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Analytical solution to logarithmic spiral trajectories with circumferential thrust and mission applications

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Astrodynamics 2022年第4期6卷 413-427页

作者： Marco Bassetto alessandro A.Quarta Giovanni Mengali Department of civil and Industrial Engineering University of PisaPisaⅠ-56122Italy

This study made use of a shape-based method to analyze the orbital dynamics of a spacecraft subject to a continuous propulsive acceleration acting along the circumferential *** the assumption of a logarithmic spiral trajectory,an exact solution to the equations of motion exists,which allows the spacecraft state variables and flight time to be expressed as a function of the angular *** is also a case characterized by specific initial conditions in which the time evolution of the state variables may be analytically *** this context,the presented solution is used to analyze circle-to-circle trajectories,where the combination of two impulsive maneuvers and a logarithmic spiral path are used to accomplish the *** determined results are then applied to the achievement of the Earth–Mars and the Earth–Venus transfers using actual data from a recent thruster developed by NASA.

关键词： circumferential thrust logarithmic spiral trajectory circle-to-circle transfer

Application of homotopy perturbation method to the radial thrust problem

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Astrodynamics 2023年第2期7卷 251-258页

作者： Lorenzo Niccolai alessandro A.Quarta Giovanni Mengali Department of civil and Industrial Engineering University of PisaI-56122Italy

The dynamics of a spacecraft propelled by a continuous radial thrust resembles that of a nonlinear *** is analyzed in this work with a novel method that combines the definition of a suitable homotopy with a classical perturbation approach,in which the low thrust is assumed to be a perturbation of the nominal Keplerian *** homotopy perturbation method provides the analytical(approximate)solution of the dynamical equations in polar form to estimate the corresponding spacecraft propelled trajectory with a short computational *** accuracy of the analytical results was tested in an orbital-targeting mission scenario.

关键词： radial thrust homotopy perturbation method nonlinear oscillator trajectory approximation

Importance of initial buoyancy field on evolution of mantle thermal structure:Implications of surface boundary conditions

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Geoscience Frontiers 2015年第1期6卷 3-22页

作者： Petar Gliovi alessandro M.Forte GEOTOP Universite du Quebec a MontrealCP 8888Succursale Centre-Ville

Although there has been significant progress in the seismic imaging of mantle heterogeneity, the outstanding issue that remains to be resolved is the unknown distribution of mantle temperature anomalies in the distant geological past that give rise to the present-day anomalies inferred by global tomography models. To address this question, we present 3-D convection models in compressible and self-gravitating mantle initialised by different hypothetical temperature patterns. A notable feature of our forward convection modelling is the use of self-consistent coupling of the motion of surface tectonic plates to the underlying mantle flow, without imposing prescribed surface velocities （i.e., p/ate-like boundary condition）. As an approximation for the surface mechanical conditions before plate tectonics began to operate we employ the no-slip （rigid） boundary condition. A rigid boundary condition dem- onstrates that the initial thermally-dominated structure is preserved, and its geographical location is fixed during the evolution of mantle flow. considering the impact of different assumed surface boundary conditions （rigid and plate-like） on the evolution of thermal heterogeneity in the mantle we suggest that the intrinsic buoyancy of seven superplumes is most-likely resolved in the tomographic images of present-day mantle thermal structure. Our convection simulations with a plate-like boundary condition reveal that the evolution of an initial cold anomaly beneath the Java-lndonesian trench system yields a long-term, stable pattern of thermal heterogeneity in the lowermost mantle that resembles the present- day Large Low Shear Velocity Provinces （LLSVPs）, especially below the Pacific. The evolution of sub- duction zones may be, however, influenced by the mantle-wide flow driven by deeply-rooted and long- lived superplumes since Archean times. These convection models also detect the intrinsic buoyancy of the Perm Anomaly that has been identified as a unique slow feature d

关键词： Dynamics: convection currents, and mantleplumes Hotspots Seismic tomography Planetary tectonics cMB topography Perm Anomaly

Influence of a non-rotating shoulder on heat generation,microstructure and mechanical properties of dissimilar AA2024/AA7050 FSW joints

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Journal of Materials Science & Technology 2018年第1期34卷 119-127页

作者： alessandro Barbini Jan carstensen Jorge F.dos Santos Helmholtz-Zentrum Geesthacht Institute of Materials Research Materials Mechanics Solid-State Joining Processes (WMP)

Friction stir welding （FSW） and stationary shoulder friction stir welding （SSFSW） were carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with thicknesses of 2 mm. A comparison between the two processes was performed by varying the welding speed while keeping the rotational speed constant, Through the analysis of the force and torque produced during welding and a simple analytical model, it was possible to show that in SSFSW there is more effective coupling with the tool and the heat produced is more efficiently distributed. This process decreases both the welding area and the diffusion at the interface of the two alloys compared with FSW. The minimum microhardness occurred at the advancing side （AS） at the interface between the thermo-mechanically affected zone （TMAZ） and the stir zone （SZ） in both processes, although the decrease was more gradual in SSFSW. This interface is also where all specimens failed for both welding technologies. An increase in tensile strength was measured in SSFSW compared with standard FSW. Furthermore, it was possible to establish the mechanical performance of the material in the fracture zone using digital image correlation.

