Distributed simulation with COTS simulation packages: A case study in health care supply chain simulation

The UK National Blood Service (NBS) is a public funded body that is responsible for distributing blood and asso-ciated products. A discrete-event simulation of the NBS supply chain in the Southampton area has been built using the commercial off-the-shelf simulation package (CSP) Simul8. This models the relationship in the health care supply chain between the NBS Processing, Testing and Is-suing (PTI) facility and its associated hospitals. However, as the number of hospitals increase simulation run time be-comes inconveniently large. Using distributed simulation to try to solve this problem, researchers have used techniques informed by SISO’s CSPI PDG to create a version of Simul8 compatible with the High Level Architecture (HLA). The NBS supply chain model was subsequently divided into several sub-models, each running in its own copy of Simul8. Experimentation shows that this distri-buted version performs better than its standalone, conven-tional counterpart as the number of hospitals increases

Reversible Computation: Extending Horizons of Computing

This open access State-of-the-Art Survey presents the main recent scientific outcomes in the area of reversible computation, focusing on those that have emerged during COST Action IC1405 "Reversible Computation - Extending Horizons of Computing", a European research network that operated from May 2015 to April 2019. Reversible computation is a new paradigm that extends the traditional forwards-only mode of computation with the ability to execute in reverse, so that computation can run backwards as easily and naturally as forwards. It aims to deliver novel computing devices and software, and to enhance existing systems by equipping them with reversibility. There are many potential applications of reversible computation, including languages and software tools for reliable and recovery-oriented distributed systems and revolutionary reversible logic gates and circuits, but they can only be realized and have lasting effect if conceptual and firm theoretical foundations are established first

Reversible Computation: Extending Horizons of Computing

This open access State-of-the-Art Survey presents the main recent scientific outcomes in the area of reversible computation, focusing on those that have emerged during COST Action IC1405 "Reversible Computation - Extending Horizons of Computing", a European research network that operated from May 2015 to April 2019. Reversible computation is a new paradigm that extends the traditional forwards-only mode of computation with the ability to execute in reverse, so that computation can run backwards as easily and naturally as forwards. It aims to deliver novel computing devices and software, and to enhance existing systems by equipping them with reversibility. There are many potential applications of reversible computation, including languages and software tools for reliable and recovery-oriented distributed systems and revolutionary reversible logic gates and circuits, but they can only be realized and have lasting effect if conceptual and firm theoretical foundations are established first

Framework for Multi-Agent Simulation of User Behaviour in E-Commerce Sites

Consumidores interagem com websites de comércio eletrónico de várias formas e as empresas que os operam dependem da otimização de métricas de sucesso tais como CTR (Click through Rate), CPC (Cost per Conversion), Basket e Lifetime Value e User Engagement para lucro. Alterar como, onde e quando o conteúdo de páginas web como por exemplo recomendação de produtos e publicidade é mostrado pode influenciar as ações dos consumidores.Vários algoritmos e técnicas em data mining e machine learning têm sido aplicados neste contexto. Sumarizar e analisar comportamento de utilizadores pode ser custoso e complicado porque é difícil extrapolar padrões que nunca ocorreram antes e os aspetos causais do sistema geralmente não são tidos em consideração. Técnicas online geralmente usadas tais como testes A/B e otimização multi-armed bandit têm o problema de ter um custo operacional elevado (incluindo o tempo, por exemplo, se um analista de dados quiser avaliar o impacto de um novo motor de recomendação passado um mês, terá de esperar esse mês para obter resultados). Porém, existem estudos sobre caracterizar comportamento e interações de utilizadores em sites de comércio eletrónico que podem ser usados para melhorar este processo.O objetivo desta dissertação é criar uma framework capaz de correr um simulação multi-agente, tendo em conta os utilizadores de um site de comércio eletrónico que reagem a estímulos que influenciam as suas ações. Extraindo dados de web mining (Web structure mining (WSM), Web usage mining (WUM) e Web content mining), que inclui tanto conteúdo estático como dinâmico de websites assim como de perfis de utilizadores, a simulação deve reportar métricas de sucesso para que a experiência possa ser avaliada. Um caso de utilização da framework é experimentar várias formas de recomendar produtos aos consumidores e estimar o impacto dessas recomendações.Customers interact with e-commerce websites in multiple ways and the companies operating them rely on optimizing success metrics such as CTR (Click through Rate), CPC (Cost per Conversion), Basket and Lifetime Value and User Engagement for profit. Changing what, how and when content such as product recommendations and ads are displayed can influence customers' actions.Multiple algorithms and techniques in data mining and machine learning have been applied in this context. Summarizing and analyzing user behaviour can be expensive and tricky since it's hard to extrapolate patterns that never occurred before and the causality aspects of the system are not usually taken into consideration. Commonly used online techniques such as A/B testing and multi-armed bandit optimization have the down side of having a high operational cost (including time e.g if a data scientist is evaluating the impact of a new recommendation engine after one month, she would need to wait an actual month to have results). However, there has been studies about characterizing user behaviour and interactions in e-commerce websites that could be used to improve this process.The goal of this dissertation is to create a framework capable of running a multi-agent simulation, by regarding users in an e-commerce website and react to stimuli that influence their actions. Furthermore, some statistical constructs such as Baysian networks, Markov chains or probability distributions can be used to guide how these agents interact with the system. By taking input from web mining (Web structure mining (WSM), Web usage mining (WUM) and Web content mining (WCM)), which includes both static and dynamic content of websites as well as user personas, the simulation should collect success metrics so that the experimentation being run can be evaluated. For example, this framework could be used to try different approaches to product recommendation and estimate the impact of it

