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Orbit determination and time synchronization for a GEO/IGSO satellite navigation constellation with regional tracking network 被引量:47
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作者 ZHOU ShanShi HU XiaoGong +9 位作者 WU Bin LIU Li QU WeiJing GUO Rui HE Feng CAO YueLing Wu XiaoLi ZHU LingFeng SHI Xin TAN HongLi 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2011年第6期1089-1097,共9页
Aiming at regional services,the space segment of COMPASS (Phase I) satellite navigation system is a constellation of Geostationary Earth Orbit (GEO),Inclined Geostationary Earth Orbit (IGSO) and Medium Earth Orbit (ME... Aiming at regional services,the space segment of COMPASS (Phase I) satellite navigation system is a constellation of Geostationary Earth Orbit (GEO),Inclined Geostationary Earth Orbit (IGSO) and Medium Earth Orbit (MEO) satellites.Precise orbit determination (POD) for the satellites is limited by the geographic distribution of regional tracking stations.Independent time synchronization (TS) system is developed to supplement the regional tracking network,and satellite clock errors and orbit data may be obtained by simultaneously processing both tracking data and TS data.Consequently,inconsistency between tracking system and TS system caused by remaining instrumental errors not calibrated may decrease navigation accuracy.On the other hand,POD for the mixed constellation of GEO/IGSO/MEO with the regional tracking network leads to parameter estimations that are highly correlated.Notorious example of correlation is found between GEO's orbital elements and its clock errors.We estimate orbital elements and clock errors for a 3GEO+2IGSO constellation in this study using a multi-satellite precise orbit determination (MPOD) strategy,with which clock error elimination algorithm is applied to separate orbital and clock estimates to improve numerical efficiency.Satellite Laser Ranging (SLR) data are used to evaluate User Ranging Error (URE),which is the orbital error projected on a receiver's line-of-sight direction.Two-way radio-wave time transfer measurements are used to evaluate clock errors.Experimenting with data from the regional tracking network,we conclude that the fitting of code data is better than 1 m in terms of Root-Mean-Square (RMS),and fitting of carrier phase is better than 1 cm.For orbital evaluation,difference between computed receiver-satellite ranging based on estimated orbits and SLR measurements is better than 1 m (RMS).For clock estimates evaluation,2-hour linear-fitting shows that the satellite clock rates are about 1.E-10 s/s,while receiver clock rates are about 1×10 13-1×10 12 s/s.For the 72-hour P 展开更多
关键词 POD time synchronization clock errors elimination SLR evaluation
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基于GPS实现电力系统高精度同步时钟 被引量:36
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作者 蒋陆萍 曾祥君 +1 位作者 李泽文 彭安安 《电网技术》 EI CSCD 北大核心 2011年第2期201-206,共6页
根据全球定位系统(global positioning system,GPS)秒时钟的随机误差和高精度晶振的累计误差互补的特点,利用数字锁相原理,通过测量GPS秒时钟与晶振秒时钟间的相位差来控制晶振秒时钟的分频系数,实时消除晶振秒时钟的累计误差,从而产生... 根据全球定位系统(global positioning system,GPS)秒时钟的随机误差和高精度晶振的累计误差互补的特点,利用数字锁相原理,通过测量GPS秒时钟与晶振秒时钟间的相位差来控制晶振秒时钟的分频系数,实时消除晶振秒时钟的累计误差,从而产生高精度秒时钟,并利用复杂可编程逻辑器件(complex programmable logic device,CPLD)设计了高精度同步时钟系统。GPS信号接收正常时,CPLD根据数字锁相原理产生高精度同步时钟;GPS信号接收不正常时,CPU调取存储的分频系数控制CPLD产生高精度时钟。仿真分析和实验结果表明该时钟系统具有很高的时间准确度和稳定性。 展开更多
关键词 全球定位系统 晶振 时钟 复杂可编程逻辑器件 秒脉冲
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Circadian Clock Genes Universally Control Key Agricultural Traits 被引量:29
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作者 Claire Bendix 《Molecular Plant》 SCIE CAS CSCD 2015年第8期1135-1152,共18页
