Search

Aiming to handle the inherent double-line frequency ripple power in single-phase power systems, a lot of active power decoupling (APD) topologies have been developed. In this paper, a general method is introduced to synthesize APD topologies. The main construction idea is to insert a rectifier/inverter into asymmetrical H-bridge circuits (AHCs) or replace the switch/diode in the AHCs with a rectifier/inverter. This approach not only reveals the formation process of existing APD topologies but also deduces new APD topologies. Finally, an experimental case study has been carried out to illustrate the feasibility and effectiveness of the proposed topology synthesis method.

Cable-stayed bridges have been commonly used on high-speed railways. The design, construction, and maintenance of cable-stayed bridges necessitate an accurate assessment of the cable temperature field. However, the temperature fields of cables have not been well established. Therefore, this research aims to investigate the distribution of the temperature field, the time variability of temperatures, and the representative value of temperature actions in stayed cables. A cable segment experiment, spanning over one year, is conducted near the bridge site. Based on the monitoring temperatures and meteorological data, the distribution of the temperature field is studied, and the time variability of cable temperatures is investigated. The findings show that the temperature distribution is generally uniform along the cross-section without a significant temperature gradient, while the amplitudes of the annual cycle variation and daily cycle variation in temperatures are significant. To accurately determine the temperature deformation of a cable, it is necessary to consider both the daily temperature fluctuations and the annual cycle of uniform temperatures. Then, using the gradient boosted regression trees method, the relationship between the cable temperature and multiple environmental variables is explored, and representative cable uniform temperatures for design are obtained by the extreme value analysis. The presented data and results provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges.

Abstract Solid‐state transformer (SST) is an attractive concept, which provides galvanic isolation and voltage scaling by means of a medium‐frequency link. In this paper, a single‐stage alternative current (AC)‐AC SST solution without bulky energy storage elements is presented. The front‐end rectifier (FER) and rear‐end inverter (REI) of the SST works at line‐frequency, while the intermediate LLC series resonant converter (SRC) fulfils the tasks of galvanic isolating and regulating the output voltage. To achieve high efficiency and bidirectional power flow capability of the SST, the zero voltage switching (ZVS) condition of the LLC SRC is comprehensively analysed, and the parameters design method of the LLC SRC is developed, where the resonant currents are constructed by applying the same gating signals to the primary‐side and secondary‐side bridges and the dead‐time is properly selected. Consequently, the presented SST has the merits of high conversion efficiency, naturally bidirectional power flow capability, potentially high power density and high reliability. The experimental results on a 1.5 kW SST prototype show that sinusoidal input and output current, ZVS operation over the full load range are achieved, and the peak efficiency is 97.63%. The experimental results verify the functionality and effectiveness of the developed methods.

At present, the energy consuming during the electrolytic copper foil preparation accounts for more than 75% of the total energy consumption. In real-life production, the process parameters are set by the operator empirically and the system may not work at the operating point with minimum energy consumption. Therefore, it is critical to establish an effective model for predicting electrolysis energy consumption to guide the parameters design. In this paper, a novel hybrid model (named PSVM-PMLP-MLR) based on stacked ensemble learning is proposed. The model is divided into two parts: the base-learning model and the meta-learning model. The support vector machine (SVM) model and multilayer perceptron (MLP) model with different input structures are established by the former first. Then the particle swarm algorithm is employed to determine the optimal value of SVM parameters and the optimal weight of MLP by minimizing the mean absolute percentage error (MAPE). The multiple linear regression (MLR) is finally employed as a meta-learning machine to compute the final predictions. Experimental results show that the regression coefficient of this model reached 0.987, and compared with the traditional SVM and MLP models, the accuracy of the model is improved by 10.29% and 8.28%, respectively.

