钒钛磁铁矿尾矿含碳球团强度性能研究

以攀枝花钒钛磁铁矿尾矿为原料,聚乙烯醇为黏结剂,研究了粒度组成、水分含量、压力、聚乙烯醇含量、配碳量等因素对尾矿含碳球团强度的影响。研究表明:球团强度随粒度细化和水分含量提高呈先升后降,随PVA含量的增加而逐步提高;随压力升高,抗压强度呈"N"字型变化,落下强度先升后降;随配碳量的提高,抗压强度先升后降,落下强度逐渐降低。获得了制备钒钛磁铁矿尾矿含碳球团的优化工艺参数为:-75μm占40%,水分含量8%,压力8 MPa,PVA含量0.6%,配碳量15%。在此条件下制得球团的抗压强度185.4 N,落下强度42.5次,完全满足工业生产中对球团强度的要求。     

钒钛磁铁矿冷压含碳球团强度性能研究

基于转底炉直接还原工艺,以钒钛磁铁矿为原料进行压制球团工艺研究,以湿球落下强度作为考察指标,通过正交实验研究了矿粉粒度、煤粉粒度、配碳量及水分等因素对该指标的影响,并对其影响规律进行了分析。得出最佳压球工艺参数为:矿粉和煤粉中-200目比例分别占15%和65%,配碳量(C/O)为1.2,水分加入量为11%。此组合下的湿球落下强度为14.8次,完全可以满足转底炉生产要求。     

配加转炉细灰冷压含碳球团强度性能研究

基于转底炉直接还原工艺,比较了转炉细灰与膨润土、有机粘结剂对含碳球团生球落下强度的影响。发现配加20%转炉细灰与配加6%膨润土造球效果相近,可用其替代膨润土。在含碳球团中配加转炉细灰,通过单因素试验研究了转炉细灰配加量、水分、成型压力、配碳量对生球落下强度的影响,并采用正交试验对影响的程度进行了分析。结果表明:随着成型压力、水分和转炉细灰配加量的增大,生球落下强度先升高后降低;随着配碳量增加,生球落下强度逐渐降低;最佳工艺参数组合为水分15%、压力15MPa、C/O为0.8、转炉细灰配入量为25%。可行性分析认为,在含碳球团中配加转炉细灰是高效利用转炉细灰的可行途径。     

高铬型钒钛磁铁矿内配碳钠基碱性球团制备

为探究高铬型钒钛磁铁矿内配碳钠基碱性球团的性能，开展了内配碳碱性球团制备工艺参数优化的试验研究。首先通过单因素试验讨论加水量、成球压力、黏结剂加入量、Na₂O加入量和配碳量对球团落下强度的影响；然后采用正交试验结合极差分析和方差分析确定影响球团落下强度的主次因素和最优工艺参数组合；最后在最优工艺参数组合条件下进行球团高温热裂性、转鼓指数和膨胀率测试。研究结果发现，球团制备的最优工艺参数组合为加水量6%、成球压力10 MPa、黏结剂加入量0.4%、Na₂O加入量1.2、配碳量1.2;影响球团性能的主次因素依次为成球压力、配碳量、Na₂O加入量、加水量、黏结剂加入量。在最优参数组合条件下，干球团在950、1 050、1 150、1 250℃下的高温热裂性分别为15%、20%、25%、35%,转鼓指数分别为82.3%、77.6%、72.8%、63.4%,膨胀率分别为108%、120%、106%、70%。上述球团制备工艺参数优化的研究结果可为后续高铬型钒钛磁铁矿碱性球团制备以及非高炉工艺回收高铬型钒钛磁铁矿中有价金属提供工艺参考...     

硫钴精矿含碳球团压力成型试验研究

以攀枝花硫钴精矿为原料,聚乙烯醇为黏结剂,采用单因素试验研究了水分含量、成型压力、硫钴精矿粒度、黏结剂用量等因素对硫钴精矿含碳球团抗压强度和落下强度的影响。结果表明:球团强度随着水分含量的增加先小幅波动后快速提高,随着黏结剂用量的增加呈先提高后降低的趋势,随着压强(成型压力建议前后一致)的增大和粒度的细化呈"N"字形变化。得出优化的硫钴精矿含碳球团制备工艺参数为:矿煤质量比5∶1,水分含量12%,成型压力6 MPa,黏结剂用量0.6%,硫钴精矿粒度-200目(74μm)占75%。此条件下制备的硫钴精矿含碳球团生球团的抗压强度为192.6 N/球,落下强度为28.4次/球;干球团的抗压强度为348.2 N/球,落下强度为57.2次/球。     

