In-situ study of the microstructure evolution during tension of a Mg-Y-Zn-Al alloy processed by rapidly solidified ribbon consolidation technique

Mg-Y-Zn-Al alloys processed by rapidly solidified ribbon consolidation(RSRC)technique exhibit an exceptional mechanical performance indicating promising application potential.This material has a bimodal microstructure consisting of fine recrystallized and coarse non-recrystallized grains with solute-rich stacking faults forming cluster arranged layers(CALs)and nanoplates(CANaPs),or complete long period stacking ordered(LPSO)phase.In order to reveal the deformation mechanisms,in-situ synchrotron X-ray diffraction line profile analysis was employed for a detailed study of the dislocation arrangement created during tension in Mg-0.9%Zn-2.05%Y-0.15%Al(at%)alloy.For uncovering the effect of the initial microstructure on the mechanical performance,additional samples were obtained by annealing of the as-consolidated specimen at 300 and 400℃ for 2 h.The heat treatment at 300℃ had no significant effect on the initial microstructure,its evolution during tension and,thus,the overall deformation behavior under tensile loading.On the other hand,annealing at 400℃ resulted in a significant increase of the recrystallized grains fraction and a decrease of the dislocation density,leading to only minor degradation of the mechanical strength.The maximum dislocation density at the failure of the samples corresponding to the plastic strain of 10-25% was estimated to be about 16-20×10^(14)m^(-2).The diffraction profile analysis indicated that most dislocations formed during tension were of non-basal and pyramidal types,what was also in agreement with the Schmid factor values revealed independently from orientation maps.It was also shown that the dislocation-induced Taylor hardening was much lower below the plastic strain of 3% than above this value,which was explained by a model of the interaction between prismatic dislocations and CANaPs/LPSO plates.

The Supersolvable Order of Hyperplanes of an Arrangement

This paper mainly gives a sufficient and necessary condition for an order of hyperplanes of a graphic arrangement being supersolvable. In addition, we give the relations between the set of supersolvable orders of hyperplanes and the set of quadratic orders of hyperplanes for a supersolvable arrangement.

Interlingual Interference in the English Language Word Order Structure of Chinese EFL Learners

This paper will focus on some common word order errors that Chinese students make.The author will present a body of contrastive material to illustrate what specific word order errors are in collected writing samples of Chinese students.Then the er⁃rors will be broken down into certain error types and be analyzed in depth.At the end of this paper,each error type occurrence rate will be calculated and the statistics will be represented in a pie chart.The paper finds out interlingual interference leads to these common errors by Chinese English language learners.

Magnetization arrangement of hard magnetic phases and mechanism of magnetization and reversal magnetization of nano-composite magnets

During the process of directional solidification,laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets,or die-upsetting of nano-composites,the arrangements of the easy-magnetization-axes of the hard magnetic phases(Nd2Fe14B,SmCo5 or Sm2Co17 type)in their designed directions have been studied.In Fe-Pt nano-composite magnets,attempts have been taken to promote phase transformation from disordered,soft magnetic A1 to ordered,hard magnetic L10 FePt phase at reduced temperatures.The dependence of the magnetization and reversal magnetization processes on the microstructures,involving the morphology and three critical sizes of particles of the FePt nano-composite magnets,are summarized. With the decrease of the nominal thickness of the anisotropic FePt film epitaxially grown on the single crystal MgO(001)substrate, the reversal magnetization process firstly changes from full domain wall displacement to partial magnetic wall pinning related to the morphology change,where the coercive force increases abruptly.The reversal magnetization process secondly changes from magnetic wall pinning to incoherent magnetization rotation associated with the particles being below the first critical size at which multi-domain particles turn into single domain ones,where the coercive force is still increased.And the reversal magnetization mode thirdly changes from incoherent to coherent rotation referred to the second critical size,where the increase of the coercive force keeps on.However,when the particle size decreases to approach the third critical size where the particles turn into the supperparamagnetic state,the coercive force begins to decrease due to the interplay of the size effect and the incomplete ordering induced by the size effect.Meanwhile,due to the size effect,Curie temperature of the ultra-small FePt particles reduces.

