Parallel Assembly Research Articles

Mathematical model and agent based solution approach for the simultaneous balancing and sequencing of mixed-model parallel two-sided assembly lines

One of the key factors of a successfully implemented mixed-model line system is considering model sequencing problem as well as the line balancing problem. In the literature, there are many studies, which consider these two tightly interrelated problems individually. However, we integrate the model sequencing problem in the line balancing procedure to obtain a more efficient solution for the problem of Simultaneous Balancing and Sequencing of Mixed-Model Parallel Two-Sided Assembly Lines. A mathematical model is developed to present the problem and a novel agent based ant colony optimisation approach is proposed as the solution method. Different agents interact with each other to find a near optimal solution for the problem. Each ant selects a random behaviour from a predefined list of heuristics and builds a solution using this behaviour as a local search rule along with the pheromone value. Different cycle times are allowed for different two-sided lines located in parallel to each other and this yields a complex problem where different production cycles need to be considered to build a feasible solution. The performance of the proposed approach is tested through a set of test cases. Experimental results indicate that considering model sequencing problem with the line balancing problem together helps minimise line length and total number of required workstations. Also, it is found that the proposed approach outperforms other three heuristics tested.

Open and closed loop manipulation of charged microchiplets in an electric field

We demonstrate the ability to orient, position, and transport microchips (“chiplets”) with electric fields. In an open-loop approach, modified four phase traveling wave potential patterns manipulate chiplets in a dielectric solution using dynamic template agitation techniques. Repeatable parallel assembly of chiplets is demonstrated to a positional accuracy of 6.5 μm using electrodes of 200 μm pitch. Chiplets with dipole surface charge patterns are used to show that orientation can be controlled by adding unique charge patterns on the chiplets. Chip path routing is also demonstrated. With a closed-loop control system approach using video feedback, dielectric, and electrophoretic forces are used to achieve positioning accuracy of better than 1 μm with 1 mm pitch driving electrodes. These chip assembly techniques have the potential to enable future printer systems where inputs are electronic chiplets and the output is a functional electronic system.

Comparison between parallel transfer matrix method and admittance sum method.

A transfer matrix method to predict absorption coefficient and transmission loss of parallel assemblies of materials which can be expressed by a 2 × 2 transfer matrix was published recently. However, the usual method based on the sum of admittances is largely used to predict also surface admittance of parallel assemblies. This paper aims to highlight differences between both methods through three examples on a parallel assembly backed by (1) a rigid wall, (2) an air cavity, and (3) an anechoic termination.

Effect of Au nanorod assemblies on surface-enhanced Raman spectroscopy

Monolayer and multilayer arrangements (consisting of disorder, parallel alignment and perpendicular superlattice) of hydrophobic gold nanorods have been prepared on silicon substrates via the evaporation-based self-assembly and the heat treatment methods, and the substrates were provided for the surface-enhanced Raman spectroscopic (SERS) examination. The perpendicular superlattice assembly of gold nanorods maximally enhanced intensities of Raman bands in comparison with parallel and disorder assemblies. Moreover, multilayer films of gold nanorods were more effective on SERS than monolayer films. The motive force of the Raman enhancement should be the adequate resonance coupling of localized surface plasmon waves at the reasonable density of spaces between neighboring rods. Moreover, the adsorption ability of analytes on the hydrophobic peripheral octadecyltrimethoxysilane groups will also improve the detection limit and develop the detection scope from aqueous to organic solutions.

Worker coordination policies in parallel station systems: performance models for a set of jobs and for continuous arrival of jobs

Varying workloads and uncertain processing times in parallel assembly cause idle times for skilled, high-cost workers. This idleness can be avoided and the utilisation of the workers improved by allowing workers to move between the stations to help each other. Worker movement between assembly stations needs efficient and feasible coordination, and therefore, this paper compares four different worker coordination policies: no helping, floater, pairs and complete helping. The dynamics of the policies are modelled by studying the parallel assembly as a continuous-time Markov process. The system is studied with two different job release cases for non-identical jobs (customised products). In the first case, a given number of jobs have to be completed by the entire system. In the second case, new jobs arrive with a Poisson-distributed rate. The models assume that when one worker helps another, their collaborative inefficiency reduces the productivity. The models are used in numerical experiments to compare the performances of worker coordination policies as average job cycle times. The main conclusions from the results suggest the use of the complete helping policy in minor collaborative inefficiency conditions, especially with a given set of jobs. The pairs policy is a reasonable alternative in major inefficiency conditions with the continuous arrival of jobs.

