Influence of core sand properties on flow dynamics of core shooting process based on experiment and multiphase simulation

The influence of core sand properties on flow dynamics was investigated synchronously with various core sands, transparent core-box and high-speed camera. To confirm whether the core shooting process has significant turbulence, the flow pattern of sand particles in the shooting head and core box was reproduced with colored core sands. By incorporating the kinetic theory of granular flow(KTGF), kinetic-frictional constitutive correlation and turbulence model, a two-fluid model(TFM) was established to study the flow dynamics of the core shooting process. Two-fluid model(TFM) simulations were then performed and a areasonable agreement was achieved between the simulation and experimental results. Based on the experimental and simulation results, the effects of turbulence, sand density, sand diameter and binder ratio were analyzed in terms of filling process, sand volume fraction(αs) and sand velocity(Vs).

Microstructure, mechanical properties and deformation mechanisms of an Al-Mg alloy processed by the cyclical continuous expanded extrusion and drawing approach

Al-Mg alloys are an important class of non-heat treatable alloys in which Mg solute and grain size play essential role in their mechanical properties and plastic deformation behaviors.In this work,a cyclical continuous expanded extrusion and drawing(CCEED)process was proposed and implemented on an Al-3Mg alloy to introduce large plastic deformation.The results showed that the continuous expanded extrusion mainly improved the ductility,while the cold drawing enhanced the strength of the alloy.With the increased processing CCEED passes,the multi-pass cross shear deformation mechanism progressively improved the homogeneity of the hardness distributions and refined grain size.Continuous dynamic recrystallization played an important role in the grain refinement of the processed Al-3Mg alloy rods.Besides,the microstructural evolution was basically influenced by the special thermomechanical deformation conditions during the CCEED process.

A review of extractive distillation from an azeotropic phenomenon for dynamic control

Extractive distillation is an effective method for separating azeotropic or close boiling point mixtures by adding a third component.Various technologies for performing the extractive distillation process have been explored to protect the environment and save resources.This paper focuses on the improvement of these advanced technologies in recent years.Extractive distillation is retrieved and analyzed from the view of phase equilibrium,selection of solvent in extractive distillation,process design,energy conservation,and dynamic control.The quantitative structure–property relationship used in extractive distillation is discussed,and the future development of extractive distillation is proposed to determine how the solvent affects the relative volatility of the separated mixture.In the steady state design,the relationship between the curvature of the residue curve and parameters of the optimal steady state is also highlighted as another field worthy of further study to simplify the distillation process.

A regeneration process-matching scaffold with appropriate dynamic mechanical properties and spatial adaptability for ligament reconstruction

Ligament regeneration is a complicated process that requires dynamic mechanical properties and allowable space to regulate collagen remodeling.Poor strength and limited space of currently available grafts hinder tissue regeneration,yielding a disappointing success rate in ligament reconstruction.Matching the scaffold retreat rate with the mechanical and spatial properties of the regeneration process remains challenging.Herein,a scaffold matching the regeneration process was designed via regulating the trajectories of fibers with different degradation rates to provide dynamic mechanical properties and spatial adaptability for collagen infiltration.This core-shell structured scaffold exhibited biomimetic fiber orientation,having tri-phasic mechanical behavior and excellent strength.Besides,by the sequential material degradation,the available space of the scaffold increased from day 6 and remained stable on day 24,consistent with the proliferation and deposition phase of the native ligament regeneration process.Furthermore,mature collagen infiltration and increased bone integration in vivo confirmed the promotion of tissue regeneration by the adaptive space,maintaining an excellent failure load of 67.65%of the native ligament at 16 weeks.This study proved the synergistic effects of dynamic strength and adaptive space.The scaffold matching the regeneration process is expected to open new approaches in ligament reconstruction.

