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Direct-to-indirect mapping for optimal low-thrust trajectories

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Astrodynamics 2024年第1期8卷 27-46页

作者： david Ottesen Ryan P.Russell Department of Aerospace Engineering and Engineering Mechanics The University of Texas at AustinAustinTexas78712USA

Optimal,many-revolution spacecraft trajectories are challenging to solve.A connection is made for a class of models between optimal direct and indirect *** transfers that minimize thrust-acceleration-squared,primer vector theory maps direct,many-impulsive-maneuver trajectories to the indirect,continuous-thrust-acceleration *** mapping algorithm is independent of how the direct solution is obtained and requires only a solver for a boundary value problem and its partial derivatives.A Lambert solver is used for the two-body problem in this *** mapping is simple because the impulsive maneuvers and co-states share the same linear space around an optimal *** numerical results,the direct coast-impulse solutions are demonstrated to converge to the indirect continuous solutions as the number of impulses and segments *** two-body design space is explored with a set of three many-revolution,many-segment examples changing semimajor axis,eccentricity,and *** first two examples involve a small change to either semimajor axis or eccentricity,and the third example is a transfer to geosynchronous *** a single processor,the optimization runtime is seconds to minutes for revolution counts of 10 to 100,and on the order of one hour for examples with up to 500 *** of these thrust-acceleration-squared solutions are good candidates to start a homotopy to a higher-fidelity minimization problem with practical constraints.

关键词： direct optimization indirect optimization impulsive maneuvers Lambert's problem two-body dynamics primer vectortheory

Loggerhead Sea Turtles Hand-Reared in Captivity: Isotopic Insights into Their Inherent Dietary Variation

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Open Journal of Ecology 2024年第5期14卷 435-454页

作者： Brenda Natasha Mejía-Guarnizo Carlos Julio Polo-Silva Guiomar Aminta Jauregui-Romero Antonio Delgado-huertas Centro de Investigaciones en Ciencias Marinas (CICIMAR-IPN) La Paz M&#233xico Marine Biology Program Faculty of Natural Sciences and Engineering Jorge Tadeo Lozano University Santa Marta Colombia Sharky Management and Consulting Oldsmar FL USA Programa de Conservació n de Tortugas y Mam&#237feros Marinos (ProCTMM) Santa Marta Colombia Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR) Armilla Spain

Stable isotope analysis is a widely used method for gathering ecological insights into the diet and feeding habitats of various species. While captive studies often limit lethal sampling and differ from wild conditions, they offer valuable insights into inherent isotopic variations among individuals, which are often assumed to reflect differences between natural populations. In the Sea Turtle Conservation Program, loggerhead turtle hatchlings from different nests were fed. Necropsies were conducted on turtles that died during this period, obtaining bone fragments for analysis. We evaluated the isotopic variation of carbon (δ13C) and nitrogen (δ15N) in bone tissue across six turtle nests (n = 66 samples) and assessed differences in Straight Carapace Length (SCL, n = 71 samples). Using SIBER and nicheROVER in R, we calculated niche width and overlap, while the simmr package determined primary prey assimilation. Despite feeding the hatchlings the same prey, we observed variations in nitrogen isotope assimilation between nests. Nests 4 and 6 had a niche width >1.8‰, indicating consistent consumption frequencies across all prey and >70% niche overlap with other nests. In contrast, nests 1 and 2 showed a narrower niche width (Mugil sp. constituted the primary diet component (>40%) across all groups. This study demonstrates how factors like competition or prey preference can influence the assimilation of diet, even when the source remains constant (inherent variation).

关键词： Stable Isotopes Caretta caretta Head-Starting Nests Straight Carapace Length

Enhanced Hoek-Brown(H-B)criterion for rocks exposed to chemical corrosion

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International Journal of Mining Science and Technology 2024年第5期34卷 609-630页

作者： Hao Li Leo Pel Zhenjiang You david Smeulders Department of Mechanical Engineering Eindhoven University of TechnologyEindhoven 5600 MBthe Netherlands Department of Applied Physics Eindhoven University of TechnologyEindhoven 5600 MBthe Netherlands Center for Sustainable Energy and Resources School of EngineeringEdith Cowan UniversityJoondalupWA 6027Australia School of Chemical Engineering The University of QueenslandBrisbaneQLD 4072Australia Gas and Energy Transition Research Centre The University of QueenslandBrisbaneQLD 4072Australia