钒钛铁精矿含碳球团直接还原试验

采用正交试验和单因素试验考察还原温度、配碳量(nC/nO)、还原时间对某钒钛磁铁矿精矿直接还原的影响。结果表明,影响含碳球团金属化率的主次因素依次为还原温度、配碳量、还原时间。优化工艺参数为:还原时间35min、还原温度1 350℃、配碳量1.25、水分9%、成型压力12MPa、黏结剂加入量0.4%,此工艺条件下含碳球团的金属化率达91.77%,还原后球团的主要物相组成为金属铁。     

硼铁精矿含碳球团还原过程强化

为了提高硼铁精矿含碳球团的还原速率,考察了机械活化、添加催化剂、配加高反应性还原剂等强化因素对球团还原行为的影响。试验结果表明:通过矿/煤机械混磨、添加Na_2CO_3、配加木炭等均可以提高碳热还原速率;矿/煤机械混磨促进效果最明显,磨矿0.5 min时即可明显加快还原速率、降低起始还原温度,继续延长磨矿时间,其还原速率增加不明显;配加木炭会促进铁晶须的发展,导致球团体积膨胀,降低金属化球团强度。综合考虑各种强化措施对还原的促进效果、对球团性能的影响、可获得性以及加工成本,认为矿/煤机械混磨是最佳选择。     

矿壳矿煤球团预还原试验研究

论述了矿煤球团用铁精矿及添加剂包壳的优点。研究了矿煤球团的配碳量、用铁精矿包壳时添加剂的种类和数量、还原温度、升温速度及气氛等因素对预还原球团强度和金属化率的影响。     

煤粉粒度对预热含碳球团抗压强度的影响

为了弄清含碳球团配煤粒度对球团抗压强度的影响规律,研究了配加不同粒度煤粉的含碳球团在中性气氛中预热至不同温度后的抗压强度。结果表明:当温度小于1 000℃时,煤粉粒度对含碳球团的抗压强度影响不大,而当温度大于1 000℃后,煤粉粒度对含碳球团的抗压强度有显著影响;当配加煤粉的粒度介于0.074~0.106mm时,含碳球团还原后的抗压强度最高,煤粉粒度过细或过大都不利于球团强度的提高;在高温还原过程中,煤粉粒度越细含碳球团的还原速率越大,金属化率越高。     

浸锌渣-煤泥-CaO冷固结球团的制备及还原性能研究

浸锌渣、煤泥均为微细粒二次固体资源。在煤泥、浸锌渣性能研究基础上,以煤泥为还原剂、CaO为粘结剂制备浸锌渣-煤泥-CaO冷固结球团,并对该球团的还原性能进行研究,以比较浸锌渣、煤泥、CaO配合料冷固结球团前后铅、锌、铁的还原效果。结果表明:在浸锌渣、煤泥、CaO质量比为100:45:10,成球水分18%、水成球压力20 MPa所得生球,其抗压强度、落下强度和爆裂温度分别为160.1 N、4.2次和580℃。生球团200℃干燥60 min所得冷固结球团的抗压强度、落下强度分别为310.4 N和6.4次。冷固结球团经1 250℃还原90 min可获得的铅、锌挥发率和铁金属化率分别为98.66%、98.87%和97.78%,其直接还原效果较非球团直接还原好。     

Applications of standard error estimates in unrestricted factor analysis: Significance tests for factor loadings and correlations.

Estimates of standard errors of factor loadings and factor correlations in the unrestricted factor analysis model can be computed for oblique or orthogonal solutions under maximum likelihood. This information can be used to test individual coefficients for significance, to evaluate whether an orthogonal or oblique structure is most consistent with sample data, or to compute confidence intervals for single parameters or confidence regions for arbitrary groups of coefficients. Because the number of parameters estimated in factor analysis is approximately the product of number of variables multiplied by number of factors, a Bonferroni correction for the critical point of the individual test statistics is recommended to control the probability of a Type I error. Several examples are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Live Load Radial Moment Distribution for Horizontally Curved Bridges

