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Distributed satellite system autonomous orbital control with recursive filtering
No full textIn this article, we propose a recursive orbital elements filter for autonomous control of Distributed Satellite Systems (DSS) that significantly reduces the variance of relative orbital elements between the observed and the desired satellite orbits. Leveraging satellite kinematics and control inputs data, combined with a model of relative dynamics, the filter provides smooth and continuous orbital control, while minimizing propellant consumption. In conjunction with Precise Point Positioning (PPP) navigation, the proposed filter enables onboard continuous low-thrust control compatible with high-performance electric propulsion. We also propose a restricted transverse/normal control law that simplifies the thruster's configurations and/or attitude manoeuvres required for propulsion pointing. The applicability and validity of our proposed techniques are verified by numerical simulations with two case studies: a constellation for Differential Interferometric Synthetic Aperture Radar (DInSAR) for global infrastructure monitoring; and a maritime domain awareness mission based on along-track interferometric synthetic aperture radar which requires single-pass interferometry for responsive ship traffic surveillance, and the coverage of a very large maritime zone with high revisit rates
Dual defect regulation of BiOCl halogen layer enables photocatalytic O2 activation into singlet oxygen for refractory aromatic pollutant removal
No full textThe generation of singlet oxygen (1O2) based on photocatalytic activation O2 is considered to have important application prospects in purifying refractory organic pollutants in water. However, the uncertain dual pathway transformation of activated O2 severely limits the generation of 1O2. In this work, we show a robust BiOCl with dual defects (adjacent I-substitution defect and Cl vacancy) in halogen layer for the selective activation of O2 to generate 1O2. Combining experiments and theoretical calculations, we confirm that dual defects are beneficial in optimizing band structures, improving carrier separation efficiency, and promoting O2 adsorption and activation. More importantly, it is confirmed that dual defects can directionally convert O2 into 1O2 by increasing the thermodynamic conversion energy barrier of non-1O2 conversion pathways and serving as a necessary site for 1O2 generation with dual functions of oxidation and reduction. Applying dual defect modified BiOCl to the removal of refractory aromatic pollutants in water, it is found that it has efficient and stable photocatalytic degradation efficiency and broad environmental adaptability. This work not only provides in-depth insights into the mechanism of photocatalytic activation of O2 to selective produce 1O2, but also lays the foundation for further development of highly active photocatalysts for environmental remediation and energy conversion
Measuring the extreme linkages and time-frequency co-movements among artificial intelligence and clean energy indices
No full textThis is the first study analyzing the volatility connectedness and time-frequency interdependence between AI index and clean energy index. Specifically, we use the QVAR frequency connectedness, Wavelet Local Multiple Correlations (WLMC) and Granger causality quantile methods to check the risk spillovers and multivariate time and frequency relationships among the eight clean energy indexes and the AI index. This is over the period from December 18, 2017 to April 4, 2023. Our results show: (1) NASDAQ OMX Geothermal Index is the strongest net sender of short- and long-term shocks in the system during extreme upside market conditions. In downturn conditions, the S&P Global Clean Energy Index is the largest net shock sender. The AI Index exports shocks at all frequencies. In addition, market connectedness among markets is stronger under extreme market conditions. (2) We find that the AI Index predominantly exhibited positive co-movements with clean energy indices, primarily concentrated within the long-term frequency domain. However, they displayed robust cooperative dynamics across all frequency domains within the context of multivariate wavelet interconnections. (3) The quantile granger causality analysis revealed that below the extreme bullish threshold (0.95), the NASDAQ CTA Artificial Intelligence & Robotics index could predict changes in the risk associated with all clean energy indices. However, under extremely bullish quantile conditions, the NASDAQ CTA Artificial Intelligence & Robotics index statistically exhibited Granger causality only with respect to the NASDAQ OMX Renewable Energy Index, NASDAQ OMX Geothermal Index, and WilderHill Clean Energy Index
Hepatic concentrations of per- and polyfluoroalkyl substances (PFAS) in dolphins from south-east Australia: Highest reported globally
