17 resultados para Transportation Services.
Resumo:
In this dissertation, we investigated two types of traveling ionospheric disturbances (TIDs)/gravity waves (GWs) triggered separately by auroral energy input during super geomagnetic storms and solar terminator (ST) under quiet geomagnetic conditions (kp<3+) using TEC measurements from the global network of GPS receivers. Research into the generation and propagation of TIDs/GWs during storms greatly enhance our understandings on the evolution processes of energy transportation from the high-latitude’s magnetosphere to the low-latitude ionosphere and the conjugated effect of TIDs propagation between the northern and southern hemispheres. Our results revealed that the conjugacy of propagation direction between the northern and southern hemispheres was subject to the influence of Coriolis force. We also figure out the evolution processes of ionospheric disturbances at the global scale. These are important topics that had not been well addressed previously. In addition, we also obtained thee wave structures of medium scale TIDs excited by the solar terminator (ST) moving over the northern America and physical mechanisms involved. Our observations confirm that the ST is a stable and repetitive source of ionospheric wave disturbances and the evidence of solar terminator generated disturbances has been demonstrated experimentally via the GPS TEC measurement. The main researches and results of this dissertation are as follows. First, the global traveling ionospheric disturbances (TIDs) during the drastic magnetic storms of October 29–31, 2003 were analyzed using the Global Position System (GPS) total electron content (TEC) data observed in the Asian-Australian, European and North American sectors. We collected the most comprehensive set of the TEC data from more than 900 GPS stations on the International GNSS Services (IGS) website and introduce here a strategy that combines polynomial fitting and multi-channel maximum entropy spectral analysis to obtain TID parameters. Moreover, in collaboration with my thesis advisor, I have developed an imaging technique of 2-dimensional map of TIDs structures to obtain spatial and temporal maps of large scale traveling ionospheric disturbances (LSTIDs). The clear structures of TEC perturbations map during the passage of TIDs were displayed. The results of our study are summarized as follows: (1) Large-scale TIDs (LSTIDs) and medium-scale TIDs (MSTIDs) were detected in all three sectors after the sudden commencement (SC) of the magnetic storm, and their features showed longitudinal and latitudinal dependences. The duration of TIDs was longer at higher latitudes than at middle latitudes, with a maximum of about 16 h. The TEC variation amplitude of LSTIDs was larger in the North American sector than in the two other sectors. At the lower latitudes, the ionospheric perturbations were more complicated, and their duration and amplitude were relatively longer and larger. (2) The periods and phase speeds of TIDs were different in these three sectors. In Europe, the TIDs propagated southward; in North America and Asia, the TIDs propagated southwestward; in the near-equator region, the disturbances propagated with the azimuth (the angle of the propagation direction of the LSTIDs measured clockwise from due north with 0°) of 210° showing the influence of Coriolis force; in the Southern Hemisphere, the LSTIDs propagated conjugatedly northwestward. Both the southwestward and northeastward propagating LSTIDs are found in the equatorial region. These results mean that the Coriolis effect cannot be ignored for the wave propagation of LSTIDs and that the propagation direction is correlated with the polar magnetic activity. (3) The day (day of year: 301) before the SC (sudden commencement) of magnetic storm, we observed a sudden TEC skip disturbances (±10 TECU). It should be a response for the high flux of proton during the solar flare event, but not the magnetic storms. Next, the most comprehensive and dense GPS network’s data from North-America region were used in this paper to analyze the medium scale traveling ionospheric disturbances (MSTIDs) which were generated by the moving solar terminator during the quiet days in 2005. We applied the multi-channel maximum entropy spectral analysis to calculated TID parameters, and found that the occurrence of ST-MSTIDs depends on the seasonal variations. The results of our study are summarized as follows: (1) MSTIDs stimulated by the moving ST (ST-MSTIDs) are detected at mid-latitudes after the passage of the solar terminator with the life time of 2～3 hours and the variation amplitude of 0.2～0.8 TECU. Spectral analysis indicated that the horizontal wavelength, average period, horizontal phase velocity of the MSTIDs are around 300±150 km，150±80 m/s and 25±15 min, respectively. In addition, ST-MSTIDs have wave fronts elongating the moving ST direction and almost parallel to ST. (2) The statistical results demonstrate that the dusk MSTIDs stimulated by ST is more obvious than the dawn MSTIDs in summer. On the contrary, the more-pronounced dawn MSTIDs occurs in winter. (3) Further analysis indicates that the seasonal variations of ST-MSTIDs occurrence frequency are most probably related to the seasonal differences of the variations of EUV flux in the ionosphere region and recombination process during sunrise and sunset period at mid-latitudes. Statistical study of occurrence characteristics of TIDs using the GPS network in North-American and European during solar maximum, In conclusion, statistical studies of the propagation characteristics of TIDs, which excited by the two common origins including geomagnetic storms and moving solar terminator, were involved with global GPS TEC databasein this thesis. We employed the multichannel maximum entropy spectral analysis method to diagnose the characteristics of propagation and evolvement of ionospheric disturbances, also, the characteristics of their regional distribution and climatological variations were revealed by the statistic analysis. The results of these studies can improve our knowledge about the energy transfer in the solar-terrestrial system and the coupling process between upper and lower atmosphere (thermosphere-ionosphere-mesosphere). On the other hand, our results of the investigation on TIDs generated by particular linear origin such as ST are important for developing ionospheric irregularity physics and modeling the transionosphere radio wave propagation. Besides, the GPS TEC representation of the ST-generated ionospheric structure suggests a better possibility for investigating this phenomenon. Subsequently, there are scientific meaning of the result of this dissertation to deeply discuss the energy transfer and coupling in the ionosphere, as well as realistic value to space weather forecast in the ionosphere region.
