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41.
魏嵬 《数学的实践与认识》2007,37(16):76-83
为给转炉设计提供依据,需要计算炉液倾动的重心.利用数学方法将实际问题进行简化,通过分析炉液倾动过程中变量间的相互关系,来确定每个倾动角度对应情况下的液面位置.利用数学中三重积分的有关应用,进一步得出转炉在每个倾动角度为α∈(0,π2)时的重心计算方法及相关结论,在理论上为工程计算重心的方法提供参考. 相似文献
42.
《Magnetic resonance in chemistry : MRC》2003,41(9):660-670
Reduced forms of iso‐α‐acids (isohumulones), used in modern beer brewing were separated and characterized by 1H and 13C NMR spectroscopy. Components from mixtures of rho‐iso‐α‐acids, tetrahydro‐iso‐α‐acids, and hexahydro‐iso‐α‐acids were isolated using high‐performance liquid chromatography (HPLC) and analyzed by use of one‐ and two‐dimensional NMR experiments. The data presented assign the identities of the main peaks in the HPLC traces for the reduced iso‐α‐acids. Previous tentative assignments regarding the cis and trans configurations and the structures of the acyl residues of the reduced iso‐α‐acids were confirmed and extensive NMR assignments were made. Furthermore, the previously unknown stereochemistry in the C‐4 side‐chain of the rho‐ and hexahydro‐iso‐α‐acids was assigned. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
43.
44.
The principle of concentrating a substance from a mixture flow in a stationary sorbent layer of infinite length that was previously
developed for gas chromatography is extended to liquid chromatography.
Translated fromIzevestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1063–1065, May, 1997. 相似文献
45.
《Magnetic resonance in chemistry : MRC》2003,41(11):949-954
We report two new asterosaponins from the Baltic starfish Asterias rubens along with their 1H and 13C NMR data. The compounds were isolated after on‐flow liquid chromatography–NMR–mass spectrometry screening indicated that they had not been identified before. The one‐ and two‐dimensional NMR experiments used to elucidate the structures were recorded using a 5 mm cryogenic probe head. The advantages of cryogenic probes for this kind of examination in comparison with conventional probe heads are discussed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
46.
Liquid chromatography-electrospray ionisation mass spectrometry was evaluated in the high-throughput analysis of microcystins and nodularins, cyanobacterial peptide hepatotoxins. Extracts originating from cyanobacterial strains and field material were separated on a 30 mm × 4 mm I.D. Merck Purospher STAR RP-18e column using a rapid gradient of aqueous formic acid and acetonitrile, ionised by electrospray technique and analysed on a Micromass Quattro II triple-quadrupole mass spectrometer operated in the selected ion recording (SIR) mode. The total analysis time per sample was 2.8 min corresponding to 514 samples a day. The system showed good robustness during a series of 320 repetitive injections of a field sample containing three major microcystins. 相似文献
47.
Summary Furocoumarins from extracts ofHeracleum genus fruits were separated using normal and reversed phase TLC and HPLC and isolated in the milligram scale using overloaded
systems of column chromatography. Binary or ternary solvents containing a polar modifier (methanol, diisopropyl ether or acetonitrile)
were used as the mobile phases.
Preliminary report on this work was presented at the 47th International Congress of Pharmaceutical Sciences of F.I.P. in Amsterdam.
The Netherlands, 30 August–5 September 1987. 相似文献
48.
S. S. Banerjee S. Goldberg Y. Myasoedov M. Rappaport E. Zeldov A. Soibel F. de la Cruz J. van der Beek M. Konczykowski T. Tamegai V. Vinokur 《Pramana》2006,66(1):43-54
Disorder and porosity are parameters that strongly influence the physical behavior of materials, including their mechanical,
electrical, magnetic and optical properties. Vortices in superconductors can provide important insight into the effects of
disorder because their size is comparable to characteristic sizes of nanofabricated structures. Here we present experimental
evidence for a novel form of vortex matter that consists of inter-connected nanodroplets of vortex liquid caged in the pores
of a solid vortex structure, like a liquid permeated into a nanoporous solid skeleton. Our nanoporous skeleton is formed by
vortices pinned by correlated disorder created by high-energy heavy ion irradiation. By sweeping the applied magnetic field,
the number of vortices in the nanodroplets is varied continuously from a few to several hundred. Upon cooling, the caged nanodroplets
freeze into ordered nanocrystals through either a first-order or a continuous transition, whereas at high temperatures a uniform
liquid phase is formed upon delocalization-induced melting of the solid skeleton. This new vortex nanoliquid displays unique
properties and symmetries that are distinct from both solid and liquid phases. 相似文献
49.
An analytical method is presented to investigate the bending-torsion vibration characteristics of a cylinder with an arbitrary cross-section and partially submerged in water. The compressibility and the free surface waves of the water are considered simultaneously in the analysis. The exact solution of structure–water interaction is obtained mathematically. Firstly, the analytical expression of the velocity potential of the water is derived by using the method of separation of variables. The unknown coefficients in the velocity potential are determined by the longitudinal and circumferential Fourier expansions along the outer surface of the cylinder and are expressed in the form of integral equations including the unknown dynamic bending deflection and torsional angle of the cylinder. Secondly, the force and torque acting on the cylinder per unit length, provided by the water, are obtained by integrating the water dynamic pressure along the circumference of the cylinder. The general solution of bending-torsion vibration of the cylinder under the water dynamic pressure is derived analytically. The integral equations included in the velocity potential of the water can be solved exactly. Finally, the eigenfrequency equation of cylinder–water interaction is obtained by means of the boundary conditions of the cylinder. Some numerical examples for elliptical columns partially submerged in water are provided to show the application of the present method. 相似文献
50.
Yangyang Jiang Chen Guo Huizhou Liu 《中国颗粒学报》2007,5(1):130-133
A magnetically rotational reactor (MRR) has been developed and used in absorbing benzene emissions. The MRR has a permanent magnet core and uses magnetic ionic liquid [bmim]FeCl4 as absorbent. Benzene emissions were carried by N2 into the MRR and were absorbed by the magnetic ionic liquid. The rotation of the permanent magnet core provided impetus for the agitation of the magnetic ionic liquid, enhancing mass transfer and making benzene better dispersed in the absorbent. 0.68 g benzene emissions could be absorbed by a gram of [bmim]FeCl4, 0.27 and 0.40 g/g higher than that by [bmim]PF6 and [bmim]BF4, respectively. The absorption rate increased with increasing rotation rate of the permanent magnet. 相似文献