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In the traditional motion control method of an unmanned sailboat, the sail and rudder are divided into two independent controllers. The sail is used to obtain the thrust and the rudder is used to adjust the yaw angle. The traditional control method does not consider the synergy between the two controllers and ignores the influence of the roll angle on sailing. It is easy for these methods to cause an excessive roll angle and large yaw angle error, which will weaken the safe navigation and accurate path tracking of an unmanned sailboat. This paper presents a collaborative control method of sail and rudder based on model predictive control. A four-degree-of-freedom kinematics and dynamics model of the unmanned sailboat considering roll angle was established, with the yaw angle and roll angle as the control objectives at the same time. The collaborative control method outputs sail angle and rudder angle simultaneously. By comparing the motion of this method and the separation control of sail and rudder under the same wind field conditions, it is verified that the collaborative control has better effects of yaw angle control and roll angle limitation and can obtain a more accurate path tracking effect. [ABSTRACT FROM AUTHOR]

Aerodynamic coefficients from wind-tunnel tests are presented for the ILCA 7 in all six degrees of freedom. Two apparent wind speeds are considered: a light wind case corresponding to 4 m s-1 at full scale and a strong wind case corresponding to 7 m s-1. The light wind tests comprise five apparent wind angles, seven sheet angles, three kicker trims and three heel angles. For the strong wind case the dinghy is assumed sailing upright and only dead downwind, but with four sheet angles and three kicker trims. The scale is 1/7, which gives a reasonable blockage in the wind-tunnel. Blockage corrections are obtained using CFD. Correct scaling of the sail stretch, and mast bend is achieved with the full-scale sail cloth and a solid stainless-steel mast exposed to a wind speed √7 times larger than at full-scale. However, the Reynolds number is √7 times smaller. The main result of the investigation is the comprehensive data set, which is available on a public server. This data can be used in a VPP to optimise downwind sailing in smooth water. Several interesting conclusions can also be drawn directly from the data. Thus, for the light wind case the best sheet angle is 90◦ regardless of the course sailed. However, for the strong wind case (dead downwind), the best angle is 80◦. In all cases the tight kicker trim produces the largest drive force and in the light wind case also the smallest side force. [ABSTRACT FROM AUTHOR]

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It has long been known that the following basic objects are obstructions to bounded tree-width: for arbitrarily large t , (1) the complete graph K t , (2) the complete bipartite graph K t , t , (3) a subdivision of the (t × t) -wall and (4) the line graph of a subdivision of the (t × t) -wall. We now add a further boundary object to this list, a t - sail. These results have been obtained by studying sparse hereditary path-star graph classes, each of which consists of the finite induced subgraphs of a single infinite graph whose edges can be partitioned into a path (or forest of paths) with a forest of stars, characterised by an infinite word over a possibly infinite alphabet. We show that a path-star class whose infinite graph has an unbounded number of stars, each of which connects an unbounded number of times to the path, has unbounded tree-width. In addition, we show that such a class is not a subclass of the hereditary class of circle graphs. We identify a collection of nested words with a recursive structure that exhibit interesting characteristics when used to define a path-star graph class. These graph classes do not contain any of the four basic obstructions but instead contain graphs that have large tree-width if and only if they contain arbitrarily large t -sails. We show that these classes are infinitely defined and, like classes of bounded degree or classes excluding a fixed minor, do not contain a minimal class of unbounded tree-width. [ABSTRACT FROM AUTHOR]

The purpose of this study was to explore the experiences of current and former sailors, staff and volunteers who were involved in an adaptive recreational sailing program and identify the factors that impact their engagement. Using an ethnographic approach, participant observations (n = 20) and qualitative interviews (n = 18) were conducted with sailors, staff and volunteers. We analyzed the data thematically and identified two main themes. 1) "Anchors away: reasons for setting sail," described the benefits of adaptive sailing including learning opportunities, leaving disability onshore, challenging stigma, building a community and engaging with nature. 2) "Running ashore: challenges with program delivery and logistics," acknowledged the various issues encountered, including issues around accessibility, equipment, scheduling, safety management, and volunteers/volunteering. The findings emphasize how adaptive sailing offers a multidimensional experience and could reduce prejudices against people with disabilities. Challenges regarding accessibility of facilities and transports as well as volunteers were identified. [ABSTRACT FROM AUTHOR]

