Line Configuration Research Articles

An exact method to incorporate ergonomic risks in Assembly Line Balancing Problems

Since ergonomic risks related to the tasks performed by each worker are generally neglected when solving the Simple Assembly Line Balancing Problem (SALBP) or partially treated in post-processing, this paper aims to incorporate ergonomic issues natively in the decision process (ErgoSALBP). For such a problem, we present a novel Mixed-Integer Linear Programming (MILP) model that linearizes and incorporates into the SALBP the Occupational Repetitive Action (OCRA). This well-known method gives ergonomic risk indicators for musculoskeletal disorders. A lexicographical approach to address the problem is proposed, where the minimum number of stations is obtained for SALBP and used as a starting point to solve a type-F ErgoSALBP (feasibility problem) focused on satisfying the maximum ergonomic risk workload. Once the exact solution is found, we establish an objective function to smooth the ergonomic risk distribution among stations. We tested a total of 2160 instances with up to 297 tasks. Our method was able to solve 94% of all instances optimally. The share of solutions found with only green stations (the ideal ergonomic condition) was 87%, surpassing the state of the art. For the instances where the model did not converge to a solution within the time limit, we present a procedure to assess the optimality gap. Furthermore, the model can be embedded as a building block for other assembly line configurations. Finally, the results provide trade-off insights for managers: the average OCRA for the line improves as the cycle time increases, which may positively impact workers’ satisfaction and product quality in the long run.

On the Angular Control of Rotating Lasers by Means of Line Calculus on Hyperboloids.

We propose a new paradigm for modelling and calibrating laser scanners with rotation symmetry, as is the case for lidars or for galvanometric laser systems with one or two rotating mirrors. Instead of bothering about the intrinsic parameters of a physical model, we use the geometric properties of the device to model it as a specific configuration of lines, which can be recovered by a line-data-driven procedure. Compared to universal data-driven methods that train general line models, our algebraic-geometric approach only requires a few measurements. We elaborate the case of a galvanometric laser scanner with two mirrors, that we model as a grid of hyperboloids represented by a grid of 3×3 lines. This provides a new type of look-up table, containing not more than nine elements, lines rather than points, where we replace the approximating interpolation with exact affine combinations of lines. The proposed method is validated in a realistic virtual setting. As a collateral contribution, we present a robust algorithm for fitting ruled surfaces of revolution on noisy line measurements.

Investigation and design methods of a compact patch antennas using 3-D MMIC for various applications

This work focused on the design, characterization and investigation of GaAs based multi-layered compact 3D MMIC based antenna. Different patch antennas were designed and characterized along with its S-parameters. Two proposed models of multi-layered patch antenna using V-shaped feeder line and planar feeder line with a spiral transmission line in metal-2 were more compact in size and showed an improvement in performance based on bandwidth compared to the traditional planar feeder line configuration. This implies the proposed planar feed line with the spiral transmission is cost effective. The newly propose planar antenna with a spiral transmission feeder line is 49% more compact in area compared to using the normal planar feeder line. The new design also has wider bandwidth with a bandwidth of 2.99% as compared to the traditional planar with a bandwidth of 1.93%, better input return loss and a slightly lower resonance frequency. Similarly, another multilayer patch antenna was proposed using a V-shaped feeder line, This V-shaped feeder line antenna model showed a much lower resonance frequency (36.50 GHz) compared to normal planar (38.92GHz) and the planar with spiral transmission line model (38.52 GHz).

PROJECT-BASED LEARNING FOR ENGINEERING STUDENTS IN THE CONTEXT OF INDUSTRY 4.0: APPLICATION TO AUTOMOTIVE ASSEMBLY SYSTEM

AbstractFourth industrial revolution called Industry 4.0 has radically transformed production systems in manufacturing companies by the integration of emerging technologies. However, manufacturers must overcome several barriers, such as the lack of qualified talent to develop and manage various high-technology systems. Assembly system design aims to define proper assembly line configurations with the optimal performances to overcome increased competitiveness in the market. Nowadays, assembly system design should consider industry 4.0 concepts integration beyond traditional aspects like system balancing and sequencing. In this paper, we introduce a project-based learning approach to teach engineering students assembly system design taking into account industry 4.0 dimension. This project is carried out in collaboration with an industrial partner to design and implement car doors assembly line. The project demonstrated students interest and prepared them better for industry 4.0 era.

