5,000 research outputs found
Editorial Parts Feeding system for Assembly:macro and micro logistics
No full textAssembly is the last phase in the process of production and involves hundreds and even thousands of different parts. Even the
omission of a single part is enough to make the product defective. Therefore, an inventory is made for each part type. Acquiring,
handling and managing a multitude of inventories is a significant burden with significant cost, both ofwhich are much higher in cases
where multiple productversions are assembled on the same assembly line.
In today's market, the intense competition drives producers to cater to different market segments by offering a larger variety of
products. This growth in product variety is broad, but applies slronglyto the assembled products. Changes in demand, volume and
product mix, as well as the appearance of new product models and components, require a proper, flexible assembly system.
Therefore, successful assembly systems design and management must deliver efficient, flexible systems that can deal with product
variety and changes in product volume and mix. A crucial part of such a system is the part supply and part feeding.
With an increasing productvariely, thousands of different parts need to be delivered just-in-time (JIT) to a multitude of assembly
stations. Some of the issues which have to be addressed are: high number of parts managed, mixed-model production, variety of
Darts' sha~esan d sizes, limited sDace at assemblv stations and mani~ulationo f a wide varietv of ~ a r t t v ~deusri ng the assemblv.
Forming efficient part-supply and'part-feeding mechanisms presents an important challenge kced by today's assembly systems.
These are crucial factors in making an assembly business sustainable and competitive
Derandomized Squaring: An Analytical Insight into Its True Behavior
No full textThe notion of the derandomized square of two graphs, denoted as G s H, was introduced by Rozenman and Vadhan as they rederived Reingold’s Theorem, SL = . This pseudorandom primitive, closely related to the Zig-Zag product, plays a crucial role in recent advancements on space-bounded derandomization. For this and other reasons, understanding the spectral expansion λ(G s H) becomes paramount. Rozenman and Vadhan derived an upper bound for λ(G s H) in terms of the spectral expansions of the individual graphs, λ(G) and λ(H). They also proved their bound is optimal if the only information incorporated to the bound is the spectral expansion of the two graphs.
The objective of this work is to gain deeper insights into the behavior of derandomized squaring by taking into account the entire spectrum of H, where we focus on a vertex-transitive c-regular H. Utilizing deep results from analytic combinatorics, we establish a lower bound on λ(G s H) that applies universally to all graphs G. Our work reveals that the bound is the minimum value of the function d⋅ x - d(d-1)χ_x(H)/χ_x'(H) in the domain (c,∞), where χ_x(H) is the characteristic polynomial of the d-vertex graph H. This bound lies far below the known upper bound for λ(G s H) for most reasonable choices for H. Empirical evidence suggests that our lower bound is optimal. We support the tightness of our lower bound by showing that the bound is tight for a class of graphs which exhibit local behavior similar to a derandomized squaring operation with H. To this end, we make use of finite free probability theory.
In our second result, we resolve an open question posed by Cohen and Maor (STOC 2023) and establish a lower bound for the spectral expansion of rotating expanders. These graphs are constructed by taking a random walk with vertex permutations occurring after each step. We prove that Cohen and Maor’s construction is essentially optimal. Unlike our results on derandomized squaring, the proof in this instance relies solely on combinatorial methods. The key insight lies in establishing a connection between random walks on graph products and the Fuss-Catalan numbers
Hierarchy of Smart Awareness in Assembly 4.0 Systems
No full textSelf-awareness and awareness as a whole are important components of artificial intelligence (AI). In particular, awareness is a central pillar of Industry 4.0. This paper reviews the literature related to smart awareness of machines and parts, and draws the hierarchy of smart awareness evolution. The paper suggests an ordered hierarchy of awareness starting with the single sensor and ending with a machinecell. The paper discuss the awareness issues related to entities in various awareness types, such as: selfawareness, through self-configuration, self-healing, and self-organizing. The paper discusses the issues related to the awareness of: sensors, parts, sub-assemblies, products, machines, and machine cells. These entities have some awareness differences and some awareness similarities discussed in this paper
Determining manager's load & control span by modeling management as a service activity
No full textThis paper shows how a production foreman and line managers can be modeled as giving variety of services. The model is essentially a queueing model with arrivals, waiting time and service. The model is first analyzed in the most general way finding the mean values of waiting times and queue length. Different management environment may have very different requirements. Our proposed model gives a good modeling solution to a variety of management styles and environments. Then, a simpler model for the control span of an assembly line foreman is developed and illustrated using a numerical example
Modeling a manager’s work as a service activity
No full textPlanning of manager’s workload is an elusive and challenging issue that has no exact quantitative tools. This paper develops for the first time (to the best of our knowledge) an analytical model that shows how a manager’s activity and its associated workload can be analyzed as a provision of various services. The model is essentially a queuing model of tasks with arrivals, waiting time, and services (with a single server). The model is first analyzed in the most general way, finding the mean values of waiting times and queue length. While the proposed model is for one manager, it is based on very general assumptions and would fit most practical environments. Then, a simpler model for determining the optimal span of control for a manager is developed and illustrated using a numerical exampl
