Critical processes for managing supplier involvement in new product development: an in-depth multiple-case study�

supplier, new product development

Interplay of air and sand: Faraday heaping unravelled

We report on numerical simulations of a vibrated granular bed including the effect of the ambient air, generating the famous Faraday heaps known from experiment. A detailed analysis of the forces shows that the heaps are formed and stabilized by the airflow through the bed while the gap between bed and vibrating bottom is growing, confirming the pressure gradient mechanism found experimentally by Thomas and Squires [Phys. Rev. Lett. 81, 574 (1998)], with the addition that the airflow is partly generated by isobars running parallel to the surface of the granular bed. Importantly, the simulations also explain the heaping instability of the initially flat surface and the experimentally observed coarsening of a number of small heaps into a larger one

Bifurcation Diagram for Compartmentalized Granular Gases

The bifurcation diagram for a vibro-fluidized granular gas in N connected compartments is constructed and discussed. At vigorous driving, the uniform distribution (in which the gas is equi-partitioned over the compartments) is stable. But when the driving intensity is decreased this uniform distribution becomes unstable and gives way to a clustered state. For the simplest case, N=2, this transition takes place via a pitchfork bifurcation but for all N>2 the transition involves saddle-node bifurcations. The associated hysteresis becomes more and more pronounced for growing N. In the bifurcation diagram, apart from the uniform and the one-peaked distributions, also a number of multi-peaked solutions occur. These are transient states. Their physical relevance is discussed in the context of a stability analysis.Comment: Phys. Rev. E, in press. Figure quality has been reduced in order to decrease file-siz

Multifractality and nonextensivity at the edge of chaos of unimodal maps

We examine both the dynamical and the multifractal properties at the chaos threshold of logistic maps with general nonlinearity $z>1$. First we determine analytically the sensitivity to initial conditions $\xi_{t}$. Then we consider a renormalization group (RG) operation on the partition function $Z$ of the multifractal attractor that eliminates one half of the multifractal points each time it is applied. Invariance of $Z$ fixes a length-scale transformation factor $2^{-\eta}$ in terms of the generalized dimensions $D_{\beta}$. There exists a gap $\Delta \eta$ in the values of $\eta$ equal to $\lambda _{q}=1/(1-q)=D_{\infty}^{-1}-D_{-\infty}^{-1}$ where $\lambda_{q}$ is the $q$-generalized Lyapunov exponent and $q$ is the nonextensive entropic index. We provide an interpretation for this relationship - previously derived by Lyra and Tsallis - between dynamical and geometrical properties. Key Words: Edge of chaos, multifractal attractor, nonextensivityComment: Contribution to the proceedings of 2nd International Conference on News and Expectations in Thermostatistics (NEXT03), Cagliari, Italy, 21-28/09/2003. Submitted to Physica

Sudden Collapse of a Granular Cluster

Single clusters in a vibro-fluidized granular gas in N connected compartments become unstable at strong shaking. They are experimentally shown to collapse very abruptly. The observed cluster lifetime (as a function of the driving intensity) is analytically calculated within a flux model, making use of the self-similarity of the process. After collapse, the cluster diffuses out into the uniform distribution in a self-similar way, with an anomalous diffusion exponent 1/3.Comment: 4 pages, 4 figures. Figure quality has been reduced in order to decrease file-siz

Ambivalentie en strategische onwetenheid rond vlees; Reflectie op de Agrofoodmonitor

Relations between the agri-food sector and society are a source of concern, in particular with regard to in-tensive livestock farming. The agri-food monitor project was set up in order to define and measure socie-ty's valuation of the agri-food sector. Because the concept of societal valuation also raises many questions, this parallel study was added in order to create space for reflection on societal valuation. The character of this reflection has been informed by widespread signals of ambivalence towards meat as well as the suspicion that because of that ambivalence people often do not want to know too many details about meat and livestock farming. This can complicate research into societal valuation. The leading ques-tion of this study is whether and how insights into ambivalence and strategic ignorance can be helpful for understanding societal valuation, in particular with respect to meat. Some questions on this topic have al-so been added to the agri-foodmonitor itself. Ambivalence (conflicting valuation) with respect to meat has increased in recent decades because on the one hand most people are attached to eating meat while on the other hand, a great deal of unsettling information on intensive livestock farming is in the air. Ambivalence leads to emotional agitation, especially when choices relating to cherished habits are involved. One way to deal with that agitation is to keep un-welcome information at a distance, in this case information about livestock farming. In doing so, people are 'strategically ignorant'. Ambivalences in society remain partly hidden by this mechanism. This study looked at the role of ambivalence and strategic ignorance by studying existing literature and by carrying out interviews with fifteen consumers about what they did and didn't want to know about food. Three themes received particular attention: rapid-growth broilers, the use of antibiotics in livestock farming and inspiration with respect to food

Scaling behavior of coarsening Faraday heaps

When a layer of sand is vertically shaken, the surface spontaneously breaks up in a landscape of small conical “Faraday heaps,” which merge into larger ones on an ever increasing time scale. We propose a model for the heap dynamics and show analytically that the mean lifetime of the transient state with N heaps scales as N −2 . When there is an abundance of sand, such that the vibrating plate always remains completely covered, this means that the average diameter of the heaps grows as t 1/2 . Otherwise, when the sand is less plentiful and parts of the plate get depleted during the coarsening process, the average diameter of the heaps grows more slowly, namely as t 1/3 . This result compares well with experimental observations

Inversion of Chladni patterns by tuning the vibrational acceleration\ud

Inverse Chladni patterns, i.e., grains collecting at the antinodes of a resonating plate, are traditionally believed to occur only when the particles are small enough to be carried along by the ambient air. We now show—theoretically and numerically—that air currents are not the only mechanism leading to inverse patterns: When the acceleration of the resonating plate does not exceed g, particles will always roll to the antinodes, irrespective of their size, even in the absence of air. We also explain why this effect has hitherto escaped detection in standard Chladni experiment

Yang-Lee zeroes for an urn model for the separation of sand

We apply the Yang-Lee theory of phase transitions to an urn model of separation of sand. The effective partition function of this nonequilibrium system can be expressed as a polynomial of the size-dependent effective fugacity $z$. Numerical calculations show that in the thermodynamic limit, the zeros of the effective partition function are located on the unit circle in the complex $z$-plane. In the complex plane of the actual control parameter certain roots converge to the transition point of the model. Thus the Yang-Lee theory can be applied to a wider class of nonequilibrium systems than those considered previously.Comment: 4 pages, 3 eps figures include