Search results

This paper aims to propose an approach for the optimization of imperfect preventive maintenance and corrective actions performed on a single machine. After maintenance, the machine returns to an age between “as good as new” and “as bad as old”.

The approach is based on fuzzy logic and simulation‐based optimization. Fuzzy logic is preferred over crisp logic because it is relatively easy to implement in this situation considering that the human factor is hardly interpreted by analytical methods because of its unpredictable nature. Simulation‐based optimization is used to have a more reactive and accurate tool for practitioners.

Taking into account the impact of the imperfections due to human factors, the period for preventive maintenance, which minimizes the expected cost rate per unit of time or maximizes the availability of the system, is evaluated by the simulation‐based optimization.

Different and more realistic maintenance levels must be considered and the traceability of a specific system could be used to determine the most appropriate failure law. For this study, cost reduction was considered as the priority, but the model can be adjusted according to the user's preferences.

This paper considers a single repairable machine as a system that undergoes periodic preventive and corrective maintenance actions. Considering maintenance imperfections, rule‐based fuzzy logic can be integrated into the maintenance program to determine the times for the periodic preventive maintenance actions.

Considering human factors in maintenance programs is indispensable to assure more accurate and realistic results. However, due to the difficulty engendered by their modeling, most theoretical maintenance models do not consider these factors. Therefore, the proposed fuzzy model in the paper can be an important tool to include them.

The concept of sustainable development (SD) is a popular response to society’s need to preserve and extend the life span of natural resources. One of the 17 goals of the SD is “education quality” (Fourth Goal of Sustainable Development [SDG-4]). Education quality is an important goal because education is a powerful force that can influence social policies and social change. The SDG-4 must be measured in different contexts, and the tools to quantify its effects require exploration. So, this study aims to propose a statistical model to measure the impact of higher education online courses on SD and a structural equation model (SEM) to find constructs or factors that help us explain a sustainability benefits rate. These proposed models integrate the three areas of sustainability: social, economic and environmental.

A beta regression model suggests features that include the academic and economic opportunities offered by the institution, the involvement in research activities and the quality of the online courses. A structural equation modelling (SEM) analysis allowed selecting the key variables and constructs that are strongly linked to the SD.

One of the key findings showed that the benefit provided by online courses in terms of SD is 62.99% higher than that of offline courses in aspects such as transportation, photocopies, printouts, books, food, clothing, enrolment fees and connectivity.

The SEM model needs large sample sizes to have consistent estimations. Thus, despite the obtained estimations in the proposed SEM model being reliable, the authors consider that a limitation of this study was the required time to collect data corresponding to the estimated sample size.

This study proposes two novel and different ways to estimate the sustainability benefits rate focused on SDG-4, and machine learning tools are implemented to validate and gain robustness in the estimations of the beta model. Additionally, the SEM model allows us to identify new constructs associated with SDG-4.

This paper aims to study the influence of innovation on micro, small and medium-sized enterprises (MSME) performance in Colombia through the 403 MSMES survey analysis. In particular, this paper measures the effect of participation in R&D alliances, product innovation and process innovation on it.

MSME performance is measured through a composite index, estimated through principal components analysis using polychoric correlations, which is based on eight self-reported assessments of MSME performance. Then, this measure of performance is related to MSME participation in R&D alliances and the product and process development stance of the MSME based on an adaptation of the Miles and Snow business classification scheme, by means of an ANOVA and a linear regression.

Colombian SMEs are not significantly benefitted from participation on R&D alliances. Instead, their performance appears to be dependent upon their internal innovation efforts directed to product development. Moreover, the results suggest that imitators get a performance almost as high as innovators.

Innovation activities in Colombian SMEs are carried out informally, as they are mostly uninterested to engage in R&D activities and to develop new products by own initiative. Moreover, few of them have an R&D department. In regard to technology, results suggest that almost half of SMEs are classified as followers, namely, they use the same technology as competitors.

