Forward-reverse switch between density-based and regional sensitivity analysis

Global sensitivity analysis is a widely used tool for uncertainty apportionment and is very useful for decision making, risk assessment, model simplification, optimal design of experiments, etc. Density-based sensitivity analysis and regional sensitivity analysis are two widely used approaches. Both of them can work with a given sample set of model input-output pairs. One significant difference between them is that density-based sensitivity analysis analyzes output distributions conditional on input values (forward), while regional sensitivity analysis analyzes input distributions conditional on output values (reverse). In this paper, we study the relationship between these two approaches and show that regional sensitivity analysis (reverse), when focusing on probability density functions of input, converges towards density-based sensitivity analysis (forward) as the number of classes for conditioning model outputs in the reverse method increases. Similar to the existing general form of forward sensitivity indices, we derive a general form of the reverse sensitivity indices and provide the corresponding reverse given-data method. Due to the shown equivalence, the reverse given-data method provides an efficient way to approximate density-based sensitivity indices. Two test examples are used to verify this connection and compare the results. Finally, we use the reverse given-data method to perform sensitivity analysis in a carbon dioxide storage benchmark problem with multiple outputs, where forward analysis of density-based indices would be impossible due to the high-dimensionality of its model outputs.     

Delay in ATP-dependent calcium inflow may affect insulin secretion from pancreatic beta-cell

Any dysfunction in the secretion of insulin and/or in its use is critical in the development of type 2 diabetes. Calcium plays a very important role in the insulin secretion mechanism from beta-cell. In this paper, we studied the dynamic interaction of glucose-induced insulin secretion mechanism through glucose metabolism and ATP-dependent calcium influx. We proposed and analyzed a four dimensional system of nonlinear delay differential equations to give insights into different possible mechanisms for maintaining plasma glucose homeostasis through calcium-induced insulin secretion. The time duration between ATP formation and subsequent calcium influx through cell membrane has been found to be critical in maintaining insulin homeostasis. How variational effects of system parameters lead to various glycemic states are demonstrated. Possibility of new potential drug therapies is also discussed through parameter recalibration.     

中空介孔硅铝球形分子筛的制备及催化裂解性能

利用沸石前驱体溶液和介孔硅球(MSS)为原料,通过水热法成功制备了具有中强酸性介孔壳的中空介孔硅铝球形分子筛(HMAS)。利用透射电镜(TEM)、扫描电镜(SEM)、X射线衍射(XRD)、N2-吸脱附、27Al核磁共振(27Al NMR)及NH3程序升温脱附(NH3-TPD)对材料的结构和性能进行了表征。研究结果表明,在MSS的中空过程中伴随有物质再分配和介孔结构的逐渐演变。MSS介孔孔道中的十六烷基三甲基溴化铵(CTAB)分子,一方面保护MSS免遭强碱性沸石前驱体溶液的溶蚀,另一方面作为形成HMAS介孔壳层的模板剂。在此CTAB分子的作用下,沸石前驱体结构单元被引入到HMAS的介孔球壳上。所得材料具有介孔结构和中强酸性,在催化裂解1,3,5-三异丙苯反应中表现出优异的催化性能。     

Shear stability of metallic glasses

The effect of sample size on the shear deformation and compressive plasticity of different metallic glasses were investigated. The experimental results showed that the deformation and fracture behaviors of samples prepared from chemically identical Zr-, Ti-, Fe-, or Mg-based metallic glass ingots were strongly dependent on the sample size and machine stiffness, and a super-high compressive plasticity was achieved in the Zr-based metallic glasses with sample size of 1.0 mm in width. It is also found that the sample size can significantly influence the density of elastic energy dissipated in the shear band: with sample size decreasing and machine stiffness increasing, the density of the elastic energy dissipated in the shear band of metallic glasses is prominently decreased, thus the shear deformation turns to be more stable, resulting in the improvement of plasticity in ductile metallic glasses and the transition from fragmentation fracture to shear fracture in brittle metallic glasses. This finding is important for the potential applications of the present metallic glasses and for designing new metallic glasses with better mechanical properties.     

扑尔敏与铬天青S荷移反应分光光度法测定扑尔敏的含量

研究了扑尔敏与铬天青S的电荷转移反应,确定了反应条件,建立了测定扑尔敏的分光光度法。扑尔敏与铬天青S在水溶液中发生电荷转移反应,常温下反应20min后可比色。电荷转移络合物的最大吸收波长是532nm,表观摩尔吸光系数为2.27×103L·mol-1·cm-1。扑尔敏质量浓度在20～160mg·L-1范围内服从比耳定律,相关系数为0.9990。当扑尔敏浓度为80mg·L-1时,六次测定结果的相对标准偏差为1.39%。测得荷移络合物的组成为1∶1、稳定常熟为1.48×105,探讨了反应机理。本方法用于测定片剂中扑尔敏的含量,结果与文献方法一致,回收率在99.0%以上。     

一类不确定非线性系统的执行器故障模糊容错控制

针对一类状态不完全可测的不确定非线性系统,研究了带有执行器故障的容错控制问题.采用 T-S模型对非线性系统进行模糊建模,利用并行分布补偿(PDC)算法设计了状态现潮器和基于状态现 潮器的客错控制,给出了保证该模糊容错控制系统稳定的充分条件.根据李雅普诺夫稳定性理论和线性 矩阵不等式(LMI),证明了所提出的模糊容错控制方法不但使得模糊控制系统渐近稳定,而且能够取得 H∞性能指标.计算机仿真结果进一步验证了所提出方法的正确性.     

荷移分光光度法测定醋酸氯己定

通过醋酸氯己定与红紫素的荷移反应来测定制剂中醋酸氯己定的含量,是利用分光光度法进行测定的。反应在乙醇-丙酮介质中进行,反应物的最大吸收波长为545 mn,表观摩尔吸光系数为1.54×10~4 L·mol-1·cm-1,相对标准偏差为0.89％(n=6),药物浓度在0-45 mg·L-1范围内呈线性关系;此方法简便易行,条件易于控制,灵敏度高,对样品的测定结果令人满意。     

正态总体均值与标准差比在简单半序约束下的最大似然估计

本文考虑两个正态总体均值和方差是未知参数,均值与标准差的比在简单半序约束下,且样本个数不同时,计算均值和标准差的最大似然估计的问题.给出了计算均值和标准差的最大似然估计的方法.同时还给出了三个总体均值与标准差的比在简单半序约束下求均值和标准差的最大似然估计的计算方法,并给出了迭代算法的模拟结果.     

Nonlocal initial problems for coupled reaction–diffusion systems and their applications

The purpose of this work is to investigate the uniqueness and existence of nonlocal initial problems for a system of nonlinear parabolic equations weakly coupled with ordinary differential equations. The system of equations is considered in bounded and unbounded spatial domains. The uniqueness of the classical solution is proved by means of comparison principles for differential inequalities. The existence of the unique solution is obtained via a monotone iterative method. Applications are given to some model problems in epidemiology and ecology.