Celina Pinto Leão

Transient and steady-state models for simulated moving bed processes: numerical solutions

Abstract The objective of this work is to compare different strategies for the numerical solution of mathematical models of simulated moving bed (SMB) processes to predict the transient and steady-state behaviour. The mathematical model is based on the true moving bed (TMB) description of SMB processes. The model assumes axial dispersion flow for the liquid phase and plug flow for the solid phase. Intraparticle mass transfer was described in terms of a simple linear driving force (LDF) approximation. The mathematical models for transient situations (TM_1 and TM_2) can be written in terms of system of partial differential-algebraic equations (PDAEs) or partial differential equations (PDEs), respectively, when the algebraic equation representing the adsorption equilibrium isotherm is inserted into the mass conservation/mass transfer kinetics equations or written as separate equation. Similarly, for steady-state the mathematical models (SSM_3 and SSM_4) are represented by a system of differential-algebraic equations (DAEs) or ordinary differential equations (ODEs). Different public domain solvers were used to numerically solve the four mathematical models described above. For the transient model TM_1 the DASSL solver was used to solve the system of PDAEs and for TM_2 the PDECOL package was used to solve the system of PDEs. For the steady-state model, the solvers COLDAE and COLNEW were used to solve the DAEs and ODEs systems, corresponding to the models SSM_3 and SSM_4, respectively. The glucose/fructose separation was used as a test case in a SMB with a 12 column configuration considering both linear and non-linear isotherms. The study of the effect of the operating conditions on the TMB performance and separation regions was also analysed. For the calculation of steady-state concentration profiles and process performance COLDAE solver is recommended because it requires less computing time and allows working with the adsorption equilibrium isotherm separately permitting easy changes on the algebraic relationship.

Testing thermal comfort of trekking boots: An objective and subjective evaluation

The study of the thermal comfort of the feet when using a specific type of shoe is of paramount importance, in particular if the main goal of the study is to attend to the needs of users. The main aim of this study was to propose a test battery for thermal comfort analysis and to apply it to the analysis of trekking boots. Methodologically, the project involves both objective and subjective evaluations. An objective evaluation of the thermal properties of the fabrics used in the boots was developed and applied. In addition, the thermal comfort provided when using the boots was also assessed both subjective and objectively. The evaluation of the thermal comfort during use, which was simulated in a laboratory environment, included the measurement of the temperature and moisture of the feet. The subjective assessment was performed using a questionnaire. From the results obtained, it was possible to define an optimal combination of fabrics to apply to trekking boots by considering the provided thermal insulation, air permeability and wicking. The results also revealed that the subjective perception of thermal comfort appears to be more related to the increase in temperature of the feet than to the moisture retention inside the boot. Although the evaluation of knits used in the boots indicated that a particular combination of fibres was optimal for use in the inner layer, the subjective and objective evaluation of thermal comfort revealed that the evaluation provided by users did not necessarily match the technical assessment data. No correlation was observed between the general comfort and specific thermal comfort assessments. Finally, the identification of thermal discomfort by specific foot areas would be useful in the process of designing and developing boots.

Design of a Lean Methodology for an Ergonomic and Sustainable Work Environment in Textile and Garment Industry

This paper presents a methodology to implement Lean Production (LP) in Portuguese Textile and Garment Industry (TGI). Lean Production is a well-known work organizational model being, nowadays, widely implemented in all sort of industries and services companies. LP responds to customers’ demand for on-time delivery of high quality products at reduced costs, through continuous waste elimination (e.g., overproduction, raw materials, energy and water more than necessary, among others). In this methodology is included, besides the Lean tools and techniques, some ergonomics tools in order to assess the ergonomic work conditions and techniques to evaluate the company sustainability. It is expected that, with the involvement of these tools, will allow the implementation of a Lean Production that creates a positive work environment for workers giving special attention to sustainable development.Copyright

An Overview of Industrial Communication Networks

The authors of this paper are grateful to national funds by FCT—Fundacao para a Ciencia e Tecnologia in the scope of the project: PEst-OE/EEI/UI0319/2014.

