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Accurate surface texture design is of great significance to improve the performances of gas bearings. In this article, the finite difference method and Newton’s method were combined to obtain the oil film pressure distribution, and the effect of rectangular groove on the lubrication performance was analyzed by changing representative texture parameters. The results show that the performances were more affected by the rectangular texture size compared with the distribution and the bottom shape of texture. The increasing of the surface texture number can only enhance the stability of the bearing. The bearing can provide 30% more bearing capacity by choosing larger size, radial arrangement and plane bottom. These results and analysis can provide technical reference for the bearing texture design.

A novel three-dimensional progressive damage model based on generalized mixed finite element method (GMPDM) was established to investigate the strength and failure behavior of notched composite laminate plate. Firstly, the stress distribution of notched isotropic plate under tension is studied, and the results are compared with the analytical solution to verify the high accuracy of the generalized mixed finite element method. Then, the strength and failure modes of three notched composite laminates are studied. The results are compared with the several groups of results to verify the high-precision of the developed GMPDM method, respectively.

As a rescue vehicle, damaged-aircraft trailer is used to move damaged aircraft quickly to restore the normal order of the airport. Several damaged-aircraft trailer parameters such as tire stiffness and damping of the suspension hydraulic system influence the dynamic performance significantly. In this article, a simplified 9 degrees of freedom model of damaged-aircraft trailer is established considering the physical parameters of suspension and tires. The relationships among the parameters of the suspension hydraulic components, the elastic force and damping force are established, and then the optimization model of the whole vehicle is obtained. In order to reduce the secondary damage to the aircraft, the multi-island genetic algorithm is used to optimize the suspension system and tire. During the calculation, the maximum vertical acceleration of damaged-aircraft trailer is taken as objective function for variable parameters of the suspension hydraulic system and the tire. As a result, the performance of the vehicle is greatly improved with the maximum acceleration of 0.2 m/s2 after optimization.

Surface texturing has been widely used to improve the performance of bearings. To further investigate the effect of surface morphology on rigid bore aerodynamic journal bearings and to improve the performance of bearings, this paper investigates the effect of surface roughness and surface texture on the static characteristics of radial rigid bore aerodynamic journal bearings using numerical analysis. The compressible Reynolds lubrication equation of the rigid bore aerodynamic journal bearing is solved by Successive Over Relaxation (SOR) and finite difference method. The static performance of the bearings with different parameters was investigated. The parameters that have been studied include the shape of the texture, the depth of the texture, the number of textures, the percentage of textures, and the surface roughness. The results show that radial rigid bore aerodynamic journal bearings with specific parameter textures have 36.32% higher load carrying capacity and 1.66% lower frictional torque compared to the case without texture.

We present a terrain traversability mapping and navigation system (TNS) for autonomous excavator applications in an unstructured environment. We use an efficient approach to extract terrain features from RGB images and 3D point clouds and incorporate them into a global map for planning and navigation. Our system can adapt to changing environments and update the terrain information in real-time. Moreover, we present a novel dataset, the Complex Worksite Terrain (CWT) dataset, which consists of RGB images from construction sites with seven categories based on navigability. Our novel algorithms improve the mapping accuracy over previous SOTA methods by 4.17-30.48% and reduce MSE on the traversability map by 13.8-71.4%. We have combined our mapping approach with planning and control modules in an autonomous excavator navigation system and observe 49.3% improvement in the overall success rate. Based on TNS, we demonstrate the first autonomous excavator that can navigate through unstructured environments consisting of deep pits, steep hills, rock piles, and other complex terrain features.

This paper improves visual-inertial systems to boost the localization accuracy for low-cost rescue robots. When robots traverse on rugged terrain, the performance of pose estimation suffers from big noise on the measurements of the inertial sensors due to ground contact forces, especially for low-cost sensors. Therefore, we propose \textit{Threshold}-based and \textit{Dynamic Time Warping}-based methods to detect abnormal measurements and mitigate such faults. The two methods are embedded into the popular VINS-Mono system to evaluate their performance. Experiments are performed on simulation and real robot data, which show that both methods increase the pose estimation accuracy. Moreover, the \textit{Threshold}-based method performs better when the noise is small and the \textit{Dynamic Time Warping}-based one shows greater potential on large noise., accepted by IFAC World Congress 2020

