Simplification and applicability studies of a hydrogen-air detailed reaction mechanism

The research of hydrogen fuel internal combustion engine (HICE) had great significance facing the challenges of energy and environmental problems. Based on the detailed hydrogen-air reaction mechanism, the pre-mix model of CHEMKIN-Pro software was selected to simplify the detailed mechanism GRI-3.0. The most important elements and reactions was chose to construct framework mechanism firstly based on the sensitivity coefficient for H₂O and NO formation, and additional elements and reactions were added to framework mechanism for complementing the oxidation path of N2 and H₂. A simplified mechanism including 24-step elementary reaction was obtained and the laminar burning velocity calculated by this simplified mechanism matches well with the detailed mechanism in a wide range. This simplified mechanism was also applied in a CFD model which predicted the cylinder instantaneous pressure and NOx emission accurately within a large range of fuel air equivalent ratio. Showing that this mechanism has good applicability.     

A new one-phase material model for the numerical prediction of critical material flow conditions in thixoforging processes

Thixoforging allows one-step forming processes of near-net shape components having excellent mechanical properties. However, the high sensitivity of thixoforging regarding process conditions requires precise modelling and determination of process related parameters. At the same time, simple numerical design proves challenging because of the inaccuracy of existing one-phase material models regarding the shear thinning flow behaviour of semi solid metals. Consequently, this paper deals with the development of a new one-phase material model providing a more precise simulation of materials’ shear rate dependency. By using this model, simulations could be performed, which allowed the prediction of solidification and flow-related component defects.     

NiH/Hβ催化剂的制备及催化正己烷异构化性能

采用浸渍还原法制备了一种新型镍氢化物/分子筛（NiH/Hβ）烷烃异构化催化剂，考察了催化剂制备条件及反应条件对其催化正己烷异构化性能的影响。结果发现，当活性组分质量分数为0.5%，反应温度为300 ℃，反应压力为2.0 MPa，氢/油摩尔比为4.0及质量空速为1.0 h^-1时，NiH/Hβ催化剂催化正己烷异构化活性最优，正己烷的转化率为83.0%，异构烷烃的选择性与收率分别达到78.6%、65.2%。根据实验结果，提出了NiH/Hβ催化剂催化正己烷异构化反应机理，证明NiH金属活性中心具有良好的加氢/脱氢功能。     

Non-linear dissolution mechanisms of sodium calcium phosphate glasses as a function of pH in various aqueous media

Phosphate glasses for bioresorbable implants display dissolution rates that vary significantly with composition, however currently their mechanisms of dissolution are not well understood. Based on this systematic study we present new insights into these mechanisms. Two-stage dissolution was observed, with time dependence initially parabolic and later linear, and a two-stage model was developed to describe this behaviour. Dissolution was accelerated by lower Ca concentration in the glass, and lower pH in the dissolution medium. A new dissolution mechanism is proposed, involving an initial stage where diffusion-controlled formation of a conversion layer occurs. Once the conversion layer is stabilised, layer dissolution reactions become rate-limiting. Under this mechanism the transition time is sensitive to the nature of the conversion layer and solution conditions. These results reveal the dependence of P₂O₅–CaO–Na₂O glass dissolution on solution pH, and provide new insight into the dissolution mechanisms, particularly regarding the transition between the two dissolution stages.     

新型限力输出保护功能柔性夹钳的设计与参数评估

柔性夹钳因具有微/纳精密操作能力, 常应用于微操作系统中, 但因抓爪无法提供恒定输出力或恒力范围小, 容易造成操作对象的损伤或脱落。根据放大模块与常力模块串联的结构形式, 设计了一种具有常力特性的柔性夹钳。基于伪刚体法, 建立放大模块中桥式机构与杠杆机构的刚度和放大率数学模型, 通过对倾斜导向梁进行分析, 得到常力模块的力-位移关系式, 计算出恒定输出力为42.5 N, 输出范围为370 μm。最后, 结合不同柔顺梁的结构参数, 运用MATLAB仿真探究了各关键参数对常力特性的影响。研究结果可为常力柔性夹钳的构型设计和分析提供一定的理论支撑。     

Microstructure and mechanical properties in the TLP joint of FeCoNiTiAl and Inconel 718 alloys using BNi2 filler

High entropy alloy(HEA) of Fe Co Ni Ti Al and Inconel 718 superalloy were firstly transient liquid phase(TLP) bonded by BNi2 filler due to the diffusion of Si and B in the filler to the base metals. The effects of bonding time on microstructure evolution and mechanical properties of the TLP joints were investigated.Owing to the complete isothermal solidification of the joints bonded for 30 min 120 min at 1100°C,no athermally solidified zones(ASZs) formed by eutectic phases were observed in the welded zone. Thus the TLP joints were only composed by the isothermally solidified zone(ISZ) and two diffusion affected zone(DAZ) adjacent to the dissimilar base metals and the negative effect of the ASZ on joint properties can be avoided. In addition, the increase of the bonding time can also make the Ti B2 borides precipitated in the DAZ near HEA and the brittle borides or carbides in the DAZ near IN718 alloy decrease and reduce the possibility of the stress concentration happened in the joints under loading. Therefore, the highest shear strength(632.1 MPa) of the TLP joints was obtained at 1100°C for 120 min, which was higher than that of the joint bonded for 30 min, 404.2 MPa. Furthermore, the extension of the bonding time made the fracture mechanism of the joint be transformed from the intergranular fracture to the transgranular fracture. However, as the brittle borides in the DAZ near IN718 can not be eliminated completely and refining of grains also happened in such region, all the TLP joints fractured inner the DAZ near IN718 alloy.     

Peptide-Mimicking Poly(2-oxazoline)s Displaying Potent Antimicrobial Properties

Poly(2-oxazoline)s have excellent biocompatibility and have been used as FDA-approved indirect food additives. The inert property of the hydrophilic poly(2-oxazoline)s suggests them as promising substitutes for poly(ethylene glycol) (PEG) in various applications such as anti-biofouling agents. It was recently reported that poly(2-oxazoline)s themselves have antimicrobial properties as synthetic mimics of host defense peptides. These studies revealed the bioactive properties of poly(2-oxazoline)s as a new class of functional peptide mimics, by mimicking host defense peptides to display potent and selective antimicrobial activities against methicillin-resistant Staphylococcus aureus both in vitro and in vivo, without concerns about antimicrobial resistance. The high structural diversity, facile synthesis, and potent and tunable antimicrobial properties underscore the great potential of poly(2-oxazoline)s as a class of novel antimicrobial agents in dealing with drug-resistant microbial infections and antimicrobial resistance.     

结合句法依存信息的方面级情感分类

引入句法依存信息到原方面术语,提出一种新的方面术语表示方法,利用Glove词向量表示单词以及单词与单词之间的依存关系,构造出包含句法依存信息的依存关系邻接矩阵和依存关系表示矩阵,利用图卷积神经网络和多头注意力机制将句法依存信息融入到方面术语中,使得方面术语表达与上下文结构高度相关。将改进后的方面词术语表示替换到现有模型后,模型泛化能力得到有效提升。对比试验和分析结果表明:该方法具有有效性和泛化性。