Enhanced thermal conductivity and stability of boron nitride/phenyl silicone rubber composites via surface modification and grain alignment

Journal of Materials Science - With the extensive use of high-power electronic appliances, polymer-based thermal insulation composites with excellent thermal properties are utilized in the field of...     

Enhanced electromagnetic microwave absorption of Fe/C/SiCN composite ceramics targeting in integrated structure and function

The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of ?31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < ?10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics.     

Aluminum based reflective nanolens arrays to improve the effectiveness of ultraviolet inactivation of Escherichia coli O157:H7 and Listeria monocytogenes in water and a sucrose solution

Food Science and Biotechnology - Aluminum based reflective nanolens arrays were developed via a series of aluminum electropolishing and anodization steps with subsequent selective dissolution of...     

基于Stateflow电力机车变流器控制设计与实现

某出口型号交流电力机车牵引控制系统要求变流器控制逻辑具备接触器控制、牵引系统数据交互、变流器故障保护、变流器启动自检等功能。针对以上功能,基于MATLAB中的Simulink/Stateflow可视化编程工具进行牵引控制模型的搭建,遵循模块化编程理念,采用较少的程序代码编写实现复杂的逻辑控制模型,生成逻辑清晰的控制功能流程图,进行半实物仿真测试,增强控制模型的可靠性。通过该变流器产品型式试验检验,验证变流器控制逻辑的功能可以满足控制系统的需求。     

Preparation and characterization of mullite whisker reinforced ceramics made from coal fly ash

Ceramics with mullite whiskers were prepared from coal fly ash and Al₂O₃ raw materials, with AlF₃ used as an additive. The phase structures and microstructures of the ceramics were identified via X-ray diffraction and scanning electron microscopy, respectively. The results show that pickling of coal fly ash is an effective method for enhancing the flexural strength of ceramics. Sintering temperature and AlF₃ addition were also key factors influencing the creation of ideal ceramics. The ceramic made from pickled coal fly ash, 6?wt% AlF₃, and sintered at 1200?°C, exhibited the highest flexural strength of 59.1?MPa, and had a bulk density of 1.32?g/cm³ and porosity of 26.8%. The results show that ceramic materials made under these conditions are ideal candidates for manufacturing ceramic proppants for the exploitation of unconventional oil and gas resources.     

航空发动机复杂扭曲叶片分步电解加工研究

为实现复杂扭曲叶片在较小间隙下的稳定加工,提出了一种分步式电解加工的工艺方法,建立了复杂扭曲叶片小间隙(0.2 mm)和大间隙下(0.5 mm)扭曲流道的流道模型,采用有限元法进行了流场仿真研究,结果表明增加流道间隙可以解决流道中涡流和流场紊乱的问题。开展了复杂扭曲叶片小间隙连续式加工和分步式加工的试验研究。结果表明,采用小间隙连续式加工,当阴极进给至3.8 mm位置时,在叶片排气边靠近叶根流道扭曲处出现短路打火情况;而采用分步式加工方式能够实现加工的顺利进行。     

SUBSCRIPTION 2018

正Four issues per volume a year,CHINA’S REFRACTORIES is distributed worldwide by airspeed delivery at no extra cost to subscribers.     

The effect of optimized carbon source on the synthesis and composition of exopolysaccharides produced by Lactobacillus paracasei

This study aimed to predict the optimal carbon source for higher production of exopolysaccharides (EPS) by Lactobacillus paracasei TD 062, and to evaluate the effect of this carbon source on the production and monosaccharide composition of EPS. We evaluated the EPS production capacity of 20 strains of L. paracasei under the same conditions. We further investigated L. paracasei TD 062, which showed the highest EPS-producing activity (0.609 g/L), by examining the associated biosynthesis pathways for EPS. Genomics revealed that fructose, mannose, trehalose, glucose, galactose, and lactose were carbon sources that L. paracasei TD 062 could use to produce EPS. We identified an EPS synthesis gene cluster that could participate in transport, export, and sugar chain synthesis, and generate 6 sugar nucleotides. Experimental results showed that the sugar content of the EPS produced using fermentation with the optimized carbon source (fructose, mannose, trehalose, glucose, galactose, and lactose) increased by 115%. Furthermore, use of the optimized carbon source changed the monosaccharide content of the associated EPS. The results of enzyme activity measurements showed significant increases in the activity of 2 key enzymes involved in the glycoside synthesis pathway. Our study revealed that optimizing the carbon source provided for fermentation not only increased the production of EPS, but also affected the composition of the monosaccharides by increasing enzyme activity in the underlying synthesis pathways, suggesting an important role for carbon source in the production of EPS by L. paracasei TD 062.     

氧化钙固体碱催化剂用于大豆油和甲醇酯交换制备生物柴油的研究

对氧化钙固体碱催化剂用于甲醇和大豆油的酯交换反应制备生物柴油（脂肪酸甲酯）进行了研究，考察了醇油摩尔比、反应温度、催化剂用量等因素对生物柴油产率的影响，以及采用四氢呋喃等溶剂溶解产物中的甘油和脂肪酸甲酯以分离回收催化剂的方法。结果表明，在醇油摩尔比为12、反应温度为65℃、催化剂用量为8％、反应1．5h的条件下，生物柴油产率达到了95％以上。重复使用实验结果表明，CaO的催化活性比K2CO3／γ-Al2O3和KF／γ-Al2O3固体碱催化剂高，寿命更长，重复使用20次后催化效果无明显下降。     

器外预硫化型MoNiP/γ-Al2O3催化剂的加氢脱硫性能研究

以二苯并噻吩为模型化合物，研究了器外预硫化型加氢催化剂MoNiP／γ-Al2O3的加氢脱硫初始活性及其储存稳定性。结果表明，使用不同配方的硫化剂，在反应温度160℃、浸渍温度160℃、浸渍时间4h、氮气热处理温度300℃的条件下制备得到的器外预硫化催化剂的加氢脱硫活性较好，部分可以达到器内预硫化催化剂的效果，但其加氢活性稍弱；二苯并噻吩在器内与器外预硫化催化剂上的加氢脱硫反应的历程类似，但是对于器外预硫化催化剂而言，二苯并噻吩的加氢脱硫主要依赖于氢解历程。器外预硫化催化剂的储存稳定性较好，长期储存后仍可以维持较高的HDS活性。