Comparison of dns of compressible and incompressible turbulent droplet-laden heated channel flow with phase transition

In this paper a turbulent channel flow with dispersed droplets is examined. The dispersed phase is allowed to have phase transition, which leads to heat and mass transfer between the phases, and correspondingly modulates turbulent flow properties. As a point of reference we examine the flow of water droplets in air, containing also the vapor of water. The key element of this study concerns the treatment of the carrier phase as either a compressible or an incompressible fluid. We compare simulation results obtained with a pseudo-spectral discretization for the incompressible flow to those obtained with a finite volume approach for the compressible flow. The compressible formulation is not tailored for low Mach flow and we need to resort to a Mach number that is artificially high for simulation feasibility. We discuss differences in fluid flow, heat- and mass transfer and dispersed droplet properties. The main conclusion is that both formulations give a good general correspondence. Flow properties such as velocity fields agree very closely, while heat transfer as characterized by the Nusselt number differs by around 25%. Droplet sizes are shown to be slightly larger, particularly in the center of the channel, in case the compressible formulation is chosen. A low-Mach compressible formulation is required for a fully quantitative comparison

Forces and functions in scientific communication: an analysis of their interplay

This article deals with the transformation of the familiar, linear scientific information chain into an interactive scientific communication “network” in response to concomitant changes in scientific research and education. Societal conditions are seen to lead worldwide to the concept of strategic research: research dominated by "economy of scope". Strategic research leads to transnational research enterprises - universities and other research institutions - with a focus on return of research capital investment, and thus on intellectual capital. This development calls for new ways of knowledge management that in turn has consequences for scientific communication. The scientific communication market is described in terms of four main forces and their interplay. These forces are the actors (the author/reader pair), accessibility, content, and applicability. Scientific communication is described in terms of its four functions: registration, awareness, certification and archive. These forces and functions allow a structural analysis of the scientific communication market and allow to discuss aspects of structural continuity in e.g. describing the transformation from a paper-based system to communication in an electronic environment. The developments in research are seen to emphasise the already existing autonomous development of a "unified archive". Also these developments lead us to review certification policies to include elements external to research and to consider new structures for communication, and publications. The new structures are a result of the interactions in the market as described by the forces and the functions. The distinction between formal and informal communication is seen to become less useful. The need to review the structure and organisation of the market becomes evident, in particular if we consider communication during research as well. This leads us to speculate if elements of the virtual organisation are of relevance. Finally, the need for a coherent research programme on scientific communication is discussed

The Non-Legume Parasponia andersonii Mediates the Fitness of Nitrogen-Fixing Rhizobial Symbionts Under High Nitrogen Conditions

Organisms rely on symbiotic associations for metabolism, protection, and energy. However, these intimate partnerships can be vulnerable to exploitation. What prevents microbial mutualists from parasitizing their hosts? In legumes, there is evidence that hosts have evolved sophisticated mechanisms to manage their symbiotic rhizobia, but the generality and evolutionary origins of these control mechanisms are under debate. Here, we focused on the symbiosis between Parasponia hosts and N2-fixing rhizobium bacteria. Parasponia is the only non-legume lineage to have evolved a rhizobial symbiosis and thus provides an evolutionary replicate to test how rhizobial exploitation is controlled. A key question is whether Parasponia hosts can prevent colonization of rhizobia under high nitrogen conditions, when the contribution of the symbiont becomes nonessential. We grew Parasponia andersonii inoculated with Bradyrhizobium elkanii under four ammonium nitrate concentrations in a controlled growth chamber. We measured shoot and root dry weight, nodule number, nodule fresh weight, nodule volume. To quantify viable rhizobial populations in planta, we crushed nodules and determined colony forming units (CFU), as a rhizobia fitness proxy. We show that, like legumes and actinorhizal plants, P. andersonii is able to control nodule symbiosis in response to exogenous nitrogen. While the relative host growth benefits of inoculation decreased with nitrogen fertilization, our highest ammonium nitrate concentration (3.75 mM) was sufficient to prevent nodule formation on inoculated roots. Rhizobial populations were highest in nitrogen free medium. While we do not yet know the mechanism, our results suggest that control mechanisms over rhizobia are not exclusive to the legume clade.</p

The split between availability and selection. Business models for scientific information, and the scientific process?

