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Development of Novel Blends based on Rubber and in-situ Synthesized Polyurethane-ureaTahir, Muhammad 16 February 2018 (has links) (PDF)
Polyurethane and the analogous ‘polyurethane-urea’ are high performance polymeric materials having remarkable properties such as high stiffness, abrasion and tear strengths. In many studies, the low strength rubbers have been blended with various types of polyurethanes for new and improved materials. However, until now, the reported heterogeneous blends offer only a narrow temperature range of application due to the high temperature softening of their polyurethane (-urea) phase. In addition, the conventional solution-or melt-blending methods are time and energy intensive, which tend to forfeit the economical realization of the reported blends. In contrast to earlier studies, a simplified reactive blending process is suggested to synthesize polyurethane-urea via a prepolymer route during blending with rubbers to obtain novel elastomeric materials having extended performance characteristics.
The reactive blending process is opted to prepare blends based on nitrile butadiene rubber (NBR) and in-situ synthesized polyurethane-urea (PUU). The blending is carried out in an internal mixer at a preset temperature of 100°C. The critical temperatures of the reactive blending process are determined from the chemo-rheological analysis of a premix, composed of a 4,4′-diphenylmethane diisocyanate (MDI)/polyether (PTMEG) based prepolymer admixed with 1,3-phenylene diamine (mPD). The prepared NBR/PUU blends exhibit highly improved mechanical properties. Contrary to previous reports, the reinforced dynamic-mechanical responses of the novel blends remain stable till very high temperatures (≥180°C).
The influence of diamine type on the in-situ synthesized polyurethane-urea and the performance of prepared blends are investigated. Four different diamines, namely 1,3-Phenylene diamine, 1,4-Bis(aminomethyl)benzene, 4,4′-Methylene-bis(2-chloroaniline) and 4,4ʹ-(1,3-Phenylenediisopropylidene)bisaniline, are selected to chain extend the prepolymer to PUU during blending with NBR. The chemical and domain structure of the PUUs are found to greatly influence the reinforced tensile and dynamic-mechanical responses of the NBR/PUU 70/30 blends.
The PUU (based on MDI/PTMEG prepolymer and mPD) is blended with polar (CR, XNBR) and nonpolar (NR, EPDM, sSBR) rubbers. PUU compatibilizes with all the rubbers irrespective of their polarity and reinforces their tensile and dynamic-mechanical characteristics. The use of blends in industrial applications, for example, in a truck tire tread compound and as a roller covering material, is examined. In a simplified tire tread formulation, the carbon black for NR-CB composite is partially replaced with an equivalent quantity of PUU for NR/PUU-CB composite of similar hardness. The dynamic mechanical investigations reveal that the energy dissipation and strain dependent softening is high in NR-CB as compared to the NR/PUU-CB composite. In another application, NBR/PUU blend is successfully tested as a rubber roller covering material. The tested blend-covered roller retains its structural integrity and develops less heat build-up as compared to the silica filled NBR-covered roller. This shows a substantial suitability of the blend-covered rollers for film, printing and textile processing machinery.
These novel blends are considered to be the promising new materials for many commercial applications including wheels, rubber rollers, belts or pump impellers.
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Beitrag zur Charakterisierung naturfaserverstärkter Verbundwerkstoffe mit hochpolymerer MatrixLampke, Thomas 23 October 2001 (has links)
Die Zielstellung dieser Dissertation besteht darin, einen Beitrag zur
Charakterisierung sowohl der Ausgangsmaterialien (Naturfasern, Polymere)
als auch ihrer Verbundeigenschaften zu leisten. Morphologische
Unterschiede der Fasern, im wesentlichen bedingt durch Erntezeitpunkt,
Röstdauer und Verarbeitungsbedingungen, haben Einfluss auf die
mechanischen Kennwerte als auch auf das Faser/Matrix-Interface des
Verbundwerkstoffs. Durch unterschiedliche Verfahren (Thermoanalyse,
Ubbelohde-Viskosimetrie, NMR-Spektroskopie, Einzelfaserzugversuch) werden
sowohl das Degradationsverhalten als auch die Prozessgrenzen bestimmt.
