Φ150 mm圆坯结晶器电磁搅拌数值模拟研究

以结晶器电磁搅拌器为研究对象,建立了Φ150 mm断面结晶器电磁搅拌过程的电磁场与流场耦合的三维数学模型,并采用有限元软件进行求解。分别模拟不同条件下的结晶器电磁搅拌电流和不同电磁搅拌频率作用下钢液在结晶器内流动状态的规律。研究结果表明:随搅拌电流的增大,钢液的切向流速增加,上部环流区缩短,下部旋转流动区域上移并扩大,搅拌电流和频率对钢液流动的影响相反;在电磁搅拌过程中,电磁搅拌使结晶器内钢液产生旋转流动阻止过热钢液下移,减弱冲击深度,使热区明显的上移。     

国内外超导材料开发进展

超导是超导电性的简称。是一种材料,如某种金属、合金或化合物在一定的温度以下,电子可以无阻地流动,电阻变为零的性质。也就是说一个由超导材料做成的线圈当通上电流以后再把它闭合起来,进人超导态以后,电流就无阻地在线圈里面流动,电流衰减时间超过十万年,十万年以上才能够看到有衰减,所以物理上就认定电阻等于零。     

腐蚀防护与保护——改变电极电位

许多腐蚀反应属于电化学性质,表明腐蚀率由电化学腐蚀电位决定。改变腐蚀电位通常会引起腐蚀率的变化。腐蚀电位的改变可通过加入氧化剂实现,不过也可以通过施加外部电流来实现。当电流在一种腐蚀金属表面的阳极和阴极之间流动时,电流越大,阳极区腐蚀得越快。     

乳化液破乳试验研究

废乳化液是轧钢过程中排放的高浓度含油废水,处理的关键是破乳。文章通过试验研究选择合适的破乳方法,对电氧化破乳和化学混凝破乳的试验条件进行选择。结果表明,最适宜的破乳方法是电氧化,电氧化破乳最佳电流范围为2.0～3.8 A,最佳电压范围为140～200 V;化学混凝破乳最佳混凝剂为聚合氯化铝,当加入量为1.5 g/L、pH值调整至7～9时,废乳化液中COD降低至8 000 mg/L以下,油含量降低至1 000 mg/L以下,悬浮物降低至1 500 mg/L以下。     

黄金矿山井下废水处理试验研究

以某黄金矿山井下废水为研究对象,进行了混凝、超声强化混凝处理和氧化处理试验研究,结果表明铁系混凝剂SF去除砷、锑效果最好,砷和锑去除率分别达99.81%和91.84%以上;超声强化混凝处理可有效提高锑除去效果;二氧化氯在低p H值条件下去除氰化物效果好,超声强化混凝和氧化可以作为该井下废水处理的主要工艺单元。     

混凝与电絮凝废水中多种金属离子协同沉淀机制研究

采用混凝和电絮凝工艺去除废水中的多种金属离子(Pb^2+、Cd^2+、Cu^2+、Ni^2+),研究混凝反应主要影响因素液相pH、混凝剂(PAC)投加量对各金属离子去除效率的影响,探讨废水pH、施加电流密度对各金属离子电絮凝去除效率的影响,阐明混凝和电絮凝多金属协同沉淀去除的机制。结果表明,PAC混凝去除废水中Pb^2+、Cd^2+、Cu^2+、Ni^2+的最佳pH为7.0,最佳投加量600mg/L,Pb^2+、Cu^2+去除效率远高于Cd2+、Ni2+;电絮凝反应金属离子去除的最佳pH为7.0,最佳电流密度为1.2~1.8mA/cm^2。混凝与电絮凝金属离子的去除效率与金属离子的半径、相对分子质量大小无关,而与金属离子的溶度积直接相关,金属离子的溶度积越低,混凝和电絮凝去除效率越高。电絮凝较混凝反应具有更高的金属离子去除效率。研究结果对于采用混凝和电絮凝工艺处理多金属污染废水具有借鉴和指导意义。     

