Floating materials seriously damage the landscape and ecosystem of rivers and visual surveillance has become an important technique for improving the water environment. However, it remains a ...challenging problem in practical applications due to small-scale targets and high scene complexity with many noise problems such as water wave disturbance, light and shadow change, and strong light emission. To address these issues, this study proposes a floating object detection and tracking method based on spatial–temporal information fusion. Specifically, this study improves the network architecture of the Single Shot Multibox Detector (SSD) by enhancing the high-resolution layers to adapt to the detection task of small floating targets. Then, an improved Kernel Correlation Filter (KCF) by introducing a fast histogram of oriented gradient (FHOG) and a pyramid scale estimation strategy is proposed to achieve the estimation of the position and size of floating objects. More significantly, a spatial–temporal information fusion strategy is applied to complement detection information with tracking information based on feature comparison. The proposed method is trained and compared with the state-of-the-art methods based on multiple scenarios. The results show that the proposed method has better performance than other methods in different scenarios, and achieves an average accuracy of more than 91% with a speed of 15.55 FPS, which prove that our method can well complete the detection and tracking task of floating objects. This work enriches the framework of “tracking by detection” and extends the application of floating object detection and tracking in surface vision.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Sharks play important ecological roles in marine ecosystems. However, due to their life-history traits and low resilience, their vulnerability increases with overexploitation. The Eastern Pacific ...Ocean (EPO) purse-seine fishery catches several pelagic sharks as bycatch. Therefore, describing the environmental preferences of bycaught sharks is crucial to improve fisheries management. This study aims to describe the environmental preferences and spatiotemporal distribution of most bycaught shark species within the EPO through Generalized Additive Models (GAMs). Results show that the silky shark (C. falciformis) is bycaught in oceanic waters on floating objects, and close to the coast in unassociated and dolphin sets. This species inhabits warm waters with low or high productivity. Oceanic whitetip shark (C. longimanus) is bycaught in warm and oceanic waters with low productivity. Meanwhile, scalloped and smooth hammerhead sharks (Sphyrna lewini &S. zygaena) are bycaught in temperate and productive waters offshore of Peru. The obtained results allowed us to identify hotspots where fisheries management can be implemented, improved, or modified (e.g., temporal closures) for reducing shark bycatch.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Introducción: En los ambientes marinos del Pacífico de Costa Rica, la actividad pesquera por la flota cerquera internacional es importante debido a su amplio alcance y fuerte impacto. Objetivo: ...Evaluar la distribución espacial de la captura de atún aleta amarilla y especies no objetivo por esa flota, y posibles correlaciones con variables ambientales y pesqueras. Métodos: Aplicamos estadísticas geoespaciales y modelos de regresión múltiple en datos de la Comisión Interamericana del Atún Tropical, del 2002 al 2011. Utilizamos una grilla del tamaño de la Zona Económica Exclusiva (ZEE) con 1 124 celdas de 22 x 22 km (unidad de análisis), para un total de 11 240 celdas-año. Resultados: El atún mediano (presumiblemente inmaduro en su mayoría), delfines, mantas y rayas fueron capturados mayormente dentro del Domo Térmico (noreste de la ZEE). Las más altas capturas de atún pequeño (inmaduro en su totalidad), tiburones, picudos, dorado, peto y diversas especies pequeñas, ocurrieron en el extremo sur. El atún grande (maduro) fue capturado especialmente en el centro de la ZEE, hacia el este del Área Marina de Manejo Montes Submarinos y el Parque Nacional Marino Isla del Coco. Los atunes, dorado, delfines, mantas y rayas mostraron gran fidelidad de sitio por asociación con variables geográficas y ambientales, a la vez que el atún pequeño estuvo asociado a lances sobre objetos flotantes y el atún grande a lances sobre delfines. La heterogeneidad de las especies no objetivo probablemente escondió la mayoría de las correlaciones. Conclusiones: La pesca está afectando los niveles tróficos más altos y es necesario un diseño de zonificación ajustado para proteger mejor el domo térmico y considerar la susceptibilidad al uso de redes de cerco.