Underground constructions often encounter water environments,where water–rock interaction can increase porosity,thereby weakening engineering ***,the failure criterion for chemically corroded rocks becomes essential in the stability analysis and design of such *** study enhances the applicability of the Hoek-Brown(H-B)criterion for engineering structures operating in chemically corrosive conditions by introducing a kinetic porosity-dependent instantaneous mi(KPIM).A multiscale experimental investigation,including nuclear magnetic resonance(NMR),X-ray diffraction(XRD),scanning electron microscopy(SEM),pH and ion chromatography analysis,and triaxial compression tests,is employed to quantify pore structural changes and their linkage with the strength responses of limestone under coupled chemical-mechanical(C-M)*** employing ion chromatography and NMR analysis,along with incorporating the principles of free-face dissolution theory accounting for both congruent and incongruent dissolution,a kinetic chemical corrosion model is *** model aims to calculate the kinetic porosity alterations within rocks exposed to varying H+concentrations and ***,utilizing the generalized mixture rule(GMR),the kinetic porositydependent mi is *** of the KPIM-enhanced H-B criterion using compression test data from 5 types of rocks demonstrated a high level of consistency between the criterion and the experimental results,with a coefficient of determination greater than 0.96,a mean absolute percentage error less than 4.84%,and a root-mean-square deviation less than 5.95 ***,the physical significance of the porosity-dependent instantaneous mi is clarified:it serves as an indicator of a rock’s capacity to leverage the confining pressure effect.

关键词： Hoek-Brown(H-B)criterion Instantaneous mi Kinetic porosity-dependency Chemical corrosion Compressive strength

Blast waveform tailoring using controlled venting in blast simulators and shock tubes

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Defence Technology（防务技术） 2024年第7期37卷 14-26页

作者： Edward Chern Jinn Gan Alex Remennikov david Ritzel Faculty of Engineering and Information Sciences University of WollongongWollongongNSW2522Australia Dyn-FX Consulting Ltd 19 Laird Ave NorthAmherstburgONN9V 2T5Canada

A critical challenge of any blast simulation facility is in producing the widest possible pressure-impulse range for matching against equivalent high-explosive *** tubes and blast simulators are often constrained with the lack of effective ways to control blast wave profiles and as a result have a limited performance *** wave shaping techniques employed in some facilities are reviewed but often necessitate extensive geometric modifications,inadvertently cause flow anomalies,and/or are only applicable under very specific *** paper investigates controlled venting as an expedient way for waveforms to be tuned without requiring extensive modifications to the driver or existing geometry and could be widely applied by existing and future blast simulation and shock tube *** use of controlled venting is demonstrated experimentally using the Advanced Blast Simulator(shock tube)at the Australian National Facility of Physical Blast Simulation and via numerical flow simulations with Computational Fluid *** venting is determined as an effective method for mitigating the impact of re-reflected waves within the blast *** control method also allows for the adjustment of parameters such as tuning the peak overpressure,the positive phase duration,and modifying the magnitude of the negative phase and the secondary shock of the blast *** paper is concluded with an illustration of the potential expanded performance range of the Australian blast simulation facility when controlled venting for blast waveform tailoring as presented in this paper is applied.

关键词： Advanced blast simulator Shock wave propagation Far-field explosion Blast loads Blast waves Computational fluid dynamics

Exercise immunology:Novel insights

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Journal of Sport and Health Science 2024年第3期13卷 277-279,I0001页

作者： david C.Nieman Human Performance Laboratory Appalachian State UniversityNorth Carolina Research CampusKannapolisNC 28081USA

The coronavirus disease 2019(COVID-19)pandemic heightened worldwide attention on the influence of exercise on the immune *** were raised about whether regular moderate-to-vigorous physical activity(MVPA)could help prevent COVID-19 or mitigate symptoms when *** MVPA bolster immunity among those most prone to COVID-19 including the elderly,obese,and immunocompromised patients?Does regular MVPA dampen systemic inflammation,thereby lessening the COVID-19 cytokine storm?

