Search Results (10)

The breaching of river levees can have dramatic economic and human impacts. In many countries, including France, laws and regulations require the assessment and inspection of hydraulic structures. Methods are required to carry out these missions. The following article presents a method for assessing the impacts of tree vegetation on the resistance of river levees to internal erosion. Indeed, the presence of trees—particularly following the decomposition of their roots—may cause damage in the structure through contact erosion, concentrated erosion, backward erosion or suffusion. The proposed method takes into account the possible presence of trees and especially roots in different parts of the levee. The method is based on the formalization and aggregation of expert knowledge. It permits the calculation of a performance indicator, which is obtained by aggregating criteria determined using formalized status indicators. The entire method is available in the article. The method was tested on two real cases. Full article

Unmanned surface vehicles (USVs) are increasingly critical in modern maritime operations, where reliable cooperative formation control under actuator failure is essential for safe navigation and efficient mission execution. Thus, this study presents an innovative fault-tolerant control strategy for USV formations, specifically addressing the challenges posed by actuator degradation, compound uncertainties, and input saturation. Concretely, the main contribution of this study is as follows. First, a detailed analysis of the USV kinematics and dynamics is conducted, and a novel position constraint model is developed through a formation transformation approach. To mitigate internal and external disturbances, a new non-singular terminal sliding mode surface is designed in conjunction with a dynamically regulated convergence law, ensuring finite-time convergence while reducing chattering. An adaptive terminal sliding mode controller is then formulated, integrating an event-triggered mechanism and an RBF neural network to compensate for model uncertainties and input saturation effects. Simulation results demonstrate that the proposed method not only achieves robust cooperative formation control under partial actuator failure but also significantly enhances the tracking accuracy and reduces the communication load compared to conventional sliding mode approaches. Full article

From the beginning of European overseas expansion in the fifteenth century, religious missions occupied an important place in the internal organisation of colonial empires. Their contribution to the ideological structuring of imperialism and the interaction with local populations is undeniable. With the emergence of the new imperialism and the scramble for Africa (after the 1870s), the missions, often anticipating the colonial political and administrative presence, enhanced their role as advocates of Europe’s “civilising mission”, above all through the education of the colonised peoples. For Portuguese decision-makers, the religious missions, with a multi-century tradition, had an important role in defending territorial claims overseas and promoting the empire’s nationalisation. However, the lack of national missionaries, Christianity’s inter-confessional competition in the nineteenth century and the emergence of international legal rules protecting missionary activities hindered Portugal’s strategies. Using sources from several archives (in Lisbon, the Vatican, and elsewhere) to emphasise the role of a transnational missionary staff and the international law of missions, this text intersects these aspects, examining their convergence in the controversial case of the exit and replacement of Jesuit missionaries in Mozambique in 1910–1911, to demonstrate the need to look at the missionary issues in the Portuguese overseas domains from perspectives that go beyond nation and empire. Full article

Autonomous spacecraft operations are at the front end of modern research interests, because they enable space missions that would not be viable only with ground control. The possibility to exploit onboard autonomy to deal with platform management and nominal housekeeping is thus beneficial to realize complex space missions, which could then rely on ground support only for the mission-critical phases. One routine operation that most spacecraft must perform is stored angular momentum management to maintain fully usable momentum exchange actuators. The execution of this activity may be scheduled, commanded from the ground, or automatically triggered when certain thresholds are reached. However, autonomous angular momentum management may interfere with other primary spacecraft operations if executed with a dedicated and separate system mode. This paper presents the magnetic management of stored angular momentum, integrated with the main attitude control system. The system design and implementation are intended for autonomous spacecraft, and it can be operated without significant ground support. The paper describes the system architecture and the attitude control laws integrated with the magnetic angular momentum management. Specifically, the capability of the autonomous system to keep the internal angular momentum far from the saturation and far from the zero-crossing levels is highlighted. The performance of an example attitude control system with four reaction wheels and three magnetic torquers is presented and discussed, with the simulation results at model-in-the-loop (MIL) level. Full article

