Showing papers by "University of Warwick published in 2022"

Aspect-based sentiment analysis via affective knowledge enhanced graph convolutional networks

Abstract: Aspect-based sentiment analysis is a fine-grained sentiment analysis task, which needs to detection the sentiment polarity towards a given aspect. Recently, graph neural models over the dependency tree are widely applied for aspect-based sentiment analysis. Most existing works, however, they generally focus on learning the dependency information from contextual words to aspect words based on the dependency tree of the sentence, which lacks the exploitation of contextual affective knowledge with regard to the specific aspect. In this paper, we propose a graph convolutional network based on SenticNet to leverage the affective dependencies of the sentence according to the specific aspect, called Sentic GCN. To be specific, we explore a novel solution to construct the graph neural networks via integrating the affective knowledge from SenticNet to enhance the dependency graphs of sentences. Based on it, both the dependencies of contextual words and aspect words and the affective information between opinion words and the aspect are considered by the novel affective enhanced graph model. Experimental results on multiple public benchmark datasets illustrate that our proposed model can beat state-of-the-art methods.

Toward Smart Manufacturing Using Spiral Digital Twin Framework and Twinchain

Abstract: Digital twins (DT) have been proposed to support and enhance manufacturing processes of the industries. The outcome of adopting DT is so encouraging that it is hoped that more than 50% of the large industries will benefit from DT by the end of 2021. Unfortunately, DT lacks a single publicly accepted narrative. In order to help researchers for building a common narrative about DT, we present an elaborated structure of DT, namely, spiral DT-framework. Furthermore, for a secure and reliable management of the DT data, we propose using the blockchain technology rather than cloud or fog. As the classical blockchain suffers from transaction confirmation delays and is vulnerable to the quantum attacks, therefore, we propose a new variant of blockchain, namely twinchain, which is quantum-resilient and offers immediate transaction confirmation. This article also presents a framework for deployment of twinchain for manufacturing of a robot surgical machine.

Investigation on effect of phase change material on the thermal runaway of lithium-ion battery and exploration of flame retardancy improvement

Abstract: Thermal safety is important for the process of storage and utilization of lithium-ion battery. Once battery thermal runaway (TR) happens, accidents are difficult to avoid. As a cooling medium for battery thermal management, phase change material (PCM) can effectively maintain the temperature under normal operations. However, the flammability of PCM makes it doubtful to work safely under extreme conditions like TR. Herein, several sets of TR experiments have been conducted on 18650 batteries covered without and with different PCMs. Paraffin PCM (PPCM) and composite PCM (CPCM) are considered to explore their effects on TR. Results demonstrate that PPCM delays the onset of TR by 277 s and lowers the battery temperature utilizing its heat absorption while CPCM has little effect. However, flammable PPCM increases the heat release significantly which brings great fire risk. Based on the foregoing, a flame-retarded PPCM mixed with hydroxide flame-retardant proved to relieve the adverse effects of PPCM as well as maintain the performance for inhibiting TR. Results show that the addition of flame retardants reduces the peak heat release rate from 29 kW to 15.5 kW, which gives guidance in the process safety assurance and fire protection design in a real engineering application of battery thermal management.

The interactive effects of socialization tactics and work locus of control on newcomer work adjustment, job embeddedness, and voluntary turnover

Abstract: Previous research has tended to focus on general best practices for onboarding organizational newcomers. In this study, we shift the conversation to instead address the question: for whom are certa...

Reactive extrusion of biodegradable PGA/PBAT blends to enhance flexibility and gas barrier properties

Abstract: Among commercial biodegradable polyesters, poly(glycolic acid) (PGA) has been rarely investigated for packaging applications, despite its unique advantages such as 100% compostability, high degree of crystallinity, high thermal stability and high gas barrier properties. The application of PGA has been limited by its mechanical brittleness, moisture sensitivity, and high melting temperature (~240 oC), restricting its processing and applications for film packaging. In this study, PGA was modified by blending with poly (butylene adipate-co-terephthalate) (PBAT) via melt-extrusion. A commercial terpolymer of ethylene, acrylic ester and glycidyl methacrylate (EMA-GMA) was selected for compatibilization. The phase morphology, rheology, thermal, mechanical and gas barrier properties of the blends were investigated. With addition of 20 wt. % EMA-GMA, the elongation of PGA/PBAT (50/50 wt. %) blends was improved from 10.7 to 145%, the oxygen permeability was reduced from 125 to 103 (cm3mm) / (m224h atm), and the water vapour barrier performance was improved by ~47%. The enhancement in ductility, oxygen and water vapor barrier properties of the flexible blends were ascribed to the interfacial bonding between PBAT and PGA enabled by EMA-GMA. The compatibilized PGA/PBAT blends with high thermal stability up to 300 oC are preferable for high temperature or hot food packaging.

Redox‐Addressable Single‐Molecule Junctions Incorporating a Persistent Organic Radical**

Abstract: Integrating radical (open-shell) species into non-cryogenic nanodevices is key to unlocking the potential of molecular electronics. While many efforts have been devoted to this issue, in the absence of a chemical/electrochemical potential the open-shell character is generally lost in contact with the metallic electrodes. Herein, single-molecule devices incorporating a 6-oxo-verdazyl persistent radical have been fabricated using break-junction techniques. The open-shell character is retained at room temperature, and electrochemical gating permits in situ reduction to a closed-shell anionic state in a single-molecule transistor configuration. Furthermore, electronically driven rectification arises from bias-dependent alignment of the open-shell resonances. The integration of radical character, transistor-like switching, and rectification in a single molecular component paves the way to further studies of the electronic, magnetic, and thermoelectric properties of open-shell species.

