The intrinsic hydrophobicity and limited light absorption especially in the near‐infrared (NIR) region of porous organic polymers are two bottlenecks impeding their applications in solar steam ...generation (SSG). Herein, we develop a 1,4,5,8‐tetrakis(phenylamino)anthracene‐9,10‐dione (TPAD)‐based covalent organic framework (COF) (TPAD‐COF) featuring both superhydrophilicity and broad light absorption covering from the entire UV/Vis to NIR regions for SSG. TPAD‐COF serving as a highly efficient photothermal conversion material without any additives displays an excellent water evaporation of 1.42 kg m−2 h−1 and achieves a high energy conversion efficiency of 94 % under 1 sun irradiation. Further extension of the light absorption range of the TPAD‐based COF is realized through post‐synthetic modification by chelating BF2 moieties. Systematic control experiments and analysis confirm that the hydrophilicity of photothermal conversion materials plays a more dominant role in the current TPAD‐based COFs for SSG.
A 1,4,5,8‐tetrakis(phenylamino)anthr‐acene‐9,10‐dione (TPAD)‐based covalent organic framework (COF) with both superhydrophilicity and broad light absorption covering the entire UV/Vis to NIR regions is developed for solar steam generation (SSG) and delivers an excellent water evaporation up to 1.42 kg m−2 h−1 with a high energy conversion efficiency of 94 % under one sun irradiation.
Investigating the impact of fertility on the wage earnings of men and women and its trends is important for understanding and coping with both the widening gender wage gap and the continuously ...declining fertility rate in China. Through an in-depth analysis of China Health and Nutrition Survey data from 1989 to 2015, the study finds that in the late 1980s, fertility had a significant positive impact on the wage earnings of men in China, while the negative impact on women's wages was not significant. Over time, the fatherhood wage premium has been declining, while the motherhood wage penalty has been rising at a faster rate, and the gender wage gap has been widening. The expansion of the market sector in China since the deepening of reforms in 1992 is an important reason for the rapid increase of motherhood wage penalty.
•This paper provides a comprehensive review of FMEA using MCDM methods.•The 169 articles were found and classified according to the used MCDM methods.•The risk factors, risk factor weighting methods ...and risk assessment methods are analyzed.•Directions for future research to adopt MCDM methods for FMEA are provided.
Failure mode and effect analysis (FMEA) is a proactive reliability management technique extensively utilized in a variety of fields. To enhance the effectiveness of FMEA, a great many multi-criteria decision making (MCDM) methods have been applied for properly evaluating the risk of failure modes over the past two decades. However, there is a lack of study concerning systematic literature review and classification of the researches on this topic. This article aims to provide a comprehensive review of the FMEA studies using MCDM approaches for evaluation and prioritization of failure modes. To do so, a total of 169 journal papers extracted from the online database over the period of 1998–2018 were selected and reviewed. These publications were classified into 10 categories according to the used MCDM methods, and analyzed in regard to the risk factors, risk factor weighting methods, and risk assessment methods in FMEA. Furthermore, a bibliometric analysis was performed based on the frequency of MCDM methods, number of citations, year of publication, appeared journals, country of origin and application areas. This research supports academics and practitioners in effectively adopting MCDM methods to overcome the deficiencies of the traditional FMEA and provides an insight into its state-of-the-art.
Charge density is one of the most important parameters of triboelectric nanogenerators since it directly determines performance; unfortunately, it is largely restricted by the phenomenon of air ...breakdown. Here, we design a self-improving triboelectric nanogenerator with improved charge density. A maximum effective charge density of 490 μC m
is obtained, which is about two times higher than the highest reported charge density of a triboelectric nanogenerator that operates in an air environment. At the beginning of the working process, the charge accumulation speed is increased 5.8 times in comparison with a triboelectric nanogenerator that is incorporated into the self-improving device. The self-improving triboelectric nanogenerator overcomes the restriction of air breakdown and exhibits an increased effective charge density, which contributes to the improvement of the output performance, and the increase of charge accumulation speed will accelerate the increase of the output power at the start of operation.
In the 2021 Mauritius/Maldives (preliminary objections) case, the Special Chamber of the International Tribunal for the Law of the Sea (ITLOS) rejected Maldives' first and second preliminary ...objections to jurisdiction, which were based on the Monetary Gold principle. However, the Special Chamber's reasoning regarding the Monetary Gold principle in this case is questionable. This article discusses the application of the principle in this case. After introducing the background to the maritime delimitation dispute between Mauritius and Maldives, this article explores the evolving jurisprudence of the Monetary Gold principle and its constitutive elements. It goes on to analyze the application of the Monetary Gold principle in the Mauritius/Maldives case and criticizes the Special Chamber's approach, arguing that the Maldives' first and second preliminary objections should have been upheld.
