Disturbance Rejection Control for Autonomous Trolley Collection Robots with Prescribed Performance

Trajectory tracking control of autonomous trolley collection robots (ATCR) is an ambitious work due to the complex environment, serious noise and external disturbances. This work investigates a control scheme for ATCR subjecting to severe environmental interference. A kinematics model based adaptive sliding mode disturbance observer with fast convergence is first proposed to estimate the lumped disturbances. On this basis, a robust controller with prescribed performance is proposed using a backstepping technique, which improves the transient performance and guarantees fast convergence. Simulation outcomes have been provided to illustrate the effectiveness of the proposed control scheme

Ameliorative Effects and Mechanism of Aqueous Extract of Moringa oleifera Leaves on Hepatic Fibrosis in Rats

To investigate the ameliorative effects and mechanism of Moringa oleifera Lam (LM) leaf aqueous extract on hepatic fibrosis (HF) in rats. 60 male SD rats were randomly divided into normal group, model group, colchicine group (100 mg/kg), and LM high, medium and low dose groups (200, 100 and 50 mg/kg), except for the normal group, rats in the remaining groups were established as HF model by intraperitoneal injection of thioacetamide (TAA) and the corresponding drugs were administered from the 5 th week. At the end of drug administration, rats were examined for body weight, liver index, liver function indexes, including serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST). HF indices including serum procollagen type III (PCIII), collagen type IV (IV-C), laminin (LN), hyaluronic acid (HA), liver hydroxyproline acid (HYP). Masson staining was used to observe liver fibrotic tissue lesions. Indicators of Liver oxidative stress, including hepatic reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD), were also detected. Real-time quantitative fluorescence PCR and protein immunoblotting were performed to detect hepatic TGF-β1/Smads pathway gene expression. Rats in the HF model group had significantly lower body weight, highly significantly increased liver index, serum ALT, AST, PCIII, IV-C, LN, HA and liver HYP concentrations compared with rats in the normal group (P<0.01). In addition, the liver tissue of rats in the model group showed a significant increase in collagen fibre deposition, severe liver fibrosis, highly significant increase in liver ROS and MDA content, and a highly significant decrease in SOD activity (P<0.01), indicating that the liver of rats in the model group was in a state of oxidative stress and fibrotic lesions, and liver function was impaired. Compared with the model group, serum ALT, AST, PCIII, IV-C, LN, HA and hepatic HYP concentrations were reduced to varying degrees in the LM group rats. In addition, collagen fibre deposition in liver tissue was significantly reduced, liver ROS and MDA content were significantly decreased, and SOD activity was significantly increased in the LM group rats, indicating that LM could reduce the level of liver oxidative stress, ameliorate liver fibrosis and protect liver function in rats (P<0.05, P<0.01). Gene expression detection of the TGF-β1/Smads pathway showed that the mRNA and protein expression of TGF-β1, Smad2, Smad3 and α-SMA genes were significantly increased in the model group compared with the control group. Compared with the model group, the liver TGF-β1, Smad2, Smad3 and α-SMA gene expressions were significantly lower in the LM high and medium dose groups (P<0.05, P<0.01), and the liver Smad3 and α-SMA gene expressions were significantly lower in the LM low dose group (P<0.05, P<0.01), indicating that LM could downregulate liver TGF-β1/Smads pathway gene expression in HF rats. LM would ameliorate TAA-induced liver fibrosis in rats by down-regulating the ROS-TGF-β1/Smads pathway

Quantum chemical calculation of coal spontaneous combustion mechanism promoted by transition metal ions

In order to study the effect of typical transition metal ions on coal spontaneous combustion under low temperature oxidation conditions, the transition metal ions of lignite (HM), gas coal (QM) and fertilizer coal (FM) were determined, and Fe (Ⅲ), Mn (Ⅲ) and Cu (Ⅱ), which are abundant in transition metal ions and have strong oxidation, were selected as the research objects. The charge distribution, frontier orbitals and Laplacian bond levels were analyzed by the quantum chemistry calculation method, and the existence of active sites was proved. Two reaction processes of Ar—CH2—CH3 to Ar—CO—CH3 with or without transition metal ions were investigated, and the thermodynamic parameters were obtained by model optimization, transition state calculation and IRC verification. The calculation results show that the activation energy barrier is 164.18 kJ/mol without transition metal ion and 158.72 kJ/mol with transition metal ion. The effect of transition metal ion on the total reaction rate is not significant. With the participation of Fe (Ⅲ), Mn (Ⅲ) and Cu (Ⅱ), the total heat releases of the reaction are 1535.52, 1834.97 and 365.93 kJ/mol, respectively, which are higher than the heat release from the oxidation of aliphatic hydrocarbons by oxygen molecules (319.93 kJ/mol). The free energy barriers of C—H in oxidized aliphatic hydrocarbons are 42.79, 4.30 and 117.29 kJ/mol, respectively, which are all lower than the activation energies of C—H oxidation by oxygen molecules (146.38 kJ/mol). The order of C—H oxidation capacity of transition metal ions from high to low is Mn (Ⅲ), Fe (Ⅲ) and Cu (Ⅱ). During the reaction process, the formation of ·OH and H+ is accompanied by further reaction with the coal structure to accelerate the spontaneous combustion process of coal. In order to verify the accuracy of the simulation results, the time and concentration of CO gas products in four different coal samples were measured by temperature programmed gas chromatography. It was found that the temperature points of CO gas products in four coal samples were similar. The coal samples with manganese ion added produced CO gas products at 90 ℃, while the other three coal samples produced CO gas products at 100 ℃. The concentration of CO gas products from large to small is Mn (Ⅲ), Fe (Ⅲ), Cu (Ⅱ) and raw coal sample, which is consistent with the calculated results. With the increase of temperature, the effect of Mn (Ⅲ) on increasing the rate of CO production gradually weakens, and the effect of iron and copper ions on catalytic coal spontaneous combustion is gradually significant. The experimental results have a certain correlation with the simulation results. Compared with oxygen molecules, transition metal ions in coal are more likely to oxidize C—H, which not only causes the free radical chain reaction to occur earlier, but also increases the heat release of the reaction and the production of ·OH and H+, thus promoting spontaneous combustion of coal. This has reference significance for the mechanism of spontaneous combustion of transition metal catalyzed coal