Circadian clocks are endogenous timers that enable plants to synchronize biological processes with daily and seasonal environmental conditions in order to allocate resources during the most beneficial times of day and... Circadian clocks are endogenous timers that enable plants to synchronize biological processes with daily and seasonal environmental conditions in order to allocate resources during the most beneficial times of day and year. The circadian clock regulates a number of central plant activities, including growth, develop- ment, and reproduction, primarily through controlling a substantial proportion of transcriptional activity and protein function. This review examines the roles that alleles of circadian clock genes have played in domestication and improvement of crop plants. The focus here is on three groups of circadian clock genes essential to clock function in Arabidopsis thaliana: PSEUDO-RESPONSE REGULATORs, GIGANTEA, and the evening complex genes EARL Y FLOWERING 3, EARLY FLOWERING 4, and LUX ARRHYTHMO. Homol- ogous genes from each group underlie quantitative trait loci that have beneficial influences on key agricul- tural traits, especially flowering time but also yield, biomass, and biennial growth habit. Emerging insights into circadian clock regulation of other fundamental plant processes, including responses to abiotic and biotic stresses, are discussed to highlight promising avenues for further crop improvement. 展开更多
关键词 circadian clock PSEUDO-RESPONSE REGULATORs GIGANTEA evening complex genes quantitative trait loci flowering time
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OsELF3 Is Involved in Circadian Clock Regulation for Promoting Flowering under Long-Day Conditions in Rice 被引量:25
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作者 Ying Yang Qiang Peng Guo-Xing Chen Xiang-Hua Li Chang-Yin Wu 《Molecular Plant》 SCIE CAS CSCD 2013年第1期202-215,共14页
Heading date is a critical trait that determines cropping seasons and regional adaptability in rice (Oryza sativa). Research efforts during the last decade have identified some important photoperiod pathway genes th... Heading date is a critical trait that determines cropping seasons and regional adaptability in rice (Oryza sativa). Research efforts during the last decade have identified some important photoperiod pathway genes that are conserved between Arabidopsis and rice. In this study, we identified a novel gene, Oryza sativa ELF3 (OsELF3), which is a putative homolog of the ELF3 gene in Arabidopsis thaliana. OsELF3 was required for the control of heading date under long-day conditions. Its Tos17-tagging mutants exhibited a delayed heading date phenotype only under long-day, but not short-day, conditions. OsELF3 was highly expressed in leaf blades, and the OsELF3 protein was localized in the nucleolus. An obvious diurnal rhythm of OsELF3 transcript level was observed, with a trough in the early day and a peak in the late night in wild-type plants. However, this expression pattern was disrupted in oself3 mutants. Further inves- tigations showed that the expression of OsGI and Ghd7 was up-regulated in the oself3 mutant, indicating that OsELF3 acts as a negative regulator upstream of OsGI and Ghd7 in the flowering-time control under long-day conditions. The rhythmic expression of circadian clock-related genes, including some OsPRR members, was obviously affected in oself3 mutants. Our results indicated that OsELF3 acts as a floral activator in the long-day photoperiodic pathway via its cross- talk with the circadian clock in rice. 展开更多
关键词 heading date photoperiod pathway circadian clock rice.
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超、特高压长线路光纤纵差保护数据同步 被引量:21
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作者 李永丽 李仲青 +4 位作者 李斌 李博通 景雷 龙英 范建忠 《天津大学学报》 EI CAS CSCD 北大核心 2007年第2期168-172,共5页
分析了目前在实际光纤纵差保护中应用的数据同步方法的缺点,尤其是SDH(synchronous digital hierar-chy)光纤自愈环网中收发数据路由不一致导致线路两侧保护装置采样数据不同步问题,提出了一种适用于超、特高压长线路光纤纵差保护的采... 分析了目前在实际光纤纵差保护中应用的数据同步方法的缺点,尤其是SDH(synchronous digital hierar-chy)光纤自愈环网中收发数据路由不一致导致线路两侧保护装置采样数据不同步问题,提出了一种适用于超、特高压长线路光纤纵差保护的采样数据同步方法,即基于时钟校正法,并通过精确线路模型的在线计算对时钟做进一步补偿校正的方法.EMTP仿真验证该方法的误差小于0.5μs.理论分析和仿真结果证明了该方法保证线路两侧保护装置采样数据同步的有效性及应用于超、特高压长线的可行性. 展开更多
关键词 光纤纵差保护 同步 时钟 延时 补偿
