Impulsive control for fast nanopositioning

In this paper we present a non-linear control scheme for high-speed nanopositioning based on impulsive control. Unlike in the case of a linear feedback controller, the controller states are altered in a discontinuous manner at specific instances in time. Using this technique, it is possible to simultaneously achieve good tracking performance, disturbance rejection and tolerance to measurement noise. Impulsive control is demonstrated experimentally on an atomic force microscope. A significant improvement in tracking performance is demonstrated.     

Teachers’ Perceptions οn the Use of Botanic Gardens as a Means of Environmental Education in Schools and the Enhancement of School Student Benefits from Botanic Garden Visits

The potential of Botanic Gardens (BGs) to contribute to environmental education is well documented. To what degree this potential is met concerning school students’ environmental education is to be considered. In Greece, Environmental Education Centres (EECs) develop Environmental Education Programmes (EEPs) for schools to implement. A questionnaire survey addressing teachers employed at the EECs in Greece investigated the use of BGs as a means of environmental education and identified their most important features in supporting school EEPs. Findings indicated that the majority of EEC teachers (90.6%) have not developed EEPs involving the use of BGs, although BGs were ranked as most suitable amongst other green spaces for conducting such programmes, particularly for primary school students. Teachers identified the need for BGs to be designed accordingly and provide the necessary infrastructure to be educationally effective that included facilitating teaching (e.g. open spaces, areas to congregate, easy access paths and indoor facilities) and plant-orientated elements as well as plant management displays. A strategy by BGs to promote their role in environmental education and a multidisciplinary design approach would maximise student benefit.     

Modified Lanthanum Catalysts for Oxidative Chlorination of Methane

Mixtures of LaOCl and LaCl₃ are promising catalysts for oxidative chlorination of methane to methyl chloride. The influence of metal dopants such as Co, Ni and Ce, which form stable chlorides under anticipated reaction conditions, on physicochemical and catalytic properties was explored. The presence of markedly redox-active dopants such as cobalt and cerium lead to a higher rate of methane conversion. However, the formed methyl chloride is strongly adsorbed and directly oxidized to CO leading to low methyl chloride selectivity. Doping with nickel weakens, in contrast, the interaction with methyl chloride leading to high methyl chloride selectivity. Angeliki A. Lemonidou is on leave from the Department of Chemical Engineering, Aristotle University Thessaloniki.     

Clarifying the nature of the distinctiveness by domain interaction in conceptual structure: Comment on Cree, McNorgan, and McRae (2006).

The conceptual structure account of semantic memory (CSA; L. K. Tyler & H. E. Moss, 2001) claims that feature correlation (the degree to which features co-occur) and feature distinctiveness (the number of concepts in which a feature occurs) interact with domains of knowledge (e.g., living vs. nonliving) such that the distinctive features of nonliving things are more highly correlated than the distinctive features of living things. Evidence for (B. Randall, H. E. Moss, J. M. Rodd, M. Greer, & L. K. Tyler, 2004) and against this claim (G. S. Cree, C. McNorgan, & K. McRae, 2006) has been reported. This comment outlines the CSA, discusses Cree et al.'s (2006) critiques of the Randall et al. (2004) experiments and the CSA, and reports new analyses of property norm and behavioral data, which replicate the results reported by Randall et al. (2004). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermodynamic analysis of hydrogen production via steam reforming of selected components of aqueous bio-oil fraction

This work presents thermodynamics analysis of hydrogen production via steam reforming of bio-oil components. The model compounds, acetic acid, ethylene glycol and acetone, representatives of the major classes of components present in the aqueous fraction of bio-oil were used for the study. The equilibrium product compositions were investigated in a broad range of conditions like temperature (400–1300 K), steam to fuel ratio (1–9) and pressure (1–20 atm). Any of the three model compounds can be fully reformed even at low temperatures producing hydrogen with maximum yield ranging from 80% to 90% at 900 K. Steam to fuel ratio positively affect the hydrogen content over the entire range of temperature studied. Conversely, higher pressure decreases the hydrogen yield. The formation of solid carbon (graphite) does not constitute a problem provided that reforming temperatures higher than 600 K and steam to fuel ratios higher than 4 for acetic acid and ethylene glycol and 6 for acetone are to be used. Thermal decomposition of the bio-oil components is thermodynamically feasible, forming a mixture containing _C(s)${\mathrm{C}}_{(\mathrm{s})}$, CH₄, H₂, CO, CO₂, and H₂O at various proportions depending on the specific nature of the compound and the temperature. Material and energy balances of complete reforming system demonstrated that the production of 1 kmol/s hydrogen from bio-oil steam reforming requires almost the same amount of energy as with natural gas reforming.     

Life Cycle Assessment of concrete manufacturing in small isolated states: the case of Cyprus

Life Cycle Assessment (LCA) is an effective and valuable methodology for identifying the holistic sustainable behaviour of materials and products. It is also useful in analysing the impact a structure has over the course of its life cycle. Currently, there is no sufficient knowhow regarding the life cycle performance of building materials used in the case of small isolated states. This study focuses on the LCA of the production of concrete for the investigation of its environmental impact in isolated island states, using the case of Cyprus as an example. Four different scenarios for the production of 1 tonne of concrete are examined: (i) manufacturing of concrete by transporting raw materials from different locations around the island, (ii) manufacturing of concrete using alternative energy resources, (iii) manufacturing of concrete with reduced transportation needs, and (iv) on-site manufacturing of concrete. The results, in terms of environmental impacts of concrete produced, indicated that the use of renewable electricity instead of fossil-fuelled electricity in isolated states can drastically improve the environmental performance of the end product. Also, the minimisation of transportation distances and the use of locally available resources can also affect, to a degree, the environmental impact of concrete production.