电渣重熔过程渣池流场数值模拟

采用商业软件ANSYS和FLUENT建立了电渣重熔过程渣池流场数学模型,分析了电渣重熔过程电磁力和热浮力共同作用下渣池流动行为,以及典型电渣重熔工艺参数(电极形貌、插入深度、填充比和电流强度)对电渣重熔过程渣池内流场的影响规律.结果表明:电磁力有利于渣池内产生逆时针涡流,浮力有利于渣池产生顺时针涡流.电极端部形貌对渣池流动影响较大,当电渣重熔电流均为5 000 A,频率为50 Hz时,平头电极所在渣池内同时存在逆时针涡流和顺时针涡流,锥形电极所在渣池内只存在逆时针涡流.电极填充比和电流都对渣池内流动行为影响较大,减小电极填充比和增大电流强度都会使渣池内逆时针涡流增加.     

混凝法在选矿废水处理中的应用现状及发展

简要描述选矿废水的来源、特点及各种处理方法的优缺点。阐述混凝法的作用机理,着重分析混凝剂、水质状况及水力条件等因素对选矿废水处理产生的影响,介绍混凝法在铅锌矿、铁矿、黄金、钨矿和磷矿等废水处理的应用现状。最后指出混凝法在选矿废水处理中的发展方向是要加强对混凝作用机理与影响因素的研究,加大对高效混凝剂的研发,同时将混凝法与尾矿库自然沉降、浓密机技术有机结合,制定合理流程,实现选厂废水零排放。     

350 mm×470 mm大方坯结晶器电磁搅拌参数优化

对350 mm×470 mm大方坯结晶器电磁搅拌的空载磁场进行了在线测量,获得了结晶器内磁感应强度分布规律。根据磁场测量结果计算了凝固前沿的电磁力及钢水流动速度,并分析了电磁搅拌参数对钢水流动速度的影响,确定了搅拌电流和频率的范围。由42CrMo钢现场实验的结果得出,当结晶器电磁搅拌电流为150 A,频率为2.5 Hz时,铸坯横断面的最大碳含量的偏差为±0.01%,带状偏析基本消除,铸坯内部质量明显改进。     

检测钢材表面缺陷的新方法

挪威埃尔肯公司发明了一种检测热轧钢坯和钢材表面缺陷的新方法,其工作原理是:当轧后的热钢坯或钢材通过有高频电流的导电线圈时,感应电流集中在钢件表面上流动,使钢件表面加热提高几度温度。如果钢件有表面缺陷,电流必定环绕障碍表面流过,这     

Rheology as Tool for Polymer Dose Assessment and Control

Rheological characteristics of sludge represent one of the few examples of fundamentally derivable properties that have also been successfully used for the improvement of actual sludge treatment processes. Previous research has suggested the use of certain sludge rheological parameters for polymer dose optimization and floc characterization. This research evaluated the use of rheological properties for characterization and control of sludge conditioning with polyelectrolytes. Rheological characteristics were compared with dewaterability in laboratory evaluations, utilizing both synthetic cellulose suspension and actual sludge. These experiments were designed to identify fundamental rheological parameters that may have the potential to be used for assessment and control of conditioning and dewatering processes. This paper reports and analyzes results from controlled laboratory experiments; evaluations of on-line rheology measurements for process control in a nearby sludge handing facility have been presented elsewhere. Laboratory conditioning indicators were capillary suction time, liquid stream (centrate) streaming current and viscosity, and solids measurements. Full-scale dewatering indicators were capillary suction time, liquid stream (filtrate) streaming current, and percent solids recovery. Results indicated lack of correlation between the proposed conditioned sludge rheology-control parameters and conditioning indices over a wide range of mixing conditions. Mixing parameters have a substantial effect on the rheological characteristics of the concentrated suspensions and shed some light upon floc strength as related to dewaterability.     

Effects of context on auditory stream segregation.

