A self-healing and conductive ionic hydrogel based on polysaccharides for flexible sensors

In this study, we proposed a self-healing conductive hydrogel based on polysaccharides and Li⁺ to serve as flexible sensors. At first, the oxidized sodium alginate(OSA) was obtained through the oxidation reaction of sodium alginate(SA). Then OSA, carboxymethyl chitosan(CMC), and agarose(AGO) were dissolved in Li Cl solution, respectively. Finally, the hydrogel was obtained through heating, mixing, and cooling processes. Because of the Schiff base structure and hydrogen bonding, the hy...     

Enhancing silica dispersion and interfacial interaction in styrene butadiene/silica rubber composites by using epoxidized styrene butadiene rubber as interfacial compatibilizer

It is usually desired but often challenging to improve the wet traction, and reduce the abrasion and rolling resistance simultaneously in tread rubber, which is referred to as “magic triangle” in tire industry. To fulfill this goal, the filler dispersion and interfacial interaction required to be improved, as they are two essential factors to concurrently govern the ultimate properties of rubber composites. Herein, we synthesized the epoxidized solution polymerized styrene butadiene rubber (ESSBR) with different epoxy level, and used them as interfacial compatibilizer to promote the silica dispersion and silica/rubber interfacial interaction. The epoxy of ESSBR would react with silanol on silica surface and co-crosslink with SSBR simultaneously, therefore build a strong bridge between rubber matrix and filler. By incorporation of 20 phr of ESSBR-15% (15% of double bonds on main chain was epoxidized), the wet grip was improved by 40%, and DIN abrasion and rolling resistance were reduced by 38% and 21%, respectively with hardly sacrifice the mechanical properties. We envisage that this study provides an approach for the fabrication of rubber composites with improved silica dispersion and strengthened interfacial interaction.     

温湿度、酸雨环境因素对外墙饰面材料耐久性的影响

对不同类型外墙腻子、外墙涂料分别在不同环境作用下进行粘结强度、柔韧性以及拉伸强度、附着力试验,探讨复杂环境作用下饰面材料的长期服役行为,研究不同环境作用下饰面材料耐久性的演变。试验结果表明,温湿度、酸雨、光照等均会影响外墙腻子、外墙涂料的使用性能,其中以酸雨对外墙腻子、外墙涂料的影响最大。因此在酸雨严重区域,应该选择耐酸性优异的饰面材料。     

磷酸铁锂电池优化多因子状态在线评估方法

针对目前锂离子电池在线估计方法不准确的问题,提出了一种基于优化充电电压片段下多个健康因子的磷酸铁锂电池健康状态综合在线评估方法,将充电电压片段内所充电量估计的电池容量与实际电池容量的误差最小作为目标,利用遗传算法寻优充电电压片段。在此基础上,分别对表征电池健康状态的充入电量、充电时间以及内部阻抗三个健康因子进行在线评估,归一化处理得到各健康因子对应的健康状态,再通过最小序列优化法实时获取电池综合健康状态。最后对磷酸铁锂电池进行老化充放电实验,对比仅采用电池内阻单因子评估方法,结果表明该方法能有效减小充电过程中电池健康状态估计误差,且适用性更强。     

淬火温度对高Ti低合金耐磨钢组织及力学性能的影响

研究了淬火温度对高Ti低合金耐磨钢组织转变、析出相和力学性能的影响,并分析了组织演变和力学性能变化的原因。结果表明:试验钢经不同温度淬火和200 ℃回火后的组织均为高位错密度板条马氏体;析出相尺寸主要为微米-亚微米-纳米三种尺度,微米级析出相呈杆棒状,亚微米以及纳米析出相呈球状,马氏体板条上分布着细小的(Ti, Mo)C析出相。随着淬火温度的升高,试验钢的屈服强度、抗拉强度和维氏硬度均先升高后降低,均在920 ℃时有最大值,分别为1248 MPa、1535 MPa和434 HV,此时伸长率为10.0%。随淬火温度升高,纳米级析出相逐渐回溶,数量减少且尺寸逐渐长大,沿轧制方向被压扁拉长的原奥氏体晶粒尺寸以及马氏体板条块尺寸略有增大,但马氏体板条宽度却无明显长大。大量的弥散分布的5～10 nm的(Ti, Mo)C粒子是促进耐磨钢硬度升高的主要因素。细小的(Ti, Mo)C析出相逐渐长大以及原奥氏体晶粒的增大都不利于耐磨钢硬度的提高。     

