298 research outputs found

    Preparation and Characterization of FeOx/Rh(111) and CoOx/Rh(111) Model Catalysts

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    多相催化剂的表面是催化反应的活性位点,表面组成、粒径和结构决定了催化剂的催化性能。真实催化剂结构复杂并且表面不均一,阻碍了表面灵敏的表征手段的运用,无法精准确定其构效关系。构建成分简单结构单一的模型催化剂表面可简化传统催化剂的复杂性,用以研究气体吸脱附、催化活性和选择性、构效关系等催化问题。本论文在超高真空环境中制备模型表面FeOx/Rh(111)和CoOx/Rh(111),应用表面科学仪器X-射线光电子能谱(XPS)和低能离子散射谱(LEIS)对模型表面进行表征,取得了如下结果: 一、在高温(1023K),低氧压(1x10-7TorrO2)条件下,制备了一个单层FeO膜,继续蒸着则生长三维...The chemical reactions occur at the surface of the catalysts, whose size, structure and composition determine the catalytic properties. However, the real catalysts are usually complex and electrically insulating, inhibiting the application of, for example, EELS, STM and AFM. Information on the surface state of a catalyst cannot be obtained. Thus, one has to resort to models in order to do surface ...学位:理学硕士院系专业:化学化工学院_物理化学学号:2052011115163

    The Relation Between Coping Styles and Lottery Addiction for Chinese Lottery Buyers

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    目的:本研究探讨我国电脑型彩票购买者的应对方式与其成瘾倾向的关系。方法:全国6省兼顾彩票销售情况选取25个城市,并抽取各市投注站及购彩者,完成自编背景信息、彩票成瘾倾向量表(LAS)和简易应对方式问卷调查,对样本进行筛选和分组,最终确定高/中/低成瘾倾向组共计452名购彩者。结果:高/中/低成瘾倾向组间消极应对总分(F(2,449)=20.46,P<0.001)和各题目上普遍呈现出高成瘾倾向组采用更多的消极应对方式;回归分析发现:消极应对方式得分越高其功能损害和情感依赖维度得分越高;"培养业余爱好,积极参加文体活动"作为积极应对方式对功能损害维度具有一定的保护作用。结论:消极应对方式可以预测购彩者的成瘾倾向

    Joint decoding algorithm of LDPC codes

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    在加性高斯白噪声(AddITIVE WHITE gAuSSIAn nOISE,AWgn)信道中设计一种低密度奇偶校验(lOW-dEnSITy PArITy-CHECk,ldPC)码的最大似然译码算法是一项具有挑战性的工作。麦克斯韦译码算法在二进制擦除信道下具有优越的性能,但把这种算法移植到其他信道却非常困难。引入了信道转换的思想实现两个不同信道之间的转换,并利用该方法成功地将麦克斯韦算法应用到AWgn信道中,提出了一种将信度传播算法和麦克斯韦算法有机结合的联合译码算法,即信度传播-麦克斯韦译码算法,该算法可缩小与最大似然译码算法之间的性能差距。仿真表明,该译码算法可打破大多数小陷阱集从而获得比信度传播译码算法更低的误帧率,并且可消除大多数信度传播译码后出现的小错误。Designing a realizable maximum likelihood(ML) decoder for low-density parity-check(LDPC) codes is always a challenging work over an additive white Gaussian noise(AWGN) channel.Although Maxwell decoder is well known for its excellent performance over the binary erasure channel(BEC),it seems that generalizing this algorithm for other channels is difficult.This paper introduces an idea called channel transformation which could realize the conversation between two different channels.A Maxwell decoder is applied to an AWGN channel.In terms of this method,and a joint decoder-BP-Maxwell(BM) decoder is proposed which combines a belief propagation(BP) decoder and a Maxwell decoder,to reduce the gap to the ML decoder in performance.Simulation results show that the BM decoding algorithm could break most small trapping sets to accomplish a lower frame error rate(FER).Moreover it also could eliminate most of the small-scale errors compared with a BP decoder.国家自然科学基金(60972053)资助课

