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The mechanism of nitrogen oxide (NO) reduction over graphite carbon-supported single-atom iron (Fe) catalyst (Fe/G) was investigated by density functional theory (DFT) and transition state theory (TST). The catalyst deactivation was also analyzed. The results revealed that the NO reduction, based on the Eley-Rideal (E-R) mechanism, underwent four stages including N2O formation and release as well as N2formation and release. However, the NO reduction only involved two stages according to Langmuir-Hinshelwood (L-H) mechanism: N2formation and release. Furthermore, for the E-R mechanism, the rate-controlling step was NO reduction, where a NO molecule was adsorbed on an Fe atom with an N, O-down structure with energy barrier of 15.5 kJ/mol, lower than that of other paths. Energy barrier analysis indicated that the energy barrier for the reduction of reactive oxygen species was higher than that for the formation of N2. Reactive oxygen species remaining on the surface of Fe atoms after NO decomposition inhibited the adsorption and reduction of NO, leading to catalyst deactivation due to the absence of active sites. The single-atom Fe species promoted the NO reduction. Kinetic analysis results suggested that, upon increasing the reaction temperature, the NO reduction rate increased more significantly than the reactive oxygen transfer rate.

Three different samples were prepared by tailoring the pre-ageing time to investigate the effect of different pre-aged states on the dynamic recrystallization behavior and properties of extruded Mg−9.5Gd−4Y−2.2Zn−0.5Zr (wt.%) alloy. The results showed that the volume fraction of fine grains was 17.4% for under-aged extruded (UAE) sample, while that of the peak-aged extruded (PAE) and over-aged extruded (OAE) samples reached 89.7% and 50.4%, respectively. Dense and fine βparticles distributed inside grains and at grain boundaries significantly improved the nucleation sites and dislocation density through the particle-stimulated nucleation mechanism. However, the dense needle-like γ’phase inhibited dislocation slip and delayed dynamic recrystallization (DRX) nucleation. The difference in the fine grains between the PEA and OAE samples was attributed to a difference in the quantity and size of the original particles, and the difference in their tensile properties was caused by different microstructural components. The higher contributions of grain boundary strengthening and precipitation strengthening mechanisms gave PAE sample better tensile properties.

The asymptotic model is applied to analyze the high-frequency electromagnetic coupling problem of the multiconductor transmission lines (MTLs). To efficiently calculate the current of MTLs in the nonuniform electromagnetic field, an extended asymptotic model combined with matrix pencil method (MPM) is proposed in this article. In the proposed method, the complicated electric field is analytically expressed using an MPM signal model first. Then, considering the basic theory of the moment of method (MOM), the previous solving process of the asymptotic model is optimized in this article to adapt to the requirements of multiple calculations. Finally, the asymptotic model is extended to calculate the current excited by the equivalent plane wave component of the signal model with a good efficiency and accuracy. Moreover, calculating the transient response by the inverse fast Fourier transform (IFFT), several numerical examples with typical nonuniform electromagnetic fields are presented to validate the reliability of the extended asymptotic model.

The effect of Zr on the microstructure and mechanical properties of 304 stainless steel joints brazed with Ag–Cu fillers was studied. The incorporation of Zr had little effect on the solid–liquid phase line of the fillers, and the melting temperature range of the fillers was narrowed, which enhanced their fluidity and wettability. The presence of Zr in the form of heterogeneous particles augmented the nucleation rate during solidification, transforming the intermittently distributed gray-black coarse dendrites into cellular crystals. This structural transformation led to fragmentation and refinement of the microstructure. The dissolution of Zr into Ag and Cu promoted the transformation of low-angle grain boundaries to high-angle grain boundaries (HAGBs), hindering crack propagation. Zr element in the brazing seam led to grain refinement and increased density of grain boundaries. The grain refinement could disperse the stress, and HAGBs could resist the dislocation movement, improving the joint strength. The results display that when Zr content was 0.75 wt.%, the maximum strength was 221.1 MPa. The fracture occurred primarily at the brazing seam, exhibiting a ductile fracture.

