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Tunable diode laser absorption spectroscopy (TDLAS) tomography is a well-established combustion diagnostic technique for imaging 2-D cross-sectional distributions of critical flow-field parameters. As two key metrics in TDLAS tomography, reconstruction accuracy and efficiency are generally traded off to satisfy either the requirement of high-fidelity image retrieval or rapid tomographic data inversion. In this article, a novel quality-hierarchical temperature imaging network for TDLAS tomography is developed based on stacked long short-term memory (LSTM). From limited line-of-sight TDLAS measurements, this network outputs two reconstructed temperature images, i.e., a coarse-quality image and a fine-quality image, with different numbers of network layers and consequently different computational costs. The coarse-quality image provides more timely temperature reconstruction, which can satisfy real-time dynamic monitoring of turbulence–chemistry interactions with a temporal resolution of tens of kilo frames per second. In contrast, the fine-quality image, which can be stored and utilized for offline analysis and diagnosis, further details the temperature reconstruction with more accurate features. Both numerical stimulation and lab-scale experiment validated the accuracy-efficiency tradeoff achieved by the proposed quality-hierarchical temperature imaging network. [ABSTRACT FROM AUTHOR]

As an in situ combustion diagnostic tool, tunable diode laser absorption spectroscopy (TDLAS) tomography has been widely used for imaging 2-D temperature distributions in reactive flows. Compared with the computational tomographic algorithms, convolutional neural networks (CNNs) have been proved to be more robust and accurate for image reconstruction, particularly in the case of limited access of laser beams in the region of interest (RoI). In practice, the flame in the RoI that requires to be reconstructed with the good spatial resolution is commonly surrounded by low-temperature background. Although the background is not of high interest, spectroscopic absorption still exists due to heat dissipation and gas convection. Therefore, we propose a pseudoinversed CNN (PI-CNN) for hierarchical temperature imaging that: 1) uses efficiently the training and learning resources for temperature imaging in the RoI with good spatial resolution and 2) reconstructs the less spatially resolved background temperature by adequately addressing the integrity of the spectroscopic absorption model. In comparison with the traditional CNN, the newly introduced pseudoinversion of the RoI sensitivity matrix is more penetrating for revealing the inherent correlation between the projection data and the RoI to be reconstructed, thus prioritizing the temperature imaging in the RoI with high accuracy and high computational efficiency. In this article, the proposed algorithm was validated by both numerical simulation and lab-scale experiment, indicating good agreement between the phantoms and the high-fidelity reconstructions. [ABSTRACT FROM AUTHOR]

Cold-mixed epoxy asphalt (CEA) has attracted extensive attention in overloaded and steel bridge pavement and maintenance engineering because of its room temperature construction and low energy consumption. However, the compatibility of epoxy resin and asphalt in CEA is still a challenge, limiting its application to some extent. This study aims to enhance the compatibility of CEA with low amounts of plant oil-based compatibilizers and suggest appropriate methods for assessing the compatibility of CEA. GO-grafted epoxidized soybean oil (GOESO) and GO-grafted soybean oil (GOSO) were synthesized and used to modify CEA. The GO and ESO (or SO) solutions were prepared at concentrations of 0.5 mg/mL and 5 mg/mL, respectively. The pH of the solution was adjusted to 5∼6 before heating. The results showed that 0.2 wt% of GO-modified oil-based compatibilizers had similar effects as 30 wt% of oil-based compatibilizers and did not significantly alter the crystal and chemical structures of the CEAs. GOESO is the preferred recommended GO-modified compatibilizer because of the enhanced compatibilizing ability of the epoxy groups in ESO. The compatibilization mechanism involved the effects of the oils on the chemical structures, curing reaction rate, and microstructures of CEAs. The proportion of asphalt particles larger than 20 μm and the reaction rate had strong correlations with the mechanical properties of the cured CEAs. Molecular dynamics simulations revealed that GOSO reduced the solubility parameter (δ) and Flory-Huggins parameter (χ) difference between components A and B by 39.4% and 65.8%, respectively, while GOESO increased the δ and χ difference between components A and B by 10.4% and 15.8%, respectively. • 0.2 wt% graphene oxide modified oil compatibilizers achieved comparable effects to 30 wt% oil-based compatibilizers. • GOESO and GOSO enhance compatibility by changing the curing reaction rate and the microstructures. • The oil with epoxy groups possibly had a strong capability of compatibility enhancement. [ABSTRACT FROM AUTHOR]