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Clinical observation on effect of scalp electroacupuncture for mild cognitive impairment 被引量:23
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作者 Hong Zhang Ling Zhao +5 位作者 Sha Yang Zhigang Chen Yingkun Li Xiaohong Peng Yulong Yang Manjia Zhu 《Journal of Traditional Chinese Medicine》 SCIE CAS CSCD 2013年第1期46-50,共5页
OBJECTIVE: To evaluate the therapeutic effect of scalp electroacupuncture for mild cognitive impairment (MCI) in the early stage. METHODS: Two hundred and thirty three MCI patients were randomly divided into three gro... OBJECTIVE: To evaluate the therapeutic effect of scalp electroacupuncture for mild cognitive impairment (MCI) in the early stage. METHODS: Two hundred and thirty three MCI patients were randomly divided into three groups: the drug group, the scalp electroacupuncture group, and the syndrome differentiation group. For the scalp electroacupuncture group, the points of Baihui (DU 20), Sishecong (EX-HN1), Fengchi (GB 20), and Shenting (DU 24) were selected. For the syndrome differentiation group, specific acupoints were added on the basis of syndrome differentiation and according to the scale for the differentiation of syndromes in vascular dementia (SDSVD) beside the acupoints used in the scalp electroacupuncture group. For the drug group, nimodipine was orally administered. Each patient was treated for two courses, eight weeks. The score differences in minimental state examination (MMSE), picture recognition, and clock drawing test were observed before and after the treatment. RESULTS: After treatment, the score differences in MMSE and clock drawing test were of obvious statistical significance among three groups (P<0.01, P<0.05). The score differences in picture recognition were of extremely statistical significance between the scalp electroacupuncture group and the syndrome differentiation group (P<0.01), while the difference was not found in the drug group (P>0.05). There were statistical significant differences in therapeutic effects between the scalp electroacupuncture group and the drug group, and between the syndrome differentiation group and the drug group (P<0.05), while no statistical difference was found between scalp electroacupuncture group and the syndrome differentiation group (P>0.05). CONCLUSION: All the three therapies may improve the cognitive function of MCI patients. The therapeutic effects in the scalp electroacupuncture and syndrome differentiation groups were basically the same, but superior to nimodipine. 展开更多
关键词 Memory disorders Electroacupunc-ture NIMODIPINE Picture recognition clock draw-ing test
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The wide-area difference system for the regional satellite navigation system of COMPASS 被引量:21
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作者 CAO YueLing HU XiaoGong +6 位作者 WU Bin ZHOU ShanShi LIU Li SU RanRan CHANG ZhiQiao HE Feng ZHOU JianHua 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2012年第7期1307-1315,共9页
The regional satellite navigation system of COMPASS (Phase I) provides both open services and authorized services. Authorized services offer differential corrections and integrity information to users to support highe... The regional satellite navigation system of COMPASS (Phase I) provides both open services and authorized services. Authorized services offer differential corrections and integrity information to users to support higher positioning, navigation and timing precision. Experimenting with real data, positioning accuracy is estimated with a 3GEO/4IGSO COMPASS constellation. The results show that with dual-frequency and single-frequency pseudo-range measurements, the positioning errors are respectively 8 and 10 m (RMS) for open service users, while for authorized users, the errors are 4 and 5 m (RMS), respectively. The COMPASS constellation geometry may cause large error to occur in the height component by 7-9 m for dualor single-frequency users, which can be effectively reduced with the differential corrections supplied by the authorized services. Multipath errors are identified and corrected for COMPASS, resulting in 25% positioning accuracy improvement for dual-frequency users and 10% improvement for single-frequency users. 展开更多
