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Herein, we systematically investigated the reaction mechanism of n-pentane cracking on the Ag/ZSM-5 bifunctional catalyst featuring both dehydrogenation and cracking capabilities. Specifically, overall cracking network of n-pentane was comprehensively constructed to show the roles of metal dehydrogenation sites and acid sites respectively, in which metal Ag could substitute the H of the Brønsted acid site to form the Al-O-Ag linkage with enhanced adsorption and activation of n-pentane, while Brønsted acid site with weak acid strength relay to promote cracking reaction. Thanks to this synergy of the two active sites, the apparent activation energy of n-pentane cracking to light olefins was decreased from 82.77 KJ/mol to 68.26 KJ/mol and the proportion of specific path (C5H12→H2+C5H10) in n-pentane monomolecular cracking reaction increased from 14.62% to 69.24%. In addition, 0.57Ag/ZSM-5 catalyst exhibited the conversion of n-pentane up to 67.55wt%, which improved the performance of the parent ZSM-5 by 13.42wt%.

Breast cancer is the most common cancer and the leading cause of death among women. KRAS is known as an oncogene, its expression also associates with cancer prognosis. The purpose of this study was to investigate the prognostic value of KRAS expression in breast cancer and its relationship with immune infiltration. Firstly, the expression level and methylation of KRAS were analyzed. Then survival analysis was used to verify the prognostic capability of KRAS expression. After that, gene functional enrichment analysis was performed. The relationship between KRAS gene expression and immune infiltration was researched later. The expression level of KRAS in breast cancer was increased (P = 2.2e−16). Tumor KRAS expression in the subtypes of basal-like, HER2-enriched, Luminal A and Luminal B were 1.64, 1.67, 1.51 and 1.42 times of normal, respectively. 13 methylation sites were different between tumor and normal tissues and associated with KRAS expression. Subsequently, Kaplan–Meier analysis suggested that the high KRAS expression group had a poor prognosis (P = 0.0028). In multivariate Cox regression analysis, KRAS expression was an independent prognostic indicator (HR = 1.353, 95% CI 1.009–1.814, P = 0.044). Gene Ontology (GO) analysis showed enrichment of epidermal growth associated pathways. Additionally, different KRAS expression levels represented different tumor immune infiltration status, which may be caused by the influence of the RAS/MAPK and RAS/PI3K pathways on the level of PD-L1. This study suggests that KRAS expression can be used as a prognostic indicator of breast cancer, and it is closely related to tumor immune infiltration.

On account of the difficulty of deploying the ground base station (BS) and the limited power consumption of smart devices in Internet of Remote Things (IoRT) networks, it is necessary to construct a system assisted by unmanned aerial vehicles (UAVs) for sustainable communication. This paper aims to study a resource allocation problem in the wireless powered communication network (WPCN) while a UAV serves as an aerial BS. The optimization goal of this paper is to maximize the minimum throughput of ground terminals (GTs) by jointly optimizing the UAV deployment, time resource allocation, and power control. Nevertheless, the optimization problem is nonlinear and non-convex, which is difficult to solve directly. Therefore, it is transformed into two sub-problems, which can be iterated alternately to maximize the minimum throughput of each device in WPCN. The successive convex approximation (SCA) technique and variable substitution are used to transform two non-convex sub-problems into solvable problems. Finally, an iterative algorithm combining two sub-problems is designed to obtain the resource allocation strategies. The numerical results show that the communication resource can be fully shared by adjusting the position of the UAV, and the efficiency and performance of the algorithm are verified.

Accurately predicting NOx emissions during boiler combustion is of significance for the operation and control of the boiler combustion systems in coal-fired power plants. According to the characteristics of the boiler combustion process with strong disturbances, highly nonlinear and multivariate coupling, a fusion model based on mutual information variable selection and Hyperopt optimized GRU neural network (MI-HGRU) is proposed. The method can accurately select the parameters of boiler combustion process base on mutual information feature selection algorithm. A GRU neural network prediction model with Hyperopt optimization is established to achieve accurate prediction of NOx emission during boiler combustion. The modeling experiment was using a NOx emission dataset from a power plant boiler in Guangdong. The experimental results show that the MI-HGRU method has higher generalization ability and prediction accuracy than the RBF, LSSVM, RNN and LSTM neural networks, with an average accuracy of 99.4%.

