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Energy consumption and performance optimisation of laser cleaning for coating removal
No full textSelective removal of coatings by lasers can facilitate the reuse of coated tools in a circular economy. In order to optimise and control the process, it is essential to study the impact of process input variables on process performance. In this paper, coating removal from tooling was carried out using a picosecond a pulsed fibre laser, in order to investigate the effects of laser pulse energy, pulse frequency, galvo scanning speed and scanning track stepover. A fractional factorial design of experiments and analysis of variance was used to optimise the process; considering cleaning rate, specific energy consumption and surface integrity as assessed by changes in surface roughness and composition of the tooling after laser cleaning. The results shows synergy between cleaning rate and specific energy with the laser pulse frequency and galvo scanning speed as the two most significant factors, while the laser pulse energy had the greatest contribution to changes in surface composition. Based on extensive experiments, the relationship between processing rate and system specific energy consumption was mathematically modelled. The paper contributes a new specific energy model for laser cleaning and provides a benchmark of the process energy requirements compared to other manufacturing processes. Additionally, the generic scientific learning from this is that the rate of energy input is a key tool for maximising cleaning rate and minimising specific energy requirements, while the intensity of energy applied, is a key metric that influences surface integrity. More complex factors, influence the surface integrity.</p
Direct propylene epoxidation with molecular oxygen over cobalt-containing zeolites
No full textDirect propylene epoxidation with molecular oxygen is a dream reaction with 100 % atom economy, but the aerobic epoxidation is challenging due to the undesired over-oxidation and isomerization of epoxide product. Herein, we report the construction of uniform cobalt ions confined in faujasite zeolite, namely Co@Y, which exhibits unprecedented catalytic performance in the aerobic epoxidation of propylene. Propylene conversion of 24.6 % is achieved at propylene oxide selectivity of 57 % at 773 K, giving a state-of-the-art propylene oxide production rate of 4.7 mmol/gcat/h. The catalytic performance of Co@Y is very stable and no activity loss can be observed for over 200 h. Spectroscopic analyses reveal the details of molecular oxygen activation on isolated cobalt ions followed by interaction with propylene to produce epoxide, in which the Co2+-Coδ+-Co2+ (2<δ<3) redox cycle is involved. The reaction pathway of propylene oxide and byproduct acrolein formation from propylene epoxidation is investigated by density functional theory calculations, and the unique catalytic performance of Co@Y is interpreted. This work presents an explicit example of constructing specific transition metal ions within zeolite matrix toward selective catalytic oxidations.<br/
THE APPLICATION OF THE ARBITRARY-ORDER GALERKIN REDUCTION METHOD TO THE DYNAMIC ANALYSIS OF A ROTOR WITH A PRELOADED SINGLE-PAD FOIL-AIR BEARING
No full textStructural insights into UbiD reversible decarboxylation
No full textThe ubiquitous UbiX-UbiD system is associated with a wide range of microbial (de)carboxylation reactions. Recent X-ray crystallographic studies have contributed to elucidating the enigmatic mechanism underpinning the conversion of α,β-unsaturated acids by this system. The UbiD component utilises a unique cofactor, prenylated flavin (prFMN), generated by the bespoke action of the associated UbiX flavin prenyltransferase. Structure determination of a range of UbiX/UbiD representatives has revealed a generic mode of action for both the flavin-to-prFMN metamorphosis and the (de)carboxylation. In contrast to the conserved UbiX, the UbiD superfamily is associated with a versatile substrate range. The latter is reflected in the considerable variety of UbiD quaternary structure, dynamic behaviour and active site architecture. Directed evolution of UbiD enzymes has taken advantage of this apparent malleability to generate new variants supporting in vivo hydrocarbon production. Other applications include coupling UbiD to carboxylic acid reductase to convert alkenes into α,β-unsaturated aldehydes via enzymatic CO2 fixation.<br/
Control flow graph, formal verification and constraint programming techniques
No full textFormal program verification is a generally undecidable problem. Bounded Model Checking (BMC) is one method that can achieve decidability by searching for violations of properties of a program up to a bound k. BMC reduces the program verification problem to the classic NP-complete Boolean Satisfiability (SAT). However, it can still lead to an exponential state-space exploration due to the program’s large and possibly unbounded loops. In this case, there might be many execution paths to traverse through a program during its symbolic execution. Therefore, the control flow or computation during the program’s execution, mainly in symbolic execution, can be represented as a directed graph named Control Flow Graph (CFG). In this work, we present the properties of the CFG and discuss the application of constraint programming techniques to reduce variable domains as a preprocessing step or during the BMC process for verifying software systems. We also describe how constraint programming can be exploited to prove the (partial) correctness of the program via proof by induction built on top of BMC
Establishing the reliability and the validity of the Arabic translated versions of the Effort Assessment Scale and the Fatigue Assessment Scale
No full textObjective: The aim was to establish the reliability and the validity of Arabic translated versions of the Fatigue Assessment Scale (FAS) and the Effort Assessment Scale (EAS). Design: The FAS and the EAS were translated from the original English following a recommended six-step approach for translating hearing-related questionnaires for different languages. The reliability of the scales was investigated using Cronbach’s alpha, item-total correlation, and inter-item correlation. Construct validity was investigated using factor analysis and the hypothesis testing method.Study sample: The translated scales were completed by 146 participants from Jordan and Saudi Arabia (age range 19-86 years old, 39% male). Participants’ hearing level ranged from normal to profound.Results: Item 3 in the translated FAS was removed to improve the scale’s construct validity. The translated version of the EAS was found to be as reliable and valid as the original EAS.Conclusion: The availability of standardized versions of the FAS and the EAS provides a quick and easy method for improving hearing rehabilitation in Arabic-speaking countries where audiology services can often be costly and not necessarily accessible to all individuals
