The high-voltage gain converter is widely employed in many industry applications, such as photovoltaic systems, fuel cell systems, electric vehicles, and high-intensity discharge lamps. This paper ...presents a novel single-switch high step-up nonisolated dc-dc converter integrating coupled inductor with extended voltage doubler cell and diode-capacitor techniques. The proposed converter achieves extremely large voltage conversion ratio with appropriate duty cycle and reduction of voltage stress on the power devices. Moreover, the energy stored in leakage inductance of coupled inductor is efficiently recycled to the output, and the voltage doubler cell also operates as a regenerative clamping circuit, alleviating the problem of potential resonance between the leakage inductance and the junction capacitor of output diode. These characteristics make it possible to design a compact circuit with high static gain and high efficiency for industry applications. In addition, the unexpected high-pulsed input current in the converter with coupled inductor is decreased. The operating principles and the steady-state analyses of the proposed converter are discussed in detail. Finally, a prototype circuit is implemented in the laboratory to verify the performance of the proposed converter.
High voltage gain dc-dc converters are required in many industrial applications such as photovoltaic and fuel cell energy systems, high-intensity discharge lamp (HID), dc back-up energy systems, and ...electric vehicles. This paper presents a novel input-parallel output-series boost converter with dual coupled inductors and a voltage multiplier module. On the one hand, the primary windings of two coupled inductors are connected in parallel to share the input current and reduce the current ripple at the input. On the other hand, the proposed converter inherits the merits of interleaved series-connected output capacitors for high voltage gain, low output voltage ripple, and low switch voltage stress. Moreover, the secondary sides of two coupled inductors are connected in series to a regenerative capacitor by a diode for extending the voltage gain and balancing the primary-parallel currents. In addition, the active switches are turned on at zero current and the reverse recovery problem of diodes is alleviated by reasonable leakage inductances of the coupled inductors. Besides, the energy of leakage inductances can be recycled. A prototype circuit rated 500-W output power is implemented in the laboratory, and the experimental results shows satisfactory agreement with the theoretical analysis.
This paper presents a dc-dc boost converter topology for low input and high output voltage applications, such as photovoltaic systems, fuel cell systems, high-intensity discharge lamp, and electric ...vehicles. The suggested configuration consists of a three-winding coupled-inductor, a single switch and two hybrid voltage multiplier cells. Furthermore, two independent hybrid voltage multiplier cells are in parallel when the single switch S is turned on, and they are in series when the switch S is turned off. So, the advantages of the proposed converter structure are summarized as follows: 1) A coupled inductor with three windings is introduced in the presented converter structure. The two secondary windings of the coupled inductor are, respectively, used to form a hybrid multiplier cell on the one hand, on the other hand, it increases the control freedom of the voltage gain, enhances the utility rate of magnetic core and power density, and reduces the stress of power components to provide a stable constant dc output voltage. 2) The two hybrid multiplier cells can absorb synchronously the energy of stray inductance, which not only reduces the current stress of corresponding diodes, but also greatly alleviates the spike voltage of the main switch, which improves the efficiency. 3) The two hybrid multiplier cells are connected in series to supply power energy for the load, so the voltage gain is extended greatly due to this particular structure. Thus, low-voltage low-conduction-loss devices can be selected and the reverse-recovery currents within the diodes are inhibited. The operating principles and the steady state analyses of the proposed converter are discussed in detail. Finally, a test prototype has been implemented in the laboratory, and the simulated and experimental results show satisfactory agreement with the theoretical analysis.
Synergistic effect of Cr(VI) reduction and 2,4,6-TCP degradation over g-C3N4 under visible light irradiation.
•The synergistic effect of Cr(VI) reduction and 2,4,6-TCP degradation was observed over ...g-C3N4 under visible light irradiation.•Acidic environment facilitates the reduction of Cr(VI) and oxidation of 2,4,6-TCP.•Both CB electrons and O2− responsible for the reduction of Cr(VI).•The active oxygen species (O2− and OH) and VB holes are responsible for the degradation of 2,4,6-TCP.
In this study, a rapid reduction of Cr(VI) and degradation of 2,4,6-trichlorophenol (2,4,6-TCP) in a simultaneous manner was reported through the catalysis of g-C3N4 under visible light (λ>420nm) irradiation. The effects of initial concentration of reactants, dissolved O2 and pH value were investigated systematically. It indicated that, under the optimized concentration, the Cr(VI) reduction and 2,4,6-TCP oxidation could be accomplished in couple of hours in the presence of g-C3N4. And also, the O2 involvement and low pH value were able to significantly improve the removal rate of Cr(VI) and 2,4,6-TCP. In addition, the reaction mechanism was investigated through monitoring the reduced states of Cr(VI) and active oxygen intermediates formed during photoreaction by ESR and XPS, as well as determining the degradation products of 2,4,6-TCP by HPLC–MS. The results supported that the redox reactions of Cr(VI) and 2,4,6-TCP can be performed simultaneously via a synergistic oxidation–reduction mechanism in the presence of g-C3N4 under visible light irradiation.
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► g-C3N4 was synthesized by directly thermal condensation of dicyandiamide. ► 2,4,6-TCP could be degraded over g-C3N4 under visible irradiation. ► O2-/OOH was the most important ...reactive species in the presence of O2. ► 2,4,6-TCP was oxidized by hole at N2 gas ambient in the presence of metal ions. ► The possible degradation pathway of 2,4,6-TCP was proposed.