The pore network in shale could influence the proportion of adsorbed gases and total gas content and thus is significantly important for the exploration and development of shale gas. The Lower Cambrian Niutitang Formation shale has been proved that have impressive shale gas exploration prospect. Ten Niutitang Formation shale samples were collected from the Micangshan-Hannan Uplift of the Southern Shaanxi area. The TOC is between 0.68% to 2.51%, averaging at 1.54%, and the mineral compositions are dominated by quartz, feldspar, and clay. The pore types comprise intergranular pore, inter-crystalline pore in clay matrix and pyrite aggregates, and organic pore. Quantitative pore structure investigation and impact factors were conducted. The pore area and pore volume are mainly contributed by macropores and mesopores, respectively. TOC, quartz and carbonate contents can jointly influence the pore space. The development of micropore in shale samples is closely related to organic matter, and which is associate with the content of quartz. [Received: November 30, 2023; Accepted: March 30, 2024]

Transmission lines are very important in electrical systems. High-frequency electromagnetic fields can couple to overhead lines. Once the wavelength of the high-frequency electromagnetic field is smaller than the height of the transmission line, the classic transmission line theory is no longer applicable. Although the traditional full-wave numerical algorithm can solve this problem, it is not efficient. Moreover, transmission lines often have multiple vertical ends and complex line layouts. In order to solve these problems, this article proposes a theoretical and effective method to solve the coupling of high-frequency electromagnetic fields with partial discontinuity transmission lines with scatterers in the presence of lossy ground. The asymptotic method with high computational efficiency is adopted, and the concept of scatterer is brought into the asymptotic method to consider more complex circuit structures. Numerical examples verify the accuracy and efficiency of the proposed method.

Due to the difficulty in collecting samples of certain effect levels, the class imbalance problem is a challenging issue in vulnerability assessment. The class imbalance problem would cause deviation of likelihood function and thus deviate the result of vulnerability assessment. Conventional assessment method ignoring it would lead to over- or under-estimation. In this article, we propose the improved kernel density estimation (IKDE) to address this issue. The proposed method first calculates the probability density function of each effect level sample. Then, the spatial characteristics are introduced in the likelihood function to reduce the impact of the class imbalance problem. The parameters in IKDE are determined by Markov Chain Monte Carlo and the probabilities of each effect level can be obtained at last. Through simulations with different class imbalance degrees and sample sizes, we illustrate the effectiveness of the proposed IKDE. Finally, a case study is carried out to assess the vulnerability of 10 kV distribution transformer excited by nanosecond electromagnetic pulse.

In this article, we propose a nonintrusive pulsed radiated susceptibility testing approach based on the long-line crosstalk setup. The objective is to reproduce the pulsed electromagnetic field coupling effect for wiring harness systems. The proposed test setup explores the crosstalk between parallel wires and imposes an additional pulse-driven wire to couple the interferences onto the wire under test. The transmission line model is exploited to represent both crosstalk and the pulsed field coupling process, demonstrating that equivalence can be achieved within a limited clearance time in general, provided the driven wire exceeds a critical length. In addition, rigorous equivalence can be obtained for particular incidences, such as broad-side illumination and end-fire excitation, under the condition of matched auxiliary equivalent terminals. Comparing this to state-of-the-art pulse injection approaches, the crosstalk-based testing method ensures the exact reproduction of field coupling effects without necessitating driven pulse predistortion, this characteristic underscores its robustness for pre-compliance pulsed field radiated susceptibility testing. Additionally, by considering a canonical double exponential interference, a pilot experiment is conducted to verify the equivalent rationale and feasibility of the proposed approach.

Herein, we constructed a novel aminofluorene-based fluorescence probe (FEN-CE) for the detection of carboxylesterase (CE) in living cells by a ratiometric near-infrared (NIR) fluorescence signal. FEN-CEwith NIR emission (650 nm) could be hydrolyzed specifically by CE and transformed to FENH with the release of the self-immolative group, which exhibited a red-shifted emission peak of 680 nm. In addition, FEN-CEshowed high selectivity for CE and was successfully used in the detection of CE activity in living cells through its ratiometric NIR fluorescence signals.

