Experimental study on tensile deformation behaviors under room and elevated temperatures induced by microstructure inhomogeneity of ZK60 Mg with a longitudinal weld

The tensile tests of the extruded ZK60 Mg containing a longitudinal weld seam were carried out at room and elevated temperatures, and the effects of induced microstructure inhomogeneity on tensile deformation behavior was clarified. The results show that the deformation mode, dynamic recrystallization(DRX), texture evolution and mechanical properties are strongly affected by the longitudinal weld seam,temperature, and loading direction. The room temperature(RT) deformation of welding zone is controlled by the dislocation slips with the association of some twins, while twinning plays significant roles in the accommodation of c-axis strain of the coarse grains on matrix zone.The deformation at RT stretched along extrusion direction(ED) and transverse direction(TD) are controlled by basal slip/twinning and basal slip/prismatic slip/twinning, respectively. During high temperature tension, the dislocation cross slip of pyramidal slip is activated, and grain boundary sliding occurred in welding zone, leading to the superplastic behavior. With the increase of tensile temperature, the predominant DRX mode is transformed from continuous DRX to discontinuous DRX. Moreover, the basal poles of the grains spread from TD towards ED with the decrease of maximum pole intensity when stretched along ED, while non-basal textures are transformed to (10-10) fiber texture when stretched along TD. The slip-dominated flow is seen during RT tension along ED, while twinning becomes predominant during RT tension along TD. The fine grain structure causes the superior RT tensile properties along ED of welding zone with ultimate tensile strength of 315 MPa and elongation to failure of 13.8%. With the increase of tensile temperature, the slipping-dominated deformation is transformed into twinning-dominated, causing the decrease of strength and increase of elongation.

Spatial Inhomogeneity of Atmospheric CO_(2) Concentration and Its Uncertainty in CMIP6 Earth System Models

This paper provides a systematic evaluation of the ability of 12 Earth System Models(ESMs)participating in the Coupled Model Intercomparison Project Phase 6(CMIP6)to simulate the spatial inhomogeneity of the atmospheric carbon dioxide(CO_(2))concentration.The multi-model ensemble mean(MME)can reasonably simulate the increasing trend of CO_(2) concentration from 1850 to 2014,compared with the observation data from the Scripps CO_(2) Program and CMIP6 prescribed data,and improves upon the CMIP5 MME CO_(2) concentration(which is overestimated after 1950).The growth rate of CO_(2) concentration in the northern hemisphere(NH)is higher than that in the southern hemisphere(SH),with the highest growth rate in the mid-latitudes of the NH.The MME can also reasonably simulate the seasonal amplitude of CO_(2) concentration,which is larger in the NH than in the SH and grows in amplitude after the 1950s(especially in the NH).Although the results of the MME are reasonable,there is a large spread among ESMs,and the difference between the ESMs increases with time.The MME results show that regions with relatively large CO_(2) concentrations(such as northern Russia,eastern China,Southeast Asia,the eastern United States,northern South America,and southern Africa)have greater seasonal variability and also exhibit a larger inter-model spread.Compared with CMIP5,the CMIP6 MME simulates an average spatial distribution of CO_(2) concentration that is much closer to the site observations,but the CMIP6-inter-model spread is larger.The inter-model differences of the annual means and seasonal cycles of atmospheric CO_(2) concentration are both attributed to the differences in natural sources and sinks of CO_(2) between the simulations.

Analysis of inhomogeneity of solidified microstructure of continuous casting copper tubular billet based on factor analysis

The horizontal continuous casting process,the initial step in TP2 copper tubular processing,directly determines the microstructure and properties of copper tubular.However,the process parameters of the continuous casting characterize time variation,multiple disturbances and strong coupling.As a consequence,their influence on a casting billet is difficult to be determined.Due to the above issues,the common factor and special factor analysis of the factor analysis model were used in this study,and the casting experiment and billet metallographic experiment were carried out to diagnose and analyze the reason of the microstructure inhomogeneity.The multiple process parameters were studied and classified using common factor analysis,2 the cast billets with abnormal microstructures were identified by GT^(2) statistics,and the most important factors affecting the microstructural homogeneity were found by special factor analysis.The calculated and experimental results show that the principal parameters influencing the inhomogeneity of solidified microstructure are the primary inlet water pressure and the primary outlet water temperature.According to the consequence of the above investigation,the inhomogeneity of the copper billet microstructure can be effectively improved when the process parameters are controlled and adjusted.

