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571.
为了直接、快速地测定赤芍配方颗粒中芍药苷和浸出物的含量,解决回流烘干法测定耗时长、操作繁琐等问题,利用近红外漫反射技术,结合偏最小二乘法(PLS),建立了测定芍药苷和浸出物含量的近红外光谱测定方法。选用积分球系统测定样品的近红外光谱,定量模型的预处理方法采用多元散射校正和一阶导数进行处理,光谱范围分别为5 492~5 103cm-1,7 428~7 201cm-1,6 942~5 322cm-1。结果表明,定量模型中芍药苷含量和浸出物含量的最佳主因子数分别为7和6,内部交叉验证均方差分别为0.082 6和0.226 0,决定系数(R2)分别为0.981 7和0.982 4,系统精密度RSD值分别为1.1%和0.9%,方法精密度RSD值分别为2.1%和1.6%,外部验证预测均方差分别为0.363和0.282。采用建立的近红外预测模型对赤芍配方颗粒进行快速测定,方法可行,分析快速、简便,结果准确,为赤芍配方颗粒的测定提供了高效方法。 相似文献
572.
论抽水的降落漏斗范围、影响半径与环境影响范围 总被引:1,自引:0,他引:1
针对降落漏斗范围、影响半径与环境影响范围等3个既有联系又有区别的水文地质问题,从其科学性和实用性两个角度,开展了系统研究工作。首先,针对降落漏斗范围,通过一般的数学模型进行了深入的理论研究,研究结论得到了Dupuit模型和Theis模型等2个成熟井流模型的验证。然后,针对影响半径,在国内外经典文献基础上,以地下水动力学发展史为主线,对其理论基础进行了科学分析,着重分析了其模型基础和几何意义,梳理了其理论上的不足和主要存在争议之处,进而分析了其适用性和实用性,同时对非Thiem模型中的广义影响半径也进行了类似研究,得到了关于各类井流模型影响半径的一般共性认识。最后,结合抽水的环境风险评估和环境监测的需要,提出了"抽水环境影响范围"概念(包括一、二类环境影响范围)和一般求解方法,并根据实际应用需要,提出了Theis模型环境影响范围的解析解,其科学性和实用性得到了一个实际典型案例的验证。 相似文献
573.
Characteristics of structural loess strength and preliminary framework for joint strength formula 总被引:1,自引:0,他引:1
The strength of structural loess consists of the shear strength and tensile strength. In this study, the stress path, the failure envelope of principal stress ( Kf line), and the strength failure envelope of structurally intact loess and remolded loess were analyzed through three kinds of tests: the tensile strength test, the uniaxial compressive strength test, and the conventional triaxial shear strength test. Then, in order to describe the tensile strength and shear strength of structural loess comprehensively and reasonably, a joint strength formula for structural loess was established. This formula comprehensively considers tensile and shear properties. Studies have shown that the tensile strength exhibits a decreasing trend with increasing water content. When the water content is constant, the tensile strength of the structurally intact soil is greater than that ofremolded soil. In the studies, no loss of the originally cured cohesion in the structurally intact soil samples was observed, given that the soil samples did not experience loading disturbance during the uniaxial compressive strength test, meaning there is a high initial structural strength. The results of the conventional triaxial shear strength test show that the water content is correlated with the strength of the structural loess. When the water content is low, the structural properties are strong, and when the water content is high, the structural properties are weak, which means that the water content and the ambient pressure have significant effects on the stress-strain relationship of structural loess. The established joint strength formula of structural loess effectively avoids overestimating the role of soil tensile strength in the traditional theory of Mohr-Coulomb strength. 相似文献
574.
Flow characteristics of thermally stratified shear flow in braided rivers are particularly complicated and poorly understood. In this study, a series of typical flow patterns was examined and their critical criteria were determined. Four flow patterns were identified: mixed, locally unstable, continuously stratified, and two-layer flow. Temperature distributions of the four types of flow patterns were analyzed and compared. The critical Froude numbers for unstable flow, , and stable flow, , were determined to be 6 and 1, respectively, and comparison of and to the peak Froude numbers, at the outer bank and at the inner bank along the anabranch, allowed the flow patterns to be assessed. Then, a discriminant based on initial Jeffreys-Keulegan stability parameters was established to distinguish the flow stages from two-layer flow to completely mixed flow. It is indicated that the three critical Jeffreys-Keulegan parameters increased with the diversion angle of braided rivers. Results also show that, compared to the stratified flow in straight and curved channels, it was more difficult for braided stratified flow to maintain as two-layer flow, and it more easily became mixed flow. Consequently, empirical expressions for stability criteria of the thermally stratified shear flow in braided rivers are presented. 相似文献
575.
戚玉彬 《中国水利水电科学研究院学报》2024,22(4):387-396
渠道底坡是影响输水能力的重要因素,但量水槽流量公式往往忽略渠道底坡。为了探究渠道底坡对流量公式的影响,以三角形量水槽为研究对象,在6种底坡的U形渠道上开展田间试验。应用能量方程式推求了流量的理论公式,基于量纲分析法分别建立不包含和包含渠道底坡的流量公式,探讨渠道底坡影响流量公式的范围。流量的理论公式表明渠道底坡是影响量水槽流量公式的因素之一。与不包含渠道底坡的流量公式相比,包含渠道底坡的流量公式测流精度显著提高,平均相对误差从2.92%降低至1.65%,最大相对误差从12.22%减小至7.37%,相对误差绝对值小于5%的比例从80.94%提升至95.89%。渠道底坡影响三角形量水槽流量公式的范围界定为1/100~1/1200,当渠道底坡小于1/1200时可以忽略。量水槽流量公式应考虑渠道底坡的影响。 相似文献
576.
577.
在现场模型试验和原型试验的基础上,对膨胀土地基的基础在浸水及不浸水两种状态下的抗拔机理进行了研究,根据双变量非饱和土强度公式,推导出了土体抗剪强度指标及吸力强度与含水量的关系公式。从而阐明了膨胀土在浸水状态下的抗拔承载力的降低机理,同时根据原型试验结果,研究了负孔隙水压力对抗拔承载力的影响,确定了其值的大小,同时指出,负孔隙水压力对于基础抗拔是一个有利因素。但却很不可靠。 相似文献
578.
针对钛合金异形内螺旋线电解加工过程中间隙流场分布不均、工件表面易发生点蚀、加工质量差等问题,对加工工艺进行了优化。设计了一种顺流换向式新型阴极结构,通过加工间隙流场仿真对阴极过液孔直径进行了优化。开展了电解液基础试验,获得了一种适用于钛合金材料高效高质量电解加工的复合电解液配方:10%NaCl+8%NaNO3+3%Na2HPO4。并采用优化后的阴极与复合电解液完成了钛合金内螺旋线的稳定可靠加工,加工表面无点蚀现象出现,成形精度达到0.04mm,阴线表面粗糙度优于Ra0.8μm。 相似文献
579.
580.
We revisit the foundational Moment Formula proved by Roger Lee fifteen years ago. We show that in the absence of arbitrage, if the underlying stock price at time T admits finite log-moments for some positive q, the arbitrage-free growth in the left wing of the implied volatility smile for T is less constrained than Lee's bound. The result is rationalized by a market trading discretely monitored variance swaps wherein the payoff is a function of squared log-returns, and requires no assumption for the underlying price to admit any negative moment. In this respect, the result can be derived from a model-independent setup. As a byproduct, we relax the moment assumptions on the stock price to provide a new proof of the notorious Gatheral–Fukasawa formula expressing variance swaps in terms of the implied volatility. 相似文献