Abbreviations: AP: Acidification Potential; CRC: Completely Recyclable Concrete; GWP: Global Warming Potential; HFO: Heavy Fuel Oil; LCA: Life Cycle Assessment; LCI: Life Cycle Inventory; LCIA: Life Cycle Impact Assessment; MPA: Mineral Products Association; ODP: Ozone Depletion Potential; POCP: Photochemical Ozone Creation Potential; PV: Photovoltaics     

A data locality methodology for matrix–matrix multiplication algorithm

Matrix-Matrix Multiplication (MMM) is a highly important kernel in linear algebra algorithms and the performance of its implementations depends on the memory utilization and data locality. There are MMM algorithms, such as standard, Strassen–Winograd variant, and many recursive array layouts, such as Z-Morton or U-Morton. However, their data locality is lower than that of the proposed methodology. Moreover, several SOA (state of the art) self-tuning libraries exist, such as ATLAS for MMM algorithm, which tests many MMM implementations. During the installation of ATLAS, on the one hand an extremely complex empirical tuning step is required, and on the other hand a large number of compiler options are used, both of which are not included in the scope of this paper. In this paper, a new methodology using the standard MMM algorithm is presented, achieving improved performance by focusing on data locality (both temporal and spatial). This methodology finds the scheduling which conforms with the optimum memory management. Compared with (Chatterjee et al. in IEEE Trans. Parallel Distrib. Syst. 13:1105, 2002; Li and Garzaran in Proc. of Lang. Compil. Parallel Comput., 2005; Bilmes et al. in Proc. of the 11th ACM Int. Conf. Super-comput., 1997; Aberdeen and Baxter in Concurr. Comput. Pract. Exp. 13:103, 2001), the proposed methodology has two major advantages. Firstly, the scheduling used for the tile level is different from the element level’s one, having better data locality, suited to the sizes of memory hierarchy. Secondly, its exploration time is short, because it searches only for the number of the level of tiling used, and between (1, 2) (Sect. 4) for finding the best tile size for each cache level. A software tool (C-code) implementing the above methodology was developed, having the hardware model and the matrix sizes as input. This methodology has better performance against others at a wide range of architectures. Compared with the best existing related work, which we implemented, better performance up to 55% than the Standard MMM algorithm and up to 35% than Strassen’s is observed, both under recursive data array layouts.     

Pediatric lumbar Chance fractures in British Columbia: chart review and analysis of the use of shoulder restraints in MVAs

Chance fractures of the skeletally immature spine classically occur in frontal motor vehicle accidents (MVAs) when the occupants are restrained by a lap belt only and undergo traumatic hyperflexion of the torso during the impact. We retrospectively examined all MVA-related Chance fractures at British Columbia's Children's Hospital since 1986, by collecting injury and seat-belt use information from chart data and imaging studies. Twenty-six patients were included in the study, 14 wore a lap belt only, seven wore a three-point restraint properly, and five were reportedly misusing the shoulder portion of a three-point restraint. The subjects ranged in age from 3 to 16 with a mean age of 10.6 years. Eleven of the 26 (42%) patients sustained abdominal viscera injuries, seven of the 26 patients suffered neurologic injury (spinal cord and/or spinal nerve injury) associated with their spinal fracture, with two cases of complete paralysis, and there was a 38% incidence of head injury. Concomitant injuries (i.e. to the head, abdomen and abdominal contents) tended to be mitigated by the presence of a properly worn shoulder restraint. This leads to the conclusion that Chance fractures can be sustained even when the occupant is using a shoulder belt to restrain their torso. The mechanism responsible for this is unknown. This may indicate that Chance fractures can be caused by a lesser degree of torso hyperflexion than previously thought. Alternatively, we also speculate that Chance fractures can occur while the torso is restrained by the shoulder belt if the hips submarine beneath the lap belt and the torso experiences hyperflexion secondary to forward excursion of the pelvis and legs during the collision. Future work is necessary to confirm these mechanisms and to find ways to prevent them. These studies will need to use computational or experimental child surrogates that can sit in a slouched posture and submarine during a collision.     

High-Temperature Anelastic and Viscoplastic Deformation of Fine-Grained Magnesia- and Magnesia/Yttria-Doped Alumina

High-temperature (1200–1550 K) mechanical-loss and shear-modulus measurements were performed on fine-grained magnesia- and magnesia/ytrria-doped alumina at low frequency (10⁻⁴−10¹ Hz), using a forced-vibration torsion pendulum. Anelastic and viscoplastic relaxation phenomena were observed, which may be associated with grain-boundary (GB) sliding and, consequently, may be dependent on the grain size and GB segregation of yttrium. The associated activation enthalpies were 800–1100 kJ/mol. GB precipitation of yttrium aluminum garnet led to enhanced mechanical loss and increased activation enthalpy. Viscoplastic deformation increased sharply as the amplitude of the applied stress increased above a "threshold" value of ∼3 MPa. The mechanical loss and creep rate of identical materials showed qualitatively similar dependence on the grain size and yttrium content. A possible micromechanism of mechanical loss could be the motion of GB dislocations, which is important for the accommodation process of GB sliding.