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This article introduces a class of Sepic-based DC-DC converters with an improved voltage multiplier cell (IVMC) for interfacing photovoltaic (PV) panels with high-voltage DC buses in renewable energy. The converters achieve a high voltage gain by optimizing the connecting of the IVMC and Sepic converter without adding additional components. The proposed converters have the advantages of high voltage gain, low input current ripple, and low voltage stress on the switch with small number of the components. Owing to the low voltage stress, a MOSFET with low on-resistance can be adopted to reduce switching and conduction losses. The low input current ripple prolongs the lifetime of the PV modules and converters. Furthermore, a lower turns ratio is conducive to reducing the volume of the coupled inductor and decreasing the leakage inductance. The passive clamp circuit recycles leakage inductance energy and limits switch voltage spikes. A detailed analysis of the operating principle and a comprehensive steady-state analysis are presented. Then a comparison with other similar converters explains the superiorities of the proposed converters. Finally, a 200 W (32 V to 380 V) prototype made in the laboratory verified the effectiveness of the proposed converter, and the experimental results are in reasonable consistent with the theoretical analysis. [ABSTRACT FROM AUTHOR]

Nonisolated high-voltage gain soft-switching dc–dc converter is an ideal candidate for distributed generation system converters. This article proposes a high-voltage gain soft switching quasi-Z-source dc–dc converter. The converter integrates a coupled inductor and switched capacitor into a quasi-Z-source network. Soft switching is achieved for all active devices in the converter by controlling the auxiliary switch Sa. By inheriting the advantages of the quasi-Z-source network and coupled-inductor/switched-capacitor, the converter has high voltage gain, high efficiency, low input current ripple, low voltage spike of main switch, and common ground. In addition, the efficiency of the converter is improved by recycling the energy of leakage inductance, resulting from an inherent active clamp of the main switch. The steady-state operation, voltage relationship, current/voltage stress, and power dissipation of each component of the converter have been analyzed and derived in detail. The properties of the proposed converter are verified by designing a 200 W prototype in the laboratory. When the input voltage is 48 V and the output voltage is 380 V, the converter efficiency reaches 96.92%, while the efficiency is 93% in a hard switching. The key waveforms of the converter obtained from the experiment agree well with the theoretical analysis results. [ABSTRACT FROM AUTHOR]

The Z-source inverter can overcome several inherent limitations of conventional inverters, realize buck–boost voltage capability with a single-stage inverter, and improve inverter's safety. However, it needs to be optimized in two aspects: mitigating the constraining effect of the shoot-through duty ratio D and the modulation index M; reduction of the inductance of the magnetic elements and the size of the magnetic core in the Z-Source network. This article presents a new quasi-Z-source inverter (qZSI) that either has a coupled-inductor multiplier voltage rectifier (CMVR) cell or an improved CMVR cell embedded into it. The CMVR qZSIs can implement a boost factor given by $k_{N}/ (1-kD)$ , $k_{N}> 1$ , which mitigates the constraining effect of D and M, as well as enables high voltage boosting with a large value of M. The CMVR qZSI has low weight of the magnetic elements in the CMVR cell due to the use of step-down transformer. The operating principle, voltage relationship between each component, and the comparison in voltage and current stress on components, magnetic elements, has been described. A 1 kW prototype was built in the laboratory to verify the validity of the proposed inverter. Experimental results are in good agreement with the analysis results. [ABSTRACT FROM AUTHOR]

Z-source inverter (ZSI) can overcome some drawbacks of classical current- and voltage-source inverter, which have features such as high reliability and buck–boost capability of single-stage inverter. This article proposes an extensible ZSI architecture, abbreviated as EZSI. The proposed architecture provides high voltage gain at a small shoot-through duty ratio, which improves the output waveform quality. It inherits the advantages of continuous input current and low dc-link voltage overshoot of quasi-ZSI. The EZSI can be constructed with modularization, using low voltage components to construct a high-power single-stage inverter. A modular analysis method of EZSI is proposed, which divides the high-dimensional state equation of inverter into several independent low-dimensional state equations and simplifies the research of EZSI. A typical EZSI (n = 2) L-mSSCL validates the correctness and feasibility of the proposed theory. Compared with the conventional high boost ZSIs, the proposed EZSI (n = 2) L-mSSCL has advantages in the aspects of boost capacity, component stress, and inverter efficiency. The operating principle, characters design rules, and power dissipation of the components is analyzed in detail. A 1-kW prototype is used for experimental validation. The theoretical analysis results match with the experimental results. [ABSTRACT FROM AUTHOR]

