太阳能、空气源热泵系统、锅炉供暖联合供热方式的探讨

本文针对唐山市某示范工程中应用的太阳能-空气源热泵-锅炉供热联合使用技术进行阐述,分析了三者联合运行的技术可行性,强调了可再生能源综合利用的必要性。     

Recent progress in reactivity study and synthetic application of N-heterocyclic phosphorus hydrides

N-heterocyclic phosphines (NHPs) have recently emerged as a new group of promising catalysts for metal-free reductions, owing to their unique hydridic reactivity. The excellent hydricity of NHPs, which rivals or even exceeds those of many metal-based hydrides, is the result of hyperconjugative interactions between the lone-pair electrons on N atoms and the adjacent σ^*(P–H) orbital. Compared with the conventional protic reactivity of phosphines, this umpolung P–H reactivity leads to hydridic selectivity in NHP-mediated reductions. This reactivity has therefore found many applications in the catalytic reduction of polar unsaturated bonds and in the hydroboration of pyridines. This review summarizes recent progress in studies of the reactivity and synthetic applications of these phosphorus-based hydrides, with the aim of providing practical information to enable exploitation of their synthetically useful chemistry.     

Al2TiO5-Al2O3复相陶瓷的研究

利用一次烧成和二次烧成两种方法制备了Al2TiO5-Al2O3复相陶瓷,研究了Al2TiO5-Al2O3复相陶瓷的烧结工艺和原料组成对其性能的影响．研究结果表明：Al2TiO5-Al2O3复相陶瓷的组成和烧成工艺对其性能具有重要影响．利用一次烧成制得的Al2TiO5-Al2O3复相陶瓷的综合性能优于二次烧成．一次烧成组成为80wt％氧化铝和20wt％钛酸铝的复相陶瓷,其吸水率仅有0．11％,显气孔率为0．32％,体积密度为3．00g·cm^-3,弯曲强度达152．88MPa,热膨胀系数为7．5×10^-6/℃．     

试论保守力具势的证明

本文借鉴热力学中一种巧妙的证明方法,用直观的物理论证给出了保守力具势的充分性证明,克服了以往在理论力学课程中只有利用复杂的数学工具才能进行充分性证明,学生难以理解的缺点．     

基于区域知识能力的空间知识溢出模型研究

围绕区域知识能力综合评价和知识溢出模型修正,综合考虑区域临近、信息、人员流动等因素,通过引入知识溢出效率系数,构建知识溢出效率系数经验公式;采用区域知识能力差距替代区域知识存量差距;采用区域知识吸收能力替代区域学习能力;并在弗森伯格划分潜在知识溢出和实际知识溢出思想的基础上,对凯尼尔斯模型进行改进,转变其仅测度区域间潜在知识溢出效应的弊端,使修正后模型直接评价区域间实际知识溢出效应值,使模型更具合理性和科学性,更加贴近我国经济运行现实。     

南水北调中线工程对汉水流域民俗体育文化的影响

民俗体育的存在、发展与变迁离不开特定的环境,一旦外部文化生态环境发生变化,必将导致该地域的民俗体育项目产生变迁.南水北调中线工程的实施对汉水流域民俗体育项目的影响大致有以下几点:改变汉水流域民俗体育文化的原真生态、导致库区原有民俗体育文化的消失与变异、移民将会对祖籍地与迁入地民俗体育文化带来双重影响.造成这一局面的原因主要由于民俗体育文化圈具有的天然惰性,而堤坝加高蓄水改变了原有的生态环境,同时外迁移民也导致了原有民俗体育项目的消失与异化.     

基于基尼系数的流域水环境污染物总量分配研究

本文从经济、社会和环境系统整体效益出发将应用在经济学领域的基尼系数应用于总量控制分配当中,分别以人口、土地面积、GDP、环境排污现状和用水量作为控制指标,建立了一种定性与定量相结合描述流域各区域间水污染物排放总量分配的层次结构优化模型,并将该模型应用于某流域,结果表明,本文提出的分配方法,克服了等比例分配的不公平性,同时又兼顾了各分区间的实际差异,是一种较好的分配方法。     

论二元经济思想与中国农村劳动力的转移

刘易斯因其在发展经济学上的突出贡献获得了诺贝尔经济学奖,他提出的二元经济思想也被广泛用于发展中国家的经济分析。我国是世界上最大的发展中国家,因此,如何正确看待刘易斯二元经济思想并分析当代中国经济,有着十分重要的理论和现实意义。本文通过分析刘易斯的二元经济思想,并结合二元经济模型来探讨中国的农村劳动力转移如何避免陷入“刘易斯陷阱”,实现农村劳动力的有效转移。     

中职实训课成绩的可靠性分析——以《零部件测绘》为例

利用数理统计的方法,对若干所学校的实训课程抽测和普测成绩进行了相关性和离散性分析,以判断其普测成绩的真实性,并找出离散性较大的个体.对原有的抽测成绩赋分方式进行改进,以探索更科学的实训课成绩评价方式,全面促进实训课程教学质量的提升.     

Comparing the magnitude and direction of asymmetry during the squat,countermovement and drop jump tests in elite youth female soccer players

ABSTRACT

The aims of the present study were to provide an in-depth comparison of inter-limb asymmetry and determine how consistently asymmetry favours the same limb during different vertical jump tests. Eighteen elite female under-17 soccer players conducted unilateral squat jumps (SJ), countermovement jumps (CMJ) and drop jumps (DJ) on a portable force platform, with jump height, peak force, concentric impulse and peak power as common metrics across tests. For the magnitude of asymmetry, concentric impulse was significantly greater during the SJ test compared to CMJ (p = 0.019) and DJ (p = 0.003). No other significant differences in magnitude were present. For the direction of asymmetry, Kappa coefficients revealed fair to substantial levels of agreement between the SJ and CMJ (Kappa = 0.35 to 0.61) tests, but only slight to fair levels of agreement between the SJ and DJ (Kappa = ?0.26 to 0.18) and CMJ and DJ (Kappa = ?0.13 to 0.26) tests. These results highlight that the mean asymmetry value may be a poor indicator of true variability of between-limb differences in healthy athletes. The direction of asymmetry may provide a useful monitoring tool for practitioners in healthy athletes, when no obvious between-limb deficit exists.