Multi-component electrocatalyst for low-temperature fuel cells synthesized via sonochemical reactions

This review presents recent advances in multi-component electrocatalysts for low-temperature fuel cells (FCs) synthesized via sonochemical reactions. As a feasible approach to develop novel electrocatalysts that can overcome the many problems of the prevailing Pt electrocatalysts, Pt- or Pd-based alloy and core–shell M@Pt nanoparticles (NPs) have been pursued. Synthesizing NPs with desirable properties often turn out to be challenging. Sonochemistry generates extreme conditions via acoustic cavitation, which have been utilized in the syntheses of various Pt and Pd NPs and Pt- and Pd-based alloy NPs. Especially, it has been reported that several M@Pt core–shell NPs can be synthesized by sonochemistry, which is hard to achieve by other methods. The principles of sonochemistry are presented with examples. Also alloy NPs and core–shell NPs synthesized by sonochemistry and those by other methods are compared.     

Synthesis of biantennary LacNAc-linked O-glycan (core 4) and glycopeptide thioester by benzyl protection strategy: rapid zinc reduction of GlcNTCA to GlcNAc by microwave irradiation

A synthetic method for the core 4 O-glycan-linked Ser and Thr was developed. Highly stereoselective 3-O- and 6-O-glycosylation was achieved by using two distinctively protected N-trichloroacetyllactosaminyl fluorides (3 and 12). Microwave-assisted Zn reduction rapidly and efficiently converted N-trichloroacetylglucosamine (GlcNTCA) to N-acetylglucosamine (GlcNAc). In order to demonstrate the usefulness of the protected core 4 O-glycan a segment (Gly³⁴-Gly⁵⁸) of emmprin (extracellular matrix metalloproteinase inducer), a cancer metastasis-related glycoprotein, was synthesized by the solid-phase method, utilizing the pentasaccharyl Thr (2) to introduce an O-glycan in place of the native N-glycan at Asn⁴⁴.     

Inner sequence based invariant subspaces in

A closed subspace is said to be invariant if it is invariant under the Toeplitz operators and . Invariant subspaces of are well-known to be very complicated. So discovering some good examples of invariant subspaces will be beneficial to the general study. This paper studies a type of invariant subspace constructed through a sequence of inner functions. It will be shown that this type of invariant subspace has direct connections with the Jordan operator. Related calculations also give rise to a simple upper bound for , where are zeros of a Blaschke product.

     

利用定压毛细管恒流装置测定岩石相对渗透率曲线

本文就用稳定法测量相对渗透率曲线中,存在的注入流量难以稳定的问题,提出了一种新的稳流方法。即利用定压毛细管恒流装置代替微量泵作以上测定。并就此用理论及实验结果证明其切实可行。     

Poly(styrene-b-ethylene oxide) copolymers as stabilizers for the synthesis of silica–polystyrene core–shell particles

Following previous works [1, 2], silica–polystyrene core–shell particles have been synthesized by dispersion polymerization of styrene in an ethanol/water mixture in the presence of a poly(styrene-b-ethylene oxide) block copolymer as stabilizer. Besides the formation of composite core–shell particles, a large number of free latex particles that do not contain silica were also formed. This number decreases as the size of the silica beads decreases from 300 to 29 nm in diameter, and becomes very low compared to the number of composite particles for the smallest silica beads used. In every case, the composite particles could be easily separated from the free latex particles by centrifugation, providing a material made of regular core–shell composite particles. On the basis of the mechanisms involved in dispersion polymerization, hypotheses were formulated to account for the formation of the silica–polystyrene composite particles. Received: 6 May 1999 Accepted in revised form: 29 June 1999     

类锂等电子系列(1s2p2p)~4 P~e和(1s2s2p)~4 P~0态的能量和精细结构研究

利用改进的马鞍点方法,截断变分方法,并考虑能量的相对论修正和质量极化效应,计算和研究了类理等电子系列的两个四重态（１ｓ２ｐ２ｐ）４Ｐ０和（１ｓ２ｓ２ｐ）４Ｐｅ态的精细结构和平均跃迁波长,并与实验和其它理论计算结果进行了比较。     

供应商企业核心竞争力的模糊综合评价模型

基于企业核心竞争力的内涵及特征,分析了供应商的核心竞争力所包含的层次,提出了一套供应商企业核心竞争力的评价指标体系．由于供应商评价问题中包含大量的不确定和模糊因素,为此将模糊集合论的思想和方法引入供应商评价中,建立了供应商模糊评价模型,并举例进行说明．     

基于组合赋权-TOPSIS法的港口分货类竞争力评价方法

随着港口建设的不断发展,相近区域港口间腹地重合,同质化竞争以及结构性的产能过剩等问题日益显现。为了正确认识港口各货类生产运营的特点,进一步明确港口的功能定位和发展方向,优化资源配置,本文综合考虑港口分货类的生产能力、作业能力和发展潜力,提出了港口分货类竞争力概念及评价指标体系,并采用组合赋权-TOPSIS法对港口分货类竞争力进行评价。最后,通过算例对评价体系和方法进行了验证。结果表明：同一港口对各货类的竞争力不同,各货类的竞争力与港口对该货种的生产能力、作业能力和发展潜力密切相关。评价结果与实际基本吻合,具有客观、有效及实用等优点,可为港口资源整合和港口集团决策提供理论依据。     

上海城市入境旅游及竞争力探析

如何培育和提升上海城市入境旅游竞争力,关系到上海旅游业的可持续发展,作者选取了1995～2004年的相关统计数据,对上海城市入境旅游市场的年际变化、空间格局、消费特征等进行分析,探讨了入境旅游的竞争力,认为优越的区位条件、良好的国际声誉、独特的文化氛围、舒适的旅游环境等,将是推动上海入境旅游快速发展的动力之所在。     

中国战略性新兴产业国际竞争力评价

以"新钻石模型"为基础,从产业环境、产业支撑和产业创新等3个维度构建战略性新兴产业国际竞争力评价指标体系.运用2005~2014年的面板数据对战略性新兴产业进行因子分析.评价结果显示,电子及通信设备制造业与医药制造业国际竞争力明显高于计算机及办公设备制造业与医疗仪器设备及仪器仪表制造业.航空航天器及设备制造业国际竞争力有很大提升潜力.电子及通信设备制造业创新能力表现突出,但战略性新兴产业整体创新能力较低.