MARTENSITIC AND R PHASE TRANSFOR MATIONS IN NiTiand NiTiHf

The ongoing collaborative research between Auburn University and Johnson Controls was described. A Ti rich binary NiTi alloy and two ternary alloys having the compositions Ni 49 Ti 51- x Hf x with 1% and 3%(more fraction) Hf were investigated. The influence of Hf content, cold working(CW) and heat treatment temperature (HT) on the martensitic and R phase transformations was thermally analyzed using differential scanning calorimetry (DSC). The crystal structures of the alloys were examined by X ray diffraction. Results showed that at low HT, the martensitic transformation temperature (TT) decreases with increasing CW for all the alloys studied. In this alloy, for a given CW, the martensite TT increases with increasing HT above 350 ℃. This phenomenon is enhanced by the presence of Hf. Different mechanisms can be responsible for the observed behavior. These mechanisms may involve interaction between phase transformations, dislocations and internal stresses. The effect of Hf substitution is likely due to the atomic size difference between Ti and Hf. A secondary phase,identified as Ti 2Ni in binary NiTi and (TiHf) 2Ni in the two ternary alloys, was observed. The influence of cold work, heat treatment and thermal cycling on the R phase (R) transformation in three alloys was also thermally analyzed. Results showed that such transformation depends on composition as well as CW and HT conditions in a complex manner. Effort was made to identify the microstructure and the factors responsible for the observed behavior in the R phase transformation.

基于相位补偿核的GNSS-SAR改进后向投影成像算法

在利用全球导航卫星系统反射信号(GNSS-R)的无源合成孔径雷达体制中,目前常采用后向投影算法进行成像处理,但该算法逐点精确聚焦的处理过程使得算法的运算量大。针对上述问题,提出了一种数据分块和构造相位补偿核的改进后向投影算法。改进算法对回波矩阵进行分块,将目标区域成像网格点的最长延迟距离与最短延迟距离等间隔划分,建立相位补偿核,通过距离向搜索操作得到各网格点的相位补偿结果,在方位向相干叠加形成子图,递归合并得到最终图像。定量分析得出,改进算法可有效降低运算量,同时节省内存。仿真结果验证了所提算法的有效性。

纳米晶NiTi记忆合金应力诱发R→B19′相变的超弹稳定性

通过对Ni_(50.2)Ti_(49.8)(at%)记忆合金丝材进行大变形冷拔和低温退火获得了平均晶粒尺寸为15 nm的纳米晶NiTi记忆合金丝材样品,然后采用应变量为6%的20次拉伸循环实验研究了纳米晶NiTi合金力致R→B19′相变的超弹稳定性。结果表明:纳米晶NiTi合金在经过20次拉伸循环变形后,其超弹应力为734 MPa,超弹应力的减小率为16%,残余应变为0.61%,此综合超弹性能优于以往粗晶NiTi记忆合金。这主要源于纳米晶NiTi记忆合金中细晶强化显著提高了合金屈服强度,因此降低合金马氏体相变过程中塑性变形,可使纳米晶NiTi记忆合金呈现高的超弹稳定性。

GNSS-R水位监测研究进展与其在我国水利行业应用展望

水位监测在水文学、水利工程、灾害防治等领域都具有非常重要的意义.传统的水位监测方法存在成本高、覆盖范围小等缺点,GNSS不仅具有导航、定位及授时的功能,还可以利用其反射信号获取反射面的特性信息并将其称为全球卫星导航系统反射测量(Global Navigation Satellite System-Reflectometry,GNSS-R).近年来,GNSS-R技术以低成本、全天候、高时空分辨率等优势为水位监测提供了一种新方法.本文对GNSS-R水位监测的研究现状、不同方法的影响因素以及当前应用过程中存在的问题进行了总结归纳提出了下一步的发展趋势,最后对其在我国水利行业的应用进行了展望.

