Design of Three-Phase Induction Motor Starting Drive Based on Electromagnetic Torque Analysis

The process of starting a three-phase induction motor consumes a very largecurrent from the power grid, which can cause voltage drops and damage the coilinsulators due to the heat generated. However, this has been overcome by using severalstarting methods including star-delta starter, starter with autotransformer, soft starter,and drive frequency or better known as VFD or VSD. In conventional soft starters, asmall reduction in voltage results in a sizable drop in electromagnetic torque. This cancause a motor with a certain load to fail to start. In this research, a three-phase inductionmotor soft starter modeling will be carried out using the method of setting the sourcevoltage and frequency, designed to overcome the low electromagnetic torque generatedby conventional soft starters. The modeling of the soft starter with thyristor control isexpected to produce high and stable electromagnetic torque. So that the soft starter withthyristor control can be a solution for conventional soft starters.

Polyandry blocks gene drive in a wild house mouse population

Gene drives are genetic elements that manipulate Mendelian inheritance ratios in their favour. Understanding the forces that explain drive frequency in natural populations is a long-standing focus of evolutionary research. Recently, the possibility to create artificial drive constructs to modify pest populations has exacerbated our need to understand how drive spreads in natural populations. Here, we study the impact of polyandry on a well-known gene drive, called t haplotype, in an intensively monitored population of wild house mice. First, we show that house mice are highly polyandrous: 47% of 682 litters were sired by more than one male. Second, we find that drive-carrying males are particularly compromised in sperm competition, resulting in reduced reproductive success. As a result, drive frequency decreased during the 4.5 year observation period. Overall, we provide the first direct evidence that the spread of a gene drive is hampered by reproductive behaviour in a natural population.

Design and Testing of a Valveless Piezoelectric Pump with Conical Vortex Diodes

The valveless piezoelectric pump delivers fluid based on the difference of flow resistance of internal tube. In this paper, a vortex diode with conical tangential tube is proposed, which possesses the great characteristic of reverse cut-off, and the analysis of the forward and reverse flow resistance of the conical vortex diode is verified by finite element analysis. Then, a valveless piezoelectric pump with conical vortex diodes as the internal channel is designed, and the prototype is manufactured. The results of the output performance experiment show that the maximum output flow rate of the valveless piezoelectric pump is 10.44 g/min at the drive frequency of 45Hz, and the maximum output pressure is 560 Pa at the drive frequency of 35Hz. The proposal of the valveless piezoelectric pump provides a good reference for more new types of valveless piezoelectric pumps.

Material discrimination and mixture ratio estimation in nanocomposites via harmonic atomic force microscopy

Harmonic atomic force microscopy (AFM) was employed to discriminate between different materials and to estimate the mixture ratio of the constituent components in nanocomposites. The major influencing factors, namely amplitude feedback set-point, drive frequency and laser spot position along the cantilever beam, were systematically investigated. Employing different set-points induces alternation of tip–sample interaction forces and thus different harmonic responses. The numerical simulations of the cantilever dynamics were well-correlated with the experimental observations. Owing to the deviation of the drive frequency from the fundamental resonance, harmonic amplitude contrast reversal may occur. It was also found that the laser spot position affects the harmonic signal strengths as expected. Based on these investigations, harmonic AFM was employed to identify material components and estimate the mixture ratio in multicomponent materials. The composite samples are composed of different kinds of nanoparticles with almost the same shape and size. Higher harmonic imaging offers better information on the distribution and mixture of different nanoparticles as compared to other techniques, including topography and conventional tapping phase. Therefore, harmonic AFM has potential applications in various fields of nanoscience and nanotechnology.

Control System of an Electromagnetic Vibrating Ring Gyroscope

Presented is a control system that is designed for an electromagnetic vibrating ring gyroscope. Three functions are realized in this control system. First, fixed amplitude of the drive-mode is guaranteed by using a variable gain control (VGC). Test result shows that the stability of the drive-mode amplitude is about 0.4% in the range of-40°C~80°C. Second, suitable drive-frequency is set up. And experimental result indicates that the suitable drive-frequency should be set between the drive-and sense-mode resonance frequencies, which results in a superior sensitivity. Third, regulation module is employed to further improve the performance.