Suppression of bremsstrahlung losses from relativistic plasma with energy cutoff.

We study the effects of redistributing superthermal electrons on bremsstrahlung radiation from hot relativistic plasma. We consider thermal and nonthermal distribution of electrons with an energy cutoff in the phase space and explore the impact of the energy cutoff on bremsstrahlung losses. We discover that the redistribution of the superthermal electrons into lower energies reduces radiative losses, which is in contrast to nonrelativistic plasma. Finally, we discuss the possible relevance of our results for open magnetic field line configurations and prospects of the aneutronic fusion based on proton-boron-11 (p-B11) fuel.

Comparative study of spread and vertical mooring configuration in floating collar net cage under irregular waves and current

Offshore aquaculture is one of the national strategic programs of the Ministry of Fishery and Ocean Affairs of Indonesia to increase national fish cultivation capacity. One solution is using a simple flexible floating collar net which is suitable for small to medium cage volume. In designing such floating net, its mooring line configuration is vital to maintain fixed position of structural part of the cage volume. The purpose of this study is to compare design aspect of two types of mooring systems, i.e., spread and vertical configuration, by investigating selected parameters: mooring line tension, collar offset, and volume reduction. The mooring configuration and floating collar net cage are analysed through a numerical model based on Morison-force equations, under environmental condition adopted from Kangean field East Java. Load cases from collinearly in-line and between-line directions under extreme waves and current condition are checked against relevant safety factor. The dynamics analysis using the time domain simulation is based on 900 seconds cut-off according to its maximum wave elevation profile to generate the hydrodynamics forces to the mooring systems.

Evaluation on displacement risks of dismantling temporary lining in tunnel and optimization on temporary lining configuration

In tunnel engineering, the temporary lining is adopted as an effective countermeasure in mitigating tunnel failure potential, often featured by extra-large cross-sections and/or driven through weak ground conditions. However, dismantling temporary linings negatively impacts primary linings. In this paper, the comprehensive research is conducted on the displacement risk caused by dismantling temporary lining based on two alternative tunneling methods (TM-1 and TM-2). Besides, the following three influence factors are taken into consideration: the axial forces in temporary linings, the thickness of preliminary linings, and the deformation modulus of ground. After that, the tunneling method optimization plan is proposed from the view of these three influence factors. The results show that TM-1 always induces invert uplift, whereas TM-2 mainly brings about invert uplift or sidewall bulging depending on which transverse or vertical linings are dominant in terms of axial force values. For TM-2, the axial force in transverse linings can suppress the development of maximum deformation increment (MDI) value at invert when the axial forces in transverse linings are smaller than those in vertical linings. It is also found that with the further increase of the axial force in transverse linings in TM-2, MDI relocates to the sidewall. Moreover, on the basis of the displacement risk evaluations, an optimization on the temporary lining configurations has been developed by replacing temporary linings with pre-tension anchor cables to reduce the risk of dismantling temporary linings. All the research results can provide some important reference for the similar tunnel engineering in the future.

Non-Abelian Frame Charge Flow in Photonic Media

In PT-symmetric systems, the notion of non-Abelian frame charges enables multiband topological characterization of degeneracies by examining the eigenvector-frame rotations. Interestingly, some features of these frame charges can be viewed as an analog of electric charges confined in conducting wires, only that they flow in momentum space along nodal lines. But different from electric charges, these frame charges are not integers, and non-Abelian signatures emerge when braiding between adjacent band nodal lines occurs, which flips the direction of the flow. In photonic systems, the photonic Γ point serves as the source or sink of such a frame charge flow due to a hidden braiding induced by the often-ignored electrostatic mode at zero frequency. This source naturally generates non-Abelian topological signatures in PT-symmetric photonic systems that can be identified even in ordinary dielectric media. We use biaxial photonic crystals as examples to show how complex nodal line configurations can be explained as the topological consequences of the frame charge flow from the Γ point to the Brillouin zone boundaries. Our results reveal that non-Abelian band topology is intrinsically manifested in general photonic systems, making them easily accessible platforms for exploring non-Abelian physics.6 MoreReceived 11 September 2022Accepted 7 April 2023DOI:https://doi.org/10.1103/PhysRevX.13.021024Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMetamaterialsSymmetry protected topological statesTopological effects in photonic systemsAtomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Pathoanatomy of pertrochanteric fractures - a postmortem study

