Bubble bursting phenomenon in Gas/Metal/Slag systems

Iron droplets can be ejected into the surrounding atmosphere or entrained into the slag phase when gas bubbles pass through the metal surface or the metal/slag interface. The phenomena occurring during passage of single bubbles through the free surface and the interface were investigated by using the in-situ X-ray transmission technique. The mass of droplets ejected into the atmosphere attained a maximum value at a certain bubble size, which depended on the surface tension of the iron melt. Bubble bursting on the free surface of iron melt ejected numerous fine iron droplets called “film droplets” and a few much larger jet droplets. Two different groups of iron droplets were also observed as entrained in the slag due to bubble passage through the iron/slag interface, although the physical phenomena are to some extent different from bubble bursting to the gas phase. This article is based on a presentation given in the Mills Symposium entitled “Metals, Slags, Glasses: High Temperature Properties & Phenomena,” which took place at The Institute of Materials in London, England, on August 22–23, 2002.     

Bubble nucleation

The theory of bubble nucleation in cavitation, degassification, and boiling is reconsidered. As background material, the theory of droplet nucleation from the vapor phase is reviewed briefly. In both cases, prior treatments contain serious errors in describing the free energy of formation of the critical nucleus. The one exception known to us for the bubble case, is the work of Landau and Lifshitz, which is correct, but which contains a minor ambiguity in the definition of the pertinent thermodynamic potential. The previous formulations of nucleation rate expressions are corrected. Implications of the results are discussed.     

Bubble Movement in Downward-Inclined Pipes

An experimental investigation with large-scale model tests of bubbles moving upward and downward in downward-inclined pipes is presented. The shape, velocity, and drag coefficient of single nonspherical air bubbles in continuous air-water flows are discussed. The bubble height depends mainly on the approach flow water velocity and the pipe slope. For stagnant bubbles, the bubble height is determined depending on these two parameters. Equilibrium of the drag and buoyancy forces is applied on single air bubbles in downward-inclined pipes. In pipes with pipe slope ranging from 0.052–0.087, the bubble drag coefficient is independent of the bubble Reynolds number. However, the bubble drag coefficient depends on the pipe slope and the approach flow water velocity. Using the approach of the equilibrium of the main forces the volume of stagnant bubbles can be predicted.     

LHJ浮选柱中的气泡特性

采用光-电探针法对LHJ浮选柱下导管内气泡尺寸及局部含气率进行了测定。考察了浮选柱结构参数及流物化参数各固素对浮选柱气泡直径及局部含气的影响.结果表明,流动压力,径向和轴向位置,pH值及起泡剂对气泡直径和含气率都有影响,而起泡剂的加入能明显降低气泡直径,同时提高含气率。     

Inclusion and Bubble in Steel—— A Review

The type, morphology and sources of inclusion in steels, including indigenous and exogenous inclusions, were discussed and reviewed. Indigenous inclusions are deoxidation products or inclusions precipitated during cooling and solidification of steel. Exogenous inclusions arise primarily from the incidental chemical （reoxidation） and mechanical interaction of liquid steel with its surroundings （slag entrainment and erosion of lining refractory）. Types and causes for the nozzle clogging were also summarized. Reasons for bubble formation and bubble size distribution in steels were discussed thereafter. Finally, morphology and causes of inclusion-related defects in continuously cast steel products were reviewed, such as flange cracking in cans, slag spots and line defects on strips.     

Multivariate multipoint linkage analysis of quantitative trait loci

We studied the nervous systems and tumors of two patients with anti-Yo-associated paraneoplastic cerebellar degeneration (PCD). In both patients the underlying tumor was an ovarian adenocarcinoma that expressed Yo antigens and contained extensive infiltrates of lymphocytes and plasma cells. The major central nervous system findings were a complete loss of cerebellar Purkinje cells with Bergmann astrogliosis. One patient had inflammatory infiltrates in the medulla and pons, and moderate axonal loss and demyelination involving the spinal cord. No inflammatory infiltrates were identified in the cerebrum, cerebellum or brain-stem of the other patient. Using quantitative Western blot analysis, deposits of anti-Yo IgG could not be demonstrated in the nervous system, possibly as a result of the loss of cells expressing Yo antigens. The detection of the anti-Yo antibody as a common marker of PCD in one patient with inflammatory infiltrates and another without infiltrates suggests that some PCD pathologically classified as "non-inflammatory" may represent a final burn-out stage of a cellular immune-mediated disorder. Our findings indicate that Purkinje cells are the main, but not necessarily the exclusive, targets of this disorder.     

