Search

Methanol steam reforming (MSR) is an attractive route for producing clean energy hydrogen. PdZn alloys are extensively studied as potential MSR catalysts for their stability and high CO2 selectivity. Here, we investigated the reaction mechanism using density functional calculations, mean-field microkinetic modeling (MF-MKM), and kinetic Monte Carlo (kMC) simulations. To overcome the over-underestimation of CO2 selectivity by log-kMC, an ads-kMC algorithm is proposed in which the adsorption/desorption rate constants were reduced under certain requirements and the diffusion process was treated by redistributing surface species each time an event occurred. The simulations show that the dominant pathway to CO2 at low temperatures is CH3OH → CH3O → CH2O → H2COOH → H2COO → HCOO → CO2. The ads-kMC predicted OH coverage is 2–3 times that of MF-MKM, while they produce similar coverage for other species. Analyses indicate that surface OH promotes the dehydrogenation of CH3OH, CH3O, and H2COOH significantly and plays a key role in the MSR process. The dissociation of water/methanol is the most important rate-limiting/rate-inhibiting step. The CO2 selectivity obtained by the two methods is close to each other and consistent with the experimental trend with temperature. Generally, the ads-kMC results agree with the MF-MKM ones, supporting the previous finding that kMC and MF-MKM predict similar results if the diffusion is very fast and adsorbate interactions are neglected. The present study sheds light on the MSR process on PdZn alloys, and the proposed scheme to overcome the stiff problems in kMC simulations is worthy of being extended to other systems. [ABSTRACT FROM AUTHOR]

This study analyzes the transmission principle and structural characteristics of a high-speed-ratio compound gear with small tooth difference. On this basis, the finite element meshing characteristic analysis model of the above gear transmission device is established. The model considers the coupling deformation of 3-stage transmission, the specific structure of the cycloid gear, the output disc, the planet carrier and the case. The stress of each key component and the transmission error of the whole machine are simulated and analyzed, and the dynamic process of the multi-tooth meshing of the pin-cycloid transmission is discussed in detail. The results show that during the operation of the reducer, the stress fluctuation range of each component is small, and they are all far below the yield limit of their materials. The two cycloidal gears always bear the load through a rigid zone and a flexible zone simultaneously. The teeth of the rigid zone are the main bearing zone, and the teeth of the flexible zone are less stressed. The total number of meshing gear teeth of the two cycloidal gears is 9-11. The transmission error curve is stable and periodic, without noticeable long waves, and the peak-to-peak value of the transmission error of the whole machine is 46.719 5″. This research provides a theoretical basis for the optimal design of dynamic characteristics and meshing characteristics of the high-speed-ratio compound gear with small tooth difference.

Elevated 1-hour post-load plasma glucose (1 hPG) concentration during the oral glucose tolerance test (OGTT) may be associated with insulin resistance and pancreatic β-cell dysfunction, and higher risks of diabetes and cardiovascular disease. We reviewed the studies related to the significance of 1 hPG during the OGTT, in which 1 hPG during the OGTT has been reported to be prevalent in 10% to 40% of people with normal glucose tolerance, and the prevalence is higher in those with impaired glucose tolerance or impaired fasting glucose. Attention should be paid to the cutoff point of 1 hPG during the OGTT for the diagnosis of diabetes and pre-diabetes in Chinese population, which may be beneficial to early diagnosis and intervention of diabetes and pr-diabetes.

This article aims to explore the most optimal pulsed laser energy density when using the pulsed laser deposition (PLD) process to prepare the MoS2 films. We gradually increased the pulsed laser energy density from 70 mJ·cm−2 to 110 mJ·cm−2 and finally determined that 100 mJ·cm−2 was the best-pulsed laser energy density for MoS2 films by PLD. The surface morphology and crystallization of the MoS2 films prepared under this condition are the best. The films consist of a high-crystallized 2H-MoS2 phase with strong (002) preferential orientation, and their direct optical band gap (Eg) is 1.614 eV. At the same time, the Si/MoS2 heterojunction prepared under the optimal pulsed laser energy density shows an opening voltage of 0.61 V and a rectification ratio of 457.0. [ABSTRACT FROM AUTHOR]

Current treatments do not support direct exposure of fracture fragments, resulting in the inability to directly observe the articular surface during surgery for accurate reduction and firm fixation. The aim of the study was to explore the treatment effect of digital virtual reduction combined with individualized guide plate of lateral tibial condyle osteotomy on tibial plateau fracture involving the lateral posterior condyle collapse. 41 patients with tibial plateau fracture involving the lateral posterior condyle collapse were recruited in the trial. All patients underwent Computed Tomography (CT) scanning before operation. After operation, fracture reduction was evaluated using Rasmussen score and function of knee joint was assessed using hospital for special surgery (HSS) score. 41 patients were followed-up 6–26 months (mean, 15.2 months). Fracture reduction was good after operation, with an average of 13.3 weeks of fracture healing without serious complications. The excellent and good rate was 97.6%. The joint movement degree was -5∘∼0∘∼135∘ with an average of 125.5∘. Digital virtual reduction combined with individualized guide plate of lateral tibial condyle osteotomy was effectively for treating tibial plateau fracture involving the lateral posterior condyle collapse. [ABSTRACT FROM AUTHOR]