Purpose The analysis carried out in this study can provide guidance for manufacturers and researchers to design a piston for the development of engines. Design/methodology/approach Running conditions for pistons have become very severe because of the high combustion pressure and increase in piston temperature in the past 10 years. The precision of the model has a great effect on the power transmission, vibration noise emission. In this paper, the model was established with lubrication and dynamic governing equations, which were solved using finite element method coupled with Runge–Kutta method. A piston of an inline six-cylinder engine was studied, and some structural parameters were used to investigate its effect on the friction loss with lubrication and dynamic motion theory. Findings Based on the analyses, the effect of the friction load at the oil groove and thermal deformation of piston skirt were added to the model, and some useful information about the friction loss and dynamic characteristics were compared. Originality/value All the results will provide guidance for the development of the piston and reduction in the friction loss and wear.

Purpose Piston ring dynamic problem plays an important role in the lubricant characteristics of a reciprocating engine, which lead to engine wear and the increased consumption of lubricating oil. A cavitation analysis of the piston ring lubrication with two-dimensional Reynolds equation has rarely been reported owing to the complex working condition. The purpose of this study is to establish a precise model that can provide guidance for the design of the piston ring. Design/methodology/approach In this paper, a cavitation model and its effect on the piston ring lubrication was studied in a simulation program based on the mass-conserving theory which is solved by means of the Newton–Raphson method. In this study, some models such as mixed lubrication, asperity contact, blow-by/blow-back flow and cavitation have been coupled with the lubrication model. Findings The established model has been compared with the traditional model that deals with cavitation by using the Reynolds boundary condition algorithm. The cavitation zone, pressure distribution and density distribution between the piston ring and the cylinder have also been predicted. Studies of the changing trend for the pressure distribution and the cavitation zone at few typical crank angles have been listed to illustrate the cavitation changing rule. The analysis of the results indicates that the developed simulation model can adequately illustrate the lubrication problem of the piston ring system. All the analyses will provide guidance for the oil film rupture and the reformation process. Originality/value A two-dimensional cavitation model based on the mass-conserving theory has been built. The cavitation-forming and -developing process for the piston ring–liner lubrication has been studied. Non-cavitation occurs in the vicinity of top dead center and bottom dead center. The non-cavitation period will be longer in the vicinity of 360° of crank angle. The density distribution in the cavitation zone can be obtained.

A damaged aircraft trailer is an essential piece of airport emergency rescue equipment which is made up of frames and multiple suspensions. As a load–force transferring mechanism, the suspension bears heavy loads which can cause fatigue damage. Therefore, reducing the maximum stress of the suspension is necessary to improve the vehicle performance. Besides, lightweight design should be considered to reduce energy consumption. Thus, lighter suspension which can bear more pressure is the optimization objective of this research. A multi-objective optimization method was carried out to analyze the suspension arm of a damaged aircraft trailer. Firstly, to investigate the dynamic characteristics and the reliability of the damaged aircraft trailer, a detailed three combined damaged aircraft trailers model was built. Based on the flexible-rigid coupled method, dynamic simulation of the damaged aircraft trailer was conducted in MSC.ADAMS. Then a suspension model was established, and the stress under different loads was measured to verify the accuracy of the finite element suspension arm model by experiments. Based on the design of experiment method, the effect of suspension arm parameters were obtained to build the approximate models. Besides, the influences of some effect parameters on optimal objectives were analyzed based on the surface response method. During the optimization process, a non-dominated sorting genetic algorithm II was adopted to optimize the mass and stress of the suspension arm. The results show that the mass of the suspension arm is reduced from 146.81 kg to 126.69 kg, which is a reduction of 14%. The maximum von Mises stress is changed from 325 MPa to 297 MPa, which is a decrease of 8.6%. This optimal method can be extended to the overall vehicle, which has an important significance in the whole damaged aircraft trailer characteristics improvement design.

