Past Challenges and the Future of Discrete Event Simulation

The American scientist Carl Sagan once said: “You have to know the past to understand the present.” We argue that having a meaningful dialogue on the future of simulation requires a baseline understanding of previous discussions on its future. For this paper, we conduct a review of the discrete event simulation (DES) literature that focuses on its future to understand better the path that DES has been following, both in terms of who is using simulation and what directions they think DES should take. Our review involves a qualitative literature review of DES and a quantitative bibliometric analysis of the Modeling and Simulation (M&S) literature. The results from the bibliometric study imply that demographics of the M&S community are rapidly changing, both in terms of the nations that use M&S and the academic disciplines from which new simulationists hail. This change in demographics has the potential to help aid the community face some of its future challenges. Our qualitative literature review indicates that DES still faces some significant challenges: these include integrating human behavior; using simulation for exploration, not replication; determining return on investment; and communication issues across a splitting community

Precise near-earth navigation with GPS: A survey of techniques

The tracking accuracy of the low earth orbiters (below about 3000 km altitude) can be brought below 10 cm with a variety of differential techniques that exploit the Global Positioning System (GPS). All of these techniques require a precisely known global network of GPS ground receivers and a receiver aboard the user satellite, and all simultaneously estimate the user and GPS satellite orbits. Three basic approaches are the geometric, dynamic, and nondynamic strategies. The last combines dynamic GPS solutions with a geometric user solution. Two powerful extensions of the nondynamic strategy show considerable promise. The first uses an optimized synthesis of dynamics and geometry in the user solution, while the second uses a novel gravity-adjustment method to exploit data from repeat ground tracks. These techniques will offer sub-decimeter accuracy for dynamically unpredictable satellites down to the lowesst possible altitudes

Simulation of product transportation in open pit mines

A research report submitted to the Faculty of Engineering and Built Environment, University of Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Masters of Science in Engineering Johannesburg, 2015Open pit mines account for more than 60 percent of all surface mines, and haulage costs account for almost 60 percent of total operating costs for these mines. It necessitates maintaining an efficient haulage system where all fleet equipment performs effectively to achieve the mine’s objectives. Discrete event simulation supported by animation offers a powerful method for evaluating such systems. This research has developed a simulation software program using Visual Basic for Application (VBA), GPSS/H (General Purpose Simulation System), and PROOF 5 animation. Remaining within the defined assumptions and boundary conditions, the research combines the powers of three software languages to build a general-purpose, data-driven, and user-friendly simulation program. The research focuses on the study and simulation of some of the important complexities of the truck haulage system. These include uncertainty or system randomness, fleet heterogeneity, multi-loader multi-dump sites, bunching of haulers, and hauler dispatching. In the developed simulation program, the user is required to provide the inputs in the user-friendly environment of VBA. The simulation program arranges the inputs in a pre-arranged format and then sends them to GPSS/H. The simulation language generates a discrete event simulation model based on the receiving structural and operational data. After simulating the system, the model generates the simulation outputs and animation commands in separate files. VBA displays a summary of the simulation results, and PROOF 5 demonstrates the results in a 2-dimensional graphical animation along with detailed information. This research also includes three case studies based on hypothetical mines for the analysis of simulation results. It establishes comparisons between the dispatching policies of fixed allocation and variable allocation of Minimize Production Requirements (MPR), and shows that the MPR policy is more suitable to achieve the quality control objectives. The developed simulation program contributes by demonstrating the powers of simulation to analyse open pit haulage systems. It also shows how simulation can be utilized as a useful technique to answer many ‘what-if?’ questions and scenarios

Pre-primary education policy between formulation and implementation: the case of Bangladesh