关键词： Stationary shoulder friction stir welding Friction stir welding Dissimilar welded joints Process analysis Microstructure analysis Mechanical behaviour

Endoscopic management of difficult common bile duct stones:Where are we now?A comprehensive review

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World Journal of Gastroenterology 2021年第44期27卷 7597-7611页

作者： Alberto Tringali Deborah costa alessandro Fugazza Matteo c.lombo Kareem Khalaf alessandro Repici Andrea Anderloni Gastroenterology and Endoscopy Unit Department of MedicineConegliano HospitalULSS 2 Marca TrevigianaConegliano 31015Italy Digestive Endoscopy Unit Department of GastroenterologyHumanitas Research Hospital IRCCSRozzano 20089MilanItaly Department of Biomedical Sciences Humanitas UniversityPieve Emanuele 20072MilanItaly

Endoscopic management for difficult common bile duct(cBD)stones still presents a challenge for several reasons,including anatomic anomalies,patients’individual conditions and stone *** recent years,variable methods have emerged that have attributed to higher stone removal success rates,reduced cost and lower adverse *** this review,we outline a stepwise approach in cBD stone *** first line therapy,endoscopic sphincterotomy and large balloon dilation are recommended,due to a 30%-50%reduction of the use of mechanical *** the other hand,cholangioscopy-assisted lithotripsy has been increasingly reported as an effective and safe alternative technique to mechanical lithotripsy but remains to be reserved in special settings due to limited large-scale *** discussed,findings suggest that management needs to be tailored to the patient’s characteristics and anatomical ***,we evaluate the management of cBD stones in various surgical altered anatomy(Billroth II,Roux-en-Y and Roux-en-Y gastric bypass).Moreover,we could conclude that cholangioscopy-assisted lithotripsy needs to be evaluated for primary use,rather than following a failed management *** addition,we discuss the importance of dissecting other techniques,such as the primary use of interventional endoscopic ultrasound for the management of cBD stones when other techniques have *** conclusion,we recognize that endoscopic sphincterotomy and large balloon dilation,mechanical lithotripsy and intraductal lithotripsy substantiate an indication to the management of difficult cBD stones,but emerging techniques are in rapid evolution with encouraging results.

关键词： common bile duct stones Balloon dilation Endoscopic retrograde cholangiopancreatography Endoscopic ultrasonography Anastomoses,Roux en y Double balloon enteroscopy Mechanical lithotripsy cholangioscopy

Pin-on-disc study of dry sliding behavior of co-free HVOFcoated disc tested against different friction materials

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Friction 2021年第5期9卷 1242-1258页

作者： Matteo FEDERIcI cinzia MENAPAcE alessandro MANcINI Giovanni STRAFFELINI Stefano GIALANELLA Department of Industrial Engineering University of TrentoTrento 32122Italy Brembo S.p.A. StezzanoBergamo 24040Italy

The dry sliding behavior of three commercial friction materials(codenamed FM1,FM2,and FM3)tested against a co‐free cermet coating produced by high‐velocity oxy‐fuel(HVOF)on gray cast‐iron discs is ***1 is a conventional low‐metallic friction material,FM2 is developed for using against HVOF‐coated discs,and FM3 is a cu‐free friction material with a low content of abrasives and a relatively high concentration of steel *** the tribological evaluation,they are tested on a pin‐on‐disc(PoD)test rig against co‐free HVOF‐coated discs,with particular attention to the running‐in stage,which is fundamental for the establishment of a friction layer between the two mating surfaces,i.e.,the pin and *** PoD tests are performed at room temperature(RT)and a high temperature(HT)of 300℃.At RT,all materials exhibit a long running‐in *** HT,no running‐in is observed in FM1 and FM2,whereas a shorter running‐in period,with respect to the RT case,is observed in FM3 followed by the attainment of a comparatively high coefficient of *** RT,the pin wear is mild in all cases but severe at ***3 shows the lowest wear rate at both ***,the coated disc shows no wear when sliding against the FM3 friction *** the results are interpreted considering the microstructural characteristics of the friction layers formed on the sliding *** findings of the present study provide insights into reducing wear in braking system components and hence reducing environmental particulate matter emissions from their wear,through the use of disc coatings.