Large-scale pipeline networks may be subject to wide-area and spatially nonuniform external electromagnetic interference. This paper presents a generalized and efficient algorithm for the calculation of inductive and conductive coupling to pipeline networks based on the two-port equivalent circuit. In the modified transmission line model of the pipeline, the external inteference are characterized by using only longitudinal voltage sources. In addition, the nonlinear polarization of coating breakdown is incorporated into the circuit model of the network. The linear pipe segments can be independently reduced to the equivalent-pi circuit with analytical parameters, which enables model order reduction of the network. Such techniques can be applied to arbitrary nonuniform excitation fields. Several test cases are used to illustrate the response characteristics of pipelines excited by interference with different spatial patterns, including geomagnetic disturbances and HVDC earth return currents.

The processes and mechanism of removing oil and water from aluminum chips were clarified through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), response surface method (RSM) and molecular dynamics (MD). The results indicate that the cutting fluid loses mass obviously at 200–300 °C and is carbonized above 400 °C. A layered arrangement of water–surfactant–oil is formed. There are strong hydrogen bonds, strong and weak van der Waals (vdW) forces between O—H in surfactant and O atom in water at 1.63, 3.27 and 5.05 Å, respectively. With the increase of temperature, the weak interaction vdW force is vanished, and the hydrogen bond is reduced. The strong vdW force and hydrogen bonds are broken and the layered arrangement of water–surfactant–oil interface is unstable and destroyed above 277 °C. The removal rate of water and oil is up to 99.7% when the chips are heated at 370 °C for 70 min with 3 cm loading thickness.

In this article, the coupling mechanism of microwave to initiating explosives (IEs) is proposed based on the dielectric polarization theory. An open-ended coaxial probe (OECP) with short-circuited terminal and single-layer samples is developed to measure the reflection coefficient of the IEs, which are powder materials with extremely limited samples (milligrams). Then, the complex permittivity (CP) ( $\varepsilon ^{\prime }-{j}\varepsilon ^{\prime \prime }$ ) of IEs can be inversed based on the spectral-domain model and the main-mode reflection coefficient. The proposed method can be applied to measure the CP of IEs within 1–18 GHz, and its accuracy is verified by alumina powders whose permittivity is known, which proves that the error is within 10%. The measured CP can be applied to establish the electromagnetic coupling model of IEs. Two kinds of IEs, i.e., HY-5 and HY-6, were taken as examples, and the dependence of their CP on the frequency was figured out. Thus, their microwave absorption factors ( $\varepsilon ^{\prime \prime }-{f}$ ) could be obtained. The electromagnetic coupling effect of HY-6 was investigated with a multiphysical simulation method, and the temperature rise characteristics of HY-6 under microwave irradiation at different frequencies were compared. The results indicate that the maximum temperature rise happens at 17 GHz, where the microwave absorption factor is the largest. The research results can be applied to guide the electromagnetic protection and storage of IE devices (IEDs) and benefit the frequency selection for microwave ignition systems, as well as the development of microwave-sensitive IE devices.

Current heterogeneous Si photonics usually bond III–V wafers/dies on a silicon-on-insulator (SOI) substrate in a back-end process, whereas monolithic integration by direct epitaxy could benefit from a front-end process where III–V materials are grown prior to the fabrication of passive optical circuits. Here we demonstrate a front-end-of-line (FEOL) processing and epitaxy approach on Si photonics 220 nm (001) SOI wafers to enable positioning dislocation-free GaAs layers in lithographically defined cavities right on top of the buried oxide layer. Thanks to the defect confinement in lateral growth, threading dislocations generated from the III–V/Si interface are effectively trapped within ∼250 nm of the Si surface. This demonstrates the potential of in-plane co-integration of III–Vs with Si on mainstream 220 nm SOI platform without relying on thick, defective buffer layers. The challenges associated with planar defects and coalescence into larger membranes for the integration of on-chip optical devices are also discussed.

