Natural-convective instability of electrochemical systems: A review

Basic theoretical and experimental results of research into natural-convective instability of electrochemical systems are considered.     

Numerical Solution of the Problem of the Limiting Current for the Copper Electrodeposition from a Solution of Cupric Sulfate and Sulfuric Acid in Conditions of Natural Convection

Equations for a boundary layer, written in self-similar variables, are integrated numerically to obtain distributions of concentration of ions Cu²⁺, H⁺, and SO₄ ^2–; a hydrodynamic velocity; partial currents of electrolyte components; and the limiting current of copper deposition and determine the Rayleigh number for the system under consideration. The results are compared with an approximate analytical solution obtained earlier.     

A semi-automatic system for activation analysis using the WWR nuclear reactor

A semi-automatic pneumatic transport system for nuclear reactors is described. The sealed polyethylene capsules containing the sample are placed into transport containers. Ten such containers are placed manually into a feeding device. All subsequent operations (irradiation, removal of the capsule from the container, and transport of the capsule to the laboratory for activity measurement) are automated. Total time from the completion of irradiation to the beginning of measurement is 10–20 sec.     

富硒蛹虫草试样中硒的形态分析

本文采用连续浸提法研究了富硒蛹虫草中硒的赋存形态。结果表明,碱溶态>盐溶态>水溶态>醇溶态>残渣态。可见,碱浸取是获取植物蛋白的有效途径,在富硒蛹虫草试样中硒主要以硒蛋白的形式存在。     

Determination of electron affinity of carbonyl radicals by means of negative ion mass spectrometry

Appearance energies of [M-H](-) ions from carbonyl compounds R-CO-R' (R,R' = H, CH(3), NH(2), OH) have been measured by means of negative ion mass spectrometry in resonant electron capture mode. Values of electron affinity of the corresponding radicals, CH(2)&dbond;C(X)O, NH&dbond;C(X)O and O&dbond;C(X)O, have been determined. Copyright 1999 John Wiley & Sons, Ltd.     

Mass-transfer problems in the electrochemical systems

The problems concerning quantitative analysis of mass-transfer processes in the electrochemical systems (ECS) are briefly reviewed. The interrelation between the mass-transfer problems in the electrochemical and heat systems is considered. Various approaches to the numerical determination of distributions of concentrations of ions of all types and electrochemical potential in the ECS are considered. The methods of allowance for the migration transfer and choosing the boundary conditions for the transfer equations and other problems are considered. Some actual lines of development of the theory of mass-transfer in the ECS are pointed out.     

Time-of-flight system for the multipurpose detector (MPD)

A conceptual design for a multipurpose detector (MPD) [1] is proposed for the study of hot and dense barony matter in collisions of heavy ions over the atomic mass range A = 1–197 at center-of-mass energies of up to 11 GeV (for Au⁷⁹⁺). The MPD experiment is scheduled to be performed at a future JINR accelerator complex facility for heavy ions, the Nuclotron-based Ion Collider Facility (NICA), which is designed to reach the required parameters with an average luminosity of L = 10²⁹ cm⁻² s⁻¹. Identification of charged hadrons (PIDs) at intermediate momenta (0.1–2 GeV/c) is achieved via time-of-flight (TOF) measurements. As a base element of the TOF detector, we consider a 10 gap MRPC with a strip or pad readout. Results from an MRCP prototype test are presented.     

Mass transfer in the rotating electrochemical cell with vertical cylindrical electrodes: the effect of rotational rate and cell geometry on the limiting current density

The mass transfer in the rotating electrochemical cell with vertical cylindrical electrodes containing a binary electrolyte is theoretically studied. The Navier-Stokes equations in the rotating system of coordinates, the equations of ionic transfer of electrolyte components, which is caused by diffusion, convection, and migration, and the condition of electroneutrality are used as the mathematic model of the process. The effects of centrifugal force and Coriolis force are studied by using the numerical simulation; the effect of geometry of electrochemical cell on the limiting mass transfer rate is determined.     

Numerical Modeling of Non-Steady-State Ion Transfer in Electrochemical Systems with Allowance for Migration

Numerical methods that are used for modeling non-steady-state ion transfer in electrochemical systems and account for the diffusion, migration, convection, and homogeneous chemical reactions are analyzed. It is shown that the violation of the electroneutrality condition (ENC) in the process of numerical solution is due to the difference equations being inconsistent with the initial differential equations. Difference schemes for numerical calculation of transfer processes, which make it possible to split a set of coupled equations, are designed and conditions for their stability are determined. The explicit difference scheme is self-consistent, i.e. it ensures that ENC is rigorously met. In the implicit difference scheme, ENC is probably violated when splitting the set of equations. To restore electroneutrality of the medium, it is proposed to use a physically substantiated analytical relation for the space charge relaxation under the action of a strong electric field.