Decomposition of light hydrocarbons on a Ni-containing glass fiber catalyst

The work is devoted to the study of the novel process of catalytic decomposition of light hydrocarbons on a catalyst at temperatures of 550 °С and 600 °C at various pressures. The CVD process is a new COx-free approach for hydrogen production. A glass fiber fabric was used as a catalyst, which was preliminarily modified by the application of additional outer layers of NiO and porous silica. A technical mixture of propane and butane was used as feedstock. The main purpose is to investigate the effects of pressure and temperature on the production of hydrogen and carbon nanofibers over a glass-based catalyst. As a result of the decomposition of the mixture, the yield of hydrogen was 266–848 L/gcat, and that of carbon nanofibers was 3–10 g/gcat. Increasing the pressure of propane-butane mixture decomposition led to an increase of the catalyst lifetime. The highest yield of hydrogen and carbon nanofibers was achieved at 1 bar and 600 °C

Synthesis of Ni-based catalysts by hexamethylenetetramine-nitrates solution combustion method for co-production of hydrogen and nanofibrous carbon from methane

It was shown that hexamethylenetetramine (HMT)is a new effective fuel for single-step solutions combustion synthesis (SCS)of supported Ni catalysts for methane decomposition into hydrogen and nanofibrous carbon. Several generalized chemical equations reflecting different ideas about combustion of the HMT−Ni(NO 3 ) 2 −Cu(NO 3 ) 2 −Al(NO 3 ) 3 −H 2 O system have been derived. On the basis of those equations the adiabatic combustion temperature (T ad )and the amount of gaseous products (n g )have been calculated depending on the ignition temperature (T 1 ), water content (m), excess fuel coefficient (φ), and the composition of the obtained solid product. The calculations have shown that T ad , depending on m and φ, changes from hundreds to thousands of degrees Kelvin. Increase of Al 2 O 3 content in the catalyst up to 0.6 increases T ad by hundreds of degrees, and that increase of the Ni:NiO ratio up to 0.5 lowers T ad by tens of degrees. Three samples of the supported unreduced 0.97NiO/0.03Al 2 O 3 catalyst were successfully prepared with the help of the SCS method using HMT as the fuel at φ=0.7. Those samples, obtained at reaction mixture preliminary heating rates V = 1, 10, 15 K/min were characterised using XRD, TEM, and SEM, and further tested in a pure methane decomposition reaction (100 L CH4 /h/g cat , 823К, 1 bar). Nanoparticles of metal Ni were found in the SCS products, in contrast to cases when other types of fuel were used with

Direct Observation of Propagating Gigahertz Coherent Guided Acoustic Phonons in Free Standing Single Copper Nanowires

We report on gigahertz acoustic phonon waveguiding in free-standing single copper nanowires studied by femtosecond transient reflectivity measurements. The results are discussed on the basis of the semianalytical resolution of the Pochhammer and Chree equation. The spreading of the generated Gaussian wave packet of two different modes is derived analytically and compared with the observed oscillations of the sample reflectivity. These experiments provide a unique way to independently obtain geometrical and material characterization. This direct observation of coherent guided acoustic phonons in a single nano-object is also the first step toward nanolateral size acoustic transducer and comprehensive studies of the thermal properties of nanowires

Phonons in Slow Motion: Dispersion Relations in Ultra-Thin Si Membranes

We report the changes in dispersion relations of hypersonic acoustic phonons in free-standing silicon membranes as thin as \sim 8 nm. We observe a reduction of the phase and group velocities of the fundamental flexural mode by more than one order of magnitude compared to bulk values. The modification of the dispersion relation in nanostructures has important consequences for noise control in nano and micro-electromechanical systems (MEMS/NEMS) as well as opto-mechanical devices.Comment: 5 page

Molecular Characterization of Podoviral Bacteriophages Virulent for Clostridium perfringens and Their Comparison with Members of the Picovirinae

