Parallel Assembly Research Articles

Fast mobility analysis for generative design applications through a real vector space representation of mobilities

During the early stages of design, mechanisms are commonly modeled as perfect joints assembled with infinitely rigid bodies. This representation enables the prediction of the system’s mobilities through a mobility analysis. However, traditional mobility analysis tools can be computationally expensive or lack critical information, such as the type or direction of mobilities. It hinders the generation of topology and configuration through generative design schemes.In this paper, we propose an alternative approach to mobility analysis based on a real vector space representation of mobilities. Our method provides relevant information for early design steps while being computationally effective through a novel formulation of series and parallel assembly topological operations. A benchmark on four selected use cases highlights an acceleration of 3 to 4 orders of magnitude compared to traditional approaches. Additionally, design rules on the joints’ positions can be automatically generated with our approach. It enables the automation of the complete design process, including topology and configuration. As such, we provide guidelines to develop a generative design scheme dedicated to the synthesis of guiding mechanisms.

MEILB2-BRME1 forms a V-shaped DNA clamp upon BRCA2-binding in meiotic recombination

DNA double-strand break repair by homologous recombination has a specialised role in meiosis by generating crossovers that enable the formation of haploid germ cells. This requires meiosis-specific MEILB2-BRME1, which interacts with BRCA2 to facilitate loading of recombinases onto resected DNA ends. Here, we report the crystal structure of the MEILB2-BRME1 2:2 core complex, revealing a parallel four-helical assembly that recruits BRME1 to meiotic double-strand breaks in vivo. It forms an N-terminal β-cap that binds to DNA, and a MEILB2 coiled-coil that bridges to C-terminal ARM domains. Upon BRCA2-binding, MEILB2-BRME1 2:2 complexes dimerize into a V-shaped 2:4:4 complex, with rod-like MEILB2-BRME1 components arranged at right-angles. The β-caps located at the tips of the MEILB2-BRME1 limbs are separated by 25 nm, allowing them to bridge between DNA molecules. Thus, we propose that BRCA2 induces MEILB2-BRME1 to function as a DNA clamp, connecting resected DNA ends or homologous chromosomes to facilitate meiotic recombination.

Improved hybrid estimation of distribution algorithm for distributed parallel assembly permutation flow shop scheduling problem

AbstractDistributed assembly permutation flow shop scheduling problem is the hot spot of distributed pipeline scheduling research; however, parallel assembly machines are often in the assembly stage. Therefore, we propose and study distributed parallel assembly permutation flow shop scheduling problem (DPAPFSP). This aims to enhance the efficiency of multi‐factory collaborative production in a networked environment. Initially, a corresponding mathematical model was established. Then, an improved hybrid distribution estimation algorithm was proposed to minimize the makespan. The algorithm adopts a single‐layer permutation encoding and decoding strategy based on the rule of the Earliest Finished Time. A local neighbourhood search based on critical paths is performed for the optimal solution using five types of neighborhood design. A dual sampling strategy based on repetition rates was introduced to ensure the diversity of the population in the later periods of iteration. Simulated annealing searching was applied to accelerate the decline of optimal value. Finally, we conduct simulation experiments using 900 arithmetic cases and compare the simulation experimental data of this algorithm with the other four existing algorithms. The analysis results demonstrate this improved algorithm is very effective and competitive in solving the considered DPAPFSP.

Broadband Aircraft Noise Attenuation Across Low and High Frequencies Using Structured Materials

Controlling broadband noise throughout the spectrum, from low to high frequencies, is a significant challenge for the aerospace, transportation, and construction industries. Although recent research has focused on low-frequency noise control solutions using acoustic metamaterial designs, the narrow-band resonances of these materials remain a limitation. This paper presents a structured material system which addresses this limitation by proposing a parallel assembly of structured materials, enabling broadening of the resonance frequency band from low to high frequencies. The study involves an arrangement of structured metamaterials and Helmholtz Resonators embedded in a layer of glass wool. By meticulously grouping individual resonant frequencies, the proposed assembly effectively attenuates noise over the frequency range of interest. The present research contributes to the development of lasting solutions for aircraft noise across a broad frequency spectrum, showing promising potential for significant noise reduction within practical constraints.