The Berlin declaration on Open Access to Knowledge in the Sciences and Humanities has resulted in a strong impetus in the discussion on business models, and in particular the model of open access. A business model is defined as just the organisation of property. Consequently, business models for scientific information are discussed on the premise that any such business model should primarily produce added value for the scientific process next to commercial value for the research institution or intermediary acting as publisher. Furthermore, any business model should be sustainable. Scientific information is thus considered an integral part of the scientific process. It is not an end product but an intermediary product subject to scientific scrutiny. The final goal is to integrate the information into the scientific process. To this end, scientific information should be widely available for selection by the user as common property. Two basic business models emerge: one with the focus on added value as selection by the user known as the ‘subscription model’; and another one with the focus on wide availability known as the ‘open access’ model. Both in the subscription model as in the open access model it is the scientific community that invests. In the subscription model scientific information is more considered as external to the scientific process in a consumer type model, while in the open access model scientific information is more seen as internal, as necessary acquisition costs for the scientific process. In the subscription model there is less incentive for broad availability of information whereas in the open access model there is less incentive to develop and maintain added value services to facilitate the selection by the reader. The organisation of property is a condition sine qua non. Although common property, the information is owned by the author claiming this property by the act of publication. Core to this claim of property is peer review being therefore core to any business model. The author is interested in protecting his moral rights against plagiarism; the publisher is interested in protecting the added value against commercial abuse. It is suggested that open access repositories could boost if repository management would guarantee protection of the moral rights of the author. In this way, the protection to the two main infringements could be split over different stakeholders. This would also allow separating the responsibility for availability coupled with peer review as a basic service from added value services coupled to selection at an optional charge. In the end, any business model has to fulfill the basic idea that scientific information is not there just for the record as a commodity, but is there to be used in research and teaching: scientific information has no value in itself

Knowledge transfer activities of scientists in nanotechnology

In this paper, we present a theory of strategic positioning that explains scientists’ strategic behavior in knowledge transfer from university to industry. The theory is based on the drivers strategic interdependence and organizational autonomy and entails three modes of behavior of scientists: mode1, mode2, and mode3 (the research entrepreneur). The results of an empirical study conducted at a research institute for nanotechnology show that, to increase the likelihood of scientists engaging in knowledge transfer to industry, scientists need to have a high need for autonomy (expressed in decision-making on collaboration with industry and join research projects) and a high need for interdependence (expressed in the need for resources such as knowledge, skills, facilities, etc.). Scientists’ academic and industry orientations do not change the effect of the strategic positioning theory on the likelihood of engagement with industry, nor the likelihood of knowledge transfer. The strategic positioning theory explains 43 % of the variance, i.e. there is a firm foundation for managerial practices for different scientist modes of strategic behavior

Variational Principles for Lagrangian Averaged Fluid Dynamics

The Lagrangian average (LA) of the ideal fluid equations preserves their transport structure. This transport structure is responsible for the Kelvin circulation theorem of the LA flow and, hence, for its convection of potential vorticity and its conservation of helicity. Lagrangian averaging also preserves the Euler-Poincar\'e (EP) variational framework that implies the LA fluid equations. This is expressed in the Lagrangian-averaged Euler-Poincar\'e (LAEP) theorem proven here and illustrated for the Lagrangian average Euler (LAE) equations.Comment: 23 pages, 3 figure

Table of Contents

Table of contents for Volume 10, Issue 3 of the Linfield Magazin

BiCMOS high-performance ICs : from DC to mm-wave

Progress with silicon and silicon germanium (SiGe) based BiCMOS technologies over the past few years has been very impressive. This enables the implementation of traditional microwave and emerging mm-wave applications in silicon. The paper gives an overview of several high-performance ICs that have been implemented in a state-of-the-art BiCMOS technology (QUBiC4). Examples of high-performance ICs are described ranging from basic building blocks for mobile applications to highly integrated receiver and transmitter ICs for applications up to the mm-wave range