Crystal structures, phase relationships, and magnetic phase transitions of R_5M_4 compounds (R = rare earths, M = Si, Ge)

Our recent studies of the crystal structures, phase transitions, and magnetic properties of intermetallic compounds RsM4 （R = rare earths; M = Si, Ge） are reviewed briefly. First, crystal structures, phase relationships, and magnetic prop- erties of several 5：4 compounds, including Nd5 Si4-xGex, Pr5 Si4_xGex, Gds-xLaxGe4, La5 Si4, and Gd5 Sn4, are presented. In particular, the canted spin structures as well as the magnetic phase transitions in PrsSi2Ge2 and PrsGe4 investigated by neutron powder diffractions and small-angle neutron scattering are reviewed. Second, the crystal structures and magnetic properties of the most studied compounds Gds（Si,Ge）4 are summarized. The focus is on the parent compound GdsGe4, which is an amazing material exhibiting magnetic anisotropy, angular dependent spin-flop transition, metastable magnetic response, Griffiths-like phase, thermal effect under pulsed fields, antiferromagnetic and ferromagnetic resonances, pro- nounced effects of impurities, and high-field induced magnetic transitions.

PHASE RELATIONSHIPS IN R-Fe PSEUDOBINARY SYSTEM (R=Dy_(0.65)Tb_(0.25)Pr_(0.1))

The phase relationships of R-Fe pseudobinary system(R=Dy0.65Tb0.25Pr0.1) have been determined using optical microscopy,X-ray diffraction,EPMA and DTA techniques.This system contains one eutectic reaction and four peritectic reactions.The four intermetallic compounds are(Dy,Tb,Pr)Fe2,(Dy,Tb,Pr)Fe3,(Dy,Tb,Pr)6Fe23 and(Dy,Tb,Pr) 2Fe17 The homogeneity regions of these compounds shift towards rare earth-rich side of the stoichiometric composition except(Dy, Tb,Pr) 2Fe17.

Phase Relationship in (Dy_(0.65)Tb_(0.25)Pr_(0.1))Fe_x Alloys (1.6≤x≤2.1)

The microstructure and phase relationship of (Dy0.65Tb0.25Pr0.1)Fex alloys in the composition range of 1.6≤x≤2.1 were investigated using optical microscopy, X-ray diffraction , DTA and EPMA techniques. The variations of microstructure and lattice parameter with the iron content,the effect of heat treatment on the microstructure and the phase relationship have been studied.The phase relationship in the vicinity of the Laves phase is proposed

Phase Relationship in Nd_2(Fe_(1-x)Ni_x)_(14) B and Pr_2(Co_(1-y)Ni_y)_(14)B Pseudo-ternary Compounds

The melting behavior,solid state phase transformation and structure of pseudo-ternary compounds Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B were studied using differential thermal analysis,optical microscopy X-ray diffraction,and electron probe micro-analysis techniques.At high temperature,eutectoid decomposition R_2(Ni,M)_(17)→R(Ni,M)_5+x-Ni(M) takes place in these two pseudo-ternary compounds,in the composition range x=0.6～1.0 and y=0.3～1.0,respectively.When x(or y)≤0.2,both Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B are single phase tetragonal.The phase constitutents of these two systems at room tempera- ture are similar in the composition range 0.6≤x(or y)≤1.0.

Phase Relationship at Subsolidus Temperature of MgO-MgAl2O4-ZrO2 Subsystem

Three groups of cylinder specimens(φ10 mm×10 mm)with 20%,30%and 40%(by mass,the same hereinafter)of ZrO2,were prepared using analytically pure MgO,Al2O3 and ZrO2 powders as the starting materials.The specimens were fired at 1600℃for 5 h,1700℃for 0 h and 1800℃for 7 h,respectively.The microstructure of the MgO-MgAl2O4-ZrO2 subsystem was studied by FESEM.The results show that(1)in the temperature range of 1600-1700℃,solid phase reactions happen in the MgO-MgAl2O4-ZrO2 subsystem,leaving three phases:periclase,spinel and ZrO2(solid dissolving with Mg2+)co-existing;spinellization affects the densification;(2)the specimen with 40%ZrO2 fired at 1800℃has heterogeneous melting microstructure;some areas form typical ternary eutectic MgO-MgAl2O4-ZrO2 with composition of MgO 35.2%-37.2%,Al2O324.2%-26.6%,and ZrO237.2%-39.8%.