Zur Einschätzung des Grenzflächenzustands werden oberflächensensitive
Verfahren (BET-Verfahren, Zeta-Potentialbestimmung, IR-Spektroskopie,
Rasterelektronen-mikroskopie) angewendet. Die Charakterisierung der durch
Compoundieren und Spritzgießen, bzw. durch Konsolidieren von
Hybridvliesen hergestellten Verbunde erfolgt mittels quasi-statischer
bzw. dynamisch-mechanischer Methoden (DMA). Fraktographische
rasterelektronenmikroskopische und IR-spektroskopische Untersuchungen
belegen die Veränderung des Interfaces durch geeignete Faserbehandlung,
Prozessparameter und Haftvermittlung. Die vorliegende Arbeit weist die
effektive Verstärkungswirkung der Naturfasern Flachs bzw. Hanf in
hochpolymeren Matrices zuverlässig nach. / The objectives of this dissertation are the characterization of the
components (natural fibers, polymers) and the resulting properties of the
composites. Due to differences in fiber morphology, mainly caused by the
date of harvest, retting and fiber separation procedures, the mechanical
properties and the fiber/matrix interface are effected. The degradation
and the limits of the process are characterized by means of thermal
analysis, Ubbelohde viscosimetry, NMR spectroscopy and single fiber
tensile test. Surface sensitive methods (BET measurements, zeta potential
measurements, IR-spectroscopy) were applied to evaluate the fiber/matrix
interface. The composites were first manufactured by compounding and
injection molding as well as by consolidation of hybrid nonwovens and
characterized by means of quasi statical and dynamic-mechanical methods.
The effect of adequate fiber treatements, process parameters and coupling
agents becomes obvious applying fractographic SEM and IR spectroscopic
measurements. The gained results indicate the strengthening effect of
natural fibers like flax and hemp on the performance of high polymers.
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Development of Novel Blends based on Rubber and in-situ Synthesized Polyurethane-ureaTahir, Muhammad 08 December 2017 (has links)
Polyurethane and the analogous ‘polyurethane-urea’ are high performance polymeric materials having remarkable properties such as high stiffness, abrasion and tear strengths. In many studies, the low strength rubbers have been blended with various types of polyurethanes for new and improved materials. However, until now, the reported heterogeneous blends offer only a narrow temperature range of application due to the high temperature softening of their polyurethane (-urea) phase. In addition, the conventional solution-or melt-blending methods are time and energy intensive, which tend to forfeit the economical realization of the reported blends. In contrast to earlier studies, a simplified reactive blending process is suggested to synthesize polyurethane-urea via a prepolymer route during blending with rubbers to obtain novel elastomeric materials having extended performance characteristics.
The reactive blending process is opted to prepare blends based on nitrile butadiene rubber (NBR) and in-situ synthesized polyurethane-urea (PUU). The blending is carried out in an internal mixer at a preset temperature of 100°C. The critical temperatures of the reactive blending process are determined from the chemo-rheological analysis of a premix, composed of a 4,4′-diphenylmethane diisocyanate (MDI)/polyether (PTMEG) based prepolymer admixed with 1,3-phenylene diamine (mPD). The prepared NBR/PUU blends exhibit highly improved mechanical properties. Contrary to previous reports, the reinforced dynamic-mechanical responses of the novel blends remain stable till very high temperatures (≥180°C).
The influence of diamine type on the in-situ synthesized polyurethane-urea and the performance of prepared blends are investigated. Four different diamines, namely 1,3-Phenylene diamine, 1,4-Bis(aminomethyl)benzene, 4,4′-Methylene-bis(2-chloroaniline) and 4,4ʹ-(1,3-Phenylenediisopropylidene)bisaniline, are selected to chain extend the prepolymer to PUU during blending with NBR. The chemical and domain structure of the PUUs are found to greatly influence the reinforced tensile and dynamic-mechanical responses of the NBR/PUU 70/30 blends.
The PUU (based on MDI/PTMEG prepolymer and mPD) is blended with polar (CR, XNBR) and nonpolar (NR, EPDM, sSBR) rubbers. PUU compatibilizes with all the rubbers irrespective of their polarity and reinforces their tensile and dynamic-mechanical characteristics. The use of blends in industrial applications, for example, in a truck tire tread compound and as a roller covering material, is examined. In a simplified tire tread formulation, the carbon black for NR-CB composite is partially replaced with an equivalent quantity of PUU for NR/PUU-CB composite of similar hardness. The dynamic mechanical investigations reveal that the energy dissipation and strain dependent softening is high in NR-CB as compared to the NR/PUU-CB composite. In another application, NBR/PUU blend is successfully tested as a rubber roller covering material. The tested blend-covered roller retains its structural integrity and develops less heat build-up as compared to the silica filled NBR-covered roller. This shows a substantial suitability of the blend-covered rollers for film, printing and textile processing machinery.
