Available nitrogen in soils and its determination by the ‘Nmin-method’ and by electroultrafiltration (EUF)

Excess nitrogen fertilizer rates are an environmental hazard. To avoid excess rates, the level of available nitrogen in the soil must be known and considered for assessing the nitrogen fertilizer rate. In arable soils nitrate and exchangeable ammonium in the rooting depth of a crop are directly available to plant roots. These two nitrogen forms are recovered with the Nmin method and they are considered in assessing the nitrogen fertilizer rate for arable crops.Besides nitrate and ammonium recovered by the Nmin method from soil samples taken in early spring, a considerable amount of organic soil nitrogen may be mineralized during the growth period and contribute to crop nutrition. The nitrogen mineralization potential can be determined in incubation tests. The absolute quantities of mineralized nitrogen thus obtained, however, are much higher than the mineralization rates under field conditions. It is for this reason that incubation tests have not obtained a major importance for assessing nitrogen fertilizer rates.With the electro-ultrafiltration (EUF) method nitrate, ammonium, and a minor portion of organic soil nitrogen are extracted from a soil suspension. There is experimental evidence that this organic nitrogen (=Norg) is easily mineralizable. Based on field experiments with cereals and maize formulae were established by which the nitrogen fertilizer rate can be calculated. In these formulae nitrate, ammonium and organic nitrogen extracted by EUF are considered.Advantages and drawbacks of the Nmin method and EUF method are discussed.     

New and Improved Tests for Adhesion

Three new methods are discussed for measuring the work G_a, required to detach unit area of an adhering material from a substrate. The first is a simple modification of the Outwater double-torsion test for long rectangular plates, bonded together. This method is suitable for evaluating aluminum-epoxy bonds, for example, or the transverse strength of fibrous composites. The second is a pull-off test for long strips adhering to a rigid surface. It seems suitable for adhesive tapes and laminates. The third is a reconsideration of the “blister” test for films and coatings, in which a circular debond at the interface is made to grow by internal pressure. The relation obtained between pull-off force F for a strip, or blow-off pressure P for a layer, takes the unusual form:

F⁴ (or P⁴) ∞ KG³_a

where K is the tensile stiffness of the detaching layer. This dependence arises from the non-linear (cubic) relation between load or pressure and deflection in these configurations. Nevertheless, the product Fθ, where θ is the angle of detachment of a strip, or Py, where y is the height of a “blister”, give direct measures of the strength of adhesion G_a, independent of the stiffness of the adhering material and of the extent of detachment.     

工业纯铝在模拟海水中的电化学腐蚀行为

为研究铝在海水中的腐蚀过程,采用电化学阻抗谱、浸泡试验、扫描电子显微镜研究工业纯铝在模拟海水中的腐蚀行为.结果表明:铝在模拟海水中发生点蚀的区域为富含Fe的晶间化合物处,点蚀半径随时间的增加而扩大.铝在模拟海水中的溶解曲线分为4个区间:活性溶解区、过渡区、过钝化区、钝化区.铝在模拟海水中,极化电位为过钝化区时,转移电阻R t随着电位的升高而变小,铝发生严重的点蚀;而极化电位为钝化区时,铝的转移电阻R t随着电位的升高基本不变,铝的溶解行为受到抑制.工业纯铝在模拟海水中发生点蚀的电位区间是-0.45～-0.65 V,钝化电位区间为-0.75～-0.85 V.     

变电站远程监控系统研究

研究了分布式Web计算技术开发远程监控系统的关键技术,就基于IP网络实现变电站远程监控的主要思路和技术问题进行说明和分析讨论.从信道带宽、网络机制、远动协议、信息安全等多方面讨论了IP网络传输时保证远动QoS的措施方法以及IP网络传输对信息安全的防护措施.     

双洞口配筋砌块砌体框支墙梁试验

为研究双洞口配筋砌块砌体框支墙梁地震前后的受力模式,在拟动力子试验前后进行了底层框架配筋砌块短肢砌体剪力墙结构三层足尺模型的竖向力静载试验.试验结果表明:托梁与上部墙体表现出良好的协同工作能力,其工作模式为拉杆拱.通过对其在拟动力试验前后的受力模式进行了比较,可知带洞口配筋砌块砌体框支墙梁结构体系在墙体受到一定损伤时,并不会使墙梁的受力机理发生明显改变.     

导电涂料的研制

为了获得性能优良的导电涂料 ,采用对比试验和正交试验的方法对导电涂料进行了研究 ,分别对导电涂料的电阻、硬度、耐冲击强度、柔韧性等性能进行了测试 ,经过试验 ,确定了无机导电涂料的最佳配方为 :石墨 10 0g ,铅酸钡 10g ,三氧化二锑 5g ,二氧化钛 35g ,碳化硅 10g ,硅酸盐溶胶 170g。以此配方研制出了一种成本较低、生产工艺简单、具有良好的导电、导热性能的无机导电涂料。     

基于无线通信方式的TV二次压降现场测试方法

针对传统的TV二次压降现场测试方法存在的问题,提出基于无线通信技术的检测方法。以提高工作效率,降低安全风险。     

电控柴油机分缸均衡控制算法及试验

柴油机各个气缸的进气量、喷油量、燃烧等存在差异,导致气缸间存在做功差异,直接影响柴油机转速的平稳性以及排放性能等。针对位置式电控柴油机,采用PI闭环控制,通过瞬时转速信号识别并计算各缸的工作差异,利用分缸均衡控制算法对油量进行补偿修正。试验结果显示低转速稳态工况转速波动由7 r/min降至3 r/min,各缸工作不均匀度由±5 r/min降至±2 r/min,在瞬态过程和高转速3 400 r/min时该算法仍然适用有效。     

一维炉系统的测试实验

一维炉是一种研究煤的热解燃烧和结渣等方面的实验系统,可用于模拟电厂煤粉的燃烧特性。以元宝山褐煤为燃料,介绍了一维炉的结构和功能,并对系统的可靠性进行了验证,利用烟气分析仪及热重分析仪对燃烧后的尾部烟气及灰渣进行了分析测定。结果表明:尾部烟气含氧量与灰渣可燃部分剩余量均在理论计算值的误差允许范围内,说明一维炉密封良好,系统内各部分正常运行,对维炉的调试和研究具有一定的参考意义。     

Dynamic buffering performance of the honeycomb paperboard filled with polyurethane

A new kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, we analyzed the mechanical behaviors of the material under different conditions and obtained the inherent influencing laws of some factors on the material＇s dynamic buffering performance. It was shown that the dynamic buffering performance varied directly with impact velocity, and inversely with the void diameter, thickness and buffeting area of the composite material.