汽车风挡玻璃用密封胶的结构与性能研究

研究了三种汽车风挡玻璃用单组分PU(聚氨酯)密封胶和SPU(硅烷改性聚氨酯)密封胶。采用红外光谱(FT-IR)、凝胶渗透色谱(GPC)法分析了三种密封胶的结构和相对分子质量,并对其固化行为、粘接性能和力学性能等进行了研究。结果表明:相对湿度越大(或固化温度越高),则三种密封胶的表干时间越短且固化速率越大;在三种密封胶的储存过程中,其表干时间和固化速率变化不大,稳定性较好;SPU密封胶与基材的粘接性能优于PU密封胶;PU密封胶的拉伸强度(≥8.2 MPa)和撕裂强度(19 N/mm)均优于SPU密封胶的拉伸强度(5.8 MPa)和撕裂强度(13 N/mm)。     

Hot Pressing of Potassium-Sodium Niobates

Compositions in the system KNbO₃-NaNbO₂ have been hot-pressed to yield ceramics with relative densities greater than 99%. Because these materials lack any degree of pyroplastic behavior, temperatures approaching those required for air sintering are needed. These hot-pressed specimens exhibit a finer microstructure than that obtainable by conventional processing. Enhanced piezoelectric coefficients are observed, and in certain compositional regions radial coupling coefficients have been increased from 32 to approximately 48%. Dielectric constants increase with densification and ac losses remain relatively high. The fine structure and improved piezoelectric activity, especially near the equimolar composition, make these materials desirable for electromechanical transducers, particularly in the 10 to 20 Mc per second range. The rate equation of Murray, Live, and Williams for hot-pressing ceramics was found to apply in this system.     

Influence of fruit ripeness and juice chaptalisation on the sensory properties and degree of typicality expressed by Sauvignon Blanc wines from Marlborough,New Zealand

Background and Aims: Interest in the typical sensory properties exhibited by Sauvignon Blanc wines from Marlborough, New Zealand, is increasing. Although critical from a winemaking standpoint, there is a significant lack of data concerning the extent to which these typical sensory characteristics are affected by fruit ripeness at harvest and juice chaptalisation. Methods and Results: Experimental Marlborough Sauvignon Blanc wines fermented from fruits at three different ripeness stages, with or without juice chaptalisation, were assessed by a panel of wine professionals from Marlborough. Results suggest that the balance between green and fruity ripe flavours that makes a Marlborough Sauvignon Blanc typical of its style would originate from the fruit ripeness at harvest. We also report that juice chaptalisation can modulate the wines' taste and mouthfeel properties and significantly affect their typicality as Marlborough Sauvignon Blanc. Conclusions: The production of Marlborough Sauvignon Blanc wines that well represent their specific style relies primarily on the ripeness of the fruit at harvest, the impact of which can be modulated by juice chaptalisation. Significance of the Study: This is the only study that has considered fruit ripeness and juice chaptalisation as two factors that condition the sensory properties and degree of typicality expressed by Marlborough Sauvignon Blanc wines.     

龙凤呈祥

介绍了我们在设计中如何充分运用传统文化元素,在原有龙形水系基础上创造了凤凰山这景观造型,以体现龙凤呈祥的主题;通过绿色游憩空间的规划设计、各种设施的建立和完善的管理,希望创造一个愉快、舒适、安全的观赛和游览环境;制定各种可持续运营措施、运用相关新技术,以恢复和重建奥林匹克公园园区生态环境.充分发挥"绿色奥运,科技奥运和人文奥运"理念.     

Sol–gel hybrid materials based on hydroxylatedpoly[bis(methoxy–ethoxy–ethoxy)phosphazene] and silica: a ceramic ionic conductor

The sol–gel synthesis of hybrid materials based on poly[bis(methoxy–ethyoxy–ethoxy) phosphazene] (MEEP) and silica and their characterization are described. MEEP is a polymer with a low glass transition temperature of −71 °C, that bears ethyleneoxide oligomers as phosphorus side groups, able to impart to the macromolecule metal co-ordination ability. This property makes MEEP an ionic conductor, but unfortunately its flow behaviour at room temperature limits its industrial development. The linkage of MEEP to a rigid inorganic network, which would overcome this problem, was pursued using the sol–gel method. The functionalization of MEEP by the introduction of free hydroxyl groups allows the formation of chemical bonds with hydrolysed tetraethoxysilane. Phosphazene-based hybrid materials with no phase separation could be obtained by this procedure. The ionic conductivity of these materials doped with lithium triflate has been investigated using a.c. impedance techniques. A conductivity value of about 3 × 10^-5 Ω^-1 cm^-1 was measured which is comparable to typical values of poly(ethylene oxide) solid electrolytes. A thermal treatment of the Li-doped samples decreases the conductivity but it still remains above 5 × 10^-6 Ω^-1 cm^-1. This revised version was published online in November 2006 with corrections to the Cover Date.     

Structural Characterization of High-Temperature Zirconia Ceramics by Perturbed Angular Correlation Spectroscopy

Perturbed angular correlation spectra of γ-rays emitted following the decay of dilute ¹⁸¹Hf in several zirconia ceramics are reported. Spectra for monoclinic and tetragonal zirconia, a tetragonal zirconia/yttria alloy, a cubic zirconia/yttria alloy, and two mixed tetragonal/cubic-phase zirconia/yttria alloys were measured as a function of temperature to 1470°C. The spectrum observed for each phase has a unique signature, and the spectrum of mixed-phase materials can be used to determine the relative amounts of the different phases. These data give a cubic/(cubic + tetragonal) phase boundary that is somewhat lower in temperature than indicated by current phase diagrams.     

真空条件下铅膏的高效混合制备

铅膏制备过程中对环保和铅膏质量的更高要求促使真空和膏技术的发展。德国爱立许公司开发出这种和膏方式并命名为爱立许真空技术。介绍了爱立许R 系列混合机 ,其结构特征为 :旋转的混合盘 ,逆流式原理下工作的旋转的混合工具和静态的壁部 /底部刮板 (多功能工具 )。以R系列混合技术为基础的爱立许真空技术和膏系统的主要特征为 :真空条件下的冷却 ,冷却作用于每个铅膏颗粒 ,完全独立于外界条件 ;密封系统保证配方准确 ,节省原料     

Transient Effects of Nuclear Radiation on the Dielectric Properties of Refractory Low-Loss Ceramics at Microwave Frequencies

Selected ceramic materials were exposed to an intense burst of nuclear radiation to determine the transient effects of such an environment on their dielectric properties at frequencies in the L, S, and X bands. The radiation source was a pulse reactor of the swimming pool type which delivers a maximum dose of 2 × 10¹⁴/cm² and 5 × 10⁵ rd gamma during a 13 ms pulse. The dielectric constant and loss of the materials under test were measured before, during, and after irradiation using a resonant cavity technique successfully adapted to the unusual conditions of the experiment. The time resolution in the dielectric measurements was 10 ms. Results are reported for polycrystalline alumina, beryllia, magnesia, boron nitride, clear and opaque fused silica, and, for comparison, four organic dielectrics. Among the materials which exhibited radiation effects, changes in dielectric constant ranged from 0.001 to 0.008 and in tan δ from a factor of 2 to several orders of magnitude.