Tensile Performance of Waterborne Epoxy Coating Immersed in Saline Solutions

Organic coatings can greatly improve the resistant abilities against the migration of harmful species into concrete, resulting in the higher durability performances of concrete structures. Therefore, it is essential to assess the engineering performances of organic coatings in the service environments. In this work, the engineering performances and microstructure of a waterborne epoxy that can be used as a component of concrete’s protective coatings were investigated. The waterborne epoxy samples were immersed in tap water, 5wt% NaCl solution and 5% Na2SO4 solution for 28 d. A direct tensile test equipped with microscopy was conducted to measure the tensile strength and failure process of the waterborne epoxy samples before and after the immersion actions. The physicochemical interactions between the environments and waterborne epoxy samples were investigated by X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) with dispersive X-ray spectroscopy (EDS). Results show that the immersion actions had limited influences on the tensile performances of the waterborne epoxy, but altered the microstructure and chemical structure to certain extents. The findings of this work would deepen the understandings in environmental actions to organic coatings, enabling a more accurate assessment of service life of concrete with organic coatings

Modelling of emissions, transport, and chemistry for air quality management within urban street canyons

This thesis presents a novel, flexible multi-box framework (MBM-FleX) for simulating the transportation and distribution of chemical species in street canyons with varying aspect ratios. The model is computationally resource-efficient and effective in capturing temporal and spatial patterns of reactive species, allowing for comprehensive sensitivity tests to investigate fast non-linear chemistry at the street scale. The studies within this thesis demonstrate the importance of considering complex photochemistry and shading effects on reactive species in urban canyons, emphasizing the influence of volatile organic compound (VOC) free radical chemistry on interconversion of odd-oxygen species. In addition, the research highlights the significance of detailed VOC chemistry for regulatory air quality modelling in street canyons, showing that neglecting VOC chemistry may lead to underestimation of nitrogen dioxide (NO$_2$) concentrations. A field monitoring campaign conducted in a deep street canyon in Naples, Italy, supports the model performance and showcases the impact of urban morphology on air quality. The findings emphasize the importance of considering vertical distribution when assessing health impacts and developing air quality control strategies. Overall, the thesis advances the understanding of air quality dynamics in urban canyons and presents a valuable tool for effective air quality management in intricate urban environments

Aqpet — An R package for air quality policy evaluation

Evaluating the effectiveness of clean air policies is important in the cycle of air quality management, ensuring policy accountability and informing future policy-making processes. However, such evaluations are challenging due to complex confounding factors such as varying weather conditions or seasonal or annual changes in air quality unrelated to the policy implementation. To address this challenge, we developed 'aqpet', a R package designed to streamline the quantification of policy effects on air quality using observational data. The package 'aqpet' includes: (1) automated-machine learning to predict air pollutants under average weather conditions – a process term as "weather normalisation"; (2) augmented synthetic control method (ASCM) to quantify the actual policy impact on air pollution. 'aqpet' offers functions for data collection and preparation, building auto-machine learning models, conducting weather normalisation, model performance evaluation and explanation, and causal impact analysis using ASCM. 'aqpet' enables fast, efficient, and interactive policy analysis for air quality management.</p

Accelerated Degradation of Coating-mortar Interface under UV Radiation in Presence of Water

The application of organic coatings is one of the most effective and economic methods to protect concrete structures from deterioration. However, organic coatings are prone to degradation under aggressive environmental actions, so the protective function may loss. While ultraviolet (UV) aging is often blamed for the degradation of organic coatings, water may play a more important role on the interfacial adhesion between the coatings and the substrate. To uncover the effect of water on the degradation performance of coating-substrate system, mortar samples coated with water-borne epoxy resin (WER) were exposed to three assigned environments, i.e., UV radiation, UV/water immersion, and UV/dry-wet cycle, up to 60 days. The surface appearance, chemical structure, wettability, and surface micro-morphology of the aged WER coatings were characterized via image process analysis, attenuated total reflectance flourier transform infrared spectroscopy (ATR&ndash;FTIR), static water contact angle, and scanning electronic microscopy (SEM). Results show that the UV/water immersion resulted in severest blistering on the WER-mortar interface, while the UV/wet-dry cycle caused the formation of micro-pinholes on the WER surface. In contrast, the UV radiation did not induce such severe aging. The data implied that water can accelerate the aging of WER-mortar system

Nondestructive measurement of water content and moisture migration of unsaturated red clays in South China

