A Modified Single-Phase Transformerless Z-Source Photovoltaic Grid-Connected Inverter

Liu, Hongpeng,Liu, Guihua,Ran, Yan,Wang, Gaolin,Wang, Wei,Xu, Dianguo The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5

In a grid-connected photovoltaic (PV) system, the traditional Z-source inverter uses a low frequency transformer to ensure galvanic isolation between the grid and the PV system. In order to combine the advantages of both Z-source inverters and transformerless PV inverters, this paper presents a modified single-phase transformerless Z-source PV grid-connected inverter and a corresponding PWM strategy to eliminate the ground leakage current. By utilizing two reversed-biased diodes, the path for the leakage current is blocked during the shoot-through state. Meanwhile, by turning off an additional switch, the PV array is decoupled from the grid during the freewheeling state. In this paper, the operation principle, PWM strategy and common-mode (CM) characteristic of the modified transformerless Z-source inverter are illustrated. Furthermore, the influence of the junction capacitances of the power switches is analyzed in detail. The total losses of the main electrical components are evaluated and compared. Finally, a theoretical analysis is presented and corroborated by experimental results from a 1-kW laboratory prototype.

Synthesis and characterization of RuO₂/poly(3,4-ethylenedioxythiophene) composite nanotubes for supercapacitors

Liu, Ran,Duay, Jonathon,Lane, Timothy,Bok Lee, Sang Royal Society of Chemistry 2010 Physical chemistry chemical physics Vol.12 No.17

<P>We report the synthesis of composite RuO<SUB>2</SUB>/poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes with high specific capacitance and fast charging/discharging capability as well as their potential application as electrode materials for a high-energy and high-power supercapacitor. RuO<SUB>2</SUB>/PEDOT nanotubes were synthesized in a porous alumina membrane by a step-wise electrochemical deposition method, and their structures were characterized using electron microscopy. Cyclic voltammetry was used to qualitatively characterize the capacitive properties of the composite RuO<SUB>2</SUB>/PEDOT nanotubes. Their specific capacitance, energy density and power density were evaluated by galvanostatic charge/discharge cycles at various current densities. The pseudocapacitance behavior of these composite nanotubes originates from ion diffusion during the simultaneous and parallel redox processes of RuO<SUB>2</SUB> and PEDOT. We show that the energy density (specific capacitance) of PEDOT nanotubes can be remarkably enhanced by electrodepositing RuO<SUB>2</SUB> into their porous walls and onto their rough internal surfaces. The flexible PEDOT prevents the RuO<SUB>2</SUB> from breaking and detaching from the current collector while the rigid RuO<SUB>2</SUB> keeps the PEDOT nanotubes from collapsing and aggregating. The composite RuO<SUB>2</SUB>/PEDOT nanotube can reach a high power density of 20 kW kg<SUP>−1</SUP> while maintaining 80% energy density (28 Wh kg<SUP>−1</SUP>) of its maximum value. This high power capability is attributed to the fast charge/discharge of nanotubular structures: hollow nanotubes allow counter-ions to readily penetrate into the composite material and access their internal surfaces, while a thin wall provides a short diffusion distance to facilitate ion transport. The high energy density originates from the RuO<SUB>2</SUB>, which can store high electrical/electrochemical energy intrinsically. The high specific capacitance (1217 F g<SUP>−1</SUP>) which is contributed by the RuO<SUB>2</SUB> in the composite RuO<SUB>2</SUB>/PEDOT nanotube is realized because of the high specific surface area of the nanotubular structures. Such PEDOT/RuO<SUB>2</SUB> composite nanotube materials are an ideal candidate for the development of high-energy and high-power supercapacitors.</P> <P>Graphic Abstract</P><P>RuO<SUB>2</SUB>/poly(3,4-ethylenedioxythiophene) composite nanotubes with high specific capacitance and fast charging/discharging capability for high-energy and high-power supercapacitor applications are reported. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b918589p'> </P>

Heterogeneous nanostructured electrode materials for electrochemical energy storage

Liu, Ran,Duay, Jonathon,Lee, Sang Bok Royal Society of Chemistry 2011 Chemical communications Vol.47 No.5

