Motor unit buckling in variable recruitment fluidic artificial muscle bundles: implications and mitigations

Fluidic artificial muscles (FAMs) are a popular actuation choice due to their compliant nature and high force-to-weight ratio. Variable recruitment is a bio-inspired actuation strategy in which multiple FAMs are combined into motor units that can be pressurized sequentially according to load demand. In a traditional ‘fixed-end’ variable recruitment FAM bundle, inactive units and activated units that are past free strain will compress and buckle outward, resulting in resistive forces that reduce overall bundle force output, increase spatial envelope, and reduce operational life. This paper investigates the use of inextensible tendons as a mitigation strategy for preventing resistive forces and outward buckling of inactive and submaximally activated motor units in a variable recruitment FAM bundle. A traditional analytical fixed-end variable recruitment FAM bundle model is modified to account for tendons, and the force-strain spaces of the two configurations are compared while keeping the overall bundle length constant. Actuation efficiency for the two configurations is compared for two different cases: one case in which the radii of all FAMs within the bundle are equivalent, and one case in which the bundles are sized to consume the same amount of working fluidvolume at maximum contraction. Efficiency benefits can be found for either configuration for different locations within their shared force-strain space, so depending on the loading requirements, one configuration may be more efficient than the other. Additionally, a study is performed to quantify the increase in spatial envelope caused by the outward buckling of inactive or low-pressure motor units. It was found that at full activation of recruitment states 1, 2, and 3, the tendoned configuration has a significantly higher volumetric energy density than the fixed-end configuration, indicating that the tendoned configuration has more actuation potential for a given spatial envelope. Overall, the results show that using a resistive force mitigation strategy such as tendons can completely eliminate resistive forces, increase volumetric energy density, and increase system efficiency for certain loading cases. Thus, there is a compelling case to be made for the use of tendoned FAMs in variable recruitment bundles.

The Persistence of the Victorian Prison: Alteration, Inhabitation, Obsolescence, and Affirmative Design

Prior scholarship tracing the origins and architecture of prisons has tended to focus on how and why prisons are built—what they are intended to achieve and their construction as an expression of the punitive philosophies of their age. It does not consider how prisons persist as time passes, perhaps beyond their anticipated operational life span, and into “obsolescence.” Focusing on the archetypal Victorian prison, and considering the alteration and inhabitation of such prisons through time, this article critically reinterprets notions of obsolescence in the built environment and explores an enduring cultural attachment to a particular and arguably archaic material manifestation of punishment.

Flow Assurance and Thermodynamic Challenges of operating CO2 Pipelines for variations in terrains and environments

The requirement for capturing and storing Carbon Dioxide will continue to grow in the next decade and a fundamental part of this is being able to transport the fluid over large geographical distances in numerous terrains and environments. The evolving nature of the fluid supply and the storage characteristics ensure the operation of the pipeline remains a challenge throughout its operational life. This paper will examine the impact of changes in the fluid composition, storage locations, ambient conditions and the various operating modes the pipeline will see throughout the lifecycle, highlight the technical design and operational challenges and finally give guidance on future developments. The thermodynamic behaviour of CO2 with and without impurities will be demonstrated utilising the fluid characterisation software, MultiflashTM. The fluid behaviour and hydraulic performance will be calculated over the expected operational envelope of the pipeline throughout field life, highlighting the benefits and constraints of using the single component module in OLGATM whilst comparing against a compositional approach when dealing with impurities. The paper will demonstrate through two case studies of varying nature including geographical environment, storage location (aquifer vs. abandoned hydrocarbon reservoir) and ambient conditions, the following issues: The impact of the storage type on the pipeline operations and how this will evolve with time; The environmental conditions and the impact these have on selection of process equipment and operational procedures (i.e. shutdown); and The impact the CO2 composition has on the design of the CO2 pipeline, and The paper will conclude with a set of guidelines for undertaking design analysis of CO2 pipelines for variations in fluid composition, storage locations and ambient conditions as well as some key operational strategies. This paper utilises the current state of the art tools and how these evolving tools are making this technically challenging area more mainstream.