一种基于非均匀磁化等离子体的修正Z-FDTD算法

对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。

利用非均匀正交激光选择谐波发射短量子路径

理论研究了谐波发射的量子路径在非均匀正交激光场下的调控机制.结果表明,在适当的双色激光偏振角和非均匀参数的组合下,不仅谐波截止能量有明显增大;谐波发射的短量子路径可以被单独选择出来对谐波连续区起到贡献作用.并且,该方案在长脉宽激光下依然适用.最后,利用谐波连续区可以获得脉宽在50 as的孤立阿秒脉冲.

不均匀地层中刚性桩复合地基变形及加固措施分析

刚性桩复合地基凭借其工后沉降小、施工周期短、整体稳定性强、社会经济效益高等优势,逐渐得到广泛应用,但也伴随着一些工程问题,如在不均匀地层下刚性桩复合地基路堤容易出现稳定性问题。本文针对不均匀地层下刚性桩复合地基典型工程案例展开研究,采用有限元软件建立三维模型,揭示改进方案前后不均匀地层下刚性桩复合地基的变形规律,研究3种加固方式对于刚性桩复合地基稳定性的增强效果。结果表明:不均匀地层下刚性桩复合地基会产生偏应力进而引起路堤差异沉降,结构稳定性较差,改进方案可以有效降低路堤沉降,提高结构整体稳定性,横梁加固可以有效提高刚性桩复合地基的水平稳定性。

矩阵奇异值分解与非齐次线性方程组系数矩阵的广义逆求解

非齐次线性方程组在多数实际工程反演问题中较为常见,对其进行有效地求解是解决实际反演问题的关键,本文通过对方程组系数矩阵进行奇异值分解,推导非齐次线性方程组系数矩阵的广义逆求解过程,给出具体的求解方法和实现步骤,使得求解算法更容易进行计算机编程.

水平非均匀场地中油气管道地震响应分析及试验

针对水平非均匀场地中埋地油气管道的地震响应,开展了埋地油气管道振动台试验和有限元模拟分析,研究了不同强度地震激励下埋地油气管道的应变和加速度响应,以及场地管周土体的加速度和位移响应规律。结果表明:研发的土箱能够满足试验的要求,试验方案合理可行;由于非均匀场地土体特性的不同,在地震激励下不同土体的动力响应不一致,进而会对管道不同区段形成不同的动力作用,加剧管道整体的动力响应;随着加载等级的提高,土体在振动过程中先是被压实,然后逐渐破坏,土体的非线性特征越来越明显,管道振动现象更为明显;相比于均匀场地条件,相同工况非均匀场地条件下的管道应变峰值和加速度峰值响应明显增大,表明非均匀场地条件下管道周围的土体破坏更为严重,管道的运动更加剧烈。建议在埋地管道抗震设计中要考虑非均匀场地条件和管周土体特性不一致对管道地震响应的增大影响。

浓度依赖的掺铕硅酸钇晶体的光学和自旋非均匀展宽

可移动量子存储器是实现长距离量子通信的一种可行方案,该方案需要量子存储介质拥有小时量级的存储寿命.同位素提纯^(151)Eu^(3+):Y_(2)SiO_(5)晶体是实现这一应用的重要候选材料,但其较宽的非均匀展宽对其光存储效率和自旋存储寿命都构成了显著限制.本文自主生长了不同掺杂浓度的同位素提纯^(151)Eu^(3+):Y_(2)SiO_(5)晶体,讨论了影响非均匀展宽的机制和未来进一步控制非均匀展宽的方法,为超长寿命可移动量子存储器的实现奠定了基础.

空间目标监视雷达大气折射修正技术研究

无线电波在大气层中传播时,大气介质的不均匀分布会对电波产生折射效应,从而影响雷达的探测精度。对于航天目标的雷达探测,影响无线电波的介质主要是电离层。本文利用实时TEC数据同化的方式,建立了电离层电子密度现报模型,实现了电离层折射率剖面的实时构建。在此基础上,利用射线描迹法完成了航天目标雷达探测的折射误差修正。结果表明,相对于单纯使用电离层经验模型-国际参考电离层(International Reference Ionosphere,IRI)模型,利用电离层同化现报模型建立的电离层折射率剖面可大大提高折射误差修正的精度。

考虑混凝土强度随机不均匀分布的重力坝动力损伤研究

重力坝所采用的大体积混凝土受到其固有特性、浇筑时的施工质量等影响容易导致强度的不均匀性。在目前的混凝土坝抗震分析中,一般将混凝土看成是一种强度分布均匀的材料,对于强度的不均匀性对大坝动力损伤的影响研究不多。基于混凝土塑性损伤理论及Weibull概率分布模型,采用Python语言对ABAQUS进行二次开发。在考虑混凝土塑性损伤的前提下,研究了混凝土强度随机不均匀分布对重力坝坝体和基岩损伤的影响。在计算中综合考虑了坝体和基岩的动力损伤、大坝与库水相互作用、无限地基辐射阻尼等,对比分析了坝体和基岩整体在各个不均匀度下震后损伤区域分布、坝体损伤面积比和损伤耗散能等动力响应,揭示了混凝土强度不均匀程度对大坝及基岩地震损伤的影响规律,研究结果可为重力坝相关的设计和施工提供参考。

