Boson peak and structural heterogeneity in ternary SiO2-Al2O3-B2O3 glasses

We use low-temperature heat capacity, low-frequency Raman scattering, and THz time domain spectroscopy in order to scale the vibrational density of states and the Boson peak in SiO₂-Al₂O₃-B₂O₃ Yb-laser host glasses. When substituting B₂O₃ for SiO₂ at constant Al₂O₃ dopant level, we find an optimal value for the ratio of B/Al in terms of mixture stability, at which the excess in the electron donor capability of Al₂O₃ (relative to the SiO₂ backbone) is compensated by the more acidic B₂O₃. At this composition, Al₂O₃ plays a mediating role in the structure of aluminoborosilicate glasses, facilitating dissolution of Yb₂O₃ and admixture of B₂O₃ into the SiO₂ network.     

ISHIGAKI Retrieval System Using 3D Shape Matching and Combinatorial Optimization

International Journal of Computer Vision - In April 2016, a massive earthquake with a magnitude of 7.3 struck Kumamoto region, Japan, causing major devastation. One of the structures that were...     

Thermal and optical properties of hyperbranched fluorinated polyimide/mesoporous SiO2 nanocomposites exhibiting high transparency and reduced thermo-optical coefficients

A series of hyper-branched polyimide (HBPI)/mesoporous SiO₂ nanocomposite films were prepared from a fluorinated anhydride (6FDA), a fluorinated triamine (TFAPOB), and mesoporous SiO₂ nanoparticles (NPs). The anhydride-terminated precursor of HBPI was functionalized using a coupling agent prior to mixing with SiO₂ NPs. The morphologies and thermal-optical properties of the nanocomposite films were investigated, with particular focus on their optical transparency, refractive indices (n), and thermo-optical (TO) coefficients. The absolute values of TO coefficients (|dn/dT|) of HBPI film (50.8 ppm/K) were significantly reduced to 13.4 ppm/K by homogeneous dispersion of 15 wt% of SiO₂ NPs. The HBPI/SiO₂ composite films exhibited high thermal stability without significant weight loss of up to 400 °C in air. The films also exhibited small coefficients of linear thermal expansion (CTEs) within the range 30–40 ppm/K. In addition, enhanced interfacial interactions between SiO₂ and HBPI significantly improve the optical transparency with cutoff wavelengths shorter than 450 nm. The refractive indices of HBPI/SiO₂ composite films were found to range from 1.477 to 1.502, which agrees well with the calculated values. This study shows that the incorporation of SiO₂ NPs in multi-functional HBPI matrix is a promising approach to prepare high performance thermally stable films for thermo-optic applications.     

GRIMSEL现场的气体渗透试验

自1976年以来，日本核废料管理基金会与研究中心（RWMC）一直在进行核废料处置的研究。最近，RWMC非常关注核废料处置库的监测、遥控以及现场勘查技术等重要的社会公众与技术问题。其中，处置库溢山气体是一项重要的安全可靠性评估项目。这项名为“工程屏障的气体渗透试验”（GMT）的研究是在瑞士Nagra的Grimsel现场实验室进行的。GMT集中研究在粮仓形的处置库中由核废料产生的气体在工程屏障中的渗透问题。在Grimsel现场，一个按比例缩小的工程屏障库由一个具有透气孔的混凝土仓和砂-膨润土缓冲材料组成，缓冲材料被放置在一个专门建造的洞室中。混凝土仓直径为2．5m，高为2．5m，放置在直径为4m的从上到下开挖而成的竖井中。在工程屏障饱和及水渗透试验之后，气体分两个阶段被注入地窖中。气体第一次被注入之后，重复进行水渗透试验，以便观察工程屏障库的变化。第二次气体注入的时候，在工程屏障及岩石圈中采用一种可以多点取样的鸡尾酒气体跟踪器。在气体注入之后，小心挖掘出工程屏障库，然后用各种方法来进行鉴定，并采用实验室以及建模程序来进行现场的模拟研究。     

Preparation of porous membranes by selective decomposition of adamantane unit in ABA‐type triblock copolymer

The mechanism of pore formation by selective decomposition of adamantane unit in an ABA‐type triblock copolymer derived from 4,4‐(hexafluoroisopropylidene)diphthalic anhydride‐2,3,5,6‐tetramethyl‐1,4‐phenylenediamine (6FDA‐TeMPD) and poly(2‐methyl‐2‐adamantylmethacrylate) (PMAdMA) was investigated on this basis. This study aims to developing a novel method of material design for high‐precision gas separation membranes and application to electric devices by improving dielectric constant. Scanning electron microscopy images showed that the membrane structure changed considerably after heating; the difference increased with the increase in adamantane content. Interestingly, the internal structure of Block(36 mol%6FDA‐TeMPD/64 mol%PMAdMA) membrane was almost unchanged although its surface structure was changed. These results suggest that the mechanism of formation of porous membrane involves the decomposition of adamantane unit from surface. In addition, more adamantane units inside the membrane were discharged to the surface of the membrane through a path formed by decomposed adamantane units. POLYM. ENG. SCI., 56:1191–1200, 2016. © 2016 Society of Plastics Engineers