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Wave Energy Optimal Control Structure With Second-Order Sliding Mode Tracking: Hardware-in-the-Loop Assessment
No full textThis article presents a hardware-in-the-loop assessment of a moment-based optimal controller including a robust
super-twisting tracking term. The aim of the overall control structure is to maximise the energy extracted by a flap-type wave
energy converter. An experimental assessment is performed via
hardware-in-the-loop testing, which allows experiments in a controlled environment and repeatable conditions. Key aspects of
the control structure are analysed in the results, with particular
focus on the behaviour of the second-order sliding mode tracking term. Robustness against modelling uncertainties and finitetime convergence are evaluated, initially for a single sea state,
and then across three different sea conditions. Excellent tracking
performance is observed for all considered operating conditions.
Finally, the super-twisting algorithm in the tracking loop is compared with the performance of a linear controller synthesised
based on Youla-Kuˇcera parametrisation, observing that the former
presents better tracking capabilities, also outperforming in terms of
energy extraction
Women's television histories: Locating women's role in emerging and developing international television.
No full textThis special issue aims to take steps towards the internationalisation of scholarship on women’s television by drawing together articles on different national contexts of television and detailing the experiences of women in various national and historical television ecologies and economies. This is, of course, merely a step, since no one issue can attend to the breadth of women’s experiences in the many national television organisations and roles. Scholarship in anglophone, Global North and Western countries has been enabled because of the confluence of various factors including: fairly stable employment prospects for academics comparable, for example, to Global South scholars; the availability of funding for such scholars to undertake travel to conferences and network with scholars; the availability of research on the topic of women’s media histories because it is in English language and universities have the library resources. Therefore, the history of women’s work in these national contexts has begun to be told but there is a pressing need for attention to, and recognition of, scholarship beyond the limited context of anglophone territories
Turning machines: a simple algorithmic model for molecular robotics
No full textMolecular robotics is challenging, so it seems best to keep it simple. We consider an abstract molecular robotics model based on simple folding instructions that execute asynchronously. Turning Machines are a simple 1D to 2D folding model, also easily generalisable to 2D to 3D folding. A Turning Machine starts out as a line of connected monomers in the discrete plane, each with an associated turning number. A monomer turns relative to its neighbours, executing a unit-distance translation that drags other monomers along with it, and through collective motion the initial set of monomers eventually folds into a programmed shape. We provide a suite of tools for reasoning about Turning Machines by fully characterising their ability to execute line rotations: executing an almost-full line rotation of 5 π / 3 radians is possible, yet a full 2 π rotation is impossible. Furthermore, line rotations up to 5 π / 3 are executed efficiently, in O ( log n ) expected time in our continuous time Markov chain time model. We then show that such line-rotations represent a fundamental primitive in the model, by using them to efficiently and asynchronously fold shapes. In particular, arbitrarily large zig-zag-rastered squares and zig-zag paths are foldable, as are y -monotone shapes albeit with error (bounded by perimeter length). Finally, we give shapes that despite having paths that traverse all their points, are in fact impossible to fold, as well as techniques for folding certain classes of (scaled) shapes without error. Our approach relies on careful geometric-based analyses of the feats possible and impossible by a very simple robotic system, and pushes conceptional hardness towards mathematical analysis and away from molecular implementation
Effect of Drought Stress on the Physiology and Early Growth of Seven Senegalia senegal (L.) Britton Provenances
No full textDecline of Senegalia senegal (Acacia senegal) in its natural range has been observed
and attributed mainly to harsh environmental conditions such as frequent drought occurrences. The objective of this study is to assess the effect of water stress on growth, biomass allocation and photosynthetic capacity in Senegalia senegal seedlings. Seeds were
collected from seven provenances in Senegal and grown under greenhouse conditions
in a randomized complete block design with 5 replications. Seedlings were subjected to
three cyclic droughts by watering them when average soil moisture content dropped to
4.7%, 2.7%, and 2.1% during the first, second, and third dry down cycles, respectively.