<P>In order to fulfil the future requirements of electrochemical energy storage, such as high energy density at high power demands, heterogeneous nanostructured materials are currently studied as promising electrode materials due to their synergic properties, which arise from integrating multi-nanocomponents, each tailored to address a different demand (<I>e.g.</I>, high energy density, high conductivity, and excellent mechanical stability). In this article, we discuss these heterogeneous nanomaterials based on their structural complexity: zero-dimensional (0-D) (<I>e.g.</I> core–shell nanoparticles), one-dimensional (1-D) (<I>e.g.</I> coaxial nanowires), two-dimensional (2-D) (<I>e.g.</I> graphene based composites), three-dimensional (3-D) (<I>e.g.</I> mesoporous carbon based composites) and the even more complex hierarchical 3-D nanostructured networks. This review tends to focus more on ordered arrays of 1-D heterogeneous nanomaterials due to their unique merits. Examples of different types of structures are listed and their advantages and disadvantages are compared. Finally a future 3-D heterogeneous nanostructure is proposed, which may set a goal toward developing ideal nano-architectured electrodes for future electrochemical energy storage devices.</P> <P>Graphic Abstract</P><P>Recent advances in applying heterogeneous nanostructures as electrode materials for electrochemical energy storage devices such as lithium–ion batteries and supercapacitors. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc03158e'> </P>

Hole-filling Based on Disparity Map for DIBR

( Ran Liu ),( Hui Xie ),( Fengchun Tian ),( Yingjian Wu ),( Guoqin Tai ),( Yingchun Tan ),( Weimin Tan ),( Bole Li ),( Hengxin Chen ),( Liang Ge ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.10

Due to sharp depth transition, big holes may be found in the novel view that is synthesized by depth-image-based rendering (DIBR). A hole-filling method based on disparity map is proposed. One important aspect of the method is that the disparity map of destination image is used for hole-filling, instead of the depth image of reference image. Firstly, the big hole detection based on disparity map is conducted, and the start point and the end point of the hole are recorded. Then foreground pixels and background pixels are distinguished for hole-dilating according to disparity map, so that areas with matching errors can be determined and eliminated. In addition, parallaxes of pixels in the area with holes and matching errors are changed to new values. Finally, holes are filled with background pixels from reference image according to these new parallaxes. Experimental results show that the quality of the new view after hole-filling is quite well; and geometric distortions are avoided in destination image, in contrast to the virtual view generated by depth-smoothing methods and image inpainting methods. Moreover, this method is easy for hardware implementation.

Electrochemical Formation Mechanism for the Controlled Synthesis of Heterogeneous MnO₂/Poly(3,4-ethylenedioxythiophene) Nanowires

Liu, Ran,Duay, Jonathon,Lee, Sang Bok American Chemical Society 2011 ACS NANO Vol.5 No.7

<P>The formation mechanism of a coaxial manganese oxide/poly(3,4-ethylenedioxythiophene) (MnO<SUB>2</SUB>/PEDOT) nanowire is elucidated herein by performing electrodeposition of MnO<SUB>2</SUB> and PEDOT on Au-sputtered nanoelectrodes with different shapes (ring and flat-top, respectively) within the 200 nm diameter pores of an anodized aluminum oxide (AAO) template. It is found that PEDOT prefers to grow on the sharp edge of the ring-shaped electrode, while MnO<SUB>2</SUB> is more likely to deposit on the flat-top electrode due to its smooth surface. The formation of coaxial nanowires is shown to be a result of simultaneous growth of core MnO<SUB>2</SUB> and shell PEDOT by an analysis of the current density resulting from electrochemical deposition. Furthermore, the structures of the MnO<SUB>2</SUB>/PEDOT coaxial nanowires were studied for their application as supercapacitors by modifying their coelectrodeposition potential. A potential of 0.70 V is found to be the most favorable condition for synthesis of MnO<SUB>2</SUB>/PEDOT coaxial nanowires, resulting in a high specific capacitance of 270 F/g. Additionally, other heterogeneous MnO<SUB>2</SUB>/PEDOT nanostructures are produced, such as nanowires consisting of MnO<SUB>2</SUB> nanodomes with PEDOT crowns as well as segmented MnO<SUB>2</SUB>/PEDOT nanowires. This is accomplished by simply adjusting the parameters of the electrochemical deposition. Finally, in smaller diameter (50 nm) AAO channels, MnO<SUB>2</SUB> and PEDOT are found to be partially assembled into coaxial nanowires due to the alternative depletion of Mn(II) ions and EDOT monomers in the smaller diameter pores.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-7/nn201106j/production/images/medium/nn-2011-01106j_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn201106j'>ACS Electronic Supporting Info</A></P>

Deep Space Universe

Liu Zheng Ran 한국콘텐츠학회 2023 한국콘텐츠학회 ICCC 논문집 Vol.2023 No.12

Deep Space Universe

Liu Zheng Ran 한국콘텐츠학회 2023 ICCC International Digital Design Invitation Exhib Vol.2023 No.12

CT Findings of Persistent Pure Ground Glass Opacity: Can We Predict the Invasiveness?