Effects of Bubble Size and Diffusing Area on Destratification Efficiency in Bubble Plumes of Two-Layer Stratification

Effects of bubble size, bubble diffusing area, and other parameters in air diffusers on destratification are studied using laboratory- and pilot-scale tanks with two layers. Dimensionless group involving such variable as bubble size, bubble diffusing area, and tank area are used to quantify these effects. Based on the results of experiments, a model is developed to predict destratification efficiency. Bubble diameter and overall tank area are found inversely related to destratification efficiency while bubble diffusing area is directly related to destratification efficiency.     

Bubble formation at nozzles in pig iron

An experimental study was undertaken to determine how several variables affect the size of gas bubbles formed at nozzles in liquid pig iron. The frequency of bubble formation was measured by an acoustic device, which could detect the vibrations produced by the bubble release. Accurate knowledge of the gas flow rate then enabled the calculation of bubble volumes. The use of large baths (60 Kg), melted by induction heating, permitted a wide range of experimental parameters: gas flow rate (0.5 to 1000 cc/s), outside nozzle diameter (0.64 to 5.1 cm), inside diameter (0.16 to 0.64 cm), chamber volume (23 to 2200 cc), nozzle depth (7.6 to 20 cm), surface tension (700 to 1500 dynes/cm) and nozzle orientation (up, down and sideways). The resulting bubble volumes were between 0.5 and 100 cc. The bubbles were found to form at the outer diameter of the nozzles due to the nonwettability of the nozzles. Furthermore, the bubbles were of a uniform size at low flow rates, but increased in volume with the flow rate, so that a constant frequency was established. In addition, the bubble volume was strongly dependent on the chamber vol-ume upstream from the nozzle. This is known as a “capacitance” effect and is due to compressibility of the gas. “Doublet” or “double bubbles” at small chamber volumes and bubble “pairs” at large chamber volumes were also observed. These phenomena re-sult in smaller bubbles, which make precise predictions of bubble size difficult. The re-sults are compared with those obtained by other investigators in aqueous and metallic systems.     

利用新生CO气泡脱除铁液中的氮

大气条件下,在灰铸铁液和钢液中分别吹入O2,CO2气体并加脱氮剂以确定脱氮能力和测定表观脱氮速率常数,结果表明,在一定范围内吹气和加脱氮剂都能有效脱氮,在1400℃灰铸铁液中吹CO2,测得表观脱氮速率常数为0．095s^-1,%^-1。此外,还对脱氮限制性环节及各种影响因素进行了讨论。     

钢液中气泡和夹杂物的去除

熔池中钢液的流动、气泡以及夹杂物的大小都影响着钢液中夹杂物的去除率.研究表明,向上流动的钢液有利于夹杂物的上浮,几乎所有的夹杂物都能在钢液上升流中上浮.向下流动的钢液对夹杂物和气泡的上浮有阻碍作用,当气泡的直径小于1mm时其在钢液中将无法上浮.在钢包精炼吹氩过程中,应使用较小的吹氩量,一方面避免产生过大的气泡而降低底吹气体的利用效率,另一方面减小熔池内的钢液流速,促进气泡和夹杂物的上浮.但吹氩量也不宜过小,必须使气泡保持一定的尺寸来保证其充分上浮.在钢包精炼过程中选择吹氩量时,应综合考虑钢液流速和气泡大小的影响.     

