There are numerous ways of segmenting a market based on consumer survey data. We introduce bagged clustering as a new exploratory approach in the field of market segmentation research which offers a few major advantages over both hierarchical and partitioning algorithms, especially when dealing with large binary data sets: In the hierarchical step of the procedure the researcher is enabled to inspect if cluster structure exists in the data and gain insight about the number of clusters to extract. The bagged clustering approach is not limited in terms of sample size, nor dimensionality of the data. More stable clustering results are found than with standard partitioning methods (the comparative evaluation is demonstrated for the K-means and the LVQ algorithm). Finally, segment profiles for binary data can be depicted in a more informative way by visualizing bootstrap replications with box plot diagrams. The target audience for this paper thus consists of both academics and practitioners interested in explorative partitioning techniques. (author's abstract) / Series: Working Papers SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

Techn. Universiẗat, Diss., 2002--Darmstadt.

In diesem Beitrag wird die Frage der Durchsetzung von Innovationen und ihrer modellhaften Darstellung behandelt. Das Proponenten-Opponenten-Modell von Jürgen Hauschildt nimmt in diesem Kontext in der deutschen Betriebswirtschaftslehre eine zentrale Position ein. Es vermag neben der Frage einer machtvollen Durchsetzung von Innovationen in Unternehmen die eminent wichtige Rolle des Lernens aller Beteiligten zu verdeutlichen. Bislang aber sind dynamische Aspekte in diesem Erklärungsansatz für die Durchsetzung von Innovationen nicht umfassend behandelt worden. Mit dem hier vorgestellten dynamischen Modellierungskonzept, das auf dem diskret angelegten Strukturgitteransatz der Perkolationstheorie beruht, wird versucht, die dynamische Betrachtungsweise zu stärken. Dieses erfolgt, indem der mit der Durchsetzung der Innovation verbundene kollektive Lernprozeß als Sickerprozeß aufgefaßt und entsprechend über diskrete Zeitschritte modelliert wird.

In diesem Beitrag wird die Frage der Durchsetzung von Innovationen und ihrer modellhaften Darstellung behandelt. Das Proponenten-Opponenten-Modell von Jürgen Hauschildt nimmt in diesem Kontext in der deutschen Betriebswirtschaftslehre eine zentrale Position ein. Es vermag neben der Frage einer machtvollen Durchsetzung von Innovationen in Unternehmen die eminent wichtige Rolle des Lernens aller Beteiligten zu verdeutlichen. Bislang aber sind dynamische Aspekte in diesem Erklärungsansatz für die Durchsetzung von Innovationen nicht umfassend behandelt worden. Mit dem hier vorgestellten dynamischen Modellierungskonzept, das auf dem diskret angelegten Strukturgitteransatz der Perkolationstheorie beruht, wird versucht, die dynamische Betrachtungsweise zu stärken. Dieses erfolgt, indem der mit der Durchsetzung der Innovation verbundene kollektive Lernprozeß als Sickerprozeß aufgefaßt und entsprechend über diskrete Zeitschritte modelliert wird.

Techn. Univ., Diss., 2002--Darmstadt

The excellent electrical and mechanical properties of carbon nanotubes (CNTs) provide interesting opportunities to realize new types of strain gauges. However, there are still challenges for the further development of CNT film strain gauges, for instance the lack of design rules, the homogeneity, stability and reproducibility of CNT films. This thesis aims to address these issues from two sides: simulation and experiment. Monte Carlo simulations show that both the sheet resistance and gauge factor of CNT films are determined essentially by the two-dimensional exclude area of CNTs. It was shown, for the first time, that the variation of the CNT film gauge factor follows the percolation scaling law. The sheet resistance and gauge factor both have a power-law divergence when approaching the percolation threshold. The standard deviation of film resistances, however, also increases correspondingly. These findings of simulations provide a general guide to the tailoring of material property of CNT films in strain sensing applications: a compromise should be made between the reproducibility, conductivity and sensitivity of CNT films depending on application purposes. From the experimental side, the processing parameters for the preparation of CNT dispersions were first investigated and optimized. The reproducibility of the film resistance is significantly improved by selecting a suitable sonication time. In strain measurements it was found that for most CNT films the film resistance responses nonlinearly to the applied strain. The dependence of the film resistance on the strain can be roughly divided into two regions with nearly linear behavior respectively. The gauge factor varies with the quality of CNTs and the depositing method. A gauge factor up to 8 was achieved in the high strain region. The nonlinear response behavior was found in simulations when the CNT waviness is properly taken into account. To achieve a high gauge factor and simultaneously retain the high conductivity and reproducibility, good-quality MWCNTs were integrated in polyethylene oxide (PEO). A high gauge factor up to 10 was achieved for the composite film with CNT weight fraction of 2.5%. The resistance and gauge factor can be tuned by changing the MWCNT weight fraction with respect to PEO. A careful comparison of simulation and experiment results show that a good qualitative agreement can be achieved between them in many respects.

