Development of novel refractory ceramic continuous fibers of fly ash and comparison of mechanical properties with those of E-glass fibers using the Weibull distribution

This study aimed to develop manufacturing technology for high-strength refractory ceramic fibers (RCFs) using fly ash, which is a highly promising material for the exterior and thermal insulation industry. The technology also contributes to reducing the environmental pollution caused by landfilling fly ash after coal is burned. Fly ash discharged from a thermal power plant, which had aluminosilicate chemical compositions, was used as the main material. As auxiliary materials, basalt, anorthite, feldspar, dolomite, and calcite were used to adjust the melt flowability, and frit, silica sand, and burr stone were used to lower the melting temperature. Moreover, the development of aluminosilicate fly ash fiber has the advantages of lower cost for raw materials and processing. Fly ash and natural rocks are inexpensive, and most of all, unlike the case for glass fiber production, the high cost of B₂O₃ is not a necessary expense. Fly ash is retrieved in powder form, which is advantageous compared to the starting materials for glass; the grinding process of raw materials can be skipped. From the fibrilization index calculation, we showed that the spinnability was influenced by the chemical composition of the salt-forming oxides in the fly ash compounds. We also found a correlation between the winding speed and the fiber diameter. The mechanical properties of a series of fly ash fibers were assessed by the Weibull distribution and then compared with those of the E-glass fibers that were melt-spun under an analogous condition.     

台阶式泄洪槽水工模型试验研究

为验证山西省某森林公园台阶式消能泄洪槽设计的合理性,通过模型试验研究了该消能泄洪槽不同流量工况下的流态、台阶平面压力、流速分布及消能效率。结果表明,在试验流量范围内,泄槽内为跌落水流和过渡水流,掺气不明显;台阶平面压力变化范围为-9.7~24.4kPa,当流量为6m^3/s时,出现最大负压9.702kPa;除#3消力池进口处外,三段台阶式消能段均为泄槽底部流速较小,对泄槽底部冲刷较小,泄槽水流表面流速最大;在不同流量下台阶式泄槽+消力池联合消能率均超过了90%,其中大部分能量消散在溢洪道台阶上。研究成果可为类似工程提供参考。     

一种基于NFC的无源智能锁及其在配电网中的应用

针对配网柜体采用的传统机械锁具管理难度大、破解容易以及可追踪性差,无法满足现代电网快速发展的多样化需求等问题。该文研制了一种基于配电物联网架构的无源高可靠性智能电子锁。其内嵌安全芯片,采用近场通信(Near Field Communication,NFC)技术完成通信及取能,无需机械钥匙开锁,无需维护更换锁具电池,并配套开发了能够实时监测锁具状态、储存开锁信息的智能锁管理系统以及配合开锁APP使用的电子钥匙,分析了智能锁具的硬件设计及系统的应用流程。最后,通过实践应用表明,该套锁具系统在运维便捷、信息安全和科学管理方面具有明显效用。     

On the limit theory of the Gaussian SQMLE in the EGARCH(1,1) model

We derive the limit theory of the Gaussian stable quasi maximum likelihood estimator for the stationary EGARCH(1,1) model when the squared innovation process has marginals with regularly varying tails. We derive regularly varying rates and limiting stable distributions. We perform Monte Carlo experiments to assess the extent of the parameter space corresponding to the invertibility condition, and the quality of the asymptotic approximation.     

Light scattering and extinction in polydisperse systems

A simple approach to predict transmittance spectra of polydisperse systems is recalled and applied to various model systems (spinel-like particles in water, pores in a spinel-like matrix) and real systems (spinel in water, diamond in water, amorphous carbon soot in isopropanol) in order to investigate principal effects of size distributions (normal/lognormal, narrow/wide, monomodal/bimodal, shift of mode positions, shift of mode heights) and optical properties (refractive index contrast, with or without absorption) on the in-line transmittance. A comparison of predicted and measured spectra showed that size distributions with more small particles cause a more significant decrease in transmittance (at least for sufficiently short wavelengths) and that laser diffraction may seriously underestimate the amount of small particles (for absorbing particles, for which the influence on transmittance is enormous, a difference of up to 30% in absolute transmittance measured via spectrophotometry has been found against predictions based on laser diffraction results).     