These novel blends are considered to be the promising new materials for many commercial applications including wheels, rubber rollers, belts or pump impellers.
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Static and dynamic behaviour of joints in schistose rock: lab testing and numerical simulationNguyen, Van Manh 14 October 2013 (has links)
The shear behaviour of rough rock joints was investigated by both laboratory testing and numerical simulation. The most powerful servo-controlled direct shear box apparatus in the world with normal forces up to 1000 kN, shear loading up to 800 kN and frequencies up to 40 Hz under full load was used to investigate the shear strength of schistose rock blocks with dimensions of up to 350 x 200 x 160 mm in length, width and height, respectively.
The experiments were performed to study the behaviour of rough rock joints under constant normal load, constant normal stiffness and dynamic boundary conditions. The joint surface of rock specimen was scanned 3-dimensional at the initial stage before shearing by new 3D optical-scanning equipment. The 3D-scanner data were used to estimate the joint roughness coefficient (JRC) and to reconstruct rough surface of rock discontinuities in numerical models. Three dimensional numerical models were developed using FLAC3D to study the macro and micromechanical shear behaviour of the joints. Numerical simulation results were compared to experimental results. Three dimensional characteristic of the joint surface including micro-slope angle, aperture, contact area and normal stress distribution were determined and analyzed.
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Mechanisches Maschinenverhalten in der PunktschweißsimulationLudwig, Tillmann, Mayr, Peter 05 July 2019 (has links)
Widerstandspunktschweißen ist das dominante Fügeverfahren in der Karosserieherstellung. Der
steigende Wunsch nach mehr Sicherheit und gleichzeitig nach einem möglichst leichten Fahrzeug,
führt zur Verwendung hochfester Stähle. Mit der Festigkeit steigen die Anforderungen an die
Prozesssteuerung und die Punktschweißzangen.
Die Simulation des Punktschweißprozesses wird verwendet, um einen materialgerechten
Schweißprozess zu entwickeln, sowie Zeit und Material für entsprechende Versuche einzusparen. In
der Simulation können physikalische Größen ermittelt werden, welche am Schweißpunkt nicht
messbar sind.
Im Vortrag wird ein FEM-Modell vorgestellt, welches den Widerstandspunktschweißvorgang
simuliert. Die erste Ausbaustufe des Modells umfasst die zu fügenden Bleche und das
Elektrodenpaar der Punktschweißzange. Die Elektrodenkraft wird zu Beginn der
Schweißsimulation auf die Elektrode aufgebracht und über den Prozesszyklus als konstant
angenommen. Diese Annahme steht im Widerspruch zu in der Praxis gemessenen
Elektrodenkraftverläufen. Diese weisen eine dynamische Änderung über der Schweißzeit auf. Der
Unterschied zwischen gemessener und in der Simulation vorgegebener konstanter Elektrodenkraft
war die Motivation zur Erstellung eines mechanischen Maschinenmodells, welches im Vortrag
präsentiert wird. Das Modell ist mit der Schweißprozesssimulation gekoppelt und errnöglicht die
numerische Untersuchung der Wirkung mechanischer Maschinenparameter auf ein
Punktschweißergebnis. Erste Ergebnisse der Schweißprozesssimulation unter Berücksichtigung des
mechanischen Maschinenverhaltens werden vorgestellt und diskutiert.
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Entwicklung und Charakterisierung von Elastomerkompositen auf Basis neuerer mikro- und nanoskaliger FüllstoffeUhl, Claudia 27 November 2007 (has links)
In der Dissertation wurden Nanokomposite mit unterschiedlichen Kautschuken (HNBR, EPDM, MAH-g-EPDM) als Basismaterial sowie diversen modifizierten Schichtsilikaten als Füllstoff hergestellt und charakterisiert. Untersucht wurden die sich ausbildenden Strukturen bzw. die Morphologie (Aggregation, mögliche Orientierungen), die mechanischen Eigenschafte (Verstärkungswirkung) sowie die Füllstoff-Füllstoff-Wechselwirkungen und die Polymer-Füllstoff-Wechselwirkungen.
