Combining a Detailed Building Energy Model with a Physically-Based Urban Canopy Model

A scheme that couples a detailed building energy model, EnergyPlus, and an urban canopy model, the Town Energy Balance (TEB), is presented. Both models are well accepted and evaluated within their individual scientific communities. The coupled scheme proposes a more realistic representation of buildings and heating, ventilation and air-conditioning (HVAC) systems, which allows a broader analysis of the two-way interactions between the energy performance of buildings and the urban climate around the buildings. The scheme can be used to evaluate the building energy models that are being developed within the urban climate community. In this study, the coupled scheme is evaluated using measurements conducted over the dense urban centre of Toulouse, France. The comparison includes electricity and natural gas energy consumption of buildings, building façade temperatures, and urban canyon air temperatures. The coupled scheme is then used to analyze the effect of different building and HVAC system configurations on building energy consumption, waste heat released from HVAC systems, and outdoor air temperatures for the case study of Toulouse. Three different energy efficiency strategies are analyzed: shading devices, economizers, and heat recovery.     

Grain boundary and volume diffusion experiments in yttrium aluminium garnet bicrystals at 1,723 K: a miniaturized study

Yb-Y inter-diffusion along a single grain boundary of a synthetic yttrium aluminium garnet (YAG) bicrystal has been studied using analytical transmission electron microscopy (ATEM). To investigate the diffusion, a thin-film containing Yb as the diffusant was deposited perpendicular to the bicrystal grain boundary by pulsed laser deposition (PLD). Structural properties and their change with time in both the diffusant source and the grain boundary are reported. The diffusion profiles are incorporated in a numerical diffusion model, which is applied to determine the grain boundary diffusion coefficient, D _gb , at 1.723 K it is equal to 3 × 10⁻¹⁵ m²/s. We find that grain boundary diffusion is 4.85 orders of magnitude faster than volume diffusion, which was determined from the same diffusion experiment. This result is discussed in the context of special versus general grain boundaries. Finally, we successfully tested the capability of synchrotron-based nano-X-ray fluorescence analysis to map micro-chemical patterns in two dimensions with sub-micrometre resolution.     

Experimental growth of åkermanite reaction rims between wollastonite and monticellite: evidence for volume diffusion control

Growth rates of monomineralic, polycrystalline åkermanite (Ca₂MgSi₂O₇) rims produced by solid-state reactions between monticellite (CaMgSiO₄) and wollastonite (CaSiO₃) single crystals were determined at 0.5 GPa dry argon pressure, 1,000–1,200°C and 5 min to 60 h, using an internally heated pressure vessel. Inert Pt-markers, initially placed at the monticellite–wollastonite interface, indicate symmetrical growth into both directions. This and mass balance considerations demonstrate that rim growth is controlled by transport of MgO. At 1,200°C and run durations between 5 min and 60 h, rim growth follows a parabolic rate law with rim widths ranging from 0.4 to 16.3 μm indicating diffusion-controlled rim growth. The effective bulk diffusion coefficient \( D_{\text{eff,MgO}}^{\text{Ak}} \) is calculated to 10^?15.8±0.1 m² s^?1. Between 1,000°C and 1,200°C, the effective bulk diffusion coefficient follows an Arrhenius law with E _a = 204 ± 18 kJ/mol and D ₀ = 10^?8.6±1.6 m² s^?1. Åkermanite grains display a palisade texture with elongation perpendicular to the reaction interface. At 1,200°C, average grain widths measured normal to elongation, increase with the square root of time and range from 0.4 to 5.4 μm leading to a successive decrease in the grain boundary area fraction, which, however, does not affect \( D_{\text{eff,MgO}}^{\text{Ak}} \) to a detectible extent. This implies that grain boundary diffusion only accounts for a minor fraction of the overall chemical mass transfer, and rim growth is essentially controlled by volume diffusion. This is corroborated by the agreement between our estimates of the effective MgO bulk diffusion coefficient and experimentally determined volume diffusion data for Mg and O in åkermanite from the literature. There is sharp contrast to the MgO–SiO₂ binary system, where grain boundary diffusion controls rim growth.     