No full textPer- and polyfluoroalkyl substances (PFAS) concentrations were investigated in hepatic tissue of four dolphin species stranded along the south-east coast of Australia between 2006 and 2021; Burrunan dolphin (Tursiops australis), common bottlenose dolphin (Tursiops truncatus), Indo-Pacific bottlenose dolphin (Tursiops aduncus), and short-beaked common dolphin (Delphinus delphis). Two Burrunan dolphin populations represented in the dataset have the highest reported global population concentrations of ∑25PFAS (Port Phillip Bay median 9750 ng/g ww, n = 3, and Gippsland Lakes median 3560 ng/g ww, n = 8), which were 50–100 times higher than the other species reported here; common bottlenose dolphin (50 ng/g ww, n = 9), Indo-Pacific bottlenose dolphin (80 ng/g ww, n = 1), and short-beaked common dolphin (61 ng/g ww, n = 12). Also included in the results is the highest reported individual ∑25PFAS (19,500 ng/g ww) and PFOS (18,700 ng/g ww) concentrations, at almost 30 % higher than any other Cetacea reported globally. Perfluorooctane sulfonate (PFOS) was above method reporting limits for all samples (range; 5.3–18,700 ng/g ww), and constituted the highest contribution to overall ∑PFAS burdens with between 47 % and 99 % of the profile across the dataset. The concentrations of PFOS exceed published tentative critical concentrations (677–775 ng/g) in 42 % of all dolphins and 90 % of the critically endangered Burrunan dolphin. This research reports for the first time novel and emerging PFASs such as 6:2 Cl-PFESA, PFMPA, PFEECH and FBSA in marine mammals of the southern hemisphere, with high detection rates across the dataset. It is the first study to show the occurrence of PFAS in the tissues of multiple species of Cetacea from the Australasian region, demonstrating high global concentrations for inshore dolphins. Finally, it provides key baseline knowledge to the potential exposure and bioaccumulation of PFAS compounds within the coastal environment of south-east Australia
Pioneering gut health improvements in piglets with phytogenic feed additives
No full textAbstract: This research investigates the effects of phytogenic feed additives (PFAs) on the growth performance, gut microbial community, and microbial metabolic functions in weaned piglets via a combined 16S rRNA gene amplicon and shotgun metagenomics approach. A controlled trial was conducted using 200 pigs to highlight the significant influence of PFAs on gut microbiota dynamics. Notably, the treatment group revealed an increased gut microbiota diversity, as measured with the Shannon and Simpson indices. The increase in diversity is accompanied by an increase in beneficial bacterial taxa, such as Roseburia, Faecalibacterium, and Prevotella, and a decline in potential pathogens like Clostridium sensu stricto 1 and Campylobacter. Shotgun sequencing at the species level confirmed these findings. This modification in microbial profile was coupled with an altered profile of microbial metabolic pathways, suggesting a reconfiguration of microbial function under PFA influence. Significant shifts in overall microbial community structure by week 8 demonstrate PFA treatment’s temporal impact. Histomorphological examination unveiled improved gut structure in PFA-treated piglets. The results of this study indicate that the use of PFAs as dietary supplements can be an effective strategy, augmenting gut microbiota diversity, reshaping microbial function, enhancing gut structure, and optimising intestinal health of weaned piglets providing valuable implications for swine production. Key points: • PFAs significantly diversify the gut microbiota in weaned piglets, aiding balance. • Changes in gut structure due to PFAs indicate improved resistance to weaning stress. • PFAs show potential to ease weaning stress, offering a substitute for antibiotics in piglet diets
Deep learning-based prediction of the remaining time and future distribution of pebble flow from real-scene images
No full textPebble flow dynamics is a crucial issue for designing and operating pebble bed reactors. The existing experimental or simulation methods are often associated with high time, resource, and effort costs. Therefore, image-based deep learning methods are explored to make real-time predictions of pebble flow dynamics directly from images. Real-scene images, captured by the high-speed camera during pebble flow experiments are used as the dataset. This paper proposes an RT-Net model based on Convolutional Neural Network (CNN) to predict the remaining time of pebble flow from experimental images. The core of the RT-Net model is the mergeable multi-branch convolutional component called ConvBlock, which effectively improves accuracy and reduces computational costs compared to traditional convolutional operators. Results show that this model is superior in both accuracy and efficiency metrics compared with typical convolutional neural networks (like AlexNet and VGGs). The proportion of test sets with prediction error within 0.05 s reaches 96.7 %, and the parameters count and inference time are 5.02 M and 1.99 ms respectively. Furthermore, to anticipate the pebble distribution at a given future time, a dual-input PreNet that combines CNN and Generative Adversarial Network (GAN) is designed, where the input includes the current pebble flow image and an arbitrarily chosen temporal displacement Δt. Targeted evaluation metrics, such as Target Similarity (TS) and Equivalent Target Similarity (TSeq) are proposed to quantitatively evaluate the model's performance. Results indicate that the Pre-Net model can make quite satisfactory predictions of the future distribution of most data, while more efforts such as a task-specific loss function are encouraged to achieve better performance
