Composite indicator for railway infrastructure management

Railway Engineering Science - The assessment and analysis of railway infrastructure capacity is an essential task in railway infrastructure management carried out to meet the required quality and...     

Analysing quadratic effects of formative constructs by means of variance-based structural equation modelling

Together with the development of information systems research, there has also been increased interest in non-linear relationships between focal constructs. This article presents six Partial Least Squares-based approaches for estimating formative constructs’ quadratic effects. In addition, these approaches’ performance is tested by means of a complex Monte Carlo experiment. The experiment reveals significant and substantial differences between the approaches. In general, the performance of the hybrid approach as suggested by Wold (1982) is most convincing in terms of point estimate accuracy, statistical power, and prediction accuracy. The two-stage approach suggested by Chin et al (1996) showed almost the same performance; differences between it and the hybrid approach – although statistically significant – were unsubstantial. Based on these results, the article provides guidelines for the analysis of non-linear effects by means of variance-based structural equation modelling.     

Plastic deformation of linear polyethylene containing row structures

The mechanical and thermal properties of highly oriented polyethylene films containing shish kebab type morphology are studied. At low deformations (strain<10%) strong work hardening is observed. Higher deformations ((40%) give rise to strain softening of the material and a decrease in the Young's modulus of as much as one-third of its initial value. In addition, the high melting component of the material originating from the shish-type crystals vanishes on higher deformation. The deformation processes are discussed from the point of view of a fibre-composite material and structural changes during the deformation are followed by transmission electron microscopy.     

On the prediction of band-limited signals from past samples

A new method is used to construct coefficients a_kn such that any band-limited signal function with highest frequency ΠW can be reconstituted from its samples from the past via

$\text{?(t)=}\text{lim}\text{n→∞}\text{σ}\text{k=1}\text{n}\text{a}{}_{\mathrm{kn}}\text{?}\text{t?}\text{kT}\text{W}$

Although the existence of such predictor coefficients can be proved for each positive T < 1, so far they have been exhibited only for $\text{T ? (0,}\text{built1}\text{2}\text{)}$ by J. L. Brown, Jr. [1]. Using the mathematical tool of power series expansions in the complex domain, T can be extended to at least $\text{T <}\text{1}\text{2}$, that is, the sampling rate has to exceed three-halves the Nyquist rate. Again the predictor coefficients a_kn do not depend on the structure of ? or on the bandwidth parameter W.     

Influence of disordering by low-temperature neutron irradiation on the superconducting transition temperature of Nb3Sn

The superconducting transition temperatureT _c of a Nb₃Sn diffusion wire has been studied as a function of low-temperature neutron irradiation (T=10 K).T _c is observed to be essentially constant until the fast neutron dose t (for neutron energiesE>0.1 MeV) exceeds a value of 10¹⁸ n/cm²; after this valueT _c decreases linearly with t up to the maximum applied dose of 1.05×10¹⁹ n/cm². Comparison with theory and other experimental data indicates that radiation-induced disorder is the primary mechanism for the observedT _c changes.Work supported by the Bundesministerium für Forschung und Technologie and by the Deutsche Forschungsgemeinschaft.     

Cracking in and around the thermally grown oxide in thermal barrier coatings: A comparison of isothermal and cyclic oxidation

In the present paper the time and temperature dependent evolution of the microstructure of TBC systems and especially of post-experimentally determined physical defects in and around the TGO for both isothermal and cyclic exposure conditions are investigated. Specimens with APS- as well as with PVD-topcoats have been oxidised between 950 and 1100°C up to a maximum duration of 5000 h followed by extensive scanning electron microscopy and subsequent interactive image analysis to measure the maximum crack lengths in and around the TGO. These cracks are additionally classified with respect to their local orientation in the TGO or its vicinity. The results of isothermal and cyclic test conditions show a number of similarities in results e.g. an unsystematic occurrence of inwardly growing, “cauliflower like” oxide or the most frequently occurring type of cracks in APS systems. Nevertheless substantial differences concerning the final failure, microstructure, crack growth behaviour and finally life time of the component between isothermal and cyclic test conditions exist. Some indications were found, that for this particular bond coat occurance of inwardly growing oxide intrusions increases the adherence of the TGO.     

Coordination in networks: An economic equilibrium analysis

Networks utilizing modern communication technologies can offer competitive advantages to those using them wisely. But due to the existence of network effects, planning and operating cooperation networks is difficult. In this paper, the strategic situation of individual agents deciding on network participation is analysed. A systematic equilibrium analysis using computer-based simulations reveals principal solution scenarios for network agents and shows that network cooperation problems might frequently be not as difficult to resolve as often feared. In particular, strategic situations are identified showing that a majority of individuals might be better off getting the optimal solution from a central principal and that in many cases simple information intermediation can solve the start-up problem notorious in network economics.     

High Order Finite Difference Approximations of Electromagnetic Wave Propagation Close to Material Discontinuities

Electromagnetic wave propagation close to a material discontinuity is simulated by using summation by part operators of second, fourth and sixth order accuracy. The interface conditions at the discontinuity are imposed by the simultaneous approximation term procedure. Stability is shown and the order of accuracy is verified numerically.     

Thermophysical Properties of Binary Mixtures of R125 + R143a in Comparison with a Simple Prediction Method

The thermal diffusivity and sound speed of binary refrigerant mixtures of R143a (1,1,1-trifluoroethane) and R125 (pentafluoroethane) have been determined for both the saturated liquid and vapor phase using dynamic light scattering (DLS). Measurements were performed for four quite different mixture compositions over a wide temperature range from 293 to 345 K approaching the vapor-liquid critical point. The results obtained corroborate the usefulness of a simple prediction method for the determination of different thermophysical properties of multicomponent mixtures in the two-phase region up to the critical point. Besides the information on the properties for the pure components, the successful application of the prediction method is also based on an exact knowledge of the critical temperature. The composition dependence of the critical temperature has been determined by observation of the vanishing meniscus between liquid and vapor phases. The mixture results are discussed in detail and compared with available literature data.     

Automatic data collection for enterprise architecture models

Enterprise Architecture (EA) is an approach used to provide decision support based on organization-wide models. The creation of such models is, however, cumbersome as multiple aspects of an organization need to be considered, making manual efforts time-consuming, and error prone. Thus, the EA approach would be significantly more promising if the data used when creating the models could be collected automatically—a topic not yet properly addressed by either academia or industry. This paper proposes network scanning for automatic data collection and uses an existing software tool for generating EA models (ArchiMate is employed as an example) based on the IT infrastructure of enterprises. While some manual effort is required to make the models fully useful to many practical scenarios (e.g., to detail the actual services provided by IT components), empirical results show that the methodology is accurate and (in its default state) require little effort to carry out.