The path-following control of the parafoil system is essential for executing missions, such as accurate homing and delivery. In this paper, the lateral path-following control of the parafoil system is studied. First, considering the relative motion between the parafoil canopy and the payload, an eight-degree-of-freedom (DOF) model of the parafoil system is constructed. Then, a guidance law containing the position deviation and heading angle deviation is proposed. Moreover, a linear active disturbance rejection controller (LADRC) is designed based on the guidance law to allow the parafoil system to track the desired path under internal unmodeled dynamics or external environmental disturbances. For the adaptive tuning of the controller parameters, a deep Q-network (DQN) is applied to the LADRC-based path-following control system, and the controller parameters can be adjusted in real time according to the system’s states. Finally, the effectiveness of the proposed method is applied to a parafoil system following circular and straight paths in an environment with wind disturbances. The simulation results show that the proposed method is an effective means to realize the lateral path-following control of the parafoil system, and it can also promote the development of intelligent controllers. Full article

The study of electrical currents in the topside ionosphere is of great importance, as it may allow a better understanding of the processes involved in the Sun–Earth interaction and magnetosphere–ionosphere–thermosphere coupling, two crucial aspects debated by the Space Weather scientific community. In this context, investigating the electrical conductivity parallel to the geomagnetic field in the topside ionosphere is of primary importance because: (1) it provides information on the capability of the ionosphere to conduct currents; (2) it relates current density and electric field through Ohm’s law; (3) it can help to quantify the dissipation of currents; (4) it is generally modeled and not locally measured by in situ missions. In this work, we used in situ measurements of electron density and temperature recorded between 2019 and 2021 by the China Seismo-Electromagnetic Satellite (CSES-01) flying with an orbital inclination of 97.4° and at an altitude of about 500 km to compute the parallel electrical conductivity in the topside ionosphere at low and middle latitudes at the two fixed local times (LT) characterizing the CSES-01 mission: around 02 and 14 LT. The results, which are discussed in light of previous literature, highlight the dependence of conductivity on latitude and longitude and are compared with those obtained using values both measured by the Swarm B satellite (flying at a similar altitude) and modeled by the International Reference Ionosphere in the same time period. In particular, we found a diurnal variation in parallel electrical conductivity, with a slight hemispheric asymmetry. Daytime features are compatible with Sq and equatorial electrojet current systems, containing “anomalous” low values of conductivity in correspondence with the South Atlantic region that could be physical in nature. Full article

The international collections of plant genetic resources for food and agriculture (PGRFA) hosted by 11 CGIAR Centers are important components of the United Nations Food and Agriculture Organization’s global system of conservation and use of PGRFA. They also play an important supportive role in realizing Target 2.5 of the Sustainable Development Goals. This paper analyzes CGIAR genebanks’ trends in acquiring and distributing PGRFA over the last 35 years, with a particular focus on the last decade. The paper highlights a number of factors influencing the Centers’ acquisition of new PGRFA to include in the international collections, including increased capacity to analyze gaps in those collections and precisely target new collecting missions, availability of financial resources, and the state of international and national access and benefit-sharing laws and phytosanitary regulations. Factors contributing to Centers’ distributions of PGRFA included the extent of accession-level information, users’ capacity to identify the materials they want, and policies. The genebanks’ rates of both acquisition and distribution increased over the last decade. The paper ends on a cautionary note concerning the potential of unresolved tensions regarding access and benefit sharing and digital genomic sequence information to undermine international cooperation to conserve and use PGRFA. Full article

