火焰原子吸收法测定中药土大黄中四种微量元素的含量

目的运用火焰原子吸收光谱法测定中药土大黄根中的Fe、Zn、Mg、Ca等4种金属元素的含量。方法用浓HNO3-HClO4消解样品,采用标准曲线法测定其4种金属元素含量。结果所测的样品中含有丰富的人体必需微量元素,尤其是Ca含量极高。方法回收率在96．90％～102．3％之间,样品相对偏差小于5％。结论方法简单、准确,结果令人满意。     

火焰原子吸收法测定中药草珊瑚叶中五种金属元素的含量

目的运用火焰原子吸收光谱法测定中药草珊瑚叶中的Fe、Zn、Mg、Ca、Cu 5种金属元素的含量。方法用浓HNO3-HCl O4消解样品,采用标准曲线法测定其5种金属元素含量。结果所测的样品中含有丰富的人体必需微量元素。方法回收率在99.35%-103.30%之间,样品相对偏差小于5%。结论该法简单、准确,结果令人满意。     

荧光法猝灭测定木槿叶中混合氨基酸的总量

在乙酸-乙酸钠缓冲介质中,氨基酸能猝灭壳聚糖-茚三酮体系荧光,基于此,对木槿叶中混合氨基酸进行测定,并对该方法的测定条件进行了讨论.线性范围为0.5～3.0 mmol/L,检出限为0.1 mmol/L.木槿叶干粉中游离氨基酸的质量分数为10.18%,相对标准偏差为1.3%,回收率为102.5%～94.3%.     

梯度表面能材料上液滴运动特性实验

对水平和30°倾角放置梯度表面能材料表面上液滴运动特性进行了可视化实验,分析了液滴在梯度表面上运动速度的变化规律,以及液滴大小和表面倾角对运动速度变化的影响.实验结果表明:在梯度表面能材料上,液滴能获得较大的宏观运动速度,并可以沿30°倾角放置的梯度表面材料上自下而上的运动;大液滴较小液滴的峰值运动速度大,运动距离更远;液滴在运动过程中出现蠕动的现象.     

交替惩罚三线性分解算法结合三维荧光光谱法同时分辨和测定酪氨酸、苯丙氨酸和色氨酸

用交替惩罚三线性分解算法(APTLD)结合三维荧光光谱法给出的二维数据对酪氨酸、苯丙氨酸和色氨酸进行了同时定性定量分析,为直接同时测定混合氨基酸中此三种物质提供了一种新的分析方法, 其测定相关系数分别为0.9987,0.9995和0.9993。采用超声波组织细胞破碎法对木槿叶中的氨基酸进行提取,利用APTLD法对提取液中氨基酸进行定量测定,测定相对标准偏差分别为0.84％,0.36％,1.59％, 回收率分别在101.0％～92.7％, 106.5％～93.0％, 103.0％～95.0％之间,方法简洁、快速、准确可靠,结果令人满意。     

Transmission loss of a flexible micro-perforated muffler with a flexible back cavity for water-filled pipelines

To reduce low-frequency noise of the water-filled pipeline system,a compact flexible micro-perforated muffler with a flexible back cavity(FMPMFBC) is proposed.The flexible pipe wall is made of a rubber-cord composite material.A numerical solution for the transmission loss is derived.Firstly,the flexible micro-perforated panel(FMPP) is equivalent to a flexible porous material based on Biot-Allard porous-elastic theory.Then,a periodic structural unit of the aramid fabric cloth is established with the two-scale method,and the equivalent stiffness matrix is obtained.Besides,a multi-layer composite model for the flexible pipe wall is constructed according to the lamination theory.Coupling with the internal sound field,the transmission loss of the FMPMFBC is calculated.On a water-filled impedance tube,the transmission loss curves of the FMPMFBC prototypes are measured with the two source-location method,and compared with those of a flexible micro-perforated muffler with a rigid back cavity(FMPMRBC)and an expansion muffler.Theoretical results are experimentally verified.The FMPMFBC is a hybrid muffler combining reflection with dissipation,capable of attenuating broadband lowfrequency noise.The transmission loss of prototype B2 in the frequency bands of [40 300] Hz and [40 1200] Hz is 36 dB and 30 dB,respectively,while the transmission loss of the same-sized expansion muffler in the corresponding frequency bands is 7 dB and 11 dB,respectively.     

Synthesis and Crystal Structure of a New Zn(II) Nitronyl Nitroxide Complex [Zn(NIT4Py)(PDA)(H2O)3]

1 INTRODUCTION Nitronyl nitroxides, independently or in combina- tion with metal ions, have been one of the most wi- dely studied systems in molecular magnetism for understanding radical-radical or metal-radical inte- ractions as well as for synthesizing organic ferroma- gnets and metal-radical magnetic materials[1～4]. Up to now, lots of metal-radical complexes have been reported[5～8]. On the other hand, cooperative inter- molecular interactions, such as coordination bonds, hydrogen bon…     

军队院校开设数学实验课的实践与体会

介绍了我们开设数学实验课的实践,阐述了数学实验课的教学目的、教学内容和教学计划安排,分析了实际教学效果.     

浅谈数学中的合情推理

合情推理是数学发现的重要方法,本文介绍了合情推理的概念、作用、途径.所论及的内容对数学教学有参考价值.     

催化光度法测定城市污泥中的痕量镍

利用Ni2 对还原型罗丹明B(RRhB)与KClO3显色反应的催化作用,对城市污泥中痕量Ni2 进行测定。结果表明,在pH 5.3的HAc-NaAc缓冲溶液中具有高灵敏的显色反应,其催化程度与Ni2 含量在0~0.07 mg/L范围内符合比耳定律。方法的检出限为4.3×10-8g/L,加标回收率为98.5%~104.6%(n=6)。本法结合萃取分离,用于测定城市污泥中的痕量镍,结果满意。