Repositório RCAAP

This paper presents a Unit Commitment model with reactive power compensation that has been solved by Genetic Algorithm (GA) optimization techniques. The GA has been developed a computational tools programmed/coded in MATLAB. The main objective is to find the best generations scheduling whose active power losses are minimal and the reactive power to be compensated, subjected to the power system technical constraints. Those are: full AC power flow equations, active and reactive power generation constraints. All constraints that have been represented in the objective function are weighted with a penalty factors. The IEEE 14-bus system has been used as test case to demonstrate the effectiveness of the proposed algorithm. Results and conclusions are dully drawn.

This paper explores the use of a multi-objective approach through the implementation of a numerical direct multiple shooting (MS) method to solve optimal control problems (OCP). When a direct MS method is used to solve the OCP, a set of `continuity constraints' emerges and should be satisfied together with the other algebraic mixed states and control constraints. To minimize the objective function and satisfy all the constraint conditions, the finite-dimensional optimization problem is reformulated as a multi-objective problem with three objectives to be optimized. An illustrative example is included to show that the present methodology is worth pursuing.

A direct multiple shooting (MS) method is implemented to solve optimal control problems (OCP) in the Mayer form. The use of an MS method gives rise to the so-called ‘continuity conditions’ that must be satisfied together with general algebraic equality and inequality constraints. The resulting finite nonlinear optimization problem is solved by a first-order descent method based on the filter methodology. In the equivalent tri-objective problem, the descent method aims to minimize the objective function, the violation of the ‘continuity conditions’ and the violation of the algebraic constraints simultaneously. The preliminary numerical experiments carried out with a set of benchmark OCP are encouraging.

This work proposes a multi-criteria decision making approach to help assessing and selecting suppliers in the olive oil sector. Olive oil is a protected agricultural product, by region and origin certificate. Therefore to select a supplier, it is of utter importance to inspect and test (taste, colour, smell, density, among others) the olive oil in addition to the supplying company. The identification of possible suppliers was done in two stages: firstly, the region of origin from which to choose possible suppliers was identified and then potential suppliers were evaluated on a set of characteristics for which minimum threshold values were set. From this study, which is not part of the research reported here, we were able to identify the suppliers of interest. Due to the several characteristics and characteristic dimensions used to choose a supplier we resort to the Analytic Hierarchy Process to rank them, this way allowing for a better choice. The rank obtained is robust as the top ranked supplier remains the same for any reasonable change in the criteria weighs and in the evaluation of the suppliers on each criterion. The involved company found the results of value, as well as the lessons learned by addressing the supplier evaluation problem using a more systematic approach.

Absenteeism is defined as the absence of a worker from his or her workplace during a normal day’s work schedule and is seen as a problem which companies face every day. The absence of an employee can result in a significant drop in productivity and the company’s daily revenue can be negatively impacted by it, which when multiplied by the absence of multiple workers in different days can have a harmful impact on the company’s financial situation. However, most managers neither understand nor have looked into the causes of their absence issue. This study took place at a company which produces cork stoppers, which deals with a problem of high absenteeism that costs around 1,200,000€ per year to the company. The main goal of this study is to identify the sectors in this com- pany which have the highest percentage of absenteeism, quantify its impact on related outcomes and diagnose its causes. The results of this study show that most absenteeism occurs in production areas and the causes are related to musculo- skeletal problems. The consequences involve various costs to the company, some of them difficult to quantify.

The absenteeism related to health and safety at work is a serious issue in the manufacturing process, and some industries can be dangerous work fields with a high level of accidents. It is important to understand what causes the accident and, if possible, apply standard procedures to minimize the risk of accidents and subsequent absenteeism. This study aims to assess the impact of the implementation of occupa-tional health and safety procedures on company absenteeism. In the compa-ny where the study took place, most work accidents and absenteeism hap-pened in the production area, with workers who directly handle raw materi-als and machines. As a result, an HSE manager was hired in order to reduce accidents by putting in place several hygiene and security measures and procedures. The results of these measures as well as absenteeism data were studied and con-clusions regarding company performance were drawn

The focus of the current study was to set the benchmark for designing school furniture for Portuguese primary schools, taking into account the characterization and analysis of a previously selected sample of students. Considering the anthropometric data of the Portuguese children with ages between six and ten years old and its treatment, it was possible to set benchmarks for the design of school furniture for Portuguese primary schools, as well as to develop a methodological guide for adjusting the furniture according to the student’s stature. The obtained results seem to be very relevant as they provide a scientific basis for the design and compatible with the anthropometric dimensions of the considered population of users.