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Lab-on-a-chip platform for high throughput drug discovery with DNAencoded chemical librariesGrünzner, S., Reddavide, F. V., Steinfelder, C., Cui, M., Busek, M., Klotzbach, U., Zhang, Y., Sonntag, F. 09 August 2019 (has links)
The fast development of DNA-encoded chemical libraries (DECL) in the past 10 years has received great attention from pharmaceutical industries. It applies the selection approach for small molecular drug discovery. Because of the limited choices of DNA-compatible chemical reactions, most DNA-encoded chemical libraries have a narrow structural diversity and low synthetic yield. There is also a poor correlation between the ranking of compounds resulted from analyzing the sequencing data and the affinity measured through biochemical assays. By combining DECL with dynamical chemical library, the resulting DNA-encoded dynamic library (EDCCL) explores the thermodynamic equilibrium of reversible reactions as well as the advantages of DNA encoded compounds for manipulation/detection, thus leads to enhanced signal-to-noise ratio of the selection process and higher library quality. However, the library dynamics are caused by the weak interactions between the DNA strands, which also result in relatively low affinity of the bidentate interaction, as compared to a stable DNA duplex. To take advantage of both stably assembled dual-pharmacophore libraries and EDCCLs, we extended the concept of EDCCLs to heat-induced EDCCLs (hi-EDCCLs), in which the heat-induced recombination process of stable DNA duplexes and affinity capture are carried out separately. To replace the extremely laborious and repetitive manual process, a fully automated device will facilitate the use of DECL in drug discovery. Herein we describe a novel lab-on-a-chip platform for high throughput drug discovery with hi-EDCCL. A microfluidic system with integrated actuation was designed which is able to provide a continuous sample circulation by reducing the volume to a minimum. It consists of a cooled and a heated chamber for constant circulation. The system is capable to generate stable temperatures above 75 °C in the heated chamber to melt the double strands of the DNA and less than 15 °C in the cooled chamber, to reanneal the shuffled library. In the binding chamber (the cooled chamber) specific retaining structures are integrated. These hold back beads functionalized with the target protein, while the chamber is continuously flushed with library molecules. Afterwards the whole system can be flushed with buffer to wash out unspecific bound molecules. Finally the protein-loaded beads with attached molecules can be eluted for further investigation
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Efficient Query Processing for Dynamically Changing DatasetsIdris, Muhammad, Ugarte, Martín, Vansummeren, Stijn, Voigt, Hannes, Lehner, Wolfgang 11 August 2022 (has links)
The ability to efficiently analyze changing data is a key requirement of many real-time analytics applications. Traditional approaches to this problem were developed around the notion of Incremental View Maintenance (IVM), and are based either on the materialization of subresults (to avoid their recomputation) or on the recomputation of subresults (to avoid the space overhead of materialization). Both techniques are suboptimal: instead of materializing results and subresults, one may also maintain a data structure that supports efficient maintenance under updates and from which the full query result can quickly be enumerated. In two previous articles, we have presented algorithms for dynamically evaluating queries that are easy to implement, efficient, and can be naturally extended to evaluate queries from a wide range of application domains. In this paper, we discuss our algorithm and its complexity, explaining the main components behind its efficiency. Finally, we show experiments that compare our algorithm to a state-of-the-art (Higher-order) IVM engine, as well as to a prominent complex event recognition engine. Our approach outperforms the competitor systems by up to two orders of magnitude in processing time, and one order in memory consumption.
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On Safe Usage of Shared Data in Safety-Critical Control SystemsJäger, Georg 16 September 2022 (has links)
Prognostiziert durch Konzepte der Industrie 4.0 und den Cyber-Physischen-Systemen, können autonome Systeme zukünftig dynamisch auf Datenquellen in ihrer Umgebung zugreifen.
Während die gemeinsame Nutzung solcher Datenquellen ein enormes Performanzpotenzial bietet, stellt die benötigte Systemarchitektur vorherrschende Sicherheitsprozesse vor neue Herausforderungen.
Die vorliegende Arbeit motiviert zunächst, dass diese nur zur Laufzeit des Systems adressiert werden könne, bevor sie daraus zwei zentrale Ziele ableitet und verfolgt.
Zum einen wird ein Beschreibungsmodel für die Darstellung von Fehlercharakteristika gemeinsam genutzter Daten vorgestellt.
Dieses generische Fehlermodell erlaubt es zum anderen eine Sicherheitsanalyse zu definieren, die eine spezifische, dynamische Systemkomposition zur Laufzeit mit Hinblick auf die zu erwartenden Unsicherheiten bewerten kann.
