连铸生产中过程参数对夹杂物分离和分布的影响

作为连铸机中一个重要的设备,中间包是连接非连续的钢包冶炼和连续的结晶器中铸坯凝固的连接设备。中间包在生产超纯净钢过程中承担着重要角色,其主要目的是尽可能细化各钢种的夹杂物并提高钢水纯净度,尤其是当钢包更换而导致进入中间包钢水条件改变时。夹杂物会影响后续压力加工过程,且经常导致材质性能失效。钢水的纯净度对满足客户性能要求起着至关重要的作用。采用比例为1:3的单流中间包水模研究了不锈钢中夹杂物的去除。水模中的浸入式水口上配备有一个粒子计数器,此计数器可以计算出直径大于25μm的粒子分离率。由于粒度分布的相似性,水模中的粒子沉积速率可以转换到实际中间包中的熔体流动。对流动改变装置(例如冲击板)的影响进行了研究,同样也研究了有无冲击板条件下的不同尺寸粒子在中间包的粒子分布状态。采用雷诺应力湍流模型,应用有限体积商业软件FLUENT,进行了数值模拟。离散相的建模采用欧拉-拉格朗日方法。表面处颗粒分离采用一种特殊的边界条件。     

Inertial Waves Occurring in a Liquid Metal Column due to Pulsed Excitation by a Rotating Magnetic Field

We present an experimental study concerning the flow inside a liquid metal column exposed to a pulsed rotating magnetic field.This paper is aimed at highly resolved,quantitative velocity measurements in the eutectic GalnSn alloy.A novel ultrasound Doppler system was used two measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane.It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution.The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures.The results demonstrate that the arising flow structure depends sensitively on the frequency of the RMF pulses.A maximum intensity of a periodic meridional flow can be observed,if the corresponding pulse frequency fp relates to the eigenperiod of the respective inertial mode in a developed regime.The electromagnetic stirring method that uses a modulated RMF offers considerable potential to enhance the stirring efficiency and to optimize the properties of castings by a well-aimed flow control during solidification.     

Application of MHD-Principles in Metallurgy

The paper describes MHD-methods for creating a pumping effect in metallurgical installations for pumping liquid metals.     

(Computer) Vision without Sight

Computer vision holds great promise for helping persons with blindness or visual impairments (VI) to interpret and explore the visual world. To this end, it is worthwhile to assess the situation critically by understanding the actual needs of the VI population and which of these needs might be addressed by computer vision. This article reviews the types of assistive technology application areas that have already been developed for VI, and the possible roles that computer vision can play in facilitating these applications. We discuss how appropriate user interfaces are designed to translate the output of computer vision algorithms into information that the user can quickly and safely act upon, and how system-level characteristics affect the overall usability of an assistive technology. Finally, we conclude by highlighting a few novel and intriguing areas of application of computer vision to assistive technology.     

Nanoindentation and Wear Characteristics of Al 5083/SiC_p Nanocomposites Synthesized by High Energy Ball Milling and Spark Plasma Sintering

Al 5083/10 wt% SiC p nano composites have been synthesized by means of high energy ball milling followed by spark plasma sintering (SPS). Nano composites produced via this method exhibited near-theoretical density while retaining the nano-grained features. X-ray diffraction (XRD) analysis indicated that the crystalline size of the ball milled Al 5083 matrix was observed to be ～25 nm and it was coarsened up to ～30 nm after SPS. Nano indentation results of nano composites demonstrated a high hardness of ～280 HV with an elastic modulus of 126 GPa. Wear and friction characteristics with addition of SiC p reinforcement exhibited significant improvement in terms of coefficient of friction and specific wear rate to that of nano structured Al 5083 alloy. The reduction in specific wear rate in the nanocomposite was mainly due to the change of wear mechanism from adhesive to abrasive wear with the addition of SiC p which resulted in high hardness associated with nano-grained microstructure.     

Use of the radiofrequency-intermodulation distortion technique to investigate intrinsic nonlinearity at the electrode-electrolyte interface

We report on investigations of nonlinear radiofrequency responses of electrolytes with Na(+) and Cl(-) ions placed within gold electrodes of a capacitor. The sample was part of a frequency-adjustable inductance-capacitance-resistance (LCR) parallel resonant circuit, and measurements were carried out using the two frequencies intermodulation distortion technique. We employed double layer model to analyze the observed nonlinearities and their dependence on ionic concentration. Electrode-electrolyte interface polarization was found to be a predominant cause of this intrinsic nonlinearity and to be dependent on electrolytic ion concentration. We also measured and calculated coefficients of resistive and capacitive components of the observed nonlinearity.     

Experimental study on fly ash capture mercury in flue gas

Systematic experiments were conducted on a fixed-bed reactor to investigate the interaction between fly ash and mercury,the results implied that fly ash can capture mercury effectively.Among different fly ashes,the unburned carbon in the FA2 and FA3 fly ashes has the highest mercury capture capacity,up to 10.3 and 9.36 μg/g,respectively,which is close to that of commercial activated carbon.There is no obvious relationship between mercury content and carbon content or BET surface area of fly ash.Petrography ...     

穿越伊比利亚半岛——西班牙、葡萄牙景观设计的交流与互动之旅

时而踏出自己熟悉的舒适空间．无疑会有助于增进交流、提升创意灵感。2009年11月纵跨西班牙、葡萄牙和北非的十目之旅．为一大批来自中国各地的建筑师和景观设计师提供了这样的机会。此次活动并非《景观设计》杂志社组织的首次海外之行,但这却是首次通过流动会议的形式所组织的海外考察。     

Two-dimensional linear-combination model fitting of magnetic resonance spectra to define the macromolecule baseline using FiTAID,a Fitting Tool for Arrays of Interrelated Datasets

Object  

To propose the determination of the macromolecular baseline (MMBL) in clinical 1H MR spectra based on T₁ and T₂ differentiation using 2D fitting in FiTAID, a general Fitting Tool for Arrays of Interrelated Datasets.     

Relevance of the skewness index in DTI exploration of multiple sclerosis

Object  To this day, no parameter can really monitor the progression of multiple sclerosis (MS). In this study, an index the skewness (S) derived from parameters calculated in diffusion tensor imaging (DTI) has been tested on MS patients for its ability to monitor the disease course. Materials and methods  Eighteen patients underwent two examinations within 3 months consisting of a clinical evaluation (EDSS) and DTI acquisitions on a 1.5 T imager. Tensor was calculated thanks to“home-made” software. Mean diffusivity (MD) and fractional anisotropy (FA) histograms were described for normal-appearing white matter (NAWM) and gray matter (GM) of patients with S and also with usually indices peak position (pp) and peak height (ph) for the whole group of patients and for two separate groups according to their clinical status (EDSS  ≤  3 and EDSS  > 3 at month 0). Results  Although no significant clinical evolution is observed over 3 months, S in GM showed a significant shift for both MD/FA histograms towards abnormal values for the whole group of patients (p = 0.02/p = 0.04) and for the group with EDSS  ≤  3 (p = 0.04/p = 0.007), while ph and pp do not. Conclusion  S in GM could be an alternative marker to monitor the disease course before the repercussion on the clinical score.