Occupant behaviour simulation for cellular offices in early design stages—Architectural and modelling considerations

Building simulation is most useful and most difficult in early design stages. Most useful since the optimisation potential is large and most difficult because input data are often not available at the level of resolution required for simulation software. The aim of this paper is to addresses this difficulty, by analysing the predominantly qualitative information in early stages of an architectural design process in search for indicators towards quantitative simulation input. The discussion in this paper is focused on cellular offices. Parameters related to occupancy, the use of office equipment, night ventilation, the use of lights and blinds are reviewed based on simulation input requirements, architectural considerations in early design stages and occupant behaviour considerations in operational stages. A worst and ideal case scenario is suggested as a generic approach to model occupant behaviour in early design stages when more detailed information is not available. Without actually predicting specific occupant behaviour, this approach highlights the magnitude of impact that occupants can have on comfort and building energy performance and it matches the level of resolution of available architectural information in early design stages. This can be sufficient for building designers to compare the magnitude of impact of occupants with other parameters in order to inform design decisions. Potential indicators in early design stages towards the ideal or worst case scenario are discussed.     

Characterization of slice-based H.264/AVC encoded video traffic using token buckets

An explicit slice-based mode type selection scheme for use in H.264/AVC has recently been developed, which reduces the burstiness effect of standard frame-based H.264/AVC by breaking up the Group of Picture structure. In this paper, slice-based encoded video streams are characterized using the token bucket traffic model and compared to standard frame-based encoded streams. Both lossless, loss bounded and delay bounded token bucket models are investigated and the high quantiles are found for the amount of loss. Loss above the amount given by the high quantiles will happen only with a very small probability. It is shown that the reduced burstiness for the slice-based video encoding leads to lower token bucket parameters compared to frame-based video encoding for a stream without scene changes, and a larger reduction in the token bucket parameters compared to the frame-based video encoding when a small amount of delay or loss is allowed for the stream with scene changes. Next, reshuffling of the frames of the video streams with scene changes is employed to better understand the effects of long-range dependence on the token bucket parameters. Only small effects are found from reshuffling the scenes, but reshuffling of the frames inside the scenes leads to lower token bucket parameters. Finally, an approach to estimate the parameters for the token bucket model using simple characteristics of the slice-based stream is developed.     

Effects of changing viewing conditions on the perceived structure of smoothly curved surfaces.

Observers' perceptions of a male and a female torso were investigated using monocular and stereoscopic images under varying conditions of illumination. Observers judged the shapes of these torsos by adjusting a gauge figure to estimate the local slant and tilt at numerous probe points arranged in a lattice over the torso's surface. The results revealed that the judged surfaces in the monocular and stereoscopic conditions were related by an affine stretching transformation in depth that accounted for approximately 95% of the between-condition variance. There was also a strong affine component between the judgments obtained for the different illumination directions, although a further analysis of the residuals indicated that changing the direction of illumination influenced perceived structure in a piecewise manner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acceptable risk as a basis for design

Historically, human civilisations have striven to protect themselves against natural and man-made hazards. The degree of protection is a matter of political choice. Today this choice should be expressed in terms of risk and acceptable probability of failure to form the basis of the probabilistic design of the protection. It is additionally argued that the choice for a certain technology and the connected risk is made in a cost-benefit framework. The benefits and the costs including risk are weighed in the decision process. A set of rules for the evaluation of risk is proposed and tested in cases. The set of rules leads to technical advice in a question that has to be decided politically.     

Solution of a Groundwater Control Problem with Implicit Filtering

In this paper we describe the application of a parallel implementation of the implicit filtering algorithm to a control problem from hydrology. We seek to control the temperature at a group of drinking water wells by placing barrier wells between the drinking water wells and a well that injects heated water from an industrial site.     

