醇-水法制备纳米NiO粉末的正交实验研究

纳米NiO粉末具有良好的催化性能、热敏性能及在各种材料中的加工性能,因而被广泛地应用在催化剂、磁性材料、电子元件材料等方面,是一种很有前途的新型功能材料。选用Ni(NO3)2.6H2O为原料,以NH4HCO3为沉淀剂,在醇-水介质中制得了纳米NiO粉末。通过扫描电子显微镜(SEM)对NiO粉末进行了表征。实验过程中,按正交表L8(27)安排了正交实验,通过方差分析确定了醇-水制备纳米NiO粉末的最佳煅烧时间、煅烧温度和醇-水比,并确定了各因素对制备过程的影响程度。     

谈化学新教材的实验设计

在高中化学教学中,用好经典装置的同时,应鼓励学生设计出比“经典装置”更好的新装置,这样不仅培养了学生的环保意识而且还发挥了化学实验在培养学生创新能力上的独特优势。     

利用粉煤灰生产SiC陶瓷原料

利用粉煤灰部分或全部代替石英砂,配以适量的锯末,在高温炉中特定的烧成制度下,采用SiO2-C还原法将粉煤灰中的二氧化硅与锯末中的碳结合制取高性能的SiC陶瓷原料。利用正交实验对合成工艺中的合成温度、保温时间、碳过量数进行了设计和探索性实验,并对合成产物中的碳化硅的含量进行了测试。研究表明,在经催化剂(FeCl26H2O)浸泡12小时,加入2%矿化剂,在1380℃的合成温度下,保温时间2小时,碳过量10%的情况下,生成的SiC陶瓷原料中SiC的含量在53.6%以上。     

突扩突跌掺气设施后泄槽底板脉动压力试验研究

有压洞出口后的突扩突跌掺气减蚀设施在水利工程中经常使用。由于水流受边界条件和掺气的影响,其流态和脉动压力往往与普通水槽的情况有很大的不同。通过水工模型试验,对突扩突跌掺气设施后泄槽底板上的脉动压力进行研究,揭示了掺气设施后泄槽底板上不同流动区域的脉动压力特性。从脉动压力的时域过程、均方根值、偏态系数、峰态系数和主频率等多方面得出冲击区、反射区和稳定区脉动压力的特性是不相同的结论。同一流量时,沿流程底板的时均压力都大于脉动压力的均方根值,在冲击区、反射区和稳定区,脉动压力的均方根值分别是同位置时均压力值的约0.5倍、0.6倍和0.7倍。研究成果可为更好地利用突扩突跌掺气设施提供有益的理论和试验依据。     

正交试验法在PAN原丝纺丝工艺中的应用

利用正交设计方法确定了PAN湿法纺丝过程中影响原丝性能最主要的因素。结果表明 :以计量泵转速、凝固浴温度、负拉伸以及蒸汽拉伸倍数作为考察对象 ,影响原丝性能的最显著因素是蒸汽拉伸倍数 ,其次是负拉伸。以负拉伸、第二拉伸、第三拉伸以及蒸汽拉伸的倍数作为考察对象 ,影响原丝性能最显著的是蒸汽拉伸倍数 ,负拉伸几乎没有影响。利用正交实验结果 ,适当调节蒸汽拉伸倍数 ,制得强度为 6.5～ 7.0cN/dtex ,线密度为 1.1～ 1.3dtex的原丝     

S-苄基-L-半胱氨酸的合成

由溴化苄和L-半胱氨酸直接合成S-苄基-L-半胱氨酸,通过正交试验及统计分析,检验了各影响因子的显著性,确定了最佳工艺条件为：反应时间2.5h,反应温度45℃,原料配比n（溴化苄）：n（L-半胱氨酸）=1：1.在此条件下反应,摩尔产率可达到95%.     

边坡可靠性分析的非线性有限元正交设计算法

非线性有限元正交设计算法，是借助于回归分析，用正交多项式拟合各岩石力学特性参数与各单元滑移面及岩体整体滑动安全余量间的函数关系，以评判边坡工程的可靠性。该法较蒙特卡罗法精度高，能满足工程计算的精度要求，且方法简单、计算时间少，不需改变有限元法的有关方程和计算程序，易为人们接受。     

Relationship between Viscoelastic and Peeling Properties of Model Adhesives. Part 1. Cohesive Fracture

The viscoelastic and peeling properties of polybutadiene/tackifying resin compatible blends have been studied in detail. Viscoelastic properties have been described through the variations of the complex shear modulus, G*(ω), as a function of frequency, ω and peeling properties through the variations of peeling force (F) as a function of peeling rate (V).

