다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

This paper presents control and coordination algorithms for groups of vehicles. The focus is on autonomous vehicle networks performing distributed sensing tasks where each vehicle plays the role of a mobile tunable sensor. The paper proposes gradient descent algorithms for a class of utility functions which encode optimal coverage and sensing policies. The resulting closed-loop behavior is adaptive, distributed, asynchronous, and verifiably correct.

Coverage control for mobile sensing networks

A review on the attention mechanism of deep learning

Thermal barrier systems have been the subject of vigorous research and development activities over the past few years, driven by the demands for enhanced reliability and substantially higher operating temperatures envisaged for the next generations of gas turbine engines. The menu of candidate materials and architectures has expanded considerably, including numerous concepts based on zirconia as well as radically different materials, multilayers and modulated distributions of porosity and chemical composition. Advances in deposition processes enable increased flexibility for tailoring composition and microstructure to local requirements within the coating system, e.g. for thermal insulation, control of interdiffusion, enhanced resistance against environmental degradation and condition monitoring. Many challenges remain but healthy and growing collaborations between the science and technology communities bode well for future progress in this area.

Emerging materials and processes for thermal barrier systems

Multi-objective meta-heuristics: An overview of the current state-of-the-art

The work described in this paper is the development of a buckling model based on the classical energy method of flange area material using a one-dimensional beam geometry assumption to predict flange wrinkling in hot deep drawing aluminium alloys with macro-textured blankholder surfaces. A series of deep drawing experiments utilising different macro-textured tool surfaces were performed to investigate the effects of process parameters and texture features on flange wrinkling. The results have shown that wrinkling occurs when the hollow dimension of radially grooved textures reached a certain magnitude dependent on process conditions. A dislocation-driven based continuum damage mechanism (CDM) material model for aluminium alloys at elevated temperatures was used to model the viscoplastic behaviour during deformation. The newly developed buckling model was validated by comparison with experimental results. The predicted results showed that the resistance to wrinkling increases with increasing forming temperature and decreasing forming speed, depending on the particular viscoplastic characteristics of the work-piece. The effects of texture ratio and draw ratio on wrinkling were found to be more significant than the effects of the temperature and strain rate. The buckling model developed in this paper can be used to model the flange wrinkling phenomena, as well as the non-isothermal feature in the hot stamping condition using the macro-textured tool surfaces.

/pdf/a-buckling-model-for-flange-wrinkling-in-hot-deep-drawing-3yjjne8mpl.pdf

A buckling model for flange wrinkling in hot deep drawing aluminium alloys with macro-textured tool surfaces

Modelling of microstructural evolution in multipass hot rolling

Effect of machining-induced residual stresses on springback of creep age formed (CAFed) AA2050 plates with asymmetric creep-ageing behaviour has been investigated experimentally and numerically in this study. A finite element (FE) model integrating unified asymmetric creep-ageing constitutive model for CAF of AA2050 has been developed through a commercial FE software-PAM-STAMP and a simplified machining-induced residual stress field for aluminium alloy plates has been proposed and implemented into the FE model. Different levels of residual stresses have been considered in the FE model and numerical results have been compared with corresponding CAF experiments and surface residual stress measurements. Results show that the springback prediction of the FE models has been significantly improved when the residual stress effect was considered. The best prediction can be achieved with a certain residual stress level for each plate thickness and the level increases with decreasing thickness of the plates produced by machining, which agrees well with the surface residual stress measurement results. For CAF of AA2050 with asymmetric creep-ageing behaviour, different springback behaviour has been observed with different residual stress levels: introduction of residual stress fields can either decrease or increase formed deflections of CAFed AA2050 plates, depending on the relative levels of residual stresses and the stresses caused by applied external forces. When the residual stress is large, subsurface of the plate may exceed the elastic limit after applying external force, leading to a significant decrease of springback in the CAFed plates.

/pdf/effect-of-machining-induced-residual-stress-on-springback-of-2vaqx1b7fn.pdf

Jianguo Lin

Papers

A buckling model for flange wrinkling in hot deep drawing aluminium alloys with macro-textured tool surfaces

Modelling of microstructural evolution in multipass hot rolling

Effect of machining-induced residual stress on springback of creep age formed AA2050 plates with asymmetric creep-ageing behaviour

Quantification of thermal residual stresses relaxation in AA7xxx aluminium alloy through cold rolling

FE simulation of asymmetric creep-ageing behaviour of AA2050 and its application to creep age forming