Combination of nuclear magnetic resonance spectroscopy and nonlinear methods to analyze the copolymerization of phosphonic acid derivatives

We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The ¹H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of r_HEMA = 1.83; r_ECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256.     

黄浦江下游吴淞口站低潮位重现期研究

黄浦江为感潮河流,低潮位重现期的确定对黄浦江航道的设计具有重要意义。为了准确估计黄浦江低潮位的重现期,以黄浦江下游吴淞口站年最低潮位序列为例,在对样本进行三性审查的基础上,分别采用传统的数理统计方法和时变矩方法进行水文频率分析。结果表明:吴淞口站年最低潮位序列在1996年发生了变异;还现修正后的序列服从位置参数线性时变的GEV模型,低潮位存在缓慢的上升趋势;一致性条件下百年一遇低潮位约为0.261 m,在非一致性条件下其重现期增大为150 a。非一致性条件下的重现期增大说明黄浦江现有的航道设计标准偏安全,航道通航保证率提高。     

仿人机器人的机械结构设计与控制系统构建

文章研发了一款适用于机器人教育教学的多功能、多用途、普适性的19自由度的小型仿人机器人,主要完成了该机器人的机械结构设计与控制系统构建工作[1]。所设计的机器人机械结构可靠性高、工艺性好、结构紧凑、样式新颖；所构建的机器人控制系统鲁棒性高、稳定性好、控制准确、反应迅速,圆满地实现了预期的设计任务。通过对优缺点的综合对比,得出组合式构型方案在功能性、实用性和稳定性等方面具有明显优势,有望通过后续软件系统的开发提高其运动效能,真正在青少年机器人教育中发挥重要作用[2]。     

基于压缩感知的移动群智感知任务分发机制

针对移动群智感知任务中区域全覆盖感知成本过高问题，提出基于压缩感知的移动群智感知任务分发（CS-TD）机制。首先提出了感知任务整体成本模型，该模型综合考虑了参与感知任务的节点个数、节点的感知次数与数据上传次数；然后基于成本模型，分析感知节点的日常移动轨迹，结合压缩感知数据采集技术，提出了一种基于感知节点轨迹的压缩感知采样方法；其次通过区域全覆盖最少节点（RCLN）算法，选出最佳节点集合，对节点进行任务分配，利用压缩感知技术恢复节点数据；最后在多次感知任务的迭代中对感知节点的可信程度进行评定，保证任务方案的最优性。对CS-TD分发模型进行多次实验验证，与已有的CrowdTasker算法相比，CS-TD算法平均成本降低了30%以上。CS-TD模型能有效降低感知节点的消耗，能在全覆盖感知任务中降低整体感知成本。     

Feasibility study to control fiber distribution for enhancement of composite properties via three-dimensional printing

The distribution of fibers in the composite (which takes into account both their locations and orientations) is one of the important factors that affect the mechanical properties of FRCs. However, this parameter depends on various factors during composite fabrication, and controlling the distribution of fibers in the produced material represents a significant challenge. In this study, the applicability of three-dimensional (3D) printing technique for controlling fiber distributions was evaluated. The fibers fabricated using a 3D printer were placed inside a mold to produce cementitious composites. Three-point bending tests were conducted and the results of the experiment were discussed.     

吹氩流量对结晶器流场影响的插钉工业试验

 结晶器吹氩流量对流场分布有明显影响，因此明确吹氩流量对结晶器内流场分布的影响规律对提高铸坯质量有重要意义。通过插钉法工业试验研究了吹氩流量对结晶器内流场分布的影响，并且定量分析了液位波动的变化。结果表明，随着吹氩流量的增大，流场形态从双环流逐步转变为复杂流和单环流。结晶器内流场形态从双环流转变为复杂流和单环流的过程中，水口附近速度逐渐增大，液位逐渐升高，弯月面速度分布逐渐转变为从水口流向窄面，液位波动也相应增大。因此，生产过程中应选择合适的吹氩流量，避免产生复杂流和单环流，以提高铸坯质量。     

