117 research outputs found

    The Purchasing Power Parity Theory and Its Empirical Testing in China

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    中文摘要 本文先介绍一些汇率的基本常识,接着介绍汇率的决定理论,在比较了传统汇率决定理论的基础上,介绍了汇率决定理论的最新进展,主要是非线性系统方面的进展。 本文着重要研究的是传统汇率决定理论中的购买力平价理论,所以接下来,文章对购买力平价理论进行了进一步认识,在经典理论的基础上进行扩展,如:在理论上考虑了交易成本和进口关税对购买力平价理论的影响;引入工资指数的工资成本汇率理论;将两国之间的购买力平价模型扩展到多国;将静态的模型发展到动态的模型。 文章接下来对购买力平价这一理论的检验方法的六个不同阶段的历史演变过程进行了回顾。第一阶段是关于PPP的早期经验文献;第二阶段是检验真实汇率随机...Abstract Before 1973 China’s exchange rate system was pegged on the US dollar. However, with the collapse of the Briton Forest System in 1971 and the first petroleum crisis in 1973, the major western countries started to adopt a floating exchange rate system in March 1973. China’s official exchange rate system followed suit. Beginning in late 1984 China adopted a managed floating exchange rate sy...学位:经济学博士院系专业:经济学院计划统计系_统计学学号:B20041000

    多元化经营与范围经济

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    本文在对比国外及国内的同类公司的基础上,剖析了多元化经营的各类模式,指出能否达到范围经济是多元化经营成败的关键,并提出正确选择多元化经营模式的战略思路

    福建省企业技术创新能力评价

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    技术创新能力的科学评价有助于企业对自身技术创新能力的动态跟踪和培育。本文先对企业技术创新能力作了界定,接着通过对目前几种常用的评价方法之间的比较,选用了客观性强的密切值法,对福建省各地区的大中型工业企业的技术创新能力作了评价

    超声速壁面凹腔自激振荡的数值研究

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    数值研究了冷态及化学反应流动情况下超燃冲压发动机中壁面二维凹腔火焰稳定器流场的非定常特性。模拟了凹腔剪切层的演化发展过程,并得到凹腔诱导的超声速流场振荡的频谱分布,计算凹腔上游有燃料射流和有化学反应的工况并对比分析其影响。并结合计算结果阐述了超声速凹腔流动的周期特性和稳焰作用机理。无射流情况下得到的振荡频率和Rossiter 预测结果一致,添加射流使剪切层升高且厚度增加,涡合并过程更充分,同时压力振荡幅度增大,频率减小。有化学反应情况下,释热的作用使剪切层进一步被托高,厚度进一步增大

    电化学联用技术研究微生物的胞外电子传递机制

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    胞外电子传递(EET)是指氧化还原反应所产生的电子在微生物细胞内和细胞外的电子受体/电子供体之间互相转移的过程,这一过程伴随着能量和物质的转化。阐明EET机制是提高微生物能量和物质转化效率的基础,为元素的生物地球化学循环、金属防腐以及生物电化学系统的应用等提供理论支撑。电化学技术作为研究电极/溶液界面电子转移的简便、有效方法,在研究微生物的直接电子传递和间接电子传递机制中发挥了重要的作用,也促进了EET机制的研究从宏观层面到微观层面不断深入。本文综述了研究微生物EET机制所涉及的电化学联用技术(包括微电极、扫描电化学显微镜、电化学联用光学显微镜和光谱电化学等);详细介绍了这些电化学联用技术的功能和优势;重点阐述了这些电化学联用技术如何推动着EET机制的研究,从宏观的生物膜层面到微观的单个微生物细胞、蛋白和分子层面不断深入;展望了新的电化学联用技术在EET研究领域的应用前景。国家重点研发计划项目项目(No.2017YFA0206500);;国家自然科学基金项目(No.21777155,21773198,U1705253,21621091)资助~

