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Search Results: 1 - 10 of 9632 matches for " ZENG Dehui "
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Fault Ride-Through Capability Enhancement of PV System with Voltage Support Control Strategy  [PDF]
Dehui Zeng, Gang Wang, Guoqing Pan, Haifeng Li
Open Journal of Applied Sciences (OJAppS) , 2013, DOI: 10.4236/ojapps.2013.32B006
Abstract: With continuously increasing of photovoltaic (PV) plant’s penetration, it has become a critical issue to improve the fault ride-through capability of PV plant. This paper refers to the German grid code, and the PV system is controlled to keep grid connected, as well as inject reactive current to grid when fault occurs. The mathematical model of PV system is established and the fault characteristic is studied with respect to the control strategy. By analyzing the effect of reactive power supplied by the PV system to the point of common coupling (PCC) voltage, this paper proposes an adaptive voltage support control strategy to enhance the fault ride-through capability of PV system. The control strategy fully utilizes the PV system’s capability of voltage support and takes the safety of equipment into account as well. At last, the proposed control strategy is verified by simulation.
Effects of nitrogen fertilization on biomass partitioning and leaf physiological characteristics of Pinus sylvestris var. mongolica seedlings on sandy soil

DENG Bin,ZENG Dehui,

生态学杂志 , 2006,
Abstract: 设计5个氮肥(NH4NO3)添加水平(g.m-2):0(CK)、10.0(N1)、20.0(N2)、40.0(N3)和50.0(N4),研究了沙地樟子松幼苗生长与生理学指标的季节变化。结果表明,添加氮肥促进了幼苗的高生长、相对生长速率、单株总生物量的增加,对叶片相对含水量没有影响;N4水平促进了叶片脯氨酸含量的积累。单叶重、株高、地径、叶重比、叶绿素(a b)、叶绿素a以及叶绿素b含量等均在N3水平下达到最大值。在1个生长季的观测中,添加氮肥主要促进了樟子松幼苗在5~7月份的生长,其中N3水平对樟子松幼苗生长发育的促进作用最大。
Eco-value level classification and ecosystem management strategy of broad-leaved Korean pine forest in Changbai Mountain

ZHENG Jingming,JIANG Fengqi,ZENG Dehui,

应用生态学报 , 2003,
Abstract: To realize the sustainable management of forest ecosystems, we should explicitly clarify the types and differences of the ecosystem services provided by different ecosystems under different conditions, with rethinking about the value of forest ecosystems; then solid management strategies and measurements will be enacted and applied to achieve the objects. The broad-leaved Korean pine forest (BLKPF) in Changbai Mountain is a unique and important forest type in China, owing to its many important ecosystem services such as preventing soil erosion, regulating climates, nutrient cycling, providing wood and non-timber forest products, etc. This paper is a preliminary study on the management strategy of BLKPF on the basis of analyzing the characters of the ecosystems and the relative importance of services they provided in this region. Based on the latest research of ecosystem services of BLKPF in Changbai Mountain, an idea of eco-value level (EVL) was introduced, and accordingly, management strategies were summarized by adopting the advanced theories in ecosystem management science and by analyzing field survey data. EVL means the relative amount of the value of ecosystem services provided by certain ecosystem, which can indicate the difference between services in given objects. The EVL classification of BLKPF implies the relative amount of the eco-value of different ecosystems including virgin forest, secondary forest, forest with human disturbance, and man-made forest in the clear-cutting sites. Analytical Hierarchical Processing method was used to formulate the equation for EVL index. Eight factors, namely, slope, soil depth, stability of soil maternal material, coverage of above-ground canopy, species diversity, regeneration rate of the stand, life span of dominant tree species, and intensity of human disturbance were chosen to build the formula. These factors belonged to three aspects affecting ecosystem services including the physical environment, community, and disturbance regime, and their selection and scaling were based on the previous studies on the BLKPF. The equation of EVL index (EI) was expressed as: EI = 0.542A1 + 0.171A2 + 0.072A3 + 0.067B1 + 0.043B2 + 0.014B3 + 0.010B4 + 0.081C1. According to the range of EI, ecosystems were classified into three types: low EVL type with EI from 1.000 to 1.874, medium EVL type with EI 1.874-2.749, and high EVL type with EI 2.749-3.623. Typical plots were surveyed and scaled with EI, and the predominant characters of each EVL type were summarized. Most forests of high EVL type were those in sites at high risk of soil erosion and hard to recover after disrupted. Forests of medium EVL type were those with worse community structure and composition, and were disturbed by human activities in relative steep sites. Forest of low EVL type were those in plane site with serious disruption or some young man-made stands. Based on the analyses of the characters of these three types, different management strategies
Decline of protective forest and its prevention strategies from viewpoint of restoration ecology: Taking Pinus sylvestris var. mongolica plantation in Zhanggutai as an example

