Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2019 ( 200 )

2018 ( 2225 )

2017 ( 2110 )

2016 ( 2090 )

Custom range...

Search Results: 1 - 10 of 126954 matches for " Zhenkui Li "
All listed articles are free for downloading (OA Articles)
Page 1 /126954
Display every page Item
Abnormal piezoresponse behavior of Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal studied by high vacuum scanning force microscopy
Huarong Zeng,Qingrui Yin,Guorong Li,Haosu Luo,Zhenkui Xu
Chinese Science Bulletin , 2003, DOI: 10.1007/BF03184184
Abstract: The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezo-response behavior related to the screening charges compensation mechanism is observed on the (111) crystal face. The significant piezoresponse degradation behavior with low piezoresponse signal under high vacuum is attributed to the instability of the polarization state due to the insufficient compensation of the intrinsic screening charges for the polarization charges in PMN-30%PT single crystal. In contrast, the remarkable domain contrast of the sample at ambient pressure is owing to the dominant surface screening charges deriving from surface adsorption, which plays an important role in determining the stability of the domain behavior and in achieving the optimal properties.
Sedimentary conditions for good coal reservoir development in the Carboniferous and Permian, Qinshui Basin
Zhenkui Jin,Chunsheng Wang
Chinese Science Bulletin , 2005, DOI: 10.1007/BF03184078
Abstract: In the Carboniferous and Permian of the Qinshui Basin, coal reservoirs are well developed. But different coal reservoirs are obviously different in distribution, thickness, and reservoir performance etc. This paper studies the factors controlling the development and distribution of good coal reservoirs from the viewpoint of sedimentology and sequence stratigraphy. The study shows that good coal reservoirs are mainly formed in marsh environments on tidal flats and delta plains. The coal reservoirs formed on tidal flats are more continuous laterally than those on delta plains. The fluctuation of sea level shows important control over the vertical and lateral distribution of coal reservoirs. Generally speaking, the coal reservoirs formed in the highstand system tracts are more abundant, thicker and more widespread, and thus the highstand system tracts are more favorable to the formation of good coal reservoirs. The coal reservoirs formed in the transgressive system tracts are lower in abundance, thinner and much less widespread, and thus the transgressive system tracts are not favorable to the formation of good coal reservoirs.
Dynamics ofdominant tree seedlings in montane evergreen broadleaved forest following a snow disaster in North Guangdong

OU Yuduan,SU Zhiyao,XIE Dandan,KE Xiandong,LI Zhenkui,

生态学报 , 2011,
Abstract: Effects of a snowstorm on forest disturbance and the canopy changes caused by forest rehabilitation resulted in changes in tree seedling composition.The species and number of tree seedlings vary with the canopy-density dynamics and are embodied in the future species composition and structure of tree layer.With the aim of revealing the seedling regeneration pattern and its response to canopy changes(as indicated by changes in leaf area index \),a 3-year investigation from 2008 to 2010 was undertaken in Cheba...
Soil arthropod diversity following an ice storm in a montane evergreen broadleaved forest in Chebaling National Nature Reserve, China

