On nonlinear thermo-electro-elasticity

Electro-active polymers (EAPs) for large actuations are nowadays well-known and promising candidates for producing sensors, actuators and generators. In general, polymeric materials are sensitive to differential temperature histories. During experimental characterizations of EAPs under electro-mechanically coupled loads, it is difficult to maintain constant temperature not only because of an external differential temperature history but also because of the changes in internal temperature caused by the application of high electric loads. In this contribution, a thermo-electro-mechanically coupled constitutive framework is proposed based on the total energy approach. Departing from relevant laws of thermodynamics, thermodynamically consistent constitutive equations are formulated. To demonstrate the performance of the proposed thermo-electro-mechanically coupled framework, a frequently used non-homogeneous boundary-value problem, i.e. the extension and inflation of a cylindrical tube, is solved analytically. The results illustrate the influence of various thermo-electro-mechanical couplings

Ein Beitrag zur tonraumbasierten Analyse und Synthese musikalischer Audiosignale

The goal of the present work is to improve the analysis and synthesis of musical audio signals by the application of tonal pitch spaces. The first part written by Gabriel Gatzsche consists of the Chapters 2 to 6. It discusses the mathematic-geometrical description of tonality on several hierarchical levels based on Fred Lerdahl’s Tonal Pitch Space, David Gatzsche’s Cadence Circle and Elaine Chew’s Spiral Array (calculation of geometric centroids within tonal pitch spaces). Using two formulas, the symmetry model generator formula and the SYM operator, it is possible 1.) to describe the emergence of the most important levels of western tonality out of an array of fifths and 2.) to generate several key related models which are centered to the corresponding symmetry tone. With that steps it becomes possible to link several existing pitch spaces into a unified framework called symmetry model. To enable also the analysis of real music signals based on pitch spaces the centroid vector within the circular pitch space is introduced. This feature vector is a low dimensional representation of important tonal properties of musical audio signals. Such properties are functional relationships, the mode, tension and relaxation or harmonic ambiguities. Furthermore the pitch class - pitch height space is introduced. This space assigns geometric positions to different octaves of a given pitch class such that ”well sounding” chords can be created by choosing a simple shaped region of the space. By transforming (rotating, translating, scaling etc.) such a region also well sounding chord transitions are generated. This leads to the development of a new musical instrument, called HarmonyPad. The HarmonyPad allows a musician to create music by interacting with pitch spaces directly. Within the second part of the dissertation consisting of the Chapters 7 to 12 Markus Mehnert investigates the applicability of the symmetry model to concrete problems of music information retrieval (MIR) particularly chord and key recognition. The state of the art in the field of key recognition focuses on the estimation of major and minor keys. Within that work a new symmetry model based algorithm is presented which exceeds the results of current algorithms clearly. Additionally a new approach is proposed which extends key recognition to the estimation of the most often used six church modes. The latter represent the character of a musical piece in a better way then the standard modes ”major” and ”minor” do. Furthermore a new benchmark is introduced which allows the comparison of the current approach with future algorithms. A new machine learning algorithm (HMM/KNN) is proposed. The new algorithm combines the approaches Hidden Markov Models and k Nearest Neighbours. In the field of chord recognition the new approach achieves better results then all of the previous algorithms. It is shown that the symmetry model feature vector leads to significant better chord recognition results then the chroma vector which represents the state of the art.Das Ziel dieser Arbeit besteht darin, Verbesserungen in der Analyse und Synthese von Audiosignalen durch Anwendung von Tonräumen zu erreichen. Im ersten Teil, der die Kapitel 2 bis 6 enthält und von Gabriel Gatzsche verfasst wurde, erfolgt die mathematisch-geometrische Beschreibung der Tonalität auf verschiedenen hierarchischen Ebenen angelehnt an Fred Lerdahls Tonal Pitch Space, David Gatzsches Kadenzkreis und Elaine Chew’s Spiral Array (Berechnung von geometrischen Schwerpunkten in Tonraummodellen). Mit Hilfe zweier Formeln, der Symmetriemodell-Generatorformel und dem SYM-Operator, wird es möglich, die Entstehung der wichtigsten Hauptebenen der abendländischen Tonalität aus einer Quintreihe zu beschreiben, verschiedene, auf eine Tonart bezogene Modelle zu erzeugen und auf den jeweiligen Symmetrieton zu zentrieren. Damit gelingt es, eine Vielzahl bereits existierender Modelle zu verbinden und in ein einheitliches als Symmetriemodell bezeichnetes Framework zu integrieren. Um auch reale Musiksignale tonraumbasiert analysieren zu können, wird mit dem Summenvektor im kreisförmigen Tonraum ein Feature-Vektor vorgestellt, der wichtige tonale Eigenschaften eines Musiksignals niedrigdimensional repräsentiert. Dazu gehören z.B. funktionstheoretische Eigenschaften, das Tongeschlecht, Spannungs- und Auflösungsbestreben oder auch harmonische Mehrdeutigkeiten. Weiterhin wird der Tonigkeits-Tonhöhenraum eingeführt, der den unterschiedlichen Oktavlagen von Tonigkeiten geometrische Positionen so zuordnet, dass durch Wahl eines Raumauschnittes „gut klingende“ Akkorde erzeugt und durch Transformation des Raumausschnittes „günstig“ ineinander übergeblendet werden können. Dies führt zur Entwicklung eines neuartigen Musikinstrumentes, das als HarmonyPad bezeichnet wird. Dieses erlaubt einem Musiker, direkt mit geometrischen Tonräumen zu interagieren und damit Musiksignale zu erzeugen. Markus Mehnert untersucht im zweiten Teil der Arbeit in den Kapiteln 7 bis 12 die Anwendbarkeit des Symmetriemodells auf konkrete Probleme des Music Information Retrieval (MIR). Hier werden sowohl die Tonart- als auch die Akkorderkennung betrachtet. Im Bereich der Tonarterkennung, die sich derzeit auf die Erkennung von Dur- und Molltonarten beschränkt, wird ein neuer Algorithmus vorgestellt, der auf dem Symmetriemodell basiert. Dieser verbessert den Stand der Technik erheblich. Darüber hinaus wird ein vollkommen neuer Ansatz vorgestellt, der die Tonarterkennung auf die sechs gebräuchlichsten Kirchentonarten erweitert, da diese besser als die reine Erkennung von Dur und Moll geeignet sind, den Charakter eines Musikstückes widerzuspiegeln. Zusätzlich wird ein neues Bewertungsmaß eingeführt, das den Vergleich mit zukünftigen Verfahren ermöglicht. Es wird ein für das MIR neues maschinelles Lernverfahren (HMM/KNN) vorgestellt, das die beiden Verfahren Hidden Markov Models und k Nearest Neighbours verknüpft. Im Bereich der Akkorderkennung werden mit diesem neuen Verfahren bessere Ergebnisse als mit allen vorhergehenden Verfahren erzielt. Dabei zeigt sich auch, dass der Merkmalsvektor des Symmetriemodells in Verbindung mit Akkorderkennung signifikant besser ist als der Chromavektor, der den Stand der Technik repräsentiert

