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Constructing 3D functional covalent organic frameworks (COFs) with both robust linkage and planar macrocycle building blocks still remains a challenge due to the difficulty in adjusting both the crystallinity and the dominant 2D structures. In addition, it is also challenging to selectively convert inert C(sp3)–H bonds into value-added chemicals. Herein, robust 3D COFs, USTB-28–M (M=Co, Ni, Cu), have been polymerized from the nucleophilic aromatic substitution reaction of D 3h-symmetric 2,3,6,7,14,15-hexahydroxyltriptycene with D 4h-symmetric hexadecafluorophthalocyanine (MPcF16) under solvothermal conditions. These chemically stable dioxin-linked COFs show isostructural tbo topology made up of three kinds of polyhedron subunits, exhibiting high Brunauer−Emmett−Teller surface areas of ≤1477 m2 g−1. In particular, the multiple polyhedron subunits in USTB-28–M could trap N -hydroxyphthalimide at their corners for easily forming stable phthalimide- N -oxyl radicals under visible-light irradiation. The generated radicals efficiently promote the aerobic oxidation of alkyl benzenes with an inert C(sp3)–H bond into various ketones. Among the three investigated COFs, the USTB-28–Co radical initiator exhibits the best photocatalytic oxidation activity, converting ethylbenzene into acetophenone with a turnover frequency of 63 h−1, which is much higher than those of the monomer CoPcF16 (8 h−1) and 2D dioxin-linked counterparts (13 h−1). This is due to the much prolonged lifetime of the excited state for USTB-28–Co based on the femtosecond transient absorption result. The present work not only presents 3D functional COFs with robust connection and permanent porosity, but also illustrates the uniqueness of porous structures of 3D COFs for high-performance photocatalysis. [ABSTRACT FROM AUTHOR]

This study searches for an effective cross-sectional shape of grooves by evaluating their trapping effect using numerical methods. Grooves are widely employed to enhance lubrication performance across various systems, including in bearings and valves, where they serve multiple functions, such as improving load-carrying capacity, addressing pressure imbalances, storing lubricant, and minimizing leakage. Beyond these roles, grooves are crucial in preventing three-body abrasive wear by capturing solid particles, such as wear debris, within the system. This study specifically focuses on the trapping effect of grooves, examining how variations in their cross-sectional shape and the Reynolds number of the lubricant used influence this effect. To evaluate the groove's trapping capability, the study analyzed particle trajectories and streamlines within the groove, as well as the number of particles effectively trapped. The results indicate that grooves with certain cross-sectional shapes, particularly those generating multiple vortices and small eddy currents, demonstrate superior trapping effectiveness. These findings contribute to the design of more efficient grooves in lubrication systems, providing insights into how groove geometry can be optimized to enhance the performance and longevity of mechanical components by mitigating wear through effective particle entrapment. This research has potential applications in the design and improvement of lubrication systems where managing wear and enhancing efficiency are critical concerns. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study searches for an effective cross-sectional shape of grooves by evaluating their trapping effect using numerical methods. Grooves are widely employed to enhance lubrication performance across various systems, including in bearings and valves, where they serve multiple functions, such as improving load-carrying capacity, addressing pressure imbalances, storing lubricant, and minimizing leakage. Beyond these roles, grooves are crucial in preventing three-body abrasive wear by capturing solid particles, such as wear debris, within the system. This study specifically focuses on the trapping effect of grooves, examining how variations in their cross-sectional shape and the Reynolds number of the lubricant used influence this effect. To evaluate the groove’s trapping capability, the study analyzed particle trajectories and streamlines within the groove, as well as the number of particles effectively trapped. The results indicate that grooves with certain cross-sectional shapes, particularly those generating multiple vortices and small eddy currents, demonstrate superior trapping effectiveness. These findings contribute to the design of more efficient grooves in lubrication systems, providing insights into how groove geometry can be optimized to enhance the performance and longevity of mechanical components by mitigating wear through effective particle entrapment. This research has potential applications in the design and improvement of lubrication systems where managing wear and enhancing efficiency are critical concerns.

