Thermal Transformation of Ring-Opened [2 2] C60 Dimer into a Wide-Bridged C120 Isomer. A Computational Evaluation of Fulvalene-Naphthalene Rearrangements

As a continuation of the studies on thermal transformation of the [2+2] C₆₀ dimer (1), the consequence of the pyracylene-rearrangement-like valence isomerization of the fulvalene partial structure at the bridge of the ring-opened product from 1, namely 2, was searched by dynamic reaction coordinate /AM1 semiempirical MO calculations. It is predicted that the fulvalene bridge of 2 rearranges into naphthalene partial structure by the concerted 'in-plane' mechanism to give a wide-bridged C₁₂₀ intermediate having twenty five-membered rings and two ten-membered rings (3). The computed energy of activation (145 kcal/mol) is 40 kcal/mol lower than those computed for pyracylene rearrangements. In contrast, the recently reported analogous rearrangement of indigo (13) to dibenzonaphthyridindione (14) is computed to occur by the stepwise 'sp³' mechanism.     

Model-based design and test of vibration energy harvester for aircraft application

This paper deals with a development process of a vibration energy harvesting device in aircraft applications. The vibration energy harvester uses ambient energy of mechanical vibration and it provides an autonomous source of energy for wireless sensors or autonomous applications. This application presents a complex engineering problem and the vibration energy harvester consists of precise mechanical part, electro-mechanical converter, electronics and a powered application. It can be perceive as a mechatronic system and a mechatronic approach was used for development of our vibration energy harvester. An essential step of development process is simulation modeling which is based on mechatronic approach. Presented model-based design of vibration energy harvester is very useful during development process and the whole development process of the autonomous energy source is presented in this paper. The main aim of the paper is an introduction of our development methodology and our approach is presented on a sample of the vibration energy harvester for aircraft applications under project ESPOSA.     

A Glass–Ceramic Derived from High TiO2-Containing Slag: Microstructural Development and Mechanical Behavior

A novel glass–ceramic material was developed from the melt of a TiO₂-containing iron-making slag with additional waste glass. The high percentage (∼20 wt% TiO₂) of this network-modifying oxide has promoted a crystallization of the parent glass, resulting in a fine-grained, homogeneous polycrystalline material with high mechanical properties ( E =120 GPa, flexural strength=∼180 MPa, and Vickers hardness=7 GPa) after a heat treatment at 1100°C for 2 h. The room temperature and elevated temperature fracture toughness were also studied. The main crystalline phases of the glass–ceramic material were of the pyroxene series until heat-treatment temperature reached 1000°C, at which titanium-rich perovskite and armalcolite crystals became the dominant phases. The end material is high-strength, aesthetically acceptable (metallic gray or opaque brown colored), and suitable for structural and architectural applications.     

Contribution to the hydration of expansive cement on the basis of metakaolinite

The study of hydration of expansive cement prepared from 64% portland cement clinker, 23% metakaolinite and 13% CaSO₄.2H₂O is described. It was found that in the course of a 10-day hydration period, all the gypsum entered the reaction with the formation of ettringite. In 7–10 days, after the termination of the expansion processes, typical stalk-like crystals were transformed into leaf-shaped or other formations. Ettringite was identified even after 4 months of hydration. Monosulphate (3CaO.Al₂O₃.CaSO₄.12H₂O) was found in none of the investigated high-expansion cement paste samples.     

Evolution of efficient real-time non-linear image filters for FPGAs

Image processing represents a research field in which high-quality solutions have been obtained using various soft computing techniques. Evolutionary algorithms constitute a class of stochastic search methods that are applicable in both optimization and design tasks. In the area of circuit design Cartesian Genetic Programming has often been utilized in combination with an algorithm of Evolutionary Strategy. Digital image filters represent a specific class of circuits whose design can be performed by means of this approach. Switching filters are advanced non-linear filtering techniques in which the main idea is to detect and filter the noise pixels while keeping the uncorrupted pixels unchanged in order to increase the quality of the resulting image. The aim of this article is to present a robust design technique based on Cartesian Genetic Programming for the automatic synthesis of switching image filters intended for real-time processing applications. The robustness of the proposed evolutionary approach is evaluated using four design problems including the removal of salt and pepper noise, random shot noise, impulse burst noise and impulse burst noise combined with random shot noise. An extensive evaluation is performed in order to compare the properties of the evolved switching filters with the best conventional solutions. The evaluation has shown that the evolved switching filters exhibit a very good trade off between the quality of filtering and the implementation cost in field programmable gate arrays.     