Optical properties and dynamic process in metal ions doped on CdSe quantum dots sensitized solar cells

In recent years, the nanostructure for solar cells have attracted considerable attention from scientists as a result of a promising candidate for low cost devices. In this work, quantum dots sensitized solar cells with effective performance based on a co-sensitized Cd S∕Cd Se：Mn2＋（or Cu2＋） nanocrystal, which was made by successive ionic layer absorption and reaction, are discussed. The optical, physical, chemical, and photovoltaic properties of quantum dots sensitized solar cells were sensitized to Mn2＋and Cu2＋dopants. Therefore, the short current（JSC）of the quantum dot sensitized solar cells is boosted dramatically from 12.351 mA∕cm2 for pure Cd Se nanoparticles to 18.990 mA∕cm2 for Mn2＋ions and 19.915 mA∕cm2 for Cu2＋ions. Actually, metal dopant extended the band gap of pure Cd Se nanoparticles, reduced recombination, enhanced the efficiency of devices, and improved the charge transfer and collection. In addition, Mn2＋and Cu2＋dopants rose to the level of the conduction band of pure Cd Se nanoparticles, which leads to the reduction of the charge recombination, enhances the lightharvesting efficiency, and improves the charge diffusion and collection. The results also were confirmed by the obtained experimental data of photoluminescence decay and electrochemical impedance spectroscopy.

水下搅拌摩擦加工CoCrFeNiMn高熵合金微观组织及力学性能

采用水下搅拌摩擦加工(UFSP)技术制备了细晶CoCrFeNiMn高熵合金,研究了细晶CoCrFeNiMn高熵合金的微观组织和力学性能。结果表明,经UFSP处理后,CoCrFeNiMn高熵合金试样的平均晶粒尺寸由母材的110μm细化至2.6μm,细晶内部出现大量孪晶,沿晶界析出少量BCC相。晶粒细化和BCC相的析出将细晶CoCrFeNiMn高熵合金的平均显微硬度由150 HV提高至310 HV,抗拉强度由349 MPa提高至938 MPa,分别达到母材的206%和269%。同时,孪晶协调了拉伸变形过程中试样应力的均匀分配,缓解了应力集中的出现。因此,细晶CoCrFeNiMn高熵合金表现出良好的伸长率。

基于原位拉伸的HTPB推进剂多尺度损伤演化分析

作为由填料和基体混合而成的复合材料,端羟基聚丁二烯(HTPB)推进剂的损伤主要涉及颗粒的破碎、基体的断裂以及粘结界面层的脱粘,为进一步探究其在外载作用下结构损伤和力学性能的演变,通过微CT、高速CCD相机,以及全原子分子动力学模拟,实现原位加载下推进剂多尺度损伤分析。结果表明,推进剂典型损伤过程起始于粘结界面层破坏,扩展于脱粘孔隙的增长,演化于孔隙的合并,加速于局部大变形的汇集,终止于基体的断裂;界面结合能和应力集中程度使得大粒径高氯酸铵(AP)颗粒最先脱粘,且孔隙率与应变呈现类指数函数关系;微观界面层牵引⁃分离曲线符合指数型内聚力模型,微观空隙的萌生与扩展破坏了其内聚性,而分子间距则影响了应力的演变。

燕山石化顺丁橡胶微观结构及性能

本文比较了燕山石化合成橡胶厂生产的镍系顺丁橡胶(YS-01)及钕系顺丁橡胶(YS-02)的顺式结构含量、分子量及分布指数的差异,并分析了微观结构参数对生胶性能、加工性能、硫化胶物理机械性能及动态力学性能的影响。结果表明:微观结构参数是影响顺丁橡胶宏观物理机械性能的关键因素,超高顺式结构及窄分子量分布指数有利于提高物理机械性能及动态力学性能。

