Special Features Of Stabilization Of The Growth Process In Plasma-arc Growth Of Single Crystals Of Refractory Compounds From SHS Products

Problems of the stability of the growth process in growing single crystals of refractory compounds (carbides and bondes of transition metals) by the method of plasma-arc remelting are considered. The main reasons behind the loss of stability of the spatial configuration of the melt (a shift of the anode lock-on of the arc from the center of the molten pool, disturbance of the symmetry of the plasma jet, superheating of the melt) are considered. The effect of cyclic perturbations in the crystallization system that appear upon replenishment on the fluctuation of the energy characteristics of the arc, the temperature of the melt, and the displacements of the crystallization surface is described. It is established that the crystallization rate and the process of coarsening of the crystallites in the formation of a columnar structure in the ingot depend on the frequency of feeding new portions and on their mass.     

The service of the hearths of arc furnaces for melting stainless steels with the use of oxygen

Conclusions During the operation of arc furnaces specializing in the melting of stainless steels, chemical and phase changes occur in the magnesite hearths which lead to the formation of a single type structure in the monolith of rammed layer and upper courses of the structure.Petrographic studies showed that the monolith was formed as a result of phase inversions of the minerals of the hearth under the influence of the silicate constituents of the slag being produced, which partly settles to the bottom after discharge of the melt. These inversions greatly affect the physicochemical properties of the hearth and especially the refractoriness. The inversions which increase the refractoriness include the process of recrystallization of the periclase and chrome-spinel with the formation of strong and dense periclase-spinel growths in the upper layers of the hearth.The reduction in the refractoriness occurs owing to the formation of montichellite under the influence of calcium slag constituents and the gradual replacement of the forsterite by this silicate, and also the partial solution of periclase in the silicate melt.The thermal resistance of the hearth is favorably affected by the fact that the new silicate formations are distributed irregularly over the height of the hearth, and the nature of the distribution depends on their fluidity and temperature gradient in the hearth. In view of this consistency, the most refractory silicates, such as forsterite and mervenite, are localized in the upper strata of the hearth, and the montichellite, being the most fusible silicate, migrates to the lower layers.The result of all the processes and phase inversions taking place in the hearth is that the refractoriness of the most important layers of hearth (upper and middle) remains high during service. The reduction in refractoriness in the lower layer cannot greatly affect the life of the hearth since this layer is quite far away from the working region of the furnace and is in the low-temperature region.Large amounts of metals are detected only in the part of the hearth located in direct contact with the furnace bath; metal does not take a large part in the processes occurring in the hearth.The positive influence of the additions of chromite on the life of the hearth of electric furnaces determined during operation, can be explained by the fact that the chromite is essential for the formation of refractory chromespinel phases [2], contributes to the formation of periclase-spinel growths in the upper parts of the hearth, and accelerates the process of removing the less refractory silicates from the upper layers of the hearth to the lower [3].     

The role of the symmetry and the flexibility of the anion on the characteristics of the nanostructures and the viscosities of ionic liquids☆

The transport properties of ionic liquids (ILs) are crucial properties in view of their applications in electrochem-ical devices. One of the most important advantages of ILs is that their chemical–physical properties and conse-quently their bulk performances can be well tuned by optimizing the chemical structures of their ions. This will require elucidating the structural features of the ions that fundamentally determine the characteristics of the nanostructures and the viscosities of ILs. Here we showed for the first time that the“rigidity”, the order, and the compactness of the three-dimensional ionic networks generated by the anions and the cation head groups determine the formation and the sizes of the nanostructures in the apolar domains of ILs. We also found that the properties of ionic networks are governed by the conformational flexibility and the symmetry of the anion and/or the cation head group. The thermal stability of the nanostructures of ILs was shown to be con-trolled by the sensitivity of the conformational equilibrium of the anion to the change of temperature. We showed that the viscosity of ILs is strongly related to the symmetry and the flexibility of the constitute ions rather than to the size of the nanostructures of ILs. Therefore, the characteristics of the nanostructures and the viscosities of ILs, especially the thermal stability of the nanostructures, can be fine-tuned by tailoring the symmetry and the conformational flexibility of the anion.     

