A review of electrolyte additives and impurities in vanadium redox flow batteries

As one of the most important components of the vanadium redox flow battery （VRFB）, the electrolyte can impose a significant impact on cell properties, performance and capital cost. In particular, the electrolyte composition will influence energy density, operating temperature range and the practical applications of the VRFB. Various approaches to increase the energy density and operating temperature range have been proposed. The presence of electrolyte impurities, or the addition of a small amount of other chemical species into the vanadium solution can alter the stability of the electrolyte and influence cell perfor- mance, operating temperature range, energy density, electrochemical kinetics and cost effectiveness. This review provides a detailed overview of research on electrolyte additives including stabilizing agents, im- mobilizing agents, kinetic enhancers, as well as electrolyte impurities and chemical reductants that can be used for different purposes in the VRFBs.

The effect of phosphate additive on the positive electrolyte stability of vanadium redox flow battery

The electrolyte is one of the most important components of vanadium redox flow battery （VRFB）. and its stability and solubility determines the energy density of a VRFB. The performance of current positive elec- trolyte is limited by the low stability of VO2＋ at a higher temperature. Phosphate is proved to be a very effective additive to improve the stability of VO2＋. Even though, the stabilizing mechanism is still not clear, which hinders the further development of VRFBs. In this paper, to clarify the effect of phosphate additive on the positive electrolyte stability, the hydration structures of VO2＋ cations and the reaction mechanisms of precipitation with or without phosphate in the supporting electrolyte of H_2SO_4 solutions were investigated in detail based on calculations of electronic structure. The stable configurations of com- plexes were optimized at the B3LYP/6-311 ＋ G（d,p） level of theory. The zero-point energies and Gibbs free energies for these complexes were further evaluated at the B3LYP/aug-cc-pVTZ level of theory. It shows that a structure of [VO_2（H_2O）_2]＋ surrounded by water molecules in H2S04 solution can be formed at the room temperature. With the temperature rises, [VO_2（H_2O）_2]＋ will lose a proton and form the interme- diate of VO（OH）_3, and the further dehydration among VO（OH）_3 molecules will create the precipitate of V_2O_5. When H_3PO_4 was added into electrolytes, the V-O-P bond-containing neutral compound could be formed through interaction between VO（OH）_3 and H_3PO_4, and the activation energy of forming the V-O-P bond-containing neutral compound is about 7 kcal tool-1 lower than that of the VO（OH）_3 dehydration, which could avoid the precipitation of V_2O_5 and improve the electrolyte stability.

Drag reduction of flow boiling with polymer additives

The drag reducing effect of polymer additive aqueous solution was investigated in flow boiling, and the polymer additives were two kinds of polyacrylamide (PAM) with relative molecular mass about 2.56×10 6 and 8.55×10 6. The frictional pressure drop was calculated according to the measured total pressure drop. The results show that the flow drag of flow boiling is reduced by adding a small amount of PAM to water when heat flux is in the range of 15.1 kW·m -2 to 47.0 kW·m -2 , when the mass fraction of PAM is higher than 2.0×10 -5 , the drag reducing effect is obvious. Drag reducing effect of PAM, whose relative molecular mass is 8.55×10 6, is slightly better than that of 2.56×10 6 at the same mass fraction, and the greater the flow rate of the additive solution, the better the effect of the drag reduction.

Bio-Diesel Based Additive for Enhancing Flow of Emulsion in Pipeline

Emulsions are difficult to transport in the oil and gas industry due to its water content and high viscosity property, thus a need arises to break these emulsions down into lighter emulsions that would make it a lot more suitable for transportation. In this research, biodiesel was synthesized and used to break down relatively viscous emulsion samples into lighter emulsion samples. An apparatus was designed with the aim of determining the flowrate of four different samples in different proportions and compositions: 80% oil and 20% water (sample A), 90% sample A + 10% of biodiesel by volume (sample B), 75% of sample A + 25% of biodiesel by volume (sample C), 60% of sample A + 40% biodiesel by volume (sample D). The results showed that it was possible to significantly increase the flow of emulsions by injecting biodiesel, which was acted as a surfactant, resulting in the lowering of the surface tension of the emulsion sample. The relevance of this research work is validated as it proffers a solution to the transportation of heavy oil and emulsions from all over the world possessing the non-Newtonian flow behavior, which results in serious problems related to its transportation.

China's Uneven Labor Flow and Its Effect on Regional Disparities—Empirical analysis based on non-parameter additive model

This paper is the first to use a non-parameter additive model in the empirical analysis of the impact of cross-regional laborflow on industrialization and economic growth in China’s eastern,central and western regions.Results indicate that laborflow has significantly different effects on the direction and intensity of impact on economic development across regions:massive labor inflow from the central and western regions to the eastern region significantly promoted the industrializationprocess and economic growth in the East,while the impact of labor outflow from the central and western regions on theregional economies is in a significantly inverted-U shaped non-linear relationship.Uneven labor flow across regions haswidened China’s regional economic disparities.