Electronic devices made of organic molecules are starting to show their transfomative power in various fields of application today. However, as with most technologies, progress is eventually bounded by how well the inner workings of the components are understood. For electronic devices, as the name suggests, this mostly concerns the behavior of electrons or, more generally, electric charge carriers. To understand and predict device properties, knowledge of the mechanisms that govern the fate of charge carriers is indispensable. In an organic material, those mechanisms are closely related to material properties on a molecular level. Thus, the micro- and macroscale are linked in a complex manner and many questions about these links are still open. This work aims to advance the understanding of three important aspects of the field: the time-evolution of charge carrier states, the mechanism of molecular doping and the efficiency of organic solar cells and photodetectors. All three are strongly affected by a common property of organic materials: disorder. Specifcally, we extend the theoretical framework of describing the time-dependence of charge carrier motion in disordered semiconductors and use it to predict the time-dependence of recombination in organic solar cells. We find that, just as transport, recombination slows down with time, and establish a quantitative method of extracting material characteristics from the measured time-dependence of recombination. To analyze the influence of molecular doping on charge transport, we develop a computational method based on percolation theory. We show that for organic semiconductors, the popular transport energy model can not be used to predict the thermoelectric properties. The latter are important since they are often used to measure the amount of free charges introduced by doping. We are able to accurately model the activation energy of conductivity and study the important length scales and the influence of molecular parameters. Finally, we investigate the consequences of disorder on the performance of solar cells and photodetectors by studying the timescale and efficiency of the separation of photo-generated positive and negative charges. We find that, depending on the conditions, separation can in fact be either enhanced or hindered by disorder effects.

The excellent electrical and mechanical properties of carbon nanotubes (CNTs) provide interesting opportunities to realize new types of strain gauges. However, there are still challenges for the further development of CNT film strain gauges, for instance the lack of design rules, the homogeneity, stability and reproducibility of CNT films. This thesis aims to address these issues from two sides: simulation and experiment. Monte Carlo simulations show that both the sheet resistance and gauge factor of CNT films are determined essentially by the two-dimensional exclude area of CNTs. It was shown, for the first time, that the variation of the CNT film gauge factor follows the percolation scaling law. The sheet resistance and gauge factor both have a power-law divergence when approaching the percolation threshold. The standard deviation of film resistances, however, also increases correspondingly. These findings of simulations provide a general guide to the tailoring of material property of CNT films in strain sensing applications: a compromise should be made between the reproducibility, conductivity and sensitivity of CNT films depending on application purposes. From the experimental side, the processing parameters for the preparation of CNT dispersions were first investigated and optimized. The reproducibility of the film resistance is significantly improved by selecting a suitable sonication time. In strain measurements it was found that for most CNT films the film resistance responses nonlinearly to the applied strain. The dependence of the film resistance on the strain can be roughly divided into two regions with nearly linear behavior respectively. The gauge factor varies with the quality of CNTs and the depositing method. A gauge factor up to 8 was achieved in the high strain region. The nonlinear response behavior was found in simulations when the CNT waviness is properly taken into account. To achieve a high gauge factor and simultaneously retain the high conductivity and reproducibility, good-quality MWCNTs were integrated in polyethylene oxide (PEO). A high gauge factor up to 10 was achieved for the composite film with CNT weight fraction of 2.5%. The resistance and gauge factor can be tuned by changing the MWCNT weight fraction with respect to PEO. A careful comparison of simulation and experiment results show that a good qualitative agreement can be achieved between them in many respects.