Nb-10Zr合金的热变形行为、组织特征及热加工图

Nb-10Zr合金可作为特种薄膜功能材料应用于太阳能行业。深入理解Nb-10Zr合金的热变形行为是实现该应用的前提,然而国内目前围绕该合金热加工过程的材料加工性能相关研究十分匮乏。建立热材料加工图可实现描述指定条件下的材料可加工性,明确合金的变形窗口,指导材料加工工艺的制定和优化。选用均匀化处理后的电铸熔炼铸锭Nb-10Zr合金,采用热模拟试验机开展了热模拟压缩试验,并基于动态材料模型,通过对应变速率敏感系数m、功率耗散系数η和失稳系数ξ的数据分析,建立了材料不同温度和应变速率条件下的流变稳态区和非稳态区的热加工图。同时,通过微观组织观察,分析和验证了加工图的准确性。研究结果表明,Nb-10Zr合金铸锭在1300℃下经24 h均匀化处理后,未出现Zr元素偏聚所形成的缺陷,也未见裂纹、气孔、疏松和夹渣等其他类型的缺陷。铸态组织中存在粗大晶粒和细小晶粒,晶粒尺寸分别为500—800μm和20—30μm。在应变为0.4和0.6条件下,Nb-10Zr合金存在2个合理的热加工窗口,即变形温度1060—1100℃和应变速率0.01—0.04 s^(-1),以及变形温度1080—1100℃和应变速率0.3—1 s^(-1)。在不同变形条件下,变形后的Nb-10Zr合金均获得了细小的动态再结晶组织。在温度1100℃和应变速率0.01 s^(-1)下,合金晶粒尺寸为80—100μm;而在温度1100℃及应变速率1 s^(-1)下,合金晶粒尺寸为40—60μm。此外,通过不同工艺制备参数下合金组织形貌的观察,证明了所确定加工窗口的合理性。本研究为Nb-10Zr生产过程中的工艺选择和工艺参数的优化提供了理论指导。

Effects of dynamic ultra-high pressure homogenization on the structure and functional properties of casein

Dynamic ultra-high pressure homogenization(UHPH)is a novel high-pressure processing technique.In this study,the effects of dynamic UHPH on the structure and functional properties of casein were systematically investigated.It was found that the functional properties of casein changed with dynamic UHPH treatment,and the treatment at 150 MPa could significantly improve casein aqueous solubility,foaming and emulsifying properties.These functional improvements could be attributed to its structural changes,since the dynamic UHPH treatment could change the secondary structure,promote the interchange reaction between the disulfide bond and the sulfhydryl group,and increase the surface hydrophobicity.The obtained results could broaden the application of casein and provide ideas for the non-thermal processing of proteins.

全配方湿法连续混炼工艺的研究

针对炭黑与橡胶混炼难度大以及传统干法混炼工艺繁琐、产生粉尘污染等问题,研究全配方(补强填料包括炭黑和白炭黑)湿法连续混炼工艺。结果表明:全配方湿法连续混炼工艺分为4个阶段,分别为补强填料和小料水分散体的制备、炭黑母胶的制备、白炭黑母胶的制备、连续混炼;全配方湿法连续混炼工艺从初期补强填料和小料水分散体的研磨到后期的连续混炼均促进了炭黑在橡胶基体中的分散,使硫化胶的物理性能和动态力学性能比传统干法混炼工艺硫化胶明显提高,同时避免了干法混炼工艺的粉尘飞扬的问题,可实现胶料的清洁化、连续化生产。

顺式结构对窄分布稀土顺丁橡胶性能的影响

对自制的三个窄分布稀土顺丁橡胶试样进行了结构剖析,研究了其顺式-1,4-结构含量与性能的关系。结果表明,三个试样均为窄分布的顺丁橡胶(分子量分布指数在2.55~2.74),生胶门尼黏度在45±5,其中顺式-1,4-结构含量较高者略大;均具有较好的焦烧安全性且硫化速率相当,与炭黑结合得较好;均具有较好的物理机械性能、耐热老化性能、耐磨性和回弹性。随着顺式-1,4-结构含量的增加,试样的压缩生热和滚动阻力降低,耐动态疲劳性能略有下降。

Nanoparticle-filled ABC Star Triblock Copolymers:A Dissipative Particle Dynamics Study