Mercury Contamination of Process and Pipeline Infrastructure - A Novel, All- Encompassing Solution for the Evaluation and Decontamination of Mercury from Pipelines and Topside Process Equipment to allow Safe Disposal

Mercury present in produced oil and gas will deposit onto the internal process infrastructure via a number of mechanisms including chemisorption and adsorption with the primary mechanism being through reaction with iron sulphide to form mercury sulphide. Due to the volumes of fluids produced and the length of time facilities are in production, even where the produced fluids have historically contained relatively low concentrations of mercury, pipeline scales containing percentage levels of mercury may be present. Thus, aged facilities and infrastructure that have reached the end of their operational life and are selected for either recycling or abandonment, may pose a serious risk to health and the environment if the decommissioning process is not managed correctly. Smelting, hot cutting or other thermal/abrasive surface preparations for example, can lead to significant release of elemental mercury, a worker exposure hazard. Alternatively, if sub-sea pipelines are abandoned in-situ, all mercury present will ultimately be transferred to the local ecosystems. Consequently, the oil and gas industry have the requirement for a complete mercury decontamination solution from initial evaluation, demonstrable cleaning efficacy through to a guarantee for the treatment and disposal of the mercury waste generated in an environmentally-friendly manner. In order to decide upon the most appropriate decontamination solution, an evaluation of the extent of mercury contamination should be undertaken. A novel approach that has recently been successfully implemented involved analysis of pipe sections by multiple analytical techniques, providing the mercury concentration in the scale/steel. From this, the total mass of mercury across the process or pipeline was approximated. Subsequently, the efficacy of the preferred chemical to remove mercury from the internal surfaces of pipework was evaluated by chemical treatment of the pipe sections under laboratory conditions. In-situ decontamination can be performed by a number of applications, including (i) the use of chemical pig trains in pipelines, (ii) closed loop circulation of chemical around topside process equipment and (iii) high pressure spraying of large surface areas such as storage tanks, FSO / FPSO vessels. The mercury waste generated is treated, on site or off site, to minimise the volume and disposed of in accordance with international regulations. An all-encompassing mercury decontamination solution is described. Trials involving the chemical treatment of steel sections have demonstrated that more than 97% of the mercury deposited can be removed from the internal surfaces of pipelines and safely disposed of, significantly reducing the risk of (i) mercury release to the environment and (ii) worker exposure to mercury during smelting activities.

Validation of a structural model of an aircraft cockpit panel: An industrial case study

Computational models of structures are widely used to inform decisions about design, maintenance and operational life of engineering infrastructure, including airplanes. Confidence in the predictions from models is provided via validation processes that assess the extent to which predictions represent the real world, where the real world is often characterised by measurements made in experiments of varying sophistication dependent on the importance of the decision that the predictions will inform. There has been steady progress in developing validation processes that compare fields of predictions and measurements in a quantitative manner using the uncertainty in measurements as a basis for assessing the importance of differences between the fields of data. In this case study, three recent advances in a validation process, which was evaluated in an inter-laboratory study 5 years ago, are implemented using a ground-test on a fuselage at the aircraft manufacturer’s site for the first time. The results show that the advances successfully address the issues raised by the inter-laboratory study, that the enhanced validation process can be implemented in an industrial environment on a complex structure, and that the model was an excellent representation of the measurements made using digital image correlation.

The Impact of Using the Total Cost of Ownership (TCO) Account for a Reusable Wooden Flat Pallet in Its Operational Phase on Respecting the Principles of Sustainable Development

Despite the commonly observed trend towards mechanization and automation of operational processes, the potential benefits of wooden pallets as an essential element of the infrastructure of logistic processes are often overlooked in considerations related to sustainable development. Aspects that are mentioned more often include the very idea of the economy itself (circular economy), characteristics of logistics (green), features of the supply chain itself (sustainable) or expectations towards transport (ecological). The authors believe that the idea of total cost of ownership (TCO) in relation to wooden pallets can be a key component of holistic thinking in terms of sustainable development. In a situation where in relation to logistics, reasonable expectations for developing sustainable supply chains are made, paying attention to such a common logistic facility, namely a cargo pallet, which is given so little attention in research, is, in the opinion of the authors, absolutely justified. Therefore, the article presents an original approach to the problem of aggregation of all costs that cargo pallets generate in their operational life cycle, using the total cost of ownership (TCO) analysis methodology. The main goal of the article, however, is to show that the total cost of ownership of a pallet (not only owning it) can become an effective tool used to significantly reduce the costs of logistic activity of enterprises (as well as whole supply chains) and support the idea of sustainable development in practice. Using the primary data from questionnaire research, the focus was on considerations that were of identification character (cognitive and explanatory considerations), which are typical for basic research that aims to explain given phenomena. Thus, the presented cognitive process covers two main areas, namely: the general theory of sustainable development and the specificity of wooden pallets as carriers used in goods trading in terms of their total costs of ownership.

