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This article investigates energy storage requirements in the submodules of a class of converters known as hybrid cascaded modular multilvel converters (HC-MMCs). The complexities arising from the usage of different submodule types and their non-conventional arrangement necessitate detailed analysis of submodule capacitor voltage ripples, which are needed for development of guidelines for sizing submodule capacitors. This paper characterizes electric charge variations in the submodule capacitors to derive expressions for capacitor voltage ripples, and to determine the energy storage requirements of the converter. The paper uses detailed electromagnetic transient (EMT) simulations and experimental results on a laboratory-scale MMC setup to verify and validate its findings. [ABSTRACT FROM AUTHOR]

Introduction: Cancer stem cells (CSCs) are the main source of tumor resistance and recurrence. At present, the main treatment for patients with advanced or metastatic bladder cancer (BCa) is cisplatin-based combination chemotherapy. However, CSCs are not sensitive to DNA-damaging drugs due to their enhanced DNA damage response (DDR) activity. Materials and methods: Bladder cancer stem cell-like cells (BCSLCs) were obtained by treating UMUC3 cells with cisplatin. The characteristics of the BCSLCs were identified by qPCR, flow cytometry, scratch wound-healing assays, transwell assays, tumorigenic ability experiments, Edu assays and Western blot assays in vivo. After BCSLCs were treated with norcantharidin (NCTD), the expression of Cdc6 and activation of the ATR-Chk1 pathway were detected by Western blotting. A subcutaneous tumor model in nude mice was successfully established to assess the anti-tumor efficacy of NCTD and cisplatin either alone or in combination in vivo. The tumor tissues were detected by immunohistochemistry. Results: The derived BCSLCs showed higher expression of stemness markers, increased invasiveness, improved resistance to multiple chemotherapeutics, and higher tumorigenic capacity in vivo. The protein expression level of chromatin-binding Cdc6 was increased in BCSLCs; however, NCTD decreased the level of chromatin-binding Cdc6 and inhibited the activation of the ATR-Chk1 pathway, which ultimately led to reduction in DDR activity in BCSLCs. NCTD enhanced the killing effect of cisplatin on BCSLCs in vitro and vivo. NCTD combined with cisplatin enhanced cisplatin-induced DNA damage in BCSLCs. Conclusion: Long-term cisplatin treatment can enrich BCSLCs. However, NCTD enhanced the killing effect of cisplatin on BCSLCs in vitro and vivo. The mechanism is inhibiting the DDR activity by reducing the expression of chromatin-binding Cdc6. [ABSTRACT FROM AUTHOR]

This paper presents a quantitative analysis of the losses of the hybrid cascaded modular multilevel converter (HC-MMC). Regulation of full-bridge (FB) submodule-capacitor voltages in an HC-MMC requires dedicated strategies that affect the voltage harmonics generated by the converter's main power stage and hence its switching patterns and losses. This paper uses an electromagnetic transient simulator (PSCAD/EMTDC) to estimate the semiconductor losses using the switches’ turn-on and turn-off characteristics. The paper examines the losses of a 45-MW HC-MMC for two recently introduced voltage-regulation methods based upon the modified sinusoidal pulse width modulation (PWM) and an existing method based upon the trapezoidal PWM. Losses of a conventional FB-MMC that offers dc-fault blocking capability are also investigated and compared with those of HC-MMC. The loss comparison results indicate that: first, the two voltage-regulation methods for HC-MMC based upon the modified sinusoidal PWM result in markedly lower semiconductor losses than the trapezoidal PWM method; second, compared with the original HC-MMC, a mixed submodule HC-MMC may lower the semiconductor losses at certain operating points with proper addition of mixed submodules; and finally, HC-MMC may have up to 9.0% lower semiconductor losses (relative) than the conventional FB-MMC. [ABSTRACT FROM AUTHOR]

This research presents a study of the hybrid cascaded modular multilevel converter. It shows that voltage regulation of the full‐bridge submodules requires special provisions for energy‐flow control between the converter's main power stage and the external ac network. Novel control and hardware methods for regulating the converter's submodule voltage and extending its linear operating range are presented. The mathematical foundations of these methods are developed using simplified converter models. Experimental results using a laboratory prototype are presented to verify the efficacy of these methods. Extensive electromagnetic transient simulation studies are also conducted to verify the proposed solutions' effectiveness in normal operating conditions as well as under dc faults. [ABSTRACT FROM AUTHOR]

