fashion retailing. Asian consumers devoured media commentary, drew inspiration from female celebrities, and treated information-seeking and discussion of luxury fashion brands with friends as a serious and enjoyable pursuit. The social status conferred by expensive fashion wear motivated them to spend on luxury brands even if their discretionary income was limited. Potential guilt in so doing was assuaged by rationalising that the quality was good and the purchase would be long lasting. Marketers targeting this valuable segment should communicate appeals to an aspirational lifestyle in traditional and social media, effective at reaching young women. Originality/value - The study reported in this article contributes to the limited published research into the luxury marketing sector in Asia by examining the buying behaviour of female Strawberry Generation consumers in Taiwan. It is the first to research and investigate the meanings attached to luxury by these individuals in the collectivist culture of Taiwan, as well as their motivations, and the factors influencing their purchase of luxury fashions. The study thus contributes with new knowledge to the buying of luxury fashion products by young female Taiwanese consumers, which may be extended to other collectivist cultures in Asia

Topic-Relevance Map: Visualization for Improving Search Result Comprehension

Peer reviewe

Random Displacement Modulus and Damping Determination

Modulus and damping values were determined for both undisturbed and remolded silty sand specimens by cyclic triaxial methods utilizing both sinusoidal and random displacement stroke control. Remolded specimens were prepared at 3 different dry unit weights using a preparation technique that gave the same formation factor as the undisturbed specimen. Results indicated that the random displacement method tends to produce results which are similar to those obtained by the sinusoidal procedure at shearing strain levels less than 10-1 %. At shearing strain levels greater than 10-1 % the random displacement method gives lower modulus and higher damping ratio values when compared to the sinusoidal procedure. In addition, stress history effects as demonstrated by the location of the cycle in the record being analyzed were observed not to be important over the sample unit weights investigated

Structure and mechanism of human DNA polymerase η

The variant form of the human syndrome xeroderma pigmentosum (XPV) is caused by a deficiency in DNA polymerase eta (Pol eta), a DNA polymerase that enables replication through ultraviolet-induced pyrimidine dimers. Here we report high-resolution crystal structures of human Pol eta at four consecutive steps during DNA synthesis through cis-syn cyclobutane thymine dimers. Pol eta acts like a 'molecular splint' to stabilize damaged DNA in a normal B-form conformation. An enlarged active site accommodates the thymine dimer with excellent stereochemistry for two-metal ion catalysis. Two residues conserved among Pol eta orthologues form specific hydrogen bonds with the lesion and the incoming nucleotide to assist translesion synthesis. On the basis of the structures, eight Pol eta missense mutations causing XPV can be rationalized as undermining the molecular splint or perturbing the active-site alignment. The structures also provide an insight into the role of Pol eta in replicating through D loop and DNA fragile sites