关键词 COMPASS equivalent satellite clock error ionospheric grid multipath error positioning error
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Expanding Roles of PIFs in Signal Integration from Multiple Processes 被引量:19
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作者 Inyup Paik Praveen Kumar Kathare +1 位作者 Jeong-II Kim Enamul Huq 《Molecular Plant》 SCIE CAS CSCD 2017年第8期1035-1046,共12页
PHYTOCHROME-INTERACTING FACTORs (PIFs) are members of the basic helix-loop-helix (bHLH) family of transcription factors in Arabidopsis. Since their discovery in phytochrome-mediated light signaling pathways, recen... PHYTOCHROME-INTERACTING FACTORs (PIFs) are members of the basic helix-loop-helix (bHLH) family of transcription factors in Arabidopsis. Since their discovery in phytochrome-mediated light signaling pathways, recent studies have unraveled new functions of PIFs in integrating multiple signaling pathways not only through their role as transcription factors directly targeting gene expression but also by interacting with diverse groups of factors to optimize plant growth and development. These include endogenous (e.g., hormonal) as well as abiotic (light, circadian, and elevated temperature) and biotic (defense responses) pathways. PIFs interact with key factors in each of these pathways and tailor the outcome of the signal integration among these pathways. This review discusses the roles of PIFs as pivotal signal integrators in regulating plant growth and development. 展开更多
关键词 circadian clock growth-defense tradeoff hormone signaling phytochrome-interacting factor ther-momorphogenesis signal integration
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Biomarkers of aging 被引量:16
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作者 Aging Biomarker Consortium Hainan Bao +118 位作者 Jiani Cao Mengting Chen Min Chen Wei Chen Xiao Chen Yanhao Chen Yu Chen Yutian Chen Zhiyang Chen Jagadish K Chhetri Yingjie Ding Junlin Feng Jun Guo Mengmeng Guo Chuting He Yujuan Jia Haiping Jiang Ying Jing Dingfeng Li Jiaming Li Jingyi Li Qinhao Liang Rui Liang Feng Liu Xiaoqian Liu Zuojun Liu Oscar Junhong Luo Jianwei Lv Jingyi Ma Kehang Mao Jiawei Nie Xinhua Qiao Xinpei Sun Xiaoqiang Tang Jianfang Wang Qiaoran Wang Siyuan Wang Xuan Wang Yaning Wang Yuhan Wang Rimo Wu Kai Xia Fu-Hui Xiao Lingyan Xu Yingying Xu Haoteng Yan Liang Yang Ruici Yang Yuanxin Yang Yilin Ying Le Zhang Weiwei Zhang Wenwan Zhang Xing Zhang Zhuo Zhang Min Zhou Rui Zhou Qingchen Zhu Zhengmao Zhu Feng Cao Zhongwei Cao Piu Chan Chang Chen Guobing Chen Hou-Zao Chen Jun Chen Weimin Ci Bi-Sen Ding Qiurong Ding Feng Gao Jing-Dong JHan Kai Huang Zhenyu Ju Qing-Peng Kong Ji Li Jian Li Xin Li Baohua Liu Feng Liu Lin Liu Qiang Liu Qiang Liu Xingguo Liu Yong Liu Xianghang Luo Shuai Ma Xinran Ma Zhiyong Mao Jing Nie Yaojin Peng Jing Qu Jie Ren Ruibao Ren Moshi Song Zhou Songyang Yi Eve Sun Yu Sun Mei Tian Shusen Wang Si Wang Xia Wang Xiaoning Wang Yan-Jiang Wang Yunfang Wang Catherine CL Wong Andy Peng Xiang Yichuan Xiao Zhengwei Xie Daichao Xu Jing Ye Rui Yue Cuntai Zhang Hongbo Zhang Liang Zhang Weiqi Zhang Yong Zhang Yun-Wu Zhang Zhuohua Zhang To 《Science China(Life Sciences)》 SCIE CAS CSCD 2023年第5期893-1066,共174页
Aging biomarkers are a combination of biological parameters to(i)assess age-related changes,(ii)track the physiological aging process,and(iii)predict the transition into a pathological status.Although a broad spectrum... Aging biomarkers are a combination of biological parameters to(i)assess age-related changes,(ii)track the physiological aging process,and(iii)predict the transition into a pathological status.Although a broad spectrum of aging biomarkers has been developed,their potential uses and limitations remain poorly characterized.An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research:How old are we?Why do we get old?And how can we age slower?This review aims to address this need.Here,we summarize our current knowledge of biomarkers developed for cellular,organ,and organismal levels of aging,comprising six pillars:physiological characteristics,medical imaging,histological features,cellular alterations,molecular changes,and secretory factors.To fulfill all these requisites,we propose that aging biomarkers should qualify for being specific,systemic,and clinically relevant. 展开更多
