西方规划师职业素养的形成及启示

规划师的角色由规划实践所承担的社会活动决定。回顾西方规划师角色的演变过程可以发现,社会对规划师的素养要求随着时代演进而叠加。研究通过对英美规划师职业操守守则、高等规划教育体系的综合分析,讨论了西方规划师的三种核心职业素养的内涵及其培养重点,包括价值观、知识和技能。在此基础上,研究分析我国所处的历史阶段、城镇化所面临的新形势,提出我国规划师应从空间形态设计师走向协调型设计师,从技术型专家走向专家型社会工作者的两种角色转变趋势,同时提出了对我国未来规划师的价值观、知识和技能等核心素养的要求。     

消除成品表面裂纹的轧制关系分析

针对方坯或板坯原始表面存在一定深度的裂纹,讨论了轧前加热烧损量对坯料裂纹深度的影响,通过对不同断面形状坯料原始裂纹深度与轧制变形关系的理论计算,编制相应的计算程序,确定了方坯或板坯原存最大裂纹深度为T0max时,消除或减轻其相应成品表面裂纹的轧制关系分析。     

An efficient lightweight design strategy for body-in-white based on implicit parameterization technique

Structural and Multidisciplinary Optimization - In the early design phase of vehicles, performing lightweight design of body-in-white (BIW) using shape, size and topology optimization is a...     

Applications of inherent strain and interface element to simulation of welding deformation in thin plate structures

Welding-induced distortion not only reduces largely manufacturing accuracy but also decreases significantly productivity due to correction works. If welding distortion can be predicted through a simple and practical method beforehand, the predictions will be helpful for taking active as well as appropriate measures to control the dimension accuracy. Based on inherent strain theory and interface element formulation, we developed a practical prediction system to compute the accumulated distortion during the welding assembly process in the current study. Using the developed prediction method, we calculated the welding distortion in a thin plate structure with considering both the shrinkage due to heat input and the gap/misalignment generated during assembly process. Meanwhile, we investigated the influences of assembly sequence and gap correction on the final distortion.     

A novel non-Lyapunov approach through artificial bee colony algorithm for detecting unstable periodic orbits with high orders

In this paper, a novel non-Lyapunov way is proposed to detect the unstable periodic orbits (UPOs) with high orders by a new artificial bee colony algorithm (ABC). And UPOs with high orders of nonlinear systems, are one of the most challenging problems of nonlinear science in both numerical computations and experimental measures. The proposed method maintains an effective searching mechanism with fine equilibrium between exploitation and exploration. To improve the performance for the optimums of the multi-model functions and to avoid the coincidences among the UPOs with different orders, we add the techniques as function stretching, deflecting and repulsion to ABC. The problems of detecting the UPOs are converted into a non-negative functions’ minimization through a proper translation, which finds a UPO such that the objective function is minimized. Experiments to different high orders UPOs of 5 wellknown and widely used nonlinear maps indicate that the proposed algorithm is robust, by comparison of results through the ABC and quantum-behaved particle swarm optimization (QPSO), respectively. And it is effective even in cases where the Newton-family algorithms may not be applicable. Density of the orbits are discussed. Simulation results show that ABC is superior to QPSO, and it is a successful method in detecting the UPOs, with the advantages of fast convergence, high precision and robustness.     

Second order accuracy in phase field modeling of normal grain growth

The first and second order accuracy of phase field modeling of normal grain growth is investigated using asymptotic analysis. It is found that the model can achieve first order accuracy but fails to gain second order accuracy. The deviation in second order accuracy is proportional to the inverse of interface thickness so that phase field simulation approaches the sharp interface prediction as interface thickness increases. This result is confirmed by comparison of phase field simulation and analytical solutions, and it well explains the effect of interface thickness on phase field simulation of grain growth observed in previous work.     

浅谈钛材换热器的管板焊接

在氧化性、中性及含氯离子的介质中,钛的耐腐蚀性能均优于普通不锈钢和铝等。但钛材的焊接性能不好,焊接时极易产生氧化、氮化和脆化等缺陷。根据钛材的焊接特性,在焊接过程中有针对性地采取合理的保护措施,制定合适的焊接工艺,严格把好各个施工环节质量关,就能保证钛材的焊接质量。     

Computational and Experimental Study of the Transient Transport Phenomena in a Full-Scale Twin-Roll Continuous Casting Machine

Metallurgical and Materials Transactions B - To gain a fundamental understanding of the transient fluid flow in twin-roll continuous casting, the current paper applies both large eddy simulation...     

Role of oxygen in surface kinetics of SiO2 growth on single crystal SiC at elevated temperatures

Understanding surface kinetics of SiO₂ growth on single crystal SiC at elevated temperatures is crucial to fabricate high-performance SiC-based devices. However, the role of oxygen in the evolution mechanism of SiC surface at atomic scale has not been comprehensively elaborated. Here, we reveal the manipulation effect of oxygen on the competitive growth of thermal oxidation SiO₂ (TO-SiO₂) and thermal chemical vapor deposition SiO₂ (TCVD-SiO₂) on the 4H-SiC substrate at 1500 °C. TO-SiO₂ is formed by the thermal oxidation of SiC, in which the substrate undergoes layer-by-layer oxidation, resulting in an atomically flat SiC/TO-SiO₂ interface. TCVD-SiO₂ growth includes the sublimation of Si atoms, the reaction between sublimated Si atoms and reactive oxygen, and the adsorption of gaseous Si_xO_y species. A relatively high sublimation rate of Si atoms at SiC atomic steps causes the transverse evolution of the nucleation sites, leading to the formation of nonuniform micron-sized pits at the SiC/TCVD-SiO₂ interface. The low oxygen concentration favors TCVD-SiO₂ growth, whose crystal quality is much better than that of TO-SiO₂ due to the high surface mobility in the thermal CVD process. We further achieve the epitaxial growth of graphene on 4H-SiC in an almost oxygen-free reaction atmosphere. Additionally, ReaxFF reactive molecular dynamic simulation results illustrate that the decrease in oxygen concentration can promote the growth kinetics of SiO₂ on single crystal SiC from being dominated by thermal oxidation to being dominated by thermal CVD.