Under Article 9 of the Vienna Convention on Diplomatic Relations, a receiving state may “at any time and without having to explain its decision” declare any member of a diplomatic staff persona non grata. A person so declared is considered unacceptable and is usually recalled to his or her home nation. If not recalled, the receiving state “may refuse to recognize the person concerned as a member of the mission.” However, despite the codification of the above rules, which is largely based on pre-existing customary international law, the opportunity for diplomatic protection is not free of issues and controversies. In recent times, unfortunately, there has been a growing tendency amongst diplomats to abuse their diplomatic status, in order to commit acts prohibited by law and claim immunity from the legal process. This paper addresses the problem of abuse of immunities and privileges and its adverse implications on the balance between immunities and the duty to respect the local laws and regulations. We analyze several past cases of declaration of persona non grata involving various countries. Full article

The multidisciplinary field of climate law and justice needs to address the topic of intellectual property, climate finance, and technology transfer to ensure effective global action on climate change. The United Nations Framework Convention on Climate Change 1992 (UNFCCC) established a foundation for the development, application and diffusion of low-carbon technologies. Against this background, it is useful to analyse how the Paris Agreement 2015 deals with the subject of intellectual property, technology transfer, and climate change. While there was discussion of a number of options for intellectual property and climate change, the final Paris Agreement 2015 contains no text on intellectual property. There is text, though, on technology transfer. The Paris Agreement 2015 relies upon technology networks and alliances in order to promote the diffusion and dissemination of green technologies. In order to achieve technology transfer, there has been an effort to rely on a number of formal technology networks, alliances, and public–private partnerships—including the UNFCCC Climate Technology Centre and Network (CTCN); the World Intellectual Property Organization’s WIPO GREEN; Mission Innovation; the Breakthrough Energy Coalition; and the International Solar Alliance. There have been grand hopes and ambitions in respect of these collaborative and co-operative ventures. However, there have also been significant challenges in terms of funding, support, and operation. In a case of innovation policy pluralism, there also seems to be a significant level of overlap and duplication between the diverse international initiatives. There have been concerns about whether such technology networks are effective, efficient, adaptable, and accountable. There is a need to better align intellectual property, innovation policy, and technology transfer in order to achieve access to clean energy and climate justice under the framework of the Paris Agreement 2015. At a conceptual level, philosophical discussions about climate justice should be grounded in pragmatic considerations about intellectual property and technology transfer. An intellectual property mechanism is necessary to provide for research, development, and deployment of clean technologies. There is a need to ensure that the technology mechanism of the Paris Agreement 2015 can enable the research, development, and diffusion of clean technologies at a scale to address the global challenges of climate change. Full article

Quantitative equivalent water thickness on canopy level (EWT_canopy) is an important land surface variable and retrieving EWT_canopy from remote sensing has been targeted by many studies. However, the effect of radiative penetration into the canopy has not been fully understood. Therefore, in this study the Beer-Lambert law is applied to inversely determine water content information in the 930 to 1060 nm range of canopy reflectance from measured winter wheat and corn spectra collected in 2015, 2017, and 2018. The spectral model was calibrated using a look-up-table (LUT) of 50,000 PROSPECT spectra. Internal model validation was performed using two leaf optical properties datasets (LOPEX93 and ANGERS). Destructive in-situ measurements of water content were collected separately for leaves, stalks, and fruits. Correlation between measured and modelled water content was most promising for leaves and ears in case of wheat, reaching coefficients of determination (R²) up to 0.72 and relative RMSE (rRMSE) of 26% and in case of corn for the leaf fraction only (R² = 0.86, rRMSE = 23%). These findings indicate that, depending on the crop type and its structure, different parts of the canopy are observed by optical sensors. The results from the Munich-North-Isar test sites indicated that plant compartment specific EWT_canopy allows us to deduce more information about the physical meaning of model results than from equivalent water thickness on leaf level (EWT) which is upscaled to canopy water content (CWC) by multiplication of the leaf area index (LAI). Therefore, it is suggested to collect EWT_canopy data and corresponding reflectance for different crop types over the entire growing cycle. Nevertheless, the calibrated model proved to be transferable in time and space and thus can be applied for fast and effective retrieval of EWT_canopy in the scope of future hyperspectral satellite missions. Full article