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Synchronized space vector pulse width modulation (SSVPWM) is widely employed in high‐power AC drive systems. The existing methods are carrier‐based, in which the carrier ratio, position of samples, and switching sequences used to generate every sample for a given SSVPWM are settled, which causes two problems: (i) the control delay changes, and a voltage phase modulation error appears suddenly during transition between different SSVPWMs with different carrier ratios, which causes motor current spikes; (ii) due to the particular switching sequences, some kinds of SSVPWM cannot get into six‐step operation by overmodulation. This paper proposes an improved type of SSVPWM based on switching angles, in which the carrier ratio of a given SSVPWM can change flexibly, and the problems mentioned above can be solved. Theories including switching angle calculation, overmodulation strategy, carrier ratio setting principle, and transition rules between different SSVPWM modes are given in this paper. Meanwhile, the switching angles change linearly with modulation index which makes it easy to implement, and the modulation error in the overmodulation region is effectively limited so that the proposed scheme is suitable in the whole modulation index range. A case study of a 5.5‐kW experimental platform is presented to validate the proposed method. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Background: Cerumen is a mixture of beeswax and plant resin made by stingless bees. It has antimicrobial and antioxidant properties and is often used in biological and therapeutic treatments. However, its adhesive characteristic makes cerumen challenging to process into powder. Methods: This study investigated the physical characteristics and antioxidant activity of the encapsulated freeze-dried dewaxed cerumen of Tetragonula laevicpes. The combination of coating materials at concentrations of 20%, 30% and 40% and carrier ratios of maltodextrin to gum arabic of 9:1, 5:5 and 3:7 were used to encapsulate dewaxed cerumen when freeze-dried; the control was maltodextrin at a concentration of 31.25%. Results: All carrier matrices showed high yields of >80% and similar powder characteristics of low moisture content, low water activity, high glass transition temperature and water dispersibility. Overall, antioxidant activities ranged from 69–80%, while the encapsulation efficiency of total phenolic content ranged from 46–68%. All carrier matrices show higher antioxidant activities than 31.25% maltodextrin, with the lowest antioxidant at 57%. Conclusions: The carrier ratio of 5:5 resulted in better physical properties and retained 68% of polyphenolic activity in powders. [ABSTRACT FROM AUTHOR]

The switching frequency of high-power inverters, such as those used in rail transit traction systems, is low, due to switching loss and heat dissipation limitations. This can result in considerable output voltage harmonics. This paper proposes an optimal SPWM strategy for traction inverters based on non-equally spaced carriers to address this issue. By dividing the fundamental wave cycle into regions according to the principle of three-phase, half-wave, and quarter-wave symmetry, the carrier width is symmetrically changed in each region, and a switching angle sequence is generated by comparing the fundamental wave with the non-isometric carrier. The proposed optimal modulation strategy has lower harmonic content than traditional strategies within a specific modulation range. Enhancing the inverter output waveform leads to increased torque accuracy, lowering additional losses in the motor and avoiding overheating. This results in improved performance, enhanced efficiency, and extended service life of the motor system. To further reduce voltage harmonics across the full-speed range, a multi-mode segmented synchronous modulation strategy is designed based on the optimal modulation strategy for different modulation ranges. Appropriate switching points are selected to improve the stability of the traction drive system across the full-speed range. The effectiveness of the proposed method is verified through simulation and experimental results. [ABSTRACT FROM AUTHOR]

Background: Cerumen is a mixture of beeswax and plant resin made by stingless bees. It has antimicrobial and antioxidant properties and is often used in biological and therapeutic treatments. However, its adhesive characteristic makes cerumen challenging to process into powder. Methods: This study investigated the physical characteristics and antioxidant activity of the encapsulated freeze-dried dewaxed cerumen of Tetragonula laevicpes. The combination of coating materials at concentrations of 20%, 30% and 40% and carrier ratios of maltodextrin to gum arabic of 9:1, 5:5 and 3:7 were used to encapsulate dewaxed cerumen when freeze-dried; the control was maltodextrin at a concentration of 31.25%. Results: All carrier matrices showed high yields of >80% and similar powder characteristics of low moisture content, low water activity, high glass transition temperature and water dispersibility. Overall, antioxidant activities ranged from 69–80%, while the encapsulation efficiency of total phenolic content ranged from 46–68%. All carrier matrices show higher antioxidant activities than 31.25% maltodextrin, with the lowest antioxidant at 57%. Conclusions: The carrier ratio of 5:5 resulted in better physical properties and retained 68% of polyphenolic activity in powders.

The switching frequency of high-power inverters, such as those used in rail transit traction systems, is low, due to switching loss and heat dissipation limitations. This can result in considerable output voltage harmonics. This paper proposes an optimal SPWM strategy for traction inverters based on non-equally spaced carriers to address this issue. By dividing the fundamental wave cycle into regions according to the principle of three-phase, half-wave, and quarter-wave symmetry, the carrier width is symmetrically changed in each region, and a switching angle sequence is generated by comparing the fundamental wave with the non-isometric carrier. The proposed optimal modulation strategy has lower harmonic content than traditional strategies within a specific modulation range. Enhancing the inverter output waveform leads to increased torque accuracy, lowering additional losses in the motor and avoiding overheating. This results in improved performance, enhanced efficiency, and extended service life of the motor system. To further reduce voltage harmonics across the full-speed range, a multi-mode segmented synchronous modulation strategy is designed based on the optimal modulation strategy for different modulation ranges. Appropriate switching points are selected to improve the stability of the traction drive system across the full-speed range. The effectiveness of the proposed method is verified through simulation and experimental results.

A bidirectional radio-on dense-wavelength-division-multiplexing (DWDM) transport system based on external light injection technique and adaptive filters is proposed. Not only were a low bit-error rate and error vector magnitude obtained, but also good performance of third-order intermodulation distortion to carrier ratio (IMD3/C) was achieved for local area network (LAN) and intelligence transport system (ITS) applications. [ABSTRACT FROM PUBLISHER]

A radio-on-multimode fiber (MMF) system based on 1.55-μm vertical-cavity surface-emitting lasers (VCSELs) and an external light injection technique is proposed and demonstrated. Low error vector magnitude, third-order intermodulation distortion to carrier ratio, and bit-error-rate values were obtained in our proposed radio-on-MMF systems. Using VCSELs as optical sources in radio-on-MMF systems are very attractive, as they are relatively simple to fabricate and potentially low cost. Such a proposed radio-on-MMF system is suitable for the short-haul microwave optical link. [ABSTRACT FROM PUBLISHER]