Adopting combination of passive design strategies to optimize building energy needs

The paper’s main goal is to analyze the efficiency of roof and wall systems based on varying insulating material layers in the tropical climatic region of Vijayawada, Andhra Pradesh, India. This research is carried out on “e-QUEST” software for energy analysis which is determined on monthly basis and the results gave evidence about energy consumption of building envelope and its operational life cycle costing. The wall and roof system have been studied for computation of the operating energy requirements and its subsequent carbon footprints which comes under concept of sustainability of building. The materials identified for insulating roof are vacuum insulated panels, wool glass, phenolic foam, expanded polystyrene, polystyrene, and for wall are cellulose, fiber glass, mineral wool, polystyrene, aero gel. Due to both have insulation of wall and roof systems the passage a source of heat minimized because of which the cooling demand is reduced on building and ultimately leads to lowering of energy consumption. Hence this study is crucial to understand the resident indoor air comfort, environmental and long-term economic benefits.

Influence of stress history on undrained cyclic shear strength evolution

Offshore infrastructure often interacts cyclically with the seabed over the operational life of a project. Previous research on the evolution of soil’s undrained strength under long term, large-amplitude cyclic loading has focused on contractile clays and demonstrated that this cyclic interaction can lead to the initial generation and later dissipation of positive excess pore pressure in the soil. This process generally leads to an initial strength reduction, with subsequent densification and soil strength gains that can have consequences on the performance of seabed infrastructure during its design life. In this paper, new experimental data from T-bar penetrometer testing in reconstituted kaolin and Gulf of Mexico clays is presented. The data illustrate how the stress history, quantified via the overconsolidation ratio, affects soil strength changes during large-amplitude cyclic loading. The experiments explore both long-term continuous loading cycles and episodic loading with packets of undrained cycles followed by quiescent consolidation periods. A critical state-based framework is used to interpret the experimental data and provide predictions of the long-term steady-state strength of both soils as a function of the initial in situ state of the soil.

Wind turbine main-bearing lubrication – Part 2: Simulation based results for a double-row spherical roller main-bearing in a 1.5 MW wind turbine

This paper is the second in a two-part study on lubrication in wind turbine main-bearings. Where “Part 1” provided an introductory review of elastohydrodynamic lubrication theory, this paper will apply those ideas to investigate lubrication in the double-row spherical roller main-bearing of a 1.5 MW wind turbine. Lubrication is investigated across a “contact conditions dataset” generated by inputting processed loads, obtained from aeroelastic simulations, into a Hertzian contact model of the main-bearing. From the Hertzian model is extracted values of roller load and contact patch dimensions, along with the time rate-of-change of contact patch dimensions. Also included in the dataset are additional environmental and operational variable values (e.g. wind speeds and shaft rotational speeds). A suitable formula for estimating film thickness within this particular bearing is then identified. Using lubricant properties of a commercially available wind turbine grease, specifically marketed for use in main-bearings, an analysis of film thickness across the generated dataset is undertaken. The analysis includes consideration of effects relating to starvation, grease thickener interactions and possible dynamic EHL effects. Results show that the modelled main-bearing would be expected to operate under mixed lubrication conditions for a non-negligible proportion of its operational life, indicating that further work is required to better understand lubrication in this context and implications for main-bearing damage and operational lifetimes. Key sensitivities and uncertainties within the analysis are discussed, along with recommendations for future work.

ACTIVE CONTROL OF THE TOPOLOGICAL PARAMETERS OF ISLAND CATALYSTS WHEN SOLID OXIDE ELECTROLYTES OF FUEL CELLS ARE DEPOSITED ON THE SURFACE

The method of active technological control of topological parameters of synthesized island catalysts on solid oxide fuel cell electrolytes is considered. The proposed method makes it possible to obtain a catalyst with a maximum active area and high adhesion to a solid oxide electrolyte, which contributes to an increase in the power of the fuel cell and an increase in the operational life. The models of two stages of formation of island films under vacuum and magnetron sputtering presented in this paper were used as a theoretical basis for the creation of a method for active technological control and control of the synthesis of island catalyst in solid oxide fuel cells. Experimental testing of the developed method has shown its efficiency and effectiveness in the creation of solid oxide fuel cells.