Magnetic contrast in the scanning electron microscope with particular reference to bubble domain structures

A study has been made of the usefulness of the SEM for the observation of magnetic bubble-like domain structures in a variety of oxide materials. The basic theory behind the technique is outlined including a rigorous evaluation of the fiekd integral for an isolated bubble and a hexagonal bubble lattice. Secondary electron trajectories have been computed and give reasonable agreement with those predicted from the model used.Experimentally it has proved possible to observe magnetic bubbles in garnet but the contrast is generally poor. Better results are obtained in hexa- and ortho-ferrites including the resolution of surface detail. The possibility of scanning electron optical detection in a bubble memory is discussed but the signal-to-noise ratio is again unfavourable for garnets.     

A semi-empirical theory of the electronic structure of ethylene with particular reference to the ionization potential

The electronic structure of the ethylene molecule is rescrutinized within the framework of the semi-empirical pi-electron theory. The lower electronic energy levels, twisting frequency, ionization potential and electron affinity are calculated without treating the so-called β parameter as empirical. A new approach for calculating the ionization potential is presented, in which an allowance is made for the change in the effective nuclear charge accompanying the actual ionization. The ionization potential is computed to be 10·757 ev, the observed value being 10·62 ev.     

Use of soft computing methods in risk assessment of electrostatic fire and explosion hazards in industries

The general problem in the theoretical and practical examination of hazards coming into existence in case of real, complicated industrial systems is basically the approximation of complicated multivariable functions of input and output variables. There is a rather new tool for solving the aforesaid problem, namely the use of soft computing methods: fuzzy logic, artificial neural networks and genetic algorithms. The new approaches can be effectively used for both the risk evaluation of working systems (checking and auditing) and—by using the predictive power of the methods—for designing and planning activities in industrial electrostatics.     

Approximate,time domain,non-stationary analysis of stochastically excited,non-linear systems with particular reference to the motion of vehicles on rough ground

An approximate state-space method for obtaining the time varying mean and covariance of non-linear systems excited by non-stationary random processes is presented. In particular the class of non-stationarity associated with the motion of a vehicle on rough ground (i.e., the process is “frequency modulated” as a result of the vehicle's variable velocity) is of interest. The method is based on a technique of modelling the input process as a “shaping filter” in the spatial domain which may be linked to the vehicle dynamic equations through the velocity function. The non-linear problem is overcome by using the technique of statistical linearization. An example is briefly discussed.     

Some methods for calculation of perturbations in nuclear reactors

Some methods for calculation of local perturbations of neutron fields and reactivity effects accompanying them are considered. Existence, uniqueness, properties and methods for finding solutions to the considered problems are discussed.     

An investigation into noise radiation from flow control valves with particular reference to flow rate measurement

Flow control valve noise has been investigated, both analytically and experimentally, for two cases of variable orifice area and variable mass flow rate. The analysis is based on Lighthill's acoustic analogy, together with Curle's theory for noise generation from fluid-solid boundary interactions. Results indicate that monitoring sound levels of valve noise could be useful as a feasible means for flow rate measurements and on-line automatic flow control in pipes.     

Prospects for and problems of using light-water supercritical-pressure coolant in nuclear reactors in order to increase the efficiency of the nuclear fuel cycle

Trends in the development of the power sector of the Russian and world power industries both at present time and in the near future are analyzed. Trends in the rise of prices for reserves of fossil and nuclear fuels used for electricity production are compared. An analysis of the competitiveness of electricity production at nuclear power plants as compared to the competitiveness of electricity produced at coal-fired and natural-gas-fired thermal power plants is performed. The efficiency of the open nuclear fuel cycle and various versions of the closed nuclear fuel cycle is discussed. The requirements on light-water reactors under the scenario of dynamic development of the nuclear power industry in Russia are determined. Results of analyzing the efficiency of fuel utilization for various versions of vessel-type light-water reactors with supercritical coolant are given. Advantages and problems of reactors with supercritical-pressure water are listed.     

The average monopole polarization charge and its relation to nuclear incompressibility and effective mass

The average monopole polarization charge for occupied states is related to the nuclear incompressibility and effective mass. This is done with a previously used approximation of a Taylor Expansion in the Hartree-Fock theory employing Skyrme interactions.     

Mesonic wakes in nuclear matter,with application to meson production in nuclear collisions

The process of meson production by a source moving uniformly through infinite nuclear matter is studied in field theoretic models in which a source-meson coupling is assumed, and in which the only effect of the nuclear medium is to modify the propagator of the mesons. If the meson dispersion relation, ω(k), in the medium becomes space-like in some region of k, k > ω(k), there is, for relativistic source velocities, energy loss to the mesonic excitations. Models of the pion propagator in nuclear matter lead to such a space-like region. Rates of pion production are calculated in the lowest order of the pion-source coupling. Consideration of higher order terms leads to an interesting class of problems which we designate as those of “non-Abelian Cherenkov radiation.” Brief consideration is given to the excitation of nuclear collective modes and to the problems of treating meson production in finite nuclei.     

Investigation of neutrino properties in experiments at nuclear reactors: Present status and prospects

The present status of experiments that are being performed at nuclear reactors in order to seek the neutrino masses, mixing, and magnetic moments, whose discovery would be a signal of the existence of physics beyond the Standard Model, is considered, along with their future prospects.     

Using the procedure of spectral projection for reactivity determination in physically large nuclear reactors

The reactivity determination methods which are based on the neutron field reconstruction procedure and the spectral-projection method are analyzed. The approximate methods of reactivity determination which can be used in practice are offered. The efficiency of the proposed methods in comparison to that of the methods applied in operation of nuclear power plants is demonstrated using computational models.     

Flocs surface functionality assessment of sonicated activated sludge in relation with physico-chemical properties

Flocs surface functional groups evolutions due to an ultrasonic treatment were investigated in respect with the mechanisms involved during sonication. Activated sludge surface functional groups changes were studied after treatment of a sample at different ultrasonic specific energies. Sludge functionality was qualitatively assessed by recording the infrared (FT-IR) spectra of centrifugation pellets. Potentiometric titration coupled with proton surface complexation modeling was used to assess the nature and quantity of ionizable functional groups present at the floc surface and in the aqueous phase. These evolutions were linked to changes of both mixed liquor biochemical composition (TSS, VSS, COD, proteins, humic like substances, polysaccharides) and physical properties (floc size and settleability). Observations carried out showed that activated sludge flocs were essentially mechanically disintegrated by ultrasonic waves: the nature of chemical bonds observed by FT-IR did not shift after ultrasonic treatment. Moreover, the total number of ionizable functional groups measured by potentiometric titrations remained constant during sonication. However, due to the solubilization of organic components induced by cavitation process, the corresponding ionizable functional groups (carboxyl, hydroxyl, amine) were transferred from particulate to soluble fraction. Moreover, due to the variable amount of proteins, humic like substances and polysaccharides solubilised, the relative contributions of carboxyl, hydroxyl and amine groups varied at floc surface.     

The 0(6) limit of the interacting boson model and its relation to triaxial nuclear models

It is shown that the 0(6) limit of the interacting boson model (IBA) corresponds to the γ-unstable model of Jean and Wilets, if one considers an infinite number of bosons in IBA (N → ∞). The rigid triaxial rotor model with γ = 30° satisfies the same selection rules, but differs considerably with respect to B(E2) values and energies.     

Balanced bright and dark field illumination for remote visual testing to detect cracks on pressure vessel of nuclear reactors

Optical Review - Remote visual testing by video cameras is the standard process for inspecting the pressure vessel of nuclear reactors. The inspectors need to find stress corrosion cracking of...