In this work, an extended temperature current–voltage (I–V) model for AlGaN/GaN high electron mobility transistors (HEMTs) is proposed. Since there is no carrier freeze‐out effect in GaN HEMTs, the current density, switching characteristics, and heat dissipation performance are significantly improved with the decrease in temperature. The threshold voltage drift phenomenon can be accurately described at various temperatures by the trapping effect control potential model. Based on Matthiessen's law, the applicable temperature range of the mobility model is further extended. At cryogenic temperatures, the saturation current, saturation velocity, and sub‐threshold swing of the device tend to saturate as well as be temperature‐independent, which can be accurately modeled by using the equivalent temperature and applying the crucial temperature to quantify the turning point. Furthermore, the SHE modeling incorporates the temperature dependence of the material's thermal conductivity. The accuracy of the model is verified by experimental data at low (4.2–300 K) and high (298–773 K) temperatures. The proposed model overcomes the limitations of existing models applied at wide ambient temperatures. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the development of surface structures, nanowire arrays (NWAS) have been widely studied because of their trapping effect. In this paper, the finite difference time domain (FDTD) method is used to simulate homogeneous and inhomogeneous NWAS. We studied the influence of the structural parameters of InGaN NWAS and inhomogeneous arrays on optical response properties. The optical response includes light absorptivity and cutoff wavelength sensitivity. The simulation results show that the inhomogeneous NWAS can increase the effective transmission distance of light on the surface, thus greatly improving the optical absorption capacity of InGaN NWAS. We can obtain high sensitivity of cut-off wavelength by adjusting the structural parameters of the side nanowires. We find that by reducing the diameters and heights of the side nanowires, a higher light absorption rate can be obtained, which is a 5% improvement compared to uniform NWAS. Therefore, the research in this paper can provide some theoretical reference for the experiment and preparation of InGaN photocathodes. [ABSTRACT FROM AUTHOR]

GaN high-electron-mobility transistors (HEMTs) have attracted widespread attention for high-power microwave applications, owing to their superior properties. However, the charge trapping effect has limitations to its performance. To study the trapping effect on the device large-signal behavior, AlGaN/GaN HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) were characterized through X-parameter measurements under ultraviolet (UV) illumination. For HEMTs without passivation, the magnitude of the large-signal output wave ( X 21 FB ) and small-signal forward gain ( X 2111 S ) at fundamental frequency increased, whereas the large-signal second harmonic output wave ( X 22 FB ) decreased when the device was exposed to UV light, resulting from the photoconductive effect and suppression of buffer-related trapping. For MIS-HEMTs with SiN passivation, much higher X 21 FB and X 2111 S have been obtained compared with HEMTs. It suggests that better RF power performance can be achieved by removing the surface state. Moreover, the X-parameters of the MIS-HEMT are less dependent on UV light, since the light-induced performance enhancement is offset by excess traps in the SiN layer excited by UV light. The radio frequency (RF) power parameters and signal waveforms were further obtained based on the X-parameter model. The variation of RF current gain and distortion with light was consistent with the measurement results of X-parameters. Therefore, the trap number in the AlGaN surface, GaN buffer, and SiN layer must be minimized for a good large-signal performance of AlGaN/GaN transistors. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the fire safety of epoxy resin (EP), two novel phosphorus–nitrogen flame retardants, which named as diphenyl allylphosphoramidate (DPCA) and N-allyl-P, P-diphenylphosphinic amide (DCA), were synthesized by acyl chloride reaction and introduced into EP for fabricating EP composites. The combustion tests showed that incorporation of 5 wt% DPCA or 5 wt% DCA into EP led to the exceptional limited oxygen index (LOI) value (27.1% or 31.6%). Besides, the peak of heat release rate of EP-5 wt% DPCA and EP-5 wt% DCA was reduced by 40.69% and 36.69%, respectively, compared to pure EP. The enhanced fire resistance of EP was ascribed to the trapping effect of fillers in the gas phase and the charring effect in the condensed phase. Furthermore, ultraviolet-visible spectra revealed that both EP-5 wt% DPCA and EP-5 wt% DCA have considerable transparency. This study is expected to broaden the application of EP in the industrial area.

Heterostructure based on single-walled carbon nanotubes (SWCNTs) and lead sulfide quantum dots (PbS QDs) is promising in high-performance visible-to-infrared detection, attributed to high gain and efficiencies of charge separation and transport. Herein, a hybrid photodetector based on the SWCNT/PbS QDs heterostructure is constructed and demonstrates negative/positive photoresponse depending on the wavelength of incident light. The dependence is mainly attributed to the trapping effects coming from the ligand states and oxygen adsorption. Compared with pristine SWCNTs device, the hybrid device demonstrates greatly enhanced (EQE ~ 503% and D* ~1.0 × 107 Jones) positive response, due to long-wavelength photoexcitation through a direct band-to-band transition, which indicates a prospective application potential. [ABSTRACT FROM AUTHOR]

In this work, the current transient method was conducted for trap analysis in the p-GaN gate high-electron-mobility transistors (HEMTs) in the OFF-state. Based on the traditional detrapping transient measurements, the pure recovery transients can be isolated by subtracting the undetected part caused by the measurement conditions. A comparison of the measured and actual recovery transients under different drain filling voltages was presented. It suggested that this method can be effective to analyze the unregular transient curves and distinguish the charge trapping type preliminarily. In addition, three traps were identified based on the time constant spectra and the hidden absolute amplitudes of traps can be corrected using the differential amplitude spectra. The information of trap levels in the buffer layer and AlGaN barrier layer was revealed, consisting of three electron traps with energy levels of 0.313, 0.265, and 0.467 eV. The identification of the traps may provide a physical foundation for better understanding of the drain-induced trapping effect during the OFF-state in p-GaN HEMTs. [ABSTRACT FROM AUTHOR]