The conventional current or voltage signal-based condition monitoring systems for DC high-voltage equipment have the disadvantages of huge volume, inconvenient operation, and low measurement bandwidth and sampling rate. To overcome these drawbacks, a simplified calculational model of the radiative near-field of the electric field in the circuit breaker valve hall is proposed. This model is based on the analytical model of the finite-length current-carrying linear ideal conductor and reveals the physical mechanism of non-invasive situational awareness based on the transient electric field of electrical devices. Predicated on this model, a reconstruction method for calculating the port transient voltage of the hybrid DC breaker is then established and verified by an artificial short-circuit test in an actual ±200 kV MMC-HVDC system. To the best of the author's knowledge, this is the first pilot short-circuit test in a full-scale MMC-HVDC system involving the hybrid DC breaker. Based on the testing data, the reconstructed and measured voltage show a relatively high degree of consistency both in time and frequency domain. The reconstructed voltage signals based on the radiation near-field not only expose the action time sequence of various electrical equipment with the response time of micro-second order, but also disclose the operation of the key devices and fault types for situational awareness in power system.

This article investigates how the accuracy of fault location estimated from a transmission line's natural frequencies is affected by imperfect modeling of HVDC power-converter stations. These systems include a large number of devices each with specific frequency-dependent characteristics, as filters, reactors and surge protection systems. While it is well-known that location errors may ensue from inaccurate termination models, it is not clear to what extent location accuracy is affected when neglecting one or more of these devices. Results show significant differences depending on the kind of transmission line and the reactor inductance. Including reactors is found not to completely avoid errors, proving the need to take into account the reactive behavior of the converter, which strongly varies according to the HVDC technology. A notable source of errors is level repulsion between station and line resonances, a phenomenon observed when the converter station presents self resonances, e.g., due to DC filters and stray capacitances in reactors. Significant loss of sensitivity to the fault position is found in these cases, impairing fault-location resolution. The first, or dominant, natural frequency of the line is more strongly affected by all these phenomena, suggesting that the standard choice of using the dominant resonance may not be an optimal strategy. Higher-order resonances are instead found to be more robust against inaccurate converter models, and appear to be more suitable for accurate fault location in case of uncertainties about the converter model.

In the analysis of high-power electromagnetic pulses (HPEMP) effects on objects above layered half-space, the traditional half-space computational electromagnetics (CEM) algorithms are often limited by high computational cost and the complexity of half-space Green's function. This study proposes a finite-difference time-domain (FDTD) method assisted by a convolution neural network (CNN), which can significantly reduce computational cost and complexity through a redivision of the computational region and the CNN-assisted prediction of the reflected wave. In this FDTD-CNN method, the FDTD region only contains the object, whereas the CNN prediction models are established for the reflected wave of the multilayered planar and the rough surfaces, avoiding the complex half-space Green's functions for characterizing the reflection effect. Numerical examples from typical half-space models are performed to illustrate the accuracy and efficiency of the proposed method. This article provides an accurate and efficient scheme that combines machine learning and traditional CEM to solve the electromagnetic coupling problem of objects over a layered half-space under an HPEMP illumination.

Small peptides represent a subset of dark matter in plant proteomes. Through differential expression patterns and modes of action, small peptides act as important regulators of plant growth and development. Over the past 20 years, many small peptides have been identified due to technical advances in genome sequencing, bioinformatics, and chemical biology. In this article, we summarize the classification of plant small peptides and experimental strategies used to identify them as well as their potential use in agronomic breeding. We review the biological functions and molecular mechanisms of small peptides in plants, discuss current problems in small peptide research and highlight future research directions in this field. Our review provides crucial insight into small peptides in plants and will contribute to a better understanding of their potential roles in biotechnology and agriculture.

Efficient probabilistic geomagnetically induced current (GIC) analysis in power grids provides tools for assessing and mitigating small-probability tail risks of geomagnetic disturbances, especially in early warning and real-time scenarios. This letter employs the reduced nodal admittance matrix (RNAM) to speed up GIC calculation based on Kron reduction. Moreover, the proposed RNAM method is used to achieve a more efficient analysis of probabilistic GICs, which considers the uncertainty of the substation grounding resistances. The novel method is compared with the classical algorithms including the nodal admittance matrix method, the Lehtinen-Pirjola method, and the bus admittance matrix method, and its efficiency improvement is illustrated with several power grid test cases.