Die als Region of Safety betitelte Analysestrategie erlaubt, in Kombination mit dem generischen Fehlermodell, die Sicherheit der auf gemeinsam genutzten Daten basierenden Kollisionsvermeidungsstrategie zweier Roboter noch zur Designzeit zu garantieren, obwohl die spezifischen Fehlercharakteristika der Daten erst zur Laufzeit bekannt werden.:List of Acronyms
List of Theorems
List of Definitions
List of Figures
List of Tables
1. Introduction – Safety in Future Smart Industries
1.1. The Example of Smart Warehouses
1.2. Functional Safety Standards
1.2.1. Overview of Functional Safety Standards
1.2.2. IEC 61508
1.3. Scope of this Thesis
1.3.1. Objectives
1.3.2. Contributions
1.3.3. Outline
1.4. Related Publications by the Author
1.5. Mathematical Notation
2. State of the Art
2.1. State of the Art in Run-Time Safety Assessment
2.1.1. Approaches at the Functional Level
2.1.2. Approaches at the Technical Level
2.1.3. Conclusions
2.2. State of the Art in Failure Modeling
2.2.1. The Definition of (Sensor) Failure Model
2.2.2. Interval-Based Failure Modeling
2.2.3. Distribution-Based Failure Modeling
2.2.4. Failure-Type-Based Failure Modeling
2.2.5. Conclusions
2.3. Conclusions from the State of the Art
3. Generic Failure Model
3.1. Defining the Generic Failure Model
3.1.1. Time- and Value-Correlated Random Distribution
3.1.2. A Failure Type’s Failure Amplitudes
3.1.3. A Failure Type’s State Function
3.1.4. Polynomial Representation of a Failure Type
3.1.5. Discussion on the Fulfillment of the Predefined Criteria
3.2. Converting a Generic Failure Model to an Interval
3.2.1. Converting a Time- and Value-Correlated Random Distribution
3.2.2. A Failure Type’s Interval
3.3. Processing Chain for Generating Generic Failure Models
3.3.1. Identifying Failure Types
3.3.2. Parameterizing Failure Types
3.3.3. Confidence Calculation
3.4. Exemplary Application to Artificial Failure Characteristics
3.4.1. Generating the Artificial Data Set – Manually Designing GFMs
3.4.2. Identifying Failure Types
3.4.3. Parameterizing Failure Types
3.4.4. Confidence Calculation
3.4.5. Comparison to State-of-the-Art Models
3.5. Summary
4. Region of Safety
4.1. Explicitly Modeling Uncertainties for Dynamically Composed Systems
4.2. Regions of Safety for Dynamically Composed Systems
4.2.1. Estimating Regions of Attraction in Presence of Uncertainty
4.2.2. Introducing the Concept of Region of Safety
4.2.3. Discussion on the Fulfillment of the Predefined Criteria
4.3. Evaluating the Concept of Region of Safety
4.3.1. Defining the Scenario and Considered Uncertainties
4.3.2. Designing a Control Lyapunov Function
4.3.3. Determining an Appropriate Value for λc
4.3.4. The Effect of Varying Sensor Failures on Regions of Safety
4.4. Summary
5. Evaluation and Integration
5.1. Multi-Robot Collision Avoidance
5.1.1. Assumptions
5.1.2. Design of the Circle and Navigation Scenarios
5.1.3. Kinematics
5.1.4. Control Policy
5.1.5. Intention Modeling by Model Uncertainty
5.1.6. Fusing Regions of Safety of Multiple Stability Points
5.2. Failure Modeling for Shared Data – A Marker Detection Failure Model
5.2.1. Data Acquisition
5.2.2. Failure Model Generation
5.2.3. Evaluating the Quality of the Failure Model
5.3. Safe Handling of Shared Data in a Collision Avoidance Strategy
5.3.1. Configuration for Region of Safety Estimation
5.3.2. Estimating Regions of Safety
5.3.3. Evaluation Using the Circle Scenario
5.3.4. Evaluation Using the Navigation Scenario
5.4. Summary
6. Conclusions and Future Work
6.1. Summary
6.2. Limitations and Future Work
6.2.1. Limitations and Future Work on the Generic Failure Model
6.2.2. Limitations and Future Work on Region of Safety
6.2.3. Future Work on Safety in Dynamically Composed Systems
Appendices
A. Defining Factors of Risk According to IEC 61508
B. Evaluation Results for the Identification Stage
C. Overview of Failure Amplitudes of Marker Detection Results
Bibliography / The concepts of Cyber-Physical-Systems and Industry 4.0 prognosticate autonomous systems to integrate sources of shared data dynamically at their run-time.