Propolis is widely used in health preservation and disease healing; it contains many ingredients. The previous study had revealed that the ethanolic or water extracts of propolis have a wide range of efficacy, such as antiviral, immune enhancement, anti-inflammatory, and so on, but its antiviral components and underlying mechanism of action remain unknown. In this study, we investigated the chemical composition, anti-porcine parvovirus (PPV) effectiveness, and immunological enhancement of propolis flavone ethanolic extracts. The chemical composition of propolis flavone was distinguished by ultra-performance liquid chromatography-quadrupole/time-of-flight tandem mass spectrometry analysis. In this study, the presence and characterization of 26 major components were distinguished in negative ionization modes to evaluate the effects of propolis flavonoid used as an adjuvant on the immune response of Landrace–Yorkshire hybrid sows immunized with an inactivated vaccine of PPV. Thirty Landrace-Yorkshire hybrid sows were randomly assigned to one of three groups, and the sows in the adjuvant groups were intramuscularly injected with PPV vaccine with a 2.0-ml propolis flavonoid adjuvant (PA) and oil emulsion adjuvant. After that, serum hemagglutination inhibition antibody titers and specific immunoglobulin (Ig)M and IgG subclasses were measured to evaluate the adjuvant effects of propolis flavonoid on the humoral immune responses, as well as peripheral lymphocyte proliferation activity and serum concentrations of Th1 and Th2 cytokines for cellular immunity. Results indicated an enhancing effect of PA on IgM, interleukins 2 and 4, interferon-γ, and IgG subclass responses. Especially in the effect of improving cellular immune response, the PA was the best. These findings suggested that PA can significantly enhance the immune responses against the PPV vaccine and could be an alternative way to improve PPV vaccination in sows. Furthermore, we screened the PF chemical components to the effectiveness of anti-PPV. Ferulic acid has an excellent anti-PPV effect.

Nanoemulsions (NE) are used widely in pharmaceutical drug formulations and vaccine preparation, and Acanthopanax senticousus polysaccharide (ASPS) is a natural bioactive compound with immunostimulatory activity. Therefore, NE-loaded ASPS is expected to provide immunological enhancement for effective treatment. In the present study, Acanthopanax senticousus polysaccharide (ASPS was encapsulated into nanoemulsions, the resultant ASPS–NE were coated with a negative charge, and the immune enhancement mechanism of these ASPS-NE formulations was analyzed. The immunosuppressive animal models (70 ICR mice, male) for the study were established using cyclophosphamide. In addition, the activation of splenocyte proliferation, phagocytosis of the macrophages, the ratio of CD4+ to CD8+, the concentrations of the cytokines in serum, Western blot analysis was used for the analysis of the P65/JNK/ikk α signaling pathway in the peritoneal macrophage s. The results revealed that the ASPS-NE could stimulated the proliferation of splenocytes and enhance immunity. The ASPS-NE induced the expression of different cytokines (TNF-α, IFN-γ, IL-2, and IL-6), could activate the expressions of P65, JNK, and ikkα, and regulated the Th1/Th2 cytokines. These findings demonstrated the potential of ASPS-NE formulations for drug delivery and to induce potent and sustained immune responses.

Recently, the strategy of using positively charged nanoparticles as new vaccine delivery systems has been widely investigated for enhancing the anti-infectious disease immune responses and has been found to efficiently improve the immune response through the targeting and activation of antigen-presenting cells. Acanthopanax senticosus polysaccharide (ASPS) is extracted from Acanthopanax senticosus and functions as an effective immunostimulatory drug. The present work encapsulated the ASPS immunopotentiator to the calcium carbonate (CaCO3) microspheres, and adopted polyethylenimine, a cationic polymer, for coating the microspheres, finally developing the novel nanoparticle (NP) delivery system with positive charge (CaCO3–ASPS–PEI). As a result, our constructed CaCO3–ASPS–PEI remarkably up-regulated CD86 and MHCII and activated macrophages, while increasing TNF-α and IL-1β production via macrophages. Moreover, the mice immunized with porcine parvovirus (PPV) antigen adsorbed onto CaCO3–ASPS–PEI nanoparticles had a significant enhancement in cytokine production, the PPV-specific IgG immune response, and the hybrid Th1/Th2 immune response (dominated by Th1), relative to the remaining groups. Based on the above results, our constructed CaCO3–ASPS–PEI NPs with positive charge may be used as the efficient adjuvant vaccine delivery system for inducing the long-time potent immune responses.

Hepatocellular carcinoma (HCC) has been reported to be the third common malignant tumor because of the high rate of mortality. Photosensitizers (PSs) based on the natural products have been widely used in clinical antitumor research contributed to their excellent biological activity. To increase the PSs' safety and efficacy of HCC, the tumor cell membrane coating drug nanocrystals featured with homologous immune escape and targeting ability and low toxicity are in high demand. In this study, we reported a targeting drug delivery system based on a modified cell membrane coating technique and drug nanocrystals. HepG2 cell membrane was modified with targeting receptor through a biochemical reaction including Maleimide reaction. Modified with the HepG2-targeting protein transferrin, the resulting TF-CCCM-HB NPs exhibited long-term stability, excellent biocompatibility, high drug loading, and low toxicity. Compared with HB NPs, TF-CCCM-HB NPs showed both excellent targeting and therapeutic efficacy in BALB/c nude mouse bearing with HepG2 tumors. Therefore, TF-CCCM, a biomimetic drug delivery platform, can be readily generalized to the delivery of various drugs and provide a sound strategy for the treatment of other cancers via changes in the corresponding homotypic cancer cell membrane.