时频电磁(TFEM)技术:数据采集参数设计

时频电磁法（TFEM）是一种应用于油气勘探领域、探测深度较大的可控源电磁方法。本文以Q地区探测目标地层为模型,基于探区噪声分析,对地质目标进行三维模拟,分析目标体电磁异常特征及规律,并对TFEM采集参数的设计进行了研究与分析。提出了等腰梯形区域测网布设、测点信号平衡的接收系统设计方法,以及基于目标异常对比分析的发射系统优化设计,同时提出针对目标的激发周期和叠加次数设置的激发参数设计方法,为TFEM勘探采集设计提供科学的借鉴和参考。     

Solid-state transformer-based new traction drive system and control

A new type of traction drive system consisting of solid-state traction transformer (SSTT), inverter unit, auxiliary inverter, traction motor and other key components is built in order to suit the demand of developing the next-generation electric traction system which will be efficient and lightweight, with high power density. For the purpose of reducing system volume and weight and improving efficiency and grid-side power quality, an efficient SSTT optimized topology combining high-voltage cascaded rectifiers with high-power high-frequency LLC resonant converter is proposed. On this basis, an integrated control strategy built upon synchronous rotating reference frame is presented to achieve unified control over fundamental active, reactive and harmonic components. The carrier-interleaving phase shift modulation strategy is proposed to improve the harmonic performance of cascaded rectifiers. In view of the secondary pulsating existing in a single-phase system, the mathematical model of secondary power transfer is built, and the mechanism of pulsating voltage resulting in beat frequency of LLC resonant converter is revealed, so as to design optimum matching of system parameters. Simulation and experimental results have verified that the traction system and control scheme mentioned in this paper are reasonable and superior and that they meet the future application requirements for rail transit.     

Numerical Investigation on the Vortex-Flow Characteristics in Rod Bundles with Mixing-Vane Spacer Grids

In nuclear reactor fuel assemblies, spacer grids are installed among the rod bundles to support the fuel rods and affect the flow field between rods. Mixing vanes, as a swirling device, are set on the upper apex of the spacer grid. Vortexes produced by mixing vanes move along the axial direction in subchannels and enhance the forced convection heat transfer between the rods and cooling-fluid medium. In this paper, a numerical simulation method was used to investigate vortex motion produced by typical AFA-3G spacer grids in a 5×5-rod bundle by Star-CCM+ software. The shear-stress transport k-ω model was used to simulate turbulence phenomena. A dimensionless parameter, Se, based on the absolute vorticity flux, was reported to specify the intensity of secondary flow. Its physical meaning is the ratio of inertial force to viscous force induced by secondary flow. The results are helpful to take advantage of spacer grids in a much more effective way in pressurized water reactors.     

改进A*算法与动态窗口法的机器人动态路径规划

针对传统A*算法自身节点搜索策略存在路径转折点多、转折角度大、可行路径不是理论上的最优路径等缺点,将传统A*算法3×3的搜索邻域扩展为7×7,同时去除扩展邻域同方向的多余子节点,改进为7×7的A*算法,消除了传统A*算法的3×3邻域搜索和节点移动方向仅为[0.25π]的整数倍的限制,优化了搜索角度。其次,针对移动机器人在复杂环境下动态路径规划问题,将改进7×7的A*算法与动态窗口算法进行融合,设计了一种全局最优路径的动态窗口评价函数,综合考虑移动速度、转角平滑度、安全性等因素,将改进7×7的A*算法与动态窗口法的融合算法与多种算法仿真比较,结果表明：改进7×7的A*算法与动态窗口法的融合算法更具有高效性和可行性。     

Ⅱ类水体光学分类方法研究进展

鉴于Ⅱ类水体本身光学性质的复杂性及其与人类生产活动的密切关系,对其进行光学分类以提高水色参数反演精度和监测Ⅱ类水体水质有着重要意义.本文对近年来使用的Ⅱ类水体光学分类方法进行了归纳和评价,主要有:基于光谱形状的水体分类法;监督分类法;聚类分析法;多波段比值法.针对目前分类方法存在的问题,提出未来的研究需要加强对光谱反射...