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Search Results: 1 - 10 of 59093 matches for " Yunfei Yang "
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Thermal Effect on the Distribution of Regular Sterane and Geological Significance  [PDF]
Yunfei Yang, Min Zhang, Julin Chen, Xiaohui Chen
Open Journal of Yangtze Oil and Gas (OJOGas) , 2017, DOI: 10.4236/ojogas.2017.24020
Abstract: In order to study thermal effect on distribution characteristics of regular sterane in humic coals, a suit of 25 coals derived from Kuqa Depression in Tarim Basin and Ordos Basin are studied to investigate the distribution of regular sterane in different maturity, which mainly discusses the thermal effect. The results show that the C27ααα/C29ααα regular sterane ratio has a linear relationship with Ro (tmax) and aromatic hydrocarbon maturity parameters in the coals from mature to high-mature stage. It suggests that the distribution of the C27, C29regular steranes will fail to reflect original source input in high evolutionary stage. On the basis of thermal simulation experiment results, it further proves that the distribution patterns result from the demethylation effect of C29 sterane in the mature to high mature evolution stage and the C27ααα/C29ααα regular sterane increases with increasing maturity. The breakage of C-C key in branched chain from C27, C29 regular steranes to make C27ααα/C29ααα regular sterane ratio invariance at high and over mature stage. Therefore, the ratio can be used to distinguish the maturity in high and over mature stage.
Edaphic factors determining variation of two ecotypes of Leymus chinensis in North China
ZHOU Chan,YANG Yunfei,
ZHOU Chan
,YANG Yunfei

自然科学进展 , 2006,
Abstract: To identify ecotypic variation of L. chinensis, the physiological characteristics and environmental factors were measured and assessed for grey-green and yellow-green ecotypes of L. chinensis grown in the salt-alkalized and aeolian sandy soils. Although both ecotypes presented a similar salt-alkaline tolerance under the experimental conditions, they differed in several aspects. The L. chinensis grown in the aeolian sandy soils had higher water potential and chlorophyll content and lower proline content in their leaves than those grown in the salt-alkalized habitat, and the grey-green ecotype of L. chinensis in both types of soils had higher water potential, chlorophyll and proline contents than the yellow-green ecotype. Besides, grey-green ecotypes had higher salt-alkaline tolerance than the yellow-green ecotype. The stepwise regression analysis showed that soil conductance and pH value were the main ecological factors affecting the physiology of L. chinensis. From the natural distribution of the two ecotypes, we considered that salt-alkaline in the soils is the leading factor in determining ecotypic variation of L. chinensis. The two ecotypes were first named grey-green and yellow-green ecotypes respectively.
The Characteristics and Causes of Dividend Policy of China’s Listed Companies—A Case Study Based on UF Network  [PDF]
Yunfei Li
Modern Economy (ME) , 2018, DOI: 10.4236/me.2018.911114
Abstract: Dividend policy is an important part of the company’s financial management, which is directly related to the company’s survival and development. Although higher incentives can increase shareholders’ confidence in the company’s development and obtain considerable profits, it will reduce the company’s retained earnings, affect the company’s further development, and the company’s expected growth rate will fall; lower dividends will bring the company more development funds, but deviate from the company’s shareholders’ wishes and damage the company’s image. A company’s dividend policy affects the company’s financial structure and investment financing activities, reflecting the company’s direct return on shareholder investment. This article starts from the “UF network”, analyzes its dividend policy, and tries to explain the reasons for this feature.
ANALYSIS ON THE FLUX OF SOIL SEED BANK AND THE SEEDLING MORTALITY IN THE COMMUNITIES OF TWO SPECIES OF SU AEDA IN THE SONGNEN PLAIN IN CHINA
松嫩平原两种碱蓬群落土壤种子库通量及幼苗死亡的分析

Yang Yunfei,
杨允菲

生态学报 , 1995,
Abstract: uaeda corniculata and S. heteroptera which are two more alkali-resisting and annotinousspecies of herb in Chenopodieceae growing in the alkalized meadow of the Songnen Plain inNortheast China were examined by random sampling on a periodical basis from their twofixed mono-dominant communities to investigate the changes in the storages of their viableseeds in soils and the dynamics of their populations . The results show that the viable seeds insolis have the greatest standing storage immediately before in...
COMPARISON OF AGE STRUCTURES OF THE TILLERS IN THE Leymus chinensis POPULATION,A CLONAL GRASS SPECIES UNDER DIFFERENT ECOLOGICAL CONDITIONS
不同生态条件下羊草无性系种群分蘖植株年龄结构的比较研究

