33 research outputs found
Sistemas de colas en tiempo discreto con entradas y servicios en bloque: estudio teórico y simulaciones comparativas
Los sistemas de colas se vienen estudiando desde inicios del siglo XX. Suele formarse una cola ante una instalación que proporciona determinado servicio. La teoría de colas pretende estudiar las fluctuaciones que se producen en estas situaciones: el número de clientes, el tiempo que debe esperar cada uno antes de ser atendido, la duración del tiempo de servicio …
En este trabajo se plantean algunos modelos de colas con un solo servidor en los que los clientes llegan y son atendidos en grupos, no necesariamente del mismo tamaño. El estudio se hace mediante simulación y mediante análisis probabilístico y se comparan los resultados obtenidos por ambos procedimientos.
Se mide la eficiencia de cada modelo en términos de acumulación de clientes y tiempos de espera de acuerdo con los parámetros que los gobiernan. También se comparan las eficiencias de los modelos planteados
Application of Optimization in Production, Logistics, Inventory, Supply Chain Management and Block Chain
The evolution of industrial development since the 18th century is now experiencing the fourth industrial revolution. The effect of the development has propagated into almost every sector of the industry. From inventory to the circular economy, the effectiveness of technology has been fruitful for industry. The recent trends in research, with new ideas and methodologies, are included in this book. Several new ideas and business strategies are developed in the area of the supply chain management, logistics, optimization, and forecasting for the improvement of the economy of the society and the environment. The proposed technologies and ideas are either novel or help modify several other new ideas. Different real life problems with different dimensions are discussed in the book so that readers may connect with the recent issues in society and industry. The collection of the articles provides a glimpse into the new research trends in technology, business, and the environment
Graph Partitioning of Transportation Networks under Disruption
This research is concerned with providing a solution capable of treating network complexity and scalability effectively so that it overcomes administrative, environmental and technique boundaries. One good approach dealing with this matter is applying graph partitioning techniques. Graph partitioning is an optimization problem with the aim of dividing a large geographical network into manageable size districts called sub-networks with less complexity in favor of balancing the workload and minimizing the communication among them, with the aim of maximizing their independency as much as possible. Over the past decades various models have been developed in such a way to satisfy a multi-objective problem such as delivery time and managerial cost. In real life, due to inevitable changes during network’s lifetime, it is vital to offer survivability and resilience in the existence of network failure and disruption. Further, it is essential to maintain functionality in critical facilities and high priority connections in the time of crisis. This paper suggests four partitioning techniques namely “Hierarchical recursive progression1^+ “(HRP1^+) and “Hierarchical recursive progression2^+ “(HRP2^+) and their extensions called “HRP1^+control” and “HRP2^+control” to solve the scalability as well as complexity of a network. For this matter, the initial balanced partition is produced on a predefined network. Furthermore two different approaches namely “complete failure update “and “partial failure update” are proposed and demonstrated in the occurrence of network disruption.
In sum, the three main objectives of this thesis are as follows:
Modeling disruption on logistics networks
Assuring and strengthen connectivity in the disrupted network for routing purposes
Developing partitioning approaches in favor of generating roughly equal sized and balanced partitions in the disrupted network
Architecting Fail-Safe Supply Chains / Networks
Disruptions are large-scale stochastic events that rarely happen but have a major effect on supply networks’ topology. Some examples include: air traffic being suspended due to weather or terrorism, labor unions strike, sanctions imposed or lifted, company mergers, etc. Variations are small-scale stochastic events that frequently happen but only have a trivial effect on the efficiency of flow planning in supply networks. Some examples include: fluctuations in market demands (e.g. demand is always stochastic in competitive markets) and performance of production facilities (e.g. there is not any perfect production system in reality).