Rationally seeded computational protein design of ɑ-helical barrels

Computational protein design is advancing rapidly. Here we describe efficient routes starting from validated parallel and antiparallel peptide assemblies to design two families of α-helical barrel proteins with central channels that bind small molecules. Computational designs are seeded by the sequences and structures of defined de novo oligomeric barrel-forming peptides, and adjacent helices are connected by loop building. For targets with antiparallel helices, short loops are sufficient. However, targets with parallel helices require longer connectors; namely, an outer layer of helix–turn–helix–turn–helix motifs that are packed onto the barrels. Throughout these computational pipelines, residues that define open states of the barrels are maintained. This minimizes sequence sampling, accelerating the design process. For each of six targets, just two to six synthetic genes are made for expression in Escherichia coli. On average, 70% of these genes express to give soluble monomeric proteins that are fully characterized, including high-resolution structures for most targets that match the design models with high accuracy.

Balancing parallel assembly lines with human-robot collaboration: problem definition, mathematical model and tabu search approach

Human-robot collaboration (HRC), as an emerging production mode, has garnered significant attention in the context of the growing smart manufacturing. This study aims to investigate the application of human-robot collaboration in parallel assembly lines and explore its potential for improving productivity, resource utilisation and flexibility. To the best of our knowledge, this is one of the first attempts to consider the combination of parallel assembly line balancing problem (PALBP) and human-robot collaboration. In this study, the parallel assembly line balancing problem with human-robot collaboration (PALBP-HRC) is introduced and characterised. The collaboration mode allows human workers and robots to execute tasks both in parallel and in collaboration. A mixed-integer programming model (MIP) that minimises the cycle time is formulated and a lower bound is proposed. Due to the NP-hardness, we develop an adapted tabu search (TS) algorithm specifically tailored for problem characterisation. Experimental results indicate that the proposed TS algorithm achieves competing performance compared to the MIP and other algorithms, including genetic algorithm (GA) and simulated annealing (SA) algorithm. The comparison between PALBP and PALBP-HRC demonstrates that the integration of human-robot collaboration to parallel assembly line can achieve significant improvements in efficiency and flexibility.

Synthesis and evaluation of antisense oligonucleotides prodrug with G-quadruplex assembly and lysosome escape capabilities for oncotherapy

The applications of antisense oligonucleotides (ASOs) in rare or common diseases treatment have garnered great attention in recent years. Nevertheless, challenges associated with stability and bioavailability still persist, hampering the efficiency of ASOs. This work presents an ASO prodrug with parallel G-quadruplex assembly and lysosome escape capabilities for oncotherapy. Our findings revealed that the end-assembled quadruplex structure effectively shielded the ASO from enzymatic degradation. Meanwhile, the conjugation of maleimide within the quadruplex enhanced cellular uptake, potentially offering an alternative cell entry mechanism that circumvents lysosome involvement. Notably, an optimized molecule, Mal2-G4-ASO, exhibited remarkable therapeutic effects both in vitro and in vivo. This work presents a promising avenue for enhancing the activity of nucleic acid drugs in oncotherapy and potentially other disease contexts.

Critical steps in the assembly process of the bacterial 50S ribosomal subunit.

During assembly, ribosomal particles in bacteria fold according to energy landscapes comprised of multiple parallel pathways. Cryo-electron microscopy studies have identified a critical maturation step that occurs during the late assembly stages of the 50S subunit in Bacillus subtilis. This step acts as a point of convergency for all the parallel assembly pathways of the subunit,where an assembly intermediate accumulates in a 'locked' state, causing maturation to pause. Assembly factors then act on this critical step to 'unlock' the last maturation steps involving the functional sites. Without these factors, the 50S subunit fails to complete its assembly, causing cells to die due to a lack of functional ribosomes to synthesize proteins. In this review, we analyze these findings in B. subtilis and examine other cryo-EM studies that have visualized assembly intermediates in different bacterial species, to determine if convergency points in the ribosome assembly process are a common theme among bacteria. There are still gaps in our knowledge, as these methodologies have not yet been applied to diverse species. However, identifying and characterizing these convergency points can reveal how different bacterial species implement unique mechanisms to regulate critical steps in the ribosome assembly process.

Heuristic and metaheuristic procedures for the Parallel Assembly Lines Balancing Problem with multi-line workstations and buffer sizing

This paper addresses the parallel assembly lines balancing problem (PALBP) with multi-line workstations, lines with different cycle times and buffer sizing. When a PALB system works with lines with different cycle times, the lines with multi-line workstations have to produce in batches; thus, the use of buffers may be needed. For the first time in the literature, this study jointly solved the PALBP and the buffer sizing problem (PALBP-B). Due to the multi-objective nature of the problem (minimising the number of workstations and the total buffer size in the multi-line workstations), several multi-objective heuristics and metaheuristics are proposed to solve the PALBP-B. Finally, an extensive computational experiment is carried out to analyse all the procedures presented.

