食品中氯丙醇脂肪酸酯含量测定的方法研究

基于GB 5009.191—2016《食品安全国家标准食品中氯丙醇及其脂肪酸酯含量的测定》,对3-氯-1,2-丙二醇脂肪酸酯和2-氯-1,3-丙二醇脂肪酸酯及其内标绝对响应值较低、多个实验室间数据差异较大等问题进行了研究,重点对正己烷、不同酯键断裂试剂和反应时间进行了验证和优化。结果表明:正己烷对测试结果无影响,最佳的酯键断裂试剂为0.5 mol/L甲醇钠-甲醇溶液,最佳酯键断裂反应时间为2 min。通过国际比对和多品牌标准品比较,确定了多个实验室间数据差异较大原因主要来自于内标物质的纯度差异以及标准曲线内标物质与样品中加入的内标物质不同。建议样品测试时,应尽可能使标准曲线使用的标准物质及内标物质与样品中添加的内标物质相同,并同法处理,从而提高数据准确性。     

致密气藏压裂水平井温度剖面影响因素分析

由于缺少水平井温度剖面预测模型,且影响温度剖面的主导因素不明确,导致根据分布式光纤温度测试数据反演解释致密气藏压裂水平井产出剖面十分困难。为此,建立了考虑多种微量热效应和裂缝系统传热的致密气藏压裂水平井温度剖面耦合预测模型,模拟分析致密气藏压裂水平井储层温度分布和井筒温度剖面特征,并采用正交实验分析和定量实验分析方法评价不同影响因素对温度剖面的影响程度。研究表明:各因素对致密气藏压裂水平井温度剖面的影响程度由大至小依次为裂缝半长、单井日产气量、储层渗透率、井筒直径、裂缝导流能力、水平段井筒倾角、储层总导热系数;主导因素为裂缝半长、单井日产气量和储层渗透率。温度模型的建立和温度剖面主导因素的确定为致密气藏压裂水平井产出剖面、裂缝参数等定量解释奠定了理论基础。     

Synergetic effect of site-controlled two-step Ca doping on magnetic and electrical properties of M-type strontium hexaferrites

M-type strontium (SrM) hexaferrites exhibiting large magnetocrystalline anisotropy, high saturation magnetization and coercivity, and narrow ferrimagnetic resonance (FMR) linewidth have a great potential for applications in high-performance motors and self-biased circulators. Ca doping in SrM hexaferrites is an effective method for tailoring the intrinsic electromagnetic parameters and modifying polycrystalline microstructure to meet the application requirements. However, the regulation mechanism of Ca doping is still obscure, and its regulation effect is not optimized. Here, the magnetic and electrical properties of SrM hexaferrites with site-controlled two-step Ca doping are reported. The spatial concentration distribution and diffusion dynamics of Ca²⁺ ions are investigated when introduced by CaCO₃ as the reactant and sintering additive, respectively. The existence of the Ca²⁺ ions in the crystallites added as the reactant reduces the diffusion of the Ca²⁺ ions in the grain boundaries added as the additive, which synergistically tailors the magnetocrystalline anisotropy field, crystallite orientation, and polycrystalline morphology, and further optimizes the coercivity, remanence, and maximum energy product. Moreover, the impact of the Ca²⁺ ions on the resistivities of the grain and grain boundary is also investigated, revealing the synergetic effect of Ca²⁺ ions at different sites on lowering the loss. These results prove the effectiveness of the site-controlled two-step Ca doping in synergistically enhancing the magnetic and electrical properties of SrM hexaferrites.