Una aproximación histórica a las representaciones contables en Colombia. (A historical approach to accounting representations in Colombia).

En este trabajo se realiza un abordaje de las representaciones contables para analizar cómo han evolucionado a través del tiempo, desde el marco interpretativo de la nueva historia. Representaciones tales como información, certificación y control, entre otras, desde el plano praxiológico han estado presentes, con dinámicas propias, en la historia de la profesión contable en Colombia, tomando como fuente las normas que se expiden desde un enfoque público, demarcando una identidad histórica que permite comprender la complejidad de los elementos que confluyen en la práctica y el saber contables contemporáneos. This paper is an approach to analyze the evolution of accounting representations in the course of time from the new history interpretative point of view. Representations such as information, certifying and control, among others, have been present in the history of the accounting profession in Colombia. They have developed following their own dynamics within the framework provided by the norms dictated by the public authorities. Their evolution demarcates a historical identity that allows the understanding of the complex ensemble of elements that shape the contemporary accounting praxis and knowledge.Historia de la contabilidad,información, certificación y control, Colombia. Accounting history, information, certifying and control, Colombia.

Predictive control in matrix converters. Part I, Principles, topologies and applications

This paper presents an overview of the predictive control principles applied to matrix converters and also the different topologies where this control technique is applied. It will be shown that the predictive strategy is a promising alternative to control matrix converters due to its simplicity and flexibility to include additional aspects in the control being suitable for different industrial applications

Predictive control in matrix converters. Part II, Control strategies, weaknesses and trends

The second part of this paper presents an overview of different control strategies and applications for matrix converters (MCs) where predictive control techniques are applied. It will be shown that predictive control is a promising alternative to control MCs due to its simplicity and flexibility to include different constrains in the con¬trol for different industrial applications such as renewable energies, grid interconnection, multi-drives systems control, among others. In addition, some limitations and weaknesses of predictive control in MCs will be discussed as well as some future trends and applications

Inventory routing for dynamic waste collection

We consider the problem of collecting waste from sensor equipped underground containers. These sensors enable the use of a dynamic collection policy. The problem, which is known as a reverse inventory routing problem, involves decisions regarding routing and container selection. In more dense networks, the latter becomes more important. To cope with uncertainty in deposit volumes and with fluctuations due to daily and seasonal e ects, we need an anticipatory policy that balances the workload over time. We propose a relatively simple heuristic consisting of several tunable parameters depending on the day of the week. We tune the parameters of this policy using optimal learning techniques combined with simulation. We illustrate our approach using a real life problem instance of a waste collection company, located in The Netherlands, and perform experiments on several other instances. For our case study, we show that costs savings up to 40% are possible by optimizing the parameters

Experimental implementation of a linear control technique for a single-phase matrix converter

This paper describes a matrix converter with a three-phase input and single-phase output that can be used as a building block for high-power cascaded converters. In this paper a sinusoidal pulse width modulation technique with a linear controller is proposed for the single-phase output matrix con¬verter. The proposed modulation and control will be used in the cascade configurations for high-power applications. Simulation and experimental results are presented to validate the proposed modulation and control approach

Indirect model predictive current control techniques for a direct matrix converter

The direct matrix converter has twenty-seven available switching states which implies that the implementation of predictive control techniques in this converter requires high computational cost while an adequate selection of weighting factors in order to control both input and output sides of the converter. In this paper, two indirect model predictive current control strategies are proposed in order to simplify the computational cost while avoiding the use of weighting factors. Both methods are based on the fictitious dc-link concept, which has been used in the past for the classical modulation and control techniques of the direct matrix converter. Simulated results confirm the feasibility of the proposed techniques demonstrating that they are an alternative to classical predictive control strategies for the direct matrix converter

A new AC/AC power converter

The Future Electrical Network will be based on the integration of different renewable energy sources. In this regard, modular bidirectional power converter architectures will get special attention. Galvanic isolation in such power converter architectures plays a vital role in confining faults. This paper presents a new AC/AC converter concept suitable for Solid State Transformer (SST) applications. The basic operation of the topology is first presented, followed by the development of suitable modulation, commutation and protection methods. The proposed idea is validated in simulation with PLECS

Indirect predictive control strategy with mitigation of input filter resonances for a direct matrix converter

In this paper an indirect model predictive current control strategy is proposed. The proposed method simplifies the computational cost while avoiding the use of weighting factors. Weighting factors are an issue for model predictive control in a direct matrix converter due to the large number of available switching states and necessity to control both input and output sides of the converter

Experimental implementation of a linear control technique for a single-phase matrix converter

This paper describes a matrix converter with a three-phase input and single-phase output that can be used as a building block for high-power cascaded converters. In this paper a sinusoidal pulse width modulation technique with a linear controller is proposed for the single-phase output matrix con¬verter. The proposed modulation and control will be used in the cascade configurations for high-power applications. Simulation and experimental results are presented to validate the proposed modulation and control approach