Microstructural characteristics of intermetallic phases in spray-deposition Al-8.5Fe-1.3V-1.7Si alloy

Analysis electron microtechnique (AEM) and high resolution electron microtechnique (HREM) studies were conducted on a spray deposition Al 8.5Fe 1.3V 1.7Si(mass fraction, %) alloy to determine the characteristics of the intermetallic phases. The results show that the striking characteristics of the microstructures in as deposited and as extruded alloys indicate the presence of a large amounts of homogeneously distributed fine particles and a few coarse particles, while small amount of eutectics consisted of α (Al) and α AlFeSi are found in local zone in as deposited alloy. The fine particle is identified to be bcc α AlFeSi phase, and the coarse particles are monoclinic α Al 13 Fe 4 equilibrium phase, bcc α AlFeSi phase and newly found hexagonal h AlFeSi metastable phase. In α Al 13 Fe 4 , stacking faults on (100) and (001) plane and microtwin on (100) twinning plane are frequently observed. The extra reflection spots in α AlFeSi reflection pattern can be induced by α AlFeSi superstructure. The hexagonal metastable phase transforms to bcc phase, and the compositions of two phases are very similar. A close crystallographic orientation relationship between hexagonal and bcc phases are determined, and HREM image shows that the interface between them is coherent. [

Characterization of Phases in an As-cast Copper-Manganese-Aluminum Alloy

Copper-manganese-aluminum （CMA） alloys, containing small additions of Fe, Ni, and Si, exhibit good strength and remarkable corrosion resistance against sea water. The alloys are used in as-cast condition, and their microstructure can show wide variations. The morphology, crystallography and composition of the phases presented in an as-cast （CMA） alloy of nominal composition Cu-14%Mn-8%Al-3%Fe-2%Ni were investigated using optical, electron optical, and microprobe analytical techniques. The as-cast microstructure consisted of the grains of fcc α and bcc β-phases alongwith intermetallic precipitates of various morphologies. The room temperature microstructure exhibited four different types of precipitates inside the α-grains： the ＇large＇ dendritic-shaped particles and the cuboid-shaped precipitates, which were rich in Fe and Mn and had an fcc structure, while the ＇small＇ dendritic-shaped particles and the globular precipitates were based on FeaAI and had DO3 structure. These four different morphologies of intermetallic precipitates exhibited discrete orientation-relationships with the α-matrix. The β-grains only contained very small cuboid shaped precipitates, which could only be resolved through transmission electron microscopy. These precipitates were found to be based on Fe3Al and had the DO3 structure.

On the Relationship between Atmospheric Carbon Dioxide and Global Temperature

The study of dynamic relationships between the atmospheric carbon dioxide and the Earth’s global temperature in the current changing climate supported the notion that the trend in the global temperature followed the trend in the atmospheric CO2 before the climate hiatus that started in the beginning of the 21st century. During the hiatus period, the heat trapped by the atmospheric CO2 is going mostly to the ocean. This conclusion is supported by comparison of the CO2 trend with the trend in the ocean heat content. The phase relationships between the CO2 and temperature are more complicated after the removal of the trends. The phase relationships are chaotic on time scales shorter than the annual time scale. During 1986-2008, the atmospheric CO2 changed in an-ti-phase with the global temperature. The phase relationship reversed in 1979 and after 2010. The atmospheric CO2 was in-phase with the global temperature on the El Nino time scale (2.3 - 7 years) except during very strong El Nino years in 1991-1999 when CO2 led the global temperature.

A STUDY OF THE T_1' PHASE IN THE Al-2.6Li-1.3Cu ALLOY

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Two new approaches for image registration based onspatial-temporal relationship

How to improve the probability of registration and precision of localization is a hard problem, which is desiderated to solve. The two basic approaches (normalized cross-correlation and phase correlation) for image registration are analysed, two improved approaches based on spatial-temporal relationship are presented. This method adds the correlation matrix according to the displacements in x- cirection and y- directions, and the registration pose is searched in the added matrix. The method overcomes the shortcoming that the probability of registration decreasing with area increasing owing to geometric distortion, improves the probability and the robustness of registration.