A fail-safe supply network is one that mitigates the impact of variations and disruptions and provides an acceptable level of service. This is achieved by keeping connectivity in its topology against disruptions (structurally fail-safe) and coordinating the flow through the facilities against variations (operationally fail-safe). In this talk, I will show that to have a structurally fail-safe supply network, its topology should be robust against disruptions by positioning mitigation strategies and be resilient in executing these strategies. Considering “Flexibility” as a risk mitigation strategy, I answer the question “What are the best flexibility levels and flexibility speeds for facilities in structurally fail-safe supply networks?” Also, I will show that to have an operationally fail-safe supply network, its flow dynamics should be reliable against demand- and supply-side variations. In the presence of these variations, I answer the question “What is the most profitable flow dynamics throughout a supply network that is reliable against variations?” The method is verified using data from an engine maker. Findings include: i) there is a tradeoff between robustness and resilience in profit-based supply networks; ii) this tradeoff is more stable in larger supply networks with higher product supply quantities; and iii) supply networks with higher reliability in their flow planning require more flexibilities to be robust. Finally, I will touch upon possible extensions of the work into non-profit relief networks for disaster management
Communities and food supply: looking at their intersection
There is an extended opinion that Food Supply Chains (FSCs) create economic value; usually by aligning different actors along the chain. However, for food microproducers, economic value is not necessarily the main driver to engage with FSCs. This opens up the discussion towards how to build FSCs with potential members that do not always recognise practical advantages in working with others. We propose explore previous research done in the area of Community Operational Research (COR) by looking microproducers not as links constituting a chain, where the weakest is removed for the benefit of the rest. We explore if there are benefits from being members from a community (Food Supply Communities, FSComs), where they identify which individual actions contribute to the collective self-construction, and vice versa. To contextualise the discussion, we use the case of a typical UK regional, county-based food marketing group which provides umbrella marketing support for specialist SMEs
OR in search for community
This year’s Keynote has a special format. The interest in Community OR has taken the form of a new Special
Interest Group that is presently taking shape. To contribute to a better understanding of the variety of interest
that is being incorporated, we have invited a number of people to present their ideas as short presentations
or pitches. Below you will find an outline of what we have today. These may help to summarise the current
thinking and (research) practices in Community OR. The presentations will be followed by a panel discussion.
Social Innovation and Community OR Communities are the main addressees for sustainable change and
improvement, at least in the European Union. There are some considerable difficulties here, as the cry for
policies that are effective in delivering this change is getting stronger and communities are getting better in
avoiding being addressed as stooges. At present OR explores contributions to the policy problem (see the
new SIG for Social Policy). It is argued that policy should be supportive to community level activities and
initiatives, rather than the reverse, if social innovation is to be promoted. Examples are presented. Organising
Suppliers: Chain or commune? Economy-based supplier structures are organised under drivers that aim at the
alignment of goals and the optimisation of resources available; however, this does not seem to apply to any
size of business. Observations on microbusinesses suggest that they do not strive for economic drivers only.
Lifestyle, family and other non-economic drivers are also part of their strategic decision making processes.
Different snapshots about UK and Mexican microbusinesses are used to illustrate possibilities that supply
chains and communities may provide. Community OR ideas are used as a framework for the comparison
Safety and Reliability - Safe Societies in a Changing World
The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management
- mathematical methods in reliability and safety
- risk assessment
- risk management
- system reliability
- uncertainty analysis
- digitalization and big data
- prognostics and system health management
- occupational safety
- accident and incident modeling
- maintenance modeling and applications
- simulation for safety and reliability analysis
- dynamic risk and barrier management
- organizational factors and safety culture
- human factors and human reliability
- resilience engineering
- structural reliability
- natural hazards
- security
- economic analysis in risk managemen
Flight delay-cost simulation analysis and airline schedule optimization
In order to meet the fast-growing demand, airlines have applied much more compact air-fleet operation schedules which directly lead to airport congestion. One result is the flight delay, which appears more frequently and seriously; the flight delay can also significantly damage airline's profitability and reputation The aim of this project is to enhance the dispatch reliability of Australian X Airline's fleet through a newly developed approach to reliability modeling, which employs computer-aided numerical simulation of the departure delay distribution and related cost to achieve the flight schedule optimization. The reliability modeling approach developed in this project is based on the probability distributions and Monte Carlo Simulation (MCS) techniques. Initial (type I) delay and propagated (type II) delay are adopted as the criterion for data classification and analysis. The randomicity of type I delay occurrence and the internal relationship between type II delay and changed flight schedule are considered as the core factors in this new approach of reliability modeling, which compared to the conventional assessment methodologies, is proved to be more accurate on the departure delay and cost evaluation modeling. The Flight Delay and Cost Simulation Program (FDCSP) has been developed (Visual Basic 6.0) to perform the complicated numerical calculations through significant amount of pseudo-samples. FDCSP is also designed to provide convenience for varied applications in dispatch reliability modeling. The end-users can be airlines, airports and aviation authorities, etc. As a result, through this project, a 16.87% reduction in departure delay is estimated to be achieved by Australian X Airline. The air-fleet dispatch reliability has been enhanced to a higher level - 78.94% compared to initial 65.25%. Thus, 13.35% of system cost can be saved. At last, this project also achieves to set a more practical guideline for air-fleet database and management upon overall dispatch reliability optimization