In a pandemic, in order to slow down the spread of the virus, protect national health, and maintain the normal operation of economic activities, countries around the world will formulate public ...policies to limit the number of citizens that can gather. Our research focuses on how to achieve optimal public policy under different conditions. Traditional SIR and SEIR models can well reflect the transmission process and obtain credible prediction results from a macro perspective, but lack the sensitivity of micro data, and cannot assess the risk of epidemic transmission brought by close contacts and sub-close contacts. Based on the Barabási-Albert scale-free network and the Random spanning tree algorithm, we generate a simulated spread network for non-specific infectious diseases. At the same time, we also generate group networks under different gather constraints. The superposition of the two forms a composite contact network. Our research work on the contact network shows that after considering close contacts and sub-close contacts, the public policy optimization problem of slowing the spread of the epidemic can be answered by the spectrum analysis of the contact network. We perform computer simulations and theoretical proofs of this model, and conduct a transmission analysis of its process.
Constructing two-dimensional (2D) polymers with complex tessellation patterns via synthetic chemistry makes a significant contribution not only to the understanding of the emergence of complex ...hierarchical systems in living organisms, but also to the fabrication of advanced hierarchical materials. However, to achieve such tasks is a great challenge. In this communication we report a facile and general approach to tessellate 2D covalent organic frameworks (COFs) by three or four geometric shapes/sizes, which affords 2D COFs bearing three or four different kinds of pores and increases structural complexity in tessellations of 2D polymers to a much higher level. The complex tessellation patterns of the COFs are elucidated by powder X-ray diffraction studies, theoretical simulations and high-resolution TEM.
With the rapid development of the Internet of things (IoT), wearable electronics, how to power them has been a great challenge, as the traditional powering method via batteries suffers from the ...problems of batteries’ limited capacity and lifetime. Piezoelectric nanogenerators (PENGs) is one of the most promising solutions, as they can convert the ubiquitous and versatile mechanical energy into electricity. Since its invention in 2006, the PENG has achieved tremendous progress. Its voltage has increased from a few millivolts to hundreds of volts, and its current has increased from nanoampere to hundreds of microamperes. In this review, the working mechanisms of PENGs are discussed at first to point out how to improve PENGs’ output theoretically. Then, according to the theoretical analysis, concrete methods including developing piezoelectric materials with high electromechanical response, structural optimization to scale up the electricity generated by individual nanomaterials are discussed. Next, considering the mismatch between the pulse signal generated by PENGs and the stable power supply requirement for conventional electronics, power extraction circuits are discussed. Finally, an outlook of future developments of high output PENGs is given.
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•The key ideas of the published works for improving PENGs’ output are sorted out and reviewed in a systematic way.•According to the theoretical analysis, materials and structural optimization for high output PENG are discussed.•Power extraction circuits for enhancing the output performance are discussed systematically.
Organic chemical reactions cause the temperature rising during coal oxidation; however, because of the complex structure of coal, it is difficult to analyze and characterize the reactions involved in ...coal low-temperature oxidation. To date, a main reaction pathway describing the heating progress during coal oxidation has not been proposed. Here, a series of cyclic chain reactions is presented to describe the oxidation mechanism during coal spontaneous combustion using quantum chemistry calculations. Main active sites and their molecular models were built. Three interactive modes of active orbitals and detailed reaction sequences of coal oxidation are proposed. The structural parameters and thermodynamic data were calculated and the orders of reactions for transformations between functional groups were identified based on their activation energies. The reaction pathway was constructed based on functional transformation relationships and the order of reactions. The results show that main reactions occurring during coal oxidation can be defined as the reactions of oxygen and hydroxide free radicals reacting with coal active sites. Methyne and carbon free radicals reacting with oxygen is the initial reaction during coal oxidation. The decomposition of peroxides linking the reaction pathway form cyclic chain. Hydroxyl and aliphatic hydrocarbon radicals as key of chain reactions consumes coal active sites and oxygen continuously. Aliphatic hydrocarbons appear to contribute more to heat release during coal oxidation due to greater heat release and lower activation energy of their reactions. Limited spontaneous reactions maintain constant apparent activation energy for the oxidation until the chain reactions are generated; the apparent activation energy then increases. Low-ranking coals have higher apparent activation energies during oxidation due to more oxygen-containing groups and side chains contain more reactions with higher activation energy. Results from this study can improve understanding of mechanism of coal oxidation and provide a guide to forecasting and preventing spontaneous combustion of coal in underground coal mines or coal stockpiles.
Asymmetric dearomatization reactions have recently emerged as a powerful tool for the rapid build-up of the molecular complexity. Chiral three-dimensional polycyclic molecules bearing contiguous ...stereogenic centers can be synthesized from readily available planar aromatic feedstocks. Here we report that an intermolecular asymmetric dearomatization reaction of α-naphthols bearing a tethered nucleophile at the C4 position of the naphthol ring is achieved by a chiral phosphoric acid. The reaction proceeds via a highly chemo- and regioselective aminative dearomatization/Michael addition sequence, affording a wide array of functionalized cyclic ketones in good yields (up to 93%) with excellent enantioselectivity (up to >99% ee). The catalyst loading can be reduced to 0.1 mol%. Preliminary mechanistic investigations identify that the enantioselectivity is established in the dearomatization step, while the Michael addition is the rate-limiting step. A working model accounting for the origin of the stereochemistry is proposed based on DFT calculations.
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