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Tao Y.-B.,Kunming University of Science and Technology | Tian H.,Chongqing Instrument Materials Research Institute | Yang C.-Z.,Kunming University of Science and Technology | Lin H.,Nanjing University of Science and Technology
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

In terms of the inadequacy of the traditional Boost-type PFC power switching devices which brings a lot of switching losses and conduction losses, and burdens with a high voltage, strong current and thermal stress, this paper proposes a new Bridgeless Topology Active Power Factor Correction (BLPFC) circuit construction. This circuit changes the two diodes in traditional rectifying bridge legs into IGBT, and adopts dual closed-loop average current control strategy to improve power factor and reduce the harmonic pollution from the grid. It can improve the system switching devices efficiently and reduce system heat dissipation and costs. This circuit is simulated using the SimPowerSystems kit in Matlab/Simulink software. Simulation results show that BLPFC provides a high efficiency, low switching losses, and can restrain current harmonics, and the input current which can keep track of the input voltage waveform well.

PubMed | Chongqing University of Technology, United Arab Emirates University and Chongqing Instrument Materials Research Institute
Type: | Journal: Materials science & engineering. C, Materials for biological applications | Year: 2014

Adverse effects of nickel ions being released into the living organism have resulted in development of high nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also improves steel properties. The cell cytocompatibility, blood compatibility and cell response of high nitrogen nickel-free austenitic stainless steel were studied in vitro. The mechanical properties and microstructure of this stainless steel were compared to the currently used 316L stainless steel. It was shown that the new steel material had comparable basic mechanical properties to 316L stainless steel and preserved the single austenite organization. The cell toxicity test showed no significant toxic side effects for MC3T3-E1 cells compared to nitinol alloy. Cell adhesion testing showed that the number of MC3T3-E1 cells was more than that on nitinol alloy and the cells grew in good condition. The hemolysis rate was lower than the national standard of 5% without influence on platelets. The total intracellular protein content and ALP activity and quantification of mineralization showed good cell response. We conclude that the high nitrogen nickel-free austenitic stainless steel is a promising new biomedical material for coronary stent development.

Hu Z.D.,Chongqing University | Yan H.,Chongqing University | Qiu H.Z.,Chongqing University | Zhang P.,Chongqing Instrument Materials Research Institute | Liu Q.,Chongqing Instrument Materials Research Institute
Wear | Year: 2012

The continuously adjustable magnetic field was performed by modifying of a four-ball tribological tester. The tribological properties of magnetorheological fluid (MRF) were studied under magnetic field. The worn surfaces of the steel balls lubricated with MRF were observed by using a scanning electron microscope (SEM). It is found that the MRF shows a controlled tribological property. Under 0.12. T of magnetic induction, the friction coefficient lubricated with MRF is four times as large as that without magnetic field. The worn surfaces, lubricated by MRF under the effect of a magnetic field, change from circle or ellipse to irregular rectangle and the diameter of wear scar decreases. Under the successive variable magnetic field, the friction coefficient increases with the enhancement in the magnetic field, and it decreases with the weakening of the magnetic field. © 2012.

Shen J.,Chongqing University | Peng C.,Chongqing University | Yin H.G.,Chongqing University | Chen J.,Chongqing University | Chen J.,Chongqing Instrument Materials Research Institute
Journal of Materials Science: Materials in Electronics | Year: 2012

The influence of minor POSS (polyhedral oligomeric silsesquioxanes) molecules additions on the microstructure and hardness of SnAgCu-xPOSS (x = 1, 3 and 5) was investigated. A mechanical mixture method was adopted by adding POSS molecules as dispersoids into SnAgCu solder to fabricate SnAgCu-xPOSS composite solders. The microstructural evolution and the hardness of the solders were investigated in details by microstructural observations, Vickers hardness tester and nanoindentation tests. The results showed that the effects of the dispersed POSS molecules in eutectic SnAgCu structure and the refined Ag 3Sn IMC particles increased the hardness of eutectic SnAgCu phase and then increased the hardness of composite solder. In addition, because of the agglomeration of POSS molecule, a coarse lath-shaped structure (composed of POSS molecules, Ag 3Sn phase and minor Cu 6Sn 5 phase) formed in SnAgCu-5POSS solder matrix, which reduced the hardness of SnAgCu-5POSS solder. © Springer Science+Business Media, LLC 2012.

Xu N.,Chongqing University | Shen J.,Chongqing University | Liu H.,Chongqing Instrument Materials Research Institute
Gongneng Cailiao/Journal of Functional Materials | Year: 2011

The effects of solution and aging treatments on a 2mm tungsten inert gas (TIG) butt welded joint was investigated by examining the microstructures and the microhardness. The results show that: At the beginning of the aging treatment (0-10h), the microhardness of the fusion zone increased sharply due to the fast increase of the diffusion rate of Al and Zn and the volume fraction of β-Mg 17(Al, Zn) 12. With the increase of the aging time, the microhardness of the fusion zone did not increase because the Al and Zn elements reached the saturated composition.