Effect of preparation conditions on the properties of microspheres prepared using an emulsion-solvent extraction process

Methylaluminoxane microspheres were prepared using a hydrocarbon-in-perfluorocarbon-emulsion solvent extraction process. The effect of the preparation conditions on the size of the microspheres was investigated. As expected, the size of the microspheres decreased with increasing stirring speed. At low surfactant concentrations the size of the microspheres was independent of the surfactant concentration. However, the size of the microspheres decreased as the surfactant concentration was further increased. The size of the microspheres was not only affected by the surfactant concentration but also by the volume ratio of the dispersed phase to the continuous phase. At a low volume ratio of the phases the effect of the surfactant on the size of the microspheres was larger than the effect of the increased volume ratio of the phases. At high volume ratios of the phases the effect of the volume ratio of phases on the size of the microspheres became more significant than the effect of the surfactant. A slow solidification increased the formation of non-spherical microspheres.     

复合材料风扇叶片榫头铺层设计及加工制造

碳纤维复合材料风扇叶片榫头段是铺层数量最多、递减铺层最集中的部位,榫头的铺层质量影响叶片的低周疲劳强度。为完成叶片榫头段的铺层设计,基于铺层设计准则,建立了一种适用于航空发动机复合材料风扇叶片榫头段铺层设计的方法。根据铺层高度大小将铺层分为结构层和插入层,在结构层铺层设计中考虑了高度递减层的角度与铺放位置。在插入层铺层设计中,考虑了单组插入层铺层数量、单组插入层内部铺层顺序及铺层角度、单组插入层形成的坡度、相邻插入层之间的错开距离等五个方面的因素,确定了单组插入层的结构及其在榫头的分布。根据设计方案对榫头进行加工制造,成型的榫头试样件厚度检测质量良好,证实了该铺层设计方法的可行性。     

Carrier Dyeing of Polyester Fibre Part II – The Influence of Carriers on the Diffusion of Disperse Dyes

The influence of carriers on the diffusion of disperse dyes in polyester fibre has been studied. The extent to which the diffusion rate of a dye is increased is independent of the chemical structure of the carrier but depends on the molar concentration of carrier in the fibre and on the chemical structure of the dye. The influence on the diffusion rate decreases with increase in temperature, and the rates of decrease increase with increase in the activation energies of diffusion of the dyes when no carrier is present. The presence of carrier reduces the activation energies of diffusion of the dyes, the reduction being related to the decrease in the entropies of activation of diffusion brought about by the plasticizing action of the carrier. This reduction in the activation energy of diffusion leads to the existence of a temperature at which the presence of carrier would have no effect on the diffusion coefficient of the dye, and above which the presence of carrier would actually reduce the diffusion coefficient. The value of this temperature depends upon the carrier concentration in the fibre and the specific dye.     

气体辅助注塑制品中玻纤取向的模拟研究

利用Moldflow软件对气体辅助注塑制品中玻纤的取向情况进行了模拟。分析了熔体温度、延迟时间、气体注入等因素对气体辅助注塑制品中玻纤取向的影响。结果表明:制品中心平面处玻纤沿流动方向排列规整,而靠近气道和模壁处玻纤的排列较为混乱;提高熔体温度和减少延迟时间都能起到降低玻纤取向程度的作用;气体的注入使气道与模壁之间的玻纤排列更加规整;在制品的中心平面上,玻纤排列均匀、规整,随着标准厚度值的增加,玻纤的排列情况基本相同,但排列规整程度均低于中心平面处。     

安全阀在线调试中阀座有效面积的反算法

在研究安全阀在线调校原理和化工企业生产特点的基础上,解决了安全阀在线调试过程中起跳压力计算的难点,即阀座有效面积的计算。提出了两种较实用的阀座有效面积的计算方法。经过对安全阀实际调校的检验,证明这两种方法是高效、精确的计算方法。     

木粉/LDPE复合材料的性能

采用低密度聚乙烯(LDPE)与木粉制得了木粉／LDPE复合材料。研究了木粉用量、表面处理剂种类及用量以及发泡剂用量对复合材料性能的影响；并对化学发泡法减轻复合材料自重的方案做了初步探讨。结果表明：当木粉用量为30份，表面处理剂用量为木粉质量的1．0％时，复合材料的综合性能最佳；添加4份AC发泡剂后，复合材料的密度从0．83g／cm^3降到0．52g／cm^3，化学发泡法可有效减轻材料的自重。     

