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Electrochemical Approach for Advanced Flow Reactors via Additive Manufacturing of High Surface Area Ti-6Al-4V Anode
Get PDFElectrochemical processes use expensive noble metal-based anodes which limit industrial implementation. In this study, a noble-metal-free Ti-6Al-4V anode is introduced in an advanced flow reactor. We demonstrate that the 3D additively manufactured electrode can provide a more projected surface area and facilitate anodic reactions under controlled electrolyte conditions. Alkaline NaOH and KOH electrolytes act as anodic electrolytes that are toxic compounds-free and enable corrosion control. Impedance and voltammetry responses to electrochemical reactions are studied. The electrochemical active surface area of the 4 rods scaffold geometry is 42 times higher than a flat plate anode. Therefore, improved charge transfer is achieved in the flow reactor incorporating the 3D Ti-6Al-4V electrode due to the increased surface area and wettability. The structure of almost non-conductive passivation on a flat plate anode is changed to unstable passivation due to the 3D scaffold structure. This enables effective charge transfer of 911 mA cm−2 at higher potentials up to 5 V for 1.5 m KOH in a non-flow condition. Furthermore, a 1 m KOH solution delays metal ion dissolution from the anode surface by acting as a corrosion-controlling medium. 3D Ti-6Al-4V is likely to be an affordable alternative anode in alkaline environmentally friendly electrochemical applications
Online and Blended Labs for Practical Mechanical Engineering
Get PDFLab training is a key element in most engineering education programs in preparation for engineering profession tasks. Universities worldwide are exploring new possibilities and different forms to arrange online and blended labs as an alternative to pure campus training. This study compares online and blended lab setups in four cases of engineering education at European technical universities. The results show that online and blended labs can achieve similar learning outcomes, with blended labs being particularly effective in combining online learning with hands-on elements. Students reported high levels of satisfaction and teachers noted the benefits of online learning environments, but common challenges included ensuring student engagement, increased self-regulation requirements, and the high effort needed to design online or blended environments. The study provides course design guidelines and discusses implications for future research and implementation in universities worldwide
Characterization of the mechanical properties of low stiffness marine power cables through tension, bending, torsion, and fatigue testing
Get PDFThe exploitation and harnessing of offshore marine renewable energy have led to an increased demand for reliable marine power cables with long service lives. These cables constitute a considerable share of the total installation cost of offshore renewable energy facilities and have high maintenance and repair costs. The critical characteristics of these power cables must be determined to reduce the risk of exceeding their ultimate strength or fatigue life, which can result in unwanted and unexpected failures. This study investigates dynamic marine power cables that are suitable for application in devices that harness energy from ocean currents, waves, and tides. Tension, bending, torsion, and fatigue tests were conducted on three dynamic power cables (1 kV, 3.6 kV, and 24 kV) that have high flexibility, i.e., low mechanical stiffness. The specimen lengths and axial pretension force were varied during the tests. The results are discussed in terms of the mechanical fatigue degradation and ultimate design load, and the key observations and lessons learned from the tests are clarified. The study’s main contribution is the results from physical component testing of the dynamic marine power cables without metallic armors, which can be used to calibrate numerical models of this type of dynamic marine power cable in the initial design of, e.g., inter-array cables between floating wave energy converters. The benefits offered by this type of cable and the importance of the results for creating reliable numerical simulation models in the future are highlighted
Long-term stability of molecular doped epigraphene quantum Hall standards: single elements and large arrays (R K/236 ≈ 109 Ω)
