The complete spectrum of image line

A derivation is presented of the complete orthonormalized spectrum, under LSA/LSM (longitudinal-section electric/magnetic) assumptions, for image line waveguiding structures by using a so-called method of partial wave phase shifts. The analysis is developed for the even LSM (TM^y) polarization, having H_y=0 and E_y as the main electric field component: the LSE analysis proceeds along dual lines. An arbitrary radiation field is described as a superposition of the LSM and LSE continua     

The stochastic model of evolution of scientific disciplines

In the paper science is regarded as a self-adapting system consisting of two subsystems. The stochastic model of one of the subsystems is proposed. The model reflects changes of the structure of a scientific discipline. As an example a model for the physics of elementary particles is presented.     

Multitone jamming rejection of FFH/BFSK linear-combining receiverover Rayleigh-fading channels

A computationally efficient BER expression for an FFH/BFSK linear-combining receiver against multitone jamming and AWGN over Rayleigh-fading channels is derived based on a Taylor series expansion. The analytical expression, validated by simulation results, allows us to efficiently analyse the system performance with higher diversity levels, which is otherwise mathematically intractable     

Computation of turbulent flows past arbitrary two-dimensional surface-mounted obstructions

The modelled equations of turbulent flow over two-dimensional bluff surface obstructions are solved numerically, using body-fitted coordinates and the k-? two-equation model of turbulence. Emphasis is placed on demonstrating a method capable of treating arbitrary geometrical configurations.Computations have been made for a number of geometrical configurations, including, amongst others, a rectangular block as well as triangular and semi-circular obstructions. Upstream conditions were purposely selected to simulate a neutrally stable atmospheric boundary layer.The low-Reynolds number version of the turbulence model was used in order to accommodate near-wall viscous effects, and some effort was devoted to the choice of empirical constants based on comparison with empirical information. Making due allowance for a number of discrepancy-causing factors, reattachment lengths obtained are deemed to be under-predicted. This is attributed to theoretical weaknesses of the two-equation model as well as numerical inaccuracies associated with the difference scheme.     

The effect of nisin on the physiology of Bifidobacterium thermophilum

The effects of nisin on lactate accumulation, growth, and Fe(III) binding by Bifidobacterium thermophilum (ATCC 25866) and Bifidobacterium breve (ATCC 15700) were investigated. Nisin inhibited lactate production by B. thermophilum at concentrations of less than 1 microg/ml, but this effect could be largely eliminated by pretreatment of the organism with 100 to 400 microM Al(III) or La(III). Nisin also inhibited the growth of B. thermophilum at concentrations of 2 to 3 microg/ml, with lower concentrations showing lag periods and/or slower rates of growth. However, Al(III) could not negate these effects, most likely because of Al(III) chelation by the trypticase-proteose-yeast extract medium. Nisin was able to increase instantaneous Fe(III) binding by both B. thermophilum and B. breve, though prolonged-time experiments (up to 120 min) with B. thermophilum indicated no difference in total Fe(III) bound. Nisin was thus able to increase the free radical reaction rate with bifidobacteria and the resultant rate of Fe(III) binding. It was concluded that nisin will normally inhibit the metabolic activity of B. thermophilum along with that of certain bacterial pathogens; however, this effect may in some instances, be abated by a pretreatment with Al(III). Moreover, by accelerating free radical action and the binding of iron by bifidobacteria, nisin may be able to potentiate their normal probiotic action.     

Hybrid LSFEM and transfinite element method for microwave circuits

A hybrid procedure is presented that combines the least-squares finite element method (LSFEM) and the transfinite element method for analysing microwave circuits. The benefits of the LSFEM for modelling the interior region of the circuit are combined with those of the transfinite element method to effectively couple the fields to semi-infinite port regions where the scattering parameters of the circuit are to be determined. The validity and efficiency of this new technique are demonstrated     

Transient cavitation effects in fluid piping systems

An accurate prediction of pressure transients and associated loadings in nuclear power plant piping systems requires a treatment of cavitation. A technique for calculating this effect in a general fluid-hammer analysis by the method of characteristics is developed. Cavitation is treated by a modified column separation model and is assumed to be a local phenomenon occurring whenever the pressure drops below the vapor pressure of the fluid. While the model is a simplification of the actual phenomena it reproduces the essential features of transient cavitation. Computational results obtained for a variety of piping arrangements demonstrate the versatility of the approach, and clearly illustrate the fact that neglecting cavitation leads to erroneous pressure-time loadings in the piping systems. Comparisons of calculated results with available experimental data, for a simple piping arrangement, show good agreement and provide validation for the computational cavitation model.