Editorial

Ohne Zusammenfassung

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Editorial

     

Kieferchirurgische Operationsplanung mit Hilfe von Techniken der virtuellen Realit?t

Zusammenfassung.   Für ein vollst?ndig computergestütztes Planungssystem zum Zwecke der kieferchirurgischen Operationsplanung ist die Bereitstellung von virtuellen Werkzeugen für den Chirurgen eine grundlegende Voraussetzung. Ausgehend von den Volumendaten mit Sch?del- und Kieferknochen des Patienten erm?glicht ein einfaches Interface unter Verwendung einer geeigneten Visualisierung und haptischer Eingabeger?te die interaktive Definition und Manipulation einzelner virtueller Knochensegmente. Wir haben moderne kraftrückgekoppelte Ger?te aus dem Niedrigpreisbereich eingebunden und auf ihre F?higkeit untersucht, das dreidimensionale Verst?ndnis im Planungsproze?durch Anlehnung an die Vorg?nge bei der chirurgischen Prozedur zu erh?hen. Durch diese Eingabeger?te ist es m?glich, die Knochensegmentierung für eine Osteotomie des Unterkiefers intuitiver und schneller durchzuführen. Die definierten Teilvolumina ergeben zusammen mit ihrer r?umlichen Neuanordnung auf Grundlage einer kephalometrischen Analyse einen Operationsplan. Nach erfolgter Planung werden die Planungsergebnisse in den Operationssaal übertragen. Die intraoperativen Techniken beinhalten die Visualisierung der Planungsergebnisse, die Steuerung der Anwendung über Sprache und die Bestimmung der Patientenposition mittels eines elektromagnetischen 3D-Trackingsystems. Eingegangen am 27. April 2000 / Angenommen am 21. Februar 2001     

Funktionelle gastrointestinale St?rungen Funktionelle Dyspepsie und Reizdarmsyndrom

Ohne Zusammenfassung     

The dream of education

Due to the indeterminacy inherent to anthropology and the necessity of human selfdesign, the dream of education is as necessary as education itself. The dream swirls about the realities of life and education; the dream supplements reality, corrects it, satisfies its unfulfilled desires; the dream penetrates reality, evades it, transcends it; it designs contrafactual modifications and alternatives. Yet, the question remains open as to what dreams are dreamed and which forms of education are realized in a particular society, and in a historical period. The difference between the dream and educational reality is irrevocable; it corresponds with the difference between the imaginary and the real. There is a tangible hiatus between imagination and reality, which, by exposing the limits of the possibilities of education to change human reality, and by revealing the limits to which humans can be educated, gives rise to ever-new compensatory dreams as well as nightmares of education.     

The Scientific Value of Cognitive Load Theory: A Research Agenda Based on the Structuralist View of Theories

In this paper, two methodological perspectives are used to elaborate on the value of cognitive load theory (CLT) as a scientific theory. According to the more traditional critical rationalism of Karl Popper, CLT cannot be considered a scientific theory because some of its fundamental assumptions cannot be tested empirically and are thus not falsifiable. According to the structuralist view of theories introduced by Joseph D. Sneed, a theory may be considered scientific even if it comprises nontestable fundamental assumptions. Rather, the scientific value of a theory results from the holistic empirical content of the overall theory net built around fundamental assumptions and from the successful applications of this theory net to explain and predict empirical findings. This latter view is helpful to explicate some implicit methodological assumptions of CLT research and to avoid the potential circularity of CLT’s fundamental assumptions. Additionally, the structuralist view of theories can be directly used to derive a research agenda for the future development of CLT.     

Trajectory tracking for a quadrotor under wind perturbations: sliding mode control with state-dependent gains

The problem of position tracking of a mini drone subject to wind perturbations is investigated. The solution is based on a detailed unmanned aerial vehicle (UAV) model, with aerodynamic coefficients and external disturbance components, which is introduced in order to better represent the impact of the wind field. Then, upper bounds of wind-induced disturbances are characterized, which allow a sliding mode control (SMC) technique to be applied with guaranteed convergence properties. The peculiarity of the considered case is that the disturbance upper bounds depend on the control amplitude itself (i.e. the system is nonlinear in control), which leads to a new procedure for the control tuning presented in the paper. The last part of the paper is dedicated to the analysis and reduction of chattering effects, as well as investigation of rotor dynamics issues. Conventional SMC with constant gains, proposed first order SMC, and proposed quasi-continuous SMC are compared. Nonlinear UAV simulator, validated through in-door experiments, is used to demonstrate the effectiveness of the proposed controls.     

Identifying paths to audience success of media products: the media decision-makers’ perspective

Research on media success factors is a fragmented field. Definitions, measures, and methods vary, and findings are often inconsistent. In an attempt to fill this perceived research gap, we distilled generic success factors of media products from the literature. Guided by theory and empirical findings, these factors were aggregated to complex concepts, building blocks of success that we further investigated in an exploratory qualitative study. We found that the building blocks are applicable to all types of media, independent of seriality and content types of media products. Subsequently the research question of this article is: Which building blocks of success are most important for media products? To answer this question, we conducted an online survey of 255 media professionals in print, audio-visual, and online media in Austria, Germany and Switzerland. To analyze our data, we deployed qualitative comparative analysis, a method based on set theory that is suitable to investigate complex causality. We conclude that four building blocks are necessary for success: “good” distribution, environmental orientation, form/design, and human resources are preconditions for achieving success in terms of audience market share. In addition, three patterns emerge in the sufficient paths (combinations of building blocks) to success. Which route to success a media product shows can be related to the width of its topical scope and the corresponding projected audience size.