Several pelagic fish species are known to regularly associate with floating objects in the open ocean, including commercially valuable species. The tuna purse seine industry takes advantage of this ...associative behavior and has been increasingly deploying free-drifting man-made floating objects, also known as fish aggregating devices (FADs). Using passive acoustic telemetry, this study describes the associative dynamics of the main targeted tropical tuna species (Thunnus albacares, T. obesus and Katsuwonus pelamis), as well as three major bycatch species, silky shark (Carcharhinus falciformis), rainbow runner (Elagatis bipinnulata) and oceanic triggerfish (Canthidermis maculata). Short-term excursions away from the FADs were frequently performed by all tuna species as well by silky sharks. These excursions were characterized by a marked diel pattern, mainly occurring during nighttime. Rainbow runners and oceanic triggerfish were much more present at the FADs and rarely performed excursions. Average continuous residence times (CRTs) ranged from 6 days, for silky shark, up to 25 days for bigeye tuna. Similar to silky shark, average CRTs for skipjack tuna and oceanic triggerfish were less than 10 days. For yellowfin tuna and rainbow runner, CRTs averaged 19 and 16 days, respectively. Bigeye and yellowfin tuna remained associated to a single drifting FAD for a record of 55 days and 607 km traveled.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Detection of floating objects in complicated aquatic environments has a wide range of applications, but it confronts significant hurdles due to the imbalance in detection accuracy and efficiency, and ...low domain generalization performance. To address these issues, this study proposes a novel floating object detection method based on double-labelled domain generalization. First, the Single Shot Multibox Detector (SSD) is improved by replacing the backbone network with a lightweight feature extraction network, and dynamic feature pyramid network is introduced to balance accuracy and efficiency. Then, this study initializes the improved SSD network based on the double-labelled data of the source domain, and filters the feature extractor bias, classification bias and location bias using pseudo-labelling and feature projection based on the un-labelled source domain data to minimize the bias to improve the domain generalization performance. The proposed method is trained on a self-constructed floating object dataset and is compared with state-of-the-art methods based on multiple scenarios. The results show that the proposed method achieves better performance in double-labelled domain generalization and conventional domain generalization tasks compared to other methods, achieving 70.33%, 22.38 f/s and 85.29% and 17.81 f/s in accuracy and speed respectively, satisfying the need for multi-scale floating object detection in complex environments and also alleviating the data labelling problem. This work effectively solves the problem of slow detection of floating objects due to the complex model structure and low generalization ability, and provides support for the rapid detection of floating objects in complex scenarios and the promotion of technology applications.
•To detect floating objects using improved detector and domain generalization.•A lightweight detection network based on MobileNetV3 is proposed.•Double-labelled source domains is proposed to improves the generalization of model.•Pseudo-labelling and feature projection are adopted for filtering bias.•Comparative analysis of our model with other similar contemporary research works.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Target search for moving and invisible objects has always been considered a challenge, as the floating objects drift with the flows. This study focuses on target search by multiple autonomous ...underwater vehicles (AUV) and investigates a multi-agent target search method (MATSMI) for moving and invisible objects. In the MATSMI algorithm, based on the multi-agent deep deterministic policy gradient (MADDPG) method, we add spatial and temporal information to the reinforcement learning state and set up specialized rewards in conjunction with a maritime target search scenario. Additionally, we construct a simulation environment to simulate a multi-AUV search for the floating object. The simulation results show that the MATSMI method has about 20% higher search success rate and about 70 steps shorter search time than the traditional search method. In addition, the MATSMI method converges faster than the MADDPG method. This paper provides a novel and effective method for solving the maritime target search problem.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Visually guided robotic capturing of a moving object often requires long-term prediction of the object motion not only for a smooth capture but because visual feedback may not be continually ...available, e.g., due to vision obstruction by the robotic arm, as well. This paper presents a combined prediction and motion-planning scheme for robotic capturing of a drifting and tumbling object with unknown dynamics using visual feedback. A Kalman filter estimates the states and a set of dynamics parameters of the object needed for long-term prediction of the motion from noisy measurements of a vision system. Subsequently, the estimated states, parameters, and predicted motion trajectories are used to plan the trajectory of the robot's end-effector to intercept a grapple fixture on the object with zero relative velocity (to avoid impact) in an optimal way. The optimal trajectory minimizes a cost function, which is a weighted linear sum of travel time, distance, cosine of a line-of-sight angle (object alignment for robotic grasping), and a penalty function acting as a constraint on acceleration magnitude. Experiments are presented to demonstrate the robot-motion planning scheme for autonomous grasping of a tumbling satellite. Two robotics manipulators are employed: One arm drifts and tumbles the mockup of a satellite, and the other arm that is equipped with a robotic hand tries to capture a grapple fixture on the satellite using the visual guidance system.
