Mechanism of Drag Reduction in Floating Plate of Paddy Field Based on CFD

In order to study drag reduction mechanism in mud parts’ operation of surface machine tools for paddy field, this paper takes floating plate, the main working part of laminating mechanism, as the research object and systematically analyzes the mechanism of action of elevation angle, curved angle, penetrating angle, and local microstructure of floating plate on working resistance and local fluid flow characteristics of the laminating structure based on VOF model in Fluent. Using ship mechanics theory and fluid lubrication theory, the drag reduction mechanism under different structural parameters of the floating plate is analyzed. The results show that, compared with the ordinary floating plate, the pressure difference resistance can be reduced by increasing the elevation angle by 60°, curved angle by 20°, and mud separation angle by 20°. The increase of the concave nonsmooth bottom surface structure can reduce viscous frictional resistance, and the total working resistance after structural optimization is comparatively reduced by 48.3%, with lowered hilling height in the forward direction and improved lubrication condition of the bottom surface, forming liquid lubrication effect. This study can provide theoretical references for the optimization design of muddy soil mud parts, mud-machine interaction research, and the development of paddy field laminating mechanism

Reaction pathway for partial hydrogenation of 1,3-butadiene over Pt/SiO2

The reaction pathway for partial hydrogenation of 1,3-butadiene over a Pt/SiO2 catalyst was explored with a combination of in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, intrinsic kinetics, and density functional theory (DFT) calculations. Under the present experimental conditions, the catalyst displayed a nearly constant product composition with similar to 97% selectivity to butenes. In situ DRIFT characterization revealed that the 1-buten-3-yl radical (1B3R), generated from the addition of one hydrogen atom to a terminal carbon of 1,3-butadiene, was the dominant intermediate in the partial hydrogenation of 1,3-butadiene. Kinetic analysis showed that the hydrogenation of 1B3R was the rate-determining step in the formation of butenes. Based on the above experimental results, DFT calculations were employed to investigate the reaction pathway with 1B3R as the intermediate on a Pt(111) surface. Interestingly, it was found that 1B3R can be easily formed from the hydrogenation of 1,3-butadiene with a di-s configuration rather than the most stable tetra-s structure on the Pt(111) surface. This hydrogenation step occurs between the non-coordinated terminal carbon and a hydrogen atom on a top site with an energy barrier of 23.2 kJ mol(-1). The second hydrogenation step from 1B3R to butenes requires relatively higher activation barriers to proceed, being consistent with the experimental kinetics. Finally, the selectivity order for butenes and the structure sensitivity of Pt-catalyzed partial hydrogenation of 1,3-butadiene were discussed.</p

Enhancement of InSe Field-Effect-Transistor Performance against Degradation of InSe Film in Air Environment

The degradation of InSe film and its impact on field effect transistors are investigated. After the exposure to atmospheric environment, 2D InSe flakes produce irreversible degradation that cannot be stopped by the passivation layer of h-BN, causing a rapid decrease for InSe FETs performance, which is attributed to the large number of traps formed by the oxidation of 2D InSe and adsorption to impurities. The residual photoresist in lithography can cause unwanted doping to the material and reduce the performance of the device. To avoid contamination, a high-performance InSe FET is achieved by a using hard shadow mask instead of the lithography process. The high-quality channel surface is manifested by the hysteresis of the transfer characteristic curve. The hysteresis of InSe FET is less than 0.1 V at Vd of 0.2, 0.5, and 1 V. And a high on/off ratio of 1.25 × 108 is achieved, as well relative high Ion of 1.98 × 10−4 A and low SS of 70.4 mV/dec at Vd = 1 V are obtained, demonstrating the potential for InSe high-performance logic device

Applying Deep Learning in the Prediction of Chlorophyll-a in the East China Sea

The ocean chlorophyll-a (Chl-a) concentration is an important variable in the marine environment, the abnormal distribution of which is closely related to the hazards of red tides. Thus, the accurate prediction of its concentration in the East China Sea (ECS) is greatly important for preventing water eutrophication and protecting the coastal ecological environment. Processed by two different pre-processing methods, 10-year (2011–2020) satellite-observed chlorophyll-a data and logarithmic data were used as the long short-term memory (LSTM) neural network training datasets in this study. The 2021 data were used for comparison to prediction results. The past 15 days’ data were used to predict the concentration of chlorophyll-a for the five following days. Results showed that the predictions obtained by both pre-processing methods could simulate the seasonal distribution of the Chl-a concentration in the ECS effectively. Moreover, the prediction performance of the model driven by the original values was better in the medium- and low-concentration regions. However, in the high-concentration region, the prediction of extreme concentrations by the two data-driven LSTM models showed underestimation, considering that the prediction performance of the model driven by the original values was better. Results of sensitivity experiments showed that the prediction accuracy of the model decreased considerably when the backward prediction time step increased. In this study, the neural network was driven only by chlorophyll-a, whose concentration in the ECS was forecasted, and the effect of other relevant marine elements on Chl-a was not considered, which is the current weakness of this study

