Non-Destructive Prediction of the Mixed Mineral Pigment Content of Ancient Chinese Wall Paintings Based on Multiple Spectroscopic Techniques.

This study first developed non-destructive and accurate methods to predict the relative contents of mixed mineral pigments in ancient Chinese wall paintings using multiple spectroscopic techniques. The colorimetry, attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR), ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy, and Raman spectroscopy were employed. Analyses were conducted including color difference, spectral reflection, ATR FT-IR spectra, and Raman mapping for simulated samples (malachite-lazurite mixed with rabbit glue samples) before and after aging. Models were then established for predicting the relative pigment contents of samples using UV-Vis-NIR and ATR FT-IR spectral data with Beer-Lambert law, and mathematical methods comprising principal component analysis (PCA) and nonlinear curve fitting. In particular, PCA and empty modeling methods combined with non-negative partial least squares were developed to predict the relative pigment contents based on Raman mapping data. The results demonstrated that approaches comprising PCA, mathematical model, and empty modeling based on the spectral data were effective at predicting the relative pigment contents. The predicted results obtained using the mathematical model based on UV-Vis-NIR spectra had an error of about 2%, and the best prediction based on ATR FT-IR spectra had an error of <3.6% at 1041 cm-1. The errors for the predictions using PCA and empty modeling based on Raman mapping data were 0.01-9.30% and 0.28-7.15%, respectively. However, the predicted relative pigment contents obtained based on ATR FT-IR data combined with the Beer-Lambert law had higher errors. The findings of this study confirm the strong feasibility of using spectroscopic techniques for quantitatively analyzing mixed mineral pigments.

Thermal effects of vertical greening with creepers in different life stages on the outdoor environment under a cold climate.

In this study, we assessed the direct and indirect thermal benefits of growing creepers on a building during four life stages (green, yellowish, yellowing, and wilting) based on field measurements of the temperature and humidity, and theoretical analysis. The results showed that the direct thermal benefits of creepers were significant in the green, yellowish, and yellowing stages, where they gradually decreased as the life stages progressed, with cooling gains of up to 8 °C in the green stage compared with the concrete wall, and the insulation benefits were still approximately 1 °C in the wilting stage. Creepers also had significant indirect thermal benefits in the green, yellowish, and yellowing stages, where the best cooling effect was obtained in the yellowish stage, but no significant indirect thermal benefits were found in the wilting stage. In addition, creepers could reduce the ambient air temperature by increasing the relative humidity in the surrounding environment. The results obtained in this study may provide a scientific reference to facilitate the construction of vertical greening in cold regions and to determine the specifications for related applications, as well as providing insights into vertical greening research at the same latitude.

Urban outdoor thermal environment and adaptive thermal comfort during the summer.

The outdoor thermal environment is an important factor when measuring the livability of a city. Residents will avoid intense heat by reducing their outdoor activities, which decreases the vitality of a city and increases the energy consumed for air conditioning. Outdoor thermal comfort has a great impact on outdoor activities; therefore, we need to evaluate and design the urban outdoor thermal environments in cold regions to improve the outdoor thermal comfort level. In this study, we conducted a questionnaire survey to assess the outdoor thermal comfort and adaptive thermal comfort in four different urban forms in Xi'an during July 2019, and measuring meteorological parameters, such as the temperature, relative humidity, wind speed, and black bulb temperature. The results are showed as follows. (1) In the cold study area, urban residents generally perceived the outdoor climate as relatively hot during the summer. (2) The participants exhibited psychological and physical adaptations in terms of their thermal comfort. In particular, when the PET was 30 °C, the MTCV was about 1.25 points higher in the later summer period than the early summer period. (3) The neutral PET differs among regions, and it is affected by the climate zone and latitude. Comparisons of our results with thermal comfort studies in different regions such as Singapore and Umeå in north Sweden showed that the thermal comfort is correlated with the regional climate and latitude. The neutral PET is higher in tropical regions. Our findings support the theoretical understanding of adaptive thermal comfort in cold regions and they provide a reference for formulating policies related to adaptive thermal comfort.

Characterization of Animal Protein-Based Binders in Ancient Chinese Wall Paintings Using Atomic Force Microscopy and Fourier Transform Infrared Spectroscopy.

In this study, the topographical characteristics of protein-based binders in ancient Chinese wall paintings and the properties of their sources were investigated and identified. Fifteen samples of protein-based binders (skin glue, bone glue, egg glue, and milk glue) before and after aging and mixing azurite were prepared. Next, the topographical characteristics, adhesive properties, and infrared spectra for each chemical group in the binders were analyzed using atomic force microscopy and attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR), and the sources of various binders were identified using ATR FT-IR and principal component analysis (PCA). Results showed that protein binders such as fish bladder, cow bone, and egg white glue had lower roughness values and good consolidation properties. The most distinctive feature of skin and bone glues before and after aging or mixed with azurite was the stretching vibration peak of CH2 deformation vibration at around 1335 cm-1, while the significant characteristics of egg and milk glue was the C=O stretching vibration in Serine at 1306 cm-1 and C=O stretching vibrations in aspartic acid and glutamic acid at 1416 cm-1. In addition, the significant differences of absorbance peaks were observed in the infrared spectra of various bone, skin, egg, and milk glue samples before and after aging while the spectral differences become insignificant after mixing with azurite. The results of PCA confirmed that egg yolk and ewe's and cow's milk were well differentiated from animal skin and bone glue regardless of whether fresh, aged, or mixed with azurite. In addition, the differences between skin and bone glues were significant, and the various types of bone glue could be also differentiated before and after aging.