爆炸荷载下矩形板的塑性动力响应

本文采用Jones-Sawczuk控制方程,导出了脉冲荷载下矩形板最大残余挠度的简单理论计算公式,并应用该公式和动态屈服条件,计算了固支方板在爆炸荷载下的最大残余挠度值,与试验结果比较,取得了令人满意的结果。     

金属离子/胆酸钠超分子水凝胶特殊温度响应性的机理研究

研究了胆酸钠溶液与金属离子溶液混合自组装而成的水凝胶随温度升高而机械强度增强的独特温度响应性. 利用透射电镜(TEM)和X射线衍射(XRD)仪表征了水凝胶中聚集体的微观形貌及分子排列方式. 考察了其流变学行为、荧光性质随温度的变化. 结果表明,升温促进凝胶形成的速率, 并提高凝胶的机械强度. 随着温度的升高, 稀土离子的荧光强度显著增强. 表面张力测量表明, 胆酸钠溶液的临界胶束浓度随温度的升高而略有降低. 综合实验事实, 我们提出随温度升高导致的凝胶强度增强行为是由胆酸钠分子在高温下聚集能力增强的结果.     

纳米CaCO3微晶的晶格畸变和反常红外特性

利用TEM、SEM、X射线衍射(XRD)和Voigt函数单峰分析法讨论了纳米CaCO₃微晶结构,解释了纳米CaCO₃微晶的反常红外吸收特性,并认为微结构中的尺寸效应使得纳米CaCO₃晶格中存在较大的畸变应力,从而引起了碳酸钙微晶的红外ν₃吸收峰有约40 cm^-1的蓝移和明显窄化。     

高效液相色谱指纹图谱应用于地黄的研究

利用高效液相色谱建立了地黄的色谱指纹图谱。采用反相C1 8柱 (5 μm ,1 5 0mm× 4.6mm) ,流动相甲醇∶水 (V V =5∶95 ) ,检测波长为 2 80nm ,流速 1 .0mL min进行实验。根据相对保留值和相对面积值对色谱指纹图谱进行分析对比研究 ,建立了控制地黄药材质量的新方法。该法为中药样品的鉴定提供了较全面的信息 ,并为HPLC在复杂组分的样品分析领域开拓了新的应用途径。     

高速列车轴承可靠性评估关键力学参量研究进展

轴承是高速列车牵引传动和轮轴系统的关键零部件. 受列车运行过程中电机转矩、齿轮啮合以及轮轨随机激励的影响,轴承可能发生疲劳破坏, 严重影响高速列车的行车安全.我国特有的复杂运用条件对轴承部件的疲劳性能提出了更高的要求,而轴承疲劳可靠性的基础理论和关键技术是我国轴承正向设计研发中的薄弱环节.可靠性评估方面的相关研究在解决轴承可靠性研究的瓶颈问题中起到了承上启下的关键作用.高速列车轴承可靠性评估手段与技术旨在获得使用环境中轴承可靠性评估的关键力学参量,并以此推动复杂激励下轴承疲劳可靠性理论研究. 因此,需要哪些关键力学参量并且在复杂的实际使用环境下如何去获取这些力学参量是进行高速列车轴承可靠性评估的关键所在.本文首先概述了高速列车轴承所处的复杂使用环境及运用中的主要失效模式,并据此分析了高速列车轴承可靠性评估所需的关键力学参量,强调了轴承内部滚滑行为和载荷分布在可靠性评估和轴承状态监测中的重要作用,之后从计算模型和测试技术等方面系统阐述了针对这两个关键力学参量的研究进展.最后提出了在高速列车轴承可靠性评估关键力学参量特征及测试技术研究中值得关注的若干问题.      

具有脉冲扰动的非线性时滞微分方程

本文研究一类脉冲非线性时滞微分方程解的性质，讨论了其解的整体存在性及非振动解的渐近性，也给出了其所有解振动的充分条件．     

碳纳米管/纳米金修饰金电极上柔红霉素电化学行为的研究

将碳纳米管与纳米金结合修饰在金电极上制成修饰电极,并用于柔红霉素(DNR)的电化学行为研究和检测.在4.4 mmol/L磷酸盐缓冲溶液(pH=5.81)中,DNR在碳纳米管-纳米金/Au电极上有一对灵敏的氧化还原峰.还原峰电流与DNR的浓度在3.2×10-8～1.0×10-6mol/L和1.0× 10-6～2.2× 1...     

The unstable behavior of cellular premixed flames induced by intrinsic instability

The unstable behavior of cellular premixed flames induced by intrinsic instability is studied by two-dimensional unsteady calculations of reactive flows. In the present numerical simulation, the compressible Navier–Stokes equation including a one-step irreversible chemical reaction is employed. We consider two basic types of phenomena to account for the intrinsic instability of premixed flames, i.e., hydrodynamic and diffusive-thermal effects. The hydrodynamic effect is caused by the thermal expansion through the flame front; the diffusive-thermal effect is caused by the preferential diffusion of mass versus heat. A disturbance with several wavelength components is superimposed on a planar flame, and the formation of a cellular flame induced by hydrodynamic and diffusive-thermal effects is numerically simulated. After the cellular-flame formation, the combination and division of cells are observed. The behavior of cellular-flame fronts becomes more unstable when the Lewis number is lower than unity, since the diffusive-thermal effect has a great influence on the unstable behavior. The cell size changes with time, and its average is greater than the critical wavelength and becomes smaller by decreasing the Lewis number. The flame velocity of cellular flames depends strongly on the length of computational domain in the direction tangential to the flame front. As the length of computational domain increases, the flame velocity becomes larger. This is because the long-wavelength components of disturbances play an important role in the shape of cellular flames, i.e., in the flame-surface area.     

Kolmogorov scaling of turbulent flow in the vicinity of the wall

How to scale even the simplest of turbulent flows continues to be a cause for considerable controversy. In the present research, a data base compiling results from channel flow direct numerical simulations and turbulent boundary layer experiments is employed to investigate the properties of shear and normal Reynolds stresses very close to the wall. Two types of scaling based on Kolmogorov length and velocity scales are analyzed. It is shown that it is highly likely that large length scales of the order of the channel half-width or the boundary layer thickness play an important role even in the innermost regions of wall-bounded turbulent flows, which hints at the persistence of Reynolds number effects in even high Reynolds number flows.     

Synthesis and magnetic properties of Co1−xZnxFe2O4+γ nanoparticles as materials for magnetic fluid hyperthermia

Nanoparticles of the single spinel phase Co_1−xZn_xFe₂O_4+γ of mean size 3-23 nm, as determined by X-ray diffraction analysis, were synthesized by the co-precipitation method followed by a temperature treatment. Magnetic studies carried out in the range of 4.5-550 K revealed gradual transition from ferrimagnetic to superparamagnetic to paramagnetic behaviour depending on the composition and particle size. The observed behaviour indicates a broad distribution of volume sizes of the nanoparticles. Particular importance can be ascribed to the composition of x=0.6 where the observed transition temperature to the paramagnetic state at 310-334 K suggests applicability of this material for magnetic fluid hyperthermia in a self-controlled regime.