1/f noise provides essential information on the interface trapping effect as well as the scattering mechanism in transistors. In this work, a systematic 1/f noise study has been carried out on the recessed-gate enhancement-mode (E-mode) GaN MOS-HEMTs under electrical and thermal stress together with the depletion-mode (D-mode) counterpart. Low-frequency (1–1000 Hz) measurement has been performed at room (25 °C) and elevated (100 °C) temperatures at different carrier densities at the drain bias of 2 V and 10 V. The results show the E-mode device has much better noise characteristics under high voltage and high temperature compared with the D-mode counterpart. Moreover, charge-noise model reveals that the improved noise behavior of the E-mode device at high density and high drain bias at 100 °C originating from the energy band alignment at high biases, where the D-mode device suffers from extra charge trapping scattering in the gate edge near the gate-to-drain access region.

Copyright of Xinjiang Agricultural Sciences is the property of Xinjiang Agricultural Sciences Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

GaN high-electron-mobility transistors (HEMTs) have attracted widespread attention for high-power microwave applications, owing to their superior properties. However, the charge trapping effect has limitations to its performance. To study the trapping effect on the device large-signal behavior, AlGaN/GaN HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) were characterized through X-parameter measurements under ultraviolet (UV) illumination. For HEMTs without passivation, the magnitude of the large-signal output wave (X21FB) and small-signal forward gain (X2111S) at fundamental frequency increased, whereas the large-signal second harmonic output wave (X22FB) decreased when the device was exposed to UV light, resulting from the photoconductive effect and suppression of buffer-related trapping. For MIS-HEMTs with SiN passivation, much higher X21FB and X2111S have been obtained compared with HEMTs. It suggests that better RF power performance can be achieved by removing the surface state. Moreover, the X-parameters of the MIS-HEMT are less dependent on UV light, since the light-induced performance enhancement is offset by excess traps in the SiN layer excited by UV light. The radio frequency (RF) power parameters and signal waveforms were further obtained based on the X-parameter model. The variation of RF current gain and distortion with light was consistent with the measurement results of X-parameters. Therefore, the trap number in the AlGaN surface, GaN buffer, and SiN layer must be minimized for a good large-signal performance of AlGaN/GaN transistors.

In this study, we investigated the effects of temperature and bias voltage on the electron transport properties of AlGaN/GaN high-electron-mobility transistors in the saturation region using a turn-on delay time. A sine wave signal was used to accurately acquire the delay time between the gate-source voltage and drain-source current signal of the device at temperatures ranging from $30\mathbf { \mathtt {^\circ }}\text{C}$ to $180\mathbf {\mathtt {^\circ }}\text{C}$ under operating conditions. With this method, we illustrated a non-monotonic relationship between the temperature and the delay time, which was closely related to the effect of temperature on saturation drift velocity and charge trapping. In addition, it suggested that the delay time increased with increasing drain-source voltage, which was ascribed to the effect of charge trapping. The validity of the proposed results has been thoroughly verified with similar phenomena on two samples. The results may be useful for further study on the electron transport of GaN HEMTs under high temperature and voltages. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A double-diode-isolation method with low parasitic capacitance devices and reverse clamping is proposed to accurately extract the high-frequency and high-voltage dynamic on-resistance ( $R_{\mathrm{ dson}}$ ) of AlGaN/GaN high electron mobility transistor (HEMT) power devices. The response time required for the drain voltage to drop back to the on-voltage of this testing circuit can reach 100 ns, and the forward voltage drop of the isolation diode is monitored in real time using low-voltage probes. A low value constant current source is built to power the testing circuit at only several mA to avoid additional self-heating effect. With these improvements, we can obtain a test frequency of more than 1 MHz, a test voltage of more than 600 V and an accuracy of higher than 97.8% for the extraction of dynamic $\text{R}_{\mathrm{ dson}}$ .

