Twinning behaviors of Mg-Sn alloy with basal or prismatic Mg_(2)Sn

The Mg-Sn alloys,with basal or prismatic Mg_(2)Sn laths,were employed to reveal the effect of precipitate orientation on twinning behavior quantitatively.The Mg-5wt.%Sn alloys with basal or prismatic Mg_(2)Sn were compressed to study the twinning behaviors.Subsequently,an Orowan strengthening model was developed to quantitatively investigate the critical resolved shear stress(CRSS)increment of precipitates on twinning.The results revealed that the prismatic precipitates hindered the transfer and growth of tensile twins more effectively compared with the basal precipitates.The decreased proportion of tensile twins containing prismatic Mg_(2)Sn might be attributed to a larger CRSS increment for tensile twins compared with that for basal precipitates.The obvious decreased twinning transfer in the alloy with prismatic Mg_(2)Sn could be due to its higher geometrically necessary dislocation and enhanced CRSS of tensile twins.Notably,the prismatic precipitates have a better hindering effect on tensile twins during compression.

区别化执行:政策实践中乡镇政府的社会动员——以DFY水库搬迁过程为例

本文是在新时代背景下以DFY水库上游保护区村居房屋整体搬迁过程为个案,探讨一种特殊的项目政策推进模式——区别化执行。研究发现,乡镇政府基于压力型体制下科层结构特点,在推进工作任务的不同阶段,通过这种动态、综合的执行手段来达到上级工作任务的及时完成和有效落实,借以实现他们在科层场域内的职业晋升愿景或不被淘汰出局。而在执行此类政策行为时,乡镇政府会针对行为对象选择性采取区别化政策执行方式,并具体呈现项目政策执行的基本行为面相,即在初始阶段对积极响应型群体的规则性执行,在胶着阶段对中性响应型群体的关系性执行以及在攻坚阶段对消极响应型群体的权威性执行。进而可见,乡镇政府这种区别化执行上级政策的实践逻辑是基于他们所处场域环境下的个体选择,更是为了因应治理体系现代化特点而形塑的综合性运作手段。同时,这种政策执行模式以及多重逻辑解释路径对乡镇其他中心工作也有一定的借鉴作用和扩展性解释力。

Effect of fluoride treatment on corrosion behavior of Mg-Ca binary alloy for implant application

The influence of hydrofluoric acid（HF） treatment on the corrosion behavior of the Mg-0.5Ca alloys was investigated by immersion specimen in sodium hydroxide and HF solutions with various concentrations and durations at room temperature.Microstructural evolutions of the specimens were characterized by atomic force microscopy,X-ray diffraction,field-emission scanning electron microscopy.The corrosion resistance was examined through potentiodynamic polarization and immersion test in Kokubo solution.The results revealed that the fluoride treated Mg-0.5Ca alloys produced by immersion in 40% HF provided more uniform,dense and thicker coating layer（12.6 μm） compared with the 35% HF treated specimen.The electrochemical test showed that the corrosion resistance of fluoride treated specimen was 35 times higher compared with the untreated Mg-0.5Ca alloy specimen in Kokubo solution.In vitro degradation rate of the fluoride treated specimens was much lower than untreated Mg-0.5Ca alloy in Kokubo solution.After immersion test the surface of 40% HF treated sample showed a few corrosion dots,while untreated specimens were fully covered by corrosion products and delamination.Fluoride treated Mg-0.5Ca alloy with 40% HF is a promising candidate as biodegradable implants due to its low degradation kinetics and good biocompatibility.

Coalescence Behaviors of Drop Swarms on Liquid-Liquid Interface

The trajectory model of dispersed phase drops and distribution model of drop diameters were derived.By numerical simulation,the analytical results indicate that a large number of dispersed phase drops accumulate on the upper plate in different directions and form a hydrodynamic area with the stream-wise location in the range of 0—0.4m,where the flow of trickling film obtains kinetic drive from flowing field.The flowing field of trickling film exhibits an unstable state if the stream-wise location is less than 0.02m,and a stable state otherwise.Moreover,different velocity vectors of drops in the x-y plane result in different interactions between the trickling film and drops.For the non-uniform distribution of drop diameters,there is a stronger interaction between the trickling film and drop if the stream-wise location is less than 0.02m,because the amplitudes of velocity vectors are higher than those in the range of 0.02—1.0m.The result reveals a complexity and diversity of stratified two-phase flowing field.On the other hand,both the basic flowing field and distributions of drop diameters have a great influence on the distributions of comparable kinetic energy of drops.The complicated motions of larger drops are helpful to coalescence because they will consume much more kinetic energy on the trickling film than those of smaller drops.The change of comparable kinetic energy of smaller drops is continuous and steady.The smaller drops are easily entrained by the liquid-liquid flowing field.