With the deepening of globalization and the increasing amount of information in international communication, requirements for accuracy in interpretation of figures are more demanding. Training methods in interpretation of figures, however, are not efficient enough for interpreters to cope with the challenges. They still make mistakes in interpretation of large integers, fractions and percentages. The types of errors include omission, syntactic error and lexical error. In this paper, machine learning based text categorization technology is used to accurately categorize a large number of texts and provide high-quality training materials for interpreters. Results show that training the interpreters with categorized texts has greatly improved the accuracy, familiarity and sensitivity in interpretation of figures. In the era of artificial intelligence, problems in interpretation also need to be solved by artificial intelligence. In the future, a large number of artificial intelligence technologies similar to machine-learning-based text categorization technology will be inevitably adopted in the field of interpretation.

Tectochrysin, a flavonoid compound, can be isolated from propolis, Alpinia oxyphylla Miq, and Lychnophora markgravii. This study evaluated the efficacy of tectochrysin in the treatment of shrimp tropomyosin (ST)-induced mouse asthma. Mice were sensitized with intraperitoneal (i.p.) injection of ST together with aluminum hydroxide as an adjuvant to establish a mouse model of asthma. Mice were i.p.-treated daily with tectochrysin. IgE levels in plasma, Th2 cytokines from both bronchoalveolar lavage (BAL) fluid and splenocytes, and CD200R on basophils in peripheral blood were measured. Histological analyses of lung tissues and accumulation of leukocytes in BAL fluid were performed. Lung eosinophil peroxidase, catalase and glutathione peroxidase activities were examined. ST was found to markedly increase eosinophilic inflammation and Th2 response in mice. Tectochrysin treatment reduced the level of IgE in plasma, the percentage of eosinophils in total white blood cells in peripheral blood, the total number of cells in BAL fluid, and eosinophil peroxidase activity in lung tissues. Tectochrysin attenuated ST-induced infiltration of eosinophils and epithelial mucus secretion in lung tissues and suppressed the overproduction of Th2 cytokines (IL-4 and IL-5) in BAL fluid. Tectochrysin also attenuated Th2 cytokine (IL-4 and IL-5) production from antigen-stimulated murine splenocytes in vitro, decreased the expression of CD200R on basophils in peripheral blood of asthmatic mice and inhibited IL-4 secretion from IgE-sensitized RBL-2H3 cells. In addition, tectochrysin enhanced catalase and glutathione peroxidase activities in lung tissues. Our findings demonstrate that TEC ameliorates allergic airway inflammation by suppressing Th2 response and oxidative stress.

Good design for the piston skirt can improve efficiency without harming emissions, while it simultaneously reduces wear and improves the reliability of the engine. In this paper, the finite element method is applied to solve the Reynolds equation to analyze the piston skirt-liner system lubrication, and the side motion of piston skirt solved with Runge–Kutta is coupled with lubrication. Some factors that have an effect on the lubrication and dynamic characteristics are selected as variables, such as the clearance, offset distance of the piston pin, bump position, curvature, the length of piston skirt, and the ellipticity of the piston skirt. The orthogonal experimental design which includes six factors with five levels is used to analyze the dominance of these structure factors, and the effects of all the responses for the structural parameters to the friction loss are also identified, and the orthogonal samples simulated by the experiment are conducted to do the regression for the piston skirt. Some regr...

Purpose This paper aims to give the guidance for the design of the bearing. Design/methodology/approach The finite element method, the multi-body dynamics method, the finite difference method and the tribology are combined to analyze the lubrication. Findings The performance parameters of crankshaft-bearing system such as the misalignment, the oil filling ratio and the oil groove are also investigated. Misalignment causes the pressure to incline on one side and the pressure increases obviously. Filling ratio has great relationship with pressure distribution; the factors influencing the filling ratio are also analyzed. Different oil groove models are investigated, as it can provide the theory for oil groove design, and three factors above are always combined to influence the lubrication characteristics. Originality/value The optimization of bearing system is conducted by orthogonal test and neural network, unlike the linear optimization theory. Neural network uses the nonlinear theory to optimize crankshaft-bearing system.