关键词 AGING SENESCENCE BIOMARKER clock
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血压昼夜节律特征及其分子调控机制 被引量:19
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作者 张振服 刘启德 杨蕾 《现代生物医学进展》 CAS 2011年第6期1181-1183,共3页
正常血压具有典型的昼夜节律特征。血压昼夜节律异常与高血压靶器官损害和心血管事件发生呈明显相关关系,是独立于血压水平的重要致病因素。血压昼夜节律的产生和维持与时钟基因的周期性表达有关。时钟基因bmal1、per2是体内生物钟系统... 正常血压具有典型的昼夜节律特征。血压昼夜节律异常与高血压靶器官损害和心血管事件发生呈明显相关关系,是独立于血压水平的重要致病因素。血压昼夜节律的产生和维持与时钟基因的周期性表达有关。时钟基因bmal1、per2是体内生物钟系统运行的关键基因,其表达水平和节律变化直接调节血压的昼夜节律。 展开更多
关键词 昼夜节律 高血压 生物钟 血管紧张素
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Plant Immune Mechanisms:From Reductionistic to Holistic Points of View 被引量:19
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作者 Jie Zhang Gitta Coaker +1 位作者 Jian-Min Zhou Xinnian Dong 《Molecular Plant》 SCIE CAS CSCD 2020年第10期1358-1378,共21页
After three decades of the amazing progress made on molecular studies of plant-microbe interactions(MPMI),we have begun to ask ourselves"what are the major questions still remaining?"as if the puzzle has onl... After three decades of the amazing progress made on molecular studies of plant-microbe interactions(MPMI),we have begun to ask ourselves"what are the major questions still remaining?"as if the puzzle has only a few pieces missing.Such an exercise has ultimately led to the realization that we still have many more questions than answers.Therefore,it would be an impossible task for us to project a coherent"big picture"of the MPMI field in a single review.Instead,we provide our opinions on where we would like to go in our research as an invitation to the community to join us in this exploration of new MPMI frontiers. 展开更多
关键词 EXTRACELLULAR IMMUNITY pattern-triggered IMMUNITY (PTI) effector-triggered IMMUNITY (ETI) heterogeneity in immune responses TRANSLATIONAL regulation CIRCADIAN clock
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针刺结合艾灸调节骨关节炎模型大鼠滑膜昼夜节律蛋白的表达 被引量:14
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作者 谈倩 李柏村 +3 位作者 李静 李佳 向宏春 蔡国伟 《中国组织工程研究》 CAS 北大核心 2022年第11期1714-1719,共6页
背景:滑膜炎症是膝骨性关节炎的主要病理特征之一,既往研究表明针灸治疗膝骨性关节炎效果显著,而针灸是否通过调控滑膜中的相关蛋白改善相关症状值得进一步研究。目的:探讨针刺结合艾灸对膝骨性关节炎大鼠滑膜组织中的生物钟蛋白(Clock... 背景:滑膜炎症是膝骨性关节炎的主要病理特征之一,既往研究表明针灸治疗膝骨性关节炎效果显著,而针灸是否通过调控滑膜中的相关蛋白改善相关症状值得进一步研究。目的:探讨针刺结合艾灸对膝骨性关节炎大鼠滑膜组织中的生物钟蛋白(Clock、Bmal1)、TRPV4和炎症因子白细胞介素1β的影响。方法:80只3月龄SPF级雄性SD大鼠随机分为对照组、模型组、针刺组、针+灸组,每组20只,后3组以手术方法制备膝骨关节炎大鼠模型,于术后第7天取右膝足三里(ST36)、犊鼻(ST35)和内膝眼(EX-LE5)进行治疗,针刺组针刺5 mm,15 min/次,1次/d,共21 d;针+灸组治疗同针刺组,并结合悬起灸。所有大鼠相应处理结束后,采用旷场实验测大鼠自发活动能力;苏木精-伊红染色观察滑膜组织病理结构;Western blot检测滑膜组织Clock,Bmal1,TRPV4的表达;免疫荧光法检测滑膜组织白细胞介素1β的表达。结果与结论:(1)与对照组比较,模型组大鼠自发活动明显降低,其滑膜组织Clock及Bmal1表达量明显降低,TRPV4和炎性因子白细胞介素1β的表达明显升高(P<0.01),并且滑膜上皮损失严重。(2)与模型组比较,针刺和针+灸均能显著改善大鼠自发活动,提高骨关节炎大鼠滑膜组织中Clock及Bmal1蛋白表达水平(P<0.05),降低TRPV4和白细胞介素1β的表达(P<0.05),改善滑膜上皮损失程度;与针刺组相比,针+灸组改善更为明显(P<0.05)。(3)相对于针刺,针刺结合艾灸更能有效调节膝骨关节炎大鼠关节炎性损伤状况,降低滑膜细胞TRPV4的表达,促进骨关节炎大鼠滑膜组织中Clock,Bmal1的表达,从而调节滑膜细胞生物钟,降低炎性因子的表达,减缓膝骨关节炎的退变。 展开更多
关键词 针灸 足三里 膝骨关节炎 生物钟 clock BMAL1 TRPV4 白细胞介素1Β
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A Domestication-Associated Gene GmPRR3b Regulates the Circadian Clock and Flowering Time in Soybean 被引量:18
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作者 Cong Li Ying-hui Li +11 位作者 Yanfei Li Hongfeng Lu Huilong Hong Yu Tian Hongyu Li Tao Zhao Xiaowei Zhou Jun Liu Xinan Zhou Scott A.Jackson Bin Liu Li-juan Qiu 《Molecular Plant》 SCIE CAS CSCD 2020年第5期745-759,共15页