酚醛泡沫塑料制备和性能研究

研究了酚醛泡沫制备工艺中一些参数条件对泡沫体性能的影响。研究发现：泡沫体的密度随发泡剂的用量增大而减小；表面活性剂的最适合用量为树脂质量的5％；固化剂的用量为树脂质量的4％-6％时可以达到发泡和固化同步的效果。泡沫体的吸水率与泡沫体的密度相关。力学实验表明：泡沫体的压缩强度随泡沫体的密度增大而增大。热重分析结果表明：泡沫体具有优秀的热稳定性能。     

晶须长径比对复合材料力学行为影响的模拟

在单向晶须增强树脂基复合材料的轴对称模型和已有研究成果基础上,利用有限元分析方法,研究该类复合材料中晶须长径比的变化对材料整体力学行为的影响.结果表明:1)晶须长径比对晶须应力作用明显大于对基体的影响;2)晶须的长径比h/r≤30时,随着晶须长径比的增大,发生在晶须端部处的集中应力急剧增加;但当长径比h/r≥30时,长径比的进一步增加对集中应力影响不大;3)随着晶须长径比的增大,界面剪切应力减小,分布曲线下移;但当长径比h/r≥30时,长径比的进一步增加对剪切应力影响不大;4)随着晶须长径比的增加,复合材料的拉伸强度逐渐增大.     

Adiabatic thermal explosion in disperse condensed systems with limited solubility of the reactants in the product layer

A mathematical model of the self-heating of dispersed solid mixtures is considered taking into account the boundary kinetics of formation of the intermediate product phase. It is shown that decreasing the ratio of the characteristic diffusion time to the characteristic reaction time can lead to a transition from the diffusion regime to the kinetic regime, resulting in a change in the effective activation energy of the synthesis and the growth pattern of the product layer. This change may be due to decreases in the heterogeneity scale of the mixture and the ratio of the activation energy of the formation of the new phase to the activation energy of diffusion. An analytical model of the solid-state reaction in the kinetic regime was developed and used to obtain temperature dependences of the coordinates and velocities of the boundaries of the growing layer.     

基于ABAQUS的降雨对群桩加固斜坡软弱土路堤的影响分析

降雨入渗是斜坡软弱地基路堤强度降低甚至失稳的一个重要因素,因此降雨条件下斜坡路堤的加固变得极其重要。本文基于ABAQUS有限元软件,结合具体工程实例,进行了一系列降雨方案下斜坡软弱地基路堤变形和稳定性分析,重点研究降雨强度和降雨时间对斜坡路堤坡面水平位移及桩体水平位移的影响,并研究了降雨强度为0.02m/h、降雨时间为18h时桩体弹性模量和桩间距对路堤顶部变形和安全系数的影响。研究结果表明:路堤坡面水平位移及桩体水平位移与降雨强度和降雨时间成正比关系;桩体弹性模量增加路堤顶部位移随之减小而安全系数变大;桩间距越小对路堤顶部沉降减小作用越明显,但可以提高路堤的安全系数。综合考虑路堤稳定性、桩体变形和经济性提出了研究工况下最佳加固方案,可供相似工程参考。     

Variation der Fettbeschaffenheit im Rindfleischangebot

Variation of the Consistency of Fat in Beef Investigated was the fat of 313 young cattle, which is purchased by the Consumer on the fresh-meat-market. Among numerous calculated factors of influence it was determined that the sex of the animals, the amount of fatty tissue as well as the localization of the tissues on the carcass are the strongest causes of variance at the nutritional composition, refractometer value, hydroxyproline content, fatty acid pattern and size of fat cells of the samples. Growth-physiological traits and the mentioned criteria of the fat composition correlate loosely with the palatibility values of the prepared meat. The positive assessment of the meat at increasing fatty tissue proportion is to be opposite of the negative changes in the biological valuation of the fatty acids. Under the aspect of nutritional value and palatibility is a mean fatty tissue proportion on the carcass and the leaving of some fatty tissue on the muscles a recommendable compromise at the offer of meat.     

