混凝土结构保护层开裂时钢筋的临界锈蚀率模型

基于弹性理论与Bazant理论模型,引入拉伸损伤的概念,对混凝土保护层内环向应力进行修正,建立了混凝土保护层开裂时的临界锈胀力与钢筋临界锈蚀率模型.考虑钢筋混凝土界面间隙及锈蚀产物在裂缝中的填充效应,探讨了完全弹性、Bazant理论模型与拉伸损伤3种不同的环向应力下,钢筋直径、保护层厚度、锈胀系数对临界锈蚀率的影响.结果表明:临界锈蚀率随钢筋直径的增大而减小,随保护层厚度、锈胀系数的增大而增大.弹性下的临界锈蚀率大于Bazant理论模型与拉伸损伤下的临界锈蚀率.最后,与Morinaga的基于试验的临界锈蚀率模型比对,验证了模型的合理性.     

Thermal diffusivity determination of solids by time-domain photoacoustic piezoelectric technique

Thermal–physical property is one of the most important properties of materials. The conventional frequency-domain photoacoustic piezoelectric(PAPE) technique has been developed as an important method for thermal diffusivity determination. In this paper, the PAPE technique is extended to time domain(TD). First, based on a simplified thermoelastic model, the TD PAPE theory under square-wave-modulated excitation was developed,the dependence of the TD PAPE signal on modulation frequency as well as material parameters was obtained, and the determination of thermal diffusivity was simulated and theoretically analyzed. Second, the experimental system and the corresponding measurement method were established. Third, thermal diffusivities of various standard samples, such as copper, aluminum, and nickel, were measured, and the effectiveness of the technique was verified. The results show that the TD PAPE technique can provide a simple, fast and effective way for thermal diffusion study.     

Constructal entransy optimizations for insulation layer of steel rolling reheating furnace wall with convective and radiative boundary conditions

Based on the entransy dissipation extremum principle for thermal insulation process, the constructal optimizations for a plane insulation layer of the steel rolling reheating furnace wall with convective and radiative boundary conditions are carried out by taking the minimization of entransy dissipation rate as optimization objective. The optimal construct of the plane insulation layer is obtained. The results show that for the convective heat transfer boundary condition, the optimal constructs of the insulation layer obtained based on the minimizations of the entransy dissipation rate and heat loss rate are obvi- ously different. Comparing the optimal construct obtained based on the minimization of the entransy dissipation rate with that based on the minimization of the heat loss rate, the entransy dissipation rate is reduced by 5.98 %, which makes the global thermal insulation performance of the insulation layer improve. For the combined convective and radiative heat transfer boundary condition, compared the insulation layer having an increasing thickness with that having constant thickness and a decreasing thickness, the entransy dissipation rates are reduced by 16.59 % and 39.72 %, respectively, and the global thermal insulation performance of the insulation layer is greatly improved.There exits an optimal constant coefficient α2,opt which leads to the minimum dimensionless entransy dissipation rate of the insulation layer. The difference between the optimal constant coefficients α2,opt obtained based on the minimizations of the entransy dissipation rate and the maximum temperature gradient of the insulation layer is small. This makes the corresponding thermal stress obtained based on the minimum dimensionless entransy dissipation rate also be small, and the global thermal insulation performance and thermal safety of the insulation layer are improved simultaneously. The results obtained can provide some guidelines for the optimal designs of the insulation layers.     

大鼠原代肝细胞的标记和移植方法

探讨CM-DiI标记大鼠原代肝细胞的最佳浓度、细胞的移植量和移植途径.采用原位胶原酶灌注和密度梯度离心法分离、纯化大鼠肝细胞,用不同浓度CM-DiI进行标记,筛选出CM-DiI的最佳标记浓度,分别从门静脉、尾静脉移植到2/3肝切除0h大鼠,对细胞移植36h后的肝组织石蜡切片和冰冻切片分别进行免疫组织化学分析和荧光观察.结果显示,4μmol·mL-1浓度的CM-DiI和肝细胞孵育5min,细胞标记率高达95%.每克大鼠残肝移植0.8mL的细胞悬液(107个·mL-1)和0.2,0.4,0.6mL移植后检测到的标记细胞数目相比有显著性差异(P0.01),经肝门静脉移植后可以检测到的标记细胞数比尾静脉多(P0.01).CM-DiI标记大鼠原代肝细胞的最佳浓度为4μmol·mL-1,标记细胞的最佳移植量为每克大鼠残肝移植0.8mL的细胞悬液(107个·mL-1)、最佳移植途径为经肝门静脉移植.     