A complete thermo–electro–viscoelastic characterization of dielectric elastomers, Part I: Experimental investigations

Dielectric elastomers are a class of solid polymeric materials that are sufficiently soft to deform under the application of an electric field due to the interaction of quasi-static electric charges. Their potential to undergo large deformations renders them promising candidates for the design of energy harvesters, sensors and soft actuators. For their application however, the influence of additional thermal effects should be taken into account as the base materials frequently show a distinct thermal sensitivity that drastically influences their mechanical response. This contribution presents the results of a wide range of experiments conducted on the popular dielectric elastomer VHB 4905™ under a combination of mechanical, thermal and electric loading scenarios. These experiments are performed in such a way that the obtained results are well suited for the identification of the necessary material parameters appearing in a thermo–electro–viscoelastic constitutive model that will subsequently be presented in the second part of the contribution

Numerical modeling of nonlinear photoelasticity

When molecular photo-switches, such as azobenzene or norbornadiene, are embedded into a sufficiently soft polymer matrix the resulting compound can undergo a mechanical deformation induced by light of a specific wavelength. These photo-sensitive compounds have the potential to be applied as soft actuators without the need for hard wired electronics or a separate energy source. Such characteristics are especially attractive in the design of micro-scale robots but also other applications such as high-speed data transfer or the conversion of photonic energy into a mechanical response holds great promise. Despite these almost futuristic possibilities, photo-sensitive polymers have not yet experienced a sufficient attention in industrial applications. One important factor to increase the acceptance of this group of soft smart materials is the formulation of a rigorous constitutive modeling approach in combination with numerical simulation methods. Thus, in this contribution we present a photo-mechanical modeling approach, departing from the fundamentals published previously. We briefly introduce the necessary constitutive equations which are subsequently utilized in combination with the respective balance laws into a finite element implementation. Finally, the capabilities of the numerical solution approach are illustrated by a simple two-dimensional bench-mark example and subsequently extended to a more complex three-dimensional problem

