Technology-transfer analysis of the materials research program “Matfo”

The commercial success of the German Federal Ministry's materials research program “Mafto” (1985–1994) was recently evaluated to determine the effectiveness of the direct-funding model in supporting innovative industrial research. Based on the results of a questionnaire, where a 97% return rate was achieved, it was found that the results obtained in 27% of the projects have already been commercialized to some degree, for 26% of the projects a commercialization of the results is planned but has not yet taken place, and for 54% of the projects no commercialization is planned. This study included only projects where at least four years had elapsed since project completion. The reasons why scientifically and technically successfully projects were not commercialized were also surveyed.     

An integrated system solution for supply chain optimization in the chemical process industry

This paper considers a complex scheduling problem in the chemical process industry involving batch production. The application described comprises a network of production plants with interdependent production schedules, multi-stage production at multi-purpose facilities, and chain production. The paper addresses three distinct aspects: (i) a scheduling solution obtained from a genetic algorithm based optimizer, (ii) a mechanism for collaborative planning among the involved plants, and (iii) a tool for manual updates and schedule changes. The tailor made optimization algorithm simultaneously considers alternative production paths and facility selection as well as product and resource specific parameters such as batch sizes, and setup and cleanup times. The collaborative planning concept allows all the plants to work simultaneously as partners in a supply chain resulting in higher transparency, greater flexibility, and reduced response time as a whole. The user interface supports monitoring production schedules graphically and provides custom-built utilities for manual changes to the production schedule, investigation of various what-if scenarios, and marketing queries. RID="*" ID="*" The authors would like to thank Hans-Otto Günther and Roland Heilmann for helpful comments on draft versions of this paper.     

27-GHz bandwidth high-speed monolithic integrated optoelectronicphotoreceiver consisting of a waveguide fed photodiode and anInAlAs/InGaAs-HFET traveling wave amplifier

A monolithic integrated photoreceiver for 1.55-μm wavelength has been designed for operation in a 20-Gb/s synchronous digital hierarchy system (SDH/SONET), based on a new integration concept. The optoelectronic integrated circuit (OEIC) receiver combines a waveguide-integrated PIN-photodiode and a traveling wave amplifier in coplanar waveguide layout with four InAlAs/InGaAs/InP-HFETs (0.7-μm gate length). The receiver demonstrates a bandwidth of 27 GHz with a low frequency transimpedance of 40 dBΩ. This is, to our knowledge, the highest bandwidth ever reported for a monolithic integrated photoreceiver on InP. Furthermore, a receiver sensitivity of -12 dBm in the fiber (20 Gb/s, BER=10^-9) and an overall optical input dynamic range of 27 dB is achieved. Optical time domain multiplex (TDM) system experiments of the receiver packaged in a module show an excellently shaped eye pattern for 20 Gb/s and an overall sensitivity of -30.5 dBm (BER=10^-9) [including erbium doped fiber amplifiers (EDFA)]     

Network Analysis of Commuting Flows: A Comparative Static Approach to German Data

The analysis of complex networks has recently received considerable attention. The work by Albert and Barabási presented a research challenge to network analysis, that is, growth of the network. The present paper offers a network analysis of the spatial commuting network in Germany. First, we study the spatial evolution of the commuting network over time. Secondly, we compare two spatial interaction model (SIM) specifications, in order to replicate the actual network structure. Our findings suggest that the commuting network appeared to become more dense and clustered, while the SIMs seem to require more sophisticated specifications, in order to replicate such a connectivity structure.     

First-Principles Study of Elastic Constants and Interlayer Interactions of Complex Hydrated Oxides: Case Study of Tobermorite and Jennite

It is a common perception that layered materials are soft in the interlayer direction. Herein, we present results of first-principles calculations of the structure and elastic constants of a class for hydrated oxides, tobermorite, and jennite, which illustrate that this is not the case, if (1) the interlayer distance is such that coulombic interlayer interactions become comparable to the iono-covalent intralayer interactions and (2) the existence of interlayer ions and water molecules do not shield the coulombic interlayer interactions. In this case, the mechanically softest directions are two inclined regions that form a hinge mechanism. The investigated class of materials and results are relevant to chemically complex hydrated oxides such as layered calcium–silicate–hydrates (C–S–H), the binding phase of all concrete materials, and the principle source of their strength and stiffness. In addition, the first-principles results may serve as a benchmark for validating empirical force fields required for the analysis of complex calcio–silicate oxides.     