资料非均一性对分析淮河流域平均气温变化趋势的影响

均一性长序列气象资料是研究气候变化的重要基础,评估资料非均一性对分析淮河流域平均气温变化的影响,对于准确理解农业、生态和水资源等领域对气候变暖的响应具有一定指导意义。本研究基于国家气象信息中心提供的淮河流域172个台站1961-2018年逐日平均气温均一化数据和观测数据,采用一元线性回归计算气温变化速率,并通过定义非均一性影响及其贡献率两个术语,定量评估气候资料非均一性对分析淮河流域平均气温变化趋势的影响。结果表明:淮河流域96个气象站点的平均气温序列表现出不均一性,占总站点数的55.8%。均一化前、后,区域年平均气温均显著上升,但非均一性导致增温速率被低估,非均一性影响为-0.015℃·10a^(-1),贡献率达到-6.6%;空间上,20.3%站点受到正影响,升温速率被高估,非均一性贡献率平均为21.3%;35.5%站点为负影响,升温速率被低估,贡献率平均为-43.6%。四季区域平均气温的非均一性影响差异较小,春、夏、秋、冬四季分别为-0.016℃·10a^(-1)、-0.014℃·10a^(-1)、-0.016℃·10a^(-1)和-0.015℃·10a^(-1);但由于夏季增温速度最慢,非均一性贡献率绝对值最大,贡献率为-40.0%,春、秋和冬季的贡献率分别为-4.7%、-8.0%和-4.3%;在春、秋和冬季,非均一性主要影响各站点的气温变化速率,但夏季有11.6%的站点在均一化前后出现了气温升降趋势的转变。

氩气中铝丝电爆炸空间形态不均匀现象及其抑制方法

铝丝电爆炸法制备纳米粉体具有低成本、高效率、产物纯度高且粒度分布可控等优势,其扩散阶段空间形态均匀性是影响纳米铝粉品质的关键因素。为此设计并搭建了铝丝电爆炸实验系统,可实现包括激光成像、分幅成像与辐射光谱分析的超快光学诊断。观测到铝丝电爆炸扩散阶段出现的等离子体晕层、“纺锤形”结构、“拉链状”结构、分层结构、局部热点、缺口、残留丝核等空间形态不均匀现象,并揭示了其产生原因包括氛围气体放电、径向非均匀汽化、热力学不稳定性、磁流体力学不稳定性。建立了基于自辐射图像的空间形态均匀性量化表征方法与判别准则。研究获得了气压与电流参数对阻性阶段及沉积能量特性的影响规律,并提出了空间形态不均匀性的抑制方法——增加气压与提高电流上升率,最终确定了可实现均匀电爆炸的参数选取方法。

深厚复杂海峡场地二维非线性地震反应特性

海峡地层常为深厚沉积盆地构造,海床微地形类型多样,海峡场地地震反应受微地形的影响显著。以跨琼州海峡通道剖面场地为研究对象,综合考虑海峡盆地构造、海床微地形和海床沉积土异质性,建立海床剖面二维精细化有限元模型;依据场址区域地震环境与历史地震活动性,选择Kik-net台网井下台阵基岩地震记录作为海床基岩输入地震动,考虑土的非线性滞回特性,模拟海峡场地的非线性地震反应。微地形效应和海床沉积土异质性对跨海峡场地地震反应的耦合影响显著,表现为盆地类共振现象、海床凹陷边缘和海床表面凸起处的反应加剧;与海峡场地基本频率接近的基岩地震动频率成分易于传播与放大;与海床水平向地震反应相比,海床地表微地形对其竖向地震反应的影响更为显著;水平向和竖向地震波传播的叠加效应会在海床表面产生面波,导致海床地表水平向地震反应放大。

非均匀流体的体积黏度:Maxwell弛豫模型

基于黏弹力学中的Maxwell弛豫理论,提出一种新颖的、可用于计算非均匀体积黏度的理论方法.该方法通过体相流体的黏性和弹性特征来计算体系的局域弛豫时间,进而结合体系的局域弛豫模量来计算体积黏度的非均匀分布.作为应用,计算了受限于平行狭缝中的Lennard-Jones流体的非均匀体积黏度,系统地研究了体密度、温度、缝宽和吸附强度等因素对体积黏度的影响.结果表明,上述因素的变化均可显著地调制狭缝中流体的体积黏度.其中,体密度和吸附强度的增大均有益于体积黏度的增强,而温度的升高将则会削弱其体积黏度.此外,毛细凝聚的发生也对受限流体的体积黏度具有显著的调制作用.

