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Purpose Marking and inspecting are key steps in hull structure construction. However, currently most marking and inspecting operations are still carried out manually, which leads to low assembly efficiency and quality. This paper aims to solve these problems through the application of digital technology: the optical projection and machine vision. Design/methodology/approach First, the assembly process model of hull construction is established in 3D design environment. Second, the process information is presented to workers in a virtual form through optical projector, which provides accurate guidance for the manual operation. On this basis, the workers can complete welding and assembly operations readily. Finally, the machine vision method is used to check the assembly results, which can decrease the subjective errors. Findings A rapid and accurate assembly positioning for hull structure construction is realized based on optical projection, which can avoid the pollution caused by the marking machine and the error caused by human. Originality/value This paper combines the advantages of optical projection and machine vision to the field of shipbuilding. The shortcomings of the traditional marking and inspection methods is effectively solved, which may provide a new way for enhancing the assembly efficiency and quality.

Since the contact line equation is a transcendental equation, the relationship between the installation angle and the shape could not be expressed by explicit functions, which made it difficult to obtain the optimal shape, this paper firstly took three evaluation parameters of the shape, overrun, shift and offset as the objective function as well as the installation angle as variables the contact line optimization model was establish. Secondly, a neural network was introduced to solve the evaluation parameters. Through training the neural network by setting the installation angle as the input, the evaluation parameters as the output, the results show that the trained neural network can respond correctly, and has the advantages which the other method do not obtain. As an example of end relief modified helical gear, the results shows that the method can reduce the grinding errors effectively. Finally, the grinding experiments proven the effectiveness of the method.

Disassemblability evaluation is an important part of product maintainability design. Currently, the disassemblability evaluation of complex products is not systematic and complete. The main problems include (1) the existing methods are limited to individual components, ignoring the evaluation of the whole product; and (2) most studies focus on the single disassembly operations rather than a complete process. To address these problems, this paper proposes a hierarchical and process-oriented evaluation framework. Firstly, from the levels of component and product, a two-level evaluation index system is constructed, and the selected evaluation indexes reflect the features of both current operation and previous disassembly process. Secondly, based on Look-up Table, virtual maintenance, and simple algebraic operations, the evaluation indexes are quantified successively. Thirdly, a hierarchical evaluation procedure is presented, which includes two levels and four types of evaluations. Based on the synthetic application of different types of evaluations, the disassemblability of a product can be fully evaluated and understood. Finally, the effectiveness of the proposed framework is verified by a case study of an electronic cabin.

In this paper, we investigate uniform decay estimate of the solution to the Petrovsky equation with memory $$\begin{aligned} u_{tt}+\Delta ^2u-\int _ 0^t g(t-s)\Delta ^2u(s)ds=0 \end{aligned}$$ with initial conditions and boundary conditions, where g is a memory kernel function. The related energy has been shown to decay exponentially or polynomially as $$t\rightarrow +\infty $$ by the theorem established under the assumption $$g'(t)\leqslant -k g^{1+\frac{1}{p}}(t)$$ with $$p\in (2,\infty )$$ and $$k>0$$ in the reference(J Funct Anal 254(5):1342–1372, 2008). Using the ideas introduced by by Lasiecka and Wang (Springer INdAM Series 10, Chapter, vol 14, pp 271–303, 2014), we prove the optimized uniform general decay result under the assumption $$g'(t)+H(g(t))\le 0$$ , where the function $$H(\cdot )\in C^1({\mathbb {R}}^1)$$ is positive, increasing and convex with $$H(0)=0$$ , which is introduced for the first time by Alabau-Boussouira and Cannarsa (C R Acad Sci Paris Ser I 347:867–872, 2009) and studied systematically by Lasiecka and Wang (Springer INdAM Series 10, Chapter, vol 14, pp 271–303, 2014). The exponential decay result and polynomial decay result in the reference (J Funct Anal 254(5):1342–1372, 2008) are the special cases of this paper by choosing special $$H(\cdot )$$ .

