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Search Results: 1 - 10 of 80978 matches for " Limei Liu "
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The λ-Characteristics of the Ring Laser Based on Non-Uniform SOA  [PDF]
Zhi Wang, Limei Zhang, Yingfeng Liu, Lanlan Liu
Journal of Computer and Communications (JCC) , 2013, DOI: 10.4236/jcc.2013.17013
Abstract: Semiconductor optical amplifier-based ring cavity laser (SOA-RL), which has been widely used in optical communications, optical fiber sensing, and biophotonics fields, can be tuned at an ultra high speed up to Mega Hertz over 100 nm bandwidth range with high SNR and flatness output. A steady-state model and segmentation algorithms are employed to investigate the gain spectra of four kinds of non-uniform SOA and the lasing wavelength of the SOA-RL. It shows that the dependence of the lasing wavelength on the average width is stronger when the light propagates from narrower to wider end than conversely, and there are some particular structures to show ultra high stability lasing wavelength. It is supposed that the main reason could be the carrier density distribution along the propagation.
Description of the FDML Laser with Quasi-steady State Model of the SOA  [PDF]
Zhi Wang, Limei Zhang, Lanlan Liu, Zhenchao Sun, Yingfeng Liu, Fu Wang
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.32B015

Experiments and simulations demonstrate that an SOA-based ring cavity can operate as a tunable laser, wavelength- swept laser or Fourier-domain-mode-locking laser according to the relation between the roundtrip frequency and the sweeping frequency of the filter.

Relationship between Cr-Al Interaction and the Performance of Cr-Al2O3 Catalysts for Isobutane Dehydrogenation  [PDF]
Deren Fang, Jinbo Zhao, Shang Liu, Limei Zhang, Wanzhong Ren, Huimin Zhang
Modern Research in Catalysis (MRC) , 2015, DOI: 10.4236/mrc.2015.42007
Abstract: A series of catalysts were prepared using the kneading molding method and the impregnation method as well as the dry mix method by using different raw materials. By using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR) techniques, we studied the relationship between the catalyst performance and the Cr-Al interaction in the catalytic dehydrogenation of isobutane. The results demonstrated that the Cr-Al interaction in the catalyst had a direct influence on the catalytic activity and the selectivity of isobutene. The catalysts prepared using the kneading molding method had higher catalytic activity and isobutene selectivity than those prepared using the dry mix method. By comparison, XRD, XPS, and TPR results showed that the greater the Cr-Al interaction in the catalyst was, the higher the catalytic activity was. Here, we propose a mechanism of isobutane dehydrogenation.
Microstructure and wear resistance of PTA clad Cr7C3/γ-Fe ceramal composite coating
LIU Junbo,WANG Limei,HUANG Jihua
自然科学进展 , 2006,
Abstract: A wear resistant Cr7C3/γ-Fe ceramal composite coating was fabricated on substrate of the hardening and tempering C degree steel by PTA (plasma transferred arc) cladding with (wt%) Fe-25Cr-7C elemental powder blends. Microstructure of the coating was characterized by OM, SEM, XRD and EDS. Wear resistance of the coating was tested under dry sliding wear condition at room temperature. The results indicate that the PTA clad ceramal composite coating has a rapidly solidified fine microstructure consisting of Cr7C3 primary particles uniformly distributed in the γ-Fe matrix and is metallurgically bonded to the C degree steel substrate. The PTA clad Cr7C3/γ-Fe ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test conditions. The excellent wear resistance of the Cr7C3/γ-Fe ceramal composite coating is attributed to the coating’s high hardness, strong covalent atomic bonding and refined microstructure.
Characteristics and neural-like differentiation of mesenchymal stem cells derived from foetal porcine bone marrow
Ying Liu,Limei Liu,Xin Ma,Yupeng Yin
Bioscience Reports , 2013, DOI: 10.1042/bsr20120023
Abstract: MSCs (mesenchymal stem cells) are a stem cell source that can be easily obtained from bone marrow. Despite the increasing importance of the pig as a large animal model, little is known about foetal pMSCs (porcine MSCs). In this study, we observed the gene expression of pluripotent markers in foetal pMSCs and the capacity of pMSCs to differentiate into adipocytes, osteocytes and neural-like cells using quantitative RT–PCR (reverse transcription–PCR), normal histological staining and immunohistochemistry. Foetal pMSCs have either a spindle or a flattened shape, and flow cytometry revealed the expression of the MSC-related proteins CD44 and CD105 (endoglin) but not CD34 and CD45. pMSCs express pluripotent markers such as Oct4 (octamer-binding transcription factor 4) and Nanog at the protein and mRNA levels. qRT-PCR (quantitative real-time PCR) analyses revealed that pMSCs expressed nestin [for NSCs (neural stem cells)]. Immunocytochemical and RT–PCR data showed that 29% and 23% of pMSCs expressed MAP2 (microtubule-associated protein 2) for neurons and β-tubulin III (Tuj1) for immature neurons, respectively, after induction of neural differentiation. These findings demonstrate the plasticity of pMSCs and their potential for use in cellular replacement therapy for neural diseases.
Study on Fingerprint Spectrum of Leaves and Stems of Viola yedoensis by SmartiTR

