Assessment of International GNSS Service Global Ionosphere Map products over China region based on measurements from the Crustal Movement Observation Network of China

The global ionosphere maps(GIM)provided by the International GNSS Service(IGS)are extensively utilized for ionospheric morphology monitoring,scientific research,and practical application.Assessing the credibility of GIM products in data-sparse regions is of paramount importance.In this study,measurements from the Crustal Movement Observation Network of China(CMONOC)are leveraged to evaluate the suitability of IGS-GIM products over China region in 2013-2014.The indices of mean error(ME),root mean square error(RMSE),and normalized RMSE(NRMSE)are then utilized to quantify the accuracy of IGS-GIM products.Results revealed distinct local time and latitudinal dependencies in IGS-GIM errors,with substantially high errors at nighttime(NRMSE:39%)and above 40°latitude(NRMSE:49%).Seasonal differences also emerged,with larger equinoctial deviations(NRMSE:33.5%)compared with summer(20%).A preliminary analysis implied that the irregular assimilation of sparse IGS observations,compounded by China’s distinct geomagnetic topology,may manifest as error variations.These results suggest that modeling based solely on IGS-GIM observations engenders inadequate representations across China and that a thorough examination would proffer the necessary foundation for advancing regional total electron content(TEC)constructions.

The Sensitivity of Model Results to Specification of Network-Based Level of Service Attributes: An Application of a Mixed Logit Model to Trave Mode Choice

The need for travel demand models is growing worldwide. Obtaining reasonably accurate level of service (LOS) attributes of different travel modes such as travel time and cost representing the performance of transportation system is not a trivial task, especially in growing cities of developing countries. This study investigates the sensitivity of results of a travel mode choice model to different specifications of network-based LOS attributes using a mixed logit model. The study also looks at the possibilities of correcting some of the inaccuracies in network-based LOS attributes. Further, the study also explores the effects of different specifications of LOS data on implied values of time and aggregation forecasting. The findings indicate that the implied values of time are very sensitive to specification of data and model implying that utmost care must be taken if the purpose of the model is to estimate values of time. Models estimated on all specifications of LOS-data perform well in prediction, likely suggesting that the extra expense on developing a more detailed and accurate network models so as to derive more precise LOS attributes is unnecessary for impact analyses of some policies.

Next Generation Network Service Provision Mode and Its Developing Trend

The provision mode of the telecommunication service has experienced an evolving process, and showing the developing trend from distributed to centralized, from integrated to separated, and from closed to open. To suit this trend, there will be three provision modes as Session Initiation Protocol (SIP) server, Open Service Access (OSA) application server and intelligent network(IN) in Next Generation Network (NGN), provides all kinds of services and applications to the subscribers. With the popularity of broadband access and Internet, the NGN will provide single telecommunication service and act as the important national infrastructure to offer various information services to the subscribers. The service provision mode will be more open, diversified, and individualized.

基于Grid Service技术的物流网格公共信息平台研究

异构数据源的有效整合是公共物流信息平台建设的关键。本文基于三层次网格服务体系结构搭建四层次物流网格体系结构,在此基础上,构建基于GridService技术的物流网格公共信息平台,实现异构物流企业信息平台的互通和数据集成。

Impact of public name resolving services on Akamai

To enhance user perceived performance,Akamai' s content distribution network(CDN) utilizes the domain name system(DNS) effectively to redirect users to close-by content replicas over short time scale.The use of DNS redirection has brought a significant advantage to Akamai' s CDN.However,the reliance on DNS also poses a fundamental threat to Akamai' s content distribution model.In particular,systematic evaluation and quantification illustrates the impact of recent emerging public DNS resolving services on Akamai' s CDN,including the degradation of corresponding user perceived performance and the benefit damnification of collaborating internet services providers(ISPs) that host Akamai's edge servers.The measurement demonstrates that a considerable penetration of public DNS resolving services(e.g.,OpenDNS and GoogleDNS) effectively corrupts the Akamai' s serving model,namely the large-scale server distribution and quick DNS redirection.

