On the Derivation of the Quasi-steady Model in Electrochemical Machining

The use is discussed of the quasi-steady model, based on theirrotationality of the electric field between the electroded,in electrochemical machining. The general equations are derivedwhich describe the process. From Maxwell's equations, a non-dimensionalparameter, dependent on the physical characteristics of theprocess, is derived. When this paramter is sufficiently small,the electric field is shown to be appromimately irrotational.A quasi-steady model is then formulated in terms of Laplace'sequation togther with an equation relating the change of themode anode surface with the electric field evaluated at theanode surface. This equation can be derived from Ohm's and Faraday'slaws. Different methods for solving the associated boundaryvalue problem are discussed.     

Numerical Solutions for Two-dimensional Annular Electrochemical Machining Problems

Present address: Department of Applied Mathematics, University of Western Ontario, London, Ontario, Canada. Numerical solutions are obtained for a quasi-steady model ofthe electrochemcial machining process for two-dimensional problemswith the electrodes being represented by closed curves, oneinside the other. The accuracy of the procedure is checked bythe solutions obtained by it for a particular case with a perturbationsolution. The two solutions agree well. The applicability ofthe numerical procedure is indicated by presenting results whichshow the making of a notch in a circular cylinder.     

New multi-phonon gamma vibrational bands in A～110 neutron-rich nuclei

The high spin states of neutron-rich 103Nb, 107Tc and 109Tc nuclei in A~110 region have been investigated by measuring prompt γ-γ-γ coincident measurements populated with the spontaneous fission of 252Cf with the Gammasphere detector array. In 103Nb, one-phonon K = 9/2 and two-phonon K = 13/2 γ-vibrational bands have been identified. In 107Tc and 109Tc, one-phonon K = 11/2 and two-phonon K = 15/2 γ-vibrational bands, in which the zero-phonon bands are based on K=7/2 excited states, have also been identified...     

On the Non-linear Stability of the Electroforming Process

The stability of the electroforming process is investigatedby both a perturbation procedure and a numerical integrationof the complete quasi-steady mathematical model. Both linearand exponential relationships between current efficiency andcurrent density are considered. The perturbation procedure iscarried out for quadratic terms. The conclusions drawn fromthe perturbation analysis and those drawn from the numericalresults agree.     

Solution of Time Dependent Electrochemical Machining Problems by a Co-ordinate Transformation

A numerical procedure for calculating the solution to two-dimensionaltime dependent electrochemical machining problems is derived.This method can be used in problems where the cathode containsinsulated portions. The electrostatic potential problem is solvedby transforming the variational integral to a domain where theboundaries become straight lines, and discretizing the resultantintegral. An implicit finite difference technique is used tointegrate the free surface equation. A variable spatial meshis incorporated into the scheme. The results are compared toa Kantorovich solution of the same problem.     

Compressible Flow Calculations by a Variational Method using Natural Boundary Conditions

The problem of steady inviscid plane subsonic flow past an aerofoilis formulated as a variational principle with the boundary conditionat the surface of the aerofoil treated as a natural boundarycondition. Numerical solutions are obtained for flow past non-liftingellipses by the application of finite differences to two differentforms of the variational principle. The numerical procedureis simpler than when the boundary condition at the surface istreated explicitly, and the solutions are of the same accuracy.     

A Perturbation Solution for a Two-dimensional Annular Electrochemical Machining Problem

Present address: Deparment of Applied Mathematics, University of Western Ontario, London, Canada. A two-dimensional electrochemical machining problem which consistsof an almost circular anode placed inside a circular cathodeis solved using a perturbation procedure. The smoothing of roughmetal parts is studied by solving the resulting perturbationequations numerically.     

MUTATION AND SISTER CHROMATID EXCHANGE INDUCTION IN CHINESE HAMSTER OVARY (CHO) CELLS BY PULSED EXCIMER LASER RADIATION AT 93 nm AND 308 nm AND CONTINUOUS UV RADIATION AT 254 nm

We compared mutagenesis and sister chromatid exchange (SCE) induction by 193 nm and 308 nm pulsed excimer laser radiation with 254 nm low intensity continuous wave UV light in Chinese hamster ovary (CHO) cells in culture. The 254 nm radiation was most mutagenic of the radiations, in accordance with expectation, and also was most effective in increasing the level of SCEs. The 193 nm radiation was mutagenic at the ouabain resistance locus, but not at the HGPRT locus. However, 193 nm radiation was also strongly cytotoxic at energies producing measurable mutations. This radiation also caused a dose-related increase in SCEs. Pulsed excimer radiation at 308 nm was mutagenic at both loci, and also increased the incidence of SCEs. Comparison of the ratio of mutants/surviving cells at the D37 after radiation showed similar values for 254 nm and 308 nm at the HGPRT locus, but at the ouabain resistance locus, the ratio for the 308 nm radiation was about 5 times that for 254 nm radiation. These results indicate that some risk for mutagenesis may accompany the use of excimer radiation in the UVA region in therapeutic applications.     

Unsteady Porous Flow with a Free Surface

Three different numerical methods for solving unsteady two-dimensionalporous flow problems with a free surface are presented. Thevelocity potential is expressed as the solution to a variationalproblem which is solved by a Rayleigh-Ritz expansion, a Kantorovichexpansion and a co-ordinate transformation method. The freesurface equation is solved by a Crank-Nicolson procedure. Thethree methods were tested on the same set of problems and theobtained results are virtually identical.