具有非线性传染率的随机SIRS流行病模型的渐近性态

研究一类具有非线性传染率且接触率系数受到白噪声干扰的随机SIRS流行病模型,证明了该模型正解的全局存在唯一性.通过构造Lyapunov函数讨论了模型解的渐近性态:当基本再生数小于1时,模型的无病平衡点是随机全局渐近稳定的;当基本再生数大于1时,随机系统的解围绕确定性模型的正平衡点振荡,且白噪声强度越高,振幅越大.最后,数值模拟结果验证了主要结论.     

普通群体与近交群体的对比分析

对普通群体与近交群体的有关概念、性质、影响因素、基因型频率的动态趋势以及随机交配率与随机交配指数对基因型频率的影响进行分析.结果表明:普通交配与近交的概念不同;随机交配率与随机交配指数性质不同;普通群体3种基因型频率在世代间的动态逐渐趋于平衡,近交群体3种基因型频率的动态趋于近交系数等于1的状态;随机交配率与基因型频率呈曲线相关,近交系数与基因型频率呈直线相关.     

环境温度对车载LNG低温绝热气瓶日蒸发率影响的实验研究

为研究环境温度对车载LNG低温绝热气瓶静态日蒸发率的影响,以450 L标准高真空多层绝热气瓶为例,采用液氮(LN2)作为工质,进行了一系列LN2日蒸发率试验,然后通过理论分析与实验测定,给出了静态日蒸发率与环境温度之间的关系,指出环境温度对车载LNG低温绝热气瓶静态日蒸发率的影响是明显的,该结论为降低低温容器蒸发率提供了参考方法和依据。     

DTMSN中一种多分组代码分发模型

现有的容延迟移动传感器网络的代码分发模型都是以实现单个分组分发为前提的,针对这一问题,提出了一种多分组代码分发模型.在该模型中,汇聚节点将代码分为l(l≥2)个相等大小的分组,并随机选择l个不同普通移动节点分别作为这l个分组的第一个分发节点;然后利用随机理论和接触率矩阵分别为各个分组建立马尔科夫过程,从而计算出各分组的分发延迟;最后得到所有分组都完成分发所需时间T的取值范围.通过仿真证明了该模型的正确性.     

基于技术溢出内生的非对称双寡头合作研发研究

合作研发是当今社会各界共同关注的重要课题。基于AJ模型,引入内生的技术溢出决策机制,建立成本不对称且产品可替代的双寡头合作研发博弈模型,揭示了成本差异、产品可替代性及自然溢出率对研发投入和社会福利的影响。根据独立性检验得到对应的博弈均衡解,并证明研发及技术溢出决策都合作将达到帕累托最优。此外,在合作研发的框架下验证了"熊彼特假说",从一个新的视角诠释了市场竞争与RD投入之间的关系。     

20个荷花品种花粉活力测定及贮藏研究

为研究荷花花粉的生活力,选择了20个荷花品种分别用TTC染色法、亚甲基蓝染色法和离体萌发法测定了花粉的染色率和萌发率,并研究了不同温度贮藏条件对花粉生活力的影响.结果表明,亚甲基蓝染色法不能作为荷花花粉生活力的测定方法,离体萌发法结果更直观和准确;20个荷花品种间的离体萌发率差异明显,最高为13.1%,最低为0;不同品种在三种贮藏温度下萌发率变化趋势相同,4℃条件下贮藏较有利于荷花花粉生活力的保持.