Pultrusion is a widely known technique for production of constant cross-section profiles, such as bars, L-shape or T-shape profiles, as well as structural tubes in polymer matrix composite materials. In some applications, requirements are demanding for profiles able to provide better thermal or sound insulation or needing a slightly higher moment of inertia without increasing the ratio between weight and strength. In such cases, hybrid pultruded profiles with core based on preforms are a possible solution. After obtaining prototypes according to the methodologies described in a previous work, and as a complement to that work, it is necessary to verify if the properties of these hybrid profiles correspond to the initial expectations, by performing destructive and non-destructive tests. Thus, tensile, compression and bending tests were performed, in order to verify the mechanical benefits achieved through the core introduction into the hollow profile and to analyse the added value brought by these new products. These values, once properly validated, can be added to existing databases related to structural calculation programs, enabling to get the adequate values for calculations regarding this kind of profiles. In addition, thermal and acoustic insulation tests were performed, in order to quantify the physical improvements achieved regarding these properties, which are extremely important in specific applications linked to the civil construction and public works, among many others. The cored profiles showed a strong adhesion between the profile and any kind of core tested as well as improved properties in terms of thermal insulation and moment of inertia. However, the sound insulation did not present significant improvements, probably due to GFRP profile external rigidity and consequent reflection.

Hybrid pultrusion is a process that can be used to fabricate different products, enclosing distinct techniques and materials. Its development comes from the need to obtain properties' reinforcement of the structural profiles obtained by pultrusion, allowing its application into specific situations, such as thermal or acoustic insulation or to increase the product's moment of inertia, without having a proportional weight increase. In this work was developed based on a novel idea of manufacturing pultruded pipes around preforms of good thermal and/or acoustic insulator materials, such as cork and polyurethane foam. However, the same terminology was already used to describe fabrication techniques in which pultruded structural profiles were combined with concrete structures in order to increase the mechanical and/or flexural resistance, diminishing the total weight. Nevertheless, no industrial equipment is currently available on the market regarding the production of hybrid pultruded products based on preforms. Thus, novel equipment has been designed to provide a good connection with a conventional existing pultrusion machine, allowing the production of pultruded pipes that involve cork and polyurethane foam preforms in a continuous way. The equipment has been developed and tested, enable obtaining hybrid pultruded products that can be applied in several situations where flexural strength, acoustic or thermal insulation must be improved relatively to conventional pultruded products, broadening the market for this type of structural products. The manufacturing equipment is prepared to work without permanent workers, needing to be refilled every 60 min and showed to be competitive, being able to add value to the conventional profiles already on the market. Preliminary tests were carried out showing clearly the improvement of the mechanical strength, thermal insulation and acoustic insulation capacities.

This paper analyses the perception of Polytechnic of Porto (P.PORTO) students about entrepreneurship education in the graduated and training courses. A survey was conducted, supported by a questionnaire followed by researchers’ guidance. The perception of entrepreneurship education and training in students’ curricula was studied. Statistical analysis was applied using SPSS tool. Due to de diversity of graduated courses in P.PORTO it was possible to analyse the perception of students from different educational areas: Engineering, Health and Social Sciences. The main conclusion was that students from all courses seem to see entrepreneurship education and training as an important issue for their future career. As future work this survey should be applied to other P.PORTO units to have an integrated perception. The results of this study will be presented to courses coordinators to promote future curricula improvements.

This work proposes a multi-criteria decision making model to assist in the choice of a strategic plan for a world-class company. The Balanced Scorecard (BSC) is a support tool of Beyond Budgeting that translates a company’s vision and strategy into a coherent set of performance measures. However, it does not provide help in choosing a strategic plan. The selection of a strategic plan involves multiple goals and objectives that are often conflicting and incommensurable. This paper proposes an integrated Analytic Hierarchy Process-Goal Programming (AHP-GP) approach to select such a plan. This approach comprises two stages. In the first stage, the AHP is used to evaluate the relative importance of the initiatives with respect to financial indicators/KPIs; while in the second stage a GP model incorporating the AHP priority scores is developed. The GP model selects a set of initiatives that maximizes the earnings before interest and taxes (EBIT) and minimizes the Capital Employed (CE). The proposed method was evaluated through a case study.

This article describes a new approach in the Intelligent Training of Operators in Power Systems Control Centres, considering the new reality of Renewable Sources, Distributed Generation, and Electricity Markets, under the emerging paradigms of Cyber-Physical Systems and Ambient Intelligence. We propose Intelligent Tutoring Systems as the approach to deal with the intelligent training of operators in these new circumstances.

Globalization is revolutionizing our way of living and the way business companies work. Technology is the reason for it, because it provides solutions that help the workers perform more effectively and efficiently and that allow for better execution. The development of relationships with the customer gives companies a better knowledge and understanding of their needs and leads to new strategies that aim at better results for the customer. Customer Relationship Management (CRM) tools are taken as important tools for this, since they help analyzing the companies’ Key Performance Indicators (KPIs). In this article we use the case of a shipping company in order to understand how such systems can contribute to such improvement. By analyzing the company’s CRM we suggest an adjustment to the business in order to get a better performance from it.