Assembly and disassembly planning are essential parts of product design, manufacture, maintenance, and recycling, which exist through the full life cycle of products. During planning, operation feasibility must be guaranteed; otherwise, it will lead to infeasible work plan which means the actual operations cannot be completed. Especially for manual assembly and disassembly in restricted space, the operation feasibility should be considered from three respects: visibility, reachability, and geometric feasibility. And the rapid and effective feasibility analysis has extremely vital significance. However, currently the simulation method requires much manual intervention, and the geometric method focuses on assembly tools, ignoring human arm. Besides, the above three respects are always analyzed separately, which reduces the analysis efficiency. To solve these problems, this paper proposes an integrated operation feasibility analysis method, which utilizes a geometric method considering human arm to analyze visibility, reachability, and geometric feasibility together. Firstly, the simplified operation models are built to describe the assembly tool and human arm using less parameters. Secondly, two kinds of global accessibility cone with depth (GACd) are respectively constructed for the feasibility analysis of the assembly tool and the human arm. Thirdly, based on the GACds and simplified operation models, the geometric feasibility is analyzed first, and then the operation feasibility is evaluated by computing the adequacy index, reachability index, and visibility index. Finally, the proposed method is verified and discussed by the examples of simulated electronic cabin and excavator. The results show that this method is reasonable and effective in restricted space.

Virtual reality (VR) has been widely used in various manufacturing industries, and VR-based virtual manufacturing has received significant attention in the current intelligent manufacturing era. Digital human models (DHMs) are essential for virtual manufacturing applications. Additionally, researching new applications of DHMs has developed into an important academic research field. This paper aims to identify the applications and research trends of DHMs in the manufacturing industry and to provide a reference for the continued development of virtual manufacturing and DHMs. We selected a total of 49 related articles from a large number of articles published between 2014 and 2019. The applications of DHMs in the manufacturing industry are analyzed from different perspectives and various relevant technical limitations are discussed. The results indicate that the applications of DHMs differ significantly between different types of fields. The automotive industry is the main application field for DHMs, and assembly/maintenance simulations and evaluations are the main application types. Additionally, there are still some limitations in the establishment of virtual environments, motion control, and DHM evaluation that should be addressed. Finally, research trends in the application of DHMs are illustrated and discussed, including the planning and assessment of human-robot collaboration systems, the combination of DHMs and augmented reality, and improved motion planning for DHMs. In summary, the application of DHMs can improve the realism and effectiveness of virtual manufacturing, and DHMs will be more widely and deeply studied and applied in various manufacturing industries in the near future. Keywords: Virtual reality, Digital human models, Virtual manufacturing, Human factors/ergonomics evaluation, Posture and motion control

Large-scale COVID-19 vaccinations are currently underway in many countries in response to the COVID-19 pandemic. Here, we report, besides generation of neutralizing antibodies, consistent alterations in hemoglobin A1c, serum sodium and potassium levels, coagulation profiles, and renal functions in healthy volunteers after vaccination with an inactivated SARS-CoV-2 vaccine. Similar changes had also been reported in COVID-19 patients, suggesting that vaccination mimicked an infection. Single-cell mRNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) before and 28 days after the first inoculation also revealed consistent alterations in gene expression of many different immune cell types. Reduction of CD8+ T cells and increase in classic monocyte contents were exemplary. Moreover, scRNA-seq revealed increased NF-κB signaling and reduced type I interferon responses, which were confirmed by biological assays and also had been reported to occur after SARS-CoV-2 infection with aggravating symptoms. Altogether, our study recommends additional caution when vaccinating people with pre-existing clinical conditions, including diabetes, electrolyte imbalances, renal dysfunction, and coagulation disorders.