Three-dimensional precision analysis with rigid and compliant motions for sheet metal assembly

This paper quantifies the detailed assembly motions by taking into account the mating gaps and gravities of fixtures and sheet metals. Finite element (FE) models are firstly generated for fixtures and parts. Their nodes are ordered according to an appointed assembly sequence where the last assembled part is behind the first one by the assembly platform or mating surface. Three noncollinear feature points are selected from each last assembled part near the mating surface. Their translational displacements (gaps) represent the part rigid motion near that surface omitting the local joint deformation. Based on the given feature point gaps, kinematic formulations are proposed to compute the rigid motions for any FE nodes behind the mating surface in assembly sequence. Compliant motions are then reached by the modified FE analysis where variable mesh method is applied to change the FE nodal coordinates using the gap-induced rigid motions and deformations. Code integrations of sequence and parallel assemblies are finally proposed and validated via simulations and experiments. Results suggest the following: (1) the proposed method is effective and accurate for engineer application; (2) the integration approach requires to be further studied for the precision analysis of more complex assemblies and implies a feasible way for adding local deformations of joints to the deterministic dimensional precision analysis.

Electromagnetic Induction Heating Bonding between Carbon Nanotubes and Metal Electrode

This paper introduces an electromagnetic induction heating method which is demonstrated to be able to bond carbon nanotubes and metal electrodes. Dielectrophoresis method is taken to realize the parallel directional assembly between carbon nanotubes and metal electrode, and then localized induction heating is adopted to bond them. This technique offers a convenient and reliable way in the practical applications of carbon nanotube interconnection. The bonding principle and process are introduced, and the experiment results are also discussed. The results show that the bonding interface exhibits good contact and electrical property.

Carbon nanotube‐based hot‐film and temperature sensor assembled by optically‐induced dielectrophoresis

The development of carbon nanotube (CNT)-based sensors remains an active area of research. Towards this end, a new method for manipulating CNTs, assembling CNT networks and fabricating CNT-based nanosensors was demonstrated in this study. CNTs were collected and concentrated by optically-induced dielectrophoresis (ODEP) forces and aligned between a pair of electrodes. This assembly was then used directly as a temperature sensor and a hot-film anemometer, which detects changes in windspeed. By offering efficient CNT collection and ready-to-use sensor fabrication, this ODEP-based approach presents a promising method for the development of CNT-based sensing applications and massively parallel assembly of CNT-lines. The developed CNT-based nanosensors may be used to measure the temperature and the flow velocity of bio-samples in the near future.

Single Nanowire Light-Emitting Diodes Using Uniaxial and Coaxial InGaN/GaN Multiple Quantum Wells Synthesized by Metalorganic Chemical Vapor Deposition

We report the controlled synthesis of InGaN/GaN multiple quantum well (MQW) uniaxial (c-plane) and coaxial (m-plane) nanowire (NW) heterostructures by metalorganic chemical vapor deposition. Two kinds of heterostructure NW light-emitting diodes (LEDs) have been fabricated: (1) 10 pairs of InGaN/GaN MQW layers in the c-plane on the top of n-GaN NWs where Mg-doped p-GaN NW is axially grown (2) p-GaN/10 pairs of InGaN/GaN shell structure were surrounded by n-GaN core. Here, we discuss a comparative analysis based on the m-plane and the c-plane oriented InGaN/GaN MQW NW arrays. High-resolution transmission electron microscopy studies revealed that the barrier and the well structures of MQW were observed to be substantially clear with regular intervals while the interface regions were extremely sharp. The c-plane and m-plane oriented MQW single NW was utilized for the parallel assembly fabrication of the LEDs via a focused ion beam. The polarization induced effects on the c-plane and m-plane oriented MQW NWs were precisely compared via power dependence electroluminescence. The electrical properties of m-plane NWs exhibited superior characteristics than that of c-plane NWs owing to the absence of piezoelectric polarization fields. According to this study, high-quality m-plane coaxial NWs can be utilized for the realization of high-brightness LEDs.

Simultaneous balancing and sequencing of mixed-model parallel two-sided assembly lines

Growing interests from customers in customised products and increasing competitions among peers necessitate companies to configure their manufacturing systems more effectively than ever before. We propose a new assembly line system configuration for companies that need intelligent solutions to satisfy customised demands on time with existing resources. A mixed-model parallel two-sided assembly line system is introduced based on the parallel two-sided assembly line system previously proposed in the literature. The mixed-model parallel two-sided assembly line balancing problem is illustrated with examples from the perspective of simultaneous balancing and sequencing. An agent-based ant colony optimisation algorithm is proposed to solve the problem. This algorithm is the first attempt in the literature to solve an assembly line balancing problem with an agent-based ant colony optimisation approach. The algorithm is illustrated with an example and its operational procedures and principles are explained and discussed.