• The interaction between 27 transition metals, O and vacancy in Mo are implemented by first-principles calculations. • The interaction between solute and O can be accurately separated into elastic and chemical contribution. • Simonovic's model indicates dilute TMS atoms can capture O and inhibit the enrichment of O in Mo. • Solute Sc, Ti, Zr, Hf, and Ta can be the top priority to inhibit O segregation and embrittlement in Mo alloys. The trapping effect of solute on oxygen (O) can be benefit for inhibiting its segregation and embrittlement at the GBs in Mo alloys. In this work, the interaction between solutes (including 27 transition metals), interstitial O and vacancy in Mo are implemented by first-principles calculations, and their trapping effects on O are evaluated by Simonovic's model. Single transition metal solute (TMS) has a strong attraction for O, and it is strengthened by the second solute for all 3 d , oversized 4 d and 5 d series. Furthermore, there is a significant synergistic effect between solute, vacancy, and oxygen for oversized solutes, i.e., the binding energy between solute atom (vacancy) and oxygen atoms is enhanced by the presence of vacancy (solute). The distribution of oxygen indicates that oxygen can be captured by dilute TMS atoms, and more oxygen atoms will be trapped as the solute concentration increases in Mo. Based on our extensive calculations, Sc, Ti, Zr, Hf, and Ta can be the top priority for suppressing the segregation and embrittlement of O in Mo alloys. It is interesting that the interaction between solute and O can be accurately separated into elastic and chemical contributions though delicate calculation, and the counterintuitive strong binding effect of fifth-nearest solute-O pairs for undersized 4 d and 5 d elements is owning to the chemical contribution driven by Coulomb interaction. [ABSTRACT FROM AUTHOR]

Owing to the formation of interface and new feature of which, the properties of nanodielectrics can be improved. ‘Hard/soft interface’ and its trap distribution can be tailored by functionalised groups. Molecular simulation results show that the interaction energy and electrostatic potential are larger for the soft interface, which indicates the greater bonding strength with the polymer matrix and electrostatic force on charge carriers. Charge transport simulation indicates that the accumulation of homo-charges would form a reverse electric field and distort electric field distribution. The injection depth would be restricted at the vicinity of sample/electrodes due to the greater trapping effect of deep traps, thus weakening the distortion in the sample bulk, thereby decreasing carrier energy and delaying the formation of impact ionisation. Based on the accumulation of carrier energy Φ = Eeλ, the idea of suppressing electron free path and carrier energy to enhance the insulation breakdown is confirmed. The classified effects of nanofillers during dc breakdown and corona-resistant are further understood from carrier energy. The introduced interfacial trap is effective in trapping carriers due to the low carrier energy under dc voltage, while ineffective in blocking the energetic charges during corona-discharge, but nanoparticles exert blocking and scattering effect against the energetic charges.

In this study, we have investigated the effect of the grain boundary (GB) on the diffusion of a Phosphorus (P) atom in alpha-Fe using molecular dynamics simulations. A Fe-P mixed dumbbell is created in the six symmetric tilt grain boundary (STGB) models. The dumbbells are allowed to migrate at different temperatures from 400 to 1,000 K, with starting positions between 5 to 10Å away from the GB core. The trajectories and mean square displacements (MSD) have been recorded to analyze the diffusion details. The Nudged Elastic Band (NEB) method has been used to study the energy barrier at different positions around the GBs. Our simulation results demonstrate that the GB structure affects the diffusion mechanisms of Fe-P dumbbell. The two low Σ favored GBs display significantly weak trapping effect, which is consistent with the formation energy distribution. The reduction in the migration barrier has been observed due to the decrease of distance from the GB center. Furthermore, the barriers of migration toward the GB are lower than the barriers of migration away from the GB. As evident by NEB calculation, absorption sink effect of GB has been observed. This effect saturates as the distance reaches 8Å or more. Our simulation results provide an insight into the GB trapping effect in alpha-Fe.

The reliability of GaN-based high-electron mobility transistors (HEMTs) is still hindered by trapping effects. Current transient spectroscopy provides an effective way to characterize traps. In this paper, we revealed a trapping behavior hidden in the recovery transients caused by the measuring voltage, and for the first time, we took advantage of it to demonstrate the ${I} _{\mathrm{ ds}}$ -related traps in these devices. We applied this method to three different HEMTs and demonstrated traps’ energy levels using Arrhenius plots. In particular, we found that the ${I} _{\mathrm{ ds}}$ -related traps in different HEMTs had different temperature dependences. A perfect exponential relationship between the degradation rate and the channel current in the linear region was identified. This method provides an effective and easy way to localize traps that capture electrons from the 2-D electron gas directly. [ABSTRACT FROM AUTHOR]

Linear and nonlinear propagation of one- and two-dimensional drift ion acoustic waves with the effects of trapping in electron–positron–ion degenerate plasma has been considered. The characteristics of the dispersion relation in a two-dimensional quantum degenerate plasma has modified significantly due to the inclusion of positrons. The variations of drift KdV and KP equation have been studied with magnetic field, positron concentration and electron degeneracy temperature. The system under consideration admits compressive solitary structures only. The present studies may be valuable to understand the propagation of drift solitary structures with special reference to white dwarf stars. [ABSTRACT FROM AUTHOR]

In a multicrystalline silicon (mc-Si) wafer, trapping effects frequently occur in the carrier lifetime measurement based on the quasi-steady-state photoconductance (QSSPC) technique. This affects the accurate measurement of the carrier lifetime of an mc-Si solar cell by causing distortions at a low injection level close to the Pmax point. Therefore, it is necessary to understand this effect and effectively minimize the trapping-center density. In this study, the variations in the minority carrier-trapping effect of hydrogen at different annealing temperatures in an mc-Si were observed using QSSPC, time-of-flight secondary ion mass spectroscopy, and atom probe tomography. A trapping effect was confirmed and occurred in the grain boundary area, and the effect was reduced by hydrogen. Thus, in an mc-Si wafer, effective hydrogen passivation on the grain area and grain boundary is crucial and was experimentally proven to minimize the distortion of the carrier lifetime.

