超声波在金属凝固中的应用与发展

简要介绍了超声波及其基本特性，综述了高能超声对金属凝固过程作用方面的研究和应用状况，提出超声处理是改善金属凝固组织，提高力学性能的有效方法，并对21世纪超声凝固细晶技术的前景进行了展望。     

基于MOPSO与凸优化算法的稀布圆阵列方向图优化

为了降低稀布阵列的峰值旁瓣电平并抑制稀布阵列的栅瓣,提出了一种多目标粒子群与凸优化相结合的方向图综合算法。该算法将多目标粒子群优化(Multi-objective particles swarm optimization,MOPSO)作为全局搜索器,凸优化算法作为局部搜索器来搜索最优解,优化的变量不仅是阵元的权值,而且还加入了阵元位置这一参数,从而能够提供更多的自由度来控制稀布阵列的性能。基于30阵元的稀布圆形阵列的仿真结果表明：与单纯使用MOPSO算法相比,本文提出的用MOPSO算法优化阵元位置,凸优化算法优化阵元权值的联合优化算法,得到的栅瓣和峰值旁瓣电平都小于-19.3　dB。     

Improved properties of low-carbon MgO-C refractories with the addition of multilayer graphene/MgAl2O4 composite powders

The paper investigated the effects of different amounts (0%, 3%, 6%, 9%) of in situ multilayer graphene/MgAl₂O₄ composite powders on the slag resistance, thermal shock resistance, and oxidation resistance of low-carbon MgO-C refractories. Comparing with commercial MgAl₂O₄, the MgAl₂O₄ in in situ multilayer graphene/MgAl₂O₄ composite powders has higher lattice strain of crystal, which can trap more Mn and Fe ions, resulting in the better slag resistance. The oxidation decarbonation layer of MgO-C specimen with 3% composite powders is 9.71 mm, which is lower than not only the specimen with other contents but also specimen containing carbon black/MgAl₂O₄ powders. Moreover, the residual strength ratio of the specimen C/MA-3 was 47.47%, which is 28.5% and 8.08% higher than specimens with no additive and with carbon black/MgAl₂O₄ powders, respectively. Both improving thermal shock and oxidation resistance properties are related with the unique nano structure, multilayer graphene in situ formed between MgAl₂O₄ grains, of added composite powders. The former is due to higher strain energy consumed by multi-deflection of cracks inside the multilayer graphene/MgAl₂O₄ composite powders. And the latter is due to the higher energy of oxidation activation of multilayer graphene/MgAl₂O₄ composite powders due to effective protection of multilayer graphene by MgAl₂O₄.     

Combustion synthesis of C/MgAl2O4 composite powders using magnesium oxalate as carbon source

In order to solve the bottleneck problems including uniform distribution, and oxidation resistance of nano carbons in oxide ceramics, C/MgAl₂O₄ composite powders were prepared with MgC₂O₄·2H₂O, MgO₂, Al₂O₃, and Al as raw materials via combustion method under argon atmosphere. The maximum adding amount of MgC₂O₄·2H₂O is 34.34 wt%. The phase compositions and microstructures of combustion products were characterized through X-ray diffraction (XRD), scanning electron microscope (SEM)/EDX, and Raman spectroscopy. The results showed that the phases of products are mainly composed of MgAl₂O₄ and carbon. The prepared MgAl₂O₄ has granular and rod-like morphologies, and the free carbon (1.172 wt%) exists between particles of MgAl₂O₄. Moreover, the addition of FeC₂O₄ as catalyst in raw materials ratio would be beneficial for improving crystallization of in situ carbon generated in the products. The oxidation activation energy of the prepared C/MgAl₂O₄ composite powders was calculated as 143.01 kJ/mol which was 22.17% higher than that of carbon black/MgAl₂O₄ powders (117.06 kJ/mol), suggesting that the C/MgAl₂O₄ composite powders prepared by combustion synthesis have excellent oxidation resistance.     

Optical properties of gadolinia-doped cubic yttria stabilized zirconia single crystals

