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Number of results: 10
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Abstract

An integrated Z-source inverter for the single-phase single-stage grid-connected photovoltaic system is proposed in this paper. The inverter integrates three functional blocks including maximum-power-point-tracking, step-up/down DC-side voltage and output grid-connected current. According to the non-minimum-phase characteristic presented in DC-side and the functional demands of the system, two constant-frequency sliding-mode controllers with integral compensation are proposed to guarantee the system robustness. By using two controllers, the effects caused by the non-minimum-phase characteristic are mitigated. Under the circumstance of that the input voltage or the grid-connected current changes suddenly, the notches/protrusions following the over-shoot/ under-shoot of the DC-bus voltage are eliminated. The quality of grid-connected current is ensured. Also, a small-signal modelling method is employed to analyze the close-loop system. A 300W prototype is built in the laboratory. A solar-array simulator (SAS) is used to verify the systematic responses in the experiment. The correctness and validity of the inverter and proposed control algorithm are proved by simulation and experimental results.
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Abstract

Canine parvovirus (CPV) causes acute gastroenteritis in domestic dogs, cats, and several wild carnivore species. In this study, the full-length VP2 gene of 36 CPV isolates from dogs and cats infected between 2016 and 2017 in Beijing was sequenced and analyzed. The results showed that, in dogs, the new CPV-2a strain was the predominant variant (n = 18; 50%), followed by the new CPV-2b (n = 6; 16.7%) and CPV-2c (n = 3; 8.3%) strains, whereas, among cats, the predominant strain was still CPV-2 (n = 9; 25%). One new CPV-2a strain, 20170320-BJ-11, and two CPV-2c strains, 20160810-BJ-81 and 20170322-BJ-26, were isolated and used to perform experimental infections. Multiple organs of beagles that died tested PCR positive for CPV, and characteristic histopathological lesions were observed in organs, including the liver, spleen, lungs, kidneys, small intestines, and lymph nodes. Experimental infections showed that the isolates from the epidemic caused high morbidity in beagles, indicating their virulence in animals and suggesting the need to further monitor evolution of CPV in China.
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Abstract

An efficient system of micropropagation via somatic embryogenesis from root-derived callus was established in Arabica coffee (Coffea arabica L.). Twenty-six callus lines were induced on MS (Murashige and Skoog, 1962) medium supplemented with combinations of NAA (0, 0.1, 0.5, 1 and 2 mg/L) plus BA (0, 1 and 2 mg/L), or 2,4-D (0, 0.1, 0.5, 1 and 2 mg/L) plus TDZ (0, 1 and 2 mg/L). Subsequently, two types of somatic embryos were obtained from callus cultures and named S-type and I-type embryos. The S-type embryos were obtained from an 18-monthold callus line which was induced and maintained at 2 mg/L TDZ and 0.1 mg/L 2,4-D near the end of each period of the subculture. These embryos have a developmental barrier, which did not pass through the torpedo stage and could be overcome by a supplement of 2 or 5 mg/L BA. The I-type embryos were induced from 3-month-old callus when transferred onto induction media, i.e., MS supplemented with TDZ (2 and 5 mg/L) plus 2,4-D (0 and 0.1 mg/L). The significantly highest response, i.e., 13.3 embryos per callus clump was obtained at 2 mg/L TDZ. In this study, the results reveal that TDZ has a crucial effect on embryogenic callus induction, proliferation and subsequent somatic embryogenesis.
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Abstract

A novel phase shift full bridge (PSFB) converter with voltage-doubler and decoupling integrated magnetics in photovoltaic (PV) systems is proposed. Considering the demand that the output voltage is higher than the input voltage in PV systems, the voltage-doubler is added to achieve higher voltage gain compared with the traditional PSFB. In order to avoid current oscillation caused by the voltage-doubler and obtain the wide zero voltage switching (ZVS) ranges, an external inductor is imposed on the circuit. Especially, to obtain much higher power density, the external inductor and transformer are integrated into one magnetic core. The operation and voltage gain of proposed converter are analyzed. Also, in order to reveal the effects the integrated magnetics gives to the converter, the decoupling condition and the expression of leakage inductor of integrated magnetics are obtained in detail. Finally a 100 W prototype converter is made and the experimental results are given to verify the analysis.
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Abstract

Sapelovirus A (SV-A) is a positive-sense single-stranded RNA virus which is associated with acute diarrhea, pneumonia and reproductive disorders. The virus capsid is composed of four proteins, and the functions of the structural proteins are unclear. In this study, we expressed SV-A structural protein VP1 and studied its antigenicity and immunogenicity. SDS-PAGE analysis revealed that the target gene was expressed at high levels at 0.6 mM concentration of IPTG for 24 h. The mouse polyclonal antibody against SV-A VP1 protein was produced and reached a high antiserum titer (1: 2,048,000). Immunized mice sera with the recombinant SV-A VP1 protein showed specific recognition of purified VP1 protein by western blot assay and could recognize native SV-A VP1 protein in PK-15 cells infected with SV-A by indirect immunofluorescence assay. The successfully purified recombinant protein was able to preserve its antigenic determinants and the generated mouse anti-SV-A VP1 antibodies could recognize native SV-A, which may have the potential to be used to detect SV-A infection in pigs.
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