A stress analysis of a shaft with a press-fitted hub subjected to cyclic axial loading

This paper presents a calculation of the stress distribution in a shaft with a press-fitted hub subjected to axial fretting fatigue. Both normal contact stresses and frictional shear stresses at the shaft-hub interface are included in the model. The solution of Airy's function is obtained by means of Fourier integrals. The results are presented for different combinations of hub length, shaft radius and non-slip area and for various values of the coefficient of friction. Special consideration was given to the axial component of the stress, σ_z, as this is the most important stress component in the initiation and propagation of fatigue cracks. Finally, the paper deduces the implications arising from the stress analysis on the fretting fatigue of the junction studied.     

Permeability of carbon refractory materials used in a blast furnace hearth

Permeability of experimental and standard micropore carbon materials, before and after the heat treatment at 1550 °C, was investigated using gas permeability measurements (GP) and mercury intrusion porosimetry (MIP). Permeability of both materials increased after the annealing. Experimental micropore carbon material was less permeable than standard one, both before and after the heat treatment. Measured gas permeabilities were compared with permeabilities determined based on MIP measurements using two different models: Hagen?Poiseuille and Carman?Kozeny equation. Using the inverse problem approach, for the first time Carman?Kozeny constant was determined for micropore carbon materials. Carman?Kozeny model gave more accurate results (i.e. close to gas permeability measurements) than Hagen?Poiseuille model. Performed investigations showed that mercury intrusion porosimetry might be alternative method to investigate infiltration resistance of low permeable materials.     

A numerical analysis of heat and mass transfer processes in a macro-patterned methane/steam reforming reactor

The presented paper focuses on a numerical analysis of a heat and mass transfer process in a novel type of methane/steam reforming reactor. The novelty of the macro-patterned reactor design lies in dividing a reformer into segments of various lengths and reactivity. Precisely, splitting the catalyst and filling the created empty volume with porous, non-reactive, thermal conducting material such as metallic foam. This approach allows for moderating a sharp temperature drop at the inlet of the reactor typical for the endothermic methane/steam reforming process. To analyze the considered system, the mathematical and numerical models of transport phenomena and the reaction kinetics were developed and implemented into an in-house solver. The kinetics of methane/steam reforming was taken from the literature. The outlet composition obtained from the kinetic model was compared with the experimental measurements and good agreement was found. The conducted numerical analysis includes cases that differ from a number and lengths of catalytic and non-catalytic segments. The obtained results indicate that the macro-patterned design is a promising strategy that allows for a significant improvement of temperature distribution in a reforming reactor. It was shown that the proposed approach could help to cut the cost of the catalyst material by allowing for the conversion of methane with a smaller amount of the catalyst close to the reference case.     

Utilisation of metallurgical sludge by multi-layer sintering

Metallurgical wastes landfills in Poland significantly grew during last four decades. Landfilled wastes are characterised by iron content at range 30–50% and zinc content about 2–3%. Therefore wastes are not interesting for the zinc smelter, on the other hand, even such low zinc content in ironmaking burden causes problem with a shaft furnace operation. So, the wastes are valuable for ironmaking due to the high iron content, provided that zinc will be removed from them. The article describes the general ways of dealing with zinc containing metallurgical wastes. In detail, the semi-industrial research conducted on sinter pot set of Stanislaw Staszic Institute for Ferrous Metallurgy is presented. The study determined the conditions under which obtained three benefits: landfilled sludge utilisation, raw materials substitution and zinc recovery.     

Flow structure and heat exchange analysis in internal cooling channel of gas turbine blade

This paper presents the study of the flow structure and heat transfer, and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade. The investigations focus on heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include corner fillet, ribs with fillet radii and special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.     

The effect of microwave treatment on the immunoreactivity of gliadin and wheat flour

Commercial gliadins and wheat flour were exposed to microwaves at power distribution of 70, 200, and 500 W for different time periods to achieve a level of applied energy doses up to 150 kJ. Ethanolic extracts (40 vol.% ethanol/water) of microwave treated samples were analyzed by ELISA with the use of either monoclonal antibodies against -gliadin or polyclonal anti-gliadin antibodies and by electrophoresis followed by immunoblotting. A significant increase in reactivity, almost 210% over the untreated control sample, was observed for gliadins exposed to the energy dose of 40 kJ. Gliadins treated with higher energy doses showed a drop in an immune response independent of monoclonal or polyclonal antibodies used in ELISA. Gliadin fractions extracted from wheat flour treated with microwaves demonstrated similar immunoreactivity changes vs applied energy, although the maximum of reactivity appeared at 30 kJ. The increase in immune response of microwave irradiated gliadins was also confirmed by immunoblotting assay with the use of sera of patients susceptible to wheat flour allergy. Reversed phase HPLC elution profiles of treated gliadins showed that the content of all gliadin fractions in microwave treated samples decreased with the increase of the dose of applied energy.     

