水泥在石膏复合胶凝材料体系中的作用

石膏复合胶凝材料是由石膏与矿渣或粉煤灰、水泥等原材料配制而成的新型胶凝材料,水泥对其性能有很大影响,掺量过少不能有效激发矿渣活性,掺量过多易引起安定性不良。通过pH值测定和水化产物的XRD图谱并结合宏观试验结果,分析了水泥在石膏复合胶凝材料水化过程中的作用及机理。结果表明,水泥除自身水化外,主要为石膏复合胶凝材料体系提供钙离子和矿渣水化需要的碱性环境,能够加快矿渣活性的激发速度,缩短石膏复合胶凝材料的凝结时间;水泥掺量少,自身水化产物少且对矿渣激发不充分,不足以形成致密的网状结构,掺量过多,钙矾石生成量大,会因膨胀而破坏已形成的结构,导致强度和耐水性能降低;水泥的最佳掺量范围为7%~10%。     

Evolution of Light Absorption and Emission Characteristics of Organic Perylene Nanoparticles through Hydrothermal Process: Application to Solar Cells

The evolution of the structural and optical characteristics of polymorphic organic perylene nanoparticles (NPs) is demonstrated by controlling the π–π interactions using a hydrothermal process. The light‐emission colors of the perylene NPs vary gradually from yellow to green to light blue with increasing hydrothermal temperature from 110 to 160 °C. An enhanced crystallinity of the NPs from 110 °C to a critical temperature T_c of 140 °C and a transition to the amorphous phase above T_c are observed. The evolution of the photo‐luminescence (PL) and optical‐absorption characteristics in terms of variations in the crystallinity and physical dimensions (size and shape) of the perylene NPs resulting from the hydrothermal process are analyzed. These results are confirmed by nanoscale PL measurements for single NPs using laser confocal microscopy. The photovoltaic characteristics of organic solar cells (OSCs) are improved through the use of the perylene NPs. It is found that the performance of the OSCs is strongly correlated with the optical‐absorption properties of the perylene NPs.     

Effect of deposition temperature and quality of free-standing diamond substrates on the properties of RF sputtering ZnO films

Highly c-axis oriented ZnO film is often deposited on diamond substrates by RF magnetron sputtering and widely used for high frequency surface acoustic wave (SAW) devices. Deposition temperature is a key factor affecting the quality of the ZnO film. Different quality polished free-standing diamond films prepared by DC Arc Plasma Jet were used as the substrates to deposit ZnO films at different temperatures. Effect of the deposition temperature and the quality of the diamond films on the properties of the ZnO films were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that highly c-axis oriented ZnO films can be much easier deposited on the optical-grade diamond films with < 111> preferred orientation than the tool-grade diamond films with < 220> preferred orientation. The optimal deposition temperature is 200 °C for highly c-axis oriented and lower roughness ZnO films. Acoustic phase velocity of more than 10,000 m/s for the SAW devices based on the ZnO/optical-grade free-standing diamond films was obtained.     

CAD/CAE技术在铸造工艺设计及优化中的应用

利用铸造工艺设计及工艺模拟软件Castsoft CAD/CAE技术对铸件毛坯模数、工艺热节、浇冒口系统、浇注过程、凝固过程进行计算从而对铸件毛坯进行工艺设计和铸造缺陷分析。依据分析结果对工艺进行改进,最后设计出合理的铸造工艺。铸造过程计算机模拟可以减少或取消新产品的工艺试验,有效地避免可能出现的铸造缺陷,保证工艺的可靠性,缩短新产品的试制周期。     

Effect of chemical composition on the response of zwitterionic glucose sensitive hydrogels studied by design of experiments

A stimuli‐responsive hydrogel that contains the anionic monomer 3‐acrylamidophenylboronic acid and the cationic monomer N‐[3‐(dimethylamino)propyl]acrylamide binds with cis‐diol groups of glucose molecules selectively and reversibly. Even though such hydrogels have good selectivity for glucose, there are still remaining thresholds that should be overcome to enhance the sensitivity (swelling pressure response magnitude) and to reduce the response time (inverse of 1st order rate constant). In this study, the sensitivity and response time of zwitterionic glucose sensitive hydrogels (GSHs) were studied with three factor DOE analysis. The DOE results show that the molar ratio of 3‐acrylamidophenylboronic acid/N‐[3‐(dimethylamino)propyl]acrylamide and the wt % of monomer in the pregel solution are the most important factors for enhancing the hydrogel sensitivity. In addition, fast response times can best be achieved by decreasing the molar ratio of cross‐linker. The results of this study will be useful as guidelines for the optimal synthesis of glucose sensitive hydrogels. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40667.     

基于OFDM技术的电力线通信系统的相位噪声估计与补偿

OFDM电力线通信系统对相位噪声非常敏感。由于电力线信道噪声大、衰减强,OFDM信号通过后发生严重失真,基于导频的公共相位误差估计效果变差。提出一种更可靠的相位噪声估计和补偿算法,能够更准确地估计公共相位误差。仿真表明该方法能够有效地抑制相位噪声。     

A study on the behavior and heat transfer characteristics of impinging sprays

The spray/wall interaction is considered as an important phenomenon influencing air-fuel mixing in the internal combustion engines. In order to adequately represent the spray/wall interaction process, impingement regimes and post-impingement behavior have been modeled using experimental data and conservation constraints. The modeled regimes were stick, rebound, spread and splash. The tangential velocities of splashing droplets were obtained using a theoretical relationship. The continuous phase was modeled using the Eulerian conservation equations, and the dispersed phase was calculated using a discrete droplet model. The numerical simulations were compared to experimental results for spray impingement normal to the wall. The predictions for the secondary droplet velocities and droplet sizes were in good agreement with the experimental data.     

液液平衡和会溶现象

提出了液体混合的通用Gibbs自由能模型,据此建立了液液平衡的双节线、旋节线和临界点方程.这些方程不仅适用于小分子液体混合物,而且亦适用于高分子溶液.计算结果表明,它们能满意地描述各种类型的液液平衡及其会溶现象.     

Environment-oriented low-cost Al2O3 ceramics with hierarchical pore structure fabricated from SiC solid waste

Environment-oriented low-cost Al₂O₃ reticulated porous ceramics with hierarchical pore structure were fabricated by the polymer sponge replica method combined with vacuum infiltration methods, using Al₂O₃ powders and SiC solid waste (SCSW) as raw material and a pore-forming agent. The effects of SCSW addition amount on mechanical properties, microstructure and pore size of Ceramics were investigated. The results showed that the thermal shock resistance of specimens increased gradually with addition of SCSW, however, the median pore diameter increased firstly and then decreased, due to the generation of mullite and liquid phase. After calcination, the residual stress was generated within the coating layer because of the difference in the thermal expansion coefficients of ceramic matrix and coating layer, which could improve the properties of Ceramics by deflecting and bifurcating crack growth path. The results showed that the best dosage of SCSW was 30 wt%.     

关于超大规模集成电路制造中的应力迁移问题

应力迁移是影响集成电路（ＩＣ）金属配线可靠性的缺陷之一。它缘起于绝缘膜与金属配线之间的热应力。本文概要介绍两种性质的绝缘膜产生的两种应力缺陷以及检测方式，并分类说明金属膜厚、线宽温度等与应力的关系。简要说明应力迁移产生的可能机理及目前采取的几种对策。