Bubble formation at nozzles in pig iron

An experimental study was undertaken to determine how several variables affect the size of gas bubbles formed at nozzles in liquid pig iron. The frequency of bubble formation was measured by an acoustic device, which could detect the vibrations produced by the bubble release. Accurate knowledge of the gas flow rate then enabled the calculation of bubble volumes. The use of large baths (60 Kg), melted by induction heating, permitted a wide range of experimental parameters: gas flow rate (0.5 to 1000 cc/s), outside nozzle diameter (0.64 to 5.1 cm), inside diameter (0.16 to 0.64 cm), chamber volume (23 to 2200 cc), nozzle depth (7.6 to 20 cm), surface tension (700 to 1500 dynes/cm) and nozzle orientation (up, down and sideways). The resulting bubble volumes were between 0.5 and 100 cc. The bubbles were found to form at the outer diameter of the nozzles due to the nonwettability of the nozzles. Furthermore, the bubbles were of a uniform size at low flow rates, but increased in volume with the flow rate, so that a constant frequency was established. In addition, the bubble volume was strongly dependent on the chamber volume upstream from the nozzle. This is known as a “capacitance” effect and is due to compressibility of the gas. “Doublets” or “double bubbles” at small chamber volumes and bubble “pairs” at large chamber volumes were also observed. These phenomena result in smaller bubbles, which make precise predictions of bubble size difficult. The results are compared with those obtained by other investigators in aqueous and metallic systems.     

Multilocus quantitative trait analysis using the multipoint identity-by-descent method

A hepatocyte-directed vector has been developed; it includes several key features thought to favor in vivo gene delivery to the liver: electrostatically neutral particles which avoid nonspecific binding to other cells, to the extracellular matrix, and to complement proteins; asialoglycoprotein receptor-mediated endocytosis which may address the complexes to the perinuclear region; and polyethylenimine (PEI)-mediated endosome buffering and swelling as an escape mechanism to the cytoplasm. This system is based on a 5% galactose-bearing polyethylenimine (PEI-gal) polymer which is condensed with plasmid DNA to neutrality. Murine (BNL CL.2) and human (HepG2) hepatocyte-derived cell lines were transfected 10(4)-10(5)-fold more efficiently than murine fibroblasts (3T3), whether transfection was assessed globally (luciferase expression from the cell extract) or following histochemical staining (beta-galactosidase). Under these conditions, over 50% of the hepatocytes were selectively transfected in the presence of 10% serum. Transfection was suppressed by removal of the targeting galactose residues, by their replacement with glucose, or by the addition of excess asialofetuin. Thus, results from comparative and competitive experiments indicate the asialoglycoprotein receptor is involved in transfection of hepatocytes with neutral PEI-gal/DNA complexes.     

进气方向对文丘里微气泡发生器气泡直径的影响

文丘里微气泡发生装置常采用自吸式进气的方式,在工程应用中可能存在微气泡通量不足的问题。采用压缩空气进气,并通过照相法重点考察了错流、逆流和并流3种进气方向对文丘里管微气泡发生器生成气泡直径的影响。结果表明：喉管处液速超过4.72 m/s时所产生的湍流剪切场才能将进入的气泡破碎成~200 μm级别的微气泡;添加3-戊醇能够稳定生成的微气泡,抑制生成的气泡在从文丘里管到测试槽表面逸出过程中的聚并和破碎过程,从而使测试槽中不同位置处气泡直径能保持生成时的微气泡的直径;3种进气方向中,错流进气因气泡进入后更贴近壁面流动,所生成气泡直径最大;而并流进气气泡脱离时间更短,使得生成气泡尺寸最小。在相同条件下,并流进气生成的微气泡比表面积最大,约是错流进气的3倍,最有利于气液传质。     