Yang Yunfei,
杨允菲

生态学报 , 1998,
Abstract: 在4次取样的平均年龄谱中,1龄级分蘖植株的数量比重是割草样本-休闲样本-放牧样地,2,3,4龄级分蘖植株为放牧样本-休闲样本-割草样地,放牧干扰可以促进各龄分节的再生存活。但是对根茎形成分蘖植株却起到了一定的削弱作用。割草干扰可以促进翌年根茎形成分蘖植株,从而使各龄级分蘖节的再生存活量减少。
THE STUDY ON SEED DISPERSAL OF PUCCINELLIA TENUIFLORA ON ALKAL1ZATION MEADOW IN THE SONGNEN PLAIN OF CHINA
松嫩平原碱化草甸星星草种子散布的研究

Yang Yunfei,
杨允菲

生态学报 , 1990,
Abstract:
A STUDY ON SEED PRODUCTION OF ANEUROLEPIDIUM CHINENSE POPULATION IN DIFFERENT ECOLOGICAL CONDITIONS
不同生态条件下羊草种群种子生产的探讨

Yang Yunfei,
杨允菲

生态学报 , 1988,
Abstract: According to the field-investigation at the fixed position during 1982 to 1985, the quantitutive analysis on three problems of the seed production of Aneurolepid-ium chinense population i.e. the relationships between their condition of ecolgical environment and the percentage of earbearing tiller, characters of spike organ or 1000-seed weigh were dicussed in this paper. It shows that grazing decreased the percentage of earbearing tiller but improved the process of dry matter production of the seed, and afte...
An Emulsion Based Microarray Method to Detect the Toxin Genes of Toxin-Producing Organisms
Ying Wang,Jiafeng Lu,Qi Yang,Yunfei Bai,Qinyu Ge
Molecules , 2011, DOI: 10.3390/molecules16097365
Abstract: Toxins produced by bacteria and fungi are one of the most important factors which may cause food contamination. The study of detection methods with high sensitivity and throughput is significant for the protection of food safety. In the present study, we coupled microarray with emulsion PCR and developed a high throughput detection method. Thirteen different gene sites which encode the common toxins of several bacteria and fungi were assayed in parallel in positive and maize samples. Conventional PCR assays were carried out for comparison. The results showed that the developed microarray method had high specificity and sensitivity. Two zearalenone-related genes were investigated in one of the ten maize samples obtained with this present method. The results indicated that the emulsion based microarray detection method was developed successfully and suggested its potential application in multiple gene site detection.
Industrial-Scale Preparation of Akebia Saponin D by a Two-Step Macroporous Resin Column Separation
Yue Wu,De Ji,Yunfei Liu,Chunfeng Zhang,Zhonglin Yang
Molecules , 2012, DOI: 10.3390/molecules17077798
Abstract: A simple and efficient procedure for the industrial preparation of akebia saponin D, one of the bioactive compounds commonly found in the well-known Chinese Medicinal herb Dipsaci Radix, was developed. First, HPD-722 was selected from among 10 kinds of macroporous absorption resins. Following this step, the purity of akebia saponin D was increased about 10 times from 6.27% to 59.41%. In order to achieve a higher purity, ADS-7 was chosen from among five kinds of macroporous absorption resins, and the purity of akebia saponin D was increased from 59.41% to 95.05%. The result indicated HPD-722 and ADS-7 were the most suitable resins to purify akebia saponin D from Dipsaci Radix. Under these conditions, large-scale preparation of akebia saponin D was carried out successfully. The preparation method is simple, efficient, and has been demonstrated to be effective for large scale preparations of akebia saponin D from Dipsaci Radix.
Age structures of modules on Leymus chinensis clonal populations in the process of restoration succession after the flooded meadow in the Songnen Plains, China
松嫩平原水淹恢复演替过程中羊草无性系种群构件的年龄结构

LI Haiyan,YANG Yunfei,
李海燕
,杨允菲

生态学报 , 2004,
Abstract: Research on age structure is an important part of population ecology. Dynamics of population and community can be predicted based on age structure. By using the method of dividing age classes of perennial rhizome grass according to vegetative propagation generations of tiller nodes, the age structures of Leymus chinensis clonal population modules were studied in the process of restoration succession of the flooded L. chinensis meadow,and the restoration process of the flooded succession was forecasted in th...
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