Directed graph-based distribution network reconfiguration for operation mode adjustment and service restoration considering distributed generation

We present a directed graph-based method for distribution network reconfiguration considering distributed generation. Two reconfiguration situations are considered: operation mode adjustment with the objective of minimizing active power loss(situation Ⅰ) and service restoration with the objective of maximizing loads restored(situation Ⅱ). These two situations are modeled as a mixed integer quadratic programming problem and a mixed integer linear programming problem, respectively. The properties of the distribution network with distributed generation considered are reflected as the structure model and the constraints described by directed graph. More specifically, the concepts of "in-degree" and "out-degree"are presented to ensure the radial structure of the distribution network, and the concepts of "virtual node" and"virtual demand" are developed to ensure the connectivity of charged nodes in every independent power supply area.The validity and effectiveness of the proposed method are verified by test results of an IEEE 33-bus system and a 5-feeder system.

内容服务:国内ISP经营的真正主题

Based on an analysis of the present situation of domestic IPSs’ management,this article points out that content service is the essential of ISP’s survival.It also discusses the measures of content service,exemplified by a statistical description of foreign information institutes’ information sources,hoping to mean some help for the establishment of ISPs’ managing mode.

The Cooperation Between ISP and CDN: A Survey

CDN is a kind of effective technology for content processing and distribution and can improve the network performance. However, the development and application of CDN are limited by some reasons, like operating system and price of ISP. In addition, ISP is suffering network congestion brought by the sudden traffic migration and infrastructure deployment of CDN without the confusion of the basic information of the network. We should balance or coordinate the relationship between ISP and CDN. And the friendliness building of CDN and ISPs will promote the user experience, effectively guarantee their service quality, improve the network operation, and reduce the content distribution cost. In this paper, we discuss the basic working principle of CDN and ISP, analyze possibility of cooperation between CDN and ISP and conclude the existing methods from a novel angle. Furthermore, some suggestions for further research and solutions in this field are provided.

职前中文教师整合技术的学科教学知识发展实证研究——基于线上实习总结的认知网络分析

职前教师的知识结构决定着其未来的教学胜任力和专业发展潜力。通过认知网络分析法,对20名职前中文教师的实习总结进行编码并构建认知网络模型,以探究其整合技术的学科教学知识(TPACK)发展轨迹及特征,发现:职前中文教师在实习中,教学法相关知识发展突出,学科内容知识有所拓展,技术知识发展不足;实习各阶段的知识呈现渐进式发展特征。比较不同专业背景组和有无教学经验组的认知网络结构发现,不同组别职前中文教师在知识发展的类型和数量上均存在显著差异:本专业组更注重专业知识的发展,跨专业组在技术知识整合上更有优势;有教学经验组比无经验组掌握了更多复合知识。国际中文教育转型发展期的职前教师培养,可从如下方面着手:引入TPACK理论,变革职前中文教师培养理念;完善教师教育课程的设置与实施,奠定TPACK发展基础;加强实习实践,促进职前中文教师TPACK知识形成。

价值网络中生产性服务业与制造业融合发展的模式研究

我国经济正处于传统制造业转型发展的关键时期。制造业的转型升级离不开基于价值链体系中先进制造业和现代服务业的深度融合。在由价值链向价值网络演化发展的不同阶段,生产性服务业从作为价值链服务环节的提供商、互补者到制造业的战略伙伴,可以通过外包、价值链延伸、嵌入式发展,积极融入制造商网络。通过提供更专业化、个性化、低成本和柔性化服务,生产性服务业能够助力先进制造业向更高价值链攀升,促进服务型制造企业成长,推动建设现代化的产业组织体系,赋能中国经济高质量发展。

