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Microplastic abundance and its relationship with sediment grain size in seagrass and bare flats of Panjang Island, Banten Bay, Indonesia
No full textMicroplastic accumulation in sediment is influenced by the grain size of sediment. Panjang Island, located in Banten Bay, has the potential to accumulate microplastics from bay-wide transport and local anthropogenic sources. This study assessed the relationship between sediment grain size and microplastics in seagrass and bare flat sediments. Sediment samples were collected from seagrass, seagrass edges, and non-seagrass areas at three stations (n = 9). Differences among sampling points were evaluated using Kruskal–Wallis, while relationship between microplastic and sediment grain size was assessed using Spearman’s coefficient and principal component analysis (PCA). Microplastic abundance ranged from 240 to 1.880 par kg-1 dw with no significant differences among sampling points (p > 0.05). Microplastics were dominated by fragments and fibers, with fine and medium sand being the dominant sediment grains. A positive correlation was observed between microplastic abundance and finer sediments (rs = 0,58), suggesting that microplastic increases with the proportion of fine sand. PCA results showed an association between microplastic abundance and sampling points located in seagrass beds, suggesting that seagrass may enhance microplastic accumulation in the sediments of Panjang Island
Distribution of target strength and fish density in Kapota Atoll, Wakatobi Waters
No full textTarget strength (TS) is an acoustic backscatter measurement that reflects fish size, whereas fish density is an important indicator of aquatic ecosystem conditions. This study aimed to describe the distribution patterns of TS and fish density in Kapota Atoll, Wakatobi Waters, using hydroacoustic technology with a single-beam chosounder, Simrad EK-15. The results showed that TS values ranged from -51.8 dB to -37.6 dB, with an average of -42.5 dB, and tended to increase with depth, indicating the presence of larger fish. The spatial distribution of fish density varied significantly both horizontally and vertically. The highest density was detected at depths of 21–25 m, with a maximum of 45,602 individuals/1000m³ and minimum of 2 individuals/1000m³. An average density of 514 individuals/1000m³ reflects a good environmental carrying capacity. The lagoon area tended to be the center of fish aggregation because of its more complex habitat, whereas depths beyond 33 m showed a significant decrease in density. The negative relationship between TS and fish density indicates that larger fish are more commonly found in deeper layers but in lower numbers. These findings provide a scientific basis for sustainable fisheries management in the Kapota Atoll
Advanced Algorithm for Fault Detection and Localization in DC Microgrids Utilizing Capacitor Current Transient Analysis for Enhanced Reliability in DER-Integrated Systems
No full textThis paper presents an advanced short-circuit (SC) fault detection and location methodology for DC microgrids (DCMGs) integrating distributed energy resources (DERs). Unisolated SC faults in DC systems present a significant challenge, leading to service disruptions and hindering effective fault detection. To address this, the proposed method capitalises on the capacitor-dominated characteristics of DCMGs by utilising capacitor current dynamics. A comprehensive DCMG system model is developed to facilitate the application and evaluation of the proposed scheme. The algorithm employs the average capacitor current and cable resistance to accurately determine the occurrence and location of faults within the DCMG network. Active DER sources (solar PV, wind, utility grid, and batteries) connect to loads via DC-DC converters, cables, relays, and circuit breakers. The method effectively detects the average capacitor current, enabling the identification of internal faults. Faults are classified as external if a set criterion is not met. Furthermore, the paper proposes a redundancy-based isolation configuration for zonal-type distributed networks. The efficacy of the methodology is rigorously validated through digital simulation studies. MATLAB/Simulink simulations of a DCMG, incorporating diverse generation sources and loads, are conducted under various fault scenarios. These include internal and external faults, as well as line-to-ground and line-to-line faults. The simulation results demonstrate the method's ability to accurately detect both low-impedance faults (LIFs) and high-impedance faults (HIFs) and to locate the faulty cable. Notably, the approach achieves fault cable detection and isolation within 2.3 ms, confirming its effectiveness and speed
Liquid Hertz impact: Low-Weber non-wetting drop dynamics
No full textA quasi-static model for the normal impact of a viscous drop on a non-wetting substrate is developed. The axisymmetric deformation of a sessile drop is described analytically using new asymptotically exact approximations to solutions of the Young-Laplace equation. Viscous dissipation is accounted for in linearized form through a damping coefficient inversely proportional to the relaxation time of small-amplitude oscillations of a viscous sessile drop. This formulation enables evaluation of the key characteristics of Hertz-type impact at low Weber numbers, including the drop spreading factor, restitution coefficient, and characteristic time scale. Comparison with experimental data demonstrates that the model reliably captures the essential features of slow, viscously damped liquid drop impacts on non-wetting surfaces
Assessment of natural radioactivity in environmental samples near Al-Nafoura oil field, Al-Jikharra, Libya
No full textThis study evaluates natural radioactivity levels in environmental samples from Al-Nafoura oil field and surrounding areas in Al-Jikharra, Libya. Fourteen samples (soil, plant, and water) were analyzed to assess radiological hazards associated with oil and gas activities. Radionuclide concentrations of , , , , and were measured using a high-purity germanium (HPGe) detector. Results show elevated radionuclide levels in several samples, with some exceeding recommended limits. Notably, accumulation was pronounced in evaporation ponds, indicating localized radiological sources. Radiation hazard indices, including , and outdoor ELCR, were calculated; all remained within safe limits except for sample SO3-3, which exhibited of 2091 Bq/kg, surpassing the permissible threshold. AGDE values exceeded the world average in plant samples, signaling potential health risks. Water-source indicators stayed within acceptable ranges but neared other limits, underscoring the need for ongoing monitoring. The findings highlight radiological pollution risks for groundwater-dependent irrigation and agriculture, urging pollution reduction, water safety assurance, and protective measures for communities and ecosystems
What can cosmic-ray knees reveal about source populations?
