Non-equilibrium grain boundary co-segregation of Boron and Magnesium in Ni3Al

The non-equilibrium grain boundary co-segregation of boron and magnesium in Ni₃Al–B–Mg alloys was determined by Auger electron spectroscopy (AES) in conjunction with ion sputtering in a cooling rate range of 0.05–269 K/s from temperatures of 1023, 1223 and 1373 K. The analytical expressions of diffusion rate equations describing non-equilibrium segregation process based on the concept that mobile solute-vacancy complexes migrating to grain boundaries is responsible for non-equilibrium grain boundary segregation of solute atoms in an alloy was used to simulate well the experimental results. The diffusion coefficients for boron atoms, boron-vacancy complexes, magnesium atoms and magnesium-vacancy complexes were determined, and the binding energy of boron-vacancy and magnesium-vacancy complexes was estimated.     

Characterization of GaN and In x Ga1−x N films grown by MOCVD and MBE on free-standing GaN templates and quantum well structures

Structural and optical studies have been performed on GaN, InGaN layers, In_0.08Ga_0.92N/GaN heterostructures, In_0.08Ga_0.92N/In_0.02Ga_0.98N single and multiquantum wells grown by metal organic chemical vapor deposition (MOCVD) and GaN by molecular beam epitaxy (MBE) on GaN templates by using transmission electron microscopy (TEM), X-ray diffraction (XRD), and photoluminescence (PL). The layers are found to be high quality with low defect density, on the order of 10⁶ cm^?2, which are mainly related to the threading dislocations originating/propagating from the hydride vapor phase epitaxy (HVPE) GaN template. The interface between the layers and substrate could not be detected by TEM and was therefore deemed to be of high quality. Convergent beam electron diffraction studies revealed that the polarity of the films is Ga-polarity, which is the same as that of the substrate. A dual structure with different compositions and having thicknesses of 10 and 25 nm was observed in InGaN layers grown on GaN in one of the heterostructure samples. The full width at half maximum (FWHM) of the XRD rocking curves of (0 0 0 2) for heterostructures and quantum wells were found to be in the range of 15–28 arcmin for a slit width of 2 mm. PL studies on GaN layers grown by MBE and MOCVD on GaN templates are reasonably similar. The PL spectra from all the MBE and MOCVD epilayers and the substrate contain a plethora of sharp peaks related to excitonic transitions. With the presence of donor-bound exciton peaks and their associated two-electron satellites, the binding energies of two distinct shallow donors (28.8 and 32.6 meV), which are attributed to Si and O, respectively, were determined. PL measurements revealed that the FWHM of the main donor bound exciton peak increased from 0.6 to 2.9 meV but no change in peak position (3.472 eV) was observed in GaN when doping with Si (5×10¹⁷ cm^?3). However, the intensities of the yellow band and the shallow donor–acceptor pair band increased 10 times as compared to that in the undoped GaN samples. In the case of InGaN/GaN heterostructures, a similar trend was observed when compared to the doped samples. In the multiquantum well In_0.08Ga_0.92N/In_0.02Ga_0.98N heterostructures, the activation energy of the exciton emission, found to be 18 meV, was the lowest in the samples studied. The peak at 3.02 eV related to the InGaN was strongly pronounced in the In_0.08Ga_0.92N/In_0.02Ga_0.98N multiquantum well structure. In the In_0.08Ga_0.92N/In_0.02Ga_0.98N quantum well structures, the change in peak position with variation of temperature from 15 to 300 K in PL spectra is “S”-shaped. The cause for the “S” shape, i.e., a red–blue–red shift, is discussed.     

2Cr13钢机械性能的回归分析

本文利用电子计算机,对长期生产中积累的大量2Cr13钢机械性能数据进行了回归分析。建立了性能之间显著性很高(α=0.01)的回归方程。可辅助设计、指导生产。     

前刀面槽型结构对D型刀片车削球墨铸铁性能的影响

通过切削力、磨损和冲击切削试验,研究了前刀面槽型结构对D型刀片车削球墨铸铁切削性能的影响。试验结果显示,刀具的第一前角对切削力的影响最大;在10°~15°范围内,刀具前角越大,切削力越低;棱带宽度大的刀片具有更加优异的耐磨损性能;具有正刃倾角的刀片显示出更优异的耐冲击性能。     

基于人脸视频的心率参数提取

为了在舒适非接触环境下检测被试者的心率变化,本文设计了一种通过普通摄像头来检测心率参数的信号处理系统。首先,将KLT(Kanade-Lucas-Tomasi)算法跟踪识别到的人脸视频图像转换到YCbCr颜色空间来进行皮肤检测,并同时转换到Cg颜色通道来提取高质量的光电容积脉搏波(Photoplethysmography, PPG)信号。然后,用Morlet复小波作为母波绘制PPG信号的小波能量谱图。最后根据心率信号的生理特性,去除伪点噪声,提取随时间变化的心率参数。实验结果表明,该方法在静息状态下的测量结果同标准仪器测量结果的平均绝对值误差|M_e|小于2 bpm(beats per minute),误差的标准差SD_e小于2.5 bpm,RMSE均小于2.6 bpm;头部运动状态下两种测量方法的|M_e|均小于2.3 bpm,SD_e均小于2.9 bpm,RMSE均小于2.9 bpm。对两种测量方法进行Bland-Altman一致性分析,其测量结果显示静息状态下差值的均数■为0.295 7 bpm,95%置信区间为-3.340 1~3.931 4 bpm;头部运动状态下■为0.383 2 bpm,95%置信区间为-3.677 1~4.443 5 bpm,表明本文提出的非接触式方法的测量结果同标准仪器的测量结果具有高度的一致性。     

浅析赖特对当代日本建筑师隈研吾的影响

赖特的建筑深受亚洲哲学与日本文化的熏陶,身为日本建筑师的隈研吾对赖特的建筑思想自然十分熟悉和赞同。赖特宣扬有机建筑观念对隈研吾有着很深的触动;他的织理性建构方法也在隈研吾的作品中有清晰的体现。本文针对隈研吾建筑作品中继承赖特的建筑思想和特点进行了简要分析,说明赖特对隈研吾产生的影响。     

黑龙江七台河东风煤矿矿难是瓦斯爆炸引起的煤尘爆炸

根据黑龙江七台河东风煤矿第一采煤区的工人全部死亡,第二、第三采煤区工人部分生存,且后者入口对着发生煤尘爆炸的出煤巷道的入口的事实,推论东风煤矿爆炸不是单纯煤尘爆炸,而是第一采煤区首先发生瓦斯爆炸,爆炸喷出的火焰扬起并引燃出煤巷道地面与墙上的煤尘,诱发严重的煤尘爆炸。第一采煤区首先发生的瓦斯爆炸与今年发生的另两次瓦斯爆炸起因是一样的,都是由于轻度瓦斯突出,受加强加大的通风的负(反)作用造成的。     

新型聚合物改性水泥砂浆材料研究

为解决沙漠化和边坡失稳带来的环境问题和经济损失,研究了高水灰比、低聚灰比的新型聚合物水泥砂浆。实验结果表明,聚氨酯和聚丙烯酸钠各以水泥质量的5%复配掺入到水泥砂浆中后,抗压强度平均提高约15%,抗折强度提高约20%,水泥基材料的韧性明显增强,吸水保水功能强。现场应用效果明显。