Allergic asthma remains an important worldwide health issue. Animal models are valuable for understanding the pathophysiological mechanisms of asthma and the development of effective therapeutics. This study aims to develop an alternative murine model induced by shrimp tropomyosin (ST) instead of ovalbumin (OVA). To investigate responses to short-term exposure to antigens, mice were sensitized with intraperitoneal injections of ST or ST plus aluminum adjuvant on days 0, 7, 14 followed by an intranasal challenge with ST for seven consecutive days. We reveal that sensitization with ST alone or ST plus aluminum induces significant levels of serum total IgE and ST-specific IgE in mice. Challenge results show that ST causes severe eosinophilic airway inflammation. Histology analysis of the lung tissues demonstrates airway inflammation and mucus hypersecretion within the bronchi in mice exposed to ST. Analysis of the cell composition in bronchoalveolar lavage fluid (BALF) shows a significant increase in eosinophil count in ST alone and ST plus aluminum groups. We also detect increased CD4+ T lymphocytes in lung tissues and production of helper T cell type 2-associated cytokines (IL-4 and IL-5) in BALF. In addition, airway hyperresponsiveness to methacholine in ST alone and ST plus aluminum groups is much higher than that in control groups. For the chronic model, mice were sensitized by ST or ST plus aluminum adjuvant for 3weeks and challenged with ST for 6weeks. We find severe structural changes in animals upon prolonged exposure to ST, including goblet cell hyperplasia, collagen deposition, and smooth muscle thickening. In conclusion, ST-induced asthma is a simple murine model for studying pathogenesis of asthma and evaluating new therapeutic drugs.

Mobile robots depend on maps for localization, planning, and other applications. In indoor scenarios, there is often lots of clutter present, such as chairs, tables, other furniture, or plants. While mapping this clutter is important for certain applications, for example navigation, maps that represent just the immobile parts of the environment, i.e. walls, are needed for other applications, like room segmentation or long-term localization. In literature, approaches can be found that use a complete point cloud to remove the furniture in the room and generate a furniture free map. In contrast, we propose a Simultaneous Localization And Mapping (SLAM)-based mobile laser scanning solution. The robot uses an orthogonal pair of Lidars. The horizontal scanner aims to estimate the robot position, whereas the vertical scanner generates the furniture free map. There are three steps in our method: point cloud rearrangement, wall plane detection and semantic labeling. In the experiment, we evaluate the efficiency of removing furniture in a typical indoor environment. We get $99.60\%$ precision in keeping the wall in the 3D result, which shows that our algorithm can remove most of the furniture in the environment. Furthermore, we introduce the application of 2D furniture free mapping for room segmentation.

The precision of the interaction model is very important to predict NVH and the reliability of an internal combustion engine. The interaction model between the crankshaft and the bearing is hard to be established precisely due to its complex interaction relationship and dynamic characteristic. In this paper, the elasto-hydrodynamic lubrication model with cavitation theory is built to couple with multi-body dynamic theory to analyze the noise and reliability of the engine, the results were compared with nonlinear spring model and hydrodynamic lubrication model based on a typical in-line six cylinder engines, such as load carrying capacity of the bearing, velocity level of the engine surface, noise level of engine surface and stress of the crankshaft. The results showed that the vibration, noise and stress prediction difference is due to the exciting of the oil film pressure distribution, rigid and flexible body that is used to build the dynamic model will lead the load capacity of the bearing to be great different. Nonlinear spring model and hydrodynamic lubrication model are precise enough to predict the vibration or noise. The All the analysis will provide the guidance for the engine NVH optimization and structural reliability design.

Piston ring dynamics play an important role in the lubricant characteristics of reciprocating engines that lead to engine wear and high consumption of lubricating oil. Due to the complexity of realistic test and working conditions, a study of cavitation with surface roughness and its effect on piston ring lubrication was conducted in a simulation program based on mass-conserving theory that is solved with the Newton-Raphson method. Lubrication models such as mixed lubrication, asperity contact, blow-by/blow-back flow, and cavitation were used in this study. The simulation algorithm consists of four processes: establishment of the three different lubrication models, dealing with the finite difference method, numerical stability treatment for the cavitation zone, and the addition of surface roughness and the shear factor to the model. Results calculated with this model were compared with two other models, and an analysis of the results indicates that the developed simulation program can illustrate problems ...

