循环水磁防垢除垢作用机理及影响因素分析

结垢是工业循环冷却水普遍存在的现象,为了研究循环水磁防垢除垢作用的机理,通过文献调研前人对循环水磁防垢的相关研究,总结了磁处理水理化性质(黏度、表面张力和氢键数量)的变化以及水垢(文石、方解石)结构的变化与系统能量的关系,并结合影响磁化水抑垢效果的因素,针对目前对于磁防垢除垢作用机理的分歧,从相关的试验结论出发,以能量为落脚点对循环水磁防垢除垢作用的机理进行了推导,即水分子经磁场作用后,增加了氢键数量形成了更多的水合离子,减少了水垢的形成,同时致使体系能量降低和活化能增加,而活化能的增加能够促进硬垢向软垢的转变。这种经磁场作用后体系能量的重新分配造成的变化解释了常见的磁处理结论,并就影响磁处理阻垢效率的因素进行了讨论。     

考虑油膜阻力的直线滚动导轨副摩擦力建模与试验

为了准确预测直线滚动导轨副的摩擦力大小及受影响因素,本文考虑导轨副的流体润滑状态,基于Hertz接触理论研究了直线导轨副摩擦力受滚珠接触角和预紧力的影响规律.基于接触理论建立了直线导轨滑块的受垂直载荷的静力学平衡方程.利用Hertz接触理论分析直线滚动导轨受外力时各列滚珠接触力的变化情况,并结合对临界载荷的分析,建立了随外载荷变化的考虑润滑油膜阻力的直线滚动导轨副摩擦力模型.以国产某型号直线滚动导轨副为研究对象,对所建立的受载摩擦力模型进行试验验证.通过试验数据与理论数据的分析和对比,验证了润滑油膜阻力、接触角和预紧力等因素对直线导轨副摩擦力的影响规律.研究表明,直线滚动导轨副摩擦力在润滑条件下,受接触角变化和预紧力退化的影响呈现有规律的变化.     

连铸方坯中心线凝固行为波动现象及变化规律

连铸坯中心线区域钢液的凝固行为与中心偏析缺陷的形成及控制密切相关。基于中碳钢连铸方坯纵断面的实际凝固组织,以中心偏析点内部二次枝晶间距计算局部冷却速率,揭示了铸坯中心线局部冷却速率的波动特征。结合连铸三维凝固模型,研究了铸坯中心线固相率波动引起局部冷却速率波动并最终影响铸坯中心组织和性能的均匀性的机理;对不同工况铸坯中心线固相率和局部冷却速率波动的周期性进行了分析对比,提出了连铸坯凝固终点位置的周期性波动机理并得到了不同拉速下凝固终点波动距离的判断方程,对于所选连铸方坯,凝固终点波动距离为25.0～27.5 mm;在此基础之上,研究了拉速对中心线固相率波动程度的影响规律,并分析了凝固终点波动距离变化对末端电磁搅拌(final electromagnetic stirring, F-EMS)和轻压下(mechanical soft reduction, MSR)作用均匀性的影响。结果表明,拉速由1.8 m/min提高至2.4 m/min后,虽然液相穴长度增加可能增加整体偏析程度,但铸坯中心线固相率波动程度降低了20%,这有利于减轻中心线偏析沿拉坯方向的波动性,提高铸坯中心质量的均匀性。并...     

复合剪刃滚筒飞剪开发应用

作为板带材连续生产线上的关键设备,飞剪的剪刃侧隙调整精度直接影响了剪切质量,带材越薄对剪刃侧隙的精度要求越高,带材越厚对设备的冲击越大。本文将剪刃侧隙精度高的直剪刃和可减弱冲击的螺旋剪刃耦合在同一根刀轴上,并通过双侧齿轮传递扭矩提高抗扭刚度,拓宽了设备剪切厚度的范围,降低了设备加工制造成本。     

基于地应力和二次损伤的预留光爆层爆破参数研究

对于地下开采,预留光爆层进行二次爆破可以保证巷道掘进面轮廓成形效果,减少围岩损伤。基于地应力、应力波和爆生气体等共同作用理论,对预留光爆层二次爆破进行参数优化。分析预留光爆层厚度对地应力重分布的影响以及二次应力对爆生裂纹扩展的影响,可知二次应力会抑制爆生裂纹扩展,且预留光爆层厚度与二次应力大小呈正相关;分析在不考虑损伤、考虑一次损伤和考虑二次损伤条件下,轴向不耦合系数及炮孔间距大小的变化,可知考虑损伤可以适当增大轴向不耦合系数和炮孔间距。以焦家金矿深部开采工程为背景,对比爆破参数优化前后爆破效果,可知在深部开采时考虑地应力和损伤,能提高半孔率和节约成本。研究结果为地下开采爆破标准化提供了理论依据。     

