PARTITION BETWEEN α-METHYL AND α-METHYLENE PROTONS IN 1H NMR SPECTRA OF COAL TARS

Cut-off points between protons in a-methyl and or-methylene groups were proposed for the evaluation of 'H NMR spectra of coal tars. The position of the cut-off points depended on the proton aromaticity and related structural features of the samples. Equations for the calculation of the cut-off points as a function of proton and carbon aromaticity, and atomic H/C ratio were proposed for the range of proton aromaticity between 0.2 and 0.6.     

ALIPHATIC C-H BOND RESPONSES IN THE 900-700 cm-1 REGION OF THE FTIR SPECTRA OF COAL TARS

Four bituminous coals were comprehensively separated by column chromatography into a number of fractions. Four aromatic hydrocarbon fractions of each tar were analyzed by FTIR spectroscopy, and the 900-700 cm^-1 spectral region was evaluated. This spectral region was found to be composed of at least 14 separate bands, which were resolved by using self-deconvolution and curve-fitting procedures. The bands near 821 cm^-1, 791 cm^-1, and 784 cm^-1 were proposed to originate from rocking vibrations of aliphatic C-H bonds. For the tar samples with a proton aromaticity between 0.21 and 0.37, these bands account for on average 12% of the total integral intensity of the 900-700 cm^-1 region. This percentage cannot likely be neglected in a correct quantitative evaluation of the region and calculation of the aromatic hydrogen concentration. However, a correct resolution of the bands can be very difficult in the FTIR spectra of a complex material, such as coal.     

Fractionation of a statistical copolymer in a demixing-solvent system: Theory and experiment

It has been shown that, under specific conditions, a demixing-solvent fractionation according to chemical composition can be applied to statistical copolymers. Formally, identical expressions have been derived for the distribution of a copolymer between coexisting phases in precipitation (sol-gel) and demixing-solvent fractionations. Theory predicts that the effects of molar mass and chemical composition cannot be separated in either of the phaseequilibrium fractionations. With demixing solvents, the partition coefficient depends steeply on copolymer composition, which enables one, e.g., to separate homopolymers from a blend. Multistep demixing-solvent fractionation of a copolymer may proceed only in specific cases, e.g., immediately below the maximum of the coexistence curve. A feasibility study was performed with a chemically heterogeneous statistical copolymer of styrene and 2-methoxyethyl methacrylate; the experimental results have confirmed the theoretical predictions. © 1993 John Wiley & Sons, Inc.     

Heat transfer evaluation of impingement cooling in hot rolling of shaped steels

The accuracy of mathematical modelling is strongly influenced by the boundary conditions assumed. A shape rolling mill was instrumented to provide on-line temperature measurements during hot rolling of steels. An inverse heat conduction technique was used to convert the measurement data to surface heat fluxes and heat transfer coefficients. The heat transfer coefficient or heat flux could then be used as the necessary boundary condition for the computation of temperature field in the entire roll and workpiece by means of conventional heat transfer analysis. The heat transfer phenomena involved and the influence of the major operating parameters on the heat transfer results have also been discussed. Finally, the paper has shown that the numerical evaluation procedure adopted has at least the same influence on the results as the accuracy of temperature sensors and the properness of experiment design.     

Matters Concerned with Development of Autonomous Cogeneration Energy Complexes on the Basis of Microhydropower Plants

In connection with the depletion of the world reserves of fuel resources and growing environmental safety requirements for power-generating facilities, the article presents a review analysis of the present state of conventional power supply systems in Russia and in the European Union countries (for the latter, the Czech Republic is taken as an example). We consider promising lines of research in the fields of energy conservation and development of efficient and environmentally clean energy sources and specific features of their process circuit solutions and technical embodiment as well as solutions necessary for putting new technologies into use in the real energy sector. In the conventional power industry, facilities implemented according to the principle of combined generation of electricity and heat—so-called cogeneration—have received wide use. Such facilities can be constructed not only on the basis of fuel engine units (gas turbines, diesel–generators, etc.) but also using renewable energy sources. It is pointed out that, with the modern scientific-technical level, the line involving the use—within combined power supply systems—of power-generating facilities having minimal negative impact on the environment has been developed to an insufficient extent. The article considers the modern state of hydraulic power engineering for estimating the possibility of using hydropower resources for development of investigations in this field. Prerequisites for constructing combined, first of all, autonomous energy sources of the micro power capacity class (up to 100 kW), in particular, a cogeneration power complex on the basis of a microhydropower plant, are considered. The results from design-theoretical and experimental investigations into the cogeneration complex structural components are outlined; a basic circuit solution for such energy source aimed at independently supplying electricity and heat for a consumer is shown, and promising ways for further improving the proposed technical solution and making it more efficient are pointed out.     

