排序方式: 共有42条查询结果,搜索用时 31 毫秒
1.
为进一步提升图像比色法测定补铁药物中铁含量的准确性及普适性,考察了拍摄环境对结果的影响,确定了适用于图像比色分析的定量参数,比较使用不同容器来盛装溶液所获得的比色结果,在最优条件下测定了实际样品中铁的含量及加标回收率。结果显示,获得可靠数据的关键是将标准溶液、待测液以及空白溶液拍摄在同一张图片上;由溶液图像R值换算的吸光度值与浓度具有最佳的线性关系;分析以比色皿、试管、点滴板为容器获得的溶液图片,都能得到适合于定量比色分析的数据;测定的加标回收率大于95%。该方法操作简便,测定结果准确,可在各种条件下的高中化学实验室中开展。 相似文献
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A novel terbium(III) coordination polymer [Tb(C7H3NO4)(C6H4NO2)(H2O)] was successfully synthesized hydrothermally and characterized by single-crystal X-ray diffraction. The complex is of monoclinic, space group P21/c with a = 9.2252(11), b = 14.1477(16), c = 10.5134(12) A, β = 95.770(2)°, V = 1365.2(3) A3, Z = 4, Dc = 2.248 g·cm-3, F(000) = 880, the final R = 0.0176 and w R = 0.0411 for 2149 observed reflections with I 2σ(I). The complex is extended into a three-dimensional network structure with 24-atom rings which are composed of Tb, C and O atoms. The complex displays green fluorescence emission in the solid state at room temperature, which corresponds to 5D4 → 7F5 transition of the Tb(III) ion. 相似文献
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基于Kirchhoff理论讨论圆截面弹性螺旋杆的动力学问题.以杆中心线的Frenet坐标系为参考系,建立用欧拉角描述的弹性杆动力学方程.讨论其在端部轴向力和扭矩作用下保持的无扭转螺旋线平衡状态.在静力学和动力学领域内讨论其平衡稳定性问题.还讨论了弹性杆平衡的Lyapunov稳定性和欧拉稳定性两种不同稳定性概念之间的区别和联系.在一次近似意义下证明了螺旋杆在空间域内的欧拉稳定性条件是时域内Lyapunov稳定性的必要条件.导出了解析形式螺旋杆三维弯曲振动的固有频率,为螺旋线倾角和受扰挠性线波数的函数.
关键词:
弹性螺旋杆
Kirchhoff动力学比拟
Lyapunov稳定性
欧拉稳定性 相似文献
4.
为扩大稀土荧光配合物的应用范围,满足水溶液中微量铬的高灵敏高选择性探测要求,制备了一种基于水分散纳米无定形水杨酸甲酯铽配合物(A-MS-Tb)的高灵敏三价铬离子荧光传感器。结果表明:在水溶液中直接反应合成的配合物A-MS-Tb为无定形的纳米沉淀,其粒子尺度在50~100 nm之间,具有与报道的配合物晶体类似的组成。该配合物在494、549、591和625 nm处呈现出强的荧光发射,归属于铽离子的5D4→7FJ(J=6,5,4,3)能级跃迁。A-MS-Tb与晶体配合物的显著差别在于其在水中的悬浮稳定性和荧光稳定性更好,这对于其作为荧光材料和离子传感器非常重要。尤其突出的是,当将三价铬离子加入到它的水悬浮溶液中后,会减弱配体与铽离子之间的配位作用,导致其绿色荧光被淬灭。据此,构建了一种高灵敏测定溶液中铬离子浓度的荧光探针,并对其分析的选择性、灵敏度和抗干扰能力进行了评价。 相似文献
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The analysis of kinematics and dynamics of an elastic rod with
circular cross section is studied on the basis of exact Cosserat
model under consideration of the tension and shear deformation of
the rod. The dynamical equations of a rod with arbitrary initial
shape are established in general form. The dynamics of a straight
rod under axial tension and torsion is discussed as an example. In
discussion of static stability in the space domain the Greenhill
criteria of stability and the Euler load are corrected by the
influence of tension and shear strain. In analysis of dynamical
stability in the time domain it is shown that the Lyapunov and Euler
stability conditions of the rod in space domain are the necessary
conditions of Lyapunov's stability in the time domain. The longitudinal,
torsional and lateral vibrations of a straight rod based on exact
model are discussed, and an exact formula of free frequency of
lateral vibration is obtained. The free frequency formulas of
various simplified models, such as the Rayleigh beam, the Kirchhoff
rod, and the Timoshenko beam, can be seen as special cases of the
exact formula under different conditions of simplification. 相似文献
7.
利用红外光谱的宏观指纹特性,对金银花中不同溶剂提取物的红外光谱图和二阶导数红外光谱图进行了整体分析.初步推测,金银花石油醚提取物中主含长链脂肪酸(酯)、小分子萜类等低极性化合物,乙酸乙酯提取物主含环烯醚萜及其苷类化合物,无水乙醇和95%乙醇提取物中主含咖啡酸类衍生物和黄酮(苷)类化合物,去离子水提取物中主含鞣质及多糖类成分.综合比较亦可知,金银花醇提取物中的主成分是以绿原酸为代表的咖啡酸类衍生物.可见,利用红外光谱法对中药提取物直接进行分析,可对其主体成分进行初步的识别,为制定下一步的提取方案和检测方法提供了方向性参考. 相似文献
8.
A Modified Exact Linearization Control for Chaotic Oscillators 总被引:3,自引:0,他引:3
The control of chaotic oscillations is investigated in this paper. A control methodology, termed input-output linearization, is modified by locally linearizing the nonlinear control law in the small neighborhood of the control goal. Its suitability for controlling chaotic oscillators is analyzed. The forced Duffing oscillator is treated as a numerical example of controlling chaotic motion to a given fixed point and a given period-2 motion. The control signals and time needed to achieve the desired goals of the modified method are compared with those of the original method. The robustness of the control law is demonstrated. 相似文献
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讨论圆截面弹性细杆在黏性介质中的平面振动. 基于Kirchhoff理论,以杆中心线的Frenet坐标系为参考系,建立其动力学方程,杆中心线为任意平面曲线时,其扭转振动与弯曲振动解耦. 讨论两端固定条件下任意形状杆的平面扭转振动,以及无扭转的轴向受压直杆和圆环杆的平面弯曲振动,导出其自由振动频率和阻尼系数. 证明空间域内压杆的Lyapunov稳定性和欧拉稳定性条件为时域内渐近稳定性的充分必要条件,或无阻尼压杆的稳定性必要条件. 圆环杆平衡恒满足渐近稳定性条件.
关键词:
弹性细杆
黏性介质
扭转振动
弯曲振动 相似文献