Parallel molecular computation of modular-multiplication with two same inputs over finite field GF(2n) using self-assembly of DNA tiles

Two major advantages of DNA computing – huge memory capacity and high parallelism – are being explored for large-scale parallel computing, mass data storage and cryptography. Tile assembly model is a highly distributed parallel model of DNA computing. Finite field GF(2n) is one of the most commonly used mathematic sets for constructing public-key cryptosystem. It is still an open question that how to implement the basic operations over finite field GF(2n) using DNA tiles. This paper proposes how the parallel tile assembly process could be used for computing the modular-square, modular-multiplication with two same inputs, over finite field GF(2n). This system could obtain the final result within less steps than another molecular computing system designed in our previous study, because square and reduction are executed simultaneously and the previous system computes reduction after calculating square. Rigorous theoretical proofs are described and specific computing instance is given after defining the basic tiles and the assembly rules. Time complexity of this system is 3n−1 and space complexity is 2n2.

Study and Evaluation of Innovative Fuel Handling Systems for Sodium-Cooled Fast Reactors: Fuel Handling Route Optimization

The research for technological improvement and innovation in sodium-cooled fast reactor is a matter of concern in fuel handling systems in a view to perform a better load factor of the reactor thanks to a quicker fuelling/defueling process. An optimized fuel handling route will also limit its investment cost. In that field, CEA has engaged some innovation study either of complete FHR or on the optimization of some specific components. This paper presents the study of three SFR fuel handling route fully described and compared to a reference FHR option. In those three FHR, two use a gas corridor to transfer spent and fresh fuel assembly and the third uses two casks with a sodium pot to evacuate and load an assembly in parallel. All of them are designed for the ASTRID reactor (1500 MWth) but can be extrapolated to power reactors and are compatible with the mutualisation of one FHS coupled with two reactors. These three concepts are then intercompared and evaluated with the reference FHR according to four criteria: performances, risk assessment, investment cost, and qualification time. This analysis reveals that the “mixed way” FHR presents interesting solutions mainly in terms of design simplicity and time reduction. Therefore its study will be pursued for ASTRID as an alternative option.

Horizontal Assembly of Single Nanowire Diode Fabricated by p-n Junction GaN NW Grown by MOCVD

Uniaxially p-n junction gallium nitride nanowires have been synthesized via metal‐organic chemical vapor deposition method. Nanowires prepared on Si(111) substrates were found to grow perpendicular to the substrate, and the transmission electron microscopy studies demonstrated that the nanowires had singlecrystalline structures with a <0001> growth axis. The parallel assembly of the p-n junction nanowire was prepared on a Si substrate with a thermally grown SiO2 layer. The transport studies of horizontal gallium nitride nanowire structures assembled from p‐ and n‐type materials show that these junctions correspond to well‐defined p-n junction diodes. The p-n junction devices based on GaN nanowires suspended over the electrodes were fabricated and their electrical properties were investigated. The horizontally assembled gallium nitride nanowire diodes suspended over the electrodes exhibited a substantial increase in conductance under UV light exposure. Apart from the selectivity to different light wavelengths, high responsivity and extremely short response time have also been obtained.

Transfer matrix method applied to the parallel assembly of sound absorbing materials.

The transfer matrix method (TMM) is used conventionally to predict the acoustic properties of laterally infinite homogeneous layers assembled in series to form a multilayer. In this work, a parallel assembly process of transfer matrices is used to model heterogeneous materials such as patchworks, acoustic mosaics, or a collection of acoustic elements in parallel. In this method, it is assumed that each parallel element can be modeled by a 2 × 2 transfer matrix, and no diffusion exists between elements. The resulting transfer matrix of the parallel assembly is also a 2 × 2 matrix that can be assembled in series with the classical TMM. The method is validated by comparison with finite element (FE) simulations and acoustical tube measurements on different parallel/series configurations at normal and oblique incidence. The comparisons are in terms of sound absorption coefficient and transmission loss on experimental and simulated data and published data, notably published data on a parallel array of resonators. From these comparisons, the limitations of the method are discussed. Finally, applications to three-dimensional geometries are studied, where the geometries are discretized as in a FE concept. Compared to FE simulations, the extended TMM yields similar results with a trivial computation time.

