Einschätzung der Folgen der demografischen Entwicklung

Entwicklungen, die sich langsam und kontinuierlich vollziehen, liegen oft im Windschatten der öffentlichen Aufmerksamkeit – selbst, wenn sie von großer Tragweite sind. Das gilt ausgeprägt für den demografischen Wandel, der das Land zunehmend verändert und insbesondere die sozialen Sicherungssysteme vor große Herausforderungen stellt. Nur eine kleine Minderheit der Bürger setzt sich jedoch intensiv mit diesem Thema auseinander. 15 Prozent beschäftigt dieses Thema sehr, 53 Prozent nur begrenzt und die übrigen kaum oder gar nicht

Control-focused, nonlinear and time-varying modelling of dielectric elastomer actuators with frequency response analysis

Current models of dielectric elastomer actuators (DEAs) are mostly constrained to first principal descriptions that are not well suited to the application of control design due to their computational complexity. In this work we describe an integrated framework for the identification of control focused, data driven and time-varying DEA models that allow advanced analysis of nonlinear system dynamics in the frequency-domain. Experimentally generated input–output data (voltage-displacement) was used to identify control-focused, nonlinear and time-varying dynamic models of a set of film-type DEAs. The model description used was the nonlinear autoregressive with exogenous input structure. Frequency response analysis of the DEA dynamics was performed using generalized frequency response functions, providing insight and a comparison into the time-varying dynamics across a set of DEA actuators. The results demonstrated that models identified within the presented framework provide a compact and accurate description of the system dynamics. The frequency response analysis revealed variation in the time-varying dynamic behaviour of DEAs fabricated to the same specifications. These results suggest that the modelling and analysis framework presented here is a potentially useful tool for future work in guiding DEA actuator design and fabrication for application domains such as soft robotics

Facile Synthesis of Boron-doped Graphitic Materials for Oxygen Reduction Purpose in Fuel Cell

Modern civilization is blamed for aggravating climate change as well as global warming by pumping millions of tonnes of greenhouse gases into the atmosphere. In addition to environmental concerns, the ever-increasing energy demand calls for new generations of power technologies to supply such a rapid rise in energy market. Fuel cells show to be placed at the cornerstone of technology development for the current century, since they could mitigate the environmental concern and meet the escalation in energy need. However, transforming to a future sustainable energy with zero to low CO2 emission needs the development of cheap fuel cells on top of a sustainable hydrogen supply. The current scientists’ and engineers’ challenge is the fabrication of cheap, durable and reliable catalyst materials for electrochemical reduction of oxygen in cathode which is a crucial factor in determining cell’s efficiency. We also looked into this area to find new cathodic materials and compared their performance against commonly mentioned materials in literature. The focus of this contribution is to compare the Oxygen Reduction Reaction (ORR) performance of widely literature cited boron-doped graphene materials with the new type of boron-doped samples known as Graphene Organic Framework (GOF). The first chapter deals with the commercialization problem by discussing cell’s internal design, classification and its operation. Subsequently, new alternative suggested substitutes such as metallic nano catalyst, metallic-graphene hybrids, polymeric and new non-metallic graphitic electrocatalysts. The chapter will continue subsequently by introducing GOF material, which are able to form the similar CBO2 structure as the previously literature cited substitutionally boron-doped graphene (BGs) formed, as a novel catalyst for ORR. The second chapter examines the material synthesis and characterization. Three samples of substitutionally boron-doped graphene, identified as BG1, BG2 and BG3, and two types of new porous GOFs materials are synthesised under various preparation strategies. In order to confirm the integration and presence of boron in synthesised samples, variety of characterization and spectroscopic analysis are performed. XRD, TGA and FTIR are exclusively applied to GOF materials since their applications to BG samples will not provide any valuable information. However Raman and XPS characterizations are executed for all samples to determine the degree of G-band shifts (i.e. the extent of doping) and corresponding surface concentration of doped boron. The third chapter provides electrochemical results of prepared materials using conventional CV and RDE techniques in electrochemistry. To complete the discussion, subsequently, the incompetency of Koutchy-Levich (K-L) method and Rotating Disk Electrode (RDE) for determining the true ORR path is explained by reviewing Koutchy-Levich (K-L) method fundamentals. Instead Rotating Ring Disk Electrode (RRDE) technique is considered to estimate the true ORR efficiency of literature materials (BGs) versus introduced GOF substances. Finally Table 3.3 provides a comprehensive review on the results achieved during my electrochemistry analysis including testing the materials in two different laboratory facilities. The fourth chapter investigates the understanding of kinetic reaction of oxygen reduction for synthesised electrode catalysts. This is a work which barely has been considered by previous studies and could be beneficial to find the right application for materials. Based on the corresponding analysis in this chapter, except for commercial 20% Pt/C and Glassy Carbon (GC) electrodes, all materials are leading the ORR through multiple parallel-series steps with reaction constants of k1, k2 and k3 >0. However for cases like BG1 and BG2, the k3 value might be very small and close to zero that we can consider two simultaneous parallel 4e- and 2e- ORR. Finally the fifth chapter gives a summary of all thesis contents including future guides for completing this research study

