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Challenges in Fatigue Research and Enforcement
No full textThis chapter describes challenges faced in fatigue research and in fatigue evaluation for various purposes including crash statistics and enforcement and for selection of appropriate countermeasures. The challenges are related to both the causes and the consequences of fatigue. Differences between sleep-related and task-related fatigue are discussed in relation to countermeasures for fatigue. The chapter also describes how individual characteristics including age, chronotype, and personality influence the development of fatigue and add to the complexity of choosing appropriate fatigue countermeasures. Difficulties in measuring and providing proof that an individual is fatigued are discussed in relation to law enforcement
Development of high performance aluminium alloys tailored for powder bed fusion-laser beam
Full text linkThe powder bed fusion-laser beam (PBF-LB) process has lately been regarded as a top choice for creating complicated structures which are not possible via conventional manufacturing. Nevertheless, the pace of alloys for PBF-LB has been slower. Commercially available alloys are derived from cast/ wrought counterparts with limited knowledge of their suitability to PBF-LB. To fully exploit the inherent advantages of PBF-LB process, there is thus a growing need to develop alloy compositions with help from computational tools. This research work focused on the development of aluminium alloy systems tailored for the PBF-LB process. Leveraging the possibilities and limitations of PBF-LB process and with the help of CALPHAD tools, two types of alloying approaches were investigated namely in-situ alloying and ex-situ mixing. The key alloy design objectives were to avoid solidification cracking while attaining higher solid solubilities combined with a refined microstructure. The mechanical property objective was >450 MPa strength and high-temperature strength up to 573 K combined with general corrosion resistance.Al-Mn-Cr-Zr based alloy system resulting from this thesis study include several variants with different amounts of alloying elements. Gas-atomised powder was used, and fully dense samples were processed using optimised PBF-LB process. This was followed by post-processing heat treatments to optimise mechanical properties. This created an alloy system with mechanical properties including yield strengths 250-500 MPa, elongation to failure 5-25% and bending fatigue 140-200 MPa. In as-printed state, strengthening was caused by a combination of solid solution strengthening and grain size effect. The strengthening from precipitates was observed after direct ageing heat treatments. The microstructure was characterised by SEM, TEM and in-situ synchrotron measurements. Long-term isothermal testing at 623 K for >1000 h showed a superior performance (-17 HV or 12% drop). High-temperature tensile testing at 573 K showed yield strengths >150 MPa, surpassing most commercially available Al-alloys.These novel high performance alloys expand the available material performance envelope and create an edge over currently available systems while completely avoiding critical or rare earth elements. Such tailored alloy systems are shown to better utilise PBF-LB processing conditions to enhance material properties thus increasing the potential applications
On the Impact of Phase Noise on Monostatic Sensing in OFDM ISAC Systems
No full textPhase noise (PN) can become a major bottleneck for integrated sensing and communications (ISAC) systems towards 6G wireless networks. In this paper, we consider an OFDM ISAC system with oscillator imperfections and investigate the impact of PN on monostatic sensing performance by performing a misspecified Cram\ue9r-Rao bound (MCRB) analysis. Simulations are carried out under a wide variety of operating conditions with regard to SNR, oscillator type (free-running oscillators (FROs) and phase-locked loops (PLLs)), 3-dB bandwidth of the oscillator spectrum, PLL loop bandwidth and target range. The results provide valuable insights on when PN leads to a significant degradation in range and/or velocity accuracy, establishing important guidelines for hardware and algorithm design in 6G ISAC systems
ULGEN: A Runtime Assurance Framework for Programming Safe Cyber-Physical Systems
No full textWe present ULGEN, a runtime assurance (RTA) framework for programming safe cyber-physical systems (CPS). In ULGEN, a system is implemented as a collection of asynchronous processes executing RTA modules which are generalizations of the well-known Simplex architecture. An RTA module is composed of a set of safe controllers (SCs), designed to guarantee certain safety specifications, and a set of advanced controllers (ACs), optimized for performance, each defined to run under the specific conditions of the operating environment, and a decision module implementing the switching logic between the controllers. A source of complexity in achieving safe CPS is that these systems often involve concurrently interacting components with different execution semantics. To this end, ULGEN allows for the definition of RTA modules with either event-driven or time-driven execution semantics and encapsulates such components into RTA modules. It further provides primitives for