Evaluation of rutting performance of stone matrix asphalt mixtures containing warm mix additives

Permanent deformation or rutting, one of the most important distresses in flexible pavements, has long been a problem in asphalt mixtures and thus a great deal of research has been focused on the development of a rheological parameter that would address the rutting susceptibility of both unmodified and modified bituminous binders. In this research, three warm mix additives(Sasobit, Rheofalt and Zycotherm) were used to modify 60-70 penetration grade base binder. The rutting potential of both modified and unmodified binders were evaluated through the multiple stress creep recovery(MSCR)-based parameter, nonrecoverable compliance(Jnr) and recovery parameter(R). Several performance tests carried on stone matrix asphalt(SMA) mixtures comprising different nominal maximum aggregate sizes(NMASs, 9.5, 12.5 and 19 mm), like Marshall stability, dynamic and static creep and Hamburg wheel tracking tests to evaluate their rutting performance. The objective of this work is to correlate MSCR test results to performance. Results indicate that for the range of the gradations investigated in this work, increasing the nominal maximum aggregate size of the gradation would increase the permanent deformation resistance of the SMA mixture. Addition of 3% sasobit to base binder leads an increase in Jnr100 about 82%. Addition of 2% rheofalt to base binder leads an recovery increase of about 9.76 % and 27.44% in stress levels of 100 and 3200 Pa, respectively. The results reveal that rutting resistance of mixtures improves as Jnr decreases. The use of the MSCR test in the rutting characterization of bituminous binders is highly recommended based on the results of this work.

固相搅拌摩擦沉积增材制造技术研究进展

搅拌摩擦沉积增材(Additive friction stir deposition,AFSD)是一种先进的固相增材制造(Additive manufacturing, AM)技术。与传统基于熔融的增材制造技术相比,它具有增材结构致密、材料低变形和过程高效节能等优势,在航空装备制造、交通运输、机械制造等领域拥有广阔的应用前景。本文综述了AFSD技术的原理、优势、组织演变特点和应用情况。重点介绍了AFSD过程中“工艺条件-微观组织-力学性能”相关性的研究现状,沉积材料力学性能受材料流动状态、界面连接机制、微观组织演变情况的综合影响。列举了AFSD技术在大型构件整体制造、高性能涂层、表面缺陷修复等领域的应用。最后,对AFSD技术进行了展望,指出该技术在工艺与组织变化耦合、原位变形条件模拟、工具头设计和新材料增材等方面需进一步研究和突破。

基于加线技术的轨道交通临客开行计划优化模型

基于运行图加线技术构建适于计划性临客开行的运行线铺画方法.以运力与客流匹配度最大化、对原运行图调整最小化为优化目标,考虑行车安全、临客加线位置、开行时间域等约束,构建临客运行线铺画非线性整数规划模型,并对其线性转换以提高求解效率.以北京地铁8号线某大型活动散场大客流为场景进行案例分析,结果表明:所构建方法能够在既有运行图上有效铺画临客运行线,满足不同行车密度及停站模式下的临客开行需求.建议在较高密度行车条件下不采用“空车直达”停站模式.

基于因果自回归流模型的因果结构学习算法

因果自回归流模型已经在非独立噪声等场景的因果方向推断问题上取得了一定的进展,但在多个结点的场景下仍存在全局结构搜索带来的准确度低和计算时间复杂度高的问题。面向非时序观察数据设计一种两阶段因果结构学习算法。在第一阶段,基于观测数据的条件独立性,对完全无向图通过条件独立性检验得到基本的因果骨架;在第二阶段,基于因果自回归流模型,通过标准化流的方法计算骨架中每条无向边在不同方向上的边缘似然概率,进而通过比较边缘似然概率进行因果方向推断。实验结果表明:该算法在多组不同参数生成的仿真因果结构数据集上均有较好的表现,与现有的主流因果结构学习算法相比,F1值平均提升15%~28%;在真实因果结构数据集实验中,该算法能够较为完整准确地学习到变量间的因果关系,与主流的因果结构学习算法相比,F1值平均提升28%~48%,具有更强的鲁棒性。

