Recent advances on graphical evaluation and review techniques

Graphical evaluation and review techniques (GERT) is a technique to study the stochastic nature of networks consists of different branches. In GERT, all branches are explained in terms of the probability that the branch is traversed and the tile to traverse the branch in case it is realized. This paper presents recent advances of the implementation of GERT in various industries. The study presents a comprehensive description of GERT and recent advances on the implementation of GERT in various industries over the period 2002-2017.Peer reviewedFinal article published.Network designGERTGraphical evaluation and review technique

The Project Scheduling Problem with Non-Deterministic Activities Duration: A Literature Review

Purpose: The goal of this article is to provide an extensive literature review of the models and solution procedures proposed by many researchers interested on the Project Scheduling Problem with nondeterministic activities duration. Design/methodology/approach: This paper presents an exhaustive literature review, identifying the existing models where the activities duration were taken as uncertain or random parameters. In order to get published articles since 1996, was employed the Scopus database. The articles were selected on the basis of reviews of abstracts, methodologies, and conclusions. The results were classified according to following characteristics: year of publication, mathematical representation of the activities duration, solution techniques applied, and type of problem solved. Findings: Genetic Algorithms (GA) was pointed out as the main solution technique employed by researchers, and the Resource-Constrained Project Scheduling Problem (RCPSP) as the most studied type of problem. On the other hand, the application of new solution techniques, and the possibility of incorporating traditional methods into new PSP variants was presented as research trends. Originality/value: This literature review contents not only a descriptive analysis of the published articles but also a statistical information section in order to examine the state of the research activity carried out in relation to the Project Scheduling Problem with non-deterministic activities duration.Peer Reviewe

Micro-macro dynamics of the online opinion evolution: an asynchronous network model approach

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This paper investigates the complex relationship between endogenous and exogenous, deterministic and stochastic stimulating factors in public opinion dynamics. An asynchronous multi-agent network model is proposed to explore the interaction mechanism between individual opinions and the public opinion in online multi-agent network community, including both the micro and the macro patterns of opinion evolution. In addition, based on random network models, a novel algorithm is provided for opinion evolution prediction. The model property analysis and numerical experiments show that the proposed asynchronous multi-agent network model can assimilate and explain some interesting phenomena that are observed in the real world. Further case studies with numerical simulation and real-world applications confirm the feasibility and flexibility of the proposed model in public opinion analysis. The results challenge the common perception that mass media or opinion facilitators play the fundamental role in controlling the development trends of public opinion. This study shows that the formation and evolution of public opinion in the presence of opinion leaders depend also on an individual’s emotional inertia and conformity pressures from peers in the same topic group

A resilience assessment framework for complex engineered systems using graphical evaluation and review technique (GERT)

System resilience characterizes the capability of maintaining the required functionality under disruptions, which is of great significance in evaluating the productivity and safety of complex engineered systems. Although most studies conduct resilience assessment from qualitative and quantitative perspectives, system functionality that reflects functional requirements for complex engineered systems needs to be elaborated. In addition, given that complex engineered systems achieve dynamic performance during disruptions, measuring the actual performance under uncertainty is imperative. To this end, this paper develops a quantitative framework to assess the resilience of complex engineered systems. The developed framework comprises three phases, functionality analysis, performance evaluation, and resilience assessment. Firstly, system functionality is analyzed using a functional tree illustrating the relationship between functions. The overall objective, primary functions, and sub-functions are identified according to task requirements. Secondly, system performance is quantified considering uncertain factors through Graphical Evaluation and Review Technique (GERT). Probabilistic branches and network logic are employed to represent the implementation of various functions. Finally, resilience assessment is carried out from the perspectives of anticipation, absorption, adaptation, and restoration abilities. A case study on the satellite network shows the effectiveness of the developed framework. The developed framework determines system functionality based on task requirements, evaluates system performance with limited information, and accurately assesses system resilience

Solution model to the resource constrained project scheduling problem RCPSP with insertion task and random duration