袋装水泥装车机及拨板机构的设计与研究

针对袋装水泥装车半自动化问题，设计一款全自动装车机。首先，根据袋装水泥车间生产状况，确定水泥装车方案，即采用抽屉式逐层装车原理，利用ＳｏｌｉｄＷｏｒｋｓ创建装车机三维模型；其次，为使水泥包快速准确地到达指定位置，针对拨板机构中的分拨板及导柱进行受力分析，建立其力学模型，推导出应力公式；最后，通过 ＡＮＳＹＳ有限元软件进行分拨板的力学仿真，为后续的优化设计提供依据。     

SiO2颗粒增强酚醛树脂基摩擦材料力学性能研究

为探讨陶瓷颗粒对树脂基摩擦材料力学性能的影响,以SiO_2颗粒增强酚醛树脂基摩擦材料为例,利用三点弯曲实验研究颗粒特征对弯曲强度的影响,建立材料内部弹性应力场分布模型,并从细观力学角度进行分析。实验结果表明:添加二氧化硅陶瓷颗粒后,复合材料的弯曲强度降低、弹性模量升高;复合材料弯曲断裂截面显示脆性断裂特征,断裂过程中裂纹遇到颗粒贯穿通过;复合材料弯曲强度随颗粒含量增加而降低,随颗粒弹性模量增加先减小后增大。理论分析表明:陶瓷复合树脂基摩擦材料内部最大应力值位于颗粒边缘处;最大应力值随颗粒与基体弹性模量比值增大而增大;复合材料的平均应力与颗粒的含量成正相关。实验和理论研究表明,陶瓷颗粒添加引起材料内部应力集中,且与颗粒弹性模量和颗粒含量成正相关。     

链条炉运行参数对燃烧及NOx排放的影响

通过数值模拟的方法研究了过量空气系数、配风方式、空气预热温度和炉排转速等运行参数对床层燃烧和氮氧化物排放特性的影响。研究结果表明:过量空气系数增大可加快床层整体反应速率,缩短反应区长度,增大床层表面氮氧化物质量浓度;合理推迟配风有利于扩展反应区整体长度,充分利用整个炉排;适当降低炉排转速有利于提高煤着火及前期反应速率,稍缩短总体反应区间;提高空气预热温度有利于煤着火和前期反应速率的提高,且有利于煤的燃尽。     

测量二次电子空间分布特征矩阵法的有效性分析

为了准确测量不同材料在实际环境中的二次电子空间分布，设计了一种新型的二次电子发射空间分布测量结构，给出了实验测量原理，用求解特征矩阵的方法对实验结果进行处理，得到了所需的二次电子空间分布。通过模拟计算对该测量方法进行了校验，模拟结果与假设二次电子空间分布函数相吻合，表明该测量方法可靠、测量精度高，为后续样机研制奠定了理论基础。     

Research on optimization design of PWR flow distribution device based on numerical simulation

ABSTRACT

In the lower chamber of pressurized water reactor (PWR), the flow distribution device is the core module to distribute coolant into the core. It has complex structure and numerous design parameters. Therefore, it has important theoretical and practical significance to optimize the device. The mesh independence verification, turbulence model selection, and data processing all can influence the numerical simulation results of the lower chamber, in order to research the influence, a numerical simulation method based on the original model of CNP1000 reactor lower chamber is proposed in this paper. In the method, an optimization design method of flow distribution device is established based on surrogate model. The main design variables and optimization objectives are determined based on the device’s structure and function characteristics. And then it respectively adopts Kriging algorithm and multi-objective genetic algorithm to establish a surrogate model of flow distribution device and optimize it globally. Finally, the optimal design variables are obtained. Compared with the device’s performance before optimization, the after optimization has smaller total pressure loss and more uniform flow. The effectiveness and practicability of proposed optimization design method can be verified.