I evaluate how the tax reform of 2012 reduced informality in Colombia both theoretically and empirically. Theoretically, I develop a labor market model and obtain simulations indicating that the reform should reduce informality significantly. Empirically, I obtain difference-in-difference estimates from two household surveys. Estimates from the repeated cross-sections data indicate small, short-term effects and large long-term effects. Estimates from the household survey panel data are in line with these results. I also simulate difference-in-difference estimates with different combinations of changes in payroll taxes and enforcement indicating that large improvements would have been needed to obtain the corresponding econometric estimates.

This chapter is intended to present the onset, evolution, and decline of Compañía Minera El Zancudo, considered the largest Colombian company in the nineteenth century. Additionally, the chapter will examine its role in both the development of manufacturing industries and the introduction of modern capitalism in the country.

The case is based on secondary information collected according to a documentary research method in which the authors selected, categorized, interpreted, and confronted different sources concerning El Zancudo.

The inception and evolution of El Zancudo involved local and foreign knowledge, techniques, and capital investments that contributed to the company growing to the point of reaching the unprecedented figure of 1,350 workers in the year 1890. Its transition from a failed local mine to a prosperous and intricate business group is full of referrals and links to foreign investment, knowledge transfer, industrial development, and an orientation toward entrepreneurship that contributed to the understanding of subsequent enterprises not only in the Antioquia region but also across the entire country.

This case study was written using limited reliable secondary sources about El Zancudo. Other significant Colombian companies in the nineteenth century (Ferrería de Pacho, Ferrería de Amagá, Empresa Textilera de Samacá, and Cervecería Bavaria) and their links to El Zancudo were mentioned but not deeply analyzed in this chapter.

The clear-cut causes that led El Zacudo to close its operations within the first decades of the twentieth century are worthy of discussion, not only by scholars and business practitioners, but also by policy makers in order to understand the phenomenon and possibly prevent existing companies from failing in a similar manner.

This case brings together the scattered literature on El Zancudo and analyzes the drivers and consequences of both its rise and fall, taking into consideration the specific historical, political, and economic contexts, furthermore, it establishes some linkages between this case and other companies under similar situations.

Colombia has one of the highest levels of inequality in landholding in the world. This inequality has persisted in spite of numerous state-led land reform efforts, which leads to the question: why has it been so difficult to reverse unequal land distribution in Colombia? To answer this question, the chapter examines the role of the state, non-state armed groups, land inequality, land reform efforts, and a history of violence to reveal the relationship between land, inequality and violence in Colombia. This chapter explores the nature of this relationship to understand Colombia’s enduring inequality and to inform theoretical approaches to statehood and power. Rather than reducing state capacity to common Weberian binary constructions of state and statelessness, I explore how state capacity takes on different forms in different regions of Colombia – analyzing how various actors shape land inequality and violence across the territory. Using a comprehensive longitudinal panel data set of displaced persons, I use a negative binomial regression model to demonstrate how land reform, land inequality, and a history of violence have directly affected current displacement of citizens. I argue that several constellations of powerful social actors have at various points converged to control land, through non-state armed groups, to exert a local form of logistical control outside the scope of the federal state, deeply affecting the dynamics violence across different territories. These groups have subsequently engaged in a land grabbing process that has resulted in a reverse form of land reform – leading to persisting inequality in Colombia.

The objective of this paper was to systematically review published studies to determine if disability limits access to health care and to attempt to identify what body functions, structures and activities and participation, as well as contextual factors (environmental and personal factors), interact with the health condition to limit this access. The AMED, CINAHL, EMBASE, Medline and psychINFO databases were searched for original study articles in English, dating from 1974 to 2008. Review articles and expert opinion were excluded. Each study had two independent reviews by either a general practitioner or specialist in rehabilitation medicine. Each study was critically appraised according to the National Service Framework for Long‐term Conditions (Department of Health, 2005a) methodology and recorded on standardised data extraction sheets. Studies of poor quality were excluded. Sixty studies were included. No randomised controlled trials were identified. Studies broadly fell into the following three main groups: database studies (n=27), quantitative surveys (n=20) and qualitative interviews (n=13). Disabled people are restricted in accessing health care and report less satisfaction with their medical care. Many of the identified studies were from the United States (US) and based on subjective reporting. More objective evidence is needed, especially in the UK, to clarify the true level of access to health care in people with disabilities. The complex, interdependent factors in providing health care to disabled people require complex solutions.