Development of efficient, flexible and affordable heat pumps for supporting heat and power decarbonisation in the UK and beyond: Review and perspectives

Abstract: Half of the global final energy consumption is related to heat, which accounts for 40% of global energy-related carbon emissions. Particularly in the UK, nearly 24 million end-users rely on gas boilers to provide heat, leading to 37% of the country’s carbon emissions. Quick and successful heat decarbonisation is critical if ambitious climate goals need to be met by the mid-21st century. Heat pumps have been recognised as a key solution to reduce carbon emissions. This would instead draw carbon-reduced electricity from the electrical grid to produce heat more efficiently. Reciprocatively, the potential flexibility offered by the growing adoption of heat pumps on a (gigawatt) scale could also potentially support the deep decarbonisation of power and reduce the costs involved in the power system balancing and upgrades. By reviewing the technical development and barriers to creating high-efficiency and high-flexibility heat pumps, this study discusses how heat pumps could support the decarbonisation of heat and power with a focus on the UK system and market, which is also useful to countries in which heating is currently relying on fossil fuels. The major hurdle that mitigates the use of heat pumps – the high cost involved – and the methods to improve the economics of the technology are also discussed. If these techno-economic challenges can be overcome, electrification of heat using heat pumps could provide a route towards decarbonising heat and power and give the two communities and industries a collaborative way of tackling climate change at the root.

Endomembranes promote chromosome missegregation by ensheathing misaligned chromosomes

Abstract: Errors in mitosis that cause chromosome missegregation lead to aneuploidy and micronucleus formation, which are associated with cancer. Accurate segregation requires the alignment of all chromosomes by the mitotic spindle at the metaphase plate, and any misalignment must be corrected before anaphase is triggered. The spindle is situated in a membrane-free "exclusion zone"; beyond this zone, endomembranes (mainly endoplasmic reticulum) are densely packed. We investigated what happens to misaligned chromosomes localized beyond the exclusion zone. Here we show that such chromosomes become ensheathed in multiple layers of endomembranes. Chromosome ensheathing delays mitosis and increases the frequency of chromosome missegregation and micronucleus formation. We use an induced organelle relocalization strategy in live cells to show that clearance of endomembranes allows for the rescue of chromosomes that were destined for missegregation. Our findings indicate that endomembranes promote the missegregation of misaligned chromosomes that are outside the exclusion zone and therefore constitute a risk factor for aneuploidy.

Update of transmission modelling and projections of gambiense human African trypanosomiasis in the Mandoul focus, Chad

Abstract: In recent years, a programme of vector control, screening and treatment of gambiense human African trypanosomiasis (gHAT) infections led to a rapid decline in cases in the Mandoul focus of Chad. To represent the biology of transmission between humans and tsetse, we previously developed a mechanistic transmission model, fitted to data between 2000 and 2013 which suggested that transmission was interrupted by 2015. The present study outlines refinements to the model to: (1) Assess whether elimination of transmission has already been achieved despite low-level case reporting; (2) quantify the role of intensified interventions in transmission reduction; and (3) predict the trajectory of gHAT in Mandoul for the next decade under different strategies.Our previous gHAT transmission model for Mandoul was updated using human case data (2000-2019) and a series of model refinements. These include how diagnostic specificity is incorporated into the model and improvements to the fitting method (increased variance in observed case reporting and how underreporting and improvements to passive screening are captured). A side-by-side comparison of fitting to case data was performed between the models.We estimated that passive detection rates have increased due to improvements in diagnostic availability in fixed health facilities since 2015, by 2.1-fold for stage 1 detection, and 1.5-fold for stage 2. We find that whilst the diagnostic algorithm for active screening is estimated to be highly specific (95% credible interval (CI) 99.9-100%, Specificity = 99.9%), the high screening and low infection levels mean that some recently reported cases with no parasitological confirmation might be false positives. We also find that the focus-wide tsetse reduction estimated through model fitting (95% CI 96.1-99.6%, Reduction = 99.1%) is comparable to the reduction previously measured by the decline in tsetse catches from monitoring traps. In line with previous results, the model suggests that transmission was interrupted in 2015 due to intensified interventions.We recommend that additional confirmatory testing is performed in Mandoul to ensure the endgame can be carefully monitored. More specific measurement of cases, would better inform when it is safe to stop active screening and vector control, provided there is a strong passive surveillance system in place.

Stability Design of Stainless Steel Structures

Abstract: The direct analysis method (DAM), featuring second-order elastic analysis with two stiffness reduction factors (τb and τg), is the primary means of stability design for steel structures in ...

Introducing the Peacekeeping Mandates (PEMA) Dataset

Abstract: Research on UN peacekeeping operations has established that operations' size and composition affect peacekeeping success. However, we lack systematic data for evaluating whether variation in tasks assigned to UN peacekeeping mandates matters and what explains different configurations of mandated tasks in the first place. Drawing on UN Security Council resolutions that establish, extend, or revise mandates of 27 UN peacekeeping operations in Africa in the 1991–2017 period, the Peacekeeping Mandates (PEMA) dataset fills this gap. It records 41 distinct tasks, ranging from disarmament to reconciliation and electoral support. For each task, the PEMA dataset also distinguishes between three modalities of engagement (monitoring, assisting, and securing) and whether the task is requested or merely encouraged. To illustrate the usefulness of our data, we re-examine Hultman, Kathman, and Shannon’s (2013) analysis of operations’ ability to protect civilians. Our results show that host governments and rebel groups respond differently to civilian protection mandates.