水性聚氨酯电导率与聚沉值的研究

研究了软（硬）段含羧基的水性阴离子纳米聚氨酯体系的n(NCO)/n(OH)比值，COOH的质量分类，反离子各类，合成方法与电导率关系及产生的原因；探讨了该体系的n(NCO)/n(OH)值，COOH的质量分数，合成方法与临界聚沉值（Cc.c)的关系和规律。并分析，比较了软（硬）段含羧基的水性阴离子聚氨酯体系电导率与Cc.c二者关系，得出了随COOH的质量分数升高，二者变化相同，随n(NCO)/n(OH)比值升高,二者变化相反的结论。     

利用鱼眼照片恢复景物的深度信息

通过照片获取深度信息的技术已经研究多年，也产生了各种算法，但这些算法或者需要一张以上的照片来计算，或者运算量比较大。此外，它们的共同点是：各种方法采用的照片是用普通镜头拍摄的。笔者给出一种新的方法：利用一张鱼眼镜头照片和少量的辅助手段来获取深度信息。建立了一种简便而又准确的辅助手段，从而可以构造景物的三维框架，最终可以实现在景物内的任意位置向任意方向进行虚拟浏览。     

Magnetic field hysteresis of critical currents in Bi(2223)/Ag tapes and a way to overcome it

Experiments showing hysteresis of critical currents versus the external magnetic field I_c(B_e) were performed with two multifilamentary Bi(2223)/Ag tapes. The I_c(B_e) hysteresis is observable in the transversal as well as in the longitudinal orientation of the long axis of the tape with respect to the magnetic field. Based on the idea that the hysteresis is the effect of trapped flux in a network of well-connected current paths, a way to overcome this effect has been proposed and experimentally verified. The induced frozen-in screening currents are split into several parallel current patterns by cycling the external magnetic field around the adjusted value. Using the proposed method, the ‘neutral’ I_c(B_e) characteristics have been found. Approximate calculations of the penetration depth of the trapped flux show that the network of well-connected current paths could be formed by several disk-shaped grains (≈ Φ8 × 0.4 μ) stacked into more or less axially ordered (quasi cylindrical) colonies of average dimensions estimated to ≈ Φ8 × 4 μm.     

Effects of shear flow on long-ranged correlations,spinodal demixing kinetics,and the location of the critical point and cloud point

A derivation of an expression for the shear rate-dependent Ornstein Zernike structure factor is discussed, together with the resulting anomalous behavior of the turbidity. The predicted scaling behavior of the turbidity, comprising the effect of both temperature and shear rate, is in good agreement with experiments on binary fluids. Then initial spinodal decomposition is discussed, and an explicit expression for the time- and shear rate-dependent effective diffusion coefficient is derived, which shows all the typical characteristics of anisotropic light scattering patterns that are observed experimentally for binary fluids. Next it is shown that the spinodal is shifted linearly with the (bare) Peclet number for not too large Peclet numbers, whereas the cloud point is singularly displaced into the unstable region due to a shear now. This is in agreement with an experiment on a two-polymer/solvent mixture and binary fluid mixtures. It is argued that light scattering is useless to determine the location of the spinodal of a sheared system.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

小麦、玉米控制灌溉技术研究

198 6～ 1998年 ,在山东省的 3个灌溉试验站 ,对冬小麦、秋玉米进行了控制灌溉试验 ,对农作物的多个生育阶段 ,按高产的要求 ,分别给予适时、适量的灌溉水 ,来控制作物不同生长期的根层土壤含水量 ,从而控制作物不同生长期根系对水分的吸收 ,培植农作物的“丰产群体结构”和与之相适应的“高产理想株型” ,适当降低无效的蒸腾量 ,使农作物能在高产的基础上再增产 .该项控制灌溉技术获得了明显的节水、增产效果 ,灌溉水的生产效率超过了 10kg/m3,产量超过了 8t/hm2 .     

内燃机车曲轴中频淬火过程的数值模拟

借助 ANSYS大型有限元分析软件 ,实现了 16 V2 4 0曲轴淬火过程的计算机模拟 ,模拟结果可直观地显示出任一时刻曲轴表面及内部的温度分布、冷却曲线以及淬火结束后的残余应力分布 ,并能预测淬硬层深度。同时对比了轴颈内圆角处进行淬火和不进行淬火两种工艺的效果 ,为现场提供了用虚拟现实方法详尽分析和研究淬火工艺的工具。     

Effects of fluoropolymer addition to an epoxy on scratch depth and recovery

Samples were prepared by addition of a fluorinated poly(aryl ether ketone) (12F-PEK) to a commercial epoxy resin and curing at either 24 °C or 70 °C. The concentrations of fluoropolymer in the samples were 0, 5, 10, 20, 30, 40, and 50%. Phase inversion facilitates the formation of more and more smooth surfaces for scratch testing with increasing fluoropolymer concentration. A progressively increasing load from 0.03 N to 12 N was administered with a diamond tip to the surfaces of the samples; depths were determined within ±7.5 nm. The original scratch depth is a function of the fluoropolymer concentration. Scratch recovery (healing) reaches values up to 95%. Plots of the residual depth versus concentration of the fluoropolymer at 4, 6, 8, and 10 N reveal minima for all forces and both temperatures. Addition of only 5% or 10% 12F-PEK improves the scratch recovery significantly. The results are explained by changes of material morphology with the fluoropolymer concentration. Electronic Publication     

Rhizobium trifolii capsular polysaccharide: a novel biopolymer with striking physical properties

The physical properties of the capsular polysaccharide of Rhizobium Trifolii (CPS) were investigated. Viscosity measurements provided information about the hydrodynamic volume of single coils, the perturbation of solvent flow and the shear-thinning behaviour of concentrated solutions. Changes in chain geometry and the development of an intermolecular network as a function of temperature were monitored using the techniques of optical rotation and dynamic oscillation. Finally, analysis of calorimetric thermograms elucidated the type of interactions between CPS and the bacterial levan. Overall, the Rhizobium polysaccharide was found to form thermally-reversible gels at an extremely low 'minimum critical gelling concentration' (c_o∼ 0.35gl^-1). At temperatures above the gel melting point (∼ 48°C), however, the compact polymer coils entangled at comparatively high concentrations (about 60 times higher than c_o). In the presence of a highly branched levan, the thermal stability of ordered CPS structures increased as a consequence of thermodynamic incompatibility between the two polymers.     

Fabrication and characteristics of tapes and test magnets made from Ag-Clad Bi-2223 superconductors

Pb_0.4Bi_1.8Sr₂Ca_2.2Cu₃O_x (Bi-2223) precursor powder was prepared by a solid-state reaction of carbonates and oxides of lead, bismuth, strontium, calcium, and copper, and the powder was then used to fabricate silver-clad tapes by the powder-in-tube technique. Transport critical current density (J_c) values>4×10⁴ A/cm² at 77K and 2×10⁵ A/cm² at 4.2 and 27K have been achieved in short tape samples. Long lengths of tape were tested by winding them into pancake coils. Recently, we fabricated a test magnet by stacking ten pancake coils, each containing three 16m lengths of rolled tape, and tested it at 4.2, 27 and 77K. A maximum generated field of 2.6 T was measured in zero applied field at 4.2K and the test magnet generated significant self-field in background fields up to 20 T. The results are discussed in this paper.