自升式移动平台结构安全评估

现在,有许多海洋平台在从事海上油气田的勘探和开发,其中自升式移动平台扮演着重要的角色.我国目前有自升式移动平台30座,这些平台大多经历了较长的服役期,有些平台的结构已发生了一些变化.如何保证这些平台的安全,最大限度地发挥其结构潜能是工程界和理论界迫切需要解决的问题.     

Calculation of Transient Stress Field During Laser Transformation Hardening Process

IntroductionHighpowerCOzlaserssdsetransformationhardeningtechniquehasbeensuccessfullyusedinindusnyforWYears.BecausethetemPeratUrefleldislocalizedinmaterialdurllglasertransfonnationhMngProcess,highthermstrCsswillgenerateinmatgrialduringlasertfansformationhardeningProcess.Therisalsohighresidualstressinmaterial,bothintCnsionandcomPression['-'].ComPressresidualstressishelptoincreasethefatigueldrimeofthelasertreatedmaterial,butthetensilestresswillshortenthefatiguelifetmeofthelasertreatedmator…     

RECENT DEVELOPMENT OF PROCESS SIMULATION AND ITS APPLICATIONS TO MANUFACTURING PROCESSES

l.IntroductionThemostboortantdrivingforceinmanufacturillistoPrOduCeabetterPrOductatalowercost.GenerallyeffecthemethodsinchideshOrtenintheleadtiminthedesigncyCle,andredUcinthetoolingcostandmaChinedOWnmeatProductionst4e.AllOfthemrewtabettertmderstandingofhO…     

Computer Simulation of Thermal-Mechanical Processing

AlterationIntroductionThereisastrongini6ractionamongtemPetalrefield,strCssfield,andmicrosttuctutulaltOrationinm8terialsduringtheirhotworking[l'2].Especiallyduringthecoolingprocess,inwhichtemPeratorechangnsgreatly,intendionsbecomemorecomplexbecauseoftransformationoccurmnce.Duringthehotdeformation,thingswillaPpearsuchas:a.hotdeformation,relatedtostressfieId,changesessentiallytheshaPeofmaterialsandcausesthevariationofthecontactstatebetWeenthedieandsample,resultinginchangeofthethermalboundnyco…     

金凤高速公路沥青混凝土路面的施工技术

高速公路在交通运输事业的发展速度不断加快,位置越来越重要。在道路建设过程中不断运用新的施工技术,尤其是沥青混凝土路面施工采用了很多新技术,在路面建设施工中发挥了巨大的作用。基于此,该文结合珠海金凤高速公路施工技术实例,对高速公路沥青混凝土路面施工方法和技术进行总结与探讨,可供同行参考。     

Dynamic response of offshore jacket structures under random loads

In this paper, the dynamic response of a scale model of a jacket offshore structure is investigated both theoretically and experimentally. The experiments were conducted both in air and in water. The in-water experiments were done in the towing tank of Memorial University to simulate the realistic operating conditions. The model was subjected to random wave loads. Froude's law of modeling was used to obtain the dimensions of the scale model based on the dimensions of an existing structure. The effects of varying the structure's weight, and the characteristics of the wave loading were investigated. The structure's weight was changed by adding weights to the structure's deck. A finite element model was designed to determine the dynamic response of the model. Excellent agreement between the experimental and theoretical results was obtained.The reaction force at the foundation was estimated from strain measurements and compared with the finite element calculations. Fair agreement was obtained.This work is the first stage of a project whose objective is to develop a method for structural damage detection using the free vibration response of the structure. The free vibration response will be obtained from the stationary random response of the structure using the random decrement method. Having an accurate model to describe the dynamic response of the structure is the first step in this study.     

Review of Secure Communication Approaches for In-Vehicle Network

In the connected vehicles, connecting interfaces bring threats to the vehicles and they can be hacked to impact the vehicles and drivers. Compared with traditional vehicles, connected vehicles require more information transfer. Sensor signals and critical data must be protected to ensure the cyber security of connected vehicles. The communications among ECUs, sensors, and gateways are connected by in-vehicle networks. This paper discussed the state-of-art techniques about secure communication for in-vehicle networks. First, the related concepts in automotive secure communication have been provided. Then we have compared and contrasted existing approaches for secure communication. We have analyzed the advantages/disadvantages of MAC and digital signatures for message authentication and compared the performance and limitations of different cryptographic algorithms. Firewall and intrusion detection system are introduced to protect the networks. The constraints and features of different intrusion detection approaches are presented. After that, the technical requirements for cryptographic mechanism and intrusion detection policy are concluded. Based on the review of current researches, the future development directions of the automotive network security have been discussed. The purpose of this paper is to review current techniques on automotive secure communication and suggest suitable secure approaches to implement on the in-vehicle networks.     

Analysis on Ground Surface Deformation and Influence of Construction Parameters Caused by Two Different Shield Machines in Double-tube Tunnelling北大核心CSCD

Based on a shield-driven running tunnel project of Hangzhou Metro Line 2, this paper carries out field measuring of the ground surface deformation caused by two different shield machines in double-tube tunnelling in soft soil areas, obtains the laws of the surface deformation caused by shield-driven double-tube tunnelling and verifies the applicability of the modified Peck formula to double-tube tunnelling. The results show that in soft soil areas the impacts on ground surface deformation caused by different shield construction parameters in the previously and subsequently excavated tunnels are different, while the surface deformation changes sharply before and after the shield machine passing through the cutting face, and a rebound phenomenon occurs when the shield tail passes through the cutting face due to the influence of the grouting; The cutterhead torque of the shield machine in soft soil areas can be composed of five calculation factors, and the calculation results are in good agreement with the measured values. The larger the opening rate of the shield cutterhead is, the larger the average torque value will be, the higher the percentage of large ground loss rate will be, and the larger the maximum ground surface settlement will be; The ratio of cutterhead torque T to mucking volume per ring Q is used as the control parameter for analyzing the ground surface settlement, and a certain positive correlation between the ratio and the surface settlement value is determined, the smaller the cutterhead opening rate is, the more accurate the fitting results will be. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Chaotic movement of vortices in superconductors of high-Tc superconducting maglev system at a high speed

Vortex motion in superconductors of higb-Tc superconducting maglev system is studied by a computational simulation.The vortex system is treated in a similar fashion,as a system where defects arc arrang...     

Multiaxial stress creep rupture mechanisms of AZ31 magnesium alloy

The maximum principal stresses, von Mises effective stresses and principal facet stresses at the time of creep rupture were compared in uniaxial, biaxial, and triaxial stress states for AZ31 magnesium alloy. The creep rupture of this alloy was experimentally controlled by cavitation, which was the result of a low damage tolerance, λ. Creep deformation could be correlated with the von Mises effective stress parameter. The failure-mechanism control parameter governing the stress state coincided with the experimental results of the rupture of the materials under multiaxial stress states. Finally, the theoretical prediction based on constrained cavity growth and continuous nucleation agreed with the experimental rupture data to within a factor of three.