Effect of microstructure inhomogeneity on hydrogen embrittlement susceptibility of X80 welding HAZ under pressurized gaseous hydrogen

Hydrogen embrittlement (HE) of high-grade pipeline welded joint is a threat to hydrogen gas transport. In this research, slow strain rate tension (SSRT) tests in high-pressure hydrogen gas, combined with hydrogen permeation tests and microstructure analysis were conducted on X80 steel, intercritical heated-affected zone (ICHAZ), fine-grained heat-affected zone (FGHAZ) and coarse-grained heat-affected zone (CGHAZ). The change of HE susceptibility from high to low was CGHAZ, FGHAZ, ICHAZ, and base metal. Microstructure was the important factor influencing hydrogen permeation and susceptibility to HE. Susceptibility to HE was increased in the order of “fine-grained massive ferrite (MF) and acicular ferrite (AF)”, “fine-grained granular bainite (GB) and MF”, “coarse-grained GB and bainite ferrite (BF) embedded with martensite-austenite (M-A) constitute”. The fine-grained MF and AF in base metal with lower hydrogen diffusivity can impede the embrittlement behaviour, while the coarse-grained GB and BF with higher hydrogen diffusivity in CGHAZ increased its susceptibility to HE.     

A cam-quadrilateral mechanism for power transmission of a twin-rotor piston engine

A quadrilateral with four invariable lengths of sides has the characteristic of transforming the variation of the diagonal length to the variation of its interior angle. Thus, the combination of two quadrilaterals with a cam forms the differential velocity drive mechanism (DVDM) of a novel twin-rotor piston engine (TRPE). The DVDM restricts the two coaxial rotors to rotate with periodical but nonuniform velocity, and the volume of working chambers created by the adjacent vane pistons of the two rotors alternately expands and then contracts. The volumetric change of working chambers is used to generate the four-stroke engine cycle. The kinematic model and the detailed position, velocity, and acceleration analysis results of the TRPE are presented. The results show that this novel engine, associated with the advantages of higher uniformity of torque and power density due to multiple power strokes per revolution of the output shaft, has a compact and totally balanced design.     

Na2SO4对低硫水泥及其混凝土性能的影响

本文探讨了单掺Na2SO4对低硫水泥及其混凝土性能的影响。结果表明:少量的Na2SO4缩短了水泥凝结时间,有利于提高混凝土的坍落度、改善混凝土坍落度损失,而且在低温时可以明显改善混凝土的早期强度。     

Thermo‐ and pH‐responsive microgels for controlled release of insulin

Microgel particles were prepared, made of hydroxypropylcellulose‐graft‐(acrylic acid) (HPC‐g‐AA) and acrylic acid(AA). The particles undergo reversible volume phase transitions in response to both pH and temperature changes while keeping the inherent properties of PAA and HPC‐g‐AA. Dynamic light scattering measurements reveal that the average hydrodynamic radius and hydrodynamic radius distributions of the microgel particles depend on temperature and pH. The microgels exhibit excellent pH sensitivity and a higher swelling ratio at higher pH in aqueous solution. In vitro release study shows that the amount of insulin released from the microgels is less at pH = 1.2 than at pH = 6.8. The results indicate that the resultant microgels seem to be of great potential for intelligent oral drug delivery. Copyright © 2012 Society of Chemical Industry     

现网实现OCP的实例

简要说明了什么是光通道保护（OCP）及为什么要采用OCP技术,并通过现网实现OCP保护的实例说明了OCP保护对传统WDM系统上大颗粒（如2.5G、10G）客户电路的保护效果。     