An adaptive large neighborhood search algorithm for parallel assembly lines scheduling problem with complex fixture constraints

In recent years, the value chain facilitates the transition of competition among enterprises from a single link to a comprehensive one, thereby driving intelligent upgrades within manufacturing enterprises. The intelligent upgrading also imposes new constraints on the traditional assembly line production mode. Inspired by the real production practices of company L, a global intelligent terminal manufacturing enterprise headquartered in China, this study addresses the parallel heterogeneous assembly line scheduling problem with fixture constraints (HALSFC). To tackle this challenging problem, we propose a mixed integer linear programming (MILP) model that aims to maximize the number of completed work orders within a specified time. To our best knowledge, this study is among the first attempts to address the HALSFC problem with setups and related work orders. Due to the NP-hardness of the problem, we propose an improved adaptive large neighborhood search algorithm (IALNS) for solving HALSFC. We evaluate both model functionalities and algorithm effectiveness using instances generated based on the real production data of company L. Extensive experimental results demonstrate the effectiveness and efficiency of IALNS compared to MILP, Tabu search algorithm (TS) and genetic algorithm (GA), especially for medium- and large-scale instances. Additionally, the sensitivity analysis of the quality inspection time, the related work orders proportion and the minimum cooling time of fixtures is also conducted.

Modeling and balancing of parallel U-shaped assembly line based on improved genetic algorithms

Aiming at the improvement of the efficiency of the assembly line in the intelligent manufacturing field, a parallel U-shaped assembly line balancing problem (PUALBP) appears. In this paper, a mathematical model of the PUALBP-I is established, and an improved genetic algorithm (IGA) is innovatively designed based on the allocation strategy. Combined with 56 classic examples, the IGA is used to solve the mathematical models of SUAL and PUAL respectively, and the balance results and the balance effect evaluation indicators are obtained. The comparison with Parallel U-line Heuristic (PUH) shows that the results of PUAL are better than SUAL, and verifies that the IGA is effective. The results demonstrate that the IGA in calculating large-scale problems is superior to the small-scale problems, which provides a useful reference for solving PUALBP.

Managing inventory in customizable multi-echelon assembly systems

We consider a general assembly system that produces variations on a single product. Customers can choose to customize any aspect of the product which corresponds to one or more stages of the assembly system. We assume that demand for the original product and the demand for any customization at any stage are all random with known probability distributions. We model this problem as a multi-echelon inventory management problem. This problem has not been studied before. Allowing for customization at any stage in an assembly system makes this problem significantly more complex than similar problems considered in the past. To solve this problem, we ‘split' the assembly line into two parallel assembly lines which we call uncommitted and committed lines. We show that the usual method of reducing the assembly system to a series is not possible in general. We develop a heuristic policy which can be used to then reduce the system into a series system. We also present numerical calculations which highlight the efficacy of the heuristic policy.

Improved ant colony algorithm for the mixed-model parallel two-sided assembly lines balancing problem

ABSTRACT In response to the increasing demand for individualized products in the ‘small-lot, multi-variety’ market, there is an urgent need to enhance the efficiency and intelligence level of assembly lines. To address this, a novel solution method for the mixed-model parallel two-sided assembly lines balancing problem (MMPTSALBP) is proposed. The first step is to define the type and layout of the parallel two-sided assembly lines. Next, a mathematical model is constructed with the objective of minimizing the number of workstations required for the MMPTSALBP, proposing an improved ant colony algorithm that utilizes double string representation for the initial solution encoding method and a double pheromone matrix update to solve the model. Its efficiency is tested on benchmark datasets according to some performance measures and classifications. A study validates its effectiveness on 25 classical arithmetic cases by comparison with the solutions of an heuristic algorithm and an artificial fish swarm algorithm that had been reported to perform well.