JIANG Fengqi,ZENG Dehui,YU Zhanyuan,

应用生态学报 , 2006,
Abstract: Aimed at the decline of protective forest in China, and applying the key principles of restoration ecology, such as ecological succession, disturbance, and population density, etc. , this paper assessed the rationality of designing elements of protective forest in decision-making level, and analyzed its relationships with the decline of the forest, taking Pinus sylvestris var. mongolica plantation in Zhanggutai sandy land as an example. It was considered that the disagreement of large-scale afforestation with succession climax in regional scale was aberrant to the ecological principles, and resuhed in the aberrancy of the objectives, steps, species composition, and stand density of protective forest establishment, being the main cause of protective forest decline. Mismanagement and frequent natural and human disturbances were also the important causes for the decline. Three strategies for preventing the decline, i. e. , better understanding damaged ecosystems, increasing material and energy input, and overcoming disturbances were put forward, and the objectives of restoring vegetation, judgment of climax for ecological succession, and application of plagioclimax in establishing artificial vegetation were discussed.
Effect of land use change on spatial distribution pattern of soil total nitrogen in Keerqin sandy land

CHEN Fusheng,ZENG Dehui,CHEN Guangsheng,

应用生态学报 , 2004,
Abstract: By using statistics and geostatistics, this paper studied the content and spatial pattern of soil total nitrogen (TN) in a glassland and an arable land of southeast Keerqin sandy land. The TN content in 0-10 cm soil layer of the arable land reclaimed from a glassland 8 years ago was not different from that of the virgin grassland, but the TN content in 10-20 cm soil layer was higher than that in the grassland (P < 0.05). The soil TN storage in the grassland was 262.36 g x hm(-2) higher than that in the arable land, and its spatial pattern was significantly different between arable land and grassland. The heterogeneity and spatial dependence of TN in each soil layer (0-10 cm and 10-20 cm) of the arable land were larger than those of the grassland, and the ranges and fractal dimensions of TN in each soil layer of the arable land were larger than those of the grassland. There existed a clear horizontal spatial structure heterogeneity and spatial distribution pattern in the arable land, while in the grassland, the horizontal spatial structure heterogeneity was very low, and the horizontal spatial distribution pattern was random and uniform. The TN content in the 0-10 cm and 10-20 cm soil layers of the arable land had no difference (P < 0.05), its spatial structure characters had some difference (P < 0.05), and its spatial distribution pattern was very similar (r = 0.683, P < 0.05). The TN content and its spatial structure characters between two soil layers of the grassland had remarkable difference (P < 0.05), but its spatial distribution pattern in the two layers was relatively similar (r = 0.395, P < 0.05). In conclusion, agricultural activity could not only influence soil TN content, but also influence its spatial structure characteristics and spatial distribution pattern. Therefore, our study might promote the further study on the effect of land use change on soil nitrogen distribution pattern and its cycling in ecosystems.
Applied ecology:Retrospect and prospect

HE Xingyuan,ZENG Dehui,

应用生态学报 , 2004,
Abstract: Applied ecology is evolved into a principal part of modern ecology that rapidly develops.The major stimulus for the development of applied ecology roots in seeking the solutions for the problems of human populations,resources and environments.Through four decades,the science of applied ecology has been becoming a huge group of disciplines.The future for the applied ecology should concern more with human-influenced and managed ecosystems,and acknowledge humans as the components of ecosystems.Nowadays and in future,the top-priorities in applied ecology should include following fields:sustainable ecosystems and biosphere,ecosystem services and ecological design,ecological assessment of genetically modified organisms,ecology of biological invasions,epidemical ecology,ecological forecasting,ecological process and its control.The authors believe that the comprehensive and active research hotspots coupled some new traits would occur around these fields in foreseeable future.
Effects of low pH on zooplankton in some suburban waterbodies of Chongqing City
Zhuang Dehui,

