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Search Results: 1 - 10 of 78196 matches for " Yongxuan Chen "
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Data Gathering in Opportunistic Wireless Sensor Networks
Yongxuan Lai,Ziyu Lin
International Journal of Distributed Sensor Networks , 2012, DOI: 10.1155/2012/230198
Abstract: The wireless sensor networks and opportunistic networks have nowadays presented a trend of technology convergence. On one hand, the nodes periodically sense the environment and continuously generate sensing data; on the other hand, the movements and sparse deployment of nodes usually lead to intermitted connected links and create some form of opportunistic communications. So it is a challenging problem to effectively collect the sensing data in opportunistic wireless sensor networks. In this paper, we propose an efficient data gathering algorithm based on location prediction in opportunistic wireless sensor networks. The algorithm first collects the network metadata such as history of node encounters and contact durations; then it creates a node contact graph, based on which predictive optimal data gathering locations are dynamically calculated and updated. Finally, the sink is controlled to move to these locations to collect sensing data, avoiding lots of unnecessary data exchanges and message transmissions. Extensive experimental results show that the proposed algorithm is effective to reduce the message transmissions and improve the data collection coverage rate. 1. Introduction The wireless sensor networks (WSNs) and the opportunistic networks (or mobile delay tolerant networks) have nowadays presented a trend of convergence [1, 2]. On one hand, the sensor network has emerged some “opportunistic" characteristics in its nature: often deployed in harsh environments, the signal is susceptible to external interference and leads to loss of messages; the node is resource-constrained; many applications would take initiative to turn off the wireless radio devices based on energy considerations, resulting a disconnected network; in mobile sensor networks, the movement of nodes also leads to opportunistic communications; in sparse sensor networks, a mobile sink node is used for message and data collection; the communication is also opportunistic [3, 4]. On the other hand, similar to the “data-centric" sensor network, the opportunistic network is also a “data-related” network. End-to-end paths are not available in the opportunistic network, and it usually adopts a “store-carry-forward" mechanism to forward messages [1, 5]. The content of packets being forwarded plays an important role in the routing scheme. So the opportunistic wireless sensor network (OWSN) is a kind of opportunistic network that consists of nodes with sensing capabilities and actively or passively adopts the form of opportunistic transmissions. Research on OWSNs is a result of technology
Isolation and biological characteristics of spiroplasmas from flower surface

Hanshou Yu,Kangqin Ruan,Yanling Ji,Yongxuan Chen,Zhiwei Wang,

微生物学报 , 2008,
Abstract: 目的]调查我国植物花上的螺原体的存在,搜集我国的螺原体资源,并研究它们的基本生物学特性.方法]常规螺原体分离、培养方法,应用暗视野显微镜和透射电子显微镜观察螺原体形态,根据16S rDNA和ITS序列构建系统发育树研究螺原体分离菌株可能的分类地位.结果]分别从油菜(Brassica napus)、杜鹃(Rhododendron simsii)、红花酢浆草(Oxalis corymbosa)3种植物花表分离到4株螺原体CNR-1和CNR-2、CNA-1、CRW-1,对其形态、部分生理生化特性及分子生物学特性进行了初步研究.这4株螺原体在R-2液体培养基中生长良好,都能通过孔径为0.22 μm的微孔滤膜;在R-2固体培养基上呈圆形或颗粒状菌落,菌落直径约50~600 μm;在生长的某个阶段可呈典型的螺旋状,菌体直径为37.04~370.40 nm,长度约0.89~11.88 μm;它们都能利用葡萄糖作为碳源,不能利用尿素;在不含胎牛血清的R-2培养基中,它们都不能生长;菌株CNR-1、CNA-1能强烈代谢精氨酸,而CNR-2和CRW-1不能代谢精氨酸;在氨苄青霉素钠浓度高达2000 U/mL的R-2培养基中,分离菌株生长良好.根据16S rDNA序列构建的系统发育树显示,分离菌株CNR-1和CNR-2、CNA-1与蜜蜂螺原体Spiroplasma melliferum聚类较近,而CRW-1与S.clarkii聚类较近;根据ITS序列构建的系统发育树显示,CRW-1形成一个单独的分枝,其它3个菌株仍与S.melliferum聚类.结论]以上结果初步表明,分离菌株CNR-1和CNR-2、CNA-1极有可能是spiroplasma melliferum,而CRW-1可能是一个新的螺原体种,但还需要血清学试验进一步验证.
Advances in classification and biodiversity of spiroplasmas-A review

