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This paper proposes an algorithm for determining the optimal capacitance by utilizing a mathematical model of a submodule (SM) capacitor in a modular multilevel converter (MMC) specifically for medium voltage motor drives (MVDs). By approximating the voltage fluctuation of the SM capacitor during low-frequency operation, it is feasible to ascertain the minimum capacitance required for the SM capacitor, ensuring that its voltage fluctuations remain within an acceptable limit that is predefined as a specified value. Moreover, the study considered the injection of both a high-frequency common-mode voltage (CMV) and a circulating current to alleviate the SM voltage fluctuation during the acceleration of motor drives. The effectiveness of the proposed method is validated through verification using time-domain simulation results obtained using the MATLAB/SIMULINK software and real-time simulation results acquired using the OPAL-RT simulator platform.

This study proposes an adaptive high-frequency injection method (AHFI) aimed at mitigating common-mode voltage (CMV) on the AC side and alleviating current stress on power semiconductor devices within each arm of a medium-voltage motor propulsion system designed for modular multilevel converters. By adjusting the quantity of high-frequency components injected into each arm according to the fluctuation coefficient, the amplitude of injected high-frequency CMV and circulating currents can be reduced across medium to rated motor speeds. This approach enhances the start-up performance of medium-voltage motor drives while diminishing CMV effects on the motor side, resulting in decreased total harmonic distortion (THD) in the three-phase output waveforms. Furthermore, the effectiveness of the proposed AHFI method in SM voltage regulation and circulating current control under low-frequency operation is thoroughly analyzed. The validity of this method is established through comprehensive mathematical scrutiny and time–domain simulations performed using MATLAB/SIMULINK software (MATLAB version R2021b), along with real-time simulations conducted employing the real-time simulator OPAL/RT via hardware-in-the-loop simulation (HILS).

This paper proposes a simple design scheme for a modular NPC inverter using thermal RC network analysis. The proposed design process is an efficient and straightforward approach to designing the heatsink for a 300 kW modular neutral-point-clamped inverter. The heatsink design plays a crucial role in achieving high power density of a power converter because the weight and size of the heatsink are primarily influenced by its type. The structure and dimensions of the heatsink are mainly determined based on the generated heat by losses of the power semiconductor switches. In this paper, a thermal RC network model was established using parameters from the power switch module and was applied to the simulation of the power converter. The thermal losses of the power semiconductor switches were calculated via this process, and the heatsink was designed according to the calculated thermal losses. The proposed design scheme was analyzed and compared with the thermal fluid dynamic model. To validate the feasibility of the proposed design process, The simulation results were compared with experimental results.

In power semiconductor systems such as inverters, managing losses is critical for optimizing performance. Inverters, which convert DC to AC for applications such as renewable energy systems, motor drives, and power supplies, are significantly affected by the thermal performance of components such as metal-oxide-semiconductor field-effect transistors (MOSFETs). Efficient thermal management is critical for the longevity and performance of power electronic systems, especially in high-power applications. Designing effective thermal management strategies for inverters reduces losses, increases efficiency, and improves performance while considering space constraints and complex component interactions. In this study, power electronics simulations and computational fluid dynamics (CFD) thermal analysis were integrated to design the inverter. Using an integrated simulation, a thermal analysis was performed based on the inverter losses per module. A power electronics simulation was used to verify the validity of the loss values in the inverter design, and the CFD thermal analysis facilitated the visual analysis of the variables to be considered. The validity of the design was evaluated through experimental verification of the inverter system. A temperature saturation of 63.9 ℃ at 60Arms was recorded in the simulation, and a temperature saturation of 45 ℃ or less at 59Arms to 60Arms was obtained for each phase in the actual test. Considering the ambient temperature difference, it showed a difference of approximately 9.9 ℃. This conclusion allows us to reduce the high probability of risk derived by considering a small margin of safety for each variable in the design. This solution can be used to compactly design real inverters and solve complex thermal problems in power semiconductor-based systems. Finally, this study analyzes the similarities and differences between CFD simulations, power electronics simulations, and real-world experimental validation, highlighting the importance of thermal management in improving the efficiency of power electronic systems, particularly inverters.

