Search

A novel bilateral impact-ionization-avalanche-transit-time (BIMPATT) diode based on AlGaN/GaN two-dimensional electron gas is proposed in this article. The BIMPATT is compatible with the available GaN high electron mobility transistor (HEMT) manufacturing process and has a shorter actual electron transit distance than existing HEMT-like IMPATT (HIMPATT) diodes. Compared with the same-sized HIMPATT, the optimum frequency of BIMPATT rises from 320 to 420 GHz and possesses a far wider operating frequency band, especially in the near 0.9 THz range. The maximum DC-RF conversion efficiency rises from 12.9% to 17.6%. The maximum RF power of BIMPATT is 3.18 W/mm, which is similar to 3.12 W/mm of the HIMPATT. Furthermore, our simulation demonstrated that the characteristics of BIMPATT are significantly affected by the length of anode and the thickness of the AlGaN barrier layer. The effects of ohmic contact resistance and background impurities on BIMPATT are also taken into account. This paper provides a reference for the design and characteristics enhancement of the lateral IMPATT devices. [ABSTRACT FROM AUTHOR]

Revealing the interactions between stand structure factors and ecosystem functions is crucial for enhancing forest soil and water conservation, as well as carbon storage. However, the optimal stand structure configuration for achieving superior ecological functions remains unclear, particularly in complex subtropical evergreen broad-leaved forests. Using Schima superba Gardn. et Champ. forests in Dongbai Mountain as a case study, this study investigated the effects of seven stand structure factors—stand density, canopy density, uniform angle index, and mixing degree—on three key ecosystem functions, water-holding function, soil improvement function, and carbon sequestration. Redundancy analysis (RDA) and structural equation modeling (SEM) were employed to quantify these relationships. The results identified stand density as the most influential factor, directly or indirectly affecting ecosystem functions by regulating other structural attributes. Optimal structural configurations were determined, including stand densities of 1228, 1532, and 1675 plants·hm−2 for maximizing water-holding function, soil improvement function, and carbon sequestration, respectively. Recommendations emphasize adjusting stand density, canopy density, uniform angle index, and mixing degree according to site-specific conditions. Practical strategies, such as replanting, intercropping, and introducing functionally complementary species, should aim to enrich vertical structure, maintain species randomness, and avoid dominance by a single species or excessive density. These findings offer actionable insights for improving the ecological functions of subtropical forests and have broader implications for sustainable forestry management, advancing regional carbon neutrality, and addressing global ecological challenges. [ABSTRACT FROM AUTHOR]

The comprehensive protection and restoration of mountains, rivers, forests, farmlands, lakes, grasslands, and deserts is critical for enhancing ecological environmental quality and fulfilling the aspirations of ecological civilization in the modern era. Centered on the key project area of the Mountain-River Project within the Luohe River Basin of the Eastern Qinling Mountains, this study employs the InVEST model to assess spatiotemporal variations in habitat quality (HQ), water yield (WY), carbon sequestration (CS), and soil retention (SR) for the years 2000, 2010, and 2020. This study further examines the trade-offs and synergies among these ecosystem services, integrates the Ordered Weighted Averaging (OWA) and GIS methodology with human activity patterns, determines the optimal management scenario, and offers targeted recommendations for optimization. The findings reveal that areas of high habitat quality, carbon sequestration, and soil retention are predominantly concentrated in the western and southwestern regions of the basin, whereas high-value zones of water yield are primarily situated in the southern and southwestern sectors. Habitat quality demonstrates significant synergies with other ecosystem services, whereas water yield presents a notable trade-off with soil retention. By conducting a comparative analysis of protection efficiency, we identified priority conservation areas predominantly located in the southern and southwestern regions of the basin. Moreover, through overlaying the priority conservation zones with the Human Footprint Index (HFI), the priority conservation area was precisely delineated to encompass 5.41 × 105 hectares. This methodology provides critical guidance for the implementation of the Mountain-River Project and offers substantial value in scientifically advancing ecological restoration initiatives. [ABSTRACT FROM AUTHOR]

Utilizing density functional theory (DFT) calculations, we systematically explored the potential of the defective NiCl2 nanosheet with Cl vacancies (VCl-NiCl2) as a gas sensor for the detection of H2, CO2, NO, O2, H2O, CO, and NO2 gases. The results revealed that NO, O2, H2O, CO, and NO2 can be chemisorbed on Ni sites around Cl vacancies with significant adsorption energy (−0.66 to −1.83 eV), accompanied by a considerable amount of charge transfer and an obvious change in the electronic and magnetic properties of the VCl-NiCl2 system. In particular, due to the short recovery times, we predicted that VCl-NiCl2 could be utilized as a promising gas sensor for CO at 398 K and O2 under ambient conditions. Our results not only further expand the potential application of NiCl2 monolayers as a gas sensor, but also offer new options for developing candidate detection materials for toxic gases. [ABSTRACT FROM AUTHOR]