Vocal Communication Between Cobots and Humans to Enhance Productivity and Safety: Review and Discussion
No full textThis paper explores strategies for fostering efficient vocal communication and collaboration between human workers and collaborative robots (cobots) in assembly processes. Vocal communication enables the division of attention of the worker, as it frees their visual attention and the worker’s hands, dedicated to the task at hand. Speech generation and speech recognition are pre-requisites for effective vocal communication. This study focuses on cobot assistive tasks, where the human is in charge of the work and performs the main tasks while the cobot assists the worker in various peripheral jobs, such as bringing tools, parts, or materials, and returning them or disposing of them, or screwing or packaging the products. A nuanced understanding is necessary for optimizing human–robot interactions and enhancing overall productivity and safety. Through a comprehensive review of the relevant literature and an illustrative example with worked scenarios, this manuscript identifies key factors influencing successful vocal communication and proposes practical strategies for implementation
Real Time Locating System for a Learning Cross-Docking Warehouse
No full textReal time locating systems (RTLS) represent today an established and reliable technology to identify, track and
monitor, in real time with any human commitment, the dynamic evolution of the spatial location of tagged entities
inside factory layout. This results in more effective and continuous monitoring of products, stock-keeping units
(SKU), and vehicles of production plants or logistic facilities. This paper targets the adoption of such RTLS in
warehousing systems focusing on the related learning opportunities to enhance the efficacy and the productivity
of the storage process which have consistent externalities during the order picking. For this purpose, a crossdocking warehouse is equipped with an ultrawideband (UWB)-based RTLS to track any forklifts traveling
activities and SKU dynamic locations. A set of relevant data is automatically generated by the interactions
between the transmitters, which are installed on board of the forklifts and connected to the SKU barcode readers,
and the receivers, which are displaced in fixed positions all over the warehouse layout for optimizing the data
transmissions. Furthermore, to yield further insights into the performed storage and retrieval operations, the daily
incoming and outcoming shipping orders are also considered at the detail level of every single SKU. All this
relevant information is merged into a unique database that evolves in real time representing the dynamic evolution
of the warehouse operations over time. A digital representation of the physical storage system is developed to
leverage such relevant datasets through adequate data analysis algorithms. A set of quantitative key performance
indicators is evaluated, and suggestions are automatically offered to the warehouse manager to improve the
storage system efficiency. The implementation of such modification, through a feedback loop, is to offer the
unique opportunity to such warehousing system to analytically learn by its process’s underperformances, as well
as to evaluate the efficacy and efficiency of the corrective actions suggested by the developed algorithms
User-centred design in public transport: Discovering mobile user needs
No full textIn recent years, the design of mobile transportation apps has become a key area for cities and transport operators. However, less common is user research for the purpose of informing design. This paper reports findings from a mixed-method user study, which examined journey planning habits, usability of commercially available mobile transportation apps, and attitudes towards probabilistic recommendation (‘predictive’) digital journey planners. The study is part of a project aimed at incorporating a structured user-centred design process in the design of mobile apps for transportation,with study methodology intended to serve as an exemplar for future user-centred mobile app projects.Such a process is important for ensuring that transport apps are as successful as possible in meeting passenger needs. Findings will inform a later mobile app prototype, based on key design implications identified in the study: designing for distinct user groups, trust, user context, and adapting user research methods in transportation
Going Online: Entrepreneurial Peer Networks in a Startup Accelerator before and during the Covid-19 Pandemic
No full textStartup accelerators – fixed-term, cohort-based entrepreneurship program(s) – aim to support entrepreneurial activity (Bergman & McMullen, 2021; Chan et al., 2020; Cohen & Hochberg, 2014; Dushnitsky & Sarkar, 2018). Key to this support is accelerators’ ability to create “social capital surrounding entrepreneurial efforts” (Hochberg, 2016, p. 33). To do so, accelerators invest significant resources in facilitating a supportive peer environment and forging social networks among entrepreneurs through an array of formal and informal social events such as weekly dinners or guest speakers but also through the unique cohort approach that has entrepreneurs from different teams work alongside throughout the program (Cohen, 2013; Cohen & Hochberg, 2014). The resulting peer entrepreneur networks are powerful conduits to the flow of resources that include knowledge, advice, referrals, but also emotional support, generally representing one of the most important mechanisms through which accelerators deliver value (e.g., Amezcua et al., 2013; Hallen et al., 2020; Yu, 2020)
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