This brief presents a behavioral macromodeling method for electronic or electrical interconnected systems, when there are frequency-characterized interconnects loaded by nonlinear terminations in systems. Analog behavioral modeling (ABM) was leveraged to capture frequency-dependent characteristics of multiconductor interconnects and properties of nonlinear terminations. Black-box macromodels were developed from the external mathematical behavior of parts, and real systems could be simulated in the SPICE circuit solver. Also, several critical points and constraints concerning ABM models were analyzed and proposed.From the validation results, the relative errors of proposed models are all less than 3%, and the execution time reduces by a factor over 10 concerning the existing interconnect model, which implies the proposed interconnect model can significantly improve the simulation efficiency, and the analysis accuracy can be guaranteed using proposed models of interconnect systems.

The existing models of the Metal-Oxide arresters (MOA) have difficulty covering the behavior prediction under surges with front time ranging from microseconds to nanoseconds. This brief presents an equation-based dynamic nonlinear model and its circuit implementation, which can describe the behavior of the MOA in a wide range of frequencies and amplitudes with the consideration of the piecewise nonlinearity and the dynamic nonlinearity characteristics. The model can be easily constructed based on the manufacturer’s data and a multiplication factor table for the dynamic characteristic. Two types of MOA used in the power distribution systems are tested to validate the proposed model. The simulated responses of MOAs are in good agreement with the measured results when the MOAs are applied to impulses with front time ranging from 20 ns to $30~\mu \text{s}$ . Both the errors of the peak voltage and the absorbed energy between simulated and measured results are less than 6%.

As a high-dimensional complex nonlinear dynamic system, the analysis of the essence of flow has always been a difficult problem, especially in the flow including phase change. In recent years, it has become a feasible method to reduce the dimension of flow structure by reduced-order modeling (ROM) methods. In this paper, through the cavitation numerical simulation of NACA0015 hydrofoil, two ROM methods are used to reduce and restore three different cavitation respectively-proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). The applicability of two methods in cavitation is discussed and reasons are analyzed. The results show that for stable cavitation, POD, DMD methods can accurately restore the flow field of a few modes with high energy. For unstable cavitation, only POD method can restore real flow field well. This situation is mainly due to the fact that POD, DMD method are applicable to different energy ratios, and different main mode selection criterion of DMD will lead to different main mode. ROM can greatly simplify the complexity of flow. Selecting a reasonable ROM can improve the accuracy of a small amount of database, and provide a basis for intelligent prediction of flow analysis.

Aberrant lysosomal alkalization is associated with various biological processes, such as oxidative stress, cell apoptosis, ferroptosis, etc. Herein, we developed a novel aminofluorene-based fluorescence probe named FANto monitor the lysosomal alkalization-related biological processes by its migration from lysosome to nucleus. FANpossessed NIR emission, large Stokes shift, high pH stability, and high photostability, making it suitable for real-time and long-term bioimaging. As a lysosomotropic molecule, FANcan accumulate in lysosomes first and then migrate to the nucleus by right of its binding capability to DNA after lysosomal alkalization. In this manner, FANwas successfully used to monitor these physiological processes which triggered lysosomal alkalization in living cells, including oxidative stress, cell apoptosis, and ferroptosis. More importantly, at higher concentrations, FANcould also serve as a stable nucleus dye for the fluorescence imaging of the nucleus in living cells and tissues. This novel multifunctional fluorescence probe shows great promise for application in lysosomal alkalization-related visual research and nucleus imaging.

Based on the framework of quantification of margins and uncertainties (QMU) method, a distribution-free QMU method is proposed for the vulnerability evaluation of electrical and electronic equipment excited by transient electromagnetic disturbances. The proposed method can provide a comprehensive evaluation of the equipment considering the stress and the strength with uncertainties. The stress is represented by the induced responses on the equipment conductors, the strength is quantified by the occurrence probability of failure obtained from the experiment. The quantile-based QMU metric can take account of the inherent probability characteristics of stress and strength, as well as the aleatory uncertainties caused by sampling variability. The quantiles and their tolerance bounds are estimated by a nonparametric estimation method based on order statistics, which is a data-driven method without being constrained by the type of probability distribution. A case study of an electronic equipment in the power plant is carried out to illustrate the evaluation procedures of the proposed method.

