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High-current Winding for SMES Cable and Its System Configuration for Photovoltaic Power Transmission
No full textThe use of electricity generated from renewable energy sources is essential for a carbon-neutral society, and countermeasures against their severe output power fluctuations are key to this. In our previous studies, we proposed a superconducting cable with energy storage function (SMES cable) as such a countermeasure and successfully demonstrated its function using a small model cable (with a current capacity of the order of 100 A) and a simple circuit model (with photovoltaic assumed by a voltage source) based on a hardware-in-the-loop simulation (HILS). In this study, a kA-class model cable was fabricated by parallel winding of a REBCO coated conductor, and a HILS-based experiment showed that the cable could be regarded just as an inductance with negligible loss. Furthermore, it was found that the application of SMES cable to photovoltaic power transmission could maximize the output power from the photovoltaic while reducing its fluctuation by appropriately combining a DC-DC converter and the current-voltage level of the photovoltaic array
A Machine Learning Classification Approach to Geotechnical Characterization Using Measure-While-Drilling Data
Get PDFBench-scale geotechnical characterization often suffers from high uncertainty, reducing confidence in geotechnical analysis on account of expensive resource development drilling and mapping. The Measure-While-Drilling (MWD) system uses sensors to collect the drilling data from open-pit blast hole drill rigs. Historically, the focus of MWD studies was on penetration rates to identify rock formations during drilling. This study explores the effectiveness of Artificial Intelligence (AI) classification models using MWD data to predict geotechnical categories, including stratigraphic unit, rock/soil strength, rock type, Geological Strength Index, and weathering properties. Feature importance algorithms, Minimum Redundancy Maximum Relevance and ReliefF, identified all MWD responses as influential, leading to their inclusion in Machine Learning (ML) models. ML algorithms tested included Decision Trees, Support Vector Machines (SVMs), Naive Bayes, Random Forests (RFs), K-Nearest Neighbors (KNNs), Linear Discriminant Analysis. KNN, SVMs, and RFs achieved up to 97% accuracy, outperforming other models. Prediction performance varied with class distribution, with balanced datasets showing wider accuracy ranges and skewed datasets achieving higher accuracies. The findings demonstrate a robust framework for applying AI to real-time orebody characterization, offering valuable insights for geotechnical engineers and geologists in improving orebody prediction and analysi
Experimental and numerical investigation on the aging behavior of CFZnL composites in salt spray environment
No full textThis study develops a class of novel carbon-fiber-Zinc-alloy-laminated (CFZnL) composites, and investigates the modulus after salt spray aging. Experimental salt spray aging and tensile tests have been sequentially performed on CFZnL composites and conventional CFRP composites, to assess the aging behavior and residual tensile modulus. It has been observed that Zn alloy layer significantly enhances the aging-resistance due to moisture absorption. In addition, a multiscale modeling approach is proposed to predict the aging behavior and moduli of CFZnL and CFRP composites. Microscale models have been established to obtain the effective diffusion coefficients and effective properties of CFRP layers. Moreover, residual properties of CFRP and Zn alloy layers are calculated using an exponential degradation model. Then, they are introduced in the macroscale model for the tensile simulation. The numerical results concur well with the experimental ones, validating the accuracy of the multiscale modeling approach. It indicates that CFZnL composites with double-side Zn alloy layers possess superior aging-resistance than others in salt spray environment. Finally, the damage mechanisms are analyzed for the aged CFRP and CFZnL composites via experimental observations
Driving factors for responsible sourcing in Europe: Motivations of renewable energy technology manufacturers
Get PDFThe paper highlights the urgent demand for sustainable energy transitions within planetary boundaries while addressing social injustices. This transformation significantly relies on increasing the proportion of renewable energy sources, which requires extensive mining and utilisation of energy transition metals like copper, cobalt, and lithium. Particular concerns arise when Indigenous lands are involved in mining operations, raising issues of human rights and environmental integrity. The European Union and the United States of America have responded to these concerns with legislative measures to enhance supply chain transparency and prevent conflicts stemming from unethical practices. The study aims to explore responsible sourcing efforts among renewable energy technology manufacturers operating in Europe in the context of these regulations and the obstacles they encounter. Through semi-structured interviews with sustainability and procurement managers, the research investigates internal and external drivers for responsible sourcing, identifying altruistic values and regulatory compliance as critical factors. Despite acknowledging the importance of responsible sourcing, supply chain complexity and resource limitations persist. Ultimately, the study suggests that while responsible sourcing initiatives have the potential to promote justice within supply chains, there is a pressing need for holistic approaches to overcome existing barriers and effectively implement sustainable practices across the renewable energy sector
