On Bianchi permutability of Bäcklund transformations for asymmetric quad-equations

We prove the Bianchi permutability (existence of superposition principle) of Bäcklund transformations for asymmetric quad-equations. Such equations and their Bäcklund transformations form 3D consistent systems of a priori different equations. We perform this proof by using 4D consistent systems of quad-equations, the structural insights through biquadratics patterns and the consideration of super-consistent eight-tuples of quad-equations on decorated cubes.     

A numerical investigation of the influence of the aspect ratio in three‐dimensional separated flows

The influence of aspect ratio in three‐dimensional, numerical experiments of separated flows is studied in the case of the backward‐facing step at Reynolds numbers 600, 800, and 950. The computational domain is designed as an actual laboratory experiment. The governing equations are the steady state, isothermal, and incompressible Navier–Stokes equations. The expansion ratio of the computational domain is 1:2. The aspect ratio varies from 1:10 to 1:40. The results of the computations focus on the spanwise variations of the length and the strength of the two eddies along the lower and upper wall. It is concluded that both numerical and laboratory experiments should be designed with an aspect ratio of at least 1:20, if only the accuracy of the position of the detachment and the re‐attachment points matters. If the accuracy of the shear‐stress distributions is also taken into account, then an aspect ratio of at least 1:30 should be chosen. Finally, if the magnitudes of the vortex centers are also considered, then only the aspect ratio of 1:40 qualifies for a realization of two‐dimensional flow conditions in the plane of symmetry. This is contrary to the common practice in the field, at least from the side of laboratory experiments, where an aspect ratio of 1:10 is still considered adequate for this purpose. Copyright © 2011 John Wiley & Sons, Ltd.     

Three‐dimensional computation for flow‐induced vibrations in in‐line and cross‐flow directions of a circular cylinder

We present numerical results for in‐line and cross‐flow vibrations of a circular cylinder, which is immersed in a uniform flow and is elastically supported by damper‐spring systems to compute vibrations of a rigid cylinder. In the case of a circular cylinder with a low Scruton number, it is well‐known that two types of self‐excited vibrations appear in the in‐line direction in the range of low reduced velocities. On the other hand, a cross‐flow vibration of the circular cylinder can be excited in the range of high reduced velocities. Therefore, we compute the flow‐induced vibrations of the circular cylinder in the wide range of the reduced velocities at low and high Scruton numbers and discuss about excitation mechanisms in the in‐line and cross‐flow directions. Copyright © 2011 John Wiley & Sons, Ltd.     

3-甲酰腙一利福霉素SV及其异构体的研究

用发酵和化学法合成的两个3-甲酰腙-利福霉素SV样品(1^#,2^#)具有不同的物理化学性质,本文用多种NMR技术,如¹H,¹³C,DEPT,¹H-¹H COSY,反相摸式的¹H-¹³C COSY及远程¹H-¹³C COSY,并结合红外及紫外一可见光谱测试结果进行综合分析,确定样1^#及样2^#分别为酰胺式主产品及亚胺醇式导构体。根据实验结果对样1^#的异构化反应进行了初步的探讨.     

中等规模多肽分子的2DNOESY实验问题

由于中等规模多肽在水溶液中运动的特殊性(ω₀τ_c≈1),2DNOESY谱上往往得不到相关讯息(采用合理的混合时间),而降低温度的余地也很小·本工作将少量氘代甲醇加到水溶液中,并将实验温度降到零下,实验取得成功。例如从一个九肽和一个十一肽的NOESY实验得到了很多残基内和残基间的NOESY相关讯息,足以作出归属并进一步计算质子间距离.     

假耧斗菜碱的二维核磁共振研究

利用1D和2D NMR及NOE差谱等方法研究了首次从自然界分离到的头对尾型BBI生物碱假耧斗菜碱(Paraquileginine)的化学位移及立体结构,对其:¹H和¹³C NMR谱线进行了全归属。本工作对研究毛莫科植物的化学分类及寻找新的有生物功能的天然药物具有参考价值。     

Eu3+、Tb3+与1-乙酰乙酰吲哚、1,10-邻菲啰啉二元、三元体系在溶液中荧光光谱研究

观察了以不同比例溶解在乙醇中的Eu3+、Tb3+、1-乙酰乙酰吲哚(HL)和1,10-邻菲啉(Phen)的荧光光谱.结果表明HL能有效地把吸收的能量传递给Tb3+,而不能有效地传递给Eu3+.讨论了HL和Phen对Eu3+、Tb3+的配位作用及其对Eu3+或Tb3+所组成的三元体系中敏化发光性能的影响.     

测定核间距的不对称2D NOESY方法2.Cis-Pt(NH3)2(Guo)2Cl2的不对称2D NOESY实验研究

应用不对称2DNOESHY实验方法研究了顺铂配合物Cis-Pt (NH₃)₂(Guo)₂Cl₂的水溶液中的构象,表明鸟苷同铂配合后其糖环构象发生明显的变化。     

Extended non-abelian gauge symmetries in the classical WZNW model

Higher spin extensions of the non-Abelian gauge symmetries for the classical WZNW model are considered. Both linear and nonlinear realizations of the extended affine Kac-Moody algebra are obtained. It is a characteristic property of the WZNW model that it admits a higher spin linear realization of the extended affine Kac-Moody algebra which is equivalent to the corresponding higher spin nonlinear realization of the same algebra. However, in both cases, the higher spin Noether currents do not span an invariant space with respect to their generating transformations. Here, the current space is extended to an invariant space which allows us to gauge the symmetry.Supported by Bulgarian Foundation on Fundamental Research under contract Ph-318/93-95.     

Approximate quasi-Newton methods

We consider the effect of approximation on performance of quasi-Newton methods for infinite dimensional problems. In particular we study methods in which the approximation is refined at each iterate. We show how the local convergence behavior of the quasi-Newton method in the infinite dimensional setting is affected by the refinement strategy. Applications to boundary value problems and integral equations are considered.The research of this author was supported by NSF grant DMS-8601139 and AFOSR grant AFOSR-ISSA-860074.