套管对埋地燃气管道阴极保护电流屏蔽探讨

分析套管对城镇燃气埋地钢管阴极保护电流产生屏蔽的原因,提出了解决方法。     

荷电雾滴上粉尘粒子的扩散沉积

采用浓度边界层理论讨论了细微粒子在荷电雾滴表面上的扩散效应。根据雾滴前向驻点处有限直径粒子的沉积行为分析了雾滴与粒子间的静电作用对小粒子捕集效果的影响。     

一维不定常等熵流的势函数

本文在将势函数引进一维不定常等熵流理论的基础上,直接应用二维无旋定常超音速流的特征线方法中的一些结果,推导出一维不定常流的特征线方程,并阐明势函数对时间偏导数的物理意义,最后还推导出一维不定常流的总焓比随马赫数M变化的关系式。     

基于区间优化的实根隔离遗传算法

提出了一种通过改进遗传算法求函数驻点值作为实根的隔离点,进而使用改进的二分法来求解近似根的方法.通过比较,该方法是可行、有效的,且具有较高的精度,并给出了相应的算例.对于该方法得到的隔离点,还可以应用其它的优化方法进行求解,这将是下一步研究的主要工作.     

Keynesian Dynamics and the Wage–Price Spiral: Identifying Downward Rigidities

We develop a constrained bivariate switching model to explore empirically the behavior of wage and price Phillips-curves for high- and low-inflation regimes. Using this switching regression technique with a structural simultaneous equations model of Phillips curves, we identify significant lower floors for wage and price inflation. We interpret these lower floors as the relevant downward rigidity for wages and prices. Such floors imply that the adverse real-wage adjustment mechanism that can be identified in the high-inflation regime may disappear in the low-inflation regime, where money-wage inflation and price inflation, and thus real-wage movements, may become rigid. Consequently, the economy may be stabilized then, but trapped in a long period of stagnation in such a low-inflation situation. Such properties of kinked wage and price Phillips-curves are thus important and could also be of help to break another important destabilizing feedback channel, the Fisher debt deflation mechanism, according to which economies, in which highly indebted firms are unable to prevent price deflation, will experience severe crisis or even economic breakdown if the resulting deflationary spiral cannot be stopped.JEL classifications: C39; E24; E31; E32; J30     

驻点法在桩群模拟中的运用

采用有限元方法建立了二维平面水流模型,并引入驻点的概念模拟水中桩柱对水流的影响,即在计算中将网格节点设置于桩柱处,并在该节点设置滞流边界条件,即流速为0 m/s.以长寿朱家坝码头的高桩码头方案为算例进行了模拟计算,结果表明该方法可以较好地模拟桩群对水流流速、流态的影响.     

磁场对熔盐射流冲击传热的影响

以永磁铁构建定磁场,进行外加磁场作用下熔盐射流冲击传热的实验研究,并得到Nusselt数Nu驻点关联式和径向分布。结果表明,在驻点区范围内,Nusselt数较无磁场作用时增大,传热得到比较明显的增强,而在壁面射流区,这种强化传热效果逐渐减弱。此外,当Reynolds数Re一定时,熔盐Nusselt数随着磁场强度的增加而增大,且驻点处强化传热效果最为显著。在Reynolds数Re=6400与磁场强度B=2800 Gs条件下,熔盐驻点Nusselt数Nu₀提高约6％,可见磁场作用对熔盐射流冲击传热具有一定的强化效果。     

机械刻划过程中的材料滞留特征分析

为研究光栅毛胚材料在机械刻划过程中滞留区的产生及分布特征。基于LEE和SHAFFER提出的正交切削滑移线场理论模型,在机械刻划塑流剖面内建立了带有滞留区特征的滑移线场模型,提出量纲一滞留区几何尺寸的计算方法。并结合有限元仿真方法获得了机械刻划三向分力,经拟合得到滞留区几何尺寸的演变规律,揭示了滞留区产生机理及分布特征。最后通过机械刻划试验,验证了槽面滞留区的分布特征及其对光栅槽质量的影响。研究结果表明：在一定的机械刻划加工工艺条件下,光栅槽面形成明显分界线,该线将光栅槽面分为塑性变形区和滞留区。因槽面分区成形机理和槽面质量不同,多道槽机械刻划槽面会发生非线性变形,最终将影响衍射光栅的光学衍射效果。此研究结果为从滞留区角度考虑大负前角刀具机械刻划槽形及槽面质量的控制优化问题提供了理论及试验依据。     

Micro-mechanisms of residual oil mobilization by viscoelastic fluids

Four typical types of residual oil, residual oil trapped in dead ends, oil ganglia in pore throats, oil at pore corners and oil film adhered to pore walls, were studied. According to main pore structure characteristics and the fundamental morphological features of residual oil, four displacement models for residual oil were proposed, in which pore-scale flow behavior of viscoelastic fluid was analyzed by a numerical method and micro-mechanisms for mobilization of residual oil were discussed. Calculated results indicate that the viscoelastic effect enhances micro displacement efficiency and increases swept volume. For residual oil trapped in dead ends, the flow field of viscoelastic fluid is developed in dead ends more deeply, resulting in more contact with oil by the displacing fluid, and consequently increasing swept volume. In addition, intense viscoelastic vortex has great stress, under which residual oil becomes small oil ganglia, and finally be carried into main channels. For residual oil at pore throats, its displacement mechanisms are similar to the oil trapped in dead ends. Vortices are developed in the depths of the throats and oil ganglia become smaller. Besides, viscoelastic fluid causes higher pressure drop on oil ganglia, as a driving force, which can overcome capillary force, consequently, flow direction can be changed and the displacing fluid enter smaller throats. For oil at pore corners, viscoelastic fluid can enhance displacement efficiency as a result of greater velocity and stress near the corners. For residual oil adhered to pore wall, viscoelastic fluid can provide a greater displacing force on the interface between viscoelastic fluid and oil, thus, making it easier to exceed the minimum interfacial tension for mobilizing the oil film.