Thermal barrier coatings (TBCs) can effectively protect the alloy substrate of hot components in aeroengines or land-based gas turbines by the thermal insulation and corrosion/erosion resistance of ...the ceramic top coat. However, the continuous pursuit of a higher operating temperature leads to degradation, delamination, and premature failure of the top coat. Both new ceramic materials and new coating structures must be developed to meet the demand for future advanced TBC systems. In this paper, the latest progress of some new ceramic materials is first reviewed. Then, a comprehensive spalling mechanism of the ceramic top coat is summarized to understand the dependence of lifetime on various factors such as oxidation scale growth, ceramic sintering, erosion, and calcium-magnesium-aluminium-silicate (CMAS) molten salt corrosion. Finally, new structural design methods for high-performance TBCs are discussed from the perspectives of lamellar, columnar, and nanostructure inclusions. The latest developments of ceramic top coat will be presented in terms of material selection, structural design, and failure mechanism, and the comprehensive guidance will be provided for the development of next-generation advanced TBCs with higher temperature resistance, better thermal insulation, and longer lifetime.
Zhang analyses the phenomenon of private supplementary tutoring from a global perspective. The expansion of such tutoring alongside schooling is among the striking global shifts since the turn of the ...century. In many countries over half of the relevant cohorts of children receive private tutoring, with that proportion in some locations exceeding 80%. The sector has far-reaching implications for social inequalities, (in)efficiencies in educational processes, study burdens on students, family finances, innovation, and employment. Yet greatly-needed government regulations have typically been slow to catch up with the phenomenon. Commentary in the volume juxtaposes countries with strong regulations with counterparts having weak regulations. Conceptually, the book considers forces changing the roles of multiple stakeholders, including governments, entrepreneurs, teachers, families and students. A useful read for students and researchers interested in comparative education and governance.
Since the first attempt that was made to obtain direct circularly polarized (CP) light from OLEDs by Meijer
et al.
in 1997, considerable efforts have been devoted to the development of circularly ...polarized organic light-emitting diodes (CP-OLEDs), particularly in the recent years. Circularly polarized electroluminescence (CPEL) based on OLEDs has attracted increasing interest for its efficient ability to generate CP light directly and wide potential applications in 3D displays, optical data storage, and optical spintronics. In this review, we systematically summarize the recent progress in chiral emitter based OLEDs with CPEL properties including CPEL based on chiral conjugated polymers, CPEL based on chiral metal complexes, and CPEL based on chiral simple organic molecules, especially chiral thermally activated delayed fluorescence (TADF) molecules. We believe that this review will provide a promising perspective of chiral emitter based OLEDs with CPEL properties for a broad range of scientists in different disciplinary areas and attract a growing number of researchers to this fast-growing research field.
This review summarizes the recent advances in CP-OLEDs based on chiral conjugated polymers, chiral metal complexes, and chiral simple organic molecules.
Nitrogen‐doped carbon (NC) materials have been proposed as next‐generation oxygen reduction reaction (ORR) catalysts to significantly improve scalability and reduce costs, but these alternatives ...usually exhibit low activity and/or gradual deactivation during use. Here, we develop new 2D sandwich‐like zeolitic imidazolate framework (ZIF) derived graphene‐based nitrogen‐doped porous carbon sheets (GNPCSs) obtained by in situ growing ZIF on graphene oxide (GO). Compared to commercial Pt/C catalyst, the GNPCSs show comparable onset potential, higher current density, and especially an excellent tolerance to methanol and superior durability in the ORR. Those properties might be attributed to a synergistic effect between NC and graphene with regard to structure and composition. Furthermore, higher open‐circuit voltage and power density are obtained in direct methanol fuel cells.
Nitrogen‐doped: A new oxygen reduction reaction electrocatalyst was obtained from ZIF‐derived porous carbon and graphene. The catalyst exhibits high activity, superior tolerance to methanol, and good stability in comparison to commercial Pt/C catalyst.
Alloy anodes are promising anode materials for lithium-ion batteries due to their high-energy capacity and safety characteristics. However, the commercial use of alloy anodes has been hindered to ...date by their low cycle life and high initial capacity loss. This review highlights the recent progress in improving and understanding the electrochemical performance of various alloy anodes. The approaches used for performance improvement are summarized, and the causes of first-cycle irreversible capacity loss are discussed. The capacity retentions and irreversible capacity losses of various alloy anodes are compared. Several alloy anodes exhibited excellent cycle life (up to 300 cycles) with high initial coulombic efficiency (80–90%) and large reversible capacity (500–700
mAh
g
−1).
This paper develops the dynamic response of a hydrolic-transmission system of wave-power devices under random wave conditions. Through theoretical calculation and experiment analysis, the ...mathematical model of the hydrolic-transmission system was built to make clear which parameters are related to electric-energy output. The working characteristics of the main parameters are developed through the designed experimental platform. The charging pressure of the accumulator, which affects the rigidity of the hydrolic-transmission system, is analyzed. The throttle valve opening and symmetrical electric loads, which affect the stability and efficiency of the electric energy output, are analyzed. Thus, the energy output curve under different parameter regulations is drawn. Through the orthogonal experimental method, the law curve is further modified, the design principle of hydraulic system parameters under the sea level condition is established, and the optimal design scheme and regulation strategy to the hydraulic conversion system of the power generation device is obtained, to solve the problem that the multiparameter coupling cannot be adjusted quickly and effectively. The energy regulation response mechanism of the hydrolic-transmission system in the wave energy power-generation system is proved.
