Finite volume schemes for dispersive wave propagation and runup

Finite volume schemes are commonly used to construct approximate solutions to conservation laws. In this study we extend the framework of the finite volume methods to dispersive water wave models, in particular to Boussinesq type systems. We focus mainly on the application of the method to bidirectional nonlinear, dispersive wave propagation in one space dimension. Special emphasis is given to important nonlinear phenomena such as solitary waves interactions, dispersive shock wave formation and the runup of breaking and non-breaking long waves.     

Study of the frequency distribution of secondary radiation resonances of small-sized pilotless vehicles

Computer simulation of a typical small-sized pilotless vehicle is carried out. Three-dimensional diagrams of the secondary radiation (scattering diagrams) of the vehicles are derived. Frequency dependences of the secondary radiation in the range 50 MHz–4 GHz are plotted. The possibilities of the object model simplification are discussed. The polarization features of object detection are studied. The possibility of object recognition against the bird’s background is evaluated.     

Fine structure of the isoscalar giant quadrupole resonance in Ca due to Landau damping?

The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in ⁴⁰Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at Ep=200 MeV$E_{\mathrm{p}}=200\text{MeV}$. Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon–nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for ⁴⁰Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle–two-hole (2p–2h) states.     

Comparison between the measured and calculated reactivity in measuring the effectiveness of the emergency protection at the stage of physical start-up of unit no. 3 at the Kalinin nuclear power plant

This paper presents comparisons between the effectiveness of the emergency protection under both stationary and nonstationary formulations calculated with the use of the RADUGA-7.5 package [1] and experimental data obtained in measuring the ??weight?? of the emergency protection in the process of physical start-up of the VVER-1000 reactor of unit no. 3 of the Kalinin NPP. On the basis of the results obtained, recommendations are given on comparing the measured and calculated reactivity and parameters determined by using its value.     

The nature of lignin from steam explosion/enzymatic hydrolysis of softwood

Effective utilization of the lignin by-product is a prerequisite to the commercial viability of ethanol production from softwood wastes using a steam explosion (SE)/enzymatic hydrolysis (EH)/fermentation process. Changes in the chemical composition of Douglas fir wood on SO₂-catalyzed SE followed by EH were assessed using conventional analytical methods and new halogen-probetechniques. A significant solubilization of hemicelluloses was observed in the SE stage, the severity of which affected subsequent fermentation of cellulose and sorption of enzymes. SE of softwood resulted in dramatic changes in the chemical structure of lignin in the residual material involving chemical reactions via the benzyl cation. This leads to a more condensed lignin with partly blocked α-reaction centres. Possible uses for this lignin are discussed.     

Studying the start-up scenario for a pulsed gyrotron with a relativistic electron beam

We present the results of studying the start-up scenario for a high-power pulsed gyrotron operated at the TE₅₃ mode for two variants of the current–voltage characteristic of a three-electrode magnetron-injection electron gun. In the standard variant of feeding the voltage to the first anode from the resistive divider, sequential generation of the TE₇₃ and TE₆₃ modes, and, finally, the operating TE₅₃ mode was observed at the edge of the pulse. The current–voltage characteristic for which only the operating mode is excited is obtained by decreasing the growth rate of the voltage applied to the first anode.     

13C NMR study of the dissociation of tartaric and citric acids

The dissociation of tartaric and citric acid was studied by the ¹³C NMR method. All four dissociation constants of tartrate and citrate were determined directly from the pH-dependent shift of signals of carbon atoms making the composition of the hydroxy acids. It was shown that on successive splitting off of protons in tartaric acid, rings are formed between the carboxy and hydroxy groups, while in citric acid such rings are not formed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 6, pp. 706–710, November–December, 1990.     

Three-Component Synthesis of 5-Arylmethylene-3-benzoylmethylenepiperazine-2,6-diones

Russian Journal of General Chemistry -