用于抵抗扭转采取边缘弹性约束下的单轴压缩下板材极限强度:一种新的综合方法

The ultimate strength of platings under compression is one of the most important factors to be addressed in the ship design.Current Rules for ship structural design generally provide explicit strength check criteria against buckling for simply supported and clamped platings.Nevertheless,ship platings generally exhibit an intermediate behaviour between the simple support and the clamped conditions,which implies that the torsional stiffness of supporting members should be duly considered.Hence,the main aim of this study is the development of new design formulas for the ultimate strength of platings under uniaxial compression,with short and/or long edges elastically restrained against torsion.In this respect,two benchmark studies are performed.The former is devoted to the development of new equations for the elastic buckling coefficients of platings with edges elastically restrained against torsion,based on the results of the eigenvalue buckling analysis,performed by Ansys Mechanical APDL.The latter investigates the ultimate strength of platings with elastically restrained edges,by systematically varying the plate slenderness ratio and the torsional stiffness of supporting members.Finally,the effectiveness of the new formulation is checked against a wide number of finite element(FE)simulations,to cover the entire design space of ship platings.

双燃料船用发动机废能回收系统的技术经济比较

Nowadays alternative and innovative energy recovery solutions are adopted on board ships to reduce fuel consumption and harmful emissions.According to this,the present work compares the engine exhaust gas waste heat recovery and hybrid turbocharger technologies,which are used to improve the efficiency of a dual-fuel four-stroke(DF)marine engine.Both solutions aim to satisfy partly or entirely the ship’s electrical and/or thermal loads.For the engine exhaust gas waste heat recovery,two steam plant schemes are considered:the single steam pressure and the variable layout(single or dual steam pressure plant).In both cases,a heat recovery steam generator is used for the electric power energy generation through a steam turbine.The hybrid turbocharger is used to provide a part of the ship’s electric loads as well.The thermodynamic mathematical models of DF engines,integrated with the energy recovery systems,are developed in a Matlab-Simulink environment,allowing the comparison in terms of performance at different engine loads and fuels,which are Natural Gas(NG)and High Fuel Oil(HFO).The use of NG always involves better efficiency of the system for all the engine working conditions.It results that the highest efficiency value achievable is 56%at 50%maximum continuous rating(MCR)engine load.

Incidence of Pitting Corrosion Wastage on the Hull Girder Ultimate Strength

The paper focuses on the assessment of the hull girder ultimate strength,combined with random pitting corrosion wastage,by the incremental-iterative method.After a brief review about the state of art,the local ultimate strength of pitted platings under uniaxial compression is preliminarily outlined and subsequently a closed-form design formula is endorsed in the Rule incremental-iterative method,to account for pitting corrosion wastage in the hull girder ultimate strength check.The ISSC bulk carrier is assumed as reference ship in a benchmark study,devoted to test the effectiveness of the incremental-iterative method,by a comparative analysis with a set of FE simulations,performed by Ansys Mechanical APDL.Four reference cases,with different locations of pitting corrosion wastage,are investigated focusing on nine combinations of pitting and corrosion intensity degrees.Finally,a comparative analysis between the hull girder ultimate strength,combined with pitting corrosion wastage,and the relevant values,complying with the Rule net scantling approach,is performed.Based on current results,the modified incremental-iterative method allows efficiently assessing the hull girder ultimate strength,combined with pitting corrosion wastage,so revealing useful both in the design process of new vessels and in the structural health monitoring of aged ships.

Dating long thrust systems on Mercury:New clues on the thermal evolution of the planet