Min D.,Chongqing University | Shen J.,Chongqing University | Lai S.,Chongqing University | Chen J.,Chongqing University | And 2 more authors.
Optics and Lasers in Engineering | Year: 2011

The effects of heat input on the low power Nd:YAG pulse laser conduction weldability of magnesium alloy AZ61 plates were investigated. The results show that for a hot-extruded AZ61 magnesium alloy plate laser conduction welding, the penetration depth and area of welds cross-section increased with an increase of the heat input. The microstructure of a band zone, which is located in the fusion zone (FZ) and close to the fusion boundary, evolved with an increase of the heat input. Moreover, an increase of the heat input increased the tendency of the formation of solidification cracking and liquation cracking. The porosities and average diameters of pores increased with an increase of the heat input but reduced sharply when a relatively large heat input was achieved. In addition, the degree of formation of craters increased linearly with an increase of the heat input. © 2010 Elsevier Ltd. All rights reserved.

Li Y.,North China Electrical Power University | Li M.,North China Electrical Power University | Li M.,Chongqing Instrument Materials Research Institute | Li R.,North China Electrical Power University | And 3 more authors.
Applied Physics Letters | Year: 2015

The length of the silicon nanowire (SiNW) is a key parameter in photovoltaic devices, as it dramatically decides the light-harvesting and carrier recombination. Here, we develop a method to determine the optimal SiNW length for photovoltaic devices, by comparing the light-harvesting efficiency of SiNWs with various lengths. The light-harvesting efficiency is measured by the light intensity in the SiNW, and the fraction of the length with high light intensity in its whole length. Under these criteria, we find that the optimal SiNW length is around 3 μm. This method is helpful in further optimization and application of SiNW-based solar cells. © 2015 AIP Publishing LLC.

Li Y.,North China Electrical Power University | Yue L.,China University of Petroleum - Beijing | Luo Y.,North China Electrical Power University | Liu W.,North China Electrical Power University | And 2 more authors.
Optics Express | Year: 2016

Silicon nanostructures have light-harvesting effects for enhancing the performance of solar cells. Based on theoretical investigations on the optical properties of silicon nanowire (Si NW), the influencing laws of the size of Si NW on its light-harvesting effect are proposed. For the first time, we reveal that the resonant wavelength of Si NW predicted by the leaky mode theory does not correspond to the actual resonant wavelength calculated by the discrete dipole approximation method, but exactly coincides with the leftmost wavelength of the resonance peak. Then, the size dependency of the resonant intensity and width of Si NW is different from that of spherical nanoparticles, which can be deduced from the Mie theory. The size dependencies of resonant intensity and width are also applicative for silver/silicon composite nanowires. In addition, it is found that the harvested light by the Si and Ag/Si NW both show significant radial locality feature. The insight in this work is fundamental for the design and fabrication of efficient light - harvesting nanostructures for photovoltaic devices. ©2016 Optical Society of America.

Song D.,North China Electrical Power University | Cui P.,North China Electrical Power University | Zhao X.,North China Electrical Power University | Li M.,North China Electrical Power University | And 4 more authors.
Nanoscale | Year: 2015

A tungsten trioxide (WO3) nanoplate array is fabricated directly on the FTO/glass substrate and used as a platinum (Pt) nanoscale supporter for a highly efficient and low Pt-consumption counter electrode (CE) in dye-sensitized solar cells (DSCs). A Pt/WO3 composite structure, with Pt nanoparticles having a diameter of 2-3 nm, increases the electrochemical catalytic activity in catalyzing the reduction of triiodide. Accordingly, the power conversion efficiency is increased from less than 1% for WO3 CE and 8.1% for Pt CE, respectively, to 8.9% for Pt/WO3 CE. Moreover, the use of Pt/WO3 CE can dramatically reduce the consumption of scarce Pt material, with a relatively low Pt-loading of ∼2 μg cm-2, while maintaining a much better performance. The excellent performance of Pt/WO3 CE is attributed to the efficient electron injection and transport via WO3 supporters, as well as the nanostructure array morphology of WO3 for deposition of fine Pt nanoparticles. This work provides an approach for developing highly catalytic and low-cost Pt based CEs, which also has implications for the development of Pt/WO3 nanoplate arrays for other applications. This journal is © The Royal Society of Chemistry.

PubMed | North China Electrical Power University and Chongqing Instrument Materials Research Institute
Type: | Journal: Scientific reports | Year: 2015

Silicon nanorod based radial-junction solar cells are competitive alternatives to traditional planar silicon solar cells. In various silicon nanorods, nanocone is always considered to be better than nanowire in light-absorption. Nevertheless, we find that this notion isnt absolutely correct. Silicon nanocone is indeed significantly superior over nanowire in light-concentration due to its continuous diameters, and thus resonant wavelengths excited. However, the concentrated light cant be effectively absorbed and converted to photogenerated carriers, since its propagation path in silicon nanocone is shorter than that in nanowire. The results provide critical clues for the design of silicon nanorod based radial-junction solar cells.

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