Improved soybean cultivars have been adapted to grow at a wide range of latitudes,enabling expansion of cultivation worldwide.However,the genetic basis of this broad adaptation is still not clear.Here,we report the id... Improved soybean cultivars have been adapted to grow at a wide range of latitudes,enabling expansion of cultivation worldwide.However,the genetic basis of this broad adaptation is still not clear.Here,we report the identification of GmPRR3b as a major flowering time regulatory gene that has been selected during domestication and genetic improvement for geographic expansion.Through a genome-wide association study of a diverse soybean landrace panel consisting of 279 accessions,we identified 16 candidate quantitative loci associated with flowering time and maturity time.The strongest signal resides in the known flowering gene E2,verifying the effectiveness of our approach.We detected strong signals associated with both flowering and maturity time in a genomic region containing GmPRR3b.Haplotype analysis revealed that GmPRR3bH6 is the major form of GmPRR3b that has been utilized during recent breeding of modern cultivars.mRNA profiling analysis showed that GmPRR3bH6 displays rhythmic and photoperiod-dependent expression and is preferentially induced under long-day conditions.Overexpression of GmPRR3bH6 increased main stem node number and yield,while knockout of GmPRR3bH6 using CRISPR/Cas9 technology delayed growth and the floral transition.GmPRR3bH6 appears to act as a transcriptional repressor of multiple predicted circadian clock genes,including GmCCAIa,which directly upregulates J/GmELF3a to modulate flowering time.The causal SNP(Chr12:5520945)likely endows GmPRR3bH6 a moderate but appropriate level of activity,leading to early flowering and vigorous growth traits preferentially selected during broad adaptation of landraces and improvement of cultivars. 展开更多
关键词 flowering time soybean landrace DOMESTICATION genome-wide association study GmPRR3b circadian clock
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电网状态监测系统GPS同步时钟的稳定性研究 被引量:15
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作者 张鹏 王少荣 程时杰 《继电器》 CSCD 北大核心 2004年第23期18-22,共5页
GPS接收机输出的秒脉冲信号在统计意义下与国际标准时间高度同步,具有相当高的精度,但是由于其误差服从正态分布,单个秒脉冲误差可能较大。为提高基于GPS的同步时钟的精度和稳定性,该文根据GPS时钟信号和晶振时钟信号精度互补的特点,提... GPS接收机输出的秒脉冲信号在统计意义下与国际标准时间高度同步,具有相当高的精度,但是由于其误差服从正态分布,单个秒脉冲误差可能较大。为提高基于GPS的同步时钟的精度和稳定性,该文根据GPS时钟信号和晶振时钟信号精度互补的特点,提出了一种利用GPS时钟同步晶振时钟的新方法,实现了高精度、高稳定度的同步时钟。所设计的GPS同步时钟不受GPS信号短时失效的影响,具有较高的可靠性和实用性,能够满足电力系统电网状态监测的要求。 展开更多
关键词 同步时钟 晶振 时钟信号 GPS信号 秒脉冲 时钟同步 GPS接收机 电网 电力系统 状态监测系统
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时钟抖动和相位噪声关系的研究 被引量:14
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作者 宋屾 焦淑红 胡尔富 《应用科技》 CAS 2006年第4期1-3,6,共4页
时钟的抖动和相位噪声是衡量时钟综合性能的最主要的指标,但是有关这2个指标之间的关系论述很少.明确说明抖动和相位噪声的含义,而且通过建立典型数学模型对2个指标的关系作出了论证.同时引入例子说明抖动性能对A/D转换系统的影响,并举... 时钟的抖动和相位噪声是衡量时钟综合性能的最主要的指标,但是有关这2个指标之间的关系论述很少.明确说明抖动和相位噪声的含义,而且通过建立典型数学模型对2个指标的关系作出了论证.同时引入例子说明抖动性能对A/D转换系统的影响,并举例说明抖动的测量值与计算值之间的区别和关系,说明时钟抖动和相位噪声是对时钟时序性能时域和频域的不同描述,它们之间存在着确定的对应关系. 展开更多
关键词 抖动 相位噪声 A/D转换器 时钟
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电流差动保护复用数字通信系统时的时钟问题 被引量:11
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作者 黄梅 沈江 《电力系统自动化》 EI CSCD 北大核心 2002年第7期70-72,共3页
为准确、迅速、不失真地在继电保护装置与通信设备之间传输数据信号 ,需要对通信系统和继电保护装置的时钟进行合理设计。文中详细分析了继电保护信号周期性误码即滑码现象产生的原因 ,以及“主—从”和“主—主”两种通信方式对继电保... 为准确、迅速、不失真地在继电保护装置与通信设备之间传输数据信号 ,需要对通信系统和继电保护装置的时钟进行合理设计。文中详细分析了继电保护信号周期性误码即滑码现象产生的原因 ,以及“主—从”和“主—主”两种通信方式对继电保护的影响。通过对国外几种电流差动保护装置的分析 ,指出主—主时钟方式的通信系统产生的滑码现象在改用主—从方式后得到了有效的消除。理论及实例分析表明 ,通信系统的主—从时钟方式是电流差动保护装置在复用数字通信系统时正确工作的理想方式。 展开更多
关键词 时钟 电流差动保护 滑码 继电保护装置 复用数字通信系统 电力系统
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Similarities and differences of city-size distributions in three main urban agglomerations of China from 1992 to 2015: A comparative study based on nighttime light data 被引量:15
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作者 高宾 黄庆旭 +1 位作者 何春阳 窦银银 《Journal of Geographical Sciences》 SCIE CSCD 2017年第5期533-545,共13页