Cubic zirconia single crystals stabilized with yttria and doped with Gd₂O₃ (0.10–5.00 mol%) were prepared by the optical floating zone method, and characterized by a combination of X-ray diffraction (XRD), and Raman, electron paramagnetic resonance (EPR), ultraviolet–visible (UV–Vis), photoluminescence excitation (PLE) and photoluminescence (PL) spectroscopic techniques. XRD and Raman spectroscopy showed that the crystal samples were all in the cubic phase, whereas the ceramic sample consisted of a mixture of monoclinic and cubic phases. The absorption spectrum showed four peaks at 245, 273, 308, and 314 nm in the ultraviolet region, and the optical band gap differed between samples with ≤3.00 mol% and those with >3.00 mol% Gd₂O₃. The emission spectrum showed a weak peak at 308 nm and a strong peak at 314 nm, which are attributed to the ⁶P_5/2 → ⁸S_7/2 and ⁶P_7/2 → ⁸S_7/2 transitions of Gd³⁺, respectively. The intensities of the peaks in the excitation and emission spectra increased with Gd³⁺ concentration, reached a maximum at 2.00 mol%, then decreased with higher concentrations. This quenching is considered to be the result of the electric dipole-dipole interactions, and this interpretation is supported by the Gd³⁺ EPR spectra, which showed progressive broadening with increasing Gd³⁺ concentration throughout the concentration range investigated.     

基于GIS的航电枢纽安全监测信息管理系统设计与应用

为解决航电枢纽安全监测海量数据统筹管理以及GIS技术结合应用程度低等问题,开发了基于GIS的航电枢纽安全监测信息管理系统。倾斜摄影技术的应用实现了高效建立工程三维数字模型,通过实景模型与工程监测的结合,为监测点可视化管理及成果可视化展示提供了条件。系统实现的技术路线,可为类似工程项目提供参考。     

Influence of sintering temperatures of ceramic targets on microstructures and photoelectric properties of titanium-doped ZnO nano-films

Thin films of Ti-doped ZnO (TZO) were prepared by RF magnetron sputtering using targets prepared with sintering temperatures in the range 1100–1500 °C; the microstructures and optoelectronic properties of the TZO targets and films were characterized by SEM, XRD, Hall Effect analysis, UV–VIS spectrophotometry and physical property measurement system. Results indicated that the target sintering temperature affected both the TZO targets and films. The Ti/Zn atomic ratios in the targets decreased progressively with increasing sintering temperature, but by a smaller amount in films prepared from them. XRD patterns showed that all films were preferentially oriented along the c axis at 2θ ~ 34° in their XRD patterns. The films sputtered with targets sintered at above 1300 °C were relatively smooth, and had larger average grain size. The target sintered at 1450 °C had the highest density. The best optoelectronic properties were found with the film sputtered from the target sintered at 1300 °C; this sample had superior crystal properties, high average optical transmittance (88.9%), and the lowest resistivity (8.47 × 10^?4 Ω cm). Furthermore, the resistivity of all the films changed with temperature between 10 and 350 K, they experienced an initial decrease followed by an increase as the temperature was raised.     

考虑航天器舱体—附件耦合效应的热颤振准则

考虑具有端部附加质量的柔性附件及其和舱体的耦合效应,本文系统地推导出了一个带柔性附件的航天器热颤振准则,并用有限元程序进行了模拟校验.该准则揭示了柔性附件和舱体的质量特性和系统热诱发振动稳定性之间的关系.当舱体的质量特性远大于柔性附件的质量特性时,该准则就退化为悬臂柔性附件的热颤振准则.     

Preparation of calcium aluminate cement by combustion synthesis and application for corundum‐based castables

Calcium aluminate cement was prepared by combustion synthesis with CaO₂, Al, and Al₂O₃ as raw materials. The effects of CaO/Al₂O₃ (C/A) molar ratios in raw materials on the phase compositions and morphologies of calcium aluminate were investigated in detail. It was found that when the C/A reduced from 1.1 to 0.74, the content of CaO·2Al₂O₃ (CA₂) in products increased, whereas contents of CaO·Al₂O₃ (CA) and 12CaO·7Al₂O₃ (C₁₂A₇) decreased; when the C/A was 0.8, the phase composition of product (CS71) was equal to that of Secar71. Additionally, the crystallines of CA and CA₂ in the product were reduced when the C/A molar ratio was decreased. And then, the bulk density, apparent porosity, permanent linear change, cold crushing strength (CCS), and cold modulus of rupture (CMOR) of the corundum‐based castables bonded with CS71, Secar7 were compared. The castables bonded with CS71 demonstrate obviously improved CCS, CMOR, and volume stability.     

藕节对莲藕淀粉多酚含量的影响

为研究藕节对莲藕提取淀粉多酚含量的影响,通过高效液相色谱-串联质谱法与高效液相色谱法分析藕节汁的酚类物质及含量,通过乙醇保护的碱提法分析莲藕淀粉多酚的组成。结果显示：通过乙醇保护的碱提法可以有效提取出淀粉中的多酚,多酚组分主要为没食子儿茶素以及儿茶素。藕节汁中没食子儿茶素的含量为565.14 μg/g（干重）,明显高于去皮藕段和藕皮,在制得莲藕淀粉时藕节原料可提高莲藕淀粉的多酚含量。