The authors examined the effect of preceding context on auditory stream segregation. Low tones (A), high tones (B), and silences (-) were presented in an ABA- pattern. Participants indicated whether they perceived 1 or 2 streams of tones. The A tone frequency was fixed, and the B tone was the same as the A tone or had 1 of 3 higher frequencies. Perception of 2 streams in the current trial increased with greater frequency separation between the A and B tones (Δf). Larger Δf in previous trials modified this pattern, causing less streaming in the current trial. This occurred even when listeners were asked to bias their perception toward hearing 1 stream or 2 streams. The effect of previous Δf was not due to response bias because simply perceiving 2 streams in the previous trial did not cause less streaming in the current trial. Finally, the effect of previous Δf was diminished, though still present, when the silent duration between trials was increased to 5.76 s. The time course of this context effect on streaming implicates the involvement of auditory sensory memory or neural adaptation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Steady Streaming around a Circular Cylinder near a Plane Boundary due to Oscillatory Flow

Steady streaming due to an oscillatory flow around a circular cylinder close to and sitting on a plane boundary is investigated numerically. Two-dimensional (2D) Reynolds-averaged Navier-Stokes equations are solved using a finite element method with a k-ω turbulent model. The flow direction is perpendicular to the axis of the cylinder. The steady streaming around a circular cylinder is investigated for Keulegan-Carpenter (KC) number of 2 ≤ KC ≤ 30 with a constant value of Stokes number (β) of 196. The gap (between the cylinder and the plane boundary) to diameter ratio (e/D) investigated is in the range of 0.0–3.0. The steady streaming structures and velocity distribution around the cylinder are analyzed in detail. It is found that the structures of steady streaming are closely correlated to KC regimes. The gap to diameter ratio (e/D) has a significant effect on the steady streaming structure when e/D<1.0. The magnitude of the steady streaming velocity around the cylinder can be up to about 70% of the velocity amplitude of the oscillatory flow. One three-dimensional (3D) simulation (KC = 10, β = 196, and e/D = ∞) is carried out to examine the effect of three dimensionality of the flow on the steady streaming. Although strong 3D vortices are found around the cylinder, the steady streaming in a cross section of the cylinder span is in good agreement with the 2D results.     

Dual Polymer Conditioning of Water Treatment Residuals

Conditioning of either wastewater biosolids or water treatment residuals conventionally utilizes a single polymer to improve subsequent dewatering. The sequential addition of two polymers has been reported to enhance biosolids dewaterability, but comparable benefits have not been demonstrated for water treatment residuals. This paper evaluated the use of cationic and nonionic polymers, singly and in combination (dual), to investigate whether dual polymer conditioning of residuals offers any advantages, and to determine whether the results could be accommodated by current mechanistic understandings. For this purpose, lab-scale tests used capillary suction time (CST), supernatant viscosity, zeta potential, streaming current, turbidity, floc size, and rheometric analyses. Comparisons of CST and viscosity results for single and dual polymer additions indicated that dual polymer use gave moderately improved dewaterability, possibly due to the increased mixing utilized for dual polymer addition. Using a cationic polymer produced a less turbid supernatant. Zeta potential and streaming current were not good indicators of conditioning efficacy when a nonionic polymer was used. Rheometric analyses were only meaningful in one selected method for treatment of the data: the area under the rheogram up to a shear rate of 30?inverse?s. Overall, implementation of dual polymer use does not appear warranted.     

An objective measurement of the build-up of auditory streaming and of its modulation by attention.

