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As an important product characteristic, maintainability is recognized as a highly significant factor in the economic success of engineering systems and products. Based on virtual reality technology, this paper aims to create an intuitive, immersive and interactive environment for product maintenance. In order to analyze and evaluate the product maintainability in a virtual maintenance environment, fuzzy comprehensive evaluation is used. At the early design stage, maintainability influencing factors are analyzed and the whole maintainability evaluation of the product is given by using fuzzy comprehensive evaluation method in virtual maintenance environment.

The paper provides a fuzzy comprehensive evaluation method for product maintainability evaluation in virtual environment.

Fuzzy comprehensive evaluation is used to evaluate product maintainability in virtual environment, and the application of virtual maintainability system is expanded.

According to maintainability requirement, the maintainability index set is built in this paper, and fuzzy comprehensive evaluation method is used to evaluate product maintainability in virtual maintenance environment at stage of early design.

The virtual design environment offers users an opportunity to interact with a virtual prototyping rather than physical models and to build a fixture configuration in a realistic way. But the virtual reality (VR) environment tends to be inaccurate because humans have difficulty in performing precise positioning tasks. Therefore, it is necessary to implement precise object manipulation methods for assembly and disassembly activities, so that users can perform modular fixture configuration design efficiently in VE. The purpose of this paper is to develop a VR‐based modular fixture assembly design system, which supports the design and assembly of modular fixture configuration in a virtual environment.

Geometric constraint‐based method is utilized to represent and treat the assembly relationship between modular fixture elements. The paper presents a hybrid method of rule‐based reasoning and fuzzy comprehensive judgment to capture the user's operation intent and recognize geometric constraint. Through degrees of freedom based analysis, a mathematical matrix is presented for representing and reducing allowable motion of fixture elements, and a constraint‐based motion navigation approach is proposed to ensure that the manipulation of a fixture component not violate that the existing constraints.

The paper finds that the proposed techniques are applicable to the convenient manipulation and accurate positioning of fixture elements in a virtual environment.

Component manipulation plays a key role in interactive virtual assembly design. The proposed approach in this paper enables interactive assembly design of modular fixture in virtual environment.

This paper presents a geometric constraint‐based approach that realizes automatic assembly relationship recognition, constraint solving and motion navigation for interactive modular fixture assembly design in a virtual environment.

This paper aims to compare the electronic properties of perylene diimide derivatives (DFPDI) and its anion radical (DFPDI.^-k.⁺) thin film by drop-coating of organic molecules on the interdigitated electrodes.

The authors compared the electronic properties of perylene diimide derivatives and its anion radical by drop-coating of organic molecules on interdigitated electrodes. Significantly, the current of perylene diimide derivatives anion radical increased by 2∼3 orders of magnitude compared to perylene diimide derivatives under a bias of 5 V, and the maximal current of anion radical that from tetrahydrofuran solution can reach 3.6 mA. Furthermore, DFPDI.^-k.⁺ thin film showed time-resistance sensitivity for acetic acid. When DFPDI.^-k.⁺ thin film was placed in acetic acid of 3.1 × 105 ppm, the current was decreased 46 times under a bias of 6 V after 8 min.

We developed the new method to prepare ambient stable perylene diimide derivatives anion radical, which shows sensitivity of absorption spectra to acid.

Perylene diimide derivatives anion radical thin film showed time-resistance sensitivity for acetic acid, suggesting potential application of perylene diimide derivatives anion radical as acid sensor.

As the core technology of blockchain, various consensus mechanisms have emerged to satisfy the demands of different application scenarios. Since determining the security, scalability and other related performance of the blockchain, how to reach consensus efficiently of consensus mechanism is a critical issue in the blockchain.

The paper opted for a research overview on the blockchain consensus mechanism, including the consensus mechanisms' consensus progress, classification and comparison, which are complemented by documentary analysis.

This survey analyzes solutions for the improvement of consensus mechanisms in blockchain that have been proposed during the last few years and suggests future research directions around consensus mechanisms. First, the authors outline the consensus processes, the advantages and disadvantages of the mainstream consensus mechanisms. Additionally, the consensus mechanisms are subdivided into four types according to their characteristics. Then, the consensus mechanisms are compared and analyzed based on four evaluation criteria. Finally, the authors summarize the representative progress of consensus mechanisms and provide some suggestions on the design of consensus mechanisms to make further advances in this field.

This paper summarizes the future research development of the consensus mechanisms.

The purpose of this paper is to develop an assembly modelling approach to be applied with a software package, to assist in the design and assembly of special purpose machines (SPMs).

A database of SPM elements was established, and an assembly relationships graph was created. Mating conditions were identified between the SPM elements, and their assembly constraints were extracted and implemented in SolidWorks application programming interface.

The implementation of this assembly modelling approach was validated by selecting SPM layouts as examples. A significant reduction in the assembly time was achieved compared to the traditional assembly procedure for the same examples.

This is a new application of assembly modelling that assists engineers and designers in the design and assembly processes of SPMs. This approach can also be applied to other machine tools with similar attributes.