Deorbit disposal of constellation satellites at the end of their operational lifetime is considered a necessary task to maintain the safety and sustainability of low Earth orbit (LEO). In LEO region, especially below 800 km, the drag sail device emerges as one of the most promising techniques to accelerate the deorbit process by the advantages of atmospheric drag. In this paper, an attitude-orbit coupled dynamics model is established for satellites equipped with pyramid drag sail devices. The number and length of support booms, the flare angle, and the initial orbital height are not limited, so that the obtained model could describe a number of drag sail systems. Then, by simplifying the attitude dynamics model in the orbital plane and considering circular orbit motions, a key parameter is proposed to evaluate the stability of the drag sail system. With this parameter, the influence of geometries on the attitude stability is analyzed for pyramid drag sails, and further conclusions about the optimal configurations are obtained from the analysis results. Finally, numerical simulations with the attitude-orbit coupled dynamics model are conducted to verify the conclusions drawn from the key parameter, and optimal configurations under three different conditions are obtained as well as simulated with deorbit missions to show the optimality. The results from this work would offer theoretical guidance to the configuration design of drag sail systems in application. [ABSTRACT FROM AUTHOR]

Laser sail‐based spacecraft—where a powerful Earth‐based laser propels a lightweight outer‐space vehicle—have been recently proposed by the Breakthrough Starshot Initiative as a means of reaching relativistic speeds for interstellar space travel. The laser intensity at the sail required for this task is at least 1 GW m−2 and, at such high intensities, thermal management of the sail becomes a significant challenge even when using materials with low linear absorption coefficients. Silicon is proposed as one leading candidate material for the sail due to its low sub‐bandgap absorption and high index of refraction, which allows for low‐mass‐density designs. However, here it is shown that the temperature‐dependent linear absorption of silicon can lead to thermal runaway at temperatures above 400–500 K for even the most optimistic viable assumptions of the material quality. Additionally, above a design‐specific threshold laser intensity, nonlinear two‐photon absorption triggers thermal runaway regardless of initial temperature. Resonator‐based designs, which concentrate the field, exhibit lower threshold intensities than geometries that minimize the electric field such as Bragg reflectors. [ABSTRACT FROM AUTHOR]

The present review describes the state of the art in the conversion of pharmaceutically active ingredients (API) in amphiphilic Ionic Liquids (ILs) as alternative drug delivery systems. In particular, we focus our attention on the compounds generated by ionic exchange and without original counterions which generate different systems in comparison with the simple mixtures. In water, these new amphiphiles show similar or even better properties as surfactants in comparison with their precursors. Cations such as 1-alkyl-3-methyl-imidazolium and anions such as dioctyl sulfosuccinate or sodium dodecyl sulfate appear as the amphiphilic components most studied. In conclusion, this work shows interesting information on several promissory compounds and they appear as an interesting challenge to extend the application of ILs in the medical field. [ABSTRACT FROM AUTHOR]

This study examines external factors that affect personal relationships. The ABC-X paradigm for understanding the effect of stressors on family crises has endured for 70 years. More recent studies have shown that stressors outside relationships can affect interpersonal relationships. The literature is dominated by evidence of stressors creating negative impacts on relationships, but this paper uses sailing to propose the idea of relationship crucibles. Such crucibles are situations that stress relationships but can result in positive impacts. [ABSTRACT FROM AUTHOR]

The impact of artificial intelligence (AI) in understanding biological processes is potentially immense. Structural elucidation of mycobacterial PE_PGRS is sustenance to unveil the role of these enigmatic proteins. We propose a PGRS "sailing" model as a smart tool to diffuse along the mycomembrane, to expose structural motifs for host interactions, and/or to ship functional protein modules at their C-terminus. [ABSTRACT FROM AUTHOR]

Demonstrations of photonically-propelled materials for solar and laser sailing have relied on indirect techniques for determining the propulsion efficiency. These methods, utilizing drop towers or cameras to determine differential displacement, are necessarily low-throughput and cannot be easily compared directly. Furthermore, the methods require sample sizes that are prohibitive to the fabrication of low TRL photonic materials (e.g. thin-film metasurfaces) that discourages rapid iterative testing. Herein, a nanocantilever-based test bed is proposed to simplify and standardize the determination of the characteristic acceleration for a given sail swatch. The proposed system is designed to allow for flexible, automated spectral analysis, requiring sample sizes ∼10 μm2. This system is scalable to the micro- and macroscale as material technologies mature and advance toward deployment scale. • Laser sources irradiating cantilever systems lead to measurable force deflection. • Quantify spectral characteristics of light sails for mission qualification. • Sail candidate materials may be directly tested for failure. • Requires swatches on the order of μm2. • Allows for high-throughput iteration. [ABSTRACT FROM AUTHOR]

