Development of an Artificial Compressibility Methodology with Implicit LU-SGS Method

A numerical method has been developed to solve the steady and unsteady incompressible Navier-Stokes equations in a two-dimensional, curvilinear coordinate system. The solution procedure is based on the method of artificial compressibility and uses a third-order flux-difference splitting upwind differencing scheme for convective terms and second-order center difference for viscous terms. A time-accurate scheme for unsteady incompressible flows is achieved by using an implicit real time discretization and a dual-time approach, which introduces pseudo-unsteady terms into both the mass conservation equation and momentum equations. An efficient fully implicit algorithm LU-SGS, which was originally derived for the compressible Eulur and Navier-Stokes equations by Jameson and Toon [1], is developed for the pseudo-compressibility formulation of the two dimensional incompressible Navier-Stokes equations for both steady and unsteady flows. A variety of computed results are presented to validate the present scheme. Numerical solutions for steady flow in a square lid-driven cavity and over a backward facing step and for unsteady flow in a square driven cavity with an oscillating lid and in a circular tube with a smooth expansion are respectively presented and compared with experimental data or other numerical results.     

Investigation of Breaking Efficiency of N-Glycosidic Bond Between Sulfonamide and Honey

Sulfonamide residue in honey existed in a form bonded to sugar via the N-glycosidic bond.It would result in the possible underestimation of concentration of sulfonamide if it is not decomposed by chemi...     

Highly Concise Synthesis of 3'-"Up"-ethynyl-5'-methylbicyclo-[3.1.0]-hexyl Purine and Pyrimidine Nucleoside Derivatives Using Rhodium(II) Carbenoid Cycloaddition and Highly Diastereoselective Grignard Reaction

Synthesis of north‐5'‐methylbicyclo[3.1.0]hexyl purine and pyrimidine nucleosides with an ethynyl group at C‐3' position has been successfully accomplished by a facile method. Methylbicyclo[3.1.0]hexanone (±)‐ 5 having three contiguous chiral centers was remarkably simply constructed only by four steps containing a carbenoid insertion reaction in the presence of rhodium(II) acetate dimer and CuSO₄, giving a correct relative stereochemistry of the generated three chiral centers. Upon Grignard reaction of (±)‐ 5 with ethynylmagnesium bromide, exclusive diastereoselectivity was observed. Condensation of glycosyl donor (±)‐ 9 with purine nucleobase afforded only the desired N⁹‐alkylated nucleoside, while condensation with pyrimidine, N³‐benzoylated uracil gave the desired N¹‐alkylated nucleoside (±)‐ 13 with the undesired O²‐alkylated nucleoside (±)‐ 14 . Probably, (±)‐ 14 would be formed due to steric hindrance caused upon approaching for N¹‐alkylation.     

ChemInform Abstract: The Infrared Spectrum of F-·H2O.

The geometry and vibrational frequencies of the F-·H₂O system are determined by ab initio calculations (SCF and CISD levels of theory).     

AN ANALOGUE OF KǘNNETH THEOREM IN STRONG HOMOLOGY

After defining the strong tensor product of strong (sub)chain complexes, it is shown that an analogue of the Kunneth theorem holds in strong homology by proving that the kernel (cokernel) of connecting homomorphisms is isomorphic to the direct sum of torsion (tensor) products of strong homology groups. An isomorphism between strong (r-stage) homology groups of inverse systems is also constructed.     

Dynamically selective multiwavelength cross-connect based on fibre Bragg gratings and mechanical optical switches

A dynamically selective multiwavelength cross-connect for wavelength division multiplexed (WDM) networks based on fibre Bragg gratings (FBGs) and optical switches is reported. Dynamically single- or multi-channel cross-connect functionality can be realized according to control of the optical switches and the FBGs' arrangement. Bit-error-rate performance with negligible power penalty is achieved in a 2.5Gbs-1x3 WDM channels over 100km conventional single-mode fibre (SMF) network demonstration. The characteristics of low channel crosstalk, uniform channel loss, high scalability and cascadability, and low cost of this device could provide more reconfiguration flexibility and network survivability for WDM networks.     

磁场逐渐增强的摇摆器

研究了用磁场增强摇摆器来提高自由电子激光器效率的机制．采用KMR方程，考虑空间电荷效应，模拟计算发现自由电子激光器的效率有了很大的提高，而且电子束能散度越大，对提高自由电子激光器效率越有帮助．因此采用磁场增强摇摆器能充分利用加速器的能量来莸得更高的自由电子激光器能量 关键词：     

DYNAMIC ANALYSIS OF AN AUTOMATIC WASHING MACHINE WITH A HYDRAULIC BALANCER

A mathematical model of a hydraulic balancer in steady state condition was derived from a whirling model of a vertical axis washing machine, with the aim of implementing a dynamic analysis of an automatic washing machine during spin drying mode. The centrifugal force acting on the hydraulic balancer depends on the centroidal distance of the fluid in the hydraulic balancer, and the centroidal distance is a function of an eccentricity of the geometric center of the hydraulic balancer from the axis of rotation. A mathematical model of the hydraulic balancer in steady state is validated by the experimental result of the centrifugal force. Experiments were performed on a washing machine during spin drying mode, and results were compared with the simulation result. The parameters affecting the vibration of the washing machine were investigated by the parameter study.     

Syntheses of Iso-Condensed Heteroaromatic Pyrroles and the Application to the Total Synthese of Natural Products

A novel method, namely the intramolecular 1,3-dipolar cycloaddition and cycloreversion ofazido-alkylidene malonates, for the preparation of iso-condensed heteroaromatic pyrroles has beendeveloped. The application of this method for the synthesis of 2,4-dihydropyrrolo[3,4-b]indole ringsystem, as well as the application of this ring system for the total syntheses of ellipticine alkaloids arereported.