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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

Exploiting blockchain for dependable services in zero-trust vehicular networks

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Frontiers of Computer Science 2024年第2期18卷 157-166页

作者： Min HAO Beihai TAN Siming WANG Rong YU ryan Wen LIU Lisu YU School of Automation Guangdong University of TechnologyGuangzhou 510006China School of Integrated Circuits Guangdong University of TechnologyGuangzhou 510006China School of Navigation Wuhan University of TechnologyWuhan 430063China School of Information Engineering Nanchang UniversityNanchang 330031China

The sixth-generation(6G)wireless communication system is envisioned be cable of providing highly dependable services by integrating with native reliable and trustworthy ***-trust vehicular networks is one of the typical scenarios for 6G dependable *** the technical framework of vehicle-and-roadside collaboration,more and more on-board devices and roadside infrastructures will communicate for information *** reliability and security of the vehicle-and-roadside collaboration will directly affect the transportation *** a zero-trust vehicular environment,to prevent malicious vehicles from uploading false or invalid information,we propose a malicious vehicle identity disclosure approach based on the Shamir secret sharing ***,a two-layer consortium blockchain architecture and smart contracts are designed to protect the identity and privacy of benign vehicles as well as the security of their private *** that,in order to improve the efficiency of vehicle identity disclosure,we present an inspection policy based on zero-sum game theory and a roadside unit incentive mechanism jointly using contract theory and subjective logic *** verify the performance of the entire zero-trust solution through extensive simulation *** the premise of protecting the vehicle privacy,our solution is demonstrated to significantly improve the reliability and security of 6G vehicular networks.

关键词： sixth-generation(6G) zero-trust block-chain vehicular networks privacy preservation

Millimetric devices for nerve stimulation:a promising path towards miniaturization

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Neural Regeneration Research 2024年第8期19卷 1702-1706页

作者： ryan M.Dorrian Anna V.Leonard Antonio Lauto Spinal Cord Injury Research Group School of BiomedicineThe University of AdelaideAdelaideSAAustralia School of Science Western Sydney UniversityPenrithNSWAustralia

Nerve stimulation is a rapidly developing field,demonstrating positive outcomes across several *** potential benefits,current nerve stimulation devices are large,complicated,and are powered via implanted pulse *** facto rs necessitate invasive surgical implantation and limit potential *** nerve stimulation devices to millimetric sizes would make these interventions less invasive and facilitate broader therapeutic ***,device miniaturization presents a serious engineering *** review presents significant advancements from several groups that have overcome this challenge and developed millimetricsized nerve stimulation *** are based on antennas,mini-coils,magneto-electric and optoelectronic materials,or receive ultrasound *** highlight key design elements,findings from pilot studies,and present several considerations for future applications of these devices.

关键词： biomedical engineering deep brain stimulation electrical engineering electrical stimulation neuromodulation peripheral nerve stimulation

The Artificial Disc Nucleus and Other Strategies for Replacement of the Nucleus Pulposus:Past,Present and Future Designs for an Emerging Surgical Solution

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Engineered Regeneration 2024年第2期5卷 269-281页

作者： Greg Sacks Vincent DeStefano Claire Parker ryan Lebens Harry Mushlin Renaissance School of Medicine at Stony Brook University Stony BrookNYUSA

Nucleus Pulposus(NP)Replacement is a developing surgical methodology for the treatment of pathology related to degeneration of intervertebral discs(IVDs).This article provides necessary context regarding the patholo-gies treated with this technology,the biomechanical structure and function of the IVD,and the procedures this technology aims to ***,it provides an overview and discussion of commercial and experimental preformed and in situ curing prosthesis designs reported in the scientific literature and summarizes the results of biomechanical and clinical studies evaluating their *** and updated information on the most recent research into NP replacement with novel hydrogel and tissue engineering(TE)strategies is *** of the NP allows for potential improvement in the treatment of degenerative spinal pathologies through minimally invasive surgical techniques.