The performance of 101-stage ring oscillator is effectively improved by the undercut process of metal gate for 28 nm high-k first metal gate-last planar CMOS technology. Using a simple over-etch process after dummy poly-Si gate formation, the undercut metal gate can be fabricated. The metal gate undercut is demonstrated to be able to effectively reduce the overlap capacitance between gate and drain, which further results in over 3.7% improvement of the maximum oscillating frequency at the same integrated circuit active current. While the comparable alternating current performance with reduced power consumption can be obtained.

Ultrashort pulse Bessel beams have gained attention for their ability to process high aspect ratio structures with precision drilling and cutting. However, focusing the beam inside transparent materials can lead to local stretching or compression due to material-air interface mismatch and nonlinear absorption, causing issues with uniformity of focus and processing depth. In this study, we propose a nonlinear compensation scheme for femtosecond pulsed Bessel beam stretching that modulates the optical phase of the pulse beam ring, achieving high-uniformity longitudinal distribution. This scheme enabled the creation of a highly uniform damaged structure measuring $540 \mu \text{m}$ in length and with a width standard deviation of only 145 nm inside fused silica. Our findings offer a new solution for ultrashort pulse laser applications in high aspect ratio drilling and fast precision cutting of transparent materials.

In this article, a kind of tightly coupled array (TCA) with nonuniform short-circuited branches (NSCBs) is proposed. It indicates that the introduction of the NSCBs fundamentally changes the working principle of the TCA and makes it operate like an electromagnetic combined antenna. Arms of the array elements, the short-circuited branches (SCBs), together with the ground plane, compose current loops, which act as magnetic dipoles, and the array elements themselves are electric dipoles, so the TCA becomes an array of electromagnetic combined dipoles in theory. Thus, the backplane short-circuited effect (BSE) and the edge truncation effect (ETE), which limit the working band of the TCA, are avoided simultaneously. Therefore, the working band of TCA remarkably improves, so that it can be applied to radiate the ultrawideband (UWB) pulses with band ratio over 10:1. Then, based on the theory of electromagnetic combined dipoles, the TCA with NSCBs is designed and optimized. A practical such TCA integrated with feeding baluns is developed and measured. The developed TCA with NSCBs has a working band of 287 MHz–6.45 GHz, and the band ratio is 22.5:1. The distance between the array and the ground plate is 20 mm, and the total height of the array antenna is 35 mm, which is only 3.4% of the wavelength of the lower cutoff frequency, which makes a low-profile UWB antenna. Finally, the TCA is excited by a UWB pulse with an amplitude of 3.06 kV, and the performance is measured and calculated in the pulse mode. It indicates that the UWB pulse radiating system has an effective potential of 3.54 kV, and the effective potential gain is 1.16.

Metal-oxide arresters (MOA), including the non-gapped MOAs (NG-MOA) and externally-gapped MOAs (EG-MOA), are the main equipment applied to protect the power system against conducted transient electromagnetic disturbances (TED). However, MOAs exhibit quite different electrical characteristics under microsecond-level and nanosecond-level transients. In order to figure out the response of MOAs under nanosecond-level TED, experimental platforms are built which contain a pulse generator with the amplitude of pulse current adjustable from 0 kA to 5 kA and the rise time of 20 ns. Then the dynamic hysteresis loops, the static V-I characteristics, the response time delay and the full response process of five types of 10-kV MOAs are investigated. From the dynamic hysteresis loops of NG-MOAs, the impedance conversion process can be seen clearly and can be explained by the grain-boundary theory. But EG-MOAs has not this conversion process due to the air-gap. And the experimental results demonstrate that there is no noticeable nanosecond-level conduction delay on NG-MOAs whereas the electric field non-uniformity of the air-gap has a significant influence on the time delay of the EG-MOAs. The response time delay of EG-MOAs changes ranging from tens of nanoseconds to hundreds of nanoseconds. This feature makes EG-MOAs more likely to raise insulation risks under nanosecond-level TED compared with NG-MOAs.