二辊轧机轧辊堆焊新技术应用

介绍了二辊粗轧机轧辊利用堆焊新技术开展堆焊修复试验与应用，并介绍了堆焊材料的选择、堆焊工艺以及取得的良好效果。     

First-Principles Study of the High-Temperature Behaviors of the Willemite-Ⅱ and Post-Phenacite Phases of Silicon Nitride

The structural and elastic properties of the recently-discovered wⅡ- and δ-Si_3N_4 are investigated through the plane-wave pseudo-potential method within ultrasoft pseudopotentials.The elastic constants show that wⅡ- and δ-Si_3N_4 are mechanically stable in the pressure ranges of 0-50 GPa and 40-50 GPa,respectively.The α→wⅡ phase transition can be observed at 18.6 GPa and 300 K.The β→δ phase transformation occurs at pressures of 29.6,32.1,35.9,39.6,41.8,and 44.1 GPa when the temperatures are100,200,300,400,500,and 600 K,respectively.The results show that the interactions among the N-2s,Si-3s,3p bands(lower valence band) and the Si-3p,N-2p bands(upper valence band) play an important role in the stabilities of the wⅡ and S phases.Moreover,several thermodynamic parameters(thermal expansion,free energy,bulk modulus and heat capacity) of δ-Si_3N_4 are also obtained.Some interesting features are found in these properties.δ-Si_3N_4 is predicted to be a negative thermal expansion material.The adiabatic bulk modulus decreases with applied pressure,but a majority of materials show the opposite trend.Further experimental investigations with higher precisions may be required to determine the fundamental properties of wⅡ- andδ-Si_3N_4.     

原位模板法在铝基底上制备TiO2纳米管阵列薄膜

采用液相沉积法，将铝基多孔阳极氧化铝（AAO）模板浸入到（NH4）2TiF6溶液中，制备出高度有序的TiO2纳米管阵列薄膜，并在不同的温度下进行了热处理。用场发射扫描电子显微镜、透射电子显微镜和X射线衍射仪等手段对试样的微观形貌、结构及物相进行了表征。结果表明，TiO2纳米管的形貌依赖于AAO的特征，薄膜是由外径大约200nm，壁厚约40nm的TiO2纳米管阵列组成，薄膜厚度约25μm。原位模板法制备的TiO2纳米管阵列薄膜为非晶态，在400℃空气中焙烧2h转变为锐钛矿相TiO2。经过650℃焙烧仍保持纳米管结构，表现出较好的热稳定性。     

电脉冲孕育处理Al-22Si合金衰退性的研究

研究了电脉冲孕育处理后不同静置时间对Al-22Si合金凝固组织中初生相形态、大小、分布的影响。结果表明，电脉冲处理后立刻浇注对Al-22Si合金有较明显的变质作用，初生Si相形态由粗大板条状变为块状，其平均尺寸由153．15μm降至77．35μm，分布也较均匀；但电脉冲处理也存在着较明显的衰退性，即随着熔体静置时间的延长孕育效果逐渐消失，当静置时间为80min时，其组织形态与未经电脉冲处理的组织相似，其平均尺寸由77．35μm升至143．67μm。     

电脉冲孕育处理对Al-5Cu合金热裂的影响

研究了不同电脉冲孕育处理参数对Al-5Cu合金热裂倾向的影响.结果表明,不同电脉冲孕育处理参数均可降低Al-5Cu合金的热裂倾向,处理后该合金热裂临界应力比未处理试样提高了约3倍.合金热裂倾向改善的原因是,电脉冲孕育处理细化了Al-5Cu合金组织,减少了共晶相的数量,缩短了合金凝固温度区间.     

Influences of Ta, Nb, or Mo additions in Zr-based bulk metallic glasses on microstructure and thermal properties

The master-alloy ingots for casting bulk metallic glasses are routinely prepared by arc melting a mixture of pure elements. This paper addresses the difficulty in achieving complete and homogeneous melting of refractory component additions in Zr-based BMGs using the above procedure, and its influences on the microstructure and thermal behavior of alloys.     

Casting structure of pure aluminum by electric pulse modification at different superheated temperatures

Electric pulse modification （EPM） is a novel technique that reduces grain size by altering the structure of a melt. It was investigated that the response of the casting structure of high pure aluminum to EPM in different superheated melts. The results indicate that the grain refining effect of a given pulse electric field holds an optimal temperature range, moreover, a lower or higher superheated temperature will both disadvantage the improvements of casting structure. It essentially lies in the cooperative action between the distorted absorption of clusters and the activated capability of atoms in the aluminum melt.     

Gold Nanocages: Engineering Their Structure for Biomedical Applications

The galvanic replacement reaction between a Ag template and HAuCl₄ in an aqueous solution transforms 30–200 nm Ag nanocubes into Au nanoboxes and nanocages (nanoboxes with porous walls). By controlling the molar ratio of Ag to HAuCl₄, the extinction peak of resultant structures can be continuously tuned from the blue (400 nm) to the near‐infrared (1200 nm) region of the electromagnetic spectrum. These hollow Au nanostructures are characterized by extraordinarily large cross‐sections for both absorption and scattering. Optical coherence tomography measurements indicate that the 36 nm nanocage has a scattering cross‐section of ～ 0.8 × 10^–15 m² and an absorption cross‐section of ～ 7.3 × 10^–15 m². The absorption cross‐section is more than five orders of magnitude larger than those of conventional organic dyes. Exposure of Au nanocages to a camera flash resulted in the melting and conversion of Au nanocages into spherical particles due to photothermal heating. Discrete‐dipole‐approximation calculations suggest that the magnitudes of both scattering and absorption cross‐sections of Au nanocages can be tailored by controlling their dimensions, as well as the thickness and porosity of their walls. This novel class of hollow nanostructures is expected to find use as both a contrast agent for optical imaging in early stage tumor detection and as a therapeutic agent for photothermal cancer treatment.     

Combined Petri net modelling and AI-based heuristic hybrid search for flexible manufacturing systems—part II. Heuristic hybrid search

This two-part paper presents modelling and scheduling approaches of flexible manufacturing systems using Petri nets (PNs) and artificial intelligence (AI)-based heuristic search methods. In Part I, PN-based modelling approaches and basic AI-based heuristic search algorithms were presented. In Part II, a new heuristic function that exploits PN information is proposed. Heuristic information obtained from the PN model is used to dramatically reduce the search space. This heuristic is derived from a new concept, the resource cost reachability matrix, which builds on the properties of B-nets proposed in Part I. Two hybrid search algorithms, (1) an approach to model dispatching rules using analysis information provided by the PN simulation and (2) an approach of the modified stage-search algorithm, are proposed to reduce the complexity of large systems. A random problem generator is developed to test the proposed methods. The experimental results show promising results.     

平展流燃烧器内湍流输运过程的数值模拟

采用任意拉格朗日一欧拉(ALE)框架下的有限体积法对平展流湍流输运特性进行了数值模拟研究。根据平展流特征对湍流模拟的κ-ε模型进行了修正，并对计算网格的生成进行了探讨，在此基础上分析了旋流强度对平展流输运特性的影响以及两个平行平展流间的相互作用。