Safety climate and its relationship with furniture companies’ safety performance and workers’ risk acceptance

This study aims to analyse the relationship between safety climate and the level of risk acceptance, as well as its relationship with workplace safety performance. The sample includes 14 companies and 403 workers. The safety climate assessment was performed by the application of a Safety Climate in Wood Industries questionnaire and safety performance was assessed with a checklist. Judgements about risk acceptance were measured through questionnaires together with four other variables: trust, risk perception, benefit perception and emotion. Safety climate was found to be correlated with workgroup safety performance, and it also plays an important role in workers’ risk acceptance levels. Risk acceptance tends to be lower when safety climate scores of workgroups are high, and subsequently, their safety performance is better. These findings seem to be relevant, as they provide Occupational, Safety and Health practitioners with a better understanding of workers’ risk acceptance levels and of the differences among workgroups.

Risk Acceptance in the Furniture Sector: Analysis of Acceptance Level and Relevant Influence Factors

ABSTRACT Risk acceptance has been broadly discussed in relation to hazardous risk activities and/or technologies. A better understanding of risk acceptance in occupational settings is also important; however, studies on this topic are scarce. It seems important to understand the level of risk that stakeholders consider sufficiently low, how stakeholders form their opinion about risk, and why they adopt a certain attitude toward risk. Accordingly, the aim of this study is to examine risk acceptance in regard to occupational accidents in furniture industries. The safety climate analysis was conducted through the application of the Safety Climate in Wood Industries questionnaire. Judgments about risk acceptance, trust, risk perception, benefit perception, emotions, and moral values were measured. Several models were tested to explain occupational risk acceptance. The results showed that the level of risk acceptance decreased as the risk level increased. High-risk and death scenarios were assessed as unacceptable. Risk perception, emotions, and trust had an important influence on risk acceptance. Safety climate was correlated with risk acceptance and other variables that influence risk acceptance. These results are important for the risk assessment process in terms of defining risk acceptance criteria and strategies to reduce risks.

Definition of a protocol for implementing lean production methodology in textile and clothing case studies

The authors of this paper would like to express their acknowledgments to the companies and to all people who accepted the challenge to participate in this study. The authors are also grateful to Portuguese Foundation for Science and Technology, under Strategic Projects PEstOE/EME/UI0252/2011 and PEst-C/EEI/UI0319/2011, for financial support.

Web-Assisted Laboratory for Control Education: Remote and Virtual Environments

The Web Assisted Laboratory for Control (WALC) engineering on-line education is described. This on-line platform was developed by a multidisciplinary team. WALC enables the access to several virtual and remote laboratories experiences on automation, process control and numerical methods. The virtual environment enables the registered user to test different control systems (hydraulic, mechanical, electrical) working in open and close loop. This environment is simulated based on the numerical solutions of the differential equations that describe the real world systems. An industrial automation network is available allowing the user to test different programs running on PLCs. The remote access to the platform is confined to pre-registered users and under a booking system ensuring that only the registered user is on-line. Other functionalities are depicted. Based on user’ feedback analysis, and since this platform was developed as a dynamic learning tool, their needs are fulfilled.

Teaching differential equations in different environments: A first approach

The use of specific softwares was the basis for a new approach for teaching ordinary and partial differential equations, in the field of heat transfer and fluid mechanics. The main objective was to enhance learning effectiveness of Numerical Methods in the post‐graduate course of Polymers Engineering at the University of Minho. This degree takes place into two different environments: at the university campus and at the industrial field. Different commercial codes were used, namely EXCEL, MATLAB, and FLUENT, as well as two tools developed in house at University of Minho: CoNum and a graphics application PDE v.1. Lectures were based on videoconferencing and other web utilities. The teaching methodology presented and discussed in this article was well received and accepted by the post‐graduate students, motivating teachers to improve their teaching/learning strategies.

Measurement rounding errors in an assessment model of project led Engineering Education

This paper analyzes the rounding errors that occur in the assessment of an interdisciplinary Project-Led Education (PLE) process implemented in the Integrated Master degree on Industrial Management and Engineering (IME) at University of Minho. PLE is an innovative educational methodology which makes use of active learning, promoting higher levels of motivation and studentsâ?? autonomy. The assessment model is based on multiple evaluation components with different weights. Each component can be evaluated by several teachers involved in different Project Supporting Courses (PSC). This model can be affected by different types of errors, namely: (1) rounding errors, and (2) non-uniform criteria of rounding the grades. A rigorous analysis of the assessment model was made and the rounding errors involved on each project component were characterized and measured. This resulted in a global maximum error of 0.308 on the individual student project grade, in a 0 to 100 scale. This analysis intended to improve not only the reliability of the assessment results, but also teachersâ?? awareness of this problem. Recommendations are also made in order to improve the assessment model and reduce the rounding errors as much as possible.