BackgroundRecent pathoanatomic studies based on 3D CT reconstructions have questioned validity of AO/OTA classification because it does not reflect the reality and requires revision. These 3D CT studies, however, do not allow analysis of all details. Therefore, we have exploited the possibility to analyze the pathoanatomy of pertrochanteric fractures on postmortem specimens. Material and methodsFrom the collection of the Institute of Anatomy, the authors obtained 16 specimens of hip joints of individuals who had sustained a pertrochanteric fracture and died within 30 days of the injury, with anteroposterior radiographs of the injured hip available in all of them. The number of major fragments and their shape, and the courses of the main fracture lines were studied. ResultsThree major fragments (a proximal head and neck fragment, a distal diaphyseal fragment and a posterior flat fragment), separated by three types of fracture lines (primary, secondary and tertiary lines) were identified. The primary line separated the proximal fragment (head and neck) from the distal diaphyseal fragment. The secondary fracture line separated the posterior flat fragment from the distal diaphyseal fragment. The tertiary fracture line split the posterior fragment into two parts. A key factor for fracture instability is the defect of the posterior cortex, which depends on the size and shape of the posterior fragment. Avulsion of the lesser trochanter and the adjacent cortex results in an unstable configuration of fracture lines on the medial side, while on the lateral side a large posterior fragment weakens the lateral trochanteric wall. ConclusionIn agreement with recent CT studies, the findings of this pathoanatomical study change, in a number of aspects, the traditional view of the pathoanatomy and classification of pertrochanteric fractures, and introduces the concept of three, instead of the traditional four, main fragments.

Design of fork-join networks of First-In-First-Out and infinite-server queues applied to clinical chemistry laboratories

This paper considers optimal design of queueing networks in which each node consists of a single-server FIFO queue and an infinite-server queue, which is referred to as incubation queue. Upon service completion at a FIFO queue, a job splits (forks) into two parts: the first part is routed to the next node on its route, and the second part is placed in the incubation queue. Routing of the jobs of multiple types is governed by a central decision maker that decides on the routes for each job type and aims to minimize the mean turnaround time of the jobs, i.e., the time spent in the system until service completion at the FIFO queue in the last node, and at all incubation queues on the job’s route, which may be viewed as a join operation. We provide explicit results for the turnaround time when all service and inter-arrival time distributions are exponential and invoke the Queueing Network Analyzer when these distributions are general. We then develop a Simulated Annealing approach to find the optimal routing configuration. We apply our approach to determine the optimal routing configuration in a chemistry analyzer line.

Dense Graphs Have Rigid Parts

While the problem of determining whether an embedding of a graph G in $${\mathbb {R}}^2$$ is infinitesimally rigid is well understood, specifying whether a given embedding of G is rigid or not is still a hard task that usually requires ad hoc arguments. In this paper, we show that every embedding (not necessarily generic) of a dense enough graph (concretely, a graph with at least $$C_0n^{3/2}(\log n)^{\beta }$$ edges, for some absolute constants $$C_0>0$$ and $$\beta $$ ), which satisfies some very mild general position requirements (no three vertices of G are embedded to a common line), must have a subframework of size at least three which is rigid. For the proof we use a connection, established in Raz (Discrete Comput. Geom. 58(4), 986–1009 (2017)), between the notion of graph rigidity and configurations of lines in $${\mathbb {R}}^3$$ . This connection allows us to use properties of line configurations established in Guth and Katz (Ann. Math. 181(1), 155–190 (2015)). In fact, our proof requires an extended version of Guth and Katz result; the extension we need is proved by János Kollár in an appendix to our paper. We do not know whether our assumption on the number of edges being $$\Omega (n^{3/2}\log n)$$ is tight, and we provide a construction that shows that requiring $$\Omega (n\log n)$$ edges is necessary.

