板形控制技术及应用

概述了板形控制原理.根据有载辊缝形状方程,分析了影响板形、板凸度的诸项因素,综合介绍了板形控制技术及发展趋势.     

PLA-g-GMA/Ope-POSS/PLA复合材料的制备与性能

为了制备具有优异强度与韧性的聚乳酸(PLA)复合材料,首先,将八聚(丙基缩水甘油醚)倍半硅氧烷(Ope-POSS)纳米粒子引入PLA中,并加入PLA接枝甲基丙烯酸缩水甘油酯(PLA-g-GMA)作为增容增韧组分;然后,通过熔融共混法制备了PLA-g-GMA/Ope-POSS/PLA复合材料;最后,通过对复合材料形态结构、热性能、力学性能及疏水性的表征分析了Ope-POSS纳米粒子及PLA-g-GMA的加入对PLA复合材料性能的影响。结果表明:PLA-g-GMA的加入对Ope-POSS纳米粒子具有良好的增容效果,可使得Ope-POSS纳米粒子在复合材料中均匀分散;随着良好分散的Ope-POSS纳米粒子的数量增加,PLA复合材料的强度、热稳定性及疏水性均得到明显的提高,韧性也随PLA-g-GMA含量增加而得到改善;当PLA-g-GMA和Ope-POSS纳米粒子含量分别为PLA的4wt%和3wt%时,PLA-g-GMA/Ope-POSS/PLA复合材料性能最佳。所得结论为POSS杂化PLA复合材料的深入研究提供了理论指导。      

Uniform and Multifunctional PEI-POSS/Carbon Encapsulation for High-Rate Performance and Surface Stabilization of Nickel-Rich Layered Cathodes in Lithium-Ion Batteries (Adv. Funct. Mater. 45/2023)

Graphene encapsulation is an attractive surface-coating technology that can simultaneously improve the rate capability and cycle stability of nickel-rich LiNi_xCo_yMn_1−x−yO₂ (NCM). Here, carbon encapsulation with the addition of polyethylenimine (PEI) and polyhedral oligomeric silsesquioxane (POSS), which can effectively suppress access to and generation of harmful factors in the electrolyte to maximize the rate performance and cycle stability of nickel-rich NCM, is described. The PEI-POSS/carbon layer not only facilitates electron and lithium-ion transport on the NCM surface but also inhibits side reactions with the electrolyte during repeated electrochemical reactions. In addition, it provides mechanical support that suppresses the formation of microcracks related to anisotropic volume change of nickel-rich NCM secondary particles and inhibits irreversible phase transitions on surface structures by mitigating electrolyte wettability. As a result, PEI-POSS/carbon-encapsulated NCM exhibits a higher rate capability (84 mAh g⁻¹ at 5 C) and cycle stability (93.5% for 100 cycles at 1 C) compared with bare NCM (0 mAh g⁻¹ at 5 C and 78.4% for 100 cycles at 1 C). In a cycle test at 45 °C, it achieves a capacity retention of 72.6% for 100 cycles at 1 C, which is a 323% improvement in performance over that of bare NCM (22.5%).     

Resource allocation in OFDMA networks based on interior point methods

This paper studies a joint optimization problem of sub‐carrier assignment and power allocation in orthogonal frequency division multiple access (OFDMA) wireless networks. A major challenge in solving the optimization problem is non‐convexity caused by the combinatorial nature of sub‐carrier assignment problem and/or non‐convex objective functions. To address the combinatorial complexity, we formulate the resource allocation problem as an optimization problem with continuous variables. We propose a novel approach based on a penalty function method and an interior point method (PM/IPM) to solve the problem. In specific, using a two‐step implementation, the penalty method is applied first to convert the non‐convex feasible region to a convex one. Then, the interior point method is deployed to solve the problem which is non‐convex only in the objective function. To evaluate the performance of PM/IPM, we apply a genetic algorithm (GA) that achieves near optimal solutions of the problem by iterative searching. Copyright © 2009 John Wiley & Sons, Ltd.     