Human-Robot cooperation (HRC) is the developing trend in the field of industrial assembly. Design and evaluation of the HRC assembly workstation considering the human factor is very important. In order to evaluate the transformational construction scenario of a manual assembly workstation to a HRC workstation fast and safely, a HRC assembly simulation system is constructed which is based on Augmented Reality (AR) with human-in-loop interaction. It enables a real operator to interact with virtual robot in a real scene, and the assembly steps of real workers can be restored and mapped to a virtual human model for further ergonomic analysis. Kinect and LeapMotion are used as the sensors for human-robot interaction decision and feedback. An automobile gearbox assembly is taken as an example for different assembly task verification, operators’ data are collected and analyzed by RULA scores and NASA-TLX questionnaires. The result shows that the simulation system can be used for the human factor evaluation of different HRC task configuration schemes.

Purpose Aiming at presenting an interaction-free assembly assistance tool, the purpose of this paper is to propose a synchronous augmented reality (AR) assembly assistance and monitoring system. The system monitors operator’s hands activity and process completeness to recognize the assembly state, then display the AR contents contextually. Design/methodology/approach An assembly behavior recognition method is proposed based on gesture recognition. An assembly completeness inspection method is proposed based on SURF feature matching. Assembly state and AR display state are solved by a novel sequential hybrid AR display control strategy. A synchronous multi-channel AR view output strategy is proposed based on QR matrix decomposition. Findings A prototype system has been developed, and case study is performed on an industrial product. Experiments are performed to verify the feasibility, efficiency and recognition accuracy of the proposed methods. Research limitations/implications The proposed system assists users to perform assembly tasks with automatic visual guidance and vision monitoring, avoiding distractions caused by redundant human–computer interactions. Practical implications All methods are integrated to work on only one head-worn device, making the proposed system portable and cheaper. The vision processing pipelines and the view output channels are reconfigurable for customization. Originality/value This paper proposes an interaction-free AR assembly assistance and monitoring system. Assembly behavior recognition and assembly completeness inspection methods are integrated to monitor the assembly state. A sequential hybrid AR display control strategy is proposed to contextually update the AR contents. A synchronous multi-channel AR view output strategy is proposed to fulfill different visualization needs.

In mechanical product design, rapid and effective simulation is invariably essential since the design flaws can be spotted by the simulation results in advance. However, currently, most designers always perform assembly process and kinematics simulation separately, which may lead to repetitive work and low design efficiency. To address the problem, this paper presents a novel method for product design which aims to integrate the assembly process and kinematics simulation seamlessly. To begin with, a semantic modeling method for part information is introduced, which is the premise and foundation to achieve the integration. Secondly, the assembly process simulation is carried out according to the defined steps derived from interactive semantic reasoning among parts. Moreover, the completed assembled model is utilized to generate kinematic pairs automatically, which can help avoid a lot of unnecessary preparations for kinematics simulation. Meanwhile, physics engine is adopted to provide a stable kinematics operation. Based on these, the assembly plan and motion characteristics of a new product can be analyzed effectively and quickly. Therefore, the designers can obtain the analytical results and attempt different design schemes readily. Finally, the effectiveness of the integrated simulation method is verified by a case study of excavator assembly process and kinematics simulation.

A comprehensive finite element method employing a subroutine to link up submodules of commercial code ANSYS is proposed to perform analysis of projection welding in quantitative detail. In order to solve the complexity due to dynamic changes in heat and electrical current flow paths, as well as temperature-dependent material properties, information about contact interfaces and the geometry of the projection areas have been taken into account. By updating parameter information among these submodules in an incremental manner, a truly thermal-electrical-mechanical coupled numerical analysis is realized for projection welding simulation. A case study of an automotive door assembly welding process is carried out and a series of experiments is conducted to confirm the validity of the newly developed method. The agreement between the experimental and numerical results is satisfactory, indicating that the incrementally coupled finite element method may be suitable for projection welding research. Finally, future work to extend this method in optimizing projection welding process design is also presented.