聚硅氧烷消泡剂的失活和再生机理

介绍了聚硅氧烷消泡剂失活和再生的现象,分析了失活过程中消泡剂分散体粒径大小和分布,泡沫体系的表面张力、接触角、硅油铺展层的厚度以及泡沫膜的结构和状态,结果表明：硅油组成的改变、硅油和疏水二氧化硅微粒的分离、消泡剂分散体粒径的变小、铺展油层的消失和白色絮凝物的出现导致消泡剂失活,其中二氧化硅硅粒-硅油的分离和泡沫膜上硅油铺展油层的消失是主要因素。失活的消泡剂中加入硅油,消泡活性可再次恢复,这主要是由于消泡剂分散体粒子中的硅油-二氧化硅硅粒比例达到最佳的状态并在泡沫膜上又形成了新的具有消泡活性的硅油铺展油层。     

回转窑中心线在线监测方法

回转窑中心线变化一般是缓慢的,窑故障的发生也具有隐蔽性和不确定性,当故障严重时会影响回转窑的正常生产,许多企业通常到回转窑运转出现故障后才发现.本文提出一种回转窑中心线的在线监测方法,此方法在检测得到窑中心线的基础上,通过监测回转窑轮带表面三点的位置,实现回转窑中心线的在线监测,使企业自己能够及时获取回转窑中心线的运行...     

Express determination of coke’s ash content by the gamma-albedo method

Continual monitoring of the ash content is required in fuel processing. The traditional thermogravitational method of determining the ash content is not suitable for use on a large scale, since the analysis is laborious, slow, and destructive. The gamma-albedo method lacks the disadvantages of the standard method and provides results of satisfactory accuracy if the chemical composition of the fuel’s mineral component is relatively constant. In the present work, attention centers on the possibility of express determination of coke’s ash content on the basis of the albedo of low-energy gamma radiation from the Fe-55 radionuclide, with corrections for the variable chemical composition—in particular, fluctuations in the calcium concentration in the ash-forming part of the fuel. To take the perturbing action of calcium into account, the X-ray fluorescence of calcium is measured. The ash content is assessed on the basis of the integral intensity of secondary radiation due to the γ-ray scattering and fluorescence of the calcium. It is clear that artificial attenuation of the secondary radiation is required, in view of the qualitatively different changes in intensity of the fluorescence and scattered radiation as a function of the calcium concentration and also the complex dependence of the integral intensity of the secondary radiation on the ash content. A model is proposed for optimizing the thickness of the attenuating filter so as to ensure equal and opposite changes in the intensity of the fluorescence and scattered radiation with variation in calcium concentration. Recommendations are made for practical application of the proposed method, in terms of the attainment of satisfactory accuracy with fluctuation in the ash content and the composition of the mineral mass. The basic metrological characteristics of the traditional and proposed methods are presented, along with the results of experimental trials.     

直缝式燃烧器W火焰锅炉新型二次风箱特性研究

为解决直流缝隙式燃烧器W火焰锅炉原设计的全通二次风大风箱由于锅炉炉膛宽度宽、风箱截面尺寸大等原因产生的炉膛中部缺风问题,华能上安电厂将4号锅炉原风箱改造为分隔型新型二次风箱。新型二次风箱改造完成后对其特性的试验研究表明,常规冷态通风时拱上、拱下各喷口及各风道区域之间风速偏差较小。单侧送风机运行且联络门关闭时,送风机停运侧各喷口风速明显低于送风机工作一侧,但通过拱上、拱下二次风门的调整,能有效缓解由于单侧送风机运行带来的喷口风速偏差。单侧送风机运行联络门开启的情况下,3个风道区域平均风速的偏差与正常双送风机运行时差别不大。与改造前相反,锅炉运行炉膛出口氧量已呈现中间高两头低的趋势,适当调整二次风箱风门开度后炉膛出口氧量分布趋于均衡,说明改造后的二次风箱风门能有效调节炉内二次风配风进而改变炉膛出口氧量分布。通过二次风箱风门开度的适当调整,能有效降低SCR入口NOx浓度,保证锅炉经济环保运行。     

丁二烯气相聚合产物分子量分布和粒径分布模型研究

对非均相催化的丁二烯气相聚合,基于聚合物多层模型,考虑催化剂颗粒间活性位初始浓度和粒径分布对聚合物分子量分布和粒径分布的影响,建立了聚合物分子量分布和粒径分布的数学模型。模拟了反应温度、催化剂颗粒间活性位初始浓度和粒径分布等因素的影响,结果表明。随着温度升高,聚合物颗粒平均粒径变小,粒径分布变窄,聚合物分子量变小,分子量分布变宽;催化剂颗粒间的活性组分负载越均匀,聚合物分子量越大,分子量分布和粒径分布越窄;随着催化剂平均粒径变大,聚合物分子量变小,分子量分布变宽,不存在催化剂颗粒粒径分布和聚合物颗粒粒径分布间的复制现象。模型模拟结果与实验结果吻合较好,可用于预测丁二烯气相聚合产物的分子量、分子量分布和粒径分布。