检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

光纤延迟线噪音对相控阵波束指向的影响

光子学报 2014年第4期43卷 29-33页

作者：苏君邱琪史双瑾电子科技大学光电信息学院成都610054

基于相位噪音和相控阵理论,运用线阵天线原始方向图函数和光纤链路噪音系数公式,根据天线波束指向实际误差进行合理近似,推导了光延迟线链路噪音系数、天线阵元数与波束指向误差的理论公式.采用常规光纤链路参量进行了仿真研究,结果表明... 详细信息

基于相位噪音和相控阵理论,运用线阵天线原始方向图函数和光纤链路噪音系数公式,根据天线波束指向实际误差进行合理近似,推导了光延迟线链路噪音系数、天线阵元数与波束指向误差的理论公式.采用常规光纤链路参量进行了仿真研究,结果表明:相控阵天线波束指向误差均方差随光纤链路噪音系数增大而增加,随天线阵元数增加而减小,指向误差与光纤延迟线链路噪音系数的1/2次方成正比,与阵元数的3/2次方成反比.在相控阵天线工作频段内,低频波段受噪音系数影响更加明显.

关键词：光纤通信相控阵天线波束形成波束指向相位噪音光链路光收发模块

Quasispecies groups in the core promoter region of hepatitis B virus

在线全文

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2002年第3期1卷 392-396页

作者： Hong Deng Jing Dong Jun Cheng Kun-Jing Huangfu shuang-shuang shi Yuan Hong Xi-Min Ren Li Li the Department of Communicable Diseases, the Second Hospital of Xi’an an Jiaotong University, Xi’an 710004, China and the Gene Therapy Research Center, Institute of Infections Diseases, the 302 Hospital of PLA, Beijing 100039, China Department of Communicable Diseases Second Hospital Xi'an Jiaotong Univ. Xi'an 710004 China Gene Therapy Research Center Institute of Infectious Diseases The 302 Hospital of PLA Beijing 100039 China

Objectives: To investigate the mutation of the basic core promoter (BCP) of hepatitis B virus (HBV) and clarify the significance of HBV quasispecies groups in patients with chronic HBV infection. Methods: A set of specific primers was synthesized according to the HBV DNA sequence of a Chinese strain. The BCP was amplified by PCR method from the serum of 40 patients with chronic HBV infection, and the PCR products of 2 patients were subcloned into pGEM Teasy vectors. Polyacrylamide gel elec- trophoresis (PAGE) was employed to display the de- letion mutations, and clones with differential length were selected to be sequenced. Sequence comparison was made to find the difference. Results: Two or three bands were displayed by PAGE in 60% patients. The results of sequence anal- ysis showed that there are some kinds of mutations in the BCP region. The substitution always occurs in TATA-like boxes, especially from T to C on 140 site. The deletion mutations were detected in TA1, TA2 and TA3. The 8bp, 20bp deletion mutations fre- quently happened. Conclusions: There is a hot deletion region in the BCP. The deletion and the substitution in the TATA- like box may influence the expression of preC/C pro- tein. The sequencing results indicate that there are HBV quasispecies groups in patients with chronic HBV infection.

关键词： hepatitis B virus basic core promoter mutation polyacrylamide gel electrophoresis quasispecies

长三角典型站点冬季大气PM2.5中OC、EC污染特征

在线全文

学校读者我要写书评

暂无评论

环境科学 2018年第3期39卷 961-971页

作者：康晖朱彬王红磊施双双南京信息工程大学气象灾害教育部重点实验室气候与环境变化国际合作联合实验室气象灾害预报预警与评估协同创新中心中国气象局气溶胶与云降水重点开放实验室南京210044

