Characterization of spray paints used in street art graffiti by a non‐destructive multi‐analytical approach

Often associated with acts of vandalism, graffiti can also be identified with the so‐called street art movement. Moreover, in the historical context of visual arts from the 20th and 21st century, graffiti spray paints feature among the materials employed in the work of representative artists such as Lucio Fontana, Richard Hamilton, Yves Klein, or David Alfaro Siqueiros. In this study, a large number of artist spray paints were analyzed by means of X‐Ray Fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), spectrophotometry, and Hyperspectral Imaging (HSI). The aim of the study was to provide a chemical characterization of the main organic and inorganic components present within the spray paint formulations by means of a complementary non‐destructive approach. Titanium white, zinc white, bismuth vanadate yellow, ultramarine, strontium sulfide, iron, and copper oxides, along a series of pigments of the azo, phthalocyanine, and quinacridone classes could be identified. High amounts of barium sulfate as well as calcium‐based extenders were also detected. FTIR analysis provided important information regarding the binder composition, mainly modified alkyd resins being identified. Additional information related to the existing chromophores as well as specific binder‐pigments interactions could also be highlighted within the HSI data sets. Overall results provide new insights on the complex chemistry of this new range of materials, which could help future investigations carried on street art graffiti, contemporary murals, or mixed‐media artworks.     

沿空掘巷小煤柱侧防瓦斯泄漏技术

针对赵庄煤业沿空掘巷存在的小煤柱侧瓦斯泄漏隐患,制定了"柔性薄喷+注浆"治理方案,采用柔性薄喷材料替代混凝土,喷涂厚度5 mm,有效解决了材料运输和开裂问题,采用高密度浅钻孔和快凝注浆材料,避免了浆液流入采空区。效果考察表明:柔性薄喷材料挂壁性和柔韧性良好,掘巷服务期间小煤柱侧未出现明显瓦斯泄漏。     

Laser stealth and laser protection properties of oxide-carbide coatings prepared by atmospheric plasma spraying

With the development of laser technology, laser-related materials have been widely studied. Both laser stealth coatings and laser protective coatings are currently the focus of attention. However, less research has been done on laser stealth and protective integrated coatings. In this paper, plasma-sprayed Y₂O₃–Ti₃AlC₂ coatings were prepared with low-power (LP) and high-power (HP) parameters, and their laser stealth and laser protection properties were characterized. The LP coating and HP coating appeared to have lower reflectivity at 1064 nm because a low-reflectivity second phase and many loose flocs on the surface are introduced, which indicates excellent laser stealth performance. When irradiated by a laser, the LP coating exhibited excellent laser protection ability, and its reflectivity increased after irradiation because Ti₃AlC₂ oxidized and decomposed and densely arranged small particles formed on the surface. The LP coating perfectly protected the 500-W laser irradiation for 20 s. In addition, the laser damage threshold of the LP coating was 5.599 s at 1000-W laser irradiation, which indicates that the LP Y₂O₃–Ti₃AlC₂ coating is a potential material with laser stealth and laser protection integration.     

Establishing Guidelines to Retain Viability of Probiotics During Spray Drying

We present the application of a model-based approach to map processing conditions suitable to spray dry probiotics with minimal viability loss. The approach combines the drying history and bacterial inactivation kinetics to predict the retention of viability after drying. The approach was used to systematically assess the influence of operational co-current spray drying conditions on residual viability. Moreover, two promising alternative drying strategies for probiotics were evaluated involving encapsulation in a hollow particle and using an “ideal-mixed” dryer system. Finally, a graph was constructed with the model to provide visual guidelines to optimize spray dying for probiotics in terms of viability and drying efficiency.     

