Inverse dynamics of underactuated flexible mechanical systems governed by quasi-linear hyperbolic partial differential equations

Diese Arbeit befasst sich mit der inversen Dynamik unteraktuierter, flexibler, mechanischer Systeme, welche durch quasi-lineare hyperbolische partielle Differentialgleichungen beschrieben werden können. Diese Gleichungnen, sind zeitlich veränderlichen Dirichlet-Randbedingungen unterworfen, welche durch unbekannte, räumlich disjunkte, also nicht kollokierte Neumann-Randbedingungen erzwungen werden. Die zugrundeliegenden Gleichungen werden zunächst abstrakt hergeleitet, bevor verschiedene mechanische Systeme vorgestellt werden können, die mit der eingangs postulierten Formulierung übereinstimmen. Hierzu werden geometrisch exakte Theorien hergeleitet, welche in der Lage sind große Bewegungen schlanker Strukturen wie Seile und Balken, aber auch ganz allgemein, dreidimensionaler Festkörper zu beschreiben. In der Regel werden Anfangs-Randwertprobleme, die in der nichtlinearen Strukturdynamik auftreten, durch Anwendung einer sequentiellen Diskretisierung in Raum und Zeit gelöst. Diese Verfahren basieren für gewöhnlich auf einer räumlichen Diskretisierung mit finiten Elementen, gefolgt von einer geeigneten zeitlichen Diskretisierung, welche meist auf finiten Differenzen beruht. Ein kurzer Überblick über derartige sequentielle Integrationsverfahren für das vorliegende Anfangs-Randwertproblem wird zunächst anhand der direkten Formulierung des Problems gegeben werden. D.h. es wird zunächst das reine Neumann-Randproblem betrachtet, bevor anschließend ganz allgemein, verschiedene Möglichkeiten zur Einbindung etwaiger Dirichlet-Randbedingungen diskutiert werden. Darauf aufbauend wird das Problem der inversen Dynamik im Kontext räumlich diskreter mechanischer Systeme, welche rheonom-holonomen Servo-Bindungen unterliegen, eingeführt. Eine ausführliche Untersuchung dieser Art von gebundenen Systemen soll die grundlegenden Unterschiede zwischen Servo-Bindungen und klassischen Kontakt-Bindungen herausarbeiten. Die daraus resultierenden Folgen für die Entwicklung geeigneter numerisch stabiler Integrationsverfahren können dabei ebenfalls angesprochen werden, bevor zahlreich ausgewählte Beispiele vorgestellt werden können. Aufgrund der sehr eingeschränkten Anwendbarkeit der sequentiellen Lösung der inversen Dynamik in Raum und Zeit, wird eine eingehende Analyse des vorliegenden Anfangs-Randwertproblems unternommen. Vor allem durch die Freilegung der hyperbolischen Struktur der zugrundeliegenden partiellen Differentialgleichungen werden sich weitere Einblicke in das vorliegende Problem erhofft. Die Erforschung der daraus resultierenden Mechanismen der Wellenausbreitung in kontinuierlichen Strukturen öffnet die Tür zur Entwicklung numerisch stabiler Integrationsverfahren für die inverse Dynamik. So kann unter anderem eine Methode vorgestellt werden, die auf der Integration der partiellen Differentialgleichungen entlang charakteristischer Mannigfaltigkeiten beruht. Dies regt zu der Entwicklung neuartiger Galerkinverfahren an, die ebenfalls in dieser Arbeit vorgestellt werden können. Diese neu entwickelten Methoden können anschlie\ss end auf die Steuerung verschiedener mechanischer Systeme angewendet werden. Darüber hinaus können die neuartigen Integrationsverfahren auch auf flexible Mehrkörpersysteme übertragen werden. Angeführt seien hier beispielsweise die kooperative Steuerung eines an mehreren flexiblen Seilen aufgehängten starren Körpers oder die Steuerung des Endeffektors eines flexiblen mehrgliedrigen Schwenkarms. Ausgewählte numerische Beispiele verdeutlichen die Relevanz der hier vorgeschlagenen, in Raum und Zeit simultanen Integration des vorliegenden Anfangs-Randwertproblems

Categorization and integration of new and innovative materials in the development process of semi-finished products at the Dr. Ing. H.C. F. Porsche Ag

This paper serves as a guideline on how to integrate new and innovative interior materials in the development process of semi-finished products in the automotive industry. Therefore automotive interior trends were researched and the interior development process of the sports car manufacturer Porsche was examined. Three categories of materials were created to allocate new materials with similar characteristics to. On this basis, respective processes for each of the three categories were designed to ensure a smooth integration of innovative materials for future projects. The paper shows that depending on the category, materials belong to, the development activities and durations vary