一种Ku频段高密度集成的陶瓷SiP封装R组件的设计

针对机载卫星通信天线尺寸小、重量轻、可靠性强的需求,结合多层陶瓷转接板布线灵活、重量轻的特点,BGA封装I/O口多、体积小的优势,提出了一种基于HTCC工艺SiP-BGA封装架构的2×4通道Ku频段双极化R组件的设计方法。利用电磁仿真软件对组件中高密度射频垂直过渡互联结构进行了仿真设计,同时设计了一款小型化薄膜功分器,以实现4通道接收信号的合成;此外,为确保组件的射频性能及工程可实现性,对整个组件的通道隔离度、散热性进行了仿真计算;最后研制出小型化、高集成度的2×4通道Ku频段R组件,其体积为13 mm×12.5 mm×2.5 mm,重量小于4 g。组件电性能测试结果与仿真设计结果吻合良好,测试结果表明,该组件在10~12.8 GHz频段内合成增益大于23 dB,输入P-1dB不小于-5 dBm。

两级串并驱动有源相控阵T/R组件

从实际应用出发,介绍了一种有源相控阵发射/接收(T/R)组件的两级串并驱动设计方案。该设计方案中移相/衰减数据的控制包含两级串并驱动,第一级串并驱动将数据锁存后送给第二级串并驱动,第二级串并驱动再将数据锁存后用于控制组件通道收发待机和移相衰减。和传统的一级串并驱动控制方式相比,该控制方式可以有效降低T/R组件对串并驱动芯片的依赖程度,缩短T/R组件研制周期,降低研制成本。经测试验证,设计的两级串并驱动T/R组件具有较低的驻波系数、较高的移相精度,且各通道的增益平坦度及通道间的增益一致性均较好。

Phase transformation behaviors and shape memory effects of TiNiFeAl shape memory alloys

Measurements of electrical resistivity, X-ray diffraction, and tensile test at room temperature and ？196°C were performed to investigate the effects of Al addition substituting Ni on the phase transformation behaviors, the mechanical properties, and the shape memory effects of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys. It is found that 1at% Al addition dramatically decreases the martensitic start transformation temperature and expands the transformation temperature range of R-phase for TiNiFeAl alloys. The results of tensile test indicate that 1at% Al improves the yield strength of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys by 40% and 64%, but de- creases the plasticity to 11% and 12% from 26% and 27% respectively. Moreover, excellent shape memory effect of 6.6% and 7.5% were found in Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys, which results from the stress-induced martensite transformation from the R-phase.

基于相差变化率的GSM-R干扰源直接定位技术

移动通信运营商在铁路沿线部署了公众移动通信网络,采用的数字全球通信系统(Global System of Mobile Communication, GSM)原理和制式与铁路全球移动通信系统(Global System of Mobile Communication for Railways, GSM-R)完全相同,对GSM-R造成了一定干扰。为了对这些干扰源进行定位,提出了一种基于相差变化率的干扰源定位技术。该技术基于二元阵列接收系统,根据阵元与干扰源之间的时空关系,初始以方位角的变化率与干扰源位置建立关系模型,借助微分变形建立了以相差变化率为自变量的干扰源位置求解模型和解算方法。为了避免采集数据中的异常样本对最终的定位结果产生影响,设计了一种基于孤立森林的异常样本过滤算法,利用数据点自身的特征属性构建多维特征空间实现异常数据点的检测和消除。搭建实景环境对铁路沿线无线电数据进行采集并开展数据分析工作,结果表明所提基于孤立森林的异常样本过滤算法能够有效剔除异常数据,提高整体样本的质量。使用相同的已知位置干扰源无线采集数据开展与基于频差变化率的定位方法和基于振幅变化率的定位方法的定位能力对比试验,统计不同方法对于每个干扰源的最小定位误差,结果表明基于频差和振幅变化率定位方法的平均定位误差分别是所提方法的7.18、20.73倍,证明了所提方法的定位精度显著优于基于频差变化率的定位方法和基于振幅变化率的定位方法,具有较高的定位精度。

In-situ synchrotron high energy X-ray diffraction study of spontaneous reorientation of R phase upon cooling in nanocrystalline Ti_(50)Ni_(45.5)Fe_(4.5)alloy

This study investigated a peculiar phenomenon of self-reorientation of thermally formed R phase in nanocrystalline Ti_(50)Ni_(45.5)Fe_(4.5)by means of in-situ syn-chrotron high energy X-ray diffraction(HE-XRD).Two samples with different average grain sizes of 40 and 90 nm were investigated.R phase in the 40-nm grain size sample was found to self-reorient gradually upon cooling,whereas the same phenomenon did not occur in the 90-nm grain size sample.This self-reorientation process is attributed to the development and evolution of an internal stress anisotropy caused by the second order continuous lattice distortion of R phase upon further cooling in the small nanograined matrix,which lacks the self-accommodation mechanism for internal stress cancellation.