A cybernetic participatory approach for policy system of systems mapping: Case study of Inclusive Economies

Traditional participatory systems modelling demands synchronous time from many experts and face-to-face interaction. This is not always feasible (e.g., during a pandemic) and can restrict which participants can be included. There are additional limitations in the effectiveness of physical paper-based modelling when handling large complex systems with numerous variables and links between them. The key challenge facing practitioners is then how can we retain the benefits of traditional participatory modelling whilst exploiting the advantages of new technologies? This paper contributes to development of an original systematic methodology inspired by Cybernetic principles. The proposed method, referred to as 5X – standing for Expose, Explore, Exploit, Explain, and Expand – offers a fully virtual co-produced environment for iterative cycle of stakeholder engagement and feedback before, during and after workshops, leading to developing more confidence in systems mapping, and promoting knowledge across policy areas. A primary application of the proposed method in a real policy setting illustrates its capability to generate a shared policy understanding of a complex inclusive economy system, where there is conflicting or dispersed knowledge about system structure, refine this understanding through online feedback channels and dynamic visualisations, and transfer this understanding to wider policy and academic partners

SIMULATION OF A MULTIPROCESSOR COMPUTER SYSTEM

The introduction of computers and software engineering in telephone switching systems has dictated the need for powerful design aids for such complex systems. Among these design aids simulators - real-time environment simulators and flat-level simulators - have been found particularly useful in stored program controlled switching systems design and evaluation. However, both types of simulators suffer from certain disadvantages. An alternative methodology to the simulation of stored program controlled switching systems is proposed in this research. The methodology is based on the development of a process-based multilevel hierarchically structured software simulator. This methodology eliminates the disadvantages of environment and flat-level simulators. It enables the modelling of the system in a 1 to 1 transformation process retaining the sub-systems interfaces and, hence, making it easier to see the resemblance between the model and modelled system and to incorporate design modifications and/or additions in the simulator. This methodology has been applied in building a simulation package for the System X family of exchanges. The Processor Utility Sub-system used to control the exchanges is first simulated, verified and validated. The application sub-systems models are then added one level higher_, resulting in an open-ended simulator having sub-systems models at different levels of detail and capable of simulating any member of the System X family of exchanges. The viability of the methodology is demonstrated by conducting experiments to tune the real-time operating system and by simulating a particular exchange - The Digital Main Network Switching Centre - in order to determine its performance characteristics.The General Electric Company Ltd, GEC Hirst Research Cent, Wemble

Generation and analysis of realistic mobility models for mobile ad hoc networks.

Simulation modeling is an integral part of conducting research in communication networks and distributed systems. In systems involving mobile nodes, accurate modeling of mobility has primary importance. Mobility has a fundamental influence on the behavior and performance of the system. However, only few mobility models have been used in nearly all simulations in the past. These models are simple and highly random. As a result, the simulation studies based on these random mobility models have been heavily criticized for their credibility. We feel that availability of a software tool with the following capability, at least in part, would alleviate this crisis. The software must facilitate researchers to: (i) model a wide range of mobility with varying degrees of realism (ii) analyze the modeled mobility visually and statistically and (iii) transport the mobility trace in a format that can be used in most widely used simulators. The development of a software tool with the above mentioned capabilities is the main contribution of this thesis. In this thesis, after presenting a comprehensive survey on realistic mobility models, we present a realistic mobility generator software called RLMobiGen that can be used to specify, generate, analyze, and then export the mobility trace. The mobility trace can then be used in the simulation studies of mobile ad hoc networks. RLMobiGen is a comprehensive, highly interactive, and user friendly software. --P.iii.The original print copy of this thesis may be available here: http://wizard.unbc.ca/record=b168630