We have studied theoretically electron spin relaxation in semiconductor quantum dots via interaction with nuclear spins. The relaxation is shown to be determined by three processes: (i) the precession of the electron spin in the hyperfine field of the frozen fluctuation of the nuclear spins; (ii) the precession of the nuclear spins in the hyperfine field of the electron; and (iii) the precession of the nuclear spin in the dipole field of its nuclear neighbors. In external magnetic fields the relaxation of electron spins directed along the magnetic field is suppressed. Electron spins directed transverse to the magnetic field relax completely in a time on the order of the precession period of its spin in the field of the frozen fluctuation of the nuclear spins. Comparison with experiment shows that the hyperfine interaction with nuclei may be the dominant mechanism of electron spin relaxation in quantum dots.
Tamara L. Schlosser, Andrew J. Lucas, Melissa Omand
et al.
Abstract. During the southwest monsoon, seasonal storms bring torrential rainfall to the South Asian subcontinent and the northern Indian Ocean. Dense cloud cover limits the amount of sunlight that reaches the ocean surface, and sediment-laden river runoff limits the depths to which light can penetrate. Changing light availability should affect phytoplankton primary productivity and its dependent biogeochemical processes, yet little is known about how subtropical weather is linked to ecosystem processes below the ocean’s surface. Here, using novel physical and bio-optical measurements from an array of free-drifting, autonomous systems in the Bay of Bengal, we show that the onset of cloudy conditions associated with “active” monsoon conditions led to >50 % reduction in gross chlorophyll productivity (GCP) near the subsurface chlorophyll maximum (SCM) relative to sunny “break” conditions. Optical backscatter measurements confirm chlorophyll fluorescence fluctuations correspond to biomass variability of a similar scale. Simultaneous bioacoustic measurements collected onboard the autonomous platforms suggest this intraseasonal variability in SCM chlorophyll and biomass generated a response in higher trophic levels. Long-term measurements from biogeochemical (BGC) Argo floats in the bay confirm the presence of intraseasonal oscillations in chlorophyll a concentration with days-to-weeks variability in magnitude similar to the regional annual cycle in the region. Our findings demonstrate that intraseasonal subtropical air-sea variability modulates important regional biogeochemical ocean processes in the Northern Indian Ocean with implications for the Indian Ocean carbon cycle.
Edwin Paipa-Sanabria, D. González-Montoya, J. Coronado-Hernández
This study reviews various green technological strategies integrated into vessels to mitigate environmental impact, focusing on atmospheric pollution and marine environment protection. The research is based on a systematic review of academic literature published between 2019 and 2024, using the Scopus and Web of Science databases and applying PRISMA criteria. The findings reveal that the main environmental issues in the naval sector include greenhouse gas emissions, harmful discharges, and invasive species that affect marine biodiversity. The analysis is framed within international regulations such as those established by the IMO and classification societies, where the most relevant indicators identified are the EEDI and EEXI. However, the results of this review emphasize that, while these regulations are fundamental, it is necessary to analyze further the technical and economic barriers affecting the widespread implementation of these technologies and develop incentive mechanisms that facilitate their adoption across different vessel types and sizes. Promising solutions include alternative fuels, new propulsion systems, and emission-reduction technologies. The conclusion underlines that although the sector is transitioning toward sustainability, economic and widespread implementation challenges remain.
This article is an exploration of the relationship between technology and warfare from prehistoric times to the present day. The subject is examined in four realms – land, naval, air and space – and three time periods defined by the dominant power source driving the weapons: muscle power, chemical reactions, and charged particles. It introduces a rigorous definition of technology. The essay focuses on the ongoing evolution of military technology throughout human history, which accelerated since the Industrial Revolution in the West and, in particular, since the commitment to science-based research and development during World War II.
Iury T. Simoes-Sousa, Cesar Rocha, Amit Tandon
et al.
Abstract. Satellite altimetry has revolutionized our understanding of ocean physics by providing global sea-surface height data. These measurements reveal the intricate dynamics of ocean mesoscale strain and vortices, and their interactions with multiple physical scales in the oceans. Although surface dynamics has been extensively studied, investigating the vertical structure of mesoscale eddies globally remains a computational challenge. In this study, we combine the comprehensive World Ocean Database (WOD) with a database of Eulerian mesoscale eddies (META3.2 DT). We pre-process and filter the WOD data, selecting quality controlled profiles at local depths greater than 100-m. By integrating WOD data with altimetry-derived mesoscale eddies, we aim to facilitate future studies on the role of mesoscale vortices in multiple processes, such as heat, mass and nutrient transport, and water-mass subduction. The analysis is performed using high-performance computing resources, with Python packages for parallel processing of the data and analysis of more than 4.2 million profiles with more than 35 million vortex observations. The dataset is available by download and by direct access through an OPeNDAP/HTTP server. Additionally, we provide the code for performing the vortex-profile matching, along with an example of use to facilitate future updates to the code and merged data. This dataset supports further research on eddy vertical structure, biogeochemical processes, and their role in climate systems across different regions and time periods.
