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In this chapter, to investigate the tensile behavior of CNTs, finite element models of single-walled carbon nanotubes (SWCNTs) in perfect and doped modes for common types of carbon nanotube (CNT) configuration, i.e., the armchair, zigzag, and chiral models, were generated using a commercial finite element software (MSC Marc). To create the computational models, nodes were placed at the locations of carbon atoms and the bonds between them were modeled using three-dimensional elastic generalized beam elements. Doped models were simulated by three different heteroatoms including silicon, nitrogen, and boron separately with the doping concentration ranging from 0 to 5%. Young’s moduli of all models were obtained and compared with the perfect structures. The results indicated that Young’s modulus of chiral SWCNTs is larger than the moduli of the armchair and zigzag SWCNTs in all models and incorporating the silicon and boron atoms into CNT led to a linear reduction in Young’s modulus which was most significant for silicon and less noticeable for boron. Regarding nitrogen doping, a different trend was observed that was a negligible and less conspicuous increment in the value of Young’s modulus by increasing the percentage of doping. Besides, this behavior was the same for all armchair, zigzag, and chiral configurations with the same dopant atom. The investigations also revealed that the structural irregularity and ripples, which are induced by dopant atoms, are a key factor which influences the tensile behavior of CNTs. Our results for Young’s modulus of doped CNTs are in good agreement with recent investigations.
This Encyclopedia covers the entire science of continuum mechanics including the mechanics of materials and fluids. The encyclopedia comprises mathematical definitions for continuum mechanical modeling, fundamental physical concepts, mechanical modeling methodology, numerical approaches and many fundamental applications. The modelling and analytical techniques are powerful tools in mechanical civil and areospsace engineering, plus in related fields of plasticity, viscoelasticity and rheology. Tensor-based and reference-frame-independent, continuum mechanics has recently found applications in geophysics and materials.
Background:
Glaucoma, a characteristic type of optic nerve degeneration in the posterior pole of the eye, is a common cause of irreversible vision loss and the second leading cause of blindness worldwide. As an optic neuropathy, glaucoma is identified by increasing degeneration of retinal ganglion cells (RGCs), with consequential vision loss. Current treatments only postpone the development of retinal degeneration, and there are as yet no treatments available for this disability. Recent studies have shown that replacing lost or damaged RGCs with healthy RGCs or RGC precursors, supported by appropriately designed bio-material scaffolds, could facilitate the development and enhancement of connections to ganglion cells and optic nerve axons. The consequence may be an improved retinal regeneration. This technique could also offer the possibility for retinal regeneration in treating other forms of optic nerve ailments through RGC replacement.
Methods:
In this brief review, we describe the innovations and recent developments in retinal regenerative medicine such as retinal organoids and gene therapy which are specific to glaucoma treatment and focus on the selection of appropriate bio-engineering principles, biomaterials and cell therapies that are presently employed in this growing research area.
Results:
Identification of optimal sources of cells, improving cell survival, functional integration upon transplantation, and developing techniques to deliver cells into the retinal space without provoking immune responses are the main challenges in retinal cell replacement therapies.
Conclusion:
The restoration of visual function in glaucoma patients by the RGC replacement therapies requires appropriate protocols and biotechnology methods. Tissue-engineered scaffolds, the generation of retinal organoids, and gene therapy may help to overcome some of the challenges in the generation of clinically safe RGCs.
Tagespflege in Bewegung
(2020)
Social work across the world has been shaped by prevailing political systems, their influence on the welfare system and hence the social work profession. This thesis examines how the social work profession evolved in South Africa focusing on the political transition from Apartheid to democracy. Particular interests of the research are the development of South African social workers professionalism regarding professional conduct and professional identity. Moreover, it brings out the manifold changes the profession had to undergo in the political transition and consequently the issues the social work profession deals with today.
For an efficient operation of a low voltage PMSM an optimized voltage usage is very important. Because of the relation between the low voltage and the high currents in this type of machine, a large voltage reserve is needed to compensate the influence of parameter mismatches and to guarantee a stable current control. As the power is limited by the low voltage in this type of hybrid drive systems, optimizing the voltage usage is also required to maximize the power and the torque availability. This paper describes a closed loop flux control to maximize the voltage usage. The controller feedback is used to estimate and maximize the available torque for each operating point.