激光涂复的搭接区分析

文章利用扫描电镜等方法对激光熔化区的单次扫描区和搭接扫描区进行分析、比较,发现了激光搭接区出现晶粒粗大、成分偏析和显微硬度下降等现象。     

Bubble and Froth Stabilizing Agents in Froth Flotation

The mineral processing industry relies heavily on froth flotation to beneficiate complex minerals. The performance of the process depends on a multitude of chemical reagents affecting the solid mineral particles as well as the air bubbles used to collect the valuable mineral particles. In flotation, bubbles and froths are transiently stable by the use of a frothing agent or the presence of inorganic electrolytes in the process water. This review presents the primary stages characterizing bubble coalescence. The effect of flotation reagents and inorganic electrolytes on the stability of bubbles and the mechanisms which delay the coalescence of bubbles are discussed. Recently it had been proposed that solid particles external to the flotation system may be intentionally added to stabilize the froth phase, which has attracted attention from the flotation community. This gave rise to additional studies on the topic. The final section of the paper was therefore designed to capture the progress made on this particular subject. The use of solid flotation aids offers a promising future to increase the recovery of valuable particles as these external particles may be customized. The advantage of solid particles over soluble reagents is that they may be recovered and re-used making them environmentally and economically attractive.     

A case of polyangiitis overlap syndrome

PURPOSE: To examine the quality of life after repair of esophageal atresia, follow-up studies were performed in 58 of 71 surviving patients (81.7%). METHODS: Fifty patients with primary anastomosis and all eight surviving patients with colon interposition were seen. The mean age was 25.3 years (range, 20 to 31). Symptoms were evaluated by a standardized interview. Quality of life assessment was performed using a visual analogue scale (0 to 100 points), the Spitzer Index (5 dimensions, 10 points), and the Gastrointestinal Quality of Life Index (GIQLI, 5 dimensions, 128 points). RESULTS: After primary anastomosis the estimated meal capacity was unrestricted in 46 patients (92%), but numerous symptoms such as recidivating cough (60%), hold up (48%), and short breath (30%) were reported. All symptoms except cough were seen more frequently in patients with colon interposition, and all of these patients suffered from periods of short breath. Quality of life scores were higher in patients with primary anastomosis compared with colon interposition. The difference in the visual analogue scale score did not reach statistical significance, but the mean Spitzer Index was 9.7 compared with 8.8 after colon interposition (P < .05). The GIQLI after primary anastomosis was similar to that in healthy controls and was significantly lower in patients with colon interposition. This was because of specific symptoms, which scored 49.3 after colon interposition compared with 61.7 after primary anastomosis (P < .05) and to 54.8 (SD 5) in healthy controls (P < .05). Physical and social functions, emotions, and inconvenience of a medical treatment scored similar in patients with primary anastomosis, colon interposition, and healthy volunteers. CONCLUSIONS: The long-term quality of life after primary anastomosis was excellent. Patients with colon interposition suffer more frequently from various gastrointestinal and respiratory symptoms, but they lead an otherwise normal life.     

气泡去除夹杂物的机理

针对非金属夹杂物引起的钢材质量问题,用高速摄像仪和图像处理软件对结晶器水模内的空气泡去除夹杂物模拟粒子的行为和机理进行了研究。结果表明,粒子通过粘附去除,俘获过程分为5个子过程,即粒子向气泡靠近并发生碰撞、粒子与气泡粘附形成液膜、液膜减到足够薄后破裂形成新的气固接触界面、粒子滑移到气泡底部、两者处于动态的稳定状态一起上浮。粒子在气泡表面上滑移时处于不稳定状态,气泡受到轻微扰动,粒子会失稳脱离液膜。     

Process interference and code overlap in dual-task performance.

Perceptual encoding processes have recently been shown to interfere with response selection in dual tasks (P. Jolicoeur & R. Dell'Acqua, 1998). Spatial cross-task compatibility (CTC) was varied to additionally manipulate code overlap across tasks. A new response-cuing paradigm was devised, in which a stimulus movement was used for later report in a perceptual task and a finger movement was used as response in a logically independent reaction task. Three experiments were conducted showing dual-task process interference, but shorter reaction times with CTC than without were also observed. This CTC priming effect was largest with high temporal overlap between the perception and reaction stimuli. The CTC effect was interpreted as resulting from overlap of code activation across tasks, whereas process interference seems to occur to prevent temporal overlap on the level of perceptual encoding and response retrieval processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)