In this doctoral thesis, an optimization model is developed in order to provide a solution strategy to the scheduling problem in new product development projects. This projects face diferent risks that affect the normal execution of activities and their due date. Therefore, the problem has been analyzed as a resource-constrained project scheduling problem (RCPSP) under a probabilistic context. Specifically, it includes parameters like the random duration of the activities and the probability of inserting additional tasks in the project network. The optimization model developed in this research has four stages: the identification of risks, the estimation of the activities duration from four redundancy based methods, the resolution of an integer linear program in order to generate the project baselines, and the selection of the best baseline through two robustness indicators. A case study to applied the proposed model is presented, which refers to the development of a leadframe material for a semiconductor package. In the developed model, two fundamental contributions are hightlighted: the integration of a detail project’s risks analysis with an optimization model that generate a robust baseline, and the adaptation of the RCPSP with random duration of activities and stochastic insertion tasks to the case of new product development project.En esta tesis doctoral, se desarrolla un modelo de optimización como estrategia de solución al problema de programación de proyectos de desarrollo de nuevos productos. Teniendo en cuenta que este tipo de proyectos son afectados por diversos riesgos que al materializarse pueden afectar la ejecución normal de las actividades y sus plazos de finalización, se ha optado por modelar el problema dentro de un contexto probabilístico y tomando como referente el problema de programación de proyectos con recursos restringidos (Resource Constrained Project Scheduling Problem: RCPSP). El RCPSP adoptado incluye como parámetros: la duración aleatoria de las actividades y la probabilidad de insertar tareas adicionales en la red del proyecto. El modelo de optimización desarrollado en esta investigación contempla cuatro etapas: la identificación de los riesgos, la estimación de la duración de las actividades a partir de cuatro procedimientos basados en duraciones redundantes, la resolución de un programa lineal entero que genera las líneas-base del proyecto, y la selección de la mejor línea-base evaluada por medio de dos indicadores de robustez. Con el fin de aplicar el modelo propuesto, se presenta un caso de estudio que hace referencia al desarrollo de un material para el marco de conexión de un circuito integrado. En el modelo desarrollado se destacan dos aportes fundamentales: la integración de un análisis detallado de riesgos del proyecto con un modelo de optimización que genera una línea-base robusta, y la adaptación del RCPSP con duración aleatoria de actividades e inserción de tareas al caso de proyectos de desarrollo de nuevos productos.Doctorad

The use of a GERT based method to model concurrent product development processes

This paper proposes a time-computing model using the Graphical Evaluation and Review Technique (GERT) to analyse concurrent New Product Development (NPD) processes. The research presented here differs from previous work carried out on concurrent engineering. First, we conceptualise a concurrent NPD process using the GERT scheduling technique and derive a method of modelling the information and communication complexities within the process. Second, we extend previous research carried out on concurrent engineering and incorporate it within our model. Finally, we present an alternative method of analysing concurrent NPD process for both researchers and project managers alike. The GERT model developed in this paper was successfully employed at two NPD firms located in Ireland and Iran

Construction Dispute Mitigation: Quantitative and Qualitative Analytic Approach with a Focus on Bidding, Out-of-Sequence Work, and Contract Analysis

The complexity of today’s construction projects deems conflicts and disputes unavoidable. The mere presence of disputes leads to productivity losses, schedule overruns, cost overruns, and quality decline. Moreover, failure to resolve disputes in a quick manner ripples these impacts and prevents successful completion of projects. Accordingly, preventing disputes prior to taking place is always better than resolving them after the fact. There are several factors that cause disputes. However, this dissertation focuses on those related to bidding, out-of-sequence (OOS) work, and contract administration of owner’s obligations, due to the significant knowledge gaps that were identified in their research streams.The goal of this research is to cover the identified knowledge gaps by providing various effective quantitative and qualitative means of dispute mitigation at the different stages of the project’s lifecycle. To this end, the research has four main objectives; each corresponding to one of the identified major knowledge gaps. The objectives are: (1) develop an advanced model for construction bid price estimation that is able to draw sound statistical inferences even in cases of data incompleteness and dynamic behaviors of competitors; (2) present contract administration guidelines for utilizing employer’s obligations clauses under the most widely used national and international standard forms of design-build contracts; (3) identify the causes and early warning signs of OOS work and their characteristics, as well as the best practices to avoid and mitigate its impacts, and (4) develop an advanced systematic model for analyzing the dynamics of OOS.The objectives were achieved through multiple analytical quantitative and qualitative methods; utilizing Bayesian statistics, decision theory, contractual examinations, surveys and meetings, statistical analysis, decision support systems, and system dynamics simulation. The research has various intellectual merits as it tackles important research areas that have not been explored before and improves areas which needed improvement. The research also has practical merits as it provides project stakeholders with models and tools that are used in multiple stages of the project cycle to mitigate disputes. The intellectual and practical outcomes of this research will partake in further understanding construction projects, minimizing disputes at different stages, and promoting healthier contracting environments