The influence of social support, financial status and lifestyle on the disparity between inflammation and disability in rheumatoid arthritis
No full textObjectives: To investigate how social support, financial status and lifestyle influence the development of excess disability in rheumatoid arthritis (RA).Methods: Data came from the Étude et Suivi des Polyarthrites Indifférenciées Récentes (ESPOIR) cohort study of people with RA. A previous analysis identified groups with similar inflammation trajectories but markedly different disability over 10 years; those in the higher disability trajectory groups were defined as having “excess disability”. Participants self-reported data on contextual factors (social support, financial situation, lifestyle) and completed patient reported outcome measures (PROMs; pain, fatigue, anxiety, depression) at baseline. The direct effect of the contextual factors on excess disability and the effect mediated by PROMs was assessed using structural equation models. Findings were validated within two independent datasets (Norfolk Arthritis Register [NOAR], Early Rheumatoid Arthritis Network [ERAN]).Results: Of 538 included ESPOIR participants (mean age [standard deviation (SD)]: 48.3 [12.2] years, 79.2% women), 200 (37.2%) were in the excess disability group. Less social support (β 0.17 [95% CI 0.08, 0.26]), worse financial situation (β 0.24 [95% CI 0.14, 0.34]), less exercise (β 0.17 [95% CI 0.09, 0.25]) and less education (β 0.15 [95% CI 0.06, 0.23]) were associated with excess disability group membership; smoking, alcohol consumption and body mass index were not. Fatigue and depression mediated a small proportion of these effects. Similar results were seen in NOAR and ERAN. Conclusions: Greater emphasis is needed on the economic and social context of people with RA at presentation; these factors might influence disability over the following decade. <br/
Effect of Clustering in Federated Learning on Non-IID Electricity Consumption Prediction
No full textWhen applied to short-term energy consumption forecasting, the federated learning framework allows for the creation of a predictive model without sharing raw data. There is a limit to the accuracy achieved by standard federated learning due to the heterogeneity of the individual clients’ data, especially in the case of electricity data, where prediction of peak demand is a challenge. A set of clustering techniques has been explored in the literature to improve prediction quality while maintaining user privacy. These studies have mainly been conducted using sets of clients with similar attributes that may not reflect realworld consumer diversity. This paper explores, implements and compares these clustering techniques for privacy-preserving load forecasting on a representative electricity consumption dataset. The experimental results demonstrate the effects of electricity consumption heterogeneity on federated forecasting and a nonrepresentative sample’s impact on load forecasting
Perspective - Formate as a key intermediate in CCU
No full textReplacing fossil feedstocks for chemicals and polymers in the chemical industry is a key step towards a future circular society. Making use of CO2 as a starting material in Carbon Capture and Utilization (CCU) or Carbon Capture and Storage (CCS) processes presents a great opportunity. Unfortunately, converting CO2 is not easy - due to its stability and inherently low reactivity either high energy inputs or nifty catalytic systems are required for its conversion. An electrochemical cell using a gas-diffusion electrode to convert CO2 into formate is such a promising system. But making formate alone does not allow us to substitute many fossil carbon-fed processes. Oxalic acid on the other hand is a potential new platform chemical for material production as useful monomers such as glycolic acid can be derived from it. Fortunately, formate can be converted into oxalate (and subsequently oxalic acid) by coupling two formates in a formate to oxalate coupling reaction (FOCR). The FOCR is a reaction that has been studied for more than 175 years and has seen widespread industrial use in the past. In this work, we critically discuss the history of the FOCR, present the most recent advances and draw a perspective for its future. We provide an overview of all (side)products obtained in FOCR and examine the various reaction parameters and their ability to influence the reaction. To understand the reaction better and improve it in the future, we critically discuss the many mechanisms proposed for the various catalytic systems in the FOCR. At last, we explore the potential to introduce new catalytic and solvent systems or co-reactants to the FOCR to improve reaction performance and broaden the range of products from CO2 derived formate
Effects of Sensor Design on the Performance of Wearable Sweat Monitors
No full textWearable sweat sensors are rapidly emerging for continuous and noninvasive monitoring of ‘wet’ parameters not included in current commercial wearables. This paper investigates the optimization of screen printed sweat sensors, intended to ultimately be compatible with large scale, roll-to-roll, fabrication. Sweat sensors containing Na+, K+ ion selective electrodes and pH sensing elements were screen printed on polyethylene naphthalate films with different electrode array designs. For sensing Na+ ions, a PEDOT:PSS transducer layer was found to effectively improve the sensor performance, showing an up to 32% sensitivity enhancement of up to 113.3mV/decade. Large working electrode sensing area was found to play an important role in achieving high electrical sensitivity, and the position of the electrodes influenced the individual sensor performance. These findings provide a solid foundation for an optimized development on wearable sweat sensors