    锂氧电池双功能还原石墨烯-LaFeO复合纳米催化剂的制备及性能

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    制备具有氧还原(ORR)与氧释放(OER)双功能催化活性的特殊孔道结构电催化剂是锂氧电池研究的挑战之一。本文以氧化石墨烯、硝酸铁、硝酸镧、柠檬酸为原料,结合溶胶凝胶和水热合成方法,制备出还原氧化石墨烯(RGO)与铁酸镧(LaFeO)复合的双功能催化剂(RGO-LaFeO)。X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和Raman光谱分析结果确认该复合催化剂由纯相钙钛矿结构LaFeO和还原氧化石墨烯组成,扫描电子显微镜(SEM)观察到LaFeO纳米颗粒均匀地负载在RGO片层表面。锂氧电池测试结果指出,相对于LaFeO纳米粒子(NP-LaFeO),RGO-LaFeO催化剂具有更好的ORR和OER催化活性,归因于RGO特殊的三维导电多孔结构与LaFeO纳米粒子的协同催化作用。以RGO-LaFeO作为阴极催化剂的锂氧电池在限1000 m Ah?g比容量、100 m A?g电流密度条件下,可实现36周稳定的充放电循环,展示出良好的应用前景。国家自然科学基金(21621091);国家重点研发计划(2016YFB0100202)资助项目~~

    Reduced Graphene Oxide-LaFeO3 Composite Nanomaterials as Bifunctional Catalyst for Rechargeable Lithium-Oxygen Batteries

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    制备具有氧还原(ORR)与氧释放(OER)双功能催化活性的特殊孔道结构电催化剂是锂氧电池研究的挑战之一。本文以氧化石墨烯、硝酸铁、硝酸镧、柠檬酸; 为原料,结合溶胶凝胶和水热合成方法,制备出还原氧化石墨烯(RGO)与铁酸镧(LaFeO_3)复合的双功能催化剂(RGO-LaFeO_3)。X射线; 衍射(XRD)、傅里叶变换红外(FTIR)光谱和Raman光谱分析结果确认该复合催化剂由纯相钙钛矿结构LaFe03和还原氧化石墨烯组成,扫描电子; 显微镜(SEM)观察到LaFe03纳米颗粒均匀地负载在RGO片层表面。锂氧电池测试结果指出,相对于LaFe03纳米粒子(NP-LaFeO_3),; RGO-LaFeO_3催化剂具有更好的ORR和OER催化活性,归因于RGO特殊的三维导电多孔结构与LaFeO_3纳米粒子的协同催化作用。以RGO; -LaFeO_3作为阴极催化剂的锂氧电池在限1000 mAh·g~(-1)比容量、100; mA·g~(-1)电流密度条件下,可实现36周稳定的充放电循环,展示出良好的应用前景。Development of electrocatalysts is one of the challenges in the development of the lithium-oxygen battery, especially the synthesis of catalysts with special pore structures and excellent bifunctional catalytic performance for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). In this article, a reduced graphene oxide-LaFeO3 (RGO-LaFeO3) nanocomposite electrocatalyst was synthesized by combining sol-gel and hydrothermal methods and using graphene oxide, lanthanum nitrate, ferric nitrate, and citric acid as raw materials. The prepared samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy. The results confirmed that the RGO-LaFeO3 was composed of pure phase LaFeO3 with a perovskite structure and RGO and that the LaFeO3 nanoparticles were loaded uniformly on the RGO layer surface. In comparison with a LaFeO3 nanoparticle (NP-LaFeO3) catalyst, RGO-LaFeO3 exhibited superior activity for both the ORR and the OER when it served as the cathode of a lithium-oxygen battery. The higher catalytic activity of the RGO-LaFeO3 is attributed to the synergistic effect of the special three-dimensional electronic conductive structure of RGO and the intrinsic catalytic property of LaFeO3. It was shown that the lithium-oxygen battery with the RGO-LaFeO3 cathode can be cycled stably up to 36 reversible cycles under conditions of a limit discharge depth of 1000 mAh.g(-1) and a 100 mAg(-1) current density for charge-discharge. The study illustrates that the RGO-LaFeO3 bifunctional electrocatalyst is a promising candidate for the cathode in lithium-oxygen batteries.National Natural Science Foundation of China [21621091]; National Key; Research and Development Program of China [2016YFB0100202

    扫描电化学显微镜用于研究生物膜微环境的电子传递

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    生物电化学系统(BESs)的核心是生物膜在电极/溶液界面的电子传递反应,研究生物膜微区环境中的电子传递有助于阐明微生物的胞外电子传递(EET)机制,从而有针对性地提高BESs中的电子转移效率。微生物的EET机制包括直接电子传递和间接电子传递,由于生物膜组成复杂,含有多种分泌物、胞外聚合物等,常规电化学方法只能从生物膜宏观层面研究EET机制,无法有效区分这两种电子传递途径的贡献。本文采用电化学循环伏安方法研究了电子穿梭体二茂铁甲醇(FcMeOH)与希瓦氏菌(Shewanella)相互作用的界面过程;基于扫描电化学显微技术构建了穿透模式,通过微电极介导FcMeOH与Shewanella反应,收集仅来自间接电子传递途径产生的电流,同时测定了Shewanella在电极/溶液界面的氧化还原性质和空间分布。本论文将电化学扫描探针显微技术应用于EET的研究,从物理化学角度揭示微生物在代谢过程中与外界的电子传输机制。国家重点研发计划项目(2017YFA0206500);;国家自然科学基金(21777155,21773198,U1705253,21621091)资助~