No full textContext. Breaks in the cosmic-ray (CR) flux spectrum encode information on the properties of CR accelerator populations producing the observed flux. Spectral steepenings, known as knees, are generally accompanied by a transition to a higher-mass composition.
Aims. We seek generic features of CR source populations that are robustly enough imprinted on knee observables to be discernible even in the presence of significant uncertainties in CR data. We explore how the diversity among population members imprints on the knee phenomenology under the assumption that a knee arises from a fixed-rigidity cutoff in the source spectrum. Our scope is explicitly exclusionary: We did not fit specific datasets, but determined which observed spectral features are incompatible with a single-population fixed-rigidity cutoff picture, which would indicate additional physics.
Methods. We used a simple theoretical model for a population of CR accelerators. Each member of the population stochastically accelerated CR to a power-law spectrum up to a cutoff rigidity that resulted from source-confinement requirements. We allowed variance among the members in the cutoff rigidity and in the power-law slope.
Results. We found that (a) the slope step of the flux spectrum is ∼0.5 and decreased weakly with increasing spread in either property, (b) composition always broke first, and (c) the difference between the break energies in composition and flux increased with increasing diversity. These trends are robust under our assumptions. Deviations from them in observed data would indicate more complex physics than encoded in our simple model.
Conclusions. From comparing these trends with observed CR knees, we conclude that (i) the primary knee at ∼4 × 1015 eV is consistent with a constant-rigidity cutoff according to KASCADE-Grande data processed with post-LHC hadronic models, but not according to other datasets, (ii) the second knee at ∼5 × 1017 eV conclusively requires more complexity than the cutoff of a single CR source population, (iii) the constant-rigidity source cutoff interpretation of the spectral feature identified by Auger at ∼1019 eV cannot be rejected when the cutoff rigidity and slope in the parent source population are substantial. Interestingly, a significant spread in slope would also result in the spectral curvature before the break, which in turn might contribute to the ankle feature
Quantifying fugitive hydrogen emissions at the component scale: High-flow sampling method
No full textHydrogen is a key energy vector in the transition to net zero with its industrial use expected to grow significantly in the next decades. At present there are no standard methods specific for hydrogen fugitive emissions quantification, and these are required to inform monitoring schemes and support regulations. On the other hand, the high flow sampling method (HFS) has been successfully used for natural gas leak rate quantification in the industry. So, in this work we present for the first time a performance evaluation of the HFS method for quantifying hydrogen leak rates
Advances in the production of traceable amount fraction and isotope ratio gas reference materials to underpin climate monitoring
No full textThe National Physical Laboratory (NPL) in the United Kingdom provides traceable gas reference materials for calibration of atmospheric gas analysers where low uncertainty measurements of the amount fraction and/or stable isotope ratio of atmospheric components are required. Primary gas Reference Materials (PRMs) are available for amount fraction traceable to the SI and, for CO2 amount fractions between 380 and 800 μmol mol-1, can be linked to the WMO-CO2-X2019 scale via the BIPM.QM-P5 comparison. Traceable stable isotope ratio PRMs for the most potent anthropogenic greenhouse gases and climate relevant species including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and carbon monoxide (CO) are available and are traceable to current globally recognised isotope reference scales including VPDB for δ13C-CO2, δ18O-CO2 and δ13C-CH4, VSMOW/SLAP for δ2H-CH4 and δ18O-N2O and Air N2 for δ15N-N2O. This paper details recent advances in the production of PRMs at NPL and outlines the PRMs and services currently being developed
Identifying vital nodes of complex networks with an improved gravity model aware of structural damage and embedding
No full textIdentifying vital nodes of complex networks is essential for protecting networks from attack, with the gravity-based methods providing an effective approach. Most existing methods merely consider the network static topology, however, the structural damage under attack is rarely taken into account. Moreover, many methods emphasize the network topological feature, but lack consideration of the node embeddings. In this article, we propose a novel gravity model by quantifying the structural damage with the network dismantling, and comprehensively incorporating both the structural and embedding features. Examining how the node removal impairs the network topology well captures the node influence on the network structure, while the node embeddings learned by graph machine learning reveal the low-dimensional features of nodes. Two metrics, the relative size of the largest connected component and network efficiency, are employed to evaluate network fragility under attack. Experiments on six real-world networks demonstrate that, compared with nine baseline methods, the proposed approach results in the most severe network fragmentation by removing fewest vital nodes, indicating its superiority in vital node identification. Furthermore, spreading ability is assessed by the SIR model, and the proposed method exhibits an advantage in spreading performance
Duality family of traveling-wave KdV equation
No full textWe reveal a duality in the traveling-wave generalized Korteweg-de Vries (GKdV) equation. Based on this duality, we propose a method for constructing families of exactly solvable equations. Equations related by the duality transformation form a duality family, enabling the derivation of solutions for all members from any single solved equation