Yuduan Ou,Zhiyao Su,Zhenkui Li,Fuchun Tong,Zexin Liu,

生物多样性 , 2009,
Abstract: In 2008, an ice storm caused extensive damage to the montane evergreen broadleaved forest in Chebaling National Nature Reserve, Guangdong Province, China. To assess the response of soil arthropod diversity and distribution to a gradient of canopy openness following the ice storm, 17 plots, each 400 m~2, were selected within a 2-ha permanent plot. Canopy openness was estimated with hemispherical photography in each plot. We sampled the litter layer and two soil layers (0-10 cm and 10-20 cm) to measure arthropod diversity and soil properties. We used two-way cluster analysis to group sites based on arthropod abundance in the litter layer. We also utilized canonical correspondence analysis to reveal relationships between soil arthropods in the 0-10 cm layer and four environmental variables, i.e., canopy openness (CO), soil organic matter (SOM), electric conductivity (EC), and natural moisture content (NMC). Results showed that abundance, richness and diversity of arthropod communities decreased with depth. A negative association was found between canopy openness and the number of arthropod groups in the litter layer; some arthropod taxa, such as the Oribatida, Prostigmata and Mesostigmata, were found in a wide range of light conditions, whereas the Hymenoptera, Symphyla, Pseudoscorpiones and Lepidoptera larvae may be photophobic. The distribution of arthropods in the 0-10 cm soil layer was closely related to CO, SOM, EC, and NMC on the first and second canonical axes. Hence, a series of changes in canopy structure and soil factors following the ice storm appeared to have affected the composition and distribution of soil arthropod communities. Findings from the present study also indicated that arthropod communities could serve as indicators to characterize the ecosystems they inhabit, thus being particularly suitable for monitoring forest regeneration and successional dynamics following ice storms.
Spatial Scan Statistics Adjusted for Multiple Clusters
Zhenkui Zhang,Renato Assun??o,Martin Kulldorff
Journal of Probability and Statistics , 2010, DOI: 10.1155/2010/642379
Abstract: The spatial scan statistic is one of the main epidemiological tools to test for the presence of disease clusters in a geographical region. While the statistical significance of the most likely cluster is correctly assessed using the model assumptions, secondary clusters tend to have conservatively high P-values. In this paper, we propose a sequential version of the spatial scan statistic to adjust for the presence of other clusters in the study region. The procedure removes the effect due to the more likely clusters on less significant clusters by sequential deletion of the previously detected clusters. Using the Northeastern United States geography and population in a simulation study, we calculated the type I error probability and the power of this sequential test under different alternative models concerning the locations and sizes of the true clusters. The results show that the type I error probability of our method is close to the nominal level and that for secondary clusters its power is higher than the standard unadjusted scan statistic. 1. Introduction Spatial and space-time scan statistics [1] have become some of the main tools in geographic disease surveillance to test the null hypothesis that geographical data are randomly distributed against a localized cluster alternative. Examples include its use for breast cancer mortality in Texas [2], giardiasis parasites in Canada [3], pneumonia in Brazil [4], lymphatic filariasis in Haiti [5], and syndromic surveillance in New York City [6]. The standard spatial scan statistic is a maximum likelihood ratio test statistic based on a circular window of variable size scanning the geographical area under surveillance. Under the null hypothesis, there are no disease clusters. Under the alternative hypothesis, there is a single geographical cluster in the region of unknown location and size. A detailed description is presented in Section 2. When the test significantly detects one cluster, it is of interest to know if there are additional clusters present in the region. The test procedure provides evidence for the presence of these so-called secondary clusters, spatial clusters not overlapping with the most likely cluster but with significantly large likelihood ratio. These secondary clusters have an associated -value but they are calculated ignoring the existence of the most likely cluster that had already been detected. One consequence of this is that these are conservative -values [1] leading to a loss in statistical power. The -values for testing for a second cluster could alternatively be calculated