implementing priority-based communication between asynchronous processes, which is a necessary feature for task prioritization mechanisms such as contingency plans and interrupt service routines. The framework also provides formal guarantees on the safe execution of RTA modules based on a formal definition of well-formedness. In ULGEN, a well-formed RTA module combines SCs and ACs in a way that guarantees the underlying safety specifications assured by the SCs while delivering the desired performance offered by the ACs. We compare the safety guarantees of ULGEN against other state-of-the-art RTA frameworks and demonstrate its efficacy in implementing safe and performant CPS by presenting an extensive experimental evaluation of five case studies both in a simulation environment and on a real robotic platform
Politics of the rurban void
Full text linkCity-centric planning in Sweden has led to the dominance of stereotyped visions for both urban and rural areas within policy and planning practice. To challenge such a limited understanding, this study conceptualizes the rurban void. The aim of this article is to operationalize the rurban void as an analytical framework that extends beyond the urban and rural conceptual divide and can clarify how a neoliberal and city-centric planning practice in Sweden de-politicizes the urban and rural outside. The article discusses the potentials of a perspective that challenges urban privilege and opens up opportunities for the re-politicisation of spatial transformation
EzSkiROS: A Case Study on Embedded Robotics DSLs to Catch Bugs Early
No full textWhen we develop general-purpose robot software components, we rarely know the full context that they will execute in. This limits our ability to make predictions, including our ability to detect program bugs early. Since running a robot is an expensive task, finding errors at runtime can prolong the debugging loop or even cause safety hazards. In this paper, we propose an approach to help developers find bugs early with minimal additional effort by using embedded Domain-Specific Languages (DSLs) that enforce early checks. We describe DSL design patterns suitable for the robotics domain and demonstrate our approach for DSL embedding in Python, using a case study on an industrial tool SkiROS2, designed for the composition of robot skills. We demonstrate our patterns on the embedded DSL EzSkiROS and show that our approach is effective in performing safety checks while deploying code on the robot, much earlier than at runtime. An initial study with SkiROS2 developers show that our DSL-based approach is useful for early bug detection and improving the maintainability of robot code
Cellulose in Quaternary Ammonium-based Solvents: Dissolution, Modification and Coagulation
Full text linkProcessing cellulose through dissolution and regeneration is essential for many applications, yet challenges are posed because it does not readily melt or dissolve in commonly used aqueous and organic solvents. Consequently, extensive efforts have been devoted to developing novel and efficient solvents for cellulose, as well as exploring new functionalization routes. Existing limitations associated with current solvents, such as solution instability, limited dissolution capacity, specific temperature requirements, solvent-related side reactions and a narrow concentration range, are nevertheless significant.Water-based solvents are of particular interest since they can be applicable in large scales. This thesis mainly focuses on quaternary ammonium hydroxides (QAHs) since they enhance cellulose dissolution compared to extensively studied NaOH(aq) with the aim of gaining deeper insight into the impact of the structural characteristics of the quaternary ammonium-based solvents on cellulose dissolution, modification and coagulation. Initially, cellulose etherification in previously investigated solvents, benzyltrimethylammonium hydroxide, tetramethylammonium hydroxide and NaOH(aq) was investigated in situ using spectroscopy and rheology techniques. The results revealed enhanced reagent solubility, improved cellulose solution stability during the reaction and less pronounced cascade reaction in QAHs, either alone or in combination. With the importance of the solvent structure highlighted for cellulose modification and inspired by the industrially used N-methylmorpholine N-oxide, a series of morpholinium salts with different alkyl chain lengths combined with hydroxide, acetate or chloride counterions were prepared and their ability to dissolve cellulose was investigated. This study aimed to examine the structural properties of the solvent governing dissolution which indeed highlighted the importance of both the cation and anion structures: morpholinium chlorides were incapable of dissolving cellulose whereas morpholinium acetates combined with DMSO and aqueous morpholinium hydroxides functioned as cellulose solvents. While alkyl chains longer than ethyl enabled room-temperature dissolution in aqueous morpholinium hydroxides (likely through improved stabilization of the hydrophobic regions of cellulose), they decreased the dissolution ability of morpholinium acetates in DMSO-based systems. Finally, the behaviour of cellulose solutions in benzyltrimethylammonium hydroxide and two of the newly developed morpholinium hydroxides during coagulation was studied which highlighted the importance of hydrophobic structural motifs for the consistency of the formed gels