While this promises substantial increases in their performance, the openness of the required system architecture poses new challenges to processes guaranteeing their safety.
This thesis firstly motivates that these can be addressed only at their run-time, before it derives and pursues two corresponding goals.
Firstly, a model for describing failure characteristics of shared data is presented.
Secondly, this Generic Failure Model is built upon to define a run-time safety assessment methodology that enables analyzing dynamic system compositions integrating shared data with respect to the expected uncertainties at run-time.
This analysis strategy, entitled Region of Safety, allows in combination with the generic failure model to guarantee the safety of robots sharing position data for collision avoidance already at design-time, although specific failure characteristics become available only at run-time.:List of Acronyms
List of Theorems
List of Definitions
List of Figures
List of Tables
1. Introduction – Safety in Future Smart Industries
1.1. The Example of Smart Warehouses
1.2. Functional Safety Standards
1.2.1. Overview of Functional Safety Standards
1.2.2. IEC 61508
1.3. Scope of this Thesis
1.3.1. Objectives
1.3.2. Contributions
1.3.3. Outline
1.4. Related Publications by the Author
1.5. Mathematical Notation
2. State of the Art
2.1. State of the Art in Run-Time Safety Assessment
2.1.1. Approaches at the Functional Level
2.1.2. Approaches at the Technical Level
2.1.3. Conclusions
2.2. State of the Art in Failure Modeling
2.2.1. The Definition of (Sensor) Failure Model
2.2.2. Interval-Based Failure Modeling
2.2.3. Distribution-Based Failure Modeling
2.2.4. Failure-Type-Based Failure Modeling
2.2.5. Conclusions
2.3. Conclusions from the State of the Art
3. Generic Failure Model
3.1. Defining the Generic Failure Model
3.1.1. Time- and Value-Correlated Random Distribution
3.1.2. A Failure Type’s Failure Amplitudes
3.1.3. A Failure Type’s State Function
3.1.4. Polynomial Representation of a Failure Type
3.1.5. Discussion on the Fulfillment of the Predefined Criteria
3.2. Converting a Generic Failure Model to an Interval
3.2.1. Converting a Time- and Value-Correlated Random Distribution
3.2.2. A Failure Type’s Interval
3.3. Processing Chain for Generating Generic Failure Models
3.3.1. Identifying Failure Types
3.3.2. Parameterizing Failure Types
3.3.3. Confidence Calculation
3.4. Exemplary Application to Artificial Failure Characteristics
3.4.1. Generating the Artificial Data Set – Manually Designing GFMs
3.4.2. Identifying Failure Types
3.4.3. Parameterizing Failure Types
3.4.4. Confidence Calculation
3.4.5. Comparison to State-of-the-Art Models
3.5. Summary
4. Region of Safety
4.1. Explicitly Modeling Uncertainties for Dynamically Composed Systems
4.2. Regions of Safety for Dynamically Composed Systems
4.2.1. Estimating Regions of Attraction in Presence of Uncertainty
4.2.2. Introducing the Concept of Region of Safety
4.2.3. Discussion on the Fulfillment of the Predefined Criteria
4.3. Evaluating the Concept of Region of Safety
4.3.1. Defining the Scenario and Considered Uncertainties
4.3.2. Designing a Control Lyapunov Function
4.3.3. Determining an Appropriate Value for λc
4.3.4. The Effect of Varying Sensor Failures on Regions of Safety
4.4. Summary
5. Evaluation and Integration
5.1. Multi-Robot Collision Avoidance
5.1.1. Assumptions
5.1.2. Design of the Circle and Navigation Scenarios
5.1.3. Kinematics
5.1.4. Control Policy
5.1.5. Intention Modeling by Model Uncertainty
5.1.6. Fusing Regions of Safety of Multiple Stability Points
5.2. Failure Modeling for Shared Data – A Marker Detection Failure Model
5.2.1. Data Acquisition
5.2.2. Failure Model Generation
5.2.3. Evaluating the Quality of the Failure Model
5.3. Safe Handling of Shared Data in a Collision Avoidance Strategy
5.3.1. Configuration for Region of Safety Estimation
5.3.2. Estimating Regions of Safety
5.3.3. Evaluation Using the Circle Scenario
5.3.4. Evaluation Using the Navigation Scenario
5.4. Summary
6. Conclusions and Future Work
6.1. Summary
6.2. Limitations and Future Work
6.2.1. Limitations and Future Work on the Generic Failure Model
6.2.2. Limitations and Future Work on Region of Safety
