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Search Results: 1 - 10 of 37085 matches for " Qingfeng Yan "
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Optimal Wavelet Packet Division Multiplexing Channel Estimator Using Tugnait Algorithm
Zhong Weizhi,Jing Qingfeng,Guo Yan
Information Technology Journal , 2013,
Abstract: Channel State Information (CSI) which can be obtained by channel estimator, is critical for the performance of Wavelet Packet Division Multiplexing (WPDM) transmission system. Considering the characteristics of WPDM and the multipath channel model, a channel estimation method based on Tugnait algorithm is proposed in this study. Without prior knowledge of the channel state, the proposed method improves the channel estimation precision especially in low Signal to Noise Ratio (SNR) condition. Theoretical analysis and simulation results show that compared with the second-order stationary statistics and Singular Value Decomposition (SVD) based channel estimator, proposed method has better performance especially in low SNR condition.
Growth Kinetics of Monodisperse Polystyrene Microspheres Prepared by Dispersion Polymerization
Fan Li,Chong Geng,Qingfeng Yan
Journal of Polymers , 2013, DOI: 10.1155/2013/754687
Abstract: Dispersion polymerization has been widely applied to the synthesis of monodisperse micron-sized polymer colloidal spheres. Many efforts have been devoted to studying the influence of initial conditions on the size and uniformity of the resultant microspheres, aiming to synthesize micron-size monodisperse colloidal spheres. However, the inner contradiction between the size and the size distribution of colloidal spheres hinders the realization of this goal. In this work, we drew our attention from the initial conditions to the growth stage of dispersion polymerization. We tracked the size evolution of colloidal sphere during the dispersion polymerization, through which we established a kinetic model that described the relationship between the monomer concentration and the reaction time. The model may provide a guideline to prepare large polymer colloidal spheres with good monodispersity by continuous monomer feeding during the growth stage to maintain the concentration of monomer at a constant value in a dispersion polymerization process. 1. Introduction As a new functional macromolecule material, monodisperse polymer microspheres have many applications in environmental conservation, biomedicine, colloid science, electronic information material, and many other areas [1–3] due to their superiority of good sphericity, size tunability, large specific surface area, and excellent absorbability [4–6]. Particularly, monodisperse micron-sized spheres are ideal materials as advanced coatings [7], fillers of chromatographic column [8, 9], standard particles of electron microscope and Coulter particle size testers, and spacers in LCD [10], which has drawn increasing interest to synthesize monodisperse micron-sized spheres [11, 12]. The first report on monodisperse polymer colloidal spheres was the polystyrene spheres prepared by Vanderhoff and Brandford [13]. So far, many synthesis strategies have been developed such as emulsion polymerization, suspension polymerization, dispersion polymerization, and seed swelling polymerization. In view of the demand of micron size and monodispersity, the former two methods are excluded because they cannot meet the two requirements at the same time. Emulsion polymerization can only gain monodisperse colloidal spheres with the size below 1?μm. Suspension polymerization may achieve large microspheres with size ranging from 10?μm to 100?μm while the microspheres possess a bad monodispersity [14]. The latter two methods are suitable for the synthesis of uniform colloidal spheres with micron size. Seed swelling polymerization,
Vitrificational cryopreservation and subsequently fertile plant regeneration from rice (Oryza sativa L.) embryogenic suspension cells
Junhui Wang,Yong Zheng,Qingfeng Yan,Qiusheng Yan,Xueqin Zhang,Chunnong Huang
Chinese Science Bulletin , 1997, DOI: 10.1007/BF02884237
Abstract:
Vitrificational cryopreservation and subsequently fertile plant regeneration from rice (Oryza sativa L.) embryogenic suspension cells

Junhui Wang,Yong Zheng,Qingfeng Yan,Qiusheng Yan,Xueqin Zhang,Chunnong Huang,

科学通报(英文版) , 1997,
Abstract:
Real-Time Air Monitoring of Trichloroethylene and Tetrachloroethylene Using Mobile TAGA Mass Spectrometry  [PDF]
Nicholas S. Karellas, Qingfeng Chen
Journal of Environmental Protection (JEP) , 2013, DOI: 10.4236/jep.2013.48A1012
Abstract:

Trichloroethylene (TCE) is a chlorinated liquid that is commonly used for metal degreasing, household and industrial dry cleaning, and in paints and glues. Tetrachloroethylene, also known as perchloroethylene (PCE), is an excellent solvent for organic materials. PCE is volatile, highly stable, non-flammable and widely used in dry cleaning. A new method has been developed for measuring TCE and PCE in ambient air in real-time. Based upon the chemical fingerprinting and concentration levels, the method was able to isolate the source of the emissions to the responsible facility. Real-time monitoring was accomplished by utilizing a low pressure chemical ionization source (LPCI) interfaced to a tandem mass spectrometer (TAGA). Monitoring the response of specific parent/daughter ion pairs, the TAGA was used to measure concentrations of TCE and PCE. By optimizing various TAGA parameters, detection limits (DL) as low as 0.5 μg/m3 was achieved for TCE and PCE. Unlike methods using cartridge sampling and GC/MS analysis, this new method provides a real time measurement for a wide range of TCE and PCE concentrations. This unique method was applied in 2000 and 2002 to measure TCE emitted from a manufacturer of stainless steel tubing in Eastern Ontario. The maximum half-hour average concentration of TCE measured downwind of the facility was 1300 μg/m3 and the maximum instantaneous level was measured at 115,000 μg/m3. The information collected by the TAGA unit was used by the