Grounded theory research on the factors that lead to doctor moral hazard

Moral hazard clearly exists among doctors, and it has a dramatic impact on doctor-patient relationships, medical costs and medical risks. This study explored the factors that lead to doctor moral hazard, as well as the interrelationships and internal regularity of these factors. This study takes doctor moral hazard as the research content and the inducing factors as the core theme, conducting grounded theory research on the causes of doctor moral hazard. Scientific understanding of doctor behavior would facilitate the prevention and control of doctor moral hazard behavior. This study used the principles and methodology of Glaser and Strauss’s grounded theory. Theoretical and snowball samplings were used to identify 24 subjects. Semi-structured in depth interviews were conducted with each subject. Themes were identified through substantial (open) coding and theoretical coding. The factors that lead to doctor moral hazard were categorized into five dimensions, i.e. motivation, opportunity, self rationalization, exposure and punishment. These five factors influence each other, forming the inducing mechanism of doctor moral hazard. This will provide useful theoretical support and method guidance for the follow-up prevention and control of moral hazard for doctors

Two new species of the planthopper genus Usana Distant, 1906 (Hemiptera, Fulgoromorpha, Achilidae) from China

Two new species of the achilid planthopper genus Usana Distant, 1906 (Hemiptera, Fulgoromorpha, Achilidae, Myconinae, Plectoderini), U. tongmaiensis Long & Huang, sp. nov. and U. rotalarius Long & Huang, sp. nov., are described and illustrated from Xizang and Chongqing. A key to all known species and a map of geographic distributions for Chinese taxa is provided

Experimental study on the buffering effects of urban trees group in dike-break floods

Abstract The process of dike-break flood propagation in typical urban street is highly complex. The presence of buildings and trees groups in urban street profoundly alters the flood dynamics, impacting the drainage capacity of the area. In this study, a generalized sink model representing a typical urban street was established, including trees groups, buildings, sidewalks, and stormwater drainage systems. The study measured the fluctuation of water levels within the street block and the pressure variation in the pressurized stormwater drainage network during the dike-break flood propagation. Furthermore, it conducted a comparative analysis to assess the influence of different arrangements of trees groups on the maximum water depth in buildings and the discharge capacity of the pressurized stormwater drainage network. Dike-break floods give rise to large-scale water leaps and the formation of thin layer water sheets near the buildings under the influence of buildings, water tank sidewalls, and tree groups. The water leap zones exhibit lateral migration and superposition on the sidewalks during the flood propagation, gradually dissipating and disappearing in the longitudinal direction of the street. In the presence of tree groups, the water levels significantly decrease in buildings and downstream street, while the discharge capacity of the pressurized stormwater drainage network shows a slight improvement as the road’s flood-carrying capacity increases. The pressure in the main pipes fluctuates due to the switching of the grate inlet drainage mode and the hydraulic transition process in the branch pipes. The research findings not only provide valuable validation data for numerical simulations but also offer theoretical guidance for urban flood management and landscape design

Research on the Gearbox Fault Diagnosis Method Based on Multi-Model Feature Fusion

The gearbox is an important component of rotating machinery and is of great significance for gearbox fault diagnosis. In this paper, a gearbox fault diagnosis model based on multi-model feature fusion was proposed that addressed the limitations of a single or few features reflecting the gearbox’s fault state. The time–frequency feature of the vibration signal was extracted, and the sensitive feature was selected. The sensitive features were extracted using a one-dimensional convolutional neural network. The parallel fusion method was used to fuse the two domain features as inputs to the support vector machine model. The radial basis kernel function and penalty factor of the support vector machine were optimized by improving the particle swarm optimization algorithm. Finally, the gearbox states were identified using the optimized support vector machine model. The results show that the recognition rate of the proposed model is 98.3%, which is higher than that of other models