The global tectonics of Mercury is dominated by contractional features mainly represented by lobate scarps,high relief ridges,and wrinkle ridges.These structures are the expression of thrust faults and are linear or arcuate features widely distributed on Mercury.Locally,these structures are arranged in long systems characterized by a preferential orientation and non-random spatial distribution.In this work we identified five thrust systems,generally longer than 1000 km.They were named after the main structure or crater encompassed by the system as:Thakur,Victoria,Villa Lobos,Al-Hamadhani,and Enterprise.In order to gain clues about their formation,we dated them using the buffered crater counting technique,which can be applied to derive the ages of linear landforms such as faults,ridges and channels.To estimate the absolute age for the end of the thrust system's activity,we applied both Le Feuvre and Wieczorek Production Function and Neukum Production Functions.Moreover,to further confirm the results obtained with the buffered crater counting method,the classic stratigraphic approach has been adopted,in which a faulted and an unfaulted craters were dated for each system.The results gave consistent ages and suggested that the most movements along major structures all over Mercury most likely ended at about 3.6-3.8 Ga.This gives new clues to better understand the tectonics of the planet and,therefore,its thermal evolution.Indeed,the early occurrence of tectonic activity in the planet's history,well before than predicted by the thermophysical models,coupled with the orientation and spatial distribution of the thrust systems,suggests that other processes beside global contraction,like mantle downwelling or tidal despinning,could have contributed to the first stage of the planet's history.

How can the holder trust the verifier?A CP-ABPRE-based solution to control the access to claims in a Self-Sovereign-Identity scenario

The interest in Self-Sovereign Identity(SSI)in research,industry,and governments is rapidly increasing.SSI is a paradigm where users hold their identity and credentials issued by authorized entities.SSI is revolutionizing the concept of digital identity and enabling the definition of a trust framework wherein a service provider(verifier)validates the claims presented by a user(holder)for accessing services.However,current SSI solutions primarily focus on the presentation and verification of claims,overlooking a dual aspect:ensuring that the verifier is authorized to access the holder’s claims.Addressing this gap,this paper introduces an innovative SSI-based solution that integrates decentralized wallets with Ciphertext-Policy Attribute-Based Proxy Re-Encryption(CP-ABPRE).This combination effectively addresses the challenge of verifier authorization.Our solution,implemented on the Ethereum platform,enhances accountability by notarizing key operations through a smart contract.This paper also offers a prototype demonstrating the practicality of the proposed approach.Furthermore,it provides an extensive evaluation of the solution’s performance,emphasizing its feasibility and efficiency in real-world applications.

Lattice Boltzmann Analysis of Fluid-Structure Interaction with Moving Boundaries

This work is concerned with the modelling of the interaction of fluid flow with flexibly supported rigid bodies.The fluid flow is modelled by Lattice-Boltzmann Method,coupled to a set of ordinary differential equations describing the dynamics of the solid body in terms its elastic and damping properties.The time discretization of the body dynamics is performed via the Time Discontinuous Galerkin Method.Several numerical examples are presented and highlight the robustness and efficiency of the proposed methodology,by means of comparisons with previously published results.The examples show that the present fluid-structure method is able to capture vortexinduced oscillations of flexibly-supported rigid body.

Lattice Boltzmann Simulation of Cavitating Flows

The onset of cavitating conditions inside the nozzle of liquid injectors is known to play a major role on spray characteristics,especially on jet penetration and break-up.In this work,we present a Direct Numerical Simulation(DNS)based on the Lattice Boltzmann Method(LBM)to study the fluid dynamic field inside the nozzle of a cavitating injector.The formation of the cavitating region is determined via a multi-phase approach based on the Shan-Chen equation of state.The results obtained by the LBM simulation show satisfactory agreement with both numerical and experimental data.In addition,numerical evidence of bubble break-up,following upon flow-induced cavitation,is also reported.

Lattice Boltzmann Methods for Multiphase Flow Simulations across Scales

The simulation of multiphase flows is an outstanding challenge,due to the inherent complexity of the underlying physical phenomena and to the fact that multiphase flows are very diverse in nature,and so are the laws governing their dynamics.In the last two decades,a new class of mesoscopic methods,based on minimal lattice formulation of Boltzmann kinetic equation,has gained significant interest as an efficient alternative to continuum methods based on the discretisation of the NS equations for non ideal fluids.In this paper,three different multiphase models based on the lattice Boltzmann method(LBM)are discussed,in order to assess the capability of the method to deal with multiphase flows on a wide spectrum of operating conditions and multiphase phenomena.In particular,the range of application of each method is highlighted and its effectiveness is qualitatively assessed through comparison with numerical and experimental literature data.