On the Lateral Behavior of the Backfill of a Skew Abutment

It is generally accepted that the interaction between a bridge and its abutment＇s backfill soil is highly nonlinear, especially under a strong earthquake loading that contains a velocity pulse. For bridges with skew abutments, the superstructure-abutment interaction can dominate the overall bridge performance. This study puts forth a new approach for predicting the lateral capacity of a skew abutment using verified high-fidelity three-dimensional continuum finite element （FE） models. The core idea is that the lateral capacity of a straight abutment is bounded from above and below by that of the abutment of a skew bridge that has the same deck-width, and that of another skew bridge （with the same angle） that has the same backwall length as the original/straight bridge, respectively. This postulation is then used in reverse to estimate the lateral capacity of a skew abutment, given the capacity of a straight but otherwise identical one with an arbitrary length. In prior research, the latter information had already been obtained in closed-form expressions that use physical parameters, such as backfill cohesion, internal friction angle and density, backwall height, and backwall-backfill friction angle. The approach presented here is constrained by the assumption that bridge deck will not rotate during loading. While this assumption is generally violated in a strong earthquake--because a skew bridge will tend to rotate, especially if its in-plane torsional rigidity is low, the model presented does serve as an anchor for parameterizing more advanced （e.g., macro-element plasticity） models that allow rotation, and also as fully parametric lateral response models for torsionally stiff （ile., multi-span, multi-bent） skew bridges.

Mixed alkaline phosphatase/sphingomyelin monolayer at the air-buffer interface: phase behavior and morphology

The glycosylphosphatidyl inositol(GPI)-anchored proteins are localized on the outer of the plasma membrane and clustered in membrane microdomain known as lipid rafts. Among them, mammalian alkaline phosphatase(AP) is an enzyme widely distributed. So, it has important biological significance to study the combination of AP with lipid monolayer. In our work, the interaction between AP and sphingomyelin has been studied at the air-buffer interface as a biomimetic membrane system by the Langmuir film technique and atomic force microscopy. The surface pressure-area isotherm for the mixed alkaline phosphatase/sphingomyelin monolayer shown the presence of a transition from a liquid-expanded phase to the liquid-expanded/liquidcondensed coexist phase. And the surface compressional modulus suggested the mixed alkaline phosphatase/sphingomyelin monolayer has larger compressibility compared with the pure sphingomyelin monolayer. Besides, according to the micrographs, we inferred when combined with lipid monolayer at the air-buffer interface, the AP molecules formed polymer not multilayer or micelle. And, according to the limiting molecules area of AP, we inferred that 12 AP molecules formed a hexagon polymer unit.

Phase behavior and interfacial properties of symmetric polymeric ternary blends A/B/AB

In this paper, the phase behavior and interracial properties of symmetric ternary polymeric blends A/B/AB are studied by dissipative particle dynamics （DPD） simulations. By using the structure factor and nematic order parameter, we carefully characterized the diversified phases and phase transitions, and established the phase diagram of such symmetric ternary blends. It can be generally divided into four regions： disordered phase （DIS） region at high temperature, ordered lameUar phase （LAM） region, bicontinuous microemulsion （BμE） channel and phase-separated phase （2P） region at low temperature with the increase of the total volume fractions of homopolymers φn, which shows good accordance with that in previous experimental and theoretical reports. Furthermore, we calculated the elastic constants of 2P and LAM phase, and discussed the transition mechanisms from 2P and LAM to BμE phase, respectively. The results show a direct relevance between the phase transitions and the change of interfacial properties. Finally, we also demonstrate that the B,uE channel becomes narrower in lower temperature caused by the temperature dependence of interfacial properties of ternary blends.