Metallo-covalent organic frameworks (M-COFs) integrate organometallic and polymer principles, with salen-type ligands offering a robust means to stabilize transition metal (TM) centers. Dual metallosalen based ligand systems (TM2C22H18N4O2) have been investigated using density functional theory (DFT) to elucidate how TM choice influences framework properties. The findings revealed that Sc, Ti, Y, and Zr atoms in these complexes exhibit pronounced out-of-plane distortions relative to the C22H18N4O2 ligand plane. Regarding thermodynamic stability, the Ti2C22H18N4O2 and ZrC22H18N4O2 complexes show superior performance compared to neighboring complexes. However, the complexes containing Ti2, Cr2, Cu2, Zr2, Mo2, and Cd2 display less chemical stability relative to adjacent systems. Additionally, Mulliken charge analysis shows that Sc2C22H18N4O2 and Y2C22H18N4O2 carry significantly higher charges than the remainder of the series, suggesting enhanced electron modulation capabilities. These insights guide the rational design of salen-based M-COFs for high-performance electrocatalysis.
This study investigates the dynamic stabilization of capacitively coupled plasma (CCP) discharges in a CF 4 / Ar environment through an automatic external L-type matching network using one-dimensional particle-in-cell/Monte Carlo collision (PIC/MCC) simulations. Driven at a source voltage of 100 V and a frequency of 27.12 MHz, the plasma system exhibits complex impedance evolution and non-linear kinetic transitions as the CF 4 mixing ratio increases. Our results demonstrate that the automatic matching algorithm, by iteratively optimizing the matching capacitances ( C (m1 )and C (m2)), achieves a series-like resonance that magnifies the electrode voltage to 3.5-4.5 times the source value. Specifically, at high electronegativity (80% CF 4), the discharge encounters a "high-resistance barrier" characterized by severe electron depletion and initial impedance mismatch. The matching network facilitates a synchronized "staircase" evolution of the electrode voltage, current, and charged species densities, effectively preventing discharge collapse and ensuring global stability. Spatial analysis reveals a fundamental heating mode transition: While low CF 4 fractions support sheath-edge localized heating ( alpha and Drift-Ambipolar modes), the 80% CF 4 case shifts to a bulk-dominated Ohmic heating regime with electron temperatures exceeding 4 eV. This transition is further confirmed by the temporal evolution of the electron energy probability function, which shows a robust recovery of the high-energy tail during the matching iterations. This work underscores that automatic external circuit matching is not merely a tool for power efficiency but acts as a vital kinetic regulator that sustains discharges in attachment-heavy, high-pressure environments, providing critical insights for industrial plasma etching processes.
Optimization of microfluidic plasma devices hinges on accurate characterization of microscale plasma-fluid-thermal coupling, a process that cannot be reliably captured by traditional single-timescale models. Here, we develop a novel self-consistent model that couples particle-in-cell/Monte Carlo collision, direct simulation Monte Carlo, and thermal conduction modules, each operating on its own tailored timescale. This model enables 1 s steady-state simulations of atmospheric-pressure direct current argon microdischarges in a 100- mu m gap with a hot tungsten cathode. Quantitative results reveal that inter-electrode gas thermal conduction ( 1.6 & times;106 W m(-2)) plays a dominant role in governing the system energy balance, thermal state of the neutral gas, and overall discharge dynamics. A 30 K drop in cathode temperature (from 2400 to 2370 K) leads to a 14% decrease in discharge current and a 68% increase in plasma dynamic resistance. We demonstrate that time-resolved gas-electrode thermal interactions govern transient plasma dynamics and device thermal management, while also showing that conventional models with fixed temperature assumptions introduce non-negligible errors in predicting key plasma parameters. This coupled model provides a robust numerical framework for the design and optimization of thermally sustained microdischarge devices.
Since 2000, the flipped classroom model has been widely adopted in higher education within the context of digital transformation; however, a comprehensive historical synthesis of review evidence remains limited. This study addresses this gap by conducting a review of reviews to clarify developmental trends, theoretical foundations, instructional designs, research methods, outcome variables, reported effects and implementation challenges, with the aim of informing sustainable education practices. Following the PRISMA framework, we systematically searched Web of Science Core Collection, Scopus, and Google Scholar for studies published between 2000 and 2024. Predefined inclusion and exclusion criteria were applied, and 25 systematic reviews met the eligibility requirements. Risk of bias and reporting quality were assessed descriptively at the review level. The results indicate generally positive perceptions among students and teachers, particularly regarding learning performance, collaboration and motivation, with the strongest evidence observed at the teaching and learning levels rather than at pedagogical or institutional levels. Substantial variation in flipped classroom designs and inconsistent reporting limited cross-study effect size synthesis. Further analysis reveals a fragmented theoretical basis and uneven attention to post-class learning processes. In response, two integrative frameworks—the Instructional Design Analysis Model for Flipped Classrooms (IDAMFC) and the Transformative Activation Theory for Flipped Classrooms (TAT-FC) are proposed to align pre-, in-, and post-class phases with learning strategies, cognitive engagement, and assessment in digitally supported environments. This study highlights the need for longitudinal designs and more comprehensive outcome measures to support sustainable educational development.
Using a two-dimensional axisymmetric direct-implicit particle-in-cell/Monte Carlo collision model, the effects of the radio frequency (RF) phase difference between the voltage waveforms applied to an inductive coil and a capacitively coupled bias electrode, theta, on a low pressure inductively coupled plasma (ICP) are investigated. The simulations reproduce phase-dependent variations in plasma density in the E-mode at low ICP power, PICP, reported experimentally by Berger et al (2017 Appl. Phys. Lett. 111 201601). As PICP increases, the dc self-bias at the wafer electrode Vbias becomes more positive and the plasma density increases, which leads to thinning sheaths and an increase of the effective capacitance of the discharge. Tuning theta rephases the expansion/collapse timing of the sheaths adjacent to the coil and bias electrode, which stronlgy affects electron transport: at theta=-180 degrees, energetic electron beams generated by sheath expansion heating at the coil, reach the RF biased electrode during the local sheath collapse. This leads to a negative current spike at the electrode at this phase, whereas at theta=-60 degrees such electron beams reach the RF biased electrode sheath, when it is expanded and the negative current spike is attenuated. The ion energy distribution function at the biased electrode exhibits theta-dependent shifts in peak position and broadening, while the electron energy probability function evolves from a theta-sensitive bi-Maxwellian in E-mode to a near-Maxwellian with weak theta dependence as PICP increases and the plasma transitions into H-mode. These results elucidate how phase control provides an effective control parameter for process optimization.