Numerical prediction of the sound transmission loss of double panel configurations with acoustic structured and poroelastic materials

The sound transmission loss of multilayer system assemblies made of Noise Control Treatments comprising metamaterials and poroelastic materials, sandwiched between two structural panels is of utmost importance in aerospace, automotive, building and several other engineering applications. The integration of acoustic metamaterials in these systems introduces a number of challenges at the level of numerical simulation in order to predict their acoustic and structural behavior. This paper presents a methodology for the numerical simulation of the sound transmission loss of structural configurations comprising acoustic metamaterials embedded in a glass wools layer, sandwiched between two elastic panels. The metamaterial is designed as a parallel assembly of four sub-metamaterials. Each of these sub-metamaterials is also a series assembly of a periodic unit cell having a neck + cavity + neck type configuration. The four sub-metamaterials are designed so that their first resonance frequencies are grouped together in order to improve the sound transmission loss at the first two natural frequencies of the double panel. The COMSOL Multiphysics finite element method solver is used. The normal incidence and diffuse field sound transmission loss numerical results are presented and discussed in comparison with results from literature for validation.

Sound attenuation analysis of a honeycomb structure with extended necks

In this paper, a honeycomb structure metamaterial consisting of 95 necks that are attached to the perforated top panel is presented and its sound absorption coefficient and transmission loss are investigated using the finite element method. Helmholtz resonators are therefore created by each honeycomb cell (cavity) and the attached neck, which is protruding within each cell. The structure has therefore a high bending stiffness due to the honeycomb mechanical performance and constitutes a sound absorber based on the parallel assembly of multiple Helmholtz resonators. This study demonstrates the importance of properly designing the diameter and the length of each neck to create a broadband sound absorption. One resonant sound absorption peak is observed when all the necks are identical, and two absorption peaks are obtained using two different sets of neck parameters. When the number of different necks increases, the sound absorption frequency band improves and when the parameters of all the necks are different, resulting in a parallel assembly of 95 different Helmholtz resonators, the sound absorption frequency band broadens. The material design studied in this paper can be useful in various applications where available space is limited and high mechanical stiffness and noise reduction are required in one structural element.

UNC-82/NUAK kinase is required by myosin A, but not myosin B, to assemble and function in the thick filament arms of C. elegans striated muscle.

The mechanisms that ensure proper assembly, activity, and turnover of myosin II filaments are fundamental to a diverse range of cellular processes. In Caenorhabditis elegans striated muscle, thick filaments contain two myosins that are functionally distinct and spatially segregated. Using transgenic double mutants, we demonstrate that the ability of increased myosin A expression to restore muscle structure and movement in myosin B mutants requires UNC-82/NUAK kinase activity. Myosin B function appears unaffected in the kinase-impaired unc-82(e1220) mutant: the recessive antimorphic effects on early assembly of paramyosin and myosin A in this mutant are counteracted by increased myosin B expression and exacerbated by loss of myosin B. Using chimeric myosins and motility assays, we mapped the region of myosin A that requires UNC-82 activity to a 531-amino-acid region of the coiled-coil rod. This region includes the 264-amino-acid Region 1, which is sufficient in chimeric myosins to rescue the essential filament-initiation function of myosin A, as well as two sites that interact with myosin head domains in the Interacting Heads Motif. A specific physical interaction between myosin A and UNC-82::GFP is supported by GFP labeling of ectopic myosin A filaments but not thin filaments. We hypothesize that UNC-82 regulates assembly competence of myosin A during parallel assembly in the filament arms.

Kinematic Analysis of a New 3-DOF Parallel Wrist-Gripper Assembly with a Large Singularity-Free Workspace

This paper introduces a novel dexterous 3-DOF parallel wrist-gripper assembly with a large singularity-free range of motion. It consists of a zero-torsion 2-DOF parallel wrist and a 1-DOF parallel gripper. The wrist produces a 2-DOF sphere-on-sphere pure rolling motion. This large singularity-free 2-DOF sphere-on-sphere pure rolling motion of the wrist allows for smooth and precise manipulation of objects in various orientations, making it suitable for applications such as assembly, pick-and-place, and inspection tasks. Using a geometrical approach, analytical solutions for the inverse and forward kinematics problems of the wrist and gripper are derived. From the inverse kinematic equations, the Jacobian matrices are derived and it is shown that the whole workspace is free of type I and type II singularities. It is shown that with a proper choice of design variables, a large singularity-free range of motion can be obtained. The absence of singularities in the whole workspace of the wrist-gripper assembly is an important feature that enhances its reliability. Finally, the correctness of the derived equations for the wrist inverse and forward kinematics are verified using MSC Adams. These results confirm the feasibility and effectiveness of the proposed parallel wrist-gripper assembly. Overall, the novel parallel wrist-gripper assembly presented in this paper demonstrates great potential for improving the efficiency and flexibility of robotic manipulators in a variety of industrial and research applications.