Synthesis and optical properties of poly[(4-(benzoxazole-2-yl)phenyl)methyl methacrylate] with 1,8-naphthalimide end group
ZhengNeng Jin,QingFeng Xu,JianMei Lu,Feng Yan,XueWei Xia,LiHua Wang,NaJun Li
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-008-0539-3
Abstract: A series of homopolymers, poly[(4-(benzoxazole-2-yl)phenyl)methyl methacrylate] (NAPH-PMABEs) containing benzoxazole side chain and 1,8-naphthalimide end group, were prepared by atom transfer radical polymerization (ATRP) and end-group modification. The structure of NAPH-PMABE was characterized by GPC, 1H-NMR and UV-vis spectra. The polymer has good solubility in common organic solvents, such as dichloromethane (CH2Cl2), tetrahydrofuran (THF), N,N-dimethylformamide (DMF), chloroform (CHCl3), acetone and toluene. The optical properties of NAPH-PMABE were investigated. Results show that NAPH-PMABE has a composite emission spectrum comprising an ultraviolet component originating from benzoxazole side chains and a green component originating from 1,8-naphthalimide end group in both solution and film. The intensity of the two emission bands can be easily tuned by changing molecular weight.
Effects of Carriers Absorption on Mach-Zehnder Interferometer Electrooptical Modulator in Silicon-on-Insulator
载流子吸收对SOI Mach-Zehnder干涉型电光调制器性能的影响

Yan Qingfeng,Yu Jinzhong,
严清峰
,余金中

半导体学报 , 2002,
Abstract: The effects of carriers absorption on Mach Zehnder interferometer electrooptical modulator based on silicon on insulator (abbreviated as SOI) are analyzed theoretically and some measures to improve device performance are proposed as well.
Design and Fabrication of Ultracompact 3-dB MMI Coupler in Silicon-on-Insulator
一种紧缩型的SOI3- d B多模干涉耦合器(英文)

Yan Qingfeng,Yu Jinzhong,Liu Zhongli,
严清峰
,余金中,刘忠立

半导体学报 , 2003,
Abstract: 采用线锥形结构 ,在 silicon- on- insulator(SOI)材料上设计并实现了一种新的紧缩型 3- d B多模干涉耦合器(MMI) .与普通的矩形结构 3- d B MMI耦合器相比 ,该器件长度减少了 4 0 % .耦合器输出均衡度为 1.3d B,过剩损耗为 2 .5 d B.
Synthesis and optical properties of poly[(4-(benzoxazole-2-yl)phenyl)methyl methacrylate] with 1,8-naphthalimide end group

ZhengNeng Jin,QingFeng Xu,JianMei Lu,Feng Yan,XueWei Xia,LiHua Wang,NaJun Li,

科学通报(英文版) , 2009,
Abstract: A series of homopolymers, poly(4-(benzoxazole-2-yl)phenyl)methyl methacrylate] (NAPH-PMABEs) containing benzoxazole side chain and 1,8-naphthalimide end group, were prepared by atom transfer radical polymerization (ATRP) and end-group modification. The structure of NAPH-PMABE was characterized by GPC, 1H-NMR and UV-vis spectra. The polymer has good solubility in common organic solvents, such as dichloromethane (CH2Cl2), tetrahydrofuran (THF), N,N-dimethylformamide (DMF), chloroform (CHCl3), acetone and toluene. The optical properties of NAPH-PMABE were investigated. Results show that NAPH-PMABE has a composite emission spectrum comprising an ultraviolet component originating from benzoxazole side chains and a green component originating from 1,8-naphthalimide end group in both solution and film. The intensity of the two emission bands can be easily tuned by changing molecular weight. Supported by National Natural Science Foundation of China (Grant Nos. 20476066 and 20571054), Science and Technology Project in Suzhou, China (Grant No. SG0718), and Project of High Technology of Jiangsu Province, China (Grant No. BG2005021)
The Effect of Peritoneal Fluid from Patients with Endometriosis on Mitochondrial Function and Development of Early Mouse Embryos
Jing Shu, Lili Xing, Guolian Ding, Qiong Luo, Xinmei Liu, Qingfeng Yan, Jianzhong Sheng, Hefeng Huang
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0082334
Abstract: Background Peritoneal fluid (PF) from patients with endometriosis can inhibit early embryo development via probable functional changes of embryo mitochondria in the early stage of embryo development. The purpose of this study was to determine the effect of PF from patients with endometriosis on mitochondrial function and development of early mouse embryos. Methodology/Principal Findings PF was collected from patients with infertility and endometriosis, infertility due to tubal factors, and normal control subjects, and the level of NO was measured. Early murine embryos were then cultured with PF from normal control subjects, those with endometriosis, and with human tubal fluid (HTF), respectively. Cleavage and blastulation rates, mitochondrial DNA (mtDNA) copy numbers, adenosine triphosphate (ATP) level, and mitochondrial membrane potential (ΔΨm) of the different groups were compared. The NO level in the PF of patients with endometriosis was significantly greater than in those without endometriosis and control patients. The embryos cultures with PF from patients with endometriosis had a lower cleavage rate and blastulation rate, and higher ATP and ΔΨm level at the 2- and 4-cell stages. No significant difference was found in mtDNA copies among the 3 groups. Conclusions/Significance PF from patients with endometriosis can inhibit early embryo development via probable functional changes of embryo mitochondria in the early stage of embryo development. Understanding the effects of PF on embryo development may assist in developing new methods of treatment for infertility.
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