Microtopography‐Guided Radial Gradient Circle Array Film with Nanoscale Resolution

Distribution of multimaterials at arbitrary positions with nanoscale resolution and over a large area substrate is essential to future advances in functional graded materials. Such stringent requirements are highly beyond the reach of current techniques, although newly developed 3D printing technologies are addressed. Here, a radial gradient circle array film with the distribution accuracy up to ≈18 nm is fabricated by using microtopographic substrate. A mathematical model is developed to guide the distribution of position, size, shape, and type of materials on an arbitrary section for the given morphology of substrate. The periodic electrical and mechanical properties of the radial gradient circle film are identified, which can be beneficial for further functionalization and applications, such as gradient refractive index lenses, microcoils, and microantennas.     

First principles computational studies of spontaneous reduction reaction of Eu(III) in eutectic LiCl‐KCl molten salt

Using first principles calculations, we study fundamental mechanism of spontaneous reduction reaction of Eu³⁺ to Eu²⁺ in eutectic LiCl‐KCl molten salt. We decouple the reaction Gibbs free energy into enthalpy and entropy contributions by using rigorous thermodynamic formalism. Key structural features of the solvation shell are characterized by the radial distribution function and the coordination number. Compared with Eu²⁺, the Eu³⁺ ion has a more rigid framework of the solvation shells, corroborating its stronger electrostatic interaction with neighboring ligands of Cl^? ions and a more favorable state on the aspect of enthalpy. Computations on vibrational frequency, however, pose significant contribution of vibrational entropy to the reaction Gibbs free energy for the reduction. Vibration frequency of Eu²⁺ is smaller than that of Eu³⁺, driving a more positive change of the entropy in the reduction reaction. Furthermore, an Eu²⁺ diffuses more quickly than an Eu³⁺ in the LiCl‐KCl molten salt with switching mechanism of ligand Cl^? ions in the solvation shell. Our results propose that the spontaneity of the reduction reaction is driven by the entropic contribution by overcoming the penalty of the reaction enthalpy.     

ACME台架蒸汽发生器传热特性数值模拟

以ACME台架的蒸汽发生器（SG）为研究对象，SG二次侧选用两流体模型，采用计算流体力学软件CFX对ACME台架的SG进行了整体直接模拟。针对稳定试验工况进行了计算，得到了SG一、二次侧的温度分布，二次侧空泡份额分布及传热管的壁温等参数沿U型管高度方向的变化，获得了二次侧较详细的流动和传热特性。计算结果表明，从第2道折流板开始，折流板底部已积聚了部分气泡，随高度的增加，折流板底部积聚的气泡越多，在弯管区附近及以上区域，已全部变为蒸汽。本文计算结果与试验结果符合较好。     

Numerical study of flow distribution uniformity for the optimization of gradient porosity configuration of porous copper fiber sintered felt for hydrogen production through methanol steam reforming micro-reactor

A macroscopic numerical method is proposed to study the flow distribution uniformity of a novel porous copper fiber sintered felt (PCFSF), which has gradient porosities and was developed as the methanol steam reforming micro-reactor catalyst support for hydrogen production for fuel cell applications. The macroscopic porous media developed by the ANSYS/FLUENT software is used to represent the PCFSF. Our results indicate that the gradient porosity can reshape the flow distribution of PCFSFs greatly, thus producing significant influence on their performance. It is further revealed that, for a PCFSF with a determined gradient porosity configuration but different reactant feed directions, the velocity uniformity can be used as a quantitative criterion to evaluate the performance of hydrogen production. Furthermore, new gradient PCFSFs are produced according to the flow distribution of original gradient PCFSFs. The preliminary experimental results of the new gradient PCFSFs of 0.8-0.9-0.7 and 0.7-0.9-0.8 exhibit better methanol conversion and H₂ flow rate. This indicates that the numerical method can be used for the optimization of PCFSFs' gradient porosity configuration, which consists of the shape and position of the interfaces between different porosity portions, the number of interfaces and the porosity distribution in different portions.