With the exception of net photosynthetic rate, stomatal conductance and transpiration at
the second and third dry down cycles, no drought by provenance interaction was found
for any trait measured. Ngane provenance had a lower root/shoot ratio and allometric
analysis revealed that Ngane allocated less biomass to roots than shoots. Ngane developed
superior growth traits and biomass production, despite similar net photosynthetic rate with
other provenances before treatments started. Overall, drought stress significantly reduced
biomass, stem height, diameter and leaf gas exchange. Total biomass was reduced by
28.5%, whereas root/shoot ratio was increased by 25% compared to control. Significant
interaction on leaf gas exchanges at the second and third dry down cycles reveals different
sensitivity levels to drought among provenances with the Ranerou provenance exhibiting
no decline in leaf gas exchange. No significant difference of stomatal limitation among
genotypes was found, which is indicative of the complex process of photosynthesis and
the need for extended times scales for measurements to better depict physiological sensitivity of Senegalia senegal to drought
The continuous flow synthesis of azos
No full textAzo compounds find use in many areas of science, displaying crucial properties for important applications as photoconductive organic pigments, fluorescent quenchers, paints, cosmetics, inks, and in the large and valuable dye industry. Due to the unstable intermediates, and the exothermic and fast reactions used in their synthesis, high value azo compounds are excellent candidates for continuous flow manufacturing. This comprehensive review covers the progress made to date on developing continuous flow systems for azo synthesis and reflects on the main challenges still to be addressed, including scale up, conversion, product purity, and environmental impact. The further development of integrated continuous flow processes has the potential to help tackle these challenges and deliver improved methods for azo compound generation
A speleothem record of hydroclimate variability in northwestern Madagascar during the mid-late Holocene
No full textWe present a continuous high-resolution precisely dated multiproxy record of hydroclimate variability at Anjohibe cave in northwestern Madagascar using speleothem AB13. The record spans from ~4484 y BP to ~2863 y BP. Stalagmite δ18O, δ13C and Sr/Ca ratios show very similar changes in hydroclimate. The mechanism controlling Sr/Ca changes, however, from prior calcite precipitation to degree of dolomite dissolution at about 4 ky BP. Our record is also in good agreement with previously published speleothem records from the same area. This agreement and multiproxy consensus indicate that AB13 provides a robust record of hydroclimate variability, including a continuous record of hydroclimate variability across the 4.2 ka event. This 4.2 ka event in Madagascar is marked by two distinct periods of drying between ~3900 y BP to 4300 y BP. A dry 4.2 ka event at this Southern Hemisphere site helps limit possible mechanisms for the event, indicating that a meridional shift to the south in the ITCZ is not responsible for the 4.2 ka event. In addition, the 4.2 ka event does not stand out as a unique dry period in our record. The longest and driest period of the record lasted ~300 years with peak dryness at ~3000 y BP. Our record differs significantly from a speleothem record from Rodrigues Island, located ~1800 km to the east of our study area in Madagascar suggesting different climatological controls on northwest Madagascar and more oceanic sites to the east
How can we research social movements? An introduction
No full textThis introductory chapter is written for beginning researchers, whether in movements or universities, for people from non-traditional academic backgrounds and non-native English speakers. We share some of our own complicated and messy routes to movement research. We also explain why researching social movements matters, and how it can genuinely help movements. This is the first methods handbook for movement researchers that takes a genuinely global perspective, rather than focussing on researchers and movements in the global North. Understanding movements means not being restricted to knowing about one movement or one academic discipline. The chapter introduces the book’s themes - the methodologies and politics of knowledge of movement research; different methods of data collection/analysis; and the uses of research for movements - followed by a chapter-by-chapter overview, highlighting the specific movements studied. The chapter concludes with reflections on the future of social movements research and a call for solidarity
Zonal control on Holocene precipitation in northwestern Madagascar based on a stalagmite from Anjohibe
No full textThe Malagasy Summer Monsoon is an important part of the larger Indian Ocean and tropical monsoon region. As the effects of global warming play out, changes to precipitation in Madagascar will have
important ramifications for the Malagasy people. To help understand how precipitation responds to climate changes we present a long-term Holocene speleothem record from Anjohibe, part of the Andranoboka cave system in northwestern Madagascar. To date, it is the most complete Holocene record from this region and sheds light on the nature of millennial and centennial precipitation changes in this region. We find that over the Holocene, precipitation in northwestern Madagascar is actually in phase with the Northern Hemisphere Asian monsoon on multi-millennial scales, but that during some shorter centennial-scale events such as the 8.2 ka event, Anjohibe exhibits an antiphase precipitation signal to the Northern Hemisphere. The ultimate driver of precipitation changes across the Holocene does not appear to be the meridional migration of the monsoon. Instead, zonal sea surface temperature gradients in the Indian Ocean seem to play a primary role in precipitation changes
in northwestern Madagascar
The Populist Hype (Chapter 44)
No full textGoing beyond an exclusive focus on populist politics, attention to the signifier ‘populism’ helps elucidate the character and effects of discourses about populism. The aim of this chapter is three-fold. First, we foreground the pivotal role played by politics, media, academia and their dynamic inter-relations in elucidating the character and effects of discourses about populism. Second, we argue that while this has so far been analysed productively in ideological terms, there are good reasons for supplementing these accounts by appealing to factors which go ‘beyond ideology’. Third, we approach the ubiquity of discourses about populism through the concept of ‘populist hype’, showing how its character and ideological effects are a product of processes that go beyond ‘mere’ ideological motivations
Procrastination, depressive symptomatology, and loneliness in later life
No full textObjectives: Procrastination is an almost universal behaviour and yet little research to date has focused on procrastination among older adults. The purpose of this study was to explore the potential asso-ciation between age and procrastination, and the potential mediating roles of depressive symptom-atology and loneliness.Method: Structural equation modelling was applied to data from 1309 participants (aged 29–92) from two waves United States Health and Retirement Study (2016–2020). Within the model, sex, education, marital status, and job status were added as covariates.Results: There was no statistically significant direct effect between age and procrastination (β = 0.06, p = 0.106). However, an indirect effect was present via depressive symptomatology (β = −0.40, p < 0.001). No mediating effect of loneliness was observed (β = − 0.01, p = 0.371). Subsequent analysis revealed that the symptoms, fatigue, loneliness, and lack of motivation significantly predicted procrastination.Conclusion: While age was not directly associated with procrastination, increasing age was associated with a decreased likelihood of depressive symptomatology, which was in turn associated with an increased likelihood of procrastination. Such findings indicates that age demonstrates no association with procrastination because of the suppressing effect of depressive symptomatology