This paper proposes a robust cooperative trajectory tracking control scheme for an unactuated floating object with multiple vessels under environmental disturbances. The object and multiple vessels ...are connected by using towlines. The proposed control scheme consists of three parts: a virtual controller for the object, a control allocation algorithm and a distributed robust time-varying formation controller for vessels. The virtual controller is first designed to obtain the control forces of the object to track the reference trajectory. To compute the optimal tension of each towline, the control allocation algorithm is introduced. Then, the time-varying relative positions from the object to vessels are gained by using a nonlinear towline model and the towline attachment geometry. Furthermore, the distributed robust time-varying formation controller is devised for vessels based on dynamic surface control technique, an adaptive law and graph theory. It is proved that the tracking errors of the object and vessels are bounded. Simulations substantiate that the proposed method can achieve good cooperative control performance and robustness, and the unactuated object can track the reference trajectory with high accuracy.
•Cooperative tracking control for an unactuated object and multi-vessel is studied.•Time-varying formation is gained via a towline model and towline attachment geometry.•The proposed control scheme is robust against environmental disturbances.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
L'article débute par l'exploration d'une série de processus psychiques individuels et systémiques avec lesquels sont aux prises les victimes d'effractions traumatiques, mais aussi ceux et celles qui ...en sont les témoins ou tentent de les aider. À travers l'exposé de plusieurs situations cliniques, nous allons montrer comment les effets des traumatismes dits extrêmes (abus sexuels, violence de masse, génocide...) convoquent la clinique du lien pour mobiliser les processus de résilience. La perspective du « comment vivre comme après » - expression empruntée à Guy Ausloos - sert de fil rouge pour conduire un travail thérapeutique engagé, qui favorise le (re)tissage de lien, les remaillages des liens filiatifs et affiliatifs, la réhumanisation.
The concept of a ‘vertical ambush corridor’ is herein introduced to marine ecosystem science. In the open ocean, adequate physical cover from which to launch an unanticipated ambush attack is ...generally lacking. An available alternative is for a predator to channel its attack vertically upward from below, rendering an unlighted approaching predator extremely difficult for a downward viewing potential prey to visually identify against the profound blackness of the deep ocean background. Moreover, within sub‐mesoscale structures wherein the ambient water is sinking, slightly warmer water temperatures within the core of the downward motion results in outward refraction of both sound and light waves, producing sound and light shadow patterns that may reduce the capacity of prey organisms to recognize the approach of an upwardly attacking predator. This suggests that presence of such submarine ‘vambush’ structures may enhance trophic transfer efficiency within marine ecosystems, as well as provide perhaps the best available explanation for such predator behaviours as the evident strong attraction to drifting flotsam and floating fish aggregation devices (FADs), as well as the repeated large amplitude ‘bounce dives’ undertaken by a large number of dominant oceanic predatory fish species. The oxygen constraints faced by water‐breathing organisms are posed as controlling factors in the potential ecological operation of these vambush structures, that in turn may have potential vulnerability to the growing global problem of ocean deoxygenation. Increased identifiable habitat granularity represented by such sub‐mesoscale features may have important utility in supporting empirical studies and applications of the comparative scientific method.
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DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
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