Get PDFIn this work we investigate the long-term stability of epitaxial graphene (epigraphene) quantum Hall resistance standards, including single devices and an array device composed of 236 elements providing R K/236 ≈ 109 Ω, with R K the von Klitzing constant. All devices utilize the established technique of chemical doping via molecular dopants to achieve homogenous doping and control over carrier density. However, optimal storage conditions and the long-term stability of molecular dopants for metrological applications have not been widely studied. In this work we aim to identify simple storage techniques that use readily available and cost-effective materials which provide long-term stability for devices without the need for advanced laboratory equipment. The devices are stored in glass bottles with four different environments: ambient, oxygen absorber, silica gel desiccant, and oxygen absorber/desiccant mixture. We have tracked the carrier densities, mobilities, and quantization accuracies of eight different epigraphene quantum Hall chips for over two years. We observe the highest stability (i.e. lowest change in carrier density) for samples stored in oxygen absorber/desiccant mixture, with a relative change in carrier density below 0.01% per day and no discernable degradation of quantization accuracy at the part-per-billion level. This storage technique yields a comparable stability to the currently established best storage method of inert nitrogen atmosphere, but it is much easier to realize in practice. It is possible to further optimize the mixture of oxygen absorber/desiccant for even greater stability performance in the future. We foresee that this technique can allow for simple and stable long-term storage of polymer-encapsulated molecular doped epigraphene quantum Hall standards, removing another barrier for their wide-spread use in practical metrology
Layer-by-Layer Assembly of CTAB-rGO-Modified MXene Hybrid Films as Multifunctional Electrodes for Hydrogen Evolution and Oxygen Evolution Reactions, Supercapacitors, and DMFC Applications
Get PDFExceptional electrical conductivity and abundance of surface terminations like-F- and OH- leading to hydrophilicity make the family of 2D transition metal carbides/nitrides and carbonitrides (MXene) excellent candidates for energy storage and conversion applications. MXenes, however, undergo restacking of nanosheets via van der Waals interaction, hindering the active sites, leading to slow electronic and ionic kinetics, and ultimately affecting their electrochemical performance. Herein, we report binder-free cetyltrimethylammonium bromide-reduced graphene oxide (CTAB-rGO)-modified MXene hybrid films on nickel foam as a promising noble metal-free multifunctional electrode synthesized via layer-by-layer assembly and dip coating techniques, which effectively reduce restacking while improving the kinetics. The properties of the as-prepared electrocatalysts are investigated using various physiochemical characterizations and electrochemical measurements to accomplish the objective of "creating one kind of electrocatalyst for multiapplication" with a thorough understanding of the relationship between the material structure, morphology, and electrocatalytic performance. In energy conversion, the synergetic effect of MXene and the CTAB-rGO support helped increase the catalytic activity of the composite for electrochemical water splitting, demonstrating a current density of 10 mA/cm(2) at an overpotential (?) of 360 V and a Tafel slope value of 56.6 mV/dec for hydrogen evolution reaction and a current density of 10 mA/cm(2) at an overpotential (?) of 179 mV and a Tafel slope value of 47.03 mV/dec for oxygen evolution reaction in an alkaline medium. The electrode material also exhibited a higher oxidation current density (373.60 mA/cm(2)) compared to that of synthesized MXene toward methanol oxidation reaction in direct methanol fuel cell application. Additionally, the energy storage potential of CTAB-rGO modified MXene as electrode materials for supercapacitors with a high specific capacitance (544.50 F g(-1) at 0.5 A g(-1)) and a good capacity retention of 87% after 5000 cycles was studied. These findings of this work showcase the potential of the electrocatalyst in both conversion and storage of electrochemical energy
VEDLIoT: Next generation accelerated AIoT systems and applications
No full textThe VEDLIoT project aims to develop energy-efficient Deep Learning methodologies for distributed Artificial Intelligence of Things (AIoT) applications. During our project, we propose a holistic approach that focuses on optimizing algorithms while addressing safety and security challenges inherent to AIoT systems. The foundation of this approach lies in a modular and scalable cognitive IoT hardware platform, which leverages microserver technology to enable users to configure the hardware to meet the requirements of a diverse array of applications. Heterogeneous computing is used to boost performance and energy efficiency. In addition, the full spectrum of hardware accelerators is integrated, providing specialized ASICs as well as FPGAs for reconfigurable computing. The project\u27s contributions span across trusted computing, remote attestation, and secure execution environments, with the ultimate goal of facilitating the design and deployment of robust and efficient AIoT systems. The overall architecture is validated on use-cases ranging from Smart Home to Automotive and Industrial IoT appliances. Ten additional use cases are integrated via an open call, broadening the range of application areas