环境科学学报(英文版) , 1995,
Abstract: Samples of zooplankton were collected for 4 times from May,1989 to May,1992 in some subur- ban waterbedies of Chongqing City, a heavy acid rain area in the southwest China. The qualitative and quanti- tative analysis results indicated that the species of zooplankton(y)were found to decIine gradually with a re- duction of pH value(x)ranging from 4.01 to 8.80. The regression equation of relation between them may be expressed as: y=1.520x-2.488(r=0.61, P<0.01,n=22)with respect to abundance of zooplankton,the mean density was abundant(3609. 23 ind./L)at pH ranging from 5.0 to 8.8,but was lower(151.50 ind./L)at pH ranging from 4.0 to 5.0. The evidence presented suggests that effects of low pH on zooplank- ton is the greatest below pH 5.0.
Influence of shelterbelts structure on snow distribution pattern in shelternets in Northeast China

FAN Zhiping,ZENG Dehui,CHEN Fusheng,ZHU Jiaojun,JIANG Fengqi,SHA Jianguo,

应用生态学报 , 2004,
Abstract: The amount of snow that falls in farmland during winter in Northeast China is the important source of soil water in farmland, so the influence of shelterbelt structure on snow distribution pattern is the key problem in order to adjust structure of shelterbelts according to porosity in management practice. Based on snow depths in shelternets composed of shelterbelts with three levels of porosity, which were shelternet No. 1, shelternet No. 2, and shelternet No. 3, the snow distribution patterns in farmland were studied. The results showed that the structure of shelternet had great influence on snow distribution in farmland. With different levels of porosities, spatial pattern of snow distribution were obviously different in three shelternets. The more variant in porosity, the more obvious difference in snow distribution pattern, and the best uniformity of snow distribution appeared in shelternet with porosity of phi 2w = 0.579, phi 2s = 0.268, in which snow depth in farmland was relative even and the variability of snow depth was the least. Consequently, the relationship of porosity of shelterbelt with snow distribution pattern could be used to guide structure adjustment and optimization management of shelterbelts.
Soil moisture characteristics at the boundary of forestland-grassland in hilly area of Loess Plateau

YOU Wenzhong,ZENG Dehui,LIU Mingguo,SONG Xide,

应用生态学报 , 2006,
Abstract: In this paper, the spatial distribution pattern of soil moisture at the boundary of forestland-grassland in hilly area of Loess Plateau was studied in dry season of June and rainy season of August 2004. The results showed that the variance coefficient of soil moisture content was smaller, and the difference of moisture content between soil layers was less significant in forestland than in grassland in June while reversed in August. There was a weak or medium differentiation of moisture content in different soil layers at the boundary of forestland-grassland. The edge effect area at the boundary was from 2 m (0.4 of tree height) outside forestland to 2 m inside forestland in June, and from 2 m outside forestland to 4 m (0.8 of tree height) inside forestland in August. The forestland-grassland landscape could be divided into 3 parts, i.e., grassland area, forest edge area, and forestland area, and the vertical distribution of soil moisture in these three parts showed different traits. In June, soil moisture content increased with increasing soil depth, with a smaller increment in grassland than in forestland, but in August, it was reversed. The vertical distribution of soil moisture at forest edge area showed an in-between feature.
Self thinning of even aged pure plantations of Pinus sylvestris var. mongolica on sandy soil

ZENG Dehui,JIANG Fengqi,FAN Zhiping,DU Xiaojun,

生态学报 , 2000,
Abstract: Since density dependent mortality is caused by the increase of tree size,it is more natural to choose an indicator of the size to express the relationship between the number of trees and the size.We chose the total stand basal area as the indicator of the size,and established an equation relating the number of trees to the total basal area of even aged pure plantations of Pinus sylvestris var. mongolica on sandy soil during their self thinning.We reviewed the -3/2 power law of plant self thinning,and suggested that although there is no satisfying evidence to support the accuracy of the slope of -3/2,it may be regarded as an ideal slope,and that with a view of various realities,we allow the existing of difference of the practical slope to the ideal one.
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