用正交曲线坐标系下的粘性层方程求解湍流分离流动

本文应用粘性层模型,采用贴体的正交曲线网格,对湍流流动进行了计算.计算结果表明,不论有无分离,该方法都能较准确地模拟.     

风车、负载与场地之间的匹配

本文讨论风车、负载与场地之间的匹配,并引入最佳传动比和有效系数等概念。也给出了典型工况下的最佳启动风速和相应的有效系数。 风车与负载的匹配 若以C_p表示风车的功率系数,则其功率为     

二甲氨基查耳酮修饰的β环糊精在不同溶剂中的光物理行为

研究了不同过渡金属离子对以二甲氨基查尔酮修饰的β环糊精在不同溶剂中的荧光猝灭问题.发现经过修饰的查尔酮在水溶液中对Cu2+具有特征的识别功能.其猝灭速率常数比其他研究的金属离子大一个数量级以上.然而当该修饰环糊精处于非水溶剂如DMF中时Cu2+离子特征识别功能不再存在,而具有平面四方电子构型的Ni2+则表现出最强的络合功能,这可能与化合物联结链中存在四个用亚乙基相联的络合位点易于生成平面四方结构有关.表明主/客体化合物在结构空间上的互补性,在它们的络合过程中具有重要意义.     

初中数学解题反思途径探析

解题反思是促进学生自身数学思维形成的重要方式,其既能使学生形成完善的知识体系,又能促进其思维开发,提高学习效率.鉴于此,本文主要对初中数学的解题反思进行探讨,以促进学生的解题效率与准确性提高.     

Dynamic Superposition and Levitation Capability of Two Confronting Ultrasonic Waves

The superposition dynamics of two confronting ultrasonic waves and their levitation capability for centimeter-sized thin disks are investigated by numerical analyses and validated by experiments. The sound pressure simulation reveals that two opposite ultrasonic waves provide a more effective standing-wave field than a single ultrasonic wave when the diameter of disk-shaped object approaches the wavelength scale. The dynamic superposition of two confronting beams facilitates the acoustic levitation of the clay disk and aluminum disk with diameters of 0.97 and 0.90. The acoustic radiation forces exerting on these thin disks are measured experimentally, which exhibit a better levitation stability for the centimeter-sized thin disks. The equilibrium levitation positions of the two disks are located near the sound pressure node, and the maximum acoustic radiation pressure on their surfaces is less than one percent of the maximum sound pressure.     

阶梯式循环冲击下煤中氢键红外光谱变化规律

煤结构中存在的大量氢键对其化学结构和性质具有重要影响。为了研究煤在冲击破坏过程中氢键的变化。设计落锤循环冲击系统,实现对煤样的循环定量冲击。利用红外光谱仪进行光谱分析。研究得出东庞1/3焦煤主要的氢键类型是free OH groups, OH…π, OH…OH, cyclic OH tetramers和OH…N以及它们随冲击破坏的变化规律。在冲击力的作用下,煤体分子间氢键吸收强度变化非常明显,自由羟基也在冲击作用下发生机械力化学反应。对红外光谱进行高斯函数拟合分峰,发现各类氢键吸收强度随着冲能量的增加而减小,但其趋势在放缓。统计两者关系,得到各类氢键的光谱吸收强度与冲击能量的拟合方程,两者符合幂函数关系。对比拟合方程的幂指数,得出氢键在受冲击破坏时发生变化的敏感性顺序：free OH groups>cyclic OH tetramers>OH…N>OH…π>OH…OH。     

Soliton Solutions,B/icklund Transformations and Lax Pair for a （3 ＋ 1）-Dimensional Variable-Coefficient Kadomtsev-Petviashvili Equation in Fluids

Under investigation in this paper is a （3 q- 1）-dimensional variable-coefficient Kadomtsev-Petviashvili equation, which describes the propagation of surface and internal water waves. By virtue of the binary Bell polynomials, symbolic computation and auxiliary independent variable, the bilinear forms, soliton solutions, Backlund transformations and Lax pair are obtained. Variable coefficients of the equation can affect the solitonic structure, when they are specially chosen, while curved and linear solitons are illustrated. Elastic collisions between/among two and three solitons are discussed, through which the solitons keep their original shapes invariant except for some phase shifts.