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1.
Thomas H. Pate 《Linear and Multilinear Algebra》2003,51(3):263-278
If 1≤k≤n, then Cor(n,k) denotes the set of all n×n real correlation matrices of rank not exceeding k. Grone and Pierce have shown that if A∈Cor (n, n-1), then per(A)≥n/(n-1). We show that if A∈Cor(n,2), then , and that this inequality is the best possible. 相似文献
2.
S.D. Christian J. Grundnes P. Klaeboe C.J. Nielsen T. Woldbaek 《Journal of Molecular Structure》1976,34(1):33-45
The infrared spectra of 1,1,2-trichloroethane were recorded from 4000 to 50 cm?1 in the vapour and liquid states. Additional spectra above 200 cm?1 of the low temperature crystal and of two crystalline solids, prepared by compressing the sample in a diamond anvil cell, were obtained. Also, infrared spectra of the liquid and of the compound dissolved in CS2 were recorded at increased pressures. Raman spectral data of the liquid (including polarization measurements) and of the low temperature crystal were obtained.The fundamental frequencies for each of the two conformers, C1 and Cs, were assigned and the results checked by normal coordinate analysis. The same diagonal and off-diagonal force constants were employed for the two conformers and the force fields were derived by means of a least squares refinement, including data for chloroethane, 1,1-dichloroethane and various deuterated species. A standard deviation of 3 % was obtained in the final fit.From the changes in relative intensities for infrared bands belonging to the C1 and Cs conformers with increasing pressure, the volume differences (ΔV¯between the conformers were determined in CS2 solution and in the pure liquid. 相似文献
3.
It has been shown that the “internal” isotope distribution within a given molecular species at the natural abundance level is accessible by a new method, SNIF-NMR, which is based on deuterium NMR. Relative internal factors, Ri/j,have been defined which enable the isotope content of a given site, i, to be compared to that of another molecular site, j, taken as the reference. Several referencing methods intended to provide direct access to relative , Ti , and , (D/H)i , site-specific parameters, are now discussed from both the theoretical and the experimental points of view. In the , which involves a time-consuming chemical transformation of the sample, the risk exists of more or leas systematic errors resulting from discriminating fractionation effects. However this technique offers, conversely, an interesting way of investigating kinetic isotope effects without the need for specific labelling. In spite of its lower spectral precision the has the advantage of being fast and less sensitive to systematic errois and may be used for direct rough routine determinations of the site-specific isotope contents. More precise results can be obtained, at the price of contaminating the sample, when an is added and signal heights are used, remembering however that the intensity parameters then have no strict physical meaning in terms of absolute isotope contents. The site-specific parameters, Ti and (D/H)i thus accessible, provide new information on the mechanisms of the fractionation effects occurring in natural conditions and examples are considered. 相似文献
4.
Raman scattering and relaxed fluorescence is observed upon cw laser excitation resonant with the lower vibrational manifold of the X(1Σo+u) → B(3Πo+u) transition of matrix isolated Br2 at liquid He temperatures. The excitation profile of the relaxed fluorescence maps out the resonances, but neither detectable enhancement of Raman scattering nor resonance fluorescence is observed. 相似文献
5.
Summary Experimental results are presented on the application of Carbosieve S (Supelco) and Spherocarb (Analabs) spherical carbon molecular sieves for the gas chromatographic separation of mixtures of permanent gases and C1–C3 hydrocarbons using a single column or two columns in series. At a programmed temperature of 35–300°C, good separation of the sample components was obtained when using helium as the carrier gas. When hydrogen was used as the carrier gas and the analysis was carried out under isothermal conditions the elution sequence of oxygen and nitrogen reversed as the temperature was increased. This behaviour was observed within a temperature range of 35–225°C for Carbosieve S, and within a temperature range of 35–300°C for Spherocarb. 相似文献
6.
Zhipeng Hou Jinbao Zhang Shifeng Xu Chunji Wu Jingjing Zhang Zihan Wang Kunlong Yang Wenquan Wang Xiaobo Du Feng Su 《Journal of magnetism and magnetic materials》2012
The phases, microstructure, and magnetic properties of Co80Zr18−xNbxB2 (x=1, 2, 3, and 4) melt-spun ribbons were investigated. The small substitution of Nb for Zr in the Co–Zr–B melt-spun ribbons resulted in the improvement of magnetic properties, especially the coercivity. The main effect of added Nb on the coercovity of Co–Zr–Nb–B melt-spun ribbons, originated from modification of the grain size of Co11Zr2 phase. The coercivity of the Co–Zr–Nb–B melt-spun ribbons depends on the annealing temperature. The optimal magnetic properties of Hc=5.1 kOe, and (BH)max=3.4 MGOe were obtained in the Co80Zr15Nb3B2 melt-spun ribbons annealed at 600 °C for 3 min. 相似文献
7.
电感耦合等离子体发射光谱法测定记号笔笔芯和墨水中铜和铬 总被引:1,自引:1,他引:1
段旭川 《光谱学与光谱分析》2006,26(7):1342-1344
报道了使用ICP-AES测定记号笔芯和墨水中的铜和铬的方法。 主要关注了不同的样品前处理方法的研究。 结果表明: 对标记用的油性记号笔笔芯和含有高分子树脂的墨水, 采用550 ℃灰化, 混合酸(VHNO3∶VHClO4=3∶1)溶解的方法处理样品, 是该类样品比较好的处理方法; 而对不含有高分子树脂的墨水, 采用直接用混合酸(VHNO3∶VHClO4=3∶1)的消解即可。 消解后的样品经稀酸酸化后, 采用ICP-AES测定铜和铬, 结果准确、稳定。该方法适合记号笔或墨水中元素的测定。 相似文献
8.
��Сǿ������Զ��κ���裬�����ϣ������ 《核聚变与等离子体物理》2018,38(3):315-322
针对聚变工程大型超导导体样品在高场下的性能测试需求,设计了内径0.6m、磁场13T的背景磁体系统。磁体系统由6层12个分离式超导线圈组成,线圈采用常规的螺线管结构,由外至内分别使用NbTi、Nb3Sn和YBCO三种超导材料绕制而成;在直径500mm的测试区域范围内产生最高达13.22T的背景磁场,均匀性不低于95%。介绍了磁体线圈主要设计参数,用有限元软件完成电磁、结构分析。结果表明,设计合理可靠,能够满足导体测试装置的需求。 相似文献
9.
10.
In this paper, we study the influence of the Aharonov–Casher effect [Y. Aharonov, A. Casher, Phys. Rev. Lett. 53 (1984) 319] on the Dirac oscillator in three different scenarios of general relativity: the Minkowski spacetime, the cosmic string spacetime and the cosmic dislocation spacetime. In this way, we solve the Dirac equation and obtain the energy levels for bound states and the Dirac spinors for positive-energy solutions. We show that the relativistic energy levels depend on the Aharonov–Casher geometric phase. We also discuss the influence of curvature and torsion on the relativistic energy levels and the Dirac spinors due to the topology of the cosmic string and cosmic dislocation spacetimes. 相似文献