Graphitic carbon nitride (g-C3N4) was synthesized by directly thermal condensation of dicyandiamide and characterized by XRD, XPS, SEM, TEM and FT-IR. Then the as-prepared catalyst was employed to degrade priority pollutant 2,4,6-trichlorophenol (2,4,6-TCP) under visible light irradiation (λ>420nm). The 2,4,6-TCP could be completely mineralized over g-C3N4, and the pseudo-first-order rate constant for 10−4M 2,4,6-TCP degradation was 0.70h−1 in the presence of 1g/L catalyst. O2-/OOH was identified as the most important reactive species contributing to 2,4,6-TCP degradation in air. Meanwhile, valence band holes (VB holes) of g-C3N4 was observed to play important roles for the degradation of 2,4,6-TCP at N2 gas ambient when metal ions were added as electron acceptors. The possible degradation pathway of 2,4,6-TCP was proposed.
Abstract The demand for orthopedic and dental implants will continue to grow, and for these applications, titanium and its alloys have been used extensively. While these implants have achieved high ...success rates, two major complications may be encountered: the lack of bone tissue integration and implant-centered infection. The surface of the implant, through its interactions with proteins, bacteria and tissue cells, plays a determining role in the success or failure of the implant. Ideally, to enhance the success of implants, their surfaces should inhibit bacterial colonization and concomitantly promote osteoblast functions. In this article, we discuss strategies for tailoring implant surfaces by exploiting the differences in the response of bacteria and osteoblasts to proteins and surface structures. Nevertheless, limitations still exist in the quest for an ideal implant surface. Further advances in this field will require concurrent development in surface modification techniques and a better understanding of the complex and highly inter-related events occurring at the implant surface after implantation.
This paper presents a robust and efficient method for license plate detection with the purpose of accurately localizing vehicle license plates from complex scenes in real time. A simple yet effective ...image downscaling method is first proposed to substantially accelerate license plate localization without sacrificing detection performance compared with that achieved using the original image. Furthermore, a novel line density filter approach is proposed to extract candidate regions, thereby significantly reducing the area to be analyzed for license plate localization. Moreover, a cascaded license plate classifier based on linear support vector machines using color saliency features is introduced to identify the true license plate from among the candidate regions. For performance evaluation, a data set consisting of 3977 images captured from diverse scenes under different conditions is also presented. Extensive experiments on the widely used Caltech license plate data set and our newly introduced data set demonstrate that the proposed approach substantially outperforms state-of-the-art methods in terms of both detection accuracy and run-time efficiency, increasing the detection ratio from 91.09% to 96.62% while decreasing the run time from 672 to 42 ms for processing an image with a resolution of 1082×728. The executable code and our collected data set are publicly available.
In recommender systems, the lack of interaction data between users and items tends to lead to the problem of data sparsity and cold starts. Recently, the interest modeling frameworks incorporating ...multi-modal features are widely used in recommendation algorithms. These algorithms use image features and text features to extend the available information, which alleviate the data sparsity problem effectively, but they also have some limitations. On the one hand, multi-modal features of user interaction sequences are not considered in the interest modeling process. On the other hand, the aggregation of multi-modal features often employs simple aggregators, such as sums and concatenation, which do not distinguish the importance of different feature interactions. In this paper, to tackle this, we propose the FVTF (Fusing Visual and Textual Features) algorithm. First, we design a user history visual preference extraction module based on the Query-Key-Value attention to model users' historical interests by using of visual features. Second, we design a feature fusion and interaction module based on the multi-head bit-wise attention to adaptively mine important feature combinations and update the higher-order attention fusion representation of features. We conduct experiments on the Movielens-1M dataset, and the experiments show that FVTF achieved the best performance compared with the benchmark recommendation algorithms.
Flexible bioelectronics for biomedical applications requires a stretchable, conductive, self-healable, and biocompatible material that can be obtained by cost-effective chemicals and strategies. ...Herein, we synthesized polypyrrole or Zn-functionalized chitosan molecules, which are cross-linked with poly(vinyl alcohol) to form a hydrogel through dynamic di-diol complexations, hydrogen bonding, and zinc-based coordination bonds. These multiple dynamic interactions endow the material with excellent stretchability and autonomous self-healing ability. The choice of Food and Drug Administration (FDA)-approved materials (poly(vinyl alcohol) and chitosan) as the matrix materials ensures the good biocompatibility of the hydrogel. The conductivity contributed by the polypyrrole allowed the hydrogel to sense strain and temperature, and the coordinated Zn significantly enhanced the antibacterial activity of the hydrogel. Moreover, using a diabetic rat model, we have proved that this hydrogel is capable of promoting the healing of the infected chronic wounds with electrical stimulation.
•Synthesis of TiO2 hybrids with exfoliated g-C3N4 was provided.•Heterojunction structures were formed and identified by several analytic techniques.•Newly prepared CNs–TiO2 hybrids showed obviously ...enhanced photocatalytic ability toward degradation of dye RhB.•Photoinduced holes made an important role on photocatalytic process.
A series of TiO2 hybrids composited with exfoliated g-C3N4 nanosheets (CNs) were successfully synthesized through a facile sol–gel method and fully characterized by X-ray diffraction patterns (XRD), Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV–vis diffuse reflectance spectra (UV–vis DRS). The CNs–TiO2 hybrids were exposed to visible light irradiation and showed much higher catalytic capability toward degrading dye rhodamine B (RhB) comparing with bare TiO2 and N-TiO2. The sample CNs–TiO2-0.05 exhibited the largest apparent reaction rate constant among all CNs–TiO2 hybrids, which was 2.4 times and 7.0 times as high as bare TiO2 and N-TiO2, respectively. The enhanced catalytic efficiency could be mainly attributed to the well-matched band gap structure with heterojunction interface, suitable specific surface area, and favorable optical property. In addition, active species trapping experiments were conducted, revealing that photoinduced holes (h+) had a severe influence on catalytic outcome, through which a possible catalytic mechanism was finally realized and proposed.
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