The present study is designed to determine the effect of major parameters on maximum total bending moments of curved girders, establish the relationship between key parameters and girder distribution factors (GDFs), and develop new approximate distribution factor equations. A level of analysis study using three numerical models was performed to establish an appropriate numerical modeling method on the basis of field test results. A total of 81 two-traffic lane curved bridges were analyzed under HL-93 loading. Two approximate GDF equations were developed based on the data obtained in this study: (1) a single GDF based on total girder normal stress; and (2) a combined GDF treating bending and warping normal stress separately. The two equations were developed based on both an averaged coefficient method and regression analysis. A goodness-of-fit test revealed that the combined GDF model developed by regression analysis best predicted GDFs. The present study demonstrated that radius, span length, cross frame spacing and girder spacing most significantly affect GDFs. The proposed GDF equations are expected to provide a more refined live load analysis for preliminary design.     

Analytical and Experimental Investigation of Bridge Girder Shear Distribution Factors

Tests on twelve bridges (six along Interstate 55 and six along Interstate 70/270 in Illinois) were performed to determine the validity of certain provisions for calculating bearing forces in the load and resistance factor design (LRFD) and the load factor design bridge specifications. The bridges were selected to be typical of Illinois interstate highway bridges and maintain a range of parameters to study. These bridges were instrumented on their beam webs with three strain gauge rosettes installed on each beam to measure shear stresses caused by loads. Static tests and slow moving 8 km/h (5?mi/h) tests with a loaded truck in specified locations were performed. Dynamic tests at highway speeds were also completed. Finite-element models were developed and compared to the test results. The study shows that the LRFD specification procedures closely approximate the shear distribution factors determined by finite-element analysis and testing.     

Effect of Convergence on Nonlinear Flow in Porous Media

The behavior of flow through porous media has been the subject of study for a long time. The relationship relating friction factor and Reynolds number using the square root of intrinsic permeability as the characteristic length is examined for flow in porous media with converging boundaries. An experimental investigation of the effect of convergence of streamlines on the linear and nonlinear parameters for different radial flow lines in a converging permeameter for different ratios of radii of the test section is also studied. In the present case, crushed rocks of sizes 11.64 and 4.73 mm were used as media and water as fluid, to develop curves relating friction factor and Reynolds number for different radial flow lines with different ratios of radii of the test section of the permeameter.     

Effect of ventilation distribution on aerosol bolus dispersion and recovery

It has been speculated that convective ventilatory inhomogeneities are an important factor influencing aerosol bolus behavior in the compromised lung. Multiple-breath 133Xe washout (MBWXe) is a commonly accepted test of ventilation distribution. By comparing aerosol bolus parameters to MBWXe in 9 healthy subjects and 14 cystic fibrosis patients with mild-to-moderate airway obstruction, we have attempted to discern the effect of altered ventilation distribution on aerosol bolus dispersion and recovery. Aerosol boluses (150-ml width) were delivered to the volumetric penetrations of 250 and 500 ml. Similar tidal volumes (approximately 1.25 liters) and flow rates (0.4 l/s) were used for aerosol bolus and MBWXe maneuvers. Associations between bolus parameters and ventilation distribution were only observed in the cystic fibrosis patients. We conclude that aerosol bolus dispersion and recovery are both influenced by convective ventilatory inhomogeneities induced by airway obstruction in these patients.     

Application of Taguchi Method on Biaxial Stretch Forming of Friction Stir Processed Mg AZ31B Alloy

The present study describes the effect of friction stir processing parameters on formability of Mg AZ31B sheet under biaxial stretching. The formability of friction stir processed sheet was studied by limiting dome height test in biaxial strain deformation mode. The experiments were carried out as per the Taguchi parametric design concepts and an L9 orthogonal array was used to study the influence of various combinations of process parameters. Statistical optimization technique, ANOVA was used to determine the optimum levels and to find the significance of each process parameter. The results indicate that the traverse speed is the most significant factor followed by the rotational speed and the tilt angle in deciding the formability of friction stir processed magnesium alloy. In addition, mathematical model was developed to establish relationship between the different process variables with formability by regression analysis.     

Confinement to the open arm of the elevated-plus maze as anxiety paradigm: Behavioral validation.