关键词： Nucleus Pulposus Intradiscal Prosthesis Hydrogel Artificial Disc Implant Spine Surgery

Machine learning for predicting the outcome of terminal ballistics events

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Defence Technology（防务技术） 2024年第1期31卷 14-26页

作者： Shannon ryan Neeraj Mohan Sushma Arun Kumar AV Julian Berk Tahrima Hashem Santu Rana Svetha Venkatesh Applied Artificial Intelligence Institute(A2I2) Deakin University75 Pigdons RdWaurn PondsVIC3216Australia

Machine learning(ML) is well suited for the prediction of high-complexity,high-dimensional problems such as those encountered in terminal *** evaluate the performance of four popular ML-based regression models,extreme gradient boosting(XGBoost),artificial neural network(ANN),support vector regression(SVR),and Gaussian process regression(GP),on two common terminal ballistics’ problems:(a)predicting the V50ballistic limit of monolithic metallic armour impacted by small and medium calibre projectiles and fragments,and(b) predicting the depth to which a projectile will penetrate a target of semi-infinite *** achieve this we utilise two datasets,each consisting of approximately 1000samples,collated from public release *** demonstrate that all four model types provide similarly excellent agreement when interpolating within the training data and diverge when extrapolating outside this *** extrapolation is not advisable for ML-based regression models,for applications such as lethality/survivability analysis,such capability is *** circumvent this,we implement expert knowledge and physics-based models via enforced monotonicity,as a Gaussian prior mean,and through a modified loss *** physics-informed models demonstrate improved performance over both classical physics-based models and the basic ML regression models,providing an ability to accurately fit experimental data when it is available and then revert to the physics-based model when *** resulting models demonstrate high levels of predictive accuracy over a very wide range of projectile types,target materials and thicknesses,and impact conditions significantly more diverse than that achievable from any existing analytical *** with numerical analysis tools such as finite element solvers the ML models run orders of magnitude *** provide some general guidelines throughout for the development,application,and reporting of ML models in terminal ballist

关键词： Machine learning Artificial intelligence Physics-informed machine learning Terminal ballistics Armour

Are school uniforms associated with gender inequalities in physical activity? A pooled analysis of population-level data from 135 countries/regions

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Journal of Sport and Health Science 2024年第4期13卷 590-598页

作者： Mairead ryan Luiza I.C.Ricardo Nicole Nathan Riikka Hofmann Esther van Sluijs Medical Research Council Epidemiology Unit University of CambridgeCambridge CB20QQUK Faculty of Education University of CambridgeCambridge CB28PQUK Hunter New England Population Health WallsendNSW 2287Australia School of Medicine and Public Health College of HealthMedicine and WellbeingUniversity of NewcastleCallaghanNSW 2308Australia Hunter Medical Research Institute New Lambton HeightsNSW 2305Australia National Centre of Implementation Science University of NewcastleCallaghanNSW 2308Australia

Purpose:It is aimed to assess whether school uniforms are associated with population-level gender inequalities in physical activity,and whether associations differ by school level,country/region income,and assessment ***:An ecological study design was *** collected data about global uniform practices using an online *** searched for country/region-level estimates of school-aged youth meeting physical activity guidelines from international surveillance *** selection was conducted in duplicate using a systematic process,and a random sample of all data was checked to ensure extraction and pooling processes were *** calculated absolute and relative gender inequalities in physical activity for each *** regression examined associations between country/region-level uniform practices(binary yes/no exposure variable) and country/region-level gender inequalities in physical activity guideline compliance(absolute and relative inequalities).We investigated moderation by school level,stratified analyses by income group,and repeated primary analyses using device-measured ***:Pooling data from 135 countries/regions(n=1,089,852),we found no association between population-level uniform practices and gender inequalities in physical activity across all ages(absolute:β=-0.2;95% confidence interval(95%CI):-1.7 to 1.3,p=0.74;relative:β=0.1;95%CI:-0.1 to 0.2,p=0.51).Subgroup analysis suggested a positive association in primary school settings(absolute:β=4.3;95%CI:-0.0 to 8.6,p=0.05).Among high-income countries,absolute inequalities were significantly greater in countries/regions with uniform practices(N=37) compared to those without(N=48)(9.1(SD=3.6) vs.7.8 percentage points(SD=4.3)).Repeating analyses using device-measured data(n=32,130;N=24) did not alter our primary *** initial descriptive statistics,we found that in countries/regions where a maj ority of schools(>50%) reportedly use uniforms,there was lower compli