对2015年1月9日~2015年1月31日临安、南京和苏州3个站点采集的PM_(2.5)样品(共计279组),使用热光反射法(thermal/optical reflectance,TOR)分析了样品中有机碳(OC)与元素碳(EC)的含量,并研究了长三角地区冬季PM_(2.5)中OC和EC的污染特征.结果表明,采样期间临安、南京和苏州的PM_(2.5)平均质量浓度分别为(123.56±61.11)、(144.77±62.91)和(156.5±68.97)μg·m-3,均超过我国《环境空气质量标准》(GB 3095-2012)规定的PM_(2.5)日均值75μg·m-3;其中3个站点OC与EC的平均质量浓度依次分别为(21.93±11.69)/(6±3.6)、(20.32±10.3)/(5.39±3.07)和(27.08±14.35)/(6.4±4.29)μg·m-3.临安作为长三角大气环境背景点,OC与EC的污染也较为严重.3个站点OC与EC的相关性为临安(R2=0.83)、南京(R2=0.72)和苏州(R2=0.72),表明冬季长三角地区的碳质气溶胶的来源较为一致和稳定.3个站点样品中的OC/EC值均大于2.0,样品的OC/EC值主要分布在2.5~6.0这个区间内,表明燃煤源和机动车尾气排放源是OC与EC的主要来源.使用EC示踪法估算临安、南京和苏州3个站点的二次有机碳(SOC)平均质量浓度分别为(9.23±5.26)、(6.82±4.36)和(12.56±7.52)μg·m-3,在OC中占比为42%、34%和46%,表明SOC是OC的重要组成部分.后向轨迹显示,PM_(2.5)、OC和EC的质量浓度与主要气团的传输路径有较好的相关性,自空气质量较差区域气团的PM_(2.5)、OC和EC的质量浓度是来自空气质量较好区域的1.14~1.7倍、1.55~2.1倍和1.94~2.47倍.

关键词： PM2.5 长三角有机碳元素碳浓度分布

Study on Thixotropic Properties of Waxy Crude Oil Based on Hysteresis Loop Area

在线全文

学校读者我要写书评

暂无评论

Engineering（科研） 2015年第7期7卷 469-476页

作者： Liping Guo Yu Wang shuang shi Xiaoyang Yu Xu Chen College of Petroleum Engineering Daqing Petroleum Institute Daqing China

Thixotropic properties are one of the low temperature rheology behaviors of gelled waxy crudes. In order to study the thixotropic behavior of gelled waxy crudes oil under cyclic loading of linear increasing and decreasing of shear rate, three different types of waxy crude oil were studied ex-perimentally by using MARSIII rheometer. It is found that hysteresis loop area could represent strength of thixotropic properties under that loading. With increasing of the rate of share rate sweep, the area of second hysteresis loop is much smaller than first one and began a slow decline from the third hysteresis loop. Areas of each hysteresis loops were decreased with increasing temperature, but it was different in decline rate—the lower the temperature, the greater the rate of decline. The maximum rate of decrease is the first hysteresis loop with exponential decline, and remaining hysteresis hoops approximately decrease linearly. In addition, based on the experi-mental results an empirical correlation is developed to describe the relationship of hysteresis loop area and rate of share rate sweep.

关键词： Waxy Crude Oil Thixotropic Hysteresis Loop Area

Evaluation of Thixotropic Models for Waxy Crudes

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Applied Sciences 2015年第6期5卷 304-312页

作者： Liping Guo Xu Chen shuang shi Yu Wang Xiaoyang Yu College of Petroleum Engineering Northeast Petroleum University Daqing China

Thixotropy is a great rheological behavior of waxy crudes oils and is of great importance for hydraulic characteristics and security of oil pipeline restart. In this paper, through the experiment of four waxy crudes, three kinds of thixotropic rheology characteristics in the conditions that shear stress decays under a constant shear rate, shear stress decays after shear rate steps up and hysteresis loop of shear rate cycle changes are studied . For eight thixotropic models, experimental data are fitted in the method of least-squares and average deviation is taken as a statistical indicator to evaluate the thixotropic models. It shows that the model with the idea of Cheng that completely reversible and totally irreversible structures both exist in waxy oil products and based on Houska model can describe thixotropic behaviors of waxy crudes most well.

关键词： Waxy Crude Oils Thixotropy Thixotropic Model

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

微机电系统后坐保险机构温度相关动态特性

吉林大学学报（工学版） 2017年第1期47卷 145-150页

作者：何光张铭袁双石北京理工大学机电工程与控制国家重点实验室北京100081

搭建了一套由高冲击加载系统、温度加载系统以及高速显微光学成像系统组成的典型微机电系统(MEMS)结构温度相关动态测试系统,用该系统对引信用MEMS后坐保险机构在温度和冲击载荷耦合环境下进行动态特性测试,得到了不同温度(-40℃~50℃)... 详细信息

搭建了一套由高冲击加载系统、温度加载系统以及高速显微光学成像系统组成的典型微机电系统(MEMS)结构温度相关动态测试系统,用该系统对引信用MEMS后坐保险机构在温度和冲击载荷耦合环境下进行动态特性测试,得到了不同温度(-40℃~50℃)下引信用MEMS后坐保险机构中滑块相对于基板框的位移-时间曲线以及速度-时间曲线。通过对比分析,得出冲击条件下温度对MEMS后坐保险机构中滑块相对于基板框的位移以及速度的影响规律。