Unit-cell scale mapping of ferroelectricity and tetragonality in epitaxial ultrathin ferroelectric films

Typically, polarization and strain in ferroelectric materials are coupled, leading to the generally accepted direct relation between polarization and unit-cell tetragonality. Here, by means of high-resolution transmission electron microscopy we map, on the unit-cell scale, the degree of tetragonality and the displacements of cations away from the centrosymmetry positions in an ultrathin epitaxial PbZr(0.2)Ti(0.8)O(3) film on a SrRuO(3) electrode layer deposited on a SrTiO(3) substrate. The lattice is highly tetragonal at the centre of the film, whereas it shows reduced tetragonality close to the interfaces. Most strikingly, we find that the maximum off-centre displacements for the central area of the film do not scale with the tetragonality. This challenges the fundamental belief in a strong polarization-tetragonality coupling in PbTiO(3)-based ferroelectrics, at such thicknesses. Furthermore, a systematic reduction of the atomic displacements is measured at the interfaces, suggesting that interface-induced suppression of the ferroelectric polarization plays a critical role in the size effect of nanoscale ferroelectrics.     

Atomic-precision determination of the reconstruction of a 90 degree tilt boundary in YBa2Cu3O7-delta by aberration corrected HRTEM

Aberration corrected high-resolution transmission electron microscopy is used to determine the reconstruction of atomic bonds of a 90 degree [100] grain boundary in YBa(2)Cu(3)O(7-delta). A precise measurement of atom positions within the grain boundary and the assessment of the oxygen stoichiometry require at the same time a high control of residual lens aberrations of the electron microscope and a good signal-to-noise ratio. This goal is achieved by the combination of spherical-aberration correction in the microscope with the numerical exit-plane wave function reconstruction from focal series. Atomic column positions for individual cations and anions are determined by the regression analysis of peak maxima in the phase image of the retrieved exit-plane wave function. The measurement accuracy is quantitatively assessed, including the statistical error related to residual noise. Changes in bondlengths between copper atoms and the apical oxygen are measured, indicating the distortion of the square pyramidal oxygen coordination of plane copper sites and the square coordination of chain copper sites in the grain boundary.     

On the influence of building design,occupants and heat waves on comfort and greenhouse gas emissions in naturally ventilated offices. A study based on the EN 15251 adaptive thermal comfort model in Athens,Greece

According to the Intergovernmental Panel on Climate Change the buildings sector has the largest mitigation potential for CO₂ emissions. Especially in office buildings, where internal heat loads and a relatively high occupant density occur at the same time with solar heat gains, overheating has become a common problem. In Europe the adaptive thermal comfort model according to EN 15251 provides a method to evaluate thermal comfort in naturally ventilated buildings. However, especially in the context of the climate change and the occurrence of heat waves within the last decade, the question arises, how thermal comfort can be maintained without additional cooling, especially in warm climates. In this paper a parametric study for a typical cellular naturally ventilated office room has been conducted, using the building simulation software EnergyPlus. It is based on the Mediterranean climate of Athens, Greece. Adaptive thermal comfort is evaluated according to EN 15251. Variations refer to different building design priorities, and they consider the variability of occupant behaviour and internal heat loads by using an ideal and worst case scenario. The influence of heat waves is considered by comparing measured temperatures for an average and an exceptionally hot year within the last decade. Since the use of building controls for shading affects thermal as well as visual comfort, daylighting and view are evaluated as well. Conclusions are drawn regarding the influence and interaction of building design, occupants and heat waves on comfort and greenhouse gas emissions in naturally ventilated offices, and related optimisation potential.     

Hydrogeologie des Kabul-Beckens (Afghanistan), Teil II: Beschaffenheit des Grundwassers

Shallow groundwater is the main source for drinking water in Kabul. It comes from a multitude of shallow handpumped wells spread over the whole city area. The groundwater is characterised by slightly oxic redox conditions. Interactions with aquifer carbonates lead to high degrees of hardness and near-neutral pH. The mostly negative water budget of the Kabul basin results in strong evaporation which leads to an increase in salt content and some undesirable constituents, including borate. Several years of drought have aggravated this problem. The shallow groundwater in the city has received tremendous amounts of pollutants due to a lack of proper waste and wastewater disposal. Common indicators are elevated concentrations of nutrients such as nitrate and faecal bacteria. The high infant mortality can at least partially be attributed to insufficient water hygiene. Acid generated during the mineralization of the waste water is hidden due to the strong pH buffering capacity. Redox and pH conditions preclude significant mobilisation of trace metals and metalloids.