We’re Not Gonna Break It! Consistency-Preserving Operators for Efficient Product Line Configuration

When configuring a software product line, finding a good trade-off between multiple orthogonal quality concerns is a challenging multi-objective optimisation problem. State-of-the-art solutions based on search-based techniques create invalid configurations in intermediate steps, requiring additional repair actions that reduce the efficiency of the search. In this work, we introduce <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">consistency-preserving configuration operators</i> (CPCOs)—genetic operators that maintain valid configurations throughout the entire search. CPCOs bundle coherent sets of changes: the activation or deactivation of a particular feature together with other (de)activations that are needed to preserve validity. In our evaluation, our instantiation of the IBEA algorithm with CPCOs outperforms two state-of-the-art tools for optimal product line configuration in terms of both speed and solution quality. The improvements are especially pronounced in large product lines with thousands of features.

Coupled aero-hydro-servo-elastic analysis of 10MW TLB floating offshore wind turbine

This paper presents a fully coupled aero-hydro-servo elastic analysis of a 10MW offshore wind turbine supported by a tension leg buoy (TLB) platform, with a taut mooring system. The study investigates the TLB's dynamic response characteristics under the northern North Sea environmental conditions with water depths of 110 metres, comparing the performance of steel, polyester, and nylon mooring line configurations. Innovating floating wind turbines requires a cost-effective system that achieves reliable performance in operational and survival conditions. The innovative system should compete with other existing FOWT types and fixed-bottom offshore wind turbines in terms of LCOE. The dynamic responses of the relatively less complex TLB platform in terms of construction and installation showed small motion and accelerations for all available mooring materials from the current supply chain, enabling the wind turbine to be installed without significant modifications to their control systems. The mooring materials' elasticity is essential in the system achieving motion response.

The Analysis of Production Line Balance Using the Moodie Young Method at X Inc.

The goal of this study is to determine how much the level of efficiency the production line at PT. X by using the Moodie young approach. The three components of the method - Line Efficiency, Balance Delay, and Smooth Index - are utilized to assess the degree of balance in the manufacturing line. The findings indicated that there were 5 work stations with 7 work elements in the real production line configuration, with a Line Efficiency of 40.29%, a Balance Delay of 59.70%, and a Smoothness Index of 9578.22. As a consequence of the research utilizing the Moodie Young approach, the new production lines are composed of 3 work stations with 7 work elements and a Line Efficiency result of 67.15%, Balance Delay of 32.84%, and Smoothness Index of 4449.71. Keywords: Line Balancing, Moodie Young, Line Efficiency, Balance Delay, Smooth Index

Integrity assessment of the mooring lines and risers of floating production systems based on numerical models generated by retroanalysis of measured data: PART II – Integrity Assessment

This work describes an integrity assessment methodology that considers field monitoring and inspection activities that gather information regarding the actual configuration of the mooring lines and risers of floating production systems (FPS). The first stage consists of calibrating numerical models representing the updated as-laid configuration, comprising “digital twins” of the FPS. Then, in the remaining stages, these models are employed to perform a series of uncoupled, hybrid and fully coupled analyses that provide the platform offsets, and the structural response of the mooring lines and risers. These are expressed in terms of offset diagrams (polar diagrams comprised by the envelope of maximum platform excursions); and the safe operational zone (SAFOP) for the risers (polar diagrams defining the envelope of safe horizontal excursions within which the riser top connections must remain to avoid violation of any riser design criterion). The integrity is assessed by comparing the SAFOP and offset diagrams, and comparing the maximum mooring line tensions with their corresponding limit values. Mitigation and contingency procedures are then recommended whenever the integrity of one or more mooring lines or risers is compromised, involving redesign steps and field interventions to adjust the as-laid configuration and return the system to a safe operational condition.

Integrity assessment of the mooring lines and risers of floating production systems based on numerical models generated by retroanalysis of measured data: PART I – Retroanalysis procedure

In the offshore oil production industry, information regarding the actual configuration of the mooring lines and risers of floating production systems (FPS) is periodically collected from field observations and surveys using remotely operated vehicles (ROVs). Taking advantage of such information, this work presents a retroanalysis procedure that updates and calibrates numerical models to represent the updated as-laid configuration of the FPS. This procedure has been implemented in association with the in-house, non-commercial SITUA-Prosim software that employs uncoupled, fully coupled and hybrid analysis formulations. The steps of the procedure are automated within the software. The application of the procedure is illustrated in a case study considering a typical FPS representative of actual offshore scenarios. This retroanalysis procedure may be seen as the first stage for the development of a digital twin for FPS, and for the establishment of an integrity assessment methodology using the updated as-laid models. The integrity of the system can be continuously reassessed by performing a series of analyses to check whether the appropriate design criteria of mooring lines and risers are still being met.

