Proton Conductivity and Thermal Properties of Ba(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

We have grown single crystals of barium dihydrogen phosphate and studied its thermal transformations during heating to 500°C and its electrotransport properties. Ba(H₂PO₄)₂ (Pccn) has been shown to undergo no phase transitions up to its dehydration temperature. The thermal decomposition of Ba(H₂PO₄)₂, accompanied by dehydration, involves two steps, with maximum rates at ~265 and 370°C, and results in the formation of barium dihydrogen pyrophosphate and barium metaphosphate, respectively. The total enthalpy of the endothermic dehydration events is–244.6 J/g. Using impedance spectroscopy, we have studied in detail the proton conductivity of polycrystalline and single-crystal Ba(H₂PO₄)₂ samples in a controlled atmosphere. Adsorbed water has been shown to have a significant effect on the proton conductivity of Ba(H₂PO₄)₂ up to 130°C. The proton conductivity of the Ba(H₂PO₄)₂ single crystals has been shown to be anisotropic. The conductivity anisotropy correlates with specific structural features of the salt. Higher conductivity values, 3 × 10^–9 to 2 × 10^–7 S/cm in the range 60–160°C, have been observed in the [100] crystallographic direction, exceeding the conductivity along [010] by an order of magnitude. The activation energy for proton conduction is 0.80 eV.     

Method of equivalent initial temperatures to account for welding stresses in strength analysis

A method of strength analysis with accounting of residual welding stresses (RWSs) is described. This consists in the calculation of such a field of initial temperatures from which upon cooling in a construction a corresponding field of residual stresses is obtained. The selected form of the representation of RWSs provides the possibility for their use during the simulation of the process of loading the welded construction by the finite element method.     

Spectral recovery by analytic continuation in crossing-based spectrum analysis

By the use of analytic continuation, the correct spectrum of an undersampled analog input signal f(a) (t) of a true bandwidth B is recovered from an aliased Fourier spectrum that is computed directly from a data set consisting of sinusoid-crossing locations {t(i)}, where the signal f(a) (t) intersects with a reference sinusoid r(t) with a frequency of W 相似文献   

Photooxidation processes for an azo dye in aqueous media: modeling of degradation kinetic and ecological parameters evaluation

Three photooxidation processes, UV/H(2)O(2), UV/S(2)O(8)(2-) and UV/O(3) were applied to the treatment of model wastewater containing non-biodegradable organic pollutant, azo dye Acid Orange 7 (AO7). Dye degradation was monitored using UV/VIS and total organic carbon (TOC) analysis, determining decolorization, the degradation/formation of naphthalene and benzene structured AO7 by-products, and the mineralization of model wastewater. The water quality during the treatment was evaluated on the bases of ecological parameters: chemical (COD) and biochemical (BOD(5)) oxygen demand and toxicity on Vibrio fischeri determining the EC(50) value. The main goals of the study were to develop an appropriate mathematic model (MM) predicting the behavior of the systems under investigation, and to evaluate the toxicity and biodegradability of the model wastewater during treatments. MM developed showed a high accuracy in predicting the degradation of AO7 when considering the following observed parameters: decolorization, formation/degradation of by-products and mineralization. Good agreement of the data predicted and the empirically obtained was confirmed by calculated standard deviations. The biodegradability of model wastewater was significantly improved by three processes after mineralizing a half of the initially present organic content. The toxicity AO7 model wastewater was decreased as well. The differences in monitored ecological parameters during the treatment indicated the formation of different by-products of dye degradation regarding the oxidant type applied.     

Spatial light modulator-controlled alignment and spinning of birefringent particles optically trapped in an array

We demonstrate the use of a phase-only liquid-crystal spatial light modulator (SLM) for polarization-controlled rotation and alignment of an array of optically trapped birefringent particles. A collimated beam incident upon a two-dimensional lenslet array yields multiple foci, scaled to produce optical gradient traps with efficient three-dimensional trapping potentials. The state of polarization of each trapping beam is encoded by the SLM, which acts as a matrix of wave plates with computer-controlled phase retardations. Control of the rotation frequency and alignment direction of the particles is achieved by the transfer of tunable photon spin angular momentum.     

Intermediate temperature proton electrolytes based on cesium dihydrogen phosphate and poly(vinylidene fluoride-co-hexafluoropropylene)

Proton conductivity, morphology, phase composition and mechanical properties of (1-x)CsH₂PO₄-xp(VDF/HFP) (x?=?0.05–0.25, weight ratio) polymer electrolytes were investigated for the first time. The chemical interaction of the organic matrix and acid salt was not observed and crystal structure of CsH₂PO₄ was preserved. A method for the synthesis of thin membranes with uniform distribution of the components was proposed. Thin flexible membranes with uniform distribution of sub-micrometer CsH₂PO₄ particles in the polymer membranes and improved hydrolytic stability were obtained firstly by using a bead mill. The mechanical strength of the hybrid polymer compounds was determined using the Vickers microhardness measurements. Proton conductivity in the (1-x)CsH₂PO₄-xp(VDF/HFP) electrolytes decreases monotonically with x increase due to the «conductor–insulator» percolation. Nevertheless, the values of proton conductivity remain sufficiently high, and along with small thickness, flexibility, improved mechanical and hydrophobic properties, it makes polymer electrolytes based on CsH₂PO₄ promising for membranes of medium-temperature fuel cells.

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Measurement of Nb3Ge heat capacity

The heat capacity of massive Nb₃Ge specimens (cast, annealed, and rapidly quenched) is measured by the adiabatic calorimetry method with periodic heat supply over the temperature range 5–30°K. Measurements and data collection were completely automated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 6, pp. 1073–1077, December, 1981.     

Effect of dietary protein content on the structure of blood vessels

It has been demonstrated in experiments on rats that prolonged (for 1-6 months) use of the diet with protein deficiency or excess (5 and 30% respectively as regards caloricity) determines the development of injuries to the aortal wall and arteries of the heart and kidneys. Vascular elasticity shows abnormality, which is the most pronounced if the animals are given the low-protein diet including butter. Sunflower oil has a protective effect which becomes manifest provided that the animals receive the high-protein diet.