Hanshou Yu?,Shuyuan Liu,Kangqin Ruan,Yongxuan Chen,Zhiwei Wang,

微生物学报 , 2009,
Abstract: Abstract: Spiroplasma spp. are helical, motile bacteria that lack cell wall and flagellum, and are enclosed within a single membrane with their genomes ranging from approximately 0.78-2.20 Mb in size, the smallest among known self-replicating prokaryotes. So they have been used as model organisms for studying movement, metabolisms and sex ratio. Currently, 34 serological groups are recognized; three of these groups encompass 15 subgroups of inter-related strains. To date, 37 species among all serogroups and subgroups have been given binomial names. Complete characterization of a new species involves numerous phenotypic and genotypic tests as outlined in the minimal standards document, including phylogenetic data and a reevaluated set of required phenotypic and genotypic tests. Spiroplasma spp. are most often found in association with insects and plants flowers, and the interactions of Spiroplasma/host can be classified as commensal, pathogenic or mutualistic. Investigation of spiroplasma resources in China and research on their biodiversity will undoubtedly improve our understanding of these important microbial resources.
A Method to Obtain the Patterns of the Transient Response of a Multivariable Control System

Huang Yongxuan,

自动化学报 , 1992,
Abstract: This paper presents a method for obtaining the transient response of a multivariable control system described by a block diagramm. By using this method, the transient response of the system subjected to any kind of inputs or disturbances can be expressed as an analytical function of time.
Isolation and characterisation of Spiroplasma sp. from Phytomia zonata (Diptera: Syrphidae)

Shuyuan Liu,Hanshou Yu,Meng Su,Yongxuan Chen,Zhiyi He,Zhiwei Wang,

微生物学报 , 2009,
Abstract: 摘要:【目的】调查我国部分昆虫螺原体的存在情况,收集我国的昆虫螺原体资源,并研究它们的基本生物学特性,初步确定其分类地位。【方法】螺原体分离、培养方法,应用暗视野显微镜和透射电子显微镜观察螺原体形态,根据16S rDNA构建系统发育树研究螺原体分离菌株可能的分类地位。【结果】从黄道蚜蝇昆虫体内分离到螺原体YY0801,并对其进行了形态学、基本生物学及分子生物学特性研究。分离菌株在R2液体培养基中生长良好,能通过孔径为0.22 μm、0.45 μm的微孔滤膜;在R2固体培养基上呈颗粒状菌落;在对数期呈典型的螺旋状;能利用葡萄糖、D-果糖作为碳源;能强烈代谢精氨酸;不能利用尿素,在含氨苄青霉素钠(2000 U/mL)的R2液体培养基中生长良好。根据16S rDNA构建的系统发育树显示,分离菌株YY0801与血清组Ⅰ的Spiroplasma melliferum 聚类较近。【结论】首次在国内从食蚜蝇科中的黄道蚜蝇(Phytomia zonata)分离到螺原体,分离菌株YY0801可能是Spiroplasma melliferum,但其确切的分类地位需要进行血清学进一步分析。
Computing the Characteristic Polynomials of a Class of Hyperelliptic Curves for Cryptographic Applications
Lin You,Guangguo Han,Jiwen Zeng,Yongxuan Sang
Mathematical Problems in Engineering , 2011, DOI: 10.1155/2011/437541
Abstract: Hyperelliptic curves have been widely studied for cryptographic applications, and some special hyperelliptic curves are often considered to be used in practical cryptosystems. Computing Jacobian group orders is an important operation in constructing hyperelliptic curve cryptosystems, and the most common method used for the computation of Jacobian group orders is by computing the zeta functions or the characteristic polynomials of the related hyperelliptic curves. For the hyperelliptic curve : 2=
Humification degrees of peat in Qinghai-Xizang Plateau and palaeoclimate change
Hua Wang,Yetang Hong,Yongxuan Zhu,Bing Hong,Qinghua Lin,Hai Xu,Xuetian Leng,Xumei Mao
Chinese Science Bulletin , 2004, DOI: 10.1007/BF02900974
Abstract: In this article we report a new and sensitive palaeoclimate proxy indicator-humification degrees of peat. Based on the comparison of humification degrees with other climate proxy records, such as λ13C time series of theC. mulieensis remains cellulose in the same peat profile, we suggest that humification degrees of peat in Qinghai-Xizang Plateau can served as a palaeoclimate proxy indicator. The higher the humification degrees of peat, the warmer-wetter the climate; on the contrary, the lower the humification degrees, the colder-drier the climate. Due to the simple method of determination, humification degree of peat is worthy studying and applying further.
Temperature variations in the past 6000 years inferred from δ18O of peat cellulose from Hongyuan, China
Hai Xu,Yetang Hong,Qinghua Lin,Bing Hong,Hongbo Jiang,Yongxuan Zhu
Chinese Science Bulletin , 2002, DOI: 10.1360/02tb9347
Abstract: Trends of the temperature variations recorded in δ18O in Hongyuan peat cellulose are similar to those recorded in δ18O of Jinchuan peat cellulose and in δ18O of Dunde ice core. Climate events have been identified to be globally homogeneous. Two notable climate transition periods have been detected in the past 6000 years, namely 4000 aBP with climate shifting from cold to warm and 1500 aBP with climate shifting from warm to relatively cold. Power spectrum analysis was performed to investigate the periodical signals in the δ18O time series. Typical periodicities of 1200—1087 a, 752 a, 444 a, 325 a, 213 a, 127—123 a, 88 a, 79 a were discovered, indicating an integrated influence on Hongyuan climate from solar, monsoon and ocean activities. Solar forcing has been addressed to be the main driving forcing of Hongyuan climate.
Particle size distribution and arsenic partitioning in sediments from a river polluted by mining