Clustering sensor nodes is an efficient approach of modeling the routing algorithms for the Wireless Sensor Networks (WSNs) that enhance the energy efficiency and network lifetime. The cluster heads (CHs) present in the clustered WSNs represent the key nodes. Since they accomplish several tasks, more energy is being consumed. Hence, it remains a significant conflict for choosing the optimal CHs. Most of the WSN routing protocol's labels particular conflicts with the "Low-Energy Adaptive Clustering Hierarchy" (LEACH) protocol. The challenge for the WSN protocols is to maintain high scalability and expand the lifespan of the network. The major challenge in enhancing the WSNs is energy efficiency. Since communication occupies many portions of the energy consumption, and efficient solution to handle this problem is effective routing. The main intention of this paper is to develop the energy-efficient routing for WSN using a hybrid meta-heuristic-based LEACH protocol. Here, the optimal CH selection is accomplished by the hybrid meta-heuristic algorithm with Sail Fish Optimization (SFO) and Jaya Algorithm (JA), and the so formed algorithm is called Limit-based Jaya Sail Fish Optimization (L-JSFO). A Multi-objective function is considered with significant constraints like "energy, distance, delay, trusts of nodes, load, and Quality of Service (QoS)". Finally, this paper compares the proposed meta-heuristic-based LEACH protocol against other WSN routing protocols. The simulation outcomes described that the proposed protocol exceeded the benchmarked protocols in terms of energy efficiency and load balancing, and proves the enhanced network lifetime. [ABSTRACT FROM AUTHOR]

The process of retrieving essential information from the dataset is a significant data mining approach, which is specifically termed as data clustering. However, nature-inspired optimizations are designed in recent decades to solve optimization problems, particularly for data clustering complexities. However, the existing methods are not feasible to process with a large amount of data, as the execution time taken by the traditional approaches is larger. Hence, an efficient and optimal data clustering scheme is designed using the devised Fractional Sail Fish-Sparse Fuzzy C-Means + Particle Whale optimization (FSF-Sparse FCM + PWO) based MapReduce Framework (MRF) to process high dimensional data. Theproposed FSF-Sparse FCM is designed by the integration of Sail Fish Optimization (SFO) with fractional concept and Sparse FCM. The proposed MRF poses two functions, such as the mapper function and reducer function to perform the process of data clustering. Moreover, the proposed FSF-Sparse FCM is employed in the mapper phase to compute the cluster centroids, and thereby the intermediate data is generated. The intermediate data is tuned in the reducer phase using Particle Whale Optimization (PWO), which is the integration of Particle Swarm Optimization (PSO) and Whale optimization algorithm (WOA). Accordingly, the optimal cluster centroid is computed at the reducer phase using the objective function based on DB-Index. The proposed FSF-Sparse FM + PWO obtained the highest accuracy of 0.903 and lowest DB-Index of 39.07. [ABSTRACT FROM AUTHOR]

We present spectral and imaging LOFAR (LOw-Frequency ARray) observations in the 20 – 40 MHz range of solar radio bursts fine structures, such as flag-like, sail-like, and dot-like that appeared on 8 April 2019. These structures were associated with type III solar radio bursts that occurred in the 40 – 80 MHz band. The mean duration and spectral widths of the fine structures range from 1.0 to 3.4 s and from 0.3 to 0.9 MHz, respectively. Additionally, we investigated the radio images of eight fine structures – two flags, two sails and four dots. This allowed us to determine their emission source sizes, which ranged from 240 to 392 arcmin2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${}^2$$\end{document}, and their frequencies from 25.58 to 39.25 MHz as well as their location. They occurred on the east side of the Sun and were most likely associated with an emerging active region NOAA AR 12738, where a weak B1.7 flare was observed. [ABSTRACT FROM AUTHOR]