IN SITU TEM STUDY ON THE R-PHASE TRANSFORMATION IN TiNi ALLOY

The R-phase transformation process in selected TiNi alloys has been studied in great detail by using in situ TEM technique. The R-phase transformation was found to be a reversible thermoelastic displacive transformation with a nucleation and growth process. The R-phase nucleates at the precipitate/matrix interface in aged specimens and grows by moving the coherent R/matrix interfaces. The stress field of Ti3Ni4 precipitates plays a much more important role in the formation of the R-phase than dislocations in aged TiNi alloy. The microstructure of the R-phase has also been studied.

Multiferroic phase transitions in manganites RMnO_3:A two-orbital double exchange simulation

The semi-quantum two-orbital exchange model is used to investigate the effect of small rare-earth ion substitution on orthorhombic RMnO 3 with A-type antiferromagnetic order,using the Monte Carlo algorithm,exact diagonalization,and zero-temperature optimization approaches.It is revealed that the substitution results in a rich multiferroic phase diagram where the coexisting A-type antiferromagnetic phase and spiral spin phase,pure spiral spin phase,coexisting spiral spin phase,the E-type antiferromagnetic phase,and the pure E-type antiferromagnetic phase emerge in sequence.The multiferroic phase transitions modulate substantially the electric polarization,which is consistent qualitatively with recent experiments.

Precipitation of Icosahedral Quasicrystalline Phase, R-phase and Laves Phase in Ferritic Alloys

Ferritic heat resistant steels involving precipitation of intermetallic phases have drawn a growing interest for the enhancement of creep strength, while the brittleness of the intermetallic phases may lower the toughness of the alloy. Therefore, it is necessary to optimize the dispersion characteristics of the intermetallics phase through microstructural control to minimize the trade-off between the strength and toughness. The effects of -Fe matrix substructures on the precipitation sequence, morphology, dispersion characteristics, and the stability of the intermetallic phases are investigated in Fe-Cr-W-Co-Si system. The precipitates of the Si-free Fe-10Cr-l.4W-4.5Co (at%) alloy aged at 873K are the R-phase but those of the Si-added Fe-10Cr-l.4W-4.5Co-0.3Si (at%) alloy are the icosahedral quasicrystalline phase. The precipitates in both the Si-free and Si-added alloys aged at 973K are the Laves phase. Matrix of the alloys is controlled by heat treatments as to provide three types of matrix substructures; ferrite, ferrite/martensite mixture and martensite. The hardening behavior of the alloys depends on the matrix substructures and is independent of the kinds of precipitates. In the alloys with ferrite matrix, the peak of hardness during aging at 873K shifts to longer aging time in comparison with that in the alloys with lath martensite matrix which contain numbers of nucleation sites.

ALTERNATIVE DESCRIPTION OF THE SHEAR PLANE OF THE R-PHASE

A high density of {110} shear planes has been observed in the R-phase (Al5CuLi3)following phase transformation from the AlCuLi icosahedral Phase. The Present paper shows that the atomic arrangement in the vicinity of the shear planes can be described as a two-dimensional periodic array of atom clusters with 5-fold symmetry. This result is obtained by projecting along the [1. 618...01] direction of the atomic positions from four adjacent lattice planes that cross the shear plane. The projection reveals that the shear plane consists of pentagonal arrangements of double triacontahedra,each pentagon incorporating 606 atoms. The calculated diffraction pattern from the pentagon has approximate 10-fold symmetry characteristic of a quasicrystal.

METASTABLE R-PHASE IN Fe-Cr-Mo AND Fe-Cr-W ALLOYS

The precipitation behaviour of Fe-Cr-Mo and Fe-Cr-W alloys during aging has been ex- perimentally studied.It was found that in the early stage of aging,a metastable R phase pre- cipitated in both alloys,it was transformed into stable μ-phase,Laves-phase,X-phase or σ-phase in the later stages.The crystallographic structure of metastable R-phase is rhombohedral with lattice parameters of a=0.9075 nm and α=74.45°.The chemical compo- sition of R-phase is Fe-(27.5—34.9)Mo-(0—25.5)Cr and Fe-(28.9—33.0)W-(9.36— 21.0)Cr in at.-% in Fe-Cr-Mo and Fe-Cr-W system,respectively.