The phase behavior of nanoparticle-filled ABC star triblock copolymers was investigated by dissipative particle dynamics simulation.Two typical structures,the three-color lamella and polygonal tiling structures,were selected to demonstrate the effect of filling the nanoparticle.Results showed that the filling effects were obvious on the lamellar structure but not on the tiling structure,where the high concentration of fillers can destroy the lamellar structures.The dynamic processes of nanoparticle filling were investigated for the lamellar and tiling structures,where three stages can be sorted by analyzing the system energies and chain conformations.Moreover,the mechanical properties were evaluated for the lamellar structures by exploring the interface tensions.The findings can help us understand the potential applications of microstructures based on complex block copolymers and nanoparticle mixtures.

浮筒辅助大型导管架结构整体拆除上浮过程动力响应特征研究

浮筒辅助大型导管架结构整体拆除作业是一个连续过程,作业过程中拆除系统的动力荷载及动力参数均会发生显著变化,传统基于某一稳定状态的结构动力响应分析方法不能准确预测拆除系统上浮过程中的动力响应。通过建立浮筒辅助大型导管架结构整体拆除上浮过程动态分析模型,对拆除系统上浮过程的动力响应特性进行研究。结果表明,整体拆除动态分析模型可以准确描述拆除系统上浮过程中浮筒及导管架浮力变化对上浮高度的影响机制,拆除系统上浮高度约为不考虑浮筒和导管架浮力变化时的90%。此外,浮筒辅助大型导管架整体拆除方法的动态稳定性较强,四级海况下拆除系统的最大偏移量仅为4.2 m,有较好的工程应用前景。

高氯酸铵/叠氮聚醚界面润湿黏附特性研究

为了提高叠氮聚醚类固体推进剂制备过程中基体与填料之间的润湿黏附性,改善料浆工艺性能,采用分子动力学计算方法,计算增塑剂类型、增塑比、键合剂类型对3,3-二叠氮甲基环氧丁烷与四氢呋喃共聚物(PBT)基体体系与AP(011)/(201)/(210)三个主要晶面结合能的影响,筛选能够有效提高高氯酸铵/叠氮聚醚类固体推进剂界面润湿黏附特性的增塑剂、增塑比和键合剂。结果表明,采用邻苯二甲酸二丁酯(DBP)作为增塑剂,BUNE作为键合剂,并选择增塑比为0.6时,高氯酸铵与PBT基体体系的结合能最高。通过接触角实验测试结果对计算结果进行验证,得到影响固体推进剂料浆中高氯酸铵与叠氮聚醚基体体系界面润湿黏附特性的主要因素及影响规律,为提高此类推进剂界面润湿黏附性与工艺性能提供指导。

湿法混炼技术制备环烷油增塑天然橡胶/白炭黑复合材料的性能

使用优选的乳化剂对增塑剂环烷油(NAP)进行乳化,制得均一稳定的NAP乳化液,采用湿法混炼技术,使用所得的NAP乳化液与天然胶乳和白炭黑(SiO_(2))浆液制备了NAP增塑的天然橡胶(NR)/SiO_(2)(NAP/NR/SiO_(2))复合材料,研究了NAP添加量对NAP/NR/SiO_(2)复合材料门尼黏度、物理机械性能、动态力学性能、SiO_(2)分散性、耐热空气老化性能和屈挠龟裂性能的影响。结果表明,NAP/NR/SiO_(2)复合材料的门尼黏度较NR/SiO_(2)复合材料显著降低,Payne效应明显减弱,而动态力学性能和加工性能则明显提升;NAP添加量为10份(质量)时,NAP/NR/SiO_(2)复合材料的综合性能达到最佳,其拉伸强度与NR/SiO_(2)复合材料相比略微下降,而扯断伸长率则有不同程度的上升;加入NAP后,NR/SiO_(2)复合材料的耐热空气老化性能和屈挠龟裂性能得到了改善。

Stress Transfer in Polymer Nanocomposites:A Coarse-grained Molecular Dynamics Study

