MRC Laboratory of Molecular Biology
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An operational semantics for true concurrency in BDI agent systems
No full textAgent programming languages have proved useful for formally modelling implemented systems such as PRS and JACK, and for reasoning about their behaviour. Over the past decades, many agent programming languages and extensions have been developed. A key feature in some of them is their support for the specification of ‘concurrent’ actions and programs. However, their notion of concurrency is still limited, as it amounts to a nondeterministic choice between (sequential) action interleavings. Thus, the notion does not represent ‘true concurrency’, which can more naturally exploit multi-core computers and multi-robot manufacturing cells. This paper provides a true concurrency operational semantics for a BDI agent programming language, allowing actions to overlap in execution. We prove key properties of the semantics, relating to true concurrency and to its link with interleaving
Graphene-passivated nickel as an efficient hole-injecting electrode for large area organic semiconductor devices
No full textEfficient injection of charge from metal electrodes into semiconductors is of paramount importance to obtain high performance optoelectronic devices. The quality of the interface between the electrode and the semiconductor must, therefore, be carefully controlled. The case of organic semiconductors presents specific problems: ambient deposition techniques, such as solution processing, restrict the choice of electrodes to those not prone to oxidation, limiting potential applications. Additionally, damage to the semiconductor in sputter coating or high temperature thermal evaporation poses an obstacle to the use of many device-relevant metals as top electrodes in vertical metal-semiconductor-metal structures, making it preferable to use them as bottom electrodes. Here, we propose a possible solution to these problems by implementing graphene-passivated nickel as an air stable bottom electrode in vertical devices comprising organic semiconductors. We use these passivated layers as hole-injecting bottom electrodes, and we show that efficient charge injection can be achieved into standard organic semiconducting polymers, owing to an oxide free nickel/graphene/polymer interface. Crucially, we fabricate our electrodes with low roughness, which, in turn, allows us to produce large area devices (of the order of millimeter squares) without electrical shorts occurring. Our results make these graphene-passivated ferromagnetic electrodes a promising approach for large area organic optoelectronic and spintronic devices
Observations of the Effects of a Clay Layer on Suction Bucket Installation in Sand
No full textSuction buckets are becoming established as a viable foundation solution for offshore wind turbines. In sand, suction-induced seepage flow reduces effective stresses at the skirt tips, which decreases penetration resistance. However, layered seabeds are often encountered in areas of offshore wind farm development. The effect of the presence of a clay layer on the suction-induced seepage flow in the sand layer is not well understood. Therefore in this study, the effects of a clay layer on suction bucket installation in dense sand was investigated. This was achieved by analyzing images of a half-bucket installed against a Perspex window. The images were captured during tests performed in a geotechnical centrifuge, such that the stress levels are realistic and relevant to field conditions. Installations in sand-over-clay were unproblematic and characterized by deformation of the sand-clay interface, with no clear interruption of the seepage flow. Installations in clay-over-sand were also successful. Uplift of the clay plug was identified as the mechanism to transfer suction to the underlying sand, creating seepage flow and thus facilitating further skirt penetration rather than terminating the installation
Exploring resilient observability in traffic-monitoring sensor networks: A study of spatial-temporal vehicle patterns
No full textVehicle mobility generates dynamic and complex patterns that are associated with our day-to-day activities in cities. To reveal the spatial-temporal complexity of such patterns, digital techniques, such as traffic-monitoring sensors, provide promising data-driven tools for city managers and urban planners. Although a large number of studies have been dedicated to investigating the sensing power of the traffic-monitoring sensors, there is still a lack of exploration of the resilient performance of sensor networks when multiple sensor failures occur. In this paper, we reveal the dynamic patterns of vehicle mobility in Cambridge, UK, and subsequently, explore the resilience of the sensor networks. The observability is adopted as the overall performance indicator to depict the maximum number of vehicles captured by the deployed sensors in the study area. By aggregating the sensor networks according to weekday and weekend and simulating random sensor failures with different recovery strategies, we found that (1) the day-to-day vehicle mobility pattern in this case study is highly dynamic and decomposed journey durations follow a power-law distribution on the tail section; (2) such temporal variation significantly affects the observability of the sensor network, causing its overall resilience to vary with different recovery strategies. The simulation results further suggest that a corresponding prioritization for recovering the sensors from massive failures is required, rather than a static sequence determined by the first-fail-first-repair principle. For stakeholders and decision-makers, this study provides insightful implications for understanding city-scale vehicle mobility and the resilience of traffic-monitoring sensor networks
Transient Crosstalk in Holographic Optical Switching Based on Wavefront Encoding
No full textThis work demonstrates that wavefront encoding technique can be used reduce the peak transient crosstalk by >10 dB in holographic optical switches based on the liquid crystal on silicon (LCOS) technology, when compared with switches based on the conventional Fourier transform optical setup. At the same time, this technique also reduces the switching time, without any modifications needed to either the LCOS device or its driving circuits
MXene Printing and Patterned Coating for Device Applications