Perovskite oxides show great promise as an alternative catalyst to the conventional nickel cermets for CO2 reduction reactions (CO2RR) in solid oxide electrolysis cells (SOECs) owing to their advantages of redox stability and coking resistance. Nevertheless, practical applications of these oxides are prevented largely by their poor CO2RR activities. Herein, a novel donor and acceptor co‐doped nonstoichiometric double perovskite, La0.3Sr1.55Fe1.5Ni0.1Mo0.4O6−δ (LSFNM), is developed with in situ exsolved FeNi3 nanoparticles to efficiently catalyze CO2RR in SOECs. Pure CO2 electrolysis over the impregnated FeNi3@LSFNM catalysts is evaluated on two types of SOECs—one with thin (ZrO2)0.89(Sc2O3)0.1(CeO2)0.01 (SSZ) electrolytes supported on 430L alloys and the other with thin La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) electrolytes supported on impregnated SmBa0.5Sr0.5Co2O5+δ (SBSCO)@LSGM anodes, producing unprecedently high current densities of 2.84 A cm−2 for the former and 3.07 A cm−2 for the latter at 1.5 V and 800 °C. Experimental analysis and density‐functional theory (DFT) calculations reveal collective synergistic catalysis of oxygen vacancies (VO..${V}_{\mathrm{O}}^{..}$), the doping Ni2+ ions and FeNi3 nanoparticles via the cooperative VO..${V}_{\mathrm{O}}^{..}$‐O(CO2), and Ni(II)–C(sp) and Ni(0)–O(CO2) interactions in LSFNM, not only facilitating CO2 chemisorption on oxygen vacancies but also destabilizing and dissociating surface carbonates in the vicinity of FeNi3 spontaneously into CO. [ABSTRACT FROM AUTHOR]

The application of polymer composites is one of the most effective methods for preventing lubrication failure in deep‐sea engineering. In this study, fluorinated graphite (FGr) microsheets were incorporated into polytetrafluoroethylene (PTFE) microparticle‐filled poly(butylene terephthalate) (PBT) composites. The tribological performance in the simulated deep‐sea environment at elevated seawater pressure equivalent to 3000 m ocean depth was investigated. The results showed that FGr enhances the flexural and compressive strengths, thermal stability, and seawater resistance of the PTFE/PBT composite. The wear rate was decreased to 96% at the critical FGr content of 4% by improving the transfer onto the metallic counterfaces, preventing direct contact and shear between friction couples. Moreover, the seawater pressure impedes composite transfer, leading to a 29% increase in the wear rate. [ABSTRACT FROM AUTHOR]

Objectives. This study aimed to identify the prevalence of multi-site work-related musculoskeletal disorders (WMSDs) in Chinese footwear industry workers from 2018 to 2020 and explore the possible influencing factors of WMSDs. Methods. 7106 subjects from 26 large shoe factories in China were investigated using the epidemiological cross-sectional survey method by using the Nordic musculoskeletal questionnaire (NMQ). Results. The total prevalence of WMSDs in the study subjects was 36.8% (2616/7106). Among them, the prevalence of multi-site WMSDs was 26.1% (1858/7106). The proportion of multi-site WMSDs involving two sites was the largest (31.38%). In addition, the results showed that the risk factors of multi-site WMSDs were gender, marital status, long current job experience, poor health, poor working posture, etc. Conclusions. The prevalence of WMSDs was high in the Chinese footwear industry. Based on the results, therefore, it seems necessary to improve work posture, work organization and workenvironment to prevent WMSDs. [ABSTRACT FROM AUTHOR]

The effects of simulated acid rain (SAR) on the photosynthetic performance of subtropical coniferous species have not been thoroughly investigated. In this study, we treated two coniferous species, Pinus massoniana (PM) and Cunninghamia lanceolata (CL), with four gradients of SAR and then analyzed their photosynthetic activities through measurements of gas exchange, prompt fluorescence (PF), delayed fluorescence (DF), and modulated reflection at 820 nm (MR820). Gas exchange analysis indicated that the decrease in the net photosynthetic rate (Pn) in PM and CL was unrelated to stomatal factors. For the PF transients, SAR induced positive K-band and L-band, a significant reduction in photosynthetic performance index (PIABS), the quantum yield of electron transfer per unit cross-section (ETO/CSm), and maximal photochemical efficiency of photosystem II (Fv/Fm). Analysis of the MR820 kinetics showed that the re-reduction kinetics of PSI reaction center (P700+) and plastocyanin (PC+) became slower and occurred at later times under SAR treatment. For the DF signals, a decrease in the amplitude of the DF induction curve reduced the maximum value of DF (I1). These results suggested that SAR obstructed photosystem II (PSII) donor-side and acceptor-side electron transfer capacity, impaired the connectivity between PSII and PSI, and destroyed the oxygen-evolving complex (OEC). However, PM was better able to withstand SAR stress than CL, likely because of the activation of a protective mechanism. [ABSTRACT FROM AUTHOR]

As for metal/zeolite supported phenol hydrodeoxygenation catalysts, it is important to improve the dispersion of metallic sites and build synergistic relationship between metallic and acid sites. The current research proposes a surface modification strategy by introducing CTAB in the NaOH etching of Beta. CTAB interacts with crystal defects to inhibit excessive crystal destruction. Aluminum atoms are protected from being removed and acid sites are reserved. Generated silicon hydroxyl groups anchor Pt0 particles. Pt0 particles are spatial resisted on the internal surface of catalysts to activate C–O bonds of phenol. Preserved acid sites provide reactive sites for dehydration reaction of cyclohexanol on the external surface of Pt/Beta-H. The high phenol conversion (i.e., 92.26 %) and cyclohexane yield (i.e., 7.18 %) were obtained at 80 °C due to the functional synergistic effect between acid and Pt0 sites. Proposed surface modification strategy proposes references for the structure design and development of efficient phenolics hydrodeoxygenation catalysts. [Display omitted] • CTAB regulates the NaOH etching sites of Beta molecular sieves. • Generated silicon hydroxyl groups anchor fine Pt particles. • Synergistic effect of Pt-acid sites of Pt/Beta catalysts is fabricated due to a hollow spatial distribution. [ABSTRACT FROM AUTHOR]