Mechanical reliability of epoxy molding compounds in plastic packages of integrated circuits (IC) is greatly affected by the compound ability to absorb moisture. In this paper, the hygro-thermal effect of a 2-layer stacked die package was investigated which emphasized on the hygroscopic stress and thermal mismatch stress. By finite element analysis (FEA), the distribution of moisture diffusion, thermo-mechanical stress, hygro-mechanical stress and hygro-thermo-mechanical stress under hygro-thermal environment were simulated and calculated. The simulation results showed that the bottom die-attach endured higher thermal stress after the moisture preconditioning under 85°C /85% RH. By simulation of hygroscopic swelling stress during reflow process, it was indicated that the critical position for the package reliability located at the corner of the bottom die and the interface between the bottom die-attach and die. Therefore, the reliability of the bottom layers is relatively low under hygro-thermal environment.

The recent breakthrough in the generation of rat embryonic stem cells (rESCs) opens the door to application of gene targeting to create models for the study of human diseases. In addition, the in vitro differentiation system from rESCs into derivatives of three germ layers will serve as a powerful tool and resource for the investigation of mammalian development, cell function, tissue repair, and drug discovery. However, these uses have been limited by the difficulty of in vitro differentiation. The aims of this study were to establish an in vitro differentiation system from rESCs and to investigate whether rESCs are capable of forming terminal-differentiated cardiomyocytes. Using newly established rESCs, we found that embryoid body (EB)-based method used in mouse ESC (mESC) differentiation failed to work for the serum-free cultivated rESCs. We then developed a protocol by combination of three chemical inhibitors and feeder-conditioned medium. Under this condition, rESCs formed EBs, propagated and differentiated into three embryonic germ layers. Moreover, rESC-formed EBs could differentiate into spontaneously beating cardiomyocytes after plating. Analyses of molecular, structural, and functional properties revealed that rESC-derived cardiomyocytes were similar to those derived from fetal rat hearts and mESCs. In conclusion, we successfully developed an in vitro differentiation system for rESCs through which functional myocytes were generated and displayed phenotypes of rat fetal cardiomyocytes. This unique cellular system will provide a new approach to study the early development and cardiac function, and serve as an important tool in pharmacological testing and cell therapy.

To study the upper limit of normal thyroid volume based children 8-10 years old in Zhejiang Province. At the same time, the revision methods of thyroid volume were discussed.The thyroid volume of 1110 children 8-10 years old in Zhejiang province, was measured by ultrasonography during the fifth national survey of IDD in 2002 and was analyzed by using SPSS 10.0 for Windows.1. Children's thyroid volume was progressively increased with age. But there was no significant difference between boys and girls. 2. The upper limit of normal thyroid volume of children at the age of 8, 9 and 10 years old in a province were 4.7, 5.3 and 6.0ml respectively. The upper limit of normal thyroid volume in children at the age of 8 and 9 is higher than the corresponding criteria of GB16398-1996. 3. Of all the four revision methods of thyroid volume, HVI was better than others.1. The upper limit of normal thyroid volume of children at the age of 8-10 years old in a province was reasonable, and these normative values were useful for the IDD surveillance in a province and were also referential for revision of Chinese national normative values for schoolchildren. 2. HVI maybe the best method to adjust the thyroid volume at present.

Hybrid P2P technique recently has become more and more popular for collaborative systems. However, reliability is issue of major importance in the server end of these systems. TMR technique for Collaborative System (CS-TMR) is presented in this paper to improve the server reliability. This software schema incorporates three homogeneous microcomputers and provides the fault-tolerant function through package interfaces to server applications. As it is COS-based, the method is more general-purpose, and programmers need not pay too much attention to the fault tolerance technology in detail. This method helps the collaborative server work in normal and degraded (duple or even single modular) modes, and can tolerate transient or permanent faults. Meanwhile, due to the importance of the server in hybrid P2P server, server application upgrade is impossible without server stop. A novel seamless software upgrade method is brought forward through the intelligent state-transition-control in CS-TMR package to reduce the cost of software upgrade.

In the title compound, C22H27ClN6O2 2+·2ClO4 −, the molecule adopts an E conformation about the C=N double bond. The quinazoline ring is approximately planar, with an r.m.s. deviation of 0.0432 Å, and forms a dihedral angle of 5.77 (4)° with the chlorophenyl ring. The crystal packing features N—H...O hydrogen bonds.