Stylised Facts and the Contribution of Simulation to the Economic Analysis of Budgeting

The application of computer simulation as a research method raises two important questions: (1) Does simulation really offer added value over established methods? (2) How can the danger of arbitrariness caused by the extended modelling possibilities be minimised? We present the concept of stylised facts as a methodological basis for approaching these questions systematically. In particular, stylised facts provide a point of reference for a comparative analysis of models intended to explain an observable phenomenon. This is shown with reference to a recent discussion in the "economic analysis of accounting" literature where established methods, i.e. game theory, as well as computer simulations are used: the susceptibility of the "Groves mechanism" to collusion. Initially, we identify six stylised facts on the stability of collusion in empirical studies. These facts serve as a basis for the subsequent comparison of four theoretical models with reference to the above questions: (1) We find that the simulation models of Krapp and Deliano offer added value in comparison to the game theoretical models. They can be related to more stylised facts, achieve a better reproduction and exhibit far greater potential for incorporating yet unaddressed stylised facts. (2) Considered in the light of the stylised facts to which the models can be related, Deliano's simulation model exhibits considerable arbitrariness in model design and lacks information on its robustness. In contrast, Krapp demonstrates that this problem is not inherent to the method. His simulation model methodically extends its game theoretical predecessors, leaving little room for arbitrary model design or questionable parameter calibration. All in all, the stylisedfactsconcept proved to be very useful in dealing with the questions simulation researchers are confronted with. Moreover, a "research landscape" emerges from the derived stylised facts pinpointing issues yet to be addressed.Computer Simulation, Stylised Facts, Methodology, Groves Mechanism, Collusion, Game Theory

Internal Jet Structure in Dijet Production in Deep-Inelastic Scattering

The internal jet structure in dijet production in deep-inelastic scattering is measured with the H1 detector at HERA. Jets with transverse energies E(T,breit) > 5 GeV are selected in the Breit frame employing kt and cone jet algorithms in the kinematic region of squared momentum transfers of 10 < Q^2 < 120 GeV^2 and x-Bjorken values of 0.0002 < x < 0.008. Jet shapes and subjet multiplicities are measured as functions of a resolution parameter. The corrected data are well described by QCD models. It is observed that jets are more collimated with increasing transverse jet energies and decreasing pseudo-rapidities, i.e. towards the photon direction. Comparisons with OPAL data show that jet shapes of jets measured in photon-photon collisions are very similar to those measured in ep collisions.Comment: 4 pages, 3 figures, to be published in the proceedings of 7th International Workshop on Deep Inelastic Scattering and QCD (DIS 99), Zeuthen, Germany, 19-23 Apr 199

Pluriliteracies teaching for learning:Conceptualizing progression for deeper learning in literacies development

Peer reviewedPublisher PD

Coarse Graining of Nonbonded Inter-particle Potentials Using Automatic Simplex Optimization to Fit Structural Properties

We implemented a coarse-graining procedure to construct mesoscopic models of complex molecules. The final aim is to obtain better results on properties depending on slow modes of the molecules. Therefore the number of particles considered in molecular dynamics simulations is reduced while conserving as many properties of the original substance as possible. We address the problem of finding nonbonded interaction parameters which reproduce structural properties from experiment or atomistic simulations. The approach consists of optimizing automatically nonbonded parameters using the simplex algorithm to fit structural properties like the radial distribution function as target functions. Moreover, any mix of structural and thermodynamic properties can be included in the target function. Different spherically symmetric inter-particle potentials are discussed. Besides demonstrating the method for Lennard--Jones liquids, it is applied to several more complex molecular liquids such as diphenyl carbonate, tetrahydrofurane, and monomers of poly(isoprene).Comment: 24 pages, 3 tables, 14 figures submitted to the Journal of Chemical Physics (JCP

How Social Media-Enabled Communication Awareness Enhances Project Team Performance

Project teams increasingly rely on computer-mediated communication. In this paper, we propose that communication within these teams benefits from a communication-awareness feature that summarizes communication at one common place. We argue that such a feature pays out specifically during action episodes, when team members engage in taskwork. We conducted two studies of 51 and 35 project teams to examine how the amount of communication during action episodes relates to team performance under low versus high communication awareness. In both studies, we technologically designed communication awareness as the availability of a feed, known from social media platforms, that displays all team-internal, computer-mediated communication. The results show that the communication-awareness feature makes communication during action episodes more beneficial, both in term of effectiveness and efficiency. Zooming into the temporal patterns of communication during action episodes further reveals that high-performing teams in the high-communication-awareness condition stick out by early and steady communication. Implications for current and future research on team communication and awareness support are discussed

When Less is More: How Short-message Feeds in Social Media Platforms Affect Collaborative Learning

Social media platforms bear the promise of enhancing interactions in collaborative learning. Yet, relatively little is known about how short-message feeds, a key feature in many social media platforms, affect collaborative learning. We report the results of a field experiment in which we manipulated the social media platform that 53 teams of four students used for a collaborative learning task over three weeks. We find that students provided with short-message feeds achieved significantly better learning outcomes than students without. While learner engagement was similar in both conditions, learner communication was more focused on the task in the condition with short-message feeds. The short-message feed led learners to curtail social communication and uncertainty statements, which mediated the effect of the short-message feeds on learning outcomes. Our study provides new insights into the effect of short-message feeds on collaborative learning and communication

DMAIC in Lithium-Ion-Battery Production

DMAIC refers to a data-driven cycle of analysis steps used for improving, optimizing and stabilizing business processes with the steps Define, Measure, Analyze, Improve, and Control (DMAIC). In this paper, we will demonstrate the Define, Measure, and Analyze steps for the calendering step in Lithium-Ion-Battery Production. It appears that the measurement system is at least questionable. Moreover, we identified influential factors for thickness and porosity of the foil

High Resolution Crystal Structures of the Wild Type and Cys-55 right-arrow Ser and Cys-59 right-arrow Ser Variants of the Thioredoxin-like [2Fe-2S] Ferredoxin from Aquifex aeolicus

The [2Fe-2S] ferredoxin (Fd4) from Aquifex aeolicus adopts a thioredoxin-like polypeptide fold that is distinct from other [2Fe-2S] ferredoxins. Crystal structures of the Cys-55 right-arrow Ser (C55S) and Cys-59 right-arrow Ser (C59S) variants of this protein have been determined to 1.25 Å and 1.05 Å resolution, respectively, whereas the resolution of the wild type (WT) has been extended to 1.5 Å. The improved WT structure provides a detailed description of the [2Fe-2S] cluster, including two features that have not been noted previously in any [2Fe-2S] cluster-containing protein, namely, pronounced distortions in the cysteine coordination to the cluster and a Calpha -H-Sgamma hydrogen bond between cluster ligands Cys-55 and Cys-9. These features may contribute to the unusual electronic and magnetic properties of the [2Fe-2S] clusters in WT and variants of this ferredoxin. The structures of the two variants of Fd4, in which single cysteine ligands to the [2Fe-2S] cluster are replaced by serine, establish the metric details of serine-ligated Fe-S active sites with unprecedented accuracy. Both the cluster and its surrounding protein matrix change in subtle ways to accommodate this ligand substitution, particularly in terms of distortions of the Fe2S2 inorganic core from planarity and displacements of the polypeptide chain. These high resolution structures illustrate how the interactions between polypeptide chains and Fe-S active sites reflect combinations of flexibility and rigidity on the part of both partners; these themes are also evident in more complex systems, as exemplified by changes associated with serine ligation of the nitrogenase P cluster