An electrochemically assisted mechanically controllable break junction approach for single molecule junction conductance measurements

We report an electrochemically assisted mechanically controllable break junction (EC-MCBJ) approach to investigating single molecule conductance. Electrode pairs connected with a gold nanobridge were fabricated by electrochemical deposition and then mounted on a homebuilt MCBJ platform. A large number of Au- molecule-Au junctions were produced sequentially by repeated breaking and reconnecting of the gold nanobridge. In order to measure their single molecule conductance, statistical conductance histograms were generated for benzene-1,4-dithiol (BDT) and 4,4′-bipyridine (BPY). The values extracted from these histograms were found to be in the same range as values previously reported in the literature. Our method is distinct from the ones used to acquire these previously reported literature values, however, in that it is faster, simpler, more cost-effective, and changing the electrode material is more convenient.      

Synthesis and high electrocatalytic performance of hexagram shaped gold particles having an open surface structure with kinks

Hexagram shaped gold particles and their analogues enclosed by high index facets with kinks have been successfully synthesized by reducing HAuCl₄ with ascorbic acid (AA) in the presence of poly(diallyldimethylammonium chloride) at room temperature. By using electron microscopy, the surfaces of the hexagram shaped Au particle were found to be {541} planes, which contain high-density steps and kinks. In addition, it was found that hexagonal shield-like and other kind of particles present in the product were analogues of the hexagram shaped Au particles structure, in that they had the same surface structure. In order to confirm the surface structure of all the prepared particles, surface structure sensitive underpotential deposition of Pb was carried out, and the cyclic voltammetric profile was in accordance with the proposed {541} surface. Finally, structure-property relationships of the Au hexagrams were experimentally analyzed by employing the electrocatalytic oxidation of AA as a probe reaction. The electrocatalytic reactions of gold cubes with low-index {100} facets and gold trioctahedra with {221} facets were studied as references. The experimental results showed that the hexagram shaped Au particles and their analogues with exposed {541} facets have the highest catalytic activity among the three kinds of gold particles, owing to the high density of kink atoms. This study should motivate us to further explore methods for the preparation of other well-defined polyhedral metal nanocrystals enclosed by high index surfaces.      

鄂尔多斯盆地大牛地气田山1段储层与沉积微相的关系

鄂尔多斯盆地大牛地气田二叠系山1段主要发育河床滞留、分流河道、河道砂坝、心滩、天然堤、决口扇、河间洼地和河漫沼泽8种沉积微相,储层主要发育在分流河道和心滩沉积微相。储层综合特征和沉积微相研究表明,影响气层产能的最敏感的参数是储层中值半径。储层喉道中值半径的大小、分布和连通性以及碎屑颗粒粒度和石英含量等地质特征决定于沉积微相展布特征。通过对区内山1段储层沉积微相和中值半径等参数的对比分析发现,天然气主要赋存于分流河道沉积微相,平面上分流河道沉积微相分布在研究区西南部河流交汇处。     

沉积背景控制下的储层预测方法——以大牛地气田TGM地区的应用为例

TGM地区是大牛地气田天然气产能建设的重要区块,但该区天然气储层层系多、厚度薄,横向非均质性强,加之地震资料分辨率低,导致精确储层预测困难。为减小TGM地区储层预测的多解性,最大限度地提高储层预测的精度,在深入分析TGM地区储层发育地质特征的基础上,提出了沉积背景控制下的储层预测思路：将TGM地区储层预测作为一个系统工程,首先从储层的沉积背景出发圈定储层发育有利区块;然后针对有利区的地质情况和地震资料特征,选取针对性的储层预测方法和技术,对储层进行精细刻画。针对TGM地区太原组、山西组和下石盒子组储层预测的结果与钻井的符合率在90%以上。     

四川盆地中国石化探区须家河组致密砂岩气勘探开发进展与攻关方向

四川盆地须家河组致密砂岩气的勘探取得了丰硕的成果,但是气藏整体表现为"储层致密、大面积含气、局部富集"的特点,开发生产中普遍呈现出储量丰度低、普遍产水和裂缝控产等特征,储量动用难度大.近年来,以有效建产和高效勘探为主要目标,应用地质-工程一体化的思路,开展了四川盆地中国石化探区须家河组的新一轮勘探开发攻关研究,在基础地...     