基于AKNN异常检验与ADPC聚类的低压台区拓扑识别方法

低压台区拓扑信息的准确记录是进行台区线损分析、三相不平衡治理等工作的基础。针对目前拓扑档案排查成本高且效率低的问题,提出一种基于自适应k近邻(adaptive k nearest neighbor,AKNN)异常检验和自适应密度峰值(adaptive density peaks clustering,ADPC)聚类的低压台区拓扑识别方法。该方法利用动态时间弯曲(dynamic time warping,DTW)距离度量低压台区用户间电压序列的相似性,通过AKNN异常检验算法检验并校正异常的用户与变压器之间的关系(简称“户变关系”),在得到正确户变关系的基础上,采用ADPC聚类算法对台区内用户进行相位识别;最后,通过实际台区算例分析验证了该方法不需要人为设置参数,能有效实现低压台区的拓扑识别,具有较高的适用性与准确性。

基于极值外推的特种车辆疲劳耐久性多轴载荷谱编制

非道路特种车辆服役载荷谱是整车结构耐久性的关键,为此提出基于极值外推的特种车辆疲劳耐久性多轴服役载荷编制方法。考虑到多轴载荷谱外推时的载荷通道之间具有相位关系,开展以临界平面损伤参量为基础的多轴载荷等效合成研究;构建极值超出量服从广义Pareto分布的多轴外推模型。利用等效合成载荷谱进行载荷外推,将基于等效合成系数获取的外推量分配到每个载荷通道上,实现考虑相位关系的多轴载荷外推。以典型工况下特种车辆的轮端六向力信号为研究对象进行多轴外推,并对比外推前后的载荷谱与采集载荷谱通道之间的相位关系、穿级计数、雨流计数和功率谱密度。研究结果表明:基于极值外推的特种车辆整车疲劳耐久性多轴载荷编制,可以实现在相同典型工况下多轴载荷谱的有效预测。

基于帕累托前沿关系求解约束多目标优化问题

为解决约束多目标优化问题中的平衡约束满足与目标函数优化以及可行域复杂等挑战,提出了基于不同帕累托前沿关系的分类搜索方法。提出一种双种群双阶段框架:进化一个辅助种群Pa和一个主种群Pm,并将进化过程分为学习阶段和搜索阶段。学习阶段,种群Pa向UPF(unconstrained Pareto front)进行搜索,而种群Pm向CPF(constrained Pareto front)进行搜索,旨在探索UPF与CPF之间的关系;完成学习后,对不同问题的UPF与CPF关系进行分类,以指导后续搜索策略;在搜索阶段,根据不同的分类关系,调整种群Pa的搜索策略,旨在使种群Pa为种群Pm提供更有效的辅助信息。基于此算法框架,对不同类型约束多目标优化问题的帕累托前沿关系进行了分类,实现了对CPF更有效的搜索。实验结果表明:所提算法与其他7种先进的约束多目标优化算法相比具有更显著的性能优势。通过学习与利用UPF与CPF的关系,能够选择更合适的搜索策略去应对具有不同特性的约束多目标优化问题,以获得更具优势的最终解集。