Abstract Trapping effects in GaN HEMTs still limit their performance. The current-transient methodology has shown advantages in characterizing traps in the device. However, the voltage drift may cause errors in measurements with high accuracy requirements. In this paper, we present a methodology to characterize traps in GaN HEMTs using the voltage-transient measurements. We demonstrate the advantages of this method in terms of simplicity and effectiveness. In particular, it avoids the said problem due to the optimized measuring circuit. With this method, we have identified the time constants and energy levels of traps in the AlGaN barrier layer and the GaN buffer layer, respectively, in the devices. Their trapping and de-trapping mechanisms were also demonstrated at various temperature measurements. A classic exponential dependence of the degradation rate on the channel current was identified. Highlights • A new method to overcome the problem of voltage changes during the monitoring of current transients to characterize traps in GaN HEMTs. • The time constants and energy levels of traps were acquired using this voltage-transient method. • An exponential dependence of the degradation rate on the channel current was identified in different samples. [ABSTRACT FROM AUTHOR]

This paper evaluates the applicability of pulsed I–V measurements as a tool for accurately extracting nonlinear gallium nitride (GaN)-based heterojunction field-effect transistor (HFET) models. Two wafers with the identical layer structure but different growth conditions have been investigated. A series of I–V measurements was performed under dc and pulsed conditions demonstrating a dramatic difference in the kink effect and current collapse (knee walkout) suggesting different trapping behaviors. However, when radio frequency (RF) I–V waveform measurements, utilizing active harmonic load–pull, were used to study the impact of these traps on the RF performance, both wafers gave good overall RF performance with no significant difference observed. This absence of correlation between pulsed I–V measurement results and RF performance raises a question about the applicability of pulsed I–V measurements alone as a tool for extracting nonlinear device models in the case of GaN HFETs. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An accurate physical model for GaN high-electron-mobility-transistors (HEMTs) device is imperative and crucial for circuit design and technology optimization. In this paper, a scalable large-signal surface-potential (SP) model of AlGaN/GaN HEMTs is presented. The drain current model is capable of accurately modeling the self-heating effect and trapping effect. The self-heating effect is modeled by embedding temperature increment into free-carrier mobility model, and the trapping effect is modeled by introducing an indirect variable effective gate voltage V\mathrm {gseff} . Moreover, the scaling and multiharmonic characteristics of the SP model are studied for the first time. The geometry-dependent thermal resistance R\mathrm {ths} is identified by the electrothermal finite-element method simulations, which is scalable with the gate width W and power dissipations P\mathrm {diss} of the device. Single-tone on-wafer load–pull measurements at operating frequency 8 GHz is carried out for verification purpose. Accurate predictions of the static (dc) $I\!-\!V$ , pulsed-gate-and-drain $I\!-\!V$ , S-parameters up to 40 GHz and large-signal harmonic performance (the fundamental, second- and third-harmonics output power, and power-added efficiency) for the devices with different gate peripheries have been achieved by the proposed model. The results of this paper can pave the way for the full application of the physical-based model in circuits design. [ABSTRACT FROM PUBLISHER]

An extensive investigation of fabricated AlGaN/GaN fin-shaped metal-insulator-semiconductor high-electron-mobility transistors (Fin-MISHEMTs) with Al2O3 dielectric is presented in this paper. Based on the pulsed I-V measurements and numerical simulation, the dynamic characteristics of GaN-based Fin-MISHEMTs were carried out under various quiescent bias conditions and temperatures. Moreover, the physical mechanisms of current collapse and dynamic on-resistance increase induced by trapping effects were analyzed. The results show that the observed nonmonotonic variation of current collapse with the gate quiescent bias voltage is resulted from the combination of gate leakage injection-related and hot-electron injection-related trapping effects. Compared with the conventional planar MISHEMTs, the current collapse of AlGaN/GaN Fin-MISHEMTs is smaller due to lower gate leakage and smaller threshold voltage shift, which is benefited from its enhanced gate controllability. The current collapse and dynamic on-resistance increase of Fin-MISHEMTs can be further suppressed by optimizing the device structure, such as designing the fin channels only under the gate. [ABSTRACT FROM AUTHOR]

