218 resultados para Adaptive Landscape
Resumo:
In the areas adjacent to the drowned Pleistocene continent of Sunda – present-day Mainland and Island SE Asia – the Austronesian Hypothesis of a diaspora of rice cultivators from Taiwan ∼4200 years ago has often been linked with the start of farming. Mounting evidence suggests that these developments should not be conflated and that alternative explanations should be considered, including indigenous inception of complex patterns of plant food production and early exchange of plants, animals, technology and genes. We review evidence for widespread forest disturbance in the Early Holocene which may accompany the beginnings of complex food-production. Although often insubstantial, evidence for incipient and developing management of rainforest vegetation and of developing complex relationships with plants is present, and early enough to suggest that during the Early to mid-Holocene this vast region was marked by different approaches to plant food production. The trajectory of the increasingly complex relationships between people and their food organisms was strongly locally contingent and in many cases did not result in the development of agricultural systems that were recognisable as such at the time of early European encounters. Diverse resource management economies in the Sunda and neighbouring regions appear to have accompanied rather than replaced a reliance on hunting and gathering. This, together with evidence for Early Holocene interaction between these neighbours, gives cause for us to question some authors continued adherence to a singular narrative of the Austronesian Hypothesis and the ‘Neolithisation’ of this part of the world. It also leads us to suggest that the forests of this vast region are, to an extent, a cultural artefact.
Resumo:
Acute respiratory distress syndrome (ARDS) is a devastating disorder characterized by increased alveolar permeability with no effective treatment beyond supportive care. Current mechanisms underlying ARDS focus on alveolar endothelial and epithelial injury caused by products of innate immune cells and platelets. However, the role of adaptive immune cells in ARDS remains largely unknown. In this study, we report that expansion of Ag-specific αβTh17 cells contributes to ARDS by local secretion of IL-17A, which in turn directly increases alveolar epithelial permeability. Mice with a highly restrictive defect in Ag-specific αβTh17 cells were protected from experimental ARDS induced by a single dose of endotracheal LPS. Loss of IL-17 receptor C or Ab blockade of IL-17A was similarly protective, further suggesting that IL-17A released by these cells was responsible for this effect. LPS induced a rapid and specific clonal expansion of αβTh17 cells in the lung, as determined by deep sequencing of the hypervariable CD3RβVJ region of the TCR. Our findings could be relevant to ARDS in humans, because we found significant elevation of IL-17A in bronchoalveolar lavage fluid from patients with ARDS, and rIL-17A directly increased permeability across cultured human alveolar epithelial monolayers. These results reveal a previously unexpected role for adaptive immune responses that increase alveolar permeability in ARDS and suggest that αβTh17 cells and IL-17A could be novel therapeutic targets for this currently untreatable disease.
Resumo:
We propose a mixed cost-function adaptive initialization algorithm for the time domain equalizer in a discrete multitone (DMT)-based asymmetric digital subscriber line. Using our approach, a higher convergence rate than that of the commonly used least-mean square algorithm is obtained, whilst attaining bit rates close to the optimum maximum shortening SNR and the upper bound SNR. Furthermore, our proposed method outperforms the minimum mean-squared error design for a range of time domain equalizer (TEQ) filter lengths. The improved performance outweighs the small increase in computational complexity required. A block variant of our proposed algorithm is also presented to overcome the increased latency imposed on the feedback path of the adaptive system.
Adaptive backstepping droop controller design for multi-terminal high-voltage direct current systems
Resumo:
Wind power is one of the most developed renewable energy resources worldwide. To integrate offshore wind farms to onshore grids, the high-voltage direct current (HVDC) transmission cables interfaced with voltage source converters (VSCs) are considered to be a better solution than conventional approaches. Proper DC voltage indicates successive power transfer. To connect more than one onshore grid, the DC voltage droop control is one of the most popular methods to share the control burden between different terminals. However, the challenges are that small droop gains will cause voltage deviations, while higher droop gain settings will cause large oscillations. This study aims to enhance the performance of the traditional droop controller by considering the DC cable dynamics. Based on the backstepping control concept, DC cables are modelled with a series of capacitors and inductors. The final droop control law is deduced step-by-step from the original remote side. At each step the control error from the previous step is considered. Simulation results show that both the voltage deviations and oscillations can be effectively reduced using the proposed method. Further, power sharing between different terminals can be effectively simplified such that it correlates linearly with the droop gains, thus enabling simple yet accurate system operation and control.
Resumo:
Previous studies suggest that public-sector accounting has moved from Public Administration (PA) to New Public Management (NPM) ideas and, more recently, towards a New Public Governance (NPG) approach. These systems are presented as mutually exclusive and competing. Focusing on accounting changes in the UK central government, this paper explores whether movements towards NPG ideas can be identified at the level of political debate. No evidence is found that NPM is a transitory state. Rather, the findings demonstrate that political debate continues to utilise predominantly NPM arguments, with the three systems viewed as containing complementary, rather than competing, schemes.
Resumo:
This paper employs a unique decentralised cooperative control method to realise a formation-based collision avoidance strategy for a group of autonomous vehicles. In this approach, the vehicles' role in the formation and their alert and danger areas are first defined, and the formation-based intra-group and external collision avoidance methods are then proposed to translate the collision avoidance problem into the formation stability problem. The extension–decomposition–aggregation formation control method is next employed to stabilise the original and modified formations, whilst manoeuvring, and subsequently solve their collision avoidance problem indirectly. Simulation study verifies the feasibility and effectiveness of the intra-group and external collision avoidance strategy. It is demonstrated that both formation control and collision avoidance problems can be simultaneously solved if the stability of the expanded formation including external obstacles can be satisfied.