To reveal the moisture migration mechanism of the unsaturated red clays, which are sensitive to water content change and widely distributed in South China, and then rationally use them as a filling material for highway embankments, a method to measure the water content of red clay cylinders using X-ray computed tomography (CT) was proposed and verified. Then, studies on the moisture migrations in the red clays under the rainfall and ground water level were performed at different degrees of compaction. The results show that the relationship between dry density, water content, and CT value determined from X-ray CT tests can be used to nondestructively measure the water content of red clay cylinders at different migration time, which avoids the error reduced by the sample-to-sample variation. The rainfall, ground water level, and degree of compaction are factors that can significantly affect the moisture migration distance and migration rate. Some techniques, such as lowering groundwater table and increasing degree of compaction of the red clays, can be used to prevent or delay the moisture migration in highway embankments filled with red clays

Robust Control of An Aerial Manipulator Based on A Variable Inertia Parameters Model

Aerial manipulator, which is composed of an UAV (Unmanned Aerial Vehicle) and a multi-link manipulator and can perform aerial manipulation, has shown great potential of applications. However, dynamic coupling between the UAV and the manipulator makes it difficult to control the aerial manipulator with high performance. In this paper, system modeling and control problem of the aerial manipulator are studied. Firstly, an UAV dynamic model is proposed with consideration of the dynamic coupling from an attached manipulator, which is treated as disturbance for the UAV. In the dynamic model, the disturbance is affected by the variable inertia parameters of the aerial manipulator system. Then, based on the proposed dynamic model, a disturbance compensation robust $H_{\infty}$ controller is designed to stabilize flight of the UAV while the manipulator is in operation. Finally, experiments are conducted and the experimental results demonstrate the feasibility and validity of the proposed control scheme

Synthesis of water-soluble chiral DOTA lanthanide complexes with predominately twisted square antiprism isomers and circularly polarized luminescence emission

One-step cyclization of a tetraazamacrocycle 5 with 70% yield in a 25-g scale was performed. Its chiral DOTA derivatives, L4, has ∼93% of TSAP coordination isomer in its Eu(III) and Yb(III) complexes in aqueous solution. [GdL4]5– exhibits a high relaxivity, making it a promising and efficient MRI contrast agent. High luminescence dissymmetry factor (glum) values of 0.285 (ΔJ = 1) for [TbL3]– and 0.241 (ΔJ = 1) for [TbL4]5– in buffer solutions were recorded

R&D outsourcing contract for the unverified value of tacit knowledge sharing

Purpose: The purpose of this paper is to provide a R&D outsourcing contract design framework to incent R&D outsourcing service providers sharing tacit and explicit knowledge. Design/methodology/approach: The author uses the principal-agent theory to builds multitask principal-agent model which focuses on two cases. One case is that the effort costs of explicit and tacit knowledge sharing are complementary, but another is the effort costs are substitutable. Findings: It was found that when the effort costs of explicit and tacit knowledge sharing are mutually complementary the multitask R&D outsourcing contract can incent tacit knowledge sharing. Moreover, the multitask R&D outsourcing contract can motivate the effort of explicit knowledge sharing to achieve system optimization, but it fails to motivate the effort of tacit knowledge sharing to achieve system optimization. Research limitations/implications: In this paper we only consider that the outsourcing relationship is short-term, so the multitask R&D outsourcing contract is formal. In fact, the outsourcing relationship may be long-term, so the multitask R&D outsourcing contract is informal. In the long-term cooperation the buyer can promise some reward which cannot be verified by court. service providers choose to trust the promise of the buyer first. Once the buyer don’t fulfill the promise, they not only lose the trust of service providers in this cooperation, but also lose social trust and are seen as dishonest enterprises. Practical implications: Our study provides a theoretical model for formulating an effective R&D outsourcing contract and promoting the transfer of explicit and tacit knowledge sharing. Originality/value: The paper extends prior literature by designing multitask R&D outsourcing contract to share the tacit knowledge. We not only consider the cost of substitution relationship between tacit knowledge and explicit knowledge, but also considered the cost of complementary relationship.Peer Reviewe

Efficiency-boosted semiconductor optical amplifiers via mode-division multiplexing

Semiconductor optical amplifiers (SOAs) are a fundamental building block for many photonic systems. However, their power inefficiency has been setting back operational cost reduction, circuit miniaturization, and the realization of more complex photonic functions such as large-scale switches and optical phased arrays. In this work, we demonstrate significant gain and efficiency enhancement using an extra degree of freedom of light—the mode space. This is done without changing the SOA’s material design, and therefore high versatility and compatibility can be obtained. Light is multiplexed in different guided modes and reinjected into the same gain section twice without introducing resonance, doubling the interaction length in a broadband manner. Up to 87% higher gain and 300% higher wall-plug efficiency are obtained in a double-pass SOA compared to a conventional single-pass SOA, at the same operating current, in the wavelength range of 1560–1580 nm