Dielectric performance of pyrochlore-type Bi2MgNb2-xTaxO9 ceramics: The effects of tantalum doping

The solid solutions based on the pyrochlore-type system Bi₂MgNb_2-xTa_xO₉ were formed in the compositional range х = 0–2.0 (Bi_1·6Mg_0·8Nb_1.6-tTa_tO_7.2, t = 0–1.6). The Rietveld method was used to refine the structure for Bi₂MgNb_2-xTa_xO₉ (x = 0, 1.0, 2.0). The increasing tantalum content led to the slight decrease in the cubic unit cell parameters from 10.56934 (4) Å for x = 0 and 10.54607 (3) Å for x = 2 (sp.gr. Fd-3m:2). At the same time, tantalum additions suppressed grain growth in the pyrochlore ceramics during sintering and made it possible to obtain materials with an average grain size of 1–2 μm (Bi_1·6Mg_0·8Ta_1·6O_7.2). The increase in the Ta⁵⁺ concentration led to the decrease in the dielectric permeability from 104 (Bi_1·6Mg_0·8Nb_1·6O_7.2) to 20 (Bi_1·6Mg_0·8Ta_1·6O_7.2) at room temperature, while the dielectric loss tangent remained lower than 0.002, which is due to the small grain size and the high porosity of the samples. An increase in temperature has practically no effect on the values of the dielectric permittivity in the entire frequency range. The samples have weak through conductivity. The activation energies of electrical conductivity varied in the range of 0.84–1.00 eV, and the less tantalum, the lower the activation energy. The electrical properties of the samples at 200 Hz to 1 MHz are described by the simplest parallel scheme.     

Thermal stability of CaCu3Ti4O12: Simultaneous thermal analysis and high-temperature mass spectrometric study

Thermal stability of calcium copper titanate was studied by differential scanning calorimetry, thermogravimetry and high-temperature mass spectrometry. Calcium copper titanate (CCTO) had no thermal effects and mass losses caused by thermal dissociation or any phase transitions, besides melting, in the temperature range of 298–1423?K. The melting point of calcium copper titanate is 1398?K. The endothermic effect at 1250?K was associated with the decomposition of copper (II) oxide segregated in the intergrain space of the CaCu₃Ti₄O₁₂-CuO ceramics. In this connection, we proposed a simple method for estimating the content of copper oxide in the CaCu₃Ti₄O₁₂-CuO composite. The processes of evaporation of CaCu₃Ti₄O₁₂ in the temperature range of 1500–2100?K were studied by high-temperature mass spectrometry. In the temperature range of 1500–1750?K, easily volatilized copper oxide was evaporated selectively from the calcium copper titanate. At the temperature of 2100?K, atomic calcium and titanium oxides, TiO and TiO₂, were present in the vapor.     

Multistage adaptive compensation of active noise interferences using block orthogonalization of signals of compensation channels

The multistage digital automatic compensators of active noise interferences have been synthesized using the block Gram-Schmidt orthogonalization and LS-algorithm based on the least squares criterion. The specified automatic compensators ensure parallel-serial processing of signals. The application of RLS-algorithm made it possible to obtain a recurrent procedure for calculation of weighting coefficients of automatic compensator modules represented in the form of multiinput weighting adders. Statistical computer simulation was used to analyze the multistage digital automatic compensators based on the RLS-algorithm with simultaneous adaptation of weighting adders of all stages. As a result of parallelization of computational process, the synthesized multistage automatic compensators made it possible to increase the speed of processing (signal sampling frequency) by one order of magnitude and more as compared to that of automatic compensators built on single-stage scheme.     

Extraction of biologically active compounds from Sideritis ssp. L.

In this study extraction of polyphenols and flavonoids from cultivated hybrid Sideritis scardica × Sideritis syriaca, known for its rich content of phenolics and flavonoids with antioxidant activity, was investigated. Extractions have been done by ethanol and water-ethanol, respectively. High equilibrium values of the extracted species were obtained—17.55 mg/(g solid) total phenolics and 5.7 mg/(g solid) total flavonoids with ethanol as solvent. The influence of the solvent on the total yield and the content of biologically active compounds were studied. Maximum polyphenolics and flavonoids extraction was observed for water-ethanol solvent ratio 20/80. Increase of the content of ethanol in the solvents led to lower total yield of extracts but higher percentage of polyphenolics. The extraction kinetics showed that 90% of the phenolic compounds were extracted during the first 2.5 h. The experimental kinetics was described by a constant effective diffusion coefficient D_e = 1.5 × 10⁻¹² m²/s in the solid, accounting for the actual particle size distribution.     