Multisurface Chemoplasticity. I: Material Model for Shotcrete

Employing a thermodynamic framework, chemomechanical couplings for shotcrete are treated in this paper. A new material model based on multisurface chemoplasticity is presented. It accounts for hydration kinetics and chemomechanical couplings related to the strength growth and the evolution of stiffness properties as well as for autogeneous shrinkage in early-age shotcrete. The underlying intrinsic material functions, which are independent of field and boundary conditions, are determined from standard material tests. As for the numerical treatment of the constitutive equations of the material model, an extended form of the return mapping algorithm is proposed. The constitutive equations are applied to a two-surface chemoplastic model, consisting of a Drucker-Prager loading surface and a tension cut-off. In a companion paper, the proposed material model is employed for 2D structural analyses of tunnels driven according to the New Austrian Tunneling Method.     

The spatial distribution of new technology-based firms: Empirical results for West-Germany

The focus of the article is to shed some more light on the spatial distribution of new technology-based firms (NTBF) and to discuss location factors which may contribute to the explanation of the variation in the incidence of NTBF between the West-German districts (“Kreise”). Based on theoretical models explaining the location decisions of new firms, hypotheses are derived and tested in an empirical model. The regression results indicate strong correlations between the occurrence of NTBF and the proximity to Research and Development (R&D) facilities comprising universities, technical colleges and non-university institutes as well as private R&D. As expected, the impact of the various facilities varies with respect to their field of specialization, showing major positive correlations with respect to technical disciplines. Moreover, the estimates reveal out differences due to spatial characteristics such as infrastructure and other structural factors. Received: 26 April 1999 / Accepted: 28 November 1999     

The “Chunnel” Fire.?II: Analysis of Concrete Damage

In Part I of this study, a material model for the in-situ behavior of rapidly heated concrete was developed that accounts explicitly for the dehydration of concrete and its cross-effects with deformation (chemomechanical couplings) and temperature (chemothermal couplings). In this part of the study, the model is used in finite-element analysis of the tunnel rings of the Channel Tunnel (the “Chunnel”) exposed to fire. An analysis of the finite-element results—i.e., the profiles of temperature, dehydration, stresses, and plastic strains—clearly shows that the thermal spalling that occured during the Chunnel fire is initiated by an in-plane biaxial compressive stress clog closed to the heated surface. The compressive stresses are caused by restrained thermal dilatation and are bounded by chemoplastic softening due to dehydration. They provoke permanent radial deformation, which can be attributed to spalling. The role of thermal damage and thermal decohesion is discussed by comparing elastic, chemoelastic, and chemoplastic stress developments during the 10 h fire exposure. It is found that the salient feature to capture the initiation of thermal spalling at a structural level is the chemoplastic softening behavior at a constitutive material level. It is also shown that a reinforcement on the cold-side, as well as steel fiber reinforcement of concrete, in tunnel rings may significantly increase the risk of thermal spalling.     

Selective LPE-growth of ln0.53Ga0.47As on semi-insulating InP

Selective liquid phase epitaxy (SLPE) of high purity(n = 2 × 10¹⁵ cm^-3) In_0.53Ga_0.47As on SiO₂-masked (100)-InP:Fe substrates has been performed and investigated using Normarski interference contrast microscopy and SEM. The infill growth was done at low temperatures (˜ 585° C) directly into chemically (HC1:CH₃COOH:H₂O₂) etched cavities without melt-etching. Square and circular recesses of 2–3 μm depth and varying size (100-500 μm) have been used in contrast to common reported regrowth experiments in long channels. Enormously enhanced growth rates have been found within the small structures. Orientation dependent growth effects are described. The realization of selectively grown areas with flat surface morphology has been achieved which is important for optoelectronic integration. Most information contained in this paper was presented at the 27th Electronic Materials Conference, Boulder, Co., June 20, 1985.     

n-Type Doping of Vapor–Liquid–Solid Grown GaAs Nanowires

In this letter, n-type doping of GaAs nanowires grown by metal–organic vapor phase epitaxy in the vapor–liquid–solid growth mode on (111)B GaAs substrates is reported. A low growth temperature of 400°C is adjusted in order to exclude shell growth. The impact of doping precursors on the morphology of GaAs nanowires was investigated. Tetraethyl tin as doping precursor enables heavily n-type doped GaAs nanowires in a relatively small process window while no doping effect could be found for ditertiarybutylsilane. Electrical measurements carried out on single nanowires reveal an axially non-uniform doping profile. Within a number of wires from the same run, the donor concentrations N _D of GaAs nanowires are found to vary from 7 × 10¹⁷ cm^-3 to 2 × 10¹⁸ cm^-3. The n-type conductivity is proven by the transfer characteristics of fabricated nanowire metal–insulator-semiconductor field-effect transistor devices.