Evaluating Chinese College Students' English Compositions:Different Writing Corrective Feedbacks between a Chinese Teacher and a Foreign Teacher & the Attitudes of College Students

The study aims to uncover the differences between a Chinese writing teacher and a foreign writing teacher in evaluating Chinese college students' English compositions and find out students' attitudes towards different kinds of feedbacks. The data collection method, sample analysis and questionnaire have been implemented to probe for the results. The results are supposed to give some suggestions to the English writing class in Chinese universities.

有序化砂轮磨削筋条表面中力对表面的效应

为了提高筋条减阻表面的加工质量,对磨粒有序化砂轮的磨削力对工件表面几何形状的影响规律进行研究。首先,根据筋条减阻表面的参数,设计能够实现筋条减阻表面加工的错位排布砂轮;其次,建立了筋条减阻表面磨削过程的简化模型,并基于有限元对工件表面形貌进行了力学仿真;最后,研究磨削速度、磨削深度、磨粒角度、排布参数等对筋条表面几何形状的影响规律,综合探讨磨削力和表面形貌之间的关系。结果表明,在磨削速度增大时,工件表面材料的隆起变形高度随着磨削力的减小而增大;在磨削深度增大时,材料的隆起变形高度随着磨削力的增大而增大;在磨粒角度增大时,材料隆起变形高度随着磨削力的增大,先增大后减小;在磨粒排布参数增大的过程中,材料隆起变形高度随着磨削力的增大而增大。

复调与回声:从《芙蓉镇》看新时期乡土小说的饮食书写策略

《芙蓉镇》作为20世纪80年代乡土伤痕小说的代表作,借助在场性观照与具身化解读的方式,直观且深刻地描绘出原乡社会在不同历史时期的秩序结构与发展态势。饮食书写是文学作品中最为常见的书写方式,以饮食书写隐喻社会生活也是常被使用的创作手法。从饮食书写的角度窥探这一时期以《芙蓉镇》为代表的乡土小说,能够梳理出关于乡土秩序更迭的“复调”与“回声”式书写策略;通过饮食书写展露乡村社会在传统伦理秩序与革命秩序不断更迭中的呈现状态,也寄寓着世俗伦理价值向度中对于原乡秩序肯定与颂扬的态度。

界限估计方法在高压配电系统地震易损性分析中的应用研究

配电系统中某一单体设备的抗震性能评估结果难以表征配电系统整体的抗震能力,高压配电系统的抗震安全性评估研究亟需开展。目前,用于结构系统可靠性评估的界限估计方法在土木工程结构领域得到应用和推广,此方法在电力系统抗震性能概率性评估中的应用较少。基于此,文中以某实际工程高压配电系统为例,采用一阶界限估计方法和二阶界限估计方法对配电系统的易损性进行研究。研究结果表明:该配电系统的超限概率大于系统中任一单体设备的超限概率;基于一阶界限估计方法求解的配电系统易损性曲线界限区间较宽,不利于工程的实际应用;基于二阶界限估计方法求解的易损性曲线界限区间窄,但下界对系统中单体设备的超限排列顺序较为敏感,在应用此方法时应特别注意。

五级流水线RISC-V微处理器的研究与设计

针对嵌入式领域低开销、高性能的应用需求,设计一种基于RISC-V开源指令集架构的32 bit微处理器。采用顺序发射、顺序执行、乱序写回的五级流水线结构,实现了整型和乘除法指令集模块组合。为了应对流水线冲突,处理器采用动态分支预测技术,设计数据相关性控制和乱序写回机制。使用Verilog进行设计并采用先进高性能总线(AHB)和高级外围总线(APB)为互联总线协议构建片上系统(SoC)。在仿真环境下通过编写RV32IM汇编指令测试程序,完成对处理器逻辑功能的验证。在Vivado综合工具下添加时序约束和物理约束条件后,对处理器代码进行逻辑综合并分析处理器硬件资源利用情况,最后将综合生成的码流文件下载到Xilinx Artix-7(XC7A200T-2FBG484I)现场可编程门阵列(FPGA)开发板中并以50 MHz的主频运行CoreMark程序,CoreMark跑分达到3.25 CoreMark/MHz。实验结果表明,处理器性能跑分与ARM Cortex-M3系列处理器基本持平,在各项技术对比指标相同的前提下,所设计的处理器跑分均优于RISC-V处理器对比项。所设计的处理器逻辑功能正确,使用较低的硬件开销,取得相对较高的性能指标,适用于成本受限的高性能嵌入式应用领域。

