Extension of Kleiser and Schumann’s influence-matrix method for generalized velocity boundary conditions

In 1980, Kleiser and Schumann introduced a novel influence-matrix method to treat the incompressibility and no-slip boundary conditions when solving the Navier–Stokes equations. They also outlined the related “tau” error correction technique which is essential for the high accuracy direct numerical simulation (DNS) of turbulent flows. However, their method is not valid for Robin type velocity boundary conditions (i.e., B(u) = αu + βu′ − γ = 0). In this note, a new influence-matrix method is introduced where the boundary condition and “tau” correction are enforced in one step using an extended influence matrix. The new method is simple and easy to be implemented. It broadens the applicability of the Kleiser and Schumann method. Examples with the new method show excellent agreement with data in the literature and the velocity field is divergence free up to machine precision.     

Decision-network polynomials and the sensitivity of decision-support models

Decision makers benefit from the utilization of decision-support models in several applications. Obtaining managerial insights is essential to better inform the decision-process. This work offers an in-depth investigation into the structural properties of decision-support models. We show that the input–output mapping in influence diagrams, decision trees and decision networks is piecewise multilinear. The conditions under which sensitivity information cannot be extracted through differentiation are examined in detail. By complementing high-order derivatives with finite change sensitivity indices, we obtain a systematic approach that allows analysts to gain a wide range of managerial insights. A well-known case study in the medical sector illustrates the findings.     

湖南省公共医疗卫生支出效率及其影响因素实证分析

利用DEA-Tobit两阶段分析法,计算出2009-2013年5年间湖南省14个地级市政府公共医疗卫生支出的综合技术效率值、纯技术效率值、规模效率值三种效率值,分析出湖南省各地级市政府公共医疗卫生支出所处规模报酬阶段,并对反映卫生支出资金配置的综合技术效率水平的外部影响因素加以回归分析.结果发现:湖南省各地区公共医疗卫生效率水平整体水平偏低并且存在明显的差异性,除长沙以外的其他地级市政府公共医疗卫生支出均处于不同程度的非充分效率水平.湖南省各地区人均生产总值及城市化水平对公共医疗卫生支出效率有显著的促进作用.教育水平、人口密度、居民人均可支配收入对湖南省公共医疗卫生支出效率的提高有阻碍作用.     

外加条件对量子点红外探测器暗电流特性的影响

考虑微米尺度和纳米尺度下电子传输对激发能的共同影响,基于电子漂移速度对外加电场的依赖,研究外加电场和外加温度对量子点红外探测器暗电流特性的影响.结果表明:外加电场在0~25kV/cm范围内时,暗电流模型和实验数据变化相吻合.暗电流随着外加电场的增加而增加,并且当外加电场小于6kV/cm时暗电流增加迅速,而当外加电场大于6kV/cm时暗电流增加缓慢.暗电流随着外加温度的增加迅速增加.该研究为量子点红外探测器的优化设计和性能提高提供了理论参考.     

温度变化对1.23 m望远镜光机系统的影响

为了实现1.23 m望远镜在环境温度从-35℃~+55 ℃变化范围内,光机系统的成像质量的指标要求,本文从原理上分析了温度变化对光机系统中光学元件面形准确度及相对位置关系的影响,推导出了主次镜间光学间隔变化与像面离焦量的比例关系.通过对1.23 m望远镜光学结构的像质分析,结合光机结构设计,搭建了适合环境温度变化的光机系统,从方案设计上满足了望远镜系统的成像要求.通过实际的成像实验,验证了温度变化导致的主次镜光学间隔变化对望远镜系统成像带来的离焦的影响,并给出了具体的温度补偿措施,即采取次镜调焦的方式,可满足具体观测实验的要求.同时,为今后1.23 m望远镜以及类似的大口径望远镜系统的实验和技术改造提出了切实可行的意见.     

酸及镧盐对钙测定的影响

用空气-乙炔原子吸收光谱法(AAS)对不同溶液中钙元素进行检测,研究了盐酸、硝酸、镧盐对Ca测定的影响.结果表明,在使用原子吸收光谱法测定Ca时,测定结果受到盐酸、硝酸、镧盐严重的负干扰.     

二元阴离子型丙烯酰胺共聚物在二价金属离子存在下相分离行为的研究

水溶性丙烯酰胺类共聚物 ,作为粘度改性剂 ,在工业上已得到广泛应用 .特别近年来 ,它们大量应用于石油工业强化采油技术 ,引起了人们很大的重视[1] .目前 ,这类用途的聚合物 ,主要在聚丙烯酰胺结构中 ,引入阴离子组分和不断增高产物分子量的方法 ,以提高聚合物溶液粘度和增粘效果 ,然而 ,在二价金属离子 (如Ｃａ2 + ,Ｍｇ2 + 等 )存在下 ,羧酸阴离子型丙烯酰胺类共聚物很容易络合发生沉淀 ,从而失去增粘作用[2 ] .同时这类聚合物中酰胺基不稳定 ,易发生水解反应转化为羧酸基 ,并随温度升高而加剧[3 ] ,因此在温度较高的应用条件下 ,二价金属…     

盐酸曲马多药物树脂制备技术的研究

采用静态法和动态法和工艺制备盐酸曲马多药物树脂,并对制备过程中体系温度,反应时间,药物溶液浓度,溶液流速等影响因素进行了研究;以正交设计对工艺进行优化。     

Kristallstruktur,Schwingungsspektrum und Normalkoordinatenanalyse von (PNP)2[ReFBr5] · H2O

Crystal Structure, Vibrational Spectrum, and Normal Coordinate Analysis of (PNP)₂[ReFBr₅] · H₂O From the complex mixture obtained by oxidative ligand exchange of [ReBr₆]^2– with BrF₃ [ReFBr₅]^2– has been isolated by ion exchange chromatography on diethylaminoethyl cellulose with 45% yield. The X-ray structure determination of (PNP)₂[ReFBr₅] · H₂O (monoclinic, space group P2₁/c with a = 21.498(2), b = 13.314(3), c = 23.945(2) Å, β = 105.235(7)°, Z = 4) reveals a completely ordered anion sublattice resulting from the solvent water linked to the F ligand by a hydrogen bond (O–F: 2.758(6) Å). Due to the stronger trans influence of Br compared with F on the F ^· –Re–Br′ axis the Re–Br′ distance is shortened by 0.6% with regard to symmetrically coordinated axes. Based on the molecular parameters of the X-Ray determination the low temperature (10 K) IR and Raman spectrum of the (Me₄N) salt is assigned by a normal coordinate analysis. The strengthening of the Re–Br′ bond due to the trans influence is indicated by an increase of the valence force constant f_d(ReBr′) = 1.43 by 8% as compared with f_d(ReBr) = 1.32 mdyn/Å of symmetric axes.