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61.
HTPB复合底排药压缩屈服应力模型研究 总被引:2,自引:0,他引:2
目前广泛应用于底排增程技术的 HTPB 复合底排药 (composite base bleed grain,CBBG) 是一种颗粒填充含能材料,战场环境中将承受冲击、温度等载荷作用. 为研究 HTPB CBBG 冲击压缩力学性能,进行了不同温度 (233$\sim$323 K) 和应变率 (1100$\sim$7900 s$^{-1}$) 下的分离式霍普金森压杆实验. 实验结果表明,各工况下,应力应变曲线均呈现屈服-$\!$-应变硬化特征,HTPB CBBG 保持高韧性. 提高应变率和降低温度均导致相同应变下的应力幅值上升,但温度较应变率对HTPB CBBG 冲击压缩力学性能的影响更为显著. 基于所研究温度范围高于 HTPB CBBG 玻璃化转变温度,通过将水平、垂直移位因子与温度的关系表示为 WLF 方程的形式,将时温等效原理引入协同模型,并计及内应力的应变率增强效应,提出了一种新的屈服应力模型.选取参考温度,利用水平、垂直移位因子-$\!$-温度曲线和屈服应力主曲线拟合模型参数.模型预测值与实验数据对比结果表明:该模型可准确表征 233$\sim$323 K 时 HTPB CBBG 屈服应力的双线性应变率相关性,明确了较低和较高应变率时,应变率效应分别主要由内应力和驱动力贡献. 相似文献
62.
Summary This research has demonstrated that the dielectric method can be used successfully for grain moisture measurements for diverse
grain types over wide ranges of temperatures if the grain moisture content is below certain (grain-specific) threshold values.
These high-moisture limits were estimated. Optimum temperature correction coefficients for 149 MHz moisture measurements were
determined for grain samples at different moisture levels. This information should be very helpful for grain moisture meter
manufacturers and for moisture meter users who need to determine grain moisture contents at temperature extremes to be able
to market grain more efficiently. 相似文献
63.
将甲酸盐掺杂在乳剂微晶不同位置处,制备成氯化银立方体微晶乳剂和{100}面扁平微晶乳剂.实验发现:作为正空穴捕获剂,适当计量的甲酸盐在不增加乳剂灰雾的前提下,可使上述乳剂的感光度提升3—8倍.甲酸盐在两种晶形乳剂的不同位置掺杂的研究结果显示,甲酸盐均匀掺杂可比表面掺杂获得更高的感光度.在两种乳剂中甲酸盐掺杂增感都可与其后的硫增感、硫加金增感以及光谱增感协同作用,进一步提升乳剂的感光性能. 相似文献
64.
65.
采用溶胶-凝胶法制备了不同烧结温度的钙钛矿类锰氧化物La0.67Sr0.33MnO3样品。实验结果表明,在1573 K以上烧结的样品,晶粒出现异常长大,晶界效应明显。随着烧结温度的提高,磁化强度逐渐增大,但样品的居里温度基本不变。此外,在1173和1573 K温度下烧结的样品,均出现了低于居里温度的金属-半导体导电行为转变。在合适的烧结条件下,可以观察到隧道磁电阻(TMR)和超大磁电阻(CMR)2种磁电阻效应。实验表明,自旋电子的输运,不仅与样品平均粒径的大小和密度有关,而且与晶界的微观结构有密切关系。 相似文献
66.
Summary A multiresidue method has been developed for identification and quantitation of the herbicides most commonly used in cultivation
of maize and grain, and of their transformation products, in soil samples. The analytes were isolated by soil column extraction
(SCE) and the extracts were purified by use of a Carbograph-1 cartridge. Analysis was performed by liquid chromatography coupled
with tandem mass spectrometric detection (LC-TISP-MS-MS) in negative-ion mode. To optimize the extraction conditions affecting
the performance of SCE, e.g. the extracting solvent used, temperature, extracting volume, and solvent flow rate, were studied.
To evaluate the matrix effect in SCE, recovery experiments were performed on soil samples, with different physical and chemical
characteristics, fortified with the 100 ng g−1 of the target compounds. Recovery data were satisfactory and the method detection limits were between 3 and 100 ng g−1, depending on the compound. 相似文献
67.
68.
The crystallographic defects inevitably incur during the solution processed organic‐inorganic hybrid perovskite film, especially at surface and the grain boundaries (GBs) of perovskite film, which can further result in the reduced cell performance and stability of perovskite solar cells (PSCs). Here, a simple defect passivation method was employed by treating perovskite precursor film with a hydrophobic tetra‐ammonium zinc phthalocyanine (ZnPc). The results demonstrated that a 2D‐3D graded perovskite interface with a capping layer of 2D (ZnPc)0.5MAn ? 1PbnI3n + 1 perovskite together with 3D MAPbI3 perovskite was successfully constructed on the top of 3D perovskite layer. This situation realized the efficient GBs passivation, thus reducing the defects in GBs. As expected, the corresponding PSCs with modified perovskite revealed an improved cell performance. The best efficiency reached 19.6%. Especially, the significantly enhanced long‐term stability of the responding PSCs against humidity and heating was remarkably achieved. Such a strategy in this work affords an efficient method to improve the stability of PSCs and thus probably brings the PSCs closer to practical commercialization. 相似文献
69.
建立了超高效液相色谱-四极杆/静电场轨道阱高分辨质谱快速筛查和确证粮谷产品中20种真菌毒素的方法。样品经乙腈(含2%(体积分数)甲酸)提取,用Captiva EMR-Lipid小柱净化,采用Thermo Hypersil Gold C18柱(100 mm×2.1 mm,1.9 μm)分离,用四极杆/静电场轨道阱高分辨质谱进行分析。在全扫描模式下以分析物的保留时间和一级母离子信息实现快速筛查,以自动触发采集的二级碎片离子信息进行确证。结果显示,目标分析物在各自的质量浓度范围内线性关系良好(相关系数r2>0.99),方法检出限为0.25~20 μg/kg,回收率为72.9%~117.8%,相对标准偏差为2.9%~15.2%(n=6)。该方法灵敏度高,结果准确、可靠,适用于粮谷产品中20种真菌毒素的快速筛查和确证。 相似文献
70.
Relationship between grain boundary diffusion in nanocrystals and amorphous microstructure
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Lin‐lin Sun Jun Wang Hong‐chao Kou Jin‐shan Li Ping‐xiang Zhang 《Surface and interface analysis : SIA》2016,48(12):1341-1344
The effects of microstructure on diffusion behaviors of Ni in Zr48Cu36Ag8Al8 alloy were investigated by transmission electron microscope and secondary ion mass spectrum. The temperature dependence of Ni diffusivities in Zr48Cu36Ag8Al8 alloy with different states (metallic glass, nanocrystals and coarse crystals) has been measured in the temperature range of 693–723 K. The results show that diffusion behavior is microstructure dependence, and the relations between the microstructure and diffusion are discussed. The activity energy of the grain boundary diffusion in nanocrystals calculated by the Suzuoka solution is about 1.433 eV/atom. It is equivalent with that of metallic glass, which is attributed to the similar microstructure between the two. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献