R-phase transformation of aged Ti-Ni shape memory alloy

Ti-50.6Ni（molar fraction, %） shape memory alloy solution treated at 850℃ for 1h followed by ageing treatment at 450℃ for 3h was studied with differential scanning calorimetry（DSC）, X-ray diffractometry（XRD） and transmission electron microscopy（TEM）. DSC measurement reveals two separate transformation peaks. XRD and TEM demonstrate that a three-stage transformation occurs. The Ti3Ni4 precipitates are coherent with the R-phase. The crystal structure of R-phase was analyzed by two diffraction patterns method. The diffraction patterns of R-phase were obtained in detail from the same region.

PHASE TRANSFORMATIONS IN RAPIDLY SOLIDIFIED TiNi SHAPE MEMORY ALLOYS

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一种T/R组件的温度自补偿电路设计

T/R组件是有源相控阵天线的关键电路模块,其发出的热量会导致芯片特性发生变化,影响组件及天线的性能。本文提出了一种T/R组件的温度自补偿电路设计方法,对其电性能进行自动温度补偿,克服了数字芯片量化误差导致的主动温度补偿精度受限的缺陷。采用该自补偿方法研制了一种温度补偿电路模块,实测结果表明,组件馈电链路的传输相位温漂减小约67%,验证了本文自补偿方法的有效性。

一种X波段硅基微流道T/R组件设计与实现

为解决相控阵雷达高集成、小型化、大功率T/R组件散热问题,设计了一种X波段硅基微流道T/R组件.该T/R组件采用三维堆叠方式,将冷却微流道嵌入硅基板中,实现一体化设计;选用四通道多功能芯片,实现多位移相、衰减功能.测试结果与理论计算吻合良好,组件的发射功率与接收增益均能达到指标要求,满足雷达系统应用需求.

秸秆还田对东北黑土水分特征及物理性质的影响

为明确秸秆还田对东北黑土水分特征及物理性质的影响,设置秸秆覆盖还田(FG)、秸秆翻埋还田(FM)和秸秆不还田翻耕(FD)3个处理,测定土壤含水量、水分特征曲线、容重、硬度、土壤三相比及结构稳定性等参数。结果表明:(1)秸秆覆盖还田可显著提高春季耕层(0~30 cm)土壤含水量,较秸秆不还田翻耕处理增幅为11.17%~150.84%;不同处理耕层土壤在水吸力中吸力段土壤含水量变化曲线平滑,秸秆覆盖还田处理具有较高的土壤持水性。(2)秸秆还田能显著提高土壤水分有效性,与秸秆不还田翻耕处理相比,秸秆覆盖还田处理0~10 cm土层土壤田间持水量提高4.85%~11.03%,土壤凋萎系数提高10.85%~18.00%;秸秆翻埋还田处理0~10 cm土层土壤重力水增加9.65%~80.73%。秸秆翻埋还田提升了土壤供水能力,土壤比水容量较秸秆不还田翻耕处理增加4.8%~10.0%。(3)与秸秆不还田翻耕处理相比,秸秆还田降低了收获后土壤紧实度,降低幅度为0.18~0.31 MPa;秸秆覆盖还田增加表层土壤容重,降低土壤孔隙度,促进三相结构趋于合理,显著增加土壤结构稳定性。(4)皮尔森相关分析表明,三相比R值与结构距离(r=0.73*)、土壤容重(r=0.70*)相关性显著,在一定范围内三相比R值的增加有利于改善并促进土壤结构稳定。综上可知,东北黑土农田实施秸秆还田是提高春季土壤含水量、增强土壤持水性、提升土壤供水能力、调节土壤紧实性、调控土壤三相比、改善土壤结构和提高土壤宜耕性的有效措施。

正相高效液相色谱法测定琥珀酸曲格列汀中的(R)-3-氨基哌啶

建立琥珀酸曲格列汀中(R)-3-氨基哌啶测定的正相高效液相色谱分析方法,用于琥珀酸曲格列汀中对起始原料(R)-3-氨基哌啶盐酸盐残留的质量控制。采用CHIRALPAK AD-H(250 mm×4.6 mm,5μm)色谱柱,以正己烷-无水乙醇(80:20)为流动相,等度洗脱,流速为1.0 mL/min;柱温为30℃;检测波长为210 nm。(R)-3-氨基哌啶在0.10~3.03μg/mL范围与峰面积呈良好的线性关系,r=0.9993;检测限为0.03048μg/mL,加标平均回收率100.5%(n=15)。本文建立的方法准确、灵敏、可靠,适用于琥珀酸曲格列汀中杂质(R)-3-氨基哌啶含量的检测。