关键词：机械设计微机电系统图像处理动态特性后坐保险

Research on Casing Damage Based on Effect of Water Injection Pressure

在线全文

学校读者我要写书评

暂无评论

Open Journal of Fluid Dynamics 2015年第2期5卷 208-214页

作者： Liping Guo Xu Chen Xiaoyang Yu shuang shi Yu Wang College of Petroleum Engineering Northeast Petroleum University Daqing China

Based on statistical analysis on the situation of casing damage and water injection pressure in Pubei Oilfield, it shows that the main forms of casing damage in Pubei Oilfield are deformation and dislocation. Dip angle and faults have a significant impact on casing damage and casing damage is closely related to water injection pressure. Through laboratory simulating experiment and theoretical calculation, the formula of critical injection pressure giving rise to casing damage is obtained and the preventive measures are drafted.

关键词： Casing Damage Water Injection Pressure Pubei Oilfield

Molecular analyses display the increasing diversity of Podostemaceae in China

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plant Diversity 2024年第3期46卷 421-424页

作者： Zhi-Zhong Li Zhun Xu shuang Wu Lang-Xing Yuan Chun-Yu Zou Yan Liu Jian-Yong Lin shi-Chu Liang Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection(Guangxi Normal University) Ministry of EducationGuilin 541006China Wuhan Botanical Garden Chinese Academy of SciencesWuhan 430074China Sino-Africa Joint Research Center Chinese Academy of SciencesWuhan 430074China Guangxi Association for Science and Technology Nanning 530023China Tropical Crops Genetic Resources Institute Chinese Academy of Tropical Agricultural SciencesHaikou 571101China Guangxi Institute of Botany Chinese Academy of SciencesGuilin 541006China Guangxi Forestry Research Institute Nanning 530028China

Podostemaceae(riverweed family),one of the largest aquatic plant families in the world,comprises about 350 species in 51 genera placed in three subfamilies,Podostemoideae,Weddellinoideae,and Tristichoideae(Koi et al.,2022).Most Podostemaceae genera(~38)are monotypic or oligotypic,with a high level of endemism(Koi et al.,2018,2022).Members of Podostemaceae adhere to rocks in fast-flowing rivers,streams,or waterfalls in the subtropics and tropics(Koi et al.,2018).As an adaptation to fastrunning currents,the morphological structure of river-weeds tends to be extremely reduced,including a loss or reduction of primary shoots or roots(Koi and Kato,2007).The vegetative mass of these plants resembles lichens or bryophytes,and are thus known commonly as“dream bryophytes”(Philbrick and Retana,1998).Podostemaceae plants flower when the water level drops during the dry *** recent years,anthropogenic factors and climate change have severely affected river weed habitats,decreasing populations of these plants.

关键词： roots season habitat

Self-assembly multifunctional DNA tetrahedron for efficient elimination of antibiotic-resistant bacteria

在线全文

学校读者我要写书评

暂无评论

Aggregate

Aggregate 2024年第1期5卷 204-215页

作者： Tiantian Wu Yu Fu shuang Guo Yanqiang shi Yuxin Zhang Zhijin Fan Bin Yang Baoquan Ding Yuhui Liao Molecular Diagnosis and Treatment Center for Infectious Diseases Dermatology HospitalSouthern Medical UniversityGuangzhouChina CAS Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in NanoscienceNational Center for Nanoscience and TechnologyBeijingChina Longgang District Central Hospital of Shenzhen ShenzhenChina

Antibiotic resistance is a major challenge in the clinical treatment of bacterial infectious ***,we constructed a multifunctional DNA nanoplatform as a versatile carrier for bacteria-specific delivery of clinical antibiotic ciprofloxacin(CIP)and classic nanoantibiotic silver nanoparticles(AgNP).In our rational design,CIP was efficiently loaded in the self-assembly double-bundle DNA tetrahedron through intercalation with DNA duplex,and single-strand DNA-modified AgNP was embedded in the cavity of the DNA tetrahedron through *** the site-specific assembly of targeting aptamer in the well-defined DNA tetrahedron,the bacteria-specific dual-antibiotic delivery system exhibited excellent combined bactericidal *** enhanced antibiotic accumulation through breaking the out membrane of bacteria,the antibiotic delivery system effectively inhibited biofilm formation and promoted the healing of infected wounds in *** DNAbased antibiotic delivery system provides a promising strategy for the treatment of antibiotic-resistant infections.

关键词： antibiotic resistance anti-infection therapy biofilm DNA nanotechnology targeted delivery