页岩纳米级孔隙结构特征及热成熟演化

以中、上扬子地区下古生界海相和中生界陆相页岩为研究对象,运用氩离子抛光-场发射扫描电子显微镜技术和氮气吸附实验测试技术对页岩储层的纳米级孔隙发育特征及热成熟演化进行探讨。结果表明:页岩主要发育了有机质孔、粒间孔、粒内孔和微裂缝等4种孔隙类型;TOC和Ro是控制页岩纳米级孔隙发育的主要因素;对于高演化页岩,不同干酪根类型的有机质孔隙发育程度的大小次序为Ⅰ型Ⅱ型Ⅲ型;石英和黏土矿物通过控制TOC的变化对纳米级孔隙发育和分布产生间接影响;页岩热成熟度演化影响页岩孔径分布和微孔、中孔和大孔相对含量的变化,在高—过成熟阶段,与有机质有关的微孔、中孔呈不断增加的趋势,在极高成熟度阶段,页岩大孔转变为中孔和微孔,有机质孔隙变小,纳米级孔隙体积呈现出先增加后减小的趋势;页岩中干酪根、可溶沥青热裂解生气作用和甲烷化作用可能是页岩有机质纳米级孔隙形成的主要原因。     

Alloying and dealloying of CuPt bimetallic nanocrystals

Bimetallic CuPt nanocrystals with size ranging from 3 to 30 nm were synthesized in the presence of either hexadecylamine or poly(vinylpyrrolidone) as a capping agent.Different growth stages of CuPt nanoparticles prepared with hexadecylamine have been investigated and a non-classic mechanism governing the formation of the metal alloy was revealed.It was found that the precursor molecules aggregate into amorphous spheres at a very early stage,followed by surface multiple nucleation,formation and combination of crystalline islands to produce a core-shell structure with surface-to-core extension of the crystallization to achieve single crystals.CuPt nanocrystals synthesized with poly(vinylpyrrolidone) grew via the classic route.Dealloying treatment was applied on these CuPt nanoalloys to selectively remove Cu.Large particles(30 nm) with Cu-rich cores exhibited hollow structures after dealloying while 3 nm particles remained solid,demonstrating that particle size and composition have a great influence on the final morphology of dealloyed particles.     

通过合金和去合金过程制备一种海绵状的纳米多孔铂以及对氧的电催化还原

采用一种简易的方法制备了海绵状的球形纳米多孔铂,首先是用循环伏安法在玻碳电极上电沉积得到铂铜合金,然后在浓硝酸中刻蚀合金去掉铜．用到场发射扫描电镜、X射线光电子能谱、X射线衍射和循环伏安法对其进行了表征．也对制备此种铂催化剂的条件进行了优化．此种铂修饰电极对氧的还原表现出很高的电催化活性,其氧的还原峰电流是相应纳米铂修饰电极的四倍．这种制备海绵状纳米多孔结构的方法以及所得到得到铂修饰电极可能在燃料电池和生物传感器等领域有着很大的应用前景．     

Influences of ultrasonic irradiation on the morphology and structure of nanoporous Co nanoparticles during chemical dealloying

The Co-61.8 wt% Al nanoparticles of 45 nm were prepared by hydrogen plasma-metal reaction (HPMR) method. The nanoparticles display core shell structure with Al13Co4 and CoAl core and aluminum oxide shell (about 2 nm). Under ultrasonic irradiation, nanoporous fcc-Co nanoparticles were produced successfully by chemically dealloying the Co-Al nanoparticles at room temperature, whereas, without ultrasonic irradiation CoAl phase could hardly react with sodium hydroxide solution. At 323 K the Co-Al nanoparticles could be dealloyed to fcc-Co and hcp-Co phases even without ultrasonic irradiation. The surface area of the dealloyed nanoparticles under ultrasonic irradiation was larger than that of the dealloyed sample without ultrasonic irradiation at the same temperature. It is believed that the microjet and shock-wave induced by ultrasonic irradiation give rise to particles size reduction, interparticle collision and surface cleaning, and accelerate the dealloying process and the phase transformation.     

微纳表面热功能结构及其脱合金原位成形方法

表面热功能结构广泛应用于热能转换与传递的各个环节,是机械与工程热物理交叉领域重要的研究方向。从加工学的角度综述了表面热功能结构的微纳发展现状和趋势。分析表明,对表面微纳结构的规则性、水热稳定性、固液界面特性的有效控制是提升传热性能的关键,也是表面微纳热功能结构加工领域的挑战。介绍了基于脱合金技术的表面纳米多孔金属结构原位成形方法及其在强化沸腾传热领域的应用现状和前景。     

基因组的进化与内含子中的基因的进化

论述了基因组整体进化过程中内含子所含的基因的进化．分析了内含子的起源方式与内含子中的基因种类的关系,并结合基因组在大小、组成等方面进化过程中内含子的演化趋势,探讨了内含子中的基因,特别是核仁小分子ＲＮＡ基因的进化规律．同时,对于内含子中的基因的进化,提出了一些可能的途径．     

