No abstract

The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite was also studied by Monte Carlo (MC) simulations. The thermodynamic calculation results reveal that the dehydration mechanism of gypsum significantly depended on ambient temperature and water vapor pressure. In the high-temperature and low water vapor pressure region, gypsum dehydrates to form γ-CaSO 4 in a single-step process (CaSO 4 ·2H 2 O → γ-CaSO 4 ); with increasing water vapor pressure, gypsum undergoes the CaSO 4 ·2H 2 O → γ-CaSO 4 → β-CaSO 4 ·0.5H 2 O reaction path and as water vapor pressure increases further, the occurrence of a two-step conversion path CaSO 4 ·2H 2 O → β-CaSO 4 ·0.5H 2 O → γ-CaSO 4 was observed. It was also found that gypsum is stable in the low-temperature and high water vapor pressure region and does not dehydrate to form any calcium sulfate hemihydrate. Finally, the rehydration mechanism of soluble anhydrite was studied by MC simulations. The simulation results are in agreement with the experimental data and support the finding that γ-CaSO 4 rehydration forms CaSO 4 ·0.67H 2 O in high relative humidity. Another important result revealed by the MC simulation is that γ-CaSO 4 has an extraordinary ability to capture water molecules from an extremely dry atmosphere, which is very useful in some fields, such as in drying processes and even for extracting liquid water from extremely dry atmosphere.

The effects of disodium malonate, disodium succinate, disodium glutarate, and disodium adipate on the crystal habit of calcium sulfate α-hemihydrate (CaSO·0.5HO, α-CSH) were studied using experimental studies and molecular dynamics simulations. The calculation and experimental results provided insight into the mechanism of the interaction between the additives mentioned above and the different faces of α-CSH that dominate the morphology of α-CSH. The calculation results indicated that the formation of high-aspect-ratio α-CSH, namely, calcium sulfate α-hemihydrate whiskers (α-CSH whiskers), in aqueous solution was due to the interaction between liquid water and side faces of the α-CSH crystal, which inhibits the growth of α-CSH along the radial direction. However, when a trace amount of crystal habit modifier, such as disodium succinate or disodium glutarate, was added to the aqueous solution, the growth rates along the directions normal to the {0 0 1} and {1 1 4} faces were considerably inhibited. Thus, α-CSH crystals with a low aspect ratio were synthesized using a hydrothermal method. In addition, the calculation methodology used in this work could provide a powerful tool for selecting suitable crystal habit modifiers for preparing α-CSH and other inorganic crystals.

The enormous building energy consumption in Shanghai necessitates the identification of standard buildings to offer guidance for the adequate design of retrofitting strategies in order to promote a sustainable built and architectural environment. In this regard, this study develops a methodological approach to establish prototypical buildings using performance index system (PIS) founded on an on-site survey. Emphasis is focused on low-rise office buildings in Shanghai. A total of 10 office parks containing 136 single low-rise office buildings in Min Hang District were systemically selected for survey and data collection. The proposed PIS includes building orientation, number of floors, window/wall ratio, heat and cold source type, plan form, and construction year. Using cluster and correlation analysis, the surveyed buildings are classified based on the impact of each PIS on the annual building energy use intensity. Based on this approach, the most influencing indexes are construction year, the number of floors, window-wall ratio and building orientation. This result refines the surveyed building samples to four prototypical buildings as representative standards for low-rise office buildings. Subsequently, typical buildings representing each of the prototypical buildings were defined. The stipulated approach provides a systematic framework for building classification, characteristic-based evaluation of building energy performance and identification of key performance index for building retrofit purposes.

Blended films were prepared from a silk fibroin (SF) solution by adding a small amount of type I collagen (<5%). The mechanical properties of the wet films modified by collagen were improved obviously. The elongation at break reached 42%, and the smaller contact angles revealed that modified films had better hydrophilicity. 1% heparin was also added to modify the SF films to further improve the in vitro antithrombogenecity. The internal structure of the modified SF films was investigated with scanning electron microscopy, x-ray diffraction and Fourier transform infrared attenuated total reflection spectroscopy. The result indicates that the addition of a small amount of collagen and heparin did not change their conformation.