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Flexible unbalanced control with peak current limitation for virtual synchronous generator under voltage sags

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Journal of Modern Power Systems and Clean Energy 2018年第1期6卷 61-72页

作者： Tianwen zheng Laijun CHEN Yan GUO Shengwei mei State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Qinghai Key Lab of Efficient Utilization of Clean Energy New Energy Photovoltaic Industry Research Center Qinghai University

Virtual synchronous generator(VSG)is gridfriendly for integrating distributed generations(DGs)since it can emulate the operation mechanism of traditional synchronous generator(SG).However,the traditional VSG control strategy,which is mainly suitable for balanced voltage conditions,may lead to power oscillations,current unbalance and even overcurrent under unbalanced voltage *** overcome this difficulty,a flexible unbalanced control with peak current limitation for VSG under unbalanced operating conditions is *** on the basic VSG control algorithm,the control strategy integrates two novel control modules,which are current reference generator(CRG)and power reference generator(PRG).The proposed control strategy can flexibly meet different operation demands,which includes current balancing,constant active or reactive *** the injected currents are kept within safety values for a better utilization of the VSG power ***,the experimental platform is *** results demonstrate the validness and effectiveness of the proposed control strategy.

关键词： Virtual synchronous generator Unbalanced control Current reference generator Power reference generator Voltage sags

The Fractal Dimensions of the Level Sets of the Generalized Iterated Brownian Motion

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Acta Mathematicae Applicatae Sinica 2013年第3期29卷 597-602页

作者： Chang-qing TONG zheng-yan lin Jing zheng Institute of applied mathematics Hangzhou Dianzi University Department of Mathematics Zhejiang University

Let{W1（t）, t∈R＋} and {W2（t）, t∈R＋} be two independent Brownian motions with W1（0） = W2（0） = 0. {H （t） = W1（｜W2（t）｜）, t ∈R＋} is called a generalized iterated Brownian motion. In this paper, the Ha... 详细信息

关键词： Hausdorff dimension packing dimension local time generalized iterated Brownian motion

Quantification of flupirtine maleate polymorphs using X-ray powder diffraction

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Chinese Chemical Letters 2016年第11期27卷 1666-1672页

作者： Yu-mei Zhao Zhi-Bing zheng Song Li Laboratory of Computer-Aided Drug Design & Discovery Beijing Institute of Pharmacology and Toxicology Laboratory of Structure Identification Beijing Institute of Pharmacology and Toxicology State Key Laboratory of Toxicology and Medical Countermeasures Beijing Institute of Pharmacology and Toxicology

Flupirtine maleate, a pharmaceutical compound for treating psychotic disease in clinics, has seven polymorphs. Form A, with better crystal stability and bioavailability, has been widely used as the pharmaceutical crystal form. Unfortunately, it is usually found in a polymorphic mixture with form B. In this study, pure crystal forms of A and B were prepared and characterized by X-ray powder diffraction （XRPD）, Fourier transform infrared spectroscopy （FT-IR） and thermal analysis. An XRPD-based method for the quantitative determination of the amount of the flupirtine maleate polymorphs form A and form B was also established through a systematic optimization of instrumental parameters. The results of the analytical methodology validation showed that the XPRD method had a broad quantitative range of 0- 100% （w/w）, good linear relationship, with R2= 0.999, excellent repeatability and precision and low limits of detection （LoD） of 0.15% （w/w） and quantification （LoQ） of 0.5% （w/w）. The results also showed that the single-peak method was not as good as the whole pattern in reducing the influence of the preferred orientation, but this can be compensated for by a systematic optimization of instrumental parameters and validating the analytical methodology to reduce errors and obtain a good, repeatable, sensitive, and accurate method. This XRPD method can be used to analyze mixtures of flupirtine maleate polymorphs （forms A and B） quantitatively and control the quality of the bulk drug.

关键词： Flupirtine maleate X-ray powder diffraction Quantitative analysis of polymorphs Preferred orientation Transmission

Anti-hepatoma Effect of DC2.4 Cells Transfected with Tumor-Associated Antigen Cdc25C In Vitro

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Current Medical Science 2022年第3期42卷 491-497页

作者： Chun-mei LI Yan-fei LI lin TIAN Qi-hui ZHANG Fang-yuan zheng Fa-rong MO School of Basic Medical Science Guangxi Medical UniversityNanning 530021China Laboratory of Hepatobiliary and Pancreatic Surgery Affiliated Hospital of Guilin Medical UniversityGuilin 541001China Guangxi Colleges and Universities Key Laboratory of Human Development and Disease Research Guangxi Medical UniversityNanning 530021China

