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The purpose of this paper is that the modular mobile robots reformed the multimachine joint mode to achieve obstacle-crossing, climbing and other multifunctional inspection in unstructured environment under the connection of the cone–hole docking mechanism.

An arc-shaped docking cone head with a posture-maintaining spring and two arc-shaped connecting rods that formed a ring round hole were designed to achieve large tolerance docking. Before active locking, the coordination between structures was used to achieve passive locking, which mitigated the docking impact of modular robots in unstructured environment. Using the locking ring composed of the two arc-shaped connecting rods, open-loop and closed-loop motion characteristics were obtained through the mutual motion of the connecting rod and the sliding block to achieve active locking, which not only ensured high precision docking, but also achieved super docking stability.

The cone–hole docking mechanism had the docking tolerance performance of position deviation of 6mm and pitch deviation of 8° to achieve docking of six degrees of freedom (6-DOF), which had a load capacity of 230 N to achieve super docking stability. Under the connection of the cone–hole docking mechanism, the modular mobile robots reformed the multimachine joint mode to achieve obstacle-crossing, climbing and other multifunctional inspection in unstructured environment.

Based on mechanical analysis of universal models, a cone–hole docking mechanism combining active and passive functions, six-dimensional constraints could be implemented, was proposed in this paper. The characteristics of the posture-maintaining spring in the cone docking head and the compression spring at the two ends of two arc-shaped connecting rods were used to achieve docking with large tolerance. Passive locking and active locking modules were designed, mitigating impact load and the locking did not require power to maintain, which not only ensured high precision docking, but also achieved super docking stability.

The purpose of this paper is to illustrate the dependence of flexible-electronics properties on the metal conductor parameters, such as the width, thickness, connection length and inner meander radius of the conductor.

This paper uses the finite element method to simulate flexible electronics with a copper conductor attached to polyimide substrate under tension, by using different parameters of the conductor.

By careful variation of copper conductor parameters, the authors obtain an optimized structure that can undergo large deformations with small stress concentrations, lending convenience for packaging.

The authors have developed an optimization method for selecting metal conductor parameters in flexible electronics.

The purpose of this paper is to present an actuator fault detection method for unmanned aerial vehicles (UAVs) based on interval observer and extended state observer.

The proposed algorithm has very little model dependency. Therefore, a six-degree-of-freedom linear equation of UAVs is first established, and then, combined with actuator failure and external disturbances in flight control, a steering gear model with actuator failure (such as stuck bias and invalidation) is designed. Meanwhile, an extended state observer is designed for fault detection. Moreover, a fault detection scheme based on interval observer is designed by combining fault and disturbances.

The method is testified on the extended state observer and the interval observer under the failure of the steering gear and bounded disturbances. The simulation results show that the two types of fault detection schemes designed can successfully detect various types of faults and have high sensitivity.

This research paper studies the failure detection scheme of the UAVs’ actuator. The fault detection scheme in this paper has better performance on actuator faults and bounded disturbances than using regular fault detection schemes.

High residual stress caused by the high temperature gradient brings undesired effects such as shrinkage and cracking in selective laser melting (SLM). The purpose of this study is to predict the residual stress distribution and the effect of process parameters on the residual stress of selective laser melted (SLMed) Inconel 718 thin-walled part.

A three-dimensional (3D) indirect sequentially coupled thermal–mechanical finite element model was developed to predict the residual stress distribution of SLMed Inconel 718 thin-walled part. The material properties dependent on temperature were taken into account in both thermal and mechanical analyses, and the thermal elastic–plastic behavior of the material was also considered.

The residual stress changes from compressive stress to tensile stress along the deposition direction, and the residual stress increases with the deposition height. The maximum stress occurs at both ends of the interface between the part and substrate, while the second largest stress occurs near the top center of the part. The residual stress increases with the laser power, with the maximum equivalent stress increasing by 21.79 per cent as the laser power increases from 250 to 450 W. The residual stress decreases with an increase in scan speed with a reduction in the maximum equivalent stress of 13.67 per cent, as the scan speed increases from 500 to 1,000 mm/s. The residual stress decreases with an increase in layer thickness, and the maximum equivalent stress reduces by 33.12 per cent as the layer thickness increases from 20 to 60µm.

The residual stress distribution and effect of process parameters on the residual stress of SLMed Inconel 718 thin-walled part are investigated in detail. This study provides a better understanding of the residual stress in SLM and constructive guidance for process parameters optimization.

Selective laser melting (SLM) is a promising additive manufacturing technology in the field of complex parts’ fabrication. High temperature gradient and residual stress are vital problems for the development of SLM technology. The purpose of this paper is to investigate the influence of substrate characteristics on the residual stress of SLMed Inconel 718 (IN718).

The SLMed IN718 samples were fabricated on the substrates with different characteristics, including pre-compression stress, materials and pre-heating. The residual stress at the center of the top surface was measured and compared through Vickers micro-indentation.

The results indicate that the residual stress reduces when the substrate contains pre-compression stress before the SLM process starts. Both substrate thermal expansion coefficient and thermal conductivity affect the residual stress. In addition to reducing the difference of thermal expansion coefficient between the substrate and the deposited material, the substrate with low thermal conductivity can also decrease the residual stress. Substrate pre-heating at 150°C reduces nearly 42.6 per cent residual stress because of the reduction of the temperature gradient.

The influence of substrate characteristics on the residual stress has been studied. The investigation results can help to control the residual stress generated in SLM processing.