This paper proposes a single-phase inverter to achieve high power factor, wide input voltage range, and ripple power decoupling without using large passive components. The proposed inverter is obtained by rearranging the positions of the switches and passive components in the exiting circuit. Given that, a wider dc input voltage range can be obtained since it is no longer bounded by half the grid peak voltage. In addition, the inherent low-frequency ripple power is buffered, rather than through increasing the capacitance, by swinging the decoupling capacitor voltage resulting in an improvement of the power density and system lifetime. Furthermore, with adopting a closed-loop control method, no dedicated power-buffering controller is required. This paper starts with introducing the derivation of the proposed inverter followed by the operation principles and circuit analysis. A comparison between the derived circuit and the original one is carried out to show the pros and cons. Finally, a 200-W prototype is constructed to demonstrate the effectiveness of the proposed topology.

The mononuclear title complex, [Ti(C2H6N)2(C12H11N2)2], was synthesized by the reaction of 1-phenyl-N-[(pyrrol-2-yl)methylidene]methanamine with Ti(NMe2)4. The TiIV atom is coordinated in a distorted octahedral geometry by four N atoms from two derivatized methanamine ligands and two N atoms from two dimethylamide ions. The dihedral angles between the pyrrole and phenyl rings in the bidentate ligands are 62.36 (9) and 78.32 (8)°. In the crystal, a weak π–π stacking interaction [centroid–centroid distance = 3.864 (2) Å] involving centrosymmetrically related molecules is observed.

For single-phase current source converter (SCSC), at least one upper device and one lower device have to be gated on and maintained at any time. Otherwise, an open-circuit of the DC-link current would occur and destroy the devices. In addition, a bulky DC-link inductor is usually required to obtain a smooth DC-link current. To address these issues, this study proposes a novel SCSC with high reliability and high-power density. In the proposed circuit, even all the switches are turned on or turned off simultaneously, neither short-circuit nor open-circuit will happen. The inductance in DC-side is reduced significantly byadopting the active power decoupling technique. First, the operation principle of the proposed converter is introduced in detail. Then, a closed-loop control method is presented to regulate the DC-link current, maintain the DC component of the decoupling capacitor voltage, and achieve sinusoidal grid current. Besides, the parameter design of the circuit and controller is investigated. Moreover, the efficiency comparison between the proposed and other SCSCs is carried out. Finally, the effectiveness of the proposed topology is verified by the experimental results. [ABSTRACT FROM AUTHOR]

This study presents a unified current-source power quality conditioner of inherent no circulating current. It is formed of a three-leg current-source ac/ac converter and a specially designed small size dc-link. Owing to the transformers-less feature and small size dc-link, the proposed topology has the benefit of high power density. In addition, without the need to address the circulating current issue, it is easier to design the controllers and filters for the circulating current compared to other existing transformer-less unified power quality conditioners. To handle the harmonic currents compensation, voltage sags/swells elimination, power factor correction simultaneously and achieve excellent dynamic and steady-state performance, a direct control method based on an extended repetitive disturbance observer is proposed. Detailed analysis of topology and operation principles is given, followed by the modulation scheme and the developed control method. Simulations and experimental results are presented to verify the effectiveness of the conditioner. [ABSTRACT FROM AUTHOR]

This study proposes an automatic cell-to-cell equaliser to balance the battery voltages in series-connected battery strings. In the proposed equaliser, each cell needs only one MOSFET, and the adjacent cells share the transformer winding. The voltage balance is automatically realised by using a pair of complementary control signals with a fixed duty cycle. What's more, no sensing circuit is required. Consequently, the proposed equaliser is cost-effective and easy-to-realise. The circuit topology and operating principles are firstly presented. Then the voltage balance analysis is given in detail. Moreover, a design guide is also given by considering four lithium-ion cells. Finally, the validity of the proposed equaliser is verified by experimental results. [ABSTRACT FROM AUTHOR]

A transformer-less dynamic voltage restorer (DVR) with bipolar voltage gain capability is proposed in this study. The DVR is formed by a three-leg ac/ac converter with its output capacitor in series with the transmission line. Since the energy used for voltage compensation is obtained from the grid, long-time voltage disturbances can be compensated without using bulky energy storage elements. As a result, the proposed DVR has the features of compact structure, light weight, and low cost. Moreover, it also has a high reliability as the commutation problem is avoided by adopting the proposed modulation strategy. A detailed analysis of the topology structure and operation principle is given, followed by the developed control method. Finally, simulations and experimental results are presented to verify the validity of the DVR. [ABSTRACT FROM AUTHOR]