A Conceptual Framework for Simulating Feedback Loops in Engineering Design

Product development is a business process that organisations use to introduce technological advancements to their products and services. Within this process, engineering design decisions define the architecture of the designed product, which, in turn, governs the structure of the product development process that ensures the quality of the delivered product. Integrating product development and engineering design processes results in a product development system characterised by networks of activities related to each other by feedback loops. Design iteration and rework are two kinds of feedback loop in product development systems. Design iteration is a form of positive feedback loop that contributes to the quality of the designed product. Rework, on the other hand, is a form of negative feedback loop that increases project duration and cost. Understanding feedback loops in product development is fundamental for effective design management and so the delivery of products on time and within budget. This research contributes a conceptual framework for (a) understanding and (b) simulating the impact of feedback loops in engineering design. The framework enables the integration of two kinds of simulation model. The first is a discrete event model that reflects the product architecture and its influence on the product development process structure, including potential rework feedback loops. The second is an agent-based model that reflects the social facets of design activity and communication behaviours within design teams including design iteration. In this way, two kinds of feedback loop are captured: rework in the discrete event model and design iteration in the agent-based model. An engineering design case study was used to validate the conceptual framework. This thesis takes a socio-technical systems perspective on engineering design processes. The conceptual framework includes relevant characteristics for simulating feedback loops in engineering design. The product architecture, which identifies individual parts that need to be designed and infers the product development structure, can be used to derive a design process workflow and so the discrete event model. In parallel, social interactions (actions, states, and behaviours) between designers are used to inform an agent-based simulation model of the design activities for each of the parts in the product architecture. Finally, the framework defines interaction points between the product development process and design activities which informs interplays between the two kinds of simulation model

Lean Product Development process structure and its effect on the performance of NPD projects

New product development (NPD) has a pivotal role in the industrial competition, and makes a basis for long‐term prosperity of companies. To survive in today's fast‐changing market environment, companies are always trying to improve the performance of their NPD projects, by implementing new approaches, such as Lean Product Development (LPD). Nevertheless, applying such approaches is not straightforward, mainly due to the high level of interdependency between development activities and the role of dynamic effects in the project performance. Understanding the combined effects of dynamic features, including feedback loops, time delays and nonlinear causal relationships, is the main step for achieving higher project performance. In this thesis, the dynamics of LPD process structure is investigated to find the ways it could affect the time, cost and quality performance of a development project. As there is no consensus about the definition of LPD among researchers in this filed, first through a comprehensive literature review different approaches to LPD are studied. Two major approaches for LPD are introduced based on the adaptation of lean manufacturing tools and techniques for optimizing NPD processes, or extracting LPD specific tools and techniques from Toyota Product Development System (TPDS). The second approach is proved to be more applicable, mainly due to fundamental differences between manufacturing and NPD environments, and the LPD process design based on TPDS is selected as the focal point for this research. The combination of Set‐Based approach to design and Concurrent Engineering in the form of SBCE is identified as the unique feature of LPD process structure which have been the topic of several researches in this field during past decade. Set‐based design approach calls for the higher number of iteration cycles at the front end of the projects, and is responsible for higher project effectiveness while increases the time and effort invested. On the other hand, concurrent engineering targets the project duration, and is an efficiency factor, but if not structured properly it could have an opposite effect through increasing the number of rework cycles. Although the performance of TPDS which is the best benchmark for LPD shows the positive effect of SBCE on the projects performance, the reasons behind it and the way through which two approaches could be structured to achieve the favourable results is not clear yet. In addition, while different types of new product development projects, based on VII their levels of complexity and innovation, are defined and executed in companies, it is not clear if SBCE approach has the same impact on all project types. To investigate the reasons behind the superiority of SBCE and its effects in different types of development projects the systems thinking approach is selected as the main research methodology to provide a holistic view on the development projects through looking on interdependencies between performance measures and process structure. System dynamics modelling is used as the research method, due to its capacity in modelling feedback loops and iteration and rework cycles, as underlying factors which determine the time, cost and quality performance in projects. The model is built based on verified structures for rework cycle and resource allocation as the platform for the model, and becomes more specific for the purpose of this research by adding structures related to the iteration cycles, number of initial concepts, and effect of project type. After passing the standard system dynamics validation tests, the model is calibrated using the historical project data from different projects in a major car manufacturing company. The calibrated and verified model then used for the policy analysis by defining different scenarios based on the number of iteration cycles during the conceptual design phase, number of initial concepts and the type of project. All types of projects show the improved performance metrics when moving towards the SBCE approach by increasing the number of iteration cycle. However, the degree of improvement for projects with higher levels of complexity is more profound. In addition, it is concluded for projects with the high level of complexity that increasing the number of initial concepts has the positive effect on all project performance measures. This research results have a methodological contribution by providing a method for rigorous representation of the impact of LPD process structure on projects performance through simulation. From the practical point of view, the developed model could be used by project managers as a guide for making informed decisions which guarantee the long‐term success of development projects