I Wayan Sumardana Eka Putra, Agus Saleh Atmadipoera, Henry Munandar Manik
et al.
Graphical Abstract
Highlight Research
• The IASL-1 entry portal in the southern and northern regions shows the emergent SOFAR channels.
• The shadow zone and the existence of a SOFAR deep sound channel in the IASL-2 and IASL-3 routes can be triggered by the emergent “saddle” SVP pattern.
• The variability seasonally and interannually due to variations in seawater properties stratification plays an important role in SOFAR channel appearances in IASLs.
• The diverse oceanographic characteristics of IASLs necessitate the implementation of sustainable marine geospatial data.
Abstract
Indonesian Maritime Continent (IMC) is responsible for the three international sea lanes, known as Indonesian Archipelago Sea Lanes (IASLs), which allowed ships to navigate across territorial waters between Pacific and Indian Oceans and vice versa. Gaining knowledge about the distinct oceanographic characteristics of the three IASLs can offer valuable insight into maritime safety and sustainable marine resource management. Therefore, this research aims to review oceanographic characteristics in IASLs regions from available previous research to provide a comprehensive insight into the processes and dynamical oceanography in IASLs region as well as determine the implications for underwater acoustic patterns. The results showed that IASL-1 route is characterized by a shallow shelf passage with homogeneous sound velocity profile (SVP), which has a deep and narrow entry portal in the southern and northern Sound Fixing and Ranging Channel (SOFAR) channels. Seasonal reversal monsoonal wind-driven current dominates the circulation. IASL-2 and IASL-3 routes transported a deep and narrow passage with complexity of seaair interactions that vary on seasonal and interannual time scales. These IASLs were established with the saddle SVP, which trigger the shadow zone and the existence of SOFAR deep sound channel with seasonal and interannual variations in seawater properties stratification. The diverse oceanographic characteristics discussed significantly influence the underwater object detection equipment, the planning time, and the strategies for underwater defense systems. Due to the implications, it is necessary to use marine geospatial database, which may be adopted to facilitate policy-making, providing approximations for marine activities and management along IASLs.
Rémi Toupin, Geoff Krause, Poppy Nicolette Riddle
et al.
In recent years, ocean governance has called for strategic action and science‐informed policy to work towards the sustainable development of the ocean, most notably as part of the UN Decade of Ocean Science for Sustainable Development (2021–2030). This common framework identifies the integration of scientific knowledge in governance as a key process to deliver solutions responding to the current challenges, opportunities, and transformations posed by global change in the oceans. This article presents a methodological approach for identifying ocean‐related research outputs and documenting research‐based knowledge integration in documents that inform ocean governance. Specifically, this study builds on an analysis of the references included in the UN Second World Ocean Assessment report to (a) identify and describe the research outputs cited in the distinct chapters of the report, (b) identify research outputs relevant to ocean governance through the analysis of citations from and to references included in the UN Second World Ocean Assessment, (c) compare both datasets to examine the position of the literature cited in the report within a broader ecosystem of ocean‐related research, and (d) present a method to identify topically relevant research that could be integrated in future ocean assessments. Our findings show distinct referencing practices across chapters and expert groups and a higher reliance on high‐profile sources in the report compared to a broader dataset of ocean research outputs. Moreover, this study highlights an innovative approach to identifying ocean research based on knowledge syntheses and considers discussion points about integrating research‐based knowledge in documents informing ocean governance.