Object: Evaluation of various new type of coronavirus pneumonia (COVID-19) normalization prevention measures and methods: Based on the actual data and transmission characteristics of the COVID-19 epidemic, this paper constructs an SEIR model for the transmission of new coronary pneumonia, which focuses on parameters such as asymptomatic infection. Result: Simulate the implementation of different types of public health preventive policies, and explore normalized preventive countermeasures. © 2021 Institute of Physics Publishing. All rights reserved.

In this paper, the stochastic stability and bifurcation of a stochastic differential equation modeling a hexagonal governor system are investigated. More precisely, we introduced the stochasticity into the model based on the parameter perturbation, and simplified the stochastic hexagonal governor system by using the stochastic center manifold theory and stochastic average theory. Besides, we investigated the local stochastic stability and global stochastic stability of the stochastic hexagonal governor system through the use of the Lyapunov exponent and singular boundary theory. And based on the invariant measure and stationary probability density, we studied the stochastic bifurcation of the stochastic hexagonal governor system. Finally, we obtained some new criteria to ensure the stochastic pitchfork bifurcation and P-bifurcation of the stochastic hexagonal governor system.

Density stratification is formed in the natural environment such as the lake water system due to the temperature difference of surface water and deep water, leading the damage of lake ecosystem. To dispel the density stratification, several researches in using liquid and gas phase jet to destruct and mix the density stratification was conducted. However, the effect in using gas-liquid two-phase jet to mix the density stratification has not been clarified. In this study, we performed the mixing experiments of density stratification with stained water and salt water. Based on the visualization method and the image processing, the density changing during the experiment was obtained in quantitatively and the dimensionless density distribution was built. Furthermore, the influence of air lift pipe in mixing was investigated. From the density distribution, we classified the result into three kinds of mixed behavior by analyzing the temporal transition of density stratification. Additionally, the mixing pattern with air lift pipe connected with the distance between the nozzle and the entrance of pipe.

A novel resin, poly(dimethylsilylene-ethynylene-phenoxyphenoxyphenylene-ethynylene), was synthesized from 1,4-bis( p-ethynylphenoxy)benzene and dimethyldichlorosilane through Grignard reaction. The structures of the monomer and the resin were characterized by elemental analysis, Fourier transform infrared, proton nuclear magnetic resonance, electron ionization-mass spectrometry and gel permeation chromatography. The thermal behaviour of the resin was examined by differential scanning calorimetry. The cured resin exhibits excellent dielectric property, high glass transition temperature, good mechanical properties and high thermal stability. The flexural strength and impact strength of the cured resin were 55.0 MPa and 10.5 KJ m−2, respectively. The degradation temperature at 5% weight loss of the cured resin arrived at 549°C in nitrogen.

Polymer composites with carbon-based nano-fillers have generated significant interest in industry and science because of their multifunctional and valuable properties. An APA-functionalized GO nanofiller (GO–APA) was prepared through the reaction between graphene oxide (GO) and 3-aminophenyl acetylene (APA) in dimethylformide (DMF) with ammonia hydroxide. Furthermore the PDSEPE/GO–APA composites were made from Poly(dimethysilyleneethynylenephenylene ethynylene) (PDSEPE) and GO–APA. FT-IR, XRD, XPS, SEM, DSC and TGA techniques were used to characterize the chemical compositions and physical and chemical properties of GO–APA and PDSEPE/GO–APA composites. As a result, the prepared PDSEPE/GO–APA composites show high thermal stabilities, excellent electrical conductivity and good flexural strength. When the weight percentage of GO–APA reaches 0.5%, the PDSEPE/GO–APA composite electrical conductivity increases by 6 orders of magnitude and the flexural strength improves by nearly 33% compared with that of cured PDSEPE resin. Copyright © 2015 John Wiley & Sons, Ltd.

