Szymon Piasecki, Marek Jasiński and Aritz Milicua
The purpose of this paper is to consider both sides of a back‐to‐back AC‐DC‐AC interface.
Abstract
Purpose
The purpose of this paper is to consider both sides of a back‐to‐back AC‐DC‐AC interface.
Design/methodology/approach
The paper presents a mathematical analysis, simulation, laboratory test in scaled model.
Findings
The two main findings comprised concept of control methods for grid AC‐DC‐AC converter applied in renewable energy sources with variable speed operation under distorted grid. Active filtering functionality in case of non‐linear current of a parallel load. Second, a control algorithm dedicated for two‐level AC‐DC converter applied in industrial networks with high‐order harmonics compensation working under hard conditions – balanced and unbalanced voltage dips.
Research limitations/implications
The paper shows preliminary results for AC‐DC‐AC converter and active filter (AF) during voltage dips and for harmonics compensation. Control methods and/or topology should be improved and tested in scale and after at high‐power system.
Practical implications
Power quality supplied/received to/from the grid can be increased. In case of low‐cost system only AF can be applied to existing non‐linear receivers. Moreover, in case of full AC‐DC‐AC converter energy saving and production is possible.
Originality/value
Presented control methods give satisfactory results. Paper presents laboratory results for grid and machine side two different power circuits during steady states and transients. Moreover, active filtering operation during voltage dips is presented.
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Marek Jasinski, Mariusz Cichowlas and Marian P. Kazmierkowski
Proposes the application of novel control strategy in power transistors (insulated gate bipolar transistors – IGBT) based on AC/DC/AC converter with active filtering function…
Abstract
Purpose
Proposes the application of novel control strategy in power transistors (insulated gate bipolar transistors – IGBT) based on AC/DC/AC converter with active filtering function. Seeks to investigate the possibilities of operating drive system under distorted line voltage with unity power factor and reduced dc‐link capacitor.
Design/methodology/approach
A novel control strategy is proposed based on direct power and direct torque control with space vectors modulators scheme which seems to be most promising. This method is investigated, implemented and examined in the laboratory setup. Different working conditions are taken into consideration.
Findings
Provides information how the proposed system works under motoring and regenerating modes. Good behaviors of the system in steady state in transience are shown. Very good stabilization of the dc‐link voltage under transient is achieved. Almost sinusoidal line current is obtained. Very good compensation of nonlinear load is also achieved.
Research limitations/implications
This is not an exhaustive investigation. The system should be tested with different input inductances (or LCL filters) and with reduced dc‐link capacitor. Moreover, laboratory tests with higher power should be performed in the future.
Practical implications
A useful source of information and an example of how a fully controlled AC/DC/AC converter with active filtering function works. It could be an important basis for a prototype for industry.
Originality/value
Although the direct power control with space vector modulator (DPC‐SVM) and direct torque control with space vector modulator (DTC‐SVM) schemes have been described in the literature separately, it is analyzed for the first time and investigated together for control of the AC/DC/AC converter. Additionally, active filtering provides a feature of power compensation. It could be the basis for a clean power system design.
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The purpose of this study is to show that the methods of the numerical simulation can be a very effective tool for a proper choice of control parameters of artificial…
Abstract
Purpose
The purpose of this study is to show that the methods of the numerical simulation can be a very effective tool for a proper choice of control parameters of artificial hyperthermia. An electromagnetic field induced by two external electrodes and a temperature field resulting from electrodes action in a 3D domain of biological tissue is considered. An important problem is the appropriate directing of heat in the region of tumor, so as to avoid damaging healthy cells surrounding the tumor. Recently, to concentrate the heat on the tumor, magnetic nanoparticles, which are introduced into the tumor, were used. The nanoparticles should be made of material that ensures appropriate magnetic properties and has a high biocompatibility with the biological tissue. External electric field causes the heat generation in the tissue domain.