Luo Limei,Liu Xiangping,

世界科学技术-中医药现代化 , 2012,
Abstract: This study was aimed to establish the IR fingerprint spectrum of leaves and stems of Viola yedoensis Makino. Leaves and stems were analyzed by intelligent single attenuated total reflection. Seven different varieties of V. yedoensis were analyzed by principal component analysis. And the non-destructive rapid identification can be carried out. It was concluded that the SmartiTR fingerprint spectrum can be used as an identification method of leaves and stems of V. yedoensis.
Entrapment of Inclusions in Diamond Crystals Grown from Fe-Ni-C System
Entrapment of Inclusions in Diamond Crystals Grown from Fe—Ni—C System

Yuxian LIU,Limei XIAO,Longwei YIN,

材料科学技术学报 , 2002,
Abstract: Diamond single crystals grown from Fe-Ni-C system at high temperature-high pressure (HPHT) usually contain inclusions related to the metallic catalyst. During the diamond growth, the metallic inclusions are trapped by the growth front or are formed through reaction between the contaminants trapped in the diamond. In the present paper, the metallic inclusions related to the catalyst were systematically examined by transmission electron microscopy (TEM). The chemical composition and crystal structure of the metallic inclusions were for the first time determined by selected area electron diffraction pattern (SADP) combined with energy dispersive X-ray spectrometry (EDS). It is shown that the inclusions are mainly composed of orthorhombic FeSi2, fcc (FeNi)23C6, and orthorhombic Fe3C, hexagonal Ni3C.
The Environmental Influence of Tourism on Vegetation in Typical Grassland Areas

LIU Limei,LV Jun,
,吕 君

资源科学 , 2009,
Abstract: 本文以内蒙古自治区四子王旗格根塔拉草原旅游中心为研究区,利用生态学中的密度、盖度、频度、重要值以及采用辛普森多样性指数(Simpson’s diversity index)和香农-威纳指数(Shannon-Weiner index)来分析植物样方的植物种类多样性,结合样方的种类组成和盖度等来探究旅游发展对草原植被的环境影响。通过旅游活动对植物种类的影响、对植物种类多样性的影响、对群落结构的影响、对群落外貌的影响分析,得知旅游活动对植被生态安全干扰的破坏在Ⅲ级以上,群落由克氏针茅占优势转变为以冷蒿为主的草原变型,今后必须加强对草原旅游开发与规划理论以及开发模式的研究。
The Value and Effect of the Tourism Industry’s Priority to Restoration and Rebuilding after Catastrophe
Hejiang Shen,Limei Yuan,Yana Liu,Ying Zhang
International Journal of Business and Management , 2009, DOI: 10.5539/ijbm.v4n8p93
Abstract: The thing about the tourism industry’s restoration and rebuilding after catastrophe has a great influence not only on sustainable development of tourism destination, as the tourism destination is concerned highly by public, but also on the social judgment on the accessibility of stricken area, except those, it even influences the works which are the restoration and rebuilding of the stricken area’s various constructions and the important criterion, depending on that, the international community determines if the stricken area should be rebuilt completely. So, the restoration and rebuilding of stricken area after catastrophe has the great value and profound meaning on reducing the tourists’ fear and worries about the area happened crisis, and exerting the tourism industry’s effect on all-round social development, which spurs the relevant industries to be reconverted as before.
Vitamin D Receptor Gene Polymorphisms on the Risk of Tuberculosis, a Meta-Analysis of 29 Case-Control Studies
Cheng Chen, Qiao Liu, Limei Zhu, Haitao Yang, Wei Lu
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0083843
Abstract: The relationship of four potentially functional polymorphisms of the vitamin D receptor (VDR) gene, ApaI, BsmI, FokI and TaqI , with tuberculosis susceptibility were considered. The aim of this meta-analysis was to explore the association between the four polymorphisms and tuberculosis risk in different ethnic backgrounds. Eligible case-control studies that were catalogued before April 1st 2013 were enrolled, and the heterogeneity between the studies was evaluated using a χ2 based Q-test. Fixed and random effect models were built to evaluate the association of the four polymorphisms with the risk of tuberculosis, and the association between the four polymorphisms and tuberculosis was expressed as the odds ratio (OR) and 95% confidence interval (CI). Finally, twenty nine qualified studies were enrolled for this meta-analysis that included 6179 tuberculosis cases and 6585 healthy controls. The variant homozygote genotype of the FokI polymorphism was associated with a significantly increased risk of tuberculosis when compared to the heterozygote and wild type homozygote genotypes in the Chinese population (ff vs. Ff+FF: ORrecessive=1.97, 95%CI: 1.32-2.93, Pbonferroni=0.0032; heterogeneity test: χ2=0.24, P=0.62). For European subjects, the homozygote and heterozygote genotypes of the BsmI polymorphism were associated with a significantly decreased risk of tuberculosis when compared to the wild type homozygote (bb+Bb vs. BB: ORdominant=0.41, 95%CI, 0.22-0.76, Pbonferroni=0.02; heterogeneity test: χ2=2.59, P=0.11). Based on the above results, we conclude that variants of the VDR gene that are homozygous for the FokI polymorphism might be more susceptible to tuberculosis in Chinese. Furthermore, larger sample studies are warranted to confirm the protective effects of BsmI variants on tuberculosis in the Europeans.
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