Integrating working and enrichment approach learning: a document

Integrating working and learning is seen as a desirable alternative to traditional training regimes. An integrated approach to working and learning is more gradual, contextual, problem oriented and cost effective. Knowledge technology aims to catalyze workplace learning, but requires the right organisational culture and brings additional costs regarding the articulation, representation and transmission of knowledge. Our approach reduces these costs by making articulation a natural part of collaborative working, designing for both informal and formal knowledge, and facilitating the transition of socially situated knowledge through enriched documents. To be successful, our approach has certain prequesites concerning organisational culture, and the nature of shared documents, organisational knowledge and work activities.     

Thermal comfort and sensation in men wearing a cooling system controlled by skin temperature

OBJECTIVE: The study was done to determine whether thermal comfort (TC), thermal sensation (TS), and subjective factors gauging environmental stress were negatively affected with different cooling methods in men exercising in chemical protective clothing. BACKGROUND: Previous studies have reported that intermittent regional cooling improved the efficacy of cooling as compared with constant cooling (CC), but no studies have addressed whether there is any improvement in thermal comfort. METHODS: Eight male volunteers exercised at moderate work intensity (425 W) in three microclimate cooling tests. The circulating fluid in the cooling garment was provided during exercise to the head (6% body surface area [BSA]), torso (22% BSA), and thighs (44% BSA) and manipulated under three methods: (a) CC, (b) pulsed cooling (PC), and (c) PC activated by mean skin temperature (T(sk)) control (PC(skin)). TC and TS ratings were recorded every 20 min during the 80-min test. RESULTS: TC and TS ratings were not different for PC(skin) and CC; thus the participants perceived PC(skin) as being similar to CC. TS was significantly warmer with PC than with PC(skin) and CC (p < .001). In PC(skin), T(sk) was significantly higher than in PC and CC (p < .001), and PC(skin) was rated as being not as warm as PC according to TS. CONCLUSION: This indicates that the PC(skin) method was perceived as being as cool as CC and cooler than PC. APPLICATION: These findings indicate that the PC(skin) cooling method is an acceptable alternative to CC and PC based on human perceptions.     

Intermittent microclimate cooling during exercise-heat stress in US army chemical protective clothing

The effectiveness of intermittent, microclimate cooling for men who worked in US Army chemical protective clothing (modified mission-oriented protective posture level 3; MOPP 3) was examined. The hypothesis was that intermittent cooling on a 2 min on-off schedule using a liquid cooling garment (LCG) covering 72% of the body surface area would reduce heat strain comparably to constant cooling. Four male subjects completed three experiments at 30 degrees C, 30% relative humidity wearing the LCG under the MOPP 3 during 80 min of treadmill walking at 224 +/- 5 W . m(-2). Water temperature to the LCG was held constant at 21 degrees C. The experiments were; 1) constant cooling (CC); 2) intermittent cooling at 2-min intervals (IC); 3) no cooling (NC). Core temperature increased (1.6 +/- 0.2 degrees C) in NC, which was greater than IC (0.5 +/- 0.2 degrees C) and CC (0.5 +/- 0.3 degrees C) ( p < 0.05). Mean skin temperature was higher during NC (36.1 +/- 0.4 degrees C) than IC (33.7 +/- 0.6 degrees C) and CC (32.6 +/- 0.6 degrees C) and mean skin temperature was higher during IC than CC ( p < 0.05). Mean heart rate during NC (139 +/- 9 b . min(-1)) was greater than IC (110 +/- 10 b . min(-1)) and CC (107 +/- 9 b . min(-1)) ( p < 0.05). Cooling by conduction (K) during NC (94 +/- 4 W . m(-2)) was lower than IC (142 +/- 7 W . m(-2)) and CC (146 +/- 4 W . m(-2)) ( p < 0.05). These findings suggest that IC provided a favourable skin to LCG gradient for heat dissipation by conduction and reduced heat strain comparable to CC during exercise-heat stress in chemical protective clothing.     

Mechanical response of novel SiOC glasses to high temperature exposition

The presented work describes mechanical properties of materials prepared by the pyrolysis of polysiloxane resins. The polymeric precursors have different chemical composition. Materials under investigation are predetermined for high temperature resistant applications usually in composite form, i.e. accompanied by some reinforcement. Instrumented hardness tests were employed for material characterisation. The Vickers hardness, Martens hardness and indentation elastic modulus were the key parameters, determined either from the standard optical technique or load–indentation depth curves. The influence of mechanical properties on the monomers ratio was established. The exposition to the temperature between 1200 °C and 1500 °C in air was applied to observe damage caused by these severe conditions.