Hourglass of constant weight

In contrast to a still common belief, a steadily flowing hourglass changes its weight in the course of time. We will show that, nevertheless, it is possible to construct hourglasses that do not change their weight.Comment: 2 pages, 1 figur

DETERMINANTEN UND KONSEQUENZEN DER UMFRAGEEINSTELLUNG. Bewertungsdimensionen unterschiedlicher Umfragesponsoren und die Antwortbereitschaft der Befragten

This article deals with two questions: a) the evaluations of surveys of different sponsors on the dimensions utility, reliability and burden as determinants of the generalized attitude towards surveys, and b) the answer or refusal of the income question as an indicator of cooperative behavior during the interview as a consequence of respondents� attitudes towards surveys. In the first part of the analysis it is furthermore tested whether the quantity of survey experience in the past moderates the strength of the observed associations. The empirical analysis with data from a local survey based on a random probability sample shows increasingly stronger associations between respondents� sponsor-specific evaluations and their attitudes towards surveys when subjects have taken part more often in surveys in the past. The perceived utility of surveys and the evaluation of scientific sponsors proves to be the strongest determinants for the generalized attitude towards surveys. Regarding the second question of this article it is found that the probability of answering or refusing to answer the income question increases considerably when the interviewees have more negative and - as indicated by their response latencies - at the same time cognitively accessible attitude towards surveys. Thus it is concluded that respondents� attitudes towards surveys have serious consequences for the quality of survey data.

Wohnungsfertigstellungen in Europa bleiben auf hohem Niveau - Weitere Ergebnisse der Euroconstruct-Winterkonferenz 2005

Nach den aktuellen Prognosen der Experten für die in der Euroconstruct-Gruppe zusammengeschlossenen 19 europäischen Länder werden die Wohnungsfertigstellungen im laufenden Jahr zwar leicht zunehmen, danach gehen sie aber bis 2008 wieder etwas zurück. Ursächlich hierfür ist die anhaltende Abwärtstendenz im Eigenheimbau. Demgegenüber halten die Fertigstellungszahlen im Geschosswohnungsbau trotz kleiner Einbußen ihr bis 2005 gestiegenes Niveau: Der Anstieg bei den Mehrfamiliengebäuden wird jedoch die Rückgänge bei Ein- und Zweifamiliengebäuden wertmäßig nicht voll kompensieren können.Wohnungsbau, Wohnungsbaupolitik, Altbaumodernisierung, Wohneigentum, Deutschland, Europa

Coefficient of tangential restitution for the linear dashpot model

The linear dashpot model for the inelastic normal force between colliding spheres leads to a constant coefficient of normal restitution, $\epsilon_n=$const., which makes this model very popular for the investigation of dilute and moderately dense granular systems. For two frequently used models for the tangential interaction force we determine the coefficient of tangential restitution $\epsilon_t$, both analytically and by numerical integration of Newton's equation. Although $\epsilon_n=$const. for the linear-dashpot model, we obtain pronounced and characteristic dependencies of the tangential coefficient on the impact velocity $\epsilon_t=\epsilon_t(\vec{g})$. The results may be used for event-driven simulations of granular systems of frictional particles.Comment: 12 pages, 12 figure

Spezielle Silazanderivate von Digallan(4) und Diindan(4) mit Ga-Ga- bzw. In-In-Bindung

Al, Ga and In can easily be incorporated in the cyclic silazane (MeSi)2(NtBu)4H2(LH2) through formal substitution of the hydrogen atoms by the metallic elements. LAlMe, LAlCl, LGaCl, LInCl as well as the side product L(H)InCl2 are obtained in high yields. X-ray structure determinations confirm the molecules LAlMe and L(H)InCl2 to be polycyclic and the metallic atoms to be four-coordinated by intramolecular nitrogen donors. When LAlCl, LGaCl and LInCl are reduced by sodium naphthalene, in the two latter cases the formation of LGaGaL and LInInL is observed. An X-ray structure determination of LInInL shows an InIn bond of 2.768(1) A° with the two indium atoms being coordinated by three nitrogen atoms each (InN ranging from 2.12(1)-2.298(7) A°). LGaGaL and LInInL can be considered as the first amides of GaII and InII

Role of interactions in ferrofluid thermal ratchets

Orientational fluctuations of colloidal particles with magnetic moments may be rectified with the help of external magnetic fields with suitably chosen time dependence. As a result a noise-driven rotation of particles occurs giving rise to a macroscopic torque per volume of the carrier liquid. We investigate the influence of mutual interactions between the particles on this ratchet effect by studying a model system with mean-field interactions. The stochastic dynamics may be described by a nonlinear Fokker-Planck equation for the collective orientation of the particles which we solve approximately by using the effective field method. We determine an interval for the ratio between coupling strength and noise intensity for which a self-sustained rectification of fluctuations becomes possible. The ratchet effect then operates under conditions for which it were impossible in the absence of interactions.Comment: 18 pages, 10 figure

Integrated knowledge utilization and evolution for the conservation of corporate know-how

Insufficient consideration of knowledge evolution is a frequent cause for the failure of knowledge-based systems (KBSs) in industrial practice. Corporate know-how about the design and manufacturing of a particular product is subject to rather rapid changes, and it is hard to specify in advance exactly what information will be requested by various users. Keeping a KBS for the conservation of corporate know-how up-to-date or even enhancing its utility, thus requires the continuous monitoring of its performance, noting deficiencies, and suggestions for improvements. In the current paper, we discuss different ways in which information collected during knowledge utilization can be exploited for system evolution. We present structure-based rule and concept editors which allow for an immediate integration and formalization of new information, even by rather inexperienced users. A prototypical knowledge conservation system for crankshaft design which was developed in cooperation between the DFKI and a German company is used to illustrate and evaluate our approach