基于虚拟点的反应流Navier-Stokes特征边界条件及其应用

针对通风条件下大尺度加氢站事故模拟,从一维局部无黏特征分析出发,发展了使用虚拟点的三维反应流Navier-Stokes无反射特征边界条件,通过引入横向项和化学反应源项,有效消除了火焰面、亚声速流场与计算域边界相互作用时产生的非物理反射,实现了计算域边界处通风条件的无反射施加,提高了开放空间数值模拟的计算效率.通过开展51 m×51 m×10 m加氢站中长管拖车、加注机意外氢气泄漏扩散的数值模拟,给出了多种风况下可燃气云扩散结果,探究了通风条件及复杂环境对可燃气云发展规律的影响,对潜在危险区域进行了定量分析,并选取最危险氢气泄漏扩散结果开展高度非均匀气云爆炸的数值模拟,对不同设备处接收的超压和冲量进行了定量转化,完成了加氢站典型事故的风险评估.

障碍物排列方式对非均匀氢-空气混合物爆炸特性的影响

通过数值模拟研究了不同障碍物排列方式对非均匀氢-空气混合物爆炸火焰动力学的影响,模拟预测的爆炸特性参数均与实验结果吻合良好。模拟结果表明,预混火焰在管内经历了球形火焰、指形火焰、锥形火焰和絮状火焰4个阶段的演化过程。火焰经过障碍物时流场严重不稳定,导致火焰发生严重畸变。当障碍物两侧布置时,火焰最先到达管道出口,压力最快达到峰值。管道顶部障碍物能显著提高爆炸压力,与底部布置相比,障碍物在管道两侧布置和顶部布置时爆炸峰值压力分别增加了23%和74%。该研究可为氢安全规划和防爆提供理论指导。

基于量子Bernoulli噪声的一维时空非齐次开放量子游荡

用量子Bernoulli噪声方法研究一维时空非齐次开放量子游荡,给出该游荡的演化性质以及极限概率分布,并表明以局部基态作为初始态时,基于量子Bernoulli噪声的一维时空非齐次开放量子游荡具有与经典随机游荡相同的极限概率分布.

Tunable spectral continuous shift of high-order harmonic generation in atoms by a plasmon-assisted shaping pulse

We delve into the phenomenon of high-order harmonic generation within a helium atom under the influence of a plasmon-assisted shaping pulse.Our findings reveal an intriguing manipulation of the frequency peak position in the harmonic emission by adjusting the absolute phase parameter within the frequency domain of the shaping pulse.This phenomenon holds potential significance for experimental setups necessitating precisely tuned single harmonics.Notably,we observe a modulated shift in the created harmonic photon energy,spanning an impressive range of 1.2 eV.This frequency peak shift is rooted in the asymmetry exhibited by the rising and falling edges of the laser pulse,directly influencing the position of the peak frequency emission.Our study quantifies the dependence of this tuning range and the asymmetry of the laser pulse,offering valuable insights into the underlying mechanisms driving this phenomenon.Furthermore,our investigation uncovers the emergence of semi-integer order harmonics as the phase parameter is altered.We attribute this discovery to the intricate interference between harmonics generated by the primary and secondary return cores.This observation introduces an innovative approach for generating semi-integer order harmonics,thus expanding our understanding of high-order harmonic generation.Ultimately,our work contributes to the broader comprehension of complex phenomena in laser-matter interactions and provides a foundation for harnessing these effects in various applications,particularly those involving precise spectral control and the generation of unique harmonic patterns.

Research on the generation method of seawater sound velocity model based on Perlin noise

In the processing of conventional marine seismic data,seawater is often assumed to have a constant velocity model.However,due to static pressure,temperature difference and other factors,random disturbances may often frequently in seawater bodies.The impact of such disturbances on data processing results is a topic of theoretical research.Since seawater sound velocity is a difficult physical quantity to measure,there is a need for a method that can generate models conforming to seawater characteristics.This article will combine the Munk model and Perlin noise to propose a two-dimensional dynamic seawater sound velocity model generation method,a method that can generate a dynamic,continuous,random seawater sound velocity model with some regularity at large scales.Moreover,the paper discusses the influence of the inhomogeneity characteristics of seawater on wave field propagation and imaging.The results show that the seawater sound velocity model with random disturbance will have a significant influence on the wave field simulation and imaging results.