Model system of binaural hearing. III. Binaural processing of information about short sounds

A model of neuronal structures of the medial superior olivary nuclei and inferior colliculus performing the determination of the direction on the source of the short (shorter than 10 ms) sound signals is presented. In the model the difference between the moments of the arrival of the two informational messages formed on the stage of monaural information processing is calculated. The result of this calculation is the firing probability of the primary detector (the neuron of the medial superior olivary nucleus). Because of the internal noise the curve of this probability as a function of the direction on the source is smoothly sloped. The estimation of the direction is the result of the statistical processing of the responses of the primary detectors ensemble. The direction on the source of sound is coded by a position of the secondary detector (the neuron of the inferior colliculus) on the direction "scale".     

Alternative operative exposures of the posterior aspect of the humeral diaphysis with reference to the radial nerve

An anatomical study was performed to define the course of the radial nerve in the posterior aspect of the arm, with particular reference to its relationship to operative exposures of the posterior aspect of the humeral diaphysis. In ten cadaveric specimens, the radial nerve was found to cross the posterior aspect of the humerus from an average of 20.7 +/- 1.2 centimeters proximal to the medial epicondyle to 14.2 +/- 0.6 centimeters proximal to the lateral epicondyle. As it crossed the posterior aspect of the humerus in each specimen, the nerve had several branches to the lateral head of the triceps; however, no branches were found innervating the medial head of the triceps in the posterior aspect of any of the specimens. At the lateral aspect of the humerus, the nerve trifurcated into a branch to the medial head of the triceps, the lower lateral brachial cutaneous nerve, and the continuation of the radial nerve into the distal part of the upper arm and the forearm. Three operative approaches were performed in each specimen. The posterior triceps-splitting approach exposed an average of 15.4 +/- 0.8 centimeters of the humerus from the lateral epicondyle to the point at which the radial nerve crossed the posterior aspect of the humerus. For the second approach, the radial nerve was mobilized proximally to allow an additional six centimeters of the humeral diaphysis to be visualized. The third approach (the modified posterior approach) involved the identification of the radial nerve distally as it crossed the lateral aspect of the humerus, followed by reflection of both the lateral and the medial heads of the triceps medially. This exposure permitted visualization of 26.2 +/- 0.4 centimeters of the humeral diaphysis from the lateral epicondyle proximally. The results after use of the modified posterior approach in seven patients were also reviewed.     

Comparison of the power and accuracy of biallelic and microsatellite markers in population-based gene-mapping methods

Because of their great abundance and amenability to fully automated genotyping, single-nucleotide polymorphisms (SNPs) and simple insertion/deletion are emerging as a new generation of markers for positional cloning. Although the efficiency and cost associated with the markers are important in the mapping of human disease genes, the power to detect the linkage between the marker and the disease locus, as well as the accuracy of the estimation of the map location of the disease gene, dictate the selection of the markers. Both the power and the accuracy depend not only on the type of the markers but also on other factors, such as the age of the disease mutation, the magnitude of the genetic effect, the marker-allele distribution in the population, mutation rates of marker loci, the frequency of the disease allele, the recombination fraction, and the methods for mapping the human disease genes. In this article, we develop a mathematical framework and the analytical formulas for calculation of the power and the accuracy and investigate the impact that the aforementioned factors have on the power and the accuracy, by using two population-based gene-mapping methods-likelihood-based linkage-disequilibrium mapping and the transmission/disequilibrium test, for both biallelic SNPs and microsatellites. These studies provide not only guidance in selection of the markers and in the design of the sample scheme for positional cloning but also insight into the biological bases of the mapping of human disease genes.     

半透水边界砂井真空联合堆载预压Hansbo固结解

把砂井地基上下边界视为半透水边界,以研究顶部垫层和底部下卧层透水特性对砂井地基固结过程的影响.根据轴对称固结方程和等应变假定,利用Hansbo法获得了真空联合堆载预压下半透水边界砂井地基的固结解答,分析了上下边界透水系数对真空和堆载预压固结度和沉降的影响,比较了真空单独预压下本文解与Indraratna等解答和周琦等解答的联系和差别.研究表明,(1)不管真空预压还是堆载预压,固结时间因子相同时地基固结度随边界透水系数增大而增大.(2)对于真空预压,下边界透水系数越大,地基的最终沉降越小,固结期间时间因子相同时的沉降也越小;上边界透水系数越大,固结期间时间因子相同时的沉降越大.(3)对于堆载预压,不管上边界还是下边界,边界透水系数越大,最终沉降不变,而固结期间时间因子相同时的沉降越大.(4)当真空预压上边界透水时,周琦等解答的固结度大于本文解答的固结度大于Indraratna等解答的固结度.为了提高真空预压的最终沉降,需减少地基下边界的透水性.     

