Failure mechanisms of thermal barrier coatings on MCrAlY-type bondcoats associated with the formation of the thermally grown oxide

The effect of the thermally grown oxide (TGO) formation on the lifetime of the thermal barrier coatings (TBC) with MCrAlY-bondcoats (BC) is reviewed. A number of factors affecting the TGO-formation and TBC-failure are discussed including the coating microstructure, geometrical (coating roughness and thickness) and processing parameters. Under given testing conditions for a specific EB-PVD-TBC-system forming a flat, uniform alumina TGO a critical TGO-thickness for TBC-failure can be defined. This TGO-morphology is, however, not necessarily optimum for obtaining long TBC-lifetime, which can be extended by formation of TGO’s with an uneven TGO/BC interface. In contrast, APS-TBC-systems are prone to formation of intrinsically inhomogeneous TGO-morphologies. This is attributed to non-uniform depletion of Y and Al underneath rough MCrAlY-surfaces as well as due to the commonly observed repeated-cracking/re-growth of the TGO during temperature cycling. The latter phenomenon depends on the exposure temperature and the mechanical properties of the APS-TBC. In both types of TBC-systems the TGO-formation and TBC-lifetime appear to be very sensitive to the manufacturing parameters, such as vacuum quality during bondcoat spraying and temperature regime of the bondcoat vacuum heat-treatment.     

Selection of coal for small district-heating stations in Poland as a method of avoiding investments in flue-gas desulphurization

Poland is one of the biggest producers of hard coal in the world and uses its domestic coal for electricity and heat generation: 42 million tons for electricity and heat production in power industry, and about 8–10 million tons used by small district-heating stations annually. Changes in demand for coal, destined for heat generation, result from the changes in the forecast structure of energy carriers to be used by local heating stations and the new emission standards coming, this year, into effect in Poland. To meet the regulations, the heat generators have to keep to environmental requirements. The cheapest solution is to burn the compliance coal. The comparison of the forecasts for coal demand and supply and the possibility of adjusting quantitative and qualitative requirements of the smaller coal consumers points out that it would be possible, when the market rules, to heal the situation between coal producers and coal consumers in Poland.     

Automatic generation of hypsometric layers for small-scale maps

This paper describes a new method for hypsometric tinting for small-scale maps. The method generalises digital elevation models by removing small unnecessary details and accentuating major valleys and ridgelines. The elevation data are filtered with lower and upper quartile filters that are combined using a drainage network. The lower quartile filter is applied in valleys, delimited by the drainage network, the upper quartile filter is used elsewhere. The level of generalisation is adjusted by simplifying the drainage network with an algorithm that removes the shortest streams. The resulting hypsometric layers match the quality standards of manually generalised reference layers and are appropriate for small-scale mapping.     

Partitioned state encoding for low power in FPGAs

The problem of finite state machine (FSM) encoding for low power in field-programmable gate arrays (FPGAs) is addressed. In this technology, one-hot encoding is typically recommended for large FSMs and binary encoding for small FSMs. A partitioned encoding approach is proposed which uses a combination of both binary encoding and zero-one-hot encoding with intermediate code size. Experimental results demonstrate that the proposed encoding approach can produce significant power savings.     

Identification of Various Transition Velocities in a Bubble Column Based on Kolmogorov Entropy

The Kolmogorov entropy (KE) algorithm was applied successfully to gas holdup fluctuations measured in a 0.102 m I.D. stainless steel bubble column equipped with a perforated plate distributor (19 holes ?? 1 mm). Nitrogen was used as the gas, while both 1‐butanol and gasoline were used as liquids. 1‐Butanol was aerated at pressures, P = 0.1 and 0.5 MPa, whereas gasoline was aerated at P = 0.1 and 0.2 MPa. Based on the peaks in the KE values under the pressures examined in both liquids, the boundaries of the following five regimes were identified: bubbly flow, first transition, second transition, coalesced bubble (4‐region flow) and coalesced bubble (3‐region flow). As the pressure increases to P = 0.5 MPa in 1‐butanol, all four transition velocities shift to higher superficial gas velocity, u_G. In addition, in gasoline at P = 0.2 MPa and u_G ≤ 0.017 m s^–1, the existence of a chain bubbling regime was detected, whereas in 1‐butanol at P = 0.5 MPa and u_G ≤ 0.02 m s^–1, both laminar and turbulent chain bubbling subregimes were identified. It was found that in 1‐butanol under ambient pressure, the second and fourth transition velocities occur earlier than in gasoline.