Dark currents of a tandem accelerator with vacuum insulation

The dark currents flowing in the high-voltage gaps of an electrostatic tandem accelerator with vacuum insulation and the effects associated with their occurrence are investigated. This accelerator, featuring a fast rate of charged particle acceleration and a large surface area of the accelerating electrodes, has been designed to produce a proton beam with an energy of 2 MeV and a constant current of up to 10 mA.     

Pulsed eddy current testing with variable duty cycle on rivet joints

In pulsed eddy current testing, repetitive excitation signals with different duty cycles have different spectral representations. This work studies the influence of duty cycle on the ability to detect holes and EDM notches beneath rivet heads in subsurface layers of stratified samples. Feature patterns for the integrity of rivet joints are proposed and verified. The proposed method has the added advantage in that no reference sample is needed while employing multiple pulse measurements, with different pulse widths. Experimental testing and modelling approaches are discussed in connection with defect depth quantification, which can be extended to the quantification of complex defects.     

Main results of the development of dispersion type IMF at A.A. Bochvar Institute

At A.A. Bochvar Institute a novel conception of IMF to burn civil and weapon’s grade Pu is currently accepted. It consists in the fact, that instead of using pelletized IMF, that features low serviceability and dust forming route of fuel element fabrication, the usage is made of dispersion type fuel element with aluminium or zirconium matrices.Dispersion fuels feature a high irradiation resistance and reliability; they can consequently reach high burnups and be serviceable under transient conditions.Three basic fuel element versions are under development in VNIINM for both thermal and fast reactors.The first version is a fuel element with a heterogeneous arrangement of fuel (PuO₂ or YSZ granules) within an Al or Zr matrix. The second version of a fuel element has a heat conducting Al or Zr alloy matrix and an isolated arrangement of PuO₂ in a fuel minielement more fully meets the ‘Rock Fuel’ requirements. According to the third version a porous meat of zirconium metallurgically bonded to a fuel cladding is formed through which a PuO₂ powder is introduced. All the versions are technologically simple to fabricate and require minimal quantities of process operations related to treating MA and Pu. Preliminary in-pile tests of IMF prototypes are presented.     

Improved ladle vacuum treatment of steel

Industrial tests of a new ladle vacuum treatment (the VODF process) in steel smelting are undertaken at OAO Severstal. Comparative analysis indicates the benefits of the new process.     

Optimisation of isolation and purification of the jack bean enzyme urease by extraction and subsequent crystallization

A detailed investigation into the isolation by extraction and the purification by crystallization of the enzyme urease from jack bean meal is presented with a view to developing a large-scale process. The effect of different extraction solvents and additives upon the resulting crystals is characterised in terms of crystal size, protein yield and protein purity. The enzymatic activity of urease is exploited in order to quantify the amount and purity of the protein obtained. The extraction procedure was optimised and all stages of the process were monitored in order to provide as detailed a picture as possible of the impact of different process stages upon the intermediate products. Almost all protein is extracted in a single extraction step. Further extraction steps using the same meal but fresh solvent yield only small additional protein yields. Less than 10% of total protein is extracted in a second step, less than 3% in a third extraction. Different solvents lead to clear differences in product quality, with no single solvent optimising all quality criteria. In addition, the point at which the acetone precipitant is introduced into the process has a clear influence on the product. Judicious choice of extraction conditions can significantly increase the size of the urease crystals at the cost of product purity, quantified by specific activity. High product purity (a maximum 138-fold increase in purity was observed with a maximum yield of 8.4%), in contrast, leads to smaller crystals. Comparison to the purest commercially available urease revealed a similar urease content.     

On the uni- and bimodality of a two-component Gaussian mixture

Several sufficient conditions are formulated for the uni- and bimodality of a mixture of two Gaussian distributions with equal variances σ² and different expectation values μ _i , i = 1, 2. An equation governing all the degenerate critical inflection points for the probability density f(x) of the mixture is derived by a statistical method. This equation describes the boundary of the uni- and bimodality domains of f(x). Nina Nikolaevna Aprausheva was born in 1940. Graduated from the Moscow State University (Department of Mechanics and Mathematics) in 1966. In 1982, defended the Cand. Sci. thesis “On the Application of Mixtures of Normal Distributions in Pattern Recognition.” Senior scientist at Dorodnicyn Computing Center, Russian Academy of Sciences. Scientific interests: mathematical statistics, computational mathematics, mathematical methods in pattern recognition, and decision theory (about 75 publications). Member of Association of Pattern Recognition and Association of. “Women in science and education.” N.N. Aprausheva’s publications have been awarded several prizes at the scientific publications contests in Computing Center of Russian Academy of Sciences. Stanislav Viktorovich Sorokin was born in 1947. Graduated from Moscow State University (Department of Computational Mathematics and Cybernetics) in 1971. Programmer at Dorodnicyn Computing Center, Russian Academy of Sciences. Scientific interests: computational mathematics, system programming, and pattern recognition (20 publications).     

Charge-coupled devices with compensated charge transfer

It was shown that charge-transfer inefficiency in charge-coupled devices can effectively be compensated by doubling the number of unit cell required for charge transfer. An empty cell should follow each charged one, and charge readout in the output unit is performed via the summation of the charges on every pair of such cells.     

Heat transfer under natural convection of liquid metal during its boiling in a system of channels

We describe an experimental installation, a model, a test procedure, and results from experimental investigations into hydrodynamics and heat transfer during the boiling of an eutectic sodium-potassium alloy in a system of two parallel channels that simulate the operating conditions of channels in a typical fast-neutron reactor.