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With the increasing penetration of wind turbine (WT) systems with permanent magnet synchronous generators (PMSGs) into the power grids, the back-to-back converter (BTB) has become the key element interfacing wind sources and power grids. Compared to the grid-following voltage source converter (GFL-VSC), the grid-forming VSC (GFM-VSC) shows voltage and frequency support capabilities, which meets the requirement of grid codes for WT systems. Usually, the linear regulator is employed to realize the tracking of voltage and current of GFM-VSCs, but it has limitations of complex parameter design and dynamic performance. Recently, the model predictive control (MPC) is a promising alternative controller due to the easy adoption and fast control response. This paper proposes a novel MPC method for BTB to achieve grid-forming function. The model-based control concept of the MPC effectively overcomes the complex parameter-tuning process of the cascaded linear regulators. In addition, the overshoot in the step-response of the active power of GFM-VSCs during transient process is effectively improved by using a new multi-objective cost function. The reduced power overshoot is beneficial for fully utilizing the overload capacity of the converter, avoiding damage to semiconductor devices and causing system blocking. Finally, the simulation and experiments have confirmed the feasibility of the proposed MPC method.

Virtual synchronous generator (VSG) control, which can provide inertia output, damp power oscillations, and offer frequency and voltage support to power grids, has become a growing trend in the control field of wind power generation. As a new technology, there are still challenges that VSG control has not solved well, such as transient overvoltage suppression. A kind of transient overvoltage, which often occurs during the commutation failures of HVDC transmission systems, will trigger a mass of wind turbine generators (WTGs) disconnecting from grids. To reduce the grid-disconnection risk of the virtual synchronous generator control-based doubly fed induction generators (VSG-DFIGs), this paper first analyzes the mechanism of the automatic voltage regulation (AVR) control usually employed by VSG-DFIGs, then proposes measures to suppress the transient overvoltage. To solve the problem of the reactive power response lag issued by VSG-DFIGs, which will further aggravate the transient overvoltage in continuous low and high voltage faults, the time constant of the AVR control is switched. To fully exploit the potential of the DFIGs’ reactive power support, the droop coefficient of the AVR control is switched during the abnormal voltage stages. The switched droop coefficient will change the rotor excitation current magnitude, thus adjusting the internal potential of a DFIG, finally better supporting or suppressing the terminal voltage during the low or high voltage periods. Simulation results based on the DIgSILENT/PowerFactory platform demonstrate that the proposed method can effectively suppress the transient overvoltage that occurs in continuous low and high voltage events caused by the commutation failures of HVDC transmission systems, reducing the number of WTGs disconnecting from the grids.

[This corrects the article DOI: 10.1371/journal.ppat.1011480.].

Development of lysosomes and mitochondria dual-targeting photosensitizer with the virtues of near-infrared (NIR) emission, highly efficient reactive oxygen generation, good phototoxicity and biocompatibility is highly desirable in the field of imaging-guided photodynamic therapy (PDT) for cancer. Herein, a new positively charged amphiphilic organic compound (2-(2-(5-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)vinyl)-3-methylbenzo[d]thiazol-3-ium iodide) (ADB) based on a D-A-π-A structure is designed and comprehensively investigated. ADB demonstrates special lysosomes and mitochondria dual-organelles targeting, bright NIR aggregation-induced emission (AIE) at 736 ​nm, high singlet oxygen (1O2) quantum yield (0.442), as well as good biocompatibility and photostability. In addition, ADB can act as a two-photon imaging agent for the elaborate observation of living cells and blood vessel networks of tissues. Upon light irradiation, obvious decrease of mitochondrial membrane potential (MMP), abnormal mitochondria morphology, as well as phagocytotic vesicles and lysosomal disruption in cells are observed, which further induce cell apoptosis and resulting in enhanced antitumor activity for cancer treatment. In vivo experiments reveal that ADB can inhibit tumor growth efficiently upon light exposure. These findings demonstrate that this dual-organelles targeted ADB has great potential for clinical imaging-guided photodynamic therapy, and this work provides a new avenue for the development of multi-organelles targeted photosensitizers for highly efficient cancer treatment.