The group‐based preemptive scheduling provides a flexible mechanism to define the preemptive relations between tasks. However, this scheduling scheme together with a resource access synchronization protocol and the requirements of fault tolerance makes the predication of a real‐time system’s behaviors more difficult than traditional scheduling scheme. The major contribution of this work is an algorithm to calculate the worstcase response time for tasks under the group‐based preemptive scheduling. This algorithm supports both the fault‐free and the primary‐alternative fault‐tolerance scheduling mechanism. Moreover, a method to calculate the minimum allowed time between two consecutive faults is also introduced. The algorithm has been implemented in a time analysis tool and integrated into a system development platform, which is compatible with the OSEK/VDX operating system standard, to verify the temporal property in the early system design step.

With the rapid economic development, China has been increasingly paying special attention to its sports and health industries. In October 2014, the State Council raised the goal to upscale the sports industry to the net worth of 5 trillion yuan by 2025. To gain further insights into the current development of tennis in China, especially the development of Women’s Tennis Association (WTA) tennis competitions, an interview with the director of Wuhan Opening Fabrice Chouquet and Mr Guoqing Yi of Wuahan Sport Investment Inc. was conducted. The paper aims to discuss these issues.

To gain further insights into the current development of tennis in China, especially the development of WTA tennis competitions, an interview with the director of Wuhan Opening Fabrice Chouquet and Mr Guoqing Yi of Wuahan Sport Investment Inc. was conducted.

The interview comprised a series of topics including motivators of tennis industries in China, the strategic position of China for WTA development, WTA choice of hosting city, effects of WTA competition events toward the hosting city, and the operation of WTA tennis competitions. Integrating the aforementioned topics with Wuhan Tennis Open, the interviewees also provided suggestions toward the future development of tennis industry in China.

This study has several limitations that are of concern to researchers in the future. First, the interviewees of this research came from Wuhan Tennis Open. Though Mr Fabrice used to be the managing director of WTA in Asia, he only knows about women tennis in China, and his viewpoints have their own limitation. Therefore, the interviewee in the future has to be the person who could hold the opinion on tennis development in China at the macro scale. Second, the questions in the interview have a wide scale, but lack depth and penetration. For instance, the interview only relates to the motive of tennis development but does not go deeply into the relation between the above two aspects. Moreover, it mentions the problems related to the tennis development. It only concentrates on the tennis tournaments but does not discuss the tennis culture and the industry. These questions need to be considered when the authors research on the development of tennis in China in the future.

Through the analysis on WTA and tennis in China, the authors can understand the development of sports in China and the Chinese sports industry in recent years.

Online comments significantly impact consumer choice and product sales. Existing research focuses on the direct effects of online comments on product sales, whereas studies on the spillover effects of online comments are relatively limited, especially for high-involvement products. This study explores the impact of online comments of competing products on focal product sales in high-involvement products.

Data mining techniques are used to collect 72,367 online comments from the Autohome platform, and sentiment analysis algorithms are used to quantify the textual information for subsequent analysis. Specifically, two panel two-way fixed-effects models are constructed to explore the impact of the average valence and quantity of online comments of competing cars on focal car sales, and analyse this impact in terms of heterogeneity across car price levels, while the moderating effect of online comments of competing cars is explored.

The results show that the average quantity of online comments of competing cars has a significant effect on the sales of the focal car in the overall sample, while the average valence of online comments of competing cars does not have a significant spillover effect. Moreover, the spillover effect varies by car price level. For high-priced cars, the average quantity of online comments of competing cars significantly and negatively affects focal car sales, and the average valence of online comments of competing cars significantly and negatively moderates the effect of the valence of focal car online comments on its sales. For lower-priced cars, online comments of competing cars don’t significantly affect focal car sales.

This study not only enriches the theory of online comments and high-involvement product sales, but also provides reference and guidance for exploring spillover effects of online comments for other products.

To setup a theoretical model for grasping cutting pieces of garment better, which will help to design a special soft gripper and push forward the automated level of garment manufacturing.

This paper first analyzed the mechanics of the grasping process and concluded the main factors that affect the success of grasping. A theoretical model named grasping fabric model (GFM) was constructed to show the mechanical relationship between the soft gripper and the fabric pieces. Subsequently, two fabric samples were selected and tested for their friction properties and critical buckling force, and the test data were substituted into the theoretical model GFM to obtain the grasping parameters required for fabric grasping layer by layer.

It was found that (1) the critical buckling force of the fabric is mainly influenced by the bending stiffness and the deformation length of the fabric during grab. (2) The difference between the friction between the soft gripper and the fabric and the friction between the fabric, that is DF1-2, has an important influence on the accuracy of grasping layer-by-layer.

It showed that the grasping parameters provided by GFM enable the two samples to be more effectively separated layer by layer, which verifies that the GFM model is strong enough for the possible application in garment automated production.

This paper aims to focus on the reliability of Sn15Bi–xAg and Sn15Bi–xCu solder joints during isothermal aging.

The effects of Ag or Cu additions on the microstructure, interfacial metallic compound layer and shear strength of Sn–15Bi (Sn15Bi) based solder joints during were investigated. The effects of Ag or Cu additions on the microstructure and tensile properties of Sn15Bi-based bulk solders were also investigated to provide a comprehensive analysis. The interfacial morphology and microstructure were observed by scanning electron microscopy and the composition in the structure was examined by energy dispersive spectrometer. The shear tests were carried out on the as-soldered and as-aged joints using a ball shear tester.

The results revealed that by adding Ag or Cu, the microstructure of Sn15Bi solder can be refined. Ag addition increased the tensile strength of Sn15Bi solder but had little effect on elongation. However, Cu addition decreased the tensile strength and elongation of Sn15Bi solder. For solder joints, Ag addition increased the shear strength and toughness of Sn15Bi/Cu joints but Cu addition decreased the shear strength and toughness of Sn15Bi/Cu joints.

The authors can potentially provide a replacement for Sn40Pb traditional solder with Sn15Bi solder by alloying Ag or Cu due to its lower cost and similar melting point as Sn–Pb solder.