Control Method of Four Wire Active Power Filter Based on Three-Phase Neutral Point Clamped T-Type Converter

An active power filter based on a three-level neutral point clamped T-type converter with LCL input filter is presented in the paper. The main goal of the paper is the analysis of a control system that ensures independent control of a current in each phase. The presented control method of the filter allows reactive power compensation and/or a higher harmonics reduction to be achieved in each phase independently, with the possibility of control tan (φ) coefficient. This allows the power flow between the phases to be minimalized and reduces the RMS values of filter currents without the need to balance grid currents. The analysis presents the possibility of an operation in different modes, which was verified by experimental results. The results have been obtained in a 20 ARMS laboratory system described in the paper. The results reveal relatively low power losses, which are a feature of the selected three-level T-type topology. Additionally, that topology, when compared to a two-level one, ensures the reduction in current ripples with the same parameters of passive components.

The spectral line asymmetry of the Doppler effect in relativistic plasmas

{In this work, we present a comparative study between the relativistic and non- relativistic Doppler effects on spectral line profiles in ultra-hot plasmas at the laboratory system. We have established an exact formula of the relativistic Doppler profile in ultra-high-temperature plasma that is not a Gaussian one (unlike the nonrelativistic Doppler profile that is Gaussian). We have also derived a new FWHM (Full Width at Half Maximum) formula of the corresponding profile that is different from the non-relativistic FWHM (sqrtlog(T=M)). We have also shown that, in the relativistic case, Doppler broadening exhibits an asymmetry of spectral line profile (non- gaussian profile). To ensure the validity of our investigation, we have compared our theoretical calculation with the experimental results that shows a good agreement.

Visualization of hydrodynamic and physico-chemical processes in rotating and vibrating containers

Variable inertial fields are an efficient way to control the behaviour of hydrodynamic systems. Forces of inertia can be used, for example, to stabilize or destabilize systems with an interface or density gradient, to mix multiphase or non-isothermal fluids. The implementation of this approach means that liquids fill the periodically moving containers. In this paper, the situations are considered when the containers perform either rotation or translational vibrations. Methods for measuring the density and velocity fields of convective flows in reacting hydrodynamic systems are described. Interferometry is used to visualize the density distribution. Particle image velocimetry (PIV) is used to study the structure and velocity of the flows. Optical instruments are installed stationary in the laboratory system. For video recording, a camera shutter is synchronized with the motion of a container, and thus the images are captured in a fixed phase of oscillations or rotation. Constructions of the containers make it possible to illuminate the working volume through transparent walls at different angles or in different planes. They also provide a compensation for the centrifugal pressure and allow interference cells to be used in overload conditions. The successful application of the methods in experimental studies of chemo-hydrodynamic processes is demonstrated.

Assessment of the National Veterinary Laboratory System Capacity for the Detection of Infectious Threats to Global Health Security in Benin

Introduction: The International Health Regulations 2005 require countries to establish laboratory systems for rapid and safe confirmation of public health emergencies including zoonoses. Objectives: This study assessed the national veterinary laboratory system capacity for the confirmation of infectious threats to global health security in Benin. Method: The study was descriptive, cross-sectional and evaluative. The non-probability sampling method with selection of the two existing veterinary laboratories were used. Two questionnaires, one observation grid and the Food and Agriculture Organization laboratory mapping tool-core were used. The system capacity was rated good if each laboratory met at least 80% of the assessed criteria. Otherwise, the capacity was rated insufficient. Results: The national veterinary laboratory system capacity in Benin was insufficient. Bohicon laboratory satisfied 27.2% of assessed criteria; With the laboratory mapping tool-core, Parakou laboratory had an average indicator of 50.7%. Laboratory collaboration and networking was the best performing domain with 66.7%. Only basic supplies category reached 80%. Laboratory budget, sample accession and availaible technology had the lowest scores. The veterinary laboratory system is facing shortage of staffs. Avian influenza virus is confirmed by the two laboratories; Bacillus anthracis and rift valley fever virus are only confirmed by Parakou laboratory. Ebola and Lassa fever are not confirmed. There is no collaboration between the laboratories in the country. Conclusion: The veterinary laboratories are not able to ensure timely detection of zoonoses and inform health system for preparedness. The development and implementation of the veterinary laboratory system improvement plan is essential for the global health security in Benin.

Quantum Cascade Laser Photoacoustic Spectroscopy Applied to Rice Flour Analysis

In the present work we applied laser photoacoustic spectroscopy (LPAS) to the analysis of food samples. In particular, we analyzed samples of different rice flours (standard and commercial ones). For this purpose, a laboratory system based on quantum cascade laser (QCL) has been developed and characterized. After that, the LPAS spectra of all the rice samples were collected with a standard error of less than 2% of the measured value and a background signal negligible compared to the sample signals. All the experimental LPAS spectra resulted to be rich in spectral features showing clear differences between each other. The experimental spectra were then analyzed by comparison with the FT-IR transition frequency recorded in our laboratory to consent a proper assignment. Finally, to put in evidence the small differences among the various rice types, the Principal Component Analysis (PCA) was applied to the recorded LPAS spectra highlighting five different groups corresponding to the five types of samples. In conclusion, the present work demonstrated the discriminating capability of LPAS technique in the case of different types of rice flour samples.

Observer Design for a Variable Moment of Inertia System

Variable moment of inertia systems are common, and a popular laboratory system of this type is the “ball-and-beam”. Such systems are, however, nonlinear and often unstable. Efficient control requires full state information (or at least partial velocities), which are generally difficult to measure. That is why the design of state observers is a relevant problem. In this paper, a new design of an observer is proposed. This new nonlinear observer uses partial output injection and the circle criterion to ensure semiglobal stability. Moreover, we present a complete modeling of the system and systematic testing of the observer in comparison to a baseline in the form of a linear observer. The results show that the designed observer outperforms its linear counterpart and does not impede control.