Implementation of high-order particle-tracking schemes in a water column model

Stochastic differential equations (SDEs) offer an attractively simple solution to complex transport-controlled problems, and have a wide range of physical, chemical, and biological applications, which are dominated by stochastic processes, such as diffusion. As for deterministic ordinary differential equations (ODEs), various numerical scheme exist for solving SDEs. In this paper various particle-tracking schemes are presented and tested for accuracy and efficiency (time vs. accuracy). To test the schemes, the particle tracking algorithms are implemented into a community wide used 1D water column model. Modelling individual particles allows a straightforward physical interpretation of the involved processes. Further, this approach is strictly mass conserving and does not suffer from the numerical diffusion that plagues grid-based methods. Moreover, the Lagrangian framework allows to assign properties to the individual particles, that can vary spatially and temporally. The movement of the particles is described by a stochastic differential equation, which is consistent with the advection–diffusion equation. Here, the concentration profile is represented by a set of independent moving particles, which are advected according to the velocity field, while the diffusive displacements of the particles are sampled from a random distribution, which is related to the eddy diffusivity field.The paper will show that especially the 2nd order schemes are accurate and highly efficient. At the same level of accuracy, the 2nd order scheme can be significantly faster than the 1st order counterpart. This gain in efficiency can be spent on a higher resolution for more accurate solutions at a lower cost.     

It starts at home? Climate policies targeting household consumption and behavioral decisions are key to low-carbon futures

Through their consumption behavior, households are responsible for 72% of global greenhouse gas emissions. Thus, they are key actors in reaching the 1.5 °C goal under the Paris Agreement. However, the possible contribution and position of households in climate policies is neither well understood, nor do households receive sufficiently high priority in current climate policy strategies. This paper investigates how behavioral change can achieve a substantial reduction in greenhouse gas emissions in European high-income countries. It uses theoretical thinking and some core results from the HOPE research project, which investigated household preferences for reducing emissions in four European cities in France, Germany, Norway and Sweden. The paper makes five major points: First, car and plane mobility, meat and dairy consumption, as well as heating are the most dominant components of household footprints. Second, household living situations (demographics, size of home) greatly influence the household potential to reduce their footprint, even more than country or city location. Third, household decisions can be sequential and temporally dynamic, shifting through different phases such as childhood, adulthood, and illness. Fourth, short term voluntary efforts will not be sufficient by themselves to reach the drastic reductions needed to achieve the 1.5 °C goal; instead, households need a regulatory framework supporting their behavioral changes. Fifth, there is a mismatch between the roles and responsibilities conveyed by current climate policies and household perceptions of responsibility. We then conclude with further recommendations for research and policy.     

TiO2 exsolution from garnet by open-system precipitation: evidence from crystallographic and shape preferred orientation of rutile inclusions

We investigated rutile needles with a clear shape preferred orientation in garnet from (ultra) high-pressure metapelites from the Kimi Complex of the Greek Rhodope by electron microprobe, electron backscatter diffraction and TEM techniques. A definite though complex crystallographic orientation relationship between the garnet host and rutile was identified in that Rt[001] is either parallel to Grt<111> or describes cones with opening angle 27.6° around Grt<111>. Each Rt[001] small circle representing a cone on the pole figure displays six maxima in the density plots. This evidence together with microchemical observations in TEM, when compared to various possible mechanisms of formation, corroborates a precipitate origin. A review of exchange vectors for Ti substitution in garnet indicates that rutile formation from garnet cannot occur in a closed system. It requires that components are exchanged between the garnet interior and the rock matrix by solid-state diffusion, a process we refer to as “open-system precipitation” (OSP). The kinetically most feasible reaction of this type will dominate the overall process. The perhaps most efficient reaction involves internal oxidation of Fe²⁺ to Fe³⁺ and transfer from the dodecahedral to the octahedral site just vacated by $ {\text{Ti}}^{ 4+ }: 6\,{\text{M}}^{ 2+ }_{ 3} {\text{TiAl}}\left[ {{\text{AlSi}}_{ 2} } \right]{\text{O}}_{ 1 2} + 6\,{\text{M}}^{ 2+ }_{ 2, 5} {\text{TiAlSi}}_{ 3} {\text{O}}_{ 1 2} = 10\,{\text{M}}^{ 2+ }_{ 3.0} {\text{Al}}_{ 1. 8} {\text{Fe}}_{0. 2} {\text{Si}}_{ 3} {\text{O}}_{ 1 2} + {\text{M}}^{2+} + 2 {\text{e}}^{-} + 1 2\,{\text{TiO}}_{ 2} . $ OSP is likely to occur at conditions where the transition of natural systems to open-system behaviour becomes apparent, as in the granulite and high-temperature eclogite facies.     

Block and boulder accumulations along the coastline between Fins and Sur (Sultanate of Oman): tsunamigenic remains?