Calculation of countercurrent separation processes—III. Computation of two interlinked columns.

The relaxation procedure is used for solution of two interlinked distillation columns. Both approaches-sequential iterative method and the block relaxation technique are compared. A new algorithm making use of simultaneous solution of all equations is proposed.     

Improvement of vascular dysfunction and blood lipids of insulin-resistant rats by a marine oil-based phytosterol compound

The syndrome that is characterized by obesity, insulin resistance, and hyperlipidemia is increasingly prevalent in all prosperous societies. It is now recognized as a major contributor to cardiovascular disease. Vascular dysfunction in the form of hypercontractility and impaired nitric oxide-mediated relaxation is a significant component of cardiovascular disease, predisposing to ischemic events. The JCR:LA-cp strain of rats exhibits all major aspects of the obesity/insulin resistance syndrome, including vascular dysfunction and ischemic lesions of the heart. Dietary lipid intake may have a marked effect on plasma lipid levels and, potentially, on vascular disease. We have investigated the effects of a novel preparation, ONC101 (a phytosterol esterified with fish oil), on plasma lipids and vascular function in the insulin-resistant JCR:LA-cp rat. Treatment of obese male rats with ONC101 from 8 to 12 wk of age resulted in no change in plasma lipid concentrations at 0.5 g/kg body weight. At the higher dose of 2.6 g/kg, plasma TG fell 50% (1.26 vs. 2.59 mmol/L, P<0.002) and cholesterol esters were significantly reduced (1.34 vs. 1.61 mmol/l, P<0.002). Food intake and body weights were unaffected by ONC101 treatment. At the low dose of 86 mg/kg, the hypercontractility of aortic rings in response to phenylephrine was normalized and the relaxant response to acetylcholine was significantly improved. The results indicate that ONC101 at high doses has significant hypolipidemic effects and, at very low doses, has beneficial effects on endothelial and vascular smooth muscle cell function. Deceased, June 22, 2001.     

Eulerian-Lagrangian model for traffic dynamics and its impact on operational ventilation of road tunnels

This contribution deals with a computational Eulerian-Lagrangian model that simulates movement of cars inside a road tunnel and its impact on operational ventilation. The model simulates moving cars as discrete objects that “fly” through the tunnel. The objects are treated with a Lagrangian momentum equation and their velocity is solved along their trajectories that are determined by the shape of the roadway. The flow of the ambient air is solved with a commercial CFD code StarCD. Due to drag force, the cars virtually change their velocity, but the latter is continuously re-set to its original value. The momentum equation for the continuous phase contains an additional source term that results from the net efflux of momentum of cars when they enter and leave a particular control volume of the solution domain. The model by Jicha et al. (Int. J. Environ. Monit. Asses. 65 (2000) 343) can simulate cars moving at different speeds and traffic rates in individual traffic lanes. As a result we obtain flow rate generated by moving vehicles as a function of traffic speed and traffic rates. Turbulence was modelled using standard k-ε model with three different formulas for extra sources of the kinetic energy of turbulence that account for additional turbulence generated by moving vehicles. The traffic-induced turbulence shows a non-negligible effect on the total flow rate inside the tunnel. The model was validated with experimental data from Chen et al. (Int. J. Wind Eng. Ind. Aerod. 73 (1998) 99), where the small-scale tunnel 1:20 was investigated. The experiments were carried out with a moving belt carrying small car-like objects. The tunnel length was 20 m, the height 36.5 cm and the tunnel had two parallel lanes. Several traffic densities and speeds were simulated, namely 10,000, 20,000 and 30,000 cars/h per lane with speeds of 20 km/h and 40 km/h.     

<Superscript>57</Superscript>Fe Mössbauer spectroscopy of synthesized ɛ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles

Magnetic nanoparticles have promising applications in many areas, for example optics, electronics, biology, medicine, etc. The primary goal of this study was to synthesize nanoparticles of magnetic ?-Fe₂O₃ embedded in amorphous SiO₂. The structure and properties of the final product have been found to depend strongly on the initial conditions of preparation. The Mössbauer spectroscopy analysis of the samples was complemented by the study of X-ray powder diffraction, magnetic measurements, and high-resolution transmission electron microscopy.