EUROPEAN CONFERENCE ON QUEUEING THEORY 2016

International audienceThis booklet contains the proceedings of the second European Conference in Queueing Theory (ECQT) that was held from the 18th to the 20th of July 2016 at the engineering school ENSEEIHT, Toulouse, France. ECQT is a biannual event where scientists and technicians in queueing theory and related areas get together to promote research, encourage interaction and exchange ideas. The spirit of the conference is to be a queueing event organized from within Europe, but open to participants from all over the world. The technical program of the 2016 edition consisted of 112 presentations organized in 29 sessions covering all trends in queueing theory, including the development of the theory, methodology advances, computational aspects and applications. Another exciting feature of ECQT2016 was the institution of the Takács Award for outstanding PhD thesis on "Queueing Theory and its Applications"

Queueing Variables and Leave-Without-Treatment Rates in the Emergency Room

Hospitals stand to lose millions of dollars in revenue due to patients who leave without treatment (LWT). Grounded in queueing theory, the purpose of this correlational study was to examine the relationship between daily arrivals, daily staffing, triage time, emergency severity index (ESI), rooming time, door-to-provider time (DTPT), and LWT rates. The target population comprised patients who visited a Connecticut emergency room between October 1, 2017, and May 31, 2018. Archival records (N = 154) were analyzed using multiple linear regression analysis. The results of the multiple linear regression were statistically significant, with F(9,144) = 2902.49, p \u3c .001, and R2 = 0.99, indicating 99% of the variation in LWT was accounted for by the predictor variables. ESI levels were the only variables making a significant contribution to the regression model. The implications for positive social change include the potential for patients to experience increased satisfaction due to the high quality of care and overall improvement in public health outcomes. Hospital leaders might use the information from this study to mitigate LWT rates and modify or manage staffing levels, time that patients must wait for triage, room placement, and DTPT to decrease the rate of LWT in the emergency room

Uma análise usando teoria de filas do problema de carregamento de pedidos no porto para abastecimento de unidades marítimas de exploração e produção de petróleo

This thesis deals with a supply system comprised of a maritime installation and a fleet of vessels that work together to deliver supply requests to offshore installations. The problem was formulated by a GI/M/S model that considers the port environment, that is, the berths are the servers, and an M/M/S model that considers the maritime environment, that is, vessels are the servers. To address the GI/M/S model, an embedded Markov chain approach was proposed whereby the states space was divided into two subsets, one representing the fully busy system and the other accounting for the situations when the system is partially idle. That representation enabled to find an analytical solution for the fully busy system, which can be combined with simple absorption analysis in the remaining states to derive the exact solution to the steady state probability equations. This contrasts with the classical approach of truncating the state space to find the approximate steady state probabilities. The M/M/S approach at the second installation enabled to address the fleet sizing problem and find solutions based on the occupancy rates of the vessels and the waiting time for impending requests.Esta tese trata de um sistema de abastecimento composto por uma instalação marítima e uma frota de embarcações que trabalham em conjunto na entrega de pedidos, para o suprimento das unidades offshore. Formulou-se o problema por um modelo GI/M/S que considera o ambiente do porto, isto é, os berços são os servidores, e um modelo M/M/S que considera o ambiente marítimo, isto é, os barcos são os servidores. Para abordar o modelo GI/M/S, propôs-se uma abordagem de cadeia de Markov embutida, em que os estados foram divididos em dois subconjuntos, um representando o sistema totalmente ocupado e outro descrevendo as situações em que o sistema está parcialmente ocioso. Essa representação permitiu encontrar uma solução analítica para o sistema totalmente ocupado, que pode ser combinado com uma análise de absorção simples nos estados restantes para derivar a solução exata para as equações de probabilidade no estado estacionário. Isso contrasta com a abordagem clássica de truncar o espaço de estados para encontrar probabilidades aproximadas de estado estacionário. A abordagem M/M/S na segunda instalação permitiu abordar o problema de dimensionamento da frota e encontrar soluções baseadas nas taxas de ocupação das embarcações e no tempo de espera para pedidos iminentes

Planning and Routing Algorithms for Multi-Skill Contact Centers

Koole, G.M. [Promotor

A Tutorial on Mathematical Modeling of 5G/6G Millimeter Wave and Terahertz Cellular Systems