The Korean government is facing growing concern over the increasing levels of fine dust. A significant contribution to this problem comes from coastal vessels. To mitigate this, an electric ship propulsion system has been proposed as a solution to reduce air pollution. The application of a fully electric propulsion system in a ship is challenging due to size, capacity limitations, and the cost investment of the battery system. To address the challenges of battery limitation and initial investment costs, the development and supply of removable battery supply systems (RBSSs) for fully electrified battery powered (F-EBP) car ferries are studied. A permanent magnet synchronous motor (PMSM) for the F-EBP car ferry using a roll-on/roll-off-type RBSS is developed in this work. Firstly, the concept of the F-EBP car ferry is discussed, and the specifications of the electric car ferry propulsion system are provided. Secondly, motor design and electromagnetic analysis are performed using finite-element analysis (FEA), where the heat sources including copper loss, core loss, and PM loss are calculated. Mechanical loss is also considered. Finally, a thermal network of the motor is built considering the lumped-parameter model. The results of the thermal analysis indicate that the motor operates within the safe region and can perform well in rated working conditions.

Histone H3 Lys4 (H3K4) methylation is a prevalent mark associated with transcription activation. A common feature of several H3K4 methyltransferase complexes is the presence of three structural components (RbBP5, Ash2L and WDR5) and a catalytic subunit containing a SET domain. Here we report the first biochemical reconstitution of a functional four-component mixed-lineage leukemia protein-1 (MLL1) core complex. This reconstitution, combined with in vivo assays, allows direct analysis of the contribution of each component to MLL1 enzymatic activity and their roles in transcriptional regulation. Moreover, taking clues from a crystal structure analysis, we demonstrate that WDR5 mediates interactions of the MLL1 catalytic unit both with the common structural platform and with the histone substrate. Mechanistic insights gained from this study can be generalized to the whole family of SET1-like histone methyltransferases in mammals.

Aviation is part of Hong Kong's constitutional identity. Article 128 of the Basic Law states that ＂the Hong Kong Government shall provide conditions and take measures to maintain the status of Hong Kong as a centre of international and regional aviation.＂ The key phrase ＂a centre of international and regional aviation＂ is commonly interpreted as meaning an ＂international aviation hub.＂ Hong Kong has indeed been a successful international aviation hub thanks to the city's overall laissez-faire economic policy and advanced infrastructure, although multiple factors have affected that status over the years. However, the Outline Development Plan for the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) provides new opportunities for Hong Kong. The GBA initiative defines the role that Hong Kong will play in the overall development of the GBA and reinforces its importance as a leading international aviation hub. This article suggests that although Hong Kong's status as a connecting airport has weakened, the GBA initiative can strengthen its role as a center of international and regional aviation.

The biological consequences of steroid hormone-mediated transcriptional activation of target genes might be difficult to predict because alternative splicing of a single neosynthesized precursor RNA can result in production of different protein isoforms with opposite biological activities. Therefore, an important question to address is the manner in which steroid hormones affect the splicing of their target gene transcripts. In this report, we demonstrate that individual steroid hormones had different and opposite effects on alternative splicing decisions, stimulating the production of different spliced variants produced from genes driven by steroid hormone-dependent promoters. Steroid hormone transcriptional effects are mediated by steroid hormone receptor coregulators that also modify alternative splicing decisions. Our data suggest that activated steroid hormone receptors recruit coregulators to the target promoter that participate in both the production and the splicing of the target gene transcripts. Because different coregulators activating transcription can have opposite effects on alternative splicing decisions, we conclude that the precise nature of the transcriptional coregulators recruited by activated steroid receptors, depending on the promoter and cellular contexts, may play a major role in regulating the nature of the spliced variants produced from certain target genes in response to steroid hormones.

THE thyroid-hormone receptors are hormone-dependent transcription factors that control expression of many target genes 1,2 . This regulation is presumably a consequence of hormone-dependent contacts between the receptors and the basal transcription machinery3. We used the yeast two-hybrid system 4,5 to identify a candidate human transcriptional mediator that interacts with both the thyroid-hormone receptor and the retinoid-X receptor in a ligand-dependent fashion. This protein, Tripl (for thyroid-hormone-receptor interacting protein), shares striking sequence conservation with the yeast transcriptional mediator Sugl (refs 6, 7). Here we show that Tripl can functionally substitute for Sugl in yeast, and that both proteins interact in vitro with the thyroid-hormone receptor, and with the transcriptional activation domains of yeast GAL4 and of herpes virus VP16.