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961.
催化褪色光度法测定微量锰(Ⅱ)的研究 总被引:6,自引:2,他引:6
本文研究在硫酸介质中,锰(Ⅱ)催化EDTA还原重铬酸银,而使之褪色的新指示反应。确定了催化褪色反应动力学条件,锰(Ⅱ)的浓度在0-0.4μg/ml范围内,工作曲线呈良好的线性关系,检测限为0.011μg/mL,该方法用于天然水及污水中锰的测定,获得满意结果。 相似文献
962.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Dai Lisheng Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Zheng Shuchen Zhong Yuanyuan 《Physical review letters》1993,71(14):2172-2175
963.
基于Kriging的泡沫填充锥形薄壁结构耐撞性6σ稳健性优化设计 总被引:1,自引:0,他引:1
锥形薄壁结构的耐撞性设计过程中,其设计变量和噪声因素都具有一定的波动性,都存在不确定性.传统的优化设计方法由于忽略不确定因素的影响,当设计变量产生波动时,往往会引起设计最优目标超出约束界限或者目标函数对设计变量的波动极为敏感,从而导致设计失效.为了考虑参数的不确定影响,论文提出了一种结合试验设计技术、Kriging近似建模技术、蒙特卡罗模拟技术和6σ质量控制理念的稳健优化设计方法,并应用该方法对泡沫填充锥形薄壁结构的耐撞性进行了优化设计.优化结果表明,该方法提高了锥形薄壁结构的耐撞性,同时也提高了设计变量的可靠性和目标函数的稳健性.由于在优化过程中调用的是Kringing模型,该方法比传统的优化方法具有更高的优化设计效率.算例表明,该方法具有非常强的工程实用性,能大幅提高产品的设计质量. 相似文献
964.
Quantum Black Hole 总被引:1,自引:0,他引:1
Wu Zhong Chao 《General Relativity and Gravitation》1998,30(1):115-121
Creation of a black hole in quantum cosmology is the third way of black hole formation. In contrast to the gravitational collapse from a massive body in astrophysics or from the quantum fluctuation of matter fields in the very early universe, in the quantum cosmology scenario the black hole is essentially created from nothing. The black hole originates from a constrained gravitational instanton. The probability of creation for all kinds of single black holes in the Kerr-Newman family, at the semiclassical level, is the exponential of the total entropy of the universe, or one quarter of the sum of both the black hole and the cosmological horizon areas. The de Sitter spacetime is the most probable evolution at the Planckian era. 相似文献
965.
Spectroscopic Diagnostics of Atmospheric Argon Microwave Plasma Based on an Inductive Coupling Window-Rectangular Resonator 下载免费PDF全文
We present a novel microwave plasma source based on an inductive coupling window-rectangular resonator. A definite volume of atmospheric argon microwave plasma is excited in the source under the input of several kilowatts of microwave power operating at 2.45 0Hz. The excitation temperature and electron temperature of the argon plasma are separately researched by using Boltzmann plot and line-to continuum intensity ratio of Ar I spectral lines. Its electron density is inferred from the Stark broadening of the Hβ line at 486.13nm. 相似文献
966.
We report on the existence of surface dark screening solitons at the interface between a dielectric medium (air) and a self-defocusing nonlinear material, taking advantage of photorefractive diffusion and drift nonlinearities. It is very interesting that a surface dark soliton is just like half of a dark soliton in bulk, but not a whole dark soliton propagating along surface. The excitation, propagation, and stability of this type of soliton are studied by using the beam-propagation method. Another interesting thing is that this type of dark soliton can be excited by a planar light beam without a necessary dark notch. 相似文献
967.
研究了赝二元立方化合物Dy(Fe_1-xGa_x)_2(x≤0.3)的磁性.观测到Ga对Fe的无序置换,导致磁性的重大改变.T>4K的磁性属于正常型,用畴壁内禀钉扎受到热激活的概念,解释了实验结果;由此导出的矫顽力随温度变化的公式(8)与实验符合得相当好.T<4K的磁性属于异常型,表现为退磁曲线有台阶和大跳跃、矫顽力随温度变化出现峰值、磁粘滞性系数与温度无关等.用畴壁隧道效应量子形核的概念,说明了实验结果,而且从理论上估算出由经典热激活到量子隧道效应的交界温度,得到的数值2.21—3.03K与实验值~3K
关键词: 相似文献
968.
Resonance scattering spectroscopy of gold nanoparticle 总被引:8,自引:1,他引:8
The gold nanoparticles in diameter of 10-95 nm have been prepared by Frens procedure, all of which exhibit a resonance scattering peak at 580 nm. The mechanism of resonance scattering for gold nanoparticle has been considered according to the wave motion theory of nanoparticle in liquid. The principle of superamolecular interface energy band(SIEB) has been set up and utilized to explain the relationship between the diameter and colors for gold nanoparticle in liquid. A novel spectrophotometric ruler for the determination of the diameter has been proposed according to the relationship of the maximum absorption wavelength and diameter. 相似文献
969.
Hai‐Jing Nie Xialing Chen Chang‐Jiang Yao Prof. Dr. Yu‐Wu Zhong Prof. Dr. Geoffrey R. Hutchison Prof. Dr. Jiannian Yao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(45):14497-14509
Electron delocalization of new mixed‐valent (MV) systems with the aid of lateral metal chelation is reported. 2,2′‐Bipyridine (bpy) derivatives with one or two appended di‐p‐anisylamino groups on the 5,5′‐positions and a coordinated [Ru(bpy)2] (bpy=2,2′‐bipyridine), [Re(CO)3Cl], or [Ir(ppy)2] (ppy=2‐phenylpyridine) component were prepared. The single‐crystal molecular structure of the bis‐amine ligand without metal chelation is presented. The electronic properties of these complexes were studied and compared by electrochemical and spectroscopic techniques and DFT/TDDFT calculations. Compounds with two di‐p‐anisylamino groups were oxidized by a chemical or electrochemical method and monitored by near‐infrared (NIR) absorption spectral changes. Marcus–Hush analysis of the resulting intervalence charge‐transfer transitions indicated that electron coupling of these mixed‐valent systems is enhanced by metal chelation and that the iridium complex has the largest coupling. TDDFT calculations were employed to interpret the NIR transitions of these MV systems. 相似文献
970.
化学拆分的新方法研究 总被引:8,自引:0,他引:8
主要介绍了近年来发展起来的两种化学拆分新方法,包括拆分和组合拆分;并简要论述了化学拆分中的手性识别现象,以及化学拆分方法在手性药物制备中的应用。 相似文献