四川盆地川西坳陷新场须家河组二段致密砂岩储层裂缝发育特征及主控因素

四川盆地川西坳陷新场须家河组二段（须二段）砂岩储层具有埋藏深、致密的特点,天然裂缝的发育对储层至关重要。通过地表露头调查、岩心观察、常规测井和成像测井解释等手段分析新场须二段气藏天然裂缝的发育特征,认为须二段储层裂缝可划分为网状缝、立缝、高角度缝、斜缝、低角度缝和平缝,以低角度缝和斜缝为主;裂缝主要发育在新场构造带中东部地区的须二段中、上亚段,走向主要为NE-SW向、NW-SE向和EW向,以EW向晚期构造裂缝最发育,并与区内现今最大主应力方向一致。基于裂缝参数与产能参数交会分析,明确不同类型裂缝对产能的贡献度,认为新场须二段气藏有效裂缝为倾角大于30°的构造裂缝（立缝、高角度缝和斜缝）。区内有效裂缝的发育受控于断裂、构造变形、岩石粒度、岩石成分和岩层厚度等多方面因素,但距离晚期SN向逆断层的距离是须二段天然构造裂缝发育的关键控制因素,其次是构造变形及构造组合样式。距离晚期SN向逆断层上盘200 m范围内的褶皱发育区可作为新场地区今后裂缝预测、评价及天然气开发的重点区域。     

Mechanically Stable Dynamic Urea Bond-Based Crosslinked Polymer Blend with Tunable Self-Healable and Physical Properties

Polymer networks crosslinked by reversible noncovalent crosslinks have been applied in self-healing and recyclable sustainable materials but result in limited mechanical strength. Herein, a crosslinked polymer blend that is based on a urethane–arcylate system with a combination of reversibly noncovalent intrachain and interchain hydrogen bonds and dynamically covalent urea bonds is developed through facile in situ photo-induced copolymerization. An essential step is the introduction of a flexibly dynamic crosslinker bearing robustly hindered urea bonds and urethane–urea structures into the network, which endows the dynamic network with a synergy of mechanical robustness and desirable self-healing ability. The dynamic networks exhibit rapid self-healing at mild conditions (70 °C, 30 min), extreme toughness (≈34.76 MJ m⁻³), high tensile strength (≈7.78 MPa), superior stretchability (≈932%), long-term stability, recyclability, and weldability. More importantly, the mechanical and self-healing properties of the resultant materials can be fine-tuned by adjusting the dynamic crosslinker content. These superior properties are attributed to the dynamic reversibility of hydrogen bonds and urea bonds as monitored by rheological tests. The extremely facile fabrication approach and superior properties of the resulting self-healing polymers can find applications in sustainable smart materials and self-healing conductive sensors.     

超高压水晶釜超声检测方法及缺陷评定

在对超高压水晶釜结构特点及缺陷产生方式分析的基础上,提出了采用准确有效的纵波、横波超声检测方法,并提出了缺陷评定方法,以确保危险缺陷的检出。     

中温固化环氧树脂基体的研究

本文阐述了一种中温固化环氧树脂基体，对其反应性、反应动力学、反应机理以及浇铸体和复合材料的性能进行了研究。     

GGMC算法目标函数值实验分析与算法改进

针对贪心最大割图半监督学习算法（简称GGMC）计算复杂度较高的问题,提出一种改进的贪心最大割图半监督学习算法（简称GGMC-Estop）。依据对GGMC算法优化过程中目标函数变化趋势的实验分析,采取两种在迭代初期停止GGMC算法运行策略,继而通过一次标准的标签传播步骤预测图上所有样本的标记来实施对GGMC的改进。典型数据集的仿真实验结果表明,在取得相近分类性能的同时,改进算法在计算速度上有很大的提高。