Impact of hydrogen on the environment

The present work considers the impact of hydrogen fuel on the environment within the cycles of its generation and combustion. Hydrogen has been portrayed by the media as a fuel that is environmentally clean because its combustion results in the formation of harmless water. However, hydrogen first must be generated. The effect of hydrogen generation on the environment depends on the production process and the related by-products. Hydrogen available on the market at present is mainly generated by using steam reforming of natural gas, which is a fossil fuel. Its by-product is CO₂, which is a greenhouse gas and its emission results in global warming and climate change. Therefore, hydrogen generated from fossil fuels is contributing to global warming to the similar extent as direct combustion of the fossil fuels. On the other hand hydrogen obtained from renewable energy, such solar energy, is environmentally clean during the cycles of its generation and combustion. Consequently, the introduction of hydrogen economy must be accompanied by the development of hydrogen that is environmentally friendly. The present work considers several aspects related to the generation and utilisation of hydrogen obtained by steam reforming and solar energy conversion (solar-hydrogen).     

A technique to compare polythiophene solid-state dye sensitized TiO2 solar cells to liquid junction devices

In this communication, we report on a technique to fabricate solid-state polythiophene-based dye sensitized solar cells (DSSCs) that can be directly compared to analogous liquid junction devices. The device configuration is based on non-porous TiO₂ thin films and one of the three undoped polythiophene hole conductors: poly[3-(11 diethylphosphorylundecyl) thiophene], P3PUT, poly(4-undecyl-2,2′-bithiophene), P4UBT, or poly(3-undecyl-2,2′-bithiophene), P3UBT. These polymers were spin coated and cast from organic solutions onto the TiO₂ films. The dense TiO₂ thin films (ca. 30 nm) were deposited on conductive glass via facile spray pyrolysis and sol–gel techniques. After that, cis-(SCN)₂ Bis(2,2′ bipyridyl-4,4′-dicarboxylate) ruthenium(II) (a.k.a. Ru N3 dye) was adsorbed on the TiO₂ surface, and the polythiophenes were utilized as hole conductors in a simplified solar cell geometry. The results were compared to the control DSSC device made with dense TiO₂ and a liquid electrolyte, or 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (a.k.a. Spiro-MeOTAD). The polythiophenes exhibited bandgaps in the range 1.9–2.0 eV, and HOMO energy levels of approximately 5 eV (vs. vacuum). The P3PUT DSSC device exhibited an AM1.5 V_OC=0.8 V, a J_SC=0.1 mA/cm², as well as an IPCE=0.5–1%. The AM1.5 short-circuit photocurrents and quantum efficiencies for DSSCs made with the polythiophenes, the Spiro-MeOTAD and the standard liquid electrolyte (I⁻/I₃⁻) were found to be identical within the limits of experimental uncertainty and reproducibility. Our results indicate that a solid-state replacement to the liquid junction is not necessarily limited by the fundamental aspect of hole transfer, one of the three fundamental aspects that must be met for an efficient DSSC. Rather than suggest that P3UBT or P4UBT could be used to create efficient “organic solar cells” with the exclusion of the Ru dye, we suggest that transparent thiophene compounds could be attractive candidates for high-surface area solid-state DSSCs, and that the technique presented can be applied to other hole conductors. It can allow a verification of one of the things necessary for the DSSC, so that parallel studies using high-surface area materials can proceed with confidence.     

意大利诺尔恰Ms6.2级地震震害异常原因分析

当地时间2016年8月24日凌晨3时36分,意大利中部拉齐奥大区列蒂省诺尔恰镇发生里氏6.2级地震。此次地震震级不大,但一些古镇震害极其严重,出现多个烈度异常区块。通过对此次地震异常区建筑结构、地质结构及地形特征解剖,运用几年来的斜坡地震动响应规律监测成果,采用数值模拟分析,揭示了震级不大、距震中较远的条件下,地形放大效应同样可造成极其严重的震害。中世纪修建并保留至今的古建筑,大多为砖木结构,整体性较差,抗震性较弱,且由于历史原因多修建在孤立突出的山头上,在地形放大作用下造成了极其严重的伤亡。     

Parameters estimation of the d.c. electrothermal model of the bipolar transistor

This paper concerns the problems of the parameter values estimation of d.c. electrothermal model of the BJT formulated for circuit analysis with SPICE. In this case, PARTS software available in SPICE cannot be used. In the paper, a new estimation algorithm for d.c. electrothermal model of the BJT is proposed. The form of the electrothermal BJT model is also presented. The estimation algorithm implemented into the computer‐controlled measurement set allows one to derive the values of the parameters automatically after the measurements of the selected isothermal characteristics and proper calculations. Copyright © 2002 John Wiley & Sons, Ltd.