The topic Cutting & Packing (C & P) has been published in many papers, and its importance within many industrial sectors is undeniable. For these reasons, several studies have been carried out on the optimization of the cutting process in order to improve the utilization of the useful area or the useful length of the raw material. Thus, this work aims to develop a computational tool that resolves the problem of minimizing losses in one-dimensional cuts. This problem is often encountered in industrial processes, where the beginning of the transformation and production of the raw material corresponds to the cutting process. To do so, the cutting problem will be formulated, and the Open Solver supplement will be used to obtain the solution.

In 2015, the UN defined well-being and decent work/economic growth as two of 17 sustainable development objectives. Nevertheless, the extreme pressure for businesses to be competitive in their markets of choice seems to be having a negative effect on workers’ well-being. In the manufacturing sector, the effective inclusion of Ergonomics in processes and installations has been proven to decrease costs related to disability, extra or overtime hours, medical care and premiums or fines for occurrences. The aim of this work was to review the existing scientific knowledge about the impact of adopting LPS (Lean Production Systems—a model used to increase competitiveness by the creation of more value for customers with fewer resources) in manufacturing companies from the point of view of Ergonomics. It reports, based on the literature reviewed, how the integration of both LPS and Ergonomics principles, from the workstation design phase onwards, can bring benefits to the workers’ welfare and simultaneously potentiate improvements in productivity. This paper also intends to present trends and opportunities for future research in this area, including in the Industry 4.0 field. In the authors’ opinion, this paper is a valuable contribution for practitioners, in manufacturing environments, and researchers.

The purpose of this paper is to present an attempt to develop an instrument containingoperational measures of lean combined with safety and ergonomic conditions in a workstation or productionline. This operational tool aims to help researchers and practitioners to prioritize and evaluate the lean implementations, as well as the ergonomic and safety conditions, in an integrated way.

Striving to improve productivity, industries have used different management approaches, being lean manufacturing the most used over recent years. Lean manufacturing is based on value creation for the customer and elimination of waste that occurs during the production process, while improving working conditions. The incorporation of ergonomic aspects in the workstation design also contributes for the referred objectives, since it will reduce awkward postures or excessive effort during work, leading to better working conditions and increased productivity. The present study highlights, through a case study in four production areas of a metallurgical industry, the benefits of using an integrated operations management approach to improve productivity and ergonomic aspects. Several ergonomic methods, such as Rapid Upper Limb Assessment (RULA), Strain Index (SI), and Rapid Entire Body Assessment (REBA), were chosen to evaluate the ergonomic situation and lean manufacturing tools such as Value Stream Mapping (VSM) and 7 wastes were also used to analyze the systems and increase the productivity by eliminating several wastes. The results of this study show that it is possible, and desirable, to consider both aspects, ergonomic conditions and productivity, during continuous improvement’ implementations. In fact, the improvements reached through the advances in ergonomic conditions can contribute very positively for productivity increasing.

The Lean manufacturing philosophy has been adopted by many different companies with the goal of responding to the economic recession which took place at the beginning of the twenty-first century. Two major motivators for this trend were reducing costs and improving customer satisfaction. Other than the known Lean methods, Human Factors and Ergonomics methods are also able to contribute to this emphasis. Thus, the creation of safe, effective workplaces emphasizing a human oriented approach, and the implementation of Ergonomics in business process management, represent two of the main conditions for the sustainable development of a company. Pinpointing the connections between Ergonomics and LPS enables us to address both at the same time. Besides, synergism between Lean and Ergonomics can be attained. The aim of this paper is to develop a tool in the form of a flowchart which will include the steps for integrating the single-minute exchange of die (SMED), a Lean tool, while considering Ergonomics. This flowchart (named “ErgoSMED”) has been validated by several case studies. We were able to demonstrate that synergism between Lean and Ergonomics can be reached. The ErgoSMED flowchart developed in this study is innovative because it combines Ergonomics with a SMED tool and is ready to be used in any production area by professionals or researchers

The study described in this work took place in the sanding and polishing area of a meta-lurgical company, where workers’ complaints due to the strength needed to perform manual tasks, as well as their repetitive pattern, led to cases of shoulder pain and tendinitis.The study aimed to evidence the benefits of using an integrated operations management approach, following lean/agile/ergonomic concepts, to improve the performance and ergonomic aspects of a production system. The results demonstrate that it is possible to reach an efficient production system, which meets safety and ergonomics requirements, by using lean and agile principles and companies should consider both ergonomic aspects and production performance during continuous improvement implementations to increase productivity and worker well-being.

In many companies in the automotive industry there are challenges in some key processes in their logistic departments, mainly in internal logistics. These challenges happen due to poorly defined rules for the transportation of goods, resulting in a great cost associated with the time lost in the process. Also, the optimization of these processes, incrementing the efficiency of internal logistics can bring competitive advantages to the companies. For that matter, this study was developed at a major tire manufacturing company and proposes a model for the optimization of in-bound logistics, viewed as an online vehicle routing problem with soft deadlines (OVRPSD), using multiple depots. The main goal of this study is the increase of efficiency in logistic, optimizing the number of vehicles to supply the machines in order to reduce the stopping time of machines due to the lack of tires to consume.