激光-电弧复合增材制造Al-Cu合金T型结构微观组织演变与熔池流动行为分析

在T型结构增材制造过程中,交叉节点处易出现冶金结合不良及重熔缺陷等问题,制约该结构性能的提升。采用激光-电弧复合增材制造技术制备了Al-Cu合金T型结构,对交叉节点处的组织形貌进行了表征,并通过数值模拟分析了节点处熔池内的温度分布以及流动特征。结果表明,在T型结构节点处能够观察到重熔作用所导致的弧形条纹特征,该区域的模拟形貌与实际结果具有良好的一致性;熔池边界处等温线分布较为密集,内部Marangoni对流导致逆时针涡流的形成,最高流速可达0.16 m/s。依据顶层晶粒形态差异,分为顶层节点重熔区(RZI)和顶层热影响区(HAZ)。其中RZI内主要为细小的树枝晶,平均晶粒尺寸相比于HAZ降低了20.8%,内部析出相主要为与α-Al基体呈非共格界面的大尺寸θ(Al_(2)Cu)相;平均显微硬度可达(98.4±6.4)HV_(0.1),相比于未重熔区最高提升约14.0%。

基于动态知识流动特征的有向技术融合预测方法

[研究目的]基于动态知识流动特征对有向的技术融合关系进行预测,有助于提高企业的研发效率及科技管理部门对科技资源的合理分配。[研究方法]首先,将IPC前4位代码作为技术单元,基于专利中主分类号与副分类号提取技术间的有向知识流动关系;然后,借鉴关联规则挖掘算法从重要性、强度和依赖度3个维度对知识流动关系进行筛选,将满足指标阈值的知识流动关系作为有向技术融合关系;最后,将有向技术融合关系预测转化为有监督的二分类任务,以机器学习算法为模型基础,结合前两个时期的技术间知识流动特征及其时序变化特征,预测下一个时期内的技术间是否存在技术融合关系。[研究结论]增材制造领域的实证分析结果显示,以代价敏感机器学习算法为预测算法,基于前两个时期的技术间知识流动特征及其时序变化特征可以有效预测下一阶段中的技术融合。随着技术的发展,技术间的单向融合愈发频繁,并逐渐演变为技术双向融合,甚至呈现多技术融合的现象。

变位磁场作用电弧增材中电弧和熔池传热与流动数值模拟

为了揭示具有纵向和横向分量的外加变位磁场对TIG电弧增材成形过程中电弧和熔池传热与流动的影响机理,基于流体动力学软件Fluent,建立了电弧与熔池耦合的三维瞬态模型。对比分析了不同角度的变位磁场对电弧形貌、电磁力、热流密度、熔池形貌及熔池速度场的影响规律与机理。结果表明:无外加磁场时,电弧与熔池对称分布,施加变位磁场时,电弧和熔池中产生周向旋转和偏向一侧的电磁力,使电弧与熔池发生旋转与偏移,熔池除了具有由内向外的流动,还具有围绕中心旋转和偏向一侧的流动;增大变位磁场的变位角度使横向磁场分量减小,纵向磁场分量增加,从而使偏向一侧的电磁力减小,周向旋转电磁力增大,进而使电弧偏转与熔池偏移减弱,熔池旋转流动趋势增强。研究结论可为后续磁控电弧增材制造传热、传质的机理分析及工艺参数的选择提供理论依据和参考。

求解分布式两阶段混合流水车间调度的反馈人工蜂群算法

针对考虑工厂适用性和附加资源的分布式两阶段混合流水车间调度问题(DTHFSP),本文提出了一种反馈人工蜂群算法(FABC),以最小化最大完成时间和总延迟时间,该算法利用一种新型反馈机制动态调整搜索策略集.为此,本文共设计了5种特点各异的搜索策略,将其用于初始策略集和备选策略集,同时,建立并调整雇佣蜂群和跟随蜂群的共享策略集,雇佣蜂阶段和跟随蜂阶段在种群划分的基础上采用随机选择和自适应选择方式确定搜索策略,在侦查蜂阶段完成后,对搜索策略集进行动态调整.文章进行了大量的计算实验,计算结果表明,FABC策略合理有效,且它对所求解的DTHFSP具有较强的搜索优势.

增材制造复杂流道水冷电机壳体对驱动电机持续功率影响的研究

目的提高量产铸造电机壳体的换热效率,确保电机在高功率持续工作状态下不会过热,从而提高电机的持续功率。方法基于增材思维对电机水冷壳体的流道进行优化,改变流道形状以增大流道表面积、消除流道涡流并减小流道与内壁的间距。通过仿真分析,不断优化迭代得到最佳的流道设计方案。运用选区激光熔化(SLM)增材技术及相应的后处理工艺,制造出复杂流道结构的电机壳体。结果采用SLM增材技术制造的AlSi10Mg铝合金壳体在x、xz、z 3个方向上的屈服强度均大于230 MPa,即使在较小壁厚的条件下,壳体强度仍满足设计要求。采用该壳体后,电机的持续功率从原量产电机的45 kW提升到50.7 kW,且仍能连续稳定运行45 min,同时电机温度未超过130℃。微观组织检测和工业CT测试结果显示,SLM电机壳体结构致密,未见气孔夹杂。该增材制造壳体的质量为6.95 kg,与量产电机壳体相比,减重约19%。结论通过增材制造技术设计制造的电机壳体整体性能良好,可以有效提高换热效率以及电机的持续功率,并实现了电机的减重。