关键词： immunity inflammation thereby

Role of climatic variability in shaping intraspecific variation of thermal tolerance in Mediterranean water beetles

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Insect Science 2024年第1期31卷 285-298页

作者： Susana Pallarés david Garoffolo Belén Rodríguez david Sánchez-Fernández Department of Zoology University of SevilleSevilleSpain Faculty of Biology Department of Ecology and HydrologyUniversity of MurciaCampus EspinardoMurciaSpain

The climatic variability hypothesis(CVH)predicts that organisms in more thermally variable environments have wider thermal breadths and higher thermal plasticity than those from more stable ***,due to evolutionary trade-offs,taxa with greater absolute thermal limits may have little plasticity of such limits(trade-off hypothesis).The CVH assumes that climatic variability is the ultimate driver of thermal tolerance variation across latitudinal and altitudinal gradients,but average temperature also varies along such *** explored intraspecific variation of thermal tolerance in three typical Mediterranean saline water beetles(families Hydrophilidae and Dytiscidae).For each species,we compared two populations where the species coexist,with similar annual mean temperature but contrasting thermal variability(continental *** population).We estimated thermal limits of adults from each population,previously acclimated at 17,20,or 25℃.We found species-specific patterns but overall,our results agree with the CVH regarding thermal ranges,which were wider in the continental(more variable)*** the two hydrophilid species,this came at the cost of losing plasticity of the upper thermal limit in this population,supporting the trade-off hypothesis,but not in the dytiscid *** results support the role of local adaptation to thermal variability and trade-offs between basal tolerance and physiological plasticity in shaping thermal tolerance in aquatic ectotherms,but also suggest that intraspecific variation of thermal tolerance does not fit a general pattern among aquatic *** such intraspecific variation could lead to inaccurate predictions of the vulnerability of aquatic insects to global warming.

关键词： acclimation capacity aquatic insects climate change heat coma temperature supercooling point thermal plasticity

Bed inventory balance and stability of dual circulating fluidized bed systems

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Particuology 2024年第1期84卷 98-106页

作者： Yangjun Wei Leming Cheng david Pallares Bo Leckner Institute for Thermal Power Engineering State Key Laboratory of Clean Energy UtilizationZhejiang UniversityHangzhou310027China Department of Space Earth and EnvironmentChalmers University of TechnologyS-41296GöteborgSweden

Experiments and modelling are conducted for general understanding on the imbalance phenomenon and for discussion on the strategies to improve the bed inventory balance and stability of a dual circulating fluidized bed(DCFB)*** experiments are carried out in a 15.5 m high pilot-scale DCFB cold test system.A fluid-dynamic DCFB model is developed based on a 1.5-dimensional semi-empirical model of an industrial CFB boiler,validated by experimental *** effects of control methods and operation conditions on the bed inventory balance and on the stability of the pilot-and large-scale DCFB systems are discussed.A"stable-unbalanced"state,where the system reaches a steady state,consisting of un-balanced bed inventories,is observed in both experiments and model *** maintain a balanced state and similar bed inventory in the DCFB systems with similar cross-sectional areas,it is recom-mended to keep similar total pressure drops or gas velocities in both reactors.

关键词： Bed inventory balance Stability Dual circulating fluidized bed(DCFB) Experiment Modelling

Artificial intelligence analysis of videos to augment clinical assessment:an overview

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Neural Regeneration Research 2024年第4期19卷 717-718页

作者： david C.Wong Stefan Williams University of Leeds Leeds Teaching Hospitals Trust LeedsUK

Observation is a fundamental part of the practice of clinical *** of movement is particularly important for the *** such as Parkinson’s disease,multiple sclerosis,stroke,epilepsy,and many others affect a person’s movement in characteristic *** some conditions,changes in the patient’s voice can be included in this-changes in sound caused by changes in the movements of *** clinician’s detection of a characteristic abnormality,and their judgment of its severity,plays a central role in both diagnosis and the assessment of prognosis or response to ***,that practice depends upon a limited resource of experienced *** addition,these experts are limited by human visual judgment,which cannot reliably or precisely detect and measure small or subtle changes in movement(Williams et al.,2023).

关键词： clinical epilepsy diagnosis

Balancing machine learning and artificial intelligence in soil science with human perspective and experience

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Pedosphere 2024年第1期34卷 9-12页

作者： david C.WEINDORF Somsubhra CHAKRABORTY Department of Earth and Atmospheric Science Central Michigan Universityount Pleasant M148859USA Agricultural and Food Engineering Department Indian Institute of TechnologyKharagpur 721302India

Machine learning and artificial intelligence continue to evolve at a rapid pace, with many potential applications related to soil science. Even so, human experience and perception play an invaluable role in characterizing soil properties, especially qualitative properties that may elude sensing/computer-based modeling approaches. The elegant solution to this conundrum relies on the synthesis of computer-aided predictive modeling with human insight and *** global population surpasses 8 billion, the importance of optimized agronomic production to feed a hungry world has never been more important.

关键词： soil elude qualitative