Towards a thermo-magneto-mechanical coupling framework for magneto-rheological elastomers

Magnetorheological elastomers (MREs) are a relatively new class of smart materials that can undergo large deformations resulting from external magnetic excitation. These are promising candidates in producing sensors and actuators. Due to their inherent chemical compositions, most polymeric materials are highly susceptible to temperature. While performing experiments on MREs that are exposed to magneto-mechanically coupled loads, maintaining a constant temperature profile is a non-trivial task for various reasons, e.g., i) experiments need to be performed in a temperature chamber that can maintain a prescribed temperature throughout a test, and ii) additional temperature gradients can be generated internally. In this paper, a thermo-magneto-mechanically coupled constitutive model is devised that is based on the total energy approach frequently used in MREs modelling and computation. Relevant constitutive equations are derived exploiting basic laws of thermodynamics that result in a thermodynamically consistent formulation. We demonstrate the performance of the proposed thermo-magneto-mechanically coupled framework with the help of two non-homogeneous boundary value problems. In both problems an axisymmetric cylindrical tube is deformed under thermo-magneto-mechanically coupled loads. In the first example the mechanical deformation is a combination of axial stretch and radial inflation whereas in the second example the cylinder is put under a mechanical load of torsion around the cylinder axis combined with an axial stretch. In both examples a circumferential magnetic field and a radial temperature gradient are applied. The results capture various thermo-magneto-mechanical couplings with the formulation proposed for MRE

A Raman technique applicable for the analysis of the working principle of promoters and inhibitors of gas hydrate formation

We report a Raman technique applicable for the in situ analysis of the development of hydrogen bonds in the liquid water‐rich phase just before the onset of gas hydrate formation. Herewith, the phase transition as well as the working principle of hydrate formation inhibitors and promoters can be analyzed

What Comes after the Trial? An Observational Study of the Real-World Uptake of an E-Mental Health Intervention by General Practitioners to Reduce Depressive Symptoms in Their Patients

Unguided and free e-mental health platforms can offer a viable treatment and self-help option for depression. This study aims to investigate, from a public health perspective, the real-world uptake, benefits, barriers, and implementation support needed by general practitioners (GPs). The study presents data from a spin-off GP survey conducted 2.5 years subsequent to a cluster-randomized trial. A total of N = 68 GPs (intervention group (IG) GPs = 38, control group (CG) GPs = 30) participated in the survey (response rate 62.4%). Data were collected via postal questionnaires. Overall, 66.2% of the GPs were female. The average age was 51.6 years (SD = 9.4), and 48.5% of the GPs indicated that they continued (IG) or started recommending (CG) the e-mental health intervention under real-world conditions beyond the trial. A number of benefits could be identified, such as ease of integration and strengthening patient activation in disease management. Future implementation support should include providing appealing informational materials and including explainer videos. Workshops, conferences, and professional journals were identified as suitable for dissemination. Social media approaches were less appealing. Measures should be taken to make it easier for health care professionals to use an intervention after the trial and to integrate it into everyday practice

Experimental and numerical investigations of the electro-viscoelastic behavior of VHB 4905TM

Dielectric elastomers are a class of electro-active polymers (EAPs) that can be used for the development of simple soft actuators, sensors and energy harvesters. Their operation principle is based on the interaction of quasi-static electric charges in combination with soft dielectrics and deformable electrodes. Due to their ability to undergo large deformations with a time dependent material response of the underlying polymer, the mechanical behaviors of EAPs can be described by a finite strain viscoelastic material model [1]. This model is here augmented in order to account for the influence of the electro-mechanical coupling. In this contribution we pursue a comprehensive electro-mechanical characterization of the popular dielectric polymer VHB 4905™. In contrast to the results of the electro-mechanical experiments published previously [2] all of these experiments are conducted without the application of a pre-stretch and are therefore well suited for the identification of the coupling parameters of the material model. The presented model shows excellent agreements with experimental findings

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival