Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. We report a novel bi-functional heterogeneous surface structure that is capable of tuning bubble nucleation, growth and departure dynamics. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of heterogeneous surfaces with distinct wettability regions. Heterogeneous surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. Taking advantage of our fabrication method, a 6 inch wafer size heterogeneous surface was prepared. Pool boiling experiments were also performed to demonstrate a heat flux enhancement up to 3X at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface.

Intense Pulsed Light sintering (IPL) uses pulsed, visible light to sinter nanoparticles (NPs) into films used in functional devices. While IPL of chalcogenide NPs is demonstrated, there is limited work on prediction of crystalline phase of the film and the impact of optical properties of the substrate. Here we characterize and model the evolution of film temperature and crystalline phase during IPL of chalcogenide copper sulfide NP films on glass. Recrystallization of the film to crystalline covellite and digenite phases occurs at 126 °C and 155 °C respectively within 2–7 seconds. Post-IPL films exhibit p-type behavior, lower resistivity (~10−3–10−4 Ω-cm), similar visible transmission and lower near-infrared transmission as compared to the as-deposited film. A thermal model is experimentally validated, and extended by combining it with a thermodynamic approach for crystal phase prediction and via incorporating the influence of film transmittivity and optical properties of the substrate on heating during IPL. The model is used to show the need to a-priori control IPL parameters to concurrently account for both the thermal and optical properties of the film and substrate in order to obtain a desired crystalline phase during IPL of such thin films on paper and polycarbonate substrates.

Sintering of metal nanowire (NW) networks on transparent polymers is an emerging approach for fabricating transparent conductive electrodes used in multiple devices. Pulsed light sintering is a scalable sintering process in which large-area, broad-spectrum xenon lamp light causes rapid NW fusion to increase network conductivity, while embedding the NWs in the polymer to increase mechanical robustness. This paper develops a multiphysical approach for predicting evolution of conductivity, NW fusion and nanoscale temperature gradients on the substrate during pulsed light sintering of silver NWs on polycarbonate. Model predictions are successfully validated against experimentally measured temperature and electrical resistance evolution. New insight is obtained into the diameter-dependent kinetics of NW fusion and nanoscale temperature gradients on the substrate, which are difficult to obtain experimentally. These observations also lead to the understanding that NW embedding in intense pulsed light sintering (IPL) can occur below the glass transition temperature of the polymer, and to a new differential thermal expansion-based mechanism of NW embedding during IPL. These insights, and the developed model, create a framework for physics-guided choice of NWs, substrate and process parameters to control conductivity and prevent substrate damage during the process.

Fabric-based personal heating patches have small geometric profiles and can be attached to selected areas of garments for personal thermal management to enable significant energy savings in built environments. Scalable fabrication of such patches with high thermal performance at low applied voltage, high durability and low materials cost is critical to the widespread implementation of these energy savings. This work investigates a scalable Intense Pulsed Light (IPL) sintering process for fabricating silver nanowire on woven polyester heating patches. Just 300 microseconds of IPL sintering results in 30% lesser electrical resistance, 70% higher thermal performance, greater durability (under bending up to 2 mm radius of curvature, washing, humidity and high temperature), with only 50% the added nanowire mass compared to state-of-the-art. Computational modeling combining electromagnetic and thermal simulations is performed to uncover the nanoscale temperature gradients during IPL sintering, and the underlying reason for greater durability of the nanowire-fabric after sintering. This large-area, high speed, and ambient-condition IPL sintering process represents an attractive strategy for scalably fabricating personal heating fabric-patches with greater thermal performance, higher durability and reduced costs.

To properly protect ancient buildings, it is vitally important to determine the health status of these structures in a timely manner. To easily, quickly, reliably, and quantitatively assess the structure health of ancient timber buildings, this paper proposes a structure health assessment method based on fuzzy matter-element theory improved by asymmetric proximity, and the specific assessment steps are given. First, a fuzzy matter-element model is constructed; then, to effectively solve the failure problem of the maximum membership principle, the fuzzy matter-element assessment model is improved by using the theory of asymmetric proximity. The weights determined by the entropy weight and clustering methods are then combined through the game theory combination weighting concept and, finally, the structural condition of the ancient timber buildings is classified into five grades: I favorable, II ordinary, III poor, IV inferior, and V dangerous. Ten evaluation factors were chosen: bearing capacity of the foundation soil, subbase deformation, foundation damage, column and foundation connection, bearing capacity of members, connection construction, member deformation, crack slope, crack depth, and decayed/insect attacked. Taking a building built in the Republican Period in Sino-Ocean Taikoo Li, Chengdu, as an example, this model was used to assess the building’s structural condition. The results show that this method is feasible to quantitatively assess the structural condition of ancient timber buildings. It is a simple and practical assessment method that can provide a decision-making basis for maintenance, protection, and reinforcement of ancient timber buildings.

Water pollution is a growing global issue; there are many approaches to treating wastewater, including chemical coagulation, physical adsorption, and chemical oxidation. The photocatalysis process has provided a solution for removing pollutants from wastewater, where the pair of the photoelectron and hole works through an asymmetric way to degrade the contaminants under UV irradiation. This method offers an alternative route for treating the pollutant with a lower energy cost, high efficiency, and fewer byproducts. A continuous-flow microfluidic reactor has a channel size from tens to thousands of micrometers, providing uniform irradiation and short diffusion length. It can enhance the conversion efficiency of photocatalysis due to the simple spatial symmetry inside the microreactor channel and among the individual channels. In addition, the bandgap of TiO2, ZnO, or other photocatalyst nanoparticles with symmetric crystal structure can be modified through doping or embedding. In this mini-review, a review of the reported continuous-flow photocatalytic microfluidic reactor is discussed from the perspective of both microreactor design and material engineering.

It is currently known that using stress wave and drilling resistance to detect the internal damage in the ancient timber structure is not a highly precise process. To improve the detection precision of this process, a simulation test was used to detect the internal damage of poplar and elm in ancient buildings. In this empirical study, we compared the detection precision of these two detection methods. Based on the idea of variable weight, we introduced three combined forecasting models based on the IOWA operator, IOWGA operator, and IOWHA operator to predict the internal damage in the ancient timber structure. The results show that the combined forecasting model based on the IOWA operator is more effective in predicting compared to a single detection method and other combined forecasting models. To be more specific, the results show that the detection precision of the combined model is increased by 25.8% and 4.7%, respectively, compared to the precision of the stress wave and drilling resistance tests. The error indicators of the combined forecasting model based on the IOWA operator are better than those of the other combined forecasting models. In addition, the analysis results based upon cross-validation theory show the combined forecasting model based on the IOWA operator has the best applicability, which provides a new practical method for evaluating internal damage of timber components in ancient buildings.

Rapidly and correctly assessing the extent of the damage to a concrete structure after a disastrous fire has great engineering significance. In this paper, an assessment method is proposed based on the game theory-normal cloud model. The surface colors of concrete, exfoliation, cracks, and hammering responses are chosen as the comprehensive assessment indices of concrete damage after fire to establish the corresponding assessment criteria. The normal cloud generator is used to calculate the certainty degree of the grading assessment index of concrete damage after fire. By adopting game theory, the objective weight obtained by the information entropy method and the subjective weight obtained by precedence chart are combined into a comprehensive weight. The comprehensive certainty degree value of concrete damage after fire is then calculated by certainty and weight matrices. The project case analysis shows the assessment results are both intuitive and realistic. This method provides a new approach to the assessment of concrete damage after fire which is more efficient and easier to apply than existing methods.