Clostridium perfringens is a Gram-positive, spore-forming anaerobic bacterium responsible for human food-borne disease as well as non-food-borne human, animal and poultry diseases. Because bacteriophages or their gene products could be applied to control bacterial diseases in a species-specific manner, they are potential important alternatives to antibiotics. Consequently, poultry intestinal material, soil, sewage and poultry processing drainage water were screened for virulent bacteriophages that lysed C. perfringens. Two bacteriophages, designated ΦCPV4 and ΦZP2, were isolated in the Moscow Region of the Russian Federation while another closely related virus, named ΦCP7R, was isolated in the southeastern USA. The viruses were identified as members of the order Caudovirales in the family Podoviridae with short, non-contractile tails of the C1 morphotype. The genomes of the three bacteriophages were 17.972, 18.078 and 18.397 kbp respectively; encoding twenty-six to twenty-eight ORF's with inverted terminal repeats and an average GC content of 34.6%. Structural proteins identified by mass spectrometry in the purified ΦCP7R virion included a pre-neck/appendage with putative lyase activity, major head, tail, connector/upper collar, lower collar and a structural protein with putative lysozyme-peptidase activity. All three podoviral bacteriophage genomes encoded a predicted N-acetylmuramoyl-L-alanine amidase and a putative stage V sporulation protein. Each putative amidase contained a predicted bacterial SH3 domain at the C-terminal end of the protein, presumably involved with binding the C. perfringens cell wall. The predicted DNA polymerase type B protein sequences were closely related to other members of the Podoviridae including Bacillus phage Φ29. Whole-genome comparisons supported this relationship, but also indicated that the Russian and USA viruses may be unique members of the sub-family Picovirinae

Symmetric cable with enhanced uniformity for broadband access

The purpose of the study is substantiation of the determining influence caused on the homogeneity of the broadband access cable by the process of application of polyethylene film-porous polyethylene film insulation on copper cores. Based on the experimental research it has been demonstrated that key electrical characteristics of the symmetrical cable with enhanced uniformity for broadband access fully meet the requirements of advanced high-speed xDSL systems and structured cabling systems

Research of electrical characteristics of increased uniformity LAN-cables

Formulation of the problem. At present, symmetric LAN cables are widely used in structured cabling systems (SCS) and fixed broadband access (BBA) networks in the world and in Russia. Practical experience of using LAN cables on real broadband access networks shows that high-quality transmission can only be achieved using high-quality highly uniform cables.Objective. Study of the dependence of the quality of LAN-cables on technological equipment and the quality of materials, which provide increased cable uniformity.Results. Based on the experimental studies carried out with the use of a modern measuring system, the main electrical characteristics of the transmission and the mutual influence of the most popular four-pair LAN-cable of the 5e category of the U/UTP4×2×0.52 type in the frequency range up to 100 MHz are determined. It is shown that to ensure high and stable transmission characteristics and mutual influence, modern technological equipment must be equipped with cable quality parameters automatic control systems and it is necessary to choose reliable suppliers when using domestic production materials.Practical significance. For the effective practical use of LAN cables on fixed broadband access networks and in SCS, it is very important to have high stability of electrical characteristics and their compliance with rather high established standards. This is possible only by ensuring high geometric and structural homogeneity of the structural elements of LAN cables

Application of unified microprocessor relay protection units in electrical machine diagnostics

The article concentrates on the topical issue connected with the detection of defects in the rotor winding of electric machines. The experimental sampling and digital processing of electrical signals from controlled windings is in the basis. The authors conducted the research using two experimental units for asynchronous motor and synchronous generator, respectively. A distinctive feature of the proposed research stands is in solving the problems of digital processing and data analysis on the basis of the application of microprocessor relay protection unit BMRZ developed in Russia. The authors applied method of wavelet decomposition to select the detailing component. They also presented the results of experiments for the breakage in the short-circuit rotor of an asynchronous motor and proved that the microprocessor-based BMRZ device is capable of digitizing at a sampling rate that meets the requirements, and in conjunction with the data processing algorithms that carry out the selective determination of hard-to-detect defects, is applicable in the diagnosis of electrical machines