    Precisely controlled resorcinol-formaldehyde resin coating for fabricating core-shell, hollow, and yolk-shell carbon nanostructures

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    MOST of China [2011CB932403, 2009CB930703]; NSFC [21131005, 21021061, 20925103, 20923004]; Fok Ying Tung Education Foundation [121011]This work provides a facile one-step sol-gel route to synthesize high-quality resorcinol-formaldehyde (RF) resin coated nanocomposites that can be further used to fabricate desired carbon nanostructures. Colloidal particles with different morphologies and sizes can be coated with high-quality RF resin shells by the proposed cationic surfactant assisted RF resin coating strategy. The as-synthesized RF resin coated nanocomposites are ideal candidates for selective synthesis of core-shell, hollow, and yolk-shell carbon nanostructures. Based on the carboxylic functional RF resin coating, graphitic carbon nanostructures can also be synthesized by employing the graphitization catalyst. The as-synthesized carbon nanostructures show the advantageous performances in several applications. Hollow carbon spheres are potential electrode materials for lithium-sulfur batteries. Hollow graphitic spheres are promising catalyst supports for oxygen reduction reaction. And yolk-shell structured Au@HCS nanoreactors with ultrathin shells exhibit high catalytic activity and recyclability in confined catalysis

    Kinases Mst1 and Mst2 positively regulate phagocytic induction of reactive oxygen species and bactericidal activity

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    该研究成果揭示了吞噬性细胞内Hippo信号通路关键激酶Mst1和Mst2通过活化Rac家族蛋白来调节线粒体向吞噬小泡募集并释放ROS来清除病原体,这个生物学过程在天然免疫和宿主防御中发挥着重要作用。该成果解析了人的Mst1基因缺失或Rac2基因突变引发免疫缺陷综合症的致病机理,为研究人类感染性疾病提供了全新的视角。 该论文的主要工作由2012级博士生耿晶、2013级博士生孙秀峰以及王平、张世浩和王晓珍等学生共同承担,并与厦门市第一医院、台湾长庚大学、中国科学技术大学等单位合作完成,通讯作者为周大旺教授和陈兰芬教授。该研究工作获得了“青年千人计划”、国家自然科学基金委和科技部的资助。Mitochondria need to be juxtaposed to phagosomes for the synergistic production of ample reactive oxygen species (ROS) in phagocytes to kill pathogens. However, how phagosomes transmit signals to recruit mitochondria has remained unclear. Here we found that the kinases Mst1 and Mst2 functioned to control ROS production by regulating mitochondrial trafficking and mitochondrion-phagosome juxtaposition. Mst1 and Mst2 activated the GTPase Rac to promote Toll-like receptor (TLR)-triggered assembly of the TRAF6-ECSIT complex that is required for the recruitment of mitochondria to phagosomes. Inactive forms of Rac, including the human Rac2D57N mutant, disrupted the TRAF6-ECSIT complex by sequestering TRAF6 and substantially diminished ROS production and enhanced susceptibility to bacterial infection. Our findings demonstrate that the TLR-Mst1-Mst2-Rac signaling axis is critical for effective phagosome-mitochondrion function and bactericidal activity.Supported by the National Basic Research Program (973) of China (2015CB910502 to L.C.), China's 1000 Young Talents Program (D.Z. and L.C.), the 111 Projects (B12001 and B06016), the Fundamental Research Funds for the Central Universities of China-Xiamen University (CXB2014004 to J.Z.; 20720140551 to L.C.; and 2013121034 and 20720140537 to D.Z.), the National Natural Science Foundation of China (31270918, 81222030 and J1310027 to D.Z.; 81372617, 81422018 and U1405225 to L.C.; 81472229 to L.H.; and 81302529 to X.L.), the Natural Science Foundation of Fujian (2013J06011 to D.Z. and 2014D007 to X.L.), the US National Institutes of Health (RO1 CA136567 for J.A.) and institutional funds from Massachusetts General Hospital (for J.A.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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