The Australian Health Informatics Competency Framework: Conceptual Design, Framework Development, and Certification Delivery
No full textThe Australian Health Informatics Competency Framework (AHICF) guides the healthcare workforce in identifying the required competencies to perform as a health informatician, and more definitively defines the foundational body of knowledge on which the discipline is based. The aim of this paper is to describe the conceptual foundations in developing the AHICF v1.0, detail the methods used to revise and publish AHICF v2.0, and explore the certification and workforce outcomes achieved. This paper contributes to the competency framework and certification discourse, and knowledge of the increasing importance and recognition of health informaticians through certification. Further, implications for workforce training and education, career advancement and recruitment strategies, are also discussed
Do unconditional cash transfers increase fertility? Lessons from a large‐scale program
No full textWe examine the impact of unconditional cash transfers (UCTs) on fertility. We develop a theoretical model that demonstrates how UCTs affect fertility decisions, time allocations for leisure, labor and childrearing, and child health through health spending. We then empirically examine the impact of UCTs on fertility in Pakistan. Our theoretical model suggests that under certain conditions, UCTs are likely to increase fertility if UCTs increase child health regardless of how they affect parental leisure, labor and childrearing time. The empirical results suggest that UCTs have a positive effect on fertility
The audit committee and dividend policy: an empirical study of the post-SOX era
No full textPurpose: Post-Sarbanes Oxley Act (SOX), the audit committee has been empowered greatly to play a central role in the corporate governance of firms. Embedded in agency theory, this study aims to examine the effect of the audit committee on the likelihood by firms to pay dividends. Design/methodology/approach: The study population is US firms in the Institutional Shareholder Services (ISS) database from 2007 to 2018. The authors apply the multivariate logit fixed-effect regression for the analyses after conducting the appropriate statistical tests. Findings: From the results of the research model, the authors find that there is a positive relationship between the size and gender diversity of the audit committee and the propensity to pay dividends suggesting that a larger audit committee with substantial women representation improve the information environment in firms leading to higher dividend distribution. The extent of busyness of the audit committee impacts negatively on the propensity to pay dividends. The results are driven by high-performing firms and not driven by specific levels of firm size. Research limitations/implications: The findings of the study give impetus to the audit committee as an important component of the corporate governance mechanism that advances the interest of stakeholders. Thus, efforts that seeks to promote the audit committee’s resourcefulness must be embraced by all stakeholders. Originality/value: To the best of the authors’ knowledge, this study is the first to focus on audit committee and dividend payout policy of US firms post-SOX. The study demonstrates how the audit committee characteristics including its size, gender diversity and busyness affect dividend policy by mitigating information asymmetry problems
Modelling structural breaks in the tourism-led growth hypothesis
No full textStructural breaks represent periods of turmoil that may influence how tourism affects economic growth. Current research on the tourism-led growth hypothesis (TLGH) measures the effect of structural breaks using dummy variables in regression models. However, the drawback of this approach is that there could be multiple structural breaks which result in an overfitting problem and reduce degrees of freedom in small samples. It also becomes difficult to isolate the effect of individual breaks when multiple structural breaks occur within the same year. We thus highlight the role of the Fourier ARDL model in addressing these shortcomings. We use three Pacific Island Countries: Fiji, Tonga, and Vanuatu as case studies to evaluate the efficacy of the Fourier ARDL model. Contrary to earlier research, our results indicate that tourism does not always lead to economic growth. Appropriate modelling of structural breaks also influences the outcome of asymmetric effects. These findings imply that future research should pay close attention to the effects of structural breaks in the TLGH