546 research outputs found

    Rapid optimization of multiple-burn rocket flights, 8 March 1968 - 8 March 1969

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    Iterative solution of boundary value problem for rapid optimization of multiple-burn rocket flight

    Deep Reinforcement Learning Based Energy Storage Arbitrage With Accurate Lithium-ion Battery Degradation Model

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    Accurate estimation of battery degradation cost is one of the main barriers for battery participating on the energy arbitrage market. This paper addresses this problem by using a model-free deep reinforcement learning (DRL) method to optimize the battery energy arbitrage considering an accurate battery degradation model. Firstly, the control problem is formulated as a Markov Decision Process (MDP). Then a noisy network based deep reinforcement learning approach is proposed to learn an optimized control policy for storage charging/discharging strategy. To address the uncertainty of electricity price, a hybrid Convolutional Neural Network (CNN) and Long Short Term Memory (LSTM) model is adopted to predict the price for the next day. Finally, the proposed approach is tested on the the historical UK wholesale electricity market prices. The results compared with model based Mixed Integer Linear Programming (MILP) have demonstrated the effectiveness and performance of the proposed framework

    An Examination of the First Years: Novice ESOL Teachers’ Experiences with Loneliness and Stress

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    The first years of work for new teachers can be particularly difficult; this is especially true for English to Speakers of Other Languages (ESOL) teachers (Brannan & Bleistein, 2012; Warford & Reeves, 2003). This study was designed to explore potential issues within this important group and specifically examined the relationship between loneliness and stress for novice ESOL teachers. Forty-seven novice ESOL teachers completed self-report measures assessing their levels of perceived stress and loneliness. The results revealed that loneliness significantly predicted perceived stress (β = .51, p \u3c .001.). Furthermore, exploratory analyses indicated that marital status influenced loneliness ratings but not stress levels. These findings indicate that for novice teachers that often teach abroad, feelings of loneliness are an important issue to consider

    Radius constraints from high-speed photometry of 20 low-mass white dwarf binaries

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    We carry out high-speed photometry on 20 of the shortest-period, detached white dwarf binaries known and discover systems with eclipses, ellipsoidal variations (due to tidal deformations of the visible white dwarf), and Doppler beaming. All of the binaries contain low-mass white dwarfs with orbital periods less than 4 hr. Our observations identify the first eight tidally distorted white dwarfs, four of which are reported for the first time here, which we use to put empirical constraints on the mass-radius relationship for extremely low-mass (<0.30 Msun) white dwarfs. We also detect Doppler beaming in several of these binaries, which confirms the high-amplitude radial-velocity variability. All of these systems are strong sources of gravitational radiation, and long-term monitoring of those that display ellipsoidal variations can be used to detect spin-up of the tidal bulge due to orbital decay.Comment: 14 pages, 5 figures, accepted for publication in The Astrophysical Journa

    Differential vascular dysfunction in response to diets of differing macronutrient composition: a phenomenonological study

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    <p>Abstract</p> <p>Background</p> <p>Vascular dysfunction can develop from consumption of an energy-rich diet, even prior to the onset of obesity. However, the roles played by different dietary components remain uncertain. While attempting to develop models of obesity in a separate study, we observed that two high-energy diets of differing macronutrient compositions affected vascular function differently in overweight rats.</p> <p>Methods</p> <p>Male Wistar rats (<it>n </it>= 6/group) were fed diets providing varying percentages of energy from fat and carbohydrate (CHO). For 10 weeks, they were fed either chow, as control diet (10% of energy from fat; 63% from CHO), chow supplemented with chocolate biscuit (30% fat; 56% CHO) or a high-fat diet (45% fat; 35% CHO). Blood concentrations of biochemical markers of obesity were measured, and epididymal fat pads weighed as a measure of adiposity. Mesenteric arteries were dissected and their contractile and relaxant properties analysed myographically. Data were tested by analysis of variance (ANOVA).</p> <p>Results</p> <p>Weight gain and plasma concentrations of glucose, insulin and leptin were similar in all groups. However, biscuit-fed animals showed increased food intake (+27%; <it>p </it>< 0.01) and elevated concentrations of TGs and NEFAs (+41% and +17%; both <it>p </it>< 0.05). High-fat-fed animals showed an increase only in NEFAs (+38%; <it>p </it>< 0.01). Arterial vasoconstriction in response to NA and KCl increased only in biscuit-fed rats (both <it>p </it>< 0.01), while vasorelaxation in response to CCh and SNP, but not histamine, was attenuated in both groups (both <it>p </it>< 0.01). Furthermore, whereas the effect of the high-fat diet was most pronounced in endothelium-dependent vasorelaxation, the biscuit diet had the greater effect on endothelium-independent vasorelaxation.</p> <p>Conclusion</p> <p>Vascular dysfunction resulting from consumption of a high-fat or combined relatively high-fat/high-CHO diet occurs through different physiological processes, which may be attributable to their differing macronutrient compositions. Combining potentially atherogenic macronutrients induces more extensive vascular impairment than that of high-fat alone, and may be attributable to the more marked dyslipidaemia observed with such a diet. Thus, these findings help clarify the role of dietary components in vascular impairment, which has implications for clinical approaches to preventing cardiovascular disease.</p

    Load and fatigue evaluation for 66kV floating offshore wind submarine dynamic power cable

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    This is the author accepted manuscript.Floating Offshore Wind technology has seen a number of prototype deployments around the world in recent years. One of the critical components that must maintain the highest possible integrity is the dynamic power cable. This paper presents the approach and applied methods for the design work that informs the development and qualification of a 66kV submarine dynamic power cable. The design envelope is quantified through coupled aero-hydrodynamic modelling, determining the ultimate load conditions for different cable configurations. The model sensitivity and convergence for an OC4 floating design are explored regarding metocean conditions, computational parameters. A lowered Lazy Wave cable configuration is chosen as most suitable design, providing a compromise between hang-off tensions and induced bending stresses. The numerical results form the basis for subsequent physical cable demonstration and validation tests.Engineering and Physical Sciences Research Council (EPSRC
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