No full textAs a thriving member of the 2D nanomaterials family, MXenes, i.e., transition metal carbides, nitrides, and carbonitrides, exhibit outstanding electrochemical, electronic, optical, and mechanical properties. They have been exploited in many applications including energy storage, electronics, optoelectronics, biomedicine, sensors, and catalysis. Compared to other 2D materials, MXenes possess a unique set of properties such as high metallic conductivity, excellent dispersion quality, negative surface charge, and hydrophilicity, making them particularly suitable as inks for printing applications. Printing and pre/post-patterned coating methods represent a whole range of simple, economically efficient, versatile, and eco-friendly manufacturing techniques for devices based on MXenes. Moreover, printing can allow for complex 3D architectures and multifunctionality that are highly required in various applications. By means of printing and patterned coating, the performance and application range of MXenes can be dramatically increased through careful patterning in three dimensions; thus, printing/coating is not only a device fabrication tool but also an enabling tool for new applications as well as for industrialization
Shallow penetrometer tests: Theoretical and experimental modelling of penetration and dissipation stages
No full textShallow penetrometers are devices that penetrate into and measure the properties of surficial offshore sediments via multi-phase tests involving penetration, dissipation, and rotation stages. In fine-grained soils such as silts and clays, these testing stages yield undrained strength, consolidation, and friction properties relevant to subsea pipeline and shallow foundation design. This paper describes toroid and hemiball devices of the scale for use in box-core samples and associated interpretation methods for the penetration and dissipation stages. The aim of the paper is to provide all tools needed to design and interpret these tests. New large-deformation finite element (LDFE) dissipation solutions are presented, which can be used for back-analysis of the dissipation stage. Results of an extensive laboratory proof testing exercise in kaolin clay, for both the hemiball and toroid penetrometers, are also reported. These results highlight the potential of the two devices to quickly and economically assess strength and consolidation characteristics of fine-grained sediments in box-core samples recovered to the deck of a site investigation vessel
Crosstalk analysis of a CMOS single membrane thermopile detector array
No full textWe present a new experimental technique to characterise the crosstalk of a thermopile-based thermal imager, based on bi-directional electrical heating of thermopile elements. The new technique provides a significantly simpler and more reliable method to determine the crosstalk, compared to a more complex experimental setup with a laser source. The technique is used to characterise a novel single-chip array, fabricated on a single dielectric membrane. We propose a theoretical model to simulate the crosstalk, which shows good agreement with the experimental results. Our results allow a better understanding of the thermal effects in these devices, which are at the center of a rising market of industrial and consumer applications
A new mechanism of strain transfer in polycrystals
No full textAt the grain boundaries of plastically deforming polycrystals, strain transfer mechanisms can accommodate the shear strain carried by slip bands and mechanical twins to prevent stress build-ups and damage. So far, only the accommodation obtained through slip (and twinning) alone has been considered in the mechanism known as slip (and twin) transfer. Here, a strain transfer mechanism that also requires the rotation of the crystal lattice is demonstrated. A region of accumulated slip develops perpendicular to the active slip plane in the impinged grain. The slip gradients enable a localized lattice rotation that accommodates the shear strain in the incoming band, preventing the build-up of interfacial stresses. The mechanism operates preferentially at the boundaries between highly misoriented grains. Facilitating strain transfer at these interfaces opens up new possibilities to improve the mechanical properties of polycrystals, as discussed
Preparing for Industry 4.0: Digital Business Model Innovation in the Food and Beverage Industry
No full textThe digitalisation of manufacturing will impact on all industries, including food and beverage: The so-called Industry 4.0 paradigm particularly denotes the exploitation and utilisation of real time data originating from an ubiquitous interconnection of objects, machines and humans (via the internet) across the entire value chain. Facilitated by an exponential growth in semiconductor and related digital capabilities, Industry 4.0 not only serves as a catalyst to improve processes or to design new product and service solutions. More fundamentally it is enabling entirely new business models which may not have been conceivable several years ago. F&b manufacturers face the challenge of both re-shaping their business model, at the same time as adapting their operations and products to this rapid socio-technological shift: This requires not only the customisation of the product service offerings of the business but also continuous adaptation and alignment of the firm’s value adding activities. However, today it is not clear, what manufacturing firms need to do to prepare for Industry 4.0 nor how to closely align Industry 4.0 initiatives with business model innovation. This paper shows by means of the first empirical investigation of UK-based food and beverage manufacturers that the application of Industry 4.0 activities is mostly tactical, and thereby decoupled from the firms’ business models. It argues that this stems from a lack of strategic envisioning on the impacts of Industry 4.0 on their entire businesses, and prevalent efficiency-oriented corporate cultures. Findings indicate that manufacturers should prioritise their I4.0 pathways early in the business strategy formulation process, in order to select the most appropriate technological solutions to enable these pathways. Whilst such prioritisation emphasises the importance to allocate resources appropriately, the dynamics of I4.0 require firms to continuously innovate their business model in order to implement I4.0. Thereby, two principle lines are key via the use of the three conceptual I4.0 pillars and the underpinning advanced mechatronics (1) to granularly segment customer needs and (2) to enhance the flexibility of value adding activities. These two approaches are mutually interdependent and hence an integrated approach through continuous business model innovation will enable manufacturers to be more responsive to individual customer needs; transforming their make-and-sell BM into sense-and-act BM. These results provide guidance for the application of Industry 4.0 in f&b manufacturing firms. This investigation is anticipated to be a starting point to develop an integrative framework to achieve consistency among business model components and achieve superior performance in light of (socio-) technological shifts for Industry 4.0