城市绿地游憩服务网络特征及不同出行模式的响应差异

【目的】随着经济社会的快速发展,城市居民亲近自然的游憩需求显著增长。在城市尺度提升绿地的蓝色和绿色游憩服务效率成为当前亟须解决的问题。【方法】以武汉市为研究区域,通过提取居民游憩出行的最短路径,利用社会网络分析软件Ucinet 6.0分别构建步行、骑行和驾车3种出行模式下的5 min、10 min和15 min城市绿地的游憩服务网络,并分析网络的整体特征、节点功能和节点类型,进而探究这些特征在不同出行模式下的响应差异。【结果】当出行时长为5 min时,骑行和驾车模式能够组织超过85%的城市绿地节点协同联系形成游憩服务网络,而步行模式下游憩服务则呈零星局部组团分布。随着出行时长的增加,3种出行模式下游憩服务网络的核心集聚功能节点占比呈上升趋势,且节点类型主要以绿色游憩服务为主。骑行和驾车模式下的边缘汇聚功能节点占比则随出行时长增加而逐渐下降,但其蓝色游憩服务型核心集聚节点的占比则逐渐上升。【结论】城市绿地游憩服务网络效率的整体提升须系统考虑不同出行模式下居民的游憩需求,并协同整合蓝色和绿色游憩空间。这些发现可以为城市绿地游憩体系的构建和完善,以及游憩资源的系统整合提供直接支持。

考虑坝基防渗体渗透溶蚀效应的特高土心墙堆石坝服役年限可靠性分析

特高土心墙堆石坝坝基防渗体非均质特征显著,影响渗透溶蚀效应下长期服役性能的准确评估。本文基于KL展开法离散了水泥基材料参数随机场,构建了水泥基材料渗流-溶蚀耦合随机模型,利用神经网络,建立了随机场与服役年限的映射关系,发展了服役年限可靠性分析方法。以长河坝工程为背景,研究了坝基防渗体渗透系数、孔隙率和固相钙浓度为随机场情况下特高土心墙堆石坝的渗流与溶蚀特征,并对特高土心墙堆石坝服役年限进行了可靠性分析。渗透溶蚀效应会增大坝基防渗体渗透系数的空间变异性;坝基防渗体渗透系数、孔隙率和固相钙浓度为随机场情况下坝体与坝基总单宽渗流量是均质情况下的0.87~1.19倍;坝基防渗体95%保证率的服役年限为63.4 a;降低主防渗帷幕区与固结灌浆区渗透系数均值、减小固结灌浆区渗透系数空间变异性,是延长服役年限较为有效的方法。特高土心墙堆石坝设计、施工、运行与维护过程中应重视渗透溶蚀效应下坝基防渗体的空间变异性。

多尺度分解下GRU-TCN集成的动力电池剩余使用寿命预测方法

精准预测动力电池的剩余使用寿命(remaining useful life,RUL)能够提前规避因电池过度使用带来的风险,为退役电池的二次利用提供决策依据,提升电池第二寿命的利用率。为了降低动力电池RUL预测任务中噪声和容量回升现象导致的非线性特征对RUL预测精度的影响,提出了一种基于集合经验模态分解(ensemble empirical mode decomposition,EEMD)、门控循环单元网络(gated recurrent unit,GRU)和时序卷积网络(temporal convolutional networks,TCN)集成的动力电池RUL预测模型。首先,使用EEMD对原始数据进行分解,动力电池容量衰退过程中由噪声和容量回升现象导致的非线性特征被分解到高频分量,而原始容量数据的主要趋势被分解到低频分量。其次,再使用GRU和TCN网络分别对高频分量和低频分量进行预测。最后,使用Attention对预测结果进行集成。在NASA数据集上的实验结果表明,本工作提出的集成模型的预测精度和对非线性特征的拟合程度都优于其他单一模型和其他同类型模型,最大平均绝对误差和最大均方根误差分别在0.52%和0.74%内,绝对误差在1个循环周期内,证明本模型有较好的RUL预测能力。