Chemical Doping of Conjugated Polymers for Thermoelectric Applications
Get PDFThe ongoing development of interconnected and wearable small devices, which together make up the so-called Internet of Things, is driving a rising need for autonomous and on-site energy supplies. Heat, an abundant and often wasted energy source, can be harnessed through thermoelectric generators that can directly convert heat into electricity. Small devices, such as health-monitoring sensors, may be powered by the heat dissipated from the human body using flexible thermoelectric generators made of organic semiconductors, like conjugated polymers. This thesis discusses polythiophenes with oligoether side chains, which are a promising class of conjugated polymers for the design of flexible, easily processable and light-weight thermoelectric generators. At first, this thesis investigates the solid-state order of these polymers and how is affected by varying the length of the oligoether side chains and by chemical doping with an oxidizing agent, F4TCNQ, and an acid, H-TFSI. It is showed that inducing order, either by shortening the side-chain length or by doping, enhances the transport properties of the materials, and so their thermoelectric performance.Secondly, this thesis studies the relationship between the solid-state order of these polymers and their mechanical properties. It is found that electrical and mechanical properties are usually correlated. The induced solid-state order not only improves the electrical conductivity but also enhances the stiffness of the materials. Partial decoupling of the electrical and mechanical properties is found to be possible if a suitable dopant is selected
Producing upgradeable bio-oil from food bio-waste via hybrid-assisted pretreatment coupled with catalytic hydrotreatment
Get PDFSlurry\ua0food waste sourced from Renova (Gothenburg, Sweden) was investigated as a model for generating upgradeable bio-oil via a hybrid-assisted\ua0pretreatment\ua0along with a catalytic hydrotreatment process. Hybrid-assisted pretreatment has been examined for extracting and stabilizing of reactive-derived substances. For the resulting bio-crude and residual solids, the properties of the heteroatoms were also examined prior to the catalytic hydrotreatment experiments. Hybrid-assisted pretreatment is an interesting solution in that it maximizes the bio-crude yield and transfers significant amounts of the nitrogenous content (De-N ∼83.3\ua0%, dry basis) into the residual solids. Nearly 87\ua0wt% of the oxygenated\ua0monomers\ua0were found in the obtained bio-crude, which possessed 52.0\ua0wt% of alcohols. The highest upgradeable bio-oil of 86.0\ua0wt% was achieved during catalytic hydrotreatment of the bio-crude and residual solids jointly: producing blends of up to 78\ua0wt% of hydrocarbons, 14\ua0wt% oxygenated and <6\ua0wt% of cyclic, aromatics, N-containing components
Kudō-continuity of conditional entropies
No full textIn this paper we introduce the notion of Kudō-continuity for real-valued functions on the space of all complete sub-σalgebras of a standard probability space. This is an a priori strengthening of continuity with respect to strong convergence. We show that conditional entropies are Kudō-continuous, and discuss an application to the study of Furstenberg entropy spectra of SAT*-spaces
Markanvisningst\ue4vlingen som verktyg i strategisk utveckling - sammanfattande slutsatser
Get PDFDenna sammanfattande rapport presenterar forskningsresultat fr\ue5n tre markanvisningst\ue4vlingar arrangerande av Marks kommun, Laholms kommun och Varbergs kommun.\ua0Redovisningen ing\ue5r i FoU-projektet\ua0T\ue4vlingar som verktyg i strategisk utveckling fr\ue5n gr\uf6na aff\ue4rsmodeller till konkreta cirkul\ue4ra designf\uf6rslag, som finansieras genom anslag fr\ue5n cmb.\ua0Bakgrunden till projektet \ue4r att markanvisningst\ue4vlingen \ue4r ett verktyg som ger kommunen en central roll i samh\ue4llsbyggandet. Kommunen \ue4r i detta fall b\ue5de arrang\uf6r, mark\ue4gare och planmyndighet. Som arrang\uf6r tar kommunen fram t\ue4vlings-program som informerar om t\ue4vlingsuppgift, bed\uf6mningskriterier och inl\ue4mningskrav. Juryns roll \ue4r att peka ut den b\ue4sta l\uf6sningen. Marken \ue4r en grundl\ue4ggande resurs som kommunen kontrollerar. Genomf\uf6randet av vinnande f\uf6rslag regleras i markanvisnings-och mark\uf6verl\ue5telseavtal. Avtalen \ue4r en hybrid mellan civil r\ue4tt och offentlig r\ue4tt