An impedance-source inverter can offer the voltage buck-boost function in a single-stage circuit. Its advantages include a simple structure, safety, and reliability. This article proposes a Cockcroft–Walton multiplier voltage (CWMV) impedance-source inverter consisting of a modified CWMV circuit and an impedance-source inverter. There are two types of circuits: the CWMV Z-source inverter (ZSI) and the CWMV quasi-Z-source inverter (qZSI). In a CWMV qZSI, the input current is continuous, the voltage overshoot across the bridge is small, and the boost capability is great, with the disadvantage is that its passive component count is increased. This article studies the static and dynamic characteristics of the two inverters. The operating modes of the CWMV qZSI is studied, the voltage and current stress of each device are analyzed, the small signal model of the circuit is established, and a proportional-integral-differential controller with good control performance is designed. Compared with existing impedance-source inverters, a CWMV qZSI has obvious advantages in terms of the voltage and current stresses on components, and also in terms of its inductor size, magnetic core volume, and overall efficiency. The theoretical analysis was verified by a 1 kW laboratory prototype. The experimental results were consistent with the theoretical analysis. [ABSTRACT FROM AUTHOR]

Due to the wide adoption of photovoltaic power generation, non-isolated high step-up DC–DC converters are becoming more and more popular. Among these converters, the switched/coupled-inductor-based converter is more attractive due to the fact that it has fewer power devices and a high efficiency. This paper presents a three-level high step-up DC–DC topology with a three-winding coupled-inductor. When compared with a conventional switched/coupled-inductor-based converter, a higher efficiency can be achieved, owing to low voltage stresses devices, fewer semiconductors in the power loop, lower current stresses, and ZCS of the main switches. The operating principle of the proposed topology is analyzed in detail via equivalent circuits, where a theoretical analysis is carried out using state space modelling. Experimental results obtained on a 24–300 V, 360 W lab prototype have verified the excellent performance of the proposed DC–DC converter. [ABSTRACT FROM AUTHOR]

A photo‐induced two/three‐component radical difluoroethylation or monofluoromethyl sulfonylation of 2‐amino aryl ethynes was smoothly finished, which gave a series of difluoroethyl or monofluoromethyl sulfonyl seven‐membered N‐heterocycles. The two radical systems featured simple/mild reaction conditions, good substrate scopes, and excellent E/Z selectivity. In addition, various radical intermediates were successfully detected by HRMS to explore the reaction process. Single‐crystal X‐ray diffraction and scaled‐up experiments examined the product scaffold and application of this cyclization system. [ABSTRACT FROM AUTHOR]

This paper presents a single-switch high-voltage gain DC–DC converter with a coupled-inductor. The proposed converter overcomes the drawbacks of traditional DC–DC converters such as insufficient boost capability and high stress on the devices. Its advantages include having a small number of switch devices, low voltage stress on the switch, and a high voltage gain. This paper analyzes the operating modes of the proposed converter in detail and derives the voltage/current stresses on the components. The efficiency of the converter and the power dissipation distribution are quantitatively studied. To verify the efficiency and feasibility of the proposed converter, a 200 W prototype was built in the laboratory. Experimental results obtained from the prototype match well with the theoretical analysis. The highest efficiency is equal to 95.82%, which can be obtained at half of the rated output power. [ABSTRACT FROM AUTHOR]

