Investigation of the Hydrate Plugging and Non-Plugging Properties of Oils

Three laboratories (Norwegian Institute of Science and Technology [NTNU], Institut Français du Pétrole [IFP], and the Colorado School of Mines [CSM]) determined hydrate plug formation characteristics in three oils, each in three conditions: (1) in their natural state, (2) with asphaltenes removed, and (3) with naturally occurring acids removed from the oil. The objective was to determine the major variables that affect hydrate plugging tendencies in oil-dominated systems, to enable the flow assurance engineer to qualitatively assess the tendency of an oil to plug with hydrates. In the past, it was indicated that chemical effects, for example, water-in-oil/hydrate-in-oil (emulsion/dispersion) stability, prevented hydrate plugs. For example, deasphalted oils provided low emulsion/dispersion stability and thus hydrate particles aggregated. In contrast pH 14-extracted oils were reported to remove stabilizing naphthenic acids, causing asphaltene precipitation on water/hydrate droplets, stabilizing the emulsion/dispersion to prevent aggregation and pluggage. This work suggests that in addition to chemistry, shear can enable plug-free operation in the hydrate region. High shear can prevent hydrate particle aggregation, while low shear encourages particle aggregation and plugging. As a result, flow assurance engineers may be able to forecast hydrate plug liability of an oil by a combination of chemistry and flow variables, such as: a) measurements of live oil emulsion stability, b) predictions of flow line shear, and c) knowledge of water cut. Plug formation qualitative trends are provided for the above three variables. Implications for flow assurance are given.     

Numerical characterization of ultraviolet ink fluid agglomeration and the surfactant effect in nanoinkjet printing

Ultraviolet (UV) ink is a major ink type used in additive manufacturing via 3D inkjet printing. A major challenge in nanoinkjet printing is ink agglomeration. Among the UV ink components, oligomers have the highest tendency to agglomerate which can agitate the stability and quality of the printing fluid and possibly lead to nanoscale nozzle clogging. In this work, the first numerical study on the UV ink fluid, UV ink is modeled by using dissipative particle dynamics to study mesoscale agglomeration. The constituents of the ink model are composed of polystyrene and polyethylene glycol as photopolymers, BZP as a photoinitiator, and SDS as a surfactant. Styrene is a prevalent and established commercial photopolymer in present 3D inkjet applications, while ethylene glycol is a photopolymer known to improve ink viscosity. The morphological characteristics of the UV ink are studied here, where the results for different models from four cases considered here show how the kind of photopolymers and their constituent ratios affect the agglomeration morphology of the fluidic system. The existence of both oligomers and monomers results in mutual morphological benefits against agglomeration, while the photoinitiator occurs between photopolymers. In addition, we find that the surfactant can reduce the average size of agglomeration and improve the dispersion uniformity by increasing the number of agglomerates. These results highlight the important role additives can play to prevent, reduce, and control various forms of agglomeration to achieve enhanced nanoinkjet printing quality. Copyright © 2017 John Wiley & Sons, Ltd.     

Research on Performance Decay Mechanism of Pt/C Catalyst in Long-Term ORR Test北大核心CSCD

In proton exchange membrane fuel cells,cost,performance and durability are important issues that are need to be resolved before commercialization. The main reason for fuel cell performance degradation during operation is the loss of electrochemical surface area during long-term aging or transient. These losses mainly come from the degradation of the catalyst metal and the corrosion of the carbon support. This is a continuous and irreversible process that will greatly shorten the service life of the fuel cell. In order to explore this problem,20%（mass fraction）Pt/C catalyst is prepared based on carbon carrier etched by sulfuric acid. The morphology characterization test shows that it is uniformly dispersed and uniform in particle size,which is considered as an excellent material for long-term oxygen reduction （ORR） stability test. Next,the ORR stability test method with different cyclic voltammetry （CV） cycles is used to observe its performance degradation,and a series of physical characterizations,e. g. transmission electron microscopy（TEM）,high-resolution electron microscopy（HRTEM）,X-ray photoelectron spectroscopy（XPS）and Raman spectroscopy （Raman）,are used to further intuitively analyzed the attenuation mechanism. It is reported that the reasons for the degradation of the stability of Pt/C catalysts are mainly from the dissolution,agglomeration,oxidation and migration of Pt particles and the corrosion of carbon supports. This study elucidates the source of the impact on the stability of fuel cells during operation,and provides a reference for designing high-stability commercial ORR catalysts. © 2022, Science Press (China). All rights reserved.     

