Mª Carmen González-Cruz

A method to design job rotation schedules to prevent work-related musculoskeletal disorders in repetitive work

Job rotation is an organisational strategy widely used in human-based production lines with the aim of preventing work-related musculoskeletal disorders (WMSDs). These work environments are characterised by the presence of a high repetition of movements, which is a major risk factor associated with WMSDs. This article presents a genetic algorithm to obtain rotation schedules aimed at preventing WMSDs in such environments. To do this, it combines the effectiveness of genetic algorithms optimisation with the ability to evaluate the presence of risk by repeated movements by following the OCRA ergonomic assessment method. The proposed algorithm can design solutions in which workers will switch jobs with high repeatability of movements with other less demanding jobs that support their recovery. In addition, these solutions are able to diversify the tasks performed by workers during the day, consider their disabilities and comply with restrictions arising from the work organisation.

Environmental Criteria in the Spanish Public Works Procurement Process

Green Public Procurement (GPP) is defined as a process of contracting products, services, and works with the least possible damage to the environment during their life cycle. In order to improve the knowledge about GPP, a study of the use of environmental tendering criteria in the Spanish public construction sector has been performed. The results of this study show that the use of environmental criteria in Spanish public sector construction procurement is low in comparison to a certain group of countries, known as “Green 7”, in the European Union. Environmental criteria is the fourth criterion in importance, but its weight in the global of the process is much lower than other criteria such as price, memory of the construction process and the delivery time. National administrations use environmental criteria more frequently because they have more resources and staff training about environmental issues. Environmental criteria are more used in the tendering of civil projects and works whose budget exceeds ten million euro due to the environmental impact of these kind and/or size of projects.

Risk Analysis of a Fuel Storage Terminal Using HAZOP and FTA

The size and complexity of industrial chemical plants, together with the nature of the products handled, means that an analysis and control of the risks involved is required. This paper presents a methodology for risk analysis in chemical and allied industries that is based on a combination of HAZard and OPerability analysis (HAZOP) and a quantitative analysis of the most relevant risks through the development of fault trees, fault tree analysis (FTA). Results from FTA allow prioritizing the preventive and corrective measures to minimize the probability of failure. An analysis of a case study is performed; it consists in the terminal for unloading chemical and petroleum products, and the fuel storage facilities of two companies, in the port of Valencia (Spain). HAZOP analysis shows that loading and unloading areas are the most sensitive areas of the plant and where the most significant danger is a fuel spill. FTA analysis indicates that the most likely event is a fuel spill in tank truck loading area. A sensitivity analysis from the FTA results show the importance of the human factor in all sequences of the possible accidents, so it should be mandatory to improve the training of the staff of the plants.

Analysis of Green Public Procurement of Works by Spanish Public Universities

Universities play an important role among public institutions because they initiate huge purchasing and contracting activities and contribute to sustainable development through education, research, and day-to-day operations. Existing studies on green public procurement (GPP) practices at Spanish universities focus on products and services. For this study, a total of 316 procedures were collected and analysed from the calls for tenders made by Spanish public universities between 2016 and 2017. The environmental criteria involved in the tenders and their weights were classified by subsector, geographical scope, and project budget. The results of this study show the use of environmental criteria in the works tendered by Spanish public universities is low (19.2%) in comparison with the results of other studies. It is therefore necessary to encourage GPP practices in the contracting process to comply with the environmental policies that universities have defined as part of their institutional policies.

EXPLAINING THE BAYES’ THEOREM GRAPHICALLY

The Bayes’ theorem on conditional probabilities is normally presented to students in introductory courses/modules on Statistics and Probability. This because most STEM students will make use of conditional probabilities in their professional lives with or without noticing. However, maybe because of the unfamiliar notation or because of the variety of ways in which this theorem can be formulated, most students have trouble understanding it. Moreover, when it comes to practical applications and problem exercises, most students (who have generally memorised its manifold ways of rearranging the conditional probabilities formula along with a few applications) struggle even more to come up with correct solutions. By means of a completely graphical approach, this paper presents an alternative way of explaining the Bayes’ theorem to STEM students. By means of diagrams and schematics the students can see the conditional probabilities represented as areas in a square. Simple geometric operations with these areas (additions and multiplications mostly) allow them, not just to understand this theorem far quicker, but to apply it confidently in almost any possible problem configuration. Overall, this paper offers an alternative or complementary way of explaining this important theorem more clearly to students that take probability courses by conveying it graphically instead of with the traditional mathematical formulae. Through a representative case study, this paper deals provides first-hand evidence about how confusing to understand the Bayes’ theorem might be at first even in simple problems, and how the understanding of this theorem is dramatically improved when presenting it graphically.