进化速率的研究与进化理论的统一

不同进化学说之间的争论大多与进化速率问题有关。在生物组织的不同层次上的进化速率研究得出了截然不同的结论,并导致相关的进化学说之间的互不相容。恒速的、匀速的、随机的分子进化(中性说)与非匀速的、适应的表型进化相矛盾;在自然选择作用下的渐进的适应进化(综合论)难以解释古生物记录所揭示的停滞与跳跃相间的、有时是爆发式的大进化现象。这些矛盾大多源于对进化速率的度量的不同,各层次的进化速率的含义也不同,各学说之间缺乏统一语言。生命史的重大进化事件发生的时间表显示出明显的非匀速特征：绝大多数重大进化事件发生在生命史的早期(40至35亿年前)和晚期(7亿年以近)。前生命的化学进化、生命起源、细胞生命的基本结构和代谢途径、以及生物进化和地球生物圈赖以建立的基础早在生命史开始后的几亿年内就已完成或确立了;复杂的高级生命和生物多样性的产生与重要的结构的进化革新发生在生命史末端的数亿年间。本文将宏进化的这种非匀速现象解释为地球生命与地球环境协进化的结果。当前进化理论的分裂是由生命科学及相关科学的发展所引起的,进化理论也必将随着各学科领域研究的深入而走向统一,走向新的综合。     

Evolution of homeothermy in mammals

We propose that mammalian homeothermy was was acquired in two steps. The first step enabled mammals to invade a nocturnal niche without an increase in resting metabolic rate. The second step enabled them to invade a diurnal niche and involved the acquisition of higher body temperatures and metabolic rates.     

论拖拉机造型演变因素

从科学技术的发展、人们生理感受的失调与平衡、人们的心理、经济性和社会的变化等五个方面论述了拖拉机造型的演变因素，反映了不同时期拖拉机工业的发展水平和人们的审美观念，为拖拉机造型设计提供了科学的依据。     

Evolution of ageing

An evolutionary view of ageing suggests that mortality may be due to an energy-saving strategy of reduced error regulation in somatic cells. This supports Orgel's 'error catastrophe' hypothesis and offers a new basis for the study of normal and abnormal ageing syndromes and of apparently immortal transformed cell lines.     

中国企业可持续发展研究:态势演进与主题演化

通过对CNKI核心数据库收录的1995～2018年的1 032篇企业可持续发展相关文献进行分析,旨在掌握国内该领域研究的态势演进与主题演化,为国内的相关研究提供参考和素材,推动中国企业和经济更好的可持续发展。采用文献计量的方法,基于CiteSpace软件从年度发文、作者和研究机构、关键词、聚类与时序图等方面进行可视化分析并绘制知识图谱。分析结果表明:研究态势整体上分布比较零散,并没有形成核心的研究群体和研究机构,也没有形成统一的研究认知和体系;研究主题总体上呈现从基础理论到发展战略再到创新管理的转变脉络。     

Glass-forming ability,microhardness, corrosion resistance,and dealloying treatment of Mg_(60-x)Cu_(40)Nd_x alloy ribbons

The influence of Nd addition on the glass-forming ability(GFA), microhardness, and corrosion resistance of Mg_(60-x)Cu_(40)Nd_x(x = 5, 10, 15, 20, and 25, at%) alloys were investigated by differential scanning calorimetry, Vickers-type hardness tests, and electrochemical methods. The results suggest that the GFA and microhardness of the amorphous alloys increase until the Nd content reaches 20at%. The corrosion potential and corrosion current density obtained from the Tafel curves indicate that the Mg_(35)Cu_(40)Nd_(25) ternary alloy exhibits the best corrosion resistance among the investigated alloys. Notably, nanoporous copper(NPC) was synthesized through a single-step dealloying of Mg_(60-x)Cu_(40)Nd_x(x = 5, 10, 15, 20, and 25) ternary alloys in 0.04 mol·L~(-1) H_2SO_4 solution under free corrosion conditions. The influence of dealloying process parameters, such as dealloying time and temperature, on the microstructure of the ribbons was also studied using the surface diffusivity theory. The formation mechanism of dealloyed samples with a multilayered structure was also discussed.     

无线传感器网络中的分布式遗传算法

受地形、气候、电磁干扰、节点分布等多重因素的影响,传统无线传感器不能很好的适应现复杂多变的测控环境,特别是较大规模的无线传感网络的健壮性和协同能力受到了复杂环境的挑战。分布式遗传算法在成熟的遗传算法基础上扩展了分布式协同机制,在可接受的复杂度范围内,提升了算法的健壮性。在WSN中引入分布式遗传算法,显著增强了网络的分布式并行特性,提升了节点协同能力和网络自组织的健壮性。通过发光二极管灯亮频率实验、同构无线网络和异构无线网络下稳定性实验和动态自适应环境变化实验,证明了分布式遗传算法能够很好地解决WSN中节点的扩展限制问题,并且提升了WSN的多变环境适应能力。     

演化问题的格林函数

数学物理方程中所要解决的一个主要问题是已知源，求其所产生的场．其中一个很重要的方法就是运用格林函数和叠加原理把源分解成很多点源，再把每个点源产生的场进行叠加．文章分析了数学物理问题演化问题中格林函数的性质以及各类格林函数之间的关系，并讨论了混合问题的情况．