Predicting the tensile creep of concrete

Over a four year period, six phases of testing were performed to observe the influence of age at loading, applied stress level, mix composition and relative humidity on the tensile creep of concrete. From these investigations it was possible to develop a model which allowed the prediction of tensile creep based on a knowledge of the compressive strength of the concrete (determined at the age of loading), the applied stress level and the relative humidity. Subsequently, this model was validated using the results from three independent investigations. Compressive creep as well as tensile creep was also obtained. This allowed a comparison of compressive creep with tensile creep and illustrated that on the basis of equal stresses, tensile creep is on average between 2 and 3 times greater than compressive creep (the maximum ratio is in excess of 8). For this investigation, however, on the basis of stress/strength ratio the difference between tensile and compressive creep is less significant. Considering a simply supported flexural reinforced concrete element, the investigation suggests that it is unwise to consider actual compressive creep equal to actual tensile creep as is often the case in design practice.     

High-precision green densities of thick films and their correlation with powder,ink, and film properties

A precise geometrical method employing optical profilometry for green density measurements of thick films is presented that provides a typical reproducibility of 0.1–0.2% theoretical density (TD) and a measurement uncertainty of 0.2–0.4% TD for layer thicknesses of around 50 μm. The procedure can be applied for all thick films with a dried thickness of 10 μm or greater. In a case study, the green densities of screen-printed zirconia layers were investigated as a function of the starting powders (grain sizes from 0.1 to 0.4 μm), the solid content, the chain length of ethyl cellulose as binder and its concentration, and two different dispersants and their concentration. Rheological ink properties, surface roughness, drying stresses from deflection measurements, the mechanical properties of green films, and the equivalent compaction pressure were measured and correlated with the green density data. Compressive binder forces and lubrication effects dominated the packing of the particles.     

Drying of Burdock Root Cubes Using a Microwave-Assisted Pulsed Spouted Bed Dryer and Quality Evaluation of the Dried Cubes

Burdock cube samples were dried using hot air and microwave pulsed spouted bed drying (MPSBD). Hot air drying was carried out at three temperatures (70, 80, and 90°C). MPSBD was carried out at three microwave power levels (1.0, 2.0, and 3.0 W/g). The results showed that MPSBD samples dried at 2.0 W/g for 30 min and at 1.0 W/g for 40 min had desirable color, flavor, and textural attributes. Gas chromatography–mass spectrometry results showed that the samples dried using MPSBD were richer in flavor compounds, especially in esters, compared to the hot air–dried samples.     

A New Drying Approach to Enhance Quality of Konjac Glucomannan Extracted from Amorphophallus muelleri

A new drying approach to enhance physical quality of konjac glucomannan extracted from Amorphophallus muelleri was studied. It consisted of a comparison between microwave vacuum drying and conventional hot-air drying. The effects of microwave vacuum drying and hot-air drying on drying kinetics and physical and structural properties such as color, bulk density, particle density, porosity, viscosity, and morphology of konjac glucomannan (KGM) flour were investigated. It can be concluded that microwave vacuum drying significantly reduced drying time and increased porosity of dehydrated products which have a positive effect on the viscosity of the KGM solution. In contrast, it decreased bulk density and particle density when compared with conventional hot-air drying. Microstructure observations revealed the presence of large cavities in the granules of microwave-vacuum-dried KGM samples. However, there was a slight change in color of the microwave-vacuum-dried samples, resulting in a lower whiteness index than the whiteness index of hot-air-dried samples. Hence, microwave vacuum drying was found to have a number of advantages over the conventional hot-air drying method. Therefore, microwave vacuum drying has potential to become a useful drying method for the industrial production of KGM flour.     

How to Adapt a Lab-Scale Freeze Dryer for Assessing Dehydrating Curves at Different Heating Conditions

A laboratory-scale freeze dryer was adapted to allow control of the heat supply and on-line monitoring of sample weight during drying under vacuum condition. Several tests were carried out to verify the reliability of the developed system. The system was also tested with 10-mm-thick banana slices, obtaining the fruit drying rate, at different sample holder plate temperatures including 20 and 30°C as well as an unheated plate. The system presented in this work represents a low-cost, flexible, and easy-to-assemble piece of equipment that allows the study and optimization of the freeze drying of foods.