Objective Cell division cyclin 25 homolog C(Cdc25C)is a tumor-associated antigen candidate gene,and this may be used as an effective target in cancer *** present study aims to evaluate the lysis effect of cytotoxic T lymphocytes(CTLs)induced by dendritic cell line DC2.4 overexpressing Cdc25C,and the feasibility of Cdc25C as a component in hepatoma *** The mouse Cdc25C gene was ligated into a lentiviral vector,and transfected into DC2.4 *** DC2.4 cell phenotype and cytokine secretion were determined by flow cytometry and ELISA,***8^(+)T cells were sorted from the spleens of C57BL/6 mice using a magnetic bead sorting kit obtained from Miltenyi Biotech,Germany,and co-cultured with DC2.4 cells for one week as effector ***,IL-2,granzyme B and perforin were detected in the CTL culture medium by ***,time-resolved fluorescence immunoassay was used to detect the immune killing effect of Cdc25C-specific CTLs on target ***,the effect of blocking MHC-I sites on target cells with a monoclonal anti-MHC-I antibody was *** The results revealed that Cdc25C could be stably overexpressed in DC2.4 cells by LV-Cdc25C ***2.4 cells transfected with LV-Cdc25C secreted more IL-6,IL-12,TNF-αand IFN-γ,and had higher expression levels of CD40,CD86,CCR7 and MHC-II than unaltered DC2.4 *** elevated Cdc25C in dendritic cells also further increased the secretion of IL-2,granzyme B and perforin to elicit Cdc25C-specific CTLs,and induced the higher cytotoxicity in Hepa1-6 cell lines(P<0.05),but this had no effect on the target cells when MHC-I monoclonal antibodies were *** DC2.4 cells transfected with LV-Cdc25C can induce specific CTLs,and result in a strong cellular immune *** dendritic cells that overexpress Cdc25C may be useful for hepatoma immunotherapy.

关键词： dendritic cells cell division cyclin 25 homolog C cytotoxic T lymphocytes hepatocellular carcinoma anti-hepatoma

Synthesis and Crystal Structure of a Three-dimensional (3D) Complex Mn(H_2O)_2(HNic)_2 (HNic=2-Hydroxynicotinic Acid)

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Chinese Journal of Structural Chemistry 2006年第5期25卷 572-576页

作者： LI Yu-mei CHE Yun-Xia zheng Ji-Min Department of Chemistry Nankai University Tianjin 300071 China

The title complex Mn（H2O）2（HNic）2 （C22H12MnN2O8, Mr = 367.18） crystallizes in monoclinic, space group P21/c with a = 7.5735（8）, b = 12.5295（13）, c = 7.6466（8）A.β = 101.2790（10）°, Z = 2, V= 711.59（13） A^3, D, = 1.714 g/cm^3,μ（MoKa） = 0.974 mm^-1, F（000） = 374, R1 （1255 observed reflections （Ⅰ 〉 2σ（Ⅰ）） = 0.0250） and wR2 = 0.0662 （all data）. In this paper, we report the complexation of Mn（Ⅱ） by the bidentate ligand 2-hydroxynicotinic acid （HNic）. In the crystal the Mn（Ⅱ） ion exhibits a deformed octahedron structure. The title complex Mn（H2O）2（HNic）2 has a three-dimensional （3D） network structure extended by hydrogen bonds, which are formed by two typical eight-membered hydrogen-bonded rings.

关键词： complex crystal structure three-dimensional network

Methyl-CpG binding domain(MBD)2/3 specifically recognizes and binds to the genomic mCpG site with a β-sheet in the MBD to affect embryonic development in Bombyx mori

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Insect Science 2023年第6期30卷 1607-1621页

作者： Tong-Yu Fu Shuang-Shun Ji Yu-lin Tian Yi-Guang lin Yu-mei Chen Qi-En Zhong Si-Chun zheng Guan-Feng Xu Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology Guangzhou Key Laboratory of Insect Development Regulation and Application ResearchInstitute of Insect Science and TechnologySchool of Life SciencesSouth China Normal UniversityGuangzhouChina

Methyl-CpG(mCpG)binding domain(MBD)proteins especially bind with methylated DNA,and are involved in many important biological processes;however,the binding mechanism between insect MBD2/3 and mCpG remains *** this study,we identified 2 isoforms of the MBD2/3 gene in Bombyx mori,MBD2/3-S and MBD2/*** analysis of MBD2/3-L,MBD2/3-S,and 7 mutant MBD2/3-L proteins deficient inβ1−β6 orα1 in the MBD showed thatβ2−β3-turns in theβ-sheet of the MBD are necessary for the formation of the MBD2/3–mCpG complex;furthermore,other secondary structures,namely,β4−β6 and anα-helix,play a role in stabilizing theβ-sheet structure to ensure that the MBD is able to bind *** addition,sequence alignment and binding analyses of different insect MBD2/3s indicated that insect MBD2/3s have an intact and conserved MBD that binds to the mCpG of target ***,MBD2/3 RNA interference results showed that MBD2/3-L plays a role in regulating *** embryonic development,similar to that of DNA methylation;however,MBD2/3-S withoutβ4−β6 andα-helix does not alter embryonic *** results suggest that MBD2/3-L recognizes and binds to mCpG through the intactβ-sheet structure in its MBD,thus ensuring silkworm embryonic development.