Millimeter wave (mmWave) and terahertz (THz) radio access technologies (RAT) are expected to become a critical part of the future cellular ecosystem providing an abundant amount of bandwidth in areas with high traffic demands. However, extremely directional antenna radiation patterns that need to be utilized at both transmit and receive sides of a link to overcome severe path losses, dynamic blockage of propagation paths by large static and small dynamic objects, macro-and micromobility of user equipment (UE) makes provisioning of reliable service over THz/mmWave RATs an extremely complex task. This challenge is further complicated by the type of applications envisioned for these systems inherently requiring guaranteed bitrates at the air interface. This tutorial aims to introduce a versatile mathematical methodology for assessing performance reliability improvement algorithms for mmWave and THz systems. Our methodology accounts for both radio interface specifics as well as service process of sessions at mmWave/THz base stations (BS) and is capable of evaluating the performance of systems with multiconnectivity operation, resource reservation mechanisms, priorities between multiple traffic types having different service requirements. The framework is logically separated into two parts: (i) parameterization part that abstracts the specifics of deployment and radio mechanisms, and (ii) queuing part, accounting for details of the service process at mmWave/THz BSs. The modular decoupled structure of the framework allows for further extensions to advanced service mechanisms in prospective mmWave/THz cellular deployments while keeping the complexity manageable and thus making it attractive for system analysts.publishedVersionPeer reviewe

A Tutorial on Mathematical Modeling of 5G/6G Millimeter Wave and Terahertz Cellular Systems

Millimeter wave (mmWave) and terahertz (THz) radio access technologies (RAT) are expected to become a critical part of the future cellular ecosystem providing an abundant amount of bandwidth in areas with high traffic demands. However, extremely directional antenna radiation patterns that need to be utilized at both transmit and receive sides of a link to overcome severe path losses, dynamic blockage of propagation paths by large static and small dynamic objects, macro-and micromobility of user equipment (UE) makes provisioning of reliable service over THz/mmWave RATs an extremely complex task. This challenge is further complicated by the type of applications envisioned for these systems inherently requiring guaranteed bitrates at the air interface. This tutorial aims to introduce a versatile mathematical methodology for assessing performance reliability improvement algorithms for mmWave and THz systems. Our methodology accounts for both radio interface specifics as well as service process of sessions at mmWave/THz base stations (BS) and is capable of evaluating the performance of systems with multiconnectivity operation, resource reservation mechanisms, priorities between multiple traffic types having different service requirements. The framework is logically separated into two parts: (i) parameterization part that abstracts the specifics of deployment and radio mechanisms, and (ii) queuing part, accounting for details of the service process at mmWave/THz BSs. The modular decoupled structure of the framework allows for further extensions to advanced service mechanisms in prospective mmWave/THz cellular deployments while keeping the complexity manageable and thus making it attractive for system analysts.publishedVersionPeer reviewe

An Operations Research approach to aviation security

Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2005.Includes bibliographical references (p. 151-163).Since the terrorist attacks of September 11, 2001, aviation security policy has remained a focus of national attention. We develop mathematical models to address some prominent problems in aviation security. We explore first whether securing aviation deserves priority over other potential targets. We compare the historical risk of aviation terrorism to that posed by other forms of terrorism and conclude that the focus on aviation might be warranted. Secondly, we address the usefulness of passenger pre-screening systems to select potentially high-risk passengers for additional scrutiny. We model the probability that a terrorist boards an aircraft with weapons, incorporating deterrence effects and potential loopholes. We find that despite the emphasis on the pre-screening system, of greater importance is the effectiveness of the underlying screening process. Moreover, the existence of certain loopholes could occasionally decrease the overall chance of a successful terrorist attack. Next, we discuss whether proposed explosives detection policies for cargo, airmail and checked luggage carried on passenger aircraft are cost-effective.(cont.) We define a threshold time such that if an attempted attack is likely to occur before this time, it is cost-effective to implement the policy, otherwise not. We find that although these three policies protect against similar types of attacks, their cost-effectiveness varies considerably. Lastly, we explore whether dynamically assigning security screeners at various airport security checkpoints can yield major gains in efficiency. We use approximate dynamic programming methods to determine when security screeners should be switched between checkpoints in an airport to accommodate stochastic queue imbalances. We compare the performance of such dynamic allocations to that of pre-scheduled allocations. We find that unless the stochasticity in the system is significant, dynamically reallocating servers might reduce only marginally the average waiting time. Without knowing certain parameter values or understanding terrorist behavior, it can be difficult to draw concrete conclusions about aviation security policies.(cont.) Nevertheless, these mathematical models can guide policy-makers in adopting security measures, by helping to identify parameters most crucial to the effectiveness of aviation security policies, and helping to analyze how varying key parameters or assumptions can affect strategic planning.by Susan Elizabeth Martonosi.Ph.D