Under the condition of high input voltage and high power, the switch losses are unbalanced for three-level neutral point clamped( 3L-NPC). It causes that the power of 3L-NPC is limited and many NPC topologies are derivated. In order to optimally select NPC topologies and modulation strategies, modulation strategies and switch loss distribution of four 3L-NPC topologies (Diode-clamped NPC, active NPC, stacked NPC and active-stacked NPC) are analyzed. A 5 kW unified prototype of NPC topologies is developed for efficiency tests. Theoretical analysis and experimental results indicate that there are mainly four modulation strategies for NPC topologies with different configuration of zero-level freewheeling path. Appropriate NPC topologies and modulation strategies can not only balance the switch losses, but also keep the same efficiency, which lays the foundation for improving the capacity of inverters. [ABSTRACT FROM AUTHOR]

The metal transfer and protective bubble images, real-time electric signal data and weld appearance were obtained in different simulated water depth wet flux-cored arc welding. The electric signal results showed that the high hydrostatic environment deteriorated the stability of the wet welding process. The poor weld appearances with porosity were displayed when it was welded in deep water. The weld dilution rate descended from 51% to 40% with increasing water depth from 0.5 m to 90 m because of arc shrinking and heat input reduction. The reduction of protective bubble size and duration caused by high water pressure was unable to maintain a stable burning arc. With increasing water depth, the increase of pores in welds strongly deteriorated the mechanical property of joints. The process of gas generation and its escape from the droplet during the droplet transfer were observed. The rise of pressure compressed gas pores and prevented the gas from escaping, which resulted in the increase of pores. [ABSTRACT FROM AUTHOR]

The high-speed accurate electromagnetic transient (EMT) simulation of the power electronic transformers (PET) has become a challenge, due to the microsecond-range time steps and the large number of high-frequency semiconductor switches and isolating transformers. Taking the input-series-output-parallel (ISOP) connected cascaded H-bridge (CHB) type dual active bridge (DAB) based PET as an example, this paper proposes a general high-speed equivalent EMT modelling method of PET. First, the isolating transformer within each DAB is discretized into two-port Norton circuits. Second, each CHB-DAB is equivalent to two single-port circuits by eliminating the internal nodes. And the input-side is represented by a Thévenin circuit and the output-side is represented by a Norton circuit. Third, all the CHB-DABs are equivalent to a two-port circuit with all the internal node information preserved. Fourth, the implementation of PET blocking is also considered for startup and fault protective actions. Fifth, the stability of the proposed discrete decoupling method of the PET is verified that it does not introduce specific limitation on the simulation step size. Finally, the developed PET models on PSCAD/EMTDC are shown to be two orders of magnitude faster than the currently available fully-detailed models with negligible loss of accuracy. [ABSTRACT FROM AUTHOR]

Program death receptor-1 (PD-1)/program death ligand 1 (PD-L1) signaling plays an important role in tumor adaptive immune resistance. The streptavidin-granulocyte-macrophage colony stimulating factor (SA-GM-CSF) surface-modified tumor cells vaccine developed through our novel protein-anchor technology could significantly promote the activation of dendritic cells. Although GM-CSF vaccine could significantly increase the number of tumor-specific CD8+T-cells, the majority of these CD8+T-cells expressed PD-1. Moreover, GM-CSF vaccine up-regulated the PD-L1 expression of tumor cells, resulting in immune resistance. Adding PD-1/PD-L1 blockade to GM-CSF vaccine therapy could significantly increase the population of CD4+ T, CD8+ T and CD8+ IFN-γ+ T but not CD4+ Foxp3+ T-cells and induced the highest production of IFN-γ. PD-1/PD-L1 blockade could effectively rescue the tumor-specific T lymphocytes generated by the GM-CSF vaccine, resulting in consistent tumor rejection. Taken together, PD-1/PD-L1 blockade combined with SA-GM-CSF-modified vaccine could effectively induce a strong specific antitumor immune response against prostate cancer. [ABSTRACT FROM AUTHOR]