外加直流电场无污染脱氧模拟研究

为了更好地提高脱氧效率,建立了渣-钢外加电场脱氧系统模拟模型。模拟分析了电场参数、电极参数、熔渣及钢液属性等对渣-钢系统中电流密度分布的影响,并对模拟结果进行试验验证。结果表明,随着系统施加电压、阳极电极直径的增加和阳极到渣-钢界面距离的缩短,系统中的最大电流密度增大;渣电阻率的降低有助于提高阳极附近的电流密度,而渣的相对介电常数的增大有利于系统中最大电流密度的提高;脱氧速率最高可以达到0.002 18%/min。     

Evolution of the epidemic process as a form of solution to its internal contradictions

The author formulated the main contradition of the epidemic process consisting of contradiction between the interaction of the motive forces of the epidemic process, since this contradiction at the same time served as the imperative condition of the origination and as the cause of the subsequent arrest of the spread of infection. The main contradiction of the epidemic process is expressed in reduction of the number and limited activity of the sources of infection, attenuation or arrest of the mechanism of transmission of the causative agents, formation of immunity in the population, the appearance of hereditary resistance in the hosts to the causative agent of the infection. The action of the principal internal contradiction of the epidemic process in the course of evolution conditions genetic variability of the causative agents of the infectious diseases, intensification of the mechanisms of excretion of the parasites from the host organism, and increase of their resistance in the external environment, formation of latent forms of infection.     

采场充填料浆流动与离析规律的试验研究

为研究采场充填料浆流动规律及充填料浆离析分层对充填体强度的影响规律,开展了充填料浆流动相似模拟试验及采场原位充填体力学强度测试试验,研究结果表明：单点下料时充填料浆流动终态坡面趋向于正态分布。流动过程中充填料浆产生离析分层现象,主要表现为充填体物料的粒径沿料浆流动方向呈先增大后减小的趋势,充填体强度沿料浆流动方向呈先减小后增大再减小的倒转“S”形趋势。采场原位充填体强度在下料口附近与标准试块强度接近,在采场中间位置附近的充填体强度最小,在距离下料点采场长度7/10左右的位置充填体强度达到最大值。研究成果能够为充填采场下料管的数量及位置设计提供依据,从而保证充填体的整体质量。     

超声波对金属相与陶瓷相间润湿角的影响

金属相与陶瓷相间的润湿性对陶瓷刀具的性能起着重要作用,为了改善固-液界面结构,提高陶瓷材料的综合性能,研究了烧结过程中超声作用产生的能量对金属相与陶瓷相间润湿角的影响.根据粉末液相烧结理论,构建了固?液双球冠润湿模型.依据润湿模型和最小能量原理,建立了润湿角与表面能、超声能、几何参数之间的关系.研究表明:在超声波作用下...     

静态留矿采矿法在二道沟金矿的应用

介绍静态留矿采矿法在二道沟金矿的应用情况,解决了软岩矿体的采矿问题,静态留矿采矿法是结合普通留矿法和削壁充填法的特点,总结出的一套新的采矿方法。静态留矿法选取了普通留矿法的回采工艺简单、采矿效率高的特点,同时也选取了削壁充填法架设溜矿井,矿石由溜矿井放出的特点;静态留矿法采用普通留矿法的采准工艺,只是在漏斗上架设溜矿井,回采过程中,矿石由溜矿井放出,也可采用间隔漏斗架设溜矿井。平场时,矿石由架设溜矿井的漏斗放出,未架设溜矿井的漏斗在回采过程中不放矿,回采结束后再统一放矿,架设溜矿井的漏斗回采结束后,放净溜井内的矿石后,炸开溜井的隔板,使溜井之间的矿石流到漏斗内,再放矿。回采过程中,留矿堆处于静止状态,能够对上下盘的软岩层起到良好的支护作用,保证采场正常上采。     

Micro-sequencing strategies for the human A33 antigen, a novel surface glycoprotein of human gastrointestinal epithelium

