Mitigation of Motor Overvoltage in SiC-Based Drives using Soft-Switching Voltage Slew-Rate (dv/dt) Profiling

In silicon carbide (SiC) device based motor drives, the high voltage slew rate (dv/dt) associated with the fast switching transitions results in excessive motor overvoltage, due to the reflected wave phenomenon, which increases the motor winding insulation stress and causes premature failure while raises electromagnetic interference (EMI) problems. This article proposes a voltage slew rate profiling approach to mitigate the motor overvoltage in SiC-based cable-fed drives. The proposed approach optimizes the rise/fall time of the output voltage according to the cable length, without altering the switching speed of the SiC devices. The proposed profiling approach is implemented using a soft-switching inverter. The optimum rise/fall time that can significantly mitigate the overvoltage is derived using frequency and time domain analysis. The auxiliary resonant commutated pole inverter (ARCPI) is adopted as a soft-switching inverter to experimentally verify the proposed slew rate profiling approach for the overvoltage mitigation. The analysis and experimental results show that the motor overvoltage is fully mitigated when the output voltage rise/fall time is set as the cable anti-resonance period, i.e. four times of the wave transmission time along the cable. Further, the slew-rate profiling approach along with the ARCPI reduces the switching loss and improve the EMI performance at high frequency region.</div

PyHGL: A Python-based Hardware Generation Language Framework

Hardware generation languages (HGLs) increase hardware design productivity by creating parameterized modules and test benches. Unfortunately, existing tools are not widely adopted due to several demerits, including limited support for asynchronous circuits and unknown states, lack of concise and efficient language features, and low integration of simulation and verification functions. This paper introduces PyHGL, an open-source Python framework that aims to provide a simple and unified environment for hardware generation, simulation, and verification. PyHGL language is a syntactical superset of Python, which greatly reduces the lines of code (LOC) and improves productivity by providing unique features such as dynamic typing, vectorized operations, and automatic port deduction. In addition, PyHGL integrates an event-driven simulator that simulates the asynchronous behaviors of digital circuits using three-state logic. We also propose an algorithm that eliminates the calculation and transmission overhead of unknown state propagation for binary stimuli. The results suggest that PyHGL code is up to 6.1x denser than traditional RTL and generates high-quality synthesizable RTL code. Moreover, the optimized simulator achieves 2.9x speed up and matches the performance of a commonly used open-source logic simulator

Quorum sensing LuxS/autoinducer-2 inhibits Enterococcus faecalis biofilm formation ability

Objective:&nbsp; To investigate the relation between biofilm formation ability and quorum sensing gene LuxS/AI-2. Materials and Methods: Enterococcus faecalis (E. faecalis) standard strain ATCC 29212 was used in the study. Long flanking homology polymerase chain reaction method was used to build the LuxS gene knockout strain. Sequential culture turbidity measurement and CFU counting were used to assess the proliferation ability of E. faecalis after the depletion of LuxS. 96-well plate assay was used to quantify the biofilm formation ability; CLSM was used to observe the attached bacteria areas, while scanning electron microscopy (SEM) was performed to observe biofilm microstructure conditions. Results: LuxS gene knockout strains were successfully constructed and identified. The results showed that proliferation ability of E. faecalis was not affected by the depletion of the luxS gene, and the biofilm formation ability of ΔLuxS 29212 significantly decreased (P&lt;0.05). Conclusions: Collectively, our studies provide the LuxS gene's key role in controlling biofilm formation of E. faecalis, which presented a negative regulation, and furthermore, providing us a possible way to conquer the persistent apical periodontitis

Research of the Impact of Heterogeneous Environmental Regulation on the Performance of China’s Manufacturing Enterprises

Promoting high-quality economic development with high-level ecological protection is one of the most important tasks in China’s new stage of development. The improvement of enterprise performance is the micro-foundation of high-quality economic development, while environmental regulations aim to reduce the negative effect of economic development on the environment. Consequently, the microeconomic effects of environmental regulation have received widespread attention in academia. Previous studies have emphasized the effect of environmental regulations on firm performance but have not reached a consensus and lack of insight on the combined effects of different types of environmental regulation. This study aims to fill this gap by considering the heterogeneity of environmental regulations and the effect of the interaction between heterogeneous environmental regulations on enterprise performance. To reveal the relationship between the different types of environmental regulations and the performance of manufacturing enterprises, and the possible impact mechanism, this study uses the fixed effect model to test the impact of different environmental regulations on the performance of manufacturing enterprises, the mediation effect model is used to check whether or not an environmental regulation affects the performance of manufacturing enterprises by improving the level of technological innovation of enterprises, and the moderating effect model is used to examine the impact of the interaction between different environmental regulations on the performance of manufacturing enterprises. The results show that command-and-control environmental regulation inhibits the performance improvement of manufacturing enterprises, while a market-based environmental regulation enhances performance by improving the technological innovation level of enterprises. Market-based environmental regulation will alleviate the disincentive effect of command-control environmental regulation on the performance of manufacturing enterprise

Numerical investigations on cold gas dynamic spray process with nano- and microsize particles

The particle velocity in cold gas dynamic spraying (CGDS) is one of the most important factors that can determine the properties of the bonding to the substrate. In this paper, the acceleration process of microscale and sub-microscale copper (Cu) and platinum (Pt) particles inside and outside De-Laval-Type nozzle is investigated. A numerical simulation is performed for the gas-particle two phase flow with particle diameter ranging from 100 nm to 50 lm, which are accelerated by carrier gas nitrogen and helium in a supersonic De-Laval-type nozzle. The carrier gas velocity and pressure distributions in the nozzle and outside the nozzle are illustrated. The centerline velocity for two types of particles, Pt and Cu, are demonstrated. It is observed that the existence of the bow shocks near the substrate prevents the smaller size particles (less than 0.5 lm) from penetrating, thus leads to poor coating in the actual practices. Furthermore, the extended straight section may have different optimal length for different size particles, and even may be unnecessary for sub-microsize particles