• Theoretical model for SHG of guided waves developed in topographic structure. • Verification of energy trapping effect for guided waves in topographical structure. • Cumulative SHG of feature guided waves observed in a welded joint. Cumulative second harmonic generation (SHG), where the amplitude of the generated second harmonic increases with propagation distance, is commonly utilized to enhance the measurability of nonlinear guided waves by providing a sufficient signal-to-noise ratio. Investigating and confirming the cumulative SHG of feature guided waves (FGWs) in topographical waveguides is crucial for accurately assessing material nonlinearity in such structures. This study examines the cumulative SHG of FGWs propagating in a typical topographic structure of a welded joint through both numerical simulations and experimental investigations. A theoretical model is developed using the semi-analytical finite-element (SAFE) method and perfectly matched layer (PML) to analyze the propagation characteristics of FGWs in a welded joint. The numerical and experimental results provide verification of the "trapping effect" of FGWs within the welded joint. Furthermore, the "cumulative effect" of SHG of FGWs is observed. Remarkably, both the experimental and numerical findings demonstrate that cumulative SHG of FGWs can be achieved by employing suitable mode selection and frequency tuning in the topographic structure, which aligns well with the theoretical predictions. This investigation contributes to advancing our understanding of cumulative SHG in FGWs propagated within topographical structures. These findings have practical implications for accurately characterizing material nonlinearity in topographic waveguides. [ABSTRACT FROM AUTHOR]

In this paper, we report high-performance blue organic light-emitting diodes (OLEDs) based on evaporated silver nanoclusters (SNCs) located near the aluminum cathode. We investigate the influence of localized surface plasmon resonance (LSPR) and trapping effects of SNCs on the performances of blue OLEDs depending on the size, distribution, and location of the SNCs. The research results reveal when the SNCs are located in the electron transporting layer, the serious trapping effect would cause reduced current density and efficiency of our blue OLEDs. Fortunately, when the SNCs are close to the cathode, owing to the electric field coupling effect between the LSPR of SNCs and the surface polarization of aluminum cathode, the resonant electric field is concentrated near the cathode, thereby enhancing the electron injection. The balanced carrier injection and transport processes improve the performance of blue OLEDs. The optimized device with SNCs located 2 nm away from the aluminum cathode achieves the highest current efficiency of 40.7 cd/A, enhancing by 15% compared to the control device without SNCs. [ABSTRACT FROM AUTHOR]

In recent years, neural networks have been successfully applied for modeling the nonlinear microwave devices as GaAs and GaN MESFETs/HEMTs. Many modeling approaches have been developed for small and large signal applications. In this contribution, a neuro-space mapping approach is proposed for modeling the trapping and the self-heating effects on GaAs and GaN devices. The Angelov empirical model is used as the coarse model, which can be adjusted using DC and Pulsed I/V measurements at different static bias points. The proposed approach is tested for the MGF1923 GaAs MESFET and for an [ABSTRACT FROM AUTHOR]

The reliability of GaN high-electron-mobility transistors remains limited by trapping, and a new way to characterize traps is through the drain current transient. In this paper, we report a differential amplitude spectrum (DAS) from which we could extract the exact amount that a trap contributes to charging/discharging from the current transient. We compared the time constant spectrum and the DAS in extracting traps’ amplitudes theoretically and experimentally. Using the DAS, we investigated the trapping effect and systematically identified the positions and mechanisms of traps with Ea values of 0.10, 0.38, 0.45, and 0.61 eV in our samples. In particular, we demonstrated that the semi-ON state with high-drain voltage in the filling process can maximize the charge trapping in both the AlGaN layer and GaN buffer. In addition, we experimentally proved that measured voltage in the linear region was the best choice for these samples. [ABSTRACT FROM PUBLISHER]

Recent studies have shown that northern vegetation has been growing in relation to a warming climate over the last four decades, especially across the transition zone between tundra and taiga. Shrub growth affects snow properties and the surface energy budget, which must be better studied to quantify shrub-snow-climate feedbacks. The objective of this research is to improve the characterization of the impact of shrubs on snow evolution, from its accumulation to its melt, usingin-situand satellite measurements. The research is presented for the Umiujaq site, Nunavik, representative of the low Arctic–Subarctic transition zone. Snow depth, measured along numerous transects spanning different land cover types is found to increase by a factor 2.5–3 between tundra and forest, while snow density decreases. This illustrates the trapping effect of vegetation well. Complementary, continuous snow depth measurements using weather stations from two sites (tundra with low shrubs and a small clearing with shrubs within the forest) show different site-dependent behaviors. Spatial analysis from high-resolution Pleiades images combined with Landsat (Normalized Difference Snow Index) and MODIS (Fractional Snow Cover) images suggest a slight delay in melt over open and dense forest areas compared to tundra and dense high shrubs. [ABSTRACT FROM AUTHOR]