Comparing the city-size distribution at the urban agglomeration(UA) scale is important for understanding the processes of urban development. However, comparative studies of city-size distribution among China's thre... Comparing the city-size distribution at the urban agglomeration(UA) scale is important for understanding the processes of urban development. However, comparative studies of city-size distribution among China's three largest UAs, the Beijing-Tianjin-Hebei agglomeration(BTHA), the Yangtze River Delta agglomeration(YRDA), and the Pearl River Delta agglomeration(PRDA), remain inadequate due to the limitation of data availability. Therefore, using urban data derived from time-series nighttime light data, the common characteristics and distinctive features of city-size distribution among the three UAs from 1992 to 2015 were compared by the Pareto regression and the rank clock method. We identified two common features. First, the city-size distribution became more even. The Pareto exponents increased by 0.17, 0.12, and 0.01 in the YRDA, BTHA, and PRDA, respectively. Second, the average ranks of small cities ascended, being 0.55, 0.08 and 0.04 in the three UAs, respectively. However, the average ranks of large and medium cities in the three UAs experienced different trajectories, which are closely related to the similarities and differences in the driving forces for the development of UAs. Place-based measures are encouraged to promote a coordinated development among cities of differing sizes in the three UAs. 展开更多
关键词 city-size distribution comparative study nighttime light data rank clock urban agglomeration
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SIS accuracy and service performance of the BDS-3 basic system 被引量:16
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作者 JinPing Chen XiaoGong Hu +8 位作者 ChengPan Tang ShanShi Zhou YuFei Yang JunYang Pan Hui Ren YueXin Ma QiuNing Tian Bin Wu Yang Yu 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS CSCD 2020年第6期105-116,共12页
On December 27,2018,the basic system of the third-generation BeiDou navigation satellite system(BDS-3)completed the deployment of its constellation of 18 MEO networking satellites as well as the construction of the op... On December 27,2018,the basic system of the third-generation BeiDou navigation satellite system(BDS-3)completed the deployment of its constellation of 18 MEO networking satellites as well as the construction of the operation control system(OCS)and began to provide basic navigation services to users worldwide.Compared with BDS-2,BDS-3 aims to offer users better navigation signals and higher precision with a series of new technologies.For example,the spaceborne atomic clock of BDS-3 is upgraded for higher performance,the Ka-band inter-satellite link is adopted for inter-satellite ranging and communication,and new B1C and B2a signals are broadcast in addition to B1I and B3I signals(compatible with BDS-2).In addition,a 9-parameter model based on a spherical harmonic function is employed for ionospheric delay corrections.Using the observation data from 18 satellites of the basic system,this paper conducts a comprehensive evaluation of the pseudorange measurement characteristics,signal-in-space(SIS)accuracy of navigation messages and global service capability of BDS-3.The results indicate that the pseudorange measurement multipath effect and observation noise of BDS-3 satellites are better than those of BDS-2;additionally,with the support of inter-satellite links,the user range error(URE)of the BDS-3 satellite broadcast ephemeris is better than 10 cm,the precision of the broadcast clock parameter is better than 1.5 ns,and the SIS accuracy is better than 0.6 m overall.Different from the traditional Klobuchar model,the BeiDou global broadcast ionospheric delay correction model(BDGIM)can provide ionospheric delay corrections better than 70%for worldwide single-frequency users.The service capability evaluation of the basic system consists mainly of the accuracy improvement of the B1I and B3I signals according to BDS-2 as well as the global positioning accuracy of the new signals.These results prove that the BDS-3 basic system has achieved the design goal;that is,both the horizontal and the vertical global positioning accur 展开更多
