Synthesis of polyanilines with pendant fluorescent units

Functionalized polyanilines containing biphenyl, terphenyl, carbazole, anthracene, and 4-n-hexylphenyl moieties were synthesized though the reaction of polyaniline in emeraldine base form with sodium salt of corresponding vinylketoaromatics with quantitative yields. Polymers were characterized with Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and thermogravimetry. The emission characteristics of these polymers in N-methyl-2-pyrrolidone solution were examined. The functionalized polyanilines exhibited an intense green emission.     

Rationally based model for evaluating the optimal refrigerant mass charge in refrigerating machines

A rationally based algorithm was proposed to evaluate the optimal mass charge into refrigerating machines. The calculated results indicate that the system performance is strongly related to the refrigerant mass charge. In the early stage of the refrigerant charge process, a sharp rise of COP is observed. The COP reaches an optimal value for a specified refrigerant charge and shows a slight drop for a further increase of refrigerant charge. Calculated results reveal similar trends to those of experimental data. The analysis of the study can well interpret the cycle transformation subject to refrigerant mass charge.     

Millimeter-wave Detectors Based on Antenna-coupled Low-barrier Schottky Diodes

The principles of construction of millimeter wave detectors based on low-barrier Schottky diodes and planar antennas are discussed. The modified planar slot antenna with low beam spillover at the resonant frequency of 94 GHz has been developed. Experiments have been carried out to investigate detecting characteristics of the diodes with differential contact resistances \( R_{j} = 1 \div 1000\;{\text{k}}\Omega \) at zero bias. Experimental data are well correspond to calculations in a simple model of detector. At \( R_{j} = 20 \div 100\;{\text{k}}\,\OmegaΩ \) the maximum of rf-to-dc voltage sensitivity - more than 10000 V/W - is obtained. At lower values of \( R_{j} = 2 \div 6\;{\text{k}}\,\Omega Ω \) a better noise equivalent power (NEP), around 10^?12 W Hz^?1/2, is predicted.     

Model and field testing of a heavy-duty gas turbine combustor

The results of stand and field testing of a combustion chamber for a heavy-duty 150 MW gas turbine are discussed. The model represented one of 14 identical segments of a tubular multican combustor constructed 1∶1 scale. The model experiments were executed at a lower pressure than that in a real gas turbine. Combustion efficiency, pressure loss factor, pattern factor, liner wall temperature, flame radiation, fluctuating pressure and NOx emission were measured at partial and full loads for both model and on-site testing. The comparison of these items in the stand and field test results led to has the development of a method of calculation and the improvement of gas turbine combustors.     

Application of hydrocarbon mixtures in small refrigerating and cryogenic machines

Application of hydrocarbon mixtures enables the creation of simple, reliable and durable refrigerating and cryogenic Joule–Thomson micro coolers for the temperature range of −73 to −183 °C. The temperature, thermal, power and hydraulic performances of a series of prototypes are presented. The results of tests demonstrate that small, single stage, sealed, lubricated compressors can be applied to these purposes. The start up and steady operation hydraulic performance of those machines are quite similar to the performance of domestic refrigerators. The last, together with the fact that in the studied micro coolers the lubricated compressors are used at temperatures down to −183 °C, ensures a large resource of operation. That is just the reason that holds out a hope for prospects in a broad field of applications for the studied prototypes, despite their lower power performances in contrast to gas micro coolers.     

Modeling of the porous nickel deposits formation and assessing the effect of their thickness on the catalytic properties toward the hydrogen evolution reaction

Hydrogen used as an energy carrier can be obtained by water electrolysis. To improve the energy efficiency of this process porous nickel catalysts are often used. The paper investigates the electrodeposition regularities and the porous nickel deposits morphology and the properties of nickel foams toward the hydrogen evolution reaction. During electrodeposition at high current density, nickel deposits with macro- and micropores are formed. The dependence between the fraction of macropores on the deposit surface and the electrolysis time is described by the empirical equation. Total porosity of loose nickel deposits is much higher than the porosity of foams. However, the surface macropores fraction of deposits studied is approximately the same, while the microporosity of loose deposits is significantly higher. The values of nickel deposits total porosity calculated by the model agree with the values obtained by experimental data. The highest density of macropores on the surface is observed for the foam thickness of 100 μm. These data correlate with the results of polarization measurements. When the foam thickness increases up to 100 μm, hydrogen evolution overvoltage in the alkali solution decreases and the efficiency of nickel foam as a cathode material increases.     

Investigation of the starting modes of the low-temperature refrigerating machines working on the mixtures of refrigerants

The starting mode of a small low-temperature Joule–Thomson refrigerating machine is in focus of the experimental investigation reported here. The refrigerating machine operates by the Linde cycle. A mixture of hydrocarbons – isobutane/ethane/methane – is used as a refrigerant. The object of cooling is a small testing chamber to be cooled down and thermostabilized at the temperature level of (?70, …, ?80) °C. The starting modes were studied under heavy-duty heat load on the system resulting from the initial thermal equilibrium between the whole system and ambience. The experimental data demonstrate a crucial effect of the low-boiling mixture components condensation in the refrigerant high-pressure flow on the machine starting performance. Excessive values of the discharge pressure, compression ratio and compressor input power have been observed during the start-up process which may last for tens of minutes affecting the refrigerating machine reliability. Some probable causes of the phenomena and countermeasures are pointed out.     

Statistical analysis of the phase separation of LDPE/PA-6 blends compatibilized with SEBS-<Emphasis Type="Italic">g</Emphasis>-MA and/or organoclays

The morphology of the binary and ternary blends prepared by the melt compounding of low density polyethylene (LDPE), PA and SEBS-g-MA (S), as well as of the composites containing the same polymers or their blends with different content of the commercial organoclay (Cloisite 20A) was studied with SEM and afterwards analyzed statistically. The statistical ensembles of the PA phase droplets embedded into the LDPE matrix were successfully described using principles of irreversible thermodynamics and the mean droplet diameters were determined. Analysis of the mean droplet diameter as a function of time allowed recognition of two regimes of the phase separated structure formation. The first process is caused by the differences in the Flory-Huggins segmental interaction parameter of the components which is mainly responsible for the phase-separating domain structure at the mechanical blending upon specific time and temperature, both typical for a specific composition. The second process of the domain structure formation is the coarsening. Both regimes were quantitatively described with the universal law for the cluster growth.     

Experimental investigation of a bottle-sublimation cooler

A bottle-sublimation cooler is an open-cycle cooler of novel design combining the advantages of Joule–Thomson and sublimation coolers. The store of a refrigerant is bottled without heat leakages at ambient temperature. Sublimation of the refrigerant solid phase is the cold-generating process in the cooler. The cooler design and a discovered effect of the solid phase spontaneous capillary-porous structuring provide autoadjustability of the system operational characteristics. The results of experimental investigations of the stored-carbon dioxide bottle-sublimation cooler are reported in this paper. The experimental set-up and procedure of the system principal parameters measurement are covered. Temperature, thermal and overall size-mass parameters of the cooler are measured and reported. Performance specification of the cooler, which had been used for refrigerating of the IR module of a star spectrophotometer during astronomical observations, is presented.