At the end of the XIXth Century the attitude towards malaria changed dramatically from fatalism and resignation to an active policy that made the eradication of the disease a possible objective. This dramatic change in the scientific political and cultural attitudes towards malaria was the result of two main phenomena: i) the impact of the scientific medicine and Pasteurian revolution on medicine and health policies, and ii) the discovery of the theoretical simplicity of the cycle of malaria transmission and of the possibility to interrupt it, by avoiding the contacts between people and the Anopheles mosquitoes. However, scientifically based strategies against malaria were in place before the discovery of the real causative agents and of the transmission cycle at the end of the XIXth century, as the origin of the scientific medicine had already produced a 'rationale' for local and national campaigns against malaria. According to Tommasi-Crudeli, for example, the cause of malaria was not a 'chemical compound', a 'miasma', but a 'living ferment', specific and autonomous. As a consequence, the aim of antimalarial measures was to eliminate the conditions indispensable to the multiplication of the specific ferment contained in the soil. The theory of malaria aetiology changed after the discovery of the transmission cycle by Ross and Grassi, but the general strategy remained the same: to eliminate one of the factors indispensable to the multiplication and diffusion of the agent. The detailed knowledge of the malaria transmission cycle made it possible to define the exact conditions which were alone responsible for the propagation of the disease and its persistence in the endemic areas. The theoretical linearity and the specificity of the 'Grassi's law' was decisive and produced a fundamental paradigmatic shift in the antimalarial policies. The essential point for the epidemiology and prophylaxis of malaria became to clarify the conditions which contribute to facilitate or to prevent the infection of the Anopheles.     

Formation of metallic phase by passing gaseous reducing agent through multicomponent oxide melt. Part 1. Theoretical principles

A model is proposed for the formation of metallic phase when gaseous reducing agent is bubbled through multicomponent oxide melt. The model includes the following stages: the formation of bubbles when gas is injected in the melt; the reduction of metal at the surface of the bubbles and its concentration in droplet form at the rear of the bubble; motion of the bubble–droplet system in a direction determined by the ratio of the uplift forces on the bubble and the gravitational forces on the droplet; entrainment of the droplets to the surface; and coalescence of the droplets and their descent on reaching a size such that the gravitational forces exceed the sum of the hydrostatic collision forces and the surface tension forces. Equations are presented for estimating the size of the gas bubble and the droplet moving in oxide melt without decrease in size; the direction of motion of the bubble–droplet system; its rate of ascent or descent; and the conditions in which the bubble–droplet system breaks down. The factors responsible for separation of the bubble and the droplet are identified: the surface properties of the oxide melt and the metallic melts and their interphase characteristics. By adjusting these parameters, the formation of metallic phase at the bottom of the vessel may be regulated.     

冶金用喷粉罐喷粉速率控制的冷态模拟试验

 为实现冶金用喷粉罐喷粉速率的稳定控制，通过冷态模拟试验，测定喷粉罐不同喷吹参数对罐内压力和输粉管路压力的影响规律，研究了罐内压力与输粉管路压力的差值Δp对喷粉速率的控制规律。研究结果表明，正常喷粉状态下，罐内压力主要由罐顶充压和流化气压力共同决定。输粉管路压力主要由载气流量决定，其值随载气流量的增大而增大。通过设置罐顶充压、流化气压力和载气流量的不同参数组合来改变Δp，可实现对喷粉速率的稳定控制。在载气流量相同条件下，喷粉速率随Δp的增大而增大；在Δp相同条件下，载气流量值越大，喷粉速率越大。     

200 t转炉交错氧枪设计优化研究

以200t转炉5孔氧枪为原型,优化设计内外喷孔相同倾斜角度下不同流量配比的交错氧枪.基于射流特性仿真研究,通过数值模拟方法,分析交错氧枪喷头射流特性与传统5孔氧枪的不同,探讨内外孔流量比变化对氧枪射流轴向速度衰减和有效冲击面积的影响规律.结果 表明:交错氧枪内孔射流轴向速度大于传统氧枪,外孔的轴向速度与传统氧枪相近,但...     

提高Q345B钢板探伤合格率的工艺措施

针对南阳汉冶特钢有限公司250mm×1 650mm断面连铸坯生产的低合金Q345B钢板探伤不合格现象,通过对不合格钢板取样进行电镜检测分析,得出中心锰偏析、硫化锰夹杂、氧化铝夹杂是导致探伤不合格的主要原因。通过优化成分来降低钢中锰元素质量分数、提高钢水洁净度、降低钢水硫质量分数、优化连铸二冷制度、严控铸机开口度等措施,铸坯中心偏析得到了改善,轧后钢板探伤质量合格率得到了提高。     

Treating bullous lung disease with Holmium YAG laser in conjunction with fibrin glue and DEXON mesh

The aim of the study was to answer the open questions concerning the development of the horse's testis. This study revealed that the seminiferous tubules originate from the sex cords of the coelomic epithelium and Leydig cells from the proximal part of mesonephric nephrons, whereas the rete and the ductuli efferentes derive from intermediate and distal parts of the mesonephric tubules. During the development the Leydig cells undergo an enormous proliferation due to the PMSG secretion in the mare. The proliferation of these cells prevent the deep penetration of the rete into the medulla and is therefore the reason for the reduced extension of the rete and mediastinum testis in the stallion, although 80% of these cells degenerate in the last third of pregnancy. The growth of the seminiferous tubules during sexual maturity reduces the rete to the extremitas capitata of the testis.