Investigation on compressive devices based on dielectric elastomer actuators

Dielectric elastomer actuators (DEAs) are an emerging technology from the larger class of artificial muscle actuators, showing interesting properties such as softness and large actuation strains. A DEA can be used to create various types of motions (such as planar, rotary, and bending) and contact forces (such as tension, biaxial compression, and bending moment). Due to its interesting properties, there are a growing number of studies on improving DEA applicability, reliability, and characteristics. Additionally, despite limited commercial use, there is a growing global push toward commercializing DEA in various sectors. In this thesis, in an effort to investigate practical applications of DEAs, their functionality is studied in applications where compressive forces are exerted by the actuator. Two different modalities in which DEAs could apply compressive forces to an encompassed object are identified. To narrow the focus of the thesis, a practical application is introduced and investigated for each modality. The first practical application, based on the first modality, introduces the use of DEAs as a compression bandage to improve blood circulation in the human leg. The proposed compression bandage could potentially enable a controlled variable compression around the lower leg. The second practical application, based on the second modality, proposes a novel gripper that uses DEAs as a mean to apply a soft touch on objects. The proposed gripper can apply up to 2N of grasping force to select objects. The gripper may be adopted as an end effectors for collaborative robotic arms, where a human operator is collaborating with the robotic arm to handle a delicate object. Typically, DEAs are actuated using high electrical voltages of several kilovolts. This operating voltage gives rise to a safety concern for practical applications where DEAs are sought to be operated in proximity to the human body. Since the two aforementioned applications require, or may require the operation of DEAs close to the human body, it is very important to study the electrical safety of DEAs and investigate methods to manage the risk of their high operating voltages. The last part of this thesis discusses the electrical safety of DEAs in scenarios where DEA circuitry is in contact with the human body, and shows that they can be safely used. Critical parameters for identification of the electrical safety of DEAs are also introduced to assist in designing safer DEAs for such applications

Progress in spherical packed-bed reactors: Opportunities for refineries and chemical industries

Giving the ever-increasing energy and raw material demand as a result of global economy growth, revisiting the traditional reactor configuration designs (which are considered to be the heart of chemical industries) can significantly reduce the capital and operational costs while addressing the larger market demand for chemicals. The spherical-reactor geometry is an attractive alternative design to traditional tubular reactors due to its lower pressure drop (which is due to feed distribution over a larger outer surface area in spherical reactors compared to the cross sectional area in conventional tubular reactors) and recompression costs as well as construction material investment (reduced wall thickness to half). This review summarizes numerical modeling and experimental research on spherical reactors from 1958 to date. Several configurations of spherical reactors have been described and categorized. A review has been performed on modeling results of numerous arrangements and combinations of tubular and spherical reactors for industrial-scale reforming processes. The superiority of spherical packed bed reactors is further discussed and additional recommendations are provided to be considered in future research. As a general conclusion, spherical reactors could be considered as a potential candidate for pilot and industrial scale reactors due to their cost-effective designs and flexibilityof operation conditions

MOESM1 of On the design of a DEA-based device to pot entially assist lower leg disorders: an analytical and FEM investigation accounting for nonlinearities of the leg and device deformations

Additional file 1. Final calf volume values in liter after wrapping and actuating the ACB

Identification of electrocatalytic oxygen reduction (ORR) activity of boron in graphene oxide; incorporated as a charge-adsorbate and/or substitutional p-type dopant

This work is investigating electrocatalytic performance of boron (B) in two diverse classes of graphene hybrid materials; i) the pillared graphene organic framework (GOF) which is a type of adsorbate-induced boron doped graphene and ii) the substitutionally boron doped graphene (i.e. integrated boron in disrupted graphene lattice (BG)). Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) are among the key tools to identify chemical states of doped boron as well as its surface composition. Electron transfer efficiency of the easily synthesised GOFs (with CBO2 active chemistries) is compared with commonly cited BGs (with distinctive CBO2/BC3 moieties) which are synthesised under more rigorous thermal conditions. The intriguing feature of swelled GOFs is due to their mild solvothermal synthesising condition while managing electrochemical oxygen reduction reaction (ORR) through a dominant 4e− pathway (i.e. based on Rotating-Disk Electrode (RDE) results). GOF has feasibility for scalable production and a performance which is comparable to former BGs materials. The new GOF undergoes subsequent structural modifications via electrochemical polishing (i.e. chronoamperometry) to enhance its ORR efficiency and conductivity. Results indicate about a 30% boost in O2-reduction performance of electrochemically reduced GOF (E.r.GOF) compared to native graphene organic framework and also substantial improvement in its former onset-potential (approx. 100 mV)

Progress in spherical packed-bed reactors:Opportunities for refineries and chemical industries

\u3cp\u3eGiving the ever-increasing energy and raw material demand as a result of global economy growth, revisiting the traditional reactor configuration designs (which are considered to be the heart of chemical industries) can significantly reduce the capital and operational costs while addressing the larger market demand for chemicals. The spherical-reactor geometry is an attractive alternative design to traditional tubular reactors due to its lower pressure drop (which is due to feed distribution over a larger outer surface area in spherical reactors compared to the cross sectional area in conventional tubular reactors) and recompression costs as well as construction material investment (reduced wall thickness to half). This review summarizes numerical modeling and experimental research on spherical reactors from 1958 to date. Several configurations of spherical reactors have been described and categorized. A review has been performed on modeling results of numerous arrangements and combinations of tubular and spherical reactors for industrial-scale reforming processes. The superiority of spherical packed bed reactors is further discussed and additional recommendations are provided to be considered in future research. As a general conclusion, spherical reactors could be considered as a potential candidate for pilot and industrial scale reactors due to their cost-effective designs and flexibilityof operation conditions.\u3c/p\u3