Nano-embossing technology on ferroelectric thin film Pb(Zr0.3,Ti0.7)O3 for multi-bit storage application
Shen Zhenkui,Chen Zhihui,Lu Qian,Qiu Zhijun
Nanoscale Research Letters , 2011,
Abstract: In this work, we apply nano-embossing technique to form a stagger structure in ferroelectric lead zirconate titanate [Pb(Zr0.3, Ti0.7)O3 (PZT)] films and investigate the ferroelectric and electrical characterizations of the embossed and un-embossed regions, respectively, of the same films by using piezoresponse force microscopy (PFM) and Radiant Technologies Precision Material Analyzer. Attributed to the different layer thickness of the patterned ferroelectric thin film, two distinctive coercive voltages have been obtained, thereby, allowing for a single ferroelectric memory cell to contain more than one bit of data.
K-RAS Gene Mutations in Patients with Non-small Cell Lung Cancer
Yang ZHANG,Zhenkui PAN,Xing ZHANG,Fei XU
Chinese Journal of Lung Cancer , 2010,
Abstract: Background and objective Recent studies indicated that Non-small cell lung cancer (NSCLC) patients with mutant K-RAS failed to benefit from adjuvant chemotherapy, and the cancer did not respond to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). These findings indicated that K-RAS gene status can be a biomarker to predict the sensitivity of EGFR TKIs. The aim of this study is to analyze K-RAS gene mutations with NSCLC patients in Cancer Center of Sun Yet-sen University. Methods 52 fresh frozen tumor tissues were collected and K-RAS genes were amplified by PCR. Then PCR amplification fragments were sequenced and analyzed. Results Somatic mutations in the codon 12 of K-RAS gene in tumors were identified from 2 of 52 (3.8%) patients. There were no relationships among K-RAS gene mutations and gender, pathology, smoking, differentiation and stage. Conclusion The frequency of K-RAS gene mutations with NSCLC in our center is very low and is similar to that in Asia patients, and is lower than that in Caucasian population.
Identification of Reference Genes for Normalizing Quantitative Real-Time PCR in Urechis unicinctus Identification of Reference Genes for Normalizing Quantitative Real-Time PCR in Urechis unicinctus
BAI Yajiao,ZHOU Di,WEI Maokai,XIE Yueyang,GAO Beibei,QIN Zhenkui,ZHANG Zhifeng
- , 2018,
Abstract: The reverse transcription quantitative real-time PCR(RT-qPCR) has become one of the most important techniques of studying gene expression. A set of valid reference genes are essential for the accurate normalization of data. In this study, five candidate genes were analyzed with ge Norm, Norm Finder, Best Keeper and ?Ct methods to identify the genes stably expressed in echiuran Urechis unicinctus, an important commercial marine benthic worm, under abiotic(sulfide stress) and normal(adult tissues, embryos and larvae at different development stages) conditions. The comprehensive results indicated that the expression of TBP was the most stable at sulfide stress and in developmental process, while the expression of EF-1-α was the most stable at sulfide stress and in various tissues. TBP and EF-1-α were recommended as a suitable reference gene combination to accurately normalize the expression of target genes at sulfide stress; and EF-1-α, TBP and TUB were considered as a potential reference gene combination for normalizing the expression of target genes in different tissues. No suitable gene combination was obtained among these five candidate genes for normalizing the expression of target genes for developmental process of U. unicinctus. Our results provided a valuable support for quantifying gene expression using RT-qPCR in U. unicinctus
Characteristics of Oolites and Their Dolomitization Mechanism of the Cambrian Zhangxia Formation at Xiaweidian Outcrop in Beijing

