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

Achieving uniform temperature within the effective gauge length in thermo-mechanical testing is crucial for obtaining accurate material data under hot stamping conditions. A new grip design for the Gleeble Materials-Simulator has been developed to reduce the long-standing problem of temperature gradient along a test-piece during thermo-mechanical tensile testing. The grip design process comprised two parts. For the first part, the new design concept was analysed with the help of Abaqus coupled Thermal-Electric Finite element simulation through the user defined feedback control subroutine. The second part was Gleeble thermo-mechanical experiments using a dog-bone test-piece with both new and conventional grips. The temperature and strain distributions of the new design were compared with those obtained using the conventional system within the effective gauge length of 40 mm. Temperature difference from centre to edge of effective gauge length (temperature gradient) was reduced by 56% during soaking and reduced by 100% at 700 °C. Consequently, the strain gradient also reduced by 95%, and thus facilitated homogeneous deformation. Finally to correlate the design parameters of the electrical conductor used in the new grip design with the geometry and material of test-piece, an analytical relationship has been derived between the test-piece and electrical conductor.

/pdf/a-novel-grip-design-for-high-accuracy-thermo-mechanical-22qlrlzsiy.pdf

A Novel Grip Design for High-Accuracy Thermo-Mechanical Tensile Testing of Boron Steel under Hot Stamping Conditions

The in-die quenching is a key stage in the hot stamping volume production chain which determines the post-formed strength of lightweight alloy components, tool life, and hot stamping productivity. In this paper, the performance of in-die quenching, reflected by the quenching efficiency (the time of work-piece held within stamping dies) and die surface temperature during the simulated hot stamping process of AA6082, was experimentally and analytically investigated. A range of in-die quenching experiments were performed for different initial work-piece and die temperatures, quenching pressures, work-piece thickness, and die clearances, under hot stamping conditions. In addition, a one-dimensional (1D) closed-form heat transfer model was used to calculate the die surface temperature evolution that is difficult to obtain during practical manufacture situations. The results have shown that the in-die quenching efficiency can be significantly increased by decreasing the initial work-piece and die temperatures. Die clearances are required to be designed precisely to obtain sufficiently high quenching rates and satisfying post-formed strength for hot-stamped panel components. This study systematically considered an extensive variety of influencing factors on the in-die quenching performance, which can provide practical guides for stamping tool designers and manufacture systems for hot-stamping volume production.

https://www.mdpi.com/2075-4701/8/4/231/pdf

Experimental investigations of the in-die quenching efficiency and die surface temperature of hot stamping aluminium alloys

http://spiral.imperial.ac.uk/bitstream/10044/1/43998/4/Paper%20Manu.pdf

Effect of forming parameters on electron beam Surfi-Sculpt protrusion for Ti–6Al–4V

When constructing a rigid tool surface with fillets using triangular Bezier surface patches for an FE forming simulation, it is difficult to determine the number of segments required to accurately model a blend arc. This paper presents a combined numerical and analytical method to investigate the error of approximating circular arcs using cubic Bezier curve segments. It is established that there is a linear variation of the error with respect to the Tangent Magnitude Parameter (TMP) in certain regions, and an approximate linear variation of the error against the number of curve segments in log–log scales. In addition, the location of the maximum error and its variation with respect to the TMP are illustrated and analysed. The results obtained are applied to the creation of rigid tool surfaces for FE forming simulations. Two FE analyses are carried out: one to simulate the process of superplastically forming a 3D rectangular box with fillet surfaces, and the other to wrap a decorative pattern onto an axisymmetric ceramic pot.

Jianguo Lin

Papers

A Novel Grip Design for High-Accuracy Thermo-Mechanical Tensile Testing of Boron Steel under Hot Stamping Conditions

Experimental investigations of the in-die quenching efficiency and die surface temperature of hot stamping aluminium alloys

Effect of forming parameters on electron beam Surfi-Sculpt protrusion for Ti–6Al–4V

Approximating circular arcs by Bézier curves and its application to modelling tooling for FE forming simulations

Influence of process parameters on properties of AA6082 in hot forming process