Veterans’ Politics and Policies towards the Veterans of the Kosovo Liberation Army

Im Zentrum dieses Beitrags stehen die Kontroversen um eine angemessene Versorgung von Veteranen und Kriegsopfern im Nachkriegskosovo. Der institutionalisierte Umgang mit Veteranen in der ehemals serbischen Provinz Kosovo, die von 1999–2008 im Rahmen eines UN-Protektorats verwaltet wurde und am 17. Februar 2008 ihre Unabhängigkeit erklärte, war geprägt von den diametral entgegengesetzten Vorstellungen der internationalen Verwaltung und der albanischen Mehrheitsbevölkerung in Bezug auf den Charakter des entstehenden Staates und damit einhergehend, die gesellschaftliche Rolle der Veteranen. Gegenstand der Untersuchung sind die Ambivalenzen, die sich aus den beiden Staatskonzeptionen für die Veteranen ergeben: dem Aufbau eines national defi nierten, befreiten Kosovo – in dem ehemaligen Befreiungskämpfern eine privilegierte Rolle zukommt – auf der einen Seite, und der Errichtung einer multi-ethnischen Gesellschaft im Rahmen einer internationalen Friedensmission, auf der anderen

The role of inflammatory mediators in the development of insulin resistance and hepatocellular carcinoma

Over the last decade, obesity has been recognized as a chronic low inflammatory state that predisposes for the development of diseases, such as obesity-associated insulin resistance and cancer. The chronic low grade inflammation under obese conditions manifests not only as increase of inflammatory mediators, such as TNF-α and IL-6 in circulation, but also in elevated free fatty acids in the bloodstream. Though, this inflammatory condition has been shown to impair insulin action and to increase the incidence of cancer development. The liver specific contribution of IL-6 signaling as well as TLR signaling through the essential adaptor molecule MyD88 in these processes remains unclear. To examine the role of hepatic IL-6 signaling in glucose homeostasis, we have conditionally inactivated the IL-6Rα in hepatocytes of mice (IL-6RαL-KO). While these animals showed no alterations in body weight gain and body fat content, IL-6RαL-KO mice developed systemic insulin resistance, manifested as attenuated insulin stimulated glucose transport in skeletal muscle and fat during hyperinsulinemic-euglycemic clamps. Insulin resistance in these mice developed in the presence of increased circulating levels of IL-6 and TNF-α that directly translated in enhanced activation of inflammatory signaling in liver and skeletal muscle, thereby impairing insulin action. Neutralization of TNF-α or ablation of Kupffer cells restored glucose tolerance in IL-6RαL-KO mice to normal, indicating that increased circulating TNF-α, derived from the Kupffer cells, impairs insulin action systemically. Thus, our results reveal an unexpected role for hepatic IL-6 signaling to limit hepatic inflammation and to protect from local and systemic insulin resistance. Moreover, TLR-mediated signaling was examined in the development of insulin resistance and HCC, using mice with hepatocyte-specific MyD88 deficiency (MyD88L-KO mice). While glucose homeostasis was largely unaltered, these mice exhibited decreased liver damage, reduced hepatic macrophage infiltration and a strong reduction in chemically induced hepatocellular carcinoma development. Interestingly, tumor livers of MyD88L-KO mice exhibit reduced JNK activation that could potentially account for the reduced liver tumorgenesis in these animals. Taken together, this study highlights the hepatic role of inflammatory IL-6 and TLR-induced signaling in the development of obesity-associated insulin resistance and hepatocellular carcinogenesis

A simultaneous space-time discretization approach to the inverse dynamics of geometrically exact strings

A continuous space-time Galerkin method is newly proposed for the numerical solution of inverse dynamics problems. The proposed space-time finite element method is combined with servo-constraints to partially prescribe the motion of the underlying mechanical system. The new approach to the feedforward control of infinite-dimensional mechanical systems is motivated by the classical method of characteristics. In particular, it is shown that the simultaneous space-time discretization is much better suited to solve the inverse dynamics problem than the semi-discretization approach commonly applied in structural dynamics. Representative numerical examples dealing with elastic strings undergoing large deformations demonstrate the capabilities of the newly devised space-time finite element method

Controlling nonlinear elastic systems in structural dynamics

This contribution deals with the feedforward control of continuous mechanical systems. After introducing a general formulation of such problems and adressing the limitations of the commonly used semi-discrete method, two numerical methods are presented that resolve these limitations