JIAN Li,HUANG Zechun,LIU Yongxuan,YANG Ziliang,

环境科学学报 , 2010,
Abstract: 摘要:采用连续提取法分析了采矿污染河流——刁江底泥和河漫滩沉积物中砷的形态变化规律及其与沉积物粒径组成的关系。结果表明,刁江流域底泥和河漫滩沉积物中As含量分布存在差异,底泥中As主要赋存在63~170μm粒级颗粒中,河漫滩沉积物中As主要赋存在<63μm粒级颗粒中。底泥和河漫滩沉积物中砷主要以铁合态、钙合态和残渣态的形式存在,且残渣态比例相对较高,表现出典型的尾砂污染特征。底泥中残渣态砷(Res-As)组成比例总体上较高,主要赋存在63~170μm粒级颗粒中,而洪水水位河漫滩沉积物中Res-As组成比例相对较低,这与不同沉积物中硫化态砷的氧化反应差异有关。中下游河段,底泥和中水水位河漫滩沉积物中Res-As总体上呈逐渐降低的趋势,铁合态砷(Fe-As)组成比例的分布与Res-As呈相反的趋势。
Exploiting Adaptive Laboratory Evolution of Streptomyces clavuligerus for Antibiotic Discovery and Overproduction
Pep Charusanti, Nicole L. Fong, Harish Nagarajan, Alban R. Pereira, Howard J. Li, Elisa A. Abate, Yongxuan Su, William H. Gerwick, Bernhard O. Palsson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033727
Abstract: Adaptation is normally viewed as the enemy of the antibiotic discovery and development process because adaptation among pathogens to antibiotic exposure leads to resistance. We present a method here that, in contrast, exploits the power of adaptation among antibiotic producers to accelerate the discovery of antibiotics. A competition-based adaptive laboratory evolution scheme is presented whereby an antibiotic-producing microorganism is competed against a target pathogen and serially passed over time until the producer evolves the ability to synthesize a chemical entity that inhibits growth of the pathogen. When multiple Streptomyces clavuligerus replicates were adaptively evolved against methicillin-resistant Staphylococcus aureus N315 in this manner, a strain emerged that acquired the ability to constitutively produce holomycin. In contrast, no holomycin could be detected from the unevolved wild-type strain. Moreover, genome re-sequencing revealed that the evolved strain had lost pSCL4, a large 1.8 Mbp plasmid, and acquired several single nucleotide polymorphisms in genes that have been shown to affect secondary metabolite biosynthesis. These results demonstrate that competition-based adaptive laboratory evolution can constitute a platform to create mutants that overproduce known antibiotics and possibly to discover new compounds as well.
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