Pragmatic Approach for Assembly Lines Selection Based on Discrete-Event Simulation

AbstractThis paper presents a pragmatic approach to the study of the influence of tasks time variability in the performance of linear and parallel assembly lines. Discrete event simulation is used to assess the performance of several configurations for two assembly line balancing problems, and for four different levels of time variability. From the simulation studies, a set of equations were developed allowing the prediction of the assembly line performance, measured by the cycle time for common ALBPs, with considerable accuracy. These equations show the interactions between the sum of average task times, the balancing difficulty of the problem and the tasks time variability, as well as the number of workstations and their level of parallelism. With these equations it's possible to reduce the search for the best candidate solutions (number of workstations and level of parallelism) for a given target cycle time, considering the time variability level of the problem. With this approach, the assembly line designer is able to select beforehand the possible feasible solutions in a more practical way when using simulation software.

Design of Digital Receiver Based on FPGA

This article is intended to introduce electronic reconnaissance digital channelized receiver design ideas based on FPGA implementation structure. It takes the use of polyphase filter implementation of Achieved using the polyphase filter bank channelized receiver as the focus, and makes use of multiple parallel receiving channels to get the results of the simulation. The channelizing is realized in the FPGA device of xc4vsx55 which belongs to Virtex4 group in Xilinx family. During the process of design, highly effective polyphase and the parallel assembly line structure's FFT flexibility are fully considered, which reduce the operand enormously and raise the operating speed.

Evaluation on Parallel Assembly Sequence

Based on the parallelism of actual assembly sequence, a unified algorithm -"Optimal order reference set" is proposed for assembly performance membership degree calculation. An evaluation index system is established according to the requirements of practical assembly process. By using analytic hierarchy process for comprehensive evaluation of indexes, concrete application steps are verified through an example of a worm gear subassembly. Practical application shows that the new method satisfied the requirements of the integrity of index system and the parallelism of practical assembly sequence.

Integrated production and staff planning for heterogeneous, parallel assembly lines: an application in the automotive industry

We consider an integrated production and staff planning problem that occurs in the automotive industry. In particular, we focus on a production environment with heterogeneous, parallel assembly lines and search for a least cost schedule for producing a forecasted demand taking into account the application of volume flexibility instruments. The problem is modelled as a (non-linear) mixed-integer programme and solved by using dynamic programming. We present two case studies that are derived from real-world data in order to show the practical usability of our method. Compared to previous approaches presented in the literature, our dynamic programming method can achieve cost improvements of more than 10%.

Self-integration of nanowires into circuits via guided growth

The ability to assemble discrete nanowires (NWs) with nanoscale precision on a substrate is the key to their integration into circuits and other functional systems. We demonstrate a bottom-up approach for massively parallel deterministic assembly of discrete NWs based on surface-guided horizontal growth from nanopatterned catalyst. The guided growth and the catalyst nanopattern define the direction and length, and the position of each NW, respectively, both with unprecedented precision and yield, without the need for postgrowth assembly. We used these highly ordered NW arrays for the parallel production of hundreds of independently addressable single-NW field-effect transistors, showing up to 85% yield of working devices. Furthermore, we applied this approach for the integration of 14 discrete NWs into an electronic circuit operating as a three-bit address decoder. These results demonstrate the feasibility of massively parallel "self-integration" of NWs into electronic circuits and functional systems based on guided growth.

Chiral plasmonics of self-assembled nanorod dimers

Chiral nanoscale photonic systems typically follow either tetrahedral or helical geometries that require four or more different constituent nanoparticles. Smaller number of particles and different chiral geometries taking advantage of the self-organization capabilities of nanomaterials will advance understanding of chiral plasmonic effects, facilitate development of their theory, and stimulate practical applications of chiroplasmonics. Here we show that gold nanorods self-assemble into side-by-side orientated pairs and “ladders” in which chiral properties originate from the small dihedral angle between them. Spontaneous twisting of one nanorod versus the other one breaks the centrosymmetric nature of the parallel assemblies. Two possible enantiomeric conformations with positive and negative dihedral angles were obtained with different assembly triggers. The chiral nature of the angled nanorod pairs was confirmed by 4π full space simulations and the first example of single-particle CD spectroscopy. Self-assembled nanorod pairs and “ladders” enable the development of chiral metamaterials, (bio)sensors, and new catalytic processes.