Enhancing disaster prevention and structural resilience of tunnels: A study on liquid hydrogen leakage, diffusion, and explosion mitigation
Get PDFThe increasing adoption of liquid hydrogen (LH2) as a clean energy carrier presents significant safety challenges, particularly in confined underground spaces like tunnels. LH2′s unique properties, including high energy density and cryogenic temperatures, amplify the risks of leaks and explosions, which can lead to catastrophic overpressures and extreme temperatures. This study addresses these challenges by investigating the diffusion and explosion behaviour of LH2 leaks in tunnels, providing critical insights into disaster prevention and structural resilience for underground infrastructure. Using advanced numerical simulations validated through theoretical calculations and experimental analogies, the study analyses hydrogen diffusion patterns, overpressure dynamics, and thermal impacts following an LH2 tank rupture. Results show that LH2 explosions generate overpressures exceeding 50 bar and temperatures surpassing 2500 °C, far exceeding the hazards posed by gaseous hydrogen leaks. Mitigation measures, such as suction ventilation and high humidity, significantly reduce explosion impacts, underscoring their value for tunnel safety. This research advances understanding of hydrogen safety in confined spaces, demonstrating the importance of integrating mitigation measures into tunnel design. The findings contribute to disaster prevention strategies, offer insights into optimizing safety protocols, and support the development of resilient infrastructure capable of accommodating hydrogen technologies in a rapidly evolving energy landscape
Doppler Positioning Using Multi-Constellation LEO Satellite Broadband Signals as Signals of Opportunity
Get PDFThis paper investigates the potential of signals of opportunity for positioning using broadband low Earth orbit constellations. We developed analytical absolute and differential models based on Doppler-shift observations from multi-constellation satellite bursts across various frequency ranges. Owing to the unavailability of multi-constellation broadband receivers, simulations were conducted with the application of two primary restrictions common for these satellites: a 30° elevation mask angle and a 15-s intermittency for observations. Signal attenuation factors were modeled, indicating that free space loss was the dominant factor whereas cloud and fog losses were minimal. The accuracy of absolute static positioning, considering the aforementioned broadband restrictions, reached 4.32 m. The kinematic receiver showed similar trends, with a degraded accuracy of 4.83 m. Tests in urban areas revealed significant accuracy degradation to approximately 10 m. However, the differential model significantly improved kinematic positioning accuracy, achieving promising sub-meter levels even with a limited number of satellites
Influence of bentonite on grinding, hydrocyclone and flotation performance
Get PDFThe thesis examined bentonite’s impact on grinding, flotation, and hydrocyclone processes in mineral processing. Adding cations (Al³, Mg², K) improved grinding efficiency by reducing particle repulsion, with Al³ being the most effective. Bentonite increased slurry viscosity, reducing mineral recovery in initial flotation, while high Ca² levels further inhibited flotation. Hydrocyclone experiments showed bentonite concentration slightly affected radial velocity and particle size distribution but increased localized pressure losses and radial pressure
Large-scale Pavement Crack Evaluation and Prediction using a Novel Spatial Machine Learning Approach
No full textThis study introduces a geocomplexity-enhanced machine learning (GML) model that integrates spatial methodologies to uncover influencing factors of crack severity obtained from human inspection and laser scanning. These two aspects, representing existing surface crack condition, are then integrated with a risk of deterioration to develop a comprehensive crack evaluation framework
The Soviet and Russian Navies. From the Cold War to the Cold war 2.0, 1945 - 2024
No full textThis handbook brings together historical and contemporary essays about Soviet and Russian military studies, to offer a comprehensive volume on the topic
From Tsushima to Berlin and the Kurile Islands: Russian and Soviet naval power, 1905-1945
No full textThis chapter examines the changing fortunes of the Russian and Soviet navies from the defeat at Tsushima during the Russo-Japanese War to the end of the Great Patriotic War. During this period, Russia and the Soviet Union struggled, in the light of economic exigencies of the early inter-war period and inevitable focus on land power as a major war with neighbouring powers loomed on the horizon, to maintain the sort of naval forces that were expected of a major naval power. As a result, Soviet ambitions to become a major naval power and develop an 'ocean-going' fleet had to be put on hold by the late 1930s. Nonetheless, a certain level of naval power had become a non-negotiable imperative, without which Russia or the Soviet Union as sovereign nations would struggle to survive. The deployment of that naval power would be hampered by the geographically dispersed nature of the Russian and Soviet fleets and flotillas