Research results at the site of Golo rebro in the village of Donji Neradovac near Vranje

У раду се представљају резултати сондажних, заштитних истраживања на налазишту Голо ребро, окарактерисаном као периферија тетрархијског-касноантичког мањег насеља у околини данашњег Врања.dvojezično, srpsko-englesko izdanj

Assembly and use experience of a 3D printerin education

[EN] An academic experience consisting of mounting and using a 3d printer in the secondary school class ofTechnology is described. Also the methodology developed by teachers responsible of the project for taskscoordination as well as the way students interacted along their work, are explained. Di erent groups ofstudents were formed in order to work in three di erent tasks: research task, documents development andassembly task. Each di erent task had its own teacher for guiding, assisting and assessing the student'swork. This kind of innovative experiences are shown not only to motivate students but also to encouragethem to face STEM (Science, Technology, Engineering and Mathematics) projects from a wider perspec-tive, integrating several areas of knowledge.[ES] Se describe la experiencia anual llevada a cabo en la clase de Tecnología de un grupo de tercero de Enseñanza Secundaria Obligatoria (ESO) sobre el montaje y operación de una impresora 3D. Se detalla la metodología empleada por el profesorado para la coordinación del trabajo tanto entre los profesores asociados a la experiencia como entre los alumnos. El alumnado se dividió en grupos para la realización de tres grandes bloques de tareas: búsqueda de información, elaboración de documentación y tareas de montaje. Cada grupo tuvo su profesor responsable para atender y evaluar el trabajo del alumnado. Se demuestra que este tipo de experiencias innovadoras no solo motiva a los estudiantes sino que les anima a afrontar los proyectos CTIM (Ciencia, Tecnología, Ingeniería y Matemáticas) desde una perspectiva más amplia, integrando distintas áreas de conocimiento.Orquín Serrano, I.; Aguado Sahagún, H.; Berenguer Sánchez, G.; Petrovic Filipovic, V. (2017). Experiencia de montaje y operación de una impresora 3D en el aula. Modelling in Science Education and Learning. 10(2):107-116. doi:10.4995/msel.2017.6619SWORD10711610

Robust switching control systems with input delay

This paper uses the concept of multiple models and the concept of switching controllers. The analog part of the system is described by a finite set of continuous-time models with input delays. The continuous-time models include unmodeled dynamics in the form of affine matrix family. By using suitable transformation, the models with input delay are converted into delay free models. Then, by using the LMI tool, the class of robust LQ controllers with the prescribed degree of stability is proposed and for every controller the upper bound for the performance index is given. The switching logic is based on the selection of minimal upper bound from the collection of upper bounds. Finally, it is shown by means of performance dominant conditions, that the resulting closed-loop is stable

Design of an H<inf>∞</inf> PI controller with given relative stability and its application to the CSTR problem

© 2018, Association of Chemists and Chemical Engineers of Serbia. All rights reserved. H∞ control theory has achieved a very high level, which is not followed by appropriate applications in industry. Some reasons are: synthesis of H∞ controllers is complex and based on the numerical Nevanlinna-Pick procedure, high order of controllers (higher than the order of the process) and sensitivity to deviation of controller coefficients (fragile controller). On the other hand, PI (PID) controllers are still dominant in industry, which places the problem of design of fixed structure controllers at the forefront. The mentioned problem is very difficult. This paper proposes a simple interactive procedure for design of H? PI controllers with the presence of constraints (given the relative stability) based on D-decomposition. The catalogue of responses to references, suppression of disturbances and minimum of H∞ criteria of control is created. Selection of controllers, based on the catalogue, is left to the user. The application of H∞ PI controllers to a CSTR (continuous stirred-tank reactor) is demonstrated

Modified approach to distillation column control

© 2017, Association of Chemists and Chemical Engineers of Serbia. All rights reserved. This paper contains methodology research for forming the control algorithm for a distillation column, modeled as TITO (two-input two-output) process. Its modified form was obtained by connecting the two parts, and this combination hasn't been applied for such a industrial plant, until now. These parts include: a simplified decoupler which was first designed and decentralized PID controller obtained using D-decomposition method for such decoupled process. The decoupler was designed in order to make process become diagonal, and parameters of PID controllers are defined for the two SISO (single-input single-output) processes starting from relation between IE (integral error) criterion and integrator gain, taking into account desired response characteristics deriving from technological requirements of controlled plant. Their connecting provides centralized control. Analysis of the processes responses, obtained by the proposed algorithm and their comparison with the results from the literature, were performed after the completion of the simulations. The proposed approach to the centralized controller design, beside its simplicity of usage and flexibility in achieving diversity of process dynamic behavior, gives better response characteristics, in comparison with existing control algorithms for distillation column in the literature

Multilinear Model of Heat Exchanger with Hammerstein Structure

© 2016 Dragan Pršić et al. The multilinear model control design approach is based on the approximation of the nonlinear model of the system by a set of linear models. The paper presents the method of creation of a bank of linear models of the two-pass shell and tube heat exchanger. The nonlinear model is assumed to have a Hammerstein structure. The set of linear models is formed by decomposition of the nonlinear steady-state characteristic by using the modified Included Angle Dividing method. Two modifications of this method are proposed. The first one refers to the addition to the algorithm for decomposition, which reduces the number of linear segments. The second one refers to determination of the threshold value. The dependence between decomposition of the nonlinear characteristic and the linear dynamics of the closed-loop system is established. The decoupling process is more formal and it can be easily implemented by using software tools. Due to its simplicity, the method is particularly suitable in complex systems, such as heat exchanger networks