关键词： embryonic development insects MBD2/3 methyl-CpG binding domain(MBD) β-sheet

How to Deploy Intelligent Reflecting Surfaces in Wireless Network:BS-side,User-side, or Both Sides?

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Journal of Communications and Information Networks 2022年第1期7卷 1-10页

作者： Changsheng You Beixiong zheng Weidong mei Rui Zhang Department of Electronic and Electrical Engineering Southern University of Science and Technology(SUSTech)Shenzhen 518055China Department of Electrical and Computer Engineering National University of SingaporeSingapore 117583Singapore School of Microelectronics South China University of Tech-nologyGuangzhou 511442China

The performance of wireless communication systems is fundamentally constrained by the random and uncontrollable wireless channel. By leveraging the recent advances in digitally-controlled metasurface, intelligent reflecting surface (IRS) has emerged as a promising solution to enhance the wireless network performance by smartly reconfiguring the radio propagation environment. Despite the substantial research on IRS-aided communications, this article addresses the important issue of how to deploy IRSs in a wireless network to achieve its optimum performance. We first compare the two conventional strategies of deploying IRS at the side of base station or users in terms of various communication performance metrics,and then propose a new hybrid IRS deployment strategy by combining their complementary advantages. Moreover,the main challenges in optimizing IRS deployment as well as their promising solutions are discussed. Numerical results are also presented to compare the performance of different IRS deployment strategies and draw useful insights for practical design.

关键词： intelligent reflecting surface(IRS) IRS deployment double-IRS system cooperative beamforming channel estimation

Feature Designed Growth of 3D Flower-like SiO2 Growing on Polyethyleneimine Modified CaCO3 Microparticles

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Chinese Journal of Chemical Physics 2012年第6期25卷 687-690,I0004页

作者： Xin-mei zheng Yan-xing Qi Gong-xuan Lu Lanzhou Institute of Chemical Physics Chinese Academy of Science Lanzhou 730000 China

We report on the ability to create complex 3D flower-like SiO2 in vitro via CaCO3 micropar- icles supported by polyethyleneimine mediated biosilicification under experimentally altered chemical influences. The morphology, structure, composition of the product have been inves- tigated with the X-ray photoelectron spectrum, scanning electron microscope, transmission electron microscope, and energy-dispersive spectroscopy. Tile overall morphologies could be controlled to shift from a characteristic network of flower-like silica sphere to a sheet-like structure by adjusting physical adsorption of different amount of polyethyleneimine onto the surface of the CaCO3 microparticles.

关键词： 3D flower-like SiO2 Polyethyleneimine CaCO3 Biomimetic pattern

Regional Evolution Features and Coordinated Development Strategies for Northeast China

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Chinese Geographical Science 2006年第4期16卷 378-382页

作者： mei lin XU Xiaopo CHEN Mingxiu College of Urban and Environmental Sciences Northeast Normal University Changchun 130024 China College of Humanities and Sciences Northeast Normal University Changchun 130117 China

Northeast China, as the most important production base of agriculture, forestry, and livestock-breeding as well as the old industrial base in the whole country, has been playin a key role in the construction and development of China＇s economy. However, after the policy of reform and open-up was taken in China. the economic development speed and efficiency ofthis area have turned to be evidently lower than those of coastal area and the national average level as well, which is so-called ＇Northeast Phenomenon＇ and ＇Neo-Northeast Phenomenon＇. In terms of those phenomena, this paper firstly reviews the spatial and temporal features of the regional evolution of this area so as to unveil the profound forming causes of ＇Northeast Phenomena＇ and ＇Neo-Northeast Phenomena＇. And then the paper makes a further exploration into the status quo of this region and its forming causes by analyzing its economy gross, industrial structure, product structure, regional eco-categories, etc. At the end of the paper, the authors put forward the basic coordinated development strategies for Northeast China. namely we can revitalize this area by means of adjustment of economic structure, regional coordination, planning urban and rural areas as a whole, institutional innovation, etc.

关键词： regional evolution spatial-temporal feature coordinated development strategy Northeast China