Shipping is a major source of carbon emissions and faces an urgent need for decarbonization. Research on vessel carbon emissions not only characterizes regional emission patterns but also provides critical evidence for targeted mitigation policies and optimized maritime management. This study quantifies vessel carbon emissions in the Port of New York and New Jersey from February to November 2023 using Automatic Identification System (AIS) data combined with the STEAM model. An activity-weighted spatial allocation method was applied to distribute emissions across 100 m × 100 m grids. Emission characteristics were analyzed across four dimensions: vessel type, operational state, temporal variation, and spatial distribution. Results show that total emissions during the study period reached approximately 136,701.8 t, with container ships contributing 62.3% of the total. Berthing operations were identified as the dominant emission source, accounting for 73.4% of total emissions, followed by tugboats and cargo vessels. Temporally, emissions peaked in October (10.8%) and were lowest in February (8.8%), reflecting variations in trade intensity and seasonal weather conditions. Spatially, emissions exhibited strong clustering around terminal berths. A sensitivity analysis was performed to assess the robustness of the emission estimates. When the load factor (LF) varied by ±10%, total emissions changed by only ±1.85%, indicating that the results are highly stable and robust. This limited variation arises from the dominance of berthing operations with relatively steady auxiliary loads and the application of the constraint LF ≤ 1, which prevents unrealistic overloading. These findings offer indicative insights that can inform port-level emission management and serve as a reference for future low-carbon policy development.
During the hydraulic performance experiment, significant vibration and noise were observed in the mixed-flow pump operating in the hump region. Cavitation occurrence in the impeller flow channels was confirmed through the transparent chamber. To analyze cavitation flow structure evolution in the mixed-flow pump, this paper integrates numerical and experimental approaches, capturing cavitation flow structures under the valley condition through high-speed photography technology. During the various stages of cavitation development, the cavitation forms are mostly vortex cavitation, cloud cavitation, and perpendicular vortex cavitation. Impeller rotation induces downstream transport of shedding cloud cavitation shedding structures. Flow blockage occurs when cavitation vortexes obstruct specific passages, accelerating cavitation growth that culminates in head reduction through energy dissipation mechanisms. Vortex evolution analysis revealed enhanced density of small-scale vortex structures with stronger localized core intensity in the impeller and diffuser. Despite larger individual vortex scales, reduced core intensity persists throughout the full flow domain. Concurrently, velocity profile characteristics across flow rates and blade sections (spanwise from tip to root) indicate heightened predisposition to flow separation, recirculation zones, and low-velocity regions during off-design operation. This study provides scientific guidance for enhancing anti-cavitation performance in the hump region.
Many studies have used various time-frequency feature extraction methods to convert ship-radiated noise into three-dimensional (3D) data suitable for computer vision (CV) models, which have shown good results in public datasets. However, traditional feature engineering (FE) has been enhanced to interface matching–feature engineering (IM-FE). This approach requires considerable effort in feature design, larger sample duration, or a higher upper limit of frequency. In this context, this paper proposes a one-dimensional network design for underwater acoustic target recognition (UATR-ND1D), only combined with fast Fourier transform (FFT), which can effectively alleviate the problem of IM-FE. This method is abbreviated as FFT-UATR-ND1D. FFT-UATR-ND1D was applied to the design of a one-dimensional network, named ResNet1D. Experiments were conducted on two mainstream datasets, using ResNet1D in 4320 and 360 tests, respectively. The lightweight model ResNet1D_S, with only 0.17 M parameters and 3.4 M floating point operations (FLOPs), achieved average accuracies were 97.2% and 95.20%. The larger model, ResNet1D_B, with 2.1 M parameters and 5.0 M FLOPs, both reached optimal accuracies, 98.81% and 98.42%, respectively. Compared to existing methods, those with similar parameter sizes performed 3–5% worse than the methods proposed in this paper. Additionally, methods achieving similar recognition rates require more parameters of 1 to 2 orders of magnitude and FLOPs.
Pooria Mostafalu, Gita Kiaee, Giorgio Giatsidis
et al.
AbstractChronic wounds do not heal in an orderly fashion in part due to the lack of timely release of biological factors essential for healing. Topical administration of various therapeutic factors at different stages is shown to enhance the healing rate of chronic wounds. Developing a wound dressing that can deliver biomolecules with a predetermined spatial and temporal pattern would be beneficial for effective treatment of chronic wounds. Here, an actively controlled wound dressing is fabricated using composite fibers with a core electrical heater covered by a layer of hydrogel containing thermoresponsive drug carriers. The fibers are loaded with different drugs and biological factors and are then assembled using textile processes to create a flexible and wearable wound dressing. These fibers can be individually addressed to enable on‐demand release of different drugs with a controlled temporal profile. Here, the effectiveness of the engineered dressing for on‐demand release of antibiotics and vascular endothelial growth factor (VEGF) is demonstrated for eliminating bacterial infection and inducing angiogenesis in vitro. The effectiveness of the VEGF release on improving healing rate is also demonstrated in a murine model of diabetic wounds.