Deubiquitinating enzymes (DUBs) regulate antiviral immune response through targeting DNA sensor signaling pathway members. As one of the DNA sensors, interferon (IFN)-γ inducible protein 16 (IFI16) play a major role in response to virus infections through activating the canonical STING/TBK-1/IRF3 signaling pathway. Only a few studies discuss the function of DUBs in IFI16-mediated antiviral response. Ubiquitin-specific protease 12 (USP12), which is one of the major members of the USP family, participates in various biological functions. However, whether USP12 regulates the nucleic acid sensor to modulate antiviral immune responses has not yet been elucidated. In this study, we found that knockout or knockdown of USP12 impaired the HSV-1-induced expressions of IFN-β, CCL-5, IL-6, and downstream interferon-stimulated genes (ISGs). Moreover, USP12 deficiency increased HSV-1 replication and host susceptibility to HSV-1 infection. Mechanistically, USP12 inhibited the proteasome-dependent degradation of IFI16 through its deubiquitinase activity, thereby maintaining IFI16 stability and promoting IFI16-STING-IRF3- and p65-mediated antiviral signaling. Overall, our findings demonstrate an essential role of USP12 in DNA-sensing signaling and contribute to the understanding of deubiquitination-mediated regulation of innate antiviral responses.

COD/NO3−-N ratio was considered to be one of the key factors achieving effective nitrite accumulation during partial denitrification. In two parallel reactors incubated with glucose as carbon source at COD/NO3−-N of 3 and 5, respectively, the microbial community structure shift and the nitrite accumulation performance during long-term operation were investigated. The maximum nitrite accumulation ratios at COD/NO3−-N of 3 and 5 were 17.9% and 47.04%, respectively. Thauera was the dominant genus in both reactors on day 220 with the relative abundance of 18.67% and 64.01%, respectively. Batch experiments with different electron acceptors suggested that the distinction in nitrite accumulation at COD/NO3−-N of 3 and 5 might be caused by the differences in the abundance of Thauera.

The effects of Y or Nb addition on the oxidation behavior of 321 steel at high temperatures were investigated by scanning electron microscopy (SEM), energy spectroscopy (EDS) and X-ray diffractometer (XRD). At the same time, the oxidation mechanism and oxidation kinetics of rare earth Y or Nb addition are explored. The results show that temperature greatly influences the high-temperature oxidation resistance of the alloys, and the oxidation phenomenon of the alloy becomes more obvious as the temperature increases. Adding 0.5 wt.% Nb or 0.045 wt.% Y elements can effectively improve the oxidation resistance of 321 stainless steel at high temperatures. The addition of rare earth Y can promote the diffusion of Cr in the matrix, leading to increased Cr content in the oxide film and the eventual formation of a dense Cr2O3 film, which effectively hinders the continuation of the oxidation reaction. As a result of the Nb addition, the outward diffusion of Cr elements can be effectively inhibited, Cr and O ion bond can be strengthened, the oxidation rate can be reduced, the adhesion rate of oxide film can be increased, and the oxidation resistance of 321 stainless steel can be improved.

In order to solve the problems of thermal protection and convenient & efficient maintenance of high-speed airborne missiles in harsh service environment, researches on two key technologies of seal for thermal protection (STP) and outfield maintenance support of thermal protection (OMSTP) of the missile bodies are carried out. Concept and relevant requirements of seal for thermal protection & convenient outfield maintenance support dual-purpose (STP-OMSTP) materials are proposed. Focusing on the needs of mass production and maintenance of the missiles, comparative tests are carried out between common repair and sealing materials matching the thermal protective coating and the STP-OMSTP materials. The results show that STP-OMSTP material has the advantages of good thermal sealing effect, quick and convenient operation, and strong environmental adaptability, which is obviously better than traditional repair and sealing materials, and is more suitable for mass production and outfield maintenance.

As an important part of the internal environment of human, intestinal flora participates in and regulates the immune inflammatory response and metabolic process of the body. It is closely related to the occurrence and development of hypertension, and has become the focus of research on hypertension. The thesis summarizes the relationship between intestinal flora and hypertension, then clarifies their effects and possible mechanisms on hypertension in terms of inflammation and immune response, brain-intestine-bone marrow axis and metabolites, focusing on the new auxiliary antihypertensive pathways that dietary intervention affects intestinal flora to improve blood pressure from salt, probiotics and polyphenols. It is hoped that more in-depth research will come out on improving hypertension through dietary intervention and Chinese herbal medicine prevention and treatment with intestinal flora as the target.