Liu, Li-Heng,Liu, Ming,Wei, Ran,Jin, Er-Hu,Liu, Yu-Hui,Xu, Liang,Li, Wen-Wu,Huang, Yong Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.5

Background: To investigate whether CT findings can predict the invasiveness of persistent cancerous pure ground glass opacity (pGGO) by correlating the CT imaging features of persistent pGGO with pathological changes. Materials and Methods: Ninety five patients with persistent pGGOs were included. Three radiologists evaluated the morphologic features of these pGGOs at high resolution CT (HRCT). Binary logistic regression was used to assess the association between CT findings and histopathological classification (pre-invasive and invasive groups). Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of diameters. Results: A total of 105 pGGOs were identified. Between pre-invasive (atypical adenomatous hyperplasia, AAH, and adenocarcinoma in situ, AIS) and invasive group (minimally invasive adenocarcinoma, MIA and invasive lung adenocarcinomas, ILA), there were significant differences in diameter, spiculation and vessel dilatation (p<0.05). No difference was found in air-bronchogram, bubble-lucency, lobulated-margin, pleural indentation or vascular convergence (p>0.05). The optimal threshold value of the diameters to predict the invasiveness of pGGO was 12.50mm. Conclusions: HRCT features can predict the invasiveness of persistent pGGO. The pGGO with a diameter more than 12.50mm, presences of spiculation and vessel dilatation are important factors to differentiate invasive adenocarcinoma from pre-invasive cancerous lesions.

Applications of Bacterial Cellulose-Based Composite Materials in Hard Tissue Regenerative Medicine

Liu Yingyu,Liu Haiyan,Guo Susu,Qi Jin,Zhang Ran,Liu Xiaoming,Sun Lingxiang,Zong Mingrui,Cheng Huaiyi,Wu Xiuping,Shanxi Medical University School and Hospital of Stomatology 한국조직공학과 재생의학회 2023 조직공학과 재생의학 Vol.20 No.7

BACKGROUND: Cartilage, bone, and teeth, as the three primary hard tissues in the human body, have a significant application value in maintaining physical and mental health. Since the development of bacterial cellulose-based composite materials with excellent biomechanical strength and good biocompatibility, bacterial cellulose-based composites have been widely studied in hard tissue regenerative medicine. This paper provides an overview of the advantages of bacterial cellulose-based for hard tissue regeneration and reviews the recent progress in the preparation and research of bacterial cellulose-based composites in maxillofacial cartilage, dentistry, and bone. METHOD: A systematic review was performed by searching the PubMed and Web of Science databases using selected keywords and Medical Subject Headings search terms. RESULTS: Ideal hard tissue regenerative medicine materials should be biocompatible, biodegradable, non-toxic, easy to use, and not burdensome to the human body; In addition, they should have good plasticity and processability and can be prepared into materials of different shapes; In addition, it should have good biological activity, promoting cell proliferation and regeneration. Bacterial cellulose materials have corresponding advantages and disadvantages due to their inherent properties. However, after being combined with other materials (natural/ synthetic materials) to form composite materials, they basically meet the requirements of hard tissue regenerative medicine materials. We believe that it is worth being widely promoted in clinical applications in the future. CONCLUSION: Bacterial cellulose-based composites hold great promise for clinical applications in hard tissue engineering. However, there are still several challenges that need to be addressed. Further research is needed to incorporate multiple disciplines and advance biological tissue engineering techniques. By enhancing the adhesion of materials to osteoblasts, providing cell stress stimulation through materials, and introducing controlled release systems into matrix materials, the practical application of bacterial cellulose-based composites in clinical settings will become more feasible in the near future.

Short Low Concentration Cisplatin Treatment Leads to an Epithelial Mesenchymal Transition-like Response in DU145 Prostate Cancer Cells

Liu, Yi-Qing,Zhang, Guo-An,Zhang, Bing-Chang,Wang, Yong,Liu, Zheng,Jiao, Yu-Lian,Liu, Ning,Zhao, Yue-Ran Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.3

Background: Prostate cancer is one of the main causes of cancer death, and drug resistance is the leading reason for therapy failure. However, how this occurs is largely unknown. We therrfore aimed to study the response of DU145 cells to cisplatin. Materials and Methods: Du145 prostate cancer cells were treated with a low dose of cisplatin for 24 h and cell viability and number were determined by MTT assay and trypan blue exclusion assay, respectively. The real time polymerase chain reaction (PCR) was used to assess responses to cisplatin treatment. Results: After 24h $2{\mu}g/ml$ treatment did not result in significant reduction in cell viability or number. However, it led to enhanced cancer cell invasiveness. E-cadherin mRNA was reduced, and vimentin, Snail, Slug, metalloproteinase 9 (MMP9) mRNA expression increased significantly, a feature of epithelial-mesenchymal transition (EMT). Conclusions: Short time low concentration cisplatin treatment leads to elevated invasiveness of DU145 cancer cells and this is possibly due to EMT.