Resumo:
随着网络技术、特别是Internet技术的发展，分布式系统的高睦能、高可靠性、高灵敏度、可扩展性和系统透明性使得基于分布式系统的应用越来越广泛。在分布式坏境下，信息系统的集成是必须认真考虑的问题。研究如何集成和统一访问分布的、异构的数据资源，实现各种数据的转换、交流与共享；以及如何建立一个开放、可扩展和异构兼容的新一代信息管理系统成为当今网络应用的重要研究方向。本文针对建立月球探测数据管理和集成系统的数据集成与操作集成两方面的内容，重点分析和研究了数据存储管理和系统集成技术，结合月球探测数据管理的应用集成需求与特点提出了基于XML技术的数据存储与管理和基于Web Service技术的系统集成方案。并利用XML／WebService技术基于Net平台开发了一个月球探测数据管理与集成系统实例。研究内容主要包括以下四个方面： （1）基于XML的数据模型与数据库存储。利用XML的自描述性、独立于平台和应用、半结构化，机器可处理、可扩展性以及便于网络传输和广泛支持的特性，实现了基于关系数据库的XML数据存储。对系统中的结构化和非结构化数据信息、都进行了XML标记定义，实现了信息存储和查询的小粒度，增强了数据的表示、查询、插入和删除等数据处理能力和效率。同时，利用XML作为月球探测数据交换和信息传输的格式，也为实现与异构系统数据的互操作提供了理想的角军决方案。（2）基于WebServices分布式信息系统集成的体系结构。在对XML、SOAP、WSDL和UDDI关键技术和标准规范进行研究与探讨基础上，针对绕月探测数据管理的需求提出了基于XML／Web Service的三层分布式结构模型。分别是表示层、应用逻辑层、服务端数据层。实现了系统功能的可迁移性和可装配性、各层间传输过程中数据流的XML化、接口定义的动态性。与传统技术开发的耦合的分布式应用系统相比，系统在跨平台性、可配置性、可伸缩性、可维护性等方面都有了大幅度的提高。（3）基于，NET平台系统的开发与实现。深入分析和研究了Mic1’osoft．NET平台的核心技术与整体技术框架，在VisLla1Sttldio．NET开发环境中利用C＃、ASP．NET、ADO．NET基于关系型数据库Oracle9i开发实现了统一身份认证系统和月球探测数据管理与集成系统。统一身份认证系统是一个通用的统一用户身份认证管理系统，包括用户管理、身份验证、实体管理、日志监控和消息、管理等功能，达到了一次登录，所有系统共用的目的。月球探测数据管理与集成系统包括数据管理、信息发布、系统管理、综合查询和应用集成五大功能模块，相对于原来的紧祸合的应用系统而言，系统的开发效率、重用性、祸合度、灵活性和自适 应性都有了很大的提高。（4）基于XML／WebServices动态系统集成。分析了传统分布式对象模型在异构环境集成的弊端，基于XML、SOAP和WSDL等技术规范基础上，实现了统一身份认证系统、月球探测数据管理与集成系统、小空间碎片数据库系统以及其它语言开发的应用系统的信息集成、实现了资源时空的有效整合。通过这些集成应用实例，充分体现和说明了Web Services术在应用系统集成方面的优越性。本研究的成果，也将为地球化学研究领域涉及海量数据的处理、管理和系统集成提供示范实例，推动地球化学数据的融合和综合应用。
