Recrystallized grains originating at large second-phase silica particles in deformed nickel crystals have faceted boundaries whose planes are parallel to {100} planes of the recrystallizing grains. ...The orientations of the recrystallizing grains are non-random, and are related to the orientations of the deformed matrix in a manner consistent with their origin at deformation zones adjacent to the particles.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The microstructures of Al–0.1Mg polycrystals deformed in plane strain compression at temperatures of 20–400
°C have been investigated by electron backscatter diffraction. At all temperatures, the ...microstructures are characterized by two types of banded substructure, primary bands of aligned low angle boundaries whose alignment to the rolling plane is a function of strain and temperature, and secondary bands which develop into grain-scale shear bands with increasing strain. Several aspects of the deformation microstructures, including the orientation dependence of subgrain parameters and the inhomogeneity of the microstructure, differ from those of single crystals of similar orientation, and this it attributed to local grain interactions.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
33.
New standards for comfort and energy use in buildings Nicol, J. F.; Humphreys, M. A.
Building research and information : the international journal of research, development and demonstration,
01/2009, Volume:
37, Issue:
1
Journal Article
Peer reviewed
Existing international standards for the specification of environments for human occupancy often 'categorize' such environments to distinguish between higher and lower 'quality'. The way in which the ...categories are presented tends to favour high-energy, closely controlled buildings. Part of the reason for this is that the Standards address 'environment' without addressing the context of the environment in a building. This situation might have occurred through the need for the heating, mechanical ventilation and air-conditioning (HVAC) industry to justify a closely defined 'product'. A new building-centred approach to environmental standards is proposed in which low-carbon buildings are favoured and adaptive standards are used to ensure comfort.
Les normes internationales actuelles concernant les spécifications environnementales relatives à l'occupation par l'homme classent souvent ces environnements pour faire la distinction entre la haute qualité et la basse qualité. La façon de présenter les catégories a tendance à favoriser les bâtiments à haute énergie, étroitement contrôlés. Cela s'explique en partie par le fait que les normes s'intéressent à l'environnement sans insister ici au contexte de l'environnement dans un bâtiment. Cette situation a pu se développer à cause de la nécessité pour l'industrie du chauffage, de la ventilation mécanique et de la climatisation (HVAC) de justifier un produit défini avec précision. Une nouvelle approche centrée sur le bâtiment est proposée qui privilégie les bâtiments sobres en carbone et selon laquelle on utilise des normes adaptatives pour assurer le confort.
Mots clés: comportement adaptatif, classement, confort, consommation énergétique, agence humaine, qualité de l'environnement intérieur, normes internationales, bâtiment sobre en carbone, confort thermique
Full text
Available for:
BFBNIB, IZUM, KILJ, NUK, PILJ, SAZU, UL, UM, UPUK
This paper shows that semi-empirical data-driven models based on a two-time-scale approximation for the magnetic and kinetic control of advanced tokamak (AT) scenarios can be advantageously ...identified from simulated rather than real data, and used for control design. The method is applied to the combined control of the safety factor profile, q(x), and normalized pressure parameter, βN, using DIII-D parameters and actuators (on-axis co-current neutral beam injection (NBI) power, off-axis co-current NBI power, electron cyclotron current drive power, and ohmic coil). The approximate plasma response model was identified from simulated open-loop data obtained using a rapidly converging plasma transport code, METIS, which includes an MHD equilibrium and current diffusion solver, and combines plasma transport nonlinearity with 0D scaling laws and 1.5D ordinary differential equations. The paper discusses the results of closed-loop METIS simulations, using the near-optimal ARTAEMIS control algorithm (Moreau D et al 2013 Nucl. Fusion 53 063020) for steady state AT operation. With feedforward plus feedback control, the steady state target q-profile and βN are satisfactorily tracked with a time scale of about 10 s, despite large disturbances applied to the feedforward powers and plasma parameters. The robustness of the control algorithm with respect to disturbances of the H&CD actuators and of plasma parameters such as the H-factor, plasma density and effective charge, is also shown.
The use of data averaging to improve the angular precision of electron backscattered diffraction (EBSD) maps is discussed. It is shown that orientations may be conveniently and rapidly averaged using ...the four Euler‐symmetric parameters which are coefficients of a quaternion representation. The processing of EBSD data requires the use of an edge preserving filter and a modified Kuwahara filter has been successfully implemented and tested. Three passes of such a filter have been shown to reduce orientation noise by a factor of ∼10. Application of the method to deformed and recovered aluminium alloys has shown that such data processing enables small subgrain misorientation (< 0.5°) to be detected reliably.
Full text
Available for:
BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
The effects of concurrent precipitation on recrystallisation during the isothermal annealing of a supersaturated and deformed Al - Mn alloy have been investigated. At low annealing temperatures ...precipitation on the prior boundaries prevents recrystallisation whereas at high temperatures recrystallisation is complete before precipitation occurs. In the temperature range 375 - 500°C, recrystallisation is affected by precipitation and complex microstructures containing high fractions of low angle boundaries are formed. It is shown that strain induced boundary migration of very large boundary areas is an important recrystallisation mechanism in this temperature range. The interactions between precipitation and recrystallisation are analysed in terms of a simple model. The heating rate is shown to substantially affect the recrystallisation behaviour.
The alignment of substructure formed during deformation by rolling in Al–0.13%Mg has been investigated using electron back-scattered diffraction (EBSD). The substructure in this material was defined ...by walls of high dislocation content, which could be imaged as low-angle boundaries. Trace distributions of those boundaries were calculated using a local Radon transform image processing method, and the boundary normal distribution estimated using data from different sections. There was no evidence for alignment of the substructural boundaries with slip planes or any other simple crystallographic element, and it seems that the substructure is orientated primarily with respect to the macroscopic or mesoscopic straining state.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
An analytical mean field model of recrystallization by strain induced grain boundary migration (SIBM), based on cellular growth, has been implemented and compared to experimental measurements of a ...single-phase Al–0.1Mg alloy deformed to moderate strains. The model is able to predict the onset (nucleation) of primary recrystallization and the kinetics and grain size. Inputs to the model are the prior grain size and the subgrain parameters of the deformation microstructure, together with published values of boundary energies and mobilities. No other parameters are required.
The predictions of grain size and recrystallization kinetics are found to be within ~25% of the measured values, and the effects of the limitations of the input data on the model are discussed. The work highlights the difficulties involved with implementing even the simplest physically based model of recrystallization, which are primarily related to problems in adequately characterizing the deformed state and inadequate knowledge of the energies and mobilities of boundaries. Improvements to the model including the incorporation of orientation (texture) dependent stored energies and crystallographic and geometric factors effecting boundary growth rates are discussed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Single crystals of orientation {110}〈001〉 of a high purity Al–0.05% Si single-phase aluminium alloy have been deformed in channel die plane strain compression at room temperature and 350°C. The ...specimens were annealed at temperatures between 250 and 400°C and detailed measurements have been made of the extensive subgrain growth which occurs in these crystals. It was found that subgrain growth tended to be discontinuous, confirming earlier experimental and theoretical work, and showing that subgrain growth is quite different from normal grain growth. The mean misorientation between subgrains decreased during annealing and this was shown to have a strong effect on the kinetics of subgrain growth. The mobilities of low angle boundaries (2.6°<
θ<5.6°) at temperatures between 250 and 400°C were determined from the subgrain growth kinetics and the activation energies for migration found to be consistent with control by lattice diffusion of solute. The boundary mobilities were found to increase rapidly with increasing misorientation and the results have been compared with the predictions of current theories.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
PDF