全钒液流电池电解液的制备及性能优化进展

全钒液流电池以其本质安全等优点成为大规模长时储能的优选,电解液作为全钒液流电池的关键组成部分,对电池性能起着至关重要的作用。对全钒液流电池电解液产业化制备方法以及钒电解液性能优化之电解液支持体系与添加剂对电解液性能的影响进行综述。并指出,目前全钒液流电池电解液产业化制备方法以化学还原法和化学还原联合电解法为主,在钒电解液性能优化方面,混酸支持电解质体系优化,以及电解液添加剂的理论研究和经济分析,是今后产业研究者应重点关注的方向。

Enhancement of Flow Boiling Heat Transfer with Surfactant

The surfactant additive octadecylamine (ODA) was used to enhance the flow boiling heat transfer of water in vertical copper tube, and the effects of the aqueous solution properties, mass fraction of ODA, mass flux and heat flux etc. on flow boiling heat transfer were investigated. In order to analyze the mechanism of enhancement on boiling heat transfer with ODA, the copper surface was detected by XPS, and the diagram of binding energy was obtained. The results show that ODA can be adsorbed on the surface of the copper wall, and affects the properties of the heating surfaces and enhances the flow boiling heat transfer of water. Only in low heat flux and in a suitable range of concentration, can ODA aqueous solution enhance flow boiling heat transfer, and the suitable mass fraction of ODA is in the range of 1×10 -5 5×10 -5 . In addition, compared with water, ODA aqueous solution does not increase the flow drag under the same experimental conditions.

O/N/S trifunctional doping on graphite felts:A novel strategy toward performance boosting of cerium-based redox flow batteries

The cerium-based redox flow battery(RFB)is regarded as a compelling gridscale energy storage technology to revolutionize the utilization of renewable energy by storing the energy in liquid electrolytes.However,its widespread implementation is impeded by the cerium redox reactions that exhibit slow kinetics on commercial graphite felt(GF)electrodes.Surface functionalization may be an available activation strategy to achieve a significant boost in the electrochemical performance of GFs.However,conventional chemical and/or electrochemical routes for the surface functionalization of GFs suffer from the issues of complication,and the deterioration of the resulting modified electrode surface over long-term cycle processes leads to catalytic activity decline.Here,we develop a facile and general strategy for introducing the functional groups to the electrode through the addition of L-cysteine into electrolytes.The-COOH,-NH_(2),and-SH groups in L-cysteine can induce oxygen/nitrogen/sulfur trifunctional doping on GF surfaces with lower deterioration rates,which enables the activated GFs to demonstrate a promising electrocatalytic activity toward cerium redox reactions and excellent durability when used as a cerium-based RFB electrode.This study proposes a rational strategy to overcome the intrinsic limitations of existing modification techniques for GFs and provides a potential pathway toward high-performance RFBs.

On Symmetry Flows of Noncommutative Kadomtsev-Petviashvili Hierarchy

We discuss symmetry flows of noncommutative Kadomtsev-Petviashvili (NCKP) hierarchy. An operatorbased formulation, alternative to the star-product approach of extended symmetry flows is presented. Noncommutative additional symmetry flows of the NCKP hierarchy are formulated. A rescaling symmetry flow which is associated with the rescaling of whole coordinates is introduced.

Explicit Analytical Solutions of Radial Permeable Power Rate Flow

The research of different kinds of permeable non-Newtonian fluid flow is increasing day by day owing to the development of science,technology and production modes.It is most common to use power rate equation to describe such flows.However,this equation is nonlinear and very difficult to derive explicit exact analytical solutions.Generally,people can only derive approximate solutions with numerical methods.Recently,an advanced separating variables method which can derive exact analytical solutions easier is developed by Academician CAI Ruixian（the method of separating variables with addition）.It is assumed that the unknown variable may be indicated as the sum of one-dimensional functions rather than the product in the common method of separating variables.Such method is used to solve the radial permeable power rate flow unsteady nonlinear equations on account of making the process simple.Four concise（no special functions and infinite series） exact analytical solutions is derived with the new method about this flow to develop the theory of non-Newtonian permeable fluid,which are exponential solution,two-dimensional function with time and radius,logarithmic solution,and double logarithmic solution,respectively.In addition,the method of separating variables with addition is developed and applied instead of the conventional multiplication one.It is proven to be promising and encouraging by the deducing.The solutions yielded will be valuable to the theory of the permeable power rate flow and can be used as standard solutions to check numerical methods and their differencing schemes,grid generation ways,etc.They also can be used to verify the accuracy,convergency and stability of the numerical solutions and to develop the numerical computational approaches.