共查询到19条相似文献,搜索用时 46 毫秒
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研制了一种基于间苯二酚分光光度法的硝酸盐自动分析仪,可以快速准确地测量水中硝酸盐氮的含量。研究结果表明:在0~20mg/L的量程范围内,本分析仪具有良好的性能,其中分析仪的标准曲线的R2值为0.9996,检出限为0.06mg/L,示值误差在0.75%以内,精密度为0.26%,抗亚硝酸盐离子干扰强。本分析仪方法灵敏度高、准确度高、精密度好、检出限低,适用于各种水体的应急及野外监测分析,与自动取样器联用可实现实验室大批量水样连续检测。 相似文献
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针对加氯系统的大滞后、时变特征,建立了串级控制模型,将Dahlin算法与Smith预估器相结合,提出了串级-多模型控制方法.仿真和实际应用结果表明,系统性能得到了较大改善. 相似文献
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本文介绍了X射线荧光光谱法检测磷酸酯抗燃油中氯含量的原理,分析了测量过程中不确定度的来源,并对其测量不确定度进行评定,为日后相关工作的开展提供宝贵的数据支撑。 相似文献
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A linear free vibration analysis of symmetric cross-ply laminated cylindrical helical springs is performed based on the first-order shear deformation theory. Considering the rotary inertia, the shear and axial deformation effects, governing equations of symmetric laminated helical springs made of a linear, homogeneous, and orthotropic material are presented in a straightforward manner based on the classical beam theory. The free vibration equations consisting of 12 scalar ordinary differential equations are solved by the transfer matrix method. The overall transfer matrix of the helix is computed up to any desired accuracy. The soundness of the present results are verified with the reported values which were obtained theoretically and experimentally. After presenting the non-dimensional graphical forms of the free vibrational characteristics of (0°/90°/90°/0°) laminated helical spring made of graphite-epoxy material (AS4/3501-6) with fixed–fixed ends, a non-dimensional parametric study is worked out to examine the effects of the number of active turns, the shear modulus in the 1–2 plane (G12), the ratio of the cylinder diameter to the thickness (D/d), and Young's moduli ratio in 1 and 2 directions (E1/E2) on the first six natural frequencies of a uniaxial composite helical spring with clamped-free, clamped-simple, and clamped–clamped ends. 相似文献
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Local adaptive differential quadrature for free vibration analysis of cylindrical shells with various boundary conditions 总被引:1,自引:0,他引:1
This paper presents the formulation and numerical analysis of circular cylindrical shells by the local adaptive differential quadrature method (LaDQM), which employs both localized interpolating basis functions and exterior grid points for boundary treatments. The governing equations of motion are formulated using the Goldenveizer–Novozhilov shell theory. Appropriate management of exterior grid points is presented to couple the discretized boundary conditions with the governing differential equations instead of using the interior points. The use of compactly supported interpolating basis functions leads to banded and well-conditioned matrices, and thus, enables large-scale computations. The treatment of boundary conditions with exterior grid points avoids spurious eigenvalues. Detailed formulations are presented for the treatment of various shell boundary conditions. Convergence and comparison studies against existing solutions in the literature are carried out to examine the efficiency and reliability of the present approach. It is found that accurate natural frequencies can be obtained by using a small number of grid points with exterior points to accommodate the boundary conditions. 相似文献