Nd^(3+)掺杂钙钛锆石(Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2))相变行为的研究

为研究钙钛锆石对放射性元素Am^(3+)的稳定固化作用,以Nd^(3+)为Am^(3+)的模拟元素,系统研究了高温固相法制备Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2)时,Nd^(3+)异价取代钙钛锆石晶格中Ca^(2+)位(0≤x≤1.0)所导致的相态演变行为。合成Ca_(1-x)Nd_(x)ZrTi_(2)O_(7+x/2)的XRD、Raman、BSE和EDS测试结果表明:钙钛锆石(Zirconolite)晶格对Nd^(3+)离子的固溶量可达70%(x=0.7),可有效实现对Am^(3+)模拟元素Nd^(3+)离子的固化。但随着Nd^(3+)掺杂量(x≤0.3)增加,Zirconolite-2M晶格中O^(2-)和Nd^(3+)的无序化程度逐渐增加、(Ca/Nd)-O键长逐渐变小,直至(x=0.4)引起Zr^(2+)、Ti^(4+)附近的O^(2-)配位数发生改变(ZrO7→ZrO8、TiO5→TiO6),Zirconolite-2M晶格结构开始向Zirconolite-4M转变。x=0.5时,陶瓷体完全转变为Zirconolite-4M晶格且O^(2-)和Nd^(3+)有序度重新变高、Ti—O键长增加;直至x=0.6、x=0.7时,陶瓷体仍为单一Zirconolite-4M结构,但晶格中O^(2-)和Nd^(3+)的有序度又逐渐降低,以至于在x=0.7陶瓷体亚晶格中微量Ca^(2+)、Zr^(4+)、Nd^(3+)离子占位转变为烧绿石(Pyrochlore)结构。而在0.8≤x≤0.9范围内,Zirconolite-4M结构完全消失,陶瓷体为多相共存状态(Pyrochlore、ZrTiO_(4)和Nd2(TiZr)_(4)O_(11)物相)。Nd^(3+)完全取代Ca^(2+)位(x=1.0)时,陶瓷体变为单一Nd2(TiZr)_(4)O_(11)固溶体相。陶瓷体晶粒的BSE和EDS分析证实了这种相变规律。

基于图转换和迁移学习的低压配电网户变关系和相位识别方法

为进一步提高低压配电网户变关系和相位识别的准确性,提出一种基于图转换和迁移学习的低压配电网户变关系和相位识别方法。首先,引入了基于格拉姆角场的图转换方法实现用电数据的二维化,以更好地发现一维时序用电数据间的差异性;然后,针对低压配电网用户数据稀缺、获取途径有限、样本数量较少等问题,基于迁移学习利用预训练好的参数权重,构建了适合户变关系和相位识别的深度学习模型。通过实验验证,所提模型在户变关系识别和相位识别中的准确率较主流方法均有所提升,拥有更好的稳定性。

文化的时相观照

人类生活世界的时间是社会化的亦即文化性的时间。其中,时间与文化相互建构,形成时间的文化规范与文化的时间秩序。因此,社会文化生活、文化现象有了时间性的样态和特征,谓之“文化时相”。它表明社会文化在不同的时间秩序、时间条件下具有不同的状态、特质,亦即不同形式的文化生活具有不同的时间范式。文化与时间的这种互规定机制,既体现在主体认知的理性跃升与修为的人文化成中,又展示于文化传承的遗传性获得与获得性遗传的交互作用中。对文化时相这些重要样态、机理,从文化-时间的交互建构关系中做出学理解析,是深化对于时间文化学和文化时间论学术探讨的重要致思之路。

长江中游城陵矶—武汉河段稳定航深计算方法改进

航道稳定航深计算是充分利用航道水深资源的前提条件,改进稳定航深的计算过程对估算航道水深潜力有重要的意义。为计算长江中游城陵矶—武汉河段航道最大稳定水深,改进了稳定航深估算法中的河相关系参数、水深修正系数及分流比计算过程,同时综合考虑分汊河段和非分汊河段的稳定航深,最后确定了城陵矶—武汉河段在不同流量、不同河宽下的稳定航深。研究结果表明:(1)通过构建城陵矶—武汉河段流量Q与河相系数α、形状系数k、河相指数β、河宽B的经验关系,可简化改进稳定航深估算法的稳定航深计算过程。(2)城陵矶—武汉河段在98%设计通航保证率流量下,150、200、250 m航宽尺度下基于自然禀赋的稳定航深分别为5.98、5.64、5.30 m;在20 000 m^(3)/s流量下,150、200、250 m航宽尺度下的稳定航深分别为12.56、11.89、11.22 m;在30 000 m^(3)/s流量下,150、200、250 m航宽尺度下的稳定航深分别为16.81、16.16、15.49 m。

