Group sequential crossover trial designs with strong control of the familywise error rate

Crossover designs are an extremely useful tool to investigators, and group sequential methods have proven highly proficient at improving the efficiency of parallel group trials. Yet, group sequential methods and crossover designs have rarely been paired together. One possible explanation for this could be the absence of a formal proof of how to strongly control the familywise error rate in the case when multiple comparisons will be made. Here, we provide this proof, valid for any number of initial experimental treatments and any number of stages, when results are analyzed using a linear mixed model. We then establish formulae for the expected sample size and expected number of observations of such a trial, given any choice of stopping boundaries. Finally, utilizing the four-treatment, four-period TOMADO trial as an example, we demonstrate that group sequential methods in this setting could have reduced the trials expected number of observations under the global null hypothesis by over 33%.     

井下液气分离器分离原理及结构改进

液气分离器就是充分利用电泵机组的高转速、气体和液体之间悬殊的密度差异进行液气离心分离。经过多年的发展,在传统的液气分离器结构基础上又出现了许多新的设计和改进,大大提高了液气分离器的分离效果。文章重点论述了液气分离器的分离原理和结构上的改进之处。     

光学全交叉网络与SW榕树（F＝S＝2）网络拓扑等价的多样性

本文对有关互连网络拓扑等价的分析方法作了简单评述。并采用互连网络拓扑等价的图分析法分析了自由空间光学互连全交叉网络与ＳＷ榕树网络的拓扑等价及其多样性，拓展了全交叉网络在数字光计算、光子交换及多处理机系统的潜在应用。     

NiCoFe/C cathode electrocatalysts for direct ethanol fuel cells

A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion^® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (V_oc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion^®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations.     

Evaluation of a palladinized Nafion™ for direct methanol fuel cell application

Palladinized Nafion™ was prepared via ion-exchange and chemical reduction method. Palladium precursors and solvent systems determined the efficiency of the incorporation and distribution of nanoparticles. The tortuous thin Pd film was formed on the surface of membrane when Na⁺-Nafion™ and water were used. Pd nanoparticles enhanced the water uptake of Nafion™ and reduced its methanol uptake. And dispersed Pd nanoparticles in Nafion™ disturbed the proton conduction and methanol permeation simultaneously in Nafion™ cluster. In order to reduce methanol permeation of Nafion™ and keep its high conductivity, it was more efficient for Pd nanoparticles to distribute near the surface of membrane. Palladinized Nafion™ improved the performance of DMFC single cell operation by reducing the methanol permeation.     

EPR Study of CO Adsorption onto CoZSM-5 Zeolite: Evidence for Spin Crossover upon Coordination and |z2, 2A1〉 Ground State

Adsorption of CO onto dehydrated cobalt-exchanged ZSM-5 zeolite was studied by CW-EPR techniques. It is shown that the reversible formation of a low spin carbonyl ¹{Co(CO) _n }⁷ adduct upon addition of carbon monoxide at p _CO>50–60 Torr involves significant change in the spin state of Co²⁺ from S=3/2 to 1/2. The spin Hamiltonian parameters of the adduct g _x =2.222, g _y =2.184, g _z =2.011, |A _x |=3.8 mT, |A _y |=3.2 mT, |A _z |=7.9 mT were determined by a computer simulation and further discussed in terms of the possible ground state and molecular structure. It is shown that the ¹{Co(CO) _n }⁷ cage complex exhibits a C_2v symmetry with |z ²,²A₁ ground state.     

基于奇偶树型交互学习机与遗传算法的密文优化系统

为使图像加密系统具备优化功能,并解决当前遗传算法无法实现全局最优、收敛速率慢等问题,提出奇偶树型交互学习机耦合全局离散遗传算法的密文优化系统。定义权值更新机制,耦合混沌映射,构造奇偶树型交互学习机及其互扰模型。将切断型轮盘赌择取机制引入均匀交叉算子中,以图像分块的相邻像素相关系数和密文信息熵为目标,根据权重理论设计加权适应度函数,提出一种全局离散遗传算法,最终形成"初始加密-密文优化"的加密结构。实验结果表明,与超混沌算法、离散遗传算法、元胞自动机相比,该系统的加密质量较好,并且具备全局优化功能,可优化所有迭代结果,使最终输出密文的信息熵最大,相关系数最小。     

农产品质量安全：呼唤深入的交叉研究

论文通过回顾我国农产品质量安全研究背景和评述我国农产品质量安全研究现状,发现我国当前有关农产品质量安全方面深入的交叉研究非常少见.论文指出,对于农产品质量安全这样一个典型的复杂课题,不仅应努力展开跨学科研究,而且需要实现学界、政界和业界的密切合作.     

基于改进NSGA-II的车间排产优化算法研究

针对NSGA-II算法在处理车间排产优化问题中出现的子代种群多样性差、收敛能力差等问题,提出了一种改进NSGA-II的车间排产优化算法。改进NSGA-II算法主要对传统NSGA-II算法的交叉和变异环节,提出新的改进自适应交叉和变异算子,通过对个体拥挤度与种群平均拥挤度进行对比,并结合种群迭代进化过程,将遗传概率与种群个体及种群进化迭代次数关联,避免盲目导向性,提高种群的收敛速度;提出新的均匀进化精英保留策略,通过自适应分层次选取种群个体,解决子代种群多样性差的问题。针对车间排产问题,选择“最大化最小交货提前期”和“最小化最大理想加工时间偏差”作为目标函数,运用改进NSGA-II算法进行实际工程的仿真分析,对比改进前后算法优化的结果,验证了算法的有效性,同时证明了其应用于实际生产排产调度问题的价值参考性。     

基于改进粒子群算法的航班降落调度问题研究

航班降落调度是多约束的整数规划问题,也是组合优化中的典型NP难题之一.针对传统粒子群算法易陷入局部最优和求解组合优化问题能力不强的缺点,提出改进策略.改进的算法通过禁忌搜索策略生成初始粒子群以满足航班调度多约束的限制,引入遗传算法的交叉变异等操作以增强粒子群间信息交流能力,重新定义惯性权重和加速度因子,以增强粒子的多样性和收敛性,加入进化交叉算子以增强粒子的局部寻优能力.通过与修补遗传算法、罚函数遗传算法进行对比,经多次运行后的结果表明,提出的改进算法的局部搜索能力和全局搜索能力都得到增强,同时也验证了算法的可行性和有效性.