Low-Power HEMT LNAs for Quantum Computing
Full text linkThe rapid development of quantum computing technology predicts much more qubits to handle in the detection, readout, and amplification of qubits than in today\u27s system. Due to the limited cooling capability of the dilution refrigerator, the current low-noise amplifiers (LNAs) are in need of ten to hundred times reduced dc power consumption yet with lowest noise temperature at qubit readout frequencies, typcially 4-12 GHz. Cryogenic indium phosphide (InP) high electron mobility transistor (HEMT) LNAs, are the standard qubit amplifier at 4 K in today\u27s superconducting quantum system. However, the power consumption of current InP HEMT LNAs is still too high for future quantum system up-scaling.A small-signal noise model of a 100-nm gate-length InP HEMTs has been characterized and extracted at 4 K ambient under low-power bias down to 1 μW. The extracted low-power small-signal noise models revealed fast degradation points of drain voltage bias for RF and noise performance.The design goals of the cryogenic LNA were tailored for a superconducting qubit readout application based on the extracted low-power small-signal noise model of the InP HEMT for optimum noise and power consumption trade-off. A cryogenic InP HEMT hybrid LNA operating in the 4-6 GHz frequency range at 200 μW with an average noise temperature of 2.0 K has been designed, fabricated, and successfully demonstrated, validating the extracted model and design methodology.An epitaxially-optimized InP HEMT was modeled with the low-power methodology. The comparison of the small-signal noise model parameters to the standard InP HEMT showed improved transconductance, matching, and noise at the same bias power. The demonstrated three-stage cryogenic 4-6 GHz LNA equipped with an optimized HEMT as the first stage achieved 2.0 K average noise temperature at 100 μW dc power dissipation, representing a new state-of-the-art. This licentiate thesis has presented experimental evidence that there is large potential in reducing dc power in the cryogenic InP HEMT LNA for qubit readout which can be important for the planned up-scaling in future quantum computing
Plasma Lipidomic n-6 Polyunsaturated Fatty Acids and Type 2 Diabetes Risk in the EPIC-Potsdam Prospective Cohort Study
No full textOBJECTIVE: Evidence on plasma n-6 polyunsaturated fatty acids (PUFAs) and type 2 diabetes risk is inconsistent. We examined the associations of lipid class-specific PUFA concentrations with type 2 diabetes risk. RESEARCH DESIGN AND METHODS: In the prospective European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam cohort (nested case-cohort study: subcohort 1,084 participants, 536 participants with type 2 diabetes, median follow-up 6.5 years), we measured plasma 18:2, 20:3, and 20:4 concentrations in 12 lipid (sub)classes, likely reflecting the plasma concentrations of linoleic acid (18:2n-6), dihomo-γ-linolenic acid (20:3n-6), and arachidonic acid (20:4n-6). The Δ-5 desaturase (D5D) activity was estimated as the 20:4/20:3 ratio. Associations with diabetes were estimated with Cox proportional hazards models. RESULTS: Higher concentrations of 18:2 were inversely associated with type 2 diabetes risk, particularly in lysophosphatidylcholines (hazard ratio [HR] per 1 SD 0.53; 95% CI 0.23-1.26) and monoacylglycerols (HR 0.59; 0.38-0.92). Higher concentrations of 20:3 in phospholipid classes phosphatidylcholines (HR 1.63; 1.23-2.14), phosphatidylethanolamines (HR 1.87; 1.32-2.65), and phosphatidylinositol (HR 1.40; 1.05-1.87); free fatty acids (HR 1.44; 1.10-1.90); and cholesteryl esters (HR 1.47; 1.09-1.98) were linked to higher type 2 diabetes incidence, and these associations remained statistically significant after correction for multiple testing. Higher 20:4 concentrations were not associated with risk. The estimated D5D activity in phospholipids and cholesteryl esters was associated with lower type 2 diabetes risk. Single nucleotide polymorphisms in the D5D-encoding FADS genes explained relatively high proportions of variation of estimated D5D activity in those lipid classes. CONCLUSIONS: Plasma n-6 PUFAs were associated differently with type 2 diabetes, depending on fatty acid and the lipid class
Approximate Inference for the Bayesian Fairness Framework
No full textAs the impact of Artificial Intelligence systems and applications on everyday life increases, algorithmic fairness undoubtedly constitutes one of the major problems in our modern society. In the current paper, we extend the work of Dimitrakakis et al. on Bayesian fairness [1] that incorporates models uncertainty to achieve fairness, proposing a practical algorithm with the aim to scale the framework for a broader range of applications. We begin by applying the bootstrap technique as a scalable alternative to approximate the posterior distribution of parameters of the fully Bayesian viewpoint. To make the Bayesian fairness framework applicable to more general data settings, we define an empirical formulation suitable for the continuous case. We experimentally demonstrate the potential of the framework from an extensive evaluation study on a real dataset and different decision settings