6.2.3. Future Work on Safety in Dynamically Composed Systems
Appendices
A. Defining Factors of Risk According to IEC 61508
B. Evaluation Results for the Identification Stage
C. Overview of Failure Amplitudes of Marker Detection Results
Bibliography
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Dynamic Covalent Chemistry for Accelerated Photoswitch Discovery and Photoswitchable Core-Shell Metal-Organic FrameworksMutruc, Dragos 07 July 2022 (has links)
Photoschalter sind Moleküle, die eine reversible lichtgesteuerte Umwandlung zwischen zwei Zuständen mit unterschiedlichen Eigenschaften durchlaufen. In den letzten zehn Jahren hat der Einbau dieser photochromen Moleküle in intelligente, auf Stimuli ansprechende Materialien zunehmende Aufmerksamkeit erregt, da sie die einzigartige Fähigkeit bieten, makroskopische Eigenschaften mit einem externen optischen Stimulus reversibel zu verstärken und zu verändern. Die begrenzte Leistung von Photoschaltern in festen Medien bleibt eine Herausforderung. In diesem Zusammenhang werden in dieser Arbeit zwei wichtige Aspekte näher untersucht. Erstens der Prozess der Entwicklung neuer Photoschalter mit maßgeschneiderten Eigenschaften und zweitens die Implementierung von Photoschaltern in feste Materialien und die damit verbundenen Herausforderungen.
Im ersten Teil dieser Arbeit wurde Dynamisch-kovalente Chemie (DCC) verwendet, um die Entdeckung und Entwicklung einer neuartigen Klasse von Photoschaltern mit drei Zuständen zu beschleunigen. Die dynamische Natur der zentralen Doppelbindung von α-Cyanodiarylethenen wurde genutzt, um ein thermodynamisches Gleichgewicht mit anderen Arylacetonitrilen herzustellen. Die entwickelte Methode kombiniert eine schnelle Diversifizierung mit einer Rasterung auf spezifische Eigenschaften, die durch einen externen Stimulus aufgedeckt werden, und ermöglicht die effiziente Untersuchung der Beziehung zwischen Struktur und den zugehörigen Eigenschaften.
Im zweiten Teil der Arbeit wird die Entwicklung und die Synthese eines Zweikomponenten-Kern-Schale-MOFs mit einem internen nicht-funktionalisierten Kompartiment, das von einer dünnen photoschaltbaren Außenschale bedeckt ist, vorgestellt. Diese Strategie ermöglicht ein effizientes Schalten des Chromophors und die resultierende dünne „intelligente“ Schale fungiert als modulare kinetische Barriere für die molekulare Gastdiffusion in das Material, die durch Licht gesteuert werden kann. / Photoswitches are molecules that undergo a reversible light-triggered conversion between two states with different properties. In the past decade, the incorporation of these photochromic molecules in smart stimuli-responsive materials has gained increased attention as it offers the unique ability to reversibly amplify and change macroscopic properties with an external optical stimulus. The limited performance of photoswitches in solid mediums remains a challenge. In this context two important aspects are studied in more detail in this thesis. First, the process of developing new photoswitches with tailored properties and second, the implementation of photoswitches in solid materials and the challenges associated with it.
In the first part of this thesis dynamic covalent chemistry (DCC) was used to accelerate the discovery and development of a novel three-state photoswitch class. The dynamic nature of the central double bond of α-cyanodiarylethenes was exploited to establish a thermodynamic equilibrium with other arylacetonitriles. The developed DCC tool combines fast and efficient diversification with screening for specific photochemical properties revealed by an external stimulus, enabling the rapid study of the relationship between structure and the associated properties.
The second part of this thesis summarizes the design and synthesis of a two-component core-shell MOF with an internal non-functionalized compartment covered by a thin photoswitchable outer shell. This strategy allows efficient switching of the chromophore and the resulting thin “smart” shell acts as a modular kinetic barrier for molecular guest diffusion into the material that can be controlled by light.
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