In order to elucidate the roles of the composition-induced stress gradient and the traps formed by chromium atoms in carbon diffusion in AISI 316L austenitic stainless steel during low temperature gas phase carburization, the carbon concentration-depth profiles were analyzed by a diffusion model considering the composition-induced stress gradient and the trapping effect. The results show that the carbon concentration-depth profiles calculated by this model show good agreement with the experimental results. The composition-induced compressive stress gradient can enhance the carbon diffusion but reduce the surface carbon concentration; these effects are not pronounced. Carbon atoms prefer to occupy the trap sites, and the detrapping activation energy (Qt = 33 kJ·mol−1) was deduced from fitting the experimental carbon concentration-depth profile. Furthermore, this applied diffusion model can be used to interpret the enhanced carbon diffusion in low temperature carburized AISI 316L.

[Display omitted] • Sediment load decreased significantly due to trapping effects of cascade reservoirs. • The change points corresponded to the timing of gigantic reservoirs construction. • Cascade reservoirs contributed 88% and 90% to streamflow and sediment load reduction. • Reservoirs greatly altered seasonal distribution of flow and flood peaks processes. Large reservoirs are widely built along rivers for flood control, hydropower generation, water supply for industry and agricultural production, and recreation. Many large reservoirs/dams built to provide multiple functions for local people are strongly influenced by the downstream flow and sediment discharge in the upstream of the Yellow River, China. In this study, we assessed the changes in the river flow and sediment discharge in responses to the construction of cascade reservoirs/dams by using continuously hydrological time series observed at six stations during 1956–2018. The temporal change in the streamflow was insignificant, but the sediment load decreased dramatically due to the trapping effects of the cascade reservoirs. The change points were detected in 1969 and 1986, which were consistent with the timing of the construction of gigantic reservoirs. We then applied the abrupt changing points to divide the whole time series into a reference period (1956–1968) and two changing periods (1969–1986 and 1987–2018). The linear regression and three machine learning models were employed to reconstruct the natural streamflow and sediment load at the downstream station, before quantifying their responses to cascade reservoirs. The annual mean streamflow and sediment load decreased by 21% and 84%, respectively, after constructing the Longyangxia and Liujiaxia reservoirs. Cascade reservoirs contributed 85.39% and 94.91% to the decreases in the streamflow and sediment discharge, respectively. Hydrological regimes have been greatly altered by the 13 cascade reservoirs, with seasonal redistribution of the streamflow and flood peak reduction because their high trapping efficiencies exceed 95%. These findings indicate that large and medium sized reservoirs have drastically altered the streamflow and sediment load, thereby intensely influencing the fluvial processes in the upstream of the Yellow River. [ABSTRACT FROM AUTHOR]

The construction of commercial surface enhanced Raman scattering (SERS) sensors suitable for clinical applications is a pending problem, which is heavily limited by the low production of high-performance SERS bases, because they usually require fine or complicated micro/nano structures. To solve this issue, herein, a promising mass-productive 4-inch ultrasensitive SERS substrate available for early lung cancer diagnosis is proposed, which is designed with a special architecture of particle in micro-nano porous structure. Benefitting from the effective cascaded electric field coupling inside the particle-in-cavity structure and efficient Knudsen diffusion of molecules within the nanohole, the substrate exhibits remarkable SERS performance for gaseous malignancy biomarker, with the limit of detection is 0.1 ppb and the average relative standard deviation value at different scales (from cm 2 to µm 2 ) is ≈16.5%. In practical application, this large-sized sensor can be further divided into small ones (1 × 1 cm 2 ), and more than 65 chips will be obtained from just one 4-inch wafer, greatly increasing the output of commercial SERS sensor. Further, a medical breath bag composed of this small chip is designed and studied in detail here, which suggested high-specificity recognition for lung cancer biomarker in mixed mimetic exhalation tests., (© 2023 Wiley-VCH GmbH.)

The effectiveness of coastal or inland forests in trapping floating debris produced by destructive tsunamis has long been discussed but never clarified quantitatively. To estimate the effectiveness, especially in reducing the damage to wooden buildings (houses) behind the forest, a nonlinear long wave equation model that includes not only destruction of the coastal forest but also a trap mechanism has been developed, and a simulation was conducted where trapping was observed during the 2011 Great East Japan tsunami. A post-tsunami survey of Sendai City showed that some houses just behind the coastal forest remained, although the inland-side houses were washed out. Based on the damage to houses, fragility curves as a function of moment by fluid force were analyzed. Although only the fringe of a coastal forest increases the fluid force due to a tsunami current concentration where a coastal forest is damaged, analyses using the model with and without the trapping function suggest that the debris-trapping function of a coastal forest greatly mitigates the damage observed in the post-tsunami survey, not only just behind the forest, but further inland, at around 1300 m from the coast. By including the trapping effect, the inundation height can be well reproduced, especially at around 2000-3000 m. The fluid force reduction was increased inland because some houses there remained standing in the tsunami and maintained resistance to the current. [ABSTRACT FROM AUTHOR]