Si-B-C ceramics with different elemental compositions and microstructures were prepared by the pyrolysis of an o-carborane-containing poly(silylene-arylacetylene) (CB-PSA) thermoset at 1000°C, 1200°C, 1300°C, and 1450°C. The thermo-oxidative stability of the ceramics was investigated by tracing the weight loss of ceramics during the isothermal oxidation at 800°C, 1000°C, and 1200°C under dry oxygen. The chemical bonding states of the ceramics before oxidation and the elemental compositions of the ceramics after oxidation were analyzed by X-ray photoelectron spectroscopy (XPS). The surface morphologies of the ceramics after oxidation were recorded using scanning electron microscopy (SEM). The results show that the Si-B-C ceramic prepared at 1450°C produces an integral borosilicate film on the surface of the ceramics when oxidized at both 1000°C and 1200°C and exhibits better oxidation resistance than the other Si-B-C ceramics prepared at 1000°C, 1200°C, and 1300°C. Oxidation temperatures, elemental compositions, and crystallites of the Si-B-C ceramics are found to influence the formation of the borosilicate films which plays an important role in the thermo-oxidative stability of the ceramics.

A PI hydroturbine governing system with saturation and double delays is generated in small perturbation. The nonlinear dynamic behavior of the system is investigated. More precisely, at first, we analyze the stability and Hopf bifurcation of the PI hydroturbine governing system with double delays under the four different cases. Corresponding stability theorem and Hopf bifurcation theorem of the system are obtained at equilibrium points. And then the stability of periodic solution and the direction of the Hopf bifurcation are illustrated by using the normal form method and center manifold theorem. We find out that the stability and direction of the Hopf bifurcation are determined by three parameters. The results have great realistic significance to guarantee the power system frequency stability and improve the stability of the hydropower system. At last, some numerical examples are given to verify the correctness of the theoretical results.

Objective: We examined the predictive macrosomia birthweight thresholds for adverse maternal and neonatal outcomes.Study design: This was a multicenter, retrospective cohort study conducted in China. We selected 178 709 singletons weighing ≥2500 g with gestational age 37–44 weeks. We categorized macrosomia with two gradations (4000–4499 g and ≥4500 g) and compared them with a normosomic reference group of infants with birthweight 2500–3999 g.Results: The risks of obstetric and neonatal complications increased when infants had a birthweight of ≥4000 g. The rates of infant mortality, Apgar score ≤3 at 5 min, respiratory and neurological disorders rose significantly among neonates weighing ≥4500 g.Conclusion: A definition of macrosomia as birthweight ≥4000 g could be beneficial as an indicator of obstetric and newborn complications, and birthweight ≥4500 g might be predictive of severe infant morbidity and mortality risk.

In this study, photoisomerizable polyacrylate containing spiropyran moieties was synthesized. By taking advantage of the photoinduced structural transformations of the spiropyran moieties, photoinduced microscopic ordering and eventually macroscopic patterns were formed in the polymer films consisting of spiropyran-containing polyacrylate (SPPA) and tetraoctylammonium bromide (TOAB). The patterns thus obtained are composed of concentric rings, which alternatively consist of macroscopic convex ridges and concave valleys, with the former being amphormous phases and the latter being ordered mesomorphous ones. It was found that the open-ring protonated merocyanine (MC) form of the spiropyran moieties, which is triggered by UV illumination, was crucial to the formation of mesomorphous structure and macroscopic patterns for this polymer−surfactant system. It is possible that the interaction between the MC form and TOAB leads to the formation of the microscopic ordering and macroscopic pattern in the polymer−TOA...

In this paper, a high speed rotor-bearing system with stochastic excitation is considered, and study the stability and Hopf bifurcation of the system by using quasi-nonintegrable Hamiltonian system theory. Then, the conditions of local and global stability of system are obtained by largest Lyapunov exponent and boundary category. Finally, the solution of FPK equation can be got, which is stationary probability density function and jointly stationary probability density function, and then, by simulating its graph to illustrate the results.

Mathematical models and numerical methods of collecting flows in urban overland, pipe network and river network were developed in this paper. Verification work was carried out at Jiaxing urban district in Zhejiang Province. Distribution, depth and velocity of waterlogging areas at Jiaxing urban district during plum storm in 1999 were numerically simulated, and comparisons with the measured data were made. The reasonably simulated results of waterlogging regimes were obtained.