Exposure to heavy metals has been related to decreased lung function in workers. However, due to limitations in statistical methods for mixtures, previous studies mainly focused on single or several toxic metals, with few studies involving metal exposome and lung function. The study aimed to evaluate the effects of co-exposure to the metal mixtures on multiple parameters of pulmonary function tests and to identify the elements that play an essential role in elastic-net regression (ENET), multivariate linear regression, bayesian kernel machine regression (BKMR), and quantile g-computation (QG-C) models. We have recruited 186 welders from Anhui (China) in 2019. And their end-of-shift urine and lung function measure data were collected with informed consent. The urinary concentrations of 23 metals were measured by inductively coupled urinary mass spectrometry. The lung function measures including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and peak expiratory flow (PEF) were also detected as outcome indicators. Four statistical methods, ENET, multivariate linear regression, BKMR, and QG-C models were used to evaluate the associations of element mixtures on lung function comprehensively. Lead and cadmium were negatively associated with FVC and FEV1, nickel and chromium were inversely associated with PEF, and strontium showed significant positive effects in linear regression models, which were consistent with the results in BKMR and QG-C models. Both BKMR and QG-C models showed a significantly negative overall effect of metal mixtures on lung function parameters (FVC, FEV1, and PEF). Meanwhile, BKMR showed the non-linear relationships of cadmium with FVC. Multi-pollutant mixtures of metals were negatively associated with lung function. Lead, cadmium, nickel, and strontium might be crucial elements. Our findings highlight a need to prioritize workers' environmental health, and guide future research into the toxic mechanisms of metal-mediated lung function injury. [Display omitted] • Four statistical methods examined the individual and mixture effects of 16 metals on lung function in welders. • Urinary concentration of the metal mixture was associated with decreased lung function in welders. • Urinary Pb, Cd, and Ni were negatively associated with lung function in welders. • Urinary Sr was positively correlated with lung function in welders. [ABSTRACT FROM AUTHOR]

Stigma is a significant barrier to effective control of HIV/AIDS, despite laws to control it. The purpose of this study was to examine factors associated with HIV stigma in a rural Chinese community. A survey was conducted in north-west Anhui province among 963 residents to assess HIV-related knowledge, attitudes, and behaviors. Participants scored a mean of 16.6/26 (63.8%) for knowledge. Sixty-eight percent of respondents held at least one fear of casual transmission, 42% would blame people living with HIV/AIDS (PLHA) for their disease, and 73% thought having HIV is shameful. More than half reported that they had observed at least one stigmatizing behavior toward PLHA in their villages. Multivariable analysis indicated that people with higher education, higher HIV knowledge, higher household wealth and who learned about HIV from professional sources were less likely to hold a stigmatizing attitude, while people who had observed discriminating behaviors toward PLHA in their community and lived in villages with fewer PLHA were more likely to hold a stigmatizing attitude. Despite education campaigns, knowledge remains low and stigmatizing attitudes and behaviors toward PLHA remain a problem. [ABSTRACT FROM AUTHOR]

Background: The proportion of older HIV-1 infected people in China has increased rapidly in recent years. Elucidation of the transmission characteristics of this high-risk population subgroup is helpful for the development of tailored interventions.Methods: A phylogenetic analysis was performed that uses available HIV-1 pol sequences amplified with nested RT-PCR from plasma samples of all newly diagnosed participants spanning from October 2017 to September 2018 in Fuyang, Anhui Province. Transmission clusters were identified as two or more sequences that shared a corresponding node with an aLRT-SH value ≥90 in the maximum-likelihood phylogenetic tree and had an overall mean genetic distance of ≤1.5%. A local transmission cluster was defined as a cluster that had more than 80% of its sequences from Fuyang. The role of older people in local HIV-1 transmission was determined using an integration of molecular and demographic data.Results: Of 362 available sequences, 14 subtypes, and 28 local transmission clusters were identified. It was found that the proportion of older people in the local transmission cluster (69/77, 89.61%) was much higher than that of younger people (46/114, 40.35%) (χ2 test, P < 0.001). In the pretreatment drug resistance analysis, the proportion of sequences with PDRMs in the local transmission cluster was not significantly different between the older people group (57.14%, 4/7) and non-old-aged group (11.11%, 1/9) (Fisher's exact test, P > 0.05).Conclusion: By combining phylogenetic analyses with demographic data, more detailed information was provided about the local transmission structure in Fuyang. These findings suggested that older people play an important role in local transmission, and more tailored interventions for this population subgroup are urgently needed. [ABSTRACT FROM AUTHOR]