空间书写:赵树理《刘二和与王继圣》的乡村秩序想象

赵树理在小说《刘二和与王继圣》中通过对三个乡村空间的聚焦,呈现了中华人民共和国成立前农村问题的复杂现实:“三角坪”的童稚游戏影射了成人世界的不平等关系;关帝庙的“说理”揭露了村级政治体系存在的弊端;合作社的“翻身”指向了改革不彻底而形成的利益不均等分享。赵树理在对三个空间书写的同时,又将寻找“农民”自主、自觉的政治可能性作为变革力量孕育融入其中。赵树理关于乡村秩序的文学想象与过渡时期的乡村历史现实产生了割裂,但他没有采取简单的处理方式去解决,而是终止了故事的发展,因而《刘二和与王继圣》呈现出一种“未完成”的状态。这种“未竟”之态非但没有成为桎梏,反而催生了赵树理的思想“缠斗”,促使他投身于社会现实的实践中,同时也推动了赵树理在创作思想上的一次飞跃。

互感器二次回路施工验收常见问题分析及防范

对某火电厂施工调试期间发生电压互感器一次设备布置差异导致相序相反、一次电压与二次电压相位相反,及电流互感器不同准确级的二次绕组使用错误,不同零序电流互感器对应负荷接线错误等问题,提出了比对设备出厂图纸与设计院图纸差异,规范二次回路接线,设备带电后进行电压与电流暂态、稳态幅值相位检查,对比直流电阻值及伏安特性参数等施工注意事项及验收的方法,有效确保了回路接线的正确性。

Preparation, stability and two-dimensional ordered arrangement of gold nanoparticles capped by surfactants with different chain lengths

Gold nanoparticles modified with C10NH2, C12NH2, C16NH2 and C18NH2 respectively have been prepared by the reverse micelle method. Nanoparticles stability and their two-dimensional (2D) ordered arrangement were studied by UV-Vis absorption spectra and LB technique. The factors, such as the chain length and the size distribution of particles, which affect the 2D ordered arrangement formation, are discussed. Experimental results show that the longer the chain length of surfactants capping the gold nanoparticles, the more stable the nanoparticles, and the more ordered 2D arrangement of gold nanoparticles.

ON THE VALENCE SEQUENCE OF AN ORDERED TREE

In computer science one often encounters ordered trees. In Ref. [1] an algorithm is designed to generate all binary trees with n vertices. In [2] there is a slightly different approach to binary trees and ordered trees in general. In these and other papers sequences of integers related to ordered trees are of importance.

Out-of-Order Execution in Sequentially Consistent Shared-Memory Systems:Theory and Experiments

Thaditional implementation of sequential consistency in shared-memory systems requires memory accesses to be globally performed in program order. Based on an event ordering model for correct executions in shared-memory systems, this paper proposes and proves that out-of-order execution does not influence the correctness of an execution providing certain condition is met. Simulation results show that out-of-order execution proposed in this paper is an effective way to improve the performance of a sequentially consistent shared-memory system.

“布局”的结构要件、艺术功能和审美原则——亚里士多德散文写作理论研究(三)

亚里士多德系统整理了古希腊早期修辞学中的结构学说,重新阐释了散文的布局艺术。在政治、典礼、诉讼三种演说类型中,说明和证明是布局艺术不可缺少的两个结构要件,序论、结束语等部分可酌情取舍。布局的艺术功能是通过精心安排结构来提高论证质量、展示演说者品性、激发听众情感共鸣,从而实现吸引和说服。亚里士多德主张整体论和有机论,要求散文布局完整、严密,这体现了他的篇章意识,也是修辞术有别于论辩术的重要特征。20世纪,古希腊布局艺术精神回响在文学结构主义思潮中,重返现代学术。亚里士多德将诗学与修辞学并举,可以引发对散文研究和现代写作学发展的重新思考。