Exposure to the open arm of the elevated-plus maze was used to assess the neurobiological correlates of anxiety in the high-anxiety-related behavior (HAB) and low-anxiety-related behavior (LAB) rat lines. The authors sought to determine whether this mild stressor could be considered a valuable anxiety test revealing specific behavioral differences. Behavioral parameters scored were submitted to a discriminant and factor analysis to investigate emotional parameters discriminating HAB and LAB rats. Principal component analysis showed that the HAB rats' behavior was driven by anxiety, whereas the LAB rats' behavior was mainly explained by locomotor activity. Moreover, the rats displayed behaviors that reflected distinct coping strategies confirming anxiogenic open arm effects and differential appraisals of the stressor dependent on the genetic predisposition to either hyper- or hypo-anxiety. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of limited mouth opening capacity (trismus) on lung function

In the present study pulmonary function test data were obtained from 15 healthy volunteers and 15 patients with slightly impaired ventilation during both normal and maximally reduced opening of the mouth (trismus, intercuspid position). The aim of the study was to examine the effects of complete trismus on pulmonary function using objective and subjective parameters. In maximally reduced mouth opening, both groups showed an impairment of all subjective and objective pulmonary function test data. In healthy volunteers, the significant changes in the test data (p < 0.05) simulated mild to moderate pulmonary impairment, whereas patients with an already impaired pulmonary function showed a marked deterioration of their initial respiratory condition. The results of the subjective and objective parameters examined indicate that an intercuspid position (trismus) further aggravates pulmonary functional impairments. Complete trismus can be considered a risk factor to pulmonary function in patients using mouth-breathing as primary or supportive mode of respiration.     

尾矿干排工艺中高泥质尾矿浆絮凝浓缩处理试验研究

尾矿干排工艺高泥质尾矿中细粒级物料的脱水较为困难。为确定某金矿高泥质尾矿合理的沉降参数,选取高泥质尾矿浆浓度、絮凝剂单耗和絮凝剂种类作为影响因素,依据单一变量试验原则,进行全泥氰化尾矿浆絮凝沉降试验及正交试验。结果表明:各因素对矿浆沉降效果的影响程度为絮凝剂种类高泥质尾矿浆浓度絮凝剂单耗;当FS3802型絮凝剂(质量分数0.1%)用量为50 g/t,高泥质尾矿浆浓度为4%时,矿浆的沉降效果最好,且此条件下,动态沉降试验装置的最高底流浓度为46.7%,已初步具备膏体性能。研究结果对选矿厂全泥氰化尾矿干排工艺中絮凝沉降各因素的控制具有很好的指导作用。     

Trophic actions of transforming growth factor alpha on mesencephalic dopaminergic neurons developing in culture

Transforming growth factor alpha messenger RNA and protein levels are highest in the striatum, the target area of mesencephalic dopaminergic neurons of the substantia nigra, suggesting a role as a target-derived neurotrophic factor for these cells. To test this hypothesis, we characterized the actions of transforming growth factor alpha on fetal rat dopaminergic neurons in culture. Transforming growth factor alpha promoted dopamine uptake in a dose- and time-dependent manner. Administration of transforming growth factor alpha at the time of plating for 2 h produced a significant increase in dopamine uptake after five days of growth in vitro. As cultures aged they became less responsive to transforming growth factor alpha, such that longer times of exposure were required to elicit a similar, but weaker, response. Dopaminergic cell survival was selectively promoted by transforming growth factor alpha, since there was an increase in the number of tyrosine hydroxylase-immunostained cells without a parallel increase in the total number of neuron-specific enolase-immunopositive cells. Neurite length, branch number and soma area of tyrosine hydroxylase-immunopositive cells also were enhanced by transforming growth factor alpha treatment. Increases in each of the dopaminergic parameters due to transforming growth factor alpha were accompanied by a rise in glial cell number, making it possible that these effects were mediated by this cell population. The neurotrophin antagonist, K252b, failed to inhibit the transforming growth factor alpha-induced increase in dopamine uptake, indicating that transforming growth factor alpha's effects were not mediated by neurotrophin mechanisms. The actions of transforming growth factor alpha on the differentiation of dopaminergic neurons only partially overlapped with those of epidermal growth factor. Thus, while transforming growth factor alpha and epidermal growth factor are believed to share the same receptor they differentially affect dopaminergic cell development in vitro. These results indicate that transforming growth factor alpha is a trophic factor for mesencephalic cells in culture and suggests that transforming growth factor alpha plays a physiological role in the development of these cells in vivo.