Joint decoding of convolution codes and estimation of multipath communication channel’s parameters on a sliding interval

Optimal and quasi-optimal non-linear recurrent algorithms of joint decoding of convolution code and estimation of unknown multipath communication channel’s parameters on a sliding interval are synthesized on the basis of mathematics technique of mixed Markov processes in discrete time. Analysis of the obtained quasi-optimal algorithm is performed using statistical modeling on PC.     

The Effect of Antibrowning Agents on Inhibition of Potato Browning,Volatile Organic Compound Profile,and Microbial Inhibition

Abstract: Burbank and Norkotah potato slices were dipped into 3% sodium acid sulfate (SAS), citric acid (CA), sodium erythorbate (SE), malic acid (MA), sodium acid pyrophosphate (SAPP), or a combination of SAS‐CA‐SE. Browning by polyphenol oxidase (PPO) obtained from potato extract with 0.04 to 0.016 g/mL of antibrowning solutions at pH 2.0 to 6.9 were measured by UV‐Vis spectroscopy. The color of slices dipped in antibrowning solutions at pHs 2 to 7 and stored at 4 °C for 15 d was measured every 5 d by colorimeter. Headspace analysis of volatiles in raw and cooked potato samples was performed by selected ion flow tube mass spectrometer (SIFT‐MS) and soft independent modelling by class analogy (SIMCA) analysis of the calculated odor activity values (OAV) determined interclass distances. Microbial growth was measured at 15 d. At unadjusted pHs (1.1 to 7.1), the PPO browning of the control and samples with SAPP was not significantly different, SAS, CA, and MA produced some inhibition and SE and SAS‐CA‐SE prevented browning. At pH 5 to 7, only SE and SAS‐CA‐SE were effective browning inhibitors. Based on the color of potato slices, SE was the most effective at pH 2 to 7, but SAS was most effective at unadjusted pH. Cooking increased volatile levels in the treated potatoes and decreased differences between volatile profiles. Differences between cooked samples may not be noticeable by the consumer because volatiles with high discriminating powers have low OAVs. SAS, CA, and SAS‐CA‐SE treatments inhibited microbial growth but SAPP, control, and SE did not, most likely due to pH. Practical Application: Antibrowning agents inhibit polyphenol oxidase, increasing shelf life and consumer acceptability of processed raw potato products by preserving the color. Their effectiveness was shown to be mainly due to a pH effect, except SE, which was not pH dependent. MA, CA, and SAS‐CA‐SE are better acidulants for inhibition of color change as well as growth of spoilage bacteria, yeast, and mold than SAPP, the industry standard.     

Energy sector of the Russian Far East: Current status and scenarios for the future

This article describes the Russian Far East's energy sector, stressing its limited energy exports, and use of separate electricity and heating grids to geographically dispersed population centers with various supply patterns distributed across a vast territory. One key strategic trend has been to strengthen the potential of the region as an energy supplier for the countries of Northeast Asia. This underlies the framework used to develop three energy scenarios of the Russian Far East's energy future through 2030: Reference, National Alternative and Regional Alternative. While the Regional Alternative case has much greater total costs for implementation, yields almost the same amount of emissions as the BAU case, and requires greater governmental efforts to bring it to reality, it looks preferable for the RFE as a whole because it has a well-balanced primary energy consumption mix, lower energy and ecology/GDP indices, and a lower fraction of energy imports; offers greater diversity of energy supply; and provides better local energy service. The authors would like to thank Boris Saneev, Alexander Sokolov, Alexander Izhbuldin from the Institute of Energy Systems, Irkutsk; Julia Savelieva from Far Eastern Coal Research; and Alla Filatova from Far Eastern Power Engineering Institute for providing technical information, and expertise.