基于小波的搜索量聚类及在变量选择中的应用

针对使用网络购物搜索量数据建立预测模型时的变量选择问题,提出一种基于连续小波变换(CWT)及其逆变换的聚类方法。算法充分考虑了搜索量的数据特征,将原始序列分解成为不同时间尺度下的周期成分,并重构为输入向量。在此基础上通过加权模糊C均值(FCM)方法进行聚类。变量选择是根据聚类后每个分类中的关键词隶属度函数值确定的,选择效果通过我国居民消费价格指数(CPI)的预测模型进行验证。结果表明,搜索量序列具有不同长度的周期成分,聚类后同组关键词具有明显的商品类型一致性。与其他变量选择方法相比,基于小波重构序列聚类的预测模型具有更高的预测精度,单步和三步预测相对误差仅为0.3891%和0.5437%,预测变量也具有清晰的经济含义,因此特别适用于解决大数据背景下高维预测模型的变量选择问题。     

高氮双相不锈钢6.2 t扁锭电渣重熔的工艺实践

2205双相不锈钢6.2 t 200 mm×1250 mm扁锭（/%:0.015~0.016C,0.15~0.16Si,1.35~1.39Mn,0,005~0.006S,0.023~0.024P,22:78~22.95Cr,5.40Ni,3.15~3.17Mo,0.193~0.194N）由20 t双极串联抽锭电渣重熔炉生产。通过采用50CaF₂-19Al₂O₃-19CaO-6MgO-6SiO₂液态熔渣,控制抽锭速度12 mm/min,电极熔化速度1100~1200 kg/h等工艺措施,扁锭表面质量良好,表面修磨量≤3 mm,满足轧制要求。     

连铸过程中电磁流体力学的数值模拟现状及发展趋势

对连铸过程中电磁流体力学的数值模拟的研究现状进行了综合评述。介绍了一种应用于连铸过程中的低频电磁流体力学数值模拟的新方法,并给出了其在圆坯旋转搅拌、CSP薄板坯电磁制动和板坯二冷辊式行波搅拌中的应用实例。该方法特点是分别建立电磁场模型和流场模型,并采用磁感应方程实现电磁场和流场模型之间的耦合。结果表明,目前的方法可较为准确地描述连铸过程中的电磁场分布和电磁流体力学特点,并能够对电磁搅拌参数和连铸工艺过程进行优化。最后,提出了连铸过程中电磁流体力学数值模拟技术的未来发展趋势。     

钛微合金化技术发展现状

介绍了单一钛以及铌钛、钒钛、锰钛、钼钛复合添加时的微合金化作用;着重分析了钛的析出热力学和钛的析出行为在薄板坯连铸连轧过程与传统连铸连轧过程中的差异,以掌握钛的析出规律;并提出了钛微合金化的技术要点,包括成分设计、冶炼技术和控轧控冷技术。对钛微合金化技术的分析将对钛微合金化的工业应用和技术发展具有一定指导意义。     

Identification of LPV Models with Non-uniformly Spaced Operating Points by Using Asymmetric Gaussian Weights

In this paper, asymmetric Gaussian weighting functions are introduced for the identification of linear parameter varying systems by utilizing an input-output multi-model structure. It is not required to select operating points with uniform spacing andmore flexibility is achieved. To verify the effectiveness of the proposed approach, severalweighting functions, including linear, Gaussian and asymmetric Gaussianweighting functions, are evaluated and compared. It is demonstrated through simulations with a continuous stirred tank reactor model that the proposed approach provides more satisfactory approximation.     

单质起爆药本质安全连续自动化生产技术

论述了单质起爆药的连续自动化生产技术、安全保障技术、多参数精确控制的配料技术、化合多参数综合控制技术、在线自动筛选、称量、装盒技术、防爆机械手自动传输技术、隔爆防爆技术和本质安全技术等多项关键技术突破情况,实现了单质起爆药生产过程的自动化合计量加料、多参数控制化合、负压水洗、在线烘干、自动筛选计量装盒以及液态、固态自动物流传输等。     

连铸坯氢氧火焰断火切割技术

采用氢氧火焰断火切割技术切割连铸坯,与不断火切割相比具有更好的社会经济效益,是建设资源节约型、环境友好型社会,走可持续发展道路的具体举措之一。     

The Future of Information Modelling and the End of Theory: Less is Limited,More is Different

The computational design strategist Cynthia Ottchen , who was previously Head of Research and Innovation at OMA, offers insights into the future of building information modelling (BIM). Now in the Petabyte Age of the data deluge, she argues that in our adoption of BIM we have to surpass mere data collection and technical optimisation and open up new ways of thinking with the creative use of ‘soft data’. Copyright © 2009 John Wiley & Sons, Ltd.     

A novel continuous arterial spin labeling approach for CBF measurement in rats with reduced labeling time and optimized signal-to-noise ratio efficiency

Objective  To develop a continuous arterial spin labeling (CASL) perfusion imaging method for cerebral blood flow (CBF) measurement in rats with reduced spin-labeling length and optimized signal-to-noise ratio (SNR _f ) per unit time. Materials and methods  In the proposed method, the longitudinal magnetization of brain tissue water in the imaging slice is prepared into a proper state before spin-labeling, and a post-tagging delay is employed after spin-labeling. The method was implemented on a 4.7 T small animal scanner. Numerical simulations and in vivo experiments were used to evaluate the performance of the method proposed. Results  With the proposed method, absolute CBF could be measured accurately from normal rat with a spin-labeling pulse as short as 400 ms, and yet employing the same formula as that used in the conventional CASL perfusion imaging method for calculation. The method also showed improved SNR _f per unit time over the conventional CASL perfusion imaging method and the pulsed arterial spin labeling perfusion imaging method FAIR. Conclusion  Compared to the conventional CASL perfusion imaging method, the proposed method would be advantageous for CBF measurement in small animals having short vascular transit time in terms of SNR _f per unit time and other benefits brought by shortened spin-labeling pulse.     

连铸二次冷却水数模控制的优势分析

介绍了连铸二冷水数模控制技术的构成,通过对比分析在同等条件下采用数模控制方式和参数控制方式时喷水量与浇铸速度的关系,得出了数模控制方式优于参数控制方式的结论.