用化学溶液法制备银基底Bi-2212超导薄膜

Bi2Sr2CaCu2Ox(Bi-2212)薄膜制备工艺相对简单,在低温下具有优异的性能,因此备受青睐,已经有不少研究小组采用真空或非真空方法成功制备出高质量的Bi-2212薄膜。一般而言,单晶基底被广泛用于Bi-2212薄膜的制备。与单晶基底不同,银基底无织构,但银基底的表面粗糙度等因素对Bi-2212的c轴织构和临界电流密度有影响。并且由于银基底对Bi系高温超导材料具有较低表面能,因此Bi-2212薄膜可以在银基底上稳定存在。以乙酸-氨水溶液为基础,开发了一种在银基底上制备Bi-2212薄膜的方法,对其中的关键步骤做了详细的研究,主要包括银基底的抛光、化学溶液的配制、烧结温度等。重复旋涂-热解过程可以消除经由一次旋涂热解带来的气泡;另外在银基底和低氧分压条件下,Bi-2212的成相温度点下移,在790℃保温5 h即可制备出单相Bi-2212薄膜。扫描电镜(SEM)观测表明,薄膜表面均匀平整无裂纹。随着烧结温度的升高,Bi-2201相开始出现并且其衍射峰的强度随烧结温度的升高迅速增加;当烧结温度为850℃时,出现了一种棒状相,能谱(EDS)分析表明该棒状相是一种缺Cu相。     

Model approach to grammatical evolution: theory and case study

Many deficiencies with grammatical evolution (GE) such as inconvenience in solution derivations, modularity analysis, and semantic computing can partly be explained from the angle of genotypic representations. In this paper, we deepen some of our previous work in visualizing concept relationships, individual structures and total evolutionary process, contributing new ideas, perspectives, and methods in these aspects; reveal the principle hidden in early work so that to develop a practical methodology; provide formal proofs for issues of concern which will be helpful for understanding of mathematical essence of issues, establishing of an unified formal framework as well as practical implementation; exploit genotypic modularity like modular discovery systematically which for the lack of supporting mechanism, if not impossible, is done poorly in many existing systems, and finally demonstrate the possible gains through semantic analysis and modular reuse. As shown in this work, the search space and the number of nodes in the parser tree are reduced using concepts from building blocks, and concepts such as the codon-to-grammar mapping and the integer modulo arithmetic used in most existing GE can be abnegated.     

A Coupled Model Between Robot Trajectories and Thermal History of the Workpiece During Thermal Spray Operation

Offline robot trajectory generation is now often used for thermal spray applications, especially for complex design parts, requiring enhanced trajectories. This technique allows decreasing the downtime of the thermal spray cell and insures the generation of optimized trajectories. Heat transfers caused by thermal spray increase the workpiece temperature during the coating application. This temperature acts directly on the resulting thermal stresses after cooling of the part down to the ambient temperature. In this study, a coupling was developed between the robot trajectory and computation of the thermal history of the workpiece during the spray operation. The method is based on the storage of the real robot trajectory (i.e., accurate in time) in a text file, and reading of this file with a C programming performed with ANSYS/FLUENT commercial code which allows computing the displacement of the thermal sources according to the trajectory and solving the transient heat conservation equation during the torch displacement. The contributions of the impinging plasma jet and the molten particle jet are taken into account in the model.     

A Topology Control Approach Reducing Construction Cost for Lossy Wireless Sensor Networks

In lossy wireless sensor networks, many links suffer from significant quality variation with time and environments. Topology control approaches need to consider such stochastic nature to yield different topologies for different application requirements. However, the metric of links must be timely obtained to speed up the topology construction. In fact, the existing approaches address it by passive monitoring, which is not timely adaptive to link quality variation. Also, timely access to the metric of all links at all power levels causes a large burden on topology control operation. We do not insist on getting the link metrics of all power levels at a time. Most urgently needed link metrics are firstly obtained by an active probing mode in this paper. If these link metrics do not meet the topology performance requirements, sub-urgently needed link metrics will be obtained on demand. At the same time, each node performs a topology control process based on the information in a smaller range (e.g., 1-hop neighborhood). Therefore, our approach has the low construct cast, which is proved in this paper. The simulation results also show that our approach outperforms the existing typical works in terms of average transmission power level, though it is slightly less efficient in terms of average delivery rate, average end-to-end delay and total energy consumption. In addition, our approach has advantage in terms of standard deviation of remaining energy under the relatively smaller required path quality bound or lower node density.