A NEW MATHEMATICAL MODEL FOR PARALLEL ASSEMBLY LINE BALANCING PROBLEM WITH ERGONOMIC CONSTRAINTS: ERGOPALBP

Parallel assembly line (PAL) systems are one of the most preferred assembly line (AL) types for high volume and mass production in real-life applications. In the PALs, a parallel assembly line balancing problem (PALBP) is basically solved according to certain priority relations and task processing times. However, academic research generally does not take into account the ergonomic strains exposed by workers at stations. It would be a more accurate approach to consider ergonomic aspects in real-life PALBPs. In this study, the ergonomic-constrained PALBP (ergoPALBP) is discussed. Accordingly, the classical PALBP mathematical model is modified by adding ergonomic constraints. The mathematical model proposed for ergoPALBP has been implemented in a PAL system as a real-life application. Both ergonomic risk factors and total station operation times obtained with mathematical models used for classical PALBP and proposed for ergoPALBP were compared. According to the results obtained, the mathematical model proposed for the ergoPALBP shows a successful performance.

Homogeneous Dual Fluorescence Count of CD4 in Clinical HIV-Positive Samples via Parallel Catalytic Hairpin Assembly and Multiple Recognitions.

Regularly measuring the level of CD4+ cells is necessary for monitoring progression and predicting prognosis in patients suffering from an infection with the human immunodeficiency virus (HIV). However, the current flow cytometry standard detection method is expensive and complicated. A parallel catalytic hairpin assembly (CHA)-assisted fluorescent aptasensor is reported for homogeneous CD4 count by targeting the CD4 protein expressed on the membrane of CD4+ cells. Detection was achieved using CdTe quantum dots (QDs) and methylene blue (MB) as signal reporters. CdTe QDs distinguished CHA-assisted release of Ag+ and C-Ag+-C and MB that has differentiated cytosine (C)-rich single-stranded DNA (ssDNA) and C-Ag+-C, generating changes in fluorescence intensity. With the assistance of the CHA strategy and luminescent nanomaterials, this method reached limits of detection of 0.03 fg/mL for the CD4 protein and 0.3 cells/mL for CD4+ cells with linear ranges of 0.1 to 100 fg/mL and 1 to 1000 cells/mL, respectively. The method was validated in 50 clinical whole blood samples consisting of 30 HIV-positive patients, 10 healthy volunteers, and 10 patients with cancer or other chronic infections. The findings from this method were in good agreement with the data from clinical flow cytometry. Due to its sensitivity, affordability, and ease of operation, the current method has demonstrated great potential for routine CD4 counts for the management of HIV, especially in communities and remote areas.

Theoretical study of interactions and structural and thermodynamical properties of nanopores within bilayer-membranes: Experimental inspiration

In this work, we consider a bilayer-membrane which is crossed by an assembly of (parallel) nanopores formed generally by peptide molecules. The deformations and thermal fluctuations of this bilayer-membrane give rise to repulsive effective pair-interactions between the parallel nanopores. Some recent experiment has revealed that the repulsive effective pair-potentials, as function of distance between adjacent nanopores, are of Born-Mayer type (soft-potential). Beside the repulsive forces, the nanopores mutually attract through the van der Waals forces. Our main goal is an extensive theoretical study of the structural and thermodynamical properties of the nanopores we consider as a dense gas system. When the bath temperature is fixed to some value (room temperature), the only remaining pertinent parameter of discussion is the nanopore-density, denoted as n, or equivalently, the peptide-molar-fraction, P/L. First, we propose a closer expression of the effective pair-potentials taking into account recent experimental measurements dealt with many lipid-bilayers (Gramicidin/DLPC, Gramicidin/C12EO5...). Second, we classify these effective pair-potentials in terms of the nanopore-density, and in particular, we show the existence of a typical nanopore-density, nc, below which the total pair-potential exhibits an energy-barrier which prevents the coagulation of the nanopores. When the nanopore-density reaches threshold, nc, the energy-barrier ceases to exist, and beyond this threshold, one assists to a complete coagulation of the nanopores. Third, we determine an exact theoretical expression of the structure factor of the nanopores, as a function of the wave-vector, within the framework of Random Phase Approximation, using a hard-disk model as a reference system. Finally, from the obtained structure factor, we extract the thermodynamical properties of the integrated nanopores, such as the virial pressure (state of equation), the isothermal compressibility and the chemical potential which are nanopore-density dependent.