Conjugated polymers with tailored donor–acceptor units have recently attracted considerable attention in organic photovoltaic devices due to the controlled optical bandgap and retained favorable ...separation of charge carriers. Inspired by these advantages, an effective strategy is presented to solve the main obstructions of graphitic carbon nitride (g‐C3N4) photocatalyst for solar energy conversion, that is, inefficient visible light response and insufficient separation of photogenerated electrons and holes. Donor‐π–acceptor‐π–donor polymers are prepared by incorporating 4,4′‐(benzoc 1,2,5 thiadiazole‐4,7‐diyl) dianiline (BD) into the g‐C3N4 framework (UCN‐BD). Benefiting from the visible light band tail caused by the extended π conjugation, UCN‐BD possesses expanded visible light absorption range. More importantly, the BD monomer also acts as an electron acceptor, which endows UCN‐BD with a high degree of intramolecular charge transfer. With this unique molecular structure, the optimized UCN‐BD sample exhibits a superior performance for photocatalytic hydrogen evolution upon visible light illumination (3428 µmol h−1 g−1), which is nearly six times of that of the pristine g‐C3N4. In addition, the photocatalytic property remains stable for six cycles in 3 d. This work provides an insight into the synthesis of g‐C3N4‐based D‐π–A‐π–D systems with highly visible light response and long lifetime of intramolecular charge carriers for solar fuel production.
A graphitic carbon nitride‐based donor‐π–acceptor‐π–donor configuration is prepared by incorporating 4,4′‐(benzoc 1,2,5 thiadiazole‐4,7‐diyl) dianiline (BD) into g‐C3N4 framework (UCN‐BD). BD acts as an electron acceptor, which endows UCN‐BD with narrow bandgap and a high degree of intramolecular charge transfer. The optimized UCN‐BD sample exhibits much superior performance for photocatalytic hydrogen evolution under visible light illumination (3428 µmol h−1 g−1).
ObjectiveThe systemic spread of colorectal cancer (CRC) is dominated by the portal system and exhibits diverse patterns of metastasis without systematical genomic investigation. Here, we evaluated ...the genomic evolution of CRC with multiorgan metastases using multiregion sequencing.DesignWhole-exome sequencing was performed on multiple regions (n=74) of matched primary tumour, adjacent non-cancerous mucosa, liver metastasis and lung metastasis from six patients with CRC. Phylogenetic reconstruction and evolutionary analyses were used to investigate the metastatic seeding pattern and clonal origin. Recurrent driver gene mutations were analysed across patients and validated in two independent cohorts. Metastatic assays were performed to examine the effect of the novel driver gene on the malignant behaviour of CRC cells.ResultsBased on the migration patterns and clonal origins, three models were revealed (sequential, branch-off and diaspora), which not only supported the anatomic assumption that CRC cells spread to lung after clonally expanding in the liver, but also illustrated the direct seeding of extrahepatic metastases from primary tumours independently. Unlike other cancer types, polyphyletic seeding occurs in CRC, which may result in late metastases with intermetastatic driver gene heterogeneity. In cases with rapid dissemination, we found recurrent trunk loss-of-function mutations in ZFP36L2, which is enriched in metastatic CRC and associated with poor overall survival. CRISPR/Cas9-mediated knockout of ZFP36L2 enhances the metastatic potential of CRC cells.ConclusionOur results provide genomic evidence for metastatic evolution and indicate that biopsy/sequencing of metastases may be considered for patients with CRC with multiorgan or late postoperative metastasis.
By the relative trace formula approach of Jacquet―Rallis, we prove the global
Gan—Gross—Prasad conjecture for unitary groups under some local restrictions for
the automorphic representations.
Intelligent reflecting surface (IRS) offers a cost-effective solution to link blockage problem in mmWave communications, and the prerequisite of which is the accurate estimation of (1) the optimal ...beams for base station/access point (BS/AP) and mobile terminal (MT), (2) the optimal reflection patterns for IRSs, and (3) link blockage. In this paper, we carry out beam training designs for IRSs assisted mmWave communications to estimate the aforementioned parameters. To acquire the optimal beams and reflection patterns, we firstly perform random beamforming and maximum likelihood estimation to estimate angle of arrival (AoA) and angle of departure (AoD) of the line of sight (LoS) path between BS/AP (or IRSs) and MT. Then, with the estimated AoDs, we propose an iterative positioning algorithm that achieves centimeter-level positioning accuracy. The obtained location information is not only a fringe benefit but also enables us to cross verify and enhance the estimation of AoA and AoD, and it also facilitates the estimation of blockage indicator. Numerical results show the superiority of our proposed beam training scheme and verify the performance gain brought by location information.
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