GUO Qiheng
,JIN Zhenkui,ZHU Xiaoer,WANG Jinyi

- , 2018,
Abstract: 摘要: 北京下苇甸剖面张夏组作为华北寒武系的标准剖面之一,鲜有人对其中的鲕粒类型及其成岩作用进行细致研究。在充分调研前人研究的基础上,通过野外观察、实测,并结合室内薄片鉴定、XRD测试等技术,对下苇甸剖面张夏组的鲕粒类型进行总结,并对鲕粒白云化机制进行分析。结果显示:(1)下苇甸张夏组鲕粒类型主要为放射鲕、同心放射鲕及单晶鲕/多晶鲕,还有少量同心鲕、复鲕及藻鲕;(2)鲕粒发生白云化,填隙物未见白云化,且放射圈层白云化程度高于同心圈层,并且放射圈层白云石颗粒围绕核心呈放射状分布,同心圈层围绕核心呈同心状分布;(3)鲕粒内部白云石颗粒多为中细晶,自形-半自形,回流渗透白云化是造成鲕粒白云化的主要成因,因此造成亮晶鲕粒石灰岩白云化程度高于灰泥鲕粒石灰岩。
Abstract: The Xiaweidian outcrop in Beijing is a typical Cambrian stratigraphic profile in North China. Previous studies focused mainly on the depositional environment of the Zhangxia Formation, whereas the oolitic types and their diagenesis of the formation are poorly understood. In this paper, field geological and microscopic petrographic observations and XRD analysis were conducted to identify the oolitic types and elucidate the mechanism of oolitic dolomitization.It comes to a conclusion as follows: (1) Major oolitic types include radial ooids, concentricradial ooids and monocrystalline/polycrystalline ooids, and minor concentric ooids, compound ooids and algae ooids. (2) Oolites are dolomitized whereas the interstitials are not, and the degree of dolomitization in the radial layer is higher than that in the concentric layer.Dolomite particles in the radial layer are radially distributed around the core, and the concentric rings occur around the core. (3) Dolomite grains in the oolites are mostly mesocrystalline or finegrained, euhedral to subhedral, and returning infiltration of dolomitization was likely the main cause of the oolitic dolomitization, which resulted in a higher degree of dolomitization of the luminescent oolite limestone than the stucco oolite limestone
Diagenesis and Porosity Evolution of Carboniferous KTⅡ Carbonates in Zanazor, Kazakhstan

伊硕,黄文辉,金振奎 ,高白水,朱小二
YI Shuo
, HUANG Wenhui,JIN Zhenkui,GAO Baishui,ZHU Xiaoer

- , 2017,
Abstract: 摘要: 石炭系KTⅡ碳酸盐岩层是扎纳若尔油田的主要勘探开发层之一,研究成岩作用对储层孔隙演化的影响具有重要意义。在薄片观察及碳氧同位素、阴极发光、流体包裹体等地化分析的基础之上,阐明了研究区KTⅡ碳酸盐岩层的主要成岩作用类型、成岩序列及其对孔隙演化的影响,并得出如下结论:(1)对储集物性有明显影响的成岩作用主要包括压实-压溶作用、胶结作用、溶蚀作用及破裂作用等;(2)划分出滩相亮晶颗粒灰岩和潮坪相灰泥石灰岩两类成岩演化模式及孔隙演化模式,前者可细分为亮晶有孔虫石灰岩和亮晶砂屑鲕粒石灰岩成岩及孔隙演化模式两种亚类;(3)成岩作用是储层储集物性的主控因素之一,岩石类型(受沉积微环境的控制)的差异决定着不同早期成岩响应,进而影响后期成岩改造,并控制着差异性储层的形成。因此,在沉积基础之上的成岩改造对储层储集性能差异性分布具有同样重要的控制作用。
Abstract: The carbonates of KTⅡ layer in Carboniferous are the main layer of exploration and development of Zanazor Oilfield. The research of diagenesis is of great significance to influence the pore evolution of reservoir. Based on the observation of thin sections, and geochemical analysis on carbon oxygen isotope, cathodoluminescence, and fluid inclusion, we expound the main diagenesis types, the diagenetic sequence and its influence on pore evolution of KTⅡ layer in the study area, and draw the following conclusions: (1) The diageneses which have obvious effects on reservoir quality include compaction, pressolution, cementation, dissolution and cataclasis, etc.; (2) There are two kinds of diagenetic evolution pattern and pore evolution model: the sparry grain limestone in shoal and mud limestone in tidal flat. Furthermore, the former can be subdivided into sparry foraminiferafusulinida limestone and sparry arene-oolitic limestone; (3) The diagenesis is one of the main controlling factors of reservoir quality. The difference of rock types (controlled by sedimentary micro environment) determines the differentia in early diagenetic response, which affects the late diagenetic reconstruction, and controls the formation of differential reservoir. Therefore, in terms of the control on the differential distribution of reservoir performance, the diagenetic alteration which is on the basis of sedimentary and depositional conditions are of equal importance
Page 1 /126954
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.