关键词： friction materials sliding wear high‐velocity oxy‐fuel(HVOF)coatings pin‐on‐disc(PoD)testing

*** and Exploring Lineage Data as a Service

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Data Intelligence 2022年第2期4卷 226-242页

作者： alessandro Spinuso Malcolm Atkinson Federica Magnoni Koninklijk Nederlands Meteorologisch Instituut De BiltUtrecht 3731 GAThe Netherlands University of Edinburgh EdinburghEdinburgh EH89ABUnited Kingdom Istituto Nazionale Geofisica e Vulcanologia RomeLazio 00143Italy

We present a set of configurable Web service and interactive tools,s-ProvFlow,for managing and exploiting records tracking data lineage during workflow *** facilitates detailed analysis of single *** helps users manage complex tasks by exposing the relationships between data,people,equipment and workflow runs intended to combine *** logical model extends the PROV standard to precisely record parallel data-streaming *** metadata handling encourages users to capture the application context by specifying how application attributes,often using standard vocabularies,should be *** metadata records immediately help productivity as the interactive tools support their use in selection and bulk *** rapidly appreciate the power of the encoded semantics as they reap the *** improves the quality of provenance for users and *** in turn facilitates analysis of collections of runs,enabling users to manage results and validate *** fosters reuse of data and methods and facilitates diagnostic investigations and *** present S-ProvFlow's use by scientists,research engineers and managers as part of the DARE hyper-platform as they create,validate and use their data-driven scientific workflows.

关键词： Provenance Productivity Workflows Human-in-the-loop Visualisation

Bjorken Flow Revisited:Analytic and Numerical Solutions in Flat Space-Time coordinates

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communications in computational Physics 2023年第1期33卷 174-188页

作者： Daniele Simeoni alessandro Gabbana Sauro Succi Universit`a di Ferrara and INFN-Ferrara I-44122 FerraraItaly Bergische UniversitatWuppertal D-42119WuppertalGermany University of cyprus Physics departmentCY-1678 NicosiaCyprus Eindhoven University of Technology 5600MB EindhovenThe Netherlands center for Life Nano Science@La Sapienza Italian Institute of TechnologyViale Regina Elena 295I-00161 RomaItaly Istituto Applicazioni del calcolo National Research Council of ItalyVia dei Taurini 19I-00185 RomaItaly

In this work we provide analytic and numerical solutions for the Bjorken flow,a standard benchmark in relativistic hydrodynamics providing a simple model for the bulk evolution of matter created in collisions between heavy *** consider relativistic gases of both massive and massless particles,working in a(2+1)and(3+1)Minkowski space-time coordinate *** numerical results from a recently developed lattice kinetic scheme show excellent agreement with the analytic solutions.

关键词： Relativistic hydrodynamics heavy-ion collisions Bjorken flow lattice kinetic solvers

Are metabolic factors still important in the era of direct antiviral agents in patients with chronic hepatitis c?

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World Journal of Gastroenterology 2013年第41期19卷 6947-6956页

作者： alessandro Grasso Federica Malfatti Roberto Testa Gastroenterology Unit Department of Internal MedicineSan Paolo Hospital

The high rate of sustained viral response(SVR)to boceprevir or telaprevir-based triple therapy in hepatitis c(HcV)-related,non-cirrhotic na ve patients or relapsers to previous antiviral treatment leads clinicians to believe that the impact of metabolic host factors on SVR is minimal when triple therapy is used,unlike what is observed with the peginterferon and ribavirin *** concept is strongly expressed by some opinion leaders on the basis of the data derived from subanalyses of registrative trials as well as from a post-hoc analysis of the phaseⅡc208 clinical *** perception of unrestrainable therapeutic success with the use of newer,more powerful antivirals is now reinforced by the brilliant results obtained with sofosbuvir,an HcV NS5B polymerase inhibitor,as well as by the data from the phaseⅡandⅢstudies on the various combinations of second-generation NS3/4A inhibitors and NS5A and/or NS5B ***,a great deal of concern has emerged from the real world scenario in which patients are often older and have more comorbidities than patients in the"world of trials".Furthermore,many of them have advanced fibrosis and previous failure with peginterferon and ribavirin *** data from the recent literature suggest that the host metabolic factors may play a minor but non-negligible role in these difficult-to-treat patients,an issue that will hopefully be investigated in further *** editorial aims to provide a detailed analysis of the role that host metabolic factors played in the past and what role they may play in the era of direct antiviral agents.

关键词： Metabolic factors Insulin resistance Direct antiviral agents chronic hepatitis c