Active decoupling methods are developed for tackling the inherent second-order ripple power. However, in all the active decoupling methods developed for single-phase current source rectifier (SCSR), the dc output voltage is limited to half the peak amplitude of the ac source voltage. That limits SCSR's wide applications. Addressing that issue this study proposes a family of two-port switching networks (TSNs) to achieve ripple power decoupling and output voltage step-up at the same time. The main circuit is formed by inserting the TSN into the dc link of a conventional SCSR. Compared with the most existing SCSRs with decoupling capability, no extra semiconductor devices are added. Related operating principle and modulation scheme are described first. Then the selection of the decoupling capacitance is discussed. A closed-loop control strategy is also introduced to achieve good compensation performance. Finally, simulations and experimental results are presented to show the effectiveness. [ABSTRACT FROM AUTHOR]

The existing active power decoupling methods for single-phase current source rectifiers (SCSRs) usually involve a lot of additional semiconductor devices or energy storage units, which is adverse to cost and efficiency. This study proposes an active power decoupling method to buffer the double-frequency ripple power. The main circuit is configured by adding only a decoupling capacitor and a diode to the traditional SCSR. Compared with the existing ones, the added components are minimised. The operating principle and modulation scheme are described. A closedloop control method is developed to enhance twice the line frequency ripple power compensation performance. The guide for the selection of the decoupling capacitance is also discussed. Simulations and experimental results are presented to show the effectiveness of the method. [ABSTRACT FROM AUTHOR]

This study presents an active third-harmonic injection indirect matrix converter (3HI2MC) topology with dual three-phase outputs. The presented 3HI2MC has the advantages of sinusoidal input and output currents, bi-directional power flow, and can provide two sets of three-phase outputs, whose frequencies and amplitudes can be regulated independently. Compared with the conventional indirect matrix converter (IMC), the input reactive power control range is extended significantly, and the converter can even work as a static compensator. Moreover, a maximal voltage transfer ratio of 0.866 is achievable under all operation conditions. Furthermore, operations of the rectifier and inverters are independent. Thus, for a 3HI2MC system containing multiple voltage-source-type inverters (VSIs), modulation and control task can be implemented flexibly by a separate controller for each VSI, while it is difficult for the conventional IMCs to achieve such a goal. All of the features above make 3HI2MC competitive for the applications that require multiple three-phase outputs such as multiple drives. After describing the topology structure, operating principles and control algorithm in detail, simulation and experimental results are presented to demonstrate the validity and effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

This study proposes a new power decoupling circuit applied to the single-phase current source converter (SCSC). Differing from the existing power decoupling technologies, the proposed power decoupling circuit could be viewed as a controlled voltage source in series with the DC inductor, and work with SCSC independently. That facilitates the separate design of the modulation schemes and the control algorithms for the power decoupling circuit and SCSC, and reduces the operation restrictions imposed by requirements. The fundamental principle of the proposed converter is analysed, and the voltage reference requirement for the buffer capacitor is investigated. To guarantee high input current quality of SCSC, a control method, where the input current is treated as a virtual control input, is proposed. Finally the effectiveness of this topology is verified by the simulations and experimental results. [ABSTRACT FROM AUTHOR]

Objectives. The present study was conducted to evaluate the activity of nanometer propolis flavone (NPF) on inhibiting porcine parvovirus (PPV) in vitro and in vivo. Methods. In vitro, the effect of NPF on cellular infectivity of PPV was carried out before and after adding drug and simultaneous adding and PPV after being mixed. In vivo, the anti-PPV effect of NPF in guinea pigs was performed. Results. The results showed that NPF could significantly inhibit PPV infecting porcine kidney- (PK-) 15 cells compared with propolis flavone (PF), and the activity of NPF was the best in preadding drug pattern. NPF at high and medium doses was able to observably restrain PPV copying in lung, gonad, blood, and spleen, decrease the impact of PPV on weight of guinea pigs, and improve hemagglutination inhibition (HI) of PPV in serum. In addition, it could also increase the contents of IL-2 and IL-6 in serum after PPV challenge. Conclusion. These results indicated that NPF could significantly improve the anti-PPV activity of PF, and its high concentration possessed the best efficacy. Therefore, NPF would be expected to be exploited into a new-style antiviral drug. [ABSTRACT FROM AUTHOR]