In this work,we used coarse-grained molecular dynamics simulation methods to investigate the dispersion and percolation behavior of nanoparticles in polymer nanocomposite.Our aim was to investigate the correlation between particle arrangement in nearby layers and the stretching performance in composite systems by exploring the stress transfer processes during different stages of the stretching process.The machine learning technique of linear regression was used to quantitatively measure the efficiency of stress transfer between particles nearby.According to our research,increasing the strength of attraction can significantly enhance the particle dispersion and affect the percolation threshold.We also noticed a non-monotonic relationship between the interaction strength and the tensile stress.Additionally,we quantified the efficiency of nanoparticles and polymers at transferring stress to nearby nanoparticles.As a result,the stress value provided by each particle in the aggregation body is significantly increased by the aggregation behavior of nanoparticles.The non-monotonic behavior is caused by two variables:the rapid disintegration of aggregates and the improved stress transfer efficiency from polymers to nanoparticles.Significantly,it was discovered that the structural rearrangement of nanoparticles during stretching is the main reason that causes the yield-like behavior seen in poorly dispersed systems.

混炼工艺对白炭黑硅烷偶联反应程度及胶料性能的影响

研究混炼工艺对白炭黑硅烷偶联反应程度及胶料性能的影响。结果表明:随着白炭黑硅烷偶联反应程度的增大,胶料的门尼焦烧时间延长,硫化速度加快,小应变下的模量减小,Payne效应降低,填料与填料之间的相互作用减弱,70℃时的损耗因子明显减小,白炭黑在胶料中的分散均匀性提高;白炭黑硅烷偶联反应程度对混炼温度的敏感度较高,混炼温度对硅烷偶联反应程度的影响大于混炼时间的影响;当混炼温度为140~145℃、混炼时间为100~180 s时,胶料的物理性能最佳。通过计算白炭黑硅烷偶联反应的表观活化能,得到大配合试验胶料混炼工艺的最佳混炼时间。

FREQUENCY CONVERSION PROPERTY AND DYNAMIC PROCESS IN SONGS OF Mingming CICADA (Oncotympana maculaticollis Motsch)

In this paper, the frequency conversion property Df Mingming cicada songs is revealedand its dynamic process is given. In every single call the prelude and coda are mostly mono-timbre sounds whose dominantsounds are mainly the basic sound （BS） with the main peak frequency of about 4000 Hz. Themajority of the loud songs consist of 5--8 vari-toned syllables （VTS） "Weiying". The process of frequency conversion consists of the pre-mixed tone "Wei", with BS as thedominant sound, mid-mixed tone and "Ying" with the inferior sound （IS2） of 3--5 octave ofBS as the dominant sound. The inferior sound （IS1） of 1.5--2 octave of BS is a sound accom-paniment of low intensity. In the process of frequency couversion, although no obviouschange occurs in the contraction frequency of sounding muscle （SMc）, about 220±25 Hz,obvious differences occur in the twitch property of it. BS, IS1 and IS2 are respectively excitedby quasi-sine and saw-tooth twitches. The velocities of upward and downward sound accom-paniment

不同硫化体系天然橡胶胶料的动态性能研究

采用橡胶加工分析仪分析不同硫化体系对天然橡胶(NR)胶料动态性能的影响。结果表明:随着频率增大,混炼胶和硫化胶的储能模量(G')均增大,而混炼胶的损耗因子(tanδ)减小,硫化胶的tanδ增大;随着应变增大,混炼胶和硫化胶的G'均减小,而混炼胶的tanδ在应变大于20%时迅速增大,硫化胶的tanδ在应变为2%时出现峰值;随着温度升高,混炼胶的G'减小、tanδ增大,而硫化胶的G'增大、tanδ减小;不同硫化体系的硫化胶在3种扫描状态下,G'从大到小的顺序为半有效硫化体系、平衡硫化体系、普通硫化体系和有效硫化体系,单硫键、双硫键与多硫键保持一定的比例可获得较高的G'。