Study on the Universal Tapered Segmental Ring Assembly Simulation Algorithm and Deviation Assessment: A Case Study on Metro Line Tunnel

Universal tapered segmental ring system has been adopted to assemble tangent and curve line elements into the shield tunnels through the relative rotation of the adjacent front and rear rings, which simplifies the formwork design, demonstrates strong universality, and is easy for quality assurance. To evaluate the position deviation caused by the taper value and propose the assembly scheme for the contractor, this article developed the universal tapered segmental ring assembly simulation technology. Firstly, the assembly procedure of the universal tapered segmental ring system both in normal case and in special case is introduced, including the interval tunnel of special rings and actual engineering that needs deviation correction. Secondly, relevant core algorithms are introduced in detail, including the coordinate position algorithm of horizontal and vertical curves and computer graphic algorithm of spatial point rotating around any axis. Finally, this article takes a background metro line tunnel as a case to validate the algorithm and illustrate the assessment methodology of universal tapered segmental ring assembly accuracy. The sections with maximum deviation are found as an alert ahead of the shield advancing. In conclusion, the algorithms and methodology proposed in this article illustrate the excellent suitability and robustness in shield tunnels adopting a universal tapered segmental ring system in the stage of both design and construction.

Research on Assembly Process Simulation of Construction Machinery Arm Based on Digital Twin

The construction machinery arm is the key component of construction machinery to complete the operation task; its assembly link directly affects the product quality and operational performance of the whole machinery. To solve the problems of low assembly efficiency and the inability to fully reflect the assembly process indexes and product characteristics in the traditional construction machinery arm assembly, this paper studies assembly process modeling and simulation for the construction machinery arm based on assembly sensing data and digital twin. By extracting and processing the assembly resource data and field measurement data of the machinery arm, the assembly process information database under the digital twin environment is constructed, which lays the foundation for the virtual assembly model construction of the machinery arm. Through the real-time data interaction between virtual space and physical space, a complete assembly of digital twin spaces is formed. Finally, taking the assembly line of an excavator armed as an example, it is shown that the digital twin-based assembly simulation can monitor the assembly process in real-time and optimize its configuration to improve assembly efficiency. Therefore, an effective closed-loop feedback mechanism is constructed for the whole assembly process of the construction machinery arm.

A FAST assembly simulation analysis method for hull blocks with engineering constraints

In order to effectively improve the assembly efficiency for hull blocks, an assembly simulation analysis method considering engineering constraints is proposed in this paper, and an integrated system of shipbuilding accuracy analysis and assembly analysis considering multi-constraints is developed. The method is divided into pre-matching model and fine matching model. In the pre-matching model, an Improved Coherent Point Drift (ICPD) algorithm is used to obtain more accurate initial matching values. The fine matching model firstly uses the Analytic Hierarchy Process (AHP) algorithm to automatically obtain the constrained weights, then the weights vector is used to add the assembly constraints for hull blocks such as straightness, hard point constraints etc. into the multi-objective optimization function. By solving the function, the optimum positioning location and the most reasonable adjustment scheme are obtained. This method shortens the occupancy time of the equipment used to build the hull, reduces the workload of the staff, and improves the efficiency and quality of shipbuilding. The integrated system adds engineering constraints analysis module and the function of automatically finding and eliminating error measurement points. Through the verification of the examples, the integrated system realizes the automation and intellectualization of the assembly for hull blocks.

Computational Sub-10 nm Plasmonic Nanogap Patterns by Block Copolymer Self-Assembly

Plasmonic nanoparticle (NP) arrays with narrow gaps have been suggested as an effective light collection solution for plasmonic structures. For an effective low-cost bottom-up strategy, block copolymer (BCP) self-assembly with evaporative metal-deposition is mentioned as one of the best effective ways to produce Au NP arrays with narrow gaps. In this paper, BCP self-assembly for nanopost-template arrays and metal-deposition over the nanotemplate surface for positional arrangement of Au NPs are described using a self-consistent field theory (SCFT) and a level-set method, respectively. According to the of BCP self-assembly simulation results, both the diameter of the cylinder post and gap size become larger due to the increase of polymerization degree (N). However, these parameters become smaller in terms of the increase of the Flory-Huggins interaction parameter χ. For plasmonic phenomena about a top-down incident wavelength of 600-nm, according to a rigorous coupled-wave analysis (RCWA), although the electric field around a single spherical post becomes larger at smaller diameter, there is no top-down plasmonic phenomenon at a gap size of 10-nm between nanoposts.

Production flow improvement and value stream mapping in a lean manufacturing world

The importance of lean manufacturing concepts has been discussed many times over the few decades. The most important elements in lean manufacturing practices are value stream mapping (VSM), Kaizen events, load leveling (heijunka), etc. In this case study, a real-world clock assembly simulation has been used to study the performance improvement in terms of production flow and lead time after introducing lean concepts. In each round of simulation, the lean concepts have been introduced one by one and performance metrics were recorded. After implementing the concepts, the productivity was improved enormously. So, this simulation study emphasizes the importance of continuous improvement of production flow through lean concepts in a real production setting.