The dynamic and lubrication characteristic analyses of the crankshaft–bearing system is quite a complex problem, and it is important to avoid asperity contact which may lead to bearing wear and increase of friction loss significantly in dynamic lubrication condition. In this paper, the dynamic characteristic that has an essential impact on lubrication was investigated over an inline six-cylinder engine. Multi-body dynamics method, tribology, finite element method (FEM), finite difference method (FDM) and component mode synthesis method (CMS) were combined to analyze the dynamic characteristic of crankshaft, oil leakage, oil film pressure, asperity contact pressure and friction loss. Then the orthogonal experiment that included 5 levels and 6 factors was conducted to obtain the training sample sets for neural network, and the probabilistic neural network (PNN) was employed to identify weather the asperity contact happened or not according to its nonlinear characteristic. The analyses which can provide the guidance for the design of main bearing, and avoid the asperity contact in the lubrication are significant to the design of the bearing at the development stage of the engine.

Journal misalignment is common in journal bearings. When severe journal misalignment takes place, it affects nearly all aspects of bearing performance. This paper provided a comprehensive analysis of misaligned journal bearings based on two different mass-conservative models which appropriately took into account film rupture and reformation. The lubrication characteristics and performance parameters including the cavitation zones, pressure distribution, density distribution, oil leakage, load capacity, moment, and attitude angle were compared with the traditional lubrication model. The results showed that cavitation has great effect on bearing performances, especially when the surface roughness is large. Therefore, it is necessary to consider the effects of journal misalignment alongside inter-asperity cavitation theory in the design and analyses of journal bearings.

A fault diagnosis model is proposed based on fuzzy support vector machine (FSVM) combined with fuzzy clustering (FC). Considering the relationship between the sample point and non-self class, FC algorithm is applied to generate fuzzy memberships. In the algorithm, sample weights based on a distribution density function of data point and genetic algorithm (GA) are introduced to enhance the performance of FC. Then a multi-class FSVM with radial basis function kernel is established according to directed acyclic graph algorithm, the penalty factor and kernel parameter of which are optimized by GA. Finally, the model is executed for multi-class fault diagnosis of rolling element bearings. The results show that the presented model achieves high performances both in identifying fault types and fault degrees. The performance comparisons of the presented model with SVM and distance-based FSVM for noisy case demonstrate the capacity of dealing with noise and generalization.

The performance and particulate emission of a diesel engine are affected by the consumption of lubricating oil. Most studies on oil consumption mechanism of the cylinder have been done by using the experimental method, however they are very costly. Therefore, it is very necessary to study oil consumption mechanism of the cylinder and obtain the accurate results by the calculation method. Firstly, four main modes of lubricating oil consumption in cylinder are analyzed and then the oil consumption rate under common working conditions are calculated for the four modes based on an engine. Then, the factors that affect the lubricating oil consumption such as working conditions, the second ring closed gap, the elastic force of the piston rings are also investigated for the four modes. The calculation results show that most of the lubricating oil is consumed by evaporation on the liner surface. Besides, there are three other findings: (1) The oil evaporation from the liner is determined by the working condition of an engine; (2) The increase of the ring closed gap reduces the oil blow through the top ring end gap but increases blow-by; (3) With the increase of the elastic force of the ring, both the left oil film thickness and the oil throw-off at the top ring decrease. The oil scraping of the piston top edge is consequently reduced while the friction loss between the rings and the liner increases. A neural network prediction model of the lubricating oil consumption in cylinder is established based on the BP neural network theory, and then the model is trained and validated. The main piston rings parameters which affect the oil consumption are optimized by using the BP neural network prediction model and the prediction accuracy of this BP neural network is within 8%, which is acceptable for normal engineering applications. The oil consumption is also measured experimentally. The relative errors of the calculated and experimental values are less than 10%, verifying the validity of the simulation results. Applying the established simulation model and the validated BP network model is able to generate numerical results with sufficient accuracy, which significantly reduces experimental work and provides guidance for the optimal design of the piston rings diesel engines.

The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study. A new model considering the asymmetric deflection is applied. Also, the thermo-hydrodynamic of the oil film in the journal bearing and straightforward elasticity theory are considered in the analysis. Based on the structure stiffness equivalent character- istic, a simple stepped shaft can reflect the entire complex structure model. The existing lubrication model, which does not con- sider this angle component, is not very precise for journal bearings. Film pressure, misalignment angle, velocity field, oil leakage, and temperature field were calculated and compared in the journal bearing analysis. The results indicate that bearing performances are greatly affected by misalignment caused by the asymmetric structure. A simple stepped shaft can effectively represent a misaligned journal bearing in a rotor-bearing system.