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In this paper, current collapse phenomena and thermal effects in normally-off and normally-on GaN HEMTs are investigated. The experimental results show that a high-off-state voltage and high-switched drain current at high junction temperature cause an increase of the on-state resistance ${{\rm{R}}_{{\rm{DSON}}}}$. Varying the switching frequency from 50 to 400 kHz, an increase of the on-state resistance is further observed for both types of GaN devices. It is evident from these experiments that the number of switching transients significantly influences the increase of the RDSON, suggesting that this increase is due to a current collapse in GaN HEMTs. A detailed comparison of the evaluated R DSON between GaN transistors and the high-speed CoolMOS-C7 transistor is presented. [ABSTRACT FROM AUTHOR]

Time constant spectra are extracted from current transients based on the Bayesian deconvolution and used to characterize traps in GaN high-electron mobility transistors. Two kinds of traps with different time constants in an actual device were identified in the AlGaN barrier layer and the GaN layer, respectively. In particular, the trapping process in the AlGaN barrier layer was identified at the region near the drain side under gate contact. Trapping mechanisms of both two traps are discussed. Additionally, we observe that the trap in the AlGaN barrier layer requires sufficient electric field to activate the trapping process and a high drain voltage ( V ds ) accelerates the trapping processes both in the AlGaN barrier layer and the GaN layer. In addition, detrapping experiments with different filling conditions were performed to confirm their spatial positions. The influence of self-heating is excluded during the experiment by keeping the power density at a very low level, and the trapping effect is the sole factor accounting for the current transients. [ABSTRACT FROM AUTHOR]

In this work, we report on the results of the electrical behavior of coplanar electrode structure X-ray detector based on PbI2 crystal. The detector with coplanar electrode similar to the Van der Pauw structure instead of conventional planar structure can partly reduce the influence of trapping effect to charge carrier transport along the $c$ -axis. According to the configuration, four operating modes of the detector were thoroughly studied. Several novel results, such as the negative polarity dark current and photocurrent under zero bias voltage, orientation polarization, short relaxation time of steady-state surface leakage current and fast photocurrent response are obtained by this kind of coplanar structure configuration. The detector has the potential to be developed as a solid state X-ray dosimeter in the medical radiation environment, providing a high sensitivity and good adaptability under positive or negative bias voltage. [ABSTRACT FROM PUBLISHER]

GaN-based heterostructure field-effect-transistors (HFETs) with graded AlGaN barrier, in which the Al mole fraction of Al x Ga 1− x N ranges from 0 to a certain value (e.g. 35%), demonstrated the potential for high-linearity applications. Based on the two-dimensional (2-D) device simulations, in this paper the trapping effects and current collapse in GaN-based HFETs with graded AlGaN barrier are investigated and analyzed. First, both the carrier profile and direct current (DC) characteristics of the device are obtained for calibration of the simulation model, and the simulation results matched the experimental measurement data very well. In addition, the transient responses of GaN-based HFETs with graded AlGaN barrier are simulated to study the trapping behaviors. As the time increases, two rising trends are observed for the transient current, which are caused by the bulk acceptor traps and surface donor traps, respectively. By comparing with the conventional GaN-based HEMT, the results show that the HFET with graded AlGaN barrier has better immunity to the surface traps, leading to smaller current collapse. [ABSTRACT FROM AUTHOR]

The aim of the present study is to verify the trapping effect of combretastatin A-4-phosphate (CA4P) on small molecular drugs in rodent tumors. Mice with H22 hepatocarcinoma were randomized into groups A and B. Magnetic resonance imaging (MRI) of T1WI, T2WI, and DWI was performed as baseline. Mice in group A were injected with Gd-DTPA and PBS. Mice in group B were injected with Gd-DTPA and CA4P. All mice undergo CE-T1WI at 0 h, 3 h, 6 h, 12 h, and 24 h. Enhancing efficacy of the two groups on CE-T1WI was compared with the signal-to-noise ratio (SNR) calculated. Concentrations of gadolinium measured by ICP-AES in the tumor were compared between groups. On the early CE-T1WI, tumors were equally enhanced in both groups. On the delayed CE-T1WI, the enhancing effect of group A was weaker than that of group B. The SNR and the concentration of gadolinium within the tumor of group A were lower than that of group B at 6 h, 12 h, and 24 h after administration. This study indicates that CA4P could improve the retention of Gd-DTPA in the tumor and MRI allowed dynamically monitoring trapping effects of CA4P on local retention of Gd-DTPA as a small molecular drug. [ABSTRACT FROM AUTHOR]