Effective Approach toward Selective Near-Infrared Dyes: Rational Design, Synthesis, and Characterization of Thieno[3,4-<i>b</i>]thiophene-Based Quinoidal Oligomers

This paper describes syntheses, photophysical properties, and electrochemical characteristics of three thieno[3,4-b]thiophene (TT)-based quinoidal oligomers OnTTO. The rigid planar backbones of these oligomers give the molecules narrow absorption bands, and the main absorption bands were significantly red-shifted when the TT units were extended and demonstrated wide transparent windows. The compound O4TTO was found to possess strong absorption in the near-infrared (NIR) region approaching 1200 nm but remained transparent in the visible region. Electrochemical experiments have shown that the energy band gaps gradually narrow when the TT units are increased. Optical properties predicted by density functional theory calculations are in good agreement with the experimental optical results. These dye molecules could be promising candidates for future NIR photodetectors, filters, and bioimaging technologies

Investigation of the Integration of Strained Ge Channel with Si-Based FinFETs

In this manuscript, the integration of a strained Ge channel with Si-based FinFETs was investigated. The main focus was the preparation of high-aspect-ratio (AR) fin structures, appropriate etching topography and the growth of germanium (Ge) as a channel material with a highly compressive strain. Two etching methods, the wet etching and in situ HCl dry etching methods, were studied to achieve a better etching topography. In addition, the selective epitaxial growth of Ge material was performed on a patterned substrate using reduced pressure chemical vapor deposition. The results show that a V-shaped structure formed at the bottom of the dummy Si-fins using the wet etching method, which is beneficial to the suppression of dislocations. In addition, compressive strain was introduced to the Ge channel after the Ge selective epitaxial growth, which benefits the pMOS transport characteristics. The pattern dependency of the Ge growth over the patterned wafer was measured, and the solutions for uniform epitaxy are discussed

Monolithic Integration of O-Band InAs Quantum Dot Lasers with Engineered GaAs Virtual Substrate Based on Silicon

The realization of high-performance Si-based III-V quantum-dot (QD) lasers has long attracted extensive interest in optoelectronic circuits. This manuscript presents InAs/GaAs QD lasers integrated on an advanced GaAs virtual substrate. The GaAs layer was originally grown on Ge as another virtual substrate on Si wafer. No patterned substrate or sophisticated superlattice defect-filtering layer was involved. Thanks to the improved quality of the comprehensively modified GaAs crystal with low defect density, the room temperature emission wavelength of this laser was allocated at 1320 nm, with a threshold current density of 24.4 A/cm&minus;2 per layer and a maximum single-facet output power reaching 153 mW at 10 &deg;C. The maximum operation temperature reaches 80 &deg;C. This work provides a feasible and promising proposal for the integration of an efficient O-band laser with a standard Si platform in the near future

High-Quality Recrystallization of Amorphous Silicon on Si (100) Induced via Laser Annealing at the Nanoscale

At sub-3 nm nodes, the scaling of lateral devices represented by a fin field-effect transistor (FinFET) and gate-all-around field effect transistors (GAAFET) faces increasing technical challenges. At the same time, the development of vertical devices in the three-dimensional direction has excellent potential for scaling. However, existing vertical devices face two technical challenges: “self-alignment of gate and channel” and “precise gate length control”. A recrystallization-based vertical C-shaped-channel nanosheet field effect transistor (RC-VCNFET) was proposed, and related process modules were developed. The vertical nanosheet with an “exposed top” structure was successfully fabricated. Moreover, through physical characterization methods such as scanning electron microscopy (SEM), atomic force microscopy (AFM), conductive atomic force microscopy (C-AFM) and transmission electron microscopy (TEM), the influencing factors of the crystal structure of the vertical nanosheet were analyzed. This lays the foundation for fabricating high-performance and low-cost RC-VCNFETs devices in the future