Inverse Dynamics of Geometrically Exact Beams

This paper is concerned with the inverse dynamics of flexible mechanical systems whose motion is governed by quasi-linear hyperbolic partial differential equations. Problems that appear by applying classical solution strategies to the problem at hand, e.g. integrating the problem at hand sequentially in space and time will be adressed in this work. Motivated by the hyperbolic structure of the underlying initial boundary value problem, two methods that are based on a simultaneous space-time integration will be presented. Special emphasize will be given to the phenomena of wave propagation within geometrically exact beams and its relevance regarding the inverse dynamics problem

Breastfeeding woman are at higher risk of vitamin D deficiency than non-breastfeeding women - insights from the German VitaMinFemin study

Background: Despite increased awareness of the adverse health effects of vitamin D deficiency, only a few studies have evaluated the vitamin D status (25-hydroxyvitamin D [25(OHD)]) of breastfeeding women and up to now, no information exits for German breastfeeding women. Therefore, the aim of study was to determine the vitamin D status of breastfeeding women compared to non-pregnant and non-breastfeeding (NPNB) women. Methods: This cross-sectional study investigated 124 breastfeeding women and 124 age and season matched NPNB women from the German "Vitamin and mineral status among German women" study. The study participants were recruited from April 2013 to March 2015 and did not take vitamin D supplements. Serum 25(OH)D was analyzed by chemiluminescent immunoassay. Results: Vitamin D deficiency (<25.0 nmol/L) was prevalent in 26.6% of the breastfeeding women. The majority of women (49.2%) showed 25(OH)D concentration between 25.0 and 49.9 nmol/L. In multiple binary logistic regression analysis, breastfeeding women had a 4.0-fold higher odds ratio (OR) (95% confidence interval [CI] 1.8, 8.7) for vitamin D deficiency than NPNB women. For breastfeeding women, the risk of vitamin D deficiency was higher in the winter and spring months (OR: 2.6, 95% CI 1.1, 6.3) and increased with lower longitude per one unit (OR 0.7, 95% CI 0.6, 0.9). Conclusion: Breastfeeding women in Germany had a higher risk of deficient vitamin D levels than NPNB women. In further studies, the optimal vitamin D status for breastfeeding women should be investigated and also the required vitamin D doses to ensure this vitamin D status. Trial registration: German Clinical Trial Register (identification number: DRKS00004789 ).Rottapharm Madaus GmbHMeda A

Exercise and Physical Activity in the Therapy of Substance Use Disorders

Exercise and physical activity are constantly gaining attention as adjuvant treatment for substance use disorders, supplementing classical pharmacological and psychotherapeutic approaches. The present work reviews studies addressing the therapeutic effects of exercise in alcohol abuse/dependence, nicotine abuse/dependence, and illicit drug abuse/dependence. In the field of smoking cessation, evidence is strong for exercise as an effective adjuvant treatment, whereas no generalizable and methodologically strong studies have been published for alcohol and drug treatment so far, allowing only preliminary conclusions about the effectiveness of exercise in these disorders. A couple of potential mechanisms are discussed, by which exercise may act as an effective treatment, as well as future directions for studies investigating exercise as a treatment strategy for substance use disorders

Psychological Effects of Whole-body Electromyostimulation Training: a Controlled Pilot Study in Healthy Volunteers

Background: Whole-body electromyostimulation (WB-EMS) training is used in popular and health sports to improve muscular performance. Little is known about the possible psychological effects of WB-EMS training. The aim of the study is therefore to investigate the possible psychological effects of WB-EMS training on subjective well-being, relaxation, mood, and perceived stress. Materials and Methods: Twenty-five healthy subjects underwent conventional WB-EMS training and Sham training (without the application of electrical stimulation) as part of a randomized, controlled pilot study in a crossover design. Subjective well-being and subjective relaxation were assessed using visual analog scales, the current state of mood was assessed with Multidimensional Mood State Questionnaires (MDBF), and the current level of stress was assessed with Recovery-Stress Questionnaires/Erholungs-Belastungs-Fragebogen (RESTQEBF) before and after training. Results: WB-EMS training has a statistically significant positive effect on subjective well-being and subjective relaxation, as well as on the awake subscale of the MDBF. No significant main effect of sequence and no interaction effects were found. Also, compared to a Sham training session, a single WB-EMS training session had no significant effect on mood, nervousness, or the current level of stress. Conclusion: Besides physiological effects, WB-EMS might also have a strong psychological impact. WB-EMS could be beneficial for people who, due to their limitations, have problems training on a regular basis and with adequate training intensity