The utilization of wind-assisted propulsion technology could reduce ship fuel consumption and emission of pollutants. In the study, the effect of steady heel angles on the aerodynamic characteristics of wing sails was investigated. Full-scale three-dimensional simulations with the ship's superstructure were conducted at heel angles of 0°–15° in all apparent wind directions. The correctness of the numerical computations is verified by comparing them with the wind tunnel experimental data. Overall, the heel is detrimental to the capture of wind energy by the wing sails. The aerodynamic forces of the sail system decrease with increasing heel angles. Specifically, the average thrust performance is attenuated by 4.7%, 13.5% and 20.5%, respectively, at heel angles of 5°, 10°, and 15° compared to the upright condition. Due to changes in the airflow distribution around the sails, the aerodynamic force of sails in heeled to windward and heeled to leeward decreases by the reduced area of the low-pressure zone on the suction side and the high-pressure zone on the pressure side, respectively. Finally, a prediction scheme for assessing the effect of rolling motion on sail performance is proposed by steady heel results. • The effect of the heel on the aerodynamic performance of wing sails is determined. • The aerodynamic forces of the sail system decrease with increasing heel angles. • Thrust performance reduction of the sail system up to 20.5% at a 15° heel angle. • Pressure distribution variations on both sides lead to sail performance reduction. [ABSTRACT FROM AUTHOR]

This article looks at a specific southern Arabian sailing vessel named the Wolf (al-Dhi'b), in order to better understand the life of a coastal trader on the southern Arabian coast that lived in the last days of commercial sail. Vessels such as the Wolf carried local products such as sardines, abalone and frankincense to northern Oman and Yemen, returning with dates and necessary foodstuffs shipped to Aden from India and East Africa. The article examines the remains of the Wolf, based on data from multiple documentation surveys, in conjunction with information gained from oral history interviews in order to highlight the central role that vessels such as the Wolf played in the maritime economic and social networks of the region. [ABSTRACT FROM AUTHOR]

Concentrating on Propertius 3.21 in particular, this article identifies a previously unnoticed network of allusions by three Roman poets (Catullus, Propertius and Ovid) to one another and to Book 1 of Apollonius Rhodius' Argonautica. It shows that these intertextual links are pivoted on the three poets' common use of the verse-ending lintea malo in scenes of departure by sea, and on their common interest in framing other aspects of the nautical context (especially the naval equipment involved and the presence of a favourable wind) in specific ways. Highlighting the presence in all three cases of departing male lovers with traditionally compromised or otherwise dubious claims to heroism, the article argues that each of the three instances shows the poet in question interacting competitively and self-consciously with the usages of his predecessor(s) (and with those usages' immediate contexts) and exploiting the choices made by them to serve his new context and to advertise his personal skill in the creative deployment of revered poetic models. [ABSTRACT FROM AUTHOR]

One of entrepreneurs' key tasks is mobilizing resources from external resource holders. Although we know how entrepreneurial ventures gain initial access to resources, we do not yet fully understand how they maintain their resource mobilization, particularly in the face of potential threats. During our 11-month study of prosocial ventures that emerged to alleviate the suffering of refugees in Germany, four attacks on the European public occurred that were allegedly committed by refugees. These attacks disrupted the German welcoming culture for refugees, potentially threatening the legitimacy of the prosocial ventures' core activities. Thus, the attacks provide a starting point for examining how new prosocial ventures are able to maintain access to resources in the face of the potential withdrawal of resource holders. Theorizing from our data, we identify three distinct approaches to explain how prosocial ventures responded to the potential threat undermining the legitimacy of their activities to maintain access to resources. These approaches differ in their initial resource mobilization (i.e., based on the venture's goal for alleviating suffering), threat appraisals, and responses to maintain resource mobilization in the face of the potential delegitimization of their core activities. Our model provides novel insights into resource mobilization and prosocial venturing. [ABSTRACT FROM AUTHOR]

A massive expansion of offshore wind capacity is targeted over the next few decades. Analyses suggest that the socio-economic benefits can be increased by interconnecting offshore systems. This article describes the precautions and boundary conditions as well as the challenges for an offshore interconnection. Furthermore, this article also presents the current approach of Amprion to achieve the goal of a future efficient offshore grid. [ABSTRACT FROM AUTHOR]

Many satellites are currently in orbit around the Earth and will remain so for years, even though they have completed their intended missions owing to their long natural de-orbiting times. Many methods have been proposed to increase the de-orbiting speed of such satellites, of which one uses atmospheric drag sails. The micro-satellite ALE-1 is equipped with a drag sail that is deployed at a distance from the satellite through the use of a boom element to ensure continuous communication and solar charging. The drag sail is also capable of separating itself from the micro-satellite if necessary to decrease the de-orbiting speed. This paper discusses an in-orbit demonstration where the aforementioned boom element is extended, as well as the deployment of the aforementioned drag sail and compares the space and ground experiment results. [ABSTRACT FROM AUTHOR]