For a low voltage IPMSM used in a hybrid drive system of a consumer car, it is of the highest importance to design a torque controller circuit that produces an accurate torque at the shaft. The accurate torque is needed to distribute the load between the combustion engine, or the manual break, and the electrical drive. As the capacitance of the batteries used in this type of car is usually very small, the control of the batteris state of charge and its output current is quite critical. Therefore, a precise torque control is elementary. Temperature changes have a large impact on the IPMSM internal parameters. Especially the permanent magnet flux and the stator resistance are affected by temperature changes. There are techniques to observe and calculate the temperature variation of these parameters. This contribution describes a method to handle the influence of temperature variation on the actual torque at the shaft, by correcting the current commands of the open loop controller.
Stellvertretende Hoffnung
(2020)
Im Recovery-Ansatz wird `Stellvertretende Hoffnung` als ein wichtiges Moment helfender Beziehungen verstanden. Psychiatrieerfahrene Personen rekonstruieren dabei immer wieder, wie (über-)lebenswichtig es für sie war, dass ein (nahestehender) Anderer – gerade in der Situation, als sie selbst alle Hoffnung auf Besserung verloren hatten – für sie stellvertretend weitergehofft hat. Auch im Peer Counseling geht es „darum, die Situation des anderen durch den gemeinsamen Erfahrungshintergrund des emotionalen und psychologischen Schmerzes empathisch zu verstehen“ (Utschakowski 2015, S. 14). Durch den gegenseitigen Austausch über gleichgelagerte Erfahrungen und über Möglichkeiten von deren Überwindung eröffnet sich plötzlich ein Ausweg, den ich nicht für möglich gehalten hätte. Betroffene spüren, nicht allein zu sein, nicht der/die* einzige zu sein, der/die* je so etwas erleben muss. Es lohnt sich aus unserer Sicht, ausgehend von diesen beiden Ansätzen (Recovery und Peer Counseling), einige Fragen an das gängige Verständnis über die helfenden Begegnungen zu stellen. Und wir regen an, darüber nachzudenken, wie man sich überhaupt selbst vertreten kann und wer für wen Stellvertreter*in sein kann oder sein müsste bzw. wer als Selbstvertreter*in und Stellvertreter*in anerkannt wird, in Situationen, in denen wir uns nicht selbst vertreten können. Und schließlich ist es notwendig, der Frage nachzugehen: Welche Inspirationen gehen von diesen Ansätzen und Diskursen für die sozialarbeiterische Professionalität aus?
Wir gehen in diesem Beitrag darüber hinaus der `Stellvertretenden Hoffnung` auf den Grund. Wir fragen dabei danach, in welchem Verhältnis Stellvertretung und Selbstvertretung zueinanderstehen, wenn Hoffnung mit ins Spiel kommt. Wir versuchen die Anliegen dieses Beitrags in einem Vierschritt zu erhellen: Zunächst wagen wir den Versuch, uns im selbstreflexiven und spekulativen Schreiben zu vergewissern, was wir unter stellvertretender Hoffnung verstehen können (Apero). In einem zweiten Schritt möchten wir uns zweier befreiungstheologisch-philosophisch-feministischer Antwortversuche widmen. Dazu nähern wir uns den Positionen von Dorothee Sölle (Stellvertretung) und Carter Heyward (Macht in Beziehungen). Wir deuten dabei diese theologisch-philosophischen Positionen nicht nur im Sinne einer spätmodernen Christologie, sondern übersetzen diese elementaren Gedanken zum Menschsein in Begegnung im säkularisierten Horizont der menschlichen Diskursivität (im Sinne von Jürgen Habermas), damit über die in diesen Positionen eingelagerte Normativität gemeinsam – mit guten Gründen – gerungen werden kann. Im dritten Schritt nähern wir uns wiederum selbstreflexiv und dialogisch dem Verhältnis von Stellvertretung und Selbstvertretung. Das abschließende Kapitel gilt der Frage, wer Stellvertretung für wen übernehmen kann und darf und wem die Sprecher*innenrolle dabei zumeist zugeschrieben wird und warum.
Menschen wachsen lassen!
(2020)