Water reduces the stability and safety of paving material, and this has been extensively studied in traditional asphalt pavement. However, the influence of water on emerging cold-mixed epoxy asphalt (CEA) has not yet been acknowledged. In addition, the microstructure composed of epoxy resin (ER) and asphalt determines the performance of the CEA binder, and the influence of water entering this structure should be focused on. Here, CEA interfacial water models were established based on experimental and molecular dynamics (MD) simulations. The distribution and motion of the interfacial water and their influence on the energy, compatibility, and mechanical properties of CEA were explored. The results showed that CEA had desirable water stability when the water content was less than 5%. Water moved and was rearranged at the interface of the CEA and tended to move toward the ER. The water diffusion coefficient increased proportionally to the quadratic of the water content, and the structure of the CEA changed from an ordered short-range arrangement to a disordered one. Water reduced the interaction between the ER and asphalt by a maximum of 41.7% but had little effect on the compatibility of the CEA. Water plasticized CEA because the glass transition temperature of the CEA decreased, and less than 3% of water decreased the modulus of the CEA by a maximum of 27.0%. Simultaneously, water also destroyed the isotropy of the properties of the CEA. The gyration radius of the CEA dropped to approximately half of the value without water. This study is positive for promoting the performance improvement of CEA and provides a framework for studying CEA modeling and evaluation with MD simulations. [ABSTRACT FROM AUTHOR]

High temperature and oxidation are two of the most critical factors that cause epoxy asphalt aging. This paper aims to clarify the variation of mechanical performance and structure of effect of cold-mixed epoxy asphalt (CEA) after thermal-oxidative (TO) aging. The mechanical properties of CEA were studied by tensile tests and dynamic mechanical analysis. The microstructure of CEA was studied by Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, SEM, and fluorescence microscopy. The results indicated that the tensile strength of CEA increased to 5.16 MPa, the elongation at break decreased to 50.3%, and the T g decreased significantly after TO aging. TO aging made the epoxy resin in CEA post-cure, oxidate, degrade and the cross-linked network break. Furthermore, the asphalt particles in CEA agglomerated and oxidized. [Display omitted] • ER underwent a post-curing reaction and degradation. • Asphalt underwent volatilization of the light components and an oxidation reaction. • Thermal-oxidative aging destroyed the original phase structure of the CEA. [ABSTRACT FROM AUTHOR]

The Drosophila lymph gland is an ideal model for studying hematopoiesis, and unraveling the mechanisms of Drosophila hematopoiesis can improve our understanding of the pathogenesis of human hematopoietic malignancies. Bone morphogenetic protein (BMP) signaling is involved in a variety of biological processes and is highly conserved between Drosophila and mammals. Decapentaplegic (Dpp)/BMP signaling is known to limit posterior signaling center (PSC) cell proliferation by repressing the protooncogene dmyc. However, the role of two other TGF-β family ligands, Glass bottom boat (Gbb) and Screw (Scw), in Drosophila hematopoiesis is currently largely unknown. Here, we showed that the loss of Gbb in the cortical zone (CZ) induced lamellocyte differentiation by overactivation of the EGFR and JNK pathways and caused excessive differentiation of plasmatocytes, mainly by the hyperactivation of EGFR. Furthermore, we found that Gbb was also required for preventing the hyperproliferation of the lymph glands by inhibiting the overactivation of the Epidermal Growth Factor Receptor (EGFR) and c-Jun N-terminal Kinase (JNK) pathways. These results further advance our understanding of the roles of Gbb protein and the BMP signaling in Drosophila hematopoiesis and the regulatory relationship between the BMP, EGFR, and JNK pathways in the proliferation and differentiation of lymph gland hemocytes. [ABSTRACT FROM AUTHOR]

Cold-mixed epoxy asphalt (CEA) is an emerging energy-saving and environment-friendly material for steel bridge decks, overload roads, and airfield pavement. Occasionally, CEA suffers from impact with high strain rates, which will be extremely detrimental to the pavement's safety and stability. Since little research deals with this dynamic mechanical behavior, this study aims to clarify the dynamic mechanical performance of CEA mixtures (CEAM) under high strain rates. First, this study evaluated the quasi-static strength evolution by Marshall stability tests. The Marshall stability of CEAM more than quadrupled within the first 20 h and 1.6 times up again when exposed at 60°C, while its flow value showed the opposite trend. Then, the dynamic mechanical behavior under different high strain rates and temperatures was investigated by split Hopkinson pressure bar tests. Results showed that the peak strain rate (146–316 s−1) was 1.7–2.0 times greater than the average strain rate (84–162 s−1). The strain–stress curves became steep as the temperature and the pressure ascended. Under the same test conditions, the peak stress and the peak dynamic modulus of CEAM were 1.7 times larger than that of cement concrete. CEAM absorbed more energy below 25°C than 60°C. All the CEAM had binder failure, and the crushed specimens had aggregates broken. The constitutive model of CEAM was established based on the statistical damage theory and the modified Weibull distribution function. Besides, multiparametric regression analysis proved a demarcation point during the impact. [ABSTRACT FROM AUTHOR]