Design/methodology/approach
The distribution of electric potential in the domain considered is described by the Laplace system of equations, while the temperature field is described by the Pennes’ system of equations. These problems are coupled by source function being the additional component in the Pennes’ equation and resulting from the electric field action. The boundary element method is applied to solve the coupled problem connected with the heating of biological tissues.
Findings
The aim of investigations is to determine an electric potential of external electrodes and the number of nanoparticles introduced to a tumor region to obtain the artificial hyperthermia state. The tests performed showed that the proposed tool to solve the inverse problem provides correct results.
Research limitations/implications
In the paper the steady state bioheat transfer problem is considered, so the thermal damage is a function of the temperature only. Therefore, the solution can be considered as the maximum ablation zone of cancer. Additionally, the choice of appropriate parameters will be affected on the position and shape of the tumor and the electrodes.
Originality/value
In the paper the inverse problem has been solved using the evolutionary algorithm, gradient method and hybrid algorithm which is a combination of the two previous.
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Diana L. Summers and Emil W. Pływaczewski
The dynamics of drug use and trafficking in Poland have changed dramatically since the early 1990s. These changes include legal definitions of drug use, the actors involved in…
Abstract
Purpose
The dynamics of drug use and trafficking in Poland have changed dramatically since the early 1990s. These changes include legal definitions of drug use, the actors involved in trafficking, and the types of drugs traversing the country. The Polish police force experienced two significant reforms in the 1990s and drug‐related legislation underwent significant reconstruction in 1997 and 2000, while drug trafficking operations continue to persist by organized criminal groups. The purpose of this study is to qualitatively investigate these police reforms and drug legislation developments since 1990, and empirically analyze the interaction effects of these reforms with drug trafficking arrests in Poland.
Design/methodology/approach
Officially reported annual data were tested using multivariate regression analyses.
Findings
The findings observed from this exploratory study suggest that both the police reforms and changes in drug‐related legislation positively affected the number of arrests for drug trafficking. Additionally, this study found support for an increase in efficiency of the policing model despite the recent decline in the strength of the police force. Interestingly, the number of police officers in the country had no effect on any of the variables.
Research limitations/implications
Quantitatively, the small number of observations poses limitations on the interpretation of the multivariate regression results. In addition, future research should include additional explanatory variables to achieve a greater comprehensive summary of the interaction effects of policing reforms and drug‐related legislation with drug trafficking arrests.
Practical implications
This paper illustrates the need for accurate and timely national‐level, systematically collected data on drug‐ and police‐related indicators that will allow for more inclusive and comprehensive analyses.
Originality/value
This study is one of the first to empirically examine potential interaction effects of police reform and drug‐related legislation on drug trafficking arrests in Poland.
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Janusz Marek Smulko, Maciej Trawka, Claes Goran Granqvist, Radu Ionescu, Fatima Annanouch, Eduard Llobet and Laszlo Bela Kish
– This paper aims to present the methods of improving selectivity and sensitivity of resistance gas sensors.
Abstract
Purpose
This paper aims to present the methods of improving selectivity and sensitivity of resistance gas sensors.
Design/methodology/approach
This paper compares various methods of improving gas sensing by temperature modulation, UV irradiation or fluctuation-enhanced sensing. The authors analyze low-frequency resistance fluctuations in commercial Taguchi gas sensors and the recently developed tungsten trioxide (WO3) gas-sensing layers, exhibiting a photo-catalytic effect.
Findings
The efficiency of using low-frequency fluctuations to improve gas detection selectivity and sensitivity was confirmed by numerous experimental studies in commercial and prototype gas sensors.
Research limitations/implications
A more advanced measurement setup is required to record noise data but it will reduce the number of gas sensors necessary for identifying the investigated gas mixtures.
Practical implications
Fluctuation-enhanced sensing can reduce the energy consumption of gas detection systems and assures better detection results.
Originality/value
A thorough comparison of various gas sensing methods in resistance gas sensors is presented and supported by exemplary practical applications.