关键词 BDS-3 SIS URE multipath effect broadcast ephemeris broadcast clock ionospheric model positioning accuracy
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Notes,outline and divergence times of Basidiomycota 被引量:16
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作者 Mao-Qiang He Rui-Lin Zhao +67 位作者 Kevin D.Hyde Dominik Begerow Martin Kemler Andrey Yurkov Eric H.C.McKenzie Olivier Raspe Makoto Kakishima Santiago Sanchez-Ramırez Else C.Vellinga Roy Halling Viktor Papp Ivan V.Zmitrovich Bart Buyck Damien Ertz Nalin N.Wijayawardene Bao-Kai Cui Nathan Schoutteten Xin-Zhan Liu Tai-Hui Li Yi-Jian Yao Xin-Yu Zhu An-Qi Liu Guo-Jie Li Ming-Zhe Zhang Zhi-Lin Ling Bin Cao Vladimir Antonin Teun Boekhout Bianca Denise Barbosa da Silva Eske De Crop Cony Decock Balint Dima Arun Kumar Dutta Jack W.Fell Jozsef Geml Masoomeh Ghobad-Nejhad Admir J.Giachini Tatiana B.Gibertoni Sergio P.Gorjon Danny Haelewaters Shuang-Hui He Brendan P.Hodkinson Egon Horak Tamotsu Hoshino Alfredo Justo Young Woon Lim Nelson Menolli Jr Armin Mesic Jean-Marc Moncalvo Gregory M.Mueller La szlo G.Nagy RHenrik Nilsson Machiel Noordeloos Jorinde Nuytinck Takamichi Orihara Cheewangkoon Ratchadawan Mario Rajchenberg Alexandre G.S.Silva-Filho Marcelo Aloisio Sulzbacher Zdenko Tkalcec Ricardo Valenzuela Annemieke Verbeken Alfredo Vizzini Felipe Wartchow Tie-Zheng Wei Michael WeiB Chang-Lin Zhao Paul M.Kirk 《Fungal Diversity》 SCIE 2019年第6期105-367,共263页
The Basidiomycota constitutes a major phylum of the kingdom Fungi and is second in species numbers to the Ascomycota.The present work provides an overview of all validly published,currently used basidiomycete genera t... The Basidiomycota constitutes a major phylum of the kingdom Fungi and is second in species numbers to the Ascomycota.The present work provides an overview of all validly published,currently used basidiomycete genera to date in a single document.An outline of all genera of Basidiomycota is provided,which includes 1928 currently used genera names,with 1263 synonyms,which are distributed in 241 families,68 orders,18 classes and four subphyla.We provide brief notes for each accepted genus including information on classification,number of accepted species,type species,life mode,habitat,distribution,and sequence information.Furthermore,three phylogenetic analyses with combined LSU,SSU,5.8s,rpb1,rpb2,and ef1 datasets for the subphyla Agaricomycotina,Pucciniomycotina and Ustilaginomycotina are conducted,respectively.Divergence time estimates are provided to the family level with 632 species from 62 orders,168 families and 605 genera.Our study indicates that the divergence times of the subphyla in Basidiomycota are 406-430 Mya,classes are 211-383 Mya,and orders are 99-323 Mya,which are largely consistent with previous studies.In this study,all phylogenetically supported families were dated,with the families of Agaricomycotina diverging from 27-178 Mya,Pucciniomycotina from 85-222 Mya,and Ustilaginomycotina from 79-177 Mya.Divergence times as additional criterion in ranking provide additional evidence to resolve taxonomic problems in the Basidiomycota taxonomic system,and also provide a better understanding of their phylogeny and evolution. 展开更多
关键词 Classification Molecular clock FUNGI SYSTEMATICS TAXONOMY
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基于Linux驱动程序的编写技术 被引量:3
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作者 李世勇 肖竟华 《电脑与信息技术》 2006年第3期43-45,72,共4页
Linux的应用已经越来越广泛,由于它免费提供源代码,许多公司企业都使用Linux作为开发平台。文章主要阐述了Linux驱动程序的基本概念以及字符设备、块设备和网络设备的特点,分析了主设备号、次设备号的用途和时钟、驱动程序接口、驱动模... Linux的应用已经越来越广泛,由于它免费提供源代码,许多公司企业都使用Linux作为开发平台。文章主要阐述了Linux驱动程序的基本概念以及字符设备、块设备和网络设备的特点,分析了主设备号、次设备号的用途和时钟、驱动程序接口、驱动模块的用法,描述了编写驱动程序的步骤。 展开更多
关键词 LINUX驱动程序 模块 中断 时钟
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