Why does the implementation of policies for educational improvement often disappoint? The literature suggests that pitfalls in the formulation stage can hamper successful implementation. This research aims to develop insights into the process of policy formulation in order to establish how this may affect subsequent policy implementation using a case study of Pre-Primary Education in Bangladesh. Uniquely, I have been able to study the development of PPE policy when it was taking place since I was directly involved in the process as a professional advisor working for a donor. The first research question investigated how the pre-primary policy was formed. This had two parts in terms of i) developing understanding of the phases of policy formulation and the stakeholders involved, and ii) analysing the discourses that informed the policy. The second research question enquired into the development of the implementation strategy and its feasibility, and compared expectations with the data available on the characteristics and impact of the initial implementation. This enabled the identification of aspects of policy formulation that shape current and future implementation. Special attention was given to the development of policy that prioritised underprivileged children throughout the process, because of the extent of unequal provision and because this was a high profile goal for educational development. The analysis of policy development derived from relevant policy documents and keyinformant interviews highlighted charismatic and politicised approaches to educational reform, which lacked the involvement of beneficiaries and those tasked with implementation. This has consequences for subsequent impact and the sustainability of the new policy. The initial implementation was generally considered inadequate and uneven by the respondents. It reflected aspirational planning linked to the EFA goals, with ambitious aims to provide a "quantitative breakthrough" in access and attainment without a realistic assessment of the resources available and the capacity to mobilise them. When the implementation strategy was updated and included in the third national programme of primary education (PEDP III), a more phased and comprehensive approach to planning was introduced. However, reports on programme implementation have identified delays and difficulties in starting PEDP III, albeit improvements between year 1 and 2 have been noted. In particular, the implementation strategies identified were insufficiently detailed and different stakeholders' needs were not properly assessed. More equitable delivery to underprivileged children remains poorly articulated. Part of the reason appears to be diminished political will and inconsistent leadership. Finally, opportunities to collaborate with the NGO service providers have not been fully exploited and the implementation planning for PEDP III appeared to have relied excessively on external expertise, with implications for the ownership and continuity of the policy on pre-school. Based on these findings, suggestions are offered to the development partners, the Government and the NGOs to improve the integration of policy and implementation strategies to increase the probability of sustained improvements in Pre Primary provision

Resilient communities through safer schools

Access to education is a basic human right. It is the 4th of the 17 Sustainable Development Goals (SDGs) and education is strongly associated with poverty reduction. Providing facilities to educate children requires construction of school buildings and rapid expansion of curricula. However, in the rush to fulfil the right to education, are children being put at risk? What attention is being given to structural safety during the construction of new school facilities? The growing consensus among stakeholders is that public school infrastructure in developing countries worldwide is particularly susceptible to natural hazards. This highlights a compelling need for developing and implementing effective, integrated, and ‘ground-real’ strategies for assessing and radically improving the safety and resilience of schools across those countries. To this aim, the paper explores two main issues: effectiveness at scale and the relevance of multiple hazard effects on the resilience of school infrastructure. Specifically, the paper first discusses the challenges associated with the World Bank Global Program for Safer School (GPSS) and the development of its Global Library of School Infrastructure (GLOSI), highlighting the issues associated with producing a tool which can be effective at scale and support nationwide risk models for school infrastructure across the world, so that fairness and relevance of investment can be achieved. This is followed by the illustration of a number of specific tools developed by the authors to expand the risk prioritization procedures used for seismic hazard, to other hazards such as flood and windstorm and to quantify the reduction in seismic fragility obtained by implementing specific strengthening strategies. Rapid visual survey forms, a mobile app, a multi-hazard risk prioritization ranking, and numerical fragility relationships are presented and their application discussed in relation to a case study in the Philippines. The proposed tools represent a first step toward a detailed multi-hazard risk and resilience assessment framework of school infrastructure. The aim is to allow stakeholders and decision-makers to quickly identify the most vulnerable structures among the surveyed stock, to guide more detailed data collection campaigns and structural assessment procedures, such as analytical vulnerability approaches, and ultimately to plan further retrofitting/strengthening measures or, if necessary, school replacement/relocation