基于电子鼻技术的臭灵丹草指纹图谱建立及谱效关系研究

目的:基于超快速气相电子鼻技术,建立15批臭灵丹草饮片的气味指纹图谱,结合谱效相关性分析,筛选与抗氧化活性相关的成分。方法:使用超快速气相电子鼻建立15批臭灵丹草饮片的气味指纹图谱,进行相似度评价。结合AroChemBase数据库进行定性分析。以DPPH自由基、ABTS自由基清除能力为指标评价臭灵丹草饮片挥发性成分的抗氧化活性,结合多元统计分析评价谱效关系,筛选与抗氧化活性关联度较大的成分。结果:建立了15批臭灵丹草饮片的气味指纹图谱,结合AroChemBase数据库标定了14个共有峰,分别为异戊烷、乙叉降冰生烯、α-蒎烯、α-水芹烯、1,8-桉叶素、5-甲基-4-壬烯、柠檬烯、二溴氯丙烷、芳樟醇、甲基丁香酚、十一酸甲酯、β-石竹烯、醋酸十一酯、覆盆子酮。臭灵丹草饮片挥发油清除DPPH、ABTS自由基的IC50分别为6.56~21.26 mg/mL、3.89~18.34 mg/mL,灰色关联度分析及偏最小二乘回归分析结果表明柠檬烯、甲基丁香酚、覆盆子酮等与其抗氧化相关性较大。结论:臭灵丹草饮片超快速气相电子鼻气味指纹图谱结合谱效关系研究初步筛选了与抗氧化能力相关性较大的3个成分,可为臭灵丹草饮片质量控制提供依据。

高效3AP-DMEA-正丁醇-水相分离CO_(2)吸收剂的开发

燃煤电厂、钢铁企业等尾气中低浓度CO_(2)的排放控制是实现“碳中和”目标的关键。目前胺法捕获CO_(2)技术被认为是最有产业化应用前景的技术。为突破现有胺法在降能耗方面的技术瓶颈,旨在开发高效的相分离CO_(2)吸收剂。探究了伯/仲胺结构对与胺-正丁醇-水吸收剂吸收CO_(2)后分相特性的构效关系,研究了叔胺结构对3-氨基丙醇(3AP)-正丁醇(NBA)-水吸收-解吸和分相性能的作用规律。实验结果显示,3AP-NBA-H_(2)O吸收剂在富CO_(2)相黏度、胺分布、体积和相变临界点等方面均具有一定的优势,表明其具有良好的分相特性。添加叔胺可以明显降低富CO_(2)相黏度,同时提高单位体积溶液的CO_(2)循环容量和解吸率。新型20%3AP-10%N,N-二甲基乙醇胺(DMEA)-40%NBA-30%H_(2)O相分离吸收剂的富相体积为61.2%,黏度仅为6.73 mPa·s,富相中胺的占比为91.2%,其解吸率和CO_(2)循环容量分别达72.00%和1.42 mol·L^(-1),分别比30%3AP-40%NBA-30%H_(2)O吸收剂提高了88.6%和86.8%,比30%单乙醇胺(MEA)溶液提高了46.8%和13.6%。

金属蜂窝/石蜡复合相变材料融化储热性能研究

针对金属蜂窝/石蜡复合相变材料融化储热过程中,金属蜂窝热传导与液相自然对流传热的竞争关系,基于流-固-热三场耦合理论,建立相变材料融化储热计算模型。开展相变石蜡融化试验,验证计算模型的正确性。进一步分析液相自然对流和金属蜂窝热传导传热的增强效应,以及两者间的竞争关系。结果表明:底部加热下的密闭方腔内相变石蜡融化储热过程可分为热传导、稳定增长、过渡和紊流等四个阶段;各阶段占总融化储热时间的比例分别为0.8%、2.3%、13.6%和83.3%。热量随着液相石蜡的自然流动实现无障碍传输,达到提升相变石蜡融化储热效率的目的。自然对流传热的增强效应随尺寸减小而显著降低,在尺寸小于2 mm后可忽略不计。金属蜂窝通过增大热传导性和传热面积,达到提升相变石蜡融化储热效率的目的。嵌入金属蜂窝后,相变材料储热过程中存在多层共融现象,且在融化区形成温度梯度。与纯石蜡储热效率相比,金属蜂窝作用呈现先增强后抑制的规律,当融化分数超出临界值0.77后,金属蜂窝将进入抑制阶段。