循环赛制中不同编排方法的比较研究

循环赛制是体育竞赛中广泛使用的一种竞赛制度,不同的竞赛秩序编排结果可能对体育竞赛的公平性造成一定的影响。本文采用文献资料、实验推演、逻辑分析等方法对目前循环赛制编排中不同轮转编排秩序的优、缺点进行比较分析。结果表明:固定轮空“0”号位在四个“角位”是解决奇数参赛者(队)轮转编排过程中某一参赛者(队)多次对阵上一轮轮空参赛者(队)这个“轮空问题”的关键;轮转方向不能解决“轮空问题”,逆时针轮转编排结果优于顺时针轮转编排;“贝格尔”编排法中,主客场编排优点和创新编排法中推进比赛进程优点相结合,可以获得一种比较完善的循环轮转秩序编排方法,适合于各种循环赛制使用。

有序排列硬质合金颗粒增强铁基复合材料的研究

目的研究有序排列硬质合金颗粒作为增强相对高铬铸铁组织与性能的影响。方法采用对WC-Co硬质合金颗粒进行预先排布固定的方式,结合离心铸造制备了有序排列硬质合金颗粒增强高铬铸铁复合材料。通过相组成和显微组织的演变分析复合材料的形成过程,并对摩擦磨损性能进行研究。结果制备的复合材料实现了硬质合金颗粒在基体上的有序排列及与基体的冶金结合。存在由颗粒表层熔解区和碳化物散布区构成的梯度过渡层,硬度也呈梯度变化,有利于降低应力集中。在载荷为100 N时,复合材料的体积磨损量相较于高铬铸铁降低了57.6%;载荷为150 N时,复合材料的体积磨损量相较于高铬铸铁降低了69.2%,硬质颗粒的有序排列可减缓磨粒磨损和剥层磨损。结论通过对增强颗粒进行有序排列,可提高复合材料性能的可设计性,抑制了过度反应,并促进梯度过渡层的形成,同时还可减少硬质颗粒的用量,改善复合材料的韧性。有序排列硬质合金颗粒可以有效提高高铬铸铁的硬度和耐磨性。

磨粒有序化砂轮滚磨外圆筋条表面的研究

为了在外圆零件表面加工出用于表面减阻的结构化筋条,基于滚齿加工原理,提出利用磨粒有序化(工程化)砂轮滚磨外圆筋条表面的加工方法。根据筋条表面的特征,对外圆筋条表面进行设计;利用筋条表面的特征参数设计了磨粒有序化砂轮,并给出实现滚磨外圆筋条表面的条件;对滚磨过程进行仿真分析,获得了磨削相关参数对筋条表面形貌的影响规律。研究结果表明:磨粒有序化砂轮能够实现对外圆筋条表面的磨削,筋条表面的主要特征为深宽比,选用合适的磨削用量和排布参数可以满足减阻功能深宽比筋条表面的滚磨。

Ni-Cr-B-Si合金预连接金刚石磨粒及其阻焊的研究

利用Ni-Cr-B-Si合金预连接金刚石,然后阻焊焊接在基体上,旨在为有序排布的金刚石工具磨粒的精确固定或焊补修复工具损毁磨粒服务。利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、拉曼光谱仪对处理后的金刚石磨粒进行表征,采用磨削试验评定其磨削性能。研究表明:在1050℃保温60 s的预连接工艺下,金刚石表面生成Cr7C3和Cr3C2两种碳化物;阻焊后金刚石磨粒仍然棱角分明,预连接层与基体结合良好;阻焊金刚石所受最大压应力为0.46 GPa,对比样钎焊金刚石所受最大压应力为0.13 GPa,阻焊金刚石受到的把持力更强;磨削试验显示,阻焊金刚石对加工材料的去除量高于钎焊金刚石,表现出更好的磨削性能。

磨粒叶序排布砂轮磨削筋条表面力的表面效应

为了探索筋条表面磨削过程中,磨粒叶序有序化砂轮的磨削力对工件表面几何形貌的影响规律,首先,根据筋条减阻表面的特征参数,设计能够实现筋条减阻表面加工的磨粒叶序排布砂轮;其次,建立筋条减阻表面磨削过程的简化模型,对工件表面形貌进行力学仿真;最后,研究磨削速度、磨削深度、磨粒角度、排布参数等对筋条表面几何形状的影响规律。结果表明,磨削速度增大时,工件表面材料的隆起变形高度随磨削力的减小而增大;磨削深度增大时,材料的隆起变形高度随磨削力的增大而减小;磨粒角度增大时,材料隆起变形高度随磨削力的增大,先增大后减小;而在叶序系数增大过程中,材料隆起变形高度随磨削力的增大而增大。