Pressureless Sintering of Si3N4 Ceramic Using AlN and Rare-Earth Oxides

Using intermediate, liquid-forming compositions in the (Y,La)₂O₃-AlN system as additives, fully dense Si₃N₄ ceramics with high strength at high temperature have been obtained by pressureless sintering. The ceramics contain rod-shaped β-Si₃N₄ with M' or K' solid solutions as grain-boundary phases. The strength of these ceramics is 1150 MPa at 1200°C, and the room-temperature toughness is maintained at }7 MPa·m^1/2. Phase relations that are pertinent to the new additive compositions are delineated to rationalize their beneficial effects on sinterability and mechanical properties.     

Automatic Video Segmentation Based on Information Centroid and Optimized SaliencyCut

Journal of Computer Science and Technology - We propose an automatic video segmentation method based on an optimized SaliencyCut equipped with information centroid (IC) detection according to level...     

Phase relationships in Si3N4-AIN-MxOy systems and their implications for sialon fabrication

Phase relationships in Si₃N₄-AIN-M_xO_y systems involving -sialon, where M represents lithium, magnesium, calcium, yttrium, neodymium, samarium, gadolinium, dysprosium, erbium and ytterbium are outlined. Their implications for the formation and fabrication of single-phase -sialon and two-phase : sialon ceramics are discussed.     

Reduction of sidewall roughness, insertion loss and crosstalk of polymer arrayed waveguide grating using vapor-redissolution technique

An efficient vapor-redissolution technique is used to greatly reduce sidewall scattering loss in the polymer arrayed waveguide grating (AWG) fabricated on a silicon substrate. Smoother sidewalls are achieved and verified by a scanning electron microscopy. Reduction of sidewall scattering loss is further measured for the loss measurement of both straight waveguides and AWG devices. The sidewall loss in straight polymer waveguide is decreased by 2.1 dB/cm, the insertion loss of our AWG device is reduced by about 5.5 dB for the central channel and 6.7 dB for the edge channels, and the crosstalk is reduced by 2.5 dB after the vapor-redissoluton treatment.     

Simultaneously increasing cryogenic strength, ductility and impact resistance of epoxy resins modified by n-butyl glycidyl ether

Epoxy resins are increasingly used in cryogenic engineering areas due to rapid developments of spacecraft and superconducting cable technologies as well as large cryogenic engineering projects (e.g., International Thermonuclear Experimental Reactor). Cryogenic mechanical properties are important parameters for epoxy resins to be employed in such areas. In this paper, a traditional reactive aliphatic diluent, namely n-butyl glycidyl ether (BGE, JX-013) with a low viscosity, was used to modify diethyl toluene diamine (DETD)-cured diglycidyl ether of bisphenol-F (DGEBF) epoxy system for enhancing cryogenic mechanical properties at liquid nitrogen temperature (77 K). The results showed that the cryogenic strength, ductility and impact resistance (impact strength) have been simultaneously enhanced by the addition of BGE with appropriate contents. Moreover, the comparison of the mechanical properties between 77 K and room temperature (RT) indicated that at the same composition, the tensile strength and Young's modulus at 77 K were higher than those at RT but the failure strain and impact resistance showed the opposite results. Finally, differential scanning calorimetry (DSC) exhibited that the glass transition temperatures (T_g) of the epoxy resins decreased with increasing the BGE content.     

XML文档信息的几种转换方法分析与应用实例

1.引言 XML(eXtensible Markup Language,可扩展标记语言)是最近几年发展十分迅速的一项技术。由于其各种突出优点,以及W3C(World Wide Web Consortium,万维网协会)正不遗余力给它制定的各项应用标准,可以预见,XML将会在更广泛和更深入的领域取得重要的应用。     

Numerical Studies of Infiltration Dynamics of Liquid–Copper and Silicon/Solid–Carbon System

Mathematical modeling of infiltration dynamics of liquid Cu-Si alloy into porous carbon is presented. Two-dimensional infiltration equations are developed using the Washburn equation in the limit of both interface and diffusion control, for situations where the capillary radius decreases either linear or parabolic, and the contact angles are assumed to exponentially decrease with time during infiltration. One major manufacturing process for the Cu-Si/C composites is liquid melt infiltration. This article focuses on nonequilibrium wetting effects and offers a fundamental approach to these complex kinetic phenomena.     

Rare-Earth Melilite Solid Solution and Its Phase Relations with Neighboring Phases

Rare-earth (R) melilite M(R) and its solid solution M'(R) are investigated. Starting with compositions of R₂Si₃O₃N₄ and R₂Si₂AlO₄N₃, the formation conditions for M(R), M'(R), and their neighboring phases have been delineated, and their lattice parameters and stoichiometry have been determined. Systematic trends in the solubility of M'(R), the unit-cell dimensions, and the competition with neighboring phases with different rare-earth ions have been identified and rationalized in terms of size effects and acid–base reactions. The compatibility between melilite and neighboring phases, including α'- and β'-SiAlON and polytypoids, is summarized in a series of tentative phase diagrams to elucidate the various phase relations for R-Si-(Al/O)-N systems.     

海底管线管跨段模糊动力可靠性分析

当海底管线受到复杂的环境载荷作用时,有必要对其动力响应和可靠性进行分析。首先,对海流和海浪作用下管跨产生涡激振动的机理进行了分析,建立了管跨在横向涡激振动下的力学模型,并应用振动理论得出振动微分方程,采用Galarkin方法求解出固有频率和动力响应规律。然后根据首超失效准则、疲劳失效准则和混合失效准则这三种模糊失效准则给出相应的模糊动力可靠性计算公式。最后给出具体算例验证了建模的可行性。从管跨的可靠性分析中看出,由海浪和海流引起的涡激振动是破坏管跨的主要因素之一。给出的管跨模型忽略了管跨端部土壤支撑的复杂性和地震载荷的作用,需要进一步做实验来探讨。