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Detalhes

Detalhes

  • Nome

    Maria Clara Vaz
  • Cargo

    Investigador Colaborador Externo
  • Desde

    01 março 2014
Publicações

2024

Sample Size Analysis for a Production Line Study of Time

Autores
da Silva, MI; Vaz, CB;

Publicação
Lecture Notes in Mechanical Engineering

Abstract
Setting labor standards is an important topic to operational and strategic planning which requires the time studies establishment. This paper applies the statistical method for the definition of a sample size in order to define a reliable cycle time for a real industrial process. For the case study it is considered a welding process performed by a single operator that does the load and unload of components in 4 different welding machines. In order to perform the time studies, it is necessary to collect continuously data in the production line by measuring the time taken for the operator to perform the task. In order to facilitate the measurements, the task is divided into small elements with visible start and end points, called Measurement Points, in which the measurement process is applied. Afterwards, the statistical method enables to determine the sample size of observations to calculate the reliable cycle time. For the welding process presented, it is stated that the sample size defined through the statistical method is 20. Thus, these time observations of the task are continuously collected in order to obtain a reliable cycle time for this welding process. This time study can be implemented in similar way in other industrial processes. © 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG.

2023

A DEA Approach to Evaluate the Performance of the Electric Mobility Deployment in European Countries

Autores
Vaz, B; Ferreira, P;

Publicação
Springer Proceedings in Mathematics and Statistics

Abstract
This work aims to assess the performance of European countries on the deployment of low-emission vehicles in road transportation. For this purpose, a model based on Data Envelopment Analysis (DEA) is used to calculate a composite indicator for several European countries, aggregating seven sub-indicators built from a data set for the 2019 year. Various virtual weight restrictions schemes of the sub-indicators are studied to explore the robustness of the performance results. By adopting the most robust scheme, the performance results obtained indicate that most European countries have the potential to improve their practices towards better road transport sustainability, by emulating the best practices observed in the four identified benchmarks. Thus, the inefficient countries should take measures to better support the market share of plug-in electric vehicles. In addition, the railway sector and the penetration of renewable energies should be enhanced to improve road transportation sustainability. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

2023

Impact of Organizational Factors on Accident Prediction in the Retail Sector

Autores
Sena, I; Mendes, J; Fernandes, FP; Pacheco, MF; Vaz, CB; Lima, J; Braga, AC; Novais, P; Pereira, AI;

Publicação
Computational Science and Its Applications - ICCSA 2023 Workshops - Athens, Greece, July 3-6, 2023, Proceedings, Part II

Abstract
Although different actions to prevent accidents at work have been implemented in companies, the number of accidents at work continues to be a problem for companies and society. In this way, companies have explored alternative solutions that have improved other business factors, such as predictive analysis, an approach that is relatively new when applied to occupational safety. Nevertheless, most reviewed studies focus on the accident dataset, i.e., the casualty’s characteristics, the accidents’ details, and the resulting consequences. This study aims to predict the occurrence of accidents in the following month through different classification algorithms of Machine Learning, namely, Decision Tree, Random Forest, Gradient Boost Model, K-nearest Neighbor, and Naive Bayes, using only organizational information, such as demographic data, absenteeism rates, action plans, and preventive safety actions. Several forecasting models were developed to achieve the best performance and accuracy of the models, based on algorithms with and without the original datasets, balanced for the minority class and balanced considering the majority class. It was concluded that only with some organizational information about the company can it predict the occurrence of accidents in the month ahead. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

2023

Economic Performance of Apparel Manufacturing Companies; [Performance Económica das Empresas de confeção de artigos de vestuário]

Autores
Vaz, B; Fernandes, B;

Publicação
Iberian Conference on Information Systems and Technologies, CISTI

Abstract
Given the relevance of the textile industry, over the years, for the portuguese economy, we intend to evaluate the economic performance of companies belonging to CAE 14131 through the indicators ROA, ROE, ROS and EVA/employees. Through the DEA technique, the BoD model is used to aggregate the various indicators in order to determine the composite indicator of 5.397 companies observed over the years 2011 to 2020, in order to deepen the knowledge about the Portuguese business economic textile sector. Through data analysis there is a progressive improvement of the indicators studied over the years which can be explained by the technological evolution occurred in this industry, although the sector under study uses mostly intensive labour. In each year, the efficient frontier is defined mostly by micro and small enterprises, which are predominantly located in the North of Portugal. © 2023 ITMA.

2023

Sustainable Short-Term Production Planning Optimization

Autores
Zanella, F; Vaz, CB;

Publicação
SN Computer Science

Abstract
This study proposes a framework for short-term production planning of a Portuguese company operating as a tier 2 supplier in the automotive sector. The framework is intended to support the decision-making process regarding a single progressive hydraulic press, which is used to manufacture cold-stamped parts for exhaust systems. The framework consists of two sequential levels: (1) a Mixed-Integer Linear Programming (MILP) model to determine the optimal production quantities per week while minimizing the total cost; (2) a dynamic production sequencing rule for scheduling operations on the hydraulic press. The two levels are combined and implemented in Excel, where the MILP model is solved using the Solver add-in, and the second level uses the optimal production quantities as inputs to determine the production sequence using a dynamic priority rule. To validate the framework, a proposed optimal plan was compared to a real plan executed by the company, and it was found that the framework could save up to 22.1% of the total cost observed in reality while still satisfying demand. To address uncertainties, the framework requires a rolling weekly planning horizon. © 2023, The Author(s).

Teses
supervisionadas

2022

Ferramenta de Maturidade Indústria 4.0: Aplicação em Ecossistemas Empresariais Regionais

Autor
JOÃO PEDRO ALMEIDA PACHECO

Instituição
IPP-ISEP

2022

Algoritmo de optimização para cacifos modulares

Autor
JOÃO RODRIGO DA SILVA NEVES VIANA

Instituição
IPP-ISEP

2022

ALGORITMO DE AVALIAÇÃO DA ESTABILIDADE DE UMA PALETE

Autor
JOÃO CORREIA DE ARAÚJO

Instituição
IPP-ISEP

2018

Video Similarity Measurement: Using Convolutional Neural Networks to Create Video Signatures

Autor
João Gabriel Marques Costa

Instituição
UP-FEUP

2018

Game Design Patterns in Serious Games for Software Engineering Education

Autor
João Miguel Fidalgo Esteves Nogueira

Instituição
UP-FEUP