1,720,955 research outputs found
Examining Budget Policies for New and Existing Facilities: A System Dynamics Approach
Get PDFSustaining acceptable service in large facility networks is a complex task, particularly under limited budgets, rapid deterioration, and increasing service demands. Policy-makers are, therefore, challenged to make efficient balance between the construction of new facilities and the renewal of existing ones to suit both the short and the long-term needs. To support policy-makers, this paper proposes an efficient decision support system using the System Dynamics (SD) simulation technique to analyse the impact of various budget allocation policies and to optimize policy decisions. The proposed system dynamics model was tested using a case study from the Toronto District school Board involving more than 400 schools. It can find the optimum budgeting strategy that minimizes the overall facility condition index and total life cycle cost over a long-term strategic plan. The system dynamics model proved its ability to find a budget allocation policy with much better results than the typical enrolment-based approach.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Large-scale Asset Renewal Optimization: GAs + Segmentation versus Advanced Mathematical Tools
Get PDFCapital renewal is an essential decision in sustaining the serviceability of infrastructure. Effectively allocating limited renewal funds amongst numerous asset components represents a large-scale combinatorial optimization problem that is difficult to solve. While various mathematical optimization techniques have been presented in the published literature, they are not very effective in handling the complexities and huge calculations related to large scale problems. More recently new evolutionary-based techniques, such as genetic algorithms (GA) have been introduced for finding near-optimum solutions to large-scale problems. Experimenting with this technique for asset renewal problems has revealed that GAs performance rapidly degrades with problem size. For instance, a previous research by Hegazy and Elhakeem (2010), could improve fund allocation for only a portion of total existing components (maximum of 8000 asset components) with degradation in optimization performance by increasing number of components. To address larger scale problems, this research investigates both evolutionary and advanced mathematical optimization techniques and seeks a goal of handling models consist of at least 50,000 asset components.
To enhance the performance of GAs for large-scale optimization problems, three aspects were considered: (1) examining different problem formulations such as integer, on-shot-binary, and step-wise binary formulation; (2) experimenting with commercial GA-based tools; and (3) introducing an innovative segmentation method to handle groups of smaller size problems, and then integrating the results. To identify the best segmentation method, similarity-based segmentation is compared to random segmentation and was found to have superior performance. Based on the results of numerous experiments with different problem sizes and comparison with previous results obtained by Hegazy and Elhakeem (2010) from the same prototype used in this study, the GAs + Segmentation approach is found to handle a problem size of 50,000 components, with better solution quality (improved optimum solution), and no noticeable degradation of optimization performance by increasing the problems size.
In addition to evolutionary algorithms, performance of one of the advanced mathematical programming tools (GAMS), and its powerful optimization engine (CPLEX), are investigated. For the mathematical representation of the asset renewal problem, best formulation is selected with regard to the definitions of easy-to-solve integer programming (IP) formulations. To reduce internal calculations, the GAMS mathematical model is coded to interact with original spreadsheet data by using GAMS data exchange (GDX) files. Based on experimentations, using advanced mathematical tools with strong (easy-to-solve) IP formulations, improved the solution quality even further in compare to GA + Segmentation.
In conclusion, this research investigated both evolutionary and advanced mathematical optimization techniques in handling very large-scale asset renewal problems, and introduced effective models for solving such problems. The developed models represent a major innovative step towards achieving large cost savings, optimizing decisions, and justifying fund allocation decisions for infrastructure asset management. While the focus of this research is on educational buildings, the developed optimization models can be adapted to various large-scale asset management problems
Combined Strategic-Tactical Planning for Facility Rehabilitation Using System Dynamics and Optimization
No full textRehabilitation programs are essential for efficiently managing large networks of infrastructure assets and sustaining their safety and operability. While numerous studies in the literature have focused on various aspects of infrastructure rehabilitation, such as rehabilitation processes, deterioration modeling, life cycle cost analysis, project financing, etc., limited efforts have investigated the overall dynamics among these functions and the development of holistic models that can analyze the long-term effect of different strategic policies and their impact on tactical rehabilitation decisions. To support strategic level of decision-making and long-term policy analysis, this research utilized System Dynamics (SD) to study the dynamic interactions among the deterioration, rehabilitation, and budgeting feedback loops. Model performance and suggested policies were also checked against reference modes and verified using various model testing methods to ensure adequacy. The proposed System Dynamics model was then expanded to incorporate four main modules including policy, physical condition, life cycle cost, and sustainability, for the purpose of backlog accumulation analysis. School building facilities were used as the focused asset domain of this study. After identification of key variables based on literature analysis, previous researches on school building facilitates, and experts’ opinion, the dynamic interactions were studied using causal loop diagraming (CLD) methods. The developed CLD was then mapped into a stock-and-flow simulation model incorporating the four integrated modules with all the underlying mathematical relationships. Numerous experiments with different policy scenarios were conducted to investigate the impact of various policies related to rehabilitation, budget distribution, government investment, and private financing. The simulation results clearly indicated that some of the commonly used policies such as condition-based prioritization methods can lead to significant long-term problems in terms of backlog, and showed that equal distribution of budget can be more effective. Simulation results also indicated that the use of private financing for backlog elimination need to be carefully analyzed to determine a proper payback scheme without a negative effect on long-term backlog projections.
The SD Model was also adopted to provide optimum policy solutions in terms of the level of budget allocated to rehabilitation of exiting school buildings and construction of new facilities to accommodate future enrolment. The proposed model used facility condition index (FCI) as an industry standard to investigate facility performance and also a utilized a facility risk index (FRI) to account for the risk of failure. The model was used to investigate and compare the effect of using enrolment-based budgeting policies versus an optimized policy solution on a network of 438 elementary school buildings. Results clearly showed that the enrolment-based approach, which has been used by education ministries for a long time, could be significantly improved with the used of policy optimization.
The policy solutions form the strategic-level analysis were used to create detailed tactical rehabilitation plans. To support the tactical level of decision-making this research investigated the performance of mathematical mixed integer programming and genetic algorithm (GA) optimization models to handle the large-scale tactical problems. First, various model formulations including an integer, a one-shot binary, and a year-by-year binary formulation were examined for their performance on large-scale problems. A year-by-year formulation was then selected for the network-level analysis and was used with GA-based optimization. To improve the performance of the GA-based model, a segmentation approach was used that was able to eliminate performance degradation, yet exhibited long processing time. Subsequently, an integer programming model was developed on the GAMS/CPLEX optimization tool that resulted in the best solution quality and fast processing time for very large-scale problems (e.g., 50,000 building components). The promising result of the proposed mathematical model was mainly attributed to the formulation of the optimization model, advancements in the used optimization tools, and the separation between project and network level analysis. Combination of the strategic and tactical models developed in this research provides a comprehensive and systematic framework for a combined analysis of rehabilitation plans at both strategic and tactical levels of facility management
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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