Three experiments studied auditory streaming using sequences of alternating “ABA” triplets, where “A” and “B” were 50-ms tones differing in frequency by Δf semitones and separated by 75-ms gaps. Experiment 1 showed that detection of a short increase in the gap between a B tone and the preceding A tone, imposed on one ABA triplet, was better when the delay occurred early versus late in the sequence, and for Δf = 4 vs. Δf = 8. The results of this experiment were consistent with those of a subjective streaming judgment task. Experiment 2 showed that the detection of a delay 12.5 s into a 13.5-s sequence could be improved by requiring participants to perform a task on competing stimuli presented to the other ear for the first 10 s of that sequence. Hence, adding an additional task demand could improve performance via its effect on the perceptual organization of a sound sequence. The results demonstrate that attention affects streaming in an objective task and that the effects of build-up are not completely under voluntary control. In particular, even though build-up can impair performance in an objective task, participants are unable to prevent this from happening. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Photon correlation analysis of cytoplasmic streaming

Laser light scattering has been used to investigate particle movements in a plant cell. Intensity autocorrelation functions are obtained by digital photon correlation of laser light scattered from cells of Nitella opaca both during cytoplasmic streaming and during the transitory cessation of streaming induced by electrical stimulation. The average velocity computed from the periodic oscillation in the intensity autocorrelation function during streaming corresponds to the velocity estimated using light microscopy. An estimate of the distribution of streaming velocities has been obtained from the decay in the amplitude of the envelope of the autocorrelation function derived from a streaming cell.     

Effects of attention and unilateral neglect on auditory stream segregation.

Two pairs of experiments studied the effects of attention and of unilateral neglect on auditory streaming. The first pair showed that the build up of auditory streaming in normal participants is greatly reduced or absent when they attend to a competing task in the contralateral ear. It was concluded that the effective build up of streaming depends on attention. The second pair showed that patients with an attentional deficit toward the left side of space (unilateral neglect) show less stream segregation of tone sequences presented to their left than to their right ears. Streaming in their right ears was similar to that for stimuli presented to either ear of healthy and of brain-damaged controls, who showed no across-ear asymmetry. This result is consistent with an effect of attention on streaming, constrains the neural sites involved, and reveals a qualitative difference between the perception of left- and right-sided sounds by neglect patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于流媒体技术的山东矿业视频监控系统

介绍流媒体技术的相关概念,并结合中钢集团山东矿业有限公司安全生产的实际需要,提出了流媒体技术在冶金矿山视频监控领域应用的设计方案,并介绍了该方案在山东矿业调度中心的成功应用.该监控系统采用了当今最流行的网络和流媒体及DLP大屏幕显示等新技术,实现了视频图像分散采集、集中监控、远程浏览的功能,达到了整个矿区地表监控"无死角、无盲区"及重点布防之目的.     

Effects of Location, Frequency Region, and Time Course of Selective Attention on Auditory Scene Analysis.

Often, the sound arriving at the ears is a mixture from many different sources, but only 1 is of interest. To assist with selection, the auditory system structures the incoming input into streams, each of which ideally corresponds to a single source. Some authors have argued that this process of streaming is automatic and invariant, but recent evidence suggests it is affected by attention. In Experiments 1 and 2, it is shown that the effect of attention is not a general suppression of streaming on an unattended side of the ascending auditory pathway or in unattended frequency regions. Experiments 3 and 4 investigate the effect on streaming of physical gaps in the sequence and of brief switches in attention away from a sequence. The results demonstrate that after even short gaps or brief switches in attention, streaming is reset. The implications are discussed, and a hierarchical decomposition model is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Incidence of Z band streaming and myofibrillar disruptions in skeletal muscle from healthy young people

Skeletal muscle tissue was obtained from the vastus lateralis or peroneus brevis muscles of 34 healthy volunteers. Focal and extensive areas of Z band streaming and disruption of myofibrillar architecture without Z band streaming were quantified in Araldite-embedded specimens examined in the phase microscope. Extensive areas of Z band streaming in more than 2.0 percent of fibers was present in only two of the 34 volunteers. Myofibrillar disruptions without Z band streaming was much less common than Z band streaming. The size of extensive areas of Z band streaming or myofibrillar disruptions was quantified by counting the number of adjacent fibrils and contiguous sarcomeres occupied by either type of lesion. These data should be of use in determining if such lesions are present in excessive amounts in suspected pathologic material.