基于GIS空间分析的宁波周边城市群研究

城市作为大规模集中的人类非农性社会经济活动在二维平面上投影点．相互之间存在着空间作用，并在整体同构、功能耦合过程中形成城市群，因此，作为系统的城市群的变动不仅仅是城市单体内在体量影响的结果，还是城市单体空间分布作为位置变量综合作用的结果．文章通过基于GIS的空间分析，对宁波周边城市群形成的机制进行实证性研究．     

Synthesis of Single Crystalline ZnO Nanoparticles by Salt-Assisted Spray Pyrolysis

LiNO₃ was used as a shield in the preparation of single crystalline ZnO particles by a spray pyrolysis process in order to prevent agglomeration and enhance the crystallinity of the ZnO. LiNO₃ was added to a precursor solution of zinc acetate dihydrate prior to its atomization by means of an ultrasonic transducer. Agglomerate-free particles having a mean particle size of 26 nm were successfully obtained after washing the product. X-ray diffractometry, field-emission scanning electron micrograph and transmission electron micrograph data indicate that the size and morphology of ZnO were strongly influenced by the operating temperature used and the residence time of the particle in the reactor.     

Changing liquid crystalline phase with field

Since 1888, the liquid crystal display (LCD) industry is facing a fierce competition due to serious limitations such as poor contrast ratio and response time. Although some new materials have offered new applications and opened new markets for LCDs, materials with improved contrast ratio are highly desirable in LCD industry to sustain in the current market. This work reports a new behaviour in nano-material-doped liquid-crystal composite which is suitable for eradicating limitations of contrast ratio. Here, a high concentration of carbon nanotubes (CNTs) is doped in liquid crystal (LC) materials wherein the CNTs form aggregates in the LC composition. In these heavily doped samples, the phase change takes place with application of bias. This reversible process improves the contrast ratio as the material oscillates between crystalline and LC phases with field.     

创新型企业的空间集聚及影响因素分析

以福建省创新型企业为例,研究分析创新型企业的空间格局特征,以及创新型企业建设与地区经济发展之间的关系.根据区位基尼系数探讨创新型企业的集聚特征.利用Moran指数与Moran散点图,分析创新型企业数量分布的全局空间自相关性与局部空间自相关性.研究表明:创新型企业的建设成效与地区经济发展水平之间呈高度正相关关系;创新型企业的建设在地区内部辐射作用强,对邻近地区正溢出效应弱,甚至产生负溢出效应.     

Tuning urea-phenanthridinium conjugates for DNA/RNA and base pair recognition

A series of novel urea-phenanthridine conjugates was prepared. The variation of linker length connecting two urea-phenanthridinium conjugates regulated their binding mode toward double stranded polynucleotides, consequently controlling selectivity of compounds toward ds-RNA over ds-DNA stabilization as well as selective fluorescence response toward addition of G-C base pair and A-U(T) base pair containing polynucleotides.     

Lattice Boltzmann simulation of particles agglomeration and rheology in a particulate flow

The dynamics and rheology of particles in a Newtonian fluid subjected to shear are simulated using Lattice Boltzmann Method. A computationally-efficient Smoothed Profile Method is used to resolve fluid-solid interactions, and the Lennard-Jones inter-particle potential is implemented to account for inter-particle forces. The use of a bi-periodic computational domain with Lees-Edward boundary conditions allows simulation for systems consisting of a large number of particles under shear. The method is validated for single and dual particle problems and an analysis is performed for multi-particle problems under a range of shear rates and particle fractions. The introduction of particle-particle interactions, which are physically important in many engineering processes, is found to have a considerable impact on the dynamics, agglomeration and rheology. The total stress exhibits high unsteadiness primarily due to the solid component contribution, at higher particle fractions. The simulations underscore the complex interplay between shear, interparticle forces and agglomeration and the complex dependencies of the rheological properties.     

含硫杯[4]芳烃衍生物的合成及其紫外光谱研究

合成并表征了三个新的含硫且带醇羟基的杯「４」芳烃衍生物,核磁共振研究表明这些杯「４」芳烃都是Ｃｏｎｅ构型,对这些化合物的紫外光主普研究表明,在非极性溶剂中,在相对高浓度中,杯芳烃衍生物以形式存在。