After showing the objective character of the peeling curves obtained, the variations of the peeling force and peeling geometry have been studied as a function of volume fraction of the tackifying resin.

In this first paper, the analysis is focused on the first domain of the peeling curves, i.e. the cohesive fracture region. In this region, the peeling properties have been related to the viscoelastic properties in the terminal region of relaxation. It is shown that the longest relaxation time, τ_o, is a reducing parameter of the peeling curves, so a peeling master curve-which is independent of temperature, resin volume fraction and polymer molecular weight-may be defined. Furthermore, the variations of the test geometry as a function of peeling rate have been investigated: the variations of the radius of curvature of the aluminium foil have been analyzed with respect to the viscoelastic behavior of the adhesive, which in fact governs the test geometry.

A detailed analysis of all these features leads to a model which allows one to calculate the peeling curves in the cohesive domain from the adhesive formulation.     

Reactive rock phosphate fertilizers and soil testing for phosphorus: The effect of particle size of the rock phosphate

North Carolina rock phosphate (NCRP) (highly carbonate—substituted apatite) was ground to produce three samples with different particle size distributions. The effectiveness of these fertilizers was compared with the effectiveness of superphosphate in a field experiment and three glasshouse experiments using lateritic soils from south-western Australia. Non-reactive Queensland rock phosphate (low carbonate-substituted apatite from the Duchess deposit) was also used in the pot experiments. Bicarbonate-soluble phosphorus extracted from the soil is widely used in Western Australia to predict plant yields from previously-applied fertilizer dressings. For both field and pot experiments bicarbonate-extractable phosphorus (soil test value) was measured and related to subsequent plant yields.As calculated from the initial slope of the relationship between yield and the level of P applied, finely powdered NCRP was about 5–32% as effective as freshly-applied superphosphate in the year of application and also for two years after application in the field experiment, and for two successive crops in the three pot experiments. For both field and pot experiments, finely powdered NCRP, was at best, 1.5–2.0 times as effective as granular NCRP. Relative to freshly-applied superphosphate, the effectiveness of rock phosphates usually decreased with increasing level of application.For each of the crops in the field experiment, the relationships between yield and phosphorus content of plants (i.e. internal efficiency curves) were similar for all fertilizers. Thus the low effectiveness of the rock phosphates relative to superphosphate was solely due to much less phosphorus being taken up by plants. By contrast, in the pot experiments internal efficiency curves differed for different fertilizers. This is attributed to differences in the rate of phosphorus uptake by plant roots during the early stages of plant growth.For both field and pot experiments, soil test calibrations (the relationship between yield and soil test value) differed for rock phosphates and superphosphate. For superphosphate, soil test calibrations also differed for the three different years after the initial application of this fertilizer in the field experiment. For the second crop in the pot experiment, soil test calibrations differed for superphosphate applied at different times (before the first and the second crop). These results point out the difficulty of applying soil testing procedures to soils that have experienced different histories of fertilizer application.     

柔性分离盘抑制圆柱涡激振动的风洞试验

该文利用附属柔性分离盘对圆柱涡激振动(VIV)控制问题进行了风洞试验研究。针对弹性支撑的圆柱及不同长度柔性分离盘的试验模型,在雷诺数7 500-40 000情况下,测定不同约化速度(3.5-18.7)下的振动瞬态位移。结果表明:柔性分离盘长度(L)/圆柱直径(D)比为0.6、0.8和1三种圆柱的横向无因次均方根振幅远小于单圆柱,涡激振动抑制效果很好,均在77.6%以上,其中L=0.8D的圆柱抑制效果最佳,几乎无振动;而L=1.2D和1.5D的圆柱反而出现振动增强,约4.5%和9%。对比单圆柱的共振区,附属柔性分离盘的圆柱共振区在约化速度上更靠后且范围更大。