On fracture toughness of nano-particle modified epoxy

A systematic study on the effects of silica and rubber nano-particles on the fracture toughness behavior of epoxy was conducted. Mode I fracture toughness (G_IC) of binary silica/epoxy, binary rubber/epoxy and ternary silica/rubber/epoxy nanocomposites with different particle weight fractions was obtained by compact tension tests. It is found that G_IC of epoxy can be significantly increased by incorporating either rubber or silica nano-particles. However, hybrid nanocomposites do not display any “synergistic” effect on toughness. Microstructures before and after fracture testing were examined to understand the role of nano-particles on the toughening mechanisms.     

二氧化硅气凝胶隔热复合材料的制备与应用

介绍了二氧化硅(SiO2)气凝胶的结构特点及隔热性能;对二氧化硅气凝胶隔热复合材料的制备方法及其应用前景进行总结并作了适当的评述;探讨了该领域今后的研究方向。     

Structural anisotropy of silica hydrogels prepared under magnetic field

Birefringence measurements have been carried out on the Pb-doped silica hydrogels prepared under various magnetic fields up to 5T. The silica gels prepared at 5T were used as a medium of crystal growth of PbBr₂, whose result implied the structural anisotropy; an aligned array of crystallites was obtained by transmission electron microscopy. While the samples prepared at 0, 1, and 3T have no birefringence, we found that the samples have negative birefringence on the order of magnitude 10^− 6 as if the direction of the magnetic field is the optic axis of a uniaxal crystal. To the authors' knowledge, the birefringent silica hydrogels were obtained by gelation under magnetic field for the first time. Also, scanning microscopic light scattering experiments have been performed. The results indicate that the characteristic length distribution for birefringent samples is narrower than that for non-birefringent ones.     

Effects of silica addition on chromium distribution in stainless-steel slag

The present study was aimed at highlighting the effect of silica on chromium distribution and enrichment in certain stainless-steel slag when basicity ranged from 0.96 to 1.96. Industrial slag samples of the CaO–Al₂O₃–MgO–SiO₂–CrO_X–Fe_XO system were investigated with different silica addition contents and soaked at the targeted regime. X-ray diffraction, electron probe micro-analyzer with wavelength-dispersive X-ray spectrometer, as well as Fourier-transform infrared spectroscopy and NIH ImageJ software were used for sample characterisation. FactSage version 6.4 was employed to calculate phase equilibria at 1200°C for the slag system to understand the crystallisation procedure. Results indicated that chromium was enriched in CaCr₂O₄ at high basicity, but in spinel at lower basicity. The spinel phase increased in size and chromium distribution with Fe(II) participated in growth with the decrease in depolymerisation of the slag structure.     

The role of familism in stress and coping processes among African American and White dementia caregivers: Effects on mental and physical health.

Objective: To explore how familism, burden, and coping styles mediate the relationships between ethnicity and the mental and physical health of caregivers. Design: A probability sample of 65 White and 95 African Americans respondents caring for an older family member with dementia was used to test hypotheses from a sociocultural stress and coping model using path analysis. Main outcome measures: Measures of caregivers' health included subjective health, self-reported diseases, blood pressure, and heart rate. Mental health measures included self-reported depression and psychological symptoms. Results: Contrary to the hypothesis, familism had an adverse effect on outcomes and was related to low education levels rather than to African American ethnicity. A buffering effect of active coping between being African American and diastolic blood pressure was found even after controlling for levels of education. Conclusions: Findings supported a core stress and coping model in which more behavior problems of care recipients were associated with poorer mental health of caregivers via greater burden and more use of avoidant coping. Results also demonstrate that this core model can be extended to physical health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coating Multi-walled Carbon Nanotubes with Uniform Silica Shells:Independent of Surface Chemistry

A facile and general method was described to coat six types of multi-walled carbon nanotubes, functionalized by either noncovalent or covalent way, with smooth silica shells. 3-Aminopropyltriethoxysilane(APTES) and pH value play important roles in the coating process and the thickness of silica shell could be controlled by the added amount of silicon alkoxides. After the removal of multi-walled carbon nanotubes by calcination, the silica nanotubes were successfully prepared.     

氢对钢质量的影响及工艺控制研究

讨论了氢在钢中的变化规律及控制效果,提出了工艺优化的措施和降低氢含量的有效方法。     

Optical fiber sensing element based on luminescence quenching of silica nanowires modified with cryptophane-A for the detection of methane

An optical fiber sensing element based on luminescence quenching of cryptophane-A/silica nanowires was successfully constructed and used to dynamically monitor methane gas at low concentration below 3.5% (v/v). The optical fiber device was designed to operate via luminescence reflection. The sensing properties of optical sensing element to methane at room temperature were characterized. The sensing element shows an intensive and stable blue luminescence when excited by UV light source at wavelength of 380 nm, and it is efficiently quenched by molecular methane. The response of the sensing element demonstrates excellent linear Stern-Volmer behavior at the fixed wavelength 439 nm within the methane concentration range between 0.1% and 3.5% (v/v). A detection limit of below 0.1% (v/v) is estimated for the methane sensing element. This newly developed methane sensing element has significant advantages over the currently available methane sensors such as fast response and recovery (within seconds), good repeatability, selectivity, and long-term stability.     

基于BIST软件测试思想的单元测试框架

BIST是一种成熟的硬件可测性设计的方法,BIST软件测试思想则借用了该技术,它主要包括模板和自治测试部分两大基本结构。在该思想的指导下,整合测试用例、测试点、插装函数、测试报告等测试要素,提出了各个要素的存储或使用方式,以路径覆盖为测试目标,提出了一种BIST软件自测试的测试框架。实践证明,该测试框架有利于BIST软件测试思想的进一步研究和实现。     

关于三阶统计量定义的研究

高阶统计量是信号处理中的一种重要方法,已经得到较为广泛的运用。本文在三阶统计量的传统定义上提出了一种新的三阶统计量定义,提出新定义较之旧定义的优越性,并通过实验验证该结论。