Search

The permanent magnet flux is an important model parameter that determines the operation of the line start permanent magnet synchronous motor. It is degraded with operating time due to the permanent magnet demagnetization which is principally caused by the armature magnetic field interaction and operating temperature. This paper introduces an observer design study aimed at estimating the permanent magnet flux of the line start permanent magnet synchronous motor from the measurement of stator currents. Derived from the mathematical description in the dq0 reference frame, a model of the motor with state variables of stator currents, magnetic fluxes and rotor angular frequency is considered. Model analysis and with a new flux variable setting allow an estimation of the rotor flux through the open loops from the stator currents. The observer is then designed with a constant gain for the system with states of stator currents and permanent magnet flux. Simulation confirms the efficiency and robustness of the designed observer.

Background: The under-representation of Vietnamese ethnic groups in existing genetic databases and studies have undermined our understanding of the genetic variations and associated traits or diseases in the population. Cost and technology limitations remain the challenges in performing large-scale genome sequencing projects in Vietnam and many developing countries. Non-invasive prenatal testing (NIPT) data offers an alternative untapped resource to study genetic variations in the Vietnamese population. Results: We analyzed the low-coverage genomes of 2,683 pregnant Vietnamese women using their NIPT data and identified a comprehensive set of 8,054,515 single-nucleotide polymorphisms, among which 8.2% were new to the Vietnamese population. Our study also revealed 24,487 disease-associated genetic variants and their allele frequency distribution, especially five pathogenic variants for prevalent genetic disorders in Vietnam. We also observed major discrepancies in the allele frequency distribution of disease-associated genetic variants between the Vietnamese and other populations, thus highlighting a need for genome-wide association studies dedicated to the Vietnamese population. Conclusions: We have demonstrated a successful analysis of NIPT data to reconstruct the Vietnamese genetic profiles. This application provides a powerful yet cost-effective approach for large-scale population genetic studies.

Bài viết giới thiệu nghiên cứu “Paintings Can Be Forged, But Not Feeling”: Vietnamese Art—Market, Fraud, and Value về thực trạng tranh giả tại Việt Nam.

Polymer nanocomposites that based on combination of nanomaterials (such as nanoparticles, nanotubes, nanorods, nanofibers, and nanosheets) and polymeric matrices are receiving great attention in research and application. However, separate and homogenous dispersion rather than aggregates of nanoparticles into matrices meet big difficulty due to large interaction between nanoparticles. The poor dispersion leads to low properties of nanocomposites. In this study, we find out the appropriate method to separately disperse cerium oxides (CeO2) nanoparticles into natural rubber, aiming to increase mechanical properties of natural rubber. The SEM images were used to evaluate the dispersion of nano CeO2 in natural rubber matrix. The mechanical properties of nanocomposites were measured after vulcanization to investigate effects of nano CeO2 amount on prepared composite. The findings exhibited that the addition of CeO2 by dispersion of nano CeO2 in water via ultrasonication before mixing with rubber latex, signific...

International audience; Recently, solid state DC circuit breaker (SSCB) using normally-on SiC-JFET offers a great protection device for DC microgrid due to its fast response time (in tens of microseconds) and low on-state losses. At the simulation stage, an appropriate model of the SiC-JFET should be built in order to reflect correctly behaviors of the breaker during faults and clearing faults processes. For instance, the fault clearing time should be in tens of microseconds. This paper presents the development of a novel model for commercial normally-on SiC-JFET in solid state circuit breaker application. The parameters of the model are first extracted from the SiC-JFET experimental data. Afterward, the operation of a SiC-JFET in a prototype of solid state breaker is evaluated by comparing the static and dynamic characteristics of SiC-JFET model, which is simulated in Matlab/Simulink, to the experimental measurement. Good agreement between simulation and experiment has been achieved and confirms the validity of the built model of the SiC JFET.

International audience

International audience

International audience; The paper presents the development of a test bench for the investigation of faults in a power drive. Firstly, the presentation is made for different components in an induction machine drive. Secondly, since the machine parameters are controlled by PWM signals via IGBT converter, a PWM generator is built in order to control the machine and create different types of faults related to the drive of the converter. Subsequently, simulation and experiment are carried out for two typical faults of the converter: intermittent gate-misfiring fault and open-circuit fault. Finally, since the machine speed is usually required for the calculation of characteristic frequencies of most faults in the induction machine, it is estimated on the basis of the slot frequency component in the spectral of stator current and total input power. The obtained results are the evidence to show that the test bench is appropriately usable for the investigation of not only the normal operation but efficiently for the fault exploration.