基于非线性规划理论的凸多面体最小平移距离算法

凸多面体的最小平移距离问题一直以来都成为计算机图形学的一个研究热点.目前已有的距离算法在稳定性、可实现性、精确度和实现效率这几方面或多或少都存在一定的缺陷.为此,从最小平移距离定义出发,引入广义分离平面概念,提出一种用非线性规划求解距离问题的新算法.算法先定义一对最优广义分离平面以确定凸多面体最小平移距离;然后,将最优广义分离平面对的搜索问题等效变换为非线性规划问题;最后,用非线性优化工具软件对非线性规划问题进行求解,从而确定最小平移距离.实验结果表明：该算法能提供一个准确的距离值和实现向量,其性能优于其他同类算法;迭代次数与多面体的顶点数呈线性关系.此外,该算法只需提供顶点信息即可实现,求解过程中避免了死循环,故实现简单、可靠.因此,此算法是一种快速而有效的距离算法.     

一类近于凸函数子族的研究

C.Selvaraj研究了单叶解析函数的一个子族K',在此基础上引进了新的函数族K'β{f(z):f(0)=f'(0)-1=0,其中f(z)在E内解析,g(z)∈C,且zf'(z)/g(z)∈P{β},它是近于凸函数的一个子集,是单叶的.探讨此类函数族的系数估计和半径问题,K'β在积分运算下的一些性质.     

笼型倍半硅氧烷改性UPR的固化性能与热性能

采用示差扫描量热仪(DSC),热重分析仪(TGA)及动态力学分析仪(DMA)研究了甲基丙烯酰氧丙基笼型倍半硅氧烷(MAP-POSS)与一缩二乙二醇型UPR、苯乙烯的等温共固化反应及动力学,测试了固化物的热性能和动态力学性能。结果表明,固化过程符合自催化反应机理,当体系中MAP-POSS质量分数为5%时,5%热失重温度和残留量5%时的温度较未加体系分别提高7℃和31℃,玻璃化转变温度降低4.2℃,热降解动力学符合1级反应。     

凸性数据的样条修匀及其应用

借助于样条技术 ,给出了利用先验信息对初始估计进行修正的新方法 .这些先验信息可以包含数据的凸性以及增减性 .同时讨论了这种数据处理方法在生存分析尤其是精算等领域中的应用 .     

Non‐convex model for sensor network localization based on connectivity

In this paper, a new model utilizing all the information derived from connectivity‐based sensor network localization is introduced. The connectivity information between any pair of nodes is modeled as convex and non‐convex constraints. The localization problem is solved by searching for a solution that would satisfy all the constraints established in the problem. A two‐objective evolutionary algorithm called Pareto Archived Evolution Strategy (PAES) is used to solve the localization problem. The solution can reach the most suitable configuration of the unknown nodes because the information on both convex and non‐convex constraints related to connectivity has been utilized. From simulation results, a relationship between the communication range and accuracy is obtained. Furthermore, a two‐level range connectivity‐based sensor network localization method is proposed to enrich the connectivity information. The two‐level range/indication of connectivity between each pair of nodes would indicate three levels of connectivity: strong, weak, or nil. A comparison on accuracy between the one‐level and two‐level ranges of connectivity is carried out by simulation using six different topological networks all containing 100 nodes. Simulation results have shown that better solution can be obtained by using two‐level range connectivity compared with the usual one‐level range connectivity‐based localization. Copyright © 2012 John Wiley & Sons, Ltd.     

High-Performance Low-k Poly(dicyclopentadiene) Nanocomposites as Achieved via Reactive Blending with Norbornene-Functionalized Larger POSS

Low dielectric constant (k) polymers with excellent comprehensive properties are useful materials in the microelectronics industry as matrix resins or encapsulation layers. With the inherent low polarization, high reactivity, good processability, and low cost, poly(dicyclopentadiene) (PDCPD) has received considerable attention as low-k materials. However, its practical application is limited by the relatively high thermal expansion and k value. Herein, three norbornene-functionalized polyhedral oligomeric silsesquioxanes (POSSs) with T₈, T₁₀, and T₁₂ polyhedral cores are synthesized and employed for enhancing the dielectric and comprehensive properties of PDCPD via reactive blending. The results show that these POSSs have good compatibility with PDCPD matrix and nano-dispersed POSSs particles could be obtained. As a result, the materials’ properties can be largely enhanced by varying the POSS content and POSS size. Especially, PT₁₂N₁₂-40 (40 wt% of T₁₂N₁₂) shows the lowest k value (2.1) and coefficient of thermal expansion (63.4 ppm°C⁻¹), highest glass transition temperature (202.5 °C), yield strength (78.0 MPa), and elastic modulus (2.36 GPa), along with excellent hydrophobicity. This study highlights a useful strategy to fabricate high-performance low-k polymer nanocomposites by using larger POSS and reactive blending, which provides useful materials for the future microelectronic industry and high frequency communication.