关键词： School policy Clothing Child Adolescent Accelerometer

Effect of TiB_(2)Addition on Microstructure and Mechanical Properties of AA8009 Alloy Fabricated by Laser Additive Manufacturing

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 67-77页

作者： Xinxing Xiong Sijie Yu Pei Wang Junfang Qi Haichao Li Xulei Wang Michael ryan Debajyoti Bhaduri Rossitza Setchi Additive Manufacturing Institute Shenzhen UniversityShenzhen518060China Henan Key Laboratory of High Performance Carbon Fiber Reinforced Composites Institute of Carbon Matrix CompositesHenan Academy of SciencesZhengzhou450046China School of Materials Science and Engineering Shanghai University of Engineering ScienceShanghai201620China School of Materials Science and Engineering Zhengzhou University of AeronauticsZhengzhou450046China High-Value Manufacturing Research Group School of EngineeringCardiff UniversityCardiffCF243AAUK

The research involves the addition of 5 vol.%TiB_(2)particles into AA8009 alloy powder to synthesize TiB_(2)/AA8009 composite parts produced via laser powder bed fusion(LPBF).The addition of the TiB_(2)particles causes the TiB_(2)/AA8009 composites with and without annealing have lower compressive strength than AA8009 alloy due to the change of the strengthening *** results further indicated that solid solution strengthening was the main strengthening mechanism of the LPBF AA8009 alloy at room temperature whereas Orowan strengthening became the primary strengthening factor after annealing at 673 *** contrast,Orowan strengthening always remained the main strengthening mechanism for the TiB_(2)/AA8009 composite,irrespective of the annealing *** addition,after annealing of the LPBF parts at 673 K,the compressive yield strength(CYS)of the unblended AA8009 alloy specimens had a~2.5 times greater reduction(from 705±16 to 459±30 MPa)compared to that of the composite TiB_(2)/AA8009 samples(from 466±23 to 368±3 MPa).Therefore,TiB_(2)particles can suppress the drop in yield strength of LPBF AA8009 alloy below 673 K,providing a theoretical and experimental basis for the applications of both LPBF AA8009 and TiB_(2)/AA8009 alloys at low and medium temperatures.

关键词： Laser powder bed fusion AA8009 alloy Microstructure Mechanical properties

Screen-printed graphite electrode on polyvinyl chloride and parchment strips integrated with genetic programming for in situ nitrate sensing of aquaponic pond water

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Information Processing in Agriculture 2024年第2期11卷 187-201页

作者： Ronnie ConcepcionⅡ Bernardo Duarte Maria Gemel Palconit Jonah Jahara BaunArgel Bandala ryan Rhay Vicerra Elmer Dadios Department of Manufacturing Engineering and Management De La Salle UniversityManila 1004 Philippines MARE-Marine and Environmental Sciences Centre.&ARNET-Aquatic Research Infrastructure Network Associated Laboratory Faculdade de Ciencias da Universidade de LisboaCampo Grande1749-016 LisboaPortugal Departamento de Biologia Vegetal da Faculdade de Ciencias da Universidade de Lisboa Campo Grande 1749-016 LisboaPortugal Department of Electronics and Computer Engineering De La Salle UniversityManila 1004 Philppines