Utkarsh Bhardwaj, Angelo Palos Teixeira, C. Guedes Soares
This paper proposes a methodology to estimate the probability of basic causes of allision accidents between vessels and offshore platforms that overcomes the problem of data scarcity required for causal analysis. The approach uses information derived from incidental data and expert elicitation, processed by a multiple attribute utility method and hierarchical Bayesian analysis. First, the methodology is detailed, briefly describing the adopted approaches. A dataset of allision incidents provided mainly by the UK Health and Safety Executive and other agencies is prepared. The features of the incidents’ causation in terms of the causal factors and basic causes are presented and discussed. A novel scheme is proposed to evaluate the annual occurrence rates of basic causes of accidents from the relative importance of each basic cause derived by the Deck of Cards method. Then, a hierarchical Bayesian analysis is conducted to predict the posterior distribution of the occurrence rate of each basic cause in the time frame under analysis. The proposed holistic methodology provides transparent estimates of allision causation probabilities from limited and heterogeneous datasets.
Based on the 10 MW OO-Star semi-submersible floating platform, this study proposes internal and external heave plates to enhance its stability and explores their influence on the platform’s hydrodynamic characteristics. The platform’s structural behavior is analyzed in both frequency and time domains using numerical simulation methods. The study investigates the effects of the porosity and number of holes (with an equal porosity) of the inner heave plate and the opening angle (with the equal area) of the external heave plate on the platform’s hydrodynamic characteristics, ultimately obtaining the optimal arrangement for the inner and external heave plates. Results indicate that the best scheme involves a 10% porosity with 16 holes, which reduces the heave amplitude by 5.7% compared to the original structure. Additionally, reducing the opening angle of the external heave plate increases the added mass and natural period in the heave and pitch directions of the platform. At an opening angle of 140°, the added mass in the heave direction can increase by 25.2% compared to the original structure. Overall, the internal and external heave plates effectively reduce the heave and pitch amplitude of the platform under severe sea conditions.
With corrections transmitted through the E6 signal, the Galileo High Accuracy Service (HAS) provides the information necessary to execute a stand-alone precise point positioning algorithm in real time. Once fully operational, the service aims to deliver an accuracy of 20 cm and 40 cm (at the 95% confidence level) in the horizontal and vertical channels, respectively.
While most of the current literature focuses on analyzing the performance of HAS in static and open-sky signal reception scenarios, this study presents the results of tests conducted in both static and dynamic conditions, including open-sky and urban canyon scenarios. The tests clearly demonstrate that utilizing HAS corrections leads to a significant reduction in positioning error across all tested environments. Furthermore, a specific analysis of HAS message availability in a harsh environment indicates that the corrections obtained from the signal in space are available approximately 95% of the time during dynamic scenario tests.
Canals and inland navigation. Waterways, Naval Science
For tracking underwater moving targets in real time, a bearings-only tracking system with a stationary double observation station was investigated. By combining the extended Kalman filter(EKF) algorithm and the unscented Kalman filter(UKF) algorithm, the bearings-only tracking system based on the EKF and UKF algorithms was simulated and compared. The results demonstrated that the double observation station system based on the two algorithms can be applied to real-time tracking of underwater moving targets, but the latter shows faster convergence and better robustness. The influence of the distance between the two stations and bearings measurement error on the real-time tracking effect was also analyzed. Simulation results showed that the effect of target tracking is reduced if the distance between the two observation stations is too small or too large. The double observation stations system based on EKF and UKF algorithms can achieve satisfactory tracking results when the distance between the two stations is 800 m; with the increase in the bearing measurement error, the tracking performance of the double observation stations system based on the two algorithms decreases, but the UKF algorithm still exhibits better tracking performance when the EKF algorithm fails to track.
The characterization of ship routes and route similarity measurement based on Automatic Identification System (AIS) data are topics of various scientific interests. Common route research approaches use available AIS identifiers of ship types. However, assessing route and similarity profiles for individual fleets requires collecting data from secondary sources, dedicated software libraries or the creation of specific methods. Using an open-source approach, public AIS and ship data, we evaluate route characteristics for the container ships of a single fleet in a six-month period, calling on two selected ports of the shipping line on the USA East Coast. We evaluate the routes in terms of length, duration and speed, whereas for the similarity measurement we employ the discrete Fréchet distance (DFD). The voyage length, duration and average speed distributions were observed to be moderately positive (0.77), negative (−0.62), and highly positively skewed based on the adjusted Fisher–Pearson coefficient of skewness (1.23). The most similar voyages were from the same ships, with the lowest discrete Fréchet distance similarity value (0.9 NM), whereas 2 different ships had the most dissimilar voyages, with the highest DFD value (14.1 NM). The proposed methodology enables assessment of similarities between individual ships, or between fleets.