    海南岛西海岸红树林软体动物多样性

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    为了掌握海南岛西海岸红树林软体动物多样性状况,本文于2015–2016年对海南岛西海岸6个主要红树林分布区软体动物的种类组成、物种多样性和群落结构的时空变化进行了研究。共采集到软体动物57科201种,主要优势种有珠带拟蟹守螺(Cerithidea cingulata)、绯拟沼螺(Assiminea latericea)、圆胖樱蛤(Pinguitellina cycladiformis)和斜肋齿蜷(Sermyla riqueti)等。年平均密度与平均生物量分别为324.13 ind./m~2和142.88 gm~2,物种数、密度和生物量均高于北部湾沿岸的其他红树林。海南岛西海岸各红树林软体动物的密度和生物量均未呈现明显的季节变化,软体动物密度存在空间上的显著差异。聚类分析结果显示,在盐度、土壤结构和红树林群落存在差异的不同红树林,软体动物种类组成相似度低。多因子AZTI海洋生物指数(M-AMBI)结果表明海南岛西海岸红树林软体动物群落未受明显扰动,生态环境质量介于一般和优良之间,但仍受到人类活动与外来植物入侵威胁,因其在候鸟迁徙中的重要作用,亟需加强管理与保护。国家自然科学基金(31670490;31600436

    Ellobiid molluscs of Chinese mangrove habitats

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    耳螺是一类特殊的原始有肺类软体动物,主要分布于热带、亚热带海陆交汇区的高潮带和潮上带。耳螺在红树林区广泛分布,且资源非常丰富,全世界已知的约240种耳螺中,至少有一半以上的种类在红树林区被记录。本文总结了耳螺与红树林的关系以及中国嗜盐耳螺的种类,综述了红树林区耳螺的种类组成、分布、生态功能、行为等的研究进展,报道了中国大陆红树林耳螺种类组成和分布特点,中国共有嗜盐耳螺11属59种(附录I),其中9属42种分布于红树林区,包括21个新记录种。提出了耳螺对环境变迁和人为干扰十分敏感,可作为海堤建设对红树林影响的重要指示物种,是未来的重要研究方向之一。The family Ellobiidae is a special group of primitive pulmonate molluscs that live in tropical and subtropical areas,mainly in high tidal and supratidal zones of coastal areas.Ellobiids occur widely and abundantly in mangrove areas.of the 240 species known globally,over half of them have been recorded in mangrove habitats.In this paper,we summarize species of halophilic ellobiids in China and the relationship between ellobiids and mangroves.We discuss the achievements of mangrove ellobiids studies in the fields of species composition,distribution,ecological function and behavior.We also report a complete list of the el-lobiid species from mangroves and their distribution within mainland China,including 21 newly recorded species.It is implied that this group is very sensitive to environmental changes and human disturbances,therefore it can be used as a bio-indicator for sea dike construction,which is an important proposed research topic in future.国家自然科学基金(40876046

    论经济转型对我国自考生源结构的影响

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    教育作为上层建筑,经济的发展变化对其产生决定性影响。我国经济体制转型对自考生源数量的不断增加、年龄构成的年轻化、职业构成的多元化和学历层次的上升及多元化有重要的影响。在当前自学考试发展环境日趋复杂的情况下,认清经济发展变化与自考的相互关系,对今后自学考试的改革和发展有着重要的理论和实践意义。福建省自学考试办公室“十五”规划课题“自学考试与经济发展的关系研究”的成果之

    消费者认知风险概念模型的研究综述

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    电子商务的出现和蓬勃发展把消费行为学中的认知风险这个概念的研究深入化的工作提到了日程上。文章回顾了消费者行为学领域中有关认知风险测量的文献,把现有的各测量理论分为不确定性后果理论、多维度理论和影响因素理论三类,阐述了各类理论的建立和发展变化,以及各模型的特点及理论贡献,并对认知风险测量的现状和未来发展趋势进行了探讨

    Talent recommendation system in big data era

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    1人才推荐系统的应用背
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