Fracture Strength of Thin Monolithic Zirconia Crowns with Varying Thickness and Configuration of Finish LinesAn In Vitro Study

Aim- The current study sought to assess the fracture strength of thin monolithic zirconia crowns of varying thickness and finish line configuration. Study design- The current study was carried out to evaluate and compare the fracture strength of monolithic zirconia crowns with chamfers and radial shoulder finish lines of 0.5, 0.8, and 1.1 mm thickness. Result- Monolithic zirconia crowns with merely 0.5 mm reduction demonstrated adequate strength for use in posterior areas. On evaluation and comparison it was observed that no statistically significant difference was found in the fracture strength of monolithic zirconia crowns with different thicknesses and finish lines was investigated. Conclusion- The 0.5 mm thickness of monolithic zirconia crowns demonstrated significant fracture resistance to withstand physiological performance, regardless of finish line type.

Experimental realization of multimode nonlinear parametric amplification from cascading four-wave mixing of dressed atoms.

The nonlinear parametric process is of great significance for achieving high-quality coherent optical signals and quantum correlated photons. With the development of classical and quantum information processing, the study of the properties of parametric processes is evolving in complex scenarios of multimode, which is limited in conventional nonlinear media due to strict phase matching, e.g. nonlinear crystals. Here we study the dressing-energy-level-cascaded four-wave mixing process to generate multimode optical parametric signals. Via cascading double-Λ type configuration of 85Rb D1 line, the non-degenerate energy-level-cascaded FWM is constructed to generate multimode self-parametric amplification. Moreover, with the dressing effects based on atomic coherence, the spatial and frequency multimode characteristics of energy-level-cascaded FWM parametric amplification, i.e., the modes number and pattern, are actively modulated by the pump fields detuning. Also, the spatial modes from the coupling of two coexisting spontaneous parametric FWMs can be controlled to reach tremendous scalability via the atomic coherence and Kerr non-linearity. The atomic coherence effects and unique phase-matching symmetry nature allow flexible modulation of the multimode property of the generated parametric signals within a nonlinear device, which paves a way for multimode classical and quantum information processing.

Optimizing task reassignments for reconfigurable multi-model assembly lines with unknown order of product arrival

This paper deals with the multi-model assembly line balancing problem (MuMALBP) in a reconfigurable environment. The considered line is composed of a fixed number of workstations and can produce different products in batches. Each product requires an appropriate line configuration. Thus, when the product changes, the line has to be reconfigured to satisfy new requirements related to task precedence and cycle time constraints. Reconfiguring the line consists in reassigning certain tasks between the existing workstations. The objective of this paper is to design a line configuration for each product while minimizing the maximum number of task reassignments whatever the sequence of product arrival. To solve this NP-hard problem, a mixed-integer linear program (MILP) is first formulated. Subsequently, a constructive heuristic and a MILP-based heuristic, named Halt-and-Fix, are developed to solve large-size problem instances. All the approaches are tested and approved on a dataset derived from the well-known instances of the assembly line balancing literature. The numerical results show that the Halt-and-Fix heuristic provides a better trade-off between solution quality and CPU time, compared to the constructive heuristic and the MILP formulation.

Wave-induced structural response analysis of the supporting frames for multiconnected offshore floating photovoltaic units installed in the inner harbor

In this study, a hydrodynamics-based structural response analysis procedure of supporting frames for multiconnected offshore floating photovoltaics (FPVs) is suggested. Based on the suggested simulation methodology, the dynamic behavioral characteristics of the system were investigated. First, rational mooring types for FPVs installed in the inner harbor were studied based on the analysis results. Subsequently, extensive parametric studies have been conducted to determine a rational design strategy for dynamic response mitigation. In this study, the effects of the initial configuration and axial stiffness of taut mooring lines, arrangement angles of FPV systems, and floater dimensions on the static and dynamic responses of supporting frames under irregular waves in the inner harbor were studied. The corner module in the multiconnected system showed critical responses among others, the investigation of which is required for safety evaluation. Furthermore, it was observed that the mooring stiffness governed the overall stiffness of the system, which was proportional to the mitigation of the dynamic responses. Finally, the unsupported length of the frame, which was defined by the floater size, was found to be the key parameter for the mitigation of structural responses.