The rocky coastline of the Sultanate of Oman between Fins and Sur is decorated by a number of large blocks and boulder accumulations forming ramparts. The blocks occur as individual rocks of up to 40 tons, as imbricated sets and as ??boulder trains.?? Landward, the deposits change into a sand/boulder mixture and distal into sands. The coast is made up of Tertiary folded limestones and beach rock of Quaternary age, both also constitute the megaclasts. The transport distance from the fractured seaward platform of 6?C10?m above mean sea level varies between 20?m and more than 50?m. We found individual blocks of recent corals and overturned blocks with attached oysters and rock pools. Terrestrial laser scanning was used to analyze geomorphologic features as well as for volumetric estimates of the block weights. Tropical cyclones such as Gonu in 2007 or Phet in 2010 are known to have affected Oman??s coastline in the past. The coastal changes during recent cyclones were minor; therefore, we interpret the block deposits as tsunamigenic. However, this interpretation is not unambiguous. The most likely source area for a tsunami is seen in the Makran Subduction Zone situated in the northern Indian Ocean. Here, at least 4?C5 tsunamigenic earthquakes are documented.     

Ion transport in porous media: derivation of the macroscopic equations using upscaling and properties of the effective coefficients

In this work, we undertake a numerical study of the effective coefficients arising in the upscaling of a system of partial differential equations describing transport of a dilute N-component electrolyte in a Newtonian solvent through a rigid porous medium. The motion is governed by a small static electric field and a small hydrodynamic force, around a nonlinear Poisson–Boltzmann equilibrium with given surface charges of arbitrary size. This approach allows us to calculate the linear response regime in a way initially proposed by O’Brien. The O’Brien linearization requires a fast and accurate solution of the underlying Poisson–Boltzmann equation. We present an analysis of it, with the discussion of the boundary layer appearing as the Debye–Hückel parameter becomes large. Next, we briefly discuss the corresponding two-scale asymptotic expansion and reduce the obtained two-scale equations to a coarse scale model. Our previous rigorous study proves that the homogenized coefficients satisfy Onsager properties, namely they are symmetric positive definite tensors. We illustrate with numerical simulations several characteristic situations and discuss the behavior of the effective coefficients when the Debye–Hückel parameter is large. Simulated qualitative behavior differs significantly from the situation when the surface potential is given (instead of the surface charges). In particular, we observe the Donnan effect (exclusion of co-ions for small pores).     

Universe models with negative bulk viscosity

The concept of negative temperatures has occasionally been used in connection with quantum systems. A recent example of this sort is reported in the paper of S. Braun et al. (Science 339:52, 2013), where an attractively interacting ensemble of ultracold atoms is investigated experimentally and found to correspond to a negative-temperature system since the entropy decreases with increasing energy at the high end of the energy spectrum. As the authors suggest, it would be of interest to investigate whether a suitable generalization of standard cosmological theory could be helpful, in order to elucidate the observed accelerated expansion of the universe usually explained in terms of a positive tensile stress (negative pressure). In the present note we take up this basic idea and investigate a generalization of the standard viscous cosmological theory, not by admitting negative temperatures but instead by letting the bulk viscosity take negative values. Evidently, such an approach breaks standard thermodynamics, but may actually be regarded to lead to the same kind of bizarre consequences as the standard approach of admitting the equation-of-state parameter w to be less than ?1. In universe models dominated by negative viscosity we find that the fluid’s entropy decreases with time, as one would expect. Moreover, we find that the fluid transition from the quintessence region into the phantom region (thus passing the phantom divide w=?1) can actually be reversed. Also in generalizations of the ΛCDM-universe models with a fluid having negative bulk viscosity we find that the viscosity decreases the expansion of the universe.     

Assessment of the ecological quality status of soft-bottoms in Reunion Island (tropical Southwest Indian Ocean) using AZTI marine biotic indices

The ability of the two synthetic marine biotic indices, AMBI and M-AMBI, to account for changes in the ecological quality of coastal soft bottoms of Reunion Island according to disturbances was assessed from macrobenthic samples collected in five sectors between 1994 and 2004. Samples were collected under non-perturbed conditions and at two sites subjected to heavy organic enrichment. Both indices are based on a classification of macrofauna into ecological groups (EG), and their transfer to tropical waters required some adaptations. These indices proved efficient in detecting a degradation of habitat quality. Their use resulted in the classification of all sites sampled between 1996 and 1998 as "good" or "high". M-AMBI nevertheless tended to result in the attribution of a slightly worse ecological quality status than AMBI. Together with an update of the EG species list for the Indian Ocean area, our results support the extension of both indices for the assessment of tropical soft bottoms.