Nitrate is the primary water-soluble macronutrient essential for plant growth that is converted from excess fish feeds,fish effluents,and degrading biomaterials on the aquaponic pond floor,and when aquacultural malpractices occur,large amounts of it retain in the water system causing increase rate in eutrophication and toxifies fish and aquaculture *** nitrate sensor prototypes still require performing the additional steps of water sample deionization and dilution and were constructed with expensive *** response to the challenge of sensor enhancement and aquaponic water quality monitoring,this study developed sensitive,repeatable,and reproducible screen-printed graphite electrodes on polyvinyl chloride and parchment paper substrates with silver as electrode material and 60:40 graphite powder:nail polish formulated conductive ink for electrical traces,integrated with 9-gene genetic expression model as a function of peak anodic current and electrochemical test time for nitrate concentration prediction that is embedded into low-power Arduino ESP32 for in situ nitrate sensing in aquaponic pond *** SPE electrical traces were designed on the two types of *** electron microscopy with energy dispersive X-ray confirmed the electrode surface *** cyclic voltammetry using 10 to 100 mg/L KNO3 and water from three-depth regions of the actual pond established the electrochemical test time(10.5 s)and electrode potential(0.135 V)protocol necessary to produce peak current that corresponds to the strength of nitrate ions during *** findings from in situ testing revealed that the proposed sensors have strong linear predictions(R2=0.968 MSE=1.659 for nSPEv and R2=0.966 MSE=4.697 for nSPEp)in the range of 10 to 100 mg/L and best detection limit of 3.15μg/L,which are comparable to other sensors of more complex *** developed three-electrode electrochemical nitrate sensor confirms that it is reliable for bot

关键词： Aquaponic water quality Electrochemical technology Genetic programming Graphite electrode Nitrate sensor Precision agriculture Printed electronics Scanning electron microscopy Screen-printed electrode Voltammetry

The Impact of a Prior Norwood Procedure on Cardiac Transplantation in Failed Fontan Physiology

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Congenital Heart Disease 2024年第3期19卷 257-266页

作者： ryan G.McQueen Nikki M.Singh Ronald K.Woods Medical College of Wisconsin Herma Heart Institute at Children’s WisconsinMilwaukeeUSA Division of Pediatric Cardiology Medical College of WisconsinHerma Heart Institute at Children’s WisconsinMilwaukeeUSA Division of Pediatric Cardiothoracic Surgery Medical College of WisconsinHerma Heart Institute at Children’s WisconsinMilwaukeeUSA

Objective:The objective of this study was to compare cardiac transplant operative and postoperative courses of patients with failed Fontan physiology who were initially palliated with a Norwood(FFN)to those without a prior Norwood(FF).Methods:A single-institution retrospective review of all patients with Fontan failure who under-went cardiac transplantation from 2003–2021 was completed-22 underwent prior Norwood(FFN)and 11 did not(FF).Descriptive and inferential statistics were calculated for operative course and patient ***:The operative course of the FFN cohort appeared to be more complex(not statistically significant,but clinically relevant)-this group exclusively experienced sternal re-entry events(3 of 22 patients)and concomitant neo-aor-tic reconstruction(6 patients),had a longer duration of surgery(median of 682 min vs.575.5 min),more time on circulatory arrest(median of 25.5 min vs.12.5 min),and more frequent use of open sternal management[50%of patients(11/22)vs.27.3%of patients(3/11)].Postoperatively,these patients underwent more mediastinal explora-tions[other than sternal closure;40.9%of patients(9/22)vs.18.2%of patients(2/11)],spent more time on mechanical ventilation(median of 5 days vs.2 days),had a longer length of stay(median of 30 days vs.19 days),and required more catheter-based re-interventions[22.7%of patients(5/22)vs.9.1%of patients(1/11)].Conclu-sion:Although underpowered,our results suggest that the operative course of FFN patients is more challenging,based mostly on neo-aortic arch *** turn,this likely leads to a more complex postoperative *** are currently collaborating with other institutions to increase the cohort size and power of the study.

关键词： Fontan Fontan failure Norwood cardiac transplantation