Truss layout optimization within a continuum

The present work extends truss layout optimization by considering the case when it is embedded in a continuum. Structural models often combine discrete and continuum members and current requirements for efficiency and extreme structures push research in the field of optimization. Examples of varied complexity and dimensional space are analyzed and compared, highlighting the advantages of the proposed method. The goal of this work is to provide a simple formulation for the discrete component of the structure, more specifically the truss, to be optimized in presence of a continuum.     

After a Terrorist Attack: Challenges for Political and Administrative Leadership in Norway

This article addresses the challenges that the terrorist attacks on 22 July 2011 in Norway created for central government and, more particularly, for the political and police leadership. The emphasis is on ‘meaning making’, focusing on how the leaders played out their reactions in the media and towards the public. When explaining the different aspects of crisis management, we draw on three organizational perspectives: emphasizing the importance of myths and symbols, formal organization and cultural–institutional traditions. The analysis is based on qualitative content analysis of central policy documents, parliamentary debates and documents, speeches made by central actors and mass media coverage in the year following the attacks. A main finding is that the response to the terrorist attacks is characterized by complex interactions between mutually influential factors, by dynamics between symbolic factors, on one hand, and structural and cultural influences, on the other.     

Wear and oxidation resistance of combustion CVD grown alumina films

Alumina thin films were synthesized on Si (100) and Ni–20Cr substrates using combustion chemical vapor deposition. Aluminum acetylacetonate (0.005 M) dissolved in ethanol was used as the precursor solution. The films deposited at 900 and 1000 °C are found to be θ-alumina and those deposited at 1100 °C to be α-alumina. The scanning electron micrographs showed the films to be made up of crystallites of two different sizes and shapes. The coefficient of friction, of alumina coated Si samples, measured using a tribometer showed high value (~ 0.7) at initial passes and subsequently saturated to low value (~ 0.5) at higher sliding distances. It was observed that the tribological properties, of the films, are not affected significantly by the crystal structure and crystallite size. Oxidation resistance of alumina-coated Ni–20Cr specimens were studied using a thermo-gravimetric analyzer by exposing them to isothermal heating at 1000 °C in 20% O₂–Ar gas mixture. The results indicated that the coated specimens are 18 times more oxidation resistant, at initial stages, compared to uncoated specimens. The resistance slowly dropped to six times, where it reached a saturation value.     

The role of Si interstitials in the migration and growth of Ge nanocrystallites under thermal annealing in an oxidizing ambient

We report a unique growth and migration behavior of Ge nanocrystallites mediated by the presence of Si interstitials under thermal annealing at 900°C within an H₂O ambient. The Ge nanocrystallites were previously generated by the selective oxidation of SiGe nanopillars and appeared to be very sensitive to the presence of Si interstitials that come either from adjacent Si₃N₄ layers or from within the oxidized nanopillars. A cooperative mechanism is proposed, wherein the Si interstitials aid in both the migration and coarsening of these Ge nanocrystallites through Ostwald ripening, while the Ge nanocrystallites, in turn, appear to enhance the generation of Si interstitials through catalytic decomposition of the Si-bearing layers.     

Friction and Wear Phenomena of Vegetable Oil–Based Lubricants with Additives at Severe Sliding Wear Conditions

The tribological responses of palm oil and soybean oil, combined with two commercial antiwear additives (zinc dialkyl dithiophosphate and boron compound), were investigated at a lubricant temperature of 100°C and under severe contact conditions in a reciprocating sliding contact. The friction coefficient of palm oil with zinc dialkyl dithiophosphate was closest to the commercial mineral engine oil, with a 2% difference. The soybean oil with zinc dialkyl dithiophosphate produced a 57% improvement in wear resistance compared to its pure oil state. The existence of boron nitride in vegetable oils was only responsive in reduction of wear rather than friction. The response of commercial antiwear additives with vegetable oils showed a potential for the future improvement in the performance of vegetable oils.     

Biocomposites based on poly(lactic acid) and seaweed wastes from agar extraction: Evaluation of physicochemical properties

Seaweed waste (SWW) is a residue or by‐product from the filtration step of the agar extraction process, and it has been explored as an inexpensive and effective filler for incorporation by melt blending into a poly(lactic acid) (PLA) matrix. PLA‐SWW biocomposites were manufactured with various contents of SWW (0, 5, 10, 15, and 20 wt %) using a sheet extrusion process. PLA was functionalized with maleic anhydride (MAH) by reactive extrusion using dicumyl peroxide (DCP) as an initiator, and it was extruded using 0, 5, and 20 wt %. SWW content. The mechanical, thermal, structural, and morphological properties of the processed biocomposites were investigated. Regarding the mechanical behavior, a slight increase in the tensile modulus was observed at low SWW content. The thermal properties indicated that the rigid amorphous phase content was enhanced in the biocomposites. This work suggests that SWW can be used as filler to develop environmental friendly biocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42320.     

Immobilization of TiO2 into Self‐Supporting Photocatalytic Foam: Influence of Calcination Temperature

Immobilization of photocatalytic powder is crucial to obtain industrially relevant purification processes. To achieve this goal, self‐supporting TiO₂ foams were manufactured by a polyacrylamide gel process. These gels were calcined at different temperatures to study the effect of the calcination temperature on foam characteristics (rigidity, crystallinity, and porosity) and its influence on photocatalytic activity. The results show that an optimal degradation is achieved for those foams calcined between 700 and 800°C. Calcination at higher temperatures results in a steep decrease in activity, explained by stability issues of the material due to formation of Na₂SO₄ phases and a larger rutile fraction.