高速公路监控网络可补偿信道增益系统设计

为解决高速公路监控图像与信道组织内数据增量值不匹配的问题,从而提升监控信息的实时传输速率,设计高速公路监控网络的可补偿信道增益系统。在可调式VGA结构体系中,连接增益放大器、峰值检测器与视频车辆检测器,完成可补偿信道增益系统的硬件设计。建立Flex服务模式,并以此为基础,定义完整的Access数据库表,实现高速公路监控网络中的GIS数据准备,联合相关硬件结构,完成高速公路监控网络可补偿信道增益系统的设计。实验结果表明,该系统可将监控图像补偿残差与信道组织内数据增量之间的差值控制在0~2.5×10^(9) bit的数值范围内,能够有效解决图像与增量值不匹配的问题,符合提升高速公路监控信息实时传输速率的实际应用需求。

学术社交网站信息服务研究——基于国外13家学术社交网站的调查

学术社交网站实现了线上知识共享,满足了用户随时随地进行学术交流的需求。文章通过网站调研、文献检索、邮件咨询等方法,对国外不同类型的13家学术社交网站的学术信息服务进行调查分析,从学术信息服务群体、服务方式、服务内容三个方面总结提炼其服务特色,并为我国学术社交网站学术信息服务发展提出建议:提升个性化服务意识,满足用户差异性需求;汲取优质资源,推动创新发展;拓宽合作范畴,打破交流壁垒。

中国先进制造业与生产性服务业关联网络结构特征

基于最新2020年中国153部门投入产出表,以生产性服务业部门为供给侧,以先进制造业部门为需求侧,构建两业关联二模网络,并分为供给网络和需求网络综合分析两业网络的结构特征。产业网络分析显示:供给网络和需求网络在不同视角下形态各异且存在核心与孤立节点,需求网络结构相比于供给网络更加稀疏;通过中心性分析对产业节点地位做了进一步的量化分析,与可视化结果基本一致;供给网络和需求网络的核心边缘结构不同,且供给网络比需求网络的拟合效果和分块效果更好;二模网络密度显示,联动性的密度主动性低于被动性,个体性的主被动密度在不同部门表现各异。

数字资产超网络嵌入、生态场域资源拼凑与制造业服务模式创新——来自华为、海尔、京东、阿里的多案例研究

从数字资产超网络嵌入视角,遵循“资源行动-资源拼凑-价值实现”逻辑思路,采用多案例研究方法,解构工业互联网平台领先企业制造业服务模式创新的过程机理。研究发现,工业互联网平台领先企业在界面融合、交互赋能、协同演化机制支撑作用下,数字资产超网络嵌入制造业数字价值生态系统,在生态场域开展资源拼凑,完成机会捕获、知识整合及知识治理,实现制造业服务模式创新,表现为制造业架构服务模式创新及制造业孵化服务模式创新。探索面向制造业龙头企业、细分行业、区域集群场景的服务模式创新范式。相关研究丰富了制造业服务模式创新理论,为工业互联网平台领先企业服务制造业数字化转型提供重要实践启示。

政务服务“一张网”深化模式设计与实施方案

为全面贯彻国务院“放、管、服”工作的总体要求,加大简政放权力度,创新政府的管理模式,提供畅通的政务服务渠道,全国各地政府相继启动打造政务“一张网”的信息化建设。本文结合“一张网”的建设方针、建设目标及建设内容,以政务服务“一张网”为基础,与“多规合一”平台的空间规划成果相融合,从而构建政务服务深化模式,形成高效便民的互联网+政务服务体系,为“一张网”政务信息化的建设提供一个科学的、切实可行的整体设计与实施方案。

我国高校图书馆面向社会开放现状调查

目前,我国高等学校图书馆面向社会开放程度还很低,服务方式和内容等都很有限。服务对象主要是单位工作人员,服务方式包括办证服务和临时阅览,服务内容以室内查阅和普通图书外借为主,对社会读者采取的管理措施包括收取一定数额押金、限制读者身份、提供较少使用权限等。另外,面向社会开放的高校图书馆在相关制度建设方面进行了有益尝试,但完善程度和制定水平参差不齐。